Abstract：
:From the mathematical study of simple models for circadian rhythm, the authors identified a clear effect of saturation in the enzyme kinetics on the promotion or suppression of a sustained oscillation. In the models, a clock gene (per gene) is transcribed to produce mRNAs, which are translated to produce proteins in the cytosol which are then transported to the nucleus and suppress the transcription of the gene. The negative feedback loop with a long time delay creates sustained oscillation. All the enzymatic reactions (e.g., degradation, translation, and modification) are assumed to be of Michaelis-Menten type. The reaction rate increases with the amount of substrate but saturates when it is very large. The authors prove mathematically that the saturation in any of the reactions included in the feedback loop (in-loop reaction steps) suppresses the oscillation, whereas the saturation of both degradation steps and the back transport of the protein to cytosol (branch reaction steps) makes the oscillation more likely to occur. In the experimental measurements of enzyme kinetics and in published circadian clock simulators, in-loop reaction steps have a small saturation index whereas branch reaction steps have a large saturation index.
journal_name
J Biol Rhythmsjournal_title
Journal of biological rhythmsauthors
Kurosawa G,Iwasa Ydoi
10.1177/0748730402238239subject
Has Abstractpub_date
2002-12-01 00:00:00pages
568-77issue
6eissn
0748-7304issn
1552-4531journal_volume
17pub_type
杂志文章abstract：:Mice homozygous for a dominant-negative allele of the Clock gene (Clock (Δ19/Δ19)) have slightly but significantly decreased male fertility. The molecular mechanism for this reduction in fertility is unknown. In the present study, we used a small hairpin RNA (shRNA) strategy to specifically knock down the Clock gene e...
journal_title：Journal of biological rhythms
pub_type： 杂志文章
doi：10.1177/0748730413486873
更新日期：2013-06-01 00:00:00
abstract：:The endogenous circadian rhythm of melatonin in humans provides information regarding the resetting response of the human circadian timing system to changes in the light-dark (LD) cycle. Alterations in the LD cycle have both acute and chronic effects on the observed melatonin rhythm. Investigations to date have firmly...
journal_title：Journal of biological rhythms
pub_type： 杂志文章,评审
doi：10.1177/074873049701200610
更新日期：1997-12-01 00:00:00
abstract：:Previous research has demonstrated a clear link between late chronotype and depression. The vulnerability factors underpinning this link, however, are unclear. Here the relationship between two specific emotion regulation strategies, cognitive reappraisal and expressive suppression, and chronotype was investigated usi...
journal_title：Journal of biological rhythms
pub_type： 杂志文章
doi：10.1177/0748730417709111
更新日期：2017-08-01 00:00:00
abstract：:Groups of Syrian hamsters were exposed to LD cycles with twilight transitions and photoperiods simulating natural lighting conditions at the summer solstice (SS), equinox, and winter solstice (WS) at 41 degrees N and at the winter solstice at the Arctic Circle (WS 66 degrees N) but with daytime illuminance truncated a...
journal_title：Journal of biological rhythms
pub_type： 杂志文章
doi：10.1177/0748730404272907
更新日期：2005-04-01 00:00:00
abstract：:In isolated slices of hypothalamus, suprachiasmatic nucleus (SCN) neurons were recorded intracellularly. Blockade of Ca++ channels increased spike duration, eliminating an early component of the afterhyperpolarization (AHP) that followed evoked spikes. The duration and reversal potential of AHPs were, however, unaffec...
journal_title：Journal of biological rhythms
pub_type： 杂志文章
doi：10.1177/074873049000500106
更新日期：1990-04-01 00:00:00
abstract：:Most of the anatomical and molecular substrates of the system that encodes changes in photoperiod in the duration of melatonin secretion, and the receptor molecules that read this signal, have been shown to be conserved in monkeys and humans, and the functions of this system appear to be intact from the level of the r...
journal_title：Journal of biological rhythms
pub_type： 杂志文章,评审
doi：10.1177/074873001129002060
更新日期：2001-08-01 00:00:00
abstract：:Numerous studies have demonstrated sleep-promoting effects of melatonin treatment in humans, as evidenced by subjects' self-reports, polysomnographic recordings, and continuous actigraphic registration of motor activity. The sleep-promoting effects of either physiological or pharmacological doses of melatonin typicall...
journal_title：Journal of biological rhythms
pub_type： 杂志文章,评审
doi：10.1177/074873049701200620
更新日期：1997-12-01 00:00:00
abstract：:African sleeping sickness is characterized by alterations in rhythmic functions. It is not known if the disease affects the expression of clock genes, which are the molecular basis for rhythm generation. We used a chronic rat model of experimental sleeping sickness, caused by the extracellular parasite Trypanosoma bru...
journal_title：Journal of biological rhythms
pub_type： 杂志文章
doi：10.1177/0748730409360963
更新日期：2010-04-01 00:00:00
abstract：:During the first 7 weeks of postnatal life, short day lengths inhibit the onset of puberty in many photoperiodic rodents, but not in Syrian hamsters. In this species, timing of puberty and fecundity are independent of the early postnatal photoperiod. Gestational day length affects postnatal reproductive development in...
journal_title：Journal of biological rhythms
pub_type： 杂志文章
doi：10.1177/0748730408322985
更新日期：2008-10-01 00:00:00
abstract：:Arctic and subarctic environments are exposed to extreme light: dark (LD) regimes, including periods of constant light (LL) and constant dark (DD) and large daily changes in day length, but very little is known about circadian rhythms of mammals at high latitudes. The authors investigated the circadian rhythms of a su...
journal_title：Journal of biological rhythms
pub_type： 杂志文章
doi：10.1177/0748730404264200
更新日期：2004-06-01 00:00:00
abstract：:Aging alters numerous aspects of circadian biology, including the amplitude of rhythms generated by the suprachiasmatic nuclei (SCN) of the hypothalamus, the site of the central circadian pacemaker in mammals, and the response of the pacemaker to environmental stimuli such as light. Although previous studies have desc...
journal_title：Journal of biological rhythms
pub_type： 杂志文章
doi：10.1177/0748730403251802
更新日期：2003-04-01 00:00:00
abstract：:Abstract The cyanobacterial clock protein KaiC regulates the circadian cycle by exhibiting rhythms in transcription, translation, and phosphorylation. KaiC phosphorylation persists in circadian cycling even under transcription-less conditions and was reconstituted in vitro by incubating KaiC, KaiA, and KaiB. This pres...
journal_title：Journal of biological rhythms
pub_type： 杂志文章
doi：10.1177/0748730406291329
更新日期：2006-10-01 00:00:00
abstract：:Many mammalian cell types show daily rhythms in gene expression driven by a circadian pacemaker. For example, cultured astrocytes display circadian rhythms in Period1 and Period2 expression. It is not known, however, how or which intercellular factors synchronize and sustain rhythmicity in astrocytes. Because astrocyt...
journal_title：Journal of biological rhythms
pub_type： 杂志文章
doi：10.1177/0748730409332042
更新日期：2009-04-01 00:00:00
abstract：:To date, it is largely unknown which light settings define the optimum to steer alertness and cognitive control during regular daytime working hours. In the current article, we used a multimeasure approach combined with a relatively large sample size ( N = 60) and a large range of intensity levels (20-2000 lux at eye ...
journal_title：Journal of biological rhythms
pub_type： 杂志文章
doi：10.1177/0748730418796438
更新日期：2018-12-01 00:00:00
abstract：:Circadian rhythms are programmed by the suprachiasmatic nucleus (SCN), which relies on neuropeptide signaling to maintain daily timekeeping. Vasoactive intestinal polypeptide (VIP) is critical for SCN function, but the precise role of VIP neurons in SCN circuits is not fully established. To interrogate their contribut...
journal_title：Journal of biological rhythms
pub_type： 杂志文章
doi：10.1177/0748730420925573
更新日期：2020-08-01 00:00:00
abstract：:Social jetlag represents the discrepancy between circadian and social clocks, which is measured as the difference in hours in midpoint of sleep between work days and free days. Previous studies have shown social jetlag to be associated with body mass index (BMI), glycated hemoglobin levels, heart rate, depressive symp...
journal_title：Journal of biological rhythms
pub_type： 杂志文章
doi：10.1177/0748730414550199
更新日期：2014-10-01 00:00:00
abstract：:Individuals of the shore crab Carcinus maenas were exposed to artificial cycles, applied in tidal antiphase, of pairs of the three major environmental variables that entrain circatidal rhythmicity in this species: salinity, temperature, and hydrostatic pressure. During entrainment, the observed locomotor activity patt...
journal_title：Journal of biological rhythms
pub_type： 杂志文章
doi：10.1177/074873049000500405
更新日期：1990-01-01 00:00:00
abstract：:Odors elicit a number of behavioral responses, including attraction and repulsion in Drosophila. In this study, the authors used a T-maze apparatus to show that wild-type Drosophila melanogaster exhibit a robust circadian rhythm in the olfactory attractive and repulsive responses. These responses were lower during the...
journal_title：Journal of biological rhythms
pub_type： 杂志文章
doi：10.1177/0748730405274451
更新日期：2005-06-01 00:00:00
abstract：:Using quantitative autoradiography, 2-(125)I-melatonin binding was investigated throughout the light:dark cycle in the suprachiasmatic nuclei (SCN), paraventricular nuclei (PVT), and pars tuberalis (PT) of adult female Siberian hamsters kept for 10 weeks in either long or short photoperiods (LP or SP, respectively). P...
journal_title：Journal of biological rhythms
pub_type： 杂志文章
doi：10.1177/074873049601100406
更新日期：1996-12-01 00:00:00
abstract：:The circadian clock plays an important role in adaptation in time and space by synchronizing changes in physiological, developmental, and behavioral traits of organisms with daily and seasonal changes in their environment. We have studied some features of the circadian activity and clock organization in a northern Dro...
journal_title：Journal of biological rhythms
pub_type： 杂志文章
doi：10.1177/0748730412455916
更新日期：2012-10-01 00:00:00
abstract：:Various aspects of mammalian endocrine physiology show a time-of-day variation with a period of 24 h, which represents an adaptation to the daily environmental fluctuations resulting from the rotation of the earth. These 24-h rhythms in hormone abundance and consequently hormone function may rely on rhythmic signals p...
journal_title：Journal of biological rhythms
pub_type： 杂志文章,评审
doi：10.1177/0748730415580881
更新日期：2015-08-01 00:00:00
abstract：:Crustaceans have frequently been used to study the neuroethology of both agonistic behavior and circadian rhythms, but whether their highly stereotyped and quantifiable agonistic activity is controlled by circadian pacemakers has, so far, not been investigated. Isolated marbled crayfish (Procambarus spec.) displayed r...
journal_title：Journal of biological rhythms
pub_type： 杂志文章
doi：10.1177/0748730408328933
更新日期：2009-02-01 00:00:00
abstract：:Photoreception in the mammalian retina is not restricted to rods and cones but extends to a small number of intrinsically photosensitive retinal ganglion cells expressing the photopigment melanopsin. These mRGCs are especially important contributors to circadian entrainment, the pupil light reflex, and other so-called...
journal_title：Journal of biological rhythms
pub_type： 杂志文章
doi：10.1177/0748730411409719
更新日期：2011-08-01 00:00:00
abstract：:The circadian clock represents an anticipatory mechanism, well preserved in evolution. It has a critical impact on most aspects of the physiology of light-sensitive organisms. These rhythmic processes are governed by environmental cues (fluctuations in light intensity and temperature), an internal circadian timing sys...
journal_title：Journal of biological rhythms
pub_type： 杂志文章,评审
doi：10.1177/0748730414557634
更新日期：2015-04-01 00:00:00
abstract：:The suprachiasmatic nucleus (SCN) drives and synchronizes daily rhythms at the cellular level via transcriptional-translational feedback loops comprising clock genes such as Bmal1 and Period (Per). Glycogen synthase kinase 3 (GSK3), a serine/threonine kinase, phosphorylates at least 5 core clock proteins and shows diu...
journal_title：Journal of biological rhythms
pub_type： 信件
doi：10.1177/0748730415573167
更新日期：2015-04-01 00:00:00
abstract：:Although pineal "synaptic" ribbons (SR) are frequently examined by means of quantitative electron microscopy, their functional significance remains unclear. The same is true for related structures--"synaptic" spherules (SPH). In the course of such studies, it has been noted that SR counts may differ from laboratory to...
journal_title：Journal of biological rhythms
pub_type： 杂志文章
doi：10.1177/074873048800300103
更新日期：1988-04-01 00:00:00
abstract：:The hypothalamic suprachiasmatic nucleus (SCN), a circadian pacemaker, is present in all mammalian brains. It has a complex organization of peptide-containing neurons that is similar among species, but calcium-binding proteins are expressed variably. Neurons containing calretinin have been described in the SCN in a nu...
journal_title：Journal of biological rhythms
pub_type： 信件
doi：10.1177/0748730416654024
更新日期：2016-08-01 00:00:00
abstract：:Nonphotic stimuli can reset and entrain circadian activity rhythms in hamsters and mice, and serotonin is thought to be involved in the phase-resetting effects of these stimuli. In the present study, the authors examined the effect of the serotonin agonist quipazine on circadian activity rhythms in three inbred strain...
journal_title：Journal of biological rhythms
pub_type： 杂志文章
doi：10.1177/074873099129000524
更新日期：1999-04-01 00:00:00
abstract：:A single light episode during the first larval stage can set the phase of adult Drosophila activity rhythms, showing that a light-sensitive circadian clock is functional in larvae and is capable of keeping time throughout development. These behavioral data are supported by the finding that neurons expressing clock pro...
journal_title：Journal of biological rhythms
pub_type： 杂志文章
doi：10.1177/0748730403260621
更新日期：2004-02-01 00:00:00
abstract：:The temporal expression pattern of the circadian clock gene period was compared between heads of the linden bug, Pyrrhocoris apterus , kept under diapause-promoting short days (SD) and diapause-preventing long days (LD) using a real-time PCR quantification. Diapause or reproduction was programmed by photoperiod during...
journal_title：Journal of biological rhythms
pub_type： 杂志文章
doi：10.1177/0748730407303624
更新日期：2007-08-01 00:00:00
