PubMed Health⌕ Search

Biomedical subjects

J M Mato

Publications and source records attributed to J M Mato.

At least 127 records · Page 7Linked to original sources
PubMed1984

Effect of monodansylcadaverine on the synthesis of phosphatidylinositol by rabbit neutrophils.

The present results show that the addition of monodansylcadaverine to rabbit neutrophils stimulates the incorporation of both [3H]inositol and [3H]glycerol into phosphatidylinositol. Monodansylcadaverine also induces the accumulation of phosphatidylinositol 4-phosphate, phosphatidic acid and diacylglycerol. These effects are all dose-dependent and occur at concentrations of monodansylcadaverine which are known to inhibit receptor-mediated endocytosis. Monodansylcadaverine has not effect on phosphatidylinositol hydrolysis or arachidonic acid release, indicating that it acts by increasing de novo synthesis of phosphatidylinositol but not its turnover. It is proposed that the effects of monodansylcadaverine on receptor-mediated endocytosis are mediated, at least in part, by its perturbing effect on lipid metabolism.

Animals↗
PubMed1984

Inhibition of phospholipid methylation by a cytosolic factor.

Rat liver cytosol contains a heat-stable factor which inhibits phospholipid methylation by rat liver microsomes. The effect of this factor on lipid methylation was dose- and pH-dependent. This factor has an Mr of approx. 3200 as estimated by gel filtration. It could not be extracted by chloroform/methanol (2:1, v/v), and its action was inhibited by incubation with subtilisin.

Animals↗
PubMed1984

Phospholipid methylation in pancreatic islets.

Glucose provokes a transient stimulation of phospholipid methylation in rat pancreatic islets, possibly by increasing phospholipid methyltransferase activity. The association of DL-homocysteine and 3-deazaadenosine inhibits phospholipid methylation. The methylation of phospholipids may play a role in the stimulus-secretion coupling for glucose-induced insulin release.

Animals↗
PubMed1983

Beta-adrenergic control of phosphatidylcholine synthesis by transmethylation in hepatocytes from juvenile, adult and adrenalectomized rats.

Changes in isoprenaline-sensitive phospholipid methyltransferase were studied in hepatocytes isolated from juvenile, mature and adrenalectomized rats. Isoprenaline produced greater stimulation of cyclic AMP accumulation in juvenile and mature adrenalectomized rats than in mature animals. Similarly, isoprenaline stimulated phospholipid methyltransferase in juvenile and mature adrenalectomized rats but had no effect in mature animals. Isoprenaline-mediated activation of phospholipid methyltransferase in adrenalectomized rats was time- and dose-dependent. In hepatocytes isolated from adrenalectomized rats incubated with [Me-3H]methionine or [3H]-ethanolamine the addition of isoprenaline increased the amount of radioactivity incorporated into phosphatidylcholine. The activation by isoprenaline of phospholipid methyltransferase was abolished by the beta-blocker propranolol and by insulin. These results indicate that rat liver the occupation of functional beta-receptors causes a stimulation of phospholipid methylation. It is suggested that, as reported previously, cyclic AMP activates phospholipid methyltransferase.

Adrenalectomy↗
PubMed1983

Effect of fatty acid anilides on the generation of arachidonic acid by human polymorphonuclear leukocytes.

The addition of oleoylanilide or linoleylanilide to human polymorphonuclear leukocytes induces a time- and dose-dependent generation of arachidonic acid. Half-maximal effect is caused by a dose of 0.2 mg linoleylanilide/ml. Fatty acid anilides also produce a time- and dose-dependent inhibition of the synthesis of triacylglycerol. Half-maximal effect is caused by 1 microgram linoleylanilide/ml. These results indicate that fatty acid anilides, which have been found in the illegal cooking oil which intoxicated thousands of Spaniards, alter lipid metabolism in human polymorphonuclear leukocytes.

Anilides↗
PubMed1983

Stimulation by epidermal growth factor of phospholipid methyltransferase in isolated rat hepatocytes.

Epidermal growth factor produces a time- and dose-dependent activation of phospholipid methyltransferase activity in hepatocytes isolated from juvenile and mature hepatectomized rats. This treatment however has no effect with hepatocytes isolated from mature or laparotomized rats. Dansylcadaverine (50 microM), an inhibitor of receptor-mediated internalization of epidermal growth factor, has no effect on basal phospholipid methyltransferase but inhibits the stimulation of this enzyme by epidermal growth factor. These results indicate a possible role of phospholipid methylation during liver proliferation.

Aging↗
PubMed1983

Paradoxical effects of adenosine on neutrophil chemotaxis.

Chemotaxis of rabbit neutrophils is most sensitive to inhibition by 3-deazaadenosine, followed by 3-deaza-(+/-)aristeromycin, 3-deaza-(+/-)aristeromycinylhomocysteine, 3-deazaadenosylhomocysteine, and adenosylhomocysteine, in that order. Although adenosine by itself had no effect on the chemotaxis of neutrophils, it essentially abolished the inhibitory effects of 3-deaza-adenosine on chemotaxis and the reduction of nitroblue tetrazolium. Paradoxically, adenosine enhanced the inhibition of chemotaxis by 3-deazaadenosylhomocysteine slightly and that of 3-deaza-(+/-)aristeromycin significantly. Adenosine alone unexpectedly inhibited phospholipid methylation to the same extent as 3-deazaadenosine, and reduced protein carboxymethylation to a lesser degree. The inhibition of these two methylation reactions by 3-deazaadenosine was, however, not substantially altered in the presence of adenosine. Drastic changes in the ratio of adenosylmethionine/nucleosidylhomocysteine were observed in the presence of adenosine, 3-deazaadenosine, 3-deaza-(+/-)aristeromycin, or of adenosine in combination with each of the latter compounds. There was no significant effect on the binding of chemotactic peptide to receptors, or on the ratio of ATP/ADP in cells treated by the analogs. These results suggest that the inhibition of methylation reactions per se is not enough to account for the inhibition of both chemotaxis and the reduction of nitroblue tetrazolium by neutrophils.

Adenosine↗
PubMed1983

Inhibitors of endocytosis perturb phospholipid metabolism in rabbit neutrophils and other cells.

Dansylcadaverine, amantadine, and rimantadine, which have been shown to inhibit the endocytosis of alpha 2-macroglobulin, epidermal growth factor, and vesicular stomatitis virus [Schlegel, R., Dickson, R. B., Willingham, M. C. & Pastan, I. (1982) Proc. Natl. Acad. Sci. USA 79, 2291-2295], were found to decrease phosphatidylcholine synthesis, chemotaxis, and internalization of a formylated peptide but to stimulate the incorporation of inositol into phosphatidylinositol in rabbit neutrophils. Dansylcadaverine decreased phosphatidylcholine synthesis by both the CDP-choline and transmethylation pathways and also inhibited the synthesis of phosphatidylethanolamine by the CDP-ethanolamine pathway. Dansylcadaverine had no effect on the phosphocholine, CDP-choline, or S-adenosyl-L-homocysteine pools but increased 2-fold the S-adenosyl-L-methionine pool. These results suggest that dansylcadaverine in some manner inhibited the condensation of CDP-choline with diacylglycerol to form phosphatidylcholine. Dansylcadaverine also inhibited phosphatidylcholine synthesis in human neutrophils, human fibroblasts, chicken embryo fibroblasts, rat hepatocytes, osteosarcoma cells, and neuroblastoma cells. It did not stimulate phosphatidylinositol synthesis in chicken embryo fibroblasts.

Animals↗
PubMed1982

Inhibition of phosphatidylcholine synthesis by vasopressin and angiotensin in rat hepatocytes.

The addition of 1 microM-vasopressin or -angiotensin to isolated rat hepatocytes induced a fast transient inhibition of the rate of incorporation of [Me-3H]choline into phosphatidylcholine. The cationophore A23187 induced a similar inhibition of phosphatidylcholine synthesis. The addition of micromolar Ca2+ to rat liver microsomes inhibited the activity of CDP-choline: 1,2-diacylglycerol cholinephosphotransferase. This inhibition is due a decrease in the Vmax. of the enzyme without affecting the Km for CDP-choline. It is concluded that Ca2+ regulates phosphatidylcholine synthesis in rat liver.

Angiotensin II↗
PubMed1982

Calmodulin regulation of phospholipid and fatty acid methylation by rat liver microsomes.

The addition of micromolar Ca2+ in the presence of ATP (10 microM) to rat liver microsomes stimulates phospholipid methylation and the formation of fatty acid methyl esters. Our data indicate that calmodulin mediates the effect of Ca2+ on both phospholipid and fatty acid methylation. This evidence includes: 1) chlorpromazine, an inhibitor of Ca2+ effects mediated through calmodulin, prevented the activation by Ca2+ plus ATP of the methylation reactions; 2) isolation of the microsomes in the presence of ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (5 mM), to remove endogenous calmodulin also prevented Ca2+ plus ATP stimulation of both phospholipid and fatty acid methylation; 3) the addition of exogenous calmodulin to microsomes isolated in the presence of 5 mM ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid restored Ca3+ plus ATP stimulation of both classes of lipids: and 4) pre-incubation of liver microsomes with an antiserum against calmodulin prevented the activation of lipid methylation by Ca2+ plus ATP.

Adenosine Triphosphate↗
PubMed1982

Phospholipid turnover during phagocytosis in human polymorphonuclear leucocytes.

We have previously observed that the phagocytosis of zymosan particles coated with complement by human polymorphonuclear leucocytes is accompanied by a time- and dose-dependent inhibition of phosphatidylcholine synthesis by transmethylation [García Gil, Alonso, Sánchez Crespo & Mato (1981) Biochem. Biophys. Res. Commun.101, 740-748]. The present studies show that phosphatidylcholine synthesis by a cholinephosphotransferase reaction is enhanced, up to 3-fold, during phagocytosis by polymorphonuclear cells. This effect was tested by both measuring the incorporation of radioactivity into phosphatidylcholine in cells labelled with [Me-(14)C]choline, and by assaying the activity of CDP-choline:diacylglycerol cholinephosphotransferase. The time course of CDP-choline:diacylglycerol cholinephosphotransferase activation by zymosan mirrors the inhibition of phospholipid methyltransferase activity previously reported. The extent of incorporation of radioactivity into phosphatidylcholine induced by various doses of zymosan correlates with the physiological response of the cells to this stimulus. This effect was specific for phosphatidylcholine, and phosphatidyl-ethanolamine turnover was not affected by zymosan. The purpose of this enhanced phosphatidylcholine synthesis is not to provide phospholipid molecules rich in arachidonic acid. The present studies show that about 80% of the arachidonic acid generated in response to zymosan derives from phosphatidylinositol. A transient accumulation of arachidonoyldiacylglycerol has also been observed, which indicates that a phospholipase C is responsible, at least in part, for the generation of arachidonic acid. Finally, isobutylmethylxanthine and quinacrine, inhibitors of phosphatidylinositol turnover, inhibit both arachidonic acid generation and phagocytosis, indicating a function for this pathway during this process.

1-Methyl-3-isobutylxanthine↗
PubMed1982

Activation of 1-alkyl-2-lysoglycero-3-phosphocholine. Acetyl-CoA transferase during phagocytosis in human polymorphonuclear leukocytes.

1-Alkyl-2-acetyl-sn-glycero-3-phosphocholine can be synthesized either by acetylation of 1-alkyl-2-lyso-sn-glycero-3-phosphocholine or by transcholination of 1-alkyl-2-acetyl-sn-glycerol. Addition of opsonized zymosan to isolated human polymorphonuclear leukocytes induces a fast, transient, up to 10-fold activation of the acetyltransferase reaction without affecting the cholinephosphotransferase pathway. Based on the following results, we propose that the generation of 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine by human polymorphonuclear leukocytes during phagocytosis is mediated by a stimulation of the acetyltransferase reaction: 1) the time course of acetyltransferase activation agrees with it being the enzyme responsible for the synthesis of 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine; and 2) a close correlation exists (r = 0.91) between the generation of 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine in response to various doses of zymosan and the magnitude of acetyltransferase activation.

Acetyltransferases↗
PubMed1982

Modulatory role of cyclic AMP in the release of platelet-activating factor from human polymorphonuclear leucocytes.

Zymosan coated with complement (Zc) was observed to induce a transient elevation of the intracellular cyclic AMP in human polymorphonuclear cells: a two- to three-fold increase was observed within 1 min after stimulation and approached prestimulation levels by 2 min incubation. These changes in cyclic AMP were not associated with significant changes in cyclic GMP levels. Zymosan caused the release of PAF and beta-glucuronidase and particle uptake, which was initiated about 5 min after stimulation. These results suggest that the transient increase in cyclic AMP content might regulate an early event during mediator release. In an attempt to study further the significance of this rise in cyclic AMP, cells were preincubated with various phosphodiesterase inhibitors. Preincubation of the cells with methylisobutylxanthine (MIX, 10(-6) M to 5 X 10(-5) M), theophylline (3 X 10(-5) to 3 X 10(-3) M) or dipyridamole (10(-6) M to 10(-4) M) enhanced the increase in cyclic AMP levels, but resulted in dose-dependent inhibition of Zc-induced mediator release. Particle uptake and beta-glucuronidase release were less sensitive than PAF release to phosphodiesterase inhibitors, which argues in favour of the independence of both phenomena. Synergistic experiments with MIX and cyclic AMP indicate that the effect of this drug is through its action on cyclic AMP levels. These results suggest that while Zc-induced cyclic AMP elevation might occur in an intracellular place critical to its effect; phosphodiesterase inhibitors may elevate cyclic AMP levels throughout the cell and therefore inhibit the biological response.

Blood Coagulation Factors↗