Quiescent NIH 3T3 (A, C, E) and E2546 (B, D, F) cells were incubated in the presence of 100 μM Brdlhd plus either 20% calf serum (A, B), 5 μg/ml insulin (C, D), or 10 ng/ml NGF plus 5 μg/ml insulin (E, F). Cells were fixed after 24 hr and analyzed for immunofluorescence using a mouse anti-BrdUrd monoclonal antibody and donkey anti-mouse IgG conjugated with Texas red. Final magnification 250 x