Myosin content of arterial thrombi. (A) The immunohistochemical detection of myosin (brown color) in a thrombus from human iliac artery (the reaction was carried out as described in “Materials and methods,” original magnification × 400). The antibody recognizes small dotlike deposits (arrows) running parallel with the erythrocytes. (B) Negative control, for which the primary antimyosin antibody has been preincubated with a 1000-fold molar excess of myosin (original magnification × 400). (C-D) Immunofluorescent confocal laser images of the same thrombus double-stained for myosin (green) and fibrin (red) as described in “Materials and methods.” The box in panel C indicates the area that is enlarged in panel D, whereas the inset in panel D shows a section not treated with antimyosin or antifibrin antibodies and inspected as indicated for this panel (autofluorescence). Original magnification × 20 for panel C and × 40 for panel D and its inset; the bar indicates the final magnification.