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Entrainment of the circadian system in rodents
Sosniyenko, Serhiy ; Sumová, Alena (advisor) ; Mareš, Jan (referee) ; Šauman, Ivo (referee)
The circadian clock located within the suprachiasmatic nuclei (SCN) of the hypothalamus responds to changes in the duration of day length, i.e. photoperiod, differently in the separate SCN parts. The aim of the study was i) to compare the effect of a long and a short photoperiod with twilight relative to that with rectangular light-to-dark transition on the daily profiles of clock gene expression and their protein levels within the rostral, middle and caudal regions of the mouse SCN; ii) to elucidate the dynamics of adjustment to a change of a long photoperiod to a short photoperiod of clock gene expression rhythms in the mouse SCN and in the peripheral clock in the liver, as well as of the locomotor activity rhythm; iii) to elucidate whether and how swiftly the immature rat fetal and neonatal molecular SCN clocks can be reset by maternal cues and iv) to reveal when and where within the rat SCN the photic sensitivity of clock gene expression develops during the early postnatal ontogenesis and to compare it with development of cfos photoinduction. Mice and rats were used for experiments; their tissues were analyzed by in situ hynridization, immunohistochemistry, RT-PCR. The data indicated that i) the twilight photoperiod provides stronger synchronization among the individual SCN cell subpopulations than the...
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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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Entrainment of the circadian system in rodents
Sosniyenko, Serhiy ; Sumová, Alena (advisor) ; Mareš, Jan (referee) ; Šauman, Ivo (referee)
The circadian clock located within the suprachiasmatic nuclei (SCN) of the hypothalamus responds to changes in the duration of day length, i.e. photoperiod, differently in the separate SCN parts. The aim of the study was i) to compare the effect of a long and a short photoperiod with twilight relative to that with rectangular light-to-dark transition on the daily profiles of clock gene expression and their protein levels within the rostral, middle and caudal regions of the mouse SCN; ii) to elucidate the dynamics of adjustment to a change of a long photoperiod to a short photoperiod of clock gene expression rhythms in the mouse SCN and in the peripheral clock in the liver, as well as of the locomotor activity rhythm; iii) to elucidate whether and how swiftly the immature rat fetal and neonatal molecular SCN clocks can be reset by maternal cues and iv) to reveal when and where within the rat SCN the photic sensitivity of clock gene expression develops during the early postnatal ontogenesis and to compare it with development of cfos photoinduction. Mice and rats were used for experiments; their tissues were analyzed by in situ hynridization, immunohistochemistry, RT-PCR. The data indicated that i) the twilight photoperiod provides stronger synchronization among the individual SCN cell subpopulations than the...
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