Ultrastructure of Taenia saginata oncospheres cultivated in artificial media.

Oncospheres of Taenia saginata cultivated in Leibovitz's medium on a cell monolayer from calf kidney developed up to 10th day of in vitro cultivation. Fine and often branched microvilli were observed on their surface. On day 5 of cultivation, the muscle system of hooks turned to a granular matter and on day 7 neither hooks nor their muscle system were found. The tegumental cytoplasm was not formed in the period of 7-60 days of cultivation. On days 7 and 10 of cultivation, a contact of oncospheres with the cells of monolayer was visible. On day 10 of cultivation, an extrusion of a portion of cytoplasm of surface cells filled with minute vesicles occurred. The bonds among cells, particularly in the centre of the oncosphere, were loosened in a 30-day-old culture and the cells were interconnected by long cytoplasmic bridges. Degenerative changes occurred on about day 40 of cultivation. The oncospheres cultivated in pure Leibovitz's medium lost the microvilli on their surface and the original tegumental cytoplasm turned to a fibrous layer already on day 5 of cultivation. Dystrophic changes in cells occurred from day 7 of cultivation and gradually increased.