Thesis (M. Med. Sc.)--University of Hong Kong, 2006.

No description available.

Thesis (Ph. D.)--University of Nevada, Reno, 2008. / "December, 2008." Includes bibliographical references (leaves 257-286). Online version available on the World Wide Web.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / O &#946;-citronelol à um Ãlcool monoterpÃnico de ocorrÃncia natural em vÃrios Ãleos essenciais como o Ãleo de citronela (obtido de Cymbopogon winterianus), de ampla utilizaÃÃo popular por suas propriedades repelentes de insetos. Recentemente, a esta molÃcula tem sido atribuÃdas outras propriedades que envolvem atividade antibacteriana, antifÃngica, antiespasmÃdica, hipotensora e vasorrelaxante. Sendo assim, objetivamos estudar suas possÃveis aÃÃes no comportamento motor do mÃsculo liso do sistema respiratÃrio de ratos Wistar. Os animais considerados nesse estudo foram divididos em 04 grupos: controle, sensibilizado, desafiado e tratado, em seguida, registros isomÃtricos, in vitro, foram obtidos a partir de anÃis isolados de traqueia. A inalaÃÃo de &#946;-citronelol (300 ÂM) preveniu a hiperreatividade traqueal mediante a adiÃÃo de K+ ou ACh em animais submetidos a um modelo de asma, no entanto, a adiÃÃo cumulativa de &#946;-citronelol (10 a 1000 ÂM), na cuba para ÃrgÃos isolados, nÃo produziu alteraÃÃo significativa das preparaÃÃes mantidas sob tÃnus basal. Em preparaÃÃes de traqueia mantidas contraÃdas, a adiÃÃo de &#946;-citronelol relaxou total e significativamente (p < 0,001; Two-Way ANOVA, seguido do teste Holm-Sidak) os anÃis de traqueia, com CI50 de 120,44 [73,29 - 197,91] ÂM para o K+ e 211,10 [114,13 â 390,46] ÂM para a ACh, e esse efeito nÃo foi alterado (p > 0,05; Teste de Mann-Whitney) apÃs o tratamento com Propranolol, L-NAME, TEA, Azul de Metileno, Ortovanadato de SÃdio, Capsazepina, Indometacina e A-967079. Em experimentos realizados com a remoÃÃo do Ca2+ e contendo EGTA, o &#946;-citronelol inibiu a contraÃÃo mediante a entrada de Ca2+ preferencialmente em canais VOC, mas em altas concentraÃÃes, pÃde atuar tambÃm nos canais ROC e SOC, esse efeito foi mais pronunciado (p < 0,001; Two-Way ANOVA, seguido do teste Holm-Sidak) na contraÃÃo promovida pela adiÃÃo de Ba2+, demonstrando uma maior especificidade em atuar nos canais de Ca2+ operados por voltagem do tipo L. O &#946;-citronelol tambÃm foi capaz de diminuir a contraÃÃo induzida pela estimulaÃÃo elÃtrica. Esses resultados demonstram que o &#946;-citronelol caracteriza-se como uma substÃncia antiespasmÃdica e miorrelaxante do mÃsculo liso respiratÃrio, e esse efeito està parcialmente relacionado à sua capacidade de reduzir principalmente o acoplamento eletromecÃnico. / The &#946;-citronellol is an alcoholic monoterpene of natural occurrence that is found in several essential oils, including the citronella oil (obtained from Cymbopogon winterianus). In general, it is widely used as insect repellent. Recently this molecule has been studied as antibacterial, antifungal, antispasmodic, hypotensive and vasorelaxant agent. We aimed to study the effects of &#946;-citronellol on smooth muscle contractility of rat airways. The animals were divided in four groups namely Control, Sensitized, Challenged and Treated. Isometric recordings were obtained from isolated preparations from tracheal tissues cut as rings. Inhalation of &#946;-citronellol (300 ÂM) before antigen (ovalbumin, OVA) challenge prevented development of tracheal hyperreactivity in response to K+ or ACh in tissues of OVA-sensitized animals. In vitro, the cumulative addition of &#946;-citronellol (10 to 1000 ÂM) did not change basal tone in tracheal smooth muscle preparations. In tracheal rings pre-contracted with K+ or acetylcholine (ACh), the addition of &#946;-citronellol fully relaxed (p < 0.001, Two-Way ANOVA, Holm-Sidak) tracheal rings with IC50 values of 120.44 [73.29 â 197.91] ÂM for K+ and 211.10 [114.13 - 390.46] ÂM for ACh. The relaxing effect of &#946;-citronellol was not altered (p > 0.05, Mann-Whitney test) after treatment with propranolol, N (G)-nitro-L- arginine methyl ester (L-NAME), tetraethylammonium (TEA), methylene blue, sodium orthovanadate, capsazepine, indomethacin and A-967079. Experiments performed in Ca2+ depleted medium containing EGTA revealed that low concentrations of &#946;-citronellol preferentially inhibited contractions induced by recruiting Ca2+ influx via voltage-operated channels (VOC), although at higher concentrations it could also inhibit either on contractions evocked with receptor-operated (ROC) or store-operated (SOC) pathways. Such effect was supported by the more pronounced inhibitory effects of &#946;-citronellol (p < 0.001, Two-Way ANOVA, Holm-Sidak) against contractions promoted in tracheal tissues maintained in Ba2+-containing medium. &#946;-Citronellol also decreased the contractions induced by electrical field stimulation. These results suggest that &#946;-citronellol has antispasmodic and myorelaxant properties on airway smooth muscle, which could be partly related to its ability in inhibiting the electromechanical coupling.

No description available.

It is generally held that adenosine 3',5'-cyclic monophosphate (cAMP) mediates smooth muscle relaxation by the activation of cAMP-dependent protein kinase (PKA). This hypothesis was tested in two intact smooth muscle preparations, the rat vas deferens and the bovine coronary artery, using exogenously applied cAMP and cAMP analogs. After 30 minutes of incubation, N⁶,2'-0-dibutyryl-cAMP (dBu-cAMP) (1 - 100 μM) inhibited phenylephrine (PE)-induced tension generation in the rat vas deferens in a dose-dependent manner. This analog (10 μM) also activated the soluble fraction of PKA but did not activate the particulate fraction kinase. In contrast, 8-bromo-cAMP (8Br-cAMP) (10 -100 μM) did not have any significant effect on inhibition of PE-induced tension after 30 minutes of incubation but, at a concentration of 10 μM, significantly activated both the soluble and particulate fractions of PKA. The time course of activation of soluble PKA activation by 8Br-cAMP (10 μM) demonstrated that the kinase was significantly activated only after 30 minutes of exposure to the analog. In the bovine coronary artery, cAMP (10 - 100 μM) relaxed potassium-depolarized helical strips and significantly activated soluble PKA in a dose-dependent manner. dBu-cAMP (10 - 100 μM) affected neither tension nor soluble PKA activity. 8Br-cAMP (10 - 100 μM) did not affect the coronary artery tension but did activate soluble PKA. Both smooth muscle preparations were homogenized with charcoal prior to the determination of PKA activity in order to minimize artifactual assay results. As a further precaution, extracellularly associated cAMP and analogs were also washed from bovine coronary artery strips after the incubation period. These controls allowed for a valid assessment of PKA activity in the cyclic nucleotide-treated tissues. The results of the tension and kinase studies demonstrate a lack of correlation between activation of PKA and inhibition of rat vas deferens contraction or relaxation of bovine coronary artery. This does not support the hypothesis that the kinase is responsible for cAMP-induced relaxation of vascular and non-vascular smooth muscle. While the mechanism by which exogenous cAMP and specific analogs induce relaxation in some smooth muscle preparations remains unclear, it can be suggested that PKA activation is not necessarily required for the final functional effect. / Medicine, Faculty of / Anesthesiology, Pharmacology and Therapeutics, Department of / Graduate

Obesity is a major risk factor for insulin resistance, type 2 diabetes, cardiovascular disease (CVD), and vascular calcification. Vascular calcification is correlated with advanced CVD and a significant predictor of cardiovascular events. Obese individuals tend to have increased levels of circulating leptin, an adipocytokine that is a significant independent predictor of cardiovascular disease. We have shown that daily intraperitoneal injections of exogenous leptin (125 μg/mouse/d) can promote vascular calcification in an ApoE-/- mouse model of atherosclerosis. This increase in calcification is associated with an increase in the expression of several osteoblast-specific markers and is independent of any affect on atherosclerotic lesion size. Our studies suggest that leptin mediates the osteogenic differentiation of vascular smooth muscle cells (VSMCs) to promote vascular calcification via a pathway involving the inhibition of glycogen synthase kinase (GSK)-3 activity. Other studies have suggested that endoplasmic reticulum (ER) stress-induced GSK-3 activity promotes the development of atherosclerosis. Therefore, we hypothesized that during the progression of vascular disease, GSK-3 functions as a checkpoint for VSMCs at which cells can commit to: i) de-differentiation, thereby contributing to atherosclerosis, or ii) osteogenic differentiation, thereby contributing to vascular calcification. We investigated the effects of modulating GSK-3 activity on the differentiation of VSMCs in vitro. We found that many of the molecular tools that are typically used to modulate ER stress can promote the expression of osteoblast-specific markers and the osteogenic differentiation of MOVAS cells. However, because many of these interventions affect multiple pathways in MOVAS cells, the specific role of the ER stress – GSK-3 pathway is difficult to discern. Future studies are required to determine the effects of direct modulation of GSK-3 on vascular calcification and to delineate the mechanisms/effects of various ER stressors in the osteogenic differentiation of VSMCs. / Thesis / Doctor of Philosophy (Medical Science)

This document only includes an excerpt of the corresponding thesis or dissertation. To request a digital scan of the full text, please contact the Ruth Lilly Medical Library's Interlibrary Loan Department (rlmlill@iu.edu).

No description available.

No description available.