Browsing by Author "Fisher, David"
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Item Carica papaya seed extract slows human sperm(Elsevier, 2019) Ghaffarilaleh, Vahid; Fisher, David; Henkel, RalfEthnopharmacological relevance: Traditional healers use Carica papaya seeds as a remedy for diseases and as a contraceptive for men and abortion in women. Material and methods: Semen samples from 35 healthy men were allowed to liquefy and subsequently incubated for 60 min in Human Tubular Fluid medium containing 1% bovine serum albumin with aqueous C. papaya seed extract at concentrations of zero, 0.025, 0.25, 2.5, 25, 250 and 2500 μg/ml. Afterwards, sperm were washed and used for assessment of capacitation and acrosome reaction, DNA fragmentation, vitality, motility, reactive oxygen species (ROS) and mitochondrial membrane potential (MMP). Results: The extract showed no effects on straight-line velocity, linearity, straightness, beat-cross frequency and the percentage of capacitated, acrosome-reacted sperm. In contrast, vitality, total motility, progressive motility, curvilinear velocity, average-path velocity and the percentages of hyper-activated, ROS-positive and MMP-intact sperm decreased significantly (P < 0.05), while the percentage of DNA-fragmented sperm increased (P < 0.05). Conclusions: Our data show that aqueous C. papaya seed extract significantly and negatively affects sperm motility parameters crucial for fertility; and thus, poses as a likely candidate for male contraception.Item Differential effects of normoxic versus hypoxic derived breast cancer paracrine factors on brain endothelial cells(MPDI, 2021) Rado, Mariam; Flepisi, Brian; Fisher, DavidThe blood-brain barrier (BBB) is a central nervous system protective barrier formed primarily of endothelial cells that regulate the entry of substances and cells from entering the brain. However, the BBB integrity is disrupted in disease, including cancer, allowing toxic substances, molecules, and circulating cells to enter the brain. This study aimed to determine the mitochondrial changes in brain endothelial cells co-cultured with cancer cells. Method: Brain endothelial cells (bEnd.3) were co-cultivated with various concentrations of breast cancer (MCF7) conditioned media (CM) generated under normoxic (21% O2 ) and hypoxic conditions (5% O2 ). The mitochondrial activities (including; dehydrogenases activity, mitochondrial membrane potential (∆Ψm), and ATP generation) were measured using Polarstar Omega B.M.G-Plate reader. Trans-endothelial electrical resistance (TEER) was evaluated using the EVOM system, followed by quantifying gene expression of the endothelial tight junction (ETJs) using qPCR. Results: bEnd.3 cells had reduced cell viability after 72 h and 96 h exposure to MCF7CM under hypoxic and normoxic conditions.Item Exosomes form tunneling nanotubes (TUNTs) in the blood-brain barrier: A nano-anatomical perspective of barrier genesis(Frontiers Media, 2022) Mentor, Shireen; Fisher, DavidThe blood-brain barrier (BBB) is a robust interface between the blood and the central nervous system. Barrier type endothelium is able to limit paracellular (PC) movement, relegating molecular flux to the transendothelial pathways of brain endothelial cells (BECs). It is, therefore, apparent that any leakage via the PC shunts would effectively nullify the regulation of molecular flux across the transcellular pathways. The application of higher-resolution scanning electron microscopy (HR-SEM) illuminates the heterogenous, morphological profile that exists on the surface of BEC membranes and the relationship between these ultrastructures during the molecular construction of the PC space between adjacent BECs. In this study developing BEC monolayers were grown on mixed, cellulose esters insert membranes in a bicameral system.Item Face-to-face versus online-based lectures: A covid-19 induced study on assessments(Frontiers Media, 2022) Fisher, David; Solomons, Deon; Makhathini, Khayelihle BrianThere is much debate regarding the impact of COVID-induced lockdown on the standard of assessments, mainly since students were assessed at home via an online assessment platform. Regular orthodox lectures and assessments were carried out during the first term, while the strictly enforced South African COVID lockdown warranted that 2nd term lectures and assessments were based online. This created the fortunate control conditions to statistically compare orthodox face-to-face with online-home-based assessments.Item High-resolution insights into the in vitro developing blood-brain barrier: Novel morphological features of endothelial nanotube function(Frontiers Media, 2021) Mentor, Shireen; Fisher, DavidHigh-resolution electron microscopy (HREM) imaging of the in vitro blood-brain barrier (BBB), is a promising modality for investigating the dynamic morphological interplay underpinning BBB development. The successful establishment of BBB integrity is grounded in the brain endothelial cells (BEC’s) ability to occlude its paracellular spaces of brain capillaries through the expression of the intercellular tight junction (TJ) proteins. The impermeability of these paracellular spaces are crucial in the regulation of transcellular transport systems to achieve homeostasis of the central nervous system. To-date research describing morphologically, the dynamics by which TJ interaction is orchestrated to successfully construct a specialized barrier remains undescribed. In this study, the application of HREM illuminates the novel, dynamic and highly restrictive BEC paracellular pathway which is founded based on lateral membrane alignment which is the functional imperative for the mechanical juxtapositioning of TJ zones that underpin molecular bonding and sealing of the paracellular space.Item The Ism between endothelial cilia and endothelial nanotubules is an evolving concept in the genesis of the BBB(MDPI, 2022) Mentor, Shireen; Fisher, DavidThe blood–brain barrier (BBB) is fundamental in maintaining central nervous system (CNS) homeostasis by regulating the chemical environment of the underlying brain parenchyma. Brain endothelial cells (BECs) constitute the anatomical and functional basis of the BBB. Communication between adjacent BECs is critical for establishing BBB integrity, and knowledge of its nanoscopic landscape will contribute to our understanding of how juxtaposed zones of tight-junction protein interactions between BECs are aligned. The review discusses and critiques types of nanostructures contributing to the process of BBB genesis. We further critically evaluate earlier findings in light of novel high-resolution electron microscopy descriptions of nanoscopic tubules.Item The paracrine effect of hypoxic and normoxic cancer secretion on the proliferation of brain endothelial cells (bend.3)(MDPI, 2022) Rado, Mariam; Fisher, David: Background: This study aimed to investigate the disruption of cell cycle phases of bEnd.3 cells exposed to cancer paracrine secretion. Cancer cells have been reported to use the secretion of paracrine factors to compromise the endothelial barrier to prepare for their passage into the parenchyma. As cancer cells are known to act differently under conditions of hypoxia, we investigated how conditional media (CM) derived from breast and glioblastoma cells incubated under conditions of normoxia and hypoxia would affect proliferation of brain endothelial cells (bEnd.3). Methods: Brain endothelial cells (bEnd.3) were cultivated with normoxic and hypoxic CM generated from breast cancer MCF7 cells and glioblastoma U-87 cells. Cell proliferation was evaluated using the trypan blue exclusion assay and phases of the cell cycle were evaluated using flow cytometry. Results: bEnd.3 proliferations was suppressed more aggressively with hypoxic CM after 72 and 96 h; cell cycle analysis showed that paracrine treatment tended to prevent BECs from entering the G2 phase, thus suppressing cell division.Item The relationship between seminal leukocytes, oxidative status in the ejaculate, and apoptotic markers in human spermatozoa(Taylor & Francis, 2013) Mupfiga, Cleyson; Fisher, David; Kruger, Thinus; Henkel, RalfThe aim of this study was to investigate the relationship between seminal leukocytes, reactive oxygen species (ROS) production in the ejaculate, and markers of apoptosis in human spermatozoa. Semen samples were collected from 60 patients attending fertility clinics at the Reproductive Biology Unit at Tygerberg Academic Hospital and Vincent Pallotti Hospital, Cape Town, South Africa. The concentration of seminal leukocytes was determined and was correlated with ROS production in the ejaculate, the percentage of superoxide (·O2 )- and hydrogen peroxide (H2O2)-positive spermatozoa, glutathione activation in the ejaculate, and with markers of apoptosis in spermatozoa, namely cysteine-dependent aspartate-directed proteases (caspase)-3/7 activation, mitochondrial membrane potential (ΔΨm), and the percentage of terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL)-positive sperm. Significant correlations with the concentration of seminal leukocytes were found for ROS production in the ejaculate, the percentage of ·O2 -positive spermatozoa, and caspase-3/7 activation in the ejaculate. Leukocytospermic samples showed significantly higher ROS production, percentage of ·O2 -positive sperm, GSH activation, and caspase-3/7 activation compared to non-leukocytospermic samples. The percentage of ·O2 -positive sperm was significantly correlated with sperm ΔΨm and caspase-3/7 activation in the ejaculate. Sperm ΔΨm and TUNEL-positive sperm did not correlate with seminal leukocyte concentration. Data demonstrate that high seminal leukocyte concentrations that leads to increased seminal ROS production, and is also associated with caspase activation in the male germ cell and increased mitochondrial ROS production. The latter could possibly be a result of disturbed ΔΨm. The activation of caspase-3/7 could then follow the increased intrinsic superoxide levels due to depleted intrinsic glutathione (GSH). These cellular events might not directly and immediately lead to DNA fragmentation as an endpoint of apoptosis because of topological hindrances.