bluuebunny/crossref_metadata_2025 huggingface dataset:
DISSOCIATION IN THE REGULATION OF LUTEINIZING HORMONE AND FOLLICLE-STIMULATING HORMONE IN A HYPERPROLACTINAEMIC RAT MODEL: INTERRELATIONSHIPS BETWEEN GONADOTROPHIN AND PROLACTIN CONTROL
Authors: TRESGUERRES J. A. F. , ESQUIFINO A. I.
Published: December 2008

Male and female Wistar rats were made hyperprolactinaemic by grafting two pituitary glands of litter-mate donors under the kidney capsule at 30 days of age. Other animals were sham-operated at the same age to serve as controls. Plasma levels of prolactin, LH and FSH were measured by double-antibody radioimmunoassay. Basal preoperative prolactin levels of ∼ 10 ng/ml increased after the transplantation in both male and female rats, reaching values of ∼ 180 ng/ml. Levels of LH were significantly reduced in these hyperprolactinaemic rats, whereas an increase in FSH values was seen. After administration of LH releasing hormone (LH-RH) a reduced LH response was seen but there was no response of FSH to LH-RH or even a decrease in FSH values. Prolactin levels were also reduced by LH-RH injection. Although an increase in prolactin levels was observed in control animals after a challenge with oestradiol benzoate, reduced increments were seen in experimental animals. The positive feedback effect of oestradiol benzoate on LH in females was reduced in pituitary-grafted rats but a potentiation of the FSH positive feedback could be clearly detected. This study suggests a dissociation of LH and FSH regulation in hyperprolactinaemia.
INVOLVEMENT OF LYSOSOMAL ENZYMES IN MOUSE EMBRYO IMPLANTATION: EFFECT OF THE ANTI-OESTROGEN, CI-628 CITRATE
Authors: PARIA BIBHAS C. , SENGUPTA JAYASREE , MANCHANDA S. K.
Published: December 2008

Implantation of embryos was studied in mice which had been ovariectomized on the afternoon of day 4 of pregnancy and injected intraperitoneally with a non-steroidal anti-oestrogen or control injection. Normal implantations were obtained in the latter mice as indicated from the positive blue-dye sites when animals were killed late in the evening of day 4. Exposure to CI-628, however, led to a significant inhibition in the number of implantations and only a small percentage of the mice exposed to the steroid antagonist showed normal implantation sites. Study of a few lysosomal enzymes in uterine tissues at the time of early embryo attachment revealed a striking change in the activity of leucyl naphthylamidase. The enzyme showed a reduction in its activity only in uterine areas which contained attached blastocysts. Acid phosphatase, β-glucuronidase and non-specific esterase did not show any such implantation-specific changes in their activity patterns. A possible role of leucyl naphthylamidase in the attachment of the embryo to the wall of the uterus has been explored.
PLASMA CONCENTRATIONS OF OXYTOCIN AND INTRAMAMMARY PRESSURE IN GOATS DURING MANUAL STIMULATION OF THE UDDER AND HAND-MILKING
Authors: MOSDØL G. , SJAASTAD Ø. V. , BLOM ANNE KRISTINE
Published: December 2008

The concentration of oxytocin in the jugular venous plasma of goats was studied by radioimmunoassay and the intramammary pressure measured upon manual stimulation of the udder and hand-milking. Before stimulation the concentrations of oxytocin were close to the limit of detection, about 3 pg/ml. Manual stimulation of the udder resulted in a shortlasting increase in plasma oxytocin in 11 out of 18 experiments carried out on nine goats. There were large variations between and within individuals in the magnitude of the oxytocin increase. Hand-milking was in general an efficient stimulus for oxytocin release. In experiments in which manual stimulation had led to a large increase in plasma oxytocin, the ensuing hand-milking did not lead to a further increase. In three experiments neither manual stimulation of the udder nor hand-milking resulted in any significant increase in plasma oxytocin.

The intramammary pressure increased upon manual stimulation of the udder and/or hand-milking in four out of six experiments. There was, in general, a close time-relationship between changes in intramammary pressure and plasma oxytocin.
SUCKLING IN THE GUINEA-PIG: THE SIMULTANEOUS RELEASE OF OXYTOCIN AND NEUROPHYSIN
Authors: ROBINSON I.C.A.F. , WOOLF C. N. , PARSONS J. A.
Published: December 2008

The release of oxytocin and neurophysin during suckling has been studied in conscious unrestrained guinea-pigs. After prior separation, mothers and litters were allowed to suckle for a period of 10 min, and the weight gain of the litter recorded as an index of milk transfer. Maternal blood samples were obtained without disturbance through previously implanted intravenous cannulae and neurophysin and oxytocin determined on unextracted plasma by specific and sensitive radioimmunoassays. In 82 out of 118 experiments the young gained weight during suckling (1·6±0·1 (s.e.m.) g/pup) and this was associated with large rises in both oxytocin and neurophysin concentrations in plasma (mean concentrations: oxytocin 65·4fmol/ml, neurophysin 360fmol/ml). Where serial samples were taken, oxytocin and neurophysin showed a rapid rise and fall in concentration closely associated with the occurrence of milk ejection as judged by the behaviour of the litter. The present results provide the first direct evidence of a spurt release of both oxytocin and neurophysin measured simultaneously during milk ejection. The conscious lactating guinea-pig thus provides a useful laboratory model in which to study hormone release during milk ejection.
EFFECTS OF MATING ON LEVELS OF OXYTOCIN AND PROLACTIN IN THE PLASMA OF MALE AND FEMALE RABBITS
Authors: FUCHS ANNA-RIITTA , CUBILE LINDA , DAWOOD M. Y.
Published: December 2008

The effects of mating on plasma levels of oxytocin and prolactin in male and female rabbits have been investigated. Blood was collected through indwelling cardiac catheters at intervals of 1, 2, 4, 6, 12, 24, 36 and 60 min after mating. In female rabbits additional samples were taken 5 h after mating, as well as daily during the ensuing pregnancy or pseudopregnancy. They were also fitted with intrauterine balloons for recording uterine activity. Copulation induced a rapid, transient rise in plasma oxytocin in female rabbits at the same time as a fall in plasma prolactin. Mating or sexual excitement had no significant effect on plasma concentrations of oxytocin or prolactin in bucks. Relatively large fluctuations of plasma oxytocin were seen in male rabbits under normal conditions and after mating, suggesting episodic release of oxytocin in a random fashion. The uterine recordings indicated that, in spite of the modest release of oxytocin, a strong sympathetic adrenal activation occurred in response to mating and this provided the overriding influence on uterine activity. During pregnancy plasma levels of prolactin rose significantly on day 4, and remained raised throughout most of gestation. Plasma prolactin fluctuated widely during the first half of pregnancy but the mean levels were higher than those found during the second half of gestation. When pseudopregnancy was induced with injection of an ovulating dose of LH, plasma prolactin rose in a similar manner as during early gestation or mating-induced pseudopregnancy. Thus, in contrast to rats, stimuli associated with mating have no direct influence on the subsequent release of prolactin in rabbits. The secretion of prolactin during gestation seems to be controlled entirely by ovarian steroids, probably progesterone.
SECRETION OF ALDOSTERONE IN THE MONOTREME MAMMAL, TACHYGLOSSUS ACULEATUS
Authors: SERNIA CONRAD , McDONALD I. R.
Published: December 2008

The secretion of aldosterone and its regulation by ACTH and angiotensin II were investigated in conscious, unrestrained echidnas with chronically implanted jugular catheters. Aldosterone was measured by radioimmunoassay after extraction and isolation by silica gel thin-layer chromatography.

The mean concentration of aldosterone in blood plasma of five male and three female echidnas was only 5·4 ± 1·3 (s.e.m.) pg/ml. During stress (surgery and anaesthesia) the mean concentration increased to 17·6 ± 3·8 pg/ml. Infusion of β1–24 ACTH at a rate of 5 units/kg per h increased the plasma concentration of aldosterone to 53·8± 9·8 pg/ml. Infusion of angiotensin II at rates of 100 and 500 ng/kg per h also increased aldosterone concentration, to 24·1 ± 8·6 and 35·1 ± 10·9 pg/ml respectively.

Production and metabolic clearance rates were measured by the constant-rate infusion of [3H]aldosterone and found to be 5·0 ± 2·2 ng/kg per h and 14·3 ±1·3 ml/kg per min respectively in the unstimulated state. Production rate was increased approximately sevenfold by the infusion of ACTH at 5 units/kg per h and fourfold and sixfold by infusion of angiotensin II at 100 and 500 ng/kg per h respectively. Metabolic clearance decreased following the infusion of ACTH or angiotensin II. Direct measurement of secretion rate by the collection of adrenal venous blood from three anaesthetized, laparotomized echidnas gave values of 9·4, 15·6 and 8·8 mg/kg per h.

It is concluded that the adrenal secretion of aldosterone in the echidna is extremely low compared with that in other mammals but the response to stress, ACTH and angiotensin II indicates the presence of typical mammalian control mechanisms for its secretion.
REPETITIVE TREATMENT WITH GONADOTROPHIN RELEASING FACTOR OR A LONG-ACTING ANALOGUE UPON GONADOTROPHIN SECRETION IN THE FERRET
Authors: GLEDHILL B. , DONOVAN B. T.
Published: December 2008

The changes in plasma levels of LH and FSH were examined after treatment of intact and ovariectomized female ferrets with a long-acting analogue of gonadotrophin releasing factor (Gn-RF) (d-Ser(But)6-LH-releasing hormone(1–9)-nonapeptide ethylamide; Hoe 766) either as a single intravenous injection or daily for 6 days. The responses were compared with those induced by daily injections of Gn-RF or 0·9% NaCl (w/v). Treatment with Gn-RF consistently induced rises in both LH and FSH release with peak levels of both hormones being reached 20 min after injection and being of similar size from day to day in individual animals. Thereafter, the gonadotrophin levels declined rapidly to approach basal values by the end of each sampling period. Treatment with Hoe 766, however, produced very high values on day 1 of treatment, with LH being raised for 10–12 and FSH for up to 24 h. Subsequent injections, on the other hand, produced an abbreviated LH response of similar size to that induced by Gn-RF and little, if any, FSH response. In ovariectomized ferrets, Hoe 766 induced a variable LH response and little FSH response at any time. In addition, basal FSH levels in the first three samples taken on each day from day 2 onwards tended to decline markedly in all of the Hoe 766-treated animals, an effect not seen in Gn-RF or 0·9% NaCl-treated controls.
A PERMANENT PREPARATION ALLOWING MEASUREMENTS OF SECRETION OF PARATHYROID HORMONE IN CONSCIOUS GOATS
Authors: HOVE KNUT
Published: December 2008

A preparation for estimations of rates of secretion of parathyroid hormone (PTH) in conscious goats is described. The procedure involved surgical isolation of a thyroid with its indwelling parathyroid gland, leaving the blood supply intact. Permanent access to the arterial and venous supplies of the preparation was secured by exteriorization of the jugular vein and carotid artery in skin-covered loops. The remaining parathyroids were removed leaving the isolated parathyroid gland as the only source of the hormone. For the seven goats operated on, the preparation has worked satisfactorily from the start in five and also in the remaining two after a reoperation to cut an accessory venous drainage. The loops have been catheterized repeatedly for extended periods of time and the preparation has proved useful for periods of up to 3 years.

Secretion of PTH was measured in one goat at two consecutive parturitions. In late pregnancy, secretion rates of 0·7–0·9 ng/kg per min were observed when the dietary calcium intake was adequate. In the first weeks of lactation, secretion increased to 1·2–1·5 ng/kg per min when the intake of calcium was adequate and to 2·0–2·2 ng/kg per min when calcium intake was inadequate. Reductions in calcium intake led to increased rates of secretion of PTH both during pregnancy and during lactation. The results indicate that the preparation may be useful in the study of changes in PTH secretion both acutely and in connection with long-term studies of dietary adaptations of the calcium metabolism.
CHARACTERISTICS OF OESTROGEN-INDUCED REFRACTORINESS IN OVINE CERVICAL SECRETION
Authors: ADAMS N. R.
Published: December 2008

Ovariectomized ewes treated with oestradiol benzoate (OB) had a reduced cervical mucus response to subsequent treatment with OB. This refractory effect was observed 48 h after a single dose of OB, but could be postponed until 72 h by a second dose of OB at 24 h. This postponement did not occur in animals which were recovering from previously induced refractoriness. Less mucus was recovered from refractory ewes, and it had an increased proportion of dry matter and normal Spinnbarkeit.

Pretreatment of ewes with 10 mg progesterone for 10 days decreased the proportion of dry matter and increased the Spinnbarkeit of mucus collected after stimulation with OB. This change was different from that produced by increasing the dose of OB. Progesterone given to ewes after 10 days treatment with OB had a detectable effect on cervical mucus, but it did not specifically decrease refractoriness. The cervix provides a convenient site for studying oestrogen-induced refractoriness in the ewe, without possible confusion by any effects of progesterone.
CLASSIFICATION OF MENSTRUAL CYCLES IN PRE- AND PERIMENOPAUSAL WOMEN
Authors: METCALF MARY G. , DONALD R. A. , LIVESEY J. H.
Published: December 2008

Urine for the analysis of pregnanediol, oestrogens, FSH and LH, was collected weekly from 50 normal menstruant women. Twenty of these women were aged ≥ 40 years and had a history of regular menstrual cycles; they are termed premenopausal. The other 30 reported a recent break in regular cyclicity and are termed perimenopausal. All menstrual cycles observed in the premenopausal women were ovulatory in type and 25–30 days in length. The 124 cycles observed in the perimenopausal women were 18–260 days in length (median, 29 days), with 52% of the ovulatory type. To describe this diversity, a systematic classification is proposed based on (1) the excretion of pregnanediol in the 12 days preceding menstruation (classes I–IV), (2) gonadotrophin output (categories A–E, and L), and (3) the length of the menstrual cycle in days. The premenstrual surge of pregnanediol was greatest in class I cycles and diminished progressively until it became undetectable in class IV. Gonadotrophin excretion was lowest in category A cycles and increased progressively until all levels were within the postmenopausal range by category E. In cycles of category L only LH (and not FSH) was raised.

In the perimenopausal women 37 cycles included episodes of high gonadotrophin excretion (categories C–L), a phenomenon which was not seen in the premenopausal women. These cycles were usually longer than 50 days and were often anovulatory in type (classes II—IV). Typically they began with the high gonadotrophin levels and the low oestrogens which characterize the postmenopausal state, and ended after a rise in oestrogen output to levels ≥ 70 nmol/24 h. It is concluded that 'anovulatory' cycles and cycles in which there are 'postmenopausal' levels of FSH and LH are common in the perimenopause and that they are rare in premenopausal women.
LACK OF EFFECT OF ANGIOTENSIN ON LEVELS OF CYCLIC AMP IN ISOLATED ADRENAL ZONA GLOMERULOSA CELLS FROM THE RAT
Authors: BELL J. B. G. , TAIT J. F. , TAIT S. A. S. , BARNES G. D. , BROWN B. L.
Published: December 2008

The effects of pure [Asp1, Val5]- and [Asn1, Val5]-angiotensin II and also [des-Asp1, Ile5]-angiotensin II (angiotensin III) on cyclic AMP and steroid outputs by dispersed rat capsular cells, comprising 95% zona glomerulosa and 5% zona fasciculata cells, have been studied.

The results showed that [Asp1, Val5]- and [Asn1, Val5]-angiotensin II, at doses between 2·5 × 10−1 1 and 2 × 10−4 mol/l, which produced typical increases in steroidogenesis, failed to increase output of cyclic AMP. This lack of effect was observed whether the nucleotide was measured by radioimmunoassay or by adrenal binding protein and under the same conditions in which 8·4 mm-K+ consistently increased the output of cyclic AMP. Instead the results showed a small but significant decrease in cyclic AMP output with angiotensin II. Similar results were obtained with incubations for 60 rather than 120 min and with medium containing a concentration of 5 or 40 g bovine serum albumin/l. Although the levels of cyclic AMP were generally higher in the presence of the phosphodiesterase inhibitor, 3-isobutyl-l-methylxanthine, the same decrease relative to basal outputs was observed with angiotensin II which increased steroidogenesis. Angiotensin III also failed to increase output of cyclic AMP at doses (2·5×10−9 to 2·5×10−6 mol/l) which produced increases in steroid output equivalent to those obtained with angiotensin II.

These results indicate that angiotensin II and III can act through a cyclic AMP- independent mechanism.
A HIGH-AFFINITY BINDING SITE FOR THE ANTIOESTROGENS, TAMOXIFEN AND CI 628, IN IMMATURE RAT UTERINE CYTOSOL WHICH IS DISTINCT FROM THE OESTROGEN RECEPTOR
Authors: MURPHY L. C. , SUTHERLAND R. L.
Published: December 2008

A high-affinity, saturable antioestrogen binding site, which does not bind oestradiol, has been reported to exist in a number of oestrogen target tissues but not in the immature rat uterus. This study reports the results of a more thorough search for this site in immature rat uterine cytosol. When concentrations of uterine cytoplasmic oestrogen receptor were selectively depleted by translocation of 90–95% of the cytoplasmic oestrogen receptor to the nucleus, saturation analysis studies revealed that the antioestrogens, tamoxifen and CI 628, were bound to high-affinity, saturable binding sites which were present at about 2·5 times the concentration of the residual oestrogen receptor sites. Oestradiol could only partially inhibit the binding of tritiated antioestrogens to their saturable binding sites in this material indicating that a significant proportion of these sites were distinct from the oestrogen receptor sites. This was confirmed in experiments where oestrogen receptor sites were saturated in vitro with oestradiol and high-affinity, saturable sites for CI 628 and tamoxifen were still present. The CI 628 and tamoxifen had high affinity for these sites with dissociation constants of 1·0–1·6 nmol/l. These specific antioestrogen binding sites were present at about 5% of the concentration of oestrogen receptors in normal immature rat uterine cytosol which probably explains their previous lack of detection in this material.
RECEPTOR HETEROGENEITY IN THE HUMAN THYROID: DIFFERENCES BETWEEN THYROTROPHIN BINDING SITES IN MEMBRANE AND NUCLEAR FRACTIONS
Authors: MANLEY S. W. , BOURKE J. R.
Published: December 2008

Binding of 125I-labelled bovine TSH to crude membrane fractions of human thyroid tissue was a saturable, hormonally specific process which yielded non-linear Scatchard plots with limiting affinities of approximately 109 and 107l/mol. Binding activity in membranes was soluble in Triton X-100, was inhibited specifically by immunoglobulins from patients with Graves's disease, and was increased by the beta-blocking drug, propranolol. In contrast, purified nuclear preparations showed a predominance of lower affinity binding, and their binding activity was insoluble in Triton and insensitive to immunoglobulins from patients with Graves's disease and to propranolol. Tryptic digestion liberated only low affinity binding activity from membranes or nuclei. It was concluded that human thyroid tissue contains independent classes of TSH-binding sites, which differ in their chemical, immunological and hormone-binding properties.
INFLUENCE OF INSULIN AND GLUCAGON ON SECRETION OF GROWTH HORMONE IN GROWING DUCKS (ANAS PLATYRHYNCHOS)
Authors: FOLTZER C. , HARVEY S. , STROSSER M. T. , MIALHE P.
Published: December 2008

An inverse age-related pattern of GH secretion has been identified in immature ducks between 2 and 9 weeks of age, the plasma level of GH falling progressively from 30–40 ng/ml at 2 weeks of age to the adult level (< 10 ng/ml) by 9 weeks of age. This decrease in GH secretion was not accompanied by any age-related changes in the concentrations of plasma immunoreactive insulin or glucagon-like immunoreactivity or in plasma glucose or free fatty acid level.

In 4- to 6-week-old ducklings the intravenous infusion of insulin (2·5 or 10 mu./kg per min for 30 min) and glucagon (0·1 or 0·5 μg/kg per min for 30 min) induced some inhibition of GH secretion, independently of changes in blood glucose level. These results suggest that although insulin and especially glucagon have direct effects on GH secretion in the duck, maturational differences in pancreatic function are unlikely to be causally related to the decrease in GH secretion during growth.
EFFECT OF NON-ESSENTIAL AMINO ACIDS ON FETAL RAT PANCREATIC GROWTH AND INSULIN SECRETION IN VITRO
Authors: MILNER R. D. G. , DE GASPARO M.
Published: December 2008

Fetal rat pancreatic rudiments explanted on day 14 of gestation were grown for 6 days in organ culture in medium containing glucose (5·5 or 16·5 mmol/l) and essential amino acids (3·5 or 13·1 mmol/l). Non-essential amino acids (alanine, aspartic acid, asparagine, glycine, proline and serine) were added to the culture medium in a number of combinations and at a maximum total concentration of 4·0 mmol/l. At the end of the period of culture rudiments were compared for DNA content, insulin concentration and quantitative morphology. The release of insulin from the rudiments was tested during 6-h incubations on day 6 of culture.

Enrichment of the culture medium with any combination of non-essential amino acids had a slight or no effect on the growth or cellular composition of the rudiment or insulin release from it. Addition of all the non-essential amino acids to medium containing 16·5 mmol glucose and 13·1 mmol essential amino acids/l caused a dramatic reduction in the net insulin accumulation by the cultured rudiment. Combinations of non-essential amino acids in which one or more were omitted did not have the same effect. These findings suggest that fetal rat pancreas grown in vitro may require both essential and non-essential amino acids for the full expression of insulin biosynthesis and secretion.
INFLUENCES OF SOME ENDOCRINE GLANDS AND OF HORMONE REPLACEMENT ON THE PORPHYRINS OF THE HARDERIAN GLANDS OF MICE
Authors: SHIRAMA KAZUHIKO , FURUYA TETSUO , TAKEO YUJI , SHIMIZU KIYOSHI , MAEKAWA KYUTARO
Published: December 2008

There are marked sex differences in the Harderian gland of the C3H/He strain of mice. Female (but not male) glands contain large amounts of porphyrin, which are readily visible as solid depositions within the lumina.

The histology and porphyrin content of the Harderian gland were examined in intact and in pregnant mice and in mice subjected to combinations of adrenalectomy, gonadectomy and administration of sex steroid hormones. In male mice, castration approximately doubled the amount of porphyrin in the Harderian gland. Castration plus adrenalectomy increased the levels over 30-fold, to levels similar to those found in female mice, although adrenalectomy alone produced no significant effect. Administration of testosterone to the male mice which had been castrated and adrenalectomized prevented the increases while progesterone treatment produced further increases in porphyrins. In intact females, the amount of porphyrin varied with the phase of the oestrous cycle; being lowest during metoestrus and highest during dioestrus. In ovariectomized–adrenalectomized females, the effects of administered sex hormones on the amount of porphyrin in the gland were the same as in males. In pregnant mice, the level was not significantly different from that in intact oestrous animals.
STUDIES ON THE MECHANISM OF SECRETION OF CORTICOSTEROIDS BY THE ISOLATED PERFUSED ADRENAL OF THE RAT
Authors: SIBLEY C. P. , WHITEHOUSE B. J. , VINSON G. P. , GODDARD C. , McCREDIE E.
Published: December 2008

A technique for the perfusion of the rat adrenal cortex is described. With tissue culture Medium 199 the preparation was responsive in terms of steroid production to both ACTH and K+ ions. Production of corticosterone and 18-hydroxydeoxycorticosterone (18-hydroxy-DOC) was stimulated by ACTH when it was administered at rates between 5 μu./min and 5 mu./min. Increasing the K+ ion concentration of the perfusate from 3·6 to 5·4 and 8·9 mmol/l stimulated the production of aldosterone, 18-hydroxycorticosterone and deoxycorticosterone, although not of corticosterone or 18-hydroxy-DOC.

This preparation has been used to study further the mechanism of secretion of corticosterone and 18-hydroxy-DOC. Thus, production of these two steroids was measured at different perfusion flows, varying between 0·1 and 0·6 ml/min, with different levels of ACTH stimulation. Corticosterone production was significantly (P < 0·001) increased by increasing flows both under control conditions and when ACTH was administered at constant rates of 50 μu./min or 1 mu./min. Production of 18-hydroxy-DOC was not affected by flow either under control conditions or with 50 μu. ACTH/min. However, when ACTH was administered at 1 mu./min, 18-hydroxy-DOC production was also significantly (P < 0·001) increased by flow.

The results are consistent with those obtained in previous in-vitro studies and have been interpreted as suggesting that the main mechanism of corticosterone secretion is simple diffusion. In contrast, 18-hydroxy-DOC secretion, at least at sub-maximal levels of stimulation, appears to require a more complex process.
ROLE OF PROSTAGLANDINS IN THE CONTROL OF THE FUNCTION OF ADRENAL GLOMERULOSA CELLS
Authors: ENYEDI P. , SPÄT A. , ANTONI F. A.
Published: December 2008

The role of prostaglandins in the control of aldosterone production was studied in isolated rat glomerulosa cells. Exogenous prostaglandin E2 in concentrations above 10−9 mol/l increased the production rate of aldosterone; this effect was attenuated by the competitive antagonist, 7-oxa-13-prostynoic acid. Prostaglandin F2α (10−9–10−5 mol/l) failed to influence the production rate of aldosterone. The aldosterone-stimulating effect of the prostaglandin precursor, arachidonic acid (5 × 10−4 mol/l), could not be blocked by inhibitors of prostaglandin synthesis. Basal production rate of aldosterone was not significantly influenced by non-steroidal anti-inflammatory drugs. Glomerulosa cells were stimulated by angiotensin II; this effect was not potentiated by arachidonic acid and was reduced only slightly by indomethacin. The cells were also stimulated by corticotrophin and potassium ions. The effect of these substances was not potentiated by arachidonic acid and was not inhibited by non-steroidal anti-inflammatory drugs. These results do not confirm the presumption that intra-adrenal prostaglandins play an essential role in the control of aldosterone secretion. Some effects of arachidonic acid and its antagonist, eicosatetraynoic acid, on aldosterone production are considered to be independent of changes in prostaglandin synthesis.
PITUITARY SENSITIVITY TO GONADOTROPHIN RELEASING HORMONE AFTER HYPERPROLACTINAEMIA INDUCED WITH NEUROLEPTICS AND DOMPERIDONE IN THE RAT
Authors: CARTER D. A. , WHITEHEAD S. A.
Published: December 2008

The effect of hyperprolactinaemia induced by dopamine-antagonist drugs on pituitary responsiveness to gonadotrophin releasing hormone (Gn-RH) and on plasma LH levels has been investigated in intact and ovariectomized rats. The animals were pretreated with haloperidol, pimozide or domperidone and the sensitivity of isolated pituitary glands to pulses of Gn-RH were tested using a perifusion system. Trunk blood, collected at the time of killing, was assayed for plasma LH and prolactin. In addition, a direct effect of the drugs on pituitary responsiveness to Gn-RH was investigated by perifusing pituitary glands taken from untreated, pro-oestrous rats in medium containing the dopamine antagonists.

The pituitary responsiveness was significantly impaired in intact rats after treatment with each of the drugs whereas no effect was observed in pretreated ovariectomized rats. None of the drug treatments altered levels of circulating LH. High concentrations of the drugs present in the perifusion medium also inhibited pituitary responsiveness although it is not known whether the concentrations of the drugs present in the pretreated animals would exert a similar effect.

The results suggest that short-term hyperprolactinaemia impairs pituitary responsiveness through a modulation of ovarian steroid secretion and that Gn-RH release is not altered. Treatment with domperidone exhibited similar effects on the parameters measured here to those caused by the two neuroleptics, indicating that this novel anti-dopaminergic drug is acting in a similar manner.
IDENTIFICATION OF STEROIDS PRODUCED BY BOVINE CHORION INCUBATED WITH [14C]ANDROSTENEDIONE
Authors: SIMONS I. M. , KING G. J.
Published: December 2008

Individual chorion taken from cows in early pregnancy (days 27, 44, 45 and 49) was incubated with [14C]androstenedione in short-term incubation in vitro. After preliminary extraction, separation and purification, metabolites were identified by recrystallization with authentic unlabelled steroids to constant specific activity. Major metabolites identified were 5β-androstane-3,17-dione (5β-androstanedione) and 5β-androstan-3α-ol-17-one (aetiocholanolone) while minor metabolites were identified as 5β-androstane-3α,17β-diol and 5β-androstan-17α-ol-3-one. There was no 14C-labelled oestradiol or oestrone detectable in the medium either as free oestrogens or as sulphates.
EFFECTS OF α-MELANOCYTE-STIMULATING HORMONE AND [8-ARGININE]-VASOTOCIN UPON MELANOGENESIS IN HAIR FOLLICLE MELANOCYTES IN VITRO
Authors: LOGAN ANN , WEATHERHEAD BRIAN
Published: December 2008

α-Melanocyte-stimulating hormone (α-MSH) has been shown to act directly on the mammalian melanocyte in short-term cultures of hair follicles obtained from the Siberian hamster. Melanogenesis was stimulated through an increase in tyrosinase activity which resulted in an increase in melanin production. The response of hair follicle melanocytes to α-MSH occurred only in follicles taken from moulting animals, implying that they show a discontinuous expression of MSH receptors during the hair follicle growth cycle. Synthetic 1–24 ACTH had no effect on melanogenesis regardless of whether the follicles came from moulting or non-moulting animals. The pineal peptide, [8-arginine]-vasotocin (AVT), inhibited melanin production without a concomitant decrease in tyrosinase activity. In this respect AVT resembled melatonin, although AVT showed a potency ratio of less than half on a molar basis. The action of AVT, like that of melatonin, must ultimately be on some post-tyrosinase step in melanin biosynthesis. In these hair follicle melanocytes AVT seems to bind to specific receptors since neither of the closely related peptides, oxytocin and [8-arginine]-vasopressin, displayed any activity in our culture system.
FETAL TESTOSTERONE IN MICE: EFFECT OF GESTATIONAL AGE AND CANNABINOID EXPOSURE
Authors: DALTERIO S. , BARTKE A.
Published: December 2008

The effect of increasing gestational age and maternal exposure to cannabinoids on body weight, ano-genital distance and androgen concentration in fetal mice was examined. Body weight increased in both male and female fetuses from days 16 to 18 (the presence of a vaginal plug was considered to indicate day 1 of pregnancy), while ano-genital distances tended to increase faster in male than in female fetuses. The concentration of testosterone increased with age in fetuses of either sex. However, at day 16, there was a significant influence of fetal sex on testosterone concentration with two non-overlapping distributions, one above and one below 300 pg/g fetal tissue, correlating with male and female gender respectively. After day 16, male fetuses tended to have higher testosterone concentrations, but some values obtained in females did overlap.

Treatment of female mice with Δ9-tetrahydrocannabinol, the main psychoactive ingredient of marihuana, from days 12 to 16 of pregnancy caused a significant (P < 0·01) increase in fetal deaths in utero. Cannabinol treatment had no effect on this parameter, but reduced body weight (P < 0·02) in female fetuses, and increased ano-genital distance (P < 0·05) in male fetal mice. The concentrations of testosterone and dihydrotestosterone were reduced in male but not in female fetuses.

The results indicate that exposure to psychoactive or non-psychoactive constituents of marihuana suppresses testosterone levels in fetal as well as in immature and adult mice, as we have previously reported. Thus, maternal exposure to cannabinoids may interfere with the process of sexual differentiation in their male offspring as a result of decreased fetal androgen production.
EFFECT OF CORPORA LUTEA ON PLACENTAL HYPERTROPHY IN RATS
Authors: ICHIKAWA SHIGETAKA , NAKAMURA YUKIO , SAWADA TSUTOMU
Published: December 2008

Prepubertal rats, induced to mate by treatment with pregnant mare serum gonadotrophin (sperm present = day 0), were used in all experiments. The reduction in the number of corpora lutea (CL) of pregnancy to four on days 10 or 13 of pregnancy produced placental hypertrophy when compared to sham-operated controls, but a reduction to six had no effect on placental growth. The removal of all primary CL on days 11 or 13 of pregnancy in pregnant rats bearing additional secondary CL induced by an injection of human chorionic gonadotrophin (hCG) on days 5 or 7 of pregnancy also resulted in placental hypertrophy. Ovarian secretion of progesterone on day 13 of pregnancy was significantly lowered after reducing CL to four in normal pregnant rats and removing primary CL from rats treated with hCG on day 5. Removal of primary CL from rats treated with hCG on day 5 had no effect on oestradiol-17β secretion, whereas reducing CL to four in normal pregnant rats significantly increased it. Daily injections of 4 mg progesterone until day 17 of pregnancy from the day of reduction of the number of CL, or from the day of removal of primary CL, prevented placental hypertrophy. These results suggest that the decrease of progesterone, but not of oestrogen, is the main factor inducing placental hypertrophy in ovariectomized pregnant rats.
RELEASE OF PROTEIN WHICH BINDS PROGESTERONE FROM THE BOVINE CORPUS LUTEUM
Authors: WILLCOX D. L. , ALISON M. R.
Published: December 2008

The nature of the proteins released together with progesterone from the bovine corpus luteum was investigated. Slices of bovine corpus luteum obtained at the mid-luteal stage of the oestrous cycle were incubated in vitro in the presence of bovine LH. Radioactive monitoring of compounds separated by gas–liquid chromatography showed that added [14C]acetate was converted to sterols and progesterone within the 2-h incubation period. Electrophoresis of the proteins recovered from the incubation medium showed the presence of a major band which migrated at the same rate as a progesterone-binding protein isolated from pooled corpora lutea. Densitometry revealed that the proteins in the incubation medium were enriched threefold in binding protein compared to those in an homogenate of corpus luteum. Equilibrium dialysis of the medium after addition of [3H]progesterone revealed the presence of a progesterone-binding activity (association constant = 106l/mol) analogous to that contained in the cytosol fraction from bovine corpus luteum.

The finding that progesterone-binding protein is released concomitantly with the hormone has implications for the granule hypothesis of steroid secretion. The existence of an intracellular steroid-binding protein complex to maintain progesterone in high intragranular concentration would be predicted from this hypothesis.
PHOTOPERIODIC MODULATION OF GONADOTROPHIN SECRETION IN CASTRATED JAPANESE QUAIL
Authors: URBANSKI H. F. , FOLLETT B. K.
Published: December 2008

Male Japanese quail were castrated when sexually immature and immediately exposed to one of the following stimulatory lighting regimes for 52 days: 11 h light: 13 h darkness/day (11L : 13D), 12L : 12D, 13L : 11D, 14L : 10D, 15L : 9D, 16L : 8D, 20L : 4D or 23L : 1D. One group was retained on short days (8L : 16D). Clearcut differences in the plasma levels of LH and FSH emerged between the various groups. Levels remained very low in castrated quail on 8L : 16D but were much greater in those on 14L : 10D, 15L : 9D, 16L : 8D, 20L : 4D and 23L : 1D, eventually becoming 15 to 20 times higher. Less pronounced castration responses developed on 13L : 11D, 12L : 12D or 11L : 13D. Alterations in photoperiod after day 52 caused an appropriate rise or fall in LH secretion. Photoperiodically induced suppressions were rapid, being highly significant within 4 days, but increases usually had a slower time course. When sexually mature quail (on 16L : 8D) were castrated and transferred to 8L : 16D they also exhibited a rapid suppression in LH secretion. Thus in quail, unlike some mammals, the photoperiodic control over gonadotrophin secretion is independent of the reproductive status of the animal at the time of castration. The results confirm the view that changes in sensitivity of the hypothalamo-pituitary axis to gonadal steroids are not a primary factor in the neural mechanisms underlying photoperiodism in quail.
INFLUENCE OF OSMOLALITY AND IONIC ENVIRONMENT ON THE SECRETION OF PROLACTIN BY HUMAN DECIDUA IN VITRO
Authors: MARKOFF EDITH , BARRY SUSAN , HANDWERGER STUART
Published: December 2008

The effects of extracellular osmolality and ions on the secretion of prolactin were examined in human decidual explants incubated for 4 h in modified Krebs–Ringer buffer. Explants incubated in media made hypersomotic (280–336 mosm/kg) with sodium, lithium or mannitol or in media made hypo-osmotic (280–224 mosm/kg) by decreasing the sodium concentration secreted the same amount of prolactin as explants incubated in control medium (280 mosm/kg). Explants incubated in calcium-deficient medium secreted 64 ± 8% (P≤0·001) less prolactin than controls (1·65 mmol Ca2+/1). Secretion was restored to control values by the addition of calcium (0·33 mmol/l) or barium (0·5, 1·0 or 2·0 mmol/l) to the medium. Prolactin secretion was unaffected by higher than control extracellular calcium concentrations, calcium ionophore A23187 (10−6, 10−9 mol/l) or lanthanum (0·5, 1·0 or 2·0 mmol/l). Changes in extracellular magnesium (0–20 mmol/l), potassium (0–55 mmol/l) or bicarbonate (0–32 mmol/l) had no effect on prolactin secretion. These results indicate that marked changes in extracellular osmolality and concentrations of sodium, magnesium and bicarbonate have no effects on decidual prolactin secretion. Calcium, however, is essential for the basal secretion of decidual prolactin.
GONADOTROPHIN, TESTOSTERONE AND PROLACTIN INTERRELATIONSHIPS IN CADMIUM-TREATED RATS
Authors: ZYLBER-HARAN E. A. , GERSHMAN H. , ROSENMANN E. , SPITZ I. M.
Published: December 2008

We have investigated the long-term effect of a single subcutaneous injection of cadmium chloride on plasma testosterone and gonadotrophin levels and the prolactin response to the dopaminergic antagonist metoclopramide in the rat. Twelve days after treatment with cadmium there was testicular necrosis, associated with a decrease in testosterone concentration and atrophy of the accessory sexual glands. By 185 days, partial recovery of the accessory sexual glands indicated by Leydig cell regeneration and a slight rise in testosterone levels had occurred. There was, however, persistent damage to the germinal epithelium. Concentrations of LH increased eightfold above controls by day 12, remained raised until 60 days and then decreased to threefold above controls at 280 days. In contrast, FSH levels reached a maximum between 60 and 130 days and remained persistently raised.

The peak prolactin response to metoclopramide in cadmium-treated rats was depressed 12 days after cadmium administration and levels remained low at 19 and 75 days. Normal prolactin responses to metoclopramide were obtained 130 days after cadmium treatment using 1·0 mg metoclopramide/kg or 280 days after treatment using 0·25 mg/kg. When control and cadmium-treated rats were castrated at 280 days and then given metoclopramide 10 days later, the prolactin response was significantly reduced. It is concluded that the impaired prolactin response to metoclopramide in cadmium-treated rats is reversible. Prolactin returns to normal in parallel with regeneration of the Leydig cells, partial restoration of the accessory sex organ weight, slight increase in plasma testosterone and decrease in LH levels. These results suggest that testosterone is not solely responsible for the maintenance of normal prolactin secretion in the male rat.
EFFECT OF ARTIFICIAL PHOTOPERIODS ON PLASMA THYROXINE-BINDING PREALBUMIN AND RETINOL-BINDING PROTEIN IN JAPANESE QUAIL
Authors: HEAF D. J. , EL-SAYED M. , PHYTHIAN B. , CARROLL J. , GLOVER J.
Published: December 2008

Variations in thyroxine-binding prealbumin (TBPA) and retinol-binding protein (RBP) concentrations in plasma were determined in Japanese quail subjected to a shortened solar lighting cycle lasting 4 months of real time. The concentration of TBPA varied inversely with the length of daily photoperiod up to 15 h (correlation coefficient r = −0·99) when a minimum level was reached of about 50% of that obtained under short days consisting of 8 h light: 16 h darkness (8L : 16D). A slight reversal in the concentration of TBPA occurred with photoperiods in excess of 16 h. The time-lag in response of the cyclic change in TBPA after the change in the lighting cycle was 8 days. The concentration of holoRBP, on the other hand, showed little change with photoperiods <15 h, but between 15 and 17·5 h it passed through peak values which were 24% and approximately 10% higher than the initial concentrations in female and male birds respectively. Total immunoreactive RBP concentrations in plasma peaked similarly in females but in males the apparent changes were not significant. The molar ratio of the two proteins (TBPA: RBP) which form a 1:1 complex in plasma also changed inversely with photoperiod from 1·6 on short (8L : 16D) to 0·6 on long (16L : 8D) days. When the ratio declined below 1·0 it was noted that rapid growth of the gonads took place and when this ratio returned to > 1·0 regression set in. The changes in plasma TBPA concentration were examined in Japanese quail subjected to sudden changes in photoperiod from short (8L : 16D) to long (20L : 4D) days and vice versa. In the group of birds transferred from short to long days the plasma level declined significantly (P<0·05) within 3 days, whereas birds changed from long to short days were more refractory in that a significant increase was seen only after 30 days. The synthesis of TBPA in liver is closely controlled by photoperiod and it seems that this protein plays an important role in the peripheral distribution of thyroxine and perhaps also influences the cyclical supply of retinol to the gonads.
HUMAN TESTIS DOES NOT SECRETE OESTRONE SULPHATE
Authors: WU F. C. W. , SWANSTON I. A. , HARGREAVE T. B. , BAIRD D. T.
Published: December 2008

The concentrations of five steroids in samples of spermatic venous blood collected from 17 men undergoing ligation of varicocoeles were compared with those in samples from the antecubital vein. There was evidence of testicular secretion of testosterone, androstenedione, oestradiol-17β and oestrone, since the ratios of the mean concentrations in spermatic venous plasma to those in peripheral venous plasma were 77·2, 9·1, 28·7 and 1·6 respectively. The testicular secretion of oestrone sulphate was minimal; the ratio of the mean concentrations in spermatic and peripheral plasma was 1·07. These results support the view derived from isotope dilution studies that almost all oestrone and oestrone sulphate in the circulation is derived from peripheral conversion of other precursor steroids.
SEXUAL DIFFERENTIATION OF THE PHOTOPERIODIC RESPONSE IN JAPANESE QUAIL
Authors: URBANSKI H. F. , FOLLETT B. K.
Published: December 2008

Plasma levels of LH are generally higher in male than in female quail. This dimorphism was found to persist in quail which had been through a breeding cycle and then gonadectomized. Under long daylengths (12 h light: 12 h darkness (12L : 12D) or 16L : 8D) ovariectomized quail had plasma levels of LH that were 55–70% of those seen in castrated birds. The difference was reduced after transfer to short days (8L : 16D) when LH concentrations fell to basal levels, but again became more pronounced when the quail were restimulated with long photoperiods. Thus, the photoperiodic response system is sexually differentiated.
PERSISTENCE OF IMMUNOREACTIVE INSULIN, GLUCAGON AND PANCREATIC POLYPEPTIDE IN THE PLASMA OF DEPANCREATIZED CHICKENS
Authors: COLCA J. R. , HAZELWOOD R. L.
Published: December 2008

The present study evaluates the possibility that an extra-pancreatic source of insulin exists in chickens. The effect of pancreatectomy on plasma levels of immunoreactive insulin (IRI), glucagon (IRG) and pancreatic polypeptide (IRAPP) was examined. Plasma levels of IRI, IRG and IRAPP were measured both in the basal state and after an i.v. challenge with known secretogogues at several times after pancreatectomy. The nature of the avian plasma immunoreactivity was further characterized by gel filtration.

Results indicated that plasma IRI and IRG persisted for 5 h, 24 h and 5 days after pancreatectomy. Furthermore, plasma levels of IRI and IRG remained responsive to the stimulus of i.v. arginine. The Sephadex G-50 elution profiles for IRI and IRG were similar for plasma obtained from both depancreatized and intact chickens. Postmortem tissue analyses indicated that the persistence of IRI and IRG in the depancreatized animals was not due to the presence of pancreatic remnants.

Plasma IRAPP decreased to undetectable levels 5 h after pancreatectomy. Although plasma IRAPP was measurable 1 and 5 days after pancreatectomy, these levels were not responsive to i.v. pentagastrin. Furthermore, gel filtration experiments indicated that the only form of IRAPP remaining after pancreatectomy had an apparent mol. wt of greater than 100 000. Such a compound was not secreted by the pancreas in vitro.

Evidence presented herein indicates that pancreatic polypeptide is the only pancreatic hormone to be eliminated from the circulation after pancreatectomy in chickens. It is suggested that the depancreatized chicken might be useful as a model of a 'selective' pancreatic polypeptide deficiency.