bluuebunny/crossref_metadata_2025_split huggingface dataset:
DOPAMINERGIC MODULATION OF ALDOSTERONE SECRETION?
Authors: McDOUGALL J. G. , SCOGGINS B. A. , BUTKUS ALDONA , COGHLAN J. P. , DENTON D. A. , FEI D. T. , HARDY K. J. , WRIGHT R. D. 
Published: December 2008

Metoclopramide (10 mg i.v. injection followed by 10 mg/h i.v. for 2 h) caused a transient rise in blood concentrations of aldosterone in sodium-replete and sodium-depleted sheep. Infusion of metoclopramide into the adrenal artery of sheep with an autotransplanted adrenal gland, at a rate to give a similar concentration of metoclopramide at the adrenal cell level (calculated from rate of infusion and adrenal blood flow), resulted in no alteration in aldosterone secretion rate in either sodium-replete or sodium-depleted animals, even though intravenous metoclopramide caused transient stimulation of aldosterone secretion in the same sheep when sodium replete.
Dopamine administered either into the adrenal arterial blood supply or intravenously had no significant effect on aldosterone secretion and did not reverse the stimulatory effects of angiotensin II on aldosterone secretion in the adrenal transplant.
The data do not support the suggestion that direct dopaminergic elements play a tonic inhibitory role in aldosterone secretion. It is possible that the agonist effect of metoclopramide on aldosterone secretion may occur by some non-dopaminergic mechanism and it is tempting to speculate that the effect is centrally mediated.
EFFECT OF OESTROGEN ON GONADOTROPHIN RELEASE IN STUMPTAILED MONKEYS (MACACA ARCTOIDES) TREATED CHRONICALLY WITH AN AGONIST ANALOGUE OF LUTEINIZING HORMONE RELEASING HORMONE
Authors: FRASER H. M. 
Published: December 2008

Nine adult female stumptailed monkeys (Macaca arctoides) treated chronically with daily s.c. injections of d-Ser(But)6des-Gly10,Proethylamide9, luteinizing hormone releasing hormone (LH-RH agonist) to inhibit ovulation, were tested for their ability to respond to an oestrogen provocation test (positive feedback). On two occasions during treatment with the LH-RH agonist (first test between 10 and 35 weeks after treatment had started; second test between 30 and 60 weeks after) the animals were given an i.m. injection of 50 μg oestradiol benzoate/kg in arachis oil. Controls were tested between days 1 and 5 of the normal cycle. In the control monkeys oestrogen induced a clear rise in LH and FSH concentrations in the blood, with highest values between 48 and 60 h after treatment. In marked contrast, none of the animals treated with LH-RH agonist showed this pattern of response. In the first test, five of the nine monkeys showed no rise in LH while in the remaining animals the response was diminished or delayed, and in the second test all nine failed to show a significant rise in LH. In all agonist-treated monkeys oestrogen failed to cause an FSH rise in either test.
Thus, chronic treatment with LH-RH agonist in the monkey either abolishes, diminishes or delays the oestrogen-induced LH surge. Since, in the primate, oestrogen appears to release LH by acting directly on the pituitary gland exposed to pulses of LH-RH from the hypothalamus it appears that the LH surge is inhibited primarily because the pituitary gland has been exposed to prolonged stimulation by the agonist.
RESPONSES OF RAT FETAL ADRENALS TO SYNTHETIC ADRENOCORTICOTROPHIC HORMONE AND α-MELANOCYTE-STIMULATING HORMONE: IN-VIVO AND IN-VITRO STUDIES
Authors: DUPOUY J. P. 
Published: December 2008

The response of the adrenals from rat fetuses at 16,18 and 20 days of gestation to 1–24 ACTH and α-melanocyte-stimulating hormone (α-MSH) was studied in vitro. The response to 1–24 ACTH increased as gestation progressed. By the end of fetal life, corticosterone release induced by ACTH from whole adrenals was greater than that observed with adrenal tissue from non-pregnant adult female rats. High doses of α-MSH also stimulated adrenal activity but the response to ACTH was always higher than that to α-MSH.
The effect of 1–24 ACTH and α-MSH on fetal adrenal growth was also compared in vivo. The adrenal atrophy induced by fetal hypophysectomy on day 17 of gestation could be prevented by i.m. administration of 10 μg 1–24 ACTH or α-MSH. However, the adrenal growth was greater in ACTH-treated fetuses than in α-MSH-treated ones. Later in gestation, between days 19 and 20, 1–24 ACTH but not α-MSH was able to prevent atrophy induced by fetal hypophysectomy.
These findings are discussed in relation to the literature on levels of ACTH and α-MSH in the plasma and pituitary glands of the rat throughout the last third of gestation. High levels of ACTH in the fetal circulation contrast sharply with very weak or undetectable concentrations of α-MSH. Since the present data suggest that both trophic and steroidogenic activities of ACTH were greater than those of α-MSH, it may be concluded that ACTH but not α-MSH plays a major physiological role during gestation in the regulation of both fetal adrenal growth and function in the rat.
RETARDATION OF FIRST OVULATION IN PUBERTAL RATS AFTER TREATMENT WITH 5α-ANDROSTANE-3α,17β-DIOL OR ITS 3β-EPIMER
Authors: KRAMER P. , MEIJS-ROELOFS H. M. A. 
Published: December 2008

The effect was studied of five daily injections of 50 μg of either 5α-androstane-3α,17β-diol (3α-androstanediol) or its 3β-epimer (3β-androstanediol), starting on day 22 of life, on sexual maturation in female rats. No difference was found in the age and body weight at first oestrus between oil-treated rats and rats treated with either 3α- or 3β-androstanediol. The only difference observed between these groups consisted of the occurrence of a 'pinhole' vaginal opening a few days before oestrus in 50% of the steroid-treated rats; in oil-treated rats immediate full vaginal opening and first oestrus coincided in ten out of 12 rats.
Different effects were obtained when the higher dose of 100 μg daily was used; effects were dissimilar in rats treated with 3α- and 3β-androstanediol. If administration of the higher dose of 3β-androstanediol was started on day 22 and continued until the day of full vaginal opening and first oestrus, a significant delay of this first oestrus, preceded by a few days of a 'pinhole' type of vaginal opening, was observed. After administration of the higher dose of 3α-androstanediol a 'pinhole' type of vaginal opening, accompanied by dioestrous-like vaginal smears, was also found, but oestrus did not occur during the period when injections were given. After the injections were stopped on day 45, first oestrus developed within 6 days in all rats.
The previous findings of others that administration of 3β-androstanediol to the immature female rat may induce precocious puberty (i.e. precocious vaginal opening and first ovulation) were not confirmed in the present study. Our results indicate that high doses of free 3α-androstanediol, and to a lesser degree 3β-androstanediol, may even delay first ovulation in the rat. A possible interference of 3α-androstanediol with the triggering of the first ovulatory gonadotrophin peaks is discussed.
POSSIBLE ROLE OF 5α-ANDROSTANE-3α,17β-DIOL IN THE CONTROL OF FOLLICLE-STIMULATING HORMONE SECRETION IN THE IMMATURE FEMALE RAT
Authors: MEIJS-ROELOFS H. M. A. , KRAMER P. , GRIBLING-HEGGE L. 
Published: December 2008

A possible role of 5α-androstane-3α,17β-diol (3α-androstanediol) in the control of FSH secretion was studied at various ages in ovariectomized rats. In the rat strain used, vaginal opening, coincident with first ovulation, generally occurs between 37 and 42 days of age. If 3α-androstanediol alone was given as an ovarian substitute, an inhibitory effect on FSH release was evident with all three doses tested (50, 100, 300 μg/100 g body wt) between 13 and 30 days of age; at 33–35 days of age only the 300 μg dose caused some inhibition of FSH release. Results were more complex if 3α-androstanediol was given in combined treatment with oestradiol and progesterone. Given with progesterone, 3α-androstanediol showed a synergistic inhibitory action on FSH release between 20 and 30 days of age. However, when 3α-androstanediol was combined with oestradiol a clear decrease in effect, as compared to the effect of oestradiol alone, was found between 20 and 30 days of age. Also the effect of combined oestradiol and progesterone treatment was greater than the effect of combined treatment with oestradiol, progesterone and 3α-androstanediol. At all ages after day 20 none of the steroid combinations tested was capable of maintaining FSH levels in ovariectomized rats similar to those in intact rats.
It is concluded that 3α-androstanediol might play a role in the control of FSH secretion in the immature rat, but after day 20 the potentially inhibitory action of 3α-androstanediol on FSH secretion is limited in the presence of oestradiol.
DRUG-INDUCED HYPERPROLACTINAEMIA AND DISCHARGES OF LUTEINIZING HORMONE EVOKED BY OESTROGEN IN OVARIECTOMIZED RHESUS MONKEYS
Authors: MARTENSZ N. D. , HERBERT J. 
Published: December 2008

Ovulatory failure associated with hyperprolactinaemia has been attributed to the inability of oestrogen to evoke a preovulatory discharge of gonadotrophins. This hypothesis was tested in ovariectomized rhesus monkeys rendered hyperprolactinaemic by treatment with two dopamine antagonists, domperidone, a compound reported not to cross the blood–brain barrier in rats, and sulpiride, a drug with known actions on both pituitary and central dopaminergic receptors. An artificial surge of oestrogen similar to that observed at mid-cycle in intact monkeys was obtained with subcutaneous capsules filled with oestradiol-17β. Treatment with either drug increased prolactin concentrations to 1·0 i.u./l or more compared with control values of 0·1–0·3 i.u./l. In the presence of these greatly increased prolactin levels, a normal discharge of LH, indistinguishable from that observed in control animals, was provoked by oestrogens in all but one drug-treated monkey. Furthermore, neither the basal (pre-oestrogen) level of LH nor the negative feedback action of oestrogen was consistently altered in hyperprolactinaemic monkeys. Administration of progesterone or 17α-hydroxyprogesterone to simulate more closely the conditions observed in intact animals during the periovulatory period did not alter the LH discharge induced by oestrogen in animals treated with domperidone.
The present results suggest that the high levels of prolactin brought about by dopaminergic blockade do not affect the positive feedback action of oestrogen. Furthermore, low levels of progestins do not sensitize the hypothalamic-pituitary axis towards an inhibitory action of prolactin on oestrogen-induced LH release. The rhesus monkey thus differs from other species, including man, in which artificially induced hyperprolactinaemia may impair or abolish the positive feedback action of oestrogen.
BIOLOGICAL AND IMMUNOLOGICAL PROPERTIES OF DIFFERENT MOLECULAR SPECIES OF HUMAN FOLLICLE-STIMULATING HORMONE: ELECTROFOCUSING PROFILES OF EIGHT HIGHLY PURIFIED PREPARATIONS
Authors: ZAIDI A. A. , FRÖYSA B. , DICZFALUSY E. 
Published: December 2008

Eight highly purified human pituitary FSH preparations and purified preparations of the α-and β-subunits of FSH were fractionated by an electrofocusing technique in the pH range of 2·5–10·0 on a sucrose density gradient. The human (h) FSH activity in each of the eluted fractions was monitored by an in-vitro bioassay and a radioimmunoassay procedure.
After electrofocusing, the overall recovery of the biological activity of the eight preparations was between 80 and 94% (mean 88%). On the other hand, the recovery of immunoreactivity ranged between 30 and 84% (mean 71%). A loss of over 85% of hFSH immunoreactivity was observed when the α- and β-subunits of hFSH were fractionated by the same procedure.
The specific loss of varying amounts of immunoreactivity in all preparations during electrofocusing was also reflected by a proportional increase in the ratios of biological activity (B) to immunoreactivity (I); preparation A, which exhibited a loss of 70% of the immunoreactivity, had a threefold increase in its B/I ratio after electrofocusing.
Significant differences were observed in the electrofocusing profiles of the eight preparations both in terms of their pI values and of their spread.
The disparity in the relative distribution of hFSH activities in different pH regions suggested major differences in the carbohydrate moieties (sialic acid content) of the preparations studied, probably as a result of the chemical manipulations involved in the purification of the hormone. It is suggested that a combination of several (but certainly not all) of the preparations might serve as a provisional International Reference Preparation for hFSH radioimmunoassays.
EFFECTS OF HYDROXYSTEROID DEHYDROGENASE INHIBITORS ON IN-VITRO AND IN-VIVO STEROIDOGENESIS IN THE OVINE ADRENAL GLAND
Authors: SINGH-ASA P. , JENKIN G. , THORBURN G. D. 
Published: December 2008

The effectiveness of trilostane and azastene as inhibitors of adrenal steroidogenesis was compared by in-vitro and in-vivo methods. A radioimmunoassay was developed for the measurement of cortisol in ovine plasma, incubation medium and tissue extract using a specific antiserum raised against cortisol 21-acetate,3-carboxymethyloxime : bovine serum albu
Trilostane (20 μmol/l) decreased cortisol synthesis and release both in unstimulated and in ACTH-stimulated adrenal tissues in vitro. The same concentration of azastene had a lesser effect on unstimulated adrenals and was completely ineffective in blocking the stimulatory action of ACTH. In vivo, trilostane suppressed adrenal steroidogenesis in pregnant and cyclic ewes but the suppression in pregnant ewes was over a longer period, and after lower doses.
It is concluded that trilostane had an inhibitory effect on ovine adrenal steroidogenesis both in vitro and in vivo.
EFFECTS OF SINGLE INJECTIONS OF BOVINE FOLLICULAR FLUID ON GONADOTROPHIN CONCENTRATIONS THROUGHOUT THE OESTROUS CYCLE OF THE RAT
Authors: HERMANS W. P. , DEBETS M. H. M. , VAN LEEUWEN E. C. M. , DE JONG F. H. 
Published: December 2008

A single injection of steroid-free bovine follicular fluid (bFF), which contains inhibin-like activity, was given to adult female rats at 09.00 h on dioestrus-2 (the day after metoestrus), dioestrus-3, pro-oestrus or oestrus. Peripheral concentrations of gonadotrophins were measured at 2-h intervals after injection. Compared with values in control animals treated with bovine plasma, injection of bFF did not influence concentrations of LH. In contrast, at all days studied injection of bFF resulted in suppressed concentrations of FSH, during a period which started between 4 and 10 h after injection and lasted 4–12 h, depending on the day of the cycle. With the exception of pro-oestrus, the period of suppression was followed by one in which fluctuating levels of FSH were found; in general, resulting levels were higher though not significantly increased. This latter effect was most pronounced on dioestrus-2 and dioestrus-3, when levels of FSH, which were already low in control animals, were first suppressed during the 6 h after injection of bFF.
These data, in conjunction with results from an earlier study in rats at dioestrus-1, showed that administration of bFF induces a fast and selective suppression of FSH secretion on all days of the cycle. This period of suppression was followed by one with fluctuating levels of FSH which showed a tendency to be higher, indicating that disturbances in FSH secretion, such as are caused by bFF, can be compensated for quickly. In this way the process of follicular maturation might be protected.
Concentrations of luteinizing hormone and progesterone in plasma during sexual development of the Khaki Campbell duck
Authors: Wilson Susan C. , Morris T. R. 
Published: December 2008

Concentrations of LH and progesterone were measured in the plasma of ducks which were, from 3 weeks of age, raised on either a constant photoperiod of 16 h light: 8 h darkness or a lighting schedule which simulated natural changes in daylength. In ducks raised on a constant photoperiod of 16 h light: 8 h darkness the plasma concentration of LH increased steeply between 7 and 3·5 weeks before the onset of lay. Concentrations of LH then declined, gradually at first, but then rapidly during the 7 days before the first oviposition in association with a pronounced increase in the plasma concentration of progesterone. During the 18 days before the first egg was laid there was a significant (P < 0·01) negative correlation between the plasma concentrations of LH and progesterone.
The patterns of LH release during sexual development of ducks raised on a schedule which simulated natural changes in daylength were variable but could be categorized according to the daylength at which each duck came into lay. In ducks coming into lay soon after the winter solstice when daylength was short (8·0–8·5 h light/day) there was a pronounced 15-fold prepubertal increase in the plasma concentration of LH although in some ducks high LH levels were not maintained until 3–4 weeks before the first oviposition and were not always followed by a rise in the plasma concentration of progesterone. In contrast, in ducks coming into lay when daylength had increased to 11·0–11·5 h light/day there were only minor fluctuations in the plasma concentration of LH until a small two- to threefold increase in LH was observed during the 2 weeks before the first oviposition.
Role of serotonin in the control of secretion of corticotrophin releasing factor
Authors: Holmes M. C. , Di Renzo G. , Beckford U. , Gillham B. , Jones M. T. 
Published: December 2008

The status of serotonin as a putative neurotransmitter involved in the control of the secretion of corticotrophin-releasing activity from the rat hypothalamus has been further investigated. The experimental model used for the investigation was the rat hypothalamus incubated in vitro. It was confirmed that serotonin causes a dose-related release of corticotrophin-releasing activity from the tissue and it was shown that this effect was mimicked by the addition to the tissue of chlorimipramine or d-fenfluramine, two drugs expected to cause an increase in the concentration of serotonin in the synaptic cleft. The effect of the latter drug was greatly reduced by the simultaneous addition of either methysergide or metergoline.
Destruction of serotonin-containing nerve terminals in the hypothalamus was caused by the intraventricular administration of the neurotoxic drug 5,7-dihydroxytryptamine. This treatment resulted in an 84% reduction of the serotonin concentration in the hypothalamus 12 days later. Hypothalami taken from animals 12 days after treatment with the drug secreted corticotrophin-releasing activity in basal amounts equal to those found in tissues taken from control rats, but showed supersensitivity in response to added serotonin. No such supersensitivity was seen in response to d-fenfluramine and a diminished response to chlorimipramine was noted. Despite its intraventricular route of administration, 5,7dihydroxytryptamine was found to increase the sensitivity of segments of anterior pituitary gland in vitro to low doses of preparations containing corticotrophin releasing factor.
These results are consistent with the view that endogenous serotonin can act as a stimulator of the secretion of corticotrophin-releasing activity from the rat hypothalamus. They also suggest that conclusions about the control of the release of this trophic material inferred from measurements of corticotrophin or corticosterone in the circulation must be viewed with caution when the drug 5,7-dihydroxytryptamine has been used, because of the development of supersensitivity both in the hypothalamus and in the anterior pituitary gland.
Diurnal changes in the plasma concentrations of corticosterone, luteinizing hormone and progesterone during sexual development and the ovulatory cycle of Khaki Campbell ducks
Authors: Wilson Susan C. , Cunningham F. J. , Morris T. R. 
Published: December 2008

Diurnal changes in hormonal concentrations were determined at various times during sexual development and during the ovulatory cycle of Khaki Campbell ducks raised either on a constant photoperiod of 16 h light: 8 h darkness (16L : 8D) or on a schedule which simulated natural changes in daylength. The ovulatory cycle of the latter group was studied when there were 11 h light/day and daylength was increasing.
In the laying duck concentrations of LH and progesterone in the plasma rose simultaneously between 7 and 4 h before ovulation and oviposition. Preovulatory concentrations of LH and progesterone in ducks subjected to photoperiods of 16L : 8D and 11L : 13D started to increase at the onset of darkness and 2 h after the onset of darkness respectively. In ducks maintained on 16L : 8D there was a rise in the concentration of corticosterone in the plasma at the onset of darkness to attain a maximum just before the onset of light. The temporal relationship of the peak of secretion of corticosterone to the cycle of light and darkness changed during sexual development of ducks raised on 16L : 8D with a 6-h advance in the phase of the rhythm between 11 weeks of age and the onset of egg laying. Highest progesterone concentrations during the day tended to coincide with the maximal secretion of corticosterone. A monophasic diurnal rhythm in the secretion of corticosterone in 11-week-old ducks maintained on natural daylength had disappeared by 15 weeks and was not re-established by 25 weeks of age. A diurnal variation in the plasma concentration of LH was not observed in the ducks maintained on 16L : 8D, although night-time LH concentrations tended to be higher than day-time concentrations in ducks raised on natural daylength. This difference was significant at 11 weeks, and at 15, 19 and 22 weeks changes in the plasma concentrations of LH during the night tended to parallel those of corticosterone.
Role of serotoninergic neurones in the control of gonadotrophin and prolactin secretion in the rat
Authors: Ruzsas Csilla , Limonta Patrizia , Martini L. 
Published: December 2008

The role of brain serotonin (5-hydroxytryptamine, 5-HT) in the control of LH, FSH and prolactin secretion was studied in two groups of experimental animals: intact adult male rats and ovariectomized adult female rats.
5-Hydroxytryptophan (5-HTP), a precursor of serotonin synthesis, and fluoxetine, a specific inhibitor of 5-HT uptake, were given either alone or together. 5-Hydroxytryptophan (50 mg/kg) was administered intraperitoneally and fluoxetine (20 μg/rat) was given into one of the lateral ventricles of the brain. Neither 5-HTP nor fluoxetine given alone affected LH secretion but combined treatment with the two drugs elicited a significant increase in serum LH levels in both intact male and ovariectomized female rats. Fluoxetine and 5-HTP, alone or together, did not modify FSH secretion in either kind of animal. In intact males and in ovariectomized females, 5-HTP induced a significant increase in prolactin release; fluoxetine alone was ineffective. In male animals treated with fluoxetine plus 5-HTP, serum prolactin levels increased but such an increase was lower than that found in the animals treated only with 5-HTP. In ovariectomized rats, the combined treatment induced an increase in serum prolactin levels similar to that found in animals treated with 5-HTP alone.
These data suggested that brain serotonin exerts a stimulating effect on LH secretion in both intact male and ovariectomized rats, but that it does not play any role in the control of FSH release in either kind of animal and that central serotoninergic pathways participate in the stimulating control of prolactin release from the anterior pituitary gland. However, some of the data also suggested the possibility of the existence in the brain of serotoninergic systems inhibiting prolactin secretion.