Histochemical analysis of animals.

(A) Histochemical analysis of myocardium in mice expressing low and high levels of hFIX. Tissue samples were stained with PTAH.14 Control indicates the normal left ventricle in a mouse expressing low levels of hFIX. Area surrounded by a rectangle is enlarged for higher magnification in the right panel. Overexpressed indicates the corresponding left ventricle with multifocal myocardial fibrosis in a mouse expressing high levels of hFIX. Area surrounded by a rectangle is enlarged for higher magnification in the right panel. Scale bars represent 100 μm. (B) Immunohistolochemical analyses of tissues from animals expressing low and high levels of hFIX. Tissue samples were stained with fibrin-specific monoclonal antibody.15 Heart indicates fibrin-stained normal myocardial vessel of control mouse, and fibrin depositions on endothelium of a vessel in a high hFIX–expressing mouse. Brain indicates normal vessel of control mouse, and abnormal vessel occluded by thrombus of high hFIX–expressing mouse. Lung indicates normal vessel of control mouse, and fibrin-positive thrombotic material–filled abnormal vessel. Original magnification, × 200.