bluuebunny/crossref_metadata_2025_split huggingface dataset:
The time-course of oxytocin secretion from cultured bovine granulosa cells, stimulated by ascorbate and catecholamines
Authors: Luck M. R. , Jungclas B. 
Published: December 2008

ABSTRACT
Bovine granulosa cells secrete oxytocin when cultured in a serum-supplemented medium. The time-course of secretion is similar to that in the early corpus luteum in vivo, with a delay of 1 to 2 days followed by a peak and decline over the first 5 days of culture. We have investigated the basis of this time-course in vitro and studied the temporal characteristics of the stimulatory actions of ascorbic acid and adrenaline on this process.
Cells cultured on stirred microcarriers showed a similar pattern of secretion of oxytocin to those cultured on conventional flat plates, despite continuing and rapid mitosis. This indicated that the secretion profile in conventional culture was not an artifact related to the cessation of mitosis. Furthermore, secretion of oxytocin and progesterone by cells on microcarriers was stimulated without a corresponding change in mitotic rate, showing that the secretion per cell had been increased.
In conventional culture, addition of ascorbic acid to culture media (0·5 mmol/l) increased the secretion of oxytocin (up to 4·5-fold) but only if ascorbic acid was present during the first day of culture. The cells showed a progressive refractoriness to stimulation after 12 h. Since the time-course of secretion was unaltered by treatment, this resulted in a delay of 1 to 2 days before the action of the ascorbate was seen. The secretion of progesterone was similarly affected but with less stimulation and less consistency. In contrast, cells treated with adrenaline (10 μmol/l) secreted more oxytocin on the day of treatment and did so at any time during culture provided that there was sufficient basal secretion of hormone. Adrenaline also failed to alter the time-course of secretion but treated cells showed a persistent response, maintaining enhanced secretion for up to 3 days after the adrenaline had been removed.
Ascorbate and adrenaline were highly synergistic in their effects, provided that the ascorbate was present from the start of culture; the response to adrenaline strongly reflected the degree of ascorbate stimulation. We conclude that granulosa cells secrete oxytocin according to an inherent time-schedule and that there is a limited period during which they can respond to ascorbate. Since ascorbate is required for the biosynthesis of oxytocin, this suggests that the availability of ascorbate during corpus luteum formation may determine the amount of oxytocin which can be released subsequently in response to catecholamines.
J. Endocr. (1988) 116, 247–258
Calcitonin inhibition of prolactin secretion in isolated rat pituitary cells
Authors: Shah G. V. , Epand R. M. , Orlowski R. C. 
Published: December 2008

ABSTRACT
Salmon calcitonin inhibited TRH-stimulated release of prolactin in isolated pituitary cells from untreated female rats. These cells were still capable of responding to the fresh addition of TRH after the removal of calcitonin. Calcitonin gene-related peptide had only a weak effect in inhibiting prolactin release in these cells.
Pituitary cells isolated from female rats which had been treated with weekly s.c. injections of 1 mg oestradiol dipropionate for 4 weeks, exhibited a marked increase in the magnitude of the inhibition of prolactin release by salmon calcitonin. Both basal and TRH-stimulated release of prolactin were inhibited by concentrations of 0·1 nmol salmon calcitonin/l or higher. Prolactin release from these cells was also inhibited at somewhat higher concentrations by calcitonin gene-related peptide. Our results demonstrate that calcitonin can directly inhibit basal as well as TRH-stimulated prolactin release by acting directly at the pituitary. The results strongly suggest that the peptide may be involved in the regulation of prolactin release in certain physiological conditions.
J. Endocr. (1988) 116, 279–286
Analysis of release of porcine relaxin by reverse haemolytic plaque assay: evidence for autoregulation
Authors: Taylor M. J. , Clark C. L. 
Published: December 2008

ABSTRACT
Relaxin release from monodispersed luteal cells derived from pregnant pigs (days 100–110 of gestation; n = 3) was detected by a reverse haemolytic plaque assay. In this technique, luteal cells were co-cultured in monolayers with ovine erythrocytes coupled to protein-A. In the presence of porcine relaxin antiserum and complement, a zone of haemolysis–a plaque–developed around relaxin-releasing luteal cells. Luteal cells were preincubated with porcine relaxin (up to 1000 ng/ml) or progesterone (up to 0·5 μg/ml) for 18 h before the plaque assay. Relaxin (but not progesterone) pretreatment inhibited subsequent relaxin release. The inhibitory effect of relaxin on its own release (autoregulation) has the potential to be a significant part of the local mechanisms which contribute to the overall control of ovarian secretion of protein hormones.
J. Endocr. (1988) 116, 287–291
Possible mechanisms responsible for the rise in plasma vasopressin associated with diabetic ketoacidosis in the rat
Authors: Charlton J. A. , Thompson C. J. , Baylis P. H. 
Published: December 2008

ABSTRACT
The plasma concentration of arginine vasopressin (AVP) is increased in diabetic ketoacidosis (DKA) in man and the rat. Although haemodynamic changes and nausea/emesis may account for the increased secretion of AVP in severe human DKA, they appear not to be responsible in moderate DKA. Streptozotocin-treated rats were studied to investigate other factors possibly involved in the secretion of AVP in DKA.
Wistar rats were injected i.p. with streptozotocin (150 mg/kg body weight). Diabetic rats were maintained on 3–4 units protamine–zinc insulin (PZI)/day for 11 days, after which PZI was withdrawn for 3 days in half the rats. The plasma concentration of AVP was greater in rats with DKA than in normal controls (mean 11·4 pmol/l compared with 1·6 pmol/l; P <0·05). Rats with DKA had higher plasma osmolality and concentrations of blood glucose, β-hydroxybutyrate and acetoacetate, but lower plasma carbon dioxide content than diabetic and normal controls (P <0·05). There were no differences in plasma levels of sodium, urea or haematocrit between rats with DKA and controls. In a separate study involving the same procedures, daily systolic blood pressure was measured using a tail cuff to occlude arterial inflow to the tail, and subsequent detection of the cuff pressure at which the first arterial pulsation appeared. No significant differences were detected between normal and diabetic rats and rats with DKA. Exponential relationships between plasma osmolality and plasma AVP (correlation coefficient, r = +0·75; P <0·01), and plasma ketone bodies and plasma AVP (r= +0·60; P <0·05) were obtained. The increase in plasma AVP in the DKA group was not due to haemodynamic changes or nausea/emesis. The results suggest that in early DKA in the rat, increases in the plasma concentration of AVP are related to the metabolic consequences of insulin deficiency and not to hypovolaemia or hypotension.
J. Endocr. (1988) 116, 343–348
Refractoriness in quail leads to a reduction in the photoperiodic drive on LH secretion
Authors: Follett B. K. 
Published: December 2008

ABSTRACT
The hypothesis was advanced that the long-day castration response in quail should become less pronounced in birds made refractory by exposure to long photoperiods. This was tested by pretreating two groups of castrated quail with testosterone for 9 weeks to suppress LH secretion whilst exposing them either to short days or to long days. The castration response was then measured on long days by withdrawing the testosterone and following the subsequent rate of increase in LH secretion. In both groups LH concentrations increased steadily for 7 weeks after removing the testosterone but the rate of increase in the group previously exposed to long days was only 50% of that in the group previously held on short days (P<0·025). The long-day castration response in quail not pretreated with testosterone was not altered by retaining the birds for 9 weeks on short days before transfer to long days.
J. Endocr. (1988) 116, 363–366
Glucocorticoid regulates secretion of epidermal growth factor in the human salivary gland adenocarcinoma cell line
Authors: Kurokawa R. , Kyakumoto S. , Ota M. 
Published: December 2008

ABSTRACT
The treatment of a human submandibular gland adenocarcinoma cell line (HSG cell line) for 48 h with triamcinolone acetonide (TA; 1–100 nmol/l) reduced the secretion of epidermal growth factor (EGF) in a closely related manner to a maximum of 66%. The reduction in the level of EGF secreted resulted in the suppression of DNA synthesis in the HSG cells to a similar extent. When the cells were incubated with TA and exogenous human EGF (hEGF), DNA synthesis was 1·7-fold higher than that without added hEGF. The removal of EGF by the addition of hEGF antibody reduced DNA synthesis in HSG cell cultures to the same extent as did TA. These results suggest that the growth inhibition of HSG cells by TA is due to the reduction in the amount of EGF secreted.
J. Endocr. (1988) 116, 451–455
Reduction of testicular blood flow and focal degeneration of tissue in the rat after administration of human chorionic gonadotrophin
Authors: van Vliet J. , Rommerts F. F. G. , de Rooij D. G. , Buwalda G. , Wensing C. J. G. 
Published: December 2008

ABSTRACT
The effect of 100IU human chorionic gonadotrophin (hCG) on testicular capillary blood flow was studied in adult male rats using a 133Xe clearance method and a radioactive microsphere technique. To investigate the role of Leydig cells in regulation of testicular blood flow after treatment with hCG, rats were pre-treated with ethane dimethylsulphonate (EDS) which selectively destroys mature Leydig cells. Six hours after treatment with hCG, testicular blood flow decreased in control and hypophysectomized rats to 25–50% of normal values, but not in EDS-pretreated animals. Prostaglandin E2 levels were also determined 6 h after an injection of hCG. A 300-fold increase in the concentration of prostaglandin E2 occurred in normal testis tissue. This rise was markedly inhibited if EDS was given 3 days before administration of hCG. Furthermore, 6 h after administration of hCG, the filling of the testicular capillary bed with methylacrylate was decreased, while in control rats and rats treated with EDS and hCG, complete filling of the capillaries was seen. Cell degeneration in some subcapsular seminiferous tubules was observed 6–10 days after treatment with hCG.
The results suggest that the hCG-induced precapillary vasoconstriction, probably mediated (in part) by prostaglandins, causes reduction in testicular blood flow 6 h after administration of hCG, and may result in cell damage.
J. Endocr. (1988) 117, 51–57
Only tissue-type plasminogen activator is secreted by immature bovine Sertoli cell-enriched cultures
Authors: Coombs R. J. , Ellison J. , Woods A. , Jenkins N. 
Published: December 2008

ABSTRACT
Two molecular variants of plasminogen activator (PA): urokinase (uPA) and tissue-type plasminogen activator (tPA), have been reported to be synthesized in the rat testis. Data obtained in this study using monospecific antibodies raised against uPA and tPA in immunoblotting and bioimmunoassay protocols consistently demonstrate that only tPA (and not uPA) is synthesized by bovine Sertoli cell-enriched cultures, and is induced by bovine FSH. Zymographic analysis of conditioned medium on gels containing plasminogen and casein showed a dominant PA proteolytic band (72 kDa) which co-migrated with human tPA. A proteolytic band (43 kDa), which was also secreted by FSH-stimulated cells, was not present when protection was afforded from auto-proteolysis by aprotinin, and was therefore concluded to be a proteolytic fragment of tPA, and not uPA.
J. Endocr. (1988) 117, 63–67
Estimating the rate of externalization of gonadotrophin-releasing hormone receptors in ovine anterior pituitary cells in vitro
Authors: Starling L. , McIntosh J. E. A. , McIntosh R. P. 
Published: December 2008

ABSTRACT
We report an estimate of the rate of externalization of unstimulated receptors for gonadotrophin-releasing hormone (GnRH), and derive from this the turnover time of the unstimulated receptor. The binding of the GnRH antagonist acetyl-d-pCl-Phe1,2,d-Trp3,d-Lys6,d-Ala10]-GnRH to dispersed sheep anterior pituitary cells was non-saturable at 37 °C. Further experiments showed that the binding had two distinct phases. We suggest that these phases correspond to the initial, saturable binding to existing plasma membrane receptors, followed by binding to receptors as they are inserted into the surface membrane. The two processes are temporally distinct, and can be inhibited independently by pharmacological manipulations. The initial phase was inhibited by treatments that could be expected to reduce the number of active receptors on the cell surface (preincubation of the cells for 30 min with 100 μg neuraminidase/ml or 50 μmol GnRH/ml), and was complete in less than 30 min after the addition of the antagonist tracer. The second phase occurred continuously in the presence of tracer, and was reduced or abolished by inhibitors of microtubule function (100 μmol vinblastine/l), protein synthesis (25 μg cycloheximide/ml), or energy metabolism (0·25 mmol 2,4-dinitrophenol/l). The rate of insertion of receptors into the plasma membrane was calculated from the rate of increase of the second phase of binding. The calculated rate implies a 100% turnover of unstimulated receptors every 150 min. In contrast, previously published estimates of the rate of internalization of the GnRH–receptor complex in the rat pituitary suggest that the stimulated receptor is turned over much faster.
J. Endocr. (1988) 117, 97–107
Regulation of preproparathyroid hormone messenger RNA and hormone synthesis in human parathyroid adenomata
Authors: Farrow S. M. , Karmali R. , Gleed J. H. , Hendy G. N. , O'Riordan J. L. H. 
Published: December 2008

ABSTRACT
Preproparathyroid hormone (preproPTH) mRNA and PTH secretion were measured in human parathyroid adenomata (n = 8) cultured in 1·0 or 3·0 mmol calcium/l and compared with changes in bovine parathyroid glands (n = 3) as a control. Incubation of bovine glands in 3·0 mmol calcium/l for 24 h resulted in a fall in mRNA levels to 47·3±21·7% (mean ± s.d.) compared with cells incubated in 1·0 mmol calcium/l, with a concomitant decrease in secretion to 62·6± 10·8%. These values fell further to 30·1 ± 15·5% and 42·1 ±18·7% respectively after 48-h incubation. One human adenoma responded to high levels of calcium in a similar manner with mRNA levels falling to 44·6± 11·9% and secretion to 30·3±17·3% within 24 h. However, in the majority of adenomata (seven out of eight), after 24-h incubation in 3·0 mmol calcium/l, mRNA levels fell to 54·1 ± 14·6% but there was no change in secretion. In two of these adenomata which were cultured for 48 h, there was no suppression of secretion despite mRNA levels having fallen to approximately 60% of control.
Incorporation of [35S]methionine into PTH secreted from human adenomatous cells was quantified by densitometry. There was no difference in the amount of radiolabelled PTH secreted from cells incubated in high levels of calcium compared with those in normal levels of calcium. In similar experiments, the effects of high calcium on the synthesis of PTH in bovine cells was assessed by determination of radiolabelled intracellular PTH. After 24 h in high calcium, there was a fall of 59·0± 10·0% in the incorporation of [35S]methionine into PTH compared with cells incubated in normal calcium.
These results suggest the existence of two or more sites of regulation of synthesis and secretion by calcium. There appears to be control at the level of transcription with suppression of mRNA levels in human adenomata and bovine glands. This may be due to a decreased rate of transcription, or an increased rate of degradation of mRNA or both. There is also evidence for a post-transcriptional site which is less sensitive in human adenomata to control by calcium than in bovine glands.
J. Endocr. (1988) 117,133–138
Food intake alters the serum growth hormone response to bovine growth hormone-releasing factor in meal-fed Holstein steers
Authors: Moseley W. M. , Alaniz G. R. , Claflin W. H. , Krabill L. F. 
Published: December 2008

ABSTRACT
The hypothesis that endocrine or nutritional factors related to feeding may affect pituitary responsiveness to an acute challenge with bovine GH-releasing factor (1–44)-NH2 (GRF) was examined in steers. In these experiments, either steers were trained to consume their total daily food allotment in a 2-h period (meal-fed) or food was withheld at the normal time of feeding (sham-fed).
In the first of three experiments, the serum GH pattern was determined around the time of feeding in meal-fed and sham-fed steers. The temporal GH rhythm in both groups appeared to be synchronized to the time of feeding, with limited pulsatile GH activity occurring 2–3 h after feeding. Baseline secretion of GH and total area under the GH response curve were lower (P<0·01) in meal-fed compared with sham-fed steers. In the second experiment, 50 μg GRF was injected i.v. in meal-fed steers at −4, −2, 0, + 2, +4, +6 and + 8 h relative to the time of feeding. The number of steers responding to GRF (53%), the amplitude of the GH peak (15·8 μg/l) and the area under the GH response curve (0·6 arbitrary units) were lower (P< 0·001) after than before feeding (90 ± 6 (s.e.m.)%, 61·3 ± 3·2 μg/l and 2·0 ± 0·3 units respectively). Of those steers responding to GRF, the GH response was significantly reduced following feeding compared with before feeding. In the third experiment, 50 μg GRF was injected i.v. in sham-fed steers at −4, −2, 0, +4 and +6 h relative to the time of sham-feeding. The amplitude of the GRF-induced GH peak (55·4 ± 9·3 μg/l), time to the GH peak (12 ± 2 min) and area under the GH response curve (0·8 ± 4 units) were not significantly different (P>0·1) among the different times of injection of GRF before or after sham-feeding. Apparently factors associated with the ingestion of feed can modulate the release of GH from the pituitary as evidenced by (a) the synchronization of the GH pattern to the time of feeding, and (b) the reduction of the serum GH response to i.v. injection of GRF following feeding.
J. Endocr. (1988) 117, 253–259
Circulating plasma cfactor-likeg immunoreactivity
Authors: Ellis M. J. , Livesey J. H. , Donald A. 
Published: December 2008

ABSTRACT
Normal human peripheral plasma, examined by direct radioimmunoassay corticotrophin-releasing factor (CRF) using seven different antisera, showed marked inhibition of tracer binding to antiserum. This apparently high Cimmunoreactiv(CRF-LI) dilute in parallel with synthetic human CRF-41.parison, most equine and ovine plasma samples had low Cconcentrations.ractionation of both normal and late pregnancy human plasma on SG-75 neutral pH indicated the majority of the CRF-LI of large molecular size. The molecular weight was estimated to be approximately 29 000 following chromatography human plasma on Sephacryl S-200.igh CRF-LIrmal plasma was reduced to barely detectable levels by methanol treatment despite the recovery of added human CRF-41 of >80%. Methanol extracts of late pregnancy human plasma, however, retained high CRF-LI which exhibited the immunoreactive and Sephadex elution characteristics of synthetic human CRF-41. 125I-Labelled human CRF-41 added to human plasma showed a reversible, time-dependent alteration in molecular size and reduction in binding to excess antiserum. These findings indicate that direct RIA of human CRF in unextracted plasma leads to spurious results and suggest the presence in human plasma of an interfering factor and/or binding substance that is not generally apparent in equine or ovine plasma under the conditions described.
J. Endocr. (1988) 117, 299–307
Hydrolysis of phosphatidylinositol by human endometrium: modulating effects of steroids on arachidonic acid and 1,2-diacylglycerol release
Authors: Bonney R. C. , Franks S. 
Published: December 2008

ABSTRACT
Phospholipase C and 1,2-diacylglycerol lipase activities were demonstrated in human endometrium using 1-stearoyl-2-[1-14C]arachidonyl phosphatidylinositol as substrate. Phosphatidylinositol is hydrolysed by phospholipase C to inositol phosphates and to 1,2-diacylglycerol which is then further metabolized by 1,2-diacylglycerol lipase to release free arachidonic acid. In the present study the radiolabelled products formed (1,2-diacylglycerol and arachidonic acid) were measured following chloroform/methanol extraction and thin-layer chromatography. Phospholipase C activity was calcium dependent and optimal at pH 5·0–5·5 and 7·5; 1,2-diacylglycerol lipase activity was also calcium dependent, with an optimum pH of 5·5. A significant increase in 1,2-diacylglycerol production was stimulated by steroid sulphates. Pregnenolone sulphate, oestrone sulphate, testosterone sulphate and dehydroepiandrosterone sulphate stimulated 4, 3·2-1·8- and 2·6-fold increases in release respectively. Oestradiol sulphate stimulated a 25% increase in diacylglycerol release which was not significantly different from the control value. Progesterone stimulated a fourfold increase but other free steroids had no effect. Arachidonic acid release was increased in the presence of oestradiol sulphate, oestrone and oestradiol but reduced by oestrone sulphate, dehydroepiandrosterone sulphate, progesterone, dehydroepiandrosterone and, to a lesser extent, by pregnenolone sulphate and testosterone sulphate. 5-Androstene-3β, 17β-diol had no effect on the liberation of either product.
This study demonstrates a potential route for the liberation of arachidonic acid from phosphatidylinositol in human endometrium. The opposing effects of steroids on phospholipase C and 1,2-diacylglycerol lipase activity could be important in regulating the release of arachidonic acid by this pathway.
J. Endocr. (1988) 117, 309–314
Effect of cortisol on the plasma and lymphoid tissue distributions of tritiated glucocorticoids in C57BL/6 mice
Authors: Durant S. , Duval D. , Homo-Delarche F. 
Published: December 2008

ABSTRACT
The mechanism of action of very high doses of corticosteroids, such as those administered as bolus doses in the treatment of inflammatory and immune diseases or those currently used in rodents to isolate the small proportion of medullary thymocytes considered to be corticoresistant, is still undefined. The possible existence of selective local concentration by some tissues, particularly lymphoid organs, cannot be excluded. Therefore, using C57BL/6 mice, the kinetics of lymphoid tissue and plasma radioactivities after i.p. injection of steroids, either alone or with an excess of non-radioactive cortisol hemisuccinate (up to 10 mg/animal, i.e. 500 mg/kg ) were studied. There was a rapid and dose-dependent retention of [3H]corticosterone and [3H]cortisol in the thymuses of cortisol-treated compared with control animals. The spleen also appeared to be capable of accumulating steroids. However, when the tissue/plasma ratio of [3H]steroid concentration and the change in extracellular space in the presence of an excess of non-radioactive cortisol were taken into consideration, only the thymus was able to concentrate steroids above concentrations in the plasma. Moreover, this effect did not appear to be specific for glucocorticoids, since tracer accumulation was also observed when sex steroids were used as tracers. The cells of the reticuloendothelial system may, in part, be responsible for this phenomenon of steroid concentration in lymphoid organs.
J. Endocr. (1988) 117, 373–378