Figure 3

The distinct morphologies and responses to inhibition of Erk activation of macrophages generated by expression of constitutively active M-Ras or H-Ras. Bone-marrow cells transduced with retroviruses expressing GFP alone or constitutively active M-Ras or H-Ras were selected for by culture for 48 h in the presence of puromycin as described, and were washed free of growth factors and seeded (1 × 10⁵/ml) into each well of a 24-well plate in 2 ml of DMEM in the presence or absence of PD98059 (25 μ M). After 5 days, the bottoms of the wells were photographed