• MeSH
• 17-hydroxykortikosteroidy moč   MeSH
• časové faktory MeSH
• cirkadiánní rytmus * MeSH
• lidé MeSH
• světlo * MeSH
• tma MeSH
• Check Tag
• lidé MeSH
• mužské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• 17-hydroxykortikosteroidy MeSH

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.

• Klíčová slova
• Djungarian hamster, arrhythmic activity pattern, circadian rhythm, cognitive performance, constant darkness, masking, running wheel,
• 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

OBJECTIVES: Light and food are important synchronizers of circadian rhythmicity. In eating disorders, the circadian rhythms of food intake and temperature are abnormal. METHODS: We analyzed the effect of the morning light application on the circadian rhythm of tympanic temperature and its association with hunger and mood changes in the sample of 25 female patients hospitalized with DSM-IV diagnosis of eating disorders (14 bulimia nervosa and 11 anorexia nervosa) and in 6 healthy women. RESULTS: Light therapy reduced interindividual variability of the temperature acrophase, synchronized the temperature and hunger rhythms and showed an antidepressant effect on patients with eating disorders. Bright light therapy normalized the circadian rhythm of body temperature in both anorexic and bulimic patients: phase advanced rhythm was delayed and phase delayed rhythm was advanced. In contrast with anorexic patients, the majority of bulimic patients had normal temperature rhythm before the therapy and this rhythm was not changed by the therapy. CONCLUSION: The light therapy normalized temperature circadian rhythm in patient with eating disorders. We hypothesize that the light therapy can also contribute to improvement of pathological eating pattern because of the functional connections between light and food entrained oscillators. The light may help to restore the irregular circadian rhythmicity induced by chaotic food intake.

• MeSH
• afekt fyziologie   MeSH
• bulimia nervosa patofyziologie   psychologie   terapie   MeSH
• chuť k jídlu fyziologie   MeSH
• cirkadiánní rytmus fyziologie   MeSH
• dospělí MeSH
• fototerapie metody   MeSH
• hlad fyziologie   MeSH
• lidé MeSH
• mentální anorexie patofyziologie   psychologie   terapie   MeSH
• přijímání potravy fyziologie   MeSH
• tělesná teplota fyziologie   MeSH
• Check Tag
• dospělí MeSH
• lidé MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• klinické zkoušky kontrolované MeSH
• práce podpořená grantem MeSH

The behavioural rhythms of organisms are thought to be under strong selection, influenced by the rhythmicity of the environment. Such behavioural rhythms are well studied in isolated individuals under laboratory conditions, but free-living individuals have to temporally synchronize their activities with those of others, including potential mates, competitors, prey and predators. Individuals can temporally segregate their daily activities (for example, prey avoiding predators, subordinates avoiding dominants) or synchronize their activities (for example, group foraging, communal defence, pairs reproducing or caring for offspring). The behavioural rhythms that emerge from such social synchronization and the underlying evolutionary and ecological drivers that shape them remain poorly understood. Here we investigate these rhythms in the context of biparental care, a particularly sensitive phase of social synchronization where pair members potentially compromise their individual rhythms. Using data from 729 nests of 91 populations of 32 biparentally incubating shorebird species, where parents synchronize to achieve continuous coverage of developing eggs, we report remarkable within- and between-species diversity in incubation rhythms. Between species, the median length of one parent's incubation bout varied from 1-19 h, whereas period length-the time in which a parent's probability to incubate cycles once between its highest and lowest value-varied from 6-43 h. The length of incubation bouts was unrelated to variables reflecting energetic demands, but species relying on crypsis (the ability to avoid detection by other animals) had longer incubation bouts than those that are readily visible or who actively protect their nest against predators. Rhythms entrainable to the 24-h light-dark cycle were less prevalent at high latitudes and absent in 18 species. Our results indicate that even under similar environmental conditions and despite 24-h environmental cues, social synchronization can generate far more diverse behavioural rhythms than expected from studies of individuals in captivity. The risk of predation, not the risk of starvation, may be a key factor underlying the diversity in these rhythms.

• MeSH
• biologická evoluce MeSH
• časové faktory MeSH
• Charadriiformes klasifikace   fyziologie   MeSH
• cirkadiánní rytmus MeSH
• druhová specificita MeSH
• fotoperioda MeSH
• hladovění veterinární   MeSH
• hnízdění fyziologie   MeSH
• periodicita * MeSH
• podněty MeSH
• predátorské chování * MeSH
• rozmnožování MeSH
• stravovací zvyklosti MeSH
• životní prostředí MeSH
• zvířata MeSH
• zygota růst a vývoj   MeSH
• Check Tag
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Serum melatonin rhythm was studied in 6 human subjects experiencing short winter days resembling light/dark (LD) 8:16 h and in 6 subjects exposed at the same time to a long, LD 16:8 h skeleton photoperiod, with 3 h of bright light in the evening and again in the morning; 4 out of the 6 subjects entrained to the simulated summer photoperiod within 3 days. In the synchronized subjects, the nocturnal melatonin signal was 3 h shorter than in those experiencing just winter days. The data indicate that humans are able to respond to environmental day length by forming a proper endogenous photoperiodic signal.

• MeSH
• časové faktory MeSH
• cirkadiánní rytmus fyziologie   MeSH
• dospělí MeSH
• lidé MeSH
• melatonin krev   MeSH
• roční období * MeSH
• světlo MeSH
• Check Tag
• dospělí MeSH
• lidé MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• melatonin MeSH

Synchronizing neural processes, mental activities, and social interactions is considered to be fundamental for the creation of temporal order on the personal and interpersonal level. Several different types of synchronization are distinguished, and for each of them examples are given: self-organized synchronizations on the neural level giving rise to pre-semantically defined time windows of some tens of milliseconds and of approximately 3 s; time windows that are created by synchronizing different neural representations, as for instance in aesthetic appreciations or moral judgments; and synchronization of biological rhythms with geophysical cycles, like the circadian clock with the 24-hr rhythm of day and night. For the latter type of synchronization, an experiment is described that shows the importance of social interactions for sharing or avoiding common time. In a group study with four subjects being completely isolated together for 3 weeks from the external world, social interactions resulted both in intra- and interindividual circadian synchronization and desynchronization. A unique phenomenon in circadian regulation is described, the "beat phenomenon," which has been made visible by the interaction of two circadian rhythms with different frequencies in one body. The separation of the two physiological rhythms was the consequence of social interactions, that is, by the desire of a subject to share and to escape common time during different phases of the long-term experiment. The theoretical arguments on synchronization are summarized with the general statement: "Nothing in cognitive science makes sense except in the light of time windows." The hypothesis is forwarded that time windows that express discrete timing mechanisms in behavioral control and on the level of conscious experiences are the necessary bases to create cognitive order, and it is suggested that time windows are implemented by neural oscillations in different frequency domains.

• Klíčová slova
• beat phenomenon, circadian rhythm, desynchronization, discrete time, social interaction, synchronization, time window,
• MeSH
• biologické modely MeSH
• časové faktory MeSH
• cirkadiánní rytmus fyziologie   MeSH
• interpersonální vztahy * MeSH
• lidé MeSH
• longitudinální studie MeSH
• vnímání času * MeSH
• Check Tag
• lidé MeSH
• mužské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• kazuistiky MeSH
• práce podpořená grantem MeSH

Many behavioral, physiological and molecular processes exhibit diurnal rhythms. Endogenous rhythms with period close to 24 hours are called circadian rhythms. Light entrains circadian rhythms to a 24 period of solar day. Circadian system consists of pacemaker, which is in mammals located in the suprachiasmatic nuclei of hypothalamus (SCN), its input and output pathways and peripheral clocks in numerous tissues. The generation of circadian rhytmicity is based on interactive transcription-translational feedback loops in SCN. These feedback loops consist of so called clock genes and their protein products which positively or negatively regulate their own transcription. Studies in rodent embros and neonates demonstrate that individual components of circadian system matures gradually during prenatal and postnatal period Mechanism of light entrainment of the circadian system develops postnatally. During early postnatal period, the developing circadian system is synchronized mainly by maternal cues.

• MeSH
• cirkadiánní rytmus fyziologie   MeSH
• lidé MeSH
• nucleus suprachiasmaticus fyziologie   MeSH
• savci fyziologie   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• anglický abstrakt MeSH
• časopisecké články MeSH
• přehledy MeSH