[The effect of coccidia of the genus Sarcocystis on the morphofunctional organization of the skeletal musculature in experimentally infected mice. I. The muscle fiber].

At the ultrastructural level, the cellular response of skeletal muscles on developing Sarcocystis muris sarcocysts has been followed in mice at different times after sporocyst feeding, i.e. in 1, 2.5, 6 and 10 months, resp. The developing cyst creates a progressive degeneration of the infected muscle cell that involves organelle disorganization and formation of numerous vacuoles in the cytoplasm as a consequence of cell edema. Products of the host cell degradation, shaped as fibrillar-granular structures, are seen to find their way to the cyst wall outgrowings, where they become denser and on being covered with membranes appear eventually in the sarcocyst ground substance. Later on, the membranes around the granules disappear. In the course of its development, the sarcocyst totally destroys not only the harbouring muscle cell and the nearest connective tissue elements of the endomysium, but also the previously intact neighbouring cells. The involvement of some proteolytic enzymes in this process is suggested.