bluuebunny/crossref_metadata_2025_split huggingface dataset:
FOLLICLE-STIMULATING HORMONE RELEASE IN HEMICASTRATED PREPUBERTAL RAMS AND ITS RELATIONSHIP TO TESTICULAR DEVELOPMENT
Authors: WALTON J. S. , EVINS JANET D. , HILLARD M. A. , WAITES G. M. H. 
Published: December 2008

Hemicastration of rams at 1 week of age resulted in compensatory growth of the remaining testis. This was associated with an increase in the concentration of FSH in peripheral plasma which was maintained until the rams were approximately 10 weeks old. Plasma concentrations of LH were similar in both entire and hemicastrated lambs during this period. Pulsatile release of LH was observed in all rams from approximately 6 weeks of age onwards. The frequency of these pulses increased and the size of each pulse declined as the animals grew older. At 16 weeks pulsatile release was almost undetectable and the basal levels of LH had increased. The increased concentration of FSH in plasma was related to the size of the remaining testis but not to its development. The return of the plasma concentration of FSH to values similar to those found in entire rams preceded the appearance of a lumen or of any primary spermatocytes in the seminiferous tubules. Restricting the development of the remaining testis in hemicastrated rams, by trapping it in the inguinal region, did not alter the FSH response to hemicastration.
The administration of gonadotrophin releasing hormone (10 μg) at 10,13 and 18 weeks of age provoked release of similar quantities of LH in both entire and hemicastrated rams. There was also a substantial release of FSH at 10 weeks of age but this response declined with age and by 18 weeks there was little FSH released in any of the animals. This loss of response occurred earlier in the hemicastrated rams.
The data suggest that in prepubertal rams the release of FSH but not of LH is restricted by a substance produced by the developing Sertoli cells.
THE PHYSIOLOGICAL SIGNIFICANCE OF ANDROGEN-INDUCED OVULATION IN THE HEN
Authors: CROZE F. , ETCHES R. J. 
Published: December 2008

The ovulation-inducing property of androgens in the laying hen was investigated. In a first experiment, four different androgens were injected subcutaneously into single-comb White Leghorn hens on the day of the last oviposition of a sequence. The hens were killed 10 h later and examined for the presence of an ovum in the oviduct. Testosterone induced ovulation in accordance to the dose injected (median effective dose, 966 ± 193 μg/hen) but the responses to 5α-dihydrotestosterone and 5α-androstane-3α, 17β-diol were not dose-related. The effect of 4-androstene-3,17-dione was more like that of progesterone since it induced ovulation 2 h earlier than the three other androgens.
The physiological significance of the ovulation response to an injection of testosterone was examined in more detail in experiment 2. Seven out of ten hens which were injected with 1 mg testosterone/kg body weight ovulated within 10 h after the injection. Blood samples were taken at hourly intervals and the concentrations of testosterone and progesterone were determined by radioimmunoassay. An injection of testosterone produced an increase in the concentration of testosterone in plasma which was considerably greater and occurred earlier than the preovulatory increase of testosterone in the control birds. The increase in the concentration of progesterone in the hens injected with testosterone was similar in magnitude but occurred earlier than the spontaneous preovulatory increase of progesterone in the control hens. The possible physiological role of testosterone in the ovulation cycle is discussed.
ROLE OF TESTOSTERONE AND OF ITS METABOLITES IN REGULATING GONADOTROPHIN SECRETION IN THE JAPANESE QUAIL
Authors: DAVIES D. T. , MASSA R. , JAMES R. 
Published: December 2008

In the Japanese quail gonadal steroids can depress plasma levels of LH and FSH. Since it is now accepted that testosterone metabolites may be metabolized to the tissue-active forms of the hormone, the in-vitro tissue incubation has been combined with steroid replacement therapy in vivo to investigate the physiological roles of various testosterone metabolites as inhibitory feedback agents on gonadotrophin secretion in quail. After the incubation of quail pituitary glands for 3 h with labelled testosterone four metabolites could be identified; androst-4-ene-3,17-dione, 5β-dihydrotestosterone (5β-DHT), 5β-androstane-3α,17β-diol and 5α-DHT. No 5α-androstane-3α,17β-diol was found. Quantitatively, androstenedione was the major metabolite and conversion of testosterone to 5β-metabolites was significantly greater than to 5α-androgens. Hypothalamic and hyperstriatal tissues converted testosterone to androstenedione, 5β-DHT and 5β-androstane-3α,17β-diol but not to 5α-DHT or 5α-androstane-3α,17β-diol.
Gonadotrophin secretion was studied in castrated quail after chronic s.c. implantation of steroid-containing silicone elastomer capsules or acute injection i.m. of steroid in ethanol: saline. Irrespective of the route of administration seven androgens, listed in descending order of potency, reduced the increased levels of plasma LH: testosterone; 5α-DHT; androstenedione; 5α-androstane-3,17-dione; 5α-androstane-3α,17β-diol; 5α-androstan-3α-ol-17-one; 5α-androstan-3β-ol-17-one. No changes in levels of plasma LH were observed after the administration of 5β-DHT, 5α-androstane-3β,17β-diol, 5βandrostane-3α,17β-diol, 5β-androstane-3,17-dione, androst-5-ene-3β,17β-diol or androst-5-en-3β-ol-17-one.
Testosterone and oestradiol-17β were effective in inhibiting secretion of both LH and FSH in young photostimulated quail and completely blocked testicular growth: 5α-DHT inhibited only the release of LH and testicular growth was unaffected.
ADENYLATE CYCLASE ACTIVITY IN THE UTERINE CERVIX OF NEONATAL AND IMMATURE MICE: INFLUENCE OF OESTRADIOL-17β
Authors: KVINNSLAND STENER 
Published: December 2008

The influence of long-term oestradiol stimulation on adenylate cyclase activity was investigated in homogenates from uterine cervices of neonatal (3-day-old) and immature (14-day-old) NMRI mice. A significant increase of enzyme activity, measured in the presence of fluoride ions (NaF), after oestradiol treatment was found in preparations from neonatal but not from those of immature female mice; this was irrespective of whether the enzyme activity was related to wet weight, amount of protein or DNA content. The enzyme activity was stimulated in vitro by NaF and 5-guanylylimidodiphosphate while isoprenalin, histamine, prolactin and oestradiol had no effect.
These results indicated an age-related difference in the effects of oestradiol in the uterine cervix of the mouse.
EFFECTS OF OESTRADIOL ON STEROID DEHYDROGENASE ACTIVITIES IN RAT CORPORA LUTEA
Authors: RODWAY R. G. , ROTHCHILD I. 
Published: December 2008

The activities of 20α-hydroxysteroid dehydrogenase and 3β-hydroxysteroid dehydrogenase in rat corpora lutea during the second half of pregnancy were measured. In luteal tissue of the intact pregnant rat, 20α-hydroxysteroid dehydrogenase activity was undetectable between days 12 and 18 of pregnancy but appeared slowly after hypophysectomy and hysterectomy on day 12. Treatment of the hypophysectomized and hysterectomized animal with oestradiol delayed this increase until day 17, at which time a rapid induction of this enzyme occurred.
In the normal pregnant rat mean luteal 3β-hydroxysteriod dehydrogenase activity increased between days 12 and 18 (P <0·05, Student's t-test) but fell rapidly after hypophysectomy and hysterectomy on day 12. Oestradiol treatment prevented this fall in activity and enzyme activity was not distinguishable from that of the intact rat.
Progesterone secretion correlated well with the activities of these two enzymes in the three conditions examined.
CONCENTRATIONS OF LUTEINIZING HORMONE, OESTRADIOL-17β AND PROGESTERONE IN THE PLASMA OF HEIFERS TREATED TO INDUCE SUPEROVULATION
Authors: SAUMANDE J. 
Published: December 2008

Concentrations of luteinizing hormone (LH), oestradiol-17β and progesterone were studied in 14 heifers treated with pregnant mare serum gonadotrophin (PMSG) and an analogue of prostaglandin F2α (PGF2α) 48 h later to induce superovulation. Plasma levels of oestradiol-17β before ovulation and of progesterone after ovulation were related to the number of ovulations but the concentrations of LH were not so related; however, hormone concentrations at the time of injection of PMSG could not be used to predict the rate of ovulation. The injected gonadotrophin also appeared to affect folliculogenesis after ovulation and this may explain the presence of large follicles in the ovary when the corpora lutea were counted.
It was possible to demonstrate by analysis of plasma levels of hormones that few non-superovulated animals were really insensitive to PMSG.
EFFECTS OF GROWTH HORMONE, PROLACTIN AND THYROXINE ON BODY WEIGHT, SOMATOMEDIN-LIKE ACTIVITY AND IN-VIVO SULPHATION OF CARTILAGE IN HYPOPITUITARY DWARF MICE
Authors: HOLDER A. T. , WALLIS M. , BIGGS P. , PREECE M. A. 
Published: December 2008

SUMMARY
Hypopituitary dwarf mice were found to have reduced levels of serum somatomedin-like activity compared with normal mice of the Snell strain. Treatment with bovine growth hormone for 3 and 7 days resulted in growth without significantly increased levels of serum somatomedin-like activity, as detected by in-vitro uptake of 35SO42− into normal rat cartilage; only after treatment for 14 days was somatomedin activity significantly raised. However, treatment for 2 days with bovine growth hormone, bovine prolactin or thyroxine resulted in a dose-dependent increase in in-vivo uptake of 35SO42− into dwarf mouse costal cartilage; growth hormone and thyroxine did not act synergistically. Ten days of treatment with growth hormone promoted a dose-dependent increase in both growth (increased weight gain and tail length) and in-vivo uptake of 35SO42−. Increase in tail length was correlated with uptake of 35SO42−. Thus, in-vivo uptake of 35SO42− into dwarf mouse costal cartilage provides a sensitive method for detecting a dose-related effect of growth hormone.
EFFECT OF NEONATAL ADMINISTRATION OF STEROIDS OR GONADECTOMY UPON OESTRADIOL-INDUCED LUTEINIZING HORMONE RELEASE IN RATS OF BOTH SEXES
Authors: GOGAN F. , BEATTIE I. A. , HERY M. , LAPLANTE E. , KORDON C. 
Published: December 2008

SUMMARY
Implantation of oestradiol into adult rats of both sexes induced different patterns of LH secretion depending on the time at which gonadectomy or testosterone injection were performed. Castration 2 h after birth allowed an LH peak to occur daily at 18.00 h, but its amplitude was lower than that of adult gonadectomized female rats treated with oestradiol. Castration 24 h after birth elicited two kinds of response; a circadian discharge of LH lower than that of male rats gonadectomized 2 h after birth or a steady low level of LH. The LH rhythmicity induced by implantation of oestradiol was not seen after castration at 8 weeks of age. Neonatal administration of testosterone to female rats prevented the LH peak induced by oestradiol that was seen in adult ovariectomized rats. Neonatal or adult ovariectomy did not interfere with the rhythmical response of LH after implantation of oestradiol. Thus, it is concluded that sexual differentiation of the hypothalamus is primarily of masculine origin.
EFFECT OF EXCESSIVE SECRETION OF GROWTH HORMONE ON TISSUES OF THE RAT, WITH PARTICULAR REFERENCE TO THE HEART AND SKELETAL MUSCLE
Authors: PRYSOR-JONES R. A. , JENKINS J. S. 
Published: December 2008

SUMMARY
Rat pituitary tumours of the GH3 cell line, secreting growth hormone (GH), were induced to grow in Wistar–Furth rats and the effect of prolonged excessive secretion of GH on various organs was investigated. Total body weight of the tumour-bearing animals increased by over 100% compared with control animals and there was widespread visceromegaly affecting especially the liver, kidney, spleen and adrenals. The heart was also considerably enlarged. The effects of excessive GH on skeletal muscle were not uniform and, using a histochemical technique, it was found that the size of type 1 muscle fibres was increased to the greatest extent whereas fibre type 2A was unaffected. Synthesis of DNA in the heart and skeletal muscle was also increased in tumour-bearing animals. Removal of the tumours was followed by a considerable regression in the size of most organs, although hypertrophy of the heart was affected least by a return to normal plasma levels of GH. It was concluded that animals bearing GH3 cell tumours provide a useful experimental model for the study of the tissue changes in acromegaly.
MECHANISMS OF CATABOLISM OF CORTICOTROPHIN-(1–24)-TETRACOSAPEPTIDE IN THE RAT IN VIVO
Authors: HUDSON ANNE M. , McMARTIN COLIN 
Published: December 2008

SUMMARY
The fragmentation of corticotrophin-(1–24)-tetracosapeptide in vivo has been studied, using tritium-labelled hormone and chromatography, in the rat. After intravenous injection the levels of peptide in the circulation declined rapidly caused by its distribution to the tissues and from 2 min after injection a range of different cleavage products appeared. Many of the fragments in the circulation after 2 min have been identified and in this way cleavage has been shown to occur after residues 1,2,8,15,16,17,19,20 and 21. It is believed that this is the result of aminopeptidase attack at the NH2 terminal, and of attack on the basic region of the molecule by trypsin-like endopeptidase followed by carboxypeptidase. The sulphoxide has been identified as a major metabolite in some experiments but the extent of its formation was very variable. Seventy per cent of the dose was distributed to the tissue beds by 1 min. Part of this was present, mainly as intact peptide, in liver and kidney but the greater proportion was found in muscle, skin and intestine where extensive degradation had already occurred. Further characterization of the fragments formed in the muscle provided good evidence that this tissue may have been the site of generation of many of the fragments which later appeared in the circulation.
GONADOTROPHIN RELEASE IN HYPOGONADAL AND NORMAL MICE AFTER ELECTRICAL STIMULATION OF THE MEDIAN EMINENCE OR INJECTION OF LUTEINIZING HORMONE RELEASING HORMONE
Authors: IDDON CAROL A. , CHARLTON H. M. , FINK G. 
Published: December 2008

SUMMARY
Electrical stimulation of the median eminence, using parameters known to cause the release of LH in normal male mice, failed to elicit any gonadotrophin response in hypogonadal (hpg) male mice. Administration of 40 ng synthetic LH releasing hormone (LH-RH) resulted in release of LH from the pituitary gland of hpg mice, although the response was significantly lower than that of normal mice. These results were consistent with the hypothesis that the hypogonadal state of the hpg mouse results from a functional absence of LH-RH in the hypothalamus rather than from a lack of response of the pituitary gland to the releasing hormone.
EFFECTS OF ARGININE AND GLUCOSE ON THE RELEASE OF INSULIN IN THE SHEEP FETUS
Authors: FOWDEN ABIGAIL L. 
Published: December 2008

SUMMARY
The effect of l-arginine on fetal insulin release has been investigated in the chronically catheterized sheep fetus and the findings have been compared with the β cell response to glucose. An infusion of arginine for 5 min (200 mg as a solution of 11·5 mmol/l) stimulated a rapid release of insulin in all the fetuses from 119 to 142 days of gestational age. The maximum insulin concentration occurred at the end of infusion; the mean insulin increase between 0 and 5 min was 18·0 ± 2·0 μu./ml (n = 20). The response to infusion of glucose for 5 min (1 g as a solution of 2·8 mol/l) was more variable and slower than that to arginine with the peak concentration of insulin occurring 10 min after the end of infusion. The mean increase in the concentration of insulin between 0 and 15 min in response to glucose was 42·5 ± 10·0 μu./ml (n = 11). The response to arginine but not to glucose was related to the gestational age of the fetus. The increment in insulin in response to glucose was dependent upon the initial concentration of fetal plasma glucose. The observations are discussed in relation to the regulation of insulin release in utero and the mechanisms of insulin secretion.
EFFECTS OF INSULIN AND GLUCAGON ON PRODUCTION OF RENIN SUBSTRATE BY THE ISOLATED RAT LIVER
Authors: MURAKAMI EIKI , HIWADA KUNIO , KOKUBU TATSUO 
Published: December 2008

SUMMARY
An isolated rat liver perfusion system was used to study the effects of insulin and glucagon on renin substrate production. Normal livers synthesized renin substrate at a rate of 28·3 ± 3·8 (s.e.m.) ng angiotensin I equiv./g liver each h (n = 8). The addition of insulin (more than 0·1 i.u.) to the perfusion significantly enhanced the production of renin substrate which was about twofold higher than normal control values (P< 0·001). However, glucagon (20 μg) did not affect the synthesis of renin substrate. These results indicated that insulin promoted the synthesis of renin substrate by the isolated rat liver.
PLASMA ANTIDIURETIC HORMONE DURING HYPOXIA AND ANAESTHESIA IN PIGS
Authors: FORSLING MARY L. , INGRAM D. L. , STANIER M. W. 
Published: December 2008

The level of antidiuretic hormone (ADH) in the plasma of pigs was studied during hypoxia, anaesthesia and a combination of the two conditions. Hypoxia, caused by making conscious pigs breathe nitrogen, elicited a rise in the level of ADH without change in plasma osmolality; the hypoxia was accompanied in some cases by a slight lowering of arterial pressure which quickly returned to its original level after the period of hypoxic breathing. Pentobarbitone anaesthesia had no significant effect on the level of ADH but halothane anaesthesia elicited a rise in ADH.
Transient high levels of ADH were seen in animals which were exposed to hypoxia during halothane or pentobarbitone anaesthesia. These high levels of ADH were sometimes, but not invariably, accompanied by a fall in arterial pressure. No consistent changes in plasma osmolality or haematocrit were associated with the raised plasma ADH.
AN UNEVEN DISTRIBUTION OF CHOLINE ACETYLTRANSFERASE ACTIVITY IN THE PITUITARY NEUROINTERMEDIATE LOBE OF THE RAT
Authors: GALLARDO MARIA G. P. , CANNATA M. A. , TRAMEZZANI J. H. 
Published: December 2008

The neurointermediate lobe of the pituitary gland of male rats was assayed for choline acetyltransferase (CAT) activity. Precise microsample punches were obtained from neurohypophysial tissue, pure pars intermedia tissue and from the junction area between them.
The level of CAT activity (pmol/h per μg protein) in the neurohypophysis, pars intermedia and junction area were 0·390 ± 0·038 (s.e.m.), 0·228 ± 0·042 and 1·824 ± 0·268 respectively. These values show an uneven distribution of CAT in the neurointermediate lobe. The hypothesis of a cholinergic system located in the junction area has been advanced.
CATECHOL OESTROGENS AND GONADOTROPHIN SECRETION IN THE EWE: AFFINITY FOR PITUITARY OESTROGEN RECEPTORS IN VITRO AND ACTION ON GONADOTROPHIN SECRETION IN VIVO
Authors: CLARKE I. J. , FINDLAY J. K. 
Published: December 2008

The binding of three catechol oestrogens, 2-OH-oestradiol-17β, 4-OH-oestrone and 2-OH-oestrone, to the ovine pituitary oestrogen receptor was measured in vitro to establish doses for the assessment of the effects of catechol oestrogens in vivo. Relative to oestradiol (100%) the compounds had receptor affinities of 30, 20 and 5% respectively. A dose of oestradiol sufficient to cause negative-feedback effects on the secretion of LH and FSH in ovariectomized ewes was established by intracarotid (i.c.) injections of 0·625–5·0 μg/dose (n = 3), and by measuring plasma levels of gonadotrophins in jugular venous samples taken at intervals of 20 min from 3 h before until 4 h after injection. A dose-dependent relationship (r = 0·88, P<0·001) was found for oestradiol and plasma LH levels. Plasma FSH was slightly (12–25%) but significantly (P<0·05) reduced by doses of 1·25–5·0 μg oestradiol, but no dose–response relationship was observed.
Ovariectomized ewes (n = 4/group) were given 2·5 μg oestradiol (i.c.) simultaneously with 83 μg 2-OH-oestradiol, 125 μg 4-OH-oestrone or 500 μg 2-OH-oestrone. These doses of catechol oestrogens were chosen as being ten times that of oestradiol, with the relative affinities for oestrogen receptor taken into account. Concurrent administration of such doses of catechol oestrogens had no effect on the negative-feedback action of oestradiol in vivo. We have concluded that catechol oestrogens in the circulation probably do not modulate the action of oestradiol on release of LH or FSH; this does not preclude a possible role for them as locally produced regulators of oestrogen action.
EFFECTS OF PASSIVE IMMUNIZATION AGAINST TESTOSTERONE ON SERUM AND PITUITARY GONADOTROPHINS: IMPLICATIONS FOR THE RELATIVE IMPORTANCE OF ANDROGENS AND INHIBIN IN THE CONTROL OF GONADOTROPHIN SECRETION IN THE MALE RAT
Authors: MAIN S. J. , DAVIES R. V. , SETCHELL B. P. 
Published: December 2008

The acute effects of a specific reduction in androgen feedback to the hypothalamus and pituitary gland have been investigated in male rats by passive immunization against testosterone. An ovine antiserum raised against testosterone which had been conjugated through position 3 to bovine serum albumin was employed.
Negative feedback control by androgens was effectively reduced by administration of the antiserum, as shown by an increase in levels of LH in the circulation. Immunized animals had a high concentration of testosterone in the circulation of which virtually all was tightly bound to antibody.
In normal animals specific increases of serum LH concentration were obtained at all ages using a low dose of antiserum. At higher doses, serum FSH concentration was also increased. The LH response was reduced by anaesthesia and sham-operation. In shamoperated rats given a high dose of antiserum for 3 days the serum concentrations of LH and FSH could not be distinguished from those which followed castration while differences were found in the pituitary contents. It was concluded that testicular androgen provides an important inhibitory feedback control of secretion of FSH as well as that of LH in the adult male rat. Some of the data can best be explained by the action of inhibin as a minor or alternative inhibitor of FSH secretion.
MONOAMINERGIC REGULATION OF GROWTH HORMONE IN THE RAT
Authors: BLUET-PAJOT M. T. , SCHAUB C. , MOUNIER F. , SEGALEN A. , DUHAULT J. , KORDON C. 
Published: December 2008

The administration of gamma-hydroxybutyrate (GHB) induced a consistent secretory episode of growth hormone (GH) in the morning followed by basal levels of secretion of GH for several hours. The measurement of endogenous noradrenaline, dopamine and serotonin (5-HT) following infusion of GHB showed that dopamine concentrations were significantly increased in the striatum; at the level of the hypothalamus, however, no significant differences were observed between control and GHB-treated animals.
The data reported in this study are consistent with the interpretation that the neurotransmitter regulation of GH release and the modulation of hypothalamic gluco-receptor systems are not fundamentally different in rodents and primates.
Clonidine, an α-adrenergic agonist, enhanced the peak of GH observed in the morning and caused a rapid increment of GH during the period when it was normally at basal levels. Under the same experimental conditions, dopamine agonists, apomorphine and levodopa, had no effect on GH secretion. The inhibition of catecholamine synthesis by α-methyl-p-tyrosine blocked the secretory episode of GH following administration of GHB and after insulin hypoglycaemia whereas the GH rise induced by clonidine was unchanged. The inhibition of 5-HT synthesis by p-chlorophenylalanine also suppressed the secretory episode of GH seen in the morning and the release of GH induced by hypoglycaemia; both being partly restored in animals pretreated with 5-hydroxytryptamine.