bluuebunny/crossref_metadata_2025_split huggingface dataset:
Growth hormone (GH) secretion in the dwarf rat: release, clearance and responsiveness to GH-releasing factor and somatostatin
Authors: Carmignac D. F. , Robinson I. C. A. F. 
Published: December 2008

ABSTRACT
The new mutant GH-deficient dwarf (Dw) rat was used to study the effects of GH-releasing factor (GRF) or somatostatin (SRIF) on GH release. In anaesthetized adult Dw female rats, i.v. injections of GRF (0·031–2·0μg) elicited a dose-dependent release of GH. Although the peak plasma GH responses to maximal GRF doses were much lower in adult Dw rats compared with normal rats of this strain (AS), the responses largely reflected their relative pituitary GH contents (140±17 μg vs 2·9±0·4 μg, AS vs Dw (means ± s.e.m.), P < 0·001). Except at 20 days of age, normal AS rats were more sensitive to GRF than Dw rats despite their larger body weight. Peak GH responses to injection of 31·25 ng GRF increased nine-fold in normal rats between 20 and 40 days, whereas the GH responses to this GRF dose diminished in Dw rats over this age range, and their pituitary GH content was only 2–5% of that of age-matched AS rats. Treatment with human GH (200 μg/day for 7 days) stimulated growth in 40-day-old Dw rats and slightly increased the GH response to a low dose of GRF. Basal GH levels in adult Dw animals were sevenfold lower than in AS rats (2·4±0·3 vs 17·6±3·3 μg/l P < 0·001) and were further suppressed by i.v. infusion of SRIF (25 μg/h). As in normal rats, a rebound GH secretion occurred in Dw rats after stopping SRIF, which was blocked by injection of anti-GRF serum. The disappearance rate of 125I-labelled rat GH from plasma was identical in AS and Dw rats. We conclude that dwarf rats show GH deficiency as early as 20 days of age; they respond to GRF, but release only small amounts of GH due to their reduced pituitary GH content. Although basal GH release is reduced in Dw rats, the levels are higher than would be expected from the 50-fold reduction in pituitary stores, and may reflect a chronic reduction in SRIF and/or increase in GRF release induced by prolonged GH deficiency in the Dw rat.
Journal of Endocrinology (1990) 127, 69–75
The O-methylation of catechol oestrogens by pig conceptuses and endometrium during the peri-implantation period
Authors: Chakraborty C. , Davis D. L. , Dey S. K. 
Published: December 2008

ABSTRACT
Pig conceptuses display a surge in oestrogen and catecholoestrogen synthetic activity during the periimplantation period. However, the pathways of catecholoestrogen metabolism in pig conceptuses and endometrium are unknown. O-Methylation is an important route of catecholoestrogen metabolism. Therefore, the O-methylations of 2- and 4-hydroxy-oestradiols (2- and 4-OH-oestradiol) by cytosol of pig conceptuses and endometrium during the periimplantation period were studied. Kinetic studies performed in tissues obtained on day 13 of pregnancy (day 0 = first acceptance of the male) indicated that the O-methylation of 2-OH-oestradiol displayed simple Michaelis–Menten kinetics in both tissues. In blastocysts, the apparent Michaelis constant (Km) and maximum velocity (Vmax) for the O-methylation of 2-OH-oestradiol were 1·4 μmol/l and 11·27 pmol/mg protein per min respectively, and when 4-OH-oestradiol was used as substrate, the values were 2·53 μmol/l and 9·86 pmol/mg protein per min respectively. The apparent Km and Vmax values for the O-methylation of 2-OH-oestradiol in endometrium were 0·77 μmol/l and 19·6 pmol/mg protein per min respectively, and for the O-methylation of 4-OH-oestradiol were 2·44 μmol/l and 10·38 pmol/mg protein per min respectively. Ontogenesis of catechol-O-methyltransferase (COMT) in conceptuses and endometrium was studied from day 10 to day 19 of pregnancy. Conceptus COMT activity was lowest on day 10 and increased gradually to day 19 of pregnancy. Because a surge of oestradiol-2/4-hydroxylase activity occurs on days 11–13, less COMT activity on these days than on the later days of pregnancy is consistent with a role for catecholoestrogens in conceptus-maternal signalling during pregnancy establishment. Endometrial COMT activity on day 10 was higher than that on later days of pregnancy. Therefore, a role for COMT in modulation of catecholoestrogen and oestrogen function during the peri-implantation period is possible.
Journal of Endocrinology (1990) 127, 77–84
Intracellular mechanisms involved in the stimulation of growth hormone release from rat anterior pituitary cells by Russell's viper venom
Authors: Hart G. R. , Caldwell G. , Burrin J. M. 
Published: December 2008

ABSTRACT
We have previously shown that a heat-stable component of Russell's viper venom (RVV) releases GH in a dose-dependent manner from cultured rat anterior pituitary cells. We have now investigated the intracellular mechanisms involved in RVV-stimulated GH release by concomitant administration of RVV with known intracellular mediators in rat pituitary cells.
3-Isobutyl-1-methylxanthine (IBMX; 0·5 mmol/l), added to cultured rat anterior pituitary cells simultaneously with RVV, at concentrations up to a maximally effective dose of 10 μg/ml, increased GH release (3·7-fold, 4·0-fold and 2·0-fold; P < 0·001) compared with the effect of venom alone. These effects were additive, indicating that RVV and IBMX stimulate through different intracellular messengers. RVV failed to increase the formation of basal or IBMX-stimulated intracellular cyclic AMP (cAMP), confirming that RVV affects GH release through a cAMP-independent pathway. 12-0-Tetradecanoylphorbol-13-acetate (TPA; 0·1 μmol/l), added simultaneously with various doses of RVV (0·1–10 μg/ml), did not increase GH release beyond the maximal effect of RVV. This result indicates that RVV might be stimulating GH release through a similar mechanism to that of TPA (by activating protein kinase C).
When pituitary cells were perifused with Ca2+-free medium or verapamil (50 μmol/l), RVV-stimulated GH release was inhibited by 65 and 42% respectively. This reflects the recognized requirement of Ca2+ for secretory processes. However, RVV (10 μg/ml) had no significant effect on intracellular free Ca2+ concentrations as measured using the fluorescent Ca2+ probe quin-2.
These findings indicate that the mechanism of action of RVV on GH release is independent of a change in both cAMP levels and intracellular free Ca2+ concentrations, and is dependent upon protein kinase C.
Journal of Endocrinology (1990) 127, 111–117
Identification and partial characterization of parathyroid hormone-related protein in human and bovine milk
Authors: Ratcliffe W. A. , Green E. , Emly J. , Norbury S. , Lindsay M. , Heath D. A. , Ratcliffe J. G. 
Published: December 2008

ABSTRACT
Parathyroid hormone-related protein (PTHrP) was measured in human and bovine milk by radioimmunoassay (RIA) and bioassay, and the molecular forms characterized by gel chromatography and immunoblotting of affinity-purified PTHrP. Mean immunoreactive PTHrP(1–34) concentrations were 23 and 87 μg/l in human and bovine milk respectively. Bioactive (BIO) PTHrP concentrations determined by cyclic AMP production by ROS 17/2·8 cells correlated significantly (P< 0·001) with those obtained by RIA (BIO = 1·04RIA−3·4, r = 0·939). Gel filtration of human and bovine milk identified several peaks with immunoactivity and bioactivity. Immunoblotting of affinity-purified PTHrP revealed multiple molecular species including components with mobilities similar to those of PTHrP and its subfragments. These studies confirm the presence of immuno- and bioactive PTHrP in milk and suggest that post-translational processing is complex and variable.
Journal of Endocrinology (1990) 127, 167–176
Control of ion transport in the thyroid: prostaglandin E2 activates cation transport on the basal membrane of cultured porcine thyroid cell monolayers
Authors: Bourke J. R. , Cragoe E. J. , Huxham G. J. , Pearson J. V. , Manley S. W. 
Published: December 2008

ABSTRACT
Confluent monolayers of cultured porcine thyroid cells transport fluid from the apical to the basal surface, forming circumscribed zones of detachment (domes) from the culture dish substrate. Stimulation of fluid transport by prostaglandin E2 (PGE2; 1 μmol/l) was associated with an increase in transepithelial potential (TEP). Intracellular potentials (equal to the potential difference across the apical membrane of the cell, Eapical) and the TEP were measured in individual domes so that the potential difference across the basal membrane of the cell (Ebasal) could be calculated from the relationship TEP = Eapical − Ebasal. The PGE2-induced increase in TEP was associated with hyperpolarization of the basal membrane, accompanied by a slight depolarization of the apical membrane. Lines of best fit by least-squares regression showed Eapical = −20·3 mV + 0·219 TEP (correlation coefficient r = 0·627; P < 0·001) and Ebasal = −20·3 mV − 0·781 TEP (r = 0·944; P < 0·001). Phenamil (1 μmol/l), a Na+ channel selective amiloride analogue, reduced the TEP from 13·25±0·58 (s.e.m.; n = 56) to 2·39±0·16 mV (n = 51; P < 0·001) and hyperpolarized the apical membrane potential from − 20·7±0·68 (n = 60) to −32·2±0·83 mV (n = 105; P < 0·001). The response of the TEP to phenamil was immediate, and was promptly reversed on washing; in contrast, addition of 5-(N-ethyl-N-isopropyl)amiloride (20 μmol/l; selective for Na+/H+ antiporters) resulted in a slow depolarization over 30 min with a slow recovery after washout. Exposure of the cultures to media of pH 7·04 (compared with the normal pH of 7·34) resulted in a reduced response to PGE2, and a reduction in magnitude of Ebasal. It was concluded that stimulation of ion transport by PGE2 in thyroid monolayers involves activation of cation transport across the basal membrane.
Journal of Endocrinology (1990) 127, 197–202
Effects of altered dietary sodium intake on hormonal profiles in salt-sensitive hypertensive rats
Authors: Hazon N. , Henderson I. W. 
Published: December 2008

ABSTRACT
Blood pressure and selected putatively influential hormones were measured in Brattleboro rats which were without diabetes insipidus and which were subjected to various manipulations in dietary sodium intake. Rats fed a control diet from weaning to 16 weeks of age showed a slow increase in blood pressure whereas rats fed a sodium-enriched diet for the same period exhibited sustained hypertension (115±3 versus 169±5 (s.e.m.) mmHg). In animals fed a sodium-enriched diet plasma concentrations of antidiuretic hormone (ADH) were significantly increased from 55±8 to 108±5 fmol/l. Rats fed the control diet from weaning (group A) and subsequently maintained on that diet or changed to a sodium-enriched diet or sodium-deficient diet showed no differences in their blood pressure. Plasma hormone concentrations were similar in these groups, with the exception of aldosterone suppression in rats switched from control to a sodium-enriched diet (0·26±0·04 versus 0·08±0·03 nmol/l; P <0·001). Animals fed the sodium-enriched diet from weaning to 16 weeks of age (group b) and either maintained on that diet or changed to a control diet showed little change in their established hypertension. Transfer to the control diet was associated with increased plasma renin concentrations (PRC) (13·8±2·1 to 122·6±6·2 nmol/l) and plasma aldosterone concentrations (0·04±0·01 to 0·08±0·01 nmol/l; P<0·001) but corticosteroids and ADH concentrations were unchanged. Rats maintained on the sodium-enriched diet from weaning to 16 weeks of age and transfered to a sodium-deficient diet exhibited increases in their established hypertensive blood pressures (maximally 205±4 versus 170±4 mmHg) together with significant increases in PRC (13·8 ±2·1 to 297±79 nmol/l; P< 0·001), aldosterone (0·04±0·01 to 0·23±0·07 nmol/l; P <0·001) and ADH (82·9±15·5 to 466±118 fmol/l; P <0·001), although plasma concentrations of corticosteroids were again unaffected. Thus it would appear that there is a critical developmental stage at which exposure to a sodium-enriched diet subsequently leads to hypertension. Abrupt withdrawal of the sodium-enriched diet produces an exaggerated hypertension involving changes in both ADH and the renin-angiotensin-aldosterone system.
Journal of Endocrinology (1990) 127, 243–248
Effects of a [Met]-enkephalin analogue ([d-Ala2,N-Me-Phe4,Met-(O)5-ol]-enkephalin) on canine pituitary function
Authors: Meij B. P. , Rijnberk A. , Mol J. A. 
Published: December 2008

ABSTRACT
In adult healthy beagle dogs, plasma concentrations of ACTH, cortisol, α-MSH, GH, prolactin and arginine vasopressin (AVP) were measured after i.v. administration of [d-Ala2,N-Me-Phe4,Met-(O)5-ol]-enkephalin (DAMME) at doses of 0·1, 0·5, 1, 5 and 10 μg/kg body weight. Significant dose-dependent increases occurred for ACTH, cortisol and GH at dose rates of 0·5, 1, 5 and 10 μg/kg body weight. Increments in plasma concentrations of prolactin were significant only at 5 and 10 μg DAMME/kg, and there was no significant effect on plasma concentrations of α-MSH and AVP. Prior i.v. administration of the opiate antagonist naloxone (0·1 mg/kg) attenuated the DAMME (10 μg/kg)-stimulated release of ACTH and cortisol. The results demonstrate that the [Met]-enkephalin analogue DAMME stimulates the release of ACTH, cortisol, GH and prolactin in dogs, and that this stimulation is, at least in part, mediated by μ-opioid receptors. The observations for ACTH and cortisol are different from those in man, where DAMME lowers their basal concentrations.
Journal of Endocrinology (1990) 127, 265–271
Immunohistochemical localization of kallikrein within the prolactin-producing cells of the rat anterior pituitary gland
Authors: Kizuki K. , Kitagawa A. , Takahashi M. , Moriya H. , Kudo M. , Noguchi T. 
Published: December 2008

ABSTRACT
The localization of tissue kallikrein in the pituitary gland of rats was investigated by an immunohistochemical technique using antiserum against rat urinary kallikrein. Kallikrein-positive cells were detected in the anterior lobe of the pituitary of both male and female rats, but were not observed in the posterior lobe of the pituitary in either sex.
The kallikrein-positive cells in the anterior pituitary of female rats in oestrus were found to correspond to the prolactin-producing cells, whereas the cells producing GH, LH and ACTH were negative for kallikrein. It is possible, therefore, that the tissue kallikrein may be involved in the production of prolactin and not that of the other anterior pituitary hormones, such as GH, LH, FSH, ACTH and TSH.
Journal of Endocrinology (1990) 127, 317–323
Binding of 125I-labelled thyrotrophin to transfected human thyrocytes (SGHTL-34 cells)
Authors: Taylor A. H. , Whitley G. St J. , Nussey S. S. 
Published: December 2008

ABSTRACT
The binding of 125I-labelled bovine TSH to a human thyroid cell line (SGHTL-34) has been studied. Binding to hormonally responsive cells was time dependent, specific and reversible. Scatchard analysis of the binding data indicated the presence of a single binding site with high affinity (intrinsic dissociation constant (Kd) = 0·25 ±0·08 nmol/l; mean ± s.e.m.; n = 4) and low capacity (maximum binding (Bmax) = 104±29 fmol/mg protein; mean ± s.e.m.; n = 4). Hill plots confirmed the presence of a single site. Kinetic data demonstrated close agreement between the Kd and Bmax obtained from the competition data (Kd = 0·23±0·35 nmol/l; Bmax = 161 ±83 fmol/mg protein; n = 6).
Journal of Endocrinology (1990) 127, 351–356
Autoantibody to growth hormone in a patient with myasthenia gravis
Authors: Okada S. , Saito E. , Oshima H. , Kinoshita M. 
Published: December 2008

ABSTRACT
An autoantibody to GH was detected in the serum from a patient with myasthenia gravis (MG) who had never been prescribed GH. Using an immunoprecipitation technique, this autoantibody was found to belong to the IgG class and had a κ chain. The dissociation constant of the antibody was 56·8 nmol/l and the binding capacity was 37 nmol/l. Serum samples from another 130 patients, including 37 with MG, were examined, but the GH autoantibody could not be detected. To our knowledge, this is the first report demonstrating the presence of a GH autoantibody.
Journal of Endocrinology (1990) 127, 533–538
Stimulation of DNA synthesis in chicken muscle satellite cells by insulin and insulin-like growth factors: evidence for exclusive mediation by a type-I insulin-like growth factor receptor
Authors: Duclos M. J. , Wilkie R. S. , Goddard C. 
Published: December 2008

ABSTRACT
Insulin-like growth factors-I and -II (IGF-I and IGF-II) stimulate proliferation, differentiation, nutrient uptake and protein accretion in muscle cells. These effects are thought to be mediated through the type-I IGF receptor although a role for the type-II IGF receptor cannot be ruled out, since it has been found in most cells studied so far. Current evidence suggests that the chicken does not have a type-II IGF receptor and therefore provides a good model to study the function of IGF peptides. We have compared the effects of insulin and insulin-like growth factors on DNA synthesis with the binding of these peptides to receptors in primary chicken muscle satellite cells.
Human IGF-I (hIGF-I), hIGF-II and porcine insulin increased thymidine incorporation into DNA by threefold in muscle satellite cells prepared from neonatal chickens. IGF-I and -II were almost equipotent, with half-maximum effective concentrations of 10 μg/l, and were 1000-fold more potent than insulin. A combination of maximum effective concentrations of all three peptides was not additive, suggesting that their effect was mediated by the same receptor.
Receptor binding studies on satellite cells demonstrated the presence of specific IGF receptors. Human IGF-I inhibited the binding of 125I-labelled hIGF-I with a much higher potency than insulin, as usually observed for a type-I IGF receptor. However, unlabelled hIGF-II exhibited a higher potency than hIGF-I in displacing 125I-labelled hIGF-I. Affinity cross-linking of 125I-labelled hIGF-I and -II, followed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis, showed that hIGF-I and -II bound to a receptor with the structural characteristics of a type-I IGF receptor and confirmed the lack of a type-II IGF receptor in these cells. The concentrations of IGF-I, -II and insulin required for biological action and to displace 125I-labelled hIGF-I binding were similar, and support the hypothesis that their effects on proliferation were mediated exclusively through a type-I IGF receptor.
Journal of Endocrinology (1991) 128, 35–42
Patterns of plasma sex hormone-binding globulin, thyroxine and thyroxine-binding globulin in relation to reproductive state and hibernation in female little brown bats
Authors: Kwiecinski G. G. , Damassa D. A. , Gustafson A. W. 
Published: December 2008

ABSTRACT
A sex hormone-binding globulin (SHBG), which bound both oestradiol and dihydrotestosterone, was studied in the plasma of adult female little brown bats throughout the annual reproductive cycle. This protein was present at low baseline levels from September to May inclusive, months which correspond to the periods of hibernation, ovulation and early pregnancy. During the second half of pregnancy in June, SHBG levels increased 15- to 30-fold and remained increased throughout lactation and anoestrus/pro-oestrus (July–August). Although SHBG was increased during late pregnancy, the fact that levels were also high during and after lactation indicates that this protein is not specific to pregnancy. Plasma concentrations of thyroxine (T4) and the percentage binding of T4 to thyroxine-binding globulin (TBG) also showed marked seasonal variations, with T4 levels exhibiting a biphasic seasonal pattern. A major peak in plasma concentrations of T4 occurred around the time of spring arousal from hibernation and subsequent ovulation, while a second peak of lesser magnitude was measured in August, corresponding to the time of pro-oestrus and the onset of mating. The percentage binding of T4 by TBG was increased during the summer months in parallel with the increase in SHBG concentrations. Electrophoretic analysis of plasma T4 binding revealed a single peak of TBG activity throughout most of the year; however, during the early lactational period TBG was resolved as a double peak, suggesting the presence of a molecular variant during this reproductive stage.
Journal of Endocrinology (1991) 128, 63–70
Growth of mouse endometrial luminal epithelial cells in vitro: functional integrity of the oestrogen receptor system and failure of oestrogen to induce proliferation
Authors: Uchima F.-D. A. , Edery M. , Iguchi T. , Bern H. A. 
Published: December 2008

ABSTRACT
Normal endometrial luminal epithelial cells isolated from ovariectomized approximately 40-day-old BALB/cCrgl mice were purified by Percoll density gradient centrifugation and grown as primary cultures in collagen gel matrix and serum-free medium. Cells increased threefold in number during the 9-day culture period. Deletion of insulin, epidermal growth factor or bovine serum albumin resulted in decreased growth. Addition of any single factor to the unsupplemented medium had no effect. Relatively high levels of cytosolic oestrogen receptors and progestin receptors were demonstrable in the cultures. Addition of oestrogen did not enhance epithelial cell proliferation. On the contrary, all doses of oestrogen (180 fmol/l to 218 nmol/l) were inhibitory. Continuous exposure to oestradiol-17β (1·8 nmol/l) for 9 days in serum-free medium resulted in a decrease in cytosolic oestrogen receptors with an associated nuclear accumulation of oestrogen receptors. A corresponding increase in cytosolic progestin receptors was also observed, indicating that no qualitative modification of the oestrogen receptor system had occurred. Thus, as previously reported for vaginal epithelial cells, oestrogen, despite its stimulation of specific product synthesis (progestin receptors), did not increase proliferation of endometrial luminal epithelial cells in this culture system.
Journal of Endocrinology (1991) 128, 115–120
Secretion of insulin-like growth factor-I (IGF-I) and IGF-binding proteins from bovine mammary tissue in vitro
Authors: Campbell P. G. , Skaar T. C. , Vega J. R. , Baumrucker C. R. 
Published: December 2008

ABSTRACT
In vitro, insulin-like growth factor-I (IGF-I) promotes both growth and development of bovine mammary tissue. In vivo, the effects of IGF-I may encompass endocrine, paracrine or autocrine mediation. We addressed the possibility of paracrine/autocrine effects of IGF-I in the mammary gland by examining the in-vitro secretion of IGF-I and IGF-binding proteins (IGFBPs) from bovine mammary tissue. Bovine mammary explants from pregnant non-lactating and lactating non-pregnant animals were found to synthesize and secrete IGF-I and IGFBPs. Mammary acini cultures, representative of mammary secretory epithelia, secreted both IGF-I and IGFBP, but synthesized only IGFBP. Concentrations of IGF-I in conditioned media from explants were 1·54 and 0·72 fmol/μg DNA for pregnant and lactating animals respectively. Concentrations of IGFBPs in conditioned media from explants were similar for both physiological states at 2529 pmol 125I-labelled IGF-I bound/pg DNA. Ligand/Western blotting procedures identified four IGFBPs of 29, 33, 37 and 44 kDa for acini cultures and five IGFBPs of 28, 31, 36, 44 and 46 kDa for explant cultures. Similar affinities for IGF-I and IGF-II were shown by IGFBP, using 125I-labelled recombinant human IGF-I as the competing ligand (median effective dose (ED50) of 0·085 pmol). When 125I-labelled bovine IGF-II was used as the ligand, only bovine IGF-II (ED50 of 0·25 pmol) inhibited binding. The addition of prolactin, insulin and cortisol, with or without GH, did not affect secretion of either IGF-I or IGFBP. This report describes the ability of normal mammary tissue to synthesize and secrete IGF-I and IGFBPs.
Journal of Endocrinology (1991) 128, 219–228