Doctoral Degrees (Medical Microbiology)

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Browsing Doctoral Degrees (Medical Microbiology) by browse.metadata.advisor "Bouic, Patrick J. D."

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    Determination of the permeability of biological membranes to various chemical markers, including anti-HIV drugs
    (Stellenbosch : University of Stellenbosch, 2009-12) Pretorius, Erina; Bouic, Patrick J. D.; University of Stellenbosch. Faculty of Health Sciences. Dept. of Pathology. Medical Microbiology.
    ENGLISH ABSTRACT: Due to modern high-throughput technologies, large numbers of compounds are produced by parallel synthesis and combinatorial chemistry. The pharmaceutical industry therefore requires rapid and accurate methods to screen new drugs leads for membrane permeability potential in the early stages of drug discovery. Around 50 % of all investigational new drugs fail in pre-clinical and clinical phases of development due to inadequate absorption/permeation, distribution, metabolism, excretion and/or unacceptable toxicity. This may be decreased by applying in vitro screening methods early in the discovery process. Reliable in vitro models can be applied to determine permeation of the test compounds, which will help avoid the wasting of valuable resources for the development of drugs that are destined to fail in preclinical and clinical phases due to insufficient permeability properties. It is important to decide as early as possible on the most promising compound and physical formulation for the intended route of administration. With awareness of the increasing importance of in vitro models in the investigations of the permeability properties of drug compounds, this research project was specifically devoted to determine the suitability of our in vitro model to evaluate and predict drug permeability. A continuous flow-through diffusion system was employed to evaluate the permeability of nine different compounds/drugs with different chemical properties, across three biological membranes. The biological membranes chosen for the present study were human vaginal mucosa, human skin tissue and human small intestine mucosa. The continuous flow-through diffusion system was furthermore utilised to investigate the effects of de-epithelialisation of mucosal surfaces, chemical enhancers, temperature, permeant concentration and formulation on the permeability of the test compounds/drugs. The in vitro permeability information and data from the flow-through diffusion model were compared to in vitro and in vivo literature studies and drug profile. An in vitro model that is able to reliably predict in vivo data will shorten the drug development period, economise resources and may potentially lead to improved product quality. In this thesis research results are reported on the permeability of the mentioned biological membranes to the various chemical markers, including anti-HIV (human immunodeficiency virus) drugs. The permeability studies will be discussed in three sections: vaginal mucosa, skin tissue, small intestine mucosa. The results of the vaginal permeability studies showed that the three peptides (MEA- 5, MDY-19 and PCI) readily penetrated the vaginal mucosa. MDY-19 had a higher flux rate than MEA-5, commensurate with its smaller molecular size (weight). The surfactant enhanced the flux rate of MDY-19 approximately 1.3 times and decreased the lag time of the peptide. Removal of the vaginal epithelium increased the flux rates of the peptides across the mucosa and may have implications for a more rapid uptake of these and other microbicides in vivo. The permeability of 1 mM MDY-19 and PCI at 37 °C were significantly (p<0.05) higher than at 20 °C. At 37 °C the AUCs of the overall mean flux values of MDY-19 and PCI increased with concentration according to well-established diffusion theory. The experiments on the permeability of different terbinafine hydrochloride formulations through human skin demonstrated that the terbinafine hydrochloride formulations used in this study, readily diffused into the skin tissue. However, no flux values for any of the terbinafine hydrochloride formulations through the skin into the acceptor fluid were found. The mean terbinafine concentrations in the skin after 24 h exposure to the three commercial, terbinafine hydrochloride formulations were 3.589, 1.590 and 4.219 μg/ml respectively. The mean terbinafine concentration in the skin exposed to the 10 mg/ml PBS/Methanol solution was higher than those from the three commercial formulations. The results of the temperature study demonstrated that an increase of 5 ºC caused a significant increase in flux values of tritiated water across skin. The flux values for tritiated water across skin at 37 ºC were on average double those at a temperature of 32 ºC. The permeability of excised human small intestine mucosa to different oral dosage drugs was investigated over a 24 h period. The four drugs selected were zidovudine, propranolol hydrochloride, didanosine and enalapril maleate. They were selected as representative model compounds of drug classes 1 (high solubility, high permeability) and 3 (high solubility, low permeability) according to the Biopharmaceutics Classification System. The flux rates of the four chosen test drugs were influenced by the length of the experiment. Between the time periods 2-4 h and 4-6 h, zidovudine’s mean flux values across small intestine tissue were respectively 1.8 and 2.0 times higher than didanosine and 2.3 and 2.2 times higher than enalapril. Propranolol’s mean flux values were respectively 1.2 and 1.4 times higher than didanosine and 1.6 higher than enalapril during both the 2-4 and 4-6 h time periods. Between both the time periods 2-4 and 4-6 h AZT’s mean flux values were 1.4 times higher than propranolol and didanosine’s mean flux values were respectively 1.3 and 1.1 times higher than enalapril during the mentioned time periods. Class 1 drugs showed a significantly higher flux rate across the jejunal mucosa compared to the class 3 drugs and these results are in line with their Biopharmaceutics Classification System classification. The in vitro model has proved to be reliable to predict permeability of class 1 and 3 drugs and also showed correlation with human in vivo data. It seems that the in vitro flow-through diffusion model used in the present study have the potential to overcome some of the problems and limitations demonstrated by other in vitro techniques and may potentially serve as a future tool for pharmaceutical companies to predict the diffusion characteristics of new drugs and different formulations, across different biological membranes. Furthermore, it may serve as a prospective method for assessing the bioequivalence of alternative (generic) vehicles or formulations containing the same drug/compound.
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    Die effek van musiek op die immuunsisteem, emosies en longfunksie tydens die standaard fisioterapeutiese behandeling van spesifieke longpatologie
    (Stellenbosch : University of Stellenbosch, 2005-03) Le Roux, Frances Hendriehetta; Bouic, Patrick J. D.; University of Stellenbosch. Faculty of Health Sciences. Dept. of Pathology. Medical Microbiology.
    There has recently been a significant transformation in the medical world, in particular regarding the relation between the mind/health and mind/illnesses. The changes are briefly a revolution whereby the new approach sees the development of an illness as an interaction between the psychological, biochemical and physiological factors. Music, which is used as a clinical intervention, is perceived first through the brain, affirms this interaction between the body systems, as well as having the capacity to modify the mind and thus the biochemistry of the body. The aim of this study was essentially to supply empirical data by measuring selective parameters while the patients were receiving music intervention during the physiotherapeutic treatment for pneumonia and bronchitis. Forty adult patients who were divided into an experimental and control group, according to a random scale, participated in the research. The dependant variables that had shown significant changes amongst the experimental group after three days of physiotherapeutic treatment were as follows: the cortisol, the cortisol: DHEA ratio plasma levels, the POMS scale (that measures different moods), the peak flow measurements of the lung functions and the immune parameters, namely, CD4+ : CD8+ ratio and B-cells. The results showed that the experimental group that was exposed to the acoustic stimuli of the Magnificat in D, BWV 243 of JS Bach, experienced a more positive mood and lower cortisol levels, while the immune markers as well as the peak flow of the lungs had improved. The results of the control group showed significant implications, in that its cortisol levels increased and the POMS subscale of anger and depression showed no significant change, while the tension decreased significantly. This research provided sufficient scientific evidence to confirm the concept of a bidirectional communication between the brain and the immune system. It also showed clearly that music had the capacity to modify emotional conditions, which again influenced the endocrine and autonomic nervous system and modulated the immune systems.
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    The relevance of apoptosis in the pathogenesis of human immunodeficiency virus-1 disease
    (Stellenbosch : Stellenbosch University, 2004-12) Cotton, Mark F.; Bouic, Patrick J. D.; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Pathology. Medical Microbiology.
    ENGLISH ABSTRACT: A simple and rapid scatter-based flow cytometric assay was developed to detect apoptosis in CD4+ and CD8+ T cells from a mixed population of cells. The assay was suitable for children. Apoptotic PBMCs were confirmed by morphologic assessment in clinical samples ex vivo and after overnight culture. The scatter-based assay was validated in a number of ways. Firstly, PBMCs were irradiated with 500 rads and cultured overnight to induce apoptosis. Thereafter, PBMCs were labeled with a CD4 MAb. CD4+ cells were sorted into apoptotic and viable populations by scatter characteristics (diminished forward and increased side scatter). Morphology was assessed by fluorescence microscopy. The majority of cells with apoptotic scatter characteristics had apoptotic morphology (chromatin condensation) (80.6%). Ninety-two percent of cells from the viable region had normal morphology. CD4+ T cell apoptosis measured by scatter was then correlated with the TdT assay for DNA fragmentation. Lastly, CD4+ T cell apoptosis by scatter and annexin V uptake were also shown to correlate. In the latter experiments, PBMC morphology and cell death by trypan blue uptake were studied simultaneously and confirmed the two flow cytometric assays. Apoptosis of CD4+ and CD8+ T cells has been shown in PBMCs from HIV infected adults analyzed after overnight culture. Since cell death may be an artifact of in vitro culture, and because there is little information on apoptosis in paediatric HIV disease, I undertook a cross-sectional analysis in PBMCs analyzed immediately ex vivo from HIV infected children and adults. Patients were studied in Denver, CO, USA. PBMCs from 21 children, 4 adolescents and 9 adults and seronegative age-matched controls were stained for CD4 and CD8 surface markers. Apoptotic cells were detected in a newly characterized flow cytometric assay by diminished forward and increased side scatter. For the scatter assay, PBMCs had been labeled initially by an indirect method involving an intermediary incubation in the presence of biotinylated MAbs at 37°C for 30 minutes prior to incubating with streptavidin-FITC at 4°C for 20 minutes. Thereafter, the intermediary incubation step was removed and PBMCs were incubated with PE-conjugated CD4+ and CD8+ MAbs. Both CD4+ and CD8+ T cell apoptosis appeared enhanced in the indirect method. The significant differences were abolished after subtraction of data from simultaneously studied time-matched controls. CD4+ and CD8+ T cell apoptosis were significantly higher in HIV-infected study subjects than in simultaneously studied seronegative controls. PBMCs were assayed immediately ex vivo and after overnight culture after stimulation by an anti-TCR MAb as well as spontaneously. There was a direct correlation between CD4+ and CD8+ T cell apoptosis and CD4+ T cell depletion. A significant correlation was also shown between apoptosis immediately ex vivo and after overnight culture. I then studied apoptosis in a South African population comprising 18 symptomatic children and 4 seroreverters. CD4+ and CD8+ T cell apoptosis were significantly higher in symptomatic HIV-1-infected children than in seroreverters and seronegative controls. CD4+ T cell apoptosis correlated with depletion of CD4+ T cell percentage in symptomatic HIV-1-infected children. I also noted elevated CD4+ T cell apoptosis in patients recovering from intercurrent disease in comparison to those who were either acutely ill or relatively asymptomatic outpatient attendees. Lastly, I compared CD4+ and CD8+ T cell apoptosis in cohorts from Denver, CO and Tygerberg Children’s Hospital, South Africa. I selected only patients with moderate or severe HIV infection from both centers. South African patients were significantly younger, more malnourished, had higher gamma globulin levels and were less likely to receive ART. CD8+ T cell apoptosis was higher in North American patients suggesting a possible impairment in CD8+ activity in the South African study subjects.