bluuebunny/crossref_metadata_2025_split huggingface dataset:
Porcine thyroid follicular cells in monolayer culture activate the iodide-responsive precursor form of transforming growth factor-β1
Authors: Cowin A J , Bidey S P 
Published: December 2008

Abstract
The release of latent transforming growth factor-β1 (TGFβ1), and conversion to the biologically active peptide, has been investigated in porcine thyroid follicular cells maintained in primary monolayer culture. Analysis by radioreceptor assay of medium conditioned for 72 h by subconfluent thyroid monolayers showed that a high proportion of the expressed TGF-β1 peptide was in the active form. Medium conditioned by iodide (10 aμmol/l)treated follicular cells contained higher levels of both active and total TGF-β1 than were present in medium conditioned by untreated cells. Exposure of cells to iodide also led to a marked decrease in [methyl-3H]thymidine incorporation that was relieved by immunoadsorption with a neutralizing antiserum against the active form of TGFβ1. Inclusion of a low dose (80 units/l) of porcine plasmin led to a small increase in incorporation of [methyl3H]thymidine, while higher doses of plasmin (1250–5000 units/l) or plasminogen (100 mg/l) significantly reduced [methyl-3H]thymidine incorporation. This inhibition was effectively reversed by immunoadsorption of TGF-β1 from the medium during the test incubations. The study therefore provides direct evidence for a stimulatory role of thyroidal iodide in enhancing the release of latent TGF-β1 peptide, and suggests that in normal thyroid follicular cells, as in other TGF-β1 producing epithelia, post-secretory processing to the biologically active molecule occurs through an endogenous cellular mechanism. It appears likely that plasmin, generated locally within the thyroid follicular microenvironment, may play a fundamental role in effecting this conversion.
Journal of Endocrinology (1995) 144, 67–73
Effect of actively immunizing sheep against growth hormone-releasing hormone or somatostatin on spontaneous pulsatile and neostigmine-induced growth hormone secretion
Authors: Magnan E , Mazzocchi L , Cataldi M , Guillaume V , Dutour A , Dadoun F , Le Bouc Y , Sauze N , Renard M , Conte-Devolx B , Oliver C 
Published: December 2008

Abstract
The physiological role of endogenous circulating GHreleasing hormone (GHRH) and somatostatin (SRIH) on spontaneous pulsatile and neostigmine-induced secretion of GH was investigated in adult rams actively immunized against each neuropeptide. All animals developed antibodies at concentrations sufficient for immunoneutralization of GHRH and SRIH levels in hypophysial portal blood. In the anti GHRH group, plasma GH levels were very low; the amplitude of GH pulses was strikingly reduced, although their number was unchanged. No stimulation of GH release was observed after neostigmine administration. The reduction of GH secretion was associated with a decreased body weight and a significant reduction in plasma IGF-I concentration. In the antiSRIH group, no changes in basal and pulsatile GH secretion or the GH response to neostigmine were observed as compared to controls. Body weight was not significantly altered and plasma IGF-I levels were reduced in these animals. These results suggest that in sheep, circulating SRIH (in the systemic and hypophysial portal vasculature) does not play a significant role in pulsatile and neostigmine-induced secretion of GH. The mechanisms of its influence on body weight and production of IGF-I remain to be determined.
Journal of Endocrinology (1995) 144, 83–90
Endotoxin administration decreases plasma insulin-like growth factor (IGF)-I and IGF-binding protein-2 in Angus × Hereford steers independent of changes in nutritional intake
Authors: Elsasser T H , Caperna T J , Rumsey T S 
Published: December 2008

Abstract
Endotoxemia and sepsis cause severe shifts in metabolism towards catabolic events. The objective of the research was to determine whether endotoxin administration changes plasma concentrations of IGF-I and IGF-binding protein-2 (IGFBP-2) in Angus × Hereford steers. In Experiment 1, mean feed intake in endotoxin-treated steers (n=6) decreased 60% within the first 24 h after endotoxin and averaged, for the duration of the 96 h test period, an intake 35·5% lower than the mean ad libitum intake recorded prior to endotoxin. Plasma concentrations of IGF-I averaged 182 ng/ml in steers before endotoxin (E. coli, 055:B5, 0·2 μg/kg, i.v. bolus) and decreased an average of 24·2% at 24 to 96 h after endotoxin. In Experiment 2, a paired feeding strategy was used to determine whether the reduced feed intake was a significant factor in changing plasma concentrations of IGF-I and IGFBP-2 after endotoxin challenge. Steers were divided into endotoxin (0·2 μg/kg, i.v., n=6) or control (saline, n=6) n=3) treatments. Each of three endotoxin-treated steers was paired to a specific control. In this fashion, the adjusted feed intake of each endotoxin-treated steer was fed to it's paired control every 24 h through 96 h after endotoxin. After endotoxin, plasma concentrations of tumour necrosis factor-α (TNF) and cortisol peaked at one and three hours, respectively. TNF returned to baseline by 8 h while cortisol returned to baseline by 24 h. Feed intake declined 60% at 24 h in endotoxin-treated steers but returned to normal by 96 h. Plasma IGF-I remained more than 28% lower in endotoxin-treated steers than in control steers through 96 h (P<0·05). IGFBP-2 was 61% lower in endotoxin-treated than control steers at 24 h (P<0·05) and gradually returned to normal levels by 96 h. The level and duration of feed offered pair-fed control steers did not affect any measured parameter. The data suggest that decreases in plasma IGF-I and IGFBP-2 which occur after endotoxin administration are not fully explained by transient changes in nutrient intake and may constitute a part of the mechanism underlying shifts in metabolism that accompany endotoxemia. The partitioning of IGFs to tissues by altered patterns of IGFBPs may be another mechanism through which the classical anabolic character of IGF-I is modified during acute disease stress.
Journal of Endocrinology (1995) 144, 109–117
Effect of bovine GH and ovariectomy on mammary tissue sensitivity to IGF-I in prepubertal heifers
Authors: Purup S , Sejrsen K , Akers R M 
Published: December 2008

Abstract
Sixteen prepubertal Holstein Friesian heifers were used to study the effect of long-term administration of bovine GH (bGH; 15 mg/day for 15 weeks) and ovariectomy (at 2·5 months of age) on GH and IGF-I receptors in mammary and liver parenchymal tissue. Heifers were slaughtered on the day after the last injection of bGH or excipient. Mammary and liver parenchymal tissue was collected for preparation of crude membranes for ligand-binding assays.
Specific binding of [125I]IGF-I to mammary membranes increased linearly with increasing membrane protein concentration and was displaced by IGF-I, less effectively by IGF-II and least effectively by insulin. Linear Scatchard plots were obtained showing the presence of a single class of high-affinity binding sites for IGF-I in prepubertal mammary tissue. Specific binding of IGF-I was unaffected by bGH treatment but tended to be higher (P<0·10) in membranes from ovariectomized heifers. Hepatic binding of GH and IGF-I was unaffected by bGH treatment and ovariectomy. However, specific binding of GH tended to be lower (P<0·06) in liver tissue from bGH-treated intact heifers compared with control heifers.
The present study confirms the presence of IGF-I receptors in prepubertal mammary tissue in agreement with the suggested involvement of IGF-I in the mechanism of action of GH on mammary glands in this period. The results, however, indicate that the stimulatory effect of GH on mammary growth is mediated via increased serum concentration of IGF-I and not by increased IGF-I binding to its mammary receptors. The present study furthermore gave no clear evidence of an interaction between ovarian secretions and GH on IGF-I receptors in mammary tissue.
Journal of Endocrinology (1995) 144, 153–158
IGF-I and IGF-II receptors in the sheep placenta: evolution during the course of pregnancy
Authors: Lacroix M C , Servely J L , Kann G 
Published: December 2008

Abstract
The role of IGFs in placental growth is poorly understood. IGF-II receptors have been characterised in the ovine placenta and used extensively for radioreceptor assay, but their evolution during placental development has not been considered. In this study, binding sites for IGF-I were characterised in the ovine cotyledon by binding and cross-linking studies and the evolution of the number of IGF-I and IGF-II receptors on placentae collected on days 50, 75, 100 and 140 of pregnancy were compared. IGF-I bound onto placental membranes with a mean association constant of 1·7 nm−1 except on day 50 when a lower association constant was observed (0·8 nm−1). Scatchard analysis of the displacement curves led to a single binding site model. IGF-II was as potent as IGF-I at displacing the binding of 125I-labelled IGF-I on those membranes, whereas insulin cross-reaction was only 1%. IGF-II bound on our placental membrane preparations with the characteristics described previously and neither IGF-I nor insulin was able to displace this binding. Affinity cross-linking studies followed by SDS-PAGE under reducing conditions demonstrated that IGF-I was linked to a protein with a molecular weight of about 135 000 Da and IGF-II to a protein of 250 000 Da. The mean ± s.e.m. number of IGF-I receptors was significantly higher on days 50 and 75 than on days 100 and 140 (154 ± 12, 105 ± 11 vs 65 ±4, 48 ±3 fmol/mg, P<0·01). The number of IGF-II receptors followed the same pattern and also showed a decrease towards the end of the pregnancy that was significant (P<0·01) only by day 140 (days 50 and 75, 1 ± 0·08; day 100, 0·75 ±0·04; day 140, 0·51 ± 0·03 pmol/mg). IGF-I receptors were observed in the trophoblast cells of cotyledons removed on day 40 whereas IGF-II receptors were observed in mesodermal cells. These data suggest that IGFs are involved in the placental growth and differentiation processes and that some effects of IGF-II are probably mediated by IGF-I receptors.
Journal of Endocrinology (1995) 144, 179–191
Induced luteal regression: differential effects on follicular and luteal inhibin/activin subunit mRNAs in the marmoset monkey
Authors: Fraser H M , Lunn S F , Whitelaw P F , Hillier S G 
Published: December 2008

Abstract
During the luteal phase of the primate ovulatory cycle the predominant inhibin/activin subunit mRNAs produced by the corpus luteum and antral follicles are those for the α- and βB-subunits respectively. The control of expression of these mRNAs and the resultant nature of the endocrine and paracrine signals which they may potentially generate has yet to be elucidated. Inhibin/activin subunit mRNAs may have a role in both the paracrine regulation of follicular and luteal function and modulation of FSH secretion. The aim of this study was to investigate the expression of inhibin/activin subunit mRNAs following luteal regression induced by either withdrawal of LH support (GnRH antagonist treatment), or by a direct inhibitory action (prostaglandin administration). Marmoset monkeys with regular ovulatory cycles were treated on day 8 and 9 of the luteal phase with either GnRH antagonist, prostaglandin or vehicle (n=3 per group). Ovaries were studied 48 h after onset of treatment (on day 10 of the luteal phase) by hybridizing frozen tissue sections with radiolabelled riboprobes specific to the inhibin/activin α-, βA- and βB-subunit mRNAs. After autoradiographic exposure, grain concentrations were quantified by image analysis. In corpora lutea from control marmosets there was high expression of α-mRNA with only marginal expression of βB-mRNA. Corpora lutea in animals treated with GnRH antagonist or prostaglandin had markedly reduced expression of α-mRNA while βB-mRNA was unchanged. In controls, all healthy antral follicles exhibited a high level of expression of βB-mRNA in the granulosa cells and low expression of α-mRNA in theca cells. This was unaffected by either treatment. βA-mRNA was found at a low level in granulosa cells but was not evident at a significant level in the corpora lutea of any of the groups. These results demonstrate (1) the marmoset corpus luteum is a source of high expression of α-subunit mRNA, (2) this α-mRNA is dependent upon LH support, (3) the process of luteal regression takes place without alteration of βB-mRNA. Antral follicle α- and βB-mRNAs are independent of the process of luteal regression or gonadotrophic withdrawal during the period of the luteal-follicular phase transition.
Journal of Endocrinology (1995) 144, 201–208
Ontogeny and ultradian rhythms of adrenocorticotropin and cortisol in the late-gestation fetal horse
Authors: Cudd T A , LeBlanc M , Silver M , Norman W , Madison J , Keller-Wood M , Wood C E 
Published: December 2008

Abstract
Fetal maturation and the timing of parturition in both sheep and primates are thought to be controlled by the hypothalamic-pituitary-adrenal axis but little is known about the endocrinology of the equine fetus. We investigated the ontogeny of plasma concentrations of adrenocorticotropic hormone (ACTH), cortisol and corticosteroid binding capacity in the late-gestation fetal horse. We also wished to determine whether there is ultradian rhythmic release of ACTH and cortisol in fetal horses and we compared fetuses to maternal and non-pregnant adult horses. Six fetuses, 278–304 days gestation (term ≈335), were catheterized and sampled daily until delivery. Mean (± s.e.m.) ACTH concentrations increased significantly from 159 ±21 to 246 ±42 pg/ml over the last 2 days before parturition. Fetal cortisol increased significantly from 3·1±1·0 to 13·4±3·7 ng/ml (mean±s.e.m.) over the last 9 days before delivery. The slope of regressions for ACTH and cortisol concentrations with respect to time were positive in all subjects and statistically significant in 3 of 6 for ACTH and 5 of 6 for cortisol. Fetal corticosteroid binding capacity declined from 49·5 ±20·5 to 16·1 ± 2·2 ng/ml (mean ± s.e.m.) over the last 10 days before parturition. However, the greatest changes in ACTH, cortisol and corticosteroid binding capacity occurred very late in gestation, during the last 48 to 72 h before parturition. Significant peaks and nadirs in plasma ACTH concentration were detected in all 20 experiments and in plasma cortisol concentration in 17 of 20 experiments using Cluster analysis. We found statistically significant periods of oscillation between 11 and 64 min in plasma ACTH (19 of 20 experiments) and cortisol (15 of 20 experiments) using power spectral density analysis. Statistically significant periods between 11 and 17 min were detected in 11 of 20 experiments for ACTH and in 8 of 20 for cortisol. We conclude that: 1) at the end of gestation, equine fetal plasma ACTH and cortisol concentrations increase while corticosteroid binding capacity decreases suggesting that there is a disproportionately large increase in unbound cortisol at this time; 2) the secretion of ACTH and cortisol is rhythmic in both fetal and adult horses; 3) most animals exhibit a period of oscillation between 11 and 17 min; and 4) there is no apparent developmental change from late gestation to adulthood in the ultradian oscillator influencing ACTH and cortisol secretion in this species.
Journal of Endocrinology (1995) 144, 271–283
Prolactin receptor gene expression in the fetal rat
Authors: Freemark M , Nagano M , Edery M , Kelly P A 
Published: December 2008

Abstract
The expression of mRNA encoding the long and short forms of the prolactin receptor (PRLR) in the fetal rat was examined using the method of reverse transcription-PCR. A 742 bp PCR product encoding the extracellular and transmembrane domains of the PRLR was detected in maternal and fetal liver and in fetal adrenal, kidney, small intestine, pancreas, brain, pituitary, thymus, lung and skin but not in fetal heart. Highest levels of the 742 bp PRLR transcript were detected in fetal adrenal (45·2% of levels in maternal liver), kidney (27·2%), small intestine (21·7%), pancreas (18·3%) and liver (10·8%), and tissue levels of the 742 bp product correlated positively (r=0·92, P<0·01) with the specific binding of the fetal lactogenic hormone rat placental lactogen II (rPL-II). These findings suggest that the PRLR may serve as a physiological binding protein for rPL-II in the rat fetus. There were striking differences in the relative expression of mRNA encoding the long and short forms of the PRLR. The long form of the receptor was expressed in maternal liver and placenta and in all fetal tissues studied except fetal heart. The short form of the receptor was also detected in maternal liver and placenta and fetal adrenal, kidney, small intestine, liver and thymus; in contrast, there was limited expression of the short-form of the receptor in fetal pancreas, pituitary and brain and no short form transcripts were detected in fetal lung, skin or heart. The results of these studies indicate widespread expression of the rat PRLR in fetal and uteroplacental tissues, implicating diverse roles for the placental prolactin-like proteins in fetal development.
Journal of Endocrinology (1995) 144, 285–292
The influence of ovarian steroids on hypothalamic-pituitary-adrenal regulation in the female rat
Authors: Carey M P , Deterd C H , de Koning J , Helmerhorst F , de Kloet E R 
Published: December 2008

Abstract
The present study examined the association between hypothalamic-pituitary-adrenal (HPA) and hypothalamic-pituitary-ovarian axes. HPA activity determined by plasma levels of adrenocorticotropin (ACTH) and corticosterone (B) was assessed in intact female rats as a function of oestrous cycle stage under resting conditions and after exposure to a 20 min restraint stress. To delineate the roles of oestradiol and progesterone in HPA axis modulation, plasma concentrations of ACTH and B were determined in ovariectomised (OVX) animals treated with oestradiol and/or progesterone under resting conditions and during exposure to the stress of a novel environment. The effects of these steroid treatments on the transcription and/or binding properties of the two corticosteroid receptors, the mineralocorticoid (MR) and glucocorticoid (GR) receptors, were also examined in hippocampal tissue. (i) Fluctuations in basal and stress-induced plasma ACTH and B concentrations were found during the oestrous cycle with highest levels at late pro-oestrus. (ii) In OVX steroid-replaced animals, basal and stress-induced activity was enhanced in oestradiol and oestradiol plus progesterone-treated animals compared with OVX controls. (iii) Cytosol binding assays revealed an oestradiol-induced decrease in hippocampal MR capacity. This decrease appears to be due to an effect of the steroid on MR transcription as in situ hybridisation analysis of MR mRNA showed an oestradiol-induced decrease in MR transcript in all hippocampal subfields. (iv) Treatment of oestradiol-primed animals with progesterone reversed the oestradiol-induced decrease in hippocampal MR capacity. Data from MR mRNA hybridisation in situ experiments indicate that this reversal may be due to an antagonism of the oestradiol effect on MR transcription. (v) Progesterone treatment with or without prior oestradiol-priming induced a significant decrease in the apparent binding affinity of hippocampal MR. We show that progesterone and its 11 β-hydroxylated derivative have a high affinity for the hippocampal MR. (vi) Neither oestradiol nor progesterone affected GR binding parameters in the hippocampus. In conclusion, we find that sex steroids modulate HPA activity and suggest that the observed effects of these steroids on hippocampal MR may underlie their concerted mechanism of action in inducing an enhanced activity at the period of late pro-oestrus.
Journal of Endocrinology (1995) 144, 311–321
The effects of ovine placental lactogen infusion on metabolites, insulin-like growth factors and binding proteins in the fetal sheep
Authors: Oliver M H , Harding J E , Breier B H , Evans P C , Gallaher B W , Gluckman P D 
Published: December 2008

Abstract
It has been suggested, but not shown, that in the fetus placental lactogen (PL) may affect the regulation of the IGFs and fetal metabolism. To examine the effects of PL on the circulating concentrations of the IGFs, IGF-binding proteins (IGFBPs), glucose, free fatty acids (FFAs) and amino nitrogen (AN), we infused late gestation sheep fetuses with recombinant ovine PL (roPL). Five chronically-catheterised sheep fetuses were infused intravenously with three 24 h infusions of saline, roPL (100 μg bolus then 500 μg over 24 h) and then saline again.
Fetal roPL infusion increased plasma oPL from 0·4 ± 0·1 to 3·3 ± 0·5 nm (mean ± s.e.m.; P<0·05; factorial analysis of variance and Scheffé's test). Fetal plasma IGF-I, IGF-II, insulin, FFAs and blood glucose were unaffected by the roPL infusion. Fetal plasma IGFBP-3, as measured by Western ligand blotting, decreased by 30% during fetal roPL infusion while other fetal plasma IGFBPs were unaffected. Fetal roPL infusion decreased fetal blood AN from 7·3 ± 0·5 to 6·6 ± 0·2 mm (P<0·05). Maternal plasma IGF-I, IGF-II, IGFBPs, insulin, FFAs, blood glucose and AN were unaffected by the fetal roPL infusion. Saline infusion had no effect on any parameter.
The data suggest that PL is not a significant determinant of plasma IGFs in the late gestation sheep fetus although there may be an indirect effect via alterations in levels of IGFBP-3. The effect of fetal roPL infusion on fetal blood AN concentrations may suggest some role for PL in the regulation of fetal amino acid metabolism.
Journal of Endocrinology (1995) 144, 333–338
Extracellular domain of prolactin receptor from bovine mammary gland: expression in Escherichia coli, purification and characterization of its interaction with lactogenic hormones
Authors: Tchelet A , Staten N R , Creely D P , Krivi G G , Gertler A 
Published: December 2008

Abstract
The cDNA of the extracellular domain of bovine prolactin receptor (bPRLR-ECD) was cloned and expressed at high yield as an insoluble protein in Escherichia coli. This protein was solubilized, refolded and purified to >98% homogeneity yielding 80 mg of monomeric fraction per 2 litres of induced culture. Its molecular mass was 25–7 kDa, as determined by SDS-PAGE in the absence of reducing agent and 24 kDa by gel filtration on a Superdex column. Binding experiments revealed that bPRLR-ECD binds to human (h) GH (hGH) with high affinity, whereas its affinity for ovine (o) or bovine (b) prolactins (PRLs) was lower and for bovine placental lactogen (bPL) very low. The affinity of bPRLR-ECD for the latter three hormones was, however, much higher than that of membrane-embedded or solubilized bPRLR. The stoichiometries of interaction of bPRLR-ECD with hGH, oPRL, bPRL and bPL were determined by gel-filtration chromatography. Even at a 3:1 ECD excess, only 1:1 complexes were detected at μm concentrations of ECD and ligand. At an up to 32-fold dilution, the complexes with oPRL, bPRL, and particularly bPL, underwent progressive dissociation, whereas the complex with hGH remained stable. Although all four hormones exhibited nearly identical activity in the Nb2 lymphoma cell bioassay, the ability of bPRLR-ECD to inhibit hormonal mitogenic activities differed, generally reflecting its affinity for the respective hormones. In view of these and previous results, we suggest that, unlike in the GH:GHR-ECD interaction, neither the stoichiometry of interaction of bovine or other PRLR-ECDs nor the affinity constants can predict the biological potency of the different lactogenic hormones.
Journal of Endocrinology (1995) 144, 393–403