bluuebunny/crossref_metadata_2025_split huggingface dataset:
The route of secretion of inhibin from the rat testis
Authors: Maddocks S. , Sharpe R.M. 
Published: December 2008

ABSTRACT
Levels of immunoactive and bioactive inhibin were measured in venous blood collected at a point just before (testicular venous) and after (spermatic venous) its passage through the mediastinal venous plexus over the anterior pole of the rete testis, and compared with levels in peripheral venous blood and testicular interstitial fluid (IF). In 15 control rats, levels of inhibin were highest in IF (8900 ± 432 ng/l; mean ± SEM) and lowest in peripheral (290 ± 32 ng/l) and testicular (288 ± 34 ng/l) venous blood, whilst levels in spermatic venous blood (633 ± 99 ng/l) were always higher (P<0.002) than the levels in testicular venous blood. The latter difference was either reduced or abolished after disruption of spermatogenesis by local heating of the testes 8, 14, or 21 days previously, and by ligation of the efferent ducts for 6 h or more, but was not affected by acute removal of the epididymis. It is concluded that inhibin secreted into seminiferous tubule fluid may be reabsorbed from the rete testis and this may be the major route by which it reaches the peripheral bloodstream in rats with normal spermatogenesis.
GROWTH HORMONE INCREASES PLASMA LEVELS OF INSULIN-LIKE GROWTH FACTOR (IGF-I) IN A TELEOST, THE GILTHEAD SEABREAM (SPARUS AURATA)
Authors: Funkenstein B. , Silbergeld A. , Cavari B. , Laron Z. 
Published: December 2008

ABSTRACT
A heterologous radioimmunoassay (RIA) was applied for the determination of immunoreactive (IR)insulin-like growth factor (IGF-I) in a teleost, the gilthead seabream (Sparus aurata). Serial dilutions of the fish plasma gave a linear curve when added to constant amounts of 125I-labelled human IGF-I(53-70) and antiserum prepared against this fragment. The RIA was used to study the effect of GH on plasma levels of IR-IGF-I in S. aurata. A single injection of human recombinant GH (1 μg/g) resulted in a significant increase in IR-IGF-I at 29, 48 and 72 h, when compared with saline-injected fish. This novel observation suggests that in fish, as in mammals, circulating IGF-I levels are modulated by GH.
Differential effects of FSH and testosterone on the maintenance of spermatogenesis in the adult hypophysectomized rat
Authors: Bartlett J. M. S. , Weinbauer G. F. , Nieschlag E. 
Published: December 2008

ABSTRACT
In order to clarify further the role of FSH in the maintenance of spermatogenesis, adult rats were treated with purified human FSH (2 × 5 IU/day per rat), testosterone (1·5 cm silicone elastomer implant) or a combination of both hormones for 2 weeks following hypophysectomy.
After hypophysectomy alone, no elongate spermatids were observed and the numbers of pachytene spermatocytes and round spermatids observed were reduced when compared with untreated controls. Testosterone supplementation alone qualitatively maintained the formation of elongate spermatids in most seminiferous tubules, whilst in FSH-treated rats increased numbers of round spermatids and pachytene spermatocytes were observed when compared with hypophysectomized animals. Formation of elongate spermatids, however, did not occur under FSH treatment alone. A combination of FSH and testosterone treatment maintained spermatogenesis in an almost quantitative fashion. Numbers of pachytene spermatocytes and round spermatids were maintained at about 80% of levels seen in intact control animals. Treatment with FSH or testosterone alone maintained testis weights at significantly higher levels than those seen in hypophysectomized controls (FSH, 0·79 ± 0·05 g; testosterone, 0·81 ± 0·07 g; hypophysectomized, 0·50 ± 0·04 g). Animals treated with FSH and testosterone showed testis weights 20% below control values (1·22 ± 0·05 vs 1·51 ± 0·06 g; P <0·05). No increases in intratesticular or intratubular androgen concentrations or in testosterone: dihydrotestosterone ratios were observed in any of the hormone-treated groups when compared with hypophysectomized controls. In all hypophysectomized animals testicular androgen concentrations were reduced to <5% of control values.
The results obtained in this study suggest that FSH is involved in the maintenance of spermatogenesis in the adult rat and that the effects of FSH are not mediated through changes in intratesticular androgens. Low levels of testosterone in combination with FSH can almost quantitatively maintain spermatogenesis in adult rats.
Journal of Endocrinology (1989) 121, 49–58
Vitamin A deficiency and tri-iodothyronine action at the cellular level in the rat
Authors: Higueret P. , Pailler I. , Garcin H. 
Published: December 2008

ABSTRACT
Young rats were given a diet with or without vitamin A for a period of 7 weeks. In rats on the vitamin A-deficient diet, the formation of tri-iodothyronine (T3) complexes with nuclear proteins was reduced, and Scatchard analysis showed a decreased capacity of nuclear T3 receptors. In these rats, a decrease in growth and a decrease in the activity of lipogenic enzymes (glucose-6-phosphate dehydrogenase, phosphogluconate dehydrogenase and l-malate dehydrogenase) occurred, which could be related to the decreased formation of T3–nuclear protein complexes.
Journal of Endocrinology (1989) 121, 75–79
Oxytocin receptors in the ovine corpus luteum
Authors: Sernia C. , Gemmell R. T. , Thomas W. G. 
Published: December 2008

ABSTRACT
There is inconclusive evidence that oxytocin acts directly on the corpus luteum and affects steroidogenesis. Since any such action would probably be mediated by oxytocin receptors, these should be present in luteal tissue. In this study, homogenates of corpora lutea from both pregnant and non-pregnant ewes were examined for oxytocin receptors by radio-receptor assay. Specific oxytocin binding was not observed in luteal tissue during the oestrous cycle. However specific binding was found in the corpora lutea of pregnant ewes; appearing at a fetal head length of approximately 0·65 cm (about 30 days of pregnancy) and persisting to a head size of 11 cm, the largest size examined in this study. The affinity (Kd) of the receptor was calculated as 2·9 ± 0·3 nmol/l (s.e.m.; n = 9), a value similar to that obtained for the uterus. The receptor number ranged from a low of 8·7± 3·2 fmol/mg protein (n = 6) at a head size of <0·65 cm, to a maximum of 40·1 ± 6·5 fmol/mg protein (n = 25) at a head size of 2·5–3·75 cm. These values were lower than our estimate of 588 ± 39 fmol/mg protein (n = 5) for the uterus. It is concluded that a direct action of oxytocin on the corpus luteum is possible but only after the first month of pregnancy and not in the corpus luteum of the oestrous cycle.
Journal of Endocrinology (1989) 121, 117–123
The interaction of arginine vasopressin and oxytocin with bovine adrenal medulla cells
Authors: Taylor A. H. , Whitley G. St J. , Nussey S. S. 
Published: December 2008

ABSTRACT
Binding of [3H]arginine vasopressin (AVP) and [3H]oxytocin to primary monolayer cultures of bovine adrenal chromaffin cells was time-dependent, and the binding sites for each peptide were specific and saturable. Studies with the V1 AVP antagonist d(CH2)5Tyr(Me)2-AVP, the V2 agonist 1-deamino-8-d-AVP and the V2 antagonist d(CH2)5d-Leu2,Val4-AVP indicated that the AVP receptor was V1 in specificity. Scatchard plots showed that each ligand interacted with a single high-affinity, low-capacity binding site: oxytocin dissociation constant (Kd) 0·29 ± 0·02 nmol/l, maximum binding capacity (Bmax) 7·6 ± 0·2 fmol/106 cells (or 4500 ± 102 sites/cell) (n = 3); AVP Kd 0·09±0·02 nmol/l, Bmax 5·1±0·63 fmol/106 cells (or 3050 ± 318 sites/cell) (n = 3). Although forskolin in concentrations from 1 nmol/l to 1 mmol/l stimulated cyclic AMP (cAMP) production in isolated chromaffin cells, this did not result in detectable catecholamine release. Neither AVP nor oxytocin in concentrations between 10 pmol/l and 10 μmol/l stimulated cAMP production in these cells. Vasopressin in concentrations as low as 10 pmol/l stimulated a sixfold increase in total inositol phosphates; the dose–response curve was triphasic. Oxytocin had little effect on total inositol phosphate accumulation at low concentrations, but concentrations above micromolar stimulated total inositol phosphate production approximately fourfold. There was no measurable release of catecholamines in response to either peptide. The physiological consequences of these AVP-induced changes in inositol phosphate concentrations remain to be elucidated.
Journal of Endocrinology (1989) 121, 133–139
Steroid hormone receptors and the sexual phenotype of the Harderian gland in hamsters
Authors: Vilchis F. , Pérez-Palacios G. 
Published: December 2008

ABSTRACT
To investigate the participation of intracellular steroid hormone receptors in the sexual transformation process of the Harderian gland, a series of experiments were undertaken in adult golden hamsters. The in-vitro labelling of cytosolic steroid-binding sites with appropriate radioligands revealed the presence of androgen, oestrogen and glucocorticoid but not progestin receptors in the glands from animals of both sexes. The androgen receptor of the female gland was further characterized because it was found to be the predominant intracellular steroid receptor. Studies of binding kinetics using [3H]7α,17α-dimethyl-17β-hydroxy-4-oestren-3-one (DMNT) as ligand, demonstrated a high affinity androgen-binding site with an apparent dissociation constant (Kd) of 0·7 nmol/l and maximal saturation binding capacity of 84·0 ± 3·0 (s.d.) fmol/mg protein. Specificity of the androgen receptor was assessed by displacement analysis; DMNT, 5α-dihydrotestosterone, testosterone and 3α-androstanediol were efficient competitors for the androgen-binding site, while oestradiol-17β, progesterone and dexamethasone exhibited very little, if any, competitive potency. The sedimentation coefficient of the androgen receptor in sucrose density gradients was 8–9 S. These data indicate that the physicochemical characteristics of the androgen receptor from the female gland are similar to those previously described in the male gland. The striking observation of a complete lack of oestrogen-inducible and oestrogen-insensitive progestin receptors in glands cytosol, even after stimulation with cholera toxin, adds further support to the concept that the androgen receptor is the key molecule mediating the hormone-induced sexual transformation of the Harderian gland in this species.
Journal of Endocrinology (1989) 121, 149–156
International Standards for human Prolactin: calibration by international collaborative study
Authors: Schulster D. , Gaines Das R. E. , Jeffcoate S. L. 
Published: December 2008

ABSTRACT
Three ampouled preparations of purified human prolactin were assessed by 20 laboratories in eight countries for their suitability to serve as International Standards for the estimation of human prolactin in serum. Bioassays (pigeon crop sac assays and NB2 cell assays) were carried out in two laboratories, radioreceptor assays by one laboratory and radioimmunoassays by 17 laboratories.
By physicochemical analysis the preparations appeared similar. Each preparation contained small amounts of contaminants and/or prolactin variants. No major differences among the three preparations were detected by immunoassay although, in one radioreceptor assay system, one of the preparations was found to differ from the other two.
On the basis of all the available information, the Expert Committee on Biological Standardization of the World Health Organization (ECBS) in 1986 established the preparation in ampoules coded 83/562 as the Second International Standard for Prolactin and in October 1988 established the preparation in ampoules coded 84/500 as the Third International Standard for Prolactin. A value of 0·053 IU (53 mIU) prolactin activity/ampoule was assigned to both the Second and Third IS on the basis that this unitage would, insofar as possible, maintain continuity of the IU defined by the First International Reference Preparation of Prolactin, human, for Immunoassay (coded 75/504).
Journal of Endocrinology (1989) 121, 157–166
The measurement and effect of growth hormone in the presence of growth hormone-binding antibodies
Authors: Pringle P. J. , Hindmarsh P. C. , Di Silvio L. , Teale J. D. , Kurtz A. B. , Brook C. G. D. 
Published: December 2008

ABSTRACT
We have developed methods for measuring the concentrations of free GH in plasma using a polyethylene glycol (PEG) separation procedure to remove antibody-bound GH within 1 h of collection. Total GH concentrations were obtained by acidification of the GH–antibody complex to release the GH followed by PEG precipitation of the antibody. The plasma GH assay had a within-assay coefficient of variation (C.V.) of 6·8% at 4·6 mU/l and a between-assay C.V. of 9·2% at 4·0 mU/l. The PEG-modified assay had a within-assay C.V. of 4·3% at 6·3 mU/l and a between-assay C.V. of 10·9% at 5·3 mU/l. Both assays had a sensitivity of 1·3 mU/l. There was good correlation between plasma and free GH concentrations in 24-h profiles in two tall children (r = 0·98; P < 0·001) and between total and free GH in the same profiles (r = 0·97; P < 0·001).
GH antibodies were measured using a highly sensitive radioimmunoassay. In children who did not develop GH antibodies there was no difference between total, plasma and free GH concentrations. In contrast, in those who developed GH antibodies both total and plasma GH concentrations were markedly increased compared with free GH concentrations. The presence of GH antibodies did not affect the growth, plasma insulin-like growth factor-I concentrations or fasting serum insulin concentration responses to 1 year of therapy with biosynthetic human GH.
Journal of Endocrinology (1989) 121, 193–199
Somatotrophin increases thyroxine-5′-monodeiodinase activity in lactating mammary tissue of the cow
Authors: Capuco A. V. , Keys J. E. , Smith J. J. 
Published: December 2008

ABSTRACT
The effect of administration of bovine somatotrophin (bST) on peripheral conversion of thyroxine (T4) to tri-iodothyronine (T3) was studied in non-pregnant lactating Holstein cows. Six cows were injected daily for 5 days with 40 mg recombinantly derived bST, while six control cows received excipient alone. Blood samples were collected hourly from 08.00 to 19.00 h on a single day the week before treatment and on days 4–5 of treatment. All other tissue samples were obtained at slaughter, 20–23 h after the last injection.
Administration of bST increased milk production and caused a 9% increase in hepatic DNA. Consumption of feed did not differ between control and bST-treated cows. Treatment did not alter serum concentrations of T4 or T3, although concentrations of thyroid hormones in the serum increased from 08.00 to 19.00 h. Activity of thyroxine-5′-monodeiodinase (5′-D) in liver and kidney was similarly unaffected. However, activity of 5′-D in mammary tissue increased approximately twofold in response to bST administration. We suggest that an increase in mammary conversion of T4 to the more biologically potent thyroid hormone T3 plays a role in mediating the galactopoietic response of dairy cattle to bST.
Journal of Endocrinology (1989) 121, 205–211
Adrenal mast cells modulate vascular and secretory responses in the intact adrenal gland of the rat
Authors: Hinson J. P. , Vinson G. P. , Pudney J. , Whitehouse B. J. 
Published: December 2008

ABSTRACT
Mast cells were identified in the rat adrenal gland, located in the walls of arterioles at the point at which they penetrate the connective tissue capsule. The mast cell products, histamine and serotonin, both caused dose-dependent increases in rates of perfusion medium flow and steroid secretion in the isolated, perfused rat adrenal gland in situ. Compound 48–80, a mast cell degranulator, caused a significant increase in perfusion medium flow rate and steroid secretion by the in-situ perfused rat adrenal. Administration of disodium cromoglycate, a mast cell stabilizer, before administration of ACTH(1–24) virtually abolished the normal flow rate increment and significantly attenuated the corticosterone secretory response to ACTH(1–24).
These observations strongly suggest that adrenal mast cells modulate both vascular and secretory responses in the intact adrenal gland of the rat.
Journal of Endocrinology (1989) 121, 253–260
Testosterone concentrations in testicular interstitial fluid collected with a push–pull cannula or by drip-collection from adult rats given testosterone or aminoglutethimide
Authors: Maddocks S. , Setchell B. P. 
Published: December 2008

ABSTRACT
This study was designed to investigate the differences in testosterone concentrations measured in testicular extracellular interstitial fluid obtained with a push–pull cannula or by post-mortem drip-collection. In the first experiment, testosterone-filled silicone elastomer capsules (2–16 cm lengths) or empty 2 cm capsules were implanted s.c. in adult male rats for 1 week. Animals were then anaesthetized and interstitial fluid was collected with a push–pull cannula for 1 h from one testis in each animal. Testicular and peripheral venous blood were then sampled and supernatant fluid was collected from the dispersed cells of the same testis. The contralateral testis in each animal was removed, and post-mortem interstitial fluid obtained by drip-collection for 20 h at 4 °C. In animals given empty capsules, testosterone concentrations in drip-collected interstitial fluid were significantly (P < 0·01) greater than testicular and peripheral venous blood levels, testicular fluid levels, and levels in interstitial fluid calculated from push–pull cannula samples. The concentrations of testosterone calculated in interstitial fluid collected with a push-pull cannula were never significantly greater than testicular venous blood levels. In animals with testosterone-filled capsules, testosterone concentrations measured in drip-collected interstitial fluid were similar to those calculated from push–pull cannulae samples, and to testicular venous blood levels. In a second experiment, a group of adult male rats was pretreated with aminoglutethimide to block steroidogenesis. Two hours later, interstitial fluid was drip-collected from the testes of these animals and from a group of vehicle-treated controls. For each animal, one testis was placed on ice and interstitial fluid collected for only 10 min, while the contralateral testis was kept at 4 °C and interstitial fluid collected for 20 h. In control animals, testosterone concentrations in interstitial fluid collected for 20 h were significantly (P < 0·01) greater than those in interstitial fluid collected for 10 min. In animals pretreated with aminoglutethimide, testosterone concentrations at 10 min and 20 h were not significantly different, and did not differ from those in control samples collected for 10 min.
We believe these results support earlier suggestions that the post-mortem drip-collection technique may give misleading results, and indicate that testosterone synthesis and secretion continues after isolation of the testis. This may also be the case with other Leydig cell products.
Journal of Endocrinology (1989) 121, 303–309
Levels of the small insulin-like growth factor-binding protein are strongly related to those of insulin in prepubertal and pubertal children but only weakly so after puberty
Authors: Holly J. M. P. , Smith C. P. , Dunger D. B. , Edge J. A. , Biddlecombe R. A. , Williams A. J. K. , Howell R. , Chard T. , Savage M. O. , Rees L. H. , Wass J. A. H. 
Published: December 2008

ABSTRACT
We have looked at the relationship between fasting levels of insulin and a small insulin-like growth factor (IGF)-binding protein (IBP-1) in a cross-sectional study of 116 normal subjects aged 5–48 years. The relationship between IBP-1 and insulin was also examined within individual normal children in over-night profiles of IBP-1 and insulin obtained from two children at each stage of puberty (Tanner stages 1–5). In the cross-sectional study high levels of IBP-1 were found in early childhood and these fell throughout puberty as fasting levels of insulin rose. Multiple regression analysis revealed that both these changes were predominantly due to pubertal development rather than to age. After the age of 16 IBP-1 levels remained low despite fasting insulin levels returning to prepubertal levels. A strong negative correlation was obtained between IBP-1 and insulin in children of 5–16 years (r = −0·63; n = 60; P <0·001), no such relationship being found after the age of 16. In the second study, IBP-1 underwent a marked circadian variation in all cases and an inverse correlation with insulin, measured at the same time, was obtained at pubertal stages 1 to 4, but not at stage 5 (pooled data stages 1–4, r = −0·69; n = 53; P <0·001). We have demonstrated that a potential inhibitor of IGF-activity is inversely related to insulin throughout the period of active GH-related growth and that this relationship weakens after puberty.
Journal of Endocrinology (1989) 121, 383–387
Augmentation by epidermal growth factor of basal and stimulated progesterone production by human luteinized granulosa cells
Authors: Richardson M. C. , Gadd S. C. , Masson G. M. 
Published: December 2008

ABSTRACT
Human granulosa cells were prepared from follicular aspirates obtained during oocyte collection for in-vitro fertilization. Following several days in culture, cells were washed and then progesterone output was measured in 2-h incubations. After culture for 3 days, incubated cells responded well to human chorionic gonadotrophin (hCG) and prostaglandin (PG) E2 with similar levels of maximum response. Exposure of cultured cells to epidermal growth factor (EGF) for 2 days (days 3–5) led to substantial increases both in basal production and in responses to hCG and PGE2 during subsequent incubations. These effects of EGF were not accompanied by measurable increases in DNA levels in cultures over this time. Results may point to a possible paracrine role for EGF-like factors modulating the activity of cells forming the early corpus luteum.
Journal of Endocrinology (1989) 121, 397–402
The in-vitro transformation of [3H]dehydroepiandrosterone into its principal metabolites in the adrenal cortex of adult castrated male rats and following steroid treatment
Authors: Canonaco M. , Andò S. , Valenti A. , Tavolaro R. , Panno M. L. , Maggiolini M. , Dessì-Fulgheri F. 
Published: December 2008

ABSTRACT
The adrenal gland of castrated adult male rats metabolized [3H]dehydroepiandrosterone in vitro to Δ4-androsten-3,17-dione (4AD), testosterone, dihydrotestosterone (DHT) and 5α-androstane-3,17-dione (5αAD). Despite the low testosterone values, DHT and 5αAD were higher 30 and especially 60 days after castration, with raised 4AD:testosterone and decreased testosterone:DHT ratios. The 5α-reductase activity thus appears to increase with time after castration. Fourteen days after castration, 4AD was the only metabolite that was raised compared with intact animals, and testosterone was comparable in sham-operated and castrated rats.
The administration of testosterone propionate to castrated rats restored testosterone values to those of intact rat adrenals, whereas 4AD values were greater. The administration of dihydrotestosterone propionate also yielded higher levels of 4AD, in the presence of a lower testosterone value. After administration of oestradiol benzoate, 4AD values were lower especially compared with the other hormone-treated groups, and there was an unexpectedly high testosterone value.
These data indicate that the adrenal gland contributes to the production of androgens, as previously noted by Andò, Canonaco, Beraldi et al. (1988) who showed increased plasma 4AD and testosterone levels in adult male rats 30 days after castration. Furthermore, adrenal androgen production in castrated animals is differentially regulated by sex steroids.
Journal of Endocrinology (1989) 121, 419–424