Abstract
Summary
1. The cytopathogenic titer of certain orphan viruses in monkey kidney tissue culture was depressed or delayed when grown in the presence of a medium which developed an acid pH. This phenomenon has been termed the apH effect. 2. Sensitivity to the “pH effect” appeared to be strain characteristic. Differences occurred among serotypes as well as within serotypes of the orphan viruses. One Coxsackie group B virus tested also demonstrated the “pH effect.” Two poliovirus types tested were minimally affected by pH variation. 3. Neutralization of tissue culture acidity with an excess of NaHCOs, or prevention of acid formation by omission of glucose restored optimal viral cy-topathogenicity. 4. The “pH effect” tended to be less evident with rapidly cytopathogenic agents or in the presence of large inocula. 5. Rate of primary isolation of orphan virus from stool suspensions was substantially decreased when acid producing tissue culture medium was used.
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