FIG. 4.

Characterization of islet-1-positive cells. Costainings for islet-1 (a), 165-kDa neurofilaments (b), acetylcholinesterase activity (c), and phalloidin (d–g) were performed on 5-day-old 129SvJ × C57BL/6J serial mouse heart sections. A cluster containing islet-1-positive cells (a) stained positively for 165-kDa neurofilaments (b) and acetylcholinesterase (c, arrows). In this first type of cluster, islet-1-positive cells (d, e, stars) were negative for phalloidin staining, whereas the surrounding cardiac tissue was positive (d, e, asterisks). Sarcomeric features colocalized with islet-1 expression in nuclei in the second type of cluster (f). Islet-1-positive cells stained by phalloidin (asterisks) are intricated within myocardial tissue and in close contact with phalloidin-positive and islet-1-negative nuclei of cardiomyocytes (g, arrows). Scale bars: (a–c) 50 μm; (d–g) 5 μm. Color images available online at www.liebertonline.com/scd