Comparison of the XTT and real-time RT-PCR assay signals with different seeding cell densities. Cells were seeded at densities ranging between 4 × 104-8 × 107 cells per 30 mm2 of well surface area. (A) XTT assay data, expressed as OD450 units, corresponding to each cell density. (B) Quantitative Real-Time RT-PCR assay data, expressed as the mean log10 copy numbers of the EFB1 transcript corresponding to each cell density. Means and standard deviations of three independent experiments are shown.