Intramitochondrial Fibers With Deoxyribo-nucleic Acid Characteristics: Observations of Ehrlich Ascites Tumor Cells2

Abstract

Ehrlich ascites tumor cells were examined in the electron microscope for mitochondrial fibers with deoxyribonucleic acid (DNA) properties similar to those demonstrated in chick embryo mitochondria. Fibers with fixation and electron-staining properties characteristic of bacterial nucleoplasm and purified DNA were repeatedly observed. The rod-shaped structures of clumped fibrils typically observed in mitochondria of most tissues after fixation with osmium tetroxide were also seen in numerous mitochondria of ascites cells after sections were stained with uranyl acetate and lead hydroxide. In many other mitochondria of these tumor cells, however, the fibers were fixed as curved, circular, or figure-eight-shaped profiles. These curved fibers were often intimately associated with a globular body observed frequently in structurally damaged mitochondria. Usually the globules appeared homogeneous, but occasionally a substructure was recognizable. A deeply staining rim partly or completely surrounded the globules. Micrographs are presented which are interpreted as indicative of a stepwise destruction of mitochondria leading to the formation of vesicular structures in the cytoplasm. The vesicular structures contain the globular products characteristic of degenerating mitochondria. In some sections, the vesicles are filled with virus-like particles. The observations are discussed in relation to a possible role of the mitochondrial fibers with DNA characteristics in neoplasia.