Phenotypic and in vitro analyses of irradiated normal versus leukemic animals. (A) Bone marrow cells were isolated from control versus irradiated (5.5 Gy) animals and labeled with antibodies to detect stem-cell populations (indicated by the box in each panel). The top panels show GFP⁻ (ie, normal) cells and the bottoms panels show GFP⁺ (ie, leukemic) cells. The data shown for each panel are gated on the Lin⁻ population. (B) Colony-forming units (CFUs) were determined for sorted GFP⁺ (leukemic) and GFP⁻ (normal) populations. Data shown are the absolute number of colonies measured per 5000 cells plated (triplicate assays). *Statistical significance(P = .009) as determined by Student t test. Error bars are SD.