bluuebunny/crossref_metadata_2025 huggingface dataset:
Gonadotrophin releasing hormone receptors and the response of pituitary gonadotrophs in culture
Authors: Bérault A. , de Almeida Catanho M.-T. Jansem , Théoleyre M. , Jutisz M.
Published: December 2008

We have investigated the effect of the time of culture on cell number, cell content of LH, cell responsiveness to gonadotrophin releasing hormone (GnRH) and binding parameters of GnRH in rat anterior pituitary cells in culture. Although a decrease in the cell number was observed during the culture period, the cell content of LH remained unchanged. The receptor affinity (Ka) in acutely dispersed cells was 0·86 × 107l/mol for [3H]GnRH and 1·36 × 1010l/mol for a highly potent agonist, d-Ser(But)6]GnRH(1–9)nonapeptide-ethylamide (GnRH-A). The affinity and binding capacity (0·3 fmol/106 cells) for iodinated GnRH-A did not change significantly during the 6-day culture period. On the contrary, the values of Ka and binding capacity (257 fmol/106 cells) for tritiated GnRH decreased by about 50% betweeen days 1 and 6 of culture. Our results suggest that 125I-labelled GnRH-A binds mostly to high-affinity and low-capacity receptor sites, while [3H]GnRH, which must be used at a higher concentration, also binds to low-affinity, high-capacity binding sites and is therefore useless for the measurement of GnRH receptor binding affinity and binding capacity. Since the biological response of the cells to GnRH increased with the time of culture, it is concluded that although GnRH action is receptor-mediated, binding capacity and biological activity are not necessarily correlated.
Hormonal changes in the immature rat after administration of pregnant mare serum gonadotrophin: influence of body weight
Authors: Wilson C. A. , ter Haar M. B. , Bonney R. C. , Buckingham J. , Dixson A. F. , Yeo T.
Published: December 2008

We have shown previously that pregnant mare serum gonadotrophin (PMSG) induces ovulation only in rats weighing over 60 g on the day of injection. The under-60 g rats do not ovulate although they secrete a preovulatory surge of a pleiomorphic form of LH. Presumably this pleiomorph is inactive.

Comparisons were made of plasma hormone concentrations in rats treated with PMSG that weighed over and under 60 g. The measurements were made on samples taken between 13.00 and 22.00 h on the day of the expected preovulatory LH surge. Prolactin and corticosterone levels were lower in the lighter group compared with the heavier group. A midday pulse of GH detected in the over-60 g animals did not occur in the under-60 g group. Levels of ACTH were slightly higher in the under-60 g rats and together with the low corticosterone concentrations indicate adrenal insensitivity. Oestradiol, progesterone and TSH concentrations were the same in the two groups. Since progesterone secretion is under LH control, the 'inactive' pleiomorphic form of LH must have steroidogenic activity. There was an indication that the under-60 g rats also secreted a pleiomorphic form of FSH.

Reports in the literature indicate that prolactin, corticosterone and GH have a positive modulatory influence on natural puberty. They may also influence precocious puberty induced by PMSG, since in the unresponsive under-60 g rat plasma levels of these three hormones were low. Perhaps the release of one or more of these hormones is dependent upon the physical maturity of the animal as represented by body weight.
Androgen 5α-reductase and 3α-hydroxysteroid dehydrogenase activities in ventral prostate epithelial and stromal cells from immature and mature rats
Authors: Orlowski J. , Bird C. E. , Clark A. F.
Published: December 2008

To study androgen-mediated differentiation in the rat ventral prostate, we separated the two principal cell types (epithelial and stromal) derived from prostates of immature and mature rats on two continuous Percoll gradients. Cells were immediately placed in culture medium. Testosterone metabolism by the two prostatic cell types was evaluated using [3H]testosterone and quantifying the formation of 5α-[3H]dihydrotestosterone (5α-DHT) and 5α-[3H]androstane-(3α or 3β), 17β-diols. In epithelial cells from both immature and mature rat prostates the major testosterone metabolites were 5α-DHT and 5α-androstane-3α, 17β-diol. Stromal cells metabolized less testosterone than did the epithelial cells. Differences in the relative levels of the various metabolites were observed for the two age groups.

To examine in more detail the changes in testosterone metabolism observed in vitro both types of cells and unfractionated cells from immature and mature rat prostates were assayed for testosterone 5α-reductase (using testosterone as substrate) and 3α-hydroxysteroid dehydrogenase (using 5α-DHT as substrate) activities (expressed as pmol substrate reduced/min per 106 cells). In immature rats both 5α-reductase and 3α-hydroxysteroid dehydrogenase activities were localized in the epithelial cell fraction (17 and 52 respectively); stromal cells showed lower 5α-reductase and 3α-hydroxysteroid dehydrogenase activity (4 and 4). Relative to epithelial cells from immature rats epithelial cells from mature rats showed a decrease in 5α-reductase (7) and an increase in 3α-hydroxysteroid dehydrogenase (160) activity while stromal 5α-reductase showed little change (3) and 3α-hydroxysteroid dehydrogenase increased to 22. Because there are more epithelial than stromal cells in the rat prostate, the former can be considered important sites for 5α-reductase and 3α-hydroxysteroid dehydrogenase activities. This contrasts with the human prostate where there is more 5α-reductase activity in the stroma than in the epithelium.
Inhibition of sexual behaviour in lactating rats
Authors: Södersten P. , Hansen S. , Eneroth P.
Published: December 2008

Treatment with oestradiol benzoate (OB; 2–250 μg) and progesterone (0·5–25 mg) failed to induce sexual behaviour in lactating rats 6 days after parturition. Removal of pups permitted the induction of sexual behaviour by OB and progesterone and the inhibitory effect of the presence of pups was proportional to the number present. Ovariectomy of lactating rats or reduction of serum prolactin levels in intact lactating rats by daily treatment with the dopamine receptor agonist bromocriptine (0·5 mg/day) permitted the induction of sexual behaviour despite the presence of suckling pups. Removal of pups from lactating rats and subsequent maintenance of high prolactin levels by daily treatment with the dopamine receptor antagonist domperidone (2·5 mg/day) maintained the state of refractoriness to the behavioural effects of OB and progesterone provided that the ovaries remained in situ. Inhibition of sexual behaviour in lactating rats could be maintained after ovariectomy by implantation of progesterone-filled, but not androgen-filled implants at the time of ovariectomy. Removal of the pups or reduction of prolactin levels by bromocriptine treatment permitted the induction of sexual behaviour by OB in ovariectomized progesterone-implanted lactating rats. Inhibition of the behaviour in ovariectomized progesterone-implanted lactating rats could be maintained after pup removal by daily domperidone treatment. Continuously raised serum progesterone or prolactin levels have no effect on the induction of sexual behaviour in female rats but the present data suggest that during lactation progesterone and prolactin act in synergy to inhibit the behaviour.
Adrenal hormones and oxidative metabolism of the garden lizard (Calotes versicolor)
Authors: Gupta B. B. Pd. , Thapliyal J. P.
Published: December 2008

Daily administration of adrenaline over a 10-day period invariably induced significant increases in the metabolic rate of the whole body and of specific tissue (liver, muscle, kidney and brain) of both intact and thyroidectomized lizards except during June (breeding season) when the presence of thyroid hormones was a prerequisite for the stimulation of oxygen consumption by the whole body, muscle, kidney and brain but not by the liver. Corticosterone had no effect on whole body oxygen consumption but stimulated, inhibited or was without influence on the oxygen consumption of individual tissues, depending on the season and the presence or absence of thyroid hormones. It is suggested that adrenaline, due to its temperature-independent calorigenic effect, acts as the emergency hormone for energy release and helps the animal to survive during hibernation (winter months) when almost all the endocrine glands are inactive.
Participation of the intermediate lobe of the pituitary gland after prolonged exposure to unpredictable stress in the rat
Authors: Pollard Irina
Published: December 2008

An ultrastructural study is described which relates cellular activity in the intermediate lobe of the pituitary gland with circulating levels of corticosterone. Exposure of male CSF rats to a signalled, unpredictable 60-day stress regimen induced intense secretory activity in all cells of the pars intermedia for the first 5 days of stressing, and thereafter secretory activity reverted back to the control condition. Blood corticosterone levels showed an initial extreme increase lasting for the first 5 days of exposure to the stress before gradually falling to re-establish a new stable level of secretion by 40 days. The possible involvement of the intermediate lobe in emotional or psychological stress when corticosterone levels are high is discussed.
A possible role for calmodulin in human thyroid cell metabolism
Authors: Ollis C. A. , MacNeil S. , Walker S. W. , Brown B. L. , Sharrard R. M. , Munro D. S. , Tomlinson S.
Published: December 2008

A protein which shared several characteristics with authentic calmodulin was extracted from human thyroid homogenates. The protein bound to fluphenazine–Sepharose and could be specifically eluted using EGTA. The eluted protein had a u.v. spectrum characteristic of calmodulin and migrated like authentic calmodulin with a calcium-dependent shift on sodium dodecyl sulphate polyacrylamide-gel electrophoresis. Calmodulin in thyroid cell extracts was shown to be biologically active, measured by its ability to activate a calmodulin-deficient cyclic GMP phosphodiesterase; this activation could be inhibited by trifluoperazine. A possible role for calmodulin in the action of TSH on the thyroid was demonstrated by studying the effects of phenothiazines and the naphthalene sulphonamide, W7, a more specific calmodulin inhibitor, on TSH-stimulated cyclic AMP levels in cultured thyroid cells. The phenothiazines and W7 were found to inhibit the accumulation of cyclic AMP in response to TSH in a concentration-dependent manner although low concentrations of W7 enhanced TSH-stimulated cyclic AMP accumulation.
Antagonism of serum tri-iodothyronine changes after injections of prolactin in the domestic fowl before and after hatching
Authors: Kühn E. R. , Decuypere E. , Hemschoote K. , Berghman L. , Paulussen J.
Published: December 2008

The influence of an intravenous injection of ovine prolactin on circulating levels of thyroid hormones was studied in Rhode Island Red embryos and chicks after hatching. In the chick embryo, 2 h after injection of 0·1 μg prolactin (on incubation day 19), serum tri-iodothyronine (T3) increased threefold; after 10 or 100 μg prolactin (on incubation day 18) serum T3 increased 15- to 25-fold. These profound increases were not observed in chicks after hatching. Serum concentrations and thyroid content of thyroxine (T4) in embryos and chicks of all ages studied were not influenced by the prolactin injections. Maximal serum concentrations of reverse T3 (rT3) were found on incubation day 18 (110·25 ± 23·36 pmol/l; 71·66 ± 15·18 pg/ml; n = 8), whereas after hatching no rT3 could be detected. An injection of 10 μg prolactin on day 18 depressed serum rT3 after 2 h to 5·68 ± 3·20 pmol/l (3·69 ± 2·08 pg/ml; n = 8; P<0·001); the effect of 100 μg prolactin was less pronounced. After hatching, chronic administration of prolactin resulted in decreased serum levels of T3, but not of T4, and hypertrophy of the follicles in the thyroid gland. It is concluded that prolactin plays a major role in the maturation of embryonic thyroid metabolism by changing the T4-5-monodeiodination into a T4-5′-monodeiodination. The hypertrophy of the thyroid gland observed after hatching following prolonged prolactin administration may be due to decreased negative feedback of T3 on the hypophysis.
Study of prolactin levels in the ferret
Authors: Smith S. V. , Forsyth I. A. , Donovan B. T.
Published: December 2008

A radioimmunoassay for canine prolactin has been used to measure prolactin in the ferret. Serial dilutions of extracts of ferret pituitary glands and of ferret plasma yielded curves that were parallel with the canine prolactin standard curve. The sensitivity, accuracy, reproducibility and precision of the assay were within acceptable limits. Plasma prolactin levels increased after the administration of thyrotrophin releasing hormone (TRH) or chlorpromazine, but not after giving luteinizing hormone releasing hormone. Female ferrets, which were anoestrous, oestrous or spayed, and male ferrets had similar basal prolactin levels when sampled under sodium pentobarbitone anaesthesia. These basal levels were higher than in conscious males and the latter also showed a lesser response to TRH. Hypophysectomy significantly reduced basal prolactin levels in female ferrets by 2 h postoperatively and abolished the response to TRH.
Neurohypophysial peptides in the human fetus: presence in pituitary extracts of immunoreactive arginine-vasotocin
Authors: Smith Alberto , McIntosh Neil
Published: December 2008

A specific and sensitive radioimmunoassay was used to demonstrate the presence of arginine-vasotocin (AVT) in human fetal pituitary extracts. The mean pituitary contents of AVT in extracts of 70–101, 102–136 and 137–172 days gestation were 0·32, 0·8 and 8·1 ng/gland respectively. Combined high-pressure liquid chromatography (HPLC) and radioimmunoassay of pooled extracts at these gestational ages confirmed the presence of AVT. Radioimmunoassay of neonatal pituitary extracts (240–280 days) did not conclusively show AVT to be present, as the material assayed did not show parallelism with dilution. However, combined HPLC and radioimmunoassay of pooled extracts at this gestational age did demonstrate the presence of an immunoreactive AVT peak. Radioimmunoassay analysis of this peak indicated that a relatively small amount of AVT (at least 0·5 ng/gland) was present in the human pituitary gland at term.
Inhibition of DNA synthesis in dermal tissue of Merino sheep treated with depilatory doses of mouse epidermal growth factor
Authors: Panaretto B. A. , Leish Z. , Moore G. P. M. , Robertson D. M.
Published: December 2008

Two groups of three Merino wethers were infused intravenously with either 0·12 mg mouse epidermal growth factor (mEGF)/kg fleece-free body weight or 0·9% (w/v) NaCl over 24 h. Sheep treated with mEGF rejected food during treatment but feed intake was kept equal for both groups.

Wool growth and plasma concentrations of mEGF were measured during the experiment. Pieces of skin taken from the wool-growing regions of the body were incubated with radioactive thymidine in order to measure its rate of incorporation into DNA. The skin was then divided at about the level of the sebaceous glands into sections that contained the upper dermis and epidermis (E sections) and those containing the generative wool-follicle bulbs (D sections).

No mEGF was detected in the controls whereas mean levels of about 35 μg mEGF/l plasma were detected during the last 4 h of infusion in the protein-treated group. After infusion, wool growth was reduced by about 20% of the mean pretreatment level in the controls and no shedding of wool fibre was evident. In the mEGF-treated sheep, on the other hand, wool growth was depressed by 75–95% of the mean pretreatment level and the fleeces were almost completely cast in all three of the animals, leaving them nude on the wool-growing regions of the body. Wool growth was restored to its pretreatment level in this group about 1 month after infusion.

The D sections of skin contributed 50–60% of skin wet weight in controls throughout the experiment. In the mEGF group, however, E sections increased in weight by about 25% and D sections decreased by 25%, relative to pretreatment values, during the 2 weeks after infusion. Both skin sections contributed equally to skin weight thereafter.

Whereas the DNA content of E sections tended to increase after mEGF treatment there was a loss of 40%, relative to pretreatment values, in the DNA content of D sections. A significant decrease in thymidine incorporation into DNA in D sections was found, which lasted for at least 72 h after the start of infusion. Thymidine incorporation into E sections was raised during this period and again at about 10–14 days after infusion, when it was increased in both skin sections.

We have concluded that the inhibition of wool growth in the mEGF-treated animals was associated with the inhibition of DNA synthesis in the dermal skin sections which contain proliferating cells of wool follicles.

J. Endocr. (1984) 100, 25–31
Pituitary–testicular interrelationships during germinal involution in the vitamin A deficient rat
Authors: Huang H. F. S. , Zaidi P. , Nieschlag E.
Published: December 2008

Pituitary–testicular relationships in mature male rats were investigated during the period of germinal involution after the induction of vitamin A deficiency (VAD).

Vitamin A deficiency caused a decrease in testicular weight, a gradual increase in the incidence of delayed spermiation, increased phagocytosis of spermatids and pyknosis of germ cell nuclei in rats aged 80 to 110 days. Both basal and gonadotrophin releasing hormone (GnRH)-stimulated serum FSH concentrations were increased by 100 days of age. During the same period, the per cent increment in GnRH-stimulated FSH secretion, pituitary FSH concentration and LH secretion remained unchanged. These results suggest that the increased serum FSH may mark specifically an alteration in the germinal epithelium. By 140 days of age, spermatogenic activity in the rats with VAD was limited to the spermatogonial proliferations so that only Sertoli cells, spermatogonia and preleptotene spermatocytes remained. At this time hypersecretion of FSH persisted while the per cent increment of GnRH-stimulated FSH secretion decreased. Concomitantly, basal and GnRH-stimulated LH concentrations were also increased in the presence of normal serum testosterone. These results indicate that a complete cessation of spermatogenesis beyond preleptotene spermatocytes is associated with a change in the secretion of both FSH and LH.

The relationship between serum LH and testosterone was normal until at least 110 days of age. By 140 days the ratio between basal LH and basal testosterone, and between total LH and total testosterone, after GnRH administration, increased in the rats with VAD. These changes may be caused by a hyporesponsiveness of the Leydig cells which may, in turn, be attributed to the cessation of spermatogenesis. J. Endocr. (1984) 100, 33–41
Induction of transient functional luteolysis in cyclic sheep by a 3 β-hydroxysteroid dehydrogenase inhibitor
Authors: Jenkin G. , Gemmell R. T. , Thorburn G. D.
Published: December 2008

The mechanism by which prostaglandin F2α terminates luteal function in the sheep is unclear even though it is used extensively in animal husbandry. At the time of luteal regression, a decrease in 3β-hydroxysteroid dehydrogenase (3β-HSD) activity is apparent in the corpus luteum, but it is not known whether the decrease in enzyme activity is the primary cause of structural luteolysis. The effect of trilostane, a 3β-HSD inhibitor, on luteal function and morphology has therefore been investigated. Intravenous injection of trilostane in the mid-luteal phase of the oestrous cycle caused a decrease in ovarian tissue progesterone content. A transient decrease in peripheral and utero-ovarian vein plasma progesterone was observed but there was no significant effect on the length of the luteal phase of the cycle. There was no significant change in plasma 13,14-dihydro-15-oxo-prostaglandin F2α during the period when plasma progesterone was depressed. Morphological examination of the corpora lutea revealed a decrease in the concentration of electron-dense granules without any other features of impending luteal regression. When plasma progesterone was reduced for more than 10 h by two injections of trilostane 4 h apart, there was again no subsequent effect on the length of the oestrous cycle or on the return to oestrus. Plasma progesterone returned to preinjection levels within 24 h of injection. This evidence suggests that competitive inhibition of 3β-HSD activity, per se, is ineffective in bringing about structural luteolysis.

J. Endocr. (1984) 100, 61–66
Ovarian aromatase activity in the domestic fowl (Gallus domesticus)
Authors: Armstrong D. G.
Published: December 2008

Fowl ovarian aromatase activity was measured by an assay based on the stereospecific elimination of tritium from [1,2-3H]testosterone. The production of tritiated water was shown to provide a valid estimate of aromatase activity under the conditions used.

The small yellow follicles and ovarian stroma contained 50% of the total ovarian aromatase activity. The activity in the thecal tissue from the rapidly growing follicles reached a maximum level in the fourth largest follicles (17% of the total ovarian activity) and thereafter declined to low levels in the largest follicle and first post-ovulatory follicle. No activity was detected in the granulosa tissue from the rapidly growing follicles.

It is proposed that the basal levels of plasma oestrogen in hens are maintained by production in the small yellow follicles and/or ovarian stroma. The variation in plasma oestrogen during the ovulatory cycle probably arises from secretion by the rapidly growing follicles.

J. Endocr. (1984) 100, 81–86
Sex differences in circadian control of LH secretion
Authors: Albers H. E. , Moline M. L. , Moore-Ede M. C.
Published: December 2008

Sex differences in the hourly values of serum LH were examined in male and female Syrian hamsters exposed to either long photoperiods (14 h light: 10 darkness; 14L: 10D) or short photoperiods (6L: 18D). In long photoperiods, females exhibited a pro-oestrous surge of LH in response to high levels of circulating oestradiol (1047·36 ± 90·68 pmol/l), while LH values in male hamsters remained essentially constant. In females housed in short photoperiods oestradiol levels were reduced by fivefold; however, a discrete surge in serum LH, similar to that seen at pro-oestrus in females exposed to long photoperiods, was observed. Although exposure to a short photoperiod eliminates the requirement of a positive feedback of oestrogen for the expression of an afternoon surge in LH, male hamsters housed in short photoperiods showed no indication of an afternoon surge in serum LH. These observations indicate that sex differences in the neural control of LH release are not the result of sex differences in oestrogen sensitivity or responsiveness.

J. Endocr. (1984) 100, 101–105
Effect of insulin on glucose uptake by the maternal hindlimb and uterus, and by the fetus in conscious pregnant sheep
Authors: Hay W. W. , Sparks J. W. , Gilbert M. , Battaglia F. C. , Meschia G.
Published: December 2008

Previous studies have demonstrated the presence of insulin receptors on the maternal surface of the placenta in several species and the specific binding of insulin to the placenta in sheep. However, both in-vitro and in-vivo studies have produced conflicting evidence concerning the effect of insulin on placental glucose uptake. To clarify this problem, we measured maternal hindlimb, uterine and fetal glucose and oxygen extractions and glucose/oxygen quotients in chronically catheterized, non-stressed, late-gestation pregnant sheep over 1 h at a constant concentration of arterial plasma glucose, and again during the next 2 h at the same glucose level but at a higher insulin concentration using glucose 'clamp' methodology. Insulin produced a 4·9-fold increase in glucose extraction and a 3·5-fold increase in glucose/oxygen quotient across the hindlimb; in contrast, insulin did not significantly affect uterine or fetal glucose extraction or glucose/oxygen quotient. We conclude that in contrast to other tissues of the pregnant ewe, placental glucose uptake and transfer are insensitive to variations in maternal insulin concentration.

J. Endocr. (1984) 100, 119–124
Possible role of dopamine in changes in LH and prolactin concentrations after experimentally induced hyperprolactinaemia in rats
Authors: Esquifino A. I. , Ramos J. A. , Tresguerres J. A. F.
Published: December 2008

Nine-month-old female rats bearing an ectopic pituitary gland (from a litter-mate) under the right kidney capsule since day 30 of life and their sham-operated controls, were treated with a dopamine agonist (lysuride) or antagonist (metoclopramide). Plasma prolactin and LH levels were measured by double-antibody radioimmunoassays. Vaginal smears were taken before and during the treatment periods. Eight months after the operation, a significant (P < 0·01) increase in basal prolactin levels together with a significant (P < 0·05) reduction in LH values and permanent dioestrus occurred in the grafted animals when compared with controls. Lysuride treatment resulted in a marked reduction in plasma prolactin levels both in control and grafted rats over the whole 12 days of treatment, together with a partial restoration of plasma LH levels on day 1. From day 7 onwards a depression in LH values was again observed. Oestrous cycles were partially restored at the beginning of the treatment, but after 7 days dioestrus returned. Metoclopramide administration induced a significant (P< 0·001) increase in basal prolactin levels in both grafted and control rats. Basal plasma LH values were unaffected in controls when compared with vehicle-treated animals. An increase could be seen in hyperprolactinaemic rats after 7 or 12 days of treatment however. The LH response to the administration of LH releasing hormone (LHRH) was greater in the experimental and control metoclopramide-treated rats when compared with vehicle-treated rats. Vaginal smears were not altered in the control animals but there was a significant increase in the number of oestrous smears in grafted animals given the dopamine antagonist partially restoring the cycle pattern. After LHRH administration plasma prolactin levels decreased in vehicle-treated grafted and control animals, whereas only a tendency to lower values or no modification in basal levels was observed with lysuride or metoclopramide treatments. All these data suggest that increased plasma prolactin levels cannot modify LH secretion directly. This influence may be exerted, however, through increased hypothalamic and in-situ pituitary dopamine detected in hyperprolactinaemic animals.

J. Endocr. (1984) 100, 141–148
Development of the oviduct in quail during sexual maturation in relation to plasma concentrations of oestradiol and progesterone
Authors: Pageaux J. F. , Laugier C. , Pal D. , Pacheco H.
Published: December 2008

The macromolecular content (DNA, soluble proteins and ovalbumin) of the magnum and the plasma concentrations of oestradiol and progesterone were studied during sexual development of the Japanese quail. Rapid growth and differentiation of the magnum began between 21 and 28 days of age and rapidly reached the laying stage in about 20 days. This rapid change in magnum size occurred in a stepwise manner: cellular proliferation was observed first, followed by the synthesis and accumulation of specific proteins. Just before and during magnum growth, plasma oestradiol and progesterone concentrations followed different patterns: the initiation of epithelial cell proliferation was preceded by a sharp decrease in plasma progesterone. Maximum cell division occurred while plasma progesterone levels continued to decrease slightly; at the same time, oestradiol increased from 0·098 to 0·453 nmol/l. The decrease and finally the cessation of cell proliferation and the concomitant increase in ovalbumin concentration were related to almost constant levels of plasma oestradiol and increasing levels of plasma progesterone. Further development of the magnum (above 2·3 g weight) involving only the accumulation of secretory products was associated with an increased value of plasma progesterone. These data are consistent with the hypothesis that there are multiple hormonal signals controlling cell proliferation and synthesis of egg-white proteins in the oviduct. Progesterone may be one of the key signals that regulates the initiation of oviduct growth in the quail.

J. Endocr. (1984) 100, 167–173
Effects of bromocriptine and naloxone on plasma levels of prolactin, LH and FSH during suckling in the female rat: responses to gonadotrophin releasing hormone
Authors: Sirinathsinghji D. J. S. , Martini L.
Published: December 2008

The roles of dopamine and the endogenous opiate peptides in the mediation of the inverse relationship between prolactin and gonadotrophin secretion during lactation were studied by comparing the effects of bromocriptine and naloxone on plasma levels of prolactin, LH and FSH during suckling in the female rat. The effects of exogenous gonadotrophin releasing hormone (GnRH) on the LH and FSH responses to bromocriptine and naloxone were also assessed. In control animals (saline), there was a marked fall in LH levels and a large increase in prolactin levels within 15 min of suckling. In response to GnRH (25 ng) there was a small progressive increase in LH levels reaching a maximum at 45 min. Both bromocriptine (500 μg) and naloxone (500 μg) markedly suppressed the suckling-induced prolactin surge when administered in two separate groups of animals. However, despite the bromocriptine-induced suppression of prolactin levels, there was no increase in LH levels which remained low throughout the suckling period. Naloxone (500 μg), however, induced a twofold increase in LH levels within 15 min suggesting that an enhanced opiate rather than dopaminergic activity may be responsible for the suppression of GnRH and hence gonadotrophin secretion during suckling. This is supported by the finding that whereas combined bromocriptine (500 μg) and GnRH (25 ng) treatment suppressed the suckling-induced prolactin rise and also induced only a small progressive increase in LH (similar to GnRH alone), combined naloxone (500 μg) and GnRH (25 ng) treatment induced a sharp sixfold increase in LH levels within 15 min while at the same time markedly suppressing prolactin levels. None of these drug treatments affected the levels of FSH.

The results of this study may thus indicate that (1) the suckling stimulus itself rather than the high prolactin levels may be responsible for the suppression of gonadotrophin secretion during lactation, (2) although dopamine may be an important physiological factor controlling prolactin secretion, it may not be involved in the regulation of LH during lactation and (3) the suckling stimulus may enhance the release of endogenous opiates within the central nervous system which could then stimulate prolactin and at the same time inhibit gonadotrophin secretion by inhibiting GnRH release. This opiate-mediated mechanism may explain the reciprocal nature of prolactin and LH secretion during lactation.

J. Endocr. (1984) 100, 175–182
Episodic release of LH in gonadectomized male Japanese quail
Authors: Urbanski H. F.
Published: December 2008

Blood samples were taken every 15 min (for 4·75 h) from six castrated quail on three separate occasions. The birds were first bled while under short days (comprising 8 h light:16 h darkness per 24 h; 8L:16D) and, subsequently, after 1 and 20 days under long days of 16L:8D. The photoperiodic alteration produced a marked increase in the mean plasma LH concentration of each bird and in four instances the rise was evident after only 1 long day. Pulsatile release patterns were not detected in the plasma LH profiles obtained during exposure to short days or after 1 long day but were pronounced in all of the birds after 20 long days. The peaks (n = 19) occurred on average every 83 ±14 (s.e.m.) min and had an amplitude of 12·3±1·2 μg/l. After 35 days under 16L: 8D three of the quail were bled more frequently (every 8 min for 2·5 h), allowing the LH pulses to be measured more precisely. Each pulse was composed of a sudden increase in secretion followed by a slower decrease which lasted for approximately 30 min. The development and functional significance of episodic LH release in the quail is discussed.

J. Endocr. (1984) 100, 209–212
Vascular and cellular changes in the decidualized endometrium of the ovariectomized mouse following cessation of hormone treatment: a possible model for menstruation
Authors: Finn C. A. , Pope M.
Published: December 2008

Ovariectomized mice were prepared for decidualization with oestrogen and progesterone and arachis oil injected into the uterine lumen. Hormone injections were then stopped and uteri examined at intervals between 31 and 84 h after the last progesterone injection. At 31 and 35 h the stroma showed a normal decidual reaction. Between 45 and 79 h the stroma underwent a series of changes which started with the congestion of dilated blood vessels with swollen erythrocytes followed by breakdown of the vessel walls and extravasation of blood. At the same time the decidual cells showed typical apoptotic changes and there was invasion by leucocytes. An outer ring of stroma did not take part in the degenerative process and eventually a central core of blood cells and degenerating decidual cells became detached and was shed into the lumen.

Animals treated in exactly the same way but with the omission of the decidual stimulus did not show such changes in the stroma. It is suggested that the changes in the endometrium resemble those of menstruation and support the suggestion that for menstruation to occur the stroma must be differentiated for implantation. This occurs during the cycle in women but does not occur in non-primates unless a decidual stimulus is applied to the uterus.

J. Endocr. (1984) 100, 295–300
A histometrical study of immunohistochemically identified mitotic adenohypophysial cells in immature and mature castrated rats
Authors: Sakuma S. , Shirasawa N. , Yoshimura F.
Published: December 2008

Two weeks after operation the effects of castration on all types of mitotic adenohypophysial cells in 30-day-old (immature) and 75-day-old (mature) male rats were studied immunohistochemically by light microscopy. The total number of mitotic cells in gland specimens increased 1·4 times in immature rats, but remained unchanged in mature animals; mitotic activity (mitotic cell number/mm2) was not affected in either age group. The population of mitotic gonadotrophs increased five to six times in comparison with intact controls. In addition, the percentage of mitotic gonadotrophs and their mitotic activity were raised in both age groups. Castration affected the mitosis of prolactin cells. The percentage of mitotic prolactin cells was reduced by one-third in castrated immature rats, but the total number and percentage of mitotic prolactin cells, as well as their mitotic activity, was reduced by about two-thirds in mature castrated rats. No significant changes in mitotic ACTH, TSH, GH and immunonegative cells were found after castration in either group of animals.

Mitotic cells were more numerous in the anterior than in the posterior region of the gland in normal (uncastrated) immature rats, but were uniformly scattered in both regions in normal mature rats. On the other hand, castration induced a high population of mitotic cells in the anterior region regardless of age. This high population was the result of the enhanced mitosis of gonadotrophs. It is concluded that 2 weeks after castration the increment of mitotic divisions of all types of pituitary cells is age-dependent, and that mitosis takes place frequently in gonadotrophs and less frequently in prolactin cells.

J. Endocr. (1984) 100, 323–328
Acute in-vivo effects of adrenocorticotrophin on plasma levels of glucagon, insulin, glucose and free fatty acids in rabbits: involvement of the alpha-adrenergic nervous system
Authors: Knudtzon J.
Published: December 2008

Intravenous injection of 8·5 nmol (1–24)ACTH increased the plasma levels of glucagon, insulin, glucose and free fatty acids in rabbits. The (1–24)ACTH-induced hyperglucagonaemia and hyperinsulinaemia started 3 and 20 min after the injection respectively. Similar increases in the plasma levels of glucagon, insulin and free fatty acids were found with 5·3 nmol (1–39)ACTH, whereas (1–4)ACTH, (4–10)ACTH, (1–10)ACTH, (11–24)ACTH, (7–38)ACTH and (18–39)ACTH (corticotrophin-like intermediate lobe peptide) injected at doses of approximately 8 nmol were inactive. Infusions with the alpha-adrenergic blocking drug, phentolamine, reduced the (1–24) ACTH-induced hyperglucagonaemia and hypergly-caemia, and augmented the (1–24)ACTH-induced hyperinsulinaemia, which now became significant after 5 min. Infusions with the beta-adrenergic blocking drug, propranolol, did not diminish the (1–24)ACTH-induced effects, but killed the rabbits after 2–4 h.

It is concluded that the acute in-vivo effects of ACTH in rabbits are modulated by the involvement of alpha-adrenergic receptors, which increased the plasma levels of glucagon and glucose, and delayed and diminished the ACTH-induced increases in the plasma levels of insulin. The (1–24)ACTH-induced increases in the plasma levels of free fatty acids were not influenced by the adrenergic blocking drugs.

J. Endocr. (1984) 100, 345–352
Human growth hormone-secreting pituitary adenoma cells in long-term culture: effects of dexamethasone and growth hormone releasing factor
Authors: Oosterom R. , Verleun T. , Lamberts S. W. J.
Published: December 2008

Growth hormone-secreting human pituitary adenoma cells in long-term culture show a decline in GH secretion. We investigated the effects of dexamethasone on GH production and on the responsiveness of the adenoma cells to various drugs. Twenty-four-hour GH secretion by cultures from seven acromegalics was consistently stimulated by 100 nM-dexamethasone. In four out of seven cultures the effect of dexamethasone occurred within 24 h. After 3 weeks in culture the decline in GH secretion by control cultures was over 90%, while in dexamethasone-treated cultures this was limited to less than 50%. The effect of dexamethasone was dose-dependent over a range of 1 nmol/l to 10 μmol/l. Dexamethasone stimulated not only GH secretion (fivefold), but also GH content (twofold). Cycloheximide and actinomycin D blocked the stimulatory effect of dexamethasone on GH secretion, the latter irreversibly. After 4 days of treatment with 100 nm-dexamethasone, the relative effects of somatostatin, prostaglandin E1, bromocriptine and thyrotrophin releasing hormone were the same in treated and untreated cultures. However, the response to synthetic GH releasing factor (GRF) was greatly enhanced by pretreatment of adenoma cells with dexamethasone (100 and 5 nmol/l). Cells unresponsive to small concentrations of GRF could be stimulated effectively by GRF after pretreatment with dexamethasone.

In conclusion, dexamethasone prevents the decline in GH production as seen in control cultures, possibly by stimulation of DNA transcription. Furthermore, the response to GRF is greatly enhanced in the presence of dexamethasone, while the relative effects of other direct GH stimulatory and inhibitory compounds seem to be unchanged.

J. Endocr. (1984) 100, 353–360
The role of neurotransmitters in mediating copulation-induced ovulation in the rat
Authors: Leipheimer R. E. , Condon T. P. , Curry J. J.
Published: December 2008

Pentobarbitone-blocked pro-oestrous rats were subjected to either limited mating (maximum of 30 mounts), all-night cohabitation with males or stimulation of the vagina and cervix with a glass rod (2 or 5 min) to determine which type of stimulus was most effective in inducing ovulation. All-night cohabitation was the most successful procedure and resulted in 100% ovulation in those rats which mated. Treatment with either phenoxybenzamine, propranolol or pimozide did not interfere with this copulation-induced ovulation whereas methysergide treatment completely blocked copulation-induced ovulation. Administration of atropine resulted in a loss of mating behaviour and these animals therefore did not ovulate. Further experiments provided evidence that administration of atropine also blocked ovulation in response to vaginal stimulation with a glass rod. Pretreatment with methysergide or atropine had no effect upon the percentage of pentobarbitone-blocked, pro-oestrous rats ovulating in response to administration of LH releasing hormone (LHRH). However, those rats given atropine shed significantly fewer ova per rat following LHRH or LH infusion when compared with controls. These results suggest that the synaptic mechanisms responsible for mediating copulation-induced ovulation are different from those mediating steroid-induced ovulation, and that ovarian cholinergic receptors may play a role in ovulation.

J. Endocr. (1984) 100, 361–365
In-vitro testosterone metabolism in the mouse preputial gland: intercellular co-operation and changes with cell maturation
Authors: Brind J. L. , Marinescu D. , Gomez E. C. , Wheatley V. R. , Orentreich N.
Published: December 2008

In-vitro [14C]testosterone metabolism was investigated in isolated cells of adult male mouse preputial sebaceous glands. Labelled steroids were extracted and chromatographed after a 2-h incubation, and were identified as 5α-dihydrotestosterone, androstenedione, 5α-androstane-3,17-dione, 5α-androstane-3α,17β-diol and 5α-androstane-3β,17β-diol, androsterone and 3-epiandrosterone. In cells separated according to state of maturity (lipid content) by isopycnic centrifugation in a metrizamide gradient, maximal testosterone metabolism occurred in large, nearly mature cells. In this population, mean hydroxysteroid 5α-reductase and 17β-hydroxysteroid dehydrogenase activities were 3·8 and 2·3 nmol/106 cells per 2 h respectively, more than 100-fold greater than in the densest population, comprised of undifferentiated and early differentiating cells. It was also found that the profile of testosterone metabolites was dependent on the proportion of the label metabolized. The metabolite index (MI), i.e. the average number of enzymatic steps undergone per molecule of metabolite, increased with increasing substrate utilization. Metrizamide showed reversible, non-specific inhibition of testosterone metabolism and reduction of the MI. Thus, it was postulated that testosterone is metabolized sequentially by different cells, with metrizamide inhibiting cellular uptake and intercellular substrate transport. This suggested that most of the metabolites would be found in the medium, rather than in the cellular compartment. Further, in incubations run without cell disaggregation, efficient substrate cycling among cells should result in a high MI, independent of metrizamide concentration and substrate utilization. These predictions were all confirmed, providing strong evidence that testosterone metabolism is a cooperative effort among several cells in this tissue.

J. Endocr. (1984) 100, 377–388
Age difference in endogenous opiate modulation of short photoperiod-induced testicular regression in golden hamsters
Authors: Chen H. J. , Targovnik J. , McMillan L. , Randall S.
Published: December 2008

Effects of age and naloxone on testicular function were studied in golden hamsters exposed to short photoperiods. Subjection of hamsters to short photoperiods of 6 h light: 18 h darkness for 6 weeks led to testicular regression in young adult (5–6 months) or middle-aged (11–12 months) golden hamsters but not in prepubertal hamsters of 1–2 months of age. The middle-aged hamsters had decreased testis width by week 4 of treatment and the young hamsters by week 5. Daily injection of naloxone at the time of'lights on' partially prevented testicular regression in young and middle-aged hamsters but the extent of regression was significantly greater in the middle-aged animals.

Plasma LH and FSH concentrations were significantly reduced in hamsters placed in short photoperiods regardless of age or testicular weight, while naloxone treatment significantly increased the LH concentrations in all age groups. Plasma β-endorphin-like immunoreactivity was significantly increased by short photoperiod or older age.

These results indicated that (a) the sensitivity of the testicular suppression to short photoperiod increases as a function of age, (b) naloxone, a specific opiate receptor blocker, can partially prevent short photoperiod-induced testicular regression and (c) ageing and short photoperiods increase β-endorphin-like immunoreactivity. It is concluded that the opiate system may be involved in ageing and photoperiod regulation of reproductive function.

J. Endocr. (1984) 101, 1–6
Immediate, short- and long-term opposite effects of oestradiol-17β on glucose metabolism in rat adipocytes: relationship with the biphasic changes in body weight and food intake
Authors: Faure A. , Vergnaud M.-Th. , Sutter-Dub M.-Th. , Sutter B. Ch. J.
Published: December 2008

The changes in the effects of oestradiol-17β on body weight, food intake and [1-14C]glucose oxidation in adipocytes were followed in sham-operated, ovariectomized and adrenalectomized–ovariectomized rats to eliminate effects of endogenous progesterone and corticosterone. During the first 5 days oestradiol induced a dramatic fall in food intake and body weight concomitant with a decrease in glucose oxidation by adipocytes, when tested 12 h and 3 days after the beginning of treatment. In-vitro incubations with oestradiol showed that this was a direct effect of this hormone. On the other hand, from days 5 to 14 of treatment, body weight and food intake increased, though they were still lower than in sham-operated controls. On day 14, as values of treated rats tended to reach those of controls, glucose oxidation in adipocytes was stimulated by oestradiol treatment. An insulin effect was still observable and none of these effects was dependent on the adrenal gland.

These biphasic changes in the parameters studied could be closely related; moreover, a relationship with other oestradiol actions on metabolism that are known to be corticosterone-dependent could be eliminated.

J. Endocr. (1984) 101, 13–19
Pituitary and gonadal response to LH releasing hormone administration in the female and male cheetah
Authors: Wildt D. E. , Chakraborty P. K. , Meltzer D. , Bush M.
Published: December 2008

Luteinizing hormone releasing hormone (LHRH, 50 μg) or saline was administered (i.m.) to adult female and male cheetahs under anaesthesia to evaluate pituitary and gonadal response. Serum LH levels did not fluctuate over a 120-min sampling period in saline-treated animals. Serum LH concentrations were raised (P < 0·05) in both female and male cheetahs after LHRH injection, the temporal response being similar to previously reported results in unanaesthetized, domestic carnivores. The magnitude of the LHRH-induced LH response was sex-dependent. Over a 120-min post-injection period both saline control and LHRH-induced LH levels were about twofold greater in males than females. Although LHRH had no acute influence on ovarian oestradiol-17β production in the female, serum testosterone levels were raised (P < 0·05) in male cheetahs by 60 min after treatment. This study (1) provides introductory endocrine information on the cheetah, an endangered species, and (2) indicates that exogenous LHRH is effective in acutely altering pituitary (female) and pituitary/gonadal (male) function in an anaesthetized, non-domestic felid.

J. Endocr. (1984) 101, 51–56