serial subcultivation of nine endothelial clones derived from three fetal calf aortas revealed proliferative life-spans in vitro of 53 -- 125 population doublings ( pds ) , compared with 60 and 143 pds for two lines of bovine fetal lung cells and 85 and 147 pds for two lines of bovine vascular smooth muscle cells .
C0015965
fetal
C1517163
fetal lung