Search results for "Infradian rhythm"
showing 4 items of 4 documents
Time-related changes in size of nuclei of pinealocytes in rats
1981
In a study of 96 adult male Sprague-Dawley rats, da- and time-related changes of the mean nuclear volume of pinealocytes were determined with the aim of testing the reproducibility of the karyometric findings described by Quay and Renzoni (1966). It is shown (i) that statistically significant differences exist between the central and peripheral mean volumes of pinealocyte nuclei/group of animals and time point (p less than 0.001), (ii) that the day and time related differences are statistically different in both regions (p less than 0.001), (iii) that in the center and periphery of the pineal body different diurnal patterns exist, and (iv) that the diurnal patterns are not parallel in the t…
Atypical 24-hour rhythms of serotonin N-acetyltransferase activity in the rat pineal gland.
1988
Previous long-term studies have shown that in the pineal gland of rats melatonin synthesis is subject to infradian rhythms with periods between 4 and 7 days. Since in these studies melatonin-related parameters were measured at one timepoint of a 24-hr cycle only, the aim of the present investigation was to extend these experiments by more frequent sampling, to characterize the infradian rhythmicity in more detail. Male Sprague-Dawley rats kept under a light schedule of LD 12:12 (lights on at 0700) were killed at 6-hr intervals on 8 consecutive days. After decapitation the pineal gland was rapidly dissected out, followed by measurements of one of the melatonin-forming enzymes, serotonin N-ac…
Circadian and Infradian Activity Rhythms in the Mammalian Pineal Body
1982
The neuroendocrine nature of the pineal organ is well established. Linked to the optic system via postganglionic sympathetic fibres coming from the superior cervical ganglia, the parenchymal cells of the pineal synthesize serotonin from tryptophan and convert it to melatonin, the most widely studied pineal substance, and other indoleamines. Melatonin synthesis is stimulated by noradrenaline released from intrapineal sympathetic nerve fibres, involving β-adrenergic mechanisms and the adenyl cyclase-cAMP-system. The rate-limiting enzyme of melatonin formation is serotonin-N-acetyltransferase (NAT) that converts serotonin to N-acetylserotonin. Hydroxyindole-O-methyltransferase (HIOMT) catalyze…
Infradian rhythms of serotonin and serotonin‐N‐acetyltransferase in the pineal gland of male rats
1983
Abstract The present investigation was carried out to determine whether in the pineal gland of male Sprague‐Dawley rats infradian rhythms with respect to serotonin, serotonin‐N‐acetyltransferase (NAT) activity, and hydroxyindole‐O‐methyltransferase (HIOMT) can be detected. The serotonin data obtained over a period of 4 weeks and subjected to power spectral analysis suggest the presence of infradian rhythms in the range of 6 and 4.3 days. NAT activity, obtained over a period of 28 days, revealed a 7‐day‐rhythm. A second peak occurring at 2.3 days remained just below the significance limit. HIOMT activity studied over a period of 8 days showed no statistically significant differences between …