bluuebunny/crossref_metadata_2025_split huggingface dataset:
Plasma somatomedin-C in fasted and refed rats: close relationship with changes in liver somatogenic but not lactogenic binding sites
Authors: Maes M. , Underwood L. E. , Ketelslegers J.-M. 
Published: December 2008

Circulating levels of somatomedins in man and rats are reduced by fasting and restored by refeeding. To determine the mechanisms for these alterations in somatomedin levels, the affinities and binding capacities of 125I-labelled bovine GH (somatogenic binding sites) and of 125I-labelled ovine prolactin (lactogenic binding sites) were assessed in liver homogenates from fasted and refed rats. Correlations were made with plasma immunoreactive somatomedin-C (Sm-C) and plasma insulin.
During fasting and refeeding there was a close temporal relationship between the fall and the rise of plasma levels of Sm-C and insulin, and the number of hepatic GH binding sites. After fasting for 1 day, plasma Sm-C dropped by 68% and plasma insulin by 76% when compared with values before fasting. At the same time, GH binding capacity was significantly reduced (7·3 ± 2·8 (s.e.m.) pmol/liver v. controls, 20·3 ± 2·1 pmol/liver; P < 0·01). Refeeding for 24 h normalized plasma insulin levels and restored GH binding capacity to values before fasting (13·2 ± 2·4 v. 20·3 ± 2·1 pmol/liver; P > 0·05). Plasma Sm-C rose significantly with refeeding and returned to initial values at day 4 of refeeding (0·82 ± 0·10 v. 0·77 ± 0·07 units/ml; P > 0·05).
In contrast, changes in prolactin binding sites correlated poorly with changes in plasma Sm-C. There was a modest decline with fasting significant only after 72 h (6·8 ± 0·6 v. 13·9 ± 3·2 pmol/liver; P < 0·05), and refeeding for 24 h did not restore prolactin binding (5·7 ± 1·2 pmol/liver).
Since a number of reports suggest that fasting induces a state of tissue insensitivity to GH, our findings suggest that the reduction in hepatic GH binding capacity might be a mechanism for the fasting-induced reduction in Sm-C. The reduction in plasma insulin, which accompanies fasting, might play a permissive role in the intracellular metabolic events involved in Sm-C and GH receptor regulation.
Is hirsutism an evolving syndrome?
Authors: Toscano Vincenzo , Adamo M. V. , Caiola Stefania , Foli Sonia , Petrangeli Elisa , Casilli Daniela , Sciarra Francesco 
Published: December 2008

The possibility that hirsutism is an evolving syndrome rather than a static condition involving only one gland has been considered. To assess this proposal 60 untreated hirsute patients aged 12–32 years were divided into five groups according to the duration of the hirsutism (< 1, 1–2, 2–3, 3–5 and > 5 years).
Peripheral plasma concentrations of LH and FSH, androstenedione, dehydroepiandrosterone sulphate, testosterone, 5α-dihydrotestosterone, 5α-androstane-3α, 17β-diol, 5α-androstane-3β, 17β-diol, cortisol, oestradiol-17β and oestrone were determined by radioimmunoassay. When the values obtained were compared with those from normal menstruating women, the results showed that in group I there was a significant increase only in the mean plasma 5α-androstane-3α, 17β-diol concentration. The mean concentration of this steroid was also raised in all other groups. In groups II and III mean basal levels of plasma dehydroepiandrosterone sulphate were also significantly increased and showed a marked increase after ACTH stimulation (1 mg tetracosactide acetate, i.m.) as did the concentrations of androstenedione and 17α-hydroxyprogesterone. Finally, in groups IV and V, a significant increase in mean plasma concentrations of LH, androstenedione, oestrone and testosterone was found in the basal condition. The clinical picture also became gradually more severe from group I to group V.
These data suggest that hirsutism could be an evolving syndrome progressively involving peripheral androgen metabolism, the adrenal gland and finally the ovary possibly through alterations of hypothalamic-pituitary function.
Effects of [1-(3-mercaptopropanoic acid)]-vasopressin and -vasotocin on the pro-oestrous progesterone surge and ovulation in immature female rats
Authors: Cheesman D. W. , Schlegel R. 
Published: December 2008

The desamino analogues of arginine-vasotocin (dAVT) and arginine-vasopressin (dAVP), when administered on the afternoon of pro-oestrus to immature female rats primed with pregnant mare serum, blocked the preovulatory progesterone surge and inhibited ovulation. Statistical analysis revealed no difference in the potency of the two compounds. At a dosage of 2·0 μg, dAVT and dAVP yielded a 70 and 87% block of ovulation respectively. Simultaneous administration of dAVT and the antipressor compound [1-deaminopenicillamine-4-valine-8-d-arginine]-vasopressin had no statistically significant inhibitory effect when compared with saline-treated controls.
These data suggest that the inhibitory effects of dAVT and dAVP on the progesterone surge and subsequent ovulation are mediated through receptor sites similar to those mediating the pressor actions of the parent hormones.
Influence of pinealectomy on the suppression of gonadotrophin secretion induced by hyperprolactinaemia in the adult male rat
Authors: McNeilly A. S. , Lincoln D. W. 
Published: December 2008

To investigate the role of the pineal gland in the long-term suppression of gonadotrophin secretion induced by prolactin, the effects of pinealectomy were studied in adult male rats with hyperprolactinaemia produced by the transplantation of two pituitary glands under the kidney capsule.
Pinealectomy had no effect on basal levels of LH, FSH or prolactin. The presence of pituitary transplants induced a significant twofold increase in prolactin levels and a prolonged suppression in both LH and FSH. These changes were not affected by pinealectomy. Castration resulted in a similar rise in plasma levels of LH and FSH in rats with and without pituitary transplants. In control rats this rise in LH and FSH was reduced by testosterone-containing silicone elastomer implants (s.c) of 10 mm in length and delayed by implants of 30 mm. These rises in LH and FSH were significantly delayed (10-mm implant) or abolished (30-mm implant) in rats with pituitary transplants indicating an increase in sensitivity of the hypothalamic-pituitary axis to the negative feedback effects of testosterone in these animals compared to controls. These responses were not affected by pinealectomy.
These results suggest that the pineal gland is not involved in the mechanism whereby pituitary grafts, possibly through their secretion of prolactin, cause long-term suppression of gonadotrophin secretion.
Changes in testicular blood flow and testosterone production during aspermatogenesis after irradiation
Authors: Wang J. , Galil K. A. A. , Setchell B. P. 
Published: December 2008

Exposure of the testes of anaesthetized adult rats to 527 rads of γ-irradiation caused testis weight to fall slowly at first and then more rapidly from 21 days afterwards, reaching a minimum at 52 days, when spermatogenesis was severely disrupted. The weights of the accessory organs and the concentrations of testosterone in peripheral blood were slightly reduced; the concentrations in blood from the testicular veins were lower than control at shorter intervals after irradiation, but at later times tended to be similar or greater than control. Testicular blood flow per testis followed testis weight closely, and as a result the production of testosterone by the smaller testes (calculated as the product of plasma flow and the veno–arterial difference in testosterone concentration) was markedly reduced especially when the rats had been stimulated with human chorionic gonadotrophin (hCG). Serum FSH and LH rose appreciably as testis weight fell but there was a proportionately greater rise in FSH than LH, in comparison with surgically castrated animals. Increased amounts of extratubular, extracellular fluid were found in the aspermatogenic testes, but injection of hCG still caused increases in capillary permeability and the amount of fluid in the testis.
These results indicate that during aspermatogenesis following irradiation (as with heat and efferent duct ligation) the capacity of the testes to secrete testosterone is severely limited by decreased testicular blood flow, not by the ability of the Leydig cells to release testosterone into their immediate environment.
Influence of certain steroids on lymphocyte transformation in sheep and goats studied in vitro
Authors: Staples L. D. , Binns R. M. , Heap R. B. 
Published: December 2008

The effect of various steroids on lymphocyte transformation was tested with peripheral blood lymphocytes (PBL) from sheep and goats. Transformation was induced with phytohaemagglutinin, pokeweed mitogen and Concanavalin A, and by allogeneic lymphocytes (mixed lymphocyte culture). Progestagens, androgens and corticosteroids inhibited mitogen-induced transformation of lymphocytes from both species. With sheep PBL, progestagens and androgens inhibited transformation at high concentrations. Progesterone and its less active metabolites 5α-pregnanedione and 20α-dihydroprogesterone were equally inhibitory. Corticosteroids were more effective than other steroids at concentrations of less than 1 μmol/l. Oestrogens had relatively little effect with the exception of diethylstilboestrol which markedly enhanced sheep PBL responses to mitogen. Structural comparisons suggested that the most suppressive C-19 and C-21 steroids possessed 4-en-3-one configuration in ring A, and that inhibitory activity was enhanced by C-17α substitution as in 17α-hydroxyprogesterone.
The steroid effects on PBL were largely unaffected by the reproductive status of the donor, were exerted during the early pre-replicative phase rather than at the time of new DNA synthesis, and were not attributable to cytotoxicity nor to changes in intracellular thymidine pools. An exception was found with the non-steroidal oestrogen, diethylstilboestrol, which enhanced the response to mitogen-treated cultures of sheep lymphocytes at both early and late phases of the cell cycle.
It is concluded that several naturally occurring steroids affect the responsiveness of PBL to mitogenic stimuli, and that progesterone and/or certain of its metabolites may be effective in vivo when present at the high concentrations found in the utero-ovarian lymphatic network draining the gravid uterus or at the trophoblast-maternal interface in the sheep and goat.
Effect of various anaesthetics on resting plasma concentrations of luteinizing hormone, follicle-stimulating hormone and prolactin in ovariectomized ewes
Authors: Clarke I. J. , Doughton B. W. 
Published: December 2008

Effects of various anaesthetics on plasma LH, FSH and prolactin levels were studied in ovariectomized ewes. In the first experimental series, conducted between June and November (late breeding season, early anoestrous season), the following treatments were given: saline (i.v.) (n = 7); single thiopentone injection (i.v.) (n = 4); induction of anaesthesia for 2 h with thiopentone (n = 5), ketamine/thiopentone mixture (n = 6), Alphathesin (n = 6) or induction with thiopentone and maintenance with halothane (n = 6). The major findings were: (1) halothane anaesthesia reduced mean plasma LH levels by preventing pulsatile secretion of LH; (2) Alphathesin had the least effect on tonic LH concentration; (3) a single thiopentone injection did not affect LH levels; (4) continuous thiopentone anaesthesia increased LH pulse amplitude; (5) plasma FSH concentration was not affected by any of the treatments; (6) ketamine/thiopentone-induced and Alphathesin-induced anaesthesia increased plasma prolactin levels.
In a second experimental series four ovariectomized ewes were anaesthetized with thiopentone for 3 h in January. In contrast to the results obtained with thiopentone in August, treatment in January reduced plasma LH pulse amplitude and mean plasma LH levels. These latter results support the hypothesis that there may be seasonal variation in responses to barbiturate anaesthesia.
Inhibition of phasic but not tonic pituitary secretion by 2-hydroxyoestrone in the rat: evidence of action as an oestrogen antagonist
Authors: Katayama Shigehiro , Fishman Jack 
Published: December 2008

Rats with 4-day oestrous cycles, implanted with intracardiac catheters, were injected with 2-hydroxyoestrone at noon on pro-oestrus and their plasma LH levels monitored at frequent intervals thereafter. A dose of 100 μg 2-hydroxyoestrone completely abolished the preovulatory LH rise in four out of ten animals tested, showing no effect in the six others. When an injection of 10 μg oestradiol 1 h before the 2-hydroxyoestrone administration was given all the rats showed an absence of the preovulatory LH surge, while it remained intact in the controls treated with oestradiol only. The principal metabolite of 2-hydroxyoestrone, 2-methoxyoestrone, exhibited no influence on the pituitary gonadotrophin release. Repeated injections of 100 pg doses of 2-hydroxyoestrone to long-term ovariectomized rats produced no change in plasma LH and prolactin levels. In animals primed with oestradiol benzoate, 2-hydroxyoestrone given 1–2 h after the priming dose blocked the phasic release of the pituitary hormones on the afternoon of the 2 subsequent days. The LH and prolactin surges in the primed animals, however, were not affected when the catechol oestrogen was injected 2 h before their appearance.
These results indicate that in the cyclic rat exogenous 2-hydroxyoestrone inhibits the preovulatory LH surge when its administration is coincident with the preovulatory oestradiol rise. In the ovariectomized rat 2-hydroxyoestrone inhibits the oestrogen-dependent priming step but does not affect either the oestrogen-independent expression of the induced surges or the tonic secretion of these pituitary hormones.
These results indicate a dissociation of central and peripheral activities in this oestradiol metabolite and suggest that this catechol oestrogen functions as an oestrogen antagonist in neuroendocrine events. Since catechol oestrogens can be formed in the brain these pharmacological responses may reflect physiological mechanisms.
Reduced adrenocortical function and increased thyroid function in fasted and refed chickens
Authors: Harvey S. , Klandorf H. 
Published: December 2008

The deprivation of food for 48 h markedly increased (P< 0·001) the corticosterone concentration in the plasma of 7- to 8-week-old chickens. When fasted birds were refed for 2 min or 5 s the corticosterone concentration fell to the level in fed birds within 30 min of refeeding. In fasted and refed birds the plasma corticosterone concentration remained lowered for at least 150 min after a 2-min period of refeeding, whereas in birds refed for 5 s the concentration had increased within 120 min to that in fasted birds. When fasted birds were refed 1, 5, 15 or 30 g diet the corticosterone level was again markedly reduced (P< 0·001) within 45 min of refeeding. The magnitude of this post-feeding decline was unrelated to the amount of food eaten, although its duration was; the level in birds refed 1, 5 or 15 g food increasing to that in fasted birds within 90, 135 and 225 min respectively. The corticosterone level in birds refed 30 g diet remained reduced for at least 225 min but increased to that in fasted birds 24 h after refeeding. The initial decline in the corticosterone concentration was unrelated to the consumption of food, since a similar reduction in the corticosterone level was observed in fasted birds which were given the sight of food but prevented from eating it by Perspex lids attached to the food troughs. This initial decline in the corticosterone level was not a result of stress, as it did not occur in fasted control birds. These results suggest that the adrenocortical changes in fasted and refed birds is initially mediated by a conditioned neural stimulus (reinforcement) and is maintained as a result of peripheral metabolic effects of ingested food.
In fasted chickens the concentration of plasma tri-iodothyronine (T3) was greatly reduced (P<0·001) in comparison with fed birds. When fasted birds were refed for 2 min or with 5, 15 or 30 g diet, the level of plasma T3 was increased (P < 0·05) 90 min after refeeding although not to the level in birds which had free access to food. The magnitude and duration of this increase was related to the amount of food consumed and was not observed in birds refed for 5 s or with 1 g food or in fasted birds given sight of but not access to food.
Ovine placental lactogen concentrations during premature delivery induced by infusion of dexamethasone or adrenocorticotrophin to the fetus
Authors: Taylor M. J. , Robinson J. S. , Jenkin G. , Thorburn G. D. 
Published: December 2008

Premature delivery was induced by intrafetal infusion of dexamethasone or (1–24)ACTH, starting between days 124 and 129 of pregnancy in twelve ewes carrying intact (n = 7) or hypophysectomized (n = 5) single fetuses. Concentrations of ovine placental lactogen (oPL) in maternal plasma were measured by specific radioimmunoassay before and during premature delivery. There was no significant change in oPL concentrations before delivery in ewes carrying either intact or hypophysectomized fetuses.
The results suggest that a prepartum decline in oPL is not an essential prerequisite for delivery, and indicate that fetal glucocorticoids are not directly responsible for the prepartum fall in oPL concentrations observed at spontaneous delivery.
Depression of sodium, chloride and calcium ions in the plasma of goldfish (Carassius auratus) and immature freshwater- and seawater-adapted eels (Anguilla anguilla L.) after acute administration of salmon calcitonin
Authors: Wales N. A. M. , Barrett A. L. 
Published: December 2008

Goldfish showed a significant reduction in their plasma sodium and calcium levels 1 h after receiving 50 i.u. calcitonin per kg body weight. When 100 i.u. calcitonin were injected there was a significant fall in circulating levels of both sodium and calcium and also of chloride ions compared with those found in untreated control animals. Administration of calcitonin to immature eels adapted to either freshwater or seawater conditions showed no significant change in plasma ion composition at doses of 10 i.u. per kg body weight or less. However, doses of 50 and 100 i.u. caused significant reductions in plasma sodium, chloride and calcium ion levels compared with sham-injected control animals.
When immature eels were given 100 i.u. calcitonin per kg body weight there were significant reductions in the plasma levels of sodium, chloride and calcium ions but the timing of these changes was slightly different. In freshwater-adapted eels, the depression of plasma sodium was seen after 30 min and lasted for up to 2 h, whilst depression of plasma chloride and calcium was not seen until 1 h after injection. In addition, whilst the lowering of plasma chloride ions lasted up to 2 h after injection, the plasma calcium had returned to the preinjection control level by this time.
In seawater-adapted eels the depression of sodium, chloride and calcium levels was seen at 30 min and the effect continued for up to 2 h after injection when the depression was no longer apparent.
Biosynthesis of pro-opiomelanocortin-related peptides in the neurointermediate lobe of the pituitary gland of the rainbow trout (Salmo gairdneri)
Authors: Rodrigues K. T. , Jenks B. G. , Sumpter J. P. 
Published: December 2008

This study concerns the biosynthesis of a number of peptides in the neurointermediate lobe of the rainbow trout, Salmo gairdneri. Among the newly synthesized peptides positively identified were four forms of α-MSH, a β-MSH and two forms of endorphin. The identification of two of the products as sequentially distinct endorphins suggests that the trout neurointermediate lobe synthesizes two pro-opiomelanocortin (POMC) molecules. This may account for the large number of peptides synthesized and secreted by the trout neurointermediate lobe. The identification of some of the products is discussed.
Pulse-chase analysis revealed no positive identification of a precursor molecule, which may indicate that trout POMC is very rapidly processed into smaller products. All of the newly synthesized peptides were secreted concomitantly. There was little if any evidence of post-translational modification of any of the peptides during their secretion.
Plasma testosterone levels in adult and neonatal female rats bearing testosterone propionate-filled silicone elastomer capsules for varying periods of time
Authors: Sommerville E. M. , Tarttelin M. F. 
Published: December 2008

Testosterone propionate (TP) was administered, by means of subcutaneous implanted silicone elastomer capsules, into adult and neonatal (aged 3 days) female rats.
In the adult rats a dose-dependent increase in plasma testosterone was measured for capsules of three different sizes (5, 10 and 20 mm crystal length). Testosterone levels reached a peak 4–8 h after insertion (5 mm, 24·6±1·4 (s.e.m.) nmol/l; 10 mm, 34·0 ± 3±8; 20 mm, 44·4 ± 3·1) and returned to control levels within 4 h after removal: the calculated half-life of testosterone was 1 h for all sizes of capsule. In neonates, a capsule of 2·5 mm crystal length was removed after 4 h subcutaneous implantation (at day 3 of age) and produced peak testosterone levels of 126·2± 11·8 nmol/l: the calculated half-life was 8·6 h which compared with a half-life of 48 h after a subcutaneous injection of 312 μmol TP (in 0·05 ml arachis oil) which produced peak levels of testosterone in 4–8 h of 84·6 ±11·8 nmol/l. Chronic implants of TP-filled capsules (2·5 mm crystal length) at 3 days of age and left in situ for 15 weeks gave a half-life of 69 h.
Removable silicone elastomer capsules were found to be a versatile vehicle for the administration of TP to rats of all ages where precise hormone treatment for a known period or prolonged administration is required. The duration and magnitude of plasma hormone levels should be established by assay in an in-vivo situation.
The use of heterologous radioimmunoassays for the measurement of follicle-stimulating hormone and luteinizing hormone concentrations in horse and donkey serum
Authors: Urwin Valerie 
Published: December 2008

Heterologous double-antibody radioimmunoassays were developed for the measurement of FSH and LH concentrations in the serum of both horses and donkeys. The FSH assay employed a rabbit anti-ovine FSH serum which showed a complete lack of cross-reaction with equine chorionic gonadotrophin (eCG) and negligible cross-reaction with equine LH. The LH assay utilized an antiserum raised against highly purified eCG. This similarly showed negligible cross-reaction with equine FSH but its high cross-reactivity with eCG prevented the measurement of equine LH concentrations in serum when eCG was also present. In both assays serial dilutions of horse and donkey serum were parallel to the standard.
The assays were used to monitor changes in serum concentrations of FSH and LH during the first 100 days of pregnancy in pony mares and jenny donkeys. In both species during pregnancy LH levels reached a peak 1–2 days after ovulation. They then decreased rapidly to baseline levels where they remained until days 35–40 when the commencement of eCG production prevented their further measurement. Serum FSH concentrations, on the other hand, continued to fluctuate markedly throughout the first 100 days of pregnancy in both the ponies and donkeys. Pronounced surges in FSH levels occurred at regular intervals in some animals but the pattern of release was quite irregular in the others.
The results of this study support the concept that it is continued pituitary FSH release, not eCG secretion, which is responsible for stimulating the secondary follicles which develop during early equine pregnancy. However, it appears likely that it is the LH-like activity of eCG which causes the subsequent ovulation and/or luteinization of these secondary follicles to produce accessory corpora lutea.