bluuebunny/crossref_metadata_2025_split huggingface dataset:
The contribution of corticosterone and testosterone to the suppression of serum LH in hyperprolactinaemic adult male rats with pituitary transplants
Authors: Weber R. F. A. , Ooms M. P. , Vreeburg J. T. M. 
Published: December 2008

ABSTRACT
The effects of hyperprolactinaemia on serum levels of LH were investigated in adult male rats of the R × U strain. Hyperprolactinaemia was induced by three pituitary grafts under the kidney capsule, transplanted on day 0 of each experiment. Special attention was paid to the contribution of prolactin-stimulated testes, adrenals and corticosterone.
In experiment 1, hyperprolactinaemia significantly reduced the serum concentrations of LH in intact rats. In spite of a significant increase in the serum levels of corticosterone, serum testosterone was not significantly affected by hyperprolactinaemia. The weights of both the adrenals and accessory sex glands were significantly increased at autopsy. In experiment 2, treatment with 10 mg corticosterone s.c. daily from day 14 to day 28 after pituitary grafting significantly reduced serum levels of both LH and testosterone. The suppression of testosterone in the hyperprolactinaemic corticosterone-treated animals was significantly less than in the corticosterone-treated control animals. The weights of the accessory sex glands were significantly increased in the hyperprolactinaemic animals. In experiment 3, rats were adrenalectomized and half of them were substituted with corticosterone. Serum testosterone levels significantly increased in both hyperprolactinaemic adrenalectomized rats and in adrenalectomized corticosterone-treated animals without any significant effect on serum LH. Again the weights of the accessory sex glands were significantly increased in the hyperprolactinaemic animals. In experiment 4, rats were adrenalectomized, gonadectomized and corticosterone treated on day 0 and then implanted with a 2, 1·5 or 1 cm silicone elastomer capsule containing testosterone. On day 28 after pituitary grafting, LH levels were significantly suppressed in animals with a 2 or 1·5 cm testosterone implant. The weights of the accessory sex glands were not increased in the hyperprolactinaemic animals.
These results show that in the male rat the inhibitory effects of hyperprolactinaemia on serum LH levels may be due to (1) increased sensitivity of the hypothalamic-pituitary axis to the negative feedback action of testosterone by prolactin and by the prolactin-stimulated corticosterone secretion and (2) stimulation of testicular testosterone secretion by prolactin, which can also explain the increased weights of the accessory sex glands. Even in the presence of high serum concentrations of corticosterone, stimulation of testicular testosterone secretion by prolactin was observed.
J. Endocr. (1987) 113,111–116
Autoradiographic localization of binding sites for oxytocin and vasopressin in the rat kidney
Authors: Stoeckel M. E. , Freund-Mercier M. J. , Palacios J. M. , Richard Ph. , Porte A. 
Published: December 2008

ABSTRACT
The distribution of [3H]vasopressin- and [3H]oxytocin-binding sites was examined, using an autoradiographical technique, in the kidney of Long–Evans and Brattleboro rats. Two types of binding sites with affinities in the nanomolar range were detected: one, located on glomeruli, bound both vasopressin and oxytocin; the other, on collecting ducts, bound vasopressin selectively. In the presence of 10 μmol oxytocin/1, [3H]vasopressin labelling was abolished in glomeruli, but only reduced in collecting ducts; [3H]oxytocin labelling was completely abolished by 10 μmol vasopressin/1. These observations are discussed in relation to known effects of neurohypophysial hormones on renal physiology.
J. Endocr. (1987) 113, 179–182
Peripheral plasma concentrations of pregnenolone sulphate, pregnenolone, progesterone and 20α-hydroxy-4-pregnen-3-one in ewes throughout the oestrous cycle
Authors: McKay S. A. , Jenkin G. , Thorburn G. D. 
Published: December 2008

ABSTRACT
Pregnenolone sulphate, pregnenolone, progesterone and 20α-hydroxy-4-pregnen-3-one concentrations in peripheral plasma of normal cyclic ewes were measured by radioimmunoassay. The concentrations of these steroids were correlated with that of progesterone. The concentrations of all the steroids measured in peripheral plasma varied in a cyclic manner and showed a significant (P <0·05) positive correlation with the concentration of progesterone.
Peripheral plasma concentrations of these steroids in ovariectomized and ovariectomized, dexamethasone-treated ewes were also determined. The plasma concentration of progesterone in ovariectomized ewes was undetectable but the concentrations of pregnenolone sulphate, pregnenolone and 20α-hydroxy-4-pregnen-3-one remained similar to those observed at oestrus. Administration of dexamethasone to ovariectomized ewes had no effect on pregnenolone sulphate or pregnenolone concentrations but 20α-hydroxy-4-pregnen-3-one concentrations, which were already very low, decreased further.
It is proposed that the ovary, probably the corpus luteum, secretes pregnenolone sulphate, pregnenolone and 20α-hydroxy-4-pregnen-3-one; however, pregnenolone sulphate and 20α-hydroxy-4-pregnen-3-one may also arise from the metabolism of circulating pregnenolone and progesterone.
J. Endocr. (1987) 113, 231–237.
Stimulation of intestinal epithelial cell proliferation in culture by growth factors in human and ruminant mammary secretions
Authors: Corps A. N. , Brown K. D. 
Published: December 2008

ABSTRACT
Samples of human and ruminant mammary secretions stimulated the proliferation of rat intestinal epithelial (RIE-1) cells in culture. The stimulation was dose-dependent, and samples taken prepartum had greater potency than those taken after parturition. When various hormones and growth factors known to be present in milk were tested, only epidermal growth factor (EGF), insulin and insulin-like growth factor I (IGF-I) stimulated the proliferation of RIE-1 cells. IGF-I was effective at lower concentrations than insulin, and the maximal stimulation induced by each of these two polypeptides was greater than that induced by EGF. The maximal stimulation induced by samples of mammary secretions was similar to that induced by insulin or IGF-I.
J. Endocr. (1987) 113, 285–290
Specific binding sites for LH/chorionic gonadotrophin, low-density lipoprotein, prolactin and FSH in homogenates of human corpus luteum. I: Validation of methods
Authors: Bramley T. A. , Stirling D. , Swanston I. A. , Menzies G. S. , Baird D. T. 
Published: December 2008

ABSTRACT
The specific binding of 125I-labelled human chorionic gonadotrophin (hCG), human low-density lipoprotein (hLDL), human FSH (hFSH) and human prolactin (hPRL) to homogenates of human corpus luteum tissue was measured.
Specific binding of 125I-labelled hCG was dependent on the temperature and duration of incubation, was inhibited by divalent metal ions or chelating agents, and increased linearly with homogenate concentration. Recovery of bound hormone was more effective using Millipore filtration or polyethylene glycol precipitation compared with centrifugation alone. Binding of 125I-labelled hCG was inhibited specifically by low levels of hCG and human LH (hLH) but not by ovine LH or bovine LH. Incubation of human luteal tissue with ice-cold citrate buffer (pH 3) released more than 90% of specifically bound 125I-labelled hCG within 5 min. This treatment inactivated LH receptors, but did not affect the immunoactivity of hLH released, enabling the measurement of released hormone by radioimmunoassay.
Scatchard plots of binding of 125I-labelled LDL to human corpus luteum demonstrated a single class of binding sites. Binding was saturable, increased linearly with increasing concentration of homogenate, and was displaceable by low concentrations of unlabelled LDL.
Binding of 125I-labelled hPRL to human luteal homogenates was increased by Mg2+ and was specific for lactogenic hormones (human prolactin, human growth hormone and ovine prolactin). Binding of 125I-labelled hFSH was not dependent on divalent metal ion concentration (in marked contrast to hFSH binding to immature pig granulosa cell receptors) and was displaced by hFSH preparations but not by hPRL, ovine LH or hCG at 1 μg/ml.
These results establish optimal conditions and hormone specificities for the measurement of human luteal gonadotrophin and LDL receptors, and methods for the estimation of hLH/hCG endogenously bound to human corpus luteum tissue.
J. Endocr. (1987) 113, 305–315
Influence of bromocriptine and oestrogen on prolactin synthesis, secretion and tumour growth in vivo in rats
Authors: Vrontakis M. E. , Thliveris J. A. , Friesen H. G. 
Published: December 2008

ABSTRACT
The effects of diethylstilboestrol implants and bromocriptine administration on serum prolactin concentrations, prolactin messenger RNA (mRNA) and pituitary tumour weight were examined. Intact female Fischer 344 rats were implanted s.c. with 10 mg diethylstilboestrol (DES) under light anaesthesia. All animals except the control group carried the implant for 7 weeks at which time the rats were subdivided into five groups: A, control; B, DES for 7 weeks; C, DES for 7 weeks followed by withdrawal of DES for 1 week; D, DES for 7 weeks followed by withdrawal of DES and administration of bromocriptine for 1 week; E, DES for 8 weeks with concurrent administration of bromocriptine during the last week. Serum concentrations of prolactin were measured by radioimmunoassay, prolactin mRNA concentrations were measured by dot-blot hybridization and sodium dodecylsulphate–polyacrylamide gel electrophoresis of the in-vitro translated mRNA. Pituitary growth was estimated by changes in pituitary weight and assessed by light and electron microscopic examination.
Treatment with DES dramatically increased serum prolactin concentrations and prolactin mRNA and induced pituitary tumour formation as shown by histological changes. Withdrawal of DES for 1 week did not lead to a decrease in pituitary tumour weight but was accompanied by a decrease in serum prolactin concentrations and prolactin mRNA from peak concentrations although they remained significantly increased above controls. Treatment with bromocriptine after DES implants were removed led to a significant reduction in pituitary tumour weight and a decrease in serum prolactin concentrations and prolactin mRNA. Histology of the pituitary tumour after the bromocriptine treatment showed pituitary cells similar to those from normal animals. In group E, when bromocriptine was administered in the presence of DES implants, no reduction in pituitary tumour weight occurred but serum prolactin concentrations and prolactin mRNA decreased almost to normal concentrations. Histology of the pituitary showed most cells remaining hypertrophied and similar in appearance to those seen in animals treated with DES alone. These results suggest that the mechanisms by which oestrogen and bromocriptine control prolactin synthesis and secretion are independent from those which influence pituitary tumour growth and regression.
J. Endocr. (1987) 113, 383–388
Diurnal variations in plasma concentrations of cortisol, prolactin, growth hormone and glucose in the fetal sheep and pregnant ewe during late gestation
Authors: McMillen I. C. , Thorburn G. D. , Walker D. W. 
Published: December 2008

ABSTRACT
We have measured fetal and maternal plasma concentrations of cortisol, prolactin, GH and glucose in samples collected during a 24-h period in 14 animals between 127 and 142 days of gestation. There was a significant increase in both the mean daily plasma cortisol concentration and mean daily coefficient of variation (C.V.) of plasma cortisol concentrations after 135 days of gestation. There was also a significant variation in the fetal plasma cortisol concentrations with a peak occurring at 19.00 h. There was a significant sinusoidal diurnal rhythm in the plasma prolactin concentrations in both the fetal sheep and pregnant ewe and the maximal prolactin concentrations occurred between 19.00 and 23.00 h (fetal) and 21.00 and 01.00 h (maternal). Although no significant diurnal variation was detected in fetal plasma GH concentrations, there was a significant sinusoidal diurnal rhythm in the plasma GH concentrations of the pregnant ewe and the maximal maternal GH concentrations occurred between 21.00 and 01.00 h. Both the fetal and maternal plasma glucose concentrations showed a significant sinusoidal diurnal rhythm. The maximal maternal and fetal glucose concentrations were measured between 21.00 and 01.00 h and between 23.00 and 03.00 h respectively. We have therefore established that diurnal variations in plasma cortisol and prolactin concentrations exist prenatally. Whether the presence of such hormonal rhythms reflects the activity of an endogenous fetal circadian pacemaker remains to be established.
J. Endocr. (1987) 114, 65–72
Plasma Met-enkephalin and catecholamine responses to insulin-induced hypoglycaemia in greyhounds
Authors: Medbak S. , Mason D. F. J. , Rees L. H. 
Published: December 2008

ABSTRACT
The involvement of endogenous opioid peptides in the stress response was investigated by measuring plasma concentrations of Met-enkephalin-like immunoreactivity (MLI), adrenaline and noradrenaline during insulin-induced hypoglycaemia in conscious greyhounds. Moreover, the molecular forms of circulating MLI were characterized using gel filtration chromatography.
In the first group of animals, i.v. administration of insulin (0·3 units/kg) provoked marked hypoglycaemia (blood glucose concentrations fell from 4·4 ± 0·1 to 1·5 ±0·2 mmol/l; mean ± s.e.m.) which was associated with significant (P< 0·001) rises in plasma MLI concentrations from a basal concentration of 45 ± 8 to a peak of 189 ±39 ng/l.
A within-subject study comparing five different insulin doses ranging from 0·004 to 0·3 units/kg showed dose-related effects on blood glucose with nadir concentrations of 4·1 ± 0·6 mmol/l (after the smallest dose of insulin) and 0·8 ± 0·1 mmol/l (after the largest dose of insulin). This was associated with dose-related rises in plasma MLI with peak concentrations of 56±17 and 558 ± 35 ng/l, plasma adrenaline with peak concentrations of 0·45± 0·06 and 15·76±1·33 nmol/l and plasma noradrenaline with peak concentrations of 0·49 ± 0·07 and 2·27 ± 0·45 nmol/l following the smallest and largest doses of insulin respectively. These results are the first demonstration of raised plasma MLI concentrations following hypoglycaemia. Moreover, they show that the hormonal responses vary with the degree of hypoglycaemia achieved. Together with reports by other investigators these findings might suggest opioid modulation of the responses of the sympathoadrenal system to hypoglycaemia. These responses were, however, not modified by the opioid antagonist naloxone.
Gel filtration chromatography of neat (unextracted) plasma revealed the predominance of large molecular weight enkephalin-containing peptides, with approximate molecular weights of 18 000 and 8000, both basally and following stimulation by hypoglycaemia.
J. Endocr. (1987) 114,81–87
Insulin-modulated interleukin-2 production by murine splenocytes and a T-cell hybridoma
Authors: Pavelić K. , Bernacki R. J. , Vuk-Pavlović S. 
Published: December 2008

ABSTRACT
Murine interleukin-2 (IL-2)-producing AOFS 21 T-cell hybridoma cells and normal murine splenocytes were stimulated in serum-free media by 16 potential mitogens/growth factors. Only insulin, concanavalin A (Con A), peptidoglycan monomer and a tumour-derived insulinoid stimulated [3H]thymidine incorporation by AOFS 21 cells and splenocytes. Supernatants of these stimulated cultures were tested for IL-2 activity which generally followed the pattern of growth stimulation. Both the mitogenicity and stimulation of IL-2 secretion by insulin were second only to the effects of Con A.
J. Endocr. (1987) 114, 89–94
Effect of prolactin, progesterone, pregnancy and lactation on DNA synthesis and DNA polymerase activities in rabbit mammary gland
Authors: Zwierzchowski L. , Niedbalski W. , Kleczkowska D. 
Published: December 2008

ABSTRACT
DNA synthesis and DNA polymerase-α, -β and -γ activities in the rabbit mammary gland were studied during hormone-directed cellular growth. It was found that during pregnancy, early lactation and after injection of prolactin, changes in the activity of DNA polymerase-α paralleled the rate of mammary gland DNA synthesis. It was also found that the amount of polymerase-α activity bound to isolated chromatin depended on the physiological state of the animal. During pregnancy and early lactation changes in the activity of chromatin-bound enzyme correlated directly with the rate of DNA synthesis (r = 0·83). Moreover, in virgin rabbits treated with prolactin the activity of chromatin-bound DNA polymerase-α increased markedly at the same time as the DNA-synthetic rate increased. No correlation of the DNA-synthetic rate was found with the activity of soluble (cytosolic) DNA polymerase-α or with the activity of soluble or chromatin-bound DNA polymerases-β and -γ.
On the basis of these results it is suggested that in the developing mammary gland both the activity and cellular distribution of DNA polymerase-α might be subject to hormonal regulation.
J. Endocr. (1987) 114, 139–145
Effect of age on renal responsiveness to parathyroid hormone and calcitonin in rats
Authors: Armbrecht H. J. , Wongsurawat N. , Paschal R. E. 
Published: December 2008

ABSTRACT
The purpose of these studies was to determine whether the responsiveness of the kidney to parathyroid hormone (PTH) and calcitonin changed with age. Experiments were performed in young (3 months old), adult (12–14 months old) and old (22–24 months old) male Fischer 344 rats fed normal diets and thyroparathyroidectomized. Parathyroid hormone was administered i.p. at 24, 12 and 2 h before death and calcitonin was given i.p. at 12 and 2 h before death. Parathyroid hormone significantly increased the conversion of 25-hydroxyvitamin D3 to 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) by renal slices from young but not adult or old animals. A similar age-related decline in the capacity of PTH to raise serum 1,25-dihydroxyvitamin D (1,25-(OH)2D) levels was also seen. Parathyroid hormone significantly decreased tubular reabsorption of phosphorus, increased concentrations of urinary cyclic AMP (cAMP) and increased serum concentrations of calcium in all age groups. In contrast, calcitonin significantly increased 1,25-(OH)2D3 production by renal slices from both young and adult animals. Calcitonin decreased serum concentrations of calcium in young but not in adult rats. These results suggest that there are maturational changes in the PTH- and cAMP-dependent pathways in the kidney but not in the calcitonin- and cAMP-independent pathways. The changes in the PTH- and cAMP-dependent pathways affect the stimulation of 1,25-(OH)2D production but not the inhibition of phosphate transport.
J. Endocr. (1987) 114, 173–178
Effects of chronic infusion of porcine relaxin on oxytocin release in lactating rats
Authors: Jones S. A. , Summerlee A. J. S. 
Published: December 2008

ABSTRACT
The effects of chronic infusion of porcine relaxin on oxytocin release were studied in lactating rats. Infusion of relaxin (4·2 μg/h for either 4 or 6 days) suppressed reflex milk ejection and reduced litter weight gain for 48 h compared with saline-infused controls. After 2 days, neither the rate of growth nor the frequency of milk ejection were significantly different from controls. For 24 h after the infusion of relaxin ended, litters gained weight more quickly than controls but there was no difference seen in the frequency of milk ejection. The effects on oxytocin release of stopping an infusion of relaxin after 3 days were investigated. There was a significant (P <0·01) rise in plasma oxytocin (up to 90 pmol/l) 30 min after the infusion was stopped, followed by a sustained rise in intramammary pressure. Treatment of relaxin-infused rats with naloxone (0·1 mg/kg) when the infusion was halted caused a more rapid release of oxytocin (within 2 min), a greater release of oxytocin (up to 140 pmol/l) and a prolonged rise in intramammary pressure.
J. Endocr. (1987) 114, 241–246
Monoclonal antibodies against human, bovine and rat prolactin: epitope mapping of human prolactin and development of a two-site immunoradiometric assay
Authors: Staindl B. , Berger P. , Kofler R. , Wick G. 
Published: December 2008

ABSTRACT
Nine mouse hybridoma cell lines producing monoclonal antibodies (MCA) against human prolactin (hPRL), 19 cell lines against bovine prolactin (bPRL) and one MCA against rat prolactin (rPRL) were established. The MCA were characterized by one- and two-site radioimmunoassays (RIA) as well as indirect immunofluorescence (IIF) and used for epitope mapping of hPRL and immunoradiometric assays (IRMA).
Interspecies cross-reactivity studies by RIA revealed two groups of anti-hPRL MCA: seven which reacted only with hPRL and two additionally recognizing bPRL and ovine prolactin (oPRL). The anti-bPRL MCA, which were tested on pituitary sections by IIF could be divided into 17 MCA cross-reacting with the closely related oPRL, and two MCA which showed additional cross-reactions with equine prolactin. The anti-rPRL antibody reacted exclusively with rPRL in direct binding RIA studies. No intraspecies cross-reactions with the closely related protein hormones placental lactogen and GH were detected.
To elucidate the antigenic surface of hPRL all MCA directed against hPRL were then used for two-site epitope mapping studies in which pairs of MCA were assessed for simultaneous reaction with the same antigen. The native hormone was incubated with the first, solid-phase bound, so called 'capture MCA', and this complex treated with a second, 125I-labelled 'detection MCA'. Based on the results of these combinations, at least three sterically non-overlapping and (taking RIA cross-reaction studies into consideration) two additional epitopes could be defined. Two antibodies (code numbers INN-hPRL-1 and INN-hPRL-9) recognizing different antigenic determinants were selected and used to elaborate a two-site IRMA with an operating range wider and a reaction time shorter than those obtained with a conventional one-site RIA.
J. Endocr. (1987) 114,311–318
Thyrotrophin-releasing hormone in human ejaculate
Authors: Rui H. , Welinder B. S. , Purvis K. , Dolva Ø. 
Published: December 2008

ABSTRACT
Immunoassayable TRH in human ejaculate was eluted from a gel column in a form with a molecular weight larger than that of the native peptide. With reverse-phase high-performance liquid chromatography (HPLC) the same activity co-eluted with standard TRH. Incubation of ejaculates at room temperature for 8 h was associated with a time-related increase in the total immunoassayable TRH. Analysis by HPLC of ejaculates after 12 h of incubation at room temperature indicated that, whereas the levels of the peptide co-eluting with native TRH declined with time, there was a concomitant increase in the concentration of a molecular species which also cross-reacted with the TRH antiserum, but which was more hydrophobic. The latter species is presumably identical to the tetrapeptide recently described by others and which may arise from the proteolytic degradation of secretory macromolecules. Although immunological activity was present in all six fractions of split ejaculates, the bulk of the peptide was associated with the later portions, implying a major vesicular contribution. However, secretions isolated from surgical preparations of the seminal vesicles contained undetectable levels of peptide, suggesting that the ejaculation process may represent a stimulus for its appearance in the semen. This study is further support for a local involvement of TRH in male reproductive function.
J. Endocr. (1987) 114, 329–334