β-gal expression in cultured cells after adenoviral transduction. CD34⁺ cells were cultured with PEG-rHuMGDF for 10 days before incubation with AdCNLacZ (MOI of 200). β-gal expression was visualized by light microscopy after cell fixation and X-gal staining as described in Materials and Methods. Photomicrograph of adenovirus infected cells (400×). Note the blue nuclear staining of successfully transduced cells. No blue coloration was detectable in any cell from samples that were similarly stained but were incubated with virus control.