bluuebunny/crossref_metadata_2025_split huggingface dataset:
Plasma levels of atrial natriuretic peptides during pregnancy and post partum in the rat
Authors: Jansakul C. , King R. G. , Boura A. L. A. , Brennecke S. P. , Handberg G. M. 
Published: December 2008

ABSTRACT
Plasma concentrations of atrial natriuretic peptides (ANP) in female Wistar rats were measured by radioimmunoassay at oestrus, during pregnancy, during parturition and between 3 h and 4 days post partum. Concentrations of ANP in rats on days 10, 15 and 17 of pregnancy were not significantly different from those in non-pregnant animals in oestrus (32·5 ± 2·2 pmol/l; mean ± s.e.m., n = 9), but levels near term (days 20 and 21 of pregnancy) were reduced by approximately 50%. However, plasma concentrations of ANP at 6, 12 and 24 h post partum were approximately twice those of non-pregnant animals in oestrus, but returned to normal levels within 4 days after parturition. Maternal plasma volume increased significantly during pregnancy, and fell 15–20% 6–24 h post partum. These results suggest that the relationship between plasma volume and the plasma concentration of ANP is reset during pregnancy and changes rapidly post partum. The results do not necessarily, however, imply any changes in the relationship between atrial pressure and the concentration of ANP.
Journal of Endocrinology (1989) 120, 113–117
Autoradiographic studies of androgen-binding sites in human benign prostatic hyperplasia in vitro
Authors: Lasnitzki I. , Takeda H. , Mizuno T. 
Published: December 2008

ABSTRACT
Steroid autoradiographic techniques were used to visualize the distribution of androgen receptor-positive cells in human benign prostatic hyperplasia grown in organ culture. The tissue consisted of alveoli embedded in dense fibromuscular stroma and lined either with one row of cuboidal secretory cells or with several layers of epithelial cells. In some explants alveoli were seen lined with spindle-shaped cells. The autoradiographs showed that in most explants both epithelium and stroma contained androgen receptor-positive cells but that the uptake was less pronounced in the stromal cells. In alveoli lined with several cell layers the basal cells seemed to incorporate less androgen than secretory cells on the luminal side. In alveoli lined with spindle-shaped cells, these were always androgen receptor-negative.
Journal of Endocrinology (1989) 120, 167–170
Oestradiol, vasoactive intestinal peptide and fibroblast growth factor in the growth of human pituitary tumour cells in vitro
Authors: Prysor-Jones R. A. , Silverlight J. J. , Jenkins J. S. 
Published: December 2008

ABSTRACT
The growth of two human prolactin-secreting cell lines developed in our laboratory has been investigated in response to a number of factors. Oestrogen stimulated the synthesis of DNA and protein and increased prolactin secretion. Dexamethasone had the opposite effect to oestrogen. In the presence of serum, epidermal growth factor (EGF) inhibited cell growth at concentrations of 5 ng/ml. Known secretagogues of prolactin (vasoactive intestinal peptide (VIP), TRH, bombesin and neurotensin) were investigated for their action on cell growth but only VIP had a stimulatory effect. Two preparations of fibroblast growth factor (FGF) were studied. One form, derived from bovine pituitary glands, stimulated human pituitary cell growth. In contrast, another FGF, of the basic type (rFGF), was inhibitory to cell growth, increasing the time for cell doubling from 30 to 72 h. This inhibitory effect of rFGF was modified but not abolished by serum, oestradiol, platelet-derived growth factor or EGF. We conclude that bovine pituitary contains at least two fibroblast growth factors, both of which stimulate fibroblast cell growth, but one stimulates and the other inhibits human pituitary tumour cell growth.
Journal of Endocrinology (1989) 120, 171–177
Effect of exogenous prolactin and bromocriptine on seasonal reproductive quiescence in the Bennett's wallaby (Macropus rufogriseus rufogriseus)
Authors: Brinklow B. R. , Loudon A. S. I. 
Published: December 2008

ABSTRACT
Two experiments were performed to investigate whether prolactin blocks the reactivation of the corpus luteum during seasonal reproductive quiescence in the Bennett's wallaby. In the first experiment three groups of non-lactating females (groups (A–C) were subjected in mid-April to photoperiods corresponding to those of the summer solstice from day 0 to day 13 of the experiment. Between days 14 and 52, photoperiods were reduced to correspond to those of the winter solstice (groups B and C). Animals in group A were maintained on the long photoperiods. Two milligrams ovine prolactin (groups A and C) or vehicle (group B) were administered on the mornings of days 14–22. In group A, no animal showed evidence of an active corpus luteum based on increased plasma progesterone levels. All animals in groups B and C exhibited reactivation of the corpus luteum. In group C, reactivation was significantly (P < 0·01) delayed by a mean of 6·3 days.
In the second experiment, two groups of non-lactating female wallabies in 'seasonal quiescence' were injected daily for 7 days with either 60 mg of the dopamine agonist bromocriptine or vehicle. The corpora lutea did not reactivate in either group. We conclude that exogenous prolactin is able to block the effect of short photoperiods in reactivating the quiescent corpus luteum during seasonal quiescence. However, the absence of an effect of bromocriptine suggests that if prolactin is the endogenous hormone responsible for maintaining seasonal quiescence it may not be under dopaminergic control at this time of year.
Journal of Endocrinology (1989) 120, 189–193
Steroids in equine testes: the identification of endogenous 19-hydroxy and 19-nor neutral steroids by gas chromatography–mass spectrometry
Authors: Dumasia M. C. , Houghton E. , Jackiw M. 
Published: December 2008

ABSTRACT
After homogenization of testicular tissue from stallions aged 1, 2 and 5 years, the unconjugated and conjugated steroids were isolated by a combined solvent–solid extraction procedure. The conjugates were further separated into glucuronides and sulphates by chromatography using Sephadex LH-20. After enzyme hydrolysis and solvolysis of the respective conjugate classes, the three extracts, unconjugated steroids, aglycones and solvolysed sulphates, were purified by chromatography using Kieselgel 60H columns. Five fractions were resolved from each extract; an aliquot of each fraction was derivatized to form the methoxime-trimethylsilyl ethers and the steroids were identified by combined gas chromatography–mass spectrometry. The results have shown that in stallion testes (1) steroidogenesis proceeds by both the 4-ene and the 5-ene pathways, (2) age-linked changes occur in both unconjugated and sulphoconjugated steroid fractions and (3) 19-hydroxy androgens and the 19-nor (C18) neutral steroids (19-norandrostenedione and 19-nortestosterone) are detected only in the unconjugated fraction whereas oestrone, the isomers of oestradiol and of 5(10)-oestrene-3,17-diol are the only steroids detected in the sulphoconjugate fraction. It is suggested that the unconjugated 19-oxygenated androgens present in stallion testes are converted to 19-nor neutral steroids by a reverse aldol reaction and a mechanism showing the putative intermediates in their formation is illustrated.
Journal of Endocrinology (1989) 120, 223–229
Stabilization, accurate determination, and purification of rat liver nuclear thyroid hormone receptor
Authors: Ichikawa K. , Brtko J. , DeGroot L. J. , Hashizume K. , Yamada T. 
Published: December 2008

ABSTRACT
Rat liver nuclear thyroid hormone receptor lost 3,5,3′-tri-iodo-l-thyronine (T3)-binding activity with a half-life of 14 days, 4 h, 139 min, 62 min, 16 min or 6 min at 0, 36, 38, 40, 43 or 45 °C respectively, when present in crude nuclear extracts. Glycerol increased the half-life of the receptor during heat inactivation. Protection was reversible by removing the glycerol. The receptor was unstable at a pH below 6·0 or above 10·0. We also found a loss of the receptor activity during the separation of bound and free hormone using the resin test. Of several conditions tested for the separation of bound and free hormone, the addition of heated nuclear extract gave the most accurate estimation of bound hormone when using the resin test. Using these characteristics of the receptor, we purified the receptor to 1220 pmol T3-binding capacity/mg protein with a final yield of 14·6 μg/4 kg rat liver.
Journal of Endocrinology (1989) 120, 237–243
Formation of 4-oestrene-3,17-dione (19-norandrostenedione) by porcine granulosa cells in vitro is inhibited by the aromatase inhibitor 4-hydroxyandrostenedione and the cytochrome P-450 inhibitors aminoglutethimide phosphate and ketoconazole
Authors: Khalil M. W. , Morley P. , Glasier M. A. , Armstrong D. T. , Lang T. 
Published: December 2008

ABSTRACT
The origin and biosynthesis of 4-oestrene-3,17-dione (19-norandrostenedione), a major steroid in porcine ovarian follicular fluid, was investigated by culturing granulosa cells from 4–6 mm follicles of prepubertal gilts with radiolabelled androstenedione and 19-hydroxyandrostenedione. Steroid metabolites were purified by solvent extraction and lipophilic column chromatography, and analysed by C18 reverse-phase high-performance liquid chromatography. 19-Hydroxyandrostenedione, 19-norandrostenedione and oestradiol-17β were obtained as major metabolites from androstenedione, while 19-norandrostenedione and oestradiol-17β were the major products from 19-hydroxyandrostenedione. Serum alone or serum plus FSH significantly enhanced formation of 19-norandrostenedione and oestradiol-17β from each substrate, compared with controls.
Micromolar concentrations (1 μmol/l) of 4-hydroxyandrostenedione, an aromatase inhibitor, significantly reduced formation of 19-norandrostenedione and oestradiol-17β by granulosa cells cultured with serum and FSH. Formation of 19-norandrostenedione and oestradiol-17β from androstenedione and 19-hydroxyandrostenedione was also significantly inhibited by aminoglutethimide phosphate, a cytochrome P-450 inhibitor known to block the conversion of androstenedione to oestrogens. Ketoconazole, an inhibitor of the cytochrome P-450 dependent 17,20-lysase, blocked formation of 19-norandrostenedione and oestradiol-17β only at millimolar concentrations. These results suggest that 19-norsteroid and oestrogen formation from C19 aromatizable androgens may share a common or overlapping pathway, and imply that 19-norsteroid and oestrogen synthesis is mediated by cytochrome P-450 dependent enzymes.
Journal of Endocrinology (1989) 120, 251–260
Effect of adrenomedullectomy and propranolol treatment on the response of gonadotrophins to chronic stress in male rats
Authors: Ariznavarreta C. , Calderón M. D. , Tresguerres J. A. F. , López-Calderón A. 
Published: December 2008

ABSTRACT
In order to study the involvement of the adrenal medulla in stress-induced inhibition of gonadotrophin secretion, we measured plasma concentrations of LH, FSH and corticosterone in adult male rats subjected to chronic restraint after surgical ablation of the adrenal medulla. In intact animals, chronic restraint (6 h daily over 4 days) induced a significant (P<0.05) decrease in plasma concentrations of LH, whereas plasma concentrations of corticosterone showed the expected significant (P<0.01) increase. Adrenomedullectomy did not significantly modify basal plasma concentrations of LH or corticosterone. In these rats, there was no significant decrease of LH after stress, while the increase in corticosterone was as significant as in sham-operated animals (P<0.01). In order to confirm the role of adrenomedullary catecholamines in stress-induced gonadotrophin inhibition another group of rats was treated s.c. with the β-adrenergic blocker propranolol (2 mg/kg twice daily). These rats showed an attenuated inhibition of LH during stress similar to that observed in adrenomedullectomized rats. Levels of FSH were significantly reduced after stress in the saline-treated group, while there were no differences between stressed or unstressed rats in the propranolol-treated group. These results may be considered as evidence that medullary catecholamines, acting through β-receptors, are factors involved in gonadotrophin inhibition during chronic stress.
Journal of Endocrinology (1989) 120, 275–279
A dual role of growth hormone as a feminizing and masculinizing factor in the control of sex-specific cytochrome P-450 isozymes in rat liver
Authors: Mode A. , Wiersma-Larsson E. , Ström A. , Zaphiropoulos P. G. , Gustafsson J.-Å. 
Published: December 2008

ABSTRACT
The effects of GH on the major constitutive sex-specific forms of cytochrome P-450 (P-45015β and P-45016α) were studied in hypophysectomized rats at the mRNA level. Time-course experiments were performed with or without simultaneous treatment with thyroxine and cortisol. Intermittent administration of GH, mimicking the male secretory pattern, caused complete masculinization of the male specific P-45016α at a pretranslational level in the absence and presence of thyroxine and cortisol. When GH was administered continuously, mimicking the female secretory pattern, the female specific P-45015β was induced, an effect that was dramatically potentiated by simultaneous treatment with thyroxine and cortisol. A synergistic effect of thyroxine and cortisol at a pretranslational level was demonstrated, although the major potentiating effect could be attributed to thyroxine. Thus it was concluded that GH, depending on its secretory pattern is the sole masculinizing factor for cytochrome P-450, and that it is also a feminizing factor, although this activity requires the synergistic action of thyroid hormones and glucocorticoids to reach its full effect.
Journal of Endocrinology (1989) 120, 311–317
Steroid concentrations in rat corpora lutea isolated during the oestrous cycle and pseudopregnancy: effect of induction of ovulation at dioestrus
Authors: Uilenbroek J. Th. J. , Woutersen P. J. A. , van der Vaart P. D. M. 
Published: December 2008

ABSTRACT
Corpora lutea could be identified under the dissection microscope up to 7 days after formation. They were isolated during the oestrous cycle and pseudopregnancy and the progesterone and 20α-OH-progesterone contents were compared with serum values of these steroids. The pattern of progesterone in serum resembled that found in the corpora lutea. However, the pattern of 20α-OH-progesterone concentrations in serum and corpora lutea were different. While 20α-OH-progesterone concentrations in the corpora lutea showed large variations during the cycle, changes in serum concentrations of 20α-OH-progesterone were relatively small. Measurement of hormone concentrations in isolated corpora lutea is therefore a sensitive method for studying corpus luteum activity.
To study whether corpora lutea derived after ovulation of immature follicles showed deficient luteal activity, rats at dioestrus (2 days before pro-oestrus) were induced to ovulate by the injection of 10 IU human chorionic gonadotrophin (hCG) and subsequent luteal activity was studied by measuring hormone concentrations in the corpora lutea on day 5 of pseudopregnancy. Concentrations of progesterone, but not of 20α-OH-progesterone, in corpora lutea derived from follicles induced to ovulate at dioestrusday 1 were significantly lower than those in corpora lutea derived from follicles induced to ovulate at prooestrus. This difference was observed not only when pseudopregnancy was induced by cervical stimulation but also when it was induced by implantation of a pituitary gland under the kidney capsule. However, in the latter case, corpora lutea already present on the day of hCG injection also became activated.
The present experiments demonstrate that by measuring hormone concentrations in isolated corpora lutea changes in luteal activity can be studied effectively. Moreover, it appears that corpora lutea derived from immature follicles contained less progesterone than those derived from fully mature follicles.
Journal of Endocrinology (1989) 120, 325–330
Insulin-like growth factor-I binding proteins in serum from the domestic fowl
Authors: Armstrong D. G. , McKay C. O. , Morrell D. J. , Goddard C. 
Published: December 2008

ABSTRACT
This investigation describes the presence of insulinlike growth factor-I (IGF-I) binding proteins in chicken serum. Whole blood was collected from broiler chickens of 7–9 weeks of age and analysed for binding proteins after gel permeation chromatography under both neutral and acidic conditions, and by polyacrylamide gel electrophoresis in the presence of 12·5% sodium dodecyl sulphate (SDS-PAGE).
When serum was chromatographed under neutral conditions, about 70% of the IGF-I immunoreactivity was associated with a large protein complex (Mr=150 000) and 20–25% was associated with an intermediate-sized protein complex (Mr = 45 000). Up to 6% of the serum IGF-I immunoreactivity was eluted in a fraction which corresponded to an Mr of about 7500 and was presumably free IGF-I. Chromatography under acidic conditions dissociated the IGF-I/protein complexes and revealed the presence of an acid-stable binding protein (Mr = 50 000–60 000).
After analysis of serum by SDS-PAGE, three monomeric IGF-I binding proteins (Mr = 28 800, 33 200 and 40 700) were detected. The largest monomer (Mr = 40 700) is probably the binding protein component of the intermediate-sized IGF-I/protein complex. The relationship between the other monomers and both the large IGF-I/protein complex and the acid-stable binding protein is not known.
Although the pattern of binding proteins in chicken serum is similar to that observed in mammals, a major difference is the presence of up to 6% of the serum IGF-I immunoreactivity in an unbound form.
Journal of Endocrinology (1989) 120, 373–378
Prenatal androgenization selectively modifies some responses to oestrogen in the prepubertal rat uterus
Authors: Arriaza C. A. , Mena M. A. , Tchernitchin A. N. 
Published: December 2008

ABSTRACT
Exposure of fetuses to some hormonally active agents may imprint permanent changes on the action of related hormones. These changes can be detected in adulthood as a modification of the degree of responsiveness to hormone action. The present study describes the effect of prenatal androgenization on the various responses to oestrogen in different types of cells in the uterus of prepubertal rats. Prenatal androgenization completely abolishes oestrogen-induced hypertrophy of uterine luminal and glandular epithelium, while it does not interfere with hypertrophy of circular myometrium and potentiates uterine eosinophilia and oedema. This dissociation between the various responses to oestrogen suggests that prenatal androgenization does not equally affect all uterine cell types.
Journal of Endocrinology (1989) 120, 379–384
A monoclonal antibody to lactogenic receptors from female rat liver
Authors: Emtner M. , Brandt J. , Johansson U. , Jouper B. , Fryklund L. , Roos P. 
Published: December 2008

ABSTRACT
Affinity-purified lactogenic receptors from female rat liver microsomal membranes were used to raise antibodies in female Balb/c mice. Mouse spleen and myeloma cells were fused and hybridoma-derived monoclonal antibodies (Mabs) were produced by in-vitro cell culture. Mab from a selected clone was sequentially purified by chromatography on a thiophilic gel and on agarose-bound protein A. The Mab was found to be of IgG1 subclass and of κ type.
The Mab recognized membrane-bound and solubilized (by the detergent heptaoxyethylene lauryl ether; G3707) receptors as well as receptors purified by affinity chromatography and subsequent sodium dodecyl sulphate (SDS) electrophoresis from female rat liver. The Mab bound to receptors from several other female rat tissues, such as ovary, kidney and adrenal, whereas there was no binding to liver receptors from cow and rabbit. Displacement experiments showed that the Mab was specific for a lactogenic type of receptor, in agreement with the finding that the Mab did not recognize receptors from male rat liver. The Mab also bound to cytoplasmic receptors (present in the supernatant after centrifugation at 100 000 g) from female rat liver, suggesting a structural similarity between the cytoplasmic and the microsomal receptors.
Analysis of purified receptors by SDS electrophoresis and subsequent Western blot with 125I-labelled Mab as a probe showed one band corresponding to an Mr of 45 500 ± 2500 (n=5). The same band was obtained with 125I-labelled human GH, showing that the Mab binds to the unit which accommodates the hormone-binding site. The binding sites are, however, not identical since the binding of Mab to the receptor did not inhibit the hormone–receptor interaction. Whether this binding unit represents the intact receptor molecule or a part of it cannot be concluded.
Journal of Endocrinology (1989) 120, 401–407
Excitation-secretion coupling: involvement of potassium channels in ACTH-stimulated rat adrenocortical cells
Authors: Gallo-Payet N. , Payet M. D. 
Published: December 2008

ABSTRACT
The mechanism by which ACTH stimulates calcium influx and steroid secretion was studied using rat adrenal glomerulosa cells, which were either freshly isolated or maintained in primary culture for 3 days. The potassium channel blocker tetraethylammonium chloride (TEA) stimulated twofold both corticosterone and aldosterone secretion; this stimulation was lower than that induced by ACTH at low concentrations (10 pmol/l). However, TEA and ACTH induced similar increases in Ca2+ influx and inositol phosphate accumulation. The three responses (steroid secretion, calcium influx and inositol phosphate accumulation) induced by TEA or low concentrations of ACTH were blocked by CoCl2. The greater stimulatory effect on steroid secretion of 10 nmol ACTH/l was decreased but not blocked by CoCl2. These data further document the complex mechanism of action of ACTH. It is postulated that, at low concentrations, ACTH binds preferentially to the high-affinity site of its receptor, leading to calcium influx by depolarization of the membrane potential, and to steroid secretion predominantly through an inositol phosphate- and Ca2+-stimulated pathway and also a cyclic AMP pathway. At higher concentrations, the hormone also binds to the low-affinity site of its receptor, largely stimulating cyclic AMP production and further increasing steroid secretion.
Journal of Endocrinology (1989) 120, 409–421