bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of lactotroph cell density on prolactin secretion in rats
Authors: Pasolli H. A. , Torres A. I. , Aoki A. 
Published: December 2008

ABSTRACT
The relationships between the stimulation of prolactin secretion and proliferation of lactotrophs was studied from a multidisciplinary standpoint in three experimental models. Administration of both oestrogen and sulpiride resulted in a significant increase in prolactin secretion and in the lactotroph population. A single injection of 10 μg oestradiol benzoate (OB) induced a twofold increase in the proliferation of lactotrophs (morphometrically as volume density), which increased further (2·5-fold) after three OB injections. Parallel changes were observed in the net counts made on lactotrophs sectioned through the nucleus to avoid possible distortions in volume density caused by hypertrophic cytoplasms. Comparable results were obtained with the mitotic index in the same groups of rats exposed to treatment with colchicine. The effect of sulpiride on proliferation of lactotrophs was also significant (1·7-fold) but less pronounced than in rats treated with oestrogens. The treatments with oestrogen and sulpiride did not stimulate lactotrophic activity in a similar way, as judged by the levels of serum prolactin and the storage patterns of small and big prolactin in pituitary glands. Serum prolactin (mean ± s.e.m.) in control ovariectomized rats was 4·0±0·9 μg/l and one and three injections of OB raised these levels to 14·4±5·0 and 28·8±4·6 μg/l respectively. The highest levels of serum prolactin were seen in sulpiride-treated rats (467·2±28·7 μg/l). Striking differences occurred in the pituitary contents of big prolactin, the control values increasing from 5·3±0·5 to 10·2±1·3 μg/mg after one OB injection and to 14· 7 ±0·7 μg/mg after three OB injections. In contrast, the concentration of big prolactin in sulpiride-treated rats was very low (1·85 ± 0·2 μg/mg), 2·8-times smaller than the controls. Other changes were also found in the small prolactin content in pituitary tissue with higher values in all the experimental models. These differences could only be detected after differential extraction of big and small molecular forms of prolactin.
In ovariectomized rats, treatment with several doses of oestrogen enhanced the proliferation observed in the lactotroph population and increased the number of mitoses. In turn, morphological data could be closely related to the higher levels of prolactin in serum and pituitary glands. A sustained stimulation of lactotrophic secretion was always followed by proliferation of lactotrophs, the number of which fluctuated in parallel with the degree of stimulation.
Journal of Endocrinology (1992) 134, 241–246
Hypothalamic-pituitary function in neonatally oestrogen-treated male rats
Authors: Pinilla L. , Garnelo P. , Gaytan F. , Aguilar E. 
Published: December 2008

ABSTRACT
Neonatal oestrogen administration to male rats permanently impaired the function of the pituitary-testicular axis possibly by inhibiting neonatal gonadotrophin secretion. To analyse the hypothalamus and/or pituitary involvement in this inhibition, pituitary responsiveness to acute stimulation with LH-releasing hormone (LHRH) was studied in vivo and in vitro in Wistar male rats injected on day 1 of age with oestradiol benzoate (OB) or olive oil. FSH and LH pituitary content and plasma concentrations were reduced in oestrogenized male rats at days 10 and 16 of age. Likewise, the in-vivo increase in gonadotrophin plasma concentrations after acute stimulation with LHRH was almost completely suppressed in 10-and 16-day-old oestrogenized males. In vitro, the increased secretion of FSH after LHRH stimulation was abolished and the LH response strongly reduced in pituitaries from oestrogenized males. Finally, the effects of neonatal oestrogenization were not abolished by treatment from day 1 to day 15 with an LHRH agonist (0·01 μg/kg per 12 h). We conclude that in male rats the effects of oestrogenization are due to both a reduction in LHRH endogenous secretion and a decrease in the pituitary responsiveness to LHRH.
Journal of Endocrinology (1992) 134, 279–286
Receptor binding and growth-promoting activity of insulin-like growth factor-I in a bovine mammary epithelial cell line (MAC-T3)
Authors: Zhao X. , McBride B. W. , Politis I. , Huynh H. T. , Akers R. M. , Burton J. H. , Turner J. D. 
Published: December 2008

ABSTRACT
Insulin-like growth factor-I (IGF-I) has been known to be mitogenic to a variety of cell types, although a growth-regulatory role for IGF-I on bovine mammary epithelial cells has not been fully investigated. In the present study, we examined the receptor binding of IGF-I and its effect on growth in a bovine mammary epithelial cell line (MAC-T3). Specific receptors for IGF-I were detected on cultured bovine mammary epithelial cells. Competitive binding revealed that half-maximal inhibition of 125I-labelled IGF-I binding by IGF-I was approximately 3 μg/l. Dissociation rate constant of the IGF-I receptor was 3·10±0·06 nmol/l (s.e.m.) with a receptor site concentration of 366 ± 8 fmol/mg protein for the average of three experiments. IGF-I exerted a positive mitogenic effect on MAC-T3 cells according to both direct DNA assay and thymidine incorporation assay. Moreover, the mitogenic effect of IGF-I on MAC-T3 cells was enhanced by the addition of fetal calf serum in the culture media. The present results suggest that the bovine mammary epithelial cell line (MAC-T3) provides a useful model system with which to study the biological actions of insulin-like growth factors on the bovine mammary secretory tissue in vitro.
Journal of Endocrinology (1992) 134, 307–312
Effect of the antiprogestin RU486 on uterine sensitivity to oxytocin in ewes in late pregnancy
Authors: Burgess K. M. , Jenkin G. , Ralph M. M. , Thorburn G. D. 
Published: December 2008

ABSTRACT
The effect of RU486, a synthetic progesterone receptor antagonist, on basal uterine prostaglandin (PG) release and release in response to oxytocin injection has been investigated in late-pregnant sheep (days 135–140 of gestation). Fifteen hours after i.m. injection of RU486 (50 mg; n = 5) or vehicle alone (n = 4), bolus injections of oxytocin (50, 500 and 5000 mU) were administered via a uterine artery ipsilateral to the pregnant uterine horn at 2-hourly intervals. Uteroovarian vein concentrations of 13,14-dihydro-15-keto PGF2α (PGFM) and PGE2 were determined before and during oxytocin stimulation. Basal concentrations of both PGFM and PGE2 were significantly (P < 0·001) increased in ewes 15 h after RU486 administration compared with ewes receiving vehicle alone. Concentrations of PGFM, but not PGE2, increased significantly (P < 0·001) following injection of each dose of oxytocin in both treated and untreated animals. The response to oxytocin, measured both as the area under the curve and as the peak height of PGFM release, was significantly (P <0·05) greater in RU486-treated ewes. There was no significant effect of oxytocin on the area or peak height of PGE2 response in either RU486-treated or control animals. These results demonstrate that treatment of late-pregnant ewes with RU486 results in an increase in basal uterine PGFM and PGE2 as well as oxytocin-stimulated PGFM release.
Journal of Endocrinology (1992) 134, 353–360
Regulation of female brain aromatase activity during the reproductive cycle of the dove
Authors: Hutchison R. E. , Wozniak A. W. , Hutchison J. B. 
Published: December 2008

ABSTRACT
Oestrogen is formed in the female dove brain. The aim of this study was to determine whether (a) the catalytic properties of the brain aromatase are similar to the ovarian enzyme and (b) aromatase activity in the female brain changes during the reproductive cycle and is influenced by steroids and environmental stimuli.
The results show that female preoptic aromatase has a higher substrate affinity than the enzyme in ovarian follicles (apparent Km: preoptic area, 7 nmol/l; ovarian follicles, 29 nmol/l), but a lower activity in the preoptic area (Vmax: preoptic area, 290 fmol/mg tissue per h; ovarian follicles, 843 fmol/mg tissue per h). In intact females with developing follicles, oestradiol-17β formation was higher in the posterior hypothalamus than the preoptic area. Females in a later stage of reproductive development (yolked follicles) had a different distribution of oestrogen formation with increased aromatase activity in the preoptic area. Preoptic and posterior hypothalamic aromatase activity of females paired with males for 10 days was positively correlated (r = 0·84, P = 0·0001; r = 0·75, P = 0·001 respectively) with ovarian development. Females with undeveloped ovaries which interacted with males had higher preoptic aromatase activity than visually isolated females with similar ovarian development, suggesting that behavioural stimuli have direct effects on brain aromatase activity which are independent of the ovary. Oestradiol benzoate treatment increased preoptic and posterior hypothalamic aromatase activity in intact and ovariectomized females, and testosterone propionate treatment increased anterior hypothalamic aromatase activity, but did not affect other areas, indicating that the distribution of induced aromatase activity is steroid-specific. Oestrogen treatment in ovariectomized or intact females did not replicate the maximal hypothalamic aromatase activity seen when the ovary contained yolked follicles.
We conclude that brain aromatase activity is related directly to ovarian condition during the reproductive cycle of the female dove. As in the male, steroids have a role in the regulation of oestrogen formation in the female hypothalamus; behavioural stimuli are also likely to be involved in the control of the brain enzyme.
Journal of Endocrinology (1992) 134, 385–396
Sex hormone concentrations in blood serum from the North Atlantic fin whale (Balaenoptera physalus)
Authors: Kjeld J. M. , Sigurjónsson J. , Árnason A. 
Published: December 2008

ABSTRACT
Blood serum concentrations of testosterone and progesterone were measured in postmortem samples taken at sea from 814 fin whales (Balaenoptera physalus) caught during the summers (June–September) of 1981–1989. The ages of 781 of these animals were also assessed. The testosterone concentrations in samples from 352 males averaged 2 nmol/l; 41 samples had concentrations of 0·1 nmol/l or lower and 34 of these came from whales aged between 2 and 14 years and showed a Gaussian type of age distribution with a peak number at 7 to 8 years. The mean testosterone concentrations in the males increased by more than fourfold between June and August. Serum progesterone concentrations of the 462 females fell into three separate groups: (1) group I with values ≤ 0·1 nmol/l; (2) group II with intermediate values of > 0·1 nmol/l but <10 nmol/l; (3) group III with values of ≥ 10 nmol/l. These three groups of females seemed to consist respectively of young sexually immature females, mature non-pregnant females and pregnant females. The age distribution in the groups indicated that puberty in females is attained chiefly between the ages of 7 and 10. The yearly pregnancy rate (that percentage of all females caught and studied in a year which had progesterone values ≥10 nmol/l) was between 35% and 55%, except in 1987 when it was 67%. The yearly pregnancy rate would range from 56% to 93% if only mature females (i.e. those with serum progesterone >0·1 nmol/l) were considered. Serum oestradiol concentrations in male and female fin whales had no relation to age, sex or pregnancy.
Journal of Endocrinology (1992) 134, 405–413
Oestrogen enhancement of the myometrial response to exogenous parathyroid hormone-related protein (PTHrP), and tissue localization of endogenous PTHrP and its mRNA in the virgin rat uterus
Authors: Paspaliaris V. , Vargas S. J. , Gillespie M. T. , Williams E. D. , Danks J.A. , Moseley J. M. , Story M. E. , Pennefather J. N. , Leaver D. D. , Martin T. J. 
Published: December 2008

ABSTRACT
Classical pharmacological studies have shown that oestrogen dominance in humans and other animals can increase the responsiveness of the uterus to many locally acting peptides. Parathyroid hormone-related protein (PTHrP) has been shown to be expressed in the pregnant and non-pregnant rat uterus and exogenous PTHrP is known to relax uterine contraction in vitro. We investigated whether oestrogen dominance can influence the responsiveness of the uterine horn to PTHrP, and further studied the localization of PTHrP mRNA and protein in the rat uterine horn using in-situ hybridization and immunohistochemistry. Exogenous PTHrP(1–34) inhibited spontaneous and electrically induced contractions in uteri isolated from non-cycling rats. Pretreatment of non-cycling rats with oestradiol-17β increased uterine sensitivity to PTHrP: EC50 values for inhibition of spontaneous contractions by PTHrP were 0·33 nmol/l, 1·1 nmol/l, 2·6 nmol/l and 7800 nmol/l in uteri from animals treated for 2 days with oestradiol-17β alone, 2 days with oestradiol-17β+1 day progesterone, 1 day with oestradiol-17β alone and in untreated rats respectively. Similar EC50 values were obtained for electrically stimulated uteri. In agreement with these findings, uterine horns from cycling rats in pro-oestrous and oestrous phases of the cycle showed a higher responsiveness to PTHrP(1–34) when compared with uterine horns taken from rats in metoestrus and dioestrus. PTHrP mRNA and protein were detected in the endometrial epithelium lining of the lumen and the endometrial glands, as well as in the myometrium of rats which were either pretreated for 2 days with oestradiol-17β or untreated. This study suggests that PTHrP may act in an autocrine and/or paracrine manner to modulate uterine motility and function.
Journal of Endocrinology (1992) 134, 415–425
Suramin affects differentiated and undifferentiated human thyroid epithelial cells in vitro
Authors: Trieb K. , Dorfinger K. , Neuhold N. , Selzer E. , Wilfing A. , Czernin S. , Hermann M. , Niederle B. , Gessl A. , Vierhapper H. , Freissmuth M. , Grubeck-Loebenstein B. 
Published: December 2008

ABSTRACT
In the last decade, suramin has become known for its antiproliferative, differentiation-inducing effects on cells and has been successfully used in the therapy of cancer patients. The present study was undertaken to investigate the effects of suramin on normal human thyroid cells in primary monolayer culture and to analyse whether it also affected cells from thyroid carcinomas. The results show that suramin, at concentrations similar to serum levels obtainable during therapy, inhibited the proliferation of thyroid cells as well as the secretion of thyroglobulin. It suppressed the activation of adenylyl cyclase in thyroid membranes and decreased the immunogenicity of the cells by reducing their surface expression of HLA-DR and ICAM-1. Although the morphology of differentiated thyroid cells remained unaffected by suramin, morphological changes compatible with differentiation were observed in cells from undifferentiated thyroid carcinomas when suramin was added to the culture medium. In conclusion, the data demonstrate that suramin has pronounced in-vitro effects on normal and neoplastic thyroid cells. It may, therefore, also be effective in patients with thyroid cancer, for whom no other form of treatment is available.
Journal of Endocrinology (1992) 134, 505–511
Pyridostigmine partially reverses dexamethasone-induced inhibition of the growth hormone response to growth hormone-releasing hormone
Authors: Trainer P. J. , Kirk J. M. W. , Savage M. O. , Grossman A. B. , Besser G. M. 
Published: December 2008

ABSTRACT
The GH response to insulin-induced hypoglycaemia and growth hormone-releasing hormone (GHRH) has been shown to be impaired in subjects with Cushing's syndrome and in healthy volunteers given oral glucocorticoids. Pyridostigmine is an anticholinesterase that stimulates GH secretion, probably by inhibition of hypothalamic somatostatin secretion. This work was designed to study the site of action of glucocorticoids in inhibiting the secretion of GH.
Eight healthy male volunteers were studied on three occasions in random order. They took 2 mg oral dexamethasone or placebo at precisely 6-hourly intervals for 48 h before receiving 120 mg oral pyridostigmine or placebo, followed 60 min later by GHRH (100 μg) i.v. Samples for measuring GH were obtained at 15 min intervals for 2 h.
The 'area under the curve' (AUC) for each of the treatments was significantly different: dexamethasone–pyridostigmine–GHRH (mean ± s.e.m., 1938 ± 631 mU/min per 1), dexamethasone–placebo–GHRH (634 ±211) and placebo–placebo–GHRH (4267 ± 1183) (P<0·02, Wilcoxon test).
In conclusion, dexamethasone given for 48 h significantly inhibited the AUC for GH following treatment with GHRH. However, pretreatment with pyridostigmine significantly reversed the inhibition although this was still partial. Our data suggested that this short-term suppressive effect of dexamethasone was independent of GHRH, and most probably relates to stimulation of the release of somatostatin.
Journal of Endocrinology (1992) 134, 513–517
Influence of ovarian steroids on myometrial sensitivity and tolerance to relaxin in the rat in vivo: lack of cross-tolerance between relaxin, salbutamol and cromakalim
Authors: Downing S. J. , Hollingsworth M. 
Published: December 2008

ABSTRACT
The influence of oestradiol benzoate and progesterone on uterine sensitivity and development of tolerance to relaxin was investigated in bilaterally ovariectomized non-pregnant rats in vivo. Bolus doses of relaxin (2–20 μg/kg i.v.) produced rapid and reversible inhibition of uterine contractions in a dose-dependent manner. Treatment with oestradiol benzoate or oestradiol benzoate plus progesterone significantly increased uterine sensitivity to relaxin over 48 h by 2·4- to 8·5-fold. Tolerance to relaxin developed during continuous infusion of the hormone at 20 μg/kg per h for 40 h. A 7·8- to 17·4-fold reduction in sensitivity to relaxin was observed in relaxin-infused rats, whereas no change in sensitivity was observed in saline-infused rats. Infusion of relaxin at 50 μg/kg per h for 40 h produced a 131·8-fold reduction in uterine sensitivity to relaxin. The uterus remained tolerant to relaxin for up to 24 h after cessation of infusion. Treatment with oestradiol benzoate and/or progesterone did not influence the extent of tolerance development, but a more rapid recovery of uterine sensitivity to relaxin was observed in rats treated with oestradiol benzoate plus progesterone. Cross-tolerance with other uterine relaxant drugs was measured to investigate possible common mechanisms of action and sites of tolerance between relaxin and a β-adrenoceptor agonist (salbutamol) and potassium channel openers (cromakalim and minoxidil sulphate). No cross-tolerance was observed between relaxin and salbutamol, or relaxin and cromakalim or minoxidil sulphate. Cross-tolerance between cromakalim and minoxidil sulphate was seen.
Journal of Endocrinology (1992) 135, 17–28
Atrial natriuretic peptide is involved in the ACTH response to stress and glucocorticoid negative feedback in the rat
Authors: Fink G. , Dow R. C. , Casley D. , Johnston C. I. , Bennie J. , Carroll S. , Dick H. 
Published: December 2008

ABSTRACT
The role of atrial natriuretic peptide (ANP) in the ACTH response to stress and the glucocorticoid negative feedback control of ACTH release was investigated in adult male homozygous Brattleboro and adrenalectomized Wistar rats respectively, using the technique of immunoneutralization. The relatively low ACTH response to stress and the lack of arginine vasopressin make the homozygous Brattleboro rat a more rigorous and simpler preparation in which to test the hypothesis that ANP is involved in the ACTH response to stress. In both sets of experiments, blood sampling and injection of sheep anti-ANP or control serum were carried out in conscious animals through intra-atrial cannulae implanted 2 days previously under halothane anaesthesia. A 30-s exposure to ether resulted in a brisk twofold increase in the plasma ACTH concentrations in homozygous Brattleboro rats infused with anti-ANP, but not control serum. The injection of either dexamethasone, a potent glucocorticoid receptor agonist, or corticosterone resulted in a rapid and marked reduction in the plasma concentrations of ACTH in Wistar rats which had been adrenalectomized, under halothane anaesthesia, at least 21 days before experimentation. The inhibitory action of dexamethasone, but not corticosterone, was significantly reduced in animals infused with anti-ANP serum.
These results show that the inhibition of ANP release into hypophysial portal blood is probably important for triggering the ACTH response to stress and that ANP may play a role in corticosteroid negative feedback control of ACTH release mediated by type II (glucocorticoid) receptors.
Journal of Endocrinology (1992) 135, 37–43
Relationship between the resting metabolic rate and hepatic metabolism in rats: effect of hyperthyroidism and fasting for 24 hours
Authors: Iossa S. , Liverini G. , Barletta A. 
Published: December 2008

ABSTRACT
We have examined the relationship between the changes in resting metabolic rate (RMR) and those in hepatic metabolism induced by hyperthyroidism and fasting for 24 h. We found that hyperthyroidism induced a significant increase in RMR, while fasting for 24 h reduced RMR in euthyroid but not in hyperthyroid rats. We have also measured oxygen consumption in isolated hepatocytes from euthyroid and hyperthyroid rats, fed or fasted for 24 h. Hyperthyroidism induced an increase in oxygen consumption in rat liver cells; fasting for 24 h increased respiratory rates in isolated liver cells from euthyroid but not from hyperthyroid rats.
The findings showed that hyperthyroidism and fasting for 24 h have opposite effects on RMR but similar effects on hepatic metabolism. The results also indicated that the increase in RMR found in hyperthyroid rats is partly due to an increase in hepatic metabolism, while no correlation exists between variations in resting and hepatic metabolism induced by 24-h fasting.
Journal of Endocrinology (1992) 135, 45–51
Salivary insulin-like growth factor-I originates from local synthesis
Authors: Ryan J. , Mantle T. , McQuaid S. , Costigan D. C. 
Published: December 2008

ABSTRACT
Insulin-like growth factor-I (IGF-I) is a GH-dependent growth factor found in its highest concentrations in plasma. It is also measurable in saliva. The origins of salivary IGF-I concentrations were studied. Intracardial administration of Sprague–Dawley rats with 125I-labelled IGF-I and subsequent analysis of plasma and saliva samples by exclusion gel chromatography and SDS-PAGE, followed by autoradiography, demonstrated the apparent inability of IGF-I to cross from the plasma pool through to saliva. 125I-Labelled IGF-I was not chromatographed immediately before injection, resulting in administration of free iodide along with the iodinated peptide. This free iodide was demonstrable in saliva, indicating that movement of substances from plasma to saliva was measurable using the levels of 125I activity administered. Free iodide in saliva was not contributed to by 125I-labelled IGF-I degradation since 125I-labelled IGF-I was shown to be stable in saliva over 24 h. These data indicated that IGF-I in saliva is produced locally. Identification of a 4·7 kb IGF-I mRNA transcript in rat parotid salivary gland was consistent with IGF-I synthesis within that tissue.
Journal of Endocrinology (1992) 135, 85–90