aging apoptosis cellularcontrolmechanisms cellularsenescence cellularsignaltransduction chemistry cyclicadenylicacid cyclicamp cyclicamp-dependentproteinkinases exercise metabolism molecularaspects muscles myocardium nervoussystem neurochemistry organic phosphates phosphoproteinphosphatases phosphoproteins physiologicalaspects physiology physiopathology proteinkinases proteins qh608p9672004 qp551 qu55n468p1984 qu55r4521993 qv285k14b1969 secondmessengersystems signaltransduction tauopathies transcriptionfactors we103e9551995