Selection of Ehrlich tumor cells in different phases of the cell cycle by ficoll gradient centrifugation.

Mouse Ehrlich ascites tumor cells were centrifuged at low speed on a linear Ficoll gradient. Cells from different fractions of the gradient were collected separately and analysed by cytological and cytochemical methods (DNA content, mean volume and number of cells). Nearly pure populations of cells in G1 or S were selected. A heterogeneous population containing 70% G2 and mitotic cells was also isolated. No ultrastructural alterations were detected in the cells after centrifugation. Selected G1 cells were cultured in vitro, their kinetic parameters were measured and compared with those of the original population. No difference was observed as far as the duration of the cycle of these cells is concerned.