bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evidence for luteotrophic and antiluteolytic actions of prolactin in rats with 5-day oestrous cycles
Authors: Sánchez-Criado J. E. , van der Schoot P. , Uilenbroek J. Th. J. 
Published: December 2008

ABSTRACT
Injection of 1 mg bromocriptine at either 08.00 or 16.00 h on the day of oestrus in rats with 5-day oestrous cycles caused a reduction in the duration of progesterone secretion by the corpus luteum during dioestrous, and a shortening of the ovarian cycle by 1 day. These effects were not present when bromocriptine was injected at 08.00 h on the day of metoestrus. The effect of bromocriptine on progesterone secretion by the corpus luteum was reversed by neutralization of the biological activity of LH at dioestrus by injection of 0·5 ml anti-LH serum at 08.00 h at metoestrus. Injection of the antiserum alone prolonged progesterone secretion by the corpus luteum, but had no effect on the length of dioestrus.
These results are interpreted as suggesting (1) that prolactin secretion on the afternoon of oestrus protects the corpus luteum of the rat ovarian cycle against the luteolytic effects of LH secretion during early dioestrus and (2) that prolactin stimulates progesterone secretion in the absence of such a luteolytic action. This response of the corpus luteum of the rat ovarian reproductive cycle to prolactin results in 5-day oestrous cycles.
J. Endocr. (1988) 117, 455–460
DEVELOPMENT OF A RADIOIMMUNOASSAY FOR OVINE TROPHOBLAST PROTEIN-1, THE ANTILUTEOLYTIC PROTEIN FROM THE SHEEP CONCEPTUS
Authors: Vallet J. L. , Bazer F. W. , Ashworth C.J. , Johnson H. M. , Pontzer C. H. 
Published: December 2008

ABSTRACT
A radioimmunoassay has been developed for quantitation of ovine trophoblast protein-1 (oTP-1), a sheep conceptus secretory protein which allows for maintenance of the corpus luteum during early pregnancy. The assay was validated for dialysed and undialysed culture medium and pregnant uterine flushings ranging from no dilution (neat) to dilutions of 1:2500 for dialysed media, 1:100-1:1000 for undialysed media and 1:50-1:1000 for pregnant uterine flushings. The assay accurately measured oTP-1 added to undiluted and diluted dialysed and undialysed culture media and pregnant uterine flushings. No cross-reaction was detectable for bovine α or γ interferon, bovine calmodulin, feline conceptus secretory proteins, equine conceptus secretory proteins, porcine conceptus secretory proteins, bovine conceptus secretory proteins and proteins in a uterine flushing collected from a non-pregnant ewe. Immunoreactivity in the assay matched that for oTP-1 throughout oTP-1 purification. This assay is the first validated assay which may be used to quantitate production of oTP-1 in culture or content of oTP-1 in uterine flushings.
Attenuation of preovulatory gonadotrophin surges by epostane: a new inhibitor of 3β-hydroxysteroid dehydrogenase
Authors: DePaolo L. V. 
Published: December 2008

ABSTRACT
Epostane, an inhibitor of 3β-hydroxysteroid dehydrogenase, was administered orally to pro-oestrous rats to evaluate further a possible role for preovulatory progesterone secretion in eliciting surges of LH and FSH. Whereas a dose of 10 mg epostane/kg had essentially no effects on preovulatory gonadotrophin surges and ovulation, 200 mg epostane/kg markedly attenuated LH and FSH surges and blocked ovulation. A dose of 50 mg epostane/kg exerted effects on LH and FSH surges and ovulation intermediate between those of doses of 10 and 200 mg/kg. Plasma concentrations of progesterone were significantly lower in all anovulatory epostane-treated rats at 18.00 and 22.00 h on pro-oestrus than those measured in vehicle-treated rats. Concurrent injection of 2 mg progesterone in rats given 200 mg epostane/kg restored gonadotrophin surges to normal, but consistently failed to reverse the inhibitory effects of epostane on ovulation. Peak plasma progesterone levels produced by the progesterone injections were eight- to tenfold higher than the highest levels measured in vehicle-treated rats during the afternoon of pro-oestrus. Insertion of progesterone capsules was less effective than injections of progesterone in restoring gonadotrophin surges to normal, even though peak plasma progesterone concentrations achieved after insertion of two 20 mm long progesterone capsules were double the peak progesterone concentrations measured in control rats. Nevertheless, taken together with recent reports showing attenuation of preovulatory gonadotrophin surges by the progesterone antagonist RU 486 (17β-hydroxy-11β-[4-dimethyl-aminophenyl]-17α-[prop-1-ynl]estra-4,9-diene-3-one), the present results provide support for a role of preovulatory progesterone secretion in enhancing oestrogen-dependent LH/FSH surges on pro-oestrus.
J. Endocr. (1988) 118, 59–68
Efficacy and specificity of monoclonal antibodies to progesterone in preventing the establishment of pregnancy in the mouse
Authors: Ellis S. T. , Heap R. B. , Butchart A. R. , Rider V. , Richardson N. E. , Wang M.-W. , Taussig M. J. 
Published: December 2008

ABSTRACT
Anti-progesterone monoclonal antibody prevents the establishment of pregnancy in BALB/c mice by the prevention of implantation when injected i.p. 32 h after mating. To determine the specificity of this effect, mice were injected with immune and non-immune purified mouse immunoglobulins. The results show that anti-implantation efficacy was due to high-affinity antibody which bound progesterone since two further mouse immunoglobulin (Ig) G1 preparations, mouse IgA and mouse IgM which failed to bind the steroid, had no effect on pregnancy rates. From a panel of anti-progesterone monoclonal antibodies, six with a high affinity (affinity constant, 0·24–0·80 litres/nmol) and specificity for progesterone were selected for additional studies. Anti-implantation efficacy for five antibodies was similar, with a 50% effective dose within the range of 0·8–2·0 nmol. Antibody reached high concentrations in plasma within 12 h after i.p. injection, and declined with a half-life of about 80 h. Purified F(ab′)2 fragments of antibody also bound progesterone, but were less effective than the native molecule in blocking pregnancy. The results show that implantation in the mouse can be blocked by a high-affinity antibody that binds progesterone and which is removed from the blood at a slow rate.
J. Endocr. (1988) 118, 69–80
Baroreceptor-independent medullary mechanism for release of vasopressin during hypotension in rats
Authors: Hashemzadeh-Gargari H. , Baertschi A. J. , Guyenet P. G. 
Published: December 2008

ABSTRACT
Plasma vasopressin (AVP) levels were measured at rest (mean arterial pressure 80–85 mmHg) and during hypotension (mean arterial pressure 38–45 mmHg) induced by ganglionic blockade (trimethaphan) in halothane-anaesthetized respirated rats with end-tidal pCO2 maintained at 34–40 mmHg. Hypotension (15 min) produced a 310% increase in plasma AVP (±60% s.e.m.) which was not reduced significantly by prior baro- and chemoreceptor denervation. The hypotension-induced rise in AVP was blocked by bilateral microinjections (40 nl) of the GABA-mimetic agent muscimol (151 pmol) into the ventrolateral medulla at obex level and significantly attenuated by injections of the same amount in the nucleus tractus solitarius. The rise in AVP was unaffected by microinjections in the pontine locus coeruleus. It was also blocked by bilateral microinjections of the glutamate-receptor antagonist kynurenate (40 nl, 1·8 nmol) into the ventrolateral medulla but unaffected by microinjections of the inactive analogue xanthurenic acid (40 nl, 1·8 nmol). A significantly smaller rise in plasma AVP (88%) was observed following bilateral nephrectomy. It is concluded that, in this preparation, hypotension produces the release of AVP via a mechanism largely independent of baro- and chemoreceptors, which requires the activation of neurones located in the caudal medulla oblongata. The same or closely related neurones may be activated by a neural or hormonal signal generated by the kidney.
J. Endocr. (1988) 118, 101–111
Changes in serum concentrations of steroids during embryonic and post-hatching development of male and female Japanese quail (Coturnix coturnix japonica)
Authors: Schumacher M. , Sulon J. , Balthazart J. 
Published: December 2008

ABSTRACT
Serum concentrations of testosterone, 5α-dihydrotestosterone, oestradiol and progesterone were measured by radioimmunoassay combined with Celite chromatography in male and female Japanese quail (Coturnix coturnix japonica) during the second half of embryonic life (days 9–17 of incubation) and during the first 5 weeks after hatching. The mean level of each of the four steroids was significantly affected by the age of the birds. An overall effect of sex was detected by analysis of variance only on oestradiol concentrations, with females having higher serum concentrations than males during most of the age range studied. Significant peaks of testosterone and progesterone were also detected around hatching time. These results are consistent with the view that oestradiol is the major hormone implicated in the sexual differentiation of reproductive behaviour in the quail. The relationships between the circulating concentrations of oestradiol during ontogeny and the critical period of differentiation as postulated by currently accepted models is also discussed.
J. Endocr. (1988) 118, 127–134
Hypothalamic hormones that release growth hormone stimulate hepatic 5′-monodeiodination activity in the chick embryo
Authors: Kühn E. R. , Vanderpooten A. , Huybrechts L. M. , Decuypere E. , Darras V. , Sharp P. J. 
Published: December 2008

ABSTRACT
Plasma GH, tri-iodothyronine (T3), thyroxine (T4) and liver 5′-monodeiodination (5′-D) activity were measured in 18-day-old chick embryos injected with thyrotrophin-releasing hormone (TRH) and human pancreatic growth hormone releasing factor (hpGRF). Injections of 0·1 and 1 μg TRH and 1·5 μg hpGRF increased the concentration of plasma GH while injection of 15 μg hpGRF had no effect. Concentrations of plasma T3 were raised after injection of TRH or hpGRF. Injections of TRH but not of hpGRF raised the concentration of plasma T4. The increases in concentration of plasma T3 after injection of TRH or hpGRF were parallelled by increases in liver 5′-D activity. An injection of 0·25 μg T4 significantly raised the concentration of T4 in plasma but had no effect on plasma T3 or liver 5′-D activity. It is concluded that the release of chicken GH by TRH or hpGRF is responsible for the observed increases in plasma concentration of T3 and liver 5′-D activity.
J. Endocr. (1988) 118, 233–236
Effects of acute stress on the patterns of LH secretion in the common marmoset (Callithrix jacchus)
Authors: O'Byrne K. T. , Lunn S. F. , Dixson A. F. 
Published: December 2008

ABSTRACT
Stressful stimuli associated with aggressive encounters and low social rank may affect female fertility in a variety of mammalian species. In these experiments we examined the effects of aggressive encounters and physical restraint in a primate chair on the patterns of LH secretion in ovariectomized, oestrogen-primed female marmosets. Receipt of aggression from a female conspecific, followed by physical restraint for collection of blood samples (at 10-min intervals for 4 h), resulted in marked declines in LH concentrations during oestradiol-induced LH surges in five animals (from 112 ± 24 μg/l to 45±12 μg/l; group means ± s.e.m.; P<0·05). This was due to reductions in LH pulse amplitude rather than to changes in pulse frequency. Decreases in plasma concentrations of LH were reversed by treating females with exogenous LH-releasing hormone (LHRH). Cortisol treatment had no effect on LH levels during oestrogen-induced LH surges. Effects of aggressive encounters and physical restraint on plasma LH were not therefore due to reduced pituitary responsiveness to LHRH or to increased plasma concentrations of cortisol. In separate experiments it was found that physical restraint alone had no effect on plasma LH in habituated subjects, and that decreases in plasma LH after receipt of aggression only occurred if animals were subsequently placed in the restraint chair. A summation of stressful effects is therefore required to produce the fall in circulating LH. A summation of social and other environmental stressors may also underlie the reduced fertility seen in free-living animals.
J. Endocr. (1988) 118, 259–264
Involvement of the cytoskeleton in the steroidogenic response of frog adrenal glands to angiotensin II, acetylcholine and serotonin
Authors: Feuilloley M. , Netchitaïlo P. , Delarue C. , Leboulenger F. , Benyamina M. , Pelletier G. , Vaudry H. 
Published: December 2008

ABSTRACT
In order to determine the role of the cytoskeleton in adrenal steroidogenesis, we have studied the effect of cytochalasin B (a microfilament-disrupting agent) and vinblastine (an antimicrotubular drug) on corticosteroid secretion by frog interrenal tissue in vitro. Perifusion of interrenal fragments with cytochalasin B (50 μmol/l) induced a marked inhibition of basal corticosteroid output. In addition, stimulation of corticosteroidogenesis by all corticotrophic factors was also inhibited by cytochalasin B. Using an immunohistochemical technique and specific anti-tubulin antiserum, we verified that vinblastine (10 μmol/l) was responsible for the disappearance of the microtubular network in adrenocortical cells. Administration of vinblastine (10 μmol/l) did not affect the spontaneous secretion of corticosterone and aldosterone and had no effect on the steroidogenic response of interrenal glands to angiotensin II and acetylcholine. In contrast, vinblastine was responsible for a marked decrease in serotonin-induced stimulation of corticosteroid production. On the other hand, data from high-performance liquid chromatography showed that infusion of cytochalasin B or vinblastine was not associated with the production of any new steroid which could interfere in the radioimmunoassays. Taken together, these data suggest that microfilaments are involved in a late and common step of corticosteroidogenesis while microtubules are only required for the coupling of the secretory response to certain corticotrophic factors such as ACTH and serotonin.
J. Endocr. (1988) 118, 365–374
Glucocorticoids in the blood plasma of the platypus Ornithorynchus anatinus
Authors: McDonald I. R. , Than K. A. , Evans B. 
Published: December 2008

ABSTRACT
Blood samples were obtained from two male and two female platypuses at various times after capture and anaesthesia for other experimental purposes. In samples obtained during ketamine–xylazine or pregnanediol anaesthesia 15–24 h after capture, the concentration of total glucocorticoids, measured as 'cortisol equivalent' in a radioligand assay, was 207– 620 nmol/l. In samples taken 14–35 h after injection of dexamethasone (0·2 mg/kg) total glucocorticoid concentration was 79–88 nmol/l.
Individual glucocorticoids were isolated on columns of Sephadex LH-20 and measured separately against appropriate standards. In all except two haemolysed samples obtained from a male that died 25 h after capture, the major glucocorticoid behaved as cortisol, contributing 77–94% of the total. The remainder was made up of varying proportions of substances behaving as corticosterone, 11-deoxycortisol and cortisone. In the haemolysed samples from the moribund animal the major reactive substance, contributing 52–54% of the total, behaved as cortisone. The total adrenal gland weight of this animal was 747 mg, compared with 200–286 mg in two others, suggesting preceding exposure to stress.
Equilibrium dialysis and polyacrylamide gel electrophoresis (PAGE) revealed no evidence for a transcortin-like glucocorticoid- and progesterone-binding protein in platypus plasma. However, as in the echidna, there was a heat-labile, high-capacity binding system migrating with albumin on PAGE.
Glucose was undetectable in the plasma of the moribund animal and only 1·7–2·8 mmol/l in the initial plasma samples from the others. In two animals, injection of glucose i.p and dexamethasone i.m. was followed by an increase in the plasma concentration of glucose to the range 3·8–9·9 mmol/l and commencement of normal swimming and feeding activity for the next 36–48 h.
J. Endocr. (1988) 118, 407–415
Stimulation of aromatase activity in the fetal rat testis by cyclic AMP and FSH
Authors: Weniger J.-P. , Zeis A. 
Published: December 2008

ABSTRACT
The effect of dibutyryl cyclic AMP and FSH on oestrogen biosynthesis was investigated in testes from 18- to 21-day-old fetal rats cultured in vitro in the presence of tritiated testosterone. Oestrone and oestradiol concentrations were measured by determination of constant specific activity after isotopic dilution.
Dibutyryl cyclic AMP and FSH markedly stimulated the conversion of testosterone into both oestrone and oestradiol at all stages studied. Oestradiol synthesis was stimulated by two- to sevenfold, while stimulation of oestrone synthesis was even greater. The results demonstrate that the aromatase enzyme system of the fetal rat testis responds to cyclic AMP and FSH.
J. Endocr. (1988) 118, 485–489
Extracellular calmodulin and its association with epidermal growth factor in normal human body fluids
Authors: Mac Neil S. , Dawson R. A. , Crocker G. , Barton C. H. , Hanford L. , Metcalfe R. , McGurk M. , Munro D. S. 
Published: December 2008

ABSTRACT
In this study we describe the occurrence of a calmodulin-like protein in normal human biological fluids. Extraction of the calmodulin-like protein from breast milk, saliva, serum and urine provided an extract with enhanced calmodulin immunoreactivity which, in the case of milk and saliva, showed a protein band co-migrating with authentic calmodulin (Mr 17 000) on sodium dodecylsulphate-polyacrylamide gel electrophoresis. However, in milk, saliva and serum a major protein band of Mr 14 000–15 000 was always observed, which we speculate may be related to calmodulin, possibly as a partially degraded form.
Estimates of biologically active calmodulin in most normal extracellular fluids were of the order which we have found will stimulate cell division when added to the extracellular medium of cells in culture. Levels ranged from 0·03 nmol/l in urine to 18·6 nmol/l in breast milk, and exhibited a quantitative relationship (r = 0·79, P < 0·01) to epidermal growth factor (EGF) levels in fluids. Where EGF concentrations varied from normal (increased in saliva 24 h after oral surgery and reduced in the urine of patients with renal failure) calmodulin concentrations were similarly affected. The presence of calmodulin in serum may in part be attributable to its release from platelets which are particularly rich in calmodulin. Release of calmodulin from the platelet was associated with that of EGF and other platelet products.
J. Endocr. (1988) 118, 501–509
Cellular distribution of somatogenic receptors and insulin-like growth factor-I mRNA in the rat liver
Authors: van Neste L. , Husman B. , Möller C. , Andersson G. , Norstedt G. 
Published: December 2008

ABSTRACT
Parenchymal and non-parenchymal cell fractions isolated from rat liver were analysed for the distribution of somatogenic receptors and for insulin-like growth factor-I (IGF-I) mRNA. The effect of hypophysectomy either alone or in combination with a single injection of human GH (hGH) on the levels of IGF-I mRNA was also studied in the two cell fractions.
The contamination of parenchymal cells in the non-parenchymal cell fraction was in the range of 2– 3%. Somatogenic receptors were found only in the parenchymal cell fraction. IGF-I mRNA was detected in both cell fractions, although the level of this mRNA was about fivefold higher in parenchymal cells. When RNA was studied by Northern gel analysis no major differences were observed in the size distribution of IGF-I transcripts in the two cell fractions.
In hypophysectomized animals, the IGF-I mRNA level was decreased to 10 and 30% of control values in the parenchymal and non-parenchymal cell fractions respectively. Treatment of hypophysectomized animals with a single dose of hGH restored IGF-I mRNA in parenchymal and in non-parenchymal cells to the extent found in intact animals.
In conclusion, our data indicate that somatogenic receptors are exclusively, and IGF-I mRNA predominantly, expressed in liver parenchymal cells compared with a total non-parenchymal cell fraction. The most marked effect of GH, correlating with the presence of somatogenic receptors, was seen in the parenchymal cells. The minor non-GH dependent expression of IGF-I mRNA suggests that this peptide may elicit effects in addition to the well-established GH-dependent activity.
J. Endocr. (1988) 119, 69–74
Growth hormone (GH) secretion in the conscious rat: negative feedback of GH on its own release
Authors: Clark R. G. , Carlsson L. M. S. , Robinson I. C. A. F. 
Published: December 2008

ABSTRACT
The negative-feedback effects of GH on its own secretion were studied in conscious male and female rats bearing indwelling double-bore venous cannulae. Intravenous infusions of human GH (hGH; 20–60 μg/h) or somatostatin (SS; 10 μg/h) were given while frequent serial microsamples of blood were withdrawn using an automatic blood-sampling system. In both sexes, i.v. infusions of hGH for 6 h inhibited endogenous GH secretory pulses, with a slow onset of the inhibition. There was no rebound GH secretion immediately following the removal of the hGH infusion, but spontaneous GH secretion gradually returned to normal. Infusions of hGH did not inhibit the pituitary GH response to repeated GH-releasing factor (GRF) injections (1 μg) given i.v. every 40 min to female rats. By contrast, infusions of SS, which also blocked spontaneous GH release, dramatically reduced the GH responses to serial GRF injections. When SS Infusions were stopped, the subsequent GRF-induced GH secretory responses were enhanced. These results show that GH can inhibit its own release when given by i.v. infusion to conscious male and female rats. Since GH responses to GRF are maintained during a GH infusion, the feedback effect of GH is unlikely to be exerted directly on the pituitary or by increasing SS release. Our results are consistent with the idea that GH feedback in the conscious rat involves an inhibition of GRF release.
J. Endocr. (1988) 119, 201–209
Neuroendocrine responsiveness to light during the neonatal period in the sheep
Authors: Ebling F. J. P. , Claypool L. E. , Foster D. L. 
Published: December 2008

ABSTRACT
Circulating prolactin concentrations were monitored during the early postnatal period in sheep to evaluate their response to photoperiod. In the first experiment, male and female lambs were exposed from 1 week of age, with their mothers, to either long days (16 h light:8 h darkness; n = 15) or short days (8 h light:16 h darkness; n = 16) to test whether they could discriminate different day lengths. In both sexes, serum prolactin concentrations were higher on long than on short days during the first 7 weeks after birth. In the second experiment, female lambs (n = 21) were raised on long days from 2 weeks of age. The superior cervical ganglia were removed bilaterally at 4 weeks of age from 14 lambs to lesion the sympathetic innervation to the pineal gland, and thus ablate the nocturnal increase in pineal melatonin secretion. After surgery, serum prolactin concentrations on long days were significantly lower in ganglionectomized lambs than in the intact controls. In the third experiment, the amplitude of the night-time melatonin rise was artificially increased in female lambs (n = 8) between 2 and 7 weeks of age to adult levels. Unrestrained lambs were infused during the 8-h dark phase of each day with melatonin by means of a self-contained, computerized syringe-pump. Concentrations of circulating prolactin did not differ from those in uninfused lambs (n = 8) with lower endogenous nocturnal melatonin. These results reveal that the sheep can discriminate photoperiod cues during the early postnatal period, and suggest that the low-amplitude melatonin rhythm in the neonatal lamb is sufficient to mediate this response.
J. Endocr. (1988) 119, 211–218