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Properties of the Ehrlich Ascites Tumor Cell as Determined by Electron Microscopy, Ultracentrifugation, and Hydrostatic Pressure¹

Department of Zoology, University of Iowa, Iowa City, Iowa 52240

Ehrlich ascites tumor cells were ultracentrifuged in a gum arabic solution, or as stacks of cells in 0.9% sodium chloride solution for periods ranging from 20 to 30 min. Those suspended in gum arabic become greatly stretched and are sometimes pulled into two parts. The nuclei are displaced centrifugally and the relatively dense nucleolus (sometimes there are more than one) is forced against the nuclear envelope and adjacent plasma membrane causing them to become greatly stretched. Sometimes the nucleolus is thrown through both the nuclear envelope and plasma membrane becoming free of the cell. The interphase chromosomes are more dense than the nucleoplasm, and they are displaced centrifugally. However, when this occurs, it is revealed that the chromosomes adhere to the nuclear envelope. The forces holding them to the inner membrane of the nuclear envelope are relatively strong, thus causing the displaced chromosomes to become greatly stretched, or even broken, before they are detached. When subjected to a comparable centrifugal force, the stratification in the ascites cells is not so complete as has been reported for certain nonmalignant somatic cells.

¹ Supported by Grants GM-5479, 4706, 09229, and HD-00699 from the NIH and Grant G-9879 from the National Science Foundation.

² Recipient of a Career Development Award, GM-11,524, from the National Institute of General Medical Sciences.

Received 1/15/68. Accepted 5/ 2/68.