Cre activity in c-myc conditional knockout and control mice. Cre expressing c-myc+/+ and c-mycfl/fl mice were crossed to mice carrying the Rosa26R allele to obtain c-myc+/+;Rosa;Alb-Cre and c-mycfl/fl;Rosa;Alb-Cre mice. Liver cyrosections (10 μm) from male and female mice were fixed and stained for Lac-Z. Photomicrographs of three 20× fields from individual sections acquired from c-myc+/+;Rosa;Alb-Cre and c-mycfl/fl;Rosa;Alb-Cre mice are shown. All panels show images that are representative of the results obtained on multiple sections from at least 2 animals per group. The results were replicated in a duplicate experiment. The contrast was adjusted across the entire image to accurately reflect the appearance of the sections under the microscope.