Rubella infected BHK-21 cell cultures although useful in immunofluorescence work have, as a rule, a very lout number of cells containing rubella virus antigen. This often presents a difficulty in reading the tests, particularly when a serum sample is being assayed for the presence of rubella specific antibodies in the IgM fraction of immunoglobulins.The reason for such a low percentage of infected cells, usually around 2 per cent, exhibiting rubella antigen is not quite dear. It has been suggested, however, that interferon or other cell products may be responsible for the inhibition of virus replication. In this connection it has been reported that production of interferon can be overcome by treating the cells with 5-iodo-2'-deoxy~dridine [IUdR] (1). It has also been reported that IUdl~ and 5-bromo-deoxyuridine [BUdR] are capable of activating the synthesis of both t~NA and DNA containing viruses (2,3,4,5).In view of the above observations, an attempt was made to determine if treatment of BHK-21 cells with these halogenated pyrimidines will increase the number of rubella antigen containing cells. The results of this investigation are reported here.BHK-21 ceil cultures were grown as monolayers in 30 ml Falcon plastic bottles, and were used for inoculation when each bottle contained approximately 6 • 105 cells. The inoculum per bottle was 0.5 ml, containing 5 • 10 a IND50 of rubella virus strain 1~-23.After 90 minutes of adsorption period at 36 ~ C, each inoculated culture received 5 ml of Eagle's minimum essential medium supplemented with 2 per cent fetal calf serum, and with or without halogenated pyrimidine, depending on the design of the experiment. After incubation for 24 hours at 36 ~ C and 72 hours at 33 ~ C, the infected monolayers were treated with trypsin-versene. The monodispersed cells were used for preparation of smears on glass coverslips. The smears were airdried, washed once in PBS and fixed in cold acetone (--20 ~ C) for 10 minutes. After allowing to drain, the smears were used for immunofluorescent staining.
I. PREFACEFowl leukosis was introduced primarily by ELLERMANN and BANG (1908), while chicken myxosarcoma by FUJINAMI (1909) and successively by Rous (1910) as diseases elicited by filtrable agents. Proliferating modes of these viruses, however, remain yet unclarified, except the only suggestive description of GAYLORD (1955) referring to Rous sarcoma.In respect to the viral tumor in mammals, on the other hand, C3Hmammary cancer called general interest, and especially, electron micrographical studies made by DMOCHOWSKI (1955), BERNHARD (1955), SUZUKI (1957) revealed the attitude of the cancer virus in the host cells, though these findings are thought to be the only exceptional case in mammalian cancer. However, GROSS (1951, 1954, 1957) reported his interesting works concerning leukemia in AK mice to explain the viral origin of this disease by way of his varied experimental procedures, though the proliferating modus of the causative virus is not yet demonstrated in the cytoplasm of leukemic cells by electron micrograph of ultra-thin sections (AMANO,
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