bluuebunny/crossref_metadata_2025_split huggingface dataset:
Age- and sex-dependent stimulation of growth rate in rats by the adrenal inhibitor trilostane
Authors: Sillence M. N. , Rodway R. G. 
Published: December 2008

ABSTRACT
The effects of the adrenal inhibitor trilostane were examined in male and female rats to determine whether growth rate could be improved by lowering circulating plasma corticosterone concentrations.
Dose–response studies revealed that in young female rats (125 g) trilostane lowered peak plasma corticosterone levels in a dose-dependent manner. In male rats plasma corticosterone concentrations were reduced only by very high doses of trilostane (200 mg/kg), while lower doses (2–8 mg/kg) actually increased them.
Five growth studies were conducted using a total of 90 rats. In female animals, daily injections of trilostane (10 mg/day) caused an age-dependent increase in growth rate ranging from 11% in 127 g rats to 30% in 164 g rats. In three out of four experiments using females, food intake was slightly increased by the drug. Food conversion efficiency was improved consistently by trilostane by up to 18%. Trilostane-treated females had significantly heavier adrenal glands and livers, but lighter kidneys than control rats. When a complete carcass analysis was performed on one experimental group, no significant differences were found. Carcass component weights relative to control values were: body weight (103%), body water (105%), fat-free solids (103%), carcass weight (103%), body length (103%), body fat (95%) and gut content (96%).
In male rats (160 g), daily injections of trilostane (10 mg) resulted in a steady and sustained depression of growth rate reflecting a similar fall in food intake, with no change in food conversion efficiency.
It is concluded that in older female rats growth rate is constrained by physiological concentrations of glucocorticoids. Younger females are either less sensitive to trilostane or to changes in plasma corticosterone levels. Male rats are less responsive to adrenal suppression by trilostane than are females of a similar age and do not exhibit an anabolic response to this drug.
J. Endocr. (1987) 113, 479–484
Inhibition of progesterone secretion by a 3β-hydroxysteroid dehydrogenase inhibitor in pregnant goats
Authors: Taylor M. J. 
Published: December 2008

ABSTRACT
Epostane, an inhibitor of 3β-hydroxysteroid dehydrogenase, was administered to goats in late pregnancy in the presence or absence of concurrent treatment with prostaglandin synthetase inhibitors (indomethacin and diclofenac sodium) and the effect on steroidogenesis in the corpus luteum and adrenal cortex determined by measurement of peripheral concentrations of progesterone and cortisol respectively. Concentrations of both steroids were reduced to about 20% of pretreatment levels within 6 h of epostane administration. Cortisol concentrations subsequently increased about 24 h after epostane administration and returned to and exceeded pretreatment values, but progesterone concentrations remained suppressed until premature delivery, which occurred in all animals 44 ± 2 h (mean ± s.e.m.) after epostane administration. However, combined administration of epostane and prostaglandin synthetase inhibitor prevented the onset of labour in the majority of animals, but progesterone secretion in animals receiving this combined treatment did not differ from that in animals given epostane alone. It is concluded that progesterone withdrawal is an important component of the mechanisms which initiate parturition in the goat and that increased prostaglandin synthesis is essential for delivery in this species, but perhaps not for luteolysis.
J. Endocr. (1987) 113, 489–493
Storage and release of secretory granules in human prolactinomas: modification by bromocriptine
Authors: Landolt A. M. , Osterwalder V. , Landolt T. A. 
Published: December 2008

ABSTRACT
Electron microscopic morphometric evaluation of the effects of bromocriptine on human prolactinomas during and after short-term parenteral (7 days) and long-term peroral (4–6 weeks) treatment showed that a reduction in size of prolactinoma cells occurs within a few days (half-time to maximum shrinkage, 2·2 days). The number of secretory granules discharged into the intercellular space increased after short-term treatment by a factor of three but the total volume of stored secretory granules did not change significantly. The total volume of cellular lysosomes, both primary and secondary, decreased significantly to about one-half of the pretreatment value. The amount of stored lipoids, end-products of lysosomal activity, decreased in specimens treated for 7 days, but returned to pretreatment levels in specimens treated for 4–6 weeks, suggesting that lysosomal material is discharged from the cells together with the secretory material.
J. Endocr. (1987) 113, 495–499
Plasma growth hormone, somatostatin, insulin and glucagon inter-relationships during infusion of human pancreatic growth hormone-releasing factor in young and adult ducks (Anas platyrhynchos)
Authors: Foltzer-Jourdainne Ch. , Harvey S. , Karmann H. , Mialhe P. 
Published: December 2008

ABSTRACT
Human pancreatic GH-releasing factor (hpGRF) increased the concentrations of plasma GH when infused i.v. into immature ducks. A dose-dependent increase in plasma GH was observed within 10 min of the start of infusion and was maintained during the 30-min infusion period. Simultaneous infusion of somatostatin S-14 prevented the increase in plasma GH induced by hpGRF, but when the infusion had finished there was a rebound increase in plasma GH. Infusion of the highest dose of hpGRF (800 ng/kg per min) in adult ducks had no significant effect on plasma GH.
Plasma somatostatin concentrations were reduced during the infusion of hpGRF in young but not in adult ducks. This observation suggests that the stimulatory effect of hpGRF on GH secretion may be partly due to its inhibitory effect on somatostatin secretion. Infusion of hpGRF in ducklings also increased the concentrations of glucagon and decreased levels of insulin in the plasma. Peripheral plasma glucagon and insulin levels in adult ducks were unaffected by hpGRF infusion. These results indicate that in ducklings, hpGRF increases plasma GH and glucagon concentrations and lowers plasma somatostatin and insulin levels. In the adult, these hormonal responses to hpGRF are not maintained. The highly stimulatory effect of hpGRF on GH secretion in ducklings may explain why plasma GH concentrations are high in these birds.
J. Endocr. (1987) 114, 25–32
Involvement of opiate receptor subtypes in the modulation of LHRH secretion by the cockerel (Gallus domesticus) mediobasal hypothalamus in vitro
Authors: Stansfield S. C. , Cunningham F. J. 
Published: December 2008

ABSTRACT
Using an in-vitro superfusion system, the relative importance of three distinct subtypes of the opiate receptor in the control of the secretion of LHRH from the mediobasal hypothalamus of the cockerel was investigated. Basal release of LHRH was increased by the antagonist naloxone, which shows some μ-receptor selectivity, in a manner which was reversed by the μ-receptor specific agonist [d-Ala2, N-Phe4-Gly-ol5]-enkephalin (DAGO) and the μ- and δ-specific agonist [d-Ala2,N-Phe4,Met(0)ol5]-enkephalin (FK 33–824). The †-specific agonist [d-Thr2,l-Leu5]-enkephalyl-Thr (DTLET) and the κ-specific agonist 1-methyl-2(3-thienylcarbonyl)-aminomethyl-5-(2-fluorophenyl)-H-2,3-dihydro-1,4-benzodiazepine (KC 6128; (+)-titfluadom) did not reverse the effect of naloxone. The δ-specific antagonist N,N-diallyl-Tyr-α-aminoisobutyricacid-Phe-Leu-OH (ICI 174,864) failed to influence basal release. Release of LHRH stimulated by increasing the potassium ion concentration of the superfusate to 48 mmol/l was reduced by DAGO in a manner which was reversed by naloxone, and by FK 33–824 in a manner which was reversed by both naloxone and ICI 174,864. The agonists DTLET and titfluadom did not affect stimulated release of LHRH. These results support the proposal that spontaneous release of LHRH is tonically inhibited by agonists acting through the μ-receptor whilst, in response to a stimulus, the δ-receptor, in addition to the δ-receptor, may be involved.
J. Endocr. (1987) 114,111–117
Lack of glucose-induced priming of insulin release in the perfused mouse pancreas
Authors: Berglund O. 
Published: December 2008

ABSTRACT
Perfusion of the mouse or rat pancreas with 20 mmol d-glucose/l caused a biphasic release of insulin. The second phase was nearly constant in the mouse but rose in the rat. Repeated pulses of 8, 20 or 30 mmol d-glucose/l did not potentiate subsequent insulin responses in the mouse, whereas repeated pulses of 20 mmol/l did in the rat. When 20 mmol d-glucose/l was introduced through the mesenteric artery or aorta of the mouse, the pattern of insulin release was the same as when it was introduced through the coeliac artery. Thus, insulin secretion in mice differs from that in rats both in not showing an increasing second phase in response to continuous stimulation with glucose and also in not showing successive enhancement in the insulin response to repeated pulses of glucose.
J. Endocr. (1987) 114, 185–189
Modulation of plasminogen activation by glucocorticoid hormones in the rat granulosa cell
Authors: Harlow C. R. , Coombs R. J. , Hodges J. K. , Jenkins N. 
Published: December 2008

ABSTRACT
Granulosa cells from immature rats primed with diethylstilbestrol (DES) showed a fivefold rise in the activity of secreted plasminogen activator (PA) in response to human FSH. The dose giving 50% of the maximum response (ED50) was 10 ng/ml. Glucocorticoid hormones significantly suppressed PA activity in both control cells and cells stimulated with FSH (ED50 = 50 nmol dexamethasone/l; 1 μmol corticosterone/l). Cortexolone (2·5 μmol/l) significantly ameliorated this suppression, indicating that the response to glucocorticoids is receptor-mediated. These data, together with the time delay required for glucocorticoids to take effect (5 h), suggest that glucocorticoids induce the production of a specific PA inhibitor in granulosa cells.
J. Endocr. (1987) 114, 207–212
Ovine allantoic fluid inhibition of prostaglandin synthesis in cotyledonary microsomes
Authors: Rice G. E. , Wong M. H. , Ralph M. M. , Thorburn G. D. 
Published: December 2008

ABSTRACT
Inhibition of microsomal prostaglandin (PG) biosynthesis by allantoic fluid, obtained from ewes at 80–120 days of gestation, was examined. Inhibition of cotyledonary microsomal PGE2 and PGF2α biosynthesis by lyophilized allantoic fluid occurred in a dosedependent manner. The concentration of allantoic fluid required to inhibit PGE2 and PGF2α production by 50% averaged 17·9 ± 3·2 (s.e.m.) mg dry weight/ml (n = 5). Microsomal PG biosynthesis was markedly enhanced by the addition of arachidonic acid (30 μmol/l). Synthesis of PGE2 and PGF2α was increased to 245 ± 65% and 184±14% of control (P<0·05, n = 5) respectively. Treatment of cotyledonary microsomes with porcine phospholipase A2 (PLA2; 0·125 units/ml) also stimulated PG synthesis, PGE2 increasing to 216 ± 27% and PGF2α to 172 ± 14% of control (P<0·05, n=5) respectively. Allantoic fluid (20 mg dry weight/ml) inhibited arachidonic acid-stimulated PG synthesis (PGE2 by 48·6 ± 13·8% and PGF2α by 44·2 ± 7·7%) and PLA2-stimulated PG synthesis (PGE2 by 60·6±11·6% and PGF2α by 74·8 ± 8·5%). Allantoic fluid, however, did not affect PLA2-stimulated release of arachidonic acid from microsomes, thus negating the possibility that allantoic fluid suppresses PG synthesis by inhibiting PLA2 activity. These data indicate that allantoic fluid inhibits PG production at the level of PG synthase enzymes. Prostaglandin inhibitor(s) in allantoic fluid may play a role in maintaining uterine quiescence throughout gestation and its withdrawal, at term, may be involved in the initiation of labour.
J. Endocr. (1987) 114, 295–300
Growth hormone secretory profiles in conscious female rats
Authors: Clark R. G. , Carlsson L. M. S. , Robinson I. C. A. F. 
Published: December 2008

ABSTRACT
An automatic method for repetitive microsampling of blood from conscious animals was used to obtain detailed GH secretory profiles from normal female rats, which were compared with those in males and ovariectomized females. Female rats showed a highly variable GH secretory pattern, with sustained periods of low, almost continuous secretion, followed by very rapid bursts of high amplitude and short duration, occurring mostly at night. There was no clear relationship between the pattern of GH secretion and the phase of the oestrous cycle in rats continuously sampled over a 5-day period. In ovariectomized rats, the day:night difference was maintained, though the nocturnal GH surges were larger and of longer duration than in intact females. Male rats produced multicomponent GH bursts which continued unchanged throughout the day and night. This study shows for the first time that female rats switch to a rapid, highly pulsatile pattern of GH release at night, which can only be resolved by rapid blood sampling over extended periods in conscious undisturbed animals.
J. Endocr. (1987) 114, 399–407
The dynamics of LH-induced desensitization of adenylate cyclase and LH receptor internalization in rat Leydig cells at physiological levels of LH
Authors: Habberfield A. D. , Dix C. J. , Cooke B. A. 
Published: December 2008

ABSTRACT
The LH-induced desensitization of adenylate cyclase and LH receptor internalization in rat Leydig cells in vitro has been investigated using sub-physiological to pharmacological concentrations of LH.
Leydig cells pretreated with LH for 1 h in the presence of a phosphodiesterase inhibitor showed a dose-dependent decrease in the subsequent response to a high dose of LH; this was significant with concentrations of > 350 fmol/l. The maximum amount of desensitization was 60%.
The time-course of LH-induced desensitization of the adenylate cyclase system was investigated; with 3 nmol LH/1 cyclic AMP was increased in a linear manner up to 45 min, after which time there was either no further production or (with the higher concentrations) a decreased rate of production. In order to determine whether the 'non-desensitized' adenylate cyclase activity was dependent upon LH, the LH-treated cells were acid-washed to remove residual LH; cyclic AMP production still continued, albeit at a lower rate, thus indicating that this adenylate cyclase activity did not require the further presence of LH. The effect of various concentrations of LH on the level of surface-associated LH receptors was determined in the presence of monensin to prevent receptor recycling. A dose- and time-dependent decrease was found; this was significant after 2 h with 3·5 pmol LH/1 and reached a maximum of 63% of the control with 3·5 nmol/l. A dose- and time-dependent reversal of desensitization occurred if the cells pretreated with LH were washed and reincubated; with 35 pmol LH/1 and after 2 h the cells were fully responsive to a challenge with fresh LH. With higher concentrations of LH in the pretreatment, partial or no recovery was found.
These studies demonstrate that physiological and sub-physiological concentrations of LH induce a rapid desensitization of Leydig cell adenylate cyclase. Internalization of occupied and unoccupied LH receptors also occurred. It is proposed that these two events are linked and may, paradoxically, and because of the low numbers of LH receptors, be necessary to maintain the normal response of Leydig cells to LH in vivo.
J. Endocr. (1987) 114,415–422
Effect of adrenalectomy on LH release in sheep during the anoestrous season
Authors: Montgomery G. W. , Martin G. B. , Locatelli A. , Pelletier J. 
Published: December 2008

ABSTRACT
An experiment was conducted to measure LH pulse frequencies in bilaterally adrenalectomized Ile-de-France ewes during the mid-anoestrous season. Seven ewes were adrenalectomized under general anaesthesia and maintained on daily injections of 3 mg deoxycorticosterone acetate (DOCA). Adrenalectomy did not affect the patterns of LH release and the mean intervals between pulses in the adrenalectomized and sham-operated control ewes were 48 and 52 min respectively. Small implants of oestradiol significantly reduced the frequency of LH pulses in both groups and, in the presence of oestradiol, there were no differences in LH release between adrenalectomized and sham-operated ewes, with the mean interpulse intervals being 91 and 89 min respectively. In a second experiment, designed to assess the effects of DOCA on LH release, the mean interpulse intervals in unoperated control ewes (46 min) and unoperated ewes given daily injections of 3 mg DOCA (47 min) were similar to those observed in adrenalectomized and sham-operated ewes. In the presence of small implants of oestradiol, the combination of DOCA and oestradiol decreased the pulse frequency significantly more than oestradiol alone (mean interpulse intervals of 85 and 65 min respectively) suggesting that DOCA may act as a progestagen in sheep. Thus alternative treatments to DOCA for the maintenance of adrenalectomized sheep must be found for future studies on the role of adrenal steroids in the reproductive system. It appears that adrenal steroids do not play a major role in the seasonal changes in LH release in the ewe.
J. Endocr. (1987) 114,437–442
IMMUNIZATION AGAINST AN INHIBIN SUBUNIT PRODUCED BY RECOMBINANT DNA TECHNIQUES RESULTS IN INCREASED OVULATION RATE IN SHEEP
Authors: Forage R.G. , Brown R.W. , Oliver K.J. , Atrache B.T. , Devine P.L. , Hudson G.C. , Goss N.H. , Bertram K.C. , Tolstoshev P. , Robertson D.M. , de Kretser D.M. , Doughton B. , Burger H.G. , Findlay J.K. 
Published: December 2008

ABSTRACT
Seven Merino–Border Leicester cross–bred ewes were immunized with a purified fusion protein, produced by recombinant DNA methods, of the a subunit of bovine inhibin. Four animals were immunized with the fusion protein alone and three with a conjugate made by coupling the fusion protein to keyhole limpet haemocyanin (KLH) using glutaraldehyde. Each animal received four injections of the fusion protein over 93 days. The animals were synchronized using progestagen sponges and subjected to laparoscopy for the determination of ovulation rates in two consecutive cycles (days 115 and 135). The immunized animals had overall mean ovulation rates for each cycle of 3.4 and 3.4 which was significantly (P < 0.001) above the rates of 1.1 and 1.4 determined for the controls, which had either received no treatment (n=5) or had been immunized with 300 μg KLH (n=4). Analysis of antisera taken on day 115 showed significant fusion protein antibodies and iodinated inhibin–binding capacity in the test but not control groups. Furthermore, antisera to the fusion protein in four out of seven ewes neutralized the inhibin bioactivity of ovine follicular fluid in an in–vitro bioassay. These data demonstrate that neutralization of inhibin can be effected by immunization with bovine inhibin a subunit and that such immunization results in increased ovulation rates as predicted from the biological role of inhibin as a suppressor of FSH.
In-vitro evidence for the autoregulation of prolactin secretion at the level of the pituitary gland in the rat
Authors: Bentley A. M. , Wallis M. 
Published: December 2008

ABSTRACT
The autoregulation of rat prolactin secretion at the level of the pituitary gland was investigated, using a static incubation system. The rate of prolactin secretion from the female anterior pituitary gland in vitro was found to be constant when the medium was changed at 20-min intervals. However, when the medium was left unchanged and secretory products were allowed to accumulate, prolactin secretion began to decline within 60 min. This effect was not observed with the male tissue, where the level of accumulated prolactin did not reach that at which the inhibition occurred using female tissue.
The nature of the putative secretory product causing the inhibition of prolactin secretion was investigated. Exogenous bovine prolactin (1–4 mg/l) caused an inhibition of endogenous rat prolactin secretion. Inclusion of monoamine oxidase in unchanged medium, to prevent dopamine accumulation in the medium (a possible consequence of co-storage and cosecretion with prolactin granules), did not prevent the inhibition observed in the control incubation. We therefore conclude that in-vitro autoregulation of prolactin secretion can occur at the level of the pituitary gland, probably due to the accumulated prolactin having a feedback action on the lactotroph. This might be of physiological significance if localized concentrations of the hormone within the gland are high.
J. Endocr. (1987) 115, 13–18
Effect of oestradiol-17β on perineal and neck skin glands in heifer calves
Authors: Blazquez N. B. , Long S. E. , Perry G. C. , Watson E. D. 
Published: December 2008

ABSTRACT
Ten 16-week-old Friesian × Hereford heifer calves were split into experimental and control groups. Experimental animals were given an implant of oestradiol-17β in the ear whilst controls were given blank implants. They were killed 14 days later. After implantation the experimental group had consistently greater (P<0·01) plasma concentrations of oestradiol-17β than the control group. After death, sebaceous gland volume in the perineal region was greater (P < 0·01) in the experimental than in the control group, whereas sebaceous gland volume in the neck was smaller (P <0·01). Sweat gland volume in the perineal region was greater (P<0·01) in the experimental than in the control group. There was no difference between groups in the volume of sweat glands in the neck.
J. Endocr. (1987) 115, 43–46
Modulation by oestrogen of thyroid hormone effects on thyrotrophin gene expression
Authors: Franklyn J. A. , Wood D. F. , Balfour N. J. , Ramsden D. B. , Docherty K. , Sheppard M. C. 
Published: December 2008

ABSTRACT
The role of oestrogen in the regulation of TSH gene expression is unclear. We have examined the effect of administration of oestrogen in the rat on serum TSH, pituitary TSH content and pituitary cytoplasmic concentrations of mRNA encoding the TSH β and α subunits, thus deriving measures of hormone release and synthesis. In addition, we have examined the effect of oestrogen on the binding of tri-iodothyronine (T3) to nuclear receptors in the anterior pituitary.
Administration of oestrogen did not affect serum concentrations of TSH in euthyroid or untreated hypothyroid rats, but did augment the effects of T3 (1 and 2 μg on serum TSH in hypothyroid animals 6 h after injection of T3. No influence of oestrogen or of thyroid status on pituitary content of TSH was seen.
A marked increase in the concentrations of TSH β and α mRNA in pituitary cytoplasm was found in hypothyroidism, compared with those in the euthyroid state. No effect of oestrogen on TSH mRNA was seen in euthyroid animals but concentrations of TSH β and α mRNA were lower in hypothyroid animals than in vehicle-treated controls. A stimulatory influence of T3 on TSH mRNA was seen 6 h after injection of T3; this stimulation was absent in oestrogen-treated rats. No effect of oestrogen on the action of T3 was evident 72 h after beginning treatment with T3. In addition to effects on serum TSH and TSH mRNA, an increase in the number of pituitary nuclear receptors for T3 was seen after oestrogen treatment.
The influences of oestrogen on serum TSH and on TSH mRNA are consistent with augmentation of thyroid hormone effects; this influence may be mediated by an increase in the number of pituitary nuclear receptors for T3.
J. Endocr. (1987) 115, 53–59