bluuebunny/crossref_metadata_2025 huggingface dataset:
Behavioural and physiological effects of prolactin in incubating ring doves
Authors: Janik D. S. , Buntin J. D.
Published: December 2008

The role of prolactin in the maintenance of incubation behaviour in ring doves was re-examined and the dose–response relationships for behavioural, target tissue and body weight changes induced by injections of prolactin were compared in doves tested during the incubation phase of the breeding cycle. Doves given injections of prolactin twice a day starting on day 4 of incubation, during a 10-day period of isolation from their mates and nests, showed a higher persistence of incubation behaviour than doves injected with saline vehicle. However, the prolactin treatment failed to maintain incubation behaviour to the same extent as that observed in non-isolated untreated breeding pairs. Liver and body weights were higher and testicular weights lower in birds treated with high doses of prolactin than in non-isolated birds which had been incubating for 14 days. Good dose-response relationships were established between body, liver, crop and testes weights and the dose of prolactin administered. However, only a weak dose–response relationship was observed between prolactin and the maintenance of incubation behaviour. Overall, females injected with prolactin displayed more quiet sitting behaviour, less body weight gain and more gonadal regression than males injected with prolactin. Males in untreated breeding pairs had higher liver weights and lower crop weights than females. It is concluded that prolactin plays a role in maintaining readiness to incubate in doves, but that other factors may also contribute to this response. Further, it appears that prolactin mediates several target tissue changes which are sex-specific during incubation.

J. Endocr. (1985) 105, 201–209
Odour recognition by male hamsters: discrimination of the hormonal state of females by odour from vaginal secretions
Authors: Steel E.
Published: December 2008

Male hamsters were tested for their interest in females on different days of the oestrous cycle. Behaviour of males towards novel females was measured and (after exposure to vaginal secretion) towards females that matched or did not match that vaginal odour. Because pro-oestrous (day 4) females lay trails of vaginal secretion and will become receptive within a few hours, it was predicted that males would show more interest in day 4 than in other dioestrous females. While males showed no preference for novel, pro-oestrous females over dioestrous females, after pre-exposure to odour, their response to females was determined by the cycle day of the vaginal secretion to which they had been exposed. Males pre-exposed to vaginal odour from females carrying large implants of oestrogen preferred to spend more time with females who matched that vaginal odour than mismatching females and to sniff them more. This preference was not seen if the females carried small oestrogen implants or had no replacement oestrogen. This suggests that pro-oestrous females (who are known to have high circulating levels of oestrogen) can, by means of their scent-marking behaviour, attract and keep males nearby until they become receptive.

J. Endocr. (1985) 105, 255–262
Changes in aromatase activity in small ovarian follicles of the domestic fowl (Gallus domesticus) during growth and atresia
Authors: Armstrong D. G.
Published: December 2008

The tritium release assay for measuring aromatase activity was adapted to measure oestrogen production in intact small ovarian follicles of the domestic fowl. The activity was measured in three types of follicle classified as normal, atretic or grossly atretic. Normal follicles were distinguished from atretic by the presence of small haemorrhages on the surface of the atretic follicles. Grossly atretic follicles were identified by their deformed shape.

The aromatase activity in normal and atretic follicles was related to follicular weight, the activity in atretic follicles being less than that in normal follicles. The aromatase activity in grossly atretic follicles was independent of follicular weight. The enzyme activity in this group of follicles was significantly less than that in either normal or atretic follicles. The significance of these results is discussed in relation to the induction of atresia within the small ovarian follicles of the domestic fowl.

J. Endocr. (1985) 105, 297–301
Hormonal regulation of growth hormone binding and responsiveness in adipose tissue and adipocytes of hypophysectomized rats
Authors: Gause I. , Edén S.
Published: December 2008

The hormonal regulation of GH binding and the effects of GH on glucose metabolism were studied in hypophysectomized rats. Male rats (130–140 g) were hypophysectomized and on the day after the operation treatment with one or a combination of two hormones was started and continued for 7 days. The different hormonal treatments were (1) cortisone acetate, (2) insulin, (3) insulin plus cortisone acetate, (4) thyroxine, (5) thyroxine plus cortisone acetate and (6) GH. Glucose metabolism was studied by determining the production of CO2 from [14C]glucose in epididymal fat pads and adipocytes and the incorporation of [14C]glucose into lipids in adipocytes. Binding of GH was measured in cell aliquots using 125I-labelled human GH.

In hypophysectomized control animals, GH binding was decreased to approximately 25% of the binding observed in adipocytes of normal rats. Insulin treatment increased GH binding by approximately 100% and the response to GH was markedly increased. Similar effects were achieved by thyroxine treatment. Basal levels of glucose oxidation were markedly decreased after hypophysectomy but were increased towards normal by insulin or thyroxine treatment. Neither cortisone nor GH treatment had any effect on GH binding or glucose metabolism.

The results show that insulin and thyroxine may be important for the GH receptor and the insulin-like effect of GH in adipocytes.

J. Endocr. (1985) 105, 331–337
Dynamics and control of progesterone receptor synthesis in the fetal uterus of the guinea-pig in organ culture
Authors: Sumida C. , Gelly C. , Pasqualini J. R.
Published: December 2008

Progesterone receptor concentrations increased in fetal guinea-pig uterus in organ culture to as high as 13·15±1·22 pmol/mg DNA without any added steroid, although cytosol and nuclear oestrogen receptor levels were very low (0·41−1·92 pmol/mg DNA). Even after a 3-day exposure to 5×10−8 m-progesterone, which inhibits its own receptor (1·14±0·31 pmol/mg DNA), progesterone receptor levels rose to 8·58±1·39 pmol/mg DNA when progesterone was removed. This replenishment was inhibited by progesterone and 5α-dihydroprogesterone but was not affected by oestradiol, tamoxifen or dexamethasone. The incorporation of [3H]thymidine into nucleic acids was not decreased by progesterone so that its inhibition of its own receptor in the explants was not due to an inhibition of cell replication. Fetal uterine explants from oestrogen-primed fetuses, after an initial decrease in progesterone receptor, also showed a rise to 7 pmol/mg DNA on day 2 which could be decreased by exposure to progesterone and replenished by removal of this hormone (6–8 pmol/mg DNA), the entire process occurring without apparent oestrogen stimulation. Progesterone rather than oestradiol appears to be a key regulator of progesterone receptor synthesis in the fetal guinea-pig uterus, although oestradiol, along with other factors, may also be involved.

J. Endocr. (1985) 105,415–421
Control of plasma levels of growth hormone, glucagon and insulin in ducklings: roles of free fatty acids and somatostatin
Authors: Foltzer Ch. , Strosser M. Th. , Harvey S. , Mialhe P.
Published: December 2008

The effects of plasma free fatty acids (FFA) and somatostatin-14 (S-14) on concentrations of plasma GH, glucagon and insulin were investigated in juvenile ducks. Oleic acid, S-14 or both were infused into 4- to 7-week-old birds and plasma GH, glucagon-like immunoreactivity (GLI), immunoreactive insulin (IRI) and FFA were measured.

An increase in plasma GH and a decrease in GLI but no change in IRI was observed after infusion of 9 mg oleic acid/kg per min. A decrease in plasma GH, FFA and IRI and an increase in plasma GLI was seen after infusion of 800 ng S–14/kg per min. These effects of S-14 on IRI and GLI were abolished when S-14 was infused simultaneously with oleic acid.

It is concluded that FFA have a direct stimulatory effect on GH secretion and an inhibitory effect on glucagon secretion. Somatostatin-14 directly inhibits the secretion of GH and its stimulatory effect on the secretion of glucagon is mediated by a depression in concentrations of plasma FFA. Finally, S-14 has no effect on plasma insulin when basal levels of plasma FFA are maintained.

J. Endocr. (1985) 106, 21–25
Changes in pituitary responsiveness to LH-releasing hormone after acute buserelin treatment: a time-course and dose–response study
Authors: Heather J. D. , Whitehead S. A.
Published: December 2008

The acute in-vivo effects of a potent LH-releasing hormone (LHRH) agonist, buserelin, on LH secretion and pituitary responsiveness to LHRH have been investigated in oestrous rats. Doses of 50, 100 and 250 ng buserelin stimulated LH release in a dose-dependent manner, the peak serum LH concentrations being measured 1 h after the treatment. Thereafter LH levels fell rapidly between 1 and 6 h and by 18 h serum LH concentrations were similar in all groups of animals. Pituitary responsiveness to a challenge with 100 ng LHRH was potentiated by 50 or 100 ng buserelin injected 1 or 2 h before the LHRH challenge. In contrast, 250 ng buserelin completely abolished the LH response to LHRH when tested 1, 2 and 4 h after treatment, but by 6 h a small but attenuated response was observed. Four hours after treatment there was no significant difference in the responses when compared with the saline-treated controls.

J. Endocr. (1985) 106, 27–30
Stimulation of ovine placental lactogen secretion by arachidonic acid
Authors: Huyler S. E. , Butler W. R. , Grandis A. , Mann C. , Figueroa J. P. , Nathanielsz P. W. , Mitchell M. , Handwerger S.
Published: December 2008

To determine whether arachidonic acid stimulates the secretion of ovine placental lactogen (oPL), arachidonic acid was infused as an intravenous bolus into pregnant ewes and fetuses. Plasma oPL concentrations were determined in mothers and fetuses before and for 5 h after infusion. The administration of 12·5 mg arachidonic acid (0·15−0·2 mg/kg, n = 11 experiments) to the pregnant ewes caused an increase in maternal plasma oPL concentrations of 73·9±15·6% (s.e.m.) and 60·8±18·1% above the pretreatment concentrations at 4 and 5 h respectively P<0·01 in each instance). The infusion of 25 mg arachidonic acid (n = 8) caused increases of 96·0±19·1% and 100·3±26·4% (P<0·005), and the stimulation was not inhibited by the cyclo-oxygenase inhibitors indomethacin and ibuprofen. In contrast to arachidonic acid, vehicle alone or palmitic acid had no effects on plasma oPL concentrations. Despite the increase in maternal plasma oPL concentrations, plasma oPL concentrations in the fetus remained unchanged after the maternal infusions. The infusion of arachidonic acid (0·5–1·5 mg/kg) directly into six fetuses had no effects on either fetal or maternal oPL concentrations. These studies indicate that (1) arachidonic acid stimulates maternal plasma oPL concentrations but has no effect on fetal oPL concentrations and (2) the stimulation of oPL secretion is not due to the conversion of arachidonic acid to prostaglandins or other cyclo-oxygenase products.

J. Endocr. (1985) 106, 43–47
[3H]Prostaglandin accumulation in vitro by baboon uterus
Authors: Jones M. A. , Kuehl T. J. , Harper M. J. K.
Published: December 2008

Uteri from mature baboons at various stages of the menstrual cycle were collected at autopsy. Transverse slices of the uteri were incubated with [3H]prostaglandins in Tyrode's buffer. Bound and free ligands were separated by filtration. Prostaglandin (PG) accumulation by the tissue slices was evaluated as a function of incubation time, PG type and concentration, temperature, wet weight of tissue and stage of the menstrual cycle. There was no significant difference in PG accumulation in response to PG type (PGE2 or PGF2α) or stage of the menstrual cycle. These results from baboon uteri were compared with those using baboon oviducts and also rabbit uteri and oviducts. Unlike the rabbit tissues, the baboon oviducts and uterine tissues did not exhibit specific net accumulation of prostaglandins.

J. Endocr. (1985) 106, 49–53
Effect of somatostatin and thyrotrophin-releasing hormone on the levels of growth hormone in the circulation of the chronically catheterized pig fetus in utero
Authors: Spencer G. S. G. , Garssen G. J. , Colenbrander B. , Meijer J. C.
Published: December 2008

The effects of i.v. administration of thyrotrophin-releasing hormone (TRH) and of somatostatin on circulating plasma levels of porcine GH in the chronically catheterized pig fetus have been examined. Growth hormone levels increased markedly (P<0·01) following TRH administration, but there was no change in thyroxine levels by 1 h after treatment. Administration of somatostatin caused a significant (P<0·05) decrease in mean GH levels, but the response was variable between pigs. Saline administration had no significant effect on GH levels. These results suggest that the mechanisms regulating postnatal GH release are present in the fetal pig, but may not be fully developed 8–12 days before delivery.

J. Endocr. (1985) 106, 121–124
Evidence for a stimulatory β-adrenergic component in the release of the ovulatory LH surge in pro-oestrous rats
Authors: Al-Hamood M. H. , Gilmore D. P. , Wilson C. A.
Published: December 2008

The effect on ovulation of intraventricular infusions of noradrenaline, adrenaline and various pharmacological agents acting on the adrenergic receptor subtypes were investigated in cyclic female rats on the day of pro-oestrus. The inhibitory effects on ovulation of the different infusions were monitored by administering the drugs before 11.00 h (several hours before the critical period for the ovulatory LH surge). In experiments designed to show how the drugs under investigation might stimulate ovulation, pentobarbitone sodium (35 mg/kg) was given at 14.30 h; this anaesthetic inhibits ovulation and its effects can be overcome by substances that advance the preovulatory LH surge.

Noradrenaline (an α-agonist) stimulated ovulation when administered on the morning of pro-oestrus to rats injected with pentobarbitone early in the afternoon of the same day. Phenoxybenzamine and phentolamine (non-selective α-antagonists) and clonidine (a selective α2-agonist) all inhibited ovulation when infused on the morning of pro-oestrus. Yohimbine (a moderately selective α2-antagonist) neither stimulated nor inhibited ovulation.

Both isoprenaline (a non-selective β-agonist) and fenoterol (a selective β2-agonist) stimulated ovulation in pentobarbitone-treated rats when administered on the morning of pro-oestrus and fenoterol was also able to overcome the pentobarbitone block when infused later in the afternoon. Propranolol (a non-selective β-antagonist) and metoprolol (a selective β1-antagonist) were stimulatory only when administered in the afternoon.

Adrenaline (both an α- and β-agonist), prenalterol (a selective β1-agonist), atenolol (a selective β1-antagonist) and ICI 118, 551 (a selective β2-antagonist) neither stimulated nor inhibited ovulation.

The effect of intraventricular infusions of two selected β-adrenergic drugs was also investigated in ovariectomized rats primed with 2 μg oestradiol benzoate 48 h previously. Isoprenaline and fenoterol were able to stimulate LH release at 40 and 10 min respectively after their administration.

These results suggest a possible involvement of a stimulatory β2-adrenergic component in the neural regulation of the preovulatory LH surge along with the well-documented α-stimulatory component, which together may mask the possible inhibitory effects of a β1-adrenergic system.

J. Endocr. (1985) 106, 143–151
Peroxidase-catalysed iodotyrosine formation in dispersed cells of mouse extrathyroidal tissues
Authors: Banerjee R. K. , Bose A. K. , Chakraborty T. K. , De S. K. , Datta A. G.
Published: December 2008

A method has been developed for the isolation of cells, high in iodine uptake and peroxidase activity, from the stomach and submaxillary gland of mice. The isolated cells could produce protein-bound monoiodotyrosine, di-iodotyrosine and an unknown iodocompound. The reactions were catalysed by peroxidase and were sensitive to antithyroid drugs and haemoprotein inhibitors but were insensitive to TSH. In-vitro iodination of stomach or submaxillary soluble proteins with the respective peroxidase yielded similar iodocompounds while thyroxine was produced when thyroglobulin was used instead.

J. Endocr. (1985) 106, 159–165
Prolactin permits the expression of a circadian variation in lipogenic responsiveness to insulin in hepatocytes of the golden hamster (Mesocricetus auratus)
Authors: Cincotta A. H. , Meier A. H.
Published: December 2008

Lipogenesis was determined at two times (07.00 and 16.00 h) during a 14-h daily photoperiod (08.00–22.00 h) in freshly prepared hamster hepatocytes with or without addition of insulin. The hamsters were pretreated for 5 days with bromocriptine (to inhibit prolactin secretion), bromocriptine and prolactin replacement, or control saline injections. Lipogenesis was determined by incorporation of [14C]acetate into total cell lipids over a 30-min interval. Lipogenesis was three times greater at 07.00 than at 16.00 h and insulin was effective in stimulating further lipogenesis only at 07.00 h. Bromocriptine pretreatment severely reduced incorporation of radiolabel at 07.00 h to levels comparable with controls at 16.00 h and completely inhibited the stimulatory effect of insulin at 07.00 h. Prolactin replacement in bromocriptine-treated hamsters reversed the inhibitory effect of bromocriptine on hepatocyte lipogenesis and promoted dramatic lipogenic responses to insulin at 07.00 h. These results indicate that insulin stimulates hepatic lipogenesis only during some portion of a day and that prolactin facilitates the lipogenic response.

J. Endocr. (1985) 106, 173–176
Central opioids: a possible role in parturition?
Authors: Leng G. , Mansfield S. , Bicknell R. J. , Dean A. D. P. , Ingram C. D. , Marsh M. I. C. , Yates J. O. , Dyer R. G.
Published: December 2008

Pregnant rats were implanted with subcutaneous minipumps to deliver either naloxone or saline. The time-course of subsequent parturition was different between the two groups: the interval between successive births was significantly shorter for the naloxone-treated rats. This supports the hypothesis that the opioid innervation of the neurohypophysis, which is known to influence oxytocin release profoundly, has a physiological role in parturition. To test the further hypothesis that this role is particularly important in a stressful environment, pregnant rats, again implanted with minipumps, were regularly transferred, at 15-min intervals beginning with the birth of the first pup, between their normal cage and the unfamiliar environment of a glass observation chamber. No difference was noted between the time-courses of parturition for the naloxone- and saline-treated groups, although the time-courses were markedly altered from those observed in rats not subjected to an unfamiliar environment. We conclude that opioid modulation of oxytocin release may play a role in 'spacing' the delivery of successive births during normal parturition.

J. Endocr. (1985) 106, 219–224
Changes in 3β-hydroxy-Δ5-steroid dehydrogenase activity in granulosa tissue during the ovulatory cycle of the laying hen (Gallus domesticus)
Authors: Armstrong D. G.
Published: December 2008

The object of this study was to examine changes in the activity of granulosa 3β-hydroxy-Δ5-steroid dehydrogenase during the ovulatory cycle of the domestic fowl. The enzyme activity in granulosa tissue from the largest follicle increased significantly during the period 8–14 h before an expected ovulation. The increase in activity occurs before the preovulatory surge of LH and near the time of lights off. During the 4–8 h period before an ovulation, i.e. the time of maximal plasma LH concentrations, 3β-hydroxy-Δ5-steroid dehydrogenase activity decreased in granulosa tissue from the largest follicle. This observation is explained by proposing that the enzyme is inhibited by the large amounts of progesterone found in the tissue at this time.

The results indicate that important biochemical changes are taking place within granulosa tissue of the largest ovarian follicle before the preovulatory LH surge.

J. Endocr. (1985) 106, 269–273
Identification of amino acid transport systems stimulated by FSH in rat testes
Authors: da Cruz Curte A. , Wassermann G. F.
Published: December 2008

Testes of 12-day-old rats preincubated (90 min) and incubated (60 min) with FSH in Krebs–Ringer bicarbonate buffer (KRB) increased their uptake of [14C]methylaminoisobutyric acid and [14C]aminoisobutyric acid. The hormone was ineffective in sodiumfree KRB. Transport of [14C]aminoisobutyric acid in the presence of methylaminoisobutyric acid (MeAIB; 30 mmol/l) was not stimulated by FSH, and uptake of [14C]cycloleucine was not increased by FSH in any of the experimental conditions used.

It was concluded that in immature rat testes FSH affects only the sodium-dependent system which permits the transport of MeAIB (transport system A) and has no effect on the sodium-independent system which prefers leucine (system L) or the sodium-dependent system which does not transport MeAIB (system ASC).

J. Endocr. (1985) 106, 291–294
Relationship of oestrogen and progesterone and their oviductal receptors in laying and non-laying 5-year-old hens
Authors: Okulicz W. C. , Fournier D. J. , Esber H. , Fredrickson T. N.
Published: December 2008

This study focuses on the relationship of ageing to reproductive function in the domestic hen. Reproductive function was assessed by egg-laying records of hens from the same flock of 4, 5 and 6 years of age. Egg laying decreased with advancing age and the percentage of non-laying hens increased. During an ovulatory cycle, plasma levels of oestrogen and progesterone (including the preovulatory surge) were similar in both the 5-year-old and 1-year-old laying hens. In both young and old non-laying hens, the preovulatory surge of progesterone was absent. Levels of oestrogen were similar for all hens, but the oestrogen-dependent oviduct was atrophied in non-laying 5-year-old hens. This reduction in oviductal size was correlated with reduced levels of magnal nuclear oestrogen receptor and cytosol progesterone receptor. These results suggest a refractoriness of the oviduct to oestrogen stimulation in the ageing hen.

J. Endocr. (1985) 106, 343–348
An examination of the proposed roles of placental lactogen in the ewe by means of antibody neutralization
Authors: Waters M. J. , Oddy V. H. , McCloghry C. E. , Gluckman P. D. , Duplock R. , Owens P. C. , Brinsmead M. W.
Published: December 2008

The physiological role of placental lactogen (PL; chorionic somatomammotrophin) in the ewe has been investigated by infusion of ewes (n = 3) on day 131 of pregnancy with sufficient ovine PL (oPL) antibody to neutralize circulating oPL for at least 12 h. Effectiveness of the antibody neutralization was defined both in vitro and in vivo according to rigorous criteria. Control ewes (n = 3) were infused simultaneously with an equivalent amount of pooled goat gamma globulin. Since both sets of ewes had previously been catheterized with jugular, utero-ovarian and femoral vein catheters and a femoral arterial catheter, it was possible to measure whole body glucose kinetics as well as muscle and uterine glucose, free fatty acid (FFA) and 3-hydroxybutyrate extraction. In addition, plasma levels of insulin, GH, prolactin, insulin-like growth factor-I (IGF-I), IGF-II, progesterone and cholesterol were determined in femoral arterial samples.

Neutralization of maternal oPL did not significantly affect whole body glucose metabolism, uterine and muscle glucose extraction, or 3-hydroxybutyrate extraction by muscle. A trend towards lower plasma FFA levels was observed after prolonged infusion, but was not statistically significant. However, plasma insulin levels rose significantly during antibody infusion after an early fall. These observations are rationalized in terms of the known requirements of ruminant metabolism during pregnancy, and contrasted with the accepted model for the role of human PL in the metabolic adjustments of pregnancy.

No change in plasma IGF-I, IGF-II or GH was observed, providing no support for the concept that oPL is responsible for maternal somatomedin generation during pregnancy. Similarly, plasma prolactin did not differ between antibody-treated and control groups. Finally, antibody neutralization had no influence on either plasma progesterone or cholesterol, mitigating against a role for oPL in progesterone production during late pregnancy in the ewe.

J. Endocr. (1985) 106, 377–386
SALMONID MELANIN-CONCENTRATING HORMONE INHIBITS CORTICOTROPHIN RELEASE
Authors: Baker B.I. , Bird D.J. , Buckingham J.C.
Published: December 2008

Melanin-concentrating hormone (MCH) is a neural peptide associated with colour change in fishes. We show here that it also inhibits corticotrophin (ACTH) secretion. Synthetic salmonid MCH at a concentration of 100 pmol/l reduced the in-vitro release of ACTH by pars distales (pDs) taken from stressed trout. At lower concentrations (10 pmol/l) the peptide inhibited CRF-41-induced secretion of ACTH by pDs removed from unstressed trout, while at higher concentrations (10 nmol/l) it reduced the corticotrophic response of rat pituitary tissue to CRF-41.
Pineal denervation by cervical sympathetic ganglionectomy suppresses the role of photoperiod on pregnancy or pseudopregnancy, body weight and moulting periods in the mink (Mustela vison)
Authors: Martinet L. , Allain D. , Chabi Y.
Published: December 2008

In mink, termination of the delayed implantation period, following reactivation of the corpora lutea, and onset of the spring moult are associated with a rise in prolactin secretion triggered by increasing daylength, while decreasing daylength induces the autumn moult. To establish whether suppression of the function of the pineal rendered the mink unresponsive to daylength changes, the superior cervical ganglion was removed bilaterally 2–4 weeks before mating. Intact and operated females were then left outdoors or were put under a lighting regime of either 15 h light: 9 h darkness (15L: 9D) or 8L: 16D. In July, at the end of the spring moult, the 15L: 9D lighting regime was changed to one of 8L: 16D. Under artificial photoperiods ganglionectomy suppressed the stimulatory role of long days and the inhibitory role of short days on prolactin secretion, and consequently on progesterone secretion and spring moult. Neither was the autumn moult, induced early in intact females by the change to a short photoperiod, advanced in ganglionectomized females, showing that the latter were unresponsive to the artificial modification of the photoperiod. However, in animals kept outdoors, prolactin and progesterone secretion and spring moult were not changed by ganglionectomy. Increase in body weight and autumn moult were only slightly delayed by the operation suggesting that other environmental factors had replaced the synchronizing effect of the daylength changes. Alternatively the desynchronization between intact females responsive to photoperiodism and those rendered unresponsive may be too slow to be observed soon after ganglionectomy.

J. Endocr. (1985) 107, 31–39
Effects of hyperprolactinaemia on reproduction in male mice
Authors: Nonomura M. , Hoshino K. , Harigaya T. , Hashimoto H. , Yoshida O.
Published: December 2008

Hyperprolactinaemia induced by pituitary isografts in male host mice was confirmed by radioimmunoassay, but plasma testosterone levels determined by radioimmunoassay in these mice showed no changes. Immunoenzyme electron microscopic observations revealed large spherical-shaped immunoreactive prolactin granules in pituitary grafts in male hosts, regardless of the sex of the donor mice, indicating the disappearance of sexual dimorphism in prolactin-producing cells in hyperprolactinaemic mice. In hyperprolactinaemic host mice the male accessory sex glands, particularly the seminal vesicle and the ventral prostate, exhibited considerable proliferation and significant increase in weight. These phenomena do not seem to be mediated by the increased action of testosterone. Such biological effects in host mice were much greater when the donor was female rather than male, and were more noticeable in C57BL mice than in C3H mice.

J. Endocr. (1985) 107, 71–76
Prolactin and calcium metabolism in pregnant ewes
Authors: Barlet J. -P.
Published: December 2008

The effect of ovine prolactin on intestinal Ca absorption and placental Ca transfer was studied in pregnant ewes. Six groups of five animals bearing a single fetus were used and injected s.c. daily between days 121 and 135. The first group was given 0·1 μg ovine prolactin/kg body wt per day, the second 0·1 μg ovine prolactin/kg body wt per day plus 0·1 μg 1α-hydroxycholecalciferol (1α-OH-D3)/kg body wt per day, the third 0 ·1 μg ovine prolactin/kg body wt per day plus 0·20 units calcitonin/kg body wt per day, the fourth 2 μg bromocriptine/kg body wt per day, the fifth 2 μg bromocriptine/kg body wt per day plus 0·1 μg ovine prolactin/kg body wt per day, and the sixth were controls injected with vehicle alone. The intestinal Ca absorption was measured on a duodenal loop tied off in vivo on day 136 and placental Ca transfer was evaluated between days 129 and 136. Ovine prolactin stimulated both intestinal Ca absorption and placental Ca transfer; these effects were further increased by 1α-OH-D3. Calcitonin had no effect on ovine prolactin-stimulated intestinal Ca absorption, but blunted the influence of ovine prolactin on Ca placental transfer. Bromocriptine decreased both intestinal Ca absorption and Ca placental transfer but these effects of bromocriptine were overcome by simultaneous injection of ovine prolactin.

J. Endocr. (1985) 107, 171–175
Progestin receptor in the thymus of ovariectomized immature rats
Authors: Fujii-Hanamoto H. , Seiki K. , Sakabe K. , Ogawa H.
Published: December 2008

By using the synthetic progestin promegestone (R5020), the location and characteristics of progestin receptors in the thymic cytosols from immature ovariectomized oestrogen-treated rats were determined. Tritiated promegestone bound to the cytosol with high affinity (dissociation constant (Kd) = 2·0± 0·3 nmol/l; promegestone > progesterone > oestradiol > corticosterone ≃testosterone) and low capacity (number of binding sites (Bmax) = 143·0 ±13·5fmol/mg protein). These values were appropriate for progestin receptors. However, an extremely high dose of dexamethasone (10 μmol/l; 1000-fold excess over [3H]promegestone) slightly inhibited the specific binding. Progestin receptors were predominantly located in the reticuloepithelial (RE)-cell fraction, with few in the thymocyte T-cell fraction. The receptor level was raised (24·9 ± 11·3 (s.e.m.) to 143·0 ± 13·5 fmol/mg protein) with increased doses of oestrogen (0–30 μg) administered in vivo. Using sucrose density gradient ultra-centrifugation it was found that the thymic progestin receptor had a sedimentation coefficient of 9 S under low-salt conditions. These results clearly suggest that the thymus of the immature female rat contains a specific progestin receptor which is mainly located in the RE cells.

J. Endocr. (1985) 107, 223–229
Effect of stress administered during pregnancy on the development of fetal testes and their subsequent function in the adult rat
Authors: Pollard I. , Dyer S. L.
Published: December 2008

When maternal stress, containing a large anxiety component, was administered during pregnancy there was a significant decrease in 3β-hydroxysteroid dehydrogenase (3β-HSD) activity in the fetal testis from days 16 to 20 of gestation, but not at birth nor in the first week after birth. However, persistent effects were found in adult males of 90 days of age. Basal testosterone concentrations in both plasma and testes and testicular 3β-HSD activity were significantly lower whilst basal plasma progesterone concentrations were significantly higher in the stressed group. When the stressed offspring were subjected to short-term stress (one session), their plasma testosterone concentration was significantly below that of the controls. It is suggested that suppressed gonadotrophin secretion during critical periods of development alters fetal testicular function, and that raised circulating levels of stress-induced hormones such as β-endorphin may be responsible for changes in gonadotrophin secretion.

J. Endocr. (1985) 107, 241–245
Electrical responses of cultured thyroid cells to serotonin
Authors: McGrath P. A. , Bourke J. R. , Huxham G. J. , Manley S. W.
Published: December 2008

Cultured porcine thyroid cells, maintained in the differentiated state by dibutyryl cyclic AMP, responded to serotonin (5-HT; 10 nmol/l to 1 μmol/l) with a depolarization of the membrane potential, but did not respond to histamine (100 μmol/l) or dopamine (1 μmol/l). The resting membrane potential of these cells was about − 71 mV, maximal concentrations of 5-HT (1 μmol/l) inducing a depolarization to approximately −53 mV. Methysergide or phenoxybenzamine, but not propranolol, abolished the response to 5-HT. Sensitivity to 5-HT was reduced by previous exposure of cultures to TSH, the β-adrenoceptor agonist salbutamol or 5-HT itself.

J. Endocr. (1985) 107, 397–401
Thyroxine concentrations and secretion rates in relation to pregnancy, lactation and energy balance in goats
Authors: Riis P. M. , Madsen A.
Published: December 2008

Plasma thyroxine (T4) concentrations were measured during pregnancy and lactation in goats on diets with different energy concentrations to study the role of T4 secretion in metabolic adaptation to pregnancy and lactation. Thyroxine distribution space (the volume of fluid required to dissolve the total pool of circulating T4 at a concentration equal to that in the plasma) and secretion rates were determined by using 125I-labelled T4 at different stages of lactation and pregnancy.

Plasma concentrations of T4 increased during lactation and reached maximum levels 4–5 months after giving birth. They then remained fairly constant for the following 2–3 months until the goats became pregnant again. Thyroxine concentrations decreased slightly during pregnancy and showed a sudden drop at the onset of lactation. Minimum concentrations were observed during the first 2–3 weeks of lactation after which time concentrations increased slowly. Average concentrations for goats on a low-energy diet were consistently lower than those in goats on a high-energy diet. The mean secretion rate was 10·4 nmol day−1 kg body wt−0·75. The distribution spaces were much lower than the total extracellular space. The average distribution space in non-pregnant and pregnant goats was 11 and 5·3% of the body weight respectively.

The decrease in T4 secretion rate and T4 distribution space during pregnancy is considered to be part of a homeorhetic adaptation to the condition. The drop in T4 secretion rate at the onset of lactation appears to be a homeostatic adaptation to a decreased fuel supply, similar to the situation with fasting or energy malnutrition.

J. Endocr. (1985) 107, 421–427
Effect of epidermal growth factor on reproductive function of ewes
Authors: Shaw G. , Jorgensen G. I. , Tweedale R. , Tennison M. , Waters M. J.
Published: December 2008

Adult Merino ewes were infused via the jugular vein with either saline (n = 5) or epidermal growth factor (EGF) (4·2 μg/kg per h, n = 6) for 24 h in either the luteal phase or the follicular phase of the oestrous cycle and reproductive function was examined.

Infusion of EGF during the luteal phase caused no detectable change in plasma progesterone or prolactin concentrations over a 7-day period compared with the controls.

Infusion of EGF during the follicular phase suppressed the oestrous rise in plasma oestradiol. Luteinizing hormone pulse amplitude was increased and pulse frequency was decreased by the end of the infusion. All control ewes had a pro-oestrous LH surge and mated, but the LH surge and oestrus were prevented by EGF infusion. Nevertheless, plasma progesterone levels rose subsequently in the EGF-infused ewes in parallel with the control ewes, suggesting that the preovulatory follicle had luteinized. Both LH and FSH rose over the 7 days after EGF infusion to levels similar to those in ovariectomized ewes.

Thus EGF appears to inhibit follicular oestradiol production, although it does not affect luteal progesterone production or follicular luteinization. We suggest that the alteration in gonadotrophin secretion patterns results from a disturbance of feedback mechanisms between the ovary and the hypothalamopituitary axis, although a direct effect in the brain or the pituitary gland cannot yet be excluded.

J. Endocr. (1985) 107, 429–436
GROWTH HORMONE-RELEASING FACTOR ANALOGUE (hGRF1-29NH2): IMMUNOREACTIVE-GRF PLASMA LEVELS AFTER INTRAVENOUS AND SUBCUTANEOUS ADMINISTRATION
Authors: Rafferty B. , Poole S. , Clarke R. , Schulster D.
Published: December 2008

A homologous radioimmunoassay (RIA) system for human growth hormone-releasing factor 1-29NH2 (hGRF 1-29-NH2) was developed and applied to the measurement of immunoreactive (IR) concentrations of the peptide in anaesthetized rats to determine some of its pharmacokinetics after i.v. and s.c. administration. Analysis of the biphasic disappearance curve of IR-hGRF-1-29NH2 from plasma after i.v. injection (10μg) gave values for the half-lives of the initial distribution phase (α) and for the elimination phase (β) of 1.9 ± 0.2 min and 10.4 ± 0.2 min respectively. There was rapid uptake of the peptide from the site of s.c. injection but comparison of areas under the plasma IR-hGRF1-29NH2/time curves showed that the estimated total amount in the circulation after s.c. injection was only 4% of that obtained after i.v. administration. A large degree of degradation of the peptide is indicated either at the site of injection or during transfer to plasma; this susceptibility to rapid breakdown is reflected in the short half-life of the peptide in the circulation. Therefore the measurement of the above parameters is a prerequisite when assessing potency of GRF analogues in-vivo and when implementing suitable dosage regimens for clinical purposes.
The involvement of calcitonin in the reproductive physiology of the rainbow trout
Authors: Björnsson B. Th. , Haux C. , Förlin L. , Deftos L. J.
Published: December 2008

Plasma from rainbow trout (Salmo gairdneri) of both sexes was sampled every month throughout an annual reproductive cycle in order to elucidate possible relationships between plasma calcitonin and free and protein-bound calcium and magnesium. This was then studied in greater detail around the time of ovulation in the female fish.

The plasma levels of the parameters studied were stable in males during the whole annual cycle and were similar to the levels found in females during at least 6 months of the cycle. Plasma levels of protein-bound calcium and magnesium as well as calcitonin were raised in the females for 6, 4 and 3 months respectively. These increases occurred concomitantly during the months before and after ovulation, but no correlations between the protein-bound ion and calcitonin levels were found during this period. With the exception of a decrease observed in December, the free plasma levels of calcium and magnesium were stable in both males and females throughout the cycle. This decrease was attributed to the high production rate of the yolkprotein precursor vitellogenin, which binds both calcium and magnesium.

In the detailed study on the ovulating females, plasma calcitonin levels were high 4 weeks before, and continued to increase until the time of ovulation, when a sharp decrease towards normal was noted. The free plasma calcium and magnesium levels were not affected, while the protein-bound levels of calcium and magnesium were found to decline towards normal for the duration of the experiment, without any obvious correlation with the time of ovulation. Regulation of calcitonin secretion seems not to be directly related to free plasma calcium levels, and it is suggested that ovarian steroids and/or gonadotrophins are involved. It is still possible, however, that calcitonin in rainbow trout may play a role in protecting the skeleton during periods of the increased calcium demand of oogenesis.

It is concluded that calcitonin plays a specific role in the reproductive physiology in female rainbow trout, which is apparently not reflected by measurable changes in blood calcium.

J. Endocr. (1986) 108, 17–23
Prolactin stimulates Na+-K+-ATPase activity located in the outer renal medulla of the rat
Authors: Pippard C. , Baylis P. H.
Published: December 2008

The effect of rat prolactin on rat renal Na+-K+-ATPase activity was investigated by a cytochemical technique. Rat prolactin caused stimulation of Na+-K+-ATPase activity only in the outer medulla of the kidney, and not in renal cortical structures. Peak enzyme activity in cultured rat renal segments occurred after tissue had been exposed to rat prolactin for 2 min, and the time of maximal stimulation did not vary with the concentration of prolactin. There was a curvilinear response in Na +-K+-ATPase activity over the rat prolactin concentration range, 0·04–40 ng/1, but higher prolactin concentrations caused inhibition of enzyme activity. Na+-K+-ATPase response was totally blocked by specific rat prolactin antiserum. Human prolactin had no consistent effect on rat medullary Na+-K+-ATPase activity. Addition of specific tri-iodothyronine and arginine vasopressin antisera to rat prolactin was without effect, confirming that the stimulatory action of rat prolactin on Na+-K+-ATPase was not due to contamination with these hormones which are known to stimulate this enzyme.

J. Endocr. (1986) 108, 95–99
Changes in aromatase activity in the neuroendocrine tissues of red grouse (Lagopus lagopus scoticus) in relation to the development of long-day refractoriness
Authors: Sharp P. J. , Armstrong D. G. , Moss R.
Published: December 2008

Changes in aromatase activity in the neuroendocrine tissues of captive male and female red grouse (Lagopus lagopus scoticus) were measured during a photoinduced breeding cycle. The gonads enlarged and subsequently regressed, as a consequence of the development of long-day refractoriness, within 84 days of transferring photoinsensitive birds from a non-stimulatory to a stimulatory daylength. The object of the study was to determine whether long-day refractoriness is related to an increase in aromatase activity in the neuroendocrine tissues which might result in a greater inhibitory action of locally produced oestrogens on the release of LH-releasing hormone.

Aromatase activity was measured and found to be present in the anterior pituitary gland, the anterior/ preoptic hypothalamus, the posterior hypothalamus and the hyperstriatum dorsale. It was higher in the hypothalamus than in the hyperstriatum dorsale and higher in the posterior than in the anterior/preoptic hypothalamus.

Aromatase activity in the posterior hypothalamus was higher in males than in females in short-day photosensitive and reproductively active birds, but not in long-day refractory birds. A similar sex difference was also observed in the anterior/preoptic hypothalamus in reproductively active birds.

Hypothalamic aromatase activity in both sexes was directly related to gonadal function, being highest in reproductively active birds and lowest in long-day refractory birds.

It is concluded that the development of long-day refractoriness is not related to an increase in aromatase activity in the neuroendocrine tissues. The decrease in aromatase activity in the neuroendocrine tissues in long-day refractory birds parallels a decrease in aggressive and territorial behaviour.

J. Endocr. (1986) 108, 129–135
Corticotrophin-releasing factor-like immunoreactivity and bioactivity of human fetal and adult hypothalami
Authors: Ackland J. F. , Ratter S. J. , Bourne G. L. , Rees L. H.
Published: December 2008

Corticotrophin releasing factor-like immunoreactivity (CRF-LI) and bioactivity, and arginine vasopressinlike immunoreactivity (AVP-LI) have been measured in extracts of human fetal and adult hypothalamic tissue and their development with the gestational age of the fetuses (12–27 weeks) studied. CRF-LI was measured by a radioimmunoassay developed for ovine corticotrophin-releasing factor (oCRF-41). Corticotrophin-releasing factor bioactivity was measured in a rat isolated anterior pituitary cell perfusion system. CRF-LI and bioactivity and AVP-LI were all detectable in fetal hypothalamic extracts from 12 to 13 weeks of gestational age. CRF-LI was also present in human fetal pituitary glands from 12 weeks of gestational age. The concentration of CRF-LI in the fetal hypothalamic extracts (9·2±11·4 ng/g, mean ± s.e.m., n = 33) showed no significant correlation with the gestational age of the fetuses. However the concentration of AVP-LI (25·0–36·8 ng/g, n = 17) did show a positive correlation (r = 0·508, P<0·05) with gestational age, as did the concentration of CRF bioactivity (471·3–556·3 ng ACTH released/g tissue, n = 13, r = 0·725, P < 0·01).

The CRF bioactivity of all fetal hypothalamic extracts was potentiated by the addition of synthetic human (h)AVP, but the bioactivity of the adult hypothalamic extracts was not, presumably because of the higher levels of AVP-LI already present in the adult extracts. Pretreatment of tissue extracts with antisera to oCRF-41 and/or hAVP reduced the CRF bioactivity of all hypothalamic extracts. Sephadex chromatography of fractions which co-eluted with synthetic oCRF-41 or hAVP contained CRF bioactivity and this bioactivity was potentiated when synthetic hAVP or oCRF-41, respectively, were added to the fractions. However, a larger molecular weight form of CRF-LI (8000–10 000 daltons), which was observed only in fetuses of 20 weeks of gestational age or less, did not contain any significant CRF bioactivity.

J. Endocr. (1986) 108, 171–180
Sex difference in the cytosolic and nuclear distribution of androgen receptor in mouse submandibular gland
Authors: Kyakumoto S. , Kurokawa R. , Ohara-Nemoto Y. , Ota M.
Published: December 2008

Cytosol and nuclear androgen receptors in submandibular glands of male and female mice were measured by an exchange assay at 0 °C. The binding of [3H]methyltrienolone to cytosol receptors in females was mostly saturated within a short period of incubation (3 h), whereas the saturation was much slower in males; suggesting that almost all of the cytosol receptors were unoccupied in females and the receptors were partially occupied in males. Nuclear receptors were extracted with pyridoxal 5′-phosphate (5 mmol/l) from nuclear fractions with 93–95% efficiency. The exchange of the bound steroids occurred by 24–48 h at 0 °C, suggesting that most of the nuclear androgen receptor was occupied. The binding was low at higher temperatures, probably due to inactivation of the receptor. Scatchard analysis showed that the apparent dissociation constants of cytosol and nuclear receptors were similar (0·8 and 0·9 nmol/l respectively) in both sexes. On the other hand, the number of androgen-binding sites in the nucleus was much higher in males than in females (1052 fmol/mg DNA and 32 fmol/mg DNA respectively), while the number in the cytosol was higher in females than in males (512 fmol/mg DNA and 368 fmol/mg DNA respectively). These observations show that androgen receptors exist mainly (74%) in the nuclei of males, while they exist mostly (94%) in the cytosol of females.

J. Endocr. (1986) 108, 267–273