bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of type 1 transforming growth factor-β on the level of aromatase cytochrome P-450 in human fetal hepatocytes
Authors: Rainey W. E. , Price T. M. , Means G. D. , Carr B. R. 
Published: December 2008

ABSTRACT
Aromatase cytochrome P-450 (P-450AROM) is the enzyme in the steroidogenic pathway controlling the formation of oestrogens from 19 carbon steroid precursors. Aromatase is present in various tissues of the human fetus. The liver is second only to the placenta in the level of P-450AROM activity in the fetus. In this study we examined the effects of type 1 transforming growth factor-β (TGFβ) on P-450AROM expression in human fetal (HF) hepatocytes. The HF hepatocytes were dispersed into single cells which were placed into monolayer cell culture until confluent. Cells were then rinsed and treated in serum-free media with dibutyryl cyclic AMP (Bu2cAMP) for 72 h. Treatment with Bu2cAMP (2 mmol/l) caused a fivefold increase in aromatase activity in hepatocytes. The increase in aromatase activity apparently represented an increase in P-450AROM enzyme as determined by immunoblotting using an antibody directed against human placental aromatase. TGFβ blocked basal, as well as Bu2cAMP increases, in aromatase activity by over 50%. The effect of TGFβ was dose-dependent with maximal inhibition observed using 2–5 ng TGFβ/ml. Immunodetectable P-450AROM decreased in parallel with activity following TGFβ treatment. The mechanism of TGFβ action was not through increasing phosphodiesterase (PDE) breakdown of cAMP since inhibition of PDE had no effect on TGFβ action. Finally we examined the level of P-450AROM mRNA using competitive polymerase chain reaction amplification. Bu2cAMP increased mRNA levels of P-450AROM by 2·5-fold, while TGFβ inhibited this induction by 35%. The results of this investigation demonstrated that TGFβ is a potent regulator of P-450AROM expression in HF hepatocytes.
Journal of Endocrinology (1992) 133, 311–320
Somatolactin, a novel pituitary protein: purification and plasma levels during reproductive maturation of coho salmon
Authors: Rand-Weaver M. , Swanson P. , Kawauchi H. , Dickhoff W. W. 
Published: December 2008

ABSTRACT
Somatolactin (SL), a newly discovered fish pituitary protein belonging to the GH/prolactin family, was isolated from coho salmon (Oncorhynchus kisutch). Antibodies were raised to purified coho SL, and a homologous radioimmunoassay was developed and validated. The assay was specific for SL as indicated by the absence of cross-reactivity with coho salmon GH, gonadotrophins I and II and less than 0·2% cross-reaction to prolactin. Serial dilutions of plasma and pituitary extracts from Oncorhynchus species including coho salmon, chinook salmon and rainbow trout were parallel to the coho salmon SL standard curve. Displacement curves for dilutions of Atlantic salmon (Salmo salar) plasma, but not pituitary extract were parallel to the standards. Plasma levels of SL were measured in coho salmon throughout the final year of reproductive maturation. During the period of gonadal growth, plasma SL levels increased and were highly correlated to oestradiol levels in females and 11-ketotestosterone levels in males. Peak levels of SL were observed at the time of final maturation and spawning in both sexes. It is hypothesized that SL may regulate some physiological aspect of reproduction.
Journal of Endocrinology (1992) 133, 393–403
Vasoactive intestinal peptide inhibits the steroid-induced LH surge in the ovariectomized rat
Authors: Weick R. F. , Stobie K. M. 
Published: December 2008

ABSTRACT
The LH surge was induced in ovariectomized rats by sequential treatment with oestradiol benzoate and progesterone. Vasoactive intestinal peptide (VIP) or saline was infused into the third cerebral ventricle from 13.30 to 16.30 h on the afternoon of the anticipated LH surge. Two blood samples were taken by jugular puncture from each animal, one at 12.00 h as a control sample and the other at 16.00, 18.00, 20.00 or 22.00 h. Saline-infused animals showed a normal LH surge, with mean plasma LH concentrations reaching a peak at 18.00 h, declining by 20.00 h and reaching control (12.00 h) levels by 22.00 h. Plasma LH in animals infused with VIP was not significantly higher than control levels at 16.00 or 18.00 h. By 20.00 h, mean LH levels in VIP-infused rats had risen to the levels seen at that time in saline-infused rats, and by 22.00 h LH had returned to control levels in VIP-infused animals. We interpret these findings to mean that VIP inhibits LH secretion during the LH surge. It does not block the surge completely, as pentobarbital during the critical period would have done; nor does VIP appear to affect the timing of the LH surge. Rather, VIP inhibits the increased LH secretion rates of the LH surge only during the period of VIP treatment and for a short time afterward.
Journal of Endocrinology (1992) 133, 433–437
Immunoreactive β-core-like material in normal postmenopausal urine: human chorionic gonadotrophin or LH origin? Evidence for the existence of LH core
Authors: Iles R. K. , Lee C. L. , Howes I. , Davies S. , Edwards R. , Chard T. 
Published: December 2008

ABSTRACT
Material with the immunochemical properties of the β-core of human chorionic gonadotrophin (hCG) can be found in the urine of normal postmenopausal women. However, we have been unable to detect intact hCG (using an assay which is specific for the α–β heterodimer of intact hCG) in serum of such subjects. The levels of serum LH and urinary β-core were compared in matched samples from 28 women (serum LH: median 27 U/l, range 4-70 U/l, urinary β-core: median 0·27 μg/l, range < 0·05–0·645 μg/l). Urine (4 litres) from three postmenopausal women was concentrated, dialysed and subjected to gel exclusion chromatography on Sephadex G-100. Fractions were analysed by specific assays for LH, intact hCG, total β-hCG (free β-subunit and intact hCG), free α-subunit and β-core. Material eluting at the expected position of the β-core fragment of hCG was detected in all three samples by the β-core, β-hCG and LH assays, despite the fact that the LH antibody does not recognize the authentic β-core of pregnancy. Electrophoresis and Western blotting of the concentrated urines revealed that material of the same molecular size as β-core was recognized by the antibody to LH but not by a monoclonal antibody raised to free β-hCG which also recognizes the β-core molecule of hCG. We conclude that the predominant core-like material identified in postmenopausal urine is probably derived from the β-subunit of LH.
Journal of Endocrinology (1992) 133, 459–466
A comparison of the clearance of ovine and human corticotrophin-releasing hormone (CRH) in man and sheep: a possible role for CRH-binding protein
Authors: Saphier P. W. , Faria M. , Grossman A. , Coy D. H. , Besser G. M. , Hodson B. , Parkes M. , Linton E. A. , Lowry P. J. 
Published: December 2008

ABSTRACT
A specific binding protein for human corticotrophin-releasing hormone (hCRH), which does not bind to the ovine hormone (oCRH), has recently been demonstrated in human plasma. No such binding protein has been found in sheep plasma. We have investigated the half-life of human and ovine CRH in man and in sheep. Peptides were measured directly in plasma with two-site immunoradiometric assays, as these assays are unaffected by the presence of inactivated peptide fragments. In man, the half-life of hCRH (30·5 ± 3·3 min; mean ± s.e.m.) was significantly (P < 0·001) less than that of oCRH (42·8 ± 6·4 min). In sheep, there was no significant difference between the half-life of hCRH (46·5 ± 7·2 min) and that of oCRH (39·8 ± 10·1 min); these half-lives were also significantly (P < 0·001) longer than that of hCRH in man. One possible explanation for the shorter half-life of hCRH in man is that the clearance of hCRH is enhanced by CRH-binding protein, although other binding proteins often have the opposite effect.
Peak ACTH and cortisol responses occurred earlier in sheep than in man, although no differences were found in the response times to oCRH or hCRH within either species. The responses were more sustained in sheep than in man, and the previously reported biphasic response was only seen in some of the sheep and not in man. Absolute responses to either peptide were greater in sheep than in man; however, in man an 8·1-fold rise in ACTH was measured in response to oCRH, while hCRH gave a significantly (P = 0·043) smaller 4·4-fold response. These experiments are discussed with particular reference to the effect of hCRH-binding protein and its possible role in potentiating the clearance of the peptide.
Journal of Endocrinology (1992) 133, 487–495
Antiprogesterone RU486 induces dissociation of LH and FSH secretion in the cyclic rat: effect of anti-inhibin serum
Authors: Sánchez-Criado J. E. , Bellido C. , López F. J. , Galiot F. 
Published: December 2008

ABSTRACT
Administration of the antiprogesterone RU486 to 4-day cyclic rats from metoestrus to pro-oestrus increases serum levels of LH while decreasing levels of FSH. If it is assumed that there is only one gonado-trophin-releasing hormone, there is no direct explanation for the decrease in FSH concentrations. The purpose of these experiments was to investigate the effect of RU486 on gonadotrophin secretion in cyclic rats during periods when the secretion of LH and FSH diverges. RU486 blunted the transient increase in FSH concentration on the afternoon of metoestrus and the compensatory ovarian hypertrophy on the next day of oestrus in unilaterally ovariectomized 4–day cyclic rats. In addition, bilateral ovariectomy reversed the effect of RU486 on the basal secretion of FSH. RU486 induced an increase in basal LH concentrations. Since ovarian inhibin decreases the basal release of FSH, and decreases in peripheral inhibin seem to be responsible for the transient rise in FSH during the oestrous cycle, the effect of RU486 on serum levels of LH and FSH during dioestrus in rats injected with a sheep anti-inhibin serum (AIS) were further evaluated. Treatment with AIS increased FSH levels in oil-treated rats without altering the levels of LH. In contrast, the effects of AIS on FSH secretion were blunted in RU486-treated rats. The results suggest that inhibin might be involved in the RU486-induced decrease of FSH secretion in cyclic rats.
Journal of Endocrinology (1992) 134, 43–49
Effects of steroid hormones on cyclic adenosine 3′,5′-monophosphate levels in the rat lung
Authors: Nabishah B. M. , Khalid B. A. K. , Morat P. B. , Alias A. K. , Zainuddin M. 
Published: December 2008

ABSTRACT
The possible role of cyclic adenosine 3′,5′-monophosphate (cAMP) in mediating the action of steroid hormones was investigated using the rat lung. Male rats were adrenalectomized and treated with olive oil, dexamethasone, corticosterone, deoxycorticosterone (DOC) or progesterone. At the end of 10 days, 100 μg isoprenaline/kg was injected intraperitoneally 5 min before the animals were killed to stimulate cAMP production. Adrenalectomy significantly decreased cAMP levels in the rat lung. Dexamethasone and corticosterone pretreatment reversed the effect of adrenalectomy whereas progesterone pretreatment but not DOC pretreatment significantly decreased lung cAMP levels. Cyclic AMP levels in normal female rats, whether pregnant or not, were not significantly different from those in male rats. We concluded that the absence of glucocorticoid, as after adrenalectomy, decreased the cAMP levels in rat lungs and that this could be reversed by either dexamethasone or corticosterone replacement. Progesterone reduced the cAMP content in rat lungs by acting as a glucocorticoid antagonist or by acting directly via progesterone receptors.
Journal of Endocrinology (1992) 134, 73–76
The ontogenic and functional relationships between growth hormone- and prolactin-releasing cells during the development of the bovine pituitary
Authors: Kineman R. D. , Faught W. J. , Frawley L. S. 
Published: December 2008

ABSTRACT
The ontogeny of GH- and prolactin-releasing cells in the developing bovine pituitary was evaluated by reverse haemolytic plaque assays which allows for the detection of hormone release from individual pituitary cells in culture. With this approach, we observed that GH-releasing cells ontogenically preceded prolactin-releasing cells. In fact, GH secretors were observed as early as 59 days of gestational age while cells that released prolactin were not identified until 98 days. The amounts of both GH- and prolactinreleasing cells increased with time to reach more than 50% and 20% of all pituitary cells near term (term ∼280 days) respectively. Interestingly, the first cells shown to release prolactin also released GH (i.e. were mammosomatotropes). This temporal and functional relationship between GH and prolactin secretors provides suggestive evidence that GH-secreting cells act as the progenitor cells for prolactin secretors via a functional intermediate, the mammosomatotrope.
Journal of Endocrinology (1992) 134, 91–96
A comparison of plasma vasopressin and oxytocin concentrations during the oestrous cycle of the ewe
Authors: Wathes D. C. , Ayad V. J. , Kumari M. , Matthews E. L. , Wathes C. M. 
Published: December 2008

ABSTRACT
Blood samples were collected twice daily (09.30 and 17.00 h) via indwelling jugular-vein cannulae from five ewes throughout an entire oestrous cycle. Additional frequent samples were taken at 30-min intervals for 8 h on each of days 3 (early luteal phase), 9 (mid-luteal phase), 12 (late luteal phase) and 0 (day of oestrus). Plasma concentrations of arginine vasopressin and oxytocin were measured in all samples by radioimmunoassay and progesterone was measured in the twice-daily samples only.
Both oxytocin and progesterone showed the expected pattern of plasma concentrations, increasing during the early luteal phase, reaching a plateau and declining either preceding (oxytocin) or at (progesterone) luteolysis. Vasopressin concentrations showed a significant dependence on the day of cycle (P<0·05, analysis of variance) with concentrations lowest at oestrus and minor peaks on days 4 and 8–9. There was no correlation between the concentrations of vasopressin and progesterone. Vasopressin values were significantly higher in the morning than in the afternoon samples (1·3 cf. 0·9 pmol/l; P<0·001). Analysis of the frequent samples showed a significant (P<0·001) dependence on the time of day for vasopressin but not oxytocin. Values were high throughout the morning, declined to a trough at 15.00 h and rose again by 17.00 h.
We conclude that there is a minor variation in the vasopressin concentration during the oestrous cycle, which is not related to the circulating progesterone concentration but could be regulated by oestradiol. We also provide evidence for a diurnal rhythm in the release of vasopressin into the plasma in the ewe. The concentrations of vasopressin measured are unlikely to be sufficient to influence the activity of the reproductive tract in vivo.
Journal of Endocrinology (1992) 134, 107–113
Metabolism of dihydrotestosterone to 3α-androstanediol in brain and plasma: effect on behavioural activity in female rats
Authors: Erskine M. S. , Hippensteil M. , Kornberg E. 
Published: December 2008

ABSTRACT
Six experiments were carried out to determine whether dihydrotestosterone (5α-androstan-17β-ol-3-one; DHT) acts to inhibit oestradiol (OE2)-induced lordosis behaviour after its metabolic conversion to 5α-androstane-3α,17β-diol (3α-androstanediol, 3α-Adiol). In experiments 1 and 2, ovariectomized rats were treated with several doses of DHT or 3α-Adiol, injected with OE2 and progesterone, and tested for lordosis responsiveness. Significant inhibition of lordosis occurred after a dose of 3α-Adiol which was approximately threefold less than the effective DHT dose. In experiments 3 and 4, plasma concentrations of DHT and 3α-Adiol were measured after the injection of these steroids to ovariectomized rats at doses shown to be both sufficient or insufficient to inhibit lordosis. Behaviourally effective dosages of DHT and 3α-Adiol produced circulating concentrations of 3α-Adiol greater than those produced by behaviourally ineffective doses of DHT or 3α-Adiol. At 30 min after injection of DHT (experiment 3), 78·8% of plasma androgens were in the form of 3α-Adiol, while after injection of 3α-Adiol, only 7·4% were DHT. When plasma DHT and 3α-Adiol were measured at 3, 6, 9 and 12 h after steroid injection (experiment 4), plasma levels of 3α-Adiol produced by the behaviourally subthreshold dose of DHT were significantly lower than levels produced by behaviourally sufficient dosages of DHT or 3α-Adiol. In experiments 5 and 6, concentrations of DHT and 3α-Adiol were measured in five brain regions 1 and 6 h after injection of behaviourally sufficient doses of these steroids to ovariectomized females. At 1 h after injection, similar levels of DHT and 3α-Adiol were measured in DHT- and 3α-Adiol-injected females, and DHT concentrations in the preoptic area were significantly higher in both groups than in any other brain area. At 6 h, animals injected with DHT had significantly higher levels of DHT in all brain areas combined than did 3α-Adiol-or vehicle-injected animals. Brain concentrations of 3α-Adiol were not different between groups injected with DHT, 3α-Adiol or vehicle at this time. In brain, 34·6% of DHT had been converted to 3α-Adiol after 1 h and 53·0% of 3α-Adiol had been converted to DHT. These results suggest that the inhibitory action of DHT on lordosis may be a consequence of its conversion to 3α-Adiol, and that this conversion may account for the higher behavioural potency of the latter steroid.
Journal of Endocrinology (1992) 134, 183–195
Changes in the plasma concentration of gastric inhibitory polypeptide and other metabolites in response to feeding in sheep
Authors: McCarthy J. P. , Faulkner A. , Martin P. A. , Flint D. J. 
Published: December 2008

ABSTRACT
Plasma concentrations of gastric inhibitory polypeptide (GIP)-like activity were determined in sheep before and after refeeding following a 48-h fast. Plasma concentrations increased significantly after feeding, from about 250 pg/ml to about 550 pg/ml. Other metabolites in plasma also increased at this time, reflecting the absorption of nutrients from the gastrointestinal tract. Significant increases were observed in the plasma concentrations of acetate, β-hydroxybutyrate and triacylglycerol. By comparing the time-courses of the changes in concentration of GIP and other metabolites in plasma, possible sites of secretion and secretagogues of GIP in ruminant animals are proposed. The results demonstrate that GIP is secreted in response to nutrient absorption in adult ruminants and that, as in simple-stomached animals, the absorption of long-chain free fatty acids plays an important role in this secretion.
Journal of Endocrinology (1992) 134, 235–240
In-vitro DNA synthesis in Leydig and other interstitial cells of the rat testis
Authors: Moore A. , Findlay K. , Morris I. D. 
Published: December 2008

ABSTRACT
Replicative DNA synthesis (125I-labelled iododeoxy-uridine incorporation) was measured in interstitial cells prepared from rat testes and separated by Percoll density gradient centrifugation. Leydig cells were identified by 125I-labelled human chorionic gonadotrophin (hCG) binding and 3β-hydroxysteroid dehydrogenase histochemistry. Continuous density gradients indicated that interstitial cell DNA synthesis was not associated with Leydig cells, and was greater in cells from the immature than from the mature rat testis. Fractionation of cells by discontinuous density gradients into Leydig cell-rich and -depleted pools did not result in a similar enrichment of DNA synthesis. Treatment of the adult rat with hCG increased DNA synthesis into both fractions but oestrogen had no effect. DNA synthesis was greater in cells from the immature rat but, in contrast to the adult, in-vivo hCG treatment had no effect, whilst oestrogen decreased synthesis. To characterize the cells synthesizing DNA further, interstitial cells were prepared from testes in which the Leydig cells were depleted by in-vivo treatment with ethane dimethanesulphonate (EDS) or depleted in their germ cells by treatment in utero with busulphan. EDS treatment had no effect on DNA synthesis by the interstitial cells in spite of the 125I-labelled hCG binding being markedly reduced. Similarly, busulphan treatment was also without effects upon DNA synthesis. Fluorescence-activated cell cycle analysis of cells from both fractions from germ cell-depleted testes indicated that only a small proportion (3%) of the interstitial cells were actively dividing and this was almost doubled in cells from the germ cell-depleted immature rat testes. The experiments showed that the majority of cells in the interstitium of the rat testes do not synthesize DNA and are not undergoing cell division. The small proportion of cells that are dividing are probably not Leydig cells. The experiments have identified a dividing interstitial cell population and, in consideration of the changes in the immature and mature rat as well as the effects of hormone treatment, they may be regarded as putative Leydig cell precursors.
Journal of Endocrinology (1992) 134, 247–255
Apparent α-inhibin subunit immunoactivity in porcine and ovine luteal extracts is due to interference by cytosolic proteases in the assay
Authors: Bramley T. A. , Menzies G. S. , Baxter G. , Webb R. , McNeilly A. S. 
Published: December 2008

ABSTRACT
Immunoreactive α-inhibin (ir-inhibin) was measured in luteal homogenates and subcellular fractions of ovine and porcine corpora lutea (CL) and in pig granulosa cells (GCs), using a sensitive radioimmunoassay specific for the 1–26 amino acid sequence of the N-terminus of the α chain of porcine inhibin (p1–26 α-inhibin). Inclusion of N-ethylmaleimide (N-EM) and/or EDTA in the immunoassay had no effect on the measurement of p1–26 α-inhibin peptide standards, on ir-inhibin levels in ovine follicular fluid and serum, or on ir-inhibin in subcellular fractions of pig GC. Fractionation of porcine GC homogenates on sucrose gradients demonstrated a major particular peak of ir-inhibin (buoyant density, 1·15–1·21 g/cm3) with variable activity in the cytosol. The particulate ir-inhibin peak was released into the cytosol by pretreatment of GC homogenates with the saponin, digitonin, prior to fractionation. Porcine GC extracts contained a protein (Mr 45 000) which immunoblotted against p1–26 α-inhibin antibody.
In the absence of inhibitors of proteolysis, apparent ir-inhibin activity was very high in extracts of sheep and pig CL. However, inclusion of N-EM or EDTA in the radioimmunoassay significantly reduced ir-inhibin levels in porcine and ovine CL extracts in a dose-dependent manner. Measurements of peptide tracer integrity indicated that porcine luteal cytosol degraded 125I-labelled p1–26 α-inhibin peptide. Subcellular fractionation studies demonstrated high levels of apparent ir-inhibin in luteal cytosol fractions, with only minor activity peaks associated with particulate fractions; however, this material was not releasable by digitonin. Immunoblotting of detergent extracts of porcine luteal particulate fractions failed to demonstrate α-inhibin material, and immunocytochemical localization studies of α-inhibin in porcine and ovine luteal sections were negative.
Our results are consistent with the intracellular packaging/storage of a form of α-inhibin (Mr similar to that of α-inhibin subunit precursor) in the porcine granulosa cell. However, luteinization of the porcine follicle was associated with a dramatic fall in ir-inhibin content, and the loss of immunostaining for α-inhibin peptides. We conclude that porcine and ovine CL contain little, if any, authentic inhibin. These studies emphasize the importance of excluding proteolytic artefacts when measuring biological peptides in luteal tissue extracts by radioimmunoassay.
Journal of Endocrinology (1992) 134, 341–352