Abstract
Quantitation by enumeration of virion particles, measurement of absorbancy at 260 nm, and densitometry on sodium dodecyl sulfate-polyacrylamide gels has shown that mouse L-M cells yielded 7- to 10-fold less endogenous C-type virions than the parental lines, L or L929. The previously noted stimulation of L-M cell virion production by a concomitant 10% increase in fetal calf serum concentration (D. A. Kindig, R. Karp, and W. H. Kirsten, 1968), was not observed.