bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of changes in the secretion of corticotrophin releasing activity using the isolated rat hypothalamus incubated in vitro
Authors: Kamstra G. S. , Thomas P. , Sadow Janet 
Published: December 2008

The secretion of corticotrophin releasing activity (CRA) from the isolated rat hypothalamus incubated in vitro was investigated under various conditions of incubation and of pretreatment of donor animals providing hypothalami. Media from hypothalamic incubations were assayed for CRA by a validated double in-vitro bioassay technique which differentiates CRA from vasopressin.
A circadian rhythm was found in the secretion of CRA in vitro from isolated hypothalami obtained from animals killed at different times of the day. Secretion of CRA increased significantly at 19.00 h (dusk) compared with the secretion rate at 07.00 h, in synchrony with a rise in plasma corticosterone levels. In addition, both plasma corticosterone concentrations and CRA secretion in vitro were higher at 07.00 h than at 19.00 h after exposure of the donor animals to a reversed light cycle for 7–10 days.
Hypothalami obtained from animals chronically treated with betamethasone in the drinking water showed a diminished secretion of CRA in vitro. Exposure of untreated animals to ether vapour for 2 min immediately before death significantly increased the subsequent secretion of CRA in vitro. Ether exposure did not significantly affect the secretion of CRA in vitro from hypothalami of betamethasone-treated rats. There was a close correlation between plasma corticosterone levels and in-vitro CRA release after these treatments. The results suggest that the secretion of CRA examined in this way is a phenomenon which can reflect the changes which occur in the activity of the hypothalamo-pituitary-adrenal system in vivo during the 24-h cycle, after glucocorticoid treatment and after ether stress.
Effect of adrenalectomy on the regulation of the secretion of gonadotrophins and prolactin in the lactating rat
Authors: van der Schoot P. , de Greef W. J. 
Published: December 2008

The suckling stimulus exerts an inhibitory action on the release of gonadotrophins during lactation. The possible involvement of the adrenal glands in this process was examined by studying the plasma levels of gonadotrophins in lactating rats ovariectomized on the day after parturition. It appeared that the suppression, throughout suckling, of the rise in levels of gonadotrophins in blood after ovariectomy occurred to the same extent in adrenalectomized and in sham-operated animals. It thus seems unlikely that adrenocortical hormones, albeit secreted in larger quantities during lactation, exert an inhibitory effect on the release of gonadotrophins.
Adrenalectomy had a marked effect on the plasma concentrations of prolactin during the second half of lactation. Whereas plasma concentrations of prolactin in the first half of lactation were similar in adrenalectomized and sham-operated rats, the concentrations in adrenalectomized rats did not undergo the reduction found in sham-operated rats. Adrenal hormones may thus be involved in the reduction of blood levels of prolactin observed in rats and in other mammals as lactation progresses.
Changes in serum concentration of luteinizing hormone in the female rat approaching puberty
Authors: Meijs-Roelofs H. M. A. , Kramer P. , Sander H. J. 
Published: December 2008

Concentrations of LH in the serum were estimated in rats bled either once or twice during a 15-day period preceding first ovulation. In rats bled once (between 09.00 and 17.00 h) serum concentrations showed little change between 15 and 9 days before first ovulation and averaged 16 μg/l (days −15 to −9). A shift in LH level, to a mean of 31 μg/l, was seen on day −8, whereafter LH concentrations increased gradually. Basal LH values of < 10 μg/l were only found until day −4.
The finding that LH values increased with age was confirmed by data from rats bled twice with an interval of ≥ 3 days between bleedings. Furthermore, both in rats bled twice at 11.00 h and in rats bled twice at 15.00 h LH concentrations were significantly higher in the second sample.
Both morning (11.00 h) and afternoon (15.00 h) LH concentrations in rats bled once also indicated a rise in LH concentrations with age but it became apparent that only morning values showed a shift in LH concentration (from ∼ 15 to ∼42 μg/l) from day −9 to day −8. In contrast, mean afternoon values showed a gradual increase from day −15 on. From day −8 on the number of rats with LH values ≥50 μg/l increased, and from day −5 on they were more frequent at 15.00 than at 11.00 h.
Thus a clear increase in LH secretion, most likely of a pulsatile nature, was found in the female rat approaching puberty. The correlation in time and possible functional relationship with late-prepubertal follicular growth is discussed.
Differences in prostaglandin E2, prostaglandin F2α and prostacyclin contents and their response to thyrotrophin stimulation and in prostaglandin-stimulated cyclic AMP response in normal and Graves's thyroid slices
Authors: Takasu Nobuyuki , Takahashi Kazunori , Ishigami Tatsuro , Yamada Takashi , Sato Seiya 
Published: December 2008

The human thyroid contained prostaglandin (PG) E2, PGF2α and 6-oxo-PGF1α, an end-metabolite of prostacyclin (PGI2), the 6-oxo-PGF1α content being the highest of these prostaglandins. Graves's thyroid contained a significantly higher amount of PGF2α and lower amounts of PGE2 and 6-oxo-PGF1α than the normal thyroid. Thyrotrophin acutely augmented the thyroid contents of PGE2, PGF2α and 6-oxo-PGF1α. The TSH-stimulated increases in PGE2 and 6-oxo-PGF1α were lower but the TSH-stimulated increase in PGF2α was significantly higher in Graves's thyroid than in the normal thyroid. Prostaglandin E2 and PGI2 stimulated human thyroid cyclic AMP synthesis, with the magnitudes of PGE2-and PGI2-stimulated increases in cyclic AMP being equal in normal and Graves's thyroid. Prostaglandin E2α did not stimulate cyclic AMP synthesis significantly.
These results provide evidence that prostaglandins play important roles in thyroid physiology and the pathophysiology of Graves's disease.
Effects of prolactin on testicular functions using an intratesticular pituitary graft
Authors: Weber R. F. A. , Ooms M. P. , Vreeburg J. T. M. 
Published: December 2008

Pituitary glands were grafted under the capsule of the left testis of rats to induce high levels of prolactin in this organ. One hundred days after implantation, significantly increased levels of prolactin were found in the tissue and the venous plasma of the left testis. Although the levels of testosterone in testicular venous plasma were not raised, the testicular content of testosterone was increased when compared to the right testis. The ratio of testosterone and dihydrotestosterone was not affected in the pituitary-grafted testis.
Since the seminiferous tubules adjacent to the pituitary graft appeared to be completely normal, it is concluded that in the rat high levels of prolactin have no direct inhibitory effect on testicular functions.
Effects of long-term treatment with LH on induction of cyclic ovarian activity in seasonally anoestrous ewes
Authors: McNatty K. P. , Hudson N. , Gibb M. , Ball K. , Fannin J. , Kieboom L. , Thurley D. C. 
Published: December 2008

ABSTRACT
The aim of the present study was to establish whether cyclic ovarian activity could be induced and then maintained in anoestrous Romney ewes by the long-term administration of regular intravenous pulses of LH (10 μg ovine LH i.v. once every 1 or 2 h for 29–91 days). The LH pulse regimen was designed to generate plasma profiles of LH that were comparable to those experienced during the luteal and follicular phases of the oestrous cycle.
The results showed that the LH treatments were capable of inducing cyclic ovarian activity, as assessed from the concentrations of progesterone in plasma, but that the treatments were inadequate for sustaining cyclic activity beyond two consecutive progestational phases. After 35–56 days of treatment, the plasma concentrations of FSH declined significantly (P <0·05) relative to those in the untreated animals. These data suggest that FSH supplementation as well as LH might be required for the long-term maintenance of cyclic ovarian activity in seasonally anoestrous ewes.
J. Endocr. (1984) 100, 67–73
Aldosterone effects on water and electrolyte metabolism
Authors: Kenyon C. J. , Saccoccio N. A. , Morris D. J. 
Published: December 2008

ABSTRACT
The effects of constant infusions of small doses of adrenal steroid hormones on sodium, potassium and water metabolism were studied in male adrenalectomized rats. An infusion of 1 μg aldosterone/day was sufficient to restore normal sodium and potassium balance in a group of rats fed an unsupplemented diet. Log doses of aldosterone (0·1–10 μg/day for 4 days) administered some days after adrenalectomy caused linear increases in the body weight of rats fed a sodium-supplemented diet (0·05 m-NaCl as drinking fluid) during 4 days of treatment. Increases in body weight correlated with renal sodium and water balance.
When steroid treatment was started at the time of adrenalectomy, sodium balance was not significantly affected although rats treated with 1 μg aldosterone/day ate more, drank less saline, produced a smaller volume of urine of greater osmolarity and gained more weight than controls. A dose of 100 μg 18-hydroxy-deoxycorticosterone/day had no significant effects. Fluid intake and urine volume were not significantly affected by 1 mg corticosterone/day but food intake, water balance and weight gain were greater than controls. Rats treated with both aldosterone and corticosterone showed a decrease in free water clearance. Aldosterone and corticosterone, both singly and in combination, reduced plasma potassium levels. Plasma sodium levels were only increased when aldosterone was administered on its own.
Long-term steroid infusions have revealed more about the physiology of aldosterone action than could acute measurements of renal function. In particular, they have indicated that dietary intake of electrolytes as well as excretion are affected, that mineralocorticoid actions are distinct from glucocorticoid actions and that there are transient effects of aldosterone on fluid regulation which are not sustained under steady-state conditions.
J. Endocr. (1984) 100,93–100
Modulation of rat pituitary gonadotrophin secretion by porcine granulosa cell 'inhibin', LH releasing hormone and sex steroids in rat anterior pituitary cells in culture
Authors: Massicotte J. , Lagacé L. , Godbout M. , Labrie F. 
Published: December 2008

ABSTRACT
The incubation of female rat adenohypophysial cells in primary culture with porcine granulosa cell culture medium (GCM) led to the complete inhibition of responses of LH and FSH to LH releasing hormone (LHRH) as well as to the inhibition of spontaneous release of FSH. These effects of GCM suggest the specificity of the 'inhibin'-like activity of this material. Granulosa cell culture medium completely reversed the stimulatory effect of oestradiol-17β on the responses of LH and FSH to LHRH, as well as reversing the stimulatory effect of progesterone, oestradiol or a combination of both steroids on the spontaneous release of FSH, while not affecting the spontaneous release of LH. The antioestrogenic effects of progesterone observed on the response of LH to 0·3 nm-LHRH were amplified in the presence of GCM while the stimulatory effects of progesterone, oestradiol or both on the response of FSH to 0·3 nm-LHRH were completely reversed by the medium. Moreover, the presence of GCM led to an additive inhibitory effect with dihydrotestosterone on the response of LH to LHRH while it completely reversed the stimulatory effect of the androgen on spontaneous and LHRH-induced FSH release. The present data show that the presence of porcine granulosa cell 'inhibin' activity can exert marked interactions with sex steroids in the control of gonadotrophin secretion. This 'inhibin' activity reversed all the stimulatory effects and potentiated all the inhibitory effects of sex steroids on gonadotrophin secretion. Although the physiological role of 'inhibin' remains to be defined well, the importance of this activity is clearly demonstrated in anterior pituitary cells in culture.
J. Endocr. (1984) 100, 133–140
Plasma concentrations of oestradiol and oestrone during perinatal development in male and female ferrets
Authors: Erskine M. S. , Baum M. J. 
Published: December 2008

ABSTRACT
The concentrations of oestradiol and oestrone in peripheral plasma of male and female ferrets 5 days before and 7, 15 and 30 days after birth were measured. Both steroids were present in high concentrations prenatally. Much lower levels were found in samples collected on day 7 and later, when the concentrations were similar to those of adult gonadectomized animals. No significant sex difference was seen for the concentration of either steroid at any age studied. These results, and those previously reported showing the absence of a circulating binding protein and the presence of oestradiol receptors in the hypothalamus in the perinatal period in this species, suggest that brains of both males and females are exposed to significant amounts of oestrogen during development. These findings lend support to the possibility that prenatal exposure to oestrogen plays a role in organizing the potential for female behaviour in male and female ferrets.
J. Endocr. (1984) 100, 161–166
Effects of gonadectomy on seasonal changes in plasma LH and prolactin concentrations in male and female starlings (Sturnus vulgaris)
Authors: Dawson A. , Goldsmith A. R. 
Published: December 2008

ABSTRACT
Intact and gonadectomized male and female starlings (Sturnus vulgaris) were held in outdoor aviaries for 1 year. Blood samples were taken frequently and assayed for LH and prolactin, and intact males were laparotomized to determine testis size.
Changes in testis size in intact males were similar to those in wild starlings with maximum size during April. Hormone levels in intact males and females also followed a similar pattern to those in wild birds although absolute levels were somewhat lower. Levels of LH increased during spring, were highest in early May and then declined rapidly as birds became photorefractory. Prolactin levels did not begin to increase until April, reached a peak in late May and then declined. In gonadectomized males and females, high levels of LH were maintained throughout the early part of the year when birds were photosensitive, but declined rapidly as they became photorefractory. This occurred at the same time as in intact birds. During photorefractoriness, LH levels in gonadectomized birds were similar to those in intact birds. Prolactin showed the same seasonal pattern in gonadectomized birds as that in intact birds. These results demonstrate that gonadal steroid feedback is unimportant in initiating and maintaining photorefractoriness and confirm that increased prolactin secretion coincides with the onset of photorefractoriness.
J. Endocr. (1984) 100, 213–218
Relationship between endogenous opioids and the oestrous cycle in the rat
Authors: Hulse G. K. , Coleman G. J. , Copolov D. L. , Clements J. A. 
Published: December 2008

ABSTRACT
The aim of this study was twofold: (1) to document changes in levels of immunoreactive β-endorphin (Ir-β-EP) in the hypothalamus, anterior pituitary gland, neurointermediate lobe and plasma during the oestrous cycle of the rat and (2) to investigate stress-induced changes in plasma Ir-β-EP at different stages of the oestrous cycle. Evidence was found that Ir-β-EP levels in the hypothalamus, anterior pituitary gland and plasma are not constant during the oestrous cycle and that the Ir-β-EP response to stress is a function of the phase of the oestrous cycle at which stress is applied. It is suggested that fluctuations in ovarian hormones may influence oestrous Ir-β-EP levels both under normal conditions and after exposure to stress.
J. Endocr. (1984) 100, 271–275
In-vivo and in-vitro secretion of prolactin by lactating rat adenohypophyses as a function of intracellular age
Authors: Mena F. , Martínez-Escalera G. , Clapp C. , Grosvenor C. E. 
Published: December 2008

ABSTRACT
Adenohypophysial prolactin of lactating rats was pulse-labelled by [3H]leucine injected i.v. at the time of removal of the pups. The [3H]prolactin concentration in the pituitary gland, analysed by polyacrylamide-gel electrophoresis, progressively fell as the time from labelling to removal of the pituitary gland increased from 8 to 24 h, which suggests that there was a loss of hormone as it aged within the gland. Suckling effectively provoked the depletion–transformation of total and [3H]prolactin (extracted at pH 7·2) when applied after 8 h but not when applied after either 16 or 24 h after removing the pups.
In rats whose pups were removed for 8 h, suckling also depleted–transformed [3H]prolactin labelled 4 h, but not that labelled 1 h before suckling. The pituitary glands of other lactating rats were labelled with [3H]leucine injected i.v. at various times before removing the glands and incubating them in medium 199. The secretion into the medium of [3H]prolactin labelled either 4, 8, 16 or 24 h beforehand was maximal during the first 30 min then declined from 30 to 240 min of incubation. However, secretion of prolactin labelled 1 h and 10 min beforehand reached a maximum after 0·5–1 h and 2 h of incubation respectively, then remained constant during the remainder of the 4-h incubation period. The total 4-h secretion of [3H]prolactin was greatest (65% of preincubation concentration) from those glands labelled 4 h before in contrast to those labelled 10 min (15%) or 1 (38%), 8 (34%), 16 (18%) or 24 h (26%) before incubation. Taken together, these data suggest that prolactin synthesized 4 h earlier is more likely to be released in response to physiological stimuli than is more recently formed prolactin or prolactin which has remained in the pituitary gland for 16 h or longer.
J. Endocr. (1984) 101, 27–32
Development of a microtitre plate enzyme immunoassay for the determination of progesterone
Authors: Munro C. , Stabenfeldt G. 
Published: December 2008

ABSTRACT
A rapid, solid-phase microtitre plate enzyme immunoassay (EIA) for progesterone is described using progesterone 3-O-carboxymethyloxime–horseradish peroxidase as the label and an antiserum raised in rabbits to a progesterone 11α-hemisuccinyl–bovine serum albumin immunogen. A competitive reaction was used with a reaction time of 2 h. Antibody-bound and free steroid were separated in a simple washing step of the antibody-adsorbed well surface. 2,2′-Azino-di-(3-ethylbenzthiazoline sulphonic acid) diammonium salt was used as the substrate with a reaction time of 1 h. A lower limit of sensitivity of 0·25 pg/well was obtained with the response being linear (logit/log) through 1000 pg/well. Results obtained by EIA and radioimmunoassay in several species gave excellent agreement (r = 0·98). This assay system allows accurate determination of progesterone in plasma with good specificity, precision and accuracy, and is suitable for the rapid assessment of luteal function and reproductive status in both clinical and research situations in a wide variety of species.
J. Endocr. (1984) 101, 41–49
Development and characterization of a radioimmunoassay to measure human tissue kallikrein in biological fluids
Authors: Bagshaw A. F. , Bhoola K. D. , Lemon M. J. C. , Whicher J. T. 
Published: December 2008

ABSTRACT
A direct radioimmunoassay has been developed to measure tissue kallikrein in human biological fluids. These fluids include serum, plasma, urine, pancreatic juice and saliva. Purified kallikreins from human urine and human saliva were used to raise rabbit antibody and each was labelled with Na125I for use in the radioimmunoassay. A comparison of the different antigen-antibody systems was then made. Bound and free enzyme were separated by a double-antibody technique. The usable range of the standard curve was from 2·5 to 100 μg kallikrein/l. The intra-assay coefficient of variation was 4·7%, the interassay coefficient of variation 8·9% and the recoveries of purified kallikrein added to the samples were 99·3, 96·0, 110·8 and 81·2% for urine, saliva, serum and plasma respectively.
Parallel dilution curves were obtained for serum and plasma, as well as for urine, saliva and pancreatic juice. However, plasma anticoagulated with EDTA or heparin gave consistently lower values than serum, when measured in the radioimmunoassay. From eight different subjects plasma (EDTA) values were on average 50% lower than those of serum. Experiments designed to determine the cause of this difference revealed that treatment of blood with some anticoagulants, in particular heparin and EDTA, resulted in a marked reduction in the amount of measurable tissue kallikrein.
J. Endocr. (1984) 101, 173–179
Effect of immunoneutralization of LH releasing hormone on LH, FSH and ovarian steroid secretion in the preovulatory phase of the oestrous cycle in the ewe
Authors: McNeilly A. S. , Fraser H. M. , Baird D. T. 
Published: December 2008

ABSTRACT
Immunoneutralization of LH releasing hormone (LHRH) by the i.v. administration of LHRH antiserum in the preovulatory period in the ewe resulted in a prompt abolition of the pulsatile secretion of LH without alteration of basal plasma levels of LH. This resulted in an immediate cessation of the pulsatile secretion of ovarian oestradiol, with no change in the secretion rate of androstenedione or plasma levels of FSH. The ovarian secretion rate of testosterone increased significantly.
Twenty to 22 h after the injection of LHRH antiserum, pulsatile secretion of LH and ovarian oestradiol and androgen secretion remained suppressed while plasma levels of FSH had increased significantly. The bolus injection of ovine LH (10 μg, i.v.) at this time caused a significant increase in oestradiol, androstenedione and testosterone, these responses being inversely related to the titre of LHRH antiserum in the plasma at this time.
These results show that (1) the secretion of oestradiol from the preovulatory sheep follicle is entirely dependent on the pulsatile secretion of LH and (2) since the secretion of ovarian androgens was not inhibited, LH may exert a short-term control over the aromatase enzyme system controlling the conversion of androgen to oestrogen in the granulosa cell of the preovulatory sheep follicle.
J. Endocr. (1984) 101, 213–219
Results of cyproheptadine treatment in dogs with pituitary-dependent hyperadrenocorticism
Authors: Stolp R. , Croughs R. J. M. , Rijnberk A. 
Published: December 2008

ABSTRACT
Administration of cyproheptadine for 2 months to five dogs with pituitary-dependent hyperadrenocorticism (PDH) at a dose rate of 0·3 mg/kg per 24 h (group 1) and to four dogs with PDH at a dose rate of 1 mg/kg per 24 h (group 2) did not result in any clinical improvement. The hyperadrenocorticoid state, as indicated by the circulating cortisol levels, the urinary corticosteroid excretion and the response of the hypothalamo-pituitary-adrenal axis to lysine-vasopressin, thyrotrophin releasing hormone and dexamethasone did not change consistently, although there was a tendency to normalization of some parameters in the dogs of group 2. However, these changes were not found to be consistent for each individual dog but were limited to one parameter per dog. It is concluded that cyproheptadine is not suitable for the treatment of PDH in the dog.
J. Endocr. (1984) 101, 311–314