A study of the population dynamics, production and potential yield of the sardine Limnothrissa Miodon (Boulenger) in Lake Kariba
- Authors: Marshall, Brian Eric
- Date: 1987
- Subjects: Fishes Lake Tanganyika sardine
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5191 , http://hdl.handle.net/10962/d1001967
- Description: The limnology of Lake Kariba, especially those aspects that affect sardine biology, are described. The hydrological regime of the lake is seen as a major influence and may be one of the reasons why the fish are very much smaller in Kariba than they are in Lakes Tanganyika or Kivu. Growth was reassessed and there appeared to be a correlation between rates of growth and limnological parameters. In particular, the fish appeared to grow faster, but smaller, in the man-made lakes and this may be a consequence of food shortages brought about by their hydrological characteristics. Mortality rates were also much higher in Kariba and this tended to support the view that the lake is a relatively unsuitable habitat for the sardines. However, estimates of biomass, expressed in terms of lake volume, contradicted this as they were very similar in both Kariba and Tanganyika. The life history strategy of Limnothrissa in Kariba was therefore to reduce its size and increase its productivity in order to maintain the maximum possible biomass and its very high P/B̄ ratio was probably the means by which this was achieved. In terms of lake volume the predicted yields from the pelagic communities of Kariba and Tanganyika were very similar, equivalent to about 20 000 t annually for Kariba. This is close to the yield predicted by several empirical models and the fishery now appears to be entering a phase where increases in effort will not be matched by increased yields. The mechanisms for controlling effort in the fishery appear to be inadequate and particular concern was expressed about the lack of co-ordination between the Zimbabwean and Zambian fishery authorities in planning the development of this shared resource.
- Full Text:
- Date Issued: 1987
- Authors: Marshall, Brian Eric
- Date: 1987
- Subjects: Fishes Lake Tanganyika sardine
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5191 , http://hdl.handle.net/10962/d1001967
- Description: The limnology of Lake Kariba, especially those aspects that affect sardine biology, are described. The hydrological regime of the lake is seen as a major influence and may be one of the reasons why the fish are very much smaller in Kariba than they are in Lakes Tanganyika or Kivu. Growth was reassessed and there appeared to be a correlation between rates of growth and limnological parameters. In particular, the fish appeared to grow faster, but smaller, in the man-made lakes and this may be a consequence of food shortages brought about by their hydrological characteristics. Mortality rates were also much higher in Kariba and this tended to support the view that the lake is a relatively unsuitable habitat for the sardines. However, estimates of biomass, expressed in terms of lake volume, contradicted this as they were very similar in both Kariba and Tanganyika. The life history strategy of Limnothrissa in Kariba was therefore to reduce its size and increase its productivity in order to maintain the maximum possible biomass and its very high P/B̄ ratio was probably the means by which this was achieved. In terms of lake volume the predicted yields from the pelagic communities of Kariba and Tanganyika were very similar, equivalent to about 20 000 t annually for Kariba. This is close to the yield predicted by several empirical models and the fishery now appears to be entering a phase where increases in effort will not be matched by increased yields. The mechanisms for controlling effort in the fishery appear to be inadequate and particular concern was expressed about the lack of co-ordination between the Zimbabwean and Zambian fishery authorities in planning the development of this shared resource.
- Full Text:
- Date Issued: 1987
The growth and reproduction of Patella granularis (Mollusca : patellogastropoda) on the south-east coast of South Africa
- Authors: Vat, Laura Suzanne
- Date: 2000
- Subjects: Patellidae Limpets -- South Africa Mollusks -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5702 , http://hdl.handle.net/10962/d1005388
- Description: Aspects of the biology and ecology of Patella granularis were investigated along a 130km stretch of the south-east coast of South Africa. Distribution, biomass, density and population structure were investigated at seven localities. In addition, a more detailed study of the growth rate and reproductive biology of populations inhabiting three different substrata (aeolianite, quartzitic sandstone and mussel shells) was conducted. The genetic relationships between these three populations was also examined, as was the foraging behaviour of the limpets inhabiting an aeolianite and a quartzitic sandstone shore. Finally, differences in food availability on the different substrata were studied. On the south-east coast, P. granularis has a wide intertidal distribution, occurring from the upper Balanoid zone through to the Cochlear zone, where it is a common inhabitant of mussel shells. The mean shell length of P. granularis was found to decrease down the shore. The largest limpets (46.6 mm shell length) were found on an offshore island in Algoa Bay. At most localities investigated, the sex ratio deviated from a 1:1 ratio with more males than females being recorded on five shores. Both limpet density and biomass were lower on the south-east coast when compared to data published for west coast populations. On the south-east coast, both density and dry biomass were highest in the lower Balanoid zone. Allozyme electrophoresis indicated that P. granularis inhabiting aeolianite, quartzitic sandstone and mussel shells are all part of a single population. Extremely high genetic identity values (0.998), low levels of heterozygosities (0.035 - 0.061), low levels of polymorphisms (25% - 31%) and low FST values (0.021) all suggest that the three populations of P. granularis form a common breeding group, despite the high levels of phenotypic plasticity observed. On all shores, P. granularis was found to grow allometrically, increasing in shell height more rapidly than shell length. Estimation of the growth rate (determined by the Von Bertalanffy growth model) of P. granularis suggested that limpets inhabiting the mussel shells grew more slowly, and attained a smaller maximum size, than those inhabiting both the aeolianite and the quartzite (K = 0.25, 0.32 and 0.33 respectively; 27.12 mm, 31.89 mm and 32.96 mm respectively). Previous work has shown that west coast P. granularis grow more quickly (K = 0.7) and reach a greater size (. 40 mm). Translocation of limpets among sites suggested that limpet size in the mussel beds was spatially constrained. Shell microgrowth bands were deposited tidally, but could not be used for aging limpets due to shell erosion. Limpets from the aeolianite had the greatest reproductive fitness, producing more eggs (.366 000/limpet) than those inhabiting quartzite (.119 500/limpet) or mussel shell limpets (.85 800/limpet). Aeolianite limpets also spawned throughout the year, whereas those from the quartzite and mussel shells spawned twice a year (once in winter and once in summer) although a great deal of interannual variability was observed. The onset of sexual maturity occurred at a similar age in all limpets (1 - 2 years) and is probably genetically entrenched. P. granularis inhabiting both an aeolianite and a quartzitic shore were active during nocturnal low tides. All limpets returned to a home scar after foraging. Whilst foraging, limpets inhabiting the aeolianite shore moved shorter distances (.17 cm) at a slower rate than those from quartzite (.30 cm). Limpets that were translocated from one substratum to the other initially moved similar distances to the source group, but after a maximum period of one week, moved distances that mirrored those moved by the resident limpets. Neither season nor tidal phase influenced the distances foraged. No directionality in foraging was found. Wear of radula teeth, particularly the pluricuspid tooth, was greater in limpets from the quartzite. It is hypothesised that the observed differences in life-history parameters and foraging behaviour of limpets both within the south-east coast and between the west and south-east coasts are related to food abundance. Chlorophyll-a, and hence microalgal biomass, was consistently higher on aeolianite (.2.5 times) than on both quartzite and mussel shells. Estimates of chlorophyll-a were higher (although not significantly) in winter. Previous studies determined that primary productivity is also higher along the west coast. Finally, the lack of evidence for migration of limpets from the low-shore to high-shore in south-east coast P. granularis is discussed. It is suggested that this species settles opportunistically within its physiological tolerances and responds morphologically to localised environmental conditions.
- Full Text:
- Date Issued: 2000
- Authors: Vat, Laura Suzanne
- Date: 2000
- Subjects: Patellidae Limpets -- South Africa Mollusks -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5702 , http://hdl.handle.net/10962/d1005388
- Description: Aspects of the biology and ecology of Patella granularis were investigated along a 130km stretch of the south-east coast of South Africa. Distribution, biomass, density and population structure were investigated at seven localities. In addition, a more detailed study of the growth rate and reproductive biology of populations inhabiting three different substrata (aeolianite, quartzitic sandstone and mussel shells) was conducted. The genetic relationships between these three populations was also examined, as was the foraging behaviour of the limpets inhabiting an aeolianite and a quartzitic sandstone shore. Finally, differences in food availability on the different substrata were studied. On the south-east coast, P. granularis has a wide intertidal distribution, occurring from the upper Balanoid zone through to the Cochlear zone, where it is a common inhabitant of mussel shells. The mean shell length of P. granularis was found to decrease down the shore. The largest limpets (46.6 mm shell length) were found on an offshore island in Algoa Bay. At most localities investigated, the sex ratio deviated from a 1:1 ratio with more males than females being recorded on five shores. Both limpet density and biomass were lower on the south-east coast when compared to data published for west coast populations. On the south-east coast, both density and dry biomass were highest in the lower Balanoid zone. Allozyme electrophoresis indicated that P. granularis inhabiting aeolianite, quartzitic sandstone and mussel shells are all part of a single population. Extremely high genetic identity values (0.998), low levels of heterozygosities (0.035 - 0.061), low levels of polymorphisms (25% - 31%) and low FST values (0.021) all suggest that the three populations of P. granularis form a common breeding group, despite the high levels of phenotypic plasticity observed. On all shores, P. granularis was found to grow allometrically, increasing in shell height more rapidly than shell length. Estimation of the growth rate (determined by the Von Bertalanffy growth model) of P. granularis suggested that limpets inhabiting the mussel shells grew more slowly, and attained a smaller maximum size, than those inhabiting both the aeolianite and the quartzite (K = 0.25, 0.32 and 0.33 respectively; 27.12 mm, 31.89 mm and 32.96 mm respectively). Previous work has shown that west coast P. granularis grow more quickly (K = 0.7) and reach a greater size (. 40 mm). Translocation of limpets among sites suggested that limpet size in the mussel beds was spatially constrained. Shell microgrowth bands were deposited tidally, but could not be used for aging limpets due to shell erosion. Limpets from the aeolianite had the greatest reproductive fitness, producing more eggs (.366 000/limpet) than those inhabiting quartzite (.119 500/limpet) or mussel shell limpets (.85 800/limpet). Aeolianite limpets also spawned throughout the year, whereas those from the quartzite and mussel shells spawned twice a year (once in winter and once in summer) although a great deal of interannual variability was observed. The onset of sexual maturity occurred at a similar age in all limpets (1 - 2 years) and is probably genetically entrenched. P. granularis inhabiting both an aeolianite and a quartzitic shore were active during nocturnal low tides. All limpets returned to a home scar after foraging. Whilst foraging, limpets inhabiting the aeolianite shore moved shorter distances (.17 cm) at a slower rate than those from quartzite (.30 cm). Limpets that were translocated from one substratum to the other initially moved similar distances to the source group, but after a maximum period of one week, moved distances that mirrored those moved by the resident limpets. Neither season nor tidal phase influenced the distances foraged. No directionality in foraging was found. Wear of radula teeth, particularly the pluricuspid tooth, was greater in limpets from the quartzite. It is hypothesised that the observed differences in life-history parameters and foraging behaviour of limpets both within the south-east coast and between the west and south-east coasts are related to food abundance. Chlorophyll-a, and hence microalgal biomass, was consistently higher on aeolianite (.2.5 times) than on both quartzite and mussel shells. Estimates of chlorophyll-a were higher (although not significantly) in winter. Previous studies determined that primary productivity is also higher along the west coast. Finally, the lack of evidence for migration of limpets from the low-shore to high-shore in south-east coast P. granularis is discussed. It is suggested that this species settles opportunistically within its physiological tolerances and responds morphologically to localised environmental conditions.
- Full Text:
- Date Issued: 2000
Perspectives on land and water politics at Mushandike Irrigation Scheme, Masvingo, Zimbabwe
- Authors: Mafukidze, Jonathan
- Date: 2019
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/76479 , vital:30573
- Description: Access to, control and ownership of land and water, amongst other natural resources in Zimbabwe, shape and affect rural lives, livelihoods, social relations and social organisation. Rural poverty has been entrenched and exacerbated by, amongst other factors, highly restricted access to these scarce resources. Historically, Zimbabwe’s rural areas (such as communal areas, smallholder irrigation schemes and resettlement areas) have existed as sites of struggles where contestations and negotiations over access to, control or ownership of these resources have taken place. Resultantly, multifaceted and dynamic social relations have been weaved and contested social spaces carved out. In rural Zimbabwe, contestations have tended to be complex, nuanced and intricate, working themselves out in different ways across time and space. In their heightened and more visible state, they have been characterised by violent physical expressions which, in the history of the country, involved two wars of liberation, the First Chimurenga (1896-1897) and the Second Chimurenga (1960s to 1980). The most recent violent manifestation was through nation-wide land invasions, politically christened the Third Chimurenga, which peaked in 2000 and continued sporadically to this day. Few studies on smallholder irrigation schemes in Zimbabwe have focused on understanding how contestations for access to scarce land and water resources are framed and negotiated at the local level. Cognisant of this lacuna, this thesis uses social constructionism in examining, as a case study, Mushandike Smallholder Irrigation Scheme in Masvingo Province in order to understand and analyse how land and water politics occur at the local level. The study deploys a qualitative research methodology approach in examining local water and land politics, which involved original irrigation beneficiaries and more recent land invaders. Findings of the thesis indicate that land and water shortages have increased considerably in the past two decades at the irrigation scheme due to the influx of land invaders into the scheme. This influx has had a negative impact on agricultural production and other livelihood strategies. Both scheme members and land invaders lay claim to land and water at Mushandike. These claims are intricately constructed and contested, and they are linked to broader issues such as partisan party-politics, policy developments, and tradition, origin, indigeneity and belonging. Though the struggles over land and water at Mushandike are firmly rooted in the concrete conditions of existence and experiences of beneficiaries and land invaders, external actors such as political leaders, state bureaucrats and traditional chiefs tend to complicate and intensify the contestations.
- Full Text:
- Date Issued: 2019
- Authors: Mafukidze, Jonathan
- Date: 2019
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/76479 , vital:30573
- Description: Access to, control and ownership of land and water, amongst other natural resources in Zimbabwe, shape and affect rural lives, livelihoods, social relations and social organisation. Rural poverty has been entrenched and exacerbated by, amongst other factors, highly restricted access to these scarce resources. Historically, Zimbabwe’s rural areas (such as communal areas, smallholder irrigation schemes and resettlement areas) have existed as sites of struggles where contestations and negotiations over access to, control or ownership of these resources have taken place. Resultantly, multifaceted and dynamic social relations have been weaved and contested social spaces carved out. In rural Zimbabwe, contestations have tended to be complex, nuanced and intricate, working themselves out in different ways across time and space. In their heightened and more visible state, they have been characterised by violent physical expressions which, in the history of the country, involved two wars of liberation, the First Chimurenga (1896-1897) and the Second Chimurenga (1960s to 1980). The most recent violent manifestation was through nation-wide land invasions, politically christened the Third Chimurenga, which peaked in 2000 and continued sporadically to this day. Few studies on smallholder irrigation schemes in Zimbabwe have focused on understanding how contestations for access to scarce land and water resources are framed and negotiated at the local level. Cognisant of this lacuna, this thesis uses social constructionism in examining, as a case study, Mushandike Smallholder Irrigation Scheme in Masvingo Province in order to understand and analyse how land and water politics occur at the local level. The study deploys a qualitative research methodology approach in examining local water and land politics, which involved original irrigation beneficiaries and more recent land invaders. Findings of the thesis indicate that land and water shortages have increased considerably in the past two decades at the irrigation scheme due to the influx of land invaders into the scheme. This influx has had a negative impact on agricultural production and other livelihood strategies. Both scheme members and land invaders lay claim to land and water at Mushandike. These claims are intricately constructed and contested, and they are linked to broader issues such as partisan party-politics, policy developments, and tradition, origin, indigeneity and belonging. Though the struggles over land and water at Mushandike are firmly rooted in the concrete conditions of existence and experiences of beneficiaries and land invaders, external actors such as political leaders, state bureaucrats and traditional chiefs tend to complicate and intensify the contestations.
- Full Text:
- Date Issued: 2019
A critical evaluation of inter-jurisdictional rules in the South African value-added tax system
- Authors: Schneider, Ferdinand Dirk
- Date: 2017
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/7971 , vital:21329
- Description: This study analysed the current inter-jurisdictional rules in the South African Value-Added Tax (VAT) system, identified shortcomings, and proposed legislative amendments or additions to address these shortcomings. The research was conducted within an interpretative post positivism paradigm, applied a qualitative research methodology, and a doctrinal research method. A detailed review of the literature was conducted to establish the theoretical basis of a good tax system and the theory underpinning indirect and consumption taxation. The literature review also included an in-depth analysis of the South African VAT system and its treatment of resident and non-resident businesses with a South African physical or economic reach, and its treatment of local and cross-border transactions, including imported services. The literature review also considered the international VAT treatment of these transactions. To obtain a wider range of expert opinions regarding shortcomings in inter-jurisdictional rules in the South African VAT system, data was collected through structured interviews with South African and global VAT and indirect tax experts, using a questionnaire that was specifically designed for this purpose. This study proposed amendments and additions to the VAT Act, dealing with the VAT registration of non-resident suppliers; addressing various issues relating to the interjurisdictional VAT rate; proposing measures in connection with imported services; and legislating the intention of the legislator to tax final utilisation or consumption. The study finally recommended the introduction of a general place of supply rule linked to residency; specific place of supply rules for electronic, broadcasting, and telecommunication services; and zero rating provisions for electronic, broadcasting, and telecommunication services provided to non-resident suppliers by resident suppliers for services initiated outside South Africa.
- Full Text:
- Date Issued: 2017
- Authors: Schneider, Ferdinand Dirk
- Date: 2017
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/7971 , vital:21329
- Description: This study analysed the current inter-jurisdictional rules in the South African Value-Added Tax (VAT) system, identified shortcomings, and proposed legislative amendments or additions to address these shortcomings. The research was conducted within an interpretative post positivism paradigm, applied a qualitative research methodology, and a doctrinal research method. A detailed review of the literature was conducted to establish the theoretical basis of a good tax system and the theory underpinning indirect and consumption taxation. The literature review also included an in-depth analysis of the South African VAT system and its treatment of resident and non-resident businesses with a South African physical or economic reach, and its treatment of local and cross-border transactions, including imported services. The literature review also considered the international VAT treatment of these transactions. To obtain a wider range of expert opinions regarding shortcomings in inter-jurisdictional rules in the South African VAT system, data was collected through structured interviews with South African and global VAT and indirect tax experts, using a questionnaire that was specifically designed for this purpose. This study proposed amendments and additions to the VAT Act, dealing with the VAT registration of non-resident suppliers; addressing various issues relating to the interjurisdictional VAT rate; proposing measures in connection with imported services; and legislating the intention of the legislator to tax final utilisation or consumption. The study finally recommended the introduction of a general place of supply rule linked to residency; specific place of supply rules for electronic, broadcasting, and telecommunication services; and zero rating provisions for electronic, broadcasting, and telecommunication services provided to non-resident suppliers by resident suppliers for services initiated outside South Africa.
- Full Text:
- Date Issued: 2017
Representation and use of indigenous heritage constructs : implications for the quality and relevance of heritage education in post colonial southern Africa
- Authors: Zazu, Cryton
- Date: 2013
- Subjects: Albany Museum (Grahamstown, South Africa) Cultural property -- Conservation and restoration -- Research -- Africa, Southern Great Zimbabwe (Extinct city) Indigenous peoples -- Material culture -- Africa, Southern Anthropological museums and collections -- Management -- Research -- Africa, Southern Cultural property -- Management -- Research Ethnoscience -- Study and teaching -- Africa, Southern
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1407 , http://hdl.handle.net/10962/d1002015
- Description: This study explores representation and use of indigenous heritage constructs with a view to identifying implications thereof for the quality and relevance of heritage education practices in post colonial southern Africa. Framed within a critical hermeneutic research paradigm under-laboured by critical realist ontology, the study was conducted using a multiple case study research design. The data collection protocol was three-phased, starting with a process of contextual profiling, within which insights were gained into discourses shaping the constitution and orientation of heritage education practices at the Albany Museum in South Africa, the Great Zimbabwe Monument in Zimbabwe and the Supa Ngwao Museum in Botswana. The second phase of data collection entailed modelling workshops in which educators engaged in discussion around the status of heritage education in post apartheid South Africa. This highlighted, through modelled lessons, some of the tensions, challenges and implications for working with notions of social transformation and inclusivity in heritage education. The third phase of data collection involved in-depth interviews. Twelve purposively selected research participants were interviewed between 2010 and 2011. Data generated across the study was processed and subjected to different levels of critical discourse analysis. Besides noting how heritage education in post colonial southern Africa is poorly framed and under-researched, this study revealed that current forms of representing indigenous heritage constructs are influenced more by socio-political discourses than the need to protect and conserve local heritage resources. The study also noted that the observed heritage education practices are oriented more towards addressing issues related to marginalisation and alienation of indigenous cultures and practices, than enhancing learners’ agency to manage and utilise local heritage resources in a more sustainable ways. Based on these findings the study recommends re-positioning heritage education within the framework of Education for Sustainable Development (ESD). ESD acknowledges both issues of social justice and the dialectical interplay between nature and culture; as such, it may allow for representation and use of indigenous heritage constructs in ways that expand current political orientations to include sustainability as an additional objective of heritage education. Given that little research focusing on heritage education has been undertaken within southern Africa, the findings of this study provide a basis upon which future research may emerge.
- Full Text:
- Date Issued: 2013
- Authors: Zazu, Cryton
- Date: 2013
- Subjects: Albany Museum (Grahamstown, South Africa) Cultural property -- Conservation and restoration -- Research -- Africa, Southern Great Zimbabwe (Extinct city) Indigenous peoples -- Material culture -- Africa, Southern Anthropological museums and collections -- Management -- Research -- Africa, Southern Cultural property -- Management -- Research Ethnoscience -- Study and teaching -- Africa, Southern
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1407 , http://hdl.handle.net/10962/d1002015
- Description: This study explores representation and use of indigenous heritage constructs with a view to identifying implications thereof for the quality and relevance of heritage education practices in post colonial southern Africa. Framed within a critical hermeneutic research paradigm under-laboured by critical realist ontology, the study was conducted using a multiple case study research design. The data collection protocol was three-phased, starting with a process of contextual profiling, within which insights were gained into discourses shaping the constitution and orientation of heritage education practices at the Albany Museum in South Africa, the Great Zimbabwe Monument in Zimbabwe and the Supa Ngwao Museum in Botswana. The second phase of data collection entailed modelling workshops in which educators engaged in discussion around the status of heritage education in post apartheid South Africa. This highlighted, through modelled lessons, some of the tensions, challenges and implications for working with notions of social transformation and inclusivity in heritage education. The third phase of data collection involved in-depth interviews. Twelve purposively selected research participants were interviewed between 2010 and 2011. Data generated across the study was processed and subjected to different levels of critical discourse analysis. Besides noting how heritage education in post colonial southern Africa is poorly framed and under-researched, this study revealed that current forms of representing indigenous heritage constructs are influenced more by socio-political discourses than the need to protect and conserve local heritage resources. The study also noted that the observed heritage education practices are oriented more towards addressing issues related to marginalisation and alienation of indigenous cultures and practices, than enhancing learners’ agency to manage and utilise local heritage resources in a more sustainable ways. Based on these findings the study recommends re-positioning heritage education within the framework of Education for Sustainable Development (ESD). ESD acknowledges both issues of social justice and the dialectical interplay between nature and culture; as such, it may allow for representation and use of indigenous heritage constructs in ways that expand current political orientations to include sustainability as an additional objective of heritage education. Given that little research focusing on heritage education has been undertaken within southern Africa, the findings of this study provide a basis upon which future research may emerge.
- Full Text:
- Date Issued: 2013
Curriculum outcomes, teaching practices and learner competencies in isiXhosa in three Grahamstown schools
- Authors: Fobe, Mila Pamella
- Date: 2014
- Subjects: Xhosa language -- Study and teaching (Primary) -- South Africa -- Grahamstown Xhosa language -- Study and teaching (Secondary) -- South Africa -- Grahamstown Language and education -- South Africa -- Grahamstown Curriculum planning Second language acquisition Public schools -- South Africa -- Grahamstown Language policy -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3630 , http://hdl.handle.net/10962/d1012072
- Description: This study looks at the curriculum outcomes, teaching practices and learner competencies in isiXhosa at three Eastern Cape schools and across three different grades, 7-9. It explores the link between language learning and teaching as well as the teaching strategies used within the classroom. In particular, the study seeks to analyse how isiXhosa is taught at three different levels of instruction, namely at Home Language (HL), First Additional Language (FAL) and Second Additional Language (SAL) levels. Qualitative methods were used, and the study took the form of interpretive case studies within the respective schools. The purpose of using multiple case studies was to investigate the reality within the three sites selected. The three schools had three extreme settings, in the sense that one of the schools is a rich isiXhosa environment and the other two schools are English environments. The tools used for data gathering were interviews, classroom observations, and an analysis of documents from the Department of Basic Education. Data was then presented and analysed in Chapter 4 and 5 against the backdrop of an extensive literature review in Chapter 2 as well as a detailed methodological approach as outlined in Chapter 3. One of the findings of this research indicates that in two of the schools the teaching culture is largely from a western perspective, whereas in one of the schools the learners are primarily isiXhosa speaking and teachers use a different linguistic approach to imparting knowledge. In the private and ex-Model C school it was found that a lack of exposure to isiXhosa is the primary cause of language problems for L2 learners. Secondly the L1 is not appropriately maintained or promoted in the school environment because it is presumed that learners are sufficiently exposed to their L1 at home. The research found therefore that in this particular schooling environment there is an inconsistency between the curricula that is taught in relation to the linguistic abilities of the learners, many of whom are mother tongue speakers of isiXhosa. Furthermore and more generally, it was found that teachers are still not well informed concerning South Africa’s Language-in-Education-Policy and there is a need for more inservice training that will focus on the nature of additional language acquisition in order to address the challenges of teaching these languages. The thesis concludes that extensive work needs to be done in order to reposition the teaching of isiXhosa at all three levels, but particularly at FAL level. This research shows that there is a disjuncture between the proposed curriculum/learning outcomes and the standards or levels achieved by the learners, more especially at FAL and SAL where oral proficiency in isiXhosa remains a challenge. Specific recommendations are contained in the final chapter of the thesis which also makes reference to the draft policy of the Ministry of Basic Education regarding the incremental introduction of the teaching of African languages from 2014 onwards. This thesis also makes takes as a point of departure the importance of multilingualism in a multicultural society such as South Africa where language is suggested as a strong factor in the fostering of social cohesion. It is for this reason that the thesis argues that the expert teaching of African languages, in this case isiXhosa, at both mother tongue and second language levels is of fundamental importance to the future of South African society.
- Full Text:
- Date Issued: 2014
- Authors: Fobe, Mila Pamella
- Date: 2014
- Subjects: Xhosa language -- Study and teaching (Primary) -- South Africa -- Grahamstown Xhosa language -- Study and teaching (Secondary) -- South Africa -- Grahamstown Language and education -- South Africa -- Grahamstown Curriculum planning Second language acquisition Public schools -- South Africa -- Grahamstown Language policy -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3630 , http://hdl.handle.net/10962/d1012072
- Description: This study looks at the curriculum outcomes, teaching practices and learner competencies in isiXhosa at three Eastern Cape schools and across three different grades, 7-9. It explores the link between language learning and teaching as well as the teaching strategies used within the classroom. In particular, the study seeks to analyse how isiXhosa is taught at three different levels of instruction, namely at Home Language (HL), First Additional Language (FAL) and Second Additional Language (SAL) levels. Qualitative methods were used, and the study took the form of interpretive case studies within the respective schools. The purpose of using multiple case studies was to investigate the reality within the three sites selected. The three schools had three extreme settings, in the sense that one of the schools is a rich isiXhosa environment and the other two schools are English environments. The tools used for data gathering were interviews, classroom observations, and an analysis of documents from the Department of Basic Education. Data was then presented and analysed in Chapter 4 and 5 against the backdrop of an extensive literature review in Chapter 2 as well as a detailed methodological approach as outlined in Chapter 3. One of the findings of this research indicates that in two of the schools the teaching culture is largely from a western perspective, whereas in one of the schools the learners are primarily isiXhosa speaking and teachers use a different linguistic approach to imparting knowledge. In the private and ex-Model C school it was found that a lack of exposure to isiXhosa is the primary cause of language problems for L2 learners. Secondly the L1 is not appropriately maintained or promoted in the school environment because it is presumed that learners are sufficiently exposed to their L1 at home. The research found therefore that in this particular schooling environment there is an inconsistency between the curricula that is taught in relation to the linguistic abilities of the learners, many of whom are mother tongue speakers of isiXhosa. Furthermore and more generally, it was found that teachers are still not well informed concerning South Africa’s Language-in-Education-Policy and there is a need for more inservice training that will focus on the nature of additional language acquisition in order to address the challenges of teaching these languages. The thesis concludes that extensive work needs to be done in order to reposition the teaching of isiXhosa at all three levels, but particularly at FAL level. This research shows that there is a disjuncture between the proposed curriculum/learning outcomes and the standards or levels achieved by the learners, more especially at FAL and SAL where oral proficiency in isiXhosa remains a challenge. Specific recommendations are contained in the final chapter of the thesis which also makes reference to the draft policy of the Ministry of Basic Education regarding the incremental introduction of the teaching of African languages from 2014 onwards. This thesis also makes takes as a point of departure the importance of multilingualism in a multicultural society such as South Africa where language is suggested as a strong factor in the fostering of social cohesion. It is for this reason that the thesis argues that the expert teaching of African languages, in this case isiXhosa, at both mother tongue and second language levels is of fundamental importance to the future of South African society.
- Full Text:
- Date Issued: 2014
Isolation and characterization of genes encoding heat shock protein 70s (hsp 70s) from two species of the coelacanth, Latimeria chalumnae and Latimeria menadoensis
- Modisakeng, Keoagile William
- Authors: Modisakeng, Keoagile William
- Date: 2007
- Subjects: Coelacanth Coelacanth -- Genetics Heat shock proteins Molecular chaperones Proteins -- Analysis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3971 , http://hdl.handle.net/10962/d1004030
- Description: The extant coelacanths have a close resemblance to the coelacanth fossil records dating back to 230mya. Like their predecessors, the extant coelacanths inhabit rocky caves at a depth of 100-300m below sea level. In the Comoros, the water temperature at these depths is estimated to fluctuate between 14-20°C. High-level adaptation to these environment and lack of competition are thought to have led to the morphological uniformity and slow change throughout the history of the coelacanths. Under stress conditions, proteins unfold or misfold leading to the formation of aggregates. Molecular chaperones facilitate the correct folding of other proteins so that they can attain a stable tertiary structure. In addition, molecular chaperones aid the refolding of denatured proteins and the degradation of terminally misfolded protein after cellular stress. Heat shock proteins form one of the major classes of molecular chaperones. Here we show that, despite high-level adaptation to a unique habitat and slow change, the genome of the coelacanth encodes the major and highly conserved molecular chaperone, Hsp70. Latimeria menadoensis and Latimeria chalumnae contain intronless hsp70 genes encoding Hsp70 proteins archetypal of known Hsp70s. Based on the coelacanth codon usage, we have shown that bacterial protein expression systems, particularly Escherichia coli, may not be appropriate for the overproduction of coelacanth Hsp70s and coelacanth proteins in general. Also interesting, was the discovery that like the rat Hsc70, the L. menadoensis Hsp70 could not reverse thermal sensitivity in a temperate sensitive E. coli DnaK mutant strain, BB2362. We also report the successful isolation of a 1.2 kb region of L. menadoensis hsp70 upstream regulatory region. This region contain three putative heat shock elements, a TATA- box and two CAAT-boxes. This regulatory region resembled the Xenopus, mouse, and particularly tilapia hsp70 promoters, all of which have been shown to drive the expression of reporter genes in a heat dependent manner. Taken together, this data is the first to strongly suggest an inducible Hsp70-base cytoprotection mechanism in the coelacanth. It further provides basis to formulate testable predictions about the regulation, structure and function of Hsp70s in the living fossil, Latimeria.
- Full Text:
- Date Issued: 2007
- Authors: Modisakeng, Keoagile William
- Date: 2007
- Subjects: Coelacanth Coelacanth -- Genetics Heat shock proteins Molecular chaperones Proteins -- Analysis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3971 , http://hdl.handle.net/10962/d1004030
- Description: The extant coelacanths have a close resemblance to the coelacanth fossil records dating back to 230mya. Like their predecessors, the extant coelacanths inhabit rocky caves at a depth of 100-300m below sea level. In the Comoros, the water temperature at these depths is estimated to fluctuate between 14-20°C. High-level adaptation to these environment and lack of competition are thought to have led to the morphological uniformity and slow change throughout the history of the coelacanths. Under stress conditions, proteins unfold or misfold leading to the formation of aggregates. Molecular chaperones facilitate the correct folding of other proteins so that they can attain a stable tertiary structure. In addition, molecular chaperones aid the refolding of denatured proteins and the degradation of terminally misfolded protein after cellular stress. Heat shock proteins form one of the major classes of molecular chaperones. Here we show that, despite high-level adaptation to a unique habitat and slow change, the genome of the coelacanth encodes the major and highly conserved molecular chaperone, Hsp70. Latimeria menadoensis and Latimeria chalumnae contain intronless hsp70 genes encoding Hsp70 proteins archetypal of known Hsp70s. Based on the coelacanth codon usage, we have shown that bacterial protein expression systems, particularly Escherichia coli, may not be appropriate for the overproduction of coelacanth Hsp70s and coelacanth proteins in general. Also interesting, was the discovery that like the rat Hsc70, the L. menadoensis Hsp70 could not reverse thermal sensitivity in a temperate sensitive E. coli DnaK mutant strain, BB2362. We also report the successful isolation of a 1.2 kb region of L. menadoensis hsp70 upstream regulatory region. This region contain three putative heat shock elements, a TATA- box and two CAAT-boxes. This regulatory region resembled the Xenopus, mouse, and particularly tilapia hsp70 promoters, all of which have been shown to drive the expression of reporter genes in a heat dependent manner. Taken together, this data is the first to strongly suggest an inducible Hsp70-base cytoprotection mechanism in the coelacanth. It further provides basis to formulate testable predictions about the regulation, structure and function of Hsp70s in the living fossil, Latimeria.
- Full Text:
- Date Issued: 2007
Intersectionality and complexity in the representation of ‘queer’ sexualities and genders in African women’s short fiction
- Authors: Du Preez, Jenny Boźena
- Date: 2019
- Subjects: Sexual minority culture , Sexual minorities' writings , African fiction -- Women authors -- History and criticism , Gender identity in literature , Short stories, South African , Feminism in literature , Political poetry , Eroticism in literature , Lesbianism in literature
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/119047 , vital:34697
- Description: This thesis sets out to contribute to the growing body of knowledge about queer sexualities and genders in Africa by examining their depiction in selected post-2000 African women’s short fiction written in English. Post-2000, the short story form has become the primary vehicle for queer representations by African women writers, and is thus an important development in the burgeoning body of queer literature by African writers. Broadly speaking, this literary formation can be defined as anti-homophobic, feminist and politically pragmatic. Using an intersectional lens, this thesis sets out to examine four significant strands in the political work these stories engage in. The chapters are structured around four main points of contention that have particular significance at the intersection of ‘queer’, ‘women’ and ‘Africa’. Firstly, I examine South African short stories that perform what I call queer conversations with history: imaginatively asserting a queer South African history, writing back against a male-dominated and heterosexist literary canon and, in doing so, contributing to the reimagination of the contemporary South African nation. Secondly, I analyse short stories from Africa that foreground the family, both as social formation and ideology. I examine how these stories ‘fracture’ this powerful and naturalised heterosexist concept by depicting the tensions and contradictions that queer characters experience in relation to family. Thirdly, I consider short stories from various African contexts that work to reconceptualise queer sexuality in relation to religious discourse in order to challenge homophobic and patriarchal religious authority. Finally, I examine queer, feminist erotic short stories by African women writers that challenges various colonialist, racist, sexist and lesbophobic discourses that have historically stifled the portrayal of sex and erotic experience between women.
- Full Text:
- Date Issued: 2019
- Authors: Du Preez, Jenny Boźena
- Date: 2019
- Subjects: Sexual minority culture , Sexual minorities' writings , African fiction -- Women authors -- History and criticism , Gender identity in literature , Short stories, South African , Feminism in literature , Political poetry , Eroticism in literature , Lesbianism in literature
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/119047 , vital:34697
- Description: This thesis sets out to contribute to the growing body of knowledge about queer sexualities and genders in Africa by examining their depiction in selected post-2000 African women’s short fiction written in English. Post-2000, the short story form has become the primary vehicle for queer representations by African women writers, and is thus an important development in the burgeoning body of queer literature by African writers. Broadly speaking, this literary formation can be defined as anti-homophobic, feminist and politically pragmatic. Using an intersectional lens, this thesis sets out to examine four significant strands in the political work these stories engage in. The chapters are structured around four main points of contention that have particular significance at the intersection of ‘queer’, ‘women’ and ‘Africa’. Firstly, I examine South African short stories that perform what I call queer conversations with history: imaginatively asserting a queer South African history, writing back against a male-dominated and heterosexist literary canon and, in doing so, contributing to the reimagination of the contemporary South African nation. Secondly, I analyse short stories from Africa that foreground the family, both as social formation and ideology. I examine how these stories ‘fracture’ this powerful and naturalised heterosexist concept by depicting the tensions and contradictions that queer characters experience in relation to family. Thirdly, I consider short stories from various African contexts that work to reconceptualise queer sexuality in relation to religious discourse in order to challenge homophobic and patriarchal religious authority. Finally, I examine queer, feminist erotic short stories by African women writers that challenges various colonialist, racist, sexist and lesbophobic discourses that have historically stifled the portrayal of sex and erotic experience between women.
- Full Text:
- Date Issued: 2019
Photophysicochemical and photodynamic studies of phthalocyanines conjugated to selected drug delivery agents
- Authors: Nombona, Nolwazi
- Date: 2012
- Subjects: Phthalocyanines Photochemistry Photochemotherapy Drug delivery systems Magnesium Zinc Nanoparticles Staphylococcus aureus
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4333 , http://hdl.handle.net/10962/d1004994
- Description: This work reports on the successful synthesis, characterisation and photophysical properties of new asymmetric metal free, magnesium and zinc phthalocyanines. The synthesis of symmetrical phthalocyanines is also reported. A selection of phthalocyanines have been conjugated, covalently linked, encapsulated or mixed with selected of drug delivery agents which include gold or silver nanoparticles, poly-L-lysine, liposomes and folic acid. The influence of delivery agent on the photophysical and photochemical properties of conjugated phthalocyanine is investigated. The studies showed that the Au nanoparticle significantly lowered the fluorescence quantum yield values of the phthalocyanines. The photodynamic activity of Zn phthalocyanine-ε-polylysine conjugates in the presence of nanoparticles towards the inactivation of Staphylococcus aureus showed high photoinactivation in the presence of silver nanoparticles. The presence of silver nanoparticels from the minimal inhibition concentration (MIC₅₀) studies showed remarkable growth inhibition for the tested conjugates even at low concentrations. The conjugate also showed no dark toxicity when evaluated using the chick choriallantoic membrane (CAM) assay. The efficiency of selected zinc phthalocyanine as photodynamic therapy (PDT) agents was investigated. The production of reactive oxygen species (ROS) and phototoxicity of the photosensitizers were assessed. Healthy fibroblast cells and breast cancer (MCF-7) cells were treated with either free phthalocyanine or phthalocyanine bound to either gold nanoparticles or encapsulated in liposomes. Cell viability studies showed the optimum phototoxic effect on non-malignant cells to be 4.5 J.cm⁻². The PDT effect of the liposome bound phthalocyanine showed extensive damage of the breast cancer cells. Gold nanoparticles only showed a modest improvement in PDT activity.
- Full Text:
- Date Issued: 2012
- Authors: Nombona, Nolwazi
- Date: 2012
- Subjects: Phthalocyanines Photochemistry Photochemotherapy Drug delivery systems Magnesium Zinc Nanoparticles Staphylococcus aureus
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4333 , http://hdl.handle.net/10962/d1004994
- Description: This work reports on the successful synthesis, characterisation and photophysical properties of new asymmetric metal free, magnesium and zinc phthalocyanines. The synthesis of symmetrical phthalocyanines is also reported. A selection of phthalocyanines have been conjugated, covalently linked, encapsulated or mixed with selected of drug delivery agents which include gold or silver nanoparticles, poly-L-lysine, liposomes and folic acid. The influence of delivery agent on the photophysical and photochemical properties of conjugated phthalocyanine is investigated. The studies showed that the Au nanoparticle significantly lowered the fluorescence quantum yield values of the phthalocyanines. The photodynamic activity of Zn phthalocyanine-ε-polylysine conjugates in the presence of nanoparticles towards the inactivation of Staphylococcus aureus showed high photoinactivation in the presence of silver nanoparticles. The presence of silver nanoparticels from the minimal inhibition concentration (MIC₅₀) studies showed remarkable growth inhibition for the tested conjugates even at low concentrations. The conjugate also showed no dark toxicity when evaluated using the chick choriallantoic membrane (CAM) assay. The efficiency of selected zinc phthalocyanine as photodynamic therapy (PDT) agents was investigated. The production of reactive oxygen species (ROS) and phototoxicity of the photosensitizers were assessed. Healthy fibroblast cells and breast cancer (MCF-7) cells were treated with either free phthalocyanine or phthalocyanine bound to either gold nanoparticles or encapsulated in liposomes. Cell viability studies showed the optimum phototoxic effect on non-malignant cells to be 4.5 J.cm⁻². The PDT effect of the liposome bound phthalocyanine showed extensive damage of the breast cancer cells. Gold nanoparticles only showed a modest improvement in PDT activity.
- Full Text:
- Date Issued: 2012
African traditional medicine-antiretroviral interactions : effects of Sutherlandia frutescens on the pharmacokinetics of Atazanavir
- Authors: Müller, Adrienne Carmel
- Date: 2011 , 2011-03-28
- Subjects: Antiretroviral agents , Medicinal plants , Traditional medicine , AIDS (Disease) -- Treatment , HIV infections -- Drug therapy , Drug interactions , Pharmacokinetics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3859 , http://hdl.handle.net/10962/d1013373
- Description: In response to the urgent call for investigations into antiretroviral (ARV)-African traditional medicine (ATM) interactions, this research was undertaken to ascertain whether chronic administration of the ATM, Sutherlandia frutescens (SF) may alter the bioavailability of the protease inhibitor (PI), atazanavir (ATV), which may impact on the safety or efficacy of the ARV. Prior to investigating a potential interaction between ATV and SF in vitro and in vivo, a high performance liquid chromatography method with ultraviolet detection (HPLC-UV) was developed and validated for the bioanalysis of ATV in human plasma and liver microsomes. An improved and efficient analytical method with minimal use of solvents and short run time was achieved in comparison to methods published in the literature. In addition, the method was selective, linear, accurate and precise for quantitative analysis of ATV in these studies. Molecular docking studies were conducted to compare the binding modes and affinities of ATV and two major SF constituents, Sutherlandioside B and Sutherlandin C, with the efflux transporter, P-glycoprotein (P-gp) and the CYP450 isoenzyme, CYP3A4 to determine the potential for these phytochemicals to competitively inhibit the binding of ATV to these two proteins, which are mediators of absorption and metabolism. These studies revealed that modulation of P-gp transport of ATV by Sutherlandioside B and Sutherlandin C was not likely to occur via competitive inhibition. The results further indicated that weak competitive inhibition of CYP3A4 may possibly occur in the presence of either of these two SF constituents. The Caco-2 cell line was used as an in vitro model of human intestinal absorption. Accumulation studies in these cells were conducted to ascertain whether extracts and constituents of SF have the ability to alter the absorption of ATV. The results showed that the aqueous extract of SF significantly reduced ATV accumulation, suggesting decreased ATV absorption, whilst a triterpenoid glycoside fraction isolated from SF exhibited an opposing effect. Analogous responses were elicited by the aqueous extract and a triterpenoid glycoside fraction in similar accumulation studies in P-gp overexpressing Madin–Darby Canine Kidney Strain II cells (MDCKII-MDR1), which signified that the effects of this extract and component on ATV transport in the Caco-2 cells were P-gp-mediated. The quantitative analysis of ATV in human liver microsomes after co-incubation with extracts and components of SF was conducted to determine the effects of SF on the metabolism of ATV. The aqueous and methanolic extracts of SF inhibited ATV metabolism, whilst the triterpenoid glycoside fraction had a converse effect. Analogous effects by the extracts were demonstrated in experiments conducted in CYP3A4-transfected microsomes, suggesting that the inhibition of ATV metabolism in the liver microsomes by these SF extracts was CYP3A4-mediated. A combination of Sutherlandiosides C and D also inhibited CYP3A4-mediated ATV metabolism, which was in contrast to the response elicited by the triterpenoid fraction in the liver microsomes, where other unidentified compounds, shown to be present therein, may have contributed to the activation of ATV metabolism. The in vitro studies revealed the potential for SF to alter the bioavailability of ATV, therefore a clinical study in which the effect of a multiple dose regimen of SF on the pharmacokinetics (PK) of a single dose of ATV was conducted in healthy male volunteers. The statistical analysis showed that the 90 % confidence intervals around the geometric mean ratios (ATV + SF/ATV alone) for both Cmax and AUC0-24 hours, fell well below the lower limit of the "no-effect" boundary of 0.8 – 1.25, implying that the bioavailability of ATV was significantly reduced in this cohort of subjects. It may thus be concluded that if the reduction in bioavailability observed in this clinical study is found to be clinically relevant, co-administration of SF commercial dosage forms and ATV in HIV/AIDS patients may potentially result in subtherapeutic ATV levels, which may in turn contribute to ATV resistance and/or treatment failure. This research has therefore highlighted the potential risk for toxicity or lack of efficacy of ARV regimens which may result when ATMs and PIs are used concurrently and that patients and health care practitioners alike should be aware of these perils.
- Full Text:
- Date Issued: 2011
- Authors: Müller, Adrienne Carmel
- Date: 2011 , 2011-03-28
- Subjects: Antiretroviral agents , Medicinal plants , Traditional medicine , AIDS (Disease) -- Treatment , HIV infections -- Drug therapy , Drug interactions , Pharmacokinetics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3859 , http://hdl.handle.net/10962/d1013373
- Description: In response to the urgent call for investigations into antiretroviral (ARV)-African traditional medicine (ATM) interactions, this research was undertaken to ascertain whether chronic administration of the ATM, Sutherlandia frutescens (SF) may alter the bioavailability of the protease inhibitor (PI), atazanavir (ATV), which may impact on the safety or efficacy of the ARV. Prior to investigating a potential interaction between ATV and SF in vitro and in vivo, a high performance liquid chromatography method with ultraviolet detection (HPLC-UV) was developed and validated for the bioanalysis of ATV in human plasma and liver microsomes. An improved and efficient analytical method with minimal use of solvents and short run time was achieved in comparison to methods published in the literature. In addition, the method was selective, linear, accurate and precise for quantitative analysis of ATV in these studies. Molecular docking studies were conducted to compare the binding modes and affinities of ATV and two major SF constituents, Sutherlandioside B and Sutherlandin C, with the efflux transporter, P-glycoprotein (P-gp) and the CYP450 isoenzyme, CYP3A4 to determine the potential for these phytochemicals to competitively inhibit the binding of ATV to these two proteins, which are mediators of absorption and metabolism. These studies revealed that modulation of P-gp transport of ATV by Sutherlandioside B and Sutherlandin C was not likely to occur via competitive inhibition. The results further indicated that weak competitive inhibition of CYP3A4 may possibly occur in the presence of either of these two SF constituents. The Caco-2 cell line was used as an in vitro model of human intestinal absorption. Accumulation studies in these cells were conducted to ascertain whether extracts and constituents of SF have the ability to alter the absorption of ATV. The results showed that the aqueous extract of SF significantly reduced ATV accumulation, suggesting decreased ATV absorption, whilst a triterpenoid glycoside fraction isolated from SF exhibited an opposing effect. Analogous responses were elicited by the aqueous extract and a triterpenoid glycoside fraction in similar accumulation studies in P-gp overexpressing Madin–Darby Canine Kidney Strain II cells (MDCKII-MDR1), which signified that the effects of this extract and component on ATV transport in the Caco-2 cells were P-gp-mediated. The quantitative analysis of ATV in human liver microsomes after co-incubation with extracts and components of SF was conducted to determine the effects of SF on the metabolism of ATV. The aqueous and methanolic extracts of SF inhibited ATV metabolism, whilst the triterpenoid glycoside fraction had a converse effect. Analogous effects by the extracts were demonstrated in experiments conducted in CYP3A4-transfected microsomes, suggesting that the inhibition of ATV metabolism in the liver microsomes by these SF extracts was CYP3A4-mediated. A combination of Sutherlandiosides C and D also inhibited CYP3A4-mediated ATV metabolism, which was in contrast to the response elicited by the triterpenoid fraction in the liver microsomes, where other unidentified compounds, shown to be present therein, may have contributed to the activation of ATV metabolism. The in vitro studies revealed the potential for SF to alter the bioavailability of ATV, therefore a clinical study in which the effect of a multiple dose regimen of SF on the pharmacokinetics (PK) of a single dose of ATV was conducted in healthy male volunteers. The statistical analysis showed that the 90 % confidence intervals around the geometric mean ratios (ATV + SF/ATV alone) for both Cmax and AUC0-24 hours, fell well below the lower limit of the "no-effect" boundary of 0.8 – 1.25, implying that the bioavailability of ATV was significantly reduced in this cohort of subjects. It may thus be concluded that if the reduction in bioavailability observed in this clinical study is found to be clinically relevant, co-administration of SF commercial dosage forms and ATV in HIV/AIDS patients may potentially result in subtherapeutic ATV levels, which may in turn contribute to ATV resistance and/or treatment failure. This research has therefore highlighted the potential risk for toxicity or lack of efficacy of ARV regimens which may result when ATMs and PIs are used concurrently and that patients and health care practitioners alike should be aware of these perils.
- Full Text:
- Date Issued: 2011
Coping in two cultures: an ecological study of mentally ill people and their families in rural South Africa
- Authors: Cumes, Heide Ulrike
- Date: 1995
- Subjects: Mental illness -- South Africa Xhosa (African people) -- Psychology Xhosa (African people) -- Religion Xhosa (African people) -- Social life and customs
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2958 , http://hdl.handle.net/10962/d1002467
- Description: This study explores severe mental illness in a South African ru~al district, moving, as with a zoom lens, from the macroperspectives of (i) Xhosa culture, and (ii) biomedicine, to the lived experience of the individual. Its methodology, predominantly qualitative, employed anthropological and psychological procedures. The fieldwork (1988-1989)encompassed a three month stay in the village of Msobomvu. Patients continued to be tracked informally until June, 1995. The empirical research has three parts. In part one, the person with a mental illness was contextualized within Xhosa cosmology and social attitudes. The cognitive and social ecologies were tapped through the narratives of high school and university students at different stages of a Western-biased education. Social attitudes regarding mental illness, and confidence in treatment by traditional healers and the hospital, were also evaluated. Traditional attitudes and supernatural beliefs of illness causation persisted in spite of Eurocentric education, with a concurrent increase in the acceptance of Western-type causal explanations commensurate with continued education. Part two considered the the patients in relation to (i) the biomedical framework (the mental and local hospitals), and (ii) their readjustment to the community after hospitalization. Data came from patient charts, interviews with medical staff, and follow-up visits in the villages. Socio-political and economic issues were salient. Part three case-studied people identified by the village residents as having a mental illness. Resources for treatment - traditional healers, mobile clinic, and village health workers - were the focus. The traditional healing system, and biomedicine, were compared for effectiveness, through the course of illness events. While biomedicine was more effective in containing acute psychotic episodes than treatment by the traditional healer, lack of appropriate resources within the biomedical setting had disastrous results for patient compliance and long-term management of the illness, particularly in people with obvious symptoms of bipolar disorder. The mental hospital emerged as an agent of control. While Xhosa culture provided a more tolerant setting for people with a mental illness, the course of severe mental illness was by no means benign, despite research suggesting a more positive outcome for such conditions in the developing world.
- Full Text:
- Date Issued: 1995
- Authors: Cumes, Heide Ulrike
- Date: 1995
- Subjects: Mental illness -- South Africa Xhosa (African people) -- Psychology Xhosa (African people) -- Religion Xhosa (African people) -- Social life and customs
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2958 , http://hdl.handle.net/10962/d1002467
- Description: This study explores severe mental illness in a South African ru~al district, moving, as with a zoom lens, from the macroperspectives of (i) Xhosa culture, and (ii) biomedicine, to the lived experience of the individual. Its methodology, predominantly qualitative, employed anthropological and psychological procedures. The fieldwork (1988-1989)encompassed a three month stay in the village of Msobomvu. Patients continued to be tracked informally until June, 1995. The empirical research has three parts. In part one, the person with a mental illness was contextualized within Xhosa cosmology and social attitudes. The cognitive and social ecologies were tapped through the narratives of high school and university students at different stages of a Western-biased education. Social attitudes regarding mental illness, and confidence in treatment by traditional healers and the hospital, were also evaluated. Traditional attitudes and supernatural beliefs of illness causation persisted in spite of Eurocentric education, with a concurrent increase in the acceptance of Western-type causal explanations commensurate with continued education. Part two considered the the patients in relation to (i) the biomedical framework (the mental and local hospitals), and (ii) their readjustment to the community after hospitalization. Data came from patient charts, interviews with medical staff, and follow-up visits in the villages. Socio-political and economic issues were salient. Part three case-studied people identified by the village residents as having a mental illness. Resources for treatment - traditional healers, mobile clinic, and village health workers - were the focus. The traditional healing system, and biomedicine, were compared for effectiveness, through the course of illness events. While biomedicine was more effective in containing acute psychotic episodes than treatment by the traditional healer, lack of appropriate resources within the biomedical setting had disastrous results for patient compliance and long-term management of the illness, particularly in people with obvious symptoms of bipolar disorder. The mental hospital emerged as an agent of control. While Xhosa culture provided a more tolerant setting for people with a mental illness, the course of severe mental illness was by no means benign, despite research suggesting a more positive outcome for such conditions in the developing world.
- Full Text:
- Date Issued: 1995
A critical analysis of housing provision, livelihood activities and social reproduction in urban communities in South Africa: the case of Ezamokuhle, Mpumalanga
- Authors: Nkambule, Sipho Jonathan
- Date: 2017
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/7788 , vital:21298
- Description: The post-apartheid South African state has formulated, introduced and implemented nationwide policies and programmes pertaining to urban housing in order to address and tackle the challenges of social reproduction in and for poor urban black communities. This however has been undermined for a number of reasons, such as state incapacities and the state’s neo-liberal overreliance on the market to remedy past injustices. At the same time households, as critical sites of social reproduction in poor urban black communities and under conditions of extreme vulnerability, engage in a range of productive and non-productive activities often in a desperate bid to construct and maintain a semblance of livelihood sustainability. The thesis seeks to critically understand the relationship between state housing programmes and the diverse livelihood activities of poor urban black households in South Africa in the context of an ongoing systemic crisis of social reproduction which exists in these urban communities. This is pursued with specific reference to eZamokuhle Township in Amersfoort, Mpumalanga Province. The thesis is framed conceptually in terms of the notion of social reproduction. In doing so, it brings together two sets of literature which are often disconnected. On the one hand, there is South African literature which critically analyses the post-apartheid state’s housing programmes including the many challenges which exist in this regard. On the other hand, there is literature which considers the urban livelihoods of poor black communities in contemporary South Africa and often from within some kind of livelihoods perspective. The thesis is innovative in bringing these two sets of literature together in terms of the overarching notion of social reproduction and providing, therefore, a more holistic and integrated understanding of the multi-dimensional character of social reproduction. The depth of the crisis of social reproduction in eZamokuhle is explicated and examined in this way but in a manner which articulates the lived experiences and agency of eZamokhule households despite vulnerability constraints and challenges.
- Full Text:
- Date Issued: 2017
- Authors: Nkambule, Sipho Jonathan
- Date: 2017
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/7788 , vital:21298
- Description: The post-apartheid South African state has formulated, introduced and implemented nationwide policies and programmes pertaining to urban housing in order to address and tackle the challenges of social reproduction in and for poor urban black communities. This however has been undermined for a number of reasons, such as state incapacities and the state’s neo-liberal overreliance on the market to remedy past injustices. At the same time households, as critical sites of social reproduction in poor urban black communities and under conditions of extreme vulnerability, engage in a range of productive and non-productive activities often in a desperate bid to construct and maintain a semblance of livelihood sustainability. The thesis seeks to critically understand the relationship between state housing programmes and the diverse livelihood activities of poor urban black households in South Africa in the context of an ongoing systemic crisis of social reproduction which exists in these urban communities. This is pursued with specific reference to eZamokuhle Township in Amersfoort, Mpumalanga Province. The thesis is framed conceptually in terms of the notion of social reproduction. In doing so, it brings together two sets of literature which are often disconnected. On the one hand, there is South African literature which critically analyses the post-apartheid state’s housing programmes including the many challenges which exist in this regard. On the other hand, there is literature which considers the urban livelihoods of poor black communities in contemporary South Africa and often from within some kind of livelihoods perspective. The thesis is innovative in bringing these two sets of literature together in terms of the overarching notion of social reproduction and providing, therefore, a more holistic and integrated understanding of the multi-dimensional character of social reproduction. The depth of the crisis of social reproduction in eZamokuhle is explicated and examined in this way but in a manner which articulates the lived experiences and agency of eZamokhule households despite vulnerability constraints and challenges.
- Full Text:
- Date Issued: 2017
Conscientious objection and the concept of worship
- Authors: Moulder, James Edward
- Date: 1977
- Subjects: Conscientious objectors -- Law and legislation -- South Africa , Conscientious objectors -- South Africa , Conscientious objection , Conscientious objection -- Religious aspects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2749 , http://hdl.handle.net/10962/d1013555
- Description: [Preface] " ... the focus of this inquiry is limited to some of the connections between conscientious objection in South Africa and the worship and imitation of Christ. More specifically, at the most general level this essay is an attempt to explore six questions: What kind of conscientious objection does South African law allow? Why are some conscientious objectors only conscientious noncombatants? Why are some Christians conscientious noncombatants? Is it appropriate to worship Christ? Does Romans 13 undermine conscientious noncompliance? And is there a prescription for servile compliance? These are, however, not the only questions which are raised in this essay. Nor are they the only questions which can and need to be asked. But they are the questions which interest me. In addition, they have not received as much attention as they deserve".
- Full Text:
- Date Issued: 1977
- Authors: Moulder, James Edward
- Date: 1977
- Subjects: Conscientious objectors -- Law and legislation -- South Africa , Conscientious objectors -- South Africa , Conscientious objection , Conscientious objection -- Religious aspects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2749 , http://hdl.handle.net/10962/d1013555
- Description: [Preface] " ... the focus of this inquiry is limited to some of the connections between conscientious objection in South Africa and the worship and imitation of Christ. More specifically, at the most general level this essay is an attempt to explore six questions: What kind of conscientious objection does South African law allow? Why are some conscientious objectors only conscientious noncombatants? Why are some Christians conscientious noncombatants? Is it appropriate to worship Christ? Does Romans 13 undermine conscientious noncompliance? And is there a prescription for servile compliance? These are, however, not the only questions which are raised in this essay. Nor are they the only questions which can and need to be asked. But they are the questions which interest me. In addition, they have not received as much attention as they deserve".
- Full Text:
- Date Issued: 1977
Morphological development in the interlanguage of English learners of Xhosa
- Authors: Hobson, Carol Bonnin
- Date: 2000
- Subjects: Grammar, Comparative and general -- Morphology Xhosa language -- Foreign speakers Xhosa language -- Morphology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2348 , http://hdl.handle.net/10962/d1002630
- Description: This study investigates the development of morphology in the interlanguage of English learners of Xhosa. A quasi-longitudinal research design is used to trace development in the oral interlanguage of six learners of Xhosa for a period of eight months. The elicitation tasks employed range from fairly unstructured conversation tasks to highly structured sentence-manipulation tasks. The learners have varying levels of competence at the beginning of the study and they are exposed to input mainly in formal contexts of learning. One of the aims of the study is to investigate whether the features of interlanguage identified in other studies appear in the learner language in this study. Most other studies discussed in the literature have investigated the features of the interlanguage produced by learners of analytic and inflectional languages. However, this study analyses the interlanguage of learners of an agglutinative language. Studies of other languages have concluded that learners do not use inflectional or agreement morphology at early stages of development and this conclusion is tested for learners of an agglutinative language in this study. Since agreement and inflectional morphology play a central role in conveying meaning in Xhosa, it is found that learners use morphology from the beginning of the learning process. Although forms may be used incorrectly and the functions of forms may be restricted, morphemes appear in the interlanguage of learners of this study earlier than other studies predict. One of the characteristics of early interlanguage and an early form of learner language called the Basic Variety (Klein & Perdue 1997) is the lack of morphology, but this feature proves to be inadequate as a measure of early development in the interlanguage of learners of a language such as Xhosa. This study concludes, therefore, that the presence of morphology in the interlanguage of learners of Xhosa cannot be an indicator of advanced language development.
- Full Text:
- Date Issued: 2000
- Authors: Hobson, Carol Bonnin
- Date: 2000
- Subjects: Grammar, Comparative and general -- Morphology Xhosa language -- Foreign speakers Xhosa language -- Morphology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2348 , http://hdl.handle.net/10962/d1002630
- Description: This study investigates the development of morphology in the interlanguage of English learners of Xhosa. A quasi-longitudinal research design is used to trace development in the oral interlanguage of six learners of Xhosa for a period of eight months. The elicitation tasks employed range from fairly unstructured conversation tasks to highly structured sentence-manipulation tasks. The learners have varying levels of competence at the beginning of the study and they are exposed to input mainly in formal contexts of learning. One of the aims of the study is to investigate whether the features of interlanguage identified in other studies appear in the learner language in this study. Most other studies discussed in the literature have investigated the features of the interlanguage produced by learners of analytic and inflectional languages. However, this study analyses the interlanguage of learners of an agglutinative language. Studies of other languages have concluded that learners do not use inflectional or agreement morphology at early stages of development and this conclusion is tested for learners of an agglutinative language in this study. Since agreement and inflectional morphology play a central role in conveying meaning in Xhosa, it is found that learners use morphology from the beginning of the learning process. Although forms may be used incorrectly and the functions of forms may be restricted, morphemes appear in the interlanguage of learners of this study earlier than other studies predict. One of the characteristics of early interlanguage and an early form of learner language called the Basic Variety (Klein & Perdue 1997) is the lack of morphology, but this feature proves to be inadequate as a measure of early development in the interlanguage of learners of a language such as Xhosa. This study concludes, therefore, that the presence of morphology in the interlanguage of learners of Xhosa cannot be an indicator of advanced language development.
- Full Text:
- Date Issued: 2000
A phenomenological investigation into the psychotherapist's experience of identifying, containing and processing the patient's projective identifications
- Authors: Thorpe, Mark Richard
- Date: 1989
- Subjects: Psychotherapist and patient Psychotherapy Methods
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3071 , http://hdl.handle.net/10962/d1002580
- Description: The aim of the study was to describe the therapist's lived experience of identifying, containing and processing the feelings, thoughts or fantasies evoked in him by the patient's projective identifications. A question which would elicit the experience of this phenomenon was formulated by examining case histories, and modified through the use of individual pilot studies. Fifteen experienced, psychoanalytically oriented psychotherapists were interviewed. The eight psychologically richest accounts were chosen for the study. Using the empirical phenomenological method, the four protocols that most clearly reflected the phenomenon were analysed in detail, while the remaining four were used to clarify areas of uncertainty. Projective identification is conceptualised as the process whereby the patient coerces the therapist to embody an un-appropriated aspect of his (patient's) world. The context of processing a patient's projective identification was discovered to be such that the therapist finds himself coerced to embody an incongruent, unfamiliar, confusing and inauthentic state of being which is consonant with the patient's perception of him. The discomfort of the experience leads the therapist to bring to awareness and thematise his feeling-state. He alternates between avoiding this state of being, which results in conf1ict with the patient and the therapist's own values, and appropriating it, which feels inauthentic. The therapist moves from a position of trying to understand the experience in relation to his own world, to the realisation that it is co-determined by the patient. From a position of reflective distance he re-appropriates aspects of his world that were closed to him while under the influence of the patient, in addition to appropriating previously unowned aspects. The therapist dialogues these appropriations with the invoked feelings, allowing him to differentiate those aspects of his feeling-state which are authentically his from those which are unowned aspects of the patient's aspects of his world that were closed to him while under the influence of the patient, in addition to appropriating previously unowned aspects. The therapist dialogues these appropriations with the invoked feelings, allowing him to differentiate those aspects of his feeling-state which are authentically his from those which are unowned aspects of the patient's world that he has been forced to embody. Through this process the therapist clarifies and gives meaning to his feelings. The therapist fee1s re1ieved and lighter, when in the service of the therapy, he temporarily gives himself over to the patient's experience of him, without feeling drawn to either disowning or appropriating it, while simultaneously remaining open to his own authentic reality. These findings were dialogued with the literature on projective identification.
- Full Text:
- Date Issued: 1989
- Authors: Thorpe, Mark Richard
- Date: 1989
- Subjects: Psychotherapist and patient Psychotherapy Methods
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3071 , http://hdl.handle.net/10962/d1002580
- Description: The aim of the study was to describe the therapist's lived experience of identifying, containing and processing the feelings, thoughts or fantasies evoked in him by the patient's projective identifications. A question which would elicit the experience of this phenomenon was formulated by examining case histories, and modified through the use of individual pilot studies. Fifteen experienced, psychoanalytically oriented psychotherapists were interviewed. The eight psychologically richest accounts were chosen for the study. Using the empirical phenomenological method, the four protocols that most clearly reflected the phenomenon were analysed in detail, while the remaining four were used to clarify areas of uncertainty. Projective identification is conceptualised as the process whereby the patient coerces the therapist to embody an un-appropriated aspect of his (patient's) world. The context of processing a patient's projective identification was discovered to be such that the therapist finds himself coerced to embody an incongruent, unfamiliar, confusing and inauthentic state of being which is consonant with the patient's perception of him. The discomfort of the experience leads the therapist to bring to awareness and thematise his feeling-state. He alternates between avoiding this state of being, which results in conf1ict with the patient and the therapist's own values, and appropriating it, which feels inauthentic. The therapist moves from a position of trying to understand the experience in relation to his own world, to the realisation that it is co-determined by the patient. From a position of reflective distance he re-appropriates aspects of his world that were closed to him while under the influence of the patient, in addition to appropriating previously unowned aspects. The therapist dialogues these appropriations with the invoked feelings, allowing him to differentiate those aspects of his feeling-state which are authentically his from those which are unowned aspects of the patient's aspects of his world that were closed to him while under the influence of the patient, in addition to appropriating previously unowned aspects. The therapist dialogues these appropriations with the invoked feelings, allowing him to differentiate those aspects of his feeling-state which are authentically his from those which are unowned aspects of the patient's world that he has been forced to embody. Through this process the therapist clarifies and gives meaning to his feelings. The therapist fee1s re1ieved and lighter, when in the service of the therapy, he temporarily gives himself over to the patient's experience of him, without feeling drawn to either disowning or appropriating it, while simultaneously remaining open to his own authentic reality. These findings were dialogued with the literature on projective identification.
- Full Text:
- Date Issued: 1989
Detached harmonies : a study in/on developing social processes of environmental education in eastern southern Africa
- Authors: O'Donoghue, Rob
- Date: 1997
- Subjects: Environmental education -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1939 , http://hdl.handle.net/10962/d1007726
- Description: Long-term social processes are explored to examine the shaping of environmental education in eastern southern Africa. The study opens with early Nguni social figurations when 'to conserve was to hunt.' It then examines colonial conservation on the frontiers of imperial expansion and developing struggles for and against wildlife preservation. These processes shaped an inversion of earlier harmonies as declining wildlife was protected in island sanctuaries of natural wilderness and 'to conserve was not to hunt.' Inside protected areas, conservation management struggles shaped new harmonies of interdependence in nature, enabling better steering choices in developing conservation science institutions. Here more reality congruent knowledge also revealed escalating risk which was linked to a lack of awareness amongst communities of 'others' outside. Within continuing conservation struggles, education in, about and for the environment emerged as new institutional processes of social control. The study examines wilderness experience, interpretation, extension, conservancies and the development of an environmental education field centre, a teacher education programme and a school curriculum. Naming and clarifying the emergent education game for reshaping the awareness and behaviour of others is examined within a developing figuration of environmental education specialists. Particular attention is given to academic and statutory processes shaping environmental education as a field of objective principles and rational processes within modernist continuities and discontinuities into the 1990's. An environmental education field centre, an earth-love curriculum and research on reserve neighbour interaction are examined as political sociologies developing within a declining power gradient and wide ranging socio-political change. Into the present, a final window on a local case of water pollution examines shifting relational dynamics revealing how environment and development education models of process may have little resonance amidst long-term socio-historical struggles and shifting controls over surroundings, others and self. A concluding review suggests that grounded critical processes engaging somewhat blind control over surroundings may yet reshape self-control and social control amongst others. The trajectories of these clarifying struggles must remain open-ended as sedimented myth and memory is reshaped within ongoing processes of escalating risk and global intermeshing.
- Full Text:
- Date Issued: 1997
- Authors: O'Donoghue, Rob
- Date: 1997
- Subjects: Environmental education -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1939 , http://hdl.handle.net/10962/d1007726
- Description: Long-term social processes are explored to examine the shaping of environmental education in eastern southern Africa. The study opens with early Nguni social figurations when 'to conserve was to hunt.' It then examines colonial conservation on the frontiers of imperial expansion and developing struggles for and against wildlife preservation. These processes shaped an inversion of earlier harmonies as declining wildlife was protected in island sanctuaries of natural wilderness and 'to conserve was not to hunt.' Inside protected areas, conservation management struggles shaped new harmonies of interdependence in nature, enabling better steering choices in developing conservation science institutions. Here more reality congruent knowledge also revealed escalating risk which was linked to a lack of awareness amongst communities of 'others' outside. Within continuing conservation struggles, education in, about and for the environment emerged as new institutional processes of social control. The study examines wilderness experience, interpretation, extension, conservancies and the development of an environmental education field centre, a teacher education programme and a school curriculum. Naming and clarifying the emergent education game for reshaping the awareness and behaviour of others is examined within a developing figuration of environmental education specialists. Particular attention is given to academic and statutory processes shaping environmental education as a field of objective principles and rational processes within modernist continuities and discontinuities into the 1990's. An environmental education field centre, an earth-love curriculum and research on reserve neighbour interaction are examined as political sociologies developing within a declining power gradient and wide ranging socio-political change. Into the present, a final window on a local case of water pollution examines shifting relational dynamics revealing how environment and development education models of process may have little resonance amidst long-term socio-historical struggles and shifting controls over surroundings, others and self. A concluding review suggests that grounded critical processes engaging somewhat blind control over surroundings may yet reshape self-control and social control amongst others. The trajectories of these clarifying struggles must remain open-ended as sedimented myth and memory is reshaped within ongoing processes of escalating risk and global intermeshing.
- Full Text:
- Date Issued: 1997
The growth of flue-cured tobacco in acid soils
- Authors: Ryding, William Wallace
- Date: 1969
- Subjects: Flue-cured tobacco -- Zimbabwe , Acid soils -- Zimbabwe
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4495 , http://hdl.handle.net/10962/d1013110
- Description: The main effects of lime, aluminium, iron and manganese were studied in field and greenhouse grown tobacco; relations between soil and plant measurements were examined. Ground limestone, ground mixed lime, ground dolomite and slaked lime at rates equivalent to 1,000 and 2,000 lb. CaC0₃/acre increased yield and quality of flue-cured tobacco both on Triassic and granite sands, whether applied early (February/March) or late (September); the highest rate and late application were often best. Yields increased with 4,000 and 6,000 lb. dolomite/acre applied late, but quality decreased when the pH was about 6.0. Lime did not affect leaf maturity as reflected by nitrogen and reducing sugars concentration . Where leaf discolouration (slate) occurred, the best quality and least discoloured leaf had the lowest manganese concentration and was grown on limed soil. On a very acid and probably nitrogen deficient soil, lime, borax and nitrogen (nitrate only tested) reduced the discolouration and improved the quality, but potassium sulphate increased discolouration and decreased quality. Calcium concentration in the leaf was increased by lime, particularly calcitic materials, and magnesium concentration was increased by dolomite. Lime also increased the filling value and petroleum ether extract, but decreased manganese, boron, chloride and sometimes potassium, and had no effect on phosphorus, nitrogen, aluminium, iron, crude fibre, nicotine, reducing sugars and equilibrium moisture. The inorganic composition of greenhouse plants was similar; generally gypsum increased calcium concentration more than calcium carbonate but it did not affect manganese concentration, which was decreased by calcium carbonate. In the stem and roots of field grown plants (dolomite only tested), the concentration of magnesium was increased but the concentrations of calcium, potassium, aluminium and iron were unaffected. Although the concentration of nitrogen was increased and that of phosphorus was decreased in the stem, these were unaffected in the roots. Aluminium and iron behaved differently to other nutrient ions, being more concentrated in the roots than aerial plant parts. Boron and magnesium deficiencies were observed in a dry and wet year, respectively, suggesting that variable mineral deficiencies can affect responses to lime. Initially soil pH was affected more by source of lime, but later mostly by rates. Slaked lime increased the soil pH more than did ground limestone, mixed lime or dolomite. In a glasshouse experiment, pH was more important than calcium supply and in the field, the largest yields were often associated with the highest pH. In pot experiments, aluminium drastically reduced yields in nutrient solution but not in soils, whereas iron was more severe in soils; manganese had little effect on yield. Manganese was readily taken up and translocated to the tops, but aluminium and iron were mainly concentrated in the roots, as was found in field grown plants. Iron decreased manganese concentration in all plant parts and aluminium decreased calcium and manganese in nutrient solution only. Although aluminium and iron generally increased the concentration of phosphorus in the roots, they did not interfere with phosphorus transport in the plant. Manganese caused the leaf to become chlorotic and when no iron was present the upper leaves became yellow, and developed brown and white lesions. However, in soil grown plants, sufficient iron was present in the soil solution to prevent break down of tissue. Yellowing of the upper leaves also occurred when plants were grown in nutrient solution with aluminium and no iron; when both were present, the plants were darker in colour. Although aluminium damaged roots in nutrient solution, high rates of iron severely damaged leaves of plants grown in soil. Since the concentrations of aluminium, iron and manganese were decreased in the soil solution by liming, they were compared with plant growth and composition in 17 different soils, with and without lime. As was expected, lime increased soil pH. It also increased exchangeable calcium, but decreased exchangeable aluminium, iron and manganese; exchangeable magnesium and potassium and resin extractable phosphorus were not affected. As the Ratio Law does not hold for all Rhodesian soils, anion adsorption will be avoided if the soils are equilibrated with O.OOOSM CaC1₂; the concentrations of the cations in solution were affected in the same way as exchangeable cations, but phosphorus was increased. There was no relationship between yield of tobacco and its chemical composition. The correlations between soil solution data and plant composition were poor, except for manganese and phosphorus; the relation between Mn ppm. in plant vsa (superscript)Mn/a (superscript)Ca + Mg (enclosed in square root sign √) in solution, and P% vs pH₂ P0₄ or pH₂ P0₄ +½ pCa, were both curvilinear. On the other hand, all measurements of exchangeable cations were poorly correlated with plant composition. Finally yield was poorly correlated with soil solution data, and pH was as satisfactory as any other measurement tested. Manganese toxicity was observed on three soils, and a probable manganese deficiency on one. It was not possible to define a limit above which manganese toxicity occurred, but manganese deficiency developed at about 63 ppm. manganese. Variations in pH and the availability of aluminium, iron and manganese occurred when soils were incubated at about field capacity, generally the main effects having developed within seven days. In all soils, there was an initial increase in soil pH and a maximum value was reached in one to four days, decreasing by variable amounts with longer periods of incubation. Although the concentration of aluminium was larger than that of iron, the relation between both ions and soil pH was curvilinear, their concentrations increasing with decreasing pH. Increased temperature of incubation increased pH with a resultant decrease in the concentration of aluminium, but in one soil it appreciably increased the availability of iron in the early periods of incubation. Autumn and spring ploughing did not affect subsequent pH or the concentration of aluminium and iron in the soil solution. Manganese concentration varied from soil to soil and was not related to soil pH. In most soils there was a decrease in manganese concentration with length of incubation and it decreased more rapidly the lower the initial concentration. Temperature effects were variable and moisture affected the behaviour of manganese more than temperature. These findings and the distribution of aluminium, iron and manganese in the plant helped to explain the poor correlations.
- Full Text:
- Date Issued: 1969
- Authors: Ryding, William Wallace
- Date: 1969
- Subjects: Flue-cured tobacco -- Zimbabwe , Acid soils -- Zimbabwe
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4495 , http://hdl.handle.net/10962/d1013110
- Description: The main effects of lime, aluminium, iron and manganese were studied in field and greenhouse grown tobacco; relations between soil and plant measurements were examined. Ground limestone, ground mixed lime, ground dolomite and slaked lime at rates equivalent to 1,000 and 2,000 lb. CaC0₃/acre increased yield and quality of flue-cured tobacco both on Triassic and granite sands, whether applied early (February/March) or late (September); the highest rate and late application were often best. Yields increased with 4,000 and 6,000 lb. dolomite/acre applied late, but quality decreased when the pH was about 6.0. Lime did not affect leaf maturity as reflected by nitrogen and reducing sugars concentration . Where leaf discolouration (slate) occurred, the best quality and least discoloured leaf had the lowest manganese concentration and was grown on limed soil. On a very acid and probably nitrogen deficient soil, lime, borax and nitrogen (nitrate only tested) reduced the discolouration and improved the quality, but potassium sulphate increased discolouration and decreased quality. Calcium concentration in the leaf was increased by lime, particularly calcitic materials, and magnesium concentration was increased by dolomite. Lime also increased the filling value and petroleum ether extract, but decreased manganese, boron, chloride and sometimes potassium, and had no effect on phosphorus, nitrogen, aluminium, iron, crude fibre, nicotine, reducing sugars and equilibrium moisture. The inorganic composition of greenhouse plants was similar; generally gypsum increased calcium concentration more than calcium carbonate but it did not affect manganese concentration, which was decreased by calcium carbonate. In the stem and roots of field grown plants (dolomite only tested), the concentration of magnesium was increased but the concentrations of calcium, potassium, aluminium and iron were unaffected. Although the concentration of nitrogen was increased and that of phosphorus was decreased in the stem, these were unaffected in the roots. Aluminium and iron behaved differently to other nutrient ions, being more concentrated in the roots than aerial plant parts. Boron and magnesium deficiencies were observed in a dry and wet year, respectively, suggesting that variable mineral deficiencies can affect responses to lime. Initially soil pH was affected more by source of lime, but later mostly by rates. Slaked lime increased the soil pH more than did ground limestone, mixed lime or dolomite. In a glasshouse experiment, pH was more important than calcium supply and in the field, the largest yields were often associated with the highest pH. In pot experiments, aluminium drastically reduced yields in nutrient solution but not in soils, whereas iron was more severe in soils; manganese had little effect on yield. Manganese was readily taken up and translocated to the tops, but aluminium and iron were mainly concentrated in the roots, as was found in field grown plants. Iron decreased manganese concentration in all plant parts and aluminium decreased calcium and manganese in nutrient solution only. Although aluminium and iron generally increased the concentration of phosphorus in the roots, they did not interfere with phosphorus transport in the plant. Manganese caused the leaf to become chlorotic and when no iron was present the upper leaves became yellow, and developed brown and white lesions. However, in soil grown plants, sufficient iron was present in the soil solution to prevent break down of tissue. Yellowing of the upper leaves also occurred when plants were grown in nutrient solution with aluminium and no iron; when both were present, the plants were darker in colour. Although aluminium damaged roots in nutrient solution, high rates of iron severely damaged leaves of plants grown in soil. Since the concentrations of aluminium, iron and manganese were decreased in the soil solution by liming, they were compared with plant growth and composition in 17 different soils, with and without lime. As was expected, lime increased soil pH. It also increased exchangeable calcium, but decreased exchangeable aluminium, iron and manganese; exchangeable magnesium and potassium and resin extractable phosphorus were not affected. As the Ratio Law does not hold for all Rhodesian soils, anion adsorption will be avoided if the soils are equilibrated with O.OOOSM CaC1₂; the concentrations of the cations in solution were affected in the same way as exchangeable cations, but phosphorus was increased. There was no relationship between yield of tobacco and its chemical composition. The correlations between soil solution data and plant composition were poor, except for manganese and phosphorus; the relation between Mn ppm. in plant vsa (superscript)Mn/a (superscript)Ca + Mg (enclosed in square root sign √) in solution, and P% vs pH₂ P0₄ or pH₂ P0₄ +½ pCa, were both curvilinear. On the other hand, all measurements of exchangeable cations were poorly correlated with plant composition. Finally yield was poorly correlated with soil solution data, and pH was as satisfactory as any other measurement tested. Manganese toxicity was observed on three soils, and a probable manganese deficiency on one. It was not possible to define a limit above which manganese toxicity occurred, but manganese deficiency developed at about 63 ppm. manganese. Variations in pH and the availability of aluminium, iron and manganese occurred when soils were incubated at about field capacity, generally the main effects having developed within seven days. In all soils, there was an initial increase in soil pH and a maximum value was reached in one to four days, decreasing by variable amounts with longer periods of incubation. Although the concentration of aluminium was larger than that of iron, the relation between both ions and soil pH was curvilinear, their concentrations increasing with decreasing pH. Increased temperature of incubation increased pH with a resultant decrease in the concentration of aluminium, but in one soil it appreciably increased the availability of iron in the early periods of incubation. Autumn and spring ploughing did not affect subsequent pH or the concentration of aluminium and iron in the soil solution. Manganese concentration varied from soil to soil and was not related to soil pH. In most soils there was a decrease in manganese concentration with length of incubation and it decreased more rapidly the lower the initial concentration. Temperature effects were variable and moisture affected the behaviour of manganese more than temperature. These findings and the distribution of aluminium, iron and manganese in the plant helped to explain the poor correlations.
- Full Text:
- Date Issued: 1969
Trials and triumphs in public office: the life and work of E J N Mabuza
- Authors: Sarimana, Ashley
- Date: 2011
- Subjects: Mabuza, E J (Enos John), 1939- Public officers -- South Africa South Africa -- Politics and government -- 20th century South Africa -- History -- 20th century South Africa -- Social conditions -- 20th century Homelands (South Africa) -- Politics and government -- 20th century Homelands (South Africa) -- History -- 20th century Homelands (South Africa) -- Social conditions -- 20th century Apartheid -- South Africa South Africa -- Race relations Actor-network theory
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3305 , http://hdl.handle.net/10962/d1003093
- Description: Enos John Nganani Mabuza's life and work is used as a case study to highlight the conceptual and methodological theories and challenges in academic biographical writing regarding history, memory and legacies. This thesis answers the question: Who was Mabuza and what is his place or relevance in South Africa's history? We over-simplify and stereotype people because it is convenient. We judge others but there is no saint without a past or a sinner without a future. Mabuza reconciled with the main liberation movements and moved from a maligned position on the political fringes to a respectable one within the emerging black economic elite. History, like reference systems and values is not calcified or static. It is prone to interpretation, adaptation, modification, invention, manipulation, decomposition and re-composition. Bourdieu's habitus-field analysis, theory or logic of practice, notions of capital (symbolic, political, social, cultural and economic) is used together with Latour's actor-network theory as the basis of analysis of the social contracts and trust bonds that Mabuza was able to create and which enabled him to navigate South Africa's socio-political and economic milieus during apartheid and the transition in the early 1990s. As people or actors, we believe in the mantra, nothing ventured, nothing gained. We exercise agency and take risks every day. We make choices and those choices have consequences. Mabuza's choices in the fields of education, politics and business had implications for how he is perceived or has been written into history. His choices put notions of identity, citizenship, power, legitimacy, ambition, elite accommodation, class, personal and professional networks, popular struggles, agency and structure under the spotlight. Mabuza's involvement in Bantustan politics, for instance, is contextualised in terms of a historical overview of the unpopular role played by traditional authorities in South Africa before and during colonialism and apartheid. His later foray into the world of business, however, was facilitated in part, by the personal and professional contacts that he made whilst he was in politics and the opportunities which opened up during the country's political transition. Mabuza adapted to changing circumstances and demonstrated a level of versatility which other Bantustan functionaries did not or could not exercise.
- Full Text:
- Date Issued: 2011
- Authors: Sarimana, Ashley
- Date: 2011
- Subjects: Mabuza, E J (Enos John), 1939- Public officers -- South Africa South Africa -- Politics and government -- 20th century South Africa -- History -- 20th century South Africa -- Social conditions -- 20th century Homelands (South Africa) -- Politics and government -- 20th century Homelands (South Africa) -- History -- 20th century Homelands (South Africa) -- Social conditions -- 20th century Apartheid -- South Africa South Africa -- Race relations Actor-network theory
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3305 , http://hdl.handle.net/10962/d1003093
- Description: Enos John Nganani Mabuza's life and work is used as a case study to highlight the conceptual and methodological theories and challenges in academic biographical writing regarding history, memory and legacies. This thesis answers the question: Who was Mabuza and what is his place or relevance in South Africa's history? We over-simplify and stereotype people because it is convenient. We judge others but there is no saint without a past or a sinner without a future. Mabuza reconciled with the main liberation movements and moved from a maligned position on the political fringes to a respectable one within the emerging black economic elite. History, like reference systems and values is not calcified or static. It is prone to interpretation, adaptation, modification, invention, manipulation, decomposition and re-composition. Bourdieu's habitus-field analysis, theory or logic of practice, notions of capital (symbolic, political, social, cultural and economic) is used together with Latour's actor-network theory as the basis of analysis of the social contracts and trust bonds that Mabuza was able to create and which enabled him to navigate South Africa's socio-political and economic milieus during apartheid and the transition in the early 1990s. As people or actors, we believe in the mantra, nothing ventured, nothing gained. We exercise agency and take risks every day. We make choices and those choices have consequences. Mabuza's choices in the fields of education, politics and business had implications for how he is perceived or has been written into history. His choices put notions of identity, citizenship, power, legitimacy, ambition, elite accommodation, class, personal and professional networks, popular struggles, agency and structure under the spotlight. Mabuza's involvement in Bantustan politics, for instance, is contextualised in terms of a historical overview of the unpopular role played by traditional authorities in South Africa before and during colonialism and apartheid. His later foray into the world of business, however, was facilitated in part, by the personal and professional contacts that he made whilst he was in politics and the opportunities which opened up during the country's political transition. Mabuza adapted to changing circumstances and demonstrated a level of versatility which other Bantustan functionaries did not or could not exercise.
- Full Text:
- Date Issued: 2011
Psigobiografiese persoonlikheidsbeskrywing van Generaal Christiaan de Wet
- Authors: Henning, Riana
- Date: 2010
- Subjects: De Wet, Christiaan Rudolf, 1854-1922 Psychology -- Biographical methods Psychoanalysis Big Five model Politicians -- Psychology South Africa -- Politics and government -- 1836-1909 South Africa -- Politics and government -- 1909-1948
- Language: Afrikaans
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2990 , http://hdl.handle.net/10962/d1002499
- Description: Hierdie is 'n psigobiografiese studie van Generaal Christiaan Rudolph de Wet. 'n Psigobiografiese studie is die bestudering van 'n persoon se volledige lewe met die doel om die persoon beter te verstaan. Psigobiografiese navorsing maak gebruik van psigologiese teorieë wat aangewend word om die biografiese data van 'n persoon se lewe te beskryf en moontlik ook te verklaar. Die individu wat bestudeer word, is gewoonlik 'n bekende, invloedryke, navolgenswaardige, interessante of modelfiguur. Daar is tans 'n oplewing in die veld van psigobiografiese studies, maar daar word nog steeds nie genoeg in die akademiese veld gedoen om psigobiografiese studies te bevorder nie. De Wet (1854-1922) is vir hierdie studie gekies omdat hy 'n interessante, dog komplekse figuur was. Hy het veral tydens die Anglo-Boereoorlog in 1899-1902 bekendheid verwerf. As 45-jarige man het De Wet in die Anglo-Boereoorlog geveg en vinnig opgang as 'n militêre leier gemaak. Sy vindingryke ontsnappingspogings het die Britse magte hoofbrekens besorg. Wat De Wet verder uniek maak, is dat hy met net drie maande skoolopleiding in die parlement gedien het, as president verkies is, die hoogste gesag in die Verdedigingsmag gehad het en 'n boek oor sy oorlogsherinneringe geskryf het. Alhoewel daar akademiese werke oor De Wet bestaan, is daar tot op hede nog geen psigobiografiese studie oor hom gedoen nie. Die doel van die studie was om die mens agter die legende na vore te bring. Daar is ook gepoog om moontlike antwoorde en verklarings op onbeantwoorde vrae te gee. Die studie het van beide kwalitatiewe en kwantitatiewe data gebruik gemaak en kan as 'n psigobiografiese gevalstudie beskryf word. Die Vyf-faktor model van Costa en McCrae (1992) is op die biografiese data van De Wet toegepas om sodoende sy persoonlikheidseienskappe te beskryf. Die bevindinge het interessante persoonlikheidseienskappe van De Wet deur middel van die Vyf-faktor model aan die lig gebring. Volgens die kwalitatiewe navorsingsbevindinge was De Wet 'n vyandige, aksie-gedrewe, bevoegde, prestasie-strewende, selfgedissiplineerde, warm, openhartige, saggeaarde en beskeie persoon. Die kwalitatiewe en kwantitatiewe data-ontledings het uiteenlopende persoonlikheidskenmerke by De Wet geïdentifiseer. Die grootste verskille het by die fasette warmte, openhartigheid en altruïsme voorgekom. Die waarde van die studie is dat 'n wetenskaplike persoonlikheidsontleding van De Wet gedoen is. Dit is ook die eerste studie waar 'n teoretiese model op De Wet se persoonlikheid toegepas is. Alhoewel die studie sekere tekortkominge toon, beklemtoon dit terselfdertyd die wenslikheid daarvan om alternatiewe modelle te gebruik tydens die ontleding van persoonlikheidskenmerke. Die studie dui ook op die behoefte aan verdere navorsing, byvoorbeeld soortgelyke ontledings en vergelykings van die persoonlikhede van ander militêre bevelvoerders (De la Rey, Smuts, Beyers, Hertzog).
- Full Text:
- Date Issued: 2010
- Authors: Henning, Riana
- Date: 2010
- Subjects: De Wet, Christiaan Rudolf, 1854-1922 Psychology -- Biographical methods Psychoanalysis Big Five model Politicians -- Psychology South Africa -- Politics and government -- 1836-1909 South Africa -- Politics and government -- 1909-1948
- Language: Afrikaans
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2990 , http://hdl.handle.net/10962/d1002499
- Description: Hierdie is 'n psigobiografiese studie van Generaal Christiaan Rudolph de Wet. 'n Psigobiografiese studie is die bestudering van 'n persoon se volledige lewe met die doel om die persoon beter te verstaan. Psigobiografiese navorsing maak gebruik van psigologiese teorieë wat aangewend word om die biografiese data van 'n persoon se lewe te beskryf en moontlik ook te verklaar. Die individu wat bestudeer word, is gewoonlik 'n bekende, invloedryke, navolgenswaardige, interessante of modelfiguur. Daar is tans 'n oplewing in die veld van psigobiografiese studies, maar daar word nog steeds nie genoeg in die akademiese veld gedoen om psigobiografiese studies te bevorder nie. De Wet (1854-1922) is vir hierdie studie gekies omdat hy 'n interessante, dog komplekse figuur was. Hy het veral tydens die Anglo-Boereoorlog in 1899-1902 bekendheid verwerf. As 45-jarige man het De Wet in die Anglo-Boereoorlog geveg en vinnig opgang as 'n militêre leier gemaak. Sy vindingryke ontsnappingspogings het die Britse magte hoofbrekens besorg. Wat De Wet verder uniek maak, is dat hy met net drie maande skoolopleiding in die parlement gedien het, as president verkies is, die hoogste gesag in die Verdedigingsmag gehad het en 'n boek oor sy oorlogsherinneringe geskryf het. Alhoewel daar akademiese werke oor De Wet bestaan, is daar tot op hede nog geen psigobiografiese studie oor hom gedoen nie. Die doel van die studie was om die mens agter die legende na vore te bring. Daar is ook gepoog om moontlike antwoorde en verklarings op onbeantwoorde vrae te gee. Die studie het van beide kwalitatiewe en kwantitatiewe data gebruik gemaak en kan as 'n psigobiografiese gevalstudie beskryf word. Die Vyf-faktor model van Costa en McCrae (1992) is op die biografiese data van De Wet toegepas om sodoende sy persoonlikheidseienskappe te beskryf. Die bevindinge het interessante persoonlikheidseienskappe van De Wet deur middel van die Vyf-faktor model aan die lig gebring. Volgens die kwalitatiewe navorsingsbevindinge was De Wet 'n vyandige, aksie-gedrewe, bevoegde, prestasie-strewende, selfgedissiplineerde, warm, openhartige, saggeaarde en beskeie persoon. Die kwalitatiewe en kwantitatiewe data-ontledings het uiteenlopende persoonlikheidskenmerke by De Wet geïdentifiseer. Die grootste verskille het by die fasette warmte, openhartigheid en altruïsme voorgekom. Die waarde van die studie is dat 'n wetenskaplike persoonlikheidsontleding van De Wet gedoen is. Dit is ook die eerste studie waar 'n teoretiese model op De Wet se persoonlikheid toegepas is. Alhoewel die studie sekere tekortkominge toon, beklemtoon dit terselfdertyd die wenslikheid daarvan om alternatiewe modelle te gebruik tydens die ontleding van persoonlikheidskenmerke. Die studie dui ook op die behoefte aan verdere navorsing, byvoorbeeld soortgelyke ontledings en vergelykings van die persoonlikhede van ander militêre bevelvoerders (De la Rey, Smuts, Beyers, Hertzog).
- Full Text:
- Date Issued: 2010
The growth and reproduction of the freshwater limpet Burnupia stenochorias (Pulmonata, Ancylidae), and an evaluation of its use as an ecotoxicology indicator in whole effluent testing
- Davies-Coleman, H D (Heather D)
- Authors: Davies-Coleman, H D (Heather D)
- Date: 2002
- Subjects: Ancylidae Effluent quality Toxicity testing
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5703 , http://hdl.handle.net/10962/d1005389
- Description: For the protection of the ecological Reserve in South Africa, the proposed introduction of compulsory toxicity testing in the licensing of effluent discharges necessitates the development of whole effluent toxicity testing. The elucidation of the effects of effluent on the local indigenous populations of organisms is essential before hazard and risk assessment can be undertaken. The limpet Burnupia stenochorias, prevalent in the Eastern Cape of South Africa, was chosen to represent the freshwater molluscs as a potential toxicity indicator. Using potassium dichromate (as a reference toxicant) and a textile whole effluent, the suitability of B. stenochorias was assessed under both acute and chronic toxicity conditions in the laboratory. In support of the toxicity studies, aspects of the biology of B. stenochorias were investigated under both natural and laboratory conditions. Using Principal Component and Discriminant Function Analyses, the relative shell morphometrics of three feral populations of B. stenochorias were found to vary. Length was shown to adequately represent growth of the shell, although the inclusion of width measurements is more statistically preferable. Two of the feral populations, one in impacted water, were studied weekly for 52 weeks to assess natural population dynamics. Based on the Von Bertalanffy Growth Equation, estimates of growth and longevity were made for this species, with growth highly seasonal. Age is not easily discerned from shell size. Egg laying occurred all year round, with early summer (peak egg lay), mid summer (a second, smaller peak in egg lay), and winter (limited presence of eggs) phases. In toxicity testing, consideration is given to the choice of the test organism based on age and sexual development. Consequently, the sexual development of B. stenochorias relative to shell length was determined with the aid of histological examinations of transverse sections of limpets, of all sizes, collected over one year. Limpets less than 3mm shell length were found to be immature in the development of the oocytes and spermatozoa, and were later chosen for acute toxicity tests. A laboratory diet was developed, for both culturing and maintaining of the limpets during toxicity tests; however, the diet requires optimisation. Under laboratory conditions, growth was linear, and individual fecundity highly variable. Successful methods for the collection of limpets from naturally occurring populations, and their acclimation to the laboratory were developed. Three B. stenochorias populations, representing different hydrological and water quality conditions, were compared to a laboratory population (maintained for three years) in their responses to the textile whole effluent and potassium dichromate. Under acute conditions, variability of mortality between limpet populations and between seasons was consistent with acceptable international standards. However, seasonal differences between feral limpets were apparent, with early summer limpets significantly more susceptible to both potassium dichromate and textile effluent than winter limpets. Although mortality occurred within the effluent at all concentrations, no 96 hour LC₅₀ values were obtained. The chronic toxicity effects of the textile whole effluent were assessed over the entire life cycle of B. stenochorias, based on survival, growth and reproductive effects. Lower concentrations of effluent (# 10%) gave greater variability of responses and toxicity than higher concentrations, with a 43 day LC₅₀ of 3.9% effluent. The No Observed Effect Concentrations for survival (over 43 days) were calculated in consecutive years as 0.1% and 1% effluent. Survival is considered a useful tool for determining toxicity endpoints using B. stenochorias. Limpet growth remained linear in effluent, with an apparent stimulation of growth at the 3-10% effluent concentration, confusing the toxicity and variability assessments. The possible addition of nutrients from the effluent points to either a potential inadequacy of the food quality provided in the chronic assessment, or the presence in the effluent of growth stimulants. Growth was also found to be too variable to allow adequate statistical conclusions about the toxicity of the effluent, although it is suggested that growth may be useful in the assessment of single compounds. Despite large individual variability in fecundity, statistical differences were discernible between effluent concentrations. The application of fecundity of B. stenochorias in hazard assessment therefore warrants further investigation. It was concluded that an assessment of textile whole effluent toxicity to B. stenochorias over an entire life cycle, and an F1 generation, is unnecessary. The development of the bucket/plastic bag method for both acute and chronic toxicity assessment of B. stenochorias was useful. In the final assessment of the usefulness of B. stenochorias as a toxicity indicator, toxicity endpoints were compared with those of the standard laboratory organism Daphnia pulex. Both in acute and chronic toxicity, B. stenochorias was found to be more sensitive. B. stenochorias is therefore considered valuable as a South African freshwater molluscan ecotoxicological indicator, with a place in hazard assessment, although further development and research is necessary before the limpet can be effectively used.
- Full Text:
- Date Issued: 2002
- Authors: Davies-Coleman, H D (Heather D)
- Date: 2002
- Subjects: Ancylidae Effluent quality Toxicity testing
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5703 , http://hdl.handle.net/10962/d1005389
- Description: For the protection of the ecological Reserve in South Africa, the proposed introduction of compulsory toxicity testing in the licensing of effluent discharges necessitates the development of whole effluent toxicity testing. The elucidation of the effects of effluent on the local indigenous populations of organisms is essential before hazard and risk assessment can be undertaken. The limpet Burnupia stenochorias, prevalent in the Eastern Cape of South Africa, was chosen to represent the freshwater molluscs as a potential toxicity indicator. Using potassium dichromate (as a reference toxicant) and a textile whole effluent, the suitability of B. stenochorias was assessed under both acute and chronic toxicity conditions in the laboratory. In support of the toxicity studies, aspects of the biology of B. stenochorias were investigated under both natural and laboratory conditions. Using Principal Component and Discriminant Function Analyses, the relative shell morphometrics of three feral populations of B. stenochorias were found to vary. Length was shown to adequately represent growth of the shell, although the inclusion of width measurements is more statistically preferable. Two of the feral populations, one in impacted water, were studied weekly for 52 weeks to assess natural population dynamics. Based on the Von Bertalanffy Growth Equation, estimates of growth and longevity were made for this species, with growth highly seasonal. Age is not easily discerned from shell size. Egg laying occurred all year round, with early summer (peak egg lay), mid summer (a second, smaller peak in egg lay), and winter (limited presence of eggs) phases. In toxicity testing, consideration is given to the choice of the test organism based on age and sexual development. Consequently, the sexual development of B. stenochorias relative to shell length was determined with the aid of histological examinations of transverse sections of limpets, of all sizes, collected over one year. Limpets less than 3mm shell length were found to be immature in the development of the oocytes and spermatozoa, and were later chosen for acute toxicity tests. A laboratory diet was developed, for both culturing and maintaining of the limpets during toxicity tests; however, the diet requires optimisation. Under laboratory conditions, growth was linear, and individual fecundity highly variable. Successful methods for the collection of limpets from naturally occurring populations, and their acclimation to the laboratory were developed. Three B. stenochorias populations, representing different hydrological and water quality conditions, were compared to a laboratory population (maintained for three years) in their responses to the textile whole effluent and potassium dichromate. Under acute conditions, variability of mortality between limpet populations and between seasons was consistent with acceptable international standards. However, seasonal differences between feral limpets were apparent, with early summer limpets significantly more susceptible to both potassium dichromate and textile effluent than winter limpets. Although mortality occurred within the effluent at all concentrations, no 96 hour LC₅₀ values were obtained. The chronic toxicity effects of the textile whole effluent were assessed over the entire life cycle of B. stenochorias, based on survival, growth and reproductive effects. Lower concentrations of effluent (# 10%) gave greater variability of responses and toxicity than higher concentrations, with a 43 day LC₅₀ of 3.9% effluent. The No Observed Effect Concentrations for survival (over 43 days) were calculated in consecutive years as 0.1% and 1% effluent. Survival is considered a useful tool for determining toxicity endpoints using B. stenochorias. Limpet growth remained linear in effluent, with an apparent stimulation of growth at the 3-10% effluent concentration, confusing the toxicity and variability assessments. The possible addition of nutrients from the effluent points to either a potential inadequacy of the food quality provided in the chronic assessment, or the presence in the effluent of growth stimulants. Growth was also found to be too variable to allow adequate statistical conclusions about the toxicity of the effluent, although it is suggested that growth may be useful in the assessment of single compounds. Despite large individual variability in fecundity, statistical differences were discernible between effluent concentrations. The application of fecundity of B. stenochorias in hazard assessment therefore warrants further investigation. It was concluded that an assessment of textile whole effluent toxicity to B. stenochorias over an entire life cycle, and an F1 generation, is unnecessary. The development of the bucket/plastic bag method for both acute and chronic toxicity assessment of B. stenochorias was useful. In the final assessment of the usefulness of B. stenochorias as a toxicity indicator, toxicity endpoints were compared with those of the standard laboratory organism Daphnia pulex. Both in acute and chronic toxicity, B. stenochorias was found to be more sensitive. B. stenochorias is therefore considered valuable as a South African freshwater molluscan ecotoxicological indicator, with a place in hazard assessment, although further development and research is necessary before the limpet can be effectively used.
- Full Text:
- Date Issued: 2002