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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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Circadian regulation of the cardiovascular system
Nováková, Jessica ; Bendová, Zdeňka (advisor) ; Galatík, František (referee)
Circadian system consist of the main circadian oscillator and the peripheral oscillators. Their function is to enable the adaptation of living organisms to the diurnal environmental changes. Circadian system regulates rhythmical expression of genes in nearly every cell of the body, thereby affecting both the physiological and behavioural processes of mammals and other animals. This bachelor's thesis summarizes a knowledge from experiments which led to the demonstration of circadian rhytms in cardiovascular system. To introduce the topic, the first discoveries of circadian rhythms in the cardiovascular system are mentioned. Then, we focus on the circadian rhythms in cardiomyocytes, vascular endothelial cells and in vascular smooth muscle cells. Another focal point of my thesis is the role of transcription factor Krüppel-like factor 15. Circadian regulation of the cardiovascular system is important for the proper function of the heart and blood vessels. Circadian disruption can cause severe pathophysiological and cardiovascular conditions, such as ventricular hypertrophy, hypertension, atherosclerosis, myocardial infarction or coronary artery disease. Key words: circadian, clock genes, cardiovascular system, cardiomyocytes, vascular endothelial cells, vascular smooth muscle cells, Krüppel-like factor...
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The photoperiodism and hibernation
Pařezová, Lucie ; Bendová, Zdeňka (advisor) ; Weissová, Kamila (referee)
Many organisms living in seasonal environments use annual changes in the length of the day for timing of their responses, such as reproduction, migration or hibernation. Hibernation allows animals to survive difficult periods associated particularly with cold temperatures and lack of food resources. This adaptation requires many physiological, morphological and behavioral changes. Some of these changes take longer, so their right timing is crucial. For most hibernators in temperate regions shortening of the photoperiod is the most reliable signal for initiation of these changes. This work describes the transduction of photoperiodic information to the melatonin signal, its effects in the pars tuberalis and the significance of this structure in seasonal physiology. A more detailed description is devoted to hibernation, and in the last chapter there is briefly mentioned photoperiodism in nonhibernating organisms. Powered by TCPDF (www.tcpdf.org)
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Developmental changes in expression levels of the chosen subunits of NMDA and AMPA receptors and action of their antagonists on physiological and epileptic phenomena
Szczurowska, Ewa Katarzyna ; Mareš, Pavel (advisor) ; Rokyta, Richard (referee) ; Bendová, Zdeňka (referee)
During early stages of postnatal development, glutamate receptors of NMDA and AMPA type, undergo intensive functional changes due to modifications of their subunit composition (Pachernegg et al., 2012: Paoletti et al., 2013). The NR2B-containing NMDARs (NR2B/NMDARs) and GluA2-lacking AMPARs (Ca 2+ -permeable) that are highly expressed in immature brain, are implicated in increased excitability, seizures generation, excitotoxicity, and neuronal death (Vizi et al., 2013). Pharmacological blockade of these types of receptors by their specific antagonists, can exhibit anticonvulsant effects at early stages of postnatal development. Therefore, we tested the influence of the IEM1460, a specific antagonist of Ca 2+ -permeable AMPARs and the Ro 25-6981 maleate, a highly selective and activity-dependent antagonist of NR2B/NMDARs on physiological excitability and epileptic phenomena induced in immature rats. Anticonvulsant action of IEM1460 was tested in two models of epileptic seizures: pentylenetetrazol (PTZ)- induced convulsions and cortical afterdischarges (ADs), induced in animals at P12, P18 and P25. Our results indicate that the effects of IEM1460 on various types of seizures depend on their sites of origin in the brain, developmental stage, and GluA2 subunit expression profile. To clarify the action...
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The disruption of the circadian system in bipolar disorder and its association with the polymorphism of L-type calcium channel
Filipovská, Eva ; Bendová, Zdeňka (advisor) ; Novosadová, Zuzana (referee)
Bipolar affective disorder is a serious psychiatric disease with prevalence of about 1% in general population. Typical symptoms are mood changes: manic periods are followed by depressions, with possible asymptomatic period of variable duration between them. It alters patient's everyday life and often leads to suicidal tendencies. Bipolar disorder is related to impaired circadian rhytms that are regulated from suprachiasmatic nuclei in hypothalamus. Impaired circadian rhytms in bipolar disorder are manifested by abnormalities of sleep and daily activity and by disrupted circadian secretion of several hormons. One of many factors that link bipolar disorder to circadian system at molecular level is the function of voltage-dependent calcium channels of L-type. Expression of these channels is regulated by the clock genes and their proper function is important for maintaining endogenous oscillations in the main oscillator located in suprachiasmatic nuclei. A common finding in patients with bipolar disorder is polymorphism of the gene for 1 subunit of the Cav1.2 channel. Abnormal function of calcium channels, consequent to the polymorphism, may be one of the causes that alter circadian rhytms in bipolar disorder. Key words: circadian system, suprachiasmatic nucleus, bipolar disorder, L-type calcium...
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Expression of AMPA glutamate receptor subunits in the suprachiasmatic nucleus of the rat
Červená, Kateřina ; Bendová, Zdeňka (advisor) ; Zemková, Hana (referee)
The main mammalian circadian pacemaker stored in suprachiasmatic nuclei of the hypothalamus (SCN) is adapted to changes in the external environement by synchronization of its endogenous period with periodic changes of light and dark during day and night. The information about light travels via glutamatergic retinohypothalamic tract to the ventrolateral part of the SCN. Activation of ionotropic glutamate receptors in this area provably mediates the transfer of information about light on the transcriptional mechanism of light-sensitive cells. The role of the NMDA type of ionotropic glutamate receptors is well studied in this field and it is known that some NMDA receptor subunits show a circadian rhythm and an increased expression after a light pulse. Signalization via AMPA type receptors is much less elucidated. The aim of this thesis was to determine which AMPA receptor subunits are expressed in the SCN of the rat and if these subunits show a daily rhythm of expression and a reactivity to light pulse, as well as to outline the possible roles of distinct AMPA receptor subunits in the SCN. Keywords: circadian rhythms, suprachiasmatic nuclei, glutamate receptors, AMPA
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The monitoring of melatonin rhythm in monozygotic tweens as a marker of genetic control of circadian rhythmicity
Spišská, Veronika ; Bendová, Zdeňka (advisor) ; Svobodová, Irena (referee)
In human population, there are individual differences in the length of endogenous period which is generated by transcriptional-translational loops of clock genes in the suprachiasmatic nucleus of the hypothalamus (SCN). On the basis of these differences we divide people into the early, late or neither chronotype. Chronotypes differ from each other mainly in the rhythm of the hormone melatonin, which is used as a marker of endogenous period. They also differ in rhythm of locomotor activity. The aim of this study was to describe a difference in the phase of the circadian system in three pairs of monozygotic twins aged 8-10 years who live together and share the same daily routine. To describe these differences, we used a questionnaire CCTQ, melatonin radioimmunoassay and actigraphy. Acording to the questionnaire, one boy was determined as early chronotype (A3), one girl was determined as late chronotype (B3) and the other children were determined as neither chronotype (A2, B2, C2, C3). Among the twins there were marked differences both in the rhythm of melatonin and in the morning activity. These differences confirmed the chronotype assessed by questionnaire in the boy A3 and the girl B3. On the contrary, differences in melatonin rhythm did not confirm neither chronotype in siblings C2 and C3, and...
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The effect of acute cold and permanent light to left ventricular of the rat heart
Vítková, Ivana ; Žurmanová, Jitka (advisor) ; Bendová, Zdeňka (referee)
Acute cold exposure increases the risk of sudden cardiac events, similarly exposure to constant light negatively affects the cardiovascular system. However, the individual effects of these factors and the effect of their combination on cardiomyocytes are not yet known. The thesis deals with the influence of a 3 day cold exposure and constant light on the expression of β-adrenergic receptors and associated G-proteins in association with apoptotic signals in the left ventricle of the Wistar rat heart. In this work apoptotic proteins BAX, BCL2, caspase 8 and important components of β-adrenergic signalization - β1, β2, G-proteins, Gas, Gi1/2 and Gi3 were determined. The relative expression of the proteins was analyzed by Western blotting. The results confirm the detrimental effect of cold and light exposure. However, the synergistic effect of these two stressors shows surprising results.
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Role of intestinal circadian clock in epithelial transport, proliferation, and tumourigenesis
Soták, Matúš ; Pácha, Jiří (advisor) ; Bendová, Zdeňka (referee) ; Herichová, Iveta (referee)
AABBSSTTRRAACCTT The molecular circadian clock enables anticipation of environmental changes. In mammals, clocks are ubiquitously present in almost all tissues and they are comprised of transcriptional-translational feedback loops of the so-called clock genes. The central clock represents the intrinsic pacemaker which is located in suprachiasmatic nuclei (SCN) of hypothalamus and synchronizes peripheral clocks. Clockwork system in alimentary tract and its regulatory link to intestinal functions are poorly understood. Therefore the objective of the thesis was to characterize molecular clock in particular parts of the rat intestine and to elucidate its link to the intestinal transport, regulation of cell cycle and neoplastic transformation in colonic tissue. We used quantitative RT-PCR (qPCR) to determine circadian profiles of mRNA expression of clock genes in the epithelium of duodenum, jejunum, ileum, and colon of rat. Furthermore, we analysed the expression of genes coding sodium chloride transporters and channels as well as cell cycle regulators in colon. To focus more precisely on different structures of intestinal epithelia we used laser capture microdissection. In addition, we performed Ussing chamber measurements to determine the colonic electrogenic transport. To study the contribution of circadian...
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Circadian system in bulbus olfactorius
Kyclerová, Hana ; Bendová, Zdeňka (advisor) ; Polidarová, Lenka (referee)
The mammalian circadian system is composed of major circadian pacemaker located in the hypothalamic suprachiasmatic nuclei and peripheral circadian oscillators. Molecular mechanism of interlocked transcription-translation feedback loops, as a characteristic of each circadian oscillator, results in circadian rhythms. Peripheral oscillators in other brain parts and body organs are driven by the signals from the suprachiasmatic nuclei. Some structures however generate oscillations independently from the major circadian pacemaker. The best described of them resides in the mammalian retina. The retinal circadian oscillator regulates local rhythmic synthesis of melatonin, retinal pH and photoreceptors viability. Recently, some studies occur charactering the existence of such an independent circadian oscillator also in bulbus olfactorius. For example, the olfactory bulb circadian oscillator drives olfactory sensitivity during the day. Studies about development of the mamalian circadian system have shown that the olfactory bulb circadian oscillator matures earlier than the major circadian pacemaker and represents its function during early development. Powered by TCPDF (www.tcpdf.org)
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