bluuebunny/crossref_metadata_2025 huggingface dataset:
MELANOPHORE-STIMULATING HORMONE-MELATONIN ANTAGONISM IN RELATION TO COLOUR CHANGE IN XENOPUS LAEVIS
Authors: DIERST-DAVIES KAY , LANDGREBE F. W. , MITCHELL G. M.
Published: December 2008

Experiments on colour change of Xenopus laevis were performed to investigate the possibility that melatonin is the physiological antagonist to melanophore-stimulating hormone (MSH). Various amounts of substandard (SS) extract of ox posterior pituitary plus melatonin were injected into the dorsal lymph sac of adult male Xenopus laevis. Normal light-adapted, completely hypophysectomized, and anterior lobectomized animals were used. Dose—response curves were obtained for different SS dosages over a wide range of melatonin concentrations. Melatonin at very low concentrations inhibited the darkening reaction to both injected SS and endogenous MSH. In all cases more melatonin was required to inhibit the effect of SS in hypophysectomized than in normal animals. The results indicate that melatonin may be a physiological MSH antagonist in Xenopus laevis and the pituitary either contains some lightening factor itself ( Hogben's 'W' substance?) or has control over another organ (pineal gland?) where a lightening factor may be present. The unusual linear-logarithmic dose—response curves are discussed.
CAPACITATION AND FERTILIZATION DURING PSEUDOPREGNANCY IN THE RABBIT
Authors: HUNTER R. H. F.
Published: December 2008

Capacitation and fertilization during pseudopregnancy in the rabbit were examined on Days 4, 6, 8, 10 and 12 after mating with vasectomized males. At each of these five stages of pseudopregnancy, ovulation was induced in ten animals by a single injection of human chorionic gonadotrophin (HCG); an additional group of oestrous rabbits was similarly injected to serve as controls. Ejaculated spermatozoa were inseminated directly into the Fallopian tubes during laparotomy performed 2 h after the ovulating injection, and 15–22 h later the eggs were examined microscopically for evidence of fertilization.

The mean number and range of induced ovulations decreased between Days 4 and 12 of pseudopregnancy. An overall recovery of 66% of the eggs resulting from these ovulations was achieved, the great majority being located in the Fallopian tubes. Fertilized eggs were obtained from 93% of the 60 does and 84% of the recovered eggs were fertilized. There was neither a decrease in the level of fertilization with advancing stages of pseudopregnancy, nor did the stage of pseudopregnancy influence the rate of development from pronuclear to four-celled eggs. Conspicuous among the small number of abnormal fertilizations were four dispermic pronuclear eggs and two digynic pronuclear eggs.

It is concluded that after injection of HCG, complete capacitation of ejaculated spermatozoa can be achieved in the Fallopian tube between Days 4 and 12 of pseudopregnancy as rapidly as in the tube of oestrous rabbits. Furthermore, a high proportion of the eggs induced to ovulate during pseudopregnancy can be fertilized, though their potential for full embryonic development requires further study.
THE ROLE OF PROLACTIN IN THE SLOUGHING CYCLE OF THE LIZARD, GEKKO GECKO L.
Authors: CHIU K. W. , PHILLIPS J. G.
Published: December 2008

Prolactin injected into hypophysectomized geckos restored the length of the sloughing cycle to normal (about 35 days) when given in doses of 0·26 i.u./g body wt on alternate days. When the doses of prolactin were increased to 0·4 i.u. the length of the sloughing cycle was reduced to about 30 days. Prolactin given to thyroidectomized geckos shortened the length of the sloughing cycle to about 28 days when administered in doses of 0·4 i.u./g on alternate days. Prolactin probably acts directly on the epidermis and not through the thyroid gland, since prolactin restored sloughing in thyroidectomized animals. Moreover, prolactin had no effect on the activity of the thyroid gland in the hypophysectomized animals as judged by the percentage uptake of 131I or the histological structure. Prolactin in doses of 0·4 i.u./g on alternate days reduced the length of the resting phase of the sloughing cycle; the renewal phase remained unaltered.
THE ANTIGENICITY OF HUMAN CHORIONIC SOMATO-MAMMOTROPHIN AND HUMAN GROWTH HORMONE IN THE RHESUS MONKEY (MACACA MULATTA)
Authors: BECK J. SWANSON , MELVIN JENNIFER M. O. , MASSON MARY B. R.
Published: December 2008

Immunization of nine rhesus monkeys with human chorionic somatomammotrophin (HCSM) consistently produced high-titre monospecific antisera that did not cross-react with the related antigen, human growth hormone (HGH). However, two monkeys immunized with HGH developed lower-titre antisera that cross-reacted with HCSM. By contrast, rabbits and goats did not discriminate to any great extent between HCSM and HGH.
SEASONAL VARIATIONS IN PRODUCTION IN VITRO OF CORTICOSTEROIDS BY THE FROG (RANA RUGULOSA) ADRENAL
Authors: CHAN S. W. C. , PHILLIPS J. G.
Published: December 2008

Cyclical changes in the activity of adrenocortical tissue are a wellestablished phenomenon in many amphibian species but up to now they have been studied by observing changes in cytology or enzyme activity, e.g. steroid-3β-ol dehydrogenase. The present study was designed to provide a measure of corticosteroid secretion throughout the seasons using the in-vitro approach. Concomitant histological changes are also recorded and together provide evidence that the adrenal tissue of Rana rugulosa shows maximum activity in the spring spawning season and reaches a minimum in winter.
THE REGULATION OF INSULIN SECRETION BY THE OVINE FOETUS IN UTERO
Authors: BASSETT J. M. , THORBURN G. D.
Published: December 2008

Foetal lambs (100–150 days' gestation) with indwelling vascular catheters were used to study the regulation of the insulin concentration in the plasma of foetal lambs in utero. Immediately after the implantation of the catheters the insulin concentration in foetal plasma was significantly correlated with the foetal glucose and fructose concentrations and with the maternal glucose concentration. On the next day the foetal insulin concentration was significantly correlated only with the maternal glucose concentration.

Both glucose and fructose, when infused i.v., increased the insulin concentration in foetal plasma, but the increases were slow and far less than those observed in newborn lambs infused with glucose or fructose. Intravenous infusion of isoprenaline or glucagon did not alter the plasma insulin concentration of foetal lambs, but both caused a rapid increase in the insulin concentration of newborn lambs. Glucagon did not potentiate the insulin response to glucose. Addition of aminophylline to a glucagon infusion failed to cause insulin secretion in foetal lambs. The results suggest the cyclic-3′,5′-AMP dependent part of the insulin secretory mechanism does not develop fully before the last week of gestation.

Gel filtration of foetal plasma on Sephadex indicated that the immunoreactive material present was insulin. No significant amounts of proinsulin were found.
COMPARISON OF EFFECTS OF PROLONGED ALDOSTERONE ADMINISTRATION ON RAT COLON AND RENAL ELECTROLYTE EXCRETION
Authors: THOMPSON B. D. , EDMONDS C. J.
Published: December 2008

Rats were given a continuous intravenous infusion of aldosterone for up to 16 days. The rate of urinary Na+ excretion was initially depressed, but 'escape' occurred in about 4 days. Diurnal variation of Na+ excretion rate persisted even when the Na+ intake rate was controlled by infusion and when there was a continuous high level of exogenous aldosterone. After stopping aldosterone infusion, a transient rise in the rate of Na+ excretion was observed. Colonic transepithelial potential difference remained elevated as long as the infusion was continued and the short-circuit current, which is largely accounted for by active Na+ absorption, was increased. Stool Na+ content was reduced. The Na+ transport system of colonic epithelium, unlike that of kidney, does not appear to escape from the effect of aldosterone.
INDUCTION OF PSEUDOPREGNANCY IN RATS WITH MEDROXYPROGESTERONE
Authors: MANTALENAKIS S. J.
Published: December 2008

A daily dose of 1 mg medroxyprogesterone acetate (MAP) injected into rats for 2, 4 or 8 consecutive days, beginning on the day of oestrus, resulted in a high implantation rate of transferred 5-day blastocysts and a high survival of foetuses to term.

The best results were obtained with daily injections of 1 or 2·5 mg of MAP for 3 consecutive days, with blastocyst transfer on day 5 between 09.00 and 12.00 h. Such rats showed a decidual reaction characteristic of pregnancy. Extension of pseudopregnancy over 15 days by daily injections of 2·5 mg MAP resulted in a decrease in blastocyst implantation and a failure of foetal survival.
THE EFFECT OF CLOMIPHENE ON THE PLASMA ANDROGENS OF PREPUBERTAL AND PUBERTAL BOYS
Authors: CATHRO D. M. , SAEZ J. M. , BERTRAND J.
Published: December 2008

Plasma levels of testosterone, androst-4-ene-3,17-dione, dehydroepiandrosterone (DHA) and dehydroepiandrosterone sulphate (DHAS) were estimated both before and after administration of clomiphene citrate to endocrinologically normal boys aged from 2–16 yr and to boys with adrenocortical hypofunction or hypogonadism. A divided daily dose of 200 mg/1·7 m2 of surface area was maintained for 15 days. The unconjugated steroids were measured by means of a double isotope derivative technique and the sulphates by gas-liquid chromatography.

The boys without testicular anomaly who were well established in puberty responded with a rise in plasma testosterone. In contrast, prepubertal boys showed a statistically significant decrease in plasma testosterone levels.

A concomitant finding was a significant rise in the plasma levels of androstenedione, DHA and DHAS. It is concluded that clomiphene does not liberate luteinizing hormone before puberty but it may well diminish its secretion. A secondary effect of clomiphene is the stimulation of adrenal C19-steroid production.
THE ALDOSTERONE SECRETORY RESPONSE TO SODIUM RESTRICTION IN CHRONICALLY HYPOPHYSECTOMIZED CORTICOTROPHIN-MAINTAINED RATS AS A FUNCTION OF DURATION AND AMOUNT OF GROWTH HORMONE TREATMENT
Authors: PALKOVITS M. , de JONG W. , van der WAL B. , de WIED D.
Published: December 2008

Daily administration of growth hormone (STH) to hypophysectomized rats treated with adrenal maintenance doses of corticotrophin restored the aldosterone secretory response (as measured by the synthetic capacity of the adrenal in vitro) to sodium restriction. Treatment with STH for the first 2 days after hypophysectomy or on the 7th day after hypophysectomy failed, but treatment during the 6th and 7th day after hypophysectomy with 100, 200 or 400 μg STH/day restored the aldosterone secretory response to sodium deprivation in a dose-dependent manner.
THE EFFECTS OF CYPROTERONE ACETATE ON THE SPONTANEOUS ACTIVITY AND SEMINAL VESICLE WEIGHT OF MALE RATS
Authors: STERN J. J. , MURPHY M.
Published: December 2008

The wheel-running activity of 19 male rats was examined before and after castration. Castration significantly reduced spontaneous activity. Testosterone propionate (TP) administration increased activity to levels before castration. Cyproterone acetate given with TP did not inhibit the increase in activity but inhibited the growth of seminal vesicles.
EFFECT OF DECREASED DIETARY PROTEIN ON THE RATE OF THYROID HORMONE SECRETION AND FOOD CONSUMPTION IN RATS
Authors: SINGH D. V. , ANDERSON R. R. , TURNER C. W.
Published: December 2008

One hundred and twenty albino female rats (Sprague-Dawley-Rolfsmeyer) were divided into five equal groups. Rates of thyroxine secretion (TSR) and food consumption were determined during the control period, and 10 and 25 days after initiation of dietary treatment. Animals in each group served as their own controls for the following modifications of their diet: (1) protein-free diet, (2) 5% protein (casein) diet, (3) 10% protein diet, (4) 15% protein diet, and (5) 20% protein diet. Purina lab chow (23·4% protein) and the 20% casein diet served as control diets. The TSR, the body weight and amount of food consumed were depressed significantly in the group fed on a protein-free diet for 10 and 25 days. The group fed 5% protein diet had a non-significant decrease in TSR as compared with the controls. Similarly, TSR was not reduced by 10, 15 or 20% protein diets. Food consumption decreased significantly in the groups fed a 5, 10 and 15% protein diet, but not in the group on 20% casein. Body weight decreased significantly in the groups on a protein-free diet and on a 5% protein diet.

It would appear from these results that protein content of the diet does not become a limiting factor for TSR until it is lower than 5%. It is suggested that the calorie intake plays a more important role in regard to TSR than a low protein content of the food.
WATER AND ELECTROLYTE DISTRIBUTION IN RAT AND GUINEA-PIG THYROID GLANDS
Authors: CHOW S. Y. , WOODBURY D. M.
Published: December 2008

Procedures for the calculation of the volume of water and the Na+, K+ and Cl− concentrations in the three anatomical compartments of the thyroid (interstitium, follicular cells and lumen) are described. There was an excellent correlation between the volume of water of these three compartments calculated from the total water, [14C]inulin space and histometric measurements of the thyroid gland and the results obtained from 3H2O-uptake studies. Na+ and K+ concentrations in the luminal fluid of rat and guinea-pig thyroid glands were the same as those in the interstitial fluid which is an ultrafiltrate of plasma. Cl− concentration in the luminal fluid of thyroid gland was usually lower than that in the interstitial fluid. The concentration depends on the amount of colloid present in the follicular lumen. In the cellular fluid of the thyroid follicle, Na+ and Cl− concentrations were low and K+ concentration was high. The Cl− equilibrium potential between the interstitial and the cellular compartments, calculated from the corresponding Cl− concentrations by the Nernst equation, was the same as for previous values reported for the intracellular potentials determined by micro-electrode techniques in both rat and guinea-pig thyroid glands. In the rat thyroid, the calculated Cl− equilibrium potential between the interstitial and the luminal compartments was the same as the measured intra-luminal potential. However, in the guinea-pig thyroid the calculated Cl− equilibrium potential between the interstitial and the luminal fluids was considerably higher than the measured intra-luminal potential.
OBSERVATIONS ON THE PINEAL GLAND, THE HARDERIAN GLANDS, THE RETINA, AND THE REPRODUCTIVE ORGANS OF ADULT FEMALE RATS EXPOSED TO CONTINUOUS LIGHT
Authors: REITER R. J. , KLEIN D. C.
Published: December 2008

Harderian gland removal caused enlargement of the uteri of adult female albino rats which were maintained in 14 h light and 10 h darkness/day. Constant light exposure led to regression of the ovaries, adrenal glands and Harderian glands while the uteri exhibited a significant hypertrophic response. None of these changes were affected by surgical removal of the Harderian glands. The eyes and the retinas of albino rats maintained under continuous illumination underwent atrophic changes with the receptor cell elements of the retinas completely disappearing within 9½ weeks.

Constant light obliterated the diurnal rhythm in the pineal enzyme, N-acetyltransferase. Neither the activity of pineal hydroxyindole-O-methyl-transferase nor the activity of pineal N-acetyltransferase were influenced by removal of the Harderian glands.
THE COMPARATIVE ACTIONS OF TESTOSTERONE PROPIONATE AND 5α-ANDROSTAN17β-OL-3-ONE PROPIONATE ON THE REPRODUCTIVE BEHAVIOUR, PHYSIOLOGY AND MORPHOLOGY OF MALE RATS
Authors: FEDER H. H.
Published: December 2008

5α-Androstan-17β-ol-3-one in its free or in its propionate form was injected systemically (125 μg/day/rat) into sexually experienced, adult, castrated, male rats. These compounds were ineffective in activating masculine behaviour patterns, despite having measurable effects on body weight, seminal vesicle weight and penile morphology. The propionate form also had strong anti-gonadotrophic properties, since when it was injected for 6 days into intact, immature, male rats it significantly reduced testicular weight.

In contrast, testosterone propionate (125 μg/day/rat) restored male sexual behaviour to the levels found before castration when injected systemically. Testosterone propionate also affected body weight, seminal vesicle weight, penile morphology and the testicular weight of immature males. These effects may have been due in part to conversion of testosterone to 5α-androstan-17β-ol-3-one, but this metabolic step does not seem to be obligatory for activation of male sexual behaviour in rats.
HUMAN FOETAL PANCREATIC INSULIN SECRETION IN RESPONSE TO IONIC AND OTHER STIMULI
Authors: MILNER R. D. G. , BARSON A. J. , ASHWORTH M. A.
Published: December 2008

Pieces of human foetal pancreas were incubated under control conditions and in media containing different stimuli of insulin release. Insulin secretion was stimulated from the pancreases of foetuses (83–625 g body weight) which were of 16–24 weeks gestational age. Potassium (60 mmol/l), barium (2·54 mmol/l) and ouabain (10−5 mol/l) were effective stimuli in all experiments. Glucagon (5 μg/ml), theophylline (1 mmol/l) and dibutyryl 3′,5′-cyclic adenosine monophosphate (1 mmol/l) stimulated insulin secretion in media containing 0, 0·6 or 3·0 mg glucose/ml. Theophylline and dibutyryl 3′,5′-cyclic adenosine monophosphate were effective in all experients and glucagon stimulated insulin release in four out of six experiments. At all ages studied, histological examination of the pancreas after each experiment revealed islets of Langerhans containing β cells. In most cases the islets were of the mantle type but occasionally bipolar islets were seen. Cellular normality, as judged by light microscopy, was preserved after periods of incubation for up to 5½ h. Glycogen was demonstrable in the pancreatic acinar tissue but not in the islets.

The results of these experiments indicate that, between the 16th and 24th week of foetal life, the human β cell is capable of releasing insulin in vitro when stimulated appropriately.
PROBLEMS IN ELECTRICAL STIMULATION OF AFFERENT PATHWAYS FOR OXYTOCIN RELEASE
Authors: URBAN I. , MOSS R. L. , CROSS B. A.
Published: December 2008

Recent investigations in the rabbit have indicated the presence of well-defined afferent nervous pathways for release of neurohypophysial oxytocin. To study these pathways for later use in hypothalamic unit recording, intramammary pressure responses (milk ejection) and arterial pressure were recorded in 45 lactating rabbits with post-pontine brainstem transection. Systematic exploration of the mid-brain tegmentum and ventromedial forebrain areas was carried out with a bipolar stimulating electrode. Release of oxytocin, shown by milk-ejection responses similar to those evoked by a 1–2 mu. synthetic oxytocin occurring in the absence of detectable pressor effects, was recorded in less than half the animals. The location of positive stimulation sites was very variable between animals and reproducibility of responses from the same site was poor. It is concluded that present evidence does not support a discrete afferent path in the mid-brain for the milk-ejection reflex and a possible explanation for the inconstant results of stimulation experiments is suggested.
EFFECT OF PROGESTERONE ON SURVIVAL OF BLASTOCYSTS IN UTERI OF OVARIECTOMIZED MICE
Authors: WEITLAUF H. M.
Published: December 2008

Mice were ovariectomized on day 4 of pregnancy and injected daily with either progesterone or oil vehicle (day 1 = the day of vaginal plug). Blastocysts were recovered on day 10, 20 or 30, counted and transferred to ovariectomized recipients. Implantation was induced and pregnancy maintained by daily injections of oestradiol and progesterone. Viability of the blastocysts was assessed by determining the percentage that developed into normal foetuses. A similar number of eggs was recovered from both groups at each time-interval; thus progesterone did not influence the retention of blastocysts by ovariectomized mice. In contrast, progesterone did influence the viability of the embryos. The percentage of blastocysts developing normally from the oil-treated animals was: 39% on day 10, 19% on day 20 and less than 1% on day 30. Corresponding percentages for the progesterone-treated animals were: 40% on day 10, 35% on day 20 and 35% on day 30.
THE EFFECTS OF HYPERMAGNESAEMIA ON CALCITONIN SECRETION IN VIVO
Authors: CARE A. D. , BELL N. H. , BATES R. F. L.
Published: December 2008

The influence of magnesium on calcitonin (CT) secretion rate has been studied in pigs by perfusion of porcine thyroid glands, isolated in situ, under controlled conditions of flow rate and blood electrolyte composition. At concentrations of 4·4–12·7 mequiv./l, magnesium stimulated CT secretion in the presence of a normal calcium concentration in the perfusate. The maximum effect was reached at a concentration of about 7 mequiv. Mg/l. At higher magnesium concentrations, the secretion rate of CT tended to revert towards that found with concentrations of calcium and magnesium within the normal range. When hypermagnesaemia was superimposed on hypercalcaemia there was a fall in the secretion rate of CT as the Mg: Ca ratio in the perfusing blood plasma approached 1. The stimulatory effect of hypermagnesaemia was usually less than that caused by an equimolar increase in plasma calcium concentration. The results suggest that changes in plasma magnesium concentration probably do not influence CT secretion under normal conditions.
EFFECTS OF PROLACTIN, CORTICOTROPHIN AND CORTISOL ON THE ADENOHYPOPHYSIS AND INTERRENAL GLAND OF ANADROMOUS THREESPINE STICKLEBACKS, GASTEROSTEUS ACULEATUS L. FORM TRACHURUS, IN WINTER AND SUMMER
Authors: LEATHERLAND J. F. , LAM T. J.
Published: December 2008

In 'winter' anadromous threespine sticklebacks (Gasterosteus aculeatus L. form trachurus), corticotrophin (ACTH) injections significantly decreased the size of epsilon-cells (corticotrophs), alpha-acidophils (somatotrophs) (with an apparent increase in the degree of degranulation) and dorsal basophils (thyrotrophs) (with an apparent increase in granulation). Corticotrophin was also found to increase interrenal nuclear size, to decrease body length and to cause the development of a green skin coloration typical of summer fish. Cortisol injections significantly decreased the size of thyrotrophs and increased the size of periodic acid—Schiff's reagent (PAS)-negative cells of the pars intermedia. Prolactin injections significantly decreased the size of the thyrotrophs and caused the development of a green skin coloration though to a lesser extent than ACTH injections.

In 'summer' sticklebacks which received fewer injections than winter fish (four compared with ten) ACTH significantly decreased the size of corticotrophs and PAS-negative cells of the pars intermedia whereas cortisol produced no significant effect on any of the cells studied.
STIMULATION OF RABBIT OVARIES BY HUMAN CHORIONIC GONADOTROPHIN IN THE ABSENCE OF ENDOGENOUS GONADOTROPHINS
Authors: BETTERIDGE K. J.
Published: December 2008

The ovulatory response of hypophysectomized rabbits to 100 i.u. human chorionic gonadotrophin (HCG) i.v. declined progressively as the interval between pituitary removal and HCG injection was increased from 0 to 12 h. Hypophysectomized rabbits were also treated with HCG 2·5 h after receiving an ovary transplanted with vascular anastomoses from an oestrous donor. The proportion of grafts showing positive follicular responses to HCG in these recipients (2/4) was the same as in similarly treated intact recipients (1/2). It was concluded that endogenous gonadotrophins were not essential for HCG to stimulate follicular growth and ovulation. Therefore, the disappearance of gonadotrophins after hypophysectomy probably reduced the effect of HCG by inducing follicular regression and unresponsiveness rather than by removing synergistic hormones.
INHIBITION OF OVULATION BY AN ANTI-PIG-LUTEINIZING HORMONE SERUM
Authors: BETTERIDGE K. J.
Published: December 2008

In rabbits, an anti-pig-luteinizing hormone serum (anti-pig-LH) inhibited coitally-induced ovulation when injected immediately post coitum and this effect persisted for at least 5 days. When administered 90 min after mating, anti-pig-LH had very little inhibitory effect on ovulation and did not prevent the establishment of normal pregnancies. Anti-pig-LH also blocked human chorionic gonadotrophin-induced ovulation in rabbits, evidently by direct cross reaction. Sufficient anti-pig-LH to block ovulation in rabbits inhibited neither ovulation nor conception in four guinea-pigs when injected 0 to 4 days before vaginal opening.
EFFECTS OF HISTOLOGICAL AND ELECTRON MICROSCOPICAL FIXATIVES ON THE INSULIN CONTENT OF THE RAT PANCREAS
Authors: GRILLO T. A. I. , OGUNNAIKE P. O. , FAOYE S.
Published: December 2008

The effects of chemical fixatives such as the aldehydes, as well as ethanol, on the insulin content of the rat pancreas were studied. Although there was some loss of insulin after the use of all the fixatives investigated it was found that glutaraldehyde preserved the greatest amount of the hormone at both room and low temperature. Insulin was still preserved in the pancreas after glutaraldehyde fixation even after the complete preparation of the tissue for histology or electron microscopy. The insulin extracted from the pancreas after fixation in formaldehyde was still biologically active and it enhanced the formation of glycogen in the rat diaphragm.
THE DISTRIBUTION OF METABOLITES OF [7α-3H]PROGESTERONE IN TISSUES OF MICE
Authors: TAYLOR W. , WRIGHT D. E.
Published: December 2008

[7α-3H]Progesterone was administered to two groups of mice. The localization of radioactivity in tissues was examined by autoradiography and by liquid scintillation counting. Particular attention was paid to the distribution of radioactivity in the liver and biliary system. The greatest amount of administered steroid was taken up by the liver, rapidly secreted into the biliary system and excreted into the gastrointestinal tract. Other tissues, including the uterus, did not take up any appreciable amount of radioactivity, and the autoradiographs showed that radioactivity was not associated with any particular region of hepatic and other cells. The biological half-life of radioactivity in the blood was 11 min in animals given labelled progesterone intravenously.
CONVERSION OF [4-14C]PROGESTERONE TO ANDROSTERONE BY FEMALE RHESUS MONKEYS (MACACA MULATTA)
Authors: PLANT T. M. , JAMES V. H. T. , MICHAEL R. P.
Published: December 2008

Labelled progesterone was administered intravenously to five, adult female rhesus monkeys and urine and faeces were collected every 24 h. Excretion of radioactivity in urine occurred most rapidly in the first 24-h period and then declined exponentially. The excretion of radioactivity in faeces reached maxima during the 2nd, 3rd or 4th 24-h periods depending on the animal studied. 76–94% (mean 86%) of the radioactivity administered was recovered within 9 days, but small quantities continued to be excreted in urine up to 16 days after injection. Generally, greater amounts of radioactivity were recovered from faeces (41–57%) than from urine (26–48%). Using different hydrolytic and extraction procedures, some 50% of the radioactivity in urine was recovered in the neutral extracts. The major metabolite in urine was androsterone which accounted for 1·1–12·2% (mean 6·0%) of the progesterone administered. Pregnanediol was not an important urinary catabolite in this species. Differences in the extent to which progesterone is metabolized to C-19 compounds in macaques, baboons, great apes and man may reflect the phylogeny of a catabolic desmolase system in anthropoid primates.
EFFECT OF SUCKLING AND OF EXTEROCEPTIVE STIMULATION UPON PROLACTIN RELEASE IN THE RAT DURING LATE LACTATION
Authors: MENA F. , GROSVENOR C. E.
Published: December 2008

The results of experiments in which the prolactin in the primiparous rat pituitary was bioassayed suggested that the failure of suckling to release prolactin after 8 h of non-suckling on day 21 post-partum was due to the fact that prolactin had been discharged from the pituitary during the 8-h non-suckling period, presumably by exteroceptive signals emanating from the general environment of the animal room. This was substantiated in other experiments in which prolactin release was assessed indirectly through its stimulatory effects upon milk secretion. In these experiments, the mammary glands of rats maintained continuously in the animal room filled faster on day 21 after complete emptying of the glands by exogenous oxytocin, than did either rats on day 14 post-partum maintained continuously in the animal room or rats isolated in a room without other rats on day 21 post-partum. The glands of the latter two groups of rats could be stimulated to fill faster provided prolactin was injected 4 h before the initial emptying of the glands. The exteroceptive stimuli in the animal room environment that stimulated the release of prolactin in the 21-day post-partum rat apparently emanated at least in part from other lactating rats and/or their litters, since faster mammary gland refilling occurred in isolated 21 day post-partum rats when they were exposed to the presence of lactating rats with their litters for 30 min halfway through the 8-h non-suckling period which preceded the initial emptying of the gland. Exposure to male rats, on the other hand, was totally ineffective. A release of prolactin occurred in response to animal room environmental stimuli in the day 14 primiparous rat provided 13–14 day old foster pups were inserted in place of the mother's own pups on day 7. Thus, the rapidly changing characteristics of the pups from 14 to 21 days of age in some manner is involved in the increasing responsiveness of the exteroceptive mechanism for prolactin release which occurs from day 14 to day 21 post-partum.
THE PROGESTERONE CONCENTRATION IN THE PLASMA OF THE GOAT DURING THE OESTROUS CYCLE AND PREGNANCY
Authors: THORBURN G. D. , SCHNEIDER W.
Published: December 2008

Progesterone concentrations in the peripheral plasma of goats were measured by a protein-binding assay. The mean concentration was extremely low on the day of oestrus (0·2 ng/ml) and was not significantly different from that found in anoestrous or ovariectomized animals. The concentration increased to a maximum of 4 ng/ml on about day 10 of the 21-day cycle, and decreased rapidly during the last 3 days of the cycle.

Plasma progesterone concentration during early pregnancy (2·5–3·5 ng/ml) was similar to the luteal phase value and remained steady from day 8 to day 60. Between days 60 and 70 there was a secondary increase in progesterone concentration which was maintained at this increased level (4·5–5·5 ng/ml) until just before parturition. In twin-bearing animals, the secondary increase was greater. Progesterone concentration decreased rapidly during the 1–2 days preceding parturition, but the concentration was still quite high on the day of parturition (1·25 ng/ml).

The progesterone concentration in peripheral plasma was markedly increased during anaesthesia and the operation. After bilateral ovariectomy of the pregnant goat, peripheral progesterone concentration fell rapidly from 9 to 2·5 ng/ml during the first ½ h and then more slowly during the next 5–6 h. The animals aborted 36–48 h later.

A consistent positive arterio—venous difference for progesterone was observed across the pregnant uterus in two unanaesthetized goats. These results indicate that the ovary is the main site of progesterone production in the pregnant goat and that production by the placenta is small and unlikely to influence the level of this hormone in the maternal circulation.
RADIOIMMUNOASSAY FOR PLASMA ANTIDIURETIC HORMONE
Authors: JOHNSTON C. I.
Published: December 2008

Antibodies to [8-lysine]-vasopressin (LVP) were produced in rabbits by a macrophage harvesting technique. Using these antibodies a radioimmunoassay for vasopressin was established using LVP as standard and for labelling with 125I. The antibody demonstrated complete cross-reactivity to [8-arginine]- and [8-ornithine]-vasopressin but concentrations of oxytocin 1000 times greater caused no displacement. A simple extraction procedure for antidiuretic hormone (ADH) in plasma is described. Employing this extraction procedure followed by radioimmunoassay, plasma levels of ADH were measured in sheep. The mean level of plasma ADH in nine sheep was found to be 5·28 ± 1·18 in arterial blood and this rose to 21·04 ± 7·29 μu./ml after haemorrhage of 10 to 20% of their blood volume.
INDUCTION OF LACTOSE SYNTHESIS BY PROLACTIN IN RABBIT MAMMARY GLAND EXPLANTS
Authors: DELOUIS C. , DENAMUR R.
Published: December 2008

The rate of biosynthesis of lactose from [14C]glucose was used to study the action of different hormone combinations on cultures of mammary explants from pseudopregnant rabbits. Insulin with or without cortisol had no effect, but insulin with prolactin induced lactose synthesis in vitro even when prolactin was not added to the culture medium until 48 h after culture began. Insulin together with cortisol and prolactin produced a greater response when used from the beginning of culture. Differences between these results and those obtained with mammary tissue from pregnant mice are discussed.
THE ROLE OF PROLACTIN IN THE REGULATION OF TESTIS FUNCTION: THE EFFECTS OF PROLACTIN AND LUTEINIZING HORMONE ON THE PLASMA LEVELS OF TESTOSTERONE AND ANDROSTENEDIONE IN HYPOPHYSECTOMIZED RATS
Authors: HAFIEZ A. A. , LLOYD C. W. , BARTKE A.
Published: December 2008

Testosterone and androstenedione levels in the plasma of hypophysectomized rats were measured by a protein-binding method (sensitivity 150 pg testosterone; precision, 10%).

Testosterone levels in the plasma of saline-treated hypophysectomized rats were undetectable (<0·3 ng/ml). Administration of 200 μg prolactin twice daily s.c. for a period of 3½ days caused a slight rise in testosterone in four rats (0·61 ± 0·35 ng/ml) while 5 μg luteinizing hormone (LH) administered in the same regimen increased testosterone levels to 1·42 ± 0·35 ng/ml (P < 0·05). Administration of prolactin ± LH (same doses) increased testosterone levels to 5·07 ± 0·51 ng/ml which is significantly higher than when LH was given alone and exceeds testosterone levels in intact adult males (4·12 ± 0·60 ng/ml).

Androstenedione levels in the plasma of saline-treated hypophysectomized rats were, in contrast to testosterone levels, very high and averaged 3·37 ± 0·60 ng/ml. This level is higher than that in saline-treated intact controls (1·89 ± 0·36 ng/ml). Treatment with prolactin, LH or prolactin + LH induced insignificant changes in androstenedione levels which were 1·80 ± 0·33, 2·02 ± 0·28 and 4·22 ± 0·75 ng/ml, respectively.

The ratio testosterone: androstenedione was calculated to be 0·37 ± 0·08 in the prolactin-treated group, 0·76 ± 0·20 in the LH-treated group and 1·47 ± 0·64 in the prolactin + LH-treated group compared with 2·36 ± 0·28 in intact control males.
THE AFFERENT PATHWAY OF THE MILK-EJECTION REFLEX IN THE MID-BRAIN OF THE GOAT
Authors: KNAGGS G. S. , McNEILLY A. S. , TINDAL J. S.
Published: December 2008

The position of the pathway for the release of oxytocin in the mid-brain was ascertained by exploration of a transverse stereotaxic plane (A4) in 23 anaesthetized goats. Electrical stimulation was applied between a monopolar electrode and an indifferent electrode in the scalp. Oxytocin release was monitored by simultaneous collection of blood samples during stimulation from a catheter in a jugular vein. The blood samples were extracted by the Sephadex G-25 or fuller's earth method and assayed for oxytocin content on the lactating guinea-pig preparation.

Oxytocin release occurred occasionally after stimulation of certain sites in the tectum, central grey and reticular formation. Regular releases of oxytocin, however, were only obtained after stimulation of a pathway which was compact and lay in the lateral tegmentum of the mid-brain in association with the spinothalamic tract. The position of this pathway corresponds to that described previously for the afferent pathway of the milk-ejection reflex in the mid-brain of the guinea-pig and rabbit. In these three species therefore, the impulses concerned in oxytocin release appear to ascend through the mid-brain in the spinothalamic tract.
A BIOCHEMICAL COMPARISON OF THE LACTOGENIC EFFECT OF PROLACTIN AND GROWTH HORMONE ON MOUSE MAMMARY GLAND IN ORGAN CULTURE
Authors: WANG D. Y. , HALLOWES R. C. , SMITH R. H. , AMOR V. , LEWIS D. J.
Published: December 2008

A biochemical comparison of the lactogenic effect of ovine prolactin and of bovine growth hormone on pregnant mouse mammary gland in organ culture was made. No qualitative differences were observed; both hormones (in the presence of insulin and corticosterone) stimulated the synthesis of casein and RNA in mouse mammary gland explants. The inhibition of RNA synthesis with actinomycin D was associated with a decrease in casein synthesis. However, quantitatively, prolactin was more efficient than growth hormone in stimulating casein synthesis.

The synthesis of casein in mouse mammary gland explants incubated in the presence of various combinations of hormones gave results which suggested that prolactin and growth hormone are operating on the same sites of action.

Analysis of, and purification by, polyacrylamide gel electrophoresis of the bovine growth hormone showed that the lactogenic effects were not due to the presence of prolactin as an impurity, but were an intrinsic property of the growth hormone.
THE OXYTOCIN-INACTIVATING ACTIVITY OF THE RAT UTERUS
Authors: BURJORJEE M. N. , MALHOTRA U. , CHAUDHURY R. R.
Published: December 2008

The oxytocin-inactivating activity (OIA) of rat uterus homogenates was studied in intact animals and in animals with bilateral intrauterine devices (IUD). In another series of experiments the OIA of the rat uterus was related to the mast cell count of uteri from intact rats and from rats with bilateral intrauterine devices. The OIA of the homogenates was significantly higher at oestrus than at dioestrus. No such increase was observed in homogenates from rats at oestrus with bilateral IUD's. The IUD caused an increase in the mast cell population at oestrus and the increase in mast cell counts observed in uterine homogenates of intact rats at dioestrus was not observed in the presence of a device. No correlation between the OIA of uterine homogenates and the mast cell population was observed in animals with or without IUD at oestrus or dioestrus.
CHANGES IN PLASMA CORTICOSTERONE LEVELS OF THE YOUNG RABBIT AFTER INJURY
Authors: LITTLE R. A.
Published: December 2008

The changes in plasma corticosterone levels and sudanophilia of the adrenal cortex after a 3-h period of bilateral hind-limb ischaemia in a thermoneutral environment were studied in 1–2, 12 and 38- to 42-day-old rabbits. There was a significant increase in plasma corticosterone accompanied by a decrease in sudanophilia of the adrenal cortex after tourniquet removal at all ages. The results indicate that there are sufficient steroids present at all ages studied for the expression of the various responses elicited by injury.
CYCLIC AMP AND HORMONE ACTION
Authors: MAJOR PATRICIA W. , KILPATRICK R.
Published: December 2008

The role of cyclic AMP in the mediation of hormone action is reviewed, including information available from 1958–1971. Evidence for its involvement in each hormone action is considered separately. The known mechanisms by which cyclic AMP stimulates specific metabolic processes are also described. Other speculations on the role of cyclic AMP in the mediation of hormone action are discussed.
LUTEINIZING HORMONE RELEASING FACTOR IN THE QUAIL HYPOTHALAMUS
Authors: SMITH P. M. , FOLLETT B. K.
Published: December 2008

Pituitaries from Japanese quail were superfused continuously for up to 12 h and the luteinizing hormone (LH) in the superfusate was measured by radioimmunoassay. After an initial period the release rate remained low and relatively constant. The introduction of hypothalamic extracts prepared from quail substantially increased immunoreactive LH release. The responses were dose-dependent. Cortical extracts caused a minor but significant response. Dopamine was inactive in the system. The technique is attractive because it allows for repetitive stimulation of the same pituitary glands with treatments being administered every 30–45 min.
CALCITONIN-LIKE ACTIVITY IN THE CIRCULATION OF OSTEOPETROTIC GREY-LETHAL MICE
Authors: MURPHY HELEN M.
Published: December 2008

Hypocalcaemia resulted from the injection of grey-lethal mouse plasma into assay mice. On bioassay, parallelism in dose—response curves was established between this factor, MRC research standard calcitonin and acid extracts from the grey-lethal mouse thyroid gland. Other lines of evidence, i.e. stability at neutral and acid pH's after ultracentrifugation for long periods, after adsorption on to silica gel and the results of enzymic and acid hydrolysis, suggest that the hypocalcaemic factor is a small polypeptide. Since a hypersecretion of calcitonin could account for most of the findings in the osteopetrosis of the grey-lethal mouse it is tentatively proposed that the hypocalcaemic factor is this hormone.
UNIT ACTIVITY IN THE DIENCEPHALON OF FEMALE RATS DURING THE OESTROUS CYCLE
Authors: DYER R. G. , PRITCHETT C. J. , CROSS B. A.
Published: December 2008

The spontaneous firing rate of 826 single cells, recorded from the anterior diencephalon of cyclic female rats, was analysed. In the thalamus no differences in the firing rates of populations of cells were observed during the 4 days of the oestrous cycle. However, during the afternoon of pro-oestrus the units recorded from the hypothalamus were faster firing than on the remaining 3 days, and were significantly more active (P < 0·05) than during the afternoon of metoestrus or dioestrus. The increase in unit activity at pro-oestrus was restricted to the ventral portion of the anterior hypothalamus. Since even sham recording sessions during pro-oestrus greatly reduced the ovulation rate, the increased unit activity is unlikely to be a sufficient cause of luteinizing hormone secretion, though it might be a necessary prerequisite or have some other sexually related significance.
PROGESTERONE CONCENTRATIONS IN MATERNAL AND FOETAL BLOOD PLASMA OF EWES
Authors: MOORE N. W. , BARRETT SUSAN , BROWN J. B.
Published: December 2008

In pregnant ewes the progesterone concentrations in plasma from the maternal jugular, ovarian (active ovary) and uterine veins and from the foetal umbilical vein were measured by a competitive protein-binding technique.

Peripheral plasma levels remained fairly uniform throughout pregnancy, whereas ovarian levels dropped at about the 130th day of pregnancy. Uterine plasma levels were low until the 80th day; foetal levels rose as pregnancy progressed.

The major sources of progesterone appeared to be the ovary (corpus luteum) and the uterus (placenta). The ovarian contribution was greater during the first two-thirds of pregnancy than later, whereas that made by the placenta was lower during the first one-third of pregnancy.
SELECTIVE UPTAKE OF RADIOACTIVITY BY THE ADRENAL CORTEX OF DEXAMETHASONE-TREATED GUINEA-PIGS AFTER THE ADMINISTRATION OF 131I-LABELLED α1–24 ADRENOCORTICOTROPHIN
Authors: GOLDER MERIEL P. , BOYNS A. R.
Published: December 2008

Normal and dexamethasone-treated guinea-pigs were injected intravenously with 50 ng 131I-labelled α1–24 adrenocorticotrophin (ACTH). The concentration of radioactivity in the adrenals of dexamethasone-treated animals was significantly greater than in the untreated group but no difference was observed among the other tissues studied. There was no change in the concentration of 125I-labelled insulin, 125I-labelled poly-l-tyrosine, 131I-labelled bovine serum albumin (BSA) or [131I]iodide in any tissue including the adrenal. Intra-adrenal radioactivity after the injection of 131I-labelled α1–24 ACTH into normal animals showed a peak approximately localized at the glomerular-fascicular border with a second peak in the zona reticularis. Dexamethasone treatment significantly enhanced the size of both peaks. There was no difference in the intra-adrenal distribution of 125I-labelled BSA, 125I-labelled insulin and 125I-labelled poly-l-tyrosine after dexamethasone administration. The effect of other proteins on the increased uptake of 131I-labelled α1–24 ACTH by the adrenal of dexamethasone-treated animals was also studied. Human luteinizing hormone (100 ng), human growth hormone (100 ng), poly-l-tyrosine (50 ng) and glucagon (10, 100 and 1000 ng) were without effect. Excess α1–24 ACTH (100 μg) and insulin (100 and 1000 ng) reduced adrenal radioactivity to the concentrations found in control animals.
THE DEGRADATION OF HUMAN PLACENTAL LACTOGEN IN NORMAL AND NEPHRECTOMIZED DOGS
Authors: ROCHMAN H. , VARNAVIDES L. A. , HAWLEY P. R.
Published: December 2008

To determine the site of degradation of human placental lactogen (HPL) the disappearance rate of 125I-labelled and unlabelled HPL was studied in intact normal and nephrectomized dogs. Methods for determining plasma levels of 125I-labelled HPL included measurement of total radioactivities, radioactivities after trichloroacetic acid precipitation and immunoprecipitation, and chromatoelectrophoresis. Plasma HPL levels were determined by a radioimmunoassay method.

In the dog, of the several organs studied, only the kidney was found to be involved in the degradation of both labelled and unlabelled hormone. The role of the kidney in the degradation of polypeptide hormones is discussed.
ADRENOCORTICAL FUNCTION IN RATS SUBJECTED TO NUTRITIONAL DEPRIVATION IN EARLY LIFE
Authors: ADLARD B. P. F. , SMART J. L.
Published: December 2008

Rats were undernourished during the foetal and suckling periods by limiting maternal food intake. Animals were weaned to an unrestricted diet at 25 days of age. Before weaning, the mean plasma corticosteroid concentration in undernourished animals was 39 μg/100 ml compared with 21 μg/100 ml in well-fed controls. At 15–17 weeks of age previously undernourished and control animals did not differ in basal plasma corticosteroid concentration. After stressful stimulation, however, levels were lower in animals subjected to early undernutrition than in controls. It is suggested that nutritional deprivation in infancy resulting in increased plasma corticosteroid levels at that time, permanently modifies the adrenocortical response to stress.
THE ENTEROHEPATIC CIRCULATION OF THYROXINE
Authors: GALTON VALERIE ANNE , NISULA B. C.
Published: December 2008

A quantitative investigation was made of the enterohepatic circulation of endogenous thyroxine (T4) in the rat. Control and cold-acclimated rats were maintained on a low iodine diet and water containing 125I-labelled iodide of known specific activity for 4 weeks. Faeces were then collected over a 3-day period. Bile was collected by means of a pipette inserted into the ligated intestine and flow rate was determined. Blood was obtained from the vena cava. The total and organic 131I content of serum, faeces and bile were measured by several techniques. From these values and the known specific activity of the [125I]iodide, the concentration of organic iodine in the various samples was calculated. In control and cold-acclimated rats, the bile: plasma organic iodide ratios were 1·02 and 1·38 respectively. Bile flow, and hence the rate of secretion of organic iodine in bile, was greatly increased in the cold rats. Nevertheless, in both cold and control rats, the amount of organic iodine excreted daily in the faeces invariably exceeded the amount secreted in bile.

In a second study in which rats were equilibrated with varying doses of 131I-labelled T4 administered daily, it was found that with increasing amounts of T4, serum T4 concentration and the urinary excretion of hormonal iodine tended to level off. In contrast the ability of the hepatic—faecal system to clear T4 appeared to be relatively unlimited with doses up to 20 μg T4/100 g body weight/day.

It was concluded that, in the rat, there is no net reabsorption of the endogenous thyroid hormone secreted into the intestine in bile.