PubMed Health⌕ Search

Biomedical subjects

G Bartosz

Publications and source records attributed to G Bartosz.

At least 19 recordsLinked to original sources
PubMed2005

Melatonin does not affect total antioxidant capacity of blood plasma in vitro.

Although melatonin has been claimed to increase total antioxidant capacity (TAC) of blood serum, this does not seem probable in view of the low physiological concentrations of this hormone in blood, in relation to other antioxidants. This study demonstrates that enrichment of blood plasma with melatonin up to micromolar concentrations does not affect TAC in vitro thus excluding any significant direct contribution of melatonin to TAC of blood plasma.

Antioxidants↗
PubMed2003

The role of multidrug resistance protein 1 (MRP1) in transport of fluorescent anions across the human erythrocyte membrane.

We employed human red blood cells as a model system to check the affinity of MRP1 (Multidrug Resistance-associated Protein 1) towards fluorescein and a set of its carboxyl derivatives: 5/6-carboxyfluorescein (CF), 2',7'-bis-(2-carboxyethyl)-5/6-carboxyfluorescein (BCECF) and calcein (CAL). We found significant differences in the characteristics of transport of the dyes tested across the erythrocyte membrane. Fluorescein is transported mainly in a passive way, while active efflux systems at least partially contribute to the transport of the other compounds. Inside-out vesicle studies revealed that active transport of calcein is masked by another, ATP-independent, transport activity. Inhibitor profiles of CF and BCECF transport are typical for substrates of organic anion transporters. BCECF is transported mainly via MRP1, as proven by the use of QCRL3, a monoclonal antibody known to specifically inhibit MRP1-mediated transport. Lack of effect of QCRL3 on CF uptake excludes the possibility of MRP1 being a transporter of this dye. No inhibition of CF accumulation by cGMP, thioguanine and 6-mercaptopurine suggests also that this fluorescent marker is not a substrate for MRP5, another ABC transporter identified in the human erythrocyte membrane.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2003

Effect of vitamin E and vitamin C supplementation on antioxidative state and renal glomerular basement membrane thickness in diabetic kidney.

The aim of this study was to analyze the effect of vitamins C and E on malondialdehyde (MDA) content and activities of key antioxidant enzymes: superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) as well as glomerular basement membrane (GBM) thickness in streptozotocin-induced diabetic kidney in rats. Wistar male rats were divided into following groups (12 rats each): the control, diabetic rats, diabetic rats whose drinking water was supplemented with vitamin C in a dose of 1.0 g/l or diet was supplemented with 200 mg of vitamin E/100 g fodder. Body weight, blood glucose and HbA1C levels and 24-hour urinary albumin excretion (UAE) were studied every week (0-12 weeks). After 6 and 12 weeks, MDA content and activities of SOD, CAT and GSH-Px were measured in the kidney homogenate supernatants. Electron micrographs of glomeruli were scanned and morphometric investigations were performed by means of computer image analysis system to compare GBM thickness. The blood glucose and HbA1C concentrations and UAE in diabetic rats were significantly higher than in the control group. An increase in the MDA level and decrease in the SOD, CAT and GSH-Px activities in the kidney of diabetic rats were observed after 6 and 12 weeks of experiment. Administration of vitamins C and E did not affect body weight, blood glucose and HbA1C levels. Both vitamin C and vitamin E decreased lipid peroxidation and augmented the activities of antioxidant enzymes studied in the kidneys of diabetic rats as well as reduced UAE, decreased kidney weight and GBM thickness. The results indicate the potential utility of antioxidant vitamins in the protection against the development of diabetic nephropathy.

Albuminuria↗
PubMed2002

The effect of verapamil on the antioxidant defence system in diabetic kidney.

BACKGROUND: The aim of this study was to examine the effect of verapamil (VP) on lipid peroxidation and activities of key antioxidant enzymes: superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px); as well as on glomerular basement membrane (GBM) thickness in streptozotocin-induced diabetic kidney in rats. METHODS: Wistar male rats were divided into three groups, 12 rats each: the control (C), diabetic rats (DR), and DR receiving VP, 7 mg/kg body weight in drinking water (DR + VP). Blood glucose (BG) and HbA(1c) levels, 24-h urinary albumin excretion (UAE) and body weight (BW) were measured every week (0-12 weeks). After 6 and 12 weeks, the animals were sacrificed and malondialdehyde (MDA) content and activities of SOD, CAT and GSH-Px were determined in the kidney homogenate supernatants. Electron micrographs of the glomeruli were scanned and morphometric investigations were performed by means of a computer image analysis system to compare the glomerular basement basal membrane (GBM) thickness. RESULTS: The levels of BG, HbA(1c) and UAE in DR were significantly higher than in the C group. A progressive increase in the MDA level and a decrease in the SOD, CAT and GSH-Px activities in the kidney of DR were observed after 6 and 12 weeks. VP administration did not affect BW changes, BG and HbA(1c) levels in DR. VP decreased lipid peroxidation and augmented the activities of antioxidant enzymes studied in the kidneys of DR as well as decreased kidney weight, GBM thickness and albuminuria in DR. CONCLUSIONS: These results confirm the role of oxidative stress in the development of diabetic nephropathy and point to the possible antioxidative mechanism of the nephroprotective action of VP.

Albuminuria↗
PubMed2002

Assay of total antioxidant capacity: comparison of four methods as applied to human blood plasma.

Four spectrophotometric methods of determination of antioxidant capacity: a method based on the scavenging of the l,1-diphenyl-2-picrylhydrazyl (DPPH) free radical, the "ferric-reducing ability of plasma" (FRAP), a method based on reduction of the 2.2'-azinobis (3-ethylbenzthiazolinesulfonate) free radical (ABTS.+) and a kinetic method based on the oxidation of dihydro-2,7-dichlorofluorescein by 2,2'-azobis(2-amidopropane) (ABAP) were compared with respect to standard antioxidants (ascorbate, glutathione, Trolox and urate) and human blood plasma. Various reactivities of standard antioxidants in different tests were found. glutathione showing a low reactivity in the FRAP assay. Kinetic measurements show that the reduction of indicators, especially by blood plasma, may not be complete at recommended times of the assays and the time of measurement is an important parameter when comparing the results.

Adult↗
PubMed2001

Hemoglobin can nitrate itself and other proteins.

Incubation of human hemoglobin with nitrite and hydrogen peroxide was found to induce autonitration and nitration of another protein (bovine serum albumin), as demonstrated by detection of nitrotyrosine residues in Western blots of separated membrane proteins. Inhibition of nitration by conversion of hemoglobin into the cyanmet form demonstrates that nitration is due to the pseudoperoxidase activity of hemoglobin. Incubation of whole erythrocytes with nitrite and hydrogen peroxide induces nitration of erythrocyte membrane proteins, much stronger when cellular catalase was inhibited with azide. These results suggest that hemoglobin and other hemoproteins may contribute to the tyrosine nitration in vivo.

Erythrocyte Membrane↗
PubMed2001

Light-dependent generation of reactive oxygen species in cell culture media.

Cell culture media (RPMI 1640, Dulbecco's Minimal Essential Medium and yeast extract-peptone-glucose medium) were found to oxidize dichlorodihydrofluorescein diacetate and dihydrorhodamine 123, and to generate spin adduct of 5,5'-dimethyl-1-pyrroline N-oxide, which indicates formation of reactive oxygen species (ROS). The production of ROS was light dependent. The main component of the media responsible for the generation of ROS was riboflavin, but tryptophan, tyrosine, pyridoxine, and folic acid enhanced the effect of riboflavin. These observations point to exposure of cells to ROS under in vitro culture conditions.

Azides↗
PubMed2001

Decreased antioxidant defense during replicative aging of the yeast Saccharomyces cerevisiae studied using the 'baby machine' method.

Replicatively senescent cells of Saccharomyces cerevisiae were obtained using the 'baby machine' method by immobilizing cells on CovaLink NH(2) plates and allowing them to divide while exchanging medium and removing daughter cells. Centrifugation in a Percoll density gradient was employed for further purification of replicatively old yeast cells. Comparison of senescent cells showing more than 20 bud scars with cells from early stationary culture demonstrated a significant reduction of total and reduced glutathione and decrease of superoxide dismutase activity during replicative aging of yeast cells.

Antioxidants↗
PubMed2001

Hypochlorous acid damages erythrocyte membrane proteins and alters lipid bilayer structure and fluidity.

Treatment of human erythrocyte membranes with active forms of chlorine (hypochlorous acid and chloramine T) resulted in a concentration-dependent inhibition of the membrane Na(+), K(+)- and Mg(2+)-ATPases. Membrane protein thiol group oxidation was consistent with inactivation of enzymes and preceded oxidation of tryptophan residues and chloramine formation. Erythrocyte exposure to hypochlorous acid led to complex changes of cell membrane rigidity and cell morphological transformations: cell swelling, echinocyte formation, and haemolysis. The inhibition of ion pump ATPases of human erythrocyte membranes may be due to direct oxidation of essential residues of enzyme (thiol groups) and structural rearrangement of the membrane.

Adenosine Triphosphatases↗
PubMed2001

Antisense hairpin loop oligonucleotides as inhibitors of expression of multidrug resistance-associated protein 1: their stability in fetal calf serum and human plasma.

Multidrug resistance-associated protein (MRP1) is a transmembrane pump protein responsible for the efflux of chemotherapeutic drugs, an important cause of anticancer treatment failure. Trying to circumvent MRP-mediated resistance we designed and synthesized hairpin loops forming antisense oligodeoxyribonucleotides (ODNs), both phosphodiesters (PO-ODNs) and their phosphorothioate analogues (PS-ODNs), to reduce the protein expression by targeting its mRNA in a sequence specific manner. Melting temperature measurements as well as polyacrylamide gel electrophoresis supported the preferential formation of a secondary structure, which was expected to protect ODNs against 3'-exonuclease degradation. ODNs and PS-ODNs designed in this work were successfully tested as antisense inhibitors of the expression of MRP1 in the leukaemia HL60/ADR cell line. Foreseeing the necessity to perform clinical studies with such ODNs we investigated their stability against the 3'-exonuclease activity of fetal calf serum and human plasma. Under the conditions, corresponding to physiological ones, we observed high stability of hairpin loop forming ODNs, especially those containing longer (e.g. 7 base pair) stems. Comparative studies on the stability of chemically unmodified hairpin loop forming ODNs and their PS-counterparts indicated that endonuclease activity did not play any important role in the process of their nucleolytic degradation. Our studies provide strong evidence for high stability of chemically unmodified hairpin loop ODNs, making them an attractive alternative to phosphorothioate analogues commonly used in antisense strategy.

Animals↗
PubMed2000

Dopamine-melanin protects against tyrosine nitration, tryptophan oxidation and Ca(2+)-ATPase inactivation induced by peroxynitrite.

The effects of dopamine-melanin (DA-melanin), a synthetic model of neuromelanin, on peroxynitrite-mediated 3-nitrotyrosine formation, oxidation of tryptophan in bovine serum albumin and inactivation of erythrocyte membrane Ca(2+)-ATPase activity were investigated in the absence and in the presence of bicarbonate. DA-melanin inhibited nitration of free tyrosine, loss of tryptophan residues and Ca(2+)-ATPase inactivation by peroxynitrite in a dose dependent manner. In the presence of bicarbonate, this inhibitory effect was lower for nitration and insignificant for oxidative protein modifications. These results suggest that neuromelanin can protect against nitrating and oxidizing action of peroxynitrite but is a worse protector against the peroxynitrite-CO(2) adduct. As peroxynitrite may be a mediator of neurotoxic processes, the obtained results suggest that neuromelanin may be important as a physiological protector against peroxynitrite.

Animals↗
PubMed2000

Oxidative stress during aging of stationary cultures of the yeast Saccharomyces cerevisiae.

Comparison of 5 d old stationary cultures of Saccharomyces cerevisiae and of cultures aged for 3 months revealed increased generation of reactive oxygen species assessed by 2', 7'-dichlorofluorescin oxidation, decreased activity of superoxide dismutase, decreased content of glutathione and increased protein carbonyl content during prolonged incubation of stationary yeast cultures. These results point to the occurrence of oxidative stress during aging of stationary cultures of the yeast. The magnitude of this stress was augmented in antioxidant-deficient strains, devoid of superoxide dismutases and catalases, and of decreased glutathione content.

Catalase↗
PubMed2000

2,7-dichlorofluorescin oxidation and reactive oxygen species: what does it measure?

Intracellular 2,7-dichlorofluorescin (H(2)DCF) oxidation is often used to measure the production of reactive oxygen species (ROS) within cells. The rate of H(2)DCF oxidation depends on the concentration of glutathione, which is an alternative target for ROS. Our results suggest that increased rate of H(2)DCF oxidation be interpreted as an indication of general oxidative stress due to a variety of reasons, including depletion of antioxidants, rather than as a specific proof of augmented ROS formation.

Enzyme Inhibitors↗
PubMed2000

Inactivation of antioxidant enzymes by peroxynitrite.

Exposure of hemolysates and whole erythrocytes to peroxynitrite (bolus of 50 micromol dm(-3)-2 mmol dm(-3)) was found to inactivate erythrocyte antioxidant enzymes: glutathione peroxidase > superoxide dismutase > catalase. Inactivation of antioxidant enzymes by peroxynitrite may be one reason for the secondary oxidative stress in peroxynitrite-treated cells. When hemoglobin was not converted into the cyanmet form, an apparent activation of glutathione peroxidase activity by peroxynitrite was observed in hemolysates; this effect was artifactual and due to the pseudoenzymatic glutathione peroxidase activity of hemoglobin.

Catalase↗
PubMed2000

Effect of stress on the life span of the yeast Saccharomyces cerevisiae.

A correlation is known to exist in yeast and other organisms between the cellular resistance to stress and the life span. The aim of this study was to examine whether stress treatment does affect the generative life span of yeast cells. Both heat shock (38 degrees C, 30 min) and osmotic stress (0.3 M NaCl, 1 h) applied cyclically were found to increase the mean and maximum life span of Saccharomyces cerevisiae. Both effects were more pronounced in superoxide dismutase-deficient yeast strains (up to 50% prolongation of mean life span and up to 30% prolongation of maximum life span) than in their wild-type counterparts. These data point to the importance of the antioxidant barrier in the stress-induced prolongation of yeast life span.

Cell Division↗