Fig. 5. Cardiomegaly in postnatal day 15 (P15) Carp-Lbh transgenic mice. Hearts of wild-type (wt; A,D,G) and transgenic (Tg; B,C,E,F,H,I) littermates at P15. (A-C) Frontal Hematoxylin and Eosin-stained sections at the levels of the atrioventricular valves. The Tg#1 heart is hyperplastic (B,E), whereas the Tg#2 heart is hypoplastic (C,F). Double-headed arrow marks the thickness of the intraventricular septum (IVS). lv, left ventricle; rv, right ventricle. (D-F) Higher magnification of hearts shown in (A-C) with close-up on IVS. Note reduced cardiomyocyte size and fusion in Tg#2 (F). (G-I) Adjacent histological sections from wt and Tg hearts shown in A-F stained with an anti-phospho-histone H3 antibody, demonstrating ventricular hyperproliferation of Tg#1 (H). (J) Average numbers of positive cells in selected areas (n=3) of the RV, IVS and LV myocardium on three different sections of each genotype per 100 DAPI-positive cells are shown. *P=0.016 versus wt.