bluuebunny/crossref_metadata_2025 huggingface dataset:
Insulin binding and action in adipocytes of pregnant rats: evidence that insulin resistance is caused by post-receptor binding defects
Authors: Sutter-Dub M. Th. , Sfaxi A. , Latrille F. , Sodoyez-Goffaux F. , Sodoyez J. C.
Published: December 2008

Insulin resistance was investigated in the adipose cell of rats which were at days 16 and 20 of pregnancy. Data are presented to relate insulin binding and biological effect, which was evaluated by the ability of insulin to stimulate [1-14C]glucose oxidation. Adipocytes from pregnant rats bound more insulin than fat cells from control (non-pregnant) animals and the number of insulin receptors per adipocyte increased during pregnancy. Basal glucose oxidation rate was decreased at 16 and 20 days of pregnancy: however, the dose–response curve for insulin-stimulated glucose oxidation was significantly depressed only after 20 days of pregnancy. The concentration at which insulin increased glucose oxidation by 50% increased with the duration of pregnancy. We conclude that during pregnancy in the rat the adipocyte response to insulin was decreased, despite an increase in insulin binding. This result suggests that a major determinant of insulin resistance in rat adipocytes during pregnancy is present after the initial insulin–receptor interaction. Consequently, a post-receptor defect may be largely responsible for the insulin resistance.

J. Endocr. (1984) 102, 209–214
Effect of calcitonin on salivary phosphorus and calcium excretion in sheep
Authors: Matsui T. , Kanagawa Y. , Yano H. , Kawashima R.
Published: December 2008

Three thyroidectomized sheep were infused intravenously with porcine calcitonin at a rate of 30 mi.u./h per kg and three sham-operated sheep were infused with vehicle for 5 h. Saliva was collected from the left parotid duct by cannulation for 10 min in every hour. Salivary secretion rates were not changed in either thyroidectomized or sham-operated sheep throughout the experiment. Before the infusion, salivary phosphorus excretion was less in thyroidectomized sheep than in sham-operated animals. Calcitonin infusion increased salivary phosphorus excretion and decreased serum phosphorus concentrations in thyroidectomized sheep. Vehicle infusion did not affect salivary phosphorus excretion in sham-operated sheep. Serum concentrations and salivary excretion of calcium were decreased by calcitonin infusion into thyroidectomized sheep but were not changed in sham-operated sheep infused with vehicle. Calcitonin infusion increased serum parathyroid hormone concentrations in thyroidectomized sheep after the decrease of serum calcium concentrations. However, vehicle infusion did not affect serum parathyroid hormone concentrations in sham-operated sheep. There was little change of cyclic AMP excretion during the experiment in either thyroidectomized or sham-operated sheep. It is concluded that calcitonin increases salivary phosphorus excretion in sheep.

J. Endocr. (1984) 102, 365–368
Receptors for thyroid-stimulating hormone in normal and pathological human thyroid tissues
Authors: Kermode J. C. , Edmonds C. J. , Morgans M. E.
Published: December 2008

The receptors for TSH have been studied in human thyroid tissue to assess their density and binding characteristics in various disease states. A single set of similar independent receptors appeared to be present in both healthy and pathological thyroid tissue. Their binding affinity for bovine TSH averaged 1·1 × 1010l/mol in healthy tissue and, with the exception of papillary carcinoma which showed some reduction, was not significantly altered in the various disease states studied. No receptors with low binding affinity were found. The number of receptors was significantly greater in toxic diffuse goitre and in hyperfunctioning follicular adenoma (but these tissues came from patients given antithyroid drugs and often iodine preoperatively), and was reduced in Hashimoto's thyroiditis. In well-differentiated thyroid carcinoma, the number of receptors was similar to or greater than in normal tissue, but in undifferentiated and medullary carcinoma, and in lymphoma of the thyroid, receptors were completely absent. Tracer-binding data obtained with human TSH were uniformly lower than the corresponding data obtained with bovine TSH, but showed an analogous pattern of differences amongst the various normal and pathological tissues.

J. Endocr. (1984) 102, 369–374
CORTICOTROPHIN-RELEASING FACTOR - MEDIATED ADRENOCORTICOTROPHIN RELEASE FROM RAT ANTERIOR PITUITARY CELLS IS POTENTIATED BY C-TERMINAL GASTRIN-RELEASING PEPTIDE
Authors: Hale A.C. , Price J. , Ackland J.F. , Doniach I. , Ratter S. , Besser G.M. , Rees L.H.
Published: December 2008

The remission of Cushing's syndrome following surgical removal of a tumour containing bombesin-like immunoreactivity (BLI), but insignificant levels of ACTH, is described. However, an acid extract of the tumour tissue caused the release of ACTH from isolated rat anterior pituitary cells in vitro. These observations led to an investigation of the effects of synthetic C-terminal gastrin-releasing peptide (GRP(14-27)) on ACTH release from isolated rat anterior pituitary cells. GRP(14-27) (10-1000 ng/ml) directly stimulated the release of ACTH in vitro, whereas lower doses (10-1000 pg/ml), ineffective themselves in eliciting ACTH release, potentiated the CRF-mediated in-vitro release of ACTH.
ABSENCE OF NUCLEAR PROGESTERONE RECEPTOR IN LH RELEASING HORMONE NEURONES IN LAYING HENS
Authors: Sterling R.J. , Gasc J.M. , Sharp P.J. , Tuohimaa P. , Baulieu E.E.
Published: December 2008

Using a double immunohistochemical technique, LH releasing hormone (LHRH) neurones and 110kDa nuclear progesterone receptor were localized in the hypothalamus of the laying hen. Nuclear progesterone receptor was widely distributed throughout the hypothalamus, occurring in the preoptic, septal, anterior and basal areas. The region where progesterone receptor was revealed in nuclei of neurones overlapped that containing LHRH neurones. However, LHRH cell bodies did not contain progesterone nuclear receptor. It is concluded that the positive feedback action of progesterone on LH release is not mediated by a genomic mechanism within the LHRH neurone.
Involvement of rat corticotrophin-releasing factor-41-related peptide and vasopressin in adrenocorticotrophin-releasing activity from superfused rat hypothalami in vitro
Authors: Gillies G. , Puri A. , Hodgkinson S. , Lowry P. J.
Published: December 2008

Superfused rat hypothalamic pieces stimulated with a high K+ medium released corticotrophin-releasing factor (CRF) as detected in the rat isolated anterior pituitary cell column bioassay. This activity has components related to ovine CRF-41 (oCRF-41) and vasopressin as assessed by the effects of specific antisera on the ACTH-releasing activity of the hypothalamic column effluent. Release of immunoactive vasopressin paralleled that of CRF bioactivity. Immunoactive oCRF-41 could not be detected, as it is likely to be below the sensitivity of present radioimmunoassays.

J. Endocr. (1984) 103, 25–29
Hormone receptors in the epiphysial cartilage
Authors: Kan K. W. , Cruess R. L. , Posner B. I. , Guyda H. J. , Solomon S.
Published: December 2008

In order to assess which hormones may exert direct effects on skeletal growth at the epiphysial growth plate, the specific binding of hormones to the epiphysial cartilage of growing dogs and rabbits was studied. Membrane fractions obtained by centrifugation of homogenates prepared from dog and rabbit growth plate cartilage at 600, 15 000 and 105 000 g showed significant specific binding of serum insulin-like activity and insulin. Binding of growth hormone and prolactin by the three membrane fractions was negligible. Saturable binding sites for triiodothyronine could be demonstrated in nuclei from the dog growth plate. Nuclear binding showed an apparent Kd of 11 ±3·6 nmol/l and a maximum binding capacity of 4·1 ± 1·6 pmol/mg DNA, a level comparable to dog liver. Using a viable chondrocyte suspension prepared from dog epiphysial cartilage, specific steroid binding in the cells could be demonstrated for [3H]dexamethasone but not 17α-methyltrienolone, oestradiol-17β or 1α,25-di-hydroxycholecalciferol. Scatchard analysis of dexamethasone binding showed high affinity binding sites having a Kd of 1·2 ± 0·35 nmol/l and a capacity of 1700 sites/cell, and a low affinity binding with a Kd of 109 ± 57 nmol/l and a capacity of 24 000 sites/cell. Steroid competition for the specific binding showed the following sequence of affinity: dexamethasone > corticosterone > 11-deoxycortisol > testosterone > oestradiol-17β. Although all of the hormones examined except prolactin have well-established physiological effects on skeletal growth, our present results suggest that some of the hormonal effects observed in intact animals are secondary and do not involve receptor–hormone interaction in cartilage as such.

J. Endocr. (1984) 103, 125–131
Stimulation of prolactin secretion by oestradiol in the rat is associated with increased hypothalamic release of thyrotrophin-releasing hormone
Authors: Franks S. , Mason H. D. , Shennan K. I. J. , Sheppard M. C.
Published: December 2008

We have studied the effect of oestradiol (OE2) on secretion of prolactin and TSH by rat pituitary glands and correlated this with changes in hypothalamic content and release of thyrotrophin-releasing hormone (TRH). Ovariectomized Wistar rats received s.c. silicone elastomer implants of OE2 at a dose known to give pro-oestrous OE2 levels. After 1 week rats were decapitated, blood was collected for assay of prolactin and TSH, blocks of hypothalamus were dissected out and pituitary glands were removed and bisected. Medium bathing hemipituitary glands was collected for measurement of prolactin and TSH after a 30-min incubation. Immunoreactive TRH was measured in medium removed from hypothalami and in extracts of homogenized hypothalami. Serum prolactin was higher in OE2-treated than in control animals (59·3 ± 19·5 (s.e.m.) vs 9·4 ± 1·5 μg/l; P<0·05) and this was associated with a threefold increase in pituitary prolactin in the medium. By contrast, TSH concentrations in serum and pituitary incubation medium were not significantly different in the two groups. There was no difference between the groups in hypothalamic content of TRH but TRH release in the incubation medium was increased by OE2 (30·2 ± 6·5 vs 10·0 ± 1·3 pg/mg protein per 30 min; P<0·01). In summary, physiological levels of OE2 stimulated prolactin secretion without change in TSH and this was associated with a threefold increase in hypothalamic release of TRH. These findings suggest that the stimulating effect of OE2 on prolactin secretion may, in part, be mediated by hypothalamic TRH.

J. Endocr. (1984) 103, 257–261
Brain sites involved in the regulation of growth hormone secretion in the young male domestic fowl
Authors: Rabii J. , Knapp L. , De La Guardia A. , Zafian P. , Lauterio T. J. , Scanes C. G.
Published: December 2008

To study brain sites involved in the regulation of GH secretion in the domestic fowl, lesions were placed in and around the hypothalamus of 1-week-old cockerels. Circulating concentrations of GH were then measured at weekly intervals for 4 weeks after the placement of lesions. At the termination of the experiment, histological procedures were used to determine the exact site of the lesion in each bird. Although a fair degree of overlap existed between the lesion sites leading to stimulation and those causing an inhibition of GH secretion, a clear distinction could be made in the overall distribution of stimulatory and inhibitory sites of GH control. A high concentration of lesion sites resulting in GH decline (presumed GH-releasing factor-rich areas) appeared to reside in the general area of the ventromedial and the arcuate nucleus of the hypothalamus. Lesion sites causing a GH rise (presumed somatostatin-rich areas), on the other hand, seemed to have a more caudal distribution. In addition, some evidence of an anterior hypothalamic distribution of these presumed 'somatostatin' neurones was observed. These agree with the existing immunohistochemical data on the distribution of somatostatin and constitute experimental evidence for localization of presumed GH-releasing factor sites within the avian brain.

J. Endocr. (1984) 103, 327–332
Acute inhibition of rat myometrial responses to oxytocin by tamoxifen stereoisomers and oestradiol
Authors: Lipton A. , Vinijsanun A. , Martin L.
Published: December 2008

The non-steroidal antioestrogen tamoxifen (trans-1-(4-β-dimethylaminoethoxyphenyl)-1,2-diphenylbut-1-ene), widely used in the treatment of breast cancer, and its oestrogenic cis-isomer rapidly inhibited contractile responses of isolated rat myometrium to supramaximal concentrations of oxytocin (1·28 × 10−6 mol/l). Both compounds were effective at concentrations comparable with the plasma concentrations of tamoxifen reached in therapy (i.e. 5 × 10−7to 5 × 10−6 mol/l). Inhibition was too rapid in onset ( < 3 min) to involve changes in RNA transcription and protein synthesis, and was not prevented or reversed by the addition of oestradiol to the bath. We conclude that the inhibition did not involve the classical oestrogen receptor pathway. Oestradiol-17β at concentrations above 10−6 mol/l also inhibited the myometrium and potentiated the effects of the antioestrogens. Our experiments suggest that the antioestrogens and oestradiol act via a similar route with tamoxifen having an equilibrium affinity approximately tenfold greater than that of oestradiol.

J. Endocr. (1984) 103, 383–388
TREATMENT OF PATIENTS WITH ADVANCED CANCER OF THE PROSTATE USING A SLOW-RELEASE (DEPOT) FORMULATION OF THE LHRH AGONIST ICI 118630 (ZOLADEX®)
Authors: Walker K.J. , Turkes A.O. , Turkes A. , Zwink R. , Beacock C. , Buck A.C. , Peeling W.B. , Griffiths K.
Published: December 2008

Twenty two patients with advanced carcinoma of the prostate have been treated for up to 3 months with the slow-release (depot) formulation of the luteinizing hormone-releasing hormone (LHRH) agonist ICI 118630. Patients were randomized to receive one of three different doses of ICI 118630 of 0·9, 1.8 or 3.6 mg. The depot preparation was injected subcutaneously every 4 weeks. At the highest dose, the concentration of testosterone in serum was significantly reduced to castrate values after 2–3 weeks of therapy. The smaller doses of ICI 118630 (1.8 or 0.9 mg every 4 weeks) similarly reduced serum testosterone concentrations although, at the lowest dose, testosterone values were not suppressed in all patients during the first month. Hormonal changes were accompanied by subjective clinical improvement in symptomatic patients and there were no significant side effects. The data clearly demonstrate the considerable therapeutic potential of ICI 118630 in the depot formulation for the treatment of advanced carcinoma of the prostate.
Autoradiographic studies of androgen-binding sites in the rat urogenital sinus and postnatal prostate
Authors: Takeda H. , Mizuno T. , Lasnitzki I.
Published: December 2008

Binding sites of [3H]testosterone and [3H]dihydrotestosterone in the rat fetal urogenital sinus and postnatal prostate and vagina grown in vitro were examined by steroid autoradiography. Distinct nuclear incorporation of both androgens appeared between 14·5 and 16·5 days of gestation in rat fetuses. Nuclear labelling in the sinus was restricted to the mesenchyme surrounding the epithelium which showed no nuclear labelling. A similar distribution of labelled cells was observed in male and female sinuses up to 18·5 days of gestation. By 20·5 days of gestation, the labelling in the ventral mesenchyme of female urogenital sinuses became less intense but persisted in the mesenchyme of the dorsal sinus wall from which the vagina is formed. In the postnatal prostate, the epithelium showed nuclear [3H]testosterone labelling at 10 days coinciding with the onset of its functional differentiation. Epithelial labelling became more intensive at 4 weeks post partum while that of the mesenchyme declined. The results suggest two phases of androgen action: formation of the prostatic buds mediated by the androgen-activated mesenchyme of the fetal urogenital sinus and the differentiation of the postnatal prostatic epithelium directly stimulated by androgens.

J. Endocr. (1985) 104, 87–92
Thyroxine treatment facilitates prolactin secretion and induces a state of photorefractoriness in thyroidectomized starlings
Authors: Goldsmith A. R. , Nicholls T. J. , Plowman G.
Published: December 2008

Sexually immature male starlings were radiothyroidectomized while held under short daylengths. They were then subjected to long (18-h) photoperiods and the testes developed rapidly and apparently normally to full maturity. As expected, thyroidectomy prevented an onset of photorefractoriness and after 140 days the testes were still fully developed (testicular width 6·5 ± 0·8 mm). Half of the birds were then given thyroxine (0·011 mmol/l) in the drinking water for 14 days while the others were maintained as controls. At the end of this time the birds still had fully developed gonads (testicular width 7·8 ± 0·3 mm) but after a further 14 days testicular regression began in the thyroxine-treated birds. The testes of all individuals in this group were fully regressed (width 1·8 ± 0·1 mm) by 56 days after the end of thyroxine administration and moulting of the flight feathers had begun. No recrudescence of the gonads was subsequently noted in the next 2 months and the birds were apparently photorefractory. The short period of thyroxine treatment also caused a rapid and prolonged increase in plasma prolactin levels from 2·0 ± 0·3 to 16·8 ± 2·6 μg/l. No testicular regression or moulting was observed in the control birds and their plasma prolactin levels remained very low (below 4·0 μg/l) throughout the experiment.

In thyroidectomized and castrated starlings held on 18-h daylengths, 14 daily injections of thyroxine 100 μg/bird per day) caused a rapid and permanent decrease in circulating FSH to basal levels (reached about 36 days after thyroxine treatment began, at which time the birds moulted). The treatment also caused a marked increase in plasma prolactin lasting for about 50 days.

J. Endocr. (1985) 104, 99–103
Changes in concentrations and rate of decline of adrenaline in the medial preoptic area and mediobasal hypothalamus of acutely ovariectomized steroid-treated rats
Authors: MacKinnon P. , Clark C. , Clement E. M. , Sheaves R.
Published: December 2008

The presence of adrenaline within the central nervous system appears to be essential for the occurrence of an oestrogen-stimulated surge of LH in both pro-oestrous and ovariectomized rats. Previous measurements of adrenergic activity based on the rate of decline of adrenaline (RDA) 2 h after injection of a synthesis inhibitor (SKF 64139) suggested that adrenergic activity increases in both the medial preoptic area (MPOA) and the mediobasal hypothalamus (MBH) at the start of the LH surge (15.00–17.00 h). The purpose of the present studies was to see whether oestrogen and progesterone affected this increase in adrenergic activity at the sites of the cell bodies (MPOA) and axon terminals (MBH) of the gonadotrophin-releasing hormone-synthesizing neurone. Rats ovariectomized at dioestrus showed a reduction in both plasma LH concentrations and RDA (P < 0·01) in the MBH between 15.00 and 17.00 h on the day of expected pro-oestrus. Oestrogen replacement at operation restored LH levels and the RDA to values found in intact rats. Injection of an antioestrogen (Cl-628), with or without oestrogen, also reduced plasma LH levels and the RDA (P < 0·01) in the MBH. Removal or replacement of oestrogen apparently had little effect on the RDA in the MPOA. In ovariectomized oestrogen-primed rats an injection of progesterone on the morning of expected pro-oestrus advanced and enhanced not only the LH surge but also the RDA in the MBH (P< 0·001). Moreover, concentrations of adrenaline in the MBH (but not the MPOA) decreased (P < 0·001) consistently over a 2-h period following injection of progesterone. These results support the suggestion that steroid-stimulated adrenergic activity in the MBH may be concerned with the preovulatory release of gonadotrophins.

J. Endocr. (1985) 104, 129–135
Passive immunization against progesterone inhibits endometrial sensitization in pseudopregnant mice and has antifertility effects in pregnant mice which are reversible by steroid treatment
Authors: Rider V. , McRae A. , Heap R. B. , Feinstein A.
Published: December 2008

Pregnant mice were injected 32 h post coitum (p.c.) with a monoclonal antibody against progesterone (5·7 or 9·5 nmol immunoglobulin G (IgG)) or 0·9% (w/v) NaCl (controls). Progesterone was injected starting on day 2, 3, 4 or 5 p.c. Progesterone reversed the antifertility effect of the lower dose of antibody when replacement began on day 2, 3 or 4, though the number of implantation sites was reduced when treatment started on day 3 or 4. By day 5 only one of six treated animals remained pregnant, showing that antibody action was reversible only up to day 4. At the higher dose of antibody, exogenous nidatory oestrogen was also required.

Pseudopregnant mice were injected 32 h p.c. with this antibody (5·7 nmol IgG) or 0·9% NaCl (controls). At 16.00 h on day 4 p.c., oil was injected into the lumen of one uterine horn and the magnitude of the decidual cell reaction was assessed 72 h later. Injected horns of antibody-treated females did not respond to intraluminal oil, whereas those of control mice increased fivefold in weight. Steroid treatment after the induction stimulus did not promote decidual growth, indicating that passive immunization reduced endometrial sensitivity. The results show that in the event that antibody fails to arrest the development of all embryos, the absence of endometrial sensitization will preclude the initiation of implantation, unless progesterone is given within 48 h of antibody treatment.

J. Endocr. (1985) 104, 153–158
Monosodium l-glutamate administration: effects on gonadotrophin secretion, gonadotrophs and mammotrophs in prepubertal female rats
Authors: Dada M. O. , Blake C. A.
Published: December 2008

We have studied gonadotrophin secretion and immunocytochemically stained gonadotrophs and mammotrophs in 35-day-old female rats which had been treated with monosodium glutamate (MSG) as neonates. We also compared our morphometric data in the saline-treated controls with those we have previously obtained in normal adult female rats. The size of the anterior pituitary glands was reduced but the serum levels, the pituitary gland concentrations and contents, and the in-vitro basal release rates of LH and FSH were not significantly altered by MSG treatment. The size of the LH and FSH cells was reduced by MSG administration, but the volume and numerical densities of LH and FSH cells, and the percentage of LH and FSH cells in the pars distalis were not affected. The results suggest that in spite of the smaller size of LH and FSH cells and of the anterior pituitary glands in the MSG-treated rats, the cells contain normal amounts of hormone and the basal LH and FSH secretion rates of the glands are not significantly depressed, contributing to the maintenance of normal serum gonadotrophin concentrations. The volume density of prolactin cells was not increased by MSG treatment. The volume density of gonadotrophs and the percentage of cells which are gonadotrophs in anterior pituitary glands of prepubertal female rats were greater than those in adult female rats, but the reverse was true for the volume density of prolactin cells, suggesting a reciprocal relationship between the relative numbers of gonadotrophs and mammotrophs in prepubertal and adult female rats.

J. Endocr. (1985) 104, 185–192
Oxytocin and vasopressin in rat hypophysial portal blood: experimental studies in normal and Brattleboro rats
Authors: Horn A. M. , Robinson I. C. A. F. , Fink G.
Published: December 2008

Oxytocin (OT) and vasopressin (VP) were measured by radioimmunoassay in hypophysial portal and peripheral blood from male Wistar rats and heterozygous and homozygous Brattleboro rats anaesthetized with urethane. In Wistar rats the concentrations of OT and VP were about 50 times greater than the concentrations in peripheral blood, whether or not the pituitary gland was left in situ during collection, and also considerably greater than the reported concentrations of the peptides in the cerebrospinal fluid. The release of both peptides was increased significantly by a lesion of the supraoptico-hypophysial tract that led to diabetes insipidus, but which left intact the external layer of the median eminence (ME). Concentrations of VP were undetectable in plasma from homozygous Brattleboro rats, but the portal plasma concentrations of VP in heterozygous Brattleboro rats were not significantly lower than in Wistar rats. The concentrations of OT in portal plasma from both types of Brattleboro rat were significantly higher than in Wistar rats.

The output of VP and OT into hypophysial portal blood of Wistar rats was not significantly affected by electrical stimulation of the suprachiasmatic, supraoptic or paraventricular nuclei or the ME using two types of stimuli, one of which produced an increase in peripheral plasma concentrations of VP and OT in intact rats and a significant increase in the release of LH-releasing hormone into hypophysial portal blood. The output of VP and OT into portal blood was also not significantly affected by either adrenalectomy with or without injection of dexamethasone or the injection of either the 5-hydroxytryptamine (5-HT) synthesis blocker, parachlorophenylalanine, or the 5-HT uptake blockers, alaproclate or zimelidine.

These results show that large amounts of OT as well as VP are released into hypophysial portal blood from fibres of the hypothalamo-neurohypophysial system that terminate in the external layer of the ME. Although distinct from the fibres that terminate in the pars nervosa (PN), the findings in Brattleboro rats show that the VP fibres of the ME system originate in neurones with a genomic mechanism for VP synthesis similar to that of the VP neurones that project to the PN. The lack of effect of adrenalectomy and the administration of 5-HT synthesis and uptake blockers must be interpreted with caution since the results obtained with electrical stimulation suggest that when the pituitary stalk is cut the release of OT and VP into portal blood approaches a maximum and may therefore be difficult to alter by experimental manipulation. The concentrations of OT and VP in portal blood are sufficiently high for these peptides to play a significant role in neural control of the anterior pituitary gland.

J. Endocr. (1985) 104, 211–224
Plasma concentrations of somatomedin-C in hypophysectomized, dwarf and intact growing domestic fowl as determined by heterologous radioimmunoassay
Authors: Huybrechts L. M. , King D. B. , Lauterio T. J. , Marsh J. , Scanes C. G.
Published: December 2008

The application of a human somatomedin-C radioimmunoassay for the determination of somatomedin-C in chicken plasma has been examined. Parallel inhibition of binding of 125I-labelled somatomedin-C to antisera raised against somatomedin-C was observed with acid-treated human and chicken plasma. The concentration of immunoreactive (IR)-somatomedin-C in the plasma of the domestic fowl appears to be GH dependent. Plasma concentrations of IR-somatomedin-C were reduced after hypophysectomy and partially restored by replacement therapy with chicken GH. The age/development pattern of circulating concentrations of IR-somatomedin-C has been determined in normal and dwarf strains of domestic fowl. Increases in the plasma concentration of IR-somatomedin-C were observed between 1 and 6 weeks of age in control male domestic fowl of either heavy (broiler type) or light (White Leghorn) strains. Thereafter, the plasma concentrations of IR-somatomedin-C remained constant in the heavy strain birds but declined in White Leghorn chicks. Plasma concentrations of IR-somatomedin-C were reduced in sex-linked dwarf chickens, in both light and heavy strains of fowl, but were unaffected in autosomal dwarf chickens.

J. Endocr. (1985) 104, 233–239
On the origin of dehydroepiandrosterone sulphate in the blood of fetal sheep
Authors: Liggins G. C. , Schellenberg J.-C. , Amato F. , Godfrey B. , Seamark R. F.
Published: December 2008

Total sulphoconjugated and unconjugated dehydroepiandrosterone (DHA) and total oestrone were measured in plasma of intact sheep fetuses, fetuses hypophysectomized at 104–112 days and fetuses bilaterally adrenalectomized at 98–101 days. At 120–127 days, the mean concentrations of total DHA and oestrone in intact fetuses (n = 13) were 29·7 ± 4·2 (s.e.m.) nmol/l and 14·3 ± 2·8 nmol/l respectively. At term, the values for total DHA and oestrone in hypophysectomized fetuses (n = 13) of 18·0 ± 1·9 nmol/l and 9·1 ±2·0 nmol/l were significantly (P <0·05) lower than the intact group whereas in the adrenalectomized fetuses (n = 8) total DHA (80·8±13·0 nmol/l) was higher (P < 0·05) and total oestrone values were similar to the intact animals. Intrafetal infusion of cortisol at term (1 mg/h for 84 h) raised levels of total oestrone in intact (n = 6; 12·3 ± 2·9 vs 31·6± 8·5 nmol/l) and adrenalectomized (n = 4; 14·2 ± 2·6 vs 190·6 ± 53·0 nmol/l) fetuses and of total DHA in hypophysectomized fetuses (n = 7; 16·0±1·9 vs 31·6 ± 8·5 nmol/l) while infusion of ACTH(1–24) (5 μg/h) was without significant effect in any group. It is concluded that the ovine fetal adrenal in late pregnancy makes no significant contribution either to the high circulating concentrations of DHA sulphate or to the substrates for placental oestrogen synthesis.

J. Endocr. (1985) 104, 279–283
The passage of 5α-dihydrotestosterone from serum into cerebrospinal fluid and LH negative feedback in castrated rhesus monkeys
Authors: Abbott D. H. , Batty K. A. , Dubey A. K. , Herbert J. , Shiers H. M.
Published: December 2008

Seven castrated monkeys were given either 50 or 100 μg 5α-dihydrotestosterone (DHT) propionate/kg per day. There was no correlation between serum and cerebrospinal fluid (CSF) levels of DHT, which remained very low in the CSF (0·3–0·6% of blood levels) despite the presence of high, supraphysiological amounts in the circulation. There was also no relation between unbound DHT in the blood and the CSF, in which all DHT is unbound. These results differ from previous work on testosterone, the metabolic precursor of DHT.

5α-Dihydrotestosterone propionate at the higher dose maintained suppressed levels of serum LH; LH in two out of four monkeys treated at the lower dose increased to levels observed in castrated, untreated rhesus monkeys. There was no predictable relationship between the amount of DHT in the CSF and levels of LH in the blood: by contrast, DHT in the blood was correlated with serum levels of LH. Levels of LH rose in monkeys in which total blood DHT fell below about 68 nmol/l and, even more obviously, if unbound DHT decreased to less than about 2 nmol/l.

Differences between the distribution of testosterone and DHT between blood and CSF cannot be explained by serum binding, lipid solubility or clearance from the brain, and suggest that there may be some mechanism for excluding DHT from the CSF. Though DHT reaches the CSF from the blood in small amounts, levels there do not relate predictably to those in the vascular compartment. It seems unlikely, therefore, that levels of intracerebral DHT are controlled by changes in those of the blood.

J. Endocr. (1985) 104, 325–330
Characteristics of bovine luteal cells in culture: morphology, proliferation and progesterone secretion in different media and effects of LH, dibutyryl cyclic AMP, antioxidants and insulin
Authors: O'Shaughnessy P. J. , Wathes D. C.
Published: December 2008

The morphological and functional characteristics of cultured bovine luteal cells were examined. Dispersed luteal cells were cultured in either Ham's F12 medium or Dulbecco's Modified Eagle's Medium (DMEM), plus 10% adult bovine serum. After 18 h of culture, fibronectin was observed to be associated with some cells showing histochemical 3β-hydroxysteroid dehydrogenase (3β-HSD) activity. In DMEM, cells adopted a fibroblast-like appearance with a doubling time of 34 h while in Ham's F12, cells retained an epithelial-like morphology with a doubling time of 91 h. Dibutyryl cyclic AMP (dbcAMP) but not LH slowed proliferation and altered cell morphology in DMEM. Addition of insulin and dbcAMP was required to maintain 3β-HSD activity in cells cultured for more than 3 days.

Progesterone secretion was significantly greater in Ham's F12 than in DMEM although there was a rapid decline in basal secretion during culture in either medium. Both LH and dbcAMP stimulated progesterone secretion although the effects of dbcAMP were significantly greater than those of LH after 18 h of culture. Addition of insulin significantly enhanced basal, LH-stimulated and dbcAMP-stimulated progesterone secretion after 3 days of culture whereas several antioxidants were without effect. These studies indicate that the morphological and functional characteristics of cultured luteal cells may be best maintained in Ham's F12 plus dbcAMP and insulin.

J. Endocr. (1985) 104, 355–361
Effects of restricted maternal contact in neonatal rats on sexual behaviour in the adult
Authors: Forsberg G. , Abrahamsson K. , Södersten P. , Eneroth P.
Published: December 2008

Rats, deprived of maternal contact and nutrition every alternate day starting on day 5 of life, attained a body weight at 45 days of age which was 50% of that of rats which had free access to maternal contact and nutrition. After 55 days of unrestricted food availability the body weight of the neonatally deprived rats was approximately 15% lower than that of the controls. Malnourished female rats showed normal behavioural oestrous cycles and became pregnant and lactated normally as young adults. After ovariectomy they showed higher lordosis quotients in response to treatment with oestradiol benzoate and progesterone than controls but lost less body weight in response to treatment with oestradiol-filled constant-release implants. Malnourished male rats ejaculated less frequently than controls in tests with sexually receptive female rats but this difference disappeared with repeated testing. The malnourished males showed longer ejaculation latencies and had somewhat higher serum concentrations of LH than controls after castration and treatment with testosterone-filled constant-release implants which reduced serum androgen concentrations to about 30% of the intact level. The results show that rats are capable of sustaining a rather severe neonatal nutritional deprivation without losing the capacity for essentially normal mating behaviour in adulthood.

J. Endocr. (1985) 104, 427–431
Identification of the major steroids in ovarian and adrenal venous plasma of the brush-tail possum (Trichosurus vulpecula) and changes in the peripheral plasma levels of oestradiol and progesterone during the reproductive cycle
Authors: Curlewis J. D. , Axelson M. , Stone G. M.
Published: December 2008

The quantitatively major steroid hormones in ovarian and adrenal venous plasma of the female brush-tail possum were identified by gas chromatography–mass spectrometry. The ovarian vein plasma samples all contained oestradiol and its concentration was highest during the pro-oestrous phase of the reproductive cycle. During this phase the concentration of progesterone was below the limit of detection but at day 13 of the oestrous cycle and pregnancy, the concentration of progesterone exceeded that of oestradiol. Cortisol and corticosterone were the major steroid hormones found in all adrenal vein samples with cortisol predominant. Androgens with a 3-oxo structure, if present, were below the limits of detection in all plasma samples. Radioimmunoassays for the measurement of progesterone and oestradiol in peripheral plasma were used to follow changes in the concentrations of these steroids during the reproductive cycle.

Progesterone in serial blood samples was low at oestrus, rose gradually until day 7 and then increased more rapidly to reach a peak level of 21–29 nmol/l at around day 13. Any differences between the pregnant and non-pregnant cycles were minor. Oestradiol was only detected around oestrus when levels were variable (53·3±20·92 (s.e.m.) pmol/l; n = 4). The results indicate that the reproductive cycle of the brush-tail possum is characterized by a single peak of oestradiol at around pro-oestrus followed by gradually increasing levels of progesterone. Pregnancy appears to have no influence on the circulating concentrations of oestradiol or progesterone.

J. Endocr. (1985) 105, 53–62
Fasting impairs LH secretion in female rats by activating an inhibitory opioid pathway
Authors: Dyer R. G. , Mansfield S. , Corbet H. , Dean A. D. P.
Published: December 2008

Two experiments were undertaken to investigate the way that fasting impairs LH secretion and to assess whether endogenous opioid mechanisms might be responsible for the impairment.

In the first experiment, pulsatile LH secretion was measured in a total of 51 chronically ovariectomized female rats. Initially 29 rats were subjected to food withdrawal for 24, 48, 72 or 120 h before the experiment. When compared with data collected from eight unfasted control rats, the 120-h fast was found to reduce significantly the mean peak and trough values of the LH pulses measured. However, in a subsequent study, the inhibition of pulsatile LH secretion by a 120-h fast was prevented in a group of eight rats given the opioid antagonist naloxone hydrochloride before the start of the blood-sampling period. Naloxone was without effect on pulsatile LH secretion in eight unfasted control rats.

In the second experiment, plasma LH concentrations were measured before and after unilateral electrical stimulation of the ventral noradrenergic tract (VNAT) in ovariectomized female rats pretreated with oestradiol benzoate. In 17 rats VNAT stimulation caused a significant rise in plasma LH, but after a 72-h fast this rise was significantly less than in unfasted control rats. However, pretreatment of fasted rats with naloxone (n = 9) significantly enhanced the VNAT-stimulated release of LH to the control values. Naloxone did not potentiate VNAT-stimulated LH release in unfasted animals (n = 6) or LH release in control unstimulated rats (n = 12).

The experiments indicate that both pulsatile LH secretion, and LH release caused by VNAT stimulation, are impaired by an acute fast. In both cases, the impairment is prevented by pretreatment with naloxone. Thus fasting probably activates an inhibitory opioid pathway within the brain to inhibit LH secretion.

J. Endocr. (1985) 105, 91–97
Mechanisms of release of prolactin from fowl anterior pituitary glands incubated in vitro: effects of calcium and cyclic adenosine monophosphate
Authors: Hall T. R. , Harvey S. , Chadwick A.
Published: December 2008

Fowl anterior pituitary glands were bisected and each half was pretreated in either Medium 199 or medium containing EGTA to deplete endogenous calcium (Ca2+) stores, after which they were incubated in Medium 199, or Ca2+-free medium, containing prolactin release-stimulating agents and verapamil, a Ca2+ channel blocker. High K+ concentrations, hypothalamic extract, synthetic thyrotrophin-releasing hormone (TRH) and dibutyryl cyclic AMP (dbcAMP) all stimulated release of prolactin from control (non EGTA-treated) hemianterior pituitary glands. The effects of TRH and dbcAMP were not additive, but the response to submaximal concentrations of TRH was augmented by theophylline, a phosphodiesterase inhibitor. Reduction of Ca2+ availability with EGTA or verapamil reduced basal release of prolactin, prevented the prolactin-stimulating effects of high K+ concentrations and TRH, and markedly attenuated responses to hypothalamic extract and dbcAMP, EGTA being more effective than verapamil. Increasing the Ca2+ concentration of the medium did not augment basal or stimulated release of prolactin.

These results suggest that both Ca2+ and cyclic AMP may act as intracellular mediators in the release of prolactin. Both basal and stimulated release of prolactin depend upon the presence of Ca2+. Although influx from the medium may be the major source of Ca2+, endogenous stores of Ca2+, perhaps mobilized by dbcAMP, may be able to maintain some release of prolactin. The prolactin-stimulating effects of TRH may be mediated by cyclic AMP.

J. Endocr. (1985) 105, 183–188
Effect of intravenous bovine growth hormone or human pancreatic growth hormone-releasing factor on milk production and plasma hormones and metabolites in sheep
Authors: Hart I. C. , Chadwick P. M. E. , James S. , Simmonds A. D.
Published: December 2008

Although it is well known that exogenous bovine GH (bGH) increases milk yield in ruminants it has not been possible to determine whether an increase in endogenous GH secretion has the same effect. The recent isolation of human pancreatic GH-releasing factor (hpGRF-44) has enabled this comparison of the effects of bGH and hpGRF-44 on milk production in sheep.

Three pairs of Dorset ewes underwent three 4-day treatments according to a Latin square design. Treatment 1 involved: 2-hourly i.v. injections (∼ 3·0 ml) of bGH (15 μg/kg; 1·8 units/mg); treatment 2: 2-hourly i.v. injections (∼3·0 ml) of hpGRF-44 (0·6 μg/kg); treatment 3: 2-hourly i.v. injections (3·0 ml) of the vehicle. Treatment periods were separated by 10 days. Sheep were milked twice daily and the milk was analysed for fat, protein and lactose. Blood samples (5·0 ml) were taken before and at 15, 45, 75 and 100 min after every third injection throughout the 4 days. Plasma was analysed for insulin, glucose, urea and non-esterified fatty acids (NEFA).

The changes in plasma GH stimulated by hpGRF-44 were consistent and repeatable throughout the 4 days of treatment. In comparison to the controls, treatment with hpGRF-44 and bGH significantly increased average plasma GH (μg/l) for the 4 days (control, 5·7±0·2 (s.e.m.); hpGRF-44, 12·3±0·4, P<0·001; bGH, 14·5±0·5, P<0·001), and this was accompanied by similar increases in milk yield (hpGRF-44, 26·7±2·6%, P<0·001; bGH, 30·7±2·9%, P<0·001) and the concentration of milk fat (g/kg) (control, 28·6±0·5; hpGRF-44, 33·2±0·5; bGH 34·8±1·5, P<0·01 for both treatments). The post-treatment decline in milk yield was much slower after hpGRF-44 than after bGH injections. Both treatments stimulated significant increases in the average concentrations of plasma insulin, glucose and NEFA, and plasma urea was significantly reduced by treatment with bGH only.

It is concluded that raising endogenous GH secretion is equally as effective as exogenous bGH in stimulating milk production in sheep.

J. Endocr. (1985) 105, 189–196
Oestrogenic regulation of testicular androgen production during development in the rat
Authors: Keel B. A. , Abney T. O.
Published: December 2008

The influence of age on the sensitivity of the testis to oestrogens was investigated. Intact male rats at 10, 25, 40 and 53 days of age were injected s.c. with vehicle, 5 or 50 μg oestradiol or diethylstilboestrol (DES)/100 g body wt twice daily for 2 days; the animals were killed 12 h after the last injection. Subsequently, the concentrations of testicular androgens and serum LH, prolactin, testosterone and androstanediol (5α-androstane-3α, 17β-diol) were measured. Testicular androgen production was determined in vitro in the presence or absence of human chorionic gonadotrophin (hCG) or dibutyryl cyclic AMP (dbcAMP). Androgens in the serum and testes displayed an age-related alternating pattern with androstanediol being the major androgen produced at 27 days of age. As a result of oestrogen treatment, serum LH concentrations were decreased while serum prolactin was increased. Serum testosterone was decreased by 36–55% in the 12-day-old group and further reduced by 95% of control values by day 55; serum androstanediol was less sensitive to oestrogen suppression. Testicular concentrations of both testosterone and androstanediol exhibited a marked reduction in 12-day-old animals as a result of oestrogen administration. These values were reduced by 85–95% at day 27 and remained suppressed even at 55 days. Basal production of testosterone was unaffected by oestrogen treatment in 12- and 27-day-old animals but was markedly decreased by day 42. Significant suppression of basal production of androstanediol was observed as early as day 12. Oestradiol treatment caused a significant reduction in hCG responsiveness of both androgens at days 12, 42 and 55. Oestrogen administration resulted in a significant (32–59%) decline in dbcAMP-responsive testosterone production in the 42-day group and a further suppression in the 55-day group. A marked inhibition of dbcAMP-stimulated androstanediol production was also observed in the 42- and 55-day groups. Testosterone production in response to dbcAMP was not significantly altered in the 12- and 27-day groups. With few exceptions the effects of oestradiol and DES on testicular function were similar. The data presented here suggest that the inhibitory effects of oestrogens become more pronounced as the animal approaches adulthood, that oestradiol and DES are similarly effective in regulating testicular function at all ages studied and that the production of both testosterone and androstanediol are suppressed by oestrogen administration.

J. Endocr. (1985) 105, 211–218
Subcellular compartmentation of prolactin in rat lactotrophs
Authors: Torres A. I. , Aoki A.
Published: December 2008

The intracellular localization of different molecular forms of prolactin was studied in various experimental models covering a wide range of secretory states.

By correlating electron microscopy, morphometry and quantification of monomeric (small) and polymeric (big) prolactin after differential extraction procedures, big prolactin was found stored in secretory granules while small prolactin was loosely associated with all organelles involved in hormone synthesis and processing. No correlation with levels of lactotrophic secretory activity was detected by either the number of secretory granules or prolactin content in lactotrophs.

J. Endocr. (1985) 105, 219–225
Influence of vitamin D on mineral metabolism, hormonal status and bone histology in lactating rats and their pups
Authors: Cancela L. , Marie P. J. , Le Boulch N. , Miravet L.
Published: December 2008

Mineral, hormonal and skeletal changes were determined in vitamin D-deficient (−D) and vitamin Dreplete (+D) mother rats and in their litters on day 20 of lactation. These results were compared with those obtained in −D mothers and pups, after giving the mothers an oral supplement (10 i.u. vitamin D3/day) during the period of lactation (20 days). Compared to +D animals, both −D lactating mothers and their pups exhibited extremely low plasma levels of 25-hydroxyvitamin D3 (25-OH-D3), diminished 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) and increased levels of immunoreactive parathyroid hormone (iPTH). Vitamin D-deficient mothers also had higher levels of calcitonin and lower levels of prolactin than +D mothers. All − D animals (mothers and pups) showed increased osteoclastic bone resorption and severe osteomalacia as shown by decreased bone ash, decreased calcification rate and increased endosteal osteoid surface, volume and thickness. In mothers treated with vitamin D3 during lactation, nearly all the plasma variables measured, as well as bone histomorphometric features, were normal. In contrast, their pups still showed rickets and osteomalacia, despite normal levels of 25-OH-D3 and calcium in the plasma. These pups had raised plasma levels of 1,25(OH)2D3 and iPTH associated with persistent stimulation of bone resorption. This study showed that (1) severe vitamin D deficiency in lactating rats produced marked osteomalacia and secondary hyperparathyroidism in both mothers and pups, and (2) vitamin D treatment of − D mother rats during lactation (10 i.u. vitamin D3/day) reversed the mineral, hormonal and skeletal abnormalities in mothers but not in pups.

J. Endocr. (1985) 105, 303–309