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Figure 4 Myocyte regeneration by bone marrow cells does not involve cell fusion. The intramyocardial injection of enhanced green fluorescent protein (EGFP)-positive male blood marrow cells in female mice acutely after coronary artery ligation induced the formation of male myocytes in the infarcted region. The newly formed myocytes are small (A; alpha-sarcomeric actin, red) and express EGFP in the cytoplasm (B, green). A small developing arteriole is also present (A; alpha-smooth muscle actin, yellow). The nuclei (C; propidium iodide, blue) contain at most one Y-chromosome (white dots) and one X-chromosome (magenta dots), indicating the male phenotype of these cells and therefore excluding cell fusion. (D) The merged images of A, B, and C. The regenerated myocytes express alpha-sarcomeric actin, EGFP (yellow-green), and one X- and one Y-chromosome.
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