Fig. 1. Growth and morphological characteristics of PMA-resistant clones. A, growth curves of wild-type K562 cells and the EMS mutagenized clones, C1 and C4, in the presence (•, {blacktriangleup}, and {blacksquare}) or absence ({circ}, {triangleup}, and {square}) of PMA (40 nM). The growth rate of the cultured cells was determined as described in "Materials and Methods." B, wild-type K562 or C1 and C4 clones were treated with or without PMA (40 nM) for 4 days, affixed to the slide by cytospin, and stained using the May-Grunwald procedure as described in "Materials and Methods." The cells were analyzed and photographed at x100 under light microscopy.