bluuebunny/crossref_metadata_2025_split huggingface dataset:
Anti-idiotypic antibody as an oestrogen mimetic: removal of Fc fragment converts agonist to antagonist
Authors: Sömjen D , Amir-Zaltsman Y , Gayer B , Mor G , Jaccard N , Weisman Y , Barnard G , Kohen F 
Published: December 2008

Abstract
Previous studies indicated that the anti-idiotypic antibody (clone 1D5) caused an increase in uterine creatine kinase (CK) activity when administered in vivo to immature female rats, indicating that the antibody has oestrogenic-like activity. It was, therefore, of interest to investigate the structural requirements of clone 1D5 to act as an oestrogen mimetic in an in vitro model system. In the present study, the effect of clone 1D5 and its proteolytic fragments, F(ab′)2, Fab′ and Fc on CK activity was examined in cultured skeletal cells having functional oestrogen receptor (ER). Incubation of female-derived calvaria cells or epiphyseal cartilage cells with clone 1D5 (8·33 nm) or oestradiol (E2) (30 nm) for 24 h caused a significant increase in CK activity, indicating that clone 1D5 acted as an agonist. On the other hand, incubation of male-derived calvaria cells devoid of a functional ER with clone 1D5 or E2 did not have any effect on CK activity. Incubation of female-derived calvaria cells with clone 1D5 and E2 did not result in any further increase in CK activity, whereas dihydrotestosterone (DHT) did not alter the response to clone 1D5. The CK response to clone 1D5, in female-derived calvaria cells was time- and dose-dependent and could be inhibited in a dose-dependent manner by the oestrogen antagonist tamoxifen. In contrast, the proteolytic fragments of clone 1D5, the F(ab′)2 dimer (12 nm) and the Fab′ monomer (24 nm), and the Fc fragment (28 nm) did not have E2-like activity in these cells. However, while the Fab′ monomer or the Fc fragment, as well as clone 1D5, did not affect the response of the female-derived calvaria cells to E2, the F(ab′)2 dimer acted like an antagonist and completely inhibited the stimulatory effect of E2 or 1D5, but was unable to block the stimulatory effect of DHT on CK in male-derived calvaria cells. Collectively, these results imply that a bivalent antibody is necessary for the observed physiological responses, and that the anti-idiotypic antibody can be converted from an agonist to an antagonist by removal of the Fc portion of the antibody molecule. Furthermore, the anti-idiotypic antibody has an oestrogenic-like effect inhibited by tamoxifen only in skeletal cells capable of responding to E2.
Journal of Endocrinology (1995) 145, 409–416
The inhibitory action of melatonin in the ovine pars tuberalis is not dependent on changes in plasma membrane potential
Authors: McNulty S , Schurov I L , Morgan P J , Hastings M H 
Published: December 2008

Abstract
Treatment of ovine pars tuberalis (oPT) cultures with forskolin activates adenylyl cyclase, leading to increased levels of cyclic AMP, activation of protein kinase A, phosphorylation of the calcium/cyclic AMP response-element binding protein and the increased synthesis and secretion of several proteins. Simultaneous treatment with melatonin inhibits or reverses these effects of forskolin. In the neonatal rat pituitary, the inhibitory effects of melatonin are mediated by changes in membrane potential.
This study therefore investigated whether the inhibitory action of melatonin in oPT cultures is also dependent on the modulation of plasma membrane potential. Treatment of cultures with the ionophore valinomycin selectively permeabilised the cell plasma membrane to potassium, thereby causing membrane hyperpolarisation. In cultures of oPT, valinomycin inhibited in a concentration-dependent manner (maximal effect 2 μm) the stimulatory action of forskolin (1 μm) on intracellular levels of cyclic AMP, indicating that the activity of adenylyl cyclase in this tissue is sensitive to hyperpolarisation of the plasma membrane. However, increasing the extracellular concentration of potassium from 5 mm to 100 mm, which would depolarise the plasma membrane, had no effect on the inhibitory action of melatonin (1 μm) in forskolin-stimulated cultures. This indicated that melatonin could be effective in cells with sustained depolarisation. To test directly whether integrity of the plasma membrane is essential for melatonin to inhibit adenylyl cyclase, cultures were treated with the cholesterol-chelating agent saponin (50 μg/ml). Saponin increased cellular permeability to trypan blue and enhanced the release of the cytoplasmic enzyme lactate dehydrogenase to the extracellular medium, demonstrating that cell plasma membranes had been permeabilised, thereby abolishing membrane polarity. In cultures pretreated with saponin there was a tendency for levels of cyclic AMP to be reduced. However, permeabilisation did not block the forskolin-stimulated increases in cyclic AMP levels nor did it alter the ability of melatonin to inhibit the production of cyclic AMP in forskolin-stimulated cultures.
This study demonstrated that, while it is possible to inhibit the stimulatory actions of forskolin in the oPT by increasing the permeability of cells to potassium and thereby hyperpolarising them, melatonin is able to inhibit cyclic AMP in permeabilised cells and so can act independently of changes in membrane potential.
Journal of Endocrinology (1995) 145, 471–478
The effect of acute immuno-neutralisation of inhibin in ewes during the early luteal phase of the oestrous cycle on ovarian hormone secretion and follicular development
Authors: Campbell B K , Gordon B M , Tsonis C G , Scaramuzzi R J 
Published: December 2008

Abstract
Ewes with ovarian autotransplants received either inhibin antiserum (10 ml i.v. raised in sheep against recombinant 32 kDa human inhibin; n=6) or sheep serum (10 ml i.v.; n=5) on day 3 of the luteal phase with additional daily injections (1 ml i.v.) from 48 h after the initial bolus until day 13. Jugular and ovarian venous blood samples were taken 4-hourly over days 2–13 of the luteal phase. Blood samples were also taken at more frequent intervals (every 10–15 min for 2–3 h) to examine pulsatile secretory responses from the ovary to endogenous and gonadotrophin-releasing hormone-induced (150 ng i.m.) LH pulses on days 4, 6, 8, 10 and 12 of the luteal phase. Plasma FSH levels, ovarian steroid secretion and ovarian follicular development were measured. The ovarian follicle population was estimated daily by real time ultrasound scanning.
Immunisation against inhibin resulted in a 3- to 4-fold increase (P<0·001) in plasma FSH levels within 8 h with levels remaining elevated over controls for 6–7 days. Within 24 h of immunisation there was an increase in the number of small ovarian follicles (P<0·05) and by 3 days after treatment immunised ewes had 4–6 large ovarian follicles/ewe with this increase in the total number of large follicles being maintained for the rest of the experimental period (P<0·05). Mean ovarian oestradiol secretion during intensive bleeds was not different from controls 24 h after immunisation, but by 3 days after immunisation it was elevated 4- to 5-fold (P<0·001) over controls with this increase being maintained throughout the experiment. Similar responses to immunisation against inhibin in androstenedione secretion were observed although mean androstenedione secretion was not elevated until 7 days after treatment. In vitro antibody titres in immunised ewes remained elevated but declined steadily (P<0·001) over the experimental period.
We conclude that the initial stimulation of follicle development and ovarian steroid secretion following passive immunisation against inhibin can be attributed to increased blood FSH. However, the fact that with time FSH declined but increased follicle development was sustained, despite maintenance of high circulating antibody titres, suggests that on a longer term basis inhibin immunisation may stimulate ovarian function by interfering with the modulation of follicle development by inhibin at an ovarian level.
Journal of Endocrinology (1995) 145, 479–490
The local differential effect of prostacyclin, prostaglandin E2 and prostaglandin F2α on mammary blood flow of lactating goats
Authors: Nielsen M O , Fleet I R , Jakobsen K , Heap R B 
Published: December 2008

Abstract
Mammary blood flow (MBF) and milk yield are closely related in dairy ruminants, but little is known about the regulation of MBF in vivo. The local effects on MBF of injections or continuous infusions into the mammary artery of prostaglandins (PG) or indomethacin (an inhibitor of prostaglandins) respectively, were investigated in surgically prepared conscious goats. Prostacyclin (PGI2) was found to be a potent stimulator of MBF which increased linearly over the dose range 50–1000 ng. PGE2 was almost as potent as PGI2 at low doses, but tachyphylaxis occurred at doses at and above 100 ng. The response to repeated injections of PGE2 quickly declined depending on the dose. PGF2α had no effect on MBF. During infusion of indomethacin into the mammary artery MBF was reduced markedly, showing that endogenous mammary prostaglandins are involved in the regulation of vasodilatation. The results indicate that PGI2 (and to a lesser extent PGE2) has an important role in the local regulation of vascular tone in the mammary gland.
Journal of Endocrinology (1995) 145, 585–591
Insulin and IGF-I binding and tyrosine kinase activity in fish heart
Authors: Gutiérrez J , Párrizas M , Maestro M A , Navarro I , Plisetskaya E M 
Published: December 2008

Abstract
A study is presented of the binding of insulin and IGF-I to their respective receptors in the heart muscle of carp (Cyprinus carpio), coho salmon (Oncorhynchus kisutch), brown trout (Salmo trutta fario) and Sprague–Dawley rats. Receptor preparations were partially purified by wheat germ agglutinin affinity chromatography. Specific binding of insulin/100 mg cardiac muscle was much lower in fish (from 5·6 to 9·2%) than in rat (52·0 ± 5·0%). In both carp and trout, insulin binding to the cardiac muscle receptor preparation was significantly higher than in the white skeletal muscle (3·4 ± 0·3%, carp and 0·9 ± 0·3%, trout) or in the red skeletal muscle of carp (5·5 ± 0·8%). Specific binding of IGF-1/100 mg fish heart preparation ranged between 44 and 68%, surpassing IGF-I binding in the rat heart (20 ± 6%). The affinity of IGF-I receptors in fish heart (Kd 0·17–0·19 nm) was higher than that in rat heart (Kd 0·40 ± 0·05 nm) or insulin receptors in fish and rat heart preparations (0·25–0·72 nm). The IGF-I receptor binding was highly specific and required at least 100 nm insulin to cause any displacement of the bound ligand. Receptor tyrosine kinase activity could be stimulated in a dose-dependent manner by insulin and IGF-I, although in equimolar doses IGF-I was more potent than insulin. Maximum stimulation of tyrosine kinase activity (210–230%) in fish heart was in the same range as in other piscine tissues (150–260%) or in rat cardiac muscle (200–250%).
Journal of Endocrinology (1995) 146, 35–44
Migratory fat deposition in European quail: a role for prolactin?
Authors: Boswell T , Sharp P J , Hall M R , Goldsmith A R 
Published: December 2008

Abstract
The present study addresses the role of prolactin as a regulator of migratory fattening in European quail (Coturnix coturnix). Plasma prolactin levels in captive birds undergoing migratory fattening in an outdoor aviary and in the laboratory were measured by radioimmunoassay with an antibody raised against recombinant-derived chicken prolactin. No strong association between prolactin and migratory fattening was apparent, and prolactin levels were more closely related to daylength, with the highest concentrations being reached on long days. Plasma prolactin profiles were similar in intact and castrated male quail. Prolactin was secreted in a daily rhythm, with the highest concentrations occurring early in the photophase. However, when birds were food-restricted for 50 days during a migratory phase, there was no difference in fat deposition between birds food-deprived for the first half of the daily photophase compared with those deprived for the second half. Fattening was reduced in the food-restricted birds relative to ad libitum-fed controls, but there was no difference in plasma prolactin levels between the groups. Injections of ovine prolactin (4 mg/kg) significantly increased food intake and body mass of birds maintained on long days, but there were no differences in fattening between birds injected in the morning compared with those injected in the afternoon. Collectively, these results do not support a major role for prolactin in the regulation of migratory fat deposition in European quail.
Journal of Endocrinology (1995) 146, 71–79
Effect of hypothyroidism on the pituitary-gonadal axis in the adult female rat
Authors: Mattheij J A M , Swarts J J M , Lokerse P , van Kampen J T , Van der Heide D 
Published: December 2008

Abstract
The pituitary-ovarian axis was studied after withdrawal of thyroid hormone in 131I-radiothyroidectomized adult female rats. Oestrous cycles became prolonged and irregular within 2 weeks after the supply of thyroid hormone was stopped. If an LH surge occurred in hypothyroid rats on the day of vaginal pro-oestrus it was significantly greater in rats which had been made hypothyroid for 4–5 weeks than in controls; in hypothyroid rats with an LH surge on pro-oestrus, plasma progesterone showed a rise similar to that in controls at pro-oestrus; the ovulation rate was decreased in hypothyroid rats. About half of the rats from which blood was sampled daily in the afternoon between 7 and 18 days after tri-iodothyronine (T3) withdrawal had 1 day of pro-oestrus; on this day the LH surge was higher than in controls. On days 2 and 1 before and days 1 and 2 after this pro-oestrus, plasma progesterone was similar to that of controls on days 2 and 1 before and days 1 and 2 after pro-oestrus respectively. However, progesterone was higher in the period before and after these days. The other hypothyroid rats showed no pro-oestrus and no LH surge during this period, while their plasma progesterone levels were high on all days. On the morning of day 10 after T3 withdrawal and 5 days after the preceding pro-oestrus, most hypothyroid rats had high progesterone and low oestradiol plasma levels. In these rats, injection of gonadotrophin-releasing hormone caused a relatively small increase in LH; it did not stimulate the secretion of oestradiol or progesterone, and it did not induce ovulation. It was concluded that hypothyroidism induces major changes in the secretion of steroids by corpora lutea and growing follicles. Whether the changed steroid metabolism is the primary cause of the observed prolongation of the oestrous cycles, the increased pro-oestrous LH surge and the reduced ovulation rate remains to be investigated.
Journal of Endocrinology (1995) 146, 87–94
Effects of growth hormone antagonists on 3T3-F442A preadipocyte differentiation
Authors: Xu B C , Chen W Y , Gu T , Ridgway D , Wiehl P , Okada S , Kopchick J J 
Published: December 2008

Abstract
We have previously shown that a bovine (b) GH antagonist, bGH-M8, which possesses three amino acid substitutions in its third α-helix, inhibits mouse 3T3-F442A preadipocyte differentiation. In the current studies, we used the bGH and human (h) GH analogs with single amino acid substitution, bGH-G119R and hGH-G120R, for determining their biological activity using the preadipocyte differentiation assay. Short-term and long-term GH-inducible events were studied during adipose differentiation, including late marker gene expression (adipocyte protein 2), immediate early gene induction (c-fos), and tyrosine phosphorylation of intracellular proteins. The results demonstrated that these GH analogs not only failed to induce these three events, but also antagonized GH induction of c-fos expression and phosphorylation of proteins of apparent molecular mass of 95 kDa. Our present study agrees with the notion that GH must bind to the GH receptor via site one and with a second GH receptor molecule (or with some yet unidentified 'second target') through GH binding site two. This interaction is important for subsequent GH-dependent biological events.
Journal of Endocrinology (1995) 146, 131–139
Enzymatic conversion of IGF-I to des(1–3)IGF-I in rat serum and tissues: a further potential site of growth hormone regulation of IGF-I action
Authors: Yamamoto H , Murphy L J 
Published: December 2008

Abstract
We recently identified and characterized a protease present in rat serum which is capable of generating des(1–3)IGF-I. In this study, we have investigated the effects of GH deficiency and replacement on the activity of this protease in rat serum and tissue extracts. Protease activity was significantly higher in sera from hypophysectomized (hypox) rats than sham-operated rats (P<0·001) and GH treatment of hypox rats (human GH, 100 μg/100 g body weight i.p. for 10 days) significantly reduced the levels towards normal. The addition of IGF-I to hypox rat serum to achieve IGF-I concentrations comparable with or greater than that seen in normal rat serum had no effect on the measured protease activity. Protease activity was also detected in tissue extracts. The level of protease activity in the various tissues from sham-operated rats demonstrated the following order: liver>testes>heart> skeletal muscle>lung>thymus>kidney>brain>spleen. In all tissue extracts examined, except that from the lung, the levels of protease activity were higher in extracts from hypox rats compared with sham-operated rats. The largest differences between tissue extracts from hypox and shamoperated rats were seen in spleen (4-fold higher), kidney (2·27-fold), testes (1·55-fold) and heart (1·31-fold). In the liver, kidney and testes, GH treatment significantly reduced protease activity. Since the pattern of serum IGF-binding proteins (IGFBPs) differ in hypox rats compared with normal rats, we determined whether these changes could result in enhanced serum binding of des(1–3)IGF-I. Sera from hypox, GH-treated hypox and sham-operated rats were incubated with either 125I-IGF-I or 125I-des(1–3)IGF-I and analyzed by Sephacryl S-200 chromatography. Under the conditions used, 125I-des(1–3)IGF-I was recovered exclusively in the 7·5 kDa peak when incubated with serum from sham-operated rats. After incubation with sera from hypox or GH-treated hypox rats approximately 20% of the 125I-des(1–3)IGF-I was recovered in the 50 kDa peak with the remaining radioactivity recovered as free peptide. These observations suggest that the generation of des(1–3)IGF-I may be inversely regulated by GH and may represent yet another site of GH regulation of IGF-I action. The changes in the pattern of serum IGFBPs which occur in GH deficiency are unlikely to negate the enhanced generation of des(1–3)IGF-I by increasing binding capacity for this IGF-I variant.
Journal of Endocrinology (1995) 146, 141–148
Changes in plasma β-cell tropin concentrations during pregnancy in rats
Authors: Davenport M , Morton J L , Cawthorne M A 
Published: December 2008

Abstract
The mechanisms which initiate and maintain the energy partitioning into maternal tissues during pregnancy are unknown. The present study shows that in each of the weeks prior to pregnancy in the rat, plasma β-cell tropin (βCT) concentrations (nmol/l) were 0·68±0·10, 0·61 ±0·14 and 0·73±0·11 (n=11, mean±s.e.m.). During early (1-3 days) pregnancy the concentration rose to 1·32 ±0·26 and by early-mid (7–10 days) pregnancy they had increased to 1·96 ±0·41. By mid-late (14–17 days) pregnancy plasma βCT concentration had declined to the prepregnancy concentrations (0·67 ± 0·16). This mid-term increase in the circultating concentration of the lipogenic hormone βCT may contribute to the deposition of lipid associated with the early period of gestation. The increased circulating βCT could be derived from the pituitary gland neurointermediate lobe or by secretion from the placenta. It should be emphasised that the measurements in the present study represent a 'snap-shot' at discrete intervals and do not provide information about the dynamic hormonal interplay which occurs physiologically.
Journal of Endocrinology (1995) 146, 177–182
Comparison of the effects of growth hormone-releasing hormone and hexarelin, a novel growth hormone-releasing peptide-6 analog, on growth hormone secretion in humans with or without glucocorticoid excess
Authors: Giustina A , Bussi A R , Deghenghi R , Imbimbo B , Licini M , Poiesi C , Wehrenberg W B 
Published: December 2008

Abstract
The aim of our study was to investigate the effect of hexarelin, a novel GH-releasing peptide-6 analog, and GH-releasing hormone (GHRH) (alone or in combination) on GH secretion in adult patients with increased somatostatin tone due to chronic glucocorticoid excess. We studied seven adult patients undergoing long-term (no less than 6 months) immunosuppressive glucocorticoid treatment for non-endocrine diseases (six females and one male, age range 42–68 years) and one subject (female, age 31 years) with endogenous hypercortisolism due to adrenal adenoma. Six normal subjects (four females and two males) matched for sex and age with the patients and not undergoing any therapy served as controls. All the subjects underwent the following three tests in random order: (1) human GHRH (1–29)NH2 (100 μg in 1 ml saline) injected as an i.v. bolus at 0 min, (2) hexarelin (100 μg in 1 ml saline) injected as an i.v. bolus at 0 min and (3) hexarelin (100 μg in 1 ml of saline) plus GHRH (100 μg in 1 ml saline) injected as an i.v. bolus at 0 min. After GHRH alone the patients with glucocorticoid excess showed a blunted GH response as compared with normal subjects (median delta GH: 0·9, range 0–5·6 μg/l vs 7·1, range 0·3–14·9 μg/l). No significant differences were observed in the steroid-treated group with respect to normal subjects after hexarelin alone (median delta GH: 15·5, range 1·9–45·2 μg/l vs 17·9, range 5·5–53·9 μg/l). The GH responses after the combined stimuli were significantly decreased in the patients with glucocorticoid excess as compared with normal subjects (median delta GH: 43·5, range 21–56·9 μg/l vs 73·7, range 19·6-116·8 μg/l). The two stimuli acted in a synergistic fashion in both groups of subjects. It may be hypothesized that hexarelin influences the GH inhibitory effect of glucocorticoids in humans, acting at the hypothalamic somatostatin level.
Journal of Endocrinology (1995) 146, 227–232
Increased natriuretic peptides in fetal hearts of diabetic rats
Authors: Mulay S , Conliffe P R , Varma D R 
Published: December 2008

Abstract
The main purpose of these studies was to determine whether diabetic pregnancy altered maternal and fetal atrial natriuretic peptide (ANP). Diabetes was induced in rats by intravenous injection of 40 mg streptozotocin/kg on day 2 of gestation. Immunoreactive ANP in plasma, amniotic fluid and hearts on day 20 of gestation was measured by radioimmunoassay; fetal cardiac natriuretic peptides (ANP, proANP and BNP) were separated by reverse-phase high pressure liquid chromatography. Diabetes caused an increase in fetal plasma insulin, placental weight, amniotic fluid volume, the ratio of the fetal heart to body weight, maternal and fetal plasma ANP, fetal cardiac ANP and fetal cardiac BNP. It is suggested that the maternal diabetes-induced increase in fetal ANP might be related to fetal myocardial hypertrophy and could contribute to hydramnios.
Journal of Endocrinology (1995) 146, 255–259