bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ontogeny of serum and pituitary gonadotrophins in male rats treated with low doses of 5α-dihydrotestosterone
Authors: Karanth S. , Gill M. K. , Dutt A. , Lehri N. , Juneja H. S. 
Published: December 2008

ABSTRACT
The effect of s.c. daily injections of 10 or 1000 ng 5α-dihydrotestosterone (DHT)/100 g body weight from birth to day 21, or from days 26 to 117 of age, on the changes in concentration of serum and pituitary gonadotrophins was investigated in male rats. Treatment with 10 ng DHT from days 1 to 21 depressed serum FSH, but not LH, at day 7, while 1000 ng DHT depressed both serum LH and FSH. Treatment with both doses of DHT reduced pituitary levels of LH and FSH at day 7, with FSH being more depressed than LH. Treatment with 10 ng DHT from days 26 to 117 increased serum FSH from days 82 to 117, while 1000 ng DHT did not have this effect. Treatment with 1000 ng, but not 10 ng, DHT between days 26 and 117 reduced pituitary levels of LH and FSH at day 40. Rats treated with the two doses of DHT from days 26 to 117 showed a difference in the responsiveness of the pituitary to LH-releasing hormone (LHRH). Treatment with 10 ng DHT enhanced LHRH-induced release of LH without affecting FSH release, while 1000 ng DHT depressed LHRH-induced release of FSH but not of LH. These findings support the view that DHT may play a modulatory role in the ontogeny of serum gonadotrophins and the responsiveness of the pituitary to LHRH during the onset of puberty in the male rat.
J. Endocr. (1986) 108, 369–375
Stimulation of in-vivo growth hormone secretion in young chickens by rat hypothalamic growth hormone-releasing factor and synthetic analogues
Authors: Scanes C. G. , Harvey S. , Rivier J. , Vale W. 
Published: December 2008

ABSTRACT
Rat hypothalamic GH-releasing factor (rhGRF), at doses between 0·1 and 10 μg/kg, increased plasma GH concentrations in immature domestic fowl 5–10 min after i.v. injection. Sodium pentobarbitone anaesthesia blunted the GH responses to rhGRF, although in both conscious and anaesthetized chicks the maximal responses were induced by a dose of 1 μg rhGRF/kg. The stimulatory effect of rhGRF on in-vivo GH secretion was less than that provoked by corresponding doses of human pancreatic GRF, but greater than that elicited by two rhGRF analogues, (Nle27)-rhGRF(1–32) and (Nle27)-rhGRF(1–29). These results demonstrate that the chicken pituitary is responsive to mammalian GRF and provide evidence of structure-activity relationships of GRF in the domestic fowl.
J. Endocr. (1986) 108, 413–416
Effect of testosterone on gonadotrophin-releasing hormone receptors in the castrated rat: preliminary evidence for a stimulatory effect of testosterone on gonadotrophin function in the male rat
Authors: Wilson C. A. , Herdon H. J. , Bailey L. C. , Clayton R. N. 
Published: December 2008

ABSTRACT
In the long-term castrated rat the negative feedback effect of testosterone is markedly reduced and the raised levels of plasma LH seen in the castrated animals are not suppressed by physiological concentrations of plasma testosterone. In this study we have measured pituitary gonadotrophin-releasing hormone (GnRH) receptor content as well as plasma and pituitary LH on days 1, 10 and 40 after castration and noted the effect of testosterone replacement on these parameters.
We found that the negative feedback effect of physiological concentrations of testosterone on plasma and pituitary LH, pituitary GnRH receptor content and response to exogenous GnRH was attenuated 10 and 40 days after castration. It is suggested that the lack of effect of testosterone in the long-term castrated rat is due to its inability to reduce the pituitary GnRH receptor content. On increasing testosterone to supraphysiological levels, the negative feedback effect was reinstated.
We also found that in rats 40 days after castration, physiological and subphysiological concentrations of testosterone significantly increased pituitary GnRH receptor content and this may explain the previous findings that low concentrations of testosterone can enhance the effect of GnRH and increase plasma LH levels.
J. Endocr. (1986) 108, 441–449
Neonatal testosterone potentiates stimulated prolactin secretion in adult oestrogen-primed rats
Authors: Dyer R. G. , Mansfield S. 
Published: December 2008

ABSTRACT
Blood samples were collected from oestrogen-primed gonadectomized adult rats before and after electrical stimulation of the preoptic part of the hypothalamus. Six groups of rats were used for the experiments. These were (a) males castrated on the first day of life, (b) males castrated after puberty, (c) females ovariectomized after puberty and (d), (e) and (f) females given testosterone propionate at birth (1·25, 0·125 and 0·0125 mg/rat respectively). Neonatal exposure of the female rats to testosterone caused a dose-dependent increase in the amounts of prolactin released to levels significantly (P<0·01) higher than those observed in male animals and in untreated females. The results indicate that although neonatal testosterone inhibits oestrogen-stimulated prolactin secretion in adult rats, the neuroendocrine apparatus controlling secretion of the hormone is capable of being activated to greater effect after exposure to androgens at the time of birth.
J. Endocr. (1986) 109, 57–60
Characterization of a soluble prolactin-binding activity in rat liver cytosol
Authors: Herington A. C. , Stevenson J. , Coulson L. , Ymer S. 
Published: December 2008

ABSTRACT
Soluble binding activity for lactogenic hormones has been detected in high-speed cytosolic preparations from the livers of 21-day-old male and female rats. No lactogenic hormone binding was detected in cytosols from rat heart, kidney, skeletal muscle or adipose tissue. Liver cytosol binding of 125I-labelled human growth hormone or ovine prolactin was dependent on time, temperature, and protein and calcium concentrations. Binding was specific for lactogenic hormones and not somatotrophic hormones. Scatchard analysis revealed linear plots with an affinity of 2·9–4·6 litres/ nmol. By gel filtration the molecular weight of the lactogen-binding activity was > 450 000. The cytosolic binding activity may be an internalized form of the membrane-bound lactogen receptor, which has similar binding characteristics, or alternatively it may be a distinct binding species, with a defined role in mediating intracellular effects of prolactin in the liver.
J. Endocr. (1986) 109, 61–66
Synergistic interaction in bovine pituitary cultures between growth hormone-releasing factor and other hypophysiotrophic factors
Authors: Ingram C. D. , Bicknell R. J. 
Published: December 2008

ABSTRACT
Synthetic human pancreatic GH-releasing factor (1–44)NH2 (GRF) and acetylcholine (ACh) were shown to evoke a dose-related release of GH from cultured bovine pituitary cells with half-maximal effective doses of 0·3 and 500 nmol/l respectively. Concentrations of ACh (10 μmol/l) and GRF (25 nmol/l) which were shown to give near maximal responses when presented alone, produced highly synergistic responses when tested in combination. This synergism was related to the ACh concentration employed, and both the ACh-induced release and ACh-induced synergism were abolished by the muscarinic antagonist, atropine. A synergistic interaction was also demonstrated between GRF and concentrations of thyrotrophin-releasing hormone (TRH) and bombesin which, in the absence of GRF, failed to elicit significant GH release. Acetylcholine stimulated a similar dose-dependent release of prolactin, but GRF was ineffectual in either directly stimulating prolactin release or affecting the response to ACh or TRH. No synergistic interaction could be detected between combinations of ACh and TRH or between ACh and bombesin. The data suggest that, in the somatotroph, GRF acts through a different second messenger pathway to ACh, TRH and bombesin and that these two pathways can be activated to produce a potentiated response. Growth hormone-releasing factor is, therefore, not only a specific GH secretagogue, but may act in concert with other hypophysiotrophic factors to regulate GH secretion from the bovine anterior pituitary.
J. Endocr. (1986) 109, 67–74
Effect of glucose, NADH and NADPH on cortisol metabolism by mononuclear cells
Authors: Klein A. , Chan A. W.-L. , Malkin A. 
Published: December 2008

ABSTRACT
Mononuclear cell preparations are capable of metabolizing cortisol to three metabolites which lack the immunosuppressive effect of their precursor. In the present study we noted a linear correlation, up to a point, between glucose concentration and the rate of human mononuclear cell cortisol metabolism in vitro. The mechanism by which glucose exerts its effect was investigated further. We observed that: (1) the effect of glucose on mononuclear cell cortisol metabolism was not influenced by insulin; (2) NADPH and NADH enhanced cortisol metabolism by disrupted cells, irrespective of whether the homogenates were dialysed or not; (3) lactate and ATP inhibited mononuclear cell cortisol metabolism and (4) almost all the glucose used was converted to lactate. It is concluded that mononuclear cell cortisol metabolism can depend on both nucleotides.
J. Endocr. (1986) 109, 181–185
Properties of synthetic-gene recombinant human epidermal growth factor: comparison with the natural growth factor from human urine and milk
Authors: Read L. C. , Summer L. , Gale S. M. , George-Nascimento C. , Ballard F. J. , Wallace J. C. 
Published: December 2008

ABSTRACT
The receptor-binding, immunological and biological properties of synthetic-gene human epidermal growth factor (EGF), produced by recombinant techniques in yeast have been compared with those of mouse submaxillary gland EGF and partially purified EGF from human urine and milk. The three forms of human EGF produced parallel concentration curves in radioreceptor assays using AG2804 Simian virus 40-transformed human lung fibroblasts and iodinated mouse or recombinant human EGF. Equivalent receptor-binding activities of urine and milk EGF were equipotent with recombinant human EGF in an homologous radioimmunoassay using recombinant human EGF antiserum with 125I-labelled recombinant human EGF, while none of the preparations was effective in competing for binding of 125I-labelled mouse EGF to mouse EGF antiserum. Urine, milk and recombinant human EGF stimulated protein synthesis and inhibited protein degradation in cultured AG2804 fibroblasts with identical potency. On a weight basis, mouse EGF was equipotent with recombinant human EGF in competitive binding to cell receptors and in effects on protein synthesis or protein degradation in AG2804 fibroblasts. It is concluded that recombinant human EGF is indistinguishable from the natural growth factor from urine or milk and shares similar biological properties with mouse EGF.
J. Endocr. (1986) 109, 245–250
Apparently normal oestrogen receptor system in ovariectomized ewes with impaired response to oestrogen after prolonged grazing on oestrogenic pasture
Authors: Tang B. Y. , Adams N. R. 
Published: December 2008

ABSTRACT
Functional abnormalities have been observed previously in the oestrogen-responsive tissues of ovariectomized ewes with permanent infertility resulting from prolonged exposure to oestrogenic pastures. In the present study, such ewes had higher rates of protein and glycoprotein synthesis in the cervix and uterus than control ewes, but the number of oestradiol-17β receptors in the nucleus was similar in each group. After treatment with oestradiol-17β, the increase in synthesis of protein and glycoprotein in the uterus and cervix was less in clover-affected ewes, but the amount of oestradiol-17β–receptor complex in the nucleus of uterine cells 6 h after ewes were injected with oestradiol-17β was similar in clover-affected and control ewes. The rate of replenishment of oestradiol-17β receptors in the cytoplasm at 24 and 48 h after oestradiol-17β injection was also similar in both groups. The abnormal function seen in the genital tract of clover-affected ewes could not, therefore, be shown to depend on changes in oestradiol-17β receptors.
J. Endocr. (1986) 109, 251–255
Effects of stimulation on steroid output and perfusion medium flow rate in the isolated perfused rat adrenal gland in situ
Authors: Hinson J. P. , Vinson G. P. , Whitehouse B. J. , Price G. M. 
Published: December 2008

ABSTRACT
Using the in-situ, isolated, perfused rat adrenal system, the actions of adrenal stimulants on steroidogenesis and perfusion medium flow rates (under constant perfusion pump conditions) have been studied. In a series of 100 experiments, initial rates of corticosterone output and flow rates were found to be positively correlated, although there was no such relationship between initial rates of aldosterone output and flow rates. Furthermore, in stable perfusion conditions, bolus injections of ACTH increased both flow rate and steroid output in a dose-related manner. In individual experiments there was a clear correlation between corticosterone and flow, but the association between aldosterone secretion rate and flow was less evident. It is possible that this discrepancy arises because of temporal differences in the responses of these two steroids. Flow was also stimulated by dibutyryl cyclic AMP (dbcAMP), with correlations with steroid output similar to ACTH, but the specific zona glomerulosa stimulants angiotensin II amide and potassium ions had, if anything, inhibitory effects on flow, but only at high concentrations.
The data suggest that ACTH and dbcAMP evoke specific responses in the adrenal vasculature, resulting in relatively decreased intraglandular vascular resistance. They furthermore suggest that the secretory functions of the inner adrenocortical zones are subject to the additional control of vascular elements in the intact gland.
J. Endocr. (1986) 109, 279–285
Testosterone metabolites do not participate in the control of hypothalamic LH-releasing hormone
Authors: Zanisi M. , Celotti F. , Ferraboschi P. , Motta M. 
Published: December 2008

ABSTRACT
To determine whether the ability of testosterone to increase intrahypothalamic LH-releasing hormone (LHRH) in orchidectomized rats might be explained by the conversion of the hormone into either its 5α-reduced or oestrogenic metabolites, testosterone, 5α-androstan-17β-ol-3-one (DHT), 5α-androstane-3α, 17β-diol (3α-diol) and 5α-androstane-3β,17β-diol (3β-diol) (2 mg/rat per day for 6 days) and oestradiol (0·1, 0·5, 1·0 and 5·0 μg/rat per day for 6 days) were injected into castrated male rats. After 6 days the rats were killed and serum LH levels and intrahypothalamic LHRH stores measured using specific radioimmunoassay procedures. Testosterone and its 5α-reduced metabolites were used in either the free alcohol or the propionate form (dipropionates in the case of the diols); oestradiol was used as oestradiol-17β or in the benzoate form.
Treatment with testosterone, DHT, 3α-diol and 3β-diol resulted in a significant decrease in serum LH levels; all the 5α-reduced testosterone derivatives were more effective than testosterone in this respect. Testosterone and DHT propionates suppressed LH release following orchidectomy totally; 3α-diol and 3β-diol dipropionates were less effective. Testosterone increased intrahypothalamic LHRH stores, this effect being much higher after testosterone propionate, i.e. when intrahypothalamic LHRH stores were restored to pre-castration levels. None of the 5α-reduced steroids was capable of modifying the low intrahypothalamic levels of LHRH found following orchidectomy; only 3α-diol dipropionate exhibited some activity, but this was much lower than that of testosterone propionate.
Oestradiol-17β was totally ineffective in decreasing serum LH in orchidectomized animals; in contrast, oestradiol benzoate progressively decreased serum LH. Oestradiol in the free form was unable to increase LHRH stores, as was oestradiol benzoate except at the highest dose.
The results suggest that the effect exerted by testosterone on hypothalamic LHRH is due to the hormone as such and does not involve its conversion into either 5α-reduced or oestrogenic metabolites.
J. Endocr. (1986) 109, 291–296
Monoclonal antibody to rat ovarian inhibin
Authors: Lee V. W. K. , Kraft N. C. , Atkins R. C. , Burger H. G. 
Published: December 2008

ABSTRACT
Ovaries from rats treated with pregnant mare serum gonadotrophin were used as a source of inhibin for raising monoclonal antibodies. The antisera were screened for binding to rat ovarian tissue sections and examined for their ability to neutralize inhibin bioactivity in vitro, i.e. the ability to abolish the suppressive action of rat inhibin on pituitary FSH secretion. Two monoclonal antibodies to rat ovarian inhibin were raised, one exhibiting complete (antibody PHM15) and the other incomplete (antibody MCA-3) neutralizing ability. Both antisera bound well to antral granulosa cells, as judged by the degree of staining using an indirect horseradish peroxidase technique. Ascites fluid from mice injected with hybridoma cells secreting antibody PHM15 also showed inhibin-neutralizing ability, and was effective against inhibin prepared from ovarian follicular fluid of rats, sheep, pigs and cows. The latter observation indicates the potential application of this antibody to the preparation and measurement of inhibin from several animal species.
J. Endocr. (1986) 109, 379–383
In-vitro secretion of inhibin-like activity by Sertoli cells from normal and prenatally irradiated immature rats
Authors: Ultee-van Gessel A. M. , Leemborg F. G. , de Jong F. H. , van der Molen H. J. 
Published: December 2008

ABSTRACT
The influence of in-vitro conditions on the production of inhibin by Sertoli cells from 21-day-old normal and prenatally irradiated rat testes was studied by measuring inhibin activity in culture media, using the suppression of the release of FSH from cultured rat pituitary cells. Sertoli cells secreted inhibin-like activity during at least 21 days of culture, and cells cultured at 37 °C produced significantly more inhibin than those cultured at 32 °C. The presence of fetal calf serum had no significant effect on inhibin production at 32 °C, while at 37 °C the production was decreased. The presence of ovine FSH stimulated inhibin secretion, while inhibin concentrations in Sertoli cell culture media were decreased after the addition of testosterone. Testosterone, added together with ovine FSH, suppressed inhibin secretion when compared with the levels found in the presence of FSH alone. The presence of spermatogenic cells decreased the release of inhibin.
From these results it was concluded that both Sertoli cells isolated from normal immature rat testes and those from testes without spermatogenic cells can secrete inhibin-like activity in culture. A number of discrepancies with in-vivo observations was observed. Therefore, it is likely that the in-vivo situation is too complicated for direct study of the regulation of inhibin production, because of mutual interactions between the testicular compartments.
J. Endocr. (1986) 109, 411–418
A novel class of inactive steroid-binding sites in female rat liver nuclei
Authors: Bechet D. M. , Perry B. N. 
Published: December 2008

ABSTRACT
Nuclear salt extracts from intact female rat liver showed insignificant levels of progesterone-, oestradiol-, testosterone- or dexamethasone-specific binding. However, brief exposure of nuclear extracts to dextran-coated charcoal (DCC) induced binding for all the above classes of steroids. This 'DCC-effect', which was reproduced neither by gel filtration nor by extensive dialysis of the nuclear extract, could not be ascribed to removal of endogenous free or loosely bound steroids. We show that rat liver nuclei contain a class of secondary binding sites (BsII), which exhibit moderate or low affinity for steroid ligands, positive co-operativity, and cross-reaction between classes of steroids. The capacity of BsII sites to bind steroids depends strictly on prior neutralization by DCC of endogenous heat-stable non-dialysable inhibitor(s). The putative roles of these BsII binding sites are discussed in relation to component(s) probably responsible for inhibitory activity.
J. Endocr. (1986) 110, 27–36
Cyclic adenosine nucleotides and growth hormone-releasing factor increase cytosolic growth hormone messenger RNA levels in cultured rat pituitary cells
Authors: Clayton R. N. , Bailey L. C. , Abbot S. D. , Detta A. , Docherty K. 
Published: December 2008

ABSTRACT
The cellular mechanisms involved in GH biosynthesis have been investigated by the measurement of steady-state levels of cytosolic GH messenger RNA (mRNA) in primary cultures of rat pituitary cells using an RNA–complementary DNA (cDNA) hybridization assay. Growth hormone mRNA–cDNA hybridization increased in a linear manner with increasing cytosol concentration. Cellular GH mRNA levels rose by an average of 2·4-fold (range, 1·6–3·3; n = five experiments) after exposure to GH-ieleasing factor (GRF(1–40); 10 nmol/l) for 3 days. Treatment with GRF increased the release of GH into the culture medium, and depleted the cellular GH content by 40%. Total GH (in the medium plus cells) after GRF treatment increased by between 1·5- and 3·8-fold, a magnitude similar to the increase in GH mRNA levels. Treatment of cells with dibutyryl adenosine 3′:5′-cyclic monophosphate (1 mmol/l) or forskolin (5 μmol/l) increased the levels of cytosolic GH mRNA by between 1·6- and 4·7-fold. These agents increased GH release into the medium, depleted cellular GH content and increased total GH in the system to the same extent as GRF (10 nmol/l). These data demonstrate that cyclic adenosine nucleotides may mediate the GRF induction of GH gene transcription. In addition, we have shown that increases in the levels of cellular GH mRNA are reflected by increased GH biosynthesis, suggesting that the regulation of hormone gene transcription is one cellular site for the control of hormone biosynthesis and, ultimately, hormone available for release.
J. Endocr. (1986) 110, 51–57
Demonstration of significant epidermal growth factor activity in murine thyroid tissue
Authors: Dagogo-Jack S. , Atkinson S. , Kendall-Taylor P. 
Published: December 2008

ABSTRACT
Epidermal growth factor (EGF) was first isolated from the mouse submaxillary gland (SMG) which remains its only known site of synthesis. Earlier work suggests that EGF may be implicated in the regulation of thyroid cell growth and proliferation. Moreover, thyroid hormones increase the EGF content of mouse SMG and mimic the maturational effects associated with EGF. The aim of this study was therefore to determine whether the mouse thyroid gland is a site of EGF production. Thyroid and submaxillary glands were homogenized in Tris-HCl, the EGF content was measured by a homologous radioimmumonassay (RIA) and receptor-binding activity assessed in a radioreceptor assay.
Epidermal growth factor was readily detectable in each thyroid extract. Dilution curves were parallel to the standard curve. Values obtained for right and left lobes of thyroid were in excellent agreement (r = 0·997, P<0·001). The intrathyroidal EGF concentration obtained by RIA was 26·1 ± 6·0 (s.e.m.) ng/mg protein (n = 40); values obtained by the receptor assay were slightly lower but correlated closely (r = 0·828, P < 0·01). Assay of homogenates prepared at the same time from the submaxillary glands of these mice showed that thyroidal EGF was not correlated with EGF content in the SMG.
These findings indicate that EGF, both biologically active and immunoreactive, is readily detectable in the mouse thyroid and that the thyroid gland is a probable site of EGF synthesis. The methodology provides a model for further studies of the regulation of EGF production and its significance in relation to thyroid disease.
J. Endocr. (1986) 110, 67–72