Optical studies on contractile structures during activity

The optical properties of myocardial fibers and skeletal fibers were compared at rest and during activity. Scattering by myocardial trabeculae is more important than by skeletal fibers but birefringence of myocardial trabeculae is less important than that of skeletal fibers. The absorbance curves of both isolated myocardial trabeculae and skeletal fibers in vivo reflect their main components; during contraction the absorbance increases mainly at 285 nm and this increase starts earlier than contraction recorded with a mechanotransducer. An absorbance change in the spectral range of 420-440 nm is also reported which could represent very early biochemical change in the contractile fibers. The technique used, combined with electrophysiological data, allows one to study different problems related to the biophysics and biochemistry of contraction.