Histopathologic and hematologic abnormalities of A/J-trac/trac mice. (A) Heart and myocardium (inset) of A/J +/? control mouse showing normal structure, higher magnification insets of boxed areas. (B) Determination of collagen deposition in heart ventricles by color-subtractive computer-assisted image analysis showed a mean of 1.9% collagen in A/J +/? controls and 14.6% in A/J-trac/trac mice, a 7-fold increase in collagen deposition (n = 5). (C) Heart and myocardium (inset) of A/J-trac/trac mouse showing cardiomyopathy with severe multifocal fibrosis. (D-L) Peripheral blood smears and histopathology of BM, spleen, and lungs. (D-F) Blood smears of A/J-trac/trac and +/? control mice at 10 weeks of age. (D) A/J +/? mouse blood smear showing normal platelet size. (E) A/J-trac/trac blood smear showing greatly enlarged platelets. (F) A/J-trac/trac blood smear showing megakaryocyte. (G-H) Vertebral BM at 15 weeks. (G) A/J +/? BM showing normal distribution of megakaryocytes. (H) A/J-trac/trac BM showing increased numbers of megakaryocytes. (I-J) Red pulp of spleen. (I) A/J +/? spleen showing normal distribution of megakaryocytes. (J) A/J-trac/trac spleen showing increased numbers of megakaryocytes. (K-L) Lungs. (K) A/J +/? lungs showing normal structure. (L) A/J-trac/trac lungs showing megakaryocytes in alveolar capillary bed (arrows). (A,C) Masson trichrome stain; bars represent 1 mm. (D-F) Wright stain. (G-L) Hematoxylin and eosin; bars represent 10 μm.