Giraffes (Giraffa camelopardalis) have evolved into a unique and extreme shape. The principle determinant of its shape is the skeleton and the overarching theme of the study was to describe how this shape is achieved throughout ontogeny. Accordingly, the study had three main objectives: 1) To describe the growth of the giraffe postcranial skeleton allometrically, 2) To interpret the allometric patterns described in an evolutionary and functional sense and 3) To reconstruct the size and shape of the extinct Giraffa sivalensis using, if feasible, allometric equations obtained in this study. Secondary objectives were to a) establish if sexual dimorphism was evident in G. camelopardalis and b) determine if growth patterns in the foetus differed from those in postnatal G. camelopardalis. Data were collected from giraffes culled as part of conservancy management in Zimbabwe. The sample included 59 animals from which vertebral dimensions were taken in 48 animals and long bone dimensions in 47 animals. Body masses ranged from 21 kg to 77 kg in foetuses and 147 kg to 1412 kg postnatally, representing 29 males and 30 females. In addition to body mass, external body dimensions were recorded from each animal. Each vertebra and unilateral long bone was dissected from the carcasses and cleaned, after which dimensions were measured with a vernier calliper, measuring board or measuring tape. Vertebral dimensions measured included body (centrum) length, height and width as well as vertebral spinous process length. Long bone dimensions included length, two midshaft diameters and circumference. Allometric equations (y=bxk) were constructed from the data, with special interest in the scaling exponent (k) to illustrate regions of positively allometric, isometric or negatively allometric growth. In the first series of analyses the growth patterns of the components of the postcranial axial skeleton were analysed. The adaptations in vertebral growth to create and maintain extraordinary shape were identified as disproportionate elongation of the cervical vertebrae after birth, increasing cross sectional diameters of the cervical vertebrae from cranial to caudal and positively allometric spinal process growth. The theory of sexual selection as a driver for neck elongation in giraffes was brought into question by showing that male and female vertebral elongation rates are similar relative to increases in body mass. The second series of analyses described the growth pattern of the long bones of the appendicular skeleton. The allometric exponents seemed unremarkable compared to the few species described previously, and it was shown that the giraffe appendicular skeleton does not elongate in the dramatic way the neck does. Limbs at birth, after lengthening with positive allometry in utero, are already elongated and slender in shape and a further increase in the gracility of the bones is either not possible or not desirable. This result implies that it is neck elongation rather than leg elongation that is the dominant factor in the evolution of the giraffe shape. Nevertheless, the front limb bones and especially the humerus may show responsiveness to increasing high loads and/ or bending moments, which may be caused by the neck mass which increases with positive allometry, or with behaviours such as splaying the forelegs during drinking. In the third component of the study ontogenetic allometric equations in extant giraffes were applied to the remains of an extinct giraffid, G. sivalensis. The procedure was unusual as it employed ontogenetic regressions instead of the more commonly used interspecific regressions. The appropriateness of each equation to estimate body mass was evaluated by calculating the prediction error incurred in both extant giraffes and okapis (Okapia johnstoni). It was concluded that, due to body shape, ontogenetic equations were adequate and perhaps preferable to interspecific equations to estimate proportions in Giraffa species. This analysis showed that G sivalensis was smaller than extant giraffes and weighed around 400 kg (range 228 kg 575 kg), with a neck length of about 147 cm and a height of 390 cm. There may be evidence of sexual dimorphism in this species, with males being about twice the body weight of females. However, if sexual dimorphism was not present and all the bones were correctly attributed to this species, then G. sivalensis had a slender neck with a relatively stocky body. In conclusion, this study established ontogenetic regression equations for the skeleton of an animal of which the body shape seems to be at the extreme limits of mammalian possibility. The value of the current study lies especially in its sample size and quality, which included an unprecedented number of giraffe body masses, vertebral and long bone dimensions. This dataset had applications in the giraffe s evolutionary biology, palaeontology and even ecology. Future studies still need to compare the findings from giraffe growth with similar data from other taxa, especially those with long legs and necks. Specifically, it would interesting to determine if positively allometric neck growth combined with isometric leg growth is found in other mammalian species. In addition, the strength of giraffe long bones and vertebrae needs to be investigated with more accuracy using parameters like second moment of area. Lastly, further palaeontological studies on other giraffid sizes are necessary to validate the current and future interpretations of fossil giraffid findings. / Thesis (PhD)--University of Pretoria, 2015. / tm2016 / Production Animal Studies / PhD

Like many other wildlife species, blue wildebeest (Connochaetes taurinus) are routinely captured for relocation purposes. Several studies have shown that physiologically this is a very stressful period for wild animals and can affect several aspects of their well-being. Little is known about the level of physiological stress experienced by blue wildebeest during capture and confinement before transport. A non-invasive approach to assess adrenocortical function as a measure of physiological stress would be preferable, as animals are not disturbed during sample collection, and therefore sampling is feedback free. Currently, however, such a non-invasive measure has not been evaluated for any wildebeest species. An adrenocorticotropic hormone (ACTH) challenge test was performed on one sub-adult male and one adult female. We examined the suitability of five enzyme immunoassays (EIAs), detecting faecal glucocorticoid metabolites (fGCM) with a 5?-3?-ol-11-one (3?,11oxo-CM), 5?-pregnane-3?,11?,21-triol-20-one (37e), 11?,21-diol-20-one (corticosterone), 11,17,21-trihydroxypregn-4-ene-3,20-dione (cortisol), and 11,17-dioxoandrostane (11,17-DOA) structure respectively, for monitoring stress-related physiological responses in blue wildebeest. After evaluating all five EIAs, it was concluded that the EIA measuring 11,17-DOA performed the best for detection of fGCMs in blue wildebeest with a 21 fold increase above the baseline in the male and a 4,7 fold increase above the baseline in the female at 12 hours post ACTH injection. Under field conditions the use of the 11,17-DOA EIA allowed the monitoring of fGCM alterations when wildebeest were captured using a mass capture technique; fGCM concentrations were elevated by 1,5 times in samples collected from animals restrained for up to 10 hours in a truck compared to those collected directly after capture (P <0,001). No significant increase in fGCM concentrations was detected in faecal samples collected directly after capture from animals of the same herd captured either on day 1 or day 2 of mass capture, indicating that the presence of a helicopter during the two days of capture was not associated with a profound stress response in wildebeest that were not captured at the time but were in the vicinity of the capture. Storage of faeces in labelled plastic containers at ambient temperature for up to 48 hours post-defecation resulted in a significant decrease in 11,17-DOA levels from 8 to 48 hours after defecation. Therefore sample collection for 11,17-DOA determination in wildebeest can occur for up to 8 hours post-defecation without the risk of substantial decreases in 11,17-DOA concentrations. By identifying a suitable assay for determining 11,17-DOA concentrations in blue wildebeest, it can now be used by researchers, wildlife managers and veterinarians to reliably monitoring the physiological stress responses to capture or other management procedures with minimum interference to the animals. We have also shown that the presence of a helicopter during capture does not appear to have a lasting influence on wildebeest 11,17-DOA concentrations, but prolonged restraint for 10 hours does. / Dissertation (MSc)--University of Pretoria, 2016. / Paraclinical Sciences / MSc / Unrestricted

An unacceptable number of wild animals die or experience morbidity as a result of capture-related complications. Capture-induced hyperthermia is believed to play a role in the morbidity and mortality of captured animals. The aims of this research were to gain a better understanding of the pathophysiological consequences of capture and capture-induced hyperthermia and to better understand the association between capture-induced hyperthermia and capture myopathy. We aimed to determine whether cooling could reduce the pathophysiological consequences of capture and protect against capture related complications like capture myopathy. Forty wild blesbok were captured from the wild and then housed in bomas at Groenkloof Nature Reserve for the duration of the study. These animals were divided into three groups which included a group of animals that were chased and cooled during immobilization (C+C), a group that was chased but not cooled during immobilization (CNC) and a control group that was not chased before or cooled during immobilization (Ct). The control group received powder diazepam in their feed two hours before they were darted to minimize their stress response to capture. The treatment groups were chased for 15 minutes before they were darted. All the animals were darted and immobilized with etorphine and azaperone. The chased and cooled group were doused with 10L of 4°C water over a 10 minute period during the immobilization. The immobilization period lasted for forty minutes in all the animals. A number of clinical and physiological parameters were measured in all the animals directly after induction into immobilization, 40 minutes later, and then on day 2, 16 and 30 post the initial capture. On these subsequent days the animals were not chased but they were simply all immobilized in their holding bomas, for data and sample collection, after they received in feed diazepam. The parameters measured and analysed included muscle and rectal temperature, PaO2, PaCo2, pH, lactate, GGT, GLDH, creatinine, BUN, CK, AST, cardiac troponin I and cortisol. The animals in the control group had normal values for all the variables measured except they were hypoxic during the immobilization. The animals that were chased developed hyperthermia, hypoxia and mild acidaemia, and they had mildly elevated concentrations of GLDH, AST, CK and creatinine indicating mild hepatic, renal and skeletal muscle damage. These animals also had severe increases in lactate and cardiac Troponin I concentrations indicating cardiac damage possibly as a result of the hypoxia that occurred during the chase and the immobilization. Despite cooling correcting the hyperthermia, it did not prevent or protect against any of these pathophysiological effects. Therefore, this capture-induced hyperthermia appeared to play a limited role in causing these effects. Therefore, capture that involves chasing animals before immobilization appears to primarily cause cardiac muscle damage. This capture-induce cardiomyopathy may have profound secondary consequences, which could result in mortality or other capture related complications. / Dissertation (MSc)--University of Pretoria, 2016. / Paraclinical Sciences / MSc / Unrestricted

Since 1982 farmers and veterinarians mainly from the North West province of South Africa noticed an increase in cattle with associated lameness and osteopathy of unknown aetiology. Affected cattle presented with varying degrees of lameness as well as peri-articular swelling especially of the stifle joint. Cattle of all ages, particularly those between the ages of 6 - 18 months developed lesions. Lesions were also noticed among different breeds, production stages and different farming enterprises (commercial and stud farming). The only common factor among the affected cattle was the environment in which they were farmed. Culling of affected animals, especially calves, reduced the number of replacement stock to a level where some farmers were not able to produce sufficient replacement stock, consequently suffering tremendous financial losses. Investigation into the aetiology of the new sporadic osteopathy was deemed necessary. Initially it was suspected that the condition was due to mineral deficiency, as affected cattle fed a supplement containing high levels of micro- and macro minerals responded positively within three weeks during a pre-trial. The study was conducted to determine the level of micro- and macro minerals required to be included in a supplement that would improve the clinical condition of cattle clinically affected by osteochondrosis. Results indicated no significant difference between supplemetary treatments. A comparison between the pre-trial and the current supplements indicated that the supplements in the present study had negative dietary cation anion difference (DCAD) values. Since negative DCAD compositions may result in mild metabolic acidosis, as supported by literature, and the acidic urine collected in a small sample of the test cattle, the hypothesis is advanced that it is unlikely that supplementation, regardless of its mineral concentration will improve the condition of the cattle if the DCAD value of the supplement is strongly negative. The hypothesis should be tested in forthcoming research and the following should be determined: (1) the specific effect a supplement with a negative DCAD value has when fed to cattle with clinical osteochondrosis, and (2) the optimal DCAD value of a supplement that would aid in limiting the severity of osteochondrosis in cattle. / Dissertation (MSc)--University of Pretoria, 2016. / Paraclinical Sciences / MSc / Unrestricted

Farmers in developing countries are faced with many diseases that limit the productivity of their animals, several of which are caused by tick infestations. To date, treatment of host animals with synthetic, chemical tick repellents and acaricides remains the method used to reduce the influence of the parasites on animal and human health. Awareness of the environmental health hazards posed by these acaricides, development of tick resistance leading to recurrent ectoparasitism, danger of misuse and presence of toxic residues in food, water and animal by-products has led to the search for safe and environmentally-friendly alternatives, one of which is the use of medicinal plants. Because there appears to be a need and to contribute to research in this field, extensive literature surveys of published scientific articles were conducted. The following aspects were addressed: the role of ticks in animal health, problems encountered in using synthetic, chemical acaricides, medicinal plants with in vitro acaricidal or tick repellent activities against immature and adult stages of ticks and bioassays employed. Veterinary databases (All Databases, CAB Abstracts and Global Health, Medline, Pubmed, Web of Science, BIOSIS Citation Index, Science Direct, Current Content Connect and Google Scholar) were searched. The search words included “acaricidal”, “tick repellent”, “medicinal plants”, “isolated compounds” and “antitick assays”. Meta-analysis was conducted using the Fixed-effect model in an Excel programme to compare the results. The tick climbing repellency and adult immersion tests were the most commonly used assays to test for repellency and acaricidal activity respectively. Ethanol was the most commonly used extractant and Rhipicephalus (Boophilus) microplus was the most commonly studied tick across all the reviewed papers. More than 200 plant species from several countries globally have tick repellent or acaricidal properties discovered using in vitro assays. A large proportion of the published work was done in tropical countries such as Brazil, India and South Africa where ticks cause major problems. The median efficiency values for acaricidal, larvicidal, egg hatching inhibition, inhibition of oviposition, repellency, acaricidal effects of the Lamiaceae and Asteraceae family using a total of 1428, 1924, 574, 281 and 68 events were 80.12 (CI95%: 79.20 - 81.04), 86.05 (CI95%: 85.13 - 86.97), 83.39 (CI95%: 82.47 - 84.31), 53.01 (CI95%: 52.08 - 53.93), 92.00 (CI95%: 91.08 - 92.93), 80.79 (CI95%: 79.87 - 81.71) and 48.34% (CI95%: 47.42 - 49.26) respectively. Extracts of some species including Azadirachta indica, Gynandropsis gynandra, Lavandula angustifolia, Pelargonium roseum and Cymbopogon species have good acaricidal and larvicidal activities with 90-100% efficacy, comparable to those of currently used acaricides, although, usually at higher dosages. Compounds with acaricidal activity such as azadirachtin, carvacrol, linalool, geraniol and citronellal were listed. As a country, South Africa is rich in vascular plant flora, possessing over 10% of the world’s vascular floral species. Only a fraction of its plants have been rigorously studied and analyzed for their biological activity against ticks and seventeen plant species based on their ethnoveterinary use in tick control were selected for this study. The plants are Aloe rupestris Baker, Antizoma angustifolia (Burch.) Miers ex Harv., Calpurnia aurea subsp. aurea (Aiton) Benth., Cissus quadrangularis L., Clematis brachiata Thunb., Cleome gynandra L., Ficus sycomorus L., Gnidia deserticola Gilg., Hypoxis rigidula Baker var. rigidula, Maerua angolensis DC., Monsonia angustifolia E. Mey. ex A.Rich., Pelargonium luridum (Andrews) Sweet, Ptaeroxylon obliquum (Thunb.) Radlk, Schkuhria pinnata (Lam.) Kuntze ex Thell., Sclerocarya birrea (A.Rich.) Hochst., Senna italica subsp. arachoides (Burch.) Lock. and Tabernaemontana elegans Stapf. Crude extracts of the above mentioned plants were prepared using four different solvents (acetone, ethanol, ethanol/water and hot water). The extracts at a concentration of 200 mg/ml were screened for their acaricidal efficacy against adult Rhipicephalus turanicus ticks using the contact assay. The plant species with the highest acaricidal efficacies for their acetone and ethanol extracts were C. aurea, S. pinnata and S. italica with mortality of 97, 93, 90% and 93, 93, 87% respectively. The ethanol/water and hot water extracts of many of the plants had low acaricidal activities (<60%). An acaricidal dose-response bioassay of two-fold graded decreasing concentrations (100 to 3 mg/ml) of the acetone and ethanol extracts of S. pinnata, C. aurea and S. italica was determined using the adult immersion tests. The LC50 values for the acetone extracts were 35.75, 111.24 and 42.05 mg/ml respectively and for the ethanol extracts were 37.07, 98.69 and 37.50 mg/ml respectively compared with the positive control (cypermethrin) with LC50 of 2.41 mg/ml. In order to evaluate the potential safety of these plants, cytotoxicity against Vero and HepG2 cells was determined. Most of the plant extracts were non-cytotoxic to the two cell lines (LC50>100 μg/ml) and there was a statistically significant higher toxicity to HepG2 cells compared with Vero cells. The ethanol/water and hot water extracts of most of the plants were less toxic to the cells (LC50>1000 μg/ml) compared with their acetone and ethanol extracts. The selectivity indices of S. pinnata, C. aurea and S. italica were low. Particularly good acaricidal activities were displayed by C. aurea subsp. aurea extracted using four different solvents on R. turanicus ticks. The plant extract also had lower cytotoxicity against the cell lines tested and was selected as the most promising plant species, based on its efficacy and potential safety for further studies. / Thesis (PhD)--University of Pretoria, 2017. / Paraclinical Sciences / PhD / Unrestricted

The aim of this study was to investigate if a vaccine can be developed against epoxyscillirosidine, to prevent yellow tulp poisoning in livestock. Moraea pallida Bak. (yellow tulp) poisoning is the most important cardiac glycoside toxicosis in ruminants in South Africa. Cardiac glycoside poisonings collectively account for about 33 and 10% mortalities due to plants, in large and small ruminants, respectively. The toxic principle contained by yellow tulp 1α, 2α-epoxyscillirosidine, is a bufadienolide. Epoxyscillirosidine, proscillaridin and bufalin, were conjugated to [hen ovalbumin (OVA), bovine serum albumin (BSA) and keyhole limpet haemocyanin (KLH)]. Adult male New Zealand White rabbits were vaccinated in 3 trials. In trial 1 (T1) and 2 (T2), experimental (n=7) and control (n=5) animals were vaccinated with epoxyscillirosidine-OVA (0.4 mg/rabbit) and OVA (0.8 mg/rabbit), respectively. In T1 Freund’s (complete and incomplete) and in T2 Montanide was used as adjuvant, respectively. In Trial 3 (T3), five equal groups of 3 animals each, were vaccinated with proscillaridin-BSA (group 1), bufalin-BSA (group 2), epoxyscillirosidine-KLH (group 3), epoxyscillirosidine-BSA (group 4) and BSA (group 5), with Montanide as adjuvant, on days (D) 0, 21 and 42 (0.8 mg/rabbit, intradermally). Blood was collected before each vaccination and at 3 weeks after the last vaccination. Antibody response was determined using an indirect ELISA. There was a poor immune response associated with the dose and/or adjuvant in T1. However, after increasing the dose of the immunogen to 0.8 mg (per rabbit) and changing the adjuvant to Montanide, in T2 and T3, antibodies against the conjugates were successfully raised. In T3, epoxyscillirosidine-KLH (group 3) induced the highest immune response. Furthermore, proscillaridin and bufalin antibodies cross-reacted with epoxyscillirosidine and its OVA conjugate in the ELISAs. Preparatory to in vitro studies to assess the efficacy of the raised antibodies to neutralize epoxyscillirosidine, a rat embryonic cardiomyocyte (H9c2) cell line was established and the cytotoxic effect of epoxyscillirosidine was determined. Cells (10 000/well) exposed to epoxyscillirosidine (10–200 μM) for 24, 48 and 72 h were evaluated using 3-(4,5- dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and the lactate dehydrogenase (LDH) assays. Cells (100 000/well) exposed to epoxyscillirosidine (40–200 μM, for 24, 48 and 72 h), were processed and viewed with a transmission electron microscope (TEM). Cell viability indicated a hormetic dose/concentration response, characterized by higher viability (relative to control) at low doses (10–40, 10 and 10–20 μM for 24, 48 and 72 h, respectively) and decreased viability at higher doses. The cytotoxic effect and ultra-structural changes were dose and time dependent. Numerous cytoplasmic vacuoles, karyolysis and damage to the cell membrane, indicative of necrosis, were observed. The animal vaccination trial was scaled up, to generate more antibodies, for the in vitro neutralization studies. Six, adult Mutton Merino whethers were vaccinated with epoxyscillirosidine-KLH (2 mg subcutaneously), on D0, 21 and 42. Immune response was determined with an indirect ELISA. Antibodies were concentrated and purified using ammonium sulphate precipitation, before evaluation of in vitro neutralization efficacy. There was no significant (p > 0.05) difference in viability, between cells exposed to a pre-incubated solution of antibodies and epoxyscillirosidine and the epoxyscillirosidine exposed control cells. The antibodies failed to neutralize the toxic effect of epoxyscillirosidine. In conclusion, conjugated epoxyscillirosidine was an effective immunogen following conjugation to carrier proteins and antibodies were raised in vaccinated animals. Although antibodies against epoxyscillirosidine-KLH were raised in sheep, they failed to neutralize the toxin in the in vitro H9c2 cell model. This is possibly because higher ratios of antibodies to toxin are needed to effectively neutralize epoxyscillirosidine than those used in this study. Since antibodies failed to neutralize epoxyscillirosidine in the current study, further studies could optimize the vaccine to produce more specific antibodies with stronger affinity and avidity to be able to neutralize epoxyscillirosidine. Furthermore, the antibody purification method could be adjusted or changed for optimal results in the future. Antibodies against the related commercially available bufadienolides, namely proscillaridin and bufalin, cross-reacted with epoxyscillirosidine and could be investigated in future studies to prevent yellow tulp poisoning by vaccination. / Thesis (PhD)--University of Pretoria, 2018. / Paraclinical Sciences / PhD / Unrestricted

Ticks and tick borne diseases remain a huge threat to livestock productivity the world over. While several efforts have been made to control ticks, current control measures are still not adequate. Conventionally, tick control programmes are heavily reliant on the use of synthetic chemical acaricides while the impact of other less frequently used control methods has not been fully established. Unfortunately, heavy chemical use has led to a number challenges that include: unsustainable high costs of acaricides, development of tick resistance, environmental pollution, contamination of animal products with chemical residues and many other topical issues. Ethnoveterinary plants are however an alternative but possibly effective, environmentally benign and safe option that can complement and in some cases substitute synthetic chemical acaricides. In this study, plant species identified in Zimbabwe and found elsewhere in southern Africa were characterised for anti-tick properties with the aim of developing an ethnobotanical product for use. The initial step involved the identification of plants through an ethnobotanical survey carried out in 4 arid and semi-arid districts of Zimbabwe, namely Muzarabani, Chiredzi, Matobo and Kadoma. These areas were purposively selected on the basis of high cattle production and high likelihood of use of traditional practices in primary animal health care. More than 51 plant species were recorded and a ranking according to frequency of mention showed that Cissus quadrangularis, Aloe sp., Lippia javanica and Psydrax livida were the most popular plants mentioned by farmers. The most common method for preparation was crushing and soaking in water before spraying the animals. Despite the farmers acknowledging that they had access challenges to the normal government-provided dipping services and having knowledge on traditional practices of tick control, the actual use of these practices was low. It was concluded that farmers and other knowledgeable people do have plants they know that have anti-tick properties, thus providing a good basis for the development of ethno-based tick control products. In order to confirm farmer claims of efficacy of the plant extracts and to find ways of increasing that efficacy, three in vitro screening experiments were done using the modified Shaw Larval Immersion Test on Rhipicephalus (Boophilus) decoloratus tick larvae. Different extraction methods were used in the screening: crude water extracts, acetone extracts and solvent – solvent fractions of acetone extracts of Maerua edulis. Results showed that contrary to the high activity reported by farmers in the surveys, water extracts were not toxic to the tick larvae. Perhaps the high activity reported by farmers, if confirmed may be associated with the repellence of volatile emissions from the plants. The addition of a liquid soap as a surfactant however increased the efficacy of the M. edulis tuber aqueous extract to activity levels comparable with those of an amitraz-based commercial acaricide, which was the positive control. The use of the organic solvent acetone as an extractant markedly increased the efficacy of 13 of the plant species under study, particularly M. edulis, Monadenium lugardae and Kleinia species. The chloroform and hexane fractions from M. edulis exhibited very high activity, possibly indicating that less-polar compounds are responsible for the observed activity. Thus, the use of water as a sole extractant is limited in terms of extracting compounds active against ticks, but organic solvents and acetone in particular increase the efficacy of the extracts. In the case of M. edulis less polar extracts and fractions were most active against the ticks. Because Maerua edulis consistently showed good activity in all prior testing, it was further tested using low-cost optimisation strategies like the use of hot water, a surfactant and a different organic solvent (methanol). Hot water extraction and use of a surfactant increased efficacy of the crude extracts of the M. edulis leaves against ticks to satisfactory levels compared to cold water extracts. There was no significant difference between the positive control and methanol-extracted M. edulis. It is, however, the use of ordinary soap that may bring relief to rural farmers who are generally unable to have access to organic solvents. From the observation that the hexane and chloroform extracts of the M. edulis leaf and roots were very active against the ticks, cytotoxicity of the extracts on African Green monkey kidney (Vero) cells and bovine dermal cells was determined to shed some preliminary insights on safety aspects of the plant. Neither extract had high toxicity against these cell lines. The LC50 was greater than 20 _g/ml which is considered as a maximum threshold for indicating toxicity of plant extracts. After confirmation that non-polar fractions of M. edulis were active against ticks and that cytotoxicity results showed that the extracts are relatively non-toxic to animal cell lines, attempts to isolate and identify the active compounds in the chloroform fractions of M. edulis were made without much success. Using column chromatography, an impure compound was isolated in the chloroform fraction but the amount was too low for characterisation by NMR. When the compound was analysed using Gas Chromatography-Mass Spectrometry, a number of chemicals in the isolate were avident but which did not have the pre requisite high similarities with the compound library to be considered. Because of the low quantities no further work was done to further purify and test the compounds against the ticks. For purposes of confirming laboratory activity under field conditions, M. edulis, C. quadrangularis and Aloe vera crude water extracts combined with a surfactant (liquid soap), were tested on Mashona cattle at Henderson Research Station (Zimbabwe) over 7 weeks during the period of peak tick infestation. Only M. edulis tuber extracts with a surfactant were as effective as the amitraz-based positive control. There was no significant difference in activity between the other plant extracts and the negative control. It can be concluded that there is scope to use M. edulis tubers extracted with locally available surfactant as a tick control product. This whole study therefore shows that ticks can be controlled using locally available plant materials provided they are prepared and applied properly. While the overall aim of the study of producing a working plant based tick control product was not met, there is sufficient data from the study to justify developing crude formulations from M. edulis that can be used to control ticks. / Thesis (PhD)--University of Pretoria, 2019. / Paraclinical Sciences / PhD / Unrestricted

No description available.

Doctor of Philosophy / Department of Anatomy and Physiology / Frank Blecha / L Tonatiuh Melgarejo / Background - Cardiovascular disease (CVD) impacts the lives of millions, and ranks as the number one killer world-wide. Despite significant research efforts, CVD remains a major burden on the national health care system, and novel therapeutic modalities to effectively and curatively fight many debilitating diseases of the heart and vasculature are urgently needed. The role of inflammation in the development of CVD has been increasingly in focus through the past decade. Elucidating upon the plethora of innate immune mechanisms likely involved in CVD therefore becomes of immediate interest. Host defense peptides (HDPs) are central elements of innate immunity, encompassing molecules (including the defensin peptides) with wide-reaching biological effects, including immunomodulation and antimicrobial activity. Hypothesis & Specific Aims - The study's main hypothesis relies upon the basic concept that the heart possesses a local innate defense system, which actively aids in fighting off a variety of "danger signals", and that a disarray in this defense contributes to development of CVD. The heart expresses beta-defensin peptides (BDs), and we theorized that these HDPs act as a local defense system within the myocardium - or in other words as "guardians of heart health". The specific aims of the experimental studies were to 1) Evaluate expression of cardiac BDs in response to inflammatory mediators, and 2) Assess the functional properties (including antimicrobial activity and immunomodulation) of synthetic BD peptides in vitro. Design & Methods - To test our hypothesis, we studied myocardial beta-defensin expression (rBDs) in a rat model, comparing levels among two experimental and one control group. Animals were exposed to lipopolysaccharide (LPS) or high-fat diet (HFD) intake - representative of exposure to either an infectious (LPS) or non-infectious (HFD) inflammatory mediator. Serum samples were collected for measurement of cytokines, inflammatory and cardiac biomarkers and lipid-profiling. Beta-defensin levels were assessed using customized Superarray assays and qRT-PCR, and all amplicon sizes on the PCR products were subsequently confirmed using agarose gel electrophoresis. Serum levels were assessed on commercial ELISA kits. Functional assessment of select rBDs included computational modeling as well as in vitro antimicrobial and cell migration assays. Results & Conclusion - Exposure to high-fat diet feeding for a period of three weeks resulted in a multifold-increase in cardiac mRNA expression of select rBDs, while short-term LPS exposure resulted in a smaller, but statistically non-significant, elevation in the myocardial expression of rBDs. Synthetic analogues of two naturally occurring cardiac rBDs were evaluated for in vitro activity. The synthetic rBD11 peptide exhibited antimicrobial activity against Staph aureus, and both rBDs exhibited chemoattraction of rat leukocytes. Our data suggests that rBDs might play a central role in the intrinsic immune mechanisms of the cardiovasuclar system, and possibly act as protectors of heart health.

No description available.