Fig. 8From: Neuromuscular electrical stimulation promotes development in mice of mature human muscle from immortalized human myoblastsCentrally located myonuclei of human and murine origin in xenografts. Unfixed cross sections were immunolabeled with antibodies to human β-spectrin (green) and human lamin A/C (red) and counterstained with DAPI (blue) to label all nuclei. Human myonuclei, positive for DAPI and human lamin A/C, and murine myonuclei, positive for DAPI but not for human lamin A/C, were quantitated in human myofibers and identified by the presence of β-spectrin at the sarcolemma. Images of human myofibers in group 2 (a, b) and group 3 (c, d) show labeling for spectrin and lamin A/C (a, c) and for both proteins and DAPI (b, d). a, b Arrows point to myofibers with nuclei labeled with antibodies to human lamin A/C. Arrowheads point to nuclei labeled with antibodies to human lamin A/C lying outside of muscle fibers. c, d Arrow points to a human myofiber with a nucleus that is unlabeled by antibodies to human lamin A/C. Arrowheads point to nuclei that lie outside of muscle fibers and that do not label with antibodies to human lamin A/C. e High magnification examples of human fibers with a myonucleus that labels with anti-human lamin A/C (E1), a nucleus lying outside a human fiber that labels with anti-human lamin A/C (E2), a human fiber with a myonucleus that fails to label for human lamin A/C (E3), and a nucleus that fails to label for human lamin A/C lying outside a human fiber (E4). f Percent of centrally located human and murine myonuclei detected in human muscle fibers in groups 2 and 3 at 4–5-weeks post-transplantation. Of the human fibers examined, <20 % was centrally nucleated (group 2 = 36/205, or 17.5 %; group 3 = 69/505 or 13.7 %). Only 2 myonuclei out of 205 (1 %) in group 2 and 7 myonuclei out of 505 (1.4 %) in group 3 failed to label with antibodies to human lamin A/C. Scale bars = 10 μmBack to article page