bluuebunny/crossref_metadata_2025_split huggingface dataset:
The self-priming action of LHRH increases the low pituitary LH and FSH response caused by ovarian factors: observations in vitro
Authors: de Koning J. , Tijssen A. M. I. , van Rees G. P. 
Published: December 2008

ABSTRACT
Pituitary glands taken from intact rats on day 2 of dioestrus and incubated with LHRH show a biphasic pattern of LH and FSH release. Initially the release of the gonadotrophins is low (first-phase or lag-phase response), but increases during further incubation with LHRH (second-phase or primed-state response).
Removal of the influence of an unidentified ovarian factor either by ovariectomy or prolonged incubation in medium only leads to an increased (lag-phase) response to LHRH. The development of the increased response after prolonged incubation was prevented by the addition of cycloheximide to the media, implicating that this process is dependent upon the synthesis of protein. Steroid-free material (bovine follicular fluid or rat ovarian extracts) prevented the development of this process. In addition, it was shown that steroid-free rat ovarian extracts were also able to induce the development of a lag phase in pituitary glands from ovariectomized rats. Finally, it was found that steroid-free ovarian extracts reversed the self-priming effect of LHRH.
The biological activity which reduced the responsiveness of the pituitary gland towards stimulation by LHRH was eliminated after the use of protein-denaturating techniques such as increased temperature or addition of methanol. The presence of this activity in ovaries, did not vary during the oestrous cycle, contrary to inhibin-like activity. Hence the ovarian factor responsible for the low lag-phase response is a protein which is probably not identical to inhibin.
It is concluded that a non-steroidal ovarian factor reduces the responsiveness of the anterior pituitary gland to LHRH. This reduced responsiveness can be reversed by LHRH, which is generally recognized as the self-priming effect of LHRH.
Journal of Endocrinology (1989) 120, 439–447
Hormonal dependence of the metrial gland: further studies on oestradiol and progesterone receptor levels in the rat
Authors: Martel D. , Monier M. N. , Roche D. , De Feo V. J. , Psychoyos A. 
Published: December 2008

ABSTRACT
The main objective of the present study was to analyse the hormonal dependence of the metrial gland formed in pseudopregnant animals following massive decidualization. On day 13 of pseudopregnancy (when the metrial gland reaches its maximal development) animals were ovariectomized and given s.c. implants of oestradiol and/or progesterone. A new implant technique for oestradiol delivery is described which provides circulating concentrations of oestradiol in the physiological range.
In addition, we extended our previous work concerning oestradiol receptor and progesterone receptor concentrations in the metrial gland of pseudopregnant rats. The low oestradiol receptor concentration which we previously reported up to day 17 was maintained until the end of pseudopregnancy (day 21–1·5 fmol/μg DNA), whereas the progesterone receptor concentration remained raised (≃3·5 fmol/μg DNA) from day 13 to day 19 and then decreased on day 21.
The correlation of metrial gland weight and kinetics of the tissue oestradiol and progesterone receptors contents with the circulating oestradiol and progesterone concentrations lead to the following conclusions. First, the maintenance of the metrial gland is strictly progesterone-dependent. It is unlike the deciduoma which regresses spontaneously, even in the presence of progesterone. Secondly, the production of oestradiol receptor, but not of progesterone receptor, appears to be repressed in the metrial gland under the influence of progesterone. Thus, the tissue retains its ability to respond to progesterone because of a high concentration of progesterone receptor. It is difficult to attribute this high tissue progesterone receptor concentration to oestradiol stimulation since, even at low levels, oestradiol induces tissue regression. We suggest that the high progesterone receptor concentration could be due to constitutive (basal) progesterone receptor production.
Journal of Endocrinology (1989) 120, 465–472
MELATONIN ANALOGUES INDUCE PIGMENT GRANULE CONDENSATION IN ISOLATED XENOPUS LEAVIS MELANOPHORES IN TISSUE CULTURE
Authors: Sugden D. 
Published: December 2008

ABSTRACT
2-Iodomelatonin, a ligand which has recently been used to identify melatonin-binding sites in the brain, produced condensation of pigment granules when added to isolated Xenopus laevis melanophores in culture. Melatonin (EC 50 = 5.7 × 10−13 mol/l), 2-iodomelatonin (EC 50 = 3.4 × 10−12 mol/l) and also 2-chloromelatonin (EC 50 = 2.9 × 10−13 mol/l) were all potent agonists in this test. Melatonin analogues in which the side-chain was conformationally restricted by linkage to the 2-position of the indole ring were inactive (EC 50 > 10−6 mol/l). The remarkable sensitivity and selectivity of this pigment condensation response suggests it will be useful in future studies of melatonin agonists and antagonists.
Inhibin concentrations in the peripheral blood of rams during a cycle in testicular activity induced by changes in photoperiod or treatment with melatonin
Authors: Lincoln G. A. , McNeilly A. S. 
Published: December 2008

ABSTRACT
Changes in the concentration of inhibin, FSH, LH and testosterone were measured in the peripheral blood of adult Soay rams during a reproductive cycle induced by exposure to an artificial lighting regimen (long days with a 16-week period of short days) or treatment with melatonin (long days with a 12-week period when melatonin was administered daily in mid-light phase to simulate the effect of short days). In both experimental situations, changes in the plasma concentrations of inhibin occurred in parallel with the cycle in the diameter of the testes with a four- to fivefold increase in the inhibin concentrations from the nadir to the peak of the testicular cycle. Increases in the plasma concentrations of FSH, LH and testosterone also occurred in association with the reactivation of the reproductive axis. The weekly changes in the plasma concentrations of inhibin were positively correlated with the changes in plasma FSH values during the developing and regressing stages of the testicular cycle but negatively correlated during the active stage.
In a group of castrated rams exposed to the same lighting regimen, the plasma concentrations of inhibin were always below the detection limit of the radioimmunoassay. The testosterone values were also very low in the castrates while the plasma concentrations of FSH and LH were 10-50 fold higher than normal and varied in relation to the light cycle.
The results show for the first time that inhibin is secreted into the peripheral blood in the ram exclusively from the testes. The positive correlation between the changes in plasma concentrations of FSH and inhibin during the developing and regressing phases of the testicular cycle indicate that FSH stimulates the secretion of inhibin. The negative correlation between FSH and inhibin in the active phase of the testicular cycle, is consistent with the role of inhibin in the negative-feedback control of FSH secretion. This is only evident because the testes undergoes reactivation of its full function during the change from the regressed to the active state which is especially obvious in the highly seasonal Soay ram.
Effect of a hypertonic saline load on plasma concentrations of atrial natriuretic peptide in fetal calves and their dams
Authors: Amadieu-Farmakis M. , Giry J. , Barlet J.-P. 
Published: December 2008

ABSTRACT
Plasma concentrations of atrial natriuretic peptide (ANP) were studied in eight adult non-pregnant cows and in two groups of six chronically catheterized bovine fetuses and their mothers in the eighth month of pregnancy. The first group of fetuses was used for studying the effect of an acute i.v. sodium load (240 mmol NaCl/fetus) on fetal ANP; the second group acted as controls. The mean basal ANP levels in the third-trimester bovine fetus were three to four times higher than maternal values (39·5 ± 5·5 and 9·4 ± 0·6 pmol/l respectively; P<0·01). Basal maternal plasma ANP levels were twice as high in pregnant cows in the third trimester of pregnancy than in non-pregnant cows (9·4 ± 0·6 and 4·3 ± 0·7 pmol/l respectively; P<0·05).
In response to an i.v. hypertonic saline injection, fetal plasma ANP levels increased significantly (P<0·01) to a maximum of 86·7± 17·6 pmol/l 10 min after the injection, and returned to baseline within 60 min after the treatment; during the 20 min following the i.v. sodium load, fetal plasma ANP correlated significantly with fetal plasma sodium concentrations (r 0·96; n=12) and with fetal plasma osmolality (r =0·94; n=12). No significant changes in maternal ANP values were observed in the two groups of animals.
These results suggest that ANP secretion is stimulated during pregnancy in cows, and that, in the bovine fetus, a hypertonic sodium load appears to be a potent stimulus for ANP release.
Journal of Endocrinology (1989) 121, 5–9
Agonists of endogenous opioid peptides suppress LH, and stimulate cortisol and growth hormone during the follicular phase in heifers
Authors: Armstrong J. D. , Johnson B. H. 
Published: December 2008

ABSTRACT
We evaluated the effects of [d-Ala2,Me,Phe4,Met(0)ol]-enkephalin (FK 33-824) and morphine, opioid receptor agonists, on concentrations of LH, cortisol and GH during the follicular phase in heifers. During three trials, oestrous cycles of Angus heifers were synchronized by two injections of prostaglandin F2α (PGF2α) resulting in 17 induced follicular phases over an 80-day period. Treatments were administered 24 h after the second injection of PGF2α. Blood samples were collected at 15-min intervals from 3 h before until 5 h after i.v. administration of 2 ml physiological saline (trials 1, 2 and 3), 0·5 mg morphine/kg (trials 1 and 2) or 1·8 μg FK 33-824/kg (trials 1 and 2) or 6·7 μg FK 33-824/kg (trial 3). Administration of both doses of FK 33-824 and morphine inhibited episodic release of LH for approximately 60 min. The concentration of cortisol was increased (P<0·05) after both doses of FK 33-824, but was unaffected (P>0·5) by morphine or saline. The serum concentration of GH was increased (P<0·01) after both doses of FK 33-824 or morphine, but saline was without effect. These results provide evidence of an inhibitory effect of opioid receptor agonists on LH (FK 33-824 and morphine) and a stimulatory effect on cortisol (FK 33-824) and GH (FK 33-824 and morphine) during the follicular phase in heifers. Divergent effects of morphine and FK 33-824 on cortisol observed in this study provide evidence that opioid-induced changes in LH, GH and cortisol result from activation of different opioid receptors.
Journal of Endocrinology (1989) 121, 11–17
Rapid proliferative response of rat thyroid gland to a single injection of TSH in vivo
Authors: Bybee A. , Tuffery A. R. 
Published: December 2008

ABSTRACT
Mitotic and labelling indices were studied in the thyroid follicular cells of the male rat within the first hour after a single injection of TSH or TSH vehicle, using the metaphase arrest agent vincristine sulphate. There was a significant increase in metaphase index over control values 5, 15, 30 and 60 min after injection of TSH. There was no significant change in the tritiated thymidine labelling index in TSH-treated rats in comparison with vehicle-injected controls. None of the metaphase figures was labelled, showing that G2 in this tissue is longer than 2 h.
Journal of Endocrinology (1989) 121, 27–30
Temporal effects of progesterone inhibition of occupied nuclear oestrogen receptor retention in the rat uterus
Authors: Okulicz W. C. 
Published: December 2008

ABSTRACT
Previous studies have shown that progesterone rapidly inhibits retention of uterine nuclear oestrogen receptor in several mammalian species. This effect of progesterone may constitute a general mechanism by which progesterone modulates oestrogen action. The objective of the present study was to examine the temporal pattern of progesterone inhibition of retention of occupied nuclear oestrogen receptors in the rat uterus at various sustained serum concentrations of progesterone. Silicone elastomer implants (1 cm) packed with crystalline oestrogen were placed s.c. in the flank region of ovariectomized adult rats. Twenty-four hours after placement of the implants, animals were either injected s.c. with 5 mg progesterone in corn oil every 24 h, treated with 2 × 5 cm implants of progesterone, or treated with 1 × 5 cm silicone elastomer implants of progesterone. Serum concentrations of progesterone at the time of necropsy were 0·47 ± 0·02, 0·18 ± 0·02 and 0·10 ± 0·01 μmol/l respectively. Control animals were given oestrogen implants alone and had a serum progesterone level of 0·03 ± 0·01 μmol/l. Occupied nuclear oestrogen receptor and cytosolic oestrogen and progesterone receptor levels (pmol/uterus) were measured between 0 and 48 h following progesterone treatment. Cytosolic progesterone receptor levels were suppressed similarly in all progesterone-treated groups compared with controls given oestrogen alone throughout the 48-h test period. Cytosolic oestrogen receptor levels were significantly suppressed at 12 h following progesterone treatment in all groups. Except for the highest (pharmacological) serum progesterone concentration, cytosolic oestrogen receptor exhibited a replenishment phase between 12 and 48 h. Although pharmacological levels of serum progesterone (0·47± 0·02μmol/l) significantly suppressed the level of occupied nuclear oestrogen receptor at 12 h, the level increased subsequently at 24 and 36 h and was equivalent to the control value (oestradiol alone) by 48 h. At a mean serum concentration of 0·18 ± 0·02 or 0·10 ± 0·01 μmol/l, the level of occupied nuclear oestrogen receptor was also suppressed significantly at 12 h, but to a lesser degree. These results show that progesterone decreases the concentration of occupied nuclear oestrogen receptor in the rat uterus and that the duration and extent of suppression of occupied nuclear oestrogen receptor is related to the serum progesterone concentration.
Journal of Endocrinology (1989) 121, 101–107
Ablation of the region anterior and ventral to the third ventricle (AV3V region) does not impede parturition in rats
Authors: Russell J. A. , Blackburn R. E. , Leng G. 
Published: December 2008

ABSTRACT
The region anterior and ventral to the third ventricle (AV3V) region is a major source of excitatory afferents to the magnocellular neuroendocrine system, and is essential for the osmotically regulated release of oxytocin. We investigated whether this input has a similarly essential role in parturition. Rats were implanted with a guide cannula in the AV3V region on days 9–18 of pregnancy. Following the birth of the third pup, rats were anaesthetized briefly with ether and either given an electrolytic AV3V lesion or a sham procedure was carried out. In eight AV3V-lesioned rats the mean (± s.e.m.) median interbirth interval following the lesion was 6·3 ± 1·2 min compared with 5·2 ± 0·6 min in 11 sham-lesioned rats. All rats completed delivery of their litters. The mean plasma concentration of oxytocin was unchanged following the sham procedure (pre-sham 17·1±2·8 pmol/l, n = 8; 15 min post-sham 18·1±2·7 pmol/l, n = 8; 30 min post-sham 19·2 ± 3·5 pmol/l, n = 8). In AV3V-lesioned rats, plasma oxytocin was significantly raised following the lesion (pre-lesion 14·6±1·3 pmol/l, n = 7; post-lesion 58·3 ± 9·8 pmol/l, n = 7) and was still higher than the sham-treated group after 30 min (55·8 ± 9·9 pmol/l). Thus there was no significant difference in the time-course of parturition between AV3V-lesioned rats and sham-lesioned rats, and no evidence that the lesion impaired the release of oxytocin. Furthermore, in rats given an AV3V lesion on the morning of the expected day of delivery, parturition was neither delayed nor disrupted, suggesting that the AV3V region does not contribute to the mechanisms controlling the onset of parturition.
Journal of Endocrinology (1989) 121, 109–115
Measurement of human growth hormone in urine: development and validation of a sensitive and specific assay
Authors: Hourd P. , Edwards R. 
Published: December 2008

ABSTRACT
A specific solid-phase immunoradiometric assay (IRMA), optimized for maximum sensitivity, has been developed for measurement of human GH (hGH) in urine. The sensitivity varied with sample size, giving a range of 0·001 to 0·003 mU/l for a sample volume of 2 ml. Recovery and dilution experiments, together with chromatography of urine samples, indicate that the method is specific for hGH. Added exogenous hGH was measured with a mean recovery of 101 ± 10% (s.d.) for 1 ml samples and 87 ± 8% for 2 ml samples. Measurements of samples diluted at 1:2 and 1:4 gave values of 97·4 and 96·6% respectively of those expected. Cross-reactions of human placental lactogen and prolactin were less than 0·008 and 0·04% respectively on a mol/mol basis. The assay was insensitive to the presence of NaCl (50–500 mmol/l), urea (50–1000 mmol/l), creatinine (1–20 mmol/l), Ca2+ ions (1–20 mmol/l), SO42− ions (1–1000 mmol/l), Mg2+ ions (0·05–50 mmol/l), 0·5–5% (w/v) glucose and a pH range of 6–9. Chromatography of unextracted samples showed that the immunoreactive material in urine eluted in a single homogenous peak with a similar position to monomeric pituitary hGH (22 kDa). Administered hGH (0·002%) was recovered in urine collected over a 2-h period following an intravenous injection. The urine output of hGH showed a good correlation with serum hGH in 18 patients following routine insulin tolerance tests and in 25 patients following an oral glucose tolerance test. Urine from normal subjects showed a mean night-time excretion of 498 ± 150 nU/h (s.d.) and a mean day-time excretion of 132 ± 93 nU/h. Preliminary results suggest that the measurement of hGH using this assay reflects the variation in blood and could be a useful diagnostic procedure.
Journal of Endocrinology (1989) 121, 167–175
Effects of cyclosporin A upon humoral and cellular immune parameters in insulin-dependent diabetes mellitus type I: a long-term follow-up study
Authors: Müller Ch. , Zielinski C. C. , Kalinowski W. , Wolf H. , Mannhalter J. W. , Aschauer-Treiber G. , Klösch-Kasparek D. , Gaube S. , Eibl M. M. , Schernthaner G. 
Published: December 2008

ABSTRACT
Patients who had been included in a randomized double-blind placebo-controlled trial on the efficacy of cyclosporin A (CyA) in producing remissions in insulin-dependent diabetes mellitus (IDDM) type I were investigated for humoral and cellular immunologic parameters. Whereas metabolic derangement before the initiation of insulin treatment led to small but significant decreases in the percentage of CD4-positive lymphocytes as well as of the activity of natural killer (NK) cells and antibody-dependent cellular cytotoxicity (ADCC), the administration of CyA did not influence any of the immunologic parameters tested, which included proliferative lymphocyte responses to mitogens and alloantigens and serum concentrations of immunoglobulins G, A and M. Thus NK cell activity, ADCC as well as the percentage of CD4-positive lymphocytes returned to normal levels in parallel with the normalization of glycosylated haemoglobin (HbAlc), but were not further influenced in their course by the administration of CyA, as compared with patients receiving placebo. Interferon-induced augmentation of NK cell activity did not differ between patients with IDDM on placebo and those under CyA therapy. All other investigated parameters also remained unchanged during the time of CyA therapy. We conclude that metabolic derangement leads to a reversible disturbance of certain cellular immune functions, but their normalization achieved by insulin treatment and their further course remains uninfluenced by the administration of CyA.
Journal of Endocrinology (1989) 121, 177–183
Seizure-induced delay of puberty in female rats: effects of age, stress and opioid antagonists
Authors: Carson R. C. , Wilkinson M. 
Published: December 2008

ABSTRACT
We have shown that pre- and post-pubertal female rats are sensitive to seizures. For example, daily convulsions commencing at 24 days of age delay puberty. Here we examine the effect of seizures at various ages. In addition, because opioid peptides are implicated in regulating the onset of puberty and are activated by convulsions, we also investigate the effect of opioid antagonists in the seizure-induced delay of puberty.
A single daily electroconvulsive shock (ECS) was given for 10 days to neonatal (days 2–11), infantile (days 15–24) and juvenile (days 22–31) rats. The treatment delayed vaginal opening (VO) in juvenile rats. Neonatal and infantile rats were unaffected. VO was also delayed by daily ECS for only 5 days in the late juvenile (days 27–31) period. The opioid receptor antagonists naloxone, naltrexone and nalmefene injected before and after single daily ECS were unable to block this effect of ECS on VO. To examine whether the effect of ECS is related to stress, we examined several stressors known to induce opioid-mediated alterations in gonadotrophin secretion. Footshock, immobilization and ether stress administered in the juvenile period (days 27–31) did not affect the timing of VO. In addition, rats anaesthetized with halothane, and then given ECS, still showed a delay of VO. These data demonstrate that rats in the late juvenile stage of development are most sensitive to convulsions. We also suggest that opioids are not critical to the mechanism by which the ECS disturbs puberty, and that ECS elicits its effect seemingly independently of the convulsive stress.
Journal of Endocrinology (1989) 121, 229–238
Impairment of glucose tolerance in hyperthyroid cats
Authors: Hoenig M. , Ferguson D. C. 
Published: December 2008

ABSTRACT
Intravenous glucose tolerance tests were performed in eight adult cats before and after a 4-week treatment with thyroxine. The untreated cats had a mean fasting blood glucose concentration of 7·7 ± 0·3 mmol/l and a mean fasting insulin concentration of 88 ± 31 pmol/l which were not significantly different from mean fasting glucose and insulin concentrations after 4 weeks of thyroxine administration (6·9 ± 0·2 mmol/l and 101 ± 28 pmol/l respectively). At 120 min after glucose injection, the glucose concentration in untreated cats returned to baseline concentrations as did the insulin concentration. However, in the hyperthyroid cats both glucose and insulin concentrations were significantly (P < 0·001) higher (13·6 ± 0·8 mmol/l and 245 ± 17 pmol/l respectively) in comparison with the baseline and untreated cats. The t½ for glucose disappearance was significantly higher in the cats rendered hyperthyroid, and the glucose disposal rate constant (K) was significantly lower in this group. It is concluded that hyperthyroidism in cats leads to impairment of glucose tolerance possibly due to peripheral insulin resistance.
Journal of Endocrinology (1989) 121, 249–251