Abstract

Laser irradiation of myofibrils in cultured neonatal rat heart cells at a wavelength of 537 nm produced subsarcomeric lesions that were visible in the phase contrast, polarizing and electron microscopes. This irradiation resulted in the production of contractile changes as frequently as the microbeaming of mitochondria. Irradiation of the cell surface via carbon particles produced similar contractile changes more often than either myofibrillar or mitochondrial irradiation. The contractile changes noted in this study appear to be dependent on extracellular calcium. © 1978.