INTERFERON PRODUCTION AND SENSITIVITY OF SEMLIKI FOREST VIRUS VARIANTS

Semliki Forest virus was passaged 10 times in series in calf kindly cells, starting with virus passaged in the mouse brain (MB virus). A variant was obtained (termed CK virus). The two viruses were antigenically indistinguishable. When grown on L cells, CK virus formed smaller plaques than MB virus. In parallel growth curve studies in calf kidney cells, a small inoculum of CK virus grew more rapidly and to a higher final titre than a comparable inoculum of MB virus, and usually stimulated production of less interferon. Pre-treatment of cells with calf interferon reduced the growth of both viruses, but especially that of MB virus. The results are considered in relation to the phenomenon of virus adaptation. It is suggested that such differences between the two variants in their relative sensitivity to and production of interferon could have played a part in the emergence of CK virus as the predominant type during serial passages in calf cells.

I wish to thank Mr H. Moores and Mr R. Sims for skilful technical assistance.

SENSITIVITY OF COCCAL AND L FORMS OF STAPHYLOCOCCUS AUREUS TO FIVE ANTIBIOTICS

Kagan, B. M. (Cedars of Lebanon Hospital, Los Angeles, Calif.), Susan Zolla, R. Busser, and Silvija Liepnieks. Sensitivity of coccal and L forms of Staphylococcus aureus to five antibiotics. J. Bacteriol. 88:630-632. 1964.-Antibiotics whose primary site of action is in the cell wall (penicillin and cephalothin) do not inhibit growth of L-phase organisms. In this study, kanamycin, neomycin, polymyxin B, lincomycin, and gentamycin were found to be more active against L-phase growth of Staphylococcus aureus in vitro than against the coccal forms. Therefore, their primary site of antimicrobial activity appears to be other than that involved in the synthesis or integrity of the cell wall.

NUCLEAR MEMBRANES OF CULTURED MAMMALIAN CELLS IN THE PERIOD PRECEDING DNA SYNTHESIS

When kidney cells are cultured directly from the rabbit, the nuclear membranes undergo a change that can be measured as an increase in electrophoretic mobility. The change appears to begin immediately upon culture and is maximal 2 hours later, after which the mobility remains constant at the elevated level. Actinomycin D and p-fluorophenylalanine, but not EDTA or ionizing radiation, suppress the increase in nuclear electrophoretic mobility. With synchronously growing L cells, no change was detected in nuclei from cells taken during various parts of the division cycle.

INTRACELLULAR FATE OF MENGO VIRUS RIBONUCLEIC ACID

Homma, M. (The Wistar Institute, Philadelphia, Pa.), and A. F. Graham. Intracellular fate of Mengo virus ribonucleic acid. J. Bacteriol. 89:64-73. 1965.-P(32)-labeled, purified preparations of Mengo virus adsorbed rapidly and irreversibly to L cells maintained in suspension cultures. At intervals after adsorption of labeled virus, the total ribonucleic acid (RNA) of infected cells was extracted by a phenol technique. Infectivity titrations on this RNA showed that it retained its full biological activity during the early part of the eclipse period. Sucrose gradient sedimentation analyses showed also that this RNA lost none of its structural integrity throughout the eclipse period. No evidence was found for a double-stranded structure involving parental RNA. When cells infected with P(32)-labeled virus were broken open during the first 7 hr after infection, no more than 20% of the parental RNA could be digested with ribonuclease. Electron microscopy indicated that only one particle in five of the purified viral populations was infectious. It is suggested that only one of five adsorbed virus particles was uncoated and that its RNA remained in the cell in an undegraded form during the eclipse period. The other adsorbed particles were not uncoated and took no part in the process of infection. The maximal transfer of parental RNA to progeny virus was 4.5%.

CYCLOHEXIMIDE: ASPECTS OF INHIBITION OF PROTEIN SYNTHESIS IN MAMMALIAN CELLS

Cycloheximide and acetoxy-cycloheximide specifically inhibit protein synthesis in L-cells growing in suspension culture. In extracts of rat liver, the drugs inhibit transfer of amino acid from soluble RNA to polypeptide. Unlike puromycin, these drugs do not accelerate release of nascent polypeptide chains. The drugs have no effect on protein synthesis in extracts of Escherichia coli.

HOMOGRAFT TARGET CELLS: SPECIFIC DESTRUCTION IN VITRO BY CONTACT INTERACTION WITH IMMUNE MACROPHAGES

Specific adherence and mutual immunologic destruction occurred after contact in vitro of immune peritoneal macrophages from C57BI/6K mice with homograft target cells from A/Jax mice. Cell destruction apparently resulted from a nonphagocytic mechanism involving cell contact rather than humoral antibody. Cell destruction was determined by a plaque technique with either immunecells or target cells as monolayers.