Fig. 6.

3T3 test cultures used for viral replication test.A, DIC image of NIH 3T3 culture incubated with tissue culture supernatant from brain cultures that had been infected for 18 hr. Arrow identifies a single cell. B, Same field as in A, showing a single fluorescent 3T3 cell (arrow). C, In parallel cultures, DIC imaging shows a group of 3T3 cells, one identified with anarrow to facilitate recognition in DIC and fluorescence.D, With fluorescent microscopy of the same field, most of the cells express GFP-mediated fluorescence. Tissue culture supernatant was taken from brain cultures 42 hr after mCMV infection. In both sets of experiments, 3T3 cells were examined 18 hr after their initial incubation with brain culture supernatant. Scale bar, 25 μm.