Natural Free-Running Period in Vertebrate Animal Populations

Lowe, Charles H.; Hinds, David S.; Lardner, Peter J.; Justice, Keith E.

doi:10.1126/science.156.3774.531

Cited by 18 publications

(2 citation statements)

References 6 publications

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“…Indeed, most synthetic cellular oscillators produce noticeably irregular rhythms 3 – 5 . In contrast, natural circadian clocks can be extremely precise 6 – 8 . It is generally not known how biological clocks create deterministic rhythms from their stochastic components, or how the architecture of clock networks responds to the constraints of molecular noise.…”

Section: Introductionmentioning

confidence: 99%

High protein copy number is required to suppress stochasticity in the cyanobacterial circadian clock

et al. 2018

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Circadian clocks generate reliable ~24-h rhythms despite being based on stochastic biochemical reactions. The circadian clock in Synechococcus elongatus uses a post-translational oscillator that cycles deterministically in a test tube. Because the volume of a single bacterial cell is much smaller than a macroscopic reaction, we asked how clocks in single cells function reliably. Here, we show that S. elongatus cells must express many thousands of copies of Kai proteins to effectively suppress timing errors. Stochastic modeling shows that this requirement stems from noise amplification in the post-translational feedback loop that sustains oscillations. The much smaller cyanobacterium Prochlorococcus expresses only hundreds of Kai protein copies and has a simpler, hourglass-like Kai system. We show that this timer strategy can outperform a free-running clock if internal noise is significant. This conclusion has implications for clock evolution and synthetic oscillator design, and it suggests hourglass-like behavior may be widespread in microbes.

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Section: Introductionmentioning

confidence: 99%

High protein copy number is required to suppress stochasticity in the cyanobacterial circadian clock

et al. 2018

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“…Rats and hamsters also display a period length close to 24 h that tends to decrease as the animals age (Rosenberg et al ., 1991). While there are some variations in tau across animals, it is also clear that period length of cycling behaviors across many species are remarkably close to 24 h even after weeks without exposure to light, or in the case of blind animals, an entire lifetime (Lowe et al ., 1967). As will be discussed in more detail in later sections, there is much research currently on understanding the tau of the molecular clock within single cells, coupled cells, or whole tissues.…”

Section: Characteristics Of Oscillating Systemsmentioning

confidence: 99%

Circadian Rhythms, the Molecular Clock, and Skeletal Muscle

Lefta

Wolff

Esser

2011

Current Topics in Developmental Biology

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Almost all organisms ranging from single cell bacteria to humans exhibit a variety of behavioral, physiological, and biochemical rhythms. In mammals, circadian rhythms control the timing of many physiological processes over a 24-h period, including sleep-wake cycles, body temperature, feeding, and hormone production. This body of research has led to defined characteristics of circadian rhythms based on period length, phase, and amplitude. Underlying circadian behaviors is a molecular clock mechanism found in most, if not all, cell types including skeletal muscle. The mammalian molecular clock is a complex of multiple oscillating networks that are regulated through transcriptional mechanisms, timed protein turnover, and input from small molecules. At this time, very little is known about circadian aspects of skeletal muscle function/metabolism but some progress has been made on understanding the molecular clock in skeletal muscle. The goal of this chapter is to provide the basic terminology and concepts of circadian rhythms with a more detailed review of the current state of knowledge of the molecular clock, with reference to what is known in skeletal muscle. Research has demonstrated that the molecular clock is active in skeletal muscles and that the muscle-specific transcription factor, MyoD, is a direct target of the molecular clock. Skeletal muscle of clock-compromised mice, Bmal1−/− and ClockΔ19 mice, are weak and exhibit significant disruptions in expression of many genes required for adult muscle structure and metabolism. We suggest that the interaction between the molecular clock, MyoD, and metabolic factors, such as PGC-1, provide a potential system of feedback loops that may be critical for both maintenance and adaptation of skeletal muscle.

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Biological Rhythms, Shiftwork, and Occupational Health

Scott¹,

LaDou²

2001

Patty's Toxicology

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“… and God divided the light from the darkness, and God called the light day , and the darkness He called night . And the evening and the morning were the first day” (Genesis 1:4–5, King James Version). Thus, as has been recognized for millennia, Homo sapiens , as well as all other living creatures on earth, are destined to live in a regular cycle of light and darkness, that is, the 24‐h solar day. For diurnal species, such as human beings, the sunlight portion of the day is the time of activity and the dark, nighttime portion the time for sleeping. Periodicity is an integral part of life. Although we are under the influence of environmental rhythms, such as the daylight–night cycle, we are also under the physiological influence of our own internal biological clock. Normally the synchronization of our biological rhythms with each other and with environmental rhythms (external time cues) maximizes our waking and sleeping performance and promotes overall well‐being. Night work is opposed to the innate drive to sleep at night and work during the daytime. This unnatural mismatch of environmental and internal temporal influences is of concern for shiftworkers due to the often disruptive effect of schedule‐related time shifts on the normal synchronization of individual biological rhythms with each other as well as with the external time cues. This chapter reviews basic chronobiological principles as they relate to shiftworker safety and health. Studies dealing with the effects of time shifts on sleep and alertness are discussed as well as performance rhythms. Research exploring the consequences of shiftwork on physical and mental health is reviewed. Countermeasures for minimizing adverse health and safety effects of sleep deprivation and biological rhythm disruption are presented, including work scheduling considerations and medical surveillance. Industrial hygiene considerations related to control of worker exposure to potential toxins during extended and rotating shifts are presented. Finally, international and U.S. regulatory policy regarding shiftwork scheduling and special provisions for shiftworkers are reviewed.

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Natural Free-Running Period in Vertebrate Animal Populations

Cited by 18 publications

References 6 publications

High protein copy number is required to suppress stochasticity in the cyanobacterial circadian clock

High protein copy number is required to suppress stochasticity in the cyanobacterial circadian clock

Circadian Rhythms, the Molecular Clock, and Skeletal Muscle

Biological Rhythms, Shiftwork, and Occupational Health

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