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Department of Biochemistry, National Cardiovascular Center Research Institute, Osaka 565-8565, Japan
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Department of Biochemistry, National Cardiovascular Center Research Institute, Osaka 565-8565, Japan
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Department of Biochemistry, National Cardiovascular Center Research Institute, Osaka 565-8565, Japan
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Department of Biochemistry, National Cardiovascular Center Research Institute, Osaka 565-8565, Japan
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Department of Biochemistry, National Cardiovascular Center Research Institute, Osaka 565-8565, Japan
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expression is regulated by circadian rhythm, starvation, CCK, gastrin, and other factors, possibly via extracellular fluid or satellite cells. CCK and gastrin receptors are expressed in vagal afferent neurons, implying that the regulation of GHS-R gene
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. In addition, fasted adult offspring from FR70 dams during gestation displayed no marked reduced α-MSH-immunoreactive fibre projection intensity in the PVN ( Breton et al . 2009 ). Maternal reduced nutrition modifies circadian rhythms in the offspring
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SUMMARY
Testosterone was measured in the peripheral blood plasma of normal men by radioimmunoassay. The results were analysed to test for the possible existence of a circadian rhythm, for fluctuations superimposed on any such rhythm, and for day-to-day variations. Unequivocal evidence of a circadian rhythm was found in all but one of the subjects studied and the cycle appeared to be accompanied by a series of fluctuations of lower amplitude lasting for 1–2 h. Samples taken from the same subjects on consecutive days showed marked variation between days, but no regular cyclic pattern. The possible existence of such a cycle is not, however, eliminated. On the basis of all the data obtained a regime is suggested for the collection of blood samples from individuals whose androgenic status is to be assessed.
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It has been suggested that prolactin secretion exhibits a circadian rhythm and is related to ovine growth hormone (OGH) secretion in the ewe (Davis, 1972; Davis & Borger, 1972, 1973). Prolactin levels in ovine jugular vein blood can fluctuate rapidly, which makes it difficult to establish a temporal pattern of secretion. This problem may be overcome by continuous blood sampling, used here to measure prolactin in rams over 24 h. This secretory pattern is compared with the secretory pattern of OGH in the same animals. In particular, the interrelationship between prolactin and OGH is examined as well as attempting to define a circadian rhythm for the secretion of these hormones.
Five Merino rams were used. Skin folding for the neck and trunk regions of each animal was scored by three independent observers (Carter, 1943). This confirmed that two rams (nos. 174 and 179) had minimal skin folding (mean score 2/18)
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Androgen-sterilized female rats were obtained by administering 10 μg testosterone propionate to pups on day 2 after birth. In contrast with ovariectomized adults, androgenized adult female rats are incapable of responding to cervical stimulation by secreting prolactin in the nocturnal surge pattern. In spite of the loss of this pattern the androgenized female rats still exhibited a daily circadian rhythm of prolactin secretion with afternoon levels three times higher than those after midnight.
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SUMMARY
The melatonin (N-acetyl-5-methoxytryptamine) content of the pineal body and serum of White Leghorn cockerels (Gallus domesticus) appears to vary cyclically, with a higher level of both found at the mid-point of the dark period than at the mid-point of the light period when the animals were kept in a diurnal light cycle. These rhythmic variations persisted, although with an apparently lower amplitude, when the animals were maintained in continuous darkness for 2 weeks. The oscillations appeared to be free-running, circadian rhythms and to be phase-locked with the locomotor activity rhythms of the individual birds studied.
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SUMMARY
The circadian rhythm of urinary 17-hydroxycorticosteroid (17-OHCS) excretion in Europeans and Equatorial Amerindians has been compared. The precise daily habits of the Equatorial Amerindians did not result in a more marked rhythm of 17-OHCS excretion. Amerindian men and women excreted much less 17-OHCS than their European counterparts; the difference is still substantial when body weight is taken into consideration. The rhythm of 17-OHCS excretion in Amerindians had a minimum and maximum corresponding to their early reveille and bedtime confirming the importance of environmental stimuli in setting the timing of the rhythm.
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Although melatonin treatment has been shown to phase shift human circadian rhythms, it still remains ambiguous as to whether exogenous melatonin can entrain a free-running circadian system. We have studied seven blind male subjects with no light perception who exhibited free-running urinary 6-sulphatoxymelatonin (aMT6s) and cortisol rhythms. In a single-blind design, five subjects received placebo or 5 mg melatonin p.o. daily at 2100 h for a full circadian cycle (35-71 days). The remaining two subjects also received melatonin (35-62 days) but not placebo. Urinary aMT6s and cortisol (n=7) and core body temperature (n=1) were used as phase markers to assess the effects of melatonin on the During melatonin treatment, four of the seven free-running subjects exhibited a shortening of their cortisol circadian period (tau). Three of these had taus which were statistically indistinguishable from entrainment. In contrast, the remaining three subjects continued to free-run during the melatonin treatment at a similar tau as prior to and following treatment. The efficacy of melatonin to entrain the free-running cortisol rhythms appeared to be dependent on the circadian phase at which the melatonin treatment commenced. These results show for the first time that daily melatonin administration can entrain free-running circadian rhythms in some blind subjects assessed using reliable physiological markers of the circadian system.
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Circannual changes of immunoreactive LH and FSH were documented on a circadian basis in January, March, June and October in four groups of subjects: seven young men, six elderly men, six elderly women and six men and women suffering from senile dementia. The sampling was serially dependent only for the young men and the core subgroups of elderly men and elderly women. A circadian rhythm for FSH was not detected in any group of subjects during any of the sampling sessions, whereas a circadian rhythm for LH was detected twice (June and October) in young men, once (October) in elderly demented patients, and not at all in the groups of elderly men and women. Both 24-h and yearly mean levels of gonadotrophins were higher in elderly subjects (two-to 25-fold according to the hormone, sex and season) than in young men. Circannual rhythms of plasma LH with large amplitudes were validated by the cosinor method, with an acrophase located in April or May. A circannual rhythm of plasma FSH was validated only in young men, with an acrophase in October. The persistence of a circannual rhythm of plasma LH with large amplitude in elderly subjects, associated with high mean levels of the hormone, especially in elderly women, suggests that this bioperiodicity of the pituitary gland is independent of gonadal function.
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Department of Physiology and Biophysics, Colorado State University, Fort Collins, Colorado 80523, U.S.A.
(Received 13 September 1977)
Mammalian pineal gland activity is controlled by environmental lighting schedules. Light exerts its influence via a neuronal pathway originating in the retina (Moore & Klein, 1974) and as a consequence of this photoperiodic control, the concentration of melatonin in the plasma is raised during periods of darkness and depressed during periods of light (Rollag & Niswender, 1976). The response of the pineal gland to photostimulation is surprisingly rapid. Within 5 min of a darkness to light transition, there is a precipitous decline in pineal N-acetyltransferase activity in the rat (Deguchi & Axelrod, 1972; Klein & Weller, 1972). In sheep, peripheral concentrations of melatonin decline within 5–10 min of a darkness to light transition (Rollag, O'Callaghan & Niswender, 1978). A circadian rhythm of blood flow to the pineal gland analogous to the rhythm of melatonin
