Appearance of Marked DNA-Degrading and Thymine Catabolic Activities in a Human Cell Infected with a Transmissible Agent. ∗

Abstract

Summary

Following infection by a transmissible cytopathic agent and with the appearance of degeneration, the following were regularly observed for thymidine-2-C¹⁴ labelled human “liver” cultures: 1. progressive increase in quantity of C¹⁴O₂ liberated, 2. progressive increase in radioactivity of the acid soluble fractions, and 3. progressive decrease in radioactivity of the acid insoluble fractions. Similar changes had not been demonstrated in uninfected culture, culture killed by freezing or by nutrient depleting, and cultures infected with vaccinia, adeno 3, herpes simplex, polio 1, or Coxsackie B1 viruses. Significant conversion of acid insoluble to acid soluble radioactive compounds was repeatedly demonstrated in uridine-2-C¹⁴ labelled “liver” cultures under all the described experimental conditions leading to cell degeneration. Formation of C¹⁴O₂ from uracil-2-C¹⁴ or uridine-2-C¹⁴ was, however, restricted to cultures treated with this DNA-degrading agent.

The authors are grateful to Dr. Holmes, Alfred I. du Pont Institute for making available to us a strain of “liver” cells adapted to grow in Holmes'synthetic medium, and for a generous supply of his chemically denned medium.