G Bartosz

..Reduction of oxidation products rather than inhibition of their formation may be the predominant mode of action of antioxidants in various assays of antioxidant activity...

..One reason for the discrepancy of results is the use of different oxidants in NEAC assays. The use of hydroxyl radical as the oxidant is not recommended in view of the high and non-specific reactivity of this species...

..Restoration of proper ROS signaling, especially inhibition of cellular sources of ROS, may thus provide new ways of therapy...

..The limits imposed by these difficulties on the precise evaluation of the amounts and rates of formation of ROS are discussed critically...

..A 10-min assay allows for determination of the induction time of appropriately diluted sample. As examples of application of this method, PRTC values of several types of beverages are reported...

..Membranes exposed to peroxynitrite showed aggregation and nitration of proteins and changes in protein organization detectable with a maleimide spin label...

..These results support the idea that more reactive species than hydrogen peroxide and superoxide are critical in the induction of luminol chemiluminescence...

..These results corroborate our previous results on compensatory antioxidant mechanisms in the mutant yeast strains...

..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...

..The magnitude of this stress was augmented in antioxidant-deficient strains, devoid of superoxide dismutases and catalases, and of decreased glutathione content...

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..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...

..The results obtained provide demonstration with respect to yeast that the ability to lower redox potential and to maintain critical thiol groups in the reduced state is an important facet of the action of antioxidants...

..Glutathione was unable to prevent the increase in ROS production caused by CdCl(2). The Deltaure2 disruptant was also hypersensitive to heat shock, like mutants lacking glutathione S-transferases...

..HOCl was found to affect the redox state of A549 by oxidation of GSH, inactivation of antioxidant enzymes and increase of ROS generation...

..These observations point to exposure of cells to ROS under in vitro culture conditions...

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..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...

..Taken together, these data suggest that yeast flavohemoglobin does not contribute to cross-protection against oxidative and nitrosative stress...

..Generally, the reactivity of at least some N-chloroamino acids may be not much lower with respect to HOCl/OCl(-)...

..These results demonstrate that permeation in the anionic form may be a minor pathway in the membrane transport of the peroxynitrite anion/peroxynitrous acid couple, especially in membranes reach in anion exchangers or channels...

..These results demonstrate a protective role for endogenous antioxidative enzymes in the protein damage by oxidative stress which triggers intracellular proteolysis...

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..The cellular effects of quercetin are therefore complex and include both antioxidant effects and induction of oxidative stress due to formation of reactive oxygen species in the extracellular medium...

..It suggests that repair of low-redox potential targets rather than prevention of their damage by superoxide is important in the antioxidant protection against oxidative stress induced by hypertonic conditions...

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..The results are compatible with the view that cytotoxic effects of peroxynitrite involve formation of secondary reactive oxygen species...

..No increased formation of reactive oxygen species was detected in cells exposed to allyl alcohol, so oxidative stress is due to depletion of cellular thiols and thus alteration in the redox state of yeast cells...

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..As the multidrug resistance-associated protein (MRP) is responsible for the transport of glutathione S-conjugates in mammalian cells, these results point to the possibility of the effect of peroxynitrite on the MRP function...

..Cell survival was augmented, and changes in biochemical parameters were ameliorated, by addition of exogenous antioxidants (ascorbic acid, glutathione and melatonin) in both strains...

..These results point to a complication of cellular effects of antioxidants by their prooxidative effects and to the usefulness of cellular tests to evaluate the biological effectiveness of antioxidants...

..Deletion of the YHB1 gene was found to augment the reduction of Fe(3+) by yeast cells which suggests that flavohemoglobin participates in regulation of the activity of plasma membrane ferric reductase(s)...

..Collectively, our data demonstrate that hypersensitivity to the Deltagrx1Deltagrx2 and Deltagrx5 disruptants to selenite is mediated by altered intracellular redox equilibrium...

..The pro-oxidant action of nitroxides at micromolar concentrations may be important in view of the proposed use of these compounds as 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...

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..There was no clear-cut dependence between the ability of various chemicals to deplete cellular GSH and their increased toxicity to a glutathione-poor mutant...

..Such nonspecific effects of curcumin on cellular membranes would produce artifacts of apoptosis measurement, since several methods are based on membrane changes...

..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...

..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...

..These results demonstrate that LIP is a significant factor determining the rate of intracellular H(2)DCF oxidation...

..These results are consistent with a role for oxidative damage during replicative senescence of Saccharomyces cerevisiae...

..These results point to the necessity of a careful interpretation of experiments in which the inhibition of free radical reactions by antioxidants is used as a proof of involvement of metal ions in a reaction...

..decolourization assay and the ferric ion reducing anti-oxidant power assay. 3. We found that components of the media such as cysteine, tyrosine, tryptophan and Phenol Red are important contributors to the TAC of cell culture media...

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..On the other hand, a simultaneous presence of a nitric oxide source and a superoxide or hydrogen peroxide decreases or increases the fluorescence of DAF-FM, respectively, resulting in biased estimates of nitric oxide production...

..This phenomenon has to be taken into account when designing treatments for lung cancer, especially for patients treated simultaneously with glucocorticoids against inflammatory symptoms...

..In whole erythrocytes, these changes were not stable and disappeared during longer incubation...

..These findings suggest that overexpression of MRP1 does not confer increased resistance to oxidative stress...

..Proapoptotic action of DPI was observed 12 h after incubation with this compound...

..A possible explanation for this effect is proposed...

..The stoichiometry of the MRP/HOCl reaction was 1:1. These results demonstrate that MRP can be one of the cellular targets for the inflammatory mediator hypochlorous acid...

..Antioxidant capacity of blood plasma (anticoagulated with EDTA) of healthy persons was found to be 559+/-49 micromol/l and 11.6+/-1.2 mmol/l of ascorbic acid equivalents for peroxynitrite and hypochlorite, respectively...

..These results point to a pro-oxidative effect of nitroxides on a range of biomolecules subjected to the action of various oxidants...

..These results indicate that TEMPO may act as an oxidant to erythrocytes, whilst extracellular ferricyanide protects against its effects...

..Monitoring changes of concentration of hydrogen peroxide incubated with melatonin using Xylenol Orange points to poor reactivity of melatonin with H2O2...

..These results show that estimation of TAC of cell extracts may be a useful parameter of assessment of oxidative stress, primarily of oxidation of thiol groups, yielding information different than TAC of body fluids...

..Apart from estrogens and androgens,thyroid hormones, and IGF-1 also take part in the stimulation of seladin-1 expression...

..These results suggest that hemoglobin and other hemoproteins may contribute to the tyrosine nitration in vivo...

..However, apparently beneficial effects of peroxynitrite have also been described, among them formation of nitric oxide and nitric oxide donors in reactions of peroxynitrite with thiols and alcohols...

..Chlorohydrins showed also a stronger hemolytic action, proportional to the lipid:erythrocyte ratio. These results are important for understanding the effects of HOCl on mammalian cells, such as might occur in inflammatory pathology...

..Additionally, we employed the PRINS technique to monitor oxidant-mediated changes in the nucleolar structure. Taken together, our results suggest the role of the yeast nucleolus in the response to oxidative stress signals...

..05). Collectively, we demonstrated that Tempol can be considered as a potent anti-apoptotic and antigenotoxic agent, but also as a cytotoxic and clastogenic chemical, depending on the concentration applied...

..Although amino acids act as scavengers of hypochlorite in plasma, the chlorinated products formed stay reactive and the pattern of their action on cells in vitro is similar to that of hypochlorite...

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..cerevisiae...

..These results show that carnitine has a direct antioxidant action against physiologically relevant oxidants...

..The destruction of amine groups content was evident for AlaCl, LysCl and SerCl. The formation of protein aggregates was observed, due mainly but not exclusively to the formation of disulphide bonds...

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..The subadditive interactions between antioxidants may affect quantitative considerations drawn from in vitro assays of antioxidant capacity of biological samples...

..These results point to another type of possible artefact of cell culture, viz. stimulation of cell proliferation by low concentrations of oxidants...

..5 mM and 6 mM, respectively, disappearing at higher concentrations of these compounds, pointing to the detection of not only protective but also toxic cellular effects of the compounds studied by the test proposed...

..These results suggest a role for superoxide-mediated membrane damage in the cytotoxic action of anthracycline antibiotics...

..Beta-carotene did not contribute discernibly to the antioxidative properties of the extracts, while lycopene had a significant contribution to the scavenging activity of methanolic mushroom extracts...

..Peroxynitrite was found to induce the release of K+ via the Na+/Cl- cotransport system, as do other oxidants. Since peroxynitrite is formed in vivo, its presence could contribute to a pathological dehydration of red blood cells...

..Lower TAC values were found for the saliva of smokers than for that of non-smokers. Drinking of a cup of instant coffee increased the hydrogen peroxide content of urine but did not decrease the TAC of urine...

..These results indicate that the increase in the mother cell volume, intrinsic to the asymmetric cell division in S. cerevisiae, may be the main mechanism limiting the reproductive capacity of in this organism...

..A similar phenomenon may limit the number of cell divisions of cultured mammalian cells. The term replicative (generative) aging may be therefore illegitimate...

..These results suggest that limitation of the division potential in the yeast is not due to a counter of cell divisions but is of growth/metabolic nature, perhaps involving attaining a limitation of cell volume...

..Taken together, it can be concluded with great certainty that novel deprenyl-related JSAKs might be especially good candidates for further anticancer investigations in vitro and in vivo and future pharmacological applications...

..We showed that caffeine used at the same concentrations manifests a more potent cyto- and genotoxic effect that may account, at least in part, for the disadvantageous effects observed for yerba mate extract...

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..We interpret this finding as due to inactivation of some important element of aldehyde detoxification by increased flux of superoxide in DeltaCuZnSOD mutants...

..This phenomenon indicates that attaining an excessive volume may be a factor contributing to the limitation of cellular divisions of yeast cells...

..These findings are followed by a general discussion of the biological relevance of apoptosis in yeast...

..We aimed to evaluate the total antioxidant capacity (TAC) of saliva in healthy Helicobacter pylori-positive and negative saliva individuals...

..No evidence of an effect of glutathione (at levels up to 20 microM) on the partition coefficient of doxorubicin was found in the pH range of 4.0-7.4. These results indicate that non-covalent doxorubicin-glutathione complexes do not form...

..Conjugates of GSH and N-acetylcysteine with monobromobimane and N-[1-pyrene]maleimide were observed among the HPLC fractions, along with unidentified derivatives...

..The presence of other oxidants, nitrite or tert-butyl hydroperoxide (t-BHP), promoted the oxidative damage induced by HOCl and led to new oxidative reactions...

..This study confirms the occurrence of oxidative stress in IUGR and demonstrates the beneficial effect of arginine/acetylsalicylic acid therapy in reducing oxidative stress in IUGR...

..These results give further evidence for the usefulness of urinary hydrogen peroxide and thiobarbituric acid reactive substances as potential biomarkers of oxidative stress and for the antioxidant action of estrogens...

..TAC was determined using the FRAP method. TAC decreased during surgery, but no further decrease in TAC was observed during reperfusion, indicating that it is a relatively stable parameter of the antioxidative barrier of the body...

..These results indicate that deleterious consequences of the lack of CuZnSOD are not limited to elevation of superoxide concentration and involve function(s) other than superoxide scavenging...

..We suggest that MgATP dependent transporter involved in Cd-GSH uptake in H. polymorpha, is similar to S. cerevisiae Ycf1-mediated vacuolar transporter responsible for accumulation of organic GS-conjugates and Cd-GSH complex...

..Determination of H2O2 in EBC may be helpful for non-invasive monitoring of oxidants production during lower respiratory tract infection...