Grain counting and cell communication

Incubation of a population of cells with tritiated uridine or hypo-xanthine leads to incorporation of radioactivity into the RNA of all but the mitotic cells. Analysis of the grain counts shows these to fall into a Poisson distribution, the median point of which corresponds 

Cell culture is the predominant and indispensable tool for virus isolation and cultivation infectivity assays and vaccine production and testing. Although some viruses are more easily isolated in animals and embryonated eggs, the modem era of virology only began when Enders et al. (1949) showed that poliovirus was able to reproduce in various kinds of human embryonic cells in culture whereas in vivo its multiplication is largely restricted to the neurons in the grey column of the spinal cord. 

In the early years primary cells were used as viral hosts. Although these have limited growth potential they support the replication of a wide variety of viruses. Continuous cell strains such as mouse L929 or human HeLa cells are now commonly used for virus growth in biochemistry laboratories, but for vaccine production untransformed, diploid cell strains are the preferred hosts. 

rather than a productive infection, the virus brings about cellular transformation this also produces characteristic changes in cell morphology and growth characteristics. This is discussed in more detail in 14.4. 

A detailed introduction to animal viruses may be found in Fenner et al. (1974). 

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