bluuebunny/crossref_metadata_2025_split huggingface dataset:
Changes in the pulsatile secretion of LH after the removal of and subsequent resuckling by pups in ovariectomized lactating rats
Authors: Maeda K.-I. , Tsukamura H. , Uchida E. , Ohkura N. , Ohkura S. , Yokoyama A. 
Published: December 2008

ABSTRACT
Changes in the pulsatile secretion of LH after removal of pups and subsequent resuckling were examined in ovariectomized lactating rats, and the change after removal of pups was compared with that after the removal of ovaries in cyclic female rats. The day of parturition was designated day 0 of lactation. All lactating rats were ovariectomized on day 2 of lactation. They were deprived of their pups for 6, 12, 18, 24 or 45 h before blood sampling on day 8 of lactation, or were resuckled by their pups for 1, 4, 7 or 12 h before blood collection after separation from pups for 24 h. Cyclic female rats were ovariectomized on the day of dioestrus and blood samples were taken 12, 18, 24 or 48 h or 6 days after ovariectomy. Typical LH pulses appeared in some animals from 12 h after the removal of pups. The mean LH level and the frequency and amplitude of LH pulses gradually increased after removal of pups, until after 45 h of separation the frequency reached the high level observed 6 days after ovariectomy in cyclic rats. The subsequent resuckling by pups after a 24-h separation decreased these three parameters of LH pulses rapidly. In contrast, the frequency of LH pulses was unchanged after ovariectomy in cyclic rats, although the mean LH level and the amplitude of LH pulses increased. These results suggest that the suckling stimulus suppresses pulsatile LH secretion in a different manner from that of ovarian steroids.
Journal of Endocrinology (1989) 121, 277–283
Effect of maternal hypothyroxinaemia during fetal life on the calmodulin-regulated phosphatase activity in the brain of the adult progeny in the rat
Authors: de Elvira M. C. Ruiz , Sinha A. K. , Pickard M. , Ballabio M. , Hubank M. , Ekins R. P. 
Published: December 2008

ABSTRACT
Calmodulin-regulated phosphatase activity was measured in the brain of 2-month-old rats born from hypothyroid and normal dams, using a fluorometric enzyme assay developed for this purpose. Calmodulin content was measured in the same brain regions by radioimmunoassay. Significant differences between groups in weight and protein content, basal phosphatase and calmodulin-regulated phosphatase activity were found. The brain region most affected was the cerebellum, where basal and calmodulin-regulated phosphatase activities, and protein content were increased. The data point towards a lasting effect of maternal hypothyroxinaemia on the brain function of the progeny.
Journal of Endocrinology (1989) 121, 331–335
γ-Aminobutyric acid regulation of neurohypophysial hormone secretion in male and female rats
Authors: Saridaki E. , Carter D. A. , Lightman S. L. 
Published: December 2008

ABSTRACT
The role of γ-aminobutyric acid (GABA) in the control of oxytocin and arginine vasopressin (AVP) release from the posterior pituitary was investigated using the GABA agonist muscimol and the GABA antagonists bicuculline and picrotoxin. Two perifusion model systems were studied using (a) intact isolated posterior pituitaries (IPP) and (b) neurosecretosomes from both male and female rats. In experiments on tissue from male rats, the stimulated release of oxytocin and AVP in both models was inhibited by muscimol, an effect which was reversed in the presence of bicuculline. Bicuculline alone increased the release of oxytocin only. Although similar responses to muscimol or bicuculline were seen in neurosecretosomes from female animals, neither agent affected oxytocin and AVP release from the intact IPP. Picrotoxin had a similar effect to bicuculline on oxytocin in isolated posterior pituitaries from male as well as female rats, although at the neurosecretosome level a paradoxical inhibition was observed.
These results provide evidence for an endogenous GABA receptor mechanism at the level of the neurosecretory terminals in both male and female rats. The sexually dimorphic IPP response suggests a second more complex mechanism involving either pituicytenerve terminal interactions and/or a secondary role of other neurotransmitters in the GABA regulation of neurohypophysial hormones.
Journal of Endocrinology (1989) 121, 343–349
Influence of tri-iodothyronine or lipid administration on the response of the pituitary-thyroid axis to exposure to cold in the newborn lamb
Authors: Wrutniak C. , Cabello G. 
Published: December 2008

ABSTRACT
The influence of the administration of tri-iodothyronine (T3) or a solution of soya oil and egg lecithin on the response of the pituitary-thyroid axis to moderate exposure to cold (4 °C for 4 h) was studied in 24-h old lambs. In control lambs, plasma concentrations of TSH, T3 and total and free thyroxine (T4) rose significantly whereas plasma concentrations of reverse T3 remained unchanged during the test.
In lambs injected i.v. with a small amount of T3 (1·23 nmol/kg) 30 min before the onset of exposure to cold, plasma concentrations of TSH, reverse T3 and total and free T4 did not change during the test.
Administration of lipid 30 min before exposure to cold induced, as expected, a sharp rise in plasma free fatty acid (FFA) concentrations and a transient increase in free T4 concentrations. In these animals, plasma concentrations of TSH increased during the test as observed in control lambs, but plasma concentrations of T3, reverse T3 and total T4 did not show any significant change, whereas free T4 levels decreased during the first 2 h.
These results strongly suggest, in contrast to previous results, that T3 exerts a negative feedback upon the hypothalamic-pituitary-thyroid axis in the new-born lamb. Moreover, it appears that a rise in plasma concentrations of FFA could affect neonatal thyroid function.
Journal of Endocrinology (1989) 121, 361–365
Production of insulin-like growth factor-II by human fetal pancreas in culture
Authors: Bryson J. M. , Tuch B. E. , Baxter R. C. 
Published: December 2008

ABSTRACT
Insulin-like growth factor-II (IGF-II) is a polypeptide hormone thought to be involved in fetal development because of its wide distribution in fetal tissues and its presence in the fetal circulation. We have developed a highly sensitive radioreceptor assay for IGF-II using rat liver microsomal membranes and have used this assay to test for the presence of IGF-II in the human fetal pancreas and the release of IGF-II by the human fetal pancreas in organ culture. IGF-II was present in extracts of pancreatic tissue (0·056 ± 0·012 pmol/mg tissue, n= 5) and was released in culture at the rate of 0·027–0·134 pmol/mg tissue per day with release being maintained for at least 3 weeks in culture. The rate of release was not affected by the gestational age of the fetus over 14 to 20 weeks but was significantly related to the rate of insulin release (r = 0·712, P < 0·001, n = 34). Chronic exposure to 12-0-tetradecanoylphorbol-13-acetate (TPA), which inhibits insulin release in the human fetal pancreas, caused an 85% drop in IGF-II production, which was reversed when TPA was removed. These studies demonstrate that IGF-II is produced by the human fetal pancreas in a pattern similar to that of insulin. We suggest that control of IGF-II release, like that of insulin, may involve protein-kinase C and that IGF-II may have a paracrine or autocrine role in the development of fetal pancreatic function.
Journal of Endocrinology (1989) 121, 367–373
Progesterone concentrations in samples of saliva from adolescent girls living in Britain and Thailand, two countries where women are at widely differing risk of breast cancer
Authors: Danutra V. , Turkes A. , Read G. F. , Wilson D. W. , Griffiths V. , Jones R. , Griffiths K. 
Published: December 2008

ABSTRACT
Menstrual-cycle patterns of salivary progesterone concentration were obtained for 131 and 245 adolescent girls up to 4 years postmenarche living in Britain and Thailand respectively. These patterns were graded on a scale of 1 (little or no activity) to 5 (activity similar to that exhibited by the mature premenopausal woman) and the frequency of these grades within groups of girls from each centre was analysed. The major finding was that British girls exhibited a predominance of higher grades of progesterone activity when compared with their Thai counterparts (n = 2 × 58) when matched for chronological and gynaecological ages (P ∼ 0·002). This was particularly so for the girls from these two matched groups in the gynaecological age range 2–4 years (P ∼ 0·03). The major contribution to this significant difference between the two groups is attributed to the greater effect of chronological age on progesterone secretion in the British girls (P ∼ 0·03) compared with the Thai girls (P ∼ 0·29). These findings may have implications for facilitating our understanding of the reason for the differing risk of breast cancer in women in both countries.
Journal of Endocrinology (1989) 121, 375–381
Effect of ouabain on cellular free calcium and cellular cyclic AMP production in response to arginine vasopressin in rat renal papillary collecting tubule cells in culture
Authors: Ishikawa S. , Saito T. 
Published: December 2008

ABSTRACT
The effect of extracellular calcium (Ca2+) on the cellular action of arginine vasopressin (AVP) was examined using an Na+, K+-ATPase inhibitor in rat renal papillary collecting tubule cells in culture. The pretreatment of cells with ouabain enhanced basal and AVP-induced cAMP production in a dose-dependent manner. The augmentation by ouabain of cellular cAMP production in response to AVP was totally abolished by co-treatment with cobalt, lanthanum, verapamil or Ca2+-free medium containing 1 mmol EGTA/l, each blocking cellular Ca2+ uptake by different mechanisms. Two other findings indicated that ouabain directly stimulated cellular Ca2+ mobilization; namely, that ouabain significantly increased 45Ca2+ influx and cellular free Ca2+ concentration ([Ca2+]i) determined by Fura-2 fluorescence. The ouabain-induced increase in [Ca2+]i was completely blocked by either cobalt or Ca2+-free medium containing 1 mmol EGTA/l. AVP at 0·1 μmol/l increased [Ca2+]i to 177·1 ±26·2 nmol/l from 92·2 ± 8·0 nmol/l (P<0·01) in renal papillary collecting tubule cells, and ouabain significantly enhanced the AVP-induced increase in [Ca2+]i. The increase of cellular free Ca2+ induced by ouabain probably binds to calmodulin to form an active complex of Ca2+-calmodulin in the cell, since two chemically dissimilar antagonists of calmodulin attenuated the enhancement by ouabain of cAMP production in response to AVP. These results therefore indicate that ouabain increases cellular Ca2+ uptake and enhances AVP-induced cellular free Ca2+ mobilization and its own second messenger cAMP production in renal papillary collecting tubule cells, and that extracellular Ca2+ is an important source for ouabain-mobilized cellular Ca2+.
Journal of Endocrinology (1989) 121, 467–477
Differential effect of difluoromethylornithine on the increases in plasma concentrations of reproductive hormones on the afternoon of pro-oestrus in the rat
Authors: Nicholson S. A. , Wynne-Jones G. A. 
Published: December 2008

ABSTRACT
In our colony of female rats (220–320 g body weight) undergoing regular 4-day oestrous cycles there were significant, marked rises in concentrations of LH, FSH and prolactin between 09.00 and 19.00 h on pro-oestrus.
The i.p. injection of difluoromethylornithine (DFMO; 40–400 mg/kg), a specific inhibitor of the activity of ornithine decarboxylase, at 15.00 h on prooestrus had a differential effect on the rise in plasma concentrations of the various hormones thereafter. The drug produced a significant, partial, dose-related suppression of the rise in plasma concentrations of LH and prolactin, but had no significant effect on the rise in FSH.
For time-course studies, 120 mg DFMO/kg were injected at 13.00, 15.00 or 17.00 h and groups of animals killed at 19.00 h. Only the injection at 15.00 h was effective in causing a significant reduction in plasma concentrations of LH and prolactin at 19.00 h. Pituitary content of the hormones was found to be unaffected by the administration of DFMO at the times and doses tested.
These results suggest that DFMO has a selective inhibitory effect on enhanced LH and prolactin secretion on the afternoon of pro-oestrus in the rat, whilst not affecting FSH release. There seems to be a limited time (after 13.00 but before 17.00 h) during which its administration is effective.
Journal of Endocrinology (1989) 121, 495–499
Tissue-specific effects of castration and ovariectomy on murine epidermal growth factor and its mRNA
Authors: Pascall J. C. , Saunders J. , Blakeley D. M. , Laurie M. S. , Brown K. D. 
Published: December 2008

ABSTRACT
The polypeptide mitogen, epidermal growth factor (EGF), was originally isolated from mouse submaxillary gland (SMG). In mice, these glands are sexually dimorphic; the SMG of male animals typically contains up to 400 pmol EGF/mg protein whereas EGF concentrations in the SMG of female mice are only 5–20 pmol/mg protein. When mice were castrated at 8 weeks of age, EGF mRNA levels in the SMG fell rapidly to the low levels observed in control female animals. Although the concentration of EGF in the SMG, measured by radioimmunoassay, also fell to very low levels (13·8 ± 0·7 (s.e.m.) pmol/mg protein) in the castrated mice, the rate of decrease was considerably slower than that of the mRNA. In contrast to the loss of EGF and EGF mRNA from mice following castration, ovariectomy led to a rise in EGF mRNA levels in SMG, with a maximal increase (approximately 100-fold) 4–6 weeks after ovariectomy. Concentrations of EGF in the SMG also rose markedly in the ovariectomized animals, from a control value of 5·4 ± 0·8 to 34·7 ± 7·9 pmol/mg protein at 6 weeks. In mice, the kidney displays the second highest level of EGF gene expression. However, in contrast to the effects on SMG, kidney EGF mRNA was not affected by either castration or ovariectomy. These results provide further evidence for the tissue-specific control of EGF gene expression in response to steroid hormones.
Journal of Endocrinology (1989) 121, 501–506
Actions of desacetyl-α-melanocyte-stimulating hormone on human adrenocortical cells
Authors: Henville K. L. , Hinson J. P. , Vinson G. P. , Laird S. M. 
Published: December 2008

ABSTRACT
The responses of human adrenocortical cells to stimulation by ACTH(1–24), desacetyl-α-MSH, α-MSH and angiotensin II amide have been compared. Both desacetyl-α-MSH, thought to be the major form of the peptide in the human pituitary and in circulating plasma, and α-MSH caused a significant stimulation of aldosterone, corticosterone and cortisol secretion. Significant stimulation of the production of these steroids was obtained with desacetyl-α-MSH at a concentration of 1 nmol/l, while the response to α-MSH was considerably less sensitive, with a minimum effective concentration of 0·1 μmol/l. These values compared with minimum effective concentrations of 1 pmol/l for ACTH and 0·1 μmol/l for angiotensin II amide. Although cell types were not separated, it is possible to conclude that none of the peptides showed any specificity for the zona glomerulosa, and in each case the same minimum effective concentration of peptide was required for both aldosterone and cortisol secretion. Yields of steroid obtained under conditions of maximal stimulation by ACTH(1–24), α-MSH and desacetyl-α-MSH were at least three to five times the basal output of aldosterone, four to eight times that for corticosterone and more than seven to sixteen times that for cortisol. Angiotensin II amide was a relatively poor stimulant with maximal stimulation only 1·5 × basal. In these experiments the minimum effective concentration for desacetyl-α-MSH (1 nmol/l) was close to the circulating concentration of desacetyl-α-MSH (0·3 nmol/l) in man, and it is thus possible that this peptide may have a physiological role in the control of adrenocortical function.
Journal of Endocrinology (1989) 121, 579–583
Uptake of 3,5,3′-l-tri-iodothyronine in human erythrocytes
Authors: Yamauchi K. , Horiuchi R. , Takikawa H. 
Published: December 2008

ABSTRACT
The mechanisms of 3,5,3′-l-tri-iodothyronine (T3) uptake into human erythrocytes were examined. Purified membranes of human erythrocytes were shown to have two classes of T3-binding sites with one being a high-affinity site (dissociation constant, 59·2±17·8 nmol/l; maximum binding capacity, 344·3 ± 95·5 fmol/μg protein). Furthermore, it was shown that there were two pathways for T3 uptake in human erythrocytes; one was saturable, stereospecific (T3»thyroxine > 3,5,3′-d-tri-iodothyronine), energydependent and dominant at 15 °C; the other was not displaced by unlabelled T3 and was energyindependent but did not occur by passive diffusion. The former pathway which, it is suggested, is a receptor-mediated transport pathway, was inhibited by monodansylcadaverine, phloretin or oligomycin at 15 or 37 °C, but the latter pathway was not inhibited by these inhibitors. Our results strongly suggest that uptake of T3 by the energy-independent pathway became predominant over the energy-dependent pathway at 37 °C and accounted for 83% of total T3 uptake of human erythrocytes.
Journal of Endocrinology (1989) 121, 585–591
Isolation of the human plasma corticotrophin-releasing factor-binding protein
Authors: Behan D. P. , Linton E. A. , Lowry P. J. 
Published: December 2008

ABSTRACT
We report the purification of human corticotrophin-releasing factor-binding protein (hCRF-BP) using repeated affinity chromatography (with the aid of synthetic CRF immobilized on Sepharose 4B solid phase) followed by gel filtration. Presence of the binding protein was tracked throughout the procedure by its ability to inhibit binding of 125I-labelled hCRF to an hCRF antiserum; normal human plasma exhibits 80% inhibition in this system whereas sheep plasma, which does not contain an hCRF-BP, has no effect. Affinity cross-linking of 125I-labelled hCRF to the purified hCRF-BP was performed using disuccinimidyl suberate (1 mmol/l). SDS electrophoresis of the purified CRF cross-linked binding protein followed by radioautography resulted in one major band of Mr 37 000 which corresponded to our original molecular weight estimate based on the elution position of the binding protein on Sephacryl S-200. A 107-fold purification of the hCRF-BP resulted in a preparation estimated to be 95% pure, with an overall yield of 5%.
Journal of Endocrinology (1989) 122, 23–31
Feedback control of vasopressin and corticotrophin secretion in conscious dogs: effect of hypertonic saline
Authors: Raff H. , Skelton M. M. , Cowley A. W. 
Published: December 2008

ABSTRACT
Glucocorticoids are known to inhibit the ACTH response to a variety of stimuli. It has been suggested that vasopressin secretion is also inhibited by glucocorticoid negative feedback. The purpose of this study was to (1) determine the ACTH response to hypertonic saline and its sensitivity to glucocorticoid negative feedback and (2) to determine whether physiological elevations of plasma cortisol inhibit subsequent vasopressin responses to hypertonic saline. Five mongrel dogs (15–18 kg) were prepared with chronic arterial and venous catheters and studied while conscious. Ten experiments were performed on each dog in a randomized design separated by at least 5 days. Each experiment consisted of a pretreatment period (from −60 to −30 min except for dexamethasone administration) during which a glucocorticoid feedback signal was applied and a stimulus period (from 0 to 30 min) during which hypertonic saline was infused. The pretreatment and stimulus periods were separated by 30 min. Pretreatments were as follows: isotonic saline (control), half-maximal and maximal cortisol infusion (5·5 or 11 nmol/kg per min), ACTH(1–24) infusion (6·8 pmol/kg per min) which produces increases in endogenous cortisol, and dexamethasone (1·5 mg i.m.) given at 17.00 h the day before experimentation. Stimuli were as follows: hypertonic saline was infused at 0·2 or 0·4 mmol/kg per min which increased plasma sodium by about 6 or 12 mmol/l respectively. NaCl infusion at 0·2 mmol/kg per min had no effect on plasma ACTH or cortisol except when subsequent to ACTH(1–24) pretreatment when plasma ACTH actually increased to 41·4 ± 2·9 pmol/l in response to hypertonic saline. NaCl infusion at 0·4 mmol/kg per min resulted in a significant increase in plasma ACTH from 5·9 ± 0·9 to 11·7 ± 2·0 pmol/l in the control group. This ACTH response was blocked by pretreatment with either dose of cortisol and dexamethasone. ACTH pretreatment, however, did not completely block the ACTH subsequent response to infusion of 0·4 mmol NaCl/kg per min. The two doses of NaCl led to significant and dose-related increases in plasma vasopressin. None of the pretreatments significantly affected the vasopressin response to hypertonic saline except for significant inhibition after overnight dexamethasone. We conclude that (1) hypertonic saline can stimulate ACTH release if plasma sodium is increased sufficiently, (2) the ACTH response to hypertonic saline is potentiated by pretreatment with ACTH making it different from other stimuli studied previously, and (3) the vasopressin response to hypertonic saline is not inhibited by short-term elevations of plasma cortisol within the physiological range.
Journal of Endocrinology (1989) 122, 41–48
Demonstration of growth hormone receptors in cultured rat epiphyseal chondrocytes by specific binding of growth hormone and immunohistochemistry
Authors: Nilsson A. , Lindahl A. , Edén S. , Isaksson O. G. P. 
Published: December 2008

ABSTRACT
Growth hormone has been reported to exert direct effects on rat and rabbit epiphyseal chondrocytes in vitro, indicating that GH interacts with specific receptors on these cells. To investigate this possibility, binding of GH to cultured rat epiphyseal chondrocytes was studied under various experimental conditions. Chondrocytes were isolated enzymatically from epiphyseal growth plates of the proximal tibia of 20-day-old male rats and were cultured in monolayer in Ham's F-12 medium supplemented with 10% calf serum and 1% of a serum substitute. The cells were seeded at various densities (25 000–200 000 cells/well) and cultured for 5–16 days. Twenty-four hours before binding experiments, the medium containing calf serum was changed for one containing serum obtained from hypophysectomized rats, in order to avoid binding of GH present in the calf serum. Binding was studied by incubating 125I-labelled human GH (hGH) with the cells in the presence or absence of various concentrations of unlabelled hGH, bovine GH (bGH), rat GH (rGH) and ovine prolactin (oPRL).
Specific binding could be demonstrated in cells cultured for 5–16 days. Binding was dependent upon time and temperature, and maximal binding was obtained by incubating the labelled hormone for 4–6 h at 24 °C. An increase in binding was noted between 7 and 12 days in culture. In cells cultured for 12 days, addition of unlabelled hGH, bGH or rGH caused a dose-dependent displacement of 125I-labelled hGH, whereas oPRL was ineffective. Scatchard analysis resulted in a linear plot, and the number of binding sites/cell was approximately 5700, with a dissociation constant of 0·46 nmol/l. The increase in binding between days 7 and 12 was independent of the density of seeded cells, but total binding was higher if the cells were seeded at a low density. By using a monoclonal antibody to the rabbit GH receptor, specific staining could be demonstrated immunohistochemically in the cultured cells. The results show the presence of GH receptors in cultured rat epiphyseal chondrocytes and also show that the culture conditions influence the expression of GH receptors.
Journal of Endocrinology (1989) 122, 69–77