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1,217 results for “circadian”
Data from: Genetic analysis of circadian responses to low frequency electromagnetic fields in Drosophila melanogaster
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Data from: critical calls: circadian and seasonal periodicity in vocal activity in a breeding colony of Panamanian golden frogs (<em>Atelopus zeteki</em>)
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Data from: The bear circadian clock doesn't 'sleep' during winter dormancy
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REV-ERBalpha mediates complement expression and circadian regulation of microglial synaptic phagocytosis
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Data from: Developmental exposure to PCB153 (2,2’,4,4’,5,5’-hexachlorobiphenyl) alters circadian rhythms and the expression of clock and metabolic genes
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Data from: Repeatability of circadian behavioural variation revealed in free-ranging marine fish
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Data from: Transcription factors involved in retinogenesis are co-opted by the circadian clock following photoreceptor differentiation
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Data from: Circadian rhythms vary over the growing season and correlate with fitness components
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Data from: Circadian rhythmicity persists through the Polar night and midnight sun in Svalbard reindeer
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Superoxide is promoted by sucrose and affects amplitude of circadian rhythms in the evening
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Growth hormone pulses are differentially regulated by the circadian clock gene Bmal1
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Figure 2 from: Krichilsky E, Vega-Hidalgo Á, Hunter K, Kingwell C, Ritner C, Wcislo W, Smith A (2020) The first gynandromorph of the Neotropical bee Megalopta amoena (Spinola, 1853) (Halictidae) with notes on its circadian rhythm. Journal of Hymenoptera Research 75: 97-108. https://doi.org/10.3897/jhr.75.47828
Figure 2 Single-plot actogram of four days of activity in dark-dark conditions showing a female, the gynandromorph, and a male M. amoena. Each bar represents the amount of times that the bee crossed the laser in a 15 minute interval. White space indicates lack of activity.
Figure 1 from: Krichilsky E, Vega-Hidalgo Á, Hunter K, Kingwell C, Ritner C, Wcislo W, Smith A (2020) The first gynandromorph of the Neotropical bee Megalopta amoena (Spinola, 1853) (Halictidae) with notes on its circadian rhythm. Journal of Hymenoptera Research 75: 97-108. https://doi.org/10.3897/jhr.75.47828
Figure 1 A Frontal view of the head showing the bilateral split between sexes (female left side of image, male right side) B detail of female (left) and male (right) mandibles and labrum, frontal view. Lateral view of the C male and D female genae and mandibles E ventral view of gynandromorph (female left side of image, male right side). Femur, apical spines, and tibia of F male and G female hindlegs H dorsal view of stinger I ventral view of metasoma (female left side of image, male right side). Scale bars: 500 μm.
Data from: Normal vision can compensate for the loss of the circadian clock.
Circadian clocks are thought to be essential for timing the daily activity of animals, and consequently increase fitness. This view was recently challenged for clock-less fruit flies and mice that exhibited astonishingly normal activity rhythms under outdoor conditions. Compensatory mechanisms appear to enable even clock mutants to live a normal life in nature. Here, we show that gradual daily increases/decreases of light in the laboratory suffice to provoke normally timed sharp morning (M) and evening (E) activity peaks in clock-less flies. We also show that the compound eyes, but not Cryptochrome (CRY), mediate the precise timing of M and E peaks under natural-like conditions, as CRY-less flies do and eyeless flies do not show these sharp peaks independently of a functional clock. Nevertheless, the circadian clock appears critical for anticipating dusk, as well as for inhibiting sharp activity peaks during midnight. Clock-less flies only increase E activity after dusk and not before the beginning of dusk, and respond strongly to twilight exposure in the middle of the night. Furthermore, the circadian clock responds to natural-like light cycles, by slightly broadening Timeless (TIM) abundance in the clock neurons, and this effect is mediated by CRY.
Data from: MicroRNAs Shape Circadian Hepatic Gene Expression on a Transcriptome-Wide Scale
A considerable proportion of mammalian gene expression undergoes circadian oscillations. Post-transcriptional mechanisms likely make important contributions to mRNA abundance rhythms. We have investigated how microRNAs (miRNAs) contribute to core clock and clock-controlled gene expression using mice in which miRNA biogenesis can be inactivated in the liver. While the hepatic core clock was surprisingly resilient to miRNA loss, whole transcriptome sequencing uncovered widespread effects on clock output gene expression. Cyclic transcription paired with miRNA-mediated regulation was thus identified as a frequent phenomenon that affected up to 30% of the rhythmic transcriptome and served to post-transcriptionally adjust the phases and amplitudes of rhythmic mRNA accumulation. However, only few mRNA rhythms were actually generated by miRNAs. Overall, our study suggests that miRNAs function to adapt clock-driven gene expression to tissue-specific requirements. Finally, we pinpoint several miRNAs predicted to act as modulators of rhythmic transcripts, and identify rhythmic pathways particularly prone to miRNA regulation.
Data from: Development of circadian oscillators in neurosphere cultures during adult neurogenesis
Circadian rhythms are common in many cell types but are reported to be lacking in embryonic stem cells. Recent studies have described possible interactions between the molecular mechanism of circadian clocks and the signaling pathways that regulate stem cell differentiation. Circadian rhythms have not been examined well in neural stem cells and progenitor cells that produce new neurons and glial cells during adult neurogenesis. To evaluate circadian timing abilities of cells undergoing neural differentiation, neurospheres were prepared from the mouse subventricular zone (SVZ), a rich source of adult neural stem cells. Circadian rhythms in mPer1 gene expression were recorded in individual spheres, and cell types were characterized by confocal immunofluorescence microscopy at early and late developmental stages in vitro. Circadian rhythms were observed in neurospheres induced to differentiate into neurons or glia, and rhythms emerged within 3–4 days as differentiation proceeded, suggesting that the neural stem cell state suppresses the functioning of the circadian clock. Evidence was also provided that neural stem progenitor cells derived from the SVZ of adult mice are self-sufficient clock cells capable of producing a circadian rhythm without input from known circadian pacemakers of the organism. Expression of mPer1 occurred in high frequency oscillations before circadian rhythms were detected, which may represent a role for this circadian clock gene in the fast cycling of gene expression responsible for early cell differentiation.
Data from: Drosophila clock is required in brain pacemaker neurons to prevent premature locomotor aging independently of its circadian function
Circadian clocks control many self-sustained rhythms in physiology and behavior with approximately 24-hour periodicity. In many organisms, oxidative stress and aging negatively impact the circadian system and sleep. Conversely, loss of the clock decreases resistance to oxidative stress, and may reduce lifespan and speed up brain aging and neurodegeneration. Here we examined the effects of clock disruptions on locomotor aging and longevity in Drosophila. We found that lifespan was similarly reduced in three arrhythmic mutants (ClkAR, cyc0 and tim0) and in wild-type flies under constant light, which stops the clock. In contrast, ClkAR mutants showed significantly faster age-related locomotor deficits (as monitored by startle-induced climbing) than cyc0 and tim0, or than control flies under constant light. Reactive oxygen species accumulated more with age in ClkAR mutant brains, but this did not appear to contribute to the accelerated locomotor decline of the mutant. Clk, but not Cyc, inactivation by RNA interference in the pigment-dispersing factor (PDF)-expressing central pacemaker neurons led to similar loss of climbing performance as ClkAR. Conversely, restoring Clk function in these cells was sufficient to rescue the ClkAR locomotor phenotype, independently of behavioral rhythmicity. Accelerated locomotor decline of the ClkAR mutant required expression of the PDF receptor and correlated to an apparent loss of dopaminergic neurons in the posterior protocerebral lateral 1 (PPL1) clusters. This neuronal loss was rescued when the ClkAR mutation was placed in an apoptosis-deficient background. Impairing dopamine synthesis in a single pair of PPL1 neurons that innervate the mushroom bodies accelerated locomotor decline in otherwise wild-type flies. Our results therefore reveal a novel circadian-independent requirement for Clk in brain circadian neurons to maintain a subset of dopaminergic cells and avoid premature locomotor aging in Drosophila.
Data from: Social forces can impact the circadian clocks of cohabiting hamsters
A number of field and laboratory studies have shown that the social environment influences daily rhythms in numerous species. However, underlying mechanisms, including the circadian system's role, are not known. Obstacles to this research have been the inability to track and objectively analyse rhythms of individual animals housed together. Here, we employed temperature dataloggers to track individual body temperature rhythms of pairs of cohabiting male Syrian hamsters (Mesocricetus auratus) in constant darkness and applied a continuous wavelet transform to determine the phase of rhythm onset before, during, and after cohabitation. Cohabitation altered the predicted trajectory of rhythm onsets in 34% of individuals, representing 58% of pairs, compared to 12% of hamsters single-housed as 'virtual pair' controls. Deviation from the predicted trajectory was by a change in circadian period (t), which tended to be asymmetric—affecting one individual of the pair in nine of 11 affected pairs—with hints that dominance might play a role. These data implicate a change in the speed of the circadian clock as one mechanism whereby social factors can alter daily rhythms. Miniature dataloggers coupled with wavelet analyses should provide powerful tools for future studies investigating the principles and mechanisms mediating social influences on daily timing.
Data from: Adaptive differences in circadian clock gene expression patterns and photoperiodic diapause induction in Nasonia vitripennis
Day length (photoperiod) and temperature oscillate daily and seasonally and are important cues for season-dependent behaviour. Larval diapause of the parasitoid Nasonia vitripennis is maternally induced following a certain number of days (switch point) of a given critical photoperiod (CPP). Both the switch point and CPP follow a latitudinal cline in European N. vitripennis populations,. We previously showed that allelic frequencies of the clock gene period correlate with this diapause induction cline. Here, we report that circadian expression of four clock genes, period (per), cryptochrome-2 (cry-2), clock (clk) and cycle (cyc), oscillates as a function of photoperiod and latitude of origin in wasps from populations from the extremes of the cline. Expression amplitudes are lower in northern wasps, indicating a weaker, more plastic, clock. Northern wasps also have a later onset of activity and longer free running rhythms in constant conditions. Per RNAi caused speeding up of the circadian clock, changed the expression of other clock genes and delayed diapause in both southern and northern wasps. These results point towards adaptive latitudinal clock-gene expression differences and to a key role of per in the timing of photoperiodic diapause induction of N. vitripennis.
Data from: Eyeless Mexican cavefish save energy by eliminating the circadian rhythm in metabolism
The eyed surface form and eyeless cave form of the Mexican tetra Astyanax mexicanus experience stark differences in the daily periodicities of light, food and predation, factors which are likely to have a profound influence on metabolism. We measured the metabolic rate of Pachón cave and surface fish at a fixed swimming speed under light/dark and constant dark photoperiods. In constant darkness surface forms exhibited a circadian rhythm in metabolism with an increase in oxygen demand during the subjective daytime, whereas cave forms did not. The lack of circadian rhythm in metabolism leads to a 27% energy savings for Pachón cave fish compared to surface fish when comparing both forms in their natural photoperiods. When surface forms were tested under constant dark conditions they expended 38% more energy than cave forms under equivalent conditions. Elimination of the circadian rhythm in metabolism may be a general feature of animals that live in perpetually dark food-limited environments such as caves or the deep sea.
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Allen Brain Atlas
Allen Brain Atlas is an Allen Institute collection of brain map atlases, datasets, APIs, and analysis tools covering mouse, human, and non-human primate brain resources.
Annotated Behaviour and Observability Dataset (ABODe)
ABODe is a University of Edinburgh DataShare dataset for behavior classification in group-housed mice using home-cage video, identities, bounding boxes, ground-plate positions, and annotator labels.
DANDI Archive for NWB datasets
DANDI is a BRAIN Initiative archive for publishing and sharing neurophysiology data, including electrophysiology, optophysiology, and behavioral data packaged as NWB and related standards.
International Brain Laboratory public data
The International Brain Laboratory public data releases expose standardized mouse decision-making experiments, including Neuropixels recordings, widefield calcium imaging, behavior, and session metadata accessed through the ONE API.
OpenNeuro
OpenNeuro is a free, open platform for sharing neuroimaging datasets, with public search, dataset pages, and download paths for web, S3, DataLad, and the OpenNeuro CLI.