DESOXYRIBOSE NUCLEIC ACID CONTENT IN THE NUCLEI OF SALAMANDER SOMATIC TISSUES

Abstract

1. Relative DNA content was determined photometrically for individual Feulgen-stained parenchymal nuclei of the liver, kidney, pancreas and granular glands of the salamander Taricha (Triturus) granulosa granulosa Skilton. Graphs of these values indicated the presence of nuclear classes falling into polyploid ratios. 2. A total of 920 liver nuclei were measured in one animal and 644 in another. A vast majority of the DNA values fell into the first class, representing the diploid condition. Only 2.6 per cent and 2.2 per cent, respectively, of the total number of nuclei constituted class II, which included values roughly double those of class I. No higher values were found. 3. In the kidney tubules, 136 and 129 nuclei were measured. All could be included in class I. 4. In the pancreas 685 nuclei were measured in one animal, 944 in another. Only 5.2 per cent and 1.6 per cent, respectively, of the total number of nuclei fell into the range of tetraploid values. No higher values occurred. 5. Degree and frequency of polyploidy was marked in the granular glands of the integument. Diploid, tetraploid, and octoploid values were obtained, and presumably higher values occurred in very large nuclei too irregular in shape for photometric measurement by the method employed. Polyploid nuclei increased in frequency with maturation of the glands and exceeded diploid types in number. A considerable number of nuclei with intermediate values suggested the occurrence of aneuploidy or of incomplete DNA replication incident to high endomitotic activity. A regular increase in nuclear volume accompanied rise in DNA content.