bluuebunny/crossref_metadata_2025_split huggingface dataset:
Relationship between external and cytoplasmic calcium concentrations, parathyroid hormone release and weight of parathyroid glands in human hyperparathyroidism
Authors: Wallfelt C. , Gylfe E. , Larsson R. , Ljunghall S. , Rastad J. , Åkerström G. 
Published: December 2008

ABSTRACT
Parathyroid hormone (PTH) release and cytoplasmic calcium concentrations were investigated at ambient calcium concentrations of 0·5–3·0 mmol/l in dispersed parathyroid cells from 44 hypercalcaemic patients with primary or uraemic hyperparathyroidism (HPT). In comparison with parathyroid cells from adult cattle, release of PTH by human preparations was reduced and values of the ambient calcium concentration causing half-maximal inhibition of PTH release (median effective dose, ED50) were significantly increased. Half-maximal inhibition of PTH release was obtained with concentrations of cytoplasmic calcium almost identical to the concentrations of ionized calcium in the plasma of the individual patients. Cytoplasmic concentrations of calcium in the parathyroid cells were inversely related to release of PTH. Concentrations of cytoplasmic calcium were significantly lower in human than in bovine cells and the ED50 for ambient calcium increase on cytoplasmic calcium was raised to the same extent as the ED50 for ambient calcium inhibition of PTH release in human compared with bovine cells. The magnitude of the increased ED50 for ambient calcium inhibition of PTH release and increase of cytoplasmic calcium concentration was similar in adenomas and sporadic as well as hereditary primary hyperplasias, but the secretion was the least aberrant in uraemic hyperplasias, although they had by far the largest glandular mass. Serum concentrations of total calcium before surgery correlated with the ED50 for ambient calcium effects of PTH release and cytoplasmic calcium, but not with glandular weight. These findings demonstrate a universally abnormal regulation of cytoplasmic calcium in HPT and its importance for PTH release, and that disturbance of cytoplasmic calcium rather than the increased glandular mass contributes to the hypercalcaemia in adenomatous and hyperplastic HPT.
J. Endocr. (1988) 116, 457–464
GALANIN ABOLISHES THE INHIBITORY EFFECT OF CHOLINERGIC BLOCKADE ON GROWTH HORMONE-RELEASING HORMONE-INDUCED SECRETION OF GROWTH HORMONE IN MAN
Authors: Chatterjee V.K.K. , Ball J.A. , Proby C. , Burrin J.M. , Bloom S.R. 
Published: December 2008

ABSTRACT
In five healthy normal male volunteers, pretreatment with the cholinergic muscarinic antagonist pirenzepine (30 mg i.v.) almost abolished the growth hormone (GH) response to a maximal dose (120 μg i.v.) of growth hormone-releasing hormone (GHRH) (GH response at 40 min 5.6 ± 1.3 mU/l with GHRH and pirenzepine vs 40.8 ± 5.3 mU/l with GHRH alone, P <0.02). Concomitant i.v. infusion of galanin (40 pmol/kg/min) with pirenzepine not only restored but significantly potentiated the GH response to GHRH (GH at 40 min 72.2 ± 10.5 mU/l, P <0.001 vs GHRH and pirenzepine, P <0.02 vs GHRH alone). Previous studies have proposed that cholinergic pathways control GH release via samatostatin and this study suggests that galanin may act by modulating hypothalamic somatostatinergic tone either directly or, possibly, by facilitating cholinergic neurotransmission.
THE SHEEP CORPUS LUTEUM SECRETES INHIBIN
Authors: Tsonis C. G. , Baird D. T. , Campbell B. K. , Leask R. , Scaramuzzi R. J. 
Published: December 2008

ABSTRACT
An experiment was performed in 20 Merino ewes in which ovarian venous blood was collected by venepuncture at surgery and at two stages of the oestrous cycle. The ovarian venous concentrations of inhibin, oestradiol-17β and progesterone were determined. The results demonstrate that during the luteal phase of the oestrous cycle the ovarian venous blood draining an ovary containing luteal tissue contains significantly more inhibin bioactivity than ovarian venous blood from an ovary not containing luteal tissue. During the follicular phase the concentration of inhibin bioactivity in ovarian venous blood was reduced compared with the luteal phase. From this data we conclude that the sheep corpus luteum secretes inhibin bioactivity into the ovarian venous blood.
A COMPARATIVE STUDY OF ENDOMETRIAL ACID PHOSPHATASE ACTIVITY IN THE MID-LUTEAL PHASE OF THE MENSTRUAL CYCLE AND IN THE PERI-IMPLANTATION STAGE IN THE RHESUS MONKEY (MACACA MULATTA)
Authors: Ghosh D. , Sengupta J. 
Published: December 2008

ABSTRACT
Acid phosphatase activity in both total and subcellular fractions of endometrium of rhesus monkey on day 5 of gestation was significantly (P <0·01) lower than levels found in tissues collected from normally menstruating monkeys on day 5 after ovulation. This endometrial response to preimplantation embryo may be related to the menstrual withdrawal in a fertile cycle.
Characterization of the regenerated Leydig cell population of the rat after destruction by ethylene-1,2-dimethanesulphonate
Authors: Edwards G. , Robertson W. R. , Morris I. D. 
Published: December 2008

ABSTRACT
The Leydig cells repopulating the adult rat testis after destruction by a single injection of the cytotoxic ethylene-1,2-dimethanesulphonate (EDS) were investigated. After 14 days, serum concentrations of LH and FSH were significantly raised and concentrations of testosterone in the serum and testis reduced. At 21 days, hormone concentrations had returned to within the normal range. Binding of 125I-labelled human chorionic gonadotrophin (hCG) to testis homogenate, however, was still less than 10% of normal. After 21 or 28 days the 125I-labelled hCG binding profiles of isolated Leydig cells from EDS-treated rats, separated on a Percoll gradient, showed a single peak similar to that of immature (25 days old) rats. After 49 days, 125I-labelled hCG binding resolved into two peaks more like that of normal adult rats. Using a quantitative cytochemical method, 3β-hydroxysteroid dehydrogenase activity in individual Leydig cells of unfixed testis sections was determined. Activity was increased by 70% (P < 0·05) in repopulating Leydig cells 21 days after EDS treatment compared with cells from vehicle-treated rats. In addition, Leydig cells were still capable of further 'in-vivo' stimulation by pharmacological doses of hCG. These data indicate that Leydig cells repopulating the testis are homogenous. Fewer cells from the newly formed population are capable of maintaining normal serum concentrations of testosterone and must thus be individually more active in secreting testosterone. In these respects, the Leydig cells repopulating the adult rat testis after EDS treatment more closely resemble those of the fetal rat testis.
J. Endocr. (1988) 117, 11–18
Stimulatory effect of insulin-like growth factor-I on [3H]thymidine incorporation, DNA content and insulin biosynthesis and secretion of isolated pancreatic rat islets
Authors: Sieradzki J. , Fleck H. , Chatterjee A. K. , Schatz H. 
Published: December 2008

ABSTRACT
The influence of insulin-like growth factor-I (IGF-I) on both the growth and function of isolated pancreatic rat islets was studied. As a measure of islet cell replication, [3H]thymidine incorporation and DNA content was estimated at the same time as parameters for (pro)insulin biosynthesis and secretion as a measure of the functional capacity of B cells. Incorporation of [3H]thymidine was measured after tissue solubilization; DNA was determinated fluorometrically. (Pro-)insulin biosynthesis was determinated by incorporation of [3H]leucine after immunoprecipitation and binding to protein A–Sepharose. There was a significant increase in both [3H]thymidine incorporation and DNA content after the culture of islets with IGF-I. IGF-I resulted also in an increase in insulin biosynthesis and secretion from isolated pancreatic islets. These results demonstrate a role of IGF-I in regulating the growth and function of pancreatic islets.
J. Endocr. (1988) 117, 59–62
The transport of plasma thyroxine in White storks (Ciconia ciconia) and the association of high levels of plasma transthyretin (thyroxine-binding prealbumin) with moult
Authors: Cookson E. J. , Hall M. R. , Glover J. 
Published: December 2008

ABSTRACT
Antisera raised against domestic fowl transthyretin (thyroxine-binding prealbumin) and quail albumin were used to identify thyroxine-binding proteins in the plasma of White storks (Ciconia ciconia) and to measure seasonal changes in these proteins. Three plasma proteins were shown to bind thyroxine (T4). They were albumin, transthyretin and a protein with an electrophoretic mobility on non-denaturing poly-acrylamide gel electrophoresis intermediate between albumin and transthyretin. There was no thyroxine-binding globulin.
The plasma concentrations of transthyretin and albumin were measured in male and female storks exposed to the photoperiodic and climatic conditions experienced during an annual cycle at 46°N,11°E. The storks were in four age groups, fledglings and 1-, 2- and 3-year-old birds. A strong correlation (P < 0·001) was found between daylength and the concentration of transthyretin during the period from February to August in the 1-, 2- and 3-year-old male and female storks, with peak values of 150–210 mg/l in May, June and July coinciding with the annual moult. Between September and January the concentration of plasma transthyretin was low, ranging between 80 and 100 mg/l. The concentration of plasma albumin was not correlated with seasonal changes in daylength and did not change during moult. It is suggested that seasonally high concentrations of plasma transthyretin may have a physiological role in moult.
J. Endocr. (1988) 117, 75–84
Thyrotrophin and prostaglandin E2 increase calmodulin levels and cyclic AMP phosphodiesterase activity in cultured porcine thyroid cells
Authors: Takasu N. , Yamada T. , Shimizu Y. 
Published: December 2008

ABSTRACT
Thyrotrophin (TSH) and prostaglandin E2 (PGE2) increased cellular cyclic AMP (cAMP), calmodulin levels and cAMP phosphodiesterase activity in cultured porcine thyroid cells. Dibutyryl cAMP (dbcAMP), a stable analogue of cAMP, increased calmodulin levels and cAMP phosphodiesterase activity. These results indicate that TSH- and PGE2-stimulated increases in calmodulin are mediated by cAMP. This increased concentration of calmodulin in turn stimulates cAMP phosphodiesterase. Double reciprocal plots of cAMP hydrolysis yielded two apparent Michaelis constants (Km); the lower in the 1 μmol/l and the higher in the 10 μmol/l range. Thyrotrophin, PGE2 and dbcAMP increased the values of maximal velocity without changing the Km values.
J. Endocr. (1988) 117, 109–114
Release of prolactin is independent of the secretion of thyrotrophin-releasing hormone into hypophysial portal blood of sheep
Authors: Thomas G. B. , Cummins J. T. , Yao B. , Gordon K. , Clarke I. J. 
Published: December 2008

ABSTRACT
In order to determine whether pituitary prolactin release was directly related to the secretion of TRH into hypophysial portal blood, serial portal and jugular venous blood samples were collected from seven lactating and three non-lactating ewes. In another experiment, samples were collected from five ovariectomized ewes while being exposed to an audio-visual stress and then later administered with chlorpromazine. Secretion of TRH was pulsatile in all ewes and independent of prolactin secretion; TRH pulses coincided with significant increases in prolactin secretion in only 15% of cases and only 29% of prolactin pulses were associated with TRH pulses. Sixty-seven per cent of suckling bouts were associated with increases in prolactin secretion, but only 22% of these were associated with significant increases in TRH secretion. Chlorpromazine increased prolactin levels fourfold but did not affect portal concentrations of TRH. Audio-visual stress was not a reliable method of causing prolactin release in this model. Mean portal concentrations of TRH and jugular concentrations of prolactin were not significantly correlated. These results show that hypothalamic TRH and pituitary prolactin are secreted independently in the sheep, implying that increases in prolactin release caused by suckling or chlorpromazine are not the direct result of increased TRH secretion.
J. Endocr. (1988) 117, 115–122
Steroid sequestration within the rat adrenal zona glomerulosa
Authors: Laird S. M. , Vinson G. P. , Whitehouse B. J. 
Published: December 2008

ABSTRACT
Accumulated data from in-vitro experiments have suggested that 18-hydroxysteroids may be stored within the intact rat adrenal zona glomerulosa. The phenomenon was further investigated by comparing the amount of steroid remaining in the zona glomerulosa tissue with that secreted into the media during incubation in vitro. The results showed that 18-hydroxydeoxycorticosterone (18-OH-DOC) and 18-hydroxycorticosterone (18-OH-B) were retained within the tissue against a considerable concentration gradient, with smaller amounts of aldosterone and corticosterone. Lysis of the intact zona glomerulosa, by preincubation in distilled water, yielded an enriched plasma membrane preparation. After subsequent incubation in Krebs–Ringer bicarbonate this preparation contained significantly more 18-OH-DOC than did the intact tissue, suggesting that tissuesequestered 18-OH-DOC is normally metabolized to other products. These may include 18-OH-B and aldosterone.
Fractionation of homogenized intact zona glomerulosa and the enriched plasma membrane preparation by density gradient centrifugation showed that tissue 18-OH-DOC banded in fractions of density 1·063– 1·21 g/ml and that its distribution was highly correlated with protein. Corticosterone, 18-OH-B and aldosterone banded like added free [3H]18-OH-DOC in fractions of density < 1·006 g/ml.
The results suggest that 18-OH-DOC is the major sequestered steroid within the rat adrenal zona glomerulosa and that this sequestration is attributable to the association of 18-OH-DOC with a high-density component of the plasma membrane.
J. Endocr. (1988) 117, 191–196
Osmoregulation in rats with long-term enhanced cerebrospinal fluid levels of vasopressin or vasoactive intestinal polypeptide
Authors: Kruisbrink J. , van Heerikhuize J. J. , Boer G. J. 
Published: December 2008

ABSTRACT
The cerebrospinal fluid level of arginine vasopressin (AVP) or vasoactive intestinal polypeptide (VIP) was enhanced chronically by implantation of a device for controlled drug delivery in the lateral ventricle of the rat. Urine production, water consumption, urine osmolality as well as urinary AVP excretion were then measured for a period of 26 days. During this period the rats were studied under normal hydration and under conditions of osmotic stress induced by water deprivation (2 days) and the drinking of 2% (w/v) NaCl (6 days), in order to see whether the capacity of central systems to react adequately to osmotic stimuli was affected by high central peptide levels.
Immediately after the central AVP treatment was started, a temporary increase was found in urinary AVP levels which was not accompanied by a change in any of the other parameters but which decreased again to control levels within 10 days. After this burst of AVP excretion, AVP-treated rats showed a tendency during periods of normal hydration for a lower urine osmolality, combined with a higher water intake and urine production without changes in urinary AVP excretion. Since there was no clear-cut correlation between urinary AVP excretion and body water turnover, this could still indicate a slowly acquired and slight inhibition of pituitary AVP release by long-term centrally administered AVP. However, the capacity of these rats to respond to osmotic stimuli was not different from the controls.
In the VIP-treated rats a slight but significant reduction in urine production was found in all three periods of normal hydration. During the osmotic stress induced by the drinking of 2% NaCl the VIP-treated rats showed a lower increase in urine production and fluid intake and a lower decrease in urine osmolality when compared with the response of the control rats. This has tentatively been interpreted as a potentiation by VIP of the activation of pituitary AVP release under these conditions.
J. Endocr. (1988) 117, 207–214
Evidence for a novel parathyroid hormone-related protein in fetal lamb parathyroid glands and sheep placenta: comparisons with a similar protein implicated in humoral hypercalcaemia of malignancy
Authors: Rodda C. P. , Kubota M. , Heath J. A. , Ebeling P. R. , Moseley J. M. , Care A. D. , Caple I. W. , Martin T. J. 
Published: December 2008

ABSTRACT
Parathyroid hormone (PTH)-like bioactivity, assayed as adenylate cyclase response in UMR 106-01 osteogenic sarcoma cells, was present in extracts of sheep fetal and maternal parathyroid glands and placenta. Preincubation of extracts with PTH(1–34) antiserum inhibited approximately 40% of the bioactivity in fetal parathyroid extracts, 50% in maternal parathyroid extracts, but only 10% of the bioactivity in the placental extract. Partial purification of placental extracts by chromatography yielded fractions containing PTH-like bioactivity which were similar in behaviour to that of PTH-related protein (PTHrP) from a human lung cancer cell line (BEN). An antiserum against synthetic PTHrP(1–16) partially inhibited the bioactivity of the placental extract and synthetic PTHrP(1–34), but had no effect on the bioactivity of bovine PTH(1–34) or bovine PTH(1– 84). The placental PTH-like bioactivity was higher in mid- than in late gestation. Fetal parathyroid glands contained the highest PTH-like bioactivity.
Thyroparathyroidectomy of one fetal twin lamb in each of 16 ewes between 110 and 125 days of gestation resulted in decreases of the plasma calcium concentration and reversal of the placental calcium gradient that existed between the ewe and the intact fetus. Perfusion of the placenta of each twin in anaesthetized ewes was carried out sequentially with autologous fetal blood in the absence of the exsanguinated fetus. The plasma calcium concentration in the blood perfusing the placenta of each twin increased, but reached a plateau at a lower concentration in the perfusing blood of thyroparathyroidectomized fetuses than in that of the intact fetuses. Addition of extracts of fetal parathyroid glands or of partially purified PTHrP resulted in further increases in plasma calcium in the autologous blood perfusing the placentae of thyroparathyroidectomized fetuses, but addition of bovine PTH(1–84) or rat PTH(1–34) had no effect. The presence of this PTH-like protein in the fetal parathyroid gland and placenta may contribute to the relative hypercalcaemia of the fetal lamb. This protein, which is similar to PTHrP associated with humoral hypercalcaemia of malignancy, stimulates the placental calcium pump responsible for maintaining a relative fetal hypercalcaemia during gestation.
J. Endocr. (1988) 117, 261–271
Specific binding of atrial natriuretic peptide increases cyclic GMP levels in human astrocytoma cells
Authors: Lyall F. , Balmforth A. J. , Morton J. J. 
Published: December 2008

ABSTRACT
Specific high-affinity binding sites (dissociation constant 100 pmol/l) for atrial natriuretic peptide (ANP) have been identified in the clone D384 derived from the human astrocytoma cell line G-CCM. Unrelated peptides such as angiotensin II, vasopressin and bradykinin did not compete for these sites. Of the atrial natriuretic peptides studied, both the human and rat ANP competed equally, while peptides with either C-or N-terminal residue missing or with no internal -S-S-bond either competed less effectively or did not compete at all. Human ANP stimulated the cells to increase their intracellular level of cyclic GMP in a time- and dose-dependent manner with maximum stimulation being approached but not reached at concentrations of 1 μmol/l. These results support both the notion that ANP has an important functional role within the brain and the concept of neurotransmitter/neuromodulator communication between neurones and glia.
J. Endocr. (1988) 117, 315–321
Social status controls LH secretion and ovulation in female marmoset monkeys (Callithrix jacchus)
Authors: Abbott D. H. , Hodges J. K. , George L. M. 
Published: December 2008

ABSTRACT
The suppression of ovulation in subordinate female marmosets was associated with suppressed pituitary LH secretion and reduced pituitary LH response to gonadotrophin-releasing hormone (GnRH). In subordinate females, basal plasma LH concentrations were commonly below 2 IU/1 (n = 5) (maximum 10·7 IU/1). Plasma oestrogen concentrations were similarly low (maximum 0·62 nmol/l) and plasma progesterone concentrations of below 30 nmol/l confirmed the anovulatory condition. This infertility condition was rapidly reversed when subordinate females (n = 5) were removed from their social groups and housed singly, when plasma LH (maximum 140·0 IU/1) and oestrogen (maximum 7·84 nmol/l) concentrations increased preceding ovulation. Infertility was rapidly reimposed when these singly housed females were re-introduced to subordinate status in new social groups, when plasma LH concentrations fell to their previous low values within 4 days; no ovulation occurred thereafter. Plasma oestrogen levels also fell, but less dramatically. The luteal phases of three of the subordinate females were shortened following the re-instatement of subordinate status. The maximum LH response of subordinate females to the highest dose of GnRH (200 ng) was only 19·1±6·7 IU/1 (mean ± s.e.m.; n=8): this contrasted with that in dominant females in either the follicular phase (40·0±13·3 IU/1; n=6) or the luteal phase (126·7±24·9 IU/1; n=10) of the ovarian cycle.
These results suggest that the social suppression of fertility in subordinate female marmosets is mediated by impaired hypothalamic GnRH secretion. Such an immediate and precise behavioural control of LH secretion and ovulation is without equal in anthropoid primates.
J. Endocr. (1988) 117, 329–339
Mesotocin and luteal function in macropodid marsupials
Authors: Curlewis J. D. , Renfree M. B. , Sheldrick E. L. , Flint A. P. F. 
Published: December 2008

ABSTRACT
Pituitary glands and corpora lutea collected at various stages of the reproductive cycle of the tammar wallaby (Macropus eugenii), were extracted and fractionated by high-performance liquid chromatography, and specific radioimmunoassays were used to measure mesotocin ([Ile8]-oxytocin) and oxytocin. Mesotocin, but not oxytocin, was identified in extracts of pituitary; the mean concentration of mesotocin in this tissue was 0·75 nmol/g wet weight. Neither mesotocin nor oxytocin was detected in extracts of corpus luteum. In female Bennett's wallabies passively immunized against mesotocin during seasonal reproductive quiescence, there was no significant effect on peripheral progesterone concentrations and there were no births, matings or changes in vaginal smears in the 2 months following treatment. Thus mesotocin is unlikely to act as a systemic luteostatic agent during seasonal quiescence.
J. Endocr. (1988) 117, 367–372
Pituitary and plasma vasopressin concentrations and fluid balance throughout the oestrous cycle of the rat
Authors: Forsling M. L. , Peysner K. 
Published: December 2008

ABSTRACT
Observations were made of fluid balance and vasopressin concentrations throughout the oestrous cycle of normally cyclic female rats housed under a 12 h light: 12 h darkness regime. Plasma vasopressin concentrations were found to increase progressively during the light period, falling again during the night on all days of the cycle except pro-oestrus. On this day, peak vasopressin concentrations of 3·32 ± 0·8 pmol/l were seen between 10.00 and 12.00 h, with lower concentrations of 1·74± 0·22 pmol/l being seen between 18.00 and 19.00 h. Urine flow appeared to reflect the changes in plasma vasopressin concentrations, being significantly lower during the light phase, with a small increase being seen over this period on pro-oestrus. Pituitary vasopressin concentrations were highest between 09.00 and 10.00 h and fell progressively over each of the 4 days of the oestrous cycle. The changes in pituitary content were greater than could be accounted for in terms of the alterations in the plasma concentrations of vasopressin.
J. Endocr. (1988) 117, 397–402