NEUROFIBRILLARY TANGLES IN THE CEREBRAL-CORTEX OF SHEEP

Neurofibrillary degeneration, including neurofibrillary tangles (NFTs) and neuritic plaques, is an important pathological hallmark of Alzhei mer's disease (AD). Unfortunately, no practical animal model of neurof ibrillary degeneration has been described. We report here the presence of structures in the cerebral cortex of sheep, Ovis aries, that resem ble Alzheimer NFTs and neuritic plaques. NFT-like structures and clust ers of degenerating neurites are stained by silver impregnation and th ioflavin-S, and are immunoreactive with antibodies against tau microtu bule-associated proteins. Viewed under the electron microscope, tau-im munoreactive tangles consist of paired helical filaments. Naturally oc curring neurofibrillary structures in sheep cortex provide a model for studying the pathobiology of Alzheimer's disease.