bluuebunny/crossref_metadata_2025_split huggingface dataset:
Serine proteases selectively control the output of 18-hydroxycorticosterone and aldosterone in stimulated zona glomerulosa tissue of the rat adrenal
Authors: Raven P. W. , McAuley M. E. , Vinson G. P. 
Published: December 2008

The finding that incubation of rat adrenal capsules (largely zona glomerulosa) with trypsin reproducibly releases aldosterone and 18-hydroxycorticosterone (18-OH-B) from tightly protein-bound tissue stores leads to the hypothesis that the secretion of these steroids may be under the control of endogenous proteases.
Rat adrenal capsule whole tissue and collagenase-dispersed cells were incubated under conditions of stimulation by (1–24)ACTH (10−7 mol/l), potassium (8·4 × 10−3 mol/l) or dibutyryl cyclic AMP (dbcAMP) (10−4 mol/l) with the addition in some flasks of one of the following protease inhibitors at the appropriate concentration for their known actions: Nα-p-tosyl-l-arginine methyl ester (TAME; 10−2 mol/l), 2-nitro-4-carboxyphenyl-N,N′-diphenylcarbamate (NCDC; 2×10−6 mol/l), Nα-benzoyl-l-arginine (BA; 10−2 mol/l), p-nitrophenyl-Nα-benzyloxycarbonyl-l-lysinate (CBZ-NL; 2×10−6 mol/l) and soybean trypsin inhibitor (STI; 1 mg/ml). The (1–24)ACTH-stimulated steroid output in dispersed cells was not affected by NCDC, BA or CBZ-NL. However, all of the inhibitors except STI produced selective effects on aldosterone and 18-OH-B production by whole capsule tissue under certain conditions. Thus TAME and NCDC significantly inhibited the dbcAMP-stimulated production of these two steroids (aldosterone values decreased from 328±35 to 128±15 and 157±32 ng/gland pair respectively) and furthermore NCDC elicited the same effect in potassium- or ACTH-stimulated whole tissue (e.g. in K+-stimulated tissue aldosterone decreased from 79±15 to 40±7 ng/gland pair). The reverse effect was shown by BA and CBZ-NL in potassium-stimulated whole tissue, and yields of aldosterone and 18-OH-B were significantly enhanced (aldosterone increased from 79±15 ng/pair to 151±14 ng in the presence of BA). The high molecular weight inhibitor STI had no effect on potassium-stimulated whole tissue, but enhanced the yield of extractable aldosterone from 9·±1·7 to 16·9±2·3 ng/pair when added to incubations of a cytosol preparation.
The results suggest that endogenous proteases in rat adrenal whole capsule tissue play specific roles in the control of aldosterone and 18-OH-B secretion. Some (type 1) whose action is mimicked by trypsin, are inhibited by TAME and NCDC and appear to be involved in the release of these two steroids from their tight (apparently covalent) binding to protein. Others (type 2) are inhibited by BA, CBZ-NL and STI, and one interpretation of their function is that they are concerned with the activation of type 1 proteases.
The mechanisms envisaged provide a selective means for control of secretion of the late-pathway steroid products in the rat adrenal zona glomerulosa. These mechanisms are not apparent in dispersed cell incubations, probably because of the loss of steroid–protein complexes in these preparations.
Concentrations of prolactin in the plasma of fetal sheep and in amniotic fluid in late gestation and during dexamethasone-induced parturition
Authors: McMillen I. C. , Jenkin G. , Robinson J. S. , Thorburn G. D. 
Published: December 2008

The concentration of prolactin in samples of fetal plasma and amniotic fluid collected from sheep with indwelling catheters has been measured by radioimmunoassay. There was considerable variation between animals in the concentration of prolactin in fetal plasma which ranged from <2 μg/l to >50 μg/l. In five out of eight fetuses which were sampled at intervals throughout the last 30 days of pregnancy, there was an increase in the concentration of prolactin in the plasma before parturition. The concentration of prolactin in amniotic fluid was consistently low (approximately 1 μg/l). Induction of premature parturition by intrafetal infusion of dexamethasone was accompanied by an increase in the concentration of prolactin in only one of three fetuses infused.
These results indicated that prolactin is present in fetal plasma but that an increase in prolactin in fetal plasma before the onset of parturition does not always occur. The low concentration of prolactin in amniotic fluid contrasts with the high concentrations of this hormone found in the amniotic fluid of the primate.
Effect of calcitonin in pregnant rats on bone resorption in fetuses
Authors: Rebut-Bonneton C. , Demignon J. , Amor B. , Miravet L. 
Published: December 2008

Fetal bone resorption was measured by an organ culture technique using fetuses from intact or thyroparathyroidectomized pregnant rats. These experiments were performed to investigate the effects of 1,25-dihydroxycholecalciferol (1,25-DHCC) and salmon calcitonin (SCT) in pregnant rats, on both fetal growth and fetal bone resorption.
Pregnant rats were given 0·1–0·5 μg 1,25-DHCC per day from day 17 of gestation: in intact rats bone resorption was increased and fetal growth decreased; 1,25-DHCC probably modified fetal bone resorption in the absence of fetal parathyroid secretion.
Infusion of SCT in minipumps (30 mu./h) did not modify plasma calcium levels in either the mother or fetuses, neither was bone resorption altered. In 1,25-DHCC-treated rats, SCT infusion resulted in an increase in fetal weight and a decrease in fetal bone resorption. On the other hand, SCT infusion was found to facilitate phosphate accumulation in fetuses.
At the end of the SCT infusion the SCT concentration was 450 ng/l in maternal plasma and 553± 60 ng/l in fetal plasma. Salmon calcitonin was shown to cross the placental barrier in the rats; it may interact with the effects of 1,25-DHCC in the fetus.
Secretion of follicle-stimulating hormone and luteinizing hormone in castrated golden hamsters during exposure to various photoperiods and to natural daylengths
Authors: Urbanski H. F. , Simpson S. M. , Ellis D. H. , Follett B. K. 
Published: December 2008

Golden hamsters were castrated and either maintained under short days of 9 h light and 15 h darkness (9L: 15D) or transferred to 12L: 12D, 13L: 11D or 16L:8D. Plasma concentrations of FSH and LH remained low under 9L: 15D and 12L: 12D for 6–8 weeks but rose markedly within 4 weeks under 13L: 11D and 16L: 8D, suggesting a more abrupt transition between non-stimulatory and maximally stimulatory photoperiods than found in Japanese quail.
Intact and castrated hamsters were exposed to natural photoperiods at a latitude of 51° 27' N (Bristol) for 12 months. In the intact animals plasma FSH and LH levels and the size of the testes decreased as the daylength shortened from 12·5 to 10·5 h during autumn. This was followed by a rise in FSH output in mid-winter with an upward trend in LH secretion. The ensuing testicular recrudescence was complete before the spring equinox. The results emphasize that under natural conditions the primary factor regulating gonadal growth is the development of refractoriness to short days. In castrated hamsters there was no significant seasonal trend in LH output. Levels of FSH remained unchanged until a peak occurred in January, the same time that a peak was seen in intact animals before testicular recrudescence. A similar peak occurred in castrated hamsters maintained in 9L: 15D in the laboratory. This suggests that even in the absence of gonadal steroid negative feedback. hypothalamo-pituitary activity changes during the photorefractory period.
Steroid production in vitro by rat ovaries during sexual maturation
Authors: Uilenbroek J. Th. J. , Woutersen P. J. A. , van der Linden R. 
Published: December 2008

To determine changes in steroidogenesis by rat ovaries during sexual maturation, ovaries obtained at various ages (days 10–35) and at the first pro-oestrus were incubated in the absence or presence of LH and the accumulation of steroids in the medium was measured.
Basal and LH-stimulated oestradiol-17β and testosterone release into the medium, expressed in pmol/4 h per mg ovary, was high at day 10 of age and at first pro-oestrus. Between days 20 and 35 basal oestradiol and testosterone release was low and could not be stimulated by LH. Addition of testosterone to the culture medium increased oestradiol production at all ages studied. Release of progesterone occurred at all ages even in LH-free medium. Incubation in the presence of LH resulted in a dose-dependent increase in progesterone with a maximal response at pro-oestrus. Androsterone and 5α-androstane-3α,17β-diol production in the absence or presence of LH was high during the entire prepuberal period. Production of 5α-reduced androgens in response to LH increased from days 10 to 20 but decreased thereafter. Similarly, 5α-reductase activity, measured in ovarian homogenates, increased from days 10 to 20 but was decreased again by first pro-oestrus. A further decrease in basal and LH-stimulated 5α-reduced androgen production occurred after first ovulation.
These results demonstrated age-related changes in steroid release after in-vitro incubation. At day 10 progesterone can be converted to aromatizable androgens allowing production of oestrogens, while after day 10 progesterone is converted to 5α-reduced C19 steroids. The decrease in 5α-reductase activity correlates with an increase in LH-stimulated testosterone and oestradiol production at the first pro-oestrus.
Sex differences in the serum concentrations of testosterone in mice and hamsters during their critical periods of neural sexual differentiation
Authors: Pang S. F. , Tang F. 
Published: December 2008

ABSTRACT
Male and female mice and hamsters were decapitated 1–5 days after birth and serum concentrations of testosterone determined by radioimmunoassay. In the two species studied, serum levels of testosterone in male pups were significantly (P <0·05) higher than those obtained in female neonates. This lends support to the hypothesis that circulating levels of testosterone play an important role in the process of neural sexual differentiation in rodents. Moreover, the sex differences in serum concentrations of testosterone in neonatal rodents together with the detectable levels of testosterone in female neonates may suggest that androgenization is a dose-dependent phenomenon. Alternatively, they may indicate that a minimum concentration of the steroid must be present for androgenization to occur during the critical period of neural sexual differentiation and that this 'threshold' is exceeded in male but not in female rodents.
J. Endocr. (1984) 100, 7–11
Relative potencies of testosterone and 5α-dihydrotestosterone on crowing and cloacal gland growth in the Japanese quail (Coturnix coturnix japonica)
Authors: Balthazart J. , Schumacher M. , Malacarne G. 
Published: December 2008

ABSTRACT
It has been suggested that testosterone is less effective at inducing crowing behaviour in young birds than in adults because of the presence of higher levels of steroid 5β-reductase in the young brain, which converts testosterone to inactive 5β-reduced metabolites. This hypothesis was tested indirectly by comparing the relative potencies of 5α-dihydrotestosterone (5α-DHT), which cannot be converted to 5β-metabolities, and testosterone at inducing crowing in young gonadectomized male and female quail. The promotion of cloacal gland growth by these treatments was also assessed since there are no age-related changes in 5β-reductase in this organ.
Silicone elastomer implants (2·5, 5 and 10 mm) containing 5α-DHT were more effective at stimulating crowing than similar implants of testosterone whilst there was little difference in their potency at inducing cloacal gland growth. These results are consistent with the hypothesis that brain steroid 5β-reductase regulates the behavioural activity of testosterone in the brain of young birds.
J. Endocr. (1984) 100, 19–23
The International Reference Preparation of Tetracosactide for Bioassay: characterization and estimation of its (1–24)corticotrophin-tetracosapeptide content by physicochemical and biological methods
Authors: Storring P. L. , Witthaus G. , Gaines Das R. E. , Stamm W. 
Published: December 2008

ABSTRACT
The preparation and nature of the International Reference Preparation of Tetracosactide for Bioassay (IRP; in ampoules coded 80/590) are described. The IRP was studied by six laboratories in five countries using in-vivo and in-vitro bioassays and various physicochemical methods.
The bulk (1–24)corticotrophin-tetracosapeptide (batch 000179) from which the IRP was prepared contained 10·4% (w/w) acetic acid and 8·3% (w/w) water; its (1–24)corticotrophin-tetracosapeptide content was estimated to be 71·7% (w/w) by amino acid analysis, 74·2% (w/w) by high performance liquid chromatography (HPLC) and 77·5% (w/w) by spectrophotometry.
(1–24)Corticotrophin-tetracosapeptide accounted for more than 90% (w/w) of the total peptide in the IRP as judged by HPLC, thin-layer chromatography, carboxymethyl-cellulose chromatography, isoelectric focusing (IEF) and electrophoresis. The homogeneity of the peptide in the IRP was similar by all methods to that in batch 000179 from which it was prepared.
The (1–24)corticotrophin-tetracosapeptide content of the IRP (with 95% confidence limits), in terms of batch 000179, was found to be 491 μg/ampoule by HPLC and spectrophotometry, 473 (433–513) μg/ ampoule by IEF and 505 (473–539) μg/ampoule by the in-vitro rat adrenocortical cell assay. A comparison in the same bioassay system of the IRP with a laboratory house standard of (1–24)corticotrophin-tetracosapeptide, which originated from a different manufacturer, gave similar results.
Accelerated thermal degradation studies of the IRP by adrenocortical cell assay, HPLC and IEF suggested that more than 99·9% of its original content of (1–24)corticotrophin-tetracosapeptide would remain after 10 years under normal storage conditions of − 20 °C in the dark. Bioassay estimates of samples of the IRP which had undergone significant degradation were higher than estimates by HPLC, indicating that molecular species other than (1–24)corticotrophin-tetracosapeptide contributed to their corticotrophic activity.
The corticotrophic activity of the IRP was demonstrated by cytochemical bioassay and by in-vivo bioassay as well as by the adrenocortical cell assay. After consideration of these data, the Expert Committee on Biological Standardization of the World Health Organization established the ampouled preparation, coded 80/590, as the International Reference Preparation of Tetracosactide for Bioassay and assigned to it a potency of 490 i.u./ampoule; thus the i.u. is represented by 1 μg (1–24)corticotrophin-tetracosapeptide.
J. Endocr. (1984) 100, 51–60
Indices of ovulation: comparison of plasma and salivary levels of progesterone with urinary pregnanediol
Authors: Metcalf M. G. , Evans J. J. , Mackenzie J. A. 
Published: December 2008

ABSTRACT
An increased daily excretion of pregnanediol, relative to that early in the menstrual cycle, is often taken to be evidence that a woman has ovulated. This paper assesses the value of alternative procedures for this purpose. Urine, plasma and saliva samples were collected during a 24-h period from 20 women during the follicular phase and from 20 women during the luteal phase. The 24-h excretion of pregnanediol was compared with (1) the concentration of progesterone in plasma, (2) the concentration of progesterone in saliva, (3) the concentration of pregnanediol in small urine samples, (4) the rate of excretion of pregnanediol and (5) the ratio of pregnanediol to creatinine in small urine samples. Each analyte increased substantially during the luteal phase. The median increases (ratio of luteal to follicular phase values) were 14·8, 3·2, 10·6, 11·9 and 11·1 respectively. By comparison, the median increase in 24-h pregnanediol output was 9·2. When the other analytes were used instead of the 24-h excretion of pregnanediol to assess the possibility of ovulation, the incidence of misclassifications (follicular samples classed as luteal and luteal samples classed as follicular) was 0, 12·8, 5·9, 2·0 and 1·0% respectively. It was concluded that the most satisfactory alternative to the measurement of 24-h pregnanediol output for the biochemical assessment of ovulation based on progesterone production was the measurement of the concentration of progesterone in plasma; the least satisfactory alternative was determination of the concentration of progesterone in saliva. If blood was not available, measurement of the ratio of pregnanediol to creatinine in a small urine sample was the preferred method.
J. Endocr. (1984) 100, 75–80
Localization of central nervous system structures mediating extracellular thirst in the female rat
Authors: Kucharczyk J. 
Published: December 2008

ABSTRACT
Water intake elicited by microinjection of the hormone angiotensin-II into the preoptic region of cyclic female rats was significantly less on days of vaginal oestrus than at dioestrus or metoestrus, whereas the drinking of 2·7% NaCl solution, to which rats also had access, did not vary with the cycle. Administration of the same dose of angiotensin-II to the subfornical organ and the lateral cerebral ventricles induced drinking at all stages of the oestrous cycle, but the volumes of water or 2·7% NaCl ingested did not vary with the cycle. Water intake after subcutaneous injection of isoprenaline, a β-adrenergic agonist which causes increased angiotensin biosynthesis, varied cyclically with the stage of the oestrous cycle. On the other hand, water and 2·7% NaCl intakes induced by intraperitoneal injection of hypertonic NaCl (a cellular stimulus of thirst) or by 24-h water deprivation (which dehydrates both the extracellular and cellular body fluid compartments) did not differ significantly at the various stages of the oestrous cycle. The finding that fluctuations in angiotensin- and isoprenaline-induced water intake parallel the changes in spontaneous 24-h drinking suggests that the preoptic region may play an important role in the maintenance of extracellular fluid balance in synchrony with the oestrous cycle.
J. Endocr. (1984) 100, 183–188
Effects of handling, anaesthesia, ovariectomy and adrenalectomy on serial measurements of plasma progesterone in 16-day pregnant rats
Authors: Bruce N. W. , Willcox D. L. , Meyer G. T. , Waddell B. J. 
Published: December 2008

ABSTRACT
The basal concentrations of progesterone in plasma of 16-day pregnant rats were measured after seven different sampling procedures. Progesterone concentrations in serial samples from rats held at the time of sampling (restrained group) were compared with those obtained from rats allowed to remain free in their cage (free group). In addition, the effects on plasma progesterone concentrations of anaesthesia induced by ether or pentobarbitone sodium, and of adrenalectomy and/or ovariectomy were studied. Over the 8-h sampling period, progesterone concentrations in the plasma of restrained rats, with or without anaesthesia, were about 30% higher and more variable than those in free rats. Progesterone concentrations rose sharply over the first 30 min in restrained rats and in those treated with ether. Rats adrenalectomized the day before sampling did not show this early rise and their progesterone concentrations were similar to those of free rats. Progesterone concentrations were lowest in ovariectomized rats which had also been adrenalectomized. These findings show that adrenal secretion can increase plasma concentrations of progesterone in pregnant rats which have been handled or anaesthetized. Such a rise might well modulate the effects of experimental stimuli.
J. Endocr. (1984) 100, 189–193
Effect of hypothalamic neuropeptides on corticotrophin release from quarters of rat anterior pituitary gland in vitro
Authors: Nicholson S. A. , Adrian T. E. , Gillham B. , Jones M. T. , Bloom S. R. 
Published: December 2008

ABSTRACT
The effect of six hypothalamic peptides on the basal release of ACTH and that induced by arginine vasopressin (AVP) or by ovine corticotrophin releasing factor (oCRF) from fragments of the rat anterior pituitary gland incubated in vitro was investigated. Dose–response curves to AVP and to oCRF were obtained, and the response to a low dose of oCRF was potentiated by a low dose of AVP. Basal release of ACTH was not affected by any of the peptides in concentrations in the range 10−12 to 10−6 mol/l, and only substance P (SP) and somatostatin (SRIF) inhibited significantly the response to oCRF in a dose-related manner. The responses to a range of doses of oCRF or AVP were reduced by 10−8 and 10 − 6 mol SP or SRIF/1, and to a greater extent by the higher dose. Except in the case of 10−6 mol SRIF/1 on the response to AVP, the response was not further diminished by preincubation of the tissue with the peptide before the stimulating agent was added. The inhibition of the responses to AVP or oCRF by 10−9 mol SP/1 was not potentiated by its combination with either 5 × 10−10 or 10−8 mol SRIF/1; the inhibitory effects were merely additive. The results suggest that although SRIF and SP are able to modulate the release of ACTH from the anterior pituitary gland, they do so only at a high concentration. In the case of SRIF these concentrations are several orders of magnitude higher than those reported to be present in the hypophysial portal blood and therefore a physiological role for this peptide in the control of ACTH secretion is unlikely.
J. Endocr. (1984) 100, 219–226
Inhibition by corticosterone of calcium inflow and insulin release in rat pancreatic islets
Authors: Billaudel B. , Mathias P. C. F. , Sutter B. C. J. , Malaisse W. J. 
Published: December 2008

ABSTRACT
Corticosterone (0·6 μmol/l) inhibited both 45Ca outflow and insulin release evoked by glucose, the combination of leucine and glutamine, 2-ketoisocaproate, gliclazide or the association of gliclazide and a tumour-promoting phorbol ester in rat pancreatic islets perifused at normal extracellular Ca2+ concentration (1·0 mmol/l). In all cases, the inhibitory action of corticosterone reached statistical significance within 10–22 min of exposure to this steroid and failed to be rapidly reversible. Corticosterone failed to affect basal 45Ca outflow and insulin release. The steroid also failed to affect the inhibitory action of glucose upon 45Ca outflow, as judged from either the glucose-induced early fall in effluent radioactivity from islets maintained at normal extracellular Ca2+ concentration or the steady-state values for 45Ca outflow from glucose-stimulated but Ca2+-deprived islets. Corticosterone caused a modest increase in 86Rb outflow from islets perifused in the presence of glucose (16·7 mmol/l). It is concluded that corticosterone impairs Ca2+ inflow into the islet cells and, by doing so, causes a progressive inhibition of insulin release. The pancreatic B cell might thus serve as a further model for the study of the rapid biological response to steroids, as presumably mediated by alteration in the biophysical properties of the plasma membrane.
J. Endocr. (1984) 100, 227–233