bluuebunny/crossref_metadata_2025_split huggingface dataset:
Possible role of dopamine in changes in LH and prolactin concentrations after experimentally induced hyperprolactinaemia in rats
Authors: Esquifino A. I. , Ramos J. A. , Tresguerres J. A. F. 
Published: December 2008

ABSTRACT
Nine-month-old female rats bearing an ectopic pituitary gland (from a litter-mate) under the right kidney capsule since day 30 of life and their sham-operated controls, were treated with a dopamine agonist (lysuride) or antagonist (metoclopramide). Plasma prolactin and LH levels were measured by double-antibody radioimmunoassays. Vaginal smears were taken before and during the treatment periods. Eight months after the operation, a significant (P < 0·01) increase in basal prolactin levels together with a significant (P < 0·05) reduction in LH values and permanent dioestrus occurred in the grafted animals when compared with controls. Lysuride treatment resulted in a marked reduction in plasma prolactin levels both in control and grafted rats over the whole 12 days of treatment, together with a partial restoration of plasma LH levels on day 1. From day 7 onwards a depression in LH values was again observed. Oestrous cycles were partially restored at the beginning of the treatment, but after 7 days dioestrus returned. Metoclopramide administration induced a significant (P< 0·001) increase in basal prolactin levels in both grafted and control rats. Basal plasma LH values were unaffected in controls when compared with vehicle-treated animals. An increase could be seen in hyperprolactinaemic rats after 7 or 12 days of treatment however. The LH response to the administration of LH releasing hormone (LHRH) was greater in the experimental and control metoclopramide-treated rats when compared with vehicle-treated rats. Vaginal smears were not altered in the control animals but there was a significant increase in the number of oestrous smears in grafted animals given the dopamine antagonist partially restoring the cycle pattern. After LHRH administration plasma prolactin levels decreased in vehicle-treated grafted and control animals, whereas only a tendency to lower values or no modification in basal levels was observed with lysuride or metoclopramide treatments. All these data suggest that increased plasma prolactin levels cannot modify LH secretion directly. This influence may be exerted, however, through increased hypothalamic and in-situ pituitary dopamine detected in hyperprolactinaemic animals.
J. Endocr. (1984) 100, 141–148
Development of the oviduct in quail during sexual maturation in relation to plasma concentrations of oestradiol and progesterone
Authors: Pageaux J. F. , Laugier C. , Pal D. , Pacheco H. 
Published: December 2008

ABSTRACT
The macromolecular content (DNA, soluble proteins and ovalbumin) of the magnum and the plasma concentrations of oestradiol and progesterone were studied during sexual development of the Japanese quail. Rapid growth and differentiation of the magnum began between 21 and 28 days of age and rapidly reached the laying stage in about 20 days. This rapid change in magnum size occurred in a stepwise manner: cellular proliferation was observed first, followed by the synthesis and accumulation of specific proteins. Just before and during magnum growth, plasma oestradiol and progesterone concentrations followed different patterns: the initiation of epithelial cell proliferation was preceded by a sharp decrease in plasma progesterone. Maximum cell division occurred while plasma progesterone levels continued to decrease slightly; at the same time, oestradiol increased from 0·098 to 0·453 nmol/l. The decrease and finally the cessation of cell proliferation and the concomitant increase in ovalbumin concentration were related to almost constant levels of plasma oestradiol and increasing levels of plasma progesterone. Further development of the magnum (above 2·3 g weight) involving only the accumulation of secretory products was associated with an increased value of plasma progesterone. These data are consistent with the hypothesis that there are multiple hormonal signals controlling cell proliferation and synthesis of egg-white proteins in the oviduct. Progesterone may be one of the key signals that regulates the initiation of oviduct growth in the quail.
J. Endocr. (1984) 100, 167–173
Effects of bromocriptine and naloxone on plasma levels of prolactin, LH and FSH during suckling in the female rat: responses to gonadotrophin releasing hormone
Authors: Sirinathsinghji D. J. S. , Martini L. 
Published: December 2008

ABSTRACT
The roles of dopamine and the endogenous opiate peptides in the mediation of the inverse relationship between prolactin and gonadotrophin secretion during lactation were studied by comparing the effects of bromocriptine and naloxone on plasma levels of prolactin, LH and FSH during suckling in the female rat. The effects of exogenous gonadotrophin releasing hormone (GnRH) on the LH and FSH responses to bromocriptine and naloxone were also assessed. In control animals (saline), there was a marked fall in LH levels and a large increase in prolactin levels within 15 min of suckling. In response to GnRH (25 ng) there was a small progressive increase in LH levels reaching a maximum at 45 min. Both bromocriptine (500 μg) and naloxone (500 μg) markedly suppressed the suckling-induced prolactin surge when administered in two separate groups of animals. However, despite the bromocriptine-induced suppression of prolactin levels, there was no increase in LH levels which remained low throughout the suckling period. Naloxone (500 μg), however, induced a twofold increase in LH levels within 15 min suggesting that an enhanced opiate rather than dopaminergic activity may be responsible for the suppression of GnRH and hence gonadotrophin secretion during suckling. This is supported by the finding that whereas combined bromocriptine (500 μg) and GnRH (25 ng) treatment suppressed the suckling-induced prolactin rise and also induced only a small progressive increase in LH (similar to GnRH alone), combined naloxone (500 μg) and GnRH (25 ng) treatment induced a sharp sixfold increase in LH levels within 15 min while at the same time markedly suppressing prolactin levels. None of these drug treatments affected the levels of FSH.
The results of this study may thus indicate that (1) the suckling stimulus itself rather than the high prolactin levels may be responsible for the suppression of gonadotrophin secretion during lactation, (2) although dopamine may be an important physiological factor controlling prolactin secretion, it may not be involved in the regulation of LH during lactation and (3) the suckling stimulus may enhance the release of endogenous opiates within the central nervous system which could then stimulate prolactin and at the same time inhibit gonadotrophin secretion by inhibiting GnRH release. This opiate-mediated mechanism may explain the reciprocal nature of prolactin and LH secretion during lactation.
J. Endocr. (1984) 100, 175–182
Episodic release of LH in gonadectomized male Japanese quail
Authors: Urbanski H. F. 
Published: December 2008

ABSTRACT
Blood samples were taken every 15 min (for 4·75 h) from six castrated quail on three separate occasions. The birds were first bled while under short days (comprising 8 h light:16 h darkness per 24 h; 8L:16D) and, subsequently, after 1 and 20 days under long days of 16L:8D. The photoperiodic alteration produced a marked increase in the mean plasma LH concentration of each bird and in four instances the rise was evident after only 1 long day. Pulsatile release patterns were not detected in the plasma LH profiles obtained during exposure to short days or after 1 long day but were pronounced in all of the birds after 20 long days. The peaks (n = 19) occurred on average every 83 ±14 (s.e.m.) min and had an amplitude of 12·3±1·2 μg/l. After 35 days under 16L: 8D three of the quail were bled more frequently (every 8 min for 2·5 h), allowing the LH pulses to be measured more precisely. Each pulse was composed of a sudden increase in secretion followed by a slower decrease which lasted for approximately 30 min. The development and functional significance of episodic LH release in the quail is discussed.
J. Endocr. (1984) 100, 209–212
Vascular and cellular changes in the decidualized endometrium of the ovariectomized mouse following cessation of hormone treatment: a possible model for menstruation
Authors: Finn C. A. , Pope M. 
Published: December 2008

ABSTRACT
Ovariectomized mice were prepared for decidualization with oestrogen and progesterone and arachis oil injected into the uterine lumen. Hormone injections were then stopped and uteri examined at intervals between 31 and 84 h after the last progesterone injection. At 31 and 35 h the stroma showed a normal decidual reaction. Between 45 and 79 h the stroma underwent a series of changes which started with the congestion of dilated blood vessels with swollen erythrocytes followed by breakdown of the vessel walls and extravasation of blood. At the same time the decidual cells showed typical apoptotic changes and there was invasion by leucocytes. An outer ring of stroma did not take part in the degenerative process and eventually a central core of blood cells and degenerating decidual cells became detached and was shed into the lumen.
Animals treated in exactly the same way but with the omission of the decidual stimulus did not show such changes in the stroma. It is suggested that the changes in the endometrium resemble those of menstruation and support the suggestion that for menstruation to occur the stroma must be differentiated for implantation. This occurs during the cycle in women but does not occur in non-primates unless a decidual stimulus is applied to the uterus.
J. Endocr. (1984) 100, 295–300
A histometrical study of immunohistochemically identified mitotic adenohypophysial cells in immature and mature castrated rats
Authors: Sakuma S. , Shirasawa N. , Yoshimura F. 
Published: December 2008

ABSTRACT
Two weeks after operation the effects of castration on all types of mitotic adenohypophysial cells in 30-day-old (immature) and 75-day-old (mature) male rats were studied immunohistochemically by light microscopy. The total number of mitotic cells in gland specimens increased 1·4 times in immature rats, but remained unchanged in mature animals; mitotic activity (mitotic cell number/mm2) was not affected in either age group. The population of mitotic gonadotrophs increased five to six times in comparison with intact controls. In addition, the percentage of mitotic gonadotrophs and their mitotic activity were raised in both age groups. Castration affected the mitosis of prolactin cells. The percentage of mitotic prolactin cells was reduced by one-third in castrated immature rats, but the total number and percentage of mitotic prolactin cells, as well as their mitotic activity, was reduced by about two-thirds in mature castrated rats. No significant changes in mitotic ACTH, TSH, GH and immunonegative cells were found after castration in either group of animals.
Mitotic cells were more numerous in the anterior than in the posterior region of the gland in normal (uncastrated) immature rats, but were uniformly scattered in both regions in normal mature rats. On the other hand, castration induced a high population of mitotic cells in the anterior region regardless of age. This high population was the result of the enhanced mitosis of gonadotrophs. It is concluded that 2 weeks after castration the increment of mitotic divisions of all types of pituitary cells is age-dependent, and that mitosis takes place frequently in gonadotrophs and less frequently in prolactin cells.
J. Endocr. (1984) 100, 323–328
Acute in-vivo effects of adrenocorticotrophin on plasma levels of glucagon, insulin, glucose and free fatty acids in rabbits: involvement of the alpha-adrenergic nervous system
Authors: Knudtzon J. 
Published: December 2008

ABSTRACT
Intravenous injection of 8·5 nmol (1–24)ACTH increased the plasma levels of glucagon, insulin, glucose and free fatty acids in rabbits. The (1–24)ACTH-induced hyperglucagonaemia and hyperinsulinaemia started 3 and 20 min after the injection respectively. Similar increases in the plasma levels of glucagon, insulin and free fatty acids were found with 5·3 nmol (1–39)ACTH, whereas (1–4)ACTH, (4–10)ACTH, (1–10)ACTH, (11–24)ACTH, (7–38)ACTH and (18–39)ACTH (corticotrophin-like intermediate lobe peptide) injected at doses of approximately 8 nmol were inactive. Infusions with the alpha-adrenergic blocking drug, phentolamine, reduced the (1–24) ACTH-induced hyperglucagonaemia and hypergly-caemia, and augmented the (1–24)ACTH-induced hyperinsulinaemia, which now became significant after 5 min. Infusions with the beta-adrenergic blocking drug, propranolol, did not diminish the (1–24)ACTH-induced effects, but killed the rabbits after 2–4 h.
It is concluded that the acute in-vivo effects of ACTH in rabbits are modulated by the involvement of alpha-adrenergic receptors, which increased the plasma levels of glucagon and glucose, and delayed and diminished the ACTH-induced increases in the plasma levels of insulin. The (1–24)ACTH-induced increases in the plasma levels of free fatty acids were not influenced by the adrenergic blocking drugs.
J. Endocr. (1984) 100, 345–352
Human growth hormone-secreting pituitary adenoma cells in long-term culture: effects of dexamethasone and growth hormone releasing factor
Authors: Oosterom R. , Verleun T. , Lamberts S. W. J. 
Published: December 2008

ABSTRACT
Growth hormone-secreting human pituitary adenoma cells in long-term culture show a decline in GH secretion. We investigated the effects of dexamethasone on GH production and on the responsiveness of the adenoma cells to various drugs. Twenty-four-hour GH secretion by cultures from seven acromegalics was consistently stimulated by 100 nM-dexamethasone. In four out of seven cultures the effect of dexamethasone occurred within 24 h. After 3 weeks in culture the decline in GH secretion by control cultures was over 90%, while in dexamethasone-treated cultures this was limited to less than 50%. The effect of dexamethasone was dose-dependent over a range of 1 nmol/l to 10 μmol/l. Dexamethasone stimulated not only GH secretion (fivefold), but also GH content (twofold). Cycloheximide and actinomycin D blocked the stimulatory effect of dexamethasone on GH secretion, the latter irreversibly. After 4 days of treatment with 100 nm-dexamethasone, the relative effects of somatostatin, prostaglandin E1, bromocriptine and thyrotrophin releasing hormone were the same in treated and untreated cultures. However, the response to synthetic GH releasing factor (GRF) was greatly enhanced by pretreatment of adenoma cells with dexamethasone (100 and 5 nmol/l). Cells unresponsive to small concentrations of GRF could be stimulated effectively by GRF after pretreatment with dexamethasone.
In conclusion, dexamethasone prevents the decline in GH production as seen in control cultures, possibly by stimulation of DNA transcription. Furthermore, the response to GRF is greatly enhanced in the presence of dexamethasone, while the relative effects of other direct GH stimulatory and inhibitory compounds seem to be unchanged.
J. Endocr. (1984) 100, 353–360
The role of neurotransmitters in mediating copulation-induced ovulation in the rat
Authors: Leipheimer R. E. , Condon T. P. , Curry J. J. 
Published: December 2008

ABSTRACT
Pentobarbitone-blocked pro-oestrous rats were subjected to either limited mating (maximum of 30 mounts), all-night cohabitation with males or stimulation of the vagina and cervix with a glass rod (2 or 5 min) to determine which type of stimulus was most effective in inducing ovulation. All-night cohabitation was the most successful procedure and resulted in 100% ovulation in those rats which mated. Treatment with either phenoxybenzamine, propranolol or pimozide did not interfere with this copulation-induced ovulation whereas methysergide treatment completely blocked copulation-induced ovulation. Administration of atropine resulted in a loss of mating behaviour and these animals therefore did not ovulate. Further experiments provided evidence that administration of atropine also blocked ovulation in response to vaginal stimulation with a glass rod. Pretreatment with methysergide or atropine had no effect upon the percentage of pentobarbitone-blocked, pro-oestrous rats ovulating in response to administration of LH releasing hormone (LHRH). However, those rats given atropine shed significantly fewer ova per rat following LHRH or LH infusion when compared with controls. These results suggest that the synaptic mechanisms responsible for mediating copulation-induced ovulation are different from those mediating steroid-induced ovulation, and that ovarian cholinergic receptors may play a role in ovulation.
J. Endocr. (1984) 100, 361–365
In-vitro testosterone metabolism in the mouse preputial gland: intercellular co-operation and changes with cell maturation
Authors: Brind J. L. , Marinescu D. , Gomez E. C. , Wheatley V. R. , Orentreich N. 
Published: December 2008

ABSTRACT
In-vitro [14C]testosterone metabolism was investigated in isolated cells of adult male mouse preputial sebaceous glands. Labelled steroids were extracted and chromatographed after a 2-h incubation, and were identified as 5α-dihydrotestosterone, androstenedione, 5α-androstane-3,17-dione, 5α-androstane-3α,17β-diol and 5α-androstane-3β,17β-diol, androsterone and 3-epiandrosterone. In cells separated according to state of maturity (lipid content) by isopycnic centrifugation in a metrizamide gradient, maximal testosterone metabolism occurred in large, nearly mature cells. In this population, mean hydroxysteroid 5α-reductase and 17β-hydroxysteroid dehydrogenase activities were 3·8 and 2·3 nmol/106 cells per 2 h respectively, more than 100-fold greater than in the densest population, comprised of undifferentiated and early differentiating cells. It was also found that the profile of testosterone metabolites was dependent on the proportion of the label metabolized. The metabolite index (MI), i.e. the average number of enzymatic steps undergone per molecule of metabolite, increased with increasing substrate utilization. Metrizamide showed reversible, non-specific inhibition of testosterone metabolism and reduction of the MI. Thus, it was postulated that testosterone is metabolized sequentially by different cells, with metrizamide inhibiting cellular uptake and intercellular substrate transport. This suggested that most of the metabolites would be found in the medium, rather than in the cellular compartment. Further, in incubations run without cell disaggregation, efficient substrate cycling among cells should result in a high MI, independent of metrizamide concentration and substrate utilization. These predictions were all confirmed, providing strong evidence that testosterone metabolism is a cooperative effort among several cells in this tissue.
J. Endocr. (1984) 100, 377–388
Age difference in endogenous opiate modulation of short photoperiod-induced testicular regression in golden hamsters
Authors: Chen H. J. , Targovnik J. , McMillan L. , Randall S. 
Published: December 2008

ABSTRACT
Effects of age and naloxone on testicular function were studied in golden hamsters exposed to short photoperiods. Subjection of hamsters to short photoperiods of 6 h light: 18 h darkness for 6 weeks led to testicular regression in young adult (5–6 months) or middle-aged (11–12 months) golden hamsters but not in prepubertal hamsters of 1–2 months of age. The middle-aged hamsters had decreased testis width by week 4 of treatment and the young hamsters by week 5. Daily injection of naloxone at the time of'lights on' partially prevented testicular regression in young and middle-aged hamsters but the extent of regression was significantly greater in the middle-aged animals.
Plasma LH and FSH concentrations were significantly reduced in hamsters placed in short photoperiods regardless of age or testicular weight, while naloxone treatment significantly increased the LH concentrations in all age groups. Plasma β-endorphin-like immunoreactivity was significantly increased by short photoperiod or older age.
These results indicated that (a) the sensitivity of the testicular suppression to short photoperiod increases as a function of age, (b) naloxone, a specific opiate receptor blocker, can partially prevent short photoperiod-induced testicular regression and (c) ageing and short photoperiods increase β-endorphin-like immunoreactivity. It is concluded that the opiate system may be involved in ageing and photoperiod regulation of reproductive function.
J. Endocr. (1984) 101, 1–6
Immediate, short- and long-term opposite effects of oestradiol-17β on glucose metabolism in rat adipocytes: relationship with the biphasic changes in body weight and food intake
Authors: Faure A. , Vergnaud M.-Th. , Sutter-Dub M.-Th. , Sutter B. Ch. J. 
Published: December 2008

ABSTRACT
The changes in the effects of oestradiol-17β on body weight, food intake and [1-14C]glucose oxidation in adipocytes were followed in sham-operated, ovariectomized and adrenalectomized–ovariectomized rats to eliminate effects of endogenous progesterone and corticosterone. During the first 5 days oestradiol induced a dramatic fall in food intake and body weight concomitant with a decrease in glucose oxidation by adipocytes, when tested 12 h and 3 days after the beginning of treatment. In-vitro incubations with oestradiol showed that this was a direct effect of this hormone. On the other hand, from days 5 to 14 of treatment, body weight and food intake increased, though they were still lower than in sham-operated controls. On day 14, as values of treated rats tended to reach those of controls, glucose oxidation in adipocytes was stimulated by oestradiol treatment. An insulin effect was still observable and none of these effects was dependent on the adrenal gland.
These biphasic changes in the parameters studied could be closely related; moreover, a relationship with other oestradiol actions on metabolism that are known to be corticosterone-dependent could be eliminated.
J. Endocr. (1984) 101, 13–19
Pituitary and gonadal response to LH releasing hormone administration in the female and male cheetah
Authors: Wildt D. E. , Chakraborty P. K. , Meltzer D. , Bush M. 
Published: December 2008

ABSTRACT
Luteinizing hormone releasing hormone (LHRH, 50 μg) or saline was administered (i.m.) to adult female and male cheetahs under anaesthesia to evaluate pituitary and gonadal response. Serum LH levels did not fluctuate over a 120-min sampling period in saline-treated animals. Serum LH concentrations were raised (P < 0·05) in both female and male cheetahs after LHRH injection, the temporal response being similar to previously reported results in unanaesthetized, domestic carnivores. The magnitude of the LHRH-induced LH response was sex-dependent. Over a 120-min post-injection period both saline control and LHRH-induced LH levels were about twofold greater in males than females. Although LHRH had no acute influence on ovarian oestradiol-17β production in the female, serum testosterone levels were raised (P < 0·05) in male cheetahs by 60 min after treatment. This study (1) provides introductory endocrine information on the cheetah, an endangered species, and (2) indicates that exogenous LHRH is effective in acutely altering pituitary (female) and pituitary/gonadal (male) function in an anaesthetized, non-domestic felid.
J. Endocr. (1984) 101, 51–56