Transgene expression in cardiomyocyte foci.

Areas of early cardiac cell lineages were visually identified at approximately day 10 of secondary culture in methylcellulose in foci of rhythmically contracting cells (A, C, E, G, arrows indicate areas of contracting cells). Cardiomyocyte foci with either no transgene (TG−) or the −0.150 kb, −0.375 kb, or −1.1 kb transgenes were assessed for EGFP expression using fluorescence microscopy (B, D, F, H). Note that the fluorescence images from the TG negative and −0.150 kb cells (B, D) have 3 times the exposure length as the −0.375 kb and −1.1 kb cells (F, H). Original magnification, × 400.