Fig. 5.

Electron micrographs of lipid particles associated with iAβ and apoE3. Neuronal cultures were incubated with 10 μm iAβ or 0.25 μm apoE3 for 24 hr. The conditioned media of these cultures were collected, filtered with a 0.45 μm Millipore filter, subjected to an initial discontinuous density gradient prepared using KBr solution, and centrifuged at 34,500 rpm for 48 hr using a SW 41-Ti rotor. After centrifugation, 12 fractions were isolated, and lipid concentration and the density in each fraction were determined. HDL fractions were then diluted with 10-fold volumes of distilled water, followed by centrifugation at 34,500 rpm for 48 hr using a SW 41-Ti rotor. Electron microscopic examination of the lower part of each solution was performed. Negative staining of electron micrographs of lipid particles in the presence of apoE and iAβ is shown (a and b, respectively). Results of immunoelectron microscopy show that exogenously added iAβ1–40 forms complexes with lipid particles as demonstrated using the antibody directed against human Aβ1–17, 6E10 (Kim et al., 1990). c, Gold labeling is considered to be associated with lipid particles. d, In contrast, lipid particles were not labeled with gold without 6E10. Scale bar, 50 nm.