bluuebunny/crossref_metadata_2025_split huggingface dataset:
Disparate effects of ACTH(1–24) and corticosterone on lipoprotein lipase in rat adipose tissue
Authors: Baggen M. G. A. , Jansen H. , Lammers R. , Verschoor L. , Birkenhäger J. C. 
Published: December 2008

ABSTRACT
The effects of corticosterone and ACTH(1–24) on lipoprotein lipase (LPL) activity of rat epididymal fat tissue were studied. Hypercorticism induced by s.c. administration of 10 mg corticosterone acetate for 3 days led to a decrease in LPL activity. This decrease could be prevented by treatment of the rats simultaneously with synthetic ACTH(1–24). Adrenalectomy also reduced LPL activity. Corticosterone and ACTH(1–24) treatment had a similar effect on LPL activity in adrenalectomized and intact rats.
These results indicate that ACTH(1–24) may affect adipose tissue LPL in the rat by a mechanism in which corticosterone is not involved.
J. Endocr. (1987) 114, 369–372
Effects of the anabolic steroid stanozolol on growth and protein metabolism in the rat
Authors: Bates P. C. , Chew L. F. , Millward D. J. 
Published: December 2008

ABSTRACT
The effects of the anabolic steroid stanozolol on whole body and muscle growth and protein metabolism in the rat have been examined. No responses could be found in normal well-fed male rats. Female rats responded to 1 mg/kg per day with an increased body and skeletal muscle growth rate and an increase in muscle protein synthesis. The anabolic action on muscle protein synthesis was due to increased RNA concentration with no change in the rate of protein synthesis per unit RNA (KRNA). Investigation of any anticatabolic effects of stanozolol treatment in male rats deprived of food for 24 h indicated no response of protein balance and turnover. However, rats treated with catabolic doses of corticosterone (50 mg/kg per day) did respond to stanozolol with decreased muscle growth inhibition due to better-maintained muscle protein synthesis. The latter response was due to a reversal of the corticosterone-induced reduction of KRNA, but with no effect on RNA concentration. Thus there appear to be at least two effects of stanozolol; an anabolic action evident only in female rats, involving increased muscle RNA concentrations, and an anticatabolic action involving inhibition of the corticosterone-induced fall in muscle RNA activity. In both cases, stanozolol influenced muscle protein synthesis with no evident effects on protein degradation.
J. Endocr. (1987) 114, 373–381
Failure of fasting and changes in plasma metabolites to affect spontaneous fluctuations in plasma concentrations of ovine placental lactogen
Authors: Butler W. R. , Huyler S. E. , Grandis A. S. , Handwerger S. 
Published: December 2008

ABSTRACT
The relationships between plasma concentrations of energy substrates and placental lactogen (PL) were investigated in pregnant ewes. In successive hourly samples of plasma PL, concentrations varied by ± 30% but were not related to general activity or feeding of the ewes or the time of day. Fasting ewes for 72 h did not alter the pattern or the mean PL titres. Insulin-induced acute hypoglycaemia, hyperglycaemia and decreases or increases in free fatty acids (FFA) all failed to alter PL levels significantly during 5-h post-treatment periods. These experiments demonstrate that PL secretion in the ewe fluctuates markedly and is unaffected by changes in plasma glucose or FFA concentrations.
J. Endocr. (1987) 114, 391–397
Retardation of preovulatory desensitization to negative oestrogen feedback: mechanism of the effect of progesterone in 5-day cyclic rats
Authors: Döcke F. , Rohde W. , Chaoui R. , Stürzebecher J. , Dörner G. 
Published: December 2008

ABSTRACT
Recent studies have shown that oestrogen can induce desensitization to its own gonadotrophin-inhibiting effect in female rats by an action on the medial preoptic area (MPOA). Probably as a consequence of this action, sensitivity to the negative oestrogen feedback declines markedly between metoestrus and dioestrus of the 4-day ovarian cycle.
To study this desensitization process in 5-day cyclic rats, females exhibiting regular 5-day vaginal cyclicity were ovariectomized on consecutive days of the cycle, injected with oestradiol benzoate (OB) or oil on the day of ovariectomy and autopsied 24 h after the injection. Estimation of the serum concentration of LH revealed that desensitization to negative oestrogen feedback occurred only between day 2 of dioestrus and pro-oestrus, i.e. 2 days later than in females with a 4-day cycle. In the latter animals, an injection of progesterone in metoestrus or early dioestrus, which induced lengthening of the ovarian cycle for 1 day, delayed the onset of desensitization to a degree similar to that found in spontaneously 5-day cyclic rats. In acutely ovariectomized females, progesterone implants placed in the MPOA, but not those located in the mediobasal hypothalamus, increased the LH-inhibiting effect of low doses of OB.
The results suggest that the prolonged secretion of progesterone recorded in 5-day cyclic rats retards follicle maturation and delays the forthcoming ovulation by acting, at least partly, on the MPOA and antagonizing the desensitizing effect of oestrogen. In this way, inhibition of gonadotrophin secretion by oestrogen is enhanced and the increase in tonic LH secretion necessary for the completion of follicle maturation is retarded.
J. Endocr. (1987) 114, 409–414
Opiate suppression of LH secretion involves central receptors different from those mediating opiate effects on prolactin secretion
Authors: Pfeiffer D. G. , Pfeiffer A. , Almeida O. F. X. , Herz A. 
Published: December 2008

ABSTRACT
The involvement of μ- and κ-opiate receptors in the regulation of LH and prolactin secretion was investigated in long-term ovariectomized rats using selective opiate receptor agonists and antagonists. The μ-agonists morphine and [d-Ala2,MePhe4,Gly5-ol]-enkephalin (DAGO) suppressed LH levels in a dose-related manner. The benzomorphane (−)-5,9-dimethyl-2′-hydroxy-2-(tetrahydrofurfuryl)-6,7-benzomorphan tartrate (MR 2034; a designated κ-agonist) also suppressed LH levels, whereas another benzomorphane κ-agonist (−)-5,9-dimethyl-2′-hydroxy-2-(2-methoxy-propyl)-6,7-benzomorphan hydrobromide (MRZ 2549) had no effect on the levels of this hormone. Pretreatment with the highly selective μ-antagonist β-funaltrexamine (β-FNA), the fumarate methyl ester derivative of naltrexone, blocked the actions of both μ-agonists and MR 2034, indicating that opiate suppression of LH secretion is mediated by μ-receptors. This was further confirmed by in-vitro studies: the KCl-induced release of LHRH from perifused hypothalami obtained from ovariectomized rats was significantly reduced by DAGO but not by MRZ 2549.
Prolactin secretion was stimulated in a dose-dependent manner by both μ- and κ-agonists. The stimulation caused by morphine and DAGO was antagonized by β-FNA, whereas that caused by the κ-agonists MR 2034 and MZR 2549 was resistant to blockade by β-FNA but not by naloxone (an antagonist which blocks all classes of opiate receptors when given in high doses). Thus prolactin secretion seems to be regulated by both μ- and κ-opiate receptors, whereas the effects on LH secretion seem to involve μ-receptors only.
J. Endocr. (1987) 114, 469–476
Relationship between maternal and fetal corticotrophin-releasing hormone-41 and ACTH levels in human mid-trimester pregnancy
Authors: Economides D. , Linton E. , Nicolaides K. , Rodeck C. H. , Lowry P. J. , Chard T. 
Published: December 2008

ABSTRACT
Samples of maternal blood, amniotic fluid and umbilical arterial and venous blood were collected from 11 women at 16–24 weeks of pregnancy. Corticotrophin-releasing hormone-41 (CRH-41) and ACTH were measured by immunoradiometric assay. The mean levels of ACTH were 11 pmol/l in maternal plasma, 12 pmol/l in fetal plasma and 9·7 pmol/l in amniotic fluid. The mean levels of CRH-41 were 1·6 pmol/l in maternal plasma and 0·7 pmol/l in fetal plasma. There was a positive correlation between maternal and fetal plasma CRH-41 and between maternal CRH-41 and ACTH. In fetal plasma there was a weak inverse correlation between CRH-41 and ACTH. This is the first demonstration of CRH-41 in the circulation of the mid-trimester human fetus, but on the basis of the present findings it is not possible to specify the exact source (fetal, placental or maternal).
J. Endocr. (1987) 114, 497–501
Plasma vitamin D-binding protein and free 1,25-dihydroxyvitamin D3 index in pregnant ewes and their fetuses in the last month of gestation
Authors: Abbas S. K. , Care A. D. , Van Baelen H. , Bouillon R. 
Published: December 2008

ABSTRACT
A radioimmunoassay for ovine vitamin D-binding protein (DBP) has been developed. This assay can also effectively measure DBP in goat plasma. A suitable ovine DBP antiserum raised in a rabbit produced a single monospecific line of precipitation when reacted against purified sheep DBP and sheep plasma. The preliminary purification of 125I-labelled ovine DBP was carried out using adsorption chromatography, and the final purification immediately before addition to the assay tubes was achieved by high-pressure liquid chromatography. Displacement of 125I-labelled ovine DBP by dilutions of sheep and goat plasma or standard DBP gave parallel curves, and only weak competition was observed with calf and pig plasma. The assay detected as little as 26 pmol DBP/1 with intra- and interassay coefficients of variation of 3 and 14% respectively. The mean plasma concentration of DBP in nine pregnant sheep (110–120 days of gestation) was 8·7 ± 0·3 (s.e.m.) μmol/l. These levels were significantly (P<0·02; paired t-test) higher than those in matched fetal plasma (6·7 ±0·4 μmol/l) obtained in utero through a catheter in a carotid artery. Plasma DBP concentrations in pregnant sheep were also significantly (P<0·02) higher than in five normal non-pregnant sheep (6·8 ± 0·5 μmol/l). The mean concentrations of total 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) in maternal and fetal plasma were 92·0 ±8·7 pmol/l and 152·5±18·0 pmol/l respectively (P<0·05). The free 1,25-(OH)2D3 index, a measure of the level of free 1,25-(OH)2D3 in plasma, was calculated as the ratio between the molar concentrations of total 1,25-(OH)2D3 and DBP. The mean value of the free 1,25-(OH)2D3 index in the fetus (2·3 × 10−5) was significantly (P<0·01) higher than that in the dam (1·1 × 10−5), thus indicating a gradient of free 1,25-(OH)2D3 during the latter part of ovine pregnancy with a mean fetal/maternal ratio of 2·1.
J. Endocr. (1987) 115, 7–12
Cyclic AMP-stimulated fluid transport in the thyroid: influence of thyroid stimulators, amiloride and acetazolamide on the dynamics of domes in monolayer cultures of porcine thyroid cells
Authors: Bourke J. R. , Matainaho T. , Huxham G. J. , Manley S. W. 
Published: December 2008

ABSTRACT
Confluent monolayer cultures of porcine thyroid cells form dome-shaped elevations by local separation from the plastic culture dish. Formation of domes by epithelial cells in culture is generally considered to be evidence of fluid transport. A computer-controlled data acquisition system was developed to quantitate fluid transport in thyroid cultures by serial measurements of dome elevation. Thyrotrophin (10 mU/ml), prostaglandin E2 (PGE2; 0-01-1 μmol/l), forskolin (1 μmol/l), 8-(4-chlorophenylthio)adenosine 3′:5′-cyclic monophosphate (0.5 mmol/l) and 3-isobutyl-1-methyl-xanthine (0.5 mmol/l) promoted increases in dome height over 5–120 min. Dome growth in the presence of PGE2 (1 μmol/l) was inhibited by amiloride (0.1–100 μmol/l), ouabain (200 μmol/l), or by removal of bicarbonate and glucose from the medium. In media of reduced bicarbonate concentration (1 mmol/l compared with the control concentration of 10 mmol/l), dome growth was inhibited by acetazolamide (0.01– 1 mmol/l). These data are consistent with cyclic AMP-stimulated transport of fluid from apical to basal pole of the cells, dependent on sodium entry through the apical pole by an Na+/H+ exchanger.
J. Endocr. (1987) 115, 19-26
How large a hormone can be measured by microencapsulated antibody?
Authors: Duffy F. A. , Wallace A. M. 
Published: December 2008

ABSTRACT
The size of molecules able to be measured in immunoassays where antibody is encapsulated within semipermeable microcapsules is restricted by the pore size of the membrane. This study was performed to determine the approximate molecular weight cut-off of this membrane. Permeability was assessed by measuring which labelled hormones were able to enter and bind their respective microencapsulated antibody. Hormones with molecular weights of less than 4000 (angiotensin II, thyroxine, 17-hydroxyprogesterone, progesterone, testosterone and androstenedione) passed freely through the pores but larger molecules, with molecular weights in excess of 10 000 (parathyroid hormone, human GH, TSH) could not. Insulin, with a molecular weight of 6000 (approximate minimum diameter 3·5 nm), had restricted entry while the next smallest hormone tested, the 1–34 amino acid portion of parathyroid hormone (molecular weight 4000; diameter 1·8 nm), was able to bind encapsulated antibody, suggesting that the pore diameter is between 1·8 and 3·5 nm. It can now be predicted that the method is able to measure compounds with a diameter within this range and with a molecular weight below 6000. Microcapsules may be useful for improving specificity of assays where a cross-reactant is too large to penetrate the membrane.
J. Endocr. (1987) 115, 47–51
Salivary oestriol and progesterone concentrations in women during late pregnancy, parturition and the puerperium
Authors: Lewis P. R. , Galvin P. M. , Short R. V. 
Published: December 2008

ABSTRACT
Oestriol and progesterone concentrations were measured by specific radioimmunoassays in the saliva of six women on a daily basis during the last month of pregnancy, at frequent intervals during labour and daily during the puerperium. Salivary steroid concentrations are thought to reflect the circulating concentrations of the free hormone, and hence may be more biologically relevant than the total plasma concentration, or the urinary excretion of a metabolite.
There was no sign of a fall in salivary oestriol or progesterone concentrations before the onset of labour. During the first and second stages, the concentrations fluctuated widely, perhaps due to alterations in uterine blood flow. After delivery of the placenta, hormone concentrations declined abruptly. Oestriol reached undetectable levels of <0·1 nmol/l within a day, whereas progesterone concentrations declined somewhat more slowly, approaching follicular-phase values after 2–3 days. This slower decline in the concentration of progesterone may be due to a leaching-out of the hormone from body fat stores. The absence of any prepartum progesterone withdrawal presumably explains the characteristic postpartum delay in the onset of lactogenesis.
J. Endocr. (1987) 115, 177–181
Relationship between unbound oestrogen receptors in the uterus and anterior pituitary gland after implantation of oestradiol-17β into rats
Authors: Castellano-Díaz E. , González-Quijano M. I. , Díaz-Chico B. N. 
Published: December 2008

ABSTRACT
This paper describes the effect of oestradiol-17β implants on unbound cytosolic and nuclear oestrogen receptors in the uterus and anterior pituitary gland of ovariectomized adult rats. Rats were ovariectomized and implanted 1 week later with oil or oestradiol-17β oil solution in silicone elastomer capsules. In the latter animals the capsules either remained in situ until decapitation (subgroup 1) or were removed 48 h after implantation (subgroup 2). Implants of oestradiol-17β caused a significant depletion in both forms of oestrogen receptor in the uterus and anterior pituitary gland of rats in subgroup 1. In subgroup 2, however, there was an almost complete return to control concentrations of uterine cytosolic receptors and anterior pituitary cytosolic and nuclear receptors. Concentrations of uterine nuclear oestrogen receptors showed only a partial recovery.
These data suggest that both forms of oestrogen receptor constitute an integrated population of oestrogen receptors, without dependence on intracellular location, and that in the presence of oestradiol these receptors are bound more quickly than they are synthesized. The results also indicate the existence of a dynamic equilibrium of unbound receptors between the cytosolic and nuclear compartments for both target organs, but show that in the absence of oestradiol this equilibrium is restored in the anterior pituitary sooner than in the uterus.
J. Endocr. (1987) 115, 205–210
Sex-related differences in renal size in mice: ontogeny and influence of neonatal androgens
Authors: Jean-Faucher Ch. , Berger M. , Gallon Ch. , de Turckheim M. , Veyssière G. , Jean Cl. 
Published: December 2008

ABSTRACT
Kidneys of adult male mice are larger than those of females because of both cellular hyperplasia and hypertrophy. Administration of testosterone to adult female mice induced cellular hypertrophy but not hyperplasia, so that the weight of the kidney remained smaller than in male mice. The sexual dimorphism in kidney size is not congenital but programmed by neonatal endogenous androgens and expressed between 30 and 40 days of age. Treatment of newborn males with cyproterone acetate and of newborn females with testosterone induced female and male patterns of renal growth respectively. It appears that neonatal endogenous androgens are required to induce the characteristic cellular hyperplasia of the kidneys of male mice. Manipulation of androgen levels during neonatal and prepubertal life was found to affect the growth response of the kidney to androgens in adult male and female mice.
J. Endocr. (1987) 115, 241–246
Effect of gonadotrophin-releasing hormone agonist-induced suppression of LH and FSH on follicle growth and corpus luteum function in the ewe
Authors: McNeilly A. S. , Fraser H. M. 
Published: December 2008

ABSTRACT
Continuous infusion of a gonadotrophin-releasing hormone (GnRH) agonist (buserelin) by osmotic minipump from day 1 of the luteal phase in five Welsh ewes resulted in a sustained suppression of plasma concentrations of FSH which increased three- to eightfold within 2 days after the end of infusion 29 days later. Plasma concentrations of LH increased three- to eightfold over the first 5 days of infusion and then became basal and non-pulsatile until 1 day after the end of infusion. Duration of the luteal phase and plasma concentrations of progesterone were not significantly different in control and treated ewes. Pulses of LH in control ewes were followed by increases in concentrations of progesterone in samples collected at 10-min intervals for 7 h on days 10 and 14 of the luteal phase. However, progesterone was also released in a pulsatile manner in the absence of LH pulses in both control and GnRH agonist-treated ewes.
After natural luteolysis, no ovulation or corpus luteum function occurred in treated ewes up to 15 days after the end of treatment on day 29, even though oestrus, indicating follicular development and oestrogen secretion, had occurred 8–11 days after treatment ended.
After 30 days of infusion the ovaries of GnRH agonist-treated ewes contained no follicles > 2·5 mm in diameter. In follicles of 1–2 mm in diameter the basal and LH-stimulated production of oestradiol and testosterone in vitro were similar in both control and GnRH agonist-treated ewes, and a similar proportion of these follicles was oestrogenic (> 370 mol oestradiol per follicle) in GnRH agonist-treated and control ewes.
These results show (1) that progesterone secretion by the corpus luteum of the ewe can be sustained in the presence of basal concentrations but absence of pulsatile secretion of LH, and progesterone is released in a pulsatile manner whether or not LH pulses are present, (2) that follicular development beyond 2·5 mm in diameter in the ewe is dependent upon adequate stimulation by both LH and FSH and (3) that the continuous infusion of GnRH agonist is a simple method for providing reproducible suppression of LH and FSH and follicular development in the ewe to allow the study of gonadotrophin action on the ovary in vivo.
J. Endocr. (1987) 115, 273–282
Effect of naloxone on oxytocin and vasopressin release during vaginocervical stimulation in the goat
Authors: Seckl J. R. , Lightman S. L. 
Published: December 2008

ABSTRACT
We have investigated the secretion of oxytocin and arginine vasopressin (AVP) during vaginocervical stimulation in the conscious goat and examined the effect of the opioid antagonist naloxone on peptide release to this stimulus. Goats were implanted with guide tubes overlying the cisterna magna under anaesthesia and allowed to recover. Vaginocervical stimulation for 60 s resulted in a marked (P < 0·01) release of oxytocin into the plasma but neither plasma AVP nor cerebrospinal fluid (CSF) concentrations of oxytocin changed significantly.
In a second series of experiments, unoperated goats were infused with saline or naloxone (4 mg bolus + 12 mg/h) in random order on two separate occasions. Infusion of naloxone had no effect on basal plasma concentrations of oxytocin or AVP. There was a marked and significant (P < 0·01) potentiation of oxytocin secretion following vaginocervical stimulation in animals infused with naloxone. Naloxone-infused animals showed a significant (P < 0·01) rise in plasma AVP after stimulation but plasma AVP did not change in the saline-infused controls.
We conclude that vaginocervical stimulation leads to the selective release of oxytocin from the neurohypophysis without affecting concentrations of oxytocin in the CSF. Endogenous opioids inhibit the stimulated secretion of oxytocin and AVP in vivo in response to vaginocervical stimulation in the goat.
J. Endocr. (1987) 115, 317–322
Involvement of endogenous opioid peptides in the neuroendocrine response of ewe lambs to the introduction of a ram
Authors: Stansfield S. C. , Knight P. G. , Al-Mauly N. Z. , Bryant M. J. 
Published: December 2008

ABSTRACT
Prepubertal ewes can, under certain circumstances, be stimulated to ovulate by the novel introduction of a ram. The endocrine response to the presence of the ram is characterized by a rapid increase in the frequency of episodic release of LH. The purpose of this study was to investigate the effect of the presence of a ram on LH pulse frequency in vivo, gonadotrophin-releasing hormone (GnRH) and β-endorphin concentrations in the median eminence, and on the influence of the endogenous opioid peptide agonist [d-Ala2,N-Phe4,Met(0)ol5]-enkephalin (FK 33–824) on basal and depolarization-induced release of GnRH from median eminence tissue superfused in vitro. The study was performed at two prepubertal ages in August and September. In September, the introduction of a ram resulted in an increase in pulsatile release of LH, which was associated with an increase in the rate of basal release of GnRH from median eminence tissue superfused in vitro, and the development of a marked ability of FK 33–824 to suppress depolarization-induced release of GnRH. The concentration of β-endorphin in the median eminence was reduced in animals exposed to the ram at this time. In contrast, the introduction of a ram in August failed to stimulate an increase in LH pulse frequency, basal release of GnRH in vitro was not altered and FK 33–824 was ineffective in reducing depolarization-induced release of GnRH. These results suggest that the premature onset of reproductive activity induced by exposure to the ram may involve the participation of the endogenous opioid peptide system.
J. Endocr. (1987) 115, 333–339