Senile Plaque Cores Research Articles

Mechanical instability of Pick bodies and their isolation in an intact form using urea solution

Isolation of Pick bodies was attempted from an autopsied brain of a patient with Pick's disease following a modified method for isolation of senile plaques cores and neurofibrillary tangles in the brains of Alzheimer's disease. Pick bodies were mechanically less stable than senile plaque cores and neurofibrillary tangles since Pick bodies were destroyed by vigorous homogenization or treatment with 1% sodium dodecyl sulfate solution. Pick bodies were released out of mother neuronal cells in an intact form by treatment with 8 M urea solution for several hours at room temperature. Finally, fine structure of Pick filaments released from Pick bodies was compared with the filaments of neurofibrillary tangles.

Aberrant phosphoinositide metabolism in Alzheimer's disease.

Since phosphoinositide-specific phospholipase C (PLC) is one of the key molecules in signal transduction, its involvement was assessed in Alzheimer's disease (AD). The phosphatidyl-inositol (PI)-specific PLC activity in the Alzheimer cytosolic and particulate fractions was not significantly different from that in the control fractions. The PI-specific PLC activity as a function of the free Ca2+ concentration was also similar between control and Alzheimer brains. These results suggest that the PI-specific PLC activity is not altered in AD. Immunostaining of a specific antibody against the PLC isozyme, PLC-delta, demonstrated that this enzyme was abnormally accumulated in neurofibrillary tangles (NFT), the neurites surrounding senile plaque (SP) cores, and neuropil threads in AD brains. Western blot analysis confirmed that PLC-delta was concentrated in the paired helical filament (PHF)-rich fraction of AD brains. PLC-delta marked the same neurons containing tau immunoreactivity and yet tau and PLC-delta often marked different structures within the same neuron, with tau more clearly on NFT and PLC-delta covering it superficially. The double stain with PLC-delta and basic fibroblast growth factor (bFGF) binding suggest that PLC-delta is an intracellular marker, showing little overlap with bFGF binding, an extracellular marker. All of this was consistent with the electron microscopy, with PLC-delta being NFT associated. Antibodies to other PLC isozymes did not produce positive immunostaining of these pathologic structures. Moreover, diffuse and amorphous deposits of PLC-delta were found to precede the accumulation of fibrillary deposits. These results suggest that PLC-delta accumulation plays a possible role in the formation of intraneuronal inclusions in AD.

Activation of protein kinase C increases the extracellular release of the transmembrane amyloid protein precursor of Alzhemier's disease

The βA4 peptide is the major consituent of the amyloif core of abundant senile plaques found in the cerebral cortex of patients with Alzheimer's disease. This amyloid peptide is synthesized as part of a large transmembrane amyloid protein precursor or APP. In addition to the highly expressed transmembrane APP isoforms, an mRNA encoding a secreted APP lacking the transmembrane domain has been identified. A cleavage of the transmembrane protein also yields an extracellular soluble APP fragment. The effect of phorbol esters on the release of the extracellular APP was studied in transfected Chinese hamster ovary cells which stably express either a transmembrane or a secreted APP isoform. The activation of protein kinase C by phorbol-12,13-dibutyrate increased the extracellular relese of the transmembrane APP resulting from its proteolytic cleavage, while 4-β-phorbol, which does not activate protein kinase C, did not significantly affect the recovery of the soluble APP. On the contrary, the recovery of APP secreted in the culture medium without proteolytic cleavage was not increased by protein kinase C-mediated phosphorylation.

Peptide Compositions of the Cerebrovascular and Senile Plaque Core Amyloid Deposits of Alzheimer′s Disease

The pathological findings of Alzheimer*s disease include amyloid deposition in cerebral blood vessels and in senile plaques. Both deposits are known to include pep-tides that contain a common sequence. Both forms of amyloid were isolated and their peptide compositions were determined. The peptides were resolved by size-exclusion chromatography in 70% formic acid, and reverse-phase chromatography in 60% formic acid, 0-40% acetonitrile. Senile plaque amyloid cores contain about 25% protein, about 70% of which is composed of peptides containing the β-amyloid sequence. Amino-terminal sequencing of the core amyloid peptides (CAPs) revealed extensive amino-terminal heterogeneity, with variable amounts of blocked amino termini. Matrix-assisted, laser-desorption-time-of-flight mass spectrometry of the CAP mixture revealed an array of peptides the molecular weights of which corresponded to peptides beginning with each of the first 11 amino acids of the β-peptide sequence and ending with Ala-42 of that sequence. The carboxyl-terminal residues were identified by tandem mass spectrometry of chymotrypsin digests. CAP possessed a minor degree of carboxyl-terminal heterogeneity. Cerebrovascular amyloid peptides (CVAPs) possessed minor degrees of both amino- and carboxylterminal heterogeneity. The major CVAP commenced at Asp-1 and ended at Val-40. Minor components of CAP possessed masses of 8000-9000 Da and the same amino terminal residues as the major components of CAP. They may be precursors to the smaller CAPs. The differences in amino termini and carboxyl termini of CAPs and CVAPs suggest that the two types of amyloid form by different pathways, on which they encounter different proteases.

Wide third ventricle correlates with low choline acetyltransferase activity of the neocortex in Alzheimer patients.

We evaluated central, temporal, and cortical atrophy by linear measurements on brain computed tomography (CT) in 17 patients with moderate to severe histologically verified Alzheimer disease (AD) compared with findings in 84 nondemented elderly controls. Measurements were adjusted for age and head size. The AD patients had wider third and lateral ventricles as well as larger temporal horns and Sylvian fissures compared with controls. Cortical atrophy tended also to be more pronounced for AD patients relative to controls. Thus measures of central and temporal atrophy clearly distinguished AD patients from normal aged individuals. In AD patients, the width of the third ventricle was significantly correlated with the choline acetyltransferase (ChAT) activity in the post-mortem frontal cortex (r = 0.65, p = 0.005) and in the temporal cortex (r = 0.59, p = 0.006). CT measures did not correlate significantly with neurofibrillary tangle or senile plaque scores. The result suggests that the width of the third ventricle better reflects the degree of cholinergic deficit than severity of histopathological changes, scores of plaques, and tangles in AD.

Senile plaques in cerebral amyloid angiopathy show accumulation of amyloid precursor protein without cytoskeletal abnormalities

The abnormal neurites that surround β-amyloid in senile plaques (SP) in Alzheimer disease contain β-amyloid precursor protein (βAPP) or abnormal filaments which react with antibodies to τ. Occasionally, βAPP and abnormal filaments are present in the same neurite. Whether both types of abnormal neurites are reactive to the presence of β-amyloid or they are instead independent from each other is unknown. To begin to clarify this issue, we comparatively studied βAPP and τ-epitopes in SP from cases of classical Alzheimer disease and cases of cerebral amyloid angiopathy, with SP but without neurofibrillary pathology. In subjects with cerebral amyloid angiopathy, about one-third of SP, the same percentage as in Alzheimer disease, were βAPPP reactive in the absence of τ-reactivity. βAPP epitopes were ultrastructurally localized in dense bodies of probable lysosomal origin, adjacent to the core of SP. These results demonstrate that βAPP and τ-reactive cytoskeletal alterations occur independently in the neurites of SP. The presence of βAPP in dystrophic neurites of SP and the localization of βAPP in lysosomes suggest that βAPP containing dystrophic neurites may play a role in the extracellular deposition of amyloid.

Alzheimer neurofibrillary tangles contain 2.1 nm filaments structurally identical to the microtubule-associated protein τ: a high-resolution transmission electron microscope study of tangles and senile plaque core amyloid

Alzheimer neurofibrillary tangles (NFT) and senile plaque core amyloid (SPCA) isolated from the brain of patients with Alzheimer's disease were freeze-dried and replicated with a new platinum-carbon (Pt-C) vertical deposition method for high-resolution transmission electron microscopy (TEM). The resolution of this vertical Pt-C replication method is superior to either of the more conventional 20° rotary replication or 45° unidirectional replication methods and is dependent on the Pt-C film thickness coating the specimen. The paired helical filaments (PHF) observed within the tangles were right-handed helices with a fairly regular twist period averaging 79.3 ± 5.9 nm and a fairly regular maximum width averaging 14.9 ± 1.0 nm. The PHF regions of minimum width were not regular and fell into three size categories: 2.4 ± 0.3 nm, 4.9 ± 0.6 nm and 9.6 ± 1.4 nm. In addition to the PHF found in the tangles, a new filament was found within all the tangles. These 2.1 ± 0.2 nm diameter filaments were triple-stranded left helices with 1.0 ± 0.2 nm diameter strands with a structure identical to bovine τ. Like bovine τ polymer a number of filaments (1.30 nm to 2.38 nm) were longer than a fully strectched τ monomer of 96 nm. Images of neuritic senile plaque core amyloid (SPCA) showed that amyloid had a more solid appearance than the NFT and its branched filament structures were unlike the ∼2.1 nm diameter filaments or the PHF found in NFT.

Arginine specific endopeptidases modify the aggregation properties of a synthetic peptide derived from Alzheimer beta/A4 amyloid.

A synthetic peptide corresponding to the first 28 amino acids of the Alzheimer disease amyloid beta/A4 peptide (3.2 kDa) aggregated to a high molecular weight (15 kDa) on SDS/urea polyacrylamide gels. Proteinase K, V8 protease, trypsin, and endopeptidase Lys-C readily degraded the aggregate. By contrast, when digested by endopeptidase Arg-C, a new polypeptide aggregate of higher molecular weight (16 kDa) was observed on denaturing gels without degraded smaller products. The new aggregate was comprised of three peptides: an intact beta/A4(1-28) and partially degraded peptides beta/A4(1-5) plus beta/A4(6-28). The results were confirmed by treatment of beta/A4 with other arginine-specific proteases: the gamma subunit of nerve growth factor and clostripain. The results indicate that arginine-specific proteases, including a growth factor processing enzyme, can nick aggregated beta/A4(1-28) amyloid and alter the configuration to produce a more complex aggregated form. If similar highly specific proteolytic mechanisms occur in the Alzheimer disease brain, the processing may promote the formation of high molecular weight aggregates that contribute to the development of relatively insoluble senile plaque core protein.

Trace and minor elements occuring in the cores of senile plaques: Identification and analysis of senile plaques in unstained tissue

Trace and minor elements occuring in the cores of senile plaques: Identification and analysis of senile plaques in unstained tissue

Unambiguous aluminum(III) localization in senile plaque core from Alzheimer's disease brains: aM. Favarato, aS. Zanoni, a,bP.F. Zatta. aDipartimento di Biologia dell'Universita' di Padova and bCentro CNR Emocianine-metalloproteine, Via Trieste 75. 35131 Padova, Italy

Unambiguous aluminum(III) localization in senile plaque core from Alzheimer's disease brains: aM. Favarato, aS. Zanoni, a,bP.F. Zatta. aDipartimento di Biologia dell'Universita' di Padova and bCentro CNR Emocianine-metalloproteine, Via Trieste 75. 35131 Padova, Italy

Aluminosilicate-lnduced Free Radical Generation by Murine Brain Glial Cells in vitro: Potential Significance in the Aetiopathogenesis of Alzheimer's Dementia

While previous studies have identified aluminosilicate deposits within the senile plaque cores from subjects with Alzheimer''s dementia, their possible role in the aetiopathogenesis of the disease remains unknown. In the present in vitro chemiluminescent study, we show that cultured murine glial cells exhibit the capacity to generate free radical and related oxygen-derived metabolites when exposed to various natural and synthetic model aluminosilicate particulate samples of differing particle size, morphology and composition. These results, if applicable to the proposed analogous in vivo situation in humans, suggest that further research into the biochemical and cellular mechanisms influencing the production and modulation of tissue-injurious free radical oxygen-derived metabolites within the brain, could have significant implications in the pathogenesis, prevention and treatment of Alzheimer''s disease.

Oxidative damage in Alzheimer's dementia, and the potential etiopathogenic role of aluminosilicates, microglia and micronutrient interactions.

While evidence implicating free radical oxidative processes in the etiopathogenesis of Alzheimer's dementia is accumulating, the specific cellular and biochemical mechanisms involved remain to be identified. The potential pathogenic role of microglial cells in neurodegenerative processes is indicated by the finding that purified murine microglial cells exposed in vitro to various model aluminosilicate particles stimulate the generation of tissue-injurious free radical reactive oxygen metabolites. Analogous inorganic aluminosilicate deposits have been reported to occur in the core of the characteristic senile plaques found in the brains of Alzheimer disease subjects. The possible modulation of free radical oxidative activity by antioxidant micronutrients and pharmacological agents, provides a rational basis for further preventative and therapeutic clinical investigations.

Neuritic pathology and dementia in alzheimer's disease

Previous studies of Alzheimer's disease (AD) have correlated the severity of dementia with either the number of senile plaques or neurofibrillary tangles. We used antibodies raised against amyloid beta/A4 protein of senile plaque cores and tau protein as well as thioflavine S and the Campbell-Switzer modification of the Hicks silver method to examine the hippocampal formation and five neocortical regions from 22 nondemented elderly control subjects and 34 demented patients with cerebral senile plaques and neurofibrillary tangles, without complicating disease processes. Ten control subjects (46%) had no beta/A4 protein deposition. Twelve control subjects (54%) had widespread beta/A4 protein deposition but no neocortical neuritic pathology. Of the 34 patients with AD-type changes, 27 (79%) had widespread senile plaques and neurofibrillary tangles, while 7 (21%) had neocortical senile plaques with few neurofibrillary tangles. All demented patients had widespread beta/A4 protein deposition and neocortical tau-immunoreactive, Hicks silver-positive dystrophic neurites. The neurites were found both free in the neuropil as well as surrounding senile plaques. Quantitative analysis showed that dystrophic neurites were significantly increased in patients with AD compared with control subjects and the number of dystrophic neurites and neurofibrillary tangles correlated with the clinical severity of dementia. Widespread cerebral beta/A4 protein deposition may be necessary but by itself is insufficient for the development of dementia in AD.

Amorphous hydroxyaluminium silicates formed under physiological saline conditions, and in CaCo3-buffered solutions. Stability and significance for Alzheimer plaque precipitates

AbstractIn an attempt to determine the nature and conditions of formation of the aluminium silicate precipitates present at the core of senile plaque in the brains of patients with Alzheimer's disease, aluminosilicate precipitates have been prepared and equilibrated for up to one year in physiological saline conditions at 40°C and a pH near 7·4. The structure and composition of these precipitates, and the associated concentrations of free silicic acid, were similar to those found in systems buffered with CaCO3at 20–25°C. Imogolite-like products with Si : Al ratios near 0·5 were obtained at silicic acid concentrations <100µm, and hydrous feldspathoid products with ratios ≥1·0 became dominant at silicic acid concentrations greater than ∼150µm. These products do not match senile plaque precipitates, which have Si : Al ratios ≥1·0, but form in an environment with <100µmSi. The relative stability of aluminium hydroxides, proto-imogolite allophane and hydrous feldspathoids are estimated from equilibrated silicic acid concentrations.

Experimental investigations into sample preparation of Alzheimer tissue specimens for nuclear microprobe analysis

Nuclear microprobe analysis was applied to the study of elemental distribution in brains sections of patients with a diagnosis of Alzheimer's disease. Stained and nonstained cryosections were studied. The work carried out shows that serious elemental losses follow the sample staining procedure. Major losses occurred in a simple rinse of the tissue section, probably reducing most of the in-vivo gradients, which shows that generally very little information can be gained from stained sections. However, in many cases stained sections are compulsory because of the requirement to recognize the area which is to be studied. All the elemental maps obtained for the neurofibrillary deposits indicate a localized concentration for Si and probably also Al, associated with the senile plaque core. Neither of these elements were found in the staining solutions used. The validity of the results is discussed as well as the possible link of Al and/or Si in the development of Alzheimer's disease.

Accumulation of amyloid precursor fragment in Alzheimer plaques

Regenerative and degenerative neurites are components of classical senile plaques found in brain tissue of patients with Alzheimer's disease (AD). Amyloid β/A4-protein derived from its precursor, amyloid β/A4-protein precursor (APP/ABPP), constitutes the major portion of the amyloid core of senile plaques. A large N-terminal portion of APP (∼Mr 100,000) is released from cells, leaving a minor C-terminal portion (∼Mr 15,000) behind. A series of antisera against various sequences of APP were prepared and used to study the localization of each sequence in brain tissue. Plaque neurites stained as intensely as neuronal cell bodies with three antisera against the N-terminal portion of APP (N-terminal to a.a. 225), whereas five other antisera directed against the other C-terminal portions of APP (a.a. 284 to C-terminal) and antisera against the Kunitz-type protease inhibitor portion of APP stained plaque neurites less intensely than neuronal cell bodies in the hippocampus. These results suggest that a major part of the APP present in the neuritic component of senile plaques is a fragment representing the N-terminal one-third of the molecule.

Amyloid in the brains of aged squirrel monkeys

In this immunocytochemical study, the brains of nine squirrel monkeys (Saimiri sciureus), ranging from 8 to 27 years of age, were examined for the presence and distribution of beta/A4 amyloid, a 4-kilodalton peptide. In aged squirrel monkeys, amyloid is associated primarily with intracerebral and meningeal capillaries and arterioles and occurs to a lesser degree as small and/or diffuse deposits in the neural parenchyma and in the dense cores of senile plaques. Cerebrovascular amyloid is found primarily in neocortex, amygdala, and septum verum and is rare or nonexistent in other subcortical gray structures, white matter, cerebellum, and spinal cord; this pattern of localization is comparable to that in humans with cerebral amyloid angiopathy. There is a significant correlation between cerebrovascular and parenchymal deposits of amyloid. However, cerebrovascular amyloid is always the most abundant form in squirrel monkeys, even in cases of severe cerebral amyloidosis. In contrast to squirrel monkeys, aged rhesus monkeys (Macaca mulatta) develop mostly parenchymal deposits of amyloid and have relatively less vascular amyloid. This species difference in the histological distribution of amyloid suggests that separate mechanisms may influence the accumulation of amyloid in cerebral blood vessels and in the neural parenchyma. These data also indicate that the squirrel monkey can serve as a model for investigations of cerebrovascular amyloidosis.

Technical aspects of nuclear microprobe analysis of senile plaques from alzheimer patients

Alzheimer's disease, a common form of senile dementia, has been proposed to be caused by aluminium. One of the interesting structures to be studied, senile plaque cores in the brain, have centres of only about 10 μm. We have investigated the possibility of applying nuclear microprobes to sections containing senile plaques. An alternative staining procedure, TMToluidin blue staining using a spray technique, is also presented. An outline is given of a procedure for preparing senile plaque specimens for nuclear microprobe analysis. This includes a technique for accurate ion beam positioning, utilizing electron microscopy-grids. The subject may be of general interest since sample preparation is one of the most important aspects in microprobe analysis of biological matter.

Defined neurofilament, tau, and beta-amyloid precursor protein epitopes distinguish Alzheimer from non-Alzheimer senile plaques.

Eight antisera and one monoclonal antibody to synthetic peptides that corresponded to domains extending over the entire length of the beta-amyloid precursor protein (beta-APP), and an antiserum to the full-length 695-amino acid form of the beta-APP, were raised to probe the composition of the core and corona of senile plaques (SPs). We localized distinct beta-APP domains, including the beta-amyloid protein or A4 region, within the SPs of 13 end-stage Alzheimer disease (AD) and 13 age-matched control samples of hippocampus and entorhinal cortex. The composition of SPs also was probed with antibodies to defined epitopes in tau (tau) as well as the large and mid-size neurofilament (NF) proteins. The most important observations were that beta-APP domains outside the A4 region were largely restricted to SP coronas in the AD samples, together with tau and NF determinants, whereas the same epitopes were absent from A4-positive blood vessels and exceptionally rare in non-AD SPs. Indeed, samples from a subset of the non-AD cases contained a considerable number of A4-positive SPs totally devoid of any of the other beta-APP, tau, and NF epitopes. These observations suggest that the deposition of the A4 protein in AD SPs results from the local processing of beta-APPs in association with tau and NF protein fragments. It is unclear whether this association is fortuitous or linked by common mechanisms. However, differences between the complement of beta-APP, tau, and NF protein epitopes in AD versus non-AD brains implicate a defect involving one or more steps in the posttranslational modification, degradation, or elimination of these proteins in AD brains, and this may account for the massive numbers of SPs that characterize AD.

Microanalysis of Alzheimer disease NFT and plaques

Electron probe energy dispersive microanalysis of isolated andin situ neurofibrillary tangles (NFT) and neuritic (senile) plaque cores have been done to investigate the levels of Al, Si, Ca and Fe in the leading lesions of Alzheimer disease neuropathology. Varying levels of Si and Al, and to a lesser extent Ca, have been co-localized in about one half of the NFT and plaques examined using X-ray mapping. The variability of detection and the low levels of Al present indicates that aluminum is not required for the formation of the NFT and that aluminosilicates are not involved in the formation of the plaque core.