The effects of paraquat on rat brain were studied. Activities of complex I (NADH: ubiquinone oxidoreductase) in mitochondrial electron transport system, lipid peroxidation and the amount of catecholamines in rat brain were measured after acute paraquat exposure. Complex I activities were significantly lower and lipid peroxides were higher in the brains of a paraquat-treated group than in those of a control group. Lipid peroxide in rat serum, however, did not increase after paraquat exposure. A study of the time dependency of paraquat effects disclosed that mitochondrial complex I activities in rat brain as well as those in rat lung and liver gradually decreased prior to the appearance of respiratory dysfunction. As compared to controls, the dopamine in rat striatum was significantly lower in the paraquat-treated group. These results suggest that paraquat after crossing the blood-brain barrier might be reduced to the radical in rat brain, which may damage the brain tissue, especially dopaminergic neurons in striatum. We therefore propose that cerebral damage should be taken into consideration on paraquat exposure. Patients may therefore need to be followed up after exposure to high doses of paraquat.

Paraquat was reduced to the paraquat radical via complex I in bovine cerebral mitochondria and accelerated lipid peroxidation. Thirty-kilodalton subunit of complex I was considered to be the radical formation site, because of its marked destruction by the paraquat radical. The lipid peroxidation by the paraquat radical was suppressed not only by superoxide dismutase (SOD) but also by mannitol. The destruction of complex I subunits via lipid peroxidation must have been caused by the hydroxyl radical which was formed from the superoxide radical. The same phenomenon was observed by using 1-methylnicotinamide (MNA), which contains the same partial structure as paraquat in itself and is metabolized from nicotinamide in a living body. We observed NADH oxidation by MNA via cerebral complex I (Km = 26.3 mM), and MNA destroyed some complex I subunits, especially 30-kilodalton protein. Paraquat might be useful for studying the pathogenesis of Parkinson's disease (PD) in vitro, and MNA is expected to be one of the causal substances of PD from the viewpoint of the oxidative stress theory.

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A new vinyl monomer (4) containing a terpyridinyl group was prepared and radically copolymerized with styrene or methyl methacrylate. The terpyridinyl groups in the resulting copolymers (5 and 6) coordinate almost quantitatively to the Fe(I1) ion and form a complex. The decrease of qinh, accompanied by the coordination to the Fe(I1) ion, suggests that the formation of the Fe(II)-complex occurs in each polymer chain with shrinking. A cyclic voltammogram of the Fe(I1)-complex of polymer 6 showed characteristic Fez+/Fe3+ redox couples at + 1,12 V vs. SCE, which was followed by a color change from purple to colorless.

SYNOPSISAs the basic research for the study of complex reactions in polymers, the complex formation of poly(viny1 alcohol) (PVA) with copper and other metals was tried. Spectroscopy, pH titration, and elementary analysis were employed in the reaction of PVA and Cu(I1) ions in aqueous solution. The complexing protonation was found in the higher pH region (above 7.0), and the maximum absorptions at 640 and 260 nm were observed. These were proportional to the concentrations of Cu(I1) ions bound to the hydroxyl groups of PVA. Formation constants of the PVA-Cu(I1) complexes were measured by applying a modified Bjerrum's method. The effects of the ratio TcP2+/T~r,, the anions in copper salts, and the degree of polymerization on the formation constants were studied. Four hydroxyl groups combined with one Cu(I1) ion in the pH range above 7.0. The stability constants for the complexes of PVA with bivalent transition metallic ions were in agreement with the Irving-William's series. The changes in viscosity, solubility, tacticity, mechanochemical phenomenon, and the other properties based on the complex formation are discussed. EXPERIMENTALMaterials PVA(NM-11 P= 1 lOO), aproduct of Nippon Synthetic Chemical Industry Co., was used. The PVA was separated into several fractions of different aver-299