Challenges on learning and teaching of fraction operations in Grade 6 - a case study in a South African primary school
- Authors: Chetty, Ashnee
- Date: 2019
- Subjects: Mathematics -- Study and teaching (Primary) Mathematics -- Study and teaching (Early childhood)
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: http://hdl.handle.net/10353/15869 , vital:40534
- Description: Literature review indicates that world over, fraction operations in primary school are challenging not only for learners but also for teachers and South Africa is not an exception. There have been studies on challenges of fraction operations, but could not locate any study at a Grade 6 level in East London education district. The purpose of this study was to assess the specific strengths and challenges in the learning and teaching of fraction operations in Grade 6 in one of the schools in this district. The research paradigm for this study was post-positivism which adopted a mixed methods approach, utilising both quantitative and qualitative methods. The population consisted of three teachers and 98 Grade 6 learners in one primary school in East London. The learners were under 18 years and in order to comply with South African ethical regulations involving humans, a letter was sent out to all 98 Grade 6 learners’ parents requesting their consent. Only 59 learners brought back the consent letters signed by a parent or legal guardian and hence, the sample consisted of 59 Grade 6 learners. There were two instruments: a survey questionnaire with 15 items for learners and two interview schedules, one for teachers and another for learners. The time to complete the questionnaire was 45 minutes and the time to complete the interviews was less than 20 minutes for learners and 40 minutes for teachers. As part of a pilot study, the questionnaire was given to six learners in 2017 cohort. Also, the questionnaire was given two colleagues teaching Grade 6 from two different schools. Furthermore, two learners from the 2017 cohort and two colleagues from two different schools were interviewed, respectively, to check the validity of the learners’ and teachers’ interview schedules. Based on the feedback, the instruments were modified for use in 2018. The learners were given the questionnaire to answer first before 10 were selected for interviews. Three teachers, one each from Grades 5, 6 and 7 were interviewed. The quantitative data were analysed to lead to a descriptive data presentation. The qualitative data were analysed thematically. It was revealed that there were similarities and differences in the manner in which teachers teach and the challenges they identified. There were similarities and differences among the responses from the learners. They found certain fraction operations challenging and their strengths were similar as well. The common outline of the learners’ strengths were being able to do like-fractions while, their challenges were on doing unlike-fractions. The teachers too concurred with the learners’ views. The learners got confused because they did not understand fractions as part of a whole. The teachers indicated knowledge of more than one teaching method. The teachers also pointed out how times tables is an essential part of being able to do operations of fractions. This study could be beneficial for teachers, learners, parents and curriculum developers. The curriculum developers need to revisit the time frame, the transition between the grades, and how often the concept of fractions appears throughout every term.
- Full Text:
- Date Issued: 2019
- Authors: Chetty, Ashnee
- Date: 2019
- Subjects: Mathematics -- Study and teaching (Primary) Mathematics -- Study and teaching (Early childhood)
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: http://hdl.handle.net/10353/15869 , vital:40534
- Description: Literature review indicates that world over, fraction operations in primary school are challenging not only for learners but also for teachers and South Africa is not an exception. There have been studies on challenges of fraction operations, but could not locate any study at a Grade 6 level in East London education district. The purpose of this study was to assess the specific strengths and challenges in the learning and teaching of fraction operations in Grade 6 in one of the schools in this district. The research paradigm for this study was post-positivism which adopted a mixed methods approach, utilising both quantitative and qualitative methods. The population consisted of three teachers and 98 Grade 6 learners in one primary school in East London. The learners were under 18 years and in order to comply with South African ethical regulations involving humans, a letter was sent out to all 98 Grade 6 learners’ parents requesting their consent. Only 59 learners brought back the consent letters signed by a parent or legal guardian and hence, the sample consisted of 59 Grade 6 learners. There were two instruments: a survey questionnaire with 15 items for learners and two interview schedules, one for teachers and another for learners. The time to complete the questionnaire was 45 minutes and the time to complete the interviews was less than 20 minutes for learners and 40 minutes for teachers. As part of a pilot study, the questionnaire was given to six learners in 2017 cohort. Also, the questionnaire was given two colleagues teaching Grade 6 from two different schools. Furthermore, two learners from the 2017 cohort and two colleagues from two different schools were interviewed, respectively, to check the validity of the learners’ and teachers’ interview schedules. Based on the feedback, the instruments were modified for use in 2018. The learners were given the questionnaire to answer first before 10 were selected for interviews. Three teachers, one each from Grades 5, 6 and 7 were interviewed. The quantitative data were analysed to lead to a descriptive data presentation. The qualitative data were analysed thematically. It was revealed that there were similarities and differences in the manner in which teachers teach and the challenges they identified. There were similarities and differences among the responses from the learners. They found certain fraction operations challenging and their strengths were similar as well. The common outline of the learners’ strengths were being able to do like-fractions while, their challenges were on doing unlike-fractions. The teachers too concurred with the learners’ views. The learners got confused because they did not understand fractions as part of a whole. The teachers indicated knowledge of more than one teaching method. The teachers also pointed out how times tables is an essential part of being able to do operations of fractions. This study could be beneficial for teachers, learners, parents and curriculum developers. The curriculum developers need to revisit the time frame, the transition between the grades, and how often the concept of fractions appears throughout every term.
- Full Text:
- Date Issued: 2019
Examining the cognitive learning effect on grade 10 students’ performance in physical science in selected schools in Umgungudlovu Education District
- Authors: Olorunda, David Oluyemi
- Date: 2019
- Subjects: Cognitive learning Learning, Psychology of
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: http://hdl.handle.net/10353/16577 , vital:40733
- Description: The study employed a quantitative as well as a qualitative approach. Four public schools in the uMgungundlovu District participated in this study. The identities of all respondents were protected. The sample included 154 participants, four Physical science educators and four Heads of department selected purposefully across four secondary schools. The study found that themajority of the learners reported that they have interest and positive attitude for Physical science but most of learners indicated they understanding when English is used as a medium of instruction in teaching Physical science but someprefer other languages to be used for their understanding. It was obvious that most parents lacked knowledge about Physical Sciences and could not assist their children. It was also indicated that their teachers are approachable especially for personal explanation giving them attention whenever they ask for assistance, creating an atmosphere that makes it easy for the learner to learn. The study reveals that learners had a high rate of their teachers motivating them enough to like physical science, by using different method for them to understand the subject and majority follow their teacher’s method but only few learners use their own method.The educators and the heads of departments confirmed that they do give the learners different method. Many learners understands what they are taught using diagrams and illustrations in order to make them understand in all subject study showed that the head of departments indicatedthat they do check the way the teachers teach for effectiveness on the part of the teachers in ,line with the curriculum assessment policy statement from the department of education .The educators said they receive their educational in- service training and done yearly at the department of education workshop and moderations. Findings from this research reveals that learners learns one way or the other through all the strategies of learning but most learners affirms that they learn more rehearsal where they have to repeat things more and that the physical sciences teacher should have more time and explain thoroughly particular term, using diagrams and illustrations in order to make them understand in all subject. The study concluded by giving general recommendations for improving learners’ participation and attitudes towards learning physical Science. Recommendations for improvement in the areas identified were III provided and topics for future research on the curriculum of Grade 10 Physical Sciences were suggested in order to improve on physical science.
- Full Text:
- Date Issued: 2019
- Authors: Olorunda, David Oluyemi
- Date: 2019
- Subjects: Cognitive learning Learning, Psychology of
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: http://hdl.handle.net/10353/16577 , vital:40733
- Description: The study employed a quantitative as well as a qualitative approach. Four public schools in the uMgungundlovu District participated in this study. The identities of all respondents were protected. The sample included 154 participants, four Physical science educators and four Heads of department selected purposefully across four secondary schools. The study found that themajority of the learners reported that they have interest and positive attitude for Physical science but most of learners indicated they understanding when English is used as a medium of instruction in teaching Physical science but someprefer other languages to be used for their understanding. It was obvious that most parents lacked knowledge about Physical Sciences and could not assist their children. It was also indicated that their teachers are approachable especially for personal explanation giving them attention whenever they ask for assistance, creating an atmosphere that makes it easy for the learner to learn. The study reveals that learners had a high rate of their teachers motivating them enough to like physical science, by using different method for them to understand the subject and majority follow their teacher’s method but only few learners use their own method.The educators and the heads of departments confirmed that they do give the learners different method. Many learners understands what they are taught using diagrams and illustrations in order to make them understand in all subject study showed that the head of departments indicatedthat they do check the way the teachers teach for effectiveness on the part of the teachers in ,line with the curriculum assessment policy statement from the department of education .The educators said they receive their educational in- service training and done yearly at the department of education workshop and moderations. Findings from this research reveals that learners learns one way or the other through all the strategies of learning but most learners affirms that they learn more rehearsal where they have to repeat things more and that the physical sciences teacher should have more time and explain thoroughly particular term, using diagrams and illustrations in order to make them understand in all subject. The study concluded by giving general recommendations for improving learners’ participation and attitudes towards learning physical Science. Recommendations for improvement in the areas identified were III provided and topics for future research on the curriculum of Grade 10 Physical Sciences were suggested in order to improve on physical science.
- Full Text:
- Date Issued: 2019
Social Media Conspicuous Consumptive Behaviour and Consumers’ Purchase Intentions of Luxury Goods
- Authors: Madzunya, Ntsundeni
- Date: 2018
- Subjects: Consumer behavior -- South Africa Social media -- Marketing
- Language: English
- Type: Thesis , Masters , MCom (Business Management)
- Identifier: http://hdl.handle.net/10353/13524 , vital:39676
- Description: Social media has grown to such a large extent that it has become a primary source of information among consumers online. The impact of the growth of popular social media sites such as Facebook and Instagram have allowed for interest in consumer online behaviour to increase. There is no specific social media model that can be used as a tool to understand its use and influence on conspicuous online consumption behaviour. The study aimed to develop and apply a model used to understand consumer behaviour in order to enhance the use of the communication landscape as a means to drive purchase intentions. Therefore, the purpose of this study was to investigate the effects of social media conspicuous consumptive behaviour on intention to purchase luxury goods. The primary objective of this study was to examine the effect of conspicuous consumptive behaviour facilitated by Instagram and Facebook on potential buyers’ intention to purchase luxury goods. The study also determined if Instagram and Facebook usage intensity has an influence on conspicuous consumptive behaviour. In addition, the study also examined the relationship between Instagram and Facebook eWOM credibility and conspicuous consumptive behaviour. The study was underpinned by a positivist paradigm, a quantitative approach and the appropriate descriptive research design. Data was collected from both primary and secondary sources. An online survey was conducted to collect primary data, through the use of a questionnaire developed from previous studies. The questionnaire was administered online through the Survey Monkey platform to a total of 364 respondents. Analysis and interpretation of findings was done using both the descriptive and inferential statistical measures, with the help of Statistical Package for Social Scientists (SPSS) 24 and Lisrel (version 9). The scales adopted for the study consisted of eight constructs, Instagram usage intensity, Instagram eWOM credibility, Instagram conspicuous consumptive behaviour, Instagram intention to purchase luxury goods, Facebook usage intensity, Facebook eWOM credibility, Facebook conspicuous consumptive behaviour, Facebook intention to purchase luxury goods. All the scales used in this study were found to be reliable and valid. ii Based on the 364 responses, the study found a positive relationship between both Facebook and Instagram usage intensity and conspicuous consumptive behaviour. Conversely, results showed that eWOM credibility on both Facebook and Instagram had no relationship with conspicuous consumptive behaviour. Lastly, Instagram conspicuous consumptive behaviour had a positive relationship with the intention to purchase luxury goods. A similar finding was found for Facebook conspicuous consumptive behaviour and the intention to purchase luxury goods. Luxury marketers are encouraged to formulate social media strategies that emphasise consumer involvement, engagement and trust; this, in turn, will increase total social media usage and influence. However, further research may want to include other popular social media platforms, such as Twitter and WhatsApp, to gain a wider understanding of the effect of social media conspicuous consumptive behaviour on intention to purchase luxury goods.
- Full Text:
- Date Issued: 2018
- Authors: Madzunya, Ntsundeni
- Date: 2018
- Subjects: Consumer behavior -- South Africa Social media -- Marketing
- Language: English
- Type: Thesis , Masters , MCom (Business Management)
- Identifier: http://hdl.handle.net/10353/13524 , vital:39676
- Description: Social media has grown to such a large extent that it has become a primary source of information among consumers online. The impact of the growth of popular social media sites such as Facebook and Instagram have allowed for interest in consumer online behaviour to increase. There is no specific social media model that can be used as a tool to understand its use and influence on conspicuous online consumption behaviour. The study aimed to develop and apply a model used to understand consumer behaviour in order to enhance the use of the communication landscape as a means to drive purchase intentions. Therefore, the purpose of this study was to investigate the effects of social media conspicuous consumptive behaviour on intention to purchase luxury goods. The primary objective of this study was to examine the effect of conspicuous consumptive behaviour facilitated by Instagram and Facebook on potential buyers’ intention to purchase luxury goods. The study also determined if Instagram and Facebook usage intensity has an influence on conspicuous consumptive behaviour. In addition, the study also examined the relationship between Instagram and Facebook eWOM credibility and conspicuous consumptive behaviour. The study was underpinned by a positivist paradigm, a quantitative approach and the appropriate descriptive research design. Data was collected from both primary and secondary sources. An online survey was conducted to collect primary data, through the use of a questionnaire developed from previous studies. The questionnaire was administered online through the Survey Monkey platform to a total of 364 respondents. Analysis and interpretation of findings was done using both the descriptive and inferential statistical measures, with the help of Statistical Package for Social Scientists (SPSS) 24 and Lisrel (version 9). The scales adopted for the study consisted of eight constructs, Instagram usage intensity, Instagram eWOM credibility, Instagram conspicuous consumptive behaviour, Instagram intention to purchase luxury goods, Facebook usage intensity, Facebook eWOM credibility, Facebook conspicuous consumptive behaviour, Facebook intention to purchase luxury goods. All the scales used in this study were found to be reliable and valid. ii Based on the 364 responses, the study found a positive relationship between both Facebook and Instagram usage intensity and conspicuous consumptive behaviour. Conversely, results showed that eWOM credibility on both Facebook and Instagram had no relationship with conspicuous consumptive behaviour. Lastly, Instagram conspicuous consumptive behaviour had a positive relationship with the intention to purchase luxury goods. A similar finding was found for Facebook conspicuous consumptive behaviour and the intention to purchase luxury goods. Luxury marketers are encouraged to formulate social media strategies that emphasise consumer involvement, engagement and trust; this, in turn, will increase total social media usage and influence. However, further research may want to include other popular social media platforms, such as Twitter and WhatsApp, to gain a wider understanding of the effect of social media conspicuous consumptive behaviour on intention to purchase luxury goods.
- Full Text:
- Date Issued: 2018
Implementation of the policy on religious equity in public schools in the East London Education District : towards a framework for religious diversity
- Makasi, Cordelia Noma-Abysinia
- Authors: Makasi, Cordelia Noma-Abysinia
- Date: 2017
- Subjects: Religious education -- South Africa -- Eastern Cape Religion and state -- South Africa -- Eastern Cape Christianity and politics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/5014 , vital:28935
- Description: The study sought to establish the implementation of the policy on religious equity in public schools in the East London Education district in the Eastern Cape Province of South Africa. Underpinned by Van Meter and Van Horn (2015) with implementation and conceptual theory and also a theory on opportunity to learn and school performance by Van Der Grift and Houtveen(2006), the study was located in the pragmatist research paradigm and followed a mixed methods approach and concurrent triangulation design. The research sampling technique was random for high school learners in selected schools and purposeful for principals, heads of departments, teachers and provincial education officials. Three methods were employed to collect data from selected public schools and from the provincial office namely; semi-structured interviews, individual interviews and observation. Quantitative data were analysed statistically and presented in the form of descriptive statistics. Qualitative data were analysed using the thematic content analysis technique. Major findings of the study are that teachers and principals understood the concept religious equity and had a fair understanding of the policy on religious equity. Schools were predominantly Christian-oriented in terms of religious practices and there were no recorded cases of religious conflict. Learners of minority religions were not compelled to attend Christian religious functions in schools and were allowed to attend their own religious functions outside school. This was established from the fact that participants cited freedom of religion as being exercised in schools. However, it was further established that there was no strategic monitoring and support for teachers in the implementation of religious equity. There were also no deliberate measures and strategies for the implementation of religious equity suggesting challenges and inconsistencies in the implementation of the policy. While there were notable challenges in the implementation of the policy, due to resistance of stakeholders to change, schools had great opportunities which could be utilized to enhance the implementation of the policy on religious equity. The study concludes by noting that, while key policy implementers had an understanding of religious equity, the situation on the ground revealed challenges and inconsistencies in the implementation of the policy which resulted in a Christian-dominated school environment at the expense of minority religions The study recommends, among other things, that that religious equity be adhered to as enshrined in the Constitution of South Africa of 1996 and the South African Schools Act of 1996. The teaching and learning environment should include Religion Education as per prescription by National Policy on Religion Education of 2003, that monitoring and support of teachers be done, and that community involvement with policy development be considered crucial as well as moral education teaching in schools. A framework for enhancing implementation of the policy on religious equity is also proposed.
- Full Text:
- Date Issued: 2017
- Authors: Makasi, Cordelia Noma-Abysinia
- Date: 2017
- Subjects: Religious education -- South Africa -- Eastern Cape Religion and state -- South Africa -- Eastern Cape Christianity and politics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/5014 , vital:28935
- Description: The study sought to establish the implementation of the policy on religious equity in public schools in the East London Education district in the Eastern Cape Province of South Africa. Underpinned by Van Meter and Van Horn (2015) with implementation and conceptual theory and also a theory on opportunity to learn and school performance by Van Der Grift and Houtveen(2006), the study was located in the pragmatist research paradigm and followed a mixed methods approach and concurrent triangulation design. The research sampling technique was random for high school learners in selected schools and purposeful for principals, heads of departments, teachers and provincial education officials. Three methods were employed to collect data from selected public schools and from the provincial office namely; semi-structured interviews, individual interviews and observation. Quantitative data were analysed statistically and presented in the form of descriptive statistics. Qualitative data were analysed using the thematic content analysis technique. Major findings of the study are that teachers and principals understood the concept religious equity and had a fair understanding of the policy on religious equity. Schools were predominantly Christian-oriented in terms of religious practices and there were no recorded cases of religious conflict. Learners of minority religions were not compelled to attend Christian religious functions in schools and were allowed to attend their own religious functions outside school. This was established from the fact that participants cited freedom of religion as being exercised in schools. However, it was further established that there was no strategic monitoring and support for teachers in the implementation of religious equity. There were also no deliberate measures and strategies for the implementation of religious equity suggesting challenges and inconsistencies in the implementation of the policy. While there were notable challenges in the implementation of the policy, due to resistance of stakeholders to change, schools had great opportunities which could be utilized to enhance the implementation of the policy on religious equity. The study concludes by noting that, while key policy implementers had an understanding of religious equity, the situation on the ground revealed challenges and inconsistencies in the implementation of the policy which resulted in a Christian-dominated school environment at the expense of minority religions The study recommends, among other things, that that religious equity be adhered to as enshrined in the Constitution of South Africa of 1996 and the South African Schools Act of 1996. The teaching and learning environment should include Religion Education as per prescription by National Policy on Religion Education of 2003, that monitoring and support of teachers be done, and that community involvement with policy development be considered crucial as well as moral education teaching in schools. A framework for enhancing implementation of the policy on religious equity is also proposed.
- Full Text:
- Date Issued: 2017
Pharmacological investigations of Kedrostis africana (L.) Cogn. and Vernonia mespilifolia Less. used in folk medicine in the Eastern Cape, South Africa
- Authors: Unuofin, Jeremiah Oshiomame
- Date: 2017
- Subjects: Medicinal plants -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/9231 , vital:34307
- Description: The prevalence of obesity and its co-morbidity is increasing in South Africa. High calorie diet, sedentary lifestyle and the cultural belief that being fat or obese signifies beauty, wellness and wealth are major causative factors. This study was undertaken to scientifically validate two major medicinal plants used traditionally in the Raymond Mhlaba Municipality for the mespilifolia Less. were used singly and in combination. According to ethnobotanical studies,these two plants are regarded as wild plants and are only used for medicinal purposes. There has been a dearth of scientific reports on the two plants and to the best of our knowledge, this study is the first to investigate the nutritional, antioxidant, antimicrobial, safety and anti-obesity potentials of the two plants and their combination. This study revealed that both plants are rich in nutrients. K. africana had greater ash (16.28 percent), crude fat (1.12 percent), Ca (2505 mg/100g), Mg (485 mg/100g) and Fe (89.95 mg/100g) while V. mespilifolia showed higher crude fibre (29.24 percent), crude protein (10.75 percent), P (400 mg/100g), Na (570 mg/100g), Cu (1.55 mg/100g) and Mn (4.70 mg/100g). K. africana and V. mespilifolia both contributed 223.37 Kcal/kg and 237.37 Kcal/kg of energy respectively. The polyphenolic evaluation of the acetone, aqueous and ethanol extracts of the plants revealed that the acetone extract of the combination of both plants had higher total phenol (144.59 mgGAE/g) and flavonoid (803.93 mgQE/g) contents, the ethanol extract of the combined plant also had the highest tannin contents (1.25 mgTAE/g), while the acetone extracts of K. Africana had the highest proanthocyanidin content (585 mgCE/g). The antioxidant assays revealed that the ethanol extract for V. mespilifolia had higher scavenging potentials of ABTS, DPPH and vinitric oxide radicals while the aqueous extract of the combination of both had higher scavenging potential for hydrogen peroxide radicals. Evaluation of antimicrobial potential of the extracts using the minimial inhibitory concentration (MIC) assay against 6 bacteria (Actinomyces odontolyticus, Lactobacillus sakei, Staphylococcus aureus, Enterobacter cloacae, Pseudomonas aeruginosa and Bacteriodes thetaiotomicron) and 4 fungi (Candida albicans, Microsporium gypsum, Penicillium chrysogenum and Trichophyton tonsurans) revealed that the plants possess antimicrobial activity. The MIC of the extracts against the tested bacterial strains ranged from 2.5 mg/mL to 5 mg/mL acetone and ethanol extracts of V. mespilifolia and the combined plants as well as the ethanol extracts of K. africana. However, no activity was observed for the acetone extract of K. africana and aqueous extracts of V. mespilifolia and the combination of both plants. Only three fungal strains (Candida albicans, Microsporium gypsum and Penicillium chrysogenum) were susceptible to the organic extracts with an MIC 0.3125 mg/mL to 5 mg/mL while the aqueous extracts showed no activity against all the fungal strains. None of the plant extracts showed any activity against Trichophyton tonsurans. The brine shrimp toxicity test revealed that all the three extracts of V. mespilifolia, aqueous and ethanol extracts of K. africana and aqueous and acetone extracts of the combination of both plants were toxic in relative to Meyer’s index and other indices of toxicity. The cytotoxic effect of the aqueous and ethanol extracts of V. mespilifolia, K. africana and their combination were also evaluated using HeLa cells. From this study, all the extracts tested had IC50 values were greater than 20 μg/mL which connotes that they are not toxic. According to the American National Cancer Institute, crude plant extracts are considered cytotoxic in an in vitro assay when concentrations 20 μg/mL and below produce 50% inhibition of tumor cells, after an exposure time of 48 hours. In vivo acute evaluation of single oral administration of 2000 and 5000/kg body weight did not produce mortality or significant behavioral changes during 14 days observation. In addition, the sub-acute administration of the aqueous extract at 200, 400 and 600 mg/kg/bwt/ day over a period of 28 days revealed no mortality or morbidity. The weekly body and organ weight of the rats were not significantly different from those of the controls and extract treated rats. The aqueous extracts at all doses did not show any significant (p > 0.05) effect on biomarkers of liver and renal damage. Haematological evaluation revealed that oral administration of aqueous extracts of K. africana, V. mespilifolia and the combination of both plants did not induce anaemia or leucocytosis in the animals. Furthermore, histopathological evaluation of the internal organs revealed no detectable inflammation at the the doses administered over a period of 28 days. These results demonstrated that the aqueous extracts of K. africana, V. mespilifolia and the combination of both plants was potentially safe for consumption orally even in chronic administration. Enzyme based in-vitro antiobesity evaluation of the aqueous and ethanolic extracts of K. africana, V. mespilifolia and their combination revealed that the ethanol extracts of both plants and their combination exhibited moderate inhibitory activities against α-amylase, α- glucosidase and pancreatic lipase. However, the standards used for the various inhibition assays exhibited much higher inhibitory actions when compared to any of the extracts. This suggests that the mechanism by which these two plants and their combination exert anti-obesity effects are probably not by inhibition of key enzymes of carbohydrate and fat metabolism.
- Full Text:
- Date Issued: 2017
- Authors: Unuofin, Jeremiah Oshiomame
- Date: 2017
- Subjects: Medicinal plants -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/9231 , vital:34307
- Description: The prevalence of obesity and its co-morbidity is increasing in South Africa. High calorie diet, sedentary lifestyle and the cultural belief that being fat or obese signifies beauty, wellness and wealth are major causative factors. This study was undertaken to scientifically validate two major medicinal plants used traditionally in the Raymond Mhlaba Municipality for the mespilifolia Less. were used singly and in combination. According to ethnobotanical studies,these two plants are regarded as wild plants and are only used for medicinal purposes. There has been a dearth of scientific reports on the two plants and to the best of our knowledge, this study is the first to investigate the nutritional, antioxidant, antimicrobial, safety and anti-obesity potentials of the two plants and their combination. This study revealed that both plants are rich in nutrients. K. africana had greater ash (16.28 percent), crude fat (1.12 percent), Ca (2505 mg/100g), Mg (485 mg/100g) and Fe (89.95 mg/100g) while V. mespilifolia showed higher crude fibre (29.24 percent), crude protein (10.75 percent), P (400 mg/100g), Na (570 mg/100g), Cu (1.55 mg/100g) and Mn (4.70 mg/100g). K. africana and V. mespilifolia both contributed 223.37 Kcal/kg and 237.37 Kcal/kg of energy respectively. The polyphenolic evaluation of the acetone, aqueous and ethanol extracts of the plants revealed that the acetone extract of the combination of both plants had higher total phenol (144.59 mgGAE/g) and flavonoid (803.93 mgQE/g) contents, the ethanol extract of the combined plant also had the highest tannin contents (1.25 mgTAE/g), while the acetone extracts of K. Africana had the highest proanthocyanidin content (585 mgCE/g). The antioxidant assays revealed that the ethanol extract for V. mespilifolia had higher scavenging potentials of ABTS, DPPH and vinitric oxide radicals while the aqueous extract of the combination of both had higher scavenging potential for hydrogen peroxide radicals. Evaluation of antimicrobial potential of the extracts using the minimial inhibitory concentration (MIC) assay against 6 bacteria (Actinomyces odontolyticus, Lactobacillus sakei, Staphylococcus aureus, Enterobacter cloacae, Pseudomonas aeruginosa and Bacteriodes thetaiotomicron) and 4 fungi (Candida albicans, Microsporium gypsum, Penicillium chrysogenum and Trichophyton tonsurans) revealed that the plants possess antimicrobial activity. The MIC of the extracts against the tested bacterial strains ranged from 2.5 mg/mL to 5 mg/mL acetone and ethanol extracts of V. mespilifolia and the combined plants as well as the ethanol extracts of K. africana. However, no activity was observed for the acetone extract of K. africana and aqueous extracts of V. mespilifolia and the combination of both plants. Only three fungal strains (Candida albicans, Microsporium gypsum and Penicillium chrysogenum) were susceptible to the organic extracts with an MIC 0.3125 mg/mL to 5 mg/mL while the aqueous extracts showed no activity against all the fungal strains. None of the plant extracts showed any activity against Trichophyton tonsurans. The brine shrimp toxicity test revealed that all the three extracts of V. mespilifolia, aqueous and ethanol extracts of K. africana and aqueous and acetone extracts of the combination of both plants were toxic in relative to Meyer’s index and other indices of toxicity. The cytotoxic effect of the aqueous and ethanol extracts of V. mespilifolia, K. africana and their combination were also evaluated using HeLa cells. From this study, all the extracts tested had IC50 values were greater than 20 μg/mL which connotes that they are not toxic. According to the American National Cancer Institute, crude plant extracts are considered cytotoxic in an in vitro assay when concentrations 20 μg/mL and below produce 50% inhibition of tumor cells, after an exposure time of 48 hours. In vivo acute evaluation of single oral administration of 2000 and 5000/kg body weight did not produce mortality or significant behavioral changes during 14 days observation. In addition, the sub-acute administration of the aqueous extract at 200, 400 and 600 mg/kg/bwt/ day over a period of 28 days revealed no mortality or morbidity. The weekly body and organ weight of the rats were not significantly different from those of the controls and extract treated rats. The aqueous extracts at all doses did not show any significant (p > 0.05) effect on biomarkers of liver and renal damage. Haematological evaluation revealed that oral administration of aqueous extracts of K. africana, V. mespilifolia and the combination of both plants did not induce anaemia or leucocytosis in the animals. Furthermore, histopathological evaluation of the internal organs revealed no detectable inflammation at the the doses administered over a period of 28 days. These results demonstrated that the aqueous extracts of K. africana, V. mespilifolia and the combination of both plants was potentially safe for consumption orally even in chronic administration. Enzyme based in-vitro antiobesity evaluation of the aqueous and ethanolic extracts of K. africana, V. mespilifolia and their combination revealed that the ethanol extracts of both plants and their combination exhibited moderate inhibitory activities against α-amylase, α- glucosidase and pancreatic lipase. However, the standards used for the various inhibition assays exhibited much higher inhibitory actions when compared to any of the extracts. This suggests that the mechanism by which these two plants and their combination exert anti-obesity effects are probably not by inhibition of key enzymes of carbohydrate and fat metabolism.
- Full Text:
- Date Issued: 2017
Adherence to antiretroviral therapy in children in Zimbabwe: a randomized control trial to validate a new self-reported adherence monitoring tool
- Authors: Mugore, Linnetie
- Date: 2014
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/54734 , vital:26607
- Description: Background: Among children taking antiretroviral therapy (ART), self-reports have been widely reported to over-estimate adherence levels. Pill count adherence levels are often lower than self-reported levels, with unannounced home pill count adherence being lower than facility based pill count adherence. There is often poor agreement between pill count adherence levels and those measured using other objective adherence measuring methods such as Medication Event Monitoring Systems (MEMS®), which is widely viewed as the gold standard for adherence measurement. Objectives: The aim of this study was to design and evaluate a new self-reported paediatric adherence monitoring tool, assess the feasibility of using pill count methods in monitoring adherence and identify challenges to reporting adherence among children on ART in rural and urban Zimbabwe. Methods A dual centre, superiority, parallel design RCT was conducted to evaluate the newly-developed visually- and verbally-cued „past 10 days‟ tool for the assessment of adherence in children on ART at two sites in Zimbabwe; Harare Central Children‟s Hospital in an urban setting, and Murambinda Mission Hospital, a rural site. Child-caregiver pairs presenting to one of these facilities for the child‟s review of ART and refill of the medication were recruited, signed informed consent obtained, and were randomised for self-reported adherence monitoring into either the experimental group („new 10-day tool‟) or the control group („PACTG-style‟ self-report tool). Data (demographic, socioeconomic, and reported adherence) were collected in individual interviews with child-caregiver pairs. Additional adherence monitoring methods used for both groups included the Morisky-8-Item Medication Adherence Scale (MMAS-8) and a facility based pill count. FGDs were held with groups of caregivers and groups of children ≥13 years of age to understand reasons for non-adherence as well as issues around reporting non-adherence. Superiority testing was conducted by comparing adherent proportions and their confidence intervals (95% CI). Further concurrent validity test was done using the Mann-Whitney U test to evaluate the relationship between the new tool and the MMAS-8 scores. Agreement between the child and caregiver reports of adherence was used as a test of reliability of the new tool using the kappa statistic. Socio-demographic, clinical and care-related factors associated with adherence were identified using reported adherence in both child and caregiver groups in a logistic regression model. Two pill count methods were assessed for feasibility using the proportions of children with complete data for calculating adherence levels, and their CI and a comparison of the two methods, a routinely-used method and one that incorporated the reported residual quantity (RRQ) of medication at last refill. Results : Analysis included 245 child-caregiver pairs, 123 in the experimental group and 122 in the control group. The median age for children was 9 years. In the experimental group, adherence by caregiver and child reports ranged from 94.3% - 98.4% and 78.4% - 96.1%, and those in the control group ranged from 89.2% - 97.5% and 71.2% - 98.1%, respectively. There was no significant difference between adherence levels in the two groups. Adherence levels measured by both the experimental and control tools were found to be associated with MMAS-8 adherence levels (p <0.05). Agreement between child- and caregiver-reported adherence was moderate though significant (kappa; 0.407, p <0.05). Only about half of the children had adequate data to compute pill counts. Proportions adherent at 95% cut-off were 39% by the „routine pill count‟ and 58% by the „Pill count RRQ‟. Being an orphan was associated with child reported-adherence whereas use of non-human reminders, having a maternal relative as a primary caregiver and knowledge of dose frequency, were all associated with caregiver-reported adherence. Major causes of non-adherence mentioned during the FGDs included interference of medication administration times with scheduling of routine socio-economic activities and lack of support from some non-biological caregivers. Reporting of non-adherence appeared to be hampered by perceptions of negative reactions by healthcare workers to these reports and by caregivers being unaware that the child missed some doses. Conclusions: The „new 10-day tool‟ was not shown to be superior to the „PACTG-style tool‟ in detecting non-adherence, however this new tool was found to be a valid and reliable adherence monitoring tool that included a moderately long recall period of 10 days, can be applied without the need for the respondent to remember names of individual medicines in the
- Full Text:
- Date Issued: 2014
- Authors: Mugore, Linnetie
- Date: 2014
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/54734 , vital:26607
- Description: Background: Among children taking antiretroviral therapy (ART), self-reports have been widely reported to over-estimate adherence levels. Pill count adherence levels are often lower than self-reported levels, with unannounced home pill count adherence being lower than facility based pill count adherence. There is often poor agreement between pill count adherence levels and those measured using other objective adherence measuring methods such as Medication Event Monitoring Systems (MEMS®), which is widely viewed as the gold standard for adherence measurement. Objectives: The aim of this study was to design and evaluate a new self-reported paediatric adherence monitoring tool, assess the feasibility of using pill count methods in monitoring adherence and identify challenges to reporting adherence among children on ART in rural and urban Zimbabwe. Methods A dual centre, superiority, parallel design RCT was conducted to evaluate the newly-developed visually- and verbally-cued „past 10 days‟ tool for the assessment of adherence in children on ART at two sites in Zimbabwe; Harare Central Children‟s Hospital in an urban setting, and Murambinda Mission Hospital, a rural site. Child-caregiver pairs presenting to one of these facilities for the child‟s review of ART and refill of the medication were recruited, signed informed consent obtained, and were randomised for self-reported adherence monitoring into either the experimental group („new 10-day tool‟) or the control group („PACTG-style‟ self-report tool). Data (demographic, socioeconomic, and reported adherence) were collected in individual interviews with child-caregiver pairs. Additional adherence monitoring methods used for both groups included the Morisky-8-Item Medication Adherence Scale (MMAS-8) and a facility based pill count. FGDs were held with groups of caregivers and groups of children ≥13 years of age to understand reasons for non-adherence as well as issues around reporting non-adherence. Superiority testing was conducted by comparing adherent proportions and their confidence intervals (95% CI). Further concurrent validity test was done using the Mann-Whitney U test to evaluate the relationship between the new tool and the MMAS-8 scores. Agreement between the child and caregiver reports of adherence was used as a test of reliability of the new tool using the kappa statistic. Socio-demographic, clinical and care-related factors associated with adherence were identified using reported adherence in both child and caregiver groups in a logistic regression model. Two pill count methods were assessed for feasibility using the proportions of children with complete data for calculating adherence levels, and their CI and a comparison of the two methods, a routinely-used method and one that incorporated the reported residual quantity (RRQ) of medication at last refill. Results : Analysis included 245 child-caregiver pairs, 123 in the experimental group and 122 in the control group. The median age for children was 9 years. In the experimental group, adherence by caregiver and child reports ranged from 94.3% - 98.4% and 78.4% - 96.1%, and those in the control group ranged from 89.2% - 97.5% and 71.2% - 98.1%, respectively. There was no significant difference between adherence levels in the two groups. Adherence levels measured by both the experimental and control tools were found to be associated with MMAS-8 adherence levels (p <0.05). Agreement between child- and caregiver-reported adherence was moderate though significant (kappa; 0.407, p <0.05). Only about half of the children had adequate data to compute pill counts. Proportions adherent at 95% cut-off were 39% by the „routine pill count‟ and 58% by the „Pill count RRQ‟. Being an orphan was associated with child reported-adherence whereas use of non-human reminders, having a maternal relative as a primary caregiver and knowledge of dose frequency, were all associated with caregiver-reported adherence. Major causes of non-adherence mentioned during the FGDs included interference of medication administration times with scheduling of routine socio-economic activities and lack of support from some non-biological caregivers. Reporting of non-adherence appeared to be hampered by perceptions of negative reactions by healthcare workers to these reports and by caregivers being unaware that the child missed some doses. Conclusions: The „new 10-day tool‟ was not shown to be superior to the „PACTG-style tool‟ in detecting non-adherence, however this new tool was found to be a valid and reliable adherence monitoring tool that included a moderately long recall period of 10 days, can be applied without the need for the respondent to remember names of individual medicines in the
- Full Text:
- Date Issued: 2014
The plasmodium falciparum exported Hsp40 co-chaperone, PFA0660w
- Authors: Daniyan, Michael Oluwatoyin
- Date: 2014
- Subjects: Molecular chaperones Heat shock proteins Proteins -- Analysis Proteins -- Structure Plasmodium Plasmodium falciparum Malaria -- Prevention -- Research
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4108 , http://hdl.handle.net/10962/d1011780
- Description: Plasmodium falciparum is the pathogen that is responsible for the most virulent, severe and dangerous form of human malaria infection, accounting for nearly a million deaths every year. To survive and develop in the unusual environment of the red blood cells, the parasite causes structural remodelling of the host cell and biochemical changes through the export of virulence factors. Among the exportome are the molecular chaperones of the heat shock protein family, of which Hsp40s and Hsp70s are prominent. PF A0660w, a type II P. falciparum Hsp40, has been shown to be exported in complex with PfHsp70-x into the infected erythrocyte, suggesting possible functional interactions. However, the chaperone properties of PF A0660w and its interactions with proteins of parasite and human origin are yet to be investigated. Using a codon optimised coding region, PF A0660w was successfully expressed in E. coli M 15 [pREP4] cells. However, the expressed protein was largely deposited as insoluble pellet, and analysis of the pellets revealed a high percentage of PF A0660w, characteristic of inclusion body formation. PF A0660w was purified from inclusion bodies using additive enhanced solubilisation and refolding buffers followed by nickel affinity chromatography. SDS-PAGE and western analysis revealed that the purified protein was of high purity. Size exclusion chromatography showed that the protein existed as a monomer in solution and the secondary structure analysis using Fourier transformed infrared spectroscopy (FTIR) confirmed the success of the refolding approach. Its monomeric state suggests that PF A0660w may be functionally different from other Hsp40 that form dimers and that for PF A0660w, dimer formation may not be needed to maintain the stability of the protein in solution, but may occur in response to functional necessities during its interaction with partner Hsp70. PFA0660w was able to significantly stimulate the ATPase activity ofPfl-Isp70-x but not Pfl-Isp70-1 or human Hsp70 (HsHsp70), suggesting a specific functional interaction. Also, PF A0660w produced a dose dependent suppression of rhodanese aggregation and cooperated with Pfl-Isp70-1, PfHsp70-x and HsHsp70 to cause enhanced aggregation suppression. Its ability to independently suppress aggregation may help to maintain substrates in an unfolded conformation for eventual transfer to partner Hsp70s during refolding processes. Also, the in vivo characterisation using a PF A0660w peptide specific antibody confirmed that PF A0660w was exported into the cytosol of infected erythrocytes. Its lack of induction upon heat shock suggests that PF A0660w may not be involved in the response of the parasite to heat stress. Overall, this study has provided the first heterologous over-expression, purification and biochemical evidence for the possible functional role of PF A0660w, and has thereby provided the needed background for further exploration of this protein as a potential target for drug discovery.
- Full Text:
- Date Issued: 2014
- Authors: Daniyan, Michael Oluwatoyin
- Date: 2014
- Subjects: Molecular chaperones Heat shock proteins Proteins -- Analysis Proteins -- Structure Plasmodium Plasmodium falciparum Malaria -- Prevention -- Research
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4108 , http://hdl.handle.net/10962/d1011780
- Description: Plasmodium falciparum is the pathogen that is responsible for the most virulent, severe and dangerous form of human malaria infection, accounting for nearly a million deaths every year. To survive and develop in the unusual environment of the red blood cells, the parasite causes structural remodelling of the host cell and biochemical changes through the export of virulence factors. Among the exportome are the molecular chaperones of the heat shock protein family, of which Hsp40s and Hsp70s are prominent. PF A0660w, a type II P. falciparum Hsp40, has been shown to be exported in complex with PfHsp70-x into the infected erythrocyte, suggesting possible functional interactions. However, the chaperone properties of PF A0660w and its interactions with proteins of parasite and human origin are yet to be investigated. Using a codon optimised coding region, PF A0660w was successfully expressed in E. coli M 15 [pREP4] cells. However, the expressed protein was largely deposited as insoluble pellet, and analysis of the pellets revealed a high percentage of PF A0660w, characteristic of inclusion body formation. PF A0660w was purified from inclusion bodies using additive enhanced solubilisation and refolding buffers followed by nickel affinity chromatography. SDS-PAGE and western analysis revealed that the purified protein was of high purity. Size exclusion chromatography showed that the protein existed as a monomer in solution and the secondary structure analysis using Fourier transformed infrared spectroscopy (FTIR) confirmed the success of the refolding approach. Its monomeric state suggests that PF A0660w may be functionally different from other Hsp40 that form dimers and that for PF A0660w, dimer formation may not be needed to maintain the stability of the protein in solution, but may occur in response to functional necessities during its interaction with partner Hsp70. PFA0660w was able to significantly stimulate the ATPase activity ofPfl-Isp70-x but not Pfl-Isp70-1 or human Hsp70 (HsHsp70), suggesting a specific functional interaction. Also, PF A0660w produced a dose dependent suppression of rhodanese aggregation and cooperated with Pfl-Isp70-1, PfHsp70-x and HsHsp70 to cause enhanced aggregation suppression. Its ability to independently suppress aggregation may help to maintain substrates in an unfolded conformation for eventual transfer to partner Hsp70s during refolding processes. Also, the in vivo characterisation using a PF A0660w peptide specific antibody confirmed that PF A0660w was exported into the cytosol of infected erythrocytes. Its lack of induction upon heat shock suggests that PF A0660w may not be involved in the response of the parasite to heat stress. Overall, this study has provided the first heterologous over-expression, purification and biochemical evidence for the possible functional role of PF A0660w, and has thereby provided the needed background for further exploration of this protein as a potential target for drug discovery.
- Full Text:
- Date Issued: 2014
Studies on existing and new isolates of Cryptophlebia leucotreta granulovirus (CrleGV) on Thaumatotibia leucotreta populations from a range of geographic regions in South Africa
- Authors: Opoku-Debrah, John Kwadwo
- Date: 2012
- Subjects: Cryptophlebia leucotreta Cryptophlebia leucotreta -- South Africa Cryptophlebia leucotreta -- Biological control Cryptophlebia leucotreta -- Life cycles Baculoviruses Lepidoptera -- Biological control Tortricidae -- Biological control Microbial insecticides Pests -- Integrated control
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5778 , http://hdl.handle.net/10962/d1005466
- Description: Baculoviruses are arthropod-specific DNA viruses that are highly virulent to most lepidopteran insects. Their host specificity and compatibility with IPM programmes has enabled their usage as safe microbial insecticides (biopesticides). Two baculovirus-based biopesticides, Cryptogran and Cryptex, which have been formulated with Cryptophlebia leucotreta granulovirus (CrleGV) have been registered for the control of false codling moth (FCM), Thaumatotibia (=Cryptophlebia) leucotreta (Meyrick) (Lepidoptera: Tortricidae) in South Africa and have been successfully incorporated into IPM programmes. However, several studies have indicated that insects can develop resistance to baculovirus-based biopesticide as was shown with field populations of codling moth (CM), Cydia pomonella (L.), which developed resistance to the biopesticide Cydia pomonella granulovirus (CpGV-M) in Europe. Other studies have shown that, under laboratory conditions, FCM populations differ in their susceptibility to Cryptogran and Cryptex. In order to investigate difference in susceptibility as well as protect against any future resistance by FCM to Cryptogran and Cryptex, a search for novel CrleGV-SA isolates from diseased insects from different geographic regions in South Africa was performed. Six geographic populations (Addo, Citrusdal, Marble Hall, Nelspruit, Baths and Mixed colonies) of FCM were established and maintained in the laboratory. Studies on the comparative biological performance based on pupal mass, female fecundity, egg hatch, pupal survival, adult eclosion and duration of life cycle of the Addo, Citrusdal, Marble Hall, Nelspruit and Mixed colonies revealed a low biological performance for the Citrusdal colony. This was attributed to the fact that FCM populations found in the Citrusdal area are not indigenous and may have been introduced from a very limited gene pool from another region. When insects from five colonies, excluding the Baths colony, were subjected to stress by overcrowding , a latent baculovirus resident in the Addo, Nelspruit, Citrusdal, Marble Hall and Mixed colonies was brought into an overt lethal state. Transmission electron micrographs revealed the presence of GV occlusion bodies (OBs) in diseased insects. DNA profiles obtained by single restriction endonuclease analysis of viral genomic DNA using BamH 1, Sa/1, Xba1 , Pst1, Xh01 , Kpn1, Hindlll and EcoR1 revealed five CrleGV-SA isolates latent within the insect populations. The new isolates were named CrleGV-SA Ado, CrleGV-SA Cit, CrleGV-SA Mbl, CrleGVSA Nels and CrleGV-SA Mix isolates. The novelty of the five CrleGV-SA isolates was confirmed by the presence of unique submolar bands, indicating that each isolate was genetically different. PCR amplification and sequencing of the granulin and egt genes from the five isolates revealed several single nucleotide polymorph isms (SNPs) which, in some cases, resulted in amino acid substitutions. DNA profiles from RFLPs, as well as phylogenetic analysis based on granulin and egt sequencing showed the presence of two CrleGV-SA genome types for the CrleGV-SA isolate. Cryptex and CrleGV-SA Ado, CrleGV-SA Cit, CrleGV-SA Mbl and CrleGV-SA Mix were placed as members of Group one CrleGV-SA, and Cryptogran and CrleGV-SA Nels isolate were placed into Group two CrleGV-SA. In droplet feeding bioassays, the median survival time (STso) for neonate larvae inoculated with Group one and two CrleGV-SA were determined to range from 80 - 88 hours (3.33 - 3.67 days), for all five colonies. LDso values for Group one and two CrleGV-SA against neonates from the Addo, Citrusdal, Marble Hall, Nelspruit and Mixed colonies varied between some populations and ranged from 0.80 - 3.12 OBs per larva, indicating some level of variation in host susceptibility. This is the first study reporting the existence of genetically distinct CrleGV baculovirus isolates infecting FCM in different geographical areas of South Africa. The results of this study have broad-ranging implications for our understanding of baculovirus-host interactions and for the application of baculovirus basedbiopesticides.
- Full Text:
- Date Issued: 2012
- Authors: Opoku-Debrah, John Kwadwo
- Date: 2012
- Subjects: Cryptophlebia leucotreta Cryptophlebia leucotreta -- South Africa Cryptophlebia leucotreta -- Biological control Cryptophlebia leucotreta -- Life cycles Baculoviruses Lepidoptera -- Biological control Tortricidae -- Biological control Microbial insecticides Pests -- Integrated control
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5778 , http://hdl.handle.net/10962/d1005466
- Description: Baculoviruses are arthropod-specific DNA viruses that are highly virulent to most lepidopteran insects. Their host specificity and compatibility with IPM programmes has enabled their usage as safe microbial insecticides (biopesticides). Two baculovirus-based biopesticides, Cryptogran and Cryptex, which have been formulated with Cryptophlebia leucotreta granulovirus (CrleGV) have been registered for the control of false codling moth (FCM), Thaumatotibia (=Cryptophlebia) leucotreta (Meyrick) (Lepidoptera: Tortricidae) in South Africa and have been successfully incorporated into IPM programmes. However, several studies have indicated that insects can develop resistance to baculovirus-based biopesticide as was shown with field populations of codling moth (CM), Cydia pomonella (L.), which developed resistance to the biopesticide Cydia pomonella granulovirus (CpGV-M) in Europe. Other studies have shown that, under laboratory conditions, FCM populations differ in their susceptibility to Cryptogran and Cryptex. In order to investigate difference in susceptibility as well as protect against any future resistance by FCM to Cryptogran and Cryptex, a search for novel CrleGV-SA isolates from diseased insects from different geographic regions in South Africa was performed. Six geographic populations (Addo, Citrusdal, Marble Hall, Nelspruit, Baths and Mixed colonies) of FCM were established and maintained in the laboratory. Studies on the comparative biological performance based on pupal mass, female fecundity, egg hatch, pupal survival, adult eclosion and duration of life cycle of the Addo, Citrusdal, Marble Hall, Nelspruit and Mixed colonies revealed a low biological performance for the Citrusdal colony. This was attributed to the fact that FCM populations found in the Citrusdal area are not indigenous and may have been introduced from a very limited gene pool from another region. When insects from five colonies, excluding the Baths colony, were subjected to stress by overcrowding , a latent baculovirus resident in the Addo, Nelspruit, Citrusdal, Marble Hall and Mixed colonies was brought into an overt lethal state. Transmission electron micrographs revealed the presence of GV occlusion bodies (OBs) in diseased insects. DNA profiles obtained by single restriction endonuclease analysis of viral genomic DNA using BamH 1, Sa/1, Xba1 , Pst1, Xh01 , Kpn1, Hindlll and EcoR1 revealed five CrleGV-SA isolates latent within the insect populations. The new isolates were named CrleGV-SA Ado, CrleGV-SA Cit, CrleGV-SA Mbl, CrleGVSA Nels and CrleGV-SA Mix isolates. The novelty of the five CrleGV-SA isolates was confirmed by the presence of unique submolar bands, indicating that each isolate was genetically different. PCR amplification and sequencing of the granulin and egt genes from the five isolates revealed several single nucleotide polymorph isms (SNPs) which, in some cases, resulted in amino acid substitutions. DNA profiles from RFLPs, as well as phylogenetic analysis based on granulin and egt sequencing showed the presence of two CrleGV-SA genome types for the CrleGV-SA isolate. Cryptex and CrleGV-SA Ado, CrleGV-SA Cit, CrleGV-SA Mbl and CrleGV-SA Mix were placed as members of Group one CrleGV-SA, and Cryptogran and CrleGV-SA Nels isolate were placed into Group two CrleGV-SA. In droplet feeding bioassays, the median survival time (STso) for neonate larvae inoculated with Group one and two CrleGV-SA were determined to range from 80 - 88 hours (3.33 - 3.67 days), for all five colonies. LDso values for Group one and two CrleGV-SA against neonates from the Addo, Citrusdal, Marble Hall, Nelspruit and Mixed colonies varied between some populations and ranged from 0.80 - 3.12 OBs per larva, indicating some level of variation in host susceptibility. This is the first study reporting the existence of genetically distinct CrleGV baculovirus isolates infecting FCM in different geographical areas of South Africa. The results of this study have broad-ranging implications for our understanding of baculovirus-host interactions and for the application of baculovirus basedbiopesticides.
- Full Text:
- Date Issued: 2012
The effects of sustained attention, workload and task-related fatigue on physiological measures and performance during a tracking task
- Authors: De Gray Birch, Casey
- Date: 2012
- Subjects: Fatigue -- Physiological aspects -- Research , Attention -- Physiological aspects -- Research , Human engineering -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5120 , http://hdl.handle.net/10962/d1005198 , Fatigue -- Physiological aspects -- Research , Attention -- Physiological aspects -- Research , Human engineering -- Research
- Description: Despite extensive research into the concept of mental fatigue there is as yet no “gold standard” definition or measurement technique available. Because of this a large amount of fatigue-related errors are still seen in the workplace. The complexity of the problem lies with the inability to directly measure mental processes as well as the various endogenous and exogenous factors that interact to produce the experienced fatigue. Fatigue has been divided into sleep-related and task-related fatigue; however the task-related aspect is evident both during normal waking hours as well as during periods of sleep deprivation, therefore this aspect is considered important in the understanding of fatigue in general. The concept of task-related fatigue has further been divided into active and passive fatigue states; however differentiation between the two requires careful consideration. Various physiological measures have been employed in an attempt to gain a better understanding of the mechanisms involved in the generation of fatigue, however often studies have produced dissociating results. The current study considered the task-related fatigue elicited by a tracking task requiring sustained attention, in order to evaluate the usefulness of various cardiovascular and oculomotor measures as indicators of fatigue. A secondary aim was to determine whether the behavioural and physiological parameter responses could be used to infer the type of fatigue incurred (i.e. an active versus passive fatigue state) as well as the energetical mechanisms involved during task performance. A simple driving simulator task was used as the main tracking task, requiring constant attention and concentration. This task was performed for approximately two hours. Three experimental groups (consisting of 14 subjects each) were used: a control group that performed the tracking task only, a group that performed a five minute auditory memory span task concurrently with the driving task after every 20 minutes of pure driving, and a group that performed a visual choice reaction task for five minutes following every 20 minute driving period. The secondary tasks were employed in order to evaluate the extent of resource allocation as well as arousal level. Performance measures included various driving performance parameters, as well as secondary task performance. Physiological measures included heart rate frequency (HR) and various time- and frequency-domain heart rate variability (HRV)parameters, pupil dilation, blink frequency and duration, fixations, and saccadic parameters as well as critical flicker fusion frequency (CFFF). The Borg CR-10 scale was used to evaluate subjective fatigue during the task, and the NASA-TLX was completed following the task. A decline in driving performance over time was supplemented by measures such as HR, HRV and pupil dilation indicating an increase in parasympathetic activity (or a reduction in arousal). An increase in blink frequency was considered as a sign of withdrawal of attentional resources over time. Longer and faster saccades were also evident over time, coupled with shorter fixations. With regards to the secondary task influence, the choice RT task did not affect any behavioural or physiological parameters, thereby contesting the active fatigue theory of resource depletion, as well as implying that the increase in demand for the same resources used by the primary task was insufficient to affect the state of the subjects. The increased load elicited by the memory span task improved driving performance and increased measures of HR, HRV, pupil dilation and blink frequency. Some of these measures produced opposite effects to what was expected; an attempt to explain the dissociation of the various physiological parameters was expressed in terms of arousal, effort and resource theories. Overall, the results indicate that the fatigue and/or reduced arousal accompanying a monotonous sustained attention task can, to some degree, be alleviated through intermittent performance of a secondary task engaging mental resources other than the ones used for the primary task. The degree to which such a task is beneficial, however, requires careful consideration as while an immediate increase in arousal and primary task performance is noted, the impact of the task on general attentional resources may be detrimental in the case of reacting should an emergency situation occur.
- Full Text:
- Date Issued: 2012
- Authors: De Gray Birch, Casey
- Date: 2012
- Subjects: Fatigue -- Physiological aspects -- Research , Attention -- Physiological aspects -- Research , Human engineering -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5120 , http://hdl.handle.net/10962/d1005198 , Fatigue -- Physiological aspects -- Research , Attention -- Physiological aspects -- Research , Human engineering -- Research
- Description: Despite extensive research into the concept of mental fatigue there is as yet no “gold standard” definition or measurement technique available. Because of this a large amount of fatigue-related errors are still seen in the workplace. The complexity of the problem lies with the inability to directly measure mental processes as well as the various endogenous and exogenous factors that interact to produce the experienced fatigue. Fatigue has been divided into sleep-related and task-related fatigue; however the task-related aspect is evident both during normal waking hours as well as during periods of sleep deprivation, therefore this aspect is considered important in the understanding of fatigue in general. The concept of task-related fatigue has further been divided into active and passive fatigue states; however differentiation between the two requires careful consideration. Various physiological measures have been employed in an attempt to gain a better understanding of the mechanisms involved in the generation of fatigue, however often studies have produced dissociating results. The current study considered the task-related fatigue elicited by a tracking task requiring sustained attention, in order to evaluate the usefulness of various cardiovascular and oculomotor measures as indicators of fatigue. A secondary aim was to determine whether the behavioural and physiological parameter responses could be used to infer the type of fatigue incurred (i.e. an active versus passive fatigue state) as well as the energetical mechanisms involved during task performance. A simple driving simulator task was used as the main tracking task, requiring constant attention and concentration. This task was performed for approximately two hours. Three experimental groups (consisting of 14 subjects each) were used: a control group that performed the tracking task only, a group that performed a five minute auditory memory span task concurrently with the driving task after every 20 minutes of pure driving, and a group that performed a visual choice reaction task for five minutes following every 20 minute driving period. The secondary tasks were employed in order to evaluate the extent of resource allocation as well as arousal level. Performance measures included various driving performance parameters, as well as secondary task performance. Physiological measures included heart rate frequency (HR) and various time- and frequency-domain heart rate variability (HRV)parameters, pupil dilation, blink frequency and duration, fixations, and saccadic parameters as well as critical flicker fusion frequency (CFFF). The Borg CR-10 scale was used to evaluate subjective fatigue during the task, and the NASA-TLX was completed following the task. A decline in driving performance over time was supplemented by measures such as HR, HRV and pupil dilation indicating an increase in parasympathetic activity (or a reduction in arousal). An increase in blink frequency was considered as a sign of withdrawal of attentional resources over time. Longer and faster saccades were also evident over time, coupled with shorter fixations. With regards to the secondary task influence, the choice RT task did not affect any behavioural or physiological parameters, thereby contesting the active fatigue theory of resource depletion, as well as implying that the increase in demand for the same resources used by the primary task was insufficient to affect the state of the subjects. The increased load elicited by the memory span task improved driving performance and increased measures of HR, HRV, pupil dilation and blink frequency. Some of these measures produced opposite effects to what was expected; an attempt to explain the dissociation of the various physiological parameters was expressed in terms of arousal, effort and resource theories. Overall, the results indicate that the fatigue and/or reduced arousal accompanying a monotonous sustained attention task can, to some degree, be alleviated through intermittent performance of a secondary task engaging mental resources other than the ones used for the primary task. The degree to which such a task is beneficial, however, requires careful consideration as while an immediate increase in arousal and primary task performance is noted, the impact of the task on general attentional resources may be detrimental in the case of reacting should an emergency situation occur.
- Full Text:
- Date Issued: 2012
"Symbiosis or death" an ecocritical examination of Douglas Livingstone's poetry
- Authors: Stevens, Mariss Patricia
- Date: 2005
- Subjects: Livingstone, Douglas Criticism and interpretation Poets, South African -- 20th century -- Criticism and interpretation Ecology in literature Ecocriticism
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2211 , http://hdl.handle.net/10962/d1002254
- Description: As the quotation in the title of this thesis indicates, Douglas Livingstone states that unless humankind can learn to live in mutuality with the rest of the natural world, the human race faces extinction. Using the relatively new critical approach of ecological literary criticism (ecocriticism) this thesis explores Livingstone's preoccupation with "symbiosis or death" and shows that the predominant theme in his ecologically-orientated poetry is one of ecological despair. Countering this is a tentative thread of hope. Possible resolution lies in the human capacity to attain compassion and wisdom through the judicious use of science, creativity, the power of art and the power of love. Livingstone's ecological preoccupation is thus informed by the universal themes which have pervaded literature since its recorded beginnings. The first chapter examines the concepts of ecology and literary ecocriticism, followed by a chapter on the life and work of Douglas Livingstone, and a review of the critical response to the five collections of poetry which predate A Littoral Zone, his final work. The remaining four chapters offer an analysis of his ecologically-orientated poetry, with the majority of the space given to an examination of A Littoral Zone. The following ecological themes are used in the analysis of the poems: evolutionary theory, humankind's relationship to nature, ecological equilibrium, and ecological destruction. The latter two themes are shown to represent Livingstone's view of the ideal and the real, or the opposites of hope and despair. The analysis interweaves an argument with the existing critical response to this collection. This thesis demonstrates that Livingstone's crucial message – the need for humankind to attain ecological sensibility or “the knowledge of right living” (Ellen Swallow) and so obviate its certain extinction – has largely been ignored in previous critical works.
- Full Text:
- Date Issued: 2005
- Authors: Stevens, Mariss Patricia
- Date: 2005
- Subjects: Livingstone, Douglas Criticism and interpretation Poets, South African -- 20th century -- Criticism and interpretation Ecology in literature Ecocriticism
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2211 , http://hdl.handle.net/10962/d1002254
- Description: As the quotation in the title of this thesis indicates, Douglas Livingstone states that unless humankind can learn to live in mutuality with the rest of the natural world, the human race faces extinction. Using the relatively new critical approach of ecological literary criticism (ecocriticism) this thesis explores Livingstone's preoccupation with "symbiosis or death" and shows that the predominant theme in his ecologically-orientated poetry is one of ecological despair. Countering this is a tentative thread of hope. Possible resolution lies in the human capacity to attain compassion and wisdom through the judicious use of science, creativity, the power of art and the power of love. Livingstone's ecological preoccupation is thus informed by the universal themes which have pervaded literature since its recorded beginnings. The first chapter examines the concepts of ecology and literary ecocriticism, followed by a chapter on the life and work of Douglas Livingstone, and a review of the critical response to the five collections of poetry which predate A Littoral Zone, his final work. The remaining four chapters offer an analysis of his ecologically-orientated poetry, with the majority of the space given to an examination of A Littoral Zone. The following ecological themes are used in the analysis of the poems: evolutionary theory, humankind's relationship to nature, ecological equilibrium, and ecological destruction. The latter two themes are shown to represent Livingstone's view of the ideal and the real, or the opposites of hope and despair. The analysis interweaves an argument with the existing critical response to this collection. This thesis demonstrates that Livingstone's crucial message – the need for humankind to attain ecological sensibility or “the knowledge of right living” (Ellen Swallow) and so obviate its certain extinction – has largely been ignored in previous critical works.
- Full Text:
- Date Issued: 2005
Metal interactions with neural substrates and their role in neurodegeneration
- Authors: Lack, Barbara Anne
- Date: 2003
- Subjects: Nervous system -- Degeneration Neurotoxicology Chemical reactions Metals -- Physiological effect Melatonin -- Physiological effect
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4391 , http://hdl.handle.net/10962/d1005709
- Description: "Life" may be characterized as a controlled stationary flow equilibrium, maintained by energy consuming chemical reactions. The physiological functioning of these life systems include at least 28 of the elements isolated on the periodic table thus far, most of which are metals. However, as with Paracelsus Principle: "The dose makes the poison", there exists a definite link between metal levels, essential and toxic, and the onset of neurodegenerative diseases. The economic costs of brain dysfunction are enormous, but this pales in comparison to the staggering emotional toll on the victims themselves and their families. In an attempt to improve the understanding of the causes of neurodegeneration, this study focuses on one potential aspect: the possible link between metals and neurotransmitter homeostasis utilising a variety of electronanalytical techniques. Adsorptive cathodic stripping voltammetry was employed to investigate the binding affinities and complex formation of melatonin and its precursor serotonin with calcium, potassium, sodium, lithium and aluminium. The results showed that all the metals studied formed complexes with both pineal indoleamines. However, the stability and affmity of the ligands toward the various metals varied greatly. The study suggests a further role for melatonin, that of metalloregulator and possible metal detoxifier in the brain, the in vivo studies which followed will further substantiate this notion. This research additionally focused on the cholinergic system, in particular acetylcholine complex formation studies with mercury, lead, cadmium, copper and zinc using the adsorptive cathodic stripping voltammetry method. The formation and characterisation of a solid mercury-acetylcholine complex lent further strength to the in situ electrochemical complex formation observed. The results showed the preference of acetylcholine for environmentally toxic heavy metals (such as Cd²⁺) over those divalent cations that occur naturally in the body. The possible metalloregulatory role melatonin played in the three brain regIOns: cerebellum, cortex and corpus striatum of male Wistar rats was studied as an in vivo extension of the earlier in vitro studies. Anodic stripping voltammetry was employed to detect metal levels present. The results showed that daily injections of melatonin was responsible for significantly decreasing copper(I), cadmium(II) and lead(II) levels in various regions of the rat brain of those animals that had undergone a pinealectomy in comparison to the saline injected group having undergone the same treatment. Histological and electrochemical stripping techniques were applied to investigate the implications of high A1³⁺ levels in the brain regions, particularly the hippocampus. Melatonin showed signs of promise in indirect symptom alleviation and by significantly decreasing A1³⁺ levels in rats that had been dosed with melatonin prior to A1³⁺ treatments in comparison with the control groups. Finally a preliminary study outlining a method for the production of a calcium selective microelectrode was undertaken. Further work is still needed to optimise the microelectrode production as well as its possible applications. However, whilst the overall conclusions of this entire multidisciplinary study may indeed only be in effect one piece of a very large puzzle on neurodegenerative diseases, this piece will no doubt serve as a building block for further ideas and work in this field.
- Full Text:
- Date Issued: 2003
- Authors: Lack, Barbara Anne
- Date: 2003
- Subjects: Nervous system -- Degeneration Neurotoxicology Chemical reactions Metals -- Physiological effect Melatonin -- Physiological effect
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4391 , http://hdl.handle.net/10962/d1005709
- Description: "Life" may be characterized as a controlled stationary flow equilibrium, maintained by energy consuming chemical reactions. The physiological functioning of these life systems include at least 28 of the elements isolated on the periodic table thus far, most of which are metals. However, as with Paracelsus Principle: "The dose makes the poison", there exists a definite link between metal levels, essential and toxic, and the onset of neurodegenerative diseases. The economic costs of brain dysfunction are enormous, but this pales in comparison to the staggering emotional toll on the victims themselves and their families. In an attempt to improve the understanding of the causes of neurodegeneration, this study focuses on one potential aspect: the possible link between metals and neurotransmitter homeostasis utilising a variety of electronanalytical techniques. Adsorptive cathodic stripping voltammetry was employed to investigate the binding affinities and complex formation of melatonin and its precursor serotonin with calcium, potassium, sodium, lithium and aluminium. The results showed that all the metals studied formed complexes with both pineal indoleamines. However, the stability and affmity of the ligands toward the various metals varied greatly. The study suggests a further role for melatonin, that of metalloregulator and possible metal detoxifier in the brain, the in vivo studies which followed will further substantiate this notion. This research additionally focused on the cholinergic system, in particular acetylcholine complex formation studies with mercury, lead, cadmium, copper and zinc using the adsorptive cathodic stripping voltammetry method. The formation and characterisation of a solid mercury-acetylcholine complex lent further strength to the in situ electrochemical complex formation observed. The results showed the preference of acetylcholine for environmentally toxic heavy metals (such as Cd²⁺) over those divalent cations that occur naturally in the body. The possible metalloregulatory role melatonin played in the three brain regIOns: cerebellum, cortex and corpus striatum of male Wistar rats was studied as an in vivo extension of the earlier in vitro studies. Anodic stripping voltammetry was employed to detect metal levels present. The results showed that daily injections of melatonin was responsible for significantly decreasing copper(I), cadmium(II) and lead(II) levels in various regions of the rat brain of those animals that had undergone a pinealectomy in comparison to the saline injected group having undergone the same treatment. Histological and electrochemical stripping techniques were applied to investigate the implications of high A1³⁺ levels in the brain regions, particularly the hippocampus. Melatonin showed signs of promise in indirect symptom alleviation and by significantly decreasing A1³⁺ levels in rats that had been dosed with melatonin prior to A1³⁺ treatments in comparison with the control groups. Finally a preliminary study outlining a method for the production of a calcium selective microelectrode was undertaken. Further work is still needed to optimise the microelectrode production as well as its possible applications. However, whilst the overall conclusions of this entire multidisciplinary study may indeed only be in effect one piece of a very large puzzle on neurodegenerative diseases, this piece will no doubt serve as a building block for further ideas and work in this field.
- Full Text:
- Date Issued: 2003
Identification of Cowdria ruminantium proteins that induce specific cellular immune responses
- Authors: Van Kleef, Mirinda
- Date: 2002
- Subjects: Ruminants--Pathogens Heartwater
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4061 , http://hdl.handle.net/10962/d1004373
- Description: Cowdria ruminantium (Cowdria) is an obligate intracellular pathogen that causes heartwater in ruminants. Cellular immunity and the type I cytokine IFN-γ have been implicated in protective immunity to heartwater. The aim of this thesis was to identify proteins of the Welgevonden isolate of Cowdria that induce lymphocyte proliferation and IFN-γ production. Differential centrifugation was found to be the simplest and most efficient method of Cowdria purification. Cowdria organisms were fractionated into their constituent proteins of between 11 and 168 kDa by continuous flow electrophoresis. The resulting fractions were tested for their ability to stimulate lymphocyte proliferation in vitro. In an attempt to simulate the natural infective process, peripheral blood mononuclear cells (PBMC) were obtained from two cattle rendered immune by infection and treatment and assayed in proliferation assays with the proteins fractions. In a parallel study, four cattle were immunised with inactivated Cowdria to determine whether their lymphocytes responded similarly. Cowdria-specific proliferation was detected for only a brief period after immunisation by infection with live organisms. This response was only detected again two to three years later. In contrast, PBMC from animals immunised with inactivated organisms were continuously responsive for at least three years. Only Cowdria proteins with molecular masses of 11, 12, 14 to 17 and 19 to 23 kDa induced proliferative responses in PBMC obtained from all six animals. Cell surface phenotypic analysis of Cowdria specific T-cell lines indicated that CD4⁺ lymphocytes were enriched over time with a concomitant increase in antigen-specific proliferation and IFN-γ production. Proteins of molecular masses 13 to 18 kDa induced CD4⁺ lymphocyte proliferation and IFN-γ production by T-cell lines from all the animals tested. Antibodies raised in a chicken and in rabbits to these low molecular weight proteins had low titres and specificity. Two-dimensional electrophoresis indicated that proteins within a single molecular weight range comprised several components with different pIs, revealing the complexity of the Cowdria proteome. This complicates the search for potentially protective antigens. Nevertheless, since they cause proliferation and IFN-γ production by lymphocytes from immunised cattle, these low molecular weight proteins merit further investigation as potential vaccine antigens. , Author: Mirinda van Kleef neé Rossouw
- Full Text:
- Date Issued: 2002
- Authors: Van Kleef, Mirinda
- Date: 2002
- Subjects: Ruminants--Pathogens Heartwater
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4061 , http://hdl.handle.net/10962/d1004373
- Description: Cowdria ruminantium (Cowdria) is an obligate intracellular pathogen that causes heartwater in ruminants. Cellular immunity and the type I cytokine IFN-γ have been implicated in protective immunity to heartwater. The aim of this thesis was to identify proteins of the Welgevonden isolate of Cowdria that induce lymphocyte proliferation and IFN-γ production. Differential centrifugation was found to be the simplest and most efficient method of Cowdria purification. Cowdria organisms were fractionated into their constituent proteins of between 11 and 168 kDa by continuous flow electrophoresis. The resulting fractions were tested for their ability to stimulate lymphocyte proliferation in vitro. In an attempt to simulate the natural infective process, peripheral blood mononuclear cells (PBMC) were obtained from two cattle rendered immune by infection and treatment and assayed in proliferation assays with the proteins fractions. In a parallel study, four cattle were immunised with inactivated Cowdria to determine whether their lymphocytes responded similarly. Cowdria-specific proliferation was detected for only a brief period after immunisation by infection with live organisms. This response was only detected again two to three years later. In contrast, PBMC from animals immunised with inactivated organisms were continuously responsive for at least three years. Only Cowdria proteins with molecular masses of 11, 12, 14 to 17 and 19 to 23 kDa induced proliferative responses in PBMC obtained from all six animals. Cell surface phenotypic analysis of Cowdria specific T-cell lines indicated that CD4⁺ lymphocytes were enriched over time with a concomitant increase in antigen-specific proliferation and IFN-γ production. Proteins of molecular masses 13 to 18 kDa induced CD4⁺ lymphocyte proliferation and IFN-γ production by T-cell lines from all the animals tested. Antibodies raised in a chicken and in rabbits to these low molecular weight proteins had low titres and specificity. Two-dimensional electrophoresis indicated that proteins within a single molecular weight range comprised several components with different pIs, revealing the complexity of the Cowdria proteome. This complicates the search for potentially protective antigens. Nevertheless, since they cause proliferation and IFN-γ production by lymphocytes from immunised cattle, these low molecular weight proteins merit further investigation as potential vaccine antigens. , Author: Mirinda van Kleef neé Rossouw
- Full Text:
- Date Issued: 2002
A framework for interpreting noisy, two-dimensional images, based on a fuzzification of programmed, attributed graph grammars
- Authors: Watkins, Gregory Shroll
- Date: 1998
- Subjects: Music -- Data processing Computer sound processing Artificial intelligence -- Musical applications Fuzzy systems
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4604 , http://hdl.handle.net/10962/d1004862
- Description: This thesis investigates a fuzzy syntactic approach to the interpretation of noisy two-dimensional images. This approach is based on a modification of the attributed graph grammar formalism to utilise fuzzy membership functions in the applicability predicates. As far as we are aware, this represents the first such modification of graph grammars. Furthermore, we develop a method for programming the resultant fuzzy attributed graph grammars through the use of non-deterministic control diagrams. To do this, we modify the standard programming mechanism to allow it to cope with the fuzzy certainty values associated with productions in our grammar. Our objective was to develop a flexible framework which can be used for the recognition of a wide variety of image classes, and which is adept at dealing with noise in these images. Programmed graph grammars are specifically chosen for the ease with which they allow one to specify a new two-dimensional image class. We implement a prototype system for Optical Music Recognition using our framework. This system allows us to test the capabilities of the framework for coping with noise in the context of handwritten music score recognition. Preliminary results from the prototype system show that the framework copes well with noisy images.
- Full Text:
- Date Issued: 1998
- Authors: Watkins, Gregory Shroll
- Date: 1998
- Subjects: Music -- Data processing Computer sound processing Artificial intelligence -- Musical applications Fuzzy systems
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4604 , http://hdl.handle.net/10962/d1004862
- Description: This thesis investigates a fuzzy syntactic approach to the interpretation of noisy two-dimensional images. This approach is based on a modification of the attributed graph grammar formalism to utilise fuzzy membership functions in the applicability predicates. As far as we are aware, this represents the first such modification of graph grammars. Furthermore, we develop a method for programming the resultant fuzzy attributed graph grammars through the use of non-deterministic control diagrams. To do this, we modify the standard programming mechanism to allow it to cope with the fuzzy certainty values associated with productions in our grammar. Our objective was to develop a flexible framework which can be used for the recognition of a wide variety of image classes, and which is adept at dealing with noise in these images. Programmed graph grammars are specifically chosen for the ease with which they allow one to specify a new two-dimensional image class. We implement a prototype system for Optical Music Recognition using our framework. This system allows us to test the capabilities of the framework for coping with noise in the context of handwritten music score recognition. Preliminary results from the prototype system show that the framework copes well with noisy images.
- Full Text:
- Date Issued: 1998
Aspects of the biology of the infaunal bivalve Mollusc Solen cylindraceus (Hanley) in the Kariega estuary
- De Villiers, Casper Johannes
- Authors: De Villiers, Casper Johannes
- Date: 1990
- Subjects: Mollusks -- South Africa -- Eastern Cape Bivalves -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5639 , http://hdl.handle.net/10962/d1005321
- Description: Solen cylindraceus is an infaunal filter-feeding bivalve inhabiting the intertidal mud banks of many southern African estuaries. It is particularly abundant in the Kariega estuary (33°41'S; 26°42'E) where it reaches densities of 400m⁻² (192g shell-free dry wt. m⁻²). The Kariega is a permanently open, marine dominated estuary about 18km in length, and S. cylindraceus is most abundant in its middle and upper reaches. Some physical characteristics of the estuary (temperature, salinity, sediment and water turbidity) are described, and the possible role of these factors in determining the density and distribution of S. cylindraceus within the Kariega estuary, is discussed. The structure of the alimentary system, gills and labial palps of S. cylintfraceus is described, all of which showed no major variation from the "typical" eulamellibranchiate form. Solen cylintfraceus was found to be a euryhaline osmoconformer with a salinity tolerance range of 15-65%. When animals were removed from their burrows, osmotic equilibration of the haemolymph was rapid (1-2 hours). By contrast, in animals left undisturbed in their burrows, osmotic equilibration was retarded (72-204 hours). It is suggested that the observed decrease in the rate of change of haemolymph osmolarity for animals in their burrows is linked to the stability of the interstitial salinity. A temperature tolerance range of 5-44°C was determined for S. cylintfraceus (in situ), in which prolonged exposure to 5°C and 40-45°C (12-36 hours respectively) resulted in a decreased burrowing ability, coma and death. Animal burrowing responses were not affected by temperatures in the range 15-35°C. Field experiments were carried out over several tidal cycles, in which the measurement of crystalline style volume was used as a means of assessing extracellular digestive activity. No major variation in style volume was recorded and it appeared that S. cylindraceus did not exhibit any cyclical pattern of style dissolution and regeneration. It is suggested that S. cylindraceus feeds continuously from the water column during high tide and possibly within its burrow, at or below the water table, during low tide. At a suspensoid concentration of 5Omg l⁻¹, S. cylindraceus was found to filter water almost continuously (90-95% of the time). Time spent filtering dropped to 68% at 100mg l⁻¹ and 32% at 500mg l⁻¹. Filtration rates for summer collected animals (25°C) were 22.86 ± 4.36ml min.⁻¹, some 3ml min.⁻¹ greater than that recorded for winter (16°C) collected animals. Filtration rate may be expressed as a function of shell length by the equations: y=0.247x¹̇⁰⁶⁶ (winter) and y=0.758x⁰̇⁸²⁶ (summer). Solen cylindraceus was capable of acclimating its filtration rate to both high and low temperatures under laboratory conditions. Filtration rate exhibited a thermal optimum in the range 15-35°C, declining at higher and lower temperatures. Q₁₀ values of filtration decreased rapidly from greater than 4 to less than 2, when the thermal optimum was reached. Maximum rates generally occurred at approximately 5°C above the temperature to which the animal had been acclimated. Optimal filtration rates (19-23ml min.⁻¹) were recorded in the salinity range 15-45%. When subjected to abrupt changes in salinity, filtration rates were immediately depressed. The extent and duration of these decreased filtration rates were dependent upon the magnitude and direction of salinity change, and were always less in animals exposed to hyper- than hyposaline conditions. Animals exposed to increased temperature and simultaneous elevated or unchanged salinity, showed a slight increase in filtration rate followed by rapid acclimation. A decrease in both temperature and salinity resulted in an initial decrease in filtration rate and a longer acclimation period. The ability of S. cylindraceus to acclimate fully within a wide temperature and salinity range, and to filter maximally in hypersaline conditions may, in part, explain its unusually high abundance in the Kariega estuary, despite it being close to the southernmost limit of the animal's geographical distribution. No significant difference in flItration rate was recorded at suspensoid concentrations of 5-100mg 1⁻¹. However, at 250 and 500mg l⁻¹ filtration rates decreased significantly, and coincided with increased levels of pseudofaecal production. Solen cylindraceus retained particles down to 2.5-3.0µm with great efficiency (ca. 60-90% efficiency). Below this particle size, retention efficiency decreased rapidly and a net production of particles was recorded below 1.51µm. Particle retention was independent of temperature (15 and 25°C) and salinity (15 and 35%). Use was made of stable carbon isotope analyses (¹³C/¹²C ratios) in an attempt to determine the important food sources of S. cylindraceus within the Kariega estuary. The results obtained demonstrated an enrichment in δ¹³ values for S. cylindraceus from the upper (-27.9%) to the middle (-25%c) and lower (-21.6%o ) reaches of the estuary, with no seasonal variation apparent. The bivalve was substantially more depleted in ¹³C relative to the dominant aquatic macrophytes Zostera capensis (-9.1 to -15.6%o) and Spartina maritima (-12.5%o). The use of δ¹³ alone, however, to unequivocally "pin point" specific food sources of a filter feeder in a predominantly detritus based food web, is limited. It is suggested that in the Kariega estuary, riparian litter and other terrestrially derived vegetation contribute to the carbon pool. A possible contribution of ¹³C depleted food sources via chemoautotrophic and/or anaerobic pathways, to the diet of S. cylindraceus, is suggested.
- Full Text:
- Date Issued: 1990
- Authors: De Villiers, Casper Johannes
- Date: 1990
- Subjects: Mollusks -- South Africa -- Eastern Cape Bivalves -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5639 , http://hdl.handle.net/10962/d1005321
- Description: Solen cylindraceus is an infaunal filter-feeding bivalve inhabiting the intertidal mud banks of many southern African estuaries. It is particularly abundant in the Kariega estuary (33°41'S; 26°42'E) where it reaches densities of 400m⁻² (192g shell-free dry wt. m⁻²). The Kariega is a permanently open, marine dominated estuary about 18km in length, and S. cylindraceus is most abundant in its middle and upper reaches. Some physical characteristics of the estuary (temperature, salinity, sediment and water turbidity) are described, and the possible role of these factors in determining the density and distribution of S. cylindraceus within the Kariega estuary, is discussed. The structure of the alimentary system, gills and labial palps of S. cylintfraceus is described, all of which showed no major variation from the "typical" eulamellibranchiate form. Solen cylintfraceus was found to be a euryhaline osmoconformer with a salinity tolerance range of 15-65%. When animals were removed from their burrows, osmotic equilibration of the haemolymph was rapid (1-2 hours). By contrast, in animals left undisturbed in their burrows, osmotic equilibration was retarded (72-204 hours). It is suggested that the observed decrease in the rate of change of haemolymph osmolarity for animals in their burrows is linked to the stability of the interstitial salinity. A temperature tolerance range of 5-44°C was determined for S. cylintfraceus (in situ), in which prolonged exposure to 5°C and 40-45°C (12-36 hours respectively) resulted in a decreased burrowing ability, coma and death. Animal burrowing responses were not affected by temperatures in the range 15-35°C. Field experiments were carried out over several tidal cycles, in which the measurement of crystalline style volume was used as a means of assessing extracellular digestive activity. No major variation in style volume was recorded and it appeared that S. cylindraceus did not exhibit any cyclical pattern of style dissolution and regeneration. It is suggested that S. cylindraceus feeds continuously from the water column during high tide and possibly within its burrow, at or below the water table, during low tide. At a suspensoid concentration of 5Omg l⁻¹, S. cylindraceus was found to filter water almost continuously (90-95% of the time). Time spent filtering dropped to 68% at 100mg l⁻¹ and 32% at 500mg l⁻¹. Filtration rates for summer collected animals (25°C) were 22.86 ± 4.36ml min.⁻¹, some 3ml min.⁻¹ greater than that recorded for winter (16°C) collected animals. Filtration rate may be expressed as a function of shell length by the equations: y=0.247x¹̇⁰⁶⁶ (winter) and y=0.758x⁰̇⁸²⁶ (summer). Solen cylindraceus was capable of acclimating its filtration rate to both high and low temperatures under laboratory conditions. Filtration rate exhibited a thermal optimum in the range 15-35°C, declining at higher and lower temperatures. Q₁₀ values of filtration decreased rapidly from greater than 4 to less than 2, when the thermal optimum was reached. Maximum rates generally occurred at approximately 5°C above the temperature to which the animal had been acclimated. Optimal filtration rates (19-23ml min.⁻¹) were recorded in the salinity range 15-45%. When subjected to abrupt changes in salinity, filtration rates were immediately depressed. The extent and duration of these decreased filtration rates were dependent upon the magnitude and direction of salinity change, and were always less in animals exposed to hyper- than hyposaline conditions. Animals exposed to increased temperature and simultaneous elevated or unchanged salinity, showed a slight increase in filtration rate followed by rapid acclimation. A decrease in both temperature and salinity resulted in an initial decrease in filtration rate and a longer acclimation period. The ability of S. cylindraceus to acclimate fully within a wide temperature and salinity range, and to filter maximally in hypersaline conditions may, in part, explain its unusually high abundance in the Kariega estuary, despite it being close to the southernmost limit of the animal's geographical distribution. No significant difference in flItration rate was recorded at suspensoid concentrations of 5-100mg 1⁻¹. However, at 250 and 500mg l⁻¹ filtration rates decreased significantly, and coincided with increased levels of pseudofaecal production. Solen cylindraceus retained particles down to 2.5-3.0µm with great efficiency (ca. 60-90% efficiency). Below this particle size, retention efficiency decreased rapidly and a net production of particles was recorded below 1.51µm. Particle retention was independent of temperature (15 and 25°C) and salinity (15 and 35%). Use was made of stable carbon isotope analyses (¹³C/¹²C ratios) in an attempt to determine the important food sources of S. cylindraceus within the Kariega estuary. The results obtained demonstrated an enrichment in δ¹³ values for S. cylindraceus from the upper (-27.9%) to the middle (-25%c) and lower (-21.6%o ) reaches of the estuary, with no seasonal variation apparent. The bivalve was substantially more depleted in ¹³C relative to the dominant aquatic macrophytes Zostera capensis (-9.1 to -15.6%o) and Spartina maritima (-12.5%o). The use of δ¹³ alone, however, to unequivocally "pin point" specific food sources of a filter feeder in a predominantly detritus based food web, is limited. It is suggested that in the Kariega estuary, riparian litter and other terrestrially derived vegetation contribute to the carbon pool. A possible contribution of ¹³C depleted food sources via chemoautotrophic and/or anaerobic pathways, to the diet of S. cylindraceus, is suggested.
- Full Text:
- Date Issued: 1990
Household, production and the organisation of cooperative labour in Shixini, Transkei
- Authors: Heron, Gavin Stewart
- Date: 1990
- Subjects: Xhosa (African people) , Agriculture -- South Africa -- Transkei , Agriculture, Cooperative -- South Africa -- Transkei , Cooperative societies -- South Africa -- Transkei
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2109 , http://hdl.handle.net/10962/d1007448 , Xhosa (African people) , Agriculture -- South Africa -- Transkei , Agriculture, Cooperative -- South Africa -- Transkei , Cooperative societies -- South Africa -- Transkei
- Description: Incidences of cooperation in agricultural activity are widespread phenomena in low-income third world communities. Two forms of cooperative labour groupings are identified in Shixini, Transkei . These are the work party and the ploughing company. It is argued that different organisational principles operate in the different cooperative forms. Work parties are based on principles of neighbourhood whi Ie ploughing companies are organised around kinship relationships. Factors which determine the principle of organisation are social values; the wider South African economic system; ecology; reciprocity; the constitution and structure of the household; economic differentiation; and labour demand and supply. The dissertation is divided into five chapters. The first is an overview of the Shixini social, economic and political systems. This chapter discusses the influence of the wider South African politico-economic system on agricultural production; the Shixini!Transkei political context; kinship and its relation to social organisation; and the likely effects of an agricultural 'betterment' scheme on the area. The second chapter is an overview of agricultural production in Shixini. It is found that the most significant determinants of agricultural production is the structure and constitution of the household and the way in which stock is distributed in the community. The third and fourth chapters describe and analyse Xhosa work parties and ploughing companies . Argument is lead as to the reasons for the specific organisational principles operating in each case. The penultimate chapter is an analysis of sacred and secular ritual. It is argued that both ritual forms reveal cooperative principles of organisation. Secular ritual dramatises the organisation of work parties while sacred ritual dramatises kinship relationships and so, the organisation of ploughing companies. , KMBT_363
- Full Text:
- Date Issued: 1990
- Authors: Heron, Gavin Stewart
- Date: 1990
- Subjects: Xhosa (African people) , Agriculture -- South Africa -- Transkei , Agriculture, Cooperative -- South Africa -- Transkei , Cooperative societies -- South Africa -- Transkei
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2109 , http://hdl.handle.net/10962/d1007448 , Xhosa (African people) , Agriculture -- South Africa -- Transkei , Agriculture, Cooperative -- South Africa -- Transkei , Cooperative societies -- South Africa -- Transkei
- Description: Incidences of cooperation in agricultural activity are widespread phenomena in low-income third world communities. Two forms of cooperative labour groupings are identified in Shixini, Transkei . These are the work party and the ploughing company. It is argued that different organisational principles operate in the different cooperative forms. Work parties are based on principles of neighbourhood whi Ie ploughing companies are organised around kinship relationships. Factors which determine the principle of organisation are social values; the wider South African economic system; ecology; reciprocity; the constitution and structure of the household; economic differentiation; and labour demand and supply. The dissertation is divided into five chapters. The first is an overview of the Shixini social, economic and political systems. This chapter discusses the influence of the wider South African politico-economic system on agricultural production; the Shixini!Transkei political context; kinship and its relation to social organisation; and the likely effects of an agricultural 'betterment' scheme on the area. The second chapter is an overview of agricultural production in Shixini. It is found that the most significant determinants of agricultural production is the structure and constitution of the household and the way in which stock is distributed in the community. The third and fourth chapters describe and analyse Xhosa work parties and ploughing companies . Argument is lead as to the reasons for the specific organisational principles operating in each case. The penultimate chapter is an analysis of sacred and secular ritual. It is argued that both ritual forms reveal cooperative principles of organisation. Secular ritual dramatises the organisation of work parties while sacred ritual dramatises kinship relationships and so, the organisation of ploughing companies. , KMBT_363
- Full Text:
- Date Issued: 1990
Development of a high pressure liquid chromatographic method for the simultaneous analysis of sulphamethoxazole and trimethoprim and its application to biological fluids and dissolution rate studies on solid oral dosage forms
- Authors: Gochin, Rosa
- Date: 1980
- Subjects: High performance liquid chromatography , Body fluids -- Analysis , Drugs -- Dosage forms
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3735 , http://hdl.handle.net/10962/d1001524
- Description: Co-trimoxazole, a combination of a 5-to-l ratio of Sulphamethoxazole (SMZ) and Trimethoprim (TMP) , is a highly effective, broad-spectrum antibacterial agent. Since its introduction in 1968, it has been extensively used in infections of the respiratory and urinary tracts. Co-trimoxazole was developed by the systematic investigation of a series of compounds whose mechanism of action was already known. As early as 1950 synergy between sulphonamides and 2,4-diaminopyrimidines was reported. This was to be expected as both groups of drugs exert their antibacterial activity by interfering with the same biochemical pathway in bacteria. TMP was chosen from among many 2,4-diaminopyrimidines tested because of its good antibacterial activity and low toxicity. SMZ was chosen from the sulphonamides available for combination with TMP because of similarity of their biological half-lives. The widespread use of the combination coupled with the fact that monitoring of the levels of all drugs in the body is becoming increasingly important has stimulated research into rapid and efficient methods for the analysis of TMP and SMZ in biological fluids. Another consequence of the immense popularity of the combination is the appearance on the market of several generic preparations of Co-trimoxazole. It is now generally recognized that drug products from different manufacturers which are chemically equivalent may not be therapeutically equivalent. This is due to the fact that the absorption rate and/or bioavailability (extent of absorption) of a poorly soluble drug may be markedly affected by its release rate from the product and by its subsequent dissolution rate in gastrointestinal fluids. Hence bioequivalence of these various products should be established
- Full Text:
- Date Issued: 1980
- Authors: Gochin, Rosa
- Date: 1980
- Subjects: High performance liquid chromatography , Body fluids -- Analysis , Drugs -- Dosage forms
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3735 , http://hdl.handle.net/10962/d1001524
- Description: Co-trimoxazole, a combination of a 5-to-l ratio of Sulphamethoxazole (SMZ) and Trimethoprim (TMP) , is a highly effective, broad-spectrum antibacterial agent. Since its introduction in 1968, it has been extensively used in infections of the respiratory and urinary tracts. Co-trimoxazole was developed by the systematic investigation of a series of compounds whose mechanism of action was already known. As early as 1950 synergy between sulphonamides and 2,4-diaminopyrimidines was reported. This was to be expected as both groups of drugs exert their antibacterial activity by interfering with the same biochemical pathway in bacteria. TMP was chosen from among many 2,4-diaminopyrimidines tested because of its good antibacterial activity and low toxicity. SMZ was chosen from the sulphonamides available for combination with TMP because of similarity of their biological half-lives. The widespread use of the combination coupled with the fact that monitoring of the levels of all drugs in the body is becoming increasingly important has stimulated research into rapid and efficient methods for the analysis of TMP and SMZ in biological fluids. Another consequence of the immense popularity of the combination is the appearance on the market of several generic preparations of Co-trimoxazole. It is now generally recognized that drug products from different manufacturers which are chemically equivalent may not be therapeutically equivalent. This is due to the fact that the absorption rate and/or bioavailability (extent of absorption) of a poorly soluble drug may be markedly affected by its release rate from the product and by its subsequent dissolution rate in gastrointestinal fluids. Hence bioequivalence of these various products should be established
- Full Text:
- Date Issued: 1980
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