Lipid peroxidation of subcellular organelles gives fluorescent products which have fluorescence and excitation spectra similar to those of lipofuscin pigments. Fluorescence and excitation spectra and total fluorescence in the 460-nanometer region are useful for qualitative identification and quantitative measurement of the Schiff base product, a molecular damage site of lipid peroxidation which develops during some aging processes.

Cytoplasmic superoxide dismutase has been purified from livers of young (6 months) and old (27 months) rats. The enzyme purified from old animals shows an age-related reduction in the specific activity, accumulation of antigenically cross-reacting material and increased sensitivity to temperature. No differences were found in the molecular weight, electrophoretic mobility, antigenicity and I ( between enzymes purified from young and old rats.This is thc first demonstration of age-related alterations in a purified form of a non-metabolic enzyme, which can be related to reduced activity. The possible role of this reduced activity i n agedependent deterioration of cellular functions is discussed.

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Calf thymus DNA was reacted with peroxidizing arachidonic acid at 37 C for 76 hr. Fluorescent DNA products increased with reaction time. These products had characteristic fluorescence spectra with maximum excitation at 315 nm and maximum fluorescence at 420 nm. Structural changes occurred in the DNA reacted with peroxidizing arachidonic acid, as observed by decreased melting point, decreased hyperchromicity, partial resistance to hydrolysis by deoxyribonuclease and by decreased template activity for rat liver RNA polymerase.