Circadian rhythms are highly important not only for the synchronization of animals and humans with their periodic environment but also for their fitness. Accordingly, the disruption of the circadian system may have adverse consequences. A certain number of animals in our breeding stock of Djungarian hamsters are episodically active throughout the day. Also body temperature and melatonin lack 24-h rhythms. Obviously in these animals, the suprachiasmatic nuclei (SCN) as the central pacemaker do not generate a circadian signal. Moreover, these so-called arrhythmic (AR) hamsters have cognitive deficits. Since motor activity is believed to stabilize circadian rhythms, we investigated the effect of voluntary wheel running. Hamsters were bred and kept under standardized housing conditions with food and water ad libitum and a 14 L/10 D lighting regimen. AR animals were selected according to their activity pattern obtained by means of passive infrared motion detectors. In a first step, the daily activity behavior was investigated for 3 weeks each without and with running wheels. To estimate putative photic masking effects, hamsters were exposed to light (LPs) and DPs and also released into constant darkness for a minimum of 3 weeks. A novel object recognition (NOR) test was performed to evaluate cognitive abilities both before and after 3 weeks of wheel availability. The activity patterns of hamsters with low wheel activity were still AR. With more intense running, daily patterns with higher values in the dark time were obtained. Obviously, this was due to masking as LPs did suppress and DPs induced motor activity. When transferred to constant darkness, in some animals the daily rhythm disappeared. In other hamsters, namely those which used the wheels most actively, the rhythm was preserved and free-ran, what can be taken as indication of a reconstitution of circadian rhythmicity. Also, animals showing a 24-h activity pattern after 3 weeks of extensive wheel running were able to recognize the novel object in the NOR test but not so before. The results show that voluntary exercise may reestablish circadian rhythmicity and improve cognitive performance.

• MeSH
• chování zvířat * MeSH
• cirkadiánní rytmus * MeSH
• kognice * MeSH
• kognitivní poruchy patofyziologie   terapie   MeSH
• křečci praví MeSH
• nucleus suprachiasmaticus fyziologie   MeSH
• paměť MeSH
• Phodopus MeSH
• pohybová aktivita * MeSH
• světlo MeSH
• zvířata MeSH
• Check Tag
• křečci praví MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

This paper uses recurrence quantification analysis (RQA) combined with entropy measures and organization indices to characterize arrhythmic patterns and dynamics in computer simulations of cardiac tissue. We performed different simulations of cardiac tissues of sizes comparable to the human heart atrium. In these simulations, we observed four classic arrhythmic patterns: a spiral wave anchored to a highly fibrotic region resulting in sustained re-entry, a meandering spiral wave, fibrillation, and a spiral wave anchored to a scar region that breaks up into wavelets away from the main rotor. A detailed analysis revealed that, within the same simulation, maps of RQA metrics could differentiate regions with regular AP propagation from ones with chaotic activity. In particular, the combination of two RQA metrics, the length of the longest diagonal string of recurrence points and the mean length of diagonal lines, was able to identify the location of rotor tips, which are the active elements that maintain spiral waves and fibrillation. By proposing low-dimensional models based on the mean value and spatial correlation of metrics calculated from membrane potential time series, we identify RQA-based metrics that successfully separate the four different types of cardiac arrhythmia into distinct regions of the feature space, and thus might be used for automatic classification, in particular distinguishing between fibrillation driven by self-sustaining chaos and that created by a persistent rotor and wavebreak. We also discuss the practical applicability of such an approach.

• MeSH
• benchmarking * MeSH
• jizva MeSH
• lidé MeSH
• nemoci převodního systému srdečního MeSH
• počítačová simulace MeSH
• srdeční síně * MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Elevace přechodu mezi komplexem QRS a úsekem ST na EKG křivce označovaná jako „časná repolarizace“ byla léta považována za fyziologickou variantu normy vyskytující se u mladých a fyzicky aktivních jedinců. V současnosti roste počet prací, které prokazují souvislost tohoto fenoménu se zvýšeným kardiovaskulárním rizikem. Studie u pacientů s idiopatickou fi brilací komor (IVF) potvrdily vyšší riziko maligních komorových arytmií u osob s časnou repolarizací. Také v běžné populaci byla elevace J bodu ve spodních svodech spojena se zvýšeným rizikem arytmické a kardiální smrti. Předkládaný článek rozebírá současný stav poznání v oblasti epidemiologie, mechanismů vzniku, kardiovaskulárního rizika a péče o pacienty s časnou repolarizací. Zároveň upozorňuje na řadu nejasností, které budou muset být v budoucnu zodpovězeny v zájmu zlepšení predikce rizika a terapie. V neposlední řadě poukazuje na podobnosti a rozdíly s ostatními syndromy spojenými s předčasnou repolarizací, ať již vrozenými (syndrom Brugadových, syndrom krátkého QT), či získanými (akutní ischemie, hypotermie), které nově označujeme souhrnným názvem „J wave syndromy“.

Elevation of the junction between the QRS complex and the ST segment on the ECG, also known as “early repolarization”, has been considered for many years a physiologic variant of the norm seen mainly in young and physically active individuals. Recently, we have seen a growing number of studies demonstrating a relationship between this phenomenon and an increased cardiovascular risk. Studies with patients suff ering from idiopathic ventricular fi brillation (IVF) have confi rmed a higher risk of malignant ventricular arrhythmias in people with early repolarization. Elevation of the J point in inferior leads is associated with higher risk of arrhythmic and cardiac death even in the general population. Our paper describes the current state of knowledge concerning the epidemiology, pathophysiological mechanisms, cardiovascular risk and management of patients with early repolarization. It also highlights a number of equivocal issues that will need to be addressed in future in order to improve the prediction of risk and therapeutic options. Last but not least, it also points to similarities and diff erences between early repolarization and other premature repolarization syndromes – either congenital (Brugada syndrome, short QT syndrome) or acquired (acute ischemia, hypothermia), generally known as “J wave syndromes”.

• Klíčová slova
• Syndrom časné repolarizace, ERS, syndrom Brugadových, „J wave syndromy“,
• MeSH
• Brugadův syndrom diagnóza   etiologie   genetika   MeSH
• elektrokardiografie MeSH
• fibrilace komor diagnóza   etiologie   komplikace   MeSH
• lidé MeSH
• náhlá srdeční smrt etiologie   prevence a kontrola   MeSH
• primární prevence MeSH
• sekundární prevence MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• přehledy MeSH

The master circadian clock located in the suprachiasmatic nuclei (SCN) is dominantly entrained by external light/dark cycle to run with a period of a solar day, that is, 24 h, and synchronizes various peripheral clocks located in the body's cells and tissues accordingly. A daily restricted normocaloric feeding regime synchronizes the peripheral clocks but has no effect on SCN rhythmicity. The aim of this study was to elucidate whether feeding regime may affect the molecular mechanism generating SCN rhythmicity under conditions in which the rhythmicity is disturbed, as occurs under constant light. The rats were maintained under constant light for 30 days and were either fed ad libitum during the whole period, or their access to food was restricted to only 6 h a day during the last 2 weeks in constant light. Locomotor activity was monitored during the whole experiment. On the last day in constant light, daily expression profiles of the clock genes Per1, Per2, Bmal1, and Rev-erbα were determined in the SCN of both groups by in situ hybridization. Due to their exposure to constant light, the rats fed ad libitum became completely arrhythmic, while those exposed to the restricted feeding were active mostly during the time of food availability. In the SCN of behaviorally arrhythmic rats, no oscillations in Rev-erbα and Bmal1 gene expression were detected, but very low amplitude, borderline significant, oscillations in Per1 and Per2 persisted. Restricted feeding induced significant circadian rhythms in Rev-erbα and Bmal1 gene expression, but did not affect the low amplitude oscillations of Per1 and Per2 expression. These findings demonstrate that, under specific conditions, when the rhythmicity of the SCN is disturbed and other temporal entraining cues are lacking, the SCN molecular clockwork may likely sense temporal signals from changes in metabolic state delivered by normocaloric food.

• MeSH
• cirkadiánní proteiny Period biosyntéza   genetika   MeSH
• cirkadiánní rytmus genetika   MeSH
• fotoperioda MeSH
• hybridizace in situ MeSH
• jaderné receptory - podrodina 1, skupina D, člen 1 biosyntéza   genetika   MeSH
• krysa rodu rattus MeSH
• nucleus suprachiasmaticus fyziologie   MeSH
• potkani Wistar MeSH
• proteiny CLOCK biosyntéza   genetika   MeSH
• stanovení celkové genové exprese MeSH
• stravovací zvyklosti fyziologie   MeSH
• světlo MeSH
• transkripční faktory ARNTL biosyntéza   genetika   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu rattus MeSH
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Trees are carbon dioxide sinks and major producers of terrestrial biomass with distinct seasonal growth patterns. Circadian clocks enable the coordination of physiological and biochemical temporal activities, optimally regulating multiple traits including growth. To dissect the clock's role in growth, we analysed Populus tremula × P. tremuloides trees with impaired clock function due to down-regulation of central clock components. late elongated hypocotyl (lhy-10) trees, in which expression of LHY1 and LHY2 is reduced by RNAi, have a short free-running period and show disrupted temporal regulation of gene expression and reduced growth, producing 30-40% less biomass than wild-type trees. Genes important in growth regulation were expressed with an earlier phase in lhy-10, and CYCLIN D3 expression was misaligned and arrhythmic. Levels of cytokinins were lower in lhy-10 trees, which also showed a change in the time of peak expression of genes associated with cell division and growth. However, auxin levels were not altered in lhy-10 trees, and the size of the lignification zone in the stem showed a relative increase. The reduced growth rate and anatomical features of lhy-10 trees were mainly caused by misregulation of cell division, which may have resulted from impaired clock function.

• MeSH
• biomasa MeSH
• buněčné dělení genetika   MeSH
• cirkadiánní hodiny genetika   MeSH
• cytokininy metabolismus   MeSH
• geneticky modifikované rostliny MeSH
• kambium fyziologie   MeSH
• kyseliny indoloctové metabolismus   MeSH
• lignin metabolismus   MeSH
• metabolom MeSH
• metabolomika MeSH
• mutace genetika   MeSH
• Populus cytologie   genetika   růst a vývoj   MeSH
• regulace genové exprese u rostlin * MeSH
• RNA interference MeSH
• rostlinné proteiny genetika   metabolismus   MeSH
• stromy cytologie   genetika   růst a vývoj   MeSH
• vazba proteinů MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Since its implementation into the clinical medicine by Willem Einthoven electrocardiography had become one of crucial diagnostic method in cardiology. In spite of this fact effects of gender differences on parameters of electrocardiographic recordings started to be studied only recently. Sex related differences in physiological ECG are only minimal in childhood but there are developing during adolescence reflecting rapidly evolving differences particularly in hormonal secretion and activity of an autonomic nervous system. The heart rate is approximately 7 % higher in women than in men, PQ and QRS intervals are longer in men while QT interval is longer in women. The ST segment in females is flatter but generally the sex-related differences in ST-T waveform patterns are relatively very small with higher level of ST segment and taller T wave in men. The effects of sex-related differences, including sex hormones, on cardiac cell injury and death and their influence in determining rhythmogenesis and action potential configuration and conduction play an important role in clinics. Women have a higher prevalence of sick sinus syndrome, inappropriate sinus tachycardia, atrioventricular nodal reentry tachycardia, idiopathic right ventricular tachycardia, and arrhythmic events in the long QT syndrome. In contrast, men have a higher prevalence of atrioventricular block, carotid sinus syndrome, atrial fibrillation, supraventricular tachycardia due to accessory pathways, Wolff-Parkinson-White syndrome, reentrant ventricular tachycardia, ventricular fibrillation and sudden death, and the Brugada syndrome.

• Publikační typ
• časopisecké články MeSH

Early-life morphine exposure causes a variety of behavioural and physiological alterations observed later in life. In the present study, we investigated the effects of prenatal and early postnatal morphine on the maturation of the circadian clockwork in the suprachiasmatic nucleus and the liver, and the rhythm in aralkylamine N-acetyltransferase activity in the pineal gland. Our data suggest that the most affected animals were those born to control, untreated mothers and cross-fostered by morphine-exposed dams. These animals showed the highest mesor and amplitude in the rhythm of Per2, Nr1d1 but not Per1 gene expression in the suprachiasmatic nuclei (SCN) and arrhythmicity in AA-NAT activity in the pineal gland. In a similar pattern to the rhythm of Per2 expression in the SCN, they also expressed Per2 in a higher amplitude rhythm in the liver. Five of seven specific genes in the liver showed significant differences between groups in their expression. A comparison of mean relative mRNA levels suggests that this variability was caused mostly by cross-fostering, animals born to morphine-exposed dams that were cross-fostered by control mothers and vice versa differed from both groups of natural mothers raising offspring. Our data reveal that the circadian system responds to early-life morphine administration with significant changes in clock gene expression profiles both in the SCN and in the liver. The observed differences between the groups suggest that the dose, timing and accompanying stress events such as cross-fostering may play a role in the final magnitude of the physiological challenge that opioids bring to the developing circadian clock.

• MeSH
• cirkadiánní hodiny * MeSH
• cirkadiánní rytmus MeSH
• krysa rodu rattus MeSH
• laktace MeSH
• morfin metabolismus   farmakologie   MeSH
• nucleus suprachiasmaticus metabolismus   MeSH
• těhotenství MeSH
• zvířata MeSH
• Check Tag
• krysa rodu rattus MeSH
• těhotenství MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH