bluuebunny/crossref_metadata_2025_split huggingface dataset:
Direct evidence in men for a role of endogenous oestrogens on gonadotrophin release
Authors: D'Agata R. , Vicari E. , Aliffi A. , Gulizia S. , Palumbo G. 
Published: December 2008

Abstract.
In six healthy subjects serum oestradiol was selectively decreased by administering an aromatase activity inhibitor, hydrotestolactone (HT). After HT administration serum oestradiol (Oe2) decreased from 18.7 ± 2.3 (sem) to 6.7 ± 0.6 pg/ml whereas testosterone (T) and dihydrotestosterone (DHT) blood levels were not modified. These oestradiol changes were associated with a significant increase in serum LH and FSH concentrations (P < 0.001). The administration of tamoxifen, an oestrogen antagonist, to 5 subjects caused a sharp increase in LH and FSH levels (P < 0.001).
Oe2 was unchanged after the treatment with tamoxifen, whereas T levels were significantly higher.
The sum of these data suggests that oestradiol under physiological conditions plays a specific role in the feedback mechanism of gonadotrophin release.
Opiate receptors and anterior pituitary hormone secretion in man. Effect of naloxone infusion
Authors: Delitala G. , Devilla L. , Arata L. 
Published: December 2008

Abstract.
The role of endogenous opioid receptors on anterior pituitary hormone secretion was evaluated by the administration of the opioid receptor antagonist naloxone. The infusion of naloxone (8 mg iv followed by 4 mg/h for 3 h) did not alter basal growth hormone (GH), prolactin (Prl) and thyrotrophin (TSH) secretion but produced a significant rise in cortisol and gonadotrophins in normal man. The infusion of the opiate antagonist appeared to increase the rate and amplitude of luteinizing hormone (LH) pulsatility.
Naloxone pre-medication (10 mg iv 30 min before testing) did not alter the pituitary response to TRH and LRH stimulation.
These results demonstrate that naloxone can modify basal anterior pituitary hormone secretion and strongly suggest an endogenous opioid modulation of some of these hormones.
Gonad-gonadotrope interactions: plasma gonadotrophin levels and tumour induction in long-term castrated rats
Authors: Linkie Daniel M. , Furth Jacob , Kourelakos Diane 
Published: December 2008

Abstract.
The patterns of gonadotrophin secretion in intact controls and in male and female rats castrated for up to 36 months were established utilizing specific radioimmunoassay methods. Plasma LH increased 14– 16-fold and FSH rose 4–8-fold in rats of either sex in the first 30 days following gonadectomy. The subsequent 30 day interval showed an additional 76% increase of LH in both sexes and increases in FSH of 32 and 61% in males and females, respectively. These levels were maintained for an additional 34 months. The number of hypophyseal gonadotrophin containing cells, studied by immunohistochemical localization techniques, increased following gonad removal in a pattern similar to that for the circulating hormones. Development of gonadotrophin secreting tumours did not correlate with plasma gonadotrophin concentrations which suggests that the gonadotropes are uniquely resistant to tumourogenesis unlike mammotropes, thyrotropes, and corticotropes.
A radioimmunoassay of serum 3,5-diiodothyronine
Authors: Kirkegaard Carsten , Faber Jens , Siersbæk-Nielsen Kaj , Friis Thorkild 
Published: December 2008

Abstract.
A radioimmunoassay (RIA) for serum 3,5-diiodothyronine (3,5-T2) was developed using small Sephadex G 25 (fine) columns. Prior to the RIA an alcohol extraction of 3,5-T2 from serum and an evaporation of the extract was performed. The recovery of 3,5-T2 added to serum was in mean (± sem) 101 ± 11%. The lower detection limit was 0.012 pmol/column corresponding to 14 pmol/l using 3 ml serum. Due to a 5% cross-reaction of the 3,5-T2 antibody with 3,5,3'-triiodothyronine (T3) individual correction for T3 present in serum was necessary. Serum 3,5-T2 levels in 52 éuthyroid controls were (mean ± SD) 105 ± 51 pmol/l. Serum levels were higher in men (125 ± 56 pmol/l) than in women (84 ± 34 pmol/ l, P < 0.005). In 17 hyperthyroid subjects serum 3,5-T2 levels were elevated (232 ± 187 pmol/l, P < 0.005). In hypothyroid patients and patients with non-toxic goitre serum 3,5-T2 levels did not differ significantly from control values, whereas 8 patients with liver cirrhosis had severely reduced serum 3,5-T2 concentrations (20 ± 23 pmol/l, P < 0.001).
Effect of inhibition of protein synthesis on thyroid cyclic AMP accumulation in vitro
Authors: Nilsson Hans , Ahrén Bo , Gustafson Åsa , Hedner Pavo 
Published: December 2008

Abstract.
When thyroid cells in vitro are stimulated by TSH for 2 h cyclic AMP (cAMP) is synthetized at a high rate during the first 25 min of stimulation, thereafter at a lower rate. The mechanism for this reduction of adenyl cyclase activity was studied in vitro using mouse thyroid tissue. As some of the cAMP formed is released from the cells the sum of cAMP in tissue and incubation medium was studied and considered to reflect the accumulated cAMP synthesis as breakdown by phosphodiesterase was minimized by 1 mm theophylline.
The TSH stimulated tissue did not release any adenyl cyclase inhibiting factor into the incubation medium. Cycloheximide, 5 μg/ml, enhanced the cAMP response to a single or repeated stimulation by TSH. Its effect was visible after 25 min of incubation and remained at about the same size for 2 h, but the levelling off of cAMP synthesis was not prevented but took place at a higher level. The effect of puromycin, 500 μg/ml, was similar to that of cycloheximide. Also actinomycin D, 1 μg/ml, enhanced the cAMP response to TSH.
It is concluded that a protein synthesis dependent inhibitor of adenyl cyclase is activated by TSH, but it accounts only for a minor part of the adenyl cyclase inhibition that takes place in the later part of a TSH stimulation of the thyroid. Additional adenyl cyclase inhibiting mechanisms must be considered.
Radioimmunoassay for 4-hydroxyoestrone in human urine
Authors: Emons Günter , Mente Claudia , Knuppen Rudolf , Ball Peter 
Published: December 2008

Abstract.
Under the protection of ascorbic acid a 4-hydroxyoestrone-bovine serum albumin conjugate was prepared containing intact 4-hydroxyoestrone as determined by gas chromatography-mass spectrometry. Using this antigen, antibodies with high affinity and specificity for 4-hydroxyoestrone were raised in rabbits. An assay procedure for the determination of 4-hydroxyoestrone in human urine and the assessment of its reliability are described. The following urinary excretion rates were found: male children 0.29 μg/24 h, female children 0.35 μg/24 h, men (20–40 years) 1.6 μg/24 h, men (>50 years) 1.8 μg/24 h, women, follic. 2.0 μg/24 h, pre-ov. 5.3 μg/24 h, luteal 2.4 μg/24 h, women, pregnant, first trim. 30.0 μg/24 h, second trim. 64.0 μg/24 h, third trim. 48.0 μg/24 h, women, post-men. 1.5 μg/24 h. Thus the amounts of 4-hydroxyoestrone excreted in human urine are about 1/3 to 1/10 of those of 2-hydroxyoestrone. During the menstrual cycle the excretion rates of 4-hydroxyoestrone are in the same order of magnitude as those of oestradiol and show a clear-cut pre-ovulatory peak.
Gel filtration and sedimentation behaviour of receptor-gonadotrophin complexes from rat ovary
Authors: Jääskeläinen Kalle , Rajaniemi Hannu , Reichert Leo E. 
Published: December 2008

Abstract.
Membrane particles of luteinized rat ovaries and immature and mature granulosa cells of rat ovarian follicles were labelled with [125I]human chorionic gonadotrophin (hCG), membranes of mature granulosa cells were also labelled with [125I]ovine follitropin (oFSH). Hormone-receptor complexes were solubilized with Triton X-100 and their physical properties were characterized by sedimentation and gel filtration. No difference in the macroscopic physical properties of the specific receptor-hCG-complex was observed between different developmental stages of granulosa cells. The Stokes radius of the specific receptor-[125I]hCG-complex was 58 Å and the sedimentation coefficient 6.7 ± 0.3 S.
The physical properties of free LH/hCG-receptor of luteinized ovaries were also characterized. The Stokes radius was found to be 57–59 Å and the sedimentation coefficient 4.8–5.6 S. Both [125I]hCG and [125I]oFSH formed non-specific complexes with ovarian as well as with non-gonadal membrane components. The sedimentation coefficient of the non-specific complex was 1.3 ± 0.5 S and the Stokes radius 49 Å. These results show that the macroscopic physical properties of the receptor-hCG-complex do not change during the maturation and subsequent luteinization of the granulosa cells. The methods used were not enough discriminating to reveal the existing structural differences between receptor-oFSH-complex and receptor-hCG-complex.
The interaction of sialidase-treated hCG with ovarian cellular membranes
Authors: Brand E. C. , Odink J. , Klok G. , van Hall E. V. 
Published: December 2008

Abstract.
The potency of human chorionic gonadotrophin (hCG) in competition for binding to a gonadal membrane fraction is remarkably enhanced by sialidase treatment. The present study was undertaken to investigate the specificity and characteristics of the binding of sialidase-treated hCG (asialo-hCG) in a particulate hCG-binding system from luteinized rat ovaries.
The competitive potency of asialo-hCG relative to hCG was 2.5, irrespective of whether [125I]hCG or [125I]asialo-hCG was used for tracer. This was due to a 2.1 times higher equilibrium association constant for asialo-hCG, whereas the estimated number of binding sites did not differ. There was no apparent difference in the stability of hCG and asialo-hCG, or in the stability of the respective hormone-receptor complexes. The effect of variation of the incubation conditions on the binding of both tracers was similar.
In accordance with the difference in the equilibrium association constant, the association velocity of asialo-hCG was more than double that of hCG.
With all of the tracers used the dissociation curves were biphasic, the size of the initial fast-dissociating fraction being inversely related to the pre-incubation time. Under identical conditions, the fast-dissociating fraction was smaller for the [125I]asialo-hCG complex than for the [125I]hCG complex. The dissociation velocities of these fractions appeared to be similar.
The results indicate that asialo-hCG binds to the hCG receptor in a way similar to the binding of the unmodified hormone, but with a higher affinity. The smaller size of the fast-dissociation form of the asialo-hCG-receptor complex may be related to the lower biological potency of the hormone derivative.
On the mechanism of action of progestins
Authors: Pérez-Palacios Gregorio , Fernández-Aparicio María A. , Medina Martha , Zacarías-Villareal Jesús , Ulloa-Aguirre Alfredo 
Published: December 2008

Abstract.
The effect of two synthetic injectable progestins, norethisterone oenanthate3 (NET-e) and medroxyprogesterone acetate (MPA) upon the hypothalamic pituitary unit was evaluated in post-menopausal women (PMW) and in castrated individuals with androgen un-responsiveness in order to gain insight into their mechanism of gonadotrophin inhibition. Continuous administration of natural progesterone (P4) to PMW by medicated vaginal rings was used as the experimental control. Elevated base line levels of serum immunoreactive gonadotrophins and normal pituitary LRH responses were found in PMW and pseudohermaphrodites. Progesterone did not affect circulating gonadotrophin levels or the pituitary LRH response in PMW.
Administration of MPA 150 mg induced a clear decrease in serum gonadotrophins and a significant decrease in LRH pituitary responsiveness in a post-menopausal woman whereas no effect was observed on serum gonadotrophins and pituitary response to LRH in a patient with androgen unresponsiveness. Administration of NET-e 200 mg resulted in a significant decrease in circulating gonadotrophins in PMW and pseudohermaphrodites, while LRH pituitary sensitivity was diminished in all subjects except one post-menopausal woman.
These results demonstrated that two structurally different synthetic progestins (NET-e and MPA) had a potent gonadotrophin inhibitory activity in PMW while natural progesterone did not, thus indicating a different mode of action. Furthermore their differing effect on individuals with complete androgen unresponsiveness suggested that antigonadotrophic activity of NET-e is mediated by its oestrogenic-progestational effect, while MPA acts through its androgenic potency and therefore requires the presence of androgen receptors.
Changes in serum somatomedin A and its binding to kidney membranes in growing rats
Authors: Hizuka Naomi , Takano Kazue , Shizume Kazuo , Hasumi Yoko 
Published: December 2008

Abstract.
Changes in serum somatomedin A levels and [125I]somatomedin A binding to membrane fractions from kidney were studied in rats 1–80 days of age. The mean level of serum somatomedin A was 0.80 U/ml at birth and increased with age; at 80 days the mean level was 7.41 ± 0.67 U/ml. There was a close correlation between serum levels of somatomedin A and body weight. Labelled somatomedin A binding to membrane fractions from kidney was highest at birth and decreased with age up to 50 days. In Scatchard analysis of the data the affinity constant did not show a clear change with age, but the binding capacity decreased with age up to 30 days. An inverse correlation was observed between serum somatomedin A levels and labelled somatomedin A binding to membrane fractions from kidney. Compared to changes in circulating somatomedin A, the change in tissue binding was modest. This observation suggests that other circulating growth factors not measured by this radioreceptor assay or altered post-receptor sensitivity to somatomedins may be involved in growth.
Effect of different calcium intakes on bone mineral composition in rats with a calcitonin secreting tumour
Authors: Myhre Lisbeth , Hongslo Cecilie F. , Gautvik Kaare M. , Ekeland Arne 
Published: December 2008

Abstract.
The effects of hypercalcitoninaemia and different calcium intakes on bone composition were studied in rats with and without a transplanted calcitonin secreting tumour (MCT). The serum concentrations of immunoreactive calcitonin (iCT) increased progressively after transplantation. After 32 weeks the serum iCT concentrations in MCT rats were about 5-fold higher and serum ionized calcium was significantly reduced compared to control animals. In rats with hypercalcitoninaemia eating a standard calcium (0.9%) diet for 32 weeks, the dry weight and calcium and sodium content of the long bones were reduced compared to control rats without tumours or rats with a prolactin secreting tumour.
The feeding of low (0.09%), medium (0.4%) and high (1.8%) calcium diets to MCT-rats resulted in corresponding levels of total and ionized serum calcium, but there was no difference in iCT concentrations. The MCT-rats taking the low calcium diet had decreased bone mass and calcium content compared to the other dietary groups.
In conclusion, rats on normal calcium intake and carrying a calcitonin secreting tumour, but not a prolactin secreting tumour, had reduced femoral dry weight and bone mineral calcium content. Different calcium intake regimens did not affect hypercalcitoninaemia due to a tumour, but parallel changes in femoral dry weight and calcium content were found.
Presence of TRF immunoreactivity in marginal islet cells in rat pancreas
Authors: Koivusalo F. , Leppäluoto J. , Knip M. , Rajaniemi H. 
Published: December 2008

Abstract.
Isolated rat pancreatic islet extracts were submitted to reverse phase high pressure chromatography (HPLC) and assayed for thyrotrophin releasing factor (TRF), glucagon and insulin in radioimmunoassays (RIA). Our anti-TRF serum was prepared by immunizing rabbits with TRF conjugated to bovine thyroglobulin (bTG) by bisdiazobenzidine. Anti-glucagon and anti-insulin sera were from a commercial source (Novo, Denmark). The concentrations of TRF, glucagon and insulin were 0.05 ± 0.02, 0.06 ± 0.02 and 1.0 ± 0.2 pmol/islet, respectively.
Formalin-fixed pancreatic sections were stained for TRF, glucagon and insulin by peroxidase, antiperoxidase (PAP) complex method. When the adjacent sections were stained for glucagon or insulin, it was observed that TRF and glucagon-specific peroxidase reactions were confined to the marginal islet cells, but insulin reactions to the central cells. The TRF-specific peroxidase reaction was clearly reduced when the anti-TRF serum was adsorbed with TRF-TG-Sepharose, whereas it was unchanged when the antiserum was pre-incubated with synthetic TRF.
The present HPLC results suggest that the islets contain TRF. Immunocytochemical studies show that the TRF-immunoreactive material, either synthesized or bound, is localized in the marginal islet cells.
Immunochemical characterization and distribution of calcitonin in the lizard
Authors: Galan F. Galan , Rogers R. M. , Girgis Samia I. , Arnett T. R. , Ravazzola Mariella , Orci L. , Maclntyre I. 
Published: December 2008

Abstract.
Immunological and chromatographic methods were used to investigate the distribution of calcitonin (CT) in various tissues of Lacerta muralis, a common wall lizard. Salmon CT-like immunoreactivity was found in high concentration in extracts of ultimobranchial gland (UBG) and in significant amounts in lung and brain extracts, but not in other tissues (oesophagus, stomach, duodenum, liver, skin, muscle and thyroid). Serial dilution of UBG, lung and brain extracts gave parallel displacement curves to that of synthetic salmon CT (sCT), but no reactivity was found in the human CT assay.
On Sephadex G-50, UBG, lung and brain extracts contained an sCT-like immunoreactive peak which co-eluted with synthetic sCT. However, on high performance liquid chromatography (HPLC) the sCT-like peak in UBG, lung and brain extracts eluted 2 ml later than synthetic sCT.
This paper describes the first immunochemical characterization of CT in the UBG of the lizard, demonstrates the distribution of extra-ultimobranchial CT and throws some light on the evolution of the calcitonins.
Inhibition of luteinizing hormone release by dopamine infusion in healthy women and in various pathophysiological conditions
Authors: Ferrari Carlo , Rampini Pietro , Malinverni Aurelio , Scarduelli Claudia , Benco Rosanna , Caldara Roberto , Barbieri Cristiano , Testori Gianpaolo , Crosignani Pier Giorgio 
Published: December 2008

Abstract.
To investigate the effect of dopaminergic stimulation on gonadotrophin release, serum LH and FSH concentrations were measured during dopamine infusion (5 μg/kg/min for 120 min) in 8 healthy women in the early follicular phase, in 12 patients with hyperprolactinaemic amenorrhoea, in 5 subjects with premature ovarian failure and in 8 with polycystic ovarian disease and raised serum LH levels. Dopamine infusion produced a significant LH decrease compared with a control study using saline in all groups; there were no significant changes in FSH concentration. Between groups analysis showed a significantly greater LH fall in patients with polycystic ovarian disease than in the other groups.
Dopamine inhibits LH release in healthy women and patients with anovulatory states of varying aetiology, and enhanced sensitivity to this inhibitory mechanism exists in polycystic ovarian disease. This finding suggests reduced dopamine activity at the median eminence level in this condition.
Effect of synthetic thyrotrophin-releasing hormone and its analogues on growth hormone secretion in the domestic fowl (Gallus Domesticus)
Authors: Scanes C. G. , Harvey S. , Morgan B. A. , Hayes M. 
Published: December 2008

Abstract.
Variations in plasma growth hormone (GH) concentrations following iv or sc administration of synthetic thyrotrophin-releasing hormone (TRH, Pyr-His-Pro-NH2) have been followed in immature and adult domestic fowl. TRH markedly stimulated GH secretion in newly hatched (1 and 2 day old) chicks and in 6-week-old cockerels but in adult male or female birds of two strains had very little effect, if any. Intravenous injection of 4 TRH analogues (Pyr-His-Mep-NH2, Pyr-Meh-Mep-NH2, Pyr-Meh-Mep-NH and Pyr-Meh-Pro-NH2) were also potent GH secretagogues in 6-week-old birds. The stimulatory effect of TRH or the TRH-analogues on GH secretion was not dose-related.
Thyroid uptake of 201Thallium and its control by TSH
Authors: Maayan Morelly L. , Volpert Eugene M. , Fine Eugene J. , Eisenberg Julius , Lopez Ernesto M. , Dawry Frank P. 
Published: December 2008

Abstract.
Patients injected with 201Thallium (201Tl) for myocardial scanning present good thyroid visualization. Determinations in mice injected with 201Tl indicated a high thyroid/serum concentration ratio (T/S). The 201Tl biological half life (t½) in serum (30-135 s) was much shorter than in thyroid (53-55 h) for human subjects and experimental animals. The 1 h 201Tl T/S ratio was comparable to that of 131I and 99m Tc, indicating presence of a gradient for 201Tl also. Increase of endogenous TSH induced by propylthiouracil led to a significant rise in T/S for 99mTc, 131I and 201Tl, whereas TSH inhibition by feeding l-thyroxine led to decrease in T/S for 99mTc and 201Tl. In vitro thyroid/medium concentration ratio (T/M) of 99mTc and 201Tl was decreased after 20' incubation with ouabain, an inhibitor of the Na+,K+, activated ATP-ase. However, perchlorate in vitro or in vivo failed to diminish the 201Tl T/M ratios or to affect the t½ of 201Tl in human subjects, whereas T/M of 201Tl was depressed by KCl addition to the medium.
The effect of insulin-like growth factor (IGF) and of human serum on steps in proteoglycan synthesis
Authors: Silbergeld Avivah , Mamet Rivka , Laron Zvi , Nevo Zvi 
Published: December 2008

Abstract.
Embryonic chick pelvic cartilages were incubated in the presence of insulin like growth factor (IGF) (1–100 μU/ml), as well as normal human serum (5%), with radiolabelled precursors of proteoglycan (PG) synthesis: L-[3-3H]serine, D-[6-3H]glucosamine and [35S]Na2SO4. IGF alone (1–15 μU/ml), stimulated in a dose-dependent manner D-[6-3H]glucosamine incorporation into tissue-bound and soluble isolated glycosaminoglycan (GAG) chains. L-[3-3H]serine incorporation into PG molecules was not stimulated by IGF (1–100 μU/ml), despite the increase in the uptake of this precursor into intact cartilage. [35S]Na2SO4 incorporation was unaffected by IGF. Serum promoted the uptake of all three precursors into tissue-bound glycosaminoglycans. It was postulated that IGF could stimulate proteoglycan synthesis not only by elongating existing chondroitin sulphate chains but also by increased synthesis of other sugar chains e.g. keratan sulphate and oligosaccharides.
Corticotrophin stimulation test: inverse correlation between basal serum cortisol and its response to corticotrophin
Authors: Kukreja Subhash C. , Williams Gerald A. 
Published: December 2008

Abstract.
Serum cortisol response to synthetic corticotrophin (B1-24-ACTH) was evaluated in 21 normal subjects. There was significant negative correlation (r = −0.633, P < 0.001) between the basal serum cortisol and the increase in serum cortisol level in response to ACTH. Two subjects had an increase in serum cortisol of less than 194 nm/l (7.0 μg/100 ml) and two additional subjects had an increase of less than 278 nm/l (10.0 μg/100 ml). All subjects had an absolute peak value greater than 583 nm/l (21.0 μg/100 ml) at 30 or 60 min post-ACTH. Inverse correlation between basal serum cortisol and the increase in serum cortisol suggests that in patients who have high basal serum cortisol levels, endogenous ACTH may already have reduced the cortisol reserve of the adrenal gland.