Studies on the properties of factors elevating the activity of mouse-plasma lactate dehydrogenase

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Abstract
The plasma of mice infected with virus elevating plasma lactate-dehydrogenase activity contains two different virus particles that can be differentiated by centrifuging and by chromatography on diethylaminoethylcellulose. The larger particle, which is easily sedimentable, assays at up to 1011 infective doses/ml. of plasma 15-20 hr. after infection, and its titre then decreases to 1O7-108 infective doses/ml. 14 days after infection. The smaller relatively non-sedimentable particle assays at 107-108 infective doses/ml. of plasma 15-20 hr. after infection, and it titre decreases only slightly during the next 14 days. Centrifuging of infected plasma produces a pellet from which RNA (about 60 [mu]g./100 ml. of plasma) can be isolated. The amount of RNA isolated from such pellets is independent of the plasma virus titre. A similar RNA-containing pellet is obtained by centrifuging plasma from apparently uninfected healthy normal mice. This pellet contains about 40 [mu]g. of RNA/100 ml. of plasma. The pellet RNA-containing material in normal plasma withstands incubation of the plasma for 10 min. at 37[degree]. Under these conditions 95% of added liver microsomes are destroyed. The base composition of the RNA pellet from plasma with an infective virus titre of 1011 infective doses/ml. and of the RNA from normal plasma has been determined.