The amounts of water-insoluble (SDS-GDFA soluble) Aβ in the APP23 Tg mice and non-Tg littermate brains. The quantification was done by EuIA. The mice ages are as in Figure 1. Solid lines, Tg mice; broken lines, control mice. (A) Aβ40. (B) Aβ42. (C) The Sum of both Aβ peptides. The water-insoluble Aβ40 begins to increase at 9 months of age, reaching a substantial level by 20 months of age in the Tg mice. The increase of the Aβ42 is less pronounced than the Aβ40 in the Tg mice. The EuIA demonstrated a ratio of Aβ40 to Aβ42 of 8.5:1.0.