(Mag. 216 K). Intranuclear replication of poliovirus in cell culture. Figure 15 is a TEM image at high magnification of a 7 h cell culture infected with poliovirus, showing a cluster of intranuclear small virus particles. The clustered particles measure approximately 22 nm. Also there are larger particles of varying diameter measuring approximately 28 nm surrounding the cluster of small particles. There were no differences between the TEM images of coxsackievirus and poliovirus cultured in vitro. Bar = 100 nm.