Neurons containing Alz-50-immunoreactive granules around the cerebral infarction: evidence for the lysosomal degradation of altered tau in human brain?

Little is known about the metabolic process of tau and tau-derived substanc es. Alz-50- and tau 2-immunoreactivities in intracellular granules of neuro ns were observed in regions surrounding infarcted foci in the human cerebra l cortex. Ultrastructurally, these granules in the fresh infarcted region e xhibited primary lysosome-like structures, while those in old infarctions w ere lipofuscin. These findings indicate that tau is metabolized within lyso somes in neurons damaged by ischemic injury in human cortical penumbra. Alz -50-positive granules were more prominent in fresh infarction than in old i nfarction. After undergoing degradation and modification, altered tau might remain, at least partially, in secondary lysosomes. (C) 2000 Elsevier Scie nce Ireland Ltd. Ail rights reserved.