bluuebunny/crossref_metadata_2025 huggingface dataset:
Growth hormone and prostatic tumours: localization using a monoclonal human growth hormone antibody
Authors: Sibley P. E. C , Harper M. E. , Peeling W. B. , Griffiths K.
Published: December 2008

The immunocytochemical detection of endogenous human GH and the binding of exogenously applied human GH in tumour tissue from patients with benign prostatic hyperplasia or prostatic carcinoma is reported. Monoclonal human GH antibody binding was exclusively to the connective tissue in both benign and carcinomatous specimens. Specificity control experiments indicated that the antibody could be absorbed with human GH but not with human prolactin. Preincubating the sections with human GH considerably altered the immunocytochemical staining, reducing the reaction product within the connective tissue in a concentration-dependent manner and revealing a binding site for GH within the cytoplasm of epithelial cells.

J. Endocr. (1984) 103, 311–315
Studies on inhibin-like peptide in gastric juice and serum of patients with duodenal ulcers
Authors: Shanbhag S. A. , Sheth A. R. , Nanivadekar S. A. , Sheth N. A.
Published: December 2008

Immunoreactive inhibin-like material (ILM) was measured by radioimmunoassay in serum and gastric juice samples of 23 fasting normal men and 23 men with duodenal ulcers (DU). Concentrations of ILM in gastric juice and serum of patients with DU were significantly higher than those in normal men (P <0·01). A strong positive correlation (r = 0·894) was observed between pH and ILM levels in gastric juice of normal men but not in patients with DU. Inhibin-like material in the gastric juice had a chromatographic profile similar to that of human seminal plasma.

J. Endocr. (1984) 103, 389–393
The oestrogenicity of equol in sheep
Authors: Kaziro R. , Kennedy J. P. , Cole E. R. , Southwell-Keely P. T.
Published: December 2008

The effects of intramuscular injection of synthetic racemic equol (±3-(4-hydroxyphenyl)-3,4-dihydro2H-1-benzopyran-7-ol) into wethers have been examined with respect to maintenance of plasma level, teat growth rate and the activity of the respiratory enzyme glucose-6-phosphate dehydrogenase. At a dose rate of 1·03 mmol/day a steady rise in 'total' (free plus conjugated) equol in plasma occurred to 1·78μmol/l in 4 days. A dose rate of 2·07 mmol/day produced only a further slight increase in plasma equol. At a lower dose rate of 0·52 mmol/day the plasma concentration reached 0·62 μmol/l in 2 days and this was not exceeded thereafter. At the dose rate of 1·03 mmol/day over 7 days significant increases in teat length and glucose-6-phosphate dehydrogenase activity occurred but no significant changes were observed at the dose rate of 0·52 mmol/day. It appears that threshold levels of intake of equol which maintain a plasma level of about 1·65 μmol/l are needed for oestrogenic effects to become apparent within a relatively short time.

Administration of 1·03 mmol/day over 5 days to ovariectomized ewes produced significant increases in uterine weight equivalent to those produced by 92 nmol stilboestrol dipropionate. Thus stilboestrol was apparently 56000 times more potent than racemic equol.

J. Endocr. (1984) 103, 395–399
Calcitonin may modulate placental transfer of calcium in ewes
Authors: Barlet J.-P.
Published: December 2008

In pregnant ewes bearing twin fetuses and fed an adequate Ca diet, the consequences of calcitonin (CT) deficiency (induced by thyroidectomy performed on day 30 of gestation, associated with daily thyroxine supplementation) differed according to the time of pregnancy. Such a deficiency had no significant effect either on fetal total body Ca content or on placental transfer of Ca in 77-day-old fetuses. On the contrary, CT deficiency for 110 days (on day 140 of pregnancy) was associated with an increased Ca concentration in fetal total body and increased placental transfer of Ca from the dam to its fetus, which did not occur in five thyroidectomized ewes supplemented with thyroxine and CT. This indicates that CT might protect the skeleton of the pregnant female against excessive demineralization by modulating placental transfer of Ca, when such a transfer becomes important, during periods of intense mineralization of the fetal skeleton.

J. Endocr. (1985) 104, 17–21
Mitogenic actions of insulin on fetal and neonatal rat cells in vitro
Authors: Crace C. J. , Hill D. J. , Milner R. D. G.
Published: December 2008

Insulin has been implicated in the regulation of fetal growth. The aim of these studies was to determine if insulin has a direct mitogenic effect on fetal and neonatal rat cells in vitro. Myoblasts and fibroblasts were isolated from skeletal muscle and grown until myotube formation began or until fibroblasts were confluent. The cultures were then incubated in the presence of insulin (10−5–10−1 units/ml) and its effects were measured by the cellular incorporation of [3H]-thymidine. Myoblasts from fetuses of 21 days of gestation showed a marked, linear dose–response to insulin, significant increases over control values being observed at 2 × 10−5 units/ml or 2 × 10−4 units/ml in five out of seven experiments. Neither myoblasts from 19-day fetuses or neonates nor fibroblasts from animals of any of the three ages showed a significant thymidine uptake response to insulin. Myoblasts released immunoreactive somatomedin-C-like activity into the culture medium, but this was not related to fetal age nor to the presence of insulin in the culture medium. The results suggest that insulin may have a direct role in fetal muscle growth.

J. Endocr. (1985) 104, 63–68
Effects of dietary energy supply on serum thyroxine, tri-iodothyronine and insulin concentrations in young horses
Authors: Glade M. J. , Reimers T. J.
Published: December 2008

The effects of meal ingestion on the circulating concentrations of the growth-regulating hormones thyroxine (T4), tri-iodothyronine (T3) and insulin were examined in weanling Thoroughbreds fed 70% (diet A), 100% (diet B) or 130% (diet C) of their energy and protein requirements. Peak insulin concentrations occurred 1, 2 and 3 h after the ingestion of diets C, B and A respectively. Increases in plasma glucose concentrations preceded the increases in serum insulin concentrations. Serum T4 concentrations increased after the ingestion of diets A and B and decreased after diet C. In contrast, serum T3 concentrations were unaffected by ingestion of diet A but increased after the ingestion of diets B and C. The increase was much greater and more rapid in the horses fed diet C. However, the decrease in T4 concentration was five times greater than the increase in T3 concentration. Accelerated insulin secretion after the ingestion of a meal high in energy (carbohydrate) content was therefore associated with decreased T4 secretion and accelerated T4 conversion to T3. However, 6 months later serum T4 and T3 concentrations were unaffected by meal ingestion.

J. Endocr. (1985) 104, 93–98
Rapid changes in growth hormone regulation and hypothalamic somatostatin after transection of anterolateral pathways to the medial-basal hypothalamus in the rat
Authors: Kakucska I. , Antal M. , Kárteszi M. , Makara G. B.
Published: December 2008

Plasma and pituitary GH content, in-vitro GH release and somatostatin-like immunoreactivity (SLI) in the stalk-median eminence were studied up to 7 days after making an anterolateral cut (ALC) around the medial-basal hypothalamus. Plasma GH concentration increased within 15 min to a very high level, then fell to a high level which was unchanged for several hours. The GH concentration then steadily decreased between days 2 and 7. The SLI content in the stalk-median eminence decreased to 3·5% of the control value within 3 days. The GH content of the anterior pituitary gland was 58·8% of the control value by 1 week after the operation but the in-vitro sensitivity to somatostatin of the GH cells failed to change. Pentobarbitone injection stimulated GH release in the sham-operated controls but decreased it in the rats with an ALC.

These findings suggest that transection of somatostatin-containing fibres is followed by a rapid rise and a lasting high concentration of plasma GH which slowly returns towards lower levels in parallel with a marked depletion of pituitary GH content. In rats with transected somatostatin innervation of the median eminence, sodium pentobarbitone probably decreases GH secretion by depressing the secretion of GH-releasing hormone.

J. Endocr. (1985) 104, 121–127
Inhibition of growth hormone release by rumen distension in female goats
Authors: Tindal J. S. , Blake L. A. , Simmonds A. D. , Hart I. C.
Published: December 2008

Six rumen-fistulated, overnight-fasted, female British Saanen goats were used. In preliminary experiments on two of the goats, evidence was obtained that inflation of a balloon with water in the cranial sac of the rumen was accompanied by inhibition of GH release. In a definitive series of experiments on the other four goats (one goat on 1 day = one experiment), a total of 96 experiments were carried out, 48 of which were balloon inflations with 2·5 litres water at 37 °C in the cranial sac of the rumen for 40 min and 48 were control experiments on alternate days. It was found that the mean plasma GH concentration of the samples taken at the end of the 40-min inflation period was significantly (P < 0·05) lower than the mean value of the samples taken at the start of inflation. Mean control values at the start and finish of inflation were not significantly different. There were no significant differences between mean plasma insulin concentrations at the start and finish of inflation in experimental and control groups. It is concluded that distension of the cranial rumen in the goat is a signal which can inhibit the release of GH.

J. Endocr. (1985) 104, 159–163
Influence of growth hormone, corticosterone, corticotrophin and changes in the environmental temperature on pituitary-ovarian function in the immature rat
Authors: Wilson C. A. , Buckingham J. C. , Morris I. D.
Published: December 2008

The influence of various endocrine and environmental factors on pituitary-ovarian function was studied in peripubertal rats treated with pregnant mare serum gonadotrophin (PMSG). Pregnant mare serum gonadotrophin induced ovulation in rats aged 27 days provided they weighed over 60 g. The response was preceded by a marked hypersecretion of LH which was detectable by radioimmunological and biological assay methods. In contrast, smaller rats of the same age did not ovulate in response to PMSG apparently because of the secretion of a pleiomorphic form of LH which, although immunoreactive, appeared to be biologically inactive. Ovarian function, assessed by response to exogenous gonadotrophins and by measurement of 125I-labelled human chorionic gonadotrophin binding, was normal despite the presence of the biologically inactive pleiomorph. Exposure of the small PMSG-treated rats to a high environmental temperature (39 °C) or treatment with corticosterone or GH altered the nature of the LH in the blood so that it was active in both assay systems and facilitated ovulation as also did ACTH. The results suggest that the abrupt change in the nature of the LH released by the pituitary gland essential for the initiation of ovulation may be affected by GH, corticosterone or a raised environmental temperature.

J. Endocr. (1985) 104, 179–183
Acute and chronic effects of a gonadotrophin-releasing hormone antagonist on pituitary and testicular function in monkeys
Authors: Akhtar F. Bint , Weinbauer G. F. , Nieschlag E.
Published: December 2008

The effects of a potent gonadotrophin-releasing hormone (GnRH) antagonist, (N-Ac-d-p-Cl-Phe1,2,d-Trp3,d-Arg6,d-Ala10)-GnRH (Org 30276), on pituitary and testicular function of adult macaque monkeys were investigated. After a study to find the correct dose in castrated monkeys, five intact adult male animals were treated with daily s.c. injections of 5 mg antagonist for 9 weeks. The treatment resulted in an immediate decline in serum LH and testosterone in three out of five animals. The two hormones remained suppressed during the 9-week treatment period. Testosterone and LH responses to a bolus injection of GnRH (50 μg i.v.) were blunted or abolished during the antagonist treatment. Testicular volumes decreased markedly and ejaculates obtained at the end of treatment were azoospermic or contained only few dead sperm. Histological examination of the testes showed complete disruption of seminiferous epithelium in these animals. A decrease of body weight was observed in the treated animals. When the treatment was ceased, all inhibitory effects of GnRH antagonists were reversible. In the other two animals no consistent suppression of pituitary or testicular function could be observed during this period, nor was a doubling of the treatment dose for a further 8 weeks capable of fully suppressing endocrine and seminal parameters in these monkeys.

It is concluded that GnRH antagonist treatment is capable of rapidly decreasing serum LH and testosterone and disrupting spermatogenesis in this primate species. Suppression effected by antagonist treatment is more rapid than that caused by GnRH agonists. The individual responses to the tested doses, however, vary markedly.

J. Endocr. (1985) 104, 345–354
Effects of 5-hydroxytryptamine uptake blockers on the release of LH and prolactin in several different experimental steroid models in the rat
Authors: Horn A. M. , Fink G.
Published: December 2008

The effect of the 5-hydroxytryptamine (5-HT) uptake blockers on the surges of LH and prolactin has been investigated in pro-oestrous rats and various experimental models used frequently to study the effects of steroids on LH and prolactin secretion in female rats. The steroid models were: rats ovariectomized on dioestrus, injected immediately with oestradiol benzoate (OB) and at 12.00 h on the next day (presumptive pro-oestrus) with progesterone (model 1); long-term ovariectomized rats injected with a single injection of OB and 72 h later with either progesterone (model 2) or OB (model 3); long-term ovariectomized rats injected daily with OB (model 4). The uptake blockers alaproclate (3–30 mg/kg) and zimelidine (20 mg/kg) were injected and blood samples withdrawn from previously implanted intra-atrial cannulae. Plasma LH and prolactin concentrations were determined by radioimmunoassay. The present study confirmed that a surge of LH occurs at about 17.00–18.00 h of the presumptive day of pro-oestrus in model 1, at about 5 h after (∼ 17.00 h) the injection of either progesterone or the second injection of OB in models 2 and 3, and diurnally in model 4, and the simultaneous occurrence of a prolactin surge in models 2 and 4. A surge of prolactin at the same time as the LH surge was shown to occur also in models 1 and 3. Alaproclate (30 mg/kg) administered at 15.00 h delayed significantly the peak of the prolactin surge in the pro-oestrous rat and models 1, 3 and 4, and in the latter the magnitude of the prolactin surge was also significantly reduced. By contrast, the peak of the prolactin surge in model 2 was significantly prolonged by alaproclate. Alaproclate had no significant effect on either the timing or the magnitude of the LH surge in the pro-oestrous rat, and models 3 and 4. The peak of the LH surge was delayed by alaproclate in model 1 and abolished in model 2, providing further evidence for the possible importance of interactions between 5-HT and progesterone in neuroendocrine control. Zimelidine had no significant effect on either the LH or prolactin surge in the pro-oestrous rat and in models 1 and 2.

These results show that normal 5-HT uptake is necessary for the normal timing and/or magnitude of the spontaneous and steroid-induced prolactin surge but is not essential for the normal timing and magnitude of the spontaneous surge of LH and the LH surge in some but not all steroid models. In terms of neuroendocrine effects alaproclate is more potent than zimelidine. The different effects of alaproclate in the different steroid models suggest that although superficially similar, different mechanisms underlie the prolactin and LH surges in these steroid models.

J. Endocr. (1985) 104, 397–406
Effects of 5-hydroxytryptamine uptake blockers on the concentration in brain of 5-hydroxytryptamine and 5-hydroxyindoleacetic acid in male rats, pro-oestrous rats and ovariectomized rats treated with oestrogen and progesterone
Authors: Horn A. M. , Watts A. G.
Published: December 2008

The aim of this study was to determine the effect of 5-hydroxytryptamine (5-HT) uptake blockade on 5-HT turnover by measuring the concentrations of 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) in brain with the aid of high performance liquid chromatography and electrochemical detection. The indoleamines were measured in the anterior hypothalamus (AH), posterior hypothalamus (PH) and raphe nuclei 30 min after the i.v. injection of either alaproclate (30 mg/kg) or zimelidine (20 mg/kg). The effect of alaproclate was studied in male rats, pro-oestrous female rats, rats ovariectomized and injected s.c. with 20 μg oestradiol benzoate (OB) on dioestrus and at 12.00 h of the next day (presumptive pro-oestrus) with 2 mg progesterone (model 1) and rats ovariectomized 3–4 weeks before an s.c. injection of 20 μg OB followed 72 h later by an s.c. injection of 2 mg progesterone (model 2). Alaproclate caused a significant decrease in the 5-HIAA/5-HT ratio in the AH and PH of the brain of male rats, in the PH and raphe nuclei in pro-oestrous rats and model 1, and in the raphe nuclei alone in model 2. Zimelidine had no effect on the 5-HIAA/5-HT ratio in any area in model 2. In male rats the injection of parachlorophenylalanine produced a marked reduction in the brain concentrations of 5-HT and 5-HIAA, but the 5-HIAA/5-HT ratio was unchanged by a subsequent injection of alaproclate. None of the pharmacological agents affected significantly the brain concentrations of noradrenaline, dopamine or dihydroxyphenylacetic acid.

These results together with the data in the preceding paper show that in female rats changes in LH and prolactin secretion produced by alaproclate may reflect changes in central 5-HT turnover.

J. Endocr. (1985) 104, 407–413
Effects of pup sucking behaviour on inhibition of sexual behaviour and ovulatory secretion of LH in lactating rats
Authors: Lindblom C. , Södersten P. , Eneroth P.
Published: December 2008

The time-interval between parturition and the display of sexual receptivity varied between 13·5 ± 0·7 and 35·9 ± 2·5 days in rats with litters of between 1 and 24 pups. Body weight gain decreased and the avidity of pup sucking behaviour, measured by the latency before the pups, placed on the ventrum of an anaesthetized mother, attached to a nipple of the mother, increased as litter size increased. Litter-shifting procedures, which introduced asynchrony between the lactational age of the mother and the age of the pups, produced deficiencies in sucking behaviour and did not prolong the time-interval between parturition and the display of sexual receptivity by the mother. By keeping the lactational age of the mother in synchrony with the age of the pups and depriving the pups of maternal contact and nutrition every alternate day, the time-interval between parturition and the display of sexual receptivity by the mother was prolonged by 17 days, the avidity of pup sucking behaviour markedly enhanced and the body weight gain of the pups retarded in comparison with mothers and pups continuously living together. The results show that the display of the first postlactational behavioural oestrus and surge of pituitary LH secretion can be greatly delayed by an increase in the avidity of pup sucking behaviour.

J. Endocr. (1985) 104, 419–425
Effects of hypophysectomy and subsequent FSH and testosterone treatment on inhibin production by adult rat testes
Authors: Au C. L. , Robertson D. M. , de Kretser D. M.
Published: December 2008

The hormonal control of inhibin production by adult rat testes was investigated using an in-vitro inhibin bioassay validated for the measurement of inhibin activity in charcoal-treated rat testicular extracts. The effect of hypophysectomy examined at 16 h, 3, 7 and 42 days after surgery showed a decrease in testicular inhibin content and seminiferous tubule fluid production by 7 days and a decrease in inhibin production by 42 days. Serum FSH and LH were suppressed 3 days after surgery. In 30-day chronically hypophysectomized adult rats treated for 3 days with twice daily s.c. injections of (a) human FSH (hFSH, 22 i.u./rat per day), (b) testosterone (5 mg/rat per day), (c) hFSH + testosterone (same doses as a and b), or (d) human chorionic gonadotrophin (hCG, 12 i.u./rat per day), hFSH or hFSH and testosterone stimulated an increase in testicular inhibin content but not in inhibin production or tubule fluid production. Testosterone and hCG had no effect on these parameters.

It is concluded that in vivo, FSH alone stimulates an increase in testicular inhibin content. The failure to observe an increase in inhibin production in vivo is attributed to the suppression of seminiferous tubule fluid production under the same experimental conditions.

J. Endocr. (1985) 105, 1–6
Heterogeneity of rat FSH by chromatofocusing: studies on in-vitro bioactivity of pituitary FSH forms and effect of neuraminidase treatment
Authors: Blum W. F. P. , Riegelbauer G. , Gupta D.
Published: December 2008

This study concerned the resolution of rat pituitary FSH utilizing chromatofocusing. Among the 11 components resolved and positively identified, ten had apparent isoelectric points (pI) between 3·1 and 5·1. Approximately 1% of pituitary FSH eluted at pH 9·4. Treatment with varying amounts of neuraminidase followed by refocusing generated FSH components of higher pI values. Treatment with other glycosidases did not alter the elution characteristics in chromato-focusing, while exclusion chromatography established an inverse relationship between apparent molecular weight and pi. Dose–response curves of various FSH components and of the reference preparation in the current radioimmunoassay system were parallel to each other. A study of their in-vitro bioactivity, utilizing granulosa cells which produce a plasminogen activator due to FSH in a dose-dependent manner, provided the following evidence: increased acidity of the components led to (1) an increase of maximum response and (2) an increase of the dose necessary for half-maximum response. Considering the observed alterations in the hetereogeneity of FSH with changing physiological states of the animal, it is concluded that qualitative changes of the FSH molecule are perhaps involved in a modulatory role in the biopotencies of the hormone.

J. Endocr. (1985) 105, 17–27
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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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
Prolactin-dependent accumulation of α-lactalbumin in mammary gland explants from the pregnant tammar wallaby (Macropus eugenii)
Authors: Nicholas K. R. , Tyndale-Biscoe C. H.
Published: December 2008

The minimal hormonal requirements for the in-vitro accumulation of α-lactalbumin have been investigated in a marsupial, the tammar (Macropus eugenii). Mammary gland explants from 24-day pregnant tammars cultured in medium containing bovine insulin, cortisol and ovine prolactin showed a progressive increase in accumulation of α-lactalbumin during 4 days of incubation. No increment was observed if prolactin was omitted from the medium. However, a similar rate of increase was observed after 3 days of culture in medium containing prolactin alone. This induction of α-lactalbumin was maximal at a prolactin concentration of approximately 0·02 mg/l, which corresponds to physiological levels during pregnancy and early lactation. The absence of an effect of bovine insulin on tammar explants is not due to a general unresponsiveness to this hormone since insulin-stimulated DNA synthesis and amino acid uptake was evident after 3 days of culture. The inclusion of tri-iodothyronine and raised concentrations of cortisol in culture media have been shown to modulate α-lactalbumin synthesis in eutherian mammals but were without effect in the tammar. In addition, increased levels of progesterone did not inhibit the induction of α-lactalbumin, confirming an earlier invivo study suggesting that progesterone withdrawal may not be the lactogenic trigger in this species. Thus the pregnant tammar is the only species yet described in which α-lactalbumin is induced maximally in vitro in response to a single hormone.

J. Endocr. (1985) 106, 337–342