bluuebunny/crossref_metadata_2025 huggingface dataset:
Angiogenesis in reproductive tissues
Authors: Findlay J. K.
Published: December 2008

Angiogenesis is the process of generating new capillaries and leads, therefore, to vascularization of tissues. This process occurs during embryological development and during pathological and physiological conditions in adult life, including those involving the reproductive organs. Recent studies, in the field of tumour biology in particular, have led to the identification of several factors responsible for inducing angiogenesis and the elucidation of ways of modulating their activity. This review summarizes our knowledge of angiogenesis in the ovary, testis, endometrium and placenta, and suggests ways in which further research might contribute to a better understanding of the processes controlling reproduction and identify new approaches to the regulation of fertility.

J. Endocr. (1986) 111, 357–366
Effects of thyroid status on brain catecholamine biosynthesis in adult rats: assessment by a steady-state method
Authors: Harris P. E. , Dieguez C. , Lewis B. M. , Hall R. , Scanlon M. F.
Published: December 2008

Effects of thyroid status on brain catecholamine turnover in adult rats were investigated using a steady-state method. Rats were treated for 3 weeks with s.c. injections of l-thyroxine (0·4 mg/kg), aminotriazole in drinking water (0·1%, w/v) or vehicle. After 2 weeks of treatment rats were implanted chronically with lateral intracerebroventricular (i.c.v.) cannulae. They were injected i.c.v. with [3H]tyrosine 1 week later. Catecholamine and tyrosine content and specific activity were measured in mediobasal hypothalamus, anterior hypothalamus and striatum, using high-performance liquid chromatography with electrochemical detection. Thyroxine treatment resulted in a significant increase in noradrenaline and dopamine synthesis localized to the mediobasal hypothalamus. Conversely, aminotriazole treatment resulted in a significant decrease in noradrenaline synthesis localized to the mediobasal hypothalamus. The localization of these changes in catecholamine turnover to the mediobasal hypothalamus suggests that they may be specific functional effects which are of importance in the overall integrated control of thyroid function.

J. Endocr. (1986) 111, 383–389
Effects of a single injection of a new depot formulation of an LH-releasing hormone agonist on spermatogenesis in adult rats
Authors: van Kroonenburgh M. J. P. G. , Beck J. L. , Vemer H. M. , Rolland R. , Thomas C. M. G. , Herman C. J.
Published: December 2008

Adult male Wistar rats were treated with a single injection (500 μg s.c.) of a new biodegradable depot formulation of the LH-releasing hormone (LHRH) analogue [d-Ser(But)6]AzGly10-LH-RH (Zoladex; ICI 118 630) to evaluate its potential for inhibiting spermatogenesis. The drug produced a marked (P≤0·05) decrease in serum concentrations of FSH, LH and testosterone with a maximum effect 14 days after treatment. Since striking focal histological changes were seen in the testis after only 1 week, at a time when changes in serum gonadotrophins were minimal, there may be a direct effect of the LHRH analogue on spermatogenesis. Degenerative changes in germ cells as well as Sertoli cells could be observed. Flow-cytometric analysis of testicular cell suspensions showed a significant decline in the absolute numbers of haploid cells (spermatids), tetraploid cells (mainly pachytene spermatocytes) and of the numbers of cells in the S-phase of the cell cycle. This suggests that the drug also inhibits proliferation of spermatogonia and/or primary spermatocytes. Testis weight, serum hormone concentrations, and histological and cytological parameters returned to essentially normal values 52 days after the injection. It is concluded that this new method of administration may have practical and pharmacokinetic advantages for the purpose of reversible inhibition of spermatogenesis.

J. Endocr. (1986) 111, 449–454
Hypoglycaemia and acute stress-induced hyperinsulinaemia in mice infected with Bordetella pertussis or treated with pertussis toxin
Authors: Sidey F. M. , Wardlaw A. C. , Furman B. L.
Published: December 2008

Intranasal infection of mice with a sublethal dose of Bordetella pertussis produced hypoglycaemia and hyperinsulinaemia. Exposure to ether vapour did not modify serum insulin concentrations in control mice, but produced a marked transient hyperinsulinaemia in mice infected with B. pertussis. A similar hyperinsulinaemia in infected, but not control, mice was also seen after a brief (10–15 s) period of anoxia (produced by exposure to an atmosphere of 100% N2 or 100% CO2), or following the injection of histamine or 2-deoxyglucose. Exposure to cold (2–4 °C) or hypoxia (8% O2 in 92% N2), however, did not alter serum concentrations of insulin in control or infected mice.

The hyperinsulinaemic response to ether stress observed in mice infected with B. pertussis was abolished by pretreatment with alloxan.

The hyperglycaemic effects of histamine and 2-deoxyglucose were attenuated or abolished in mice infected with B. pertussis. However, none of the stimuli which produced hyperinsulinaemia in the infected mice resulted in any further lowering of the blood glucose concentration.

Pretreatment of mice with pertussis toxin (150 ng/mouse, i.v.) produced hypoglycaemia similar in magnitude to that found in animals infected with B. pertussis. Moreover, exposure of mice treated with pertussis toxin to ether vapour produced marked hyperinsulinaemia.

It is suggested that the metabolic alterations seen in animals infected with B. pertussis may be mediated by pertussis toxin.

J. Endocr. (1987) 112, 113–122
Recombinant human insulin-like growth factor: testing the somatomedin hypothesis in hypophysectomized rats
Authors: Skottner A. , Clark R. G. , Robinson I. C. A. F. , Fryklund L.
Published: December 2008

The in-vivo biological activity of recombinant methionyl insulin-like growth factor I (met-IGF-I) was demonstrated in hypophysectomized rats by following blood glucose after an i.v. bolus injection of met-IGF-I; a dose-dependent decrease in blood sugar was seen. Membrane transport was studied using the non-metabolizable amino acid α-aminoisobutyric acid; stimulation was obtained with the highest dose used (90 μg/rat). To test the original somatomedin hypothesis, growth studies were performed in hypophysectomized rats. Two or three doses of met-IGF-I were given with three different administration regimes (i.v. or s.c. infusion, or s.c. injections twice daily) for 6 or 8 days. Little growth-promoting activity was observed, with a significant effect on body weight gain obtained only when met-IGF-I was given continuously at the highest dose used (180 μg/day). No effect was seen on the in-vivo uptake of radioactive sulphate into cartilage. Epiphyseal cartilage width increased slightly at the highest dose of met-IGF-I, but only when the hormone was given by infusion. When 180 μg met-IGF-I/day were given by injections, a significant effect on longitudinal bone growth was obtained (90 μm above control). The levels of IGF in the serum were not measurably increased after s.c. administration of met-IGF-I, whereas after i.v. infusion, significantly raised levels were obtained at the higher dose rates (3·0 ± 0·3 and 2·8 ± 0·1 units/ml). Growth hormone was much more effective than met-IGF-I even at 50-fold lower doses.

Priming the animals with 10 mu. bovine GH/day followed by combined infusions of GH and met-IGF-I did not reveal any potentiating effects of met-IGF-I in the presence of GH. We conclude that met-IGF-I is a relatively poor growth-promoting agent when given systemically, and that somatomedins are more likely to act as local growth factors rather than as circulating mediators of the growth-promoting effects of GH.

J. Endocr. (1987) 112, 123–132
Dissociation between the ovarian factors controlling sexual receptivity and preovulatory secretion of LH in cyclic female rats
Authors: Södersten P. , Eneroth P.
Published: December 2008

Ovariectomy and treatment with oestradiol benzoate (10 μg OB) on the day before behavioural oestrus eliminated the preovulatory surge of LH and reduced the level of sexual receptivity on the following day. Sexual behaviour, but not the LH surge, was restored by progesterone (0·5 mg) given 18 h later. Injection of OB on the day after behavioural oestrus induced a small release of LH and normal sexual behaviour on the following day. Ovariectomy on the day after behavioural oestrus reduced the stimulatory effect of OB on sexual behaviour and eliminated its weakly stimulatory effect on LH release. Sexual behaviour, but not the small LH surge, was restored in these animals by progesterone (0·5 mg) given 18 h later. Treatment of rats ovariectomized 2 days before the day of the LH surge with implants containing oestradiol or injections of oestradiol (1 μg) induced LH surges but the amplitudes of these LH surges were much smaller than those of the normal LH surge. Treatment of intact rats with OB increased serum progesterone levels 24 h later, an effect which was eliminated by ovariectomy. Injections of LH (20 μg) into intact rats on the day after behavioural oestrus also increased serum progesterone concentrations but failed to stimulate sexual behaviour. It is suggested that OB treatment of intact rats on the day after behavioural oestrus stimulates sexual behaviour by inducing a surge of LH secretion which activates ovarian secretion of progesterone. Thus, oestrogen and progesterone but not the LH surge are essential for sexual behaviour. Whereas oestradiol and progesterone restore normal sexual behaviour in ovariectomized rats, additional ovarian factors may be required for induction of normal LH surges.

J. Endocr. (1987) 112, 133–138
Interference of dimethyl α-(dimethoxyphosphinyl) p-chlorobenzyl phosphate (SR-202) in thyroid hormone. metabolism: evidence of inhibition of monodeiodination
Authors: Liniger C. , Pometta D. , Burger A. G.
Published: December 2008

SR-202 is a non-iodinated potential lipid-altering agent. When administered (100 mg) three times per day for 3 days to six euthyroid subjects it was associated with a 30 ± 3% (mean ± s.e.m.) fall in 3,3′,5-tri-iodothyronine(T3)(P < 0·001), a reciprocal 104 ± 14% rise in 3,3′,5′-tri-iodothyronine (reverse T3, rT3) (P < 0·01), and a 37 ± 7% rise in thyroxine (T4) (P < 0·001). Basal and TRH-stimulated TSH did not change. These results suggested that SR-202 was acting as an inhibitor of the peripheral monodeiodination of T4 to T3.

During a second study the same subjects received the same dose of SR-202 for a further 3 days following 15 days of progressive substitutive treatment with l-T4, which they continued to take at 200 μg/day until the end of the study. Despite higher levels of thyroid hormones in the substituted subjects, similar results were observed, serum T3 falling by 40 ± 2% (P < 0·001), serum rT3 and T4 rising by 168 ± 24% (P < 0·01) and 37 ± 9% (P < 0·01) respectively. These changes provide compelling evidence that SR-202 is an inhibitor of the peripheral conversion of T4 to T3 that acts on thyroid hormone metabolism without provoking a counter-regulatory pituitary response. It might prove to be a useful tool for the clinical investigation of thyroid function.

J. Endocr. (1987) 112, 171–175
Influence of the cryptorchid testis on the regeneration of rat Leydig cells after administration of ethane dimethane sulphonate
Authors: Risbridger G. P. , Kerr J. B. , de Kretser D. M.
Published: December 2008

Leydig cells were selectively eliminated from the testis by treatment with the cytotoxin, ethane dimethane sulphonate. Rats were then made unilaterally cryptorchid and the morphological and functional response of the interstitial tissue in abdominal compared with scrotal testes was examined for up to 8 weeks. Regeneration of new Leydig cells occurred more rapidly in the interstitial tissue of abdominally cryptorchid testes compared with the interstitial tissue of contralateral scrotal testes. More rapid recovery of Leydig cells was coincident with significant increases in the bioactivity of a local factor(s), collected from interstitial fluid of cryptorchid testes, which stimulated testosterone production by isolated Leydig cells in vitro. These results support the theory that the production of a local factor(s) plays a role in the regeneration of Leydig cells and is affected by damage to the seminiferous epithelium.

J. Endocr. (1987) 112, 197–204
Identification, properties and effect of hormones on rat preputial gland peroxidase
Authors: De P. K. , Banerjee R. K.
Published: December 2008

A highly active soluble peroxidase has been identified in the preputial glands of the rat. The enzyme was detectable in the sebaceous secretion of the glands and showed catalytic properties characteristic of true peroxidase. It had a native molecular weight of around 73 000 as determined by gel-permeation studies. Immunologically the enzyme cross-reacted with an antiserum against bovine lactoperoxidase. Administration of progesterone resulted in a significant increase in the total activity of the enzyme, while testosterone and oestradiol had no such effect. The enzyme had a similar molecular weight and similar catalytic and immunological properties to rat uterine fluid peroxidase but differed markedly in respect to sensitivity to oestradiol.

J. Endocr. (1987) 112, 239–245
Effect of a non-viral fraction of acquired immunodeficiency syndrome plasma on the vulnerability of lymphocytes to cortisol
Authors: Klein A. , Bruser B. , Robinson J. B. , Pinkerton P. H. , Malkin A.
Published: December 2008

We have observed previously that the rate of cortisol catabolism by lymphocytes (CCL) was indicative of the vulnerability of these cells to cortisol. We attempted to ascertain whether cortisol-sensitive lymphocytes (e.g. thymocytes) metabolize cortisol at a different rate from cortisol-resistant cells and whether lymphocytes in which cortisol catabolism is inhibited become cortisol sensitive. The work was facilitated by the observation that an ethanol extract plasma from patients with acquired immunodeficiency syndrome (AIDS) and AIDS-related complex (ARC) had the capacity to inhibit CCL.

The capacity of thymocytes to metabolize cortisol was found to be 11 times lower than that of peripheral lymphocytes. Inhibition of CCL with an ethanol extract of plasma from AIDS/ARC patients made the cells vulnerable to cortisol, causing them to die at a rate seven times greater than that of control samples. It is suggested that these findings may have important implications with regard to the nature of lymphocyte depletion in AIDS/ARC patients or in people at risk of developing the syndrome.

J. Endocr. (1987) 112, 259–264
Inhibition of post-partum maternal behaviour in the rat by injecting an oxytocin antagonist into the cerebral ventricles
Authors: van Leengoed E. , Kerker E. , Swanson H. H.
Published: December 2008

Endogenous oxytocin released into the brain at parturition may stimulate the onset of maternal behaviour. In this study an attempt was made to block spontaneous maternal behaviour following natural delivery in Wistar rats by the injection of an antagonist of oxytocin into the cerebral ventricles. The analogue antagonist, d(CH2)5-8-ornithine-vasotocin, was administered by injection into a chronically implanted cannula in the right lateral ventricle at hourly intervals, beginning immediately after the expulsion of the first pup. The antagonist did not interfere with the normal progress of parturition or birth-related behaviours.

After delivery of the last pup, mothers rested for 40 min in the test cage with the pups having been removed. Four pups and standard nesting material were then presented. Latency to pup carrying and duration of pup manipulation, nest building, and time spent on the nest with the pups, as well as duration of autogrooming and general activity were determined. Saline-injected controls started gathering the pups immediately and usually showed all elements of maternal behaviour within 10 min. Antagonist-treated mothers showed a marked delay in the onset of pup grouping and other maternal behaviours. At the end of 1 h, two out of six mothers had not yet picked up a single infant. Pups left overnight with their mothers were gathered into the nest and suckled, and no long-term effects of the antagonist were evident on retesting.

The effectiveness of oxytocin antagonist in suppressing the rapid onset of post-partum maternal behaviour supports the hypothesis that centrally released oxytocin is involved in this process. It is noteworthy that these effects were obtained in Wistar rats, a strain in which oxytocin has failed to accelerate responsiveness to pups in virgin females.

J. Endocr. (1987) 112, 275–282
Endocrine and behavioural factors affecting water balance in sheep subjected to isolation stress
Authors: Parrott R. F. , Thornton S. N. , Forsling M. L. , Delaney C. E.
Published: December 2008

The effect of stress on drinking, water balance and endocrine profile was studied using ten castrated rams. Individual sheep were exposed to 30-h periods of total isolation (psychological stress) or physical separation from their social group (control). Plasma was analysed for haematocrit, osmolality, electrolyte levels and concentrations of cortisol and arginine vasopressin. Isolation stress significantly reduced water intake, increased haematocrit and plasma concentration of cortisol, but did not alter osmolality or vasopressin concentration. The physiological effects of this self-imposed water restriction contrast with those obtained by depriving the sheep of water for 24 h under conditions that were not stressful, i.e. by keeping them grouped together. These results suggest that cortisol may act to defend plasma volume in sheep exposed to acute stress. The results also indicate that vasopressin probably should not be considered to be a 'stress hormone' in the sheep.

J. Endocr. (1987) 112, 305–310
Production and metabolic clearance of angiotensinogen in conscious rats as measured by steady-state isotope dilution
Authors: Little M. H. , Sernia C.
Published: December 2008

Previous studies on the hormonal regulation of hepatic angiotensinogen relied on in-vitro liver preparations and on the measurement of changes in plasma concentration. In this study 125I-labelled angiotensinogen was used to measure simultaneously the production rate (PR) and metabolic clearance rate (MCR) in conscious rats by the constant-rate infusion and single-injection methods. Male rats received daily s.c. injections of isotonic saline (as control), 1 mg corticosterone acetate (CA), 25 μg 17β-oestradiol benzoate (OB) or 20 μg thyroxine (T4) per 100 g body weight. On day 7 of treatment 125I-labelled angiotensinogen was infused into a jugular vein at a rate of 1 μl/h by osmotic minipumps and blood samples taken 4, 5 and 6 days later. The PR of angiotensinogen increased from 576 ± 28 (s.e.m.; n = 9) to 954 ± 63 (n = 9), 1010±84 (n = 9) and 2359±150 (n = 10) μg/h per kg following treatment with CA, OB and T4 respectively. In contrast, the PR of rat albumin did not change significantly from 218 ± 8 (n = 7) mg/h per kg. All three hormones increased MCR from 13 ± 1 (n = 17) ml/h per kg to 17± 1 (n = 9), 18 ± 2 (n = 9) and 27 ± 2 (n = 9) ml/h per kg for CA, OB and T4 respectively. Single-injection experiments on five rats showed angiotensinogen to be distributed into three compartments with a half-time of disappearance of 4·4 ± 1 min, 116±11 min and 13·1 ±2·6 h. It was concluded that the production of angiotensinogen in vivo is at least tenfold higher than the reported in-vitro rates, that the clearance of angiotensinogen is under hormonal regulation and that angiotensinogen is distributed between at least three compartments.

J. Endocr. (1987) 112, 391–397
Pancreatic somatostatin, glucagon and insulin during post-hatch growth in the duck (Anas platyrhynchos)
Authors: Foltzer Ch. , Harvey S. , Mialhe P.
Published: December 2008

Pancreatic somatostatin-like immunoreactivity (SLI), immunoreactive insulin (IRI) and glucagon-like immunoreactivity (GLI) were measured during growth in ducks. The content of each hormone increased progressively but at different rates in the dorsal, ventral and splenic lobes of the pancreas. In the almost fully grown duck, the splenic lobe contained 80 and 63% of the total content of GLI and SLI respectively but low levels of IRI (23%), which were highest in the dorsal lobe (53%). In contrast to the hormonal content, only total GLI concentrations increased during development, the SLI concentrations remaining stable and IRI concentrations declining during growth. Gel filtration of pancreatic extracts indicated that most of the SLI in the pancreas of young and adult birds was somatostatin-14, although somatostatin-28 was present in the ventral lobe of young birds and larger molecular forms were present in the ventral and dorsal lobes. These changes in pancreatic hormonal content and concentration are dissimilar to age-related changes in SLI, GLI and IRI previously observed in the plasma of ducks. Plasma levels of pancreatic hormones may thus be controlled by hormonal and/or neural factors during post-hatch growth.

J. Endocr. (1987) 113, 65–70
Serotoninergic regulation of corticosterone secretion in domestic fowl
Authors: Cheung A. , Hall T. R. , Harvey S.
Published: December 2008

The effects of serotoninergic drugs on adrenocortical function in domestic fowl were examined. Administration of the serotonin receptor agonist 2-(1-piperazinyl)quinoline maleate (quipazine), an inhibitor of serotonin metabolism, N-methyl-N-2-propynylbenzylamine HCl (pargyline), as well as serotonin itself, all increased plasma concentrations of corticosterone. The maximum responses to serotonin and quipazine occurred 1 h after treatment. The quipazine-stimulated response was partly prevented by the serotonin antagonist cyproheptadine. Cockerels pretreated with dexamethasone, a synthetic steroid known to inhibit pituitary ACTH release, showed attenuated responses to subsequent quipazine, pargyline or serotonin injection. Serotonin, quipazine and cyproheptadine did not affect corticosterone release directly from the adrenal gland incubated in vitro, nor did they affect adrenal responsiveness to ACTH stimulation. The neurotoxin 5,6-dihydroxytryptamine injected into day-old chicks decreased plasma concentrations of corticosterone for up to 7 days after treatment, with corresponding decreases in the hypothalamic concentration of serotonin, but not dopamine or noradrenaline concentrations. These results show that adrenal corticosterone secretion is regulated by a central serotoninergic system, probably acting on the hypothalamo-pituitary-adrenal axis.

J. Endocr. (1987) 113,159–165
Effect of sialoadenectomy, treatment with epidermal growth factor (EGF) antiserum and replacement of EGF on the epidermis in mice
Authors: Tsutsumi O. , Kubota Y. , Oka T.
Published: December 2008

Epidermal growth factor (EGF) was present at a mean concentration of 266±18 (s.e.m.) pmol/mg wet tissue in the submandibular gland of 3-month-old male mice; it was also present in plasma at a concentration of 364±149 pmol/l. Sialoadenectomy (removal of the submandibular glands) decreased the plasma EGF content to undetectable levels (< 16·5 pmol/l), lowered the concentration of EGF in the skin from 1·22±0·11 to 0·47±0·08 fmol/mg wet tissue and reduced the thickness of the epidermis from 28·9±2·7 to 11·0±0·8 μm in 3 weeks (P < 0·001). Epidermal growth factor antiserum given to sialoadenectomized mice further decreased the thickness of the epidermis to 8·3 ±0·6 μm. No appreciable change was observed in the dermis and subcutaneous tissue. In sialoadenectomized mice, replacement of EGF prevented the decrease in thickness of the epidermis in a dose-dependent manner when started immediately after the operation. Treatment with EGF also effectively restored the normal morphology of the epidermis when its thickness had declined to its lowest level. These results suggest that EGF plays a physiological role in the maintenance of the epidermis.

J. Endocr. (1987) 113, 193–197
Endogenous testosterone enhances growth hormone (GH)-releasing factor-induced GH secretion in vitro
Authors: Ohlsson L. , Isaksson O. , Jansson J.-O.
Published: December 2008

The influence of endogenous gonadal steroids in male and female rats on basal and growth hormone-releasing factor (GRF)-stimulated GH secretion from perifused anterior pituitaries was studied. After 75 min of perifusion with basal medium, freshly dissected pituitaries were exposed to human GRF(1–44) (10 nmol/l) for 15 min. Neonatal (day 1–2) or prepubertal (day 25) gonadectomy of male rats suppressed baseline GH release (ng/min per mg dry weight) as well as GRF-stimulated GH release by 40–70%. This effect was slightly more pronounced in neonatally gonadectomized animals. In prepubertally gonadectomized male rats, the suppression of GH release was completely reversed by testosterone replacement therapy. In female rats, prepubertal gonadectomy did not affect GH secretion from perifused pituitaries. However, treatment of ovariectomized female rats with oestradiol reduced baseline and GRF-induced GH release to levels lower than those observed in sham-operated or vehicle-treated ovariectomized animals. The data suggest that testicular androgen secretion in adult male rats increases the pituitary GH release in response to GRF in vitro, whereas ovarian oestrogen secretion is of less importance for the GRF responsiveness of female rat pituitaries.

J. Endocr. (1987) 113,249–253
Secretion of LH in spontaneously hypertensive rats
Authors: Rodriguez-Padilla M. , Bellido C. , Pinilla L. , Aguilar E.
Published: December 2008

Weights of testes, seminal vesicles, ventral prostate and pituitary, plasma testosterone and LH concentrations, pituitary LH content and concentration, the LH in-vivo response after LHRH administration (1 μg), and basal and LHRH-stimulated secretion in vitro were analysed in adult male spontaneously hypertensive (SH) and normotensive control (WKY) rats.

Spontaneously hypertensive rats showed: (1) testis and pituitary hypertrophy; (2) seminal vesicle and ventral prostate atrophy; (3) increased plasma testosterone and LH concentrations; (4) increased pituitary LH content and concentration; (5) unchanged net increase of plasma concentrations of LH 15 and 45 min after administration of 1 μg LHRH; and (6) increased basal LH secretion in vitro with a normal response to LHRH stimulation.

These results provide evidence that SH rats show increased LH secretion with a normal response to LHRH stimulation. The coexistence of high plasma concentrations of testosterone with seminal vesicle and ventral prostate atrophy suggest a reduction in the effectiveness of testosterone in these structures.

J. Endocr. (1987) 113, 255–260
Specific binding sites for gonadotrophin-releasing hormone, LH/chorionic gonadotrophin, low-density lipoprotein, prolactin and FSH in homogenates of human corpus luteum. II: Concentrations throughout the luteal phase of the menstrual cycle and early pregnancy
Authors: Bramley T. A. , Stirling D. , Swanston I. A. , Menzies G. S. , McNeilly A. S. , Baird D. T.
Published: December 2008

Corpora lutea were obtained from 52 women undergoing laparotomy during the luteal phase of the menstrual cycle. In addition, stromal, thecal and granulosa cell preparations were obtained from seven women undergoing ovariectomy during the late follicular–preovulatory phase of the cycle. The specific binding of a 125I-labelled gonadotrophin-releasing hormone (GnRH) agonist [d-Ser(But)6] GnRH(1–9)-ethylamide (buserelin) and of human chorionic gonadotrophin (hCG), human FSH (hFSH), human prolactin (hPRL) and human low-density lipoprotein (hLDL) to tissue homogenates was measured under optimal conditions. Bound LH/hCG was estimated by elution with acid-citrate buffer, followed by radioimmunoassay of released hormone.

Binding of GnRH agonist, though variable, was highest in mid-luteal corpus luteum and high binding was also present in three out of four corpora lutea of pregnancy. Binding of LH/hCG increased significantly with luteinization, reaching maximal levels in the mid-luteal phase before falling significantly. Occupancy of LH receptors by bound LH was relatively constant throughout the luteal phase (10·7–35·3%), but occupancy increased to >90% in corpora lutea from early pregnancy. Binding of hFSH was variable, with only five out of 50 corpora lutea having binding greater than 10 pg/μg DNA. Similarly, hPRL binding varied markedly with only six out of 44 having binding greater than 50 pg/μg DNA. Binding of LDL was highest in the early- to mid-luteal phases of the cycle.

In corpora lutea from all stages of the menstrual cycle (excluding corpora albicantia), GnRH agonist binding was highly correlated with the levels of unoccupied and occupied LH receptors (P < 0·001; n = 49 and n = 48 respectively) and with LDL receptors (P< 0·002; n = 49). Binding of GnRH agonist was also correlated with PRL binding (P<0·05; n = 21) but not with FSH receptors (P>0·4; n = 25). In addition, LDL binding was associated with PRL (P< 0·005; n = 21) and FSH receptors (P<0·05; n = 25) and with endogenously bound LH (P<0·03; n = 48), but not with unoccupied LH receptors (P = 0·8; n = 49). Moreover, in corpora lutea from the mid-luteal phase, there was a strong association between GnRH agonist binding and LDL receptors (P<0·02; n = 23). The correlations between GnRH agonist binding and a number of important indices of luteal function suggest a physiological role for GnRH-like factors in the human corpus luteum.

J. Endocr. (1987) 113, 317–327
Receptors for lactogenic hormones in the ovine corpus luteum. II: Specific inactivation of ovine prolactin
Authors: Bramley T. A. , Menzies G. S. , McNeilly A. S. , Friesen H. G.
Published: December 2008

Sheep corpus luteum homogenates and membrane fractions discriminate between 125I-labelled human GH (hGH) and ovine prolactin (oPRL). The present studies were designed to establish whether ovine luteal tissue possessed a prolactin-specific inactivating enzyme. Preincubation of sheep luteal microsomes and cytosol fractions with 125I-labelled hGH had little effect on the ability of the hormone to rebind to pig luteal lactogenic receptors. In contrast, sheep luteal tissue fractions markedly decreased the binding ability of 125I-labelled oPRL. However, despite the profound loss of receptor-binding activity, there was no change in protein-bound radioactivity, nor in the elution profile of 125I-labelled oPRL by gel chromatography on Sephadex G-100. Moreover, the disparity between 125I-labelled hGH and oPRL was not overcome by preincubation of sheep luteal membranes with protease inhibitors of differing specificities.

We conclude that the disparity between the binding of hGH and oPRL in ovine tissues was due to the selective inactivation of oPRL. However, the activity responsible did not degrade the hormone extensively, nor was its action blocked by a range of protease inhibitors.

J. Endocr. (1987) 113, 375–381
Vasopressin receptors influencing the secretion of ACTH by the rat adenohypophysis
Authors: Buckingham J. C.
Published: December 2008

The effects of selective agonists and antagonists of type 1 (V1) and type 2 (V2) vasopressin receptors on the secretion of ACTH in vitro by segments of adenohypophysial tissue and in vivo in rats pretreated with pentobarbitone and chlorpromazine were studied in the presence and absence of the 41 amino acid-containing peptide, corticotrophin-releasing factor-41 (CRF-41). The non-selective vasopressin receptor agonist, arginine vasopressin (AVP) and the V1-receptor agonist, felypressin caused dose-related increases in ACTH release in vivo and in vitro but the V2-receptor agonist, desmopressin was only weakly active in this respect. Their actions in vitro were antagonized competitively by the V1-receptor antagonist, d(C2H5)2-AVP, but were unaffected by the V2-receptor antagonist, d(CH2)5-d-Iso2-Thr4-AVP. Arginine vasopressin, felypressin and desmopressins in concentrations considerably lower than those necessary to elicit directly the release of ACTH, potentiated, in a dose-related manner, the activity of CRF-41 in vitro. The potentiating effects were not antagonized by the V2-receptor antagonist or by low concentrations of the V1 -receptor antagonist. At a higher concentration, the V1-receptor antagonist reduced, but did not abolish, the potentiating effects of AVP and its analogues. However, at this concentration, it also exhibited weak intrinsic activity and, like the agonists, potentiated the response to CRF-41. The results suggest that the direct effect of AVP on ACTH release is mediated by V1-like receptors. The vasopressin receptors involved in the potentiation of CRF-41 activity appear to be different.

J. Endocr. (1987) 113, 389–396
INHIBITION OF FSH-STIMULATED GRANULOSA CELL FUNCTION BY A SYNTHETIC FRAGMENT OF THE PORCINE INHIBIN α-SUBUNIT: EVIDENCE FOR INVOLVEMENT OF GnRH RECEPTORS
Authors: Hillier S.G. , Tsonis C.G. , Wickings E.J. , Eidne K.A.
Published: December 2008

The bioactivity of a synthetic peptide fragment which mimics the N-terminal sequence of the 134-amino-acid porcine Inhibin α-subunit (pl- α1-26-Gly27Tyr28-OH) was tested and compared with the bioactivity of GnRH in rat granulosa cell cultures. Granulosa cells from immature female rat ovaries were cultured with hFSH and testosterone to stimulate the production of cyclic AMP, progesterone and oestradiol. Addition of pl- α1-26-Gly27Tyr28-OH to the culture medium caused a dose-dependent suppression of all three parameters (ID50 700-1,000 nmol/l). GnRH caused similar but higher-potency inhibition (ID50 2-4 nmol/l). Suppression of granulosa cell function by both peptides was fully reversible by a synthetic GnRH antagonist. Moreover, specific binding of the porcine inhibin fragment to ovarian GnRH receptors was demonstrated by radioreceptor assay. This is evidence that the porcine inhibin α-subunit fragment suppresses FSH-induced rat granulosa cell function via a mechanism of action similar to that of GnRH.
Influence of a prolactin- and ACTH-secreting tumour on oestrous cyclicity, the pro-oestrous surges of LH and prolactin and ovarian hypertrophy in the rat
Authors: Krieg R. J. , Rogers J. P. , Seibel H. R.
Published: December 2008

These studies were designed to investigate the effects of a prolactin- and ACTH-secreting tumour (7315a) on reproductive cyclicity, pro-oestrous surges of LH and prolactin and ovarian hypertrophy in the rat. Normal adult Buffalo rats, which are syngeneic to the 7315a tumour, were found to have a significant prooestrous prolactin surge and a relatively low-level preovulatory LH surge. Within 14 days of s.c. injection of dispersed tumour cells, a small tumour was detectable by palpation in one rat, but measurable tumours were not observed until day 18. The pro-oestrous surge of LH, but not of prolactin, was effectively suppressed by day 17. Cessation of reproductive cyclicity (anoestrus) was apparent within 19·4±1·1 days of injection of tumour cells. Removal of a single ovary showed that there was no change in ovarian weight before anoestrus in the tumour-bearing animals. Subsequent hypertrophy of the second ovary was augmented during the early stages of tumour development (days 8 and 13), and this corresponded to the unexpected finding that the gonadotrophin surges on days 8 and 13 were significantly increased when compared with controls. Ovarian hypertrophy was not significantly different from that in controls after suppression of the gonadotrophin surge (day 17). The results suggest that inhibition of the preovulatory LH surge might be a critical event in the tumour-induced cessation of reproductive cyclicity. The fact that pre-surge concentrations of prolactin did not increase substantially until the conspicuous onset of tumour prolactin secretion on day 21 indicated that the preovulatory LH surge might be inhibited by relatively low levels of tonically secreted prolactin.

J. Endocr. (1987) 114, 41–48
Modulation by endogenous opioid peptides of the secretion of LHRH from cockerel (Gallus domesticus) mediobasal hypothalamic tissue
Authors: Stansfield S. C. , Cunningham F. J.
Published: December 2008

An in-vitro superfusion system was used to study the effects of the endogenous opioid peptides [Met]-enkephalin (and its long-lasting analogue [d-Ala2, Met]-enkephalinamide), [Leu]-enkephalin and β-endorphin and of the opiate antagonist naloxone, on the secretion of LHRH from the mediobasal hypothalamus of the cockerel. The effects of the compounds on both basal release of LHRH and on release stimulated by a depolarizing pulse of increased extra-cellular potassium ion (64 mmol/l) were investigated. None of the endogenous opioid peptides altered basal release of LHRH; however, both [Met]-enkephalin (10 μmol/l) and [d-Ala2,Met]-enkephalinamide (1 μmol/l) significantly (P<0·05) reduced the response to depolarization. Neither [Leu]-enkephalin nor β-endorphin (0·1–10 μmol/l) were effective. Naloxone (1 μmol/l) administered alone significantly (P<0·05) increased basal release of LHRH and abolished the inhibitory effects of [Met]-enkephalin and [d-Ala2,Met]-enkephalinamide on depolarization-induced release. These results suggest that the endogenous opioid peptides exert a tonic inhibitory influence on LHRH secretion by the mediobasal hypothalamus of the cockerel.

J. Endocr. (1987) 114, 103–110
The role of the hypothalamic β-adrenergic system in controlling the LH rise in short-term castrated rats
Authors: Al-Hamood M. H. , Gilmore D. P. , Wilson C. A. , Tuohy-Jones P. , Drummond S. , Gopalan C.
Published: December 2008

Intraventricular infusions of adrenaline and various pharmacological agents acting on β-adrenergic receptor subtypes were carried out in rats orchidectomized 16 h previously. Infusions (10 μl) of solutions containing the drugs were administered under anaesthesia induced with alphaxalone and alphadolone. Levels of LH were measured in plasma collected immediately before and at predetermined intervals after the infusion.

The acute rise in LH levels after castration was increased still further by isoprenaline (a mixed β1- and β2-agonist), fenoterol (a β2-agonist) and atenolol (a β1-antagonist). In contrast, prenalterol (a β1-agonist) and (2RS,3RS)-3-isopropylamino-1-(7-methylindan-4-yloxy)butan-2-ol (ICI 118 551) (a selective β2-antagonist) were inhibitory to LH release. Adrenaline itself, salbutamol (another selective β2-agonist), propranolol (a mixed β-antagonist) and metoprolol (a β1-antagonist) did not significantly alter plasma LH concentrations at the doses administered. The stimulatory effect of isoprenaline on LH release was partially reduced when given together with ICI 118 551, but was not affected when administered simultaneously with atenolol. The inhibitory effect of ICI 118 551 was, however, prevented by concomitant administration with fenoterol, as was that of prenalterol when infused with atenolol. The results suggest that the hypothalamic mediation of the short-term changes in LH release in response to castration is exerted, at least in part, through the activation of a β2-stimulatory component and the suppression of a β1-inhibitory component.

J. Endocr. (1987) 114, 167–172
Effect of thyrotrophin on epidermal growth factor receptors in monolayer cultures of porcine thyroid cells
Authors: Atkinson S. , Kendall-Taylor P.
Published: December 2008

Primary cultures of porcine thyroid cells, grown as monolayers, showed saturable binding of epidermal growth factor (EGF). Scatchard analysis resolved the binding to a high-affinity/low-capacity site (dissociation constant = 0·17 nmol/l, maximal binding capacity = 1·67 pmol/106 cells) and a low-affinity/high-capacity site. Preincubation of thyroid monolayers with TSH for 3 days caused an increase in binding of 125I-labelled EGF due to an increase in the number of receptors, with the binding affinity unchanged. This effect was dose-dependent within the range of TSH concentrations 0·01–100 mu/l. The same effect was seen with dibutyryl cyclic AMP (10–1000 μmol/l). When the protein synthesis inhibitor cycloheximide was included in the TSH preincubation, the increase in EGF binding was abolished. The TSH effect on EGF binding was not mediated by thyroid hormones, since neither thyroxine (T4) nor tri-iodothyronine (T3) at 01 nmol/l–10 μmol/l could mimic the effect of TSH, nor could antisera to T3 or T4 neutralize the effect of TSH. The concentration of extracellular iodide (10 nmol/l–10 mmol/l) had no effect on the binding of 125I-labelled EGF. The results demonstrate that TSH increases the number of receptor sites for binding of EGF to thyroid monolayers in vitro. This effect is dependent upon protein synthesis and is mediated by cyclic AMP but not by thyroid hormones or iodide. This effect on binding of EGF may contribute to the trophic action of TSH.

J. Endocr. (1987) 114, 179–184
Improvements in the determination of the turnover rate of plasma thyroxine in avian species: application to the Japanese quail
Authors: Cookson E. J. , Glover J.
Published: December 2008

The disappearance of the thyroid hormone thyroxine (T4) from plasma in fully grown male Japanese quail can be described as a first order process with a rate constant of 0·178 ± 0·013/h (mean±s.e.m., n = 8), which represents a half-life of 3·90 h. A small amount of [125I]T4 in relation to total circulating T4 was injected i.v. into Japanese quail and plasma samples were taken at appropriate time-intervals for the determination of residual plasma radioactivity. The rate of disappearance of [125I]T4 was subsequently equated to the turnover rate of the endogenous hormone. Previous methods were modified to overcome problems arising from possible disturbance of plasma T4 metabolism, recirculation of radiolabelled iodide, and to purify the [125I]T4 from the plasma samples. By using labelled T4 of very high specific activity, the amount of [125I]T4 administered was kept much smaller than has been used in previous studies on Japanese quail, thus limiting any interference with plasma T4 dynamics. To minimize any disturbance of plasma T4 metabolism, only four blood samples were taken, at three-hourly intervals after the injection of [125I]T4. The rapid turnover of T4 produced a large amount of labelled inorganic iodide, the re-entry of which into the plasma T4 pool was inhibited by s.c. administration of sodium thiocyanate 1 h before injection of[125I]T4. Assay of the true [125I]T4 turnover was significantly improved over that used in previous studies by purifying the [125I]T4 from the plasma samples chromatographically. The samples were applied to small Sephadex G-25 columns with sodium hydroxide (0·1 mol/l) as the eluant. This simple procedure clearly separated the [125I]T4 from the other radioiodinated plasma components such as free iodide, non-hormonal iodinated proteins and triiodothyronine (T3), thus enabling a more accurate assessment of the residual labelled T4 concentration in the plasma and hence the T4 half-life.

The future application of this method to the study of plasma T4 turnover under various experimental conditions is discussed and the possible involvement of T4 turnover studies in the assessment of T4 to T3 conversion is considered.

J. Endocr. (1987) 114, 191–198
Forskolin and thyrotrophin stimulation of rat FRTL-5 thyroid cell growth: the role of cyclic AMP
Authors: Ealey P. A. , Ahene C. A. , Emmerson J. M. , Marshall N. J.
Published: December 2008

The adenylate cyclase stimulator forskolin increases intracellular cyclic AMP (cAMP) in rat FRTL-5 cells within minutes and, after a lag phase of 20–24 h, an increase of cells in metaphase is seen. The dose– response relationships were similar in both systems, with significant increases in the number of metaphases observed at ∼0·1 μmol/l and a doubling of cAMP levels at 1 μmol/l, whilst doses of 0·1 mmol/l and above proved cytotoxic. An involvement of intracellular cAMP as a positive intermediate in cell division was further suggested by the finding that a low dose of forskolin (0·1 μmol/l) potentiated TSH stimulation of mitosis. Isobutyl methyl xanthine (IBMX), a phosphodiesterase inhibitor, also acted as a mitogen and potentiated TSH action. Moreover, the simultaneous inclusion of low doses of IBMX and forskolin additionally potentiated TSH stimulation of mitosis. An analogue of cAMP, dibutyryl cAMP, also stimulated mitosis and acted over a restricted dose range, with maximal stimulation at 1 mmol/l.

We conclude that cAMP may act as a positive signal for FRTL-5 thyroid cell proliferation.

J. Endocr. (1987) 114, 199–205
Effect of asymmetrical reductions of photoperiod on pineal melatonin, locomotor activity and gonadal condition of male Syrian hamsters
Authors: Hastings M. H. , Walker A. P. , Herbert J.
Published: December 2008

This study investigated the relationship of two overt circadian rhythms, locomotor activity and melatonin synthesis in the pineal gland, by comparing their responses to asymmetrical reductions in photoperiod. Transfer of male Syrian hamsters from long to short daylengths led to an increase in the duration of both locomotor activity and the period of melatonin synthesis. Over the course of re-entrainment, the two rhythms were held in a stable phase relationship, and the direction of the switch did not influence the rate of decompression or the final phase relationships established after 8 weeks in short daylengths. Decompression of the activity rhythm was not influenced by pinealectomy. Exposure to short photoperiods caused gonadal regression and a consequent decline in serum testosterone levels from 10 to <1 nmol/l. The direction of the photoperiodic switch did not affect the time-course of gonadal regression. These data demonstrate the important influence of photoperiod upon the duration of the nocturnal peak of melatonin production by the pineal and also demonstrate that this effect is one example of a more widespread response of the circadian system. A qualitatively similar signal controls both locomotor activity and melatonin synthesis, although the neural basis of this common mechanism is unclear.

J. Endocr. (1987) 114, 221–229
Influence of streptozotocin-induced diabetes on the concentration of immunoreactive somatostatin in the retina and peripheral blood of the rat: effect of insulin treatment
Authors: Ariznavarreta C. , Fernandez-Durango R.
Published: December 2008

Changes in somatostatin-like immunoreactivity (SLI) were examined in the retina and peripheral blood of diabetic rats treated with streptozotocin (STZ) and insulin. There was no change in retinal SLI content at 4 and 11 days after administration of STZ but, thereafter, SLI increased progressively in the diabetic animals by 220% at 18 days and 300% at 27 days. Plasma SLI levels increased by 500% at 11 days and maintained similar levels thereafter. Diabetic animals treated with insulin (3–5 i.u. daily) for 27 days showed a significant (P < 0·01) decrease of retinal and plasma SLI levels compared with untreated diabetic animals. It is concluded that there is a significant increase of retinal and plasma SLI levels in diabetic rats which tends to normalize after several days of insulin treatment.

J. Endocr. (1987) 114, 363–367