Browsing by Author "Fisher, D"

Now showing 1 - 5 of 5
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    An electrophysiological exploration into the Sertoli cell, utilizing plant extracts with a view to contraception
    (University of the western cape, 2003) Mosoval, Faisel; Fisher, D; Johnson, Q
    Certa in medicinal plant extracts have been shown to have a contraceptive effect on male rats (Rajasekaran et al. , 1988) and mice (Kong et al., 1986). A possible site for the mechanism of action has been identified as the testis. The Sertoli cell s within the seminiferous tubules of the teste s are of fundamental importance to the developing sperm. These cells create a unique environment, which, without, would lead to the cessation of spermatogenesis (Gow et al. , 199 9). Know ledge of the Sertoli cell is thus essential in understanding the control of developing germ cells within the seminiferous tubules of the testis.
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    Face-to-face versus online-based lectures: A COVID-19 induced study on assessments
    (Frontiers in Education, 2022) Fisher, D
    The students were found to be resilient in adapting to things and learning, online presentations, and computer-based assessments. No gender-based difference or advantage to adjusting to newly introduced blended learning and concomitant changes in learning assessment strategies was found. The online-home-based assessments proved to incentivize prior learning and preparation for assessments by implementing strict time limits or assessments and randomizing the selections of questions and respective (MCQ) answer choices.
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    In vitro effects of rooibos herbal tea (Aspalathus linearis) against methamphetamine on the mouse blood brain barrier
    (University of the Western Cape, 2014) Prinsloo, Tarryn Kay; Fisher, D; Gamieldien, K
    Methamphetamine (MA), also known as ‘Tik’, has detrimental short- and long-term psychological and morphological effects on the central nervous system (CNS). The lipophilic nature of MA allows it to cross the blood-brain barrier (BBB) which normally plays a protective role in limiting solute exchange (including narcotics) into the neuronal tissue. Numerous studies have indicated that MA not only crosses the BBB but is implicated in distorting its crucial role in that it increases the permeability of the endothelial cells and thereby compromises its core homeostatic function. The speculated mechanism by which MA elicits its effects involves elevated ROS production which may be reversed by antioxidant treatment. Rooibos herbal tea (Aspalathus linearis) which is well documented for its antioxidative properties and ROS scavenging abilities may therefore be the ideal candidate to reverse the harmful ROS-induced effects of MA. The aim of the study was to investigate the in vitro ameliorating potential of fermented rooibos (Rf) against the MA-induced effects on mouse brain endothelial (bEnd5) cells by utilizing various assays (trypan blue exclusion and XTT viability assays) and physiological parameters (cell numbers, viability, monolayer permeability and cell cycle phases) over a period of 96 hrs. Statistical analysis was performed using the Wilcoxon rank sum test with P<0.05 denoted as significant. Once-off exposure to physiological MA concentrations and Rf resulted in % viability similar to controls by 96 hrs with suppression observed only when the cells were exposed to daily MA (0.1-1000 μM) (P≤0.0063). Exposure to supraphysiological concentrations (≥100 μM) of MA greatly suppressed viability (P≤0.0463). Both daily and once-off treatment to the combinations initially resulted in increased viability however by 96 hrs was similar to- or exceeding the controls (P≤0.0180). MA exposure also resulted in decreased live cell numbers (P≤0.0339) with no effect when exposed to Rf by 96 hrs. The combinations resulted in cell numbers comparable to controls. Dose-dependent increases in electrical resistance were observed in response to singular MA and Rf treatment with lower MA concentrations displaying significant decreases (P≤0.0064). Similar trends were observed with combinations however greater resistance was observed. Increased G1-phase populations (P≤0.0495) in response to singular MA and Rf exposure was noted followed by decreased S-phase fractions (P≤0.0356). While MA decreased G2-M phase cells (P≤0.0498) it was unaffected by Rf. In contrast, the combination of MA and Rf decreased events in the G1-phase (P≤0.0483), with an increased S-phase population (P≤0.0415). In conclusion, the single compounds displayed mirroring effects, decreasing the cells’ permeability and causing G1-phase arrest. The modulatory effects of Rf in combination with MA was illustrated with the restoration of viability and live cell numbers comparable to that of controls, and a more restrictive monolayer as well as reversal of the G1-phase arrest. Findings suggest that Rf may reverse the adverse effects of MA on the BBB.
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    In vitro modulatory effects of fermented rooibos extract (Aspalathus linearis) against ethanol-induced effects on the mouse blood-brain barrier
    (University of the Western Cape, 2014) Mentor, Shireen; Fisher, D; Cummings, F.; Gamieldien, K.
    Alcohol abuse is a growing crisis within South Africa, with severe health and socio-economic implications. Alcohol compromises the function of the blood-brain barrier (BBB), and thus its ability to regulate the homeostatic environment of the CNS is interrupted. In this study, an in vitro model of the BBB was utilized to study the effects of selected concentrations of alcohol (25mM-200mM) and the ameliorating effects of fermented rooibos (Aspalathus linearis) (0.003125%-1%), in an attempt to reverse the harmful oxidative effects of alcohol. The literature clearly states that alcohol (ethanol) compromises the BBB by reactive oxygen species (ROS) production and, therefore, rooibos, a shrub high in antioxidants and widely utilized nationally, was added to alcohol-exposed mouse brain endothelial (bEnd5) cells with the view to reverse the alcohol-induced effects on the BBB model. Alcohol-treated (25mM-400mM) bEnd5 monolayers expressed no toxicity, however, cell numbers were significantly suppressed (P<0.0274). To validate this finding, the activity of the mitochondria was investigated in order to understand if the cell’s metabolism was related to the decrease in cell division. Results showed that for both acute and chronic exposure there was a decrease in mitochondrial activity (MA) for a period of 24-48 hours, thereafter, the MA of the bEnd5 cells returned to normality. However, in experiments which chronically (600mM and 800mM) exposed cells to alcohol over a period of 96 hours, MA was suppressed and did not return to normal. Fermented rooibos caused a biphasic response to cellular proliferation at 24-72 hours, where the lower concentrations (0.0625-0.125 %) caused an increase in cellular proliferation and the higher concentrations (0.5-1%) resulted in a relative decrease in cellular proliferation. The long-term effect, after acute exposure, however, resulted in cell suppression at 96 hours (P<0.0073). With respect to the MA, bEnd5 cells exposed to fermented rooibos showed that lower concentrations (0.003125-0.0125%) were suppressed at 24 hours and was elevated at 48 hours and96 hours for all concentrations. The exception being the highest concentration (0.1%), which showed a depression in MA (P<0.05). Treating cells with both alcohol and rooibos, resulted in exacerbated suppressing of the MA. The physiological function of the BBB model was investigated by monitoring the permeability using transendothelial electrical resistance (TEER) studies and the in vitro model used in this study was endorsed for the first time using high resolution scanning electron microscopy. TEER indicated incidental changes in the permeability, only at 24 hours, for both acute and chronic exposure to alcohol and rooibos. A novel finding, within this study, was the increase in electrical resistance across the formation of the cell monolayer, after treatment with alcohol. The data lead to the hypothesis for the effect of ROS on resistivity and provides a rationale to explain the effects of combinatory treatments that were expected to ameliorate the negative effect of alcohol, however, this study showed synergistically negative effects on the bEnd5 cells. In summary the main findings in this study were: (a) alcohol was not toxic on bEnd5cells, (b) alcohol increased the permeability across monolayers of bEnd5 cells and(c) rooibos did not significantly reverse the ROS-induced effects of alcohol, but exacerbated the effects. Rooibos treatment caused the following: (i) biphasic effect on cellular proliferation, (ii) an increase in MA, and (iii) a cyclic effect in TEER studies.
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    The role of infections and leukocytes in male infertility
    (Blackwell Publishing Ltd, 2021) Henkel, R; Offor, U; Fisher, D
    Declining birth rates are one of the problems facing society today. Male counterparts are responsible for about half of the infertility cases, and genitourinary tract infections may play a contributing role in approximately 15% of male infertility cases. Leukocytospermia is an established indicator of infection in the male urogenital tract, although other microorganisms such as bacteria and virus may also be contributors to the etiology of male infertility. The pathophysiology of these infectious agents may be initiated by a local inflammatory reaction resulting in an increase in reactive oxygen species (ROS). This results in testicular injury, thereby affecting sperm morphology, sperm motility, sperm viability and elevation of the seminal leukocyte as a result of the genital tract infection. The infectious and inflammatory changes can result in male infertility. It is proposed that high concentrations of seminal leukocyte and infectious agents may affect sperm function resulting in clumping of motile spermatozoa, decreasing acrosomal functionality and also causing alterations in sperm morphology.