Increase in platelets in the peripheral blood and in megakaryocytes in bone marrow and spleen of induced double transgenic hCD34tTA × BCR/ABL mice. Cells in panels were stained with Wright Giemsa, except for panel H, which demonstrates Gr-1 staining (brown color) with a hematoxylin counterstain. (A) Peripheral blood and (B) bone marrow from a nontransgenic littermate are shown. Thrombocytosis developed within several months after induction of BCR/ABL expression (C-D, peripheral blood). Consistent with this finding in peripheral blood was an increase in the number of megakaryocytes in the bone marrow. (E) Stains of a cytospin of bone marrow cells and (F) a bone marrow section from another animal are shown. High numbers of megakaryocytes were also found in the spleens of induced animals (G) as well as invasion of myeloid cells into the liver (H). Original magnification, × 20.