Fig. 3. ß-Galactosidase activity detected in mammary gland epithelial cells in primary cultures and AdCre1-infected mammary gland epithelial outgrowths. (A) 80% of MECs infected with Adß-gal at an MOI of 50 are ß-galactosidase positive, magnification 100x; (B) not infected with Adß-gal, 100x. (C) 71% of R26R MECs infected with AdCre1 at an MOI of 50 are ß-galactosidase positive, 100x. (D,E) X-gal and whole mount staining with carmine aluminum of two primary outgrowths of a single primary culture 15 weeks post transplantation. 9472R, 15 day pregnant, 40x (D); 9471R, virgin, 10x (E).