Alzheimer patients and Down patients: cerebral preamyloid deposits differ ultrastructurally and histochemically from the amyloid of senile plaques

Alzheimer patients: preamyloid deposits are immunoreactive with antibodies to extracellular domains of the amyloid precursor protein

In patients with Alzheimer's disease, in patients with Down's syndrome and in aged non-demented individuals, anti-beta-protein antibodies label not only the fibrillary amyloid, but also preamyloid deposits. The latter are made up of amorphous material lacking the tinctorial, optical and ultrastructural properties of amyloid fibrils. To investigate the antigenic profile of preamyloid deposits, we have carried out an immunohistochemical study on specimens of cerebral cortex from 4 Alzheimer patients and two non-demented individuals, using antibodies to the beta-protein (anti-SP28), the C-terminal region of the amyloid precursor protein (APP) (anti-SP20) and an APP extracellular epitope between residues 50 and 100 (anti-preA4). Anti-preA4 and anti-SP28 immunoreactivity was found to be present in preamyloid deposits, whereas anti-SP20 immunoreactivity was not. These findings suggest that an extracellular portion of APP, close to the N-terminus of the molecule, participates with beta-protein in the composition of preamyloid deposits.

Widespread serum amyloid P immunoreactivity in cortical amyloid deposits and the neurofibrillary pathology of Alzheimer's disease and other degenerative disorders

Amyloid P (AP) component is present in all types of systemic amyloid deposits. Recently, it has been shown to be also present in cerebral amyloid lesions of Alzheimer's disease (AD). In this study, we used immunocytochemical methods to extend these findings at the electron microscope level and characterize the spectrum of AP immunoreactivity in neurofibrillary pathology (NFP) of AD and other neurodegenerative disorders including Down's syndrome (DS), Creutzfeldt-Jakob, Parkinson's, Pick's and diffuse Lewy body diseases and progressive supranuclear palsy. In AD and DS, AP immunoreaction product was evident in all the classical amyloid lesions and NFP in a large sample of all cortical areas examined. The distribution and relative intensity of immunostaining was similar to that of thioflavin S staining in serial sections. In many cases, however, plaques and vessels stained by anti-AP serum were not apparent with thioflavin S. Serial sections immunostained with antiserum to amyloid A, C-reactive protein or to other proteins involved in systemic amyloidoses and the acute phase response showed no evidence of staining in any of the cerebral lesions. Electron microscopy confirmed that AP immunoreactivity was associated with the abnormal filaments characteristic of NFP as well as amyloid fibrils found in plaques and vessels showing congophilic amyloid angiopathy. Plaques of Creutzfeldt-Jakob disease, Pick bodies of Pick's disease, tangles and Lewy bodies in Parkinson's disease and a subpopulation of Lewy bodies in the diffuse Lewy body disease coexistent with AD were also stained. With the exception of vessels in two of the five cases, AP was not detected in age-matched controls. Our observations indicate AP to be a consistent feature of cerebral NFP and amyloid deposits.

Hereditary cerebral hemorrhage with amyloidosis--Dutch type: its importance for Alzheimer research

Alzheimer's disease is now commonly regarded as a form of 'amyloid encephalopathy'. Amyloid deposits in the cerebral blood vessels and parenchyma consist mainly of a unique protein called amyloid beta protein (A beta P), which has a molecular weight of 4 kDa and is 42 amino acids long. These deposits are thought to be of pathogenetic importance in Alzheimer's disease. Recently, therefore, attention has been focused on the process of turnover of the precursor of A beta P to amyloid fibrils, and the deposition and persistence of A beta P in this disease. The study of several other diseases with cerebral A beta P deposition can be informative in this respect, because they allow the comparison of different pathogenetic mechanisms that lead to this type of deposition. One of these diseases is hereditary cerebral hemorrhage with amyloidosis- Dutch type (HCHWA-D), which is the subject of this review.

Amyloid beta-protein in cerebral amyloid angiopathy, senile plaques, and preamyloidotic lesions in subcortical arteriosclerotic encephalopathy (Binswanger disease)

Cerebral vascular amyloid deposits, senile plaques and neurofibrillary tangles have been found in subcortical arteriosclerotic encephalopathy (Binswanger disease). A mouse antiserum, prepared against a 43-amino acid synthetic peptide homologous to the amyloid beta-protein of Alzheimer disease (anti-SP43), revealed immunoreactive amyloid deposits in meningeal and intracortical blood vessels, senile plaques, intraneuronal amyloid and preamyloid in a neuropathologically confirmed case of Binswanger disease previously reported to have cerebral vascular amyloid deposits. These lesions contained sulfated glycosaminoglycans as determined by the Alcian blue/critical electrolyte concentration method. Similar findings were not observed in a case of Binswanger encephalopathy without cerebral amyloid deposits. Our study indicates that amyloidotic lesions in Binswanger encephalopathy with cerebral amyloid deposits contain amyloid beta-protein and sulfated glycosaminoglycans.

Synaptophysin and chromogranin A immunoreactivities in senile plaques of Alzheimer's disease

Immunolabelling for synaptophysin and chromogranin A, two polypeptides associated with small clear and large dense core synaptic vesicles respectively, has been performed on tissue sections of the temporal cortex in Alzheimer's disease in combination with anti-A4 amyloid labelling. The dystrophic neurites in many senile plaques were observed to be labelled by the anti-synaptophysin or anti-chromogranin A antibodies. Some diffuse amyloid deposits, demonstrated by antibodies against synthetic amyloid A4 peptides, were associated with a punctuate increase in synaptophysin or chromogranin A immunoreactivity. The labelling of dystrophic plaque neurites may reflect the accumulation in these processes of synaptic vesicles or material derived from them. We suggest also that the punctuate increase in synaptophysin and chromogranin A immunoreactivities associated with some A4 amyloid deposits may be an early event reflecting neuronal dysfunction.

Two methods for flat embedding sections in LR white cut from paraffin blocks

Two simple methods are described for flat embedding of sections cut from paraffin blocks of brain tissue in the hydrophilic resin LR White. The ability of fresh resin to polymerize when added to already cured resin is exploited. In the first method, a tissue section with a drop of LR White is pressed to the bottom of a gelatin capsule using a blank block. In the second method, the section in a drop of resin is sandwiched between the sawed halves of a blank block. After curing, thin sections containing large areas of tissue can be collected and processed for immunocytochemistry.

Acute phase proteins are present in amorphous plaques in the cerebral but not in the cerebellar cortex of patients with Alzheimer's disease

Using immunohistochemical staining for beta-amyloid proteins in the brains of Alzheimer patients two basic types of plaques can be found: 'amorphous' or 'diffuse' non-congophilic plaques and classical plaques. Acute phase proteins alpha 1-antichymotrypsin, complement factors and P-component ('plaque-associated molecules') have been reported in both types of plaques in the cerebral cortex. In the present study we could not find immunoreactivity for these acute phase proteins in the amorphous plaques in the cerebellar cortex. These proteins seem to be essential for formation of classical plaques.

Alzheimer patients and Down patients: abnormal presynaptic terminals are related to cerebral preamyloid deposits

In Alzheimer's disease, in Down syndrome and in normal aging, scattered deposits of amyloid fibril precursors occur in both cerebral cortex and subcortical grey structures. Within such preamyloid deposits, no degenerating neurites with paired helical filaments have ever been observed. This study, carried out on brains from Alzheimer patients and Down patients, reports on the relationship between preamyloid deposits and neuritic changes. These changes were represented by presynaptic terminal swellings immunolabeled by antisynaptophysin and antiubiquitin antibodies, not by Alz50. These findings support the view that the deposition of amyloid fibril precursors in the neuropil is closely related to presynaptic terminals, although whether the former precedes or follows the development of presynaptic terminal changes is still undetermined.

Parenchymal preamyloid and amyloid deposits in the brains of patients with hereditary cerebral hemorrhage with amyloidosis--Dutch type

Hereditary cerebral hermorrhage with amyloidosis--Dutch type, one of the 'cerebral beta-amyloid diseases', like Alzheimer's disease, is characterized by extensive deposition of amyloid in small cerebral vessels. We investigated the presence of parenchymal beta-protein deposits in two Dutch patients with hereditary cerebral hemorrhage with amyloidosis. Immunostaining with anti-SP28 revealed a full spectrum of these deposits, varying from preamyloid deposits to burned-out plaques. However, their density is less than in Alzheimer's disease, and immunostaining with Alz50 and anti-PHF did not show abnormal neurites in and around amyloid deposits in these two patients.

Cerebral preamyloid deposits and congophilic angiopathy in aged dogs

The brains of 7 dogs aged 6 to 18 years have been histochemically and immunohistochemically investigated at the light- and electron microscopy levels for preamyloid deposits and amyloid fibrils to verify the hypothesis that the accumulation of cleavage products of amyloid precursor protein is related not only to Alzheimer's disease but also to the normal aging of the brain. Preamyloid deposits were detected in the neuropil of the cerebral cortex and neostriatum, whereas amyloid fibrils were found in the walls of parenchimal and leptomeningeal vessels. The densities of preamyloid deposits in the neuropil and of deposits of amyloid fibrils in the vessel walls were higher in the brains of the most aged dogs. These findings suggest that aging of the canine brain is characterized by an accumulation of intermediate cleavage products of the amyloid precursor protein in both the neuropil and the vessel walls, and by processing of these products to amyloid fibrils in the vessel walls.