The susceptibility of a variety of cell lines of different mammalian origin to cytotoxic (CT) induction by either ultraviolet light-irradiated reovirus type 2 (UVR2) or viable reovirus type 2 plus the protein synthesis inhibitor, cycloheximide, was examined. The following groups of cells were found to be susceptible to CT-induction: certain tumor cells and spontaneously transformed cell lines of human origin and certain virally and spontaneously transformed cell lines of murine origin. The following groups of cells were found to be resistant: normal human diploid cell lines, primary and continuous cell cultures of subhuman primates, primary mouse cells, normal rat kidney cells and baby hamster kidney cells. Susceptibility to CT-induction could not be related to the adsorption of virus to cells, nor to the capacity of the cell to support virus replication.

Double-stranded ribonucleic acid ( RNA ) extracted from purified reoviruses of all three serotypes and from type 3 virus-infected cells was analyzed by polyacrylamide gel electrophoresis. It was calculated that each RNA includes 10 segments: 3 large, 3 intermediate, and 4 small fragments corresponding to molecular weights of about 2.5, 1.4, and 0.8 × 10 6 daltons, respectively, or a total of 15 × 10 6 daltons.

Yellow-head virus (YHV), a highly virulent virus of cultured penaeid shrimp, was originally isolated from the black tiger shrimp Penaeus monodon in Thailand. It was initially described as a baculovirus, but was recently reported to be a n RNA-containing virus. The present study reaffirms the genome of highly purified YHV to be an unsegmented single-stranded RNA with negative polarity and of approximately 22 kb size. When analysed by SDS-PAGE, the purified virus yielded at least 4 viral structural proteins of 170, 135,67 and 22 kDa. The 135 kDa protein was determined to be glycosylated. YHV, as with VSV, a rhabdovirus, was found to agglutinate chicken red blood cells. The highly flexible enveloped bacilliform YHV particles measured 50-60 X 190-200 nm. Since the virus had a number of properties in common with rhabdoviruses, particularly plant rhabdoviruses, it was provisionally classified as a rhabdovirus.

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