The fine structure of the mitotic process of solid hepatoma cells of rat has been described. The replication and migration of centrioles, appearance and disappearance of spindle tubules and kinetochores, and movement and replication of chromosomes resemble those reported in other cell systems.

It has been observed that the nucleoli persist throughout all stages of cell division. The Golgi apparatus retains its discrete entity of laminar and vesicular components during the entire mitotic cycle. Remnants of the nuclear envelopes have been observed in all phases, even in telophase, after the reconstruction of the nuclear membrane of the daughter cells is completed. Penetration of rough endoplasmic reticula into the mitotic apparatus may appear in metaphase and anaphase. In telophase, cytokinesis is initiated by symmetrical invagination of the plasma membrane and, at certain stages, mitochondria may move freely in the region of the intercellular bridge which connects the daughter cells.

The mitotic activities of these tumor cells represent the behavior of the cellular organelles in natural and unaltered nutritional environment.


This research has been supported by USPHS Grant, CA-05312, from National Cancer Institute.


Reported at the Annual Meeting of the Society for Cell Biology, November, 1966, Houston, Texas.

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