constant light Dotaz Zobrazit nápovědu
455 s. : il.
- Konspekt
- Ortopedie. Chirurgie. Oftalmologie
- NLK Obory
- oftalmologie
Circadian regulation of behavior worsens with age, however, the mechanism behind this phenomenon is still poorly understood. Specifically, it is not clear to what extend the ability of the circadian clock in the suprachiasmatic nuclei (SCN) to generate the rhythm is affected by aging. This study aimed to ascertain the effect of aging on the functioning of the SCN of mPer2Luciferasemice under unnatural lighting conditions, such as constant light (LL). Under LL, which worsened the age-induced effect on behavioral rhythms, a marginal age-dependent effect on in vitro rhythmicity in explants containing the middle, but not the rostral/caudal, regions of the SCN was apparent; the proportion of mice in which middle-region SCN explants were completely arrhythmic or had an extremely long period (>30 h) was 47% in aged mice and 27% in adults. The results suggest that in some of the aged animals, LL may weaken the coupling among oscillators in specific sub-regions of the SCN, leaving other sub-regions better synchronized. In the standard light/dark cycle and in constant darkness, the SCN ability to produce bioluminescence rhythms in vitro was not compromised in aged mice although aging significantly affected their SCN-driven locomotor activity rhythms. Therefore, our results demonstrate that although age worsened the SCN output rhythm, the SCN molecular core clock mechanism itself was relatively resilient to aging in these same animals. The results suggest the involvement of pathways downstream of the core clock mechanism which are responsible for this phenomenon.
- MeSH
- chování zvířat fyziologie MeSH
- cirkadiánní proteiny Period genetika metabolismus MeSH
- cirkadiánní rytmus fyziologie MeSH
- fotoperioda * MeSH
- luciferasy MeSH
- myši knockoutované MeSH
- myši MeSH
- nucleus suprachiasmaticus fyziologie MeSH
- pohybová aktivita MeSH
- regulace genové exprese fyziologie MeSH
- stárnutí fyziologie MeSH
- světlo * MeSH
- zvířata MeSH
- Check Tag
- mužské pohlaví MeSH
- myši MeSH
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články 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
Physiological functions of the gastrointestinal tract (GIT) are temporally controlled such that they exhibit circadian rhythms. The circadian rhythms are synchronized with the environmental light-dark cycle via signaling from the central circadian clock located in the suprachiasmatic nucleus (SCN) of the hypothalamus, and by food intake. The aim of the study was to determine the extent to which disturbance in the SCN signaling via prolonged exposure to constant light affects circadian rhythms in the liver, duodenum, and colon, as well as to determine whether and to what extent food intake can restore rhythmicity in individual parts of the GIT. Adult male rats were maintained in constant light (LL) for 30 days and fed ad libitum throughout the entire interval or exposed to a restricted feeding (RF) regime for the last 14 days in LL. Locomotor and feeding behaviors were recorded throughout the experiment. On the 30th day, daily expression profiles of clock genes (Per1, Per2, Rev-erbα, and Bmal1) and of clock-controlled genes (Wee1 and Dbp) were measured by real-time reverse transcriptase-polymerase chain reaction (RT-PCR) in the duodenum, colon, and liver. By the end of the LL exposure, rats fed ad libitum had completely lost their circadian rhythms in activity and food intake. Daily expression profiles of clock genes and clock-controlled genes in the GIT were impaired to an extent depending on the tissue and gene studied, but not completely abolished. In the liver and colon, exposure to LL abolished circadian rhythms in expression of Per1, Per2, Bmal1, and Wee1, whereas it impaired, but preserved, rhythms in expression of Rev-erbα and Dbp. In the duodenum, all but Wee1 expression rhythms were preserved. Restricted feeding restored the rhythms to a degree that varied with the tissue and gene studied. Whereas in the liver and duodenum the profiles of all clock genes and clock-controlled genes became rhythmic, in the colon only Per1, Bmal1, and Rev-erbα-but not Per2, Wee1, and Dbp-were expressed rhythmically. The data demonstrate a greater persistence of the rhythmicity of the circadian clocks in the duodenum compared with that in the liver and colon under conditions when signaling from the SCN is disrupted. Moreover, disrupted rhythmicity may be restored more effectively by a feeding regime in the duodenum and liver compared to the colon.
- MeSH
- časové faktory MeSH
- cirkadiánní hodiny fyziologie účinky záření MeSH
- duodenum fyziologie MeSH
- fotoperioda MeSH
- játra fyziologie MeSH
- kolon fyziologie MeSH
- krysa rodu rattus MeSH
- pohybová aktivita MeSH
- potkani Wistar MeSH
- potravinová deprivace MeSH
- regulace genové exprese fyziologie účinky záření MeSH
- stanovení celkové genové exprese MeSH
- světlo MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- mužské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Exposure to lipopolysaccharide (LPS) during prenatal development leads to various changes in neurobiological and behavioural patterns. Similarly, continuous exposure to constant light (LL) during the critical developmental period of the circadian system affects gene expression in various tissues in adulthood. Given the reciprocal nature of the interaction between the circadian and the immune systems, our study primarily investigated the individual effects of both interventions and, more importantly, their combined effect. We aimed to explore whether there might be a potential synergistic effect on circadian rhythms and their parameters, focussing on the expression of clock genes, immune-related genes, and specific genes in the hippocampus, pineal gland, spleen and adrenal gland of rats at postnatal day 30. Our results show a significant influence of prenatal LPS and postnatal LL on the expression profiles of all genes assessed. However, the combination of prenatal LPS and postnatal LL only revealed an enhanced negative effect in a minority of the comparisons. In most cases, it appeared to attenuate the changes induced by the individual interventions, restoring the measured parameters to values closer to those of the control group. In particular, genes such as Nr1d1, Aanat and Tph1 showed increased amplitude in the pineal gland and spleen, while the kynurenine enzymes Kynu and KatII developed circadian rhythmicity in the adrenal glands only after the combined interventions. Our data suggest that a mild immunological challenge during prenatal development may play a critical role in triggering an adaptive response of the circadian clock later in life.
- MeSH
- cirkadiánní rytmus * fyziologie MeSH
- epifýza mozková metabolismus MeSH
- hipokampus metabolismus MeSH
- krysa rodu rattus MeSH
- lipopolysacharidy * MeSH
- nadledviny metabolismus MeSH
- potkani Wistar MeSH
- slezina * metabolismus MeSH
- světlo * MeSH
- těhotenství MeSH
- transkriptom MeSH
- zpožděný efekt prenatální expozice * metabolismus MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- mužské pohlaví MeSH
- těhotenství MeSH
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
Cortisol and other adrenal steroids are typically secreted in a pulsate fashion and plasma concentrations can vary widely during a 24-hour period. To investigate daily rhythmicity of plasma adrenocorticotrophin (ACTH) concentration, as well as rectal temperature (RT), sample collections were performed in five Quarter Horses housed in individual boxes under natural light/dark (L/D) cycle followed by constant darkness. The two variables exhibited 24-h rhythmicity under the L/D cycle. Whereas rhythmicity of RT persisted in constant darkness, rhythmicity of ACTH concentration did not. These findings strongly suggested that ACTH secretion in the horse is not under circadian control and is modulated only by environmental light.
The circadian clock regulates bodily rhythms by time cues that result from the integration of genetically encoded endogenous rhythms with external cycles, most potently with the light/dark cycle. Chronic exposure to constant light in adulthood disrupts circadian system function and can induce behavioral and physiological arrhythmicity with potential clinical consequences. Since the developing nervous system is particularly vulnerable to experiences during the critical period, we hypothesized that early-life circadian disruption would negatively impact the development of the circadian clock and its adult function. Newborn rats were subjected to a constant light of 16 lux from the day of birth through until postnatal day 20, and then they were housed in conditions of L12 h (16 lux): D12 h (darkness). The circadian period was measured by locomotor activity rhythm at postnatal day 60, and the rhythmic expressions of clock genes and tissue-specific genes were detected in the suprachiasmatic nuclei, retinas, and pineal glands at postnatal days 30 and 90. Our data show that early postnatal exposure to constant light leads to a prolonged endogenous period of locomotor activity rhythm and affects the rhythmic gene expression in all studied brain structures later in life.
- Publikační typ
- časopisecké články MeSH
