Myocytes, CardiacMyocardiumCells, CulturedHeartAnimals, NewbornCardiomegalyMutationMyocardial ContractionRats, Sprague-DawleyHeart VentriclesPhenotypeRats, WistarCalciumMolecular Sequence DataMitochondria, HeartMice, TransgenicSignal TransductionMutation, MissenseMice, KnockoutCell DifferentiationApoptosisPedigreeMyocardial Reperfusion InjuryCardiotonic AgentsSarcomeresEmbryonic Stem CellsMice, Inbred C57BLBase SequenceCell SizeGATA4 Transcription FactorRNA, MessengerCalcium Channels, L-TypeIsoproterenolDisease Models, AnimalAmino Acid SequenceHypertrophyConnexin 43Gene Expression RegulationMuscle CellsMuscle ProteinsCalcium SignalingTranscription FactorsSarcoplasmic Reticulum Calcium-Transporting ATPasesReverse Transcriptase Polymerase Chain ReactionSarcolemmaCell LineCardiac MyosinsGene ExpressionBlotting, WesternSodium-Calcium ExchangerCardiomyopathiesHeterozygoteMyocardial IschemiaMyoblasts, CardiacExonsTime FactorsPhosphorylationVentricular MyosinsVentricular RemodelingHomozygoteAdrenergic beta-Agonists