Figure 1.

Population growth kinetics of the transfectants in serum-free culture. The cells (1 × 10⁴ cells per well) were seeded in type I collagen-coated 24-well culture plates, and they were counted daily for 6 days. HSYzeo (□) and HSYR2/R1 (▵) had doubling times of 18 h and 19 h, respectively, whereas HSYR2-IIIb (○) proliferated with a doubling time of 52 h. Three independent experiments were performed with duplicate wells. Each point indicates a mean ± SD.