Figure 1. CR serum delays senescence and extends the lifespan of normal human diploid fibroblasts. (A) Cumulative growth curves of various normal human fibroblast lines cultured in medium containing 10% of either AL (red lines) or CR (blue lines) rat serum. Data obtained with IMR-90 (I90-79) (left panel), IMR-90 (I90-26) (middle panel) and WI-38 (right panel) are shown. PDL, population doublings (B) Representative photomicrographs of early passage IMR-90 cells (PDL 25) grown in medium with 10% FBS (upper panel) and after undergoing serial subpassages in the present of AL (left panels) or CR (right panels) rat serums are shown. Original magnification: X100.