bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of a prenatal androgen peak on rat brain sexual differentiation
Authors: Perakis A. , Stylianopoulou F.
Published: December 2008

Exposure of the developing female brain to a 5α-dihydrotestosterone surge on day 18 of gestation resulted in defeminization and slight masculinization of the brain. In contrast, abolition of the androgenic effects of the testosterone peak naturally occurring in male fetuses on day 18 of gestation by exposure of the developing male brain to cyproterone acetate, at that time, resulted in demasculinization while feminization was not affected. On the basis of these results, we suggest that both the prenatal testosterone peak and the high testosterone levels occurring in males neonatally are necessary for aromatization sufficient to effect complete male rat brain sexual differentiation.

J. Endocr. (1986) 108, 281–285
Neonatal screening for congenital adrenal hyperplasia: a programme based on a novel direct radioimmunoassay for 17-hydroxyprogesterone in blood spots
Authors: Wallace A. M. , Beastall G. H. , Cook B. , Currie A. J. , Ross A. M. , Kennedy R. , Girdwood R. W. A.
Published: December 2008

We have assessed the feasibility of screening newborn babies for congenital adrenal hyperplasia (CAH) by the direct measurement of 17-hydroxyprogesterone (17-OHP) in blood spots collected on filter paper (Guthrie cards) for the phenylketonuria, hypothyroidism and galactosaemia screening programmes run in Scotland. The procedure described for CAH uses an iodinated 17-OHP tracer and a specific 17-OHP antiserum sheathed within semipermeable nylon microcapsules. The method does not require a solvent extraction step, is inexpensive, precise, efficient and, therefore, practical for large-scale use. With this system the value of a neonatal screening programme was assessed in a retrospective analysis and a prospective trial.

The retrospective study of 15 paediatric cases of CAH illustrated that at least half were not diagnosed within 3 weeks of birth. Analysis of the original Guthrie card samples revealed increased levels of 17-OHP in all cases. The prevalence of CAH as calculated in the retrospective study was 1 in 20 907 with a range (within 95% confidence limits) of from 1 in 12 675 to 1 in 32 604 (n = 301 450). In the prospective trial a total of 92 051 consecutive samples was screened. Five cases of CAH were correctly identified with a current false positive rate of 0·042%. Analysis of urinary steroids confirmed defective adrenal 21-hydroxylase activity in all positive cases. In the prospective trial the prevalence was 1 in 18 401 with a range of from 1 in 7 422 to 1 in 50006.

We conclude that mass screening for CAH is both feasible and desirable.

J. Endocr. (1986) 108, 299–308
The physiological significance of arginine vasopressin in potentiating the response to corticotrophin-releasing factor in sheep
Authors: Redekopp C. , Livesey J. H. , Sadler W. , Donald R. A.
Published: December 2008

In order to assess the physiological importance of endogenous arginine vasopressin (AVP) in augmenting the ACTH response to corticotrophin-releasing factor (CRF), the response to CRF during hypertonic saline infusion in six Coopworth sheep was examined. A 4-h infusion of 5% (w/v) NaCl (3·8 ml/min) resulted in significantly (P < 0·01) greater rises in ACTH and cortisol, but not aldosterone, than were observed after CRF alone. Infusion of hypertonic saline without CRF resulted in a highly significant (P < 0·001) rise in plasma osmolality and AVP but no significant change in plasma ACTH, cortisol or aldosterone.

It is concluded that a marked but physiological increase in peripheral (and presumably central) levels of AVP does not result in any demonstrable change in plasma ACTH concentration. However, under these conditions, the ACTH and cortisol responses to CRF are considerably augmented.

J. Endocr. (1986) 108, 309–312
FSH-induced aromatase activity in porcine granulosa cells: non-competitive inhibition by non-aromatizable androgens
Authors: Chan W. K. , Tan C. H.
Published: December 2008

The aim of this study was to examine the inhibitory effect of the non-aromatizable androgens on FSH-stimulated aromatase activity in porcine granulosa cells. The cells were isolated from medium-sized follicles (4–6 mm) of prepubertal pigs, and cultured under chemically defined conditions in the presence of FSH (1 μg/ml, NIADDK-oFSH-S13) with and without the androgens for an initial 48-h induction period. Subsequently, the spent medium was replaced with fresh medium containing only testosterone as substrate and the cells were reincubated for a further 6 h. The conversion of this steroid to oestradiol-17β during this latter 'test' period was taken as a measure of the aromatase activity. The addition of 5α-dihydrotestosterone (DHT) into cultures of FSH-stimulated cells during the induction period resulted in a definite dose-dependent inhibition (30–70%) of the aromatase activity expressed in the test period. This inhibitory action, of the mixed non-competitive type, is characterized by a decrease in the apparent Vmax and an increase in the Km value, suggestive of an androgen inhibition of FSH-stimulated aromatase synthesis. This inhibition was also shown by the other 5α- and 5β-reduced androgens: 5β-androstanedione was the most effective, while DHT was the least. Other steroids such as pregnenolone and progesterone were inhibitory, but testosterone and diethylstilboestrol were stimulatory. These results suggest an important mechanism for the intrafollicular control of oestrogen synthesis, involving a possible reciprocal relationship between aromatase and 5α-reductase activities.

J. Endocr. (1986) 108, 335–341
Seasonal changes in concentrations of plasma hormones in the male ring dove (Streptopelia risoria)
Authors: Lea R. W. , Sharp P. J. , Klandorf H. , Harvey S. , Dunn I. C. , Vowles D. M.
Published: December 2008

Seasonal changes in concentrations of plasma LH, prolactin, thyroxine (T4), GH and corticosterone were measured in captive male ring doves exposed to natural lighting at latitude 56 °N. Plasma LH levels decreased steeply in autumn when the daylength fell below about 12·5 h but increased in November as the birds became short-day refractory. In comparison with plasma LH concentrations in a group of short-day refractory birds exposed to 6 h light/day from the winter solstice, plasma LH levels in birds exposed to natural lighting increased further in spring after the natural daylength reached about 12·5 h. There were no seasonal changes in plasma prolactin concentrations and plasma T4 concentrations were at their highest during December, January and February, the coldest months of the year. The seasonal fall in plasma LH levels in September was associated with a transitory increase in plasma T4, a transitory decrease in plasma corticosterone and a sustained increase in plasma GH.

It is suggested that in the ring dove, short-day refractoriness develops rapidly in November to allow the bird to breed when the opportunity arises, during the winter and early spring. The annual breeding cycle is synchronized by a short-day induced regression of the reproductive system in the autumn, the primary function of which may be to enable the birds to meet the energy requirements for the annual moult. The changes in plasma T4, corticosterone and especially of GH at this time of year are probably concerned with the control of moult or the associated changes in energy requirements.

J. Endocr. (1986) 108, 385–391
Measurement of lipogenesis in isolated preputial gland cells of the rat and the effect of oestrogen
Authors: Alves A. M. , Thody A. J. , Fisher C. , Shuster S.
Published: December 2008

Lipogenesis was measured in isolated preputial gland cells of female rats after ovariectomy and after the administration of oestradiol benzoate. Ovariectomy decreased preputial gland cell lipogenesis and also altered the pattern of lipid synthesis, producing a relative decrease in the proportion of polar lipids and an increase in the proportion of 'triglycerides'. Although daily administration of 2 or 10 μg oestradiol benzoate for 7 days produced slight increases in preputial gland cell lipogenesis in ovariectomized rats, the effects were not significant. A single injection of 10 μg oestradiol benzoate, however, produced significant increases in preputial gland cell lipogenesis of ovariectomized rats at both 2 and 24 h and, moreover, at 24 h the pattern of polar lipid and triglyceride labelling was restored to normal. Prior administration of actinomycin D reduced the lipogenic effect of oestradiol benzoate. Oestradiol benzoate had little or no effect on preputial gland cell lipogenesis in male rats. These results confirm that oestrogen is able to stimulate preputial lipogenesis in female rats. Whether this action of oestrogen is related to its pheromone-producing effect on the preputial glands is not yet known.

J. Endocr. (1986) 109, 1–7
Sexual dimorphism of messenger RNA isolated from neonatal rat brain
Authors: Adcock I. M. , Greenstein B. D.
Published: December 2008

The rat brain is sexually dimorphic with respect to structure and function, and there is evidence that these differences are effected in the fetus through changes in protein synthesis, some of which may result from the intervention of gonadal steroids. To investigate this, messenger RNA (mRNA) from the limbic system and cerebellum of neonatal rats was prepared, translated in a rabbit reticulocyte system in vitro and the products were analysed by two-dimensional electrophoresis and fluorography. Some of the results were further analysed using image analysis. There was a striking sexual dimorphism in the patterns of incorporation of [35S]methionine into proteins using mRNA from the limbic system, in that groups of proteins were apparently present in male-but not in female-derived fluorograms and vice versa. One protein, tentatively identified from its coordinates as α-tubulin, was more abundant in male-derived fluorograms. Although there were no clear-cut qualitative sex differences using mRNA derived from the cerebellum, that derived from the male cerebellum appeared to be consistently more active. These results provide direct evidence for a sexual dimorphism at the transcriptional level in the neonatal limbic system of the rat.

J. Endocr. (1986) 109, 23–28
Central adrenergic activity in the mediobasal hypothalamus is temporally related to surge outputs of gonadotrophins in oestrogen-stimulated infant female rats
Authors: Clement E. M. , MacKinnon P. C. B. , Sheaves R.
Published: December 2008

In the mediobasal hypothalamus (MBH) of prooestrous rats or acutely ovariectomized oestrogentreated adults a marked but short-lived increase in adrenergic activity occurs at 16.00 h, 2 h before the oestrogen-dependent surge of gonadotrophins at 18.00 h. In this study oestrogen-stimulated (noon on day 1) 22-day-old female rats were used which are known to produce surge levels of prolactin at 18.00 h on day 2 and surges of both prolactin and LH at 18.00 h on day 3; although similar treatment of 18-day-old animals or oil-treated 22-day-old rats failed to produce these effects. Radioenzymatic assays of adrenaline concentrations and of the activity of its synthesizing enzyme (phenylethanolamine-N-methyl transferase; PNMT, EC 2.1.1.28) in the MBH of oestrogen-treated 22-day-old rats showed significant (P< 0·05–0·01) increases in both parameters at 16.00 h (i.e. 2 h before surge levels of gonadotrophins) on days 2 and 3 when compared with other times of day. Such effects were not seen in oil-treated 22-day-old animals or in oestrogen-treated 16-day-old rats. Noradrenaline and dopamine concentrations in the MBH of oestrogen-treated 22-day-old rats remained at baseline levels on days 2 and 3 with the exception of noradrenaline at 17.00 h on day 3 when levels appeared higher (P<0·05) than at either 15.00 or 16.00 h. Subsequent measurements of PNMT activity in oestrogen-treated 22-day-old rats at 4-hourly intervals throughout days 2 and 3 showed the presence of a clear circadian rhythm with peak levels occurring at 16.00 h. In conclusion, a temporal relationship (not necessarily specific) exists between increased adrenergic activity in the MBH of oestrogen-treated 22-day-old rats and a surge of gonadotrophins (LH and/or prolactin) 2 h later. This relationship apparently depends on an oestrogen-stimulated circadian rhythm of PNMT activity.

J. Endocr. (1986) 109, 45–51
Myosin light chain kinase and cyclic AMP-dependent protein kinase activities and calmodulin levels in placental and non-placental regions of the rabbit myometrium
Authors: Matsui K. , Higashi K. , Yoshimura T. , Ito M. , Miyamoto E.
Published: December 2008

Myosin light chain kinase activity in the placental region of the rabbit myometrium on day 28 of gestation was 4·7±0·1 (mean ± s.e.m.) nmol/min per mg protein, which was significantly higher than that (3·6 ± 0·1 nmol/min per mg protein) in the non-placental region. The amount of calmodulin in the placental region was 4·2 ± 0·1 μg/mg protein, which was significantly higher than that (3·2 ± 0·1 μg/mg protein) in the non-placental region. In contrast, cyclic AMP-dependent protein kinase activities showed no difference between the two regions.

These findings suggest that calcium- and calmodulin-dependent protein phosphorylation is activated mainly in the placental region, and uterine contractions can occur more strongly in this part than in the non-placental region. Such enzymatic phenomena may be related to the mechanism whereby the placenta separates from the myometrium after delivery of the fetus.

J. Endocr. (1986) 109, 97–100
Morphological changes in the pituitary and thyroid of the rat in hypobaric hypoxia
Authors: Gosney J. R.
Published: December 2008

When a group of adult male Wistar rats was exposed to a barometric pressure of 380 mmHg for 28 days in an hypobaric chamber, profound changes occurred in their hypothalamic-pituitary-thyroidal axes in comparison with normobaric controls. The thyroid glands of the hypoxic animals had an inactive appearance, comprising large colloid-filled follicles lined by low epithelium. The thyrotrophs of the pars distalis of the pituitary glands were markedly decreased in number. They occupied only 0·41% of the total cell population in contrast with 1·34% in the controls (P<0·001); a total population which is itself decreased in the hypoxic animals. Classical 'thyroidectomy cells' were not seen. These observations support previous studies which indicate suppression of thyroid function in an hypoxic environment, and tend to suggest that this is a consequence of a direct effect of hypoxia on the hypothalamus or pituitary gland, rather than on the thyroid itself.

J. Endocr. (1986) 109, 119–124
A testosterone-independent reduction in net photoperiodic drive triggers photorefractoriness in male tree sparrows (Spizella arborea)
Authors: Wilson F. E.
Published: December 2008

An experiment was performed to determine whether photorefractoriness in male tree sparrows is triggered by a testosterone-independent reduction in net photoperiodic drive or by a photoperiod-induced hypersensitivity of the hypothalamic-pituitary axis to testosterone negative feedback. Photosensitive male tree sparrows were transferred from 8 h light: 16 h darkness (8L: 16D) to 20L: 4D. Birds were castrated bilaterally on day 28 of photostimulation. Beginning on day 33 and weekly thereafter until day 54, birds were given replacement testosterone (0–1·49 μmol) in s.c. polydimethylsiloxane capsules. Plasma samples collected on days 36, 43, 50 and 57 were assayed for LH. Plasma LH concentrations in birds without replacement testosterone were regarded as reflecting net photoperiodic drive in the absence of testosterone feedback, and the slopes of curves relating the logarithm of plasma LH concentration to dose of replacement testosterone were taken as quantitative measures of testosterone feedback sensitivity. The results showed that a testosterone-independent reduction in net photoperiodic drive beginning between days 43 and 50 preceded any change in sensitivity to testosterone negative feedback. Such results provide compelling evidence that a testosterone-independent mechanism triggers the photorefractory state in male tree sparrows.

J. Endocr. (1986) 109, 133–137
Varying the patterns and concentrations of gonadotrophin-releasing hormone stimulation does not alter the ratio of LH and FSH released from perifused sheep pituitary cells
Authors: McIntosh J. E. A. , McIntosh R. P.
Published: December 2008

Our aim was to determine whether release of LH and FSH can be controlled differentially by the characteristics of applied signals of stimulatory gonadotrophin-releasing hormone (GnRH) alone, free of the effects of steroid feedback or other influences from the whole animal. The outputs of both gonadotrophins were significantly correlated (r≈0·90; P<0·0005) when samples of freshly dispersed sheep pituitary cells were perifused in columns for 7 h with medium containing a range of concentrations of GnRH in various patterns of pulses. Hormone released in response to the second, third and fourth pulses from every column was analysed in detail. Dose–response relationships for both LH and FSH were very similar when cells were stimulated with 5–8500 pmol GnRH/1 in 5-min pulses every hour. When GnRH was delivered in pulses at a maximally stimulating level, the outputs of both hormones increased similarly with increasing inter-pulse intervals. Efficiency of stimulation (release of gonadotrophin/unit stimulatory GnRH) decreased (was desensitized) with increasing pulse duration in the same way for both hormones. Thus, varying the dose, interval and duration of GnRH pulses did not alter the proportions of LH and FSH released in the short-term from freshly dissociated cells. However, the same cell preparations released more LH relative to FSH when treated with maximally stimulating levels of GnRH for 3 h in the presence of 10% serum from a sheep in the follicular phase of its ovulatory cycle compared with charcoal-treated serum. Because there was no gonadotrophin synthesis under the conditions used in vitro these results suggest that changes in the LH/FSH ratio seen in whole animals are more likely to result from differential clearance from the circulation, ovarian feedback at the pituitary, differential synthesis in intact tissue or another hormone influencing FSH secretion, rather than from differences in the mechanism of acute release controlled by GnRH.

J. Endocr. (1986) 109, 155–161
Thyrotrophin-releasing hormone does not accumulate glycosylated thyrotrophin, but changes heterogeneous forms of thyrotrophin within the rat anterior pituitary gland
Authors: Mori M. , Kobayashi I. , Kobayashi S.
Published: December 2008

We have investigated the effect of TRH on the accumulation of glycosylated TSH in the rat anterior pituitary gland. Hemipituitaries from adult male rats were incubated in medium containing [3H]glucosamine in the presence of TRH. [3H]Glucosamine-labelled TSH in media and pituitaries was measured by immunoprecipitation and characterized by isoelectric focusing after affinity chromatography. Incorporation of [3H]glucosamine into immunoprecipitable TSH in the media and pituitaries increased progressively with the period of incubation. Although the release of [3H]glucosamine-labelled and unlabelled TSH into media was stimulated by the addition of TRH in a time- and dose-dependent manner, TRH administration did not alter the amounts of labelled or unlabelled TSH in the anterior pituitary lobes. The anterior pituitaries were found, by isoelectric focusing analysis, to be composed of four major component peaks of [3H]glucosamine-labelled TSH. Administration of TRH caused profound changes in the radioactivity of these components and evoked new radioactive peaks, resulting in the appearance of six components in total. The present data provide evidence that TRH significantly changes the heterogeneity of glycosylated TSH in the anterior pituitary without altering the amount of the glycosylated form.

J. Endocr. (1986) 109, 227–231
Changing renin substrates in human pregnancy
Authors: Tetlow H. J. , Broughton Pipkin F.
Published: December 2008

Renin substrate of high molecular weight was identified in plasma from pregnant women, non-pregnant subjects and in samples of umbilical arterial and venous plasma, using gel filtration chromatography. The proportion existing in the high molecular weight form in pregnant women was significantly increased above that of non-pregnant subjects by 11 weeks after the last menstrual period and continued to rise to term. In contrast, the proportion in fetal plasma was significantly lower than that of the non-pregnant group. High molecular weight renin substrate was itself heterogeneous and appeared to consist of four sub-groups. In non-pregnant adults the first peak, eluting near the void volume of the column, was the largest. In the fetus this profile was reversed. The elution profile in maternal plasma had changed markedly by as early as 8 weeks of gestation. Thereafter, it was possible to see increasing dominance of the minor 'intermediate' peaks visible in the non-pregnant adult until, in the third trimester, the high molecular weight form was eluted as a large broad band with little evidence of the individual peaks. Oestrogens are the most likely stimulus for the increased production of the high molecular weight renin substrate in pregnant women. In the fetus, although the same form of renin substrate is stimulated, the actual amount in the high molecular weight range is very small. This may be because oestrogens are sulphated in the fetus or because the fetal liver is not very responsive to the stimulation. The similarity between the profiles of mother and fetus may indicate a common source of production of renin substrate in the feto-placental unit.

J. Endocr. (1986) 109, 257–262
Lactogenic response of cultured mouse mammary epithelial cells to mouse placental lactogen
Authors: Thordarson G. , Villalobos R. , Colosi P. , Southard J. , Ogren L. , Talamantes F.
Published: December 2008

The ability of mouse placental lactogen (mPL), mouse prolactin (mPRL), mouse GH (mGH) and ovine prolactin (oPRL) to stimulate synthesis of α-lactalbumin was tested in a primary culture of mouse mammary gland epithelial cells. Mammary tissue was obtained from 10-day pregnant Swiss Webster mice, enzymatically dissociated and the cells were cultured on floating collagen gels for 5 days. The basic culture medium consisted of Nutrient Mixture F12/Dulbecco's Modified Eagle's Medium (1:1, v/v), containing 10 mg insulin/1, 5 mg cortisol/l, 10 μg epidermal growth factor/l, 5 g bovine serum albumin/l and 50 mg gentamycin/l. Mouse PL, mPRL, mGH and oPRL were added to the basic medium in concentrations from l μg/l to l mg/l. Accumulation of α-lactalbumin in the culture medium was measured. For that purpose, mouse α-lactalbumin was purified from mammary tissue obtained from lactating Swiss Webster mice and a radioimmunoassay was developed. Mouse PL, mPRL and oPRL stimulated a dose-dependent increase in α-lactalbumin secretion. Mouse GH also caused a significant, but dose-independent, increase in α-lactalbumin secretion. Mouse PL showed the greatest activity in stimulating α-lactalbumin secretion. It was concluded that mPL is an important lactogenic hormone in the latter half of pregnancy in the mouse, when circulating mPRL concentrations are low.

J. Endocr. (1986) 109, 263–274
Androgen regulation of the androgen receptor of the quail uropygial gland: application of a [3H]mibolerone exchange assay
Authors: Amet Y. , Abalain J.-H. , di Stefano S. , Daniel J.-Y. , Tea K. , Floch H. H. , Robel P.
Published: December 2008

An exchange assay for androgen receptors in the quail uropygial gland using [3H]mibolerone was established. The most efficient exchange conditions were 3 days of incubation at 15 °C. Under these conditions, androgen receptors were stable in the presence of sodium molybdate, and the exchange of [3H]mibolerone with endogenous testosterone bound to cytosolic or nuclear androgen receptors was maximal. Less than 5% of [3H]mibolerone-binding sites occurred in the extracted nuclear pellets. Using this exchange technique, it was shown that androgen receptors in the uropygial gland of photostimulated male quail or castrated quail treated with testosterone were activated and that their concentrations in both cytosolic and nuclear fractions were increased. These results confirm the androgen dependency of the quail uropygial gland, and show that it is an organ which can be used as a model for the study of androgen action in sebaceous glands.

J. Endocr. (1986) 109, 299–306
Effect of epidermal growth factor on the membrane potential of cultured porcine thyroid cells
Authors: Bourke J. R. , McGrath P. A. , Huxham G. J. , Waters M. J. , Manley S. W.
Published: December 2008

Cultured porcine thyroid cells maintained in media containing TSH exhibited a membrane potential of −50 mV, and hyperpolarized by about 10 mV within 1 h of the addition of epidermal growth factor (EGF; 10 ng/ml). Follicle cells had depolarized to −45 mV after 4 h of exposure to EGF. Cells maintained in dibutyryl cyclic AMP (dbcAMP) did not alter their membrane potential when exposed to EGF for up to 4 h. Cultures washed to remove the TSH or dbcAMP hyperpolarized to − 75 mV within 30 min, and a reversible depolarization to − 60 mV was observed on addition of EGF. It was concluded that EGF acts as a physiological antagonist of TSH and also exerts a separate depolarizing influence on cultured thyroid cells.

J. Endocr. (1986) 109, 321–324
Circulating insulin-like growth factor-binding proteins in fetal, neonatal and adult sheep
Authors: Butler J. H. , Gluckman P. D.
Published: December 2008

A specific radioimmunoassay for insulin-like growth factor I (IGF-I) has been used to study the distribution of circulating IGF-I on its carrier proteins in sheep. Serum or plasma samples obtained from fetal, neonatal and adult sheep were chromatographed at neutral pH on Sephadex G-200 columns. IGF-I eluted primarily in the 20 000–100 000 dalton region and to a lesser extent in the 20 000–100 000 dalton region in the adult. In the fetus, IGF-I eluted primarily in the 20 000–50 000 dalton region. Studies in the neonatal lamb showed IGF-I activity to fluctuate between different size binding proteins but by 7 days after birth the pattern was similar to that of the adult. When labelled IGF-I and IGF-II were added to serum which was chromatographed over Sephadex G-200 at a neutral pH, binding was displayed in the 50 000– 100 000 dalton region for both adult and fetus. However in the fetus, but not in the adult, binding of 125I-labelled IGF-II was also found at > 200 000 daltons. These studies demonstrate that the distribution of IGF-binding proteins varies between the adult and the fetal lamb. The appearance of the 150 000 dalton binding protein is coincidental with the appearance of the somatogenic receptor in the infant liver and is consistent with the GH-dependent nature of this form of binding protein in other species. The marked developmental changes in the circulating form of IGF-I in the perinatal lamb may be of functional significance and lead to altered biological availability of circulating IGF-I.

J. Endocr. (1986) 109, 333–338
Purification of dispersed rat adrenal zona glomerulosa cells by Percoll density gradient centrifugation and the isolation of a population of cells highly responsive to adrenocorticotrophin
Authors: Chu F. W. , Hyatt P. J.
Published: December 2008

Percoll density gradient centrifugation is a simple, inexpensive and convenient method to eliminate contaminating zona fasciculata (ZF) cells from unpurified rat adrenal capsular glomerulosa (ZG) cell preparations (with less than 0·1% ZF cells in the final cell preparation). Basal steroid (aldosterone and corticosterone) output by the purified (PG) cells was unchanged. These purified cells, although free from ZF contamination, were more highly responsive than expected to ACTH (3 nmol/l). When PG cells were further separated by Sephadex column filtration, the filtered PG cells exhibited the steroidogenic response of ZG cells purified by unit gravity sedimentation and Sephadex column filtration, i.e. reduced basal steroid output and an ACTH response reduced to that stimulated by K+ (8·4 mmol/l). Although the cells retained in the column resembled the filtered PG cells ultrastructurally, they showed unchanged basal steroid output and a high ACTH response with increased latepathway activity (the conversion of corticosterone to aldosterone). By combining Percoll density gradient centrifugation and Sephadex column filtration we have a method for the isolation and study of both the high-and low-response rat ZG cells which are free from ZF contamination.

J. Endocr. (1986) 109, 351–358
Tri-iodothyronine and phenytoin reduce prolactin messenger RNA levels in cultured rat pituitary cells
Authors: Davis J. R. E. , Lynam T. C. , Franklyn J. A. , Docherty K. , Sheppard M. C.
Published: December 2008

Thyroid hormones may regulate prolactin gene transcription. We have previously found that phenytoin inhibits tri-iodothyronine (T3) nuclear binding, and have suggested that phenytoin may act as a partial T3 agonist. We have therefore investigated the effects of phenytoin and T3 on prolactin release and gene transcription, using the technique of cytoplasmic dot hybridization with complementary DNA probes to estimate prolactin messenger (m) RNA concentrations in cytoplasm from cultured rat pituitary cells.

Tri-iodothyronine treatment led to a small but significant fall in prolactin release by 72 h, but caused marked dose- and time-dependent reductions in prolactin mRNA levels at 48–72 h. Phenytoin, however, caused more rapid falls in both prolactin release and mRNA concentrations. Neither T3 nor phenytoin significantly altered GH mRNA levels. These studies suggest effects of phenytoin similar, but not identical, to those of T3 in the lactotroph.

J. Endocr. (1986) 109, 359–364
Cytoplasmic progesterone receptors in uterine tissue of the snapping turtle (Chelydra serpentina)
Authors: Mahmoud I. Y. , Colás A. E. , Woller M. J. , Cyrus R. V.
Published: December 2008

A high affinity progesterone-binding component was detected in the cytosol of the uterus of the snapping turtle, Chelydra serpentina. Density gradient centrifugation indicated that binding of [3H]progesterone and [3H]promegestone (R5020) was to a fraction with a heavier sedimentation coefficient than bovine serum albumin (BSA) appearing as a broader peak in the 6–7 S region; it was not affected by excess cortisol. Another binding peak, lighter than BSA and appearing with [3H]R5020 and [3H]progesterone near the 4 S region, was affected by excess cortisol. Excess progesterone decreased both the heavier and lighter peaks. Analysis of steroid specificity revealed that, of the natural steroids, progesterone had the highest affinity for the uterine cytosol. This was followed by deoxycorticosterone, 5α-pregnanedione, testosterone, oestradiol-17β, corticosterone, 5α-dihydrotestosterone and cortisol. Non-linear regression analysis of saturation data indicated the presence of two classes of high affinity binding sites: progesterone-binding sites (R-sites) with equilibrium association constants (Ka) of 2·9 ± 0·28 litres/nmol (mean ± 95% confidence limit) for [3H]R5020 and 0·34 ± 0·20 litres/nmol for [3H]progesterone, and corticosteroid-binding globulin-like sites (G-sites) with Ka of 4·5 ± 1·6 litres/nmol for progesterone. The concentration of R-sites was between 0·66 ± 0·10 and 2·6 ± 0·55 pmol/mg protein while that of G-sites was between 0·73 ± 0·05 and 5·0 ± 0·27 pmol/mg protein. DEAE-cellulose filtration assay also confirmed the presence of R-sites and G-sites in the cytosol. R-sites were detectable without oestrogen priming during the preovulatory and vitellogenic phases (low progesterone, high oestrogen concentrations) when the ovarian follicles are mature (18–22 mm diameter). During the early postovulatory phase (high progesterone, low oestrogen concentrations), when the ovarian follicles are immature (5–7 mm diameter) and active corpora lutea are present, the R-sites were undetectable even after oestrogen priming. This indicates that progesterone might have an inhibitory and oestrogen a stimulatory role in the regulation of R-sites.

J. Endocr. (1986) 109, 385–392
EFFECT OF LONG-TERM INFUSION OF AN LH-RELEASING HORMONE AGONIST ON TESTICULAR FUNCTION IN BULLS
Authors: Rechenberg W. v. , Sandow J. , Klatt P.
Published: December 2008

Continuous administration of LH-releasing hormone (LHRH) agonists is an effective method of suppressing testosterone secretion in the male. The effect of the LH-releasing hormone (LHRH) agonist, buserelin, administered to bulls by constant infusion from osmotic minipumps was studied. In one experiment with four treated and one control bull, 109 pg buserelin/day were administered for 22 days. Immediately after implantation, serum testosterone concentrations rose from below 35 nmol/l to 35-105 nmol/l, and all four buserelin-infused bulls showed increased testosterone secretion during the treatment period. After removal of the minipumps, testosterone concentrations decreased to pretreatment levels. In a second experiment bulls were infused for 42 days (four treated and one control), and identical results were obtained. Testosterone secretion was stimulated (52-87 nmol/l serum) during the entire treatment period. These results demonstrate that conditions for stimulation of the pituitary-testicular axis may vary between species. Infusion of low doses of LHRH-agonists in bulls has an extended stimulatory effect without immediate desensitization of gonadotrophin release.
Effect of graded doses of gonadotrophin-releasing hormone on serum LH concentrations in mares in various reproductive states: comparison with endogenously generated LH pulses
Authors: Alexander S. L. , Irvine C. H. G.
Published: December 2008

Luteinizing hormone release induced by a range of small (3·3–33 μg) and large (300–500 μg) i.v. doses of gonadotrophin-releasing hormone (GnRH) was measured in acyclic (n = 4), luteal phase (n = 3) and follicular phase (n = 5) mares and compared with endogenously generated LH pulses in the same reproductive states. Extrapolation from log–linear dose–response curves showed that an LH pulse comparable to an endogenous one would be simulated by i.v. injection of 7·0 (n = 4) and 4·1 (n = 6) μg GnRH in luteal and follicular phase mares respectively; a much smaller dose than the 500 μg usually given clinically or experimentally. In acyclic mares (n = 4), LH pulses occurred too infrequently to be characterized. At small doses of GnRH the amount of LH released by the same dose was similar in all three reproductive states, although the steroid hormone milieu differed markedly. This implies that observed differences between states in mean (± s.e.m.) serum LH concentrations (0·7 ± 0·01, 1·2 ± 0·03 and 11·6 ± 0·33 (μg/l) in acyclic, luteal and follicular phase mares respectively) were produced by differences in GnRH pulse frequency and/or amplitude and not by steroid-mediated changes in pituitary response to GnRH. In acyclic, luteal and follicular phase mares, LH pulse frequency was: immeasurably low, 0·09 and 1·14 pulses/h respectively, which supports the important contribution of pulse frequency to determining mean LH concentration. The LH response to large doses of GnRH was significantly greater in the luteal than in the follicular phase, and was greater than the response to 33 μg in the luteal phase but not in the other two states. Thus, to a large but not to a small dose of GnRH, the pituitary appeared most responsive in the luteal phase. Therefore, in studies of the physiology of the hypothalamic-pituitary system, small doses of GnRH, which induce physiologically sized LH responses, may be preferred to large doses, which result in a level of stimulation to which the pituitary is never naturally exposed and to which it may respond in a non-physiological manner.

J. Endocr. (1986) 110, 19–26
The origin of circulating calcitonin gene-related peptide in the rat
Authors: Zaidi M. , Bevis P. J. R. , Abeyasekera G. , Girgis S. I. , Wimalawansa S. J. , Morris H. R. , MacIntyre I.
Published: December 2008

It is known that in addition to the calcitonin precursor the calcitonin gene also encodes a novel peptide, calcitonin gene-related peptide (CGRP). This potent vasodilator has been found in the circulation of man. This present study demonstrates that CGRP is also found in the circulation of the rat and that plasma CGRP comes from two different sources: the thyroid, a major source in old rats, and the perivascular nerves probably at all ages.

J. Endocr. (1986) 110, 185–190
Reduced affinity of intestinal receptors for 1,25-dihydroxycholecalciferol in phosphorus-deficient chicks
Authors: Bar A. , Hurwitz S.
Published: December 2008

The binding of 1,25-dihydroxycholecalciferol (1,25-(OH)2D3) to its intestinal receptor was studied in chicks fed a phosphorus (P)-deficient diet. The equilibrium association constant (Ka) was determined by Scatchard analysis. Association (Kass) and dissociation (Kdis) rate constants were determined in experiments on hormone uptake and release respectively. The Ka, determined at 4, 12 and 19 °C, decreased progressively during P deficiency, due to the decrease in Kass, but Kdis was not affected. During prolonged P deficiency the concentration of binding sites (Nmax) also decreased. Duodenal calcium-binding protein (CaBP) increased during 10 days of P deficiency and then decreased.

The long-term decrease in receptor affinity and Nmax may account for the observed reduction in receptor occupancy and the decrease in the high level of intestinal CaBP stimulated during early P deficiency. The resulting decrease in Ca absorption may minimize the hypercalcaemia induced by the deficiency.

J. Endocr. (1986) 110, 217–223
Control of sex steroid-binding protein (SBP) in the male little brown bat: relationship of plasma thyroxine levels to the induction of plasma SBP in immature males
Authors: Kwiecinski G. G. , Damassa D. A. , Gustafson A. W.
Published: December 2008

The seasonally reproductive male little brown bat (Myotis lucifugus lucifugus) exhibits marked increases in plasma concentrations of sex steroid-binding protein (SBP) in the spring following arousal from hibernation. In this species an increase in SBP levels is induced prematurely in male bats aroused during the first half of hibernation and housed under long photoperiods; however, this rise is inhibited in bats housed under short photoperiods. In order to investigate the physiological role of the thyroid gland in the regulation of plasma SBP activity, plasma total thyroxine (T4) and SBP concentrations were determined in immature male little brown bats prematurely aroused from the first half of hibernation and maintained on either a short or long photoperiod. For this purpose a radioimmunoassay for the measurement of total T4 in bat plasma was established and validated. The results showed that immature male little brown bats aroused prematurely from hibernation and housed under a long spring-like photoperiod exhibited marked increases in plasma T4 and SBP concentrations, while animals housed under a short photoperiod showed only marginal increases in SBP, and plasma T4 remained undetectable. These results suggest that the thyroid gland, through the action of T4, may normally play an important role in the control of the post-arousal rise in plasma SBP concentrations in the little brown bat.

J. Endocr. (1986) 110, 271–278
Effect of human α-atrial natriuretic polypeptide on adrenocortical function in man
Authors: Ohashi M. , Fujio N. , Kato K. , Nawata H. , Ibayashi H. , Matsuo H.
Published: December 2008

To determine the effects of atrial natriuretic polypeptide (ANP) on plasma levels of ACTH, cortisol, aldosterone and dehydroepiandrosterone (DHEA), synthetic human α-ANP (hα-ANP) was infused i.v. into eight normotensive, disease-free volunteers, at a dose and duration previously found to be sufficient to produce apparent cardiovascular and renal effects.

The mean basal concentration of plasma ACTH determined by radioimmunoassay was 18·2 ± 3·1 ng/l. Plasma ACTH concentrations tended to be decreased during the infusion in all subjects. However, the change in plasma ACTH concentrations during infusion of hα-ANP was essentially the same as that during the infusion of saline. The mean plasma cortisol concentration was significantly suppressed from 25 to 40 min after the end of synthetic hα-ANP infusion. At 90 min after infusion, the mean plasma level of cortisol reverted to the pretreatment level. There was a non-significant increase in plasma renin activity following the infusion. The mean plasma aldosterone concentration was reduced by 15% (P < 0·05) during the infusion and returned to preinfusion levels 10 min after termination of the infusion, after which the mean plasma concentration declined to the level seen during infusion. Administration of hα-ANP had no significant influence on plasma DHEA concentrations, but there was a tendency to decrease during the infusion.

Our data suggest that synthetic hα-ANP inhibits adrenocortical steroidogenesis in man.

J. Endocr. (1986) 110, 287–292
Increase in DNA polymerase α activity associated with DNA synthesis due to FSH or oestrogen in ovaries of immature rats
Authors: Usuki S. , Shioda M.
Published: December 2008

DNA polymerase activities and DNA content of ovaries from immature intact rats (4–29 days after birth), hypophysectomized rats and hormone-treated hypophysectomized rats were measured. During normal ovarian growth DNA polymerase α activity and DNA content of ovaries increased. The polymerase activity decreased gradually after hypophysectomy without any alteration in the DNA content. Administration of ovine FSH (2 μg/day) or oestradiol-17β (1 mg/day) to hypophysectomized rats enhanced ovarian DNA content and DNA polymerase α activity, whereas DNA polymerase β activity did not change significantly. These results suggest that DNA polymerase α participates in DNA synthesis in these ovaries. The specific activity of DNA polymerase α (the activity per μg DNA) in the ovaries increased between 4 and 14 days after birth, and then remained almost constant; the specific activity declined gradually after hypophysectomy. Administration of FSH or oestradiol-17β but not of ovine LH, progesterone or testosterone to hypophysectomized rats restored the specific activity. Mixing experiments with different kinds of ovarian extracts suggested that no activators of DNA polymerase α were present in the extracts.

These results suggest that FSH or oestrogen causes the induction of DNA polymerase α accompanied by DNA synthesis during cell proliferation in ovaries of immature rats.

J. Endocr. (1986) 110, 353–360
Potentiation of the somatogenic and lactogenic activity of human growth hormone with monoclonal antibodies
Authors: Aston R. , Holder A. T. , Preece M. A. , Ivanyi J.
Published: December 2008

Monoclonal antibodies of certain epitope specificity have been shown to produce a marked dose-dependent enhancement of the somatogenic and lactogenic activity of human GH (hGH). Two antibodies (EB1 and EB2), binding to distinct antigenic determinants and expressed on both hGH and human chorionic somato-mammotrophin (hCS), significantly enhanced the hGH-stimulated uptake of 35S-labelled sulphate into cartilage. Similarly, these antibodies enhanced the lactogenic activity of both hGH and hCS in the pigeon crop sac test. Two hGH specific monoclonal antibodies (QA68 and NA71), defining a further two epitopes, exhibited only modest enhancing or inhibitory activity in these assays, whereas the binding of certain combinations of monoclonal antibodies resulted in either reversal of enhancement or inhibition of hormone activity. Univalent antibody fragments derived from EB1 were as enhancing as the intact antibody indicating that bivalency dependent mechanisms were not involved in the phenomenon. Enhancing monoclonal antibodies were relatively poor inhibitors of 125I-labelled hGH binding to liver microsomal receptors, which is in contrast with their previously described property of potent suppression of hGH interaction with lymphoid cell receptors. It is tentatively concluded that 'restriction' of hormone binding to particular hGH receptors, relevant to somatic growth or lactogenic activity, may play a role in the enhancement phenomenon of hGH in vivo.

J. Endocr. (1986) 110, 381–388
Effect of prostaglandins E2 and F2α on membrane calcium binding, Ca2+/Mg2+-ATPase activity and membrane fluidity in rat myometrial plasma membranes
Authors: Deliconstantinos G. , Fotiou S.
Published: December 2008

Myometrial plasma membrane (MPM) preparations from rats treated with oestradiol were obtained by discontinuous sucrose-gradient centrifugation. The preparations contained calcium-stimulated and magnesium-dependent ATPase (Ca2+/Mg2+-ATPase). A dramatic decrease in the activity of Ca2+/Mg2+-ATPase was observed when preparations were treated with 0·025–10μmol protaglandins E2 and F2α (PGE2 and PGF2α)/l. In contrast, there was a marked increase in MPM-bound 5′-nucleotidase activity at low concentrations (up to 2 μmol/l) of PGE2 and PGF2α; higher concentrations (up to 10 μmol/l), however, led to a progressive inhibition of enzyme activity. Association (specific and non-specific binding) of PGE2 and PGF2α with MPM at pH 7 was found to require Ca2+ (half-maximal concentration approximately 0·7 mmol/l). Changes in the allosteric properties of MPM-bound 5′-nucleotidase by concanavalin A (as reflected by changes in the Hill coefficient) indicated a fluidization of the membrane induced by PGE2 and PGF2α. The steady-state fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene-labelled MPM decreased in PGE2- and PGF2α-treated MPM from 1·24 ± 0·04 (s.d.) to 0·66 ± 0·01 and 0·74 ± 0·01 respectively, which is consistent with a general increase in membrane fluidity. It is suggested that PGE2 and PGF2α promote changes in the physical properties of MPM which may be relevant to the induction of uterine contractions by enzymatic regulation of intracellular calcium concentrations.

J. Endocr. (1986) 110, 395–404