bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of androgens on bioactivity and immunoreactivity of pituitary FSH in GnRH antagonist-treated male rats
Authors: Sharma Om P. , Khan Shafiq A. , Weinbauer Gerhard F. , Arslan Mohammed , Nieschlag Eberhard 
Published: December 2008

Abstract
The effects of androgens on the bioactivity and molecular composition of pituitary FSH were examined in intact and GnRH antagonist-suppressed male rats. Eight groups of adult Sprague-Dawley rats were subjected to the following treatments: antagonist (75 μg/day by osmotic minipumps; sc), testosterone-filled Silastic implants (3×5 cm, sc), dihydrotestosterone-filled Silastic implants (3×5 cm, sc), E2 benzoate (15 μg/day, sc), and combined administration of antagonist with either steroid for 3 weeks. At the end of the treatment period, pituitaries were dissected out and homogenised. FSH content was determined in the pituitary extracts by an in vitro bioassay and a radioimmunoassay. Individual pituitary extracts from rats treated with vehicle, testosterone and testosterone + antagonist were subjected to isoelectric-focusing on sucrose density gradients performed in the pH range from 3.5 to 7.0. Individual isoelectric-focusing fractions (100-120) were analysed for bioactive and immunoreactive FSH. Treatment with antagonist, E2 or antagonist + E2 caused a significant decrease in pituitary FSH, whereas testosterone and dihydrotesterone alone or in combination with antagonist prevented the decrease in pituitary FSH. The effects of all treatments on both bioactive and immunoreactive FSH were similar. Testosterone treatment not only maintained FSH synthesis but also altered the molecular composition of pituitary FSH. Following treatment with testosterone there was a shift of maximal FSH bioactivity to the more acidic pH range. On the other hand, less bioactivity was recovered than corresponding immunoreactivity in the higher pH region, resulting in significantly reduced ratios of bioactivity to immunoreactivity of FSH. No significant differences were found in the isoelectric-focusing profiles or bioactivity to immunoreactivity ratios of pituitary FSH in animals treated with testosterone alone or in combination with antagonist. The results demonstrate that testosterone not only maintained the synthesis of both bioactive and immunoreactive FSH in male rats, but also influences the molecular composition of pituitary FSH. These effects of testosterone on pituitary FSH appear not to be mediated through hypothalamic GnRH.
The effect of fasting on thyroidal T4-5'monodeiodinating activity in mice
Authors: Wu Sing-yung 
Published: December 2008

Abstract
Complete fasting induces a significant decrease of serum T3 and a fall in TSH in rodents and man. To evaluate the effect of starvation on thyroidal T4 5'monodeiodinating activity, in vitro conversion of T4 to T3 by thyroid and liver homogenate from one to three days fasted mice was compared with homogenates from control mice on animal chow. 5'monodeiodinating activity was significantly lower in thyroid homogenates of fasted mice than in those of chow-fed control [100±5.0 and 92±5.0 pmol T3·(mg protein)−1·h−1 at 48 and 72 h fasting, respectively, vs 132±5.0 pmol T3·(mg protein)−1·h−1 of fed control, p<0.01]. A similar decrease in thyroidal 5'monodeiodinating activity was seen in the liver. The decrease in thyroidal 5'monodeiodinating activity induced by fasting was not reversed by the supplementation of homogenates with the thiol-protecting agent, dithiothreitol (0.2–4.0 mmol/l). Physiological replacement of T4, 0.58 nmol·(100 g)−1·day−1, did not alter the effect of starvation in either the thyroid or liver. TSH (0.02 IU/day) injection, on the other hand, stimulated 5'monodeiodinating activity in homogenates of thyroids from 3-days fasted mice which was no different from TSH-treated fed control. It is postulated that starvation-induced decrease in thyroidal T4 to T3 converting activity may play a role, together with decreased hepatic 5'monodeiodinating activity, in fasting-induced low serum T3 in mice.
Differential regulation of steroidogenic enzymes metabolizing testosterone or dihydrotestosterone by human chorionic gonadotropin in cultured rat neonatal interstitial cells
Authors: Murono Eisuke P. 
Published: December 2008

Abstract
The present studies examined the effects of hCG on steroidogenic enzyme activities involved in the metabolism of testosterone or dihydroststosterone in cultured rat neonatal interstitial cells. 5α-reductase and 17β-hydroxysteroid dehydrogenase activities, which are involved in the conversion of testosterone to dihydrotestosterone and androstenedione, respectively, were low in cultured neonatal interstitial cells, were unresponsive to hCG and declined to undetectable levels during 14 days of culture. However, Δ5-3β-hydroxysteroid dehydrogenase-isomerase activity, which is involved in the biosynthesis of testosterone, and 5α-androstane-3α-hydroxysteroid dehydrogenase and 5α-androstane-3β-hydroxysteroid dehydrogenase activities, which are involved in the conversion of dihydrotestosterone to 5α-androstan-3α, 17β-diol and 5α-androstan-3β, 17β-diol, respectively, were maintained or increased by hCG during the same culture period. These results demonstrate that 5α-reductase and 17β-hydroxysteroid dehydrogenase activities do not play a significant role in regulating testosterone accumulation in fetal/neonatal Leydig cells, and they suggest that these cells are adapted to maintain high testosterone but low dihydrotestosterone levels. The present results demonstrate also that fetal/neonatal Leydig cells differ from immature or adult Leydig cells with respect to the sensitivity of 5α-reductase activity to LH/hCG.
The effects of secretin on prolactin, estradiol, vasoactive intestinal polypeptide, and somatostatin levels in women
Authors: Holst N. , Jenssen T. G. , Burhol P. G. , Haug E. 
Published: December 2008

Abstract.
The effect of graded doses of intravenous secretin (0.5, 1.0, and 2.0 CU · kg−1 · h−1) on serum prolactin and estradiol levels, as well as plasma vasoactive intestinal polypeptide and somatostatin levels was studied in 6 normally cycling and healthy women, and compared with the hormone levels obtained by a control infusion with physiologic saline (0.15 mol/l). A significant decrease in serum prolactin concentrations was found with increasing doses of secretin at steady-state levels of plasma secretin (+30 to +60 min). A significant negative correlation (p<0.007, r=−0.2764) existed between serum prolactin and plasma secretin concentrations at steady-state conditions. No effect of graded doses of secretin was observed on serum estradiol levels and plasma concentrations of vasoactive intestinal polypeptide and somatostatin. The results suggest a dose-related inhibitory effect of secretin on prolactin release in women.
Erythrocyte-associated triiodothyronine in the rat: a source of hormone for target cells
Authors: Francon Jacques , Osty Jeannine , Chantoux Françoise , Blondeau Jean-Paul 
Published: December 2008

Abstract
The accumulation of T3 by rat erythrocytes and its transfer to cultured rat hepatocytes were investigated. The amount of erythrocyte-associated T3 in whole rat blood was determined at 37°C. The ratio of erythrocyte-associated T3 to plasma total T3 was 0.235 over a wide range of T3 concentrations, i.e. there is 25 times as much T3 in the erythrocyte compartment as free in the plasma. Influx and efflux of T3, which were shown previously to be carrier-mediated, proceeded rapidly (t½ ≈ 12–15 sec at 25°C). These results suggest that erythrocytes are involved in the supply of T3 to target cells. This was checked by studying [125I]T3 uptake by cultured rat hepatocytes incubated either with erythrocyte suspensions pre-equilibrated with labelled T3 or with extracellular medium from the same erythrocyte suspensions. In protein-free medium, the initial velocity of T3 uptake was 1.5-fold faster in the presence of the erythrocyte suspension. Uptake was saturable, the apparent Km of T3 uptake (nmol/l) was 163±13 in the absence of erythrocytes and 102±6 in their presence. Vmax (fmol · min−1 · well−1) was similar in both cases (477 ± 26 and 511 ± 20, respectively). In the presence of diluted plasma (1:16 dilution) and in the presence of the erythrocyte suspension, a 2-fold increase of initial velocity was obtained. Plasma by itself increased (4–5 times) the initial velocity of uptake. The time-courses and kinetic constants of T3 binding to hepatocyte nuclear receptors were similar whether hepatocytes were incubated with or without erythrocytes. These results show that part of the erythrocyte-associated T3 adds to the free pool of hormone and can thus be considered as a biologically active compartment, suggesting that rat erythrocytes may serve as a blood-carrier for T3.
High-fat feeding induces tissue-specific alteration in proportion of activated insulin receptors in rats
Authors: Nagy Karoly , Levy Joseph , Grunberger George 
Published: December 2008

Abstract
High dietary fat intake causes glucose intolerance and insulin resistance in man and in laboratory rats. We studied possible mechanisms of this insulin resistance in rat kidney, muscle and liver. In high-fat fed rats the body weight, plasma insulin concentration, plasma glucose levels, and serum triglyceride concentration were significantly higher than in the control rats. 125I-insulin binding to kidney basolateral membrane insulin receptors from high-fat fed rats was lower than in control rats. Basal as well as insulin-stimulated tyrosine kinase activity per insulin receptor was higher in the highfat fed group, accompanied by increased autophosphorylation of the β-subunit of the receptor and higher proportion of tyrosine-phosphorylated insulin receptors. In contrast, both in the skeletal muscle and the liver the insulin-stimulated tyrosine kinase activity per insulin receptor was significantly lower in high-fat fed animals, accompanied by diminished autophosphorylation of the β-subunit of the receptor and lower proportion of tyrosinephosphorylated receptors. Our results indicate tissue-specific alterations in transmembrane signaling induced by high-fat feeding in target tissues for insulin which in turn might contribute to the observed insulin resistance.
Paradoxical growth hormone response to thyrotropin-releasing hormone in acromegaly. Clinical correlations and prognostic value
Authors: De Marinis Laura , Mancini Antonio , Zuppi Paolo , Anile Carmelo , Maira Giulio 
Published: December 2008

Abstract.
We have investigated the effect of TRH on the release of GH in 20 acromegalic patients (14 females and 6 males) before and after selective removal of a pituitary tumour via transsphenoidal route. The follow-up period was 8 years. Pre-operatively the paradoxical response was present in 15 patients (75%). Mean GH values in TRH responders were significantly lower than in non-responders. According to the size and expansion diffusion of the adenoma, the patients were divided into 3 classes. The percentage of paradoxical response in patients in class III was significantly lower than in the other two classes. Postoperatively, mean GH values in pre-operative TRH responders were significantly lower than in non-responders; among 15 responders, 13 (86%) had postoperative GH levels under 5 μg/l; among 5 non-responders only 2 (40%) had GH values under 5 μg/l. Postoperatively 8 patients still had GH responsiveness to TRH: 6 with GH levels persistently (follow-up 8 years) under 5 μg/l and 2 with elevated GH values. The other 7 patients, who were responders pre-operatively and non-responders postoperatively, persistently exhibited low GH levels, except one subject who showed an increase in GH levels with reappearance of the paradoxical response, two years after surgery. These results suggest: 1. the paradoxical response may be expressed only when the hypothalamus-pituitary interactions are intact; 2. the disappearance of the paradoxical response cannot surely suggest a remission, and 3. the presence of a pre-operative paradoxical response is a good prognostic feature.
D-(—)-β-hydroxybutyrate inhibits catecholamine-stimulated lipolysis and decreases β-adrenoceptors' affinity in human fat cells but not in lymphomonocytes
Authors: De Pergola G. , Cignarelli M. , Corso M. , Garruti G. , Di Paolo S. , Giorgino R. 
Published: December 2008

Abstract.
The effect of D-(—)-β-hydroxybutyrate, at concentrations commonly achieved during ketoacidosis in humans (10 mmol/l), on human fat cell lipolysis in vitro was the aim of this study. The basal lipolysis was not modified and β-hydroxybutyrate did not affect forskolin- or dibutyryl-cAMP-stimulated glycerol release, whereas it markedly inhibited isoproterenol-stimulated lipolysis. In membranes of intact adipocytes exposed to D-(—)-β-hydroxybutyrate for 1 h, we found a decrease in β-adrenoceptor affinity in saturation experiments and a shift to the right of the isoproterenol-mediated radioligand ([125I]-cyanopindolol) displacement curve. These findings suggest that β-hydroxybutyrate inhibits catecholamine-stimulated lipolysis by decreasing β-adrenoceptor affinity. No effect of β-hydroxybutyrate was found on β-adrenoceptor binding of intact mononuclear cells of peripheral blood. In conclusion, the β-adrenoceptor affinity lowering effect of β-hydroxybutyrate is seemingly specific to human fat cells and might represent a feed-back mechanism that prevents an uncontrolled breakdown of triglycerides and indirectly regulates its own production rate.
Renal calcium and magnesium handling in experimental diabetes mellitus in the rat
Authors: Anwana Atim B. , Garland Hugh O. 
Published: December 2008

Abstract.
Metabolic and renal clearance techniques were used to examine kidney function in conscious and anesthetised streptozotocin diabetic rats. All diabetics showed an enhanced calcium and magnesium excretion compared to controls. However, the renal handling of these ions in relation to other electrolytes varied with different experiments. In non-infused conscious rats, the excretion of all ions was higher in diabetics, but the increased output of Ca2+ and Mg2+ was far greater than that of other electrolytes. In infused anesthetised diabetics only the outputs of Ca2+ and Mg2+ were significantly raised. This resulted from a significant reduction in the tubular reabsorption of both ions (% Ca2+ reabsorption: Controls 97.0±0.5; Diabetics 86.1±2.1; p<0.001). Insulin treatment reversed these changes. Major differences therefore exist in the renal handling of Ca2+ and Mg2+ in control and diabetic kidneys. Such differences do not simply parallel changes in the handling of other ions, and thus represent specific Ca2+ and Mg2+ lesions. Anesthetised infused diabetic rats also showed a reduced glomerular filtration rate and urine output compared to controls. Such differences may relate to an altered fluid balance in the two groups, different responses to surgery and anesthesia, or the degree of hyperglycemia in diabetic animals.
Differential effects of interleukin 1α and 1β on cultured human and rat thyroid epithelial cells
Authors: Rasmussen Å. Krogh , Kayser L. , Bech K. , Feldt-Rasmussen U. , Perrild H. , Bendtzen K. 
Published: December 2008

Abstract
The effects of human recombinant interleukin 1α (20 pg/1-2 μg/l) and 1β (200 pg/1-20 μg/l) on two systems of thyroid cells have been compared. The thyroglobulin and cAMP secretion and the DNA content of human thyroid cells cultured in monolayer and of continuously grown rat thyroid cells, Fischer rat thyroid cell line have been studied. The growth of the rat thyroid cell line was inhibited by interleukin 1β (20 ng/1-20 μg/l), but not by interleukin 1α. None of the cytokines changed the cAMP production of the rat thyroid cells. In contrast, both cAMP production and thyroglobulin secretion were inhibited dose-dependently by the cytokines in human thyroid cells in secondary cultures. These results caution the interpretation and extrapolation of changes induced by interleukin 1 from one cell system to the other.
Contractile effect of oxytocin and 1-deamino-1-carba-2-tyrosine (O-methyl)-oxytocin in myometrial tissue from non-pregnant and term pregnant women
Authors: Norström Anders , Andersson Ann , Vilhardt Hans 
Published: December 2008

Abstract.
The contractile effect of the analogue 1-deamino-1-carba-2-tyrosine (O-methyl)-oxytocin (carbetocin) on isolated strips from the human myometrium was compared with that of oxytocin. Neither oxytocin nor carbetocin affected contractile activity in strips from nonpregnant women, but both peptides stimulated contractile activity in strips from women at term pregnancy (2× 10−11 mol/l, and 10−10 mol/l, respectively). Thus, carbetocin is almost as potent as oxytocin with regard to stimulating myometrial contractions at term.
[125I]melatonin binding sites in membrane preparations of quail brain: characteristics and diurnal variations
Authors: Yuan He , Pang Shiu Fun 
Published: December 2008

Abstract.
The binding of [125I]melatonin, a labelled ligand of melatonin, to quail brain membrane preparations was studied. Kinetic studies indicated that the binding of [125I]melatonin to membrane preparations of quail brains collected at mid-light was time-dependent and reversible. The Kd value determined from kinetic analysis was 614 pmol/l, similar to the Kd 705±81 pmol/l obtained from saturation experiments. The [125I]melatonin binding sites in quail brain membrane had the following order of pharmacological affinities: melatonin >6-chloromelatonin >N-acetylserotonin >5-hydroxytryptamine >>5-methoxytryptophol, tryptamine, L-tryptophan, 5-hydroxytryptophan, 5-hydroxyindole-3-acetic acid, 1-acetylindole-3-carboxaldehyde, 3-acetylindole. Compounds known to act on serotonergic, adrenergic or acetylcholinergic receptors were inactive as compared with melatonin. Our results demonstrated the presence of specific melatonin binding sites in the quail brain membrane preparations. In addition, saturation studies demonstrated that [125I]melatonin binding sites in quail brain membrane preparations were 42% higher at mid-light (39.6±2.2 fmol/mg protein) than at mid-dark (22.6±2.5 fmol/mg protein), with no significant variation in their binding affinities.
Neurohypophyseal function of an ectopic posterior lobe in patients with growth hormone deficiency
Authors: Yamanaka Chutaro , Momoi Toru , Fujisawa Ichiro , Kikuchi Kiyoshi , Kaji Masayuki , Yorifuji Tohru , Sasaki Hiroshi , Sudo Masakatsu , Konishi Junji , Mikawa Haruki 
Published: December 2008

Abstract.
We studied the neurohypophyseal function of 20 patients with complete GH deficiency owing to pituitary stalk transection by means of the water deprivation and the hypertonic saline infusion test. In TI-weighted magnetic resonance images, high-signal intensity of the posterior lobe of the hypophysis was missing in all the patients. An ectopic posterior lobe was observed at the proximal stump of the transected stalk in 17 patients, whereas the 3 patients without ectopic posterior lobe had overt diabetes insipidus or intractable nocturnal enuresis. After water deprivation, 3 patients with large ectopic posterior lobes (length along the pituitary stalk axis exceeding 5 mm) showed urinary osmolality and plasma AVP levels as high as those of 13 patients with partial GH deficiency in whom magnetic resonance images revealed no abnormalities. On the other hand, 14 patients with small ectopic posterior lobes (length less than 5 mm) showed significantly lower urinary osmolality and plasma AVP levels than the patients with large ectopic posterior lobes (p<0.01 and p<0.01, respectively) and the patients with partial GH deficiency (p<0.01 and p<0.01, respectively). Urinary osmolality in the patients with small ectopic posterior lobes, however, was higher than that in 3 patients without ectopic posterior lobes (p<0.01). During the hypertonic saline infusion test, peak plasma AVP levels in the patients with small ectopic posterior lobes were significantly lower than those in the patients with partial GH deficiency (p<0.01). These findings suggest that the remaining neurohypophyseal function in patients with transected pituitary stalk correlates with the size of the ectopic posterior lobe, and that partial diabetes insipidus may be the diagnosis in some of the patients with small ectopic posterior lobes.
Effect of one year continuous subcutaneous infusion of a somatostatin analogue, octreotide, on early retinopathy, metabolic control and thyroid function in Type I (insulin-dependent) diabetes mellitus
Authors: Kirkegaard Carsten , Nørgaard Kirsten , Snorgaard Ole , Bek Toke , Larsen Michael , Lund-Andersen Henrik 
Published: December 2008

Abstract.
Growth hormone is assumed to be involved in the development of diabetic retinopathy. In a randomized study we evaluated the possible effects of one year treatment with a somatostatin (SRIH) analogue, octreotide, on early retinopathy and on metabolism in Type I (insulin-dependent) diabetes mellitus. Eleven patients were allocated to treatment with a continuous sc infusion of 400 μg octreotide per day and 9 served as controls. Only 7 patients from each group completed the study. Three octreotide-treated patients left the study owing to severe diarrhea. The subjects were evaluated at entry, after 2, 6 and 12 months treatment, and 2 months after withdrawal. Octreotide induced a decrease in GH secretion, expressed as the area under the 24 h serum GH profiles (p<0.05), and of the serum levels of IGF-I (p<0.05). The entire decline in GH levels occurred during the daytime, whereas the nocturnal levels were unaffected. Retinopathy, as assessed by determination of the blood retina barrier permeability, by colour fundus photography, and flurescein angiography was unchanged in both groups. Apart from a decline in insulin requirements, octreotide had no major effect on glycemic control, but induced a mild transient pituitary hypothyroidism, not clinically relevant. We conclude that treatment with octreotide for one year has modest effects on GH, IGF-I, and glucose metabolism, but has no significant effect on early retinopathy in Type I (insulin-dependent) diabetes.