bluuebunny/crossref_metadata_2025_split huggingface dataset:
2-Hydroxyoestradiol acutely inhibits prolactin secretion from the superfused pituitary glands of normal female rats: evidence for a cyclical effect
Authors: Banks P. K. , Inkster S. E. , White N. , Jeffcoate S. L. 
Published: December 2008

ABSTRACT
Catecholoestrogens are naturally occurring metabolites of oestrogens which are found in brain tissue and for which a neuroendocrine role has been postulated. However, reports of their effects on prolactin secretion are ambiguous and as yet no defined function has been attributed to them.
The effects of 2-hydroxyoestradiol (2-OHE2) and dopamine on the release of prolactin in vitro by perfused pituitary glands from normal adult female rats at different stages of the oestrous cycle have been investigated. The purity and stability of the 2-OHE2 preparation before and after exposure to pituitary tissue was confirmed by radioenzymatic assay and subsequent thin-layer chromatography. Dopamine (500 nmol/l, 100 nmol/l) was found consistently to suppress release by 60%; this effect was immediate and reversible upon removal of the dopamine. In contrast, the effects of 2-OHE2 (10 nmol/l, 100 nmol/l) were found to vary during the cycle. No effect on prolactin release was evident during either dioestrus or pro-oestrus, but during oestrus a similar, though less potent, suppression of prolactin secretion to that of dopamine was observed (35% suppression compared with controls).
The cyclical variation in the suppressive effect of 2-OHE2 on prolactin secretion in the female rat is compatible with a postulated neuroendocrine role for this catecholoestrogen.
J. Endocr. (1986) 111, 199–204
Melanocyte-stimulating hormone and the regulation of tyrosinase activity in hair follicular melanocytes of the mouse
Authors: Burchill S. A. , Thody A. J. 
Published: December 2008

ABSTRACT
Skin tyrosinase activity increases during hair growth in C3H–HeA*vy mice and reaches higher levels in young (30- to 35-day-old) mice when the hair follicular melanocytes synthesize the black pigment, eumelanin, than in older (6-month-old) mice when they produce the golden yellow pigment, phaeomelanin. To examine the regulation of the melanocytes at these different stages we have compared the effect of α-MSH and other agents that act, through cyclic AMP-dependent mechanisms, on skin tyrosinase activity in both young and old mice during hair growth, initiated by plucking. Daily administration of α-MSH, isoprenaline or theophylline increased coat darkness, and skin tyrosinase activity in the younger mice 7–9 days after plucking, but they were ineffective in the older mice. Similarly α-MSH, 8-bromo-cyclic AMP or theophylline increased tyrosinase activity in skin explants from the younger mice incubated for up to 24 h but had no effect in explants from older mice. Cyclic GMP had no effect on tyrosinase activity in skin explants from both young and old mice. It is suggested that whereas cyclic AMP-dependent mechanisms may operate to regulate tyrosinase activity in the hair follicular melanocytes of younger mice that produce eumelanin these systems may not operate in the older mice when these melanocytes synthesize phaeomelanin. Phaeomelanin synthesis, unlike that of eumelanin, may not depend upon tyrosinase and its regulation by cyclic AMP and this could explain the low levels of this enzyme in the skin and its failure to respond to α-MSH and other activators of the cyclic AMP system during periods of phaeomelanin production.
J. Endocr. (1986) 111, 225–232
Reproductive hormone secretion and spermatogenic function in thyroidectomized rams receiving graded doses of exogenous thyroxine
Authors: Chandrasekhar Y. , D'Occhio M. J. , Setchell B. P. 
Published: December 2008

ABSTRACT
This study aimed to obtain a better understanding of the relationship between circulating thyroxine (T4) concentrations and reproductive endocrine function in the ram. Mature Merino rams were thyroidectomized and supplemented with 0, 30, 100 and 300% of normal T4 for 10 weeks. Thyroidectomy had no apparent effect on spermatogenic function but interfered with sperm maturation, the latter being returned to normal by 30% T4 replacement. Circulating testosterone levels were reduced by thyroidectomy and restored to control levels by 30% T4; when T4 levels were supranormal (300%), circulating testosterone levels were again reduced. The lowered circulating testosterone levels in thyroidectomized rams occurred as a result of suppressed testosterone secretion from the testis, observed under basal conditions and also following LH-releasing hormone (LHRH) and human chorionic gonadotrophin injection. In thyroidectomized rams, sex hormone binding globulin (SHBG) levels were depressed without changes in testosterone clearance rate (TCR), while in rams with supranormal T4 levels, TCR was increased without changes in SHBG levels. Subnormal levels of T4 also restored to normal the reduced LH pulse frequency in thyroidectomized rams. Reduced LH pulse frequency, together with diminished LH release following LHRH injection in thyroidectomized rams, suggested effects of T4 at the hypothalamo-pituitary axis. The present study demonstrates that complete lack of thyroid hormones suppresses normal reproductive endocrine function in the ram, but that this can be restored to normal by 30% T4 replacement. The results support the theory that T4 plays a permissive rather than a regulatory role in reproductive function in males.
J. Endocr. (1986) 111, 245–253
Effect of androgen on androgen receptors in cultured human epididymis
Authors: Vázquez M. H. , de Larminat M. A. , Blaquier J. A. 
Published: December 2008

ABSTRACT
Optimal assay conditions were developed to determine androgen receptor concentrations in samples of human epididymis. Pretreatment of cytosol with mersalyl, as well as the inclusion of molybdate in the homogenization buffers, resulted in a substantial increase in the number of soluble sites detected. A high yield of nuclear and microsomal binding sites was obtained by prolonged incubation (12 h) in 0·6 mol NaCl/l.
Organ culture for 6 days resulted in a major loss of androgen-binding sites. In the absence of androgen in the culture media, only 20% of the original sites were found in cultured tissue. Inclusion of dihydrotestosterone (0·1 μmol/l) in the media resulted in samples containing twice as many sites as controls. It is concluded that androgens influence the number of androgen-binding sites in cultured human epididymis in a manner analogous to that described for rat epididymis in vivo.
J. Endocr. (1986) 111, 343–348
Preliminary endocrinological evaluation of a sustained-release formulation of the LH-releasing hormone agonist d-Ser(But)6Azgly10LHRH in premenopausal women with advanced breast cancer
Authors: Walker K. J. , Turkes A. , Williams M. R. , Blamey R. W. , Nicholson R. I. 
Published: December 2008

ABSTRACT
Twenty-four premenopausal women with advanced breast cancer were treated with a sustained-release (depot) formulation containing 3·6 mg of the LH-releasing hormone agonist d-Ser(But)6Azgly10 LHRH (ICI 118630), given s.c. every 4 weeks for periods of up to 5 months. Although ICI 118630 initially stimulated LH and FSH secretion, serum gonadotrophin concentrations were suppressed on continued treatment. Increased LH and FSH concentrations were associated with relatively normal ovarian activity during the first month of treatment, but low progesterone concentrations were found in all patients thereafter. In 22 out of 24 women, oestradiol concentrations fell during the second month to values equivalent to those observed in oophorectomized or postmenopausal women. In two patients, persistent but reduced oestradiol production was recorded throughout. No appreciable side-effect of the drug was observed.
J. Endocr. (1986) 111, 349–353
Effects of forskolin on the morphology and function of the rat thyroid cell strain, FRTL-5: comparison with the effects of thyrotrophin
Authors: Yun K. , Yamashita S. , Izumi K. , Yonemitsu N. , Sugihara H. 
Published: December 2008

ABSTRACT
The effect of diterpene forskolin, a potent stimulator of cyclic AMP (cAMP) in the rat thyroid cell strain FRTL-5, was compared with that of TSH. Forskolin stimulated both the release of cAMP into the culture medium and the accumulation of cAMP in the cytoplasm in a dose-dependent manner, within the range of 0·1–1000 μmol/l. Maximum cAMP concentrations were reached within 15 min of stimulation with forskolin. This is comparable with the effects of TSH. Forskolin also induced morphological changes in cultures of FRTL-5 cells, producing conspicuous cell retraction with arborization and numerous microvilli on the cell surface, specific reorganization of the microfilaments and modulation of the distribution of tubulin and fibronectin. Morphological changes induced by forskolin were always observed 20 to 30 min earlier, and in a higher percentage of cells, than the changes induced by TSH. Cell proliferation, however, was stimulated more effectively by TSH than by forskolin. These observations suggest that TSH might exert its effect on the morphology and growth of FRTL-5 cells, at least in part, through cAMP. The control of morphology and growth might not, however, be regulated solely by the adenylate cyclase and cAMP system.
J. Endocr. (1986) 111, 397–405
In-vitro binding of gonadotrophin to fish ovary
Authors: Jamal Uddin Md. , Bhattacharya S. 
Published: December 2008

ABSTRACT
Binding of piscine and mammalian gonadotrophin to plasma membranes from the ovaries of a fish, the murrel (Channa punctatus), clearly suggests that the fish ovary possesses distinct and specific binding sites for both piscine and mammalian gonadotrophins. Maximum specific binding of 125I-labelled human chorionic gonadotrophin (125I-hCG) and 125I-labelled silver carp gonadotrophin (125I-scG) was obtained at 30 °C and pH 7·5 during 2 h of incubation. In competitive binding studies, binding of radiolabelled scG was effectively inhibited by piscine gonadotrophins while LH and hCG had less effect and FSH showed no inhibition. By using plasma membrane preparations from kidney, skeletal muscle, brain and ovary it could be shown that specific binding of radiolabelled gonadotrophins was restricted to ovarian tissue. Binding characteristics of both 125I-scG and 125I-hCG to a preparation of murrel ovarian plasma membranes showed saturability with high affinity and low capacity. Scatchard plot analysis gave a higher dissociation constant for hCG (Kd = 235 pmol/l) than for scG (Kd= 127 pmol/l). Maximum binding capacity of scG was about twofold higher (6·27 fmol/mg protein) than that of hCG (3·76 fmol/mg protein). An increase in gonadotrophin binding resulted in a greater formation of pregnenolone from cholesterol, indicating functional relevance. At a concentration of 8 mmol/l, Ca2+ markedly inhibited the binding of gonadotrophin. The physiological importance of this inhibition is discussed.
J. Endocr. (1986) 111, 407–413
Prolonged secretion of prolactin in response to thyrotrophin-releasing hormone after hypothalamo-pituitary disconnection in the ewe
Authors: Thomas G. B. , Cummins J. T. , Hammond J. M. , Horton R. J. E. , Clarke I. J. 
Published: December 2008

ABSTRACT
Surgical disconnection of the ovine hypothalamus from the pituitary gland (hypothalamo-pituitary disconnection; HPD) has provided a useful experimental model for studying the control of gonadotrophin secretion. The objective of the present study was to define the characteristics of prolactin secretion using stimuli acting through the hypothalamus or directly on the pituitary gland in HPD ewes. Prolactin responses to either a stressful stimulus or the dopaminergic antagonists metoclopramide (20 mg i.v.) or chlorpromazine (50 mg i.v.) seen in intact animals (sham-HPD) were completely abolished by HPD. Injection of TRH (100 μg i.v.) caused an immediate release of prolactin in both groups of ewes. In the HPD ewes plasma prolactin concentrations remained raised for at least 3 h after TRH injection, whereas in sham-HPD ewes prolactin concentrations began to decline after 20 min. Administration of bromocriptine (1 mg i.v.) 10 min after TRH inhibited the prolonged response to TRH in HPD ewes. The results support the hypothesis that prolactin exerts a short-loop feedback effect on its own secretion at the hypothalamic level.
J. Endocr. (1986) 111, 433–438
Activation of sexual behaviour in castrated rats: the role of oestradiol
Authors: Södersten P. , Eneroth P. , Hansson T. , Mode A. , Johansson D. , Näslund B. , Liang T. , Gustafsson J.-Å. 
Published: December 2008

ABSTRACT
Sexual behaviour was induced in castrated male rats with oestradiol-17β- or testosterone-filled constant-release implants. Testosterone-induced sexual behaviour was unaffected by treatment with the 5α-reductase inhibitor 17β-N,N-diethylcarbamoyl-4-aza-5α-androstan-3-one (4-MA; 16·7 mg/day) but treatment with the aromatization inhibitor 1,4,6-androstatriene-3,17-dione (ATD; 10 mg/day) prevented testosterone from inducing the behaviour. Sexual behaviour could be activated in castrated rats treated with testosterone plus ATD by treatment with 4-MA or with implants filled with a low dose of oestradiol. Lordosis behaviour induced in ovariectomized rats with testosterone-filled implants and progesterone was blocked by ATD treatment and could not be activated with 4-MA but oestradiol implants restored the display of lordosis in the testosterone plus ATD-treated females. 4-MA inhibited the in-vitro formation of [14C]5α-dihydrotestosterone from [14C]testosterone by combined preoptic and hypothalamic tissue at all doses tested and a high dose of oestradiol exerted a similar effect. The results suggest that androgen aromatization is required for testosterone-activated female sexual behaviour but not for testosterone-activated male sexual behaviour. It is suggested that oestradiol normally acts to control the sexual behaviour of male rats by modifying neural androgen metabolism.
J. Endocr. (1986) 111, 455–462
Effect of long-term infusion of ovine corticotrophin-releasing factor in the immature ovine fetus
Authors: Wintour E. M. , Bell R. J. , Carson R. S. , MacIsaac R. J. , Tregear G. W. , Vale W. , Wang X.-M. 
Published: December 2008

ABSTRACT
Synthetic ovine corticotrophin-releasing factor (oCRF) was infused continuously into the jugular veins of six ovine fetuses for 5–11 days. Two fetuses receiving 0·1 and 1·0 μg oCRF/h from gestational days 134 and 135 respectively, lambed prematurely on days 141 and 140 respectively. Three out of four fetuses receiving oCRF at 2·4 μg/h, from 125 days of gestation, delivered spontaneously at 131, 131 and 136 days, whilst one died in utero at 132 days. Two fetuses receiving vehicle only or oCRF intra-amniotically, were born at 148 and 145 days respectively, whilst six fetuses chronically cannulated but not infused were born at 149·8 ±2·1 (s.d.) days. In ewes lambing at term, maternal plasma progesterone concentrations were 41·4±11·4 (s.e.m.; n = 5), 28·8±7·8 (n = 6), 17·1 ±4·8 (n = 5) and 7·9± 1·1 (n = 4) nmol/l on 3, 2, 1 and 0 days respectively before the lambs were born. No such decrease in maternal plasma progesterone concentrations was seen in the oCRF-infused fetuses. Fetal plasma concentrations of immunoreactive ACTH were maintained above normal in oCRF-infused fetuses, but some desensitization to bolus oCRF injections occurred in these fetuses. Four of the five fetuses born prematurely were sufficiently mature to survive, being able to stand, breathe and suckle. It is concluded that continuous oCRF infusions into immature fetuses can accelerate maturation of a number of organs and systems culminating in the premature delivery of viable lambs.
J. Endocr. (1986) 111, 469–475
Interference in the cytochemical assay of plasma vasopressin by a circulating factor induced by salt-loading in man
Authors: Baylis P. H. , Pippard C. , Burd J. M. 
Published: December 2008

ABSTRACT
Infusion of hypertonic saline into six normal volunteers caused an increase in plasma osmolality from 286·8 ± 1·7 (mean ± s.e.m.) to 307·6 ± 2·6 mosmol/kg (P<0·001), a 7·1% increase in estimated blood volume, a rise in plasma immunoreactive arginine vasopressin (AVP) concentrations from 1·3 ± 0·2 to 12·7 ±3·6 pmol/l (P<0·001) but no change in plasma AVP concentrations (2·1 ±0·9 and 1·9 ± 1·3 pmol/l) as measured by a cytochemical technique based on the ability of AVP to stimulate rat renal medullary Na+ /K+-ATPase activity. Addition of synthetic AVP to plasma obtained before, during and after hypertonic saline infusion also failed to stimulate Na+/K+-ATPase activity. The results suggest that infusion of hypertonic saline interfered with the cytochemical assay for AVP by inhibiting AVP-stimulated medullary Na+/K+-ATPase activity. We conclude that the use of this cytochemical method to detect plasma AVP has severe limitations under these experimental conditions.
J. Endocr. (1986) 111, 495–499
Transient increases in progesterone in daily and 2-hourly saliva specimens from adolescent girls
Authors: Truran P. L. , Leith H. M. , Read G. F. 
Published: December 2008

ABSTRACT
Daily progesterone profiles obtained from saliva specimens from 101 peri- and postmenarcheal girls showed episodic 'spikes' which reached up to 600 pmol/l from baselines of approximately 40 pmol/l. The authenticity of progesterone in the 'spike' specimens was established using gas chromatography–mass spectrometry. 'Spikes' of progesterone occurred in 5·3% of premenarcheal saliva specimens but in only 1–2% of specimens from girls who were 4–6 years postmenarche. Two-hourly specimens from 53 pre-and postmenarcheal girls had 'spike' frequencies similar to those measured in daily specimens.
J. Endocr. (1986) 111, 513–518
DEMONSTRATION OF THYROTROPHIN β-SUBUNIT MESSENGER RNA IN RAT PITUITARY CELLS IN PRIMARY CULTURE - EVIDENCE FOR REGULATION BY THYROTROPHIN-RELEASING HORMONE AND FORSKOLIN
Authors: Franklyn J.A. , Wilson M. , Davis J.R. , Ramsden D.B. , Docherty K. , Sheppard M.C. 
Published: December 2008

ABSTRACT
We have reported previously the effect of thyroid status in vivo on pituitary cytoplasmic concentrations of messenger RNA (mRNA) encoding the thyrotrophin (TSH) β-subunit (Franklyn, Lynam, Docherty et al, 1985). Studies in vitro of the regulation of TSH β gene transcription have been confined to thyrotrophic tumour cells. We now report the demonstration of TSH β-subunit mRNA in non-tumorous rat pituitary cells in primary culture. Treatment of cells with thyrotrophin-releasing hormone (TRH) and with forskolin resulted in a marked increase in cellular concentration of TSH β-mRNA. These results suggest that TRH exerts a direct effect on the pretranslational events involved in TSH synthesis and further that the adenylate cyclase system may be involved in the regulation of synthesis. We have thus described a novel system for the study of TSH β-subunit gene expression in normal rat pituitary cells in vitro.
Hormone regulation of the rodent Harderian gland: binding properties of the androgen receptor in the male golden hamster
Authors: Vilchis F. , Hernandez A. , Perez A. E. , Perez-Palacios G. 
Published: December 2008

ABSTRACT
Studies were conducted in castrated golden hamsters to assess whether sexual dimorphism and sensitivity to sex steroid hormones in the rodent Harderian gland are mediated by an interaction of androgens with specific intracellular receptors. Physical properties, binding kinetics and stereospecificity of the androgen receptor were analysed using [3H]mibolerone as the radioligand. The presence of [3H]mibolerone–androgen receptor complexes with a sedimentation coefficient of 7–8S was demonstrated in Harderian gland cytosol by a linear sucrose gradient ultracentrifugation technique using a vertical rotor. Kinetic analysis revealed an androgen-binding site with an apparent dissociation constant of 0·3±0·07 (s.d.) nmol/l and a saturation binding capacity of 113±15 fmol/mg protein. Displacement studies indicated that unlabelled mibolerone, methyltrienolone, 5α-dihydrotestosterone and testosterone were efficient competitors for the androgen-binding sites, while progesterone, 17β-oestradiol, dexamethasone, dehydroepiandrosterone, ethiocholanolone and 5α-16-androsten-3-one were not. Experiments in long-term castrated animals revealed that the Harderian gland androgen receptor concentration and sedimentation coefficient remained unmodified. The results of these studies were interpreted as demonstrating the presence of a specific high-affinity intracellular androgen receptor in the male hamster Harderian gland.
J. Endocr. (1987) 112, 3–8
Diurnal progesterone rhythms in the female mouse
Authors: Bailey K. J. 
Published: December 2008

ABSTRACT
The patterns of peripheral progesterone concentrations were investigated in a number of murine models on a 13 h light: 11 h darkness lighting regime. The pattern in the intact mouse at dioestrus was compared with that in the ovariectomized mouse. A diurnal pattern was recorded in both, maxima occurring around the end of the light period; no conspicuous nadir was recorded, levels of progesterone remaining relatively constant over a 14-h period. Adrenalectomized mice displayed no such rhythm, indicating that the adrenal is responsible for any diurnal rhythm in peripheral plasma progesterone concentrations at dioestrus. At pro-oestrus in intact animals a similar rhythm was observed, but the maximum levels of progesterone were approximately five times greater than at dioestrus and, moreover, persisted in adrenalectomized mice, indicating that the rhythm of adrenal secretion of progesterone is masked by ovarian secretion. Ovariectomized mice with implants of oestradiol-17β displayed a similar rhythm to that of intact mice at dioestrus, but had significantly higher plasma progesterone levels around the time of the maxima although not over the total 24-h period. An s.c. injection of oestradiol benzoate superimposed on oestrogen levels produced by implants had no significant effect on plasma progesterone levels. Also at pro-oestrus the pattern of peripheral LH concentration was investigated in both the intact and the adrenalectomized mouse. For both, maxima were recorded just before darkness, at 19.00 h, in advance of the progesterone surge. In adrenalectomized mice this surge at 19.00 h was attenuated. The possible role of adrenal progesterone in ovulation and the mechanisms by which endogenous oestrogens might enhance adrenal progesterone output are considered.
J. Endocr. (1987) 112, 15–21
Effect of nutrition and immunization against somatostatin on growth and insulin-like growth factors in sheep
Authors: Bass J. J. , Gluckman P. D. , Fairclough R. J. , Peterson A. J. , Davis S. R. , Carter W. D. 
Published: December 2008

ABSTRACT
The effect of immunizing against somatostatin (SRIF), with SRIF conjugated to bovine thyroglobulin, was examined in cross-bred sheep fed either cut pasture or lucerne pellets. Plasma concentrations of GH were unaffected by SRIF immunization, but were lower in pellet-fed sheep. Plasma concentrations of insulin-like growth factor I (IGF-I) increased after immunization in sheep on both diets. Pasture-fed sheep had lower plasma concentrations of IGF-I than those on pellets. Sheep showed a small increase in growth rate in response to immunization. Immunization had no effect on carcass composition and did not affect plasma concentrations of IGF-II, free fatty acids or glucose. The results show that even though SRIF immunization increases plasma concentrations of IGF-I, it does not necessarily result in a large increase in growth rate.
J. Endocr. (1987) 112, 27–31