bluuebunny/crossref_metadata_2025 huggingface dataset:
Efficacy and specificity of human parathyroid hormone analogues as antagonists in intact clonal osteogenic sarcoma cells
Authors: Kubota M. , Ng K. W. , Murase J. , Noda T. , Moseley J. M. , Martin T. J.
Published: December 2008

Five synthetic analogues of human parathyroid hormone (hPTH), (Tyr34)hPTH(3–34) amide, (5–34) amide, (7–34) amide, (8–34) amide and (9–34) amide, were tested for their ability to antagonize hPTH action specifically in intact cultured cells. Clonal rat osteogenic sarcoma cells were used (UMR 106–06 line) which respond to PTH with an increase in cyclic AMP (cAMP) formation. The most potent antagonists were (Tyr34)hPTH(3–34) amide and (5–34) amide, which inhibited the effect of hPTH(2·4 nmol/l) with half maximally effective concentrations of 0·1 μmol/l. When conditioned medium was used from a human lung cancer cell line producing osteoblast adenylate cyclase-stimulating activity, these two analogues were capable of inhibiting the increase in cAMP production. The specificity of the antagonism was indicated by the inability of the analogues to influence the effects of prostaglandin E2 or of calcitonin, which are alternative stimulators of cAMP production in the osteogenic sarcoma cells. Only (Tyr34)hPTH(3–34) amide showed some PTH-like agonist activity at high concentrations. These analogues should prove valuable in the investigation of PTH actions on target cells and of tumour products which appear to act through the PTH receptor.

J. Endocr. (1986) 108, 261–265
The mechanism of the effect of oxytocin on plasma concentrations of glucose, insulin and glucagon in conscious dogs
Authors: Vilhardt H. , Krarup T. , Holst J. J. , Bie P.
Published: December 2008

Injections and infusions of oxytocin into conscious dogs caused an increase in plasma concentrations of glucose, insulin and glucagon. When blood glucose was clamped at a raised level the injection of oxytocin still increased insulin and glucagon concentrations in plasma. Infusion of somatostatin suppressed plasma concentrations of glucagon and insulin but did not prevent oxytocin-induced increments in blood glucose. Injection of oxytocin still caused a marked release of glucagon, whereas the insulin response was greatly diminished. When endogenous insulin and glucagon secretion was suppressed by infusion of somatostatin and glucose levels were stabilized by concomitant infusions of glucagon and insulin, injections of oxytocin did not alter blood glucose concentrations. It is concluded that the increase in blood glucose following the administration of oxytocin is secondary to the release of glucagon and that oxytocin exerts a direct stimulatory effect on glucagon and possibly insulin secretion.

J. Endocr. (1986) 108, 293–298
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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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
Endocrine changes associated with the termination of photorefractoriness by short daylengths and thyroidectomy in starlings (Sturnus vulgaris)
Authors: Dawson A. , Goldsmith A. R. , Nicholls T. J. , Follett B. K.
Published: December 2008

When starlings (Sturnus vulgaris) are transferred from short to long days, hypothalamic content of gonadotrophin-releasing hormone (GnRH) and pituitary gonadotrophin content eventually decrease, as birds become photorefractory, to values lower than they were on short days. This implies that both should increase as photorefractoriness is terminated some time after transfer from long to short days. Further, since thyroidectomy causes termination of photorefractoriness in birds held on long days, this should also result in an increase in hypothalamic GnRH and pituitary gonadotrophin contents. This study tests these hypotheses.

Male starlings were transferred from short to long days for 10 weeks, by which time they should have become photorefractory. One group of birds was then killed; blood was collected, hypothalami and pituitaries were excised, and the stage of moult and testicular weights recorded. The remaining birds were then kept on long days, transferred to short days or thyroidectomized and kept on long days. Groups of birds in each treatment group were killed and sampled 2, 8 and 14 weeks later. Hypothalamic content of GnRH, and pituitary and plasma FSH and prolactin concentrations, were measured by radioimmunoassay.

In birds sampled after 10 weeks of long days, hypothalamic content of GnRH was quite low, pituitary and plasma levels of FSH were very low, testes were small and pituitary and plasma prolactin levels were high. In intact birds kept on long days, hypothalamic GnRH content decreased further and remained low. Pituitary and plasma FSH levels remained low, testes remained small and pituitary and plasma prolactin levels decreased slowly. In intact birds transferred to short days, hypothalamic GnRH content increased to values significantly (P<0·01) higher than in birds kept on long days. Pituitary FSH content increased (P<0·01) but plasma FSH levels remained low and testes remained small in most birds. Pituitary and plasma prolactin levels decreased rapidly. In thyroidectomized starlings kept on long days, hypothalamic GnRH content increased to the same values as in birds on short days, pituitary FSH content increased markedly and testes grew although plasma FSH remained low. Pituitary and plasma prolactin levels decreased slowly.

These results demonstrate that short days activate the hypothalamus to a state of 'readiness to function' and confirm that the thyroid glands are involved in this response.

J. Endocr. (1986) 110, 73–79
Development and steroidogenic activity of preantral follicles in the neonatal rat ovary
Authors: Carson R. , Smith J.
Published: December 2008

The neonatal rat ovary is completely devoid of antral follicles until the twelfth day of age. During this period the ovary becomes steroidogenically active and responsive to gonadotrophins. The aim of this study was to correlate the onset of ovarian androgen and oestrogen production in vitro with the first appearance of distinct granulosa and theca cells. Although ovarian aromatase activity increased significantly on day 7 of age, ovarian oestrogen production was limited by low progesterone and testosterone production until day 12 of age. Increased aromatase activity on day 7 and androgen production on day 12 were coincident with the first appearance of granulosa and theca cells respectively. These functional and morphological changes were not associated with significant alterations in ovarian weight or concentrations of LH or FSH in serum.

J. Endocr. (1986) 110, 87–92
Somatostatin immunoneutralization stimulates thyroid function in fowl
Authors: Lam S.-K. , Harvey S. , Hall T. R. , Spencer G. S. G.
Published: December 2008

The influence of somatostatin on thyroid function has been examined in immature domestic fowl passively immunized with somatostatin antiserum. Plasma thyroxine (T4) and tri-iodothyronine (T3) concentrations were markedly increased within 10 min of antisomatostatin administration and remained raised for at least 5 h. The increases in the T3 and T4 concentrations following somatostatin immunoneutralization were directly related to the volume of antisera administered. The increase in the T3 concentration exceeded the increase in the T4 concentration, resulting in a T3: T4 ratio greater than unity. While the raised T4 concentration began to decline 30 min after antisomatostatin administration, raised T3 concentrations were sustained for at least 2 h, and further increased the plasma T3: T4 ratio.

These results demonstrate that somatostatin immunoneutralization stimulates thyroid function in fowl. The magnitude and rapidity of the thyroidal responses to somatostatin immunoneutralization suggests that they occur independently of the hypothalamic-pituitary-thyroid axis. Somatostatin appears to exert a tonic inhibitory control on avian thyroid function, possibly by effects mediated at the thyroid gland to inhibit T4 release and by peripheral effects to suppress the conversion of T4 and T3.

J. Endocr. (1986) 110, 127–132
Changes in ornithine decarboxylase activity in ovarian follicles of the laying hen (Gallus domesticus) during the ovulatory cycle
Authors: Armstrong D. G.
Published: December 2008

Fowl ovarian ornithine decarboxylase activity was measured at 20, 10 and 3 h before an expected ovulation in granulosa and thecal tissues from follicles at various stages of development. An increase in the enzyme activity between 10 and 3 h before an expected ovulation was assumed to be caused by preovulatory increase in plasma LH concentration.

The activity in granulosa tissue increased with increasing size of the follicle. In the largest (F1) follicle there was an 11-fold increase in granulosa ornithine decarboxylase specific activity between 10 and 3 h before ovulation. In the third (F3) and fifth (F5) largest follicles there was a 1·9- and 2-fold increase respectively.

The enzyme activity in thecal tissue from the follicular hierarchy decreased with increasing size of the follicle and the F3 thecal preparation was the only tissue to respond to the preovulatory LH surge. In contrast, ornithine decarboxylase activity in thecal tissue from small (< 5 mm) non-atretic follicles increased by two- to threefold after the preovulatory LH surge. The activity in atretic follicles of the same size was low and remained unchanged throughout the ovulatory cycle.

J. Endocr. (1986) 110, 211–216
Inhibitory effects of bromocriptine on mammary development and function in lactating mice
Authors: Knight C. H. , Calvert D. T. , Flint D. J.
Published: December 2008

Five experiments were conducted. In the first, the plasma prolactin concentration of lactating mice was significantly reduced 3, 6 and 12 h after a single injection of 0·2 mg bromocriptine at 09.00 h, but recovered to normal levels at 24 h. A second injection at 17.00 h (i.e. total dose of 0·4 mg) completely prevented this recovery. Prolactin concentration was also reduced after the s.c. implantation of a solid pellet of bromocriptine.

Once daily injections of bromocriptine for 7 days starting 1-day prepartum (early lactation group) or on day 5 of lactation (established lactation group) significantly reduced milk yield, assessed from the weight gain of the litter or estimated by a tritiated water dilution procedure. In early lactation the degree of inhibition was positively related to the size of the suckling litter (three pups, no inhibition; nine pups, 16·4% inhibition; 14 pups, 40·8% inhibition), but in established lactation an inhibition of 25–30% was observed, regardless of litter size. Twice-daily injections and s.c. implants of bromocriptine both reduced milk yield by a greater amount (approximately 45%), but in no case was secretion completely suppressed. The inhibitory effect of bromocriptine was prevented by the simultaneous administration of ovine prolactin (0·4 mg).

Lactogenesis was apparently not affected by bromocriptine treatment. At the end of the early lactation treatment period, the mammary glands of bromocriptine-treated animals were significantly smaller and contained fewer cells than those of controls, but this was not the case in animals treated during established lactation.

It is suggested that suppression of prolactin secretion by bromocriptine treatment may reduce milk yield both indirectly, by inhibiting development of the gland and thereby reducing the size of the secretory cell population, and directly, by reducing the activity of individual secretory cells. The observation that lactation was not completely inhibited suggests that prolactin may not be the only galactopoietic hormone in the mouse.

J. Endocr. (1986) 110, 263–270
A comparison of the effects of gonadal steroids on naloxone-induced LH secretion in gonadectomized rats
Authors: Spencer G. M. , Whitehead S. A.
Published: December 2008

The effects of the opiate antagonist naloxone on serum LH concentrations was investigated in gonadectomized rats given different regimes of steroid pretreatment. Two injections of testosterone given 48 and 24 h before naloxone treatment failed to reinstate LH responses to this drug in castrated rats while subcutaneous testosterone-filled silicone elastomer capsules implanted for a week were effective in this respect. Injections of oestrogen, oestrogen plus progesterone or progesterone alone all restored LH responses to naloxone in ovariectomized rats when given 48 and/or 24 h before drug treatment, although the magnitude of these responses varied according to the precise steroid treatments. The hypothalamic-pituitary axis was also responsive to naloxone just before the progesterone-induced LH surge in oestrogen-primed ovariectomized rats. Results show that gonadal steroids are permissive to the effects of opiate drugs, but they suggest that endogenous opioid systems do not necessarily mediate the negative feedback effects of steroids. Some other factor(s), as yet unidentified in the rat, may control the opioid modulation of gonadotrophin secretion or exert an independent inhibitory effect on gonadotrophin release.

J. Endocr. (1986) 110, 327–334
An in-situ isolated rat adrenal perfusion system for study of neurally mediated catecholamine secretion: effects of morphine, a Met-enkephalin analogue, and naloxone on catecholamine secretion
Authors: Bouloux P.-M. G. , Perrett D. , Sopwith M. , Besser G. M.
Published: December 2008

An in-situ isolated rat adrenal perfusion technique has been devised to study the opioid control of neurally mediated adrenomedullary catecholamine release. Adrenomedullary catecholamine secretion was induced by electrical stimulation of the cut end of the left descending thoracic sympathetic chain on platinum electrodes. The half-maximal stimulatory potential (ED50) of the system was 8 V, 20 Hz, with 300μs pulse width. Basal release of catecholamine from the adrenal was constant using a perfusion flow rate of 100–300μl/min, but increased significantly with increasing perfusion temperature over the range 36–38 °C. Following repetitive 30-s stimulation of the left thoracic sympathetic chain, and 3-min fraction collections, the total amount of catecholamine released per fraction remained within 80–100% of the maximum release for up to eight consecutive stimuli. The release of catecholamines was completely blocked by hexamethonium (0·1 mmol/l), but recovered to preblockade values within two further stimuli. Using the ED50 and the first three stimuli as control, the effects of morphine (10 nmol/l–1 mmol/l), d-Ala2-MePhe4-Met-enkephalin-(O5)-ol (DAMME; 10 nmol/l–0·1 mmol/l) and naloxone (10 nmol/l– 10 μmol/l) on the response to the next three stimuli were compared. Morphine, DAMME or naloxone did not significantly alter the amount of catecholamine released by this form of stimulation. Therefore in the rat, under the conditions used, there is no evidence for mu (μ) or delta (†) opiate modulation of neurally mediated catecholamine release from the rat adrenal medulla.

J. Endocr. (1986) 111, 7–15
Evidence of gonadal steroid-independent changes in activity of the central LH-releasing hormone pulse generator in developing bull calves
Authors: D'Occhio M. J. , Gifford D. R. , Weatherly T. , Setchell B. P.
Published: December 2008

To ascertain whether temporal changes in activity of the hypothalamo-pituitary axis in prepubertal bulls may occur independently of shifts in sensitivity to steroid feedback, the acute post-castration rise in serum gonadotrophins was monitored in bull calves castrated at monthly intervals from 4 to 9 months of age. Since a major feature of the gonadotrophin profiles of developing bulls is a change in LH pulse frequency early in life, pulsatile LH secretion after castration was used as an index of activity of the central LH-releasing hormone (LHRH) pulse generator. Relative to the day of castration (day 0) bull calves (n = 4) were bled at 20-min intervals for 8 h on day −3 and at 10-min intervals for 4 h on days 3, 5 and 7. During the first week after castration, 4-month-old bulls showed a higher (P<0·05) frequency of LH pulses compared with bulls at 8 and 9 months (1·13, 0·88 and 0·75 pulses/h respectively; pooled s.e.m.= 0·13). Mean LH levels before castration were higher (P<0·05) in 4-month-old bulls than in bulls at 7, 8 and 9 months (0·92, 0·37, 0·31, 0·38 μg/l respectively; pooled s.e.m. = 0·12). After castration mean LH levels did not differ with age. Mean FSH levels did not differ among age groups either before or after castration. Increased serum LH levels in 4-month-old bulls confirmed the transient rise in LH secretion that occurs at this time in developing bull calves. Age-related differences in LH pulse frequency observed after castration suggested that in prepubertal bulls changes in activity of the central LHRH pulse generator can occur independently of steroid feedback mechanisms.

J. Endocr. (1986) 111, 67–73
Relaxin acts centrally to inhibit oxytocin release during parturition: an effect that is reversed by naloxone
Authors: Jones S. A. , Summerlee A. J. S.
Published: December 2008

Experiments were carried out to establish whether infusion of relaxin prolongs gestation and labour in the rat by suppressing release of oxytocin, and whether the effects of relaxin on birth could be reversed by the opioid antagonist naloxone. Female rats were implanted with subcutaneous osmotic minipumps for the infusion of purified porcine relaxin into the jugular vein for 84 h from either day 19 or day 20 of gestation. Infusion of relaxin delayed the onset of labour and in those animals which delivered during relaxin infusion, delivery was longer by approximately 45 min. Plasma oxytocin levels 40 min after delivery of the first fetus were 45·25 ± 3·6 pmol/l (mean ± s.d.) in unoperated controls and significantly (P < 0·01) depressed (23·89 ± 3·9) in rats that delivered during infusion of relaxin. Rats that delivered after the infusion of relaxin had finished, gave birth significantly (P < 0·05) faster than controls and plasma oxytocin levels were significantly (P < 0·01) raised (77·87 ±15·9 pmol/l). Naloxone treatment (1 mg/kg; i.m.) given immediately after the delivery of the first fetus reversed the inhibitory effect of relaxin and the interval between successive deliveries was slightly faster than that of controls. Plasma oxytocin levels in relaxin-infused naloxone-treated rats were significantly (P < 0·01) higher than values in unoperated control rats. The results confirm that relaxin suppresses oxytocin release possibly through an opioid system and this may be important in the control of the timing of birth.

J. Endocr. (1986) 111, 99–102
Induction of ovulation during anoestrus in two breeds of sheep with multiple injections of LH alone or in combination with FSH
Authors: Wallace J. M. , McNeilly A. S. , Baird D. T.
Published: December 2008

The gonadotrophic requirements for the induction of ovulation and formation of a viable corpus luteum in two breeds of seasonally anoestrous sheep of differing fecundity was investigated.

Welsh Mountain (n = 20) and Damline ewes (n = 19) were given LH or FSH either alone or in combination. Luteinizing hormone was injected i.v. at an increasing frequency for 72 h (one injection every 3 h for 24 h, one every 2 h for 24 h, and one every hour for 24 h) and FSH was injected in an identical manner for the first 36 h of treatment.

Exogenous LH alone and in combination with FSH induced a preovulatory LH surge in all 19 ewes and ovulation in 18 out of 19 ewes of both breeds. However exogenous FSH alone was ineffective. The incidence of normal corpus luteum function in ewes induced to ovulate was low and not related to treatment, timing or magnitude of the LH/FSH surge. It is concluded that in both breeds studied (a) it is the infrequency of LH pulses which limits the development of preovulatory follicles during seasonal anoestrus, (b) that the requirement for FSH remains unknown, and (c) that the induction of inadequate corpora lutea during seasonal anoestrus reflects either defects in hormonal priming of the preovulatory follicle and/or inappropriate luteotrophic support after ovulation.

J. Endocr. (1986) 111, 181–190
Sexual dimorphism in immunoneutralization of bioactivity of rat and ovine inhibin
Authors: van Dijk S. , Steenbergen J. , Gielen J. Th. , de Jong F. H.
Published: December 2008

Inhibin was partially purified from bovine follicular fluid using chromatography on immobilized Procion Red 3B and anion-exchange chromatography. Ovariectomized Texel ewes were immunized against the inhibin-containing fraction from the Procion Red 3B column and the immune response was subsequently boosted with similar fractions or with the preparation obtained from the anion-exchange column. The potencies of the resulting antisera were evaluated in an invitro bioassay system for estimating inhibin activity, using dispersed rat pituitary cells. The antisera were found to inhibit the bioactivity of inhibin preparations from ovarian follicular fluid of bovine, porcine, ovine or human origin, as well as inhibin activity in ovine testicular lymph and rete testis fluid, in culture media from rat granulosa and rat Sertoli cells and in homogenates of rat ovaries and testes. These results indicate that the inhibin molecules from several species contain a common bioactive moiety. The results also showed that the antiserum was more effective in neutralizing inhibin activity from ovarian than from testicular sources in both sheep and rat, indicating a sex-related difference in the inhibin molecules within a species.

J. Endocr. (1986) 111, 255–261
Differential effects of catecholoestradiol-17β and oestradiol-17β on concentrations of plasma LH in the fetal pig
Authors: Parvizi N.
Published: December 2008

The effects of 2-hydroxyoestradiol-17β and oestradiol-17β on the concentration of serum LH was studied in fetal pigs. 2-Hydroxyoestradiol-17β (5 μg/fetus; n = 6), oestradiol-17β (5 μg/fetus; n = 7) or vehicle (n = 6) were injected i.v. into chronically catheterized fetal pigs at gestational ages of 105–108 days. Seven additional fetuses at the same age served as untreated controls. 2-Hydroxyoestradiol-17β but not oestradiol-17β resulted in a rapid decline in plasma LH levels from 0·82 ± 0·21 (s.e.m.) to 0·21 ± 0·05 μg/l within 20 min of injection. Baseline concentrations of plasma LH in the mothers were low (0·72 ±0·2 μg/l) and were not affected by catecholoestrogen or oestrogen treatment of fetuses. The results suggest that catecholoestrogens do not modulate LH secretion in fetal pigs through an oestrogenic action. It is possible that they act by modifying catecholamine metabolism or neurotransmission.

J. Endocr. (1986) 111, 297–300
Developmental changes in gonadotrophins and testicular gonadotrophin receptors in the pig, from neonatal to adult life
Authors: Vandalem J. L. , McNamara M. , Petit R. , Hennen G.
Published: December 2008

Changes in the concentrations of LH and FSH testicular receptors have been studied in the pig, from neonatal to adult life, and correlated with blood LH, FSH and testosterone concentrations.

Quantification of gonadotrophin receptors was performed in equilibrium binding studies, using homologous systems. The presence of high-affinity binding sites for LH and FSH (association constant (Ka): LH ∼ 20 litres/nmol; FSH ∼ 10 litres/nmol) was demonstrated in the testes of all animals studied. The apparent affinity of LH and FSH receptors did not change significantly with age.

During the first weeks of life, there was a transient rise in LH receptor content, reaching a maximum of 8·7 ± 2·2 (mean ± s.e.m.) pmol/g testis at 24 days of age. This was correlated with a peak in testosterone secretion and reflects the second wave of interstitial cell proliferation in the pig. A second increase in the number of LH receptors occurred after 12 weeks of age and corresponds to pubertal maturation and final differentiation of adult Leydig cells. During this period, circulating concentrations of testosterone markedly increased without any significant variation in LH blood levels, suggesting a change in testicular sensitivity to LH in the maturing pig.

A continuous increase in FSH receptor content was observed from the neonatal to the adult pig. This increase occurred in two phases. During the first 2 months of life, the increase in the number of FSH receptors exceeded that of testis growth rate and resulted in an increase in FSH receptor concentrations which reached a peak at 12·1 ± 1·8 pmol/g testis, at week 9. After this time the increase in the amount of FSH receptors was slower than that of testis weight gain, leading to a decrease in receptor concentration.

Since changes in the amounts of LH and FSH receptor concentrations were not correlated with variations in gonadotrophin concentrations in the blood, an inductive role for FSH on LH receptors, as has been shown in the rat, could thus not be demonstrated in the pig.

J. Endocr. (1986) 111, 301–308