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Figure 4 (A) Photomicrographs of cardiac myocytes in the anterior aspect of left ventricular (LV) free wall at the age of 17 weeks in sham (left), myoblast (MB) (center), and MB + cardiotrophin (CT) (right) groups. The bar indicates 50 µm. (B) Relative cross-sectional area of cardiac myocytes in the LV (open bars), the free wall (solid bars), and the septum (striped bars) of the LV. Myocyte size was normalized to a mean value of Dahl salt-sensitive rats at the age of six weeks. *p < 0.05 vs. sham group by analysis of variance and Bonferroni's multiple-comparison t test. p < 0.05 versus the septum wall by paired t test. Values are means ± SEM. (C) Phase-contrast photomicrographs of cultured neonatal rat ventricular cardiac myocytes (CM). Cardiac myocytes were treated as described for 48 h. The media from parental myoblasts showed no morphologic changes compared with control. The media from CT-1–transferred myoblasts induced myocardial cell hypertrophy, similar to that seen in 1 nM CT-1–incubated CMs. Myoblast_CT-1 = CT-1–transferred myoblasts.