The circadian clock is a set of regulatory steps that oscillate with a period of approximately 24 hours influencing many biological processes. These oscillations are robust to external stresses, and in the case of genotoxic stress (i.e. DNA damage), the circadian clock responds through phase shifting with primarily phase advancements. The effect of DNA damage on the circadian clock and the mech...

Mammalian circadian behavior is governed by a central clock in the suprachiasmatic nucleus of the brain hypothalamus, and its intrinsic period length is believed to affect the phase of daily activities. Measurement of this period length, normally accomplished by prolonged subject observation, is difficult and costly in humans. Because a circadian clock similar to that of the suprachiasmatic nuc...

BACKGROUND Circadian clocks regulate the gene expression, metabolism and behaviour of most eukaryotes, controlling an orderly succession of physiological processes that are synchronised with the environmental day/night cycle. Central circadian pacemakers that control animal behaviour are located in the brains of insects and rodents, but the location of such a pacemaker has not been determined i...

The absence of circadian zeitgebers in the social environment causes circadian misalignment, which is often associated with sleep disturbances. Circadian misalignment, defined as a mismatch between the sleep-wake cycle and the timing of the circadian system, can occur either because of inadequate exposure to the light-dark cycle, the most important synchronizer of the circadian system, or reduc...

Developmental and physiological responses are regulated by light throughout the entire life cycle of higher plants. To sense changes in the light environment, plants have developed various photoreceptors, including the red/far-red light-absorbing phytochromes and blue light-absorbing cryptochromes. A wide variety of physiological responses, including most light responses, also are modulated by ...

In response to exogenous rhythms of light and temperature, most organisms exhibit endogenous circadian rhythms (i.e. cycles of behavior and gene expression with a periodicity of approximately 24 h). One of the defining characteristics of the circadian clock is its ability to synchronize (entrain) to an environmental rhythm. Entrainment is arguably the most salient feature of the clock in evolut...

The mammalian circadian system synchronizes daily timing of activity and rest with the environmental light-dark cycle. Although the underlying molecular oscillatory mechanism is well studied, factors that influence phenotypic plasticity in daily activity patterns (temporal niche switching, chronotype) are presently unknown. Molecular evidence suggests that metabolism may influence the circadian...

Chloroplast-encoded genes, like nucleus-encoded genes, exhibit circadian expression. How the circadian clock exerts its control over chloroplast gene expression, however, is poorly understood. To facilitate the study of chloroplast circadian gene expression, we developed a codon-optimized firefly luciferase gene for the chloroplast of Chlamydomonas reinhardtii as a real-time bioluminescence rep...

BACKGROUND Daily rhythms of mammalian physiology and endocrinology are regulated by circadian pacemakers. The master circadian pacemaker resides in the suprachiasmatic nucleus, which is located in the hypothalamus of the brain, but circadian oscillators also exist in peripheral tissues. Because many studies have demonstrated apparent circadian variations in the frequency of cardiovascular disor...

Circadian rhythms are essential to health. Their disruption is associated with metabolic diseases in experimental animals and man. Local metabolic rhythms represent an output of tissue-based circadian clocks. Attempts to define how local metabolism is temporally coordinated have focused on gene expression by defining extensive and divergent "circadian transcriptomes" involving 5%-10% of genes a...