The neurobiology of Alzheimer's disease

Designing nanodiscs as versatile platforms for on-demand therapy

Nowadays, there has been an increasing utilization of nanomedicines for disease treatment. Nanodiscs (NDs) have emerged as a novel platform technology that garners significant attention in biomedical research and drug discovery. NDs are nanoscale phospholipid bilayer discs capable of incorporating membrane proteins and lipids within a native-like environment. They are assembled using amphiphilic biomacromolecular materials, such as apolipoprotein A1 or membrane scaffold proteins (MSPs), peptides, and styrene-maleic acid polymers (SMAs). NDs possess well-defined sizes and shapes, offering a stable, homogeneous, and biologically relevant environment for studying membrane proteins and lipids. Their unique properties have made them highly desirable for diverse applications, including cancer immunotherapy, vaccine development, antibacterial and antiviral therapy, and treating Alzheimer's disease (AD) and diabetes-related conditions. This review discusses the classifications, advantages, and applications of NDs in disease therapy.

Apolipoprotein D

ApoD is a 25 to 30 kDa glycosylated protein, member of the lipocalin superfamily. As a transporter of several small hydrophobic molecules, its known biological functions are mostly associated to lipid metabolism and neuroprotection. ApoD is a multi-ligand, multi-function protein that is involved lipid trafficking, food intake, inflammation, antioxidative response and development and in different types of cancers. An important aspect of ApoD's role in lipid metabolism appears to involve the transport of arachidonic acid, and the modulation of eicosanoid production and delivery in metabolic tissues. ApoD expression in metabolic tissues has been associated positively and negatively with insulin sensitivity and glucose homeostasis in a tissue dependent manner. ApoD levels rise considerably in association with aging and neuropathologies such as Alzheimer's disease, stroke, meningoencephalitis, moto-neuron disease, multiple sclerosis, schizophrenia and Parkinson's disease. ApoD is also modulated in several animal models of nervous system injury/pathology.

Fast axonal transport: a site of acrylamide neurotoxicity?

The cellular and molecular site and mode of action of acrylamide (ACR) leading to neurotoxicity has been investigated for four decades, without resolution. Although fast axonal transport compromise has been the central theme for several hypotheses, the results of many studies appear contradictory. Our analysis of the literature suggests that differing experimental designs and parameters of measurement are responsible for these discrepancies. Further investigation has demonstrated consistent inhibition of the quantity of bi-directional fast transport following single ACR exposures. Repeated compromise in fast anterograde transport occurs with each exposure. Modification of neurofilaments, microtubules, energy-generating metabolic enzymes and motor proteins are evaluated as potential sites of action causing the changes in fast transport. Supportive and contradictory data to the hypothesis that deficient delivery of fast-transported proteins to the axon causes, or contributes to, neurotoxicity are critically summarized. A hypothesis of ACR action is presented as a framework for future investigations.

The nitration product 5-nitro-gamma-tocopherol is increased in the Alzheimer brain

Oxidative stress and quasi-inflammatory processes recently have been recognized as contributing factors in the pathogenesis of Alzheimer's disease (AD). Reactive nitrating species have specifically been implicated in AD based on immunochemical and instrumental detection of nitrotyrosine in AD brain protein. The significance of lipid-phase nitration has not been investigated in AD. This study documents a significant two- to threefold increase in the lipid nitration product 5-nitro-gamma-tocopherol in affected regions of the AD brain as determined by high-performance liquid chromatography with electrochemical detection. In a bioassay to compare the relative potency of alpha-tocopherol and gamma-tocopherol against nitrative stress, rat brain mitochondria were exposed to the peroxynitrite-generating compound SIN-1. The oxidation-sensitive Kreb's cycle enzyme alpha-ketoglutarate dehydrogenase was inactivated by SIN-1, in a manner that could be significantly attenuated by gamma-tocopherol (at <10 microM) but not by alpha-tocopherol. These data indicate that nitric oxide-derived species are significant contributors to lipid oxidation in the AD brain. The findings are discussed in reference to the neuroinflammatory hypothesis of AD and the possible role of gamma-tocopherol as a major lipid-phase scavenger of reactive nitrogen species.

Beta-amyloid precursor detected in human cerebral cortex

1. Amyloid deposition is one of the pathologic hallmarks of Alzheimer's disease. Since the isolation of the beta-amyloid gene, which revealed that the amyloid forming 4 kD protein is part of a larger precursor, interest has focused on the process by which amyloid is generated and deposited. 2. The authors have developed an immunologic means of detecting amyloid precursor proteins in human brain. 3. The method involves the expression of human beta-amyloid precursor cDNA in a recombinant vaccinia virus, so that antibodies are produced against the precursor proteins in their native forms. 4. By using this expression system, the amyloid precursor immunogens incorporate post-translational modifications that normally occur in vivo; this cannot be achieved with small synthetic peptides. 5. Using antibodies to the 695 residue amyloid precursor, we have detected using Western blot analysis a protein of approximately 120 kD in samples of cerebral cortex from three subjects with Alzheimer's disease and one control subject. 6. Additional antibodies to other amyloid-related proteins have been developed. These are being used to assess the differential expression of the various amyloid precursors and subdomains in additional cases.

Electrochemical analysis of protein nitrotyrosine and dityrosine in the Alzheimer brain indicates region-specific accumulation

HPLC with electrochemical array detection (HPLC-ECD) was used to quantify 3,3'-dityrosine (diTyr) and 3-nitrotyrosine (3-NO2-Tyr) in four regions of the human brain that are differentially affected in Alzheimer's disease (AD). DiTyr and 3-NO2-Tyr levels were elevated consistently in the hippocampus and neocortical regions of the AD brain and in ventricular cerebrospinal fluid (VF), reaching quantities five- to eightfold greater than mean concentrations in brain and VF of cognitively normal subjects. Uric acid, a proposed peroxynitrite scavenger, was decreased globally in the AD brain and VF. The results suggest that AD pathogenesis may involve the activation of oxidant-producing inflammatory enzyme systems, including nitric oxide synthase.

Category-specific semantic deficits in focal and widespread brain damage: a computational account

Category-specific semantic impairments have been explained in terms of preferential damage to different types of features (e.g., perceptual vs. functional). This account is compatible with cases in which the impairments were the result of relatively focal lesions, as in herpes encephalitis. Recently, however, there have been reports of category-specific impairments associated with Alzheimer's disease, in which there is more widespread, patchy damage. We present experiments with a connectionist model that show how "category-specific" impairments can arise in cases of both localized and widespread damage; in this model, types of features are topographically organized, but specific categories are not. These effects mainly depend on differences between categories in the distribution of correlated features. The model's predictions about degree of impairment on natural kinds and artifacts over the course of semantic deterioration are shown to be consistent with existing patient data. The model shows how the probabilistic nature of damage in Alzheimer's disease interacts with the structure of semantic memory to yield different patterns of impairment between patients and categories over time.

Double dissociation of semantic categories in Alzheimer's disease

Data that demonstrate distinct patterns of semantic impairment in Alzheimer's disease (AD) are presented. Findings suggest that while groups of mild-moderate patients may not display category specific impairments, some individual patients do show selective impairment of either natural kinds or artifacts. We present a model of semantic organization in which category specific impairments arise from damage to distributed features underlying different types of categories. We incorporate the crucial notions of intercorrelations and distinguishing features, allowing us to demonstrate (1) how category specific impairments can result from widespread damage and (2) how selective deficits in AD reflect different points in the progression of impairment. The different patterns of impairment arise from an interaction between the nature of the semantic categories and the progression of damage.

Neuropathology of synthetic beta-amyloid peptide analogs in vivo

Considerable evidence exists demonstrating that beta-amyloid protein and its fragments 1-40 and 25-35 (beta (25-35)) are neurotoxic to cells in the rat hippocampus both in culture and in vivo. This neurotoxicity has been correlated to the aggregational state of the peptides. Previously we have shown that beta (25-35) produces a cavitational lesion in rat hippocampus and also reduces the enzyme or transmitter expressions in two subcortical structures whose axons project to the hippocampus: the locus coeruleus (LC) and the medial septum. In the present study, we further investigated the amino acid sequence that might be responsible for these effects. A series of synthetic peptide analogs of beta (25-35) with glycine substituted for serine, asparagine, lysine and methionine at positions 26, 27, 28 and 35, respectively, were injected at a 3 nmol dosage into the rat hippocampus once a week for 2 weeks. The damage to the hippocampus and immunohistochemistry of the LC and medial septum were examined 1 week following the second treatment. All of the synthetic peptides with glycine substitution produced damage to the hippocampal tissue. This damage was similar to that seen with beta (25-35). However, the reduction of enzyme expressions in the LC and medial septum was less from these substituted peptides than from that of beta (25-35). While beta (25-35) application resulted in a similar reduction of tyrosine hydroxylase (TH) and glutamate (Glu) immunoreactivities in the LC, only TH was significantly reduced in the substituted peptide groups. The least reduction of TH and Glu immunoreactivities in the LC was observed in rats treated with peptides in which glycine replaced either lysine or methionine. In the basal forebrain medial septum, the application of beta (25-35) resulted in a marked decrease in choline acetyltransferase (ChAT) immunoreactivity. This reduction was found to be less by each of the synthetic peptides. These results suggest that the biological activity of beta (25-35) is sensitive to changes in the primary structure of the peptide. Among the 4 amino acid residues examined, lysine and methionine at positions 28 and 35 appear to play more important roles in determining the action of beta (25-35).

The effects of aspartic acid-bond isomerization on in vitro properties of the amyloid beta-peptide as modeled with N-terminal decapeptide fragments

The 42-amino acid A beta, the major constituent of the senile plaque deposits of the brains of Alzheimer's disease patients, exhibits a high degree of heterogeneity at its N-terminus. Isomerization of aspartic acid bonds at residues 1 and 7 renders A beta more prone to aggregate and form extended structure as it was shown by in vivo and in vitro studies. We recently demonstrated the ability of mid-chain aspartic acid-bond isomerization to break the dominant helical structure of the N-terminal decapeptide fragment by CD. In the current study we use molecular modeling to show that insertion of the extra -CH2-group into the decapeptide backbone results in the formation of stable reverse-turns and destabilizes the helical conformer that competes with the extended structure at the full-sized peptide level. The molecular modeling also reveals a limited propensity of the diisomerized peptide to form extended structure directly. Anti-A beta pAb 2332 is more sensitive for the non-isomerized status of the decapeptide than that of the full-sized peptide. mAb 6E10, raised against unmodified A beta recognizes only the unmodified decapeptide or the peptide isomerized at the first aspartic acid in a conformation-dependent manner, but does not recognize the mid-chain isomerized or diisomerized decapeptide in any circumstance. The diisomerized decapeptide was used as immunogen to generate polyclonal antibody 14943 that is not selective for the isomerized status of either the full-size peptide or the decapeptide, but recognizes the isomerized peptides preferentially when the peptide antigen structures are conserved during the enzyme-linked immunoassay procedure. Owing to the aberrant behavior of the full-sized A beta peptide during standard RP-HPLC, serum stability studies that indicate extracellular stability can be more effectively performed on the decapeptide fragments. Remarkably, the diisomerized peptide exhibits a significantly increased stability towards serum peptidases compared with the unmodified or monoisomerized peptides, suggesting a possible mechanism of the retention of the isomerized A beta peptide in the affected brains.

Quantitation of Alzheimer's amyloid peptide and identification of related amyloid proteins by dot-blot immunoassay

In Alzheimer's disease, the main component of amyloid deposits is a 39-43 amino acid peptide referred to as amyloid peptide or A beta. A crucial issue in the study of this disorder is to define the sequence of events that lead to amyloid deposition. In the present study, a new approach was developed that allows to specifically solubilize A beta peptide trapped within amyloid deposits and to quantify its amount by dot-blot immunoassay. The present method also permits to isolate components tightly bound to A beta and that are likely to catalyze its aggregation. Biochemical A beta quantitation was performed in 4 Brodmann areas from 17 elderly individuals exhibiting different degrees of amyloidosis. In parallel, classical neuropathology was done by histochemical and immunohistochemical methods. A beta amounts (pmol) were correlated to the number of amyloid deposits determined by neuropathology showing high statistical significance. Moreover, amyloid-binding proteins including apolipoprotein E and heparan sulfate proteoglycans were also found associated to A beta in the amyloid preparation. The present biochemical procedure is a new and reliable method to quantify amyloid deposition in brain. Furthermore, it allows to detect amyloid-associated components such as apolipoprotein E, that may be involved in the pathological process of amyloidogenesis.

Visual evoked potentials in early Alzheimer's dementia: an exploratory study

Topographical maps of visual evoked potentials (VEPs) were recorded from 10 possible Alzheimer's disease (AD) patients and 10 control subjects. The purpose of the study was to determine if the two types of VEPs could function as a diagnostic screening for AD. Results of the statistical analysis did not reveal any latency differences between VEPs for the components elicited by either the pattern shift visual evoked potential (PSVEP)--or flash visual evoked potential (FVEP)--elicited components for AD patients compared with the control subjects; however, the information provided insight into results that are frequently lost with conventional evoked potential data. Statistically significant differences in amplitude were found between the P1 and the N2 of the PSVEP at 124, 126, and 130 ms, and at 116 ms for the FVEP.

Cytological demonstration of features of Alzheimer's disease using brain smear technique

The major diagnostic histopathological features of moderate to severe Alzheimer's disease (AD) are amyloid rich neurofibrillary tangles (NFTs) and neuritic plaques (NPs) containing beta A4 peptide. As the frequency of stereotactic brain biopsies is increasing, the diagnostic cytological features of AD are of relevance. Our study presents the brain smear features of five autopsied patients with moderate to severe AD both clinically and pathologically. NFTs and NPs were identified in 100% of smears. Amyloid neuropil threads (NTs), a more recently identified hallmark of AD, were also seen in all smears. Segmental beta A4 peptide deposition within vessels, clustering of plaques around capillaries, and NTs were more obvious by the smear technique than in histological sections.

Synthetic post-translationally modified human A beta peptide exhibits a markedly increased tendency to form beta-pleated sheets in vitro

The beta-amyloid peptide (A beta) is the major constituent of senile plaques, one of the hallmark neuropathological lesions of Alzheimer's disease. Recently a post-translationally modified analogue of the human beta-amyloid peptide, which contains isoaspartic residues in positions 1 and 7, was isolated from parenchyma and leptomeningeal microvasculature of Alzheimer's disease patients [Roher, A. E., Lowenson, JD., Clarke, S., Wolkow, C., Wang, R., Cotter, R. J., Reardon, I. M., Zürcher-Neely, H. A., Heinrikson, R. L., Ball, M. J. & Greenberg, B. D. (1993) J. Biol. Chem. 268, 3072-3083]. We used circular dichroism and Fourier-transform infrared spectroscopy to characterize the conformational changes on human A beta upon substitution of Asp1 and Asp7 to isoaspartic residues. We found that the intermolecular beta-pleated-sheet content is markedly increased for the post-translationally modified peptide compared to that in the corresponding unmodified human or rodent A beta sequences both in aqueous solutions in the pH 7-12 range, and in membrane-mimicking solvents (such as aqueous octyl-beta-D-glucoside or aqueous acetonitrile solutions). These findings underline the importance of the originally alpha-helical N-terminal regions of the unmodified A beta peptides in defining its secondary structure and may offer an explanation for the selective aggregation and retention of the isomerized A beta peptide in Alzheimer's-disease-affected brains.

Human and rodent Alzheimer beta-amyloid peptides acquire distinct conformations in membrane-mimicking solvents

The major constituent of senile plaques (one of the hallmark lesions of Alzheimer's disease) is a 42(43)-amino-acid polypeptide, termed the A4 or beta-amyloid peptide. The beta-amyloid peptide or A4 is derived from one or more larger beta-amyloid precursor proteins. The precursor protein from whence the A4 peptide is derived is highly conserved throughout evolution, and humans, monkeys, dogs, and bears develop brain deposits of A4 peptide in amyloid fibrils. However, similar accumulations of A4 amyloid are negligible in the brains of rats and mice for reasons that remain unexplored. Notably, the A4 sequence of rodents, deduced from the cDNA clones, differs only in three amino acids from the A4 isolated from the brain of humans. Hence, these differences could account for the inability of rodents to develop Alzheimer-like A4 amyloid plaques. To test this hypothesis directly, using physical and chemical model systems, we synthesized, purified, and characterized A4 peptides corresponding to the human and rodent sequences. Circular dichroic and Fourier-transform infrared spectroscopy were used with various membrane-mimicking solvents, different peptide concentrations, and variable pH to identify those environmental conditions that promoted beta-pleated sheet formation of the human versus rodent A4. At an intermediate alkaline pH (< or = 10), the rodent peptide has more beta-pleated sheet structure than the human sequence. The beta-pleated sheets for both peptides could be eliminated at very high pH (> or = 12). The amount of the beta-structure increased in an octyl glucoside solution, compared to that found in SDS, as well as in several of the other solutions tested here. This suggests that particles originated from prior membrane damage may play a role in the stabilization of beta-pleated sheets with subsequent formation of amyloid deposits. Finally, we found that higher beta-pleated sheet content was observed for the rodent sequences in acetonitrile/water mixtures. In contrast, more beta-pleated sheets were detected with the human A4 in trifluoroethanol/water mixtures at neutral pH. Remarkably, at relatively low peptide concentrations, only the human sequences assumed an extended secondary structure. These data suggest that subtle inter-species amino-acid differences may account for the inability of the rodent peptide to form amyloid fibrils in situ.

A serine-->proline change in the Alzheimer's disease-associated epitope Tau 2 results in altered secondary structure, but phosphorylation overcomes the conformational gap

Monoclonal antibody Tau 2 was raised against bovine tau protein, was reported to recognize a conformational epitope, and stained tau was found in neurofibrillary tangles of Alzheimer's disease, but not normal human tau. We synthesized tetradeka peptides corresponding to the original bovine sequence, its serine-->proline substituted analog, the genuine human sequence of this region, and the bovine epitope phosphorylated on the crucial serine. The secondary structure of the peptides was determined by circular dichroism. It was found that only the original bovine epitope showed a tendency to form the beta-pleated sheets characteristic of the neurofibrillary tangles. The spectra of the human peptide, its analog, and the phosphorylated bovine sequence were very similar, featuring a weak, helical beta-turn character. Eventual phosphorylation of epitopes of this otherwise heavily phosphorylated protein may overcome inter-species conformational gaps.

Immunological and conformation characterization of a phosphorylated immunodominant epitope on the paired helical filaments found in Alzheimer's disease

The immunological recognition pattern of one of the most commonly used monoclonal antibodies, PHF-1, which detects the paired helical filaments of Alzheimer's disease, exhibits a high degree of similarity with the recognition of a polyclonal antibody, anti-T3P, raised against a synthetic phosphopeptide, GAEIVYKS(Phospho)PVVSGD, corresponding to amino acids 389-402 of the microtubule-associated protein tau. A panel of 16 synthetic non-phosphorylated and phosphorylated peptides, excised from different regions of tau and peptide analogs thereof, were used to show that PHF-1 is indeed directed against the T3 fragment. Circular dichroism spectroscopy shows that the phosphorylated peptide exhibits a limited propensity to form intramolecular beta-pleated sheets, and alteration is found in the reverse-turn structure that dominates the middle section of the molecule. The shift in the turn-forming amino acids may also allow a stacking procedure, may interfere with microtubule assembly, and, consequently, may be accountable for deposit formation.

Immunohistochemical analysis of the basal forebrain in Alzheimer's disease

An immunohistochemical analysis utilizing antibodies to glial fibrillary acid protein (GFAP), microglia, beta-amyloid, amyloid P-component, neurofibrillary tangles (NFT), and microtubule associated protein-tau (MAP-tau) was performed on the cholinergic basal forebrain in Alzheimer's disease (AD). This severely compromised system, which includes the nucleus basalis of Meynert, is largely responsible for the massive loss of cortical and subcortical cholinergic innervation in the diseased state. Our study juxtaposes the basal forebrain immunohistopathology to the hippocampus, amygdala, and entorhinal cortex in AD. Key findings include a progressive degeneration of these cholinergic neurons characterized by the formation of immunoreactively atypical NFT, the loss of intraneuronal lipofuscin, a lack of senile plaque and beta-amyloid deposition within the basal forebrain, and end-stage gliosis without residual extracellular NFT. These structural and compositional differences suggest a unique pathogenesis of the basal forebrain separate from other cortical regions in AD.

Characteristics of Epstein-Barr virus transformed B cell lines from patients with Alzheimer's disease and age-matched controls

The characteristics of B cell lines isolated from patients with Alzheimer's disease (AD) and age-matched controls were investigated after having been transformed by Epstein-Barr virus (EBV). After isolation of mononuclear blood cells and in vivo or in vitro EBV infection, 35 and 21 lymphoblastoid cell lines (LCLs) were generated from 19 patients with AD (mean age 79.4 years) and 21 age-matched controls (mean age 80.0 years), respectively. B lymphocytes from AD patients were immortalised more easily than those from controls; the percentage of in vitro EBV infected LCLs (B95-LCLs) obtained in the AD group was significantly higher (76.2% versus 33.3% in the control group) and the mean time required for establishment was significantly lower (20.2 and 21.9 days versus 26.7 and 60.9 days in the control group). The EBV receptor and surface immunoglobulin (Ig) analyses showed no difference between the two groups. The expression of Epstein-Barr early antigens (EA) and viral capsid antigens (VCAs) revealed a tendency to higher viral replication in LCLs from AD patients; however, VCA expression remained limited to a small number of cells and did not affect overall cell growth. Finally, qualitative and quantitative differences were observed in the pattern of Ig production. Whereas spontaneously established LCLs from AD patients were generally monoclonal (80% of LCLs versus 33% in the control group), B95-LCLs were all polyclonal and secreted more IgM and IgA than those from controls; the mean IgM level was significantly higher in B95-LCLs from the AD group. These results suggest that B cells derived from AD patients seemed to be less differentiated than cells from age-matched controls.

Reversible beta-pleated sheet formation of a phosphorylated synthetic tau peptide

Serine416 of human tau protein is believed to be phosphorylated in Alzheimer neurofibrillary tangles. We synthesized a fragment of tau, consisting of amino acids 408-421 in both non-phosphorylated and serine416-phosphorylated forms. Circular dichroism in a trifluoroethanol-water mixture indicated a beta-turn----beta-pleated sheet conformational transition upon phosphorylation. The beta-structure formation is intermolecular and can be inhibited by addition of Ca2+ ions or a phosphorylated tripeptide, but not with its non-phosphorylated analog. The presence of the phosphorylated tau peptide did not facilitate the formation of beta-pleated sheets of a phosphorylated neurofilament fragment. Multivalent cations induced a conformational transition of this phosphorylated neurofilament peptide, but the effect was less specific than the transition induced in the tau fragment, and it could also be reversed with the competing phosphorylated tripeptide.

Prolongation of magnetic resonance T2 time in hippocampus of human patients marks the presence and severity of Alzheimer's disease

Spin-spin relaxation time (T2) was measured in the hippocampal formation, thalamus, and cortical white matter in 13 patients with probable Alzheimer's disease (AD), 11 elderly normal individuals, 23 healthy young persons, and 9 subjects diagnosed with multi-infarct dementia. A 0.04 tesla magnetic resonance scanner was used. Hippocampal T2 values for all AD patients exceeded those of any non-AD individual, regardless of age or dementia due to infarction. Further, these T2 values were highly correlated (+ 0.96) with the severity of functional and cognitive impairment of the AD patients. This T2 prolongation was not observed at the other sites examined. These results suggest that hippocampal T2 prolongation may provide a specific marker by which AD pathology can be detected, characterized, and followed in vivo.

A comparative study of histological and immunohistochemical methods for neurofibrillary tangles and senile plaques in Alzheimer's disease

Several studies have demonstrated that the accurate visualization and quantification of pathological lesions in neurodegenerative disorders depend on the reliability of staining methods. In an attempt to gain a better assessment of the density and distribution of the neuropathological markers of Alzheimer's disease, we compared the staining efficiency of a modified thioflavine S protocol for neurofibrillary tangles (NFT) and senile plaques (SP) to different argentic impregnation techniques (Bielchowsky, Gallyas, Globus, Campbell-Switzer-Martin) and to immunohistochemical stainings obtained with two different antibodies against the amyloid beta protein A4 and the microtubule-associated tau protein. The modified thioflavine S technique (MTST) detects up to 60% more SP and up to 50% more NFT than the Bielschowsky and Globus methods, respectively. The results obtained with the specific antibodies are comparable to those obtained with the MTST, but these immunotechniques are more expensive and time consuming for routine neuropathological evaluation, and the appropriate antibodies are not always commercially available. Furthermore, the morphological appearance of NFT and SP with MTST is greatly improved when compared to the classical thioflavine S and the increased signal-to-noise ratio between specifically stained structures and background permits an accurate semi-automatic quantification.

Latent herpes simplex virus type 1 in normal and Alzheimer's disease brains

A viral aetiology has long been suspected for Alzheimer's disease (AD) but until now, techniques have not been sufficiently sensitive to provide clear evidence for or against the presence of any viral genome in AD brain. We have used the very highly sensitive method of polymerase chain reaction to look for herpes simplex virus type 1 (HSV1) DNA, specifically the viral thymidine kinase (TK) gene, in autopsy brain specimens. DNA-samples from HSV-infected and uninfected Vero cells have been examined concurrently to provide standard "HSV-positive" and "HSV-negative" samples, the latter guarding also against false positives caused by cross-contamination. To preclude false negatives, we have checked the presence of the human gene, hypoxanthine phosphoribosyl transferase. In all specimens from 8 AD patients and 6 normal individuals (temporal, frontal and hippocampal), we have found viral TK sequences. In contrast, in preliminary studies on lymphocytes from normals and AD patients, we did not find TK sequences. It is postulated that factors such as number or expression of viral genes and host susceptibility might be related to incidence of AD.

Cytoskeletal alterations might account for the phylogenetic vulnerability of the human brain to Alzheimer's disease

A theory is presented here in the attempt to explain why Alzheimer's disease (AD) primarily affects areas of the human brain that have been acquired recently in phylogenesis. Disturbances in cytoskeletal function are proposed to play a fundamental role in triggering the sequence of pathologic events leading to the occurrence of AD-related histopathological markers and to the degeneration and death of neurons. These deficits are supposed to occur more likely in neuronal populations that possess a high degree of plasticity, the substrate of memory functions, and that constitute, in fact, the phylogenetically new telencephalic regions of the human brain.

Human neuroblastoma cells treated with aluminium express an epitope associated with Alzheimer's disease neurofibrillary tangles

A number of studies have implicated aluminium as a possible factor in the pathogenesis of Alzheimer's disease (AD). Following an examination of the uptake of aluminium by human neuroblastoma cells in culture, treated with a range of concentrations of aluminium complexed with ethylene-diaminetetra-acetic acid (EDTA), we have now carried out an immunocytochemical study. Using an antibody to phosphorylated tau protein, which reacts specifically with AD neurofibrillary tangles (NFT), we have found that after treatment periods of 16 days to 8 weeks with aluminium-EDTA, the cells show positive staining with this antibody. No such reaction was detected in cells grown in medium alone, nor in aluminium-EDTA-treated cells subjected to the same immunocytochemical procedure but without added primary antibody. Cells grown in medium plus EDTA, which contains a low level of aluminium contamination, showed a slight reaction. Our system may provide a suitable model for studying the early changes which lead to NFT formation.

Amyloid angiopathy--a rare cause of intracerebral hemorrhage

The cerebral amyloid angiopathy (CAA), morphologically characterized by amyloid deposition in the vessel walls which are altered to rigid tubes, is a chronic disease of the cortical and meningeal vessels and can cause intracerebral hemorrhages (1.5% of all intracerebral bleedings). We report the course of five surgically treated patients with lobar space-occupying intracerebral hemorrhages and CAA confirmed by histological examination. All patients were elderly (74-84 years), in good condition, and self-providing before the hemorrhage. There were no signs of dementia of the Alzheimer's type. In four cases, CT showed a hematoma in the parieto-occipital, and in one case in the temporo-parietal, region. After surgical evacuation, two patients recovered, one patient remained in bad condition, and two patients died from recurrent hemorrhage within two weeks. Spontaneous intracerebral hemorrhage of lobar localization in an elderly patient strongly suggests CAA. The prognosis seems to be poor in cases with recurrent hemorrhage, the other patients presented an uneventful course, comparable with patients operated on for intracerebral bleeding of other origin. Further investigations are necessary to elucidate the prognosis of this entity.

Aluminum toxicity and Alzheimer's disease. Is there a connection?

Similarities between Alzheimer's disease and aluminum toxicity have led to the suggestion that a causal relationship may exist. However, the two disorders differ in many respects. The author reviews the evidence concerning the relationship between aluminum toxicity and Alzheimer's disease and answers the question, is there a connection?

Clinicopathological analysis of dementia disorders in the elderly

The relative incidence of the major types of dementia disorders and the agreement rates between clinical and pathological diagnosis were analysed in consecutive autopsy series of 675 demented subjects from 3 hospitals (mean age 79.5 years, SD 9.6). Clinical assessment followed the DSM-III and ICD-9-NA criteria and NINCDS/ADRDA criteria for probable Alzheimer disease (AD) (McKhann et al. 1984), histological criteria for the diagnosis of AD those of the NIH/AARP Work Group (Khachaturian 1985) using a 4-degree rating scale for plaques and tangles in neocortex and hippocampus (Morris et al. 1988), and the criteria by Tierney et al. (1988) for 'pure' AD. Vascular dementia (MID) and other disorders were diagnosed according to current pathologic criteria. Clinical diagnosis of AD/SDAT was made in 59.2%, of MID in 21.7%, of mixed AD + MID in 3.1%, and of Parkinson's disease (PD) and other disorders in 16%. At autopsy, 76.7% fulfilled histological criteria for AD/SDAT, but only 60% were 'pure' forms, while 8.2% had additional features of PD and 7.9% coexisting vascular lesions indicating mixed SDAT + MID. 15.7% were MID with no or very little AD pathology, 7.4% other CNS disorders. 0.3% of the brains showed no abnormality beyond age-related changes. AD/SDAT had its highest incidence in a psychiatric population, MID and PD + SDAT in general and geriatric hospital cohorts. The overall coincidence rates for clinical and pathological diagnosis of AD/SDAT were 85.2%, for MIX and MID 60.5-61.9%, but only 51% for PD-PD/AD. These data and the results of other recent studies emphasize the need for more appropriate clinical and pathological criteria in the diagnosis of the dementias.

Antibodies to viral antigens, xenoantigens, and autoantigens in Alzheimer's disease

Sera from 19 patients with Alzheimer's disease (AD) and 21 control subjects were studied by immunofluorescence and enzyme immunoassay for antibody activity against various viruses and 12 self- and non-self-antigens. Total IgG mean level was significantly higher in the AD group; the IgG level was above 15 g/L in 52.8% of AD patients versus 14.3% of control subjects. Antiviral antibody titers showed no significant differences except for antibodies to herpes simplex virus-1, which were increased in control group. In contrast, autoantibodies were more frequently found in AD patients, and the prevalence of antibodies to spectrin, peroxidase, and thyroglobulin was significantly increased. Thus, in our series, autoimmune but not antiviral responses were heightened in at least 42% of AD patients (versus 9% of the control group) suggesting the existence of two subpopulations in the AD group.

Boston Naming Test in Alzheimer's disease

The 60-item Boston Naming Test (BNT) was administered to 55 subjects: 15 mildly-to-moderately demented patients meeting NINCDS-ADRDA criteria for "probable" Alzheimer's disease (AD), 15 age-equivalent normal control (NC) subjects, and--for purposes of validation--25 additional subjects with other forms of dementia (OD). A cutting score of 51 correctly classified 80% of AD patients and 86% of NC subjects. To facilitate rapid screening of confrontation-naming performance in these populations, three 30-item shortened versions of the BNT were constructed. Even and Odd Versions were equivalent for AD, NC, and OD subjects; high correlations between these two and the 60-item BNT permit easy extrapolation to a total BNT score. A new Empirical Version, derived from performance of our AD and NC reference groups, maintained most of the intergroup discrimination of the full BNT.