bluuebunny/crossref_metadata_2025 huggingface dataset:
Paradoxical LH and prolactin responses to naloxone after chronic treatment with morphine
Authors: Almeida O. F. X. , Schulz R. , Herz A.
Published: December 2008

A series of experiments was conducted in adult male rats to study the development of tolerance to and dependence on morphine in the neural processes controlling LH and prolactin secretion. The central mechanisms controlling both these hormones became tolerant following chronic application of the opiate agonist; this was seen in the form of diminished responsiveness to the agonist with time. There was an apparently greater degree of tolerance in the mechanisms regulating LH secretion than in those regulating prolactin secretion.

In parallel experiments, the opiate antagonist naloxone was used to test for the development of dependence in rats chronically treated with morphine. While behavioural signs of physical dependence (withdrawal) were evident, the LH and prolactin responses proved to be the same as those observed in response to acute administration of opiate agonists (i.e. naloxone respectively decreased and increased serum LH and prolactin concentrations in animals chronically treated with morphine). This paper may represent the first report of such paradoxical responses to naloxone. It also demonstrates that opioid tolerance and dependence may exist as two separate phenomena in vivo.

J. Endocr. (1986) 108, 181–189
Effects of oestradiol, the oestrous cycle and pregnancy on weight, metabolism and cytosol receptors in the uterus of the brush-tail possum (Trichosurus vulpecula)
Authors: Curlewis J. D. , Stone G. M.
Published: December 2008

Uterine weight, RNA, DNA, protein content, in-vitro rate of protein synthesis, cytosol oestrogen and progesterone receptors were examined after administration of oestradiol to ovariectomized animals and on days 0, 5, 9 and 13 of the non-pregnant cycle and day 13 of pregnancy. In ovariectomized animals, oestradiol increased uterine weight, RNA: DNA and protein: DNA ratios and the concentration of cytosol receptors for oestradiol and progesterone. During the oestrous cycle there was a linear increase in uterine weight and a significant effect of the corpus luteum on the weight of the ipsilateral uterus. Changes in RNA, DNA and protein content between days 0 and 5 were not observed, but between days 5 and 13 RNA: DNA and protein: DNA ratios increased and the DNA: tissue weight ratio decreased. Thus, cellular hypertrophy and/or increased metabolic activity rather than hyperplasia occur over this period, which is coincident with the known rise in plasma progesterone levels. The rate of in-vitro protein synthesis (per unit tissue protein) during the non-pregnant cycle was greatest at day 0. These changes in uterine metabolic activity were associated with alterations in cytosol receptor concentrations for both steroids. Cytosol progesterone receptor concentrations were highest at day 0 after which they declined to a minimum at day 13. Cytosol oestradiol receptor concentrations, however, rose between days 0 and 5 and then declined. Although lutectomy on day 8 of the cycle does not interfere with the development of a histologically normal luteal phase, high peripheral progesterone levels which occur after day 8 in intact animals are associated with major increases in uterine metabolic activity.

The unilateral effect of the corpus luteum on uterine weight was associated with a decrease in DNA: g tissue ratio and an increase in rate of in-vitro protein synthesis indicating hypertrophy and/or extracellular accumulation of secreted material as well as enhanced metabolic activity. There was a significant effect of pregnancy on uterine weight at day 13 and this was associated with an increase in DNA content of both uteri. There was a unilateral effect of pregnancy on RNA: DNA ratio and in-vitro rate of protein synthesis, but not on uterine weight.

J. Endocr. (1986) 108, 201–210
Sodium dependence of the thyrotrophin-induced depolarization in cultured porcine thyroid cells
Authors: Hambleton T. A. , Bourke J. R. , Huxham G. J. , Manley S. W.
Published: December 2008

Cultured porcine thyroid cells exhibit a resting membrane potential of about − 73 mV and depolarize to about − 54 mV on exposure to TSH. The depolarizing response to TSH was preserved in a medium consisting only of inorganic salts and buffers, but was abolished in sodium-free medium, demonstrating dependence on an inward sodium current. Increasing the potassium concentration of the medium resulted in a reduction in the resting membrane potential of 60 mV per tenfold change in potassium concentration, and a diminished TSH response. A hyperpolarizing TSH response was observed in a sodium- and bicarbonate-free medium, indicating that a hyperpolarizing ion current (probably carried by potassium) was also enhanced in the presence of TSH. Tetrodotoxin blocked the TSH response. We conclude that the response of the thyroid cell membrane to TSH involves increases in permeability to sodium and potassium, and that the thyroid membrane ion channels bear some similarity to the voltage-dependent sodium channels of excitable tissues, despite the absence of action potentials in the thyroid.

J. Endocr. (1986) 108, 225–230
Different mechanisms controlling FSH and LH release in Japanese quail (Coturnix coturnix japonica): evidence for an inherently spontaneous release and production of FSH
Authors: Hattori A. , Ishii S. , Wada M.
Published: December 2008

Plasma concentration of FSH and LH and their content in the adenohypophyses of Japanese quail were estimated by homologous radioimmunoassays based on chicken hormones. The results consistently showed that the plasma concentration of FSH was slightly higher than that of LH, although the FSH content in the adenohypophysis was much lower than that of LH in immature, mature and acutely photostimulated quail. These results prompted experiments in vitro to determine whether the difference was intrinsic. Adenohypophyses were collected and each cut mid-sagittally into two halves; one half was incubated for 20 h with or without chicken hypothalamic extract, and the medium was changed every 1 or 2 h to estimate the FSH and LH released. The other half served to estimate the initial content of FSH and LH in the adenohypophysis. The amount of FSH released was three times more than the original content even when adenohypophyses were incubated without hypothalamic extract, and the residual FSH content in the pituitary after 20 h of incubation was equal to the initial FSH content. In contrast, under the same incubation conditions, little LH was released and the residual LH content was decreased. When hypothalamic extract was added to the medium, LH release was enhanced sixfold compared with the control, whereas the increase in FSH was less than twofold. Spontaneous FSH release was markedly decreased in a Ca2+-deficient incubation medium, suggesting that the release was not due to leakage but to an active secretion mechanism. We therefore suggest, for the first time, that the release and production of FSH are largely autonomous, whereas release and production of LH are rigidly controlled and regulated by the releasing hormone in avian species.

J. Endocr. (1986) 108, 239–245
Influence of acute intracerebroventricular (i.c.v.) administration of adrenocorticotrophin (ACTH) on LH secretion in male rats: effect of pretreatment (i.c.v.) with ACTH antiserum on the serum LH response to an acute ether stress
Authors: Mann D. R. , Evans D. C. , Jacobs V. L. , Collins D. C.
Published: December 2008

Adult male rats with chronic indwelling intracerebroventricular (i.c.v.) and jugular catheters were given an i.c.v. injection (over 1 min) of 1, 10, 100 ng or 1 μg ACTH(1–24), or 300 ng ACTH(4–10) or saline, and blood samples were taken 0, 5, 15, 30 and 60 min later. Increasing dosages of ACTH(1–24) caused a dose-related rise in serum LH levels. Peak levels of serum LH (ranging from 157 to 473% of pretreatment levels) were reached 5–15 min after treatment, and then serum LH values returned to pretreatment levels by 60 min. The serum LH response to 1 μg ACTH(1–24) did not differ from the response to 100 ng ACTH(1–24). Administration (i.c.v.) of 300 ng ACTH(4–10) was also effective in increasing serum LH values. Repeated withdrawal of blood during the experiment increased serum corticosterone values in all groups including saline-treated), but i.c.v. administration of ACTH(1–24) or ACTH(4–10) did not further increase serum corticosterone levels. Two additional groups of rats were injected i.p. with either saline or pentobarbital (30 mg/kg body weight) 1 h before i.c.v. administration of 10 ng ACTH(1–24) and blood samples were taken as in the other groups. The animals in these groups did not show a rise in serum LH concentrations in response to ACTH(1–24). In a third experiment, rats were pretreated (i.c.v.) with either ACTH antiserum (ACTH-Ab) or normal rabbit serum 15 min before a 2-min ether stress. The ether stress evoked a significant rise in serum LH concentrations within 15 min. Serum LH levels then fell below the 0-min value by 60 min. Pretreatment with ACTH-Ab failed to alter the serum LH response to this acute stress. The failure of ACTH-Ab to alter the response to stress suggests that the central nervous system ACTH does not play a physiological role in this process. Alternatively, we cannot be certain that the potency of the ACTH-Ab was sufficient to neutralize central nervous system ACTH effectively.

J. Endocr. (1986) 108, 275–280
Effects of various melatonin treatments on plasma prolactin concentrations in the ewe
Authors: Poulton A. L. , English J. , Symons A. M. , Arendt J.
Published: December 2008

Ewes were treated with s.c. implants of melatonin in mid-April, mid-May and mid-June. From mid-June, other animals were given oral doses of melatonin daily at 16.30 h and another group was maintained under a short (8 h light: 16 h darkness) artificial photoperiod (lights out 16.30 h). Serial blood samples were taken from all animals in June and July. Plasma prolactin concentrations were significantly reduced in ewes treated in May and June (implant, oral and photoperiod treatments) but not in those treated in April. After treatment in June, prolactin levels were significantly suppressed after 7 days of oral and implant melatonin therapy, and after 28 days of a short artificial photoperiod. Melatonin treatment appeared more efficient than an artificial photoperiod in reducing plasma prolactin concentrations.

J. Endocr. (1986) 108, 287–292
Endocrine control of smoltification in anadromous salmonids
Authors: Barron M. G.
Published: December 2008

The parr–smolt transformation (smoltification) of juvenile anadromous salmonids involves a morphological, physiological and behavioural metamorphosis of the fish from a freshwater-adapted form to a saltwater-adapted form. Several endocrine glands are activated during the period of smoltification, including pituitary, thyroid, and interrenal tissues. The pituitary-thyroid axis appears to be the endocrine system most directly involved in controlling smoltification. A plasma thyroid hormone surge occurs during smoltification which appears to influence various tissues and other endocrine systems, and to induce the well-documented developmental changes associated with smoltification.

The pituitary-interrenal axis has been implicated in several smoltification-related events, including development of hypo-osmotic regulatory ability. A plasma cortisol surge closely follows the thyroid hormone surge during smoltification, but in contrast to anuran metamorphosis, the peaks do not coincide. Despite recent attention, the role of the corticosteroids in development of hypo-osmotic regulatory ability remains unclear. The other endocrine tissues of the salmonids appear to be acting trophically with the thyroid hormones, or to have little involvement in the control of smoltification.

J. Endocr. (1986) 108, 313–319
Pregnancy-associated changes in ovarian immunoreactive β-endorphin in rats
Authors: Autelitano D. J. , Lolait S. J. , Smith A. I. , Funder J. W.
Published: December 2008

Ovaries from pregnant and postpartum Sprague–Dawley rats were examined for content of immunoreactive β-endorphin by radioimmunoassay, and for its localization by the peroxidase-antiperoxidase technique. In addition, the molecular forms of β-endorphin immunoreactivity were separated by gel chromatography and reverse-phase high performance liquid chromatography (RP-HPLC). Ovaries from rats early in pregnancy showed intense granular cytoplasmic staining of luteal cells, with an even distribution of granular material throughout the cytoplasm. By middle to late pregnancy the staining pattern was changed, with immunoreactive material showing a less granular and unevenly distributed staining pattern and with some areas of the cytoplasm totally devoid of immunoreactive material. The concentrations of immunoreactive β-endorphin measured during pregnancy were significantly lower than levels in mature non-pregnant rat ovary. The ovarian concentration of immunoreactive β-endorphin fell progressively during pregnancy and early lactation, returning to normal cyclic rat levels at 20 days post partum. The ovarian concentration of β-endorphin-like material was lowest at 6 days post partum (0·53 ± 0·08 ng/g wet weight; mean ± s.e.m.), representing approximately 10% of the concentration found in pooled ovaries from randomly cyclic adult rats. Gel chromatography revealed only a single peak of immunoreactive β-endorphin, co-eluting with 3·5 kD molecular weight ovine β-endorphin(1–31). This contrasts with gel profiles of adult cyclic rat ovary, where large molecular weight species pro-opiomelanocortin (31 kD) and β-lipotrophin (11·5 kD) are also present. On RP-HPLC the predominant species of low molecular weight immunoreactive material co-eluted with β-endorphin(1–31).

These data show that pregnancy in the rat is associated with marked changes in the levels, cellular localization and chromatographic profiles of ovarian β-endorphin. The aetiology and physiological significance of these changes remains to be established.

J. Endocr. (1986) 108, 343–350
Increased monoester lipase activity in red blood cells during hyperthyroidism
Authors: Cohen J. , Somma-Delpero C. , Verine A. , Codaccioni J. L. , Boyer J.
Published: December 2008

Human red blood cells (RBC) contain a monoester lipase (MEL) activity which is tightly associated with the cell membrane and has its active site externally oriented, as inferred from the ability of the intact cell to hydrolyse an exogenously added lipid substrate. Membrane-bound MEL activity was measured by a radiochemical assay in intact RBC from 29 untreated hyperthyroid patients. The mean (±s.d.) MEL level was higher (P < 0·01) in these patients (1220 ± 212 mu./1012 RBC) than in the control group (1010 ± 120 mu./1012 RBC). There was no difference between men and women. The increase in MEL values was associated with significantly (P < 0·001) decreased values of mean cellular volume and mean cellular haemoglobin content. A continued study of 13 patients, who became euthyroid with treatment, showed a normalization of the MEL values in RBC. The increased lipolytic potency of RBC represents a new characteristic of hyperthyroid patients. Further exploration of the possible diagnostic or prognostic implications of this enzymatic change seems warranted.

J. Endocr. (1986) 108, 357–359
Relationships between plasma progesterone levels and testicular testosterone production in the rat fetus: effects of maternal ovariectomy
Authors: Habert R. , Picon R.
Published: December 2008

The present study was performed to examine whether circulating progesterone regulates testicular testosterone production in the fetal rat. Progesterone levels in fetal plasma were found to increase from day 14·5 to day 16·5; thereafter they reached a plateau between days 16·5 and 18·5 (80 nmol/l) and decreased threefold between days 18·5 and 21·5. The addition of progesterone, within the range of normal plasma concentrations, induced a dose-dependent increase in testosterone produced in vitro by the testes on days 16·5 and 18·5 but not on day 20·5. However, in 18·5-day-old fetuses, individual plasma progesterone levels were not correlated with testicular testosterone production in vivo and in vitro. Furthermore, maternal bilateral ovariectomy induced a significant fall in plasma progesterone in 18·5-day-old fetuses; this was not associated with a reduction in plasma testosterone nor in testicular testosterone content, although the amount of testosterone secreted by the testis incubated in vitro was slightly but significantly reduced. It is concluded that circulating progesterone does not regulate testicular testosterone production in vivo although the testis may use plasma progesterone as a substrate. On day 18·5 after maternal ovariectomy, the decrease in plasma progesterone levels was similar in fetuses and mothers, suggesting that most fetal progesterone originates from maternal plasma.

J. Endocr. (1986) 108, 361–367
Aldosterone regulates salivary sodium secretion in cattle
Authors: Riad F. , Lefaivre J. , Tournaire C. , Barlet J.-P.
Published: December 2008

Intravenous infusion of aldosterone (10 μg/kg body wt per h for 5 h) in four 2-month-old calves decreased salivary and urinary sodium (Na+) concentration and increased salivary potassium (K+) concentration without modifying salivary flow or urinary K+ concentration. Intravenous angiotensin II infusion (0·3 μg/kg body wt per min for 1 h) in four Na+-replete 16-month-old bulls decreased salivary Na+ concentration and increased that of K+. It also increased plasma cortisol and plasma aldosterone concentrations, and decreased plasma renin activity (PRA). In four 16-month-old bulls Na+ deficiency (induced by chronic cannulation of the righ parotid duct and loss of saliva for 5 days) had similar effects to those observed following aldosterone infusion in calves: a decrease in salivary Na+/K+ ratio. This decrease was associated with an increase in PRA and an increase in plasma aldosterone concentration. In these animals a close positive relationship was observed between PRA and plasma aldosterone concentration (r = 0·91; n = 20; P < 0·01). Thus in cattle, during Na+ deficiency, the effect of aldosterone on parotid glands participates in the regulation of Na+ metabolism.

J. Endocr. (1986) 108, 405–411
The dopaminergic regulation of anterior pituitary 45Ca2+ homeostasis and prolactin secretion
Authors: Schrey M. P. , Clark H. J. , Franks S.
Published: December 2008

A role for the regulation of cellular Ca2+ homeostasis in the dopaminergic control of prolactin secretion was investigated in rat anterior pituitary glands. Withdrawal of dopamine stimulated the uptake of 45Ca2+ into hemipituitary tissue by 48% after 3 min. Radioisotope desaturation from tissue prelabelled with 45Ca2+ was significantly retarded in the presence of dopamine. Withdrawal of dopamine rapidly stimulated 45Ca2+ efflux from prelabelled tissue by 79% and was accompanied by a three- to fourfold rise in prolactin secretion. The 45Ca2+ efflux response to dopamine withdrawal was reduced in tissue prelabelled in the presence of dopamine. Agonist displacement with metoclopramide mimicked the effect of dopamine withdrawal on 45Ca2+ efflux and prolactin secretion.

These observations demonstrate that the stimulation of prolactin release by dopamine withdrawal is accompanied by a redistribution of cellular Ca2+ and support the hypothesis that dopamine inhibits secretion by decreasing Ca2+ influx in the mammotroph cell.

J. Endocr. (1986) 108, 423–429
Influence of hypothyroidism on the lipolytic activity of norepinephrine in the newborn lamb
Authors: Wrutniak C. , Cabello G.
Published: December 2008

The effects of hypothyroidism on the lipolytic activity of norepinephrine were assessed in the newborn lamb. Lambs were separated into three groups: group A were controls; groups B and C were made hypothyroid by administration of benzylthiouracil from birth until 11 days of age.

In control lambs, plasma free fatty acid concentrations, used as an index of lipolytic activity, increased significantly (plus 0·45 mmol/l) during the infusion of norepinephrine, whereas they did not change in hypothyroid lambs (group B). Adding thyroxine and tri-iodothyronine to the infusion medium (group C) immediately restored the free fatty acid response to norepinephrine in hypothyroid lambs (plus 0·41 mmol/l).

These results suggest that thyroid hormones could modulate the lipolytic activity of catecholamines in the newborn lamb without a latent period.

J. Endocr. (1986) 108, 451–454
Plasma release of atrial natriuretic peptide in response to blood volume expansion
Authors: Anderson J. V. , Christofides N. D. , Bloom S. R.
Published: December 2008

The response of plasma atrial natriuretic peptide (ANP) concentration to acute intravascular volume expansion was measured in ten male Wistar rats. An infusion of 3 ml polygelene colloidal solution at 37 °C over 45 s produced peak venous pressure rises of 1·5cm water. A highly significant (P<0·001) rise of immunoreactive plasma ANP from 24·4 ± 2·2 (mean ± s.e.m.) pmol/l to a peak of 70·0±10·5 pmol/l occurred within 2·5 min. Plasma ANP concentrations had virtually returned to basal levels (32·7 ± 2·7 pmol/l) 30 min after this acute volume load. A further infusion of 10 ml polygelene colloidal solution in 2 min produced peak venous pressure rises of 10 cm water and caused a dramatic and significant (P< 0·001) increase of plasma ANP concentration to a peak of 534·8 ± 38·5 pmol/l, occurring 7·5 min after infusion. The plasma ANP concentration had fallen but remained above basal levels 30 min later (137·2 ± 26·4 pmol/l).

Similar results were obtained using an identical protocol but with whole rat blood instead of polygelene solution as the volume-expanding agent. Gel column chromatography suggested that the majority of the immunoreactive ANP in rat plasma was of similar molecular size to rat α-ANP(1–28).

These results support the hypothesis that blood volume expansion is a potent stimulus for the release of ANP into plasma.

J. Endocr. (1986) 109, 9–13
Melanocyte-stimulating hormone, tyrosinase activity and the regulation of eumelanogenesis and phaeomelanogenesis in the hair follicular melanocytes of the mouse
Authors: Burchill S. A. , Thody A. J. , Ito S.
Published: December 2008

Skin tyrosinase levels and the eumelanin and phaeomelanin contents of the hair were measured in pubertal and adult C3H–HeA*vy mice that grow dark and golden yellow hair respectively. Hair growth was initiated by plucking and the skin tyrosinase levels, which increased during the growth of new hair and peaked at around 9 days after plucking, were higher during the growth of dark hair in the pubertal mice than during the growth of yellow hair in the adult mice. Although there was only a twofold difference in the phaeomelanin contents of these two types of hair, the dark hair of the pubertal mice contained over 20 times more eumelanin than the golden-yellow hair of the adult mice. These results suggest that the changes in coat colour in C3H–HeA*vy mice are due mainly to changes in eumelanin synthesis by the hair follicular melanocytes and that the production of this pigment requires higher levels of the enzyme tyrosinase than does the production of phaeomelanin. These changes did not appear to be related to plasma α-MSH levels. Nevertheless, administration of α-MSH increased skin tyrosinase activity in the pubertal mice that were growing dark hair and produced a twofold increase in the eumelanin content of the hair. However, it had no such effects in adult mice and also failed to affect the phaeomelanin content of the hair in both groups of mice. In contrast to α-MSH, bromocriptine decreased skin tyrosinase levels and the eumelanin content and increased the phaeomelanin content of the hair in pubertal mice. These effects of bromocriptine were unrelated to plasma immunoreactive α-MSH levels and were not restored when α-MSH was administered together with the dopamine agonist.

Although the present results support the idea that α-MSH increases coat darkening in the C3H–HeA*vy mouse through its actions on tyrosinase activity and eumelanin synthesis, it seems that these actions are more dependent on changes at the melanocyte level than changes in circulating α-MSH. The present results further suggest that dopaminergic mechanisms may also play a direct regulatory role in the control of coat colour in this mouse.

J. Endocr. (1986) 109, 15–21
An immunocytochemical and electron microscopic study of the hyt mouse anterior pituitary gland
Authors: Noguchi T. , Kudo M. , Sugisaki T. , Satoh I.
Published: December 2008

The hyt mutant mouse used in this study has a hypoplastic thyroid gland and is characterized by retarded somatic growth, very low to undetectable levels of plasma thyroxine (T4), and increased levels of plasma thyroid-stimulating hormone (TSH). This congenital hypothyroid mouse is therefore an ideal model for studying the effects of thyroid hypofunction on the adenohypophysis.

The anterior pituitary of the hyt mouse appeared less granular than that of the normal control when viewed by light microscopy, owing to a decrease in the population of somatotrophs. Many cells, in various stages of transformation into 'thyroidectomy cells', were recognized by the appearance of the characteristic granules and dilated rough endoplasmic reticulum. In some cases, the enlarged rough endoplasmic reticulum also contained spherical electron-dense secretory granules. In addition there were many cells undergoing mitosis and these were identified as thyrotrophs by their characteristic granules.

Administration of T4 during the first 40 days of life prevented the abnormal changes in the hyt anterior pituitary.

A reduction in immunoreactive thyrotrophin-releasing hormone (TRH) levels was seen in the median eminence of the hyt mouse. Treatment with T4 restored this to normal, suggesting that the reduced TRH content of the hypothalamus of the mutant mouse may be due to T4 deprivation.

J. Endocr. (1986) 109, 163–168
Effects of two enkephalin analogues, morphine sulphate, dopamine and naloxone on prolactin secretion from rat anterior pituitary glands in vitro
Authors: Bentley A. M. , Wallis M.
Published: December 2008

Experiments were carried out on the antagonistic effects of opiates on the inhibition by dopamine of prolactin secretion from rat anterior pituitary glands. Dose–response and time-course experiments were carried out using both static incubation of paired hemipituitary glands and perifusion of whole glands. Dopamine (10–1000 nmol/l) was found to have an inhibitory effect on prolactin secretion, but at a lower concentration (0·1 nmol/l) a small stimulation was observed. Against an inhibition established with 100 nmol dopamine/l in static incubation, the three opiates under study, morphine sulphate, Leu5enkephalin and d-Ala2,Met5-enkephalin (DAME), had a maximum antagonistic effect at 50–1000 nmol/l in a 90-min incubation. Morphine and DAME were rather more effective than Leu5-enkephalin, possibly because of degradation of the latter. Naloxone reversed the effect of morphine. All three opiates showed little effect on dopamine-inhibited prolactin secretion in a perifusion system. The data accord with previous suggestions that prolactin secretion may be stimulated both by very low concentrations of dopamine and by opiates acting to reverse the inhibition exerted by higher dopamine concentrations. It should be noted that both morphine and the enkephalins have similar effects on prolactin secretion, despite their normal specificity for different opiate receptors; their actions on the pituitary may thus be rather non-specific.

J. Endocr. (1986) 109, 313–320
Effect of adrenocorticotrophin on cortisol and androstenedione secretion from dispersed cells of guinea-pig adrenal zonae fasciculata and reticularis
Authors: Robertson W. R. , Davison B. , Anderson D. C. , Frost J. , Lambert A.
Published: December 2008

We have studied cortisol and androstenedione secretion by dispersed cells of the outer zona fasciculata (ZF) plus zona glomerulosa, and the inner zona reticularis (ZR) plus medulla of the guinea-pig adrenal. The ZF and ZR were microdissected apart, the cells dispersed and incubated (200 000 cells/ml) for 90 min in the presence of adrenocorticotrophin (ACTH; 500 ng/l), dibutyryl cyclic AMP (dbcAMP; 1 mmol/l), pregnenolone, 17-hydroxypregnenolone, 17-hydroxyprogesterone, 11-deoxycortisol and 21-deoxycortisol. The steroid concentrations were 5–25 μmol/l. Cortisol secretion was assayed by radioimmunoassay. There was no detectable cortisol secretion ( < 50 nmol/l) from the ZR in the controls (no additive) or after dbcAMP stimulation. Adrenocorticotrophin-stimulated cortisol secretion was also low (range < 50–340 nmol/l). In contrast the ZF secreted 177–379 (control), 828–2052 (dbcAMP) and 2863–9735 (ACTH) nmol cortisol/l. There was no detectable (i.e. < 2 nmol/l) cAMP production by ZR or ZF either basally (no ACTH) or after ACTH stimulation (500 ng/l). Challenge of the ZR cells with each cortisol precursor steroid (5 μmol/l) increased (P < 0·05) cortisol secretion over that seen with the corresponding basal and ACTH-stimulated controls. Thus pregnenolone, 17-hydroxypregnenolone, 17-hydroxyprogesterone, 11-deoxycortisol and 21-deoxycortisol (converted directly to cortisol by 21-hydroxylase) gave rise to (mean ± s.d., n = 4) 406 ± 86, 680 ± 180, 1307 ± 111, 1141 ± 234 and 3160 ± 419 nmol cortisol/l respectively. The corresponding figures for the ZF prepared from the same adrenal cortex were 3919 ± 309, 4122 ± 97, 5766 ± 615, 5035 ± 260 and 6954 ± 755 nmol cortisol/l. With pregnenolone (25 μmol/l), cortisol secretion increased to 7847 ± 1424 (ZR) and 12880 ± 982 nmol/l (ZF), a ZR:ZF ratio of 0·6 compared with 0·1 for pregnenolone at 5 μmol/l. Androstenedione was secreted in the basal state by both ZF and ZR in similar quantities, i.e. 3·7 ± 0·3 and 3·7 ± 0·4 nmol/l (n = 9 and 14 respectively). Both cell types were ACTH sensitive, with androstenedione secretion increasing to 28 ± 4·8 (ZF) and 12·5 ± 0·9 (ZR) nmol/l.

There was a direct correlation (r = 0·924, P < 0·05) between total adrenal weight and body weight, between the percentage ZR in the cortex and adrenal weight (r = 0·96, P < 0·05) and between the percentage ZR and body weight (r = 0·981, P< 0·05). In a mature animal (800–1000 g) the ZR may occupy > 66% of the adrenal cortex. The mean diameters of cells from the ZF and ZR were 21 and 25 μm respectively.

J. Endocr. (1986) 109, 399–404
Central inhibition of oxytocin release in the rabbit: role of the midbrain
Authors: Tindal J. S. , Blake L. A.
Published: December 2008

Transection of the ventral central grey and surrounding midbrain tegmentum in anaesthetized lactating rabbits caused repeated milk ejections which, on comparison with the effects of i.v. infusions of synthetic oxytocin, synthetic arginine-vasopressin or a mixture of the two, were attributed to continuous release of 1·25–2·5 mu. oxytocin/min, although it is not known whether lesser amounts of vasopressin might also have been released. It is suggested that the ascending midbrain reticular formation, which is known to project rostrally through this region, controls the central inhibition of oxytocin release via the previously described septo-hippocampo-subicular route to the hypothalamus.

J. Endocr. (1986) 109, 405–409
LOCALIZATION AND HORMONAL REGULATION OF THE NON-SPECIFIC LIPID TRANSFER PROTEIN (STEROL CARRIER PROTEIN2) IN THE RAT TESTIS
Authors: van Noort M. , Rommerts F.F.G. , van Amerongen A. , Wirtz K.W.A.
Published: December 2008

In testis tissue from mature rats the non-specific lipid transfer protein (nsLTP), also called sterol carrier protein2 (SCP2), is concentrated in the Leydig cells and cannot be detected in Sertoli cells or germinal cells. Conclusions were reached after cell fractionation studies with normal testis tissue and after selective destruction of Leydig cells or germinal cells in vivo.

The amount of nsLTP (SCP2) in testis tissue increased twofold 48 h after two daily injections of human chorionic gonadotrophin (100 i.u., s.c.) and decreased twofold after plasma luteinizing hormone levels were suppressed to almost undetectable levels with silicone elastomer implants containing testosterone.

The specific localization in the Leydig cells and the luteinizing hormone-dependent cellular concentration of nsLTP/SCP2 support the possibility that this protein could play a role in the regulation of steroidogenesis by regulating the availability of cholesterol for the P450 side-chain cleavage enzyme in the mitochondria of Leydig cells.
Relationship between the vitamin D content of maternal milk and the vitamin D status of nursing women and breast-fed infants
Authors: Cancela L. , Le Boulch N. , Miravet L.
Published: December 2008

This work was designed to study the effect of the vitamin D content of human milk on the vitamin D status of exclusively breast-fed infants, and the relation between milk and maternal serum concentrations of vitamin D during the first month of lactation. Serum levels of calcium (Ca), phosphorus (P), magnesium (Mg) and 25-hydroxyvitamin D (25-OH-D) were determined in a racially heterogenous population of nursing women, between days 3 and 5 (L3), 15 and 18 (L15) and 30 and 45 (L30) post partum. The same parameters were determined in the serum of 1-month-old breast-fed infants. Maternal milk samples were obtained at L3, L15 and L30 and analysed for Ca, P, Mg, vitamin D and 25-OH-D content. Milk levels of Ca, P and Mg were found to be within the range previously described by other authors. No correlation was found between serum and milk levels of vitamin D and 25-OH-D in nursing mothers. The 25-OH-D concentration in milk was related to its vitamin D content and strongly correlated (P < 0·001) with the 25-OH-D levels in the serum of exclusively breast-fed infants. No significant changes were observed in maternal serum levels of 1,25-dihydroxyvitamin D (1,25-(OH)2D3) measured at L3 and L30, or between maternal and infant levels of 1,25-(OH)2D3 at L30. This study emphasizes the importance of the 25-OH-D content of maternal milk, in being primarily responsible for the vitamin D concentrations found in the serum of exclusively breast-fed infants. In contrast, serum levels of 1,25-(OH)2D3 measured in the breast-fed baby seemed mainly related to its calcaemia.

J. Endocr. (1986) 110, 43–50
Effects of lactation and season on plasma prolactin concentrations and response to bromocriptine during lactation in the Bennett's wallaby (Macropus rufogriseus rufogriseus)
Authors: Curlewis J. D. , White A. S. , Loudon A. S. I. , McNeilly A. S.
Published: December 2008

Prolactin concentration was measured in plasma collected each week for 13 months from lactating and non-lactating Bennett's wallabies (Macropus rufogriseus rufogriseus). In non-lactating animals, prolactin concentrations decreased towards the end of the study but such changes did not appear to fit a seasonal pattern. Prolactin concentrations were low during early lactation and at a similar level to non-lactating animals, increased significantly during late pouch life (February–May), and then returned to non-lactating levels at a time coincident with permanent exit of the joey from the pouch. Temporary removal of joeys from their mothers in April was followed by a rapid decline in prolactin concentrations which remained low for 24 h until the joey was returned to its mother, whereupon prolactin concentrations increased significantly within 2 h.

The effect of a single injection of bromocriptine (5 mg/kg) on lactation, embryonic diapause and plasma prolactin concentrations was examined at two stages of lactation. In November (lactational diapause), bromocriptine had no effect on prolactin concentrations but two out of four suckling joeys died on days 13 and 14 after treatment, and three out of four females gave birth on days 27, 27 and 28. Bromocriptine treatment in April (seasonal diapause) was followed by a significant reduction in prolactin concentrations and reduced growth rate of joeys belonging to treated females. New births were not observed.

In view of the effect of bromocriptine on plasma prolactin concentrations in late lactation and the demonstration that domperidone (a dopamine antagonist) significantly increases plasma prolactin concentrations, it would seem that dopamine can act as a prolactin inhibitory hormone in this as in other mammalian species.

J. Endocr. (1986) 110, 59–66
Differential potency of oestradiol-17β and diethylstilboestrol on separate groups of responses in the rat uterus
Authors: Grunert G. , Porcia M. , Tchernitchin A. N.
Published: December 2008

The present study describes the effects of oestradiol-17β and diethylstilboestrol (DES) on several oestrogenic responses in the immature rat uterus Diethylstilboestrol was (1) weaker than oestradiol in inducing uterine eosinophilia, water imbibition and mitoses, (2) as strong as oestradiol in eliciting epithelial hypertrophy at 24 h after treatment, and (3) stronger than oestradiol in eliciting the reduction of epithelial cell height at 6 h after treatment and myometrial cell hypertrophy at 24 h after treatment. In addition, differences among the mitotic responses to oestrogen of the different uterine cell types were also detected. The above dissociation of the effects of DES and oestradiol-17β is in agreement with the hypothesis that eosinophil-mediated non-genomic responses, genomic responses and cell proliferation are mediated by independent mechanisms, involving different receptors which may have different affinities for both compounds. The eosinopenia and eosinophil degranulation under DES treatment suggest an explanation for the effect of DES on water imbibition. The dissociation among genomic responses from the different uterine cell types supports the hypothesis that different kinds of cytosol-nuclear oestrogen receptors exist.

J. Endocr. (1986) 110, 103–114
Ontogeny of prolactin receptors in rat decidual tissue: binding by a locally produced prolactin-like hormone
Authors: Jayatilak P. G. , Gibori G.
Published: December 2008

The objectives of this investigation were to determine whether decidual tissue possesses specific binding sites for prolactin, and to examine whether the locally produced prolactin-like hormone binds to these receptors. Characterization of the binding of prolactin to decidual tissue from rats at day 9 of pseudopregnancy revealed specific, high-affinity sites. Binding approached saturation with increasing concentrations of either the ligand or the protein. Cytosolic extracts of day-9 decidual tissue, containing various amounts of decidual luteotrophin which possesses several of the physiological and biochemical characteristics of prolactin, displaced the binding of 125I-labelled prolactin to decidual membranes in a linear fashion. Prolactin-binding sites were detectable 72 h after induction of decidualization and 48 h after the appearance of decidual luteotrophin in the decidua. Prolactin receptor concentrations increased significantly between days 8 and 9, reached a plateau between days 9 and 12 and declined abruptly on days 14 and 15, accompanied by a similar decline in decidual luteotrophin concentration in the tissue. Thus rat decidual tissue possesses specific receptors for prolactin to which decidual luteotrophin locally produced can bind, thereby suggesting an auto/paracrine role for this substance.

J. Endocr. (1986) 110, 115–121
Superior cervical ganglionectomy prevents gonadal regression and increased plasma prolactin concentrations induced by long days in goats
Authors: Maeda K.-I. , Mori Y. , Kano Y.
Published: December 2008

The effects of the abolition of the diurnal change in melatonin secretion on the photoperiodic response of the gonadal axis and prolactin secretion to long days were examined in female goats. Female Saanen goats, reared under short-day conditions (8 h light: 16 h darkness; lights on at 05.00 h) at 22±2 °C for 5 months, were bilaterally superior cervical ganglionectomized (SCGX). One month after surgery, both SCGX and intact control goats were divided into two groups. Animals in group 1 were maintained under short days and those in group 2 moved to long days (16 h light: 8 h darkness; lights on at 05.00 h). In group 1, both SCGX and intact goats ovulated periodically and basal plasma prolactin levels were maintained throughout the day. In intact controls, exposure to long days suppressed ovulation and increased prolactin secretion for the first 150–200 days of exposure. The animals became photorefractory after this time; ovulation recurred and prolactin secretion returned to basal levels. Superior cervical ganglionectomy abolished or weakened the suppression of gonadal function and eliminated the increase in prolactin secretion induced by exposure to long days in the intact controls.

These results suggest that the pattern of melatonin secretion under long days is necessary to induce the photoperiodic response of gonadal function and prolactin secretion to long days and that, under natural conditions, melatonin regulates the seasonal changes in gonadal function and prolactin secretion by mediating the effect of long days.

J. Endocr. (1986) 110, 137–144
Somatomedin C/insulin-like growth factor I: simplified purification procedure and biological activities of the purified growth factor
Authors: Morrell D. J. , Ray K. P. , Holder A. T. , Taylor A. M. , Blows J. A. , Hill D. J. , Wallis M. , Preece M. A.
Published: December 2008

Human somatomedin C has been purified from Cohn fraction IV paste by a simplified procedure using chromatofocusing, hydroxylapatite chromatography and reverse-phase high performance chromatography. The purified material has a specific activity by somatomedin C radioimmunoassay of 9160 units/mg (1 unit is defined as the amount of somatomedin present in 1 ml normal adult male human serum), representing a 650 000-fold purification, and possesses sulphation, mitogenic and insulin-like activities (specific activities of 3388 units/mg, 832 units insulin equivalents/mg and 1122 units/mg respectively). Somatomedin C is shown to be a potent stimulator of DNA synthesis (50% maximum stimulation at 150 fmol/ml) in isolated chondrocytes derived from costal cartilage, a major physiological target tissue.

J. Endocr. (1986) 110, 151–158
Ultrastructural modifications provoked by tamoxifen either alone or combined with oestradiol in the uteri of fetal or newborn guinea-pigs
Authors: Pasqualini J. R. , Lecerf F.
Published: December 2008

The ultrastructural changes in the uterine epithelial cells of fetal and newborn guinea-pigs were examined by transmission electron microscopy after the administration of tamoxifen, oestradiol or a combination of tamoxifen and oestradiol.

Tamoxifen provoked a substantial alteration of the mitochondria and the rough endoplasmic reticulum with the formation of numerous vacuoles and secretory granules, indicating an enhancement of synthetic and secretory activities. The mixture of oestradiol and tamoxifen increased the effect and most organelles became irreversibly altered, particularly in the uteri of newborn animals after a long treatment.

It is concluded that, in addition to the agonistic oestrogen effects of tamoxifen on uterine growth, DNA and protein contents, tamoxifen also acts as an agonist on the ultrastructural changes of the uterine epithelial cells during the perinatal period of the guinea-pig.

J. Endocr. (1986) 110, 197–202
Effects of iodide and thyroxine on iodine-deficient mouse thyroid: a morphological and functional study
Authors: Many M.-C. , Denef J.-F. , Hamudi S. , Cornette C. , Haumont S. , Beckers C.
Published: December 2008

The effects of iodide and thyroxine (T4) on female mice fed a low iodine diet (LID) for 8 weeks were analysed by morphological, stereological and biochemical methods. Iodide was given at a dose of 10 μg/day (HID) or 1 μg/day (MID), either alone or together with daily injections of 1 μg T4 for 8 or 40 days.

With HID, the thyroid weight and the numbers of follicles and cells remained higher than in controls, although cell necrosis occurred. Colloid volume increased and iodine was stored within the gland: a colloid goitre with non-functioning follicles was produced. With MID, the glands resumed an almost normal appearance. With T4 and LID, progressive normalization occurred, but after 40 days thyroid weight and numbers of follicles and cells remained higher than in controls. Glandular iodine content slowly increased and reached control value. The proportions of 125I-labelled tri-iodothyronine (T3) and T4 in thyroglobulin were reduced. With T4 and HID, the glands resumed a normal appearance. Neither necrosis nor folliculoneogenesis was noted. The proportions of 125I-labelled T3 and T4 in thyroglobulin were reduced, but T3 and T4 serum levels were higher than with HID. With T4 and MID, a normal state was obtained as early as day 8. After 40 days the gland was morphologically and functionally inactive.

In conclusion, the association of T4 and iodide seems to be the best way to obtain a rapid and complete involution of thyroid hyperplasia. The administration of T4 prevents the deleterious effects of an excess of iodine on follicular cells, and causes the gland to enter a slow-functioning state.

J. Endocr. (1986) 110, 203–210
Effect of underfeeding on testosterone–LH feedback in the bull
Authors: Gauthier D. , Coulaud G.
Published: December 2008

This study was conducted to investigate the hypothesis that the low LH pulsatility induced by underfeeding may result from an altered negative-feedback response to testosterone in cattle.

Eight 21-month-old Aubrac bulls were divided into two equal groups. The first group (group H) received a high level of nutrition (producing a gain in weight of 570 g/day) and the second group (group L) a low level of nutrition (producing a loss in weight of 330 g/day). After 52 days of underfeeding the bulls were hemicastrated, castrated 7 days later and then injected with 30 mg testosterone daily for 14 days, 10 mg daily for 7 days and 2·5 mg daily for 7 days.

After hemicastration, LH pulsatility was higher (P < 0·001) in group H (9·0 pulses in 24 h) than in group L (5·3 pulses in 24 h). After castration this value was the same in the two groups (24 pulses in 24 h). When the bulls were injected daily with 30 or 10 mg testosterone, the number of LH pulses in 24 h was lower (P < 0·05) in group L (14·3 and 9·8 pulses in 24 h with 30 mg, and 17·3 pulses in 24 h with 10 mg) than in group H (27·8 and 25·5 pulses in 24 h with 30 mg, and 24·0 pulses in 24 h with 10 mg). When the animals received 2·5 mg testosterone daily, the number of LH pulses was the same in both groups (20·3 pulses in 24 h).

These results indicate that the negative-feedback response of the LH-releasing system to testosterone is modified by underfeeding in the bull.

J. Endocr. (1986) 110, 233–238
Evidence for the presence of the pituitary insulin secretagogue β-cell trophin in human plasma
Authors: Salvatoni A. , Dunmore S. J. , Morton J. L. , Etienne A. T. , Beloff-Chain A. , Abraham R. R.
Published: December 2008

It has been demonstrated that the insulin secretagogue β-cell-trophin, ACTH(22–39), is present in human plasma. The hormone, separated from plasma by affinity chromatography on a corticotrophin-like intermediate-lobe peptide antibody column, behaves similarly to synthetic β-cell-trophin on a gel filtration column and on reverse-phase high-performance liquid chromatography. Sufficient amounts of the hormone were isolated from the plasma of two patients with Nelson's syndrome to demonstrate its biological activity on the perfused rat pancreas.

J. Endocr. (1986) 110, 303–307