Phase shifting two coupled circadian pacemakers: implications for jet lag

Flights across time zones produce an abrupt displacement of the environmental time cues (zeitgebers), and the endogenous circadian timing system resynchronizes only gradually to the new schedule. A coupled two-oscillator model can simulate the human circadian system in temporal isolation and in artificial zeitgeber cycles. The model is here shown to explain the major features of resynchronization of circadian rhythms after time zone shifts, i.e., the rate of adjustment depends on the rhythm being measured, the number of time zones crossed, the flight direction (eastward or westward), and the strength of the zeitgebers in the new time zone. Investigations of the contribution of different model parameters to system performances suggest that intersubject differences in pacemaker periods may be a major factor in the observed variability in the effects of time zone shifts on circadian rhythms. With individualized period estimate the models can simulate case studies in which four subjects recorded their sleep-wake and core body temperature rhythms throughout simple and complex patterns of transmeridian flights.

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Nonphotic entrainment of the human circadian pacemaker

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1998.274.4.r991 ◽

1998 ◽

Vol 274 (4) ◽

pp. R991-R996 ◽

Cited By ~ 32

Author(s):

Elizabeth B. Klerman ◽

David W. Rimmer ◽

Derk-Jan Dijk ◽

Richard E. Kronauer ◽

Joseph F. Rizzo ◽

...

Keyword(s):

Circadian Rhythms ◽

Light Exposure ◽

Core Body Temperature ◽

Biological Clock ◽

Bright Light ◽

Circadian Pacemaker ◽

Temperature Rhythms ◽

Blind Individuals ◽

Nonphotic Entrainment ◽

Core Body

In organisms as diverse as single-celled algae and humans, light is the primary stimulus mediating entrainment of the circadian biological clock. Reports that some totally blind individuals appear entrained to the 24-h day have suggested that nonphotic stimuli may also be effective circadian synchronizers in humans, although the nonphotic stimuli are probably comparatively weak synchronizers, because the circadian rhythms of many totally blind individuals “free run” even when they maintain a 24-h activity-rest schedule. To investigate entrainment by nonphotic synchronizers, we studied the endogenous circadian melatonin and core body temperature rhythms of 15 totally blind subjects who lacked conscious light perception and exhibited no suppression of plasma melatonin in response to ocular bright-light exposure. Nine of these fifteen blind individuals were able to maintain synchronization to the 24-h day, albeit often at an atypical phase angle of entrainment. Nonphotic stimuli also synchronized the endogenous circadian rhythms of a totally blind individual to a non-24-h schedule while living in constant near darkness. We conclude that nonphotic stimuli can entrain the human circadian pacemaker in some individuals lacking ocular circadian photoreception.

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Skin surface temperature rhythms as potential circadian biomarkers for personalized chronotherapeutics in cancer patients

Interface Focus ◽

10.1098/rsfs.2010.0012 ◽

2010 ◽

Vol 1 (1) ◽

pp. 48-60 ◽

Cited By ~ 28

Author(s):

Christopher G. Scully ◽

Abdoulaye Karaboué ◽

Wei-Min Liu ◽

Joseph Meyer ◽

Pasquale F. Innominato ◽

...

Keyword(s):

Circadian Rhythms ◽

Skin Temperature ◽

Cancer Patients ◽

Infrared Imaging ◽

Core Body Temperature ◽

Dynamic Assessment ◽

Invasive Approach ◽

Circadian Timing ◽

Circadian Phase ◽

Temperature Rhythms

Chronotherapeutics involve the administration of treatments according to circadian rhythms. Circadian timing of anti-cancer medications has been shown to improve treatment tolerability up to fivefold and double efficacy in experimental and clinical studies. However, the physiological and the molecular components of the circadian timing system (CTS), as well as gender, critically affect the success of a standardized chronotherapeutic schedule. In addition, a wrongly timed therapy or an excessive drug dose disrupts the CTS. Therefore, a non-invasive approach to accurately detect and monitor circadian rhythms is needed for a dynamic assessment of the CTS in order to personalize chronomodulated drug delivery schedule in cancer patients. Since core body temperature is a robust circadian biomarker, we recorded temperature at multiple locations on the skin of the upper chest and back of controls and cancer patients continuously. Variability in the circadian phase existed among patch locations in individual subjects over the course of 2–6 days, demonstrating the need to monitor multiple skin temperature locations to determine the precise circadian phase. Additionally, we observed that locations identified by infrared imaging as relatively cool had the largest 24 h temperature variations. Disruptions in skin temperature rhythms during treatment were found, pointing to the need to continually assess circadian timing and personalize chronotherapeutic schedules.

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Circadian control of thermoregulation in the squirrel monkey, Saimiri sciureus

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1979.236.3.r153 ◽

1979 ◽

Vol 236 (3) ◽

pp. R153-R161

Author(s):

C. A. Fuller ◽

F. M. Sulzman ◽

M. C. Moore-Ede

Keyword(s):

Body Temperature ◽

Circadian Rhythms ◽

Core Body Temperature ◽

Saimiri Sciureus ◽

Temperature Rhythm ◽

Circadian Time ◽

Tightly Coupled ◽

Temperature Rhythms ◽

Colonic Temperature ◽

And Control

The characteristics and control of the circadian rhythms of core body temperature (colonic) and skin temperature (tail) were studied in chair-acclimatized squirrel monkeys (Saimiri sciureus). When animals were entrained to a light-dark cycle (12 h 600 lx; 12 h less than 1 lx) these two temperatures displayed prominent, reproducible, tightly coupled circadian rhythms. In contsant light of 600 lx, where no other effective circadian time cues were present, both temperature rhythms persisted with free-running periods. Within each animal, however, these rhythms were not as tightly coupled to one another as in LD. On occasion colonic and tail temperature rhythms free-ran with different circadian periods and some animals demonstrated "splitting" of the colonic temperature rhythm, with the colonic temperature rhythm displaying a bimodal pattern. These results suggest that the circadian rhythm of body temperature in primates is under the control of more than one potentially independent circadian oscillator.

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Integration & Volatility across Global Indices in different Time Zones: Some Evidence

Restaurant Business ◽

10.26643/rb.v118i9.8028 ◽

2019 ◽

Vol 118 (9) ◽

pp. 187-192

Author(s):

Dr.Madavi Eswara

Keyword(s):

Time Zone ◽

Global Indices ◽

Securities Exchanges ◽

Time Zones ◽

Test Outcomes ◽

Multivariate Exponential

This paper examines the association of value instability crosswise over Global Indices of seven securities exchanges. Utilizing every day information of these seven nations situated in various time zones, this paper attempts to call attention to the nearness of nonsynchronous exchanging impacts utilizing open and close logarithmic returns of seven securities exchange files including Indian Indexat the middle. The hilter kilter effect of unpredictability overflow is analyzed by a multivariate exponential general autoregressive restrictive heteroskedastic model utilizing an example of 1742 perceptions taken from Oct 2011 to November 2018. The test outcomes give out many fascinating actualities alongside cost and unpredictability overflow from one market to the next because of time zone impact and additionally, influence impact is seen from the eastern markets' nearby value child Indian file open cost.

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Circadian rhythms, sleep, and anti-cancer treatments

10.1093/oso/9780198778240.003.0016 ◽

2018 ◽

Author(s):

Pasquale F. Innominato ◽

David Spiegel

Keyword(s):

Quality Of Life ◽

Circadian Rhythms ◽

Biological Functions ◽

Cancer Treatments ◽

Anti Cancer ◽

Timing System ◽

Physical Wellbeing ◽

Circadian Timing System ◽

Chemotherapy Agents

The circadian timing system temporally regulates biological functions relevant for psycho-physical wellbeing, spanning all the systems related to health. Hence, disruption of circadian rhythms, along with sleep cycles, is associated with the development of several diseases, including cancer. Moreover, altered circadian and sleep functions negatively impact on cancer patients’ quality of life and survival, above and beyond known determinants of outcome. This alteration can occur as a consequence of cancer, but also of anti-cancer treatments. Indeed, circadian rhythms govern also the ability of detoxifying chemotherapy agents across the 24 hours. Hence, adapting chemotherapy delivery to the molecular oscillations in relevant drug pathways can decrease toxicity to healthy cells, while increasing the number of cancer cells killing. This chronomodulated chemotherapy approach, together with the maintenance of proper circadian function throughtout the whole disease challenge, would finally result in safer and more active anticancer treatments, and in patients experiencing better quality and quantity of life.

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Measuring Circadian Advantage in Major League Baseball: A 10-Year Retrospective Study

International Journal of Sports Physiology and Performance ◽

10.1123/ijspp.4.3.394 ◽

2009 ◽

Vol 4 (3) ◽

pp. 394-401 ◽

Cited By ~ 19

Author(s):

W. Christopher Winter ◽

William R. Hammond ◽

Noah H. Green ◽

Zhiyong Zhang ◽

Donald L. Bliwise

Keyword(s):

Retrospective Study ◽

Athletic Performance ◽

Major League Baseball ◽

Time Zone ◽

Winning Percentage ◽

Circadian Time ◽

Game Outcome ◽

Time Zones ◽

Home Field Advantage ◽

Major League

Purpose:The effect of travel on athletic performance has been investigated in previous studies. The purpose of this study was to investigate this effect on game outcome over 10 Major League Baseball (MLB) seasons.Methods:Using the convention that for every time zone crossed, synchronization requires 1 d, teams were assigned a daily number indicating the number of days away from circadian resynchronization. With these values, wins and losses for all games could be analyzed based on circadian values.Results:19,079 of the 24,121 games (79.1%) were played between teams at an equal circadian time. The remaining 5,042 games consisted of teams playing at different circadian times. The team with the circadian advantage won 2,620 games (52.0%, P = .005), a winning percentage that exceeded chance but was a smaller effect than home field advantage (53.7%, P < .0001). When teams held a 1-h circadian advantage, winning percentage was 51.7% (1,903–1,781). Winning percentage with a 2-h advantage was 51.8% (620–578) but increased to 60.6% (97–63) with a 3-h advantage (3-h advantage > 2-hadvantage = 1-h advantage, P = .036). Direction of advantage showed teams traveling from Western time zones to Eastern time zones were more likely to win (winning percentage = .530) than teams traveling from Eastern time zones to Western time zones (winning percentage = .509) with a winning odds 1.14 (P = .027).Conclusion:These results suggest that in the same way home field advantage influences likelihood of success, so too does the magnitude and direction of circadian advantage. Teams with greater circadian advantage were more likely to win.

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Physical exercise accelerates reentrainment of human sleep-wake cycle but not of plasma melatonin rhythm to 8-h phase-advanced sleep schedule

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00345.2009 ◽

2010 ◽

Vol 298 (3) ◽

pp. R681-R691 ◽

Cited By ~ 48

Author(s):

Yujiro Yamanaka ◽

Satoko Hashimoto ◽

Yusuke Tanahashi ◽

Shin-ya Nishide ◽

Sato Honma ◽

...

Keyword(s):

Circadian Rhythms ◽

Physical Exercise ◽

Sleep Onset ◽

Exercise Group ◽

Control Group ◽

Temporal Isolation ◽

Melatonin Rhythm ◽

Plasma Melatonin ◽

Shift Schedule ◽

Sleep Schedule

Effects of timed physical exercise were examined on the reentrainment of sleep-wake cycle and circadian rhythms to an 8-h phase-advanced sleep schedule. Seventeen male adults spent 12 days in a temporal isolation facility with dim light conditions (<10 lux). The sleep schedule was phase-advanced by 8 h from their habitual sleep times for 4 days, which was followed by a free-run session for 6 days, during which the subjects were deprived of time cues. During the shift schedule, the exercise group ( n = 9) performed physical exercise with a bicycle ergometer in the early and middle waking period for 2 h each. The control group ( n = 8) sat on a chair at those times. Their sleep-wake cycles were monitored every day by polysomnography and/or weight sensor equipped with a bed. The circadian rhythm in plasma melatonin was measured on the baseline day before phase shift: on the 4th day of shift schedule and the 5th day of free-run. As a result, the sleep-onset on the first day of free-run in the exercise group was significantly phase-advanced from that in the control and from the baseline. On the other hand, the circadian melatonin rhythm was significantly phase-delayed in the both groups, showing internal desynchronization of the circadian rhythms. The sleep-wake cycle resynchronized to the melatonin rhythm by either phase-advance or phase-delay shifts in the free-run session. These findings indicate that the reentrainment of the sleep-wake cycle to a phase-advanced schedule occurs independent of the circadian pacemaker and is accelerated by timed physical exercise.

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