Benchmark value chain clusters, agglomeration economies and dynamic externalities : an intergrated approach to regional economic development
- Authors: Zeelie, Eben Johannes
- Date: 2009
- Subjects: Industrial clusters , Regional economics , Regional economic disparities , Economic development , Regional planning
- Language: English
- Type: Thesis , Doctoral , DBA
- Identifier: vital:8594 , http://hdl.handle.net/10948/1086 , Industrial clusters , Regional economics , Regional economic disparities , Economic development , Regional planning
- Description: From the broad overview of the cluster literature, the proposition emerges that the manipulation of regional economic structural and cluster factor conditions within a geographically proximate region can translate into sustainable regional economic growth outcomes. As a first step in exploring this research, a theoretical framework for the conceptualisation of industry clusters was established and a methodological framework applied to statistically identify major manufacturing value chain clusters in the Eastern Cape Province. This methodology combines a strength-of-linkage measure for all pairs of supply and use sectors (as revealed in the systematic analysis of intermediate purchasing and sales patterns in the South African Final Supply and Use Tables: 2002) with the application of Ward’s hierarchical cluster algorithm to map the national benchmark value chain clusters in the South African national economy. The ensuing national value chain benchmark cluster framework was then transposed to the Eastern Cape Province to reveal cluster concentrations and gaps that exist in the value chain clusters in the province. The methodology applied in this study provides an objective and clear perspective of inter-industry linkages in the South African economy and produces more detailed and evenly distributed clusters than traditional cluster identification methodologies. Secondary linkages were determined for each of the twenty-six core value chain clusters to depict the diversity of sectors linked to the respective core clusters. In transposing the national benchmark value chain cluster framework onto the Eastern Cape Province economy, a number of distinct advantages emerge. Firstly, it reveals gaps in value chain cluster groupings that may be filled through industry recruiting or regional business development strategies. However, not all industries absent from value chain clusters in the region are equally attractive for recruitment. Henceforth, the number of direct and indirect linkages to industries absent from the Eastern Cape Province serves as a measure of their relative attractiveness when considering their recruitment into the region. vi The benchmark value chain cluster framework alone does not explain which agglomeration externalities are generated and exploited within each cluster, but it served as the overarching framework for the remainder of the research. Accordingly, the value chain cluster framework was applied to evidence whether specialisation, competition or diversity (represented by MAR, Porter and Jacobs economies respectively) is the operative mechanism in generating cluster growth in the Eastern Cape Province. Since agglomeration externalities are not directly observable, construct-valid indicators for the various externalities, as well as appropriate mechanisms to empirically assess the statistical relevance of MAR-, Porter and Jacobs economies in stimulating cluster growth, were established. This thesis added to agglomeration literature by disaggregating the standard measure of diversity externalities into two unique diversity indicators, namely supply diversity (SDiv) and use diversity (UDiv). The SDiv- and UDiv coefficients measure the degree to which a value chain cluster’s supplying/user sectoral mix at provincial level differs from that of the cluster grouping at the national level. This distinction between supply-and use diversity developed in this study firstly provides a clearer insight into the relative regional presence of supplying- and using sectors to the various value chain clusters, and secondly, serves as a useful mechanism to regional policymakers in identifying industries that may be targeted for investment into a region. Therefore, by separating the diversity into its two components, a clear distinction can be drawn between the impact of supplying- and using sectors on value chain cluster growth in a particular region. From a narrow perspective, the empirical findings validate both the Marshall Arrow Romer- (small positive impact of regional cluster concentration) and the Jacobs theory (significant positive impact of cluster supply- and use diversity on cluster growth), while it invalidates Porter’s theory (no correlation between competition and cluster performance). The positive effect size recorded between the level of value chain cluster concentration and differential growth indicates that policy makers in the Eastern Cape Province will be well advised to direct growth interventions towards larger concentrated clusters, than towards smaller, incipient value chain clusters. Additionally, vii the effectiveness of targeted inward FDI to the Eastern Cape Province may be raised by evaluating the economic impact against current value chain cluster structure, as well as the effect on the supply- and use diversities of existing value chain clusters in the province. This thesis has also illustrated that value chain clusters that are concentrated in the region, show a positive effect size with the level of supply diversity in the region. Conversely, value chain clusters that reflect high levels of competitiveness record a positive effect size with use diversity. Policy interventions aimed at raising the performance of value chain clusters typified by smaller players in a competitive environment, should therefore consider raising the respective levels of use diversity in the region. This research awakens the proposition that a reliance on a serendipitous approach to generate dynamic externalities is not sufficient, and that certain factor conditions favour the transfer of tacit knowledge between cluster members. Accordingly, this research empirically explored whether statistically significant relationships can be detected between the common cluster elements, or factor conditions, that serve as conduits for the transfer of dynamic externalities and value chain cluster growth in the Eastern Cape Province. The findings indicate that linkages with knowledge generating institutions in the Eastern Cape Province do, albeit to a relatively small extent, have an impact on value chain cluster growth, and validates the assertion that cognitive enhancing institutions contribute to cluster growth. The importance of backward and forward linkages in nurturing regional growth is signified by the moderate effect size recorded by the level of vertical linkages and total value chain cluster growth. Similarly, a moderate effect size was recorded between the level of horizontal linkages and value chain cluster growth, which shows that cooperation amongst competing firms do stimulate cluster and regional growth in the Eastern Cape Province and affirms the proposition that inter-firm linkages on both vertical- and horizontal levels stimulate cluster growth. An expectation was that the institutional framework conditions would have a significant impact on value chain cluster growth in the Eastern Cape Province. However, the empirical findings reflect that the institutional framework conditions have no statistical impact on value chain cluster growth. The study also found a moderate, positive effect size between value chain cluster size (number of employees) and growth, which shows viii that size matters in regional growth. In other words, in contrast to their European counterparts, the larger the number of employees per value chain cluster, the greater the impact on value chain cluster growth in the Eastern Cape Province.
- Full Text:
- Date Issued: 2009
- Authors: Zeelie, Eben Johannes
- Date: 2009
- Subjects: Industrial clusters , Regional economics , Regional economic disparities , Economic development , Regional planning
- Language: English
- Type: Thesis , Doctoral , DBA
- Identifier: vital:8594 , http://hdl.handle.net/10948/1086 , Industrial clusters , Regional economics , Regional economic disparities , Economic development , Regional planning
- Description: From the broad overview of the cluster literature, the proposition emerges that the manipulation of regional economic structural and cluster factor conditions within a geographically proximate region can translate into sustainable regional economic growth outcomes. As a first step in exploring this research, a theoretical framework for the conceptualisation of industry clusters was established and a methodological framework applied to statistically identify major manufacturing value chain clusters in the Eastern Cape Province. This methodology combines a strength-of-linkage measure for all pairs of supply and use sectors (as revealed in the systematic analysis of intermediate purchasing and sales patterns in the South African Final Supply and Use Tables: 2002) with the application of Ward’s hierarchical cluster algorithm to map the national benchmark value chain clusters in the South African national economy. The ensuing national value chain benchmark cluster framework was then transposed to the Eastern Cape Province to reveal cluster concentrations and gaps that exist in the value chain clusters in the province. The methodology applied in this study provides an objective and clear perspective of inter-industry linkages in the South African economy and produces more detailed and evenly distributed clusters than traditional cluster identification methodologies. Secondary linkages were determined for each of the twenty-six core value chain clusters to depict the diversity of sectors linked to the respective core clusters. In transposing the national benchmark value chain cluster framework onto the Eastern Cape Province economy, a number of distinct advantages emerge. Firstly, it reveals gaps in value chain cluster groupings that may be filled through industry recruiting or regional business development strategies. However, not all industries absent from value chain clusters in the region are equally attractive for recruitment. Henceforth, the number of direct and indirect linkages to industries absent from the Eastern Cape Province serves as a measure of their relative attractiveness when considering their recruitment into the region. vi The benchmark value chain cluster framework alone does not explain which agglomeration externalities are generated and exploited within each cluster, but it served as the overarching framework for the remainder of the research. Accordingly, the value chain cluster framework was applied to evidence whether specialisation, competition or diversity (represented by MAR, Porter and Jacobs economies respectively) is the operative mechanism in generating cluster growth in the Eastern Cape Province. Since agglomeration externalities are not directly observable, construct-valid indicators for the various externalities, as well as appropriate mechanisms to empirically assess the statistical relevance of MAR-, Porter and Jacobs economies in stimulating cluster growth, were established. This thesis added to agglomeration literature by disaggregating the standard measure of diversity externalities into two unique diversity indicators, namely supply diversity (SDiv) and use diversity (UDiv). The SDiv- and UDiv coefficients measure the degree to which a value chain cluster’s supplying/user sectoral mix at provincial level differs from that of the cluster grouping at the national level. This distinction between supply-and use diversity developed in this study firstly provides a clearer insight into the relative regional presence of supplying- and using sectors to the various value chain clusters, and secondly, serves as a useful mechanism to regional policymakers in identifying industries that may be targeted for investment into a region. Therefore, by separating the diversity into its two components, a clear distinction can be drawn between the impact of supplying- and using sectors on value chain cluster growth in a particular region. From a narrow perspective, the empirical findings validate both the Marshall Arrow Romer- (small positive impact of regional cluster concentration) and the Jacobs theory (significant positive impact of cluster supply- and use diversity on cluster growth), while it invalidates Porter’s theory (no correlation between competition and cluster performance). The positive effect size recorded between the level of value chain cluster concentration and differential growth indicates that policy makers in the Eastern Cape Province will be well advised to direct growth interventions towards larger concentrated clusters, than towards smaller, incipient value chain clusters. Additionally, vii the effectiveness of targeted inward FDI to the Eastern Cape Province may be raised by evaluating the economic impact against current value chain cluster structure, as well as the effect on the supply- and use diversities of existing value chain clusters in the province. This thesis has also illustrated that value chain clusters that are concentrated in the region, show a positive effect size with the level of supply diversity in the region. Conversely, value chain clusters that reflect high levels of competitiveness record a positive effect size with use diversity. Policy interventions aimed at raising the performance of value chain clusters typified by smaller players in a competitive environment, should therefore consider raising the respective levels of use diversity in the region. This research awakens the proposition that a reliance on a serendipitous approach to generate dynamic externalities is not sufficient, and that certain factor conditions favour the transfer of tacit knowledge between cluster members. Accordingly, this research empirically explored whether statistically significant relationships can be detected between the common cluster elements, or factor conditions, that serve as conduits for the transfer of dynamic externalities and value chain cluster growth in the Eastern Cape Province. The findings indicate that linkages with knowledge generating institutions in the Eastern Cape Province do, albeit to a relatively small extent, have an impact on value chain cluster growth, and validates the assertion that cognitive enhancing institutions contribute to cluster growth. The importance of backward and forward linkages in nurturing regional growth is signified by the moderate effect size recorded by the level of vertical linkages and total value chain cluster growth. Similarly, a moderate effect size was recorded between the level of horizontal linkages and value chain cluster growth, which shows that cooperation amongst competing firms do stimulate cluster and regional growth in the Eastern Cape Province and affirms the proposition that inter-firm linkages on both vertical- and horizontal levels stimulate cluster growth. An expectation was that the institutional framework conditions would have a significant impact on value chain cluster growth in the Eastern Cape Province. However, the empirical findings reflect that the institutional framework conditions have no statistical impact on value chain cluster growth. The study also found a moderate, positive effect size between value chain cluster size (number of employees) and growth, which shows viii that size matters in regional growth. In other words, in contrast to their European counterparts, the larger the number of employees per value chain cluster, the greater the impact on value chain cluster growth in the Eastern Cape Province.
- Full Text:
- Date Issued: 2009
Bioconditioning and nitrogen fertility effects of selected cyanobacteria strains on two degraded soils in the Eastern Cape Province, South Africa
- Authors: Maqubela, Mfundo Phakama
- Date: 2009
- Subjects: Nostoc , Cyanobacteria , Soil fertility -- Testing , Soils -- Nitrogen content , Cyanobacteria -- Biotechnology
- Language: English
- Type: Thesis , Doctoral , PhD (Soil Science)
- Identifier: vital:11959 , http://hdl.handle.net/10353/558 , Nostoc , Cyanobacteria , Soil fertility -- Testing , Soils -- Nitrogen content , Cyanobacteria -- Biotechnology
- Description: Some cyanobacteria strains have biofertilization and bioconditioning effects in soils. The objective of this study was to identify cyanobacteria with potential to improve the N fertility and structural stability of degraded soils and evaluate their effectiveness in soils of the Eastern Cape, South Africa. Isolation and characterization of the indigenous cyanobacteria strains with desirable properties was first to be undertaken because their effects are known to differ from strain to strain. Cyanobacteria strains 3g, 3v, and 7e were identified from 97 strains isolated from selected soils. Nostoc strains 3g and 3v had greater ability to produce exocellular polysaccharides (EPS) but low potential to fix atmospheric N2 (4.7 and 1.3 nmol C2H4 μg chl-1 h-1, respectively). On the other hand, strain 7e had the highest capability to fix atmospheric N2 (16.1 nmol C2H4 μg chl-1 h-1) but had the least ability to produce EPS. Evaluation of the strains was done in glasshouse studies starting with Nostoc strain 9v isolated from a Tanzanian soil, followed by the indigenous strains isolated from soils in Hertzog and Qunu, South Africa. Inoculation was done by uniformly applying cyanobacteria on the surface of potted soils at a rate of 6 g m-2. First harvest and soil sampling took place after six weeks, and the top 25 mm of the soil was mixed, replanted, and sampled again after a further six weeks (second harvest). Inoculation with Nostoc strain 9v increased soil N by 40 percent and 17 percent in Guquka and Hertzog soils, respectively, and consequently increased maize dry matter yields by 40 and 49 percent. Soil C increased by 27 percent and 8 percent in Guquka and Hertzog soils, respectively, and this increase was significantly associated with that of soil N (R2 = 0.838). Higher contents of soil C, soil N and mineral N, however, were found in non-cropped soils. Scanning Electron Microscopy (SEM) revealed coatings of EPS on soil particles and fragments of non-cropped inoculated soils, with iii other particles enmeshed in networks of filaments, in contrast to cropped and/or non-inoculated soils. The proportion of very stable aggregates was increased by inoculation but cropping with maize reduced the aggregate stability. Inoculating Hertzog soil with indigenous strains 3g and 7e increased the nitrate N in the first cropping by 49 percent and 69 percent respectively, in cropped soils. In the second cropping increases in mineral N were 41 percent and 43 percent in 3g and 7e inoculated soils, respectively. Maize dry matter yields were higher on inoculated soils both in the first and second harvest in response to the improved N status of the soil. Increases in aggregate MWD in cropped soil as determined by fast wetting, mechanical breakdown and slow wetting were 85 percent, 33 percent, 33 percent, respectively, for 3g inoculation, 64 percent, 41 percent, and 41 percent, respectively, for 7e inoculation and 60 percent, 24 percent, 50 percent for inoculation with 9v. In non-cropped soil, increases in MWD as determined by fast wetting, mechanical breakdown and slow wetting were 11 percent, 0 percent, 7 percent, respectively for 3g inoculation, 21 percent, 11 percent, and 7 percent, respectively for 7e inoculation, and 25 percent, 36 percent, and 19 percent for strain 9v inoculation. Scanning electron microscopy observations, which were confirmed by chemical results, revealed that inoculated soils had high EPS and filaments that encouraged soil aggregation and improved aggregate stability. Results of this study show that cyanobacteria strains isolated and selected for their ability to fix atmospheric N2 and produce EPS improved the fertility status and aggregate stability of degraded soils from South Africa.
- Full Text:
- Date Issued: 2009
- Authors: Maqubela, Mfundo Phakama
- Date: 2009
- Subjects: Nostoc , Cyanobacteria , Soil fertility -- Testing , Soils -- Nitrogen content , Cyanobacteria -- Biotechnology
- Language: English
- Type: Thesis , Doctoral , PhD (Soil Science)
- Identifier: vital:11959 , http://hdl.handle.net/10353/558 , Nostoc , Cyanobacteria , Soil fertility -- Testing , Soils -- Nitrogen content , Cyanobacteria -- Biotechnology
- Description: Some cyanobacteria strains have biofertilization and bioconditioning effects in soils. The objective of this study was to identify cyanobacteria with potential to improve the N fertility and structural stability of degraded soils and evaluate their effectiveness in soils of the Eastern Cape, South Africa. Isolation and characterization of the indigenous cyanobacteria strains with desirable properties was first to be undertaken because their effects are known to differ from strain to strain. Cyanobacteria strains 3g, 3v, and 7e were identified from 97 strains isolated from selected soils. Nostoc strains 3g and 3v had greater ability to produce exocellular polysaccharides (EPS) but low potential to fix atmospheric N2 (4.7 and 1.3 nmol C2H4 μg chl-1 h-1, respectively). On the other hand, strain 7e had the highest capability to fix atmospheric N2 (16.1 nmol C2H4 μg chl-1 h-1) but had the least ability to produce EPS. Evaluation of the strains was done in glasshouse studies starting with Nostoc strain 9v isolated from a Tanzanian soil, followed by the indigenous strains isolated from soils in Hertzog and Qunu, South Africa. Inoculation was done by uniformly applying cyanobacteria on the surface of potted soils at a rate of 6 g m-2. First harvest and soil sampling took place after six weeks, and the top 25 mm of the soil was mixed, replanted, and sampled again after a further six weeks (second harvest). Inoculation with Nostoc strain 9v increased soil N by 40 percent and 17 percent in Guquka and Hertzog soils, respectively, and consequently increased maize dry matter yields by 40 and 49 percent. Soil C increased by 27 percent and 8 percent in Guquka and Hertzog soils, respectively, and this increase was significantly associated with that of soil N (R2 = 0.838). Higher contents of soil C, soil N and mineral N, however, were found in non-cropped soils. Scanning Electron Microscopy (SEM) revealed coatings of EPS on soil particles and fragments of non-cropped inoculated soils, with iii other particles enmeshed in networks of filaments, in contrast to cropped and/or non-inoculated soils. The proportion of very stable aggregates was increased by inoculation but cropping with maize reduced the aggregate stability. Inoculating Hertzog soil with indigenous strains 3g and 7e increased the nitrate N in the first cropping by 49 percent and 69 percent respectively, in cropped soils. In the second cropping increases in mineral N were 41 percent and 43 percent in 3g and 7e inoculated soils, respectively. Maize dry matter yields were higher on inoculated soils both in the first and second harvest in response to the improved N status of the soil. Increases in aggregate MWD in cropped soil as determined by fast wetting, mechanical breakdown and slow wetting were 85 percent, 33 percent, 33 percent, respectively, for 3g inoculation, 64 percent, 41 percent, and 41 percent, respectively, for 7e inoculation and 60 percent, 24 percent, 50 percent for inoculation with 9v. In non-cropped soil, increases in MWD as determined by fast wetting, mechanical breakdown and slow wetting were 11 percent, 0 percent, 7 percent, respectively for 3g inoculation, 21 percent, 11 percent, and 7 percent, respectively for 7e inoculation, and 25 percent, 36 percent, and 19 percent for strain 9v inoculation. Scanning electron microscopy observations, which were confirmed by chemical results, revealed that inoculated soils had high EPS and filaments that encouraged soil aggregation and improved aggregate stability. Results of this study show that cyanobacteria strains isolated and selected for their ability to fix atmospheric N2 and produce EPS improved the fertility status and aggregate stability of degraded soils from South Africa.
- Full Text:
- Date Issued: 2009
Breaking down subtle and implicit racial divides in higher education institutions : an educational management perspective
- Toni, Mademoiselle Noluthando
- Authors: Toni, Mademoiselle Noluthando
- Date: 2009
- Subjects: Racism in higher education -- South Africa -- Port Elizabeth , Educational change -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Doctoral , DEd
- Identifier: vital:9529 , http://hdl.handle.net/10948/876 , Racism in higher education -- South Africa -- Port Elizabeth , Educational change -- South Africa -- Port Elizabeth
- Description: This thesis examined the manifestations of the various forms of racism in a South African institution of higher learning, the Nelson Mandela Metropolitan University (NMMU). The study further attempted to confront racism from the perspective of finding ways in which human relations of a diversified higher education population could be improved. As the issue at hand in this study relates to racism, critical race theory (CRT) was explored in an attempt to understand different perceptions and ways of dealing with racial inequality. CRT recognizes the complexities of racism and the construction of race as a way of justifying political, economic and social inequality (Stovall, 2006:247). This understanding played a role in making sense of perceived racial discrimination which is also connected to gender, age and social class. CRT conceptual tools, such as stories and counter stories featured strongly in the data collection process. Understanding the relationships of power, race and racism, as advocated by CRT, was vital in the process of analyzing data, reporting on the findings, and the proposed recommendations. The empirical data and literature provided insight in the design of a ‘Wheel of Humanity’ which serves as a succinct portrayal of ideas that can work in nurturing acceptable, to better, human relations. The study revealed that Meta-stereotypes influenced the perceptions of racist attitudes, behaviours and practices. As much as overt forms of racism were reported as minimal, subtle and implicit forms still exist, and are aggravated by the ‘culture of power’ that is taken for granted. The success of initiatives designed for the purposes of going beyond race, and adopting a humane approach in instilling the principles of ubuntu, depends on changing attitudes and preconceived ideas.
- Full Text:
- Date Issued: 2009
- Authors: Toni, Mademoiselle Noluthando
- Date: 2009
- Subjects: Racism in higher education -- South Africa -- Port Elizabeth , Educational change -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Doctoral , DEd
- Identifier: vital:9529 , http://hdl.handle.net/10948/876 , Racism in higher education -- South Africa -- Port Elizabeth , Educational change -- South Africa -- Port Elizabeth
- Description: This thesis examined the manifestations of the various forms of racism in a South African institution of higher learning, the Nelson Mandela Metropolitan University (NMMU). The study further attempted to confront racism from the perspective of finding ways in which human relations of a diversified higher education population could be improved. As the issue at hand in this study relates to racism, critical race theory (CRT) was explored in an attempt to understand different perceptions and ways of dealing with racial inequality. CRT recognizes the complexities of racism and the construction of race as a way of justifying political, economic and social inequality (Stovall, 2006:247). This understanding played a role in making sense of perceived racial discrimination which is also connected to gender, age and social class. CRT conceptual tools, such as stories and counter stories featured strongly in the data collection process. Understanding the relationships of power, race and racism, as advocated by CRT, was vital in the process of analyzing data, reporting on the findings, and the proposed recommendations. The empirical data and literature provided insight in the design of a ‘Wheel of Humanity’ which serves as a succinct portrayal of ideas that can work in nurturing acceptable, to better, human relations. The study revealed that Meta-stereotypes influenced the perceptions of racist attitudes, behaviours and practices. As much as overt forms of racism were reported as minimal, subtle and implicit forms still exist, and are aggravated by the ‘culture of power’ that is taken for granted. The success of initiatives designed for the purposes of going beyond race, and adopting a humane approach in instilling the principles of ubuntu, depends on changing attitudes and preconceived ideas.
- Full Text:
- Date Issued: 2009
Cattle production on communal rangelands of South Africa and the potential of acacia karroo in improving Nguni beef production
- Authors: Mapiye, Cletos
- Date: 2009
- Subjects: Nguni cattle -- South Africa -- Eastern Cape , Beef cattle -- South Africa -- Eastern Cape , Beef cattle breeds -- South Africa -- Eastern Cape , Beef cattle -- Breeding -- South Africa -- Eastern Cape , Communal rangelands -- South Africa -- Eastern Cape , Grazing -- South Africa -- Eastern Cape , Range management -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD (Animal Science)
- Identifier: vital:11161 , http://hdl.handle.net/10353/d1000989 , Nguni cattle -- South Africa -- Eastern Cape , Beef cattle -- South Africa -- Eastern Cape , Beef cattle breeds -- South Africa -- Eastern Cape , Beef cattle -- Breeding -- South Africa -- Eastern Cape , Communal rangelands -- South Africa -- Eastern Cape , Grazing -- South Africa -- Eastern Cape , Range management -- South Africa -- Eastern Cape
- Full Text:
- Date Issued: 2009
- Authors: Mapiye, Cletos
- Date: 2009
- Subjects: Nguni cattle -- South Africa -- Eastern Cape , Beef cattle -- South Africa -- Eastern Cape , Beef cattle breeds -- South Africa -- Eastern Cape , Beef cattle -- Breeding -- South Africa -- Eastern Cape , Communal rangelands -- South Africa -- Eastern Cape , Grazing -- South Africa -- Eastern Cape , Range management -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD (Animal Science)
- Identifier: vital:11161 , http://hdl.handle.net/10353/d1000989 , Nguni cattle -- South Africa -- Eastern Cape , Beef cattle -- South Africa -- Eastern Cape , Beef cattle breeds -- South Africa -- Eastern Cape , Beef cattle -- Breeding -- South Africa -- Eastern Cape , Communal rangelands -- South Africa -- Eastern Cape , Grazing -- South Africa -- Eastern Cape , Range management -- South Africa -- Eastern Cape
- Full Text:
- Date Issued: 2009
Chang liver cell line as a model for Type II Diabetes in the liver and possible reversal of this condition by an indigenous medicinal plant
- Authors: Williams, Saralene Iona
- Date: 2009
- Subjects: Diabetes -- Alternative treatment , Medicinal plants , Traditional medicine , Liver -- Diseases
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10339 , http://hdl.handle.net/10948/d1016179
- Description: The incidence of Type 2 Diabetes Mellittus (T2DM) is increasing world wide. In Africa the limited access to health care and the insidious course of the disease lead to more severe illness and diabetic complications. There is a need to find alternative approaches to treatment and prevention that address the problems and needs of Africa. Sutherlandia frutescens (S.frutescens) is a traditional herbal plant with known anti-diabetic properties, the precise mechanism of action of S.frutescens is not known. In order to develop new approaches for treatment and prevention of T2DM the pathophysiology of T2DM must be understood. T2DM is the final outcome of a multi-organ disease characterized by early defects in muscle, adipocytes, hepatocytes and pancreatic β-cells. In this study the role of the liver was investigated because of its central role in glucose and lipid metabolism. It is hard to differentiate between all the influences in an in vivo model, so the aim of this study was to develop an in vitro model of T2DM in Chang liver cells and to determine if S.frutescens can reverse the state of insulin resistance in this model. Different culture media conditions were screened to identify a method that can be used as the T2DM model in Chang liver cells. Serum free medium (MCBD-201) supplemented with human diabetic serum, (2.5%-10%), high insulin concentrations (0.1μM-1μM), high fructose concentrations (1-10mM). and a combination of high insulin and high fructose was used for this screening. Chang liver cells cultured in MCBD-201 medium supplemented with 1mM fructose and 0.1μM insulin showed reduced glucose uptake and increased lipid accumulation. The effect of two S.frutescens extracts, two anti-diabetic drugs, metformin and ciglitazone, and a hypolipidemic drug ciprofibrate were determined and shown to increase glucose uptake and reduce lipid accumulation. It was postulated that exposing the cells to excess nutrients in the form of high fructose would stimulate the cells to become adipogenic and accumulate lipids, which would interfere with the glucose uptake and induce insulin resistance. Gene expression of PPARγ, PPARα, and SREBP-1 transcription factors regulating lipid metabolism was determined in Chang liver cells cultured in insulin resistance inducing medium over a 48 hour time course. The expression of PPARγ, known to stimulate adipogenesis was increased after 6, 24 and 48 hours of exposure (P(H1)<0.0001). The expression of PPARα, known to stimulate β-oxidation expression, was significantly decreased after 24 hours of exposure (P(H1)<0.0001). The presence of the plant extracts in the insulin resistance inducing media protect against this increase in adipogenesis and decrease in β-oxidation after 48 hours of exposure by increasing PPARα expression and decreasing PPARγ expression. A PCR Array was performed which identified 32 more potential molecular targets of S.frutescens. Five of the 32 targets identified with the PCR Array were validated using qRT-PCR. These genes play a role in lipid and glucose metabolism and protection against oxidative stress and inflammation. In summary a cellular model of insulin resistace in hepatocytes has been established and the capacity of S.frutescens to reverse this process has been demonstrated by acting as a dual PPARγ/α agonist. New genes have been identified in the development of insulin resistance and as targets of S.frutescens.
- Full Text:
- Date Issued: 2009
- Authors: Williams, Saralene Iona
- Date: 2009
- Subjects: Diabetes -- Alternative treatment , Medicinal plants , Traditional medicine , Liver -- Diseases
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10339 , http://hdl.handle.net/10948/d1016179
- Description: The incidence of Type 2 Diabetes Mellittus (T2DM) is increasing world wide. In Africa the limited access to health care and the insidious course of the disease lead to more severe illness and diabetic complications. There is a need to find alternative approaches to treatment and prevention that address the problems and needs of Africa. Sutherlandia frutescens (S.frutescens) is a traditional herbal plant with known anti-diabetic properties, the precise mechanism of action of S.frutescens is not known. In order to develop new approaches for treatment and prevention of T2DM the pathophysiology of T2DM must be understood. T2DM is the final outcome of a multi-organ disease characterized by early defects in muscle, adipocytes, hepatocytes and pancreatic β-cells. In this study the role of the liver was investigated because of its central role in glucose and lipid metabolism. It is hard to differentiate between all the influences in an in vivo model, so the aim of this study was to develop an in vitro model of T2DM in Chang liver cells and to determine if S.frutescens can reverse the state of insulin resistance in this model. Different culture media conditions were screened to identify a method that can be used as the T2DM model in Chang liver cells. Serum free medium (MCBD-201) supplemented with human diabetic serum, (2.5%-10%), high insulin concentrations (0.1μM-1μM), high fructose concentrations (1-10mM). and a combination of high insulin and high fructose was used for this screening. Chang liver cells cultured in MCBD-201 medium supplemented with 1mM fructose and 0.1μM insulin showed reduced glucose uptake and increased lipid accumulation. The effect of two S.frutescens extracts, two anti-diabetic drugs, metformin and ciglitazone, and a hypolipidemic drug ciprofibrate were determined and shown to increase glucose uptake and reduce lipid accumulation. It was postulated that exposing the cells to excess nutrients in the form of high fructose would stimulate the cells to become adipogenic and accumulate lipids, which would interfere with the glucose uptake and induce insulin resistance. Gene expression of PPARγ, PPARα, and SREBP-1 transcription factors regulating lipid metabolism was determined in Chang liver cells cultured in insulin resistance inducing medium over a 48 hour time course. The expression of PPARγ, known to stimulate adipogenesis was increased after 6, 24 and 48 hours of exposure (P(H1)<0.0001). The expression of PPARα, known to stimulate β-oxidation expression, was significantly decreased after 24 hours of exposure (P(H1)<0.0001). The presence of the plant extracts in the insulin resistance inducing media protect against this increase in adipogenesis and decrease in β-oxidation after 48 hours of exposure by increasing PPARα expression and decreasing PPARγ expression. A PCR Array was performed which identified 32 more potential molecular targets of S.frutescens. Five of the 32 targets identified with the PCR Array were validated using qRT-PCR. These genes play a role in lipid and glucose metabolism and protection against oxidative stress and inflammation. In summary a cellular model of insulin resistace in hepatocytes has been established and the capacity of S.frutescens to reverse this process has been demonstrated by acting as a dual PPARγ/α agonist. New genes have been identified in the development of insulin resistance and as targets of S.frutescens.
- Full Text:
- Date Issued: 2009
Characterisation of the cellulolytic and hemicellulolytic system of Bacillus Licheniformis SVD1 and the isolation and characterisation of a multi-enzyme complex
- Authors: Van Dyk, Jacoba Susanna
- Date: 2009
- Subjects: Lignocellulose Lignocellulose -- Biotechnology Lignocellulose -- Biodegradation Plant biotechnology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3936 , http://hdl.handle.net/10962/d1003995
- Description: The biological degradation of lignocellulose into fermentable sugars for the production of liquid transportation fuels is feasible and sustainable, but equires a variety of enzymes working in synergy as lignocellulose is a complex and recalcitrant substrate. The cellulosome is a multi-enzyme complex (MEC) with a variety of cellulolytic and hemicellulolytic enzymes that appears to facilitate an enhanced synergy and efficiency, as compared to free enzymes, for the degradation of recalcitrant substrates such as lignocellulose and plant cell walls. Most of the studies on cellulosomes have focused on a few organisms; C. thermocellum, C. cellulovorans and C. cellulolyticum, and there is only limited knowledge vailable on similar complexes in other organisms. Some MECs have been identified in aerobic bacteria such as Bacillus circulans and Paenibacillus curdlanolyticus, but the nature of these MECs have not been fully elucidated. This study investigated the cellulolytic and emi-cellulolytic system of Bacillus licheniformis SVD1 with specific reference to the presence of a MEC, which has never been reported in the literature for B. licheniformis. A MEC of approximately 2,000 kDa in size, based on size exclusion chromatography using Sepharose 4B, was purified from a culture of B. licheniformis. When investigating the presence of enzyme activity in the total crude fraction as well as the MEC of a birchwood xylan culture, B. licheniformis was found to display a variety of enzyme activities on a range of substrates, although xylanases were by far the predominant enzyme activity present in both the crude and MEC fractions. Based on zymogram analysis there were three CMCases, seven xylanases, three mannanases and two pectinases in the crude fraction, while the MEC had two CMCases, seven xylanases, two mannanases and one pectinase. The pectinases in the crude could be identified as a pectin methyl esterase and a lyase, while the methyl esterase was absent in the MEC. Seventeen protein species could be detected in the MEC but only nine of these displayed activity on the substrates tested. The possible presence of a β-xylosidase in the crude fraction was deduced from thin layer chromatography (TLC) which demonstrated the production of xylose by the crude fraction. It was furthermore established that B. licheniformis SVD1 was able to regulate levels of enzyme expression based on the substrate the organism was cultured on. It was found that complexed xylanase activity had a pH optimum of between pH 6.0 and 7.0 and a temperature optimum of 55oC. Complexed xylanase activity was found to be slightly inhibited by CaCl2 and inhibited to a greater extent by EDTA. Complexed xylanase activity was further shown to be activated in the presence of xylose and xylobiose, both compounds which are products of enzymatic degradation. Ethanol was found to inhibit complexed xylanase activity. The kinetic parameters for complexed xylanase activity were measured and the Km value was calculated as 2.84 mg/ml while the maximal velocity (Vmax) was calculated as 0.146 U (μmol/min/ml). Binding studies, transmission electron microscopy (TEM) and a bioinformatic analysis was conducted to investigate whether the MEC in B. licheniformis SVD1 was a putative cellulosome. The MEC was found to be unable to bind to Avicel, but was able to bind to insoluble birchwood xylan, indicating the absence of a CBM3a domain common to cellulosomal scaffoldin proteins. TEM micrographs revealed the presence of cell surface structures on cells of B. licheniformis SVD1 cultured on cellobiose and birchwood xylan. However, it could not be established whether these cell surface structures could be ascribed to the presence of the MECs on the cell surface. Bioinformatic analysis was conducted on the available genome sequence of a different strain of B. licheniformis, namely DSM 13 and ATCC 14580. No sequence homology was found with cohesin and dockerin sequences from various cellulosomal species, indicating that these strains most likely do not encode for a cellulosome. This study described and characterised a MEC that was a functional enzyme complex and did not appear to be a mere aggregation of proteins. It displayed a variety of hemi-cellulolytic activities and the available evidence suggests that it is not a cellulosome, but should rather be termed a xylanosome. Further investigation should be carried out to determine the structural basis of this MEC.
- Full Text:
- Date Issued: 2009
- Authors: Van Dyk, Jacoba Susanna
- Date: 2009
- Subjects: Lignocellulose Lignocellulose -- Biotechnology Lignocellulose -- Biodegradation Plant biotechnology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3936 , http://hdl.handle.net/10962/d1003995
- Description: The biological degradation of lignocellulose into fermentable sugars for the production of liquid transportation fuels is feasible and sustainable, but equires a variety of enzymes working in synergy as lignocellulose is a complex and recalcitrant substrate. The cellulosome is a multi-enzyme complex (MEC) with a variety of cellulolytic and hemicellulolytic enzymes that appears to facilitate an enhanced synergy and efficiency, as compared to free enzymes, for the degradation of recalcitrant substrates such as lignocellulose and plant cell walls. Most of the studies on cellulosomes have focused on a few organisms; C. thermocellum, C. cellulovorans and C. cellulolyticum, and there is only limited knowledge vailable on similar complexes in other organisms. Some MECs have been identified in aerobic bacteria such as Bacillus circulans and Paenibacillus curdlanolyticus, but the nature of these MECs have not been fully elucidated. This study investigated the cellulolytic and emi-cellulolytic system of Bacillus licheniformis SVD1 with specific reference to the presence of a MEC, which has never been reported in the literature for B. licheniformis. A MEC of approximately 2,000 kDa in size, based on size exclusion chromatography using Sepharose 4B, was purified from a culture of B. licheniformis. When investigating the presence of enzyme activity in the total crude fraction as well as the MEC of a birchwood xylan culture, B. licheniformis was found to display a variety of enzyme activities on a range of substrates, although xylanases were by far the predominant enzyme activity present in both the crude and MEC fractions. Based on zymogram analysis there were three CMCases, seven xylanases, three mannanases and two pectinases in the crude fraction, while the MEC had two CMCases, seven xylanases, two mannanases and one pectinase. The pectinases in the crude could be identified as a pectin methyl esterase and a lyase, while the methyl esterase was absent in the MEC. Seventeen protein species could be detected in the MEC but only nine of these displayed activity on the substrates tested. The possible presence of a β-xylosidase in the crude fraction was deduced from thin layer chromatography (TLC) which demonstrated the production of xylose by the crude fraction. It was furthermore established that B. licheniformis SVD1 was able to regulate levels of enzyme expression based on the substrate the organism was cultured on. It was found that complexed xylanase activity had a pH optimum of between pH 6.0 and 7.0 and a temperature optimum of 55oC. Complexed xylanase activity was found to be slightly inhibited by CaCl2 and inhibited to a greater extent by EDTA. Complexed xylanase activity was further shown to be activated in the presence of xylose and xylobiose, both compounds which are products of enzymatic degradation. Ethanol was found to inhibit complexed xylanase activity. The kinetic parameters for complexed xylanase activity were measured and the Km value was calculated as 2.84 mg/ml while the maximal velocity (Vmax) was calculated as 0.146 U (μmol/min/ml). Binding studies, transmission electron microscopy (TEM) and a bioinformatic analysis was conducted to investigate whether the MEC in B. licheniformis SVD1 was a putative cellulosome. The MEC was found to be unable to bind to Avicel, but was able to bind to insoluble birchwood xylan, indicating the absence of a CBM3a domain common to cellulosomal scaffoldin proteins. TEM micrographs revealed the presence of cell surface structures on cells of B. licheniformis SVD1 cultured on cellobiose and birchwood xylan. However, it could not be established whether these cell surface structures could be ascribed to the presence of the MECs on the cell surface. Bioinformatic analysis was conducted on the available genome sequence of a different strain of B. licheniformis, namely DSM 13 and ATCC 14580. No sequence homology was found with cohesin and dockerin sequences from various cellulosomal species, indicating that these strains most likely do not encode for a cellulosome. This study described and characterised a MEC that was a functional enzyme complex and did not appear to be a mere aggregation of proteins. It displayed a variety of hemi-cellulolytic activities and the available evidence suggests that it is not a cellulosome, but should rather be termed a xylanosome. Further investigation should be carried out to determine the structural basis of this MEC.
- Full Text:
- Date Issued: 2009
Characterisation of the plasmodium falciparum Hsp40 chaperones and their partnerships with Hsp70
- Authors: Botha, Melissa
- Date: 2009
- Subjects: Heat shock proteins Plasmodium falciparum Protein folding Molecular chaperones Malaria
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3938 , http://hdl.handle.net/10962/d1003997
- Description: Central to this research, 40 kDa Heat shock proteins (Hsp40s) are known to partner (or cochaperone) 70 kDa Heat shock proteins (Hsp70s), facilitating the selection and transfer of protein substrate to Hsp70 and the stimulation of the protein folding ability of Hsp70. Members of the diverse Hsp70-Hsp40 protein complement of Plasmodium falciparum have been implicated in the cytoprotection of this malaria parasite, and are thought to facilitate the protein folding, assembly and translocation tasks required by the parasite to commandeer the infected human erythrocyte subsequent to invasion. In particular, the parasite has evolved an expanded and specialised 43- member suite of Hsp40 proteins, 19 of which bear an identifiable export motif for secretion into the infected erythrocyte cytoplasm where they potentially interact with human Hsp70. Although type I Hsp40 proteins are representative of typical regulators of Hsp70 activity, only two of these proteins are apparent in the parasite’s Hsp40 complement. These include a characteristic type I Hsp40 termed PfHsp40, and a larger, atypical type I Hsp40 termed Pfj1. Both Hsp40 proteins are predicted to be parasite-resident and are most likely to facilitate the co-chaperone regulation of the highly abundant and stress-inducible Hsp70 homolog, PfHsp70-I. In this work, the co-chaperone functionality of PfHsp40 and Pfj1 was elucidated using in vivo and in vitro assays. Purified recombinant PfHsp40 was shown to stimulate the ATPase activity of PfHsp70-I in in vitro single turnover and steady state ATPase assays, and co-operate with PfHsp70-I in in vitro aggregation suppression assays. In these in vitro assays, heterologous partnerships could be demonstrated between PfHsp70-I and the human Hsp40, Hsj1a, and human Hsp70 and PfHsp40, suggesting a common mode of Hsp70-Hsp40 interaction in the parasite and host organism. The functionality of the signature Hsp40 domain, the Jdomain, of Pfj1 was demonstrated by its ability to replace the equivalent domain of the A. tumefaciens Hsp40, Agt DnaJ, in interactions with the prokaryotic Hsp70, DnaK, in the thermosensitive dnaJ cbpA E. coli OD259 deletion strain. An H33Q mutation introduced into the invariant and crucial HPD tripeptide motif abrogated the functionality of the J-domain in the in vivo complementation system. These findings provide the first evidence for the conservation of the prototypical mode of J-domain based interaction of Hsp40 with Hsp70 in P. falciparum. Immunofluorescence staining revealed the localisation of PfHsp40 to the parasite cytoplasm, and Pfj1 to the parasite cytoplasm and nucleus in cultured intraerythrocytic stage P. falciparum parasites. PfHsp70-I was also shown to localise to the parasite cytoplasm and nucleus in these stages, consistent with the literature. Overall we propose that PfHsp40 and Pfj1 co-localise with and regulate the chaperone activity of PfHsp70-I in P. falciparum. This is the first study to identify and provide evidence for a functional Hsp70-Hsp40 partnership in P. falciparum, and provides a platform for future studies to elucidate the importance of these chaperone partnerships in the establishment and survival of the parasite in the intraerythrocytic-stages of development.
- Full Text:
- Date Issued: 2009
- Authors: Botha, Melissa
- Date: 2009
- Subjects: Heat shock proteins Plasmodium falciparum Protein folding Molecular chaperones Malaria
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3938 , http://hdl.handle.net/10962/d1003997
- Description: Central to this research, 40 kDa Heat shock proteins (Hsp40s) are known to partner (or cochaperone) 70 kDa Heat shock proteins (Hsp70s), facilitating the selection and transfer of protein substrate to Hsp70 and the stimulation of the protein folding ability of Hsp70. Members of the diverse Hsp70-Hsp40 protein complement of Plasmodium falciparum have been implicated in the cytoprotection of this malaria parasite, and are thought to facilitate the protein folding, assembly and translocation tasks required by the parasite to commandeer the infected human erythrocyte subsequent to invasion. In particular, the parasite has evolved an expanded and specialised 43- member suite of Hsp40 proteins, 19 of which bear an identifiable export motif for secretion into the infected erythrocyte cytoplasm where they potentially interact with human Hsp70. Although type I Hsp40 proteins are representative of typical regulators of Hsp70 activity, only two of these proteins are apparent in the parasite’s Hsp40 complement. These include a characteristic type I Hsp40 termed PfHsp40, and a larger, atypical type I Hsp40 termed Pfj1. Both Hsp40 proteins are predicted to be parasite-resident and are most likely to facilitate the co-chaperone regulation of the highly abundant and stress-inducible Hsp70 homolog, PfHsp70-I. In this work, the co-chaperone functionality of PfHsp40 and Pfj1 was elucidated using in vivo and in vitro assays. Purified recombinant PfHsp40 was shown to stimulate the ATPase activity of PfHsp70-I in in vitro single turnover and steady state ATPase assays, and co-operate with PfHsp70-I in in vitro aggregation suppression assays. In these in vitro assays, heterologous partnerships could be demonstrated between PfHsp70-I and the human Hsp40, Hsj1a, and human Hsp70 and PfHsp40, suggesting a common mode of Hsp70-Hsp40 interaction in the parasite and host organism. The functionality of the signature Hsp40 domain, the Jdomain, of Pfj1 was demonstrated by its ability to replace the equivalent domain of the A. tumefaciens Hsp40, Agt DnaJ, in interactions with the prokaryotic Hsp70, DnaK, in the thermosensitive dnaJ cbpA E. coli OD259 deletion strain. An H33Q mutation introduced into the invariant and crucial HPD tripeptide motif abrogated the functionality of the J-domain in the in vivo complementation system. These findings provide the first evidence for the conservation of the prototypical mode of J-domain based interaction of Hsp40 with Hsp70 in P. falciparum. Immunofluorescence staining revealed the localisation of PfHsp40 to the parasite cytoplasm, and Pfj1 to the parasite cytoplasm and nucleus in cultured intraerythrocytic stage P. falciparum parasites. PfHsp70-I was also shown to localise to the parasite cytoplasm and nucleus in these stages, consistent with the literature. Overall we propose that PfHsp40 and Pfj1 co-localise with and regulate the chaperone activity of PfHsp70-I in P. falciparum. This is the first study to identify and provide evidence for a functional Hsp70-Hsp40 partnership in P. falciparum, and provides a platform for future studies to elucidate the importance of these chaperone partnerships in the establishment and survival of the parasite in the intraerythrocytic-stages of development.
- Full Text:
- Date Issued: 2009
Characterisation of Trypanosomal Type III and Type IV Hsp40 proteins
- Louw, Cassandra Alexandrovna
- Authors: Louw, Cassandra Alexandrovna
- Date: 2009
- Subjects: Trypanosoma Heat shock proteins African trypanosomiasis Epidemic encephalitis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3926 , http://hdl.handle.net/10962/d1003985
- Description: The heat shock protein-70 (Hsp70) family of molecular chaperones are ubiquitous highly conserved proteins that are critical for the viability of cellular homeostasis. The ATPase activity of Hsp70 proteins is critical to their function as the affinity of a given Hsp70 for non-native substrate is modulated by ATP binding and hydrolysis. When bound to ATP, Hsp70s possess a low affinity for a given substrate protein, while the hydrolysis of ATP to ADP causes a conformational change that results in a high affinity for substrate proteins. The basal ATPase activity of Hsp70s is too low to facilitate their function in vivo, and co-chaperones are essential to modulate the efficient protein folding by Hsp70. Heat shock protein-40 (Hsp40) heat shock proteins are essential for the in vivo function of Hsp70s by stimulating the ATPase activity of these proteins and facilitating transfer of substrates. The Type III class of Hsp40 proteins have not been well characterised due to their poor levels of conservation at the primary sequence level. This is due to the fact that Type III Hsp40s only contain a J-domain and a poorly conserved C-terminal region. The newly identified Type IV class of Hsp40s, contain an abrogated HPD tripeptide motif in the J-domain and have also not been extensively studied. Trypanosoma brucei (T. brucei) is a unicellular flagellated protozoan parasite. It is the causative agent of Human African Trypansomiasis (HAT) which results in thousands of deaths and devastating agricultural losses in many parts of Africa. T. brucei undergoes a complex lifecycle that is characterised by the transition from an insect vector to a mammalian host in markedly different conditions of temperature, pH, nutrient availability and respiratory requirements. It has been proposed that molecular chaperones may enhance the survival of these parasites due to their cytoprotective effect in combating cellular stress. Due to the fact that T. brucei infection is invariably fatal if left untreated, and that no novel treatment regimens have been developed recently, the identification of potential novel drug targets among proteins essential to the parasite’s survival in the host organism is an attractive aspect of T. brucei research. Because Type III Hsp40s are poorly conserved with respect to Hsp40s found in the human host, the identification of any of these proteins found to be essential to T. brucei survival in humans could potentially make attractive novel drug targets. An in depth in silico investigation into the Type III Hsp40 complement as well as partner Hsp70 proteins in T.brucei was performed. T. brucei possesses 65 Hsp40 proteins, of which 47 were classed as Type III and 6 of which were identified as being putative Type IV Hsp40s. A small but significant number (5) of Type III TbHsp40s contained tetratricopeptide (TPR) domains in addition to the J-domain. The J-domains of the Type III TbHsp40 complement were found to be conserved with respect to those of canonical Hsp40 proteins, although the mutation of certain residues that play a key role in Hsp40-Hsp70 interaction was noted. Potential partnerships of these proteins in the parasite was also investigated. The coding regions of three previously uncharacterised TbHsp40s were successfully amplified from T. brucei TREU927 genomic DNA and cloned into an expression vector. Tbj1, a Tcj1 ortholog, was selected for further study and successfully expressed and biochemically characterised. Tbj1 expressed in E. coli was found to be insoluble, but large amounts were recovered with the aid of a denaturing purification followed by refolding elution strategies, and the bulk of the protein recovered was in compact monomeric form as determined by size-exclusion chromatography fast protein liquid chromatography (SEC-FPLC). The addition of Tbj1 to a thermally aggregated substrate resulted in increased levels of aggregation, although Tbj1 was able to assist two Hsp70 proteins in the suppression of aggregation. Tbj1 proved unable to stimulate the ATPase activity of these same Hsp70s, and could not rescue temperature sensitive cells when replacing E.coli DnaJ and CbpA. It was concluded that Tbj1 does not possess independent chaperone activity, but could display Hsp40 co-chaperone properties under certain circumstances. This could allude to a specialised function in the T. brucei parasite. The lack of human orthologues to Tbj1 could result in the attractiveness of this protein as a novel drug target.
- Full Text:
- Date Issued: 2009
- Authors: Louw, Cassandra Alexandrovna
- Date: 2009
- Subjects: Trypanosoma Heat shock proteins African trypanosomiasis Epidemic encephalitis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3926 , http://hdl.handle.net/10962/d1003985
- Description: The heat shock protein-70 (Hsp70) family of molecular chaperones are ubiquitous highly conserved proteins that are critical for the viability of cellular homeostasis. The ATPase activity of Hsp70 proteins is critical to their function as the affinity of a given Hsp70 for non-native substrate is modulated by ATP binding and hydrolysis. When bound to ATP, Hsp70s possess a low affinity for a given substrate protein, while the hydrolysis of ATP to ADP causes a conformational change that results in a high affinity for substrate proteins. The basal ATPase activity of Hsp70s is too low to facilitate their function in vivo, and co-chaperones are essential to modulate the efficient protein folding by Hsp70. Heat shock protein-40 (Hsp40) heat shock proteins are essential for the in vivo function of Hsp70s by stimulating the ATPase activity of these proteins and facilitating transfer of substrates. The Type III class of Hsp40 proteins have not been well characterised due to their poor levels of conservation at the primary sequence level. This is due to the fact that Type III Hsp40s only contain a J-domain and a poorly conserved C-terminal region. The newly identified Type IV class of Hsp40s, contain an abrogated HPD tripeptide motif in the J-domain and have also not been extensively studied. Trypanosoma brucei (T. brucei) is a unicellular flagellated protozoan parasite. It is the causative agent of Human African Trypansomiasis (HAT) which results in thousands of deaths and devastating agricultural losses in many parts of Africa. T. brucei undergoes a complex lifecycle that is characterised by the transition from an insect vector to a mammalian host in markedly different conditions of temperature, pH, nutrient availability and respiratory requirements. It has been proposed that molecular chaperones may enhance the survival of these parasites due to their cytoprotective effect in combating cellular stress. Due to the fact that T. brucei infection is invariably fatal if left untreated, and that no novel treatment regimens have been developed recently, the identification of potential novel drug targets among proteins essential to the parasite’s survival in the host organism is an attractive aspect of T. brucei research. Because Type III Hsp40s are poorly conserved with respect to Hsp40s found in the human host, the identification of any of these proteins found to be essential to T. brucei survival in humans could potentially make attractive novel drug targets. An in depth in silico investigation into the Type III Hsp40 complement as well as partner Hsp70 proteins in T.brucei was performed. T. brucei possesses 65 Hsp40 proteins, of which 47 were classed as Type III and 6 of which were identified as being putative Type IV Hsp40s. A small but significant number (5) of Type III TbHsp40s contained tetratricopeptide (TPR) domains in addition to the J-domain. The J-domains of the Type III TbHsp40 complement were found to be conserved with respect to those of canonical Hsp40 proteins, although the mutation of certain residues that play a key role in Hsp40-Hsp70 interaction was noted. Potential partnerships of these proteins in the parasite was also investigated. The coding regions of three previously uncharacterised TbHsp40s were successfully amplified from T. brucei TREU927 genomic DNA and cloned into an expression vector. Tbj1, a Tcj1 ortholog, was selected for further study and successfully expressed and biochemically characterised. Tbj1 expressed in E. coli was found to be insoluble, but large amounts were recovered with the aid of a denaturing purification followed by refolding elution strategies, and the bulk of the protein recovered was in compact monomeric form as determined by size-exclusion chromatography fast protein liquid chromatography (SEC-FPLC). The addition of Tbj1 to a thermally aggregated substrate resulted in increased levels of aggregation, although Tbj1 was able to assist two Hsp70 proteins in the suppression of aggregation. Tbj1 proved unable to stimulate the ATPase activity of these same Hsp70s, and could not rescue temperature sensitive cells when replacing E.coli DnaJ and CbpA. It was concluded that Tbj1 does not possess independent chaperone activity, but could display Hsp40 co-chaperone properties under certain circumstances. This could allude to a specialised function in the T. brucei parasite. The lack of human orthologues to Tbj1 could result in the attractiveness of this protein as a novel drug target.
- Full Text:
- Date Issued: 2009
Citizen participation, decentralization and inclusive development : a survey on citizen participation and decentralization in South Africa with specific reference to the Eastern Cape c.2005
- Authors: Robino, Carolina
- Date: 2009
- Subjects: Local government -- Citizen participation , Decentralization in government -- South Africa , Political planning -- Citizen participation , Community development, Urban -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:9084 , http://hdl.handle.net/10948/875 , Local government -- Citizen participation , Decentralization in government -- South Africa , Political planning -- Citizen participation , Community development, Urban -- South Africa -- Eastern Cape
- Description: Contemporary debates about development confer a prominent role to citizen participation and decentralization. Growing scepticism about the efficacy of narrowly conceived measures add pressure to reform development both theoretically and in practical terms. There is a greater understanding that ‘traditional’ development approaches and policies need to be reformulated and decentralization and citizen participation have been proposed as remedies to previous development failures. It is frequently argued that citizen participation will improve the efficiency and efficacy of public services. Citizen participation is meant to render local government more accountable and to contribute to deepening democracy, by reinforcing representative democratic institutions with participatory forms. At the same time, decentralization reforms have been proposed as a response to the failures of highly centralized states. From a political perspective, it is argued, decentralization reforms can help the central state gain legitimacy and have been seen as a strategy for maintaining political stability. It has been repeatedly suggested that physical proximity makes it easier for citizens to hold local officials accountable for their performance. From an economic perspective, decentralization can improve the match between the mix of services provided by the public sector and the preferences of the local population. It has also been noted that people are more willing to pay for services that respond to their priorities and that increased competition between local governments generates spaces for more creative responses adapted to local needs. But then, can decentralization and citizen participation live up to the faith and expectations that they have inspired? I argue that the literature commonly over-emphasises the role of citizen participation and decentralization in development and what these processes and reforms can achieve. Much of the evidence is anecdotal in nature and tends to neglect the specific contexts in which these processes take place. Also largely ignored are political economy considerations and a critical exploration of the relationship between these two key words. At best, when their interrelationships are addressed decentralization and citizen participation are conceived as based on a symbiotic relationship. I suggest, however, that the relationship between these two processes is not as straightforward as most of the literature assumes. The meanings of these two key words in current development lexicon are explored and critically assessed. I argue that whether or not the rising prominence of these two words actually means the emergence of a new development agenda is a moot point. It critically depends on the understandings of these ambiguous terms. The thesis adopts a political economy approach. Combined with this is an awareness of the broader historical and socio-economic context in which citizen participation and decentralization take place. The thesis applies these ideas triangulating diverse research methods and data sources. It combines a literature review and documentary analysis, a survey conducted with municipal authorities and civil society organizations in the Eastern Cape as well as structured interviews with Ward councillors and with key informants. From a theoretical perspective, the study lays a foundation for understanding the relationship between development policies outcomes and the nature of citizen participation and decentralization in developing countries. This, in turn, provides a basis from which citizen participation and decentralization in South Africa can be assessed and understood. The thesis presents evidence from a case study of the Eastern Cape, South Africa. By revealing how different dimensions of decentralization and citizen participation operate and intersect, the findings demonstrate, that contrary to common knowledge, citizen participation and decentralization are frequently at odds. Moreover, contrary to frequent statements, the research also shows that opening new spaces for participation in decentralized local governance can result in fewer changes and disappointing results at best, undermining the transformative potential of the concepts of participation and decentralization.
- Full Text:
- Date Issued: 2009
- Authors: Robino, Carolina
- Date: 2009
- Subjects: Local government -- Citizen participation , Decentralization in government -- South Africa , Political planning -- Citizen participation , Community development, Urban -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:9084 , http://hdl.handle.net/10948/875 , Local government -- Citizen participation , Decentralization in government -- South Africa , Political planning -- Citizen participation , Community development, Urban -- South Africa -- Eastern Cape
- Description: Contemporary debates about development confer a prominent role to citizen participation and decentralization. Growing scepticism about the efficacy of narrowly conceived measures add pressure to reform development both theoretically and in practical terms. There is a greater understanding that ‘traditional’ development approaches and policies need to be reformulated and decentralization and citizen participation have been proposed as remedies to previous development failures. It is frequently argued that citizen participation will improve the efficiency and efficacy of public services. Citizen participation is meant to render local government more accountable and to contribute to deepening democracy, by reinforcing representative democratic institutions with participatory forms. At the same time, decentralization reforms have been proposed as a response to the failures of highly centralized states. From a political perspective, it is argued, decentralization reforms can help the central state gain legitimacy and have been seen as a strategy for maintaining political stability. It has been repeatedly suggested that physical proximity makes it easier for citizens to hold local officials accountable for their performance. From an economic perspective, decentralization can improve the match between the mix of services provided by the public sector and the preferences of the local population. It has also been noted that people are more willing to pay for services that respond to their priorities and that increased competition between local governments generates spaces for more creative responses adapted to local needs. But then, can decentralization and citizen participation live up to the faith and expectations that they have inspired? I argue that the literature commonly over-emphasises the role of citizen participation and decentralization in development and what these processes and reforms can achieve. Much of the evidence is anecdotal in nature and tends to neglect the specific contexts in which these processes take place. Also largely ignored are political economy considerations and a critical exploration of the relationship between these two key words. At best, when their interrelationships are addressed decentralization and citizen participation are conceived as based on a symbiotic relationship. I suggest, however, that the relationship between these two processes is not as straightforward as most of the literature assumes. The meanings of these two key words in current development lexicon are explored and critically assessed. I argue that whether or not the rising prominence of these two words actually means the emergence of a new development agenda is a moot point. It critically depends on the understandings of these ambiguous terms. The thesis adopts a political economy approach. Combined with this is an awareness of the broader historical and socio-economic context in which citizen participation and decentralization take place. The thesis applies these ideas triangulating diverse research methods and data sources. It combines a literature review and documentary analysis, a survey conducted with municipal authorities and civil society organizations in the Eastern Cape as well as structured interviews with Ward councillors and with key informants. From a theoretical perspective, the study lays a foundation for understanding the relationship between development policies outcomes and the nature of citizen participation and decentralization in developing countries. This, in turn, provides a basis from which citizen participation and decentralization in South Africa can be assessed and understood. The thesis presents evidence from a case study of the Eastern Cape, South Africa. By revealing how different dimensions of decentralization and citizen participation operate and intersect, the findings demonstrate, that contrary to common knowledge, citizen participation and decentralization are frequently at odds. Moreover, contrary to frequent statements, the research also shows that opening new spaces for participation in decentralized local governance can result in fewer changes and disappointing results at best, undermining the transformative potential of the concepts of participation and decentralization.
- Full Text:
- Date Issued: 2009
Civil society's quest for democracy in Zimbabwe: origins,barriers and prospects, 1900-2008
- Authors: Magure, Booker
- Date: 2009
- Subjects: Civil Society -- Zimbabwe Zimbabwe -- Politics and government -- 1980 Zimbabwe -- Economic conditions Zimbabwe -- History
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2798 , http://hdl.handle.net/10962/d1003008
- Description: This thesis is a critical examination of the origins, barriers and prospects for a working class-led civil society as it sought to democratise Zimbabwe’s post-colonial state. It is an interdisciplinary but historically informed analysis of how advanced capitalist development promoted the emergence of social movement unionism with a potentiality to advance democracy in Zimbabwe. Despite occurring on a much smaller and thinner scale, the evolution of civil society in colonial Zimbabwe was akin to what happened in 19th century Britain where capitalist expansion presented a foundation for democratisation. However, big underlying barriers exist in Zimbabwe, resulting from various forms of authoritarian structures and forcible mobilisation strategies emanating from colonialism and the protracted war of liberation. ZANU PF’s violent reaction to memory contests by non-participants in the war of liberation seeking an alternative political agenda attest to the controversial and polemical nature of struggles over memory and forgetting in contemporary Zimbabwean politics. These structural impediments forestalled the organic growth of civil society in Zimbabwe, thereby explaining its inchoate status and the failure to significantly determine the course of public policy. While recognising the democratic aspirations and capacities of the working class in precipitating political change, this thesis takes into consideration the impact of other factors on state-society relations. These include deepening state barbarism, globalisation, and technological advances in communication, transnational civil society, a dysfunctional economy, migration and remittances. Finally this thesis presents an optimistic scenario about the prospects for civil society and democratisation in Zimbabwe. I argue that the revival of the productive sectors of the economy can possibly strengthen the labour movement and revive its capacities for ushering in a democracy.
- Full Text:
- Date Issued: 2009
- Authors: Magure, Booker
- Date: 2009
- Subjects: Civil Society -- Zimbabwe Zimbabwe -- Politics and government -- 1980 Zimbabwe -- Economic conditions Zimbabwe -- History
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2798 , http://hdl.handle.net/10962/d1003008
- Description: This thesis is a critical examination of the origins, barriers and prospects for a working class-led civil society as it sought to democratise Zimbabwe’s post-colonial state. It is an interdisciplinary but historically informed analysis of how advanced capitalist development promoted the emergence of social movement unionism with a potentiality to advance democracy in Zimbabwe. Despite occurring on a much smaller and thinner scale, the evolution of civil society in colonial Zimbabwe was akin to what happened in 19th century Britain where capitalist expansion presented a foundation for democratisation. However, big underlying barriers exist in Zimbabwe, resulting from various forms of authoritarian structures and forcible mobilisation strategies emanating from colonialism and the protracted war of liberation. ZANU PF’s violent reaction to memory contests by non-participants in the war of liberation seeking an alternative political agenda attest to the controversial and polemical nature of struggles over memory and forgetting in contemporary Zimbabwean politics. These structural impediments forestalled the organic growth of civil society in Zimbabwe, thereby explaining its inchoate status and the failure to significantly determine the course of public policy. While recognising the democratic aspirations and capacities of the working class in precipitating political change, this thesis takes into consideration the impact of other factors on state-society relations. These include deepening state barbarism, globalisation, and technological advances in communication, transnational civil society, a dysfunctional economy, migration and remittances. Finally this thesis presents an optimistic scenario about the prospects for civil society and democratisation in Zimbabwe. I argue that the revival of the productive sectors of the economy can possibly strengthen the labour movement and revive its capacities for ushering in a democracy.
- Full Text:
- Date Issued: 2009
Compensation for polarization mode dispersion and nonlinear birefringence in a multichannel optical fibre system
- Authors: Waswa, David Wafula
- Date: 2009
- Subjects: Fiber optics , Nonlinear optics , Polarization (Light)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10375 , http://hdl.handle.net/10948/885 , Fiber optics , Nonlinear optics , Polarization (Light)
- Description: Polarization mode dispersion (PMD) is stochastic in nature and continues evolving in an unpredictable manner according to the changing environment. Nonlinear birefringence in multichannel systems alters the polarization states of the bits, so that they vary from one bit to the next in a way that is difficult to predict. These are the two major signal-impairment effects that are inherent in optical fibre transmission links which can seriously degrade network performance. It is therefore extremely challenging to compensate for both linear and nonlinear birefringence in multichannel systems. The purpose of this thesis is to investigate the interaction between PMD and nonlinear induced birefringence in a fibre with consideration of mode coupling. A sound knowledge of this interaction is necessary in designing a linear and nonlinear polarization mode dispersion compensator for WDM systems, as was successfully carried out in this study. The investigation shows that the effect of nonlinear birefringence alone depolarizes the signal, while in high PMD links where polarization mode coupling is high, the nonlinear birefringence effect couples with second-order PMD such that it may reduce the penalty and improve the signal DOP. Further investigation shows that when nonlinear birefringence becomes significant, asymmetry arises between the two principal axes of the fibre, such that it is only one axis which experiences the effect of nonlinear birefringence. It is found out that along this vii axis, there exists a critical point in pump power where the nonlinear birefringence cancels PMD in the link and improves the signal. An adaptive compensator to cancel PMD and nonlinear birefringence was designed based on feedforward DOP-monitoring signal. The compensator was tested both at laboratory level and on the Telkom buried fibre link and found to be functioning as intended. It was able to adaptively track and compensate PMD in the link in less than a second. The compensator was able to cancel PMD in the link up to a maximum of 30 ps. The compensator improved the DOP of the worst signal by more than 100 percent.
- Full Text:
- Date Issued: 2009
- Authors: Waswa, David Wafula
- Date: 2009
- Subjects: Fiber optics , Nonlinear optics , Polarization (Light)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10375 , http://hdl.handle.net/10948/885 , Fiber optics , Nonlinear optics , Polarization (Light)
- Description: Polarization mode dispersion (PMD) is stochastic in nature and continues evolving in an unpredictable manner according to the changing environment. Nonlinear birefringence in multichannel systems alters the polarization states of the bits, so that they vary from one bit to the next in a way that is difficult to predict. These are the two major signal-impairment effects that are inherent in optical fibre transmission links which can seriously degrade network performance. It is therefore extremely challenging to compensate for both linear and nonlinear birefringence in multichannel systems. The purpose of this thesis is to investigate the interaction between PMD and nonlinear induced birefringence in a fibre with consideration of mode coupling. A sound knowledge of this interaction is necessary in designing a linear and nonlinear polarization mode dispersion compensator for WDM systems, as was successfully carried out in this study. The investigation shows that the effect of nonlinear birefringence alone depolarizes the signal, while in high PMD links where polarization mode coupling is high, the nonlinear birefringence effect couples with second-order PMD such that it may reduce the penalty and improve the signal DOP. Further investigation shows that when nonlinear birefringence becomes significant, asymmetry arises between the two principal axes of the fibre, such that it is only one axis which experiences the effect of nonlinear birefringence. It is found out that along this vii axis, there exists a critical point in pump power where the nonlinear birefringence cancels PMD in the link and improves the signal. An adaptive compensator to cancel PMD and nonlinear birefringence was designed based on feedforward DOP-monitoring signal. The compensator was tested both at laboratory level and on the Telkom buried fibre link and found to be functioning as intended. It was able to adaptively track and compensate PMD in the link in less than a second. The compensator was able to cancel PMD in the link up to a maximum of 30 ps. The compensator improved the DOP of the worst signal by more than 100 percent.
- Full Text:
- Date Issued: 2009
Constructing the intellectually disabled person as a subject of education: a discourse analysis using Q-methodology
- Authors: McKenzie, Judith Anne
- Date: 2009
- Subjects: Foucault, Michel, 1926-1984 Learning disabled -- Education -- South Africa Discourse analysis -- Methodology Discourse analysis Children with mental disabilities -- Education -- South Africa Q technique Special education -- South Africa Children with disabilities -- Education -- South Africa Right to education Intelligence tests -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3017 , http://hdl.handle.net/10962/d1002526
- Description: The education of intellectually disabled (ID) people is constructed within mass education systems as a problem requiring specialised intervention, separation from “normal” school contexts and the application of professional expertise. A social model of disability resists these practices from a human rights perspective and underpins an inclusive education approach. In this study, a post-structuralist disability studies theoretical framework, drawing particularly on the work of Foucault, was used to examine discourses that construct the intellectually disabled person as a subject of education. The study was conducted in Buffalo City, South Africa at a time when an inclusive education policy is being implemented in the country. The research questions were: What discourses are deployed in the representation and educational practices of those identified as ID? What are the effects of these discourses in constructing the ID subject and associated educational practice? The study utilises Q-methodology, a factor analytic method that yields whole patterns of responses for analysis. A process of sorting selected statements along the dimension of agree to disagree was completed by three groups of participants, namely adults with ID, parents of people with ID and professionals working with ID. Discourses of representation and of educational practice were identified through statistical and interpretive analysis, following the discourse analysis school of Q-methodology. The findings of this study reveal the operation of power in a medico-psychological gaze that makes ID visible and supervises disability expertise within education. Representations of ID suffused with religious notions support the exercise of pastoral power by disability experts. Human rights discourses in education can marginalise ID people if applied uncritically. Fixed notions of impairment constrain an intellectually disabled subject who is vulnerable and incompetent. This study argues instead for a theory of (poss)ability, underpinned by an understanding of the situational and shared nature of competence and a fluid conception of impairment. Human rights should be supplemented by an ethics of care and belonging in the community (ubuntu). A research agenda supporting this effort would examine the ways in which ID people work on themselves as subjects (subjectivisation) and explore the potential for resistance in this process.
- Full Text:
- Date Issued: 2009
- Authors: McKenzie, Judith Anne
- Date: 2009
- Subjects: Foucault, Michel, 1926-1984 Learning disabled -- Education -- South Africa Discourse analysis -- Methodology Discourse analysis Children with mental disabilities -- Education -- South Africa Q technique Special education -- South Africa Children with disabilities -- Education -- South Africa Right to education Intelligence tests -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3017 , http://hdl.handle.net/10962/d1002526
- Description: The education of intellectually disabled (ID) people is constructed within mass education systems as a problem requiring specialised intervention, separation from “normal” school contexts and the application of professional expertise. A social model of disability resists these practices from a human rights perspective and underpins an inclusive education approach. In this study, a post-structuralist disability studies theoretical framework, drawing particularly on the work of Foucault, was used to examine discourses that construct the intellectually disabled person as a subject of education. The study was conducted in Buffalo City, South Africa at a time when an inclusive education policy is being implemented in the country. The research questions were: What discourses are deployed in the representation and educational practices of those identified as ID? What are the effects of these discourses in constructing the ID subject and associated educational practice? The study utilises Q-methodology, a factor analytic method that yields whole patterns of responses for analysis. A process of sorting selected statements along the dimension of agree to disagree was completed by three groups of participants, namely adults with ID, parents of people with ID and professionals working with ID. Discourses of representation and of educational practice were identified through statistical and interpretive analysis, following the discourse analysis school of Q-methodology. The findings of this study reveal the operation of power in a medico-psychological gaze that makes ID visible and supervises disability expertise within education. Representations of ID suffused with religious notions support the exercise of pastoral power by disability experts. Human rights discourses in education can marginalise ID people if applied uncritically. Fixed notions of impairment constrain an intellectually disabled subject who is vulnerable and incompetent. This study argues instead for a theory of (poss)ability, underpinned by an understanding of the situational and shared nature of competence and a fluid conception of impairment. Human rights should be supplemented by an ethics of care and belonging in the community (ubuntu). A research agenda supporting this effort would examine the ways in which ID people work on themselves as subjects (subjectivisation) and explore the potential for resistance in this process.
- Full Text:
- Date Issued: 2009
Cost and reward as motivating factors in distributed collaborative learning assignments : a grounded theory analasis
- Van Niekerk, Johanna Cornelia
- Authors: Van Niekerk, Johanna Cornelia
- Date: 2009
- Subjects: Group work in education -- South Africa , Team learning approach in education -- South Africa , Education -- Experimental methods
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:9764 , http://hdl.handle.net/10948/1103 , Group work in education -- South Africa , Team learning approach in education -- South Africa , Education -- Experimental methods
- Description: The objective of this research study was to obtain a better understanding of the factors that affect lecturer and student participation in distributed collaborative learning assignments (DCLAs). A substantial number of courses worldwide have included DCLAs in their curricula in an attempt to teach students virtual communication and teaming skills, and to allow distributed students to learn course content collaboratively in a virtual environment. The execution and management of these assignments have proven to be more challenging that expected. Several attempts reported on in the literature had to be abandoned when cost exceeded the rewards for both lecturers and students. In a fouryear cyclical action research project carried out at the PETech (Port Elizabeth Technikon, currently part of the Nelson Mandela Metropolitan University, South Africa), ICT students at several of the PETech campuses were required to complete a DCLA in virtual teams. This project also had to be terminated when it was realised that virtual team learning was minimal and the time investment unacceptably high. For the research study reported on in this thesis the data collected during the four “preresearch” cycles and the experiences reported in the literature were analysed. The lessons learnt were applied to a new additional DCLA cycle which formed part of an ICT course, although this execution still showed room for improvement. A second additional cycle was then executed which had a high participation rate and was overwhelmingly labelled by the participating students as a valuable and enjoyable learning experience. Analysis of the factors affecting participation in DCLAs shows that they are numerous and tightly interlinked, and that each factor is able to take on a wide range of values. This complicates descriptive reporting as each of the DCLAs was unique with unique outcomes and would have to be reported as such in order to iii ABSTRACT iv gain an understanding of the factors. Hence, a level of abstraction was needed, which was accomplished by applying the traditional Glaserian grounded theory method to the data collected during the four “preresearch” and the two additional cycles, and from the literature on the topic. The outcome is a perceived costs and rewards (PCR) theory for participation in DCLAs. As participation is crucial for the learning experience of each student as well as his/her team members in an action learning environment, deciding on participation by continually calculating the costs versus rewards became the focal point of the theory. To the best of the author’s knowledge this research study makes a theoretical contribution to the existing body of ICT educational knowledge in the form of a perceived costs and rewards theory for DCLA participation and a practical contribution in that it provides a theory that can be used to explain, understand, interpret and predict participation in DCLAs. This research study provides guidance for future research in both of these areas.
- Full Text:
- Date Issued: 2009
- Authors: Van Niekerk, Johanna Cornelia
- Date: 2009
- Subjects: Group work in education -- South Africa , Team learning approach in education -- South Africa , Education -- Experimental methods
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:9764 , http://hdl.handle.net/10948/1103 , Group work in education -- South Africa , Team learning approach in education -- South Africa , Education -- Experimental methods
- Description: The objective of this research study was to obtain a better understanding of the factors that affect lecturer and student participation in distributed collaborative learning assignments (DCLAs). A substantial number of courses worldwide have included DCLAs in their curricula in an attempt to teach students virtual communication and teaming skills, and to allow distributed students to learn course content collaboratively in a virtual environment. The execution and management of these assignments have proven to be more challenging that expected. Several attempts reported on in the literature had to be abandoned when cost exceeded the rewards for both lecturers and students. In a fouryear cyclical action research project carried out at the PETech (Port Elizabeth Technikon, currently part of the Nelson Mandela Metropolitan University, South Africa), ICT students at several of the PETech campuses were required to complete a DCLA in virtual teams. This project also had to be terminated when it was realised that virtual team learning was minimal and the time investment unacceptably high. For the research study reported on in this thesis the data collected during the four “preresearch” cycles and the experiences reported in the literature were analysed. The lessons learnt were applied to a new additional DCLA cycle which formed part of an ICT course, although this execution still showed room for improvement. A second additional cycle was then executed which had a high participation rate and was overwhelmingly labelled by the participating students as a valuable and enjoyable learning experience. Analysis of the factors affecting participation in DCLAs shows that they are numerous and tightly interlinked, and that each factor is able to take on a wide range of values. This complicates descriptive reporting as each of the DCLAs was unique with unique outcomes and would have to be reported as such in order to iii ABSTRACT iv gain an understanding of the factors. Hence, a level of abstraction was needed, which was accomplished by applying the traditional Glaserian grounded theory method to the data collected during the four “preresearch” and the two additional cycles, and from the literature on the topic. The outcome is a perceived costs and rewards (PCR) theory for participation in DCLAs. As participation is crucial for the learning experience of each student as well as his/her team members in an action learning environment, deciding on participation by continually calculating the costs versus rewards became the focal point of the theory. To the best of the author’s knowledge this research study makes a theoretical contribution to the existing body of ICT educational knowledge in the form of a perceived costs and rewards theory for DCLA participation and a practical contribution in that it provides a theory that can be used to explain, understand, interpret and predict participation in DCLAs. This research study provides guidance for future research in both of these areas.
- Full Text:
- Date Issued: 2009
Determination and validation of plants used by resource-limited farmers in the ethno veterinary control of gastro-intestinal parasites of goats in the Eastern Cape Province, South Africa
- Authors: Maphosa, Viola
- Date: 2009
- Subjects: Medicinal plants -- South Africa -- Eastern Cape , Parasites -- Control -- South Africa -- Eastern Cape , Traditional medicine -- South Africa -- Eastern Cape , Goats -- Parasites -- Control , Traditional veterinary medicine -- South Africa , Sustainable agriculture -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD (Animal Science)
- Identifier: vital:11164 , http://hdl.handle.net/10353/d1000997 , Medicinal plants -- South Africa -- Eastern Cape , Parasites -- Control -- South Africa -- Eastern Cape , Traditional medicine -- South Africa -- Eastern Cape , Goats -- Parasites -- Control , Traditional veterinary medicine -- South Africa , Sustainable agriculture -- South Africa -- Eastern Cape
- Full Text:
- Date Issued: 2009
- Authors: Maphosa, Viola
- Date: 2009
- Subjects: Medicinal plants -- South Africa -- Eastern Cape , Parasites -- Control -- South Africa -- Eastern Cape , Traditional medicine -- South Africa -- Eastern Cape , Goats -- Parasites -- Control , Traditional veterinary medicine -- South Africa , Sustainable agriculture -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD (Animal Science)
- Identifier: vital:11164 , http://hdl.handle.net/10353/d1000997 , Medicinal plants -- South Africa -- Eastern Cape , Parasites -- Control -- South Africa -- Eastern Cape , Traditional medicine -- South Africa -- Eastern Cape , Goats -- Parasites -- Control , Traditional veterinary medicine -- South Africa , Sustainable agriculture -- South Africa -- Eastern Cape
- Full Text:
- Date Issued: 2009
Development of a process for the preparation of linalool from CIS-2-pinanol
- Authors: Buddoo, Subash Ramnarain
- Date: 2009
- Subjects: Odors , Perfumes -- History , Perfumes -- Formulae , Fermentation
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:10425 , http://hdl.handle.net/10948/d1016219
- Description: Linalool is a key intermediate for the production of important fragrance chemicals such as geraniol, nerol, geranial, and neral. Linalool can be produced via a two-step process from α-pinene which is a major component of crude sulphated turpentine (CST) a foul-smelling, volatile waste product of the pulp and paper industry. The key step in this process is the pyrolysis step which involves the isomerisation of cis-2-pinanol to linalool and requires high temperatures (600-650°C) and is not very selective due to the decomposition of the product itself under these conditions. A client of the CSIR, Teubes Pty. Ltd., is a manufacturer of flavour and fragrance compounds for the local and international fragrance market and expressed an interest in producing linalool since the company would then gain access to other valuable fragrance chemicals via relatively simple processes. Earlier work conducted by AECI, R & D did not meet with much success since the selectivity to linalool was very poor and the process could hardly be deemed as scalable. The main objective of this project was therefore to develop a process for the selective isomerisation of cis-2-pinanol to linalool with minimum by-product formation and using process equipment that could be scaled to full-scale production. Since cis-2- pinanol could not be purchased in sufficient quantities for process development, a process had to be developed for the bench-scale preparation of kilogram quantities of cis-2-pinanol from α-pinene obtained from the client. Although this synthesis formed a minor part of this investigation, several process improvements and innovations were introduced to produce high quality cis-2-pinanol, in very good yields at kilogram scale. A major part of this investigation was the design and set up of a pyrolyis rig capable of operating at elevated temperatures (400 - 750°C) for the evaluation of various process parameters. Various vaporizer, reactor, and condensation systems were evaluated for their ability to cope with the demanding conditions on a consistent basis. The initial part of the investigation was a screening exercise to evaluate various process parameters as well as solvents, materials of construction, catalysts, etc. A comprehensive statistical design was also conducted to determine the critical process parameters and the model obtained was used to predict the optimum conditions required for the preparation of in-specification product on a consistent basis. These conditions were used in the preparation of a 1kg sample which was required by theclient for market evaluation purposes. The use of a novel microreactor system was also evaluated for the pinanol pyrolysis reaction. To our knowledge, this is the first time that a microreactor has been successfully used for this type of reaction in the Fragrance industry and a patent application is being filed by the CSIR. The kinetics of the reaction in both the tubular reactor system and the microreactor system was investigated. Computer modelling studies on both the systems were also conducted. The raw material cost to produce a kilogram of linalool is $1.40. There is a significant margin of 60.8 percent between the raw material cost of linalool and the current selling price ($3.57/kg). This clearly indicates that the project is potentially feasible from an economic point of view and we can now proceed with confidence to the next stage which is the engineering design, building and commissioning of the large scale pyrolysis rig. The rest of the process steps will be conducted on existing equipment currently present at the CSIR’s large scale facility (Imbiza in Isando, Gauteng).
- Full Text:
- Date Issued: 2009
- Authors: Buddoo, Subash Ramnarain
- Date: 2009
- Subjects: Odors , Perfumes -- History , Perfumes -- Formulae , Fermentation
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:10425 , http://hdl.handle.net/10948/d1016219
- Description: Linalool is a key intermediate for the production of important fragrance chemicals such as geraniol, nerol, geranial, and neral. Linalool can be produced via a two-step process from α-pinene which is a major component of crude sulphated turpentine (CST) a foul-smelling, volatile waste product of the pulp and paper industry. The key step in this process is the pyrolysis step which involves the isomerisation of cis-2-pinanol to linalool and requires high temperatures (600-650°C) and is not very selective due to the decomposition of the product itself under these conditions. A client of the CSIR, Teubes Pty. Ltd., is a manufacturer of flavour and fragrance compounds for the local and international fragrance market and expressed an interest in producing linalool since the company would then gain access to other valuable fragrance chemicals via relatively simple processes. Earlier work conducted by AECI, R & D did not meet with much success since the selectivity to linalool was very poor and the process could hardly be deemed as scalable. The main objective of this project was therefore to develop a process for the selective isomerisation of cis-2-pinanol to linalool with minimum by-product formation and using process equipment that could be scaled to full-scale production. Since cis-2- pinanol could not be purchased in sufficient quantities for process development, a process had to be developed for the bench-scale preparation of kilogram quantities of cis-2-pinanol from α-pinene obtained from the client. Although this synthesis formed a minor part of this investigation, several process improvements and innovations were introduced to produce high quality cis-2-pinanol, in very good yields at kilogram scale. A major part of this investigation was the design and set up of a pyrolyis rig capable of operating at elevated temperatures (400 - 750°C) for the evaluation of various process parameters. Various vaporizer, reactor, and condensation systems were evaluated for their ability to cope with the demanding conditions on a consistent basis. The initial part of the investigation was a screening exercise to evaluate various process parameters as well as solvents, materials of construction, catalysts, etc. A comprehensive statistical design was also conducted to determine the critical process parameters and the model obtained was used to predict the optimum conditions required for the preparation of in-specification product on a consistent basis. These conditions were used in the preparation of a 1kg sample which was required by theclient for market evaluation purposes. The use of a novel microreactor system was also evaluated for the pinanol pyrolysis reaction. To our knowledge, this is the first time that a microreactor has been successfully used for this type of reaction in the Fragrance industry and a patent application is being filed by the CSIR. The kinetics of the reaction in both the tubular reactor system and the microreactor system was investigated. Computer modelling studies on both the systems were also conducted. The raw material cost to produce a kilogram of linalool is $1.40. There is a significant margin of 60.8 percent between the raw material cost of linalool and the current selling price ($3.57/kg). This clearly indicates that the project is potentially feasible from an economic point of view and we can now proceed with confidence to the next stage which is the engineering design, building and commissioning of the large scale pyrolysis rig. The rest of the process steps will be conducted on existing equipment currently present at the CSIR’s large scale facility (Imbiza in Isando, Gauteng).
- Full Text:
- Date Issued: 2009
Discourse and the oppression of nonhuman animals: a critical realist account
- Authors: Mitchell, Leslie Roy
- Date: 2009
- Subjects: Animal rights Animal welfare -- Moral and ethical aspects Critical realism Critical discourse analysis Animal industry -- Moral and ethical aspects Livestock -- Social aspects Human-animal relationships Agriculture -- Moral and ethical aspects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1318 , http://hdl.handle.net/10962/d1003951
- Description: This work examines the use of nonhuman animals in the farming industry and seeks to understand why this practice takes place and what supports its continuation. The research is approached from a critical realist perspective and after a description of past and current practices in the industry, it uses abduction and retroduction to determine the essential conditions for the continuation of the phenomenon of nonhuman animal farming. One essential condition is found to be the existence of negative discourses relating to nonhuman animals and this aspect is examined in more detail by analyzing a corpus of texts from a farming magazine using Critical Discourse Analysis. Major discourses which were found to be present were those of production, science and slavery which construct the nonhumans respectively as objects of scientific investigation, as production machines and as slaves. A minor discourse of achievement relating to the nonhumans was also present. Further analysis of linguistic features examined the way in which the nonhumans are socially constructed in the discourses. Drawing on work in experimental psychology by Millgram, Zimbardo and Bandura it was found that the effects of these discourses fulfil many of the conditions for bringing about moral disengagement in people thus explaining why billions of people are able to support animal farming in various ways even though what happens in the phenomenon is contrary to their basic ethical and moral beliefs.
- Full Text:
- Date Issued: 2009
- Authors: Mitchell, Leslie Roy
- Date: 2009
- Subjects: Animal rights Animal welfare -- Moral and ethical aspects Critical realism Critical discourse analysis Animal industry -- Moral and ethical aspects Livestock -- Social aspects Human-animal relationships Agriculture -- Moral and ethical aspects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1318 , http://hdl.handle.net/10962/d1003951
- Description: This work examines the use of nonhuman animals in the farming industry and seeks to understand why this practice takes place and what supports its continuation. The research is approached from a critical realist perspective and after a description of past and current practices in the industry, it uses abduction and retroduction to determine the essential conditions for the continuation of the phenomenon of nonhuman animal farming. One essential condition is found to be the existence of negative discourses relating to nonhuman animals and this aspect is examined in more detail by analyzing a corpus of texts from a farming magazine using Critical Discourse Analysis. Major discourses which were found to be present were those of production, science and slavery which construct the nonhumans respectively as objects of scientific investigation, as production machines and as slaves. A minor discourse of achievement relating to the nonhumans was also present. Further analysis of linguistic features examined the way in which the nonhumans are socially constructed in the discourses. Drawing on work in experimental psychology by Millgram, Zimbardo and Bandura it was found that the effects of these discourses fulfil many of the conditions for bringing about moral disengagement in people thus explaining why billions of people are able to support animal farming in various ways even though what happens in the phenomenon is contrary to their basic ethical and moral beliefs.
- Full Text:
- Date Issued: 2009
Ecological role of estuarine brachyuran crabs in mangrove and salt marsh estuaries, Eastern Cape, South Africa
- Authors: Vorsatz, Jeanne Pauline
- Date: 2009
- Subjects: Crabs -- South Africa -- Mangrove Estuary , Crabs -- South Africa -- Salt Marsh Estuary , Salt marsh ecology , Mangrove ecology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10698 , http://hdl.handle.net/10948/1108 , Crabs -- South Africa -- Mangrove Estuary , Crabs -- South Africa -- Salt Marsh Estuary , Salt marsh ecology , Mangrove ecology
- Description: Crabs are conspicuous inhabitants of temperate salt marshes and tropical mangroves and interact with their environment through several processes. However, detailed information on crab community processes is absent for most South African estuaries and nearshore coastal regions. This study evaluated the primary producers supporting crab species in the salt marsh dominated Swartkops estuary and the mangrove Mngazana estuary. Various methods estimating crab abundances were also assessed in different microhabitats and the larval distribution of crabs in the coastal zone was also investigated. Various methods for estimating crab abundance have been employed in the past, each with its inherent biases. The microhabitat of a mangrove forest in Australia was structurally altered by the manipulation of the litter, pneumatophores and the associated algae. These alterations did not affect the behavioural activity or the numbers of crabs recorded in any of the experimental treatments by either visual counts or pitfall traps. However, the number of crabs caught in the pitfall traps differed between the sites. Species-specific behaviour which was not investigated in this study may bias crab abundance estimates when using pitfall traps and therefore requires further investigation. Benthic consumers inhabiting shallow coastal environments may ultimately have the origin of their nutrition in a number of possible sources. Isotopic and gut content analysis of Thalamita crenata and juvenile Scylla serrata in the Mngazana estuary in South Africa revealed that these two portunids are able to share a habitat by resource partitioning. Differences were noted for species-specific utilization of primary producers not only between seasons within a site, but also between sites. This highlighted the use of locally produced primary producers sustaining food webs in estuaries. Mangrove production in the Mngazana estuary is very important and contributes to most of the carbon in the underlying sediments in the mangrove forest. However, the relatively large number of species and biomass encountered in this estuary may also be attributed to the fact that the different species are able to exploit of a number of different resources. The variation in stable isotope analysis of the different crab species throughout the estuary indicated that these crabs able to occupy the same habitat by feeding on a number of different resources and may preferentially select for a specific primary producer. A stable isotope of crabs in the salt marsh Swartkops estuary indicated that the dominant primary producer sustaining crab communities may even take place on a relatively smallscale. Sesarma catenata found at the inner marsh site recorded more depleted carbon signatures than those encountered in the other sites approximately 100 m away, and reflected signatures similar to the locally-encountered inner marsh plants. The relatively enriched nitrogen signatures of the anthropogenically-impacted Swartkops estuary is an indication of extensive inputs due to urbanization and industrialization, in contrast to the relatively pristine Mngazana estuary which exhibited low nitrogen signatures. Emphasis has been placed on the abiotic component of the exchange of nutrients and energy, although living organisms may also be transported, both actively and passively, between ecosystems. Little variation in either species composition or abundance was found between seasons for the larval distribution of brachyuran crabs on the east coast of South Africa. Due to the lack of published larval descriptions, larvae could not be identified to species level and it was therefore not possible to identify whether the larvae were hatched or spawned in an estuary or in a marine environment, or whether the larvae originated in the northern tropical regions. Frequent wind-reversals which are common in this region may retain larvae close inshore and supply the southern temperate locations with larvae from the northern locations. In conclusion, this study has shown that in highly productive systems with a number of potential primary producers, the crabs that inhabit the estuary show a marked diversity in resource utilization which could potentially allow a number of closely related species to occupy different trophic levels. This study also highlights the importance of locally produced sources in an estuary, which may occur on very small scales and this needs to be factored in with the design of any future stable isotope studies of this nature.
- Full Text:
- Date Issued: 2009
- Authors: Vorsatz, Jeanne Pauline
- Date: 2009
- Subjects: Crabs -- South Africa -- Mangrove Estuary , Crabs -- South Africa -- Salt Marsh Estuary , Salt marsh ecology , Mangrove ecology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10698 , http://hdl.handle.net/10948/1108 , Crabs -- South Africa -- Mangrove Estuary , Crabs -- South Africa -- Salt Marsh Estuary , Salt marsh ecology , Mangrove ecology
- Description: Crabs are conspicuous inhabitants of temperate salt marshes and tropical mangroves and interact with their environment through several processes. However, detailed information on crab community processes is absent for most South African estuaries and nearshore coastal regions. This study evaluated the primary producers supporting crab species in the salt marsh dominated Swartkops estuary and the mangrove Mngazana estuary. Various methods estimating crab abundances were also assessed in different microhabitats and the larval distribution of crabs in the coastal zone was also investigated. Various methods for estimating crab abundance have been employed in the past, each with its inherent biases. The microhabitat of a mangrove forest in Australia was structurally altered by the manipulation of the litter, pneumatophores and the associated algae. These alterations did not affect the behavioural activity or the numbers of crabs recorded in any of the experimental treatments by either visual counts or pitfall traps. However, the number of crabs caught in the pitfall traps differed between the sites. Species-specific behaviour which was not investigated in this study may bias crab abundance estimates when using pitfall traps and therefore requires further investigation. Benthic consumers inhabiting shallow coastal environments may ultimately have the origin of their nutrition in a number of possible sources. Isotopic and gut content analysis of Thalamita crenata and juvenile Scylla serrata in the Mngazana estuary in South Africa revealed that these two portunids are able to share a habitat by resource partitioning. Differences were noted for species-specific utilization of primary producers not only between seasons within a site, but also between sites. This highlighted the use of locally produced primary producers sustaining food webs in estuaries. Mangrove production in the Mngazana estuary is very important and contributes to most of the carbon in the underlying sediments in the mangrove forest. However, the relatively large number of species and biomass encountered in this estuary may also be attributed to the fact that the different species are able to exploit of a number of different resources. The variation in stable isotope analysis of the different crab species throughout the estuary indicated that these crabs able to occupy the same habitat by feeding on a number of different resources and may preferentially select for a specific primary producer. A stable isotope of crabs in the salt marsh Swartkops estuary indicated that the dominant primary producer sustaining crab communities may even take place on a relatively smallscale. Sesarma catenata found at the inner marsh site recorded more depleted carbon signatures than those encountered in the other sites approximately 100 m away, and reflected signatures similar to the locally-encountered inner marsh plants. The relatively enriched nitrogen signatures of the anthropogenically-impacted Swartkops estuary is an indication of extensive inputs due to urbanization and industrialization, in contrast to the relatively pristine Mngazana estuary which exhibited low nitrogen signatures. Emphasis has been placed on the abiotic component of the exchange of nutrients and energy, although living organisms may also be transported, both actively and passively, between ecosystems. Little variation in either species composition or abundance was found between seasons for the larval distribution of brachyuran crabs on the east coast of South Africa. Due to the lack of published larval descriptions, larvae could not be identified to species level and it was therefore not possible to identify whether the larvae were hatched or spawned in an estuary or in a marine environment, or whether the larvae originated in the northern tropical regions. Frequent wind-reversals which are common in this region may retain larvae close inshore and supply the southern temperate locations with larvae from the northern locations. In conclusion, this study has shown that in highly productive systems with a number of potential primary producers, the crabs that inhabit the estuary show a marked diversity in resource utilization which could potentially allow a number of closely related species to occupy different trophic levels. This study also highlights the importance of locally produced sources in an estuary, which may occur on very small scales and this needs to be factored in with the design of any future stable isotope studies of this nature.
- Full Text:
- Date Issued: 2009
Effect of processing on the efficacy and safety of Solanum Aculeastrum Dunal berries
- Authors: Aboyade, Oluwaseyi Mayode
- Date: 2009
- Subjects: Medicinal plants -- South Africa -- Eastern Cape , Plant extracts , Drugs -- Effectiveness , Berries , Solanum , Solanum Aculeastrum -- Effectiveness
- Language: English
- Type: Thesis , Doctoral , PhD (Botany)
- Identifier: vital:11302 , http://hdl.handle.net/10353/d1001051 , Medicinal plants -- South Africa -- Eastern Cape , Plant extracts , Drugs -- Effectiveness , Berries , Solanum , Solanum Aculeastrum -- Effectiveness
- Description: General Abstract There has been a steady increase in the use of medicinal plants in the last two decades in both developed and developing countries for prevention, management and treatment of diseases. This increase has been due to reasons such as ease of access, better cultural acceptability and compatibility, cost effectiveness and also the bid to “go natural”. Unfortunately, the notion that herbal medicines are relatively safe because they are natural has led to serious and potentially fatal consequences in phytotherapy. The lack of rigorous research to prove the effectiveness and safety of many medicinal plants is of great concern to the health care system. This thesis therefore addresses not just the efficacy, but also the safety of the extracts of the berry of Solanum aculeastrum - a medicinal plant used, among other things, for the treatment of breast cancer in the Eastern Cape Province of South Africa. Particular attention was paid to the possible effect of different processing methods of the berry extracts on inflammation, cytotoxicity, and toxicity. In studying the comparative effects of various processing methods, four different preparations of the extracts were investigated. These include fresh, dried, boiled fresh, and boiled dried berries. While the effect of processing on the anti-inflammatory properties of the extracts was not dose dependent, the percentage reduction in inflammation was highly significant and more prominent in both concentrations of the boiled fresh berries than the reference drug, indomethacin. Furthermore, the four extracts varied in their ability to act either centrally or peripherally in their effect on pain. Assessment of the analgesic response using the formalin test showed that, at both concentrations tested, none of the extracts inhibited the first phase of the formalin test. Furthermore, it was observed that boiling had differing results on the activity of the iii fresh and dried extracts. While boiling of the dried berries reduced pain in the rats, the opposite trend was observed with the boiled fresh berries. Results of the influence of processing of the berries on cytotoxicity indicated that the extracts are potent inhibitors of human breast, cervical and colonic carcinoma cells and the non-cancerous cells (both the actively dividing and confluent Chang liver cells). Although, in terms of relative potency, the fresh berries appeared to be the most active of the extracts, processing of the berries caused an increase in apoptotic cells and a subsequent decrease in the necrotic cells. The effect of processing on the safety of the berry of S. aculeastrum on the rats fed for 28 days was also investigated. The various doses (1, 10 and 25 mg/kg body weight) of all the four extracts did not alter the activity and the weight of the animals throughout the period of treatment. A reduction in organ to body weight ratio of the heart, kidney, liver and spleen was observed in all the extracts. Regarding the haematological parameters, different patterns of effect were observed between the extracts and within the treated doses. The observed alterations in the biochemical parameters by the various extract of Solanum aculeastrum berries at all the doses may have consequential effects on the normal functioning of these organs. In conclusion, this study has shown that there is some justification for the traditional use of the berries of Solanum aculeastrum in the treatment of inflammation related ailments and cancer. However, the medicinal use of the plant also poses considerable health risks. Investigation conducted into the plant’s safety revealed that the berry extracts were nephrotoxic, hepatotoxic, haematotoxic and at higher doses, fatal. Another concern with regard to the plant’s safety is the non-selectivity of its extracts in the inhibition of carcinoma, actively dividing and un-dividing cells. Assessment of the effect of the processing on the berry’s efficacy and safety as herbal iv remedy produced mixed results. On the one hand, processing seemed to improve the extract’s anti-inflammatory and analgesic activity, while reducing its cytotoxic potential. On the other hand, a reduction in the toxicity was observed on the processed extracts compared to the fresh ones. This may be an indication that processing has an overall beneficial effect on the medicinal properties of the plant and should thus be considered as a method of making the berries of Solanum aculeastrum safer for use as a herbal remedy.
- Full Text:
- Date Issued: 2009
- Authors: Aboyade, Oluwaseyi Mayode
- Date: 2009
- Subjects: Medicinal plants -- South Africa -- Eastern Cape , Plant extracts , Drugs -- Effectiveness , Berries , Solanum , Solanum Aculeastrum -- Effectiveness
- Language: English
- Type: Thesis , Doctoral , PhD (Botany)
- Identifier: vital:11302 , http://hdl.handle.net/10353/d1001051 , Medicinal plants -- South Africa -- Eastern Cape , Plant extracts , Drugs -- Effectiveness , Berries , Solanum , Solanum Aculeastrum -- Effectiveness
- Description: General Abstract There has been a steady increase in the use of medicinal plants in the last two decades in both developed and developing countries for prevention, management and treatment of diseases. This increase has been due to reasons such as ease of access, better cultural acceptability and compatibility, cost effectiveness and also the bid to “go natural”. Unfortunately, the notion that herbal medicines are relatively safe because they are natural has led to serious and potentially fatal consequences in phytotherapy. The lack of rigorous research to prove the effectiveness and safety of many medicinal plants is of great concern to the health care system. This thesis therefore addresses not just the efficacy, but also the safety of the extracts of the berry of Solanum aculeastrum - a medicinal plant used, among other things, for the treatment of breast cancer in the Eastern Cape Province of South Africa. Particular attention was paid to the possible effect of different processing methods of the berry extracts on inflammation, cytotoxicity, and toxicity. In studying the comparative effects of various processing methods, four different preparations of the extracts were investigated. These include fresh, dried, boiled fresh, and boiled dried berries. While the effect of processing on the anti-inflammatory properties of the extracts was not dose dependent, the percentage reduction in inflammation was highly significant and more prominent in both concentrations of the boiled fresh berries than the reference drug, indomethacin. Furthermore, the four extracts varied in their ability to act either centrally or peripherally in their effect on pain. Assessment of the analgesic response using the formalin test showed that, at both concentrations tested, none of the extracts inhibited the first phase of the formalin test. Furthermore, it was observed that boiling had differing results on the activity of the iii fresh and dried extracts. While boiling of the dried berries reduced pain in the rats, the opposite trend was observed with the boiled fresh berries. Results of the influence of processing of the berries on cytotoxicity indicated that the extracts are potent inhibitors of human breast, cervical and colonic carcinoma cells and the non-cancerous cells (both the actively dividing and confluent Chang liver cells). Although, in terms of relative potency, the fresh berries appeared to be the most active of the extracts, processing of the berries caused an increase in apoptotic cells and a subsequent decrease in the necrotic cells. The effect of processing on the safety of the berry of S. aculeastrum on the rats fed for 28 days was also investigated. The various doses (1, 10 and 25 mg/kg body weight) of all the four extracts did not alter the activity and the weight of the animals throughout the period of treatment. A reduction in organ to body weight ratio of the heart, kidney, liver and spleen was observed in all the extracts. Regarding the haematological parameters, different patterns of effect were observed between the extracts and within the treated doses. The observed alterations in the biochemical parameters by the various extract of Solanum aculeastrum berries at all the doses may have consequential effects on the normal functioning of these organs. In conclusion, this study has shown that there is some justification for the traditional use of the berries of Solanum aculeastrum in the treatment of inflammation related ailments and cancer. However, the medicinal use of the plant also poses considerable health risks. Investigation conducted into the plant’s safety revealed that the berry extracts were nephrotoxic, hepatotoxic, haematotoxic and at higher doses, fatal. Another concern with regard to the plant’s safety is the non-selectivity of its extracts in the inhibition of carcinoma, actively dividing and un-dividing cells. Assessment of the effect of the processing on the berry’s efficacy and safety as herbal iv remedy produced mixed results. On the one hand, processing seemed to improve the extract’s anti-inflammatory and analgesic activity, while reducing its cytotoxic potential. On the other hand, a reduction in the toxicity was observed on the processed extracts compared to the fresh ones. This may be an indication that processing has an overall beneficial effect on the medicinal properties of the plant and should thus be considered as a method of making the berries of Solanum aculeastrum safer for use as a herbal remedy.
- Full Text:
- Date Issued: 2009
Effects of marine reserves on the biology of rocky intertidal limpets along the southern coast of South Africa
- Nakin, Motebang Dominic Vincent
- Authors: Nakin, Motebang Dominic Vincent
- Date: 2009
- Subjects: Limpets Marine parks and reserves -- South Africa Marine biology -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5680 , http://hdl.handle.net/10962/d1005365
- Description: Limpets are harvested by people in South Africa, but are selected in terms of species and size. The effects of marine reserves on the biology of commonly exploited (Helcion concolor and Scutellastra longicosta) and rarely exploited species (Cellana capensis and Scutellastra granularis) were investigated on the southeast coast of South Africa at two reserve and two non-reserve sites. For each species, a 4-way nested ANOVA was used to test the effects of month, reserve, site (nested within reserve) and area (nested within site and reserve) on population density, size structure and recruitment of these limpets. The data were collected monthly over 20 months. The overall results indicated a gradient of exploitation among species, S. longicosta was the most heavily exploited species and S. granularis the least exploited species. However, there was also a gradient of exploitation between reserves and non-reserves. Xhora was the most heavily exploited site while Nqabara was less heavily exploited. Of the two reserve sites, Cwebe had more poachers than Dwesa. In most analyses, the month x area (reserve (site)) interaction was significant. However, this was largely an artifact due to comparisons of areas in different sites and significant differences between areas within sites occurred in relatively few months. Densities were greater inside reserves for all species except C. capensis. For S. longicosta and H. concolor this was expected but not for S. granularis and the result possibly reflects its opportunistic exploitation in the absence of the preferred species or indirect effects of reserves. Commonly exploited species and the rarely exploited C. capensis clearly showed greater mean and maximum sizes in reserves but there were month/site (reserve) interactions. Months with significant differences between reserves and nonreserves in both mean and maximum sizes generally occurred more often for commonly exploited than rarely exploited species, but C. capensis showed the strongest reserve effect on maximum size. Interview surveys showed that, although not normally exploited, C. capensis is sometimes mistaken for H. concolor and this suggests that large individuals are unintentionally harvested outside reserves. There were no significant reserve effects on recruitment for any species. Although Xhora had the lowest densities and limpet sizes, it showed the highest recruitment especially for S. longicosta, suggesting that larvae can be transported far from where they are released and settle in non-reserve sites regardless of adult densities. Reserve as a main factor was not significant for the rarely exploited species, but there was a significant month x reserve interaction, with non-reserves having greater GSI values than reserves in most months. Growth rates were examined using individual tagging and cohort analysis. The two techniques gave different results, with individual tagging giving higher growth estimates than cohort analysis. Except for the territorial species S. longicosta, growth was higher in non-reserves and inversely correlated with population density. Mortality estimates using the Cormack-Jolly-Seber model indicated that the rarely exploited species had significantly greater capture probabilities in reserves while no significant reserve effects were observed for the commonly exploited species. Reserve effects on survival probability were significant only for S. longicosta, with reserves being greater than nonreserves and no significant effects for any other species. Enhanced survival in reserves was attributed to the effects of human exploitation. In theory, marine protected areas show increases in densities, sizes and reproductive output of exploited species, but the present results revealed that the efficacy of reserves depends on the status of the species, not only whether it is exploited or non-exploited, but also whether it is territorial.
- Full Text:
- Date Issued: 2009
- Authors: Nakin, Motebang Dominic Vincent
- Date: 2009
- Subjects: Limpets Marine parks and reserves -- South Africa Marine biology -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5680 , http://hdl.handle.net/10962/d1005365
- Description: Limpets are harvested by people in South Africa, but are selected in terms of species and size. The effects of marine reserves on the biology of commonly exploited (Helcion concolor and Scutellastra longicosta) and rarely exploited species (Cellana capensis and Scutellastra granularis) were investigated on the southeast coast of South Africa at two reserve and two non-reserve sites. For each species, a 4-way nested ANOVA was used to test the effects of month, reserve, site (nested within reserve) and area (nested within site and reserve) on population density, size structure and recruitment of these limpets. The data were collected monthly over 20 months. The overall results indicated a gradient of exploitation among species, S. longicosta was the most heavily exploited species and S. granularis the least exploited species. However, there was also a gradient of exploitation between reserves and non-reserves. Xhora was the most heavily exploited site while Nqabara was less heavily exploited. Of the two reserve sites, Cwebe had more poachers than Dwesa. In most analyses, the month x area (reserve (site)) interaction was significant. However, this was largely an artifact due to comparisons of areas in different sites and significant differences between areas within sites occurred in relatively few months. Densities were greater inside reserves for all species except C. capensis. For S. longicosta and H. concolor this was expected but not for S. granularis and the result possibly reflects its opportunistic exploitation in the absence of the preferred species or indirect effects of reserves. Commonly exploited species and the rarely exploited C. capensis clearly showed greater mean and maximum sizes in reserves but there were month/site (reserve) interactions. Months with significant differences between reserves and nonreserves in both mean and maximum sizes generally occurred more often for commonly exploited than rarely exploited species, but C. capensis showed the strongest reserve effect on maximum size. Interview surveys showed that, although not normally exploited, C. capensis is sometimes mistaken for H. concolor and this suggests that large individuals are unintentionally harvested outside reserves. There were no significant reserve effects on recruitment for any species. Although Xhora had the lowest densities and limpet sizes, it showed the highest recruitment especially for S. longicosta, suggesting that larvae can be transported far from where they are released and settle in non-reserve sites regardless of adult densities. Reserve as a main factor was not significant for the rarely exploited species, but there was a significant month x reserve interaction, with non-reserves having greater GSI values than reserves in most months. Growth rates were examined using individual tagging and cohort analysis. The two techniques gave different results, with individual tagging giving higher growth estimates than cohort analysis. Except for the territorial species S. longicosta, growth was higher in non-reserves and inversely correlated with population density. Mortality estimates using the Cormack-Jolly-Seber model indicated that the rarely exploited species had significantly greater capture probabilities in reserves while no significant reserve effects were observed for the commonly exploited species. Reserve effects on survival probability were significant only for S. longicosta, with reserves being greater than nonreserves and no significant effects for any other species. Enhanced survival in reserves was attributed to the effects of human exploitation. In theory, marine protected areas show increases in densities, sizes and reproductive output of exploited species, but the present results revealed that the efficacy of reserves depends on the status of the species, not only whether it is exploited or non-exploited, but also whether it is territorial.
- Full Text:
- Date Issued: 2009
Establishing experimental systems for studying the replication biology of Providence virus
- Authors: Walter, Cheryl Tracy
- Date: 2009
- Subjects: Insects -- Viruses Insects -- Diseases Insects -- Parasites Host-virus relationships RNA viruses DNA Insects as carriers of disease
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3928 , http://hdl.handle.net/10962/d1003987
- Description: Providence virus (PrV) is a member of the Tetraviridae, a family of small, positive sense, single-stranded RNA viruses, which characteristically infect the midgut tissue of heliothine larvae. PrV is the only known tetravirus that replicates in cultured insect cells. The virus comprises a monopartite genome resembling members of the genus Betatetravirus with the capsid precursor protein undergoing autoproteolytic cleavage at its C-terminus consistent with other tetravirus capsid precursor proteins. Analysis of viral cDNA predicted the presence of three potential overlapping gene products (from 5` to 3`): (1) p130, a protein of unrecognized nucleotide or amino acid homology with a 2A-like processing site at its N-terminus; (2) p104, the replicase ORF, which was found to be phylogenetically related to tombus-and umbraviruses replicases. The presence of a read-through stop signal in the p104 ORF was proposed to produce and amino terminal product with a predicted MW of 40 kDa (p40) and (3) the capsid protein precursor (81 kDa) which has two 2A-like processing sites at its N-terminus. Metabolic radiolabelling of viral translation products in persistently infected MG8 cells and in vitro translation of the individual ORFs were performed in order to analyse the expression of PrV gene products. p130 was translated with no evidence of 2A-like processing. Two products of 40 kDa and 104 kDa were translated from the p104 ORF, indicating that the read-through stop signal was likely to be functional. Finally, the capsid protein precursor ORF produced a major translation product of 68 kDa corresponding to the capsid protein precursor as well a peptide of 15 kDa that was attributed to the activity of the second 2A-like site at the N-terminus of the p81 ORF. The subcellular distribution of viral RNA (vRNA) and p40 in MG8 cells was investigated using immunofluorescence and biochemical fractionation. The results showed that p40/p104 and vRNA accumulated in polarized, punctate structures in some but not all MG8 cells and in some cases, co-localization was observed. This thesis concludes that PrV is a novel tetravirus with significant similarities plant carmolike viruses that should be re-classified at the family level.
- Full Text:
- Date Issued: 2009
- Authors: Walter, Cheryl Tracy
- Date: 2009
- Subjects: Insects -- Viruses Insects -- Diseases Insects -- Parasites Host-virus relationships RNA viruses DNA Insects as carriers of disease
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3928 , http://hdl.handle.net/10962/d1003987
- Description: Providence virus (PrV) is a member of the Tetraviridae, a family of small, positive sense, single-stranded RNA viruses, which characteristically infect the midgut tissue of heliothine larvae. PrV is the only known tetravirus that replicates in cultured insect cells. The virus comprises a monopartite genome resembling members of the genus Betatetravirus with the capsid precursor protein undergoing autoproteolytic cleavage at its C-terminus consistent with other tetravirus capsid precursor proteins. Analysis of viral cDNA predicted the presence of three potential overlapping gene products (from 5` to 3`): (1) p130, a protein of unrecognized nucleotide or amino acid homology with a 2A-like processing site at its N-terminus; (2) p104, the replicase ORF, which was found to be phylogenetically related to tombus-and umbraviruses replicases. The presence of a read-through stop signal in the p104 ORF was proposed to produce and amino terminal product with a predicted MW of 40 kDa (p40) and (3) the capsid protein precursor (81 kDa) which has two 2A-like processing sites at its N-terminus. Metabolic radiolabelling of viral translation products in persistently infected MG8 cells and in vitro translation of the individual ORFs were performed in order to analyse the expression of PrV gene products. p130 was translated with no evidence of 2A-like processing. Two products of 40 kDa and 104 kDa were translated from the p104 ORF, indicating that the read-through stop signal was likely to be functional. Finally, the capsid protein precursor ORF produced a major translation product of 68 kDa corresponding to the capsid protein precursor as well a peptide of 15 kDa that was attributed to the activity of the second 2A-like site at the N-terminus of the p81 ORF. The subcellular distribution of viral RNA (vRNA) and p40 in MG8 cells was investigated using immunofluorescence and biochemical fractionation. The results showed that p40/p104 and vRNA accumulated in polarized, punctate structures in some but not all MG8 cells and in some cases, co-localization was observed. This thesis concludes that PrV is a novel tetravirus with significant similarities plant carmolike viruses that should be re-classified at the family level.
- Full Text:
- Date Issued: 2009