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Biomedical subjects

G Cervato

Publications and source records attributed to G Cervato.

34 records · Page 2Linked to original sources
PubMed1988

N-pyrene dodecanoyl sulfatide as membrane probe: a study of glycolipid dynamic behavior in model membranes.

An N-linked pyrene-dodecanoyl sulfatide was employed to measure the ratio of excimer fluorescence to monomer fluorescence intensities (E/M). The E/M values provided information about both the dynamic behavior and the structural distribution of the labelled glycolipid in note dispersion of micellar sulfatides and multilamellar vesicles of different phospholipids. Most of the labelled sulfatide seems to be located in domains sequestered from the surrounding phospholipids still above the phase transition temperature of the vesicles. The glycolipids sequestered in these domain environments are less sensitive to the structural changes that the addition of cholesterol or Ca2+ can induce in the phospholipid regions during the phase transition.

Fluorescent Dyes↗
PubMed1988

Erythrocyte D-glucose transport activity in reconstituted model membranes of different lipid composition.

The stereospecific influx of D-glucose into liposomes formed on sonication of different glyco- and phospholipids with transport proteins from human erythrocyte ghosts solubilized with Triton x-100 was measured as an index of their total D-glucose transport activity. Specific D-glucose transport increased when acidic phospho- and glycolipids (especially sulfatide) were added to the phosphatidylcholine bilayers of the model membranes while cholesterol strongly inhibited the process. The modulation of D-glucose transport activity and its possible correlation with the lipid composition and the chemico-physical state of the erythrocytes is discussed.

Cerebrosides↗
PubMed1987

Interactions of insulin with sulfatide-containing vesicles of phosphatidylcholine at different pHs.

Positively charged insulin is described to induce aggregation of phosphatidylcholine vesicles containing 10 mol% sulfatide at acidic pH. Techniques including light-scattering, Sepharose chromatography, centrifugation, trapped volume determination, circular dichroism and fluorescence polarization, demonstrate that large amounts of negatively charged insulin remain firmly associated to the vesicles upon raising the pH to 7. This is surprising, since only trace amounts of insulin associate to the sulfatide-containing vesicles upon direct incubation at pH 7. The possible molecular explanation of the phenomenon and the relevance of these findings to the actions of insulin in vivo are discussed.

Circular Dichroism↗
PubMed1987

Preparation of spin-labelled sulfatides for EPR studies on model membranes.

Using the N-hydroxysuccinimide ester of the fatty acids, galactosylceramide I3-sulfate containing a 5-or 16-doxyl-stearoyl residue was prepared in good yield by acylation of the galactosylsphingosine I3-sulfate (lysosulfatide) obtained from the saponification of the bovine brain sulfatide. The EPR behavior of the two semisynthetic sulfatides was analyzed in natural sulfatide micelles and in multilamellar vesicles of egg phosphatidylcholine. The evaluated parameters demonstrate that these spin-labelled sulfatides can be used for the study of sulfatide behavior in lipid structures.

Animals↗
PubMed1986

Fluorospectroscopic studies of mixtures of distearoylphosphatidylcholine and sulfatides with defined fatty acid compositions.

Simple study models characteristic for lamellar organization of distearoylphosphatidylcholine and sulfatide have been prepared for fluorospectroscopic investigations on the influence of these glycolipids on the chemico-physical properties of lecithin bilayers. The motion of 1,6-diphenyl-1,3,5-hexatriene in mixed lecithin-sulfatide bilayers changed with temperature, with the compositional ratio of the two lipids, with the presence of divalent cations such as Ca2+ and with the fatty acid composition of sulfatide moiety. Steady-state fluorescence measurements of the average motion of the fluorophore permit evaluation of the gel to liquid-crystalline phase transition in all these membrane models containing different sulfatides.

Fatty Acids↗
PubMed1986

Calorimetric properties of mixtures of distearoylphosphatidylcholine and sulfatides with definite fatty acid composition.

The thermotropic behavior of multilamellar liposomes prepared from mixtures of distearoyllecithin and sulfatide of definite fatty acid composition, has been studied by DTA calorimetry. The saturated stearoyl- and lignoceroyl-sulfatides do not modify significatively both the delta H and the Tm of the phase transition of the lecithins. These parameters, on the contrary, are decreased by all the sulfatides containing unsaturated fatty acids. A contrasting effect is at last exhibited by alpha-OH-stearoylsulfatide which promotes a decrease in delta H but not in Tm of the phase transition. The possibility that these sulfatide properties can influence the dynamic interactions and the sovramolecular organization of the phospholipid bilayers has been discussed.

Calorimetry↗
PubMed1984

ESR studies of the dynamics of dipalmitoylglycerophosphocholine-sulfatide model membranes.

The effects of sulfatide on the fluidity and surface dynamics of bilayered and micellar model membranes of dipalmitoylglycerophosphocholine containing sulfatide were studied as a function of gel-to-liquid-crystalline state of the lipids by electron spin resonance. 5- and 15-nitroxystearic acid were employed as spinlabel probes for the region close to the surface and that close to the nonpolar core of lipid structures. The sulfatide effect is completely different above and below the gel-to-liquid-crystalline phase transition point, the glycolipid promoting a more disordered state below it and having a condensing effect above the phase transition temperature.

Colloids↗
PubMed1983

Fusion of sulfatide-containing vesicles of phosphatidylcholine.

Positively charged albumin is described as a 'useful tool' to induce both aggregation and fusion of phosphatidylcholine vesicles containing sulfatide. Techniques that include light-scattering, Sepharose chromatography, centrifugation, electron microscopy, trapped volume determination and scanning calorimetry demonstrate that extensive fusion occurs during aggregation when sulfatide concentrations are above 4-5 mol%. The rate of fusion increases with time for 1-2 h, then reaches a plateau. Fusion occurs extensively above the transition temperature of the phospholipid and is strongly inhibited by increasing concentration of vesicle cholesterol. The significance of both membrane fluidity and sulfatide-phospholipid organization in the fusion mechanism are discussed.

Chemical Phenomena↗
PubMed1983

Electron spin resonance studies on the dynamics of phosphatidylcholine-sulfatide model membranes.

The effects of sulfatide on the fluidity and surface dynamics of bilayered and micellar model membranes of egg phosphatidylcholine containing sulfatide were studied by electron spin resonance (ESR). 5-Nitroxystearic acid and 15-nitroxystearic acid were employed as spin-label probes for the region close to the surface and that close to the hydrophobic core of lipid structures. In the vesicular structures, the signals generated by 5-nitroxystearic acid showed that the presence of sulfatide reduced the mobility of the hydrocarbon chains around the probe. The effect increased with increasing glycolipid concentration. The decrease in membrane fluidity was also monitored with the 15-nitroxystearic acid probe, although to a lesser extent. We think that sulfatide causes strong side-to-side head-group interactions on the bilayer surface, causing the lipid chains to assemble in a more rigid fashion, though this effect may be balanced in part by the disordered mechanical coupling of glycolipid acyl chains in the apposite faces of the hydrophobic core of the bilayer. Reduction of this mechanical coupling between apposite lipids when there was transition from a bilayered to a micellar structure resulted in a further increase in the order of the system.

Electron Spin Resonance Spectroscopy↗
PubMed1976

Synthesis of N-acetylcysteine compounds.

The preparation of some anilides, esters and amides of N-acetyl and N,S-diacetyl-cysteine is described. Of the compounds synthesized, particular interest was aroused by the p-hydroxyanilide derivatives of N-acetyl and N,S-diacetyl-L-cysteine owing to their analgesic, antiinflammatory and antipyretic activity.

Acetylcysteine↗
PubMedDate not supplied

Effect of red wine consumption on rat liver peroxidation.

To evaluate the role of wine polyphenols and that of alcohol on lipid peroxidation indexes and membrane composition in the liver, 40 Sprague-Dawley rats were fed for 28 days with a commercial AIN-76 diet to which was added one of four different beverages: red wine, alcohol solution, dealcoholated wine, or water. The beverage provided 26% of the caloric intake. Peroxidation indexes and antioxidative enzymes were determined: no significant differences were detected in catalase and glutathione peroxidase whereas superoxide dismutase was significantly lower in the wine-treated animals (220.3 +/- 15.4 vs. 342.2 +/- 43.0 U/mg protein of controls). The following significant differences in hepatic variables were observed: increased alpha-tocopherol concentration in the alcohol group (0.17 +/- 0.02 vs. 0.11 +/- 0.01 microgram/mg protein of controls); increased concentration of cytochrome P450 in the rats given wine (0.75 +/- 0.06 vs. 0.51 +/- 0.08 nmol/mg protein of the alcohol group); increased concentration of cytochrome b5 in wine and dealcoholated wine treatment groups (0.30 +/- 0.01 vs. 0.23 +/- 0.02 nmol/mg protein of controls). The liver membrane fatty acid composition of the wine and dealcoholated wine groups was similar and showed an increase in the saturated fatty acid percentage and a decrease in the polyunsaturated one. The data presented indicate that the main action of polyphenols seems to be an induction of cytochrome activity and that the modality of red wine administration adopted combined with an adequate diet does not provoke any apparent physiological effect on the animals.

Animals↗
PubMedDate not supplied

In vitro and in vivo studies with anionic sulfatide-liposomes containing adriamycin.

Neutral and negatively charged liposomes containing Adriamycin (ADM) were examined for efficiency of drug entrapment and stability in serum. The greatest entrapment of ADM was obtained with negatively charged liposomes containing sulfatide. Moreover, these sulfatide-containing liposomes were more stable than other liposomes in the presence of serum. Tissue distribution studies indicated that the levels of ADM were increased several-fold in mouse liver and spleen after i.v. injection of the drug entrapped in sulfatide-liposomes, while levels of the drug were significantly diminished in the heart. Finally, the in vivo antitumor activity of ADM in liposomes containing sulfatides resulted in significantly greater survival rates than free ADM or ADM entrapped in liposomes without sulfatides.

Animals↗
PubMedDate not supplied

Bilayer-micelle transition in phosphatidylcholine-sulfatide mixtures.

Sulfatides are membrane-bound glycosphingolipids which tend to associate in micellar forms in water. In this study, combining the data obtained by several techniques, including 31P-NMR, DTA calorimetry, freeze-fracture electron microscopy, trapped volume and turbidity measurements plus enzymatic determination of outer-side "marker ganglioside", have enabled us to establish that bilayered liposomes of phosphatidylcholine formed in the presence of increasing amounts of sulfatide are stable up to 30 mol % glycolipid. Above thus, bilayered lipids progressively start to break up into micellar forms with bilayer-micelle transition complete at sulfatide concentrations above 80 mol %. The gel-to-liquid-crystalline phase transition of a dipalmitoylphosphatidylcholine-sulfatide dispersion is shown to strongly influence the equilibrium between micellar and bilayered forms, the micelles being present at higher concentrations as the fluidity of the system decreases. The possibility that such structural transitions may occur in vivo and effectively contribute to the modulation of some biological properties of the membranes is discussed.

Calorimetry↗
PubMedDate not supplied

Interaction of bilirubin with small unilamellar vesicles of dipalmitoylphosphatidylcholine.

Interaction of bilirubin with phospholipid bilayers was studied at physiological pH above and below the gel-liquid crystalline phase transition of small unilamellar vesicles of dipalmitoylphosphatidylcholine. Chromatographic, calorimetric and 1H-NMR evidences strongly suggest that dianion form of bilirubin binds to the polar heads of the phosphatidylcholines protruding from the outer leaflet of the vesicles, whilst acid bilirubin, which is insoluble in water, is hydrophobically inserted into the lipophilic region of the bilayers. The surface-bound bilirubin is promptly removed from vesicles, whilst the acid form hydrophobically inserted into the vesicles is firmly bound to the membrane in the gel state. This pool of bilirubin could perturb the chemico-physical properties of the membrane (i.e., fluidity, phase transition, etc. ...) thus contributing to perturbation of the biological properties of living cells.

Bilirubin↗
PubMedDate not supplied

Thermotropic behavior of dipalmitoylphosphatidylcholine-sulfatide liposomes.

The thermotropic behavior of multilamellar liposomes prepared from mixtures of sulfatide and dipalmitoylphosphatidylcholine has been studied by DTA calorimetry. The cooperative unit size and the enthalpy change of the main transition decrease concomitant with the increase of the sulfatide-phospholipid mole ratio. The origin of these effects and their dependence on the sulfatide content suggest that the in-plane distribution of sulfatide and the physical state of the lipid bilayer are affected by the sulfatide-phospholipid mole ratio.

Calorimetry, Differential Scanning↗