bluuebunny/crossref_metadata_2025_split huggingface dataset:
Beta-adrenergic stimulation of the release of ACTH- and LPH-related peptides from the pars intermedia of the rat pituitary gland
Authors: Tilders F.J. H. , Post M. , Jackson S. , Lowry P.J. , Smelik P. G. 
Published: December 2008

Abstract.
The intermediate lobe of the rat pituitary gland produces a series of peptides related to ACTH and LPH. The spontaneous and isoproterenol-stimulated release of such peptides was studied during in vitro superfusion of rat neurointermediate lobes with Krebs-Ringer medium. Products released into the superfusion medium were quantified by direct measurement or after chromatography on Sephadex G-50. ACTH bioactivity was determined by use of adrenal cortical cell suspension assay. In addition, NH2-terminal ACTH, CO2H-terminal ACTH, α-MSH and β-endorphin radioimmunoassays were used. The results show that
1. neurointermediate lobes of rats secrete spontaneously various ACTH- and LPH-related peptides in amounts proportional to the amounts in which these peptides are found in extracts of the neurointermediate lobe;
2. the β-adrenergic agonist, isoproterenol, stimulated the spontaneous release of various peptides, including α-MSH, ACTH, CLIP, glycosylated CLIP, and β-endorphin-like peptides;
3. isoproterenol induced a dose-dependent (10−9–10−7 m), parallel increase in the release of α-MSH and ACTH following similar time courses and showing indentical EC50 values (about 10−8 m).
Although the spontaneous release of α-MSH and ACTH from rat neurointermediate lobes is not strictly coupled under the conditions used in this study, isoproterenol seems to affect the spontaneous release of these peptides to the same relative extent.
Effect of dietary calcium on secretion of calcitonin and gastrin in rats with medullary thyroid carcinoma
Authors: Hongslo Cecilie F. , Myhre Lisbeth , Flaten Olav , Johannessen Jan W. , Gautvik Kaare M. , Ekeland Arne 
Published: December 2008

Abstract.
Rats transplanted with medullary thyroid carcinoma (MTC) were divided into 3 groups which received for 34 weeks diets with low (0.09%), medium (0.40%) or high (1.80%) calcium content with a calcium/phosphate ratio 2:1. After 6 weeks the different calcium regimens produced corresponding variations in serum calcium and inverse changes in serum magnesium. No alterations in serum proteins were observed.
Serum immunoreactive calcitonin (iCT) was unaltered until week 28 of the experiment, but thereafter increased rapidly by about 4-fold. No difference in serum iCT was observed between the 3 groups at any time. Immunoreactive serum gastrin was reduced in rats on medium and low calcium diet compared to those on a high calcium diet. After 28 weeks, when serum iCT was rising, gastrin values fell in rats on high calcium diet to levels approaching those in the other groups. With increased serum iCT (weeks 28–34) serum gastrin concentrations were low and equal in the 3 groups despite different serum calcium concentrations. Electronmicroscopic examination of tumours from the various diet groups did not reveal significant ultrastructural differences.
In conclusion: low, medium and high calcium intake gave corresponding changes in serum calcium. Diet-induced hypercalcaemia was not normalized by elevated serum iCT. In contrast, serum immunoreactive gastrin maintained by high calcium diet was suppressed by hypercalcitoninaemia.
Immunohistological demonstration of ACTH-like immunoreactivity in the foetal adrenal medulla in the 23rd week of gestation
Authors: Ito Seiki , Iwanaga Toshihiko , Yamada Yukio , Suzuki Toshimitsu , Sudo Norihito , Momotsu Takeshi , Shibata Akira 
Published: December 2008

Abstract.
By an indirect immunofluorescence technique and silver impregnation, cells reacting with anti-1-18ACTH antiserum were demonstrated in the foetal adrenal medulla only in the 23rd week of gestation. They were not found in the foetal adrenal glands before the 23rd week or after 29th week and after birth. The result was confirmed by immunohistological examination using anti-1-18ACTH rabbit IgG purified by affinity chromatography. No cells in the foetal adrenal medulla in the 23rd week of gestation were stained positively by using anti-β-MSH and anti-β-endorphin antisera. This finding suggested, therefore, that the synthetic mechanism of ACTH-like immunoreacticvity in the foetal adrenal glands was different from that in the pituitary. In view of the findings that some phaeochromocytoma contained ACTH-like immunoreactivity, the present study suggested that the origin of the phaeochromocytoma containing ACTH-like immunoreactivity may be the cells of the foetal adrenal medulla in about the 23rd week of gestation.
The endocrinology of testicular germinal cell tumours
Authors: Aiginger P. , Kolbe H. , Kühböck J. , Spona J. , Geyer G. 
Published: December 2008

Abstract.
Oestradiol (Oe2), testosterone (T), luteinizing hormone (LH), follicle stimulating hormone (FSH), β-human chorionic gonadotrophin (β-hCG) and alpha-l foetoprotein (AFP) were measured in blood samples taken from 63 patients with testicular tumours. In patients without tumour recurrence (n = 31) AFP, Oe2 and T were within the normal range, β-hCG was negative, LH levels were marginally elevated and FSH concentrations were significantly elevated. In patients with tumour recurrence (n = 32) Oe2 was significantly elevated, whereas the T levels varied considerably and were therefore statistically not different from the patients without tumour recurrence. The β-hCG positive subgroup of the recurrence group, however, demonstrated significantly elevated T levels. T levels were highest in patients with 51 to 500 U β-hCG/l. On the other hand T was normal or even low normal in β-hCG negative-AFP positive patients. In all subgroups decreasing FSH levels and decreasing LH responses to LRH were among the earliest signs of tumour recurrence.
The observations suggest that moderate hCG levels are able to stimulate testicular T production, whereas high levels no longer increase T serum concentrations. Increased conversion rates from steroid precursors to oestradiol seem to be a feature of β-hCG positive as well as β-hCG negative testicular tumours.
Mechanism of creatinuria in experimental hyperthyroidism
Authors: Carter Willam J. , Benjamin Wieke S. van der Weijden , Faas Fred H. 
Published: December 2008

Abstract.
Using rats pre-labelled by [14C]creatine injection, the mechanism of creatinuria induced by experimental hyperthyroidism during a 20 day treatment period has been examined. The excess creatine excretion is the result of increased release of creatine from muscle and increased excretion of creatine synthesized de novo. The increased excretion of newly synthesized creatine in hyperthyroidism appears to occur because of decreased creatine uptake by muscle, an increased rate of creatine synthesis, or a combination of both factors. The radioactive creatine content of hyperthyroid skeletal muscle was reduced at the time of death indicating an increased rated of creatine loss during the treatment period. In spite of the increased loss of labelled creatine, the specific activity of creatine obtained from hyperthyroid skeletal muscle was higher than control. This finding is probably due to decreased uptake of unlabelled creatine by hyperthyroid skeletal muscle during the treatment period. In contrast to skeletal muscle, the radioactive creatine content of hyperthyroid myocardium was higher than control at the time of death suggesting a decreased rate of creatine loss during the treatment period.
Plasma insulin, C-peptide, and blood glucose in portal, hepatic and peripheral veins in liver cirrhosis. Effect of intravenous tolbutamide
Authors: Pelkonen R. , Kallio H. , Suoranta H. , Karonen S.-L. 
Published: December 2008

Abstract.
The responses of portal, hepatic and peripheral venous blood glucose (BG), plasma insulin (IRI) and C-peptide (IRC) levels to iv tolbutamide (200 mg) have been determined in 9 non-diabetic patients with liver cirrhosis and in 6 control subjects. The basal levels of plasma IRI and IRC were similar in patients and controls as were the portal and peripheral BG levels. In the hepatic vein, however, the BG-levels were higher in cirrhotic patients than in controls. After tolbutamide administration the BG-levels were unchanged in the cirrhotic patients but a significant fall in hepatic vein BG was observed in controls. In both groups of subjects the highest post-tolbutamide IRI-levels were found in the portal vein whereas the corresponding IRC-levels were as high in the hepatic as in the portal vein. The increments of portal venous IRI and IRC were signifiantly higher in controls as compared to the cirrhotic patients. Nevertheless, in the peripheral veins the increments of IRI and IRC were very similar in both groups of subjects or even less in the control subjects.
The results suggest that in patient with liver cirrhosis the secretion of insulin is not increased but slightly decreased. The production of glucose by the liver also seems to be increased either due to insulin resistance or portal venous shunting of insulin.
Insulin secretory response to different secretagogues in hyper- and hypothyroid mice
Authors: Ahrén Bo , Lundquist Ingmar 
Published: December 2008

Abstract.
The influence of long-term changes in thyroid state on insulin secretion was investigated in vivo in mice. Hyperthyroidism was induced by daily injections of i.-triiodothyronine and hypothyroidism by a single injection of 131I. Four different insulin secretagogues were used to characterize the insulin secretory response, i.e. glucose, the β2-adrenoceptor agonist terbutaline, the cholinergic agonist carbachol and the synthetic C-terminal octapeptide of cholecystokinin, CCK-8.
In the hyperthyroid mice the plasma glucose level was moderately decreased. Despite this lower glucose level the insulin response to terbutaline and glucose were potentiated by about 200%. Insulin response to CCK-8 and carbachol was less enhanced, by about 100 and 50%, respectively. Liver and muscle glycogen levels were markedly reduced.
The hypothyroid animals showed reduced insulin responses to all secretagogues; after terbutaline by 100%, after carbachol by 70%, after glucose and CCK-8 by 50%. Plasma glucose and muscle glycogen levels were normal, whereas liver glycogen levels were moderately enchanced.
Insulin release induced by β-adrenoceptor stimulation was most markedly affected by the thyroid state, which thus may be of importance for the balance between the β- and α-adrenoceptors of the insulin cell. Since thyroid activity influenced the insulin response to all secretagogues it cannot be excluded that the thyroid state also exerts effects not related to the adrenoceptors.
Characterization of triton-solubilized TSH receptors from human thyroid plasma membranes
Authors: Iida Yasuhiro , Konishi Junji , Kasagi Kanji , Ikekubo Katsuji , Kuma Kanji , Torizuka Kanji 
Published: December 2008

Abstract.
The TSH receptor from human thyroid plasma membranes has been solubilized in 10 mm Tris/HCl, 50 mm NaCl, pH 7.4 containing 0.5% triton X-100. Binding of [125I]TSH to the soluble receptor showed rapid and reversible kinetics and reached a maximum within 30 min at 37°C, by 1 h at 25°C and by 24 h at 4°C. Optimal pH was 7.4. The soluble receptor retained specificity with cross-reactivity only to crude hCG (0.03%). Scatchard plots were curvilinear, indicating the presence of at least two binding sites. The high affinity site showed an affinity constant of 1.1 × 109 m−1 with binding capacity of 1.3 × 10−10 m/mg protein. TSH-binding inhibitor immunoglobulins from patients with Graves' disease inhibited [125I]TSH binding to the soluble receptor in a dose-dependent manner. NaCl inhibited the TSH binding and this was ascribed to the decrease in the receptor capacity. Trypsin, neuraminidase and phospholipase C treatment of the solubilized receptor had no effect on TSH binding. The apparent molecular weight of the receptor, determined by gel filtration on Sepharose® 6B, was approximately 300 000.
A possible role of arginase in the regulation of polyamine biosynthesis in the rat thyroid
Authors: Matsuzaki Shigeru , Suzuki Mitsuo , Hamana Koei 
Published: December 2008

Abstract.
Effect of chronic methylthiouracil (MTU) treatment on the thyroid arginase activity and thyroidal concentration of arginine, ornithine and other amino acids was studied in the rat. The activity of thyroid arginase increased significantly at 15 days of MTU treatment and the elevated enzyme activity was reduced to normal by l-thyroxine (T4) injection. The thyroidal concentration of polyamines was increased by MTU and decreased by T4 with the exception of spermine. The thyroidal concentration of arginine and lysine, a substrate and an inhibitor for arginase respectively decreased significantly, while that of ornithine remained unchanged after MTU treatment. T4 injected to MTU-pretreated rats restored the decreased arginine concentration to normal. These results suggest that ornithine supply for polyamine biosynthesis is regulated by the level of both arginase and lysine in the thyroid.
Changes in the cyclic nucleotides (cCMP, cAMP and cGMP) of rat thyroid induced by prolonged administration of LATS and TSH
Authors: Ochi Yukio , Hosoda Shiro , Hachiya Takashi , Yoshimura Manabu , Miyazaki Tadayoshi , Kajita Yoshihiro 
Published: December 2008

Abstract.
It has recently been suggested that cyclic CMP (cCMP) has a physiological role in cell function. In this study, we examined the content of cCMP, cAMP & cGMP and each hydrolyzing enzyme (phosphodiesterase, (PDE)) in rat thyroid during administration of LATS and TSH for 7 days (Exp. 1), and also in the thyroid of rats given methylthiouracil (MTU) for 4 months (Exp. 2). Each cyclic nucleotide was determined by RIA, and PDE activity was determined according to Kuo's method.
Exp. 1: the wet weight of thyroid in the LATS and TSH group increased 3 and 2 times respectively, from the control. Both the LATS and TSH groups showed increased plasma T4 and T3 levels. In both groups the cAMP content per wet weight of thyroid was increased slightly, but cGMP content did not change. In contrast, the cCMP content decreased markedly. Both the LATS and TSH groups showed an increase of cAMP-PDE activity in the thyroid, and no change of cGMP-PDE, while cCMP-PDE decreased markedly. In all groups levels of these 3 cyclic nucleotides and PDE activities in plasma were unaffected.
Exp. 2: in the MTU group the thyroid weight increased 4.5 times over the control, and plasma T4 and T3 levels were extremely low. The cAMP content in whole thyroid gland and also per mg wet weight was increased markedly, but cGMP content did not change. cCMP content decreased significantly. The plasma cAMP level increased slightly, but the plasma cGMP and cCMP levels did not change.
The increase of cAMP content and cAMP-PDE activity, and conversely the decrease of cCMP content and cCMP-PDE in the thyroid by LATS and TSH stimulation, suggest that cCMP may play a physiologically important role within the cells, similar to cAMP in the mechanism of hormone action.
Oestrogen synthesis by bovine foetal placenta at normal parturition
Authors: Larsson K. , Wagner W. C. , Sachs M. 
Published: December 2008

Abstract.
In vitro conversion of C19-[3H]androstenedione and C21-[3H]pregnenolone steroids to oestrogens was studied in tissue cultures prepared from bovine cotyledons collected 10–240 min after natural parturition. A total of 17 cows was used, 15 had normal parturitions and 2 cows required assistance due to weak and prolonged labour.
At collection of tissues, blood samples were drawn from the cows and peripheral plasma oestrogen levels were determined by radioimmunoassay. Percentage conversion to unconjugated and conjugated oestrogens was estimated for each cow from 6 tissue culture replicates for each precursor. The steroids were extracted with toluene and separated by phenolic extraction and column chromatography. The repeatability of conversion rate was very high.
Incubation with androstenedione yielded consistently higher conversion rates than incubation with pregnenolone. Independent of precursor the conversion rates, within cows, ranked unconjugated Oe1 > conjugated Oe1 > unconjugated Oe2 > conjugated Oe2. The conversion rates decreased significantly with increasing intervals from parturition to collection of material. Lower conversion rates were found for cultures of tissues from the 2 cows with weak labour when compared to cultures from normally calving cows. The sire of the foetus had an influence on conversion rate in the tissue cultures. The plasma oestrogen concentrations of the cows decreased significantly with an increased interval from parturition to blood-sampling. With the exception of one cow, the tissue culture conversion rates and the plasma oestrogen levels of the cows were significantly correlated.
The relationship of plasma gonadotrophins and steroid concentrations to body growth in girls
Authors: Parra A. , Cervantes C. , Sánchez M. , Fletes L. , García-Bulnes G. , Argote R. M. , Sojo I. , Carranco A. , Arias R. , Cortés-Gallegos V. 
Published: December 2008

Abstract.
Plasma concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH), 17 alpha-hydroxyprogesterone (17α-OHP), 17β-oestradiol (Oe2) and progesterone (P) were measured in 352 healthy girls aged 6.0 to 15.9 years, as a function of age (CA), weight, height and calculated lean body mass (LBM) and total body fat (TBF). The earliest hormonal changes were a fall in mean plasma FSH concentrations together with a small but significant rise in plasma Oe2 well in advance of any sign of pubertal development. The next changes were a progressive rise in plasma FSH and 17α-OHP concentrations without further increments in plasma Oe2; these changes corresponded to a mean body weight of 29.8 kg, a mean height of 132.0 cm (initiation of the adolescent growth spurt), a mean LBM of 24.7 kg and a mean TBF of 5.1 kg. The last events were a progressive rise in plasma LH and Oe2 and less marked in P, which occurred in association with a mean body weight of 40.0 kg, a mean height of 142.0 cm (time of peak velocity of weight and height gain), a mean LBM of 31.8 kg and a mean TBF of 9.1 kg. Significant quadratic equations were disclosed between plasma FSH and LH versus CA, weight, height and LBM, and a significant linear correlation was observed between each gonadotrophin and TBF. These results show an association, not necessarily causal, between a 'critical level' of body composition and hormonal changes at the start of the adolescent growth spurt, as well as with late hormonal events at the time of peak velocity in weight and height gain. On the other hand, LBM rather than TBF seems more closely associated with the initiation and progression of puberty.
Effects of fasting on thyroid hormone levels and kinetics of reverse triiodothyronine in cattle
Authors: Blum J. W. , Kunz P. 
Published: December 2008

Abstract.
The effects of starvation for 5 days on plasma levels, and for 3.5 days on kinetics, of 3,3′,5′-triiodothyronine (reverse T3, rT3) were studied in steers. During the 5 day starvation period alterations of plasma levels of thyroxine (T4), 3,5,3′-triiodothyronine (T3), immunoreactive insulin (IRI), glucose, free fatty acids (FFA), urea and protein were determined. During starvation rT3 did not change, while T4 and T3 (total and free), IRI and glucose decreased and FFA, urea and protein increased (P < 0.05). During re-alimentation changes of T4 and T3 (total and free), IRI, FFA and urea were partially reversed and rT3 slightly increased, but the difference was not statistically significant with respect to mean values observed during fasting. During intravenous rT3 infusions (3.85 pmol/kg/min) for 300 min in fed and fasted steers plasma rT3 levels increased rapidly, reaching steady-state levels around 2 nmol/l between 180 and 300 min, and decreased after termination of the infusions. In fed as compared to fasted animals the total clearance rate was higher (2.63 ± 0.30 and 1.72 ± 0.21 ml/kg/min, respectively; P < 0.025) and the exponential constant (k1) of the initial phase of disappearance of rT3 from plasma after the end of the infusions was greater (0.11 ± 0.02 and 0.05 ± 0.01, respectively; P < 0.025). The data show that plasma rT3 levels in steers do not increase during starvation, which is in contrast to man, rabbits and sheep. This may be due to reduced availability of T4, serving as a substrate for rT3 and to the relatively high clearance rate of rT3 even during fasting, as compared to that of rabbits and man. That energy deficiency was sufficiently severe, was suggested by the marked responses of T4, T3, IRI, glucose, FFA and urea to starvation.
Oral contraception in diabetic women. Diabetes control, serum and high density lipoprotein lipids during low-dose progestogen, combined oestrogen/progestogen and non-hormonal contraception
Authors: Rådberg Thomas , Gustafson Anders , Skryten Asbjörn , Karlsson Kirsten 
Published: December 2008

Abstract.
Thirtyeight women with insulin-dependent diabetes were randomly allocated to contraception with either a progestogen only (Lynestrenol 0.5 mg daily) (LYN), a combined oral contraceptive (OC) (Ethinyl oestradiol 50 μg + Lynestrenol 2.5 mg) (EE + LYN) or a non-hormonal intrauterine device (IUD). Diabetes control (i.e. insulin dosage, blood and urinary glucose and body weight) and the lipid concentration in serum and in high density lipoprotein (HDL) were assessed before and during six months use of the respective contraceptives.
In the LYN group urinary glucose excretion increased 10% in spite of unchanged blood glucose, body weight and insulin requirement. All serum lipids decreased; triglycerides by 40% (P < 0.01), cholesterol by 13% (P < 0.01) and phospholipids by 12% (P = 0.06), without alteration of HDL lipids. In the group using combined OC (EE + LYN) the insulin requirement increased by 7% (P < 0.01) without any change in body weight or blood and urinary glucose. Serum as well as HDL lipids remained unchanged. In the IUD group neither diabetes control nor serum or HDL lipids were altered.
It is concluded that in insulin-dependent diabetics the progestogen (LYN) has little influence on diabetes control but has a marked, though probably not adverse, effect on lipid metabolism. The combined OC (EE + LYN) may impair glucose homeostasis slightly but has little influence on serum or HDL lipids. These findings seem to differ from those obtained in non-diabetics during administration of contraceptive steroids and these differences suggest that absence of endogenous insulin production enhances the effects of progestogen and reduces the effects of synthetic oestrogens on lipid metabolism.
Sex-specific action of antiandrogens on androgen induced changes in hepatic microsomal 3β-hydroxysteroid dehydrogenase and 5α-reductase activity in the rat
Authors: Lax E. Rodney , Schriefers Herbert 
Published: December 2008

Abstract.
The ability of two antiandrogens, cyproterone acetate and flutamide, to block the induction of microsomal 3β-hydroxysteroid dehydrogenase and repression of microsomal 5α-reductase in rat liver following administration of 5α-dihydrotestosterone was investigated in male and female castrated and female gonadintact rats. Although both antiandrogens blocked the effects of 5α-dihydrotestosterone on the seminal vesicles and uteri of gonadectomized rats at the doses employed, cyproterone acetate showed no antiandrogenic activity against the two enzyme activities. On the contrary when cyproterone acetate was administered alone it elicited a response similar to that seen after androgen administration; when given simultaneously with 5α-dihydrotestosterone, the induction of 3β-hydroxysteroid dehydrogenase activity was greater than after either steroid alone. In contrast the non-steroidal antiandrogen, flutamide, which had no intrinsic effect on either enzyme activity, effectively blocked 5α-dihydrotestosterone mediated changes in the enzyme activities of female rats regardless of gonadal status. However the influence of 5α-dihydrotestosterone administration on these enzyme activities in male rats was not prevented.