scholarly journals Central and peripheral oscillators in mammals: A guided tour through a network of clocks

2004 ◽  
Vol 26 (1) ◽  
pp. 23-25
Author(s):  
Fabienne Guillaumond ◽  
Nicolas Cermakian
Keyword(s):  
Circadian Rhythms ◽  
Circadian System ◽  
Oscillator System ◽  
Peripheral Oscillators ◽  
Circadian Oscillators ◽  
Guided Tour ◽  
Different Tissues

For decades, the circadian system of animals was viewed as a single or a few centralized structures driving all overt physiological circadian rhythms. Recent data have questioned this view and have revealed a much more complex and dynamic picture. We now know that circadian oscillators are also present in many different tissues and constitute part of a hierarchical circadian system. In this article, we describe this multi-oscillator system that constitutes the basis for the variety of physiological rhythms.

scholarly journals Involvement of Melatonin in the Regulation of the Circadian System in Crayfish

2018 ◽  
Vol 19 (7) ◽  
pp. 2147
Author(s):  
Leonor Mendoza-Vargas ◽  
Elizabeth Guarneros-Bañuelos ◽  
Armida Báez-Saldaña ◽  
Fabiola Galicia-Mendoza ◽  
Edgar Flores-Soto ◽  
...  
Keyword(s):  
Circadian Rhythms ◽  
Social Dominance ◽  
Procambarus Clarkii ◽  
Circadian System ◽  
Temporal Organization ◽  
Dominance Status ◽  
Cellular Targets ◽  
Circadian Oscillators ◽  
Burrowing Behavior ◽  
External Time

Melatonin (MEL) is an ancient molecule, broadly distributed in nature from unicellular to multicellular species. MEL is an indoleamine that acts on a wide variety of cellular targets regulating different physiological functions. This review is focused on the role played by this molecule in the regulation of the circadian rhythms in crayfish. In these species, information about internal and external time progression might be transmitted by the periodical release of MEL and other endocrine signals acting through the pacemaker. We describe documented and original evidence in support of this hypothesis that also suggests that the rhythmic release of MEL contributes to the reinforcement of the temporal organization of nocturnal or diurnal circadian oscillators. Finally, we discuss how MEL might coordinate functions that converge in the performance of complex behaviors, such as the agonistic responses to establish social dominance status in Procambarus clarkii and the burrowing behavior in the secondary digging crayfish P. acanthophorus.

Molecular Biology and Physiology of Circadian Clocks

2019 ◽  
Author(s):  
Ruifeng Cao
Keyword(s):  
Circadian Rhythms ◽  
Circadian System ◽  
Feedback Loops ◽  
The Body ◽  
Endogenous Rhythms ◽  
Peripheral Oscillators ◽  
Physiological Processes ◽  
And Behavior ◽  
Photic Input ◽  
Master Clock

Circadian rhythm is the approximately 24-hour rhythmicity that regulates physiology and behavior in a variety of organisms. The mammalian circadian system is organized in a hierarchical manner. Molecular circadian oscillations driven by genetic feedback loops are found in individual cells, whereas circadian rhythms in different systems of the body are orchestrated by the master clock in the suprachiasmatic nucleus (SCN) of the anterior hypothalamus. SCN receives photic input from retina and synchronizes endogenous rhythms with the external light/dark cycles. SCN regulates circadian rhythms in the peripheral oscillators via neural and humoral signals, which account for daily fluctuations of the physiological processes in these organs. Disruption of circadian rhythms can cause health problems and circadian dysfunction has been linked to many human diseases.

Disrupted circadian rhythms in VIP- and PHI-deficient mice

2003 ◽  
Vol 285 (5) ◽  
pp. R939-R949 ◽  
Author(s):  
Christopher S. Colwell ◽  
Stephan Michel ◽  
Jason Itri ◽  
Williams Rodriguez ◽  
J. Tam ◽  
...  
Keyword(s):  
Circadian Rhythms ◽  
Wheel Running ◽  
Activity Rhythm ◽  
Activity Patterns ◽  
Circadian System ◽  
Diurnal Rhythms ◽  
Constant Darkness ◽  
Light Cycle ◽  
Wild Type ◽  
Deficient Mice

The related neuropeptides vasoactive intestinal peptide (VIP) and peptide histidine isoleucine (PHI) are expressed at high levels in the neurons of the suprachiasmatic nucleus (SCN), but their function in the regulation of circadian rhythms is unknown. To study the role of these peptides on the circadian system in vivo, a new mouse model was developed in which both VIP and PHI genes were disrupted by homologous recombination. In a light-dark cycle, these mice exhibited diurnal rhythms in activity which were largely indistinguishable from wild-type controls. In constant darkness, the VIP/PHI-deficient mice exhibited pronounced abnormalities in their circadian system. The activity patterns started ∼8 h earlier than predicted by the previous light cycle. In addition, lack of VIP/PHI led to a shortened free-running period and a loss of the coherence and precision of the circadian locomotor activity rhythm. In about one-quarter of VIP/PHI mice examined, the wheel-running rhythm became arrhythmic after several weeks in constant darkness. Another striking example of these deficits is seen in the split-activity patterns expressed by the mutant mice when they were exposed to a skeleton photoperiod. In addition, the VIP/PHI-deficient mice exhibited deficits in the response of their circadian system to light. Electrophysiological analysis indicates that VIP enhances inhibitory synaptic transmission within the SCN of wild-type and VIP/PHI-deficient mice. Together, the observations suggest that VIP/PHI peptides are critically involved in both the generation of circadian oscillations as well as the normal synchronization of these rhythms to light.

Light-induced suppression of the rat circadian system

1995 ◽  
Vol 268 (5) ◽  
pp. R1111-R1116 ◽  
Author(s):  
P. Depres-Brummer ◽  
F. Levi ◽  
G. Metzger ◽  
Y. Touitou
Keyword(s):  
Locomotor Activity ◽  
Body Temperature ◽  
Circadian Rhythms ◽  
Prolonged Exposure ◽  
Light Exposure ◽  
Continuous Light ◽  
Circadian System ◽  
Short Exposure ◽  
Complete Suppression ◽  
Continuous Darkness

In a constant environment, circadian rhythms persist with slightly altered period lengths. Results of studies with continuous light exposure are less clear, because of short exposure durations and single-variable monitoring. This study sought to characterize properties of the oscillator(s) controlling the rat's circadian system by monitoring both body temperature and locomotor activity. We observed that prolonged exposure of male Sprague-Dawley rats to continuous light (LL) systematically induced complete suppression of body temperature and locomotor activity circadian rhythms and their replacement by ultradian rhythms. This was preceded by a transient loss of coupling between both functions. Continuous darkness (DD) restored circadian synchronization of temperature and activity circadian rhythms within 1 wk. The absence of circadian rhythms in LL coincided with a mean sixfold decrease in plasma melatonin and a marked dampening but no abolition of its circadian rhythmicity. Restoration of temperature and activity circadian rhythms in DD was associated with normalization of melatonin rhythm. These results demonstrated a transient internal desynchronization of two simultaneously monitored functions in the rat and suggested the existence of two or more circadian oscillators. Such a hypothesis was further strengthened by the observation of a circadian rhythm in melatonin, despite complete suppression of body temperature and locomotor activity rhythms. This rat model should be useful for investigating the physiology of the circadian timing system as well as to identify agents and schedules having specific pharmacological actions on this system.

scholarly journals Timing metabolism in cartilage and bone: links between circadian clocks and tissue homeostasis

2019 ◽  
Vol 243 (3) ◽  
pp. R29-R46 ◽  
Author(s):  
Cátia F Gonçalves ◽  
Qing-Jun Meng
Keyword(s):  
Rheumatoid Arthritis ◽  
Circadian Rhythms ◽  
Circadian System ◽  
Tissue Homeostasis ◽  
Circadian Clocks ◽  
Clock System ◽  
Metabolic Functions ◽  
Biochemical Mechanisms ◽  
Skeletal Disorders ◽  
Bone Physiology

The circadian system in mammals is responsible for the temporal coordination of multiple physiological and behavioural processes that are necessary for homeostasis. In the skeleton, it has long been known that metabolic functions of chondrocytes, osteoblasts and osteoclasts exhibit intrinsic circadian rhythms. In addition, results from animal models reveal a close connection between the disruption of circadian rhythms and skeletal disorders such as rheumatoid arthritis, osteoarthritis and osteoporosis. In this review, we summarise the latest insights into the genetic and biochemical mechanisms linking cartilage and bone physiology to the circadian clock system. We also discuss how this knowledge can be utilised to improve human health.

Evolution Analysis of the Circadian Clock Protein KaiB

2013 ◽  
Vol 647 ◽  
pp. 391-395
Author(s):  
Liu Sen ◽  
Song Liu
Keyword(s):  
Circadian Rhythms ◽  
Circadian Clock ◽  
Feedback Loop ◽  
Circadian System ◽  
Circadian Rhythmicity ◽  
Physiological Functions ◽  
Clock System ◽  
Evolution Analysis ◽  
Clock Protein

Regulation of daily physiological functions with approximate a 24-hour periodicity, or circadian rhythms, is a characteristic of eukaryotes. So far, cyanobacteria are only known prokaryotes reported to possess circadian rhythmicity. The circadian system in cyanobacteria comprises both a post-translational oscillator (PTO) and a transcriptional/translational feedback loop (TTFL). The PTO can be reconstituted in vitro with three purified proteins (KaiA, KaiB, and KaiC) with the existence of ATP. Phase of the nanoclockwork has been associated with the phosphorylation states of KaiC, with KaiA promoting the phosphorylation of KaiC, and KaiB de-phosphorylating KaiC. Here we studied the evolution of the KaiB protein. The result will be helpful in understanding the evolution of the circadian clock system.

Dormancy, Diapause, and the Role of the Circadian System in Insect Photoperiodism

2020 ◽  
Vol 65 (1) ◽  
pp. 373-389 ◽  
Author(s):  
David S. Saunders
Keyword(s):  
Clock Genes ◽  
Animal Experiments ◽  
Transcript Abundance ◽  
Circadian System ◽  
Gene Transcript ◽  
Light Cycle ◽  
Peripheral Oscillators ◽  
Circadian Clock Genes ◽  
Similar Phase

Whole-animal experiments devised to investigate possible association between photoperiodic time measurement and the circadian system (Bünning's hypothesis) are compared with more recent molecular investigations of circadian clock genes. In Sarcophaga argyrostoma and some other species, experimental cycles of light and darkness revealed a photoperiodic oscillator, set to constant phase at dusk and measuring night length repeatedly during extended periods of darkness. In some species, however, extreme dampening revealed an unrepetitive (i.e., hourglass-like) response. Rhythms of clock gene transcript abundance may also show similar phase relationships to the light cycle, and gene silencing of important clock genes indicates that they play a crucial role in photoperiodism either alone or in concert. However, the multiplicity of peripheral oscillators in the insect circadian system indicates that more complex mechanisms might also be important.

Involvement of proteins in light resetting ocular circadian oscillators of Aplysia

1990 ◽  
Vol 258 (1) ◽  
pp. R256-R262
Author(s):  
U. Raju ◽  
S. J. Yeung ◽  
A. Eskin
Keyword(s):  
Light Treatment ◽  
Circadian System ◽  
Phase Shifting ◽  
Extracellular Potassium ◽  
Dependent Manner ◽  
Amino Acid Incorporation ◽  
Two Dimensional Gel Electrophoresis ◽  
Circadian Oscillators ◽  
Acid Incorporation ◽  
Effect Of Inhibitors

The effect of inhibitors of protein synthesis on the phase shifting action of light was investigated. Anisomycin and cycloheximide appeared to block advance phase shifts produced by light. This result suggested that light might phase shift by changing the synthesis of some proteins. Examining proteins separated by two-dimensional gel electrophoresis, we found that incorporation of amino acids into 11 proteins was changed during a 6-h light pulse. Nine of these 11 proteins were affected by light in a phase-dependent manner. Elevated extracellular potassium and 8-bromo-guanosine 3',5'-cyclic monophosphate (cGMP), two treatments that mimic effects of light on the rhythm, also changed amino acid incorporation into a number of proteins. All of the five proteins affected by 8-bromo-cGMP were also affected in the same manner by light. Three proteins were affected similarly by elevated potassium, light, and 8-bromo-cGMP. Exposure of eyes to label at different times after light treatment showed that the effects of light on some proteins were long lasting. In addition, some proteins were not affected during light but were affected only several hours after light. Some of the eye proteins affected by light were also altered by serotonin (5-HT), another phase-shifting agent. The proteins affected by light, elevated potassium, 8-bromo-cGMP, and 5-HT are candidates for components of the circadian system either as an element of the entrainment pathway or the oscillator mechanism.

scholarly journals Melatonin administration can entrain the free-running circadian system of blind subjects

2000 ◽  
Vol 164 (1) ◽  
pp. R1-R6 ◽  
Author(s):  
SW Lockley ◽  
DJ Skene ◽  
K James ◽  
K Thapan ◽  
J Wright ◽  
...  
Keyword(s):  
Circadian Rhythms ◽  
Core Body Temperature ◽  
Circadian System ◽  
Melatonin Treatment ◽  
Circadian Phase ◽  
Melatonin Administration ◽  
Free Running ◽  
Physiological Markers ◽  
Core Body ◽  
First Time

Although melatonin treatment has been shown to phase shift human circadian rhythms, it still remains ambiguous as to whether exogenous melatonin can entrain a free-running circadian system. We have studied seven blind male subjects with no light perception who exhibited free-running urinary 6-sulphatoxymelatonin (aMT6s) and cortisol rhythms. In a single-blind design, five subjects received placebo or 5 mg melatonin p.o. daily at 2100 h for a full circadian cycle (35-71 days). The remaining two subjects also received melatonin (35-62 days) but not placebo. Urinary aMT6s and cortisol (n=7) and core body temperature (n=1) were used as phase markers to assess the effects of melatonin on the During melatonin treatment, four of the seven free-running subjects exhibited a shortening of their cortisol circadian period (tau). Three of these had taus which were statistically indistinguishable from entrainment. In contrast, the remaining three subjects continued to free-run during the melatonin treatment at a similar tau as prior to and following treatment. The efficacy of melatonin to entrain the free-running cortisol rhythms appeared to be dependent on the circadian phase at which the melatonin treatment commenced. These results show for the first time that daily melatonin administration can entrain free-running circadian rhythms in some blind subjects assessed using reliable physiological markers of the circadian system.

scholarly journals Circadian Clock and The Cardiometabolic Risk

2010 ◽  
Vol 2 (2) ◽  
pp. 16
Author(s):  
Anna Meiliana ◽  
Andi Wijaya
Keyword(s):  
Circadian Rhythms ◽  
Cardiometabolic Risk ◽  
Clock Genes ◽  
Epidemiological Data ◽  
Circadian System ◽  
Temporal Organization ◽  
Liver Fat ◽  
Peripheral Tissues ◽  
The Central Nervous System ◽  
Rotation Of The Earth

BACKGROUND: Epidemiological data reveal parallel trends of decreasing sleep duration and increases in metabolic disorders such as obesity, diabetes and hypertension. There is growing evidence that these trends are mechanistically related.CONTENT: The circadian system orchestrates the temporal organization of many aspects of physiology, including metabolism, in synchrony with the 24 hours rotation of the Earth. The circadian system is a complex feedback network that involves interactions between the central nervous system and peripheral tissues. Circadian regulation is intimately linked to metabolic homeostasis and that dysregulation of circadian rhythms can contribute to disease. Conversely, metabolic signals also feed back into the circadian system, modulating circadian gene expression and behavior.SUMMARY: Both inter- and intraorgan desynchrony may be involved in the pathogenesis of cardiometabolic disease attributable to effects in brain and multiple metabolic tissues including heart, liver, fat, muscle, pancreas and gut. Efforts to dissect the molecular mediators that coordinate circadian, metabolic, and cardiovascular systems may ultimately lead to both improved therapeutics and preventive interventions.KEYWORDS: circadian rhythms, clock genes, nuclear receptor, sleep, obesity, cardiometabolic risk

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