ABSTRACT
In patients with Alzheimer’s disease (AD), large numbers of senile plaques are found throughout the cerebral neocortex and hippocampus. These senile plaques, which are present in small numbers in the brains of aged mammals and normal elderly individuals, are observed in large numbers only in AD and thus are specific for this disorder. Classic neuritic senile plaques consist of a spherical cluster of altered neurites surrounding an amyloid core composed of 5-10 nm wide fibrils that can be visualized on light microscopy by staining with Congo Red or Thioflavin S (Terry, 1985). In these plaques, microglia are intimately associated with the amyloid cores, and there are surrounding astrocytes with processes that project through the altered neurites toward the amyloid core. In many cases of AD, amyloid fibrils are also found in the walls of cerebral blood vessels (Glenner, 1983).
