bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence for reorganization of the neuroendocrine centres regulating pulsatile LH secretion in rats receiving neonatal monosodium-l-glutamate treatment
Authors: Rose P. A. , Weick R. F.
Published: December 2008

Previous research has shown that the combination of anterior hypothalamic deafferentation (AHD) and electrolytic lesions of the anterior part of the arcuate nuclei blocks pulsatile LH secretion in ovariectomized rats, but that neither lesion alone was effective. Furthermore, the combination of AHD with arcuate lesions produced by neonatal treatment with monosodium-l-glutamate (MSG) does not block pulsatile LH release. To distinguish between the various possible reasons for this result, AHD and electrolytic lesions of the arcuate nuclei were combined in rats which had been treated neonatally with MSG or saline of equal osmolarity. One week after brain surgery, venous catheters were installed and blood samples taken at 5-min intervals for up to 3 h for assay of plasma LH. Rats treated with MSG and bearing AHD and electrolytic lesions of the arcuate nuclei continued to show pulsatile secretion of LH. Where the electrolytic lesions were posterior and dorsal to the anterior arcuate nuclei, however, LH release was blocked whether AHD was performed or not, but only in rats treated with MSG. None of the lesion combinations blocked pulsatile LH secretion in rats treated with saline. These results suggest that neonatal MSG treatment leads to a reorganization of the hypothalamus such that the role normally played by the arcuate nuclei in the regulation of pulsatile LH secretion is taken over by other hypothalamic structures.

J. Endocr. (1987) 113, 261–269
Difference in the response of follicular maturation and ovulation between early and late lactating rats after removal of the litter
Authors: Taya K. , Sasamoto S.
Published: December 2008

The mechanisms responsible for the 24-h difference in the time of the next ovulation after litter removal between early and late lactating rats were investigated.

At 11.00 h on day 5 of lactation, concentrations of oestradiol-17β and inhibin activity in ovarian venous plasma were lower than those on day 17, corresponding to the absence of healthy Graafian follicles. After removal of the litter on day 5 of lactation a small surge of FSH with a steady increase in basal levels of LH occurred to initiate follicular maturation, and ovulation occurred 4 days later. After removal of the litter on day 17 of lactation a surge of FSH was not observed, due to high levels of inhibin activity in ovarian venous plasma, until the time of preovulatory surges of gonadotrophin which occurred 2 days later and resulted in ovulation the next morning. Prolactin concentrations decreased similarly in both groups abruptly after removal of the litter. A decrease in plasma concentrations of progesterone occurred 42 h after removal of the litter on day 5, though it occurred 18 h after removal of the litter on day 17.

These results indicate that the 24-h delay of ovulation after litter removal on day 5 of lactation, as compared with the time of ovulation after litter removal on day 17, is due probably to the absence of healthy antral follicles and high activity of corpora lutea secreting progesterone at the time of litter removal.

J. Endocr. (1987) 113, 271–276
Effects of human placental lactogen and growth hormone on the production of insulin and somatomedin C/insulin-like growth factor I by human fetal pancreas in tissue culture
Authors: Swenne I. , Hill D. J. , Strain A. J. , Milner R. D. G.
Published: December 2008

We have investigated the ability of glucose, human GH and human placental lactogen (hPL) to alter the content and release of somatomedin C/insulin-like growth factor I (SM-C/IGF-I), and the biosynthesis, content and release of insulin from cultured human fetal pancreas. Fetal pancreatic explants obtained from glands following prostaglandin-induced abortion between 12 and 21 weeks of gestation were maintained in free-floating culture for 3–5 days before the experiments. The explants were then cultured for 3 days in medium containing either 2·7 or 16·7 mmol glucose/l with or without GH (4·5 or 45·5 nmol/l) or hPL (4·6 or 46·5 nmol/l). Serum-free medium from the final 24 h of culture was collected and SM-C/IGF-I and insulin were measured radioimmunologically in both conditioned medium and tissue explants extracted with acid ethanol. Insulin biosynthesis, determined by immunoprecipitation of [3H]leucine incorporated into insulin, was not significantly altered by any experimental variable. Incubation in the presence of 16·7 mmol glucose/l caused an increase of insulin release from explants, but had no consistent action on insulin content, compared with medium containing 2·7 mmol glucose/l. The pancreatic content and release of SM-C/IGF-I were independent of these glucose concentrations. Neither GH nor hPL altered insulin or SM-C/IGF-I content or release in the presence of the lower glucose concentration. At the higher glucose concentration, 45·5 nmol GH/1 did not alter insulin release but caused a significant increase in SM-C/IGF-I content. When present with 16·7 mmol glucose/l hPL (46·5 nmol/l) promoted significant increases in both insulin content and release (59 and 47% respectively) and significantly increased pancreatic SM-C/IGF-I content and release (114and 117% respectively).

The results suggest that, during tissue culture, glucose enhances the insulin output of human fetal pancreatic explants obtained in the second trimester. The ability of hPL to modulate B-cell function raises the possibility that this peptide may contribute to pancreatic development during fetal life and to total fetal body growth by increasing insulin production.

J. Endocr. (1987) 113, 297–303
Subcellular distribution of [3H]oestradiol-17β and salt resistance of nuclear oestrogen complexes in the rat uterus after in-vivo administration of [3H]oestradiol-17β
Authors: Batra S.
Published: December 2008

The distribution of injected [3H]oestradiol-17β into nuclear and post-nuclear fractions as well as resistance to KCl (0·6 mol/l) extraction of nuclear oestrogen-binding sites in the rat uterus were studied. Both ovariectomized untreated and oestrogen-treated rats were used. One hour after injection of [3H]oestradiol into ovariectomized rats, 373 and 195 fmol/100 mg uterus were recovered in the nuclear and post-nuclear fractions respectively. About 17% of the nuclear-associated [3H]oestradiol was resistant to KCl extraction. After 18 h, the amount of [3H]oestradiol decreased to about 30% of that found after 1 h, and about 23% of nuclear complex remained resistant to extraction. In cardiac tissue, practically no [3H]oestradiol accumulated in the nuclear fractions and the amount recovered in post-nuclear fractions was about one-third of that in the uterine post-nuclear fractions. In the ovariectomized oestrogen-treated rats the distribution of [3H]oestradiol in nuclear and post-nuclear fractions was very similar and the proportion of the total nuclear fraction inextractable by KCl slightly higher (26%) than in untreated rats. After 18 h, while measurable amounts of [3H]oestradiol were found in post-nuclear fractions, no radioactivity was detected in the nuclear fraction. The results demonstrate the existence of salt-resistant nuclear oestrogen-binding sites in the mature ovariectomized rat uterus in vivo. Further, oestrogenization of ovariectomized rats did not significantly influence the amount or proportion of salt-resistant nuclear sites.

J. Endocr. (1987) 113, 333–337
Inhibition of the response of thyrotrophin to thyrotrophin-releasing hormone by thyroxine in hypothyroid rats treated with iopanoic acid: evidence suggesting an intrinsic biological activity of thyroxine without prior conversion to 3,5,3′-tri-iodothyronine
Authors: Boado R. J. , Zaninovich A. A.
Published: December 2008

The effects of a physiological replacement dose of thyroxine (T4) on the response of plasma TSH to TRH in hypothyroid rats were studied. Animals were treated with iopanoic acid (IOP; 5 mg/100 g body weight) or vehicle 24, 12 and 1·5 h before the experiment. Thereafter, 800 ng T4/100 g body weight were administered i.v. and 20 min later 1 μg TRH/100 g body weight was injected i.v. In control rats the basal concentration of TSH was 1450 ± 300 (s.e.m.) mu./l. The plasma concentration of TSH 10 min after injection of TRH increased to 167 ± 14% of the mean basal value (P < 0·001). The injection of T4 significantly (P < 0·05) reduced the TSH response to TRH in both IOP-treated (118 ± 15%) and vehicle-treated (108 ± 15%) rats compared with untreated controls. Tri-iodothyronine (T3) was undetectable in the plasma of all rats, whereas the plasma concentration of T4 was 121 ± 19 nmol/l in IOP-treated and 139 ± 23 nmol/l in vehicle-treated rats 30 min after injection of 800 ng T4/100 g body weight. In pituitary cells of control rats, cytoplasmic radioactivity 30 min after injection of [125I]T4 was 1·28 ± 0·13 × 10−2% (76 ± 6% T4 and 17 ± 3% T3), whereas that in nuclei reached 0·42 ± 0·36 × 10−2% (51 ± 4% T4 and 28 ± 3% T3) of the injected dose. In IOP-treated rats there was an increase in total cytoplasmic radioactivity (P < 0·05), with a decreased proportion of [125I]T3 (0·12 ± 0·07%; P < 0·01), whereas nuclear T3 was significantly (P < 0·005) lower than in controls (0·057 ± 0·025 vs 0·22 ± 0·022 pmol T3/mg DNA). Administration of 25 μg unlabelled T4 along with the tracer reduced cytoplasmic radioactivity in both control and IOP-treated rats (P < 0·05), without a detectable change in nuclear radioactivity. The results suggest that T4, at a physiological replacement dose, possesses an intrinsic capacity to regulate secretion of TSH following administration of TRH to hypothyroid rats.

J. Endocr. (1987) 113, 349–354
Receptors for lactogenic hormones in the porcine corpus luteum: properties and luteal phase concentrations
Authors: Bramley T. A. , Menzies G. S.
Published: December 2008

Homogenates of pig corpora lutea contained specific, high-affinity receptors for ovine prolactin (oPRL) and human GH (hGH). Specific hormone binding was enhanced by divalent metal ions, but only when included in the binding reaction. Divalent metal ions did not act by increasing the recovery of bound hormone by low-speed centrifugation, but appeared to promote the formation of a more stable hormone– receptor complex. Both oPRL and hGH tracers were bound in similar amounts and with similar affinities by pig luteal homogenates and the concentrations of either unlabelled hormone required to displace specific binding of either tracer by 50% were identical.

In contrast, 125I-labelled oGH failed to bind to pig luteal homogenates and oGH competed poorly for hGH or oPRL binding. Only hormones with prolactin-like activity competed for 125I-labelled oPRL binding.

Specific prolactin binding was low in recently ovulated and early luteal phase corpora lutea, increased significantly in the mid-luteal phase and declined once more in the late luteal phase. Receptor concentrations increased with increasing gestational age.

J. Endocr. (1987) 113, 355–364
Receptors for lactogenic hormones in the ovine corpus luteum. I: A major discrepancy in the specific binding of radiolabelled ovine prolactin and human growth hormone
Authors: Bramley T. A. , Menzies G. S. , McNeilly A. S. , Friesen H. G.
Published: December 2008

The characteristics of the binding of 125I-labelled human GH (hGH) and ovine prolactin (oPRL) were studied in the ovine corpus luteum. Although oPRL is the homologous ligand for sheep lactogenic receptors, its binding was significantly and consistently lower than that of 125I-labelled hGH. This was not due to iodination damage of oPRL since: (1) 125I-labelled oPRL tracers which bound poorly relative to 125I-labelled hGH in the ovine corpus luteum were equipotent in the pig and rat corpus luteum, (2) the differences between 125I-labelled hGH and oPRL binding persisted with tracers of equivalent biopotency and (3) the iodination procedure affected neither oPRL bioactivity in the Nb2 tumour assay nor its binding activity with ovine corpus luteum receptors.

Ovine luteal receptors were specific for lactogenic hormones. The specific binding of 125I-labelled hGH or oPRL could be inhibited completely by incubation with either unlabelled hormone, with similar potencies. However, oGH inhibited binding only at much higher concentrations, consistent with its known contamination with oPRL. Moreover, 125I-labelled oGH was not bound specifically to sheep luteal tissue.

Fractionation of sheep luteal homogenates on sucrose density gradients (with or without cell-surface membrane perturbation by digitonin) demonstrated that binding of 125I-labelled hGH and 125I-labelled oPRL peaked in the same regions of the gradients, coincident with a number of luteal cell-surface membrane markers.

We conclude that the marked discrepancy between the binding of hGH and oPRL tracers by sheep luteal tissue was not due to iodination damage of oPRL, binding of 125I-labelled hGH to somatogenic receptors or differential binding to luteal cell-surface versus intracellular receptors.

J. Endocr. (1987) 113, 365–374
Effects of ovarian inhibin on pulsatile release of gonadotrophins and secretion of LHRH in ovariectomized rats: evidence against a central action of inhibin
Authors: de Greef W. J. , Eilers G. A. M. , de Koning J. , Karels B. , de Jong F. H.
Published: December 2008

Intraperitoneal administration of bovine follicular fluid (bFF) decreased plasma concentrations of FSH in ovariectomized rats after 2–3 h, while plasma LH and prolactin were unaffected. In untreated ovariectomized animals the concentrations of these hormones were found to show pulsatile variations. Concomitant occurrence of peak values of LH and FSH was found in about 40% of the pulses. No pulses of FSH were observed after i.p. treatment with bFF or partly purified preparations of inhibin from bFF, but the pulsatile release of LH and prolactin remained similar. Infusion of bFF into the lateral ventricle of the brain did not alter the concentrations of FSH, whereas administration of bFF into the pituitary gland diminished the plasma concentrations of FSH.

Anaesthesia (urethane plus xylazine) did not prevent the occurrence of the pulses of FSH and LH, but it reduced the pulse amplitude and clearance. During this anaesthesia, the concentrations of LHRH in the hypophysial stalk plasma decreased by 30% after administration of bFF, but did not alter after treatment with partly purified preparations of inhibin. It is concluded that the inhibin-like activity in bFF suppresses pulsatile FSH secretion in ovariectomized rats by an action on the pituitary gland, but has no effect on the pulsatile release of LH and prolactin.

J. Endocr. (1987) 113, 449–455
Biopotency and site of action of drugs affecting testicular steroidogenesis
Authors: Lambert A. , Mitchell R. , Robertson W. R.
Published: December 2008

The effect of etomidate (an anaesthetic), epostane (WIN 32729; an inhibitor of ovarian and adrenal steroidogenesis) and cyproterone acetate (an antiandrogen) on testosterone secretion from mouse Leydig cells stimulated with LH (5 i.u./l) was tested. The concentration of drug which inhibited testosterone secretion by 50% was 11·5±1·1 (s.e.m.) μmol/l for cyproterone acetate, 1·2 ± 0·2 μmol/l for etomidate and 0·23 ± 0·03 μmol/l for epostane.

The effect of all three drugs on testicular steroidogenesis was completely reversible. Thus testicular cells which had been washed after exposure to a >95% inhibitory dose of drug responded in a similar manner to hormone stimulation as cells similarly washed and which had not been exposed to the drug.

The sites of the antisteroidogenic effect of epostane, etomidate and cyproterone acetate were established using a method based on the sequential stimulation by the exogenous precursor steroids of the various steps leading to the biosynthesis of testosterone. It was concluded that etomidate acts at the sequence between LH binding and pregnenolone production, epostane acts at 3β-hydroxysteroid dehydrogenase and cyproterone acetate inhibits 3β-hydroxysteroid dehydrogenase and C17,20-lyase.

J. Endocr. (1987) 113, 457–461
HYPOTHALAMO-HYPOPHYSIAL BLOOD FLOW: A NOVEL CONTROL MECHANISM IN PITUITARY FUNCTION?
Authors: Eckland D.J.A. , Lightman S.L.
Published: December 2008

The flow rate of portal plasma was measured during hypothalamo-hypophysial portal sampling in the rat using a modified Worthington-Fink technique. In rats rendered hypothyroid with propylthiouracil, there was a significant 140% increase in portal plasma flow. Median eminence stimulation also increased portal plasma flow by 41%. Orchidectomy and adrenalectomy had no effects on plasma flow. Modification of flow rate in the hypothalamo-hypophysial vascular bed may represent a further mechanism involved in the control of pituitary function.
Noradrenergic stimulation of serotonin release from rat pineal glands in vitro
Authors: Aloyo V. J. , Walker R. F.
Published: December 2008

The pharmacodynamics of serotonin (5-hydroxytryptamine; 5-HT) uptake and release were studied in rat pineal glands. Initially, uptake was tested by incubating pineals with several concentrations of [3H]5-HT. The incubation media also contained [14C]mannitol to which cells are impermeable. Since [14C]mannitol accumulates only in extracellular spaces, the radio-labelled sugar was used to determine the differential distribution of [3H]5-HT in pineal compartments.

Intracellular accumulation of 3H in pineal glands increased linearly as a function of time for [3H]5-HT concentrations ranging from 1 to 10 μmol/l. The ratio of 3H to 14C also increased for the same time-interval, indicating that the glands accumulated [3H]5-HT preferentially in non-extracellular spaces. [3H]5-HT accumulated in pineal glands which were denervated for more than 7 days before testing, suggesting that uptake is not restricted to adrenergic terminals but also occurs in pinealocytes.

In addition to uptake, spontaneous and noradrenaline-stimulated release of [3H]5-HT was tested in perifusion and/or step-transfer systems. Spontaneous release of [3H]5-HT was biphasic consisting of rapid and slower efflux phases. In contrast, release of [14C]mannitol was monophasic, characterized exclusively by rapid efflux. Since [14C]mannitol does not enter cells, the rapid and slower phases of [3H]5-HT efflux may represent release from pineal extracellular and intracellular compartments respectively. The identity of [3H]5-HT in pineal glands and perifusion media was confirmed by thin-layer chromatography. When l-noradrenaline was added to the perifusion media, [3H]5-HT efflux during the slower phase of release was significantly increased above the non-stimulated state. In contrast, d-noradrenaline was significantly less effective than l-noradrenaline in releasing [3H]5-HT. Noradrenaline also stimulated [3H]5-HT release from denervated glands, suggesting that pinealocytes secrete 5-HT in response to noradrenergic signals.

Since the pineal is innervated by fibres of the sympathetic division of the autonomic nervous system, differential release of 5-HT may occur in response to changing levels of glandular noradrenaline.

J. Endocr. (1987) 114, 3–9
Effect of oestrogen treatment on gonadotroph function in adult male rats
Authors: Saade G. , London D. R. , Clayton R. N.
Published: December 2008

The effect of oestradiol-17β on the hypothalamo-pituitary axis of intact adult male rats was studied. A single injection of oestradiol did not change the serum LH response to gonadotrophin-releasing hormone (GnRH) 48 h or 7 days after the injection, while administration of oestrogen over 66 days suppressed basal serum LH to <3·1 μg/l and did not enhance the LH response to GnRH at any time.

Treatment of ovariectomized rats with oestradiol capsules, however, enhanced the LH response to GnRH on days 3 and 14 of the treatment as compared with the control group (P<0·02 and P<0·05 respectively). Long-term treatment with oestradiol suppressed intrapituitary LH and FSH contents as well as pituitary GnRH receptors (P<0·0004, P<0·005 and P<0·001 respectively), whereas serum and intrapituitary prolactin levels were increased. To exclude the possible inhibitory effect of hyperprolactinaemia on LH responsiveness to GnRH, oestradiol-implanted rats were treated with bromocriptine. This prevented the rise in serum prolactin, but failed to enhance the LH response to GnRH.

Neither short- nor long-term treatment with oestradiol given under conditions shown to be effective in female animals stimulated the hypothalamo-pituitary-gonadotrophin axis in adult male rats.

J. Endocr. (1987) 114,95–101
Vasoactive intestinal peptide increases intracellular free calcium in rat and human pituitary tumour cells in vitro
Authors: Prysor-Jones R. A. , Silverlight J. J. , Jenkins J. S.
Published: December 2008

Prolactin secretion by a human pituitary tumour cell line produced in our laboratory was stimulated by TRH, vasoactive intestinal peptide (VIP) and epithelial growth factor (EGF). All raised the intracellular concentration of free calcium (Ca2+i) of cells loaded with a fluorescent quinoline Ca2+ indicator in suspension, but the effect of TRH was much more rapid and less prolonged than that of VIP and EGF. Both TRH and VIP also increased Ca2+i in GH3 rat pituitary tumour cells, but in this cell line the effect of VIP was only found in attached cells grown on cover-slips. In both human and rat cell lines, the increase in Ca2+i produced by TRH was independent of extracellular calcium, whereas this was a requirement for the action of VIP and EGF. It is concluded that the prolactin secretogogues, VIP and probably EGF, increase Ca2+i through an effect on plasma membrane calcium channels and that this effect differs from that of TRH.

J. Endocr. (1987) 114, 119–123
Visualization of X-chromosome inactivation mosaicism of Tfm gene in XTfm/X+ heterozygous female mice
Authors: Takeda H. , Suzuki M. , Lasnitzki I. , Mizuno T.
Published: December 2008

The testicular feminization (Tfm) locus, which produces a deficiency in androgen receptors, is located on the X-chromosome. Steroid autoradiographic techniques were used to demonstrate the mosaicism of the X-chromosome inactivation in two androgen target tissues of XTfm/X+ heterozygous female mice.

In the mesenchyme of urogenital sinuses of wild-type female fetuses (X+/X+), more than 95% of the cells were androgen-receptor positive (labelled with [3H]testosterone) while in that of heterozygous fetuses (XTfm/X+), about half of the cells were receptor positive (Tfm gene inactive). Statistical analysis of coherent clone size was applied to the heterozygous mesenchyme of the urogenital sinus and the coherent clone size of receptor-positive cells was estimated to be two or three cells per clone. This small clone size suggests that considerable cell mixing occurred in the tissue during embryonic development.

Androgen binding in the mammary gland rudiments was restricted to the mesenchymal cells only in close vicinity to the epithelial mammary bud. In the wild-type rudiments most of the mesenchymal cells beneath the epithelium were receptor positive, while in heterozygous rudiments, receptor-positive and -negative cells intermingled. This observation suggests that in the wild-type mammary gland rudiments the epithelial bud may induce the formation of androgen receptors in adjacent mesenchymal cells rather than attract pre-existing receptor-rich mesenchymal cells.

J. Endocr. (1987) 114, 125–129
Change of mosaic pattern by androgens during prostatic bud formation in XTfm/X+ heterozygous female mice
Authors: Takeda H. , Lasnitzki I. , Mizuno T.
Published: December 2008

The testicular feminization (Tfm) gene, which is characterized by a deficiency in androgen receptors, is located on the X-chromosome. Using steroid autoradiography, the mosaicism of the Tfm gene has been demonstrated in the androgen target tissues of XTfm/X+ heterozygous female mouse fetuses and the effects of androgens on the mosaic pattern analysed.

In the mesenchyme of urogenital sinuses of wild-type female fetuses (X+/X+), more than 95% of the cells were androgen-receptor positive (labelled with [3H]testosterone) while in that of heterozygous fetuses (XTfm/X+), only half of the cells were receptor positive (Tfm gene inactive), and receptor-positive cells and -negative cells formed small irregular patches. When the heterozygous sinuses were cultured in vitro in the presence of androgens, the sinuses underwent male sexual development and formed epithelial buds (prostate gland rudiments) projecting into the surrounding mesenchyme. Autoradiographic analysis revealed that the mosaicism of the mesenchyme disappeared around the developing epithelial buds: almost all the mesenchymal cells in close vicinity to the buds were receptor positive while in the outer layers receptor-positive and -negative cells coexisted. The proportion of receptor-positive cells was greatly increased in the mesenchyme beneath the non-budding area of the sinus epithelium. This androgen-induced increase was observed before the onset of bud formation. The results obtained in the thymidine incorporation experiments suggest that the increase of receptor-positive cells beneath the sinus epithelium might be explained by the migratory behaviour of the androgen-incorporating cells rather than by their selective proliferation.

J. Endocr. (1987) 114, 131–137
Patterns of LH and FSH in men during high-frequency blood sampling
Authors: Scheele F. , Lambalk C. B. , Schoemaker J. , van Kessel H. , de Koning J. , van Dieten J. A. M. J. , van Rees G. P. , de Vries Robles-Korsen T. J. M.
Published: December 2008

The aim of the study was to test the hypothesis that in serial determinations of concentrations of LH and FSH involving blood samples taken every minute, the observed pulses of LH and FSH which last less than 3–4 min might not be a physiological phenomenon but part of the 'noise' of the radioimmunoassay or blood-sampling technique.

Blood was sampled every minute for a period of 90 min in six men. During the first 45 min, blood was sampled by means of vacuum tubes only. During the second 45 min, sampling took place with a syringe via a rubber stopper, either using a tourniquet (n = 3) or flushing the cannula with heparinized saline.

Three criteria were used to identify variations in the patterns of LH and FSH as true hormonal changes. First, a threshold was used which had to be exceeded by the difference between nadir and maximum values before a pulse could be identified. An average of approximately six pulses per 90 min was found in both the LH and FSH series. The majority of these pulses lasted less than 3–4 min. In two subjects, larger LH pulses of longer duration were measured. Secondly, differences between duplicate measurements of nadir and/or maximum values of more than one-third of the amplitude of a pulse were considered unacceptable. This involved about 75% of the pulses. Thirdly, the reproducibility of the hormone variations was estimated. In one subject, concentrations of LH were measured four times in four separate assays. Measurement of FSH concentrations in this subject and of LH and FSH in the samples from the other five subjects were repeated once again, but only in those parts of the series of samples which had shown hormone variations beyond the threshold composed of acceptable duplicate measurements. Only the larger variations of longer duration, as found earlier in two of the LH series, were reproducible.

The different blood-sampling techniques used had no significant influence on the frequency of pulses.

It was concluded that a rapid, small amplitude, pulsatile pattern of release of LH and FSH is probably not present in men or is obscured by limitations of current techniques of radioimmunoassay.

J. Endocr. (1987) 114, 153–160
Control of magnocellular oxytocin neurones by the region anterior and ventral to the third ventricle (AV3V region) in rats
Authors: Blackburn R. E. , Leng G. , Russell J. A.
Published: December 2008

The involvement of the region anterior and ventral to the third ventricle (AV3V region) in the control of oxytocin release was investigated using electrical stimulation and electrolytic lesioning techniques in the rat. Electrical stimulation (0·5 mA, 50 Hz, 15–25 s) of the AV3V region of lactating rats evoked a reproducible rise in intramammary pressure equivalent to that induced by 0·25–0·5 mu. oxytocin (i.v.). Increases in circulating concentrations of oxytocin, as determined by specific radioimmunoassay, confirmed that AV3V stimulation released oxytocin in both lactating and non-lactating rats. The increases in plasma oxytocin concentration evoked by electrical stimulation of the AV3V region were dependent upon intensity and frequency of stimulation, and electrode position. A significant (P<0·05) increase followed stimulation at 25 Hz and 0·1 mA, and a maximal response was obtained with 50 Hz and 1·0 mA. Stimulation of the area in and around the nucleus medianus produced the greatest rise in oxytocin secretion.

The milk-ejection reflex was not abolished after acute electrolytic ablation of the AV3V region in urethane-anaesthetized lactating rats, but electrolytic lesion of the AV3V region prevented the increase in plasma oxytocin concentration which normally followed an osmotic stimulus (1 ml 1·5 mol NaCl/l, i.p.),

These studies provide evidence that the AV3V region is a major source of excitatory afferents to oxytocin neurones; this input is essential for the osmoresponsiveness of these neurones but plays little role in the control of such neurones during reflex milk ejection.

J. Endocr. (1987) 114, 253–261
Thyroid hormone modulation of thyrotrophin-releasing hormone (TRH) and TRH-Gly levels in the male rat reproductive system
Authors: Pekary A. E. , Bhasin S. , Smith V. , Sugawara M. , Swerdloff R. S. , Hershman J. M.
Published: December 2008

Thyrotrophin-releasing hormone (TRH) occurs in high concentrations in the rat ventral prostate and its concentration is regulated in a positive dose–response manner by testosterone in castrated rats. α-Amidation of the tetrapeptide precursor, TRH-Gly, is a rate-limiting step in TRH biosynthesis. To investigate further the hormonal regulation of TRH biosynthesis in prostatic tissue, Sprague–Dawley rats of approximately 250 g were injected s.c. with either physiological saline or 3 mg propylthiouracil (PTU) daily for 5 days. The reproductive tissues were boiled in acetic acid (1 mol/l), dried and extracted with methanol. The methanol extracts were measured for TRH immunoreactivity (TRH-IR) and TRH-Gly-IR by radioimmunoassay. Hypothyroidism induced by PTU significantly increased TRH-IR and TRH-Gly-IR levels in prostate and testis and reduced these levels in epididymis but did not affect the serum concentrations of testosterone compared with those of controls. Corresponding changes in TRH and TRH-Gly in the rat prostate were established by high-pressure liquid chromatography. To control for possible pharmacological effects of PTU on TRH biosynthesis, additional experiments were carried out on castrated rats receiving testosterone replacement and treatment with PTU plus methimazole. Treatment with thyroxine (T4) significantly reduced the increase in prostatic TRH levels due to hypothyroidism, despite the drug-induced blockade of the conversion of T4 to tri-iodothyronine. These effects parallel similar observations made in rat spinal cord and pancreas. This study demonstrates that in the male rat reproductive system the levels of TRH and its immediate biosynthetic precursor, TRH-Gly, are regulated by thyroid hormones.

J. Endocr. (1987) 114, 271–277
Receptors for lactogenic hormones in the ovine corpus luteum. III: Inhibition of 125I-labelled human growth hormone binding by a high molecular weight factor in ovine corpus luteum cytosol
Authors: Bramley T. A. , Menzies G. S. , McNeilly A. S. , Friesen H. G.
Published: December 2008

Ovine luteal cytosol fractions inhibited the specific binding of 125I-labelled human GH and ovine prolactin (oPRL) to ovine luteal microsomes in a dose-dependent fashion. Inhibition was dependent on divalent cation concentrations, and was abolished by divalent metal ion chelating agents or by boiling. Inhibition was not due to ionic strength or salt effects on hormone binding, the release of endogenously bound oPRL into the cytosol fraction during tissue disruption and fractionation, or the presence of a soluble (or solubilized) lactogenic receptor in ovine cytosol preparations. Gel chromatography of cytosol fractions gave a molecular weight for the inhibitor of approximately 50 000.

J. Endocr. (1987) 114, 383–389
Long-term in-vitro maintenance of growth hormone secretion from human somatotrophinomas with cortisol, and its effects on growth hormone-releasing factor
Authors: Daniels M. , White M. C. , Kendall-Taylor P.
Published: December 2008

The effect of cortisol (206 nmol/l) on GH secretion from enzymatically dispersed human somatotrophinoma cells in long-term culture was studied using adenomas from 13 patients with acromegaly. Basal GH secretion from cultures of three out of five tumours measured during periods of 4 hours declined to < 10 μu. GH/culture within 21 days. Secretion from two other tumours measured during 24 h also declined but GH concentrations were still readily detectable (> 100 μu./culture) by 28 or 58 days after cell dispersal. The decline in GH secretion was reversed in all seven tumours when cultures were maintained in cortisol-supplemented medium (CM), 4-h secretion rates being increased or retained at ≥ 100 μu./culture for as long as the studies were continued (range 18–291 days), and 24-h secretion rates at > 1000 μu./culture (range 28–58 days). GH secretion and content from cultures of two additional somatotrophinomas were increased by treatment with cortisol for 5 or 9 days but there was no concomitant effect on cell number.

During long-term maintenance of cultures in CM (range 5–40 days), cortisol partially or completely blocked the 4-h GH response to a test dose of GH-releasing factor (GRF) (20 nmol/l) in five out of six tumours, and to a dose range of GRF (0·01–20 nmol/l) in two of them. However, when cultures maintained in this way (range 7–89 days) were rinsed and acute studies performed in medium without added cortisol, a significant (P < 0·05) stimulatory effect of GRF either at a test dose of 20 nmol/l or with a dose range (0·02–20 nmol/l) was observed in all six tumours tested.

In conclusion, long-term maintenance of human somatotrophinoma cells in medium supplemented with cortisol (206 nmol/l) prevents the early decline in GH secretion and extends their functional lifespan for several weeks or months. However, the stimulatory effects of GRF during such treatment are usually partially or completely blocked in the presence of medium containing cortisol but restored when cortisol is excluded from the medium.

J. Endocr. (1987) 114, 503–509
ACTH and adrenal aerobic glycolysis. I: Effects of O-nitrophenylsulphenyl and other ACTH analogues, vasoactive intestinal peptide and human parathyroid hormone(1–34) on lactic acid, steroid and cyclic AMP production by mouse adrenocortical cells
Authors: Hinson J. , Birmingham M. K.
Published: December 2008

The structural requirements in the ACTH molecule for evocation of the glycolytic response in suspensions of mouse adrenal cells were investigated by examining the effects of analogues containing modifications at positions 8,9 and 10 and of peptides containing homologies with the amino-terminal segment of ACTH. Introduction of a nitrophenylsulphenyl (NPS) group into the tryptophan moiety at position 9 of ACTH(1–24) greatly reduced both the potency and the capacity for maximal glycolytic response. It also virtually abolished cyclic AMP formation. In contrast, the capacity for a maximal steroidogenic response remained unimpaired in the NPS derivative, although steroidogenic potency was reduced to 0·4% of that of ACTH(1–24).

Replacement of the tryptophan moiety with phenylalanine had intermediate inhibitory effects on glycolysis and steroid output; replacement with alanine virtually abolished both these responses. Replacement of arginine in position 8 with lysine in the Phe9 analogue caused a fifty-fold increase in glycolytic potency, but rendered it steroidogenically inactive. Cyclic AMP production was abolished in the Ala9 analogue and greatly impaired in the Phe9 and Lys8,Phe9 analogues. Replacement of the glycine moiety in position 10 with l-alanine, d-alanine, β-alanine or α-aminoisobutyric acid had little or no effect on steroidogenic or glycolytic capacity, although potency was reduced with all substitutions excepting l-alanine.

Vasoactive intestinal peptide, which contains homologies with positions 3, 7, 15 and 16 of ACTH, proved completely inactive in dispersed mouse adrenal cells under our experimental conditions, in contrast to human parathyroid hormone(1–34) (hPTH (1–34)) which contains homologies with positions 3, 4, 5, 9 and 11 and was steroidogenic at the lowest concentration tested (0·1 nmol/l), eliciting an eleven-fold increase in steroid production, a response which might be physiologically relevant. It induced near maximal steroidogenesis at a concentration of 10 nmol/l, without affecting cyclic AMP production, and stimulated glycolysis at concentrations above 10 nmol/l, accompanied by a slight rise in cyclic AMP levels.

The examples of dissociation between glycolysis and steroidogenesis suggest that different receptors may mediate the two responses. The examples of increased steroidogenesis unaccompanied by a rise in cyclic AMP accord with the concept that cyclic AMP is not an obligatory second messenger for the steroidogenic response.

J. Endocr. (1987) 115, 61–69
Intratesticular injection of glycerol as a model for studying the quantitative relationship between spermatogenic damage and serum FSH
Authors: Weinbauer G. F. , Drobnitzky F. , Galhotra M. M. , Nieschlag E.
Published: December 2008

Intratesticular injection of glycerol (1,2,3-trihydroxypropane) was evaluated as an experimental approach for studying the relationship between spermatogenic activity, i.e. relative proportion of euspermatogenic and aspermatogenic tubules in the testis, and serum concentrations of FSH. Adult rats received a single intratesticular injection of either 400 μl distilled water or five different doses of glycerol, ranging from 25 to 400 μl, and were killed after 1 or 4 weeks respectively. Injection of glycerol caused focal destruction, so that the same testes contained intact tubules, tubules with spermatogonia and Sertoli cells only, and tubules devoid of cellular material. There was a close correlation (r=−0·896) between the frequency of intact tubules and the dose of glycerol, and a similarly strong correlation (r= −0·908) between acellular tubules and the dose of glycerol. A correlation existed between FSH and euspermatogenic tubules (r= −0·758, n=122) and, conversely, between FSH and acellular tubules (r=0·820, n=122), while the correlation for tubules containing spermatogonia and Sertoli cells was only marginal (r=− 0·055). The exact relationship between FSH and spermatogenic activity in the testis was used to estimate the minimal amount of spermatogenic tissue necessary for maintaining normal serum concentrations of FSH. Only the disruption of spermatogenesis in more than 30% of seminiferous tubules in each testis caused increased serum concentrations of FSH. Serum concentrations of FSH reached the range found in castrated rats when less than 1 % of tubules were intact.

These findings demonstrate (1) that a single intratesticular injection of glycerol is suitable for the study of the relationship between spermatogenic activity in the testis and FSH and (2) that a quantitative relationship exists between the extent of spermatogenic damage and serum concentrations of FSH. The observation that, in the rat, serum FSH has a diagnostic value for the extent of spermatogenic damage may be of importance for clinical evalution of testicular disorders.

J. Endocr. (1987) 115, 83–90
Structural plasticity in the rat supraoptic nucleus during gestation, post-partum lactation and suckling-induced pseudogestation and lactation
Authors: Montagnese C. M. , Poulain D. A. , Vincent J.-D. , Theodosis D. T.
Published: December 2008

In the supraoptic nucleus (SON) of parturient and lactating rats, large portions of the surface membranes of almost all oxytocinergic neurones are directly juxtaposed with no glial interposition. A significant number of the same neurones are also contacted by the same presynaptic terminal ('double' synapses).

Our present observations have revealed that direct appositions between adjacent neurones in the SON increase quite rapidly during the day before parturition. 'Double' synapses also become visible during late gestation, but they appear more progressively. Earlier studies have shown that 1 month after weaning, as in virgin rats, there are again very few appositions and 'double' synapses in the nucleus. We show here that the SON can remain structurally modified, and to the same degree, beyond normal weaning time so long as lactation is prolonged by renewing suckling litters. However, if the mothers are deprived of their pups immediately after birth, neuronal appositions disappear within 2 days and 'double' synapses by 10 days. In non-pregnant primiparous rats, continuous exposure to suckling litters leads to pseudogestation and eventually lactation (in 16–22 days). Examination of the SON in such animals revealed that the oxytocinergic system is already modified by day 12 of dioestrus; during suckling-induced lactation, the anatomical changes are identical to those seen during a normal post-partum lactation.

These observations indicate that neither gestation nor suckling alone are indispensable for the anatomical reorganization of the SON apparent at lactation. However, suckling is important in maintainingthe structural changes during prolonged lactation, and can lead to restructuring of the nucleus by inducing pseudogestation and lactation in non-pregnant animals. Taken together with earlier data, these results suggest that hormonal factors, especially oxytocin and gonadal steroids, may act singly or, more probably, in synergy to produce the structural plasticity of the adult oxytocinergic system.

J. Endocr. (1987) 115, 97–105
Relation between aggressive behaviour and circadian rhythms in cortisol and testosterone in social groups of talapoin monkeys
Authors: Martensz N. D. , Vellucci S. V. , Fuller L. M. , Everitt B. J. , Keverne E. B. , Herbert J.
Published: December 2008

Circadian rhythms in cortisol and testosterone in both blood and cerebrospinal fluid (CSF) were studied in four groups of male and female talapoin monkeys. Samples were taken 4 h apart under two conditions: whilst the sexes were kept separate (isosexual) and again after 24 h of interaction (heterosexual). There were similar rhythms in cortisol in males and females during the isosexual condition, though in blood (but not in CSF) mean levels were higher in females. Heterosexual interaction increased cortisol levels in both sexes (though more so in males), and also altered the shape of the rhythm, acrophase being delayed by 4 h in males and by 2 h in females. The amplitude of the rhythm was not altered. Cortisol levels were positively correlated in both males and females with the amount of aggression received from other males, but not from females nor with the animals' social rank.

Circadian rhythms in serum testosterone in males were also altered by heterosexual interaction. Access to females delayed acrophase by 2 h, but had no effect on mean levels (unlike the effect on cortisol). As for cortisol, the amplitude of the testosterone rhythm remained unchanged. Serum testosterone was negatively correlated with aggression from males, but not from females nor with sexual interaction. This was associated with a pronounced decrease in the levels of testosterone during the night, not observed in males receiving no aggression from others. There was a non-significant trend towards a positive correlation between social rank and serum testosterone.

These results show that social behaviour in groupliving primates has major effects on the parameters of the circadian pattern of secretion of both cortisol and testosterone. Aggression received from males seems to be a potent factor associated with the daily rhythms in both hormones, though there may be rank-related effects in the case of testosterone.

J. Endocr. (1987) 115, 107–120
α-Adrenoreceptor blockade with thymoxamine reduces basal thyrotrophin levels but does not influence circadian thyrotrophin changes in man
Authors: Valcavi R. , Dieguez C. , Azzarito C. , Artioli C. , Portioli I. , Scanlon M. F.
Published: December 2008

We have tested the hypothesis that α-adrenergic drive is involved in the nocturnal increase in TSH in man. Seven mildly hypothyroid women (basal TSH levels 5·0–11·0 mU/1), aged 38–60 years, and nine euthyroid women, aged 27–60 years, were studied. Subjects underwent α-adrenergic blockade by infusion of thymoxamine (210 μg/min from 19.00 to 24.00 h); the same women were used as controls, with saline infused on different nights. Subjects were not allowed to sleep during the study period.

A clear evening rise in basal TSH levels was apparent in both normal subjects and patients. Although overall secretion of TSH was slightly decreased in normal subjects (mean ± s.e.m. area under the curve, 29·93 ± 0·96 vs 30·71 ±mU/1 per h; P<0·05), thymoxamine infusion did not produce any major alteration in the gradual rise in TSH levels during the evening (incremental change above baseline +0·96± 0·21 during control infusion and + 0·97 ± 0·27 mU/1 during thymoxamine infusion). In mildly hypothyroid patients the TSH changes were exaggerated and α-adrenergic blockade caused a reduction in basal TSH levels and a delayed rise in TSH (incremental change above baseline +2·93 ± 1·42 during control infusion and +2·26 ± 0·73 mU/1 during thymoxamine infusion; P < 0·02). Overall TSH secretion was significantly decreased by thymoxamine (mean ± s.e.m. area 106 ± 2·45 mU/1 per h vs 123·32 ± 3·68 in the control study; P<0·0001). As expected, no circadian change was observed in basal prolactin levels in either controls or patients.

Although α-adrenergic pathways may play a role in modulating the nocturnal increase in basal TSH levels, our data suggest that the evening rise in TSH is not a consequence of a primary increase in α-adrenergic drive. The increased TSH changes of mildly hypothyroid patients may, however, be sustained by increased central α-adrenergic stimulation of the TSH secretion.

J. Endocr. (1987) 115, 187–191