Mice and diets. One-month-old male mice of the long-lived B6C3F1 strain were purchased from Harlan (Indianapolis, IN) and maintained as described after weaning (15). Mice were housed in groups of 4 per cage and fed a non-purified diet, PMI Nutrition International Product #5001 (Purina Mills, Richmond, IN). At 5 months of age, the mice were individually housed, and randomly assigned to one of two groups, control (CON) or long-term CR (LTCR). CON mice were fed 93 kcal per week of a defined control diet (AIN-93M, Diet No. F05312, BIO-SERV). LTCR mice were fed 52.2 kcal per week of a defined CR diet (AIN-93M 40% Restricted, Diet No. F05314, BIO-SERV). The LTCR mice consumed approximately 40% fewer calories than mice in the CON mice. The CR diet was enriched so that the CR mice consumed approximately the same amount of protein, vitamins, and minerals per gram body weight as the control mice. Keywords = CR mimetics Keywords = microarray profiling Keywords = drug discovery Keywords = gene-expression biomarkers