bluuebunny/crossref_metadata_2025_split huggingface dataset:
Metabolic effects of cortisol, ACTH, adrenalin and insulin in the marsupial sugar glider, Petaurus breviceps
Authors: Bradley A. J. , Stoddart D. M. 
Published: December 2008

ABSTRACT
The effects of cortisol, ACTH, adrenalin and insulin on indices of carbohydrate, fat and protein metabolism were investigated in the conscious marsupial sugar glider Petaurus breviceps.
Short-term i.v. infusion of cortisol at dose rates of 0·02, 0·2 and 1·0 mg/kg per h caused the plasma glucose concentration to rise sharply from the normal range of 3·3–4·4 to 8·1–8·7 mmol/l at the end of the infusion period without significant alteration in plasma free fatty acid (FFA), amino acid or urea concentrations. Infusions of ACTH at dose rates of 0·02, 0·06 and 0·45 IU/kg per h caused a similar rise in plasma glucose concentration; however, this was now accompanied by an elevation in plasma FFA concentration, but again without significant changes in either plasma amino acid or urea concentrations. Infusion of adrenalin at 10 μg/kg per h caused an increase in the plasma concentrations of both glucose and FFA. Intravenous injections of 0·15 IU insulin/kg caused a rapid and marked decrease in the plasma glucose concentration within 30 min and an increase in the plasma free cortisol concentration. Associated with this change was a marked rise in the plasma concentration of both FFA and free cortisol. The rise in free cortisol was, however, significantly reduced by infusion of glucose. Pretreatment with five daily i.m. injections of 1 mg cortisol acetate/kg, which produced an increase in plasma free cortisol concentration to near the maximum of the physiological range, caused a marked reduction in insulin sensitivity. Cortisol pretreatment caused an increase in the plasma FFA and amino acid concentrations.
Petaurus breviceps is highly sensitive to the metabolic effects of glucocorticoids and is similar in this respect to the brush-tailed possum Trichosurus vulpecula. The interactive effects between insulin and glucocorticoids on carbohydrate, fat and protein metabolism in Petaurus breviceps are similar to those shown by Trichosurus vulpecula and some eutherian mammals but contrast with the pattern described for two macropodid marsupials, the red kangaroo Macropus rufus and the quokka Setonix brachyurus.
Journal of Endocrinology (1990) 127, 203–212
Characterization of insulin-like growth factor-binding protein in ovine amniotic fluid
Authors: Wang J.-F. , Fraher L. J. , Hill D. J. 
Published: December 2008

ABSTRACT
We have characterized an insulin-like growth factor (IGF)-binding protein present in ovine amniotic fluid. Using an activated charcoal-binding assay, whole amniotic fluid specifically bound approximately 20–30% of 125I-labelled human (h) IGF-II added, while the binding of 125I-labelled hIGF-I was minimal. Radioimmunoassay for IGF-I or -II in ovine biological fluids showed that values in amniotic fluid were 9- to 13-fold less than in fetal plasma, while gel filtration of amniotic fluid on Sephadex G-50 eluted with 1 mol acetic acid/l revealed no additional binding activity which had been complexed to IGFs at neutral pH. Together, these observations suggest that the binding activity in amniotic fluid is largely unsaturated. Competition studies for the displacement of 125I-labelled IGF-II binding to amniotic fluid by increasing amounts of unlabelled IGF-I or -II, using the charcoal assay, showed that IGF-II was 30-fold more potent than IGF-I. Scatchard analysis revealed a single class of binding site for IGF-II, with a binding affinity of 0·68 ±0·18 litres/nmol (mean ± s.d., n = 3). Ligand blot analysis of amniotic fluid by separation on 8% SDS-PAGE, transfer to nitrocellulose membranes, incubation with 125I-labelled IGF-II and autoradiography revealed a single band of IGF-binding protein with approximate molecular size of 38 kDa. Additional IGF-binding species of 20, 28, 48 and > 180 kDa were present in ovine fetal plasma. Separation of amniotic fluid on Concanavalin A–Sepharose revealed that it had little carbohydrate content. These results show that ovine amniotic fluid contains an unsaturated, non-glycosylated IGF-binding protein with high affinity for IGF-II. These characteristics differ from those of the IGF-binding proteins purified from human amniotic fluid.
Journal of Endocrinology (1990) 127, 325–333
Cytosolic glucocorticoid receptors in the porcine lung during development and after hypophysectomy or thyroidectomy
Authors: Yarney T. A. , Kendall J. Z. , Randall G. C. B. 
Published: December 2008

ABSTRACT
The ontogeny of fetal lung glucocorticoid receptors and their regulation by the fetal pituitary, adrenal and thyroid gland during lung maturation were investigated. Sites with a specificity typical of glucocorticoid receptors were detectable in lung cytosol, with the order of potency of steroids being dexamethasone > cortisol > corticosterone > 11- -deoxycorticosterone > progesterone > 17α-hydroxyprogesterone > oestradiol -17β ≃ testosterone ≃ androstenedione ≃ oestrone. The binding affinity for [3H]dexamethasone was high (Kd = 0·23–0·60 nmol/l) and showed an age-related decrease during the perinatal period when cortisol levels were high. After charcoal treatment of the cytosol, however, a decrease in binding affinity was not as clearly evident. The Kd decreased following hypophysectomy of fetuses; thyroidectomy had no significant effect. The concentration of glucocorticoid receptors was high from day 82 to day 100 of gestation (1437 fmol/mg protein) and declined progressively to a lower value at term and following birth (660 fmol/mg protein). Hypophysectomy, but not thyroidectomy, prevented the age-related decline in receptor concentration. Lung glycogen content declined with fetal ageing in association with increases in plasma concentrations of cortisol and thyroxine and with changes in Kd and Bmax, but appeared to be more closely associated with concentrations of thyroxine. Hypophysectomy of fetuses decreased concentrations of both cortisol and thyroxine and prevented the depletion of lung glycogen content. Preliminary results from thyroidectomized fetuses showed decreases in plasma thyroxine and lung glycogen content compared with day-82 fetuses. Plasma cortisol levels, however, were consistent with a fetal age of 113 days. The effects of thyroxine on lung glycogen depletion, therefore, appear to occur, at least in part, through a pathway independent of glucocorticoid receptors.
Journal of Endocrinology (1990) 127, 341–349
Regulation of interleukin-6 release by human thyrocytes
Authors: Weetman A. P. , Bright-Thomas R. , Freeman M. 
Published: December 2008

ABSTRACT
Autoimmune thyroiditis is characterized by lymphocytic accumulation within the thyroid which may be the result, in part, of immunomodulatory cytokine secretion by thyrocytes. We have tested human thyroid cell cultures (n = 9) for interleukin-6 (IL-6) release using two bioassays. IL-6 was detected in all culture supernatants under basal conditions and was increased by γ-interferon, tumour necrosis factor and TSH in a dose-dependent manner. The bioactivity was confirmed as IL-6 by immunoblotting experiments and could not be accounted for by contamination of the thyroid cell cultures with fibroblasts, lymphocytes or monocytes. Circulating IL-6 levels were not raised in patients with Graves' hyperthyroidism. Exogenous recombinant IL-6 reduced cyclic AMP production in response to TSH when added to thyroid cell cultures. Since IL-6 plays a major role in B cell differentiation and T cell activation, release of IL-6 by thyrocytes may increase the intrathyroidal autoimmune response in Graves' disease and Hashimoto's thyroiditis. Our results also suggest that IL-6 may modulate thyroid cell function.
Journal of Endocrinology (1990) 127, 357–361
The influence of adrenal hormone status on neuroendocrine peptides in the rat anterior pituitary gland
Authors: Jones P. M. , O'Halloran D. J. , Ghatei M. A. , Domin J. , Bloom S. R. 
Published: December 2008

ABSTRACT
Neuropeptide Y (NPY), neurotensin (NT), substance P (SP) and vasoactive intestinal peptide (VIP) are four structurally unrelated neuroendocrine peptides which affect anterior pituitary function. All four peptides appear to be locally synthesized in the anterior pituitary gland and have been shown to be regulated by thyroid and/or sex hormone status. We show here that NT, SP and VIP but not NPY are influenced by adrenal hormone status in the male rat pituitary gland. Adrenalectomy increased the content of VIP (35·4±4·0 (s.e.m.) vs control 11·9±1·1 pmol/g wet weight) but decreased that of SP (18·8±2·3 vs control 36·7 ±3·9 pmol/g wet weight). Adrenalectomy combined with castration decreased the content of SP (14·6±3·5 vs control 36·7±3·9 pmol/g wet weight) but had no effect on VIP content. Treatment with dexamethasone produced significant decreases in NT, SP and VIP contents (17·8±2·3 vs control 32·6±3·4 pmol/g wet weight, 5·5±0·9 vs control 36·7±3·9 pmol/g wet weight and 4·2±0·6 vs control 11·9±1·1 pmol/g wet weight respectively). The changes in pituitary peptide contents occurred in parallel with changes in mRNA levels, suggesting that alterations in glucocorticoid hormone status can alter the synthesis of these peptides. These results, together with the known effects of these neuroendocrine peptides suggest possible functions for locally produced SP and VIP in regulating the secretion of adrenocorticotrophin and/or other proopiomelanocortin-derived peptides. The differential effects of adrenalectomy and adrenalectomy combined with castration on VIP suggests that the regulation of this pituitary peptide is complex, and may be dependent, in part at least, on gonadal factors.
Journal of Endocrinology (1990) 127, 437–444
The adult dogfish (Scyliorhinus canicula L.) testis: a model to study stage-dependent changes in steroid levels during spermatogenesis
Authors: Sourdaine P. , Garnier D. H. , Jégou B. 
Published: December 2008

ABSTRACT
The unit structure of the testis of Scyliorhinus canicula L. is the seminiferous lobule arranged in topographically distinct zones and comprised of cysts formed by steroid-producing Sertoli cells associated with germ cells at an identical stage of spermatogenesis. In this experiment, testicular tissues from different dogfish corresponding to the zones of lobules with spermatogonia (A), spermatocytes (B), early spermatids (C) and late spermatids (D) were dissected out and pooled. They were either used for steroid radioimmunoassay or incubated to measure steroid production in response to dogfish pituitary extract or to dibutyryl cyclic AMP (dbcAMP). Our results indicate that testosterone is the main testicular androgen in this species. Furthermore, marked changes in the distribution of steroids were observed according to the zone of spermatogenesis, testosterone concentrations being highest in zones A and D. The relative contents of this hormone (steroid levels normalized to an equivalent number of Sertoli cells) as well as of Δ4-androstenedione and of progesterone increased from A to D. The concentrations of Δ4-androstenedione and progesterone were highest in zone D. Relative contents of 5α-androstane-3α,17β-diol, dihydrotestosterone and 11-ketotestosterone were very low in A when compared with the other zones. Finally, whereas no significant stage-related variation in the concentration of oestradiol-17β and 17α-hydroxy, 20β-dihydroprogesterone was observed, the relative content of these steroids was lowest in zone A. Incubation experiments revealed that dogfish pituitary extract and dbcAMP can stimulate androgen synthesis (about twofold) and that a stage-related change of steroid responsiveness to dbcAMP exists (only zones A and D were responsive). Overall, the results of this study indicate that germ cells most probably influence Sertoli cell steroidogenesis and responsiveness in the adult dog fish testis.
Journal of Endocrinology (1990) 127, 451–460
Responses to protein deficiency of plasma and tissue insulinlike growth factor-I levels and proteoglycan synthesis rates in rat skeletal muscle and bone
Authors: Yahya Z. A. H. , Bates P. C. , Millward D. J. 
Published: December 2008

ABSTRACT
The relative biological importance of plasma levels of insulin-like growth factors (IGFs) is uncertain since the IGFs may act through endocrine mechanisms involving circulating IGFs secreted by the liver, or by autocrine/paracrine mechanisms with IGF production in or close to their target cells. We report here studies in rats designed to examine this problem with an investigation of the changes in plasma and tissue concentrations of IGF-I in relation to the inhibition of bone and muscle growth and proteoglycan synthesis, a putative IGF-I-sensitive process, by protein deficiency. Over a 3-week period in young well-fed growing rats, there were marked increases in plasma IGF-I, whereas in the protein-deficient animals in which growth was inhibited concentrations fell markedly. In bone, concentrations of IGF-I were initially 20% of plasma, did not increase with age and were minimally influenced by protein deficiency. In skeletal muscle, concentrations of IGF-I were initially 3% of plasma, did not increase with age, but did fall with protein deficiency. In bone, the inhibition of proteoglycan synthesis by the protein deficiency was not correlated with changes in tissue IGF-I concentrations and was poorly correlated with changes in plasma hormone concentrations, although in the latter case an exponential relationship could be fitted to the data from the initial control and subsequent protein-deficient animals. In muscle, the changes in proteoglycan synthesis were significantly linearly correlated with changes in tissue IGF-I compared with an exponential relationship with plasma concentrations from the initial control and subsequent protein-deficient animals. These data demonstrate that neither plasma IGF-I concentrations nor the level of total extractable tissue IGF-I can be assumed to be unequivocal determinants of IGF-I status.
Journal of Endocrinology (1990) 127, 497–503
RAT MELANIN CONCENTRATING HORMONE DOES NOT MODIFY THE RELEASE OF CRH-41 FROM RAT HYPOTHALAMUS OR ACTH FROM THE ANTERIOR PITUITARY IN VITRO
Authors: Navarra P. , Tsagarakis S. , Coy D. H. , Rees L.H. , Besser G. M. , Grossman A. B. 
Published: December 2008

ABSTRACT
It has been suggested that melanin concentrating hormone (MCH) possesses potent corticotrophin (ACTH) inhibitory activity, on the basis of the inhibitory effects displayed by salmon MCH on ACTH release from either trout or rat isolated pituitary fragments. Recently, rat MCH has been characterised, and this prompted us to investigate the putative inhibitory activity of synthetic rat MCH on basal and stimulated ACTH secretion from freshly-dispersed rat pituitary cells or incubated rat pituitary fragments, as well on KCl (28 mmol/l) or noradrenaline-evoked release of corticotrophin releasing hormone-41 (CRH-41) from rat hypothalamic explants in vitro. There were no effects of rat MCH on either CRH-41 or ACTH release in vitro.
Identification of 11,13-dihydroxy-14-octadecaenoic acid as a circulating Na+/K+-ATPase inhibitor
Authors: Lichtstein D. , Samuelov S. , Gati I. , Felix A. M. , Gabriel T. F. , Deutsch J. 
Published: December 2008

ABSTRACT
Two digitalis-like compounds (DLC) were purified to homogeneity from bovine plasma. The purification procedure consisted of organic extractions and batch chromatography followed by three subsequent separations using reverse-phase high-performance liquid chromatography. The presence of a DLC in the different fractions was monitored by their ability to inhibit (a) [3H]ouabain binding to rat brain synaptosomes, and (b) microsomal Na+/K+-ATPase activity. Using mass spectrometry and nuclear magnetic resonance spectroscopy the structure of one of the DLCs was identified as 11,13-dihydroxy-14-octadecaenoic acid. It is suggested that this new hydroxy, unsaturated, fatty acid derivative may regulate Na+/K+-ATPase activity under some physiological and pathological conditions.
Journal of Endocrinology (1991) 128, 71–78
Effects of full-length and truncated insulin-like growth factor-I on nitrogen balance and muscle protein metabolism in nitrogen-restricted rats
Authors: Tomas F. M. , Knowles S. E. , Owens P. C. , Read L. C. , Chandler C. S. , Gargosky S. E. , Ballard F. J. 
Published: December 2008

ABSTRACT
The ability of insulin-like growth factor-I (IGF-I) to protect against losses of body protein during periods of dietary nitrogen restriction has been evaluated in young rats. Recombinant human IGF-I was administered by osmotic pumps at dose rates of 0, 1·2 or 2·9 mg/kg per day over a 7-day period beginning with the transfer of animals from an 18% to a 4% protein diet. A fourth group received the potent truncated IGF-I analogue, des(1–3)IGF-I, at a dose of 1·2 mg/kg per day over a comparable 7-day period. Plasma IGF-I levels were reduced by 60% following nitrogen restriction, a reduction that was partly prevented by IGF-I administration, especially at the higher dose, but not measurably by des(1–3)IGF-I. The major IGF-binding protein circulating in blood, IGFBP-3, demonstrated a similar pattern of change.
A significant (P<0·05) protection of body weight was achieved in the low dose IGF-I and des(1–3)IGF-I groups, but only after differences in food intake had been eliminated by analysis of covariance. Nitrogen balances were not significantly different unless analysis of covariance was used to adjust for the nitrogen intakes, whereupon all treatment groups showed improved balance, especially the animals treated with the low IGF-I dose and des(1–3)IGF-I (both P<0·01). The rate of muscle protein breakdown calculated from the urinary excretion of 3-methylhistidine was not significantly altered by the treatments, but fell progressively throughout the 7 days. The fractional rate of muscle protein synthesis measured on the final day was increased by 31, 26 and 21% respectively by the low and high doses of IGF-I and by des(1–3)IGF-I. Organ weights (g/kg body weight) showed no effects of IGF-I treatment except for 16% increases in the weight of kidneys in the high dose IGF-I and the des(1–3)IGF-I groups. Carcass analyses demonstrated higher water and lower fat contents (all P< 0·01) in the same groups. These results suggest that exogenous IGF-I and especially des(1–3)IGF-I can partly protect body protein reserves during nitrogen restriction.
Journal of Endocrinology (1991) 128, 97–105
Purification and assay of insulin-like growth factor-binding protein-1: measurement of circulating levels throughout pregnancy
Authors: Wang H. S. , Perry L. A. , Kanisius J. , Iles R. K. , Holly J. M. P. , Chard T. 
Published: December 2008

ABSTRACT
Insulin-like growth factor-binding protein-1 (IGFBP-1) has been purified from amniotic fluid by anion exchange, hydrophobic interaction and gel filtration chromatography. The overall recovery of the purification process was 12·2%. The purified IGFBP-1 yielded a single band on SDS-PAGE gel but showed two bands (34 kDa and 68 kDa) on Western blot under non-reducing conditions. Polyclonal antisera were raised by immunization of sheep using the purified IGFBP-1. The best antiserum bound 50% of 125I-labelled IGFBP-1 at a final dilution of 1:500 000. A radioimmunoassay for IGFBP-1 was developed. This assay had a minimum detection limit of 5 μg/1, and was used to determine serum levels in non-pregnant and pregnant women. There was no cross-reaction with a wide variety of materials tested. Serum IGFBP-1 levels in non-pregnant individuals (33±16 (s.D.) μg/1) were found to be significantly lower than those in the second (96±64 μg/1) and third trimesters (95 ±60 μg/1) of pregnant women. During pregnancy, circulating IGFBP-1 levels increased rapidly in the first trimester and reached a peak at 12–13 weeks of gestation (107±75 μg/l). The level then remained at 80±53 to 103±70 μg/l until term.
Journal of Endocrinology (1991) 128, 161–168
Long-term effect of a sheep antiserum to rat growth hormone in vivo in rats is explained by the rat anti-sheep immunoglobulin response
Authors: Madon R. J. , Panton D. M. , Flint D. J. 
Published: December 2008

ABSTRACT
A specific antiserum to rat GH (anti-rGH) raised in sheep was used in young male and lactating rats. In both models a group of rats was found which appeared to generate a low response (low responders) to the injected sheep immunoglobulin, and was characterized by the ability of the antiserum to cause inhibition of growth for more than 21 days in the male rats, and to abolish milk yield when prolactin concentrations were lowered in the females. In the groups which generated a high response to the anti-rGH (high responders), growth was retarded for only 2–3 days in male rats, with a moderate milk yield maintained in lactating animals.
The low-response animals were found to have a significantly longer half-life for circulating anti-rGH, when compared with the high-response animals. After 21 days, in the age-matched male rats, levels of anti-rGH were undetectable in the high-responders, whereas the low-response animals, which were nearly 160 g lighter, still had approximately 4·5 ml anti-rGH/1 in their circulation. This anti-rGH was still capable of neutralizing GH, as concentrations of insulin-like growth factor-I (IGF-I) were 13·6±3·5 (mean ± s.e.m.) and 76·9±2·0 nmol/l in the low-response and high-response groups respectively. The reason for these differences would appear to be that the immune response mounted by these low-response animals to the exogenous sheep immunoglobulin (i.e. rat anti-sheep) 7 days after treatment was less than 10% of that seen in the high-response group.
In male animals the concentration of IGF-I was positively correlated with growth rate.
It is concluded that the effectivenes of the anti-rGH was related to its clearance rate which in turn depended on the ability of the animal to mount an effective anti-sheep response.
Journal of Endocrinology (1991) 128, 229–237
Analysis of the receptor specificity of tolerance induction in stress versus opioid-related prolactin secretion in rats
Authors: Matton A. , Buydens P. , Finné E. , Govaerts J. , Vanhaelst L. 
Published: December 2008

ABSTRACT
The effects of restraint stress and opiates on prolactin secretion in male rats have been measured. Both induced a short-lived increase in prolactinaemia. Experimental evidence indicates that both opioids and restraint stress bring about their actions by the activation of opioid receptors. When restraint stress was followed by administration of the specific κ-agonist bremazocine, a second prolactin peak was observed. In contrast, morphine (predominantly a μ-agonist) lost its prolactin-stimulating capacity when given after a period of restraint stress. This indicates cross-tolerance between restraint stress and morphine. Tolerance was overcome when the dose of morphine was doubled, and an increase in prolactin secretion could again be obtained. The cross-tolerance phenomenon argues that a common opioid receptor is involved in morphine- and restraint stress-stimulated prolactin release. In another set of experiments, in which morphine administration replaced restraint stress as a means of inducing tolerance, a second rise in prolactinaemia was seen only with bremazocine and not with a further administration of morphine. This suggests a morphine (μ) receptor-specific development of tolerance. Two consecutive administrations of bremazocine also produced tolerance, in this case for the κ-receptor. This illustrates the rapid and receptor-specific development of tolerance for the prolactin-releasing capacity of opioid compounds.
Journal of Endocrinology (1991) 128, 281–285