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Circadian rhythms and photoperiodism in insects
STEHLÍK, Jan
In this thesis we present experimental data and discuss circadian rhythm regulation in the housefly, Musca domestica. Our findings suggest that, although differences in the mechanisms of circadian rhythm regulation between Musca domestica and Drosophila melanogaster are not as fundamental as was originally expected, they still provide interesting insight into the evolution of biological clocks. We also studied possible involvement of one of the circadian clock genes, timeless, in photoperiodic induction of diapause in a drosophilid fly, Chymomyza costata. We found the transcription of tim gene to be strongly disrupted in CNS of npd-mutant (non-photoperiodic-diapause) larvae. Analysis of genomic structure of tim gene revealed that the promoter of timelessnpd allele carries a large deletion, a possible cause of disruption of photoperiodic calendar function in npd-mutant larvae of C. costata.
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Molecular mechanisms of mammalian circadian clocks, its sensitivity to constant light and aging
Novosadová, Zuzana ; Sumová, Alena (advisor) ; Doležel, David (referee) ; Mráz, Miloš (referee)
Many processes in mammalian body exhibit circadian rhythms. These rhythms are driven by an intricate system composed of the central pacemaker, suprachiasmatic nuclei (SCN) in the brain, which entrains the peripheral oscillators in various organs, such as pancreas, liver, colon and lungs. Circadian clocks are autonomously driven in each cell based on molecular circuits involving so called clock genes, such as BMAL, CLOCK, PER and CRY. Age- dependent impairment of physiological functions of mammalian body, such as behaviour and metabolic functions, has been well documented. However, it has not been fully elucidated whether the impairment is linked with worsening of the circadian clock function. The aim of our study was to find out whether i) aging affects basic properties of the circadian clock in SCN and peripheral organs, such as pancreas, colon, liver and lungs, ii) aging- induced changes in glucose homeostasis affect the properties of the circadian clock in the pancreas, and iii) the sensitivity of circadian clock in SCN and peripheral organs to disturbances in environmental lightning conditions is altered during aging. We used groups of adult (9 months) and aged (25 months) animals which were subjected to 3 different light regimes, namely to light/dark regime (LD 12:12), constant light (LL) and...
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Circadian clocks in the brain and their function
Miklasová, Veronika ; Sumová, Alena (advisor) ; Kubová, Hana (referee)
In the brain, there is a center regulating circadian rhythms, which is located in the SCN. Outside these nuclei, there are other structures, which contribute significantly to coordination of circadian rhythms. Most of those nuclei are located in the hypothalamus and are connected with the SCN. These areas are involved in the management of basic physiological functions such as thermoregulation, food intake, sleep/wake cycles, hormonal secretion and control of locomotor activity. Outside the hypothalamus, there are other clocks, which work according to their location, e.g., clock in the limbic system participates in the control of cognitive functions. The olfactory lobe and retina harbor autonomous clocks that operate independently of the SCN. This work is focused on summary of the information about the selected extra- SCN oscillators in the brain their regulation of physiological functions. Key words: clock genes, circadian clocks, brain
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