Electron microscopy of cells cultured in serum-free medium after inoculation of swine vesicular disease virus.

Morphological alterations of IB-RS-2 cells cultured in serum-free maintenance medium after inoculation of swine vesicular disease virus (SVDV) were studied electron-microscopically. Cells harvested 0 to 3 hours after inoculation showed no alterations. Cellular alterations were observed from 4 to 7 hours after inoculation. Many vacuoles appeared just beneath the cytoplasmic membrane and were separated by thin cytoplasm. Narrow pathways were sometimes seen in the degenerative cells. They occasionally ran from the vacuole just beneath the cytoplasmic membrane to the nuclear cistern. Ribosome-like granules were seen along the narrow pathway or diffusely in the cytoplasm, or accumulated to form an islet. Membrane-bound bodies were frequently noticed in the central region of the cell. Cytoplasmic blebs were sometimes seen projecting from the cell surface. Vacuoles, narrow pathways and cytoplasmic blebs were absent in cells cultured in the medium with serum. So serum might exert some effects on the cytoplasmic membrane or cytoskeletal framework. Crystalline arrays of SVDV were found in the cytoplasm of degenerative cells harvested from 4 to 7 hours after inoculation. They were near the ribosome-like granules and membrane-bound bodies, but had no relationship with vacuoles just beneath the cytoplasmic membrane and narrow pathway. Their size and morphology were the same as those seen in the cells cultured in the medium with serum.