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Biomedical subjects

G Perry

Publications and source records attributed to G Perry.

At least 145 records · Page 8Linked to original sources

Glycoxidation and oxidative stress in Parkinson disease and diffuse Lewy body disease.

Oxidative stress is well accepted as an important pathogenic factor in Parkinson disease, based largely on indirect evidence. Recently, we have developed antibodies that recognize specific advanced glycation end-products (anti-pentosidine and anti-pyrraline), protein modifications that are potentiated by oxidative stress in a process termed glycoxidation. We applied these antibodies immunocytochemically to affected regions in Parkinson disease and diffuse Lewy body disease brains. Additionally, we used antibodies to heme oxygenase-1, a putative marker of oxidative stress response. Immunoreactivity to pentosidine, pyrraline, and heme oxygenase-1 was seen in the substantia nigra of Parkinson disease and the neocortex of diffuse Lewy body disease. Heme oxygenase-1 was further demonstrated by immunoelectron microscopy in intimate association with filaments of cortical Lewy bodies. Immunolocalization of advanced glycation end-products and a marker of oxidative stress response induction provides evidence that glycoxidation and oxidative stress may be an important pathogenic factor in diseases characterized by Lewy body formation, and furthers the evidence that cytoskeletal proteins and their inclusions are susceptible to oxidative stress.

Aged↗

Quantitative solubilization and analysis of insoluble paired helical filaments from Alzheimer disease.

In this study, we evaluate the ability of several solvents to solubilize insoluble paired helical filaments (PHF) of Alzheimer disease. Specifically, we use protein extraction and reduction in the volume of insoluble material as quantitative assays to establish solvents of PHF. Using sequential categories of protein solvent to analyze insoluble PHF, only alkali or exhaustive proteolysis are effective in completely solubilizing PHF, while a variety of denaturants are ineffective. Alkali does not affect the phosphorylation state of PHF and complete dephosphorylation of PHF with hydrofluoric acid does not affect PHF solubility. These findings suggest that the 'hyperphosphorylation' of PHF proteins is not responsible for PHF insolubility. However the in vitro glycation of tau generates PHF that are insoluble in SDS and soluble in alkali. These findings suggest that protein crosslinks, including advanced glycation endproduct-derived crosslinks which were recently described in Alzheimer disease, play a major role in effecting PHF insolubility in vivo.

Adolescent↗

Trypsin interaction with the senile plaques of Alzheimer disease is mediated by beta-protein precursor.

In this study we demonstrate by in situ binding that trypsin interacts with the senile plaques found in Alzheimer disease. Characterization of various potential trypsin binding proteins shows that trypsin binding is mediated by beta-protein precursor (beta PP)-the progenitor of amyloid-beta in senile plaques. Using specific antisera against various proteins to sterically block trypsin blocking, we found that only those antibodies raised against proteins or peptides containing the Kunitz protease inhibitor domain were able to abolish binding. By analogy with other protease/inhibitor interactions, we speculate that the binding of trypsin to beta PP could involve concomitant beta PP cleavage. Therefore, beta PP in protecting against potentially damaging proteolysis could simultaneously liberate beta PP fragments or intermediate precursors of amyloid-beta deposits.

Alzheimer Disease↗

Plasma membrane fragility in dystrophic neurites in senile plaques of Alzheimer's disease: an index of oxidative stress.

This study presents evidence for plasma membrane abnormalities of the dystrophic neurites in senile plaques of Alzheimer's disease. We found that the plasma membranes of dystrophic neurites are more labile to fixation than those membranes of other cells of the senile plaque or of normal neurites distant from senile plaques. Further, we found vesicles in the extracellular space adjacent to dystrophic neurites and similar to those within them, suggesting that the increased lability seen in our preparations may, in vivo, be associated with release of neuritic contents. Plasma membrane alterations may be critical to deposition of amyloid-beta in senile plaques from the abundant beta-protein precursor of dystrophic neurites. The consequences of altered membrane integrity, such as calcium influx, lipid peroxidation and free radical damage, could also be responsible for many of the pathological correlates of the disease.

Alzheimer Disease↗

Filament heterogeneity within the dystrophic neurites of senile plaques suggests blockage of fast axonal transport in Alzheimer's disease.

In this study, the direct comparison of biopsy and autopsy tissue by morphological and immunocytochemical techniques, respectively, was used to document cytoskeletal changes of dystrophic neurites (DN) of senile plaques in Alzheimer's disease. This dual approach demonstrated several unreported abnormalities which, together with analogous findings in several experimental models, suggest that DN are associated with deficiencies in fast axonal transport and replacement of the cytoskeleton by an array of related abnormal filaments.

Actin Cytoskeleton↗

alpha-calcium-calmodulin-dependent kinase II is associated with paired helical filaments of Alzheimer's disease.

Alzheimer's disease (AD) is characterized pathologically by two distinguishable deposits in the brain, namely senile plaques and neurofibrillary tangles (NFT). Senile plaques are composed of fragments of the amyloid precursor protein, whereas NFT are composed primarily of paired-helical filaments (PHF). The latter are in turn composed principally of the microtubule-associated protein, tau. Tau in PHF is highly and unusually phosphorylated but the mechanisms leading to this unusual phosphorylation are not known. Using a combination of immunoblotting and kinase assays, we demonstrate that a discreet set of kinases copurify with PHF. One of these kinases was found by immunoblotting to be alpha-calcium-calmodulin-dependent kinase II (alpha-CaM kinase). Immunogold labeling revealed that alpha-CaM kinase was localized to a novel globular membranelike structure found at the ends of PHF. Since previous studies have shown alpha-CaM kinase to be involved in memory, its association with PHF may have important implications in understanding memory loss in AD. We also discuss the possibility that the association of alpha-CaM kinase with PHF may indicate sites where tau protein is converted into PHF.

Alzheimer Disease↗

beta PP and Tau interaction. A possible link between amyloid and neurofibrillary tangles in Alzheimer's disease.

Extracellular deposition of amyloid fibrils and intraneuronal accumulation of paired helical filaments (PHFs) are the neuropathological hallmarks of Alzheimer's disease. The major constituent of amyloid fibrils is a 39- to 43-residue peptide (termed A beta), which is derived from a 695- to 770-amino-acid precursor protein (termed beta PP). The main component of PHFs identified so far is the microtubule-associated protein tau. Yet, there is no direct evidence of interconnection between these two pathological states. We report here that antibodies to an epitope located between residues 713 and 723 of beta PP770 (ie, the transmembrane region of beta PP distal to A beta) consistently labeled PHFs in the brain of Alzheimer patients. Solid phase immunoassay showed that a peptide homologous to residues 713 to 730 of beta PP770 bound tau proteins. This beta PP peptide spontaneously formed fibrils in vitro and, in the presence of tau, generated dense fibrillary assemblies containing both molecules. These data suggest that beta PP or beta PP fragments containing the tau binding site are involved in the pathogenesis of PHFs in Alzheimer's disease.

Alzheimer Disease↗

Alterations of low molecular weight acid phosphatase protein level in Alzheimer's disease.

We have previously reported that the activity of low molecular weight (LMW) acid phosphatase, which can remove tyrosine-linked phosphates of epidermal growth factor receptor, was significantly decreased in Alzheimer brains. In the present study, a specific antibody was prepared to analyze the protein level of this enzyme. Western blot analysis indicated that the level of LMW acid phosphatase protein was significantly reduced, whereas the activity of LMW acid phosphatase per enzyme molecule was not changed in Alzheimer brains. These results suggest that the reduction of LMW acid phosphatase activity in Alzheimer brains is due to its decreased protein level in Alzheimer's disease.

Acid Phosphatase↗

Evidence for oxidative stress in Pick disease and corticobasal degeneration.

Oxidative stress is increasingly implicated in a number of neurodegenerative disorders characterized by abnormal filament accumulation in affected neurons, including Alzheimer disease, Parkinson disease, and amyotrophic lateral sclerosis. To further evaluate the role of oxidative stress in the neurodegenerative process and the accumulation of abnormal filaments, we examined the pathologic lesions in Pick disease and of corticobasal degeneration with immunocytochemistry by using antisera to heme oxygenase-1 (HO-1) - a putative marker of oxidative injury. Immunoreactivity to HO-1 was demonstrated in ballooned neurons, Pick bodies, neuropil threads, and glial inclusions (the latter two in a case of corticobasal degeneration). By immunoelectron microscopy, HO-1 immunolabelling of Pick bodies was closely associated with the abnormal filaments comprising the inclusion. Apparently unaffected neurons in all cases showed only background levels of HO-1 immunoreactivity. These data suggest that oxidative stress is important in the formation of the lesions characteristic of Pick disease and corticobasal degeneration. Moreover, taken together with our previous demonstration that HO-1 immunoreactivity is associated with the neurofibrillary pathology of Alzheimer disease, progressive supranuclear palsy, and subacute sclerosing panencephalitis, it appears that oxidative stress specifically targets the cytoskeleton in a variety of neurodegenerative disorders characterized by abnormal filament accumulation.

Alzheimer Disease↗

Apolipoprotein E interaction with the neurofibrillary tangles and senile plaques in Alzheimer disease: implications for disease pathogenesis.

Apolipoprotein E (ApoE) genotype is a significant risk factor for the development of Alzheimer disease (AD) and the ApoE protein is associated with senile plaques (SP) and neurofibrillary tangles (NFT), the pathological lesions of AD. Despite this data, the relevance of ApoE to the disease pathogenesis is unknown. In this study we sought to understand the role that ApoE protein could play in the pathogenesis of AD. Using an in situ binding technique, we showed that ApoE bound avidly to SP and NFT in diseased brain. Molecular characterization of ApoE binding suggested that binding to NFT was mediated by tau, the main protein component of NFT, and that ApoE binding to SP was mediated by amyloid-beta, the main protein component of SP. There was no significant difference in binding or binding characteristics between the different ApoE isoforms, ApoE3 and ApoE4. These findings suggest that the interaction of ApoE with tau and amyloid-beta proteins in AD could play a important role in the formation of NFT and SP, respectively, contributing to the pathogenesis of AD.

Alzheimer Disease↗

Characterization of the association of phospholipase C-delta with Alzheimer neurofibrillary tangles.

Phosphoinositide-specific phospholipase C (PLC) is a key enzyme in signal transduction. We have previously demonstrated that an antibody to the PLC isozyme, PLC-delta, intensely stained neurofibrillary tangles (NFT) in the brain tissue of AD patients [Am. J. Pathol., 139 (1991) 737-742]. To clarify the crucial involvement of abnormal PLC-delta accumulation contributing to the formation of NFT, we performed light and electron microscopic immunocytochemistry. To determine PLC-delta's association with NFT, its resistance to solubilization was also studied. Anti-PLC-delta antibody marked the same NFT-bearing neurons containing tau immunoreactivity with tau more clearly on NFT filaments and PLC-delta covering it superficially at the light microscope level. The double stained preparations with anti-PLC-delta antibody and bFGF binding suggested that PLC-delta is an intracellular marker and is not retained after neuronal death. Employing immunoperoxidase and immunogold electron microscopic immunocytochemistry, we found that the antibody to PLC-delta reacts mostly with amorphous granular materials, and occasionally with some abnormal filaments within NFT. Nevertheless, PLC-delta in NFT was resistant to removal by high salt or ionic detergent, indicating it is an integral NFT component. These results indicate that antigenic determinants unique to PLC-delta are mainly present intraneuronally on the amorphous granular components of NFT as well as the abnormal filaments, suggesting PLC-delta's interactions and possible role in the formation of intraneuronal filamentous inclusions in AD.

Aged↗

Extracellular neurofibrillary tangles reflect neuronal loss and provide further evidence of extensive protein cross-linking in Alzheimer disease.

In this report we quantitatively assess the numbers of intracellular and extracellular neurofibrillary tangles (NFT) in the brains of a series of individuals with Alzheimer's disease and of controls and correlate these with neuronal loss. Our data indicate that in some cases, NFT are not removed from the brain throughout the disease process. This finding, together with our previous demonstration of carbonyl-related modifications in NFT, provides additional evidence that the protein constituents of NFT are resistant to proteolytic removal, possibly as a result of extensive cross-links. Additionally, correlation between the number of NFT and neuronal loss indicates that there are at least two distinct mechanisms responsible for neuronal death in Alzheimer's disease that are directly and indirectly related to the presence of neurofibrillary pathology.

Aged↗