EFFECTS OF GAMMA-IRRADIATION ON CELLS AND THEIR CONSTITUENTS

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The effects of ionizing, and ultraviolet radiation, of visible light, and of ultrasound on cells and their constiuents are being studied. Phthalocyanines, a class of Azaporphyrins with maximum absorption in the 600-700 nm region, are efficient photosensitizers for killing of mammalian cells and may be candidates to replace hematoporphyrin derivatives in photodynamic therapy (PDT) of tumors. A comparison of the quantum yields for superoxide radial photogeneration at 615 nm from a variety of Phthalocyanines with their cytotoxicity to cultured mammalian cells suggests that superoxide is not the lethal agent. In a new photochemical reaction, the decarboxylation radicals formed from peptides and carboxylic acids by photolysis at 313 nm in the presence of various Metallophthalocyanines were identified by spin trapping and electron spin resonance. These reactions might be involved in the undesirable phototoxicity induced by sunlight following photodynamic therapy. The photochemical formation of superoxide and of decarboxylatedpeptide radicals by visible light (404-615 nm) from the antitumor agents Carboquone, Mitomycin C and Strptonigrin were investigated because of the possibility of combining chemo with phototherapy. Continuing our studies on the effect of continuous wave and pulsed 1 Megahertz ((MHz) ultrasound on aqueous solution, the effect of varying the pulse repetition frequency on transient cavitation and on the formation of hydroxyl radicals was examined. The obstacles associated with spin-trapping oxygen-derived radicals inside cells were studied and the results indicate that the primary radicals react with the spin traps;however, the 5,5-Dimethyl-1-Pyrroline-N-Oxide spin adduct with hydroxyl radicals decays very rapidly in the interior of the cell.