RESUMO
Ubiquitin, an intracellular marker of non-lysosomal protein degradation was immunocytochemically and biochemically detected in paired helical filaments (PHF) of aged and Alzheimer's disease brains. Seven micron thick paraffin serial sections of the hippocampus were stained with PHF, or UBIQUITIN, or TAU antibodies using an indirect immunoperoxidase technique. The neuroplasm, axons, dendrites, neurophil threads of degenerating neurons from the stratum pyramidale and surrounding neuroparenchyma were intensely stained by the above types of antibodies. The cell bodies of these neurons had a specific shape, implicating the accumulation of intracellular cytoskeletal components. Using gel electrophoresis, Western blot and immunoblot techniques, ubiquitin epitopes were detected in PHF, where they were linked to tau protein. These results suggest that ubiquitin may be involved in the regulation of cellular events or degradation of the cytoskeletal protein tau,incorporated into PHF. Deposition of PHF in the perikarya of susceptible neurons may lead to their metabolic changes, reorganization of cytoskeletal components, impaired neuronal function, cell degeneration and death. (AU)