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Structural determinants of regulation of surface delivery of NMDA receptors in mammalian cells
Danačíková, Šárka ; Horák, Martin (advisor) ; Bendová, Zdeňka (referee)
N-methyl-D-aspartate (NMDA) receptors are ligand-gated ion channels activated by agonist glutamate and co-agonist glycine. They play a key role in mediating the fast excitatory synaptic neurotransmission in the mammalian central nervous system. To create a functional heterotetrameric receptor, the presence of two GluN1 subunits combined with GluN2 or GluN3 subunits is necessary. Previous studies confirmed the importance of M3 transmembrane helix and extracellularly localized cysteines in regulation of surface expression of functional NMDA receptors. The aim of my thesis is to elucidate an influence of clinically relevant mutations in M3 transmembrane helix and the role of all known cysteines that form disulphide bonds on surface delivery of NMDA receptor expressed in heterologous monkey kidney fibroblasts cell culture (COS-7). Using molecular biology methods, immunocytochemistry and microscopy I found that the clinically relevant mutations M641I and Y647S in GluN1 subunit and also the mutations of particular cysteines forming disulphide bonds caused substantial decrease of surface expression of NMDA receptors. Furthermore, I discovered that the effect of mutated GluN1 subunits on decrease of surface expression depends on the subunit composition. The contribution of my results lies in elucidating the...
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Interplay between adenosine signaling and the circadian system
Škrle, Jan ; Bendová, Zdeňka (advisor) ; Houdek, Pavel (referee)
Sleep is regulated primarily by the two processes, by Process C and S. Process C represents circadian regulation by circadian system; Process S represents the homeostatic sleep drive. Circadian system controls the timing of many physiological functions including body temperature rhythms, locomotor activity rhythms, periodically changing hormones levels etc. Process C contributes to sleep regulation mainly by setting lower and upper thresholds for a sleep pressure. When the sleep pressure reaches one of these thresholds, falling asleep or waking is promoted. However, the sleep architecture is altered by a phase of endogenous oscillators as well. The homeostatic sleep drive is based on a sleep- wake history with the sleep pressure rising during a wakefulness and lowering during sleep. This mechanism is responsible for a modification in structure of a recovery sleep following a sleep deprivation. Due to the effects of adenosine on sleep regulation, adenosine signalling is considered to play a critical role in the homeostatic sleep drive. These two processes were thought to be independent of each other, but new data show that there is a reciprocal regulation between them. The aim of this work was to conclude, where these two processes meet, with a special attention on processes, where the adenosine...
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Assessment of the influence of artificial lighting simulating a natural photoperiod and spectrum on the parameters of circadian rhythms of healthy volunteers
Gesztesová, Kristina ; Bendová, Zdeňka (advisor) ; Jelínková, Dana (referee)
The alternation of light and darkness on planet Earth has led to the development of endogenous systems that operate with a period of roughly 24 hours. We refer to these systems as circadian. For optimal functioning of the human circadian system, regular synchronization by an external stimulus is required. Light is a strong stimulus for synchronization for humans, but it should be noted that the outcome of this light synchronization depends critically on a number of factors. These factors include the timing and duration of the light pulse, as well as light parameters like spectrum and intensity. Commonly used interior lighting is often not optimal for the human endogenous circadian system, which is why the alternative of so-called biodynamic lighting (lighting that adequately stimulates the human organism) is being used more lately. As part of the experiment, we verified the effect of the newly created biodynamic lighting on the parameters of the circadian rhythm of healthy volunteers. Using methods of melatonin profile analysis, analysis of temperature records and actigraphy, we confirmed the influence of our experimental lighting.
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Effect of ketamine on light-induced changes in the circadian system
Kratina, Alex ; Bendová, Zdeňka (advisor) ; Valeš, Karel (referee)
The circadian system is controlled by the suprachiasmatic nuclei of the hypothalamus (SCN) and ensures optimal timing of physiological processes. Synchronization of this system with external light conditions is based on the activation of NMDA receptors during light exposure in the subjective night. Ketamine is a non-competitive antagonist of NMDA receptors used as a safe anesthetic, whose subanesthetic doses act as an antidepressant with a rapid onset of action, and increase proliferation in some parts of the brain. There are hypotheses about the possible effect of subanesthetic doses of ketamine on the circadian system, altough this effect has not yet been tested. This work aims to investigate the effect of a single subanesthetic dose of ketamine on the circadian system of the rat, especially on light-induced changes in locomotor activity and light-induced markers in the SCN and dentate gyrus, which represents one of the strongly proliferative areas of the brain. Our results show that ketamine decreases light pulse-induced c-FOS protein expression in the SCN at the onset of the subjective night, but increases this expression in the dentate gyrus under the same conditions. Reduction of c-FOS expression in the SCN correlates with the behavioral output of the circadian system and thus suppresses the...
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Regular physical activity as a circadian Zeitgeber
Fenclová, Aneta ; Bendová, Zdeňka (advisor) ; Červená, Kateřina (referee)
The function of almost every cell in the body is regulated by the circadian system. At the whole-body level, this system consists of the main oscillator, which is formed by the suprachiasmatic nucleus of the hypothalamus, and peripheral oscillators of individual organs and tissues. This system is sensitive to periodic changes in the external environment, particularly to the alternation of light and darkness, and under unfavorable lighting conditions, it can lead to desynchronization of both this timing system with the solar cycle and the mutual desynchronization of individual organs and tissues. This temporal mismatch of physiological processes can cause a range of diseases and metabolic disorders, and can be partially prevented by regular physical activity. Daily oscillations of circadian rhythms in many cardiovascular and metabolic parameters also determine the ideal time of day for anaerobic performance. This bachelor's thesis is a selection and comparison of information from professional literature and available studies dealing with the mutual influence of physical activity and circadian rhythms. There are works mentioned here that test the effect of physical activity on internal desynchronization of the melatonin rhythm and sleep pattern, on the circadian synchronization of skeletal muscle, as...
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Development of the circadian system after systemic potentiation of GABAergic transmission in early ontogenesis
Dušek, Jakub ; Bendová, Zdeňka (advisor) ; Mareš, Pavel (referee)
The circadian system is the evolutionary response of organisms to repetitive geophysical conditions and allows organisms to devote their energy to solving sudden changes. Although the circadian system developed to help organisms survive and thrive in dynamic conditions, system itself is sensitive to external changes. During critical developmental period of the mammalian CNS, the neonatal period, the circadian systém is significantly vulnerable. Benzodiazepines, pharmaceuticals widely prescribed for half a century, interfere with GABAergic transmission, which is critical type of signaling for the functioning of the circadian systém. The purpose of this thesis is to determine whether and how the development and functioning of the circadian system is altered after administration of a drug from the benzodiazepine class, clonazepam, during the critical developmental period. This thesis examines changes in the expression profile of selected genes in the hippocampus, olfactory bulb and frontal cortex of two ontogenetic stages of rats. Results of this work suggest that benzodiazepines administred in the neonatal period disrupt the development of the circadian system and that these changes, particularly in the hippocampus, persist for certain time. Key words: circadian system; circadian rhythms;...
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The effect of long-term morphine application on clock genes expression in the rat brain
Pačesová, Dominika ; Bendová, Zdeňka (advisor) ; Roubalová, Lenka (referee) ; Polidarová, Lenka (referee)
The circadian and opioid systems are systems involved in maintaining homeostasis in the body. Disruption of the circadian system disturbs the proper timing of physiological processes, which can result in the development or exacerbation of pre-existing pathological conditions, including addiction. One of the factors that can influence the precise synchronization of the circadian system is the use and abuse of opioids. The interrelationship between the circadian and opioid systems is poorly studied. To this end, the present study investigated the effect of morphine and methadone on the rat circadian system in adulthood and during development. The aim of this dissertation was to observe the effect of acute morphine administration on the expression of clock genes in the suprachiasmatic nuclei (SCN) of adult rats, and to investigate the effect of long-term morphine or methadone administration and withdrawal on the expression of clock genes in the SCN and on the activity of the enzyme AA-NAT in the pineal gland of adult rats. Proper development of the circadian clock contributes significantly to the maintenance of health in adulthood and ensures good adaptability of the organism to changes in the external environment. No study to date has focused on examining the effects of opioid administration during...
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Emotional transition and nonstructural changes in mouse models of autism
Nováková, Rozálie ; Kubik-Zahorodna, Agnieszka (advisor) ; Bendová, Zdeňka (referee)
Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder characterised by repetitive behaviour and impairments in social behaviour and social communication. The whole aetiological heterogeneity is still not fully elucidated. It is then very important to focus on experimental research, especially on animal models, to help with drug development and recovery. To broaden the variability of focus of behavioural tests on mouse sociability, a new modification of a test to assess transfer of emotional information was proposed. A similar test was published recently for the first time, but it is still not common to use it in mice. Results show that it is possible to measure transfer of fear between conspecifics only during their immediate direct encounter through behavioural evaluation, but not in further standardised anxiety-evaluating tests. Self-grooming behaviour was the only parameter significantly affected by transferred anxiety in the experimental setup used, and therefore should be considered as the most sensitive behavioural parameter describing animal emotional state. However, the variability in individual animal behaviour is still considerably large, which confounds the results to a great degree. Such a behavioural test for transfer of emotional information may be especially useful in...
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Physical and mental performance of morning and evening chronotypes in different times of day
Červená, Kateřina ; Bendová, Zdeňka (advisor) ; Jelínková, Dana (referee) ; Větrovský, Tomáš (referee)
Circadian rhythmicity, which evolved in accordance with the rhythmicity of the external environment tied to the earth's rotation, governs the regular rhythms of our physiology and behavior. The central circadian clock in the suprachiasmatic nuclei of the hypothalamus controls the roughly 24-hour rhythmicity of many peripheral clocks of most cells of the body, that can be observed from the molecular to the behavioral level. The intrinsic circadian period (τ) in humans is on average slightly longer than 24 h, but may also be slightly shorter. Individuals with a short τ are referred to as morning chronotypes, whereas individuals with a long τ are referred to as evening chronotypes. However, the majority of the population belongs to the so-called intermediate chronotype. The molecular mechanism of circadian oscillations controlled by the circadian clock has been shown to be closely linked to cellular metabolism. Many physiological processes important for physical and cognitive performance are also regulated by the circadian system. The main aim of both studies was to quantify the difference in performance during morning and evening testing in subjects of a pronounced evening and morning chronotype. While the motivation for conducting Study A was practical, with the aim of identifying potential biases...
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The effect of pineal melatonin on insulin production
Hovorková, Adéla ; Bendová, Zdeňka (advisor) ; Horníková, Daniela (referee)
Both production and secretion of insulin depend on the circadian rhythms. These are set by the internal circadian clock reacting to the external stimuli such as the light or the darkness. The central clock synchronization of the rhythmic processes in the organism is formed by the structure so-called suprachiasmatic nucleus. Secretion of melatonin, aka "hormone of the night," is controlled by the central clock and serves to align them with the peripheral clocks. Peripheral clocks are located, for example, in pancreas, liver or other body organs. Langerhans' islets in pancreas consist of -, - and -cells. These play an important role in maintaining glucose homeostasis as they produce hormones insulin and glucagon, key blood glucose level regulators. This text describes how the corruption of circadian system by a light pulse at night impacts insulin secretion. A phase shift results in melatonin secretion anomaly (increase), which inhibits insulin levels and thus gives rise to elevated glucose levels. Hyperglycaemia and insulin resistance because of a long-term rhythm corruption may result in type 2 diabetes. Key words: circadian rhythm, SCN, melatonin, MT1 receptor, MT2 receptor, β-cell, insulin, glucagon, insulin resistance, type 2. diabetes
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