bluuebunny/crossref_metadata_2025_split huggingface dataset:
Changes in inhibin-A (α-βA dimer) and total α inhibin in the peripheral circulation and ovaries of rats after gonadotrophin-induced follicular development and during the normal oestrous cycle
Authors: Fahy P A , Wilson C A , Beard A J , Groome N P , Knight P G 
Published: December 2008

Abstract
Recent modifications to a previously reported two-site IRMA have permitted the measurement of serum/plasma concentrations and ovarian contents of inhibin-A (α-βA dimer) in pregnant mare serum gonadotrophin (PMSG)treated immature female rats and adult rats throughout the 4-day oestrous cycle. For comparison, total α inhibin levels were also measured by α subunit-directed inhibin RIA and found to be at least tenfold higher (relative to the same 32 kDa bovine inhibin standard used to calibrate both assays). In immature female rats, serum levels of inhibin-A dimer and total α inhibin increased within 3 h of PMSG injection and rose in parallel over the next 48 h to values four- to fivefold higher than pretreatment levels. Ovariectomy led to a rapid and parallel fall in both inhibin-A dimer and total α inhibin; initial half-lives (±95% confidence intervals) were 22 ± 4 and 20 ± 5 min respectively. In adult rats, marked fluctuations in plasma concentrations and ovarian contents of inhibin-A dimer and total α inhibin occurred during the 4-day oestrous cycle, most notably between the morning of pro-oestrus and the morning of oestrus. Plasma levels of inhibin-A dimer and total α inhibin peaked on the afternoon of pro-oestrus just before the preovulatory gonadotrophin surge. After ovulation, both inhibin-A dimer and total α inhibin fell abruptly (two- to threefold by 0200 h on oestrus; P<0·001), while FSH showed a secondary rise which peaked at 0700 h on oestrus. Although IRMA- and RIA-derived inhibin values generally followed a similar pattern across the 4-day cycle (plasma: r=0·52, P<0·001; ovary: r=0·41, P<0·001), a transient rise in plasma and ovarian inhibin-A dimer was detected at 0700 h on oestrus (P<0·01) which was unaccompanied by a rise in total α inhibin. This rise in plasma inhibin-A dimer was probably responsible for terminating the post-ovulatory FSH surge since FSH levels declined steadily over the next 15 h. Overall, plasma inhibin-A dimer and FSH concentrations across the whole cycle were negatively correlated (r= −0·22, P<0·01) whereas no correlation existed between total α inhibin and FSH (r= −0·11, P=0·12).
Journal of Endocrinology (1995) 147, 271–283
Multiple mechanisms of heterologous β-adrenoceptor regulation in rat uterus
Authors: Nimmo A J , Whitaker E M , Morrison J F B , Carstairs J R 
Published: December 2008

Abstract
The inhibitory effects of catecholamines on rat myometrium mediated by β-adrenoceptors are modulated by ovarian steroids. Previously reported findings of radioligand binding studies on myometrial membranes have demonstrated changes in the numbers of β-adrenergic binding sites following ovarian steroid treatment. However, these changes were not accompanied by parallel functional changes. In the present study, we have investigated possible mechanisms of heterologous β-adrenoceptor regulation by ovarian steroids. Binding studies were performed on myometrial membrane and cytosolic preparations from rats which had been ovariectomized and subsequently received no hormonal treatment or had been treated with oestradiol, progesterone or combined oestradiol and progesterone. The β-adrenergic antagonist [125I]iodocyanopindolol and the unlabelled competing agonist, isoprenaline, were used in the present studies. Hormonal treatment had no effect on the concentration of β-adrenergic binding sites in the myometrium (i.e. the number of membrane-bound and cytosolic binding sites per mg protein). However, significant changes were found in the total number of binding sites; these were associated with the hormone-induced tissue hypertrophy. In myometrium from ovariectomized-alone rats, approximately 50% of β-adrenergic binding sites were present in the cytosolic fraction. Oestradiol treatment, either on its own or in combination with progesterone, resulted in the translocation of binding sites to the cell membrane. However, in the absence of progesterone only 33% of the membrane-bound binding sites bound the β-adrenergic agonist, isoprenaline, with a high affinity, suggesting that the majority of these membrane-bound binding sites represented non-functional β-adrenoceptors. Progesterone treatment resulted in a doubling in number of the high affinity membrane-bound receptors. As a result of our findings we propose that oestrogen and progesterone act together in regulating β-adrenoceptor function: it is proposed that oestrogens increase the number of β-adrenergic binding sites associated with the cell membrane while progesterone promotes the coupling of these binding sites to their effector mechanisms thus leading to an increase in the number of functional β-adrenoceptors.
Journal of Endocrinology (1995) 147, 303–309
The role of intracerebral insulin in the effect of nutrition on gonadotrophin secretion in mature male sheep
Authors: Miller D W , Blache D , Martin G B 
Published: December 2008

Abstract
The effect of nutrition on gonadotrophin secretion may be exerted through a central metabolic signal that reflects nutritional status. We have previously found that glucose and insulin concentrations are elevated in the cerebrospinal fluid (CSF) of rams in which the secretion of gonadotrophins has been stimulated by a nutritional supplement of lupin grain (Lupinus angustifolius). In the present study, we tested the hypothesis that insulin and/or glucose is a metabolic modulator of GnRH secretion and mediates the effects of nutrition on gonadotrophin secretion. Six mature rams were fed a diet that maintained live weight and then given a series of infusions, each for 12 h/day for 4 days, in a cross-over design. The treatments were: artificial CSF (aCSF), glucose (50 μmol/h) in aCSF, insulin (0·6 ng/h) in aCSF, and glucose (50 μmol/h) plus insulin (0·6 ng/h) in aCSF; all infused at a rate of 5 μl/min. At the same time as the infusion treatments, two other groups of four rams without cerebral cannulae were fed either the maintenance diet or the same diet supplemented with 750 g lupin grain per head per day for 4 days, again in a cross-over design. Rams fed the lupin supplement showed an increase in both LH pulse frequency and mean FSH on day 4 (P<0·05). Infusion of aCSF or glucose did not affect gonadotrophin secretion. Rams infused with insulin or insulin plus glucose showed an increase (P<0·05) in LH pulse frequency but no increase in FSH concentrations on day 4 of infusion. The magnitude of the LH response to insulin was similar to the nutritional response of feeding lupin supplements. There was no effect of any of the infusion treatments on plasma prolactin or insulin secretion. These data show that changes in insulin concentrations in the CSF lead to changes in LH secretion and support the hypothesis that insulin is a metabolic modulator of GnRH secretion and mediates the effects of nutrition on gonadotrophin secretion.
Journal of Endocrinology (1995) 147, 321–329
Anti-progesterone effects on maternal recognition and behaviour imprinted during first pregnancy in mice
Authors: Crombie D L , Hayes J S , Heap R B , Wang M-W 
Published: December 2008

Abstract
Anti-progesterone treatment using specific anti-progesterone antibodies or a progesterone receptor (PR) antagonist during first pregnancy impairs postpartum maternal behaviour in mice. This effect is demonstrable only if the treatment is given during pregnancy but not immediately after parturition. The purpose of the present studies was to investigate if maternal behaviour is also impaired by anti-progesterone treatment in subsequent pregnancies.
Studies with a monoclonal antibody to progesterone (DB3; 4·5 nmol/mouse) showed that injection of females on day 17 of second pregnancy did not cause maternal rejection but the latency of pup retrieval was prolonged especially during the first 3 days of lactation. This phenomenon was not observed in animals that had previous experience of full length lactation. Experiments were carried out with mifepristone (RU486; 10 μg/mouse) injected at day 17 of first, second or third pregnancies. Pup rejection (22·5% vs 12·3%) and prolongation of the retrieval latency (62·3 ± 13·3 vs 19·7 ± 6·5 s; P<0·02) were observed following the first pregnancy. No abnormal behavioural effects were found in mothers treated in second or third pregnancy who had prior full length lactation experience. Control females subjected to only one pup retrieval test after first delivery rejected their pups if treated in their second pregnancy (27.3% vs 4·4%; P<0·001) and displayed a marginal prolongation of the retrieval latency period (20·9 ± 7·0 vs 7·4 ± 2·6 s). Anti-progesterone treatment had no negative influence when administered during third pregnancy.
To determine whether treatment with RU486 (50 μg/mouse, day 17) during first pregnancy has any residual effects, maternal response was monitored after completion of second pregnancy where no treatment was given. Females who exhibited both maternal rejection and prolonged retrieval latency following first pregnancy did not demonstrate any carryover effects during second lactation, indicating that there is no long-term consequence of RU486 treatment. These results suggest that: (i) anti-progesterone treatment of pregnant mice prevents maternal recognition and disrupts postpartum behaviour in females who had no, or very limited, nursing experience; (ii) there is a progesterone-dependent imprinting mechanism during the first pregnancy that is disrupted by anti-progesterone antibody or PR antagonist; and (iii) this imprinting mechanism and first lactation are important components of the consolidation of neural pathways that are associated with the establishment of normal maternal behaviour.
Journal of Endocrinology (1995) 147, 331–337
The relative importance of the oligosaccharide units in human chorionic gonadotropin (CG) for LH/CG receptor activation in rat Leydig cells and mouse Leydig tumor cells
Authors: van Loenen H J , van Gelderen-Boele S , Flinterman J F , Merz W E , Rommerts F F G 
Published: December 2008

Abstract
The biological properties of deglycosylated human chorionic gonadotropin (DhCG), obtained by hydrogen fluoride treatment (HF-DhCG) of intact hCG or by oligonucleotide-directed mutagenesis (CHO-DhCG), and that of their fully glycosylated counterparts, were tested in terms of cAMP and steroid production in rat Leydig cells and in mouse Leydig tumor cells (MA-10 cells). In both cell types, HF-DhCG and CHO-DhCG possessed comparable biological activities. The maximum for DhCG-induced cAMP production was approximately 12% of that of intact hCG when tested in rat Leydig cells, and only 2% when tested in MA-10 cells. DhCG possessed significant steroidogenic activity in both cell types. In MA-10 cells the maximum for DhCG-induced steroidogenesis was 30–50% of that of intact hCG, while in rat Leydig cells DhCG and hCG induced similar steroidogenic maxima. Based on its ED50, DhCG possessed 10–17% of the steroidogenic potency of intact hCG in rat Leydig cells, while in MA-10 cells DhCG was only 2-fold less potent than hCG. When accurate hormone-receptor binding data are absent, the intrinsic receptor-stimulating activity of a ligand can still be estimated at full receptor occupancy, provided that over the whole dose range the biological response is proportional to receptor stimulation. The present data show that in transfected MA-10(P+29) cells which over-express rat phosphodiesterase, the hormone-induced stimulation of cAMP and steroid production is directly coupled to receptor activation up to maximal occupation of the LH/CG receptor. The intrinsic receptor-stimulating activity of DhCG, measured in MA-10(P+29) cells in terms of DhCG-induced steroidogenesis, appeared to be 7- to 10-fold lower than that of intact hCG. As it is known from the literature that DhCG possesses 2- to 3-fold higher affinity to the LH/CG receptor than intact hCG, this increased binding affinity of DhCG may partly compensate for the 7- to 10-fold reduction in the intrinsic receptor-stimulating activity, resulting in only a 2-fold reduction in steroidogenic potency of DhCG. In terms of adenylyl cyclase stimulation in MA-10(P+29) cells, DhCG possessed approximately 50-fold lower receptor-stimulating activity than intact hCG, being similar to that observed in wild-type MA-10 cells. This study clearly shows that the oligosaccharide units in hCG are not essential for LH/CG receptor activation, and that the relative receptor-stimulating activity of DhCG to that of hCG is highly dependent on whether cAMP or steroid production is measured as an index for bioactivity, and whether bioactivity is tested in rat Leydig cells or MA-10 cells.
Journal of Endocrinology (1995) 147, 367–375
1,25-Dihydroxyvitamin D3-induced upregulation of the thyrotropin-releasing hormone receptor in clonal rat pituitary GH3 cells
Authors: Atley L M , Lefroy N , Wark J D 
Published: December 2008

Abstract
1,25-Dihydroxyvitamin D3 (1,25-(OH)2D3) is active in primary dispersed and clonal pituitary cells where it stimulates pituitary hormone production and agonist-induced hormone release. We have studied the effect of 1,25-(OH)2D3 on thyrotropin-releasing hormone (TRH) binding in clonal rat pituitary tumour (GH3) cells. Compared with vehicle-treated cells, 1,25-(OH)2D3 (10 nmol/l) increased specific [3H]MeTRH binding by 26% at 8 h, 38% at 16 h, 35% at 24 h and reached a maximum at 48 h (90%). In dose–response experiments, specific [3H]MeTRH binding increased with 1,25-(OH)2D3 concentration and reached a maximum at 10 nmol/l. Half-maximal binding occurred at 0·5 nmol 1,25-(OH)2D3/l. The vitamin D metabolite, 25-OH D3, increased [3H]MeTRH binding but was 1000-fold less potent than 1,25-(OH)2D3. In equilibrium binding assays, treatment with 10 nmol 1,25-(OH)2D3/l for 48 h increased the maximum binding from 67·4 ± 8·8 fmol/mg protein in vehicle-treated cells to 96·7 ± 12·4 fmol/mg protein in treated cells. There was no difference in apparent Kd (1·08 ± 0·10 nmol/l for 1,25-(OH)2D3-treated and 0·97 ± 0·11 nmol/l for vehicle-treated cells). Molecular investigations revealed that 10 nmol 1,25-(OH)2D3/l for 24 h caused an 8-fold increase in TRH receptor-specific mRNA. Actinomycin D (2 μg/ml, 6 h) abrogated the 1,25-(OH)2D3-induced increase in [3H]MeTRH binding. Cortisol also increased [3H]MeTRH binding but showed no additivity or synergism with 1,25-(OH)2D3. TRH-stimulated prolactin release was not enhanced by 1,25-(OH)2D3. We conclude that the active vitamin D metabolite, 1,25-(OH)2D3, caused a time- and dose-dependent increase in [3H]MeTRH binding. The effect was vitamin D metabolite-specific and resulted from an upregulation of the TRH receptor. Further studies are needed to determine the functional significance of this novel finding.
Journal of Endocrinology (1995) 147, 397–404
Neural expression of the pituitary GH gene
Authors: Render C L , Hull K L , Harvey S 
Published: December 2008

Abstract
It is well established that GH-like proteins and mRNA are present in extrapituitary tissues, but it is not known whether this reflects ectopic transcription of the pituitary GH gene or the expression of a closely related gene. This possibility was, therefore, further investigated.
Immunoreactive (IR) GH-like proteins were readily measured by RIA and immunoblotting in hypothalamic and extrahypothalamic brain tissues of the domestic fowl, in which GH-IR was similar in size and antigenicity to pituitary GH. RT-PCR of mRNA from these brain tissues, with oligonucleotide primers spanning the coding region of pituitary GH cDNA, also generated cDNA fragments identical in size (689 bp) to pituitary GH cDNA. The amplified brain cDNA sequences contained BamH1 and Rsa1 cleavage sites similar to those located in pituitary GH cDNA. These cDNA sequences also hybridized with a cDNA probe for chicken GH cDNA, producing moieties of expected size that were identical to the hybridizing moieties in pituitary tissue. The nucleotide sequences of the PCR products generated from hypothalamic and extrahypothalamic brain tissues, determined by a modified cycle dideoxy chain termination method, were also identical to pituitary GH cDNA. This homology extended over 594 bp of the hypothalamic cDNA fragment (spanning nucleotides 65 to 659 of the pituitary GH cDNA and its coding region for amino acids 4 to 201) and 550 bp of the extrahypothalamic cDNA fragment (spanning nucleotides 76 to 626 of pituitary GH cDNA and its coding region for amino acids 8 to 190).
These results clearly establish that pituitary GH mRNA sequences are transcribed in hypothalamic and extrahypothalamic tissues of the chicken brain, in which GH-IR proteins are abundantly located. However, as GH mRNA could not be detected in the chicken brain by Northern blotting, its turnover may be more rapid than in pituitary tissue. The local production of GH within the brain nevertheless suggests that it has paracrine roles in modulating neural or neuroendocrine function.
Journal of Endocrinology (1995) 147, 413–422
Differential regulation of plasma levels of insulin-like growth factors-I and -II by nutrition, age and growth hormone treatment in sheep
Authors: Hua K M , Hodgkinson S C , Bass J J 
Published: December 2008

Abstract
Plasma levels of IGFs-I and -II were measured in 4-month-old ewe lambs (n=20) and 2-year-old ewes (n=16), which were well fed (n=18) or fasted (n=18) for 3 days. Half of each nutrition group was given daily (0900 h) injections of bovine GH (bGH, 0·1 mg/kg body weight per day) for 3 days. Blood samples were collected immediately before the GH injection every morning.
Plasma IGFs were extracted by acid gel permeation chromatography using a Waters Protein Pak 125 column, fitted to a Pharmacia fast protein liquid chromatography system, then freeze-dried, reconstituted (at pH 7·4) and estimated by RIA.
At the end of the experiment, IGF-I levels in plasma were increased (P<0·01) by exogenous bGH in both fed ewes and lambs but not in the fasted animals; plasma IGF-I levels were depressed by fasting (P<0·01) at all ages. IGF-I levels were also found to be significantly higher (P<0·01) in ewes than lambs.
In contrast, plasma IGF-II concentrations were depressed (P=0·02) by administration of bGH in all groups and elevated in the ewes (P<0·05) by fasting. However, the lambs showed no significant changes in IGF-II with fasting. The IGF-II levels were significantly higher (P<0·001) in lambs than ewes.
Results from the present study demonstrate that GH administration stimulated an increase in plasma IGF-I and induced a decrease in plasma IGF-II. On the other hand, fasting depressed plasma IGF-I and elevated plasma IGF-II in the sheep. A significant GH/nutrition interaction for IGF-I (P<0·01), but not for IGF-II, and a significant nutrition/age interaction for IGF-II (P<0·01), but not for IGF-I, in the present study suggest that GH has a greater stimulating effect on plasma levels of IGF-I in the fed rather than fasted sheep and that nutrition has a greater influence on plasma levels of IGF-II in the older rather than younger animals, indicating that plasma IGFs-I and -II are differentially regulated by nutrition, GH and developmental stage in postnatal sheep.
Journal of Endocrinology (1995) 147, 507–516
Could abnormalities in insulin-like growth factors and their binding proteins during pregnancy result in gestational diabetes?
Authors: Cwyfan Hughes S C , Johnson M R , Heinrich G , Holly J M P 
Published: December 2008

Abstract
A number of dramatic changes have been documented in the insulin-like growth factors (IGFs-I and -II) and their binding proteins (IGFBPs) during pregnancy. In this study we have tested the hypothesis that a failure of the normal proteolytic modification of IGFBP-3 is responsible for gestational diabetes by examining serum samples taken in the third trimester from 29 women with uncomplicated pregnancies, 21 women with established Type 1 diabetes and 20 women with gestational diabetes. Analysis of IGFBP-3 by Western immunoblotting revealed that it was present in a modified form, migrating at around 29 kDa, in the circulation of all of the women investigated. Semiquantification of the activity of the protease which modifies the IGFBP-3 demonstrated considerable variation between individuals in their ability to fragment radiolabelled IGFBP-3 following a 45-min co-incubation. Surprisingly, in one individual (with gestational diabetes) there was no detectable protease activity even though her endogenous IGFBP-3 had been modified. However, overall there was no clear-cut difference in protease activity between the different groups.
Radioimmunometric analysis of IGF-I revealed significantly higher levels in women with gestational diabetes than either of the other two groups (P<0·05). Similarly IGFBP-3 levels were also increased in these same women (P<0·05). In contrast, IGF-II levels did not alter between the three groups.
In conclusion, our hypothesis was not supported by these data and gestational diabetes was found not to be associated with any reduction in the activity of the circulating IGFBP-3 protease which could have decreased the availability of the IGF nor with any alteration in IGFs which could explain the onset of diabetes in these women.
Journal of Endocrinology (1995) 147, 517–524
Stimulation of hepatic insulin-like growth factor-binding protein-1 and -3 gene expression by octreotide in rats
Authors: Flyvbjerg A , Schuller A G P , van Neck J W , Groffen C , Ørskov H , Drop S L S 
Published: December 2008

Abstract
It has recently been demonstrated in various clinical experiments that native somatostatin and its long-acting analogues increase circulating levels of insulin-like growth factor-binding protein-1 (IGFBP-1) within 1–2 h, independent of effects on circulating insulin or glucose levels. Using human hepatoma cells in vitro the somatostatin analogue, octreotide, has been shown to increase IGFBP-1 mRNA within 24 h indicative of a direct stimulatory effect of octreotide on IGFBP-1 synthesis. In order to ascertain whether octreotide acutely stimulates IGFBP-1 mRNA in vivo, placebo or two doses of octreotide were injected subcutaneously into three groups of rats. One hour after saline or octreotide administration, liver, kidney and serum were obtained for the measurement of IGFBPs-1 to -6 mRNA in tissue and IGFBPs and IGF-I in serum. Octreotide increased liver IGFBP-1 (562%) and IGFBP-3 (23%) mRNA expression with a concomitant rise in the circulating 30 kDa (106%) and 38–42 kDa (23%) IGFBPs. No detectable changes were seen in other liver IGFBP transcripts, other circulating IGFBPs or in any of the kidney IGFBP transcripts. Serum IGF-I increased by 37% in the animals receiving the high octreotide dose. No concomitant changes were observed in glucose or insulin levels.
These data show that octreotide acutely stimulates hepatic IGFBP-1 and -3 mRNA in vivo in rats. The stimulating effect on IGFBP-3 presents a possible hitherto unknown form of regulation of IGFBP-3 whilst the effect on IGFBP-1 indicates that the stimulatory effect of octreotide on circulating IGFBP-1 described in clinical trials may be due to increased hepatic production. The present findings may be of importance in the clinical use of octreotide.
Journal of Endocrinology (1995) 147, 545–551