Thesis (Ph. D.)--University of Hong Kong, 1999. / Includes bibliographical references (leaves 204-228).

Thesis (Ph. D.)--University of Washington, 1996. / Vita. Includes bibliographical references (leaves [86]-93).

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Proefschrift Universiteit Maastricht. / Met bibliogr., lit. opg. - Met samenvatting in het Nederlands.

Made available in DSpace on 2014-06-11T19:27:18Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-07-08Bitstream added on 2014-06-13T18:31:18Z : No. of bitstreams: 1 zanoli_jcc_me_araca.pdf: 862916 bytes, checksum: 14a8c6ca70d93c05133bf28113b4bac8 (MD5) / Abamectina é uma lactona macrocíclica pertencente à família das avermectinas, utilizada mundialmente como agente antiparasitário em animais de criação e estimação, além do emprego agrícola como princípio ativo dos inseticidas e nematicidas. Mitocôndrias são responsáveis pela conversão da energia liberada pelo transporte de elétrons e armazenamento como energia de ligação na molécula de ATP, um componente metabólico essencial. Interferências em sua síntese ou utilização caracterizam mecanismos pelos quais os xenobióticos podem expressar toxicidade aguda ou crônica. Neste trabalho, os efeitos da abamectina na bioenergética de mitocôndrias isoladas de fígado de rato foram avaliados. Nas concentrações utilizadas (5 a 25 µM), abamectina causou inibição da cadeia respiratória, sem afetar a atividade das enzimas NADH desidrogenase, succinato desidrogenase e o potencial de membrana, comportando-se de maneira semelhante à oligomicina e ao atractilosídeo. A principal atuação da abamectina foi reduzir o potencial mitocondrial de fosforilação oxidativa, diminuindo os níveis de ATP provavelmente como resultado de sua ação direta sobre a FoF1-ATPase, uma vez que inibiu a atividade desta enzima, e/ou sobre o translocador de ADP/ATP. A inibição mais acentuada da atividade fosfohidrolase em mitocôndrias intactas desacopladas do que em mitocôndrias rompidas juntamente com a inibição da despolarização do potencial de membrana induzida pelo ADP sugerem que a abamectina atuou inibindo mais especificamente o translocador de ADP/ATP do que a FoF1-ATPase / Abamectin is a macrocyclic lactone belonging to the avermectin family, used worldwide as antiparasitic agent in farm animals and pets, and agricultural employment as the active ingredient of insecticides and nematicides. Mitochondria are responsible for converting the energy released by electron transport and storage as the binding energy molecule ATP, an essential metabolic component. Interference in its synthesis or utilization characterize mechanisms by which xenobiotics can express acute or chronic toxicity. In this study, the effects of abamectin in the bioenergetics of mitochondria isolated from rat liver were evaluated. At the concentrations used (5-25 mM), abamectin caused inhibition of the respiratory chain without affecting the activity of enzymes NADH dehydrogenase, succinate dehydrogenase and the membrane potential, behaving similarly to oligomycin and Atractyloside. The main activity of abamectin was to reduce the potential of mitochondrial oxidative phosphorylation, decreasing ATP levels probably as a result of its direct action on the Fo-F1 ATPase, since it inhibited the activity of this enzyme, and/or the ADP/ATP translocator. The more pronounced inhibition of the fosfohydrolase activity in intact uncoupled mitochondria than in disrupted mitochondria, in addition to the inhibition of the ADP-stimulated depolarization of mitochondrial membrane potential suggest that abamectin acted more specifically by inhibiting the ADP/ATP translocator than the FoF1-ATPase

The histochemical localisation of ATPase enzymatic activity at the level of the electron microscope was carried out on adult and newborn kidney tissue pre-fixed in 5% glutaraldehyde buffered with 0.1 M sodium cacodylate. Both the lead method at pH 7.2 and the calcium method at pH 9.4 were used. The effects of the modifiers PHMB and L-cysteine were also studied. In the adult rat kidney, the observations of other investigators on kidney ATPase activity were substantiated. Reaction precipitate was localised at the brush border of the proximal tubules, the membranes of the basal and lateral interdigitations of the proximal and distal tubules, and the plasma membranes of the podocytic foot processes. PHMB exerted an inhibitory effect on distal tubular activity at both pH 7.2 and pH 9.4, while cysteine was inhibitory only at pH 9.4. Glomerular ATPase activity was inhibited by PHMB and L-cysteine at pH 9.4. In the newborn rat kidney, ATPase enzymatic activity was observed in the tubular elements as well as in the glomeruli. In the undifferentiated tubules, reaction product was abundant on the lateral membranes between individual cells. The luminal and basal plasma membranes, which were simple in contour, showed little or no accumulation of precipitate. However, as the microvilli became long and slender in the early stages of the differentiation of the brush border, there was a concomitant increase in the intensity of the ATPase enzymatic reaction. Similarly, reaction product became associated with the developing basal interdigitations. In the immature glomerulus, reaction precipitate was most often observed where two sets of membranes were in apposition. With differentiation, enzymatic activity was localised primarily on the podocytic foot processes. The localisation of ATPase activity at pH 9.4 was found to be influenced by the time of pre-fixation in glutaraldehyde while ATPase activity at pH 7.2 was not affected. At pH 7.2, neither tubular nor glomerular ATPase enzymatic activity responded to PHMB or L-cysteine. For both adult and newborn kidneys, the correlation between structure and function was briefly considered. The adult kidney is an important and efficient homeostatic organ. In urine formation various substances are transported across the cell membranes of the glomeruli and tubules. Ultrastructurally, the glomeruli and tubules show modifications characteristic of cells engaged in active transport processes. There is a large increase in plasma membrane surface area, as exemplified by the intricate inter-digitations of the podocytic foot processes, the elaborate basal and lateral infoldings, and the brush border of the proximal tubules. Much ATPase activity was found associated-with these plasma membranes. The newborn kidney is not as efficient as the adult kidney in maintaining body homeostasis. It is not only functionally but also morphologically immature. Most of the tubules and glomeruli are undifferentiated and do not show specialisations of the plasma membranes as seen in the adult kidney. There is also a relatively smaller amount of ATPase present in the newborn kidney. For both adult and newborn kidneys, it was postulated that at least two types of ATPases with different pH optima are present on the plasma membranes of the tubules and glomeruli. / Medicine, Faculty of / Graduate

The work presented here included the development of a highly sensitive method to estimate the size and complexity of poly(ADP-ribose). This involved radiolabeling of the precursor pools, purification of polymers using a boronate resin, polymer fractionation according to size by molecular sieve chromatography and analysis of polymer complexity by enzymatic digestion to nucleotides which were quantified by strong anion exchange chromatography.

No description available.

No description available.

Objective: The aim was to determine if isolated rat cardiomycytes could be protected from ischaemic cell death by preincubation with adenosine or adenosine agonists. Methods: Cardiomyocytes isolated from rat hearts were preincubated in the presence of adenosine, CCPA (2-chloro-N6-cyclopentyladenosine), or carbachol prior to concentration into an ischaemic slurry. Effects of glycolysis and of isoprenaline were determined by addition of iodoacetic acid or isoprenaline to the ischaemic incubates and by exclusion of glucose from all media. Rates of ischaemic contracture were determined and survival of the myocytes versus paired control preparations was determined after various times of ischaemia, following resuspension of the cells in isotonic or hypotonic media. Results: Adenosine and CCPA produced only a small reduction of the rates of contracture and death of isolated myocytes. Carbachol gave no significant protection. Neither the degree of injury of control cells nor the amount of protection by CCPA was altered in the presence of added isoprenaline. Protection was abolished by the A1 receptor blocker sulphophenyl theophylline, iodoacetic acid, and exclusion of glucose. Conclusions: Adenosine and adenosine agonists afford a minimal degree of protection to ischaemic isolated myocytes by a glucose dependent mechanism. This protection does not appear to account for the larger degree of protection seen in intact hearts, following similar preconditioning protocols. The failure of adenosine to protect may be related to the quiescent state of isolated cardiomyocytes, or be species specific in that adenosine may not be the trigger for preconditioning in rats.Cardiovascular Research 1993;27:1670-1676.