Changes in mRNA expression of APP, BACE1, and Sp1 in the frontal association cortex of aged monkeys after developmental exposure to Pb. The frontal association cortical tissue of 23-year-old control (Con) and Pb-exposed (Pb-E) monkeys were analyzed for mRNA expression of APP, BACE1, and Sp1. The mRNA expression of APP, BACE1, and Sp1 were validated by real-time PCR. Data shown represent the mean ± SEM (4 animals in each group). Values marked with an asterisk are significantly different from their corresponding controls (p < 0.05) as determined by Student's t test.