bluuebunny/crossref_metadata_2025_split huggingface dataset:
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
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.
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

SUMMARY
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

SUMMARY
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

SUMMARY
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

SUMMARY
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.
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.
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

SUMMARY
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

SUMMARY
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

SUMMARY
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.