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Neurofibrillary Tangles and Senile Plaques in Aged Bears

Linda C. Cork D.V.M., Ph.D., Richard E. Powers M.D., Dennis J. Selkoe M.D., Peter Davies M.D., James J. Geyer M.S., Donald L. Price M.D.
DOI: http://dx.doi.org/10.1097/00005072-198811000-00006 629-641 First published online: 1 November 1988


In aged human beings and in individuals with age-associated degenerative disorders, particularly Alzheimer's disease (AD), neurons develop cytoskeletal abnormalities, including neurofibrillary tangles (NFT) and senile plaques (SP). Senile plaques occur in several nonhuman species; however, NFT, with ultrastructural or immunocytochemical similarities to those occurring in humans, have not been identified in other mammals. In this study of five aged bears (Ursus, 20-30 years of age), we identified cytoskeletal abnormalities similar to those occurring in humans. An aged Asiatic brown bear had NFT, composed of straight 10-16-nm filaments, that were immunoreactive with antibodies directed against: phosphorylated epitopes of neurofilaments (NF); tau; A68 (a protein enriched in AD); and an antigen associated with paired helical filaments (PHF). An aged polar bear had numerous SP; neurites of these plaques were immunoreactive with antibodies against phosphorylated epitopes of NF, but NFT were not identified. These results indicate that nonprimate species develop age-related cytoskeletal abnormalities similar to those occurring in humans. Investigations of the comparative pathology of aged mammals may be useful in elucidating the pathogeneses of these abnormalities.

Key Words
  • Aging
  • Alzheimer's disease
  • Cytoskeleton
  • Hippocampus