ABNORMAL NEURITIC ARCHITECTURE IDENTIFIED BY DI-I IN PICKS-DISEASE

The fluorescent stain Di-I combined with confocal microscopy identifie d an abnormal neuritic pattern in the cortices of frontal and anterior temporal lobes in Postmortem tissues from patients with Pick's diseas e (PD). Focal, dense neuritic aggregates 50 to 200 mum in diameter wer e scattered throughout all cortical layers. The three-dimensional anal ysis provided by confocal microscopy revealed the neuritic clusters to consist of enlarged, randomly arrayed, dystrophic neurites that were not associated with amyloid deposits, astrocytic processes or capillar ies. In the intervening neuropil, there were fewer neurites compared t o controls. The occipital cor-tex, which is unaffected in PD, showed a neuritic architecture comparable to normal controls as did affected b rain tissues from patients with Alzheimer's disease or remote, ischemi c infarction. This neuritic pattern is, thus far, unique to PD and may reflect the loss of specific subpopulations of cortical neurons and p roliferation of neurites of the remaining neurons.