Magister Scientiae - MSc (Medical BioSciences)

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The antioxidant potential of indigenous herbal extracts and their antimicrobial effect on human keratinocytes
(Universty of the Western Cape, 2023) Mpeke, Dimpho; Rahiman, Farzana
Medicinal plants are rich sources of antioxidants and due to their many biological properties, are used in the treatment and prevention of many skin-related conditions as alternative therapy to replenish and improve the skin’s barrier functions. Plant extracts produce secondary metabolites, known as phytochemicals which play an important role in their growth and development. These phytochemicals possess strong antioxidant and antimicrobial activities. Reactive oxygen species (ROS) play a pivotal role in the development of several allergic or inflammatory skin diseases. Antioxidants have the potential to counteract these ROS-induced effects, protecting the skin against free radicals. The purpose of this study was to determine the antioxidant potential of the hydroethanolic extracts of Galenia africana, Kigelia africana and Lessertia frutescens and their effect on the antimicrobial skin barrier.
To explore the effect of prednisolone on blood-brain barrier endothelial cells treated with lipopolysaccharides.
(Universty of the Western Cape, 2024) Siebrits, Michaela Nicole; Makhathini, Khayelihle Brain
The blood-brain barrier (BBB) is primarily regulated by highly selective endothelial cells. Inflammation of the brain capillaries can compromise the BBB’s functioning. Methylprednisolone (M-Pred), a synthetic glucocorticoid, is generally prescribed to treat inflammation, though little is known of its effect on inflamed brain capillaries. This study evaluated the effectiveness of M-Pred in ameliorating the LPS-induced inflammatory response in the in vitro BBB model. Cultured brain endothelial cells (bEnd.3) were exposed to LPS (500, 1000, 2000 ng/ml) and co-treated with selected concentrations of M-Pred (10, 20, 40 μM). Cell viability, cell toxicity, and cell proliferation, bEnd.3 monolayer permeability (Transendothelial Electrical Resistance) were investigated, while ELISA kits were used to quantify pro-inflammatory cytokines, TNF-α and IL-1β.
The development of a sars-cov-2 pseudoparticle assay for the detection of neutralizing antibodies in sera from covid-19 patients
(University of the Western Cape, 2024) Daniels, Ame-Leigh; Shaw, Megan L.
The COVID-19 pandemic has caused devastating effects on the global socio-economic landscape. Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is the causative agent of COVID-19, and infections have led to approximately 7 million fatalities worldwide. Previous findings have confirmed that neutralizing antibodies are a highly predictive measure of immune protection. Thus, measuring SARS-CoV-2 neutralizing responses after infection or vaccination remains a priority, especially in the event of newly emerging SARS-CoV-2 variants. Due to the limitations of working with live virus in a BSL3 facility, pseudoparticles are an alternative tool used to study viral surface proteins. This research aims to develop a SARSCoV-2 pseudoparticle system to detect neutralizing antibodies in sera from previously infected or vaccinated individuals. The use of vesicular stomatitis virus (VSV) as a vector for the pseudoparticle system, provides several advantages over the lentivirus system including faster assay time, and lack of interference from antiretroviral drugs present in sera from HIVpositive patients on antiretroviral therapy (ART). The latter is particularly relevant in South Africa where there are more than 7.8 million HIV people living with HIV. After generating VSV pseudoparticles bearing the SARS-CoV-2 spike from the Wuhan/D614G, Beta, Delta and Omicron variants, a neutralizing assay was optimized using characterized human monoclonal antibodies. The assay was then applied to a sample set of patient sera and the ID50 values were compared to those obtained using a lentivirus-based SARS-CoV-2 neutralization assay. The comparison highlighted a strong concordance between the VSV and lentivirus neutralization assays particularly for the Wuhan/D614G and Omicron variants. The findings indicate that the development of a VSV-based neutralization assay is a valuable contribution to our ongoing efforts to characterize protective immune responses arising from SARS-CoV-2 infection or vaccination.
The phenomenon of skin lightening among young adults, and the effect of selected plant extracts on tyrosinase and melanogenesis activity
(University of the Western Cape, 2023) Opperman, Laurentia Joan; Rahiman, F Fisher
Skin lightening practice refers to the use of skin lightening products to achieve a fairer skin complexion. This is common practice among people of several Asian, North American, South American countries. On the African continent, the practice is popular in countries such as Nigeria, Togo, Senegal, Mali and South Africa. It has been reported that skin lightening products contain dangerous chemicals such as hydroquinone, mercury and steroids. The chronic use of these chemicals can lead to severe adverse effects such as skin irritations, skin infections and skin damage. Despite the health risks associated with this practice, demand and prevalence is on the rise as the global skin lightening industry is estimated to be worth USD 24 billion by 2027 and, thus, arises the need to identify less toxic alternatives. Africa`s forests are known as the world`s second largest tropical reservoir and holds significant biodiversity resources in which only 10.8% of its flora is known to be applied in traditional medicine. As the use of skin lightening agents are accompanied with the emergence of several complications, several studies have shown the use of natural plant extracts as a potential alternative with limited side effects to current synthesized skin lightening products. Plants are well known as an alternate treatment option for various ailments and the diversity of plants used in traditional medicine globally has been estimated between approximately 10 000 to 53 000 species. Considering the growing demand of skin lighteners which lead to an increase in the emergence of side effects and the alternative prospects presented by plant extracts, the overall aim of this study is to investigate the perceptions, knowledge and practice of skin lightening among young adults ata university within the Western Cape, South Africa. In addition, the study aims to evaluate the potential effect of plant extracts on melanin and enzyme tyrosinase activity on skin cells. The objectives were as follows: 1) to conduct a cross-sectional survey among male and female young adults aged 18 to 30 to explore their perceptions on skin lightening, 2) to conduct a comprehensive literature search on in vitro and in vivo studies to identify plant extracts capable of inhibiting melanogenesis and enzyme tyrosinase activity and 3) to assess the in vitro bio-activity of selected plant extracts on melanocytes.
The effect of doxorubicin encapsulated chitosan alginate nanoparticles and curcumin on multidrug resistant colon cancer cell lines
(University of the Western Cape, 2024) Audrey Masindi, Mutshidzi; Star, Khoza
Purpose: Although chemotherapeutic drugs have improved the survival rate of patients diagnosed with colorectal cancer, resistance to chemotherapy frequently leads to therapeutic failure and poor patient outcomes. Multidrug resistance (MDR) is a serious threat to cancer treatment efficacy and may be linked to the overexpression of drug efflux pumps. P-glycoprotein (P-gp) is a drug efflux transporter that triggers doxorubicin (DOX) resistance. This has led to an interest in chitosan alginate nanoparticles (CANPs) as novel anticancer drug carriers and curcumin (CUR) as an inhibitor of P-gp. Chitosan (CS) and alginate (ALG) are among the most extensively used polymers for nanoparticle (NP) preparation as they possess excellent non-toxic and biodegradable characteristics. The aim of this study was to investigate the effect of DOX encapsulated CANPs and CUR on MDR colon cancer cell lines (Caco-2 cells).
Dexamethasone's impact on LPS-induced inflammation of blood-brain barrier endothelial cells
(University of the Western Cape, 2023) Jeftha, Tershlin; Fisher, David
The blood-brain barrier (BBB) serves as a protective and regulatory barrier between the blood and the brain. Microvascular endothelial cells provide homeostatic regulation of the central nervous system (CNS). BBB integrity is compromised by inflammation, which contributes to a wide range of neurological disorders. It has been shown that glucocorticoids (GCs) have anti-inflammatory functions on a variety of cells. A particular example is Dexamethasone (Dex), which is used for the treatment of inflammatory conditions and has recently been found to be effective in attenuating COVID-19. Aim: The purpose of this study was to determine whether low or high concentrations of Dex can attenuate the inflammatory response induced by LPS on the in vitro BBB model.
In vitro neuroprotective potential of phyllanthin in MPP+- induced toxicity in SH-SY5Y neuroblastoma cells
(University of the Western Cape, 2023) Delport, Joshua; Ekpo, Okobi
Parkinson’s disease (PD) is the second most common age-related neurodegenerative disease after Alzheimer’s disease, with an estimated 9 million people projected to be affected worldwide by the year 2030. PD is associated with numerous motor symptoms such as tremor, bradykinesia (slowness of movements), hypokinesia (reduction in movement amplitude) and akinesia (absence of normal unconscious movements). However, in addition to these motor symptoms, several nonmotor manifestations are common, such as sensory symptoms (pain, tingling), hyposmia, sleep disturbance, depression, and cognitive impairment.
An evaluation of the biopesticidal characteristics of Helichrysum marifolium and Helichrysum patulum and their effects on animal metabolism
(University of the Western Cape, 2002) Speelman, Abigail; Johnson, Quinton
There are a number of pesticides that are suspected to be endocrine disrupters Many of these pesticides are man-made. Endocrine disrupters are chemicals that can lead to an increase in birth defects, sexual abnormalities, and reproductive failure. Marine animals seem to be the most vulnerable to the effects of pesticides since the ocean is the final sink for many pollutants. Endocrine disrupters can exert their effects in many ways. They can either bind to the hormone's receptor and mimic the hormone, or block the action of the hormone' An experiment done of newborn female rats injected with 1mg DDT/day on days 2-4 after birth had early onset of puberty and accelerated loss of fertility. In another experiment, vinclozolin (also a pesticide) at dosage levels of 3mg/kg/day resulted in feminized male rats in the womb, and an abnormal number of nipples were observed (11). Pesticides can be absorbed through the skin, by inhalation or oral ingestion. There are, however, important quantitative differences between the various derivatives. The skin poorly absorbs DDT in solution, whereas dieldrin absorption by the skin is very efficient. The major effects of insecticides in humans are qualitatively similar and cause effects on the central nervous system (9). Endocrine disrupters encompass more than just environmental estrogens and include any agent that adversely affects any aspect of the entire endocrine system. Endocrine disrupters are usually either natural products or synthetic chemicals that mimic, enhance, or inhibit the action of natural hormones (5). Low levels of many endocrine-disrupting chemicals can lead to high levels in the body tissues of animals and humans. This is due to the fact that many endocrine disrupters are stored in fat tissues through biomagnifications (2).
The effects of doxorubicin loaded chitosan-alginate nanoparticles on SK-N-BE(2) neuroblastoma cells
(University of the Western Cape, 2022) Rahman, Ziyaad; Hiss, Donavon
Cancer is a life-threatening disease and one of the leading causes of death globally. Cancer was thought to be associated with developed countries only but it is increasingly becoming a major health challenge in developing countries, including South Africa. Neuroblastoma is a form of cancer that affects the very early forms of nerve cells and is the most common extra-cranial solid tumour in children. It develops mainly in the adrenal medulla and the sympathetic ganglia. The focus of the present study is the development of a doxorubicin-loaded nanoparticle drug delivery system for the treatment of neuroblastoma. The biological diversity of the neuroblastic tumours that occur in patients has led to a divided approach in therapeutic strategies. Recent research efforts are aimed at designing therapies that will exploit the key oncogenic features of tumours, either within the tumours, in the tumour microenvironment, or both. Although doxorubicin chemotherapy is known to be generally very effective, previous studies have shown that it may result in the undesired toxicity of cardiomyocytes, cardiac fibroblasts, cardiac progenitor cells, endothelial progenitor cells, smooth muscle cells, and mesenchymal stem cells.
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.
The influence of maternal nicotine exposure on neonatal lung development: An enzymatic and metabolic study
(University of the Western Cape, 1999) Kordom, Chontrelle; Martiz, G.S; de Kock, M
Chapter I, the literature review, gives the reader a sound background knowledge of the following: normal lung structural development in humans and rats, metabolic development with reference to structural development, tobacco smoke and nicotine and the effect of nicotine and smoking on metabolism. This will enable the reader to understand the motivation for this study and to give insight to the following chapters. Chapter II comprises the influence of maternal nicotine exposure on the enzymes, hexokinase and phosphofructokinase. The aim of this study was to determine the influence of maternal nicotine exposure during pregnancy and lactation on the enzymes involved in the control of energy metabolism of developing lungs of rats at postnatal days 1, 7,14,21 and 49. The objectives were to determine the effect of maternal nicotine exposure during gestation and lactation on, (a) the activity of selected allosteric enzymes, hexokinase (HK) andphosphofructokinase (PFK), (b) the influence of various ATP concentrations and ATP/ADP ratios within the reaction medium on the activity of these enzymes and (c) to express the activity of these enzymes as a function of age and (d) to correlate the findings with the stage of neonatal lung structural development as explained in the literature. Female Wistar rats were used in this study. The pregnant rats were randomly assigned as a control and an experimental (nicotine) group. The experimental dams received a single dosage of 1 mg nicotinel/ kg body weight/day subcutaneously and the controls received the same volume of saline. The enzymatic activity was determine by means of spectrophotometery. It was found that HK and PFK activity are age dependent.
The effects of Exomis micriphylla and Atriplex lindleyi on metabolism and health
(University of the Western Cape, 2002) Moses, Cheyrl
For many decades people have used plants for healing various ailments. Plant products have been used in herbal remedies especially for their anti-infective properties. The following study was undertaken to assess the anti-infective value of Atriplex lindleyi and to determine how the plant extract effects metabolism, and health of male rats. Plant anatomy was done to determine which components are present in the plant leaves and to assess which components might be responsible for the production or storage of the chemical products within the leaves that may contain the secondary chemical. The leaves were sectioned using a freeze microtome. Liquid CO2 and Hamilton's freeze solution was used to freeze the plant leaves and sections were made ranging from 15-25 microns. Elemental analysis was also done on the plant material to determine the concentration of selected elements within the plants. The analyses were done using the Unicam Solaar M series atomic absorption spectrometer. Four microbes were used for the antimicrobial screening. Various concentrations of the plant extract was prepared and tested against Staphylococcus aureus (ATCC29213), Pseudomonas aeruginosa (ATCC27853), Mycobacteium smegmatis and Candida albicans (ATCC10231). Amphotericin B served as the positive control for C. albicans whilst Ciprofloxacin was used for the three bacterial strains. Screening was done using the disc diffusion method. Metabolic studies were done on 20 Wistar male albino rats. This was done to assess the metabolic, haematological and histological effects of the herbal extract on the animals. The one component within the leaf that seemed to be most outstanding was the sclereids. Since sclereids have a protective function, it can be speculated that secondary compound storage and/or production might occur at this site, but further studies are required before absolute conclusions can be drawn in this regard. The difference in the elemental concentrations between the soil and plant samples was not statistically significant. The antimicrobial screening showed no herb-induced inhibitory effects on the four selected microbes at either of the extract concentrations used. The metabolic studies showed a significant increase (p<0.05) in urine excretion on days 15 and 45. This significance might indicate that the plant has diuretic properties. There is a significant decrease (p<0.05) in the urine pH values between the control and experimental groups. The urine pH however, remained alkaline. The herbal extract caused a significant decrease (p<0.05) in the Haemoglobin levels. There was a significant increase (p<0.05) in both the mean cell volume (MCV) and Hematocrit percentage of the rats on the herbal extract. The mean cell haemoglobin count (MCHC) significantly decreased (p<0.05) in the rats on the herbal extract. All white blood cell parameters remained (p>0.05).Even though there was no herb-induced effect on the white cell parameters, the decrease in the red blood cell parameter Haemoglobin, may be reason for concern. Histological sections of the liver and testes showed no differences between the control and experimental rat groups. Whilst this medicinal herb showed no antimicrobial effects, it may possibly have diuretic value. Given its favourable safety profile, further studies on this medicinal plant should be pursued even though it had an input on certain blood biochemical indices, all of which though remained within physiologically normal Iimits.
Tumour suppression and subdual of cancer (tussc) in elephants: An in vitro study to shed light on Peto’s paradox
(University of the Western Cape, 2022) Jansen van Vuuren, Amѐlia; de Kock, Maryna
Logic would suggest that cancer incidence is related to body mass and longevity. Gigantic animals such as elephants with a longer lifespan (more lifetime of cell divisions) and a larger body size (more cells) will have more time during their lifetime to accumulate a cancer-causing mutation in comparison to small-bodied, short-lived animals, such as mice. However, several studies and the mere existence of large-bodied, long-lived mammals such as elephants and whales, suggest that there is no correlation between body mass, lifespan and cancer incidence across different mammalian species. This is a phenomenon known as Peto’s paradox. As there is a selection for large body size in evolution, there is likely also a selection for cancer suppression mechanisms that allow an organism to grow large and reproduce successfully. One of the rationales in the African savanna elephant (Loxondonta africana) is the duplication of a crucial tumour suppressor gene (TP53) encoding the tumour protein 53 (p53).
Structural and functional aspects of sperm after transit through the fallopian tube of the sheep
(University of the Western Cape, 1996) Hendricks, Shamila; Van der Horst, G.; Van Niekerk, F.
Ejaculated mammalian spermatozoa have the potential for fertilization. The acquisition of the ability to fertilize a fully invested oocyte occurs during the passage through the female reproductive tract. These post-ejaculatory maturational changes include the processes of capacitation and the acrosome reaction. The Fallopian tube has been accepted as the site of completion of these events while their initiation may occur either in the uterus or in the Fallopian tube. The role and/or interaction of the Fallopian tube with sperm to undergo these molecular events, are poorly understood. This study attempts to demonstrate the influence on sperm of the environment of the Fallopian tube which could initiate certain structural and functional alterations with respect to capacitation and the acrosome reaction; this study does not attempt to define the exact nature of the interaction between spermatozoa and the Fallopian tube. In this study the ur vivo situation is mimicked, exposing sperm to the oviduct under laboratory conditions. Pre- and post-migratory sperm were compared. The specific structural and functional aspects examined in this study include motility, morphology, localization of N-acetyl-D-glucosamine receptors and the acrosomal status. Motility is important to ensure successful migration to the site of fertilization. Special attention was focussed on the incidence of hyperactivation after transit through the Fallopian tube. The term hyperactivation has been used to describe the frantic movement of sperm before they undergo the acrosome reaction and often serves as a biological marker for capacitation. Motility analyses were performed using the CASMA system, the Sperm Motility Quantifier (SMQ). The biological state of hyperactivation occurred in a small population of spermatozoa after transit through the Fallopian tube. A morphologically normal sperm is a direct product of spermatogenesis and epididymal maturation. No gross morphological alterations have been reported to occur to sperm within the female. tract, Instead, elimination of sperm with gross morphological aberrations (whether as a direct function of the female tract or intrinsic sperm factors) has been shown. Measurement of the sperm head dimensions were performed in this study using the Flexible Image Processing System (FIPS). No obvious morphological disparities were present in the samples of ram sperm used. No obvious morphological alterations/selections occurred during transit through the Fallopian tube. Ram sperm head dimensions are defined. Fusion between spermatozoa and the egg vestments is a crucial step in fertilization. Exposure of audiogenic structures on sperm is a component of capacitation. The presence of these receptors is important in species-specific interaction and its absence play a significant role in infertility. FITC-conjugated wheatgerm agglutinin was used to identify and localize N-acetyl-D-glucosamine- like receptors on the sperm membrane surface. This surface component is believed to play an important role in sperm-egg interaction. Membrane alterations associated with receptor activity (allowing for sperm -zona binding) appear to have occurred after transit through the Fallopian tube. The acrosome reaction has, to date, been recognised as the most reliable indicator of the completion of capacitation. It is generally accepted that the acrosome reaction of the fertilizing sperm occurs at the zona pellucida surface, that previously acrosome-reacted sperm may also bind to the ZP. FITC- conjugated peanut agglutinin was selected as a probe for acrosomal status extermination. An increase in the incidence of acrosome-reacted sperm was observed after transit through the Fallopian tube. A small population of spermatozoa, therefore, appear to have acquired (wholly or partially) fertilizing potential after transit through the Fallopian tube.
The influence of maternal nicotine exposure on development lung as gas exchanger: the protective effect of copper
(University of the Western Cape, 1998) Dennis, Henriette; Maritz, G.S.; de Kock, M
The influence of tobacco smoking on the developing fetus is well reported. Maternal nicotine exposure during pregnancy and lactation interferes with fetal and neonatal lung growth and development, rendering the lungs more susceptible to damage and disease. interference with the normal developmental processes at any stage may compromise the gas exchange function of the lungs. Maternal nicotine exposure during gestation and lactation causes a decrease in the elastic tissue content of the lturgs, which may lead to the formation of emphysema-like lesions. Elastic tissue is catalysed by lysyl oxidase, an extracellular, copper dependent en4rmq from its soluble to its insoluble state. It is suggested that lesions occur in lturgs exposed to nicotine because of a decrease in lung copper content, which will, in turn, cause decreased lysyl oxidase activity. The aim of this study was thus to determine and quantify the effects of maternal nicotine exposure on the development of the fetal and neonatal rat lung as a gas exchanger and to establish whether copper supplementation will protect the lungs against these adverse effects of maternal nicotine exposure. The pregnant rats were divided into four experimental groups. One group received nicotine (lmdkg body weight/day) subcutaneously. Another received copper (lmg/kg body weighVday), while a third group received nicotine (lmglkg body weight/day) in addition to copper (lmg/kg body weighUday). Control rats received sterile saline. These subcutaneous injections were given throughout gestation and lactation. The results obtained showed that maternal nicotine exposure suppresses alveolarization in the fetal and neonatal lung. The lungs of the offspring exposed to nicotine during gestation and lactation have a reduced radial alveolar count, and a decreased alveolar number. All this points to a reduced internal surface area available for gas exchange. Copper supplementation during gestation and lactation prevents the adverse effects of maternal nicotine exposure on development of the lungs of the offspring. Therefore, the lungs of the copper supplemented animals can develop to its full potential as gas exchangers
The antioxidant properties of melatonin during chemical hypoxia and reoxygenation injury in rat ventricular myocytes
(University of the Western Cape, 2000) Salie, Ruduwaan; Dietrich, Daneel; Lochner, Amanda
It is well known that ischaemia chemical hypoxia followed by reperfusion is not always accompanied by recovery of myocardial function and often produces further cell damage (Hearse et al., 1973). This phenomenon commonly referred to as the oxygen paradox (Hearse et al., 1973), is usually characterised by extensive tissue damage and the formation of oxygen free radicals / reactive oxygen species (ROS). As the work on free radicals progressed it became apparent that there is a fine balance between cellular systems that produce free radicals and those that sustain their tolerable levels, to maintain normal cell function (Ferrari et al., 1990). The relative importance of free radicals in the production of irreversible cell damage, as well as the mechanisms involved are not fully understood. Using the rat mode of myocardial infarction followed by reperfusion, many investigators employed various antioxidants / free radical scavengers in various combinations at different stages of hypoxia / reoxygenation with the intention of reducing free radical mediated damage (Meerson et al., 1981; Shlafer et al., 1982; Stewart et al., 1983; Hess et a1., 1983; McCord and Fridovich, 1973). There is also an increasing interest in defining new antioxidants of high potency, low toxicity and good solubility properties in aqueous as well as organic phases. Recently it has been shown that melatonin (n-acetyl-5-methoxytryptamine) has the ability to directly scavenge free radicals (Reiter, 1993) It was therefore the aim of this study, to investigate oxidative stress during chemical hypoxia and reoxygenation in isolated rat ventricular myocytes and to study the antioxidant effects sf 6sl4fsnin, employed at different stages of chemical hypoxia and / or reoxygenation. To reveal the phenomenon of oxidative stress using laser scanning confocal microscopy, myocytes were preloaded with tetramethyl rhodamine (TMRM) together with one of the following fluorophores: (i) dihydric loro fluorescein diacetate (DCDHF) or dihydrorhodaminel23 (DHR) to illustrate the formation of HzOz and / or ROS; or (ii) fluo'3, AM (fluo) to show changes in intracellular free calcium. In superfused myocytes, chemical hypoxia was induced for 12.5 min by the addition of 1.5 mM KCN and 20 mM deoxy glucose to the superfusion buffer followed by 0, 1.5 or 15 min reoxygenation. Cells were also exposed to 27 .5 min chemical hypoxia without reoxygetration. Melatonin (50 pM) was added at different time intervals during the experimental protocol. All the myocytes (untreated and melatonin treated), indicated increased DCDHF but not DHR or fluo fluorescence under control oxygenated conditions (norrroxia). This probably implicate nonanal physiological levels of H2O2 and I or ROS and presumably an intact endogenous antioxidant system, since none of the cells suffered any damage. It was also indicated that melatonin had no effect on H2O2 and / or ROS formation and the viability of any of the cells during normoxia. Exposure of myocytes to chemical hypoxia for 12.5 min caused contracture and damage to 70 - 89 % of cells. This was associated with the generation of H2O2 and/ or ROS, an increase in intracellular calcium but maintenance of membrane potential. Early reoxygenation did not exacerbate or improve the changes observed during chemical hypoxia. Melatonin protected myocytes from hypoxic induced damage and increased cell viability from 20 to 80 % (p<0.05). Melatonin treated cells had reduced levels of ROS and intracellular calcium. The protection conferred by melatonin during exposure of cells to 12.5 min chemical hypoxia disappears if chemical hypoxia is prolonged to 27.5 min. After 27 -5 mn chemical hypoxia > 85 Vo of cells showed marked morphological changes and were considered to be irreversibly damaged. Myocytes indicated increased DCDHF; DHR and fluo fluorescence, implicating increased H2O2 and I or ROS formation and increased intracellular calcium respectively, after 12.5 min chemical hypoxia. However, the application of melatonin, effectively scavenged H2O2 and / or ROS and protected cells only for the first 14.5 min of chemical hypoxia, after which all of the cells indicated increased H2O2 and / or ROS formation, increased intracellular calcium and suffered irreversible damage. Presumably, as chemical hypoxia progressed, the accumulation of H2O2, the formation of ROS and degradation of endogenous antioxidant enzymes transpired, which resulted in damage to the majority of cells by the end of this period.
The influence of maternal nicotine exposure on neonatal rat lung septal status
(University of the Western Cape, 1995) Thomas, Ruby Ann; Dietrich, D; Maritz, G.S.
The aim of this study was to determine the effect of maternal nicotine exposure on the status of rat lung alveolar septa of 1 to 2l day old offspring. Wistar dams were injected subcutaneously, using a dosage of 1 mg nicotine/kg body mass/day, and treatment commenced 7 days after conception, up to the third week after parturition. The data obtained showed an increase in septal cellularity, with a decrease in type I: type II cell ratio as a result of type I cell destruction and type II cell proliferation. The type I cells appear to be more sensitive to the effect of nicotine than type II cells. Data also illustrate swelling of type II and endothelial cell mitochondria, blebbing of both type I and endothelial cells and rupturing of the blood-air barrier in the nicotine exposed lungs of the rats of all the age groups. Iamellar body count are significantly higher in the type 11 cells of nicotine exposed lungs in all age groups compared to the control lungs. The number of capillaries per unit length of septum was also significantly less than that of the control lungs. Other morphological changes which were also observed in the nicotine exposed offspring in all the age groups are: loss of type II cell microvilli, swelling of type I and endothelial cells, and grouping of type II cells within the septal interstitial (an indication of proliferation). The results clearly indicate that maternal nicotine exposure interfered with the morphometric and morphologic characteristics of the alveolar septal of the lung tissue of the neonatal rats.
Ecology and conservation of high altitude amphibians
(UWC, 2002) Geland, C; Channing, A
This study looked at the breeding ecology of the anurans, found in the Landdroskop mountain range in Grabouw, and some recommendations as to their conservation are made. There is very little known about the frogs in South Africa and this study aims to el cite some of the factors that influence the vocalization of these frogs and the periods that these frogs breed.
Circadian activity rhythms and early gene expression in the suprachiasmatic nucleus of a diurnal rodent, Rhabdomys pumilio
(UWC, 2001) Thomas, D; Hofmeyer, MD; Bennett, N; Cooper, HM
Although humans are diurnal in behavior, animal models used for the study of circadian rhythms are mainly restricted to nocturnal rodents. This study focused on circadian behavior and gene expression in a diurnal rodent from South Africa, the four-striped field mouse (Rhabdomys pumilio). In contrast to nocturnal rodents which have rod-dominated retinas, the retina of this field mouse contained approximately an equal amount of cones as rods. The cones included short-wavelength (blue-sensitive) and mid-wavelength (green-sensitive) cones. In order to characterize the behavioral pattern of daily activity, locomotor rhythms were studied under different light regimes using an automated data recording system. Under conditions of natural daylight which include dawn and dusk transitions, R. pumilio showed activity restricted to the daytime period. Activity was concentrated around morning and evening hours with a decrease during mid-day.
Student experiences of life science practicals
(UWC, 2001) Faroe, D.L; Jonker, L.E
Science Educationists seem to agree that practical work should form an important component of any science course. Many students arrive at University without having been exposed to any practical work, while others were exposed to a range of different practical activities. This background seems to impact how students experience and benefit from laboratory work at University. This research is aimed at determining what first-year students' experiences of the life science practical course were. Reflective journals were used as a tool to get students' opinions about their experiences in the practical classes. Interviews served to clarify the problems that seemed to surface.

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