Fig. 2. Expression patterns of GFP (A) and of -actinin in the same field (B). GFP is diffusely distributed in the single transfected cardiomyocyte (arrow, A). -actinin (B) is clearly localized in striated myofibrils in both the GFP transfected cell (arrow) and the neighboring untransfected cell (asterisk). (C) Myofibril content versus days in culture. The open symbols show results for mock transfected cardiomyocytes, and the closed symbols show results for cardiomyocytes transfected with GFP alone. Cells were transfected after 1 day (circles) or 2 days (squares) in culture and viewed 1 day or 3 days post-transfection. Each point represents the mean±s.e.m. from 4 to 27 transfected cells. No significant difference was observed between the mock-transfected cardiomyocytes and cardiomyocytes expressing GFP.