bluuebunny/crossref_metadata_2025_split huggingface dataset:
BIOLOGICAL SIGNIFICANCE OF ACTIVE AND INACTIVE RENIN IN MAN
Authors: LIJNEN P. , AMERY A. , FAGARD R. , VERSCHUEREN L. 
Published: December 2008

SUMMARY
The biological significance of active and inactive renin was investigated by comparison of an in-vitro assay of active, total and inactive plasma renin concentration (PRC), plasma renin activity (PRA) and plasma concentrations of angiotensin I and II with an in-vivo change in mean arterial blood pressure (MAP) produced by antagonism of angiotensin with treatment with saralasin and by blockade of angiotensin-converting enzyme by treatment with captopril.
A significant relationship between the changes in MAP during treatment with saralasin and captopril with the pretreatment levels of PRA, active and total PRC and angiotensin II were found; while the pre-existing level of inactive renin was not a predictor for the hypotensive effect of saralasin and captopril. During treatment with saralasin and captopril significant increases in PRA, plasma angiotensin I concentration and total and active PRC were found and no change in inactive PRC was observed.
ABSENCE OF OESTRADIOL-17β DEHYDROGENASE FROM THE PROGESTERONE-DOMINATED MOUSE UTERUS
Authors: CLARK B. F. 
Published: December 2008

SUMMARY
In the mouse uterus the development of sensitivity to a decidualizing stimulus requires large amounts of progesterone and small amounts of oestradiol-17β. During this process progesterone induces changes in the sensitivity of the tissues of the uterus to oestrogen. From observations of human endometrium it has been suggested that progesterone modulates the biological activity of oestradiol-17β by stimulating the metabolic conversion of oestradiol-17β to oestrone. Accordingly [6,7-3H]oestradiol-17β was injected subcutaneously into ovariectomized mice at various stages of the development of sensitivity to a decidualizing injection of oil into the uterine lumen. Radioactivity was extracted 4 h later, fractionated and identified. There was no alteration in the amounts of oestradiol, oestrone or water-soluble metabolites in the uteri whether the mice were treated with progesterone or with progesterone plus oestrogen or whether the uterine horns were decidualized for 24 or 48 h. The results suggest that in vivo the metabolism of oestradiol-17β by the uterus is not stimulated by progesterone.
ROLE OF CALCITONIN IN CALCIUM HOMOEOSTASIS IN THE CHICK EMBRYO
Authors: BAIMBRIDGE K. G. , TAYLOR T. G. 
Published: December 2008

SUMMARY
A radioimmunoassay for chicken calcitonin (CT) was used to study changes in the normal levels of CT in the circulation of chick embryos during incubation and in hatched chicks. The hormone was detectable in embryos whenever the plasma concentration of calcium was greater than 2·5 mmol/l. The level of CT at the time of 'pipping' was exceptionally high but when pipping was artificially advanced or retarded the peak of CT was dissociated from the physiological event of pipping. When embryos were injected with calcium, CT secretion was stimulated but the maximum level induced was substantially less than the normal peak level observed at pipping although an extreme degree of hypercalcaemia developed. When CT was removed from the embryonic circulation by injecting anti-CT plasma, a mild but statistically significant hypercalcaemia developed and in another experiment exogenous CT significantly decreased an artificially induced hypercalcaemia. The β-antagonist, propranolol, decreased and the β-agonist, isoprenaline, increased concentrations of CT in the circulation.
We suggest that the role of CT in the chick embryo may be to restrict the hypercalcaemia resulting from the large movement of calcium from the eggshell to the developing embryo and its yolk-sac and that one of the natural stimuli for the release of CT in the late stages of incubation could be β-adrenergic.
SHORT-TERM EFFECT OF TWO PESTICIDES ON THE SURVIVAL, OVARIAN 32P UPTAKE AND GONADOTROPHIC POTENCY IN A FRESHWATER CATFISH, HETEROPNEUSTES FOSSILIS (BLOCH)
Authors: SINGH H. , SINGH T. P. 
Published: December 2008

The effects of pesticides containing either an organophosphate malathion (Cythion) or an organochloride endrin (Hexadrin) on the survival, ovarian 32P uptake and the gonadotrophic potency of the pituitary gland and serum of Heteropneustes fossilis were studied for 96 h. Hexadrin was found to be more toxic than Cythion. Reduced ovarian 32P uptake and a significantly decreased level of total gonadotrophin in the pituitary gland and serum were seen when fish were placed either in a drug concentration that had been found to kill half the fish in 96 h or in a safe concentration of Hexadrin and Cythion in aquarium water. Administration of LH or homologous pituitary extract during the exposure of the fish to the pesticides increased the ovarian 32P uptake.
The data suggest that these pesticides retarded gonadotrophin secretion which in turn reduced ovarian 32P uptake. However, they did not interfere with the effects of exogenous LH or pituitary extract at the dose levels tested.
CONCENTRATIONS OF CORTICOSTERONE AND LUTEINIZING HORMONE IN PLASMA DURING THE OVULATORY CYCLE OF THE DOMESTIC HEN AND AFTER THE ADMINISTRATION OF GONADAL STEROIDS
Authors: WILSON SUSAN C. , CUNNINGHAM F. J. 
Published: December 2008

Plasma concentrations of corticosterone and LH were measured in hens in relation to the ovulation of an egg either early or late in a sequence and also in hens injected with gonadal steroids. In hens about to ovulate an egg early in the sequence, the plasma concentration of LH rose at the onset of darkness while levels of corticosterone remained low. As levels of LH fell during the 4 h preceding ovulation, those of corticosterone increased steeply to reach a maximum at about the time of ovulation, which is shortly after dawn. In contrast, in hens about to ovulate an egg late in a sequence, the concentration of LH in plasma fell and that of corticosterone tended to increase during the hours of darkness. During the 7 h preceding ovulation the temporal relationship of LH to corticosterone was similar to that observed before an early ovulation such that levels of corticosterone increased rapidly on the descending slope of the preovulatory LH surge and reached maximum values at the time of oviposition and ovulation.
Injections of oestradiol benzoate and testosterone propionate did not alter plasma concentrations of either corticosterone or LH. On the other hand, the injection of progesterone was associated with a rapid fall in levels of corticosterone. It is suggested that progesterone may suppress the pituitary–adrenal system and thus modulate the pattern of corticosterone secretion during the ovulatory cycle.
ANDROGEN RECEPTOR IN THE THUMB PAD OF RANA ESCULENTA: DYNAMIC ASPECTS
Authors: DELRIO GIOVANNI , CITARELLA FRANCA , D'ISTRIA MICHELA 
Published: December 2008

The androgen receptor (dissociation constant, 6 × 10−9 mol/l) present in the 105 000 g cytosol fraction of the thumb pad of Rana esculenta is hormone dependent. The number of testosterone binding sites decreased in the absence of the testes and in long-term castrated animals (75 days) became undetectable.
Administration of testosterone (50 ng) induced the replenishment of the cytoplasmic androgen receptor; its concentration also varied during the annual reproductive cycle.
HORMONAL REGULATION OF ANDROGEN-BINDING PROTEIN IN LAMB TESTES
Authors: CARREAU S. , DROSDOWSKY M. A. , PISSELET C. , COUROT M. 
Published: December 2008

Androgen-binding protein (ABP) was measured in the testes of 50-day-old lambs. The animals were hypophysectomized and treatment lasting for 5 days was begun 15 days after surgery. In hypophysectomized but otherwise untreated lambs (control group), no 5α-dihydrotestosterone binding was detectable in testicular cytosol. One out of four lambs gave a positive response with FSH treatment (25 fmol ABP/mg protein), whereas a restoration of the synthesis of ABP was noted in all LH-treated animals (19 ± 9 (s.e.m.) fmol ABP/mg, n = 4). No synergism between the two gonadotrophins was observed in lambs treated simultaneously with FSH and LH (19 ± 4 fmol ABP/mg, n = 5). Testosterone treatment elicited a greater response (37 ± 9 fmol ABP/mg, n = 5) than FSH or LH alone and the response was not increased by the simultaneous addition of FSH (38 ± 10 fmol ABP/mg, n = 5). Whatever the treatment, no influence was observed either on the number of supporting cells (undifferentiated Sertoli cells) or the length of the seminiferous tubules (P > 0·05); the diameter of tubules was significantly increased in the group treated with FSH and LH.
It is postulated that testosterone may have a direct effect on the production of ABP by the supporting cells of the impuberal lamb.
METABOLIC CHANGES IN TESTICULAR CELLS FROM RATS AFTER LONG-TERM EXPOSURE TO 37 °C IN VIVO OR IN VITRO
Authors: ROMMERTS F. F. G. , DE JONG F. H. , GROOTEGOED J. A. , VAN DER MOLEN H. J. 
Published: December 2008

Biochemical properties of isolated Leydig cells, Sertoli cells and spermatocytes from rat testes have been investigated after in-vivo or in-vitro exposure of these cells to abdominal temperature (37 °C). The rate of production of testosterone and pregnenolone by isolated Leydig cells from cryptorchid and normal testes from mature rats was not different. Production of pregnenolone by mitochondria prepared from cryptorchid testes was 6·7 times higher than production by mitochondria from normal testes.
Sertoli cells prepared from immature rats and incubated in vitro at 32 or 37 °C showed, on day 1 of the culture period, an initial twofold increase in the secretion of androgen-binding protein which was absent after 6 days in culture. In contrast, incorporation of [3H]leucine into secreted proteins was stimulated twofold on day 1 as well as by day 6 of culture. Secretion of oestradiol was increased 30-fold by day 6 when compared with the level found on day 1 when cells had been cultured at 37 °C and the increased secretion of oestradiol was maintained for approximately 2 days when the temperature of incubation was decreased to 32 °C Spermatocytes isolated from seminiferous tubules incubated for 20 h at 37 °C were active in the synthesis of RNA. No degeneration of these cells was observed in testes of 25-day-old rats 5 days after experimental cryptorchidism, whereas under similar conditions massive degeneration of spermatocytes was shown in the testes of mature rats.
These results suggest that the effects of temperature on the different testicular cells greatly depend on the experimental conditions used to study the effect of temperature.
STIMULATORY ACTION OF ANGIOTENSIN II ON WATER AND ELECTROLYTE TRANSPORT BY THE PROXIMAL COLON OF THE RAT
Authors: DE LOS RIOS A. DIEZ , LABAJOS M. , MANTECA A. , MORELL M. , SOUVIRON A. 
Published: December 2008

In segments of isolated proximal colon from bilaterally adrenalectomized and nephrectomized rats 10−12 g angiotensin/ml added to the serosal medium stimulated fluid transfer and sodium transport whose increase was accompanied by a decrease in transepithelial potential difference and short circuit current. Transepithelial electrical resistance remained unchanged. Replacement of chloride by sulphate in the bathing medium blocked the response to angiotensin. This suggested that angiotensin stimulated a coupled NaCl transport. Administration of aldosterone also blocked the response to angiotensin, suggesting that a low concentration of endogenous aldosterone is partly responsible for the action of angiotensin. This would explain the necessity for some form of pretreatment such as bilateral adrenalectomy and nephrectomy.
Hydraulic conductivity of proximal colon sacs was computed from the variation in the water flow from serosa to mucosa in response to an osmotic shock. A significant (P < 0·01) increase in the hydraulic conductivity of the proximal colon of bilaterally adrenalectomized and nephrectomized rats was found when 10−12 g angiotensin/ml was present in the serosal bathing medium. The observed decrease in the transepithelial potential difference has been related to an action of angiotensin on the paracellular shunt pathway.
CORRELATION OF CYCLIC AMP AND CYCLIC GMP ACCUMULATION AND STEROIDOGENESIS DURING STIMULATION OF BOVINE LUTEAL CELLS WITH LUTEINIZING HORMONE
Authors: LING W. Y. , WILLIAMS M. T. , MARSH J. M. 
Published: December 2008

The relationship between LH-induced steroidogenesis and the production of cyclic AMP and cyclic GMP was studied as a function of LH dose and time in isolated luteal cells from pregnant cows. Submaximal steroidogenic concentrations of LH caused a transient but significant rise in cyclic AMP that peaked after incubation for 5 min. A consequent rise in progesterone occurred at 30 min even though cyclic AMP had returned to the basal level at that time. Higher steroidogenic doses of LH elicited a maximum increase of cyclic AMP at 5 min and this was sustained for up to 1 h; the related progesterone production was significantly raised at 15 min and reached a maximum plateau at 30 min. The corresponding levels of cyclic GMP did not appear to be altered by any of the LH concentrations used.
The present study has provided direct evidence that even at very low doses of LH, cyclic AMP plays an intermediary role in the stimulation of steroidogenesis in a mixed population of cells isolated from the bovine corpus luteum. Cyclic GMP, on the other hand, did not appear to play a role in the action of LH on the same population of luteal cells.
PINEALECTOMY MILDLY DISTURBS THE SECRETORY PATTERNS OF PROLACTIN AND GROWTH HORMONE IN THE UNSTRESSED RAT
Authors: WILLOUGHBY J. O. 
Published: December 2008

Secretory profiles of prolactin and growth hormone (rGH) over a period of 6 h were obtained from unrestrained pinealectomized or sham-operated control male rats, both groups having been chronically implanted with right atrial cannulae and acclimatized to isolation in special blood sampling cages with a strict cycle of 12 h light: 12 h darkness (L: D). Hormone profiles were obtained from 2 h before to 4 h after the commencement of the light period.
In intact animals, secretion of prolactin was episodic without a clear ultradian rhythm except that secretory bursts tended to be larger during the dark period. Furthermore, a peak of prolactin occurred regularly at the commencement of the light period, even though subsequent peaks were diminished in amplitude. Mean concentrations of prolactin during the dark period were significantly higher than later daytime values, supporting the view that there is a diurnal prolactin rhythm. Pinealectomy altered the secretory patterns in prolactin so that peaks became more prominent early in the light period but mean concentrations of prolactin eventually fell as they did in control animals and there was no difference in concentrations of prolactin over a period of 6 h between the two groups. Pinealectomy, therefore, slightly delayed the fall in mean prolactin concentrations which normally occurs in the light period.
Secretion of rGH was rhythmic with interpeak intervals and mean concentrations in which there were no differences between control and pinealectomized groups. Inhibition of secretory episodes of rGH by the interface between darkness and light was impaired in pinealectomized animals with a delay in the appearance of the first diurnal trough.
It was concluded that pinealectomy attenuates L: D cycle regulation of secretory rhythms of prolactin and rGH to a minor degree.
MECHANISM OF THE SELECTIVE SURGE OF FOLLICLE-STIMULATING HORMONE IN DIOESTROUS RATS DURING THE INDUCTION OF OVULATION BY HUMAN CHORIONIC GONADOTROPHIN
Authors: SASAMOTO SHUJI , TAYA KAZUYOSHI 
Published: December 2008

A selective surge of FSH with a small concomitant rise in LH occurred invariably in rats when ovulation was induced by injecting human chorionic gonadotrophin (HCG) at various reproductive stages such as day 15 of lactation and in 29-day-old immature rats as well as in dioestrous animals. No FSH surge occurred on day 3 of lactation or in 26-day-old immature rats in which ovulation could not be induced by HCG. The FSH surge occurred 6–18 h after HCG treatment regardless of the time of day of injection of HCG. Ovulation began by 12 h and was completed by 18 h after injection of HCG.
Pituitary responsiveness to luteinizing hormone releasing hormone (LH-RH) with respect to FSH release strikingly increased at 01.00 h on day 1 after HCG injection at 17.00 h of dioestrus (day 0) to levels similar to those of the group at 01.00 h of oestrus, when the greatest response was noted during the normal cycle. With regard to LH release pituitary responsiveness to LH-RH at 01·00 h on day 1 markedly increased but the response was only about half of the response at 01·00 h of oestrus and one third of the response at 17.00 h of pro-oestrus when the greatest response was noted during the normal oestrous cycle.
These results indicate that during ovulation the pituitary gland of the rat is highly responsive to LH-RH with respect to the release of FSH, for which secretory changes in the ovary after an ovulating dose of HCG may be responsible.
LUTEINIZING HORMONE RELEASING FACTOR IN PITUITARY STALK PLASMA FROM LONG-TERM OVARIECTOMIZED RATS: EFFECTS OF STEROIDS
Authors: SARKAR D. K. , FINK G. 
Published: December 2008

The concentration of LH releasing factor (LH-RF) was measured by radioimmunoassay in blood collected from the cut pituitary stalk of long-term ovariectomized rats anaesthetized with Althesin. Stalk plasma LH-RF concentrations were increased immediately after ovariectomy (carried out at oestrus) and low at 2 and 4 days after operation. The concentrations then began to increase to reach a level at 24–28 days which was significantly higher than the concentrations during the oestrous cycle except for the time of the ovulatory surge at pro-oestrus. This pattern was similar to that of the concentrations of LH in jugular venous plasma taken from the same animals before exposure of the pituitary stalk. Like peripheral plasma LH concentrations, the concentrations of LH-RF in stalk plasma fluctuated and fell significantly and rapidly after the intravenous injection of 1 μg oestradiol-17β. The release of LH-RF in long-term ovariectomized rats, into which had been implanted an oestradiol-containing Silastic capsule, was similar to the diurnal pattern of LH release; the afternoon increase in stalk plasma LH-RF concentration could be blocked by sodium pentobarbitone administered at 13.00 h and augmented by administering this anaesthetic at 13.00 h of the preceding day. The stalk plasma LH-RF concentrations in animals injec[unk]d with oestradiol benzoate (OB) followed 72 h later with either OB or progesterone were lower than the concentrations in animals injected only with oil.
These data show that in the rat (1) ovarian steroids could moderate LH release ('negative feedback') by inhibiting LH-RF release, and that in long-term ovariectomized animals (2) the oestradiol-induced circadian pattern of LH release is due to a circadian pattern of LH-RF release, and (3) the surge of LH produced by administering OB followed by either OB or progesterone is probably due mainly to a massive increase in the responsiveness of the anterior pituitary gland to LH-RF.
A COMPARISON OF THE EFFECTS OF FOUR ERGOT DERIVATIVES ON PROLACTIN SECRETION BY DISPERSED RAT PITUITARY CELLS
Authors: DELITALA G. , YEO T. , GROSSMAN ASHLEY , HATHWAY N. R. , BESSER G. M. 
Published: December 2008

The inhibitory effects of dopamine and various ergot alkaloids on prolactin secretion were studied using continuously perfused columns of dispersed rat anterior pituitary cells. Bromocriptine (5 nmol/l) and lisuride hydrogen maleate (5 nmol/l) both inhibited prolactin secretion, the effects persisting for more than 3 h after the end of the administration of the drugs. A similar although less long-lasting effect was observed with lergotrile (50 nmol/l) and the new ergoline derivative, pergolide (5 nmol/l). These effects contrasted with the rapid disappearance of the action of dopamine. The potency estimates of the ergots relative to that of dopamine were: lergotrile, 2·3; bromocriptine, 13; lisuride, 15; pergolide, 23.
The dopamine-receptor blocking drugs, metoclopramide and haloperidol, antagonized the prolactin release-inhibiting activity of the compounds; bromocriptine and lisuride showed the highest resistance to this dopaminergic blockade.
The results suggested that the direct effect of the ergot derivatives on dispersed pituitary cells was mediated through dopamine receptors and emphasized the long-lasting action of bromocriptine and lisuride in vitro.
PROGESTERONE LEVELS AFTER INDUCTION OF OVULATION IN DIOESTROUS RATS
Authors: SHIROTA MARIKO , SASAMOTO SHUJI 
Published: December 2008

Maximal levels of progesterone in the plasma after premature ovulation induced by either the administration of human chorionic gonadotrophin (HCG) or LH-releasing hormone (LH-RH) to dioestrous (day 0) rats were observed from 33 to 45 h but decreased 3 h earlier than after spontaneous ovulation. This suggested an earlier decline in the secretory activity of corpora lutea formed from premature ovulations than that of corpora lutea formed during a normal oestrous cycle.
The next spontaneous ovulation occurred 4 days (day 5) after premature ovulation induced by LH-RH on day 0. A single s.c. injection of 2·5 μg oestradiol-17β (OE2) at 10.00 h on day 2 to these animals advanced the next spontaneous ovulation by 1 day. A normal number of oocytes was shed, indicating that earlier secretion of oestrogen on day 2 had advanced the next spontaneous ovulation. A single injection of 2·5 μg OE2 to normal 4-day cyclic rats at metoestrus failed to advance the next ovulation. An earlier decline of progesterone levels in the plasma of rats after premature ovulation as compared with spontaneous ovulation may explain the greater effectiveness of oestrogen in the former group.
The progesterone surge was observed during the period of premature ovulation in both HCG- and LH-RH-treated groups. This progesterone release in the periovulatory period may be responsible for the inhibition of gonadotrophin surges on the expected day of prooestrus (day 1).
INHIBITION OF SECRETION OF LUTEINIZING HORMONE INDUCED BY ELECTROCHEMICAL STIMULATION OF THE ANTERIOR CINGULATE CORTEX MEDIATED BY A β-ADRENERGIC MECHANISM
Authors: CACERES A. , TALEISNIK S. 
Published: December 2008

Release of LH occurred in ovariectomized, oestrogen-primed rats when the medial preoptic area (mPOA) was electrically stimulated with monophasic square pulses of 1 ms duration (50 Hz, 150 μA, 15 s on and 15 s off for 30 min). Electrochemical stimulation of the anterior cingulate area applied immediately after the first 15 min period of stimulation in the mPOA completely prevented the rise in LH normally observed during the following 15 min. This effect was suppressed either by selective blockade of noradrenaline synthesis with diethyldithiocarbamate, or following systemic or intraventricular injection of the βadrenergic blocker, propranolol, whereas it did not change after systemic atropine, pimozide or phenoxybenzamine. Isoprenaline, a β-adrenergic agonist, injected into the third ventricle of rats stimulated in the mPOA mimicked the effect of the cortical stimulation, this effect was also blocked by propranolol. Intraventricular administration of propranolol or of isoprenaline had no effect on the release of LH induced by the injection of gonadotrophin releasing hormone, showing that their action is not directly on the pituitary gland. Intraventricular injection of noradrenaline, which failed to affect the release of LH induced by stimulation in the mPOA, inhibited this release when animals were pretreated with phenoxybenzamine. On the other hand, the LH-releasing potency of noradrenaline was greatly increased if the β-receptors were blocked.
From these results it may be concluded (1) that inhibition of the secretion of LH evoked by electrochemical stimulation of the anterior cingulate cortex is mediated by an adrenergic mechanism involving a β-receptor and (2) that noradrenaline exerts an inhibitory effect on the secretion of LH through a β-receptor in addition to the known facilitatory action through an α-receptor.