bluuebunny/crossref_metadata_2025 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

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

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

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

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

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

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

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

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

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

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

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

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

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
Changes in the pulsatile secretion of LH after the removal of and subsequent resuckling by pups in ovariectomized lactating rats
Authors: Maeda K.-I. , Tsukamura H. , Uchida E. , Ohkura N. , Ohkura S. , Yokoyama A.
Published: December 2008

Changes in the pulsatile secretion of LH after removal of pups and subsequent resuckling were examined in ovariectomized lactating rats, and the change after removal of pups was compared with that after the removal of ovaries in cyclic female rats. The day of parturition was designated day 0 of lactation. All lactating rats were ovariectomized on day 2 of lactation. They were deprived of their pups for 6, 12, 18, 24 or 45 h before blood sampling on day 8 of lactation, or were resuckled by their pups for 1, 4, 7 or 12 h before blood collection after separation from pups for 24 h. Cyclic female rats were ovariectomized on the day of dioestrus and blood samples were taken 12, 18, 24 or 48 h or 6 days after ovariectomy. Typical LH pulses appeared in some animals from 12 h after the removal of pups. The mean LH level and the frequency and amplitude of LH pulses gradually increased after removal of pups, until after 45 h of separation the frequency reached the high level observed 6 days after ovariectomy in cyclic rats. The subsequent resuckling by pups after a 24-h separation decreased these three parameters of LH pulses rapidly. In contrast, the frequency of LH pulses was unchanged after ovariectomy in cyclic rats, although the mean LH level and the amplitude of LH pulses increased. These results suggest that the suckling stimulus suppresses pulsatile LH secretion in a different manner from that of ovarian steroids.

Journal of Endocrinology (1989) 121, 277–283
Effect of maternal hypothyroxinaemia during fetal life on the calmodulin-regulated phosphatase activity in the brain of the adult progeny in the rat
Authors: de Elvira M. C. Ruiz , Sinha A. K. , Pickard M. , Ballabio M. , Hubank M. , Ekins R. P.
Published: December 2008

Calmodulin-regulated phosphatase activity was measured in the brain of 2-month-old rats born from hypothyroid and normal dams, using a fluorometric enzyme assay developed for this purpose. Calmodulin content was measured in the same brain regions by radioimmunoassay. Significant differences between groups in weight and protein content, basal phosphatase and calmodulin-regulated phosphatase activity were found. The brain region most affected was the cerebellum, where basal and calmodulin-regulated phosphatase activities, and protein content were increased. The data point towards a lasting effect of maternal hypothyroxinaemia on the brain function of the progeny.

Journal of Endocrinology (1989) 121, 331–335
γ-Aminobutyric acid regulation of neurohypophysial hormone secretion in male and female rats
Authors: Saridaki E. , Carter D. A. , Lightman S. L.
Published: December 2008

The role of γ-aminobutyric acid (GABA) in the control of oxytocin and arginine vasopressin (AVP) release from the posterior pituitary was investigated using the GABA agonist muscimol and the GABA antagonists bicuculline and picrotoxin. Two perifusion model systems were studied using (a) intact isolated posterior pituitaries (IPP) and (b) neurosecretosomes from both male and female rats. In experiments on tissue from male rats, the stimulated release of oxytocin and AVP in both models was inhibited by muscimol, an effect which was reversed in the presence of bicuculline. Bicuculline alone increased the release of oxytocin only. Although similar responses to muscimol or bicuculline were seen in neurosecretosomes from female animals, neither agent affected oxytocin and AVP release from the intact IPP. Picrotoxin had a similar effect to bicuculline on oxytocin in isolated posterior pituitaries from male as well as female rats, although at the neurosecretosome level a paradoxical inhibition was observed.

These results provide evidence for an endogenous GABA receptor mechanism at the level of the neurosecretory terminals in both male and female rats. The sexually dimorphic IPP response suggests a second more complex mechanism involving either pituicytenerve terminal interactions and/or a secondary role of other neurotransmitters in the GABA regulation of neurohypophysial hormones.

Journal of Endocrinology (1989) 121, 343–349
Influence of tri-iodothyronine or lipid administration on the response of the pituitary-thyroid axis to exposure to cold in the newborn lamb
Authors: Wrutniak C. , Cabello G.
Published: December 2008

The influence of the administration of tri-iodothyronine (T3) or a solution of soya oil and egg lecithin on the response of the pituitary-thyroid axis to moderate exposure to cold (4 °C for 4 h) was studied in 24-h old lambs. In control lambs, plasma concentrations of TSH, T3 and total and free thyroxine (T4) rose significantly whereas plasma concentrations of reverse T3 remained unchanged during the test.

In lambs injected i.v. with a small amount of T3 (1·23 nmol/kg) 30 min before the onset of exposure to cold, plasma concentrations of TSH, reverse T3 and total and free T4 did not change during the test.

Administration of lipid 30 min before exposure to cold induced, as expected, a sharp rise in plasma free fatty acid (FFA) concentrations and a transient increase in free T4 concentrations. In these animals, plasma concentrations of TSH increased during the test as observed in control lambs, but plasma concentrations of T3, reverse T3 and total T4 did not show any significant change, whereas free T4 levels decreased during the first 2 h.

These results strongly suggest, in contrast to previous results, that T3 exerts a negative feedback upon the hypothalamic-pituitary-thyroid axis in the new-born lamb. Moreover, it appears that a rise in plasma concentrations of FFA could affect neonatal thyroid function.

Journal of Endocrinology (1989) 121, 361–365
Production of insulin-like growth factor-II by human fetal pancreas in culture
Authors: Bryson J. M. , Tuch B. E. , Baxter R. C.
Published: December 2008

Insulin-like growth factor-II (IGF-II) is a polypeptide hormone thought to be involved in fetal development because of its wide distribution in fetal tissues and its presence in the fetal circulation. We have developed a highly sensitive radioreceptor assay for IGF-II using rat liver microsomal membranes and have used this assay to test for the presence of IGF-II in the human fetal pancreas and the release of IGF-II by the human fetal pancreas in organ culture. IGF-II was present in extracts of pancreatic tissue (0·056 ± 0·012 pmol/mg tissue, n= 5) and was released in culture at the rate of 0·027–0·134 pmol/mg tissue per day with release being maintained for at least 3 weeks in culture. The rate of release was not affected by the gestational age of the fetus over 14 to 20 weeks but was significantly related to the rate of insulin release (r = 0·712, P < 0·001, n = 34). Chronic exposure to 12-0-tetradecanoylphorbol-13-acetate (TPA), which inhibits insulin release in the human fetal pancreas, caused an 85% drop in IGF-II production, which was reversed when TPA was removed. These studies demonstrate that IGF-II is produced by the human fetal pancreas in a pattern similar to that of insulin. We suggest that control of IGF-II release, like that of insulin, may involve protein-kinase C and that IGF-II may have a paracrine or autocrine role in the development of fetal pancreatic function.

Journal of Endocrinology (1989) 121, 367–373
Progesterone concentrations in samples of saliva from adolescent girls living in Britain and Thailand, two countries where women are at widely differing risk of breast cancer
Authors: Danutra V. , Turkes A. , Read G. F. , Wilson D. W. , Griffiths V. , Jones R. , Griffiths K.
Published: December 2008

Menstrual-cycle patterns of salivary progesterone concentration were obtained for 131 and 245 adolescent girls up to 4 years postmenarche living in Britain and Thailand respectively. These patterns were graded on a scale of 1 (little or no activity) to 5 (activity similar to that exhibited by the mature premenopausal woman) and the frequency of these grades within groups of girls from each centre was analysed. The major finding was that British girls exhibited a predominance of higher grades of progesterone activity when compared with their Thai counterparts (n = 2 × 58) when matched for chronological and gynaecological ages (P ∼ 0·002). This was particularly so for the girls from these two matched groups in the gynaecological age range 2–4 years (P ∼ 0·03). The major contribution to this significant difference between the two groups is attributed to the greater effect of chronological age on progesterone secretion in the British girls (P ∼ 0·03) compared with the Thai girls (P ∼ 0·29). These findings may have implications for facilitating our understanding of the reason for the differing risk of breast cancer in women in both countries.

Journal of Endocrinology (1989) 121, 375–381
Effect of ouabain on cellular free calcium and cellular cyclic AMP production in response to arginine vasopressin in rat renal papillary collecting tubule cells in culture
Authors: Ishikawa S. , Saito T.
Published: December 2008

The effect of extracellular calcium (Ca2+) on the cellular action of arginine vasopressin (AVP) was examined using an Na+, K+-ATPase inhibitor in rat renal papillary collecting tubule cells in culture. The pretreatment of cells with ouabain enhanced basal and AVP-induced cAMP production in a dose-dependent manner. The augmentation by ouabain of cellular cAMP production in response to AVP was totally abolished by co-treatment with cobalt, lanthanum, verapamil or Ca2+-free medium containing 1 mmol EGTA/l, each blocking cellular Ca2+ uptake by different mechanisms. Two other findings indicated that ouabain directly stimulated cellular Ca2+ mobilization; namely, that ouabain significantly increased 45Ca2+ influx and cellular free Ca2+ concentration ([Ca2+]i) determined by Fura-2 fluorescence. The ouabain-induced increase in [Ca2+]i was completely blocked by either cobalt or Ca2+-free medium containing 1 mmol EGTA/l. AVP at 0·1 μmol/l increased [Ca2+]i to 177·1 ±26·2 nmol/l from 92·2 ± 8·0 nmol/l (P<0·01) in renal papillary collecting tubule cells, and ouabain significantly enhanced the AVP-induced increase in [Ca2+]i. The increase of cellular free Ca2+ induced by ouabain probably binds to calmodulin to form an active complex of Ca2+-calmodulin in the cell, since two chemically dissimilar antagonists of calmodulin attenuated the enhancement by ouabain of cAMP production in response to AVP. These results therefore indicate that ouabain increases cellular Ca2+ uptake and enhances AVP-induced cellular free Ca2+ mobilization and its own second messenger cAMP production in renal papillary collecting tubule cells, and that extracellular Ca2+ is an important source for ouabain-mobilized cellular Ca2+.

Journal of Endocrinology (1989) 121, 467–477
Differential effect of difluoromethylornithine on the increases in plasma concentrations of reproductive hormones on the afternoon of pro-oestrus in the rat
Authors: Nicholson S. A. , Wynne-Jones G. A.
Published: December 2008

In our colony of female rats (220–320 g body weight) undergoing regular 4-day oestrous cycles there were significant, marked rises in concentrations of LH, FSH and prolactin between 09.00 and 19.00 h on pro-oestrus.

The i.p. injection of difluoromethylornithine (DFMO; 40–400 mg/kg), a specific inhibitor of the activity of ornithine decarboxylase, at 15.00 h on prooestrus had a differential effect on the rise in plasma concentrations of the various hormones thereafter. The drug produced a significant, partial, dose-related suppression of the rise in plasma concentrations of LH and prolactin, but had no significant effect on the rise in FSH.

For time-course studies, 120 mg DFMO/kg were injected at 13.00, 15.00 or 17.00 h and groups of animals killed at 19.00 h. Only the injection at 15.00 h was effective in causing a significant reduction in plasma concentrations of LH and prolactin at 19.00 h. Pituitary content of the hormones was found to be unaffected by the administration of DFMO at the times and doses tested.

These results suggest that DFMO has a selective inhibitory effect on enhanced LH and prolactin secretion on the afternoon of pro-oestrus in the rat, whilst not affecting FSH release. There seems to be a limited time (after 13.00 but before 17.00 h) during which its administration is effective.

Journal of Endocrinology (1989) 121, 495–499
Tissue-specific effects of castration and ovariectomy on murine epidermal growth factor and its mRNA
Authors: Pascall J. C. , Saunders J. , Blakeley D. M. , Laurie M. S. , Brown K. D.
Published: December 2008

The polypeptide mitogen, epidermal growth factor (EGF), was originally isolated from mouse submaxillary gland (SMG). In mice, these glands are sexually dimorphic; the SMG of male animals typically contains up to 400 pmol EGF/mg protein whereas EGF concentrations in the SMG of female mice are only 5–20 pmol/mg protein. When mice were castrated at 8 weeks of age, EGF mRNA levels in the SMG fell rapidly to the low levels observed in control female animals. Although the concentration of EGF in the SMG, measured by radioimmunoassay, also fell to very low levels (13·8 ± 0·7 (s.e.m.) pmol/mg protein) in the castrated mice, the rate of decrease was considerably slower than that of the mRNA. In contrast to the loss of EGF and EGF mRNA from mice following castration, ovariectomy led to a rise in EGF mRNA levels in SMG, with a maximal increase (approximately 100-fold) 4–6 weeks after ovariectomy. Concentrations of EGF in the SMG also rose markedly in the ovariectomized animals, from a control value of 5·4 ± 0·8 to 34·7 ± 7·9 pmol/mg protein at 6 weeks. In mice, the kidney displays the second highest level of EGF gene expression. However, in contrast to the effects on SMG, kidney EGF mRNA was not affected by either castration or ovariectomy. These results provide further evidence for the tissue-specific control of EGF gene expression in response to steroid hormones.

Journal of Endocrinology (1989) 121, 501–506
Actions of desacetyl-α-melanocyte-stimulating hormone on human adrenocortical cells
Authors: Henville K. L. , Hinson J. P. , Vinson G. P. , Laird S. M.
Published: December 2008

The responses of human adrenocortical cells to stimulation by ACTH(1–24), desacetyl-α-MSH, α-MSH and angiotensin II amide have been compared. Both desacetyl-α-MSH, thought to be the major form of the peptide in the human pituitary and in circulating plasma, and α-MSH caused a significant stimulation of aldosterone, corticosterone and cortisol secretion. Significant stimulation of the production of these steroids was obtained with desacetyl-α-MSH at a concentration of 1 nmol/l, while the response to α-MSH was considerably less sensitive, with a minimum effective concentration of 0·1 μmol/l. These values compared with minimum effective concentrations of 1 pmol/l for ACTH and 0·1 μmol/l for angiotensin II amide. Although cell types were not separated, it is possible to conclude that none of the peptides showed any specificity for the zona glomerulosa, and in each case the same minimum effective concentration of peptide was required for both aldosterone and cortisol secretion. Yields of steroid obtained under conditions of maximal stimulation by ACTH(1–24), α-MSH and desacetyl-α-MSH were at least three to five times the basal output of aldosterone, four to eight times that for corticosterone and more than seven to sixteen times that for cortisol. Angiotensin II amide was a relatively poor stimulant with maximal stimulation only 1·5 × basal. In these experiments the minimum effective concentration for desacetyl-α-MSH (1 nmol/l) was close to the circulating concentration of desacetyl-α-MSH (0·3 nmol/l) in man, and it is thus possible that this peptide may have a physiological role in the control of adrenocortical function.

Journal of Endocrinology (1989) 121, 579–583
Uptake of 3,5,3′-l-tri-iodothyronine in human erythrocytes
Authors: Yamauchi K. , Horiuchi R. , Takikawa H.
Published: December 2008

The mechanisms of 3,5,3′-l-tri-iodothyronine (T3) uptake into human erythrocytes were examined. Purified membranes of human erythrocytes were shown to have two classes of T3-binding sites with one being a high-affinity site (dissociation constant, 59·2±17·8 nmol/l; maximum binding capacity, 344·3 ± 95·5 fmol/μg protein). Furthermore, it was shown that there were two pathways for T3 uptake in human erythrocytes; one was saturable, stereospecific (T3»thyroxine > 3,5,3′-d-tri-iodothyronine), energydependent and dominant at 15 °C; the other was not displaced by unlabelled T3 and was energyindependent but did not occur by passive diffusion. The former pathway which, it is suggested, is a receptor-mediated transport pathway, was inhibited by monodansylcadaverine, phloretin or oligomycin at 15 or 37 °C, but the latter pathway was not inhibited by these inhibitors. Our results strongly suggest that uptake of T3 by the energy-independent pathway became predominant over the energy-dependent pathway at 37 °C and accounted for 83% of total T3 uptake of human erythrocytes.

Journal of Endocrinology (1989) 121, 585–591
Isolation of the human plasma corticotrophin-releasing factor-binding protein
Authors: Behan D. P. , Linton E. A. , Lowry P. J.
Published: December 2008

We report the purification of human corticotrophin-releasing factor-binding protein (hCRF-BP) using repeated affinity chromatography (with the aid of synthetic CRF immobilized on Sepharose 4B solid phase) followed by gel filtration. Presence of the binding protein was tracked throughout the procedure by its ability to inhibit binding of 125I-labelled hCRF to an hCRF antiserum; normal human plasma exhibits 80% inhibition in this system whereas sheep plasma, which does not contain an hCRF-BP, has no effect. Affinity cross-linking of 125I-labelled hCRF to the purified hCRF-BP was performed using disuccinimidyl suberate (1 mmol/l). SDS electrophoresis of the purified CRF cross-linked binding protein followed by radioautography resulted in one major band of Mr 37 000 which corresponded to our original molecular weight estimate based on the elution position of the binding protein on Sephacryl S-200. A 107-fold purification of the hCRF-BP resulted in a preparation estimated to be 95% pure, with an overall yield of 5%.

Journal of Endocrinology (1989) 122, 23–31
Feedback control of vasopressin and corticotrophin secretion in conscious dogs: effect of hypertonic saline
Authors: Raff H. , Skelton M. M. , Cowley A. W.
Published: December 2008

Glucocorticoids are known to inhibit the ACTH response to a variety of stimuli. It has been suggested that vasopressin secretion is also inhibited by glucocorticoid negative feedback. The purpose of this study was to (1) determine the ACTH response to hypertonic saline and its sensitivity to glucocorticoid negative feedback and (2) to determine whether physiological elevations of plasma cortisol inhibit subsequent vasopressin responses to hypertonic saline. Five mongrel dogs (15–18 kg) were prepared with chronic arterial and venous catheters and studied while conscious. Ten experiments were performed on each dog in a randomized design separated by at least 5 days. Each experiment consisted of a pretreatment period (from −60 to −30 min except for dexamethasone administration) during which a glucocorticoid feedback signal was applied and a stimulus period (from 0 to 30 min) during which hypertonic saline was infused. The pretreatment and stimulus periods were separated by 30 min. Pretreatments were as follows: isotonic saline (control), half-maximal and maximal cortisol infusion (5·5 or 11 nmol/kg per min), ACTH(1–24) infusion (6·8 pmol/kg per min) which produces increases in endogenous cortisol, and dexamethasone (1·5 mg i.m.) given at 17.00 h the day before experimentation. Stimuli were as follows: hypertonic saline was infused at 0·2 or 0·4 mmol/kg per min which increased plasma sodium by about 6 or 12 mmol/l respectively. NaCl infusion at 0·2 mmol/kg per min had no effect on plasma ACTH or cortisol except when subsequent to ACTH(1–24) pretreatment when plasma ACTH actually increased to 41·4 ± 2·9 pmol/l in response to hypertonic saline. NaCl infusion at 0·4 mmol/kg per min resulted in a significant increase in plasma ACTH from 5·9 ± 0·9 to 11·7 ± 2·0 pmol/l in the control group. This ACTH response was blocked by pretreatment with either dose of cortisol and dexamethasone. ACTH pretreatment, however, did not completely block the ACTH subsequent response to infusion of 0·4 mmol NaCl/kg per min. The two doses of NaCl led to significant and dose-related increases in plasma vasopressin. None of the pretreatments significantly affected the vasopressin response to hypertonic saline except for significant inhibition after overnight dexamethasone. We conclude that (1) hypertonic saline can stimulate ACTH release if plasma sodium is increased sufficiently, (2) the ACTH response to hypertonic saline is potentiated by pretreatment with ACTH making it different from other stimuli studied previously, and (3) the vasopressin response to hypertonic saline is not inhibited by short-term elevations of plasma cortisol within the physiological range.

Journal of Endocrinology (1989) 122, 41–48
Demonstration of growth hormone receptors in cultured rat epiphyseal chondrocytes by specific binding of growth hormone and immunohistochemistry
Authors: Nilsson A. , Lindahl A. , Edén S. , Isaksson O. G. P.
Published: December 2008

Growth hormone has been reported to exert direct effects on rat and rabbit epiphyseal chondrocytes in vitro, indicating that GH interacts with specific receptors on these cells. To investigate this possibility, binding of GH to cultured rat epiphyseal chondrocytes was studied under various experimental conditions. Chondrocytes were isolated enzymatically from epiphyseal growth plates of the proximal tibia of 20-day-old male rats and were cultured in monolayer in Ham's F-12 medium supplemented with 10% calf serum and 1% of a serum substitute. The cells were seeded at various densities (25 000–200 000 cells/well) and cultured for 5–16 days. Twenty-four hours before binding experiments, the medium containing calf serum was changed for one containing serum obtained from hypophysectomized rats, in order to avoid binding of GH present in the calf serum. Binding was studied by incubating 125I-labelled human GH (hGH) with the cells in the presence or absence of various concentrations of unlabelled hGH, bovine GH (bGH), rat GH (rGH) and ovine prolactin (oPRL).

Specific binding could be demonstrated in cells cultured for 5–16 days. Binding was dependent upon time and temperature, and maximal binding was obtained by incubating the labelled hormone for 4–6 h at 24 °C. An increase in binding was noted between 7 and 12 days in culture. In cells cultured for 12 days, addition of unlabelled hGH, bGH or rGH caused a dose-dependent displacement of 125I-labelled hGH, whereas oPRL was ineffective. Scatchard analysis resulted in a linear plot, and the number of binding sites/cell was approximately 5700, with a dissociation constant of 0·46 nmol/l. The increase in binding between days 7 and 12 was independent of the density of seeded cells, but total binding was higher if the cells were seeded at a low density. By using a monoclonal antibody to the rabbit GH receptor, specific staining could be demonstrated immunohistochemically in the cultured cells. The results show the presence of GH receptors in cultured rat epiphyseal chondrocytes and also show that the culture conditions influence the expression of GH receptors.

Journal of Endocrinology (1989) 122, 69–77
Gonadotrophin-releasing activity of neurohypophysial hormones: I. Potential for modulation of pituitary hormone secretion in rats
Authors: Evans J. J. , Robinson G. , Catt K. J.
Published: December 2008

Neurohypophysial hormones have been implicated in the control of anterior pituitary function, and oxytocin has been shown to stimulate gonadotrophin excretion and ovarian follicular development in certain species. To determine the role of neurohypophysial peptides in the control of gonadotrophin release, their actions on LH and FSH secretion were analysed in rats in vivo and in vitro. In adult female rats, administration of oxytocin during early pro-oestrus advanced the spontaneous LH surge and markedly increased peripheral LH levels at 15.00 h compared with control animals. In cultured pituitary cells from adult female rats, oxytocin and vasopressin elicited dose-related increases in LH and FSH release. Such responses were not affected by a potent gonadotrophin-releasing hormone (GnRH) antagonist that abolished GnRH agonist-induced release of LH and FSH. Oxytocin did not enhance GnRH agonist-stimulated gonadotrophin release to the same extent as it increased basal secretion, but at low concentrations of GnRH agonist the effects were additive. The gonadotrophin responses to oxytocin and vasopressin were inhibited by the specific neurohypophysial hormone antagonists, [d(CH2)5d-Ile2,Ile4,Arg8]vasopressin and [d(CH2)5Tyr (Me),Arg8]vasopressin. These results provide direct evidence that neurohypophysial hormones can stimulate gonadotrophin secretion through a receptor system distinct from the GnRH receptor. Such a mechanism could represent a complementary hypothalamic control system for long-term modulation of LH and FSH secretion by exerting a basal or tonic influence on gonadotrophin production.

Journal of Endocrinology (1989) 122, 99–106