All Phenotypes Tg(Myh6-MYL3*)#Dsc MGI Mouse

abnormal cardiac muscle tissue morphology ( J:178377 )

• papillary muscle fibers show a shift of actomyosin cross-bridge mass from the thick filament backbone toward the thin filaments in rigor

abnormal myocardium layer morphology ( J:195614 )

• myocardium exhibits reduced myosin content

thick interventricular septum ( J:195614 )

• increase in interventricular septal wall thickness in systole and in diastole

enlarged heart ( J:195614 )

• large increase heart size at 2 months of age

• however, no myofilament disarray or fibrosis is seen

increased heart weight ( J:178377 )

• increase in heart weight-to-body weight ratio

cardiac hypertrophy ( J:178377 , J:195614 )

• hearts exhibit cardiac hypertrophy which increases with age (J:178377)

• however, ventricles appear normal (J:178377)

• increase in interventricular septal wall thickness in systole and in diastole, however, ejection fraction and cardiac output are normal, indicating that hearts hypertrophy as mice grow older but do not exhibit functional abnormalities (J:195614)

abnormal myocardial fiber physiology ( J:195614 )

• 15% and 44% decrease in maximal force in skinned muscle fibers of 3 and 7 month old mice, respectively compared to wild-type mice indicating reduced contractile force

• slight, but significant, decrease in the calcium sensitivity of force in muscle fibers

• the fraction of total myosin cross-bridges that can attach to actin during maximal calcium activation is decreased about 15% in the myocardium