Figure 2. Endonuclease activity in gel filtration fractions of human tears. A shows the agarose gel of products from hydrolysis of pUC19 human tears (diluted 1:5) Aliquots were removed from the reaction mixture at successive 15-min. intervals (Lanes 1–6); Lane 7 shows sc pUC19 incubated only. The forms of the plasmid are indicated as relaxed (r) and supercoiled (sc). B demonstrates endonuclease activity profile of fractions superimposed on the absorbance elution profile from filtration of human tears (2.5 ml) on Sephadex G-100 column. (□) stands for absorbance; (●) stands for DNA hydrolyzing activity profile calculated by the densitometry of bands in the agarose gel electrophoresis of plasmid DNA sc pUC19. Each point represents the activity resulting from incubation of 5 μl of the various fractions with the plasmid.