Figure 6

Removal of the 2 mM thymidine post-treatment at 48 hours, but not at 72 hours, prevents cellular senescence. Cells were treated with 1 mM thymidine prior to electroporation and then recovered in 1 mM thymidine. At 48 hours and 72 hours, as indicated, cultures were washed 2× with PBS and fresh medium was added ("w/o": washed out). At 144 hours, cells were assayed for senescence-associated β-galactosidase activity. All images are at 20× magnification.