bluuebunny/crossref_metadata_2025_split huggingface dataset:
Heterogeneity of rat FSH by chromatofocusing: studies on serum FSH, hormone released in vitro and metabolic clearance rates of its various forms [ill]
Authors: Blum W. F. P. , Gupta D. 
Published: December 2008

ABSTRACT
Rat pituitary FSH was fractionated by chromatofocusing between pH 6 and 3. Ten components were resolved having apparent isoelectric points between 3·1 and 5·1. A comparative study of pituitary FSH and FSH secreted in vitro by quartered pituitary glands in the presence and in the absence of gonadotrophin-releasing hormone (GnRH) revealed similar patterns of charged species of intracellular and released FSH. Although GnRH increased FSH secretion about fourfold, no influence on the pattern of charged species was observed. Utilizing exclusion chromatography and chromatofocusing, pituitary FSH was compared to serum FSH which had been extracted by immunoaffinity chromatography. The results demonstrate for serum FSH a larger molecular size and a relative shift to more acidic components. Metabolic clearance rates of eight FSH components separated by chromato-focusing were measured in adult male rats. Half-lives varied between 13 min and several hours. A correlation existed between decrease of isoelectric points and decrease of metabolic clearance rates. These findings suggest that (1) all hypophysial FSH components are secreted into the circulation at similar rates and (2) the more acidic FSH components which appear to contain increased sialic acid, have a longer circulatory half-life and are more abundant in serum. It is concluded that sialylation may be involved in modulating serum FSH levels.
J. Endocr. (1985) 105, 29–37
The influence of vitamin D metabolites on collagen synthesis by chick cartilage in organ culture
Authors: Dickson I. R. , Maher P. M. 
Published: December 2008

ABSTRACT
When growth cartilage from rachitic chicks was cultured in the presence of the calcium-regulating hormone 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3), collagen resorption was increased and collagen synthesis decreased compared to control cultures containing no hormone. The minimum concentration of the hormone that caused a statistically significant inhibition of collagen synthesis was 10 −8 mol/l. Collagen synthesis by growth cartilage from normal chicks was also reduced by 1,25-(OH)2D3, showing that it was not an abnormal response of vitamin D-depleted tissue. 25-Hydroxyvitamin D3 and 24,25-dihydroxyvitamin D3 also inhibited collagen synthesis by cultures of growth cartilage but only at higher metabolite concentrations. 1,25-Dihydroxyvitamin D3 (10−7 mol/l) did not significantly inhibit collagen synthesis by cultures of articular fibrocartilage and of sternal cartilage, tissues that do not calcify physiologically. The minimum concentration of 1,25-(OH)2D3 (10−9 mol/l) necessary to cause decreased collagen synthesis by embryonic chick calvaria was lower than the value obtained with growth cartilage; this suggests that bone cells may be more sensitive to the hormone in this respect than are growth cartilage chondrocytes. These findings provide evidence of a direct role of 1,25-(OH)2D3 in the control of endochondral bone formation which is consistent with its primary role in the maintenance of plasma calcium homeostasis.
J. Endocr. (1985) 105, 79–85
Effect of different growth hormone-releasing factors on the concentrations of growth hormone, insulin and metabolites in the plasma of sheep maintained in positive and negative energy balance
Authors: Hart I. C. , Chadwick P. M. E. , Coert A. , James S. , Simmonds A. D. 
Published: December 2008

ABSTRACT
Three experiments were conducted to compare the ability of different preparations of growth hormone-releasing factor (GRF) to stimulate GH secretion in sheep maintained in positive and negative energy balance.
In experiment 1 five sheep were injected (i.v.) with three preparations of human pancreatic GRF (hpGRF-44, hpGRF-40, hpGRF-29-NH2) and one preparation of rat hypothalamic GRF (rhGRF-29-NH2) all at 98·0 pmol/kg, or control vehicle, in a Latin square design when the animals either had free access to food or were fed half their maintenance requirements. Analysis of plasma samples, obtained before and for 150 min after injection, revealed that the reduced food intake resulted in the expected changes in body weight and circulating GH, insulin, glucose, urea and non-esterified fatty acids. The maximum post-injection concentrations of GH did not differ between either the two levels of feeding or the four GRF preparations but the mean post-injection concentration of GH was significantly higher for all GRF treatments on the restricted ration (P < 0·001). The mean post-injection response to rhGRF-29-NH2 was less than that obtained with hpGRF-44 for sheep with food available ad libitum (P < 0·05) and was clearly more persistent for all GRF treatments in animals fed the reduced diet (P < 0·001).
In experiment 2 the same five sheep were injected i.v. with rhGRF-29-NH2 (98·0 pmol/kg) when they had free access to food and after food had been withdrawn for 3 days. The peak concentrations of plasma GH and the speed of the response did not differ between feeding and food deprivation but the average post-injection concentration of GH was higher (P < 0·05) when the animals were deprived because the response was more persistent.
In experiment 3 the effects of i.v. injection of hpGRF-10-NH2, hpGRF-10-OH and hpGRF-10-OCH3 were examined at three different doses (8, 80 and 800 nmol/kg) each in three sheep. None of these treatments stimulated a significant increase in circulating GH.
J. Endocr. (1985) 105, 113–119
Effect of epidermal growth factor on glucosamine-6-phosphate synthetase activity in the colon of neonatal mice
Authors: Hiramatsu M. , Kashimata M. , Minami N. , Minami N. , Kumegawa M. 
Published: December 2008

ABSTRACT
Epidermal growth factor (EGF), administered subcutaneously to neonatal mice at daily doses of 1, 2 and 4 μg/g body weight for 3 days, significantly increased glucosamine-6-phosphate synthetase activity in the colon. A single injection of EGF at doses of 2 and 4 μg/g body weight also significantly increased enzyme activity. When administered to mature mice, EGF (4 μg/g body weight for 3 days) had no apparent effect on the enzyme activity. From these results, we suggest that EGF acts as a trophic factor for the maturation of the colonic mucosa of neonatal mice.
J. Endocr. (1985) 105, 197–200
Dissociation between testicular morphogenesis and functional differentiation of Leydig cells
Authors: Patsavoudi E. , Magre S. , Castanier M. , Scholler R. , Jost A. 
Published: December 2008

ABSTRACT
The aim of the study was to determine whether Leydig cells differentiate in vitro in gonads in which the formation of seminiferous cords is prevented by culture in a medium containing fetal calf serum. Appearance of 3β-hydroxysteroid dehydrogenase-positive cells and release of testosterone in the medium occurred at the same age irrespective of whether or not the gonads developed seminiferous cords. It is concluded therefore that testicular morphogenesis with the formation of seminiferous cords is not a prerequisite for the emergence and functional differentiation of Leydig cells.
J. Endocr. (1985) 105, 235–238
Plasma and tissue concentrations of melatonin after midnight light exposure and pinealectomy in the pigeon
Authors: Vakkuri O. , Rintamäki H. , Leppäluoto J. 
Published: December 2008

ABSTRACT
The effect of midnight light exposure and pinealectomy on plasma and tissue concentrations of immunoreactive melatonin was studied in the pigeon. Light exposure of 80 min reduced plasma melatonin by 85%. The melatonin concentration fell to 50% of the original value during 12 min. Pinealectomy reduced plasma melatonin so that at midnight about 36 h after the operations the melatonin concentration of pinealectomized pigeons was about 55% of that of sham-operated pigeons. Two weeks after the operations plasma melatonin of pinealectomized pigeons had increased to 64% of that of sham-operated birds. At midday, melatonin levels were unaffected by the operations. The light–dark rhythm of plasma melatonin was also observed in pinealectomized pigeons. In tissue determinations pinealectomy was found to reduce hypothalamic melatonin significantly, suggesting that the pineal is the main source of hypothalamic melatonin. In the Harderian glands a significant increase of melatonin concentrations was observed after pinealectomy. These glands may therefore be the compensatory organs, explaining the presence of circulating melatonin after pinealectomy.
J. Endocr. (1985) 105, 263–268
Multiple forms of somatostatin-like immunoreactivity in the hypothalamus and amygdala of the rat: selective localization of somatostatin-28 in the median eminence
Authors: Pierotti A. R. , Harmar A. J. 
Published: December 2008

ABSTRACT
The presence of multiple forms of somatostatin-like immunoreactivity (SSLI) in the rat hypothalamus was confirmed using a sensitive radioimmunoassay in conjunction with gel filtration chromatography and high performance liquid chromatography (HPLC). Gel filtration chromatography of hypothalamic extracts revealed the presence of four forms of SSLI with estimated molecular weights of 1500, 3000, 6000 and 10000. Analysis by HPLC indicated that the 1500 and 3000 mol. wt forms of SSLI corresponded respectively to somatostatin-14 (SS14) and somatostatin-28 (SS28) whereas the 6000 and 10 000 mol. wt forms eluted together as a composite peak of high molecular weight somatostatin (HMW-SS). The proportions of SS14 (63%), SS28 (12%) and HMW-SS (25%) present in the hypothalamus were similar to those in the amygdala (59, 9 and 32% respectively). In contrast, the median eminence contained a greater proportion of SS28 than the other tissues: SS14, SS28 and HMW-SS were present in the proportions 40:24:26%. These results show that the rat median eminence differs from the hypothalamus as a whole in containing SS14 and SS28 in almost equimolar concentrations. The localized abundance of SS28 in the nerve terminals of the median eminence suggests a specific role for this peptide in the hypothalamic regulation of growth hormone secretion.
J. Endocr. (1985) 105, 383–389
Can the transition into anoestrus in the ewe be accounted for solely by insufficient tonic LH secretion?
Authors: Legan S. J. , Goodman R. L. , Ryan K. D. , Foster D. L. , Karsch F. J. 
Published: December 2008

ABSTRACT
It has been proposed that a seasonal increase in oestradiol negative feedback elicits anoestrus by preventing a key step in the preovulatory sequence of endocrine events, namely a sustained increase in tonic LH secretion. In the present study we compared the patterns of serum LH, FSH, oestradiol and progesterone after regression of the last corpus luteum of the breeding season, with their respective patterns during an ovulatory cycle in the late breeding season (samples obtained every 4 h from eight ewes). After regression of the last corpus luteum of the breeding season, serum LH and oestradiol showed distinct deviations from their respective late breeding season patterns. The rise in tonic LH secretion was curtailed. Further, there were no marked increases in oestradiol, despite a distinct, although brief, tonic LH rise; thus there were no gonadotrophin surges. If the hypothesis that the transition into anoestrus is caused solely by insufficient tonic LH secretion were correct, the brief increase in LH should have induced a transient rise in oestradiol. Since this was not the case, these results suggest that a decreased ovarian response to LH may also contribute to the termination of oestrous cyclicity at the transition to anoestrus.
J. Endocr. (1985) 106, 55–60
Inhibitory effect of colchicine and vinblastine on transport of glucagon receptors to the plasma membrane in cultured rat hepatocytes
Authors: Watanabe J. , Kanamura S. , Kanai K. , Asada-Kubota M. , Oka M. 
Published: December 2008

ABSTRACT
The role of microtubules in the regulation of glucagon receptors on cultured rat hepatocytes was studied. Antimicrotubular reagents, colchicine and vinblastine, did not affect the binding of 125I-labelled glucagon to hepatocytes at 4°C. At 20 and 37 °C, however, the reagents reduced the binding after 60 or 90 min of incubation. Scatchard analysis indicated that the reduction in the binding was due to loss of glucagon-receptor populations. If hepatocytes were preincubated with both unlabelled glucagon and the reagents at 37 °C, the binding of the ligand to the cells decreased markedly after a certain delay. The reagents did not inhibit the internalization of the ligand in the cells until 30 min of incubation at 37 °C. The results suggest that the microtubule system plays a role in the transport of glucagon receptors to the plasma membrane, which is followed by their internalization.
J. Endocr. (1985) 106, 125–131
Repeated thyrotrophin stimulation of thyroid secretion: lack of refractoriness in vivo
Authors: Bagchi N. , Brown T. R. 
Published: December 2008

ABSTRACT
It has been reported that prior exposure of thyroid tissue to TSH in vitro induces a state of refractoriness to new challenges of the hormone. We have investigated the effect of repeated TSH treatment on thyroid secretion to determine whether such refractoriness exists in vivo. The rate of thyroid secretion was estimated by measuring the rate of hydrolysis of labelled thyroglobulin from mouse thyroid glands in vitro. The thyroid glands were labelled in vivo with 131I and then cultured for 20 h in the presence of mononitrotyrosine, an inhibitor of iodotyrosine deiodinase. The rate of hydrolysis of labelled thyroglobulin was measured as the percentage of radioactivity released as free iodotyrosines and iodothyronines into the gland and the medium at the end of incubation. Thyrotrophin was administered in vivo at hourly intervals for 2–4 injections. The corresponding control group received saline injections every hour except for the last injection when they received TSH. The peak rates of thyroglobulin hydrolysis, measured 2 h following the last injection, were similar in animals receiving two, three or four TSH injections and were not different from those in the control groups. Serum tri-iodothyronine and thyroxine concentrations 2 h after the last injection were higher in the groups receiving multiple TSH injections. Thyroidal cyclic AMP accumulation in response to TSH was markedly depressed in the group receiving multiple injections compared with the group receiving a single injection of TSH in vivo. These data indicate that (1) the stimulatory effect of TSH on thyroidal secretion is not diminished by prior administration of the hormone in vivo, (2) repeated TSH administrations in vivo cause refractoriness of the adenylate cyclase response to TSH and (3) a dichotomy exists between the secretory response and the adenylate cyclase response to repeated administrations of TSH.
J. Endocr. (1985) 106, 153–157
Role of the uterine cervix in inhibition of sexual behaviour in lactating rats
Authors: Forsberg G. , Södersten P. , Eneroth P. 
Published: December 2008

ABSTRACT
Treatment of ovariectomized rats with progesterone-filled constant-release implants, which increased serum progesterone concentrations to 99·4 ±5·0 nmol/l, facilitated the induction of lordosis behaviour by subsequent treatment with oestradiol benzoate (OB, 10 μg). Concurrent treatment with the dopamine receptor antagonist domperidone (two daily injections of 2·5 mg/rat), which increased serum prolactin concentrations, did not inhibit the behavioural response of ovariectomized progesterone-treated rats to OB. If the treatment was combined with stimulation of the uterine cervix it inhibited lordosis to a level which was comparable with that of progesterone–domperidone-treated rats, which had been ovariectomized and from which the pups had been removed on the day of parturition. The cervical stimulation did not increase the amount of prolactin secreted by the pituitary gland in response to an injection of domperidone. The behavioural effect of cervical stimulation was blocked by injecting an anaesthetic paste (0·1 ml lidocain–prilocain) intravaginally against the cervix. The effect of cervical stimulation, or of parturition, lasted only for a few days and sexual behaviour was inhibited during a prolonged period of lactation. Sucking by the pups on the nipples of the mother may be required for preventing sexual behaviour during the entire period of lactation.
J. Endocr. (1985) 106, 183–188
Effects of cortisol and progesterone on insulin binding and lipogenesis in adipocytes from normal and diabetic rats
Authors: Mendes A.-M. , Madon R. J. , Flint D. J. 
Published: December 2008

ABSTRACT
Cortisol implants in normal and diabetic rats reduced body weight, adiposity, insulin receptor concentration and both basal and insulin-stimulated rates of lipogenesis in isolated adipocytes, whilst insulin sensitivity was unchanged. In normal but not diabetic rats these changes were accompanied by increased serum glucose and insulin concentrations.
In contrast, progesterone implants in normal and diabetic rats increased body weight gain, adiposity, insulin receptor concentration and both basal and insulin-stimulated rates of lipogenesis in adipose tissue, again without affecting insulin sensitivity. Progesterone did not affect serum insulin concentrations in normal or diabetic rats but accelerated the decline in serum glucose concentrations which occurred during an overnight fast in diabetic rats.
The results suggest that (1) cortisol inhibits lipogenesis in adipose tissue without affecting insulin sensitivity, (2) cortisol reduces insulin binding in adipose tissue without a requirement for hyperinsulinaemia, which might itself indirectly lead to down-regulation of the insulin receptor, and (3) in diabetic rats progesterone stimulates lipogenesis in adipose tissue without any increase in food intake or serum insulin concentrations suggesting that progesterone may have a direct anabolic role in adipose tissue.
J. Endocr. (1985) 106, 225–231
Naloxone-induced secretion of LH in the male Syrian hamster: modulation by photoperiod and gonadal steroids
Authors: Roberts A. C. , Hastings M. H. , Martensz N. D. , Herbert J. 
Published: December 2008

ABSTRACT
The role of endogenous opiates in the regulation of photoperiodically induced testicular regression was studied in the male Syrian hamster. In reproductively active hamsters exposed to a long photoperiod (LD; 16 h light: 8 h darkness) or to short days (SD; 8 h light: 16 h darkness) for 20 weeks or to SD after pinealectomy, administration of naloxone, a competitive opiate receptor antagonist, at doses of 2·5–20 mg/kg, significantly increased serum LH concentrations. In marked contrast, these doses of naloxone did not produce any change in LH levels in reproductively quiescent hamsters exposed to SD for 8 weeks.
The influence of gonadal steroids on the LH response to naloxone was studied in hamsters castrated or castrated and implanted s.c with a capsule containing testosterone. Naloxone did not induce LH release in castrated hamsters maintained in LD or in SD, but this response was restored in LD but not SD when serum testosterone concentrations were maintained at levels similar to those observed in intact reproductively active hamsters.
These results show that inhibition of reproduction by the photoperiod prevents naloxone-induced LH release in the male hamster. This lack of response to naloxone is not due, however, to the lower testosterone titres present in these animals compared with reproductively active animals. Responsiveness to naloxone can be restored when the animal is rendered insensitive to the inhibitory photoperiod either by removal of the pineal gland or by induction of photorefractoriness by extended exposure to SD.
J. Endocr. (1985) 106, 243–248
Time-dependent effects of oestradiol and progesterone on hypothalamic catecholamine turnover in ovariectomized rats
Authors: Hiemke C. , Bruder D. , Michel M. C. , Ghraf R. 
Published: December 2008

ABSTRACT
Long-term ovariectomized rats received a single injection of 20 μg oestradiol benzoate (OB) which reduced the serum levels of LH for at least 3 days. The inhibitory effects were accompanied by time-dependent alterations of noradrenaline and dopamine turnover rates in the mediobasal hypothalamus (MBH) and the preoptic-anterior hypothalamic brain area (POAH). Oestradiol markedly interfered with the time-dependent variations of noradrenaline and dopamine turnover seen in the MBH of untreated ovariectomized animals during daylight hours. In the POAH the turnover rate of noradrenaline decreased 2 days after priming with OB and then increased in the afternoon of day 3. The increase of noradrenaline turnover in the POAH was accompanied by a low afternoon turnover rate of dopamine in the M BH and by an increased sensitivity of the LH secretory system to progesterone.
Dopamine and noradrenaline turnover involve a time element. While the negative feedback actions of oestradiol do not seem to be associated with changes in dopamine or noradrenaline turnover, the results support the view that the induction of LH afternoon surges depends upon an increase of stimulatory noradrenergic inputs to the POAH and a decrease of inhibitory dopaminergic inputs in the MBH.
J. Endocr. (1985) 106, 303–309
Effects of dopamine and morphine on immunoreactive somatostatin and LH-releasing hormone secretion from hypothalamic fragments in vitro
Authors: Lengyel A. M. J. , Grossman A. , Bouloux P.-M. G. , Rees L. H. , Besser G. M. 
Published: December 2008

ABSTRACT
Dopamine and morphine modulate GH and LH release, probably at a hypothalamic locus. To investigate this in more detail, we studied the influence of these substances on somatostatin and LH-releasing hormone (LHRH) release from rat hypothalamic fragments in vitro. Hypothalamic fragments were incubated in Earle's medium. After 60 min of preincubation, medium from two 20-min incubations was collected and somatostatin and LHRH levels measured by radioimmunoassay. Dopamine (10 nmol/l–0·1 mmol/l) induced a progressive increase (r = 0·41; P <0·01) in basal somatostatin levels. K + (30 mmol/l)-induced somatostatin release was also increased (r = 0·54; P <0·01) by increasing doses of dopamine. Metoclopramide (10 μmol/l) blocked the dopamine (1 μmol/l)-induced increase in somatostatin release. No significant relationship between dopamine and LHRH was found either basally or after K + (30 mmol/l) stimulation. Basal somatostatin was negatively correlated (r = −0·63; P <0·01) with morphine concentrations. No significant correlation was found after K+ (30 mmol/l) depolarization. Basal LHRH release was not influenced by morphine, while K +(30 mmol/l)-induced release was significantly lower than controls only at a concentration of 10 nmol/l. These results suggest that dopamine and morphine act at a hypothalamic level to modulate GH release through alterations in somatostatin secretion. Dopamine and morphine have no consistent effect on hypothalamic LHRH release.
J. Endocr. (1985) 106, 317–322