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Molekulární mechanismus cirkadiánních hodin a jejich synchronizace v trávicím systému potkana
Polidarová, Lenka ; Sumová, Alena (advisor) ; Doležel, David (referee) ; Zeman, Michal (referee)
The circadian system controls the timing of behavioral and physiological processes in most organisms with a period of about 24 h. In mammals, the circadian system consists of the central oscillator in the suprachiasmatic nuclei (SCN) and peripheral oscillators located in numerous organs such as the liver, heart, lung, muscles, intestines etc. Peripheral oscillators are cell-autonomous, they could also work independently of the SCN entrained by a feeding cycle. The misalignment of the endogenous timekeeping system, due to e.g. irregular daily schedule or shiftwork, may lead to the development of severe diseases including sleep disorders, gastrointestinal (GI) problems and various types of cancer. Therefore, understanding the molecular mechanism of the circadian clock may facilitate the treatment of diseases caused by malfunction of the circadian system. In my PhD thesis, I focused on the determination and synchronization of circadian clocks within the rat digestive system and on their development during ontogenesis. Moreover, the circadian system of a rat strain with pathology, i.e., spontaneously hypertensive rat (SHR) was also studied. We identified the circadian clocks in the individual parts of the intestine and ascertained that these clocks are mutually synchronized with the phase-delay along...
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Photoperiodic modulation of the central circadian clock in the suprachismatic nucleus and in the peripheral clock in the liver
Parkanová, Daniela ; Doležel, David (referee)
Most physiological processes in mammals follow daily oscillations. These circadian rhythms are driven by central oscillator located in the suprachiasmatic nucleus (SCN) of hypothalamus. The SCN coordinates rhythmical activity of the subsidiary peripheral oscillators distributed in many different tissues. In gastrointestinal system, the peripheral clocks and metabolism are closely linked. The mechanism of circadian oscillations is based on transcriptional-translational feedback loops, which drive rhythmic expression of the clock genes. The entrainment with external conditions is essential for proper function of the circadian clock. While the SCN is driven mainly by the light-dark cycle, synchronization of the peripheral clocks depend on many factors, such as feeding and fasting. The length of the light part of the day, i.e. photoperiod, changes throughout the year rapidly and circadian system has to adapt to the changes all the time. However, a mechanism of adjustment to the change in the photoperiod has not been fully understood. The aim of this work was to elucidate the effect of change in the photoperiod on the central SCN clock and on the peripheral clock in the liver. Firstly, we focused on dynamics of adjustment of these clocks to the change from a long photoperiod, with 18 hours of light, to...
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