Abstract
Summary
L-Cystine enables viruses of the Akron strain of antigenic type 1 polio-virus to grow on in vitro monkey kidney cells at comparatively high temperatures; at lower temperatures little or no exogenously supplied L-cystine is needed by these viruses. These results were shown for Akron viruses of 3 different degrees of genetic ability to grow at higher temperatures. The activity of L-cystine is not due to its slight lowering of the pH during plaque development. L-Cysteine and glutathione are active. DL-cystathionine is slightly active, and a sample of D-cystine showed slight activity. Rare plaques produced at temperatures too high for the L-cystine supply contained hot-adapted mutants.
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