HeartMyocardiumHeart RateChick EmbryoCells, CulturedHeart FailureMyocardial ContractionHeart DiseasesMyocytes, CardiacHeart TransplantationHeart Defects, CongenitalHeart AtriaCalciumCell AggregationFetal HeartTime FactorsCell DifferentiationGuinea PigsCell SeparationHeart ValvesVentricular FunctionAction PotentialsAnimals, NewbornIon ExchangeMembrane PotentialsSarcolemmaIsoproterenolFlow CytometryKineticsModels, CardiovascularSodiumMyofibrilsMercaptoethylaminesHeart BlockCulture TechniquesSodium-Calcium ExchangerMice, Inbred C57BLStem CellsIon ChannelsHeart VentriclesElectric ConductivityCell DivisionPotassiumQuinuclidinyl BenzilateRats, Sprague-DawleyIron RadioisotopesSarcoplasmic ReticulumHeart Arrest, InducedPerfusionCardiotonic AgentsAdenosine TriphosphateRats, WistarHeart Function TestsOuabainElectrophysiologyGene Expression Regulation, DevelopmentalRNA, MessengerRats, Inbred StrainsImmunohistochemistryModels, BiologicalCell CountCyclic AMPCalcium ChannelsTissue Culture TechniquesSpleenVerapamilReceptors, MuscarinicCell LineageRabbitsMyocardial IschemiaCarbacholStrontiumSignal TransductionVeratrinePhenotypeReceptors, Adrenergic, betaT-LymphocytesCell ProliferationOxygen ConsumptionTetrodotoxinParasympathomimeticsCell LineMitochondria, HeartCoronary DiseaseHemodynamicsMicroscopy, ElectronPatch-Clamp TechniquesCell CommunicationDose-Response Relationship, DrugClone CellsMuscle ProteinsMolecular Sequence DataBariumLactatesCell TransplantationDisease Models, AnimalMice, KnockoutT-Lymphocyte SubsetsOligomycinsImmunophenotyping