Toxicity paraquat

Another area of active research is the development of stable low molecular weight metal complexes, which could serve as SOD mimics. Fridovich has described a complex of mangsmese (III) with desferral, which can catalyse the dismutation of superoxide anion in vitro and can protect green algae against paraquat toxicity (Beyer and Fridovich, 1989). This manganese-desferral complex was evaluated in models of circulatory shock and also found to improve survival rate (de Garavilla etal., 1992). 

In bacteria (Escherichia coli), paraquat is concentrated, reduced to the monocation radical, and combines with molecular oxygen to produce the superoxide radical within the cell. Copper and iron are essential mediators in bactericidal effects. The cytoplasmic membrane is the target organelle in paraquat toxicity to E. coli, and extent of damage correlates positively with levels of these metals (Kohen and Chevion 1988). 

Asztalos, B., J. Nemcsok, I. Benedeczky, R. Gabriel, A. Szabo, and OJ. Refaie. 1990. The effects of pesticides on some biochemical parameters of carp (Cyprinus carpio L). Arch. Environ. Contam. Toxicol. 19 275-283. Autor, A.P. (ed.). 1977. Biochemical Mechanisms of Paraquat Toxicity. Academic Press, New York. 240 pp. Babich, H., M.R. Palace, and A. Stern. 1993. Oxidative stress in fish cells in vitro studies. Arch. Environ. Contam. Toxicol. 24 173-178. 

Combs, G.F. and F.J. Peterson. 1983. Protection against acute paraquat toxicity by dietary selenium in the chick. Jour. Nutr. 13 538-545. 

Hampson, E.C.G.M. and S.M. Pond. 1988. Ultrastructure of canine lung during the proliferative phase of paraquat toxicity. Brit. Jour. Exp. Pathol. 69 57-68... 

Heitkamp, M. and O.R. Brown. 1982. Cellular Mechanisms of Paraquat Toxicity. U.S. Fish Wildl. Serv., Tech. Paper 107 29-36. 

Kitazawa, K., T. Kobayashi, T. Shibamoto, and K. Hirai. 1988. Effects of methylprednisolone on acute lung paraquat toxicity in sheep. Amer. Rev. Respir. Dis. 137 173-180. 

Leung, T.S., S.M. Naqvi, and N.Z. Naqvi. 1980. Paraquat toxicity to Louisiana crayfish (Procambarus clarkii). Bull. Environ. Contam. Toxicol. 25 465-469. 

Omaye, S.T. and A.K. Reddy. 1980. Early and delayed biochemical effects of paraquat toxicity on rat lung. Exp. Molec. Pathol. 33 84-89. 

Onyeama, H.P. and F.W. Oehme. 1984. A literature review of paraquat toxicity. Vet. Human Toxicol. 26 494-502. 

Sharp, C.W., A. Ottolenghi, and H.S. Posner. 1972. Correlation of paraquat toxicity with tissue concentrations and weight loss of the rat. Toxicol. Appl. Pharmacol. 22 241-251. 

Smith, L.L. 1985. Paraquat toxicity. Phil. Trans. R. Soc. Lond. 311B 647-657. 

Szabo, L., B. Matkovics, K. Barabas, and G. Oroszlan. 1986. Effects of various thiols on paraquat toxicity. Comp. Biochem. Physiol. 83C 149-153. 

Wegener, T., B. Sandhagen, K.W. Chan, and T. Saldeen. 1988. V-acetylcysteine in paraquat toxicity toxicological and histological evaluation in rats. Uppsala Jour. Med. Sci. 93 81-89. 

What is the major target organ for paraquat toxicity, and what are the two main reasons for this ... 

Combination of superoxide ion with the cation radical (MV+0 of methyl viologen (l,T-dimethyl-4,4 -bipyridinium ion, Paraqnat) is one of the best-documented examples of a stoichiometric 02 - radical coupling reaction. The initial addition to give an unstable diamagnetic product is assumed to be at a-carbon atoms (which possess the maximum unpaired spin density in the cation radical), followed by formation of a dioxetane-like intermediate that decomposes to a complex mixture of products (Scheme 13). This process may provide a means to explain the mechanism of Paraquat toxicity. Several other reports have proposed direct coupling of 02 - to cation radicals. ... 

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