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Circadian system and reproduction
Hrubá, Anežka ; Lužná, Vendula (advisor) ; Ladislavová, Lucie (referee)
Due to the alternation of day and night, mammals have developed internal circadian clocks, helping to synchronize physiological processes with the external environment. The circadian system is hierarchically organized, with central clocks located within suprachiasmatic nuclei of the hypothalamus (SCN). The main signal for setting the clocks to the external time is light, which enters the SCN through retina. The SCN communicate with peripheral oscillators in other organs, including reproductive ones, via hormonal signals, thereby synchronizing a variety of physiological processes. At the molecular level, clocks are controlled by clock genes. Cicradian system has a significant impact on reproduction. It is manifested by rythmical expression of clock genes and production of hormones in reproductive organs, as well as a success in reproduction if the clock's function is proper, and problems with reproduction if it is not. From a gender perspective, a several differences between women and men has been found throughout the SCN. Likewise, there are differences in chronotypes between both sexes over the course of their lives. Biological rhythms also include circannual rhythms, contributing to the timing of reproduction at the proper season of the year. Animals mate at different time depending on the length...
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Molecular mechanisms of entrainment of the fetal circadian clocks
Lužná, Vendula ; Sumová, Alena (advisor) ; Šauman, Ivo (referee) ; Štaud, František (referee)
In order to adapt to changing external conditions, organisms developed the endogenous biological clock for predicting daily alterations. This so-called circadian system drives functions and processes in the whole body with an approximately 24h period. The central oscillator, located in hypothalamic suprachiasmatic nuclei (SCN), is synchronized by light and subsequently sends the information about the time of the day to the rest of the body. Even in the ontogenesis, the functional SCN clock is crucial for proper development as well as health later in life. Since the maturation of embryonic SCN is not completed before birth, maternal signals seem to play a fundamental role in setting and synchronizing the fetal clock. During my PhD studies, we focused on elucidating the nature of maternal signals and their diverse impact on fetal SCN of rat and mouse models. We have revealed that developing SCN is able to sense distinct signals related to various maternal behavioral regimes. Importantly, we have discovered eminent role of glucocorticoids in synchronizing the fetal SCN, along with their ability to accelerate SCN development. These observations point out the importance of regular daily routine and noxious effect of stress during pregnancy. Since the mother communicates with the fetus through placenta...
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