Studies on Mammary Tumor Inducing Virus in Mice (Bittner Virus). ∗

Abstract

Summary

1). Zone electrophoresis of high-speed centrifugal pellets from virus-containing defatted and decaseinated strain A milk has led to good recovery of mammary tumor-inducing activity and to its localization in electrophoretic pattern. Nucleic acid determinations have shown presence of considerable quantities of RNA in pellets from similarly treated A strain milk and absence of DNA. High-speed centrifugal pellets from defatted and decaseinated strain A milk treated with either ribonuclease or cold 75% ethanol retained tumor-inducing activity. 2) Characteristic particles of 700 Å average diameter, have been observed in sections of high-speed centrifugal pellets of agent-harboring RIII and A strain milk which have shown high tumor-inducing activity. They have also been found following treatment of pellets with fluorocarbon. Similar particles have been observed in considerably smaller number in pellets of Af strain milk without tumor-inducing activity. The relationship of these particles to the origin of mammary tumors of mice requires further study.