Establishment and Growth Kinetics of the Mutant Ehrlich‐Lettré Ascites Cell Strain Hd33 In Permanent Suspension Culture1,2

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Abstract
Cells of a mutant in vivo subline of the Ehrlich-Lettre mouse ascites tumour (ELAT) were converted to growth in suspension culture. Kinetic analysis revealed the selective character of the conversion process; without a detectable adaptation period, a fraction of about 2 .times. 10-5 of the explanted cells continued to grow in vitro. The resulting, mutant Ehrlich-Lettre ascites cell strain was designated HD33 and propagated uninterruptedly from 1974 on. The corresponding in ELAT subline HD33 was derived from the HD33 ascites cell strain by intraperitoneal retransplantation. In HD33 cell suspension cultures, the population doubling time, the average intermitotic interval, as determined by videomonitoring, and the average duration of the cell cycle, as determined from percentage of labelled mitoses (PLM) data, were all measured at 15 hr. Cell loss and quiescent compartments were insignificant. The duration of the G1 phase was effectively zero. Both PLM data and [3H]/[14C] thymidine double-labelling measurements revealed an S-phase duration of between 11 and 12 hr. The G2 phase lasted 3-5 hr. The HD33 strain differs from comparable suspension strains of wild-type Ehrlich ascites cells in the insignificant role of density-dependent inhibition in growth, and the striking prolongation of the S phase which is associated with an excessive, cytoplasmic storage of glycogen by the mutant cells.