bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of pregnant mare serum gonadotrophin and oestradiol benzoate on enzymes associated with xenobiotic metabolism in immature and hypophysectomized female rats
Authors: Williams M. T. 
Published: December 2008

ABSTRACT
Treatment of immature (22-day-old) female Sprague–Dawley rats with pregnant mare serum gonadotrophin (PMSG) resulted in a significant increase in hepatic microsomal cytochrome P-450 concentrations when compared with animals treated with 0·9% (w/v) NaCl solution. Cytochrome P-450 concentrations in microsomes from control and PMSG-treated animals were 0·49 ± 0·07 and 0·78 ± 0·18 nmol/mg microsomal protein respectively (mean ± s.d.). When hypophysectomized rats were treated with PMSG no significant difference was observed between saline-treated and PMSG-treated animals (0·84 ± 0·06 vs 0·88± 0·08 nmol/mg microsomal protein). Cytochrome b5 concentration and NADPH–cytochrome c reductase and ferricyanide reductase activities were not significantly affected by PMSG treatment. Similar results were obtained when immature and hypophysectomized rats were treated with oestradiol benzoate.
Hepatic glutathione (GSH) S-transferase activity was significantly stimulated over control values when hypophysectomized or immature animals were treated with PMSG, oestradiol benzoate or 3-methyl-cholanthrene. Treatment of animals simultaneously with PMSG or oestradiol benzoate and 3-methyl-cholanthrene resulted in higher transferase activity than did either treatment alone. Oestradiol benzoate or PMSG treatment of immature female rats resulted in an approximate twofold increase in hepatic aryl hydrocarbon hydroxylase (AHH) activity. However, AHH activity in hypophysectomized animals was not significantly increased by PMSG or oestradiol benzoate treatment.
It is concluded that PMSG or oestradiol benzoate treatment of immature female rats resulted in increased total cytochrome P-450 concentration and AHH activity in hepatic microsomes. Glutathione S-transferase activity was also stimulated. Neither PMSG nor oestradiol benzoate stimulated cytochrome P-450 levels or AHH activity in hypophysectomized rats. However, GSH S-transferase activity was stimulated similar to that in immature animals.
Conceivably, the PMSG effect observed in immature rats may be due to PMSG-stimulated increases in plasma oestradiol concentrations which interact at the hypothalamo-pituitary axis. The ability of oestradiol benzoate to mimic the effects of PMSG and the known action of PMSG to increase plasma oestradiol levels in immature rats would tend to support this hypothesis. The lack of increase in cytochrome P-450 concentrations and AHH activity in hypophysectomized female rats would further support the involvement of the pituitary gland in the response to PMSG rather than a direct effect of PMSG or oestradiol benzoate on the liver. Since GSH S-transferase activity is stimulated in both intact and hypophysectomized rats, this system may be under a different control mechanism.
J. Endocr. (1985) 104, 315–321
Relationship between adrenocorticotrophin bioactivity in blood and cerebrospinal fluid of rhesus monkeys
Authors: Beckford U. , Herbert J. , Jones M. T. , Martensz N. D. , Nicholson S. A. , Gillham B. , Hamer J. D. 
Published: December 2008

ABSTRACT
Adrenocorticotrophin levels, measured by a cytochemical bioassay, were determined in the plasma and cerebrospinal fluid (CSF) of adult female rhesus monkeys which were ovariectomized and receiving oestrogen replacement therapy. In control monkeys, ACTH bioactivity was found in both CSF (10·2±1·8 ng/l) and plasma (186 ± 51 ng/l) in samples taken at 14.00 h (lights on: 07.00–19.00 h). Dexamethasone treatment (0·2 mg/kg) twice daily for 4 days suppressed plasma ACTH levels (52·8 ± 25·2 ng/l) but had no effect on CSF levels (7·6± 2·7 ng/l). Raising plasma ACTH, either by daily injections of a long-acting preparation of ACTH(1–24) for 6 days or by bilateral adrenalectomy (and subsequently withdrawing cortisol replacement therapy) also resulted in no detectable changes in ACTH levels in the CSF. A regression analysis between ACTH in the plasma and CSF from samples taken throughout the experiments showed no correlation. In contrast, measurement of ACTH by radioimmunoassay, whilst satisfactory for determination of this peptide in plasma, could not identify authentic ACTH in the CSF. It is concluded that bioactive ACTH does not enter the CSF in detectable quantities from either the peripheral vascular compartment or from the animal's own pituitary gland, and that reducing ACTH secretion from the pituitary also has no effect on levels of ACTH in the CSF. This is in marked contrast to other pituitary peptide hormones, including prolactin, which is secreted together with ACTH during 'stress' but which, unlike ACTH, enters the CSF relatively easily.
J. Endocr. (1985) 104, 331–338
Corticosterone storage within the adrenal cortex: evidence for a sulphate conjugate
Authors: Henry F. J. , Bassett J. R. 
Published: December 2008

ABSTRACT
Incubation of homogenized rat adrenal glands with sulphatase for 18 h resulted in a significant increase in the amount of unconjugated corticosterone that could be extracted from the gland and which could not be attributed to de-novo synthesis of corticosterone during the incubation. Therefore corticosterone may be stored within the adrenal gland as a sulphate conjugate rather than as unconjugated hormone. Exposure of animals to footshock stress resulted in an increase in the amount of unconjugated corticosterone in the gland and a disappearance of the conjugate form. The rapid disappearance of the sulphate conjugate may reflect the activation of a steroid sulphatase by ACTH. However, the release of corticosterone from a storage form such as corticosterone sulphate could not explain entirely the initial increase in plasma corticosterone concentration following the stress. It was calculated that a pair of adrenal glands would have to store up to 20 nmole corticosterone in order to account for the initial increase in plasma corticosterone. This level was much greater than that extracted from a pair of glands (4·8 nmol) even after sulphatase pretreatment.
J. Endocr. (1985) 104, 381–386
Parachlorophenylalanine blocks the spontaneous pro-oestrous surge of prolactin as well as LH and affects the secretion of oestradiol-17β
Authors: Horn A. M. , Fink G. 
Published: December 2008

ABSTRACT
The effect of the 5-hydroxytryptamine synthesis inhibitor, parachlorophenylalanine (PCPA), on the spontaneous, pro-oestrous surges of prolactin and LH was investigated in conscious female rats implanted with an intra-atrial cannula. The LH surge was blocked in all animals treated with PCPA, but the prolactin surge was blocked in six out of ten animals and unaffected in four out of ten animals. There was a significant correlation between the plasma concentrations of prolactin and oestradiol-17β, surges of prolactin occurred in animals with plasma oestradiol-17β concentrations of 120 pmol/l and above, and the LH surge was blocked in animals in which the oestradiol-17β concentration was less than 188 pmol/l plasma. These results show that (i) PCPA can block the pro-oestrous prolactin as well as the LH surge, (ii) in addition to a central action PCPA may depend also on its peripheral effect on the secretion of oestradiol-17β and (iii) on average, lower plasma concentrations of oestradiol-17β are required for triggering the prolactin compared with the LH surge.
J. Endocr. (1985) 104, 415–418
SUPPRESSION OF LUTEAL PROGESTERONE SECRETION IN THE STUMPTAILED MACAQUE BY AN ANTAGONIST ANALOGUE OF LUTEINIZING HORMONE RELEASING HORMONE.
Authors: Fraser H.M. , Baird D.T. , McRae G.I. , Nestor J.J. , Vickery B.H. 
Published: December 2008

ABSTRACT
The dependence of progesterone secretion from the corpus luteum on pituitary gonadotrophin was examined in the cyclic stumptailed macaque by studying the effects of a single s.c. injection of a potent LH releasing hormone (LHRH) antagonist, [N–Ac–D–Nal(2)1, D–pCl–phe2, D–Trp3, D–hArg(Et2)6, D–Ala10] LHRH.
A dose of 100 μg antagonist/kg administered on days 9/10 of the luteal phase in three monkeys caused a marked temporary suppression of serum concentrations of LH and progesterone during the following 32 h but levels still remained detectable and after 2 days serum hormone concentrations returned to the normal luteal-phase range. When the same animals were treated with 300 μg antagonist/kg at the same period during a subsequent cycle, serum LH levels were close to or at the limits of detection of the bioassay for the next 48 h and progesterone concentrations declined steadily, reaching non-detectable values by 48 h. In two monkeys the progesterone levels remained suppressed and they menstruated prematurely; in the third monkey the progesterone concentration rose to just above baseline and menstruation occurred at the expected time. Administration of 300μg antagonist/ kg on days 6/7 of the luteal phase in a further three monkeys also suppressed progesterone concentrations but not to baseline values, and after 2 days a normal progesterone profile was regained. These results suggest that the corpus luteum of the stumptailed macaque is largely dependent on pituitary gonadotrophin support during the mid to late luteal phase.
Hypothalamic gonadotrophin-releasing hormone and pituitary and plasma FSH and prolactin during photostimulation and photorefractoriness in intact and thyroidectomized starlings (Sturnus vulgaris)
Authors: Dawson A. , Follett B. K. , Goldsmith A. R. , Nicholls T. J. 
Published: December 2008

ABSTRACT
Changes in concentrations of hypothalamic gonadotrophin-releasing hormone (GnRH) and pituitary and plasma FSH and prolactin were measured in intact and thyroidectomized female starlings (Sturnus vulgaris) after transfer from short to long photoperiods.
In intact birds, hypothalamic GnRH did not increase significantly during the first 6 weeks of photostimulation, but by 12 weeks, as birds became photorefractory, it had decreased to levels significantly lower than those before photostimulation. In thyroidectomized birds, which did not become photorefractory, hypothalamic GnRH remained high after 12 weeks of photostimulation. Pituitary FSH increased in both intact and thyroidectomized birds; it then decreased to low levels in intact photorefractory birds, but remained high in thyroidectomized birds. Plasma FSH increased to a peak after 2 weeks, but by 6 weeks it had decreased to low levels in both groups. In intact birds there was a 70-fold increase in pituitary prolactin during the first 6 weeks, and levels were still high after 12 weeks of photostimulation. In thyroidectomized birds, pituitary prolactin remained low. The results suggest that while the initial effect of long daylengths is to cause gonadal maturation, the ultimate effect is to switch off the reproductive system.
J. Endocr. (1985) 105, 71–77
A black background facilitates the response to stress in teleosts
Authors: Gilham I. D. , Baker B. I. 
Published: December 2008

ABSTRACT
This work examines the difference in responsiveness to stress which characterizes fish adapted to white and black backgrounds. Trout were maintained in black or white tanks for 2 weeks and then subjected to intermittent intense or moderate noise stress for periods between 1 h and 5 days, or to the stress of being injected daily with a large volume of liquid for 3 days. Plasma cortisol concentrations increased more readily and to a greater extent in fish from black tanks in response to moderate stress or brief intense stress. Dexamethasone suppressed the stress-induced rise of cortisol in white-adapted fish but was only partially effective in trout from black backgrounds. These differences in plasma cortisol between black- and white-adapted fish can be related to the different titres of plasma ACTH, apparently derived from the pars distalis.
Removal of the neurointermediate lobe (NIL) from black-adapted eels markedly depressed the normal rise in plasma cortisol elicited by noise stress. It is suggested that products from the NIL may modulate the stress response of the hypothalamo-pituitary axis although other routes through which background colour could affect the pituitary responsiveness to stress are also considered. In several cases, stress also enhanced the secretion of MSH from the NIL.
J. Endocr. (1985) 105, 99–105
The priming effect of LH-releasing hormone: effects of cold and involvement of new protein synthesis
Authors: Curtis A. , Lyons V. , Fink G. 
Published: December 2008

ABSTRACT
The possible involvement of protein synthesis in the priming effect of LH-releasing hormone (LHRH) has been investigated in vitro using hemipituitary glands from pro-oestrous rats. Cycloheximide (7·1 μmol/l) blocked the priming effect of LHRH (elicited by 8·5 nmol LHRH/1) and protein synthesis (assessed by gel electrophoresis of 35S-labelled pituitary proteins). Pituitary glands were also incubated at 0–1 °C followed by incubation at 37 °C. While incubation at 0 °C for either 1 or 2 h reduced LH release and blocked protein synthesis, the LH response to LHRH in a subsequent 1-h incubation at 37 °C was similar to that during the corresponding period in pituitary glands incubated throughout at 37 °C. Incubation with medium alone at 0 °C during the first hour followed by incubation with LHRH at 37 °C during the second hour resulted in an LH response to LHRH which was similar to that in glands incubated with LHRH for 2 successive hours at 37 °C. Two-dimensional gel electrophoresis showed that LHRH priming was associated with the synthesis of a new protein of approximately 69000 molecular weight and with changes in the isoelectric point of two other high molecular weight proteins. These results suggest that the priming effect of LHRH involves the synthesis of a new protein as well as post-translational changes (possibly phosphorylation) in two other proteins and that exposure to cold may prime the pituitary gland to LHRH possibly by stimulating intracellular Ca2+ release and/or protein phosphorylation.
J. Endocr. (1985) 105, 163–168
Behavioural and physiological effects of prolactin in incubating ring doves
Authors: Janik D. S. , Buntin J. D. 
Published: December 2008

ABSTRACT
The role of prolactin in the maintenance of incubation behaviour in ring doves was re-examined and the dose–response relationships for behavioural, target tissue and body weight changes induced by injections of prolactin were compared in doves tested during the incubation phase of the breeding cycle. Doves given injections of prolactin twice a day starting on day 4 of incubation, during a 10-day period of isolation from their mates and nests, showed a higher persistence of incubation behaviour than doves injected with saline vehicle. However, the prolactin treatment failed to maintain incubation behaviour to the same extent as that observed in non-isolated untreated breeding pairs. Liver and body weights were higher and testicular weights lower in birds treated with high doses of prolactin than in non-isolated birds which had been incubating for 14 days. Good dose-response relationships were established between body, liver, crop and testes weights and the dose of prolactin administered. However, only a weak dose–response relationship was observed between prolactin and the maintenance of incubation behaviour. Overall, females injected with prolactin displayed more quiet sitting behaviour, less body weight gain and more gonadal regression than males injected with prolactin. Males in untreated breeding pairs had higher liver weights and lower crop weights than females. It is concluded that prolactin plays a role in maintaining readiness to incubate in doves, but that other factors may also contribute to this response. Further, it appears that prolactin mediates several target tissue changes which are sex-specific during incubation.
J. Endocr. (1985) 105, 201–209
Odour recognition by male hamsters: discrimination of the hormonal state of females by odour from vaginal secretions
Authors: Steel E. 
Published: December 2008

ABSTRACT
Male hamsters were tested for their interest in females on different days of the oestrous cycle. Behaviour of males towards novel females was measured and (after exposure to vaginal secretion) towards females that matched or did not match that vaginal odour. Because pro-oestrous (day 4) females lay trails of vaginal secretion and will become receptive within a few hours, it was predicted that males would show more interest in day 4 than in other dioestrous females. While males showed no preference for novel, pro-oestrous females over dioestrous females, after pre-exposure to odour, their response to females was determined by the cycle day of the vaginal secretion to which they had been exposed. Males pre-exposed to vaginal odour from females carrying large implants of oestrogen preferred to spend more time with females who matched that vaginal odour than mismatching females and to sniff them more. This preference was not seen if the females carried small oestrogen implants or had no replacement oestrogen. This suggests that pro-oestrous females (who are known to have high circulating levels of oestrogen) can, by means of their scent-marking behaviour, attract and keep males nearby until they become receptive.
J. Endocr. (1985) 105, 255–262
Changes in aromatase activity in small ovarian follicles of the domestic fowl (Gallus domesticus) during growth and atresia
Authors: Armstrong D. G. 
Published: December 2008

ABSTRACT
The tritium release assay for measuring aromatase activity was adapted to measure oestrogen production in intact small ovarian follicles of the domestic fowl. The activity was measured in three types of follicle classified as normal, atretic or grossly atretic. Normal follicles were distinguished from atretic by the presence of small haemorrhages on the surface of the atretic follicles. Grossly atretic follicles were identified by their deformed shape.
The aromatase activity in normal and atretic follicles was related to follicular weight, the activity in atretic follicles being less than that in normal follicles. The aromatase activity in grossly atretic follicles was independent of follicular weight. The enzyme activity in this group of follicles was significantly less than that in either normal or atretic follicles. The significance of these results is discussed in relation to the induction of atresia within the small ovarian follicles of the domestic fowl.
J. Endocr. (1985) 105, 297–301
Hormonal regulation of growth hormone binding and responsiveness in adipose tissue and adipocytes of hypophysectomized rats
Authors: Gause I. , Edén S. 
Published: December 2008

ABSTRACT
The hormonal regulation of GH binding and the effects of GH on glucose metabolism were studied in hypophysectomized rats. Male rats (130–140 g) were hypophysectomized and on the day after the operation treatment with one or a combination of two hormones was started and continued for 7 days. The different hormonal treatments were (1) cortisone acetate, (2) insulin, (3) insulin plus cortisone acetate, (4) thyroxine, (5) thyroxine plus cortisone acetate and (6) GH. Glucose metabolism was studied by determining the production of CO2 from [14C]glucose in epididymal fat pads and adipocytes and the incorporation of [14C]glucose into lipids in adipocytes. Binding of GH was measured in cell aliquots using 125I-labelled human GH.
In hypophysectomized control animals, GH binding was decreased to approximately 25% of the binding observed in adipocytes of normal rats. Insulin treatment increased GH binding by approximately 100% and the response to GH was markedly increased. Similar effects were achieved by thyroxine treatment. Basal levels of glucose oxidation were markedly decreased after hypophysectomy but were increased towards normal by insulin or thyroxine treatment. Neither cortisone nor GH treatment had any effect on GH binding or glucose metabolism.
The results show that insulin and thyroxine may be important for the GH receptor and the insulin-like effect of GH in adipocytes.
J. Endocr. (1985) 105, 331–337
Dynamics and control of progesterone receptor synthesis in the fetal uterus of the guinea-pig in organ culture
Authors: Sumida C. , Gelly C. , Pasqualini J. R. 
Published: December 2008

ABSTRACT
Progesterone receptor concentrations increased in fetal guinea-pig uterus in organ culture to as high as 13·15±1·22 pmol/mg DNA without any added steroid, although cytosol and nuclear oestrogen receptor levels were very low (0·41−1·92 pmol/mg DNA). Even after a 3-day exposure to 5×10−8 m-progesterone, which inhibits its own receptor (1·14±0·31 pmol/mg DNA), progesterone receptor levels rose to 8·58±1·39 pmol/mg DNA when progesterone was removed. This replenishment was inhibited by progesterone and 5α-dihydroprogesterone but was not affected by oestradiol, tamoxifen or dexamethasone. The incorporation of [3H]thymidine into nucleic acids was not decreased by progesterone so that its inhibition of its own receptor in the explants was not due to an inhibition of cell replication. Fetal uterine explants from oestrogen-primed fetuses, after an initial decrease in progesterone receptor, also showed a rise to 7 pmol/mg DNA on day 2 which could be decreased by exposure to progesterone and replenished by removal of this hormone (6–8 pmol/mg DNA), the entire process occurring without apparent oestrogen stimulation. Progesterone rather than oestradiol appears to be a key regulator of progesterone receptor synthesis in the fetal guinea-pig uterus, although oestradiol, along with other factors, may also be involved.
J. Endocr. (1985) 105,415–421
Control of plasma levels of growth hormone, glucagon and insulin in ducklings: roles of free fatty acids and somatostatin
Authors: Foltzer Ch. , Strosser M. Th. , Harvey S. , Mialhe P. 
Published: December 2008

ABSTRACT
The effects of plasma free fatty acids (FFA) and somatostatin-14 (S-14) on concentrations of plasma GH, glucagon and insulin were investigated in juvenile ducks. Oleic acid, S-14 or both were infused into 4- to 7-week-old birds and plasma GH, glucagon-like immunoreactivity (GLI), immunoreactive insulin (IRI) and FFA were measured.
An increase in plasma GH and a decrease in GLI but no change in IRI was observed after infusion of 9 mg oleic acid/kg per min. A decrease in plasma GH, FFA and IRI and an increase in plasma GLI was seen after infusion of 800 ng S–14/kg per min. These effects of S-14 on IRI and GLI were abolished when S-14 was infused simultaneously with oleic acid.
It is concluded that FFA have a direct stimulatory effect on GH secretion and an inhibitory effect on glucagon secretion. Somatostatin-14 directly inhibits the secretion of GH and its stimulatory effect on the secretion of glucagon is mediated by a depression in concentrations of plasma FFA. Finally, S-14 has no effect on plasma insulin when basal levels of plasma FFA are maintained.
J. Endocr. (1985) 106, 21–25
Changes in pituitary responsiveness to LH-releasing hormone after acute buserelin treatment: a time-course and dose–response study
Authors: Heather J. D. , Whitehead S. A. 
Published: December 2008

ABSTRACT
The acute in-vivo effects of a potent LH-releasing hormone (LHRH) agonist, buserelin, on LH secretion and pituitary responsiveness to LHRH have been investigated in oestrous rats. Doses of 50, 100 and 250 ng buserelin stimulated LH release in a dose-dependent manner, the peak serum LH concentrations being measured 1 h after the treatment. Thereafter LH levels fell rapidly between 1 and 6 h and by 18 h serum LH concentrations were similar in all groups of animals. Pituitary responsiveness to a challenge with 100 ng LHRH was potentiated by 50 or 100 ng buserelin injected 1 or 2 h before the LHRH challenge. In contrast, 250 ng buserelin completely abolished the LH response to LHRH when tested 1, 2 and 4 h after treatment, but by 6 h a small but attenuated response was observed. Four hours after treatment there was no significant difference in the responses when compared with the saline-treated controls.
J. Endocr. (1985) 106, 27–30