Conservation of photoperiod-responsive mechanisms in humans

In animals, circadian pacemakers respond to seasonal changes in day length by making corresponding adjustments in the durations of diurnal and nocturnal periods of circadian rhythms; these adjustments mediate effects of photoperiod on breeding and other seasonally recurring phenomena. Little is known about photoperiod responses of human circadian pacemakers. To investigate this question, we recorded and compared circadian rhythm profiles of 15 individuals after chronic exposures to short (8 h) and long (14 h) nights. As occurs in animals, durations of nocturnal periods of active melatonin secretion (11.9 +/- 1.6 vs. 10.3 +/- 1.3 h, df = 14, t = 4.583, P < 0.0005, paired t test), high prolactin secretion (12.9 +/- 2.1 vs. 9.9 +/- 2.2 h, df = 11, t = 2.917, P < 0.01), and sleep (10.6 +/- 0.8 vs. 7.6 +/- 0.4 h, df = 14, t = 17.122, P < 0.0005) were longer after exposure to long nights than after short ones. Durations of nocturnal periods of low rectal temperature (11.6 +/- 2.3 vs. 9.5 +/- 1.6 h, df = 12, t = 3.912, P < 0.001) and rising cortisol secretion (10.8 +/- 1.6 vs. 9.3 +/- 1.9 h, df = 14, t = 3.130, P < 0.005) were also longer. Some of these differences persisted during 24-h periods of enforced wakefulness in constant dim light, indicating that prior exposure to the two regimes induced abiding changes in the timing of internal processes, such as circadian pacemaker oscillations, that control the durations of nocturnal and diurnal periods of the rhythms.

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Photoperiodic regulation of prolactin secretion: changes in intra-pituitary signalling and lactotroph heterogeneity

Journal of Endocrinology ◽

10.1677/joe.0.1800351 ◽

2004 ◽

Vol 180 (3) ◽

pp. 351-356 ◽

Cited By ~ 29

Author(s):

JD Johnston

Keyword(s):

Environmental Conditions ◽

Seasonal Changes ◽

Mammalian Species ◽

Prolactin Secretion ◽

Day Length ◽

Pars Tuberalis ◽

Photoperiodic Regulation ◽

Pituitary Lactotroph

Many mammalian species utilise day-length (photoperiod) to adapt their physiology to seasonal changes in environmental conditions, via secretion of pineal melatonin. Photoperiodic regulation of prolactin secretion is believed to occur via melatonin-mediated changes in the secretion of a putative prolactin secretagogue, tuberalin, from the pituitary pars tuberalis. Despite the in vivo and in vitro evidence in support of this intra-pituitary signalling mechanism, the identity of tuberalin has yet to be elucidated. This paper reviews recent advances in the characterisation of tuberalin and the regulation of its secretion. Furthermore, the hypothesis that pituitary lactotroph cells display heterogeneity in their response to changing photoperiod and tuberalin secretion is examined.

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Mammalian Circadian Clock and Its Resetting

Physiology ◽

10.1152/physiologyonline.1991.6.3.129 ◽

1991 ◽

Vol 6 (3) ◽

pp. 129-134

Author(s):

H Illnerova

Keyword(s):

Circadian Rhythm ◽

Circadian Clock ◽

Complex Structure ◽

Day Length ◽

Circadian Pacemaker ◽

Melatonin Production

Data on resetting circadian rhythm in melatonin production suggest a complex structure of the underlying pacemaker and explain why the circadian pacemaker functions also as a calendar measuring day length. The pacemaker is entrainable not only by light but by various drugs as well.

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Decreased day length and light intensity as factors inducing reproduction in Gammarus lacustris lacustris Sars

Canadian Journal of Zoology ◽

10.1139/z82-376 ◽

1982 ◽

Vol 60 (11) ◽

pp. 2962-2965 ◽

Cited By ~ 16

Author(s):

B. G. E. de March

Keyword(s):

Light Intensity ◽

Seasonal Changes ◽

Climatic Conditions ◽

Day Length ◽

Arctic Ecosystems ◽

Gammarus Lacustris ◽

Temperature Conditions ◽

Short Day ◽

Dim Light

Gammarus lacustris cultures were maintained in the laboratory under different light and temperature conditions during a 5-year period. Reproduction occurred only in adults which had been held at a short day length (12 h light) or in dim light for several weeks. Changes in photoperiod are the most consistent seasonal changes in temperature and arctic ecosystems, hence the response to light ensures regular annual reproduction in spite of unusual climatic conditions.

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The Circadian Rhythm of Intact Parathyroid Hormone-(1–84): Temporal Correlation with Prolactin Secretion in Normal Men

The Journal of Clinical Endocrinology & Metabolism ◽

10.1210/jcem-71-6-1556 ◽

1990 ◽

Vol 71 (6) ◽

pp. 1556-1560 ◽

Cited By ~ 15

Author(s):

F. C. LOGUE ◽

W. D. FRASER ◽

D. ST. J. O'REILLY ◽

D. A. CAMERON ◽

A. J. KELLY ◽

...

Keyword(s):

Circadian Rhythm ◽

Parathyroid Hormone ◽

Temporal Correlation ◽

Prolactin Secretion ◽

Intact Parathyroid Hormone ◽

Normal Men

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Phase-advance shifts of human circadian pacemaker are accelerated by daytime physical exercise

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.2001.281.1.r197 ◽

2001 ◽

Vol 281 (1) ◽

pp. R197-R205 ◽

Cited By ~ 98

Author(s):

Toshihiko Miyazaki ◽

Satoko Hashimoto ◽

Satoru Masubuchi ◽

Sato Honma ◽

Ken-Ichi Honma

Keyword(s):

Physical Exercise ◽

Single Pulse ◽

Time Of Day ◽

Phase Advance ◽

Circadian Pacemaker ◽

Light Conditions ◽

Melatonin Rhythm ◽

Dim Light ◽

The Difference ◽

Isolation Facility

Effects of forced sleep-wake schedules with and without physical exercise were examined on the human circadian pacemaker under dim light conditions. Subjects spent 15 days in an isolation facility separately without knowing the time of day and followed a forced sleep-wake schedule of a 23 h 40-min period for 12 cycles, and physical exercise was imposed twice per waking period for 2 h each with bicycle- or rowing-type ergometers. As a result, plasma melatonin rhythm was significantly phase advanced with physical exercise, whereas it was not changed without exercise. The difference in phase was already significant 6 days after the start of exercise. The amplitude of melatonin rhythm was not affected. A single pulse of physical exercise in the afternoon or at midnight significantly phase delayed the melatonin rhythms when compared with the prepulse phase, but the amount of phase shift was not different from that observed in the sedentary controls. These findings indicate that physical exercise accelerates phase-advance shifts of the human circadian pacemaker associated with the forced sleep-wake schedule.

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Salivary Melatonin Concentrations in a Sitting and a Standing Position

Journal of Hormones ◽

10.1155/2013/236325 ◽

2013 ◽

Vol 2013 ◽

pp. 1-4 ◽

Cited By ~ 2

Author(s):

Tomoaki Kozaki ◽

Toshihiko Arata ◽

Ayaka Kubokawa

Keyword(s):

Light Condition ◽

Standing Position ◽

Sitting Position ◽

Melatonin Secretion ◽

Salivary Melatonin ◽

Dim Light ◽

Age Range

This study aimed to examine differences in salivary melatonin concentrations between the sitting and standing positions. Ten subjects (age range: 20–22 years; 5 males and 5 females) participated in the study and provided written consent. In the sitting condition, the subjects sat on a chair from 23:30 h to 1:00 h, whereas in the standing condition, the subjects sat on a chair from 23:30 h to 0:30 h and stood on the floor from 0:30 h to 1:00 h. Saliva samples were obtained at 0:25 h and 1:00 h from all subjects. The experiment was performed under a dim light condition (<10 lx). No significant differences were observed in melatonin concentrations between the two positions at 0:25 h; however, melatonin concentrations in the standing condition were significantly greater than those in the sitting condition at 1:00 h. These results show that melatonin secretion is significantly greater in the standing position than that in the sitting position.

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An intraruminal soluble glass bolus containing melatonin — a potential system for early lamb production

Proceedings of the British Society of Animal Production (1972) ◽

10.1017/s0308229600034668 ◽

1997 ◽

Vol 1987 ◽

pp. 25-25

Author(s):

A.L. Poulton ◽

A.M. Symons ◽

M.I. Kelly ◽

J. Arendt

Keyword(s):

Seasonal Changes ◽

Commercial Application ◽

Economic Pressure ◽

Melatonin Secretion ◽

Melatonin Treatment ◽

Neural Signal ◽

Breeding Activity ◽

Soluble Glass ◽

Potential System ◽

The Hours

Seasonal changes in daylength (photoperiod) are effectively monitored by the eye transmitting a neural signal to the pineal gland which responds by secreting a hormone, melatonin, during the hours of darkness. Decreasing daylength is accompanied by an increase in the duration of melatonin secretion and stimulates breeding activity in sheep.It has been demonstrated that both timed (afternoon feeding and injection) and continuous (subcutaneous and vaginal implant) administration of supplementary melatonin to ewes in mid-summer mimics the effect of short or decreasing photoperiod and can advance the onset of breeding activity. Such treatments can also increase relative fecundity at early mating by phase-advancing the mid-breeding season peak in ovulation rate. As the U.K. is not sufficient in lamb production and bearing in mind the economic pressure for early lamb marketing, effective melatonin treatment offers considerable potential for commercial application.

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Agomelatine: Its Role in the Management of Major Depressive Disorder

Clinical Medicine Insights Psychiatry ◽

10.4137/cmpsy.s7989 ◽

2012 ◽

Vol 4 ◽

pp. CMPsy.S7989 ◽

Cited By ~ 8

Author(s):

Daniel P. Cardinali ◽

María F. Vidal ◽

Daniel E. Vigo

Keyword(s):

Bipolar Disorder ◽

Major Depressive Disorder ◽

Circadian Rhythm ◽

Depressive Disorder ◽

Seasonal Affective Disorder ◽

Rapid Onset ◽

Depressive Illness ◽

Melatonin Secretion ◽

Major Depressive ◽

Onset Of Action

Circadian rhythm abnormalities, as shown by sleep/wake cycle disturbances, constitute one the most prevalent signs of depressive illness; advances or delays in the circadian phase are documented in patients with major depressive disorder (MDD), bipolar disorder, and seasonal affective disorder (SAD). The disturbances in the amplitude and phase of rhythm in melatonin secretion that occur in patients with depression resemble those seen in chronobiological disorders, thus suggesting a link between disturbed melatonin secretion and depressed mood. Based on this, agomelatine, the first MT1/MT2 melatonergic agonist displaying also 5-HT2C serotonergic antagonism, has been introduced as an antidepressant. Agomelatine has been shown to be effective in several animal models of depression and anxiety and it has beneficial effects in patients with MDD, bipolar disorder, or SAD. Among agomelatine's characteristics are a rapid onset of action and a pronounced effectiveness for correcting circadian rhythm abnormalities and improving the sleep/wake cycle. Agomelatine also improves the 3 functional dimensions of depression—emotional, cognitive, and social—thus aiding in the full recovery of patients to a normal life.

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Molecular Cloning, Characterisation, Tissue Distribution, and mRNA Expression Changes under Different Light Regimes of Brain and Muscle Arnt-Like Protein-1 (BMAL1) in Columba Livia

Avian Biology Research ◽

10.3184/175815617x14951979279277 ◽

2017 ◽

Vol 10 (3) ◽

pp. 156-163 ◽

Cited By ~ 1

Author(s):

Y. Wang ◽

H.M. Yang ◽

Y.B. Li ◽

W. Cao

Keyword(s):

Circadian Rhythm ◽

Light Exposure ◽

Columba Livia ◽

Full Length ◽

Day Length ◽

Mrna Levels ◽

Tyto Alba ◽

Full Length Cdna ◽

Light Regimes ◽

Significant Difference

Brain and muscle Arnt-like protein-1 (BMAL1) plays an important role in circadian rhythm, which is involved in daily behaviours and physiological activities. However, little is known about the molecular function of BMAL1 in the Pigeon ( Columba livia). In our study, the full-length cDNA of Bmal1 was cloned and sequenced from the Pigeon for the first time, and submitted to the GenBank to obtain the accession number (KF906247). The full-length cDNA of Bmal1 consists of 2,488 nucleotides, and encodes 634 amino acids. Phylogenetic analysis showed that it bore the greatest similarity to Bmal1 from the Chicken ( Gallus gallus) and Barn Owl ( Tyto alba). The amino acid sequence of the Pigeon BMAL1 contained a HLH domain and two PAS domains, which are involved in forming hetero-homodimers with the CLOCK as the positive element of the circadian rhythm. The results of real-time quantitative PCR of Bmal1 under different light regimes showed that the amplitude and expression pattern of Bmal1 were strongly affected by day length. Bmal1 was most highly expressed in the pancreas. Relative to Bmal1 expression level under 12 h of light exposure, it was increased significantly in the pituitary gland, ovary and uterus under 15 h of light exposure ( P < 0.05). However, other tissues, including the hypothalamus, heart, liver, spleen, kidney, intestines, crureus, and pectorals exhibited no significant difference ( P < 0.05) under the two light regimes. This is the first study to investigate Bmal1 mRNA levels in various tissues under different light cycles, and thereby provide data for further study of the molecular and regulatory mechanisms of Bmal1 and circadian clock genes of the Pigeon.

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