bluuebunny/crossref_metadata_2025 huggingface dataset:
Opioid peptides of the pituitary and hypothalamus: changes in pregnant and lactating rats
Authors: Petraglia F. , Baraldi M. , Giarrè G. , Facchinetti F. , Santi M. , Volpe A. , Genazzani A. R.
Published: December 2008

Immunoreactive (Ir) β-endorphin concentrations were determined in plasma, anterior pituitary (AP), neurointermediate pituitary lobe (NIL) and mediobasal hypothalamus (MBH) of pregnant (12–14 and 18–20 days) and fertile control rats, during labour and lactation. Immunoreactive Met-enkephalin concentrations were also evaluated in the MBH.

Concentrations of Ir β-endorphin in plasma, AP and NIL of rats during early and late pregnancy were significantly higher than in controls, the plasma and AP contents showing an increasing pattern in the second half of gestation. During labour, Ir β-endorphin concentrations in plasma and AP reached the highest values, whereas those in NIL remained unchanged. Lactating rats showed Ir β-endorphin concentrations in NIL and plasma in a range similar to that found in pregnant rats, resulting in concentrations in the AP not significantly different from those of non-pregnant controls.

Immunoreactive β-endorphin and Ir Metenkephalin concentrations in MBH of pregnant rats were almost twice as high as in controls, rising markedly during labour; during lactation levels were in the same range as in non-pregnant controls.

These results indicate that pregnancy and labour are characterized by high plasma, pituitary and hypothalamic concentrations of Ir β-endorphin as well as by high hypothalamic Ir Met-enkephalin levels, and that Ir β-endorphin concentrations vary differently during pregnancy, lactation and labour in the two pituitary lobes, supporting the existence of different control mechanisms in the AP and NIL.

J. Endocr. (1985) 105, 239–245
Effects of growth hormone-releasing factor(1–44) on growth hormone release from human somatotrophinomas in vitro: interaction with somatostatin, dopamine, vasoactive intestinal peptide and cycloheximide
Authors: White M. C. , Daniels M. , Kendall-Taylor P. , Turner S. J. , Mathias D. , Teasdale G.
Published: December 2008

The effect of GH-releasing factor(1–44) (GRF) alone, or together with somatostatin (SRIF), dopamine (DA), vasoactive intestinal peptide (VIP) or cycloheximide was studied in a total of ten human somatotrophinomas using a static cell culture system. Growth hormone-releasing factor (2·0×10−8 mol/l) significantly (P<0·05) stimulated GH release from nine out of ten tumours over 4-h incubations, and a dose-related effect (2·0×10−10−2·0×10−8 mol/l) was observed in five tumours thus studied.

Repeated GRF (2·0×10−8 mol/l)-mediated GH release was seen during 96% (n = 25) of experiments performed on six tumours over 4 h and up to 27 days in culture. Growth hormone-releasing factor (2·0×10−8 mol/l) also stimulated GH release from five out of seven somatotrophinomas during 60-min incubations.

Somatostatin (6·1×10−9 mol/l) completely inhibited GRF-induced GH secretion from four tumours studied over 4 h, but in each case there was significant (P<0·05) 'rebound' of GH release from cultures exposed to both GRF and SRIF during a subsequent recovery period. Dopamine suppressed basal GH release from two out of four tumours, but in each case had a greater inhibitory effect on GRF-mediated GH release. Vasoactive intestinal peptide directly stimulated GH release from two out of three tumours, and the effects were additive to maximal stimulatory doses of GRF. Cycloheximide significantly (P< 0·01) enhanced GRF-stimulated release of GH during a 60-min incubation, but inhibited both basal and GRF-stimulated release over 4 and 8 h. We conclude that a static cell culture system can be used successfully to study the action of GRF on human somatotrophinoma tissue for up to 27 days in culture. Human somatotrophinomas seem to be only rarely unresponsive to the stimulatory action of GRF, which is itself significantly modulated by SRIF, DA and VIP. De-novo protein synthesis appears to be necessary for the full expression of GRF activity on human somatotrophinoma tissue.

J. Endocr. (1985) 105, 269–276
Hypothalamo-pituitary regulation of thyrotrophin secretion in chronically catheterized Brattleboro rats
Authors: Wolf B. A. , Hugues J.-N. , Aratan-Spire S. , Reinberg A. , Voirol M.-J. , Czernichow P.
Published: December 2008

Plasma TSH rhythms were measured in Brattleboro (DI) and control Long–Evans (LE) rats with an intracardiac catheter allowing repeated sampling in conscious unstressed animals. The TSH response to thyrotrophin-releasing hormone (TRH; 500 ng/100 g body weight) was also determined. Finally, hypothalamic and pancreatic TRH concentrations and TRH-degrading activity (TRH-DA) were measured by specific radioimmunoassay. Long–Evans rats had a 24-h rhythm with a major modulatory 8-h component. In DI rats, only the 24-h rhythm was detected. The mean 24-h rhythm-adjusted mean TSH level was higher in DI than in LE rats (1·38±0·05 and 1·14 ± 0·06 μg/l respectively, P<0·01). The peak TSH response to TRH was significantly increased in DI rats while the pituitary concentration of TSH was also higher (0·93 ± 0·09 vs 0·39± 0·06 μg/mg wet weight in LE, P<0·001). Hypothalamic TRH and TRH-DA were similar in both strains. The response to propyl-thiouracil-induced hypothyroidism was identical in both strains. We conclude that DI rats have a normal pituitary sensitivity to tri-iodothyronine but a central dysfunction in the pituitary environment leading to some alterations of TSH secretion.

J. Endocr. (1985) 105, 277–283
Physiological control of growth hormone secretion by thyrotrophin-releasing hormone in the domestic fowl
Authors: Klandorf H. , Harvey S. , Fraser H. M.
Published: December 2008

Immature cockerels (4- to 5-weeks old) were passively immunized, with antiserum raised in sheep, against thyrotrophin-releasing hormone (TRH). The administration of TRH antiserum (anti-TRH) at doses of 0·5, 1·0 or 2·0 ml/kg lowered, within 1 h, the basal concentration of plasma GH for at least 24 h. The administration of normal sheep serum had no significant effect on the GH concentration in control birds. Although the GH response to TRH (1·0 or 10·0 μg/kg) was not impaired in birds treated 1 h previously with anti-TRH, prior incubation (at 39 °C for 1 h) of TRH (20 μg/ml) with an equal volume of anti-TRH completely suppressed the stimulatory effect of TRH (10 pg/kg) on GH secretion in vivo. These results suggest that TRH is physiologically involved in the hypothalamic control of GH secretion in the domestic fowl.

J. Endocr. (1985) 105, 351–355
Volumetric control of arginine vasotocin and mesotocin release in the frog (Rana ridibunda)
Authors: Nouwen E. J. , Kühn E. R.
Published: December 2008

Adult male frogs (Rana ridibunda) were subjected to several volumetric and osmometric stimuli and the influence on circulating concentrations of arginine vasotocin (AVT) and mesotocin was studied by the use of highly specific radioimmunoassays. During progressive blood withdrawal (haemorrhage group) urine flow decreased to zero, whereas no change occurred in the plasma and urine osmolality. Control levels of 34·3±7·3 pmol AVT/1 gradually increased up to 638·3±179·1 pmol/l (P<0·001) after a blood loss of up to 50–60% of the blood volume. Plasma mesotocin concentrations also increased from 42·4±9·2 to 70·8±12·0 pmol/l (n = 7). Hypervolaemia, produced by the repeated intravenous injection of isotonic Ringer solution, increased the urine flow and osmolality compared to controls but had no influence on the plasma levels of AVT and mesotocin. Hypernatraemia without volume change profoundly increased the urine osmolality but the urine flow was not affected; the plasma concentrations of AVT and mesotocin remained at the control level. Finally, during a 1-h immobilization stress a pronounced antidiuresis occurred in the presence of a constant plasma and urine osmolality and control plasma levels of AVT and mesotocin.

It is concluded that the release of AVT and, to a smaller extent, of mesotocin is under volumetric control.

J. Endocr. (1985) 105, 371–377
Effect of theophylline on nuclear retention of oestrogen-receptor complexes: correlation with oestrogen responses
Authors: Steinsapir J. , Rojas A. M. , Bruzzone M. E. , White A. , Alarcón O. , Fuentes I. , Fierro C. , González O. , Ampuero R. , Fuentes M. , Bitrán J.
Published: December 2008

In the ovariectomized adult rat uterine oedema induced by 0·01 and 0·1 μg oestradiol-17β/100 g body weight increased further in the presence of theophylline. Nuclear retention of oestrogen-receptor complexes also increased in response to theophylline both in vivo and in vitro. Theophylline decreased the number of eosinophils in the blood and concurrently decreased oestrogen-induced uterine eosinophilia at doses of 0·001, 0·01, 0·1, 1, 10 or 30 μg oestradiol/100 g body weight, through a mechanism independent of glucocorticoids. There was, therefore, no correlation between changes in the number of uterine eosinophils and changes in uterine wet weight induced by theophylline and oestrogen. It is suggested that the presence of oestrogen-receptor complexes in the nucleus for at least 4 h is a prerequisite for the induction of uterine oedema and growth in the presence of theophylline and oestradiol-17β.

J. Endocr. (1985) 105, 397–403
Studies of the heterogeneity of human pituitary LH by fast protein liquid chromatography
Authors: Stockell Hartree A. , Lester J. B. , Shownkeen R. C.
Published: December 2008

The Pharmacia fast protein liquid chromatography system was employed to fractionate a purified preparation of human LH (hLH) on the anion exchanger Mono Q at pH 7·8 into 14 sub-fractions. Each of the sub-fractions was characterized by its behaviour on polyacrylamide gel electrophoresis, sodium dodecyl sulphate (SDS) gel electrophoresis, LH receptor binding activity and sialic acid content. All sub-fractions contained sialic acid, were active in binding to LH receptors, and exhibited components typical of hLH subunits on SDS gel electrophoresis. None of the sub-fractions was homogeneous with respect to charge. There is evidence that part of the heterogeneity results from the presence in some molecules of an internal proteolytic cleavage within the β-subunit, and fractions enriched in species containing such cleavages were prepared by this method.

J. Endocr. (1985) 105,405–413
Possible role of prolactin in the inhibitory effect of testosterone on the hypothalamic-pituitary-testicular axis in the rat
Authors: Tresguerres J. A. F. , Perez Mendez L. F. , Lopez-Calderon A. , Esquifino A. I.
Published: December 2008

To study the role of testosterone on the regulation of the hypothalamic-pituitary-testicular axis, young intact male Wistar rats were given acute (24 h) or chronic (5 days) subcutaneous treatments of 500 μg testosterone propionate (TP) or vehicle alone. Plasma LH, prolactin and testosterone levels were measured both basally and after administration of LH-releasing hormone (LHRH) or human chorionic gonadotrophin (hCG) by means of specific radioimmunoassay systems using materials supplied by the NIADDK. After acute treatment with TP there was an increase in basal plasma testosterone concentrations and no modification in the hCG response when compared with vehicle-treated animals. No difference could be detected in basal plasma testosterone levels after the chronic treatment, but a significant reduction in the hCG response was observed. Both acute and chronic treatments with TP resulted in a significant decrease of basal plasma LH levels. A reduced LH response to LHRH in acutely treated rats and no response in the chronically treated rats was detected. Plasma prolactin levels showed an increase after both acute and chronic treatments. To evaluate the possible role of the increased plasma prolactin levels on the above modifications during TP treatment, another group of animals was treated with TP and bromocriptine (dopamine agonist) simultaneously to avoid the increase in plasma prolactin levels. In this situation, neither basal plasma LH levels nor the response to LHRH were altered when compared to vehicle-treated rats; a normal testosterone response to hCG stimulation was observed in spite of the high basal plasma testosterone levels. All these observations suggest that increased prolactin levels may exert a modulatory role on the negative feedback effect of testosterone both at the testicular and central levels.

J. Endocr. (1985) 105, 423–427
Alteration of prolactin control in adult rats treated neonatally with sex steroids
Authors: Vaticón M. D. , Fernández Galaz M. C. , Tejero A. , Aguilar E.
Published: December 2008

Androgenized, oestrogenized and control female and male rats were used to establish possible differences in the alteration of the prolactin control system. Neonatal treatment involved administration of oestradiol benzoate or testosterone propionate (TP) on days 1 and 5 to the males and on day 5 to the females. Oil-treated animals were used as controls. Plasma prolactin levels were measured in these animals during adulthood (a) before gonadectomy, performed on day 80, and 27 days after gonadectomy and (b) on the 2 days (at 10.00 and 17.00 h) after administration of a single dose of TP to gonadectomized animals. Oestrogenized rats had the highest plasma prolactin concentrations just before and after gonadectomy. Testosterone propionate increased plasma prolactin levels in all groups. This response was more notable in the female than in the male groups, and was highest in the oestrogenized animals. Temporal rhythms of the prolactin response to TP were daily, perhaps circadian, with increased levels in the afternoon compared with those in the morning. This pattern was not present in oestrogenized females and androgenized males. Results suggest (a) that oestrogens and androgens given neonatally differ in their ability to alter the prolactin control system, and (b) that females seem to be more sensitive than males to changes in hypothalamic differentiation induced by neonatal steroid treatment.

J. Endocr. (1985) 105, 429–433
Effects of a fragment of human growth hormone-releasing factor in normal and 'Little' mice
Authors: Clark R. G. , Robinson I. C. A. F.
Published: December 2008

The 'Little' mouse is characterized by a body growth rate 60% of normal due to a defect in the synthesis and storage of GH in the anterior pituitary gland. We have now investigated the effects of GH releasing factor (GRF) in these mice and in normal animals. The pituitary GH content in Little mice was only 4% of that in normal C57: +/+ mice, and was not affected by twice daily i.p. injections of human (h) GRF1-29NH2 (0·2−2 μg) for 14 days. This treatment also had no effect on body growth. In anaesthetized normal mice, single i.v. injections of 0·1 or 2 μg hGRF1-29NH2 released large amounts of GH into the plasma, whereas this peptide was ineffective in Little mice, whether or not they had been pretreated with GRF. Therefore, although pituitaries of Little mice contain significant amounts of GH, this pool is not releasable by GRF. This suggests that the dwarfism in Little mice may be partly due to a pituitary defect in GRF receptors or their stimulus-secretion coupling, rather than a deficiency in hypothalamic GRF.

J. Endocr. (1985) 106, 1–5
Induction of selective release of FSH in castrated male rats bearing an ovarian transplant by the administration of human chorionic gonadotrophin
Authors: Watanabe G. , Taya K. , Sasamoto S.
Published: December 2008

The present study was undertaken to determine whether hypothalamic differentiation is involved in the selective release of FSH during the periovulatory period using adult male rats castrated and implanted with an ovary.

Adult male rats (70–90 days old) were castrated and an ovary obtained from a prepubertal female rat (26 days old) was immediately grafted subcutaneously. Four weeks later, human chorionic gonadotrophin (hCG, 10 i.u.) was injected i.v. into the experimentally manipulated rats to induce ovulatory changes in the grafted ovaries. Another group of similarly prepared rats was injected with 0·9% (w/v) NaCl solution as controls. After injection of hCG, plasma concentrations of FSH increased significantly by 6 h, reached peak values at 12 h and declined to control levels at 36 h. On the other hand, plasma concentrations of LH were reduced by 6 h and decreased further during the next 36 h. An abrupt fall in plasma concentrations of oestradiol-17β occurred within 3 h of the administration of hCG. Histological examination revealed that ovulatory changes and luteinization of follicles were induced in grafted ovaries by 18 h after the injection of hCG. Thirty-six hours after treatment with hCG, a set of newly formed corpora lutea was observed in grafted ovaries and plasma concentrations of progesterone were raised. Treatment with oestradiol-17β did not inhibit the selective release of FSH after the administration of hCG, suggesting that the abrupt decrease in secretion of oestradiol-17β from the grafted ovary is not involved in the occurrence of the FSH surge.

These results indicate that a selective release of FSH can be induced in castrated male rats bearing an ovarian transplant probably due to decreased secretion of inhibin by the luteinized follicles in the grafted ovaries. Sex differentiation of the hypothalamus is not, therefore, involved in the selective surge of FSH.

J. Endocr. (1985) 106, 31–36
Antioestrogen inhibition of oestradiol-induced alterations in hypothalamic noradrenaline turnover
Authors: Hiemke C. , Poetz B. , Ghraf R.
Published: December 2008

Long-term (4–6 weeks) ovariectomized rats were injected with either oestradiol benzoate (OB; 20 μg s.c.) or monohydroxytamoxifen (MTAM; 0·2 mg i.p.) plus OB. Oestradiol benzoate was administered at 12.00 h on day 0 and MTAM was given immediately before OB, followed by further injections twice daily to maintain sufficiently high antioestrogen levels. When given alone, OB reduced the serum levels of LH during the morning (08.00–09.00 h) and afternoon (17.30–18.30 h) hours of day 3 after priming. The feedback actions of OB on LH release were accompanied by time-dependent alterations of noradrenaline turnover in the preoptic–anterior hypothalamic brain area (POAH). On day 3 after priming the noradrenaline turnover rate was reduced in the morning and increased in the afternoon. The increase correlated with an enhanced sensitivity of the LH secretory system to progesterone. The antioestrogen MTAM blocked the OB-induced sensitization of LH release to the stimulatory action of progesterone and interfered with the stimulatory long-term effect of oestradiol on hypothalamic noradrenaline turnover.

The data strongly support the view that the oestrogen-induced afternoon increase of noradrenaline turnover in the POAH represents a pre-requisite for the induction of LH surges. The stimulatory effect of oestradiol on hypothalamic noradrenaline turnover seems to be mediated by a classical oestrogen receptor mechanism.

J. Endocr. (1985) 106, 37–42
Multiple molecular forms of prolactin during pregnancy in women
Authors: Pansini F. , Bergamini C. M. , Malfaccini M. , Cocilovo G. , Linciano M. , Jacobs M. , Bagni B.
Published: December 2008

The distribution of isomorphic forms of prolactin in the serum of pregnant women was studied by gel filtration chromatography. Using this technique we were able to resolve three peaks, detected by radioimmunoassay: they were termed 'big-big', 'big' and 'little' prolactin in order of decreasing size, with approximate molecular weights > 100 000, 50 000 and 21 000 respectively. They displayed a comparable immunoreactivity to the antiserum employed in the radioimmunoassay, as determined in competition experiments. The relative amount of each hormone form in serum changed during the third trimester of pregnancy. At week 33 of pregnancy, 'little' prolactin accounted for 63·2 ± 7·7% of the total circulating hormone present in the serum of five normal pregnant women. During the progression of pregnancy, there was a gradual increase in the low molecular weight prolactin, so that, at the time of delivery, the larger forms of the hormone were present only in small amounts.

J. Endocr. (1985) 106, 81–85
Iodothyronine kinetics in the rabbit: an experimental model
Authors: Pearce C. J. , Byfield P. G. H. , Veall N. , Himsworth R. L.
Published: December 2008

Turnover studies of thyroxine (T4), 3,5,3′-tri-iodothyronine (T3) and 3,3′,5′-tri-iodothyronine (rT3) have been performed in the rabbit. A novel modification of a conventional radioimmunoassay has been used to measure specific 125I-labelled iodothyronines in small volumes of plasma in the presence of other 125I-labelled metabolites. Kinetic analysis of plasma disappearance of tracer was performed by a new theoretical approach. For T4 the mean (±s.d.) plasma concentration, clearance and production rates were 34±12 nmol/l, 109±19 ml/kg per day and 3·7±1·4 nmol/kg per day respectively (n = 9). For T3 the corresponding values were 2·04±0·42 nmol/l, 1·52±0·29 litres/kg per day and 3·07±0·76 nmol/kg per day (n = 8), and for rT3 0·12±0·04 nmol/l, 5·7±1·7 litres/kg per day and 0·69±0·23 nmol/kg per day (n = 8). The combination of these two new methodologies affords a simple and convenient means of studying iodothyronine metabolism under normal and abnormal conditions. The techniques employed may be generally applied to turnover studies of other compounds of physiological interest which can be measured by radioimmunoassay.

J. Endocr. (1985) 106, 87–94
Age, sex and gonadal influences on oestrogen receptor content in the rat liver
Authors: Rochman H. , Rosner B. , Mathey B. , Getz G. E. , Hospelhorn V.
Published: December 2008

Liver cytosol oestrogen receptor (OR) content of intact and gonadectomized male and female rats of defined age (1–18 months) was measured by the controlled pore glass bead assay. The OR content of animals of both sexes aged 3 weeks was low to insignificant (0·12±0·04 (s.e.m.) pmol/g wet wt liver). In the intact animal, liver OR reached maximum levels at an earlier age in the male (1·35±0·12 pmol/g at 28–32 weeks) than in the female (4·89±0·17 pmol/g at 44–52 weeks). In the mature female the OR is thus maintained at a level threefold greater than in males of comparable age.

Levels of OR in the gonadectomized male tended to be higher, at all ages, than those in the intact male but this difference was not statistically significant. Ovariectomy was associated with a decreased OR content in rats aged less than 6 months and an increase in the older rats, but these effects (of ovariectomy) were not statistically significant.

In the females, regression analysis of pooled data, combining all ages, indicated a significant positive correlation between OR and liver wet weight, independent of gonadal status; no such relationship was found with the males.

The results indicate that factors influencing liver cytosol OR content include maturity, age and sex whereas the gonads have little obvious effect. These findings lend further support to the concept that sex differences exist in the liver.

J. Endocr. (1985) 106, 95–102
Liver angiotensin II receptors in the rat: binding properties and regulation by dietary Na+ and angiotensin II
Authors: Sernia C. , Sinton L. , Thomas W. G. , Pascoe W.
Published: December 2008

Recent evidence suggests that angiotensin II (AII) acts on the liver via specific receptors. The aims of this study were to examine the general binding properties of these receptors in the rat and to determine the role of dietary Na+ and AII in the regulation of AII receptors.

Binding of 125I-labelled Ile5-AII to liver membranes was saturable and behaved as a single class of sites with an affinity (Ka) of 2·9 l/nmol and a Hill coefficient of 0·99. Kinetic analysis of AII binding gave estimates for the rates of association and dissociation of 42 l/μmol per min and 1·5 × 10−2/min respectively. The binding of analogues exhibited the following order of potency: Val5-AII > Ile5-AII > AIII > Sar1-Ala8-AII > Sar1-Gly8-AII > AI > des-Asp-AI > C4−C8 pentapeptide > Phe1-Tyr8-AII > neurotensin > luteinizing hormone-releasing hormone. Binding was enhanced by Mg2+ and Ca2+ and inhibited by EDTA and the reducing agent dithiothreitol. Low dietary Na+ affected in a biphasic manner both the Ka and concentration (Ro) of liver AII receptors. Initially, Ro decreased from 25·9±3·8 (control) to 16±1·9 (s.e.m.) pmol/g tissue by 1·5 days but thereafter it rapidly increased to 47·3±8·7 pmol/g tissue (3·5 days) and remained elevated to the end of the experiment, 8·5 days later. The Ka initially increased from 2·7±0·3 (control) to 4·3±0·5 l/nmol (1·5 days) and then decreased steadily to 1·2±0·1 l/mol (8·5 days). The effect of AII was examined by infusing 24 pmol AII/kg per min for 5 days into the jugular vein by subcutaneous osmotic minipumps. The response was qualitatively similar to that for low dietary Na +. It was concluded that the rat liver has a high content of specific AII receptors that are responsive to changes in Na+ and AII.

J. Endocr. (1985) 106, 103–111
Prolactin permits the expression of a circadian variation in insulin receptor profile in hepatocytes of the golden hamster (Mesocricetus auratus)
Authors: Cincotta A. H. , Meier A. H.
Published: December 2008

Insulin receptor profile was determined in freshly isolated hamster hepatocytes at two times (07.00 and 16.00 h) during a 14-h daily photoperiod (08.00–22.00 h). The hamsters were pretreated for 5 days with bromocriptine (to inhibit prolactin release), bromocriptine and prolactin replacement, or control saline injections. The insulin receptor profile was determined by Scatchard plot analysis. The insulin receptor number (high and low affinity) was three times greater at 07.00 than at 16.00 h among saline-injected controls. However, their affinities did not differ. Bromocriptine pretreatment reduced (70%) both the high and low affinity receptor numbers and increased the affinity of the high affinity receptor at 07.00 h. Prolactin replacement in bromocriptine-treated hamsters restored the receptor profile at 07.00 h to control values. These data indicate that prolactin facilitates the expression of a circadian variation in insulin receptor profile.

J. Endocr. (1985) 106, 177–181
Thyrotrophin stimulation of mitogenesis of the rat thyroid cell strain FRTL-5: a metaphase index assay for the detection of thyroid growth stimulators
Authors: Ealey P. A. , Emmerson J. M. , Bidey S. P. , Marshall N. J.
Published: December 2008

Thyroid-stimulating hormone (TSH) has been shown to stimulate mitosis in cultures of the continuous thyroid cell strain FRTL-5, and this system may be used to quantify the growth-promoting effects of thyroid stimulators. Removal of TSH from the culture medium led to a progressive decline in the metaphase index (MI) to zero, after 7 days. Thus the cell culture conditions may be manipulated so that metaphases are absent in control cultures, i.e. in the absence of TSH. Restimulation with TSH caused an increase in mitosis only after a lag-phase of 20–24 h. A maximum MI was observed between 40 and 50 h, with a secondary peak between 70 and 75 h. An immunoglobulin G (IgG) preparation from a thyrotoxic patient with a small goitre which was a potent stimulator of adenylate cyclase in these cells produced a similar time-course. A dose–response relationship to TSH was obtained 47 h after addition of the hormone. Significant stimulation was observed with 10 mu. TSH/1, and maximal stimulation with 1 unit TSH/1; the highest dose tested (10 units TSH/1) slightly decreased the MI below the maximum. Stimulation of these cells appeared to be TSH specific, since FSH, human chorionic gonadotrophin, LH and isoproterenol did not induce mitosis. Epidermal growth factor under the experimental conditions employed was unable to induce mitosis. However, an increase in mitosis was observed with the adenylate cyclase stimulator forskolin. These experiments confirm the mitogenic properties of TSH and we describe a metaphase index assay for the detection of thyroid growth promotors.

J. Endocr. (1985) 106, 203–210
Intersexuality in five pigs, with particular reference to oestrous cycles, the ovotestis, steroid hormone secretion and potential fertility
Authors: Hunter R. H. F. , Cook B. , Baker T. G.
Published: December 2008

Reproductive tissues, steroid hormone secretion, and sexual behaviour have been examined in five gilts, in each of which the right gonad was an ovotestis. Although from different females, these animals were sired by the same boar and each possessed an XX sex chromosome constitution as determined by karyotype analysis of blood cells. Despite variable amounts of testicular tissue in the ovotestis and unilateral development of a prominent epididymis, four of the animals had oestrous cycles of normal duration (20–22 days) and extended periods of standing oestrus (3–6 days). The fifth animal did not have detectable oestrous cycles but was extremely aggressive in the presence of a mature boar. Two of the gilts were mated, and there were small numbers of embryos in each uterine horn 23 and 26 days later. Removal of the ovary did not prompt compensatory hypertrophy in the ovarian portion of the ovotestis, nor did injection of pregnant mare serum gonadotrophin stimulate detectable follicular growth in ovarian tissue adjoining testicular tissue.

Concerning the aetiology of this intersex condition, the unilateral appearance of an ovotestis precludes any simple involvement of a translocated portion of the Y chromosome or systemic effects of unusual titres of the putative H–Y antigen. However, bearing in mind a predisposition to gonadal asymmetry in eutherian mammals, a case is advanced for apposition or incorporation of adrenocortical tissue in the right embryonic ovary. The resultant virilization of neighbouring reproductive tissues would stem from adrenocortical androgen synthesis.

J. Endocr. (1985) 106, 233–242
Prolactin in cerebrospinal fluid increases the synthesis and release of hypothalamic γ-aminobutyric acid
Authors: Locatelli V. , Apud J. A. , Gudelsky G. A. , Cocchi D. , Masotto C. , Casanueva F. , Racagni G. , Müller E. E.
Published: December 2008

The effect of intracerebroventricularly (i.v.t.)-injected rat prolactin (2 μg/rat) on the function of tuberoinfundibular γ-aminobutyric acid (GABA)ergic neurones was assessed in adult male rats by measuring the activity of glutamic acid decarboxylase (GAD) in the mediobasal hypothalamus (MBH) and the concentrations of GABA in hypophysial portal plasma and in the anterior pituitary gland. Fourteen hours after i.v.t. injection of rat prolactin the activity of GAD in the MBH was significantly (P <0·05) increased and it remained elevated for at least 16 h after injection.

The mean concentrations of GABA in hypophysial portal plasma and in the anterior pituitary were twice those found in vehicle-treated controls 16 h after administration of rat prolactin; no significant effects were observed at earlier time-periods. A significant (P <0·01) and long-lasting decrease in endogenous plasma prolactin concentrations was detected 2 h after the i.v.t. injection of rat prolactin and the concentrations remained suppressed for up to 16 h. The present results are consistent with the concept that the activity of tuberoinfundibular GABAergic neurones is regulated, at least in part, by circulating prolactin. The ability of prolactin to accelerate the synthesis and release of GABA in the MBH might constitute a short loop feedback system by which the hormone regulates its own secretion.

J. Endocr. (1985) 106, 323–328
Binding of glucocorticoid to the androgen receptor of mouse submandibular glands
Authors: Maruyama S. , Sato S.
Published: December 2008

An increase in esteroprotease activity, a known cytodifferentiating response to androgen in the submandibular gland, occurred after cortisol acetate, dexamethasone or methyltrienolone (R1881) treatment in castrated genetically normal male (X/Y-castrated) mice, but not in normal male (X/Y) and testicular feminized male (Tfm/Y) mice. A peak with specific binding for [3H]cortisol appeared in sucrose density gradient patterns of extracts from X/Y-castrated mice and in almost the same fraction number as that for [3H]R1881 binding. However, peaks specific for neither [3H]cortisol nor [3H]R1881 binding were observed in Tfm/Y mice. The peak binding [3H]cortisol in extracts from X/Y-castrated mice, as well as the one binding [3H]R1881, were inhibited by unlabelled R1881 and cyproterone acetate, an antiandrogen; the peak was not, however, affected by unlabelled oestradiol-17β. The binding capacity of [3H]cortisol determined by Scatchard analysis was similar to that of [3H]R1881 (103 and 106 fmol/mg protein respectively). The Kd value of [3H]cortisol, however, was about 13·6-fold higher than that of R1881. These results suggest that cortisol has the ability to promote androgenic cytodifferentiating action in the mouse submandibular gland by binding to its androgen receptors, if androgens are absent or deficient.

J. Endocr. (1985) 106, 329–335
31P-Nuclear magnetic resonance spectroscopy of rat pituitary tumours in vivo
Authors: Prysor-Jones R. A. , Silverlight J. J. , Jenkins J. S. , Stevens A. N. , Rodrigues J. L. , Griffiths J. R.
Published: December 2008

31P-Nuclear magnetic resonance (NMR) spectra were obtained in the living rat from 19 implanted prolactin-secreted pituitary tumours. Seven major peaks were found including those arising from the high energy phosphorus metabolites ATP and phosphocreatine. Intracellular pH of the tumours was measured and a relationship with prolactin secretion was observed, the highest plasma prolactin concentrations being associated with an intracellular pH >7·18. Repeated NMR measurements in three tumours over periods of up to 21 days revealed progressive changes with age, shown by an increase in inorganic phosphate, a decrease in high energy phosphorus metabolites and a decrease in prolactin secretion. It is concluded that NMR spectroscopy provides a useful method of studying intracellular events which accompany hormone secretion in vivo.

J. Endocr. (1985) 106, 349–353
Effects of LH-releasing hormone antagonist or lesions of the medial basal hypothalamus on periovulatory gonadotrophin release in female rats
Authors: Rush M. E.
Published: December 2008

Follicle-stimulating hormone release on the morning of oestrus was examined by using two different techniques which eliminate LH-releasing hormone (LHRH) stimulation of the pituitary gland. Cyclic female rats were given a potent LHRH antagonist (ALHRH) or were subject to electrolytic lesions of the medial basal hypothalamus (MBH) before or after the pro-oestrous phase of FSH release. Administration of ALHRH at 14.00, 15.30 and 17.00 h or lesioning of the MBH between 11.30 and 13.00 h on pro-oestrus entirely blocked the preovulatory LH surge and both phases of FSH release. Ovulation was abolished in all of these animals. However, when ALHRH was given at 20.30, 22.00 and 23.30 h or lesions of the MBH made between 20.00 and 21.30 h on pro-oestrus after the prooestrous FSH and LH surges had occurred, the oestrous phase of FSH release was indistinguishable from that of saline-treated control rats. Ovulation occurred in all of these animals, and the mean number of ova shed was eight/rat. The conclusions are that (1) the pro-oestrous phase of FSH release is dependent upon the hypothalamic hormonal stimulation by LHRH and (2) the oestrous phase of FSH release is entirely independent of direct LHRH stimulation, or any hypothalamic stimulus.

J. Endocr. (1985) 106, 361–366
Effects of photoperiod, pinealectomy and castration on body weight and daily torpor in Djungarian hamsters (Phodopus sungorus)
Authors: Vitale P. M. , Darrow J. M. , Duncan M. J. , Shustak C. A. , Goldman B. D.
Published: December 2008

During the autumn and winter Djungarian hamsters (Phodopus sungorus) exhibit regression of the gonads, development of a white winter pelage, loss of body weight and daily torpor. These seasonal events are largely regulated by changes in photoperiod. The present experiments were designed to examine the role of the testes and the pineal gland in photoperiodically induced daily torpor and body weight loss. Hamsters displayed a loss of body weight and daily torpor when exposed to a short-day photoperiod in a cold environment, but these phenomena did not occur in hamsters exposed to long days and cold. Testicular regression is probably a precondition for the display of torpor, since daily torpor was almost totally inhibited in hamsters which were exposed to short days and in which testosterone was administered from subcutaneous silicone elastomer implants. Nevertheless, decreased testosterone secretion alone is not a sufficient condition for induction of daily torpor, since torpor was rarely observed in hamsters exposed to long days, even after castration. In addition to decreased testicular activity, the pineal gland is also involved in establishing conditions for torpor. Thus, pinealectomy prevented the display of torpor by castrated hamsters exposed to short days. Body weight changes were also found to be influenced by both testicular hormone and pineal activity. These observations indicate that the pineal gland is involved, as a part of the photoperiodic mechanism, in regulating a variety of physiological events and that some of these actions of the pineal are independent of its extensively described actions on the reproductive axis.

J. Endocr. (1985) 106, 367–375
Validation of a sensitive direct assay for melatonin for investigation of circadian rhythms in different species
Authors: Webley G. E. , Mehl H. , Willey K. P.
Published: December 2008

The role of melatonin in animals which do not show marked seasonal changes in reproduction is disputed, in part because of the wide variation in reported concentrations. One reason for this may be the difficulties associated with the measurement of low molar concentrations of melatonin and the presence of a wide variety of potentially cross-reacting substances. The availability of a high affinity antiserum has allowed an assay, with low cross-reactivity and good sensitivity, to be established for the direct measurement of melatonin in a wide range of biological fluids, in particular serum, plasma and follicular fluid from man and rat. The high affinity of the antiserum enabled a tritium label of high specific activity to be used, removing the problems associated with the iodination of a small molecular weight compound. Melatonin concentrations in the assay were evaluated by four different methods: UV absorbance, gas chromatography, comparison of the immunoreactive concentrations of the label with the expected concentration by dilution and by comparison with a previously established assay which uses the same antiserum.

Melatonin was measured in serum from twelve healthy women over two 24-h periods; eight women with normal menstrual cycles and four taking the contraceptive pill. Concentrations were found to range from 19·8 to 215 pmol/l during the day in both groups. In women with normal menstrual cycles peak concentrations of 513·2 ± 54·1 (s.e.m.) pmol/l were recorded at 04.00 h, whereas higher concentrations were found in women taking the pill, reaching a peak of 849·12 ± 21·8 (s.e.m.) pmol/l at 04.00 h. Similar melatonin concentrations were measured in the two 24-h periods.

In the adult male rat, serum melatonin concentrations varied from 92·66 ± 37·9 (s.e.m.) pmol/l at 12.00 h, rising to 526 ± 55·6 (s.e.m.) pmol/l at 04.00 h.

This direct assay is more practical and robust than the assays currently available. The careful validation of assay characteristics allows its widespread use in both clinical studies and the investigation of the role of melatonin in different species.

J. Endocr. (1985) 106, 387–394
POSSIBLE ROLE OF UTERINE CONTRACTIONS IN THE SHORT-TERM FLUCTUATIONS OF PLASMA ACTH CONCENTRATION IN FETAL SHEEP
Authors: Lye S.J. , Wlodek M.E. , Challis J.R.G.
Published: December 2008

Uterine contractions, induced by the administration of oxytocin to sheep between d 123-144 of pregnancy, were associated with a mean transient decrease in fetal PaO2 of 2.8 mm Hg within 5 min. These changes were associated with a rapid increase in the concentration of ACTH in fetal plasma. There was a significant (P<0.05) increase in the percentage change (+40 to +47%) over basal ACTH levels in fetal plasma at +5, +15 and +20 min after oxytocin. Administration of saline had no significant effect on intrauterine pressure, fetal PaO2 or fetal plasma ACTH levels. We speculate that increases in uterine activity and/or transient decreases in fetal PaO2 may contribute to short-term fluctuations in plasma ACTH in fetal sheep.
Homologous ligand regulation of gonadotrophin-releasing hormone receptors in vivo: relationship to gonadotrophin secretion and gonadal steroids
Authors: Naik S. I. , Saade G. , Detta A. , Clayton R. N.
Published: December 2008

A single injection of gonadotrophin-releasing hormone (GnRH) (60 ng s.c., 42·9 nmol) induced biphasic GnRH receptor regulation in normal intact adult female mice. A transient 22% receptor decrease occurred 30–60 min after injection of GnRH when peak serum decapeptide concentrations were reached (137 ± 41 (s.e.m.) ng/l). This GnRH receptor decrease occurred shortly after the peak serum LH values at 15–30 min. The subsequent rapid (within 1 h) return of GnRH receptor levels to normal suggested transient receptor occupancy by GnRH rather than true receptor loss. At 8 h after injection of GnRH a significant 35% increase in GnRH receptors was consistently observed, when serum GnRH levels were undetectable and serum LH had returned to basal levels. This receptor increase was not due to increased receptor affinity, and was prevented by a non-specific protein synthesis inhibitor.

Ovariectomy, which caused a 50% fall in GnRH receptors (59·4 ± 4·9 fmol/pituitary gland in intact controls; 26·9 ± 2·6 in ovariectomized mice) abolished the induction by GnRH of its own receptors, although the initial transient decrease occurred over the period of the acute serum LH and FSH rise. Despite a 50% reduction in GnRH receptors in ovariectomized mice, increased serum gonadotrophin levels and responsiveness to GnRH were maintained, indicating dissociation between receptor changes and gonadotrophin levels.

No GnRH receptor up-regulation was observed 8 h after a single GnRH injection (60 ng s.c.) in either intact or orchidectomized normal male mice. However, the same treatment doubled GnRH receptors in GnRH-deficient (hpg) female mice.

While GnRH appears to up-regulate its own receptors by a direct action on pituitary gonadotrophs in the GnRH-deficient mouse its action in the normal female mouse pituitary appears secondary to stimulation of a gonadal product, presumably oestrogens.

J. Endocr. (1985) 107, 41–47
Ovarian cyclic GMP concentration and guanylate cyclase activity in immature rats after treatment with pregnant mare serum gonadotrophin
Authors: Patwardhan V. V. , Lanthier A.
Published: December 2008

We have previously reported that the LH-induced decrease in the concentration of ovarian cyclic GMP (cGMP) in the rabbit was accompanied by a drop in ovarian guanylate cyclase activity. The present experiments were carried out to see if the increase in cGMP concentration that occurs in immature rat ovaries after stimulation with pregnant mare serum gonadotrophin (PMSG) is also accompanied by changes in guanylate cyclase activity. Total ovarian cGMP, along with ovarian weight, was found to be increased at 16 h after PMSG treatment. Ovarian concentrations of cGMP, however, increased only after that period (at 20, 24 and 48 h) and the increase was progressive. Guanylate cyclase activity was found in both the cytosol and 100 000 g particulate fractions of the immature rat ovaries. Forty-three hours after PMSG treatment, activity in the particulate fraction was found to be significantly increased. This increase in guanylate cyclase activity was also found at 20 h but not at 16 h. Thus, the increase in ovarian cGMP concentration in immature rats after PMSG treatment was accompanied by increased guanylate cyclase activity.

J. Endocr. (1985) 107, 77–81
Evidence for pituitary regulation of placental lactogen in the rat
Authors: Voogt J. L. , Pakrasi P. L. , Johnson D. C. , Dey S. K.
Published: December 2008

The present studies examined whether the pituitary hormones, particularly prolactin, have any role in the regulation of rat placental lactogen (rPL) secretion. Total rPL was measured using a lymphoma cell bioassay. Hypophysectomy on day 13 of pregnancy increased total serum rPL levels above those of intact control rats and delayed for 3 days the decline in rPL usually seen by day 14. To test the effect of early hypophysectomy on rPL secretion, a delayed implantation model was used. Hypophysectomy was carried out on day 3, progesterone (2 mg) was given daily until day 8 and oestrone (1·0 μg) was given on day 8. This initiated implantation on day 9, which is 4 days later than normal. Rats hypophysectomized on day 3 had high serum levels of rPL (10–13 mg/l) 7 days after initiation of implantation compared with control values of 2–3 mg/l, and these levels remained raised for the duration of the experiment. Termination of maintenance injections of steroids did not affect the high levels of rPL for several days, even though there was fetal and placental resorption. When a pair of anterior pituitaries was transplanted under the kidney capsule on day 13 (day 9 of development) of rats hypophysectomized on day 3, serum rPL levels still increased for the next 3 days. However, unlike similarly treated rats not receiving transplants, rPL levels fell rapidly thereafter and were only 5% of those in control animals 1 week later. Only the intact rats and those hypophysectomized either on day 3 or 13 and given daily maintenance doses of steroids had normal pregnancies; the other two groups in which steroid injections were stopped on day 15 showed various degrees of resorption or abortion. It is suggested that the pituitary, possibly because of its prolactin secretion, is important in the regulation of rPL secretion.

J. Endocr. (1985) 107, 121–126
Steroid concentrations in fluid from human ovarian antral follicles during pregnancy
Authors: Westergaard L. , McNatty K. P. , Christensen I. J.
Published: December 2008

Steroid concentrations in fluid from 138 ovarian antral follicles obtained from 30 pregnant women were measured and compared with those in aspirates of 151 follicles of similar size (i.e. diameter 2–6 mm) from 61 non-pregnant women who had normal regular menstruations. The follicles were classified as healthy or atretic by flow cytometric DNA measurement of the granulosa cells contained in the follicular fluid aspirate.

Nine (7%) of the follicles from pregnant women and 21 (14%) of those from non-pregnant women were healthy, and the remainder atretic (P>0·05). Androstenedione was the most abundant steroid in all follicles. Mean progesterone levels in follicular fluid from pregnant women were significantly (P<0·05) higher than in follicular fluid from non-pregnant women. In pregnant women progesterone levels were significantly (P<0·01) higher in fluid from healthy than from atretic follicles. In contrast, no significant differences in steroid concentrations were found between fluid from healthy and atretic follicles in non-pregnant women.

We conclude that antral ovarian follicles may develop normally to a diameter of around 6 mm during the third trimester of human pregnancy. We also conclude that these follicles accumulate steroids in the follicular fluid in amounts which equal those found in follicles of similar size in the ovaries of non-pregnant women, but that the composition of intrafollicular steroids during pregnancy is modified towards higher concentration of progesterone. The reason for this increased intrafollicular progesterone level is unclear.

J. Endocr. (1985) 107, 133–136