bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pro-opiomelanocortin messenger RNA levels increase in the fetal sheep pituitary during late gestation
Authors: Yang K. , Challis J. R. G. , Han V. K. M. , Hammond G. L. 
Published: December 2008

ABSTRACT
Plasma levels of ACTH and cortisol in fetal sheep increase progressively during late pregnancy, providing the stimulus for birth. However, little information is available concerning either sources of pro-opiomelanocortin (POMC, the precursor to ACTH) or changes in POMC gene expression, which may be responsible for the elevated fetal plasma ACTH concentrations. We therefore studied the relative amount of POMC mRNA in fetal sheep hypothalami, anterior pituitaries and adrenals at discrete times of pregnancy between day 60 and term (approximately 145 days) and from newborn lambs. Total RNA from these tissues was analysed by Northern blot hybridization using a human POMC DNA probe, and the amount of POMC mRNA was expressed relative to the signal obtained for 18S ribosomal RNA. A single 1·2 kb transcript was detected by day 60 in the anterior pituitary, and its relative amount did not change significantly until after days 125–130. Pituitary POMC mRNA levels increased significantly at days 138–143, remained elevated at term and increased further in newborn lambs. In contrast, POMC mRNA was undetectable in hypothalami and adrenal glands of fetuses at all ages.
The results suggested that the prepartum rise in plasma ACTH concentrations in fetal sheep is due to increased POMC biosynthesis in the fetal pituitary. The increase in POMC mRNA occurs at a time when fetal plasma cortisol concentrations are elevated, indicating that the negative feedback effects of circulating glucocorticoids on the fetal hypothalamicpituitary axis may be obscured by other mechanisms that increase pituitary POMC mRNA accumulation during the last week of gestation.
Journal of Endocrinology (1991) 131, 483–489
Iodide uptake and organification, tri-iodothyronine secretion, cyclic AMP accumulation and cell proliferation in an optimized system of human thyroid follicles cultured in collagen gel suspended in serum-free medium
Authors: Kraiem Z. , Sadeh O. , Yosef M. 
Published: December 2008

ABSTRACT
An experimental system was established for measuring cell function and proliferation of human thyroid follicles cultured in collagen gel suspended in serum-free medium. Optimal culture conditions were defined and the system was characterized. The human thyrocytes were functional as indicated by their ability to respond to a TSH stimulus (as low as 1–10 μU/ml). in a time- and dose-dependent fashion, with at least a 15-fold increase in iodide uptake and organification, tri-iodothyronine (T3) secretion (demonstrated to derive from de-novo T3 biosynthesis) and cyclic AMP accumulation. Moreover, the same system allowed the measurement of cell proliferation (as indicated by thymidine incorporation and DNA content) following epidermal growth factor (EGF) and phorbol ester challenge under conditions of cell density and medium identical to those for the differentiated functions. The functional responses and cell proliferation were markedly higher compared with those of the same cells in the presence of serum or maintained in monolayer culture. Normal cell polarity, which critically determines functional capacity of thyroid follicles was maintained (as demonstrated by electron microscopy) by the use of collagen gel and serum-free medium. The use of thyroid cells of human origin assumes great importance in view of the wide species differences reported. Cryopreservation of cells rather than the necessity of using freshly derived cells confers greater convenience. The present model system provides a powerful tool for studying human thyroid physiology and pathophysiology.
Journal of Endocrinology (1991) 131, 499–506
Localization and endogenous concentration of endothelin-like immunoreactivity in human placenta
Authors: van Papendorp C. L. , Cameron I. T. , Davenport A. P. , King A. , Barker P. J. , Huskisson N. S. , Gilmour R. S. , Brown M. J. , Smith S. K. 
Published: December 2008

ABSTRACT
The aim of this study was to investigate the localization of endothelin-like immunoreactivity (ET-IR) in human placenta, chorion and amnion and to compare the endogenous concentration of immunoreactive endothelin (ET) in these tissues before and after the onset of labour. ET-IR was detected in the endothelium of stem vessels in placental villi, as well as in decidual stromal cells in the basal maternal plate, by immunocytochemistry using a primary polyclonal rabbit antibody. A specific radioimmunoassay was used to detect endogenous concentration of ET in homogenized placental tissues. The endogenous concentration of ET-IR was significantly greater in amnion than in chorion and placenta (amnion 249 ±13 fmol/g; chorion 190 ±11 fmol/g; placenta 169±14 fmol/g; means ± s.e.m.; n = 12; P < 0·01). No significant difference was seen before or after the onset of labour. The detection of ET-IR in placenta, chorion and amnion suggests that the ETs may play a role in the paracrine control of human uterine function.
Journal of Endocrinology (1991) 131, 507–511
Degradation and distribution of brain natriuretic peptide in porcine tissues
Authors: Marumo F. , Matsubara O. , Masaki Y. , Togashi K. , Ando K. , Hasegawa N. 
Published: December 2008

ABSTRACT
Brain natriuretic peptide (BNP) is a novel peptide that has actions similar to atrial natriuretic peptide (ANP). The present study investigated BNP localization in the heart, ANP and BNP contents in several organs, and ANP and BNP clearance through these organs. In the morphological study, it was shown that porcine BNP-like immunoreactivity was mainly distributed in the granules of the atrium. The content of porcine BNP-like immunoreactivity in the atrium was extremely high, about 100-fold greater than in the ventricle. From the determination of porcine BNP and ANP contents of such organs as the heart, kidney and liver and also plasma, it was shown that porcine BNP concentration was approximately one order of magnitude lower than that of ANP, and clearance rates of ANP and porcine BNP from these organs were similar and not significantly different between the organs. These results suggest that the modes of secretion and degradation of porcine BNP are not the same as those of ANP.
Journal of Endocrinology (1992) 132, 101–106
Relaxin increases the firing rate of supraoptic neurones and increases oxytocin secretion in the rat
Authors: Way S. A. , Leng G. 
Published: December 2008

ABSTRACT
In urethane-anaesthetized ovariectomized rats, injection of porcine relaxin (7·5 and 15 μg/kg, i.v.) caused a sustained increase in circulating plasma oxytocin and vasopressin concentrations; 10 μg relaxin/rat i.v. produced a smaller but significant increase in plasma oxytocin concentration in conscious ovariectomized rats. A significant increase in oxytocin concentration and inhibition of the spontaneous milk-ejection reflex was also seen in anaesthetized (ovary intact) lactating rats following injection of relaxin (7·5 μg/kg, i.v.). To investigate whether relaxin acts by increasing the electrical activity of oxytocin neurones or by facilitating stimulus-secretion coupling in the pituitary, the electrical activity of neurones in the supraoptic nucleus was recorded in urethane-anaesthetized lactating rats and in ovariectomized rats. Porcine relaxin (10 μg/rat, i.v.) increased the firing rate of both oxytocin and vasopressin neurones in the supraoptic nucleus in lactating rats. The response to relaxin was unaffected by subsequent injection of naloxone (1 mg/kg, i.v.). Oxytocin neurones were also activated by injection of relaxin (10 μg/rat) into ovariectomized rats. Combining the electrophysiological data, the neuronal activation following relaxin was significantly correlated with the level of spontaneous activity prior to relaxin injection. The results show that relaxin acts centrally to increase circulating plasma oxytocin and vasopressin concentrations by an opioid-independent mechanism.
Journal of Endocrinology (1992) 132, 149–158
Release of proinsulin from the human fetal β cell
Authors: Tuch B. E. , Roberts E. C. , Darby K. B. 
Published: December 2008

ABSTRACT
β cells in the human fetal pancreas are immature in that they release little or no insulin in response to nutrients, such as glucose. The aim of this study was to examine further the immaturity of these cells, specifically regarding the storage and release of the precursor of insulin, proinsulin.
Explants of human fetal pancreas were cultured in vitro for 3 weeks. Levels of proinsulin remained relatively constant throughout at 0·04±0·002 (s.e.m.) pmol/mg per day with a molar ratio of proinsulin to insulin of 2·2 ± 0·11%. This low ratio was slightly greater than that observed in culture medium conditioned by adult human islets (0·3±0·1%), but similar to that found in acid–ethanol extracts of cultured explants (1·4 ± 0·3%). Passaging of human fetal pancreas for 3 months in diabetic nude mice, which should have caused some maturation of the fetal β cell, did not change the proportion of proinsulin present. Culture of explants in the presence of 12-O-tetra-decanoylphorbol-13-acetate resulted in some inhibition of proinsulin release, but much less than that for insulin, so that the molar ratio increased to 15·4±1·6% from the control 3·5 ± 0·3%. Static stimulation of cultured explants with 10 mmol Ca2+/l, 10 mmol theophylline/l, and these two agents together caused 15-, 4- and 10-fold enhancement respectively of proinsulin release; glucose, leucine, arginine and KCl had no effect. In contrast, all these agents caused significant insulin release, the last four to a much smaller extent (⩽ three fold) than the first three (10-, 19- and 65-fold respectively). Calcium channel blockers, verapamil and nifedipine, inhibited insulin but not proinsulin release.
The ability of different agents to modulate the release of proinsulin from the human fetal β cell, socalled regulated rather than constitutive secretion, as well as the low relative amount of proinsulin present show that this cell is more mature than was previously thought.
Journal of Endocrinology (1992) 132, 159–167
Regulation of cytosolic free calcium in isolated rat osteoclasts by calcitonin
Authors: Moonga B. S. , Alam A. S. M. Towhidul , Bevis P. J. R. , Avaldi F. , Soncini R. , Huang C. L.-H. , Zaidi M. 
Published: December 2008

ABSTRACT
It is now established that calcium is a second messenger mediating the action of calcitonin on the osteoclast. We have demonstrated that an increase in the concentration of intracellular free calcium ([Ca2+]i) is associated with (and possibly mediates) the functional effects of calcitonin, including an acute reduction of cell spread area (the R effect) and, in the longer term, a reduction in enzyme release. The present study addresses questions relating to mechanisms of calcitonin action on osteoclast [Ca2+]i. We have used asusuberic(1–7) eel and human calcitonin as agonists, and an indo-1-based dual-emission microspectrofluorimetric method for the measurement of [Ca2+]i in single osteoclasts. Whilst asusuberic(1–7) eel calcitonin caused a biphasic increase in [Ca2+]i, human calcitonin produced only a monophasic [Ca2+]i response of a much lower magnitude. Each biphasic response consisted of a rapid initial transient increase, occurring within seconds of exposure, followed by a sustained increase in [Ca2+]i. The magnitude of the latter response was more variable, but was consistently below the peak value of [Ca2+]i. The sustained phase of the calcitonin effect was abolished in extracellular Ca2+-free medium. This phase is therefore dependent on extracellular [Ca2+] ([Ca2+]e) whilst the rapid transient increase appeared to be dependent on Ca2+i redistribution. The effects of calcitonin on [Ca2+]i were concentration-dependent, with neither latency nor oscillations. Repetitive 30-s exposures to calcitonin failed to produce subsequent responses. There was a marked concentration-dependent correlation between changes in osteoclast [Ca2+]i and the magnitude of the R effect. Thus the likely components of the biphasic [Ca2+]i response are a rapid redistribution followed by the transmembrane flux of Ca2+. We suggest that the increase in [Ca2+]i may mediate, in part, the inhibitory effect of calcitonin.
Journal of Endocrinology (1992) 132, 241–249
Immunolocalization of mineralocorticoid receptor in human kidney, pancreas, salivary, mammary and sweat glands: a light and electron microscopic immunohistochemical study
Authors: Sasano H. , Fukushima K. , Sasaki I. , Matsuno S. , Nagura H. , Krozowski Z. S. 
Published: December 2008

ABSTRACT
Using a polyclonal antibody against a synthetic fusion protein corresponding to 167 amino acids of the N-terminal region of the human renal mineralocorticoid receptor (MR), an immunohistochemical study was performed to investigate the intraglandular and intracellular localization of the receptor in human kidney, salivary gland, pancreas, mammary gland and sweat gland both at the light and electron microscopic levels. In the kidney, immunoreactivity was observed in distal convoluted tubules, branches of Henle's loop, and collecting tubules in the renal cortex, and papillary and Henle's loops' ducts in the renal medulla. No significant differences in the distribution of immunoreactivity were observed using different fixatives (10% neutral formalin, 100% methanol, 4% paraformaldehyde, PLP (periodate–lysine–2% paraformaldehyde) solution and Zamboni solution) and processing methods (paraffin embedding and frozen sectioning). Immunoreactivity in the kidney was observed in both the cytoplasm and nucleus, with cytoplasmic staining predominant, regardless of the methods of tissue preparation. Immunoelectron microscopy, employing a pre-embedding method, demonstrated the presence of immunoreaction precipitates in nuclei, endoplasmic reticulum, perinuclear cisternae, free cytoplasm and cell membranes. In nuclei, immunoreactivity was observed in euchromatin but not in heterochromatin, which is consistent with an association of MR with specific DNA regulatory elements located in transcriptionally active euchromatin. In other organs, MR was expressed in cells of the excretory ductal system where mineralocorticoids are known to play a role in electrolyte homeostasis.
Journal of Endocrinology (1992) 132, 305–310
Daily administration of gonadotrophin-releasing hormone increases pituitary gonadotroph number and pituitary gonadotrophin content, but not serum gonadotrophin levels, in female rats on day 1 of dioestrus
Authors: Kotsuji F. , Hosokawa K. , Tominaga T. 
Published: December 2008

ABSTRACT
Gonadotrophin-releasing hormone (GnRH) has been shown to regulate the synthesis and release of gonadotrophins acutely, yet few studies have investigated the chronic effects of this agent on pituitary gonadotrophins. In the present study we determined the effect of chronic administration of GnRH on the female rat pituitary gland. Rats of 8 weeks of age were injected s.c. with various doses of GnRH daily for 30 days. After completion of the GnRH treatment, treated rats and age-matched controls were killed by decapitation at 09.00 h on the first day of dioestrus, as determined from vaginal smears. Treatment with 10 ng–10 μg GnRH/day increased pituitary contents of FSH and LH in a dose-dependent manner. The change in FSH content was much greater than that of LH content. The pituitary FSH content of rats treated with 40 μg GnRH was significantly less than that of rats treated with 10 μg GnRH. There was a marked increase in the number of cells which stained positively for FSH (266%) and LH (28%) in the anterior pituitary of rats given 10 μg GnRH, but there was no demonstrable change in the areas of single cells stained positively for FSH and LH. Serum levels of LH, FSH and oestradiol were not affected by the GnRH treatment. These data indicate that chronic administration of GnRH is capable of increasing the pituitary gonadotrophin content and numbers of FSH and/or LH-stained cells and that FSH cells are affected more than LH cells by the GnRH treatment. The increase in pituitary gonadotrophin content, however, does not necessarily produce an increase in circulating levels of gonadotrophins.
Journal of Endocrinology (1992) 132, 395–400
Circulating maternal immunoreactive inhibin levels during pregnancy in the rat: effects of oophorectomy, hypophysectomy, hemihysterectomy, delayed implantation and pseudopregnancy
Authors: Yohkaichiya T. , Irby D. , de Kretser D. M. 
Published: December 2008

ABSTRACT
This study examines the source of inhibin in the maternal circulation of pregnant rats by measuring serum immunoactive inhibin levels following a range of experimental procedures. Ovariectomy at days 7, 13 or 19 of gestation, with maintenance of pregnancy by supplementation with progesterone and oestradiol dipropionate, led to a profound fall of serum inhibin levels in comparison with controls, demonstrating that the ovary is a major source of circulating inhibin. This conclusion was supported by the inhibition of the late rise (days 16–22) in serum inhibin in pregnant rats which were hypophysectomized on day 15 and maintained with oestrogen and progesterone supplementation. These data support the view that the rise in serum inhibin from days 16 to 22 is due to re-activation of follicular development in preparation for the post-partum oestrus. Reduction of fetal numbers by hemihysterectomy on days 7, 13 or 19 did not alter serum inhibin levels. Induction of delayed implantation by ovariectomy on day 3 and progesterone supplementation together with initiation of reimplantation by the addition of oestradiol dipropionate on day 7 or 11 did not significantly alter inhibin levels. The induction of pseudopregnancy by mating to vasectomized rats did not result in the maintenance of stable serum inhibin levels until oestrous cycles recommenced. Taken together, the studies have identified the ovary as the predominant source of circulating maternal inhibin levels throughout pregnancy in the rat.
Journal of Endocrinology (1992) 132, 469–475
Effects of in-vivo administration of insulin-like growth factor-I on the rate of glucose utilization in the soleus muscle of the rat
Authors: Dimitriadis G. , Parry-Billings M. , Dunger D. , Bevan S. , Colquhoun A. , Taylor A. , Calder P. , Krause U. , Wegener G. , Newsholme E. A. 
Published: December 2008

ABSTRACT
This study investigated the effects of insulin-like growth factor-I (IGF-I) administered to rats in vivo on the soleus muscle isolated from these rats. In order to study the interactions between IGF-I and insulin, the soleus muscles were incubated in the presence of various concentrations of insulin. IGF-I (190–200 μg) was given twice daily; the rats were killed 1 h after one injection of IGF-I (acute administration) or after treatment with IGF-I for 10 days (prolonged administration). The level of IGF-I in plasma was increased by ∼ 100% after acute administration and by around 30% after 10 days of treatment with IGF-I. Acute administration of IGF-I to the rats increased the flux of glucose to hexose monophosphate and the rates of lactate formation and glycogen synthesis in the soleus muscles; however, the responsiveness of these muscles to insulin was lost: the increase in the rate of glucose utilization by IGF-I at physiological concentrations of insulin (10 or 100 mU/l) was similar to that observed at maximal concentrations of insulin (1000 mU/l). Similar results were obtained after prolonged treatment of the rats with IGF-I; however, the increase in the rate of glucose utilization was less pronounced than when IGF-I was given acutely and the muscles were still capable of responding to insulin. These results suggest that: (a) acute or chronic increases in the serum level of IGF-I in the rat in vivo increase the basal rate of glucose utilization in skeletal muscle; this increase is independent of insulin; (b) the effects of insulin on the rate of glucose utilization are not additive to those of IGF-I; however, this may depend on the level of IGF-I in serum.
Journal of Endocrinology (1992) 133, 37–43
Effects of insulin-like growth factor-I (IGF-I) infusion and dietary tri-iodothyronine (T3) supplementation on growth, body composition and plasma hormone levels in sex-linked dwarf mutant and normal chickens
Authors: Tixier-Boichard M. , Huybrechts L. M. , Decuypere E. , Kühn E. R. , Monvoisin J.-L. , Coquerelle G. , Charrier J. , Simon J. 
Published: December 2008

ABSTRACT
This study used a sex-linked dwarf mutant (SLD) chicken to evaluate growth-promoting and metabolic effects of recombinant human insulin-like growth factor-I (rhIGF-I) treatment. The SLD chicken is characterized by a 30% reduction in body weight and by high plasma GH levels, low plasma IGF-I and triiodothyronine (T3) levels and very low GH binding on liver membranes, suggesting reduced functional GH receptors compared with normal chickens. The effects of a continuous s.c. infusion by osmotic mini-pump of 0·1 mg rhIGF-I/kg per day from 4 to 8 weeks of age on body weight, bone growth and body composition were investigated in female SLD and normal chicks. In addition, half of the birds received a dietary supplement of T3 (0·1 parts per million). Plasma levels of IGF-I, GH, T3, thyroxine and insulin were followed during the treatment. In normal chicks, rhIGF-I infusion had no effect on growth and little effect on plasma hormone levels except for a decrease in plasma insulin. In dwarf chicks, rhIGF-I infusion slightly increased body weight but had no effect on longitudinal bone growth. In addition, plasma GH levels were decreased and T3 levels remained lower than in normal chicks. Normal and dwarf chicks showed a decrease in abdominal fat after both IGF-I administration and T3 supplementation, the treatments having additive effects in dwarf chicks only. The combined rhIGF-I and T3 treatment restored a quasi-normal hormonal pattern in dwarf chicks, except for insulin which remained lower than in normal chicks. These results suggest that IGF-I in the chicken has no direct endocrine effect on statural growth.
Journal of Endocrinology (1992) 133, 101–110