Some Mechanisms of Formation of Polyploid and Heteroploid Cells in a Murine Ascites Tumor <italic>In Vitro</italic>

Abstract

This paper records the behavior in vitro of cells, at and about the time of their division, in an ascites subline of a naturally occurring murine epithelioma. Under the conditions of these experiments, uninuclear cells of higher ploidy are formed from uninuclear cells of lower ploidy through the intermediate stage of a binuclear cell. The production of the intermediate binuclear cell depends on failure of cytoplasmic cleavage at the time of attempted division of a uninuclear cell. When a binuclear cell divides to produce 2 uninuclear daughters, the chromosomes of both nuclei come together on a single metaphase plate, anaphase and telophase appearing normal. Cytoplasmic cleavage is successful, and two uninuclear daughters are formed. Uninuclear daughters of higher ploidy so produced are viable and capable of further mitoses, which may be normal or may vary in the modes of their division. In a binuclear cell that fails to cleave in successive attempts at division, the chromosomes come together on a single metaphase plate on each occasion, which results in a cell of successively higher ploidy. Rarely, multipolar separation of chromosomes results in reduction of the chromosome complement of a cell. Similar multipolar divisions may give rise to binuclear and trinuclear cells that are usually viable and may undergo further division.