Agradecimentos Meus pais, pelo apoio em todos os sentidos, durante esses três anos de Mestrado. Gisele Akemi Oda, minha orientadora brasileira, e Verónica Sandra Valentinuzzi, minha orientadora na Argentina (cuja orientação infelizmente não pôde ser oficializada por questões burocráticas). Barbara Tomotani e Patricia Tachinardi, colegas de laboratório, que me suportaram durante as longas estadias em Anillaco, e participaram ativamente no planejamento, execução, análise e discussão de todos os experimentos de campo e laboratório. Mirian Marques, que, juntamente com minha orientadora Gisele Oda, me introduziu ao mundo da Cronobiologia e me mostrou o que é fazer uma boa ciência. José Paliza, que construiu a maior parte dos equipamentos de laboratório e campo, e garantiu que nossas idéias saíssem do papel. Funcionários e Pesquisadores do CRILAR, por tornarem minha estadia em Anillaco uma experiência prazerosa e contribuírem com discussões frutíferas. AbstractDaily rhythms are found in the biological variables of many organisms, in parallel to the environmental day and night. Most of those rhythms are not mere reactions to the cyclic stimulus of the environment. They are actually circadian rhythms, endogenously generated by an internal timer, the circadian oscillator, which sustains a non-24-hour rhythm under constant conditions, but is synchronized to a 24-hour period when exposed do a cyclic environment. In mammals, this oscillator is located in the brain, and can be synchronized by the daily light-dark cycle (LD cycle) of day and night. Subterranean animals remain most of the time in an underground habitat, where environmental conditions vary less markedly than aboveground.Therefore, there are doubts whether these animals maintain circadian rhythms and whether their circadian oscillators rely on the LD cycle for environmental synchronization. We attempted to answer those questions in subterranean rodents of the species Ctenomys cf.knighti (tuco-tucos). In the field, we performed direct visual observations to assess their temporal pattern of light-exposure. In the lab, we build the Phase Response Curve (PRC), which consists in an indirect measurement of the circadian oscillator responses to light stimuli applied at different times of the day. Finally, computer simulations of an oscillator model were used to integrate these previous data. We verified that tuco-tucos expose themselves to light pulses that are irregularly distributed through day-light hours, raising some questions about its validity as an environmental synchronizer. However, the PRC results indicated that the tucotucos circadian system responds to light stimuli in a way similar to non-subterranean animals.We then verified three hypothesis: either the light-exposure temporal information was enough for the synchronization of the circadian system, despite its apparent irregularity; or the tucotuco's PRC present some feature that facilitates the synchronization by the observed lightexposure regimen; or the tuco-tuco's circadian system rely on anoth...
São Paulo July 2016 Ficha catalográficaComissão Julgadora: Prof(a). Dr(a).Prof(a). Dr(a). Prof(a). Dr(a).Prof(a). Dr(a Carreira Improta and Jefferson Silva. They were more than my labmates. We have been through some happy and some not so happy moments in the long-lasting travels to Anillaco, helping one another in our experiments. In the paper discussions, together with our supervisors, we ventured into the wilderness of abstract concepts.
Resumo. A manifestação de ritmos biológicos nos mais diversos organismos é reconhecida desde a antiguidade, mas os princípios básicos responsáveis por sua geração começaram a ser desvendados somente no século passado, e continuam até os dias atuais. Nesse contexto, um grande marco foi a descoberta de uma rede de genes cujos processos de transcrição e tradução são regulados entre si e que constituem a maquinaria básica do sistema oscilatório endógeno. Esta revisão visa descrever o funcionamento desta maquinaria em mamíferos, detalhando seus atuais componentes e como isso se propaga para todo o organismo.Palavras-chave. Ritmo circadiano, regulação gênica, núcleos supraquiasmáticos, genes relógios. REGULATION OF GENE EXPRESSION IN THE MAMMALIAN CIRCADIAN CLOCKWORKAbstract. The expression of biological rhythms in most organisms is recognized since antiquity, but the basic principles responsible for their generation have only been unraveled from the last century on. In this context, a great mark was the discovery of a net of genes whose transcription and translation processes are regulated between each other and constitute the basic machinery of the endogenous oscillatory system. This review aim to describe how this machinery works in mammals, detailing its current components, and how it is propagated all over the organism.
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