bluuebunny/crossref_metadata_2025 huggingface dataset:
ADRENOCORTICAL FUNCTION TESTS IN DOGS WITH HYPERFUNCTIONING ADRENOCORTICAL TUMOURS
Authors: MEIJER J. C. , LUBBERINK A. A. M. E. , RIJNBERK A. , CROUGHS R. J. M.
Published: December 2008

The response has been studied in nine dogs with hyperadrenocorticism due to adrenocortical tumours to the administration of dexamethasone, insulin, lysine-vasopressin and tetracosactide by measuring the changes in plasma cortisol concentration. Administration of dexamethasone did not produce a decrease in the plasma concentration of cortisol in any of these dogs. Administration of insulin caused slight increases in the plasma concentration of cortisol in four out of eight dogs. Lysine-vasopressin increased the plasma concentration of cortisol in eight out of nine dogs, three responded supranormally. Eight out of the nine dogs responded to tetracosactide administration, three responded supranormally. It is concluded that in the dog, in contrast to man, the lysine-vasopressin test cannot be used to differentiate between pituitary-dependent hyperadrenocorticism and hyperadrenocorticism due to an adrenocortical tumour. Apparently pituitary ACTH is not completely depleted in dogs with hyperfunctioning adrenocortical tumours.
SUPPRESSION OF SERUM LEVELS OF LUTEINIZING HORMONE BY SHORT- AND LONG-LOOP NEGATIVE FEEDBACK IN OVARIECTOMIZED WOMEN
Authors: MIYAKE A. , AONO T. , KINUGASA T. , TANIZAWA O. , KURACHI K.
Published: December 2008

The suppressive effects of short- and long-loop negative feedback on serum levels of LH were assessed after administration of human chorionic gonadotrophin (HCG) and conjugated oestrogens.

Fourteen ovariectomized women were injected intravenously with 5 mg conjugated oestrogens, eight of these patients were also given an intramuscular injection of 10 000 i.u. HCG 8 h later, while the other six patients were given a control injection of 0·9% saline. The serum levels of LH decreased by similar amounts in both groups of women. Thirteen other ovariectomized women were initially injected with 10 000 i.u. HCG, i.m., seven of these patients were also given an i.v. injection of 5 mg conjugated oestrogens 8 h later, while the remaining six patients received a control injection of 0·9% saline. The results showed that conjugated oestrogens could further suppress the serum level of LH which had been reduced by prior HCG treatment. In six ovariectomized women who received i.m. saline injections at the start of the experiment and 8 h later, the serum levels of LH did not change significantly.

It is concluded that the suppression of the serum concentrations of LH by long-loop negative feedback after administration of 5 mg conjugated oestrogens is greater than that by short-loop negative feedback after treatment with 10 000 i.u. HCG.
INTERRELATION OF THE PITUITARY–THYROID SYSTEM AT BIRTH IN MAN
Authors: BYFIELD P. G. H. , BIRD DAPHNE , LAND MARIANNE , YEPEZ R. , HIMSWORTH R. L.
Published: December 2008

Samples of cord blood derived from 105 normal babies after uncomplicated deliveries were assayed for thyroxine (T4), tri-iodothyronine (T3), reverse tri-iodothyronine (rT3), throxinebinding globulin (TBG) and thyrotrophin (TSH). The values for T3, rT3 and TSH were log-normally distributed (geometric means 0·62 nmol/l, 3·28 nmol/l and 10·9 mu./l respectively) and those for T4 and TBG were normally distributed (means 126 nmol/l and 13·7 mg/1). The data were systematically analysed and no evidence was obtained to suggest that the concentration of TSH, which varied widely, was regulated by any of the thyroid hormones alone or in combination. There was a direct relation between the concentrations of T4 and T3 in the cord blood at birth but not between either of these and rT3. There is thus no evidence of a functional interdependence of the hypothalamic-pituitary-thyroid system in man at birth.
EFFECTS OF PINEALECTOMY ON THE SECRETION OF LUTEINIZING HORMONE, TESTOSTERONE AND PROLACTIN IN RAMS EXPOSED TO VARIOUS LIGHTING RÉGIMES
Authors: BARRELL G. K. , LAPWOOD K. R.
Published: December 2008

Two experiments were carried out to study the effects of controlled lighting régimes on plasma levels of LH, testosterone and prolactin in Romney rams. In the second experiment the rams were either pinealectomized or sham-operated so that the role of the pineal gland in mediating seasonal changes in reproduction could be examined.

Levels of testosterone and prolactin were considerably influenced by the lighting schedule. Peak plasma concentrations of testosterone were associated with periods during which the daily photoperiod decreased, whereas plasma levels of prolactin showed a pattern of changes approximately in phase with the lighting cycles. Mean plasma concentrations of LH were low in all groups of rams, which made the detection of significant effects of any treatment very unlikely. Pinealectomy reduced the effects of changes in the daily photoperiod on the patterns of secretion of testosterone and prolactin. These findings establish the pineal gland as an organ which influences the endocrine responses of rams to photoperiodic stimuli and it is concluded that the pineal gland is probably important as a mediator of seasonal reproductive changes in these animals.
TISSUE DISTRIBUTION OF IMMUNOREACTIVE SOMATOSTATIN IN THE SOUTH AFRICAN CLAWED TOAD (XENOPUS LAEVIS)
Authors: SHAPIRO B. , SHEPPARD M. , KRONHEIM S. , PIMSTONE B. L.
Published: December 2008

Immunoreactive somatostatin is present in the brain, gut and pancreas of the South African clawed toad, but is absent from the skin, a rich source of many other brain–gut peptides.
RETENTION OF PLASMA SOMATOMEDIN ACTIVITY IN THE FOETAL RABBIT FOLLOWING DECAPITATION IN UTERO
Authors: HILL D. J. , DAVIDSON P. , MILNER R. D. G.
Published: December 2008

One rabbit foetus within each litter was decapitated in utero on day 24 of gestation. Plasma somatomedin activity and costal cartilage metabolism were studied 5 days later in the experimental foetuses and control litter-mates. Somatomedin was assayed by the uptake of [35S]sulphate in vitro into costal cartilage from intact foetuses. Uptake was proportional to logarithmic increases in the concentration of both foetal and maternal rabbit plasma. The mean (± 1 s.d.) somatomedin activity of four plasma pools, each pool being derived from the intact foetuses within each of four litters, was 1·3 ± 0·3 compared with a potency of unity for the reference pool of maternal plasma. The plasma somatomedin activity of decapitated foetuses did not differ significantly from that of control litter-mates when analysed by rank test, but the costal cartilage of decapitated foetuses took up less [35S]-sulphate in basal medium when compared with that of intact litter-mates. The headless body weight of the decapitated foetuses did not rank in a position significantly different from the one expected. The concentration of plasma growth hormone in the decapitated foetuses was less than 5 ng/ml and that of the intact foetuses was more than 157 ng/ml. It is concluded that plasma somatomedin activity in the rabbit foetus is not dependent on foetal growth hormone.
FUNCTIONAL LUTEOLYSIS IN THE PSEUDOPREGNANT RAT: EFFECTS OF PROSTAGLANDIN F2α AND 16-ARYLOXY PROSTAGLANDIN F2α IN VITRO
Authors: HALL A. K. , ROBINSON J.
Published: December 2008

The present work concerns the luteolytic effects of prostaglandin (PG) F2α and its analogue, 16-aryloxy PGF2α, upon isolated luteal cells. Varying doses of these two prostaglandins were incubated with cells in the presence or absence of an optimum stimulatory dose of LH (1 μg/ml). The total contents of progesterone and 20α-dihydroprogesterone in flasks were determined after the incubation periods by radioimmunoassay. Both prostaglandins inhibited basal synthesis of progesterone and 20α-dihydroprogesterone, maximum inhibition occurring at concentrations of either PG of between 250 and 500 ng/ml. In this dose range both prostaglandins were found to abolish LH-stimulated progestogen synthesis completely. These effects were discernible within 5 min of incubation. The studies demonstrated that the onset of PG-induced luteolysis in vitro is characterized by an inhibition of the biosynthesis of both progesterone and its weakly progestogenic metabolite, 20α-dihydroprogesterone; induction of 20α-hydroxysteroid dehydrogenase activity by either PG was not found in incubations extending up to 60 min. In contrast to their relative potencies in vivo, PGF2α and 16-aryloxy PGF2α were essentially equipotent in this in-vitro system.
STUDIES WITH FRAGMENTS OF A HIGHLY ACTIVE ANALOGUE OF LUTEINIZING HORMONE RELEASING HORMONE
Authors: SANDOW J. , KÖNIG W.
Published: December 2008

The minimal structural requirements for gonadotrophin releasing activity were studied with fragments of a highly active analogue of luteinizing hormone releasing hormone (LH-RH), [d-Ser(But)6]LH-RH(1–9)nonapeptide-ethylamide (Hoe 766). All fragments are related to the C-terminal structure of LH-RH and have increased enzyme stability. Ovulation in phenobarbitone-blocked rats was induced with a median effective dose/rat, of 1·9 μg of the (3–9)-heptapeptide, Trp-Ser-Tyr-d-Ser(But)-Leu-Arg-Pro-ethylamide and 6·8, 18·0 and 38·3 μg for the (4–9), (5–9) and (6–9) fragments respectively. The (3–9)-heptapeptide and (4–9)-hexapeptide induced release of LH and FSH in phenobarbitone-blocked rats with a ratio similar to that of LH-RH. Degradation of LH-RH by enzyme preparations of liver, kidney and hypothalamic or anterior pituitary tissue was not modified by addition of the (3–9)-heptapeptide fragment. The organ distribution of the 125I-labelled (3–9)-heptapeptide fragments was similar to LH-RH, but not to Hoe 766. The peptide accumulated in liver and kidney, but was eliminated from the anterior pituitary gland 15 min after i.v. injection, whereas Hoe 766 showed progressive accumulation in the pituitary gland (tissue: plasma ratio = 6·6 after 60 min). In contrast to C-terminal fragments of LH-RH, the corresponding fragments of nonapeptide analogues retained significant biological activity, and the minimal structural requirements for LH release may be related to the C-terminal sequence of LH-RH.
ACUTE REGULATION OF INSULIN RELEASE BY THE PITUITARY GLAND IN RELATION TO HYPERINSULINAEMIA AND OBESITY
Authors: BELOFF-CHAIN ANNE , BOGDANOVIC S. , CAWTHORNE M. A.
Published: December 2008

The pituitary glands from mice rendered obese by gold thioglucose treatment and by dietary manipulation, and pituitary glands from lean mice after a high food intake or a glucose load, were shown to stimulate insulin secretion from isolated pancreatic islets. The insulin releasing activity of pituitary glands from obese (ob/ob) mice was reduced by fasting for 24 and 48 h. Results obtained with pituitary glands from ob/ob and from lean ob/ + and + /+ mice suggest that the insulin releasing property manifests a gene dosage effect. Pituitary glands from 3-week-old (young) ob/ob mice stimulated insulin secretion to the same extent as pituitary glands from 3-month-old (adult) ob/ob mice. The pancreatic islets of young ob/ob mice were shown to be somewhat more responsive to stimulation by the pituitary factor than were lean ob/ + or + / + islets from this age group. The concept that high insulin level, partly under pituitary control, and high caloric intake may be interlinked and may, in combination, be a major factor in producing obesity is discussed. Furthermore, it is suggested that the pituitary insulin releasing factor may play a role in the early development of obesity in the animal models studied.
AN EXTRA-ADRENAL ACTION OF ADRENOCORTICOTROPHIN: PHYSIOLOGICAL INDUCTION OF LIPOLYSIS BY SECRETION OF ADRENOCORTICOTROPHIN IN OBESE RABBITS
Authors: LAFONTAN M. , AGID R.
Published: December 2008

The effect of minor stressful stimuli (saline infusions or venepunctures) on lipid mobilization (estimated by plasma free fatty acids (FFA) and glycerol levels) was studied in two strains of conscious rabbits of various ages. Infusions of 0·9% (w/v) NaCl solution induced a prompt increase of FFA levels in naturally obese rabbits while this effect was absent in younger lighter animals. Administration of propranolol (a β-adrenoceptor blocking drug) beforehand did not prevent lipid mobilization. Adipose tissue in vitro was completely unresponsive to the lipid mobilizing action of adrenaline. The initial output of ACTH induced by stressful stimuli was quickly followed by the increase in the plasma concentration of FFA. A highly significant correlation (r = 0·84 or 0·85; P< 0·01) existed between plasma ACTH and FFA levels 30 and 60 min after the start of stress. Dexamethasone completely prevented lipid mobilization while adipose tissue in vivo and in vitro responded strongly to ACTH. Consequently the lack of response of plasma FFA concentrations in corticosteroid-treated rabbits seemed to be linked to the failure of the pituitary gland to mobilize ACTH rather than to the unresponsiveness of adipose tissue to the pituitary hormone.

Our data indicate that in the rabbit, under conditions of stress, ACTH is of greater physiological importance than catecholamines in the control of lipolysis.
METABOLISM OF PROLACTIN IN MICE WITH A HIGH INCIDENCE OF MAMMARY TUMOURS: EVIDENCE FOR GREATER CONVERSION INTO A NON-IMMUNOASSAYABLE FORM
Authors: SINHA Y. N. , BAXTER S. R.
Published: December 2008

Monomeric mouse prolactin containing small amounts of 125I-labelled prolactin was administered to adult female mice of a high (C3H/St) and low (C57BL/St) mammary tumour strain. Their endogenous prolactin had been suppressed with 2-bromo-α-ergo-cryptine. The chromatographic profile, on Sephadex G-100, of prolactin in the serum of mice injected with mouse prolactin was compared by direct measurement (radioactivity count) and by radioimmunoassay (RIA) at several intervals after injection. With both methods, the injected hormone was found in the serum in predominantly two molecular sizes, the so-called 'big' and 'little' forms. Although 'little' prolactin in both strains constituted a constant 80% of the total hormone at most intervals by direct measurement, it comprised a comparatively smaller proportion by RIA. In addition, the RIA-determined 'little' prolactin, after reaching maximum levels at 15 min, progressively decreased with time, the decrease being greater in the C3H/St than in the C57BL/St strain. Similar experiments with mouse growth hormone revealed no such discrepancies between the radioactivity counts and the RIA measurements. A fraction of both 'big' and 'little' forms in the C3H/St strain failed to precipitate completely after the material had been incubated with an antiserum to mouse prolactin. These results demonstrate that the prolactin injected into mice is metabolized in serum into two non-immunoreactive forms, one that elutes with the same elution volume on Sephadex G-100 column as the monomer and the other that elutes as the 'big' form. Furthermore, the loss of immunoreactivity of monomeric mouse prolactin is greater in the high-tumour C3H/St strain than in the low-tumour C57BL/St strain.

Endogenous immunoreactive prolactin, on the other hand, was found mainly in the 'big' form in the serum of female mice of the C3H/St strain under basal conditions, whereas it was present only in the 'little' form in comparable mice of the C57BL/St strain, even though pituitary extracts of both strains contained mainly the 'little' form. These results support the concept that monomeric prolactin in the systemic circulation of the tumour-prone C3H/St strain is largely in a non-immunoreactive form.
NON-SELECTIVE INHIBITION OF BASAL GLUCAGON RELEASE BY [d-CYS14]-ANALOGUES OF SOMATOSTATIN IN THE RAT
Authors: MÄRKI FRITZ , KAMBER BRUNO , RINK HANS , SIEBER PETER
Published: December 2008

The effects of two [d-Cys14]-analogues of somatostatin on basal plasma levels of glucagon, insulin and glucose were determined in unanaesthetized rats to re-examine a glucagon-selective action of these peptides which has been claimed by others. Somatostatin, [d-Cys14]-somatostatin and [d-Trp8, d-Cys14]-somatostatin caused a short-lasting, dose-dependent decrease of plasma glucagon and insulin but they had no significant influence on plasma glucose. Glucagon and insulin reached the nadir 2 min after intravenous injection of the peptides (dose range 1–10 μg/kg) or 5 min after subcutaneous administration (30 and 300 μg/kg). At the nadir, insulin was decreased to a greater extent than glucagon and the effects of all three peptides were equipotent. However, in the period after the nadir and at high doses, the time-course of some effects of the analogues on either glucagon or insulin differed from that of somatostatin. Thus, these [d-Cys14]-analogues may show partial kinetic dissociation of effects on glucagon and insulin but they are not truly selective inhibitors of glucagon release.
HYPERALDOSTERONISM IN THE SODIUM-DEPLETED RAT: MECHANISM OF ALDOSTERONE STIMULATION BY PERITONEAL DIALYSIS WITH GLUCOSE SOLUTION
Authors: SPÄT A. , NAGY K. , ÉVA TARJÁN
Published: December 2008

Peritoneal dialysis with 5% glucose solution was carried out in dexamethasone-pretreated rats. Dialysis brought about a severe loss of sodium and a slight loss of potassium into the peritoneal fluid. This kind of sodium depletion took place without any decrease in total body-water space, thus it evoked a severe fall in plasma sodium concentration.

Plasma renin activity and the serum concentration of aldosterone increased in response to dialysis. Peak values in renin activity were attained within 60 min, whereas aldosterone concentrations exhibited a continuous rise until at least 120 min. Despite the correlation of renin and aldosterone values, neither the administration of an angiotensin I converting enzyme inhibitor (SQ 20,881) nor the reduction of plasma renin activity by indomethacin could reduce hyperaldosteronism evoked by peritoneal dialysis. Therefore, it is assumed that there is no causal relationship between renin and aldosterone in this kind of acute, severe sodium depletion.
EFFECTS OF AGE AND TESTICULAR FUNCTION ON THE PITUITARY–THYROID SYSTEM IN MALE RATS
Authors: CHEN H. J. , WALFISH P. G.
Published: December 2008

Old male rats of 22–24 months and young ones of 3–5 months were studied to find the effects of ageing, of orchidectomy and of orchidectomy and treatment with testosterone propionate (TP) on the basal serum concentrations of thyrotrophin (TSH) and on the total and free concentrations of tri-iodothyronine (T3) and thyroxine (T4) in the serum. The changes in TSH after treatment with thyrotrophin releasing hormone (TRH) were also observed. Intact old rats had significantly (P < 0·001) lower basal T4 and T3 as well as lower (P < 0·05) testosterone concentrations than were present in young rats. They also had higher basal TSH and per cent free T4 but lower absolute free T3 concentrations than had young rats. Two weeks after orchidectomy, basal TSH concentrations were slightly but significantly (P < 0·05) decreased in both young and old rats while T4 decreased significantly (P < 0·05) only in the young. The responses of TSH to TRH were also reduced by orchidectomy in both age groups with the old rats being less responsive than the young. Orchidectomy and treatment with pharmacological doses of TP produced similar effects on the pituitary-thyrotrophic response for both old and young rats but a greater effect occurred in the basal T4 response in young rats. In all groups basal TSH was influenced by orchidectomy or by treatment with TP but was always higher in the aged rat. Tri-iodothyronine concentration was always lower in the older rat and was not altered by orchidectomy or by treatment with TP in either young or old rats.

These results indicate that (1) in the male rat these age-specific effects on the thyroid–pituitary system are probably due, not only to a reduction in thyroid gland function and plasma T4 protein-binding, but also to a concomitant hyporesponsiveness of the aged male rat pituitary thyrotroph to TRH stimulation and (2) there is probably a significant influence of testicular function on the pituitary–thyroid system of the male rat.
EFFECT OF PREPUBERTAL HEMIORCHIDECTOMY ON THE RESPONSE OF THE TESTIS TO LUTEINIZING HORMONE
Authors: SELIN LIISA , MOGER W. H.
Published: December 2008

Administration of FSH to hypophysectomized male rats has been shown to increase the capacity of the testes to secrete testosterone in response to LH. Studies were done to assess the effect of increased endogenous FSH on the response of the testis to LH. At 17 and 24 days of age, animals hemiorchidectomized at 10 days of age had significantly higher serum FSH levels and testicular weights than sham-operated rats. To study the testicular response to LH in vivo, hemiorchidectomized animals were sham-operated and the sham-operated animals were hemiorchidectomized at 17 or 24 days of age. Luteinizing hormone (30 μg/100 g body wt) or saline was administered immediately after the operation and the animals were autopsied 90 min later. Chronic hemiorchidectomy significantly increased the serum testosterone response to LH at 17 but not at 24 days of age. The testicular response to LH in vitro was also investigated. Testes from rats hemiorchidectomized or sham-operated at 10 days of age and killed at 17 and 24 days of age were incubated for 3 h in the presence or absence of 100 ng LH/ml incubation medium. Significantly more 5α-androstane-3α,17β-diol and androsterone were produced by the testes from hemiorchidectomized than from sham-operated animals at 17 days of age but not at 24 days of age. The production of testosterone in vitro was not influenced by hemiorchidectomy at either age. These results suggest that serum FSH concentration is the factor limiting LH responsiveness before but not after the prepubertal increase in FSH levels. However, treatment of intact rats from 10 to 16 days of age with 20 μg rat FSH/day did not increase the serum testosterone response to LH.
SEROTONIN INVOLVEMENT IN THE CONTROL OF PHASIC LUTEINIZING HORMONE RELEASE IN THE RAT: EVIDENCE FOR A CRITICAL PERIOD
Authors: COEN C. W. , MacKINNON P. C. B.
Published: December 2008

A marked surge of luteinizing hormone (LH) occurs daily at 18.00 h in oestrogen-treated ovariectomized rats maintained under regular lighting from 06.00 to 20.00 h. The administration of p-chlorophenylalanine (PCPA), p-chloroamphetamine or 5,6-dihydroxytryptamine in treatments designed to cause a severe depletion of brain serotonin abolished this daily surge. Synthesis of serotonin may be temporarily restored in PCPA-treated animals by the administration of the serotonin precursor, 5-hydroxytryptophan. The effectiveness with which restoration of synthesis resulted in restoration of the LH surge varied according to the time at which the precursor was administered, the optimal time being 10.00 h. The results suggest that there is an essential, permissive function performed by serotonin in the production of the LH surge and that this function occurs during a critical period.
EFFECTS OF CHEMORECEPTOR AND BARORECEPTOR STIMULATION ON THE DISCHARGE OF HYPOTHALAMIC SUPRAOPTIC NEURONES IN RATS
Authors: HARRIS M. C.
Published: December 2008

Experiments have been performed to examine the effects of activating the carotid body chemoreceptors and the arterial baroreceptors on the discharge of neurones within the hypothalamic supraoptic nucleus of the rat. Chemoreceptors were activated by intracarotid injection of 0·9% NaCl solution equilibrated with 100% CO2. The baroreceptors of the carotid sinus and aortic arch were activated by raising the blood pressure with an intravenous injection of phenylephrine.

Chemoreceptor stimulation activated and baroreceptor stimulation inhibited the discharge of all the phasically discharging neurones tested. Neither stimulus had any consistent effect on non-phasically discharging neurones, although slight inhibition occasionally occurred. Anaesthesia of the carotid bifurcation abolished the effects of cardiovascular stimulation on the supraoptic neurones. Responses resumed when the anaesthesia wore off. However, the anaesthesia also seemed to alter the phasic pattern of discharge.

The results are discussed with reference to the influence of the cardiovascular receptors upon the neurones in the supraoptic nucleus, and with reference to possible roles for the cardiovascular reflexes in control of vasopressin secretion.
PROLACTIN RELEASE IN PARENT RING DOVES AFTER BRIEF EXPOSURE TO THEIR YOUNG
Authors: BUNTIN J. D.
Published: December 2008

A pigeon crop sac radioreceptor assay was used to measure changes in pituitary prolactin levels in parent ring doves of both sexes on the third day after hatching of their young. After a deprivation of 17 h from the squabs, exposure to a 3-day-old squab for 1 h resulted in a significant decrease in the prolactin content of the pituitary gland as compared with levels obtained in control birds deprived of their young for 18 h. No significant sex differences in prolactin levels were observed in either group. Because exposure to the young also promotes prolactin-induced crop sac growth, it appears probable that the squab-induced decrease in prolactin content of the pituitary gland reflects the release of prolactin into the circulation. Accordingly, the environmental regulation of prolactin secretion in parent ring doves appears similar to that observed in lactating mammals.
DEPENDENCE OF SPONTANEOUS AND ANGIOTENSIN-INDUCED DRINKING IN THE RAT UPON THE OESTROUS CYCLE AND OVARIAN HORMONES
Authors: FINDLAY A. L. R. , FITZSIMONS J. T. , KUCHARCZYK J.
Published: December 2008

The influence of the oestrous cycle on spontaneous and dipsogen-induced drinking was studied in female rats. Spontaneous fluid intake was lowest on the day of oestrus. Drinking induced by subcutaneous isoprenaline, and by angiotensin II (injected into the preoptic area), also showed marked cyclical variation, being lower at pro-oestrus and oestrus than at other stages of the cycle. Drinking induced by subcutaneous hypertonic NaCl or by intracranial carbachol did not vary with the oestrous cycle. Cyclicity of spontaneous and of angiotensin-induced water intake was not apparent in rats before puberty or after ovariectomy. Ovariectomy reduced drinking in response to isoprenaline. Treatment with oestradiol benzoate (20 μg) caused a reduction in spontaneous water intake, but a marked increase in the drinking response to isoprenaline. Treatment with oestradiol benzoate and progesterone (2·5 mg) caused a larger decrease in spontaneous water intake and an insignificant increase in isoprenaline-induced drinking. Water intake induced by subcutaneous hypertonic saline was unaffected by gonadal steroids. The results provide further evidence for the view that the thirst of extracellular origin, in which the renin–angiotensin system is involved, is brought about by mechanisms different from those that respond to cellular dehydration. Only drinking caused by activation of extracellular mechanisms appeared to be sensitive to the ovarian cycle and to ovarian hormones.
CIRCADIAN PHASE-DEPENDENT PROLACTIN MECHANISMS IN HEPATIC LIPOGENESIS OF A TELEOST
Authors: HORSEMAN N. D. , MEIER A. H.
Published: December 2008

In the teleost, Fundulus grandis, injections of prolactin early in the light phase cause an immediate 50% depression in the rate of hepatic lipogenesis ([14C]acetate incorporation); 10 h later, that rate has returned to levels not different from controls. Injections of prolactin late in the light phase cause an even more dramatic immediate depression of lipogenesis (79%) followed by a gradual increase in lipogenic rate which is 2·6 times higher than the control rate after 24 h. The stimulation of lipogenesis by prolactin is blocked by simultaneous treatment with indomethacin, an inhibitor of prostaglandin synthesis. These circadian phase-dependent effects of prolactin on hepatic lipogenesis are discussed with reference to possible mechanisms of action exerted by endogenous prolactin rhythms.
EFFECTS OF INTRACRANIAL IMPLANTATION OF OESTRADIOL AND DIHYDROTESTOSTERONE ON THE SEXUAL BEHAVIOUR OF THE LIZARD ANOLIS CAROLINENSIS
Authors: CREWS DAVID , MORGENTALER ABRAHAM
Published: December 2008

Intrahypothalamic implantation of oestradiol and dihydrotestosterone rapidly restored sexual behaviour in castrated, sexually inactive Anolis carolinensis. Implants in areas other than the anterior hypothalamus-preoptic area failed to elicit sexual behaviour. Male aggressive behaviour was unaffected by intracranial hormone implants. Histological examination of the renal sex segment, a secondary sex structure, gave no indication of leakage into the peripheral plasma. The effectiveness of oestradiol and dihydrotestosterone in inducing male courtship behaviour when administered intracranially was compared with the relative ineffectiveness of systemic injections of these hormones.
IDENTIFICATION AND PURIFICATION OF A NEW PROTEIN FROM WATER-SOLUBLE EXTRACTS OF HUMAN ADRENAL GLAND
Authors: AL-AWQATI M. A. , GORDON Y. B. , CHARD T.
Published: December 2008

An homogenate of human foetal adrenal gland was subjected to negative immunoabsorption by column chromatography using anti-whole human serum coupled to Sepharose 4B. Two peaks were eluted and used to immunize rabbits. The antisera produced were absorbed and tested for specificity by double immunodiffusion.

Two antigens, which appeared to be specific to the adrenal gland, were identified having molecular weights of 25 000 and 65 000 as determined by gel filtration. The lower molecular weight antigen was isolated by physicochemical methods and found to be a protein. The amino acid composition is reported.
EFFECTS OF HYDROXYLATED DERIVATIVES OF VITAMIN D3 AND OF AQUEOUS EXTRACTS OF SOLANUM MALACOXYLON ON THE ABSORPTION OF CALCIUM, PHOSPHATE, SODIUM, POTASSIUM AND WATER FROM THE JEJUNUM OF PIGS
Authors: FOX J. , CARE A. D.
Published: December 2008

The effects of hydroxylated derivatives of vitamin D3 and aqueous extracts of Solanum malacoxylon on the intestinal absorption of calcium, phosphate, sodium, potassium and water have been studied in unstressed vitamin D-replete pigs each of which was surgically prepared beforehand with a Thirty–Vella loop of jejunum. The addition, for six 1 h periods of perfusion, of 1,25-dihydroxycholecalciferol (1,25-(OH)2D3) or 1α-hydroxycholecalciferol at similar concentrations (3·6–3·75 pmol/ml) to the solution used to perfuse the intestinal loop caused a rapid increase in the absorption of calcium but increased the absorption of phosphate only after a delay of at least 12 h. The absorption of both calcium and phosphate reached a maximum on the day following the addition of the vitamin D derivative to the perfusate. The addition of 25-hydroxycholecalciferol (25-(OH)D3) at a concentration of 3·75 pmol/ml was without effect on absorption except for a small increase in the absorption of phosphate on the following day. However, at higher concentrations (> 250 pmol 25-(OH)D3/ml) the absorptions of calcium and phosphate were both increased rapidly. 24,25-Dihydroxycholecalciferol was without effect on absorption at the concentration tested (3·6 pmol/ml).

Aqueous extracts (1%) of the leaf of S. malacoxylon showed similar effects on absorption to those of 1,25-(OH)2D3. However, there was one point of difference; the absorption of phosphate was stimulated with a similar time course to that of calcium in contrast to its delayed response to 1,25-(OH)2D3.

The absorption rates of water, sodium and potassium were not consistently affected by 1,25-(OH)2D3 or S. malacoxylon. However, the major effects of these derivatives were usually seen on the day following the day of addition to the perfusate. In contrast, 25-(OH)D3 at high concentrations had a marked effect on the absorption of water, sodium and potassium on the day of addition.
VARIATION IN SIZE OF THE 'READILY RELEASABLE POOL' OF LUTEINIZING HORMONE DURING THE OESTROUS CYCLE OF THE RAT
Authors: PICKERING A. J.-M. C. , FINK G.
Published: December 2008

The size of the 'readily releasable pool' of luteinizing hormone at various times of the oestrous cycle has been determined by injecting a supramaximal dose of luteinizing hormone releasing factor (LH-RF) i.v. into rats anaesthetized with sodium pentobarbitone. In an attempt to block replenishment of the 'pool' during release, cycloheximide was administered 30 min before LH-RF. A 20-fold increase in pool size occurred between the morning of dioestrus and the evening of pro-oestrus in the absence of any significant change in total pituitary content of LH. This suggests that increased responsiveness may be brought about by a change in the receptor-release apparatus and/or a transfer of LH from a 'storage pool' which leads to an apparent increase in the proportion of LH available for release.
PROLACTIN RECEPTORS IN THE MAMMARY GLAND, CORPUS LUTEUM AND OTHER TISSUES OF THE TAMMAR WALLABY, MACROPUS EUGENII
Authors: SERNIA C. , TYNDALE-BISCOE C. H.
Published: December 2008

Specific binding of radio-iodinated ovine prolactin to subcellular tissue fractions of the tammar wallaby (Macropus eugenii) was investigated. Specific binding was found, in order of decreasing binding activity, in the lactating mammary gland, corpus luteum, corpus albicans, adrenal gland and ovary. Specific binding was absent in kidney, liver, brain and inactive mammary gland.

The mean association constant (Ka at 23 °C) was determined as 0·90 × 109, 2·20 × 109, 2·44 × 109, 3·38 × 109 and 10·98 × 1091/mol for mammary gland, adrenal, corpus albicans, corpus luteum and ovary respectively. The mean receptor concentration (N) varied from 92·87 × 10−14 mol/mg protein for the mammary gland to 1·03 × 10−14 mol/mg protein for the ovary. The concentration in the corpus luteum varied between tissue pools collected at different times of the annual breeding cycle.

The specificity for prolactin was shown in the mammary gland and corpus luteum by the failure of ovine FSH, LH, GH and TSH to displace 125I-labelled ovine prolactin, whereas it was displaced readily by both ovine and bovine prolactin.
URINARY EXCRETION OF OESTRONE, OESTRADIOL-17β AND OESTRIOL IN PREGNANCIES COMPLICATED BY STEROID SULPHATASE DEFICIENCY
Authors: MUJAJI B. W. , TOUMBA K. J. , OAKEY R. E.
Published: December 2008

The urinary excretion of oestrone, oestradiol-17β and oestriol was measured by gas–liquid chromatography in 24 h urine specimens, collected after 34 weeks of gestation from each of eight women whose pregnancies were complicated by steroid sulphatase deficiency and from each of 21 pregnant women without this complication. Mean (±s.d.) values μmol/24 h, sulphatase deficient; normal) were: oestrone, 0·7 ± 0·2; 2·5 ± 1·3; oestradiol-17β, 0·5 ± 0·2; 1·6 ± 0·5: oestriol, 2·0 ± 0·9; 54·4 ± 19·9. Thus, mean oestrone and oestradiol-17β excretions were only 30% of normal whilst mean oestriol excretion was reduced by more than 90%. Consequently, the mean ratio of urinary oestriol/(oestrone + oestradiol-17β changed from 13·7 ± 2·3 in normal pregnancy to 1·6 ± 0·6 in pregnancies complicated by steroid sulphatase deficiency. The greater fall in oestriol excretion in this condition, in comparison with that of oestrone and oestradiol-17β, emphasizes the importance of conjugated 16-oxygenated C19 steroids in the biosynthesis of oestriol in human pregnancy. The change in the relative proportions of the three urinary oestrogens implies that in the precursor pool of normal pregnancy the concentration of 16-oxy-C19 steroids relative to that of the 16-deoxy-C19 steroids, is much greater in the sulphate fraction than it is in the unconjugated fraction.

The measurement of the urinary oestriol/(oestrone+oestradiol-17β) ratio may have the potential to make it possible to distinguish, before birth, between pregnancies complicated by steroid sulphatase deficiency and those with foetal adrenal hypoplasia.
CONCENTRATIONS OF 6-OXO-PROSTAGLANDIN F1α IN THE MATERNAL AND FOETAL PLASMA OF SHEEP DURING SPONTANEOUS AND INDUCED PARTURITION
Authors: MITCHELL M. D. , ANDERSON ANNE B. M. , BRUNT JANE D. , CLOVER LINDA , ELLWOOD D. A. , ROBINSON J. S. , TURNBULL A. C.
Published: December 2008

The concentrations of 6-oxo-prostaglandin F1α (6-oxo-PGF1α) have been determined in maternal and foetal plasma from nine chronically catheterized sheep during late pregnancy and parturition. Labour occurred either spontaneously (three sheep) or was induced by continuous intrafoetal infusion of Synacthen (ACTH 1–24; 0·24 mg/24 h; three sheep) or dexamethasone (1 mg/24 h; three sheep). During spontaneous and Synacthen-induced parturition, concentrations of 6-oxo-PGF1α in maternal and foetal plasma remained at basal levels until 24 h before delivery. At varying times during the 24 h before delivery, levels of 6-oxo-PGF1α in maternal and foetal plasma were generally increased. When parturition was induced with dexamethasone, however, no increase was observed in the foetal plasma although the concentration of 6-oxo-PGF1α in maternal plasma was raised close to delivery.
A RADIOIMMUNOASSAY FOR NEUROTENSIN IN HUMAN PLASMA
Authors: BLACKBURN A. M. , BLOOM S. R.
Published: December 2008

A specific radioimmunoassay for neurotensin in human plasma has been developed capable of detecting changes of 5 pmol/l with 95% confidence. Neurotensin-like immunoreactivity has been detected in human plasma in two molecular forms and rises by 27 ± 8 (s.e.m.) pmol/l (n = 9) after ingestion of food.
RELAXIN INHIBITS SPONTANEOUS AND PROSTAGLANDIN-DRIVEN MYOMETRIAL ACTIVITY IN ANAESTHETIZED RATS
Authors: PORTER D. G. , DOWNING SANDRA J. , BRADSHAW JANE M. C.
Published: December 2008

Porcine relaxin (250 guinea-pig units/mg) infused intravenously into anaesthetized rats at 20 μg/h reversibly abolished spontaneous intra-uterine pressure cycles yet left the myometrium responsive to oxytocin in doses of 4–8 mu. The inhibition was found to be primarily of the frequency, rather than of the amplitude, of pressure cycles. Relaxin (5 or 10 μg) was capable of completely suppressing uterine activity driven by prostaglandin F2α infusion in oestrogen-treated ovariectomized rats. Whereas the β-adrenergic blocker, propranolol, had no effect on relaxin-induced inhibition, phentolamine, an α-blocker, significantly delayed the relaxin effect. It is unlikely, however, that relaxin operates through an α-inhibitory receptor. The results show that relaxin acts primarily as a frequency modulator and is capable of antagonizing an exogenous myometrial stimulant.
CELLULAR LOCALIZATION OF A PROLACTIN-LIKE ANTIGEN IN THE RAT BRAIN
Authors: TOUBEAU G. , DESCLIN J. , PARMENTIER M. , PASTEELS J. L.
Published: December 2008

The distribution of immunoreactive neurones and fibres was studied in rat brain using an antiserum to rat prolactin. Neurones containing the immunoreactive material were localized in the arcuate, ventromedial, premamillary, supraoptic and paraventricular nuclei of the hypothalamus. Immunoreactive nerve fibres were widely distributed within the brain. No differences were observed in labelling between male and female rats, or as a consequence of hypophysectomy.
VARYING RESPONSE TO LUTEINIZING HORMONE OF TWO LUTEAL CELL TYPES ISOLATED FROM BOVINE CORPUS LUTEUM
Authors: URSELY JOCELYNE , LEYMARIE PIERRE
Published: December 2008

Luteal cell suspensions obtained by enzymatic digestion of pregnant cow corpus luteum were found to be heterogenous and mainly made up of two types of cells of different sizes. The large cells (37 μm, average diameter) could be separated from the small ones (18 μm, average diameter) by sedimentation at unit gravity in a gradient of Ficoll–bovine serum albumin. A comparative in-vitro study of the synthesis of progesterone by the two types of cells indicated striking differences between them. The average content and the synthesis of progesterone in the absence and presence of a saturating dose of bovine LH after incubation for 2 h were 0·07, 0·12 and 6·9 pg/cell for the small cells and 0·65, 2 and 10 pg/cell for the large ones. Moreover, the sensitivity to low concentrations of LH was 100 to 1000 times higher for the small cells than for the large ones. oestradiol-17β at concentrations ranging from 5 × 10−10 to 5 × 10−4 mol/l exerted a dose–dependent inhibition on the stimulation of LH in both cell types.

These results suggest a possible involvement of both cell types in the synthesis of progesterone in vivo with a greater contribution by the small cells to stimulation induced by LH.

Moreover, it appears that small cell suspensions could be a useful model system for in-vitro studies of the control of the synthesis of progesterone in cow corpus luteum.
EFFECT OF PRIOR GONADOTROPHIN INJECTION ON THE RISING PHASES OF SIMULATED PREOVULATORY SURGES OF LUTEINIZING HORMONE AND FOLLICLE-STIMULATING HORMONE IN THE PLASMA OF PHENOBARBITONE-BLOCKED, PRO-OESTROUS RATS
Authors: ELIAS KATHLEEN A. , BLAKE C. A.
Published: December 2008

Experiments were performed to determine whether the initial rise in the level of LH in peripheral plasma which occurs during its preovulatory surge in plasma may modulate the subsequent patterns of rising of LH and FSH which occur during pro-oestrus. Two cannulae were inserted into the right atrium of the heart of pro-oestrous rats previously given phenobarbitone to block the preovulatory surges of LH and FSH in plasma. One cannula was used for blood collection and injections and the other for infusions. Vehicle, 0·2 or 2·0 μg rat LH, or 1·0 μg rat FSH was injected 60 min before a 90 min infusion of 0·9% saline or of LH releasing hormone (LH-RH) which was infused at a rate of 50 ng/h to simulate the LH and FSH surges. Plasma LH rose more than 12-fold or 125-fold 5 min after injection of 0·2 or 2·0 μg rat LH respectively. At 60 min, the level of LH in plasma was basal or raised about fourfold respectively. The plasma LH and FSH responses to LH-RH in these rats were similar to those of control animals. Infusion of LH-RH caused levels of LH in plasma to increase about fourfold during an initial rising phase. This was followed by a marked increase in levels of plasma LH during a rapid rising phase, an effect attributed to self-priming by LH-RH. Plasma FSH was not raised after 25 min but was increased 60 min after the start of infusion of LH-RH. Injection of FSH did not alter the plasma LH response to LH-RH. The results suggest that the delayed rise in plasma FSH in response to LH-RH is not influenced by, nor is it the result of, a prior increase in levels of LH in peripheral plasma and that the marked increase in plasma LH attributed to self-priming by LH-RH is not the result of a positive feedback of peripheral plasma LH on its own secretion.
MECHANISM OF THE FIRST SPONTANEOUS GONADOTROPHIN SURGE AND THAT INDUCED BY PREGNANT MARE SERUM AND EFFECTS OF NEONATAL ANDROGEN IN RATS
Authors: SARKAR D. K. , FINK G.
Published: December 2008

The mechanism of the first (pubertal) preovulatory gonadotrophin surge was investigated in Wistar rats by measuring (1) LH releasing factor (LH-RF) in pituitary stalk plasma and in extracts of hypothalamic and preoptic tissue, (2) LH and FSH in peripheral plasma and extracts of anterior pituitary tissue and (3) the LH and FSH response to LH-RF. The mechanism of the first surge appeared broadly to resemble that in the adult. That is, the gonadotrophin surge which occurs on the afternoon of the day before vaginal opening was found to coincide with a surge of immunoreactive LH-RF in pituitary stalk plasma and a significant increase in pituitary responsiveness to LH-RF. The magnitude of the change in pituitary responsiveness was, however, less at puberty than in the adult while the peak of the LH-RF surge was higher at puberty. The surges of LH-RF in stalk plasma and gonadotrophin in peripheral plasma corresponded relatively precisely with a fall in the preoptic and hypothalamic content of LH-RF and in the pituitary content of LH and FSH, suggesting that, in contrast with the adult, the synthesis of LH-RF and gonadotrophin at puberty cannot keep up with their release. A significant increase in stalk plasma LH-RF concentration occurring concomitantly with a surge of LH could be induced on the afternoon of Day 32 of life by administering pregnant mare serum (PMS) on Day 30 (about 10 days before vaginal opening). This, together with other evidence, suggests that the timing of the first gonadotrophin surge depends upon the capacity of the ovary to secrete oestradiol in the form of a surge. The fact that no significant increase in the pituitary responsiveness to LH-RF occurred in PMS-treated rats could account for the fact that the height of the gonadotrophin surge in these animals is only a third that of the spontaneous surge. No significant change in peripheral plasma LH or stalk plasma LH-RF concentrations was found around the time of vaginal opening or cornification in female rats given 1·25 mg testosterone propionate on Day 4 (androgenized female rats). Studies on the effect of ovariectomy and/or adrenalectomy suggested that the ovary and adrenal are involved in the timing of vaginal opening in normal but not in androgenized female animals.
EFFECTS OF TAMOXIFEN ON THE BINDING AND METABOLISM OF TESTOSTERONE BY HUMAN PROSTATIC TISSUE AND PLASMA IN VITRO
Authors: HABIB F. K. , RAFATI G. , ROBINSON M. R. G. , STITCH S. R.
Published: December 2008

The in-vitro metabolism of testosterone in benign and malignant prostatic tissue was examined and distinct quantitative differences between the two types of specimens were observed. The major metabolite of testosterone in the hyperplastic prostate was 5α-dihydrotestosterone and a high 3α(β)-hydroxysteroid dehydrogenase activity was also detected.

In the malignant tissue, 5α-reductase activity was considerably reduced and there was little or no androstanediol formed; the 17β-dehydrogenase activity was, however, higher than in the benign tissue. The decrease in 5α-reductase was always followed by a compensatory change in the 3α(β)-hydroxysteroid dehydrogenase of the malignant prostate. The present study revealed that the ratio of the mean activities of 5α-reductase to 3α(β)-hydroxysteroid dehydrogenase in the two types of specimen always remained a constant.

Although the antioestrogen, tamoxifen, induced an inhibitory effect on the activities of 5α-reductase and 17β-hydroxysteroid dehydrogenase in the gland, the present investigation also suggested that tamoxifen stimulated the activity of 3α(3β)-hydroxysteroid dehydrogenase. In blood, the action of tamoxifen appeared to be confined to the displacement of androgens from the binding sites on the sex hormone binding globulin.
CONCENTRATIONS OF LUTEINIZING HORMONE IN THE PLASMA OF HEMICASTRATED COCKERELS
Authors: WILSON SUSAN C. , DE REVIERS M.
Published: December 2008

The concentrations of LH in plasma were measured, using a radioimmunoassay, during sexual development of intact cockerels and cockerels hemicastrated at 2 weeks of age. The pattern of LH secretion during maturation was characterized by a series of at least four consistently observed periods of rising and falling blood levels of the hormone. Levels of luteinizing hormone were higher in hemicastrated than in intact cockerels between 2 and 4 weeks after the operation (4–6 weeks of age) and then fell to values below those seen in intact cockerels between 8 and 11 weeks of age. Thereafter, until 28 weeks of age, levels of LH in plasma in both hemicastrated and intact birds were similar. The transient changes in LH concentration after hemicastration were thought to be a direct consequence of an alteration in the concentration of testicular steroids in the blood after the removal of one gonad.