Intraneuronal cylindrical particles in Alzheimer's disease.

In this report we describe an unusual form of intraneuronal cylindrical particles (CP) in the brain of a 69-year-old man with typical Alzheimer's disease (AD). A large number of CP were seen in cortical neurons in the frontal and parietal lobes. The CP were always seen within the cisternae of endoplasmic reticulum, had a 25- to 30-nm-thick trilaminar wall and measured 80-95 nm in cross-sectional diameter. In an occasional neuron, the CP were seen next to filamentous constituents of neurofibrillary tangles. The remaining neurons containing CP appeared normal. A similar finding has been reported in another case of AD and also in two cases with other conditions, thus indicating that the presence of CP is not limited to AD. Morphologically similar intracisternal CP have been observed in the macrophages in certain strain of mice following implantation of dibenzanthracene. The CP in human brains and experimental animals show a remarkable resemblance to rhabdovirus and certain murine endogenous virus particles. The nature of these intraneuronal CP in human brains and their significance, if any, remain undetermined.