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Mechanisms of maternal entrainment of the fetal circadian clock
Černá, Barbora ; Sumová, Alena (advisor) ; Balaštík, Martin (referee)
Our body is influenced by many cyclical changes in the environment, such as day and night or seasons. To predict these changes and react to them in time, the organism is equipped with inner clock, which rhythmically influences many physiological processes, such as sleep or metabolic rhythms. Disrupting our inner rhythms at molecular and behavioral levels contributes to many serious disorders. It is necessary that all mechanisms of the inner circadian clock are developed and set up properly. Circadian clocks are set up by the mother, who passes rhythmical information about day and night cycle on to her embryo. Though a great attention is devoted to revealing the nature of this synchronization between the mother and her pup, the mechanisms of this process have not been fully understood yet. The aim of this thesis is to contribute to actual understanding of this synchronization. Experiments, performed in this thesis, relate to studying the ability of maternal signals to synchronize embryos with the environment. Feeding and light regime of pregnant rats was manipulated and the effect of these changes on the neuronal activity within the suprachiasmatic nuclei of 19-day embryos was analyzed.
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Molecular mechanisms of circadian clock entrainment by daily regime in food intake
Kapoun, Jiří ; Sumová, Alena (advisor) ; Červená, Kateřina (referee)
Circadian clocks form an endogenous time-keeping system present in most organisms, synchronizing physiological and behavioural processes with perodically changing environmental conditions. The system comprises of the master clock in the suprachiasmatic nuclei of the hypothalamus and numerous subsidiary clocks in peripheral tissues. Its molecular design is constituted by the clock genes, which are rhythmically expressed, form a series of transcriptional/translational feedback loops and influence the expression of various other genes involved in metabolic pathways. The peripheral clocks are dependent on the master clock, although they can be entrained with external cues like food intake timing and diet composition. This desynchronization leads to the distruption of clock gene oscillation, which can potentially have serious impact on metabolic processes and increase the risk of metabolic disorders. The aim of this thesis is to summarize current knowledge on the relationship of molecular chronobiology and nutrition with a focus on the molecular mechanisms through which can food, especially its intake timing and composition, influence the crosstalk between clock gene expression and cellular metabolism. The thesis also emphasises the potential effect of circadian clock disruption on the risk of metabolic...
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Interaction between circadian clock and macrophages in the adipose tissue
Honzlová, Petra ; Sumová, Alena (advisor) ; Horáková, Olga (referee)
Well functioning circadian system is crucial component of healthy organism and its disruption can result in impairment of metabolic functions with consequential development of obesity and type 2 diabetes mellitus. Obesity is in general caused by enhanced migration of pro- inflammatory polarized macrophages (M1) into adipose tissue. We have shown, that interaction of this type of macrophages with adipose tissue had significant effect on rhythmic expression of clock genes in adipocytes. We further investigated effect of high fat diet and diet enriched by omega-3 fatty acids on circadian oscillations in WAT and differently polarized macrophages. This diet affected oscillations in adipose tissue and in M0 and M2 polarized macrophages. These results support previous findings of effect of omega-3 fatty acids on metabolism and suggest their effect on circadian system as well. Key words: circadian rhythms, adipose tissue, macrophages, omega-3 fatty acids, high fat diet
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Circadian clock in hippocampus
Šuchmanová, Karolína ; Sumová, Alena (advisor) ; Mareš, Pavel (referee)
Hippocampus is one of the main components of the limbic system. It plays an important role in the process of memory formation and recent literature shows that, like in other peripheral organs and brain structures, there is a circadian clock present in the hippocampus. The aim of the thesis was to study the hippocampal circadian clock under various conditions. The first part of the thesis examines the influence of glucocorticoid hormones on the clock gene expression in the hippocampus. Glucocorticoids are mammalian steroid hormones secreted from the adrenal glands that affect many processes in the organism. The glucocorticoid secretion is under the control of the circadian system, causing their levels to exhibit a pronounced diurnal rhythm. The hippocampus provides feedback to the hypothalamo-pituitary-adrenal (HPA) axis and is thus involved in the regulation of glucocorticoid hormone secretion. Hippocampal neurons also express glucocorticoid hormone receptors (GR). This thesis explores the effect of the absence of glucocorticoid hormones on the clock gene expression in the hippocampus. The absence of glucocorticoids was due to adrenalectomy and its effect was further compared with the effect of endogenous glucocorticoid replacement by daily injections of the GR agonist dexamethasone, emulating...
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Other factors influencing daytime melatonin levels.
Rácz, Beáta ; Vondra, Karel (advisor) ; Kršek, Michal (referee) ; Sumová, Alena (referee)
Circadian rhythms are important for the adaptation of the organism to the changes of the environment. The internal biological clock (pacemaker) has a rhythm which is slightly longer or shorter than 24 hours. Melatonin is a pineal hormone produced during the dark period. The gastrointestinal tract is the main extrapineal source and the main source of melatonin during the light period. There are missing studies which are focused on the effects of the food on steroid hormones. Aim: To elucidate the effect of the food on selected hormone levels in two consequent studies of eight healthy nonsmoker premenopausal women in follicular phase of their menstrual cycle. Results: 1) 16 hours long monitoring: The levels of melatonin decreased significantly two hours after lunch. Cortisol levels were decreasing throughout the whole day and an additional decrease was found two hours after lunch. We were the first to report the significant connections of estradiol and SHBG to food intake. 2) Monitoring after different stimuli: Levels of melatonin increased 40 minutes after the i.v. application of glucose. In oGTT this increase was slower. Cortisol has decreased after the application of glucose, more apparently after its i.v. application. The breakfast led to increase of cortisol levels. OGTT and i.v.GTT caused some...
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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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