Figure 2. Overexpression of cyclin B1, but not CDC2, increases the proliferative capacity of P3 neonatal rat cardiomyocytes.

(A) Proliferation of tropomyosin-positive neonatal cardiomyocytes following transfection is shown (means±S.E.M.; n=3). (B) Protein expression levels of cyclin B1 and CDC2 in vector, cyclin B1 and/or CDC2 transfected neonatal cardiomyocytes. (C) A representative kinase assay showing cyclin B1–CDC2 kinase activities in transfected cultures is presented. Relative levels of histone H1 phosphorylation in transfected cardiomyocytes are represented graphically below (means±S.E.M.; n=3). *P<0.05 compared with vector controls.