RT-PCR of viral RNA extracted from the supernatants of NB-DNJ-treated MDBK cells. MDBK cells were grown to confluency in six-well plates, infected with cytopathic BVDV, and incubated for 3 days in the absence or presence of 4.5 mM (1,000 μg/ml) NB-DNJ. Yield assays were performed with the resulting culture medium supernatants. Viral RNA was purified from the culture medium supernatants of both plaque and yield assays, and RT-PCR was performed as described in Methods. The samples were analyzed by electrophoresis in a 1.5% agarose gel and stained with ethidium bromide. Lanes: 1, 100-bp DNA ladder; 2, culture medium from uninfected cells; 3, plaque assay culture medium from infected cells, no NB-DNJ; 4 and 5, products of a PCR on 1:10 and 1:100 dilutions, respectively, of the sample used in lane 3; 6, plaque assay culture medium from infected cells maintained in 4.5 mM NB-DNJ; 7 and 8, products of a PCR on 1:10 and 1:100 dilutions, respectively, of the sample used in lane 6; 9, yield assay culture medium from cells incubated with plaque assay supernatant from untreated cells; 10 and 11, products of a PCR on 1:10 and 1:100 dilutions, respectively, of the sample used in lane 9; 12, yield assay culture medium from cells incubated with plaque assay supernatant from NB-DNJ-treated cells; 13 and 14, products of a PCR on 1:10 and 1:100 dilutions, respectively, of the sample used in lane 12; 15, RT-PCR product using a cDNA control.