Research Data (University of Pretoria)
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Item Law applicable to substantive issues in international commercial arbitration : an African Perspective(University of Pretoria, 2023) Schoeman, Elsabe; Wethmer-Lemmer, Marlene; lawrenciaoppongpeprah@gmail.com; Oppong Peprah, LawrenciaThis thesis examines the law applicable to substantive issues in international commercial arbitration from an African perspective. More specifically, the thesis examines the methods used by arbitrators to assign the applicable substantive law in the absence of the parties’ choice in Egypt, Ghana, South Africa and Côte d’Ivoire. Considering the vital role of the law applicable in determining the rights and obligations of the parties to international commercial arbitration, the thesis seeks to identify the most efficient method for assigning the applicable law in the absence of the parties’ choice. To this end, the thesis explores existing literature including scholarly works on the topic, the national and selected institutional arbitration laws in Egypt, Ghana, South Africa, Côte d’Ivoire and elsewhere, to identify the common methods and strategies used by arbitrators in the selection of the law applicable to the merits of the dispute. The thesis scrutinises these methods to provide a comprehensive evaluation of the efficiency, predictability and legitimacy of each identified method from an African perspective. Ultimately, the thesis proposes a method that can enhance predictability and legal certainty for when arbitrators must assign the applicable substantive law in African international commercial arbitration, thereby promoting the development of a conducive business environment in the region. Moreover, by establishing a consistent regulatory framework for determining the substantive law in the absence of the parties’ choice, Africa may reinforce its position in the global legal landscape by developing its own distinctive jurisprudence in international commercial arbitration.Item Is investment mediation the future of investor-state dispute settlement (ISDS) in Africa?(University of Pretoria, 2023) Kabre, Jonathan; chelangatfaith37@gmail.com; Chelangat, FaithInternational investment disputes have traditionally been resolved through Investor- State Dispute Settlement (ISDS) as administered by the International Centre for Settlement of Investment Disputes(ICSID). Prior to the current discontentment on settlement of investment disputes, foreign investors were more inclined to ISDS than domestic courts. The system of ISDS offered a neutral forum for an investor to sue and claim compensation for breach of an investment- related obligation by the Host State, without immunity obstacles. However, ISDS has faced growing criticism including, perceived biasness, lack of transparency, exorbitant costs and lengthy duration spent on arbitration proceedings, unpredictability of awards and erroneous decisions, among others. In Africa, there is dissatisfaction regarding under-representation of African ADR experts, regulatory chill, and costly awards that cripple African economies. The UNCITRAL Working Group III is alive to the criticism around ISDS, and has submitted options of reform to improve the system of settling investment disputes. This research examines one of the reforms; promoting ADR methods. It seeks to assess the feasibility of investment mediation, an ADR method, as a possible alternative to ISDS. The research evaluates the advantages of mediation pointing out that it is a confidential process that offers a neutral ground for the disputing parties to negotiate and settle amicably, thus preserving their relationship. Additionally, mediation is time and cost- effective and grants all States, investors and SMEs, access to ISDS. Most importantly, the research situates mediation within ‘cooling-off’ periods stipulated in International Investment Agreements and investment regulations. The findings of the study seeks to provide valuable insights into how investment mediation can be effectively utilized as a possible alternative to ISDS.Item Racial discrimination and the evacuation of international armed conflict territory : the case of Russia and Ukraine(University of Pretoria, 2023) Grobler, Chazanne; mbongeniawncube@gmail.com; Ncube, Mbongeni A.W.On 24 February 2022, Russian armed forces, under the instructions of Vladimir Putin, launched a military operation into Ukraine, invading the neighbouring territory and launching full-scale ground operations in regions of Ukraine causing many to flee in a bid to evacuate. Reports also presented strong evidence that Ukrainian officials at border posts regulating evacuation seemingly gave preferential treatment to Europeans, particularly white Europeans, while not allowing black migrants access to trains and effectively not allowing them to evacuate. The research seeks to address the treatment of black migrants in Ukraine during the war and outline the injustice not from a political stance but from the lens of International Humanitarian Law and the violation of the rules and the rights conferred by International Humanitarian Law. It is essential first to investigate if migrants are protected by International Humanitarian Law, and if they are privy to the right articulated in Article 35 of the Geneva Convention (IV) which affords protected persons the right to leave a territory party to conflict. Additionally, an inquiry will be made to determine whether the right includes protection against discrimination.Item The effects of neonicotinoids and increasing temperatures on the thermoregulation and flight ability of South African honey bees, Apis mellifera scutellata (Lepeletier)(University of Pretoria, 2023) Pirk, Christian Walter Werner; lauracatherinebester@gmail.com; Bester, Laura CatherinePredicted climatic changes throughout the southern African region are likely to affect the distribution of ecological zones, significantly impact agricultural yield, and influence the timing of the flowering season. Climate change has the potential to influence pollinators, especially the honey bee; reducing survival, affecting behaviour and physiology, as well as impacting biodiversity and agriculture. Similarly, agriculturally significant neonicotinoid pesticides have been found to negatively impact many aspects of honey bee physiology and survival. Their widespread usage in Africa and the effects on its pollinators therefore necessitates further investigation. The physiological and behavioural thermoregulatory activities of Apis mellifera scutellata, and how they are affected by exposure to three neonicotinoid active ingredients (clothianidin, imidacloprid and thiamethoxam), was investigated. On an individual level, a baseline thermotolerance for A.m. scutellata was established (LT50=53.77 °C). Exposure to sublethal neonicotinoid doses elicited a 3 °C drop in the LT50 of A.m. scutellata. Flight efficiency and associated parameters were assessed under three different ambient temperatures, both with and without sublethal neonicotinoid exposure. Using flight parameters as a proxy for flight muscle function and by extension thermoregulatory ability, it was found that the majority of parameters were not significantly impacted in A.m. scutellate. However, the honey bees’ ability to initiate flight at all was severely affected. Colony level thermoregulatory efficiency was measured using a custom built, in-hive monitoring system that recorded internal hive temperatures at five second intervals over three months. This monitoring was performed both before and after sublethal neonicotinoid exposure. Following neonicotinoid exposure, it was observed that the hives exhibited considerable resilience in terms of maintaining the closely regulated temperatures in the brood frame area. However, the outlying areas within the hive showed more unpredictable fluctuation. These three studies demonstrate that 1) individual LT50 dropped by 3 °C, 2) flight initiation was impaired and 3) colony level thermoregulation efficiency was reduced in non-brood areas, when exposed to sub-lethal neonicotinoid active ingredients clothianidin, imidacloprid and thiamethoxam. More importantly, these results highlight the importance of how the effects may be further exacerbated in the context of both local and global climatic change. These changes include the increased frequency and intensity of extreme weather events. The unique agricultural landscape of South Africa encompasses commercial, small scale and subsistence farming practices that employ varied uses of insecticides, which further contribute to these effects. The results of the studies demonstrate the importance of further research into the effect of these insecticides on honey bees in the unique agricultural context.Item The effects of process conditions of an alkaline seaweed extraction process on yield and on biostimulant activity of the extract(University of Pretoria, 2022) Kornelius, Gerrit; schalk.lubbe@agritechnovation.co.za; Lubbe, David SchalkSeaweed extracts (SWEs) comprise the single largest category of agricultural crop biostimulants. The global biostimulants market is much smaller, but faster growing than the markets for either traditional mineral fertilizers or agrochemicals. They are applied at low volumes and concentrations and stimulate plant growth, nutrient use efficiency and stress responses, thus contributing significantly to sustainable crop production. Alkaline extraction is the most often used process to produce SWEs. It can be operated at ambient or elevated temperatures and pressures. The process studied in this work is the Ambient Alkaline Extraction (AAE) process. It benefits from lower energy costs and simpler equipment than the higher temperature processes, at the expense of longer residence times of days rather hours. The seaweed used as biomass raw material was Australian Bull Kelp Durvillaea potatorum. The experimental work was conducted on an existing, successful commercial AAE production plant, as well as pilot (1/64th) and bench (1/1800th) scale plants. The process conditions and relationships have, as far as is known, not been published before for any commercial alkaline extraction plant, and for bench scale work only at elevated temperatures. Measurements were developed to track process conditions relating to overall process yield. In addition, six biostimulant properties of the SWE product, as assessed by the tomato seed germination and growth bio-assay were measured at different SWE concentrations and combinations of process conditions (temperature, alkali concentration, water:biomass ratio and residence times). Statistically significant (P<0.05) biostimulant effects of the SWE were reported for the vast majority of process conditions tested, but also statistically significant effects of process conditions on the quantum of growth stimulation. The results can be used in the design of new production plants or retrofits to existing plants, and in selecting optimal process conditions not only for process yield and throughput, but also for biostimulant effects of the SWE product. In general, there is of course not only a single set of optimal conditions, since conditions for optimal outcomes on different biostimulant parameters can be different, and these can also be different from those for optimal production outcomes such as throughput and yield. Optimal conditions therefore depend on the relative desirability of the different (and in some cases, competing) outcomes.Item Digital data for “Stocking rate and organic waste type affect development of three Chrysomya species and Lucilia sericata”(University of Pretoria, Faculty of Natural and Agricultural Sciences, Department of Zoology and Entomology, 2019) Parry, Nina Jennifer; Pieterse, Elsje; Weldon, Christopher William; cwweldon@zoology.up.ac.zaTables detailing the mass of larvae of four species of Calliphorid flies feeding on waste products (kitchen waste, swine manure and abattoir waste) over time, their survival at the end of feeding and body composition (dry mass, body water content, carbohydrates, lipids and protein). The species are Chrysomya chloropyga, C. megacephala, C. putoria and Lucilia sericata. Data are arranged according to waste type first (separated by batches), then survival, waste reduction and body composition.Item Allele size of microsatellite markers in S. noctilio and R script for the model predicting sex ratios(University of Pretoria. Faculty of Natural and Agricultural Science, Department of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute, 2011) Queffelec, Josephine; Wooding, Amy L.; Slippers, Bernard; Bernard. slippers@fabi.up.ac.zaA table of allele sizes was compiled for 13 microsatellites for 67 males Sirex noctilio from the Western Cape province of South Africa and 77 males from the KwaZulu-Natal province. The dataset also contains (ii) a script for the design of a state-space model predicting the sex-ratio within a population of S. noctilio.Item Antioxidant supplementation can reduce the survival costs of amino acid intake in honeybees(University of Pretoria, 2014) Archer, C. Ruth; Kohler, Angela; Pirk, Christian Walter Werner; Oosthuizen, Vinette; Apostolides, Zeno; Nicolson, Sue W.; Archer@demogr.mpg.deOver-consuming amino acids is associated with reduced survival in many species, including honeybees. The mechanisms responsible for this are unclear but one possibility is that excessive intake of amino acids increases oxidative damage. If this is the case, antioxidant supplementation may help reduce the survival costs of high amino acid intake. We tested this hypothesis in African honeybees (Apis mellifera scutellata) using the major antioxidant in green tea, epigallocatechin-3-gallate (EGCG). We first determined the dose-range of EGCG that improved survival of caged honeybees fed sucrose solution. We then provided bees with eight diets that differed in their ratio of essential amino acids (EAA) to carbohydrate (C) (0:1, 1:250, 1:100, 1:75, 1:50, 1:25, 1:10, 1:5 EAA:C) and also in their EGCG dose (0.0 or 0.4 mM). We found that bees fed sucrose only solution survived better than bees fed EAA diets. Despite this, bees preferred a diet that contained intermediate ratios of EAA:C (ca. 1:25), which may represent the high demands for nitrogen of developing nurse bees. EGCG supplementation improved honeybee survival but only at an intermediate dose (0.3–0.5 mM) and in bees fed low EAA diets (1:250, 1:100 EAA:C). That EGCG counteracted the lifespan reducing effects of eating low EAA diets suggests that oxidative damage may be involved in the association between EAAs and lifespan in honeybees. However, that EGCG had no effect on survival in bees fed high EAA diets suggests that there are other physiological costs of over-consuming EAAs in honeybees.Item Digital data for “Adult diet of a tephritid fruit fly does not compensate for impact of a poor larval diet on stress resistance”(Department of Zoology and Entomology, University of Pretoria, 2018) Weldon, Christopher William; cwweldon@zoology.up.ac.zaTables detailing the initial condition, desiccation and starvation resistance, dehydration tolerance, and body composition (carbohydrates, glycogen, lipids, and protein) of adult marula fruit flies, Ceratitis cosyra. Data are arranged according to larval diet (low yeast or high yeast), adult diet (none, sugar, or sugar + hydrolysed yeast), and sex (female or male) of each fly, as well as the stress experienced by the fly (desiccation or starvation).Item Data : Clinopyroxene megacrysts from Marion Island, Antarctic Ocean : Evidence for a late stage shallow origin(Department of Geology, University of Pretoria, 2018) Roberts, R. James; James.roberts@up.ac.zaClinopyroxene megacrysts (up to 5 cm) from a scoria cone on Marion Island, Antarctic Ocean are zoned, with compositionally distinct low (Al+Ti) and high (Al+Ti) patches arranged haphazardly throughout crystals. Inclusions of olivine, pyrrhotite, oxides, sulphides, and rounded inclusions with euhedral micro-crystals interpreted as former melt inclusions are observed. Olivine inclusions have variable compositions, ranging from primary Ti-poor crystals to Ti-rich crystals hosting secondary haematite crystals formed by hydrogenation. The crystals contain voids, which are concentrated in the middle of each crystal, indicating that the initial crystal growth was skeletal. Subsequent crystallisation filled in the skeletal framework, creating the patchy zoning in the crystals. The Marion Island megacrysts are not homogenous, but the combination of crustal clinopyroxene compositions, primary and hydrogenated olivine, and the mode of eruption in scoria eruptions indicates that these crystals most likely formed in a shallow magma chamber. Primary olivines crystallised from a mafic magma as well as secondary altered olivines are incorporated into a rapidly growing megacryst in a super-saturated, fluid-rich environment, prior to being ejected onto surface in a scoria eruption.Item Ultrasonographic evaluation of fetal development in the rat(Pretoria : University of Pretoria. Faculty of Veterinary Science. Dept. of Companion Animal Clinical Studies, 2018) Kirberger, Robert M.; Bester, Elizabeth G.; Robert.kirberger@up.ac.zaThe study objectives were to measure gestational sac (GS) diameter and crown-to-rump (CR) length in conscious pregnant rats and to determine the chronological ultrasonographic appearance of heart beat and fetal organogenesis. The study formed part of a unilateral surgical salpingectomy trial with 16 female Sprague-Dawley rats (Rattus norvegicus). Ten rats were operated on with six controls before all were mated at 8-10 weeks of age. Gestation length was taken as 22 days. Rats were manually restrained for abdominal ultrasonography and were scanned from day 7 until day 19 or 20 post-mating followed by immediate euthanasia. Measurements’ were taken from two GSs per rat. The presence of several early GSs in a row were described as a “string of pearls”. As a fetus developed features of organogenesis were recorded. There was no significant difference in GS diameters and CR length between the test and control groups. Mean GS diameters ranged from 2.9 mm (day 7) to 18.1 mm (day 20). A string of pearls was seen on days 8-11. The CR length ranged from 1.6 mm (day 11) to 26.4 mm (day 20). A heart beat was first seen on day 11 and the echogenic vertebral column at day 14-15. From day 16, ribs, feet and the isoechoic lungs and liver were seen. The lungs became hyperechoic to the liver from day 18-19. The tail and mandible were visible on day 18 and the aorta and caudal vena cava were seen on day 19, as well as an occasional bladder. These measurements and staged in utero ultrasonographic appearance of various organ and skeletal structures will assist in a reasonably accurate prediction of the day of impending parturition by laboratory personnel and researchers.Item Ultrasonographically determined renal values and comparisons to serum biochemistry renal parameters in aged semi-captive cheetahs (Acinonyx jubatus)(Adrian S.W. Tordiffe University of Pretoria, Faculty of Veterinary Science, Department of Paraclinical Sciences., 2016) Kirberger, Robert M.; Tordiffe, Adrian Stephen Wolferstan; adrian.tordiffe@up.ac.zaCheetahs in captivity have a high prevalence of chronic renal diseases. Abdominal diagnostic ultrasound is a useful diagnostic modality to evaluate the urinary tract and can give an immediate indication of renal status but lacks sensitivity and specificity for early renal changes in domestic carnivores. We ultrasographically evaluated the renal volumes, a variety of renal dimensions, interarcuate artery resistivity indices as well as aortic diameters and the length of the ventral aspect of the 6th lumbar vertebras in 27 aged semi-captive anesthetized cheetahs. A number of ultrasound ratios were determined to evaluate renal size and the dimensions and ratios were compared to serum creatinine and urea values as well as urine specific gravity. There were minimal differences for all values between left and right kidneys. Mean kidney length was 65 .4 mm (range 54.9-76.9) with left kidney length ratios to L6 length being 1.60 (range1.27-2.06) and to the aortic diameter 7.69 (range 4.54-10.72). Significant correlations between left renal length as well as length:L6 ratio to creatinine values were found ((r -0.66) and (r -0.60) respectively). The mean RI values of the different sedation/anesthetic protocols ranged from 0.46 -0.55. 4 – 0.66. Left renal length and L6 ventral vertebral body length as well as left kidney RI values should be measured in all cheetah abdominal ultrasound examinations. These measurements, together with serum creatinine, urea and urine specific gravity values may be relatively sensitive indicators of early renal pathology in the absence of gross ultrasonographic changes.Item Living on the edge : daily, seasonal and annual body temperature patterns of Arabian Oryx in Saudi Arabia(Public Library of Science, 2017) ncbennett@zoology.up.ac.za; Bennett, Nigel CharlesHeterothermy, the ability to allow body temperature (Tb) to fluctuate, has been proposed as an adaptive mechanism that enables large ungulates to cope with the high environmental temperatures and lack of free water experienced in arid environments. By storing heat during the daytime and dissipating it during the night, arid-adapted ungulates may reduce evaporative water loss and conserve water. Adaptive heterothermy in large ungulates should be particularly pronounced in hot environments with severely limited access to free water. In the current study we investigated the effects of environmental temperature (ambient, Ta and soil, Ts) and water stress on the Tb of wild, free-ranging Arabian oryx (Oryx leucoryx) in two different sites in Saudi Arabia, Mahazat as-Sayd (MS) and Uruq Bani Ma’arid (UBM). Using implanted data loggers wet took continuous Tb readings every 10 minutes for an entire calendar year and determined the Tb amplitude as well as the heterothermy index (HI). Both differed significantly between sites but contrary to our expectations they were greater in MS despite its lower environmental temperatures and higher rainfall. This may be partially attributable to a higher activity in an unfamiliar environment for translocated animals in UBM. As expected Tb amplitude and HI were greatest during summer. Only minor sex differences were apparent that may be attributable to sex-specific investment into reproduction (e.g. male-male competition) during rut. Our results suggest that the degree of heterothermy is not only driven by extrinsic factors (e.g. environmental temperatures and water availability), but may also be affected by intrinsic factors (e.g. sex and/or behaviour).Item Comparative serum fatty acid profiles of captive and free-ranging cheetahs (Acinonyx jubatus) in Namibia(University of Pretoria, Faculty of Veterinary Science, Department of Paraclinical Sciences., 2015) Mienie, Lodewyk J.; adrian.tordiffe@up.ac.za; Tordiffe, Adrian Stephen WolferstanCheetahs (Acinonyx jubatus) are highly specialised large felids, currently listed as vulnerable on the IUCN red data list. In captivity, they are known to suffer from a range of chronic non-infectious diseases. Although low heterozygosity and the stress of captivity have been suggested as possible causal factors, recent studies have started to focus on the contribution of potential dietary factors in the pathogenesis of these diseases. Fatty acids are an important component of the diet, not only providing a source of metabolisable energy, but serving other important functions in hormone production, cellular signalling as well as providing structural components in biological membranes. To develop a better understanding of lipid metabolism in cheetahs, we compared the total serum fatty acid profiles of 35 captive cheetahs to those of 43 free-ranging individuals in Namibia using gas chromatograph mass spectrometry. The unsaturated fatty acid concentrations differed most remarkably between the groups, with all of the polyunsaturated and monounsaturated fatty acids, except arachidonic acid and hypogeic acid, detected at significantly lower concentrations in the serum of the free-ranging animals. The influence of age and sex on the individual fatty acid concentrations was less notable. This study represents the first evaluation of the serum fatty acids of free-ranging cheetahs, providing critical information on the normal fatty acid profiles of free-living, healthy individuals of this species. The results raise several important questions about the potential impact of dietary fatty acid composition on the health of cheetahs in captivity.Item Simultaneous stressors : interactive effects of an immune challenge and dietary toxin can be detrimental to honeybees(Pretoria: University of Pretoria. Faculty of Natural and Agricultural Sciences. Department of Zoology & Entomology, 2012) Angela.koehler@unine.ch; Kohler, Angela; Pirk, Christian Walter Werner; Nicolson, Sue W.Recent large-scale mortality of honeybee colonies is believed to be caused by multiple interactions between diseases, parasites, pesticide exposure, and other stress factors. To test whether a dual challenge has an additive effect in reducing survival, we experimentally stimulated the immune system of caged Apis mellifera scutellata workers from six colonies by injecting saline or Escherichia coli lipopolysaccharides (LPS), and additionally fed them the alkaloid nicotine (0 µM, 3 µM and 300 µM in 0.63 M sucrose). Workers did not increase their sucrose intake to compensate for the immune system activation, and those injected with E. coli LPS decreased their intake on the highest nicotine concentration. In the single challenges, injection and high nicotine doses negatively affected survival. All injected worker groups showed reduced survival. Without nicotine, survival of the saline and E. coli LPS worker groups was similar, but survival of E. coli LPS-challenged workers dropped below that of the saline groups when additionally challenged by nicotine, with bees dying earlier at higher nicotine concentrations. In the dual challenge of saline injection and dietary nicotine, a reduced effect on survival was observed, with lower mortality than expected from the summed mortalities due to the single challenges. However, additive and synergistic effects on survival were observed in workers simultaneously challenged by E. coli LPS and nicotine, indicating that interactive effects of simultaneous pathogen exposure and dietary toxin are detrimental to honeybee fitness.Item Resistance of developing honeybee larvae during chronic exposure to dietary nicotine(Pretoria : University of Pretoria. Faculty of Natural and Agricultural Sciences. Department of Zoology & Entomology, 2014) Archer@demogr.mpg.de; Human, Hannelie; Archer, C. Ruth; Du Rand, Esther Elizabeth; Pirk, Christian Walter Werner; Nicolson, Sue W.The effects of pesticides on honeybee larvae are less understood than for adult bees, even though larvae are chronically exposed to pesticide residues that accumulate in comb and food stores in the hive. We investigated how exposure to a plant alkaloid, nicotine, affects survival, growth and body composition of honeybee larvae. Larvae of Apis mellifera scutellata were reared in vitro and fed throughout development on standard diets with nicotine included at concentrations from 0 to 1000 lg/100 g diet. Overall mortality across all nicotine treatments was low, averaging 9.8% at the prepupal stage and 18.1% at the white-eyed pupal stage, but survival was significantly reduced by nicotine. The mass of prepupae and white-eyed pupae was not affected by nicotine. In terms of body composition, nicotine affected water content but did not influence either protein or lipid stores of white-eyed pupae. We attribute the absence of consistent negative effects of dietary nicotine to detoxification mechanisms in developing honeybees, which enable them to resist both natural and synthetic xenobiotics.Item A new design for honeybee hoarding cages for laboratory experiments(Pretoria: University of Pretoria. Faculty of Natural and Agricultural Sciences. Department of Zoology & Entomology, 2012) Angela.koehler@unine.ch; Kohler, Angela; Nicolson, Sue W.; Pirk, Christian Walter WernerItem Nutrition affects stress resistance in African honeybees (Apis mellifera scutellata)(Pretoria: University of Pretoria. Faculty of Natural and Agricultural Sciences. Department of Zoology & Entomology, 2014) Wright, Geraldine A.; archer@demogr.mpg.de; Archer, C. Ruth; Pirk, Christian Walter Werner; Nicolson, Sue W.1. Nutrition plays an important role in physiological stress resistance and by adjusting their intake of key nutrients, such as protein and carbohydrate, many animals can better resist stress. 2. Poor nutrition may contribute to the widespread and on-going declines of honeybee populations by increasing their vulnerability to abiotic (e.g. pesticides) and biotic (e.g. diseases) stressors. However, we do not know how nutrition affects stress resistance in social insects such as honeybees. 3. Here, we examined how exposure to the toxic secondary metabolite nicotine, a neurotoxin that shares structural similarities with the neonicotinoid pesticides, and low temperatures affected nutrient regulation in honeybees using the Geometric Framework of nutrition. 4. Groups of queenless, newly emerged worker bees were given diets containing specific ratios of protein and carbohydrate to determine, first, how toxin exposure and ambient temperature affected their nutrient intake and, secondly, how nutrition affected survival under stress. 5. We find that low temperatures and nicotine interacted to reduce survival in African honeybees that ate low protein, high carbohydrate diets. However, bees fed a high protein diet were better able to survive insult with these interacting stressors. 6. Although protein conferred a survival benefit in honeybees exposed to these dual stressors, when allowed to self-select their diet, caged workers did not shift their intake towards a higher protein food to improve their survival under these stressful conditions. 7. We discuss the possible constraints on nutrient regulation in honeybees and the role that diet could play in their decline.Item Die effek van organiese en anorganiese selenium op die immuunsisteem van skape(University of Pretoria, 2006-12-07) Van Ryssen, J.B.J.; upetd@up.ac.za; Jansen van Rensburg, ChristineAFRIKAANS: Die effek van die organiese en anorganiese vorme van selenium op sekere parameters van die immuunsisteem van skape, is ondersoek. Die potensiele gevaar wat die supplementering van hierdie twee seleniumbronne teen hoë vlakke in die dieet, op die immuunstelsel van skape inhou, is ook bestudeer. Daar is verder ook gekyk na die mate van akkumulering van selenium wat in verskillende weefsels in die liggaam, na supplementering van organiese en anorganiese selenium teen verskillende konsentrasies, plaasvind. 'n Seleniumryke gis is as bron van organiese selenium gebruik en aan drie groepe Vleismerino skape gesupplementeer teen vlakke van 6 mg/skaap/dag, 1.5 mg/skaap/dag en 0.75 mg/skaap/dag. Natriumseleniet is as bron van anorganiese selenium gebruik om drie ander groepe diere teen dieselfde vlakke te supplementeer. 'n Sewende groep, wat geen seleniumsupplementering ontvang het nie, het as kontrole gedien. Die supplementering van organiese selenium teen vlakke van 6 mg/skaap/dag, 1.5 mglskaap/dag en 0.75 mg/skaap/dag, het, in vergelyking met anorganiese selenium, tot 'n betekenisvolle hoër akkumulering van selenium in die skelet- en hartspier gelei. Selenium wat in 'n organiese vorm teen vlakke van 6 mg/skaap/dag en 1.5 mg/skaap/dag gesupplementeer is, het 'n betekenisvolle hoër akkumulering van selenium in die volbloed, plasma, nierkorteks en lewer, veroorsaak. Geen betekenisvolle verskille tussen organiese en anorganiese selenium is, in terme van seleniumakkumulering in die volbloed, plasma, nierkorteks en lewer, by 'n supplementeringsvlak van 0.75 mg/dag waargeneem nie. Daar is ook gevind dat die seleniumvlakke in die volbloed nie betekenisvol van mekaar verskil het wanneer die diere met 0.75 en 1.5 mg/dag anorganiese selenium gesupplementeer is nie. Dit dui daarop dat seleniumkonsentrasie in die volbloed moontlik nie 'n akkurate voorspeller van seleniuminname, wanneer diere anorganiese selenium in die dieet ontvang, is nie. Die gemiddelde superoksiedproduksie deur gestimuleerde neutrofiele was betekenisvol laer vir die groep met 'n 0.75 mg/dag anorganiese seleniumsupplementering. Hierdie resultate stel voor dat selenium, wat as natriumseleniet teen 'n vlak van 0.75 mg/dag aan skape gesupplementeer word, as antioksidant optree. Die antioksidatiewe eienskappe veroorsaak 'n opruiming van superoksied, wat deur die gestimuleerde neutrofiele geproduseer word. Die hoer T limfosietteIlings en laer kreatien fosfokinase aktiwiteit in die serum van hierdie groep dui op 'n beter membraanbeskerming van die T limfosietmembrane en spierselmembrane en steun die hipotese dat 'n inname van 0.75 mg/dag anorganiese selenium, bo-op die selenium wat natuurlik in die dieet teenwoordig is, as antioksidant in die liggaam optree. Die skape wat 1.5 mg/dag natriumseleniet as supplement ontvang het, het die hoogste primêre en sekondere antiliggaamproduksie teen perd eritrosiete getoon. Die gemiddelde primere antiliggaamproduksie teen perd eritrosiete van die groep diere wat 6 mgldag anorganiese selenium ontvang het, was betekenisvollaer as die gemiddelde primere antiliggaamproduksie van die ander groepe gewees. Hierdie onderdrukking van antiliggaamproduksie kan toegeskryf word aan 'n vergiftigingseffek van 'n hoë anorganiese seleniuminname, wat nie by organiese selenium waargeneem is nie. Dit is moontlik as gevolg van die pro-oksidant eienskappe van 'n hoë vlak van seleniet. Hierdie pro-oksidant eienskappe van hoë vlakke van natriumseleniet inname word ondersteun deur die definitiewe spierskade wat 'n supplementering van 6 mg/dag natriumseleniet veroorsaak het. 'n Inname van 6 mg/dag selenium, in beide organiese en anorganiese vorm, asook 1.5 mg selenium in anorganiese vorm, het tot 'n vergroting van die lewer gelei. Aangesien hierdie effek reeds by 'n veel laer vlak van aanvulling van anorganiese selenium gevind word, kan aangeneem word dat die inname anorganiese selenium 'n groter stremming op die lewer plaas. Daar word, na aanleiding van hierdie projek, aanvaar dat anorganiese selenium teen 'n supplementeringsvlak van 0.75 mg/dag/skaap, bo-op die selenium wat natuurlik in die dieet voorkom, voordelig vir die immuunsisteem is en membraanskade doeltreffend beperk. Hierdie vlak is ongeveer ekwivalent aan 'n totale seleniuminame van 0.44 mg selenium/kg gewig/dag, waarvan minstens 75% uit 'n anorganiese selenium bestaan. Geen toksiese effekte is by hierdie vlak waargeneem, soos in die geval by die hoër vlakke van anorganiese selenium, nie. Alhoewel die supplementering met hoër vlakke van organiese selenium nie werklik toksiese effekte, buiten die vergroting van die lewer, getoon het nie, is daar ook geen positiewe effekte op die immuunsisteem en beskerming van selmembrane, by laer vlakke gevind nie. Organiese selenium blyk slegs doeltreffend te wees as voersupplement waar die doel is om dierlike produkte, vir mensegebruik, met selenium te verryk. Hierdie supplementering kan dan ook met 'n hoer mate van veiligheid uitgevoer word as wat die geval met anorganiese selenium is. ENGLISH: The effects of organic and inorganic forms of selenium on the immune system of sheep have been investigated and the potential danger of high dietary levels has also been studied. The extent by which the accumulation of selenium in various tissues occurs, after supplementation of either organic or inorganic selenium at differing concentrations was also investigated. Selenium rich yeast as a source of organic selenium was used as a supplement at, respectively, 6mg/sheep/day, 1.5mg/sheep/day and 0.75mg/sheep/day to three groups of Mutton Merino sheep. Sodium selenite as source of inorganic selenium was used to supplement another three groups of animals at the same levels. A seventh group who did not receive any selenium supplementation served as a control. Supplementation of organic selenium in a yeast form led to significantly higher levels of selenium in the skeletal muscles and heart compared to sodium selenite in all three groups whereas supplementation of organic selenium at 6mg and 1.5mg/sheep/day led to significantly higher selenium levels in whole blood, plasma and kidney cortex compared to the groups supplemented with inorganic selenium at the same concentrations. It was also found that the selenium levels in whole blood did not differ significantly between the animals on 0.75 and 1.5mg/day inorganic selenium indicating that the selenium concentration in whole blood is possibly not an accurate indicator of selenium intake in the case of animals receiving inorganic selenium in their diet. The mean superoxide production by stimulated neutrophils was significantly lower in the group supplemented with inorganic selenium at 0.75mg/day suggesting that selenium, at that concentration, can act as an antioxidant. The anti-oxidative properties of selenium caused a scavenging of neutrophil-derived superoxide. This group of sheep also had a higher T¬lymphocyte count and lower creatinine phosphokinase activity in serum indicating a protection of T-Iymphocyte membranes and support the hypothesis that 0.75mg/day inorganic selenium can act as an anti-oxidant in the body. The sheep on 1.5mg/day sodium selenite supplementation produced the highest primary and secondary antibodies against horse erythrocytes. On the other hand, animals receiving inorganic sodium selenite at 6mg/day produced significantly lower levels of primary antibodies than any of the other groups indicating the poisonous effect of high inorganic selenium supplementation that was not observed with the animals on organic selenium supplementation. This is possible because of the pro-oxidative properties of high selenium levels. These pro-oxidative properties of high selenium levels produced by the high intake of sodium selenite are supported by specific muscle damage caused by the supplementation of 6mglday sodium selenite. An intake of 6mglday of selenium in both forms, as well as l.5mg selenium in inorganic form, led to enlargement of the liver. Because this effect was found at a much lower level with inorganic selenium supplementation, it can be concluded that inorganic selenium places a greater stress on the liver. With these results in mind, the conclusion can be drawn that inorganic selenium supplemented at a level of 0.75 mg/day/sheep, together with the natural occuring feed selenium, can be advantageous for the immune system by effectively protecting cell membranes against neutrophil mediated oxidative damage. This level is approximately equal to a total selenium intake of 0.44mglkg live weight/day, of which at least 75% consists of inorganic selenium. No toxic effect was observed at this level, as was the case with higher levels of inorganic selenium. Supplementation with high levels of organic selenium did not lead to any definitive toxic effects, except enlargement of the liver, but there were also no positive effects on the immune system or protection of the cell membranes found at lower levels. Organic selenium seems to be effective only in the case where it is used as food supplement with the purpose to enrich animal products for human use. Thus it would appear from the results of the study, that organic selenium offers a safer method of dietary supplementation.Item An investigation into the nature and extent of substance abuse and preventable diseases in Nongoma, KwaZulu Natal : implications for social work(University of Pretoria, 2003) Lombard, Antoinette; upetd@up.ac.za; Mathe, Sipho VimbaHealth is defined by the World Health Organization as not merely the absence of disease or infirmity but as a state of complete physical, mental and social well being. In the concept of Social Health, ill-health is viewed as the interaction of a number of factors, some of which may appear to bear no direct etiological relationship to a morbid condition. The study was primarily aimed at determining the nature and extent of alcohol and other drugs abuse and common preventable diseases in Nongoma, KwaZulu-Natal. The objectives of the study were presented as follows:- To study and review relevant literature pertaining to the historical background and socio-economic and political dimensions of alcohol and other drug use, misuse and abuse in South Africa.
- To conceptualize primary health care (PHC) within a developmental perspective as a theoretical framework for the study.
- To do situation analysis on drug related health and social problems among selected institutions and centres in Nongoma.
- To investigate the nature and extent of use of alcohol, marijuana and their relationship with T.B., HIV/AIDS and mental health among village communities of Nongoma.
- To formulate guidelines for an integrative, intersectoral prevention model of alcohol and other drug abuse and related preventable diseases for Nongoma based on the research findings.
- To make recommendations based on the findings of the current study.