The development of a plate-based assay to detect the activation status of ARF1 GTPase in Plasmodium falciparum parasites
- Authors: Du Toit, Skye Carol
- Date: 2023-10-13
- Subjects: ARF1 , GTPase , Plasmodium falciparum , Malaria , Drug resistance , Drug targeting , Enzyme-linked immunosorbent assay , Proteins
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424654 , vital:72172
- Description: The exponential rise in antimalarial drug resistance in the most infectious malaria species, Plasmodium falciparum, has emphasised the urgency to identify and validate novel drug targets that decrease parasite viability upon inhibition. In addition to several publications indicating that the regulation of human Arf1 GTPase activity (mediated by ArfGEFs and ArfGAPs) serves as a pertinent drug target for cancer research, the identification of Arf1 and its regulatory proteins in Plasmodium falciparum led to the question whether these protein homologs could be exploited as drug targets for anti-malarial drug therapies. To investigate this prospect, the establishment of a novel in vitro colorimetric ELISA-based assay was needed to be able to detect changes in the activation status of P. falciparum Arf1 (PfArf1) in parasite cultures exposed to potential Arf1 inhibitors. By exploiting the selective protein interaction that occurs between active GTP-bound Arf1 and its downstream effector, GGA3, an assay protocol was established that could be used to detect the activation status of purified, truncated PfArf1 obtained from E. coli and endogenous PfArf1 sourced from parasite lysates. The assay relies on the use of anti-Arf1 antibodies to detect the binding of active PfArf1 in the lysates of inhibitor-exposed cultured parasites to GST-GGA3 immobilised in glutathione-coated plates. The results from chemical validation experiments conducted using the novel assay developed in this study, using the known ArfGEF inhibitor brefeldin A (BFA) and ArfGAP inhibitors Chem1099 and Chem3050, yielded the anticipated results: decrease in active PfArf1 after parasite incubation with the ArfGEF inhibitor, and increased active PfArf1 after ArfGAP inhibition. The results confirmed PfArf1 as a potential anti-malarial drug target and encourages the further development of this assay format for the identification of subsequent inhibitors in library screening campaigns. Additional pilot experiments were conducted to further explore whether the assay could detect the activation status of human Arf1 using HeLa cell lysates and to provide further evidence that the assay could be exploited as a tool in the identification of Arf1 GTPase inhibitors with BFA and the known ArfGAP inhibitor, QS11. The results suggested that, while the assay can detect the increase in active cellular Arf1 due to the inhibition of human ArfGEF following BFA treatment, subsequent treatment with QS11 showed no evidence of a reduction in active human Arf1 due to ArfGAP inhibition. Further experimentation is required to investigate the ability the assay to confirm inhibition of human Arf1 deactivation by ArfGAP inhibitors and develop the assay as a useful tool to support cancer drug discovery, in addition to antimalarial drug discovery projects aimed at Arf1. , Thesis (MSc) -- Faculty of Science, Biochemistry and Microbiology, 2023
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- Date Issued: 2023-10-13
Optimization of an intranasal levodopa nanocrystalline formulation for delivery to the brain
- Authors: Kakono, Chiedza
- Date: 2023-03-29
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/420709 , vital:71771
- Description: Thesis embargoed. Probable release date in 2025. , Thesis (MSc (Pharm)) -- Faculty of Pharmacy, Pharmacy, 2023
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- Date Issued: 2023-03-29
Quantifying feed intake and feeding intensity using two experimental conditions and the effect of different feeding strategies on the production parameters of farmed South African abalone, haliotis midae
- Authors: Wortley, Ross Michael
- Date: 2023-03-29
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/${Handle} , vital:71932
- Description: As abalone are slow-growing animals there is a high investment of capital, running costs and labour in commercial abalone farming. Revenue needs to be maximised by achieving fast growth rates. A foremost driver of abalone growth is feed intake and feeding intensity of the abalone as well as the feeding regimen a farm utilises. While feed intake is well-documented in H. midae, there is a paucity of information regarding this aspect in abalone above 70 g and the relationship between feeding intensity, feed conversion rate (FCR) and daily growth rate needs to be documented. Similarly, there are a limited number of studies dealing with the effects of different pellet types of the same formulation, that differ only in shape and size, on feed intake and production in H. midae. This study made use of both a controlled laboratory experiment and commercial-scale farm experiment with the aim of testing whether feed intake information produced under laboratory conditions can provide good estimates of feed intake under farming conditions, which can further be implemented into feeding strategies on abalone farms. This study quantified daily feed intake (F) in 10 – 20 g, 100 – 110 g and 150 – 160 g abalone weight classes using two different pellet types and determined the relationship between the duration of feed availability and feed intake under laboratory conditions. The effect of three different pellet type strategies (fed daily: a leaf-only strategy = L d-1, a short-pellet only strategy = SP d-1, and a strategy that used both = B d-1) on abalone production parameters under farming conditions such as growth rate, feed conversion ratio (FCR), feeding intensity (FI) and weight variation of 30 – 40 g H. midae was also investigated. A commercial-scale farm study was designed to test the effect of four commercially relevant feeding regimens (three size-specific regimens and one commercially practiced feeding method) on the growth, FCR, feeding intensity and weight variation of these three abalone weight classes while taking into account an economic model to assess the profitability of each feeding regimen. Daily feed intake as a percentage of body mass (% BM d-1) was a function of abalone weight class between the 10 – 20 g and two larger weight classes 100 – 110 g and 150 – 160 g p < 0.0001), however feed intake was not different between the 100 – 110 g and 150 – 160 g weight classes. Pellet type did not affect feed intake in all abalone weight classes (p = 0.15). Feed intake (F) was positively linearly correlated with duration of feed availability (h) in the 10 – 20 g weight class (r2 = 0.76, p <0.00001) and logarithmically correlated in the 100 – 110 g (r2 = 0.25, p < 0.02) and 150 – 160 g (r2 = 0.52, p < 0.0001) weight classes (10 – 20 g abalone-1: 3 F (% BM) = 0.02(h) + 0.1976, 100 – 110 g abalone-1: F (% BM) = log10(h)*0.17 + 0.17, 150 – 160 g abalone-1: F (% BM) = log10(h)*0.36 + 0.07). There was no significant difference in monthly average abalone weight, daily growth rate (G), FCR and feeding intensity between each pellet type strategy (G: p = 0.60, FCR: p = 0.62, FI: p = 0.54 ). However, abalone grew well over the 112-day growth period with average abalone weight increasing significantly between each monthly sample time (pooled pellet type strategy: Huynh-Feldt correction; p < 0.00001). Furthermore, abalone fed the leaf-only pellet type strategy (L d-1) fell into higher weight classes after a 112-day growth period (Z test: 50 – 70 g: 72%) which was 16.1 % higher compared to the SP d-1 and B d-1 strategies. Daily growth rate (r2 = 0.34, p < 0.01) and FCR (r2 = 0.42, p < 0.004) was negatively correlated and FCR was positively correlated with daily feeding intensity, respectively (G = - 2.59 (FI) + 1.526, FCR = 8.8082 (FI) – 2.7108). Feeding regimen affected the production parameters of three abalone weight classes. The method practiced on the farm resulted in the best growth in the 10 – 20 g abalone weight class. The farm feeding method resulted in slower yet more efficient growth rates (lowest FCR values) in the abalone weight classes, 100 – 110 g and 150 – 160 g abalone- 1. However, size-specific feeding regimens resulted in the fastest growth rates but resulted in higher FCR values (less efficient). The relationship between feeding intensity, daily growth rate and FCR all showed that an increase in feeding intensity results in increased daily growth rates and FCR values. The economic model suggests that the higher FCR values associated with size-specific regimens, which have higher associated costs to producing abalone, were greatly outweighed by the growth attained by the abalone in the 100 – 110 g and 150 – 160 g weight classes. The size-specific regimens generated a higher potential monetary value of abalone after a 112-day period, which would consequently result in higher income for abalone farms. For abalone ranging from 100 – 110 and 150 – 160 grams, the economic model suggested that in a quarterly grading schedule (112 days) that abalone be fed the size specific daily rations, which is a function of body mass, at 0.35 % BM d-1 and 0.352 % BM d-1, respectively. The two experimental conditions used in this study produced feed intake and production parameter information that is beneficial to South African abalone farmers. The small-scale laboratory study produced information on feed intake that can be used as reference values as to what abalone in these weight classes can consume on a daily basis. The laboratory study can provide estimates of feed intake under farming conditions but should only be used as minimum 4 values when determining size-specific feeding regimens. To maximise abalone growth, farmers should utilise size-specific feeding regimens for abalone above 30 g. Daily growth rate and FCR can be predicted as a function of the abalone’s feeding intensity. Further studies are needed to determine the effects of abalone weight class on production parameters when testing different pellet types as well as an exploration into behavioural studies focusing on diet preferences. Additionally, future studies need to take into consideration abalone above the weight of 100 g with additional focus of research on behavioural, genetic and environmental aspects on abalone feed intake. , Thesis (MSc) -- Faculty of Science, Ichthyology and Fisheries Science, 2023
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- Date Issued: 2023-03-29
Gamification technology in teaching: Exploring how mathematics teachers make use of Kahoot! Gamification to facilitate learning of probability in classrooms
- Authors: Mbete, Ayanda
- Date: 2022-10-14
- Subjects: Gamification , Kahoot! , Mathematics Study and teaching (Elementary) South Africa Eastern Cape , Probabilities , Educational technology , Rural schools South Africa Eastern Cape , Technological Pedagogical Content Knowledge , Cultural-historical activity theory
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/405311 , vital:70160
- Description: This study seeks to examine the use of Kahoot! as a gamification technology in practice with Grade six teachers to explore its use in supporting the learning of Probability in Mathematics in rural primary schools. Purposive sampling was adopted wherein nine Grade six mathematics teachers from four rural primary schools in Amathole East district were selected as participants of the study. In addition, to inform this qualitative case study, an interpretive paradigm was adopted. Data was collected using semi-questionnaires, semi-structured interviews, non-participant observations, workshop discussions and reflective journals. The TPACK by Mishra & Koehler (2009) and Vygotsky’s (1978) socio-cultural theory were employed as the lenses through which all the proceedings of the study were based. The key findings indicate that integrating Kahoot! gamification technology, in the ‘Probability’ lesson, has positive consequences such as bringing fun into the classroom, enhancing learner participation, prompt feedback and offering a learner-driven approach to learning as opposed to the conventional teaching strategies. The findings also revealed that enabling and constraining factors are associated with using Kahoot! in teaching: the ICT infrastructure, teachers’ competency levels and the environment in which teaching and learning occurs. This study concluded that the use of Kahoot enhances the learning of probability in rural under-resourced primary schools. This study recommended the integration of Kahoot gamification into the mathematics curriculum. , Thesis (MEd) -- Faculty of Education, Education, 2022
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- Date Issued: 2022-10-14
M.M. Hala: Memoirs of an Umkhonto WeSizwe Cadre
- Authors: Hala, Mzimasi Mike
- Date: 2022-10-14
- Subjects: African National Congress , Umkhonto we Sizwe (South Africa) , Anti-apartheid movements South Africa , Anti-apartheid activists South Africa , South Africa Politics and government 1948-1994 , Hani, Chris, 1942-1993 , Holomisa, Bantu, 1955- , Bisho massacre
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/406785 , vital:70307
- Description: Born in Komani (Queenstown) in 1959 and detained for Congress of South African Students (COSAS) activities while still at school, Mzimasi Mike Hala departed South Africa via Swaziland in 1981 and joined uMkhonto WeSizwe (MK). Trained in Angola, Cuba and East Germany, he commanded Cacuso camp in Angola, until redeployed to South Africa in 1987 to work underground in Venda and Cape Town. Following the unbanning of the liberation movements in 1990, he was appointed Commander of MK’s Transkei Region, where he was in charge of Chris Hani’s personal security. For reasons of space, the memoir does not proceed beyond his integration into the South African National Defence Force (SANDF) with the rank of Lieutenant-Colonel and second-in-command of SANDF Group 46 in Mthatha. Besides its value as a primary source of previously undocumented information, the thesis seeks to bridge the gap between the academic literature on MK and the lived experience of MK soldiers. Having considered both the academic literature and the published MK memoirs in Chapter One, the thesis refers back to the literature in narrative chapters Two to Five. Consolidating its findings in its conclusion, the final chapter is divided into three sections: the political culture of MK, MK gender dynamics and the consequences of the political merger of the “exiles,” including MK, and the “inziles” who subsequently came to dominate the ANC. , Thesis (MA) -- Faculty of Humanities, Institute of Social and Economic Research, 2022
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- Date Issued: 2022-10-14
Puma (Puma concolor) diet and habitat use in south-west New Mexico
- Authors: Bernard, Kelly Monica Tandi
- Date: 2022-10-14
- Subjects: Puma Food New Mexico , Puma Habitat New Mexico , Puma Nutrition New Mexico , Puma Conservation New Mexico , Carnivorous animals New Mexico , Red deer , Elk , Mule deer , Ungulates
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/362752 , vital:65359
- Description: The puma (Puma concolor) is a wide-ranging large felid species occupying an extensive geographic range throughout North and South America, and site-specific research on their diet is important for local management. Like other large felids, puma diet may differ between sexes due to size dimorphism, and between seasons due to changes in prey vulnerability and availability. This study assessed the influence of sex and season on puma diet in south-west New Mexico in terms of prey species and prey size categories. Pumas specialised on mule deer and elk throughout the year, and killed a range of other species of different sizes. The diet of the smaller female puma was nested within the diet of males, supporting the size-nested strategy. The effect of puma sex on prey species and size categories was independent of season, and vice versa, and the probability of a female making a medium-sized kill such as mule deer was higher than for males, while the probability of an extra-large kill such as elk was substantially greater for males. The probability of pumas killing either mule deer or elk in each season was similar, and greater than other species categories. Additionally, individual puma strongly influenced all prey species and size categories killed. The results from this study concur with previous findings on the importance of mule deer and elk in puma diet, and suggest that puma predation may also impact a number of other species, particularly smaller herbivores like collared peccary, and mesocarnivores such as skunks. , Thesis (MSc) -- Faculty of Science, Zoology and Entomology, 2022
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- Date Issued: 2022-10-14