bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cortisol stimulates whole body calcium uptake and the branchial calcium pump in freshwater rainbow trout
Authors: Flik G. , Perry S. F. 
Published: December 2008

ABSTRACT
Exposure of rainbow trout to a reduced ambient calcium level (from 490 to 25 μmol Ca2+/l) caused hypocalcaemia and induced a rapid increase (within 1 h) in systemic cortisol levels. Under conditions of low environmental calcium concentrations, cortisol levels remained increased for at least 8 days. After this time the in-vitro Ca2+-transport capacity of branchial basolateral membrane vesicles was increased due to stimulation of Ca2+-ATPase activity, presumably as a result of chloride cell proliferation. Pituitary prolactin cells were unaffected by low ambient calcium levels. Fish kept in water containing 490 μmol Ca2+/l and treated with cortisol for 7 days displayed an increase in whole body calcium uptake and an enhancement of the branchial calcium transport capacity; concomitantly, hypercalcaemia was observed. We conclude that, in the rainbow trout, cortisol exerts hypercalcaemic effects by stimulating Ca2+ uptake from the water and that this effect forms an intrinsic part of the established mineralocorticoid action of cortisol in fish.
Journal of Endocrinology (1989) 120, 75–82
Osteocalcin during the reproductive cycle in normal and diabetic rats
Authors: Verhaeghe J. , Van Herck E. , Van Bree R. , Van Assche F. A. , Bouillon R. 
Published: December 2008

ABSTRACT
Concentrations of osteocalcin were measured in plasma and bone of normal and diabetic rats during the reproductive cycle and compared with plasma 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) concentrations. The age-dependence of osteocalcin was also examined. Plasma concentrations of osteocalcin levels were low but detectable in 21-day-old fetuses (3·7 ± 0·3 nmol/l); osteocalcin concentrations were highest in weaning rats (104 ± 9 nmol/l) and decreased thereafter. In adult rats, plasma concentrations of both osteocalcin and 1,25-(OH)2D3 increased during the last days of normal pregnancy, and even more so in rats fed a diet low in calcium and phosphate. After an early post-partum decline, osteocalcin concentrations in plasma remained at non-pregnant levels in lactating rats fed a high calcium/phosphate diet while their 1,25-(OH)2D3 concentrations were higher than in non-pregnant rats; however, lactating rats fed a low calcium/phosphate diet showed increasing osteocalcin concentrations.
In spontaneously diabetic BB rats, plasma osteocalcin concentrations were severely decreased compared with those in non-diabetic rats, more than would have been expected from their decreased 1,25-(OH)2D3 concentrations. Moreover, plasma osteocalcin did not increase during pregnancy or lactation in diabetic rats, even when fed a low calcium/phosphate diet. Fetuses of diabetic rats also had lower plasma osteocalcin levels than fetuses from non-diabetic rats or than weight-matched fetuses from semistarved rats. In contrast to plasma osteocalcin concentrations, bone osteocalcin concentrations and content were not altered by pregnancy, lactation, low calcium/phosphate diet or diabetes.
These data show that plasma osteocalcin concentrations change during the reproductive period in normal rats but not in diabetic rats, and that osteocalcin levels do not seem to be regulated solely by 1,25-(OH)2D3.
Journal of Endocrinology (1989) 120, 143–151
Vulnerability of the human Leydig cell to radiation damage is dependent upon age
Authors: Shalet S. M. , Tsatsoulis A. , Whitehead E. , Read G. 
Published: December 2008

ABSTRACT
Testicular function was studied in three groups of patients previously treated for malignant disease, and a control group of adult males. The adult patients in groups one and two underwent unilateral orchidectomy for a testicular tumour but only in group two was this followed by post-operative high-dose irradiation (30 Gy) to the remaining testis. Four of the five boys in group three had a unilateral orchidectomy between the ages of 1 and 4 years and all five received a similar dose of irradiation (27·5–30 Gy) to the scrotum as in group two. The five subjects in group three were studied between the ages of 12 and 34 years.
In group one the median basal testosterone level (16·0 nmol/l) was normal and the basal gonadotrophin levels mildly but significantly increased, reflecting a resetting of the pituitary-testicular axis following unilateral orchidectomy. In group two the median basal testosterone level (12·5 nmol/l) was significantly lower and the median basal FSH and LH levels were significantly higher than the respective values in group one, indicating that irradiation to the testis in adult life may damage both the germinal epithelium and the Leydig cells. All five males in group three showed grossly increased FSH and LH levels, with a median basal testosterone level (< 2·5 nmol/l) significantly lower than groups one and two. None of the five showed a testosterone response to a stimulation test with human chorionic gonadotrophin or underwent puberty spontaneously.
The severe reduction in testosterone levels in group three compared with group two, despite the similarity of radiation dose received, suggests a much greater vulnerability to radiation-induced Leydig cell damage in the prepubertal boy compared with the adult male.
Journal of Endocrinology (1989) 120, 161–165
Multiple forms of rat prolactin and growth hormone in pituitary cell subpopulations separated using a Percoll gradient system: disulphide-bridged dimers and glycosylated variants
Authors: Bollengier F. , Velkeniers B. , Hooghe-Peters E. , Mahler A. , Vanhaelst L. 
Published: December 2008

ABSTRACT
Prolactin and GH cells from rat pituitary glands were separated into three main fractions on discontinuous Percoll gradient layers. SDS-PAGE and subsequent immunoblotting of these fractions revealed that: (1) multiple rat prolactin (rPRL) molecular variants were present in total culture, Percoll layer 1 and 2; four variants were clear-cut: Mr ∼23 000, Mr doublet ∼25 000–26 000, Mr ∼40 000 and Mr ∼42 000; (2) cell cytosol from Percoll gradient layer 1 was particularly enriched in prolactin; (3) cells from gradient layer 1 secreted into the culture medium only prolactin in detectable amounts; (4) three distinct molecular forms of rat growth hormone (rGH) were recorded in layer 3: Mr ∼36 000,24 000 and 20 000; the 20 000 variant was paramount; and (5) cells from layer 3 secreted both rPRL and rGH into the culture medium.
Reduction experiments showed that, on the one hand, 42 000 and 40 000 rPRL variants and, on the other hand, 36 000 rGH variants are disulphide-bridged dimers. An important finding was the presence of glycosylated rPRL and rGH: indeed Concanavalin A–Sepharose 4B affinity chromatography indicated that 26 000 rPRL and 24 000 rGH display a very strong affinity for lectin. Competitive inhibition tests showed that this affinity is specific and not due to hydrophobic binding. When rPRL was submitted to deglycosylation in conditions specific for O-linked glycoproteins, the 26 000 rPRL variant disappeared. The biological role of glycosylated rPRL is as yet unknown.
Journal of Endocrinology (1989) 120, 201–206
Interstitial fluid volume in the rat testis: androgen-dependent regulation by the seminiferous tubules?
Authors: Maddocks S. , Sharpe R. M. 
Published: December 2008

ABSTRACT
Regulation of testicular interstitial fluid (IF) volume has been investigated in adult male rats in which the Leydig cells were selectively destroyed with a single i.p. injection of ethane dimethane sulphonate (EDS). Following this treatment, some animals also received testosterone supplementation by s.c. injection every 3 days, beginning either from the time of EDS injection, or 3–12 days afterwards. The volume of IF obtained by drip collection was determined, and testosterone and gonadotrophin concentrations measured in blood and in IF. Testosterone levels in IF and serum became undetectable by 3 days after EDS treatment. IF volume was reduced by 50% (P < 0·01) to reach a minimum level between 6 and 9 days after treatment. However, this decline was prevented in the absence of Leydig cells by supplementation with testosterone from the time of EDS injection, a treatment which also kept gonadotrophins at minimum or undetectable levels. Furthermore, the reduced IF volume seen up to 9 days after treatment with EDS alone could be restored to control levels within 3 days by a single injection of testosterone. The results obtained demonstrate that androgens, but not Leydig cells or gonadotrophins, are required for the maintenance of interstitial fluid volume in the adult rat testis. It is suggested that the seminiferous tubules may mediate this response, through an androgen-dependent mechanism.
Journal of Endocrinology (1989) 120, 215–222
An acid-stable insulin-like growth factor (IGF)-binding protein from pig serum inhibits binding of IGF-I and IGF-II to vascular endothelial cells
Authors: Gopinath R. , Walton P. E. , Etherton T. D. 
Published: December 2008

ABSTRACT
The effects of a porcine insulin-like growth factor (IGF)-binding protein on binding of IGF-I and IGF-II to porcine aortic endothelial cells (PAEC) were determined. Binding of 125I-labelled IGF-I and -II to IGF receptors was inhibited by IGF-binding protein. IGF-binding protein inhibited binding of IGF-I and -II in a dose-dependent manner with half-maximal inhibition occurring at 5·43 and 108 μg/l respectively. A125I-labelled IGF-I–IGF-binding protein complex, formed by incubating 125I-labelled IGF-I with IGF-binding protein overnight at 4 °C, did not effectively bind to endothelial IGF receptors. Addition of IGF-binding protein to PAEC previously incubated with IGF-I caused a marked dissociation of bound IGF-I (47% dissociation within 12 h). These results indicate that the acid-stable IGF-binding protein which appears to be a part of the 150 kDa GH-dependent binding protein, blocks binding of IGF-I and -II by the IGF receptors and appears to exhibit a higher affinity for IGF-I than the endothelial type-I IGF receptor. The ramifications of this latter point with respect to transfer of circulating IGFs (bound to their IGF-binding proteins) across the vascular endothelium are not clear.
Journal of Endocrinology (1989) 120, 231–236
Role of the adrenal cortex in chronic stress-induced inhibition of prolactin secretion in male rats
Authors: López-Calderón A. , Ariznavarreta C. , Calderón M. D. , Tresguerres J. A. F. , Gonzalez-Quijano M. I. 
Published: December 2008

ABSTRACT
The response of prolactin to chronic stress in intact, adrenalectomized and adrenomedullectomized male rats was studied. Immobilization stress in intact animals induced a significant increase in plasma concentrations of prolactin after 20 and 45 min and a significant decrease when the rats were submitted to chronic restraint (6 h daily for 4 days). Five weeks after adrenomedullectomy, plasma prolactin and corticosterone responses to chronic stress were not modified. In contrast, the inhibitory effect of chronic stress on prolactin secretion was totally suppressed by adrenalectomy. When treated with dexamethasone during the 4 days of restraint, adrenalectomized stressed rats showed similar plasma concentrations of prolactin to the intact stressed rats. These data indicate that the adrenal cortex is able to play an inhibitory role on prolactin secretion during stress only through a prolonged release of glucocorticoids.
Journal of Endocrinology (1989) 120, 269–273
Circulating reproductive hormones and hypothalamic oestradiol and progestin receptors in infertile Zucker rats
Authors: Whitaker E. M. , Robinson A. C. 
Published: December 2008

ABSTRACT
Plasma concentrations of LH, FSH, prolactin and progesterone were measured during the oestrous cycle in obese (fa/fa) and non obese (Fa/?) Zucker rats. In obese rats the mid-afternoon surge of LH during prooestrus was reduced compared with that in non-obese rats (P<0.05), and the maximum concentrations of FSH and prolactin declined more slowly during oestrus. Progesterone concentrations were higher during most of the oestrous cycle in obese rats. Oestradiol and progestin receptors were measured in the hypothalamus of female Zucker rats. Lower concentrations of oestradiol receptors were found in the preoptic area of obese rats (P<0.05). Concentrations of oestradiol receptors in the medial basal hypothalamus were also lower in obese rats, though the difference was not statistically significant. Concentrations of progestin receptors were similar in both phenotypes in the preoptic area and media basal hypothalamus. It seems likely that the abnormalities in reproductive hormones and oestradiol receptors contribute to the infertility of obese female Zucker rats. The underlying mechanism has still to be determined.
Journal of Endocrinology (1989) 120, 331–336
The effect of a 72-h fast on plasma levels of pituitary, adrenal, thyroid, pancreatic and gastrointestinal hormones in healthy men and women
Authors: Beer S. F. , Bircham P. M. M. , Bloom S. R. , Clark P. M. , Hales C. N. , Hughes C. M. , Jones C. T. , Marsh D. R. , Raggatt P. R. , Findlay A. L. R. 
Published: December 2008

ABSTRACT
Seventeen human subjects fasted without electrolyte replacement for 3 days and hormone levels were measured before, during and after the fast. Immediate consequences of the fasting state in healthy human subjects include a marked increase in plasma cortisol, ACTH, β-endorphin, β-lipotrophic hormone, adrenaline, noradrenaline and dopamine. Levels of all these hormones were much greater on the first morning of the fast than in the post-prandial state, even though the plasma glucose level was no lower than that observed on the morning before the fast began. A clear fall in TSH and tri-iodothyronine (T3) levels was observed, but thyroxine levels did not change significantly. Insulin levels fell whereas proinsulin levels did not fall during the fast, though they did rise markedly upon re-feeding. An increase in GH levels was particularly apparent in male subjects, but was also seen in females when evening samples were compared. Pancreatic glucagon showed a modest rise during the fast, but fell again on refeeding; total glucagon also rose as the fast proceeded, but increased markedly upon re-feeding. Levels of gastrin and peptide YY remained low during the fast. Plasma electrolyte levels were unchanged. The following were closely correlated: cortisol with ACTH, T3 with log10TSH, dopamine with noradrenaline, and (negatively, during the fast) pancreatic glucagon with glucose.
Journal of Endocrinology (1989) 120, 337–350
Characterization of insulin-like growth factor binding proteins in ovine tissue fluids
Authors: Hodgkinson S. C. , Moore L. , Napier J. R. , Davis S. R. , Bass J. J. , Gluckman P. D. 
Published: December 2008

ABSTRACT
Competitive tracer binding studies using radio-iodinated insulin-like growth factor-I and -II (125I-labelled IGF-I and 125I-labelled IGF-II) together with size exclusion chromatography and IGF-I affinity chromatography have been used to characterize IGF binding protein activity in ovine tissue fluids. Binding proteins of >200, 150 and 40–50 kDa were revealed in these studies and shown to be widely distributed in body fluids. Thus, the > 200 kDa binding protein, which is IGF-II specific, is present in plasma from mature sheep, colostrum and follicular fluid as well as fetal sheep plasma. This may be the ovine equivalent of the soluble type-2 IGF receptor recently identified in rat serum. The presence of a 150 kDa binding protein, of mixed specificity for IGF-I and IGF-II, in fetal and mature sheep plasma was confirmed in these studies. This protein, previously believed to be restricted to vascular fluids, was also identified in mammary lymph, follicular fluid and as a minor component in vitreous humor. Binding proteins of 40–50 kDa were revealed in every fluid tested and multiple variants with distinct specificities were also suggested. This was investigated by IGF-I affinity chromatography using mature sheep plasma. Following passage through the affinity adsorbent, binding of 125I-labelled IGF-I to proteins in the 40–50 kDa region was abolished but when 125I-labelled IGF-II was used as tracer, a binding protein of 40–50 kDa was still observed.
Thus sheep plasma contains at least two 40-50 kDa binding proteins. The competitive tracer binding studies indicated that one such protein demonstrates mixed specificity for IGF-I and -II while the other strongly favours IGF-II.
Journal of Endocrinology (1989) 120, 429–438
Maternal pinealectomy abolishes the diurnal rhythm in plasma melatonin concentrations in the fetal sheep and pregnant ewe during late gestation
Authors: McMillen I. C. , Nowak R. 
Published: December 2008

ABSTRACT
We have investigated the effect of pinealectomy of ewes in pregnancy on the presence of the diurnal rhythm in fetal and maternal plasma concentrations of melatonin. Six ewes were pinealectomized between 104 and 118 days of gestation. Fetal and maternal blood samples were collected during 24-h periods between 125 and 140 days of gestation in the pinealectomized ewes and in an intact control (n = 4). There was a significant diurnal rhythm in both fetal and maternal plasma concentrations of melatonin in the control group. In this group, the fetal and maternal plasma melatonin concentrations were significantly higher in the dark (128·4±6·2 and 192·2± 10·7 pmol/l respectively) than in the light (46·2 ± 4·2 and 25·8 ± 2·1 pmol/l respectively). However there was no diurnal rhythm in either the fetal or maternal plasma melatonin concentrations in the pinealectomized group between 125 and 140 days of gestation. In contrast to the control animals, there was also no light–dark difference in the fetal or maternal plasma melatonin concentrations in four pinealectomized animals sampled frequently in the 3–7 days preceding delivery (mean length of gestation 146·5 days). However, in the pinealectomized sheep there was a gradual increase in the combined light–dark fetal plasma melatonin concentrations during late gestation from 27·9 ± 2·8 pmol/l (at 15–20 days before delivery) to 95·2± 14·1 pmol/l on the day of delivery.
We have therefore demonstrated that the maternal pineal is the major source of the diurnal rhythm in maternal and fetal plasma melatonin concentrations. However maternal pinealectomy does not appear to remove all the melatonin immunoreactivity from the maternal and fetal plasma in late gestation.
Journal of Endocrinology (1989) 120, 459–464
Effects of ethanol and inhibitors of its metabolism on the circulating levels of Met-enkephalin in greyhounds
Authors: Medbak S. , Mason D. F. J. , Rees L. H. 
Published: December 2008

ABSTRACT
The mechanisms involved in the release of Metenkephalin-like immunoreactivity (MLI) into the circulation following oral administration of ethanol and chlorpropamide were investigated in dogs. The origin of plasma MLI and the sites where it may be metabolized were also studied. Moreover, the molecular nature of circulating MLI was characterized.
In conscious animals oral administration of ethanol (0·15 ml/kg) led to a significant (P<0·01) rise in plasma MLI concentrations in chlorpropamidepretreated animals from a basal level of 43 ± 6 (mean ± s.e.m.) to a peak of 66 ± 8 ng/l. Similar rises in MLI concentrations were observed following administration of ethanol with disulfiram and ethanol with chlorpropamide and captopril. In contrast, the administration of ethanol alone or ethanol with 4-methylpyrazole resulted in a decrease in plasma MLI concentrations.
Comparisons of two different doses of i.v. acetaldehyde, the first metabolite of ethanol, showed that plasma MLI concentrations rose significantly (P<0·05) only after the larger dose (8 mg/kg), rising from 45±7 to 81 ± 18 ng/l. These results suggest that acetaldehyde is the active component in the chlorpropamide+ ethanol-induced MLI secretion.
Plasma MLI was also measured following acetaldehyde infusion in adrenalectomized dogs with and without hexamethonium treatment. Acute bilateral adrenalectomy resulted in a decrease (P<0·05) in plasma MLI concentrations, but the levels remained detectable. Moreover, subsequent acetaldehyde infusion led to rises in plasma MLI similar to those observed in animals with intact adrenals. These MLI responses were not altered by the concurrent i.v. administration of hexamethonium. Gel filtration chromatography revealed that Met-enkephalin exists in the circulation predominantly in larger molecular forms with approximate sizes of 18 000 and 8000 Da in the basal state, after stimulation and following adrenalectomy.
Journal of Endocrinology (1989) 120, 473–480
Effect of the body condition of ewes on the secretion of LH and FSH and the pituitary response to gonadotrophin-releasing hormone
Authors: Rhind S. M. , McMillen S. , McKelvey W. A. C. , Rodriguez-Herrejon F. F. , McNeilly A. S. 
Published: December 2008

ABSTRACT
The effects of body fat content (body condition) of ewes on hypothalamic activity and gonadotrophin-releasing hormone (GnRH) secretion and on pituitary sensitivity to GnRH were investigated using Scottish Blackface ewes. Two groups of 12 ewes were fed so that they achieved either a high body condition score (2·98, s.e.m. = 0·046; approximately 27% of empty body weight as fat) or a low body condition score (1·94, s.e.m. = 0·031; approximately 19% of empty body weight as fat) by 4 weeks before the period of study. Thereafter, they were differentially fed so that the difference in mean condition score was maintained. Oestrus was synchronized, and on day 11 of the subsequent cycle half of the ewes of each group were ovariectomized. On day 12, the remaining ewes were injected (i.m.) with 100 μg prostaglandin F2α analogue and ovariectomized 30 h later. Numbers of large ovarian follicles and corpora lutea present at ovariectomy were recorded. Blood samples were collected at 15-min intervals for 12 h on day 10 of the cycle (luteal phase) and at 10-min intervals from 24 to 30 h after prostaglandin injection (follicular phase). At days 2 and 7 after ovariectomy, samples were collected at 15-min intervals for 8 h and ewes were then injected with 10 μg GnRH and samples were collected for a further 3 h. Samples were assayed for LH and FSH. Ewes in high body condition had more more large follicles than ewes in low body condition during the luteal phase (15·3 vs 6·5; P < 0·05) and follicular phase (11·5 vs 7·0; NS) and a slightly higher mean ovulation rate (1·50 vs 1·20; NS). However, during the luteal and follicular phases of the cycle before ovariectomy there was no effect of condition score on mean LH or FSH concentrations or mean LH pulse frequency or pulse amplitude. Two days after ovariectomy, ewes of high body condition had a higher mean LH pulse frequency than ewes of low body condition (P < 0·05) and higher mean FSH concentrations (P < 0·05). Mean LH concentration and pulse amplitude were not affected. LH and FSH profiles were not affected by body condition on day 7. GnRH-induced increases in LH and FSH concentrations on days 2 and 7 were not affected by body condition. At day 7, but not day 2, ewes ovariectomized during the luteal phase of the cycle had a significantly (P < 0·05) greater GnRH-induced LH release compared with ewes ovariectomized during the follicular phase. It is concluded that body condition directly affects hypothalamic activity and GnRH secretion, but not pituitary sensitivity to GnRH, and that effects on reproductive performance are also mediated through changes in ovarian hormones or in hypothalamo-pituitary sensitivity to ovarian hormones.
Journal of Endocrinology (1989) 120, 497–502