Peak staining of cardiomyocytes. Immunostaining with σ1-antibodies of heart section from the cohabitant group 10 wpi. PRV antigen was detected in numerous cardiomyocytes in the ventricle (red color). This represents the time of peak staining in the cohabitant group and positive staining was observed in both the compact (right side) and spongy layer (mid to left side). Magnified sections (*) in the top left corner clearly show the cytoplasmatic staining of the cardiomyocytes outlining the nucleus. Vacuolization in a positive stained cardiomyocyte is visible in the bottom magnified picture.