Orientador: Gabriel Forato Anhê / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-21T11:52:59Z (GMT). No. of bitstreams: 1 Faria_JulianadeAlmeida_M.pdf: 3166901 bytes, checksum: d6395a9feadc0393429b22df87066881 (MD5) Previous issue date: 2012 / Resumo: O aumento da produção hepática de glicose (PHG) é o principal componente que contribui para os elevados valores da glicemia de jejum em indivíduos obesos com Diabetes Mellitus tipo 2 (DM2). ...Observação: O resumo, na íntegra, poderá ser visualizado no texto completo da tese digital / Abstract: The increase in hepatic glucose production (HGP) is the main component that contributes to high values of fasting glucose levels in obese individuals with diabetes mellitus type 2 (DM2). ...Note: The complete abstract is available with the full electronic document / Mestrado / Farmacologia / Mestra em Farmacologia

Phosducin (Pdc) is a 28 kDa binding partner for the G protein beta gamma subunit dimer (G-beta-gamma) found abundantly in the photoreceptor cells of the retina and pineal gland. In the retina, light-dependent changes in cAMP and Ca2+ control the phosphorylation of Pdc at serine 73 and 54, respectively, which in turn controls the binding of Pdc to G protein beta gamma subunit dimer . G protein beta gamma subunit dimer binding has been proposed to facilitate light-driven transport of G protein beta gamma subunit dimer from the site of phototransduction in the outer segment of the photoreceptor cell to the inner segment, thereby decreasing light sensitivity and contributing to the process of light adaptation. Dopamine and melatonin are neuromodulators whose concentrations in the retina vary reciprocally during the circadian cycle, with dopamine high during the day and melatonin high during the night. Together, they control numerous aspects of light and dark adaptation in the retina. In this study, we have investigated the possible roles of dopamine and melatonin in regulating Pdc phosphorylation. Using phosphorylation-site specific antibodies to serines 54 and 73, we show that dopamine decreases the phosphorylation of both sites. This decrease is blocked by D4 receptor antagonists and pertussis toxin, indicating that dopamine causes a decrease in photoreceptor cell cAMP and Ca2+ concentration via the D4 receptor coupled to the Gi protein. Conversely, melatonin increases the phosphorylation of both S54 and S73, most likely via the inhibition of dopamine synthesis. These results demonstrate that dopamine and melatonin control the phosphorylation state of phosducin by changing the concentration of cAMP and Ca2+ in photoreceptor cells, and they suggest that dopamine and melatonin may contribute to the light-induced movement of the photoreceptor G protein by regulating Pdc phosphorylation.

published_or_final_version / Physiology / Doctoral / Doctor of Philosophy

published_or_final_version / Physiology / Doctoral / Doctor of Philosophy

published_or_final_version / Physiology / Doctoral / Doctor of Philosophy

No description available.

Motilitätsstörungen des Magen-Darm-Traktes können bei kritisch kranken Patienten auf der Intensivstation zu einem lebensbedrohlichen Krankheitsbild führen. Dabei spielen eine Vielzahl von Pathomechanismen eine Rolle, wobei das Interesse dieser Arbeit den Wirkungen des Tag-Nacht-Hormons Melatonin gilt. Da aus anderen Untersuchungen eine protektive Funktion des Melatonins postuliert werden kann, ist sein Einfluss auf die Peristaltik am Meerschweinchendünndarm untersucht worden. Dabei wurde durch kontinuierliche Perfusion eines Dünndarmsegments im Organbad eine gerichtete Peristaltik induziert. Der Schwellendruck, bei dem eine Kontraktionswelle ausgelöst wurde, als Messparameter herangezogen. Durch Zugabe von Melatonin (in den Konzentrationen: 10 pM, 1nM, 0,1µM und 10 µM) in das Organbad konnte kein Einfluss auf dem Schwellendruck nachgewiesen werden. Auch der Melatoninrezeptorantagonist Luzindol führte zu keiner Änderung des Schwellendruckes. Ein signifikanter Anstieg des Schwellendruckes und damit ein inhibitorischer Einfluss auf die Dünndarmperistaltik konnte lediglich durch den partiellen Agonisten 2Phenylmelatonin nachgewiesen werden. Wesentliche Ergebnisse dieser Arbeit zeigen den Einfluss von Melatonin unter Hypoxiebedingungen des Dünndarmes, bei dem Luzindol den inhibitorischen Effekt auf die Darmperistaltik verstärkt. Die Melatoningabe führt zu keiner protektiven Wirkung auf die Darmperistaltik unter Hypoxiebedingungen. Damit ist zu vermuten, dass der protektive Effekt des Melatonins auf die Darmperistaltik nicht durch seine Eigenschaften als Radikalfänger, sondern über Melatoninrezeptoren vermittelt wird. In den Versuchen mit dem Opioid Fentanyl ist eine signifikante Hemmung der Dünndarmperistalik ebenso unter Blockade des Melatoninrezeptorantagonisten Luzindol festzustellen. Bei Versuchen mit Propofol wurde durch Zugabe von Melatonin oder Melatoninrezeptoragonisten eine Verstärkung der Hemmung der Dünndarmmotilität durch Propofol nachgewiesen. In unseren Versuchen bestätigten wir, dass Midazolam eine hemmende Wirkung auf die Dünndarmperistalik hat. Eine vorherige Zugabe von Melatonin hatte dabei keinen Einfluss auf die hemmende Wirkung von Midazolam, wohingegen Luzindol die Hemmwirkung von Midazolam verstärkte. Somit hat das endogene Melatonin möglicherweise einen protektiven Einfluss, der jedoch durch exogene Zugabe von Melatonin nicht verstärkt wird und nicht nachgeahmt werden kann. Insgesamt zeigen die Untersuchungen, dass Melatonin per se keinen gesicherten Einfluss auf die Peristaltik hat, möglicherweise aber in Wechselwirkung mit Anästhetika. / Effects of Melatonin on intestinal peristalsis. In vitro-study on guinea-pig small intestine.

Wound healing is a dynamic process that ultimately leads to restoration of tissue integrity and function. The pineal gland hormone melatonin is known for its anti-oncotic, anti- inflammatory and immuno-modulatory effects. However, its role in wound healing has not been established. Since melatonin is synthesised endogenously, we primarily sought to investigate whether the melatonin receptors played a role in the wound healing process. Using immunohistochemical methods and Western blot analysis we observed that MT₁ was normally absent in the rat skin but was strongly expressed on day 1 to day 3 post wounding in the epidermis adjacent to the wound edge. MT₁ expression was restricted to the stratum granulosum and stratum spinosum layers of the epidermis in the rat wounds. MT₁ expression declined thereafter and became nonexistent by day 21 when the wound had completely healed. In contrast, MT₂ was constitutively expressed in all the layers of the normal rat epidermis. MT₂ expression gradually decreased at the injury site following wounding but returned to the normal profile by day 21. Aged rat epidermis showed similar MT₁ and MT₂ expression as adult rats. The profile of tissue distribution of MT₁ and MT₂ in the human epidermis was comparable to the rat epidermis. In the CVUs MT₁ and MT₂ localisation profiles resembled that of a healing wound, akin to a day 1 or day 3 rat dermal wound, during the inflammatory phase. Surprisingly, in contrast to all the tissues investigated, MT₁ was also localised in the stratum basale layer of the keloid epidermis. MT₂ localisation in the same keloid tissues however resembled normal human skin profiles. Secondly, we determined the effects of exogenously administered melatonin, on scarring and wound healing, using a full thickness incisional model of wound healing in rats. Melatonin treatment significantly improved the quality of scarring by day 21. However, our findings would have been strengthened by a more explicit wound closure analysis, measurement of granulation tissue weight, tensile strength, hydroxyl proline content and immunohistochemical assessments of neutrophil infiltration, macrophages, fibroblasts, myofibroblasts and reepithelialization. The treatment also accelerated the angiogenic process and enhanced the VEGF protein profile. Arginase generates proline, the building block for collagen synthesis. Melatonin treatment increased arginase activity and consequently would increase collagen synthesis from day 1. An increase in NOS activity and therefore NO production is known to be detrimental during inflammation. However, various studies have also shown that the NO is essential for granulation tissue formation. Melatonin treatment significantly decreased iNOS activity during the acute inflammatory phase in this study, but significantly increased iNOS activity during the resolving phase. Other markers of inflammatory response and repair were also examined in this study. COX-2 has been shown to play an anti-inflammatory role and melatonin increased COX-2 activity and protein following wounding. SOD (the antioxidant enzyme) activity was also significantly increased during the chronic inflammatory phase on melatonin administration. HO-1 and HO-2 isoforms have also been previously demonstrated to participate in the repair process. Melatonin treatment increased up-regulation of both HO-1 and HO-2 protein expression in the wounded skin. A significant decrease in all the mitochondrial enzyme activities (except complex-II-III), was observed post wounding. Melatonin treatment restored the complex activities to near normal levels. Melatonin also protected mitochondrial membrane integrity and reduced oxidative stress as evidenced by the maintained level of aconitase and citrate synthase activities at near normal levels. In vitro experiments using macrophage and fibroblast cell lines illustrated that melatonin may decrease NOS activity and protein profiles indirectly by stimulating arginase activity and thereby depleting the availability of arginine. This study is the first to fully demonstrate the distribution of melatonin receptors in normal and abnormal wounds. Improvement in the quality of scarring in a rat model of wound healing on melatonin administration is promising but much more quantitative work and preclinical studies are required before melatonin advances into clinical assessment.

Thesis (M.Sc.)--York University, 2004. Graduate Programme in Biology. / Typescript. Includes bibliographical references (leaves 87-115). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: LINK NOT YET AVAILABLE.

Thesis (M. Phil.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves 71-100). Also available in print.