Figure 3.

(a) Brain TCA-precipitable (open bars) and non–TCA-precipitable ¹²⁵I radioactivity (solid bars) after intracerebral microinjections of ¹²⁵I-Aβ_1-40 (60 nM) into the caudate nucleus in mice, expressed as a percentage of total ¹²⁵I radioactivity in the brain; mean ± SD of three to five animals. (b) Left panel shows HPLC elution profile of brain tissue 60 minutes after intracerebral microinjection of ¹²⁵I-Aβ_1-40 (60 nM). Separation was performed for 30 mg of brain tissue on a reverse-phase HPLC column, using a 30-minute linear gradient of 25–83% acetonitrile in 0.1% TFA, pH 2. ¹²⁵I-Aβ_1-40 eluted at 52%, corresponding to the elution time of Aβ_1-40 standard. Right panel shows SDS-PAGE analysis of brain tissue supernatant at 30 minutes (lane 1) and 60 minutes (lane 2) after intracerebral microinjection of ¹²⁵I-Aβ_1-40 (60 nM). The radioactivity in the brain eluted as a single peak on HPLC, with the same retention time as the Aβ_1-40 standard (data not shown). Aliquots of lyophilized sample were subjected to 10% Tris-tricine SDS-PAGE, transferred to a nitrocellulose membrane, and exposed to x-ray film. (c) Plasma TCA-precipitable (open bars) and non–TCA-precipitable ¹²⁵I radioactivity (filled bars) after intracerebral microinjections of ¹²⁵I-Aβ_1-40 (60 nM) into the caudate nucleus in mice, expressed as a percentage of total ¹²⁵I radioactivity in plasma; mean ± SD of three to five animals.