bluuebunny/crossref_metadata_2025_split huggingface dataset:
High-affinity receptor for insulin-like growth factor II in rat liver: properties and regulation in vivo
Authors: Bryson J. M. , Baxter R. C. 
Published: December 2008

ABSTRACT
Receptors for insulin-like growth factor II (IGF-II) have been identified in many tissue types and have been shown to differ widely in their specificities and affinities. We have characterized the IGF-II receptor in rat liver microsomal membranes, both in the intact membrane and in a solubilized extract. Binding was time- and temperature-dependent and was unaffected by changes in pH in the range 6–9. Half-maximal displacement was obtained with 0·33 ng IGF-II/ml standard, and Scatchard analysis showed a class of receptors with an affinity for IGF-II of 1·33 ± 0·36 × 1010 litres/mol which increased threefold in the presence of Ca (1 mmol/l) to 3·74 ± 0·89 × 1010 litres/mol. There was also a threefold decrease in the rate of dissociation in the presence of Ca. Cross-reactivity with IGF-I was < 1% and there was no cross-reactivity with insulin.
Infusion of rat GH or prolactin for 1 week, at the rate of 175–200 μg/day, into female rats had no effect on IGF-II binding in control animals, but rat GH infusion caused a 60% increase (P< 0·001) in binding in hypophysectomized rats by increasing the number of receptors.
These studies demonstrate that rat liver microsomal membranes contain a highly specific, high-affinity receptor for IGF-II which may be under partial GH control
J. Endocr. (1987) 113, 27–35
Recovery of the components of the hypothalamo-pituitary-adrenocortical axis in the rat after chronic treatment with prednisolone
Authors: Nicholson S. A. , Campbell E. A. , Gillham B. , Jones M. T. 
Published: December 2008

ABSTRACT
Male Wistar-derived rats (200–250 g) were treated for 14 days with prednisolone 21-sodium succinate at a concentration of 1035 μmol/l in their drinking water. The drug was then replaced with normal tap water and groups of animals were killed at various times during recovery, trunk blood being collected after decapitation. At the same time, hypothalamic slices, anterior pituitary gland fragments and adrenals were removed and their responsiveness assessed by exposure to appropriate stimuli in vitro. Tissues were also extracted to measure changes in content of hormones during recovery. Treatment with prednisolone produced marked reductions in body weight gain, adrenal weight and pituitary ACTH content, but no significant change in hypothalamic corticotrophin-releasing factor (CRF) bio- or immunoreactivity. The ACTH content was restored by 5 days after withdrawal but adrenal weight remained significantly reduced after 9 days of recovery. The responsiveness of the hypothalamus to acetylcholine in vitro was markedly inhibited and was still significantly reduced 7 days after withdrawal. The responsiveness of the anterior pituitary gland to synthetic CRF or arginine vasopressin and that of the adrenal gland to ACTH added in vitro were restored simultaneously after 7 days of withdrawal. In vivo, recovery was assessed by measurement of the response to laparotomy stress. Treatment with prednisolone prevented the increase in the plasma concentrations of ACTH and corticosterone produced by stress, and these responses recovered by 5 days (corticosterone) and 7 days (ACTH) after withdrawal. The abolition of the circadian rhythms of ACTH and corticosterone by treatment was also reversed by 5 days after withdrawal. This pattern of recovery is different from that which we observed after long-term treatment with dexamethasone, where the responsiveness of the hypothalamus and adrenal gland in vitro recovered before that of the anterior pituitary gland.
J. Endocr. (1987) 113, 239–247
Evidence for reorganization of the neuroendocrine centres regulating pulsatile LH secretion in rats receiving neonatal monosodium-l-glutamate treatment
Authors: Rose P. A. , Weick R. F. 
Published: December 2008

ABSTRACT
Previous research has shown that the combination of anterior hypothalamic deafferentation (AHD) and electrolytic lesions of the anterior part of the arcuate nuclei blocks pulsatile LH secretion in ovariectomized rats, but that neither lesion alone was effective. Furthermore, the combination of AHD with arcuate lesions produced by neonatal treatment with monosodium-l-glutamate (MSG) does not block pulsatile LH release. To distinguish between the various possible reasons for this result, AHD and electrolytic lesions of the arcuate nuclei were combined in rats which had been treated neonatally with MSG or saline of equal osmolarity. One week after brain surgery, venous catheters were installed and blood samples taken at 5-min intervals for up to 3 h for assay of plasma LH. Rats treated with MSG and bearing AHD and electrolytic lesions of the arcuate nuclei continued to show pulsatile secretion of LH. Where the electrolytic lesions were posterior and dorsal to the anterior arcuate nuclei, however, LH release was blocked whether AHD was performed or not, but only in rats treated with MSG. None of the lesion combinations blocked pulsatile LH secretion in rats treated with saline. These results suggest that neonatal MSG treatment leads to a reorganization of the hypothalamus such that the role normally played by the arcuate nuclei in the regulation of pulsatile LH secretion is taken over by other hypothalamic structures.
J. Endocr. (1987) 113, 261–269
Difference in the response of follicular maturation and ovulation between early and late lactating rats after removal of the litter
Authors: Taya K. , Sasamoto S. 
Published: December 2008

ABSTRACT
The mechanisms responsible for the 24-h difference in the time of the next ovulation after litter removal between early and late lactating rats were investigated.
At 11.00 h on day 5 of lactation, concentrations of oestradiol-17β and inhibin activity in ovarian venous plasma were lower than those on day 17, corresponding to the absence of healthy Graafian follicles. After removal of the litter on day 5 of lactation a small surge of FSH with a steady increase in basal levels of LH occurred to initiate follicular maturation, and ovulation occurred 4 days later. After removal of the litter on day 17 of lactation a surge of FSH was not observed, due to high levels of inhibin activity in ovarian venous plasma, until the time of preovulatory surges of gonadotrophin which occurred 2 days later and resulted in ovulation the next morning. Prolactin concentrations decreased similarly in both groups abruptly after removal of the litter. A decrease in plasma concentrations of progesterone occurred 42 h after removal of the litter on day 5, though it occurred 18 h after removal of the litter on day 17.
These results indicate that the 24-h delay of ovulation after litter removal on day 5 of lactation, as compared with the time of ovulation after litter removal on day 17, is due probably to the absence of healthy antral follicles and high activity of corpora lutea secreting progesterone at the time of litter removal.
J. Endocr. (1987) 113, 271–276
Effects of human placental lactogen and growth hormone on the production of insulin and somatomedin C/insulin-like growth factor I by human fetal pancreas in tissue culture
Authors: Swenne I. , Hill D. J. , Strain A. J. , Milner R. D. G. 
Published: December 2008

ABSTRACT
We have investigated the ability of glucose, human GH and human placental lactogen (hPL) to alter the content and release of somatomedin C/insulin-like growth factor I (SM-C/IGF-I), and the biosynthesis, content and release of insulin from cultured human fetal pancreas. Fetal pancreatic explants obtained from glands following prostaglandin-induced abortion between 12 and 21 weeks of gestation were maintained in free-floating culture for 3–5 days before the experiments. The explants were then cultured for 3 days in medium containing either 2·7 or 16·7 mmol glucose/l with or without GH (4·5 or 45·5 nmol/l) or hPL (4·6 or 46·5 nmol/l). Serum-free medium from the final 24 h of culture was collected and SM-C/IGF-I and insulin were measured radioimmunologically in both conditioned medium and tissue explants extracted with acid ethanol. Insulin biosynthesis, determined by immunoprecipitation of [3H]leucine incorporated into insulin, was not significantly altered by any experimental variable. Incubation in the presence of 16·7 mmol glucose/l caused an increase of insulin release from explants, but had no consistent action on insulin content, compared with medium containing 2·7 mmol glucose/l. The pancreatic content and release of SM-C/IGF-I were independent of these glucose concentrations. Neither GH nor hPL altered insulin or SM-C/IGF-I content or release in the presence of the lower glucose concentration. At the higher glucose concentration, 45·5 nmol GH/1 did not alter insulin release but caused a significant increase in SM-C/IGF-I content. When present with 16·7 mmol glucose/l hPL (46·5 nmol/l) promoted significant increases in both insulin content and release (59 and 47% respectively) and significantly increased pancreatic SM-C/IGF-I content and release (114and 117% respectively).
The results suggest that, during tissue culture, glucose enhances the insulin output of human fetal pancreatic explants obtained in the second trimester. The ability of hPL to modulate B-cell function raises the possibility that this peptide may contribute to pancreatic development during fetal life and to total fetal body growth by increasing insulin production.
J. Endocr. (1987) 113, 297–303
Subcellular distribution of [3H]oestradiol-17β and salt resistance of nuclear oestrogen complexes in the rat uterus after in-vivo administration of [3H]oestradiol-17β
Authors: Batra S. 
Published: December 2008

ABSTRACT
The distribution of injected [3H]oestradiol-17β into nuclear and post-nuclear fractions as well as resistance to KCl (0·6 mol/l) extraction of nuclear oestrogen-binding sites in the rat uterus were studied. Both ovariectomized untreated and oestrogen-treated rats were used. One hour after injection of [3H]oestradiol into ovariectomized rats, 373 and 195 fmol/100 mg uterus were recovered in the nuclear and post-nuclear fractions respectively. About 17% of the nuclear-associated [3H]oestradiol was resistant to KCl extraction. After 18 h, the amount of [3H]oestradiol decreased to about 30% of that found after 1 h, and about 23% of nuclear complex remained resistant to extraction. In cardiac tissue, practically no [3H]oestradiol accumulated in the nuclear fractions and the amount recovered in post-nuclear fractions was about one-third of that in the uterine post-nuclear fractions. In the ovariectomized oestrogen-treated rats the distribution of [3H]oestradiol in nuclear and post-nuclear fractions was very similar and the proportion of the total nuclear fraction inextractable by KCl slightly higher (26%) than in untreated rats. After 18 h, while measurable amounts of [3H]oestradiol were found in post-nuclear fractions, no radioactivity was detected in the nuclear fraction. The results demonstrate the existence of salt-resistant nuclear oestrogen-binding sites in the mature ovariectomized rat uterus in vivo. Further, oestrogenization of ovariectomized rats did not significantly influence the amount or proportion of salt-resistant nuclear sites.
J. Endocr. (1987) 113, 333–337
Inhibition of the response of thyrotrophin to thyrotrophin-releasing hormone by thyroxine in hypothyroid rats treated with iopanoic acid: evidence suggesting an intrinsic biological activity of thyroxine without prior conversion to 3,5,3′-tri-iodothyronine
Authors: Boado R. J. , Zaninovich A. A. 
Published: December 2008

ABSTRACT
The effects of a physiological replacement dose of thyroxine (T4) on the response of plasma TSH to TRH in hypothyroid rats were studied. Animals were treated with iopanoic acid (IOP; 5 mg/100 g body weight) or vehicle 24, 12 and 1·5 h before the experiment. Thereafter, 800 ng T4/100 g body weight were administered i.v. and 20 min later 1 μg TRH/100 g body weight was injected i.v. In control rats the basal concentration of TSH was 1450 ± 300 (s.e.m.) mu./l. The plasma concentration of TSH 10 min after injection of TRH increased to 167 ± 14% of the mean basal value (P < 0·001). The injection of T4 significantly (P < 0·05) reduced the TSH response to TRH in both IOP-treated (118 ± 15%) and vehicle-treated (108 ± 15%) rats compared with untreated controls. Tri-iodothyronine (T3) was undetectable in the plasma of all rats, whereas the plasma concentration of T4 was 121 ± 19 nmol/l in IOP-treated and 139 ± 23 nmol/l in vehicle-treated rats 30 min after injection of 800 ng T4/100 g body weight. In pituitary cells of control rats, cytoplasmic radioactivity 30 min after injection of [125I]T4 was 1·28 ± 0·13 × 10−2% (76 ± 6% T4 and 17 ± 3% T3), whereas that in nuclei reached 0·42 ± 0·36 × 10−2% (51 ± 4% T4 and 28 ± 3% T3) of the injected dose. In IOP-treated rats there was an increase in total cytoplasmic radioactivity (P < 0·05), with a decreased proportion of [125I]T3 (0·12 ± 0·07%; P < 0·01), whereas nuclear T3 was significantly (P < 0·005) lower than in controls (0·057 ± 0·025 vs 0·22 ± 0·022 pmol T3/mg DNA). Administration of 25 μg unlabelled T4 along with the tracer reduced cytoplasmic radioactivity in both control and IOP-treated rats (P < 0·05), without a detectable change in nuclear radioactivity. The results suggest that T4, at a physiological replacement dose, possesses an intrinsic capacity to regulate secretion of TSH following administration of TRH to hypothyroid rats.
J. Endocr. (1987) 113, 349–354
Receptors for lactogenic hormones in the porcine corpus luteum: properties and luteal phase concentrations
Authors: Bramley T. A. , Menzies G. S. 
Published: December 2008

ABSTRACT
Homogenates of pig corpora lutea contained specific, high-affinity receptors for ovine prolactin (oPRL) and human GH (hGH). Specific hormone binding was enhanced by divalent metal ions, but only when included in the binding reaction. Divalent metal ions did not act by increasing the recovery of bound hormone by low-speed centrifugation, but appeared to promote the formation of a more stable hormone– receptor complex. Both oPRL and hGH tracers were bound in similar amounts and with similar affinities by pig luteal homogenates and the concentrations of either unlabelled hormone required to displace specific binding of either tracer by 50% were identical.
In contrast, 125I-labelled oGH failed to bind to pig luteal homogenates and oGH competed poorly for hGH or oPRL binding. Only hormones with prolactin-like activity competed for 125I-labelled oPRL binding.
Specific prolactin binding was low in recently ovulated and early luteal phase corpora lutea, increased significantly in the mid-luteal phase and declined once more in the late luteal phase. Receptor concentrations increased with increasing gestational age.
J. Endocr. (1987) 113, 355–364
Receptors for lactogenic hormones in the ovine corpus luteum. I: A major discrepancy in the specific binding of radiolabelled ovine prolactin and human growth hormone
Authors: Bramley T. A. , Menzies G. S. , McNeilly A. S. , Friesen H. G. 
Published: December 2008

ABSTRACT
The characteristics of the binding of 125I-labelled human GH (hGH) and ovine prolactin (oPRL) were studied in the ovine corpus luteum. Although oPRL is the homologous ligand for sheep lactogenic receptors, its binding was significantly and consistently lower than that of 125I-labelled hGH. This was not due to iodination damage of oPRL since: (1) 125I-labelled oPRL tracers which bound poorly relative to 125I-labelled hGH in the ovine corpus luteum were equipotent in the pig and rat corpus luteum, (2) the differences between 125I-labelled hGH and oPRL binding persisted with tracers of equivalent biopotency and (3) the iodination procedure affected neither oPRL bioactivity in the Nb2 tumour assay nor its binding activity with ovine corpus luteum receptors.
Ovine luteal receptors were specific for lactogenic hormones. The specific binding of 125I-labelled hGH or oPRL could be inhibited completely by incubation with either unlabelled hormone, with similar potencies. However, oGH inhibited binding only at much higher concentrations, consistent with its known contamination with oPRL. Moreover, 125I-labelled oGH was not bound specifically to sheep luteal tissue.
Fractionation of sheep luteal homogenates on sucrose density gradients (with or without cell-surface membrane perturbation by digitonin) demonstrated that binding of 125I-labelled hGH and 125I-labelled oPRL peaked in the same regions of the gradients, coincident with a number of luteal cell-surface membrane markers.
We conclude that the marked discrepancy between the binding of hGH and oPRL tracers by sheep luteal tissue was not due to iodination damage of oPRL, binding of 125I-labelled hGH to somatogenic receptors or differential binding to luteal cell-surface versus intracellular receptors.
J. Endocr. (1987) 113, 365–374
Effects of ovarian inhibin on pulsatile release of gonadotrophins and secretion of LHRH in ovariectomized rats: evidence against a central action of inhibin
Authors: de Greef W. J. , Eilers G. A. M. , de Koning J. , Karels B. , de Jong F. H. 
Published: December 2008

ABSTRACT
Intraperitoneal administration of bovine follicular fluid (bFF) decreased plasma concentrations of FSH in ovariectomized rats after 2–3 h, while plasma LH and prolactin were unaffected. In untreated ovariectomized animals the concentrations of these hormones were found to show pulsatile variations. Concomitant occurrence of peak values of LH and FSH was found in about 40% of the pulses. No pulses of FSH were observed after i.p. treatment with bFF or partly purified preparations of inhibin from bFF, but the pulsatile release of LH and prolactin remained similar. Infusion of bFF into the lateral ventricle of the brain did not alter the concentrations of FSH, whereas administration of bFF into the pituitary gland diminished the plasma concentrations of FSH.
Anaesthesia (urethane plus xylazine) did not prevent the occurrence of the pulses of FSH and LH, but it reduced the pulse amplitude and clearance. During this anaesthesia, the concentrations of LHRH in the hypophysial stalk plasma decreased by 30% after administration of bFF, but did not alter after treatment with partly purified preparations of inhibin. It is concluded that the inhibin-like activity in bFF suppresses pulsatile FSH secretion in ovariectomized rats by an action on the pituitary gland, but has no effect on the pulsatile release of LH and prolactin.
J. Endocr. (1987) 113, 449–455
Biopotency and site of action of drugs affecting testicular steroidogenesis
Authors: Lambert A. , Mitchell R. , Robertson W. R. 
Published: December 2008

ABSTRACT
The effect of etomidate (an anaesthetic), epostane (WIN 32729; an inhibitor of ovarian and adrenal steroidogenesis) and cyproterone acetate (an antiandrogen) on testosterone secretion from mouse Leydig cells stimulated with LH (5 i.u./l) was tested. The concentration of drug which inhibited testosterone secretion by 50% was 11·5±1·1 (s.e.m.) μmol/l for cyproterone acetate, 1·2 ± 0·2 μmol/l for etomidate and 0·23 ± 0·03 μmol/l for epostane.
The effect of all three drugs on testicular steroidogenesis was completely reversible. Thus testicular cells which had been washed after exposure to a >95% inhibitory dose of drug responded in a similar manner to hormone stimulation as cells similarly washed and which had not been exposed to the drug.
The sites of the antisteroidogenic effect of epostane, etomidate and cyproterone acetate were established using a method based on the sequential stimulation by the exogenous precursor steroids of the various steps leading to the biosynthesis of testosterone. It was concluded that etomidate acts at the sequence between LH binding and pregnenolone production, epostane acts at 3β-hydroxysteroid dehydrogenase and cyproterone acetate inhibits 3β-hydroxysteroid dehydrogenase and C17,20-lyase.
J. Endocr. (1987) 113, 457–461
HYPOTHALAMO-HYPOPHYSIAL BLOOD FLOW: A NOVEL CONTROL MECHANISM IN PITUITARY FUNCTION?
Authors: Eckland D.J.A. , Lightman S.L. 
Published: December 2008

ABSTRACT
The flow rate of portal plasma was measured during hypothalamo-hypophysial portal sampling in the rat using a modified Worthington-Fink technique. In rats rendered hypothyroid with propylthiouracil, there was a significant 140% increase in portal plasma flow. Median eminence stimulation also increased portal plasma flow by 41%. Orchidectomy and adrenalectomy had no effects on plasma flow. Modification of flow rate in the hypothalamo-hypophysial vascular bed may represent a further mechanism involved in the control of pituitary function.
Noradrenergic stimulation of serotonin release from rat pineal glands in vitro
Authors: Aloyo V. J. , Walker R. F. 
Published: December 2008

ABSTRACT
The pharmacodynamics of serotonin (5-hydroxytryptamine; 5-HT) uptake and release were studied in rat pineal glands. Initially, uptake was tested by incubating pineals with several concentrations of [3H]5-HT. The incubation media also contained [14C]mannitol to which cells are impermeable. Since [14C]mannitol accumulates only in extracellular spaces, the radio-labelled sugar was used to determine the differential distribution of [3H]5-HT in pineal compartments.
Intracellular accumulation of 3H in pineal glands increased linearly as a function of time for [3H]5-HT concentrations ranging from 1 to 10 μmol/l. The ratio of 3H to 14C also increased for the same time-interval, indicating that the glands accumulated [3H]5-HT preferentially in non-extracellular spaces. [3H]5-HT accumulated in pineal glands which were denervated for more than 7 days before testing, suggesting that uptake is not restricted to adrenergic terminals but also occurs in pinealocytes.
In addition to uptake, spontaneous and noradrenaline-stimulated release of [3H]5-HT was tested in perifusion and/or step-transfer systems. Spontaneous release of [3H]5-HT was biphasic consisting of rapid and slower efflux phases. In contrast, release of [14C]mannitol was monophasic, characterized exclusively by rapid efflux. Since [14C]mannitol does not enter cells, the rapid and slower phases of [3H]5-HT efflux may represent release from pineal extracellular and intracellular compartments respectively. The identity of [3H]5-HT in pineal glands and perifusion media was confirmed by thin-layer chromatography. When l-noradrenaline was added to the perifusion media, [3H]5-HT efflux during the slower phase of release was significantly increased above the non-stimulated state. In contrast, d-noradrenaline was significantly less effective than l-noradrenaline in releasing [3H]5-HT. Noradrenaline also stimulated [3H]5-HT release from denervated glands, suggesting that pinealocytes secrete 5-HT in response to noradrenergic signals.
Since the pineal is innervated by fibres of the sympathetic division of the autonomic nervous system, differential release of 5-HT may occur in response to changing levels of glandular noradrenaline.
J. Endocr. (1987) 114, 3–9