Daunorubicin distribution in cytoplasts prepared from U-937 and U-A10 cells. Cytoplasts (enucleated cells) were prepared from U-937 cells (A and B) and from U-A10 cells (C and D) by treating cells with cytochalasin B and then pelleting through a discontinuous Ficoll gradient. Cytoplasts were exposed to daunorubicin at 500 ng/mL for 1 hour before being washed, visualized by fluorescence microscopy, and photographed. Shown are photographs of typical single cytoplasts with the images centered within the frame.