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Biomedical subjects

B Cestaro

Publications and source records attributed to B Cestaro.

71 records · Page 4Linked to original sources
PubMed1980

Hydrolysis of di- and trisialo gangliosides in micellar and liposomal dispersion by bacterial neuraminidases.

The hydrolysis of di- and trisialo gangliosides by bacterial neuraminidases was investigated. Slow rates of hydrolysis were obtained with micellar dispersions of the pure gangliosides; the rates increased considerably with mixtures of ganglioside and phospholipids, such as phosphatidylcholine or sphingomyelin. The greatest rates of hydrolysis were obtained with mixtures containing 5-10 mol% ganglioside and 90-95% phospholipid. With the aid of the nonpenetrating reagent trinitrobenzenesulfonic acid, it was ascertained that this mixture consisted of sealed, unilamellar vesicles in which the ganglioside was distributed symmetrically between the two layers of the liposome. When the relative proportion of the ganglioside was increased, the dispersions contained liposomes admixed with micelles of ganglioside and phospholipid. The rates of hydrolysis of the ganglioside could be correlated with the percentage of sealed vesicles in each mixture. Experiments in which another ganglioside (GM1) or cholesterol was incorporated into the mixed dispersions further supported this conclusion. It is suggested that the rate of hydrolysis is affected predominantly by interactions between the carbohydrate chains of ganglioside molecules. The data emphasize that ganglioside metabolism can be best studied when the latter are part of biological or model membranes.

Clostridium perfringens↗
PubMed1980

Hydrolysis of gangliosides in micellar and liposomal dispersion by bacterial neuraminidases.

Aqueous dispersions of pure gangliosides contain micelles of these compounds. In this dispersion state, the rates of hydrolysis of the neuraminyl residues by bacterial neuraminidases are slowest. Incorporation of gangliosides into mixed dispersion with other lipids or into mixed micelles with bile salts considerably increases the reaction rates. The greatest reaction rates are obtained when di- or trisialogangliosides are incorporated into unilamellar vesicles of lecithin or sphingomyelin.

Clostridium perfringens↗
PubMed1978

Studies on brain cytosol neuraminidase. II. Extractability, solubility and intraneuronal distribution of the enzyme in pig brain.

The origin and properties of cytosolic neuraminidase (acylneuraminyl hydrolase, EC 3.2.1.18) from pig brain were studied. 1. The brain extracts containing the cytosol derived from neuronal bodies and glial cells carry 0.69 munits neuraminidase/g fresh tissue. The behaviour of neuraminidase during extraction closely paralleled that of authentic cytosolic enzyme, lactate dehydrogenase; whereas, it differed from that of the lysosomal enzymes, beta-hexosaminidase and beta-galactosidase, also found in the extracts. 2. Nerve endings from either crude or purified preparations, when treated by hypoosmotic shock, released neuraminidase activity up to a maximum of 1.25 munits/g fresh tissue. The behaviour of releasable neuraminidase was always identical to that of lactate dehydrogenase and very similar to that of ATPase and acetylcholinesterase. Typical lysosomal enzymes, however, such as beta-galactosidase and beta-hexosaminidase, behaved differently under the same conditions. This neuraminidase activity is thought to be derived from the cytosol of nerve endings. 3. The specific activity of neuraminidase in nerve-ending cytosol is 15--20 times that in neuronal body and glial cell cytosol. Some properties (pH, Km value, V/t relationship) of the cytosolic enzymes of different origin are similar; others (stability on standing at 4 degrees C; resistance to freezing and thawing) are different. Hypoionic solutions caused both cytosolic neuraminidases to slowly precipitate and to assume a stable insoluble form which was still active.

Animals↗
PubMed1976

Brain neuraminidases and gangliosides.

A number of data of kinetics nature indicate that brain neuraminidases (the cytosol and the membrane bound enzyme) recognize the physical state of gangliosidic substrate, with immediate modification of the activity. The interactions between the enzyme(s) and the different physical forms of the substrate are still to be studied at the molecular level. The knowledge of these phenomena would greatly help understanding the role played by gangliosides in the neuronal plasma membrane.

Allosteric Regulation↗
PubMed1975

Studies on brain cytosol neuraminadase. I. Isolation and partial characterization of two forms of the enzyme from pig brain.

1. Two forms of cytosol neuraminidase (EC 3.2.1.18) (neuraminidase A and neuraminidase B) were isolated and purified from pig brain homogenate, by proceeding through the following steps: centrifugation of brain homogenate at 105 000 X g (1h); ammonium sulphate fractionation (35-55% saturated fraction); column chromatography on Biogel A 5 m; column chromatography on hydroxy apatite/cellulose gel; affinity chromatography on Affinose-tyrosyl-p-nitrophenyloxamic acid. The separation of the two forms of neuraminidase was provided by chromatography on hydroxylapatite/cellulose gel. Neuraminidase A was purified about 500-fold; neuraminidase B about 400-fold. 2. The pH optima and the maximum activities in various buffers were different for neuraminidase A and B (for instance the pH optimum was in sodium acetate/acetic acid buffer, 4.7 for neuraminidase A and 4.9 for neuraminidase B). Ions affected in a different way the two enzymes: K+ activated neuraminidase A but not neuraminidase B; Na+ and Li+ inhibited neuraminidase A at a higher degree than neuraminidase B. Neuraminidase B seemed to be moderately activated by some bivalent cations (Ca2+; Mg2+; Zn2+); neuraminidase A did not. The Km values for sialyllactose were different: 2.2-10(-3) M for neuramindase A; 0.46-10(-3) M for neuraminidase B.

Animals↗
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↗
PubMedDate not supplied

Mild brain ischemia increases cerebral lipid peroxidation and activates leukocytes in the peripheral blood of rats.

This study evaluated local and systemic leukocyte changes, respectively in the jugular and femoral veins, after an acute reduction of cerebral blood flow (oligoemia) in rats submitted either to permanent bilateral carotid occlusion (BCO) (no. = 36) for 5 hours or to sham operation (no. = 33). In a subgroup of rats (no. = 13) the extent of neural damage was histologically assessed. As a marker of biochemical brain changes the entity of the iron-ascorbate induced lipid peroxidation of synaptosomes was assessed in vitro by measuring malondialdehyde (MDA) reactive products. Five hours after surgery, the percentage of aggregated leukocytes and of activated neutrophils reducing the NBT were significantly higher in BCO rats (p < 0.05). However, leukocyte changes did not differ significantly between the jugular and the femoral districts. The brains of BCO rats showed tiny foci of neuronal necrosis. Synaptosomes obtained from the BCO animals showed a small but highly significant increase of MDA production (p < 0.01). Long-lasting brain oligoemia increases the production of lipid peroxidative metabolites, and causes the occurrence of tiny foci of neuronal necrosis in different brain regions. The lack of a significant gradient in aggregated leukocytes and activated neutrophils between the jugular and femoral venous districts demonstrates that leukocytes are stimulated in the peripheral blood by even mild biochemical and morphological brain damage.

Animals↗