Figure 8.

Abnormal PrP (PrP^d) accumulation and membrane distortions on the surface of neurons and astrocytes in scrapie-infected sheep brain tissue. PrP^d is labeled with immunogold particles. A. PrP^d on the plasma membrane of a neuron without morphological changes. B. Complex dendrite membrane disturbances (microfolding-asterisks) associated with the formation of abnormal pits (not immunolabeled). C. PrP^d accumulation associated with the formation of excess coated pits (arrows) and with the transfer to membranes of adjacent processes (arrow heads). D. coated membrane invaginations, one of which shows a spiral, twisted neck (not immunolabeled). E. PrP^d on the plasma membrane of astrocytic processes containing abundant glial filaments. Parts of the plasmalemma of some processes have linear segments (arrowheads) suggesting increased membrane rigidity and incipient fibril formation. Adapted from (78).