Fig. 3.

Ultrasmall immunogold labeling (silver intensified) of PrP and PrP-res in N2a + 22L cells lightly fixed and then permeabilized in situ for antigen detection. (Top) A typical low-power image where many grains are on the plasma membrane (arrowhead) and dispersed in the cytoplasm. Nuclei (N) and clusters of IAP retroviruses (arrow) are not labeled. (Middle) Grains over PrP amyloid fibers in characteristic crisscrossing bundles (A) and also over RER membranes (arrows). Label was not seen over mitochondrial cristae (m) as representatively depicted. (Bottom) PrP does not localize over the 25-nm virus-like dense particles but can be associated with the outer RER membrane. (Scale bars: 100 nm.)