bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of a specific insulin-like growth factor-I/somatomedin-C receptor on high density, primary monolayer cultures of bovine articular chondrocytes: regulation of receptor concentration by somatomedin, insulin and growth hormone
Authors: Watanabe N. , Rosenfeld R. G. , Hintz R. L. , Dollar L. A. , Smith R. L. 
Published: December 2008

ABSTRACT
In order to obtain a phenotypically stable cell population of chondrocytes, high density primary monolayer cultures of bovine articular chondrocytes were established. Using these cultures, a specific insulin-like growth factor-I/somatomedin-C (IGF-I/SM-C) receptor was demonstrated and characterized. At 15 °C steady-state binding was attained by 5 h, and averaged 25% per 2·2 × 106 cells. Fifty per cent displacement of 125I-labelled IGF-I/SM-C by unlabelled IGF-I/SM-C occurred at concentrations of only 2·3 ng/ml, whereas IGF-II and porcine insulin were approximately 15-and 1000-fold less potent respectively. Scatchard analysis gave a linear plot, with a calculated association constant of 2·26 × 109 l/mol and a receptor number of 15 400 sites per cell.
Preincubation of chondrocyte monolayers with either IGF-I/SM-C or porcine insulin at 37 °C for 20 h resulted in reduction of 125I-labelled IGF-I/SM-C binding in a dose-dependent manner, although higher concentrations were required with insulin. More than 40% down-regulation of the receptor occurred with IGF-I/SM-C at concentrations of 10 nmol/l and nearly 70% reduction at 50 nmol/l. Interestingly, after preincubation with either human (h) or bovine (b)GH, 40% down-regulation of 125I-labelled IGF-I/SM-C binding was observed at concentrations of 10 μmol/l. Local production of IGF-I/SM-C by chondrocytes in response to GH stimulation may have occurred, but, because only 120 pmol IGF-I/SM-C and < 30 pmol IGF-I/SM-C per litre were recovered from serum-free conditioned media preincubated with bGH and hGH respectively, this was not established.
These studies demonstrate that cultured bovine articular chondrocytes possess a highly specific IGF-I/SM-C receptor, and that this receptor population is regulated not only by IGF-I/SM-C and insulin but also by high concentrations of either hGH or bGH. These results are consistent with the growth-promoting action of IGF-I/SM-C on skeletal tissues, and suggest the possibility that GH itself may play its own role to modulate IGF-I/SM-C receptors on chondrocytes.
J. Endocr. (1985) 107, 275–283
Vasopressin secretion as a possible target of the γ-aminobutyric acid-mediated component of the corticosteroid feedback effect
Authors: Ács Zs. , Lutz-Bucher B. , Koch B. , Stark E. 
Published: December 2008

ABSTRACT
The inhibition of γ-aminobutyric acid (GABA) synthesis did not interfere with the suppressive effect of dexamethasone on the stress-induced rise of plasma corticosterone levels in vasopressin-deficient homozygous Brattleboro rats. In dexamethasone-treated heterozygous rats corticosterone and vasopressin secretion increased after stress provided GABA synthesis was inhibited. The results indicate that inhibition of corticotrophin secretion by corticosteroids may in part be mediated by enhancement of GABA synthesis and a consequent inhibition of vasopressin release.
J. Endocr. (1985) 107, 303–307
Increased sensitivity of the osmotic control of vasopressin in sheep with deoxycorticosterone acetate-induced hypertension
Authors: Brooks D. P. , Share L. , Crofton J. T. , Guthe C. , Ling W. D. , Bohr D. F. 
Published: December 2008

ABSTRACT
The development of hypertension induced by deoxycorticosterone acetate (DOCA) in sheep was accompanied by increases in both the plasma concentration and the urinary excretion of vasopressin. The vasopressin response to an osmotic stimulus (i.v. infusion of 0·85 mol NaCl/l at 4 ml/min for 75 min) was studied before and after the development of hypertension induced by DOCA in six sheep. Before DOCA implantation, the osmotic stimulus resulted in an increase of plasma osmolality (POSM) from 290 ± 1 to 303 ± 1 (s.e.m.) mosmol/kg H2O and in plasma vasopressin concentration (PAVP) from 0·23 ± 0·04 to 1·07 ± 0·15 μu./ml. At least 30 days after DOCA implantation when mean arterial blood pressure had risen from 81 ± 3 to 117 ± 5 mmHg, the same osmotic load caused an increase in POSM from 290 ± 2 to 298± 2 mosmol/kg H2O and PAVP from 0·45 ± 0·05 to 2·02 ± 0·27 μu./ml. POSM and PAVP were significantly correlated in every experiment. However, the slope of the relationship increased significantly (P<0·01) after the animals had developed hypertension (0·185± 0·026 vs 0·070 ± 0·011 (μu. vasopressin/ml)/(mosmol/kg H2O)). The intercepts were similar. After the DOCA implant had been removed osmotic sensitivity returned to normal.
J. Endocr. (1985) 107, 309–315
Regulation of testosterone production in Leydig cells from fetal mice under dynamic conditions: effect of human chorionic gonadotrophin and 8-bromo-cyclic AMP
Authors: Pointis G. , Latreille M. T. 
Published: December 2008

ABSTRACT
The temporal release of testosterone by Leydig cells from 18-day-old mouse fetuses in response to human chorionic gonadotrophin (hCG) and to 8-bromo-cyclic AMP (8-bromo-cAMP) was investigated under short-term incubation (180 min) conditions. A rapid and large increase in testosterone release was induced by a 5-min exposure to hCG (20 i.u./l) or 8-bromo-cAMP (10 mmol/l). The testosterone response of fetal Leydig cells to the two gonadotrophic stimuli was Gaussian in distribution with a peak value of testosterone by 15–20 min. Repeated exposure to hCG resulted in a reduced testosterone response but an increased accumulation of cAMP. The apparent resistance of fetal Leydig cells to hCG could not be overcome either by increasing the hCG concentration (to 2000 i.u./l) or by exposing the cells to 8-bromo-cAMP (10 mmol/l). Continuous exposure to hCG (200 i.u./l) divided into multiple small doses (each 8 i.u./l) induced testosterone secretion with different kinetic characteristics: a three-fold longer time-lag between hormone exposure and the peak value; a twofold greater testosterone response (P<0·001) and a gradual decrease of testosterone secretion. Oestradiol significantly reduced basal and hCG-stimulated testosterone production only at a high concentration (10 μmol/l). These results indicate that continuous or pulsatile exposure to hCG can induce refractoriness of fetal Leydig cells. The similarity between the actions of hCG and 8-bromo-cAMP on fetal steroidogenesis suggests that this rapid defect is not primarily due to a depletion of gonadotrophin receptors but results from disruption of regulatory mechanisms at the post-receptor level.
J. Endocr. (1985) 107, 409–414
Seasonal influence on thyroidal response to thyrotrophin-releasing hormone in cattle and buffaloes
Authors: Khurana M. L. , Madan M. L. 
Published: December 2008

ABSTRACT
The effect of thyrotrophin-releasing hormone (TRH) on the circulating plasma levels of tri-iodothyronine (T3) and thyroxine (T4) was determined in the same group of animals (four cattle and four Murrah buffaloes) during hot dry (HD), hot humid (HH) and cold environmental conditions. Plasma T3 and T4 concentrations were measured during 2 h before and up to 12 h after the administration of TRH (200 μg i.v.). In the preinjection period in both cattle and buffaloes T3 levels were significantly lower in HH conditions. No significant difference in basal (preinjection) T3 levels was observed during HD and cold seasons in cattle. The highest T3 levels were obtained in buffaloes during HD season with intermediate values during the cold months. Plasma T4 levels in these animals were reversed during HD and HH months. In both cattle and buffaloes there was a biphasic response of T3 and T4 to TRH treatment and this varied with time and in size. The season significantly affected the T3 response to TRH in cattle and buffaloes but the T4 response differed in the two species. The ratio of T4/T3 was higher during HH condition compared with other seasons in both cattle and buffaloes. The climate significantly affected the thyroidal response to TRH.
J. Endocr. (1986) 108, 57–61
Oestriol and non-protein-bound oestriol concentrations in human peripheral plasma before labour and delivery
Authors: Moutsatsou V. , Oakey R. E. 
Published: December 2008

ABSTRACT
The concentration of oestriol and the proportion of this hormone not bound to plasma protein were measured using radioimmunoassay and centrifugal ultrafiltration respectively, in 55 samples of plasma obtained from 12 women in the last 2 to 7 weeks of uncomplicated pregnancy. Among individuals, the mean plasma concentration of oestriol varied from 25·8 to 94·8 nmol/l; in nine subjects, there was a tendency for oestriol concentrations to increase as delivery approached. The mean proportion of oestriol not bound to plasma protein in the different subjects varied from 13·1 to 18·9%, but values from any individual subject remained essentially constant during the periods of study. These measured values were used to calculate, for each sample, the apparent concentration of oestriol not bound to plasma protein. The results were combined with analogous values for oestradiol and progesterone obtained from the same plasma samples and described in a previous study. It was found that (i) the mean ratio of the concentration of oestriol and oestradiol was 0·75, (ii) the mean concentration of non-protein-bound oestriol was 8·7 times that of non-protein-bound oestradiol, and (iii) in individual subjects, there was no consistent trend as delivery approached in the ratio of the concentration of progesterone to that of oestriol in either the total or non-protein-bound form.
J. Endocr. (1986) 108, 75–80
Ontogeny and oestradiol dependence of vitamin D-binding protein blood levels in chickens
Authors: Nys Y. , Bouillon R. , Van Baelen H. , Williams J. 
Published: December 2008

ABSTRACT
The concentration of 25-hydroxyvitamin D3-binding protein (DBP) was measured, by immunodiffusion, in the blood of chickens from embryonic stages to sexual maturity. Low levels of DBP and 1,25-(OH)2D3 were detectable in the blood of chick embryos from the 12th and 17th day of incubation respectively and stayed at the same low levels until hatching. The blood concentration of DBP doubled between the 1st and 5th days of life, then increased slowly and reached the mean level of the adult male at 7–8 weeks of age. The concentration of DBP was independent of vitamin D status in growing chickens. A large increase was observed in DBP blood levels in hens just before sexual maturity. This change, and those observed in moulting hens, followed the variations in plasma concentrations of oestradiol more closely than those of progesterone or testosterone. Moreover, a large increase in plasma DBP levels was induced in immature chickens by oestradiol (0·5 mg/day), but not by testosterone or progesterone. Finally, the experimental suppression of egg shell formation and the associated decrease in 1,25-(OH)2D3 plasma levels had no effect on plasma DBP concentrations. However, 1,25-(OH)2D3 and DBP levels were higher in hens laying shell-less eggs than in immature pullets. The increases in DBP levels at hatching, in immature pullets treated with oestrogens, in hens laying uncalcified eggs and at the onset of egg production were associated with increases in 1,25-(OH)2D3, suggesting a relationship between the levels of DBP and 1,25-(OH)2D3 in the blood.
J. Endocr. (1986) 108, 81–87
Testosterone maintains pituitary and serum FSH and spermatogenesis in gonadotrophin-releasing hormone antagonist-suppressed rats
Authors: Rea M. A. , Marshall G. R. , Weinbauer G. F. , Nieschlag E. 
Published: December 2008

ABSTRACT
Groups of adult male rats were treated continuously for 30 days with either vehicle or the potent gonadotrophin-releasing hormone (GnRH) antagonist, (N-Ac-d-Nal(2)1,d-pCl-Phe2,d-Trp3,d-hArg (Et2)6,d-Ala10)-GnRH (RS 68439; 35 μg/day). In addition, groups of vehicle- and antagonist-treated rats received s.c. testosterone implants sufficient to maintain serum testosterone concentrations 3·5- to 5-fold higher than those of vehicle-treated control rats. After 30 days of antagonist treatment serum LH, FSH and testosterone concentrations were at or below the detection limits of their respective assays and pituitary FSH content and GnRH receptor binding were reduced, relative to control animals, by 77 and 98% respectively. Testis weight in antagonist-treated rats was reduced by 75% and spermatogenesis was suppressed to an extent comparable to that observed in hypophysectomized rats. Testosterone, which caused a 40% reduction in serum FSH relative to control animals, prevented the antagonist-induced fall in both serum and pituitary FSH, but not GnRH receptors, below that observed in the vehicle plus testosterone-treated group. Furthermore, spermatogenesis in the antagonist plus testosterone-treated group was indistinguishable from that observed in control animals. It is concluded that testosterone is capable of maintaining serum and pituitary FSH levels in vivo, under conditions which presumably render the pituitary insensitive to hypothalamic GnRH.
J. Endocr. (1986) 108, 101–107
Comparison of particle-associated progesterone and oxytocin in the ovine corpus luteum
Authors: Rice G. E. , Jenkin G. , Thorburn G. D. 
Published: December 2008

ABSTRACT
The subcellular distribution of progesterone and oxytocin within the ovine corpus luteum was investigated using differential and density gradient centrifugation. Progesterone and oxytocin were associated with particles which sedimented to a density of 1·049–1·054 g/ml and 1·054–1·061 g/ml respectively. Particle-associated progesterone did not, however, display physical or biochemical characteristics consistent with its storage within secretory granules. When particle-associated progesterone was incubated in HEPES buffer at 37 °C, 70% of the total progesterone was recovered in the incubation medium. The remaining stable particle-associated progesterone was not affected by treatments which stimulated oxytocin release and which have been shown to cause the release of peptides and biogenic amines from secretory granules. These results suggest that particle-associated progesterone represents the intercalation of progesterone into cell membranes and they do not support the hypothesis that progesterone is stored, in a protein-bound form, in luteal secretory granules.
J. Endocr. (1986) 108, 109–116
A novel pituitary protein (7B2)-like immunoreactivity is secreted by a rat phaeochromocytoma cell line (PC12)
Authors: Suzuki H. , Tischler A. S. , Christofides N. D. , Chretien M. , Seidah N. G. , Polak J. M. , Bloom S. R. 
Published: December 2008

ABSTRACT
High concentrations of a novel pituitary protein (7B2) have been shown to be present in the PC12 rat phaeochromocytoma cell line by radioimmunoassay. 7B2-like immunoreactivity (IR-7B2) was released from PC12 cells into the incubation medium in response to stimulation by a depolarizing concentration of K+, and this K+-evoked release was inhibited by Co2+, The major IR-7B2 in PC12 cell and medium appeared to be identical to that in porcine pituitary gland as judged by both gel permeation chromatography and by reverse-phase high performance liquid chromatography (HPLC). Gel permeation chromatography of extracts of cell and medium revealed two IR-7B2 peaks, the earlier eluting at a elution coefficient (Kav) of 0·30 and the later at a Kav of 0·54. In medium, over 90% of the IR-7B2 eluted as the earlier peak. Fractionation of extracts of cell and medium on reverse-phase HPLC showed three main IR-7B2 peaks eluting at 43, 44·5 and 46% acetonitrile/water with 0·1% trifluoroacetic acid. The findings suggest that IR-7B2 might be released by calcium-mediated exocytosis.
J. Endocr. (1986) 108, 151–155
Vasopressin and oxytocin responses to acute and chronic osmotic stimuli in man
Authors: Williams T. D. M. , Abel D. C. , King C. M. P. , Jelley R. Y. , Lightman S. L. 
Published: December 2008

ABSTRACT
The regulation of both arginine vasopressin (AVP) and oxytocin secretion was studied during rapid and prolonged osmotic stimuli in normal adult volunteers. In five subjects given an intravenous infusion of 0·85 mol NaCl/l at 0·05 ml/kg per min over 2 h there was a significant (P<0·05) rise only in plasma AVP, with no significant change in plasma levels of oxytocin. In six further subjects 5 days of restriction to 500 ml fluid daily resulted in significant increases of both plasma and 24-h urinary AVP, whereas there was no change in corresponding oxytocin levels. During another 5-day period in which the same subjects were given an additional 200 mmol sodium as well as having their fluid intake restricted to 1000 ml daily, there were again significant rises in plasma and 24 h urinary AVP with no change in corresponding oxytocin levels. We conclude that, in man, AVP is selectively secreted in response to both dehydration and high sodium intake, whilst even after the stimulus of rapidly increasing plasma osmolality during intravenous infusion of hypertonic saline the rise in oxytocin is not statistically significant. It therefore appears unlikely that oxytocin has a significant role in the physiological control of fluid balance in man.
J. Endocr. (1986) 108, 163–168
Urine pH and the relationship between urine flow and urinary prostaglandin E excretion in the rat
Authors: Haylor J. , Lote C. J. 
Published: December 2008

ABSTRACT
The relationship between urine flow and urinary prostaglandin E (PGE) excretion was investigated at constant urine pH in the anaesthetized rat. The urine pH was maintained at approximately pH 6 or pH 8 by the intravenous infusion of either ammonium chloride or sodium bicarbonate respectively.
Two distinct patterns in the relationship between PGE excretion and urine flow were observed. The first showed a fall in urinary PGE excretion as the urine flow increased over the low flow range of 2–5 ml/h, and was common to both experiments. The second relationship, however, showed a marked difference between the ammonium chloride and sodium bicarbonate experiments since: (a) in acidic urine (pH 6), PGE excretion increased (P < 0·002) with the urine flow, attaining a rate of 87± 6 pmol/h (n = 6) at the highest level of flow achieved (12 ml/h); (b) in alkaline urine (pH 8), PGE excretion was significantly (P < 0·01) higher but did not increase with urine flow, remaining constant at approximately 90 pmol/h (n = 6).
The lack of any additive effect on urinary PGE excretion between increasing the urine flow and making the urine alkaline may be explained by both stimuli acting through a common mechanism, a concept which is consistent with the hypothesis that PGE may be reabsorbed in the distal nephron. The flow-dependency of urinary PGE excretion could therefore result from a reduction in reabsorption rather than the increase in passive secretion proposed previously. In addition, PGE excretion in alkaline urine may be a more appropriate index of renal PGE synthesis, since above a urine pH of 7·5 its excretion is independent of both urine pH and urine flow.
J. Endocr. (1986) 108, 247–253
Effects of vasopressin-glycine and vasopressin-glycine-lysine-arginine on renal function in the rat
Authors: Lote C. J. , McVicar A. J. , Smyth D. G. 
Published: December 2008

ABSTRACT
The peptides vasopressin-Gly and vasopressin-Gly-Lys-Arg occur as part of the sequence of the vasopressin-neurophysin precursor molecule and may be released from the hypothalamus and/or pituitary. [8-Lysine]-vasopressin-Gly (LVP-Gly) and [8-lysine]-vasopressin-Gly-Lys-Arg were administered i.v. to conscious, water-diuretic rats. The renal effects of the peptides were assessed by comparison with the actions of [8-lysine]-vasopressin (LVP) which was administered to separate groups of rats.
LVP-Gly and LVP-Gly-Lys-Arg were weakly antidiuretic. LVP-Gly-Lys-Arg was the more potent of the two peptides, but on a molar basis it only had about 10% of the antidiuretic activity of LVP. LVP-Gly and LVP-Gly-Lys-Arg at 10 pmol/h per 100 g body weight (equivalent to the maximal antidiuretic dose of LVP) slightly decreased (P < 0·001) urine flow without causing significant changes in urine osmolality.
LVP (10 pmol/h per 100 g body weight) promoted a marked natriuresis (P < 0·001 ) but LVP-Gly and LVP-Gly-Lys-Arg were not natriuretic, even at the dose which was markedly antidiuretic (100 pmol/h per 100 g body weight). Osmolal output decreased at all doses during administration of the extended peptides, but was not significantly changed in the control group or by LVP. Inulin clearance was decreased by about 30% during administration of both LVP and LVP-Gly-Lys-Arg at 100 pmol/h per 100 g body weight.
It is concluded that LVP-Gly and LVP-Gly-Lys-Arg show weak antidiuretic activities and that the effect on urine flow may be partly due to a decrease in glomerular filtration rate (GFR). The decrease in osmolal output produced by the peptides is also a likely consequence of an effect on GFR. It is suggested that LVP-Gly and LVP-Gly-Lys-Arg have a low potential for activation of tubular vasopressin receptors, as shown by the weak antidiuretic activity and lack of a natriuretic action, but that they have a relatively stronger action on glomerular vasopressin receptors.
J. Endocr. (1986) 108, 255–260
Efficacy and specificity of human parathyroid hormone analogues as antagonists in intact clonal osteogenic sarcoma cells
Authors: Kubota M. , Ng K. W. , Murase J. , Noda T. , Moseley J. M. , Martin T. J. 
Published: December 2008

ABSTRACT
Five synthetic analogues of human parathyroid hormone (hPTH), (Tyr34)hPTH(3–34) amide, (5–34) amide, (7–34) amide, (8–34) amide and (9–34) amide, were tested for their ability to antagonize hPTH action specifically in intact cultured cells. Clonal rat osteogenic sarcoma cells were used (UMR 106–06 line) which respond to PTH with an increase in cyclic AMP (cAMP) formation. The most potent antagonists were (Tyr34)hPTH(3–34) amide and (5–34) amide, which inhibited the effect of hPTH(2·4 nmol/l) with half maximally effective concentrations of 0·1 μmol/l. When conditioned medium was used from a human lung cancer cell line producing osteoblast adenylate cyclase-stimulating activity, these two analogues were capable of inhibiting the increase in cAMP production. The specificity of the antagonism was indicated by the inability of the analogues to influence the effects of prostaglandin E2 or of calcitonin, which are alternative stimulators of cAMP production in the osteogenic sarcoma cells. Only (Tyr34)hPTH(3–34) amide showed some PTH-like agonist activity at high concentrations. These analogues should prove valuable in the investigation of PTH actions on target cells and of tumour products which appear to act through the PTH receptor.
J. Endocr. (1986) 108, 261–265
The mechanism of the effect of oxytocin on plasma concentrations of glucose, insulin and glucagon in conscious dogs
Authors: Vilhardt H. , Krarup T. , Holst J. J. , Bie P. 
Published: December 2008

ABSTRACT
Injections and infusions of oxytocin into conscious dogs caused an increase in plasma concentrations of glucose, insulin and glucagon. When blood glucose was clamped at a raised level the injection of oxytocin still increased insulin and glucagon concentrations in plasma. Infusion of somatostatin suppressed plasma concentrations of glucagon and insulin but did not prevent oxytocin-induced increments in blood glucose. Injection of oxytocin still caused a marked release of glucagon, whereas the insulin response was greatly diminished. When endogenous insulin and glucagon secretion was suppressed by infusion of somatostatin and glucose levels were stabilized by concomitant infusions of glucagon and insulin, injections of oxytocin did not alter blood glucose concentrations. It is concluded that the increase in blood glucose following the administration of oxytocin is secondary to the release of glucagon and that oxytocin exerts a direct stimulatory effect on glucagon and possibly insulin secretion.
J. Endocr. (1986) 108, 293–298