Faecal source tracking and water quality in the Eastern Cape, South Africa
- Authors: Luyt, Catherine Diane
- Date: 2013
- Subjects: Water quality -- South Africa -- Grahamstown , Waterborne infection -- Management , Drinking water -- Contamination -- South Africa -- Grahamstown
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6052 , http://hdl.handle.net/10962/d1018242
- Description: Water quality is concerning as many still lack access to safe drinking water. Alternate sources such as rivers (FC up to 1600 CFUs/100 mL) and rainwater are often polluted. Rainwater tanks require maintenance to improve water quality, but could be used for non-potable purposes or irrigation. Grahamstown infrastructural failures initiate deviations from DWAF 1996 domestic water guidelines for microorganisms within the distribution system. Frequent testing can decrease risks of waterborne diseases. Limitations to this are inaccessibility of rural areas, distances from testing centres and costs. The low cost H2S strip test able to be used onsite by communities, may aid in risk assessment. H2S strip test results are not affected by sulphate (14 to 4240 mg/L) or nitrite (up to 47 mg/L). Transportation of the H2S strip tests between 10 and 32°C does not modify results significantly. Similarly to other studies: Klebsiella spp.; Enterobacter spp. and Serratia spp. were isolated from H2S strip tests. The mH2S strip test corresponds best with HPC in treated water, while in untreated river water it has approximately 90% correspondence with FCs, while survival of FC causes discrepancies with the H2S test after 22 days. A faecal coliform inactivation rate of 0.1 CFUs/ day, may be longer than many pathogens. Faecal source tracking, not currently practised in South Africa, could aid health risk assessments for disaster management, which would improve the NMMP programme. Bacterial survival times could propose the time period for which water is unsafe. Bifidobacteria and Rhodococcus are proposed to help identify the faecal pollution source. But enumeration of Rhodococcus is too lengthy (21 days). The tracking ratio of bifidobacteria (between 0.1 to 6.25) is not source definitive. The bifidobacteria survival rate, could indicator the time since faecal pollution. The bifidobacteria average survival rate is 2.3 CFUs per day for both groups. The culturability and selectivity of agar is still poor, with total bifidobacteria less selectively culturable. Enterococci overgrowth of TB was decreased by Beerens media. SUB is still useful to identify potential human faecal inputs. A single tracking method is thus not suitable alone, but requires a combination of techniques.
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- Date Issued: 2013
Falcipains as malarial drug targets
- Authors: Kanzi, Aquillah Mumo
- Date: 2013
- Subjects: Malaria Malaria -- Chemotherapy Plasmodium falciparum Antimalarials -- Development Cysteine proteinases Cysteine proteinases -- Inhibitors Papain Drug development Bioinformatics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3897 , http://hdl.handle.net/10962/d1003842
- Description: Malaria is an infectious disease caused by parasites of the Plasmodium genus with mortality rates of more than a million annually, hence a major global public health concern. Plasmodium falciparum (P. falciparum) accounts for over 90% of malaria incidence. Increased resistance to antimalarial drugs by the Plasmodium parasite, coupled with the lack of an effective malaria vaccine necessitates the urgent need for new research avenues to develop novel and more potent antimalarial drugs. This study focused on falcipains, a group of P. falciparum cysteine proteases that belong to the clan CA and papain family C1, that have emerged as potential drug targets due to their involvement in a range of crucial functions in the P. falciparum life cycle. Recently, falcipain-2 has been validated as a drug target but little is known of its Plasmodium orthologs. Currently, there are several falcipain inhibitors that have been identified, most of which are peptide based but none has proceeded to drug development due to associated poor pharmacological profiles and susceptibility to degradation by host cysteine proteases. Non-peptides inhibitors have been shown to be more stable in vivo but limited information exists. In vivo studies on falcipain-2 and falcipain-3 inhibitors have also been complicated by varying outcomes, thus a good understanding of the structural variations of falcipain Plasmodium orthologs at the active site could go a long way to ease in vivo results interpretation and effective inhibitor design. In this study, we use bioinformatics approaches to perform comparative sequence and structural analysis and molecular docking to characterize protein-inhibitor interactions of falcipain homologs at the active site. Known FP-2 and FP-3 small molecule nonpeptide inhibitors were used to identify residue variations and their effect on inhibitor binding. This was done with the aim of screening a collection of selected non-peptide compounds of South African natural origin to identify possible new inhibitor leads. Natural compounds with high binding affinities across all Plasmodium orthologs were identified. These compounds were then used to search the ZINC database for similar compounds which could have better binding affinities across all selected falcipain homologs. Compounds with high binding affinities across all Plasmodium orthologs were found.
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- Date Issued: 2013
Female changes : the violation and violence of women in Ovid's Metamorphoses
- Authors: Champanis, Leigh Alexandra
- Date: 2013
- Subjects: Ovid, 43 B.C. - 17 or 18 A.D. -- Criticism and interpretation Ovid, 43 B.C. - 17 or 18 A.D. -- Metamorphoses Rape Women -- Violence against Violence in women
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3614 , http://hdl.handle.net/10962/d1006024
- Description: Ovid’s interest in women and their lives is apparent throughout his texts, but is especially so in the Metamorphoses. This study analyses the violation and violence of women in the Roman poet’s epic and sets out to uncover the governing social mores and values that perhaps shaped the representations of women in the text. It examines how Ovid’s narratives may betray his values and attitudes and those of his audience as well as looking at the various ways that the poet and his rape episodes have been read. After surveying the literature on rape in Ovid’s Metamorphoses, Ars Amatoria and the Fasti, a brief historical context for the Metamorphoses is provided; women’s lives in Rome, the rape laws that existed during this time, as well as Roman sexuality are then examined. After this, a close textual analysis of different rape episodes in the Metamorphoses is presented, including the episodes of nymphs as victims, the silencing of rape victims and sexually ‘aggressive’ women, in order to reveal and examine the patterns that emerge. While Ovid’s intentions and attitudes towards women, as they are found in the Metamorphoses, have been read by some as sympathetic, by others as misogynistic and still others as more neutral, it is concluded that, although there is space for various readings, as a poet, Ovid was ‘opportunistic’ in his choice of materia and, above all, he wished to stimulate and delight his audience. While his personal values may not necessarily be reflected in his works and his readers may never know the ‘true’ intentions behind the poem, the Metamorphoses does hold up a mirror to the negative treatment of women and exposes the gender inequalities that existed during Ovid’s time. As a poet, however, Ovid’s conceived role is to entertain his audience and despite his somewhat problematic treatment of women and rape victims, he does just that.
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- Date Issued: 2013
Fish and fisheries of Bangweulu wetlands, Zambia
- Authors: Huchzermeyer, Carl Friedrich
- Date: 2013
- Subjects: Bangweulu Swamps (Zambia) , Fisheries -- Zambia -- Bangweulu Swamps , Fishes -- Zambia -- Bangweulu Swamps , Fishery management -- Zambia -- Bangweulu Swamps , Fishing -- Zambia -- Bangweulu Swamps , Fishing -- Economic aspects -- Zambia -- Bangweulu Swamps , Fish stock assessment -- Zambia -- Bangweulu Swamps , Fish as food -- Zambia -- Bangweulu Swamps , Conservation of natural resources -- Zambia -- Bangweulu Swamps , Sustainable development -- Zambia -- Bangweulu Swamps
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5203 , http://hdl.handle.net/10962/d1003927 , Bangweulu Swamps (Zambia) , Fisheries -- Zambia -- Bangweulu Swamps , Fishes -- Zambia -- Bangweulu Swamps , Fishery management -- Zambia -- Bangweulu Swamps , Fishing -- Zambia -- Bangweulu Swamps , Fishing -- Economic aspects -- Zambia -- Bangweulu Swamps , Fish stock assessment -- Zambia -- Bangweulu Swamps , Fish as food -- Zambia -- Bangweulu Swamps , Conservation of natural resources -- Zambia -- Bangweulu Swamps , Sustainable development -- Zambia -- Bangweulu Swamps
- Description: Bangweulu Wetlands is a 6000 km² public-private-partnership conservation area in northeastern Zambia, lying on the south-eastern margins of the Bangweulu Swamps, Congo River system. The area is important for wildlife conservation, tourism and as a fishing ground for the local inhabitants. This study provides a baseline of the fish and fisheries of this area. The conservation area is situated on the transition zone between woodland, floodplain and swamp. A total of 42 fish species representing 12 taxonomic families were collected. The fish fauna of the area was characterised by a diversity of small cyprinids (14 species), cichlids (9 species), clariid catfishes (4 species) and mormyrids (4 species). Species such as Clarias gariepinus, C. ngamensis, Marcusenius macrolepidotus, Tilapia rendali, T. sparrmanii and several small Barbus species were shared with adjacent floodplain systems such as the upper Zambezi and Kafue rivers. Fishing was undertaken by fishing groups consisting of a fisherman and his family, or a group of men fishing together. Access to the fishing grounds was controlled by traditional fishing leaders, who collected tribute from fishermen. Fishing groups utilised fixed, distinct fishing areas determined by ancestry. The most important time for fishing was during the drawdown phase of the floodplains, from March until June. During the dry season fewer groups were engaged in fishing, with many having returned to farming activities. The main fishing methods of the floodplain fishery were basket traps and mosquito-mesh funnel nets set into earth fish barriers (fish weirs) constructed on the plains, various mesh sizes of gillnets, hook longlines and seine nets. The use of fish spears, drag baskets and piscicides was of lesser importance. Most fishing gears were constructed of a variety of natural and modern, manufactured materials. The fishery was multi-species and 23 fish species were recorded from in catch. The three most important species in the catches were C. gariepinus, T. rendalli and M. macrolepidotus. Together these contributed 67% by weight to the catch. Catch-per-unit-effort (CPUE) for the different gears was 0.4 ± 0.3 kg.trap.night⁻¹ for basket traps, 2.7 ± 4.6 kg.net.night⁻¹ for funnel nets, 0.3 ± 0.5 kg.50 m net.night⁻¹ for gill nets, 3.5 ± 6.3 kg.100 hooks.night⁻¹ for longlines, 1.79 ± 1.11 kg.haul⁻¹ for mosquito-mesh seine nets and 6.87 ± 6.27 kg.haul⁻¹ for larger-mesh seine nets. The weight of average daily landings of fishing groups, using a variety of gears was 7.8 ± 7.4 kg. Fishermen were able to maintain the same catch rate between dry and wet seasons, with no significant differences (p < 0.05) in daily landings between seasons. Yield per fisherman for a seven month season, which required 2-3 relocations due to falling water level, was 1.64 t based on catch assessment, and 1.9 t from a socio-economic survey. A tentative yield per area estimate for the area was 2I7 kg.ha⁻¹ over the three month shallow-floodplain fishing season. Most fish landed in the fishery were processed into sundried or smoke-dried products. These were used for 1) home consumption, 2) trade with village farmers (from up to 70 km inland of the fishing grounds) in exchange for staple starch meal, and 3) sold to urban fish traders, reaching markets as distant as Lubumbashi in Democratic Republic of Congo. Fish traders toured fishing camps to buy fish, supporting auxiliary industries such as transport and accommodation services. The price for dried fish at source was 3.14 ± 1.34 USDlkg and the market price reported for the Zambian Copperbelt was 6.14 ± 2.54 USD/kg. Typical returns on investment in fish trading were estimated as 68-77%. The fishery was considered to be biologically and socially sustainable. By harvesting a seasonally transient assemblage of species with high productivity and biological turnover rates and with life histories adapted to high mortality, fishermen were able to maintain a stable and viable livelihood. Management recommendations for the area were that a fisheries management plan be developed that would seek to strengthen the traditional system of rights-allocation, address problems between fishing and tourism activities, and enhance communication between fisheries and conservation stakeholders. To do this it was recommended that: 1) conservation authorities recognise the importance of the fishery, 2) no changes to current effort levels and fishing methods were necessary, 3) points 1 and 2 above be used to improve communication and trust between conservation authorities and fishermen, 4) customary resource-access mechanisms be understood and strengthened so that local inhabitants' rights to the resource are protected, 5) fishermen help formulate and accept conservation and tourism rules, 6) tourists and guides be made aware of the function of the fishery, 7) a fisheries management forum of key community, government and conservation stakeholders be formed to shape and implement the fisheries management plan, 8) locally-adapted bylaws be created to legitimise crucial floodplain gears currently considered illegal (e.g. mosquito-net gears, fish weirs), 9) no intervention to formalise fish trading be made, and 10) a trained person with a fisheries background be hired oversee the implementation of the recommendations.
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- Date Issued: 2013
Fixed points of single-valued and multi-valued mappings with applications
- Authors: Stofile, Simfumene
- Date: 2013
- Subjects: Fixed point theory Mappings (Mathematics) Coincidence theory (Mathematics) Metric spaces Uniform spaces Set-valued maps
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5397 , http://hdl.handle.net/10962/d1002960
- Description: The relationship between the convergence of a sequence of self mappings of a metric space and their fixed points, known as the stability (or continuity) of fixed points has been of continuing interest and widely studied in fixed point theory. In this thesis we study the stability of common fixed points in a Hausdorff uniform space whose uniformity is generated by a family of pseudometrics, by using some general notations of convergence. These results are then extended to 2-metric spaces due to S. Gähler. In addition, a well-known theorem of T. Suzuki that generalized the Banach Contraction Principle is also extended to 2-metric spaces and applied to obtain a coincidence theorem for a pair of mappings on an arbitrary set with values in a 2-metric space. Further, we prove the existence of coincidence and fixed points of Ćirić type weakly generalized contractions in metric spaces. Subsequently, the above result is utilized to discuss applications to the convergence of modified Mann and Ishikawa iterations in a convex metric space. Finally, we obtain coincidence, fixed and stationary point results for multi-valued and hybrid pairs of mappings on a metric space.
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- Date Issued: 2013
For the people : an appraisal comparison of imagined communities in letters to two South African newspapers
- Authors: Smith, Jade
- Date: 2013
- Subjects: Daily Sun (Johannesburg, South Africa) , Times (Johannesburg, South Africa) , Mass media and social integration -- South Africa , Language and languages -- Usage , Mass media and language -- South Africa , Mass media and culture -- South Africa , Belonging (Social psychology)
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2385 , http://hdl.handle.net/10962/d1016264
- Description: This thesis reports on the bonds that unify imagined communities (Anderson 1983) that are created in 40 letters prominently displayed on the opinions pages of the Daily Sun, a popular tabloid, and The Times, a daily offshoot of the mainstream national Sunday Times. An APPRAISAL analysis of these letters reveals how the imagined communities attempt to align their audiences around distinctive couplings of interpersonal and ideational meaning. Such couplings represent the bonds around which community identities are co-constructed through affiliation and are evidence of the shared feelings that unite the communities of readership. Inferences drawn from this APPRAISAL information allow for a comparison of the natures of the two communities in terms of how they view their agency and group cohesion. Central to the analysis and interpretation of the data is the letters’ evaluative prosody, traced in order to determine the polarity of readers’ stances over four weeks. Asymmetrical prosodies are construed as pointing to the validity of ‘linguistic ventriloquism’, a term whose definition is refined and used as a diagnostic for whether the newspapers use their readers’ letters to promote their own stances on controversial matters. Principal findings show that both communities affiliate around the value of education, and dissatisfaction with the country’s political leaders, however The Times’ readers are more individualistic than the Daily Sun’s community members, who are concerned with the wellbeing of the group. The analysis highlights limitations to the application of the APPRAISAL framework, the value of subjectivity in the analytical process, and adds a new dimension to South African media studies, as it provides linguistic insights into the construction of imagined communities of newspaper readership.
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- Date Issued: 2013
Gametogenesis, gonadal recrudescence, restraint and spawning patterns in Nile perch, Lates niloticus (Linnaeus, 1758)
- Authors: Kahwa, David
- Date: 2013
- Subjects: Nile perch -- Victoria, Lake Gametogenesis Oogenesis Spermatogenesis Nile perch -- Spawning -- Victoria, Lake Nile perch -- Induced spawning -- Victoria, Lake Nile perch -- Reproduction -- Endocrine aspects -- Victoria, Lake Fish culture -- Victoria, Lake
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5182 , http://hdl.handle.net/10962/d1001834
- Description: The Nile perch, Lates niloticus (Linnaeus, 1758), is a predacious freshwater fish widely distributed throughout the Afro-tropic eco-zone. The species was introduced to Lake Victoria in the early 1950s and by 1980 it had dominated the fisheries of Lake Victoria. This was followed by a dramatic decrease in the Nile perch fisheries production due to uncontrolled exploitation. The purpose of this thesis is to provide fundamental knowledge that can be applied in aquaculture and fisheries management through the study of the reproductive biology of L. niloticus. The research was aimed at the studying of the diverse aspects of the reproductive biology of L. niloticus in the Lake Victoria, Ugandan populations. This included reproductive patterns in relation to proximate environmental conditions, size at sexual maturity, gonad and gamete structure, gametogenesis and induced ovulation. The size at 50% sexual maturity for female Nile perch was 59.4 cm, which is lower than the earlier reported size of greater than 90 cm total length. Male L. niloticus matured at 57.8 cm total length in Lake Victoria. Microscopy revealed that L. niloticus from Lake Victoria had one spawning period that started in November and ended in March. Type I atresia occurred at high frequency from March to June, and type III atresia was present from July to September and between November and December. Spermatogenesis in L. niloticus is cystic and sperm development is the result of asynchronous activation of the germ cells. Type II spermatozoa are simple, uni-flagellate aquasperm with no acrosome. Oogenesis in L. niloticus differed from that of other fishes in that no cortical alveoli were present in any stage of oogenesis. Numerous oil globules were present in the primary yolk vesicle stage. This formed one centrally positioned, large oil globule in the tertiary yolk vesicle oocytes during final oocyte maturation. Clove oil was an effective sedative and an anaesthetic for the handling of L. niloticus. Induction time was more rapid at clove oil concentrations of 50 - 100 μl L⁻¹ than in fish exposed to clove oil concentrations less than 50 μl L⁻¹. Fish exposed to high concentrations exhibited significantly short induction times of less than 240 seconds. On average, fish recovered within 673 ± 58 seconds for all the concentrations used. Prolonged exposure of L. niloticus to low clove oil concentrations of 2.5 - 10 μl L⁻¹ did not change the blood plasma cortisol, glucose, and the lactate and chloride ion concentration, relative to the control treatment. Captive breeding was attempted by conducting induced spawning experiments. Only final oocyte maturation was achieved using a decapeptide Gonadotropin Releasing Hormone (Dargin, sGnRH-MET), combined with a water-soluble dopamine receptor antagonist metoclopramide. This thesis suggests a research approach that provides a basis for aquaculture of the new species by first studying reproductive biology patterns and then linking the information to gonad and gamete structure so that spawning times can be estimated. It further provides insights into aspects of the reproductive biology of the species and the effects of hormonal intervention on oocytes by showing at which stage of oocyte development hormones should be applied in L. niloticus. Clove oil can be used to sedate and anaesthetise L. niloticus broodfish to reduce the stress related to the handling of large specimens.
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- Date Issued: 2013
GDR development policy with special reference to Africa, c. 1960-1990
- Authors: Van der Heyden, Ulrich Klaus Helmut
- Date: 2013
- Subjects: Germany -- Foreign relations -- Africa , Germany -- Foreign economic relations -- Africa , Africa -- Foreign relations -- Germany , Africa -- Foreign economic relations -- Germany , Africa -- Politics and government -- 1960- , Africa -- History -- 1960-
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2531 , http://hdl.handle.net/10962/d1001860
- Description: This thesis explores the political, economic and theoretical underpinnings of the German Democratic Republic’s (GDR’s) development policies towards the Third World between c.1960 and 1990. Particular attention is paid to Africa. Case studies of assistance to SWAPO and the ANC further focus the attention of the reader on southern Africa in particular. Aspects of both military and civilian aid are considered, including both development initiatives overseas in Africa, and development training for Africans within the GDR itself. Since German “reunification”, the GDR’s history has been explored largely from a West German perspective. The present work attempts to provide a more balanced view of successes and shortcomings of the GDR’s policies towards, and interaction with, African countries and liberation movements. It also aims to bring to the attention of English-speaking readers German archival sources, other primary sources and published works which they would otherwise have been unlikely to encounter. From its formation, the GDR made strenuous efforts to develop relations with countries which were either free from colonial dependency or were struggling for freedom. Over the course of thirty years, it followed a number of different approaches, and developed diverse objectives. These were shaped in the wider context of the cold war, the Hallstein doctrine (which established that the FRG – and, in effect, its allies - would not establish or maintain diplomatic relations with any state that recognised the GDR), the relationships between the GDR and partner socialist states, and the economic difficulties faced by the GDR. Arising from this complex situation, from time to time, both internally in the GDR and in terms of its foreign affairs, tensions and discrepancies arose between theoretical objectives and political and economic reality. Despite these severe constraints, during the period under review, the volume and range of the GDR’s relationships with developing countries increased dramatically. For example, between 1970 and 1987, the number of developing countries with which the GDR had foreign economic relations on the basis of international agreements grew from 23 to 64. Viewed within its economic context, the state was arguably far more committed to development aid than the Federal Republic of Germany. In addition, there is a great deal of evidence that “solidarity” with developing nations and the oppressed enjoyed a considerable degree of popular support.
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- Date Issued: 2013
Genetics and thermal biology of littorinid snails of the genera Afrolittorina, Echinolittorina and Littoraria (Gastropoda: Littorinidae) from temperate, subtropical and tropical regions
- Authors: Matumba, Tshifhiwa Given
- Date: 2013
- Subjects: Littorinidae -- South Africa Littorinidae -- Brunei Littorinidae -- Adaptation -- South Africa Littorinidae -- Adaptation -- Brunei Littorinidae -- Effect of temperature on -- South Africa Littorinidae -- Effect of temperature on -- Brunei Littorinidae -- Physiology Snails -- South Africa Snails -- Brunei Gastropoda -- South Africa Gastropoda -- Brunei Intertidal animals -- South Africa Intertidal animals -- Brunei
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5588 , http://hdl.handle.net/10962/d1001953
- Description: With the anticipated effects of climate change due to global warming, there is concern over how animals, especially ectotherms, will respond to or tolerate extreme and fluctuating environmental temperature stress. Littorinid snails are intertidal ectotherms that live high on the shore where they experience both extreme and variable conditions of temperature and desiccation stress, and are believed to live close to their tolerance limits. This study investigated the thermal biology of littorinid snails of the genera Afrolittorina, Echinolittorina and Littoraria from temperate, subtropical and tropical regions in South Africa and Brunei Darussalam using thermal tolerance, heart function, and proteome approaches. The effects of conditions, such as rate of change in temperature, acclimation, heat shock, season and starvation were also tested. In addition, the evolutionary relationships and genetic diversity between and within the South African Afrolittorina spp. were investigated using mitochondrial and nuclear markers. Genetic results confirmed that these are two distinct species, with the brown to black A. knysnaensis predominant in the cool-temperate region of South Africa and the pale blue-grey A. africana in the subtropical region. There was low genetic variation and differentiation within each species, suggesting high gene flow among populations as a result of the effects of ocean currents on the dispersal of their planktotrophic larvae. Tests using exposure to high temperatures revealed differences in the thermal tolerances, heart performance and protein profiles of species from different latitudes, regions and zones on the shore. Thermal tolerance conformed to expectations, with clear, statistically significant trends from high tolerance in subtropical species to lower tolerance in temperate species. However, for Afrolittorina spp., there were no significant differences in the thermal tolerances of conspecifics from different regions, though there was a significant difference in thermal tolerance between juveniles and adults. Overall, adults of all species showed higher thermal tolerances than juveniles. Although lethal temperatures for these species were higher in summer than winter, laboratory acclimation had no effect on heat coma temperatures. All species showed some regulation of heart rate, with a degree of independence of heart rate from temperature across mid-range temperatures. The tropical species showed quick induction and good regulation of heart rate followed by the subtropical and temperate species, which displayed mixed responses including regulation, partial regulation and lack of regulation. Overall, tropical Echinolittorina spp. showed good regulation, while the subtropical E. natalensis and Littoraria glabrata exhibited a mixture of partial regulation and regulation. The subtropical/temperate Afrolittorina spp. showed high individual variability, some animals exhibiting regulation, while others did not. These effects seem to be largely phylogenetically determined as there were no differences in the heart rate responses of Afrolittorina spp. from different regions. The temperatures at which heart rate became independent of temperature (thermoneutral zone) were within the range experienced under natural conditions. In addition, there were differences in Arrhenius breakpoint and endpoint temperatures, showing a trend from higher in tropical animals to lower for temperate animals. Conditions such as acclimation, heat shock and starvation had little or no effect on heart performance. However, a slow increase in temperature induced good regulation of heart rate with noticeable shifts of breakpoints and endpoints for Afrolittorina spp. Lastly, there were differences in the proteome responses between and within Afrolittorina spp. as a function of species, size and treatment. Although both large and small A. knysnaensis had a greater number of protein spots in their proteome than A. africana (though the difference was not significant), the later showed significantly higher differential expression of certain proteins following heat stress. In addition, juveniles of both species displayed greater numbers of protein spots in their proteome than adults. The results indicate a difference in the physiological and biochemical responses (i.e. adaptations) of these snails to temperature, and this seems to relate to differences in biogeography, phylogeny, species identity and ecology. The ability to regulate heart rate is phylogenetically determined, while thresholds and lethal limits correspond to biogeography and species ecology. The proteome seems to correspond to species ecology. The results also indicate that these littorinids can tolerate high temperature stress and in this respect they are well suited to life in the intertidal zones or habitats where temperature and other stresses or conditions are extreme and can change abruptly. However, the limited ability of these snails to acclimate to different temperatures suggests that they are already living close to their tolerance limits with small safety margins or narrow thermal windows and so may be vulnerable to small rises in substratum temperature and/or solar radiation.
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- Date Issued: 2013
Governance and management of urban trees and green spaces in South Africa: ensuring benefits to local people and the environment
- Authors: Chishaleshale, Mwale
- Date: 2013
- Subjects: Trees in cities -- South Africa , Urban forestry -- South Africa , Community forestry -- South Africa , City planning -- South Africa , Human-plant relationships -- South Africa , Urban ecology (Biology -- South Africa , Urban ecology (Sociology) -- South Africa , Natural resources -- South Africa , Trees in cities -- Law and legislation -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4739 , http://hdl.handle.net/10962/d1006035 , Trees in cities -- South Africa , Urban forestry -- South Africa , Community forestry -- South Africa , City planning -- South Africa , Human-plant relationships -- South Africa , Urban ecology (Biology -- South Africa , Urban ecology (Sociology) -- South Africa , Natural resources -- South Africa , Trees in cities -- Law and legislation -- South Africa
- Description: In the face of rapid urbanization and global climate change, urban trees and green spaces (UTGS) can contribute to the welfare of people and the urban environment. Urban trees and green spaces can assist to address urbanization challenges related to environmental degradation. While functions of UTGS have been well documented in the developed world, they have not yet received full attention in much of sub-Saharan Africa. Consequently, UTGS are under threat from urban development and fragmentation. Notably, the problems associated with UTGS also fall into the governance realm and indications are that poor governance and management of UTGS can negatively influence the potential benefits of UTGS to local people and the environment. This formed a basis for this research. The main objective of the study was to determine the current governance and management approaches to UTGS in South Africa. Through document search and review, the study determined the governance institutions influencing UTGS at national level and at provincial level (in the Limpopo and Eastern Cape Provinces). Face-to-face and online survey methods were used to determine the extent to which 28 local municipalities had adopted planned, systematic and integrated management of UTGS. The snowball approach was used to determine the key actors involved in UTGS activities and interviews were conducted to establish the roles and capabilities of these actors. A total of 540 household interviews were conducted to determine the institutional factors influencing local peoples’ ability to access, plant and use UTGS. The findings of the study showed that UTGS have not been adequately covered in existing governance institutions and practice at national and provincial levels. Local government municipalities were not managing their UTGS in a planned or systematic manner due to constraining factors such as insufficient funds, insufficient personnel, lack of equipment and lack of political support. Only 7.1 % of the surveyed municipalities had an urban tree management plan and an estimate of the urban tree stock; 32.1 % had tree policies; 28.6 % had tree bylaws; 21.4 % had tree planting schedules; 10.7 % had tree maintenance schedules and only 3.6 % had tree inspection schedules. Key actors involved in UTGS activities differed among levels of government. The actors included national and provincial government departments, local government municipalities, Non-Governmental Organizations, private sector companies and local volunteers. Most of the actors, however, either planted trees or provided tree seedlings to municipalities and the local people. Tenure security was a key institutional factor affecting peoples’ ability to plant, use or even remove trees from their residential plots. The same applied to trees in the streets and public parks. Whereas most respondents did not require permission to plant (79.8 %) or remove (75 %) trees on their residential plots, a majority of them required permission to plant and remove trees from streets (over 70 %) and public parks (over 80 %). However, with regard to planting and removing urban trees in public open spaces, 54% of the respondents indicated that permission was not required suggesting a lack of clarity among local residents on the issue. Overall, the findings of this study indicate that there is no political recognition and support for UTGS at almost all levels of government. This has resulted in the lack of incorporation of UTGS in urban planning and development and has caused UTGS to receive limited funding to permit planned and systematic management. Given the current rates of urbanization and urban development, the lowly prioritised UTGS are vulnerable to exploitation. To conserve UTGS and promote their potential contribution to local people and the environment, UTGS must be recognized and placed on political and development agendas. There is a need to develop national guidelines for UTGS management, assess the extent of the urban forest resource in local municipalities, clearly define the roles and capabilities of different actors, integrate UTGS in the urban planning and development system, and most of all seek to involve the local people in overall management and governance of UTGS.
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- Date Issued: 2013
Government debt levels and the systemic risks associated with post-crisis fiscal policies
- Authors: Koekemoer, Jonathan
- Date: 2013
- Subjects: Finance, Public Debts, Public -- South Africa Fiscal policy Monetary policy -- South Africa
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:1031 , http://hdl.handle.net/10962/d1004168
- Description: The study analyses the concepts of intergenerational equity and fiscal sustainability in South Africa. The question raised is whether or not South Africa can adopt stimulatory fiscal measures, with a simultaneous increase in debt, so as to improve long-term growth potential in a sustainable manner without creating an excessive burden on future generations. The debate surrounding the use of stimulatory fiscal policy has come to the fore once again as monetary policy has become a restricted and ineffective macroeconomic policy tool in certain countries after the world-wide financial crisis and the Euro-debt crisis. Fiscal sustainability risks and high debt levels remain a source of concern in the United States and the Euro-zone, while South Africa presently seems to be at no great risk. With South Africa’s intention to become a developmental state, the use and appropriateness of fiscal policy is considered. An overlapping-generations model is used to determine whether or not future generations will be burdened due to current stimulatory policy. The use of fiscal rules in South Africa is discussed and considered in light of various political incentives and constraints. The conclusion given is that the possible use of a procedural fiscal rule, such as the ‘golden rule’, may add credibility to the current regime, while a numerical fiscal rule is seen as unnecessary given South Africa’s responsible use of fiscal policy thus far. As it stands, there is little possibility or risk that the public debt in South Africa will become too high in the near future. Although South Africa has been affected by the crisis, the developmental nature of the economy has been sustained through the use of responsible discretionary fiscal policy, putting South Africa in a positive position to meet its long-run growth potential.
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- Date Issued: 2013
Green zone nation : the securitisation and militarisation of the 2010 FIFA World Cup, South Africa
- Authors: McMichael, Christopher Bryden
- Date: 2013 , 2013-04-22
- Subjects: World Cup (Soccer) (2010 : South Africa) -- Safety measures -- Research Fédération internationale de football association Militarism -- Research -- South Africa Sports -- Political aspects -- Research -- South Africa Police -- South Africa South Africa -- Armed Forces Crime -- South Africa Violent crimes -- South Africa Violent crimes -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2752 , http://hdl.handle.net/10962/d1001622
- Description: This thesis explores the relationship between the safety and security measures for the 2010 FIFA World Cup and the militarisation of urban space and policing in post-apartheid South Africa. In particular, it focuses upon how the South African state and FIFA, the owners of the World Cup franchise, worked to present the World Cup as an event which required exceptional levels of security – resulting in a historically unprecedented joint police and military operation across host cities. However, in contrast with previous research on these security measures, this thesis aims to interrogate the political and commercial forces which constructed security and positions them against a backdrop of intensified state violence and social exclusion in South Africa. Concurrently, the South African case was indicative of an international militarisation of major events, with policing operations comparable to national states of emergency. This is representative of the ‘new military urbanism’ in which everyday urban life is rendered as a site of ubiquitous risk, leading to the increased diffusion of military tactics and doctrines in policing and policy. While the interpenetration between urbanism and militarism has often been studied against the context of the ‘war on terror’, in the case of South Africa this has primarily been accelerated by a pervasive social fear of violent crime, which has resulted in the securitisation of cities, the remilitarisation of policing and the intensification of a historical legacy of socio-spatial inequalities. The South African government aimed to use the World Cup to ‘rebrand’ the country’s violent international image, while promising that security measures would leave a legacy of safer cities for ordinary South Africans. The concept of legacies was also responsive to the commercial imperatives of FIFA and a range of other security actors, including foreign governments and the private security industry. However these policing measures were primarily cosmetic and designed to allay the fears of foreign tourists and the national middle class. In practice security measures pivoted around the enforcement of social control and urban marginalisation while serving as a training ground for an increasingly repressive state security apparatus. Security was as much a matter of fortifying islands of privilege and aiding a project of financial extraction as protecting the public from harm. , Microsoft� Office Word 2007 , Adobe Acrobat 9.53 Paper Capture Plug-in
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- Date Issued: 2013
Growth and gonad size in cultured South African abalone, Haliotis midae
- Authors: Riddin, Nicholas Alwyn
- Date: 2013
- Subjects: Haliotis midae -- South Africa , Haliotis midae fisheries -- South Africa , Abalone culture -- South Africa , Abalones -- Physiology -- South Africa , Abalones -- Growth -- South Africa , Abalones -- Feeding and feeds -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5180 , http://hdl.handle.net/10962/d1001651 , Haliotis midae -- South Africa , Haliotis midae fisheries -- South Africa , Abalone culture -- South Africa , Abalones -- Physiology -- South Africa , Abalones -- Growth -- South Africa , Abalones -- Feeding and feeds -- South Africa
- Description: According to farm records, cultured Haliotis midae (50-70 g.abalone⁻¹) were growing 10% slower in winter when compared to summer. This reduction in growth rate also coincided with enlarged gonads. Initial trials showed that there were differences in mean monthly growth rates ranging from 1.97 – 5.14 g abalone⁻¹ month⁻¹, and gonad bulk index (GBI) also varied between months (GBI range: 26.88 ± 12.87 to 51.03 ± 34.47). The investment of energy into gonad tissue growth did not compromise whole body growth as the abalone continued to gain weight throughout the reproductive periods, probably due to gonadal growth. Growth of this size class of abalone was not influenced by water temperature or day length, suggesting favourable on-farm culture conditions (regression analyses, p > 0.05). There is no need to implement a seasonal dietary regime. Cultured H. midae were fed artificial diets with different protein sources, including only soya, only fishmeal, a combination of soya and fishmeal, and these were compared to kelp-fed abalone. Kelp-fed abalone grew slower than those fed artificial feeds (p>0.05). Gonad growth was the greatest when soya meal was included in the diet (average GBI: 74.91 ± 23.31), while the average gonad size of abalone fed the fishmealbased diet had gonads which were 38% smaller, and kelp-fed abalone had gonads which were 75% smaller than those of the abalone fed on diets containing soya meal. The increased gonad mass in abalone fed on diets including soya meal could be attributed to phytoestrogenic activity, as a result of the presence of isoflavones found in the soya plant; this remains to be tested. The use of soya in brood stock diet development is advised. The influence of dietary protein to energy ratio (1.41 – 2.46 g MJ⁻¹) on growth and gonad size was tested. Protein and energy levels within the ranges tested (22 and 33% protein; 13.5 and 15.6 MJ kg⁻¹) did not interact to influence growth rates of cultured H. midae. GBI increased from 50.67 ± 4.16 to 83.93 ± 9.35 units as a function of dietary protein to energy ratio (y = 42.02 x⁰·⁸¹; r² = 0.19; regression analysis: F₁¸₃₈ = 8.9; p = 0.005). In addition, protein level influenced gonad size, with gonad growth being greater in abalone fed the high protein diet (factorial ANOVA: F₁¸₃₂ = 7.1, p = 0.012). Canning yields were reduced by 7% when the protein content was increased, while increasing the quantity of dietary energy improved canning yields by ~ 6% (one-way ANOVA: F₁¸₂₈ = 14.4, p= 0.001). The present study provided evidence that although growth rates are varying seasonally, reproductive investment is not hindering weight gain. Gonad growth can be influenced if desired by farms, depending on the level of soya inclusion, as well as the protein to energy ratio in the diet. Monthly variation in growth and gonad size, as well as the influence of diet on gonad growth were highlighted, and the implications for farm application and further research were discussed.
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- Date Issued: 2013
High-throughput modelling and structural investigation of cysteine protease complexes with protein inhibitors
- Authors: Kroon, Matthys Christoffel
- Date: 2013
- Subjects: Cysteine proteinases Cysteine proteinases -- Inhibitors Papain Cystatins Malaria -- Chemotherapy Homology (Biology) Protein-protein interactions
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3885 , http://hdl.handle.net/10962/d1001619
- Description: The papain-like cysteine protease family (C1 proteases) is highly important because of its involvement in research and industrial applications and its role in various human diseases. Protein inhibitors are an important aspect of C1 protease biology and are relevant to its clinical, industrial and research importance. To study the interaction between the proteases and the inhibitors it is very useful to have accurate structural models of the protease-inhibitor complexes. To this end, a high-throughput pipeline for modelling complexes of papain-like cysteine proteases and protein inhibitors was implemented and tested (Tastan Bishop & Kroon, 2011). The pipeline utilizes a novel technique for obtaining modelling templates by using superpositioning to combine coordinates from separate experimental structures. To test the pipeline, models of complexes with known structures (test set) were modelled using many different templates and the resultant models evaluated to compare the quality of the different templates. It was found that use of the new technique to obtain templates did not introduce significant errors, while allowing closer homologs to be used for modelling - leading to more accurate models. The test set models were also used to evaluate certain steps of the modelling protocol. The effect of Rosetta energy minimization on model accuracy and the use of Rosetta energy and DOPE Z-score values to identify accurate models were investigated. Several complexes were then modelled using the best available templates according to criteria informed by the previous results. A website was built that allows a user to download any of the metrics or models produced in the study. This website is accessible at http://rubi.ru.ac.za/cpmdb
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- Date Issued: 2013
How community participation and stakeholder involvement can improve recycling : an investigation of initiatives and opportunities in Simunye
- Authors: Myeni, Jabu R
- Date: 2013
- Subjects: Recycling (Waste, etc.) -- Swaziland Refuse and refuse disposal -- Swaziland -- Citizen participation
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:803 , http://hdl.handle.net/10962/d1006457
- Description: This report presents the findings of a research project whereby the initiatives and opportunities for municipal solid waste (MSW) recycling were investigated in the town of Simunye, in Swaziland with a view to establish how recycling, in particular household waste recycling, can be improved through stakeholder involvement and community participation during the planning and implementation of a sustainable system for household waste recycling in Simunye. The reason for focusing on household waste was because source separation of household waste was identified as a potential area for improving efficiencies and cutting costs by the local authority. It was deemed necessary to conduct research because there was a history of failure in respect of household recycling. In 2006 an initiative, by the local authority, for separating household waste at source had ended up in failure. The participation rates of the households turned out to be very low even though they had been issued, free of charge, some plastic bags for sorting the waste. Some of the households were found using the bags for other purposes rather than recycling. As a result, the initiative had to be suspended (White, 2010). There is a new move to revive the project in order to cut costs and minimize wastages. This time around the local authority is determined for the new project to be a success story. Since the underlying causes for the failure of the previous initiative were never investigated formally (Khumalo, 2010), the starting point would be to identify and try to eliminate all the potential barriers to recycling through a consultative process to start with.
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- Date Issued: 2013
How do teachers characterise their teaching for conceptual understanding and procedural fluency?: a case study of two teachers
- Authors: Junius, Daniel Franscius , Danie Junius
- Date: 2013
- Subjects: Mathematics -- Study and teaching (Secondary) -- Namibia Mathematics -- Study and teaching -- Case studies
- Language: English
- Type: text , Thesis , Masters , MEd
- Identifier: vital:1360 , http://hdl.handle.net/10962/d1001426
- Description: Over many years the practice or art of teaching Mathematics posed itself as, not only being different from the practice of teaching any other subject, but to have many challenges and opportunities that ask for exploration and understanding. Just after independence in 1990, Namibia has embarked upon a reform process for the entire education system. Many changes were brought about to create a uniform, equal system for all. However, many challenges still remain to be addressed. Mathematics education remains one of the key areas where Namibian teachers can contribute towards the improvement of the subject. Unsatisfactory results, under-qualified teachers, and a negative disposition towards Mathematics are some of the challenges. These challenges are not unique to Namibia. Across the globe psychologists, philosophers and educators continue to engage in debates and research projects in search of answers and solutions for the improvement of Mathematics education. Despite encountering numerous obstacles, many teachers are dedicated and achieve outstanding results with their learners. This thesis reports on a research project that focused on the Mathematics teaching practice of two teachers whose experiences can make a positive contribution to the improvement of Mathematics teaching in Namibia. Furthermore, this case study investigated and attempted to understand the Mathematics teaching practices of two proficient teachers who each claimed to have a specific and unique approach to teaching Mathematics. The one claimed to be mainly procedural in her Mathematics teaching, while the other one claimed to teach mainly in a conceptual manner. Both achieve very good results with their classes and attribute their own teaching orientations to a process of several experiences they went through as students and in their careers. The study revealed that both claims are substantiated and that each teacher was consistent in her claimed approach. Many challenges and constraints were encountered by both teachers, but in their unique and specific ways each teacher’s chosen teaching approach supported them to overcome these. It was evident from the findings that each teacher’s practice came about as an evolutionary process over an extended period of time. As many challenges and limitations are universal, it is believed that in sharing experiences, teachers can benefit from each other by improving their practice. It was clearly stated by both participants that the re-thinking of and reflecting on their own practices provided them with new insights and motivation. Peer support and sharing of practices contribute positively towards the improvement of the teachers’ classroom practices.
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- Date Issued: 2013
Hungry but silent: a content analysis of media reporting on the 2011-2012 famine in Somalia
- Authors: Stupart, Richard
- Date: 2013
- Subjects: Famines -- Political aspects -- Somalia Somalia -- In mass media Famines in mass media
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3500 , http://hdl.handle.net/10962/d1006054
- Description: This dissertation examines media coverage of the 2011- 2012 famine in Somalia by the websites of BBC News, CNN and Al Jazeera. Using both quantitative and qualitative content analyses, it asks why coverage of the famine began as late as it did, despite ample evidence of the coming famine. It further surveys the famine-related news reports for evidence of four paradigms through which the causes of famine can be understood; as a Malthusian competition between population and land, as a failure of food entitlements as conceived of by Sen (1981), as critical political event (Edkins, 2004), or as an issue of criminality (Alex de Waal, 2008). Findings include a dramatic silencing of victim’s accounts of famine, despite a reliance on their photographic images, as well as an overwhelming preference for Malthusian accounts of the famine. Late media coverage is explored via a new-values paradigm which links the sudden outburst of media coverage for the famine to a formal UN declaration, and suggests that this may have created a new elite-relevance to the event which did not exist before, and therefore making it of relevance to domestic publics.
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- Date Issued: 2013
Identification and evaluation of key factors for rehabilitation of shores denuded of mussels (Perna perna) along the Transkei Coast, South Africa
- Authors: Macala, Lukholo
- Date: 2013
- Subjects: Mussels -- Ecology -- South Africa -- Transkei , Mussels -- Conservation -- South Africa -- Transkei , Mussels -- Growth -- South Africa -- Transkei , Mussels -- Effect of human beings on -- South Africa -- Transkei , Mussels -- Reproduction -- South Africa -- Transkei , Perna -- South Africa -- Transkei
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5611 , http://hdl.handle.net/10962/d1002966 , Mussels -- Ecology -- South Africa -- Transkei , Mussels -- Conservation -- South Africa -- Transkei , Mussels -- Growth -- South Africa -- Transkei , Mussels -- Effect of human beings on -- South Africa -- Transkei , Mussels -- Reproduction -- South Africa -- Transkei , Perna -- South Africa -- Transkei
- Description: Mussels play an important supplementary role in the diet of local communities on the Transkei coast in the Eastern Cape province of South Africa. The exploitation of mussels date back to about 1350 years ago, but in the last 3 decades, exploitation of the brown mussel Perna perna has become unsustainable with mussels collected as small as 30-40mm when they are only just sexually mature. Dye and Dyantyi (2002) developed a technique to rehabilitate areas denuded of adult mussels. The government sponsored Mussel Rehabilitation Project (MRP) to use this technique but only some sites have been successfully rehabilitated, reaching c. 80 % cover within a year whilst others only reach about 5%. At an unexploited site (Riet River), I tested the effects of mussel size and wave strength on the effectiveness of the rehabilitation technique, hypothesizing that different size classes may respond differently due to differences in their energy allocation (growth vs reproduction), while wave action determines food supply. Small (1-2cm) and large mussels (3-4cm) were deployed for rehabilitation at 2 exposed and 2 sheltered sites, separated by 100s m. A similar study was repeated in Coffee Bay where shores are exploited. Six sites were selected, 3 sites that had been successfully rehabilitated and 3 that were unsuccessful according to the MRP. Again, two size classes were used but these differed from the first experiment. Mussels of 3-4cm size were now rated as small and 5-6cm as large. Two methods were used to re-attach mussels, the original and the same method with the addition of mesh bags during mussel deployment. Treatments were examined on three occasions at approximately one month intervals. At Riet River, the sites chosen did not show differences in wave strength (measured using dynamometers) or water flux (measured using erosion of cement balls) so that water motion was excluded from the analyses. Small mussels grew faster and had weaker attachment than large mussels. There was no difference in condition index between small and large mussels, or in the numbers of recruits settling among the byssus threads of deployed mussels of the two size classes. In Coffee Bay, there was no relationship between rehabilitation success and maximum wave force, and no difference in bulk water flux among sites. Small mussels deployed using mesh bags survived better than non-meshed or large mussels of either treatment. There was no difference in condition index (CI) between mesh and no-mesh, or between small and large mussels. As in the case of Riet River, small mussels grew faster than large mussels, but large mussels attached stronger than small mussels, with no effect of mesh. Although the factors that improve reseeding of mussels can be identified (use of mesh, use of small mussels, choice of sites with high recruitment rates), successful long-term rehabilitation requires appropriate subsequent management of re-seeded sites.
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- Date Issued: 2013
Immobilisation of electric eel acetylcholinesterase on nanofibres electrospun from a nylon and chitosan blend
- Authors: Mafuma, Tendai Simbarashe
- Date: 2013
- Subjects: Acetylcholinesterase Acetylcholinesterase -- Inhibitors Electric eel Biosensors Immobilized enzymes Pesticides -- Environmental aspects Pesticides -- Toxicology Nylon Chitosan Nanofibers Electrospinning
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3886 , http://hdl.handle.net/10962/d1001620
- Description: Organophosphates and carbamates are potent inhibitors of the neurotransmitter acetylcholinesterase. This inhibition results in the blocking of nerve signal transference into the post synaptic neuron leading to loss of muscle action and death. Because of the universal mechanisms of signal transduction in animals, these inhibitors have been widely used as agricultural pesticides as well as chemical warfare agents (nerve agents). Health issues associated with pesticide usage result from the fact that both the pesticides and their breakdown products often end up in water and food sources as well as in the soil. As a result, there has been an increase in the number of studies aimed at the detection of these pesticides in the environment. One popular research area is enzyme based biosensor construction. Some important criteria for consideration during the construction of biosensors are the importance of a suitable solid support as well as the enzyme immobilisation method. Recently, there has been increased interest in using nano-scale material e.g. using nanoparticles as enzyme support material. This is largely due to their advantages such as large surface area to volume ratio as well as reduced mass transfer resistance. Electrospinning is a straight forward and cost effective method for producing nanofibres from any soluble polymer(s). The applications of electrospun nanofibres have been reported in clinical studies, biofuel production as well as bioremediation. In this study two polymers were selected: nylon for its mechanical stability and chitosan for its biocompatibility and hydrophilicity, for the fabrication of electrospun nanofibres which would function as immobilisation support material for acetylcholinesterase. The first objective of this study was to electrospin nanofibres from a nylon-6 and chitosan blend solution. A binary solvent system consisting of formic acid and acetic acid (50:50) successfully dissolved and blended the polymers which were subsequently electrospun. Scanning electron microscopy characterisation of the nanofibres showed that (i) a nylon-6: chitosan ratio of 16%: 3% resulted in the formation of bead free nanofibres and (ii) the fibres were collected in non-woven mats characterised by different size nanofibres with average diameters of 250 nm for the main fibres and 40 nm for the smaller nanofibres. Fourier transform infra-red (FT-IR) analysis of the nanofibres indicated that a new product had been formed during the blending of the two polymers. The second aim of the study was to carry out a facile immobilisation of electric eel acetylcholinesterase via glutaraldehyde (GA) cross-linking. Glutaraldehyde solution 5% (v/v) resulted in the immobilisation of 0.334 mg/cm² of acetylcholinesterase onto the nanofibres. The immobilisation procedure was optimised with reference to acetylcholinestease and crosslinker concentrations, incubation time and the cross-linking method. A comparative investigation into the optimum pH and temperature conditions, pH and thermal stabilities, substrate and inhibition kinetics was then carried out on free and immobilised acetylcholinesterase. The final objective of this study was to determine the storage stabilities of the immobilised and free enzymes as well as the reusability characteristics of the immobilised acetylcholinesterase. Several conclusions were drawn from this study. Acetylcholinesterase was successfully immobilised onto the surface of nylon-6:chitosan nanofibres with retention of its activity. There was a shift in the pH optimum of the immobilised acetylcholineseterase by 0.5 units towards a neutral pH. Although both free and immobilised acetylcholinesterase exhibited the same optimum temperature, immobilised acetylcholinesterase showed enhanced thermal stability. In terms of pH stability, immobilised acetylcholinesterase showed greater stability at acidic pH whilst free acetylcholinesterase was more stable under alkaline pH conditions. Relative to free acetylcholinesterase, the immobilised enzyme showed considerable storage stability retaining ~50% of its activity when stored for 49 days at 4°C. Immobilised acetylcholinesterase also retained > 20% of its initial activity after 9 consecutive reuse cycles. When exposed to fixed concentrations of carbofuran or demeton-S-methyl sulfone, immobilised acetylcholinesterase showed similar inhibition characteristics to that of the free enzyme. The decrease in enzyme activity observed after immobilisation to the nanofibres may have been due to several reasons which include some enzyme molecules being immobilised in structural conformations which reduced substrate access to the catalytic site, participation of the catalytic residues in immobilisation and enzyme denaturation due to the reaction conditions used for acetylcholinesterase immobilisation. Similar observations have been widely reported in literature and this is one of the major drawbacks of enzyme immobilisation. In conclusion, nylon-6:chitosan electrospun nanofibres were shown to be suitable supports for facile acetylcholinesterase immobilisation and the immobilised enzyme has potential for use in pesticide detection. Future recommendations for this study include a comparative study of the GA cross-linking method for AChE immobilisation which will lead to more intensely bound enzyme molecules to prevent non-specific binding. An investigation into the effect of inhibitors on stored immobilised AChE, as well as reactivation and reuse studies, may also be useful for determining the cost-effectiveness of reusing immobilised AChE for pesticide detection in environmental water samples. Several models have been designed for the determination of the kinetic parameters for immobilised enzymes. These take into account the mass transfer resistance as well as the overall charge of the immobilisation matrix. The use of these models to analyse experimental data will give a clear understanding of the effects of immobilisation on enzyme activity
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- Date Issued: 2013
In-silico analysis of Plasmodium falciparum Hop protein and its interactions with Hsp70 and Hsp90
- Authors: Clitheroe, Crystal-Leigh
- Date: 2013
- Subjects: Plasmodium falciparum , Heat shock proteins , Molecular chaperones , Homology (Biology) , Protein-protein interactions , Malaria -- Chemotherapy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3896 , http://hdl.handle.net/10962/d1003819 , Plasmodium falciparum , Heat shock proteins , Molecular chaperones , Homology (Biology) , Protein-protein interactions , Malaria -- Chemotherapy
- Description: A lessor understood co-chaperone, the Hsp70/Hsp90 organising protein (Hop), has been found to play an important role in modulating the activity and co-interaction of two essential chaperones; Hsp90 and Hsp70. The best understood aspects of Hop so far indicate that residues in the concave surfaces of the three tetratricopeptide repeat (TPR) domains in the protein bind selectively to the C-terminal motifs of Hsp70 and Hsp90. Recent research suggests that P. falciparum Hop (PfHop), PfHsp90 and PfHsp70 do interact and form complex in the P. falciparum trophozooite and are overexpressed in this infective stage. However, there has been almost no computational research on malarial Hop protein in complex with other malarial Hsps.The current work has focussed on several aspects of the in-silico characterisation of PfHop, including an in-depth multiple sequence alignment and phylogenetic analysis of the protein; which showed that Hop is very well conserved across a wide range of available phyla (four Kingdoms, 60 species). Homology modelling was employed to predict several protein structures for these interactions in P. falciparum, as well as predict structures of the relevant TPR domains of Human Hop (HsHop) in complex with its own Hsp90 and Hsp70 C-terminal peptide partners for comparison. Protein complex interaction analyses indicate that concave TPR sites bound to the C-terminal motifs of partner proteins are very similar in both species, due to the excellent conservation of the TPR domain’s “double carboxylate binding clamp”. Motif analysis was combined with phylogenetic trees and structure mapping in novel ways to attain more information on the evolutionary conservation of important structural and functional sites on Hop. Alternative sites of interaction between Hop TPR2 and Hsp90’s M and C domains are distinctly less well conserved between the two species, but still important to complex formation, making this a likely interaction site for selective drug targeting. Binding and interaction energies for all modelled complexes have been calculated; indicating that all HsHop TPR domains have higher affinities for their respective C-terminal partners than do their P. falciparum counterparts. An alternate motif corresponding to the C-terminal motif of PfHsp70-x (exported to the infected erythrocyte cytosol) in complex with both human and malarial TPR1 and TPR2B domains was analysed, and these studies suggest that the human TPR domains have a higher affinity for this motif than do the respective PfHop TPR domains. This may indicate potential for a cross species protein interaction to take place, as PfHop is not transported to the human erythrocyte cytosol.
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- Date Issued: 2013