摘要：

Incorporation of tritium from thymidine-methyl-H3 (TMH3) in the Laredo strain of Entamoeba histolytica grown at room temperature in the CLG medium, as in the K9 strain grown at 37 C, occurs in both nucleus and cytoplasm. Most extensive cytoplasmic activity is detected during periods of most pronounced growth. Nuclear activity is generally evenly dispersed, but in some instances it is restricted to portions of the peripheral chromatin. The cytoplasmic label is shown to be due in part or wholly to ingestion of DNA of the nonmultiplying protoplasts of the associate cell (Bacteroides) used to support growth of amebae in CLG medium. This cytoplasmic label is unstable and at least some of it serves as precursor material for nuclear DNA of amebae. Experiments done with appropriate RNase and DNAse digestions, and unlabeled carrier compounds thymidine, uridine, thymidylic acid and uridylic acid, indicate that TMH3 is highly specific for DNA in this cell system and that the thymidine kinase salvage pathway is probably involved in TMH3 utilization.

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