Cellular pathology in mouse embryonic brain cells following in vitro penetration by sporozoites ofEimeria papillata

The pathology that occurs in mouse embryonic brain (MEB) cells that have been penetrated by sporozoites ofEimeria papillata was studied by light and electron microscopy. At the light microscopy level the greatest number of intracellular parasites was seen at 15 and 45 min postinoculation (PI). The monolayer of MEB cells had begun to round up by 45 min PI, and by 60 min PI most of the cells were stripped from the coverslip. Little ultrastructural damage was seen in MEB cells just penetrated by the parasites at 15 min PI, and no host cell membrane was seen around the sporozoites that had just entered the cells. Flexing and bending of the sporozoites within the MEB cell caused vacuolization of cell cytoplasm and in some cases rupture of host cell membrane. Sporozoites leaving the host cells at 15 min PI caused a rupture of the host cell membrane at the apical end of the parasite, and both host cell membrane and cytoplasm were attached to the surface of the parasite. MEB cells still attached to coverslips at 45 min PI demonstrated complete degeneration.