Nuclei from Normal and Leukemic Mouse Spleen. III. The Desoxypentosenucleic Acid Content per Nucleus Calculated from Total Cell Counts* NANCYA. MIZENANDMARYL. PETERMANN

In a study of the nucleic acid content of isolated nuclei, the average desoxypentosenucleic acid (DNA) content of nuclei from transplanted leukemic spleen (line 9421) was found to be increased to 1.45 times the normal value (6). Since only 5-10 per cent of the nuclei were recovered, however, the possibility arose that these nuclei were not repre sentative of the total population. Since all the DNA is in the nucleus, the average DNA per cell or per nucleus can also be calculated from the total DNA content of any tissue if cell counts can be made on the whole organ (8). Previous total cell counts were unreliable (6), because many nuclei were trapped in networks of connective tissue fibers. This difficulty has now been overcome by a more thorough homogenization of the material, and reliable total cell counts have been obtained. The DNA content per cell has been calculated for normal spleen and for spontaneous and trans planted leukemic spleen. New data on isolated nu clei have also been obtained. The average DNA contents per nucleus obtained by the two methods are in close agreement. As had been anticipated from the lower DNA content of whole leukemic spleen, the number of cells per gram of spleen is considerably reduced in leukemia.