Search PubMed⌕ Search

Biomedical subjects

P Marche

Publications and source records attributed to P Marche.

At least 73 records · Page 4Linked to original sources
PubMed1985

Phosphoinositide turnover in erythrocyte membranes in human and experimental hypertension.

The metabolism of phosphoinositides, a class of membrane lipids involved in Ca2+ -transport and/or mobilization systems was investigated in patients with moderate essential hypertension and in Sabra rats. Experiments were performed in vitro on isolated erythrocyte membranes by measuring the 32P-labelling of phosphatidylinositol 4,5-bisphosphate (PI-P2) and of phosphatidylinositol 4-phosphate (PI-P) following the incubation of membranes with [gamma-32P] ATP. In untreated essential hypertensives (n = 31) or in hypertensive patients whose blood pressure was controlled by beta-blocker therapy (n = 20), 32P-PI-P2 was significantly higher than in normotensive controls (n = 30); no significant difference was observed between the two groups of hypertensive patients. In Sabra rats fed on a low Na diet, 32P-PI-P2 levels were significantly higher in hypertensive-prone animals (SBH) than in hypertensive-resistant animals (SBN). When the animals were fed a high Na diet or were DOCA/salt treated, 32P-PI-P2 did not change in either substrain, although such conditions differentially affected the blood pressure of SBH and SBN. Our data indicate that the modification of phosphoinositide metabolism is not a consequence of the blood pressure elevation, but can be considered as an intrinsic membrane defect which may be associated with functional alterations of Ca2+ fluxes which in hypertensives result in an enhanced intracellular Ca2+ level.

Adrenergic beta-Antagonists↗
PubMed1985

Serotonin release and phosphoinositide breakdown in thrombin-induced activation of human platelets.

The release reaction and the metabolism of inositol lipids were studied in parallel in washed human platelets following the activation by low doses of thrombin. The breakdown of phosphatidylinositol 4,5-bisphosphate (PI-P2) was accompanied by the release of serotonin. These events preceded the breakdown of the other phosphoinositides and the release of alpha-granules and lysosome constituents, respectively. The secretion of serotonin probably is triggered by products of thrombin-induced activation of the phospholipase C directed against PI-P2.

Blood Platelets↗
PubMed1985

Atrial natriuretic factor inhibits Ca(2+)-dependent K+ fluxes in cultured vascular smooth muscle cells.

The interaction of the synthetic fragment Arg101-Tyr126 of atrial natriuretic factor (ANF) with Ca(2+)-dependent K+ efflux was studied in the following six different cell models: cultured vascular smooth muscle cells from rat aorta; isolated rat glomeruli; human platelets; cultured endothelial cells from bovine aorta; peritoneal mouse macrophages; human red cells. In human red cells and mouse macrophages, the dose-response curves of K+ efflux as a function of Ca2+ ionophore, A23187, concentration were not modified by addition of ANF. In endothelial cells and platelets, ANF slightly inhibited Ca(2+)-dependent K+ efflux. In renal glomeruli, ANF inhibits about one-third of this flux and in vascular smooth muscle cells ANF induced a five- to tenfold increase in the EC50 of A23187 effect. In experiments performed at constant concentrations of A23187, the IC50 of ANF was approximately 10(-9) mol/l. Similar results were obtained in mouse macrophages with cyclic GMP (cGMP). Our results suggest that ANF is able to counterbalance an increase in cytosolic free Ca2+ content in vascular smooth muscle and some glomerular cells. This effect may result from the ability of this hormone to stimulate cGMP synthesis.

Animals↗
PubMed1985

[Effects of aminoglycosides on phosphoinositide metabolism in renal proximal tubules. In vivo and in vitro studies].

Phosphoinositides play a major role in the interaction between aminoglycosides and renal epithelial cells. We therefore investigated both in vivo and in vitro, in isolated proximal tubules and in various parts of the rabbit kidney, the influence of neomycin, gentamicin and amikacin on the phosphoinositide metabolism. This was carried out by measuring the 32p incorporation into phosphatidylinositol 4,5-bisphosphates (PI-P2) and phosphatidylinositol 4-phosphates (PI-P). In aminoglycoside-treated animals, compared to untreated controls, the 32 p-PI-P2 and 32p-PI-P levels were decreased and increased respectively in proximal tubules and in cortical areas but these levels were unchanged in papilla and in medulla. Similar variations could be obtained after exogenous addition of aminoglycosides. PI-P2 is a key membrane component in the regulation of both the Ca2+ transport and the intracellular Ca2+ mobilization. Thus, the aminoglycoside-induced modifications of the phosphoinositide metabolism may be considered as a primary event in the drug toxicity which may result from alterations in the cell calcium homeostasis.

Amikacin↗
PubMed1985

Polyphosphoinositides and cell activation.

This review surveys various aspects of the metabolism of inositol containing lipids and focuses upon the role of polyphosphoinositides in the triggering of physiological responses of platelets. Since the latter responses are evoked by a rise in cytosolic Ca2+ concentration the relationship between the phosphoinositide metabolism and the intracellular Ca2+ mobilization is discussed.

Animals↗
PubMed1985

Molecular membrane organization in normal and pathological platelets: changes in inositide metabolism and membrane fluidity.

The role of platelet plasma membrane in mediating cellular response to external stimuli was investigated by studying phosphatidylinositol turnover and structural physical molecular alterations. Phosphoinositide turnover was evaluated by phosphatidylinositol breakdown and phosphatidic acid (PA) synthesis. The membrane structure was investigated by measuring fatty acid chain organization, flexibility and movements using the spin label method. When platelets are stimulated by thrombin, a rapid phosphatidylinositol bisphosphate (PIP2) breakdown is observed, accompanied by an immediate PA synthesis. At the same time a membrane-bound calcium liberation within the cell is revealed by the decrease in chlortetracycline fluorescence, and the dense granule constituent serotonin is released from the cell. These events result in disorganization of the platelet membrane as estimated by the decrease in order parameter. All these thrombin-induced effects occur in the presence of EDTA, thus being independent of external calcium and aggregation. By contrast ionophore A 23187 does not induce any PIP2 breakdown nor structural disorganization and the dense granule release measured at 10 seconds is only very weak. These results were confirmed by studies on pathological platelets in which PIP2 breakdown was normal when release was normal, such as in Glanzman thrombasthenia, or did not occur when no granule release was measurable as in Gray-platelet syndrome. It is suggested that membrane-bound calcium has a structural rather than a functional role.

Blood Platelet Disorders↗
PubMed1985

[Phosphoinositide metabolism in essential and experimental hypertension].

The metabolism of phosphoinositides, a class of membrane lipids that appears to be intimately involved in the regulation by the membrane of the intracellular Ca2+ level, has been reported to be modified in the erythrocyte of the spontaneously hypertensive rat (SHR and SHR/SP). In order to elucidate the link between the phosphoinositide alteration and hypertension, the metabolism of phosphoinositides was studied in human essential hypertension and in Sabra rats under various patho-physiological conditions. Experiments were performed in vitro on isolated ghost membranes by measuring the radioactivity incorporated into triphosphoinositides (PI-P2) and diphosphoinositides (PI-P) following the incubation of membranes with [gamma 32P]-ATP. 32P-PI-P2, in moderate untreated essential hypertensive controls (n = 31) was higher than in normotensives (n = 30) (1.18 +/- 0.06 vs 0.92 +/- 0.04, 32P nmol/15 min/mg prot, p less than 0.005); 32P-PI-P2 and 32P-PI-P in hypertensive patients treated with beta-blocking agents (n = 20) did not differ from the values observed in untreated hypertensives. In Sabra rats, 32P-PI-P2 values were 0.79 +/- 0.03 and 1.32 +/- 0.08 for SbN and SbH, respectively (8-11 animals per group); difference was significant. 32P-PI-P values varied similarly. Both 32P-PI-P2 and 32P-PI-P did not change significantly when animals were fed a high sodium diet or were injected with DOCA, though such treatments rose the blood pressure. Our data indicate that the modification of phosphoinositide metabolism that we observed both in rat and human hypertension is not a consequence of the blood pressure elevation, but may be considered as an intrinsic membrane defect. Changes in the phosphoinositide metabolism may therefore be associated with the functional and structural alterations concerning the transmembrane Na+ and Ca2+ fluxes which may be of pathogenic importance.

Adult↗
PubMed1983

Triphosphoinositide breakdown and dense body release as the earliest events in thrombin-induced activation of human platelets.

The activation by thrombin of human platelets prelabelled with 32P induced a 30-40% decrease in 32P-triphosphoinositides (TPI) in the first 10 sec; the decrease in the other 32P-labelled phosphoinositides occurred by 20-30 sec. At 10 sec., the intensity of these effects was maximum with 0.2-0.4 U/ml thrombin. Under these conditions, 53, 20 and 15% of the dense granule, alpha-granule and lysosome constituents, respectively were released and thromboxane B2 synthesis reached only 10% of its maximum. Together with experiments carried out with chlorpromazine - or PGE1 - treated platelets, our results suggest the existence of a close relationship between TPI-breakdown and dense body release which appear to be the earliest events resulting from the activation of human platelets by thrombin.

Blood Platelets↗
PubMed1983

Physicochemical studies on the antigen-antibody complexes of two monoclonal antibodies against rabbit thymocytes.

We have characterized two monoclonal antibodies directed against rabbit thymocyte antigens. Using internally labelled MD3 cells (a transformed T-cell line), ART-F immunoprecipitated a membrane glycoprotein of 95,000 mol. wt, while ART-A immunoprecipitated two major glycoproteins, one of 95,000 mol. wt, the other of 105,000 mol. wt as analysed on reduced SDS-PAGE. ART-A recognizes 650,000 sites both on rabbit thymocytes and MD3 cells with an association constant of 1.5 X 10(5)/M. ART-F shows a biphasic binding curve with a high affinity constant of 3.3 and 0.6 X 10(8)/M and a low affinity constant of 2.2 and 6.9 X 10(5)/M for thymocytes and MD3 cells respectively. The numbers of high affinity and low affinity antigens are 200,000 for the former and 800,000 for the latter. On the basis of the kinetic data, the difference between low and high affinity is attributed to the difference in association-rate constants. The affinity constants calculated from the reaction-rate constants are in good agreement with those obtained from equilibrium measurements. While ART-F prevents the binding of ART-A, ART-A does not inhibit the affinity binding of ART-F. The analysis of the equilibrium, inhibition and kinetic data allow us to present a model for the structural relation of the epitopes recognized on the T-cells by the two monoclonal antibodies.

Animals↗
PubMed1983

Impairment of membrane phosphoinositide metabolism by aminoglycoside antibiotics: streptomycin, amikacin, kanamycin, dibekacin, gentamicin and neomycin.

Like many amphiphilic cationic drugs, aminoglycosides are able to produce phospholipidosis, mainly by inhibiting enzymes involved in phospholipid metabolism. Phosphoinositides have been suggested to function as receptors for aminoglycosides. Therefore, we investigated the influence of these drugs upon phosphoinositide metabolism by measuring the 32P-incorporation into the polyphosphoinositides, using the rat erythrocyte membrane as a model. Depending upon the experimental conditions, neomycin induced a decrease and/or an increase in the 32P-labeling of triphosphoinositides (TPI) and of diphosphoinositides (DPI), respectively. These variations were rapid and depended upon the drug concentration. At 0.3 mM, neomycin reversed the distribution of radioactivities associated with DPI and TPI without modifying the total radioactivity incorporated. This drug concentration altered neither the Mg++-activated TPI-specific phosphomonoesterase activity nor the Ca++-activated polyphosphoinositide phosphodiesterase activity. It appears likely that the drug inhibits the DPI-kinase activity, by interacting with DPI and thereby lowering the substrate availability. Over the range of concentrations studied (up to 1-2 mM), gentamicin, kanamycin and dibekacin behave as neomycin. However, their effects could be observed only at drug concentrations higher than those of neomycin. By contrast, streptomycin and amikacin did not alter the 32P-labeling of TPI and of DPI. The order of potency of aminoglycosides for the impairment of the phosphoinositide interconversion was neomycin, gentamicin, dibekacin, kanamycin. A possible relationship between the toxicity of aminoglycosides and their capacity to impair the phosphoinositide metabolism is discussed.

Amikacin↗
PubMed1982

Metabolism of phosphoinositides in the rat erythrocyte membrane. A reappraisal of the effect of magnesium on the 32P incorporation into polyphosphoinositides.

The metabolism of phosphoinositides was investigated in the red blood cell membrane of the rat by measuring 32P-incorporation into phospholipids after incubation of membranes with [gamma-32P]ATP in a medium containing magnesium. A new chromatographic procedure has been developed which facilitates the separation of triphosphoinositide, diphosphoinositide and phosphatidylinositol from the phospholipids present in lipid extracts of incubated 'ghost' under our experimental conditions only two phospholipids, diphosphoinositide and triphosphoinositide, were 32P-labelled. Furthermore, the results indicate that either di-or triphosphoinositide could be labelled preferentially, depending upon the magnesium concentration of the incubation medium. This clarifies some apparent discrepancies reported in the literature between the 32 P labelling of polyphosphoinositides observed in intact erythrocytes and that observed with 'ghost' membranes. In addition, the enzymatic pathways involved in the phosphoinositide metabolism are discussed.

Animals↗
PubMed1982

Phospholipid phosphorylation in erythrocyte of spontaneously hypertensive rats.

The rapid turnover of phosphoinositides within membranes suggests that these lipids play an important role in membrane function. Since various abnormalities have been described in the erythrocyte membrane of the spontaneously hypertensive rat (SHR) we have studied the turnover of phosphoinositides in the erythrocyte of SHR and age-matched normotensive Wistar-Kyoto rat (WKY). This was achieved by measuring the incorporation of 32P into inositol lipids after incubation of 1) intact erythrocytes with [32P]orthophosphate and 2) isolated ghost membranes with [gamma-32P]ATP. In both series of experiments more than 99% of the radioactivity incorporated into lipids was into the polyphosphoinositides diphosphoinositide (DPI) and triphosphoinositide (TPI). In both intact erythrocytes and ghost membranes, the levels of 32P incorporated into DPI and TPI were significantly different in SHR than in WKY. Further analysis of factors known to influence the labeling of DPI and TPI indicated that this could be ascribed to decreased activities of phosphatidylinositol kinase and/or DPI kinase, with respect to ATP as substrate. Moreover comparison of data obtained in intact cells with those obtained with ghost membranes suggests that within the SHR erythrocyte, membrane-cytosol interactions may occur that could also be responsible for the alteration of phosphoinositide labeling observed in hypertensive animals. Since phosphoinositides have been reported to be involved in the Ca2+-gating system of membrane, our findings could be associated with the abnormal Ca2+ binding and transport recently described in SHR erythrocyte.

Animals↗
PubMed1981

Vitamin D3 metabolite injections to thyroparathyroidectomized pregnant rats: effects on calcium-binding proteins of maternal duodenum and of fetoplacental unit.

Fetomaternal relationships with respect to vitamin D metabolism were investigated in thyroparathyroidectomized (TPTX) pregnant rats, with or without treatment with different vitamin D3 metabolites. Calcium-binding protein (CaBP) in maternal duodenum was used as an index of 1,25-(OH)2D3 status of the mother. Pregnant rats were TPTX on day 12.5 and CaBP was measured on 21.5 days of gestation by RIA in maternal duodenal mucosa and in the fetoplacental unit (placenta, fetal membranes, and fetal intestine). In the duodenum of TPTX mothers, the CaBP concentration was reduced by 50%. This fall was associated with a decrease of 1,25-(OH)2D in maternal plasma. CaBP in maternal duodenum increased by the administration of 1,25-(OH)2D3 or 1,24,25-(OH)3D3. In contrast, 24,25-(OH)2D3 injections to TPTX mothers were ineffective. In both placenta and fetal membranes, CaBPs decreased by 20% in TPTX mothers and were normalized only in 1.25-(OH)2D3-treated TPTX mothers. In the fetal intestine, CaBP variations paralleled those of maternal duodenal CaBP. The data indicate that plasma levels of 1,25-(OH)2D in TPTX pregnant rats are partly under the control of maternal parathyroid glands, and they support that even in pregnancy, the CaBP concentration in maternal duodenum may well reflect the 1,25-(OH)2D status of the mother. The CaBP synthesis in placenta and fetal membranes are vitamin D-dependent, and their regulation differs from that of intestinal CaBP. It app]ears that 1 alpha-hydroxylase activities of the fetoplacental unit (placenta and fetal kidney) are blunted in TPTX animals and that CaBP synthesis in the fetus depends on the presence of 1 alpha-hydroxylated vitamin D3 metabolites in the mother.

24,25-Dihydroxyvitamin D 3↗
PubMed1980

Intestinal calcium-binding protein. A protein indicator of enterocyte maturation associated with the terminal web.

The vitamin D-dependent calcium-binding protein (CaBP) was studied in relation to the age of the cell, in isolated epithelial cell populations removed from rat duodenum. Alkaline phosphatase and thymidine kinase activities were used as markers to characterize differentiated villus cells and undifferentiated (mitotically active) crypt cells, respectively. CaBP distribution along the length of the villus, as established by radioimmunoassay, appears as a gradient increasing from the crypt to the tip of the villus. CaBP concentration in cells is shown to be (i) negatively correlated with the thymidine kinase activity of cells, and (ii) positively correlated with the alkaline phosphatase activity of cells. This indicates that CaBP is absent in crypt cells and appears in differentiated cells with the development of the brush border. Thus CaBP, like alkaline phosphatase, can be considered as an indicator of enterocyte maturation. These data were also confirmed by studying the cellular localization of the protein. In addition both indirect immunofluorescence and immunoperoxidase staining methods reveal that antibody against CaBP decorates the terminal web, but not the microvilli of the brush border of mature absorptive cells. The results suggest that CaBP may act as a modulator of some Ca2+-mediated biochemical processes at the level of the enterocyte brush border.

Alkaline Phosphatase↗
PubMed1979

Immunocytochemical localization of a calcium-binding protein in the rat duodenum.

The cellular localization of the vitamin D-dependent calcium-binding protein (CaBP) in the duodenum of rat was studied using indirect immunofluorescence and immunoperoxidase-staining methods. Specific positive reaction product, indicative of the presence of CaBP, was exclusively located within the villous part of the duodenal mucosa. Moreover, CaBP was detected mainly within the supranuclear region of the cytoplasm of absorptive cells and also at the level of their basal laminae. CaBP was not demonstrable either in the nuclei or associated with the brush border membrane of absorptive cells. Also, CaBP was neither detectable in goblet cells nor in sub-epithelial layers. When the specific anti-CaBP antiserum was replaced by nonimmune rabbit serum or when it was preabsorbed on a CaBP-Sepharose conjugate, no positive immunostaining was seen. Together with recent biochemical data our observations agree well with the view that CaBP may act as an intracellular "buffer" by protecting the cell against too high Ca2+ concentrations.

Animals↗
PubMed1979

Vitamin D-dependent calcium-binding protein. Changes during gestation, prenatal and postnatal development in rats.

During the perinatal period, calcium metabolism is stressed. As intestinal Ca-binding protein is considered as a molecular expression of the hormonal effect of 1,25-dihydroxycholecalciferol (1,25(OH)2D3), Ca-binding protin measurements may document the vitamin D roles during this period. We describe the variations of Ca-binding protein concentrations in the rat during the last 5 days of gestation, in the maternal duodenum, placentas, fetal membranes and fetal intestines. We also report intestinal Ca-binding protein changes from birth until weaning. The evolution of the maternal intestinal Ca-binding protein, which increases on day 19.5 of gestation, is consistent with that of calcium intestinal absorption and may be explained by increased 1,25(OH)2D3 production. Placental Ca-binding protein rises from day 17.5 until the end of gestation, and may be related to the profile of calcium transfer from mother to fetuses. It is noteworthy that the placental Ca-binding protein is predominantly found in the fetal part of the organ where materno-fetal exchanges occur. The yolk sac synthesizes substantial amounts of Ca-binding protein. In the fetal membranes, Ca-binding protein plateaus from day 17.5 until day 20.5 and decreases on day 21.5. The Ca-binding protein presence in the fetal placenta and in the yolk sac may suggest that these tissues are also targets for vitamin D. In the fetus the intestinal Ca-binding protein s is detected as early as day 17.5 of gestation and increases markedly during the last day of gestation. From birth and during the first 3 weeks of postnatal life, the intestinal Ca-binding protein concentration does not change. It undergoes a sharp rise just at the time of weaning. We have also shown that the specific distribution of Ca-binding protein along the intestine is acquired during intrauterine life and does not change with sucking or weaning. The two main changes of intestinal Ca-binding protein, observed just before birth and at weaning, may reflect the intestinal maturation and/or variations in vitamin D metabolism.

Aging↗