Plasma melatonin concentrations in hibernating marmots: absence of a plasma melatonin rhythm

1984 ◽  
Vol 247 (6) ◽  
pp. R1062-R1066 ◽  
Author(s):  
G. L. Florant ◽  
M. L. Rivera ◽  
A. K. Lawrence ◽  
L. Tamarkin
Keyword(s):  
Time Of Day ◽  
Tissue Temperature ◽  
Constant Darkness ◽  
Circadian Pacemaker ◽  
Melatonin Secretion ◽  
Melatonin Concentration ◽  
Ambient Temperatures ◽  
Melatonin Rhythm ◽  
Plasma Melatonin ◽  
Deep Hibernation

Plasma melatonin concentrations were measured throughout bouts of hibernation in marmots maintained in a short photoperiod (light-dark 8:16) and ambient temperature of 5 or 15 degrees C. Melatonin concentration was also measured in two animals maintained in constant darkness. As an animal entered hibernation, plasma melatonin concentrations dropped to basal levels when body temperature reached 25 degrees C, and they remained low until arousal. During deep hibernation plasma melatonin values did not vary significantly (P greater than 0.05) with respect to time of day or different ambient temperatures. With nocturnal arousal plasma melatonin levels were similar to euthermic night values. Lack of a plasma melatonin rhythm during hibernation suggests that the pineal gland is not temperature compensated during hibernation, and due to the low tissue temperature of the pineal the circadian pacemaker driving melatonin secretion is incapable of stimulating a rhythm.

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

2001 ◽  
Vol 281 (1) ◽  
pp. R197-R205 ◽  
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.

Inhibition of nighttime melatonin secretion in cattle: threshold light intensity for dairy heifers

2001 ◽  
Vol 81 (1) ◽  
pp. 153-156 ◽  
Author(s):  
T. J. Lawson ◽  
A. D. Kennedy
Keyword(s):  
Light Intensity ◽  
Key Words ◽  
Latin Square ◽  
Exposure Period ◽  
Melatonin Secretion ◽  
Melatonin Concentration ◽  
Dairy Heifers ◽  
Plasma Melatonin ◽  
Light Intensities ◽  
Lower Light

Five pre-pubertal Holstein heifers were exposed for 16 h to a light intensity of 400 lx and thereafter to intensities of 0, 50, 100, 200, or 400 lx for an additional 8 h (5 x 5 Latin square design). Exposure to all intensities inhibited (P < 0.05) melatonin secretion for the initial few hours (of the 8-h exposure period); melatonin concentration subsequently increased, particularly with the lower light intensities. Only the highest light intensity (400 lx) suppressed (P < 0.05) plasma melatonin concentrations for the entire 8-h exposure period. Key words: Threshold, supplemental, light, intensity, inhibition, melatonin, heifer

scholarly journals Testis development in the Japanese eel is affected by photic signals through melatonin secretion

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e12289
Author(s):  
Ji-Yeon Hyeon ◽  
Jun-Hwan Byun ◽  
Eun-Su Kim ◽  
Yoon-Seong Heo ◽  
Kodai Fukunaga ◽  
...  
Keyword(s):  
Close Association ◽  
Japanese Eel ◽  
Constant Darkness ◽  
Melatonin Secretion ◽  
Time Resolved ◽  
Migration Patterns ◽  
Testis Development ◽  
Plasma Melatonin ◽  
Short Day ◽  
And Migration

Objective According to reported spawning characteristics of Japanese eel, Anguilla japonica, which exhibit spawning and migration patterns that are synchronized with lunar cycles and photoperiod, we hypothesized that a close association exists between specific photic signals (daylight, daylength, and moonlight) and endocrinological regulation. Given the photic control in melatonin secretion, this hypothesis was tested by investigating whether melatonin signals act as mediators relaying photic signals during testis development in the eel. Methods We examined changes in melatonin-secretion patterns using time-resolved fluorescence immunoassays in sexually immature and mature male Japanese eels under the condition of a new moon (NM) and a full moon (FM). Results The eye and plasma melatonin levels exhibited a nocturnal pattern under a 12-h light: dark cycle (12L12D) or under constant darkness (DD), but not with constant light (LL). Eye melatonin levels were similar under the 12L12D and short-day (9L15D) conditions. In the long-day condition (15L9D), secreted plasma melatonin levels were stable, whereas short-day melatonin secretion began when darkness commenced. Sexual maturation began at 8 weeks following intraperitoneal injection of human chorionic gonadotropin (hCG), and NM exposure led to significantly higher eye and plasma melatonin levels compared with those detected under FM exposure.

Melatonin rhythms in fetal and maternal circulation during pregnancy in sheep

1987 ◽  
Vol 252 (6) ◽  
pp. E799-E802 ◽  
Author(s):  
S. M. Yellon ◽  
L. D. Longo
Keyword(s):  
Biological Clock ◽  
Time Of Day ◽  
Day Length ◽  
Maternal Circulation ◽  
Fetal Circulation ◽  
Melatonin Rhythm ◽  
Plasma Melatonin ◽  
Term Births ◽  
Seasonally Breeding ◽  
Female Sheep

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.

The Effect of Moderate Weight Loss on Overnight Melatonin Secretion

1990 ◽  
Vol 156 (6) ◽  
pp. 875-877 ◽  
Author(s):  
I. M. Anderson ◽  
S. E. Gartside ◽  
P. J. Cowen
Keyword(s):  
Weight Loss ◽  
Melatonin Level ◽  
Melatonin Secretion ◽  
Plasma Melatonin ◽  
Healthy Women ◽  
Before And After

Overnight plasma melatonin level was measured in ten healthy women before and after a 4300 kJ (1000 kcaI) diet in which they lost an average 3.1 kg. This weight loss did not significantly alter melatonin levels.

Annual changes in 6-sulphatoxymelatonin excretion in man

1988 ◽  
Vol 117 (4) ◽  
pp. 470-476 ◽  
Author(s):  
Christopher J. Bojkowski ◽  
Josephine Arendt
Keyword(s):  
Intermediate Phase ◽  
Urine Samples ◽  
Plasma Samples ◽  
Annual Change ◽  
Melatonin Secretion ◽  
Normal Volunteers ◽  
Plasma Melatonin ◽  
Annual Rhythm ◽  
Major Urinary Metabolite ◽  
Annual Changes

Abstract: A recently developed RIA for 6-sulphatoxymelatonin, the major urinary metabolite of melatonin, has been used to investigate the annual change in melatonin secretion in humans. Twenty plasma samples were taken from 18 volunteers throughout a 24-h period and simultaneous 6-hourly urine samples were also collected. Plasma melatonin and urinary 6-sulphatoxymelatonin were measured by RIA. 6-Sulphatoxymelatonin assayed in the urine samples was shown to be a good index of the rhythmic characteristics of the plasma melatonin secretion. To study annual changes in excretion four sequential 6-hourly urine samples were collected at monthly intervals from 16 normal volunteers for 13 months. Cosinor curves were fitted to the 6-sulphatoxymelatonin excretion data and the 24-h rhythm was described by the cosinor parameters: amplitude, mesor and acrophase. Significant differences in the acrophase were found during the year. The summer acrophase was phase advanced relative to the winter acrophase by about 1.5 h while intermediate phase positions were observed in spring/autumn. The 24-h excretion of urinary 6-sulphatoxymelatonin was remarkably consistent and there was no annual rhythm. In contrast, the daytime 6-sulphatoxymelatonin excretion between 12.00–18.00 h showed a statistically significant seasonal rhythm, with peaks in December/January and in July.

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

2010 ◽  
Vol 298 (3) ◽  
pp. R681-R691 ◽  
Author(s):  
Yujiro Yamanaka ◽  
Satoko Hashimoto ◽  
Yusuke Tanahashi ◽  
Shin-ya Nishide ◽  
Sato Honma ◽  
...  
Keyword(s):  
Circadian Rhythms ◽  
Physical Exercise ◽  
Sleep Onset ◽  
Exercise Group ◽  
Control Group ◽  
Temporal Isolation ◽  
Melatonin Rhythm ◽  
Plasma Melatonin ◽  
Shift Schedule ◽  
Sleep Schedule

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

High salt mimics effects of light pulses on circadian pacemaker in cultured chick pineal cells

1991 ◽  
Vol 260 (4) ◽  
pp. R769-R776 ◽  
Author(s):  
M. Zatz ◽  
H. M. Wang
Keyword(s):  
Dominant Role ◽  
Red Light ◽  
Phase Shifts ◽  
Membrane Depolarization ◽  
Cell Swelling ◽  
Circadian Pacemaker ◽  
Cell Shrinkage ◽  
Phase Dependence ◽  
Melatonin Rhythm ◽  
High Concentrations

Chick pineal cells in static culture display a persistent photosensitive circadian rhythm of melatonin production and release. Pulses of white light or darkness, in otherwise constant red light, induce phase shifts in subsequent cycles whose magnitude and direction depend on the phase at which the pusle is given. Such "phase-dependent phase shifts" are mediated by effects on the underlying pacemaker. We reported previously that inhibiting the Na+-K+-adenosinetriphosphatase with ouabain evokes phase shifts with the same phase dependence as those induced by pulses of darkness. Two of the consequences of inhibiting the Na+ pump are membrane depolarization and cell swelling. To test the relevance of these effects and to distinguish between them, we exposed chick pineal cells to pulses of high concentrations of added KCl, which should cause both membrane depolarization and cell shrinkage. We also compared the effects of added NaCl, sodium gluconate, and mannitol, which should cause cell shrinkage without comparable depolarization. Each of these hypertonic solutions induced phase shifts in the melatonin rhythm with the same phase dependence as those caused by pulses of light rather than those caused by ouabain or darkness. These results argue strongly against a dominant role for changes in membrane potential in phase shifting the melatonin rhythm. Rather, they suggest that cell swelling may mediate the darklike effects of ouabain on the circadian pacemaker in chick pineal cells and indicate that cell shrinkage mimics the effects of light.

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