bluuebunny/crossref_metadata_2025 huggingface dataset:
INVOLVEMENT OF INHIBIN IN THE REGULATION OF FOLLICLE-STIMULATING HORMONE CONCENTRATIONS IN PREPUBERTAL AND ADULT, MALE AND FEMALE RATS
Authors: HERMANS W. P. , VAN LEEUWEN E. C. M. , DEBETS M. H. M. , DE JONG F. H.
Published: December 2008

Administration of steroid-free bovine follicular fluid (bFF), containing inhibin-like activity, depressed levels of FSH measured 4 h after injection in intact adult and 35-day-old female rats, but not in younger females. Suppression of FSH was also observed in intact male rats, aged 55 days, but not in older and younger male rats. Eight hours after injection of bFF, FSH levels were depressed in 15-day-old and older immature and adult rats of both sexes. Male and female rats, gonadectomized 2 days earlier, responded similarly to bFF treatment as did the intact animals.

In a second experiment it was found that the rise of FSH levels, occurring within 8 h of gonadectomy, decreased with age in male and increased with age in female rats. Steroid treatment was found to prevent the rise in FSH levels partially in 15-day-old male and completely in 25-day-old female rats, whereas treatment with bFF was fully effective in blocking the FSH rise in both immature and adult rats of both sexes.

It is concluded that inhibin might be a major physiological factor in a fast-acting control of FSH concentrations from at least the age of 25 days onwards in female rats. In male rats its physiological significance might be limited to the prepubertal period, despite the fact that pituitary secretion of FSH is suppressed by exogenous inhibin-like activity at all ages studied.
INCREASE IN THE RESPONSE TO ADRENOCORTICOTROPHIN OF ISOLATED MATERNAL ADRENAL CELLS FROM SHEEP IN LATE PREGNANCY
Authors: GLICKMAN J. A. , PATRICK J. E. , CHALLIS J. R. G.
Published: December 2008

Adrenal cells were prepared from non-pregnant (anoestrous) sheep, from ewes at days 50, 100 and 130 of pregnancy and at term, and from animals at 1–5 days post partum. The ability of the cells to respond to adrenocorticotrophin (ACTH1–24), α-melanocyte-stimulating hormone (α-MSH), or combinations of these peptides has been examined in vitro. There was a progressive rise in the basal output of cortisol during pregnancy and in the absence of adrenocorticotrophin the cortisol output from adrenal cells of late pregnant and post-partum sheep was significantly greater than that from the non-pregnant animals. Adrenocorticotrophin increased cortisol output by adrenal cells at all times tested. In anoestrous sheep the amount of ACTH required to produce half the maximum output of steroid (ED50) was 8 pg/ml. The ED50 increased in early pregnancy to 112 pg/ml and then fell to < 5 pg/ml between day 100 and term. At term both the stimulation ratio and the absolute increment in cortisol output elicited by a maximal concentration of ACTH were greater than at any other time tested in pregnant or non-pregnant sheep. Cortisol output during pregnancy was not increased by α-MSH, although at term the stimulatory effect of ACTH1–24 was partially antagonized by α-MSH.

These results suggest that there may be an increase in the responsiveness of the maternal adrenal during pregnancy, although the factor(s) responsible remains unknown.
BINDING OF HUMAN CHORIONIC GONADOTROPHIN TO TESTICULAR BIOPSY TISSUE FROM INFERTILE MEN AND THE EFFECT OF PRIOR TREATMENT WITH HUMAN CHORIONIC GONADOTROPHIN
Authors: SHARPE R. M. , WU F. C. W. , HARGREAVE T. B.
Published: December 2008

The binding of 125I-labelled human chorionic gonadotrophin (HCG) to testicular tissue obtained by biopsy from 27 infertile men has been investigated. Fresh tissue cut into pieces was used for these studies as homogenization and/or freezing severely reduced the ability of testicular tissue to bind HCG. In five infertile men who had a normal endocrine profile and normal testicular histology, 10·3 ± 1·4 (s.d.) pg 125I-labelled HCG were bound/mg testis, which was similar to binding (7·9 ± 3·6 pg/mg) to testicular tissue obtained from three apparently normal men who underwent orchidectomy for prostatic carcinoma. However, in five infertile men with germ cell aplasia binding was increased to 16·6 ± 5·7 pg/mg tissue. Fourteen infertile men were injected 24 h before biopsy with HCG, and this treatment consistently, and in most cases significantly, reduced the testicular binding of 125I-labelled HCG compared with that found in untreated, infertile men. It was concluded that measurement of HCG-binding in testicular biopsy specimens is feasible and may prove useful in assessing similarities between Leydig cell function in man and animals.
ABSENCE OF A DIURNAL RHYTHM IN LORDOSIS BEHAVIOUR INDUCED BY OESTROGEN IN GONADECTOMIZED RATS
Authors: ERSKINE M. S. , MARCUS J. I. , BAUM M. J.
Published: December 2008

Gonadectomized rats bearing s.c. Silastic capsules containing crystalline oestradiol-17β diluted with cholesterol, or oestradiol-17β dissolved in sesame oil were tested for the presence of a diurnal rhythm in the display of lordotic behaviour. In experiment 1, female rats received four consecutive tests at intervals of 8 h in a lighting regimen of 12 h light: 12 h darkness beginning 4, 14 and 28 days after implantation of 5 mm capsules of oestradiol. After a single test on day 4, male rats were tested on days 14–15 only, at the same times as the female rats. Female animals were tested while vaginal–cervical stimulation was prevented by vaginal masking beginning 35 days after implantation of oestradiol. In experiment 2, lordotic responsiveness of female rats was assessed beginning 4 days after implantation of oestradiol once on each of 3 consecutive days, with each test occurring at a different time of day. Finally, in experiment 3, female rats were tested as in experiment 1 beginning 4 days after implantation of lower threshold amounts of oestradiol in oil-filled capsules. In no experiment were changes in lordotic behaviour observed as a function of the time of day. These findings failed to support recent reports of a sexually dimorphic rhythm in lordotic responsiveness to oestradiol in the rat.
EFFECTS OF ADRENALECTOMY ON REPRODUCTION IN THE MOUSE
Authors: WHITE BARBARA M. , GIDLEY-BAIRD A. A. , EMMENS C. W.
Published: December 2008

Survival of mice treated with sesame seed oil after adrenalectomy was very low and suggested no beneficial effect, whereas treatment with progesterone improved the chances of survival. Treatment with desoxycorticosterone acetate (DOCA) and methyl prednisolone acetate also increased the number of animals surviving after adrenalectomy. The corticosteroids were significantly more effective in ensuring survival than was progesterone. There was no significant difference in survival between mice receiving a single injection of 10 mg DOCA and those being given an injection of 1·0 mg DOCA per day for 3 days after the operation. To ensure minimum interference of exogenous corticosteroid with the experimental investigation, animals routinely received only a single injection of 1·0 mg DOCA after the operation.

The chance of survival after adrenalectomy was higher in pregnant than in non-pregnant mice. There was a significant linear increase in survival during the first 5 days of pregnancy. Progesterone and prolactin both appeared to be involved in increasing the chance of survival in adrenalectomized pregnant mice.

Adrenalectomy had no effect on the number of mice mating and ovulating. Adrenalectomized mice were apparently having normal cycles and 4 weeks after adrenalectomy they were able to mate and ovulate. Compensatory ovulation was seen in hemi-ovariectomized mice and was not abolished by adrenalectomy. Implantation was also unaffected by the operation.
CHANGES IN THE ADENOHYPOPHYSIS AND GENITAL TRACT OF CRYPTORCHID RATS: SOME MORPHOLOGICAL AND PHARMACOLOGICAL ASPECTS
Authors: PEREIRA O. C. M. , PICARELLI ZULEIKA P. , HAYASHI H.
Published: December 2008

It has been confirmed that cryptorchidism may affect the control mechanism of gonadotrophin secretion. This has been based on morphological aspects of the adenohypophysis of cryptorchid rats which have shown an increase in basophilic and vacuolated basophilic cells, an increase known to be related to the production of gonadotrophin. The morphological alterations observed in the testes, prostates, seminal vesicles and ductus deferentes of these cryptorchid animals, the quiescence and the responses of their seminal vesicles and ductus deferentes to sympathomimetic and parasympathomimetic drugs indicated that these cryptorchid animals may be somewhere between normal and castrated rats, although not equidistant from either. Comparison of wet weights and of occurrence of spontaneous contractions, and determination of drug parameters in seminal vesicles and ductus deferentes taken from normal, castrated or cryptorchid rats, suggested that the development and the spontaneous or the pharmacological responses of male accessory organs of reproduction are independent phenomena.
DISTRIBUTION OF ADRENOCORTICOTROPHIC AND LIPOTROPHIC PEPTIDES IN THE RAT
Authors: JACKSON SUE , LOWRY P. J.
Published: December 2008

Intermediate and anterior lobes from the pituitary glands of female Wistar rats were freshly dissected and chromatographed on Sephedex G-50 and BioGel P6. Fractions were monitored with radioimmunoassays for NH2- and CO2H-terminal adrenocorticotrophin (ACTH), α-melanocyte-stimulating hormone (α-MSH), and α- and β-endorphin. A large molecular weight, glycosylated form of corticotrophin-like intermediate lobe peptide (CLIP) which we have termed big CLIP, and a β-MSH-like molecule were identified in the pars intermedia and in both lobes, a major peak of activity with the elution characteristics and cross-reactivity of γ-lipotrophic hormone (γ-LPH) was detected. In the pars distalis, the larger peptides 1–39 ACTH and β-LPH predominated, whereas in the pars intermedia, the smaller peptides α-MSH, CLIP, β- and α-endorphin were more abundant. Chromatography of rat plasma revealed peaks of immunoreactivity in the corresponding positions to those detected in the pituitary gland.
IMMUNOCHARACTERISTICS OF OESTROGEN AND ANDROGEN TARGET CELLS IN THE ANTERIOR PITUITARY GLAND OF THE CHICK EMBRYO AS DEMONSTRATED BY A COMBINED METHOD OF AUTORADIOGRAPHY AND IMMUNOHISTOCHEMISTRY
Authors: GASC J.-M. , SAR M. , STUMPF W. E.
Published: December 2008

The distribution of oestrogen and androgen target cells in the anterior pituitary gland of the chick embryo on days 10, 12 and 15 of incubation was studied 1 h after the injection of tritium-labelled steroid hormone using the thaw–mount autoradiographic technique. Oestradiol target cells were localized in the caudal zone that corresponds to the so-called 'caudal lobe', while androgen target cells were found throughout the rostral and caudal lobes of the anterior pituitary gland. With a combined autoradiography and immunohistochemistry technique, most of the oestrogen target cells showed immunoreactivity to turkey LH antiserum but not to adrenocorticotrophin (1–24) and β-thyrotrophin antisera. In contrast, androgen target cells did not show positive immunoreactivity to the three antisera used. The results suggested a direct and early involvement of oestrogens but not of androgens in the feedback regulation of pituitary gonadotrophin secretion in the chick embryo.
STIMULATION OF CORTISOL SECRETION IN VITRO FROM THE INTERRENAL TISSUE OF THE CICHLID FISH, SAROTHERODON AUREUS, BY ADRENOCORTICOTROPHIN OR CYCLIC AMP
Authors: ILAN Z. , YARON Z.
Published: December 2008

A superfusion system was developed in which secretion of cortisol from the interrenal tissue of Sarotherodon aureus could be stimulated by ACTH. Head kidneys from four fish were cut into fragments and superfused with Eagle's basal medium containing 4 mm-NaHCO3 and bovine serum albumin (50 mg/100 ml). The superfused medium was collected every 15 min before stimulation and every 5 min thereafter. Cortisol was measured in the medium by radioimmunoassay. The rate of cortisol secretion increased considerably after a 5 min pulse of 0·1 mu. porcine ACTH/ml, reaching a peak of 11·64 ± 2·40 (s.e.m.) ng/min (n = 5) after 20 min. In the subsequent 35 min the secretion rate decreased to a level of 0·49 ± 0·21 ng/min which was within the range of the baseline (0·2–0·7 ng/min). The amount of cortisol secreted by the superfused tissue in response to the corticotrophin, calculated from the area under the peak, was dose-dependent at the range of 0·06–273 mu. ACTH.

Cortisol secretion in this system could also be stimulated by a crude pituitary extract from the same fish. Using the dose–response line, the adrenocorticotrophic activity in the pituitary gland of S. aureus was estimated as 0·2 i.u./g or 1·87 mu. per gland, in porcine ACTH equivalents.

It was possible to substitute ACTH with dibutyryl cyclic AMP. The response of the interrenal tissue, i.e. the increase in secretion of cortisol, was dose-dependent at the range of 2–20 mmol/l. The response of the superfused interrenal tissue to ACTH could be extended by the addition of the synthetic phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine (0·1 mmol/l), to the medium. These results indicated that the stimulation of cortisol secretion from the interrenal tissue of this fish by ACTH is, most probably, mediated by cyclic AMP as a second messenger.
EFFECT OF INHIBITION OF CONVERTING ENZYME ON INACTIVE RENIN IN THE CIRCULATION OF SALT-REPLETE AND SALT-DEPLETE NORMAL SUBJECTS
Authors: MILLAR J. A. , HAMMAT M. T. , JOHNSTON C. I.
Published: December 2008

Angiotensin II exerts an inhibitory influence on active renin release from the kidney. To assess a possible role for angiotensin II in the release of inactive renin, levels in the circulation were measured before and at regular intervals after the administration of captopril, an orally active inhibitor of angiotensin I-converting enzyme, to 12 salt-replete and six salt-deplete normal subjects. Concurrent measurements of active renin, angiotensin I and angiotensin II were also performed. Basal inactive renin in the salt-deplete group was increased compared with the salt-replete subjects, but inactive renin remained constant in both groups after treatment with captopril. There were significant increases in concentrations of both active renin and angiotensin I after treatment with captopril in all subjects and corresponding decreases in angiotensin II. These results suggested that angiotensin II does not influence the release of inactive renin, in contrast with its role in the release of active renin.
EVIDENCE FOR A ROLE OF GLUCOCORTICOIDS IN THE DEVELOPMENT OF INSULIN RESISTANCE AFTER ISCHAEMIC LIMB INJURY IN THE RAT
Authors: BARTON R. N. , PASSINGHAM B. J.
Published: December 2008

Bilateral hind-limb ischaemia in the rat is known to cause insulin resistance, as shown by a sustained rise in plasma glucose concentration with a decreased metabolic clearance rate but no fall in plasma insulin. However, when the concomitant rise in the plasma concentration of corticosterone was diminished by an inhibitor of its biosynthesis, trilostane (WIN 24 540), the hyperglycaemia became transient. The mechanism of this effect has now been studied by measuring the rate of disappearance of [5-3H,U-14C]glucose and the concentration of insulin in plasma. Trilostane did not alter the rate of glucose production or the 3H: 14C ratio (an index of recycling through gluconeogenic precursors). It did, however, raise the metabolic clearance rate while lowering the plasma insulin concentration, i.e. peripheral sensitivity and/or responsiveness to insulin was increased. Insulin resistance was restored by giving corticosterone together with trilostane. Thus an increased concentration of corticosterone in the plasma was necessary for the full development of insulin resistance following ischaemic limb injury. It was, however, probably not the only factor since a similar dose of corticosterone did not lead to hyperglycaemia in uninjured rats.
EFFECT OF ADMINISTRATION OF DOPAMINERGIC AGONISTS ON THE UTERINE RESPONSIVENESS TO OESTROGEN IN MATURING RATS
Authors: HERNANDEZ D. E. , ALVAREZ E. O.
Published: December 2008

The purpose of the present work was to investigate whether the administration of a dopamine agonist (2-bromo-α-ergocryptine) was able to interfere with the normal change in uterine sensitivity to oestrogen that occurs around the onset of puberty in the rat.

To determine the change in uterine sensitivity groups of rats at 25, 30 or 35 days of age were killed (to find the initial uterine weight) or ovariectomized with or without oestrogen replacement therapy (0·05 μg/100 g body wt, daily for 5 days) and then killed to determine the final uterine weight. Comparisons were made between initial and final uterine weights. Five days before the animals reached 25, 30 or 35 days of age, one group was injected with 2-bromo-α-ergocryptine (0·5 mg/100 g body wt daily for 5 days) and another one with solvent (control rats). At the ages specified (25, 30 and 35 days of age) both groups were subjected to the ovariectomy schedule. Results showed that the bromocriptine treatment was effective in blocking the normal uterine change in sensitivity that occurs at 30 days of age. At 35 days of age the dopamine agonist was able to counteract the action of oestrogen in maintaining the uterine weight 5 days after ovariectomy. The results are interpreted as suggesting that the mechanism of change in uterine responsiveness to oestrogen in maturing rats is mediated by prolactin.
SEDIMENTATION PROFILES OF THE OESTROGEN RECEPTOR FROM BREAST TUMOURS OF MAN AND RAT USING VERTICAL-TUBE ROTOR CENTRIFUGATION
Authors: FREEDMAN B. , HAWKINS R. A.
Published: December 2008

In rat mammary tumours and uteri it was found that reaction time, ionic strength, reproductive state and storage in liquid nitrogen affected the form of the oestrogen receptor detected by sucrose density-gradient analysis using a vertical-tube rotor. A standard method of gradient analysis was defined. The sedimentation profile of the oestrogen receptor was compared in three types of experimental rat mammary tumour of known hormonal sensitivity. These were two lines of ovary-independent transplantable tumours and those tumours induced by dimethylbenz(a)anthracene (DMBA) which are mainly ovary-dependent. In all three types of tumour the 8S receptor was the predominant molecular form (32 out of 36 tumours induced by DMBA and 11 out of 13 transplantable tumours). Sedimentation profiles of the oestrogen receptor were also examined in 46 human breast carcinomata found to be receptor-positive by the dextran-coated charcoal technique. Of these, 17 were found to be receptor-negative by gradient analysis and 28 out of 29 receptor-positive tumours contained 8S receptor. It was concluded that (1) 8S receptor is the predominant molecular form in both human and rat mammary tumours, (2) molecular form of receptor is not related to ovarian dependence in these rat mammary tumours and (3) gradient analysis seems unlikely to provide additional discrimination in the prediction of response to endocrine therapy over that provided by simpler methods.
PROTEIN COMPOSITION OF THE THYROID COLLOID IN PATIENTS WITH HYPERTHYROIDISM
Authors: ANDERBERG B. , ENESTRÖM S. , GILLQUIST J. , SMEDS S.
Published: December 2008

Analysis of the protein composition of the thyroid colloid was performed in 28 patients operated on for hyperthyroidism. Fifteen of the patients were treated before the operation with carbimazole combined with thyroxine and 13 were treated with propranolol alone. Colloid was collected by micropuncture of single follicles in peroperative thyroid biopsies. The protein composition was analysed by microgel electrophoresis and densitometry, both in the colloid samples and in the supernatant fraction of homogenates of microbiopsies from the thyroid specimens.

The analyses showed that, during treatment with carbimazole and thyroxine, the relative amount of the larger thyroglobulin aggregates (S-TG) was decreased compared with the relative amount observed in the colloid from normal thyroid tissue. In the hyperfunctioning thyroid tissue from the propranolol-treated patients the protein composition of the colloid was similar to that observed in normal tissue and the relative amount of the S-TG fractions was significantly higher than in the carbimazole- and thyroxine-treated group.

It may be concluded that the increased release of thyroid hormones in hyperthyroidism is not combined with changes in the protein composition of the thyroid colloid. The decreased relative amount of the S-TG fractions in the thyroid colloid from patients treated with carbimazole and thyroxine was probably due to an insufficient capacity to iodinate thyroglobulin.
DELAY OF OVULATION IN RATS WITH SODIUM PENTOBARBITONE: APPARENT DIFFERENCES BETWEEN RATS WITH 4- OR 5-DAY REPRODUCTIVE CYCLES
Authors: VAN DER SCHOOT P.
Published: December 2008

In rats with 4- or 5-day reproductive cycles various responses to the blockade of ovulation with sodium pentobarbitone at pro-oestrus (or at pro-oestrus and on the next day) were compared. The blood concentrations of oestradiol decreased rapidly during the 24 h period after injection of sodium pentobarbitone at pro-oestrus in rats with 5-day cycles. In those with 4-day cycles this response took almost a day to develop. Injection of sodium pentobarbitone at pro-oestrus and on the next day interfered with ovulation of the present crop of large follicles in rats with 5-day cycles. In 4-day cyclic rats this procedure delayed ovulation of these follicles by 48 h. Receptive behaviour was absent on the day after the second injection of sodium pentobarbitone in rats with 5-day cycles; some receptivity was, however, induced by the injection of gonadotrophin. The latter injection resulted in the release of a low number of eggs; fertilization of these eggs, however, did not occur. In 4-day cyclic rats receptive behaviour was recorded on the day after the second injection of sodium pentobarbitone: fertilization of delayed ovulated eggs took place normally but pregnancy was seen only rarely.

The results indicated clear differences in responses to blockade of ovulation with sodium pentobarbitone between rats with 4- or 5-day cycles. The differences most probably result from a more advanced 'age' of preovulatory follicles at pro-oestrus of 5-day cycles compared with those of 4-day cycles. Experimental delay of ovulation reveals ageing changes and the probable onset of atresia at an earlier time after blockade in 5-day cyclic than in 4-day cyclic rats.
IS VASOPRESSIN IN THE CIRCULATION OF THE DOG FREELY FILTERABLE?
Authors: SHARE LEONARD , CROFTON JOAN T.
Published: December 2008

Studies were carried out to determine whether endogenously secreted vasopressin in the circulation of the dog is freely filterable. Blood from anaesthetized dogs was pumped through a dialysis coil and ultrafiltration was achieved by increasing the outflow pressure from the coil. In some cases, the dogs were hydrated before the experiment. A specific, precise radioimmunoassay was used to measure the concentration of vasopressin in the ultrafiltrate and the simultaneously sampled plasma. The concentration of vasopressin in the ultrafiltrate was consistently lower than that in the plasma at concentrations ranging from 1·7 to 335 μu./ml in the latter, and the extent of the binding was lower in the hydrated than in the non-hydrated dogs. At plasma levels of vasopressin of 2–20 μu./ml, vasopressin binding averaged only about 12%, whereas it averaged 40% at plasma concentrations greater than 20 μu./ml. This binding was not an artifact caused by some limitation of the ultrafiltration system because vasopressin dissolved in a salt solution and subjected to ultrafiltration in the system was freely filterable.
PROLIFERATIVE ACTIVITY AND CELL MIGRATION IN THE ADRENAL CORTEX OF FETAL AND NEONATAL RATS: AN AUTORADIOGRAPHIC STUDY
Authors: BERTHOLET J. Y.
Published: December 2008

The aim of this experiment was to examine, using autoradiographic techniques, proliferative activity in the adrenal cortex of rats on day 20 of fetal life, and to follow the fate of labelled cells 48, 168, 336 and 672 h after injection of [3H]thymidine. On day 20 of fetal life, labelled cells were more numerous in the zona glomerulosa than in the other zones. The fate of the labelled cells in each cell compartment showed centripetal migration, but their displacement from day 20 of pregnancy up to 5 days post partum, combined with a reduction in the size of the adrenal gland, suggested a real migration. The centripetal movement was found in the cortex when growth had effectively ceased.
INTERRELATIONSHIP BETWEEN THYROID AND GONADAL FUNCTION IN FEMALE JAPANESE QUAIL KEPT UNDER SHORT AND LONG PHOTOPERIODS
Authors: PÉCZELY P. , PETHES G. , RUDAS P.
Published: December 2008

The concentrations of progesterone, testosterone, oestrone, oestradiol, thyroxine (T4) and tri-iodothyronine (T3) in the plasma of 8-week-old female Japanese quail exposed to short (6 h light: 18 h darkness; 6L: 18D) and long (18L: 6D) photoperiods were determined by radioimmunoassay after ovariectomy, thyroidectomy and treatment with T4. In birds exposed to short days treatment with T4 slightly increased both the concentrations of progesterone, oestrone and oestradiol in plasma and the weight of the ovaries, while ovariectomy increased the testosterone and oestradiol concentrations in plasma. In birds exposed to a long photoperiod, treatment with T4 reduced the level of all the sex steroids measured, ovarian weight and egg production. Thyroidectomy increased the concentration of progesterone in plasma and decreased that of oestradiol. Photostimulation decreased the concentration of T4 in plasma of intact birds while it was ineffective in ovariectomized birds. Ovariectomy did not influence the concentration of T4 in the plasma of birds exposed to either long or short days but the level of T3 was slightly increased in the plasma of birds exposed to short days and markedly increased in the photostimulated group. It would seem, therefore, that whilst there is a distinct relationship between thyroid function and that of the ovary the relationship between ovarian and thyroid function is less marked.
l-THYROXINE, CORTISOL AND DIET AFFECT THE LEVEL OF AMYLASE IN THE PAROTID GLAND OF DEVELOPING RATS
Authors: KUMEGAWA MASAYOSHI , MAEDA NORIHIKO , YAJIMA TOSHIHIKO , TAKUMA TAISHIN , IKEDA EIKO , MINAMIDE CHIKAGE
Published: December 2008

The effects of cortisol (10 μg/g body weight) and l-thyroxine (T4; 0·2 μg/g body weight) on the activity of parotid gland amylase in young rats were investigated. Administration of cortisol or T4 for 5 consecutive days from day 5 after birth caused the precocious appearance of amylase, T4 having almost twice the effect of cortisol. Cortisol and T4 did not have synergistic effects. In thyroidectomized-adrenalectomized rats, T4 increased amylase activity but cortisol did not. The increase in enzyme activity after day 20 was much less in rats thyroidectomized on day 10 than in rats adrenalectomized on day 10. These results suggest that T4 has a direct effect on the early increase of amylase activity (days 15–25) and that the action of glucocorticoid requires the presence of endogenous thyroid hormones. The hormone-induced level of amylase in intact rats was less than that of normal adult rats. Forced weaning of intact rats resulted in a further increase in amylase activity, suggesting that further amylase accumulation (after day 25) may be due to dietary factors.
MECHANISM(S) BY WHICH ADRENALECTOMY AND CORTICOSTERONE INFLUENCE PROLACTIN RELEASE IN THE RAT
Authors: LEUNG F. C. , CHEN H. T. , VERKAIK S. J. , STEGER R. W. , PELUSO J. J. , CAMPBELL G. A. , MEITES J.
Published: December 2008

The possible direct effect of corticosterone on release of pituitary prolactin was examined in a system using incubation for 8 h. Corticosterone at either 0·1 or 1 μg/ml medium had no significant effect on in-vitro prolactin release but 10 or 100 μg/ml medium produced a significant inhibition of release of prolactin. Release of LH, FSH and thyroid-stimulating hormone were not altered by 0·1, 1 or 10 μg corticosterone/ml, indicating that its action at the concentration of 10 μg/ml was specific on release of prolactin. Corticosterone injected at doses of 1 or 5 mg/kg into hypophysectomized rats with two pituitary grafts underneath the kidney capsule produced a significant fall in serum levels of prolactin when compared with control hypophysectomized rats with two pituitary grafts. Examination with the electron microscope showed that about one third of the lactotrophes from adrenalectomized rats after corticosterone injection exhibited patterns which suggested a decrease in protein synthesis when compared with lactotrophes from adrenalectomized rats given only the vehicle injection. These observations indicated that inhibition of release of prolactin by corticosterone could be exerted directly on the pituitary gland, and that the rise of serum levels of prolactin after adrenalectomy might have been due to the removal of direct inhibition by corticosterone.

Male rats were adrenalectomized and 2–3 weeks later, concentrations of dopamine and noradrenaline in the medial basal hypothalamus were measured and found not to be different from values in intact rats. Dopamine metabolism also was not altered in the median eminence. The dopaminergic agonist, l-DOPA, inhibited, and the antagonists, pimozide and haloperidol, stimulated release of prolactin in both adrenalectomized and intact rats. Serotonin (5-HT) metabolism in the medial basal hypothalamus and anterior hypothalamus of adrenalectomized rats was not significantly different from values in intact rats, but a higher concentration of 5-HT was observed in the medial basal hypothalamus of adrenalectomized rats when compared with the values in intact rats. A serotonergic agonist, fluoxetine, and an antagonist, cyproheptadine, had no apparent effect on release of prolactin in intact rats, but fluoxetine produced a significant rise, and cyproheptadine, a significant lowering of serum levels of prolactin in adrenalectomized rats. These results suggest that 5-HT, but not dopamine, may be involved in the rise of prolactin after adrenalectomy.
ENHANCEMENT OF UTERINE CERVIX EXTENSIBILITY IN OESTROGEN-PRIMED MICE FOLLOWING ADMINISTRATION OF RELAXIN
Authors: FIELDS P. A. , LARKIN L. H.
Published: December 2008

The present studies indicated that the extensibility of the mouse uterine cervix was significantly increased by administration of as little as one unit of highly purified preparation of porcine relaxin. No significant change in tensile strength of the cervix was noted when doses were administered that caused increased cervical extensibility and formation of the interpubic ligament. A low coefficient of correlation was found between interpubic ligament formation and increased extensibility of the cervix in oestrogen-primed immature female mice.
RELATIVE CONTRIBUTIONS OF OESTRADIOL AND PROGESTERONE TO THE MAINTENANCE OF SEXUAL RECEPTIVITY IN MATED FEMALE HAMSTERS
Authors: LISK R. D. , REUTER L. A.
Published: December 2008

Sexual receptivity was measured as total lordosis duration (TLD) per 10 min test period with mating tests standardized across 24 h by giving the first test at the time when the lights were switched off (0 h) during a schedule of 14 h light: 10 h darkness and re-testing at intervals of 2 h. Long-term (14 days), high-level oestrogen treatment was necessary to achieve TLD scores similar to those found in female hamsters treated with oestrogen plus progesterone for 3 days. Mating of female animals treated with oestrogen only always resulted in a significant decrease in TLD scores at later tests (0 v. 2 h). If progesterone was given after the test at 0 h, a significant increase in TLD score was found at the test at 2 h and this increase was maintained across several tests. By 8 h TLD scores had decreased significantly in progesterone-treated mated female hamsters. Progesterone appeared to have, therefore, at least two roles in the regulation of sexual responsiveness in the female hamster: (a) under normal conditions of oestrogen exposure (1–3 days) progesterone was necessary for the induction of sexual receptivity and (b) progesterone was necessary for the maintenance of sexual responsiveness following short-term (10 min) mating in female hamsters treated with oestrogen only. In the oestrogen- and progesterone-treated female animal which is no longer receptive as a result of previous exposure to progesterone plus having been mated, sexual receptivity can be re-induced by treatment with a larger dose of progesterone. These findings have indicated that progesterone is the primary hormonal agent which regulates sexual receptivity in the mated female hamster. Furthermore, the eventual inhibitory effect of progesterone on sexual receptivity was not absolute even in the mated female animal but rather represents some form of habituation to that particular dosage of progesterone to which the animal had been previously exposed.
DISTRIBUTION OF ACCEPTOR SITES FOR ANDROGEN-RECEPTOR COMPLEXES BETWEEN TRANSCRIPTIONALLY ACTIVE AND INACTIVE FRACTIONS OF RAT VENTRAL PROSTATE CHROMATIN
Authors: DAVIES P. , THOMAS P. , BORTHWICK N. M. , GILES M. G.
Published: December 2008

Rat ventral prostate chromatin was separated into two main fractions by controlled digestion with micrococcal nuclease. The soluble fraction obtained after lysis of digested nuclei with EDTA (1 mmol/l), the S2 fraction, represented approximately 17% of the original nuclear DNA, and showed properties consistent with transcriptional activity, i.e. enrichment in nascent RNA, non-histone protein and endogenous RNA polymerase B activity as well as depletion in histones. The fraction sedimented after lysis of nuclei, fraction P, comprised approximately 60% of nuclear DNA, was depleted in nascent RNA, non-histone proteins and endogenous RNA polymerase B activity, but had a higher content of histones. In an attempt to relate the concentration of acceptor sites for androgen-receptor complexes with transcriptional activity, it was shown that the S2 fraction was enriched in these acceptor sites. However, if measurements were based on the intact cell the transcriptionally inactive portion contained 2·5–3 times as many 'acceptor' sites, although these sites had lower affinity for androgen-receptor complexes than had those in the transcriptionally active fraction.
EFFECTS OF ANTISERUM TO LUTEINIZING HORMONE ON THE STRUCTURE AND FUNCTION OF RAT LEYDIG CELLS
Authors: GONDOS B. , RAO A. , RAMACHANDRAN J.
Published: December 2008

The influence of LH on morphology and function of Leydig cells was investigated in adult rats by selective neutralization of endogenous hormone with specific antibodies. Administration of antiserum to LH to mature male Sprague–Dawley rats for 8 days caused a significant decrease in testis weight and levels of testosterone in serum but had no effect on the overall number of interstitial cells per testis. The ability of interstitial cells isolated from antiserum-treated animals to produce testosterone in response to exogenous LH was also significantly lower than that of cells derived from animals treated with normal rabbit serum. Although the number of interstitial cells was similar in the treated and control groups, morphological studies indicated a major decrease in the number of fully differentiated Leydig cells in the antiserum-treated animals. Furthermore, neutralization of LH with antiserum resulted in disruption of the endoplasmic reticulum and accumulation of dense bodies resembling lysosomes in the Leydig cells. These results suggested that the primary trophic action of LH is to induce and maintain the steroidogenic capacity of the Leydig cells.
INHIBITION BY NORMAL IMMUNOGLOBULINS OF THYROTROPHIN-STIMULATED PRODUCTION OF CYCLIC AMP IN SLICES OF NORMAL HUMAN THYROID
Authors: BIDEY S. P. , MARSHALL N. J. , EKINS R. P.
Published: December 2008

Slice preparations of normal human thyroid tissue have been used to investigate the effect of normal immunoglobulin G (IgG) on thyrotrophin (TSH)-induced accumulation of cyclic AMP. Incubation of slices in the presence of both TSH and normal IgG for 20 min reduced the stimulation of cyclic AMP accumulation elicited by TSH alone by approximately 30%. However, preincubation of slices with IgG for 100 min before addition of TSH virtually abolished the response to TSH. The latter effect of normal IgG was reversible, and removal of IgG before exposure to TSH allowed an unimpaired cyclic AMP response to TSH. The implications of these observations with respect to the application of this system to the functional bio-detection of thyroid-stimulating antibodies in IgG fractions from thyrotoxic sera are discussed.
PANCREATIC β-CELL FUNCTION IN THE FETAL FOAL AND MARE
Authors: FOWDEN ABIGAIL L. , BARNES R. J. , COMLINE R. S. , SILVER MARIAN
Published: December 2008

Insulin secretion and the factors influencing β-cell function were investigated in the chronically catheterized fetal foal and mare during the second half of gestation. The response of the fetal β cells to exogenous glucose was also examined. The mean concentration of insulin in the fetal foal was 7·5 ± 0·5 (s.e.m.) μu./ml (n = 20) which was significantly less than the corresponding maternal value of 49·0 ± 5·0μu./ml (n = 20, P<0·01). The insulin concentration in non-pregnant horses was 24·5 ± 1·5 μu./ml (n = 5) which was significantly less than the value in the pregnant animals (P<0·01). However, there was no significant difference in the mean glucose concentration between the groups of adult animals.

The insulin concentration was related to the endogenous glucose level in both adult and fetal horses. Wide variation in the maternal insulin concentration was observed above a glucose concentration of about 5·0 mmol/l. The mean concentration of insulin in pregnant mares decreased with increasing gestational age while the mean glucose concentration remained unaltered throughout the second half of gestation. There was no change in the basal concentrations of insulin or glucose in the fetus with gestational age although the fetal β-cell response to exogenous glucose appeared to increase with increasing fetal age after 270 days of gestation (term 330 days). There was a significant arterio-venous difference in the concentration of insulin across the gravid uterus in the mare when the arterial insulin level was greater than 30 μu./ml. Below this value, there was no consistent uptake of insulin by the uterus. The observations are discussed in relation to the regulation of insulin release in utero and the effects of pregnancy on maternal β-cell function.
EFFECTS OF NEONATAL ADRENALECTOMY AND CASTRATION ON HORMONAL CHANGES IN PUBERTAL BULLS
Authors: PETERSON A. J. , BASS J. J. , PAYNE E.
Published: December 2008

Plasma samples from intact, adrenalectomized, adrenalectomized and castrated and castrated bulls were assayed for LH, testosterone, androstenedione and oestradiol-17β from birth to 26 weeks of age. The adrenalectomized bulls, unlike the intact bulls, failed to show a rise in androstenedione at 14·5 weeks of age or a rise in testosterone at 20 weeks of age. Testosterone levels in the castrated animals remained below 0·4 ng/ml whereas androstenedione reached levels similar to those in intact bulls by 26 weeks of age. In all animals the concentration of oestradiol-17β in plasma remained below 25 pg/ml, although intact bulls had the highest levels. Levels of LH rose after castration but not after adrenalectomy. These data show that in bull calves absence of the adrenal glands during prepuberty delays the rise in pubertal testosterone by at least 10 weeks.
EFFECT OF AN INTRA-UTERINE DEVICE ON INTRACELLULAR RELATIONSHIPS OF THE UTERINE OESTROGEN RECEPTOR, PARTICULARLY DURING PREGNANCY
Authors: MYATT LESLIE , CHAUDHURI GAUTAM , ELDER M. G. , LIM LOUIS
Published: December 2008

The presence of an intra-uterine device in the rat results in a lower nuclear concentration of the oestrogen receptor in the treated horn at pro-oestrus when it is compared with the contralateral control horn. This effect was also seen after the administration of hyperphysiological doses of oestradiol and when the horn was exposed in vitro to high concentrations of oestradiol. The cyclic changes during the oestrous cycle in the activity of the oestrogen-induced enzyme peroxidase were similar in the treated and control horns. These observations have discounted the possibility that the relatively lower nuclear receptor content in the treated horn at pro-oestrus was due to a decreased exposure to oestrogen. A significantly lower nuclear content was also observed in the treated horn on days 4 and 5 of pregnancy. This was not associated with a deficiency in cytosol receptor content which increased concurrently with that of the control horn in the 6 days of pregnancy that were studied. The proportional content of the putative cytosol factor implicated in receptor translocation was similar in both horns, increasing on days 4 and 6 in concert with reported changes in 'induced protein' synthesis. There appeared to be reduced levels of nuclear receptor at a time when blastocyst implantation normally occurs.
ALTERATIONS IN PROGESTERONE RECEPTORS IN THE RAT UTERUS BEARING AN INTRA-UTERINE DEVICE DURING THE OESTROUS CYCLE AND EARLY PREGNANCY
Authors: MYATT LESLIE , ELDER M. G. , LIM LOUIS
Published: December 2008

The binding characteristics, content and intracellular distribution of cytosolic and nuclear progesterone receptors have been investigated, using [3H]progesterone as ligand, in the rat uterus bearing a unilateral intra-uterine device (IUD) during the oestrous cycle and from days 3 to 6 of pregnancy. The dissociation constants of nuclear and cytosolic progesterone–receptor complexes for IUD-containing and control uterine horns were similar. Cytosolic receptor concentrations in the IUD-containing uterus were always lower but changed in a manner similar to the control during the periods studied. Nuclear receptor concentrations in the control horn reflected changes in hormone levels during the oestrous cycle although concentrations measured were greater than previously reported. However, in IUD-containing uteri the pattern was completely reversed with minimal levels at pro-oestrus. Nuclear receptor concentrations were little different in both horns during early pregnancy. Total progesterone receptor synthesis determined between metoestrus and pro-oestrus in IUD-containing horns was significantly less than that of control horns. This correlated with the attenuated rise of nuclear oestrogen receptor levels previously observed between these times in IUD-containing uterine horns.
INITIATION OF FOLLICULAR MATURATION AND OVULATION AFTER REMOVAL OF THE LITTER FROM THE LACTATING RAT
Authors: TAYA KAZUYOSHI , SASAMOTO SHUJI
Published: December 2008

In order to elucidate the mechanism of the resumption of follicular activity and ovulation in rats, levels of FSH, LH and prolactin in plasma and pituitary gland and ovarian follicular development were quantified after removal of the litter on day 3 of lactation (day of parturition = day 0 of lactation). Such removal resulted in ovulation of 13 oocytes 4 days later, a number comparable with that found in normal cyclic rats. Plasma levels of prolactin were high during lactation but markedly decreased after removal of the litter. Although plasma concentrations of FSH and LH did not change during days 3–7 of lactation, there was an FSH surge between 24 and 30 h after removal of the litter. Plasma concentrations of LH also increased slightly but significantly by 24 h after removal of the litter and this value persisted during the following 2 days. Surges of FSH, LH and prolactin occurred at 17.00 h 3 days after pups were removed. Removal of the litter did not increase pituitary contents of FSH, LH and prolactin and a marked reduction in pituitary levels of FSH and LH, but not of prolactin, occurred at 17 00 h 3 days after removal of the litter.

A quantitative study of follicular development indicated that follicles larger than 401 μm in diameter were absent during days 3–7 of lactation. However, the number and size of antral follicles increased by 30 h after removal of the litter, probably due to the increases in plasma levels of FSH and LH, and follicles larger than 601 μm in diameter appeared 3 days after the young were removed. Although ovulation could not be induced by human chorionic gonadotrophin from days 3 to 5 of lactation, its administration 30 h after removal of the litter produced ovulation in all rats by the following morning.

These results indicated that a moderate increase in FSH, although below the amounts released at the preovulatory surge, together with basal levels of LH which were within the range observed on the day of dioestrus during the normal cycle were responsible for the initiation of follicular maturation after removal of the litter.
EFFECT OF THE SUCKLING STIMULUS ON SECRETION OF PROLACTIN AND LUTEINIZING HORMONE IN CONSCIOUS AND ANAESTHETIZED RATS
Authors: ISHERWOOD K. M. , CROSS B. A.
Published: December 2008

Luteinizing hormone and prolactin were measured in plasma samples taken from conscious and anaesthetized, lactating, suckled rats after overnight separation from their litters except for one pup. In the conscious rats, there was a marked fall in plasma LH concentration (P < 0·05), and a large increase in that of prolactin (P < 0·01) within 30 min of returning the pups to the mothers. When the mothers were anaesthetized with urethane and then suckled by their litters, there was no significant change in plasma LH values, but prolactin values rose significantly (P < 0·05) after 2·5 h of suckling. However, suckling caused no significant change in plasma concentrations of LH or prolactin when the milk-ejection frequency was doubled (P < 0·001) by administering xylazine to urethane-anaesthetized mothers. It was concluded that the conscious lactating rat, separated from her litter overnight, is a very sensitive model for studying the neural events controlling LH and prolactin secretion during suckling. Anaesthesia by urethane blocks this sensitized response, but the blockade is not associated with interference in the milk-ejection reflex.
EFFECT OF PROGESTERONE ON THE SECRETION AND PERIPHERAL ACTION OF INSULIN AND GLUCAGON IN THE INTACT RAT
Authors: ASHBY J. P. , SHIRLING D. , BAIRD J. D.
Published: December 2008

The plasma insulin response to glucose and arginine was increased in intact female rats implanted with progesterone. This change was not mediated by increased energy intake since the insulin response to glucose was similarly enhanced in progesterone-treated rats pair-fed with controls. In contrast, similar levels of pancreatic glucagon were observed in the plasma of both control and experimental rats during arginine stimulation. Thus the molar ratio of insulin to glucagon may be increased in the plasma of progesterone-treated rats following a mixed meal. This change may represent a physiological adaption to a demonstrable resistance to the peripheral actions of insulin in non-adipose soft tissue. The hyperglycaemic and lipolytic actions of exogenous glucagon were also impaired in progesterone-treated rats. It is suggested that an increase in the molar ratio of insulin to glucagon will favour hepatic lipogenesis and the peripheral deposition of fat.