1. Dideoxyinosine (ddI) has recently been approved for the treatment of patients with HIV infection. As increasing numbers of such patients are pregnant, we wished to define the rate and mechanism(s) of ddI transfer by the placenta to the foetus. Using isolated single perfused human term placental cotyledons, the drug was shown to cross the placenta from mother to foetus at a rate of 25% that o...

Endonuclease V, encoded by the nfi gene, initiates removal of the base analogs hypoxanthine and xanthine from DNA, acting to prevent mutagenesis from purine base deamination within the DNA. On the other hand, the RdgB nucleotide hydrolase in Escherichia coli is proposed to prevent hypoxanthine and xanthine incorporation into DNA by intercepting the noncanonical DNA precursors dITP and dXTP. Bec...

Twenty-one variant clones of Friend erythroleukemia cell were isolated and characterized. Seventeen clones were resistant to induction of hemoglobin synthesis by one of eight drugs that have been reported to induce erythroid differentiation in clone 745. Four clones re sponded hypersensitively to dimethyl sulfoxide or hypoxanthine. The variant clones were treated with inducing drugs to determin...

Methotrexate (MTX)(2 x 10(-8) M) inhibited DNA synthesis in CCRF-CEM cells, causing cells to accumulate in early S phase while cellular RNA content and cell size continued to increase. Two-parameter flow cytometric analysis of DNA and RNA showed these cells to be unbalanced with excessive RNA relative to DNA content. Fifty % of cells remained viable after a 96-hr exposure to 2 x 10(-8) M MTX. I...