New drugs, particularly antibiotics, are urgently required to combat the increasing problem of antibiotic resistant human pathogens. Due to the scarcity of products available today, the pharmaceutical industry is now under pressure to reassess compounds derived from plants, soil and marine organisms. Pharmaceutical companies are showing renewed interest in marine biotechnology as the oceans represent a rich source of both biological and chemical diversity of novel molecular structures with anti-cancer, anti-inflammatory and antibiotic properties. Formerly unexplored locations, such as deep ocean sediments, show great potential as a source of genetically novel microorganisms producing structurally unique secondary metabolites. In this research, a metabolite producing marine Pseudoalteromonas strain, known as AP5, was initially used to develop methods for the detection, optimisation of production and extraction of bioactive metabolites from other potentially novel marine isolates. Two hundred and seventy six (276) marine isolates from water and sediment samples from the Antarctic Ocean and Marion Island were isolated. Ten visually different isolates were screened for bioactivity against Gram-positive and -negative bacteria, fungi and yeast. Three out of the 10 isolates, WL61 , WL 114 and WL 136, appeared to be novel Streptomyces spp. showing activity against different test organisms. Many of these marine microorganisms are difficult to culture in the laboratory, particularly when they are cultivated continuously in shake flasks as they can stop producing bioactive compounds. The cultivation of marine isolates in bioreactors may be a more beneficial process for the optimisation of metabolite production compared to conventional liquid fermentation techniques whereby the solid-liquid-air interface of membrane bioreactors can imitate the natural environment of microbes. The membrane bioreactor system is a stable growth environment with low shear that supports steady-state biofilm growth consisting of a high cell density due to a high mass transfer of nutrients and oxygen to the cells. This approach was employed and isolates WL61, WL114 and WL136 were immobilised onto ceramic membranes using Quorus single fibre bioreactors (SFR). The SFRs were used to establish the most suitable growth medium for continuous secondary metabolite production. The best growth conditions were applied to the Quorus multifibre bioreactor (MFR) for scale up of biologically active metabolites, highlighting the potential of bioreactor technology for use in bioprospecting for isolating and screening novel and known organisms for new and interesting natural products. Furthermore, the Quorus MFR was shown to be suitable for the production of high yields of antimicrobial metabolites and is an efficient new fermentation production system. Purification by HPLC fractionation was used to characterise four major compounds from isolate WL 114 extracts. NMR structure elucidation identified one of the two primary compounds as Bisphenol A. The complete chemical structure for the second potent bioactive compound could not be determined due to the low concentration and volume of material. / KMBT_363 / Adobe Acrobat 9.54 Paper Capture Plug-in

Background: A post-exposure regrowth model utilizing the well-tried Bactec radiometric system, which would simulate in vivo situations at the site of invasive disease, was developed to measure drug activity against multiplying Mycobacterium tuberculosis. Aims: The aims of this dissertation were to (a) construct a radiometric model simulating drug efficacy relating to the combined bactericidal activity and delays in regrowth due to the action of anti¬tuberculosis (TB) agents, (b) compare the killing kinetics of drugs singly and in combinations by the time-kill curve method, with the radiometrically-determined regrowth model, and (c) assess whether the Bactec radiometric regrowth model could predict likely bactericidal activities of drugs. Design and methods: Drug concentrations in the time-kill curve method were in a range of achievable drug concentrations at the site of infection and in multiples of the minimal inhibitory concentration (MIC), (1x, 2x or 3x, and 8x). Exposure times of 6h, 24h, 48h and 72h were used and these were based on pharmacokinetic data reflecting likely periods of in vivo exposure in TB lesions. Standardized inocula of approximately 106CFU/mi of actively multiplying M. tuberculosis strains were used. The same concentrations, exposure times and bacterial concentrations were used for the assessment of radiometrically-determined post-exposure regrowth times of M. tuberculosis. Growth times were recorded as the number of days required to reach a predetermined growth index (GI) level in the Bactec system, and were expressed as T400 readings in days. Simple linear regression and a mathematical logistic model were used to assess whether the radiometric post-exposure regrowth model could predict the bactericidal activity of the drugs. For drug combination studies, 1MIC of isoniazid (INH) and rifampicin (RMP) were used singly and in combination while 2MIC of ethambutol (EMB), streptomycin (SM), ofloxacin (OFL) and amikacin (AMK) were used in combinations studies. Colony counts at Oh and following 24h exposures were performed and regrowth patterns were determined using the T400 method. M. tuberculosis H37Rv was tested and subsequently resistant strains. Results: INH and RMP were highly bactericidal while EMS showed moderate activity in the time-kill curve method. The three drugs produced the best curves, showing longer regrowth times and markedly depressed rates of regrowth in the Sactec post-exposure regrowth model. Using simple linear regression, a linear relationship between bacterial survivors and the radiometric regrowth times, T400, was achieved for all drugs tested. Even better agreement was found when control-related regrowth times, (T-C) 400, were used in the analysis. Conditions compromising the linear relationsbip in the radiometric regrowth model, for OFL and less markedly EMS and AMK, were likely postantibiotic effects (PAEs) brought on by the short exposure time (6h), and drug carry-over effects due to concentrations ≥ 8 MIC for INH, RMP and 8M (10x and 20x MICs). The mathematical logistic model showed good correlation between bactericidal activity and regrowth for INH and RMP but not for EMB, SM, OFL and AMK. Drug combination effects in the two techniques depended on the criteria used to describe synergy. Generally, it was found in drug combination experiments that the drugs did not influence each other to a meaningful extent. Discussion and conclusions: For prediction of bactericidal activity, interpretation of the radiometrically-determined regrowth model needs to accommodate PAEs and the effect of subinhibitory concentrations. The validity of the mathematical logistic model is not clear. Technical aspects of future studies such as better organism dispersal, need to be improved to achieve a more reliable evaluation based on the logistic model. For drug combination studies, the radiometric regrowth model yielded findings that were difficult to interpret in relation to published data, reinforcing the need for the use of internationally standardized techniques which would give statistically reliable data. The radiometrically-determined regrowth model showed good discrimination between the standard activities of anti- TB agents, correlating with clinical efficacy. It is simple to perform and could prove to be useful for the screening of candidate anti- TB drugs. Improved technical stringency and the evaluation of poorly active control drugs, are however needed before proof of validity of the model can be established. / Dissertation (MSc (Medical Microbiology))--University of Pretoria, 2007. / Medical Microbiology / unrestricted

No description available.

Within the past several years, a great deal of attention has been focused on the phenomena of drug-drug interactions and their importance in the therapeutic regimen of patients for whom multiple therapeutic agents might be indicated. The rather sudden concern for this aspect of medical and pharmaceutical practice is evidenced by the proliferation of literature devoted to the topic for both professions. While iatrogenic disease has long been recognized as one of the hazards inherent in prescribing practices, only isolated reports of specific interactions were found until recently. Although it cannot be said with certainty when the first interaction of two drugs was noticed, such possibilities began to come to light with the observation that concomitant administration of an antacid with a tetracycline would impair the absorption or the anti- biotic (1). A concerted effort to bring order to our recognising and understanding of such interactions has taken place only within the past ten years

Introduction: Despite the tremendous advances made with regard to synthetic organic medicinals within the last two decades, heavy reliance is still placed on plant products. This is especially true of the anthracene derivatives used medicinally as purgatives, and which are derived principally from senna, cascara, rhubarb, frangula and aloes. While particular attention has been paid to the chemistry of the former group in recent years, aloes has been largely neglected, possibly due to the fact that the Aloe species are confined largely to areas where extensive research facilities are lacking, such as Africa , India and the West Indies. Thus research in Europe has been confined largely to the lump aloes of commerce, derived from relatively few species. In 1953 a comprehensive report by Hodge (103) appeared on "The Drug Aloes of Commerce, with Special Reference to the Cape Species". Hodge observed that South Africa abounds in species just as abundant as A.ferox, (which is the prime source of Cape aloes), and advised that a systematic chemical survey might show certain of these to be not only higher yielders of bitter aloetic juice but also sources of a superior drug product. Consequently an investigation along these lines is presented here, and it is observed that several species apart from A.ferox not only contain aloin, but also yield a large volume of aloetic juice. Only pharmacologic studies can reveal if the juice of these species is as safe as that of A.ferox, but without doubt they could be used for the extraction of crystalline aloin. Concurrently, the distribution of the Aloe resins, said by some to be purgative themselves, has been studied. The investigation has revealed that the structurally similar compound homonataloin enjoys an equally wide distribution as aloin. However, almost invariably it is confined to small species yielding little aloetic juice, apart from which nothing is known regarding its pharmacologic properties. It is interesting to note that the resin distribution in the homonataloin-containing species is very similar to that of the aloin-containing species, but differs widely from. that of the species containing neither of these principles. Apart from aloin and homonataloin, aloinoside and chrysophanol also occur in Aloe species, and together with the resins, these indicate that when all the South African Aloe species have been investigated, they may well be of chemotaxonomic value. Within the comparatively short space of the last decade some work has been performed on aspects of the metabolism of such anthracene-containing species as Rheum, Rhamnus and Rumex. These investigations have shown that the anthracene derivatives are not merely waste products, but perform definite metabolic functions. The latter portion of this work has been devoted to this relatively neglected aspect of the Aloe species.

Thesis (MScMedSc (Biomedical Sciences. Medical Physiology))--Stellenbosch University, 2008. / Background and purpose. To limit ischaemic injury, rapid restoration of coronary blood flow is required, which will in turn reduce infarct size. However, reperfusion itself causes myocyte death – a phenomenon termed lethal reperfusion-induced injury, which limits protection of the ischaemic myocardium. Thus the reperfusion of irreversibly damaged myocytes may accelerate the process of cell necrosis. Additive protection of the ischaemic myocardium in the form of adjunct therapy remains a topic of intensive research. Levosimendan, a calcium sensitizing agent with positive inotropic effects has in several studies been found to alleviate the damaging effects of reperfusion injury. Levosimendan has been shown to be a KATP channel opener. These channels have been implicated to play an important role in ischaemic preconditioning (IPC). With this knowledge, the aim of this study was to determine whether levosimendan and IPC have certain cardioprotective mechanisms in common and whether protection with pharmacological preconditioning could be elicited with levosimendan. In this study, we investigated whether: 1) the isolated guinea pig heart could be protected by ischaemic preconditioning (IPC) and postconditioning (IPostC), 2) the heart could be pharmacologically pre- and postconditioned, using levosimendan (LPC & LPostC), 3) a combination of IPC & LPC had an additive protective effect on the heart, 4) the KATP (both mitochondrial and sarcolemmal) channels are involved in this protection and 5) the pro-survival kinases of the RISK (reperfusion injury salvage kinase) pathway are involved. Experimental approach. Isolated perfused guinea pig hearts were subjected to three different IPC protocols (1x5, 2x5 and 3x5 minutes of ischaemia) or levosimendan (0.1μM) preconditioning, before coronary artery occlusion (CAO – 40min@36.5ºC), followed by 30 minutes of reperfusion. Hearts were also subjected to a combination of IPC & LPC, to establish whether they had additive protective effects. In addition, hearts were pre-treated with levosimendan directly before induction of sustained ischaemia (without washout of the drug – levosimendan pre-treatment (LPT)) for 10min. With the postconditioning protocol, iii the hearts were subjected to 3x30second cycles of ischaemia/reperfusion or levosimendan/vehicle. In a separate series of experiments, hearts were treated with KATP channel blockers (for both sarcolemmal & mitochondrial), before LPC, LPT and LPostC. The endpoints that were measured were: cardiac reperfusion function, myocardial infarct size and RISK pathway expression and phosphorylation (PKB/Akt and extracellular signal-regulated kinase – ERK42/44). Results. IPC, IPostC, LPC & LPostC decreased myocardial infarct size significantly compared with their controls (21.9±2.2%, 21.4±2.2%, 20.6±3.1% and 20.6±1.8% respectively vs. 46.4±1.8% for controls, p<0.05). The combination of IPC & LPC had no additive protective effect. Pre-treating the hearts with levosimendan (without washout), before index ischaemia, proved to be the most effective method of cardioprotection (infarct size: 5.8±0.9% vs. 46.4±1.8% for controls, p<0.001). With LPT a significant increase (p < 0.05 vs. control) in phosphorylation of ER42/44 was also observed. An increase in the activity of one of the RISK pathway kinases, ERK42/44 seems to be one of the reasons for LPT’s efficacy. Treating the hearts with KATP channel blockers before subjecting them to LPC, LPT & LPostC abolished the protective effects induced by levosimendan, suggesting a role for the sarcolemmal and mitochondrial KATP channels in levosimendan-induced cardioprotection. Conclusions and implications. 1) Isolated guinea pig hearts could be pre- and postconditioned within the setting of ischaemia, 2) Hearts could be pharmacologically pre- and postconditioned with levosimendan, 3) levosimendan pre-treatment is the most effective way to reduce infarct size, possibly acting by increasing the phosphorylation of ERK42/44, 4) Myocardial protection was not increased by combining IPC & LPC (suggesting similar mechanisms of protection), 5) LPC, LPT and LPostC were abolished by both sarcolemmal and mitochondrial KATP channel blockers. .LPC and especially LPT, could be useful before elective cardiac surgery while LPostC may be considered after acute coronary artery events.