Figure 3.

Aβ levels in the brain and Aβ productions in vitro. A–C, Comparison of Aβ in TBS, SDS, and FA and total Aβ, Αβ₄₀, and Αβ₄₂ among groups at 3, 6, and 9 months of age (n = 10 in each group). Aβ in the brain was extracted sequentially in TBS, 2% SDS, and 70% FA water solution. Aβ peptide concentrations in the brain of animals were measured by ELISA. D–F, Comparison of total Aβ, Aβ₄₀, and Aβ₄₂ in serum at 3, 6, and 9 months of age. Aβ peptide concentrations in the serum of animals were measured by ELISA. G–H, Aβ production of cortical neurons in vitro. The cortex of 1-month-old female APP+/−p75+/+ and APP+/−p75−/− mice was isolated and cultured at 2.5 × 10⁵/ml in Neurobasal A/B27 with 0.5 mm glutamine, 5 ng/ml bFGF, 10,000 U/ml penicillin, and 1 mg/ml streptomycin in triplicate. Both culture medium and cell lysate prepared in RIPA buffer were collected after culture for 3 (G) and 5 (H) days and measured for Aβ by ELISA. * and ** denote p < 0.05 or p < 0.01 versus APP+/−p75+/+ mice.