Immunohistochemical analysis of poly-ADP-ribosylation. Poly-ADP-ribosylated proteins (A) or AIF (B) were detected on frozen sections from donor (a and c) and failing (b and d) left ventricular tissue samples with antibodies against poly-ADP-ribose polymers (1:100; Calbiochem) or against AIF (1:100; Chemicon), using the ABC method and DAB as chromogen. Sections were counterstained with hematoxylin. Control sections from donor and failing hearts were simultaneously stained with omission of the primary antibody and no significant staining was observed (data not shown). Three samples were evaluated from both donor and failing hearts and representative pictures are shown. The indicated regions on the pictures recorded with low magnification (squares in pictures a, b, c, and d) are also shown in higher magnification, labeled by capital letters (A, B, C and D), respectively.