A STUDY OF NUCLEIC ACID SYNTHESIS IN ASCITES TUMOR CELLS BY TWO-EMULSION AUTORADIOGRAPHY

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Abstract
Ehrlich ascites tumor cells from mice injected simultaneously with H -thymidine and uridine-2-c14 were autoradiographed by a two-emulsion technique that allows one to distinguish cells labeled with H3 only from those labeled with C14 only or with both H3 and C14. With the use of the above-mentioned radioactive compounds, it was possible to distinguish cells synthesizing DNA only from those synthesizing only RNA or both RNA and DNA. It was found that in tumor cells, in the exponential phase of growth, the uptake of RNA precursor (uridine-2-C14) proceeds at the same rate for the entire length of the mitotic cycle, with the exception of a brief period from late prophase to completion of telophase. At the cessation of the exponential phase of tumor growth, DNA synthesis, as revealed by the uptake of H3-thymidine, decreases rapidly, but RNA synthesis continues at the same rate at least until the 13th day after an inoculum of 2 million tumor cells.