Analysis of p21 expression during differentiation. Image analysis of cytospins shown in Fig 6 as described in the text. (A) Proportion of cells positive for p21. Cy3 staining over Hoechst nuclei corrected for background signal are quantified as a percentage of nuclei present. (B) Intensity of p21 staining. p21 fluorescence intensity at different days. Cy3 signal extracted and intensity collected for the mask area for each cell as described in the text. Intensities shown in the figure represent the mean sum of all cell profiles generated.