bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence for an increased opioid inhibition of LH secretion in hyperprolactinaemic ovariectomized rats
Authors: Carter D. A. , Cooper J. S. , Inkster S. E. , Whitehead S. A.
Published: December 2008

The effects of acute and sub-chronic hyperprolactinaemia on the positive feedback action of progesterone in oestrogen-primed ovariectomized rats have been compared. A single injection of ovine prolactin administered with progesterone had no effect on the LH surge measured 5 h later although hyperprolactinaemia induced by 5-day treatment with the dopamine antagonist, domperidone, markedly attenuated the surge. Repeated injections of naloxone (5 mg/kg) during the development of the progesterone-stimulated LH surge completely reversed this inhibitory effect of hyperprolactinaemia, but had no apparent effect on the positive feedback action in control animals. In oestrogen-primed animals similar treatment with naloxone (0·4 and 5 mg/kg) stimulated LH secretion but the increase was significantly smaller than that observed after injecting progesterone. It is suggested that hyperprolactinaemia increases the inhibitory opioid modulation of LH release and that this effect is responsible for the impairment of the positive feedback action of progesterone.

J. Endocr. (1984) 101, 57–61
Pars distalis cell quantification in normal adult male and female rats
Authors: Dada M. O. , Campbell G. T. , Blake C. A.
Published: December 2008

We analysed cell types in the pars distalis of normal young adult male and female rats with respect to their percentages and the relative volumes they occupy. In male rats the percentages of the cell types were: prolactin 49·80, GH 22·67, LH 5·04, FSH 4·22, ACTH 2·93 and TSH 2·09, The volume densities were: prolactin 20·48, GH 20·95, LH 7·34, FSH 6·73, ACTH 3·75 and TSH 3·19. In female rats the percentages of the cell types were: prolactin 52·40, GH 20·30, LH 5·89, FSH 4·06, ACTH 2·53, TSH 2·40 and the volume densities were: prolactin 28·09, GH 20·86, LH 8·11, FSH 5·46, ACTH 3·49 and TSH 2·91. The percentages of pars distalis cells which did not stain with the antisera to the six classical hormones were 17·47 in male and 16·48 in female rats.

The results suggest that (1) in both sexes the number (N) of prolactin cells > N of GH cells > N of gonadotrophs > N of TSH or ACTH cells, (2) the percentage of each cell type was similar in both sexes, (3) the volume density (Vv) of prolactin cells was greater than the Vv of GH cells in female but not in male rats and in both sexes the Vv of GH cells > the Vv of gonadotrophs > the Vv of TSH or ACTH cells, (4) in both sexes the volume (V) of prolactin cells < the V of GH cells < the V of gonadotrophs, the V of TSH cells or the V of ACTH cells, (5) the V of prolactin cells was greater in female than in male rats and (6) approximately 17% of the cells in the pars distalis of both sexes did not contain 'immunoreactive' prolactin, GH, LH, FSH, TSH or ACTH.

J. Endocr. (1984) 101, 87–94
Serum oestradiol and preovulatory follicular development before in-vitro fertilization
Authors: Hillier S. G. , Parsons J. H. , Margara R. A. , Winston R. M. L. , Crofton M. E.
Published: December 2008

Twenty-three in-vitro fertilization (IVF) treatment cycles (four unstimulated and 19 clomiphene-stimulated) were assessed retrospectively to discern relationships among serum oestradiol (OE2) titre on the day that human chorionic gonadotrophin (hCG) was given and the number and size of ovulatory follicles available for aspiration of oocytes during laparoscopy 32–38 h after hCG injection. Since 12 of the cycles succeeded to the stage of embryo replacement and two normal term pregnancies resulted, the series as a whole offers a useful referent data base. When only one ovulatory follicle developed (n = 8) the average volume of aspirated follicular fluid was approximately 6 ml, equivalent to a follicular diameter between 22 and 23 mm. When multiple follicles developed (mean 2·7/patient, n = 15), average fluid volume/follicle was not significantly different, averaging approximately 5·5 ml. Serum OE2 titre on the morning before hCG was injected ranged between 0·9 and 5·5 nmol/l and corresponded to the number of follicles aspirated at laparoscopy. There was a highly significant linear correlation (r = 0·85, P <0·001) between this OE2 value (X nmol/l) and total aspirated fluid volume (Y ml) where Y = 2·07 + 3·65 X. Thus taking 6 ml as the 'typical' fluid volume, the calibration line and its 95% confidence limits could be used to establish provisional 'ideal' pre-hCG serum OE2 titre ranges corresponding to the development of one, two or three mature ovulatory follicles. This information, combined with a knowledge of the number of presumptive preovulatory follicles present (assessed by ovarian ultrasound), can aid the timing of the hCG injection before IVF.

J. Endocr. (1984) 101, 113–118
Inhibition of acetylcholine receptor synthesis by thyroid hormones
Authors: Shainberg A. , Brik H. , Bar-Shavit R. , Sampson S. R.
Published: December 2008

Studies were made on the effect of thyroid hormones on the level of acetylcholine receptors (AChR) in cultured rat skeletal muscle. Treatment of differentiated myotubes in vitro with thyroxine (T4; 2 × 10−7 mol/l) for 2–3 days caused a marked decrease in the amount of AChR (P<0·05) and an increase in activity of Na+-K+-ATPase (P<0·05). There was no significant effect of hormone treatment on other muscle proteins, such as creatine kinase and acetylcholinesterase. Measurements of the turnover rate of AChR in T4-treated myotubes showed only a very slight effect of T4 on the rate of AChR degradation. To study the mechanism by which the hormone exerts its effect, muscle cells were labelled with radioactive amino acid and the rate of its incorporation into AChR protein was measured. The AChR was then isolated using anti-AChR antibodies. The specific activity of labelled AChR was lower in hormone-treated cells. These experiments suggest that the decreased level of AChR in response to thyroid hormone treatment is due to a partial suppression of receptor synthesis.

J. Endocr. (1984) 101, 141–147
Ovariectomy does not abolish proceptive behaviour cyclicity in the common marmoset (Callithrix jacchus)
Authors: Kendrick K. M. , Dixson A. F.
Published: December 2008

Unlike in other non-human primates, ovariectomy of the female marmoset did not alter heterosexual interactions. Proceptive behaviour bouts retained the same cyclicity, duration and frequency within tests as during the ovarian cycle. Significant rises in plasma levels of cortisol, progesterone, oestrone and testosterone were found during these proceptive behaviour bouts and in cortisol, progesterone and oestrone at their onset. Results suggest a role for adrenocortical steroids in both maintaining female sexuality and regulating its cyclicity during ovarian cycles in this primate.

J. Endocr. (1984) 101, 155–162
Ovarian steroid metabolism and oestrogens in the corpus luteum of the tammar wallaby
Authors: Renfree M. B. , Flint A. P. F. , Green S. W. , Heap R. B.
Published: December 2008

Ovaries were obtained from tammar wallabies at various stages of the reproductive cycle to examine the occurrence of oestrogens in corpora lutea, and the synthesis and metabolism of steroids in the corpus luteum and ovarian cortical and interstitial tissues. Corpora lutea contained oestradiol-17β and oestrone during embryonic diapause and at all stages of pregnancy studied after blastocyst activation. Aryl sulphatase, 3β-hydroxysteroid dehydrogenase and 17β-oxidoreductase were shown to be present in luteal and other ovarian tissues by incubation in vitro with labelled substrates. Aromatase was undetectable in corpora lutea or in interstitial tissue, but was present in the ovarian tissues (including follicles) which remained after removal of corpora lutea. The probable source of the oestrogens detected in the corpus luteum is discussed in relation to their role in the inhibition of follicular development during embryonic diapause.

J. Endocr. (1984) 101, 231–240
Cyclic GMP phosphodiesterase and guanylate cyclase activities in rabbit ovaries and the effect of in-vivo stimulation with LH
Authors: Patwardhan V. V. , Lanthier A.
Published: December 2008

The activities of guanylate cyclase and cyclic GMP (cGMP) phosphodiesterase, enzymes that are responsible for maintaining tissue levels of cGMP, were determined in the ovaries of rabbits killed without treatment or 4 h after administration of LH. Ovarian activities of the two enzymes were determined in the 100 000 g supernatant fraction (cytosol) and the resulting pellet (particulate fraction). Significant phosphodiesterase and cyclase activities were detected in both the cytosol and particulate fractions. Administration of LH had no significant effect on phosphodiesterase activity in either of the tissue fractions. On the other hand, LH caused a significant drop in guanylate cyclase activity in the cytosol and particulate fractions. This drop in the cyclase activity may be the cause of the decreased rabbit ovarian concentrations of cGMP that we have previously observed after LH stimulation.

J. Endocr. (1984) 101, 305–310
Histochemical studies on steroid dehydrogenases in the testis of the goat (Capra hircus)
Authors: Bilaspuri G. S. , Guraya S. S.
Published: December 2008

Detailed histochemical localization of 3β-hydroxysteroid dehydrogenase (3β-HSD) and 17β-HSD was made in the goat testis using both NAD and NADP coenzymes. The substrates used for 3β-HSD were dehydroepiandrosterone (DHA) and pregnenolone whereas 17β-HSD was localized with testosterone and oestradiol. In general, the activity of the enzymes varied with the cell type, substrate and coenzyme. In seminiferous tubules, DHA and NAD were the preferred substrate and coenzyme respectively for 3β-HSD. In addition, in interstitial tissue, NAD was the preferred coenzyme with DHA whereas no such preference existed with pregnenolone. 17β-Hydroxysteroid dehydrogenase showed a similar pattern in the two main compartments of the testis, as testosterone and oestradiol were equally utilized and NAD was the preferred coenzyme in both these compartments. The activities of the enzymes increased during the process of spermiogenesis and were higher in seminiferous tubules than in interstitial tissue, especially in elongated spermatids and spermatozoa.

J. Endocr. (1984) 101, 359–363
Ovarian oestrogen-dependent maturation of the LH/FSH surge mechanism during prepubertal development in the gilt
Authors: Foxcroft G. R. , Elsaesser F. , Stickney K. , Haynes N. B. , Back H. L.
Published: December 2008

An involvement of ovarian secretions and in particular oestradiol-17β in the maturation of the positive feedback mechanism controlling gonadotrophin surge secretion was studied in prepubertal gilts. The LH/FSH responses to an intramuscular injection of age- and body weight-related doses of oestradiol benzoate (OB) were compared in intact gilts at 60 days of age with or without oestradiol-17β pretreatment from 30 to 52 days of age. Four further groups of gilts were challenged with OB at 160 days and were intact, ovariectomized at 60 days, ovariectomized at 60 days and given oestrogen therapy from days 60 to 130 or ovariectomized at 130 days.

A significant increase in the magnitude of LH surge responses to OB and a decrease in the time to the first consistent period of surge secretion in intact gilts at 160 compared to 60 days of age confirmed earlier studies and is considered to represent a real maturational change in positive feedback activity. A longer response interval was also present in the majority of ovariectomized gilts. Furthermore a significant reduction in the magnitude of OB-induced LH responses at day 160 occurred in gilts ovariectomized at day 60 compared to those ovariectomized at day 130 and with intact control animals. Oestrogen therapy after ovariectomy at day 60 effectively restored the magnitude of the LH response however.

It is concluded that maturation of the positive feedback mechanism is ovarian, and probably oestrogen, dependent.

J. Endocr. (1984) 101, 371–380
Anaesthesia with alphaxalone plus alphadolone acetate blocks the oestrogen-stimulated LH surge and impairs pulsatile LH secretion in ovariectomized female rats
Authors: Dyer R. G. , Mansfield S.
Published: December 2008

Two experiments were undertaken to assess further the action of the steroid anaesthetic alphaxalone upon LH secretion in chronically ovariectomized female rats.

For the first experiment, 31 rats were given two injections of oestradiol benzoate (20 μg/100 g body weight), each 72 h apart, to stimulate an LH surge 6 h after the second injection. However, one group of seven rats was anaesthetized with alphaxalone throughout the 6-h period and a second group of eight was similarly anaesthetized only for the last 2 h of the 6-h period. The steroid-stimulated LH surge was blocked in both groups of rats anaesthetized with alphaxalone.

The second experiment involved a comparison of pulsatile LH secretion in animals which were either unanaesthetized (n = 8) or anaesthetized with alphaxalone (n = 9). In six out of nine rats the anaesthetic did not affect the maximum or minimum plasma LH concentrations but significantly slowed the frequency at which LH pulses were measured. In the remaining three anaesthetized rats the drug blocked pulsatile LH secretion.

The experiments confirm that some secretion of LH continues during alphaxalone anaesthesia but indicate also that the drug has a more deleterious action upon the oestrogen-stimulated LH surge than believed hitherto.

J. Endocr. (1984) 102, 27-31
Interaction of epidermal growth factor with receptors on human and porcine thyroid membranes
Authors: Humphries H. , MacNeil S. , Munro D. S. , Tomlinson S.
Published: December 2008

Recent evidence suggests that epidermal growth factor (EGF) may play an important role in the regulation of thyroid growth and function. We have examined the interaction of murine EGF (mEGF) with human and porcine thyroid membranes and compared this with the binding of bovine TSH (bTSH) using 125I-labelled hormones as tracers. The characteristics of the binding of mEGF were found to be similar for human and porcine thyroid membranes. Epidermal growth factor bound with high affinity (affinity constant = 1·4 × 109 l/mol); the density of binding sites was low compared with the TSH receptor. At 37 °C, the binding of 125I-labelled EGF was maximal at 1 h and was saturable in the presence of unlabelled EGF; half-maximal inhibition was at 1 ng EGF/tube (0·5 nmol/l) using 0·5 mg membrane protein/tube. Unlabelled bTSH had no effect on the binding of labelled EGF. Similarly, unlabelled EGF did not affect the binding of labelled TSH; hence it was concluded that mEGF and bTSH bound to independent sites. Epidermal growth factor had no effect on adenylate cyclase activity in membranes prepared from human non-toxic goitre; increasing concentrations of EGF did not affect basal, TSH-stimulated or fluoride-stimulated enzyme activity.

J. Endocr. (1984) 102, 57–61
Release of oxytocin and vasopressin by magnocellular nuclei in vitro: specific facilitatory effect of oxytocin on its own release
Authors: Moos F. , Freund-Mercier M. J. , Guerné Y. , Guerné J. M. , Stoeckel M. E. , Richard Ph.
Published: December 2008

The release of endogenous oxytocin and vasopressin by rat paraventricular and supraoptic nuclei in vitro during a 10-min period, 30 min after beginning the incubation, was measured radioimmunologically. Mean basal hormone release per 10 min and per pair of nuclei was: 128·4 ± 12·4 (s.e.m.) pg vasopressin (n = 15) and 39·0 ± 3·0 pg oxytocin (n = 66) for supraoptic nuclei from male rats; 273·9 ± 42·6 pg vasopressin (n = 11) and 34·2 ± 3·5 pg oxytocin (n = 15) for supraoptic nuclei from lactating rats; 70·0 ± 8·6 pg vasopressin (n = 52) and 21·8 ± 1·3 pg oxytocin (n = 68) for paraventricular nuclei from male rats; 59·1 ± 8·6 pg vasopressin (n = 10) and 27·0 ± 4·6 pg oxytocin (n = 16) for paraventricular nuclei from lactating rats.

In male and lactating rats, both nuclei contained and released more vasopressin than oxytocin. For oxytocin alone, the paraventricular nucleus of male rats contained and released significantly less hormone than the supraoptic nucleus. This difference was not apparent in lactating rats. For vasopressin alone, the paraventricular nucleus contained and released significantly less hormone than the supraoptic nucleus in both male and lactating rats. When the hormone released was calculated as a percentage of the total tissue content the release was about 0·9% for oxytocin from both nuclei in male and lactating rats and also for vasopressin in lactating rats, but was only about 0·5% for vasopressin from both nuclei in male rats.

The influence of oxytocin and analogues of oxytocin (including one antagonist) upon the release of oxytocin and vasopressin was studied. Adding oxytocin to the incubation medium (0·4–4 nmol/l solution) induced a dose-dependent rise in oxytocin release from both nuclei of male or lactating rats. A 4 nmol/l solution of isotocin had a similar effect to a 0·4 nmol/l solution of oxytocin, but arginine-vasopressin never affected basal release of oxytocin. In no case was vasopressin release modified.

An oxytocin antagonist (1 μmol/l solution) significantly reduced basal oxytocin release and blocked the stimulatory effect normally induced by exogenous oxytocin, as did gallopamil hydrochloride (D600, 10 μmol/l solution), a Ca2+ channel blocker, or incubation in a Ca2+-free medium.

These findings are discussed in relation to the literature on the central effects of neurohypophysial peptides. It may be concluded that the regulatory role of endogenous oxytocin in the hypothalamus on the milk-ejection reflex could result from its local release in the extracellular spaces of magnocellular nuclei.

J. Endocr. (1984) 102, 63–72
A novel oestrogen-binding species in rat granulosa cells
Authors: Kudolo G. B. , Elder M. G. , Myatt L.
Published: December 2008

The dissociation constants (Kd) and steroid specificities of oestrogen-binding species in rat granulosa cell cytosol and nuclei have been studied. Preliminary work, where diethylstilboestrol was employed as competitor in binding assays, identified the oestrogen receptor in whole ovarian tissue nuclei (Kd 0·35 ±0.09 nmol/l) and cytosol (Kd 0·39 ± 0·03 nmol/l). Isolation of granulosa cells revealed that the majority of this receptor (75–96%) was present in these cells. Specificity studies on the binding of [3H]oestradiol in granulosa cell cytosol indicated the presence of an additional class of oestrogen-binding sites which were, however, not present in nuclei. Saturation analysis over an extended range of [3H]oestradiol concentrations and using unlabelled oestradiol as competitor revealed a binding species of Kd 45·8± 6·9 nmol/l (capacity 16·7 pmol/mg cytosol protein) for oestradiol in addition to the cytosol oestrogen receptor of Kd 0·58 ± nmol/l (capacity 2·8 pmol/mg cytosol protein). The low affinity of this novel species implies that the dextran-coated charcoal techniques used in previous studies on ovarian oestrogen-binding species would cause dissociation of ligand and not allow it to be measured.

The second oestrogen-binding species displayed affinity for oestradiol-17β, oestriol, oestrone, testosterone, 5α-dihydrotestosterone, methyltrienolone, progesterone and the antioestrogens tamoxifen, nafoxidine and clomiphene citrate. The species, however, did not bind diethylstilboestrol, a characteristic shared with other low affinity cytosol oestrogen-binding species which have been reported in dog prostate, chick oviduct and male rat liver but not shared with uterine type II oestrogen receptors. It can be further distinguished from the oestrogen receptor by differential ammonium sulphate precipitation and the stability of its ligand binding at temperatures above 55 °C where the oestrogen receptor–ligand interaction is rapidly lost.

Concentrations of nuclear oestrogen receptor in granulosa cells (2200 sites/cell) were similar to those found in other target tissues but a high proportion of this receptor (70%) was 'unoccupied' or available for binding at 4 °C and the majority (75%) was resistant to extraction with 0·4 m-KCl. As the second oestrogen-binding species could not be detected in granulosa cell nuclei it is unlikely to be involved directly in eliciting genomic responses to hormonal stimulation. It is more probable that it regulates the level of the free intracellular steroid to which the oestrogen receptor of the granulosa cell (the predominant site of oestrogen biosynthesis) is exposed.

J. Endocr. (1984) 102, 83–91
Sexual maturation in male mice treated with cyproterone acetate from birth to puberty
Authors: Jean-Faucher Ch. , Berger M. , De Turckheim M. , Veyssiere G. , Jean Cl.
Published: December 2008

Cyproterone acetate was administered every 2 days from 1 to 39 days of age to male mice which were killed 24 h or 20 days after the last injection. Cyproterone acetate caused a significant reduction in the relative weights of the epididymis, vas deferens, seminal vesicle and preputial gland, which was still evident at 60 days after birth. Testicular and epididymal androgens (testosterone and dihydrotestosterone) and circulating LH and FSH concentrations were equal to or higher than those of controls at 60 days. Cyproterone acetate did not inhibit spermatogenesis but all males were infertile. The results suggest that the peripheral effects of testosterone are necessary, during early stages of sexual maturation, in order to obtain subsequent full development of the accessory sex organs.

J. Endocr. (1984) 102, 103–107
The inhibitory effect of opiates on gonadotrophin secretion is dependent upon gonadal steroids
Authors: Bhanot R. , Wilkinson M.
Published: December 2008

We have attempted to clarify the physiological involvement of endogenous opiates in the steroid-mediated control of gonadotrophin release. Our studies showed that there was an acute reduction in the inhibitory effects of endogenous opiates on LH and FSH release following gonadectomy in the rat. This was indicated by a significant reduction in the ability of naloxone to stimulate serum LH/FSH levels (sampled at 15 min) in 26-day-old female rats 48 h after ovariectomy. Luteinizing hormone was highly sensitive to the inhibitory effects of the synthetic met-enkephalin analogue, FK 33-824, at this time (sampled at 90 min). An unexpected observation was that long-term absence of gonadal steroids also disrupted the ability of exogenous opiates, FK 33-824 and morphine, to influence LH release. This was seen as an inability of FK 33-824 (1·0 or 3·0 mg/kg) to inhibit LH secretion. The effects of gonadectomy on opiate control of LH occurred at all developmental stages and were not due to a disruption of sexual maturation. Opiate involvement in prolactin secretion did not appear to be adversely affected by an absence of gonadal steroids. Another novel aspect of this work was that the opiatergic component in the control of gonadotrophin secretion could be reinstated in long-term gonadectomized rats by treatment with oestradiol benzoate or testosterone propionate. Similarly, priming with increasing dosages of oestradiol benzoate which resulted in progressively lower LH levels gave larger naloxone responses. This steroid–opiate interdependency suggests that the negative feedback influence of gonadal steroids on LH secretion is conveyed, in part, by hypothalamic opiate peptides. Our results therefore provide a neurochemical basis for gonadal steroid negative feedback.

J. Endocr. (1984) 102, 133–141
Perineal muscles: possible androgen regulation of glucocorticoid receptor sites in the rat
Authors: DuBois D. C. , Almon R. R.
Published: December 2008

The glucocorticoid receptor population of the androgen-dependent levator ani–bulbo cavernosus muscle complex in response to both androgen withdrawal and androgen replacement was examined in rats. (1) After castration the concentration of receptor sites more than doubled. The increase in the sites began within the first 24 h after castration and reached a plateau level within 7 days. (2) Parallel dry weight studies demonstrated that no loss in muscle mass is observed until 48 h after castration. (3) In a second series of experiments, both the regrowth of the muscle and the number of receptor sites in response to androgen injections were examined. By day 11 of injection, the muscle had increased in dry weight to a point where it was equal to the size of this muscle in normal intact male controls. (4) During this process, the concentration of receptor sites began to decline 5 days after the beginning of injections and reached control or below control values by 11 days.

J. Endocr. (1984) 102, 225–229
Effects of prolactin, progesterone and ovariectomy on metabolic activities and insulin receptors in the mammary gland and adipose tissue during extended lactation in the rat
Authors: Flint D. J. , Clegg R. A. , Knight C. H.
Published: December 2008

Prolactin implants prevented the decline in milk yield and the resumption of oestrous cycles which occurred between days 22 and 28 in untreated lactating rats. Ovariectomy and progesterone implants only partially prevented the decline in milk yield despite preventing the occurrence of oestrous cycles. All three treatments increased total RNA content of the mammary gland compared with controls. In untreated rats there were no changes in mammary DNA content or the number of insulin receptors whereas lipoprotein lipase (LPL) activity decreased significantly during the declining phase of lactation. In contrast, the number of insulin receptors, LPL activity and glucose incorporation into lipid increased in adipose tissue. Prolactin prevented the increase in insulin receptors and lipid synthesis and significantly decreased LPL activity in adipose tissue. Progesterone stimulated LPL activity in the mammary gland and also prevented the increase in lipid synthesis and insulin receptors in adipose tissue but was without effect on LPL activity whereas ovariectomy stimulated LPL activity in the mammary gland but prevented only the increase in the number of insulin receptors in adipose tissue.

The results show that raising the serum prolactin concentration can prevent the decline in milk yield during extended lactation and whilst part of this effect may be due to a direct effect on the mammary gland and an indirect effect due to inhibition of oestrous cycles, prolactin may also produce part of its effect on milk synthesis by inhibiting competitive metabolic processes in tissues such as adipose tissue.

J. Endocr. (1984) 102, 231–236
Evidence for the participation of a melanin-concentrating hormone in physiological colour change in the eel
Authors: Gilham I. D. , Baker B. I.
Published: December 2008

The hormonal and nervous control of colour change in the eel has been investigated. The only bioactive forms of MSH found in eel pituitary extracts or secreted by eel pituitary cultures were forms of α-MSH; no β-MSH was detected. After transfer of eels from a black to a white background, the melanin concentration in skin melanophores was accompanied by a rapid decline in plasma α-MSH titres. Hypophysectomy resulted in melanin concentration, and pituitary extracts injected into hypophysectomized eels caused melanin dispersion. This effect was eliminated if the pituitary extracts were first incubated with a specific α-MSH antiserum or if the antiserum was injected into the hypophysectomized eel. However, injection of α-MSH antiserum into intact, black-adapted eels failed to result in melanin concentration although the same antiserum was effective in causing pallor in black-adapted toads. Partially purified preparations of teleost melanin-concentrating hormone (MCH), free from catecholamines, induced melanin concentration when injected into black-adapted eels and this effect was significantly potentiated by injections of α-MSH antiserum. The denervation of melanophores on the pectoral fin had only a slight effect on the responses of the melanophores to humoral agents. It is concluded that the control of physiological colour change in the eel is largely hormonal, and involves the antagonistic effects of α-MSH and a melanin-concentrating agent which is probably MCH.

J. Endocr. (1984) 102, 237–243
Some effects of parathyroidectomy on cell-mediated immune responses in the rat
Authors: Perris A. D. , Edwards D. J. , Atkinson M. J.
Published: December 2008

Xenografts of mouse tail skin to the rib cages of normal and sham-parathyroidectomized rats caused an increase in plasma calcium concentration and concomitant increase in bone marrow mitosis. Neither was elicited in aparathyroid rats and graft survival was prolonged in these animals.

No hypercalcaemic episode was associated with the delayed hypersensitivity response induced by painting rat ears with oxazolone. Compared with the response in sham-parathyroidectomized rats, that in parathyroidectomized rats was enhanced although both responses were less than that in normal rats.

Parathyroidectomy of parental donors did not affect the ability of their splenic lymphocytes to mount a graft-versus-host response in F1 hybrid recipients. When sham-operated and aparathyroid parents were sensitized with F1 hybrid lymphocytes no differences were observed in a subsequent graft-versus-host response in F1 recipients. However, when aparathyroid F1 recipients were employed a marked reduction in the graft-versus-host reaction was observed.

Thus the clonal expansion of cells with specific reactivity to certain antigens in secondary lymphoid tissue, which is driven by those same specific antigens, is not affected or only moderately affected by the parathyroid status of the animal. However, the more general increase in lymphocyte numbers promoted by non-specific mitogenic lymphokines is markedly impaired in the hypocalcaemic parathyroidectomized rat. Furthermore, the parathyroid gland is essential for the development of a hypercalcaemic episode which follows antigenic challenge and causes cell proliferation in primary lymphoid tissues. This surge of mitosis could serve to replenish the depleted pools of virgin T and B lymphocytes in the secondary lymphoid tissue which occur as a result of their response to antigens.

J. Endocr. (1984) 102, 257–263
The use of salivary progesterone assays in the assessment of ovarian function in postmenarcheal girls
Authors: Read G. F. , Wilson D. W. , Hughes I. A. , Griffiths K.
Published: December 2008

Menstrual cycle profiles of salivary progesterone were derived from daily samples obtained from 75 postmenarcheal girls aged between 12 and 17 years. Data were analysed to establish the proportion of girls exhibiting ovulatory cycles in each of several age groups following menarche or in groups based solely on chronological age. 'Luteal'-phase profiles of salivary progesterone, which were similar in shape to those characteristic of mature premenopausal women, were taken to indicate the probable occurrence of ovulation. The percentage of cycles in those subjects judged to be ovulatory, grouped according to gynaecological age, rose from 14% in the first year to 56% in the fourth year. Those classified according to chronological age, and where sufficient data permitted reliable estimates of the percentage of subjects ovulating, rose from 11% at 12 years of age to 64% for girls aged 16. These data are in reasonable concordance with published data using plasma progesterone and urinary methods for establishing ovulatory incidence, and indicate the value of salivary progesterone measurements in studies of ovarian function in adolescence.

J. Endocr. (1984) 102, 265–268
Varying sensitivity to the negative oestrogen feedback during the ovarian cycle of female rats: evidence for the involvement of oestrogen and the medial preoptic area
Authors: Döcke F. , Rohde W. , Gerber P. , Chaoui R. , Dörner G.
Published: December 2008

The gonadotrophic response to a single injection of oestradiol benzoate (OB) was studied in acutely ovariectomized adult rats during the different stages of a 4-day ovarian cycle. The results showed a sudden decline of the sensitivity to the gonadotrophin-inhibiting effect of OB between metoestrus and dioestrus. This desensitization to the negative oestrogen feedback was probably caused by an oestrogen action on the medial preoptic area (MPOA). In rats ovariectomized and implanted with OB in the MPOA in metoestrus, an s.c. injection of OB on the presumptive day of pro-oestrus did not lower the circulating LH and FSH levels, whereas a clear suppression of gonadotrophin secretion was seen in females implanted with cholesterol in the MPOA or implanted with OB in the hypothalamic ventromedial–arcuate region. Similar findings were obtained in rats which had been ovariectomized 3–4 weeks before implantation. A final experiment demonstrated that bilateral lesioning of the MPOA also reduced the sensitivity to the negative feedback action of oestrogen in long-term ovariectomized rats. In all experiments performed, diminution of the oestrogen-induced inhibition of LH secretion was more marked than that of suppression of FSH secretion. It is proposed that desensitization to the negative oestrogen feedback, probably resulting from an inhibitory oestrogen action on medial preoptic neurones, is a prerequisite for adequate gonadotrophic support of preovulatory follicle maturation in the presence of a continuously rising oestrogen concentration in the blood.

J. Endocr. (1984) 102, 287–294
Progesterone interaction with eosinophils and with responses already induced by oestrogen in the uterus
Authors: Grunert G. , Porcia M. , Neumann G. , Sepúlveda S. , Tchernitchin A. N.
Published: December 2008

Progesterone pretreatment decreases oestrogen-induced uterine eosinophilia and other non-genomic responses that are possibly mediated by eosinophils. To investigate the mechanisms of this interaction, the present study describes the effects of progesterone on oestrogenic responses already induced by oestrogen treatment and the in-vivo and in-vitro effects of progesterone on blood eosinophils.

Progesterone treatment of oestrogen-pretreated animals potentiated uterine eosinophilia 24 h after progesterone treatment but decreased it at later times and increased eosinophil degranulation in vivo. In addition, progesterone degranulated blood eosinophils in vitro. These findings demonstrate interaction of progesterone with oestrogenic responses mediated by eosinophils.

Progesterone interaction with other oestrogenic responses was analysed for comparison; evidence is shown suggesting a role of eosinophils in oestrogeninduced uterine luminal fluid accumulation.

J. Endocr. (1984) 102, 295–303
Interaction of prostaglandin E2 and β-adrenergic catecholamines in the regulation of uterine smooth muscle motility and adenylate cyclase in the rat
Authors: Krall J. F. , Barrett J. D. , Jamgotchian N. , Korenman S. G.
Published: December 2008

Prostaglandin E2 (PGE2) increased the force of the spontaneous contractions of the rat myometrium and decreased the sensitivity of the uterus to the relaxing effects of the specific β-adrenergic catecholamine agonist isoprenaline. Prostaglandin E2, at concentrations above 10 μmol/l, increased cyclic AMP production by intact muscle strips. The muscle strips were far more sensitive, however, to the inhibitory effect PGE2 had on isoprenaline-dependent cyclic AMP production (threshold <0·001 nmol/l). Both PGE2 and isoprenaline stimulated adenylate cyclase activity of a myometrial subcellular (particulate) fraction in a guanyl nucleotide-requiring manner. When present in saturating concentrations (100 μmol/l), the stimulatory effects were not additive, suggesting that the receptors for the two agonists competed for the same catalytic subunit of adenylate cyclase or for the same guanyl nucleotide-requiring factor which couples receptors and enzyme. If muscle strips were incubated with PGE2 before the preparation of the adenylate cyclase-containing particulate fraction, the enzyme became less responsive to stimulation by guanyl nucleotide and by isoprenaline and PGE2 in the presence of guanyl nucleotide. The PGE2 receptor may therefore interact with the β-adrenoreceptor to inhibit isoprenaline-dependent cyclic AMP production by intact muscle cells by desensitizing adenylate cyclase, possibly at the level of the guanyl nucleotide-dependent coupling step.

J. Endocr. (1984) 102, 329–336
Evaluation of the biological properties of parathyroid hormone and analogues in a vascularly isolated parotid gland-based assay
Authors: Wright R. D. , Blair-West J. R. , Nelson J. F. , Tregear G. W. , Rosenblatt M.
Published: December 2008

Infusion of bovine parathyroid hormone (bPTH) preparations into the arterial blood supply of the vascularly isolated parotid gland in anaesthetized sheep increases salivary phosphate concentration and gland blood flow rate with rapid onset and offset of action. These responses have been used as a bioassay for PTH and PTH analogues and for assessing the properties of an in-vitro inhibitory analogue [Nle-8, Nle-18, Tyr-34]bPTH-(3–34)amide. [Nle-8, Nle-18, Tyr-34]bPTH-(1–34)amide at 10− 9 to 10 −8 mol/l was four to five times more potent than bPTH(1–34) on both salivary phosphate and blood flow assays. Human PTH(1–34) was not significantly more potent than bPTH(1–34). The [Nle-8, Nle-18, Tyr-34]bPTH-(3–34)amide analogue had very slight agonist activity at 3 × 10−7 mol/l and at a 100:1 ratio of analogue to PTH it completely inhibited the action of bPTH(1–34) on phosphate secretion and gland blood flow. It caused partial inhibition at 10:1 and had no evident effect at 1:1. These results differ from previous in-vitro results and indicate that the preparation may be valuable for evaluation of agonist and antagonist analogues of PTH. The vascularly isolated parotid gland of the sheep permits repeated random testing of analogues in a control–test–control sequence and the results indicate high sensitivity to PTH in a rapidly reactive invivo system with two responding parameters.

J. Endocr. (1984) 102, 375–379
Effect of insulin on free fatty acid uptake by hepatocytes in the duck
Authors: Gross R. , Mialhe P.
Published: December 2008

To elucidate the hypolipacidaemic effect of insulin in ducks, its action on the uptake of free fatty acids (FFA) by duck hepatocytes was determined. At low doses (10 mu./l) insulin stimulated FFA uptake. This effect was not observed with higher doses of insulin (20, 30 and 50 mu./l). Growth hormone at physiological concentrations and corticosterone (14·4 nmol/l) decreased basal activity, probably by reducing glucose metabolism and consequently α-glycerophosphate (α-GP) supply. Insulin was able to reverse the inhibition induced by GH and corticosterone on both FFA uptake and α-GP production. These results therefore suggest that the hypolipacidaemic effect of insulin may be partly mediated by its action on hepatic FFA uptake.

J. Endocr. (1984) 102, 381–386
Further characterization of corticotrophin releasing factor activity from a bronchial tumour
Authors: Kirkland S. C. , Lumsden J. L. , Ellison M. L.
Published: December 2008

The nature of corticotrophin releasing factor (CRF) activity secreted by a human bronchial carcinoid cell line was investigated. The CRF activity in incubation media exposed to bronchial tumour cells was concentrated by preparative high pressure liquid chromatography (HPLC). Analytical HPLC resolved the CRF activity into several different forms.

The incorporation of [3H]leucine and other [3H]amino acids into materials which co-eluted with CRF activity when fractionated by analytical HPLC suggested that the bronchial carcinoid cells were secreting peptide CRF(s). The most abundant radioactive material was shown to have a molecular weight of 12 000 by sodium dodecyl sulphate gel electrophoresis. This radioactive fraction also stimulated ACTH secretion by rat pituitary cell cultures in a dose-responsive manner.

J. Endocr. (1984) 103, 91–96
Prolactin stimulates steroidogenesis by human luteal tissue in vitro
Authors: Hunter M. G.
Published: December 2008

Human luteal tissue recovered from varying stages of the luteal phase was minced and incubated for 3 h and the effect of human chorionic gonadotrophin (hCG), prolactin and hCG + prolactin on progesterone and oestradiol production measured. While hCG generally enhanced both progesterone and oestradiol synthesis, prolactin alone at either 20 or 200 μg/l had no significant effect on steroidogenesis. When prolactin was added along with hCG in four of six corpora lutea, however, progesterone production significantly increased and in three of six corpora lutea oestradiol production was increased above that induced by hCG alone. It is concluded that prolactin may play some role in the control of steroidogenesis by the human corpus luteum.

J. Endocr. (1984) 103, 107–110
Studies on the control of prostaglandin production by the hypothalamus in relation to LH release in the rat
Authors: Brown C. G. , Poyser N. L.
Published: December 2008

Prostaglandin (PG) and thromboxane (TX) synthesis by homogenates of the hypothalamus of rats has been measured in relation to the preovulatory surge of LH. Prostaglandin and TX production by the median eminence (ME) was five to ten times higher than that by the anterior hypothalamus/preoptic area (AH-POA). Prostaglandin E2 and PGF2α were the major prostaglandins synthesized by the ME and AH-POA respectively. During the 4-day oestrous cycle, the PG-and TX-synthesizing capacity of the ME showed daily changes, being high at 06.00 and 22.00 h and, with the exception of pro-oestrus, low at 18.00 h. There was an additional peak of PGE2 production by the ME at 18.00 h on pro-oestrus coincident with the preovulatory LH surge. Progesterone treatment stimulated PGE2 synthesis by the ME of long-term ovariectomized, oestradiol-primed rats but not by the ME of acutely ovariectomized, oestradiol-primed rats. 2-Hydroxyoestradiol had no effect on PG and TX production by the ME at 18.00 h on dioestrus or 18.00 h on pro-oestrus. Noradrenaline stimulated PG and TX synthesis by the ME at the former time but not at the latter time.

Prostaglandin F2α-synthesizing capacity of the AH-POA peaked at 22.00 h on each day of the 4-day cycle. There was also an additional peak at 14.00 h on each day except dioestrus. Similar peaks occurred in the production of PGE2 and TXB2, except on pro-oestrus when the production of each compound remained low. There was no association between increased PGE2 production by the AH-POA and the preovulatory surge of LH. Noradrenaline, but not 2-hydroxy-oestradiol, stimulated PG and TX production by the AH-POA at 18.00 h on both dioestrus and pro-oestrus. Progesterone stimulated PGE2, PGF2α and 6-oxo-PGF1α production by the AH-POA of acute, ovariectomized, oestradiol-primed rats but not of long-term ovariectomized, oestradiol-primed rats.

Flurbiprofen, a cyclo-oxygenase inhibitor, prevented the preovulatory LH surge in two rats and delayed the LH surge by 2 h in four rats. It also reduced PG and TX production by the ME and AH-POA. Overall, the present studies show that there is an increase in PGE2-synthesizing capacity of the ME at the time of the preovulatory LH surge in the rat, and that the administration of an inhibitor of prostaglandin synthesis interferes with the timing of the LH surge.

J. Endocr. (1984) 103, 155–164
Evidence for episodic but not circadian activity in plasma concentrations of adrenocorticotrophin, cortisol and thyroxine in dogs
Authors: Kemppainen R. J. , Sartin J. L.
Published: December 2008

Concentrations of immunoreactive (i) ACTH, cortisol and thyroxine were determined in plasma samples obtained at 20-min intervals for 25 h in nine normal and two adrenalectomized dogs. The dogs were exposed to a 12 h light:12 h darkness photoperiod for 30 days before the sampling period. Episodic secretion of iACTH and cortisol was evident in each normal dog, with an average of 9·0 iACTH peaks and 10·1 cortisol peaks in a 24-h period. Levels of iACTH and cortisol were significantly correlated in each normal dog, but periods of dissociation between levels of the two hormones were apparent. A sex difference in 24-h mean iACTH and cortisol levels, numbers of cortisol peaks, and amplitude of iACTH peaks was observed, with females showing higher mean levels and greater peak frequency and amplitude in each instance. Adrenalectomy resulted in a 50- to 150-fold increase in mean iACTH concentrations with an apparent increase in iACTH peak amplitude. Cortisol levels were unchanging in the adrenalectomized dogs.

Thyroxine concentrations showed episodic variation in each of the normal dogs, but the mean number of peaks (3·3/24-h period) was considerably less than for iACTH or cortisol. Female dogs had significantly higher 24-h mean levels of thyroxine than did males. No circadian rhythmicity was obvious for the plasma levels of any of the three hormones measured.

J. Endocr. (1984) 103, 219–226
Blockade of LH and FSH secretion by LH-releasing hormone, by the LH-releasing hormone analogue, buserelin, and by combined treatment with LH-releasing hormone and oestradiol benzoate
Authors: Schuiling G. A. , Pols-Valkhof N. , van der Schaaf-Verdonk G. C. J. , Koiter T. R.
Published: December 2008

The LH and FSH release-stimulating (experiment 1) and -blocking (experiment 2) effects of LH-releasing hormone (LHRH) and of the LHRH analogue d-Ser(But)6-des-Gly10-LHRH-ethylamide (buserelin), as well as the effect of combined treatment with LH RH and oestradiol benzoate (OB; experiment 3) on the 'supra-maximally' LHRH-stimulated release of LH and FSH were studied in rats ovariectomized for 2 weeks. Pretreatment with LHRH (250 or 500 ng/h) or buserelin (250 ng/h) for 6 days was effected by means of subcutaneously implanted Alzet osmotic minipumps; control rats received a 'sham pump', i.e. a piece of silicone elastomer with the dimensions of a minipump. Oestradiol benzoate (3 μg/injection) or solvent was injected subcutaneously 75 and 27 h before the induction of LH/FSH responses.

Experiment 1 revealed that after infusion of LHRH and buserelin, both at the rate of 1 μg/h, plasma LHRH concentrations were established which were about twice as low as the plasma buserelin concentrations. This might suggest that buserelin has a longer half-life than LHRH. As an LH and FSH release-stimulating substance, however, it appeared that buserelin was about as effective as LHRH. Experiment 2, however, suggested that as an LH/FSH release-blocking agent buserelin was much more effective than LHRH. In addition, after buserelin pretreatment the pituitary glands contained much less LH and FSH than after LHRH pretreatment at both dose levels used. However, this may also (at least partly) be due to the fact that buserelin has a longer half-life so that after infusion of buserelin and LHRH at the same rate the plasma concentrations of buserelin are higher than those of LHRH; after buserelin infusion the pituitary gland is therefore stimulated at a higher intensity.

Experiment 3 showed that in OB-injected, sham-implanted rats the LHRH-stimulated secretion of LH and FSH was significantly higher than in the oil-injected, sham-implanted rats. In the LHRH-pretreated rats (LHRH: 250 ng/h for 6 days), however, the already depressed LHRH-stimulated secretion of LH and FSH was still further depressed by OB treatment.

These latter results suggest that the increase of the pituitary LHRH responsiveness during exposure to oestrogen requires a reduction of the LHRH stimulation, which is normally caused by the negative feedback of oestrogen on the hypothalamus.

J. Endocr. (1984) 103, 301–309