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A new method, which enabled the first immunohistochemical documentation of abnormal prion protein (PrP) in all patients with Creutzfeldt-Jakob disease (CJD), was established. This method designated as "hydrolytic autoclaving" revealed punctate PrPCJD stainings around the neuronal cell bodies and dendrites in CJD brains. These punctate stainings were almost identical with that of synaptophysin, suggesting PrPCJD accumulations in the synaptic structures. Subcellular fractionation revealed that prion protein in Creutzfeldt-Jakob disease (PrPCJD) was most concentrated in the synaptosomal fraction. In CJD patients with a long clinical course, synaptophysin immunoreactivity decreased, and synaptic PrPCJD accumulated with a wider distribution. These results suggest that synaptic PrPCJD accumulations might be responsible for the neuronal dysfunction and degeneration in CJD.

Alpha B-crystallin, a major protein of the vertebrate lens, is found in the central nervous system (CNS) and is a major protein component of Rosenthal fibers (RF), intracytoplasmic inclusions within astrocytes. Its level of expression in the normal CNS is low and appears to be confined to glial cells, both astrocytes and oligodendrocytes. A number of human brains displaying a variety of pathologic changes were examined by immunohistochemistry with an anti-alpha B-crystallin antiserum and increased immunoreactivity was found in astrocytes and oligodendrocytes without the formation of RFs. Furthermore, some neurons in neurodegenerative disorders were also immunolabeled with the anti-alpha B-crystallin antiserum. Thus, the accumulation of alpha B-crystallin appears to be part of the repertoire of reactive processes of CNS glial cells and some neurons in pathologic conditions.

Ultrastructural immunoreactivities of alpha B-crystallin, glial fibrillary acidic protein (GFAP), ubiquitin, and vimentin in Rosenthal fibers (RFs) isolated from an Alexander's disease brain were investigated using nonosmium and low-temperature embedding technique. The morphology of RFs embedded in Lowicryl K4M resin was well preserved after treatment with 0.5% Triton X-100. alpha B-crystallin immunoreactivity was present in RFs of various sizes and was the strongest in loosely scattered deposits, which were considered to be the initial stage of RFs. Glial fibrillary acidic protein immunoreactivity in RFs was heavy, homogeneous throughout RFs, and equivalent to that in networks of glial filaments. Immunoreactivities of both alpha B-crystallin and GFAP were mainly restricted to the high electron-dense areas within RFs and were proved to exist close to each other by double immunolabeling. Rosenthal fibers were negative for vimentin. Ubiquitin immunoreactivity was relatively homogeneous in RFs with small diameters, but in RFs with large diameters, the immunoreactivity diminished in the center. Based on these observations, combined with the tendency of self-aggregation of alpha B-crystallin, it is conceivable that RFs are huge aggregation products of alpha B-crystallin involving GFAP, and that ubiquitination may be a consequent phenomenon, as it may be in other intracytoplasmic inclusions, such as neurofibrillary tangles and Lewy bodies.