bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of restriction of placental growth on the concentrations of insulin, glucose and placental lactogen in the plasma of sheep
Authors: Falconer J. , Owens J. A. , Allotta E. , Robinson J. S. 
Published: December 2008

ABSTRACT
The effect of restricting placental growth on maternal glucose, insulin and placental lactogen was investigated in 16 ewes carrying singleton lambs. Uterine caruncles were removed from seven ewes (caruncle ewes) before pregnancy, resulting in reduced placental size and retarded intra-uterine fetal growth. The concentration of insulin in maternal plasma was similar in both control and caruncle ewes. The concentration of glucose was significantly higher in the caruncle than in the control ewes (3·26 ± 0·15 (s.e.m.) mmol/l, number of observations (n) = 9, vs 2·75 ± 0·1, n = 9, P<0·02, and 3·27 ±0·16, n = 7, vs 2·46± 0·11, n = 12, P<0·001, for the carotid artery and utero-ovarian vein respectively). The concentration of ovine placental lactogen (oPL) in the utero-ovarian vein was reduced in the caruncle compared with the control ewes (283± 65 μg/l, n = and 705±106 μg/l, n = 18, P<0·02, respectively). Restriction of placental growth by removal of endometrial caruncles similarly reduced the concentrations of oPL in maternal arterial plasma (231±54 μg/l, n = 9, and 621±96 μg/l, n = 18, P<0·002). Production of oPL by the placenta was also reduced by limiting placental growth to 30±11 μg/min, n = 8, compared with 133±43 μg/min, n = 15, P<0·05, for the controls. Production of oPL per gram of placenta in the caruncle group, although only 34% of the control value, was not reduced significantly. These observations are consistent with the hypothesis that oPL may be involved in the redirection of maternal glucose during pregnancy to maximize the amount available for the fetus.
J. Endocr. (1985) 106, 7–11
Precocious ovulation induced by human chorionic gonadotrophin in the immature female rat: comparison of follicle growth induced by treatment with human chorionic gonadotrophin and by electrical stimulation of the hypothalamus
Authors: Meijs-Roelofs H. M. A. , Kramer P. , Osman P. 
Published: December 2008

ABSTRACT
Precocious first ovulation, preceded by an endogenous preovulatory LH surge, could be predictably induced in immature female rats by administering repeated injections of human chorionic gonadotrophin (hCG). Administration of a dose of 0·05–0·075 i.u. hCG, four times a day from day 28 to day 31 of age resulted in a highly constant ovulatory response: at 4·0±0·0 days after the start of treatment 7·7±0·3 (n = 15) ova were found. Use of a higher dose of hCG (0·1 i.u.) resulted in lower numbers of ova (5·6±0·4, n = 7; P<0·005) whereas use of a lower dose of hCG (0·025–0·038 i.u.) resulted in a less constant timing of the induced ovulation at 5·4±0·2 days after the start of treatment (n = 7; P<0·0005). In animals treated with the dose of 0·05–0·075 i.u. hCG, a positive correlation was found between body weight at the start of treatment and the number of ova released (r = 0·75, n = 25; P<0·001).
Ovarian follicle dynamics were studied on the various days of hCG treatment (dose 0·05–0·075 i.u.) and compared with the follicle changes that take place after electrical stimulation of the hypothalamus, performed on day 28, a treatment known to result in first ovulation 4–5 days later. In both groups a decrease in the number of the smallest and the middle-sized antral follicles as compared with their respective controls was seen, whereas numbers of follicles in the largest, 'ovulatable' size classes gradually increased. The pattern was more conspicuous in the hCG-treated group, presumably related to greater constancy in timing of the ovulatory response in this group.
The present data support the view that endogenous changes in LH secretion during late prepuberty (which have been found to take place) play a significant role in stimulating late-prepubertal follicle growth and the ensuing first ovulation.
J. Endocr. (1985) 106, 61–66
Induction of ovulation in vitro in the hen: dependency of the response to LH on age and rate of lay
Authors: Moudgal R. P. , Razdan M. N. 
Published: December 2008

ABSTRACT
Two experiments were conducted on White Leghorn hens to investigate the effect of different concentrations of LH on the frequency of induction of ovulation in vitro of ovarian follicles collected 18–20 h before the expected time of ovulation from birds of three different ages (7, 18 and 30 months) or of the same age but laying short (three to four) or long (more than seven) sequences of eggs. The ability of LH to induce ovulation was directly related to the age of the donors of the follicles. Follicles derived from hens laying short sequences of eggs were less responsive to the ovulation-inducing effects of LH than were follicles from birds laying long sequences. These observations suggest that the sensitivity of ovarian follicles to the ovulation-inducing effects of LH declines with age and is greater in hens laying long sequences of eggs than those laying short sequences.
J. Endocr. (1985) 106, 67–69
Infantile ovariectomy potentiates the stimulatory effect of oestrogen/progesterone on LH secretion in the rat
Authors: Wilkinson M. , Bhanot R. 
Published: December 2008

ABSTRACT
Ovariectomy of prepubertal rats (9 days of age) eliminates the ability of the opiate peptide FK 33-824 to inhibit LH secretion when tested 19 days later. We have investigated whether this removal of opiate inhibition would modify the LH/FSH response to stimulation with oestradiol benzoate/progesterone priming. Ovariectomy of rats during infancy (9 days after birth) amplifies the stimulatory effects of these steroids on LH/FSH secretion when tested 19 days later. This amplification was not seen in rats ovariectomized before (day 24) or after puberty (day 43) and tested 19 days later. The pituitary content of LH/FSH does not appear to contribute to this phenomenon, though increased responsiveness to injected gonadotrophin-releasing hormone (GnRH) is clearly involved; ovariectomy at day 9 is considerably more effective than ovariectomy at day 24 of life in enhancing the response to GnRH.
We conclude that infantile ovariectomy either removes, or prevents the development of, a hypothalamic inhibitory mechanism which normally modulates the responsiveness of the pituitary to stimulation with GnRH.
J. Endocr. (1985) 106, 133–139
Influence of neonatal hemicastration on in-vitro secretion of inhibin, gonadotrophins and testicular steroids in male rats
Authors: Ultee-van Gessel A. M. , Leemborg F. G. , de Jong F. H. , van der Molen H. J. 
Published: December 2008

ABSTRACT
Pituitary secretion of FSH in male animals is regulated, at least partly, by a protein hormone, inhibin, which is produced by Sertoli cells in the testes. To establish at which age the role of testicular inhibin in the regulation of FSH secretion becomes apparent, groups of male rats were hemicastrated or sham-operated on day 1 of life and pituitary and testicular function were investigated in vitro at 21, 42 or 63 days of age.
Testis weights were increased in hemicastrated rats at all ages studied. Peripheral concentrations of gonadotrophins generally showed a good correlation with the concentrations of FSH and LH measured in the medium of hemipituitary glands which were incubated in vitro at 37 °C in the absence or presence of LH-releasing hormone. Peripheral testosterone concentrations in hemicastrated animals were not significantly different from those in sham-operated rats at all ages studied. Steroid production by Leydig cells in vitro was not significantly influenced by hemicastration. The secretion of inhibin by Sertoli cells from 21-day-old hemicastrated rats was decreased while Sertoli cells from 42- and 63-day-old hemicastrated animals secreted slightly but not significantly more inhibin than Sertoli cells from sham-operated rats.
It is concluded that although compensatory increases of testosterone and inhibin production at later ages make it difficult to draw conclusions about the relative importance of inhibin in the feedback regulation of FSH secretion at different ages, it is likely that inhibin plays a role in the feedback of FSH in immature, rather than in mature male rats.
J. Endocr. (1985) 106, 259–265
Hydrolysis of deoxycorticosterone-21-yl sulphate and dehydroepiandrosterone sulphate by microsomal preparations of human placentae: evidence for a common enzyme
Authors: Egyed J. , Oakey R. E. 
Published: December 2008

ABSTRACT
The human placenta can hydrolyse both dehydroepiandrosterone-3β-yl sulphate (DHASO4−) and deoxycorticosterone-21-yl sulphate (DOCSO4−). There is some uncertainty as to whether the same or different enzymes are responsible for hydrolysis of these substrates. As a fresh approach to this problem we have compared the quantities of DHASO4− and DOCSO4− hydrolysed by microsomal preparations of placentae obtained from 14 normal pregnancies and from 14 pregnancies complicated by steroid sulphatase deficiency.
Under the conditions used, and standardizing the results to unit time and quantity of protein, 1380–8830 fmol DHASO4− were hydrolysed by 14 normal placentae whereas < 1000 fmol DHASO4− were hydrolysed by the other 14 placentae, thereby designated as steroid sulphatase deficient. Net hydrolysis of DOCSO4− by the preparations of normal tissue was 9–52 fmol; hydrolysis of this substrate by steroid sulphatase-deficient tissues was indistinguishable from that by boiled tissue (< 29 fmol). Thus preparations of placentae which hydrolysed DHASO4− also hydrolysed DOCSO4− ; tissues which did not hydrolyse DHASO4− also failed to hydrolyse DOCSO4−.
The quantities of DHASO4− and DOCSO4− hydrolysed by the 28 individual placentae showed a positive correlation (r = 0·91, P < 0·001). The apparent Michaelis constants for hydrolysis of DHASO4− and DOCSO4− were 38 and 274 μmol/l respectively.
These results are consistent with the proposal that these substrates are hydrolysed by a common enzyme.
J. Endocr. (1985) 106, 295–301
Functional development of the oxytocin release mechanism and its role in the initiation of parturition in the rat
Authors: Higuchi T. , Uchide K. , Honda K. , Negoro H. 
Published: December 2008

ABSTRACT
Developmental changes in levels of oxytocin in the blood and the pituitary gland and in oxytocin responses to oxytocin-releasing stimuli were investigated in the rat from the fetus close to term to the 40-day-old young adult. The oxytocin content of the pituitary gland rose gradually from fetuses of 21 days of gestation to 40-day-old rats. Pituitary oxytocin levels expressed in terms of body weight also increased up to day 25 after birth and declined slightly thereafter. In contrast, serum concentrations of oxytocin increased from day 21 of pregnancy up to day 5 after birth but were stable thereafter. Oxytocin levels in both blood and the pituitary gland were equal in 23-day-old fetuses and 1-day-old infants born on day 22 of pregnancy. There was no difference in serum and pituitary oxytocin levels in newborn pups and unborn littermates of day 22 or 23 of gestation. The i.p. injection of hypertonic saline induced a significant increase in serum oxytocin levels on day 5 and later, but no effect in the fetus on day 22 of gestation and in the 1-day-old infant. The responsiveness to the osmotic stimuli increased after 5 days of age. The i.p. injection of diethyl-dithiocarbamate, a noradrenaline synthesis inhibitor, or phenobarbitone was effective in raising blood oxytocin levels only in rats older than 10 and 20 days of age respectively. These findings, that a gradual increase in oxytocin levels in both blood and the pituitary gland without an apparent increase in its release and the absence of a pituitary response to oxytocin-releasing stimuli during the perinatal period, do not support a role for fetal oxytocin in the initiation of labour in the rat.
J. Endocr. (1985) 106, 311–316
Evidence for a spinal site at which opioids may act to inhibit the milk-ejection reflex
Authors: Wright D. M. 
Published: December 2008

ABSTRACT
Morphine was injected into the lumbar subarachnoid space of anaesthetized lactating rats (7–10 days post partum) to examine its effect on the milk-ejection reflex at a spinal level. Although the delay until the first milk-ejection response to the suckling of hungry pups was variable (3–60 min) the subsequent responses occurred at regular intervals of 7·5± 0·4 min; milk-ejection responses were detected by measurement of intramammary pressure and by the characteristic behaviour of the pups. Injection of morphine (4–50 μg) via a cannula inserted into the spinal subarachnoid space inhibited reflex milk ejection in a dose-related manner without affecting the sensitivity of the mammary gland to exogenous oxytocin (1 mu., i.v.); injection extradurally was without effect. The opiate antagonist naloxone (10 μg), when injected intrathecally, did not significantly alter the pattern of reflex milk ejection or the amplitude of the intramammary pressure response, but prevented the inhibitory effect of morphine when administered with the opiate. Pethidine (250 and 400 μg) also inhibited the milk-ejection reflex.
It is unlikely that the effect of spinal administration of morphine occurred as the result of the transportation to a supraspinal site since release of oxytocin evoked by intraventricular injection of hypertonic sodium chloride (3 mol/l) was blocked by intraventricular injection of morphine (4 μg) but not by a much larger dose (40 μg) injected intrathecally.
J. Endocr. (1985) 106, 401–407
CATECHOL OESTRADIOL CONTROL OF FSH-STIMULATED GRANULOSA CELL STEROIDOGENESIS
Authors: Hudson K.E. , Hillier S.G. 
Published: December 2008

ABSTRACT
Catechol oestrogens are formed in the ovary but it is not known if they have a local function. Working with primary granulosa cell cultures prepared from immature rat ovaries, we found that the presence of 2-hydroxyoestradiol in the culture medium (48 h incubation) dramatically enhanced the steroidogenic response (progesterone production) to human FSH (100 ng/ml). The effect of 2-hydroxyoestradiol was dose-dependent and maximal (approximately 40 times the response to FSH alone) at 3.0 μM. The stimulatory action of 1.0 μM 2-hydroxyoestradiol was >10 times more than that of 1.0 μM oestradiol but only half that of 1.0 μM testosterone; other catechol oestrogens (2-hydroxyoestrone, 4-hydroxyoestradiol, 2-methoxyoestradiol and 2-methoxyoestrone) were not stimulatory. The stimulatory actions of 2-hydroxyoestradiol and testosterone were partially additive and each was antagonized in the same way by the presence of a specific antiandrogen (SCH16423). These observations suggest a role for intrafollicular catechol oestradiol in modulating FSH-stimulated granulosa cell steroidogenesis; its mechanism of action may be similar to that of testosterone.
CORTISOL IS NATRIURETIC IN THE IMMATURE OVINE FETUS.
Authors: Wintour E.M. , Coghlan J.P. , Towstoless M. 
Published: December 2008

ABSTRACT
Cortisol was infused, intravenously, for 4 h continuously into 5 chronically cannulated ovine fetuses at 111-120 days of gestation (term is 142-152 days). The dose used was 100 μg/h, and raised fetal blood cortisol concentrations from 8.2±4.0 to 56.5±19.0 nmol/l (values are mean ± SEM). The effects observed were 1) a 4-5 fold increase in sodium and chloride excretion, 2) a doubling of potassium excretion and free water clearance, 3) no significant changes in urine pH, urea and creatinine excretions, and 4) an increase in urine osmolality from 129±7.5 to 154.4±11.3 mosmol/kg water. There were no significant changes in any of the measured parameters in 5 fetuses infused with 0.9% NaCl for 4 h. It is suggested that the hyponatremia and inability to retain sodium observed in many premature or very low birth weight babies may be due to the fact that their kidneys are behaving as fetal rather than neonatal organs and responding to the high plasma cortisol concentrations found in such babies with a natriuresis.
Electrical responses of cultured porcine thyroid cells to adrenergic agents
Authors: McGrath P. A. , Bourke J. R. , Huxham G. J. , Manley S. W. 
Published: December 2008

ABSTRACT
The membrane potential of cultured porcine thyroid follicular cells depolarized by up to 20 mV from the resting value of about − 73 mV on exposure to β-adrenoceptor agonists. A similar response was induced by TSH or dibutyryl cyclic AMP. α-Adrenoceptor agonists were without effect. The receptor subtype was shown to be (at least predominantly) β2 by the order of potency for β-agonists (isoprenaline ≅ fenoterol⪢adrenaline >noradrenaline) and by the relative potency of selective β-antagonists (ICI 118,551 ⪢atenolol). The α-agonist phenylephrine had no effect on the TSH response but weakly inhibited the β-agonist response. Rather than a physiological antagonism between α- and β-adrenoceptor-mediated responses, this effect was shown to be due to the weak β-antagonist effect of phenylephrine since the α-antagonist phentolamine failed to potentiate the depolarizing response to the mixed agonist nor-adrenaline, and also failed to block the inhibitory action of phenylephrine on the β-agonist effect. Sensitivity to β-agonist was enhanced by omission of serum from the culture medium and reduced by exposure to β-agonists or a high concentration of TSH or dibutyryl cyclic AMP.
J. Endocr. (1985) 107, 23–30
Pituitary gonadotrophin-releasing hormone receptor up-regulation in vitro: dependence on calcium and microtubule function
Authors: Young L. S. , Naik S. I. , Clayton R. N. 
Published: December 2008

ABSTRACT
Exogenous cyclic adenosine nucleotides increase gonadotrophin-releasing hormone (GnRH) receptors in intact cultured rat pituitary cells in a similar manner to that observed with GnRH itself. In this study the calcium and microtubule dependency of GnRH receptor up-regulation was examined in vitro. Treatment of pituitary cells in Ca2+ and serum-containing media with either GnRH (1 nmol/l), K+ (58 mmol/l) or dibutyryl cyclic AMP (dbcAMP; 1 mmol/l) for 7–10 h routinely resulted in a 50–100% increase in GnRH receptors. Incubation of pituitary cells with the calcium channel blocker verapamil, for 7 h, or the calcium chelator EGTA, for 10 h, had no effect on basal receptor levels but prevented the increase in GnRH receptors stimulated by either GnRH, K+ or dbcAMP. Luteinizing hormone release measured with the same stimulators over a 3-h period was prevented by both verapamil and EGTA. Calcium ionophore (A23187) increased GnRH receptors by 40–60% at low concentrations (10 and 100 nmol/l) while higher concentrations (10 and 100 μmol/l) reduced receptor levels. Luteinizing hormone release was not increased by receptor-stimulating concentrations of A23187, but was by higher concentrations (10 μmol/l). None of these pretreatments, for up to 10 h, impaired the subsequent LH response of the cells to increasing doses of GnRH.
Vinblastine (1 μmol/l did not affect basal receptor levels but markedly reduced the increase in GnRH receptors stimulated by GnRH, K+ and dbcAMP. This concentration of vinblastine had no effect on LH release. These results indicate that receptor stimulation by GnRH, K+ and dbcAMP is a calcium-dependent process requiring the integrity of the microtubule system and there is a different calcium requirement for the processes of GnRH receptor up-regulation and LH secretion.
J. Endocr. (1985) 107, 49–56
Cortisol kinetics and fluid distribution in brook trout (Salvelinus fontinalis)
Authors: Nichols D. J. , Weisbart M. , Quinn J. 
Published: December 2008

ABSTRACT
Cortisol kinetics were examined in brook trout (Salvelinus fontinalis) to assess possible relationships with body fluid distribution during acclimation to sea water (SW). The disappearance curve of [3H]cortisol in plasma, after a bolus injection, was analysed by compartmental analysis using a three-pool mammillary model. The results indicated that only ∼ 10% of the total exchangeable cortisol was located in the plasma pool. Over 75% of the total cortisol was associated with a large slowly exchanging pool and the remaining cortisol was located in a second extravascular tissue pool which was in rapid exchange with the plasma pool.
Two days after transfer of trout from fresh water to SW, when plasma chloride concentration was at a new steady state, body weight, intracellular fluid volume, haematocrit and inulin clearance rate were lowered but plasma, blood and extracellular volumes were unaltered. Cortisol plasma clearance rate was unaltered but plasma cortisol concentration, cortisol secretion rate, total cortisol pool size and interpool transport rates were increased. These results are consistent with an acute role for cortisol in SW adaptation of brook trout.
The fraction of the total cortisol cleared was smaller and the average time that cortisol spent in the tissue pools was slightly longer in trout after transfer to SW, possibly reflecting altered fluid dynamics. The fractional disappearance rate was larger at higher plasma cortisol concentrations in the SW trout. This relationship is compatible with the hypothesis that cortisol protein binding protects cortisol from metabolism.
J. Endocr. (1985) 107, 57–69
Single nephron function during prolactin-induced pseudopregnancy in the rat
Authors: Walker J. , Garland H. O. 
Published: December 2008

ABSTRACT
Whole kidney and renal micropuncture techniques were used to investigate the effects of chronic prolactin treatment on kidney function in anaesthetized female rats. At the whole kidney level, glomerular filtration rate (GFR) and fluid reabsorption were both significantly (P<0·02) increased in the hormone-treated group. At the single nephron level, GFR and proximal fluid reabsorption were also increased (P<0·05) by prolactin treatment. Fractional reabsorption was also enhanced at the proximal tubular level in hormone-treated animals. Such changes in renal function are similar to those seen in rat pregnancy and cervically stimulated pseudopregnancy. Since circulating prolactin concentrations are increased in both reproductive states, the hormone may play an important role in establishing the characteristic renal changes seen therein.
J. Endocr. (1985) 107, 127–131