bluuebunny/crossref_metadata_2025 huggingface dataset:
PITUITARY REGULATION OF LEYDIG CELL FUNCTION IN THE ADULT MALE RAT
Authors: HAUGER R. L. , CHEN Y.-D. I. , KELCH R. P. , PAYNE A. H.
Published: December 2008

The effects of hypophysectomy on serum testosterone, 125I-labelled hCG binding to testicular membranes and on testicular responsiveness were studied in adult rats. Serum testosterone decreased rapidly over the first 6 h after hypophysectomy. LH receptors were determined (pmol/testis) by measuring the specific binding of 125I-labelled hCG in membrane preparations of testes of rats hypophysectomized 1, 2, 3, 6, 9, or 15 days earlier. Hypophysectomy did not result in a decrease in 125I-labelled hCG binding on day 1 but this had decreased to 40% of that in intact controls by day 2. A gradual decline was found between days 2 and 6 at which time hCG binding had decreased to 15%. No further decrease occurred between days 6 and 15. Scatchard analysis indicated that the decline in hCG binding was due to a decrease in binding capacity and not to a decrease in binding affinity. FSH, testosterone, dihydrotestosterone, and oestradiol were unable to prevent the decline in hCG binding. Although serum testosterone, testicular testosterone content, and 125I-labelled hCG binding decreased rapidly after hypophysectomy, testicular responsiveness to LH was biphasic. The intraperitoneal administration of 25 μg LH 2 h before decapitation increased testosterone in the circulation to a greater extent in animals hypophysectomized for 1 day than in intact controls while hCG binding affinities and capacities had not changed. Two or three days after hypophysectomy testicular responsiveness to LH was similar to that of intact controls even though hCG binding in hypophysectomized animals had decreased to 40 and 28% of intact controls respectively.

It is concluded that (1) the testis is dependent on anterior pituitary hormones for maintenance of testicular LH receptors and testosterone secretion, (2) FSH, testosterone, dihydrotestosterone, or oestradiol cannot prevent the decline in testicular LH receptors resulting from hypophysectomy, and (3) steroidogenic capacity of the testis persists significantly longer than the hCG binding capacity of the testis.
OVARIAN AND ADRENAL STEROIDS DURING PREGNANCY AND THE OESTROUS CYCLE IN THE RAT
Authors: OGLE T. F. , KITAY J. I.
Published: December 2008

Changes in adrenocortical function of the rat during the 4-day oestrous cycle and pregnancy were studied in vivo and in vitro. Regulation of adrenal production of progesterone and corticosterone was of particular interest. Morning (09.00 h) plasma concentrations of corticosterone were similar at each phase of the cycle, but a higher concentration was found in the afternoon (15.00 h pro-oestrus). However, the rate of progesterone utilization for corticosterone production by adrenal homogenates was essentially unchanged at all periods of the cycle. Therefore, the activities of the 21- and 11β-hydroxylating systems appeared not to be important determinants of plasma corticosterone levels (coefficient of determination (r2) = 0·06). These results indicate that adrenal secretion of progesterone is not specifically regulated during the cycle. On the other hand, resting plasma levels of corticosterone declined by 80–85% from the value on the morning of pro-oestrus between days 5 and 12 of pregnancy and then increased on day 22 and after parturition. These fluctuations did not result from alterations in the rate of metabolic clearance but rather, were closely coupled to the capacity of adrenal tissue to convert progesterone to corticosterone (r2 = 0·87). These findings suggest that progesterone utilization may be specifically curtailed at the expense of corticosterone production at days 5 and 12 of pregnancy. Concurrent measurements of adrenal venous progesterone and ovarian venous progesterone (under stressful conditions) showed that the adrenal gland secretes 2–10 times more progesterone than the ovary at all stages of the oestrous cycle, on day 22 of pregnancy, and on the first day of lactation. Thus, the adrenal gland is capable of secreting large amounts of progesterone which, if present at the appropriate time, may inhibit, delay or facilitate ovulation and onset of mating behaviour as described by other workers. Under such circumstances, however, progesterone secretion appears not to be specifically regulated but seems instead to be due to precursor spillover, since the proportionate secretion of corticosterone does not change.
PLASMA TESTOSTERONE LEVELS IN DONKEYS IN THE TROPICS
Authors: GOMBE S. , KATONGOLE C. B.
Published: December 2008

Department of Animal Physiology, University of Nairobi, Chiromo, Nairobi, Kenya

(Received 1 February 1977)

The concentration of testosterone in the plasma of most male domestic and laboratory animals, for example bulls (Thibier, 1975), boars (Andresen, 1976) and rats (Mock, Kamel, Wright & Frankel, 1975) is usually in excess of 10 nmol/l. In seasonal breeders such as sheep, values as high as 90 nmol/l have been reported in the summer before the breeding season (Falvo, Buhl, Reimers, Foxcroft, Dunn & Dziuk, 1975). In contrast, Katongole (1971) found that in a temperate summer, plasma testosterone concentrations in Equidae, including the donkey, were 4·5 nmol/l or less. It was, therefore, of interest to investigate whether the basal plasma testosterone concentrations in donkeys would be higher and more stable in the tropics.

Six potent adult male donkeys were kept in a large pen, fed rhode grass and given free access to salt and water. Blood
PITUITARY RESPONSE TO METOCLOPRAMIDE IN THE RAT
Authors: FANG V. S. , ZIMO D. A. , BYYNY R.
Published: December 2008

Department of Medicine, The University of Chicago, Chicago, Illinois 60637, U.S.A.

(Received 14 February 1977)

Metoclopramide is a potent stimulator of prolactin release in man (Delitala, Masala, Alagna & Devilla, 1975; Judd, Lazarus & Smythe, 1976; McCallum, Sowers, Hershman & Sturdevant, 1976); its possible effect on other anterior pituitary hormones is not known. We have carried out two experiments with male Sprague-Dawley rats, 130–150 g in weight; the results presented here demonstrate that metoclopramide specifically stimulates the release of prolactin.

Groups of five rats were injected s.c. with 0·9% saline (5 ml/kg body wt) containing 0-10 mg metoclopramide/kg (supplied by A. H. Robins Co., Richmond, Virginia). Thirteen minutes later the rats were immobilized with ketamine (supplied by Bristol Laboratories, Syracuse, New York), 100 mg/kg, i.p.; ketamine does not affect the level of prolactin in the plasma of rats (Lawson & Gala, 1974). Blood was drawn by heart puncture within 2
ACTIONS OF GROWTH HORMONE, PROLACTIN AND THYROXINE ON SERUM SOMATOMEDIN-LIKE ACTIVITY AND GROWTH IN HYPOPITUITARY DWARF MICE
Authors: HOLDER A. T. , WALLIS M.
Published: December 2008

Hypopituitary dwarf mice (Snell's strain) were found to have much reduced levels of serum somatomedin when compared with normal mice (apparently normal members of the Snell strain). Treatment with bovine growth hormone, prolactin or thyroxine induced growth in these animals; this was accompanied in each case by increased levels of serum somatomedin (primarily somatomedin C). Growth hormone had a dose-dependent growth-promoting effect, but this was not reflected in dose-dependent increases in serum somatomedin levels. These results are in accordance with the concept that somatomedin is involved in the regulation of overall somatic growth, but it seems likely that other factors are also involved.
NEONATAL ISLET CELL TRANSPLANTATION IN THE DIABETIC RAT: EFFECT ON HEPATIC ENZYME ACTIVITY AND GLUCOSE HOMEOSTASIS
Authors: MANGNALL YVONNE , SMYTHE ANNE , SLATER D. N. , MILNER GILLIAN R. , MILNER R. D. G. , TAYLOR C. B. , FOX M.
Published: December 2008

Intraperitoneal transplantation of collagenase-digested, isogeneic, neonatal rat pancreatic tissue successfully reversed streptozotocin-induced diabetes in 77% of recipients. The low serum immunoreactive insulin, hyperglycaemia, glycosuria and weight loss, characteristic of the diabetic animal, were corrected and the reduced activities of hepatic glucokinase and pyruvate kinase, and the low glycogen concentration of the liver of diabetic rats were restored to normal. Forty-three per cent of the successfully transplanted rats became normoglycaemic within 1 month of transplantation whereas 57% took from 1 to 6 months to achieve normoglycaemia and displayed a mild glucose intolerance when subjected to a glucose load. The rats which had not become normoglycaemic 6 months after transplantation showed some amelioration of the diabetic state, as shown by increased serum immunoreactive insulin and hepatic glycogen concentration and a slow weight gain compared with diabetic controls.
RELEASE OF IMMUNOREACTIVE AND RADIOACTIVELY PRELABELLED ENDOGENOUS (PRO-)INSULIN FROM ISOLATED ISLETS OF RAT PANCREAS IN THE PRESENCE OF EXOGENOUS INSULIN
Authors: SCHATZ H. , PFEIFFER E. F.
Published: December 2008

To study the influence of insulin on its own secretion, collagenase-isolated islets of rat pancreas were prelabelled with [3H]leucine for 2 h. After washing the islets, (pro-)insulin release was stimulated by glucose in the presence or absence of exogenous insulin (up to 2·5 mu./ml).

Hormone release was unchanged by the presence of exogenous insulin as judged by determination of both immunoreactive insulin and radioactivity incorporated into the proinsulin and insulin fractions of the medium. No direct feedback mechanism for insulin secretion was apparent from this study.
REGULATION OF INSULIN AND GLUCAGON SECRETION FROM A HUMAN ISLET CELL ADENOMA
Authors: BONE A. J. , GUMPERT R. W. , HOWELL S. L. , SHELDON J. , TELLEZ-YUDILEVICH M. , TYHURST M. , WHITTAKER P. G. , ZAHEER F.
Published: December 2008

The regulation of insulin biosynthesis, and insulin and glucagon secretion have been investigated in a human islet cell adenoma, by incubation of tumour fragments.

Both biosynthesis and secretion of insulin were strongly stimulated by incubation of islet tumour cells in the presence of increasing glucose concentrations in the range 2–8 mmol/l. However, 20 mm-glucose or 20 mm-glucose plus isobutyl methylxanthine (IBMX), both of which provide potent secretagogues for normal B cells, failed to stimulate proinsulin biosynthesis and secretion from the tumour cells. Overall rates of secretion, expressed as a proportion of total insulin content, were up to 20-fold higher than those expected for normal pancreatic tissue.

Glucagon secretion from the tumour was stimulated by low glucose concentrations; normal A cells also respond in this way under these conditions. However, no stimulation of glucagon secretion occurred in the presence of IBMX. There was therefore a major alteration in the regulation both of insulin and glucagon secretion, in that release of neither hormone was stimulated by cyclic AMP.

Ultrastructural examination showed the tumour to be rather heterogeneous. A and B cells with normal storage granule content and structure were seen, as well as a rather larger number of B cells containing some granules of atypical appearance. The insulin content of the tumour (13 i.u./g wet wt) was consistent with 6–8% of the tumour cells being B cells.
INFLUENCE OF RESTRAINT ON PLASMA PROLACTIN AND CORTICOSTERONE IN FEMALE RATS
Authors: SMITH S. W. , GALA R. R.
Published: December 2008

The effect of restraint on plasma prolactin and corticosterone concentrations was investigated in chronically catheterized, ovariectomized (OVX) or ovariectomized, oestrogen-treated (OVX-PEP) rats. Restraint was induced by tying the hind legs together. In OVX rats, prolactin levels were unchanged following restraint, either during the morning (10.00 h) or afternoon (14.00 h). Prolactin levels increased in OVX-PEP animals when restraint was initiated in the morning; when restraint was initiated in the afternoon the prolactin response depended upon the level of prolactin before restraint. If levels were low (pre-surge) the response to restraint was similar to that observed in the morning; if prolactin levels were high (surge) the response to restraint was reversed and the prolactin level declined. The morning prolactin response to restraint was significantly inhibited and the afternoon surge was retarded in adrenalectomized OVX-PEP (OVX-PEP-ADX) rats; however, in OVX-PEP animals maintained on 0·9% NaCl drinking solution, the morning prolactin response to restraint was also blunted, although the afternoon surge was normal. In OVX-PEP-ADX animals injected with either vehicle alone, or 2 or 4 mg corticosterone for 4 days, and sampled on the morning of day 5, the prolactin response to restraint was absent. Furthermore, when OVX-PEP animals were injected daily with either vehicle or 4 mg corticosterone/day, they showed no increase in prolactin in response to restraint when values were compared with those of uninjected animals. Corticosterone levels after restraint were higher than initial values in all of the above experimental conditions.
EVIDENCE FOR AN INFLUENCE OF MAMMARY TUMOUR VIRUS ON PROLACTIN SECRETION IN THE MOUSE
Authors: SINHA Y. N. , SALOCKS C. B. , VANDERLAAN W. P. , VLAHAKIS G.
Published: December 2008

The mouse mammary tumour virus (MTV) is usually transmitted through milk. Foster-nursing the young of the C3H/He strain, which carries MTV in its milk, on C57BL/He dams (an MTV-negative strain) prevents infection with the milk-borne MTV and significantly alters the natural incidence of mammary tumours in the former, and vice versa. The influence of foster-nursing on prolactin secretion in C3H and C57BL mice has been examined, using two sub-strains of these mice, one maintained by Heston and the other by Strong. Prolactin levels were compared after inducing acute prolactin release with perphenazine. The MTV-positive C3H mice of both sub-strains, had prolactin levels substantially lower than those in the MTV-negative C57BL sub-strains, basally and after perphenazine administration. Foster-nursing the young of the C3H strain with dams of the C57BL strain and vice versa significantly altered this characteristic pattern of prolactin secretion. A brief pre-exposure of C3H young to the milk of their own mothers virtually abolished the effect of foster-nursing. The results showed a marked influence of the strain of the nursing mother on the adult pattern of prolactin secretion, and suggested that the milk-borne MTV may have a role in the regulation of prolactin secretion in some strains of mice. The foster-nursing-induced differences in serum prolactin patterns elicited by perphenazine were unrelated to the amount of prolactin depleted from the pituitary gland and this suggests that the metabolism of the hormone may differ in mouse strains positive and negative for certain types of MTV.
MEASUREMENT OF FREE AND OCCUPIED CYTOPLASMIC AND NUCLEAR ANDROGEN RECEPTOR SITES IN RAT VENTRAL PROSTATE GLAND
Authors: DAVIES PETER , THOMAS PHILIP , GRIFFITHS KEITH
Published: December 2008

A method has been developed which allows the estimation of occupied and unoccupied androgen receptor sites in both cytoplasmic and nuclear fractions of rat ventral prostate. The procedure involves precipitation of receptor proteins and incubation of precipitates with labelled 5α-dihydrotestosterone. Uptake of 3H-labelled steroid at 0–4 °C gives an indication of free receptor, whereas binding at a raised temperature (15 °C) allows estimation of occupied receptor. Non-specific binding was measured in the presence of a 100-fold excess of unlabelled 5α-dihydrotestosterone. The exchange method was specific for androgens, and specific binding was detected only in fractions of androgen-dependent tissues. The method can be applied to cytosol, whole nuclei, chromatin and salt-extractable and salt-resistant protein preparations from nuclear fractions, and gives a reliable estimate of total receptor sites when occupied as compared with control measurements of unoccupied sites.
METABOLISM OF [14C]TESTOSTERONE BY HUMAN FOETAL AND ADULT BRAIN TISSUE
Authors: JENKINS J. S. , HALL C. J.
Published: December 2008

The metabolism of [14C]testosterone in vitro by various areas of the human foetal brain has been studied and compared with that of adult brain. The predominant metabolites were 5α-dihydrotestosterone and 5α-androstane-3α,17β-diol, and also androstenedione, and all areas of the foetal brain showed similar activity. In the foetal pituitary gland, the activity of 5α-reductase was less prominent than that of 17β-hydroxysteroid-dehydrogenase. Small quantities of oestradiol-17β were produced from testosterone by the hypothalamus, temporal lobe and amygdala only, and no aromatization could be detected in the pituitary gland. 5α-Reductase activity was much lower in adult brain tissues and no oestradiol was identified in adult temporal lobe tissue.
RELEASE OF NEUROPHYSINS I AND II DURING AND AFTER PARTURITION IN COWS
Authors: LEGROS J. J. , PEETERS G. , MARCUS S. , DE GROOT W. , REYNAERT R.
Published: December 2008

Bovine neurophysin I and neurophysin II (bNpI and bNpII) have been assayed by radioimmunoassay in the jugular venous blood of cows during parturition.

In general, low bNpI levels were detected on the day before labour began and during the first stage of labour. Neurophysin I was present in appreciable quantities in blood taken during the second stage of labour and in most cows the concentrations rose to a maximum during the expulsive stage. After delivery, the concentration of bNpI in the blood diminished. This pattern of release is similar to that reported for oxytocin at parturition in cows.

As with bNpI, maximum levels of bNpII occurred during the expulsive stage of labour in some animals. In others, bNpII concentrations were very low or absent. Low concentrations of bNpII were found at the other stages of labour. Examination of the results from individual animals indicated that the release of the two neurophysins can be independent.
THE DELAYED ANOVULATION SYNDROME: INFLUENCE OF HORMONES AND CORRELATION WITH BEHAVIOUR
Authors: HENDRICKS S. E. , McARTHUR D. A. , PICKETT S.
Published: December 2008

Experiments were conducted to assess the influence of the ovary and various steroid treatments on the development of the delayed anovulatory syndrome (DAS) in female rats. The influence of neonatally administered androgen on the development of ovarian function and female sexual behaviour was studied. It was found that neither the presence of the ovary nor the administration of oestrogen or androgen affected the time-course of the DAS. Doses of androgen which produced the DAS had little effect on female sexual behaviour and there was no evidence of time-dependent changes in sexual behaviour comparable to the time-dependent changes of ovarian physiology observed during the DAS.
TESTICULAR RECEPTORS FOR LUTEINIZING HORMONE AFTER IMMUNONEUTRALIZATION OF GONADOTROPHIN RELEASING HORMONE IN THE MALE RAT
Authors: HAUGER R. L. , KELCH R. P. , CHEN YII-DER IDA , PAYNE ANITA H.
Published: December 2008

The effects of immunoneutralization of endogenous gonadotrophin releasing hormone (GnRH) on the serum concentrations of testosterone and gonadotrophins and the binding of 125I-labelled human chorionic gonadotrophin (HCG) to testicular membrane fractions were studied in adult male rats. Four days after the administration of 1 ml anti-GnRH serum, the level of testosterone in the serum decreased to 44% of the concentration before the injection, whereas administration of normal rabbit serum had no effect. Multiple injections of anti-GnRH serum for 4 days dramatically suppressed the secretion of gonadotrophins in rats orchidectomized 2 months earlier. In intact male rats treated identically, immunoneutralization of GnRH decreased the level of serum testosterone to 32% of the concentration present in saline-treated controls, but did not decrease the number of testicular binding sites for HCG (LH). Administration of testosterone or oestradiol for 3 or 6 days caused a marked reduction in the concentration of serum gonadotrophins but did not decrease the number of LH receptors. This study provides further support for the concept that one releasing hormone governs secretion of both FSH and LH. In addition, these studies indicate that selective reduction of gonadotrophins for 3–6 days has no effect on the number of testicular LH receptors. This suggests that pituitary hormones other than gonadotrophins may be important in the maintenance of testicular receptors for LH.
CHANGES IN STEROID CONCENTRATION IN THE OVARIES OF IMMATURE RATS TREATED WITH PREGNANT MARE SERUM GONADOTROPHIN AND HUMAN CHORIONIC GONADOTROPHIN
Authors: BAUMINGER S. , ECKSTEIN B. , LINDNER H. R.
Published: December 2008

The concentrations of testosterone, progesterone and 20α-hydroxypregn-4-en-3-one (20α-OHP) were measured in the ovaries of immature rats in which ovulation was induced by treatment with pregnant mare serum gonadotrophin (PMSG) and, 48 h later, with human chorionic gonadotrophin (HCG). The concentration of testosterone in the tissue increased significantly 48 h after treatment with PMSG, reached a peak 4 h after the administration of HCG and declined to the basal level 4 h later. Increases in the levels of progesterone and 20α-OHP were observed 4 h after the administration of HCG. Whereas the level of 20α-OHP continued to rise during the subsequent 30 h, progesterone levels declined near the presumed time of ovulation (12 h after administration of HCG). It is concluded that 20α-hydroxysteroid dehydrogenase activity is present in the immature rat ovary before ovulation and that an increase in the production of testosterone in the ovaries of rats treated with PMSG and HCG precedes increased production of progesterone and 20α-OHP in these ovaries.
ANDROGEN PRODUCTION AND SKIN METABOLISM IN HIRSUTISM
Authors: KUTTENN FRÉDÉRIQUE , MOWSZOWICZ IRÉNE , SCHAISON GILBERT , MAUVAIS-JARVIS PIERRE
Published: December 2008

The concentrations of testosterone, androstenedione and dihydrotestosterone (DHT) in the plasma and 5α-androstane-3α,17β-diol (androstanediol) in the urine were measured in 40 women with hirsutism of ovarian, adrenal and idiopathic origin. Conversion of [3H]testosterone to DHT, 3α- and 3β-androstanediols was also studied in homogenates of pubic skin obtained from 15 of the patients. Results were compared with values obtained from normal men and women.

Values for the levels of testosterone, DHT and androstenedione in the plasma and androstanediol in the urine of hirsute women were all above control levels, especially for plasma androstenedione and urinary androstanediol (P < 0·001). This finding was particularly marked in patients with hirsutism of ovarian origin. Conversion of [3H]testosterone to 5α-reduced metabolites by homogenates of skin obtained from hirsute women was significantly greater than by homogenates of skin from normal women (P < 0·001) but was the same as the value for normal men. The highest values for conversion were obtained from the patients with idiopathic hirsutism.

These results indicate that androstenedione is the principal androgen secreted in hirsutism. In sexual skin this steroid may be converted to DHT and 3α-, and 3β-androstanediols and the increased activity of testosterone 5α-reductase may result in an exaggerated 'utilization' of androstenedione in this tissue. The high rate of excretion of androstanediol in the urine of patients with idiopathic hirsutism may be explained by the fact that this steroid is an end-product of testosterone metabolism.
SERUM 5α-ANDROSTANE-3α,17β-DIOL, ANDROSTERONE AND TESTOSTERONE CONCENTRATIONS IN THE IMMATURE MALE RAT: INFLUENCE OF TIME OF DAY
Authors: MOGER W. H. , MURPHY P. R.
Published: December 2008

Department of Physiology and Biophysics, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada, B3H 4H7

(Received 22 April 1977)

The concentration of testosterone in the serum of the adult rat varies significantly over a 24 h period (Kinson & Lui, 1973; Howland, 1975; Wilson, McMillan, Seal & Ahmed, 1976). However, studies on circadian variations in serum testosterone concentrations in immature male rats have yielded conflicting results. Grotjan & Johnson (1976) reported significant changes with time in 25–26-day-old Holtzman rats, whereas Döhler & Wuttke (1976) did not observe significant changes in 13–18 or 25–30-day-old Sprague–Dawley rats maintained on the same lighting schedule (14 h light: 10 h darkness).

Recently we reported that from 20–35 days of age, 5α-androstane-3α,17β-diol (androstanediol) is the predominant androgen in the circulation of male rats (Moger, 1977). This study was undertaken to determine temporal variations in the concentrations of androstanediol, androsterone and testosterone.

Forty-nine male Sprague
SEPARATION OF A LABELLED FRAGMENT FROM PROTEIN SYNTHESIZED IN VITRO BY THE PARS INTERMEDIA OF THE MOUSE PITUITARY GLAND
Authors: ISHERWOOD H. M. , THORNTON V. F.
Published: December 2008

Department of Anatomy, King's College, London, WC2R 2LS

(Received 12 May 1977)

The biosynthetic activity of the pars intermedia of the mouse pituitary gland was investigated by studying the fate of labelled amino acids incorporated into relatively large-molecular-weight products (Thornton & Isherwood, 1975). It was reported that label was actively incorporated in vitro into a protein (referred to as 'labelled P1') with a molecular weight of about 75 000 (Isherwood & Thornton, 1977). However, more recent observations suggest that 'labelled P1' is a complex between a protein and a labelled peptide. The purpose of this communication is to give a brief account of some of the findings which led to this conclusion.

Full details of the incubation and cellulose acetate electrophoresis procedures are given in Isherwood & Thornton (1977). Posterior pituitary glands from male, Schofield mice were incubated in media containing [3H]leucine and [3H]phenylalanine (50 μCi/ml). In one experiment, posterior
GONADOTROPHINS, TESTOSTERONE AND SPERMATOGENESIS IN NEONATALLY IRRADIATED MALE RATS: EVIDENCE FOR A ROLE OF THE SERTOLI CELL IN FOLLICLE-STIMULATING HORMONE FEEDBACK
Authors: DE JONG F. H. , SHARPE R. M.
Published: December 2008

Peripheral concentrations of FSH in the male rat seem to be regulated in part by a protein hormone, inhibin, which originates from the testes. In an attempt to ascertain which type of testicular cell secretes inhibin, groups of male rats were irradiated prenatally or on days 4, 6 or 8 of postnatal life, and killed at 21, 51 or 81 days of age together with castrated and intact controls. The concentrations of FSH and LH in the pituitary gland, and FSH, LH and testosterone in the plasma were estimated for each animal, and the numbers of each class of intratubular cell in the testes were calculated.

Rats irradiated neonatally had fewer Sertoli cells than controls at all ages studied, while the numbers of Sertoli cells in rats irradiated prenatally were higher than those in controls on day 21. The number of spermatogenic cells was usually decreased in rats irradiated postnatally. In the rats irradiated prenatally normal numbers of spermatogenic cells were found at day 51. Numbers of spermatogenic cells were significantly correlated with the number of Sertoli cells at the ages of 51 and 81 days.

The concentration of FSH in the plasma usually increased in the postnatally irradiated animals on days 21 and 51, but not on day 81; prenatal irradiation did not result in altered levels of FSH at any age. Peripheral levels of LH and testosterone were not affected by irradiation.

The concentration of FSH in the plasma was negatively correlated with the number of Sertoli cells in all age groups, whereas significant correlations between the level of FSH and the number of spermatogenic cells were only found at days 51 and 81. It is concluded from these data that the Sertoli cell is the most likely source of inhibin.
AUTORADIOGRAPHIC LOCALIZATION OF THE BINDING OF 125I-LABELLED PROLACTIN TO RAT TISSUES IN VITRO
Authors: COSTLOW M. E. , McGUIRE W. L.
Published: December 2008

The binding of 125I-labelled prolactin to normal rat tissues was examined with autoradiographic techniques. Tissue slices were incubated with 125I-labelled ovine prolactin in the presence or absence of excess unlabelled hormone to distinguish between the specific and the non-specific localization of grains. Specific binding was found in the liver, adrenal gland and kidney from female rats, and in the mammary gland, ovary, testis and prostate gland. Conversely, fat, muscle, heart, lung, and spleen from female rats and uterine tissue did not bind 125I-labelled prolactin appreciably, or show competition for binding in the presence of unlabelled hormone. In the testis, prolactin bound exclusively to Leydig cells; in the prostate gland, binding was localized in the secretory epithelium. Kidney tubules in the cortex displayed specific prolactin localization whereas the medulla did not bind prolactin. Adrenal medulla showed no hormone binding; however, the zona reticularis and to a lesser extent the zona fasciculata bound prolactin. In the ovary, grains were limited to the theca and to a lesser extent the corpus luteum and follicles. In all cases, binding was essentially abolished when unlabelled prolactin was included in the incubation medium.

These results confirm reports of the presence of prolactin receptors in these tissues and serve to identify the cells within a particular organ that respond to prolactin.
EFFECT OF HYPOPHYSECTOMY ON BINDING OF HUMAN CHORIONIC GONADOTROPHIN TO IMMATURE AND ADULT RAT OVARIES
Authors: SIEBERS J. W. , ENGEL W.
Published: December 2008

The binding of 125I-labelled human chorionic gonadotrophin (HCG) to ovarian tissue was studied in hypophysectomized immature and adult rats. The ability of the ovaries of adult rats to bind HCG was markedly reduced within 3 days of hypophysectomy and remained low for at least 20 days. The extent of the reduction depended on the stage of the oestrous cycle at which hypophysectomy was performed. The highest loss of HCG binding capacity was seen in rats hypophysectomized at dioestrus II, while rats hypophysectomized at the oestrous stage exhibited similar HCG binding to control rats at the same stage of the cycle. Scatchard analysis indicated that the reduction in the capacity of the ovary to bind HCG after hypophysectomy was caused by the loss of specific receptors and not by a decrease in binding affinity. In contrast to adult rats, in immature rats the HCG binding capacity of the ovaries did not change during the 3 days after hypophysectomy, but after this a slow decline took place. Twenty days after pituitary ablation, almost identical values for binding of HCG were found in immature and adult rats. Since hypophysectomy in adult rats causes a rapid regression of large follicles, our results indicate that the remaining HCG binding activity arises largely from small follicles which are known to be unaltered by the deprivation of hypophysial hormones. This assumption is supported by our observation that in the ovaries of 25-day-old immature rats, which lack large follicles, only a slow decrease in the ability of the ovaries to bind HCG occurs in the 20 days after the operation.
STIMULATION OF PROSTAGLANDIN ACCUMULATION IN THE RAT ANTERIOR PITUITARY GLAND BY LUTEINIZING HORMONE RELEASING HORMONE IN VITRO
Authors: BARDEN N. , BETTERIDGE A.
Published: December 2008

The addition of luteinizing hormone releasing hormone (LH-RH) to cultures of monolayers of rat anterior pituitary cells was shown to increase both the concentrations of prostaglandins E1 and E2 (PGE) in the cells and the release of LH over similar ranges of concentrations of LH-RH (10−6 to 10−10 mol/l). The peak concentration of PGE was observed after 2·5 h. The stimulation of the level of PGE in the cells by LH-RH was completely inhibited by two inhibitors of prostaglandin synthetase, which only partially inhibited the stimulation of LH release. Therefore the increased concentration of PGE was not obligatory for the effect of LH-RH on LH release. It was also shown that monobutyryl cyclic AMP stimulated the intracellular concentration of PGE and it is suggested that the stimulation of PGE levels may be mediated by increased levels of cyclic AMP in the cells after the addition of LH-RH.
INHIBITION OF MATURATION OF ISOLATED RAT OOCYTES BY PORCINE FOLLICULAR FLUID
Authors: TSAFRIRI A. , CHANNING CORNELIA P. , POMERANTZ S. H. , LINDNER H. R.
Published: December 2008

The inhibitory action of porcine follicular fluid (FF1) on the spontaneous maturation of isolated rat oocytes was studied. Both FF1 and a low-molecular-weight fraction thereof (PFF1) inhibited the maturation of oocytes in culture. When the oocytes were scrutinized for maturation after culturing for 6 h in a medium containing 50% (v/v) FF1, the incidence of germinal vesicle breakdown (GVB) was reduced from 75 to 53% (P < 0·001) in oocytes collected 20 h after administration of pregnant mare serum gonadotrophin (PMSG), and from 94 to 53% (P < 0·01) in oocytes collected from preovulatory follicles 44 h after treatment with PMSG. Prolongation of the culture period to 20 h resulted in an increase in the number of oocytes undergoing GVB to 58% (harvested 20 h after PMSG treatment; P < 0·001) or 71% (44 h after treatment with PMSG; P > 0·05). Inhibition of GVB by PFF1 occurred at concentrations ≥ 0·085 mg protein/ml; the extent of inhibition was related directly to the concentration of inhibitor and inversely to the duration of culture and the developmental stage of the follicles from which the oocytes were derived. The inhibition of the resumption of meiosis by FF1 or PFF1 was overcome by ovine LH (5 μg/ml). However, GVB was delayed even in the presence of LH, compared with controls cultured in the absence of the inhibitor. These results demonstrate that the maturation-inhibiting action of porcine follicular fluid is not species specific and that the sensitivity of the rat oocyte to the inhibitor changes during the course of follicular development.
DISTRIBUTION OF CORTICOTROPHIN RELEASING FACTOR ACTIVITY WITHIN THE HYPOTHALAMIC-PITUITARY COMPLEX OF RATS AND CATTLE
Authors: YASUDA NAOKI , GREER MONTE A. , GREER SUSAN E. , PANTON PATRICIA
Published: December 2008

An assay system involving cultured rat adenohypophysial cells from either intact or adrenalectomized donors was used to study the distribution of corticotrophin releasing factor (CRF) activity in the hypothalamic-pituitary complex of rats and cattle. In the rat hypothalamus, CRF activity was most concentrated in the median eminence, but CRF was present in the stalk and the posterior pituitary gland in much higher concentrations than in the median eminence in both species. The dose–response slopes for the median eminence, stalk and pars nervosa of the posterior pituitary gland were parallel to each other, suggesting a qualitative similarity between the CRF activity in these tissues. Rat posterior pituitary glands may also contain another CRF component which has a much flatter dose–response curve, but is detectable in smaller quantities of posterior pituitary tissue than is the other type of CRF.
EFFECT OF PROSTAGLANDIN E2 ON MASCULINE SEXUAL BEHAVIOUR IN THE RAT
Authors: CLEMENS L. G. , GLADUE B. A.
Published: December 2008

Intracerebral infusion of prostaglandin E2 (PGE2) facilitated copulatory behaviour of longterm castrated rats. Castrated rats were given daily systemic injections of testosterone propionate (50 pg) or oil vehicle, and then 30 min before behavioural testing they received an intrahypothalamic infusion of either PGE2 or saline. Rats receiving PGE2 in addition to systemic testosterone showed more copulatory behaviour than those receiving PGE2 or testosterone alone.
INTERACTION OF THYROTROPHIN WITH THE HUMAN THYROTROPHIN RECEPTOR
Authors: SMITH B. REES , PYLE GWYNETH A. , PETERSEN V. B. , HALL R.
Published: December 2008

The relationship between the binding of thyrotrophin (TSH) to receptors and the production of cyclic AMP has been investigated using crude human thyroid membranes. Receptor binding was studied by use of 125I-labelled bovine TSH, which had been purified by absorption to and elution from human thyroid membranes. This 125I-labelled material showed the same biological activity as the unlabelled hormone. Binding studies at equilibrium indicated that the association constant of the TSH–membrane interaction decreased as the amount of TSH bound increased. Kinetic data did not provide definite evidence that this was due to an effect of increasing receptor occupancy on the dissociation rate constant. Detectable stimulation by TSH of cyclic AMP production by the membranes was observed with as little as 30 μu. (1 ng) hormone. Increasing amounts of TSH over the range 0–250 μu. caused increases in the production of cyclic AMP, proportional to the amount of hormone bound. With larger amounts of TSH, increasingly greater amounts of bound hormone were required to give corresponding increases in cyclic AMP formation, and addition of TSH in amounts greater than 16 mu. resulted in progressive inhibition of cyclic AMP formation. Kinetic studies indicated that receptor binding was not rate-limiting in the stimulation of cyclic AMP production by TSH.
CHARACTERISTICS OF THE OVULATORY RELEASE OF LUTEINIZING HORMONE IN FINN, FINN × SUFFOLK AND SUFFOLK EWES
Authors: WHEATON J. E. , RAABE T. I. , BURRILL M. J.
Published: December 2008

Department of Animal Science, University of Minnesota, St Paul, Minnesota 55108, U.S.A.

(Received 12 July 1977)

In sheep, the level of luteinizing hormone (LH) reaches a maximum 5–12 h before the onset of oestrus (Wheatley & Radford, 1969) and ovulation takes place 23–25 h after this peak (Cumming, Buckmaster, Blockey, Goding, Winfield & Baxter, 1973). However, it has been suggested that there is a relationship between the dynamics of the release of LH at oestrus and the rate of ovulation (Thimonier & Pelletier, 1971; Land, Pelletier, Thimonier & Mauleon, 1973). To increase the rate of ovulation, Finn sheep have been used in cross-breeding programmes (Boylan, 1975). This investigation was conducted to determine whether the release of LH at oestrus in Finn, Finn × Suffolk (F × S) and Suffolk ewes differs in the time of onset, magnitude or duration.

Mature Finn, F × S and Suffolk ewes weighing 44 ±
A RELATIONSHIP BETWEEN PLASMA CONCENTRATIONS OF TESTOSTERONE AND CORTICOSTEROIDS DURING SEXUAL AND AGGRESSIVE BEHAVIOUR IN THE BOAR
Authors: LIPTRAP R. M. , RAESIDE J. I.
Published: December 2008

Copulation with an oestrous sow or exposure to an aggressive boar resulted in a sharp rise in the concentration of corticosteroids in the plasma of boars, and subsequently, an immediate increase in the concentration of testosterone. Placing a test boar in close proximity to an oestrous sow for a period of 10 h caused three peaks in the concentration of corticosteroids in the plasma, each of which preceded a peak testosterone concentration. An inhibitor of 11 β-hydroxylation, metyrapone, was administered intravenously to limit corticosteroid production. One injection of 5 mg metyrapone/kg body weight or three injections of 4 mg metyrapone/kg body weight did not interfere with the response of the testes to stimulation by luteinizing hormone or human chorionic gonadotrophin. Peak values in the concentrations of corticosteroids and testosterone in the plasma after injection of adrenocorticotrophic hormone were limited to approximately one half when metyrapone was given. Similarly, metyrapone treatment reduced the response, in terms of plasma steroid levels, when test boars were exposed to an oestrous sow or an aggressive boar. The results show that an increase in the concentration of testosterone in the plasma during sexual or aggressive behaviour in the boar is highly correlated with an increase in the concentration of corticosteroids.
BLOOD–TESTIS BARRIER: EVIDENCE FOR INTACT INTER-SERTOLI CELL JUNCTIONS AFTER HYPOPHYSECTOMY IN THE ADULT RAT
Authors: HAGENÄS L. , PLÖEN L. , EKWALL H.
Published: December 2008

To study the hormonal dependence of the blood–testis barrier, adult rats were hypophysectomized and the ultrastructural integrity of the inter-Sertoli cell junctional complex was examined at various times with a lanthanum tracer technique. It was found that the structural integrity of the inter-Sertoli cell junctions and their capacity to exclude lanthanum from the adluminal compartment were preserved up to 35 days after hypophysectomy. Furthermore, transport of newly formed spermatocytes through the inter-Sertoli cell junctions still occurred 20 days after hypophysectomy. It is therefore concluded that the function of the inter-Sertoli cell junctional complex is not directly dependent on gonadotrophic or androgenic hormones, but is regulated by other mechanisms.
TIMING OF OVULATION IN RATS DURING EXPOSURE TO CONTINUOUS LIGHT: EVIDENCE FOR A CIRCADIAN RHYTHM OF LUTEINIZING HORMONE SECRETION
Authors: MCCORMACK C. E. , SRIDARAN RAJAGOPALA
Published: December 2008

In order to determine whether the timing of ovulation in rats was controlled by an endogenous circadian rhythm, the hour of ovulation was determined by observing tubal ova during laparotomy in adult rats exposed to full animal room illumination (150 lux) during daily photoperiods of 14 h (full LD), continuous 150 lux illumination (full LL), daily dim (0·2 lux) photoperiods of 14 h (dim LD), continuous 0·2 lux illumination (dim LL) or continuous darkness (DD). Rats in all groups except those exposed to full LL continued normal cyclic ovulation. By the second oestrous cycle, most rats in the full LL group failed to ovulate, even though they showed characteristic cyclic changes in the vaginal smear pattern. The hour at which ovulation occurred was similar in rats exposed to full LD, dim LD or DD but was delayed in rats exposed to full LL or dim LL; the longer the period of exposure, the greater was the delay. For a given length of exposure, ovulation was delayed more in full LL than in dim LL. The full LL used in this study produced persistent vaginal oestrus within 40 days, whereas the dim LL did not. The delayed ovulation in rats exposed to dim LL was associated with a delayed preovulatory surge of LH. These results are consistent with the hypothesis that the timing of the preovulatory surge of LH and ovulation are controlled by an endogenous circadian rhythm, which in most rats has a periodicity in continuous light of slightly longer than 24 h.
INDUCTION OF PROLACTIN AND LUTEINIZING HORMONE RELEASE BY HISTAMINE IN MALE AND FEMALE RATS AND THE INFLUENCE OF BRAIN TRANSMITTER ANTAGONISTS
Authors: DONOSO A. O.
Published: December 2008

The levels of prolactin and LH in the plasma of rats were determined at various times after intraventricular injection of histamine. Doses of 5 and 60 μg histamine (free base) in male rats, anaesthetized with ether, induced an increase in the level of prolactin in the plasma, whilst producing a slight decrease in the concentration of LH. Injection of 5 μg histamine at 14.00 h into female rats at all stages of the oestrous cycle caused prolactin to be released; the effect was greatest at oestrus and at day 1 of dioestrus. Histamine also gave rise to a marked increase in the level of LH in the plasma when administered to pro-oestrous rats, but had no effect when injected at the other stages of the oestrous cycle.

The effect of histamine on the release of prolactin in ovariectomized, oestradiol benzoate: progesterone-primed (OVX,OB:P) rats was found to be dose-related, and the level of LH in the plasma was increased by as little as 1·25 μg.

Pretreatment with adrenergic (phenoxybenzamine and propranolol) and cholinergic (atropine) antagonists failed to block the stimulatory effects of histamine on prolactin secretion, but pretreatment with methysergide (serotonin antagonist) increased the histamine-induced release of prolactin in male rats. Antagonists did not modify the response of prolactin to histamine in OVX,OB:P-primed rats. The histamine-induced release of LH in OVX,OB:P-primed rats was slightly reduced by pretreatment with phenoxybenzamine, propranolol and atropine, but not by methysergide.

These results indicate that histamine facilitates the release of prolactin. The stimulatory action of histamine on both pro-oestrous and OVX,OB:P-primed but not male rats suggests that histamine may be involved in LH release in the rat.

Results obtained in animals pretreated with transmitter antagonists, which were unable to prevent histamine-induced hormone release, suggest that the actions of this amine are not mediated by cholinergic, noradrenergic or serotonergic mechanisms.
INTERNAL QUALITY CONTROL OF RADIOIMMUNOASSAYS
Authors: KEMP K. W. , NIX A. B. J. , WILSON D. W. , GRIFFITHS K.
Published: December 2008

A modified cumulative sum technique has been applied to radioimmunoassay quality control data. The method is approximately 50% more efficient in detecting systematic changes in the mean and variance of quality control values for plasma samples than more widely used conventional methods. The salient features of the technique have been restricted to changes in the mean quality control value of a plasma pool, but potential applications to changes in variance and as a diagnostic aid to problems in radioimmunoassay have been evaluated. The method is independent of computing facilities and statistical expertise since all computations have been presented in the form of a nomogram and thus can be used by technicians at the bench.
NEUROHYPOPHYSIAL HORMONAL CONTROL OF KIDNEY FUNCTION IN THE EUROPEAN EEL (ANGUILLA ANGUILLA L.) ADAPTED TO SEA-WATER OR FRESH WATER
Authors: BABIKER M. M. , RANKIN J. C.
Published: December 2008

Low doses of arginine-vasotocin (AVT), isotocin and oxytocin (1 pg–1 ng/kg body weight) were antidiuretic in eels adapted to fresh water but not in those adapted to sea-water. High doses (more than 10 ng/kg) were always diuretic. No effects on tubular water reabsorption were observed and the glomerular filtration rate (GFR) was proportional to the maximum reabsorptive rate for glucose (Tm (glucose)) in eels adapted to sea-water. Increases in urinary flow appeared therefore to result from glomerular recruitment. Infusion of AVT or isotocin at low rates reduced the GFR and urinary flow of freshwater eels to the levels found in seawater eels. Vasopressin (lysine or arginine) had no direct effect on kidney function in freshwater eels but blocked both the diuretic and antidiuretic actions of the other hormones. When infused into seawater eels it was diuretic. This effect could have been due to blockade of the actions of endogenous AVT and/or isotocin.
EFFECTS OF INHIBITORS OF CATECHOLAMINE SYNTHESIS AND CATECHOLAMINE AGONISTS ON MORPHINE- AND HYPOGLYCAEMIA-INDUCED RELEASE OF GROWTH HORMONE IN THE RAT
Authors: BLUET-PAJOT M. T. , SCHAUB C.
Published: December 2008

Unité de Neuroendocrinologie, INSERM, U.159, 2 ter Rue d'Alesia, 75014 Paris, France

(Received 16 August 1977)

It is known that catecholamines play an important role in the regulation of growth hormone (GH) secretion, but the effects of dopamine and alpha- and beta-adrenergic agonists on the release of GH in the rat are controversial (Collu, Fraschini, Visconti & Martini, 1972; Kato, Dupre & Beck, 1973; Durand, Martin & Brazeau, 1977). It has been proposed (Bluet-Pajot, Schaub & Nassiet, 1976; Bluet-Pajot & Schaub, 1977; Durand et al. 1977) that the conflicting data obtained in the rat may be due to the anaesthesia; most of the GH responses reported to be atypical in the rat, compared with those of primates, were obtained under urethane anaesthesia, which is known to result in long-lasting and irreversible endocrine imbalance.

In contrast, neurotransmitters or experimental hypoglycaemia do not appear to induce paradoxical GH responses in rats treated