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Biomedical subjects

W Bors

Publications and source records attributed to W Bors.

61 records · Page 4Linked to original sources
PubMedDate not supplied

Radical intermediates during the oxidation of nitropropanes. The formation of NO2 from 2-nitropropane, its reactivity with nucleosides, and implications for the genotoxicity of 2-nitropropane.

The chemistry of the nonenzymatic oxidation of the rat liver carcinogen, 2-nitropropane, and its anionic form, propane-2-nitronate, was investigated using pulse radiolysis and EPR/spin trapping with 3,5-dibromo-4-nitrosobenzenesulfonic acid as the trapping agent. The results suggest that, following initial oxidation to a secondary alkyl radical, propane-2-nitronate is effectively degraded in a peroxidative chain reaction with the intermediary formation of peroxyl and NO2.radicals. The latter radical was shown to react appreciably fast with ribonucleosides, deoxyribonucleosides, and guanosine nucleotides. It is proposed that nonenzymatic formation of NO2.radicals after enzymatic oxidation of propane-2-nitronate to the corresponding secondary alkyl radical accounts for the induction of DNA damage observed after exposure of rats to 2-nitropropane.

Free Radicals↗
PubMedDate not supplied

Kinetic investigations of the autoxidation of adrenalin.

Generation rates of superoxide anions (O2-) by autoxidizing adrenalin at pH 9.5 were determined in solutions containing either superoxide dismutase (0.85 M-1 S-1) or hydroxylamine (0.0185 M-1 S-1) as competitive scavengers. The rate constants of O2- with adrenalin and hydroxylamine were calculated for neutral and alkaline solutions. The respective values were for adrenalin: 5.6 X 10(4) M-1 S-1, pH 7.8; 7.0 X 10(3) M-1 S-1, pH 9.5--and for hydroxylamine 5.9 X 10(4) M-1 S-1, pH 7.8; 3.4 X 10(4) M-1 S-1, pH 9.5. The effects of various competitors and O2- sources on the rate constants were compared.

Epinephrine↗
PubMedDate not supplied

Radical functions in vivo: a critical review of current concepts and hypotheses.

Most of the basic knowledge about radical reactions comes from radiation chemical studies in vitro. In view of the rapidly increasing knowledge on radical reaction in vivo, it is important to reconcile the fundamental physico-chemical reaction characteristics of radicals with the need to explain their alleged biological effects. Severe problems in the understanding of their in vivo action remain unsolved. An example is phagocytosis, which seems to be a paradigm of a 'deleterious' radical process. The exact mechanism is not clear; so it is an open question whether the intruder is eventually killed by radicals (like OH) or by endproducts of radical reactions (like H2O2 and/or HOCl). It is even more difficult to understand signalling by radicals: owing to their chemical nature they are 'unspecifically' reacting species--they withdraw or add electrons--and thus their reactions are governed by redox-properties. Since all radicals have different redox characteristics and different molecular shapes, the usual key-and-keyhole picture for molecular interaction does not apply, as there, is no reactive site conceivable which has the property of reacting with radicals 'specifically. Our intent in this article is: (i) to briefly review some fundamental characteristics of in vitro radical reactions, (ii) to extrapolate from this to the conditions in vivo, and (iii) to discuss current hypotheses concerning the redox-regulation of cellular signalling. This leads us to the tentative conclusion that radicals per se must be tolerated by the cell and do not threaten its life, if they stay below a certain concentration limit. The main biological implication of radical-reactions seems to be that the cell derives signals from the balance of oxidative versus reductive processes and that radicals may interact with pathways of intra- and intercellular communication.

Animals↗