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Synchronization of peripheral circadian clocks during ontogenesis.
Paušlyová, Lucia ; Sumová, Alena (advisor) ; Hock, Miroslav (referee)
The circadian system is an important coordinator of physiological functions of a mammalian organism. It comprises of a central oscillator represented by cells in the suprachiasmatic nuclei of hypothalamus (SCN) and peripheral oscillators in most if not all cells of peripheral tissues. The peripheral oscillators, similarly to the central ones, generate circadian oscillations at the level of so called clock genes and their protein products. In peripheral tissues, oscillations in expression of the individual clock genes are autonomous, however, they need to be synchronized to ensure their robust rhythmic expression. The peripheral clocks are synchronized mainly by rhythmical signals from the SCN, including signals regulating food intake. Disturbances in the clock gene expressions, as well as impaired synchronization signals, can result in various pathophysiological states. Spontaneously hypertensive rat (SHR) strain is a convenient animal model to study potential connection between the disturbed circadian system and progressive development of hypertension and metabolical diseases in mammals. Various studies have shown differences in the rhythmical expression of clock genes between SHR strain and normotensive Wistar/Wistar-Kyoto strain. The aim of this thesis is to provide insight into the early...
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Circadian clock during ontogenesis
Olejníková, Lucie ; Sumová, Alena (advisor) ; Hock, Miroslav (referee)
Circadian system enables adaptation of organisms to periodic changes in environment on the Earth. In mammals, it consists of central pacemaker in the suprachiasmatic nuclei (SCN) of hypothalamus and of oscillators that reside in other brain areas as well as in the peripheral organs and tissues. Ontogenetic development of the circadian system is a gradual process and the most dramatic changes undergo during the late embryonic and early postnatal stage. For its proper function, not only the morphological development of its individual parts, but also development of their entrainment to external environment and among each other, is important. The oscillations in clock gene expressions in the SCN occur already before birth, but in view of the fact that the levels of their protein products are undetectable, at this developmental stage, the ability of SCN to generate these oscillations in vivo has been discussed. After birth, the levels of these proteins rise and the rhythms in clock genes expression achieve the adult-like level at the postnatal age, when the synaptogenesis in the SCN is completed. The presence of a functional maternal circadian system is not necessary for the endogenous development of the SCN clock in pups, because the maternal SCN only entrains the clock and the circadian oscillations thus...
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