Tissue transduction. (A) Tissue distribution of βgal expression 3 weeks following delivery of 2.4 × 10⁸ TU GP64/CMV-βgal. Control animals received injection of PBS (7 β-gal; 3 PBS). Error bars indicate mean ± SEM. (B) Localization of βgal expression in tissues (magnification, 20×). One-month-old mice were injected via tail vein over 2 consecutive days with 2.4 × 10⁸ TU GP64/CMV-βgal. Three weeks after injection, the mice were killed and organs (liver, heart, spleen, kidney, and lung) harvested and X-gal stained.