bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

SUMMARY
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

SUMMARY
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

SUMMARY
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

SUMMARY
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

SUMMARY
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

SUMMARY
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

SUMMARY
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

SUMMARY
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

SUMMARY
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

SUMMARY
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

SUMMARY
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

SUMMARY
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

SUMMARY
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

SUMMARY
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

SUMMARY
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

SUMMARY
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

SUMMARY
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

SUMMARY
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.
A STUDY OF THE RELATIONSHIP BETWEEN THE THYROID GLAND AND SEBUM SECRETION IN THE RAT
Authors: THODY A. J. , SHUSTER S. 
Published: December 2008

SUMMARY
Thyroidectomy of intact and castrated rats produced significant reductions in their rates of sebum secretion. Replacement therapy with thyroxine (T4) increased the rate of sebum secretion of the castrated-thyroidectomized rats. Treatment with testosterone propionate also stimulated sebum secretion in castrated-thyroidectomized rats. When given together these two hormones had an additive effect on the rate of sebum secretion.
Thyrotrophic hormone (TSH) stimulated sebum secretion in castrated-hypophysectomized, but not in thyroidectomized rats.
It is concluded that TSH affects sebum secretion through its action on the thyroid, presumably by stimulation of T4 secretion.
EFFECTS OF PINEALECTOMY AND CONSTANT LIGHT AND DARKNESS ON PROLACTIN LEVELS IN THE PITUITARY AND PLASMA AND ON PITUITARY ULTRASTRUCTURE OF THE RAT
Authors: RELKIN R. , ADACHI M. , KAHAN S. A. 
Published: December 2008

SUMMARY
The effects of constant light, constant darkness and diurnal lighting, in combination with pinealectomy or sham-pinealectomy, on pituitary and plasma concentrations of radioimmunoassayable prolactin were investigated in 8-week-old male and virgin female rats. Two to three days after operation random groups of pinealectomized and sham-pinealectomized animals of the same sex were placed together in either continous light, continuous darkness or diurnal light, and killed 21 days later. Compared with sham-operated diurnally-illuminated controls, constant darkness caused a decrease in pituitary prolactin content and a rise in plasma prolactin levels. Pinealectomy or constant illumination reversed the effect of constant darkness, resulting in an increase in pituitary prolactin content and a fall in plasma prolactin levels when compared with sham-operated diurnally-illuminated controls. Electron microscopy of lactotrophic cells of the sham-pinealectomized animals exposed to constant darkness revealed few cytoplasmic granules, whereas these cells in the sham-pinealectomized animals exposed to constant light contained abundant granules; compared with the former groups, lactotrophic cells of sham-pinealectomized rats exposed to diurnal lighting revealed an intermediate degree of granulation.
ROLE OF MONOAMINES IN OVULATION: EVIDENCE FOR A SEROTONINERGIC PATHWAY FOR INHIBITION OF SPONTANEOUS OVULATION
Authors: LABHSETWAR A. P. 
Published: December 2008

SUMMARY
The effect of a monoamine oxidase inhibitor (MAOI) (mebanazine) given alone or in combination with 5-hydroxy-dl-tryptophan (5-HTP) or dihydroxyphenylalanine (l-DOPA) on spontaneous ovulation was tested in 4-day cyclic rats. Injections of the MAOI or 5-HTP alone, which cause a selective rise in the hypothalamic serotonin level, blocked spontaneous ovulation in 32% and 0% of rats, respectively, and in 73% of rats when given together. By contrast, a combination of MAOI and l-DOPA, which causes a selective rise in the hypothalamic catecholamines, did not block ovulation. A single injection of α-methyl-p-tyrosine, but not of α-methyl-m-tyrosine, blocked ovulation in 100% of rats. These results provide experimental support for the existence of a serotoninergic component in the control of ovulation.