FIG. 5.

Electron microscopy of virus-infected cells. BHK-21 cells were infected (16 h; multiplicity of infection, 5) with WT, M7⁻FRT, or M7REV viruses as indicated. The pictures shown are representative of at least 10 sections per sample. The heterogeneity in the cross-sectional area of the M7⁻FRT virions presumably reflects some tangential cuts, as would be expected with a densely packed population. We saw no evidence for abnormal virion morphologies in the absence of gp150.