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Biomedical subjects

P Hochstein

Publications and source records attributed to P Hochstein.

At least 55 records · Page 3Linked to original sources
PubMed1985

t-butyl hydroperoxide-induced perturbations of human erythrocytes as a model for oxidant stress.

Erythrocytes were incubated with t-butyl hydroperoxide in the presence and absence of hemoglobin as a model system for oxidative stress and the alterations in the structure and integrity of the membranes were investigated. The results showed that in the presence of hemoglobin a significant modification in the membrane surface charge was induced but no such alteration was observed in peroxidized hemoglobin-free membranes. As increased hemoglobin oxidation occurred in the erythrocytes, membrane lipid peroxidation diminished, suggesting a protective role for methemoglobin in t-butyl hydroperoxide-induced lipid peroxidation. Electrophoresis on polyacrylamide gels showed modification of the cytoplasmic protein region but no high molecular weight aggregates formed at the concentrations of the hydroperoxide used in this work. The results suggest that the t-butyl hydroperoxide/normal erythrocyte system seems to be an instructive model for membrane perturbations characteristic of oxidative disorders.

Erythrocyte Membrane↗
PubMed1985

Conservation of vitamin C by uric acid in blood.

Urate at physiological concentrations increased the stability of ascorbate in human serum approximately fivefold. These measurements were made by depleting human serum of urate with uricase. In model experiments (using phosphate buffer instead of serum), urate protected against iron-induced ascorbate oxidation and, to a lesser extent, pH-induced ascorbate oxidation. In both human serum and in phosphate buffer, urate exerted its protective effect without itself undergoing measurable oxidation as determined by spectrophotometric and high pressure liquid chromatography (HPLC) techniques. These experiments suggest an important physiological role for urate in preserving ascorbate in blood and other biological fluids.

Ascorbic Acid↗
PubMed1984

Inhibition of microsomal lipid peroxidation by cytosolic protein in presence of ADP and high concentration of Fe2+.

Microsomal lipid peroxidation induced by NADPH, but not by ascorbate, was found to be inhibited by liver cytosol. This inhibition was not dependent on glutathione and was enhanced by ADP in presence of Fe2+ at a concentration of 50 microM or higher. ATP was also effective, but not AMP or cyclic AMP. The cytosolic factor appeared to be a protein as it was heat-labile (greater than 70 degrees C), was non-dialyzable and was precipitated by ammonium sulfate and acetone. It was stable for several months in frozen state and also when heated at 50 degrees C for 10 min. The inhibition by the cytosolic protein was obtained by producing a lag in the activity of lipid peroxidation and was reversed by ceruloplasmin but not by catalase, cytochrome c, hemoglobin or superoxide dismutase. This inhibitory effect by cytosol was limited to formation of lipid peroxides whereas oxygen uptake and NADPH oxidation remained unaffected. Regulation of lipid peroxidation by nucleotide-Fe complexes and cytosolic proteins is indicated by these studies.

Adenosine Diphosphate↗
PubMed1984

Inhibition of free radical-induced DNA damage by uric acid.

Single-strand DNA breaks were produced in isolated rat liver nuclei incubated with 3 separate oxygen free radical generating systems: xanthine oxidase-acetaldehyde plus Fe(II); hematin-R(H)OOH; Fe(II)-H2O2. Uric acid inhibited the induction of damage in the first two systems only. At concentrations below those found in human plasma, it was particularly effective against strand breaks produced by hematin-cumene hydroperoxide. These results offer additional evidence that uric acid may function as a cellular protective agent against superoxide and hydroperoxyl free radical-induced cytotoxicity toxicity.

Acetaldehyde↗
PubMed1984

The effects of isouramil on erythrocyte mechanics: implications for favism.

Isouramil is one of the two aglycones derived from broad beans (Vicia faba) with the capacity to autoxidize and generate hydrogen peroxide. During its incubation with erythrocytes in vitro, it causes a marked decrease in cellular deformability at low shear forces, as measured by cone plate viscometry. At the same time the membrane shear modulus of elasticity, as determined by the dimensions of pressure induced pseudopods (PIPs), is increased. These experiments suggest that alterations in the mechanical properties of erythrocyte membranes may be the basis for changes in cellular deformability and hence, erythrocyte sequestration in G-6PD deficient cells exposed to peroxide-generating agents, such as isouramil.

Barbiturates↗
PubMed1983

Dual effects of ascorbate on serotonin and spiperone binding in rat cortical membranes.

Ascorbate-induced lipid peroxidation, as measured by malonyldialdehyde (MDA) production, caused irreversible decreases in Bmax of both [3H]5-HT and [3H]spiperone binding. CaCl2 (4 mM) inhibited ascorbate-induced MDA formation at ascorbate concentrations greater than 0.57 mM, but not at less than or equal to 0.57 mM. Under the standard assay conditions (5.7 mM ascorbate and 4 mM CaCl2), CaCl2 inhibited the MDA production caused by ascorbate by 88%, and the loss in [3H]5-HT binding by 57%. Ascorbate still decreased [3H]5-HT binding when lipid peroxidation was completely inhibited by EDTA. This additional effect of ascorbate was reversible after washing the membranes. Other reducing agents (dithiothreitol, glutathione, and metabisulfite) also decreased the binding of [3H]serotonin. In contrast, [3H]spiperone binding was not affected by ascorbate in the absence of lipid peroxidation or by other reducing agents. These experiments demonstrate that ascorbate has a dual and differential effect on serotonin binding sites. First, ascorbate-induced lipid peroxidation irreversibly inactivates both [3H]5-HT and [3H]spiperone binding. Second, independent of lipid peroxidation, there is a direct, reversible effect of ascorbate on [3H]serotonin but not on [3H]spiperone binding, which is probably due to the difference in the biochemical nature of the two serotonin binding sites.

Animals↗
PubMed1982

The effect of malonyldialdehyde on erythrocyte deformability.

The addition of malonyldialdehyde (5-20 micro M) to human erythrocytes results in a marked decrease in cellular deformability as measured with a counter-rotating, cone plate Rheoscope when low shear forces (2.5-25 dynes/sq cm) are applied. At high shear forces (125-500 dynes/sq cm), malonyldialdehyde at 5 micro M had no effect on deformability, although at concentrations of 10 and 20 micro M a small but statistically significant decrease was evident. These effects of this crosslinking agent are observed in the absence of alterations in cell volume and intracellular viscosity. The results obtained are in accord with the view that the polymerization of membrane constituents may contribute to the events that lead to the removal from the circulation of either aging cells or cells exposed to peroxidation-initiating agents.

Erythrocytes↗