The circadian system controls the timing of behavioral and physiological functions in most organisms studied. The review addresses the question of when and how the molecular clockwork underlying circadian oscillations within the central circadian clock in the suprachiasmatic nuclei of the hypothalamus (SCN) and the peripheral circadian clocks develops during ontogenesis. The current model of the molecular clockwork is summarized. The central SCN clock is viewed as a complex structure composed of a web of mutually synchronized individual oscillators. The importance of development of both the intracellular molecular clockwork as well as intercellular coupling for development of the formal properties of the circadian SCN clock is also highlighted. Recently, data has accumulated to demonstrate that synchronized molecular oscillations in the central and peripheral clocks develop gradually during ontogenesis and development extends into postnatal period. Synchronized molecular oscillations develop earlier in the SCN than in the peripheral clocks. A hypothesis is suggested that the immature clocks might be first driven by external entraining cues, and therefore, serve as “slave” oscillators. During ontogenesis, the clocks may gradually develop a complete set of molecular interlocked oscillations, i.e., the molecular clockwork, and become self-sustained clocks., A. Sumová, Z. Bendová, M. Sládek, R. El-Hennamy, K. Matějů, L. Polidarová, S. Sosniyenko, H. Illnerová., and Obsahuje bibliografii a bibliografické odkazy
Kofein podaný večer snižuje ospalost a zvyšuje pozornost a schopnost poznávat. Zpožďuje však též časový cirkadiánní systém, neboť následující den po podání je zpožděn rytmus v tvorbě melatoninu, ukazatele fáze cirkadiánních hodin. Vynucená desynchronizace mezi spánkem a dobou vysoké noční hladiny melatoninu, která signalizuje subjektivní noc jedince, vede k narušení celého cirkadiánního systému., Evening caffeine consumption attenuates sleepiness and increases attention and cognitive abilities. In addition, it delays the circadian timekeeping system, as the next day after caffeine consumption the human melatonin rhythm, a circadian clock phase marker, is delayed. Forced desynchrony of sleep and the interval of high melatonin levels, which indicates a subjective night for an individual, leads to a disruption of the circadian system., and Helena Illnerová.
Prof. Jiří Velemínský was in particular an extraordinary and enthusiastic scientist. He was one of the first who investigated botanical genetics on the molecular level, thus he is regarded as founder of this research field in the Czech Republic. Prof. Jiří Velemínský was an excellent organizer of Czech research activities and also he was an outstanding personality. He died 23 February 2008. and Helena Illnerová.