The circadian rhythm of body temperature

Refinetti, Roberto; Menaker, Michael

doi:10.1016/0031-9384(92)90188-8

Cited by 590 publications

(287 citation statements)

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“…The lower temperature in the study by Bligh and Harthoorn (1965) can be explained by the fact that they measured body temperature in the camel's hump, whereas Bouâouda et al (2014) The robustness of the core body temperature rhythm was between 40 and 80%, depending on whether it was calculated for individual animals or for the group as a whole, which is consistent with the findings in sheep, goats, horses, and cattle (Piccione et al, 2003). When the animals were maintained in a stable environment (without a light-dark cycle or a cycle of ambient temperature), core body temperature still exhibited near-24-hour rhythmicity, thus confirming the endogenous nature of the rhythm previously documented in a large number of species (Refinetti, 2010), including the camel (El-Allali et al, 2013). Records longer than the 2 days evaluated in this study would be needed to document the existence of a self-sustaining biological clock responsible for the generation of endogenous rhythmicity.…”

Section: Discussionsupporting

confidence: 83%

Daily rhythms of physiological parameters in the dromedary camel under natural and laboratory conditions

Alhaidary

Abdoun

Samara

et al. 2016

Research in Veterinary Science

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See next page for additional authorsThis is an author-produced, peer-reviewed version of this article. © 2016, Elsevier. Licensed under the Creative Commons NonCommercial-NoDerivs 4.0 license. Details regarding the use of this work can be found at: http://creativecommons.org/licenses/by-nc-nd/4.0/. Abstract Camels are well adapted to hot arid environments and can contribute significantly to the economy of developing countries in arid regions of the world. Full understanding of the physiology of camels requires understanding of the internal temporal order of the body, as reflected in daily or circadian rhythms. In the current study, we investigated the daily rhythmicity of 20 physiological variables in camels exposed to natural oscillations of ambient temperature in a desert environment and compared the daily temporal courses of the variables. We also studied the rhythm of core body temperature under experimental conditions with constant ambient temperature in the presence and absence of a light-dark cycle. The obtained results indicated that different physiological variables exhibit different degrees of daily rhythmicity and reach their daily peaks at different times of the day, starting with plasma cholesterol, which peaks 24 minutes after midnight, and ending with plasma calcium, which peaks 3 hours before midnight.Furthermore, the rhythm of core body temperature persisted in the absence of environmental rhythmicity, thus confirming its endogenous nature. The observed delay in the acrophase of core body temperature rhythm under constant conditions suggests that the circadian period is longer than 24 hours. Further studies with more refined experimental manipulation of different variables are needed to fully elucidate the causal network of circadian rhythms in dromedary camels.

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Section: Discussionsupporting

confidence: 83%

Daily rhythms of physiological parameters in the dromedary camel under natural and laboratory conditions

Alhaidary

Abdoun

Samara

et al. 2016

Research in Veterinary Science

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“…C ircadian rhythms are endogenous oscillations in behavior and gene expression with near-24-h periodicity observed in most living organisms. Circadian rhythms are known to regulate a wide range of processes including cell cycles, body temperature, metabolism, and behavior (1)(2)(3)(4)(5). The mammalian suprachiasmatic nucleus (SCN), a network of ∼20,000 neurons located in the hypothalamus of the brain, functions as the body's master pacemaker and mediates the entrainment of peripheral tissue oscillators to light/dark cycles (6,7).…”

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confidence: 99%

Functional network inference of the suprachiasmatic nucleus

Abel

Meeker

Granados‐Fuentes

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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In the mammalian suprachiasmatic nucleus (SCN), noisy cellular oscillators communicate within a neuronal network to generate precise system-wide circadian rhythms. Although the intracellular genetic oscillator and intercellular biochemical coupling mechanisms have been examined previously, the network topology driving synchronization of the SCN has not been elucidated. This network has been particularly challenging to probe, due to its oscillatory components and slow coupling timescale. In this work, we investigated the SCN network at a single-cell resolution through a chemically induced desynchronization. We then inferred functional connections in the SCN by applying the maximal information coefficient statistic to bioluminescence reporter data from individual neurons while they resynchronized their circadian cycling. Our results demonstrate that the functional network of circadian cells associated with resynchronization has small-world characteristics, with a node degree distribution that is exponential. We show that hubs of this small-world network are preferentially located in the central SCN, with sparsely connected shells surrounding these cores. Finally, we used two computational models of circadian neurons to validate our predictions of network structure.

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“…The mechanisms governing the T b change may be a factor. Circadian T b oscillations involve changes in the thermoregulatory set point (29), whereas the T b changes in the above-mentioned studies likely represent deviations from the set point. To better evaluate a potential influence of the circadian T b changes on hypercapnic V E responsiveness, the daily V E /V O 2 pattern during CO 2 breathing could be compared among animals with very different T b oscillations.…”

Section: Discussionmentioning

confidence: 98%

Circadian pattern of ventilation during acute and chronic hypercapnia in conscious adult rats

Seifert

Mortola

2002

American Journal of Physiology-Regulatory, Integrative and Comp

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Seifert, Erin L., and Jacopo P. Mortola. Circadian pattern of ventilation during acute and chronic hypercapnia in conscious adult rats. Am J Physiol Regulatory Integrative Comp Physiol 282: R244-R251, 2002; 10.1152/ajpregu. 00290.2001.-Because metabolism is a determinant of the ventilatory chemosensitivity, we tested the hypothesis that the ventilatory response to acute and prolonged hypercapnia is adjusted to the circadian oscillations in oxygen consumption (V O2). Adult rats were instrumented for measurements of body temperature (Tb) and activity by telemetry. Pulmonary ventilation (V E) was measured by the barometric method and V O2 by the flow-through method. In the acute experiments, 16 conscious rats entrained to a 12:12-h light (L)-dark (D) cycle (lights on 7:00 AM) were exposed to air, 2%, and then 5% CO2 in normoxia (30-45 min each) at 11:00 AM and 11:00 PM. In a separate group of seven rats, simultaneous recordings of all variables were made continuously for 3 consecutive days in air followed by 3 days in 2% CO2 in normoxia, in a 12:12-h L-D cycle (lights on 7:00 AM). In air, all variables were significantly higher at night, whether rats were studied acutely or chronically. Acute CO2 exposure had similar significant effects at 11:00 AM and 11:00 PM on V E (ϳ25 and 100% increase with 2 and 5% CO2, respectively) and V O2 (ϳ8% drop with 5% CO2), such that the hyperventilatory response (% increase in V E/V O2 from air) was similar at both times. Chronic CO2 breathing increased V E at all times of the day, but less so during the L phase (ϳ15 vs. 22% increase in L and D, respectively), when activity was lower. However, V O2 was reduced from the air level (ϳ10% drop) in the L, such that the V E/V O2 response was similar between L and D. The same result was obtained when the V E/V O2 response was compared between the L and D phases for the same level of activity. These results suggest that, throughout the day, the hypercapnic hyperpnea, whether during acute or prolonged CO2, is perfectly adjusted to the metabolic level.control of breathing; chemosensitivity; barometric method; oxygen consumption IN MAMMALS AND BIRDS, blood gas homeostasis depends on the matching of pulmonary ventilation (V E) to metabolism. Indeed, a close coupling between V E and oxygen consumption (V O 2 ) has been found under a variety of conditions where V O 2 is either raised or lowered (20). Variations in metabolism are also associated with changes in V E chemosensitivity (19). A higher V O 2 , as during muscular exercise (35) or cold exposure (12), is accompanied by a greater absolute increase in V E in response to acute hypoxia or hypercapnia, whereas reflex hyperpnea is lower whenVO 2 is reduced, such as with myxedema (36) or semi-starvation (6). Hence, the V E chemoreflex response seems to track V O 2 . This would tend to minimize fluctuations in blood gases in normoxia and when chemosensory drive is elevated.Oxygen consumption presents a circadian oscillation. Although the daily high values of V O 2 generally occur when an animal i...

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The circadian rhythm of body temperature

Cited by 590 publications

References 344 publications

Daily rhythms of physiological parameters in the dromedary camel under natural and laboratory conditions

Daily rhythms of physiological parameters in the dromedary camel under natural and laboratory conditions

Functional network inference of the suprachiasmatic nucleus

Circadian pattern of ventilation during acute and chronic hypercapnia in conscious adult rats

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