bluuebunny/crossref_metadata_2025 huggingface dataset:
DOPAMINERGIC CONTROL OF OXYTOCIN RELEASE IN LACTATING RATS
Authors: CLARKE G. , LINCOLN D. W. , MERRICK LYNDA P.
Published: December 2008

During suckling, anaesthetized lactating rats release regular (about every 7 min) but brief )ulses of oxytocin (0·5–1·0 mu.) which produce single transient increases in intramammary [unk]ressure. Drugs which selectively impair synaptic transmission were used to determine the [unk]ole of dopamine and noradrenaline in regulating this natural reflex. Diethyldithiocarbamate 100–200 mg/kg, i.v.) and α-methylparatyrosine (100–400 mg/kg, i.v.) which inhibit the [unk]ynthesis of catecholamines both blocked the suckling-induced release of oxytocin. The milk[unk]jection reflex was also inhibited in a dose-dependent manner by the intravenous administraion of the dopamine antagonists, fluphenazine (0·7 mg/kg), pimozide (1·4 mg/kg), cis-lupenthixol (4·5 mg/kg) and metoclopramide (6·0 mg/kg), and caused a significant inhibition P < 0·01) of the reflex in 50% of the rats tested. The α-adrenoceptor antagonist phenoxy[unk]enzamine (1·4 mg/kg) was similarly effective. Dopamine (40 μg), bromocriptine (10 μg), [unk]pomorphine (100 μg), noradrenaline (10 μg) and phenylephrine (2 μg) injected into the;erebral ventricles evoked a sustained release of oxytocin which produced multiple increases n intramammary pressure; isoprenaline (4 μg) was ineffective. The release of oxytocin evoked [unk]y dopamine and noradrenaline was prevented by cis-flupenthixol and phenoxybenzamine respectively. None of the drugs used affected the mammary sensitivity to exogenous oxytocin lor were their actions modified by pretreatment with propranolol (1 mg/kg). The results [unk]uggest that the neural pathway for the reflex release of oxytocin during suckling in the rat [unk]ontains both dopaminergic and noradrenergic synapses, the latter acting through α-[unk]drenoceptors and being distal in the pathway to the dopaminergic component.
EFFECTS OF PHOTOPERIOD ON HYPOTHALAMIC LUTEINIZING HORMONE RELEASING HORMONE IN THE MALE HAMSTER
Authors: PICKARD G. E. , SILVERMAN A. J.
Published: December 2008

Male hamsters were maintained on long (14 h light: 10 h darkness; 14L: 10D) or short (6L: 18D) photoperiods. Animals on short-days had reduced levels of LH in the serum and anterior pituitary gland, decreased androgen in the circulation and regressed testes and accessory sex organs. These same hamsters had significantly raised concentrations of hypothalamic luteinizing hormone releasing hormone (LH-RH). There was no significant difference in the response to exogenous LH-RH between groups maintained on long- and shortdays. Castration significantly reduced levels of LH-RH in the hypothalamus in the long-day animals but had little effect on this parameter in short-day animals which had already undergone testicular regression. The increased levels of LH-RH in the hypothalami of both intact and castrated hamsters on non-stimulatory photoperiods is interpreted as a decreased release of the neurohormone which subsequently results in a decreased release of LH.
RELATIONSHIP BETWEEN PLASMA SOMATOMEDIN ACTIVITY AND LEVELS OF CORTISOL AND FREE FATTY ACIDS FOLLOWING STRESS IN PIGS
Authors: SPENCER G. S. G.
Published: December 2008

Somatomedin activity, cortisol and free fatty acids have been measured in the plasma of eight Pietrain pigs at various times after stress. Somatomedin activity decreased immediately, reached a minimum after 15 min and remained low throughout a 3·5 h period. Cortisol levels rose to a peak after 15 min and regained normal levels after 60 min. Free fatty acid levels increased to a peak level about 3 h after stress.

The possibility of inhibitors of the bioassay for somatomedin activity influencing the results are discussed.
A METHOD FOR ISOLATION BY GEL ELECTROFOCUSING OF ISOHORMONES B AND C OF HUMAN PROLACTIN FROM AMNIOTIC FLUID
Authors: BEN-DAVID MENASHE , CHRAMBACH ANDREAS
Published: December 2008

Human prolactin from amniotic fluid, consisting of isohormones B and C (major), was radio-iodinated after storage of the hormone for 3 years at −70 °C, and yielded a Ferguson plot in polyacrylamide gel electrophoresis that was indistinguishable from the original except that the zones of isohormone B and C were fused. However, isohormones B and C of 125I-labelled human prolactin were separated on isoelectric focusing in polyacrylamide gel, using Ampholine carrier ampholytes (pI range 5–8), taurine (pI 5·1) as anolyte and β-alanine (pI 6·9) as catholyte. After 20 h of electrofocusing at 0–4 °C, 1000 V, both isohormones reached constant pH (isoelectric) positions on the gel. The apparent isoelectric points of human prolactin B and C were 5·96 and 5·62 Micro-preparative gel electrofocusing followed by excision and re-electrofocusing of the gel slices containing human prolactin B and C, yielded zones of homogeneous isohormones B and C.
FOLLICLE-STIMULATING HORMONE RELEASE IN HEMICASTRATED PREPUBERTAL RAMS AND ITS RELATIONSHIP TO TESTICULAR DEVELOPMENT
Authors: WALTON J. S. , EVINS JANET D. , HILLARD M. A. , WAITES G. M. H.
Published: December 2008

Hemicastration of rams at 1 week of age resulted in compensatory growth of the remaining testis. This was associated with an increase in the concentration of FSH in peripheral plasma which was maintained until the rams were approximately 10 weeks old. Plasma concentrations of LH were similar in both entire and hemicastrated lambs during this period. Pulsatile release of LH was observed in all rams from approximately 6 weeks of age onwards. The frequency of these pulses increased and the size of each pulse declined as the animals grew older. At 16 weeks pulsatile release was almost undetectable and the basal levels of LH had increased. The increased concentration of FSH in plasma was related to the size of the remaining testis but not to its development. The return of the plasma concentration of FSH to values similar to those found in entire rams preceded the appearance of a lumen or of any primary spermatocytes in the seminiferous tubules. Restricting the development of the remaining testis in hemicastrated rams, by trapping it in the inguinal region, did not alter the FSH response to hemicastration.

The administration of gonadotrophin releasing hormone (10 μg) at 10,13 and 18 weeks of age provoked release of similar quantities of LH in both entire and hemicastrated rams. There was also a substantial release of FSH at 10 weeks of age but this response declined with age and by 18 weeks there was little FSH released in any of the animals. This loss of response occurred earlier in the hemicastrated rams.

The data suggest that in prepubertal rams the release of FSH but not of LH is restricted by a substance produced by the developing Sertoli cells.
DIFFERENCE IN CONCENTRATION OF PROGESTERONE IN PLASMA BETWEEN PREGNANT AND NON-PREGNANT QUOKKAS (SETONIX BRACHYURUS)
Authors: CAKE M. H. , OWEN F. J. , BRADSHAW S. D.
Published: December 2008

The plasma progesterone concentrations during pregnancy and the oestrous cycle of the quokka were measured daily after each had been initiated by the removal of pouch young. Progesterone levels ranged from 0·6 ng/ml in the early stages of the oestrous cycle to about 2·5 ng/ml at the peak of the luteal phase. There was no significant difference between pregnant and non-pregnant states before the removal of the pouch young nor in the latter half of the cycle. However, the plasma progesterone concentration on days 3–4 after removal of the pouch young was significantly greater in pregnant animals when compared with nonpregnant animals at the same stage and also when compared with the levels before removal of young. This early peak in the concentration of progesterone in peripheral plasma is discussed in relation to the development of the previously dormant blastocyst.
THE PHYSIOLOGICAL SIGNIFICANCE OF ANDROGEN-INDUCED OVULATION IN THE HEN
Authors: CROZE F. , ETCHES R. J.
Published: December 2008

The ovulation-inducing property of androgens in the laying hen was investigated. In a first experiment, four different androgens were injected subcutaneously into single-comb White Leghorn hens on the day of the last oviposition of a sequence. The hens were killed 10 h later and examined for the presence of an ovum in the oviduct. Testosterone induced ovulation in accordance to the dose injected (median effective dose, 966 ± 193 μg/hen) but the responses to 5α-dihydrotestosterone and 5α-androstane-3α, 17β-diol were not dose-related. The effect of 4-androstene-3,17-dione was more like that of progesterone since it induced ovulation 2 h earlier than the three other androgens.

The physiological significance of the ovulation response to an injection of testosterone was examined in more detail in experiment 2. Seven out of ten hens which were injected with 1 mg testosterone/kg body weight ovulated within 10 h after the injection. Blood samples were taken at hourly intervals and the concentrations of testosterone and progesterone were determined by radioimmunoassay. An injection of testosterone produced an increase in the concentration of testosterone in plasma which was considerably greater and occurred earlier than the preovulatory increase of testosterone in the control birds. The increase in the concentration of progesterone in the hens injected with testosterone was similar in magnitude but occurred earlier than the spontaneous preovulatory increase of progesterone in the control hens. The possible physiological role of testosterone in the ovulation cycle is discussed.
AN IMPROVED METHODOLOGY FOR THE EXTRACTION AND PARTIAL PURIFICATION OF PORCINE HYPOTHALAMIC CORTICOTROPHIN RELEASING FACTOR
Authors: BRISTOW A. F. , MONTAGUE D. , SYNETOS D. , JENKINS G. , COCKAYNE D. , SCHULSTER D.
Published: December 2008

In most previous reports material with corticotrophin releasing factor (CRF) activity has been obtained from hypothalami after extraction with dilute aqueous acid. Such conditions allow substantial proteolytic degradation. By adopting conditions designed to precipitate proteases and by using information on the nature of CRF gained from earlier studies, rapid large scale extraction and partial purification of porcine hypothalamic CRF in high yield was achieved. After extraction with 0·2 m-HCl: acetone (1: 1, v/v), centrifugation and ultrafiltration, considerable preliminary purification of the CRF activity was achieved by adsorption onto carboxymethylcellulose and subsequent elution at increased salt concentration. Following ion-exchange chromatography of the extract on carboxymethylcellulose, CRF activity was obtained in good yield (minimal effective dose of about 1–2 μg/ml) for ACTH release in an in-vitro CRF bioassay utilizing a coupled isolated pituitary cell–adrenal cell system. The data indicated that the previously reported heterogeneous corticotrophin releasing factors of low activity may be a consequence of proteolytic degradation.
QUANTITATIVE RELATIONSHIPS BETWEEN OESTRADIOL-17β IN THE MILK AND BLOOD OF LACTATING BUFFALOES
Authors: BATRA S. K. , ARORA R. C. , BACHLAUS N. K. , PAHWA G. S. , PANDEY R. S.
Published: December 2008

The concentration of oestradiol-17β was measured by radioimmunoassay in the milk and blood of lactating buffaloes after insemination. The concentration of oestradiol-17β in milk was observed to be two to three times higher when compared with that in plasma samples. Major peaks of oestradiol-17β in milk coincided with similar but smaller peaks occurring in plasma samples. In animals which were not pregnant, the major peak of oestradiol-17β was recorded on the day of oestrus.
ROLE OF TESTOSTERONE AND OF ITS METABOLITES IN REGULATING GONADOTROPHIN SECRETION IN THE JAPANESE QUAIL
Authors: DAVIES D. T. , MASSA R. , JAMES R.
Published: December 2008

In the Japanese quail gonadal steroids can depress plasma levels of LH and FSH. Since it is now accepted that testosterone metabolites may be metabolized to the tissue-active forms of the hormone, the in-vitro tissue incubation has been combined with steroid replacement therapy in vivo to investigate the physiological roles of various testosterone metabolites as inhibitory feedback agents on gonadotrophin secretion in quail. After the incubation of quail pituitary glands for 3 h with labelled testosterone four metabolites could be identified; androst-4-ene-3,17-dione, 5β-dihydrotestosterone (5β-DHT), 5β-androstane-3α,17β-diol and 5α-DHT. No 5α-androstane-3α,17β-diol was found. Quantitatively, androstenedione was the major metabolite and conversion of testosterone to 5β-metabolites was significantly greater than to 5α-androgens. Hypothalamic and hyperstriatal tissues converted testosterone to androstenedione, 5β-DHT and 5β-androstane-3α,17β-diol but not to 5α-DHT or 5α-androstane-3α,17β-diol.

Gonadotrophin secretion was studied in castrated quail after chronic s.c. implantation of steroid-containing silicone elastomer capsules or acute injection i.m. of steroid in ethanol: saline. Irrespective of the route of administration seven androgens, listed in descending order of potency, reduced the increased levels of plasma LH: testosterone; 5α-DHT; androstenedione; 5α-androstane-3,17-dione; 5α-androstane-3α,17β-diol; 5α-androstan-3α-ol-17-one; 5α-androstan-3β-ol-17-one. No changes in levels of plasma LH were observed after the administration of 5β-DHT, 5α-androstane-3β,17β-diol, 5βandrostane-3α,17β-diol, 5β-androstane-3,17-dione, androst-5-ene-3β,17β-diol or androst-5-en-3β-ol-17-one.

Testosterone and oestradiol-17β were effective in inhibiting secretion of both LH and FSH in young photostimulated quail and completely blocked testicular growth: 5α-DHT inhibited only the release of LH and testicular growth was unaffected.
ADENYLATE CYCLASE ACTIVITY IN THE UTERINE CERVIX OF NEONATAL AND IMMATURE MICE: INFLUENCE OF OESTRADIOL-17β
Authors: KVINNSLAND STENER
Published: December 2008

The influence of long-term oestradiol stimulation on adenylate cyclase activity was investigated in homogenates from uterine cervices of neonatal (3-day-old) and immature (14-day-old) NMRI mice. A significant increase of enzyme activity, measured in the presence of fluoride ions (NaF), after oestradiol treatment was found in preparations from neonatal but not from those of immature female mice; this was irrespective of whether the enzyme activity was related to wet weight, amount of protein or DNA content. The enzyme activity was stimulated in vitro by NaF and 5-guanylylimidodiphosphate while isoprenalin, histamine, prolactin and oestradiol had no effect.

These results indicated an age-related difference in the effects of oestradiol in the uterine cervix of the mouse.
NUCLEAR RECEPTOR FOR OESTROGEN IN THE BABOON ENDOMETRIUM: DETECTION, CHARACTERIZATION AND VARIATION IN ITS CONCENTRATION DURING THE MENSTRUAL CYCLE
Authors: MARTEL DOMINIQUE , MALET CATHERINE , MONIER MARIE-NOELLE , DUBOUCH PIERRE , PSYCHOYOS ALEXANDRE
Published: December 2008

The present paper describes studies conducted to detect and characterize the nuclear receptor for oestrogen in the baboon endometrium. Only 10% of the [3H]oestradiol nuclear receptor complexes were extracted with a 0·5 m-KCl solution. This solubilized receptor migrated as a 4·4S peak during 5–20% sucrose gradient centrifugation. The oestrogen receptor was not bound to oestrogen in the nuclei under normal physiological conditions. Using an unlabelled competitor addition technique with intact nuclei the variation in oestrogen-receptor concentration of baboon endometrium during the menstrual cycle was measured. This concentration increased slightly during the first week of the cycle, being maximal on day 7 before ovulation (2500 molecules/cell), then decreasing gradually, reaching the lowest level (300 molecules/cell) on day 5 after ovulation, where it remained until the end of the cycle.
FOLLICULAR DEVELOPMENT IN THE IMMATURE GUINEA-PIG
Authors: PEDDIE M. J.
Published: December 2008

A method for making statistical comparisons between populations and types of antral follicles within the ovary of the immature guinea-pig is described. This was used to demonstrate that atresia in the antral follicles first appeared at around 14 days of age, but that the population of healthy antral follicles remained remarkably consistent throughout the second half of the prepubertal period, since neither the total number of healthy antral follicles nor the proportion of atretic follicles changed significantly. However, the maximum diameter of the antral follicles gradually increased with age, from 400 μm at 7 days to 1000 μm at 28 days, 4 days before the vagina first opened. Because the percentage distribution of all types of follicles was so consistent at any age, although individuals showed substantial differences in the numbers of follicles within each ovary, it is suggested that mechanisms operate which regulate the total population of antral follicles within the ovary.
EFFECTS OF OESTRADIOL ON STEROID DEHYDROGENASE ACTIVITIES IN RAT CORPORA LUTEA
Authors: RODWAY R. G. , ROTHCHILD I.
Published: December 2008

The activities of 20α-hydroxysteroid dehydrogenase and 3β-hydroxysteroid dehydrogenase in rat corpora lutea during the second half of pregnancy were measured. In luteal tissue of the intact pregnant rat, 20α-hydroxysteroid dehydrogenase activity was undetectable between days 12 and 18 of pregnancy but appeared slowly after hypophysectomy and hysterectomy on day 12. Treatment of the hypophysectomized and hysterectomized animal with oestradiol delayed this increase until day 17, at which time a rapid induction of this enzyme occurred.

In the normal pregnant rat mean luteal 3β-hydroxysteriod dehydrogenase activity increased between days 12 and 18 (P <0·05, Student's t-test) but fell rapidly after hypophysectomy and hysterectomy on day 12. Oestradiol treatment prevented this fall in activity and enzyme activity was not distinguishable from that of the intact rat.

Progesterone secretion correlated well with the activities of these two enzymes in the three conditions examined.
CONCENTRATIONS OF LUTEINIZING HORMONE, OESTRADIOL-17β AND PROGESTERONE IN THE PLASMA OF HEIFERS TREATED TO INDUCE SUPEROVULATION
Authors: SAUMANDE J.
Published: December 2008

Concentrations of luteinizing hormone (LH), oestradiol-17β and progesterone were studied in 14 heifers treated with pregnant mare serum gonadotrophin (PMSG) and an analogue of prostaglandin F2α (PGF2α) 48 h later to induce superovulation. Plasma levels of oestradiol-17β before ovulation and of progesterone after ovulation were related to the number of ovulations but the concentrations of LH were not so related; however, hormone concentrations at the time of injection of PMSG could not be used to predict the rate of ovulation. The injected gonadotrophin also appeared to affect folliculogenesis after ovulation and this may explain the presence of large follicles in the ovary when the corpora lutea were counted.

It was possible to demonstrate by analysis of plasma levels of hormones that few non-superovulated animals were really insensitive to PMSG.
CONCENTRATIONS OF OXYTOCIN IN THE PLASMA AND AMNIOTIC FLUID OF RHESUS MONKEYS (MACACA MULATTA) DURING THE LATTER HALF OF PREGNANCY
Authors: MITCHELL M. D. , MOUNTFORD L. A. , NATALE R. , ROBINSON J. S.
Published: December 2008

A specific radioimmunoassay for oxytocin has been established with a sensitivity of 0·8 pg/tube. This assay has been applied to the measurement of oxytocin in serial samples of peripheral plasma and amniotic fluid from pregnant rhesus monkeys, collected at weekly intervals by venepuncture and amniocentesis. Concentrations of oxytocin in both fluids were generally low and showed no trends throughout the latter half of gestation.
EFFECTS OF GROWTH HORMONE, PROLACTIN AND THYROXINE ON BODY WEIGHT, SOMATOMEDIN-LIKE ACTIVITY AND IN-VIVO SULPHATION OF CARTILAGE IN HYPOPITUITARY DWARF MICE
Authors: HOLDER A. T. , WALLIS M. , BIGGS P. , PREECE M. A.
Published: December 2008

Hypopituitary dwarf mice were found to have reduced levels of serum somatomedin-like activity compared with normal mice of the Snell strain. Treatment with bovine growth hormone for 3 and 7 days resulted in growth without significantly increased levels of serum somatomedin-like activity, as detected by in-vitro uptake of 35SO42− into normal rat cartilage; only after treatment for 14 days was somatomedin activity significantly raised. However, treatment for 2 days with bovine growth hormone, bovine prolactin or thyroxine resulted in a dose-dependent increase in in-vivo uptake of 35SO42− into dwarf mouse costal cartilage; growth hormone and thyroxine did not act synergistically. Ten days of treatment with growth hormone promoted a dose-dependent increase in both growth (increased weight gain and tail length) and in-vivo uptake of 35SO42−. Increase in tail length was correlated with uptake of 35SO42−. Thus, in-vivo uptake of 35SO42− into dwarf mouse costal cartilage provides a sensitive method for detecting a dose-related effect of growth hormone.
EFFECT OF NEONATAL ADMINISTRATION OF STEROIDS OR GONADECTOMY UPON OESTRADIOL-INDUCED LUTEINIZING HORMONE RELEASE IN RATS OF BOTH SEXES
Authors: GOGAN F. , BEATTIE I. A. , HERY M. , LAPLANTE E. , KORDON C.
Published: December 2008

Implantation of oestradiol into adult rats of both sexes induced different patterns of LH secretion depending on the time at which gonadectomy or testosterone injection were performed. Castration 2 h after birth allowed an LH peak to occur daily at 18.00 h, but its amplitude was lower than that of adult gonadectomized female rats treated with oestradiol. Castration 24 h after birth elicited two kinds of response; a circadian discharge of LH lower than that of male rats gonadectomized 2 h after birth or a steady low level of LH. The LH rhythmicity induced by implantation of oestradiol was not seen after castration at 8 weeks of age. Neonatal administration of testosterone to female rats prevented the LH peak induced by oestradiol that was seen in adult ovariectomized rats. Neonatal or adult ovariectomy did not interfere with the rhythmical response of LH after implantation of oestradiol. Thus, it is concluded that sexual differentiation of the hypothalamus is primarily of masculine origin.
EFFECT OF EXCESSIVE SECRETION OF GROWTH HORMONE ON TISSUES OF THE RAT, WITH PARTICULAR REFERENCE TO THE HEART AND SKELETAL MUSCLE
Authors: PRYSOR-JONES R. A. , JENKINS J. S.
Published: December 2008

Rat pituitary tumours of the GH3 cell line, secreting growth hormone (GH), were induced to grow in Wistar–Furth rats and the effect of prolonged excessive secretion of GH on various organs was investigated. Total body weight of the tumour-bearing animals increased by over 100% compared with control animals and there was widespread visceromegaly affecting especially the liver, kidney, spleen and adrenals. The heart was also considerably enlarged. The effects of excessive GH on skeletal muscle were not uniform and, using a histochemical technique, it was found that the size of type 1 muscle fibres was increased to the greatest extent whereas fibre type 2A was unaffected. Synthesis of DNA in the heart and skeletal muscle was also increased in tumour-bearing animals. Removal of the tumours was followed by a considerable regression in the size of most organs, although hypertrophy of the heart was affected least by a return to normal plasma levels of GH. It was concluded that animals bearing GH3 cell tumours provide a useful experimental model for the study of the tissue changes in acromegaly.
MECHANISMS OF CATABOLISM OF CORTICOTROPHIN-(1–24)-TETRACOSAPEPTIDE IN THE RAT IN VIVO
Authors: HUDSON ANNE M. , McMARTIN COLIN
Published: December 2008

The fragmentation of corticotrophin-(1–24)-tetracosapeptide in vivo has been studied, using tritium-labelled hormone and chromatography, in the rat. After intravenous injection the levels of peptide in the circulation declined rapidly caused by its distribution to the tissues and from 2 min after injection a range of different cleavage products appeared. Many of the fragments in the circulation after 2 min have been identified and in this way cleavage has been shown to occur after residues 1,2,8,15,16,17,19,20 and 21. It is believed that this is the result of aminopeptidase attack at the NH2 terminal, and of attack on the basic region of the molecule by trypsin-like endopeptidase followed by carboxypeptidase. The sulphoxide has been identified as a major metabolite in some experiments but the extent of its formation was very variable. Seventy per cent of the dose was distributed to the tissue beds by 1 min. Part of this was present, mainly as intact peptide, in liver and kidney but the greater proportion was found in muscle, skin and intestine where extensive degradation had already occurred. Further characterization of the fragments formed in the muscle provided good evidence that this tissue may have been the site of generation of many of the fragments which later appeared in the circulation.
GONADOTROPHIN RELEASE IN HYPOGONADAL AND NORMAL MICE AFTER ELECTRICAL STIMULATION OF THE MEDIAN EMINENCE OR INJECTION OF LUTEINIZING HORMONE RELEASING HORMONE
Authors: IDDON CAROL A. , CHARLTON H. M. , FINK G.
Published: December 2008

Electrical stimulation of the median eminence, using parameters known to cause the release of LH in normal male mice, failed to elicit any gonadotrophin response in hypogonadal (hpg) male mice. Administration of 40 ng synthetic LH releasing hormone (LH-RH) resulted in release of LH from the pituitary gland of hpg mice, although the response was significantly lower than that of normal mice. These results were consistent with the hypothesis that the hypogonadal state of the hpg mouse results from a functional absence of LH-RH in the hypothalamus rather than from a lack of response of the pituitary gland to the releasing hormone.
EFFECTS OF ARGININE AND GLUCOSE ON THE RELEASE OF INSULIN IN THE SHEEP FETUS
Authors: FOWDEN ABIGAIL L.
Published: December 2008

The effect of l-arginine on fetal insulin release has been investigated in the chronically catheterized sheep fetus and the findings have been compared with the β cell response to glucose. An infusion of arginine for 5 min (200 mg as a solution of 11·5 mmol/l) stimulated a rapid release of insulin in all the fetuses from 119 to 142 days of gestational age. The maximum insulin concentration occurred at the end of infusion; the mean insulin increase between 0 and 5 min was 18·0 ± 2·0 μu./ml (n = 20). The response to infusion of glucose for 5 min (1 g as a solution of 2·8 mol/l) was more variable and slower than that to arginine with the peak concentration of insulin occurring 10 min after the end of infusion. The mean increase in the concentration of insulin between 0 and 15 min in response to glucose was 42·5 ± 10·0 μu./ml (n = 11). The response to arginine but not to glucose was related to the gestational age of the fetus. The increment in insulin in response to glucose was dependent upon the initial concentration of fetal plasma glucose. The observations are discussed in relation to the regulation of insulin release in utero and the mechanisms of insulin secretion.
EFFECTS OF INSULIN AND GLUCAGON ON PRODUCTION OF RENIN SUBSTRATE BY THE ISOLATED RAT LIVER
Authors: MURAKAMI EIKI , HIWADA KUNIO , KOKUBU TATSUO
Published: December 2008

An isolated rat liver perfusion system was used to study the effects of insulin and glucagon on renin substrate production. Normal livers synthesized renin substrate at a rate of 28·3 ± 3·8 (s.e.m.) ng angiotensin I equiv./g liver each h (n = 8). The addition of insulin (more than 0·1 i.u.) to the perfusion significantly enhanced the production of renin substrate which was about twofold higher than normal control values (P< 0·001). However, glucagon (20 μg) did not affect the synthesis of renin substrate. These results indicated that insulin promoted the synthesis of renin substrate by the isolated rat liver.
PLASMA ANTIDIURETIC HORMONE DURING HYPOXIA AND ANAESTHESIA IN PIGS
Authors: FORSLING MARY L. , INGRAM D. L. , STANIER M. W.
Published: December 2008

The level of antidiuretic hormone (ADH) in the plasma of pigs was studied during hypoxia, anaesthesia and a combination of the two conditions. Hypoxia, caused by making conscious pigs breathe nitrogen, elicited a rise in the level of ADH without change in plasma osmolality; the hypoxia was accompanied in some cases by a slight lowering of arterial pressure which quickly returned to its original level after the period of hypoxic breathing. Pentobarbitone anaesthesia had no significant effect on the level of ADH but halothane anaesthesia elicited a rise in ADH.

Transient high levels of ADH were seen in animals which were exposed to hypoxia during halothane or pentobarbitone anaesthesia. These high levels of ADH were sometimes, but not invariably, accompanied by a fall in arterial pressure. No consistent changes in plasma osmolality or haematocrit were associated with the raised plasma ADH.
ROLE OF THE OVARY IN THE SEXUAL DIFFERENTIATION OF PROLACTIN AND GROWTH HORMONE CELLS IN THE MOUSE ADENOHYPOPHYSIS DURING POSTNATAL DEVELOPMENT: A STEREOLOGICAL MORPHOMETRIC STUDY BY ELECTRON MICROSCOPY
Authors: SASAKI F. , SANO M.
Published: December 2008

To clarify the role of the ovary in the sexual differentiation of prolactin and growth hormone cells, the anterior pituitary glands of mice ovariectomized before or after puberty were studied by a stereological morphometric technique with the electron microscope. A marked sex difference was observed in the relative proportions of these two types of cells in normal adult control animals. In male mice about 52% of anterior pituitary cells were growth hormone cells and about 10% were prolactin cells, while in female mice prolactin cells represented about 39% and growth hormone cells about 37% of the anterior pituitary cell population. Ovariectomy before puberty reduced the proportion of prolactin cells to about 10% and increased growth hormone cells to about 50% of the cell population. The size of prolactin cells and the development of their cell organelles was also reduced. Ovariectomy after puberty had less marked effects. These results suggest that ovariectomy before puberty induced the male phenotype by inhibition of the differentiation of prolactin cells and stimulation of the differentiation of growth hormone cells. The significance of these results in relation to the sexual differentiation of the pituitary gland is discussed.
PROGESTERONE SECRETION AND OVARIAN BLOOD FLOW IN THE PREGNANT RAT
Authors: BRUCE N. W. , MEYER G. T. , DIMMITT S. B.
Published: December 2008

A venous outflow technique was used to monitor the rates of ovarian blood flow and progesterone secretion simultaneously during periods of 2–3 h in nine rats pregnant for 16 days and anaesthetized with sodium pentobarbitone. The rate of ovarian blood flow was 0·460 ± 0·135 (s.d.) ml/min and that of progesterone secretion was 27·2 ± 7·0 μg/h per ovary. Within rats, progesterone secretion was unrelated to the rate of ovarian blood flow (common correlation coefficient, r = 0·136; degrees of freedom = 61; P, not significant) but the latter was inversely related to the arterio-venous difference in the concentration of progesterone (r = −0·731; P <0·01).
IDENTIFICATION AND QUANTIFICATION OF STEROIDS IN THE SERUM OF RAINBOW TROUT DURING SPERMIATION AND OOCYTE MATURATION
Authors: CAMPBELL C. M. , FOSTIER A. , JALABERT B. , TRUSCOTT B.
Published: December 2008

17α-Hydroxy-20β-dihydroprogesterone and 17α-hydroxyprogesterone were found in higher concentrations in serum from female Salmo gairdneri undergoing final oocyte maturation immediately before ovulation than in serum from spermiating male trout. Other steroids (11-deoxycorticosterone, 11-deoxycortisol and progesterone) which have been implicated in oocyte maturation and/or ovulation in lower vertebrates were not identified at such high concentrations and the differences between the serum of both sexes were not so great. These results confirm that 17α-hydroxy-20β-dihydroprogesterone and 17α-hydroxyprogesterone, the most potent inducers of trout oocyte maturation in vitro, are present in the blood when oocyte maturation occurs. The concentration of testosterone was found to be higher in serum from female than from male trout indicating that testosterone is unlikely to be the principal androgen in trout. High concentrations of 11-oxotestosterone in male and barely detectable levels in female fish support the hypothesis that 11-oxotestosterone is an important androgen in the regulation of testicular activity.
ACTIVATION BY CORTICOSTEROIDS OF STEROID METABOLIZING ENZYMES IN OVINE PLACENTAL EXPLANTS IN VITRO
Authors: RICKETTS A. P. , GALIL A. K. A. , ACKLAND NICOLA , HEAP R. B. , FLINT A. P. F.
Published: December 2008

A technique has been developed for the study of placental steroid synthesis in tissue culture. Explants of sheep placentas recovered in the last third of gestation produced progesterone and converted labelled androstenedione into unconjugated and conjugated oestrogens. Cortisol added to the medium stimulated 17α-hydroxylase and aromatizing enzyme activities. The results are discussed in relation to the proposal that the rise in secretion of fetal cortisol before parturition has a direct effect on the activation of placental enzymes catalysing the conversion of progesterone to oestrogens.
AN UNEVEN DISTRIBUTION OF CHOLINE ACETYLTRANSFERASE ACTIVITY IN THE PITUITARY NEUROINTERMEDIATE LOBE OF THE RAT
Authors: GALLARDO MARIA G. P. , CANNATA M. A. , TRAMEZZANI J. H.
Published: December 2008

The neurointermediate lobe of the pituitary gland of male rats was assayed for choline acetyltransferase (CAT) activity. Precise microsample punches were obtained from neurohypophysial tissue, pure pars intermedia tissue and from the junction area between them.

The level of CAT activity (pmol/h per μg protein) in the neurohypophysis, pars intermedia and junction area were 0·390 ± 0·038 (s.e.m.), 0·228 ± 0·042 and 1·824 ± 0·268 respectively. These values show an uneven distribution of CAT in the neurointermediate lobe. The hypothesis of a cholinergic system located in the junction area has been advanced.
CATECHOL OESTROGENS AND GONADOTROPHIN SECRETION IN THE EWE: AFFINITY FOR PITUITARY OESTROGEN RECEPTORS IN VITRO AND ACTION ON GONADOTROPHIN SECRETION IN VIVO
Authors: CLARKE I. J. , FINDLAY J. K.
Published: December 2008

The binding of three catechol oestrogens, 2-OH-oestradiol-17β, 4-OH-oestrone and 2-OH-oestrone, to the ovine pituitary oestrogen receptor was measured in vitro to establish doses for the assessment of the effects of catechol oestrogens in vivo. Relative to oestradiol (100%) the compounds had receptor affinities of 30, 20 and 5% respectively. A dose of oestradiol sufficient to cause negative-feedback effects on the secretion of LH and FSH in ovariectomized ewes was established by intracarotid (i.c.) injections of 0·625–5·0 μg/dose (n = 3), and by measuring plasma levels of gonadotrophins in jugular venous samples taken at intervals of 20 min from 3 h before until 4 h after injection. A dose-dependent relationship (r = 0·88, P<0·001) was found for oestradiol and plasma LH levels. Plasma FSH was slightly (12–25%) but significantly (P<0·05) reduced by doses of 1·25–5·0 μg oestradiol, but no dose–response relationship was observed.

Ovariectomized ewes (n = 4/group) were given 2·5 μg oestradiol (i.c.) simultaneously with 83 μg 2-OH-oestradiol, 125 μg 4-OH-oestrone or 500 μg 2-OH-oestrone. These doses of catechol oestrogens were chosen as being ten times that of oestradiol, with the relative affinities for oestrogen receptor taken into account. Concurrent administration of such doses of catechol oestrogens had no effect on the negative-feedback action of oestradiol in vivo. We have concluded that catechol oestrogens in the circulation probably do not modulate the action of oestradiol on release of LH or FSH; this does not preclude a possible role for them as locally produced regulators of oestrogen action.
MACROPODID MARSUPIAL LUTEINIZING HORMONE: VALIDATION OF ASSAY PROCEDURES AND CHANGES IN CONCENTRATIONS IN PLASMA DURING THE OESTROUS CYCLE IN THE FEMALE TAMMAR WALLABY (MACROPUS EUGENII)
Authors: SUTHERLAND R. L. , EVANS SUSAN M. , TYNDALE-BISCOE C. H.
Published: December 2008

A heterologous double antibody radioimmunoassay employing a rabbit anti-ovine LH antiserum (GDN no. 15) has been developed for the assessment of concentrations of LH in macropodid marsupial pituitary extracts and plasma. In this radioimmunoassay system highly purified ovine, rat, human and kangaroo LH preparations demonstrated apparently parallel dose–response curves, as did serial dilutions of crude pituitary extracts from a wide range of Australian marsupial species and serial dilutions of plasma from ovariectomized, oestrous and LH releasing hormone (LH-RH)-treated marsupials. The assay has been used to monitor changes in immunoreactive LH in the plasma of the female tammar wallaby. Basal concentrations of LH in non-oestrous female wallabies were in the range < 0·20–1·90 ng/ml with many animals having values at or near the limit of detection of the assay. Concentrations of LH were markedly increased following ovariectomy (1·7–7·0 ng/ml), on the day of oestrus (10·0–> 50 ng/ml) and following administration of LH-RH (9·5–> 25·0 ng/ml). Plasma from hypophysectomized animals had no detectable LH immunoactivity, A well-defined LH surge, lasting approximately 12 h, was associated with oestrus. Mating occurred approximately 8 h before, and ovulation approximately 24 h after, the maximal concentration of LH in plasma.
EFFECTS OF HYPOTHALAMIC DEAFFERENTATION AT DIFFERENT LEVELS ON METABOLISM OF HEPATIC STEROIDS IN RATS
Authors: MODE AGNETA , ENEROTH PETER , GUSTAFSSON JAN-ÅKE , HÖKFELT TOMAS , SKETT PAUL
Published: December 2008

The metabolism of 4-[4-14C]androstene-3,17-dione in the microsomal fraction of livers from male and female rats was investigated after hypothalamic deafferentation at two levels. It was found that frontal deafferentation at the retrochiasmatic level caused a complete 'feminization' of hepatic steroid metabolism in the male rat but was without effect in the female animal. Transection rostral to the suprachiasmatic nuclei was without effect in both sexes. A complete transition from male to female hepatic steroid metabolism after retrochiasmatic deafferentation was reached on day 4 after the operation and persisted for at least 10 weeks. The present results, taken together with previous investigations, indicate that the release of a 'feminizing' factor from the pituitary gland of the male rat is inhibited by a factor produced in, or transported through, the periventricular anterior hypothalamic region including the suprachiasmatic area. No effect on the hepatic steroid metabolism was observed after blinding of the rats suggesting that a diurnal rhythm is not essential to this control mechanism.
EFFECTS OF PASSIVE IMMUNIZATION AGAINST TESTOSTERONE ON SERUM AND PITUITARY GONADOTROPHINS: IMPLICATIONS FOR THE RELATIVE IMPORTANCE OF ANDROGENS AND INHIBIN IN THE CONTROL OF GONADOTROPHIN SECRETION IN THE MALE RAT
Authors: MAIN S. J. , DAVIES R. V. , SETCHELL B. P.
Published: December 2008

The acute effects of a specific reduction in androgen feedback to the hypothalamus and pituitary gland have been investigated in male rats by passive immunization against testosterone. An ovine antiserum raised against testosterone which had been conjugated through position 3 to bovine serum albumin was employed.

Negative feedback control by androgens was effectively reduced by administration of the antiserum, as shown by an increase in levels of LH in the circulation. Immunized animals had a high concentration of testosterone in the circulation of which virtually all was tightly bound to antibody.

In normal animals specific increases of serum LH concentration were obtained at all ages using a low dose of antiserum. At higher doses, serum FSH concentration was also increased. The LH response was reduced by anaesthesia and sham-operation. In shamoperated rats given a high dose of antiserum for 3 days the serum concentrations of LH and FSH could not be distinguished from those which followed castration while differences were found in the pituitary contents. It was concluded that testicular androgen provides an important inhibitory feedback control of secretion of FSH as well as that of LH in the adult male rat. Some of the data can best be explained by the action of inhibin as a minor or alternative inhibitor of FSH secretion.
HORMONES MODULATE THE CONCENTRATION OF CYTOPLASMIC PROGESTIN RECEPTORS IN THE BRAIN OF MALE RING DOVES (STREPTOPELIA RISORIA)
Authors: BALTHAZART J. , BLAUSTEIN J. D. , CHENG M. F. , FEDER H. H.
Published: December 2008

A cytoplasmic progestin receptor has been characterized in the brain of castrated ring doves using an in-vitro assay that measures the binding of a synthetic progestin, [3H]17α,21-dimethyl-19-nor-pregna-4,9-diene-3,20-dione(promegestone; R5020). The affinity of the receptor was similar in both the hyperstriatum and the hypothalamus (Kd≃4 × 10−10 mol/l). Its concentration was higher in the anterior hypothalamus–preoptic area (63 ± 4 fmol/mg (s.e.m.) protein) than in other brain regions (posterior hypothalamus, 33 ± 5; hyperstriatum, 28 ± 3; midbrain, 17 ± 4 fmol/mg protein; n = 7). Progesterone and R5020 competed well for binding but oestradiol and 5β-dihydrotestosterone did not. Corticosterone and, to a lesser extent, testosterone and 5α-dihydrotestosterone competed for binding but much higher concentrations were required than for progestins. Injections of testosterone (200 pg testosterone propionate daily for 7 days) significantly increased the concentration of progestin receptors in the anterior and posterior hypothalamus without having any significant effect on other brain areas. Shorter treatment, lasting for 2 days, with testosterone propionate (200 μg daily), 5α-dihydrotestosterone (200 μg daily) or oestradiol benzoate (50 μg daily) did not always cause this increase but seven injections of oestradiol benzoate (50 pg daily for 7 days) were even more effective than seven injections of testosterone propionate (200 μg daily for 7 days). These data suggested that the sensitivity to progesterone of the brain of the bird changes as a consequence of increases in the level of testosterone in the circulation.
INTERNATIONAL COLLABORATIVE STUDY OF N.I.B.S.C. RESEARCH STANDARD FOR HUMAN PARATHYROID HORMONE FOR IMMUNOASSAY
Authors: ZANELLI JOAN M. , GAINES DAS ROSE E.
Published: December 2008

The use of a Research Standard for human parathyroid hormone (PTH) in a collaborative study by 17 laboratories in ten countries is described. Results of this study showed that the Research Standard was not distinguishable by immunoreactive criteria from the other preparations and laboratory working standards of human PTH included in the study. It was, however, shown to be distinguishable from the International Reference Preparation for Parathyroid Hormone, Bovine, for Immunoassay by immunoreactive criteria and by heterogeneity of estimates in terms of bovine PTH. The Research Standard had appropriate biological activities in three different in-vitro bioassay systems and appeared to be stable under conditions of accelerated degradation. This material in ampoules coded 75/549 is now available internationally as N.I.B.S.C. Research Standard for human PTH for immunoassay.
ONSET OF SYNTHESIS OF PROGESTERONE BY OVINE PLACENTA
Authors: RICKETTS A. P. , FLINT A. P. F.
Published: December 2008

The extra-ovarian contribution to progesterone levels in the circulation has been measured in ovariectomized ewes in which pregnancy was maintained by treatment with medroxy-progesterone acetate. Since adrenal production of progesterone is low this procedure allows the determination of placental secretion. Placental production of progesterone has been shown to rise initially between 50 and 70 days of gestation, with a second phase of increase between 90 and 120 days of gestation. Both periods of increased secretion of progesterone were reflected in rises in progesterone production by placental explants in organ culture and in the activity of 3β-hydroxysteroid dehydrogenase in the tissue. The activity of 3β-hydroxysteroid dehydrogenase exceeded the rate of progesterone production by approximately 30-fold, and it appears unlikely, therefore, that this enzyme is rate-limiting in the synthesis of progesterone. Surgical reduction of the number of cotyledons led to compensation by an increase in weight of individual cotyledons with no significant increase in specific 3β-hydroxysteroid dehydrogenase activity or rate of production of progesterone in organ culture. It was concluded that the rise in placental production of progesterone in the middle period of gestation is unlikely to result either from an increase in 3β-hydroxysteroid dehydrogenase activity or from exposure to factors stimulating placental growth.
SYNERGISM BETWEEN BOVINE SEMINAL PLASMA EXTRACT AND TESTOSTERONE PROPIONATE IN SUPPRESSING SERUM CONCENTRATIONS OF GONADOTROPHINS IN ACUTELY CASTRATED RATS: A ROLE FOR INHIBIN
Authors: PEEK J. C. , WATKINS W. B.
Published: December 2008

The rise in concentrations of FSH and LH in serum seen 24 h after castration was suppressed by the administration of an extract of bull seminal plasma or testosterone propionate at the time of castration. Whereas testosterone propionate preferentially suppressed LH, the seminal plasma extract suppressed FSH and LH equally. Small doses of bull seminal plasma extract and testosterone, that had little effect separately, acted synergistically to suppress levels of FSH and LH to those found in intact animals, while combinations of larger doses had little further effect. This selective interaction suggests how inhibin and testosterone might together regulate concentrations of FSH and LH in the blood of the male rat.
EFFECT OF MORPHINE ON THE RELEASE OF THYROID-STIMULATING HORMONE STIMULATED BY EXPOSURE TO COLD, THYROIDECTOMY AND THE ADMINISTRATION OF THYROTROPHIN RELEASING HORMONE IN MALE RATS
Authors: MURAKI TAKAMURA , NAKADATE TERUO , TOKUNAGA YUKIKO , KATO RYUICHI
Published: December 2008

Morphine reduced the release of thyroid-stimulating hormone (TSH) which was stimulated by exposure to cold and by thyroidectomy as well as reducing the basal level of TSH in the serum of male rats. The inhibitory effect of morphine was antagonized by naloxone which did not enhance the basal or cold-induced TSH release. Pretreatment with morphine did not reduce the release of TSH induced by exogenous thyrotrophin-releasing hormone (TRH) but enhanced it. This effect of morphine was also antagonized by naloxone. The above results suggested that the effect of morphine in reducing levels of serum TSH was not mediated by blocking the effect of TRH on the anterior pituitary gland, but that it was probably mediated by the inhibition of the release of TRH.
MONOAMINERGIC REGULATION OF GROWTH HORMONE IN THE RAT
Authors: BLUET-PAJOT M. T. , SCHAUB C. , MOUNIER F. , SEGALEN A. , DUHAULT J. , KORDON C.
Published: December 2008

The administration of gamma-hydroxybutyrate (GHB) induced a consistent secretory episode of growth hormone (GH) in the morning followed by basal levels of secretion of GH for several hours. The measurement of endogenous noradrenaline, dopamine and serotonin (5-HT) following infusion of GHB showed that dopamine concentrations were significantly increased in the striatum; at the level of the hypothalamus, however, no significant differences were observed between control and GHB-treated animals.

The data reported in this study are consistent with the interpretation that the neurotransmitter regulation of GH release and the modulation of hypothalamic gluco-receptor systems are not fundamentally different in rodents and primates.

Clonidine, an α-adrenergic agonist, enhanced the peak of GH observed in the morning and caused a rapid increment of GH during the period when it was normally at basal levels. Under the same experimental conditions, dopamine agonists, apomorphine and levodopa, had no effect on GH secretion. The inhibition of catecholamine synthesis by α-methyl-p-tyrosine blocked the secretory episode of GH following administration of GHB and after insulin hypoglycaemia whereas the GH rise induced by clonidine was unchanged. The inhibition of 5-HT synthesis by p-chlorophenylalanine also suppressed the secretory episode of GH seen in the morning and the release of GH induced by hypoglycaemia; both being partly restored in animals pretreated with 5-hydroxytryptamine.