bluuebunny/crossref_metadata_2025 huggingface dataset:
Oestrogens in fetal and maternal fluids throughout pregnancy in the pig and comparisons with the ewe and cow
Authors: Robertson H. A. , Dwyer R. J. , King G. J.
Published: December 2008

In order to correlate the concentrations of oestrogens in the fetal fluids of the pig with those observed in the maternal blood and urine, changes in the concentrations of oestrone, oestradiol-17β, oestrone sulphate, oestradiol sulphates and oestrone glucuronide were assessed throughout pregnancy in the fetal and maternal fluids. In general, the pattern of change was similar for all oestrogens measured in both fetal and maternal fluids. Since the concentration of oestrogens in allantoic fluid during early pregnancy is reflected in the concentration of these steroids in maternal plasma and excreted in the maternal urine, the rise and fall of oestrogen concentrations around day 30 is suggestive of synthesis followed by a virtual cessation of oestrogen production until the fetus or placenta again produce increasing amounts detectable after day 45. These findings contrast sharply with those in the cow and the ewe where, although similar peaks in oestrogen concentrations are observable in allantoic fluid during early pregnancy, they are not reflected in blood.

J. Endocr. (1985) 106, 355–360
Effect of intraventricular injection of 5,6-dihydroxytryptamine on spermatogenesis and plasma testosterone levels in the rat
Authors: Das T. K. , Mazumder R. , Biswas N. M.
Published: December 2008

Quantitative evaluation of spermatogenesis at stage VII of the cycle of the seminiferous epithelium and radioimmunoassay of plasma testosterone were performed in adult Wistar rats after intraventricular injection of 5,6-dihydroxytryptamine (5,6-DHT). The rats were killed 2, 10 and 21 days after injection. Brain 5-hydroxytryptamine (5-HT) and plasma testosterone levels were found to be significantly lower in all rats treated with 5,6-DHT. A significant reduction in step 7 spermatid count was also observed after 10 and 21 days. Supplementation with human chorionic gonadotrophin for 21 days in rats injected with 5,6-DHT partially prevented the step 7 spermatid degeneration and increased testosterone levels without producing any effect on brain concentrations of 5-HT. These results suggest that changes in testicular steroidogenesis and spermatogenesis are secondary to pituitary gonadotrophin release which, in turn, is under the influence of brain 5-HT neurones.

J. Endocr. (1985) 106, 395–400
REAPPEARANCE OF THYMUS OF AGEING RATS AFTER ORCHIDECTOMY
Authors: Fitzpatrick F.T.A. , Kendall M.D. , Wheeler M.J. , Adcock I.M. , Greenstein B.D.
Published: December 2008

There was no visible thymus in ageing rats of 18 months, and 7 days after orchidectomy there was still no evidence of a thymus. By 30 days after the operation, however, there was a well-defined and well developed bilobular thymus overlying the heart, although it was smaller than those observed in 10-week-old rats. Histologically, the tissue appeared normal, was well vascularized, filled with lymphocytes and several mitotic figures were also seen. When compared with sham-operated animals, blood from these animals had a significantly higher lymphocyte count. These results have important implications for the possible enhancement of the immune system with associated improvement of health during ageing.
Calmodulin regulation of cellular cyclic AMP production in response to arginine vasopressin, prostaglandin E2 and forskolin in rat renal papillary collecting tubule cells in culture
Authors: Ishikawa S. , Saito T. , Kuzuya T.
Published: December 2008

The effect of calmodulin on the stimulation of cyclic AMP production by arginine vasopressin (AVP), prostaglandin E2 (PGE2) and forskolin was examined in cultured renal papillary collecting tubule cells of the rat. In the presence of the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine submaximal concentrations of AVP (1 nmol/l), PGE2 (20 nmol/l) and forskolin (240 nmol/l) significantly increased cellular cyclic AMP accumulation by 2·3-, 6·0- and 8·4-fold respectively. Two chemically dissimilar inhibitors of calmodulin, namely trifluoperazine and N-(6-aminohexyl)-5-chloro-1-naphthalenesulphonamide (W-7), attenuated the AVP-, PGE2- and forskolin-stimulated cellular production of cyclic AMP in a dose-related manner. Cellular production of cyclic AMP was inhibited by 50% (ID50) by doses ranging from 16 to 28 μmol trifluoperazine/1 and 35 to 44 μmol W-7/1. Basal accumulation of cellular cyclic AMP was also decreased by treatment with either trifluoperazine or W-7, but the effective dose was higher than that which inhibited cellular cyclic AMP production stimulated by AVP, PGE2 and forskolin. Since forskolin directly activates adenylate cyclase at a site of the catalytic unit and the cellular action of AVP to activate adenylate cyclase is mediated through receptor-guanine nucleotide regulatory-catalytic units, the present study indicates calmodulin regulation of basal, AVP-, PGE2-and forskolin-activated adenylate cyclase in the papillary collecting tubule cells. The inhibition of AVP- or PGE2-induced cellular cyclic AMP production by treatment with either Ca2+-free medium or verapamil, a blocker of cellular Ca2+ uptake, was demonstrated and suggests that an increase in cytosol Ca2+, which interacts with calmodulin to form an active complex is, at least in part, due to the increased cellular influx of Ca2+ from the extracellular space.

J. Endocr. (1985) 107, 15–22
Changes in ovarian steroidogenesis in prepuberal rats induced to ovulate by low doses of human chorionic gonadotrophin
Authors: Uilenbroek J. Th. J. , Meijs-Roelofs H. M. A. , Woutersen P. J. A. , Kramer P. , van Cappellen W. A. , Gribling-Hegge L. A. , de Greef W. J.
Published: December 2008

To determine whether the decrease in ovarian 5α-reduced androgen production before first ovulation might be caused by an increase in serum LH, prepuberal female rats were injected at 28–31 days of age with low doses of human chorionic gonadotrophin (hCG) (0·05–0·075 i.u., four times daily). This treatment resulted in ovulation of six to ten ova per rat on day 32 in all animals.

Treatment with hCG resulted in a gradual decrease in ovarian content and production (i.e. content in ovary and medium after 4 h of incubation) of 5α-dihydrotestosterone (DHT) and 5α-androstane-3α,17β-diol. The ovarian content of DHT and the production of 5α-androstane-3α,17β-diol decreased within 24 h after the first injection of hCG. Oestradiol content and production increased between 24 and 48 h after the start of treatment and was maximal on day 31 (day of pro-oestrus).

Activities of 5α-reductase and aromatase were measured in ovarian homogenates obtained on days 29–31. Activity of 5α-reductase in hCG-treated rats was lower than that in control rats on all days studied. Aromatase activity in hCG-treated rats increased between days 29 and 31.

It was concluded that multiple injections of low doses of hCG, which may induce ovulation, cause a decrease in 5α-reduced androgen production, which is probably due to a decrease in 5α-reductase activity. The subsequent increase in oestradiol production corresponds with an increase in aromatase activity. The results indicate that the decrease in 5α-reductase activity as observed in ovaries of spontaneously ovulating rats might be caused by the gradual increase in serum LH, which has been found to occur during the last week before first ovulation.

J. Endocr. (1985) 107, 113–119
An androgen-independent mechanism maintains photorefractoriness in male tree sparrows (Spizella arborea)
Authors: Wilson F. E.
Published: December 2008

A series of experiments was performed to clarify whether photorefractoriness in male tree sparrows is maintained by an androgen-dependent mechanism. Castration did not raise plasma LH in photorefractory males held under a daily photoperiod of 20 h light: 4 h darkness (20L: 4D). Castrated photorefractory males were implanted with the antiandrogen cyproterone or injected s.c. with the antiandrogen flutamide to determine whether androgens which may be resistant to castration inhibit LH secretion. Neither cyproterone nor flutamide raised plasma LH above values found in castrated control birds. Castrated photorefractory males were treated with testosterone to determine whether plasma LH in photorefractory males is androgen-suppressible. Concentrations of plasma LH were independent of plasma testosterone over a wide range of concentrations. The lack of LH response to castration, to castration coupled with antiandrogen therapy, and to castration coupled with testosterone replacement argues that photorefractoriness in male tree sparrows is maintained by an androgen-independent mechanism.

J. Endocr. (1985) 107, 137–143
Effects of maternal sodium depletion on the composition of ovine fetal fluids
Authors: Bell R.J. , McDougall J.G. , Wang X. , Wintour E.M.
Published: December 2008

Effects of maternal sodium depletion on the composition of ovine fetal fluids were studied. Maternal Na depletion was achieved by 48-h drainage of parotid saliva. There was a significant decrease in both maternal and fetal plasma Na concentration, indicating that both mother and fetus had experienced the Na-depletion stimulus. There was a significant increase in maternal blood aldosterone but the change in fetal blood aldosterone was not significant. In animals where there was an increase in fetal blood aldosterone the increase could be accounted for by transfer of aldosterone across the placenta from the mother. There was a significant decrease in fetal urinary Na concentration and Na excretion and the urinary Na/K ratio fell in seven out of eight studies. These observations are consistent with the hypothesis that fetal Na depletion sensitizes the fetal kidney to the action of circulating aldosterone as in the adult.

J. Endocr. (1985) 107, 177–182
Developmental changes in the rate of production of an unusual testosterone metabolite, 4-androstene-3α,17β-diol, by chick liver microsomes
Authors: Darby N. J. , Spencer S. , Lodola A. , Burnet F. R.
Published: December 2008

Testosterone is produced by the chick embryo testis from the 13th day of incubation. We have investigated the ability of microsomes prepared from the fetal and neonatal liver to metabolize testosterone and have found that the principal metabolite generated by microsomes in the presence of NADPH is 4-androstene-3α,17β-diol. The rate of production of this metabolite declined sharply over the time of hatching. Conversely, 16α-hydroxytestosterone production increased transiently just after hatching. Our findings indicate that chick liver microsomes contain a 3α-hydroxysteroid dehydrogenase (3α-hydroxysteroid: NAD(P) oxidoreductase, EC 1.1.1.50) whose activity changes during development.

J. Endocr. (1985) 107, 205–209
Comparison of glucose-induced changes in electrical activity, insulin release, lactate output and potassium permeability between normal and ob/ob mouse islets: effects of cooling
Authors: Scott A. M. , Dawson C. M. , Gonçalves A. A.
Published: December 2008

A comparison has been made between the glucose-induced changes in electrical activity, insulin release, lactate output and potassium permeability in normal and ob/ob obese (Norwich strain) mice. The electrical response of the islet membrane to high glucose (22·2 mmol/l) stimulation was different in the two types of mice, generating continuous spike activity in normal but producing bursts of activity in ob/ob mouse islets. The absolute amounts of insulin and lactate produced by ob/ob islets in response to both basal and high glucose concentrations were greater than the absolute amounts produced by normal islets, though the ratio of the amount produced in high glucose concentrations to the amount produced in basal glucose concentrations was not significantly different between normal and ob/ob islets for both parameters. Glucose-induced changes in potassium permeability were smaller in ob/ob than in normal mice. Cooling from 37 to 27 °C, during steady-state glucose stimulation, reduced both lactate output and insulin release, the temperature coefficients being similar in both types of mice. The effect of temperature reduction on electrical activity was more marked in the islets of ob/ob mice than in those of normal mice; spike frequency was unaffected in normal but reduced in ob/ob mice, whereas spike amplitude was decreased in both. Cooling-induced inhibition of potassium permeability was greater in the islets of ob/ob mice than in those of normal mice. These results show that this new colony of ob/ob mice (Norwich strain) is comparable to normal mice in terms of the dynamics of insulin release and lactate output in response to glucose, but that the response of the β-cell membrane electrical activity and potassium permeability to glucose is different.

J. Endocr. (1985) 107, 265–273
A chronic technique for high frequency blood sampling/transfusion in the freely behaving rat which does not affect prolactin and corticosterone secretion
Authors: Wiersma J. , Kastelijn J.
Published: December 2008

A blood sampling/blood transfusion technique is described for chronically cannulated freely behaving rats. The procedure permits high frequency sampling for several hours at a maximum rate of one blood sample per min. Prolactin and corticosterone were used as indicators of stress.

In male rats the prolactin concentration in blood obtained by rapid decapitation was not significantly different from that obtained through a cannula. A blood volume reduction of 1 or 2 ml did not affect prolactin or corticosterone secretion; however, a reduction of 3 ml or more increased corticosterone secretion but did not consistently increase prolactin secretion. When blood volume reduction was compensated for by blood transfusion, frequent blood sampling did not affect prolactin or corticosterone secretion in dioestrous rats. The surges of prolactin secretion during the afternoon of pro-oestrus and pseudopregnancy were also unaffected by high frequency blood sampling.

It is therefore concluded that the blood sampling/ transfusion procedure described does not stress the animals. Its advantages include not only the possibility of following individual hormone profiles, but also the economic and ethical aspects of reducing the number of animals needed for experimentation.

J. Endocr. (1985) 107, 285–292
Changes in total and free concentrations of steroid hormones in the plasma of women throughout pregnancy: effects of medroxyprogesterone acetate in the first trimester
Authors: Willcox D. L. , Yovich J. L. , McColm S. C. , Schmitt L. H.
Published: December 2008

The total (protein-bound plus free) and free concentrations of progesterone, oestradiol-17β and cortisol were measured serially throughout pregnancy in the plasma of two groups of women whose pregnancies went to term. Group A (n = 53) experienced an uneventful low-risk pregnancy with a spontaneous abortion rate of 8·6%. Women in group B (n = 22) were treated orally with medroxyprogesterone acetate (MPA; 80–120 mg daily) until 18 weeks gestation for threatened abortion within the first 6 weeks of pregnancy.

In both groups of women the proportion of each hormone circulating in the free or unbound form remained constant despite the overall increases which occurred in total circulating hormone concentrations as pregnancy progressed. The steroid hormonal profiles in the first half of pregnancy were similar in both groups of women. However, from weeks 20 to 40 total and free progesterone concentrations were significantly (P < 0·05 in each case) higher in group B compared with group A. Conversely, total and free oestradiol-17β concentrations were lower (P < 0·005 and P < 0·01 respectively) in group B. At this stage it is not known if these differences were attributable to the administration of MPA to women in group B or to altered placental steroidogenesis as a result of earlier uterine bleeding.

J. Endocr. (1985) 107, 293–300
Circadian rhythm of melatonin in the pineal gland of the Japanese quail (Coturnix coturnix japonica)
Authors: Cockrem J. F. , Follett B. K.
Published: December 2008

Melatonin was measured by radioimmunoassay in homogenates of pineal glands from quail (Coturnix coturnix japonica) kept under different photoperiods and in darkness. Under 8-, 12- and 16-h daylengths melatonin levels were increased during the dark period, the duration of the increase depending on the duration of the dark period. As the daylength was increased the peak occurred closer to lights-off, reflecting the more rapid melatonin rise under the longer photoperiods. The pineal melatonin rhythm continued in darkness with an amplitude relative to that seen under a light/dark cycle of slightly less than one-half after 2 days in darkness and one-third after 6 days in darkness. The corresponding average periods of the rhythm were 25·5 h and 25·7 h. These results show that there is a circadian rhythm of melatonin in the pineal gland of the quail which is entrained by light/dark cycles and which continues in darkness.

J. Endocr. (1985) 107, 317–324
Increased dopaminergic inhibition of prolactin in the hypoprolactinaemic IPL nude rat
Authors: Cohen H. , Sabbagh I. , Guillaumot P. , Bertrand J.
Published: December 2008

In this study, aimed at investigating whether dopaminergic regulation of prolactin could be implicated in the hypoprolactinaemia observed in the IPL nude rat, dopaminergic inhibition of prolactin was suppressed using a catecholamine synthesis inhibitor α-methyltyrosine (MT) and a dopaminergic antagonist sulpiride.

Adult male rats (IPL nude and normal) were injected through implanted atrial cannulae with either MT (250 mg/kg) or physiological saline (control). Rats were decapitated 2 h after the injection. Plasma prolactin levels, compared with basal values, increased by 15·6 ± 1·9 (s.e.m.)- and 5·89 ± 0·6-fold in IPL nude and normal rats respectively. This difference was highly significant. The pituitary prolactin content was decreased in both groups.

In a second experiment, adult male IPL nude or normal rats were injected with either sulpiride (1 mg/kg) or saline and decapitated 2, 4, 8, 12, 14 and 24 h later. Plasma prolactin levels, compared with basal values, were increased in rats injected with sulpiride by 9·2 ± 1·8 and 3·4 ± 0·7-fold in IPL nude and normal rats respectively. The pituitary prolactin content was reduced more in IPL nude than in normal sulpiride-injected rats. These data suggest that prolactin secretion, as well as synthesis, is under an increased dopaminergic inhibition in the male IPL nude rat.

J. Endocr. (1985) 107, 325–329
In-vivo activity of the LH-releasing hormone pulse generator in castrated and intact male rats
Authors: Dluzen D. E. , Ramirez V. D.
Published: December 2008

The in-vivo LH-releasing hormone (LHRH) output from the mediobasal hypothalamus of conscious freely moving sham-castrated, acutely castrated (immediately after castration) and long-term castrated (> 20 days after castration ) adult male rats has been studied. Five rats in each of the three conditions were perfused for an 8-h period (11.00–19.00 h). One animal in each condition was perfused for a 24-h period. In the sham-castrated and acutely castrated, but not in the long-term castrated rats, apparently random surges of LHRH output (> 5·6 pmol/l), separated by periods of non-detectable activity, were observed throughout the perfusion period. The LHRH output of the long-term castrated rats was characterized by an extremely low overall mean release and markedly attenuated pulse amplitudes, with both parameters significantly lower than those of the sham-and acutely castrated rats. These results indicate that the raised blood levels of LH in long-term castrated rats do not appear to be the consequence of high amplitude and high overall release of LHRH.

J. Endocr. (1985) 107, 331–340
An enzyme-linked immunosorbent assay for the measurement of thyroglobulin in human serum using mouse monoclonal antibodies
Authors: Kilduff P. , Black E. G. , Hall R. , McGregor A. M.
Published: December 2008

A robust, rapid, sensitive and specific enzyme-linked immunosorbent assay (ELISA), using an in-house immunoglobulin-A-sub-class mouse monoclonal human-thyroglobulin antibody (WNSM2), with a sensitivity of 1·51 pmol/l has been established for the measurement of thyroglobulin in serum. Standard curves in varying dilutions of human serum were similar to standard curves obtained in serum-free medium, thus demonstrating no significant cross-reactivity with any serum proteins other than thyroglobulin. Levels of serum thyroglobulin detected by ELISA correlated significantly (r = 0·93, P < 0·001) with those from a standardized and well-characterized radioimmunoassay. The coefficients of variation within and between ELISA assays were 3·9 and 7·1% respectively. Thyroglobulin was detectable in 87% of 54 normal subjects who had no history of thyroid or autoimmune disease, the mean (±s.d.) for this group being 15 ± 6·6 pmol/l with a range of 1·51–53 pmol/l. Using this assay, levels of thyroglobulin were shown to be significantly (P < 0·002) increased in patients with untreated hyperthyroid Graves' disease compared with normal subjects.

J. Endocr. (1985) 107, 383–387
A novel form of ectopic human chorionic gonadotrophin β-subunit in the serum of a woman with epidermoid cancer
Authors: Nagelberg S. B. , Cole L. A. , Rosen S. W.
Published: December 2008

A novel form of free human chorionic gonadotrophin β-subunit (hCGβ) was found in serum from ElBre, a woman with epidermoid carcinoma of unknown origin. ElBre hCGβ was larger than standard (pregnancy urine) hCGβ when analysed by gel chromatography (apparent molecular weight 54 000 vs 44000). This size difference appeared to be due to a larger carboxyterminal extension (CTE) of ElBre hCGβ since thermolysin cleavage of the CTE from standard hCGβ and Elbre hCGβ yielded core products of the same size. Oligosaccharides, O-linked to serine or threonine, were present in ElBre hCGβ, presumably on its CTE as judged by the complete binding of desialylated ElBre hCGβ to immobilized peanut agglutinin (this lectin is specific for terminal galactose linked β1 → 3 to N-acetylgalactosamine, a disaccharide exposed after desialylation of the O-linked oligosaccharides of standard hCGβ). ElBre hCGβ, however, was incompletely recognized by antisera specific for the CTE of standard hCGβ, especially the carbohydrate-sensitive antiserum R141.

The O-linked oligosaccharides of standard hCGβ are heterogeneous in size; 13% are of the largest (hexasaccharide) form. In contrast, over 50% of the O-linked oligosaccharides in hCGβ from the JAr choriocarcinoma cell line are hexasaccharides. Like desialylated ElBre hCGβ, desialylated JAr hCGβ bound completely to peanut agglutinin, but was incompletely recognized by antisera to the hCGβ-CTE. Furthermore, JAr hCGβ was intermediate in size between standard hCGβ and ElBre hCGβ when analysed by gel chromatography (apparent molecular weight 49 000). Thus, we propose that ElBre hCGβ had an even higher proportion of large O-linked oligosaccharides than had JAr hCGβ. Moreover, the N-linked oligosaccharides of ElBre hCGβ differed from standard hCGβ; only 55% of ElBre hCGβ bound to Concanavalin A versus 89% of standard hCGβ. These data further support the concepts of aberrant glycosylation by neoplastic tissues and carbohydrate heterogeneity of hCGβ produced by various tissues.

J. Endocr. (1985) 107, 403–408
Cranial irradiation for cerebral and nasopharyngeal tumours in children: evidence for the production of a hypothalamic defect in growth hormone release
Authors: Blacklay A. , Grossman A. , Ross R. J. M. , Savage M. O. , Davies P. S. W. , Plowman P. N. , Coy D. H. , Besser G. M.
Published: December 2008

A synthetic 29-amino acid analogue of human pancreatic GH-releasing hormone (GHRH(1–29)NH2) has recently been shown to stimulate the release of GH in normal subjects. We have studied the GH response to GHRH(1–29)NH2 in nine children irradiated for brain and nasopharyngeal tumours, who were not growing and were deficient in GH as assessed by insulin-induced hypoglycaemia. Serum GH rose in response to GHRH(1–29)NH2 in all the children, and in five the peak serum GH response was > 20 mu./l. The data suggest that when hypothalamo-pituitary irradiation results in GH deficiency, this is due to a failure of the synthesis or delivery of endogenous GH RH from the hypothalamus to the pituitary cells. It also suggests that it may be possible to treat such children using synthetic GHRH in place of exogenous GH.

J. Endocr. (1986) 108, 25–29
Effect of ketoconazole on adrenocorticotrophic hormone secretion in vitro and in vivo
Authors: Burrin J. M. , Yeo T. H. , Ashby M. J. , Bloom S. R.
Published: December 2008

The direct effects of ketoconazole on ACTH secretion have been investigated using a rat pituitary cell culture system. Ketoconazole had no significant effects on basal ACTH secretion, corticotrophin-releasing factor- or arginine vasopressin-stimulated ACTH secretion, nor did it affect dexamethasone inhibition of ACTH secretion. In-vivo studies demonstrated an increased ACTH level (168 vs 76 ng/l) accompanied by a fall in plasma corticosterone (193 vs 307 μg/l) in normal rats given ketoconazole (24 mg/kg, five oral doses given 8 hourly). No effects were seen in adrenalectomized rats or at lower doses (6 mg/kg) in normal or adrenalectomized rats. A high dose of ketoconazole (24 mg/kg, twice daily oral doses) also caused increased ACTH levels in normal rats (129 vs 86 ng/l) when given for 7 days. No effects were seen in adrenalectomized rats or on plasma corticosterone levels in normal rats. Our data suggest that ketoconazole at these doses has no direct effects on pituitary ACTH secretion but causes an increase in plasma ACTH due to its inhibition of adrenal steroid synthesis.

J. Endocr. (1986) 108, 37–41
Oestrous cycle-related LH responsiveness to naloxone: effect of high oestrogen levels on the activity of opioid receptors
Authors: Petraglia F. , Locatelli V. , Facchinetti F. , Bergamaschi M. , Genazzani A. R. , Cocchi D.
Published: December 2008

Endogenous opioid peptides have a tonic inhibitory control on LH secretion, participating in the functional changes of the hypothalamic-pituitary-ovarian axis. To evaluate the activity of the endogenous opioid systems during the oestrous cycle, we measured plasma LH levels after naloxone administration (5 mg/kg, s.c.) at 09.00 and 16.00 h on all days of the cycle (two further measurements were taken at 14.00 and 18.00 h on the day of pro-oestrus) and after one dose or one week's treatment with oestradiol benzoate (OB; 0·2 μg/rat). Concentrations of LH were measured in the same experimental models after injection of LH-releasing hormone (LHRH; 1 μg/kg, i.p.) or saline. Naloxone induced a significant rise in LH levels on the day of oestrus, dioestrus day-1 and dioestrus day-2; this response was blunted on the morning of pro-oestrus and absent in the afternoon and after acute and chronic OB treatment. Conversely LHRH was most effective in increasing LH levels on the day of pro-oestrus and in OB-treated rats.

These results indicate that opioid mechanisms, independently of the time of day and the pituitary responsiveness, exhibit a reduced activity when preovulatory changes occur, probably as a result of increased oestrogen levels.

J. Endocr. (1986) 108, 89–94
Modulation of thyrotrophin release from an intracellular pool by pre-exposure to thyrotrophin-releasing hormone and dibutyryl cyclic AMP
Authors: Davis J. R. E. , Sheppard M. C.
Published: December 2008

Amplification of desensitization of TSH response to thyrotrophin-releasing hormone (TRH) may be important mechanisms in the regulation of its secretion. We have investigated this possibility in vitro, using monolayer culture of rat anterior pituitary cells. Cells (1–1·5 × 105/250 μl per well) were cultured for 72 h, exposed to TRH or dibutyryl cyclic AMP (dbcAMP) for 6 or 8 h, washed, and then treated for 4 h with various doses of TRH, or with K+ (55 mmol/l) as a non-specific secretagogue. Pretreatment with TRH (20 nmol/l) for 8 h reduced subsequent TSH release: basal release fell to 64% of the control value (1·01±0·10 μg/l pretreated, 1·58 ± 0·16 control) and release in response to TRH (100 nmol/l) to 69% of the control (2·7 ± 0·19 μg/l vs 3·98 ± 0·22); K+ response was reduced to 86% of the control (3·77 ± 0·21 μg/l vs 4·39 ± 0·20), significantly less than the other reductions. The extent of the parallel downward shift of the TRH dose–response curve was proportional to dose and duration of prior TRH exposure. There was no significant change in the dose of TRH required to cause half-maximal TSH release (ED50: pretreated 4·8, control 2·8 nmol TRH/l) suggesting depletion of an intracellular pool of TSH rather than 'desensitization'. After 6-h pretreatment with dbcAMP, subsequent TSH responses were augmented: basal release was 130% of the control, response to TRH (100 nmol/l) was 137% and to K+ it was 132% of the control, with a parallel upward shift of the TRH dose–response curve but no change in cellular TSH content. We suggest that an intracellular pool of TSH exists which can be depleted by prior TRH exposure without a desensitization effect. The size of this pool may be increased by dbcAMP, indicating that cyclic nucleotides may modulate the availability of TSH to an acutely releasable intracellular pool.

J. Endocr. (1986) 108, 211–217
Effect of anterior hypothalamic deafferentation and continuous growth hormone infusion on the hepatic synthesis of α2u-globulin in the male rat
Authors: Chatterjee B. , Demyan W. F. , Gustafsson J.-Å. , Harris M. W. , Hökfelt T. , Norstedt G. , Roy A. K.
Published: December 2008

Anterior hypothalamic deafferentation and infusion of human GH (hGH) in the normal male rat caused a marked reduction in the hepatic concentration of α2u-globulin, an androgen-dependent protein. Although s.c. injections of hGH (twice-daily) resulted in more than a 50% reduction in the hepatic level of α2u-globulin, the same dose of hGH when administered continuously through osmotic minipumps caused a threefold greater inhibition. The decreased hepatic concentration of α2u-globulin after hGH administration was associated with corresponding changes in the hepatic level of translatable α2u-globulin messenger RNA. Continuous infusion of hGH through osmotic minipumps and removal of the anterior hypothalamic influence on GH secretion by deafferentation also caused a marked reduction in the cytoplasmic androgen-binding activity of the rat liver. These results suggest that alterations in the level and pattern of GH secretion may influence hepatic androgen-binding activity and α2u-globulin synthesis.

J. Endocr. (1986) 108, 351–355
The mechanism of the prolonged stimulatory effect of corticotrophin on pregnenolone production by guinea-pig adrenocortical mitochondria
Authors: Lambert F. , Lammerant J. , Kolanowski J.
Published: December 2008

The postulated prolonged stimulatory influence of ACTH on the adrenocortical mitochondrial synthesis of pregnenolone in response to ACTH was studied in adrenal mitochondria isolated from control guinea-pigs and from animals treated s.c. with 100 μg ACTH(1–24) twice daily on the day before the animals were killed. The animals from both groups were injected with 100 μg ACTH s.c. 30 min before killing. The mitochondrial production of pregnenolone (expressed in nmol per mg mitochondrial protein after 10-min incubation) increased from 1·52 ± 0·46 (s.e.m.) in the control group to 4·50 ± 0·59 for mitochondria from ACTH-treated animals, despite a similar free cholesterol content in the mitochondria, even when determined after a previous in-vivo treatment with aminoglutethimide to block further metabolism of cholesterol into pregnenolone. In addition, in the presence of an excess of exogenous cholesterol (100 μmol/l), the production of pregnenolone remained higher for mitochondria from ACTH-treated animals. In contrast, when the calcium concentration in the incubation medium was raised to 1 mmol/l, with subsequent enhancement in pregnenolone synthesis, the mitochondrial pregnenolone production became similar for both groups (8·28 ± 1·11 nmol in the ACTH-treated group and 9·55 ± 1·90 nmol in the control group), even in the presence of 100 μmol cholesterol/l (13·5 ±1·80 nmol in ACTH-treated animals and 14·8 ± 1·93 nmol in controls). Cycloheximide treatment administered on the day before the animals were killed was without any effect on pregnenolone production in control animals (3·51 ± 0·43 nmol before and 3·65 ± 0·63 nmol after cycloheximide treatment). In contrast, the pregnenolone production by mitochondria from ACTH-treated guinea-pigs injected with cycloheximide was reduced to a level similar to that observed in the control group (5·82± 0·23 nmol in the absence and 3·09± 0·32nmol in the presence of cycloheximide treatment).

The results of the present study suggest that the prolonged stimulatory effect of ACTH on pregnenolone production involves an increase in the synthesis of a protein factor which promotes the availability of cholesterol to the side-chain cleavage system. Other mechanisms such as a stimulated synthesis of the side-chain cleavage complex itself or an increased total mitochondrial cholesterol content are not supported by our data.

J. Endocr. (1986) 108, 377–384
Regulation of stages VI and VIII of the rat seminiferous epithelial cycle in vitro
Authors: Toppari J. , Vihko K. K. , Räsänen K. G. E. , Eerola E. , Parvinen M.
Published: December 2008

Plasminogen activator (PA) is secreted cyclically (in stages VII and VIII) by rat seminiferous tubules. To investigate whether this can be maintained and influenced in vitro, tubule segments from stages VI and VIII of the epithelial cycle were cultured for 3 days in chemically defined medium supplemented with testosterone, FSH, or a combination of testosterone, FSH, insulin and retinoic acid (4F).

Morphological and flow cytometric analyses of stage VI tubules suggested a roughly normal differentiation to stage VIII. They developed an increased PA secretion on day 3 of culture. Stage VIII tubules, however, did not develop all the characteristics of stage XII. Step 8 spermatids did not elongate and step 19 spermatids failed to develop into spermatozoa. Secretion of PA on day 3 was not significantly different to that on day 1. The 4F combination very significantly stimulated PA secretion in both stages, but FSH alone was effective only in stage VIII. Most of the secreted PA had a molecular weight of 43 000 in both stages, suggesting that it is of urokinase type.

The results suggest that stage VI is more able to differentiate in vitro for 3 days than stage VIII; the cyclic secretion pattern of PA was partially maintained in tubule segments from stage VI. Follicle-stimulating hormone had an effect on PA secretion only in stage VIII, whereas the 4F combination was stimulatory in both stages. The retinoic acid in this combination may be of importance in the regulation of PA secretion by seminiferous tubules.

J. Endocr. (1986) 108, 417–422
CORTICOSTEROIDS SUPPRESS PLASMINOGEN ACTIVATION IN THE BOVINE SERTOLI CELL
Authors: Jenkins N. , Ellison J.D.
Published: December 2008

Bovine FSH stimulated a six fold increase in secretion of plasminogen activator by immature bovine Sertoli cells with half-maximum response (ED50) at 145ng/ml. Treatment with FSH and either dexamethasone, cortisol or corticosterone produced a dose-dependent suppression of PA activity, with ED50 values of 35, 320 and >650nmol/l respectively. Effects of dexamethasone required over 6 h incubation to become significant (P < 0.001), and were blocked by inhibitors of RNA synthesis and translation. These data demonstrate direct effects of corticosteroids on Sertoli cells, resulting in the synthesis of antiprotease factors which antagonize the actions of FSH.
Involvement of protein kinase C in mouse mammary gland development
Authors: Caulfield J. J. , Bolander F. F.
Published: December 2008

The relationship between kinase C activity and mammary gland differentiation was investigated by following kinase activity throughout the mouse reproductive cycle and by pharmacologically perturbing the kinase, while monitoring biochemical differentiation. Protein kinase C activity declined during pregnancy and remained low throughout lactation, suggesting an inverse relationship with milk protein expression. This negative association was further supported by the use of quercetin (50–100 μmol/l) and gossypol (50 μmol/l), which are both protein kinase C inhibitors. These compounds doubled α-lactalbumin levels in mammary explants cultured with hormones. However, a phorbol ester, known to activate protein kinase C, had no effect on α-lactalbumin production, although it did stimulate this milk protein 2·5-fold in the presence of the calcium ionophore, A23187. In the absence of raised calcium levels, protein kinase C activity therefore appeared to be inversely correlated with biochemical differentiation; but, in the presence of increased calcium concentrations, both calcium and the kinase acted synergistically to augment hormone-induced α-lactalbumin expression.

J. Endocr. (1986) 109, 29–34
Changes in the granule population of gonadotrophs of hypogonadal (hpg) and normal female mice associated with the priming effect of LH-releasing hormone in vitro
Authors: Lewis C. E. , Morris J. F. , Fink G. , Johnson M.
Published: December 2008

Changes in the size and position of secretory granules in pituitary gonadotrophs have been studied in relationship to LH release and self-priming induced by LH-releasing hormone (LHRH) in pituitary glands from normal and hypogonadal (hpg) female mice. Hemipituitary glands were preincubated and then incubated for either 1 or 2 h in the absence or presence of LHRH (8·5 nmol/l). The glands were either processed for ultrastructural morphometry or homogenized for the determination of pituitary LH content. Morphometry was carried out on gonadotrophs identified by immunocytochemistry for LHβ using the thin/semi-thin section method. Pituitary LH content and the amount of LH released were determined by radioimmunoassay.

The amount of LH released in response to the first and second hours of incubation with LHRH were similar in hpg and normal mice with a clear priming effect (three- to fourfold increase in pituitary responsiveness to LHRH) occurring in both strains. Despite a substantially reduced total number of granules (and amount of LH) in unstimulated hpg gonadotrophs, the number of granules in the outer 500 nm marginal zone of the cells was similar to that in normal mice. This could explain the similar amount of LH released from normal and hpg glands by the first LHRH challenge. The initial exposure to LHRH was also associated with a marked translocation of secretory granules from the central to the outer marginal region of cytoplasm subjacent to the gonadotroph plasmalemma, such that in 'primed' glands 60% of granules were found in this marginal zone compared with 40% (hpg) or 33% (normal) in unstimulated glands. The mean diameter of granules in the marginal zone was significantly less than that of granules in the central zone of the gonadotrophs of unstimulated glands from both normal and hpg animals. Exposure to LHRH for 1 h was associated with an increase in the number of small granules in the marginal zone and a significant decrease in the mean diameter of the gonadotroph granule population as a whole.

After the primed release of LH, increased proportions of granules were still located in the marginal zone of gonadotrophs, indicating that granule migration continued during the second hour of exposure to LHRH in which primed release occurred. The primed release was associated with a detectable reduction in both the LH and granule content of gonadotrophs in normal, but not hpg glands. The ultrastructural correlates of LH release and LHRH priming were similar in the two strains of mice, and therefore in mice neither the releasing nor the priming effect of LHRH depends upon previous exposure of the pituitary gland to LHRH or ovarian factors. The priming effect was associated with a marked shift of granules towards the plasmalemma and a decrease in granule size which most likely resulted from increased post-translational processing within secretory granules.

J. Endocr. (1986) 109, 35–44
Growth hormone responses to growth hormone-releasing factor (1–29) in euthyroid, hypothyroid and hyperthyroid rats
Authors: Dieguez C. , Jordan V. , Harris P. , Foord S. , Rodriguez-Arnao M. D. , Gomez-Pan A. , Hall R. , Scanlon M. F.
Published: December 2008

In order to investigate whether the impaired GH secretion associated with hypothyroidism and hyperthyroidism is due to a hypothalamic or a pituitary disorder, we have studied plasma GH responses to GH-releasing factor (1–29) (GRF) in euthyroid, hypothyroid and hyperthyroid rats. Hypothyroid rats showed a significant (P< 0·001) reduction in GH responses to GRF (5 μg/kg) at 5 min (350 ± 35 vs 1950 ±260 μg/l), 10 min (366±66 vs 2320 ± 270 μg/l) and 15 min after GRF injection (395 ± 72 vs 1420 ± 183 μg/l; means ± s.e.m.) compared with euthyroid rats. Hyperthyroid rats showed a significant (P<0·05) decrease in GH responses to 5 μg GRF/kg after 30 min (200±14 vs 325 ± 35 μg/l) but not at other time-points, or after the administration of 1 μg GRF/kg. These data indicate that in hypothyroidism and perhaps hyperthyroidism there is an alteration in the responsiveness of the somatotroph to GRF administration.

J. Endocr (1986) 109, 53–56
Effects of porcine relaxin on the length of gestation and duration of parturition in the rat
Authors: Jones S. A. , Summerlee A. J. S.
Published: December 2008

Experiments were carried out to investigate the effects of porcine relaxin on the course of gestation and delivery in the rat. Plasma relaxin was maintained at approximately 600 nmol/l from day 19 to day 23 of gestation by i.v. infusion from chronically implanted minipumps. Relaxin significantly (P<0·001) prolonged the length of gestation in 17 rats compared with controls, without causing dystocia or affecting the number of live births. Six rats gave birth during relaxin infusion. In these animals there was a significant (P<0·001) increase in the interval between successive deliveries compared with control animals, resulting in prolonged labour. The remaining 11 rats gave birth after the infusion was completed, when the interval between successive deliveries was significantly (P< 0·025) shorter than controls. The results are consistent with the hypothesis that relaxin has a central action suppressing the release of oxytocin as well as a peripheral action on the myometrium and cervix.

J. Endocr. (1986) 109, 85–88
Raised levels of calcium-binding protein in plasma following insulin-induced hypoglycaemia in the pig
Authors: Maunder E. M. W. , Pillay A. V. , Chapman C. , Care A. D.
Published: December 2008

Insulin-induced hypoglycaemia in the pig elicited sharp increases in the plasma concentrations of vitamin D-dependent calcium-binding protein (CaBP) and cortisol and a decrease in plasma inorganic phosphate. Glucose infusion following insulin administration abolished the increases in plasma CaBP and cortisol in response to insulin and reduced the hypophosphataemia. The percentage increases in plasma CaBP and cortisol in response to insulin-induced hypoglycaemia were reduced when the pigs were fed a low-calcium diet, but the hypophosphataemic response was similar.

We conclude that insulin-induced hypoglycaemia leads to increased plasma CaBP in pigs fed a normal calcium diet, which is associated with the hypoglycaemia rather than being a direct effect of insulin. We therefore suggest that plasma CaBP may represent more than a mere uncontrolled leak from its sites of storage.

J. Endocr. (1986) 109, 101–106
Bilateral maintenance of rabbit corpora lutea by the feto-placental unit
Authors: Nowak R. A. , Klein J. S. , Pulido D. M. , Bahr J. M.
Published: December 2008

The present study was undertaken to determine (1) whether the rabbit feto-placental unit maintains corpora lutea systematically and/or locally and (2) the interrelationships between conceptus number, luteal weight, luteal progesterone concentrations and serum progesterone levels. Thirty-three does were divided into the following treatment groups: (I) bilaterally pregnant, two ovaries; (II) unilaterally pregnant, two ovaries; (III) bilaterally pregnant, one ovary; (IV) unilaterally pregnant, one ovary, contralateral and (V) unilaterally pregnant, one ovary, ipsilateral. Blood samples were obtained from all rabbits on days 6, 9, 12, 15, 18 and 21 post coitum. Does were killed on day 21, and the percentage of viable fetuses, fetal weights, and luteal weights recorded. Blood samples and corpora lutea were analysed for progesterone.

Serum progesterone levels were similar for all groups until day 9 post coitum. Levels in groups III, IV and V declined significantly between days 9 and 12 following removal of one ovary at day 9. Fetal viability, fetal weights and luteal progesterone concentrations did not differ among any of the groups. Luteal weights did not differ among groups I, III, IV and V, but luteal weights of animals in group II were lower than those of group I (P<0·05). Ratios of viable fetuses to number of corpora lutea ranged from 1:11–10:5. No differences were observed in serum progesterone, luteal weights or luteal progesterone concentrations among animals with two conceptuses and those with seven or more, but serum progesterone levels in does with only one conceptus were lower than those in does with more (P<0·05). These results indicate that the feto-placental unit maintains corpora lutea systemically and that the high rate of pregnancy failure by day 21 in does with only one conceptus is due to the inability of a single conceptus to maintain normal serum progesterone levels even though the corpus luteum weight is not affected.

J. Endocr. (1986) 109, 107–110
Stimulation of steroid production in isolated rat Leydig cells by unknown factors in testicular fluid differs from the effects of LH or LH-releasing hormone
Authors: Rommerts F. F. G. , Hoogerbrugge J. W. , van der Molen H. J.
Published: December 2008

After the addition of charcoal-treated testicular fluid to Leydig cells isolated from 22-day-old rats, pregnenolone production could be increased to a maximum of tenfold within 30 min in a dose-dependent manner. Testicular fluid, but not serum, further increased pregnenolone formation threefold when pregnenolone production by Leydig cells was stimulated by the addition of LH-releasing hormone (fourfold), LH (25-fold) and 22R-hydroxycholesterol (300-fold). The effect of testicular fluid on steroid production in the presence of 22R-hydroxycholesterol was not inhibited by cycloheximide whereas cycloheximide completely inhibited the effect of LH. It appears unlikely that steroids, lipoproteins or other plasma components constitute the stimulatory agents in testicular fluid. The biologically active principles may be locally produced factors with a molecular weight > 25 000. Similar biological activities could be shown in testicular lymph from boars but not in systemic lymph from boars nor in charcoal-treated bovine follicular fluid. The presumably locally produced factor(s) may amplify the effect of LH and can thus act as a local modulator(s).

J. Endocr. (1986) 109, 111–117