scholarly journals A Mathematical Model to Characterize the Role of Light Adaptation in Mammalian Circadian Clock

2021 ◽  
Vol 8 ◽  
Author(s):  
Yuzeng Shi ◽  
Yu Liu ◽  
Ling Yang ◽  
Jie Yan
Keyword(s):  
Mathematical Model ◽  
Circadian Clock ◽  
Light Adaptation ◽  
Light Stimulus ◽  
Circadian System ◽  
Jet Lag ◽  
Short Term ◽  
Adaptation Mechanism ◽  
Role Of Light

In response to a light stimulus, the mammalian circadian clock first dramatically increases the expression of Per1 mRNA, and then drops to a baseline even when light persists. This phenomenon is known as light adaptation, which has been experimentally proven to be related to the CRTC1-SIK1 pathway in suprachiasmatic nucleus (SCN). However, the role of this light adaptation in the circadian rhythm remains to be elucidated. To reveal the in-depth function of light adaptation and the underlying dynamics, we proposed a mathematical model for the CRTC1-SIK1 network and coupled it to a mammalian circadian model. The simulation result proved that the light adaptation is achieved by the self-inhibition of the CRTC1/CREB complex. Also, consistently with experimental observations, this adaptation mechanism can limit the phase response to short-term light stimulus, and it also restricts the rate of the phase shift in a jet lag protocol to avoid overly rapid re-entrainment. More importantly, this light adaptation is predicted to prevent the singularity behavior in the cell population, which represents the abolishment of circadian rhythmicity due to desynchronization of oscillating cells. Furthermore, it has been shown to provide refractoriness to successive stimuli with short gap. Therefore, we concluded that the light adaptation generated by the CRTC1-SIK1 pathway in the SCN provides a robust mechanism, allowing the circadian system to maintain homeostasis in the presence of light perturbations. These results not only give new insights into the dynamics of light adaptation from a computational perspective but also lead us to formulate hypotheses about the related physiological significance.

scholarly journals Bright light during lactation alters the functioning of the circadian system of adult rats

2000 ◽  
Vol 278 (1) ◽  
pp. R201-R208 ◽  
Author(s):  
M. M. Canal-Corretger ◽  
T. Cambras ◽  
J. Vilaplana ◽  
A. Díez-Noguera
Keyword(s):  
Motor Activity ◽  
Activity Rhythm ◽  
Bright Light ◽  
Circadian System ◽  
Constant Darkness ◽  
Adult Rats ◽  
Light Pulses ◽  
Circadian Time ◽  
Role Of Light

To examine the role of light in the maturation of the circadian pacemaker, twelve groups of rats were raised in different conditions of exposure to constant bright light (LL) during lactation: both duration and timing of LL were varied. We studied the motor activity rhythm of the rats after weaning, first under LL and then under constant darkness (DD). In DD, two light pulses [at circadian time 15 (CT15) and CT22] were applied to test the response of the pacemaker. Greater exposure to LL days during lactation increased the number of rhythmic animals and the amplitude of their motor activity rhythm in the LL stage and decreased the phase delay due to the light pulse at CT15. The timing of LL during lactation affected these variables too. Because the response of the adult to light depended on both the number and timing of LL days during lactation, the exposure to light at early stages may influence the development of the circadian system by modifying it structurally or functionally.

scholarly journals Circadian Clock and OxInflammation: Functional Crosstalk in Cutaneous Homeostasis

2020 ◽  
Vol 2020 ◽  
pp. 1-9 ◽  
Author(s):  
Elena Frigato ◽  
Mascia Benedusi ◽  
Anna Guiotto ◽  
Cristiano Bertolucci ◽  
Giuseppe Valacchi
Keyword(s):  
Circadian Clock ◽  
Redox Homeostasis ◽  
Physiological Role ◽  
Protective Role ◽  
Circadian System ◽  
Circadian Disruption ◽  
Cellular Damage ◽  
Lifestyle Risk Factors

Circadian rhythms are biological oscillations that occur with an approximately 24 h period and optimize cellular homeostasis and responses to environmental stimuli. A growing collection of data suggests that chronic circadian disruption caused by novel lifestyle risk factors such as shift work, travel across time zones, or irregular sleep-wake cycles has long-term consequences for human health. Among the multiplicity of physiological systems hypothesized to have a role in the onset of pathologies in case of circadian disruption, there are redox-sensitive defensive pathways and inflammatory machinery. Due to its location and barrier physiological role, the skin is a prototypical tissue to study the influence of environmental insults induced OxInflammation disturbance and circadian system alteration. To better investigate the link among outdoor stressors, OxInflammation, and circadian system, we tested the differential responses of keratinocytes clock synchronized or desynchronized, in an in vitro inflammatory model exposed to O3. Being both NRF2 and NF-κB two key redox-sensitive transcription factors involved in cellular redox homeostasis and inflammation, we analyzed their activation and expression in challenged keratinocytes by O3. Our results suggest that a synchronized circadian clock not only facilitates the protective role of NRF2 in terms of a faster and more efficient defensive response against environmental insults but also moderates the cellular damage resulting from a condition of chronic inflammation. Our results bring new insights on the role of circadian clock in regulating the redox-inflammatory crosstalk influenced by O3 and possibly can be extrapolated to other pollutants able to affect the oxinflammatory cellular processes.

Expression of circadian clock genes in retinal dopaminergic cells

2007 ◽  
Vol 24 (4) ◽  
pp. 573-580 ◽  
Author(s):  
RONALD DORENBOS ◽  
MASSIMO CONTINI ◽  
HAJIME HIRASAWA ◽  
STEFANO GUSTINCICH ◽  
ELIO RAVIOLA
Keyword(s):  
Circadian Clock ◽  
Light Adaptation ◽  
Clock Genes ◽  
Negative Control ◽  
Circadian Oscillators ◽  
Interesting Candidate ◽  
Circadian Clock Genes ◽  
Core Components ◽  
A Site

The mammalian neural retina contains single or multiple intrinsic circadian oscillators that can be directly entrained by light cycles. Dopaminergic amacrine (DA) cells represent an especially interesting candidate as a site of the retinal oscillator because of the crucial role of dopamine in light adaptation, and the widespread distribution of dopamine receptors in the retina. We hereby show by single-cell, end-point RT-PCR that retinal DA cells contain the transcripts for six core components of the circadian clock: Bmal1, Clock, Cry1, Cry2, Per1, and Per2. Rod photoreceptors represented a negative control, because they did not appear to contain clock transcripts. We finally confirmed that DA cells contain the protein encoded by the Bmal1 gene by comparing immunostaining of the nuclei of DA cells in the retinas of wildtype and Bmal1−/− mice. It is therefore likely that DA cells contain a circadian clock that anticipates predictable variations in retinal illumination.

scholarly journals Role of Light Stimulus in the Development of Strabismus

1980 ◽  
Vol 8 (1) ◽  
pp. 35-38
Author(s):  
Katsuko MASUDA ◽  
Yukihiko MITSUI
Keyword(s):  
Light Stimulus ◽  
Role Of Light

A Mathematical Model of the Human Circadian System and Its Application to Jet Lag

1992 ◽  
Vol 9 (2) ◽  
pp. 148-159 ◽  
Author(s):  
Alexander Gundel ◽  
Michael B. Spencer
Keyword(s):  
Mathematical Model ◽  
Circadian System ◽  
Jet Lag

scholarly journals Epigenetic regulation of the circadian clock: role of 5-aza-2′-deoxycytidine

2017 ◽  
Vol 37 (3) ◽  
Author(s):  
Tatsunosuke Tomita ◽  
Ryoji Kurita ◽  
Yoshiaki Onishi
Keyword(s):  
Gene Expression ◽  
Dna Methylation ◽  
Circadian Clock ◽  
Lymphoblastic Leukemia ◽  
Cpg Islands ◽  
Circadian System ◽  
Clock System ◽  
Specific Pcr ◽  
Clinical Strategies

We have been investigating transcriptional regulation of the BMAL1 gene, a critical component of the mammalian clock system including DNA methylation. Here, a more detailed analysis of the regulation of DNA methylation of BMAL1 proceeded in RPMI8402 lymphoma cells. We found that CpG islands in the BMAL1 and the PER2 promoters were hyper- and hypomethylated, respectively and that 5-aza-2′-deoxycytidine (aza-dC) not only enhanced PER2 gene expression but also PER2 oscillation within 24 h in RPMI8402 cells. That is, such hypermethylation of CpG islands in the BMAL1 promoter restricted PER2 expression which was recovered by aza-dC within 1 day in these cells. These results suggest that the circadian clock system can be recovered through BMAL1 expression induced by aza-dC within a day. The RPIB9 promoter of RPMI8402 cells, which is a methylation hotspot in lymphoblastic leukemia, was also hypermethylated and aza-dC gradually recovered RPIB9 expression in 3 days. In addition, methylation-specific PCR revealed a different degree of aza-dC-induced methylation release between BMAL1 and RPIB9. These results suggest that the aza-dC-induced recovery of gene expression from DNA methylation is dependent on a gene, for example the rapid response to demethylation by the circadian system, and thus, is of importance to clinical strategies for treating cancer.

Role of affect in short-term memory for paired associates.

1968 ◽  
Vol 78 (3, Pt.1) ◽  
pp. 494-501 ◽  
Author(s):  
Calvin F. Nodine ◽  
James H. Korn
Keyword(s):  
Short Term Memory ◽  
Short Term ◽  
Term Memory ◽  
Paired Associates
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