In search of a regime of responsibility and accountability for perpetrators of torture with reference to persons with special responsibility for protecting human rights
- Authors: Odeku, Kolawole Olusola
- Date: 2008
- Subjects: Human rights -- Accountability -- Perpetrators of torture -- Torture
- Language: English
- Type: Thesis , Doctoral , LLD
- Identifier: vital:11112 , http://hdl.handle.net/10353/101 , Human rights -- Accountability -- Perpetrators of torture -- Torture
- Description: orture is a serious violation of human rights and it is strictly prohibited by numerous human rights instruments. The prohibition of torture enshrines one of the most fundamental values of a democratic society. Its prohibition in a national constitution commits the country, and specifically its law enforcement officers, to performing their duties with due regard to the essential dignity of every human being. The irony is that the law enforcement officials and the security agents who are entrusted with the responsibility of maintaining law and order in the society sometimes breach the law which they have sworn to uphold. Most of the perpetrators of acts of torture are usually those in positions of state power. In addition, other persons who wield other forms of authority or influence also perpetrate torture. It is contended that both civil and criminal responsibilities of the perpetrators should be explored by bringing them to justice in order to serve as deterrence to others. Despite being stringently outlawed, torture continues to be practised in many countries in the world. The underlying assumption is that, although the prohibition of torture has become part of customary international law, the practice of torture remains widespread. Torturers and those who order or encourage torturers to ply their trade or acquiesce in their doing so, enjoy virtual impunity from prosecution within their own jurisdictions. In many cases, the majority of the torturers go unpunished because they are, most often than not, agents or officials of the state. Nowadays, there are various international human rights instruments prohibiting torture. Violations of the provisions of these instruments by states or individuals will attract necessary and appropriate sanction. The erring state or individual will be held accountable and if found liable, sanctions as contained in the instruments banning torture will be invoked accordingly. It must be stressed that condemnation of torture is universal and its prohibition forms not only part of customary international law, but has joined that narrow category of crimes so egregious as to demand universal criminal jurisdiction. There is no save haven for perpetrators because the various mechanisms and adjudicating bodies of state parties and the United Nations have competent jurisdictions to right the wrong. Furthermore, it must be stressed that there can be no justification for torture because CAT and other important international human rights instruments assume increasing importance tools which have realistic prospects for eliminating torture.
- Full Text:
- Date Issued: 2008
- Authors: Odeku, Kolawole Olusola
- Date: 2008
- Subjects: Human rights -- Accountability -- Perpetrators of torture -- Torture
- Language: English
- Type: Thesis , Doctoral , LLD
- Identifier: vital:11112 , http://hdl.handle.net/10353/101 , Human rights -- Accountability -- Perpetrators of torture -- Torture
- Description: orture is a serious violation of human rights and it is strictly prohibited by numerous human rights instruments. The prohibition of torture enshrines one of the most fundamental values of a democratic society. Its prohibition in a national constitution commits the country, and specifically its law enforcement officers, to performing their duties with due regard to the essential dignity of every human being. The irony is that the law enforcement officials and the security agents who are entrusted with the responsibility of maintaining law and order in the society sometimes breach the law which they have sworn to uphold. Most of the perpetrators of acts of torture are usually those in positions of state power. In addition, other persons who wield other forms of authority or influence also perpetrate torture. It is contended that both civil and criminal responsibilities of the perpetrators should be explored by bringing them to justice in order to serve as deterrence to others. Despite being stringently outlawed, torture continues to be practised in many countries in the world. The underlying assumption is that, although the prohibition of torture has become part of customary international law, the practice of torture remains widespread. Torturers and those who order or encourage torturers to ply their trade or acquiesce in their doing so, enjoy virtual impunity from prosecution within their own jurisdictions. In many cases, the majority of the torturers go unpunished because they are, most often than not, agents or officials of the state. Nowadays, there are various international human rights instruments prohibiting torture. Violations of the provisions of these instruments by states or individuals will attract necessary and appropriate sanction. The erring state or individual will be held accountable and if found liable, sanctions as contained in the instruments banning torture will be invoked accordingly. It must be stressed that condemnation of torture is universal and its prohibition forms not only part of customary international law, but has joined that narrow category of crimes so egregious as to demand universal criminal jurisdiction. There is no save haven for perpetrators because the various mechanisms and adjudicating bodies of state parties and the United Nations have competent jurisdictions to right the wrong. Furthermore, it must be stressed that there can be no justification for torture because CAT and other important international human rights instruments assume increasing importance tools which have realistic prospects for eliminating torture.
- Full Text:
- Date Issued: 2008
Information technology support for transformation in higher educational institutions in South Africa
- Authors: Roets, Rina Annette
- Date: 2008
- Subjects: Education, Higher -- South Africa Educational change -- South Africa Universities and colleges -- South Africa Universities and colleges -- South Africa -- Administration Information technology -- South Africa Educational technology -- South Africa Education, Higher -- Technological innovations -- South Africa Knowledge management
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1145 , http://hdl.handle.net/10962/d1002775
- Description: Higher Education Institutions (HEIs) have been in a state of change, and in South Africa, the term “transformation” is used to describe the changes occurring. These changes have implications for the structure, processes and focus of HEIs, and as such have implications for Information Technology (IS/ICT) support for HEIs. IS/ICT support for organisations is predicated on several factors, such as effective informational and technical support at all levels of the organisation, but especially support for the strategic goals of the organisation (alignment). For organisations in a state of rapid change other issues need to be considered, such as flexibility, and new and diverse information and communication needs. This paper investigates the use of Information Technology to support HEIs in transformation. The research examines factors that make HEIs less amenable to rationalist techniques such as mixed management styles and a “different” value chain. The difficulties for IS/ICT support of HEIs at all managerial levels is discussed, especially the issue of alignment with institutional goals. Thereafter, transformation of HEIs and the possibility of IS/ICT support in achieving the ill-defined goal of transformation is examined. The research uses management and IS/ICT theories such as the widely used and reported Porter’s value chain, Anthony’s information model, and Minzberg’s organisational model to suggest an analysis model for HEIs (Applegate, McFarlan and McKenney, 1996; Minzberg, 1979; Ward and Peppard, 2002). Furthermore, from the analysis of the literature, a model of antecedent factors for successful HEI transformation supported by IS/ICT is proposed. The research makes use of a comparative case study approach in which 3 (three) South African HEIs are investigated through the “lens” of the developed model. The major finding of the research is that the potential use of IS/ICT support for HEIs is not optimal in the three cases examined. Results of the analysis suggest that: • IS/ICT alignment with organisational goals at HEIs is low and holistic IS/ICT strategic management is lacking. The areas of Knowledge Management and Communication Management are conducted informally and Knowledge Management, especially, is not fully exploited. • The greatest area of concern is the lack of IS/ICT support for academic management, where academics are increasingly required to perform administrative and managerial tasks. • The merger/incorporation information needs have not caused major system problems, but other intangible aspects of the mergers/incorporations could be better supported by IS/ICT. The research concludes with a set of actions that should ensure a higher level of support, amongst which are the more holistic management of IS/ICT especially for Academic management needs, and particularly the use of IS/ICT in innovative ways to overcome the challenges of the “transformed” Universities: There are areas of excellence but the full possibilities afforded by technology are not exploited maximally in support of transformation. Research suggests that the reasons for this are mainly the lack of holistic strategic management of IS/ICT.
- Full Text:
- Date Issued: 2008
Information technology support for transformation in higher educational institutions in South Africa
- Authors: Roets, Rina Annette
- Date: 2008
- Subjects: Education, Higher -- South Africa Educational change -- South Africa Universities and colleges -- South Africa Universities and colleges -- South Africa -- Administration Information technology -- South Africa Educational technology -- South Africa Education, Higher -- Technological innovations -- South Africa Knowledge management
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1145 , http://hdl.handle.net/10962/d1002775
- Description: Higher Education Institutions (HEIs) have been in a state of change, and in South Africa, the term “transformation” is used to describe the changes occurring. These changes have implications for the structure, processes and focus of HEIs, and as such have implications for Information Technology (IS/ICT) support for HEIs. IS/ICT support for organisations is predicated on several factors, such as effective informational and technical support at all levels of the organisation, but especially support for the strategic goals of the organisation (alignment). For organisations in a state of rapid change other issues need to be considered, such as flexibility, and new and diverse information and communication needs. This paper investigates the use of Information Technology to support HEIs in transformation. The research examines factors that make HEIs less amenable to rationalist techniques such as mixed management styles and a “different” value chain. The difficulties for IS/ICT support of HEIs at all managerial levels is discussed, especially the issue of alignment with institutional goals. Thereafter, transformation of HEIs and the possibility of IS/ICT support in achieving the ill-defined goal of transformation is examined. The research uses management and IS/ICT theories such as the widely used and reported Porter’s value chain, Anthony’s information model, and Minzberg’s organisational model to suggest an analysis model for HEIs (Applegate, McFarlan and McKenney, 1996; Minzberg, 1979; Ward and Peppard, 2002). Furthermore, from the analysis of the literature, a model of antecedent factors for successful HEI transformation supported by IS/ICT is proposed. The research makes use of a comparative case study approach in which 3 (three) South African HEIs are investigated through the “lens” of the developed model. The major finding of the research is that the potential use of IS/ICT support for HEIs is not optimal in the three cases examined. Results of the analysis suggest that: • IS/ICT alignment with organisational goals at HEIs is low and holistic IS/ICT strategic management is lacking. The areas of Knowledge Management and Communication Management are conducted informally and Knowledge Management, especially, is not fully exploited. • The greatest area of concern is the lack of IS/ICT support for academic management, where academics are increasingly required to perform administrative and managerial tasks. • The merger/incorporation information needs have not caused major system problems, but other intangible aspects of the mergers/incorporations could be better supported by IS/ICT. The research concludes with a set of actions that should ensure a higher level of support, amongst which are the more holistic management of IS/ICT especially for Academic management needs, and particularly the use of IS/ICT in innovative ways to overcome the challenges of the “transformed” Universities: There are areas of excellence but the full possibilities afforded by technology are not exploited maximally in support of transformation. Research suggests that the reasons for this are mainly the lack of holistic strategic management of IS/ICT.
- Full Text:
- Date Issued: 2008
Integrating natural sciences and indigenous knowledge systems for rural economic development: a model for rural enterprise development, health and nutrition initiatives in the Eastern Cape, South Africa
- Authors: Lupuwana, Pumezo
- Date: 2008
- Subjects: Natural resources -- South Africa -- Eastern Cape , Nutrition -- South Africa -- Eastern Cape , Rural development -- South Africa -- Eastern Cape , Economic development projects -- South Africa -- Eastern Cape , Community development -- South Africa -- Eastern Cape , Poverty -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD (Ethnobotany)
- Identifier: vital:11884 , http://hdl.handle.net/10353/81 , Natural resources -- South Africa -- Eastern Cape , Nutrition -- South Africa -- Eastern Cape , Rural development -- South Africa -- Eastern Cape , Economic development projects -- South Africa -- Eastern Cape , Community development -- South Africa -- Eastern Cape , Poverty -- South Africa -- Eastern Cape
- Description: This study demonstrated that the demographic profile of the Eastern Cape Province portrayed high levels of poverty and underdevelopment in the mostly rural population. This is despite the fact that the Eastern Cape is characterized by a rich endowment of natural resources, hosting a wide range of natural plant species, numerous rivers, water springs from mountains and no less than six biomes due to the variety of climatic conditions prevalent in the Province. In contrast, the natural resources found in the Province were regarded to have a high potential to grow and transform the economy of the Province. In this study, the integrated approach was conceptualized, developed and implemented in action within the rural communities selected with varying degrees of success, as a function of the material and objective socio-economic conditions prevailing in each community. A model for rural enterprise development based on agricultural production utilizing the principles of Community-Public-Private Partnerships was conceptualized and executed with the assistance of specialist professionals from various disciplines and organizations. Case studies structured on the basis of methodologies derived from the integration of natural sciences and indigenous knowledge systems were conducted to demonstrate the feasibility of the conceptual framework of the study as indicated by the following case studies. The first case study undertaken was the development of agricultural enterprises in the selected rural communities in joint ventures through the commercial production of food and vegetable crops for local markets and to provide nutrition for the rural communities as the first line of therapy against the HIV/AIDS infection and other diseases associated with malnutrition. The second case study was the establishment of an agricultural enterprise in partnership between rural communities, government agencies and agricultural specialist for the commercial production of grain crops, namely, Sorghum alternating with Wheat to satisfy the demand of local markets for these crops. The third case study was the establishment of a community-based enterprise through the commercial production of two Pelargonium plant species, namely, Pelargonium reniforme and P. sidoides. The two species had a high market demand in the pharmaceutical industry; hence, the plant species were V domestically cultivated to satisfy the industry demand and to ensure the survival of the plant species. The enterprise succeeded in sustaining the livelihoods of the rural communities and conserving the plant species. The fourth case study was the commercial production of essential oil-producing plants in six selected rural communities providing employment for some of the members of these communities even though the initial phase of the start-up enterprise was a trial cultivation to determine the suitability of the environmental and climatic conditions for the propagation of the selected essential-producing plants. The demand for essential oils in local and international markets was determined to relatively high. The incorporation of Indigenous Knowledge Systems of the rural communities in the planning and implementation processes in the areas of Commercial Agricultural Production and Primary Health Care resulted in a gradual paradigm shift on the part of rural communities from a dependence mindset to one of self-reliance that is critical for sustainable rural economic development and the improvement of rural livelihoods. An integrated approach in the strategic planning and execution that involved the rural communities by government stakeholders, the academic community and other stakeholders from the Private Sector was piloted. The recognition of Indigenous Knowledge Systems by all the relevant stakeholders and their essential role in rural enterprise development, food production and primary health care as a pre-requisite for a successful transformation agenda was highlighted as never before. An all-inclusive approach that accorded the rural communities the status of equal partnership had a positive impact on most aspects of planning and implementing programmes for sustainable rural economic development and biodiversity conservation. Working in partnership with rural communities was found to be a challenge; hence, an understanding of the sub-cultures and the social dynamics that often manifested themselves in the form of internecine conflicts became necessary for successfully initiating the research programme in the rural communities. Furthermore, recognition of the rural communities as an integral part of the solution towards biodiversity conservation and the sustainable exploitation of natural resources was found to be a critical component for an effective strategy to ensure the continued survival of the endangered plant species. This attitude underpinned the co-operation of the rural communities and the overarching goals of rural transformation towards the consistent and sustainable improvement of rural livelihoods. Theapproach also marked a radical shift from all the preceeding practices in biodiversity conservation and the management of sustainable natural resource utilization. The study demonstrated that the integration of Indigenous Knowledge Systems and Natural Sciences for sustainable rural economic development with the ultimate strategic objective of contributing towards the reduction of poverty, the improvement of the quality and cost-effectiveness of primary health care and adequate food production is feasible.
- Full Text:
- Date Issued: 2008
- Authors: Lupuwana, Pumezo
- Date: 2008
- Subjects: Natural resources -- South Africa -- Eastern Cape , Nutrition -- South Africa -- Eastern Cape , Rural development -- South Africa -- Eastern Cape , Economic development projects -- South Africa -- Eastern Cape , Community development -- South Africa -- Eastern Cape , Poverty -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD (Ethnobotany)
- Identifier: vital:11884 , http://hdl.handle.net/10353/81 , Natural resources -- South Africa -- Eastern Cape , Nutrition -- South Africa -- Eastern Cape , Rural development -- South Africa -- Eastern Cape , Economic development projects -- South Africa -- Eastern Cape , Community development -- South Africa -- Eastern Cape , Poverty -- South Africa -- Eastern Cape
- Description: This study demonstrated that the demographic profile of the Eastern Cape Province portrayed high levels of poverty and underdevelopment in the mostly rural population. This is despite the fact that the Eastern Cape is characterized by a rich endowment of natural resources, hosting a wide range of natural plant species, numerous rivers, water springs from mountains and no less than six biomes due to the variety of climatic conditions prevalent in the Province. In contrast, the natural resources found in the Province were regarded to have a high potential to grow and transform the economy of the Province. In this study, the integrated approach was conceptualized, developed and implemented in action within the rural communities selected with varying degrees of success, as a function of the material and objective socio-economic conditions prevailing in each community. A model for rural enterprise development based on agricultural production utilizing the principles of Community-Public-Private Partnerships was conceptualized and executed with the assistance of specialist professionals from various disciplines and organizations. Case studies structured on the basis of methodologies derived from the integration of natural sciences and indigenous knowledge systems were conducted to demonstrate the feasibility of the conceptual framework of the study as indicated by the following case studies. The first case study undertaken was the development of agricultural enterprises in the selected rural communities in joint ventures through the commercial production of food and vegetable crops for local markets and to provide nutrition for the rural communities as the first line of therapy against the HIV/AIDS infection and other diseases associated with malnutrition. The second case study was the establishment of an agricultural enterprise in partnership between rural communities, government agencies and agricultural specialist for the commercial production of grain crops, namely, Sorghum alternating with Wheat to satisfy the demand of local markets for these crops. The third case study was the establishment of a community-based enterprise through the commercial production of two Pelargonium plant species, namely, Pelargonium reniforme and P. sidoides. The two species had a high market demand in the pharmaceutical industry; hence, the plant species were V domestically cultivated to satisfy the industry demand and to ensure the survival of the plant species. The enterprise succeeded in sustaining the livelihoods of the rural communities and conserving the plant species. The fourth case study was the commercial production of essential oil-producing plants in six selected rural communities providing employment for some of the members of these communities even though the initial phase of the start-up enterprise was a trial cultivation to determine the suitability of the environmental and climatic conditions for the propagation of the selected essential-producing plants. The demand for essential oils in local and international markets was determined to relatively high. The incorporation of Indigenous Knowledge Systems of the rural communities in the planning and implementation processes in the areas of Commercial Agricultural Production and Primary Health Care resulted in a gradual paradigm shift on the part of rural communities from a dependence mindset to one of self-reliance that is critical for sustainable rural economic development and the improvement of rural livelihoods. An integrated approach in the strategic planning and execution that involved the rural communities by government stakeholders, the academic community and other stakeholders from the Private Sector was piloted. The recognition of Indigenous Knowledge Systems by all the relevant stakeholders and their essential role in rural enterprise development, food production and primary health care as a pre-requisite for a successful transformation agenda was highlighted as never before. An all-inclusive approach that accorded the rural communities the status of equal partnership had a positive impact on most aspects of planning and implementing programmes for sustainable rural economic development and biodiversity conservation. Working in partnership with rural communities was found to be a challenge; hence, an understanding of the sub-cultures and the social dynamics that often manifested themselves in the form of internecine conflicts became necessary for successfully initiating the research programme in the rural communities. Furthermore, recognition of the rural communities as an integral part of the solution towards biodiversity conservation and the sustainable exploitation of natural resources was found to be a critical component for an effective strategy to ensure the continued survival of the endangered plant species. This attitude underpinned the co-operation of the rural communities and the overarching goals of rural transformation towards the consistent and sustainable improvement of rural livelihoods. Theapproach also marked a radical shift from all the preceeding practices in biodiversity conservation and the management of sustainable natural resource utilization. The study demonstrated that the integration of Indigenous Knowledge Systems and Natural Sciences for sustainable rural economic development with the ultimate strategic objective of contributing towards the reduction of poverty, the improvement of the quality and cost-effectiveness of primary health care and adequate food production is feasible.
- Full Text:
- Date Issued: 2008
Inter-level health service referral of women in labour
- Authors: Jantjes, Louisa
- Date: 2008
- Subjects: Childbirth -- South Africa , Medical referrals -- South Africa , Midwives -- South Africa , Labor (Obstetrics) -- Complications
- Language: English
- Type: Thesis , Doctoral , DCur
- Identifier: vital:10010 , http://hdl.handle.net/10948/986 , Childbirth -- South Africa , Medical referrals -- South Africa , Midwives -- South Africa , Labor (Obstetrics) -- Complications
- Description: Although it is considered an everyday occurrence, childbirth is nonetheless an important and dramatic experience in the life of every woman. Childbirth, a normal physiological state in the life of a woman, can be an awe-inspiring and exciting experience, but sometimes disconcerting experiences may also occur. Women sometimes see labour as the end to a long drawn out process following pregnancy and therefore attribute great significance to all occurrences during labour. When complications occur in a usually uncomplicated process of labour, the health care provider must be able to make quick and effective management decisions and implement appropriate interventions. This may include the referral of women in labour to a level of care where complications can be dealt with more effectively, thereby ensuring the best maternal and neonatal outcomes. Patient referral is regarded as a fundamental component of the health care system therefore a well functioning system should ensure that patients are treated in the appropriate manner at the appropriate place at the lowest possible cost to the health system. The goal of this research study was to explore and describe the inter-level health service referral of women in labour by midwives, in order to design guidelines for midwives and other relevant health care providers involved in inter-level health service referral of women in labour in the South African public health care sector. The research design used for this study is a combination of qualitative and quantitative approaches. The paradigmatic perspective of this study was based on the World Health Organization’s Health for All Model. Appropriate data collection and analysis strategies were used for the different stages of the study. Data collection commenced only after permission to conduct the research had been obtained from relevant authorities and University of Port Elizabeth and the Nelson Mandela Metropolitan University structures. Informed consent was obtained from participants included in the study. In stage 1 of this research project, a profile of midwives at lower level maternity care centres was compiled and the perceptions and experiences of midwives working at lower level maternity services, who are responsible for inter-level health referrals of women in labour, were described. Stage 2 described, by means of analysis of maternity case records, aspects of the inter-level referral of women in labour including the profiles of women admitted to midwife obstetric units (MOUs) who are v referred to higher levels of care. Of significance in this study is the appropriateness of midwifery referrals and the maternity care implemented by health care providers during inter-level health service referral of women in labour. In stage 3 clinical guidelines for midwives and other relevant maternity care providers, to assist them in the inter-level health service referral of women in labour, were developed. Findings from stage 1 of this research study revealed that midwives were generally well qualified and sufficiently experienced in the management of women in labour who need referral. Disconcerting findings relating to human and material resource shortages were discovered; these included major problems with patient transportation and difficulties with communication relating to inter-level health service referral of women. These shortages adversely affected midwives’ ability to efficiently care for women during the inter-level health service referral of women in labour in the research area. Stage 2 of the study yielded results of questionable standards of care to women and infants included in the study. A further disturbing finding from the study is the poor state of record keeping. The development of the provisional guidelines in stage 3 of the study was informed by the four main themes identified from the research findings. Before embarking on guideline development, the researcher familiarized herself with theory related to the clinical guidelines. These included clarifying the concept ‘clinical guidelines’, justifying the need for developing clinical guidelines as well as giving consideration to concerns about clinical guidelines. The research findings as well as literature related to these findings informed the researcher on the development of the guidelines. Provisional guidelines were therefore developed on responsibilities of role players in inter-level health service referral of women in labour at first level of referral, namely the midwife obstetric units, transport personnel and maternity care providers at the referral hospital. Steps were taken throughout the study to adhere to ethical standards of research. The researcher will ensure that the research report is available to all health authorities involved, the participants included in the study and the health care providers who may benefit from the research findings.
- Full Text:
- Date Issued: 2008
- Authors: Jantjes, Louisa
- Date: 2008
- Subjects: Childbirth -- South Africa , Medical referrals -- South Africa , Midwives -- South Africa , Labor (Obstetrics) -- Complications
- Language: English
- Type: Thesis , Doctoral , DCur
- Identifier: vital:10010 , http://hdl.handle.net/10948/986 , Childbirth -- South Africa , Medical referrals -- South Africa , Midwives -- South Africa , Labor (Obstetrics) -- Complications
- Description: Although it is considered an everyday occurrence, childbirth is nonetheless an important and dramatic experience in the life of every woman. Childbirth, a normal physiological state in the life of a woman, can be an awe-inspiring and exciting experience, but sometimes disconcerting experiences may also occur. Women sometimes see labour as the end to a long drawn out process following pregnancy and therefore attribute great significance to all occurrences during labour. When complications occur in a usually uncomplicated process of labour, the health care provider must be able to make quick and effective management decisions and implement appropriate interventions. This may include the referral of women in labour to a level of care where complications can be dealt with more effectively, thereby ensuring the best maternal and neonatal outcomes. Patient referral is regarded as a fundamental component of the health care system therefore a well functioning system should ensure that patients are treated in the appropriate manner at the appropriate place at the lowest possible cost to the health system. The goal of this research study was to explore and describe the inter-level health service referral of women in labour by midwives, in order to design guidelines for midwives and other relevant health care providers involved in inter-level health service referral of women in labour in the South African public health care sector. The research design used for this study is a combination of qualitative and quantitative approaches. The paradigmatic perspective of this study was based on the World Health Organization’s Health for All Model. Appropriate data collection and analysis strategies were used for the different stages of the study. Data collection commenced only after permission to conduct the research had been obtained from relevant authorities and University of Port Elizabeth and the Nelson Mandela Metropolitan University structures. Informed consent was obtained from participants included in the study. In stage 1 of this research project, a profile of midwives at lower level maternity care centres was compiled and the perceptions and experiences of midwives working at lower level maternity services, who are responsible for inter-level health referrals of women in labour, were described. Stage 2 described, by means of analysis of maternity case records, aspects of the inter-level referral of women in labour including the profiles of women admitted to midwife obstetric units (MOUs) who are v referred to higher levels of care. Of significance in this study is the appropriateness of midwifery referrals and the maternity care implemented by health care providers during inter-level health service referral of women in labour. In stage 3 clinical guidelines for midwives and other relevant maternity care providers, to assist them in the inter-level health service referral of women in labour, were developed. Findings from stage 1 of this research study revealed that midwives were generally well qualified and sufficiently experienced in the management of women in labour who need referral. Disconcerting findings relating to human and material resource shortages were discovered; these included major problems with patient transportation and difficulties with communication relating to inter-level health service referral of women. These shortages adversely affected midwives’ ability to efficiently care for women during the inter-level health service referral of women in labour in the research area. Stage 2 of the study yielded results of questionable standards of care to women and infants included in the study. A further disturbing finding from the study is the poor state of record keeping. The development of the provisional guidelines in stage 3 of the study was informed by the four main themes identified from the research findings. Before embarking on guideline development, the researcher familiarized herself with theory related to the clinical guidelines. These included clarifying the concept ‘clinical guidelines’, justifying the need for developing clinical guidelines as well as giving consideration to concerns about clinical guidelines. The research findings as well as literature related to these findings informed the researcher on the development of the guidelines. Provisional guidelines were therefore developed on responsibilities of role players in inter-level health service referral of women in labour at first level of referral, namely the midwife obstetric units, transport personnel and maternity care providers at the referral hospital. Steps were taken throughout the study to adhere to ethical standards of research. The researcher will ensure that the research report is available to all health authorities involved, the participants included in the study and the health care providers who may benefit from the research findings.
- Full Text:
- Date Issued: 2008
Isokinetic force profile of the cervical spine in a healthy adult urban South African population
- Authors: Olivier, Pierre Emile
- Date: 2008
- Subjects: Cervical vertebrae , Neck -- Muscles , Muscle strength -- Testing
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10102 , http://hdl.handle.net/10948/982 , Cervical vertebrae , Neck -- Muscles , Muscle strength -- Testing
- Description: The aim of this study was to establish reference data for the cervical spine’s dynamic force characteristics in a healthy adult urban South African population aged 19 to 69 years. The reference data was classified according to gender discriminate age categories. In total ten gender discriminate age categories, five male and five female, were created; 19 to 29, 30 to 39, 40 to 49, 50 to 59 and 60 to 69-year-olds. The force characteristics measured, analysed and used to generate reference data in stanine format were: absolute peak torque (P-), relative peak torque (P-/BW), peak power (Pow-), relative peak power (Pow-/BW), peak work (W-), relative peak work (W-/BW), torque acceleration energy (TAE-), maximal voluntary cervical muscle contraction range of motion (MVCR-), controlled full range of joint motion (CFR-), joint angle at peak torque (Jang@P-) and peak torque ratios for cervical flexion (-F), extension (-E), lateral flexion to the dominant (-LD) and non-dominant (-LN) sides. In addition biographic and anthropometric data was also collected. Data, grouped in the ten gender discriminate age categories were compared and statistically and practically significant differences were highlighted between the gender discriminate age categories. Inferential statistics used included ANOVA and Cohen’s d. A significance level of α = .05 was used in all inferential statistical analyses. Correlations between various anthropometric and isokinetic strength variables were also explored.
- Full Text:
- Date Issued: 2008
- Authors: Olivier, Pierre Emile
- Date: 2008
- Subjects: Cervical vertebrae , Neck -- Muscles , Muscle strength -- Testing
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10102 , http://hdl.handle.net/10948/982 , Cervical vertebrae , Neck -- Muscles , Muscle strength -- Testing
- Description: The aim of this study was to establish reference data for the cervical spine’s dynamic force characteristics in a healthy adult urban South African population aged 19 to 69 years. The reference data was classified according to gender discriminate age categories. In total ten gender discriminate age categories, five male and five female, were created; 19 to 29, 30 to 39, 40 to 49, 50 to 59 and 60 to 69-year-olds. The force characteristics measured, analysed and used to generate reference data in stanine format were: absolute peak torque (P-), relative peak torque (P-/BW), peak power (Pow-), relative peak power (Pow-/BW), peak work (W-), relative peak work (W-/BW), torque acceleration energy (TAE-), maximal voluntary cervical muscle contraction range of motion (MVCR-), controlled full range of joint motion (CFR-), joint angle at peak torque (Jang@P-) and peak torque ratios for cervical flexion (-F), extension (-E), lateral flexion to the dominant (-LD) and non-dominant (-LN) sides. In addition biographic and anthropometric data was also collected. Data, grouped in the ten gender discriminate age categories were compared and statistically and practically significant differences were highlighted between the gender discriminate age categories. Inferential statistics used included ANOVA and Cohen’s d. A significance level of α = .05 was used in all inferential statistical analyses. Correlations between various anthropometric and isokinetic strength variables were also explored.
- Full Text:
- Date Issued: 2008
Journalists' perceptions of their roles and identities with regard to the new partnership for Africa's development
- Kanyegirire, Andrew Steve Tumuhirwe
- Authors: Kanyegirire, Andrew Steve Tumuhirwe
- Date: 2008
- Subjects: New Partnership for Africa's Development Journalists -- Africa Journalism -- Africa Mass media -- Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3443 , http://hdl.handle.net/10962/d1002897
- Description: This qualitative study features in-depth interviews with selected continental African journalists and offers exploratory insights into how they perceive themselves in terms of their journalistic roles and/or sub-identities with regard to the New Partnership for Africa’s Development (NEPAD). The study also examines correlations between their perceptions and their news stories on NEPAD. Grounded in the libertarian and social responsibility theories of journalism, and reading these theories from the standpoint of Africa, this study posits the neutral, watchdog, social agenda and development journalism sub-identities to explain the respondents’ journalistic identifications. Hence, the study explores how the journalists respond to NEPAD’s (pan)-Africanist and development journalism interpellations. The study draws on postcolonial theoretical perspectives to address questions concerning African identity and the wider NEPAD/African context of research. Findings indicated that the journalists perceive a role for themselves as neutral-objectivist information disseminators as well as social agenda enactors that conscientise their readers about NEPAD. Thus, the journalists tend to implicitly portray a pluralistic understanding of their roles that enables them to balance the ideals of journalism against the development and Africanist aspirations of NEPAD. Although the journalists were found to uphold oppositional stances towards NEPAD, they do not question it from outside of its own neo-liberal discourse. In fact, they still represent themselves as aspiring to its Africanism and remaining sympathetic to its development plans. Overall, they exhibit multiple identifications, and yet they often tend to lean towards their neutral-objectivist journalistic sub-identity. Ultimately, they prioritise the dominant libertarian-professional model of journalism over and above NEPAD’s interpellations. The study also examined the journalists’ interpretations of what they do and the apparent translation of this into their stories. Although in both their stories and interviews discourse they showed a broader orientation towards libertarianism, the findings show that the link between the two is not straightforward.
- Full Text:
- Date Issued: 2008
- Authors: Kanyegirire, Andrew Steve Tumuhirwe
- Date: 2008
- Subjects: New Partnership for Africa's Development Journalists -- Africa Journalism -- Africa Mass media -- Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3443 , http://hdl.handle.net/10962/d1002897
- Description: This qualitative study features in-depth interviews with selected continental African journalists and offers exploratory insights into how they perceive themselves in terms of their journalistic roles and/or sub-identities with regard to the New Partnership for Africa’s Development (NEPAD). The study also examines correlations between their perceptions and their news stories on NEPAD. Grounded in the libertarian and social responsibility theories of journalism, and reading these theories from the standpoint of Africa, this study posits the neutral, watchdog, social agenda and development journalism sub-identities to explain the respondents’ journalistic identifications. Hence, the study explores how the journalists respond to NEPAD’s (pan)-Africanist and development journalism interpellations. The study draws on postcolonial theoretical perspectives to address questions concerning African identity and the wider NEPAD/African context of research. Findings indicated that the journalists perceive a role for themselves as neutral-objectivist information disseminators as well as social agenda enactors that conscientise their readers about NEPAD. Thus, the journalists tend to implicitly portray a pluralistic understanding of their roles that enables them to balance the ideals of journalism against the development and Africanist aspirations of NEPAD. Although the journalists were found to uphold oppositional stances towards NEPAD, they do not question it from outside of its own neo-liberal discourse. In fact, they still represent themselves as aspiring to its Africanism and remaining sympathetic to its development plans. Overall, they exhibit multiple identifications, and yet they often tend to lean towards their neutral-objectivist journalistic sub-identity. Ultimately, they prioritise the dominant libertarian-professional model of journalism over and above NEPAD’s interpellations. The study also examined the journalists’ interpretations of what they do and the apparent translation of this into their stories. Although in both their stories and interviews discourse they showed a broader orientation towards libertarianism, the findings show that the link between the two is not straightforward.
- Full Text:
- Date Issued: 2008
Managing conflict across cultures, values and identities: a case study in the South African automotive industry
- Authors: Mayer, Claude-Hélène
- Date: 2008
- Subjects: Conflict management -- South Africa Automobile industry and trade -- South Africa Automobile industry workers -- South Africa Communication in management -- South Africa Intercultural communication -- South Africa Culture conflict -- South Africa Diversity in the workplace -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1174 , http://hdl.handle.net/10962/d1002790
- Description: Over the past fifty years, interest in the field of conflict management and peacekeeping has developed worldwide. During the same time, the potential for trans-ultural) conflict has escalated. This can mainly be attributed to the trend towards globalisation, as well as the growing complexity of societies increasingly experiencing more intercultural encounters or cultural transition situations and work-related or organisational conflicts. Cultural transition situations occur in the South African international automotive industry where the emergence of international co-operation, such as joint ventures (driven by globalisation) and new diversity management trends, have changed the way business is conducted. Due to these changes, employees of diverse origins with different cultures, values and identities work together, experiencing work-related conflicts. The purpose of this study was to assess managerial perspectives on conflict, identity and values, as well as on how (trans-cultural) conflict is managed in a selected international organisation in the South African automotive industry. The contribution of this study is twofold, namely to increase the understanding of the complexities of conflict in organisations; and to provide recommendations for conflict resolution strategies to manage (trans-cultural) conflict constructively by considering the values and identity aspects of those individuals involved. This study comprises a single explanatory case study which made use of qualitative data collection and analysis to investigate managerial perspectives on conflict, identity and values, as well as the management thereof, in the selected international organisation in the South African automotive context. Based on the main findings from this case study, it could be concluded that managers with diverse backgrounds experience work-related conflicts which are related to value and identity concepts in the selected organisation. The conflicts experienced fell into the categories of Communication and Treatment, Position and Competition, Organisation and Race and Gender.An overview of the occurrence frequency of value statements revealed that equality, communication and respect were the most commonly indicated values in conflicts. These value concepts include sub-concepts such as: · for equality: race, gender and human equality; · for communication: open, personal, free, decent, calm and proactive communication; and · for respect: mutual respect for self and others. With regard to value concepts and according to value domains of Schwartz (1994) and Schwartz and Bilsky (1987), the value dimensions of selftranscendence comprised the highest number of value statements. This dimension included the value domains of universalism and benevolence. Conflict in the data material was interlinked with identity. The extracts, based on the key words of the identity factors, demonstrated that the identity factors were related to either a weakening or strengthening effect on identities. Social and identity multiplicity in managers provides creativity spaces and flexibility in cases of strong identity patterns. Particularly with weak identities, the existence of conflict potentials could lead to complex conflicts and challenges in conflict management. Communication was most often mentioned as important to successful conflict resolution management and included examples such as round-table talks, smooth communication, face-to-face communication and room meetings. Communication was followed in frequency by strategies of internal intervention, which included the use of the formal structure of the organisation to resolve conflicts.
- Full Text:
- Date Issued: 2008
- Authors: Mayer, Claude-Hélène
- Date: 2008
- Subjects: Conflict management -- South Africa Automobile industry and trade -- South Africa Automobile industry workers -- South Africa Communication in management -- South Africa Intercultural communication -- South Africa Culture conflict -- South Africa Diversity in the workplace -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1174 , http://hdl.handle.net/10962/d1002790
- Description: Over the past fifty years, interest in the field of conflict management and peacekeeping has developed worldwide. During the same time, the potential for trans-ultural) conflict has escalated. This can mainly be attributed to the trend towards globalisation, as well as the growing complexity of societies increasingly experiencing more intercultural encounters or cultural transition situations and work-related or organisational conflicts. Cultural transition situations occur in the South African international automotive industry where the emergence of international co-operation, such as joint ventures (driven by globalisation) and new diversity management trends, have changed the way business is conducted. Due to these changes, employees of diverse origins with different cultures, values and identities work together, experiencing work-related conflicts. The purpose of this study was to assess managerial perspectives on conflict, identity and values, as well as on how (trans-cultural) conflict is managed in a selected international organisation in the South African automotive industry. The contribution of this study is twofold, namely to increase the understanding of the complexities of conflict in organisations; and to provide recommendations for conflict resolution strategies to manage (trans-cultural) conflict constructively by considering the values and identity aspects of those individuals involved. This study comprises a single explanatory case study which made use of qualitative data collection and analysis to investigate managerial perspectives on conflict, identity and values, as well as the management thereof, in the selected international organisation in the South African automotive context. Based on the main findings from this case study, it could be concluded that managers with diverse backgrounds experience work-related conflicts which are related to value and identity concepts in the selected organisation. The conflicts experienced fell into the categories of Communication and Treatment, Position and Competition, Organisation and Race and Gender.An overview of the occurrence frequency of value statements revealed that equality, communication and respect were the most commonly indicated values in conflicts. These value concepts include sub-concepts such as: · for equality: race, gender and human equality; · for communication: open, personal, free, decent, calm and proactive communication; and · for respect: mutual respect for self and others. With regard to value concepts and according to value domains of Schwartz (1994) and Schwartz and Bilsky (1987), the value dimensions of selftranscendence comprised the highest number of value statements. This dimension included the value domains of universalism and benevolence. Conflict in the data material was interlinked with identity. The extracts, based on the key words of the identity factors, demonstrated that the identity factors were related to either a weakening or strengthening effect on identities. Social and identity multiplicity in managers provides creativity spaces and flexibility in cases of strong identity patterns. Particularly with weak identities, the existence of conflict potentials could lead to complex conflicts and challenges in conflict management. Communication was most often mentioned as important to successful conflict resolution management and included examples such as round-table talks, smooth communication, face-to-face communication and room meetings. Communication was followed in frequency by strategies of internal intervention, which included the use of the formal structure of the organisation to resolve conflicts.
- Full Text:
- Date Issued: 2008
Melatonin and anticancer therapy interactions with 5-Fluorouracil
- Authors: Cassim, Layla
- Date: 2008
- Subjects: Melatonin Melatonin -- Therapeutic use Antineoplastic agents Fluorouracil Fluorouracil -- Toxicology Cancer -- Treatment
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3746 , http://hdl.handle.net/10962/d1003224
- Description: On the basis of clinical studies, some researchers have advocated that the neurohormone and antioxidant melatonin, shown to possess intrinsic anticancer properties, be used as co-therapy in cancer patients being treated with the antineoplastic agent 5-fluorouracil, as increased patient survival times and enhanced quality of life have been observed. The focus of this research was thus to investigate the mechanisms of this seemingly beneficial drug interaction between 5-fluorouracil and melatonin. Metabolism studies were undertaken, in which it was established that there is no hepatic metabolic drug interaction between these agents by cytochrome P450, and that neither agent alters the activity of this enzyme system. Co-therapy with melatonin is thus unlikely to alter plasma levels of 5-fluorouracil by this mechanism. Novel mechanisms by which 5-fluorouracil is toxic were elucidated, such as the induction of lipid peroxidation, due to the formation of reactive oxygen species; decreases in brain serotonin, dopamine and norepinephrine levels, possibly leading to depression; hippocampal shrinkage and morphological alterations and lysis of hippocampal cells, which may underlie cognitive impairment; and a reduction in the nociceptive threshold when administered acutely. All these deleterious effects are attenuated by the co-administration of melatonin, suggesting that the agent exhibits antidepressive and analgesic properties, in addition to its known antioxidative and free radical-scavenging abilities. This suggests that melatonin cotherapy can significantly decrease 5-fluorouracil-induced toxicity, but this may also exert a protective effect on cancer cells and thus compromise the anticancer efficacy of 5-fluorouracil. It was, furthermore, found that stimulation of indoleamine 2,3-dioxygenase activity, mediated by increases in superoxide anion and interferon-γ levels, may underlie resistance to 5-fluorouracil therapy. Melatonin was shown to increase superoxide anion levels in vivo, and this is believed to be by conversion to the metabolite and known oxidant 6- hydroxymelatonin. This highlights that the possible deleterious effects of melatonin metabolites should be studied further. Serum corticosterone levels and cytokine profiles are unaltered by both 5-FU and melatonin, suggesting that these agents may be used by HIV infected individuals without promoting the progression to AIDS. It can thus be concluded that melatonin co-therapy is potentially useful in countering 5-fluorouracil toxicity.
- Full Text:
- Date Issued: 2008
- Authors: Cassim, Layla
- Date: 2008
- Subjects: Melatonin Melatonin -- Therapeutic use Antineoplastic agents Fluorouracil Fluorouracil -- Toxicology Cancer -- Treatment
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3746 , http://hdl.handle.net/10962/d1003224
- Description: On the basis of clinical studies, some researchers have advocated that the neurohormone and antioxidant melatonin, shown to possess intrinsic anticancer properties, be used as co-therapy in cancer patients being treated with the antineoplastic agent 5-fluorouracil, as increased patient survival times and enhanced quality of life have been observed. The focus of this research was thus to investigate the mechanisms of this seemingly beneficial drug interaction between 5-fluorouracil and melatonin. Metabolism studies were undertaken, in which it was established that there is no hepatic metabolic drug interaction between these agents by cytochrome P450, and that neither agent alters the activity of this enzyme system. Co-therapy with melatonin is thus unlikely to alter plasma levels of 5-fluorouracil by this mechanism. Novel mechanisms by which 5-fluorouracil is toxic were elucidated, such as the induction of lipid peroxidation, due to the formation of reactive oxygen species; decreases in brain serotonin, dopamine and norepinephrine levels, possibly leading to depression; hippocampal shrinkage and morphological alterations and lysis of hippocampal cells, which may underlie cognitive impairment; and a reduction in the nociceptive threshold when administered acutely. All these deleterious effects are attenuated by the co-administration of melatonin, suggesting that the agent exhibits antidepressive and analgesic properties, in addition to its known antioxidative and free radical-scavenging abilities. This suggests that melatonin cotherapy can significantly decrease 5-fluorouracil-induced toxicity, but this may also exert a protective effect on cancer cells and thus compromise the anticancer efficacy of 5-fluorouracil. It was, furthermore, found that stimulation of indoleamine 2,3-dioxygenase activity, mediated by increases in superoxide anion and interferon-γ levels, may underlie resistance to 5-fluorouracil therapy. Melatonin was shown to increase superoxide anion levels in vivo, and this is believed to be by conversion to the metabolite and known oxidant 6- hydroxymelatonin. This highlights that the possible deleterious effects of melatonin metabolites should be studied further. Serum corticosterone levels and cytokine profiles are unaltered by both 5-FU and melatonin, suggesting that these agents may be used by HIV infected individuals without promoting the progression to AIDS. It can thus be concluded that melatonin co-therapy is potentially useful in countering 5-fluorouracil toxicity.
- Full Text:
- Date Issued: 2008
Molecular characterization of the Hsp70/Hsp90 organizing protein (Hop) phosphorylation, subcellular localization and interaction with Hsp90
- Authors: Daniel, Sheril
- Date: 2008
- Subjects: Molecular chaperones Phosphorylation Proteins Heat shock proteins Surface plasmon resonance Cytosol
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3996 , http://hdl.handle.net/10962/d1004056
- Description: Hop (Hsp70-Hsp90 Organizing Protein) is a co-chaperone of two major molecular chaperones, Hsp70 and Hsp90, and acts by transferring substrates from Hsp70 to Hsp90. Although under normal conditions Hop is predominantly localized within the cytosol, Hop has been detected in the nucleus under certain conditions including cell cycle arrest. A putative nuclear localization signal (NLS) has been identified within Hop, which overlaps with the TPR2A domain (previously shown to be critical for Hop-Hsp90 interactions). Hop is phosphorylated in vitro by two cell cycle kinases, namely, casein kinase II (CKII) at S189 and cdc2-kinase at T198; both residues are found upstream of the putative NLS and TPR2A domain. Mimicking phosphorylation at either phosphorylation site appeared to affect the subcellular localization of Hop. The aim of this study was to characterize Hop with respect to its phosphorylation status in vivo, as well as its subcellular localization pattern under heat stress and determine how these properties affected its interaction with Hsp90 as a co-chaperone. Dephosphorylation of proteins under normal and heat shock conditions changed the isoform composition of Hop, providing strong evidence that Hop was phosphorylated in vivo. Surface plasmon resonance (SPR) and glutatione-S-transferase (GST) co-precipitation studies showed that a cdc2-kinase phosphorylated mimic of Hop disrupted Hop-Hsp90 binding. A full length Hop-EGFP construct, as well as substitution mutants of the predicted NLS residues within the Hop-EGFP construct, were transfected into baby hamster kidney (BHK)-21 cells in order to establish the subcellular localization of Hop under heat stress and to test whether predicted residues were critical for nuclear localization of Hop. Under normal conditions, both Hop-EGFP and the NLS mutants were predominantly cytosolic, but when the cells were subjected to heat stress, Hop and its NLS-mutants were localized to both the cytosol and the nucleus. SPR and GST co-precipitation studies showed that substitution of the residues within the major arm of the putative NLS abrogated Hop-Hsp90 interactions. The data obtained from this study, showed for the first time, that Hop was phosphorylated in vivo and suggested that phosphorylation of Hop by cdc2-kinase could inhibit Hop-Hsp90 interactions. Moreover, these results suggested that the subcellular localization of Hop was dependent on stress levels of the cell, particularly heat stress. We propose that the nuclear localization of Hop may be primarily regulated by stress and secondarily by cell cycle arrest. The major arm of the putative NLS did not affect the localization of Hop directly, but was shown to be critical for Hop-Hsp90 binding in vitro. The results of this study suggested that binding of Hop to Hsp90 sequestered Hop within the cytosol and that Hsp90 acted as a cytosolic retention factor for Hop. Both phosphorylation of Hop, and its subcellular localization, appeared to be intimately related to its interaction with Hsp90 as a co-chaperone.
- Full Text:
- Date Issued: 2008
- Authors: Daniel, Sheril
- Date: 2008
- Subjects: Molecular chaperones Phosphorylation Proteins Heat shock proteins Surface plasmon resonance Cytosol
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3996 , http://hdl.handle.net/10962/d1004056
- Description: Hop (Hsp70-Hsp90 Organizing Protein) is a co-chaperone of two major molecular chaperones, Hsp70 and Hsp90, and acts by transferring substrates from Hsp70 to Hsp90. Although under normal conditions Hop is predominantly localized within the cytosol, Hop has been detected in the nucleus under certain conditions including cell cycle arrest. A putative nuclear localization signal (NLS) has been identified within Hop, which overlaps with the TPR2A domain (previously shown to be critical for Hop-Hsp90 interactions). Hop is phosphorylated in vitro by two cell cycle kinases, namely, casein kinase II (CKII) at S189 and cdc2-kinase at T198; both residues are found upstream of the putative NLS and TPR2A domain. Mimicking phosphorylation at either phosphorylation site appeared to affect the subcellular localization of Hop. The aim of this study was to characterize Hop with respect to its phosphorylation status in vivo, as well as its subcellular localization pattern under heat stress and determine how these properties affected its interaction with Hsp90 as a co-chaperone. Dephosphorylation of proteins under normal and heat shock conditions changed the isoform composition of Hop, providing strong evidence that Hop was phosphorylated in vivo. Surface plasmon resonance (SPR) and glutatione-S-transferase (GST) co-precipitation studies showed that a cdc2-kinase phosphorylated mimic of Hop disrupted Hop-Hsp90 binding. A full length Hop-EGFP construct, as well as substitution mutants of the predicted NLS residues within the Hop-EGFP construct, were transfected into baby hamster kidney (BHK)-21 cells in order to establish the subcellular localization of Hop under heat stress and to test whether predicted residues were critical for nuclear localization of Hop. Under normal conditions, both Hop-EGFP and the NLS mutants were predominantly cytosolic, but when the cells were subjected to heat stress, Hop and its NLS-mutants were localized to both the cytosol and the nucleus. SPR and GST co-precipitation studies showed that substitution of the residues within the major arm of the putative NLS abrogated Hop-Hsp90 interactions. The data obtained from this study, showed for the first time, that Hop was phosphorylated in vivo and suggested that phosphorylation of Hop by cdc2-kinase could inhibit Hop-Hsp90 interactions. Moreover, these results suggested that the subcellular localization of Hop was dependent on stress levels of the cell, particularly heat stress. We propose that the nuclear localization of Hop may be primarily regulated by stress and secondarily by cell cycle arrest. The major arm of the putative NLS did not affect the localization of Hop directly, but was shown to be critical for Hop-Hsp90 binding in vitro. The results of this study suggested that binding of Hop to Hsp90 sequestered Hop within the cytosol and that Hsp90 acted as a cytosolic retention factor for Hop. Both phosphorylation of Hop, and its subcellular localization, appeared to be intimately related to its interaction with Hsp90 as a co-chaperone.
- Full Text:
- Date Issued: 2008
Novel aspects of platinum-amine coordination compounds: their chemistry and anticancer application
- Authors: Bouwer, Yolanda
- Date: 2008
- Subjects: Coordination compounds , Platinum compounds , Antineoplastic agents
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10444 , http://hdl.handle.net/10948/d1021052
- Description: The aim in this thesis, was to synthesize novel platinum coordination compounds, in order to develop compounds with improved anticancer action which could lead to an improved understanding of the mechanism by which they operate and at the same time, improve synthetic methods for their products. The initial work included the development of a novel synthetic method for 1R,2R-diaminocyclohexaneoxalato-platinum(II) (oxaliplatin), by using an essentially non-aqueous solvent medium and direct ligand exchange at elevated temperatures. This was done by a study of the kinetics of the reaction in a variety of conditions; such as relative reagent concentrations and ratios as well as solvent mixtures. An effective method was developed which could be applied industrially. An international patent was taken out on this method. Various amine complexes of platinum(II) were synthesized using chloro, bromo and oxalato groups as leaving groups. The non-leaving groups were selected having certain specific characteristics in mind. Novel mononitroplatinum(IV) complexes were synthesized, mostly with oxalato leaving groups. One of these in particular, had excellent anticancer behaviour. Another trichloromononitro complex was also synthesized with very good anticancer properties. Two international patents were filed for the latter two compounds. As far as possible, all compounds were studied by spectrometric, chromatographic and thermal methods. They were also tested against 3 cancer cell lines namely cervical (Hela), Colon (HT29) and Breast (MCF7) cancer cells.
- Full Text:
- Date Issued: 2008
- Authors: Bouwer, Yolanda
- Date: 2008
- Subjects: Coordination compounds , Platinum compounds , Antineoplastic agents
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10444 , http://hdl.handle.net/10948/d1021052
- Description: The aim in this thesis, was to synthesize novel platinum coordination compounds, in order to develop compounds with improved anticancer action which could lead to an improved understanding of the mechanism by which they operate and at the same time, improve synthetic methods for their products. The initial work included the development of a novel synthetic method for 1R,2R-diaminocyclohexaneoxalato-platinum(II) (oxaliplatin), by using an essentially non-aqueous solvent medium and direct ligand exchange at elevated temperatures. This was done by a study of the kinetics of the reaction in a variety of conditions; such as relative reagent concentrations and ratios as well as solvent mixtures. An effective method was developed which could be applied industrially. An international patent was taken out on this method. Various amine complexes of platinum(II) were synthesized using chloro, bromo and oxalato groups as leaving groups. The non-leaving groups were selected having certain specific characteristics in mind. Novel mononitroplatinum(IV) complexes were synthesized, mostly with oxalato leaving groups. One of these in particular, had excellent anticancer behaviour. Another trichloromononitro complex was also synthesized with very good anticancer properties. Two international patents were filed for the latter two compounds. As far as possible, all compounds were studied by spectrometric, chromatographic and thermal methods. They were also tested against 3 cancer cell lines namely cervical (Hela), Colon (HT29) and Breast (MCF7) cancer cells.
- Full Text:
- Date Issued: 2008
Novel camphor derivatives as potential asymmetric alkylation auxiliaries
- Authors: Skiti-Mama, Neliswa
- Date: 2008
- Subjects: Alkylation , Chemistry, Organic
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10372 , http://hdl.handle.net/10948/1077 , Alkylation , Chemistry, Organic
- Description: The investigation has been focussed on the synthesis and characterisation of camphor-derived chiral auxiliaries that incorporate two camphor skeletons and an evaluation of their stereodirecting potential in ester α-benzylation reactions. Two regioisomeric camphorquinone-derived monoketals were synthesised and identified by 1D- and 2D-NMR, and X-ray crystallography. The stereo-directing potential of the alcohols that resulted from reduction of these ketones as chiral auxiliaries in the alkylation of carboxylate ester derivatives has been studied. The diastereoselectivities shown by NMR spectroscopy range from 14- 30 % d.e. for (1R,2 S, 3R) -2 ,2-[ (1R, 2 S, 3R) -bornane-2,3-dioxy] - bornan-3-ol and 68-74 % d.e. for (1R, 2S ,3R) -3 ,3-[ (1R, 2S ,3R) - bornane-2, 3 -dioxy]bornan-2-ol with selectivities that correlate with the size of the alkyl group in the ester moiety. Trapping of the enolates generated from (1R, 2S ,3R)-2, 2 -[(1R,2 S, 3R) -bornane- 2,3-dioxy]bornan-3-yl propanoate afforded both E- and Z-silyl ketene acetal derivatives in the ratio of 64:36 confirming the formation of both possible enolate structures during enolization. Chiral auxiliaries containing a hemiaminal ether blocking group as well as two chiral alcohols containing monothio-ketal blocking groups have also been synthesised. α-Benzylation of their corresponding propanoate esters afforded the alkylated product with disappointingly low diastereos electivities. Asymmetric reduction of α-keto esters attached to (1R, 2 S, 3R) - 2,2- [ (1R,2 S, 3R) -bornane-2, 3 -dioxy]bornan-3-ol and (1R, 2S ,3R) - 3,3- [ (1R,2 S, 3R) -bornane-2, 3 -dioxy]bornan-2-ol with metal hydrides proceeded with selectivities of up to 30 % d.e. Modelling of the keto ester derivatives at DFT levels provided useful insights into possible conformations adopted by the two α-keto esters and hence the preferred face of attack by metal hydride during reduction.
- Full Text:
- Date Issued: 2008
- Authors: Skiti-Mama, Neliswa
- Date: 2008
- Subjects: Alkylation , Chemistry, Organic
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10372 , http://hdl.handle.net/10948/1077 , Alkylation , Chemistry, Organic
- Description: The investigation has been focussed on the synthesis and characterisation of camphor-derived chiral auxiliaries that incorporate two camphor skeletons and an evaluation of their stereodirecting potential in ester α-benzylation reactions. Two regioisomeric camphorquinone-derived monoketals were synthesised and identified by 1D- and 2D-NMR, and X-ray crystallography. The stereo-directing potential of the alcohols that resulted from reduction of these ketones as chiral auxiliaries in the alkylation of carboxylate ester derivatives has been studied. The diastereoselectivities shown by NMR spectroscopy range from 14- 30 % d.e. for (1R,2 S, 3R) -2 ,2-[ (1R, 2 S, 3R) -bornane-2,3-dioxy] - bornan-3-ol and 68-74 % d.e. for (1R, 2S ,3R) -3 ,3-[ (1R, 2S ,3R) - bornane-2, 3 -dioxy]bornan-2-ol with selectivities that correlate with the size of the alkyl group in the ester moiety. Trapping of the enolates generated from (1R, 2S ,3R)-2, 2 -[(1R,2 S, 3R) -bornane- 2,3-dioxy]bornan-3-yl propanoate afforded both E- and Z-silyl ketene acetal derivatives in the ratio of 64:36 confirming the formation of both possible enolate structures during enolization. Chiral auxiliaries containing a hemiaminal ether blocking group as well as two chiral alcohols containing monothio-ketal blocking groups have also been synthesised. α-Benzylation of their corresponding propanoate esters afforded the alkylated product with disappointingly low diastereos electivities. Asymmetric reduction of α-keto esters attached to (1R, 2 S, 3R) - 2,2- [ (1R,2 S, 3R) -bornane-2, 3 -dioxy]bornan-3-ol and (1R, 2S ,3R) - 3,3- [ (1R,2 S, 3R) -bornane-2, 3 -dioxy]bornan-2-ol with metal hydrides proceeded with selectivities of up to 30 % d.e. Modelling of the keto ester derivatives at DFT levels provided useful insights into possible conformations adopted by the two α-keto esters and hence the preferred face of attack by metal hydride during reduction.
- Full Text:
- Date Issued: 2008
On the optical characterization of photovoltaic devices
- Authors: Gxasheka, Andile Richman
- Date: 2008
- Subjects: Photovoltaic power systems -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10529 , http://hdl.handle.net/10948/692 , Photovoltaic power systems -- South Africa
- Description: Semiconductor materials used for making photovoltaic (PV) cells have defects and impurities due to constraints of keeping production costs low. Electrically active defects that are distributed over the bulk material lead to reduced overall performance of a photovoltaic (PV) cell. In this study an adaptable Light Beam Induced Current (LBIC) system was designed in order to characterize the local performance of PV cells. The system uses a laser source and objective lens mounted vertically above the sample on the X-Y stage. Two current pre-amplifiers are used for converting the photo-generated current from the PV cell and the signal from the reflection detector cell into a voltage that can be measured by the data acquisition board. Two configurations for measuring the photo-current maps of either bare cells or encapsulated PV mini-modules can be used. To add flexibility it was envisaged that the system would be built in such a way that it allows easy integration of carrier lifetime mapping capabilities while keeping costs to a minimum. The carrier lifetime measurement technique integrated into the LBIC system is based on the optical Open-Circuit Voltage-Decay (OCVD) method. In a single-crystalline silicon PV cell that was tested, photo-current and opencircuit voltage LBIC scans revealed shunting behaviour due to scratch marks on the front surface. The marks are believed to have been caused by poor handling during manufacturing process. Reduced photo-current due to edge shunting was observed towards the edges of the PV cell. In another sample of single crystalline silicon cell an edge shunt resulted in a 30 percent drop in photo-current measured. LBIC measurements performed on multi-crystalline cells revealed nonuniformities such as enhanced photo-current on one side of grain boundaries. These asymmetric enhancements of local photo-current are attributed to the incline of the grain boundary into the bulk of the material. LBIC results obtained from mini modules showed a high degree of mismatching from cell to cell. It is well known that mismatching can degrade the performance of a PV module with series connected cells. The LBIC measurements presented also illustrated the negative effects of delamination on the photo-current of PV modules. The LBIC measurements performed on mini PV modules highlight some of the benefits of using an LBIC technique as a tool for investigating PV cell’s local photo-current response. The effective lifetime maps obtained highlight the importance of optical OCVD method as a tool that can be used in conjunction with conventional LBIC technique. Effective minority carrier lifetimes around 40 ms were measured on a single crystalline silicon cell of 2.5 x 2.5 cm2. Local features such as cracks and lifetime degrading defects were revealed by LBIC maps and were also confirmed on effective lifetime maps. The results presented demonstrate the importance of using effective carrier lifetime maps to complement photocurrent maps of PV cells and identification of areas where defects are located.
- Full Text:
- Date Issued: 2008
- Authors: Gxasheka, Andile Richman
- Date: 2008
- Subjects: Photovoltaic power systems -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10529 , http://hdl.handle.net/10948/692 , Photovoltaic power systems -- South Africa
- Description: Semiconductor materials used for making photovoltaic (PV) cells have defects and impurities due to constraints of keeping production costs low. Electrically active defects that are distributed over the bulk material lead to reduced overall performance of a photovoltaic (PV) cell. In this study an adaptable Light Beam Induced Current (LBIC) system was designed in order to characterize the local performance of PV cells. The system uses a laser source and objective lens mounted vertically above the sample on the X-Y stage. Two current pre-amplifiers are used for converting the photo-generated current from the PV cell and the signal from the reflection detector cell into a voltage that can be measured by the data acquisition board. Two configurations for measuring the photo-current maps of either bare cells or encapsulated PV mini-modules can be used. To add flexibility it was envisaged that the system would be built in such a way that it allows easy integration of carrier lifetime mapping capabilities while keeping costs to a minimum. The carrier lifetime measurement technique integrated into the LBIC system is based on the optical Open-Circuit Voltage-Decay (OCVD) method. In a single-crystalline silicon PV cell that was tested, photo-current and opencircuit voltage LBIC scans revealed shunting behaviour due to scratch marks on the front surface. The marks are believed to have been caused by poor handling during manufacturing process. Reduced photo-current due to edge shunting was observed towards the edges of the PV cell. In another sample of single crystalline silicon cell an edge shunt resulted in a 30 percent drop in photo-current measured. LBIC measurements performed on multi-crystalline cells revealed nonuniformities such as enhanced photo-current on one side of grain boundaries. These asymmetric enhancements of local photo-current are attributed to the incline of the grain boundary into the bulk of the material. LBIC results obtained from mini modules showed a high degree of mismatching from cell to cell. It is well known that mismatching can degrade the performance of a PV module with series connected cells. The LBIC measurements presented also illustrated the negative effects of delamination on the photo-current of PV modules. The LBIC measurements performed on mini PV modules highlight some of the benefits of using an LBIC technique as a tool for investigating PV cell’s local photo-current response. The effective lifetime maps obtained highlight the importance of optical OCVD method as a tool that can be used in conjunction with conventional LBIC technique. Effective minority carrier lifetimes around 40 ms were measured on a single crystalline silicon cell of 2.5 x 2.5 cm2. Local features such as cracks and lifetime degrading defects were revealed by LBIC maps and were also confirmed on effective lifetime maps. The results presented demonstrate the importance of using effective carrier lifetime maps to complement photocurrent maps of PV cells and identification of areas where defects are located.
- Full Text:
- Date Issued: 2008
Physical activity in the lives of two generations of black professional women in the Nelson Mandela Metropolitan Municipality
- Authors: Walter, Cheryl Michelle
- Date: 2008
- Subjects: Physical education for women , Physical fitness for women , Women -- Health and hygiene
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10089 , http://hdl.handle.net/10948/664 , Physical education for women , Physical fitness for women , Women -- Health and hygiene
- Description: The association between physical inactivity, adverse health and hypokinetic diseases has been widely researched. There is an increased risk of being overweight, and of developing certain chronic diseases and suffering premature death associated with physical inactivity (Young, Miller, Wilder, Yanek & Becker, 1998). Recent surveys and studies have revealed that the majority of the South African population has moved extensively along the epidemiological transition towards a disease profile related to Western lifestyle, where deaths due to chronic diseases of lifestyle is a great cause for concern (Steyn, 2006). Black women, in particular, have been identified as a high risk group with the highest levels of inactivity and the highest levels of overweight and obesity in the country (SADHS, 1998; WHO, 2005). Although there is a growing body of knowledge and research on physical activity in general, there is still a lack of data on the determinants and barriers to participation in physical activity (Lambert & Kolbe-Alexander, 2006). Cultural patterns and economic, political and ideological orders affect the participation of women in sport (Hargreaves, 1994:5). Black women in South Africa have been disadvantaged by the past government’s policy of apartheid, and have also been marginalized and oppressed in their own patriarchal societies. The first democratically elected government in 1994, however, committed itself to gender equality and women’s emancipation, with constitutional guarantees on equality and an affirmative action policy to address gender inequalities. In order to evaluate the extent of the beneficial impact of these political changes in women’s lives, this study proposed to investigate physical activity patterns in the lives of two generations of black professional women (teachers, nurses, social workers and public managers) from the Nelson Mandela Metropolitan Municipality. The objectives that guided the research were: • To describe and compare the physical activity patterns and health status of two generations of black women through questionnaires, physical activity records and mechanical devices. • To explore and describe the psychosocial context and socio-cultural influences on physical activity in the lives of the participants. xi • To explore and describe the participants’ perceptions and attitudes, motivations and constraints relating to physical activity. • To use the research findings to compile guidelines to promote physical activity participation among black women. A mixed method approach using both quantitative and qualitative methods was selected to achieve an holistic understanding of physical activity in the lives of black South African women. The older generation (OG) of professional women was comprised of community teachers, nurses, social workers and public managers (n=111, aged 35 to 45 years, mean age = 39.87 years). These women, through their occupations, were in constant contact with the community and could be regarded as role models who influence community lifestyle, attitudes and behaviour. The younger generation (YG) (n=69, aged 18 to 21 years, mean age = 20.12 years) was comprised of teaching, nursing, social work and public management students in the Nelson Mandela Metropolitan Municipality. The objective of the quantitative section of the study was to provide baseline information on the physical activity patterns and health status of these two generations of black professional women. Physical activity and health questionnaires were administered and the ActiGraph GT1 accelerometer was used to provide an objective measure of energy expenditure. The objective of the qualitative data collection was to explore and describe the psychosocial context and socio-cultural influences on physical activity in the lives of the participants, and to investigate their attitudes to and perceptions of physical activity, and their motivations and constraints related to it. In-depth qualitative interviews were held with the participants who wore the ActiGraph, and a group of 47 were interviewed (sample size determined by data saturation from the interviews). An explorative-descriptive research design was used in the study. The sampling method was purposive and criterion-based. The younger generation of students were mostly selected from the various campuses of the Nelson Mandela Metropolitan University, while additional student nurses were recruited from the Lilitha Nursing College in the Nelson Mandela Metropolitan Municipality. The older generation of professionals were recruited from schools and clinics in the areas of New Brighton, Kwa-Zakhele, Zwide, Motherwell and Kwa-Nobuhle (all historically black areas), the Eastern Cape Department of Social Development, non-government organizations and the Nelson Mandela Metropolitan Municipality. xii The quantitative data were analysed by means of descriptive and inferential statistics. The qualitative data was analysed according to the steps described in Creswell (2003). The results of the quantitative data indicated that prevalence of overweight and obesity among both the YG and OG was high. The mean BMI for the YG and OG were 24.71 kg/m2 and 31.27 kg/m2, respectively, with 41% of the YG and 86% of the OG falling into the overweight/obesity category. BMI was significantly greater (p<.05) for the OG than for the YG. In addition, both the OG and YG had satisfactory scores for the health-related behaviour measures (the Belloc and Breslow Lifestyle Index and the HPLP). All the physical activity measurements (the FIT Index of Kasari, the GPAQ and the ActiGraph data) confirmed that both the YG and OG were not sufficiently physically active. They did not meet the Centre of Disease Control (CDC) and American College of Sports Medicine (ACSM) recommendation of engaging in at least 30 minutes of moderate-intensity physical activity on most, or preferably all, days of the week. The YG were significantly more active than the OG in all the physical activity measuring instruments. They were still, however, not reaching the health enhancing physical activity (HEPA) level (≥7 days of any combination of moderate and vigorous activity, ≥ 3000 METmins/week). Pearson Product Moment correlations were calculated to determine the relationship among the various measurements of physical activity o the one hand and the relationship between the measurements of physical activity and the health-related behaviour measurements on the other hand. The correlational analyses highlighted a good cross-validation of the various measures of physical activity. There was a significant correlation between the measures of leisure time physical activity, that is the FIT Index, and the leisure domain of the GPAQ. There was also a significant relationship in the area of walking or steps taken, that is the ActiGraph steps and the GPAQ transport domain. There was also a significant relationship between the overall measures of physical activity, that is the GPAQ total score, and the ActiGraph calories. The correlations between the various physical activity and health related behaviour measures revealed that only the leisure related physical activity measurements, that is, the FIT index and the GPAQ leisure domain, had a significant correlation with the two health related behaviour measures, namely the Belloc and Breslow Lifestyle Index and the HPLP, respectively. xiii The results from the qualitative data revealed that both the OG and YG had positive attitudes towards physical activity participation (displayed by their awareness of the many benefits, their expressed intention to start exercising, the encouragement given to their children in relation to physical activity participation), even though the majority of them were not active on a regular basis. Participants recognized the educational, recreational and developmental importance of being physically active, a shift in attitude from their own upbringing and lifestyles. Regardless of how firmly people may believe that physical activity is beneficial to their health, there are many barriers, whether real or perceived, that represent significant potential obstructions to the adoption, maintenance, or resumption of participation in physical activity (Booth et al., 1997). Three sub-themes were identified in relation to the barriers to physical activity participation, namely personal factors, environmental factors and socio-cultural factors. The personal factors included time constraints, stress and tiredness, lack of motivation, negative school experiences, negative associations with exercise and financial constraints. The environmental factors included residential areas, availability of recreation and sports facilities, and safety. The socio-cultural factors were lack of social support, exercise “not being a part of African culture”, traditional roles of males and females, dress code, exercise associated with the young, exercise associated with undesirable weight loss and negative comments by the community. On the basis of research findings, guidelines were drawn up for the promotion of physical activity participation among black women.
- Full Text:
- Date Issued: 2008
- Authors: Walter, Cheryl Michelle
- Date: 2008
- Subjects: Physical education for women , Physical fitness for women , Women -- Health and hygiene
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10089 , http://hdl.handle.net/10948/664 , Physical education for women , Physical fitness for women , Women -- Health and hygiene
- Description: The association between physical inactivity, adverse health and hypokinetic diseases has been widely researched. There is an increased risk of being overweight, and of developing certain chronic diseases and suffering premature death associated with physical inactivity (Young, Miller, Wilder, Yanek & Becker, 1998). Recent surveys and studies have revealed that the majority of the South African population has moved extensively along the epidemiological transition towards a disease profile related to Western lifestyle, where deaths due to chronic diseases of lifestyle is a great cause for concern (Steyn, 2006). Black women, in particular, have been identified as a high risk group with the highest levels of inactivity and the highest levels of overweight and obesity in the country (SADHS, 1998; WHO, 2005). Although there is a growing body of knowledge and research on physical activity in general, there is still a lack of data on the determinants and barriers to participation in physical activity (Lambert & Kolbe-Alexander, 2006). Cultural patterns and economic, political and ideological orders affect the participation of women in sport (Hargreaves, 1994:5). Black women in South Africa have been disadvantaged by the past government’s policy of apartheid, and have also been marginalized and oppressed in their own patriarchal societies. The first democratically elected government in 1994, however, committed itself to gender equality and women’s emancipation, with constitutional guarantees on equality and an affirmative action policy to address gender inequalities. In order to evaluate the extent of the beneficial impact of these political changes in women’s lives, this study proposed to investigate physical activity patterns in the lives of two generations of black professional women (teachers, nurses, social workers and public managers) from the Nelson Mandela Metropolitan Municipality. The objectives that guided the research were: • To describe and compare the physical activity patterns and health status of two generations of black women through questionnaires, physical activity records and mechanical devices. • To explore and describe the psychosocial context and socio-cultural influences on physical activity in the lives of the participants. xi • To explore and describe the participants’ perceptions and attitudes, motivations and constraints relating to physical activity. • To use the research findings to compile guidelines to promote physical activity participation among black women. A mixed method approach using both quantitative and qualitative methods was selected to achieve an holistic understanding of physical activity in the lives of black South African women. The older generation (OG) of professional women was comprised of community teachers, nurses, social workers and public managers (n=111, aged 35 to 45 years, mean age = 39.87 years). These women, through their occupations, were in constant contact with the community and could be regarded as role models who influence community lifestyle, attitudes and behaviour. The younger generation (YG) (n=69, aged 18 to 21 years, mean age = 20.12 years) was comprised of teaching, nursing, social work and public management students in the Nelson Mandela Metropolitan Municipality. The objective of the quantitative section of the study was to provide baseline information on the physical activity patterns and health status of these two generations of black professional women. Physical activity and health questionnaires were administered and the ActiGraph GT1 accelerometer was used to provide an objective measure of energy expenditure. The objective of the qualitative data collection was to explore and describe the psychosocial context and socio-cultural influences on physical activity in the lives of the participants, and to investigate their attitudes to and perceptions of physical activity, and their motivations and constraints related to it. In-depth qualitative interviews were held with the participants who wore the ActiGraph, and a group of 47 were interviewed (sample size determined by data saturation from the interviews). An explorative-descriptive research design was used in the study. The sampling method was purposive and criterion-based. The younger generation of students were mostly selected from the various campuses of the Nelson Mandela Metropolitan University, while additional student nurses were recruited from the Lilitha Nursing College in the Nelson Mandela Metropolitan Municipality. The older generation of professionals were recruited from schools and clinics in the areas of New Brighton, Kwa-Zakhele, Zwide, Motherwell and Kwa-Nobuhle (all historically black areas), the Eastern Cape Department of Social Development, non-government organizations and the Nelson Mandela Metropolitan Municipality. xii The quantitative data were analysed by means of descriptive and inferential statistics. The qualitative data was analysed according to the steps described in Creswell (2003). The results of the quantitative data indicated that prevalence of overweight and obesity among both the YG and OG was high. The mean BMI for the YG and OG were 24.71 kg/m2 and 31.27 kg/m2, respectively, with 41% of the YG and 86% of the OG falling into the overweight/obesity category. BMI was significantly greater (p<.05) for the OG than for the YG. In addition, both the OG and YG had satisfactory scores for the health-related behaviour measures (the Belloc and Breslow Lifestyle Index and the HPLP). All the physical activity measurements (the FIT Index of Kasari, the GPAQ and the ActiGraph data) confirmed that both the YG and OG were not sufficiently physically active. They did not meet the Centre of Disease Control (CDC) and American College of Sports Medicine (ACSM) recommendation of engaging in at least 30 minutes of moderate-intensity physical activity on most, or preferably all, days of the week. The YG were significantly more active than the OG in all the physical activity measuring instruments. They were still, however, not reaching the health enhancing physical activity (HEPA) level (≥7 days of any combination of moderate and vigorous activity, ≥ 3000 METmins/week). Pearson Product Moment correlations were calculated to determine the relationship among the various measurements of physical activity o the one hand and the relationship between the measurements of physical activity and the health-related behaviour measurements on the other hand. The correlational analyses highlighted a good cross-validation of the various measures of physical activity. There was a significant correlation between the measures of leisure time physical activity, that is the FIT Index, and the leisure domain of the GPAQ. There was also a significant relationship in the area of walking or steps taken, that is the ActiGraph steps and the GPAQ transport domain. There was also a significant relationship between the overall measures of physical activity, that is the GPAQ total score, and the ActiGraph calories. The correlations between the various physical activity and health related behaviour measures revealed that only the leisure related physical activity measurements, that is, the FIT index and the GPAQ leisure domain, had a significant correlation with the two health related behaviour measures, namely the Belloc and Breslow Lifestyle Index and the HPLP, respectively. xiii The results from the qualitative data revealed that both the OG and YG had positive attitudes towards physical activity participation (displayed by their awareness of the many benefits, their expressed intention to start exercising, the encouragement given to their children in relation to physical activity participation), even though the majority of them were not active on a regular basis. Participants recognized the educational, recreational and developmental importance of being physically active, a shift in attitude from their own upbringing and lifestyles. Regardless of how firmly people may believe that physical activity is beneficial to their health, there are many barriers, whether real or perceived, that represent significant potential obstructions to the adoption, maintenance, or resumption of participation in physical activity (Booth et al., 1997). Three sub-themes were identified in relation to the barriers to physical activity participation, namely personal factors, environmental factors and socio-cultural factors. The personal factors included time constraints, stress and tiredness, lack of motivation, negative school experiences, negative associations with exercise and financial constraints. The environmental factors included residential areas, availability of recreation and sports facilities, and safety. The socio-cultural factors were lack of social support, exercise “not being a part of African culture”, traditional roles of males and females, dress code, exercise associated with the young, exercise associated with undesirable weight loss and negative comments by the community. On the basis of research findings, guidelines were drawn up for the promotion of physical activity participation among black women.
- Full Text:
- Date Issued: 2008
Phytoplankton chlorophyll a concentration and community structure in two temporarily open/closed estuaries in the Eastern Cape, South Africa
- Authors: Gama, Phumelele Thuthuka
- Date: 2008
- Subjects: Estuarine ecology -- South Africa , Chlorophyll -- South Africa , Estuaries -- South Africa , Phytoplankton populations -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10621 , http://hdl.handle.net/10948/707 , Estuarine ecology -- South Africa , Chlorophyll -- South Africa , Estuaries -- South Africa , Phytoplankton populations -- South Africa
- Description: River flow is important in controlling phytoplankton distribution in estuaries. Data on the effect of river inflow on phytoplankton distribution patterns in temporarily open/closed estuaries is lacking. This study investigated the influence of river inflow on size-fractionated phytoplankton biomass (Chl a), community composition and environmental parameters measured monthly over three years in two temporarily open/closed estuaries in the Eastern Cape, South Africa. A once-off primary production study over an annual cycle was completed in the Van Stadens and Maitland estuaries. The study monitored physical, chemical and biological characteristics in both estuaries to examine the effects of changes in environmental factors and river inflow. Daily sampling of physico-chemical and biological variables from river to sea was carried out in the Van Stadens to investigate short-time scale effects of changes in environmental factors and river inflow on the phytoplankton biomass. Five and three stations in the main channel of the Van Stadens and Maitland estuaries respectively were sampled at 0.5 m below the water surface and 0.5 m above the sediment surface for biological and chemical variables and at the surface, 0.25 m and every 0.5 m thereafter for physical parameters. Five stations adjacent to the main channel along the estuary were monitored for groundwater macronutrient concentrations and five additional sites located within the upper catchment of the Van Stadens River were sampled on a quarterly basis over two years. Both estuaries were characterised by distinct hydrological conditions, an overwash, an open, a closed and a semi-closed mouth phase. Flooding in the Maitland and Van Stadens estuaries in 2001 and 2002 caused sediment scour, altered channel morphology and brought about breaching of the mouth. Flood driven mouth-breaching events occurred three and four times in each of the estuaries during the study. The mouth stayed open 20 – 25 percent and was closed 60 – 65 percent of the time. In the Van Stadens the closed overwash mouth condition occurred approximately 10 – 20 percent of the time while in the Maitland it occurred less with the semi-closed mouth condition occurring 10 – 20 percent of the time. Incidents related to mouth opening not associated with strong river floods occurred approximately 10 – 15 percent of the time, although in the Maitland a semi-closed mouth state persisted more frequently than in the Van Stadens Estuary. During flooding events salinity dropped to low levels (< 5 psu) but soon recovered to brackish conditions when river flow was reduced and marine water penetrated deep upstream. Reduction in river flow combined with marine sediment deposition resulted in the closure of the mouth. During closed mouth conditions strong onshore storm surges and spring high tides introduced marine water through overwash that kept salinity high. In both estuaries salinity showed a negative correlation with rainfall (R2 = 0.12), indicative of the strong influence of marine overwash that kept salinity high thus masking the influence of freshwater. High rainfall in the Van Stadens Estuary caused high levels of turbidity that reduced light penetration at depth. Light attenuation was positively correlated with the high rainfall (R 2 = 0.26) suggesting that increased turbidity was linked to rainfall induced discharge. In contrast, in the Maitland Estuary light attenuation did not show any correlation with increased rainfall possibly because of the reduced water depth and increased euphotic zone following the floods in 2002. High river inflow introduced macronutrients in both estuaries such that dissolved inorganic phosphates (DIP) and dissolved inorganic nitrogen (DIN) concentrations in the Van Stadens Estuary were strongly correlated with rainfall (R2 = 0.78 and 0.57 respectively). In the Maitland Estuary DIP and DIN concentrations remained significantly higher (p < 0.05) compared to that in the Van Stadens suggesting that the Maitland catchment contributed greater nutrient input into the estuary and may be associated with farming activities. Phytoplankton chlorophyll a (Chl a) ranged from 0.8 – 13.9 μg L-1 in the Van Stadens and in the Maitland Estuary from 5.3 – 138 μg L-1 during the 3-year study. During the open mouth condition Chl a biomass and primary production ranged from 5.4 – 52.9 μg Chl a L-1 and 1.2 – 11.7 mg C m-2 d-1 in the Maitland and in the Van Stadens from 1.6 – 9.8 μg Chl a L-1 and 1.2 - 14 mg C m-2 d-1 respectively. Maximum annual primary production in the Maitland and Van Stadens estuaries was 8.8 and 5.1 g C m-2 y-1 respectively. When the mouth was open in the Van Stadens Estuary the microphytoplankton (> 20 μm) accounted for > 65 percent of the Chl a, whereas during closed mouth conditions they accounted for about 55 percent of the Chl a biomass. Chlorophytes became the dominant taxon in the dry summer months but were replaced by cryptophytes and dinoflagellates during the wet season. When nutrient concentrations were low during low flow conditions in the Van Stadens Estuary mixotrophic microphytoplankton became an important fraction of the water column together with phototrophic dinoflagellates and cryptophytes. In the Maitland large sized chlorophytes were the dominant taxa in late spring and summer seasons and made up more than 80 percent of the cell numbers. In the Maitland before the floods in 2002 cyanophytes were the dominant group in late spring contributing more than 75 percent in cell abundance. Data from the short-term study in the Van Stadens Estuary showed similarities and differences in the Chl a response to increased river inflow. High river inflow initially reduced Chl a biomass followed by a recovery period of a couple of days compared to a 8 – 10 week recovery period in studies monitored over seasonal and annual temporal scales. The responses may be dissimilar but help to illustrate that there are similar response patterns to environmental forcing necessary to support phytoplankton biomass at different temporal scales. This study has demonstrated that flooding events caused by strong river flow cause breaching of the mouth, a reduction in salinity and marked nutrient input. Although the causes of flooding can be similar in both estuaries the resultant effects are varied and can alter the ability of the estuary to retain water. This study was able to demonstrate that the supply of macronutrients from the catchment was strongly correlated with rainfall (R2 = 0.67) and that phytoplankton growth mainly depended on an allochthonous source of macronutrients although internal supplies could be critical at times in controlling microalgal biomass.
- Full Text:
- Date Issued: 2008
- Authors: Gama, Phumelele Thuthuka
- Date: 2008
- Subjects: Estuarine ecology -- South Africa , Chlorophyll -- South Africa , Estuaries -- South Africa , Phytoplankton populations -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10621 , http://hdl.handle.net/10948/707 , Estuarine ecology -- South Africa , Chlorophyll -- South Africa , Estuaries -- South Africa , Phytoplankton populations -- South Africa
- Description: River flow is important in controlling phytoplankton distribution in estuaries. Data on the effect of river inflow on phytoplankton distribution patterns in temporarily open/closed estuaries is lacking. This study investigated the influence of river inflow on size-fractionated phytoplankton biomass (Chl a), community composition and environmental parameters measured monthly over three years in two temporarily open/closed estuaries in the Eastern Cape, South Africa. A once-off primary production study over an annual cycle was completed in the Van Stadens and Maitland estuaries. The study monitored physical, chemical and biological characteristics in both estuaries to examine the effects of changes in environmental factors and river inflow. Daily sampling of physico-chemical and biological variables from river to sea was carried out in the Van Stadens to investigate short-time scale effects of changes in environmental factors and river inflow on the phytoplankton biomass. Five and three stations in the main channel of the Van Stadens and Maitland estuaries respectively were sampled at 0.5 m below the water surface and 0.5 m above the sediment surface for biological and chemical variables and at the surface, 0.25 m and every 0.5 m thereafter for physical parameters. Five stations adjacent to the main channel along the estuary were monitored for groundwater macronutrient concentrations and five additional sites located within the upper catchment of the Van Stadens River were sampled on a quarterly basis over two years. Both estuaries were characterised by distinct hydrological conditions, an overwash, an open, a closed and a semi-closed mouth phase. Flooding in the Maitland and Van Stadens estuaries in 2001 and 2002 caused sediment scour, altered channel morphology and brought about breaching of the mouth. Flood driven mouth-breaching events occurred three and four times in each of the estuaries during the study. The mouth stayed open 20 – 25 percent and was closed 60 – 65 percent of the time. In the Van Stadens the closed overwash mouth condition occurred approximately 10 – 20 percent of the time while in the Maitland it occurred less with the semi-closed mouth condition occurring 10 – 20 percent of the time. Incidents related to mouth opening not associated with strong river floods occurred approximately 10 – 15 percent of the time, although in the Maitland a semi-closed mouth state persisted more frequently than in the Van Stadens Estuary. During flooding events salinity dropped to low levels (< 5 psu) but soon recovered to brackish conditions when river flow was reduced and marine water penetrated deep upstream. Reduction in river flow combined with marine sediment deposition resulted in the closure of the mouth. During closed mouth conditions strong onshore storm surges and spring high tides introduced marine water through overwash that kept salinity high. In both estuaries salinity showed a negative correlation with rainfall (R2 = 0.12), indicative of the strong influence of marine overwash that kept salinity high thus masking the influence of freshwater. High rainfall in the Van Stadens Estuary caused high levels of turbidity that reduced light penetration at depth. Light attenuation was positively correlated with the high rainfall (R 2 = 0.26) suggesting that increased turbidity was linked to rainfall induced discharge. In contrast, in the Maitland Estuary light attenuation did not show any correlation with increased rainfall possibly because of the reduced water depth and increased euphotic zone following the floods in 2002. High river inflow introduced macronutrients in both estuaries such that dissolved inorganic phosphates (DIP) and dissolved inorganic nitrogen (DIN) concentrations in the Van Stadens Estuary were strongly correlated with rainfall (R2 = 0.78 and 0.57 respectively). In the Maitland Estuary DIP and DIN concentrations remained significantly higher (p < 0.05) compared to that in the Van Stadens suggesting that the Maitland catchment contributed greater nutrient input into the estuary and may be associated with farming activities. Phytoplankton chlorophyll a (Chl a) ranged from 0.8 – 13.9 μg L-1 in the Van Stadens and in the Maitland Estuary from 5.3 – 138 μg L-1 during the 3-year study. During the open mouth condition Chl a biomass and primary production ranged from 5.4 – 52.9 μg Chl a L-1 and 1.2 – 11.7 mg C m-2 d-1 in the Maitland and in the Van Stadens from 1.6 – 9.8 μg Chl a L-1 and 1.2 - 14 mg C m-2 d-1 respectively. Maximum annual primary production in the Maitland and Van Stadens estuaries was 8.8 and 5.1 g C m-2 y-1 respectively. When the mouth was open in the Van Stadens Estuary the microphytoplankton (> 20 μm) accounted for > 65 percent of the Chl a, whereas during closed mouth conditions they accounted for about 55 percent of the Chl a biomass. Chlorophytes became the dominant taxon in the dry summer months but were replaced by cryptophytes and dinoflagellates during the wet season. When nutrient concentrations were low during low flow conditions in the Van Stadens Estuary mixotrophic microphytoplankton became an important fraction of the water column together with phototrophic dinoflagellates and cryptophytes. In the Maitland large sized chlorophytes were the dominant taxa in late spring and summer seasons and made up more than 80 percent of the cell numbers. In the Maitland before the floods in 2002 cyanophytes were the dominant group in late spring contributing more than 75 percent in cell abundance. Data from the short-term study in the Van Stadens Estuary showed similarities and differences in the Chl a response to increased river inflow. High river inflow initially reduced Chl a biomass followed by a recovery period of a couple of days compared to a 8 – 10 week recovery period in studies monitored over seasonal and annual temporal scales. The responses may be dissimilar but help to illustrate that there are similar response patterns to environmental forcing necessary to support phytoplankton biomass at different temporal scales. This study has demonstrated that flooding events caused by strong river flow cause breaching of the mouth, a reduction in salinity and marked nutrient input. Although the causes of flooding can be similar in both estuaries the resultant effects are varied and can alter the ability of the estuary to retain water. This study was able to demonstrate that the supply of macronutrients from the catchment was strongly correlated with rainfall (R2 = 0.67) and that phytoplankton growth mainly depended on an allochthonous source of macronutrients although internal supplies could be critical at times in controlling microalgal biomass.
- Full Text:
- Date Issued: 2008
Plant aphid interactions : effects of diuraphis noxia and rhopalosiphum padi on the structure and function of the transport systems of leaves of wheat and barley
- Authors: Saheed, Sefiu Adekilekun
- Date: 2008
- Subjects: Russian wheat aphid Rhopalosiphum padi Aphids -- Host plants Wheat -- Diseases and pests
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4225 , http://hdl.handle.net/10962/d1003794
- Description: The infestation of the cultivated grain crops by phloem feeding aphids has generated a great deal of interest over the years, due to the serious damage they cause to the crops and yield losses that result. The mechanism of the interaction between aphids and host plants remains largely unknown in spite of efforts to understand the basis of aphid feeding on grain crops. Greater efforts are required to explain the mechanism(s) of this interaction in order to achieve sustainable agriculture. This thesis focused on an investigation of the mechanism of feeding by the Russian wheat aphid, Diuraphis noxia Mordvilko (RWA) and the bird cherry-oat aphid, Rhopalosiphum padi L. (BCA) on barley and wheat cultivars. These two aphids co-occur naturally, but they inflict very different feeding effects on host plants. Structural and functional approaches were employed to investigate their feeding habits and these were then related to the observed differences in their host plants. Transmission electron microscopy (TEM) techniques were used to study the ultrastructural damage, while fluorescence microscopy techniques – using aniline blue fluorochrome (a specific stain for callose) and 5, 6-CFDA (a phloem-mobile fluorophore) – were employed to investigate the functional response to damage via wound callose formation and phloem transport capacity respectively. RT-PCR and quantitative real-time RT-PCR techniques were used to investigate the regulation of the genes involved in callose synthesis and degradation at the transcriptional level. Morphological observation of the damage caused by the aphids show that infestation by RWA results in extensive leaf chlorosis, necrosis and rolling, while infestation by BCA does not lead to any observable symptoms within the same period. Interestingly, the population study shows that BCA breeds faster than RWA within the two-week experimental period. The ultrastructural study of feeding damage caused by the two aphids on the vascular bundles of susceptible barley cv Clipper, shows a different patterns of damage. Probing the vascular bundles results in the puncturing of vascular parenchyma by both aphids, but severe damage occurs in sieve tubes-companion cell complex during sustained feeding by RWA. In contrast, less damage occurs when BCA feeds on the phloem. Drinking from the xylem by RWA results in deposition of a large quantity of electron-dense watery saliva, which apparently seals the xylem vessels completely, by blocking all the pit membrane fields between the xylem vessels and associated parenchyma cells. In contrast, drinking from xylem by BCA results in deposition of a dense, granular saliva into the xylem vessels only, which does not appear to totally occlude the pit membrane fields. This is the first known report in which ultrastructural evidence of aphids’ drinking in xylem is provided. The comparative effects of RWA feeding on a susceptible Betta and resistant Betta-Dn1 wheat cultivars showed that after two weeks, the Betta cultivar expressed damage symptoms such as chlorosis, necrosis and leaf roll, while few chlorotic patches and necrotic spots occur in resistant Betta-Dn1 cultivars. An ultrastructural investigation of the feeding damage caused to all leaf tissues revealed, for the first time, that RWA is capable of both intra- and inter-cellular probing within mesophyll cells. Probing in the mesophyll cells induces a more severe damage in susceptible Betta than in the resistant Betta-Dn1 counterpart. Similar differences in damage occurred during feeding in the thin-walled sieve tubes of the phloem, with the sieve tubes of the Betta showing more damage than that of the resistant Betta-Dn1. However, drinking from xylem resulted in the characteristic occlusion of metaxylem vessels by copious deposition of saliva by RWA in both Betta and Betta-Dn1 cultivars. In all cases of probing, feeding, and drinking by RWA in both cultivars, all probed cells with evidence of salivary material deposit and those cells adjacent to salivary material deposit, exhibit significant damage in susceptible Betta cultivar, whereas similar cells in Betta-Dn1 cultivars do not show as damage as severe. Investigation of the functional response of the plants to feeding by aphids through the deposition of wound-induced callose shows that formation and deposition of wound callose occurs in both longitudinal and cross veins within 24h of feeding by RWA. This deposition increases through short-term feeding (72h) and prolonged feeding (14d). This is in sharp contrast to the observations with BCA feeding,where little or no callose formation occurs within the same time frame. Callose formation and deposition occurs only when a higher population of BCA feeds on barley leaves. This is the first report of aphid-induced wound callose by BCA. In all cases of callose deposition, aphid stylet tracks were associated with callose and the deposition of callose appears to be a permanent feature, because wound callose remained in the leaf tissues even after 120h of the aphids’ removal. Wound callose signals (defence and anti-defence) are discovered to be transported in the phloem tissues and are dependent on the direction of assimilate flow. Examination of the possible regulation of wound callose genes at the transcriptional level shows that the two expressed glucan synthase gene sequences (GSL – genes involved in callose formation) analysed did not show any significant increase or regulation upon aphid infestation. Contrary to expectation, all three aphid-induced β-1, 3-glucanases (genes which are thought to be involved in callose degradation) showed higher expression in RWA-infested tissue than in BCA-infested tissue. The results of the feeding damage on the transport capacity of the phloem shows that BCA infestation does not lead to a significant reduction in the phloem transport capacity during short-term feeding (72h), while RWA-infested leaves showed considerable reduction in the transport capacity of the phloem within the same period. However, prolonged feeding (14d) by BCA induces a considerable reduction on the transport capacity of the phloem on the infested tissues. In contrast, a marked reduction in the transport capacity of the phloem occurs in RWA-infested leaves and in most cases, complete cessation of transport ensues. In conclusion, these data collectively suggest that RWA is a serious and most destructive phloem feeder in comparison to the BCA. RWA causes severe damage to all cellular tissues of the host plants, which result in apoplasmic and symplasmic isolation of xylem and phloem tissues, while BCA infestation does not result in such isolation within the same time and population levels. Resistance genes appear to function by conferring resistance to cell damage on the resistant cultivars during aphid feeding. Responses by plants to aphid infestation via wound callose deposition are again shown to be species-specific. A quick response results when RWA feeds, even at a very low population level, while a response occurs only at a higher infestation level by BCA, and this response was shown as not regulated at the transcriptional level. Differences in the damage to leaf tissues and wound callose deposition eventually lead to varying degrees of damage to the transport capacity of the phloem. These differences in the damage signatures are hereby suggested to be the cause of the diversity in the observed damage symptoms and the yield losses upon infestation by the two aphid species.
- Full Text:
- Date Issued: 2008
- Authors: Saheed, Sefiu Adekilekun
- Date: 2008
- Subjects: Russian wheat aphid Rhopalosiphum padi Aphids -- Host plants Wheat -- Diseases and pests
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4225 , http://hdl.handle.net/10962/d1003794
- Description: The infestation of the cultivated grain crops by phloem feeding aphids has generated a great deal of interest over the years, due to the serious damage they cause to the crops and yield losses that result. The mechanism of the interaction between aphids and host plants remains largely unknown in spite of efforts to understand the basis of aphid feeding on grain crops. Greater efforts are required to explain the mechanism(s) of this interaction in order to achieve sustainable agriculture. This thesis focused on an investigation of the mechanism of feeding by the Russian wheat aphid, Diuraphis noxia Mordvilko (RWA) and the bird cherry-oat aphid, Rhopalosiphum padi L. (BCA) on barley and wheat cultivars. These two aphids co-occur naturally, but they inflict very different feeding effects on host plants. Structural and functional approaches were employed to investigate their feeding habits and these were then related to the observed differences in their host plants. Transmission electron microscopy (TEM) techniques were used to study the ultrastructural damage, while fluorescence microscopy techniques – using aniline blue fluorochrome (a specific stain for callose) and 5, 6-CFDA (a phloem-mobile fluorophore) – were employed to investigate the functional response to damage via wound callose formation and phloem transport capacity respectively. RT-PCR and quantitative real-time RT-PCR techniques were used to investigate the regulation of the genes involved in callose synthesis and degradation at the transcriptional level. Morphological observation of the damage caused by the aphids show that infestation by RWA results in extensive leaf chlorosis, necrosis and rolling, while infestation by BCA does not lead to any observable symptoms within the same period. Interestingly, the population study shows that BCA breeds faster than RWA within the two-week experimental period. The ultrastructural study of feeding damage caused by the two aphids on the vascular bundles of susceptible barley cv Clipper, shows a different patterns of damage. Probing the vascular bundles results in the puncturing of vascular parenchyma by both aphids, but severe damage occurs in sieve tubes-companion cell complex during sustained feeding by RWA. In contrast, less damage occurs when BCA feeds on the phloem. Drinking from the xylem by RWA results in deposition of a large quantity of electron-dense watery saliva, which apparently seals the xylem vessels completely, by blocking all the pit membrane fields between the xylem vessels and associated parenchyma cells. In contrast, drinking from xylem by BCA results in deposition of a dense, granular saliva into the xylem vessels only, which does not appear to totally occlude the pit membrane fields. This is the first known report in which ultrastructural evidence of aphids’ drinking in xylem is provided. The comparative effects of RWA feeding on a susceptible Betta and resistant Betta-Dn1 wheat cultivars showed that after two weeks, the Betta cultivar expressed damage symptoms such as chlorosis, necrosis and leaf roll, while few chlorotic patches and necrotic spots occur in resistant Betta-Dn1 cultivars. An ultrastructural investigation of the feeding damage caused to all leaf tissues revealed, for the first time, that RWA is capable of both intra- and inter-cellular probing within mesophyll cells. Probing in the mesophyll cells induces a more severe damage in susceptible Betta than in the resistant Betta-Dn1 counterpart. Similar differences in damage occurred during feeding in the thin-walled sieve tubes of the phloem, with the sieve tubes of the Betta showing more damage than that of the resistant Betta-Dn1. However, drinking from xylem resulted in the characteristic occlusion of metaxylem vessels by copious deposition of saliva by RWA in both Betta and Betta-Dn1 cultivars. In all cases of probing, feeding, and drinking by RWA in both cultivars, all probed cells with evidence of salivary material deposit and those cells adjacent to salivary material deposit, exhibit significant damage in susceptible Betta cultivar, whereas similar cells in Betta-Dn1 cultivars do not show as damage as severe. Investigation of the functional response of the plants to feeding by aphids through the deposition of wound-induced callose shows that formation and deposition of wound callose occurs in both longitudinal and cross veins within 24h of feeding by RWA. This deposition increases through short-term feeding (72h) and prolonged feeding (14d). This is in sharp contrast to the observations with BCA feeding,where little or no callose formation occurs within the same time frame. Callose formation and deposition occurs only when a higher population of BCA feeds on barley leaves. This is the first report of aphid-induced wound callose by BCA. In all cases of callose deposition, aphid stylet tracks were associated with callose and the deposition of callose appears to be a permanent feature, because wound callose remained in the leaf tissues even after 120h of the aphids’ removal. Wound callose signals (defence and anti-defence) are discovered to be transported in the phloem tissues and are dependent on the direction of assimilate flow. Examination of the possible regulation of wound callose genes at the transcriptional level shows that the two expressed glucan synthase gene sequences (GSL – genes involved in callose formation) analysed did not show any significant increase or regulation upon aphid infestation. Contrary to expectation, all three aphid-induced β-1, 3-glucanases (genes which are thought to be involved in callose degradation) showed higher expression in RWA-infested tissue than in BCA-infested tissue. The results of the feeding damage on the transport capacity of the phloem shows that BCA infestation does not lead to a significant reduction in the phloem transport capacity during short-term feeding (72h), while RWA-infested leaves showed considerable reduction in the transport capacity of the phloem within the same period. However, prolonged feeding (14d) by BCA induces a considerable reduction on the transport capacity of the phloem on the infested tissues. In contrast, a marked reduction in the transport capacity of the phloem occurs in RWA-infested leaves and in most cases, complete cessation of transport ensues. In conclusion, these data collectively suggest that RWA is a serious and most destructive phloem feeder in comparison to the BCA. RWA causes severe damage to all cellular tissues of the host plants, which result in apoplasmic and symplasmic isolation of xylem and phloem tissues, while BCA infestation does not result in such isolation within the same time and population levels. Resistance genes appear to function by conferring resistance to cell damage on the resistant cultivars during aphid feeding. Responses by plants to aphid infestation via wound callose deposition are again shown to be species-specific. A quick response results when RWA feeds, even at a very low population level, while a response occurs only at a higher infestation level by BCA, and this response was shown as not regulated at the transcriptional level. Differences in the damage to leaf tissues and wound callose deposition eventually lead to varying degrees of damage to the transport capacity of the phloem. These differences in the damage signatures are hereby suggested to be the cause of the diversity in the observed damage symptoms and the yield losses upon infestation by the two aphid species.
- Full Text:
- Date Issued: 2008
Practical and scalable synthesis of N-Alkyl-N,N'Diacylhydrazines
- Authors: Gouws, Melissa Claire
- Date: 2008
- Subjects: Chemistry, Organic , Acylation , Insecticides
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:10406 , http://hdl.handle.net/10948/696 , Chemistry, Organic , Acylation , Insecticides
- Description: The work presented in this thesis is concerned with the evaluation of potential synthetic routes for the diacylhydrazine group of compounds, and particularly, unsymmetrical diacylhydrazines. Diacylhydrazines form the basis for a relatively new group of insecticides that have molt accelerating properties, and which are considered to offer substantial advantages over other insecticides used for the control of certain insects. The overall objective for this study is to evaluate different potential synthetic routes for a model diacylhydrazine with the view to define potentially scaleable routes. The compound selected for this study was the unsymmetrical diacylhydrazine, N-[N-(tertbutyl) phenylcarbonylamino](4-methylphenyl)-carboxamide since it offers the same range of challenges that would be expected for the synthesis of other similar unsymmetrical diacylhydrazines. Thus, the synthesis of unsymmetrical diacylhydrazines require two reaction steps: The first step is the synthesis of the intermediate mono-acylhydrazine, while the second step is the synthesis of the desired diacylhydrazine from the intermediate mono-acylhydrazine. The most important factor in the two-step reaction sequence is to obtain a high degree of selectivity for the desired mono-acylhydrazine isomer. Acylation of t-butylhydrazine using 4-methylbenzoyl chloride can produce the desired product N-[(tert-butyl)amino](4-methylphenyl)carboxamide in yields above 90 percent, but this reaction produces a variety of by-products, including the “wrong” isomer (N-amino-N- (tert-butyl)(4-methylphenyl)carboximide). Unexpected byproducts for this particular acylation reaction, not previously reported in the literature have also been identified during this investigation. This includes a de-butylated diacylhydrazine, (4-methylphenyl)- N-[(4-methylphenyl)carbonylamino] carboxamide. Although the reaction between tert-butylhydrazine and 4-methylbenzaldehyde is very selective giving near quantitative yields of the desired hydrazone, the subsequent conversion of the hydrazone into the desired mono-acylhydrazine is problematic. The most promising route appears via bromination to form the hydrazidic bromide, followed by hydrolysis of the hydrazidic bromide. Yields for the bromination reaction during this investigation were somewhat higher than that reported previously in literature. Hydrolysis of the hydrazidic bromide, apparently also results in the hydrolysis of the reaction product to give an ester of the free acid (when an ester solvent is used). The synthesis of N-[N-(tert-butyl)phenylcarbonylamino](4-methyl phenyl)carboxamide was only briefly considered to evaluate essentially two approaches, namely: · The conversion of the monoacylhydrazine, N-[(tert-butyl)amino](4- methylphenyl)carboxamide, by acylating with either benzoyl chloride or methylbenzoate (gave 86 percent N-[N-(tert-butyl)phenylcarbonylamino](4-methyl phenyl)carboxamide when benzoyl chloride was used as acylating agent); and · The one-pot conversion of the hydrazone, [(1E)-2-(4-methylphenyl)-1- azavinyl](tert-butyl)]amine, by bromination/hydrolysis and acylation. In this case, benzoyl chloride (2 percent N-[N-(tert-butyl)phenylcarbonylamino](4-methyl phenyl)carboxamide), benzoic acid (80.67 percent N-[N-(tertbutyl) phenylcarbonylamino](4-methylphenyl)carboxamide) were evaluated as potential acylating agents.
- Full Text:
- Date Issued: 2008
- Authors: Gouws, Melissa Claire
- Date: 2008
- Subjects: Chemistry, Organic , Acylation , Insecticides
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:10406 , http://hdl.handle.net/10948/696 , Chemistry, Organic , Acylation , Insecticides
- Description: The work presented in this thesis is concerned with the evaluation of potential synthetic routes for the diacylhydrazine group of compounds, and particularly, unsymmetrical diacylhydrazines. Diacylhydrazines form the basis for a relatively new group of insecticides that have molt accelerating properties, and which are considered to offer substantial advantages over other insecticides used for the control of certain insects. The overall objective for this study is to evaluate different potential synthetic routes for a model diacylhydrazine with the view to define potentially scaleable routes. The compound selected for this study was the unsymmetrical diacylhydrazine, N-[N-(tertbutyl) phenylcarbonylamino](4-methylphenyl)-carboxamide since it offers the same range of challenges that would be expected for the synthesis of other similar unsymmetrical diacylhydrazines. Thus, the synthesis of unsymmetrical diacylhydrazines require two reaction steps: The first step is the synthesis of the intermediate mono-acylhydrazine, while the second step is the synthesis of the desired diacylhydrazine from the intermediate mono-acylhydrazine. The most important factor in the two-step reaction sequence is to obtain a high degree of selectivity for the desired mono-acylhydrazine isomer. Acylation of t-butylhydrazine using 4-methylbenzoyl chloride can produce the desired product N-[(tert-butyl)amino](4-methylphenyl)carboxamide in yields above 90 percent, but this reaction produces a variety of by-products, including the “wrong” isomer (N-amino-N- (tert-butyl)(4-methylphenyl)carboximide). Unexpected byproducts for this particular acylation reaction, not previously reported in the literature have also been identified during this investigation. This includes a de-butylated diacylhydrazine, (4-methylphenyl)- N-[(4-methylphenyl)carbonylamino] carboxamide. Although the reaction between tert-butylhydrazine and 4-methylbenzaldehyde is very selective giving near quantitative yields of the desired hydrazone, the subsequent conversion of the hydrazone into the desired mono-acylhydrazine is problematic. The most promising route appears via bromination to form the hydrazidic bromide, followed by hydrolysis of the hydrazidic bromide. Yields for the bromination reaction during this investigation were somewhat higher than that reported previously in literature. Hydrolysis of the hydrazidic bromide, apparently also results in the hydrolysis of the reaction product to give an ester of the free acid (when an ester solvent is used). The synthesis of N-[N-(tert-butyl)phenylcarbonylamino](4-methyl phenyl)carboxamide was only briefly considered to evaluate essentially two approaches, namely: · The conversion of the monoacylhydrazine, N-[(tert-butyl)amino](4- methylphenyl)carboxamide, by acylating with either benzoyl chloride or methylbenzoate (gave 86 percent N-[N-(tert-butyl)phenylcarbonylamino](4-methyl phenyl)carboxamide when benzoyl chloride was used as acylating agent); and · The one-pot conversion of the hydrazone, [(1E)-2-(4-methylphenyl)-1- azavinyl](tert-butyl)]amine, by bromination/hydrolysis and acylation. In this case, benzoyl chloride (2 percent N-[N-(tert-butyl)phenylcarbonylamino](4-methyl phenyl)carboxamide), benzoic acid (80.67 percent N-[N-(tertbutyl) phenylcarbonylamino](4-methylphenyl)carboxamide) were evaluated as potential acylating agents.
- Full Text:
- Date Issued: 2008
Prevalence of Escherichia coli O157:H7 in water and meat and meat products and vegetables sold in the Eastern Cape Province of South Africa and its impact on the diarrhoeic conditions of HIV/AIDS patients
- Authors: Abong'o, Benard Omondi
- Date: 2008
- Subjects: Foodborne diseases , Diarrhea , Escherichia coli , HIV infections , AIDS (Disease) , Bacterial diseases
- Language: English
- Type: Thesis , Doctoral , PhD (Microbiology)
- Identifier: vital:11263 , http://hdl.handle.net/10353/87 , Foodborne diseases , Diarrhea , Escherichia coli , HIV infections , AIDS (Disease) , Bacterial diseases
- Description: Water and food borne Escherichia coli O157:H7 could be one of the pathogens posing high health risk to patients suffering from Acquired Immunodeficiency Syndrome (AIDS) because of its incrimination in diarrhoea cases in AIDS patients. The present study, which was conducted between March 2005 and August 2006, investigated the prevalence of E. coli O157:H7 in water, meat and meat products and vegetables and its impact on diarrhoeic conditions of confirmed and non-confirmed HIV/AIDS patients in the Amathole District in the Eastern Cape Province of South Africa. The water samples used in the study were obtained from stand pipes supplying treated drinking water to communities residing in Fort Beaufort, Alice, Dimbaza and Mdantsane whereas borehole waters were sampled from Ngwenya and Kwasaki. The meat and meat products and vegetable samples were purchased from shops, butcheries, supermarkets and open air markets in Fort Beaufort, Alice and Mdantsane. The stool swabs used in the study were obtained from HIV/AIDS and outpatient clinics at Frere Hospital in East London. A total of 180 each of water, meat and meat products and vegetable samples and another 360 stool samples were analyzed for E. coli O157:H7. Presumptive E. coli O157 was isolated from the samples by culture-based methods and confirmed using Polymerase Chain Reaction techniques. Anti-biogram as well as risk assessment were also carried out using standard methods. The viable counts of presumptive E. coli O157 for water samples ranged between 3.3 × 104 and 1.71 × 105 CFU/ml, and between 1.8 × 104 and 5.04 × 106 CFU/g for meat and meat products, whereas those for vegetables ranged between 1.3 × 103 and 1.6 × 106 CFU/g. The counts of presumptive E. coli O157 for the water and vegetable samples were not significantly different whereas those for meat and meat products were found to be significantly different (P ≤ 0.05). The prevalence rates of presumptive E coli O157 in meat and meat products was 35.55 percent (64/180), and 25.55 percent (46/180) and 21.66 percent (39/180) for water and vegetables respectively. Prevalence of presumptive E. coli O157 in the stool samples of HIV/AIDS patients was 36.39 percent (131/360), of which 56.5 percent (74/131) and 43.5 percent (57/131) were from stools of confirmed and non-confirmed HIV/AIDS patients, respectively. Molecular analysis of representative presumptive E. coli O157 indicated that 10.29 percent (4/39) of vegetables; 14.81 percent (4/27) of water and 38.46 percent (5/13) of meat and meat products carried E. coli O157:H7. Also 36 percent (9/25) and 17.24 percent (5/29) of the stool samples were positive for E. coli O157:H7. Antimicrobial susceptibility profile revealed that all of the E. coli O157:H7 isolated from water, meat and meat products and vegetables as well as those isolated from stools of confirmed and non-confirmed HIV/AIDS patients were resistant (R) to gentamycin and erythromycin. However, 75 percent (20/27) of these isolates were resistant (R) to ampicillin and tetracycline whereas approximately 25 percent (6/27) were resistant (R) to nalidixic acid, ceftriaxone, and chloramphenicol. All the isolates (27/27) were susceptible (S) to amikacin. Probability of risk of E. coli O157:H7 infection was high for confirmed HIV/AIDS patients than for the non-confirmed HIV/AIDS patients. Estimated probability of risk of E. coli O157:H7 due to ingestion of water was 1.00 for 100 confirmed and non-confirmed HIV/AIDS patients. Risk due to meat and meat products was estimated at 0.27 and 0.20 and for vegetables at 0.21 and 0.15 per 100 confirmed and non-confirmed HIV/AIDS patients. The findings of this study predicted a possible link between E. coli O157:H7 isolated from drinking water, meat and meat products and vegetables and diarrhoeic conditions in both confirmed and non-confirmed HIV/AIDS patients, and concludes that confirmed HIV/AIDS patients can be at higher risk of contracting water and food borne E. coli O157:H7 than nonconfirmed HIV/AIDS patients. It is thus recommended that proper water treatment and food handling, maximum food and water safety and sanitation as well as personal body hygiene should be maintained, in order to prevent E. coli O157:H7 infections. Education initiatives and active surveillance of E. coli O157:H7 should be taken by all the stake-holders working directly or indirectly towards ensuring enduring sound public health.
- Full Text:
- Date Issued: 2008
- Authors: Abong'o, Benard Omondi
- Date: 2008
- Subjects: Foodborne diseases , Diarrhea , Escherichia coli , HIV infections , AIDS (Disease) , Bacterial diseases
- Language: English
- Type: Thesis , Doctoral , PhD (Microbiology)
- Identifier: vital:11263 , http://hdl.handle.net/10353/87 , Foodborne diseases , Diarrhea , Escherichia coli , HIV infections , AIDS (Disease) , Bacterial diseases
- Description: Water and food borne Escherichia coli O157:H7 could be one of the pathogens posing high health risk to patients suffering from Acquired Immunodeficiency Syndrome (AIDS) because of its incrimination in diarrhoea cases in AIDS patients. The present study, which was conducted between March 2005 and August 2006, investigated the prevalence of E. coli O157:H7 in water, meat and meat products and vegetables and its impact on diarrhoeic conditions of confirmed and non-confirmed HIV/AIDS patients in the Amathole District in the Eastern Cape Province of South Africa. The water samples used in the study were obtained from stand pipes supplying treated drinking water to communities residing in Fort Beaufort, Alice, Dimbaza and Mdantsane whereas borehole waters were sampled from Ngwenya and Kwasaki. The meat and meat products and vegetable samples were purchased from shops, butcheries, supermarkets and open air markets in Fort Beaufort, Alice and Mdantsane. The stool swabs used in the study were obtained from HIV/AIDS and outpatient clinics at Frere Hospital in East London. A total of 180 each of water, meat and meat products and vegetable samples and another 360 stool samples were analyzed for E. coli O157:H7. Presumptive E. coli O157 was isolated from the samples by culture-based methods and confirmed using Polymerase Chain Reaction techniques. Anti-biogram as well as risk assessment were also carried out using standard methods. The viable counts of presumptive E. coli O157 for water samples ranged between 3.3 × 104 and 1.71 × 105 CFU/ml, and between 1.8 × 104 and 5.04 × 106 CFU/g for meat and meat products, whereas those for vegetables ranged between 1.3 × 103 and 1.6 × 106 CFU/g. The counts of presumptive E. coli O157 for the water and vegetable samples were not significantly different whereas those for meat and meat products were found to be significantly different (P ≤ 0.05). The prevalence rates of presumptive E coli O157 in meat and meat products was 35.55 percent (64/180), and 25.55 percent (46/180) and 21.66 percent (39/180) for water and vegetables respectively. Prevalence of presumptive E. coli O157 in the stool samples of HIV/AIDS patients was 36.39 percent (131/360), of which 56.5 percent (74/131) and 43.5 percent (57/131) were from stools of confirmed and non-confirmed HIV/AIDS patients, respectively. Molecular analysis of representative presumptive E. coli O157 indicated that 10.29 percent (4/39) of vegetables; 14.81 percent (4/27) of water and 38.46 percent (5/13) of meat and meat products carried E. coli O157:H7. Also 36 percent (9/25) and 17.24 percent (5/29) of the stool samples were positive for E. coli O157:H7. Antimicrobial susceptibility profile revealed that all of the E. coli O157:H7 isolated from water, meat and meat products and vegetables as well as those isolated from stools of confirmed and non-confirmed HIV/AIDS patients were resistant (R) to gentamycin and erythromycin. However, 75 percent (20/27) of these isolates were resistant (R) to ampicillin and tetracycline whereas approximately 25 percent (6/27) were resistant (R) to nalidixic acid, ceftriaxone, and chloramphenicol. All the isolates (27/27) were susceptible (S) to amikacin. Probability of risk of E. coli O157:H7 infection was high for confirmed HIV/AIDS patients than for the non-confirmed HIV/AIDS patients. Estimated probability of risk of E. coli O157:H7 due to ingestion of water was 1.00 for 100 confirmed and non-confirmed HIV/AIDS patients. Risk due to meat and meat products was estimated at 0.27 and 0.20 and for vegetables at 0.21 and 0.15 per 100 confirmed and non-confirmed HIV/AIDS patients. The findings of this study predicted a possible link between E. coli O157:H7 isolated from drinking water, meat and meat products and vegetables and diarrhoeic conditions in both confirmed and non-confirmed HIV/AIDS patients, and concludes that confirmed HIV/AIDS patients can be at higher risk of contracting water and food borne E. coli O157:H7 than nonconfirmed HIV/AIDS patients. It is thus recommended that proper water treatment and food handling, maximum food and water safety and sanitation as well as personal body hygiene should be maintained, in order to prevent E. coli O157:H7 infections. Education initiatives and active surveillance of E. coli O157:H7 should be taken by all the stake-holders working directly or indirectly towards ensuring enduring sound public health.
- Full Text:
- Date Issued: 2008
Purification, characterisation and application of inulinase and transferase enzymes in the production of fructose and oligosaccharides
- Authors: Mutanda, Taurai
- Date: 2008
- Subjects: Fructose Transferases Oligosaccharides
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4448 , http://hdl.handle.net/10962/d1007734
- Description: Inulin hydrolysis can occur as a result of the action of exoinulinases and endoinulinases acting alone or synergistically. Exoinulinases cleave the non-reducing β-(2, I) end of inulin releasing fructose while endoinulinases act on the internal linkages randomly to release inulotrioses (F₃), inulotetraoses (F₄) and inulopentaoses (F₅) as major products. Fructosyltransferases act by cleaving a sucrose molecule and then transferring the liberated fructose molecule to an acceptor molecule such as sucrose or another oligosaccharide to elongate the short chain fructooligosaccharide. The production of high yields of oligosaccharides of specific chain length from simple raw materials such as inulin and sucrose is a challenge. Oligosaccharides of chain length up to degree of polymerisation (DP) 5 and fructose were produced using preparations of three commercial microbial enzymes. Production of these novel oligosaccharides was achieved by employing response surface methodology (RSM) with central composite experimental design (CCD) for optimising product yield. Using a crude Novozyme 960 endoinulinase preparation isolated from Aspergillus niger, the following conditions gave a high inulooligosaccharide (lOS) yield, temperature (60 ºC), 150 g/L inulin concentration, 48 h incubation; pH 6.0 and enzyme dosage of 60 U/ml. Under these conditions, inulotrioses (70.3 mM), inulotetraoses (38.8 mM), and inulopentaoses, (3.5 mM) were produced. Response surface regression predicted similar product levels under similar conditions. The crude endoinulinase was purified through a three step purification procedure with a yield of 1.11 % and 3.5 fold purification. The molecular weight of this endoinulinase was estimated to be 68 .1 kDa by SDS-PAGE and its endoinulinase nature was confirmed by native PAGE. The purified endoinulinase was more efficient in production of lOS than the crude endoinulinase preparation. The purified endoinulinase demonstrated a high affinity for the inulin substrate (Km[subscript] 3.53 mM, Vmax[subscript] 666.67 μmol/min/ml). Pectinex Ultra SP-L, a commercial crude enzyme preparation isolated from Aspergillus aculeatus is a cocktail of several enzymes including a fructosyltransferase. The crude enzyme showed both transfructosylation and hydrolytic activity in 200 to 600 g/L sucrose. The main fructooligosaccharides produced from sucrose were l-kestose (GF₂), nystose (GF₃) and fructofuranosyl nystose (GF₄). After the first RSM, with the coded independent variables of temperature, incubation time, pH and sucrose concentration, the highest levels of GF₂, was 68.61 mM, under sucrose concentration 600 g/L, temperature 60°C, enzyme dosage 20 U/ml , pH 5.6, after 4 h incubation. A sucrose concentration of 400 g/L favoured the synthesis of high levels of GF₃ and GF₄. In the second RSM the maximal yields of GF₂, GF₃ and GF₄ were 152.07 mM, 131.38 mM and 43.99 mM respectively. A purified fructosyltransferase did not synthesise GF₄. Ammonium ions were demonstrated to enhance the yield of FOS. A mixture of glucose and fructose was used as substrate for FOS synthesis and no FOS were formed. Glucose was shown to be an end product inhibitor of the fructosyltransferase and therefore hinders the formation of high FOS yield. Fructozyme, isolated from Aspergillus ficuum is a mixture of exo and endoinulinases with the former being predominant was used for fructose production from inulin hydrolysis. The exoinulinase was purified to electrophoretic homogeneity by a three step purification procedure. The molecular weight of the enzyme was estimated to be 53 kDa with a 2 I % yield and 4.2-fold. Response surface regression was used to predict the maximum fructose levels achievable under the combinations of temperature, enzyme dosage and incubation time. A reaction time (48 h), enzyme dosage (100 U/ml) and inulin concentration (150 g/l) at pH 5.0 at 50°C gave higher fructose levels (106.6 mg/ml) using crude exoinulinase as compared to 98.43 mg/ml using the purified exoinulinase. These findings indicate that higher levels of fructose require longer incubation periods and higher inulin substrate concentrations with higher enzyme dosage. The crude exoinulinase preparation gave fairly higher levels of fructose than the purified exoinulinase and this is due to the presence of other hydrolytic enzymes in the crude preparation. The conditions established by RSM and CCO were adequate in producing high yield of oligosaccharides and fructose and can therefore be applied for their industrial production since they are in high demand due to their health benefits as prebiotics.
- Full Text:
- Date Issued: 2008
- Authors: Mutanda, Taurai
- Date: 2008
- Subjects: Fructose Transferases Oligosaccharides
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4448 , http://hdl.handle.net/10962/d1007734
- Description: Inulin hydrolysis can occur as a result of the action of exoinulinases and endoinulinases acting alone or synergistically. Exoinulinases cleave the non-reducing β-(2, I) end of inulin releasing fructose while endoinulinases act on the internal linkages randomly to release inulotrioses (F₃), inulotetraoses (F₄) and inulopentaoses (F₅) as major products. Fructosyltransferases act by cleaving a sucrose molecule and then transferring the liberated fructose molecule to an acceptor molecule such as sucrose or another oligosaccharide to elongate the short chain fructooligosaccharide. The production of high yields of oligosaccharides of specific chain length from simple raw materials such as inulin and sucrose is a challenge. Oligosaccharides of chain length up to degree of polymerisation (DP) 5 and fructose were produced using preparations of three commercial microbial enzymes. Production of these novel oligosaccharides was achieved by employing response surface methodology (RSM) with central composite experimental design (CCD) for optimising product yield. Using a crude Novozyme 960 endoinulinase preparation isolated from Aspergillus niger, the following conditions gave a high inulooligosaccharide (lOS) yield, temperature (60 ºC), 150 g/L inulin concentration, 48 h incubation; pH 6.0 and enzyme dosage of 60 U/ml. Under these conditions, inulotrioses (70.3 mM), inulotetraoses (38.8 mM), and inulopentaoses, (3.5 mM) were produced. Response surface regression predicted similar product levels under similar conditions. The crude endoinulinase was purified through a three step purification procedure with a yield of 1.11 % and 3.5 fold purification. The molecular weight of this endoinulinase was estimated to be 68 .1 kDa by SDS-PAGE and its endoinulinase nature was confirmed by native PAGE. The purified endoinulinase was more efficient in production of lOS than the crude endoinulinase preparation. The purified endoinulinase demonstrated a high affinity for the inulin substrate (Km[subscript] 3.53 mM, Vmax[subscript] 666.67 μmol/min/ml). Pectinex Ultra SP-L, a commercial crude enzyme preparation isolated from Aspergillus aculeatus is a cocktail of several enzymes including a fructosyltransferase. The crude enzyme showed both transfructosylation and hydrolytic activity in 200 to 600 g/L sucrose. The main fructooligosaccharides produced from sucrose were l-kestose (GF₂), nystose (GF₃) and fructofuranosyl nystose (GF₄). After the first RSM, with the coded independent variables of temperature, incubation time, pH and sucrose concentration, the highest levels of GF₂, was 68.61 mM, under sucrose concentration 600 g/L, temperature 60°C, enzyme dosage 20 U/ml , pH 5.6, after 4 h incubation. A sucrose concentration of 400 g/L favoured the synthesis of high levels of GF₃ and GF₄. In the second RSM the maximal yields of GF₂, GF₃ and GF₄ were 152.07 mM, 131.38 mM and 43.99 mM respectively. A purified fructosyltransferase did not synthesise GF₄. Ammonium ions were demonstrated to enhance the yield of FOS. A mixture of glucose and fructose was used as substrate for FOS synthesis and no FOS were formed. Glucose was shown to be an end product inhibitor of the fructosyltransferase and therefore hinders the formation of high FOS yield. Fructozyme, isolated from Aspergillus ficuum is a mixture of exo and endoinulinases with the former being predominant was used for fructose production from inulin hydrolysis. The exoinulinase was purified to electrophoretic homogeneity by a three step purification procedure. The molecular weight of the enzyme was estimated to be 53 kDa with a 2 I % yield and 4.2-fold. Response surface regression was used to predict the maximum fructose levels achievable under the combinations of temperature, enzyme dosage and incubation time. A reaction time (48 h), enzyme dosage (100 U/ml) and inulin concentration (150 g/l) at pH 5.0 at 50°C gave higher fructose levels (106.6 mg/ml) using crude exoinulinase as compared to 98.43 mg/ml using the purified exoinulinase. These findings indicate that higher levels of fructose require longer incubation periods and higher inulin substrate concentrations with higher enzyme dosage. The crude exoinulinase preparation gave fairly higher levels of fructose than the purified exoinulinase and this is due to the presence of other hydrolytic enzymes in the crude preparation. The conditions established by RSM and CCO were adequate in producing high yield of oligosaccharides and fructose and can therefore be applied for their industrial production since they are in high demand due to their health benefits as prebiotics.
- Full Text:
- Date Issued: 2008
Queens, pseudoqueens and laying workers reproductive competition in the Cape Honeybee (Apis mellifera capensis Eschscholtz)
- Authors: Muerrle, Thomas Martin
- Date: 2008
- Subjects: Honeybee Honeybee -- Reproduction
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5750 , http://hdl.handle.net/10962/d1005437
- Description: In honeybees (Apis mellifera L.) the queen monopolises reproduction. However, especially after queen loss, workers can lay eggs, but are unable to mate. They produce haploid male offspring (drones) from unfertilised eggs via arrhenotokous parthenogenesis. In contrast, workers of the honeybee subspecies Apis mellifera capensis Eschscholtz typically produce diploid female offspring from unfertilised eggs thelytokously. After queen loss and without queen-derived brood A. m. capensis colonies can successfully requeen from worker-derived brood. This, however, is a relatively rare event in wild populations. Moreover, workerderived queens were described to be smaller, more worker-like and reproductively inferior. On the other hand, the fixation of the thelytokous trait relies mainly on sufficient numbers of viable drones produced by worker-derived queens. Small numbers of reproductively inferior worker-derived queens in A. m. capensis populations would be clearly counterintuitive. It is therefore necessary to quantify the significance of worker-dependant queen rearing pathways on the individual (queen) and on population level.Reproductive inferiority of worker-derived queens could not be confirmed on the individual (queen) level when comparing parameters indicating potential reproductive success of queen- and worker-derived queens. Queen- and worker-derived queens clearly showed a congruent range of reproductive performance. In queen rearing preference tests, increased acceptance of worker-derived female larvae was exactly counterbalanced by increased mortality, resulting in an equal number of eclosing virgin queens from an equal number of grafts in both test groups. Larval survival and successful eclosion is a prerequisite for a queen’s reproductive success. I found no difference in eclosion success for queen- and worker-derived virgin queens, indicating a similar potential for reproductive success in both queen types. Assessments of the developmental patterns of colonies headed by both queen and worker-derived queens in long-term experiments revealed no significant differences in reproductive success. Colonies headed by queen-derived queens and colonies headed by worker-derived queens could not be separated when comparing the different developmental pathways observed or from differences in worker-force. Reproductive dominance in A. m. capensis appeared tobe determined by a function of relative compositional and absolute quantitative pheromonal patterns, where individuals, which produce compositionally most queen-like blends in highest quantities, occupy top positions. Queen- and worker-derived virgin queens occupied intermediate positions between pseudoqueens and mated queens. However, no significant differences between the pheromonal status of queen- and worker-derived virgin queens were observed, suggesting a similar range of reproductive dominance for both queen types. In behavioural bioassays queen- and worker-derived virgin queens appeared to be similarly attractive to clustering workers and to drones in a drone congregation area, indicating no differences in potential reproductive success for queens from both origins for those parameters. The significant influence of the queen substance 9-ODA on attractiveness to workers and drones was confirmed. Rare requeening events from worker-derived female brood in queenless A.m. capensis do not satisfactorily explain the fixation of the thelytokous trait at a population level. I observed A. m. capensis worker ovipositing into empty artificial queen cell cups in queen-right colonies. The queen was confined behind a queen excluder grid in a separate compartment of the colony, to imitate reduced pheromonal flow, similar to swarming or superseding colonies. Eggs oviposited by workers in artificial queen cell cups were readily accepted for queen rearing and successful eclosion of viable virgin queens was observed. Consequently I suggested an alternative worker-dependant reproductive pathway in A. m. capensis, which was never described before: In swarming or superseding queenright colonies, laying workers may directly compete with the queen for reproductive success by ovipositing (instead of the queen) into natural queen cell cups. At a population level this reproductive tactic may result in large numbers of worker-derived queens of high reproductive quality in natural populations of A. m. capensis.
- Full Text:
- Date Issued: 2008
- Authors: Muerrle, Thomas Martin
- Date: 2008
- Subjects: Honeybee Honeybee -- Reproduction
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5750 , http://hdl.handle.net/10962/d1005437
- Description: In honeybees (Apis mellifera L.) the queen monopolises reproduction. However, especially after queen loss, workers can lay eggs, but are unable to mate. They produce haploid male offspring (drones) from unfertilised eggs via arrhenotokous parthenogenesis. In contrast, workers of the honeybee subspecies Apis mellifera capensis Eschscholtz typically produce diploid female offspring from unfertilised eggs thelytokously. After queen loss and without queen-derived brood A. m. capensis colonies can successfully requeen from worker-derived brood. This, however, is a relatively rare event in wild populations. Moreover, workerderived queens were described to be smaller, more worker-like and reproductively inferior. On the other hand, the fixation of the thelytokous trait relies mainly on sufficient numbers of viable drones produced by worker-derived queens. Small numbers of reproductively inferior worker-derived queens in A. m. capensis populations would be clearly counterintuitive. It is therefore necessary to quantify the significance of worker-dependant queen rearing pathways on the individual (queen) and on population level.Reproductive inferiority of worker-derived queens could not be confirmed on the individual (queen) level when comparing parameters indicating potential reproductive success of queen- and worker-derived queens. Queen- and worker-derived queens clearly showed a congruent range of reproductive performance. In queen rearing preference tests, increased acceptance of worker-derived female larvae was exactly counterbalanced by increased mortality, resulting in an equal number of eclosing virgin queens from an equal number of grafts in both test groups. Larval survival and successful eclosion is a prerequisite for a queen’s reproductive success. I found no difference in eclosion success for queen- and worker-derived virgin queens, indicating a similar potential for reproductive success in both queen types. Assessments of the developmental patterns of colonies headed by both queen and worker-derived queens in long-term experiments revealed no significant differences in reproductive success. Colonies headed by queen-derived queens and colonies headed by worker-derived queens could not be separated when comparing the different developmental pathways observed or from differences in worker-force. Reproductive dominance in A. m. capensis appeared tobe determined by a function of relative compositional and absolute quantitative pheromonal patterns, where individuals, which produce compositionally most queen-like blends in highest quantities, occupy top positions. Queen- and worker-derived virgin queens occupied intermediate positions between pseudoqueens and mated queens. However, no significant differences between the pheromonal status of queen- and worker-derived virgin queens were observed, suggesting a similar range of reproductive dominance for both queen types. In behavioural bioassays queen- and worker-derived virgin queens appeared to be similarly attractive to clustering workers and to drones in a drone congregation area, indicating no differences in potential reproductive success for queens from both origins for those parameters. The significant influence of the queen substance 9-ODA on attractiveness to workers and drones was confirmed. Rare requeening events from worker-derived female brood in queenless A.m. capensis do not satisfactorily explain the fixation of the thelytokous trait at a population level. I observed A. m. capensis worker ovipositing into empty artificial queen cell cups in queen-right colonies. The queen was confined behind a queen excluder grid in a separate compartment of the colony, to imitate reduced pheromonal flow, similar to swarming or superseding colonies. Eggs oviposited by workers in artificial queen cell cups were readily accepted for queen rearing and successful eclosion of viable virgin queens was observed. Consequently I suggested an alternative worker-dependant reproductive pathway in A. m. capensis, which was never described before: In swarming or superseding queenright colonies, laying workers may directly compete with the queen for reproductive success by ovipositing (instead of the queen) into natural queen cell cups. At a population level this reproductive tactic may result in large numbers of worker-derived queens of high reproductive quality in natural populations of A. m. capensis.
- Full Text:
- Date Issued: 2008
Reconstructing ionospheric TEC over South Africa using signals from a regional GPS network
- Authors: Opperman, B D L
- Date: 2008
- Subjects: Global Positioning System Global Positioning System -- Data processing Electrons -- South Africa Ionosphere -- South Africa Ionospheric radio wave propagation -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5487 , http://hdl.handle.net/10962/d1005273
- Description: Radio signals transmitted by GPS satellites orbiting the Earth are modulated as they propagate through the electrically charged plasmasphere and ionosphere in the near-Earth space environment. Through a linear combination of GPS range and phase measurements observed on two carrier frequencies by terrestrial-based GPS receivers, the ionospheric total electron content (TEC) along oblique GPS signal paths may be quantified. Simultaneous observations of signals transmitted by multiple GPS satellites and observed from a network of South African dual frequency GPS receivers, constitute a spatially dense ionospheric measurement source over the region. A new methodology, based on an adjusted spherical harmonic (ASHA) expansion, was developed to estimate diurnal vertical TEC over the region using GPS observations over the region. The performance of the ASHA methodology to estimate diurnal TEC and satellite and receiver differential clock biases (DCBs) for a single GPS receiver was first tested with simulation data and subsequently applied to observed GPS data. The resulting diurnal TEC profiles estimated from GPS observations compared favourably to measurements from three South African ionosondes and two other GPS-based methodologies for 2006 solstice and equinox dates. The ASHA methodology was applied to calculating diurnal two-dimensional TEC maps from multiple receivers in the South African GPS network. The space physics application of the newly developed methodology was demonstrated by investigating the ionosphere’s behaviour during a severe geomagnetic storm and investigating the long-term ionospheric stability in support of the proposed Square Kilometre Array (SKA) radio astronomy project. The feasibility of employing the newly developed technique in an operational near real-time system for estimating and dissimenating TEC values over Southern Africa using observations from a regional GPS receiver network, was investigated.
- Full Text:
- Date Issued: 2008
- Authors: Opperman, B D L
- Date: 2008
- Subjects: Global Positioning System Global Positioning System -- Data processing Electrons -- South Africa Ionosphere -- South Africa Ionospheric radio wave propagation -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5487 , http://hdl.handle.net/10962/d1005273
- Description: Radio signals transmitted by GPS satellites orbiting the Earth are modulated as they propagate through the electrically charged plasmasphere and ionosphere in the near-Earth space environment. Through a linear combination of GPS range and phase measurements observed on two carrier frequencies by terrestrial-based GPS receivers, the ionospheric total electron content (TEC) along oblique GPS signal paths may be quantified. Simultaneous observations of signals transmitted by multiple GPS satellites and observed from a network of South African dual frequency GPS receivers, constitute a spatially dense ionospheric measurement source over the region. A new methodology, based on an adjusted spherical harmonic (ASHA) expansion, was developed to estimate diurnal vertical TEC over the region using GPS observations over the region. The performance of the ASHA methodology to estimate diurnal TEC and satellite and receiver differential clock biases (DCBs) for a single GPS receiver was first tested with simulation data and subsequently applied to observed GPS data. The resulting diurnal TEC profiles estimated from GPS observations compared favourably to measurements from three South African ionosondes and two other GPS-based methodologies for 2006 solstice and equinox dates. The ASHA methodology was applied to calculating diurnal two-dimensional TEC maps from multiple receivers in the South African GPS network. The space physics application of the newly developed methodology was demonstrated by investigating the ionosphere’s behaviour during a severe geomagnetic storm and investigating the long-term ionospheric stability in support of the proposed Square Kilometre Array (SKA) radio astronomy project. The feasibility of employing the newly developed technique in an operational near real-time system for estimating and dissimenating TEC values over Southern Africa using observations from a regional GPS receiver network, was investigated.
- Full Text:
- Date Issued: 2008