Circadian rhythms are biological rhythms that repeat at approximately 24 hours. In humans, circadian rhythms have an average period of 24.2 hours. The 24-hour patterns of light and dark on the retina synchronize circadian rhythms to the local time on earth. Lighting characteristics affecting circadian rhythms are very different than those affecting visual responses. Lack of synchronization betw...

Glossary Circadian challenge: Situations in which the circadian timing system needs to adapt to changes in environmental time cues (e.g., jet lag and shift work). Circadian entrainment: Circadian rhythms are endogenous, but they are sensitive to the environment. Entrainment mechanisms exist to synchronize the endogenous circadian period of about 24 h to the environmental day–night cycle of exac...

conclusions the study findings highlight the importance of the mental aspect of fatigue in this working group. these results have possible implications for workers’ health and well-being and for the design of shift work systems, for industrial workers. background shift work is a well-recognized occupational health hazard in both industrialized and industrially developing countries. prolonged wo...

INTRODUCTION The human circadian timing system generates multiple circadian rhythms. One of the characteristics of a rhythm is the phase. The circadian phase could be defined as the time at which the circadian rhythm of a variable reaches a particular state (Van Dongen, 1998). Substantial inter-individual differences in the circadian phase of several variables have been observed (Foret, 1982; K...

Based on a reduced circadian oscillator model in Drosophila [Smolen, Biophys. J. 83, 2349 (2002)], the effects of light noise and time delay on a circadian oscillator near a Hopf bifurcation are studied by using numerical computation. When the light-controlled parameter is suprathreshold, it was found that the circadian oscillations can be induced by light fluctuation. There is an optimal light...

Circadian clocks are internal molecular time-keeping mechanisms that enable organisms to adjust their physiology and behavior to the daily surroundings. Misalignment of circadian clocks leads to both physiological and health impairment. Post-transcriptional regulation and translational regulation of circadian clocks have been extensively investigated. In addition, accumulating evidence has shed...

The temporal order of physiology and behaviour in mammals is regulated by the coordination of the master circadian clock in the suprachiasmatic nucleus (SCN) and peripheral clocks in various tissues outside the SCN. Because the circadian oscillator(s) in the olfactory bulb (OB) is regarded as SCN independent, we examined the relationship between the SCN master clock and the circadian clock in t...

Circadian clocks are self-sustaining timekeepers found in almost all organisms on earth. The filamentous fungus Neurospora crassa is a preeminent model for eukaryotic circadian clocks. Investigations of the Neurospora circadian clock system have led to elucidation of circadian clock regulatory mechanisms that are common to all eukaryotes. In this work, we will focus on the Neurospora circadian ...

Circadian rhythms occur in most of the living organisms, and with a 24 hour periodicity govern a number of physiological and metabolic functions. During the past few years, an important research effort has uncovered new trails that intersect between circadian rhythms and metabolic pathways. At a molecular level, the clock machinery is responsible for the establishment of a circadian epigenome, ...

A central mechanism for controlling circadian gene amplitude remains elusive. We present evidence for a "facilitated repression (FR)" model that functions as an amplitude rheostat for circadian gene oscillation. We demonstrate that ROR and/or BMAL1 promote global chromatin decondensation during the activation phase of the circadian cycle to actively facilitate REV-ERB loading for repression of ...