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1
Farr, Lynne, Catherine Todero, and Lonna Boen. "Reducing Disruption of Circadian Temperature Rhythm Following Surgery." Biological Research For Nursing 2, no. 4 (April 2001): 257–66. http://dx.doi.org/10.1177/109980040100200405.
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Temperature and other circadian rhythms are disrupted following surgery and other traumatic events. During recovery, coordination between temperature rhythms and other rhythmic physiologic processes is reduced. Studies of animals and humans have shown that return of synchrony is not immediate, but that it is important in the recovery process. The purpose of this study was to test a combination of cues that have been shown to adjust the timing of circadian temperature rhythm. The combined cues consisted of timed ingestion of caffeine and protein foods and adjustment of the sleep/wake cycle. The intervention was tested in 26 age-and gender-matched maxillofacial surgery patients. Patients were randomly assigned to control or experimental groups. Circadian temperature rhythm was measured by continuous monitoring with axillary probes and miniature recorders before and after surgery. Following surgery, both experimental and control subjects displayed 24-hour circadian temperature rhythms; however, the peak-to-trough difference was decreased more following surgery in the control subjects than in the subjects who had prepared for surgery by practicing the intervention. Control subjects also had less day-to-day stability in the phase of their rhythms following surgery. These results suggest that the intervention reduced circadian disruption following surgery and provides a way for patients to prepare themselves to resist rhythm changes.
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Kubištová, Aneta, Veronika Spišská, Lucie Petrželková, Leona Hrubcová, Simona Moravcová, Lenka Maierová, and Zdeňka Bendová. "Constant Light in Critical Postnatal Days Affects Circadian Rhythms in Locomotion and Gene Expression in the Suprachiasmatic Nucleus, Retina, and Pineal Gland Later in Life." Biomedicines 8, no. 12 (December 7, 2020): 579. http://dx.doi.org/10.3390/biomedicines8120579.
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The circadian clock regulates bodily rhythms by time cues that result from the integration of genetically encoded endogenous rhythms with external cycles, most potently with the light/dark cycle. Chronic exposure to constant light in adulthood disrupts circadian system function and can induce behavioral and physiological arrhythmicity with potential clinical consequences. Since the developing nervous system is particularly vulnerable to experiences during the critical period, we hypothesized that early-life circadian disruption would negatively impact the development of the circadian clock and its adult function. Newborn rats were subjected to a constant light of 16 lux from the day of birth through until postnatal day 20, and then they were housed in conditions of L12 h (16 lux): D12 h (darkness). The circadian period was measured by locomotor activity rhythm at postnatal day 60, and the rhythmic expressions of clock genes and tissue-specific genes were detected in the suprachiasmatic nuclei, retinas, and pineal glands at postnatal days 30 and 90. Our data show that early postnatal exposure to constant light leads to a prolonged endogenous period of locomotor activity rhythm and affects the rhythmic gene expression in all studied brain structures later in life.
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McGoogan, Jennifer M., and Vincent M. Cassone. "Circadian regulation of chick electroretinogram: effects of pinealectomy and exogenous melatonin." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 277, no. 5 (November 1, 1999): R1418—R1427. http://dx.doi.org/10.1152/ajpregu.1999.277.5.r1418.
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Melatonin is an important component of the avian circadian system. This study investigates the effects of pinealectomy (Pin-X) and melatonin implantation (Mel) on electroretinogram (ERG) rhythms in chicks. Feeding rhythms were monitored to obtain a phase reference for ERG recordings. Pin-X and Mel had little or no effect on feeding rhythms. Sham-operated Pin-X and vehicle implantation had no effect on ERG rhythms in the light-dark (LD) cycle or constant darkness (DD). ERG a- and b-wave amplitudes were higher during the day than during the night. The a- and b-wave implicit times were shorter during the day than during the night. a-Wave sensitivity was higher during the night than during the day, whereas b-wave sensitivity was not rhythmic. Pin-X abolished the circadian rhythm of b-wave amplitude and implicit time in DD but had no effect on a-wave rhythmicity. Mel abolished the rhythm of b-wave amplitude and of a- and b-wave implicit time in DD. Neither treatment affected ERG in LD. These results suggest that the circadian system regulates rhythmic visual function in the retina at least partially through Mel. The role played by the pineal gland and Mel may be specific to some physiological modalities (e.g., vision) while not influencing others (e.g., feeding).
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Dosseville, Fabrice, Sebastien Moussay, Jacques Larue, Antoine Gauthier, and Damien Davenne. "Physical Exercise and Time of Day: Influences on Spontaneous Motor Tempo." Perceptual and Motor Skills 95, no. 3 (December 2002): 965–72. http://dx.doi.org/10.1177/003151250209500301.
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To identify whether spontaneous motor rhythm is influenced by external or internal events and whether this rhythm fluctuates across the day in parallel with heart rate diurnal variations, we simultaneously recorded heart rate and spontaneous motor rate before and after a pedaling task performed five times a day by 10 healthy human subjects. Each subject performed a Spontaneous Motor Tempo, i.e., a finger-tapping task, at a comfortable and spontaneous cadence. Pre- and postexercise Spontaneous Motor Tempo was measured as well as heart rate. There were diurnal variations in Spontaneous Motor Tempo. Both measures increased significantly after pedaling, suggesting that cardiac and spontaneous rhythms are influenced simultaneously after a moderate exercise. Also, finger-taps occurred most frequently around the initiation of the heart systole. These results suggest that a putative internal clock might regulate Spontaneous Motor Tempo and that cardiac rhythm might influence this tempo
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Keeney, Hillary, and Bradford Keeney. "The Rhythm Detox: A shaking body reset and fascinating rhythm infusion." Dance, Movement & Spiritualities 7, no. 1-2 (November 1, 2020): 7–16. http://dx.doi.org/10.1386/dmas_00012_1.
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Rhythm not only connects the notes of a song into pleasing melody, it also organizes much of our everyday experience. Everything has an underlying rhythm including speech, thoughts and how bodies move through space. When people feel stuck, lifeless or in need of a creative inspirational reset, we propose paying more attention to the rhythms organizing their somatic expression rather than only attending to inner psychological states. This can be done through what we call a ‘Rhythm Detox’, a brief two-step movement practice. Step one begins with a simple body shake performed without listening to any percussion. Step two involves playing a recording of any lively, syncopated rhythms and enacting a unique means of catching the surprising changes and off beats. This experimental means of resourcefully interrupting, shaking up and reinvigorating the rhythms organizing your daily movement habits can be done alone or with others and as often as needed throughout the day.
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DOYLE, SUSAN E., MICHAEL S. GRACE, WILSON McIVOR, and MICHAEL MENAKER. "Circadian rhythms of dopamine in mouse retina: The role of melatonin." Visual Neuroscience 19, no. 5 (September 2002): 593–601. http://dx.doi.org/10.1017/s0952523802195058.
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Both dopamine and melatonin are important for the regulation of retinal rhythmicity, and substantial evidence suggests that these two substances are mutually inhibitory factors that act as chemical analogs of day and night. A circadian oscillator in the mammalian retina regulates melatonin synthesis. Here we show a circadian rhythm of retinal dopamine content in the mouse retina, and examine the role of melatonin in its control. Using high-performance liquid chromatography (HPLC), we measured levels of dopamine and its two major metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), in retinas of C3H+/+ mice (which make melatonin) and C57BL/6J mice that are genetically incapable of melatonin synthesis. In a light/dark cycle both strains of mice exhibited daily rhythms of retinal dopamine, DOPAC, and HVA content. However, after 10 days in constant darkness (DD), a circadian rhythm in dopamine levels was present in C3H, but not in C57 mice. C57 mice given ten daily injections of melatonin in DD exhibited a robust circadian rhythm of retinal dopamine content whereas no such rhythm was present in saline-injected controls. Our results demonstrate that (1) a circadian clock generates rhythms of dopamine content in the C3H mouse retina, (2) mice lacking melatonin also lack circadian rhythms of dopamine content, and (3) dopamine rhythms can be generated in these mice by cyclic administration of exogenous melatonin. Our results also indicate that circadian rhythms of retinal dopamine depend upon the rhythmic presence of melatonin, but that cyclic light can drive dopamine rhythms in the absence of melatonin.
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Xia, Canwei, and Yanyun Zhang. "Lack of daily heart rate rhythms in Adélie penguin chicks during the polar day." Polar Record 55, no. 6 (November 2019): 411–16. http://dx.doi.org/10.1017/s0032247420000017.
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AbstractDaily rhythms enable organisms to adapt to daily fluctuations in environmental factors. Do organisms still exhibit 24-h rhythms when living in habitats without obvious daily cycles in external signals? To answer this question, we measured the heart rates of six Adélie penguin (Pygoscelis adeliae) chicks on Inexpressible Island during the polar day between 15 and 21 January 2019. Averaged heart rates were between 186 and 233 beats/min for individual chicks. Both fast Fourier transformation and autocorrelation were employed to assess the daily rhythmicity. Based on fast Fourier transformation, a significant contribution of daily rhythm in heart rate variation was found only in one individual. Small effect size of significant autocorrelation coefficients was found in two individuals, while there was no significant autocorrelation coefficient for 24-h time lag in four other individuals. In summary, no prevailing daily rhythm of heart rate was found in these Adélie penguin chicks. We propose that the lack of daily rhythm in Adélie penguin chicks could be an adaptation to the local environment in the polar regions, but that the adaptive value thereof remains to be investigated.
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Huffeldt, Nicholas Per, and Flemming R. Merkel. "Sex-specific, inverted rhythms of breeding-site attendance in an Arctic seabird." Biology Letters 12, no. 9 (September 2016): 20160289. http://dx.doi.org/10.1098/rsbl.2016.0289.
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In contrast to daily rhythms that are common in the presence of the geophysical light–dark cycle, organisms at polar latitudes exhibit many diel activity patterns during natural periods of continuous solar light or darkness (polar day and night, respectively), from 24 h rhythms to arrhythmicity. In Arctic Greenland (73.7° N, 56.6° W) during polar day, we observed breeding-site attendance rhythms of thick-billed murres ( Uria lomvia ; n = 21 pairs), a charadriiform seabird, which provide biparental care at the colony. We found that U. lomvia egg-incubation and chick-brooding attendance is rhythmic and synchronized to the geophysical day (mean period length [rhythm duration] ± 95% confidence interval = 24.13 ± 0.52 h). Individual pair members had temporally segregated, sex-specific colony-attendance rhythms that were opposite (inverted) to each other, and these sex-specific rhythms were prominent at the population level. Our results provide a basis for investigating circadian systems at polar latitudes and sex-specific parental-care strategies.
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Cambras, T., M. M. Canal, A. Torres, J. Vilaplana, and A. Diez-Noguera. "Manifestation of circadian rhythm under constant light depends on lighting conditions during lactation." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 272, no. 4 (April 1, 1997): R1039—R1046. http://dx.doi.org/10.1152/ajpregu.1997.272.4.r1039.
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Adult rats transferred to continuous illumination (LL) show a disruption of circadian rhythms, although the mechanisms underlying this effect are not yet well known. In previous experiments, we found that when rats were born and raised under LL they showed an ultradian pattern during the first 10 days after weaning, but afterward they generated a circadian rhythm that was maintained until adulthood. It was not clear whether this evolution was attributable to the influence of the rhythm of the mother or to the effect of constant light. Here, we have studied the motor activity rhythm of young rats maintained under LL after weaning, taking into account the conditions to which they were exposed during lactation [LL or continuous darkness (DD)]. To check the possible effect of the rhythm of the dam, on the day of delivery some of the dams were blinded, others were subjected to a restricted feeding schedule of 3 h/day, and the others were used as controls. For each rat, the period of the circadian rhythm and the percentage of variance explained by this rhythm were calculated. Results show that all rats maintained under LL during lactation expressed a circadian rhythm in their motor activity. However, rats maintained under DD during lactation did not. This effect did not seem to be dependent on the type of dam. These results suggest that the rhythm of the dams does not affect the manifestation of the rhythm of the pups and that the expression of circadian rhythmicity under constant bright light depends on the lighting conditions under which the animals were maintained during lactation, which could affect the development of the circadian pacemaker or the retina.
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Yvert, Blaise, Pascal Branchereau, and Pierre Meyrand. "Multiple Spontaneous Rhythmic Activity Patterns Generated by the Embryonic Mouse Spinal Cord Occur Within a Specific Developmental Time Window." Journal of Neurophysiology 91, no. 5 (May 2004): 2101–9. http://dx.doi.org/10.1152/jn.01095.2003.
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Spontaneous rhythmic activity is a ubiquitous phenomenon in developing neural networks and is assumed to play an important role in the elaboration of mature circuitry. Here we describe the day-by-day evolution of spontaneous activity in the embryonic mouse spinal cord and show that, at a specific developmental stage, 2 distinct rhythms coexist. On embryonic days E12.5 and E13.5, we observed a single type of regularly recurring short spike-episodes synchronized across cervical, thoracic, and lumbar levels. By E14.5, in addition to this motor rhythm, another type of spontaneous synchronous activity appeared, characterized by much longer lasting episodes separated by longer time intervals. On E15.5, these long episodes disappeared. Short episodes were less numerous and more irregular except at the cervical level where a rhythm was occasionally observed. By E16.5, this cervical rhythm became more robust, whereas the lumbar level fell almost silent. Surprisingly, at E17.5, spontaneous activity resumed at caudal levels, now characterized by numerous erratic short episodes. A striking ontogenetic feature of spontaneous activity was the occurrence of long episodes only at E14.5. Although concomitant at all levels of the spinal cord, long episodes displayed different patterns along the spinal cord, with tonic firing at the thoracic level and rhythmic discharge with occasional sequences of left/right alternation at the lumbar level. Thus at E14.5, the originally synchronized network has started to segregate into more specialized subnetworks. In conclusion, this work suggests that ongoing spontaneous rhythms do not follow a smooth evolution during maturation, but rather undergo profound changes at very specific stages.
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Bailey, Michael J., Phillip D. Beremand, Rick Hammer, Deborah Bell-Pedersen, Terry L. Thomas, and Vincent M. Cassone. "Transcriptional Profiling of the Chick Pineal Gland, a Photoreceptive Circadian Oscillator and Pacemaker." Molecular Endocrinology 17, no. 10 (October 1, 2003): 2084–95. http://dx.doi.org/10.1210/me.2003-0121.
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Abstract The avian pineal gland contains both circadian oscillators and photoreceptors to produce rhythms in biosynthesis of the hormone melatonin in vivo and in vitro. The molecular mechanisms for melatonin biosynthesis are largely understood, but the mechanisms driving the rhythm itself or the photoreceptive processes that entrain the rhythm are unknown. We have produced cDNA microarrays of pineal gland transcripts under light-dark and constant darkness conditions. Rhythmic transcripts were classified according to function, representing diverse functional groups, including phototransduction pathways, transcription/translation factors, ion channel proteins, cell signaling molecules, and immune function genes. These were also organized relative to time of day mRNA abundance in light-dark and constant darkness. The transcriptional profile of the chick pineal gland reveals a more complex form of gene regulation than one might expect from a gland whose sole apparent function is the rhythmic biosynthesis of melatonin. The mRNAs encoding melatonin biosynthesis are rhythmic as are many orthologs of mammalian “clock genes.” However, the oscillation of phototransductive, immune, stress response, hormone binding, and other important processes in the transcriptome of the pineal gland, raises new questions regarding the role of the pineal gland in circadian rhythm generation, organization, and avian physiology.
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de Goede, Paul, Satish Sen, Yan Su, Ewout Foppen, Vincent-Joseph Poirel, Etienne Challet, and Andries Kalsbeek. "An Ultradian Feeding Schedule in Rats Affects Metabolic Gene Expression in Liver, Brown Adipose Tissue and Skeletal Muscle with Only Mild Effects on Circadian Clocks." International Journal of Molecular Sciences 19, no. 10 (October 15, 2018): 3171. http://dx.doi.org/10.3390/ijms19103171.
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Restricted feeding is well known to affect expression profiles of both clock and metabolic genes. However, it is unknown whether these changes in metabolic gene expression result from changes in the molecular clock or in feeding behavior. Here we eliminated the daily rhythm in feeding behavior by providing 6 meals evenly distributed over the light/dark-cycle. Animals on this 6-meals-a-day feeding schedule retained the normal day/night difference in physiological parameters including body temperature and locomotor activity. The daily rhythm in respiratory exchange ratio (RER), however, was significantly phase-shifted through increased utilization of carbohydrates during the light phase and increased lipid oxidation during the dark phase. This 6-meals-a-day feeding schedule did not have a major impact on the clock gene expression rhythms in the master clock, but did have mild effects on peripheral clocks. In contrast, genes involved in glucose and lipid metabolism showed differential expression. In conclusion, eliminating the daily rhythm in feeding behavior in rats does not affect the master clock and only mildly affects peripheral clocks, but disturbs metabolic rhythms in liver, skeletal muscle and brown adipose tissue in a tissue-dependent manner. Thereby, a clear daily rhythm in feeding behavior strongly regulates timing of peripheral metabolism, separately from circadian clocks.
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Paragliola, Rosa Maria, Andrea Corsello, Eliana Troiani, Pietro Locantore, Giampaolo Papi, Giulia Donnini, Alfredo Pontecorvi, Salvatore Maria Corsello, and Cinzia Carrozza. "Cortisol circadian rhythm and jet-lag syndrome: evaluation of salivary cortisol rhythm in a group of eastward travelers." Endocrine 73, no. 2 (February 4, 2021): 424–30. http://dx.doi.org/10.1007/s12020-021-02621-4.
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Abstract Purpose The activity of the hypothalamus–pituitary–adrenal axis plays a crucial role as an endogenous stress-reactive system. Lifestyle and work often interfere with the endogenous circadian rhythms and can modify the physiological patterns of stress-hormones secretion, including cortisol. We evaluated the cortisol circadian rhythm in the “jet-lag syndrome” that is the most known condition associated with the desynchronization of the circadian rhythm. Methods To assess the modifications of cortisol secretion after a long-haul flight, we compared baseline and post-travel salivary cortisol rhythm in a group of 28 healthy eastward travelers (from the U.S.A. or Canada to Italy). The salivary samples were collected about 1 week before the departure at 11 p.m. on day 0 and at 8 a.m., 12 a.m. (midday) and 11 p.m. on day 1 (R0). The same samples were obtained after the landing, the day they flew back home (R1). Results Statistical analysis showed a significant difference between R0 and R1 for each sample considered (p < 0.005). In particular, the post-travel salivary cortisol levels detected at 11 p.m. both on day 0 and on day 1, were significantly higher than at baseline. Post-travel morning salivary cortisol levels were lower compared with basal rhythm and increased during the morning, reaching the acrophase at 12 a.m. Conclusions In eastward travelers, crossing more than five time zones, the cortisol circadian rhythm after the return to the East “remained behind,” being synchronized with the West time. This impaired cortisol secretion can contribute to the pathogenesis of the jet-lag syndrome.
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Bashkireva, Tatiana, Anastasia Bashkireva, Sergey Chibisov, Alexander Severin, Alexander Morozov, and Nadezhda Fateeva. "Assessment of driver biorhythms as a factor of labor safety." E3S Web of Conferences 164 (2020): 03029. http://dx.doi.org/10.1051/e3sconf/202016403029.
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The paper provides a biorhythmological assessment of the health of a driver’s team in conditions of joint activity in terms of heart rate variability. Measurements were taken during the working day using Holter monitoring in AnnaFlash2000 software and statistical processing ISCIM6. The cardiogram of the heart was recorded during the working day from 8.00 to 18.00 hours. It was revealed that the rhythmic processes of acrophase and heart rate bathyphase, which testify to the leading role of hypoxia, hypercapnia and desynchronosis of ultradian rhythms, influence the joint professional activity of drillers. The examined drivers found a violation of the synchronization of biological rhythms and desynchronosis at various levels of regulation of heart rhythm regulation. Both drivers, working in different biological rhythms, have a low degree of compatibility and belong to the group of production risk, which negatively affects occupational safety.
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SPIES, CORNELIA M., MAURIZIO CUTOLO, RAINER H. STRAUB, GERD-RÜDIGER BURMESTER, and FRANK BUTTGEREIT. "More Night Than Day — Circadian Rhythms in Polymyalgia Rheumatica and Ankylosing Spondylitis." Journal of Rheumatology 37, no. 5 (April 1, 2010): 894–99. http://dx.doi.org/10.3899/jrheum.091283.
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The circadian rhythm of symptoms in patients with chronic inflammatory diseases is well known. Circadian rhythms could be used to identify targets for time-adapted antiinflammatory therapies, which are administered prior to the flare of cytokine synthesis and inflammatory activity. In recent years, the diurnal variations in rheumatoid arthritis have been described precisely for pain, stiffness, and functional disability, as well as the underlying cyclic variations in hormone levels and cytokine concentrations. This review summarizes the current knowledge on circadian rhythms in other rheumatic diseases, focusing on polymyalgia rheumatica and ankylosing spondylitis.
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Durgan, David J., Randy F. Crossland, and Robert M. Bryan. "The rat cerebral vasculature exhibits time-of-day-dependent oscillations in circadian clock genes and vascular function that are attenuated following obstructive sleep apnea." Journal of Cerebral Blood Flow & Metabolism 37, no. 8 (January 1, 2016): 2806–19. http://dx.doi.org/10.1177/0271678x16675879.
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Circadian clock components oscillate in cells of the cardiovascular system. Disruption of these oscillations has been observed in cardiovascular diseases. We hypothesized that obstructive sleep apnea, which is associated with cerebrovascular diseases, disrupts the cerebrovascular circadian clock and rhythms in vascular function. Apneas were produced in rats during sleep. Following two weeks of sham or obstructive sleep apnea, cerebral arteries were isolated over 24 h for mRNA and functional analysis. mRNA expression of clock genes exhibited 24-h rhythms in cerebral arteries of sham rats (p < 0.05). Interestingly, peak expression of clock genes was significantly lower following obstructive sleep apnea (p < 0.05). Obstructive sleep apnea did not alter clock genes in the heart, or rhythms in locomotor activity. Isolated posterior cerebral arteries from sham rats exhibited a diurnal rhythm in sensitivity to luminally applied ATP, being most responsive at the beginning of the active phase (p < 0.05). This rhythm was absent in arteries from obstructive sleep apnea rats (p < 0.05). Rhythms in ATP sensitivity in sham vessels were absent, and not different from obstructive sleep apnea, following treatment with L-NAME and indomethacin. We conclude that cerebral arteries possess a functional circadian clock and exhibit a diurnal rhythm in vasoreactivity to ATP. Obstructive sleep apnea attenuates these rhythms in cerebral arteries, potentially contributing to obstructive sleep apnea-associated cerebrovascular disease.
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Abelló, P., D. G. Reid, and E. Naylor. "Comparative locomotor activity patterns in the portunid crabs Liocarcinus holsatus and L. depurator." Journal of the Marine Biological Association of the United Kingdom 71, no. 1 (February 1991): 1–10. http://dx.doi.org/10.1017/s0025315400037346.
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The free-running locomotor activity rhythms of freshly-captured swimming crabs Liocarcinus holsatus and L. depurator have been studied in constant conditions in the laboratory. L. holsatus captured in the intertidal zone of sandy beaches showed strong circatidal activity rhythms with maximum activity at high tide. L. holsatus captured in the sublittoral zone had a clear tendency to show circadian activity rhythms with highest activity during day-time hours. L. depurator occurred only sublittorally and showed circadian activity patterns with highest activity during the night. Exposure to hydrostatic pressure cycles of tidal amplitude and periodicity, entrained strong circatidal activity rhythms in previously arhythmic L. holsatus. This activity pattern also showed a marked circadian component. Exposure to the same regime entrained a circadian rhythm, but not a circatidal rhythm in L. depurator. In the sublittoral zone L. depurator is active mainly during the night, whereas L. holsatus, is active mainly during the day. This may constitute a behavioural mechanism for minimizing competitive interactions between these two sympatric crabs.
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Monteferrante, Gabriela Aprigia, Maysa Mariana Cruz, Guilherme Mogadouro, Victoria de Oliveira Fantini, Patrícia Oliveira Castro, Patricia Anne Halpin, and Camilo Lellis-Santos. "Cardiac rhythm dance protocol: a smartphone-assisted, hands-on activity to introduce concepts of cardiovascular physiology and scientific methodology." Advances in Physiology Education 42, no. 3 (September 1, 2018): 516–20. http://dx.doi.org/10.1152/advan.00028.2017.
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Physiology teaching resources have advanced to include innovative pedagogical approaches that meet the learning expectations of the current generation of students, while at the same time ensuring content delivery is accurate and the use of technologies is appropriate. We developed a quick experimental assay protocol to introduce the basic concepts of cardiac rhythms, and to demonstrate simultaneously that smartphone applications are a reliable and cost-effective tool for data collection in teaching the scientific method and performing physiology activities. The cardiac rhythm dance (CRD) protocol engages students in dancing a cardiac cyclelike movement to the rhythm of classical, pop, and samba music, and measuring their own cardiac frequency. Students collected their own data using the app Instant Heart Rate (Azumio). The CRD protocol allowed students to conclude that cardiac cycle-like movements paced by a pop song could represent the normal cardiac rhythm, whereas a classical song induced a significant reduction of heart rate, and the samba song significantly increased heart rate compared with the pop song. After group discussion, students considered that the pop rhythm is more realistic of day-by-day movement rhythms and is equivalent to the steady state of daily cardiac rhythms. Students considered the bradycardic and tachycardic movements to the dancing performed to the classical and samba rhythms, respectively. Thus the CRD protocol provides a multiple sensory-based and active learning resource that can engage students in learning cardiovascular physiology and recognizes smartphones as scientific instruments for collecting data during hands-on activities.
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Jin, Shichao, Yanjun Su, Yongguang Zhang, Shilin Song, Qing Li, Zhonghua Liu, Qin Ma, et al. "Exploring Seasonal and Circadian Rhythms in Structural Traits of Field Maize from LiDAR Time Series." Plant Phenomics 2021 (September 6, 2021): 1–15. http://dx.doi.org/10.34133/2021/9895241.
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Plant growth rhythm in structural traits is important for better understanding plant response to the ever-changing environment. Terrestrial laser scanning (TLS) is a well-suited tool to study structural rhythm under field conditions. Recent studies have used TLS to describe the structural rhythm of trees, but no consistent patterns have been drawn. Meanwhile, whether TLS can capture structural rhythm in crops is unclear. Here, we aim to explore the seasonal and circadian rhythms in maize structural traits at both the plant and leaf levels from time-series TLS. The seasonal rhythm was studied using TLS data collected at four key growth periods, including jointing, bell-mouthed, heading, and maturity periods. Circadian rhythms were explored by using TLS data acquired around every 2 hours in a whole day under standard and cold stress conditions. Results showed that TLS can quantify the seasonal and circadian rhythm in structural traits at both plant and leaf levels. (1) Leaf inclination angle decreased significantly between the jointing stage and bell-mouthed stage. Leaf azimuth was stable after the jointing stage. (2) Some individual-level structural rhythms (e.g., azimuth and projected leaf area/PLA) were consistent with leaf-level structural rhythms. (3) The circadian rhythms of some traits (e.g., PLA) were not consistent under standard and cold stress conditions. (4) Environmental factors showed better correlations with leaf traits under cold stress than standard conditions. Temperature was the most important factor that significantly correlated with all leaf traits except leaf azimuth. This study highlights the potential of time-series TLS in studying outdoor agricultural chronobiology.
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Cella, L. K., E. Van Cauter, and D. A. Schoeller. "Diurnal rhythmicity of human cholesterol synthesis: normal pattern and adaptation to simulated "jet lag"." American Journal of Physiology-Endocrinology and Metabolism 269, no. 3 (September 1, 1995): E489—E498. http://dx.doi.org/10.1152/ajpendo.1995.269.3.e489.
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The diurnal rhythm of cholesterol synthesis was determined by deuterium incorporation from body water in five normolipemic men studied during a 24-h baseline period and on the 1st, 2nd, and 4th days of a simulated 12-h time zone shift achieved by delaying sleep times and, starting on the 2nd day, meal-times. Profiles of plasma cortisol and thyrotropin (TSH) were obtained simultaneously. Under baseline conditions, cholesterol synthetic rates varied from essentially zero in the morning to maximal values around midnight. On the 1st shifted day, this diurnal variation was unaltered despite sleep-wake reversal. The diurnal pattern of cholesterol synthesis, however, was shifted 5 h on the 2nd shifted day and approximately 12 h on the 4th. The diurnal variation of synthetic rate cholesterol fractional synthesis and plasma cortisol levels was negatively correlated on both the baseline day and the 1st shifted day. A positive correlation with the TSH rhythm was found on the 1st day only. During the 2nd and 4th days, the rhythm of cholesterol synthesis adapted faster than the rhythms of cortisol and TSH. These findings indicate that cholesterol synthesis is not acutely entrained by the sleep-wake cycle nor is it primarily entrained by the circadian clock.
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Shiraishi, Masashi, Takumi Odan, Osamu Yamanaka, and Hiraku Nishimori. "Influence of Labor Conditions and Interaction Among Individuals on Circadian Activity Rhythms in the Ant Camponotus Japonicus." Journal of Robotics and Mechatronics 33, no. 3 (June 20, 2021): 582–89. http://dx.doi.org/10.20965/jrm.2021.p0582.
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In this study, we investigated the relationship between the activity rhythms of Camponotus japonicus worker ants and their interactions. Specifically, one or two workers collected from either inside or outside the nest in a breeding colony were placed in a measurement system under a constant dark condition, and their activity rhythms were measured for 14 days. We thereby examined the relationship between the activity rhythm in the system and the experimental conditions, which consisted of four different combinations of working locations during breeding (in/outside the nest) and single/double workers (one ant / two ants) in the measurement system, over a total of 96 samples. A large number of the sampled ants (about 90% of the total) showed circadian activity rhythms. The proportion of circadian activity rhythm was lower and the dispersion of the period was larger in the circadian activity rhythm observed in single workers collected from within the nest than in the other three experimental conditions. In all four experimental conditions, the amplitude of the circadian activity rhythm decayed on an approximate 5-day scale. These results provide quantitative evidence that the activity rhythm of ants is determined by the location of labor and individual interactions during breeding.
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Brynychová, Kateřina, Miroslav E. Šálek, Eva Vozabulová, and Martin Sládeček. "Daily Rhythms of Female Self-maintenance Correlate with Predation Risk and Male Nest Attendance in a Biparental Wader." Journal of Biological Rhythms 35, no. 5 (July 17, 2020): 489–500. http://dx.doi.org/10.1177/0748730420940465.
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Parents make tradeoffs between care for offspring and themselves. Such a tradeoff should be reduced in biparental species, when both parents provide parental care. However, in some biparental species, the contribution of one sex varies greatly over time or between pairs. How this variation in parental care influences self-maintenance rhythms is often unclear. In this study, we used continuous video recording to investigate the daily rhythms of sleep and feather preening in incubating females of the Northern Lapwing ( Vanellus vanellus), a wader with a highly variable male contribution to incubation. We found that the female’s sleep frequency peaked after sunrise and before sunset but was low in the middle of the day and especially during the night. In contrast, preening frequency followed a 24-h rhythm and peaked in the middle of the day. Taken together, incubating females rarely slept or preened during the night, when the predation pressure was highest. Moreover, the sleeping and preening rhythms were modulated by the male contribution to incubation. Females that were paired with more contributing males showed a stronger sleep rhythm but also a weaker preening rhythm. If more incubating males also invest more in nest guarding and deterring daylight predators, their females may afford more sleep on the nest during the day and preen more when they are off the nest. Whether the lack of sleep in females paired with less caregiving males has fitness consequences awaits future investigation.
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Weibel, L., K. Spiegel, C. Gronfier, M. Follenius, and G. Brandenberger. "Twenty-four-hour melatonin and core body temperature rhythms: their adaptation in night workers." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 272, no. 3 (March 1, 1997): R948—R954. http://dx.doi.org/10.1152/ajpregu.1997.272.3.r948.
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To determine whether the melatonin (MT) rhythm is adapted to a permanent nocturnal schedule, 11 night workers were studied during their usual 24-h cycle, and 8 day-active subjects during two 24-h cycles, once with night sleep and once after an acute shift of their sleep period to daytime. Rectal temperature (Tre) was continuously recorded. In day-active subjects, the MT rhythm was not affected by the acute shift in the sleep period, whereas the Tre rhythm was split in a biphasic pattern with the circadian descending phase during the night of sleep deprivation and a second descending trend during day sleep. Night workers showed a great variability in their MT profiles, with the onset of the MT release varying between 2145 and 0505. In contrast, the Tre rhythm was homogeneously entrained to their usual sleep-wake cycle, with the onset of the descending trend initiated before sleep onset so that the large decrease was found, in some subjects, to be uncoupled with their MT increase. The night-active schedule did not induce any amplitude modification of the Tre and the rhythms compared with day-active subjects sleeping at night. No relationship between work-dependent factors and the extent of the MT shift could be found. These results show the great variability in the timing of MT secretion among night workers, in contrast to the homogeneity of their Tre rhythm. The exact mechanisms by which night workers adapt their circadian systems have not yet been identified.
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Satoh, Yoko, Hiroshi Kawai, Naomi Kudo, Yoichi Kawashima, and Atsushi Mitsumoto. "Time-restricted feeding entrains daily rhythms of energy metabolism in mice." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 290, no. 5 (May 2006): R1276—R1283. http://dx.doi.org/10.1152/ajpregu.00775.2005.
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Energy metabolism, oxygen consumption rate (V̇o2), and respiratory quotient (RQ) in mice were monitored continuously throughout 12:12-h light-dark cycles before, during, and after time-restricted feeding (RF). Mice fed ad libitum showed robust daily rhythms in both parameters: high during the dark phase and low during the light phase. The daily profile of energy metabolism in mice under daytime-only feeding was reversed at the beginning of the first fasting night. A few days after daytime-only feeding began, RF also reversed the circadian core body temperature rhythm. Moreover, RF for 6 consecutive days shifted the phases of circadian expression patterns of clock genes in liver significantly by 8–10 h. When mice were fed a high-fat (HF) diet ad libitum, the daily rhythm of RQ dampened day by day and disappeared on the sixth day of RF, whereas V̇o2 showed a robust daily rhythm. Mice fed HF only in the daytime had reversed V̇o2 and RQ rhythms. Similarly, mice fed HF only in the daytime significantly phase shifted the clock gene expression in liver, whereas ad libitum feeding with HF had no significant effect on the expression phases of liver clock genes. These results suggested that V̇o2 is a sensitive indicator of entrainment in the mouse liver. Moreover, physiologically, it can be determined without any surgery or constraint. On the basis of these results, we hypothesize that a change in the daily V̇o2 rhythm, independent of the energy source, might drive phase shifts of circadian oscillators in peripheral tissues, at least in the liver.
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Yang, Shutong, Aiyi Liu, Adam Weidenhammer, Robert C. Cooksey, Donald McClain, Myung K. Kim, Greti Aguilera, E. Dale Abel, and Jay H. Chung. "The Role of mPer2 Clock Gene in Glucocorticoid and Feeding Rhythms." Endocrinology 150, no. 5 (January 29, 2009): 2153–60. http://dx.doi.org/10.1210/en.2008-0705.
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The circadian clock synchronizes the activity level of an organism to the light-dark cycle of the environment. Energy intake, as well as energy metabolism, also has a diurnal rhythm. Although the role of the clock genes in the sleep-wake cycle is well characterized, their role in the generation of the metabolic rhythms is poorly understood. Here, we use mice deficient in the clock protein mPer2 to study how the circadian clock regulates two critical metabolic rhythms: glucocorticoid and food intake rhythms. Our findings indicate that mPer2−/− mice do not have a glucocorticoid rhythm even though the corticosterone response to hypoglycemia, ACTH, and restraint stress is intact. In addition, the diurnal feeding rhythm is absent in mPer2−/− mice. On high-fat diet, they eat as much during the light period as they do during the dark period and develop significant obesity. The diurnal rhythm of neuroendocrine peptide αMSH, a major effector of appetite control, is disrupted in the hypothalamus of mPer2−/− mice even though the diurnal rhythm of ACTH, the αMSH precursor, is intact. Peripheral injection of αMSH, which has been shown to enter the brain, restored the feeding rhythm and induced weight loss in mPer2−/− mice. These findings emphasize the requirement of mPer2 in appetite control during the inactive period and the potential role of peripherally administered αMSH in restoring night-day eating pattern in individuals with circadian eating disorders such as night-eating syndrome, which is also associated with obesity.
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Honma, K., S. Honma, M. Kohsaka, and N. Fukuda. "Seasonal variation in the human circadian rhythm: dissociation between sleep and temperature rhythm." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 262, no. 5 (May 1, 1992): R885—R891. http://dx.doi.org/10.1152/ajpregu.1992.262.5.r885.
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The circadian rhythms of sleep-wakefulness, rectal temperature, and plasma melatonin were measured in 10 healthy male subjects for five consecutive seasons. To minimize direct effects of seasonally changing environmental factors, the subjects stayed in a living facility for 4 days in each season, where ambient temperature, humidity, and social contacts were controlled, while the light intensity of the living room was substantially influenced by natural daylight. Seasonal variations were found in the timing of sleep, the mean body temperature, the phases of circadian temperature and melatonin rhythms, and the phase relation between sleep and the rectal temperature rhythm. The subjects went to bed earliest in summer, intermediate in spring and autumn, and latest in winter. A similar but more pronounced seasonality was observed in the wake-up time, which was earlier in summer than in winter. The acrophases of the rectal temperature and plasma melatonin rhythms, which were calculated by fitting a cosine curve, were located in an earlier time of day in summer than in winter. The phase-angle difference of the rectal temperature rhythm to sleep varied seasonally and was more positive in summer than in winter. These findings indicate that not only the external (to the local time) but also the internal (between circadian rhythms) phase relations of the human circadian rhythms depend on season.
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Cella, L. K., E. Van Cauter, and D. A. Schoeller. "Effect of meal timing on diurnal rhythm of human cholesterol synthesis." American Journal of Physiology-Endocrinology and Metabolism 269, no. 5 (November 1, 1995): E878—E883. http://dx.doi.org/10.1152/ajpendo.1995.269.5.e878.
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To test whether the diurnal rhythm of cholesterol synthesis in humans is entrained to meal timing, the effect of a 6.5-h delay of mealtimes was investigated in four normal lipidemic male subjects. Cholesterol fractional synthetic rate was measured by deuterium incorporation from body water using blood sampling every 2 h. The baseline was a 24-h control period in which three Western-style meals were consumed at 0700, 1150, and 1640, followed by 3 days in which meals were delayed by 6.5 h, i.e., meals consumed at 1330, 1820, and 2310 without changing the sleep-wake and light-dark cycles. Cholesterol synthesis was maximal at 2200 +/- 0200 and minimal at 1130 +/- 0050 on the baseline day. On day 1 of the shifted meals, the maximum was delayed 6.0 +/- 0.5 h and the nadir was not changed. On day 3, the maximum was delayed 8.6 +/- 3.7 h and the minimum was delayed 6.5 +/- 2.4 h from baseline. The mean amplitude of the cholesterol rhythm was significantly greater on day 3,233 +/- 35%, compared with baseline which was 109 +/- 15%. A strong negative correlation (r = -0.66 +/- 0.10) was found between the rhythms of cholesterol synthesis and cortisol during the baseline day, but there was a phase delay in the rhythm of cholesterol synthesis relative to cortisol on day 1 and day 3. Findings indicate that the 24-h variation in cholesterol synthesis is strongly dependent on meal timing.
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Johnston, Jonathan D., and Debra J. Skene. "60 YEARS OF NEUROENDOCRINOLOGY: Regulation of mammalian neuroendocrine physiology and rhythms by melatonin." Journal of Endocrinology 226, no. 2 (June 22, 2015): T187—T198. http://dx.doi.org/10.1530/joe-15-0119.
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The isolation of melatonin was first reported in 1958. Since the demonstration that pineal melatonin synthesis reflects both daily and seasonal time, melatonin has become a key element of chronobiology research. In mammals, pineal melatonin is essential for transducing day-length information into seasonal physiological responses. Due to its lipophilic nature, melatonin is able to cross the placenta and is believed to regulate multiple aspects of perinatal physiology. The endogenous daily melatonin rhythm is also likely to play a role in the maintenance of synchrony between circadian clocks throughout the adult body. Pharmacological doses of melatonin are effective in resetting circadian rhythms if taken at an appropriate time of day, and can acutely regulate factors such as body temperature and alertness, especially when taken during the day. Despite the extensive literature on melatonin physiology, some key questions remain unanswered. In particular, the amplitude of melatonin rhythms has been recently associated with diseases such as type 2 diabetes mellitus but understanding of the physiological significance of melatonin rhythm amplitude remains poorly understood.
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Lakin-Thomas, Patricia L., Gooch Van D., and Mark Ramsdale. "Rhythms of differentiation and diacylglycerol in Neurospora." Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences 356, no. 1415 (November 29, 2001): 1711–15. http://dx.doi.org/10.1098/rstb.2001.0966.
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Although the fungus Neurospora crassa is a relatively simple lower eukaryote, its circadian system may be more complex than previously thought. In this paper we review evidence suggesting that there may be several output pathways coupled in complex ways to a single oscillator, or that there may be more than one oscillator driving independent output pathways. We have described two new rhythms in Neurospora that are not tightly coupled to the rhythm of conidiation bands that is the standard assay for the state of the Neurospora circadian clock. The first is a rhythm in the timing of differentiation, i.e. the production of aerial hyphae and spores. Large regions of the mycelium differentiate synchronously, as if responding to a spatially widespread signal. This rhythm may be distinct from the timer that sets the determination switch controlling the spatial pattern of conidiation bands. The second new rhythm is an oscillation in the levels of the neutral lipid diacylglycerol (DAG). This rhythm is found in all regions of a colony and is not always in phase with the rhythm of conidiation bands. The DAG rhythm shares some characteristics with the differentiation rhythm and has the potential to act as the signal that induces rhythmic differentiation.
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Yamanaka, Yujiro, Satoko Hashimoto, Yusuke Tanahashi, Shin-ya Nishide, Sato Honma, and Ken-ichi Honma. "Physical exercise accelerates reentrainment of human sleep-wake cycle but not of plasma melatonin rhythm to 8-h phase-advanced sleep schedule." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 298, no. 3 (March 2010): R681—R691. http://dx.doi.org/10.1152/ajpregu.00345.2009.
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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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Payne, Nicholas L., Dylan E. van der Meulen, Ruan Gannon, Jayson M. Semmens, Iain M. Suthers, Charles A. Gray, and Matthew D. Taylor. "Rain reverses diel activity rhythms in an estuarine teleost." Proceedings of the Royal Society B: Biological Sciences 280, no. 1750 (January 7, 2013): 20122363. http://dx.doi.org/10.1098/rspb.2012.2363.
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Activity rhythms are ubiquitous in nature, and generally synchronized with the day–night cycle. Several taxa have been shown to switch between nocturnal and diurnal activity in response to environmental variability, and these relatively uncommon switches provide a basis for greater understanding of the mechanisms and adaptive significance of circadian (approx. 24 h) rhythms. Plasticity of activity rhythms has been identified in association with a variety of factors, from changes in predation pressure to an altered nutritional or social status. Here, we report a switch in activity rhythm that is associated with rainfall. Outside periods of rain, the estuarine-associated teleost Acanthopagrus australis was most active and in shallower depths during the day, but this activity and depth pattern was reversed in the days following rain, with diurnality restored as estuarine conductivity and turbidity levels returned to pre-rain levels. Although representing the first example of a rain-induced reversal of activity rhythm in an aquatic animal of which we are aware, our results are consistent with established models on the trade-offs between predation risk and foraging efficiency.
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Morera-Fumero, A. L., P. Abreu-Gonzalez, E. Diaz-Mesa, and R. Gracia-Marco. "1177 – Day/night cortisol rhythm in healthy subjects." European Psychiatry 28 (January 2013): 1. http://dx.doi.org/10.1016/s0924-9338(13)76263-1.
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Fisher, C., J. Chen, G. Harris, J. Young, E. Jones, and D. O’Donnell. "Symptom/Rhythm Detection Using 7 Day Event Monitors." Heart, Lung and Circulation 21 (January 2012): S107. http://dx.doi.org/10.1016/j.hlc.2012.05.267.
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Mariani, David, and Alessandro Capitanini. "Clima ambientale e clima emotivo: due pilastri evolutivi poco tangibili ma tremendamente importanti per la nostra vita." Giornale di Clinica Nefrologica e Dialisi 32, no. 1 (February 20, 2020): 11–14. http://dx.doi.org/10.33393/gcnd.2020.1100.
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Our evolutionary history is based on four fundamental pillars: physical activity, nutrition, inner mood and external environment. We live at the rhythm of an inner clock that leads everything we do, the so called circadian rhythm. The circadian system, that is ubiquitous across species, generates ~24 h rhythms in virtually all biological processes, and allows them to anticipate and adapt to the 24 h day/night cycle, thus ensuring optimal physiological function. During the day our organism spends its energy in order to complete catabolic pathways which help us in our relationship with the external environment, while at night anabolic pathways, repairing, strengthening and growth-orientated, prevails. External environment can influence both our circadian rhythm and our body chemistry. Within the last 100 years, environmental conditions are extremely changed: the artificial light (also by televisions screens, smartphones and computers) is lighting up our world 24 hours a day, the background noise is a constant in our everyday life and the air pollution represent risk factors for our health and well-being by causing or facilitating diseases. Also our inner mood, emotions and environment are crucial for human beings’ and planet’s health and for the future of mankind. (healthy_habits)
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Lewy, Hadas, Zvi Naor, and Israel E. Ashkenazi. "Rhythmicity of luteinizing hormone secretion expressed in vitro." European Journal of Endocrinology 135, no. 4 (October 1996): 455–63. http://dx.doi.org/10.1530/eje.0.1350455.
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Lewy H, Naor Z, Ashkenazi IE. Rhythmicity of luteinizing hormone secretion expressed in vitro. Eur J Endocrinol 1996;135:455–63. ISSN 0804–4643 In the present study we explored the possibility that the pituitary functions as an autonomous clock and is capable of generating rhythms of luteinizing hormone (LH) release independently of hypothalamic control. Pituitaries from estrous or diestrous day 1 female mice were perifused separately with Medium-199. Effluent samples were collected at 10-min intervals and assayed for LH levels. Fourier analysis and curve-fit analysis served to elucidate the presence of prominent periods whose significance was then determined by best-fit cosinor. The latter method was used to determine additional parameters for the significant rhythm. All perifused pituitaries exhibited LH release patterns that were composed of significantly long ultradian rhythms (approximately 16 and 8 h, p < 0.001). Continuous stimulation with gonadotropin-releasing hormone (GnRH) or estradiol did not alter the periods of the observed rhythms but affected other rhythm parameters. Gonadotropin-releasing hormone increased the mesor of the rhythm and estradiol increased the amplitude. The results indicate that pituitary gonadotropes are capable of producing rhythms of LH release for a long duration in vitro, in the absence of hypothalamic control. Both GnRH and estradiol affect different rhythm parameters but do not change the periods of these rhythms. Israel E Ashkenazi, Department of Human Genetics, Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
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Resuehr, David, Gang Wu, Russell L. Johnson, Martin E. Young, John B. Hogenesch, and Karen L. Gamble. "Shift Work Disrupts Circadian Regulation of the Transcriptome in Hospital Nurses." Journal of Biological Rhythms 34, no. 2 (February 4, 2019): 167–77. http://dx.doi.org/10.1177/0748730419826694.
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Circadian misalignment between sleep and behavioral/feeding rhythms is thought to lead to various health impairments in shift workers. Therefore, we investigated how shift work leads to genome-wide circadian dysregulation in hospital nurses. Female nurses from the University of Alabama at Birmingham (UAB) Hospital working night shift ( n = 9; 29.6 ± 11.4 y) and day shift ( n = 8; 34.9 ± 9.4 y) participated in a 9-day study measuring locomotor activity and core body temperature (CBT) continuously. Additionally, cortisol and melatonin were assayed and peripheral blood mononuclear cells (PBMCs) were harvested for RNA extraction every 3 h on a day off from work. We saw phase desynchrony of core body temperature, peak cortisol, and dim light melatonin onset in individual night-shift subjects compared with day-shift subjects. This variability was evident even though day- and night-shift nurses had similar sleep timing and scheduled meal times on days off. Surprisingly, the phase and rhythmicity of the expression of the clock gene, PER1, in PBMCs were similar for day-shift and night-shift subjects. Genome-wide microarray analysis of PBMCs from a subset of nurses revealed distinct gene expression patterns between night-shift and day-shift subjects. Enrichment analysis showed that day-shift subjects expressed pathways involved in generic transcription and regulation of signal transduction, whereas night-shift subjects expressed pathways such as RNA polymerase I promoter opening, the matrisome, and endocytosis. In addition, there was large variability in the number of rhythmic transcripts among subjects, regardless of shift type. Interestingly, the amplitude of the CBT rhythm appeared to be more consistent with the number of cycling transcripts for each of the 6 subjects than was melatonin rhythm. In summary, we show that shift-work patterns affect circadian alignment and gene expression in PBMCs.
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Emery, R. J. N., A. Kathiresan, D. M. Reid, and C. C. Chinnappa. "Ecotypic differences in rhythmicity of ethylene production in Stellaria longipes: the possible roles of ACC, MACC, and ACC oxidase." Canadian Journal of Botany 75, no. 7 (July 1, 1997): 1027–33. http://dx.doi.org/10.1139/b97-114.
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The alpine tundra ecotype of Stellaria longipes is characterized by a dwarf phenotype, whereas the prairie ecotype can be semidwarf or highly elongated depending on its environment. Related to their ability to elongate, these ecotypes also show divergent abilities to produce and respond to ethylene. The prairie ecotype produces a strong daily rhythm of ethylene, which is maintained even following stress events such as wind. The alpine ecotype exhibits a much less pronounced rhythm but greatly increases ethylene production in response to stress. We investigated what differences in ethylene synthesis might be responsible for the ability of the prairie ecotype to produce a large and regular daily rhythm of ethylene production, which in the alpine ecotype is weaker or sometimes absent. Levels of the immediate precursor to ethylene, 1-aminocyclopropane-1-carboxylate (ACC), and its major conjugate, malonyl ACC (MACC) showed no rhythm across the course of a day. Moreover ACC levels remained stable during an entire growth cycle (21 days) in the prairie ecotype, even though ethylene is known to increase especially during periods of rapid elongation. By contrast, assays of ACC oxidase performed in vivo and in vitro showed rhythms of activity similar to those of ethylene production observed in the prairie ecotype. However, the levels of ethylene produced in the ACC oxidase assays were considerably higher than levels of ethylene normally produced by unstressed plants, and the rhythm of ACC oxidase activity was observed in both ecotypes, despite the fact that alpine Stellaria longipes exhibits a less pronounced ethylene rhythm. Thus, we concluded that although ACC oxidase activity may partially account for rhythmic production of ethylene in prairie ecotypes, other controlling factors such as spatial separation of ACC from ACC oxidase should be investigated. Key words: ACC oxidase, ecotypes, ethylene, phenotypic plasticity, rhythmicity, Stellaria longipes.
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Yellon, S. M., and L. D. Longo. "Melatonin rhythms in fetal and maternal circulation during pregnancy in sheep." American Journal of Physiology-Endocrinology and Metabolism 252, no. 6 (June 1, 1987): E799—E802. http://dx.doi.org/10.1152/ajpendo.1987.252.6.e799.
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In many seasonally breeding species, the nocturnal melatonin rhythm is part of an endogenous biological clock mediating information about day length to time the onset of puberty and the annual adult reproductive cycle. To determine whether timekeeping persists during pregnancy, we studied the pattern of melatonin in circulation in sheep during the last trimester of gestation. We measured plasma melatonin concentrations in the chronically catheterized ewe and fetus (n = 6) over a 48-h period (every 1-4 h) at approximately 120 days gestation. A typical rhythm was present in the pregnant ewes; plasma melatonin was low during the day and remained increased throughout the night. In the fetus, a modest 24-h pattern was detected, which lagged 0.5-1.5 h behind that of the maternal circulation. In combination with findings later in gestation (126 and 135 days) or even during parturition, it is clear that melatonin rhythms were sustained in all pregnant ewes and a 24-h pattern was present in the fetus. In those sheep that went to full term, births occurred during the night at 0130 +/- 2.6 h (mean +/- SE, n = 3). These findings suggest that measurement of day length is maintained in female sheep during the last trimester of pregnancy. Moreover, information about day length and/or time of day may be transferred across the placenta, because the pattern of melatonin in fetal circulation follows the maternal circadian melatonin rhythm.
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Bertram, Richard, Marcel Egli, Natalia Toporikova, and Marc E. Freeman. "A mathematical model for the mating-induced prolactin rhythm of female rats." American Journal of Physiology-Endocrinology and Metabolism 290, no. 3 (March 2006): E573—E582. http://dx.doi.org/10.1152/ajpendo.00428.2005.
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For the first 10 days of pregnancy and the first 12 days of pseudopregnancy, the secretion of prolactin (PRL) from pituitary lactotrophs is rhythmic, with two surges/day. This rhythm can also be triggered by bolus injection of oxytocin (OT). We describe a mathematical model for the initiation, maintenance, and termination of the OT-induced PRL rhythm. In our model, the mechanism for this circadian rhythm is mutual interaction between lactotrophs and neuroendocrine dopamine (DA) neurons. This rhythm is, under normal lighting conditions, entrained by the suprachiasmatic nucleus (SCN) but persists in the absence of input from the SCN. We postulate that OT injection triggers the rhythm by activating a population of bistable hypothalamic neurons that innervate and inhibit DA neurons. The bistable nature of these neurons allows them to act as a memory device, maintaining the rhythm long after OT has been cleared from the blood. The mechanism for this memory device and the arguments supporting it are detailed with computer simulations. Finally, we consider potential targets for a rhythm-terminating factor and make predictions that may be used to determine which mechanism is operational in terminating the OT- or mating-induced PRL rhythm.
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Salfer, Isaac J., and Kevin J. Harvatine. "Night-restricted feeding of dairy cows modifies daily rhythms of feed intake, milk synthesis and plasma metabolites compared with day-restricted feeding." British Journal of Nutrition 123, no. 8 (January 8, 2020): 849–58. http://dx.doi.org/10.1017/s0007114520000057.
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AbstractThe timing of feed intake can alter circadian rhythms of peripheral tissues. Milk synthesis displays a daily rhythm across several species, but the effect of feeding time on these rhythms is poorly characterised. The objective of this experiment was to determine if the time of feed intake modifies the daily patterns of milk synthesis, plasma metabolites and body temperature in dairy cows. Sixteen lactating Holstein dairy cows were randomly assigned to one of the two treatment sequences in a cross-over design with 17 d periods. Treatments included day-restricted feeding (DRF; feed available from 07.00 to 23.00 hours) and night-restricted feeding (NRF; feed available from 19.00 to 11.00 hours). Cows were milked every 6 h on the last 7 d of each period, and blood samples were collected to represent every 4 h over the day. Peak milk yield was shifted from morning in DRF to evening in NRF, while milk fat, protein and lactose concentration peaked in the evening in DRF and the morning in NRF. Plasma glucose, insulin, NEFA and urea nitrogen concentration fit daily rhythms in all treatments. Night feeding increased the amplitude of glucose, insulin and NEFA rhythms and shifted the daily rhythms by 8 to 12 h (P < 0·05). Night feeding also phase-delayed the rhythm of core body temperature and DRF increased its amplitude. Altering the time of feed availability shifts the daily rhythms of milk synthesis and plasma hormone and metabolite concentrations and body temperature, suggesting that these rhythms may be entrained by food intake.
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Dispersyn, Garance, Laure Pain, and Yvan Touitou. "Circadian Disruption of Body Core Temperature and Rest–Activity Rhythms after General (Propofol) Anesthesia in Rats." Anesthesiology 110, no. 6 (June 1, 2009): 1305–15. http://dx.doi.org/10.1097/aln.0b013e3181a10225.
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Background General anesthesia is commonly associated with sleep disorders, fatigue, drowsiness, and mood alterations in patients. The authors examined whether general (propofol) anesthesia can impact the circadian temporal structure by disturbing circadian rest-activity and body temperature rhythms under normal light-dark conditions (light-dark 12:12 h) in rats. Methods A group of rats was anesthetized with propofol, and another was injected with 10% Intralipid, which was used as a control lipidic solution. The authors examined six groups of rats according to the Zeitgeber time of intraperitoneal administration (ZT6, ZT10, ZT16) and the substance injected (propofol or Intralipid). Results On the day after anesthesia, propofol induced a significant 60- to 80-min phase advance of both rest-activity and body temperature rhythms. A significant 45- to 60-min phase advance of body temperature and a significant 20-min phase advance of rest-activity were still observed on the second day after anesthesia. The amplitudes of both rest-activity and body temperature rhythms were decreased on the first and second days after anesthesia. The 24-h mean rest-activity rhythm was decreased on the day after anesthesia, whereas the 24-h mean body temperature rhythm was not modified. Conclusion The results demonstrate the disturbing effects of propofol anesthesia on the circadian time structure in rats under normal light conditions.
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Heide, O. M., R. W. King, and L. T. Evans. "Semidian rhythmicity in the flowering response of Pharbitis nil to changes in temperature." Functional Plant Biology 25, no. 2 (1998): 183. http://dx.doi.org/10.1071/pp97117.
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Our earlier experiments on flowering in the short day plant Pharbitis nil involved far- red/dark (FR/D) interruptions of 90 min duration at various times during a continuous light, constant temperature period before a single inductive dark period. They revealed a rhythm with a period of 12 h, hence semidian. We concluded that the phasing of this semidian rhythm determined the length of darkness required for floral induction. This conclusion has since been challenged so we sought other pretreatments which reveal the semidian rhythm. Interruptions at 12°C–17°C for 45–90 min at various times prior to the inductive dark period were as effective as FR/D in eliciting the semidian rhythm, with significant effects on flowering persisting for at least three cycles in constant conditions in continuous light. The rhythmic response to 12°C pretreatments was 3 h out of phase with that to FR/D pretreatments. Flowering responses to the semidian rhythm exposed by 12°C pretreatments were additive to and independent of those to a circadian rhythm. Some evidence was obtained of reversal of the inhibition or promotion of flowering by FR/D or 12°C by exposure immediately afterwards to the other pretreatment at times of their opposite effect. Pretreatments at 12°C, like those with FR/D, either reduced (if promotive) or extended (if inhibitory) the length of the dark period required for floral induction in this short day plant.
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O'Donnell, Aidan J., Kimberley F. Prior, and Sarah E. Reece. "Host circadian clocks do not set the schedule for the within-host replication of malaria parasites." Proceedings of the Royal Society B: Biological Sciences 287, no. 1932 (August 12, 2020): 20200347. http://dx.doi.org/10.1098/rspb.2020.0347.
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Circadian clocks coordinate organisms' activities with daily cycles in their environment. Parasites are subject to daily rhythms in the within-host environment, resulting from clock-control of host activities, including immune responses. Parasites also exhibit rhythms in their activities: the timing of within-host replication by malaria parasites is coordinated to host feeding rhythms. Precisely which host feeding-related rhythm(s) parasites align with and how this is achieved are unknown. Understanding rhythmic replication in malaria parasites matters because it underpins disease symptoms and fuels transmission investment. We test if rhythmicity in parasite replication is coordinated with the host's feeding-related rhythms and/or rhythms driven by the host's canonical circadian clock. We find that parasite rhythms coordinate with the time of day that hosts feed in both wild-type and clock-mutant hosts, whereas parasite rhythms become dampened in clock-mutant hosts that eat continuously. Our results hold whether infections are initiated with synchronous or with desynchronized parasites. We conclude that malaria parasite replication is coordinated to rhythmic host processes that are independent of the core-clock proteins PERIOD 1 and 2; most likely, a periodic nutrient made available when the host digests food. Thus, novel interventions could disrupt parasite rhythms to reduce their fitness, without interference by host clock-controlled homeostasis.
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McWatters, Harriet. "Pace of life: Complexity at the heart of the plant clock." Biochemist 26, no. 1 (February 1, 2004): 15–17. http://dx.doi.org/10.1042/bio02601015.
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Circadian rhythms are found in most organisms. They are endogenous rhythms of activity, hormone production or gene expression with a cycle length of approximately 24 hours. A central clock, whose principle role appears to be co-ordinating internal rhythms with the daily rhythm of day and night (Figure 1) controls the different observed rhythms in a single organism. In animals, fungi and cyanobacteria, this circadian clock is formed from loops of negative regulation of gene and protein expression1. Whether this is also true of plant clocks is the subject of some current debate.
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De Miguel, F. F., and H. Aréchiga. "CIRCADIAN LOCOMOTOR ACTIVITY AND ITS ENTRAINMENT BY FOOD IN THE CRAYFISH PROCAMBARUS CLARKI." Journal of Experimental Biology 190, no. 1 (May 1, 1994): 9–21. http://dx.doi.org/10.1242/jeb.190.1.9.
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The aim of our experiments has been to study the effect of light and food in the locomotor activity rhythm of the crayfish Procambarus clarki. Experiments were carried out under light:dark (LD) cycles of 12 h:12 h, under continuous darkness (DD) and under continuous light (LL). Under LD cycles, two peaks of activity were observed during the night phase of the cycle, while resting was characteristic of the day phase. Under DD or LL, it was possible to follow a free-running rhythm with a periodicity of 22.3±0.84 h in DD and 24.8±0.27 h in LL, typical of circadian rhythms of nocturnal species. A single delivery of food in the day phase of the LD cycle resulted in an outburst of locomotor activity that lasted for several hours. In the ensuing days, an activity peak appeared in phase with the time of food delivery. The food-related activity peak could be followed for up to 2 weeks without food reinforcement. Under DD and LL, food induced an activity rhythm in previously arrhythmic animals. Here the period was longer than 24 h in DD (26.2±0.12 h) and shorter in LL (22.5±0.46 h). Together, these results strongly suggest that light and food may play a role entraining a locomotor activity rhythm in crayfish.
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Sládek, Martin, Zuzana Jindráková, Zdenka Bendová, and Alena Sumová. "Postnatal ontogenesis of the circadian clock within the rat liver." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 292, no. 3 (March 2007): R1224—R1229. http://dx.doi.org/10.1152/ajpregu.00184.2006.
Full textAbstract:
In mammals, the circadian oscillator within the suprachiasmatic nuclei (SCN) entrains circadian clocks in numerous peripheral tissues. Central and peripheral clocks share a molecular core clock mechanism governing daily time measurement. In the rat SCN, the molecular clockwork develops gradually during postnatal ontogenesis. The aim of the present work was to elucidate when during ontogenesis the expression of clock genes in the rat liver starts to be rhythmic. Daily profiles of mRNA expression of clock genes Per1, Per2, Cry1, Clock, Rev-Erbα, and Bmal1 were analyzed in the liver of fetuses at embryonic day 20 (E20) or pups at postnatal age 2 (P2), P10, P20, P30, and in adults by real-time RT-PCR. At E20, only a high-amplitude rhythm in Rev-Erbα and a low-amplitude variation in Cry1 but no clear circadian rhythms in expression of other clock genes were detectable. At P2, a high-amplitude rhythm in Rev-Erbα and a low-amplitude variation in Bmal1 but no rhythms in expression of other genes were detected. At P10, significant rhythms only in Per1 and Rev-Erbα expression were present. At P20, clear circadian rhythms in the expression of Per1, Per2, Rev-Erbα, and Bmal1, but not yet of Cry1 and Clock, were detected. At P30, all clock genes were expressed rhythmically. The phase of the rhythms shifted between all studied developmental periods until the adult stage was achieved. The data indicate that the development of the molecular clockwork in the rat liver proceeds gradually and is roughly completed by 30 days after birth.
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Albers, H. E., L. Yogev, R. B. Todd, and B. D. Goldman. "Adrenal corticoids in hamsters: role in circadian timing." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 248, no. 4 (April 1, 1985): R434—R438. http://dx.doi.org/10.1152/ajpregu.1985.248.4.r434.
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The 24-h patterns of circulating cortisol and corticosterone were determined in male hamsters housed under a 14:10 light-dark cycle. Corticoid levels varied significantly over the 24-h sampling period with peak levels of both hormones occurring near the onset of the daily dark phase. The ratio of cortisol to corticosterone changed dramatically during the day. Corticosterone levels were significantly higher than cortisol during the early part of the light phase; however, cortisol levels became significantly higher than corticosterone when both hormones began their daily rise. To examine whether the circadian rhythm of cortisol secretion could be involved in the physiological control of hamster circadian organization, cortisol was infused at approximately physiological levels into adrenalectomized hamsters either continuously or in a 24-h rhythm. No significant differences were observed in the timing of circadian wheel-running rhythms in hamsters housed in LD 16:8, LD 14:10, or LL when cortisol was infused continuously, in a 24-h rhythm that mimicked the cortisol rhythm of intact hamsters, or in a 24-h rhythm several hours out of phase with the rhythm of intact hamsters. Provision of cortisol in a 24-h rhythm appeared to promote the survival of adrenalectomized hamsters since hamsters receiving a 24-h pattern of cortisol survived the experimental protocol significantly longer than those receiving the same dose of cortisol continuously.
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Udoh, Uduak S., Jennifer A. Valcin, Telisha M. Swain, Ashley N. Filiano, Karen L. Gamble, Martin E. Young, and Shannon M. Bailey. "Genetic deletion of the circadian clock transcription factor BMAL1 and chronic alcohol consumption differentially alter hepatic glycogen in mice." American Journal of Physiology-Gastrointestinal and Liver Physiology 314, no. 3 (March 1, 2018): G431—G447. http://dx.doi.org/10.1152/ajpgi.00281.2017.
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Multiple metabolic pathways exhibit time-of-day-dependent rhythms that are controlled by the molecular circadian clock. We have shown that chronic alcohol is capable of altering the molecular clock and diurnal oscillations in several elements of hepatic glycogen metabolism ( 19 , 44 ). Herein, we sought to determine whether genetic disruption of the hepatocyte clock differentially impacts hepatic glycogen content in chronic alcohol-fed mice. Male hepatocyte-specific BMAL1 knockout (HBK) and littermate controls were fed control or alcohol-containing diets for 5 wk to alter hepatic glycogen content. Glycogen displayed a significant diurnal rhythm in livers of control genotype mice fed the control diet. While rhythmic, alcohol significantly altered the diurnal oscillation of glycogen in livers of control genotype mice. The glycogen rhythm was mildly altered in livers of control-fed HBK mice. Importantly, glycogen content was arrhythmic in livers of alcohol-fed HBK mice. Consistent with these changes in hepatic glycogen content, we observed that some glycogen and glucose metabolism genes were differentially altered by chronic alcohol consumption in livers of HBK and littermate control mice. Diurnal rhythms in glycogen synthase (mRNA and protein) were significantly altered by alcohol feeding and clock disruption. Alcohol consumption significantly altered Gck, Glut2, and Ppp1r3g rhythms in livers of control genotype mice, with diurnal rhythms of Pklr, Glut2, Ppp1r3c, and Ppp1r3g further disrupted (dampened or arrhythmic) in livers of HBK mice. Taken together, these findings show that chronic alcohol consumption and hepatocyte clock disruption differentially influence the diurnal rhythm of glycogen and various key glycogen metabolism-related genes in the liver. NEW & NOTEWORTHY We report that circadian clock disruption exacerbates alcohol-mediated alterations in hepatic glycogen. We observed differential responsiveness in diurnal rhythms of glycogen and glycogen metabolism genes and proteins in livers of hepatocyte-specific BMAL1 knockout and littermate control mice fed alcohol. Our findings provide new insights into potential mechanisms by which alcohol alters glycogen, an important energy source for liver and other organs.
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Hazlerigg, David G., and Gerald A. Lincoln. "Hypothesis." Journal of Biological Rhythms 26, no. 6 (November 30, 2011): 471–85. http://dx.doi.org/10.1177/0748730411420812.
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Circannual rhythms are innately timed long-term (tau ≈ 12 months) cycles of physiology and behavior, crucial for life in habitats ranging from the equator to the Poles. Here the authors propose that circannual rhythm generation depends on tissue-autonomous, reiterated cycles of cell division, functional differentiation, and cell death. They see the feedback control influencing localized stem cell niches as crucial to this cyclical histogenesis hypothesis. Analogous to multi-oscillator circadian organization, circannual rhythm generation occurs in multiple tissues with hypothalamic and pituitary sites serving as central pacemakers. Signals including day length, nutrition, and social factors can synchronize circannual rhythms through hormonal influences, notably via the thyroid and glucocorticoid axes, which have profound effects on histogenesis. The authors offer 4 arguments in support of this hypothesis: (1) Cyclical histogenesis is a prevalent process in seasonal remodeling of physiology. It operates over long time domains and exhibits tissue autonomy in its regulation. (2) Experiments in which selected peripheral endocrine signals are held constant indicate that circannual rhythms are not primarily the product of interacting hormonal feedback loops. (3) Hormones known to control cell proliferation, differentiation, and organogenesis profoundly affect circannual rhythm expression. (4) The convergence point between photoperiodic input pathways and circannual rhythm expression occurs in histogenic regions of the hypothalamus and pituitary. In this review, the authors discuss how testing this hypothesis will depend on the use of cellular/molecular tools and animal models borrowed from developmental biology and neural stem cell research.
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Brown, G. M. "Day-Night Rhythm Disturbance, Pineal Function and Human Disease." Hormone Research 37, no. 3 (1992): 105–11. http://dx.doi.org/10.1159/000182410.
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