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Biomedical subjects

G Bartosz

Publications and source records attributed to G Bartosz.

At least 19 recordsLinked to original sources
PubMed1995

Transport of bimane-S-glutathione in human erythrocytes.

Export of glutathione S-conjugate of bimane (BSG) was studied in human erythrocytes. Characteristics of the BSG transport is similar to that of dinitrophenyl-S-glutathione (DNP-SG). BSG transport has two kinetic components, one of high affinity and low capacity (Km = 7.4 +/- 0.2 mumol/ml cells, Vm = 2.7 +/- 0.1 nmol/min per ml RBC) and another of low affinity and high capacity (Km = 242 +/- 8 mumol/ml cells, Vm = 9.6 +/- 1.6 nmol/min per ml RBC). BSG export is inhibited by vanadate (Ki = 65 +/- 6 microM) and fluoride (Ki = 11.4 +/- 0.8 mM). Activation energy of the transport is 67 +/- 7 kJ/mol. BSG transport is independent of membrane potential; its rate increases with pH in the pH range of 6-8, in line with the assumption that the anionic conjugate is cotransported with proton. BSG import to erythrocyte membrane inside-out vesicles is stimulated by ATP. Fluorimetric measurements of BSG export require low amounts of cells and may also be useful for other cell types as an alternative to studies of glutatione S-conjugate transport using radioactive substrates.

Biological Transport↗
PubMed1995

Effect of inhibitors on the transport of dinitrophenyl-S-glutathione in human erythrocytes.

Effect of inhibitors on and pH dependence of the export of dinitrophenyl-S-glutathione (DNP-SG), a glutathione S-conjugate formed upon in vivo conjugation of 1-chloro-2,4-dinitrobenzene to glutathione, was studied in intact human erythrocytes. The transport was inhibited by orthovanadate (IC50 = 80 microM) and fluoride (IC50 = 9 nM). Erythrocyte anion exchange (Band 3) protein inhibitors DIDS and SITS did not exert any significant effect on the transport. The transport rate increased with increasing extracellular pH in the range of 6.0-8.0. The Arrhenius activation energy of the process was 72.4 +/- 1.3 kJ/mol. Membrane potential, extracellular sodium/potassium concentration ratio and extracellular osmolality in the range 300-600 mOsm did not influence the export rate.

Biological Transport↗
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↗
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↗
PubMed1991

Interaction of ethanol and xylene in their effects on erythrocytes and other haematological parameters in the rat.

Rats were given ethanol in drinking water for 8 months, followed by inhalation exposure (5 h daily) to 12,000 mg m-3 xylene for 9 days. Combined exposure to xylene and ethanol induced the same changes in the haematological, biochemical and biophysical parameters of the erythrocyte membrane as those found previously in our experiment with toluene-ethanol. Macrocytosis, a decrease in sedimentation rate and erythrocyte packing difference, as well as decreased fluidity of the erythrocytes membrane in the middle zone of the lipid bilayer, were the most significant changes of exposure to ethanol and xylene.

Animals↗
PubMed1991

Spin label detection and free radical nature of DNA damage by hydralazine.

1. Incubation with hydralazine was shown to induce degradative changes of calf thymus DNA spin-labeled with 3-(2-bromoacetamido)-2,2,5,5-tetramethyl-1-pyrrolidono-1-oxyl and 4-(2-bromoacetamido)-2,2,6,6-tetramethylpiperidino-1-oxyl detectable from electron spin resonance specta. 2. Hydralazine, especially in the presence of Fe2+ induced formation of thiobarbituric acid (TBA)-reactive DNA degradation products. 3. The formation of TBA-reactive products was prevented by catalase, EDTA and scavengers of .OH radicals and enhanced by superoxide dismutase which suggests that .OH radicals formed by the Fenton mechanism mediate the DNA damage by hydralazine-Fe2+.

Catalase↗
PubMed1991

Hydralazine stimulates production of oxygen free radicals in Eagle's medium and cultured fibroblasts.

The effect of hydralazine on the oxygen free radical production was studied in whole cultured murine liver fibroblasts and mitochondrial and microsomal fractions of the cells by ESR spin trapping with DMPO and measurement of Tiron semiquinone formation. Hydralazine itself was found to generate free radicals in phosphate buffer and especially in Eagle's Minimal Essential Medium. Most of the adduct of the spin trap DMPO was due to its reaction with hydralazine-induced hydroxyl radical. Moreover, this compound stimulated free radical formation in fibroblasts. These data suggest that hydralazine alters the cellular free radical metabolism which may have implications for the biological activity of this drug.

Animals↗
PubMed1991

Effect of hyperthermia and lipid peroxidation on the erythrocyte membrane structure.

The hyperthermic exposure (39-49 degrees C) of human erythrocyte membranes augmented their lipid peroxidation stimulated by 0.1 mM FeCl3 + 1.5 mM ascorbate while having no significant influence on the non-stimulated lipid peroxidation. No effect of hyperthermia and lipid peroxidation on the post-exposure fluidity of the erythrocyte membrane lipids was found by the fluorescence anisotropy of hexatriene and trimethylaminophenylhexatriene, and excimerization efficiency of pyrene. Exposure to iron/ascorbate increased the accessibility of membrane protein tryptophan residues to acrylamide as judged by fluorescence quenching. These results suggest a higher sensitivity of membrane protein organization than of membrane lipid fluidity to the effect of the system inducing lipid peroxidation.

Ascorbic Acid↗
PubMed1991

Erythrocyte aging: physical and chemical membrane changes.

The mammalian erythrocyte is an interesting model for studies of membrane aging. Experimental approaches to this problem involve, first of all, comparison of properties of erythrocytes separated by density because red blood cell age correlates with density in principle. Other approaches to study red cell membrane aging, such as hypertransfusion, are also discussed. A number of physical and chemical changes occur in erythrocytes with aging. Crucial to the elucidation of aging mechanisms is to determine which are primary and which are secondary. Immunoglobulin G binding triggers cellular removal and seems necessary for the recognition of senescent erythrocytes. Cellular deformability decreases while fragility to hemolytic factors generally increases and surface charge density does not alter. Perhaps more important are reactions of reactive oxygen species with membrane constituents and subsequent proteolysis. These are implicated as causative factors in red cell aging, immunoglobulin binding and recognition of senescent erythrocytes.

Animals↗
PubMed1990

Hyperthermia, unlike ionizing radiation and chemical oxidative stress, does not stimulate proteolysis in erythrocytes.

1. Oxidative stress by phenazine methosulfate stimulated proteolysis in erythrocytes. 2. Gamma-irradiation of erythrocytes in the range of 50-1000 Gy also resulted in the induction of proteolysis. 3. Though it has been suggested that hyperthermia imposes an oxidative stress on a cell, hyperthermic exposure of erythrocytes (30 min, 39-49 degrees C) did not stimulate proteolysis during subsequent incubation of whole cells or hemolysates. 4. Proteolytic degradation of spectrin was accelerated during incubation of membranes isolated from cells heated above 45 degrees C but this effect seems to be due rather to thermal denaturation of spectrin than to oxidative modification of cellular proteins by hyperthermia.

Amino Acids↗