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Biomedical subjects

G Bartosz

Publications and source records attributed to G Bartosz.

At least 73 records · Page 4Linked to original sources
PubMed1995

Resistance to ionizing radiation and antioxidative defence in yeasts. Are antioxidant-deficient cells permanently stressed?

Radiation sensitivity of the yeast (Saccharomyces cerevisiae) strains defective in catalase and superoxide dismutase, and of decreased level of glutathione was compared. Small differences in the radiation sensitivity pointed to the highest sensitivity of the wild-type strain as compared with the antioxidant-defective mutants. Heat shock increases the radiation resistance to a different extent, the response being highest in the wild-type strain and lowest in the glutathione-deficient strain. Catalase induction by heat shock follows the same pattern, significant activity of this enzyme being detectable in the glutathione-deficient mutant under normal growth conditions. These results suggest that compensatory induction of elements of the antioxidant defence system may occur in yeast mutants deficient in antioxidants under normal growth conditions.

Acatalasia↗
PubMed1995

Peroxides inhibit the glutathione S-conjugate pump.

Tert-Butyl hydroperoxide (100-300 microM) was found to inhibit the active efflux of dinitrophenyl-S-glutathione (DNP-SG) from human erythrocytes. From among amino acid peroxides generated by irradiation of amino acid (proline, valine and leucine) solutions, valine hydroperoxide (150 microM) had a similar effect on the DNP-SG transport. As the transport of glutathione S-conjugates is an important step of cellular detoxication, these results indicate that oxidative stress may impair cellular resistance to chemical stress of other kinds. t-Butyl and amino acid peroxides upon interaction with hemoglobin and whole erythrocytes produce free radicals which may be responsible for the damage to the glutathione S-conjugate pump of the erythrocyte membrane.

Biological Transport, Active↗
PubMed1995

What determines the antioxidant potential of yeast cells?

Reactivity which organic radicals was compared in yeast (Saccharomyces cerevisiae) strains defective in catalase and superoxide dismutase, and with a decreased level of glutathione. Yeast cell homogenates did not show considerable strain-related differences in the ability to scavenge nitroxide (TEMPO) stable free radicals and alkoxyl free radicals generated by decomposition of the free radical initiator AAPH. The "total antioxidant status" based on scavenging of ABTS free radicals showed a good correlation with the radiation resistance of the yeasts. These results point to the importance of other factors, apart from antioxidative enzymes and glutathione, in the determination of cellular resistance to ionizing radiation and other types of free-radical stress.

Acatalasia↗
PubMed1995

Nitrite-induced export of glutathione disulfide from erythrocytes.

Export of glutathione disulfide (GSSG) from human erythrocytes induced by several agents (H2O2, t-butyl hydroperoxide, phenazine methosulfate and NaNO2/) was compared. NaNO2 treatment was found optimal for induction of GSSG transport. GSSG was exported from NaNO2-treated erythrocytes mainly via the low-affinity kinetic component. The transport rate increased with increasing pH in the pH range of 6.5-8.0. The transport was inhibited by fluoride, vanadate and intracellular DNP-SG. On the basis of the obtained results, a possibility of existence of one common low-affinity transporter for glutathione S-conjugates and GSSG is discussed.

Biological Transport↗
PubMed1995

Stimulation of erythrocyte membrane Mg(2+)-ATPase activity by glutathione S-conjugates.

Pig erythrocyte membrane Mg2+-ATPase activity was stimulated by various glutathione S-conjugates. For alkyl S-conjugates, the Km for the stimulation was lower, the more hydrophobic was the conjugate. 2,4-Dinitrophenyl-S-(N-acetyl)cysteine also stimulated the Mg2+-ATPase activity, suggesting a low specificity of the ¿glutathione S-conjugate pump¿. The Km values for the stimulation by 2,4-dinitrophenyl conjugates were lower than predictable on the basis of hydrophobicity which indicates a high affinity of the transporter for these conjugates.

Acetylcysteine↗
PubMed1994

Stimulation of erythrocyte membrane Mg(2+)-ATPase activity by dinitrophenol and other membrane-disturbing agents.

Erythrocyte membrane Mg(2+)-ATPase activity was stimulated by echinocytogenic agents (2,4-dinitrophenol and salicylate), a stomatocytogenic agent Triton X-100 and other membrane-disturbing agents including hydrophobic organic anions, alcohols and detergents. Various possible mechanisms of the stimulation are possible but apparently most probable one consists in induction of membrane phospholipid scrambling by the compounds studied (as demonstrated for DNP) and of aminophospholipid translocase (flippase) activity.

2,4-Dinitrophenol↗
PubMed1994

The interactions of modified lipoproteins with human erythrocyte membranes.

The interactions of native and modified lipoproteins with erythrocyte membranes were studied via electron paramagnetic resonance (EPR). The in vitro incubation of minimally oxidized and glycated low density lipoprotein (LDL) with erythrocyte membranes of normal subjects induced a slight rigidification of the membrane lipids. The glycated LDL also caused alterations in conformation of normal and diabetic erythrocyte membrane proteins. In contrast both oxidized and glycated high density lipoprotein (HDL) caused no significant changes in the organization of membranes. These, new findings suggest that the modified LDL may influence the structure of erythrocyte membrane components.

Diabetes Mellitus↗
PubMed1993

Erythrocyte behavior in free-flow electrophoresis is independent of erythrocyte age.

Enzyme activities (acetylcholinesterase, fluorescein diacetate hydrolase, superoxide dismutase), membrane protein band 4.1a/4.1b ratio and density of various fractions of rabbit erythrocytes separated did not show differences between various fractions of erythrocytes separated by free-flow electrophoresis. Also, electric field deflection of lightest and densest fractions of erythrocytes did not differ. These results point to the lack of changes in surface charge density during in vivo erythrocyte aging.

Acetylcholinesterase↗
PubMed1993

Organic anions exhibit distinct inhibition patterns on the low-Km and high-Km transport of S-(2,4-dinitrophenyl)glutathione through the human erythrocyte membrane.

The low-Km and high-Km components of S-dinitrophenyl-glutathione (DNPSG) uptake by inside-out vesicles of human erythrocytes show different pH profiles and inhibition properties with organic anions. Both components are competitively inhibited by various polyvalent anions, including glutathione conjugates, conjugated steroid hormones and bile salts, and bilirubin ditaurate. A variety of monovalent anions, including glucuronidated and sulphated drugs and taurocholate, inhibit the high-Km system only. Taurocholate is taken up by the erythrocyte vesicles in an ATP-dependent manner. The anionic dyes fluorescein, Indocyanine Green and bromosulphophthalein inhibit the low-Km system competitively and the high-Km system non-competitively. The study shows that interactions between different types of biologically occurring conjugates can occur at the level of the transport step out of erythrocytes. The kinetic properties suggest overlapping substrate specificities for the two systems, in which the low-Km component is physiologically more important for transport of glutathione conjugates and polyvalent organic anions, whereas the high-Km component is of significance for transport of monovalent organic anions. Low- and high-Km transport of DNPSG is also observed in plasma membrane vesicles from rat, pig and bovine erythrocytes.

Animals↗
PubMed1993

Increased generation of superoxide radicals in the blood of MS patients.

Increased generation of superoxide radical (O2-) in the blood stimulated with phorbol myristate acetate (PMA) has been found in multiple sclerosis (MS) patients. All the subjects studied were non-smokers and received the same hospital diet. In the MS group treated with prednisone superoxide radical generation was lower than in untreated patients, but was still above the level of O2- generation in controls. Plasma lipid peroxidation products, measured as thiobarbituric-reactive substances, were slightly elevated in both prednisone treated and non-treated MS patients in comparison with controls. Erythrocyte superoxide dismutase activity (SOD) was at the same level in MS and control groups. These results suggest that increased generation of reactive oxygen species may occur in MS patients during acute relapse. This phenomenon may be involved in the pathomechanism of demyelinating disorders.

Adult↗
PubMed1993

Neutral serine proteinase and metalloproteinase strongly bound to human erythrocyte membrane.

Human and bovine erythrocyte ghosts contain a proteolytic system strongly related to membranes. Two proteinases were isolated from human erythrocyte ghosts depleted in most peripheral proteins by extraction with Triton X-100, chromatography on DEAE-cellulose and preparative electrophoresis (SDS-PAGE). The enzymes which were strongly bound to membrane serine proteinase (relative molecular weight 23 kD) and metalloproteinase (28 kD), are probably the integral membrane proteins.

Chromatography, DEAE-Cellulose↗
PubMed1992

Low- and high-Km transport of dinitrophenyl glutathione in inside out vesicles from human erythrocytes.

Kinetic studies on the low- and high-Km transport systems for S-2,4-dinitrophenyl glutathione (DNP-SG) present in erythrocyte membranes were performed using inside-out plasma membrane vesicles. The high-affinity system showed a Km of 3.9 microM a Vmax of 6.3 nmol/mg protein per h, and the low-affinity system a Km of 1.6 mM and a Vmax of 131 nmol/mg protein per h. Both uptake components were inhibited by fluoride, vanadate, p-chloromercuribenzoate (pCMB) and bis(4-nitrophenyl)dithio-3,3'-dicarboxylate (DTNB). The low-Km uptake process was less sensitive to the inhibitory action of DTNB as compared to the high-Km process. N-Ethylmaleimide (1 mM) inhibited the high-Km process only. The high-affinity uptake of DNP-SG was competitively inhibited by GSSG (Ki = 88 microM). Vice versa, DNP-SG inhibited competitively the low-Km component of GSSG uptake (Ki = 3.3 microM). The high-Km DNP-SG uptake system was not inhibited by GSSG. The existence of a common high-affinity transporter for DNP-SG and GSSG in erythrocytes is suggested.

Biological Transport↗
PubMed1992

Irradiation increases proteolysis in erythrocyte ghosts: a spin label study.

X- and gamma-irradiation of human erythrocyte membranes (250-1000 Gy) was found to decrease the ratio of weakly to strongly immobilized signal height of membrane-bound maleimide spin label (Mal-6). Subsequent incubation of spin-labeled membranes at ambient temperature (21 degrees C) induced a progressive increase in this ratio, faster for membranes irradiated with low doses which was hampered by protease inhibitors. These results demonstrate that ionizing radiation stimulates proteolysis of erythrocyte membrane proteins by membrane-associated proteases.

Blood Proteins↗
PubMed1991

Scanning tunneling microscopy of human erythrocyte membranes.

Images of surfaces of human erythrocyte ghosts, lecithin liposomes, spectrin, erythrocyte membrane skeleton, concanavalin A and concanavalin A--decorated erythrocyte ghosts were obtained by scanning tunneling microscopy. The dimensions and surface topography of some membrane structures are described and discussed.

Concanavalin A↗
PubMed1991

Decreased oxidant-induced proteolysis in erythrocytes with enhanced antioxidative defence enzymes due to Down's syndrome.

Erythrocytes of Down syndrome patients, having increased activity of superoxide dismutase and glutathione peroxidase, showed a similar increase in intracellular proteolysis upon stimulation with 1 mmol/l phenylhydrazine than normal erythrocytes. There were no differences in the magnitude of Heinz body formation following the treatment or in the proteolysis of exogenous oxidized substrate. These results demonstrate a protective role for endogenous antioxidative enzymes in the protein damage by oxidative stress which triggers intracellular proteolysis.

Adult↗
PubMed1991

Consequences of the presence of elongated variant of the major transmembrane protein (Band 3 protein) in the human erythrocyte.

Among 56 persons studied, 6 were heterozygous with respect to the elongated variant of the Band 3 protein (anion transporting protein) of the erythrocyte membranes. Erythrocytes containing the variant Band 3 protein did not exhibit morphologic abnormalities, alterations in electron spin resonance spectra of maleimide-spin labeled membranes. In the rate of membrane 'self-digestion' or in chloride permeability. They did however show an increased membrane binding of hemoglobin and aldolase.

Anion Exchange Protein 1, Erythrocyte↗