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1.
Prostaglandin-like material was released from finely cut guinea-pig ileum or human intestinal mucosa during incubation with Krebs solution. The tissue inactivated some of the released material and added PGE2. There was no significant change in release of prostaglandin-like material when pure cholera toxin was incubated with guinea-pig ileum or human intestinal mucosa. The work is discussed in relation to the action of cholera toxin . 相似文献
2.
John G. Gerber Walter C. Hubbard Alan S. Nies 《Prostaglandins & other lipid mediators》1979,17(4):623-627
We studied the uterine venous plasma concentrations of prostaglandins E2, F2α, 15 keto 13,14 dihydro E2 and 15 keto 13,14 dihydro F2α in late pregnant dogs in order to evaluate the rates of production and metabolism of prostaglandin E2 and F2α in pregnancy . We used a very specific and sensitive gas chromatography-mass spectrometry assay to measure these prostaglandins. The uterine venous concentrations of prostaglandin E2 and 15 keto 13,14 dihydro E2 were 1.35±.27 ng/ml and 1.89±.37 ng/ml, respectively; however, we could not find any prostaglandin F2α and very little of its plasma metabolite in uterine venous plasma. Since uterine microsomes can generate prostaglandin F2α and E2 from endoperoxides, prostaglandin F2α production must be regulated through an enzymatic step after endoperoxide formation. Prostaglandin E2 is produced by pregnant canine uterus in quantities high enough to have a biological effect in late pregnancy; however, prostaglandin F2α does not appear to play a role at this stage of pregnancy. 相似文献
3.
Effect of prostaglandin E2 on vascular responses of the rabbit kidney to nerve stimulation and noradrenaline, in vitro and in situ 总被引:2,自引:0,他引:2
The effect of prostaglandin E2 on vascular responses of the rabbit kidney to renal nerve stimulation and noradrenaline was examined and as a test of the hypthesis that prostaglandins of the E series may be involved in the regulation of adrenergic neuroeffector transmission. Intraarterial administration of prostaglandin E2 to the kidney caused marked inhibition of vascular responses to nerve stimulation whereas the responses to noradrenaline were not significantly altered. In the preparation, vascular responses to both nerve stimulation and noradrenaline were inhibited by prostaglandin E2 infusion, although its effect on responses to nerve stimulation was approximately twice that observed on responses to noradrenaline.It is concluded that prostaglandin E2 acts primarily at a prejunctional level of adrenergic neuroeffector transmission in the kidney, although a postjunctional effect has also been observed. 相似文献
4.
Somatocrinin (growth hormone releasing factor) in vitro bioactivity; Ca++ involvement, cAMP mediated action and additivity of effect with PGE2 总被引:4,自引:0,他引:4
Paul Brazeau Nicholas Ling Frederick Esch Peter Böhlen Christiane Mougin Roger Guillemin 《Biochemical and biophysical research communications》1982,109(2):588-594
The release of GH induced by purified hypothalamic GRF or native or synthetic tumor-derived GRF is antagonized by the presence of CoCl2; it is simulated by 8Br .cAMP, IBMX, cholera toxin, forskolin, with identical maximal effects (Emax). Somatocrinin (GRF) stimulates the efflux of cAMP by the pituitary cells in parallel to the release of GH. Addition of either 8Br .cAMP, IBMX, cholera toxin or forskolin to a maximally stimulating dose of GRF does not increase the response which remains GRF-Emax. In contradistinction with these results PGE2 releases GH with a dose-response curve different from that of GRF, and the combination of PGE2 + GRF produces an Emax far greater than that due to either agonist alone; showing a true additivity. The name is proposed to replace the acronym GRF. 相似文献
5.
John G. Gerber Walter C. Hubbard Robert A. Branch Alan S. Nies 《Prostaglandins & other lipid mediators》1978,15(4):663-670
We determined the effect of 2 mg/kg intravenous furosemide on the production and metabolism of prostaglandin E2 in the utero-placental unit of pregnant dogs. Uterine venous prostaglandins E2 and 15-keto-13,14-dihydro E2 were measured by gas chromatography-mass spectrometry. Even though the dose of furosemide was adequate to effect a good diuresis, neither the production nor the metabolism of prostaglandin E2 by the uterus was altered by that dose of the drug. Using radioactive microspheres to measure hemodynamic parameters, we observed no change in uterine vascular resistance while renal vascular resistance decreased. Although the renal concentration of furosemide may be higher than the uteroplacental concentration, there is so far no evidence that usual doses of furosemide enhance the production or inhibit the metabolism of prostaglandin E2. 相似文献
6.
The diarrhea observed in patients which cholera is known to be related to secretion of water and electrolytes into the intestinal lumen. However, the exact mechanisms involved in these secretory processes have remained unclear. Although it is clear that purified toxin acts on epithelial cell metabolism, its activity on Na+ transport across intestinal mucosa is equivocal: reported either to prevent net Na+ absorption or to cause net secretion of Na+ from serosa to mucosa. Since total transmural Na+ fluxes across “leaky” epithelia involve very significant movement via a paracellular shunt pathway, we studied the effects of cholera toxin on the cellular and paracellular pathways of Na+ movement. Unidirectional Na+ fluxes were examined as functions of applied potential in control tissues and in tissues from the same animal treated with purified cholera toxin. Treatment of rabbit ileum in vitro with toxin stimulated the cellular component of serosa-to-mucosa Na+ flux (from per cm2 under control conditions to per cm2 after treatment with toxin, ). The effect of cholera toxin on Na+ movement through the cells from mucosa to serosa appeared to be insignificant. Finally, a marked decrease in the Na+ permeability () and no detectable significant changes in transference number for Na+ of the paracellular shunt pathway were observed following treatment with cholera toxin. These results provide direct evidence for the hypothesis that purified cholera toxin stimulates active sodium secretion but has minimal effect on sodium absorption. 相似文献
7.
Investigations were made into the effects of crude and pure preparations of cholera toxin on the release of prostaglandin-like substances (PLS) from rabbit ileum. Perfusion of ileal loops
with buffer containing crude toxin was followed by a release of PLS into the perfusate, in amounts up to 37.5 ng/30 min (PGE2 equivalents). In contrast, no detectable PLS was released when ileal loops were perfused with pure toxin. Similarly, pieces of ileum opened longitudinally released PLS in amounts up to 107 ng PGE2/g tissue when incubated with crude toxin for 1–4 hr, but no release of PLS was detected in the presence of pure toxin under comparable conditions.Treatment of rabbits with indomethacin, 1.6 mg/kg p.o., had no effect on the accumulation of fluid in ileal sacs injected with crude or pure cholera toxin. These results support the view that prostaglandins do not play an essential role in the action of cholera toxin. 相似文献
8.
Investigations were made into the effects of crude and pure preparations of cholera toxin on the release of prostaglandin-like substances (PLS) from rabbit ileum. Perfusion of ileal loops in vivo with buffer containing crude toxin was followed by a release of PLS into the perfusate, in amounts up to 37.5 ng/30 min (PGE2 equivalents). In contrast, no detectable PLS was released when ileal loops were perfused with pure toxin. Similarly, pieces of ileum opened longitudinally released PLS in amounts up to 107 ng PGE2/g tissue when incubated with crude toxin for 1–4 hr, but no release of PLS was detected in the presence of pure toxin under comparable conditions.Treatment of rabbits with indomethacin, 1.6 mg/kg p.o., had no effect on the accumulation of fluid in ileal sacs injected with crude or pure cholera toxin. These results support the view that prostaglandins do not play an essential role in the action of cholera toxin. 相似文献
9.
Normal rat kidney (NRK) cells growth arrested by picolinic acid and isoleucine deprivation exhibit an increased response to certain agents (i.e., prostaglandin E1, (?)-isoproterenol, and cholera toxin) which elevate intracellular cyclic AMP levels. The enhanced hormonal response is apparently due, at least in part, to increased adenylate cyclase activity. Adenylate cyclase activities measured in the presence of GTP, GTP plus prostaglandin E1, and GTP plus (?)-isoproterenol are increased two- to threefold in membranes prepared from treated cells. In contrast, basal activity is potentiated only 20 to 50% and activity determined in the presence of fluoride is only marginally altered. Also of interest is the increase in cholera toxin activation of cyclase activity in the treated cells. Lower concentrations of cholera toxin (5 ng/ml) are required to achieve maximal stimulation of cyclase activity from picolinic acid-treated and isoleucine-deprived cells; maximal stimulation of control cell adenylate cyclase is attained with 25 to 50 ng/ml cholera toxin. Picolinic acid treatment and isoleucine deficiency both have been shown to arrest NRK cell growth in the G1 phase of the cell cycle. However, results with cells arrested in G1 by serum starvation and by growth to high cell population density indicate that G1 specific growth arrest does not appear to account for the increase in hormonal responsiveness. Chelation of inhibitory metals and proteolytic activation also do not appear to be involved in the mechanism by which picolinic acid enhances cyclic AMP formation. Rather, the results suggest that the treated cells have an increased amount of an active GTP-dependent function required for hormone and cholera toxin stimulation of adenylate cyclase. Thus, picolinic acid treatment and isoleucine deprivation may provide a useful means of modulating the GTP-dependent step required to potentiate hormonal responsiveness. 相似文献
10.
M.J. Peek I.S. Fraser C.A. Phillips T.M. Resta P.M. Blackwell R. Markham 《Prostaglandins & other lipid mediators》1985,29(1):3-18
Two methods for measuring human endometrial prostaglandin production were compared. Endometrial samples from eight patients were incubated over eight hours by a perifusion and a superfusion technique. The collected fractions were assayed by radioimmunoassay for PGE2 and PGF2α.There was no significant difference between the perifusion and superfusion methods for the pattern and amount of PGE2 and PGF2 production with time. Significantly higher production levels of PGE2 and PGF2α were found in secretory phase endometria than in proliferative phase endometria. Histological examination of the tissue specimens by light and electron microscopy showed that both methods caused gross tissue damage after eight hours experimentation. The superfusion method produced more morphological damage than the perifusion method. However, no tissue damage could be detected after one hour of incubation with either method.Over an eight hour period neither the perifusion nor the superfusion technique appears to be a good indicator of endometrial prostaglandin production. Either reflect the situation. 相似文献
11.
Three calcium-binding ligands in the cytosol of rat small intestine have been separated using Sephadex G-75 column chromatography. The estimated molecular weights of these ligands were 85,000, 10,000, and 800, respectively. The two high-molecular-weight ligands were found only in young rats, while the low-molecular-weight calcium-binding ligand was found in all age groups and appeared to be a calcium-bound prostaglandin metabolite. Oral administration of arachidonic acid increased and PGE2 decreased calcium absorption, while PGF2 administration showed no discernible effect on this parameter. These results suggest that the intestinal calcium transport mechanism may be modulated by prostaglandins and related metabolites. 相似文献
12.
Gisèle Berthillier Jacque dAlayer Ariane Monneron 《Biochemical and biophysical research communications》1982,109(2):297-304
ADP-ribosylation of the adenylate cyclase regulatory subunit by cholera toxin is a major tool for the study of this enzyme. Investigation of the brain enzyme has been hampered up to now by the failure to demonstrate cholera toxin-dependent ADP-ribosylation of membrane-bound proteins. Synaptosomes prepared by flotation from fresh brains homogenized in the presence of protease inhibitors yielded membranes of which several proteins could be ADP-ribosylated by the toxin. The same membranes subjected to mild proteolysis could not be ADP-ribosylated. Adenylate cyclase activation and ADP-ribosylation were simultaneous processes. The major labeled species was of 47,000 Mr. It was solubilized by Lubrol-PX, together with other labeled polypeptides. As analyzed on sucrose gradients, the 47,000 Mr protein was found both in the 3S region, and in the adenylate cyclase containing fraction (9.1S). 相似文献
13.
Lipopolysaccharide from (LPS) and BCG cell walls (BCGcw) are recognized immunoadjuvants that directly stimulate some macrophage functions. The macrophage cell line J774.1 and peritoneal exudate cells (PEC) from mice can be stimulated by LPS or other adjuvants to synthesize and release protein factor(s) that activate thymus-derived lymphocytes. We have utilized J774.1 cells and PEC to demonstrate that an increase in ornithine decarboxylase (ODC) activity is a marker of early biochemical changes in adjuvant-stimulated macrophages. BCGcw and LPS increased ODC within 2 hours in J774.1 cells as well as murine peritoneal exudate macrophages. Maximal increases in ODC were detected 4 hours after the addition of adjuvants to J774.1 cells. The marked increases (12–23 fold) in ODC observed with BCGcw (20 μg/ml) did not appear to involve an effect on cell proliferation which was suppressed by this adjuvant. Cycloheximide inhibited the induction of ODC by LPS and BCGcw in the macrophage cell line. Evidence that the induction of ODC may be promoted by an increase in cyclic AMP was provided by experiments demonstrating that prostaglandin E1 (PGE1) and 8-bromo-adenosine-3′:5′-monophosphate (8Br-cyclic AMP) can mimic the effects of LPS and BCGcw in J774.1 cells. These observations indicate that one of the early biochemical changes in macrophages promoted by adjuvants is an induction of ODC. 相似文献
14.
Electron spin resonance detection of free radicals in the mercaptan-activation and UV-inactivation of neocarzinostatin 总被引:3,自引:0,他引:3
Differentiation of chick embryo myoblasts requires both cell-cell recognition and cell-cell fusion. Prostaglandin E1 is known to play a role in controlling fusion, and a specific receptor has been postulated. We demonstrate two peaks of specific binding activity for prostaglandin E1 during myoblast differentiation : one at 36 hours and one at 44 hours of culture. The prostaglandin binding activity of both peaks is sensitive to the inhibitors of prostaglandin synthesis, indomethacin and aspirin, and to the antibiotic tunicamycin. The 36 hour peak of binding activity occurs at the same time as the process of cell-cell recognition (24–36 hours) and recognition and prostaglandin binding exhibit similar sensitivity to indomethacin, aspirin and tunicamycin. 相似文献
15.
H E Sheerin 《Life sciences》1979,24(17):1609-1615
Serotonin has previously been implicated as the cause of the diarrhea associated with carcinoid syndrome and the amine has been shown by others to be an intestinal secretagogue in preparations of intestinal loops . In the present paper the action of serotonin on isolated segments of rabbit ileal mucosa stripped of muscle layers was studied . Serotonin (10?4M) caused an abrupt significant rise in short-circuit current (Isc) across the mucosal epithelial cell layer but this effect was transient. No change was observed in tissue conductance. In this preparation, serotonin did not alter 22Na, 36Cl or residual ion fluxes across the mucosa. High blood serotonin levels for a period of several days also did not alter ion fluxes or Isc in isolated rabbit ileum. Therefore, it is concluded that serotonin must cause its secretory activity observed by some mechanism other than a direct action on epithelial cell transport mechanisms. 相似文献
16.
L. Üstünes M. Claeys G. Laekeman A.G. Herman A.J. Vlietinck A. Özer 《Prostaglandins & other lipid mediators》1985,29(5):847-865
Two fractions with prostaglandin E-like activity were isolated from onion () by using XAD-2 adsorption, silicic acid column chromatography and thin layer chromatography. The fractions were analyzed by gas chromatography/mass spectrometry and were characterized as isomeric mixtures of 9,10,13-trihydroxy-11-octadecenoic and 9,12,13-trihydroxy-10-octadecenoic acid, which are lipoxygenase metabolites of linoleic acid. Bio-assay, for which cascade superfusion was used and the rabbit coeliac and mesenteric arteries and the rat fundus strip were employed as assay organs, was utilized to monitor the bio-active profile throughout the isolation procedures. The activity of 1 μg of the pharmacologically active fractions T1 and T2 was found to be equivalent to that of respectively 1.33 and 0.63 ng of prostaglandin E2. 相似文献
17.
H Cramer R Hammers P Maier H Schindler 《Biochemical and biophysical research communications》1978,84(4):1031-1037
Cholera toxin was found to induce high accumulations of cyclic AMP in the isolated choroid plexus of the rabbit and in the incubation medium. The accumulation showed a characteristic lag phase of at least 30 min and continued for at least 3 hours. Inactivated cholera toxin was unable to increase cyclic AMP levels. There was only a moderate effect of cholera toxin on cyclic AMP “low Km” phosphodiesterase activity in homogenates. The effect of cholera toxin on cyclic AMP levels confirms the existance of a potent cyclic AMP generating system in the choroid plexus which is activated also by β-adrenergic agonists, histamine and prostaglandin E1. 相似文献
18.
Vonda G. Reeves-Darby John A. Turner Rajendra Prasad ashok K. Chopra Parvathi Chary Mary H. Clench Johnny W. Peterson John R. Mathias 《FEMS microbiology letters》1995,134(2-3):239-244
Abstract We analysed the small intestine myoelectric responses of anesthetized New Zealand albino rabbits to Escherichia coli lysates containing an enterotoxin cloned from Salmonella typhimurium . Migrating action potential complex, which consisted of rapid bursts of action potentials and secretion of fluid, was observed only in ileal loops injected with the enterotoxin-containing lysate. Migrating action potential complex produced by Stn usually propagated aborally, which was typical of cholera toxin, but orad or bidirectional propagation occurred from a single point of origin when activity was intense. Gell lysates from an E. coli clone containing vectors alone, as well as proximal control segments injected with phosphate-buffered saline, gave neither a change in motility nor fluid secretion. These results show that Stn caused dramatic changes in intestinal motility and substantial fluid production. 相似文献
19.
F Couraud H Rochat S Lissitzky 《Biochemical and biophysical research communications》1978,83(4):1525-1530
The protein neurotoxin II from the venom of the scorpion Hector was labeled with 125I by the lactoperoxidase method to a specific radioactivity of about 100 μCi/μg without loss of biological activity. The labeled neurotoxin binds specifically to a single class of non intereacting binding sites of high affinity (KD = 0.3 – 0.6 nM) and low capacity (4000 – 8000 sites/cell) to electrically excitable neuroblastoma cells. Relation of these sites to the action potential Na+ channel is derived from identical concentration dependence of scorpion toxin binding and increase in duration and amplitude of action potential. The protein neurotoxin II from the sea anemone also affects the closing of the action potential Na+ ionophore in nerve axons. The unlabelled sea anemone toxin modifies 125I-labeled scorpion toxin II binding to neuroblastoma cells by increasing the apparent KD for labeled scorpion toxin without modification of the number of binding sites. It is concluded that both scorpion toxin II and sea anemone toxin II interact competitively with a regulatory component of the action potential Na+ channel. 相似文献
20.
Recent reports suggest that prostaglandins, rather than cAMP, play a major role in mediating cholera toxin-induced water and electrolyte secretion from rabbit intestinal loops. We examined the role of prostaglandins in mediating toxin-induced pancreatic and gastric exocrine secretion. In these tissues, indomethacin, a potent inhibitor of prostaglandin synthesis, did not alter the stimulatory effects of cholera toxin on increases in cellular cAMP or enzyme secretion. Moreover, the addition of cholera toxin did not alter prostaglandin E2 release from either tissue. In contrast to their effects in rabbit intestinal loops, prostaglandins do not regulate cholera toxin-induced enzyme secretion from the guinea pig pancreas or stomach. 相似文献