bluuebunny/crossref_metadata_2025 huggingface dataset:
Relationship between unbound oestrogen receptors in the uterus and anterior pituitary gland after implantation of oestradiol-17β into rats
Authors: Castellano-Díaz E. , González-Quijano M. I. , Díaz-Chico B. N.
Published: December 2008

This paper describes the effect of oestradiol-17β implants on unbound cytosolic and nuclear oestrogen receptors in the uterus and anterior pituitary gland of ovariectomized adult rats. Rats were ovariectomized and implanted 1 week later with oil or oestradiol-17β oil solution in silicone elastomer capsules. In the latter animals the capsules either remained in situ until decapitation (subgroup 1) or were removed 48 h after implantation (subgroup 2). Implants of oestradiol-17β caused a significant depletion in both forms of oestrogen receptor in the uterus and anterior pituitary gland of rats in subgroup 1. In subgroup 2, however, there was an almost complete return to control concentrations of uterine cytosolic receptors and anterior pituitary cytosolic and nuclear receptors. Concentrations of uterine nuclear oestrogen receptors showed only a partial recovery.

These data suggest that both forms of oestrogen receptor constitute an integrated population of oestrogen receptors, without dependence on intracellular location, and that in the presence of oestradiol these receptors are bound more quickly than they are synthesized. The results also indicate the existence of a dynamic equilibrium of unbound receptors between the cytosolic and nuclear compartments for both target organs, but show that in the absence of oestradiol this equilibrium is restored in the anterior pituitary sooner than in the uterus.

J. Endocr. (1987) 115, 205–210
Sex-related differences in renal size in mice: ontogeny and influence of neonatal androgens
Authors: Jean-Faucher Ch. , Berger M. , Gallon Ch. , de Turckheim M. , Veyssière G. , Jean Cl.
Published: December 2008

Kidneys of adult male mice are larger than those of females because of both cellular hyperplasia and hypertrophy. Administration of testosterone to adult female mice induced cellular hypertrophy but not hyperplasia, so that the weight of the kidney remained smaller than in male mice. The sexual dimorphism in kidney size is not congenital but programmed by neonatal endogenous androgens and expressed between 30 and 40 days of age. Treatment of newborn males with cyproterone acetate and of newborn females with testosterone induced female and male patterns of renal growth respectively. It appears that neonatal endogenous androgens are required to induce the characteristic cellular hyperplasia of the kidneys of male mice. Manipulation of androgen levels during neonatal and prepubertal life was found to affect the growth response of the kidney to androgens in adult male and female mice.

J. Endocr. (1987) 115, 241–246
Effect of gonadotrophin-releasing hormone agonist-induced suppression of LH and FSH on follicle growth and corpus luteum function in the ewe
Authors: McNeilly A. S. , Fraser H. M.
Published: December 2008

Continuous infusion of a gonadotrophin-releasing hormone (GnRH) agonist (buserelin) by osmotic minipump from day 1 of the luteal phase in five Welsh ewes resulted in a sustained suppression of plasma concentrations of FSH which increased three- to eightfold within 2 days after the end of infusion 29 days later. Plasma concentrations of LH increased three- to eightfold over the first 5 days of infusion and then became basal and non-pulsatile until 1 day after the end of infusion. Duration of the luteal phase and plasma concentrations of progesterone were not significantly different in control and treated ewes. Pulses of LH in control ewes were followed by increases in concentrations of progesterone in samples collected at 10-min intervals for 7 h on days 10 and 14 of the luteal phase. However, progesterone was also released in a pulsatile manner in the absence of LH pulses in both control and GnRH agonist-treated ewes.

After natural luteolysis, no ovulation or corpus luteum function occurred in treated ewes up to 15 days after the end of treatment on day 29, even though oestrus, indicating follicular development and oestrogen secretion, had occurred 8–11 days after treatment ended.

After 30 days of infusion the ovaries of GnRH agonist-treated ewes contained no follicles > 2·5 mm in diameter. In follicles of 1–2 mm in diameter the basal and LH-stimulated production of oestradiol and testosterone in vitro were similar in both control and GnRH agonist-treated ewes, and a similar proportion of these follicles was oestrogenic (> 370 mol oestradiol per follicle) in GnRH agonist-treated and control ewes.

These results show (1) that progesterone secretion by the corpus luteum of the ewe can be sustained in the presence of basal concentrations but absence of pulsatile secretion of LH, and progesterone is released in a pulsatile manner whether or not LH pulses are present, (2) that follicular development beyond 2·5 mm in diameter in the ewe is dependent upon adequate stimulation by both LH and FSH and (3) that the continuous infusion of GnRH agonist is a simple method for providing reproducible suppression of LH and FSH and follicular development in the ewe to allow the study of gonadotrophin action on the ovary in vivo.

J. Endocr. (1987) 115, 273–282
Effect of naloxone on oxytocin and vasopressin release during vaginocervical stimulation in the goat
Authors: Seckl J. R. , Lightman S. L.
Published: December 2008

We have investigated the secretion of oxytocin and arginine vasopressin (AVP) during vaginocervical stimulation in the conscious goat and examined the effect of the opioid antagonist naloxone on peptide release to this stimulus. Goats were implanted with guide tubes overlying the cisterna magna under anaesthesia and allowed to recover. Vaginocervical stimulation for 60 s resulted in a marked (P < 0·01) release of oxytocin into the plasma but neither plasma AVP nor cerebrospinal fluid (CSF) concentrations of oxytocin changed significantly.

In a second series of experiments, unoperated goats were infused with saline or naloxone (4 mg bolus + 12 mg/h) in random order on two separate occasions. Infusion of naloxone had no effect on basal plasma concentrations of oxytocin or AVP. There was a marked and significant (P < 0·01) potentiation of oxytocin secretion following vaginocervical stimulation in animals infused with naloxone. Naloxone-infused animals showed a significant (P < 0·01) rise in plasma AVP after stimulation but plasma AVP did not change in the saline-infused controls.

We conclude that vaginocervical stimulation leads to the selective release of oxytocin from the neurohypophysis without affecting concentrations of oxytocin in the CSF. Endogenous opioids inhibit the stimulated secretion of oxytocin and AVP in vivo in response to vaginocervical stimulation in the goat.

J. Endocr. (1987) 115, 317–322
Involvement of endogenous opioid peptides in the neuroendocrine response of ewe lambs to the introduction of a ram
Authors: Stansfield S. C. , Knight P. G. , Al-Mauly N. Z. , Bryant M. J.
Published: December 2008

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

J. Endocr. (1987) 115, 333–339
Plasma concentrations of vasopressin and a prostaglandin F2α metabolite in women with primary dysmenorrhoea before and during treatment with a combined oral contraceptive
Authors: Hauksson A. , Åkerlund M. , Forsling M. L. , Kindahl H.
Published: December 2008

Oral contraceptives reduce menstrual pain but the interaction with vasopressin and prostaglandin F2α, two uterine stimulants related to the condition, is unknown. Ten women with a history of moderate to severe dysmenorrhoea were studied. Repeated blood samples were taken during a first menstrual cycle without treatment, during the first 21 days of a second cycle when they received an oral contraceptive (150 μg levonorgestrel and 30 μg ethynyloestradiol) and on the first or second day of the bleeding following hormonal withdrawal. Measurements were made of plasma concentrations of arginine vasopressin, 15-keto-13,14-dihydroprostaglandin F2α, oestradiol-17β, progesterone, ethynyloestradiol, levonorgestrel, FSH, LH and prolactin, and serum osmolality was measured. Seven of the women rated their discomfort as moderate to severe on the first two menstruations, but as none or light at the withdrawal bleeding; with the rating scale for degree of pain that was used, this decrease in pain was significant (P< 0·001). The plasma concentration of vasopressin in these seven women showed significant variation, with the highest concentrations being obtained at the beginning of the two painful menstruations (3·76 ± 0·76 and 1·75 ± 0·30 (s.e.m.) pmol/l and at ovulation in the control cycle (1·91±0·58 pmol/l). During treatment the concentrations were consistently low, except on the first day of withdrawal bleeding (2·33±0·35 pmol/l). The concentrations of the prostaglandin F2α metabolite showed less variation, but again the values at withdrawal bleeding (271 ± 39 pmol/l) were not different from those obtained over the painful menstruations (255 ± 24 and 217 ± 25 pmol/l. The plasma concentrations of ovarian and adenohypophysial hormones, as well as osmolality, were normal throughout. The remaining three women had no, or only slight, menstrual pain in the control cycle and no menstrual peaks in the concentration of vasopressin or prostaglandin F metabolite. The present results gave no evidence for a reduced release of vasopressin and/or prostaglandin F2α that could explain the beneficial effect of oral contraceptives in dysmenorrhoea. Instead, it is possible that this effect is due to a decreased sensitivity of the uterus to these factors.

J. Endocr. (1987) 115,355–361
Age-related release of prolactin by the pituitary and the pituitary-hypothalamic complex in vitro: an attempt to describe the development of the hypothalamic prolactin-inhibiting and -releasing activities in male rats
Authors: Karanth S. , Dutt A. , Juneja H. S.
Published: December 2008

We have recently demonstrated that the pituitary hypothalamic complex (PHC) is a good model for studying interactions between the hypothalamus and pituitary in vitro. The amount of prolactin secreted by the PHC is an index of prolactin secreted by the pituitary in the presence of hypothalamic control, while the amount released by the whole pituitary alone is an index of prolactin secreted in the absence of hypothalamic control. The amount of prolactin secreted by the PHC has been regarded as an index of hypothalamic prolactin-releasing activity (HPRA), while the difference in the amounts of prolactin secreted by the whole pituitary and the PHC is the hypothalamic prolactin-inhibiting activity (HPIA). Attempts were made to correlate HPRA and HPIA to the development of serum concentrations of prolactin from days 7 to 77 in male rats. The HPRA increased steadily from days 7 to 56, decreased significantly on day 63 and thereafter remained unchanged until day 77. The HPIA was low on days 7 and 14 and increased steadily up to day 49, with no further significant variations. The developmental patterns of HPRA and HPIA were comparable up to day 49. Serum concentrations of prolactin increased significantly until day 28 and remained fairly constant until day 49. The weight of the pituitary gland increased from 1·0± 0·03 mg (mean ± s.e.m.) on day 7 to 7·76 ± 0·32 mg on day 63 and remained unchanged thereafter. The weight of the hypothalamic islet was 31·5 ± 2·88 mg on day 7, 34·83 ±1·45 mg on day 14 and 50·4 ± 4·01 mg on day 21. After day 21 the weights of the hypothalamic islets were not significantly altered, except on day 49.

It was concluded that serum concentrations of prolactin are regulated by interaction or competition between HPRA and HPIA at the level of the pituitary.

J. Endocr. (1987) 115, 405–409
Administration of testosterone to wether lambs: effects on protein and energy metabolism and growth hormone status
Authors: Lobley G. E. , Connell A. , Buchan V. , Skene P. A. , Fletcher J. M.
Published: December 2008

The effects of episodic infusion of testosterone into the vascular system on energy expenditure, nitrogen retention and whole body protein synthesis (determined from [1-14C]leucine kinetics) were studied in castrated male lambs under conditions of controlled food intake. Comparisons were made between a 10-day control period and a 10-day treatment period for each lamb. Infusion of testosterone produced a significant increase in heat production, but the magnitude (198 kJ/day, +2·5% was less than the differences in energy expenditure expected between entire and castrated male ruminants. The retention of nitrogen improved by 1·24 g/day ( + 22%) in response to the administration of androgen, and this was accompanied by a decrease in amino acid oxidation. Total protein synthesis also declined, and the anabolic nature of testosterone supply must, therefore, be effected through a reduction in the breakdown of protein, the mechanism being similar to that proposed for certain anabolic steroids and the β-agonist, clenbuterol. Contrary to other reports, the presence of testosterone had no effect on the plasma concentration of GH.

J. Endocr. (1987) 115, 439–445
Plasma gonadotrophin concentrations, pituitary gonadotrophin content and pituitary responsiveness to LHRH in rats treated with LHRH and oestradiol benzoate
Authors: Schuiling G. A. , Pols-Valkhof N. , Moes H. , Koiter T. R.
Published: December 2008

Suppression of gonadotrophin secretion during prolonged treatment with a high dose of LHRH was studied. Long-term ovariectomized rats were infused for 6 days with various doses of LHRH (25, 50, 100, 250 or 500 ng/h) with or without simultaneous treatment with oestradiol benzoate (OB; 3 μg/s.c. injection); a further group was treated with OB only. The effects of these treatments were studied on plasma concentrations of LH and FSH, the pituitary content of LH and FSH and on LH and FSH secretion in vitro (perifusion) in the unstimulated state and following maximal LHRH stimulation (1 μg LHRH/ml perifusion medium).

Administration of LHRH caused a dose-dependent reduction in plasma concentrations of LH and FSH and depleted the pituitary LH/FSH stores. Treatment with OB lowered the plasma concentration of LH to about 30% and that of FSH to about 65% of the control values. Administration of OB plus a low dose of LHRH (25 or 50 ng/h) markedly stimulated the secretion of LH but not of FSH, so that the plasma concentrations of LH were fully restored to the control value. With higher rates of LHRH infusion, OB caused no enhancement of the plasma concentrations of LH and FSH.

The experiments in vitro revealed a sensitizing, i.e. stimulatory effect, of OB on LHRH-stimulated LH and FSH secretion. However, the higher the rate of infusion of LHRH the smaller the sensitizing effect. Interpolation from dose–response curves showed that an LHRH infusion rate of about 150 ng/h (which would establish a plasma concentration of LHRH of about 68 pmol/l) would have no effect. With still higher rates of infusion of LHRH, the effect of OB was either inhibitory (LH) or absent (FSH).

The present experiments show that, depending on dose and length of treatment, both LHRH and OB can have variable effects on the secretion of LH and FSH: LHRH, while depleting and desensitizing the pituitary gland, stimulates the release of LH, whilst OB, which is known to suppress the secretion of LHRH by the hypothalamus, augments the rates of unstimulated and LHRH-stimulated LH and FSH secretion. The augmenting effect of OB on the latter component of LH and FSH secretion can be suppressed with high doses of LHRH. However, these experiments also show that even with doses as high as 500 ng LHRH/h, infused continuously for 6 days, plasma concentrations of LH and FSH are not reduced by more than 60–70%.

J. Endocr. (1987) 115, 469–475
Regulation of major histocompatibility complex class II antigen expression by the FRTL-5 rat thyroid cell line
Authors: Weetman A. P. , Green C. , Borysiewicz L. K.
Published: December 2008

We have used the continuously growing FRTL-5 rat thyroid cell line to examine the regulation of major histocompatibility complex (MHC) class II (or la) antigen expression. Of the various stimuli investigated, only the supernatant from activated T cells or recombinant γ-interferon induced Ia expression. All Ia-inducing activity was removed from the T cell supernatant by acid dialysis, suggesting that γ-interferon is the single critical mediator for class II antigen expression. Its action was not TSH dependent but expression of class II antigens increased from the G0-G1 to the S and G2 phases of the cell cycle, so that TSH enhanced Ia expression by its action on cell division. Other agents including lectins, hormones, epidermal growth factor, a calcium ionophore and a phorbol ester did not induce Ia expression. Substances known to inhibit murine macrophage Ia expression (cortisol, prostaglandin E2 and 5-hydroxytryptamine) had no effect on FRTL-5 Ia expression. The use of this thyroid cell line has permitted direct examination of modulators in the absence of any possible effects from contaminating non-thyroid cells present in primary cultures and the results suggest that, of the agents tested, only γ-interferon has significance in the context of Ia antigen expression by the thyroid.

J. Endocr. (1987) 115, 481–487
Thyroid status affects the regulation of prolactin mRNA accumulation by tri-iodothyronine and thyrotrophin-releasing hormone in cultured rat anterior pituitary cells
Authors: Wood D. F. , Docherty K. , Ramsden D. B. , Shennan K. I. J. , Sheppard M. C.
Published: December 2008

The effects of tri-iodothyronine (T3) and TRH on prolactin mRNA accumulation in monolayer pituitary cell cultures prepared from both euthyroid and hypothyroid rats were investigated. Basal prolactin mRNA concentrations and prolactin release into culture medium were increased in hypothyroid cultures, the increase being related to the duration of hypothyroidism in vivo. The inhibitory effects of T3 seen in euthyroid cells were preserved in cells derived from hypothyroid animals, and the degree of inhibition was greater in cells from the most severely hypothyroid rats. However, the stimulation of prolactin synthesis and secretion induced by TRH in euthyroid cultures was not found in the hypothyroid cells. Hypothalamic and anterior pituitary TRH content were measured in similarly hypothyroid and euthyroid rats. A large hypothalamic pool of TRH was found, which was unchanged in hypothyroidism, whereas anterior pituitary TRH content was increased in the hypothyroid rats. The consequent down-regulation of anterior pituitary TRH receptors may explain the poor response of prolactin to TRH seen in vitro.

J. Endocr. (1987) 115, 497–503
INTERFERON SEQUENCE HOMOLOGY AND RECEPTOR BINDING ACTIVITY OF OVINE TROPHOBLAST ANTILUTEOLYTIC PROTEIN
Authors: Stewart H.J. , McCann S.H.E. , Barker P.J. , Lee K.E. , Lamming G.E. , Flint A.P.F.
Published: December 2008

Sequencing of the 40 N-terminal amino acids of the blastocyst protein responsible for blocking corpus luteum regression in early pregnancy in sheep revealed a 37% homology with human α-interferon; 28% of the remaining amino acid changes were conservative. 125I-Labelled human α-interferon bound to membrane receptors from sheep uteri with an approximate Kd of 4 × 10−11 M; binding was inhibited by unlabelled α-interferon or purified blastocyst antiluteolytic protein. The blastocyst antiluteolytic protein therefore closely resembles the interferon-α family of antiviral proteins.
INHIBIN GENE EXPRESSION IN THE HUMAN CORPUS LUTEUM
Authors: Davis S.R. , Krozowski Z. , McLachlan R.I. , Burger H.G.
Published: December 2008

We report inhibin α- and βA -subunit gene expression in the human corpus luteum and placenta using human α-subunit and bovine βA -subunit nucleic acid probes. In addition, we have demonstrated the presence of immunoreactive and bioactive inhibin in human corpora lutea. Our findings suggest that this tissue is a significant source of inhibin during the luteal phase of the normal human menstrual cycle.
Regulation of tyrosinase synthesis by α-melanocyte-stimulating hormone in hair follicular melanocytes of the mouse
Authors: Burchill S. A. , Virden R. , Fuller B. B. , Thody A. J.
Published: December 2008

Tyrosinase activity was increased in hair follicular melanocytes of C3H-HeAvy mice during the hair cycle and reached higher levels on days 6–8 after plucking than on day 12. Similarly, the rate of incorporation of [35S]methionine into tyrosinase was greater on days 6–8 than on day 12, but the relative difference was much less. α-MSH had no effect on tyrosinase activity or the rate of [35S]methionine incorporation on day 12 and, while it increased both on days 6 and 8, it had a greater effect upon the latter. Pulse-chase experiments showed that the half-life of tyrosinase was 3·5 h and that this was unaffected by α-MSH.

The results indicate that the increases in tyrosinase activity which occur during the hair cycle involve changes in both the synthesis and activation of the enzyme and that the predominant effect of α-MSH is on the former of these two processes.

J. Endocr. (1988) 116, 17–23
Stimulation of chick adrenal steroidogenesis by avian parathyroid hormone
Authors: Rosenberg J. , Pines M. , Hurwitz S.
Published: December 2008

Dispersed chick adrenocortical cells were incubated with avian parathyroid hormone (aPTH) or ACTH. Accumulation of cyclic AMP (cAMP), activity of cAMP-dependent protein kinase and the secretion of corticosterone and aldosterone, in response to these hormones, were measured.

Accumulation of cAMP and activity of cAMP-dependent protein kinase were stimulated by both aPTH and ACTH as well as by cholera toxin. Cyclic AMP production followed a similar time-course when stimulated by either peptide hormone. Stimulation of steroid hormone secretion was detectable after 20 min of incubation with ACTH, but only after 40 min with aPTH. The maximal steroid hormone secretion by adrenocortical cells was similar when induced by either peptide hormone. The aPTH concentrations needed for half-maximal response of corticosterone and aldosterone secretion were higher than those for ACTH (2·5- and 2-fold respectively), but still within the physiological range. The 11β-hydroxylase inhibitor metyrapone inhibited the secretion of both corticosterone and aldosterone when induced by either aPTH or ACTH.

The results suggest that aPTH is almost as potent as ACTH in stimulating the secretion of corticosterone and aldosterone from chick adrenocortical cells and utilizes a cAMP-dependent pathway similar to that of ACTH.

J. Endocr. (1988) 116, 91–95
Pulsatile administration of gonadotrophin-releasing hormone stimulates, in oestrogen-treated anaesthetized ovariectomized ewes, a surge release of LH qualitatively and quantitatively different from that induced by oestradiol in conscious ovariectomized ewes
Authors: Wright P. J. , Clarke I. J.
Published: December 2008

The nature of the gonadotrophin-releasing hormone (GnRH) stimulus of the pituitary necessary for the oestrogen-induced plasma LH surge was studied in ovariectomized ewes. The sheep were treated with oestradiol benzoate (50 μg i.m.) at 0 h, and the hypothalamic contribution to the LH surge was blocked by pentobarbitone anaesthesia over the time during which the surge was expected (11–31 h). Pituitary responsiveness to exogenous GnRH (100 ng) administered i.v. in a pulsatile mode (once per hour or once per 20 min) over the period 15–30 h was assessed from plasma concentrations of LH. Neither of the GnRH treatments induced patterns of LH secretion similar to those seen in conscious ovariectomized ewes given oestrogen only. Plasma LH secretion in response to hourly GnRH pulses was less (P<0·01) than that associated with oestrogen-induced plasma LH surges in conscious control ewes. With pulses of GnRH administered every 20 min the amount of LH released was greater (P<0·05) than that in oestrogen-treated conscious control ewes. In contrast to the single surge induced by oestradiol in conscious ewes, GnRH pulses given every 20 min elicited phasic patterns of LH secretion consisting of two or three distinct surges. The failure of GnRH treatment to elicit an LH surge similar to an oestrogen-induced surge could reflect inappropriate GnRH treatment regimens, and/or inadequate priming of the pituitary with GnRH after induction of anaesthesia but before GnRH treatment.

J. Endocr. (1988) 116, 143–148
Effects of transplantation on mouse adrenal chromaffin cells
Authors: Jousselin-Hosaja M.
Published: December 2008

The effects of long-term transplantation on the ultrastructure of adrenaline- and noradrenaline-storing cells from the adrenal medulla were determined using morphometric methods. Mouse adrenal medulla were freed from the adrenal cortex and grafted into the occipital cortex of the brain. Two types of chromaffin cells were identified by electron microscopy in grafts fixed with glutaraldehyde and osmium tetroxide. Noradrenaline-type cells were predominant and formed 70–80% of the surviving population of grafted chromaffin cells. A minority of the chromaffin cells contained medium-sized granules (140–210 nm in diameter) (medium granule cell; MGC) with finely granular moderately electron dense cores. Morphometric analysis of noradrenaline phenotype cells and MGC cells in transplants showed no significant differences compared with the noradrenaline-storing cells of normal adrenal glands. In contrast, noradrenaline-type cells and MGC cells in the grafts had areas of secretory vesicles which were significantly (P<0·01) larger and areas of rough endoplasmic reticulum which were significantly (P<0 ·01) smaller than those of the adrenaline-storing cells of normal adrenal glands.

It was concluded that long-term transplantation caused no degenerative changes in the ultrastructure of mouse adrenal chromaffin cells.

J. Endocr. (1988) 116, 149–153
Effects of passive immunization with antisomatostatin serum on plasma corticosterone concentrations in young domestic cockerels
Authors: Cheung A. , Harvey S. , Hall T. R. , Lam S.-K. , Spencer G. S. G.
Published: December 2008

Young cockerels (6–8 weeks old) were injected with serum from sheep immunized against somatostatin-14 (anti-SRIF) or normal sheep serum (NSS). Blood samples were withdrawn periodically for the determination of plasma corticosterone concentration by radioimmunoassay. With frequent (every 10 min) sampling, NSS-treated control animals exhibited increased plasma corticosterone levels, presumably as a stress response to the experimental manipulation. Anti-SRIF stimulated a much greater increase in plasma corticosterone concentrations and a peak response was observed within 10 to 20 min, when the plasma corticosterone level reached more than twice that of the corresponding control value. With less frequent sampling, plasma corticosterone increased with anti-SRIF administration to as much as nine times the corresponding control value, and the peak response occurred much later. Under pentobarbitone anaesthesia, which itself increased basal corticosterone concentrations, anti-SRIF treatment promoted further increases in plasma corticosterone levels although to a smaller magnitude compared with conscious birds. The results suggest that endogenous somatostatin may play a role in the regulation of adrenocortical function in the domestic fowl. The mechanism of response may involve a central component.

J. Endocr. (1988) 116, 179–183
A comparison of the vasopressin response of rats to intraperitoneal and intravenous administration of hypertonic saline, and the effect of opioid and aminergic antagonists
Authors: Forsling M. L. , Matziari C. , Aziz L.
Published: December 2008

The vasopressin response of rats to i.p. injection of hypertonic sodium chloride (1·5 mol/l) was compared with that following i.v. infusion of 1·05 mol sodium chloride/l. The two regimes produced a similar vasopressin response in terms of the osmotic threshold, although the slopes of the plot of plasma vasopressin levels against plasma osmolality were not identical. Pretreatment with naloxone and levallorphan increased the resting vasopressin levels and effectively potentiated vasopressin release in response to hypertonic saline by reducing the osmotic threshold for hormone release. Thus, opioid peptides appear to exert an inhibitory effect on vasopressin release under resting and stimulated conditions. The adrenoreceptor antagonists propanolol, phenyoxybenzamine and phentolamine produced a fall in resting vasopressin concentrations while propanolol and phenoxybenzamine potentiated the osmotic release of vasopressin in association with a fall in the osmotic threshold. This would suggest that noradrenergic pathways are excitatory at rest while having an inhibitory effect on the osmotic response. Metoclopramide also produced a fall in resting plasma vasopressin concentrations while increasing the osmotic response. In contrast haloperidol did not affect the vasopressin response.

J. Endocr. (1988) 116, 217–224
Association of progesterone with a unique particulate fraction of the human corpus luteum
Authors: Bramley T. A. , Menzies G. S.
Published: December 2008

Homogenates of human corpus luteum were fractionated on continuous sucrose density gradients, with and without pretreatment with digitonin to perturb plasma membranes. Fractions of each gradient were assayed for steroid content and a range of plasma membrane and intracellular organelle markers. Progesterone and oestradiol were associated with a particulate fraction (buoyant density, 1·08–1·13 g/cm3). The buoyant density distribution of these steroids was distinct from those of the luteal cell plasma membrane and intracellular organelle markers tested. Treatment with digitonin increased the buoyant density of both progesterone and oestradiol. If steroids are contained in distinct vesicles, these vesicles may be involved in the sequestration of newly synthesized steroid and its movement to the cell surface for release into the circulation.

J. Endocr. (1988) 116, 307–312
Endogenous opioid peptide modulation of LH secretion in the ewe lamb: possible involvement of 5-hydroxytryptamine
Authors: Stansfield S. C. , Knight P. G. , Howles C. M. , Cunningham F. J.
Published: December 2008

Evidence from several species suggests that the endogenous opioid peptides participate in the regulation of gonadotrophin and prolactin secretion. The aim of the present study involving intact and ovariectomized prepubertal ewe lambs was to compare the effects in vivo of an opioid peptide agonist d-Ala2,N-Phe4,Met(0)ol5]-enkephalin (FK 33–824) and antagonist, naloxone, on concentrations of LH and prolactin in plasma, and levels of neurotransmitter metabolites in cerebrospinal fluid (CSF), with their effects in vitro on the release of gonadotrophin-releasing hormone (GnRH) and neurotransmitters from isolated median eminences.

Infusion of FK 33–824 (0·5 mg/30 min) in vivo depressed plasma LH levels in both intact and ovariectomized lambs; this effect could be reversed by naloxone. In ovariectomized lambs, the inhibitory action of FK 33–824 on plasma LH levels was associated with a 13% rise in the concentration of the metabolite of 5-hydroxytryptamine, 5-hydroxyindolacetic acid (5-HIAA). Concurrent administration of naloxone resulted in an abrupt 33% fall in CSF levels of 5-HIAA.

No significant changes in plasma concentrations of prolactin or CSF concentrations of the metabolites of dopamine were observed in response to the administration of FK 33–824 or FK 33–824 plus naloxone.

That FK 33–824 inhibited LH release through a central mechanism was confirmed using superfused median eminences in vitro. Thus FK 33–824 (1 μmol/l) greatly diminished the release of GnRH induced by the introduction of a depolarizing stimulus (36 mmol K+/l) in tissue obtained from both intact and ovariectomized ewe lambs. Since neurotransmitter levels in superfusate samples were below the limit of detection of the high-performance liquid chromatography assay, it remains to be ascertained whether FK 33–824 concomitantly affected neurotransmitter release.

These results lead us to conclude that FK 33–824 inhibits the secretion of LH, but not prolactin, in intact and ovariectomized prepubertal ewe lambs. The action of FK 33–824 is mediated, at the level of the median eminence, through a reduction of GnRH release. It is tentatively suggested that FK 33–824 may exert this inhibitory effect by stimulating the release of 5-hydroxytryptamine.

J. Endocr. (1988) 116, 403–411
Action of 1,25-dihydroxyvitamin D3 on phospholipid metabolism of human bone cells in culture
Authors: Haining S. A. , Galloway J. H. , Brown B. L. , Guilland-Cumming D. F.
Published: December 2008

It has recently been proposed that the action of 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) on bone metabolism may be mediated by changes in phospholipid metabolism. The effects of vitamin D metabolites on the incorporation of radiolabelled precursors into corresponding phospholipid classes were investigated using cells arising from cultured explants of normal human bone with osteoblast-like characteristics. Treatment with 1,25-(OH)2D3 increased the incorporation of serine, measured as the ratio of [3H]serine in phosphatidylserine (PS) to [14C]ethanolamine in phosphatidylethanolamine (PE), in a time- and dose-dependent manner. The maximum effect on PS/PE of 141·6 ± 5·9% over control (P = 0·022) was observed at a dose of 0·1 nmol 1,25-(OH)2D3/l, maintained for 24 h. Incubations with 25-hydroxyvitamin D3 (0·1 μmol/l) and 24,25-dihydroxyvitamin D3 (10 nmol/l) had no effect. Supraphysiological doses (0·1 μmol/l) of 1,24,25- and 1,25,26-trihydroxyvitamin D3 showed similar effects to those of 1,25-(OH)2D3, emphasizing the importance of 1α-hydroxylation. Incorporation of [14C]choline into phosphatidylcholine, calculated as a ratio to PE, was not affected by treatment with vitamin D metabolites. However, [3H]inositol uptake into phosphatidylinositol was almost doubled when compared with control uptake within 2 h of treatment with 1,25-(OH)2D3 (0·1 μmol/l). This may be of relevance, considering the importance of phosphoinositide metabolism in influencing the intracellular calcium concentration. These results support a role for 1,25-(OH)2D3 in the modulation of phospholipid metabolism in human bone cells, which in turn may be involved in the action of 1,25-(OH)2D3 in bone mineralization.

J. Endocr. (1988) 116,435–441
Changes with age in the number and size of anterior pituitary cells in female mice from suckling to adulthood
Authors: Sasaki F.
Published: December 2008

Changes with age in the number and size of anterior pituitary cells in female mice were calculated during their postnatal development by using a stereological morphometric study with electron microscopy. The number of parenchymal cells increased in mice from 20 to 30 days of age, and did not change around puberty, after which the number increased to the adult level. The number of somatotrophs increased with age in almost the same manner as the parenchymal cells. The number of lactotrophs increased with age and were significantly different each time they were measured. The number of non-granulated cells did not increase in mice from 20 days of age to adulthood; at 20 days of age, the number was at the same level as in the adult mice. The other types of cells increased by only a small number.

The sizes of all types of cells increased during postnatal life. Somatotrophs and lactotrophs became the same size as in adults by the onset of puberty. Non-granulated cells and other types of cells reached adult size at 5 days after puberty. Lactotrophs and somatotrophs had adult ultrastructural features on the day of puberty.

Sizes and ultrastructural features of anterior pituitary cells reached adult levels on the day of puberty, but their numbers were still fewer than in adult mice.

The increase in the volume of the anterior pituitary with age arose mostly from an increase in the number and the size of somatotrophs and lactotrophs before puberty, increases in the size of somatotrophs and the number of lactotrophs around puberty, and an increase in the number of both types of cells after puberty.

J. Endocr. (1988) 117,5–10
Immunoreactive vasopressin and oxytocin in hypothalamo-hypophysial portal blood of the Brattleboro and Long–Evans rat: effect of adrenalectomy and dexamethasone
Authors: Eckland D. J. A. , Todd K. , Lightman S. L.
Published: December 2008

Immunoreactive vasopressin and oxytocin were measured in the hypothalamo-hypophysial portal blood of both Long–Evans and homozygous Brattleboro rats. Adrenalectomy caused an increase in vasopressin immunoreactivity in portal blood in the Long–Evans strain, whilst administration of dexamethasone to these adrenalectomized animals resulted in a reduction in portal vasopressin immunoreactivity to levels below those seen in sham-operated animals. This vasopressin immunoreactivity co-eluted with synthetic vasopressin on high-pressure liquid chromatography (HPLC), and diluted in parallel in radioimmunoassay. In Brattleboro rats, however, although vasopressin-like immunoreactivity was detected, the portal concentration did not vary with the adrenal status of the animal, nor did it show the characteristics of standard vasopressin on HPLC or in immunoassay. Oxytocin was present in the portal blood of both Long–Evans and Brattleboro rats at similar very high concentrations, but did not vary in response to adrenalectomy. These results are consistent with a role for vasopressin, but not oxytocin, in the hypothalamic response to adrenalectomy and glucocorticoid feedback. Neither vasopressin immunoreactivity nor oxytocin appear to subserve this role in the homozygous Brattleboro rat.

J. Endocr. (1988) 117, 27–34
Interaction of endogenous chicken gonadotrophin-releasing hormone-I and -II on chicken pituitary cells
Authors: King J. A. , Davidson J. S. , Millar R. P.
Published: December 2008

The presence of two endogenous forms of gonadotrophin-releasing hormone (GnRH) in the chicken hypothalamus (chicken GnRH-I ([Gln8]GnRH) and chicken GnRH-II ([His5,Trp7,Tyr8]GnRH)), and the stimulation of gonadotrophins by both forms, suggests the possible existence of GnRH receptor subtypes and gonadotroph subtypes in the chicken pituitary. This question was investigated by assessing the effects of various combinations of the two known forms of chicken hypothalamic GnRH and antagonist analogues of GnRH on LH release from dispersed chicken anterior pituitary cells in both static and perifused systems. The relative inhibition of chicken GnRH-I-stimulated and chicken GnRH-II-stimulated LH release by 12 GnRH antagonists did not differ significantly, suggesting a single GnRH receptor type. Chicken GnRH-II was approximately sixfold more potent than chicken GnRH-I in releasing LH. Release of LH in response to maximal doses of chicken GnRH-I and chicken GnRH-II and to a mixture of both was similar and the two peptides were not additive in their effects, consistent with the presence of a single type of LH gonadotroph and a GnRH receptor which binds both forms of GnRH. Each form of GnRH desensitized cells to subsequent stimulation with the other form, providing additional evidence for a single type of LH gonadotroph. These findings suggest that chicken GnRH-I and -II stimulate gonadotrophin release through a single GnRH receptor type on a single class of LH gonadotroph in the chicken pituitary.

J. Endocr. (1988) 117,43–49
Characterization of immunoreactive dynorphin in human phaeochromocytomas
Authors: Howlett T. A. , Besser G. M. , Rees L. H.
Published: December 2008

The prodynorphin-derived opioids, dynorphin (DYN) and α-neoendorphin (αNE) were studied in 24 human phaeochromocytomas and related tumours. Nineteen tumours, extracted in HCl (0·1 mol/l), contained concentrations of immunoreactive DYN (ir-DYN) ranging from < 0·5 to 794 pmol/g wet weight. None of the extracts in HCl contained ir-αNE (all < 2·4 pmol/g). Sephadex G-50 gel filtration chromatography of ir-DYN in HCl (0·1 mol/l) extracts of six tumours revealed three small peaks of ir-DYN of higher molecular size (approximately 12 000, 6000 and 3000 daltons), a minor peak of ir-DYN eluting just after DYN(1–17), and a broad major peak, consisting of at least three components, which was significantly retarded and eluted after the salt volume of the column. High-pressure liquid chromatography (HPLC) of these extracts revealed multiple peaks of ir-DYN, most of which did not coelute with any synthetic DYN peptides. On both gel filtration chromatography and HPLC, one of the minor peaks coeluted with DYN(1–32). None of the peaks of ir-DYN coeluted with DYN(1–17) which had been acetylated using acetic anhydride.

Extracts of the same tumours in acetic acid (0·1 mol/l) yielded similar values for ir-DYN content, but parallelism in the assay was improved. Sephadex G-50 chromatography revealed a different pattern of ir-DYN with a major peak coeluting with DYN(1–17) and, in two tumours, a minor peak coeluting with DYN(1–8). Studies with HPLC revealed, however, that substantial degradation of synthetic DYN occurred during extraction in acetic acid (0·1 mol/l) in spite of the precautions taken.

Phaeochromocytomas frequently contain ir-DYN in concentrations which may approach that of the mammalian pituitary. These tumours did not, however, contain ir-αNE and, with the possible exception of a small amount of DYN(1–32), the ir-DYN present did not correspond with any known sequences. Thus, whilst prodynorphin is expressed in phaeochromocytomas, it does not seem to be processed to the usual end-products, and post-translational modifications therefore seem likely. Enzymatic degradation of DYN may occur during extraction in acetic acid (0·1 mol/l), and this medium should, therefore, be avoided in studies of such labile peptides.

J. Endocr. (1988) 117, 123–132
The stability in vitro of bioactive and immunoreactive LH in human blood and plasma
Authors: Tsatsoulis A. , Mavroudis K. , Frost J. , Lambert A. , Shalet S. M. , Robertson W. R.
Published: December 2008

The degree of stability in vitro of bioactive and immunoreactive LH in human blood, plasma and serum was examined. Bioactivity and immunoreactivity of LH were assayed by the dispersed mouse Leydig cell assay and by standard radioimmunoassay respectively, using the same reference preparation (first international reference preparation for human pituitary LH 68/40 for immunoassay).

Bioactive and immunoreactive LH were stable in blood and plasma at 22 °C for up to 4 and 24 h respectively, and in blood at 4 °C for up to 24 h. There was no loss of biological or immunological LH activity in plasma which had been either snap-frozen and stored at −70 °C, allowed to freeze at −20 °C and stored at that temperature or kept at 4 °C for 24 h and then stored at − 70 °C. Likewise, the levels of LH in plasma and serum which had been stored at either − 20 or − 70 °C and then thawed and refrozen up to four times remained unchanged. In addition, the biological and immunological activity of LH was not affected after vortexing samples of plasma or serum for up to 60 s. Bioactive LH was also stable in plasma samples after prolonged storage (up to 9 months) at either −70 or −20 °C.

We conclude that LH bioactivity and immunoreactivity are stable in blood and plasma following a variety of treatments commonly experienced during normal handling of a blood sample after venepuncture.

J. Endocr. (1988) 117, 139–145
Secretion rates and short-term patterns of gonadotrophin-releasing hormone, FSH and LH in the normal stallion in the breeding season
Authors: Irvine C. H. G. , Alexander S. L.
Published: December 2008

Pituitary venous blood was collected by a painless non-surgical cannulation method from five ambulatory stallions at 5-min intervals for 5–6 h during the breeding season. In four adult stallions, statistical analysis showed that pulses of gonadotrophin-releasing hormone (GnRH) and LH were coincident (P <0·01), as were pulses of FSH and LH (P <0·05). Furthermore, the patterns of changes in concentration of FSH and LH were highly correlated in each of the four stallions. However, seemingly ineffective pulses of GnRH were also observed, with 28% of GnRH pulses failing to induce a significant gonadotrophin pulse.

In the four adult stallions the amplitude of pituitary venous gonadotrophin pulses varied markedly but no correlation with GnRH pulse amplitude was observed. Peak secretion of FSH, but not LH, during pulses was correlated with the length of the interpulse interval. Consequently, the ratio of FSH to LH during peaks was least (P <0·02) when the interpulse interval was 30 min or less. Thus, differential FSH and LH secretion was achieved within a constant steroid milieu.

Two stallions had regular contact with oestrous mares, and in these horses the secretion of GnRH and gonadotrophins occurred almost continuously with rapid, rhythmic pulses superimposed upon a tonic background. Mean (± s.d.) interval between GnRH pulses was 31·4 ± 9·8 min and 27·7 ± 10·1 min. This secretory pattern was not observed in the two stallions which had infrequent contact with oestrous mares, although the small numbers precluded statistical testing of this apparent difference. No GnRH pulses were observed in one of these stallions, while in the other mean (± s.d.) GnRH pulse interval was 45·0 ± 48·7 min, the large variance being partly due to rapid pulses during a period in which the stallion teased mares. The fifth stallion was pubertal, and GnRH and LH secretion occurred in 15 and 0% of samples respectively, while low levels of FSH secretion were observed in 37% of samples and jugular testosterone levels were immeasurably low.

We conclude that there is a statistically significant synchrony between pulses of GnRH, LH and FSH in the pituitary venous blood of stallions. Furthermore, decreasing intervals between gonadotrophin pulses result in a significant reduction in secretion of FSH but not LH.

J. Endocr. (1988) 117, 197–206
The role of thyroid hormones in the growth hormone response to protein restriction in the domestic fowl (Gallus domesticus)
Authors: Lauterio T. J. , Scanes C. G.
Published: December 2008

The possible role of thyroid hormones in the rise in plasma GH observed in protein-restricted chicks was examined. Increased sensitivity of protein-restricted chicks to secretagogue challenge (TRH or GH-releasing factor) appears to account, at least in part, for increased GH concentrations in protein-restricted chicks. Thyroid hormones administered acutely were able to suppress plasma GH concentrations in protein-restricted chicks. Further, chronic thyroid hormone supplementation to low protein diets normalized circulating thyroid hormone concentrations and also normalized the response to GH secretagogue challenge. This decreased sensitivity to TRH provocation occurred without an accompanying change in plasma concentrations of insulin-like growth factor-I, a reputed inhibitor of GH secretion in the chicken.

J. Endocr. (1988) 117, 223–228