[State of the contractile apparatus during the development of a pathological process in the muscles. II. The effect of Ca2+ on the morphology of spreading necrosis caused by UV light].

Using phase-contrast technique and electron microscopy, a study was made of morphological changes of contractile system of striated muscle fibre during the spreading necrosis caused by ultraviolet light damage. It has been shown that the degree of manifestation of destructive changes in the contractile system depends upon Ca2+-ion concentration. The ultrastructural study of the damage region, under condition of muscle fibre stretching, made it possible to reveal the initial stages of formation of this pathological process. A possible contribution of intracellular membranous structures in spreading the destructive process along the muscle fibre is discussed.