bluuebunny/crossref_metadata_2025_split huggingface dataset:
MECHANISM OF ACTION OF GLUCOCORTICOIDS IN INDUCTION OF OVINE PARTURITION: EFFECT ON PLACENTAL STEROID METABOLISM
Authors: ANDERSON ANNE B. M. , FLINT A. P. F. , TURNBULL A. C. 
Published: December 2008

SUMMARY
Maternal plasma progesterone levels in sheep may fall dramatically during the last few days of gestation and following the administration of glucocorticoids to the foetus. To investigate the mechanism of the fall, metabolism of [3H]pregnenolone and/or [3H]progesterone in vitro by ovine placental tissue was studied in five ewes before and after intra-foetal administration of dexamethasone in a dosage sufficient to induce parturition, and in one ewe after the spontaneous onset of labour at 143 days of gestation. Manual separation of maternal and foetal placental tissues showed that, in 11 out of 12 cases, the foetal and not the maternal placenta produced progesterone from pregnenolone in vitro. Total activities of cholesterol side-chain cleavage enzyme and 3β-hydroxysteroid dehydrogenase in the foetal placenta were not influenced by intra-foetal dexamethasone. Before administration of dexamethasone, homogenates of foetal placenta converted [3H]progesterone to 20α-hydroxy [3H]pregn-4-en3-one in the presence of NADPH. Within 12 h of administration of dexamethasone, and after the natural onset of labour at 143 days, large amounts of 17α,20α-dihydroxy[3H]pregn4-en-3-one were formed from [3H]progesterone. Intra-foetal dexamethasone treatment also induced the formation of 17α,20α-dihydroxy[3H]pregn-4-en-3-one by minced foetal placental tissue incubated with [3H]pregnenolone. This change in steroid metabolism did not occur in foetal placental tissue from a sham-operated animal receiving no dexamethasone. Assay of progesterone in foetal placentae showed that the increased formation of 17α,20αdihydroxypregn-4-en-3-one was unlikely to be caused by a change in the specific activity of added 3H-labelled precursor, although the production of 17α,20α-dihydroxypregn-4-en3-one in vitro increased at a time when both foetal placental and utero-ovarian venous levels of progesterone were decreasing in response to dexamethasone treatment. These observations indicate that intra-foetal dexamethasone treatment induces a placental 17α-hydroxylase enzyme, which is also present in foetal placental tissue after the spontaneous onset of labour at term.
EFFECTS OF ACUTE AND CHRONIC STRESS ON PLASMA CORTICOSTERONE LEVELS IN THE PREGNANT AND NON-PREGNANT MOUSE
Authors: BARLOW SUSAN M. , MORRISON P. J. , SULLIVAN F. M. 
Published: December 2008

SUMMARY
Plasma corticosterone levels were measured in the pregnant and non-pregnant mouse after acute and chronic stress. Acute surgical stress in the non-pregnant mouse increased plasma corticosterone from a mean resting level of 2·3 to 50·6 μg/100 ml 1 h after operation. By 24 h after operation, levels had fallen back to 7·6 μg/100 ml. In the pregnant mouse an acute surgical stress on day 14 of pregnancy increased plasma corticosterone levels to 525 μg/100 ml 1 h after surgery from a resting value of 80 μg/100 ml, with a return to resting levels by 24 h. During the chronic stress of 24 h restraint, plasma corticosterone levels in the non-pregnant mouse reached a peak (81·0 μg/100 ml) 1 h after the start of restraint and were still raised (mean 24·0 μg/100 ml) after 24 h. In the pregnant restrained mouse a peak value of 733 μg/100 ml was seen at 1 h, with levels maintained at around 500–600 μg/100 ml during the next 16 h of restraint. Increased levels of 268 μg/100 ml were still present at 24 h. After the chronic stress of 24 h food deprivation, plasma corticosterone levels in the non-pregnant and pregnant mice were raised after 7 h to levels slightly lower than those observed in the restrained groups, and at 24 h levels in the respective restrained and fooddeprived groups were similar, suggesting that food deprivation is a powerful chronic stressor in the mouse.
During chronic stress in the pregnant mouse where plasma corticosterone levels of around 600 μg/100 ml were maintained for some hours, protein binding studies indicated that 10 μg/100 ml was free, unbound corticosterone. The physiological and pathological consequences of such high levels of free corticosterone during stress in pregnancy are discussed.
FURTHER STUDIES ON THE AFFERENT PATH OF THE MILK-EJECTION REFLEX IN THE BRAIN STEM OF THE RABBIT
Authors: TINDAL J. S. , KNAGGS G. S. 
Published: December 2008

SUMMARY
When the afferent pathway of the milk-ejection reflex, which we had previously reported, was surgically severed bilaterally in the mid-brain of the lactating rabbit, the reflex release of oxytocin in response to suckling was blocked for up to 11 days; unilateral severance did not block the reflex. The position and discrete nature of the pathway were also further substantiated by electrical stimulation experiments in acute studies in the anaesthetized rabbit. Some animals, however, did not release oxytocin in response to stimulation of the pathway. Furthermore, whereas stimulation of this reflex pathway in the guinea-pig brain at intervals of a few minutes evokes release of oxytocin after each stimulation, in the present study the release of oxytocin in the rabbit in response to repeated electrical stimulation was either progressively attenuated or did not occur at all after the initial release. There appears, therefore, to be a powerful overriding central inhibitory mechanism in the rabbit which can prevent release of oxytocin, even when the appropriate stimulus for release is applied.
A NEW METHOD FOR THE PRODUCTION OF EXPERIMENTAL DIABETES IN RABBITS
Authors: PAKRASHI ANITA , MUKHERJEE SAMIR K. 
Published: December 2008

SUMMARY
Oral administration of 250 mg hydrochlorothiazide/kg, with previous i.v. injection of 4 i.u. soluble insulin or s.c. injection of protamine-zinc insulin, has been found to produce stable hyperglycaemia in rabbits irrespective of sex. It is thought that insulin helps the selective action of hydrochlorothiazide on the β cells by removing the protective glucose barrier. Although stimulation of glucagon or some extra-pancreatic mechanism at the initial stage could not be altogether ruled out, the central action of the drug is supported by the finding that the hydrochlorothiazide-induced hyperglycaemia was lowered by the sulphonylurea derivative, chlorpropamide.
INFLUENCE OF ANAESTHETICS ON BASAL, PERPHENAZINE-INDUCED AND THYROTROPHIN RELEASING HORMONE-INDUCED PROLACTIN SECRETION IN OVARIECTOMIZED, OESTROGEN-TREATED RATS
Authors: LAWSON D. M. , GALA R. R. 
Published: December 2008

SUMMARY
Plasma levels of prolactin were determined, by radioimmunoassay, in ovariectomized, oestrogen-treated rats after administration of ether, sodium pentobarbitone, urethane, chloral hydrate or ketamine. These anaesthetics, when administered alone, induced sustained increases in the plasma level of prolactin (continuous ether inhalation), no change in prolactin secretion (urethane), or depressions in the level of prolactin (sodium pentobarbitone, chloral hydrate and ketamine). These same anaesthetics when given before perphenazine failed to alter the stimulatory effect of this phenothiazine on prolactin secretion. Sodium pentobarbitone did not alter the normal increase in prolactin concentration after intra-arterial administration of synthetic thyrotrophin releasing hormone (TRH). These results indicated that anaesthetics do not affect the response of either the central nervous system or the anterior pituitary to perphenazine or TRH although they affect prolactin secretion when administered alone. The site of action of anaesthetics must, therefore, be different from that of perphenazine or perphenazine must be capable of overcoming their influence by direct action on the pituitary.
MAINTENANCE OF MALE SEXUAL BEHAVIOUR BY COMBINED TREATMENT WITH OESTROGEN AND DIHYDROTESTOSTERONE IN CD-1 MICE
Authors: WALLIS C. J. , LUTTGE W. G. 
Published: December 2008

SUMMARY
After castration, adult male sexually experienced CD-1 strain mice were treated with dihydrotestosterone (200 μg/day, DHT), oestradiol benzoate (1 μg/day, OB) or DHT (200 μg/ day) plus OB (1 μg/day). Oestradiol benzoate and the combined treatment DHT+OB maintained male sexual behaviour at levels comparable to a group of intact control mice, while DHT maintained behaviour at a lower level. Halving all hormone dosages resulted in a decrease in the number of OB-treated animals mating and a complete loss of mating in the DHT-treated animals. The decrease in dosage did not result in any change in the behaviour of the mice receiving both hormones. Adrenalectomy was found to have no effect on the mating behaviour of the OB-treated and untreated animals, but it did reduce the number of DHT+OB-treated animals mating. Thus, both OB alone and combined DHT+OB treatment can maintain male mating behaviour in castrated CD-1 strain mice and these effects do not appear to be due to the effects of oestradiol on the adrenal.
EFFECT OF IONIC STRENGTH AND IONIC COMPOSITION OF ASSAY BUFFERS ON THE INTERACTION OF THYROXINE WITH PLASMA PROTEINS
Authors: SUTHERLAND R. L. , BRANDON M. R. , SIMPSON-MORGAN M. W. 
Published: December 2008

SUMMARY
When plasma proteins are diluted with buffer the ionic strength and ionic composition of that buffer affects the interactions between thyroxine (T4) and its plasma protein-binding sites. Increases in phosphate, chloride or barbiturate ion concentration from 50 to 200 mmol/l caused a significant decrease in the affinity of plasma proteins for T4, and a concurrent increase in the concentration of unbound T4. These results cannot be completely accounted for by changes in ionic strength since at the same ionic strength different anions caused quantitatively different effects on unbound T4 concentration. The degree of depression of T4 binding by the three anions studied was in the order barbiturate > chloride > phosphate.
The results of a systematic study on the composition of diluent buffer systems indicated that when a 50 mm-sodium phosphate–100 mm-NaCl buffer (pH 7·4) was used as a plasma diluent, there were unlikely to be gross changes in the T4-binding properties of plasma proteins with dilution.
THE EFFECTS OF HYPOPHYSECTOMY AND OF BOVINE GROWTH HORMONE ON THE RESPONSES TO TESTOSTERONE OF PROSTATE, PREPUTIAL, HARDERIAN AND LACHRYMAL GLANDS AND OF BROWN ADIPOSE TISSUE IN THE RAT
Authors: EBLING F. J. , EBLING ERIKA , RANDALL VALERIE , SKINNER J. 
Published: December 2008

SUMMARY
The relative responses to testosterone of the prostate, preputial, Harderian, and lachrymal glands, the seminal vesicles and the brown adipose tissue, have been compared in litter-mate, castrated and hypophysectomized–castrated rats, with or without treatment with bovine GH. The responses of both prostate and preputial glands, though not the seminal vesicles, were reduced by hypophysectomy, and restored by GH. Growth hormone had some independent action on the preputial glands, but most of its effect was synergistic with testosterone. The response of brown adipose tissue to testosterone was similarly reduced by hypophysectomy, but was not restored by the GH. The weights of the Harderian and lachrymal glands were not affected by castration, but they were considerably reduced by hypophysectomy. Growth hormone had a slight restorative effect on the Harderian glands, but none on the lachrymal glands.
DIFFERENCES IN SERUM CORTICOSTERONE PATTERNS IN INDIVIDUAL RATS: RELATIONSHIP TO OVULATORY CYCLES
Authors: RAMALEY JUDITH A. 
Published: December 2008

SUMMARY
Blood samples were collected on several occasions from Sprague–Dawley–derived rats by means of cardiac puncture at 8 h intervals over a 24 h period. Rats were sampled four times before ovariectomy, after ovariectomy and after replacement therapy with oestradiol benzoate. It was discovered that each rat tended to maintain a distinct pattern of serum corticosterone. While some rats developed hormonal rhythms, other rats showed no evidence of such rhythms as indicated by patterns of serum corticosterone concentration. The majority of rats that did not show daily corticosterone rhythms were found to have irregular ovulatory cycles as indicated by vaginal smears. Each characteristic hormonal pattern remained after ovariectomy and subsequent oestrogen replacement although resting levels of corticosterone were lower after ovariectomy and higher after oestrogen treatment than before the operation. It is concluded that the presence of an adrenal rhythm is usually associated with regular vaginal smear cycles.
EFFECTS OF OVARIAN STEROIDS AND PROLACTIN ON THE SEQUENTIAL DEVELOPMENT OF NESTING BEHAVIOUR IN FEMALE BUDGERIGARS
Authors: HUTCHISON R. E. 
Published: December 2008

SUMMARY
As intact, breeding female budgerigars approach egg-laying, they spend an increasing amount of time in the nestbox and nest hollow. The brood patch area begins to defeather and becomes vascular and the oviduct increases in weight. Precursory albumen forms in the tubular glands of the oviduct.
Oestradiol (OB) treatment in combination with prolactin (OB + PL) induced ovariectomized budgerigars to display nesting behaviour which did not differ from that shown by intact females in the 3 days immediately preceding egg-laying. In contrast, OB induced only the initial phase of the nesting sequence and the effects of OB in combination with progesterone (OB + PR) were intermediate between treatments with OB alone and OB + PL. Incubation of artificial eggs occurred only in the OB + PL group and the latency to display of the incubation posture was shorter in the OB + PL group than in the OB + PR group.
No incubation posture was displayed by the OB-treated group.
Oviduct development was not influenced by prolactin, but progesterone induced precocious development of tubular glands in the magnum region of the oviduct. Treatment with OB + PR induced uniform development of precursor albumen in the tubular glands. Development of the brood patch occurred with both OB + PL and OB + PR treatment. However, OB + PR resulted in defeathering which was advanced in relation to vascularity when compared with intact breeding females, whereas defeathering and vascularity of the OB + PL group did not differ from that of intact females at egg-laying.
These results indicate that prolactin in combination with oestradiol was more effective than progesterone not only in inducing the later phases of nesting behaviour but also in initiating incubation behaviour and defeathering of the brood patch area.
EFFECTS OF TESTOSTERONE MEDIATED OR MODULATED BY PITUITARY FACTORS
Authors: DE MOOR P. , ADAM-HEYLEN M. , VAN BAELEN H. , VERHOEVEN G. 
Published: December 2008

SUMMARY
Adult rats of both sexes were either gonadectomized or hypophysectomized and gonadectomized. Three to eight weeks later they were treated for 14 consecutive days with oil or with 75 or 200 μg testosterone propionate (TP) per 100 g body weight. The animals were killed and for each sex the gonadectomized animals were compared with the hypophysectomized-gonadectomized animals as far as their NADPH- and NADH-dependent 3α-hydroxysteroid dehydrogenases (3α-HSD) in renal microsomes, transcortin levels in serum and five organ weights relative to total body weight were concerned. For two of the latter, i.e. the relative kidney and prostatic weights, no significant differences were found.
Transcortin levels, relative adrenal weights and renal NADPH-dependent 3α-HSD activities were higher in oil-treated gonadectomized animals than in oil-treated hypophysectomized-gonadectomized animals. The opposite was found for the relative weights of uterus and seminal vesicles and renal NADH-dependent 3α-HSD activities. These differences between gonadectomized and hypophysectomized-gonadectomized animals disappeared after TP treatment as far as transcortin levels were concerned but remained for the five other parameters.
After gonadectomy sexual differences subsisted for all parameters studied. But whereas intact male rats had higher NADH-dependent 3α-HSD activities than female rats the opposite was found after gonadectomy. After gonadectomy plus hypophysectomy the between sex differences disappeared as far as transcortin levels were concerned but remained in the other parameters studied.
INCREASED CONCENTRATIONS OF 17α,20α-DIHYDROXYPREGN-4-EN-3-ONE IN MATERNAL AND FOETAL PLASMA NEAR PARTURITION IN SHEEP
Authors: FLINT A. P. F. , GOODSON JANE D. , TURNBULL A. C. 
Published: December 2008

SUMMARY
Using specific radioimmunoassays, 17α,20α-dihydroxypregn-4-en-3-one and progesterone were measured in maternal utero-ovarian venous plasma from four sheep during parturition induced with dexamethasone and two sheep at spontaneous delivery. 17α,20α-Dinydroxypregn-4-en-3-one was also measured in maternal jugular venous and foetal posterior vena caval plasma from one dexamethasone-induced animal over the same period. Basal utero-ovarian venous levels of 17α,20α-dihydroxypregn-4-en-3-one were in the range 3– 7 ng/ml; at the time of the pre-labour fall in maternal progesterone, the concentration of 17α,20α-dihydroxypregn-4-en-3-one increased, reaching 17–76 ng/ml at delivery. Maternal levels fell rapidly after delivery. In contrast to foetal progesterone concentrations, which are low, foetal 17α,20α-dihydroxypregn-4-en-3-one levels were approximately the same as those in the maternal utero-ovarian vein. Maternal jugular venous levels in one animal were 50–80% of those in the utero-ovarian vein. These findings confirm earlier results obtained in vitro which indicated that exposure to glucocorticoid results in increased activity of a steroid 17α-hydroxylase in the ovine foetal placenta.
A COMPARISON OF VARIATIONS IN PLASMA LUTEINIZING HORMONE CONCENTRATIONS IN MALE AND FEMALE DOMESTIC CHICKENS (GALLUS DOMESTICUS) FROM HATCH TO SEXUAL MATURITY
Authors: SHARP P. J. 
Published: December 2008

SUMMARY
Changes in plasma LH concentrations were followed in chickens of both sexes from hatch to sexual maturity using a radioimmunoassay. Mean levels of LH were lower in the females than in the males at all stages of development. These levels rose rapidly in both sexes during the first week after hatch to maxima of 6·5 ± 1·2 (s.e.m.) ng/ml (n = 6) in the males and 4·6 ± 0·6 ng/ml (n = 6) in the females. Thereafter levels of the hormone in the circulation stabilized in the males but fell over a period of 1 or 2 weeks in the females to 2·5–3 ng/ml.
Plasma LH levels started to rise steeply in both sexes when they were between 16 and 19 weeks old at the same time as there was an increase in the rate of comb growth. Afterwards in six of the males studied in detail the mean plasma LH level rose significantly (P < 0·01) over a period of 5–8 weeks from 8·1 ± 1·2 to 13·2 ± 1·9 ng/ml. In a parallel study on six females the rate of LH secretion increased for approximately 3 weeks and then decreased for about the same period forming a prepubertal LH peak. The first eggs were laid between 22 and 25 weeks of age when mean plasma LH levels had fallen to about 1·8 ng/ml. The mean plasma LH level in these hens when they were laying (1·8 ± 0·3 ng/ml) was significantly lower (P < 0·01) than when they were sexually immature (2·7 ± 0·3 ng/ml). The duration of the period of rapid comb growth in each bird was closely related in the males to the time during which prepubertal LH levels were rising rapidly, and in the females to the duration of the prepubertal LH peak.
Differences in mean plasma LH concentrations in individual birds of either sex before the onset of puberty appeared to be related to subsequent reproductive performance.
SPECIFIC RELEASE OF BOVINE NEUROPHYSIN II DURING ARTERIAL OR VENOUS HAEMORRHAGE IN THE COW
Authors: LEGROS J. J. , REYNAERT R. , PEETERS G. 
Published: December 2008

SUMMARY
An almost specific release of neurophysin II with only minor release of neurophysin I was found during venous or arterial haemorrhage in five cows. Our data confirm the results of experiments in vitro in which vasopressin has been found to be associated with neurophysin II within neurosecretory granules.
SEXUAL BEHAVIOUR IN CASTRATED RABBITS TREATED WITH TESTOSTERONE, OESTRADIOL, DIHYDROTESTOSTERONE OR OESTRADIOL IN COMBINATION WITH DIHYDROTESTOSTERONE
Authors: ÅGMO A. , SÖDERSTEN P. 
Published: December 2008

SUMMARY
Sexual behaviour and the function of the accessory sexual glands were studied in castrated rabbits injected with testosterone benzoate (TB), oestradiol benzoate (OEB), dihydrotestosterone benzoate (DHTB) or OEB in combination with DHTB. Testosterone benzoate (1 mg daily for 90 days) stimulated the sexual behaviour more than any of the other steroids. The combination of OEB (0·33 mg) and DHTB (1 mg) was no more effective than either of these steroids given alone. The function of the accessory sexual glands was stimulated to a level comparable to that of intact animals given TB. Dihydrotestosterone benzoate was, however, not very effective in this respect. Oestradiol benzoate alone or in combination with DHTB caused hypertrophy and very low secretory activity of the seminal vesicles. These results suggest that testosterone itself is active both in the brain and in the accessory sexual glands in rabbits. This is in contrast to the rat, in which aromatization to oestradiol in the brain and reduction to DHT in the periphery seems to be important.
PROTEIN BINDING OF PLASMA CORTISOL IN THE FOETAL LAMB NEAR TERM
Authors: FAIRCLOUGH R. J. , LIGGINS G. C. 
Published: December 2008

SUMMARY
Binding of cortisol to plasma proteins was studied in the foetal lamb by equilibrium dialysis at 37 °C. At 122 days of pregnancy the mean level of transcortin expressed as cortisolbinding capacity was 28 ± 6 (s.d.) ng cortisol/ml plasma. During the last 14 days of pregnancy there was a progressive increase in transcortin-binding capacity to 85 ± 14 ng cortisol/ ml plasma. A sharp increase in the concentration of both protein-bound and unbound cortisol was observed over the same period. A rise in the concentration of total cortisol from around 3 to 42 ng/ml was associated with an increase in unbound cortisol from 0·2 to a maximum of 2·1 ng/ml. The concentration of albumin-bound cortisol was approximately equal to that of unbound cortisol. The mean value for the transcortin–cortisol affinity constant was 1·15 × 108 l/mol.
It is concluded that an increase in transcortin-binding capacity is partly responsible for the prepartum increase of corticosteroid levels observed in normal foetal lambs.
ANALYSIS OF THE ROLE OF ENDOGENOUS PROLACTIN ON FLUID AND SODIUM CHLORIDE ABSORPTION BY THE RAT JEJUNUM
Authors: MAINOYA J. R. 
Published: December 2008

SUMMARY
Intestinal absorption of fluid and NaCl in rats is significantly decreased after hypophysectomy and increased in rats with pituitary implants. Oestrogen and reserpine significantly stimulate mucosal fluid and NaCl transfer in both normal and adrenalectomized rats, comparable to the effects of administration of prolactin. In intact rats, ergocryptine enhanced intestinal absorption of fluid and NaCl; however, it failed to exert any effects in adrenalectomized rats. Adrenalectomy alone had no adverse effects on intestinal absorption in saline-compensated rats. The administration of corticosterone alone or together with prolactin significantly enhanced intestinal absorption, although the effect of corticosterone alone was more variable. These data strongly suggest that increased endogenous prolactin levels produce stimulatory effects on intestinal absorption of fluid and NaCl by the rat jejunum.