Restoration of hematopoiesis in cultures after the removal of catalase. (A) Recovery of hematopoiesis after the removal of catalase. Photomicrograph of phase contrast images showing differences between cultures maintained in catalase for 5 weeks and cultures from which catalase was removed after 4 weeks. Original magnification, × 100 as described in Figure 1C. (B) Recovery of clonal progenitors in LTBMCs after the removal of catalase after week 4. The results shown are representative of 3 similar experiments and the data shown are the mean and SD of 3 to 5 replicates.