title: Intensity fluctuation spectroscopy monitors contractile activation in "resting" cardiac muscle.
abstract: Intensity fluctuations in a laser beam scattered by nonbeating isolated rat cardiac muscle varied directly with the calcium concentrations in the bathing fluid. The steady-state level of these fluctuations varied directly with calcium-dependent force suggesting that the intensity fluctuations reflect an interaction of calcium ions with the myofilaments. The demonstration that both a portion of resting force and the frequency of intensity fluctuations vary directly with calcium even in quiescent conditions indicates that some contractile activation is present in the resting muscle.
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D006321:Heart / Q000502:physiology*; D007834:Lasers; D009124:Muscle Proteins / Q000502:physiology; D009200:Myocardial Contraction / Q000187:drug effects; D051381:Rats; D012542:Scattering, Radiation; D013057:Spectrum Analysis
chemical_list: D009124:Muscle Proteins; D002118:Calcium