Sindbis virus infection of cultured mosquito cells was found to have no effect on the growth ofthese cells; instead, a persistent infection ofthe culture followed an initial acute phase of rapid virus synthesis. Nearly all ofthe cells in the acute stage of infection were found to actively release virus in an infectious-center assay and to contain significant amounts of virus antigen as determined by immunofluorescence. Cells in the persistent phase of infection released few virions into the media, and only a small percentage of the cultured cells could be demonstrated to contain detectable amounts of virus antigen by immunofluorescence assay. In spite of the fact that nearly 100% of the cells in the persistent phase of infection were found to be virus negative by the two assays described above, the culture as a whole totally excluded the expression of superinfecting virus, as did cells in the acute phase, suggesting that most of the persistently infected cells did, indeed, contain virus information. Prevention of reinfection of the cells in the persistent phase by eliminating extracellular virus resulted in a curing of the culture such that it responded to infection by added virus much as would an uninfected culture.

Aedes albopictus (mosquito) celLs persistently infected with Sindbis virus for a period of 6 months release into the medium a low-molecular-weight material capable of specifically reducing the yields of Sindbis virus during the "acute phase" of infection in mosquito cells. The antiviral activity was produced in detectable levels at 3 days after infection, and its concentration in the extracellular medium increased thereafter. The antiviral activity was inactivated by treatment with the enzyme protease K and heat. It was not activated by treatment with antibody prepared against extracts of Sindbis virus-infected BHK-21 cells. The antiviral activity differs from interferon produced by vertebrate cells in that it is virus specific as well as cell specific.

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Chemical Stripping of the urinary bladder mucosa was studied in 38 cats using 5 to 25% formaldehyde solutions. The contact time varied from 1 to 20 min. With a 20% solution and contact time of 1 min, total denudation was possible without necrosis of subepithelial layers. In such cases, complete reepithelialisation and normal bladder dynamics were seen within 3-4 weeks after formaldehyde instillation. Signs of formaldehyde intoxication due to vesical resorption were not observed.