bluuebunny/crossref_metadata_2025 huggingface dataset:
Unfilled nuclear oestrogen receptors in the rat brain and pituitary gland
Authors: Clark C. R. , MacLusky N. J. , Naftolin F.
Published: December 2008

This study describes the presence of a population of oestrogen receptors in cell nuclei from the pituitary gland and brain of untreated and oestradiol-treated ovariectomized rats. The receptors behaved as if they were not occupied by oestradiol. These 'unfilled' oestrogen receptors could be distinguished from occupied nuclear receptor sites on the basis of their ability to bind [3H]oestradiol at low temperatures (0–4 °C). Occupied receptors bound labelled [3H]oestradiol only under exchange conditions at an increased temperature (25 °C). Unfilled and occupied nuclear receptors were physicochemically similar in terms of sedimentation coefficients in sucrose density gradients containing 0·4 m-KC1 (4–5S), equilibrium dissociation constants for reaction with [3H]oestradiol (0·2–0·6 nmol/l) and ligand specificity. In ovariectomized rats, unfilled receptors constituted more than 75 % of the total nuclear receptor population. One hour after i.v. treatment with oestradiol (3·6 μg/kg), both total and unfilled nuclear receptor concentrations increased and then subsequently declined over the next 12 h. The increase in unfilled sites was, however, proportionately less than that occurring in the filled component; at 1 h after oestradiol injection unfilled sites constituted less than 20% of the receptors present in brain and pituitary cell nuclei. The physiological significance of unfilled nuclear oestrogen receptors remains unknown. The observations that they exist in various oestrogen target tissues and that their levels are influenced by oestradiol treatment suggest a possible role for these receptors in the mechanism of oestrogen action.
Role of the organum vasculosum laminae terminalis in the control of gonadotrophin secretion in rats
Authors: Piva F. , Limonta P. , Martini L.
Published: December 2008

The organum vasculosum laminae terminalis (OVLT) was destroyed by radiofrequency lesions in regularly cycling and in long-term ovariectomized adult rats. After OVLT lesion practically all cyclic females (16 out of 22) became dioestrous, as indicated by vaginal smears. At the time of killing these animals (8 days after the lesion) serum LH levels were undetectable, while serum FSH was as low as in cyclic animals in dioestrus. In the few OVLT-lesioned animals which exhibited some sort of oestrous cyclicity, serum LH showed a small subphysiological increase at pro-oestrus: this was not accompanied by a parallel increase in serum FSH and in these animals a delayed peak of FSH occurred on the day of oestrus. Ovariectomized rats bearing OVLT lesions had serum titres of LH and FSH as high as those of ovariectomized control rats. It is suggested that the OVLT may play a role in the control of the cyclic release of gonadotrophins but is not involved in the tonic regulation of gonadotrophin secretion.
Plasma cortisol response to thyrotrophin releasing hormone and luteinizing hormone releasing hormone in healthy kennel dogs and in dogs with pituitary-dependent hyperadrenocorticism
Authors: Stolp R. , Croughs R. J. M. , Meijer J. C. , Rijnberk A.
Published: December 2008

The change in the plasma concentration of cortisol after the administration of thyrotrophin releasing hormone (TRH) and LH releasing hormone (LH-RH) was studied in normal dogs and in dogs with pituitary-dependent hyperadrenocorticism (PDH). The normal dogs showed a small but significant increase in the plasma concentration of cortisol 15 min after intravenous injection of TRH and LH-RH. In ten of the dogs with PDH the response to TRH was not significantly different from that in the normal dogs, but in 13 the response was significantly greater. In 15 of the dogs with PDH the response to LH-RH administration was within or below the range of responses in the normal dogs and in only one dog was the response to LH-RH greater than that in the normal dogs. These findings are discussed in relation to the pathogenesis of PDH.
Comparison of human and porcine thyroid membranes for radioreceptor assay of bovine thyrotrophin and thyrotrophin-binding inhibiting immunoglobulins
Authors: Humphries Hazel , Dirmikis Susan M. , Munro D. S.
Published: December 2008

A detailed comparison between the use of human and porcine thyroid membranes for the radioreceptor assay (RRA) of bovine TSH (bTSH) and thyrotrophin-binding inhibiting immunoglobulins (TBIIg) is reported. Bovine thyroid membranes were also investigated but were found to be far less satisfactory than either human or porcine thyroid membranes. The affinity constant (Ka) of the interaction of bTSH with porcine thyroid membranes (Ka = 3·3 × 109l/mol) measured by Scatchard analysis was higher than with human thyroid membranes (Ka = 2·1 × 108l/mol). Porcine thyroid membranes were more sensitive for the assay of bTSH (detection limit 30 μu., half-maximal inhibition 0·3 mu.) than human thyroid membranes (detection limit 200 μu., half-maximal inhibition 7·4 mu.). Preincubation of membranes from either species with immunoglobulin rich in long-acting thyroid stimulator (LATS) inhibited the saturable binding of 125I-labelled TSH to a greater extent than did normal immunoglobulin. The binding of 125I-labelled TSH to porcine membranes was more sensitive to the inhibitory effect of LATS-immunoglobulin and was also less affected by normal immunoglobulin than was binding to human thyroid membranes. When assayed with each type of membrane preparation there was good correlation between the RRA of immunoglobulins prepared from patients with Graves's disease and from normal subjects (n = 18) (r = 0·85, P <0·001, n = 73). The incidence of positive TBIIg in untreated Graves's disease was greater for porcine than for human thyroid membranes.
Peptides derived from pro-opiocortin in the pituitary gland of the dogfish, Squalus acanthias
Authors: Denning-Kendall P. A. , Sumpter J. P. , Lowry P. J.
Published: December 2008

Combined rostral, median and neurointermediate lobes from 650 pituitary glands of the dogfish Squalus acanthias were extracted in 0·1 m-HCl and subjected to filtration on Sephadex G-50. Fractions were monitored for ACTH, α-MSH, γ-MSH and endorphin by heterologous radioimmunoassay, corticotrophin-like intermediate lobe peptide (CLIP) and γ-MSH by homologous radioimmunoassay, and methionine enkephalin after enzymatic digestion. The majority (about 99%) of the immunoreactivity detected was present as small peptides, with α-MSH, CLIP and γ-MSH predominant. The single peaks of ACTH, α-MSH and CLIP contrasted with many distinct peaks of endorphin-like immunoreactivity. The γ-MSH radioimmunoassays monitored different peptides; the heterologous assay revealed a single major peak, while the homologous assay detected a number of distinct small peptides. The results suggested that there may be more than three distinct forms of MSH in the dogfish pituitary gland. Small amounts of much larger proteins were detected by a number of the radioimmunoassays, suggesting that peptides related to ACTH, γ-MSH and lipotrophin are derived from common pro-opiocortin-type precursor molecules in this phylogenetically ancient cartilaginous fish.
Differential changes in body composition during growth and progesterone treatment in intact female rats
Authors: Ashby J. P. , Shirling D. , Baird J. D.
Published: December 2008

Female rats implanted with progesterone gained weight more rapidly than control animals and had a greater percentage of total body fat. The proportion of fat in the carcase of control animals also increased as they gained weight. Comparison of progesterone-treated rats with a group of weight-matched controls demonstrated that the effects of progesterone treatment on fat deposition exceeded those which would be expected to accompany their accelerated growth. Excess fat was deposited at the expense of the protein component of fat-free solid.
Effect of ovariectomy on the course of gestation in the grey squirrel (Sciurus carolinensis)
Authors: Webley G. E. , Johnson Elizabeth
Published: December 2008

In the grey squirrel pregnancy continues in the absence of the ovaries from day 16 of gestation. Since the investigation was performed on squirrels caught in the wild the stage of gestation was estimated from plasma progesterone levels, volume of corpora lutea at ovariectomy and date of parturition for those squirrels which did give birth. Three squirrels ovariectomized in early pregnancy did not give birth. Plasma progesterone levels after ovariectomy were lower than those found in normal pregnant squirrels suggesting that the corpora lutea are a continuing source of progesterone even at a time when pregnancy can continue in their absence.
Metabolic clearance rate in sheep of a met-enkephalin analogue estimated by radioimmunoassay
Authors: Bolton J. E. , Livesey J. H. , Donald R. A.
Published: December 2008

A sensitive and specific radioimmunoassay developed for measuring the met-enkephalin analogue d-ala2-met(0)5-ol-enkephalin (DAMME) was used to study the pharmacokinetics of DAMME in the circulation of sheep. Plasma concentrations of DAMME were measured at varying time-intervals after an intravenous bolus injection or following a constant intravenous infusion of the analogue. The mean metabolic clearance rate of DAMME was 2·8 ml/min per kg, the mean circulating half-life was 52 min and the mean volume of distribution was 190 ml/kg. The longer circulating time of the analogue when compared with that of naturally occurring met-enkephalin would appear to explain its prolonged analgesic effect.
Effect of Ca2+ deprivation on release of luteinizing hormone induced by luteinizing hormone releasing hormone from female rat pituitary glands in vitro
Authors: de Koning J. , Tijssen A. M. I. , van Dieten J. A. M. J. , van Rees G. P.
Published: December 2008

Continuous exposure of hemi-pituitary glands from intact female rats to LH releasing hormone (LH-RH) in vitro displayed three phases in the pattern of LH release: during the first hour release of LH was low (first phase response), then it increased to a higher level during the second hour and remained constant during the next 2 h (second phase response), after which there was a refractoriness of LH release (third phase response). The initial phase response of pituitary glands from intact rats was blocked by EGTA (a Ca2+ chelator) but there was a small but significant increase in the rate of LH release during the second phase response. This increase could be prevented by inhibition of protein synthesis by cycloheximide. Cycloheximide and EGTA did not affect basal release of LH by glands from intact rats, neither did EGTA affect the high basal release of LH by glands from ovariectomized rats. However, the LH-RH-induced release of LH from pituitary glands of ovariectomized rats, which did not show the initial phase of low LH release, was completely suppressed by EGTA throughout a 4-h incubation period.

The pattern of LH release stimulated by the combination of N6-monobutyryl cyclic AMP and theophylline (mbcAMP/theophylline) showed an initial phase of low LH release lasting 4 h after which it increased. The magnitude of the effect was small compared with the action of LH-RH. As it did with LH-RH, EGTA completely blocked the initial response, but allowed a small increase in the rate of LH release thereafter; this increase could also be blocked by inhibition of protein synthesis.

Addition of EGTA to media during pretreatment of pituitary glands from intact rats with either LH-RH or mbcAMP/theophylline did not impair the facilitatory effect of these secretagogues on the responsiveness of the glands to subsequent exposure to LH-RH and cycloheximide and normal Ca2+ levels. The restoration of Ca2+ levels after withdrawal neither affected basal nor LH-RH-induced release of LH.

Exclusion of Ca2+ from the media during a 6-h incubation of pituitary glands from intact rats with LH-RH prevented the glands from becoming refractory to subsequent stimulation by LH-RH, which occurs when normal Ca2+ concentrations are present.

The results suggested that extracellular Ca2+ is obligatory for LH release and the induction of refractoriness by LH-RH. In contrast, that part of the action of LH-RH which is cyclic AMP-mediated and protein synthesis-dependent is not affected by withdrawal of extracellular Ca2+.
Molecular composition of human luteinizing hormone: biological and immunological profiles of highly purified preparations after electrofocusing
Authors: Zaidi A. A. , Qazi M. H. , Diczfalusy E.
Published: December 2008

Five highly purified human pituitary LH preparations (candidate preparations for a new International Reference Preparation (IRP) and coded A to E) and three highly purified commercial preparations (referred to as Kabi I, II and III) were fractionated by electrofocusing on a sucrose density gradient with ampholytes in the pH range of 3·5–10·0 The LH activity was monitored in each of the eluted fractions by an in-vitro bioassay and a radioimmunoassay procedure and the profiles of biological activity and immunoreactivity were compared with those of the first IRP of Human Pituitary Luteinizing Hormone for Immunoassay (code no. 68/40).

The overall recovery of the biological activity after electrofocusing of the nine preparations ranged between 75 and 92% (mean 86%) and was higher (P < 0·05) than that of the immunological reactivity which varied between 71 and 94% (mean 79%).

The profiles of the biological activity and immunological reactivity were in close agreement with each other in all preparations. Significant differences were, however, observed in the distribution of various molecular species between the currently used standard and the eight other highly purified preparations.

The ratios of biological activity (B) to immunoreactivity (I) of preparation B and of the three Kabi preparations were significantly higher than those of the other five preparations, both before and after electrofocusing. After electrofocusing, a slight but significant (P < 0·05) rise in the B/I ratios was observed, suggesting that some biologically inactive immunoreactive material was removed during fractionation. All purified preparations lacked the characteristic 'acidic' human LH species which accompanies FSH and which is abundant in the IRP (69/104) and is also present in aqueous extracts of postmenopausal pituitary glands.

A comparison of the electrofocusing profiles of the nine highly purified preparations with those of human LH from plasma and individual pituitary glands revealed marked differences, suggesting that the methods used for the purification of the hormone significantly altered its molecular composition.
Hormones and the differentiation of type A spermatogonia in mouse cryptorchid testes incubated in vitro
Authors: Haneji Tatsuji , Nishimune Yoshitake
Published: December 2008

In order to study hormonal effects on testicular germ cell differentiation, especially on type A spermatogonia, artificially induced cryptorchid testes of adult mice were cultured in a medium containing testosterone, dihydrotestosterone, tri-iodothyronine, dibutyryl 3′: 5′ cyclic adenosine monophosphate, human chorionic gonadotrophin, LH, FSH, insulin and transferrin. These substances, with the exception of FSH, showed no stimulatory effect on the differentiation of type A spermatogonia. However, FSH activated cell division in type A spermatogonia and stimulated them to differentiate, while LH showed neither the promotion of differentiation nor a synergistic effect on FSH-mediated germ cell differentiation.
A progesterone binding component in porcine ovarian follicular fluid
Authors: Fleming A. D. , McGaughey R. W.
Published: December 2008

Steroid hormone concentrations (progesterone, oestrone, oestradiol-17β) in porcine follicular fluids were measured by radioimmunoassay. In confirmation of several previous studies, as follicular maturation proceeded, the concentrations of all three steroids increased, although the relative amounts of the oestrogens decreased compared to progesterone. Analysis of fluids for steroid-binding components was undertaken using ion-exchange chromatography, gel filtration and steroid-binding assays. Evidence is presented in support of a labile binding component which exhibits high affinity and low capacity for progesterone and little or no affinity for oestradiol. Our findings are discussed in relationship to the known retention of progesterone within preovulatory follicles and to previous reports of steroid-binding components in follicular fluids.
Fetal and maternal production and metabolism of gastrin in sheep
Authors: Shulkes Arthur , Chick Patricia , Hardy K. J.
Published: December 2008

In the sheep fetus, plasma levels of gastrin are raised above adult levels from 2 weeks before birth. This observation initiated the present study on the maternal and fetal secretion rate, metabolism and placental transfer of gastrin. The experiments were performed on conscious pregnant ewes with chronically cannulated fetuses and on newborn lambs. Metabolic clearance rate (MCR), production rate (PR) and placental transfer of gastrin were measured by alternate steady-state infusion of gastrin into the mother and fetus. Plasma levels of gastrin were measured by radioimmunoassay.

Metabolic clearance rate was similar in the pregnant and non-pregnant ewe (8·4± 1·1 (s.e.m.) and 9·0±1·4 ml/min per kg) respectively. However, fetal MCR was significantly increased. Term was 145 days. Metabolic clearance rate was 15·5 ± 1·7 at 110–125 days of gestation, 25·6 ± 2·9 at 126–135 days, 29·7 ± 4·9 at 136–145 days and remained raised in the first 2 weeks post partum.

Gastrin did not cross the placenta in either direction. Placental destruction of gastrin was not responsible for the increased fetal MCR as umbilical artery and umbilical vein levels were not significantly different during fetal gastrin infusion. Furthermore, MCR remained raised in the newborn lambs. Gastrin PR was significantly increased at all ages.

The results showed that the previously reported fetal hypergastrinaemia is from fetal sources and is not a result of immaturity of clearance mechanisms. In fact, fetal MCR was significantly increased. The increased fetal plasma gastrin levels are due to an increased rate of production from the fetus.
Studies of a human growth hormone preparation used for clinical treatment in Great Britain
Authors: Stein Janet , Lester John , Fosten Amanda , Shownkeen Ratna C. , Hartree Anne Stockell
Published: December 2008

This report describes some of the properties of a clinical-grade preparation of human growth hormone (hGH) extracted from acetone-preserved autopsy human pituitary glands and used in Great Britain from 1967 to 1980. Gel filtration of this hGH on Sephadex G-100 yielded (on a weight basis) an average of 48% of a high molecular weight fraction, 10% of an intermediate fraction expected to contain dimeric forms of the hormone and 33% of a fraction considered to be the hGH monomer. The immunoassay potency of the monomer fraction was twice that of the clinical-grade preparation and the amino-acid composition of the monomer fraction agreed well with that obtained from published hGH sequence data. The results of polyacrylamide-gel electrophoresis (under reducing and dissociating conditions) and amino-acid analysis of the high molecular weight fraction suggest that it contains around 30% of aggregated hGH as well as other material not separated from hGH by the purification procedure.
Localization of thioesterase II, the chain-length regulatory enzyme of milk fatty acid synthesis, in rat mammary gland epithelial cells
Authors: Nolin Janet M. , Thompson Betty J. , Smith Stuart
Published: December 2008

Two approaches were used to establish the intercellular distribution of fatty acid synthetase and thioesterase II in the lactating rat mammary gland. Thioesterase II is the chain-length regulatory enzyme in the biosynthesis of the medium-chain fatty acids characteristic of milk fat. Using immunohistochemical techniques, immunoreactive fatty acid synthetase was found in both mammary adipocytes and epithelial cells; in contrast, immunoreactive thioesterase II was confined to the epithelial cells. In metabolic studies, adipocytes and epithelial cells were isolated from lactating rat mammary glands after digestion with collagenase and thermolysin, and their lipogenic activity was studied using isotopically labelled acetate. Consistent with the immunohistochemical data, adipocytes synthesized exclusively long-chain fatty acids whereas epithelial cells synthesized predominantly medium-chain fatty acids. The results indicate that the capacity for synthesis of medium-chain fatty acids is a unique property of the epithelial cell component of the mammary gland.
Effect of progesterone on the non-genomic response to oestrogen in the rat
Authors: Grunert Germana , Tchernitchin A. N.
Published: December 2008

Different effects of oestrogen are mediated separately, by independent mechanisms of action. Accordingly, it has been shown that it is possible to dissociate these effects under various conditions which stimulate or inhibit responses selectively. The present study describes the action of progesterone on non-genomic responses to oestrogen stimulation which, it has been suggested, are mediated by eosinophils.

Oestrogen induced an increase in the number of eosinophils in the rat uterus, an increase in uterine wet weight and oedema of deep endometrial stroma (measured as decrease in cellular density). Progesterone induced a slight oedematous reaction in superficial endometrial stroma but did not induce uterine eosinophilia. Progesterone pretreatment of oestrogen-treated rats did not block oestrogen-induced uterine eosinophilia and oedema but induced an increase in the degranulation of uterine eosinophils. Therefore the number of eosinophils decreased without any change in the uterine oedema induced after 6 h of oestrogen action. The results corroborate previously published evidence of a dissociation of the action of oestrogen in independent groups of responses. Progesterone, a known blocker of some oestrogenic responses, did not block the effects mediated by eosinophils at 6 h after oestrogen administration; any change in these effects at later times can be explained by an earlier eosinophil degranulation under the action of progesterone.
Thyroid function in adrenaline-induced changes in the intermediary metabolism of the chequered water-snake (Natrix piscator)
Authors: Gupta S. C. , Thapliyal J. P.
Published: December 2008

Injection of adrenaline in ten daily doses of 100 μg each into the chequered water-snake, Natrix piscator, stimulated glycogenolysis and lipid esterification in the liver and lipolysis in the adipose tissue of control snakes. In both thyroidectomized and control snakes plasma protein levels decreased significantly after hormone treatment, although there was no change in concentrations of muscle glycogen and plasma lactic acid. In thyroidectomized snakes, the hormone stimulated oxidation of the free fatty acids but had no significant effect on the synthesis of the triglycerides. It is suggested that in these snakes the presence of the thyroid hormones is a prerequisite for the response of most of the metabolic processes to adrenaline.
Effects of pancreatectomy, tolbutamide and insulin on glucose fluxes in chickens
Authors: Danby R. W. , Martin I. K. , Gibson W. R.
Published: December 2008

The effects of pancreatectomy and of injection of insulin or tolbutamide on glucose fluxes in chickens were examined. This was prompted by earlier observations that tolbutamide seems not to require the presence of pancreatic insulin for its acute hypoglycaemic action in this species. Rates of appearance (Ra) and disappearance (Rd) of glucose were estimated by isotope dilution using [14C]glucose in single-injection experiments and [14C]glucose and [6−3H]glucose in priming-injection + constant-infusion experiments.

Six hours after sub-total pancreatectomy (splenic lobe remained in situ), chickens were hyperglycaemic (16·7 v. 10·4 mmol glucose/l in controls), had a larger sampled glucose pool (4·41 v. 3·10 mmol) and a higher average rate of glucose utilization (41·7 v. 33·3 μmol/kg per min) than sham-operated controls as estimated in single-injection experiments. Tolbutamide (50 mg/kg injected i.v.) reduced Ra in intact chickens from 33·9 to 1·1 μmol/kg per min and reduced Ra in pancreatectomized chickens from 42·2 to 10·2 μmol/kg per min. In priming-injection + constant-infusion experiments tolbutamide again reduced Ra significantly. In all cases Rd tended to fall, apparently as a result of the developing hypoglycaemia. Tolbutamide did not affect the volume of extracellular fluid (sucrose space). In single-injection experiments, insulin (1 unit/kg injected i.v.) reduced Ra by 56% and transiently increased Rd by 39%.

It was concluded that pancreatectomy and injection of insulin or tolbutamide produce responses in glucose movements in chickens that are qualitatively similar to those in mammals. In chickens the hypoglycaemic action of tolbutamide, which persists in the absence of the pancreas, depends on an inhibition of glucose release by the liver.
Pimozide-induced chronic hyperprolactinaemia and quantitative initiation of spermatogenesis in maturing rats
Authors: Nag S. , Sanyal S. , Biswas N. M.
Published: December 2008

When pimozide was given to maturing rats, a rise in the level of prolactin in the serum was accompanied by a fall in LH. There was also incomplete initiation of spermatogenesis as well as simultaneous adrenal hypertrophy. Bilateral adrenalectomy failed to prevent hyperprolactinaemia-induced antispermatogenic response, while a significant ameliorating effect was observed with LH, indicating that hyperprolactinaemia influenced the quantitative initiation of spermatogenesis by affecting the secretion of LH.
Flurothyl-induced convulsions delay the onset of sexual maturation in the female rat
Authors: Wilkinson M. , Bhanot R. , Pincock J. A. , Donald L.
Published: December 2008

We have investigated whether sexual maturation in female rats is affected by repeated flurothyl-induced convulsions. This treatment had no effect on the normal age-related increase in body weight though puberty (vaginal opening) was significantly delayed when compared with non-convulsed control rats. In an attempt to probe the mechanism of this delaying effect we observed that (1) anterior pituitary response to gonadotrophin releasing hormone in vitro was normal in terms of LH release but FSH secretion was impaired and (2) progesterone injection in oestrogen-primed convulsed rats failed to generate an ovulatory-type surge of LH or FSH. Basal serum levels and basal in-vitro secretion of LH and FSH were normal. We conclude that repeated convulsions adversely affect the hypothalamo-pituitary-gonadotrophin system of immature female rats.
Androgen and oestrogen dynamics in hyperthyroidism
Authors: Ridgway E. C. , Maloof Farahe , Longcope Christopher
Published: December 2008

Using constant infusions of [3H]testosterone and [14C]oestradiol or [3H]androstenedione and [14C]oestrone the dynamics of androgen and oestrogen metabolism and production in patients with hyperthyroidism were measured.

The metabolic clearance rates of testosterone and oestradiol were decreased but those of androstenedione and oestrone were within the normal range. The conversion ratios of testosterone to androstenedione and of testosterone to dihydrotestosterone (DHT) were decreased whereas those of androstenedione to testosterone and androstenedione to DHT were increased. These changes could be explained by increased serum levels of sex hormone binding globulin which binds testosterone and DHT but not androstenedione.

The fraction of androstenedione infused into and measured as oestrone in the blood was normal in seven out of nine subjects and the fraction of testosterone infused and measured as oestradiol was normal in all nine subjects.

The production rates of testosterone and oestradiol were in the normal range but the production rates of androstenedione and oestrone were raised in half the subjects.
Thyroid xanthine oxidase and its role in thyroid iodine metabolism in the rat: difference between effects of allopurinol and tungstate
Authors: Kawada J. , Shirakawa Y. , Yoshimura Y. , Nishida M.
Published: December 2008

The role of xanthine oxidase in thyroid function was studied in the rat in vivo by different approaches. Allopurinol, an inhibitor of xanthine oxidase, was administered by mixing it with a powdered diet (16 mg/100 g body wt per day for 10 days). This treatment significantly reduced the total uptake of iodide and inhibited the organification of iodide in the rat thyroid gland. Thyroid xanthine oxidase and dehydrogenase were almost completely inactivated by tungstate, which was given to rats (100 p.p.m./animal per day in drinking water for 10 days) maintained on a purified diet containing low levels of molybdenum. Under these conditions, no inhibitory effect was observed on synthesis of thyroid hormones. It therefore seemed reasonable to assume that the suppressive effect of allopurinol on the biosynthesis of thyroid hormones is not mediated by xanthine oxidase.
Regulation of plasma immunoreactive glucagon in obese hyperglycaemic (ob/ob) mice
Authors: Flatt P. R. , Bailey C. J. , Buchanan K. D.
Published: December 2008

This study examines the role of glucagon in the pathogenesis of the obese hyperglycaemic (ob/ob) syndrome in mice. Plasma C-terminal immunoreactive glucagon concentrations were measured in fed and fasted ob/ob mice at different ages between 5–40 weeks, and in 20-week-old mice after the administration of established stimulators and inhibitors of glucagon secretion. Plasma glucagon concentrations were inappropriately raised irrespective of age, nutritional status and the accompanying prominent changes in plasma glucose and insulin concentrations. Glucose suppressed plasma glucagon in the fed but not the fasted state, suggesting a dependence on the marked hyperinsulinaemia associated with feeding. Administration of 0·25 units insulin/kg to fasted mice failed to affect plasma glucagon and glucose concentrations. Increasing the dose to 100 units/kg restored the normal suppressive actions of insulin. Fasted mice showed an exaggerated glucagon response to arginine but not to the parasympathomimetic agent pilocarpine. Fed mice displayed normal plasma glucagon responses to the sympathomimetic agents noradrenaline and adrenaline. Administration of insulin antiserum or 2-deoxy-l-glucose raised plasma glucagon concentrations of fed mice. Contrary to the lack of suppression by glucose in the fasted state, heparin-induced increase in free fatty acids reduced plasma glucagon concentrations. This study demonstrates inappropriate hyperglucagonaemia and defective A-cell function in ob/ob mice. The extent of the abnormality is exacerbated by fasting and appears to result from insensitivity of the A-cell to the normal suppressive action of insulin.
Regulation of ovine placental lactogen: lack of correlation with progesterone secretion
Authors: Taylor M. J. , Jenkin G. , Robinson J. S. , Thorburn G. D.
Published: December 2008

After administration of an inhibitor of 3β-hydroxysteroid dehydrogenase activity to late-pregnant sheep, a sharp and significant fall in progesterone concentrations in peripheral plasma was noted, and lowered levels were sustained for up to 24 h. However, no significant change in the secretion of ovine placental lactogen (oPL) was noted. These results indicate that progesterone secretion does not regulate secretion of oPL during pregnancy.
Oestradiol-17β in the blood during seasonal reactivation of the diapausing blastocyst in a wild population of tammar wallabies
Authors: Flint A. P. F. , Renfree Marilyn B.
Published: December 2008

Oestradiol-17β was measured by radioimmunoassay in cardiac blood from 143 pregnant and post-partum tammar wallabies shot in the wild during reactivation of the diapausing blastocyst, embryonic development, birth and post-partum oestrus. A transient rise in circulating oestradiol on 3 January coincided with or shortly preceded corpus luteum growth and blastocyst expansion; before 5 January mean corpus luteum weight was 14·3± 0·44 mg (n = 65), while thereafter it exceeded 20 mg in two-thirds of the animals. Expanded blastocysts were first noted on 5 January. A second rise in the concentration of oestradiol in plasma, which occurred in late January, preceded parturition and coincided with follicular maturation; the mean (± s.e.m.) oestradiol concentration before 17 January was 27·9 ±1·10 pmol/l (n = 110), whereas on or after this date it was 57·3 ± 4·15 pmol/l (n = 33). Thus oestradiol levels in peripheral plasma increased at parturition and post-partum oestrus, and showed a rise early in gestation which may be related to the termination of diapause.
Progesterone and glucose metabolism in the female rat adipocyte: effect on hexokinase activity
Authors: Sutter-Dub M.-Th. , Vergnaud M.-Th.
Published: December 2008

Progesterone decreases the oxidation of 2-deoxyglucose and glucose through the pentose-phosphate pathway in isolated female rat adipocytes and, therefore, the effect of this steroid on the activity of the phosphorylating enzyme, hexokinase, was studied. After a 30-min incubation in vitro, progesterone decreased total hexokinase activity but did not affect the isoenzyme-I activity. Progesterone had no direct effect on fat cell cytosol hexokinase and its action on glucose oxidation was not affected by variations in the concentration of Mg2+, the cofactor of hexokinase. Our data suggest that the decreased activity of hexokinase in the presence of progesterone is due to a decrease in the activity of the insulin-sensitive isoenzyme-II. This results from the steroid acting at a step beyond enzyme activation and may be mediated by a feedback mechanism.
Absence of nocturnal autonomic prolactin secretion during lactation in the rat
Authors: Yogev L. , Terkel J.
Published: December 2008

During pseudopregnancy in the rat prolactin is secreted autonomously in a characteristic pattern of two daily surges, one nocturnal and one diurnal. The present study investigated whether, during lactation, prolactin secretion occurred in an autonomous nightly surge pattern, in addition to secretion resulting from suckling stimulation. Nocturnal levels of prolactin were measured daily for 2 weeks in lactating rats which were separated from their young from 21.00 to 06.00 h. It was found that no nocturnal prolactin surges were present throughout the 2 weeks of lactation. In addition, it was observed that after pups were removed for 3 h prolactin levels were lower during the first week of lactation than during the second week. It was concluded that lactational dioestrus is distinguished from pseudopregnancy by the absence of autonomous secretion of prolactin in the pattern of a nocturnal surge.
Oxytocin, vasopressin and neurophysins in the hypothalamo-neurohypophysial system of the human fetus
Authors: Burford G. D. , Robinson I. C. A. F.
Published: December 2008

The content of vasopressin, oxytocin and their related neurophysins was measured in the hypothalamus and pituitary gland of mid-trimester human fetuses. Vasopressin was present in both tissues approximately 3–4 weeks before oxytocin. The levels of the hormones in the pituitary gland increased 1000-fold over the next 3–4 months. During this time, the very high vasopressin/oxytocin ratio gradually decreased but did not reach unity in the period studied. In contrast, both the vasopressin-associated neurophysin and the oxytocin-associated neurophysin appeared in the pituitary gland at the same gestational age and showed the same exponential increase with fetal age. Lower levels of the neurophysins and the nonapeptides were found in the hypothalamus and the levels increased more slowly with fetal age. Our results suggest that the high vasopressin/oxytocin ratios observed in fetal life are due to differences in the rate of maturation of the hormone precursor, rather than to differences in the rate of de-novo synthesis.
Luteinizing hormone levels in aged female laboratory rodents as measured by a radioimmunoassay and a radioreceptor assay
Authors: Parkening T. A. , Collins T. J. , Smith E. R.
Published: December 2008

Plasma levels of LH were measured in young sexually mature (2- to 5-month-old) and aged (13- to 20-month-old) female C57BL/6 mice, Syrian hamsters and Wistar rats using a radioimmunoassay (RIA) and a radioreceptor assay (RRA). There were no statistically significant differences when comparing data from the two assays when examining young oestrous and dioestrous mice. Aged oestrous and dioestrous mice exhibited significantly higher levels of LH as measured by RIA than by RRA. Levels of LH analysed by RIA were also higher in aged mice compared with those in younger mice. Comparing LH concentrations with the two types of assays in younger dioestrous and aged anoestrous hamsters produced similar results. In contrast, aged pseudopregnant rats exhibited significantly lower levels of plasma LH than younger dioestrous females and there were no differences in RIA and RRA values. There were also no differences when comparing data from the two assays in younger rats. The mean (± s.e.m.) RRA: RIA ratios of 0·96 ± 0·05 (oestrous) and 0·96 ± 0·04 (dioestrous) for younger mice and 0·92 ± 0·08 for younger hamsters were significantly higher than the ratios of 0·66 ± 0·72± 0·05 and 0·71 ± 0·05 respectively of their aged counterparts. The mean RRA: RIA ratios in the two age groups of rats were almost identical (0·79 ± 0·05 and 0·80 ± 0·10). These studies suggested that a portion of the higher LH levels detectable by RIA in some aged female rodents results from qualitative changes in the LH molecule.
Seasonal rhythms of plasma gonadotrophins: their persistence in elderly men and women
Authors: Touitou Yvan , Lagoguey Michel , Bogdan André , Reinberg Alain , Beck Hervé
Published: December 2008

Circannual changes of immunoreactive LH and FSH were documented on a circadian basis in January, March, June and October in four groups of subjects: seven young men, six elderly men, six elderly women and six men and women suffering from senile dementia. The sampling was serially dependent only for the young men and the core subgroups of elderly men and elderly women. A circadian rhythm for FSH was not detected in any group of subjects during any of the sampling sessions, whereas a circadian rhythm for LH was detected twice (June and October) in young men, once (October) in elderly demented patients, and not at all in the groups of elderly men and women. Both 24-h and yearly mean levels of gonadotrophins were higher in elderly subjects (two-to 25-fold according to the hormone, sex and season) than in young men. Circannual rhythms of plasma LH with large amplitudes were validated by the cosinor method, with an acrophase located in April or May. A circannual rhythm of plasma FSH was validated only in young men, with an acrophase in October. The persistence of a circannual rhythm of plasma LH with large amplitude in elderly subjects, associated with high mean levels of the hormone, especially in elderly women, suggests that this bioperiodicity of the pituitary gland is independent of gonadal function.
Somatomedin activity and growth hormone levels in body fluids of the fetal pig: effect of chronic hyperinsulinaemia
Authors: Spencer G. S. G. , Hill D. J. , Garssen G. J. , Macdonald A. A. , Colenbrander B.
Published: December 2008

Chronic hyperinsulinaemia in the presence of euglycaemia was obtained in pig fetuses between 90 and 104 days gestational age (term is 114 days) by the implantation of insulin-filled osmotic minipumps. At 104 days these fetuses were compared with both saline-implanted controls and with unoperated fetuses from the same sows.

Mean plasma GH levels were the same in all three treatment groups and were much greater than in the maternal peripheral venous circulation. Levels of GH in amniotic fluid were low, and even lower levels were measured in lung fluid. Glucose and protein levels were also lower in amniotic fluid than in plasma and lower still in lung fluid. In contrast, somatomedin activity was higher in amniotic and lung fluids than in fetal plasma and, when expressed relative to protein content, was highest in lung fluid. Insulin-treated fetuses had significantly (P < 0·05) higher levels of somatomedin activity than control fetuses, but despite this were neither longer nor heavier than control fetuses. From these data it is concluded that neither insulin nor somatomedin directly affect fetal growth.
Studies of the human chorionic gonadotrophin-like substance of human pituitary glands and its significance
Authors: Hartree Anne Stockell , Shownkeen Ratna C. , Stevens V. C. , Matsuura Shuji , Ohashi Masanobu , Chen Hao-Chia
Published: December 2008

Radioimmunoassays utilizing antisera specific for the carboxyl-terminal portion of human chorionic gonadotrophin (hCG) β-subunit were used to measure the concentration in human pituitary extracts of an immunoactive hCG factor (hCG′) which was different from human LH (hLH). The content of hCG′ from different human pituitary pools collected between 1966 and 1979 was relatively constant at 0·5–1·1 μg per gland. The hCG′ concentrations observed in acetone-dried powder of individual human pituitary glands (0·4–26 ng/mg) were close to those reported for full-term placental powder. After separation and partial purification of human pituitary glycoprotein hormones, pituitary hCG′ was found mainly in the crude human FSH (hFSH) fraction. It was separated from hFSH by diethylaminoethyl–cellulose chromatography at pH 7 and by gel filtration on Sephadex G-100. On gel filtration its molecular size was larger than that of hLH or hFSH and it was strongly bound to Concanavalin A–Sepharose. The most active preparations of pituitary hCG' obtained by these procedures were approximately 5 per cent as potent by specific radioimmunoassay as hCG purified from pregnancy urine. Although the hCG′ content in individual pituitary glands was more variable than the hLH content, on average pituitary hCG′ was estimated to be around 25- to 50-fold less than the content of hLH, hFSH or human TSH in the human pituitary gland.
Effects of oestradiol, progesterone and androstenedione on the pulsatile secretion of luteinizing hormone in ovariectomized ewes during spring and autumn
Authors: Martin G. B. , Scaramuzzi R. J. , Henstridge J. D.
Published: December 2008

The effects of oestradiol-17β, androstenedione, progesterone and time of the year on the pulsatile secretion of LH were tested in ovariectomized Merino ewes (n = 32). The steroids were administered by small subcutaneous implants, and the LH pulses were observed in samples taken at intervals of 15 min for 12 h in spring 1979, autumn 1980 and spring 1980, seasons corresponding to successive periods of anoestrus, breeding season and anoestrus.

During spring, oestradiol alone was able to reduce the frequency of the LH pulses, while progesterone, either alone or in combination with oestradiol, had little effect. During autumn, on the other hand, neither oestradiol nor progesterone could significantly reduce the frequency of the pulses when administered independently, whereas the combined treatment was very effective. Androstenedione had no significant effect on pulse frequency at either time of the year, either alone or in any combination with oestradiol and progesterone.

The basal levels of LH, over which the pulses are superimposed, were reduced by oestradiol alone in both seasons. Progesterone alone had no consistent effects, but interacted significantly with oestradiol and this combined treatment maintained low basal levels most effectively at all times. Androstenedione had no significant effect.

The amplitude of the pulses increased throughout the course of the experiment. Within seasons, the amplitudes were significantly higher in the presence of oestradiol and progesterone, but were not significantly affected by androstenedione.

It was concluded that certain of the ovarian steroids exert negative feedback on the tonic secretion of LH primarily by reducing the frequency of the pulses, and that the changes in LH secretion attributable to season and phases of the oestrous cycle can be accounted for entirely by the responses of the hypothalamus to oestradiol and progesterone. The role of the androstenedione secreted by the ovary in the ewe remains obscure.
The splanchnic removal of cortisol from plasma of anaesthetized adult guinea-pigs
Authors: Manin M. , Tournaire C. , Delost P.
Published: December 2008

To evaluate the role of the liver in cortisol catabolism the extraction ratio of both cortisol and cortisone by the organs of the splanchnic area was estimated in guinea-pigs anaesthetized with pentobarbitone. The [3H]cortisol and [3H]cortisone concentrations were measured in portal and sus hepatic venous plasma during a constant infusion of [3H]cortisol or [3H]cortisone. The extraction ratio of cortisol was estimated to be 10–14% in the splanchnic area and the viscera, while in the liver it had a small negative value suggesting that the liver had produced as much or more cortisol than it had taken up. All the cortisone (95%) formed from cortisol in the viscera was eliminated from the plasma compartment by the liver. Some 75–80% of the infused cortisone was converted to cortisol; rather less of the infused cortisol was converted to cortisone (32%). Using estimates of plasma flow derived from sham-operated animals, the uptake of cortisol by the various organs was calculated. The splanchnic area extracted 41% of the infused cortisol from the plasma: 25–27% as cortisol and 13–16% as cortisone. The liver appeared to take up cortisone preferentially. The conversion of cortisone into cortisol within the liver seems to be important in limiting the amount of cortisol removed from the plasma by the splanchnic area. The liver is also important in inactivating the steroids although other sites are probably also involved.
Effect of α2u-globulin on serum concentration of gonadotrophins and testicular activity in oestrogen-treated rats
Authors: Biswas N. M. , Ghosh P. K. , Ghosh K. K. , Neuhaus O. W.
Published: December 2008

Adult male rats were given injections of oestradiol-17β (50 μg/100 g body wt per day) for 7 days. When they were killed 14 days after the last injection, serum levels of gonadotrophins and testosterone and weights of accessory sex organs were less, testicular 17β-hydroxysteroid dehydrogenase 17β-HSD activity was suppressed and spermatogenesis was inhibited. Administration of α2u-globulin (1·5 mg/day) for 14 days to oestrogen-treated rats and for 10 days to control rats resulted in increased concentrations of gonadotrophins and testosterone in the serum. Accessory sex organ weight and spermatogenesis appeared to be normal while 17β-HSD activity increased in oestrogen-treated rats after treatment with α2u-globulin. It was concluded that α2u-globulin has an effect on testicular function in oestrogenized rats by inducing gonadotrophin and testosterone synthesis.