Showing papers on "Pinealectomy published in 1978"
TL;DR: Evidence is reported for the presence of a specific melatonin receptor in the supernatant fraction of several organs in hamster and rat tissues and human ovaries.
Abstract: MELATONIN, a secretion of the pineal gland, has profound inhibitory effects on the development and maturation of gonadal organs in mammals1. Pinealectomy of the rat or hamster results in premature enlargement of the uterus and ovary2,3 in females and gonadal organs in males4,5, while melatonin administration reverses the effects of pinealectomy and suppresses gonadal growth and maturation in these species1. The physiological site and mechanism of action are uncertain. The hormone seems to act both in the central nervous system and at peripheral sites; previous studies have demonstrated inhibition of luteinising hormone (LH) and follicle stimulating hormone (FSH) secretion by the pituitary5,6 as well as inhibition of oestrogen and progesterone synthesis by ovarian tissue slices7,8. Since other hormones are known to exert their effects through binding to receptor proteins in target organs, we have examined melatonin binding in hamster and rat tissues and human ovaries, and here report evidence for the presence of a specific melatonin receptor in the supernatant fraction of several organs.
148 citations
01 Jun 1978-Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology
TL;DR: The results differ from those obtained previously by Menaker and his co-workers on the house sparrow, in which pinealectomy always resulted in arrhythmia, but it is proposed that this model fits both the starling and the sparrow data and clarifies some previously unexplained results.
Abstract: Removal of the pineal organ from starlings had drastic effects on their freerunning circadian activity rhythms; in birds kept in continuous darkness the period (τ) shortened and the activity time (α) lengthened. Concomitantly bothτ andα became relatively unstable and the separation between activity and rest time was obscured. In a few birds activity became continuous and apparently arrhythmic. The activity rhythms of the birds were entrainable to a 12∶12 h light-dark cycle.
121 citations
TL;DR: Results suggest that the trout retina is a melatonin-synthesizing tissue that is present in highest concentration during the photophase portion of a light-dark cycle.
Abstract: Trout retinae were shown to contain melatonin, which was present in highest (p<.05) concentration during the photophase portion of a light-dark cycle. Pinealectomy was found not to perturb either the rhythm or the titer of retina melatonin. These results suggest that the trout retina is a melatonin-synthesizing tissue.
80 citations
TL;DR: There was a dissociation between the rhythms of activity and behavioral receptivity following photoperiod reversal, suggesting that two circadian thythms that are thought to be regulated by a common circadian system can become uncoupled from each other.
70 citations
TL;DR: It was found that severing the optic tract (optictract-section) did not alter the rhythm of melatonin measured in the plasma, which indicates that the trout pineal may monitor the environmental photoperiod directly, thereby controlling the rhythmic fluctuations in plasma melatonin.
Abstract: In a preliminary investigation, what appeared to be melatonin was measured in the plasma of pinealectomized trout using a specific and sensitive radioimmunoassay. Later, following the combined procedures of thin-layer chromatography and radioimmunoassay, the immunogenic molecule measured in pinealectomized trout plasma was verified as melatonin. After this validation procedure, plasma melatonin titers were assessed using RIA in pinealectomized, sham pinealectomized or intact rainbow trout either at mid-photophase or mid-scotophase. Results demonstrated that pinealectomy significantly reduced plasma melatonin measured at mid-scotophase, compared to the midscotophase values for either the sham-operated or intact animals. Interestingly, pinealectomized animals continued to show significantly elevated, mid-scotophase plasma melatonin titers when compared to the mid-photophase values. The same was true for the sham-operated and intact groups.
In a second experiment, it was found that severing the optic tract (optictract-section) did not alter the rhythm of melatonin measured in the plasma. This indicates that the trout pineal may monitor the environmental photoperiod directly, thereby controlling the rhythmic fluctuations in plasma melatonin. Optic tract-section did cause a significant increase in the mid-scotophase melatonin titer. This increase may be due to stress caused by sensory deprivation.
68 citations
TL;DR: Pinealectomy in the rat induces a significant increase of the arterial blood pressure within 15 days from the surgical procedure; this hypertension is still present 30 and 60 days after pinealectomy while after 90 days it returns to the normal range.
Abstract: Pinealectomy in the rat induces a significant increase of the arterial blood pressure within 15 days from the surgical procedure; this hypertension is still present 30 and 60 days after pinealectomy while after 90 days it returns to the normal range. Histological examination of the kidneys of pinealectomized hypertensive rats shows wall thickening and lumen narrowing of the arterioles, adventitial and periadventitial fibrosis, dense glomeruli. The vascular lesions are not diffuse but patchily distributed. Body weight is higher in pinealectomized rats compared with normal and sham-operated animals: this difference becomes significant about 40 days after pinealectomy and gradually decreases until it disappears at the end of the third month. Food and water intake is higher in pinealectomized rats up to the 7th week; during the 8th week they return to the normal range.
63 citations
53 citations
TL;DR: It was concluded that while the pineal is not necessary for maintaining the daily thermal rhythm in the avian body, it has a thermoregulatory role, in that it prevents rise in body temperature in warm acclimatized and chronic cold exposed birds.
Abstract: Diurnal rhythm in body temperature of pigeons subjected to different experimental conditions (pinealectomized, sham-operated, melatonin-implanted, cold-exposed) was studied under a 12 h light and 12 h dark regimen. The body temperature of pigeons during photophase was higher than that during scotophase in the normal as well as every treatment group studied. Pinealectomized pigeons showed higher body temperature in the photophase as well as scotophase, than that of the normal and sham-operated birds when examined 2 or 3 weeks following the post-surgical acclimatization to 25 or 3 degrees C. However, subcutaneous implantation of melatonin pellets into pinealectomized pigeons nullified or even reversed the hyperthermic effect of pinealectomy. Exposure of pigeons to--18 degrees C for 280 min during photophase as well as scotophase, produced a marked drop in body temperature in pinealectomized, sham-operated and normal pigeons. The pinealectomized pigeons exhibited a higher body temperature than that of the sham-operated and normal ones when exposed to--18 degrees C during the photophase, but not during the scotophase. It was concluded that while the pineal is not necessary for maintaining the daily thermal rhythm in the avian body, it has a thermoregulatory role, in that it prevents rise in body temperature in warm (25 degrees C) acclimatized and chronic cold (3 degrees C) exposed birds. In acute short-term cold (--18 degrees C) exposure however, the temperature regulatory role of the pineal was not effective during the scotophase.
51 citations
TL;DR: The effects of pinealectomy on pituitary and plasma gonadotropin levels and gonadal development in female goldfish exposed to various photoperiod-temperature regimes during different seasons were examined.
Abstract: The effects of pinealectomy on pituitary and plasma gonadotropin levels and gonadal development in female goldfish exposed to various photoperiod-temperature regimes during different seasons were examined. Pinealectomy during autumn had no effect on either pituitary or plasma hormone levels or gonadal development. When goldfish are pinealectomized in spring and exposed to long photoperiod conditions, the ovaries regress and plasma gonadotropin levels are significantly depressed compared to sham operated animals. Sham operated goldfish exposed to short photoperiod conditions in spring had regressing ovaries whereas pinealectomized animals under this regime either spawned or had ovaries in the late vitellogenic phase. Plasma gonadotropin titres in the pinealectomized group were significantly lower than those of sham operated animals. The pineal can be either stimulatory or inhibitory to gonadal development depending on the photoperiod regime to which the animals are exposed. The pineal apparently influences gonadal activity by modulating gonadotropin secretion. A diurnal variation in plasma gonadotropin levels was also observed in both sham operated and pinealectomized goldfish exposed to a long photoperiod warm-temperature regime in spring.
48 citations
TL;DR: In this paper, the effects of pineal removal on daily variations and levels of some liver and plasma metabolites were examined in the goldfish, Carassius auratus, and the results showed that pinealectomy abolishes the liver glycogen daily variation and decreases hepatic glycogen levels in goldfish maintained on specific photoperiod regimes during spring and summer.
41 citations
TL;DR: In a study of pineal gland influences on hormone secretory profiles, blood samples were collected from 4 pinealectomized and 4 sham-operated rams which were subjected to a 14.5 h daily photoperiod and a nocturnal elevation of plasma prolactin (Prl) levels was substantially abolished by pinealectomy.
Abstract: In a study of pineal gland influences on hormone secretory profiles, blood samples were collected at 20 min intervals for 26 h from 4 pinealectomized and 4 sham-operated rams which were subjected to a 14.5 h daily photoperiod. Plasma levels of luteinizing hormone (LH) and testosterone (T) underwent rapid pulsatile fluctuations in all rams. Pinealectomized rams produced more LH than the sham-operated rams and a similar trend was recorded for plasma T data, since T secretion closely followed that of LH. A nocturnal elevation of plasma prolactin (Prl) levels displayed by sham-operated rams was substantially abolished by pinealectomy. Also a rise in cortisol secretion during the morning hours recorded from 3 of the sham-operated rams was absent in 2 of the pinealectomized rams. The possible significance of the pineal gland in the regulation of secretion of these hormones is discussed.
TL;DR: It is suggested that the pineal gland and melatonin may exert an antagonistic effect on the biological activity of androgens administered to castrated rats and that melatonin can reduce the growth of the accessory sex organs of intact, pinealectomized rats, in spite of a high concentration of LH in the serum.
Abstract: In castrated prepubertal rats, pinealectomy enhanced the testosterone-induced growth response of the seminal vesicles and melatonin inhibited this effect in a dose-related manner. In entire animals, the serum concentration of LH was increased after pinealectomy with no significant changes in other parameters. Administration of melatonin to intact, pinealectomized rats did not affect the serum concentrations of LH or testosterone but caused a dose-related decrease in the weight of the seminal vesicles. The highest dose of melatonin tested reduced the weight of the ventral prostate gland and the uptake of radioactivity by both the ventral prostate gland and the testes after injection of [5-3H]uridine. It is suggested that the pineal gland and melatonin may exert an antagonistic effect on the biological activity of androgens administered to castrated rats and that melatonin can reduce the growth of the accessory sex organs of intact, pinealectomized rats, in spite of a high concentration of LH in the serum. The well-known inhibitory influence of systemically administered melatonin on the accessory sex organs in male rats may be due to its antagonistic effect at a peripheral level.
TL;DR: When melatonin is continuously available (from a subcutaneous deposit) it counteracts the antigonadotrophic influence of the pineal gland in light restricted or blinded hamsters, i.e., it causes a "functional pinealectomy".
Abstract: N-acetyl-5-methoxytryptamine, melatonin, is synthesized within and secreted from the pineal gland. Although the concentration of this constituent in the blood is diminished after surgical removal of the pineal gland it does not completely disappear. Other potential contributors to blood titers of melatonin include the retinas, the Harderian glands and the gastro-intestinal tract. Melatonin has a potent antigonadotrophic action in the Syrian hamster ( a highly photosensitive species) provided the indole is given during a restricted portion of the light phase of the light-dark cycle. This so-called sensitive period falls late in the light phase; melatonin acutely administered at other times has virtually no inhibitory influence on the reproductive physiology of hamsters. When melatonin is continuously available (from a subcutaneous deposit) it counteracts the antigonadotrophic influence of the pineal gland in light restricted or blinded hamsters, i.e., it causes a "functional pinealectomy". Furthermore, chronically available melatonin negates the antigonadotrophic capability of acute melatonin injections.
TL;DR: The results are interpreted as indicating that the inhibitory effect of the pineal in dark-reared, sham-operated prepuberal male rats is exerted at the level of hypothalamic secretion of TRH.
Abstract: An experiment was performed on 21-day-old male rats to determine the combined effects of pinealectomy, constant light and darkness, and intraperitoneal (i.p.) thyrotropin-releasing hormone (TRH) on pi
TL;DR: A 1-year experiment was conducted to determine the role of the pineal gland in the seasonal sexual, antler development and feeding patterns of deer and it is suggested that pinealectomized bucks shed their velvet later and dropped their antlers earlier than the control deer.
Abstract: A 1-year experiment was conducted to determine the role of the pineal gland in the seasonal sexual, antler development and feeding patterns of deer. Three mature male whitetailed deer were pinealectomized. These animals along with four normal bucks were housed in individual outdoor pens. Blood samples were drawn bi-weekly and analyzed for calcium and phosphorus, alkaline phosphatase, and total androgens. Changes in antler growth, pelage, body weight and feed consumption were recorded. Both groups of deer followed the same pattern of increased body weight and feed consumption in the summer and a decline during rut and throughout the following winter months. While the feed consumptions of the ablated bucks were lower (P<.05) than the controls, the intakes of DDM/BW'7 s and DE/ .75 9 Kg . BW kg were not different. Serum alkahne phosphatase activity was lower in the ablated animals, and it did not peak in early antler growth as it did in the controls. Serum androgens were lower in the ablated deer but followed the same seasonal pattern as the intact deer with an annual low in May and a peak in late November. The pinealectomized bucks shed their velvet later and dropped their antlers earlier than the control deer. Pelage changes were slightly altered. A pair of twin bucks raised in normal daylight until pinealectomized and sham operated exhibited more striking differences. The former buck shed its antlers 5 months later than normal. It is suggested that
TL;DR: It is concluded that intracranial surgery alone (SPX) and without visible brain damage can affect mechanisms of glucose homeostasis, and that at least in some circumstances such a surgical effect is not only different from effects of surgical pinealectomy (PX), but is also probably not pineal-dependent.
Abstract: Alloxan-diabetic male rats were used to test effects of pinealectomy (PX) and of sham-pinealectomy (SPX) on blood glucose levels at mid-dark in the daily light-dark (LD 12:12) cycle. Animals received a diabetogenic dose of alloxan 10 days postoperatively. Blood glucose was measured on days -1,1,2,3,4,5,7,10 and 15 after 8-hour fasts. Pinealectomized (PX) and non-operated (C) animals were equivalent in their hyperglycemia following alloxan. SPX animals contrastingly showed significantly less response to alloxan than did animals of the other two groups. This difference of the SPX animals was in terms of lower hyperglycemia, better maintenance of body weight and of survival. It is concluded that intracranial surgery alone (SPX) and without visible brain damage can affect mechanisms of glucose homeostasis, and that at least in some circumstances such a surgical effect is not only different from effects of surgical pinealectomy (PX), but is also probably not pineal-dependent.
TL;DR: It is suggested that the neuro-endocrine disturbances, due to removal of the pineal gland in the new-born animals, are latent and become evident after reserpine administration, as reflected in an increased tumor incidence.
Abstract: After reserpine treatment the incidence of dimethyl-benzathrance-induced tumors was found to be significantly higher in pinealectomised rats than in intact or thymectomised ones. A very high rate of DMBA-leukemia was observed in immune deficient pinealectomised rats after reserpine administration. It is therefore suggested that the neuro-endocrine disturbances, due to removal of the pineal gland in the new-born animals, are latent and become evident after reserpine administration, as reflected in an increased tumor incidence.
TL;DR: Melatonin elicits luteinization in CL-CEA rats through the brain serotoninergic system and is significantly counteracted by feeding the animals with a tryptophan-poor diet or by injecting methiothepin, a blocker of central serotoninergic receptors.
Abstract: Continuous light (CL) induces constant estrous anovulatory (CEA) syndrome and blockade of pineal gland activity. Chronic treatment with melatonin is able to overcome the anovulatory state in about 70% of CL-CEA rats, and the luteinizing effect of melatonin is significantly counteracted either by feeding the animals with a tryptophan-poor diet or by injecting methiothepin, a blocker of central serotoninergic receptors. It appears that melatonin elicits luteinization in CL-CEA rats through the brain serotoninergic system.
TL;DR: The pineal gland, associated with the dark period of the day, appears to influence response to both ketamine and GHB in the chick, and the ketamine response was augmented when chicks were pretreated with serotonin, N-acetylserotonin or melatonin.
TL;DR: In this article, a coupled radioenzymatic method was used to measure the dopamine-beta-hydroxylase (DBH) activites of intact control and intracranial surgery animals.
Abstract: Hypothalamic and plasma dopamine-beta-hydroxylase [DBH, EC 1.14.2.1] activites were measured by a coupled radioenzymatic method. Animals representing five experimental groups [intact controls, adrenalectomized, pinealectomized, adrenalectomized pinealectomized, doubly sham-operated] were killed and sampled at 8 times through the 24-hr daily cycle, 15 days postoperation, and at 50-52 days of age. Hypothalamic DBH in intact control animals had statistically significant fluctuations in relation to time of day. These changes were lost or dampened in groups that had had intracranial surgery and were characteristically shifted by adrenalectomy, either alone or with pinealectomy. Plasma DBH fluctuations in the same animals resembled those in hypothalamus in some features (e.g., peak near mid-dark; shift in daily maxima and minima after adrenalectomy) and differed in others [e.g., no effect of intracranial surgery or of sham operation; adrenalectomized pinealectomized animals resembled the solely pinealectomized]. Although temporal patterns in hypothalamic DBH activity thus differed in the experimental animal groups, the daily means of hypothalamic DBH activity were similar.
Journal Article•
TL;DR: It has been demonstrated that administration of the pineal extract lowers serum, hepatic, adrenal and testicular cholesterol of rat and that pinealectomy causes reverse effects, and the inhibiting role played by the Pineal gland in the lipid metabolism is demonstrated.
Abstract: The study contains the data gathered with time with regard to the involvment of the pineal gland in the lipid metabolism. Thus, it has been demonstrated that administration of the pineal extract lowers serum, hepatic, adrenal and testicular cholesterol of rat and that pinealectomy causes reverse effects. Administration of melatonin did not cause significant alterations. The same pineal extract reduced cholesterolemia, biliary cholesterol and serum phospholipids in rabbits whereas the absence of the pineal gland caused an increase in cholesterolemia, total lipids and FFA. Pineal treatment reduced the major lipid components of the blood and aorta in experimental atheromatosis induced in rabbits. The results presented in this paper demonstrate the inhibiting role played by the pineal gland in the lipid metabolism.
01 Jan 1978
TL;DR: Differences between pinealectomized and sham operated animals may be due to a shift of a daily variation in pituitary prolactin levels, which depends on photoperiod and time of sampling.
Abstract: Pinealectomy has an influence on pituitary prolactin levels in goldfish maintained under certain photoperiod-temperature regimes. The effects of pinealectomy on pituitary prolactin content depend on photoperiod and time of sampling. Thus, differences between pinealectomized and sham operated animals may be due to a shift of a daily variation in pituitary prolactin levels. The pineal in fishes may thus be involved in photoperiod influences on daily prolactin rhythms.
20 Jun 1978
TL;DR: It is considered that the pineal body plays a role not only in initiating but also in propagating convulsions, and that it may have a depressive action on motor activities in mice.
Abstract: We designed a simple technique for surgical excision of the pineal body in mice. Such can be accomplished in 10 min by a skilled worker and there are no lesions whatever.In pinealectomized El-strain mice the appearance of convulsions was inhibited up to 30 days, while intact El-mice were all fallen into convulsions by being shaken up and down on a flat carton. Pentazole-induced convulsions propagate from one dd-mouse to another in an aggregated state, but such propagation did not occur in pinealectomized animals.Exploratory movements of pinealectomized dd-mice increased as compared to intact animals and the increase was always more extensively observed in El-mice in which, even in the intact animals, the exploratory movements were much more than those of dd-mice.From the above-mentioned experiment, it is considered that the pineal body plays a role not only in initiating but also in propagating convulsions, and that it may have a depressive action on motor activities in mice.
TL;DR: Plasma prolactin (Prl) titers were determined by radioimmunoassay in conscious, freely moving male rats which had either had sham operations or had been pinealectomized and the area under the curve of Prl release, which was greater at night than in the daytime, was significantly lowered by pinealectomy.
Abstract: Plasma prolactin (Prl) titers were determined by radioimmunoassay in conscious, freely moving male rats which had either had sham operations or had been pineal-ectomized. Values were determined during
TL;DR: The effects of blinding alone or in combination with pinealectomy, castration and melatonin treatment on nerve growth factor (NGF) in submaxillary glands of mice were tested.
TL;DR: It is demonstrated that both the pineal and adrenal glands influence the release of pituitary hormones in animals maintained in a reduced photoperiod.
Abstract: The influence of pinealectomy (Px) and/or adrenalectomy (Adx) on reproductive processes was examined in female rats maintained in a reduced photoperiod (8 h L:16 h D). Estrous cycle length, number of ova ovulated and organ weights (ovaries, uterus or pituitary gland) were not significantly altered by either surgical procedure. Moreover, the critical period for LH release as defined by Nembutal blockade was unaffected by these treatments. In contrast, serum LH levels on proestrus (third proestrus subsequent to surgery) were reduced overall by Px. In Px-Adx rats either the magnitude of the LH surge was subnormal or the onset of the LH rise was delayed. The time periods selected for blood sampling did not allow us to distinquish between these 2 effects. In any case,serum LH values were markedly depressed at 1700 h in Px-Adx animals. At this time serum progesterone concentrations were also reduced in this group of rats. Both Px and/or Adx significantly altered the time course of serum prolactin on proestrus and at 1700 h in Px-Adx animals, serum concentrations were significantly elevated above control levels. Our data demonstrate that both the pineal and adrenal glands influence the release of pituitary hormones in animals maintained in a reduced photoperiod.
TL;DR: The pituitary content and concentration of LH and the content of FSH were increased by pinealectomy in both intact and castrated rats, which may suggest that the pineal gland exerts an inhibitory action on the hypothalamic-pituitary axis that seems to be independent of the testicular function.
Abstract: Twenty-eight-day-old male Wistar rats were pinealectomized and/or castrated. Animals were killed 26 days later and anterior pituitaries were dissected out, weighed, and their content of LH and FSH measured by RIA. Pinealectomized rats showed higher body weights than sham-operated animals, which suggests an inhibitory influence of the pineal on growth. The weights of pituitaries were increased by both pinealectomy and castration. However, in pinealectomized rats, but not in castrated, the elevated pituitary weights seemed to be due to the high body weights of those animals. The pituitary content and concentration of LH and the content of FSH were increased by pinealectomy in both intact and castrated rats. This finding may suggest that the pineal gland exerts an inhibitory action on the hypothalamic-pituitary axis that seems to be independent of the testicular function. (Endocrinology 102: 1534, 1978)
TL;DR: The present results demonstrate that in young female rats both the pineal gland and dual sensory deprivation have additional independent antigonaldal effects.
Abstract: Previous studies show that the suppression of gonadal function in blind-anosmic rats is dependent on the pineal gland. The present results demonstrate that in young female rats both the pineal gland and dual sensory deprivation have additional independent antigonaldal effects.
TL;DR: Hamsters which had been blinded, pinealectomized, or a combination of both, were unilaterally ovariectomizing on day four of the estreous cycle and necropsied on the same day of the cycle, four days later.