bluuebunny/crossref_metadata_2025_split huggingface dataset:
In-vitro secretion of prolactin and growth hormone in the presence of melatonin by pituitary gland from mink kept under long or short days
Authors: Meunier M. , Brebion P. , Chêne N. , Servely J.-L. , Martinet L. 
Published: December 2008

ABSTRACT
Mink anterior pituitaries were incubated in Medium 199 for up to 9 or 13 days. Biological activity of prolactin and GH was determined. Daily concentrations of prolactin and GH in the incubation medium were also measured by radioimmunoassay and radioreceptor assay. When females were kept under short days for several weeks before the experiment, a significant decrease in prolactin secretion by the anterior pituitary was observed as compared with that in females maintained under long days. In contrast, secretion of GH was not modified by the photoperiodic history of the animals. Pineal gland denervation by ablation of the superior cervical ganglia a few months before the experiment, or addition of melatonin to the incubation medium of anterior pituitaries from intact or ganglionectomized females, did not modify the secretion of prolactin and GH. The pituitary gland does not therefore seem to be a direct target site for melatonin in transducing the duration of daylength on the hypothalamo-pituitary axis.
J. Endocr. (1988) 119, 287–292
Hormonal regulation of DNA polymerase-β activity in the rat thyroid gland
Authors: Nagasaka A. , Yoshida S. , Nakai A. , Ohyama T. , Iwase K. , Ohtani S. , Nakagawa H. , Masunaga R. , Kato S. , Kawabe T. , Kataoka K. 
Published: December 2008

ABSTRACT
Using hypophysectomized rats, it has been shown that DNA polymerase-β activity in the adrenal gland and testis is largely influenced by pituitary trophic hormones. Sucrose gradient centrifugation of thyroid extracts revealed three peaks of DNA polymerase-β activity sedimenting at 3·3S, 7·3S and 12S. Of these, hypophysectomy induced a decrease in the 3·3S DNA polymerase-β, whereas other molecular forms were affected only slightly. DNA polymerase-α and -γ activities were unaffected by hypophysectomy. These changes in DNA polymerase-β caused by hypophysectomy were reversed by daily i.p. injection of TSH. Furthermore, stimulation of the thyroid by excess TSH induced by the administration of 1-methyl-2-mercaptoimidazole resulted in an increase of all forms of thyroid DNA polymerase-β.
These results show that the level of DNA polymerase is relatively constant after hypophysectomy but that DNA polymerase-β in the rat thyroid gland is also modulated by TSH mainly through the change of activity of the polymerase-β which sediments at 3·3S.
J. Endocr. (1988) 119, 303–308
The rebound release of growth hormone (GH) following somatostatin infusion in rats involves hypothalamic GH-releasing factor release
Authors: Clark R. G. , Carlsson L. M. S. , Rafferty B. , Robinson I. C. A. F. 
Published: December 2008

ABSTRACT
We have studied the rebound secretion of GH following short-term somatostatin (SS) infusions in conscious rats, using an automatic sampling system for withdrawing frequent microsamples of blood. Intravenous infusions of SS (5–50 μg/h per rat) inhibited spontaneous GH secretion, but when SS was withdrawn there was a large burst of rebound GH secretion. A sub-anaesthetic dose of urethane reduced such rebound bursts of GH, suggesting a hypothalamic involvement in rebound GH secretion. Passive immunization with an antibody against rat GH-releasing factor (GRF) attenuated the rebound GH secretory response to the withdrawal of an SS infusion (GH concentration during rebound secretion was 26±21 μg/l vs 475 ± 127 μg/l (mean ± s.e.m.), after 0·5 ml anti-GRF serum or non-immune serum respectively). The inhibition of GH rebound secretion was related to the dose of anti-GRF serum administered. Intravenous infusions of human GH (20– 100 μg/h per rat) also reduced the size of the rebound GH secretion following SS withdrawal, in both male and female rats. We suggest that the rebound GH secretion that follows SS withdrawal in vivo is caused mainly by a hypothalamic release of GRF. Exogenous GH inhibits SS-induced rebound GH secretion in the conscious rat, possibly by inhibiting hypothalamic GRF release.
J. Endocr. (1988) 119, 397–404
Inhibitory effect of neurohypophysial peptides on cyclic AMP accumulation by isolated hepatocytes of the trout
Authors: Lahlou B. , Fossat B. , Porthé-Nibelle J. , Bianchini L. , Guibbolini M. 
Published: December 2008

ABSTRACT
Cyclic AMP levels were measured in freshly isolated hepatocytes of the rainbow trout. Compared with basal values, the average levels were increased up to 60 times in a dose-dependent manner either by mammalian glucagon (concentration range 1 nmol– 1 μmol/l; dose giving half maximum response (EC50) 0· 18 μmol/l) or by forskolin (concentration range 0·1–100 μmol/l; EC50 about 10 μmol/l). These stimulatory effects were partially inhibited by fish or mammalian neurohypophysial hormones used at relatively high concentrations (1–5 μmol/l). It is suggested that these results are evidence for the presence of V1-type receptors in fish hepatocytes. Together with previous results obtained with gills on the hormonal inhibition of adenylate cyclase activity, they suggest that teleost fish may possess only V1-type receptors (or two V1-related types), while the V2 receptors have evolved (or have become functional) in higher vertebrates.
J. Endocr. (1988) 119, 439–445
Influence of neonatal opioid blockade or injections of gonadotrophin-releasing hormone on the timing of puberty in female rats: correlation of opioid effects with occupation of hypothalamic μ-opioid receptors
Authors: Landymore K. M. , Wilkinson M. 
Published: December 2008

ABSTRACT
Hypothalamic opioid peptides have been implicated in the timing of sexual maturation in several species. We have examined the effects of neonatal opioid blockade on the timing of puberty in the female rat and have compared these with the effects of neonatal GnRH injection. Intermittent naloxone (2·5 mg/kg) or GnRH (200 ng/100 g body wt) injected s.c. at 6-h intervals for the first 10 days of life only slightly advanced the mean day of vaginal opening (VO). However, the degree of precocity was significantly more marked in a subgroup of drug-injected rats. In contrast, injections of the long-acting opioid antagonist naltrexone (50 mg/kg) had no effect on the timing of VO.
The results suggested that the duration of opioid receptor blockade is critical in determining the degree of opioid antagonist effect. Therefore, additional studies were performed to compare receptor occupancy of naloxone and naltrexone in 9-day-old rat pups. An exvivo binding assay was utilized to determine the availability of hypothalamic opioid-binding sites at various intervals following a single s.c. injection of antagonist. The time-course of inhibition of tritium labelled [d-Ala2-N-Me-Phe4,Gly5-ol]-enkephalin ([3H]DAGO) binding (μ-opioid sites) revealed that naloxone occupies the μ-receptor for a relatively short period of time. Naloxone (2·5 and 50 mg/kg) produced extensive inhibition of [3H]DAGO binding at 30 min following injection but binding was 100% of control at 1 h and 3·5 h respectively. In contrast, hypothalamic binding in naltrexone-treated (50 mg/kg) pups did not reach 50% of control values until 12 h and 100% of control values at 20 h after injection. The results are consistent with naltrexone's role as a long-acting antagonist but indicate that this blockade is not sustained for 24 h as previously indicated by indirect assessment with opiate challenge tests. Our data demonstrate that the duration of μ-opioid receptor occupancy is an important consideration in attempting to understand why intermittent, but not more continuous, blockade of opioid receptors induces some degree of sexual precocity in female rats. Also of interest is the observation that anterior pituitary stimulation with GnRH, during the first 10 days of life, can modify the timing of sexual maturation.
J. Endocr. (1988) 119, 447–452
Inhibition of testicular and somatic development after treatment of the postnatal rat with the Leydig cell cytotoxic ethylene dimethanesulphonate
Authors: Morris I. D. , Lendon R. G. , Zaidi A. 
Published: December 2008

ABSTRACT
The Leydig cell cytotoxic ethylene dimethanesulphonate (EDS) was administered s.c. daily (50 mg/kg) to male rats aged 5–16 days. Apart from loss of weight and that the eyelids unfused earlier, no gross toxicity was observed during treatment. On day 17 testis weights, serum testosterone concentrations, testicular serum testosterone content and 125I-labelled human chorionic gonadotrophin (hCG) binding to testicular homogenates were reduced. Serum LH and FSH concentrations were elevated.
The testes did not recover from EDS treatment and at 63 and 120 days were minute (<2% of control), and the prostate and seminal vesicles were small although not completely atrophied. In addition, body weights were substantially reduced. Serum and testicular testosterone and 125I-labelled hCG binding to testicular homogenates were reduced but not absent. Serum LH and FSH concentrations were increased. Light microscopy of the adult testes showed that EDS treatment inhibited the development of the seminiferous tubules. Most of the tubules were devoid of germ cells and Sertoli cells were rare. Occasionally tubules also contained spermatogonia and spermatocytes but no signs of spermiogenesis. The testes were composed mainly of closely packed interstitial tissue with no lymphatic space. The interstitial cells resembled Leydig cells and stained for 3β-hydroxysteroid dehydrogenase. Histochemically identified Leydig cells were absent during treatment but reappeared when treatment was withdrawn. Testicular Leydig cell numbers were only 7% of control values in the 63-day-old EDS-treated rat. The effect on the testis of EDS treatment administered at a crucial time of testicular development may be explained by withdrawal of androgen; however, the systemic effects indicate non-specific toxicity so any explanation of these changes must be viewed with caution.
J. Endocr. (1988) 119, 467–474
Effect of maternal hyperglycaemia on insulin secretion by monolayer cultures of pancreatic cells from neonatal rats: a perifusion study
Authors: Takao F. , Kagawa S. , Sakamoto K. , Matsuoka A. 
Published: December 2008

ABSTRACT
The effect of maternal hyperglycaemia on the function of neonatal B cells was examined using a perifusion technique in pancreatic monolayer cultures of neonatal rats from normoglycaemic mothers (C), and those made slightly hyperglycaemic (SH) and highly hyperglycaemic (HH) by injection of streptozotocin. Monolayer cultures were kept for 7 days in medium containing 5·5 mmol glucose/l plus 1 mmol 2-deoxy-glucose/l. On day 0, B cells in the C group responded to 16·7 mmol glucose/l, 10 mmol leucine/l and 10 mmol 2-ketoisocaproate/l in a monophasic fashion with no significant rise in the second phase. However, compared with the C group, a significant increase in the second-phase secretion in response to glucose and 2-ketoisocaproate was observed in the SH group, although there was no difference in the first-phase secretion. In the HH group the insulin secretion was lower in the first phase but not in the second phase. After culture for 7 days, B cells in the C group showed a biphasic response to the secretagogues, with a great increase in the second-phase secretion. In the SH group, the second phase of insulin secretion was increased but the increment was far less than that in the C group. The secretory response was remarkably low in the HH group compared with other groups. From these results, we conclude that at an early stage of culture slight maternal hyperglycaemia causes a hypersensitivity of neonatal B cells but impairs the normal development of the function of B cells during culture, and that high hyperglycaemia results in impaired insulin secretion throughout the whole period of culture studied.
J. Endocr. (1988) 119, 493–499
Effects of morphine and naloxone on plasma levels of LH, FSH, prolactin and growth hormone in the immature male pig
Authors: Trudeau V. L. , Meijer J. C. , van de Wiel D. F. M. , Bevers M. M. , Erkens J. H. F. 
Published: December 2008

ABSTRACT
The effects of acute i.v. administration of gonadotrophin-releasing hormone (GnRH; 0·1 μg/kg), morphine (3 mg/kg) and/or naloxone (0·5 mg/kg) on LH and FSH secretion was evaluated in young male pigs (approximately 6 weeks old) with venous brachiocephalic cannulae. The effects of morphine and/or naloxone treatments on prolactin and GH were also evaluated. The influence of morphine on hypophysial hormone secretion was also examined 2 days after castration. Animals treated with morphine and/or naloxone were compared with saline-injected control animals. Injection of GnRH induced 400 and 50% increases in LH and FSH respectively. Morphine and/or naloxone did not influence LH secretion in intact or castrated animals. Morphine suppressed (P < 0·01) FSH levels 40–60 min after injection whereas naloxone had no effect. Castration eliminated morphine-induced suppression of FSH. Injection of morphine followed by naloxone resulted in acutely raised (P < 0·05) FSH concentrations. Morphine induced a threefold increase (P < 0·01) in prolactin within 30 min of injection and naloxone inhibited the effect of morphine. Levels of GH were increased (P < 0·01) 20 min after morphine treatment and this increase was delayed when naloxone was given immediately after morphine. Naloxone alone did not affect prolactin or GH secretion. Castration caused increases in LH (P < 0·05) and FSH (P < 0·01), did not influence prolactin or GH, and reduced plasma testosterone to undetectable (< 1·0 nmol/l) levels. These results suggest that in young male pigs the hypothalamic-hypophysial axis is responsive to GnRH and gonadal negative feedback. The opiate/LH pathway appears to be non-functional or incomplete, while the opiate/FSH pathway seems to be active. Morphine stimulated the release of prolactin probably via a naloxone-sensitive opiate receptor.
J. Endocr. (1988) 119, 501–508
Effect of α-melanocyte-stimulating hormone on tyrosinase activity in hair follicular and epidermal melanocytes of the mouse
Authors: Seechurn P. , Burchill S. A. , Thody A. J. 
Published: December 2008

ABSTRACT
In this study, the effect of α-MSH on tyrosinase activity was compared in epidermal and hair follicular melanocytes of mice. It had no effect on epidermal tyrosinase activity in dorsal skin from neonatal non-agouti black mice (C57BL/6J) in both in-vivo and in-vitro experiments. Theophylline and 8-bromocyclic (c)AMP were similarly without effect in in-vitro experiments. In-vivo administration of α-MSH and theophylline for 7 days was also without effect on epidermal tyrosinase activity in ear skin of adult non-agouti mice, and the same was true for α-MSH in wild-type agouti mice. Activation of the epidermal melanocytes in the non-agouti and wild-type agouti mice with ultraviolet radiation also failed to bring about a response to α-MSH and to theophylline in the case of the former. No tyrosinase activity was detected in the epidermis of viable yellow mice (C3H-HeAvy), but, as shown previously, tyrosinase activity was present in the hair follicle when the hair was actively growing and was increased in those mice given either α-MSH or theophylline. α-MSH and theophylline had no such effects on hair follicular tyrosinase activity in the non-agouti mice.
The present results suggest that α-MSH- and cAMP-dependent mechanisms have little or no importance in the regulation of tyrosinase expression in mouse epidermal melanocytes. α-MSH may, however, regulate tyrosinase expression in hair follicular melanocytes, but even in these melanocytes its action may be restricted to mice that express the agouti gene.
J. Endocr. (1988) 119, 517–522
DEMONSTRATION OF MELATONIN-BINDING SITES ON THE PARS TUBERALIS OF THE RAT
Authors: Williams L. M. , Morgan P. J. 
Published: December 2008

ABSTRACT
Melatonin-binding sites have previously been identified in the suprachiasmatic nucleus (SCN) and median eminence (ME) of the rat. We have further investigated the localization of melatonin-binding sites in the rat hypothalamus and pituitary using the ligand [125I] iodomelatonin and in-vitro autoradiography. The presence of specific melatonin-binding sites in the SCN is confirmed; however the second area of melatonin binding is identified as the pars tuberalis of the pituitary and not the ME as previously described. No other areas which bound melatonin were found in either the pituitary or the hypothalamus.
Thyrotrophin-releasing hormone-related polypeptides in rabbit prostate and semen are different from those in rabbit hypothalamus
Authors: Cockle S. M. , Morrell J. M. , Smyth D. G. 
Published: December 2008

ABSTRACT
TRH-related peptides were extracted from the hypothalamus and prostate gland of the rabbit. The peptides were fractionated by gel exclusion chromatography and located by trypsin digestion and radioimmunoassay with antibodies to TRH amide and TRH–Gly Lys. In the hypothalamus TRH-related peptides containing approximately 16 and 30 residues were observed: in these peptides the extensions to the TRH sequence were exclusively in the C-terminal direction. In addition, the three-residue form of TRH was also present. In the prostate complex, the predominant TRH-related peptide contained approximately 50 residues and the extension to the TRH tripeptide was on the N-terminal side; a three-residue form of immunoreactive TRH was also demonstrated. The same pattern of TRH-related peptides was shown to be present in rabbit semen. The results reveal the existence of a novel TRH-related polypeptide in the prostate and semen which does not occur in the hypothalamus. This peptide appears to undergo secretion.
Journal of Endocrinology (1989) 120, 31–36
Oestrogen receptors and effects of oestradiol administration on mRNA synthesis in the limbic system of the neonatal female rat
Authors: Greenstein B. D. , Adcock I. M. 
Published: December 2008

ABSTRACT
There is sexual dimorphism of specific species of mRNA in the neonatal rat brain and this sexual dimorphism may be imprinted by steroids of testicular origin during the perinatal period. According to current theories, only aromatizable androgens may cause sexual differentiation of sexual behaviour and function in the adult. The effects of oestradiol benzoate on mRNA synthesis in the neonatal female limbic system were therefore studied. In addition, cytosolic and nuclear oestrogen receptors were measured after administration of testosterone propionate, oestradiol benzoate or dihydrotestosterone (DHT). An attempt was made to distinguish between the brain oestrogen receptor and the plasma oestrogen-binding protein, alphafoetoprotein (AFP) by isoelectric focussing. After injection of 50 μg oestradiol benzoate s.c. to neonatal female rats, the expression of mRNA coding for sexually dimorphic proteins appeared to be changed to a male-type pattern. The overall density of labelling was noticeably greater and specific changes in labelled proteins were observed. These effects were observed within 3 h of injection. Both testosterone and oestradiol caused a marked depletion of cytosolic oestrogen receptors in the limbic system whereas DHT was ineffective in this respect. Nuclear receptors were present in equal abundance in male- and female-derived nuclei and only oestradiol was able to cause a significant (P < 0·025) increase in nuclear oestrogen receptors. The receptor and AFP could be distinguished by isoelectric focussing, since the pI of the receptor was 7·05, while that of AFP was 4·5. These results are consistent with the possibility that oestradiol alters transcription in the neonatal rat brain and may do this through the oestrogen receptor. Nevertheless, it is also possible that oestradiol could alter post-transcriptional events such as the stability of mRNA or the binding of tRNA to the polysomal complex.
Journal of Endocrinology (1989) 120, 83–88
Growth hormone regulates the level of insulin-like growth factor-I mRNA in rat skeletal muscle
Authors: Isgaard J. , Nilsson A. , Vikman K. , Isaksson O. G. P. 
Published: December 2008

ABSTRACT
Levels of mRNA for the insulin-like growth factor-I (IGF-I) in rat heart and skeletal muscle and its dependence on GH were investigated using a solution hybridization assay. Levels of IGF-I mRNA decreased following hypophysectomy, and replacement therapy with human GH (hGH) normalized heart and skeletal muscle levels. The stimulatory effect of hGH was dose-dependent, the lowest effective dose being 100 μg. A significant increase of IGF-I mRNA was observed 60 min after s.c. administration of 100 μg hGH and the maximum increase was apparent 6–12 h after hGH injection. Administration of 200 μg IGF-I or 11 μg insulin did not significantly change levels of IGF-I mRNA. The results show that GH regulates the level of IGF-I mRNA in rat heart and skeletal muscle and give further support to the hypothesis that locally produced IGF-I might be a local mediator for the direct stimulatory effect of GH on the growth and development of heart and skeletal muscle.
Journal of Endocrinology (1989) 120, 107–112
Stress alters immune function and disease resistance in chinook salmon (Oncorhynchus tshawytscha)
Authors: Maule A. G. , Tripp R. A. , Kaattari S. L. , Schreck C. B. 
Published: December 2008

ABSTRACT
We examined the effects of acute stress on the immune system and disease resistance of juvenile chinook salmon (Oncorhynchus tshawytscha) in laboratory and clinical trials. Immune function, as measured by the ability of lymphocytes from the anterior kidney to generate specific antibody-producing cells (APC) in vitro, was depressed 4 h after stress, when plasma cortisol levels were highest. At the same time, resistance to the fish pathogen, Vibrio anguillarum, was also depressed. Compared with controls, plasma cortisol and APC of stressed fish were unchanged after 24 h, and disease resistance was enhanced as evidenced by higher survival rate and longer mean time to death of mortalities. After 7 days, even though numbers of APC were depressed, plasma cortisol concentration and disease resistance did not differ from controls. This pattern was generally the same, independent of the type of stress applied: i.e. being held out of water in a dipnet for 30 s, manipulation during hatchery operations for 4 h, or transportation for 9 h. These and earlier findings suggest that similar endocrine-immune interactions operate in the mammalian and salmonid systems during acute stress.
Journal of Endocrinology (1989) 120, 135–142
Stimulation of ornithine decarboxylase activity by arginine vasopressin in the rat medullary thick ascending limb of Henle's loop
Authors: Charlton J. A. , Baylis P. H. 
Published: December 2008

ABSTRACT
The effect of arginine vasopressin (AVP) on rat renal ornithine decarboxylase (ODC) activity was investigated by a cytochemical technique optimized for use in the medullary thick ascending limb of Henle's loop (mTAL). Stimulation of ODC activity by AVP was confined to the mTAL. Peaks in enzyme activity in cultured rat renal segments occurred after tissue had been exposed to AVP for 3 or 8 min and these times of maximal stimulation did not change with the concentration of AVP. There was a dose-dependent response in ODC activity over the AVP concentration range 0·01–10 fmol/l. The ODC response to AVP was totally blocked by specific antiserum to AVP and reduced by 70% with the specific inhibitor to ODC, difluoromethyl ornithine.
Journal of Endocrinology (1989) 120, 195–199