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Zamani, M. R. and Y. S. Allen (2001). "Nicotine and its interaction with beta-amyloid protein: a short review." Biol Psychiatry 49(3): 221-32.
Two features of Alzheimer's disease (AD) are beta-amyloid protein (betaAP) deposition and a severe cholinergic deficit. beta-Amyloid protein is a 39- to 43-amino acid transmembrane fragment of a larger precursor molecule, amyloid precursor protein. It is a major constituent of senile plaque, a neuropathologic hallmark of AD, and has been shown to be neurotoxic in vivo and in vitro. The cholinergic neurotransmission system is seen as the primary target of AD. However, other systems are also found to show functional deficit. An association between cholinergic deficit and betaAP is suggested by a negative correlation between cigarette smoking and AD. Evidence hitherto suggests that betaAP causes neuronal death possibly via apoptosis by disrupting calcium homeostasis, which may involve direct activation or enhancement of ligand-gated or voltage-dependent calcium channels. Selective second messengers such as protein kinases are triggered that signal neuronal death. Nicotine or acetylcholinesterase inhibitors can partially prevent the neurotoxicity of betaAP in vivo and in vitro. However, the exact mechanism by which nicotine provides its protective effects is not fully understood, but clearly there are protective roles for nicotine. Here, some aspects of betaAP neurotoxicity and nicotinic intervention as a protective agent are discussed.

Yu, P. H. (2001). "Involvement of cerebrovascular semicarbazide-sensitive amine oxidase in the pathogenesis of Alzheimer's disease and vascular dementia." Med Hypotheses 57(2): 175-9.
Fibrillary tangles and senile plaques resulting from advanced aggregation of beta-amyloid and other proteins are pathological characteristics of Alzheimer's disease (AD). Cerebral amyloid angiopathy is quite common in AD. In fact, amyloid fibrils fuse to and emanate from the vascular basement membrane. Semicarbazide-sensitive amine oxidase (SSAO), located in outer membranes of vascular smooth muscles and endothelia, catalyzes deamination of methylamine-producing formaldehyde and hydrogen peroxide. SSAO is also involved in lymphocyte adhesion and is up-regulated in response to inflammation. SSAO-mediated generation of formaldehyde can induce protein (i.e. beta-amyloid) cross-linkage, deposition and subsequently plaque formation in the compartment adjacent to the cerebrovessels. Formaldehyde may cause cytotoxicity, which induces inflammation and release of more SSAO, producing a cascade of toxic cycle. Increased SSAO-mediated reaction may be chronically involved in the pathogenesis of vascular dementia and AD. Copyright 2001 Harcourt Publishers Ltd.

Yasojima, K., H. Akiyama, et al. (2001). "Reduced neprilysin in high plaque areas of Alzheimer brain: a possible relationship to deficient degradation of beta-amyloid peptide." Neurosci Lett 297(2): 97-100.
Neprilysin is an enzyme capable of degrading beta-amyloid protein. We measured neprilysin mRNA and protein levels in brain and peripheral organs of Alzheimer disease (AD) and control cases. Neprilysin mRNA levels were lowest in the hippocampus and temporal gyrus, which are vulnerable to senile plaque development. They were highest in the caudate and peripheral organs which are resistant to senile plaque development. Levels in AD were significantly lower than controls in the hippocampus and midtemporal gyrus but not in other brain areas or peripheral organs. We also measured levels of the mRNA for the neuronal marker microtubule-associated protein-2. They were remarkably constant in all brain areas and were not lowered in AD, indicating that the neprilysin mRNA reduction in the hippocampus and temporal gyrus was not correlated with simple neuronal loss. Relative levels of neprilysin protein generally paralleled those of the mRNA. These results suggest that deficient degradation of beta-amyloid protein caused by low levels of neprilysin may contribute to AD pathogenesis.

Yamaguchi, A., S. Sugihara, et al. (2001). "Alzheimer beta amyloid deposition enhanced by apoE epsilon4 gene precedes neurofibrillary pathology in the frontal association cortex of nondemented senior subjects." J Neuropathol Exp Neurol 60(7): 731-9.
To clarify how Alzheimer disease pathology develops in the brains of nondemented subjects, we examined the interrelations among the amounts and morphology of Abeta deposition, neurofibrillary pathology, and apolipoprotein E (ApoE) genotype in the frontal association cortex of 101 autopsy brains from patients aged between 40 to 83. Senile plaque density correlated well with the logarithmic data of insoluble Abeta measured by enzyme immunoassay (EIA). The amounts of Abeta42-ETA increased dramatically in the late preclinical stage, whereas the AP42+ plaque density increased in the early preclinical stage. Neurofibrillary pathology appeared only in the areas with severe Abeta deposition and in subjects aged over 70. The ApoE epsilon4 allele enhanced the Abeta3 deposition in presenile subjects. Plaque-associated glial Abeta was prominent in subjects with mild to moderate Abeta deposition. The morphology of cerebral Abeta deposition changed from diffuse plaques with small amounts of Abeta in each plaque in the early preclinical stage to primitive/neuritic plaques with larger amounts of Abeta in each plaque in the late preclinical stage. Our findings suggest that the prevention of Abeta deposition in the late preclinical stage can be a rational therapeutic target, especially in elderly people with ApoE epsilon4 allele.

Wyss-Coray, T., C. Lin, et al. (2001). "TGF-beta1 promotes microglial amyloid-beta clearance and reduces plaque burden in transgenic mice." Nat Med 7(5): 612-8.
Abnormal accumulation of the amyloid-beta peptide (Abeta) in the brain appears crucial to pathogenesis in all forms of Alzheimer disease (AD), but the underlying mechanisms in the sporadic forms of AD remain unknown. Transforming growth factor beta1 (TGF-beta1), a key regulator of the brain's responses to injury and inflammation, has been implicated in Abeta deposition in vivo. Here we demonstrate that a modest increase in astroglial TGF-beta1 production in aged transgenic mice expressing the human beta-amyloid precursor protein (hAPP) results in a three-fold reduction in the number of parenchymal amyloid plaques, a 50% reduction in the overall Abeta load in the hippocampus and neocortex, and a decrease in the number of dystrophic neurites. In mice expressing hAPP and TGF-beta1, Abeta accumulated substantially in cerebral blood vessels, but not in parenchymal plaques. In human cases of AD, Abeta immunoreactivity associated with parenchymal plaques was inversely correlated with Abeta in blood vessels and cortical TGF-beta1 mRNA levels. The reduction of parenchymal plaques in hAPP/TGF-beta1 mice was associated with a strong activation of microglia and an increase in inflammatory mediators. Recombinant TGF-beta1 stimulated Abeta clearance in microglial cell cultures. These results demonstrate that TGF-beta1 is an important modifier of amyloid deposition in vivo and indicate that TGF-beta1 might promote microglial processes that inhibit the accumulation of Abeta in the brain parenchyma.

Wirths, O., G. Multhaup, et al. (2001). "Intraneuronal Abeta accumulation precedes plaque formation in beta-amyloid precursor protein and presenilin-1 double-transgenic mice." Neurosci Lett 306(1-2): 116-20.
beta-Amyloid peptides are key molecules that are involved in the pathology of Alzheimer's disease (AD). The source and place of the neurotoxic action of Abeta, however, is still a matter of controversial debates. In the present report, we studied the neuropathological events in a transgenic mouse model expressing human mutant beta-amyloid precursor protein and human mutant presenilin-1 in neurons. Western blot and immunohistochemical analysis revealed that intracellular Abeta staining preceded plaque deposition, which started in the hippocampal formation. At later stages, many neuritic Abeta positive plaques were found in all cortical, hippocampal and many other brain areas. Interestingly, intraneuronal Abeta staining was no longer detected in the brain of aged double-transgenic mice, which correlates with the typical neuropathology in the brain of chronic AD patients.

Wegiel, J., K. C. Wang, et al. (2001). "The role of microglial cells and astrocytes in fibrillar plaque evolution in transgenic APP(SW) mice." Neurobiol Aging 22(1): 49-61.
Ultrastructural reconstruction of 27 fibrillar plaques in different stages of formation and maturation was undertaken to characterize the development of fibrillar plaques in the brains of human APP(SW) transgenic mice (Tg2576). The study suggests that microglial cells are not engaged in Abeta removal and plaque degradation, but in contrast, are a driving force in plaque formation and development. Fibrillar Abeta deposition at the amyloid pole of microglial cells appears to initiate three types of neuropil response: degeneration of neurons, protective activation of astrocytes, and attraction and activation of microglial cells sustaining plaque growth. Enlargement of neuronal processes and synapses with accumulation of degenerated mitochondria, dense bodies, and Hirano-type bodies is the marker of toxic injury of neurons by fibrillar Abeta. Separation of amyloid cores from neurons and degradation of amyloid cores by cytoplasmic processes of hypertrophic astrocytes suggest the protective and defensive character of astrocytic response to fibrillar Abeta. The growth of cored plaque from a small plaque with one microglial cell with an amyloid star and a few dystrophic neurites to a large plaque formed by several dozen microglial cells seen in old mice is the effect of attraction and activation of microglial cells residing outside of the plaque perimeter. This mechanism of growth of plaques appears to be characteristic of cored plaques in transgenic mice. Other features in mouse microglial cells that are absent in human brain are clusters of vacuoles, probably of lysosomal origin. They evolve into circular cisternae and finally into large vacuoles filled with osmiophilic, amorphous material and bundles of fibrils that are poorly labeled with antibody to Abeta. Microglial cells appear to release large amounts of fibrillar Abeta and accumulate traces of fibrillar Abeta in a lysosomal pathway.

Webster, S. D., M. D. Galvan, et al. (2001). "Antibody-Mediated Phagocytosis of the Amyloid beta-Peptide in Microglia Is Differentially Modulated by C1q." J Immunol 166(12): 7496-503.
Microglial ingestion of the amyloid beta-peptide (Abeta) has been viewed as a therapeutic target in Alzheimer's disease, in that approaches that enhance clearance of Abeta relative to its production are predicted to result in decreased senile plaque formation, a proposed contributor to neuropathology. In vitro, scavenger receptors mediate ingestion of fibrillar Abeta (fAbeta) by microglia. However, the finding that cerebral amyloid deposition in a transgenic mouse model of Alzheimer's disease was diminished by inoculation with synthetic Abeta has suggested a possible therapeutic role for anti-Abeta Ab-mediated phagocytosis. Microglia also express C1qR(P), a receptor for complement protein C1q, ligation of which in vitro enhances phagocytosis of immune complexes formed with IgG levels below that required for optimal FcR-mediated phagocytosis. The data presented here demonstrate FcR-dependent ingestion of Abeta-anti-Abeta complexes (IgG-fAbeta) by microglia that is a function of the amount of Ab used to form immune complexes. In addition, C1q incorporated into IgG-fAbeta enhanced microglial uptake of these complexes when they contained suboptimal levels of anti-Abeta Ab. Mannose binding lectin and lung surfactant protein A, other ligands of C1qR(P), also enhanced ingestion of suboptimally opsonized IgG-fAbeta, whereas control proteins did not. Our data suggest that C1qR(P)-mediated events may promote efficient ingestion of Abeta at low Ab titers, and this may be beneficial in paradigms that seek to clear amyloid via FcR-mediated mechanisms by minimizing the potential for destructive Ab-induced complement-mediated processes.

Walsh, D. M., D. M. Hartley, et al. (2001). "In vitro studies of amyloid beta-protein fibril assembly and toxicity provide clues to the aetiology of Flemish variant (Ala692-->Gly) Alzheimer's disease." Biochem J 355(Pt 3): 869-77.
In a Flemish kindred, an Ala(692)-->Gly amino acid substitution in the amyloid beta-protein precursor (AbetaPP) causes a form of early-onset Alzheimer's disease (AD) which displays prominent amyloid angiopathy and unusually large senile plaque cores. The mechanistic basis of this Flemish form of AD is unknown. Previous in vitro studies of amyloid beta-protein (Abeta) production in HEK-293 cells transfected with cDNA encoding Flemish AbetaPP have shown that full-length [Abeta(1-40)] and truncated [Abeta(5-40) and Abeta(11-40)] forms of Abeta are produced. In an effort to determine how these peptides might contribute to the pathogenesis of the Flemish disease, comparative biophysical and neurotoxicity studies were performed on wild-type and Flemish Abeta(1-40), Abeta(5-40) and Abeta(11-40). The results revealed that the Flemish amino acid substitution increased the solubility of each form of peptide, decreased the rate of formation of thioflavin-T-positive assemblies, and increased the SDS-stability of peptide oligomers. Although the kinetics of peptide assembly were altered by the Ala(21)-->Gly substitution, all three Flemish variants formed fibrils, as did the wild-type peptides. Importantly, toxicity studies using cultured primary rat cortical cells showed that the Flemish assemblies were as potent a neurotoxin as were the wild-type assemblies. Our results are consistent with a pathogenetic process in which conformational changes in Abeta induced by the Ala(21)-->Gly substitution would facilitate peptide adherence to the vascular endothelium, creating nidi for amyloid growth. Increased peptide solubility and assembly stability would favour formation of larger deposits and inhibit their elimination. In addition, increased concentrations of neurotoxic assemblies would accelerate neuronal injury and death.

Volkow, N. D., Y. S. Ding, et al. (2001). "Imaging brain cholinergic activity with positron emission tomography: its role in the evaluation of cholinergic treatments in Alzheimer's dementia." Biol Psychiatry 49(3): 211-20.
One of the strategies in the treatment of Alzheimer's disease is the use of drugs that enhance cholinergic brain function, since it is believed that cholinergic dysfunction is one of the factors that contributes to cognitive deterioration. Positron emission tomography is a medical imaging method that can be used to measure the concentration, kinetics, and distribution of cholinergic-enhancing drugs directly in the human brain and assess the effects of the drugs at markers of cholinergic cell viability (vesicular transporters, acetylcholinesterase), at muscarininc and nicotinic receptors, at extracellular acetylcholine, at markers of brain function (glucose metabolism and blood flow), and on amyloid plaque burden in vivo in the brains of patients with Alzheimer's disease. In addition, these measures can be applied to assess the drugs' pharmacokinetic and pharmacodynamic properties in the human brain. Since the studies are done in living human subjects, positron emission tomography can evaluate the relationship between the drugs' biological, behavioral, and cognitive effects; monitor changes in brain function in response to chronic treatment; and determine if pharmacologic interventions are neuroprotective. Moreover, because positron emission tomography has the potential to identify Alzheimer's disease during early disease, it can be used to establish whether early interventions can prevent or delay further development.

Turner, R. S. (2001). "Alzheimer's disease in man and transgenic mice: females at higher risk." Am J Pathol 158(3): 797-801.

Tomidokoro, Y., K. Ishiguro, et al. (2001). "Abeta amyloidosis induces the initial stage of tau accumulation in APP(Sw) mice." Neurosci Lett 299(3): 169-72.
To clarify how Abeta deposits induce secondary tauopathy, the presence of phosphorylated tau, glycogen synthase kinase 3alpha (GSK3alpha), GSK3beta, cyclin-dependent kinase 5 (CDK5), mitogen-activated protein kinase (MAPK) and fyn were examined in the Tg2576 brain showing substantial brain Abeta amyloidosis and behavioral abnormalities. Phosphorylated tau at Ser199, Thr231/Ser235, Ser396 and Ser413 accumulated in the dystrophic neurites of senile plaques. The major kinase for tau phosphorylation was GSK3beta. Smaller contributions of GSK3alpha, CDK5 and MAPK were suggested. Thus, brain Abeta amyloidosis has a potential role in the induction of tauopathy leading to the mental disturbances of Alzheimer's disease.

Thorsen, G., J. Bergquist, et al. (2001). "Stereoselective determination of amino acids in beta-amyloid peptides and senile plaques." Anal Chem 73(11): 2625-31.
A novel method for the determination of the enantiomeric composition of peptides is presented. In this paper, the focus has been on beta-amyloid peptides from deceased Alzheimer's disease patients. The peptides are hydrolyzed using mineral acid. The free amino acids are derivatized with the chiral reagent (+)- or (-)-1-(9-anthryl)-2-propyl chloroformate and subsequently separated using micellar electrokinetic chromatography (MEKC) and detected using laser-induced fluorescence (LIF) detection. The high separation efficiency of the MEKC-LIF system, yielding approximately 1 million theoretical plates/m for most amino acids, facilitates the simultaneous chiral determination of nine amino acids. The samples that have been analyzed were standard 1-40 beta-amyloid peptides, in vitro precipitated beta-amyloid fibrils, and human senile plaque samples.

Terai, K., A. Iwai, et al. (2001). "Apolipoprotein E deposition and astrogliosis are associated with maturation of beta-amyloid plaques in betaAPPswe transgenic mouse: Implications for the pathogenesis of Alzheimer's disease." Brain Res 900(1): 48-56.
A transgenic mouse expressing the human beta-amyloid precursor protein with the 'Swedish' mutation, Tg2576, was used to investigate the mechanism of beta-amyloid (Abeta) deposition. Previously, we have reported that the major species of Abeta in the amyloid plaques of Tg2576 mice are Abeta1-40 and Abeta1-42. Moreover, Abeta1-42 deposition precedes Abeta1-40 deposition, while Abeta1-40 accumulates in the central part of the plaques later in the pathogenic process. Those data indicate that Abeta deposits in Tg2576 mice have similar characteristics to those in Alzheimer's disease. In the present study, to understand more fully the amyloid deposition mechanism implicating Alzheimer's disease pathogenesis, we examined immunohistochemically the distributions of apolipoprotein E (apoE) and Abeta in amyloid plaques of aged Tg2576 mouse brains. Our findings suggest that Abeta1-42 deposition precedes apoE deposition, and that Abeta1-40 deposition follows apoE deposition during plaque maturation. We next examined the relationship between apoE and astrogliosis associated with amyloid plaques using a double-immunofluorescence method. Extracellular apoE deposits were always associated with reactive astrocytes whose processes showed enhancement of apoE-immunoreactivity. Taken together, the characteristics of amyloid plaques in Tg2576 mice are similar to those in Alzheimer's disease with respect to apoE and astrogliosis. Furthermore, apoE deposition and astrogliosis may be necessary for amyloid plaque maturation.

Szczepanik, A. M., S. Funes, et al. (2001). "IL-4, IL-10 and IL-13 modulate A beta(1--42)-induced cytokine and chemokine production in primary murine microglia and a human monocyte cell line." J Neuroimmunol 113(1): 49-62.
A hallmark of the immunopathology associated with Alzheimer's disease (AD) is the presence of activated microglia surrounding senile plaque deposits of beta-amyloid (A beta) peptides. A beta peptides have been shown to be potent activators of microglia and macrophages, but little is known about endogenous factors that may modulate their responses to amyloid. We investigated whether the 'anti-inflammatory' cytokines IL-4, IL-10 and IL-13 could regulate A beta-induced production of the inflammatory cytokines IL-1 alpha, IL-1 beta, TNF-alpha, IL-6 and the chemokine MCP-1. A beta(1-42) time- and dose-dependently induced the production and secretion of these inflammatory proteins in the human THP-1 monocyte cell line and in primary murine microglia, similar to what was observed for lipopolysaccharide (LPS) stimulated cells. IL-10 was found to suppress all A beta and LPS-induced inflammatory proteins measured (IL-1 alpha, IL-1 beta, IL-6, TNF-alpha and MCP-1) in both cell types with the exception of LPS-induced MCP-1 in THP-1 cells where no change was observed. In contrast to the inhibition observed for IL-10, both IL-4 and IL-13 enhanced MCP-1 secretion. IL-4 and IL-13 reduced IL-6 secretion, but effects on IL-1 alpha, IL-1 beta or TNF-alpha were dependent on cell type and stimulus conditions. Additional experiments using RT-PCR showed that IL-4, IL-10 and IL-13 mRNA is found to be present in human brain tissue. These results show that IL-4, IL-10, and IL-13 differentially regulate microglial responses to A beta and may play a role in the inflammation pathology observed surrounding senile plaques.

Su, J. H., M. Zhao, et al. (2001). "Activated caspase-3 expression in Alzheimer's and aged control brain: correlation with Alzheimer pathology." Brain Res 898(2): 350-7.
Several studies have suggested that activated caspase-3 has properties of a cell death executioner protease. In this study, we examined the expression of activated caspase-3 in AD and aged control brains. Activated caspase-3 immunoreactivity was seen in neurons, astrocytes, and blood vessels, was elevated in AD, and exhibited a high degree of colocalization with neurofibrillary tangles and senile plaques. These data suggest that activated caspase-3 may be a factor in functional decline and may have an important role in neuronal cell death and plaque formation in AD brain.

Steinhoff, T., E. Moritz, et al. (2001). "Increased cystatin c in astrocytes of transgenic mice expressing the k670n-m671l mutation of the amyloid precursor protein and deposition in brain amyloid plaques." Neurobiol Dis 8(4): 647-54.
Cystatin C is an essential secretory cofactor for neurogenesis with potent protease inhibitor activities. Polymorphisms of cystatin C are genetically associated with Alzheimer's disease (AD), and the L68Q mutation causes hereditary cerebral hemorrhage with amyloidosis of the Icelandic type, in which cystatin C and beta-amyloid are colocalized in cortical blood vessels. To determine whether cystatin C and beta-amyloid also colocalize in brain amyloid plaques, we analyzed transgenic mice expressing the Swedish APP (SweAPP) mutation. We found high levels of cystatin C in astrocytes surrounding beta-amyloid plaques, and discrete layers of cystatin C attached to amyloid plaque cores covered by a layer of beta-amyloid. In addition, cystatin C accumulated in reactive astrocytes throughout the brain, independently of, and before the onset of, amyloid plaque formation. These results show that expression of SweAPP is associated with increased cystatin C in reactive astrocytes, and they suggest an early role of cystatin C in appositional amyloid plaque growth. Copyright 2001 Academic Press.

Steiner, H., T. Revesz, et al. (2001). "A pathogenic presenilin-1 deletion causes abberrant Abeta 42 production in the absence of congophilic amyloid plaques." J Biol Chem 276(10): 7233-9.
Familial Alzheimer's disease (FAD) is frequently associated with mutations in the presenilin-1 (PS1) gene. Almost all PS1-associated FAD mutations reported so far are exchanges of single conserved amino acids and cause the increased production of the highly amyloidogenic 42-residue amyloid beta-peptide Abeta42. Here we report the identification and pathological function of an unusual FAD-associated PS1 deletion (PS1 DeltaI83/DeltaM84). This FAD mutation is associated with spastic paraparesis clinically and causes accumulation of noncongophilic Abeta-positive "cotton wool" plaques in brain parenchyma. Cerebral amyloid angiopathy due to Abeta deposition was widespread as were neurofibrillary tangles and neuropil threads, although tau-positive neurites were sparse. Although significant deposition of Abeta42 was observed, no neuritic pathology was associated with these unusual lesions. Overexpressing PS1 DeltaI83/DeltaM84 in cultured cells results in a significantly elevated level of the highly amyloidogenic 42-amino acid amyloid beta-peptide Abeta42. Moreover, functional analysis in Caenorhabditis elegans reveals reduced activity of PS1 DeltaI83/DeltaM84 in Notch signaling. Our data therefore demonstrate that a small deletion of PS proteins can pathologically affect PS function in endoproteolysis of beta-amyloid precursor protein and in Notch signaling. Therefore, the PS1 DeltaI83/DeltaM84 deletion shows a very similar biochemical/functional phenotype like all other FAD-associated PS1 or PS2 point mutations. Since increased Abeta42 production is not associated with classical senile plaque formation, these data demonstrate that amyloid plaque formation is not a prerequisite for dementia and neurodegeneration.

Stalder, M., T. Deller, et al. (2001). "3D-Reconstruction of microglia and amyloid in APP23 transgenic mice: no evidence of intracellular amyloid." Neurobiol Aging 22(3): 427-34.
Microglia cells are closely associated with compact amyloid plaques in Alzheimer's disease (AD) brains. Although activated microglia seem to play a central role in the pathogenesis of AD, mechanisms of microglial activation by beta-amyloid as well as the nature of interaction between amyloid and microglia remain poorly understood. We previously reported a close morphological association between activated microglia and congophilic amyloid plaques in the brains of APP23 transgenic mice at both the light and electron microscopic levels [25]. In the present study, we have further examined the structural relationship between microglia and amyloid deposits by using postembedding immunogold labeling, serial ultrathin sectioning, and 3-dimensional reconstruction. Although bundles of immunogold-labeled amyloid fibrils were completely engulfed by microglial cytoplasm on single sections, serial ultrathin sectioning and three-dimensional reconstruction revealed that these amyloid fibrils are connected to extracellular amyloid deposits. These data demonstrate that extracellular amyloid fibrils form a myriad of finger-like channels with the widely branched microglial cytoplasm. We conclude that in APP23 mice a role of microglia in amyloid phagocytosis and intracellular production of amyloid is unlikely.

Schub, T. (2001). "Alzheimer's cure?" Lab Anim (NY) 30(4): 12.

Sandberg, G., W. Stewart, et al. (2001). "The prevalence of the neuropathological lesions of Alzheimer's disease is independent of race and gender." Neurobiol Aging 22(2): 169-75.
Senile plaques (SP) and neurofibrillary tangles (NFT) are the lesions characteristic of Alzheimer's disease (AD). In this study, we examined variation in the proportion of individuals who had these lesions by race, age, and gender in a series of 138 autopsies conducted at the Office of the Chief Medical Examiner of the State of Maryland between 1990 and 1998. Cases were selected on the bases of age between 40 to 79 years and non-natural manner of death, and included 73% males, 61% subjects < 65 years of age, and 42% African Americans. Observations were conducted on histologic sections of the hippocampus, entorhinal cortex, and inferior temporal cortex stained with silver (Hirano method) and immunostained for Abeta-amyloid. We found that SP and NFT are strongly associated with age. These lesions begin to appear in the early to late 40s, depending on the anatomic location, and become common in the 6th decade, preceding by one to two decades the age at which AD becomes clinically prevalent. No difference in the prevalence of SP or NFT was found by gender or between whites and African Americans. The latter is in contrast to epidemiologic studies that suggest AD is more prevalent in African Americans than in whites.

Rossner, S., J. Apelt, et al. (2001). "Neuronal and glial beta-secretase (BACE) protein expression in transgenic Tg2576 mice with amyloid plaque pathology." J Neurosci Res 64(5): 437-46.
We measured tissue distribution and expression pattern of the beta-site amyloid precursor protein (APP)-cleaving enzyme (BACE) in the brains of transgenic Tg2576 mice that show amyloid pathology. BACE protein was expressed at high levels in brain; at lower levels in heart and liver; and at very low levels in pancreas, kidney, and thymus and was almost absent in spleen and lung when assayed by Western blot analysis. We observed strictly neuronal expression of BACE protein in the brains of nontransgenic control mice, with the most robust immunocytochemical labeling present in the cerebral cortex, hippocampal formation, thalamus, and cholinergic basal forebrain nuclei. BACE protein levels did not differ significantly between control and transgenic mice or as a result of aging. However, in the aged, 17-month-old Tg2576 mice there was robust amyloid plaque formation, and BACE protein was also present in reactive astrocytes present near amyloid plaques, as shown by double immunofluorescent labeling and confocal laser scanning microscopy. The lack of astrocytic BACE immunoreactivity in young transgenic Tg2576 mice suggests that it is not the APP overexpression but rather the amyloid plaque formation that stimulates astrocytic BACE expression in Tg2576 mice. Our data also suggest that the neuronal overexpression of APP does not induce the overexpression of its metabolizing enzyme in neurons. Alternatively, the age-dependent accumulation of amyloid plaques in the Tg2576 mice does not require increased neuronal expression of BACE. Our data support the hypothesis that neurons are the primary source of beta-amyloid peptides in brain and that astrocytic beta-amyloid generation may contribute to amyloid plaque formation at later stages or under conditions when astrocytes are activated. Copyright 2001 Wiley-Liss, Inc.

Rossner, S., G. Mehlhorn, et al. (2001). "Increased neuronal and glial expression of protein kinase C isoforms in neocortex of transgenic Tg2576 mice with amyloid pathology." Eur J Neurosci 13(2): 269-78.
We investigated the influence of five- to sevenfold neuronal overexpression of the Swedish mutation of human APP695 (APPsw) in the transgenic mouse strain Tg2576 on neocortical protein kinase C (PKC) expression and subcellular distribution. Using specific antibodies to PKC alpha, PKC beta, PKC gamma, PKC epsilon and PKC zeta isoforms for Western blot analysis, we observed increased immunoreactivity for PKC alpha and PKC gamma isoforms in crude tissue homogenates from the neocortex of 16-month-old APPsw mice as compared with nontransgenic littermates, which was not present in 6 month-old Tg2576 mice. We also observed elevated levels of PKC alpha, PKC beta, PKC gamma and PKC zeta in membrane fractions and reduced concentrations of PKC alpha and PKC gamma in cytosolic fractions of aged Tg2576 mice, indicating that these PKC isoforms are in their activated state. In young, 6-month-old Tg2576 mice, however, the increase in membrane-bound PKC isoforms and concomitant decrease in cytosolic PKC isoforms was much less pronounced, demonstrating the age-dependent nature of alterations in PKC isoforms. Immunocytochemistry of brain sections supported these findings and revealed increased neuronal labelling for PKC alpha, PKC gamma and PKC lambda isoforms in neocortex of 16-month-old APPsw mice compared with nontransgenic littermates, with the increase being strongest for PKC gamma and PKC lambda isoforms. Additionally, PKC gamma and to a lesser extent PKC lambda isoforms were induced in reactive astrocytes in proximity to amyloid plaques. Our data indicate that neuronal overexpression of APPsw causes a dynamic change in neuronal expression and activation of multiple PKC isoforms known to be regulators of proteolytic amyloid precursor protein (APP) processing (PKC alpha) and of neuronal survival (PKC lambda and PKC zeta). The induction of the PKC gamma and PKC lambda isoforms in reactive astrocytes surrounding amyloid plaques might be required for astrocyte activation and astrocytic cytokine expression in response to amyloid plaque formation.

Roberds, S. L., J. Anderson, et al. (2001). "BACE knockout mice are healthy despite lacking the primary beta-secretase activity in brain: implications for Alzheimer's disease therapeutics." Hum Mol Genet 10(12): 1317-24.
Alzheimer's disease (AD) is a neurodegenerative disorder characterized by accumulation of amyloid plaques and neurofibrillary tangles in the brain. The major components of plaque, beta-amyloid peptides (Abetas), are produced from amyloid precursor protein (APP) by the activity of beta- and gamma-secretases. beta-secretase activity cleaves APP to define the N-terminus of the Abeta1-x peptides and, therefore, has been a long- sought therapeutic target for treatment of AD. The gene encoding a beta-secretase for beta-site APP cleaving enzyme (BACE) was identified recently. However, it was not known whether BACE was the primary beta-secretase in mammalian brain nor whether inhibition of beta-secretase might have effects in mammals that would preclude its utility as a therapeutic target. In the work described herein, we generated two lines of BACE knockout mice and characterized them for pathology, beta-secretase activity and Abeta production. These mice appeared to develop normally and showed no consistent phenotypic differences from their wild-type littermates, including overall normal tissue morphology and brain histochemistry, normal blood and urine chemistries, normal blood-cell composition, and no overt behavioral and neuromuscular effects. Brain and primary cortical cultures from BACE knockout mice showed no detectable beta-secretase activity, and primary cortical cultures from BACE knockout mice produced much less Abeta from APP. The findings that BACE is the primary beta-secretase activity in brain and that loss of beta-secretase activity produces no profound phenotypic defects with a concomitant reduction in beta-amyloid peptide clearly indicate that BACE is an excellent therapeutic target for treatment of AD.

Remarque, E. J., E. L. Bollen, et al. (2001). "Patients with Alzheimer's disease display a pro-inflammatory phenotype." Exp Gerontol 36(1): 171-6.
BACKGROUND: Inflammation plays a pivotal role in amyloid plaque progression thereby contributing to Alzheimer's disease-related neurodegeneration. We hypothesized that patients with Alzheimer's disease have an innate pro-inflammatory phenotype, as compared to control subjects without dementia. METHODS: Patients with a diagnosis of probable Alzheimer's disease (n=12) and control subjects without signs of dementia (n=18) were enrolled. Whole blood samples were stimulated ex vivo with endotoxin under standard conditions. Cytokine levels were assessed by ELISA and compared by Mann-Whitneyll-test after log transformation. RESULTS: Patients with Alzheimer's disease had seven- to ten-fold higher IL-1beta production relative to the amount of IL-10 both at the low (p=0.006) and high concentration of endotoxin (p=0.007). Subjects who display a pro-inflammatory phenotype as defined by a high IL-1beta/IL-10 ratio had 13.0-fold higher odds (95% CI: 2.1-82) to have dementia. CONCLUSION: The data support the hypothesis that a pro-inflammatory phenotype contributes to the development of Alzheimer's disease.

Quinn, J., F. Davis, et al. (2001). "Beta-amyloid plaques induce neuritic dystrophy of nitric oxide-producing neurons in a transgenic mouse model of Alzheimer's disease." Exp Neurol 168(2): 203-12.
A causative role for nitric oxide has been postulated in a number of neurodegenerative diseases. Using histochemical and immunohistochemical methods, we examined the effect of beta-amyloid plaques on nitric oxide-producing cells in transgenic mice which overexpress a mutant human amyloid precursor protein (APP). In 14-month-old animals, nitric oxide synthase (NOS)-positive dystrophic neurites were observed frequently in the cerebral cortex and hippocampus of all of 16 plaque-bearing transgenic animals and in none of 16 wild-type animals. Double labeling of NOS and beta-amyloid revealed that 90% of beta-amyloid plaques were associated with NOS-containing dystrophic neurites. In 7-month-old animals, beta-amyloid plaques were very rare, but those present were frequently associated with NOS-positive neuritic dystrophy. We conclude that beta-amyloid plaques induce neuritic dystrophy in cortical neurons containing NOS in this model of AD, and hypothesize that this finding may be relevant to the mechanism of beta-amyloid neurotoxicity in human AD.

Pratico, D., K. Uryu, et al. (2001). "Increased lipid peroxidation precedes amyloid plaque formation in an animal model of Alzheimer amyloidosis." J Neurosci 21(12): 4183-7.
Oxidative stress is a key feature in the Alzheimer's disease (AD) brain and manifests as lipid peroxidation (LPO). Isoprostanes (iPs) are specific and sensitive markers of in vivo LPO. To determine whether amyloid beta (Abeta) deposition in vivo is associated with increased LPO, we examined iP levels in a transgenic mouse model (Tg2576) of AD amyloidosis. Urine, plasma, and brain tissues were collected from Tg2576 and littermate wild-type (WT) animals at different time points starting at 4 months of age and continuing until 18 months of age. Levels of urinary 8,12-iso-iPF(2alpha)-VI were higher in Tg2576 than in WT animals as early as 8 months of age and remained this high for the rest of the study. A similar pattern was observed for plasma levels of 8,12-iso-iPF(2alpha)-VI. Homogenates from the cerebral cortex and hippocampus of Tg2576 mice had higher levels of 8,12-iso-iPF(2alpha)-VI than those from WT mice starting at 8 months of age. In contrast, a surge of Abeta 1-40 and 1-42 levels as well as Abeta deposits in Tg2576 mouse brains occurred later, at 12 months of age. A direct correlation was observed between brain 8,12-iso-iPF(2alpha)-VI and Abeta 1-40 and 1-42. Because LPO precedes amyloid plaque formation in Tg2576 mice, this suggests that brain oxidative damage contributes to AD pathogenesis before Abeta accumulation in the AD brain.

Papaioannou, N., P. C. Tooten, et al. (2001). "Immunohistochemical investigation of the brain of aged dogs. I. Detection of neurofibrillary tangles and of 4-hydroxynonenal protein, an oxidative damage product, in senile plaques." Amyloid 8(1): 11-21.
In the aging dog brain lesions develop spontaneously. They share some morphological characteristics with those of Alzheimer 's disease in man. Diffuse and primitive plaques are well known, whereas neuritic plaques rarely develop. Neurofibrillary tangles have not been seen in the canine. The aim of the present investigation was to study major age-related changes of the dog's brain using paraffin sections with respect to cross-immunoreactivity of tau, A beta protein and other immunoreactive components including hydroxynonenal protein, which is a marker for oxidative damage. The occurrence of neurofibrillary tangles and of the protein tau therein was studied in serial brain sections of two dogs with the Gallyas stain and by immunohistochemistry with three different antibodies against tau. Senile plaques were stained with a monoclonal anti-A beta (residues 8-17), polyclonal anti-apolipoprotein E and a monoclonal antibody against 4-hydroxynonenal (HNE). Amyloid deposits and controls were screened by Congo red staining viewed in fluorescent light, followed by polarized light for green birefringence. With the Gallyas stain and one of the antisera against tau, neurofibrillary tangles were revealed in a similar dispersed pattern, whereas the other antitau antisera gave negative results. With the anti-HNE a positive reaction was found in cerebral amyloid deposits and in vascular wall areas where amyloid deposition was confirmed by Congo-red staining, and in perivascular cells and in some neurons. These results indicate that the canine with his tangles and plaques which show oxidative changes, forms a spontaneous modelfor understanding the early changes and their interrelationships in Alzheimer's disease.

Nilsson, L. N., K. R. Bales, et al. (2001). "Alpha-1-antichymotrypsin promotes beta-sheet amyloid plaque deposition in a transgenic mouse model of Alzheimer's disease." J Neurosci 21(5): 1444-51.
Alpha(1)-antichymotrypsin (ACT), an acute-phase inflammatory protein, is an integral component of the amyloid deposits in Alzheimer's disease (AD) and has been shown to catalyze amyloid beta-peptide polymerization in vitro. We have investigated the impact of ACT on amyloid deposition in vivo by generating transgenic GFAP-ACT-expressing mice and crossing them with the PDGF-hAPP/V717F mice, which deposit amyloid in an age-dependent manner. The number of amyloid deposits measured by Congo Red birefringence was increased in the double ACT/amyloid precursor protein (APP) transgenic mice compared with transgenic mice that only expressed APP, particularly in the hippocampus where ACT expression was highest, and the increase was preceded by elevated total amyloid beta-peptide levels at an early age. Our data demonstrate that ACT promotes amyloid deposition and provide a specific mechanism by which inflammation and the subsequent upregulation of astrocytic ACT expression in AD brain contributes to AD pathogenesis.

Nihashi, T., S. Inao, et al. (2001). "Expression and distribution of beta amyloid precursor protein and beta amyloid peptide in reactive astrocytes after transient middle cerebral artery occlusion." Acta Neurochir (Wien) 143(3): 287-95.
BACKGROUND: In the brains of Alzheimer's disease patients, beta amyloid protein is the major component of senile plaque. In ischemic stress, beta amyloid precursor protein (APP) and beta amyloid peptide are reported to be upregulated. METHOD: Using Male Wistar-ST rats, expression and distribution of APP and beta amyloid peptide were examined immunohistochemically after transient ischemia induced by a 2-h middle cerebral artery occlusion (MCAO). After reperfusion for 3, 7, 14, 30 and 60 days, brains were removed and immunostaining was performed. FINDINGS: The reactive astrocytes with APP were observed in the periphery of infarct from 3 days to 60 days post-occlusion. The immunoreactivity of beta amyloid peptide was also localized in the reactive astrocytes in the peripheral zone of infarct at 7, 14, and 30 days post-occlusion. However, beta amyloid expression was not identified at 3 days or 60 days post MCAO. Transient ischemia temporarily induced beta amyloid peptide expression in reactive astrocytes, but this expression peaked at 30 days and disappeared at 60 days. INTERPRETATION: These findings suggested that beta amyloid peptide was derived from the processing of APP produced in the same reactive astrocytes and the production of the peptide stopped within 60 days after the ischemic stress.

Mori, T., D. Paris, et al. (2001). "Cholesterol accumulates in senile plaques of Alzheimer disease patients and in transgenic APP(SW) mice." J Neuropathol Exp Neurol 60(8): 778-85.
Mounting evidence suggests that cholesterol may contribute to the pathogenesis of Alzheimer disease (AD). We examined whether cholesterol might be present in senile plaques, a hallmark neuropathological feature of AD. We employed 2 different fluorometric-staining techniques (filipin staining and an enzymatic technique) for the determination of cholesterol in brains of postmortem confirmed AD patients and in nondemented, age-matched histopathologically normal controls. AD patient brains showed abnormal accumulation of cholesterol in congophilic/birefringent dense cores of senile plaques that was essentially absent in histopathologically normal controls. To determine whether increased senile plaque-associated cholesterol occurred generally in all plaques or was restricted to a specific subset, quantitative analysis was performed. Data indicate abnormal accumulation of cholesterol in cores of mature plaques but not in diffuse or immature plaques. Additionally, transgenic mice that overexpress the "Swedish" amyloid precursor protein (Tg APP(SW), line 2576) exhibited a similar pattern of abnormal cholesterol accumulation in mature, congophilic amyloid plaques at 24 months of age that was absent in their control littermates or in 8-month-old Tg APP(SW) mice (an age prior to amyloid deposition). Taken together, our results imply a link between cholesterol and AD pathogenesis and suggest that cholesterol plays an important role in the formation and/or progression of senile plaques.

Matsuoka, Y., M. Picciano, et al. (2001). "Inflammatory responses to amyloidosis in a transgenic mouse model of Alzheimer's disease." Am J Pathol 158(4): 1345-54.
Mutations in the amyloid precursor protein (APP) and presenilin-1 and -2 genes (PS-1, -2) cause Alzheimer's disease (AD). Mice carrying both mutant genes (PS/APP) develop AD-like deposits composed of beta-amyloid (Abeta) at an early age. In this study, we have examined how Abeta deposition is associated with immune responses. Both fibrillar and nonfibrillar Abeta (diffuse) deposits were visible in the frontal cortex by 3 months, and the amyloid load increased dramatically with age. The number of fibrillar Abeta deposits increased up to the oldest age studied (2.5 years old), whereas there were less marked changes in the number of diffuse deposits in mice over 1 year old. Activated microglia and astrocytes increased synchronously with amyloid burden and were, in general, closely associated with deposits. Cyclooxygenase-2, an inflammatory response molecule involved in the prostaglandin pathway, was up-regulated in astrocytes associated with some fibrillar deposits. Complement component 1q, an immune response component, strongly colocalized with fibrillar Abeta, but was also up-regulated in some plaque-associated microglia. These results show: i) an increasing proportion of amyloid is composed of fibrillar Abeta in the aging PS/APP mouse brain; ii) microglia and astrocytes are activated by both fibrillar and diffuse Abeta; and iii) cyclooxygenase-2 and complement component 1q levels increase in response to the formation of fibrillar Abeta in PS/APP mice.

Masliah, E., A. Sisk, et al. (2001). "Neurofibrillary pathology in transgenic mice overexpressing V717F beta-amyloid precursor protein." J Neuropathol Exp Neurol 60(4): 357-68.
Overexpression of mutated human amyloid precursor protein (hAPP717V-->F) under control of the platelet-derived growth factor promoter (PDAPP minigene) in transgenic (tg) mice results in plaque formation and astroglial activation similar to Alzheimer disease (AD). However, the extent of the neurofibrillary pathology in this model is less understood. In order to determine if these mice develop AD-like neurofibrillary pathology, vibratome sections from PDAPP tg mice (4- to 20-months-old) were immunolabeled with antibodies against phosphorylated tau (AT8) and phosphorylated neurofilaments (SMI 312, TA51), and analyzed by laser scanning confocal and electron microscopy. Phosphorylated neurofilament-immunoreactive dystrophic neurites in plaques were first seen in mice at 10 to 12 months of age, while phosphorylated tau-immunoreactive dystrophic neurites were observed after 14 months of age. Immunoelectron microscopic analysis revealed that phosphorylated neurofilament immunoreactivity was diffusely distributed along filamentous aggregates (12-15 nm in diameter) in the plaque dystrophic neurites, and occasionally in neuronal cell bodies. In contrast, phosphorylated tau immunoreactivity was observed as clusters distributed along filamentous structures accumulating in the dystrophic neurites and around neurotubules in the axons. However, no paired helical filaments were observed. Taken together, these studies indicate that the PDAPP tg model recapitulates early cytoskeletal pathology similar to that observed in AD.

Luo, Y., B. Bolon, et al. (2001). "Mice deficient in BACE1, the Alzheimer's beta-secretase, have normal phenotype and abolished beta-amyloid generation." Nat Neurosci 4(3): 231-2.

Litchfield, S. and Z. Nagy (2001). "New temperature modification makes the Bielschowsky silver stain reproducible." Acta Neuropathol (Berl) 101(1): 17-21.
The Bielschowsky silver impregnation can be used as a single stain for the diagnosis of Alzheimer's disease. It impregnates both the amyloid and neuritic components of the senile plaques and it reliably stains neurofibrillary tangles. However, we find that the stain is highly sensitive to changes of the ambient temperature. Since the diagnostic criteria for Alzheimer's disease rely on a semi-quantitative assessment of neuritic plaques and neurofibrillary tangles the reproducibility of the Bielschowsky stain is important. In this study we compare three different modifications of the Bielschowsky stain with the methenamine silver stain and with immunohistochemistry for the beta-amyloid and the hyperphosphorylated tau proteins. We found that the most reliable and easily reproducible modification of the Bielschowsky silver impregnation is the one that uses incubations at 5 degrees C.

Lee, C. W., Z. P. Zhuang, et al. (2001). "Isomerization of (Z,Z) to (E,E)1-bromo-2,5-bis-(3-hydroxycarbonyl-4-hydroxy)styrylbenzene in strong base: probes for amyloid plaques in the brain." J Med Chem 44(14): 2270-5.
In developing probes for detecting beta-amyloid (Abeta) plaques in the brain of Alzheimer's disease (AD), we have synthesized 1-bromo-2,5-bis-(3-hydroxycarbonyl-4-hydroxy)styrylbenzene (5, BSB). Due to the presence of two double bonds, formation of four different isomers is possible. Four isomers, E,E-5, E,Z-5, Z,E-5, and Z,Z-5, were prepared. Surprisingly, all showed strong fluorescent labeling of Abeta plaques in the brain of postmortem brain sections of patients with confirmed AD. In vitro binding assay also showed that all four isomers of BSB (E,E-5, E,Z-5, Z,E-5, and Z,Z-5) displayed a similar high binding affinity inhibiting the binding of [(125)I]E,E-6, 1-iodo-2,5-bis-(3-hydroxycarbonyl-4-methoxy)styrylbenzene (IMSB) to Abeta(1-40) aggregates. The inhibition constants (K(i)) of E,E-5, E,Z-5, Z,E-5, and Z,Z-5 were 0.11 +/- 0.01, 0.19 +/- 0.03, 0.27 +/- 0.06, and 0.13 +/- 0.02 nM, respectively. Due to the fact that geometric stability of these styrylbenzenes is unknown, and the conversion of Z,Z-5 to E,E-5 may occur automatically in the binding or labeling assaying conditions, we have investigated the kinetics of conversion of Z,Z-5 to E,E-5 by NMR in D(2)O/NaOD at elevated temperatures (70, 95, and 115 degrees C). The activation energy was determined to be 14.15 kcal/mol. The results strongly suggest that the isomeric conversion at room temperature in aqueous buffer solution is unlikely. All of the styrylbenzene isomers clearly showed potential as useful tools for studying Abeta aggregates in the brain. The data suggest that, despite the rigidity of this series of styrylbenzenes, the binding sites on Abeta aggregates may have certain flexibility and the binding pockets could be adaptable for binding to other smaller ligands. Such information could be exploited to develop new ligands for detecting amyloid plaques in AD.

Le, R., L. Cruz, et al. (2001). "Plaque-induced abnormalities in neurite geometry in transgenic models of Alzheimer disease: implications for neural system disruption." J Neuropathol Exp Neurol 60(8): 753-8.
Neurites that pass through amyloid-beta deposits in Alzheimer disease (AD) undergo 3 changes: they develop phosphorylated tau immunoreactivity; the density of SMI-32-positive dendrites diminishes; and they also develop a marked alteration in their geometric features, changing from being nearly straight to being quite curvy. The extent to which the latter 2 phenomena are related to phosphorylated tau is unknown. We have now examined whether amyloid-beta deposits in APP695Sw transgenic mice, which have only rare phosphorylated tau containing neurites. develop these changes. We found that dendritic density is diminished within the boundaries of amyloid-beta plaques, with the greatest loss (about 80%, p < 0.001) within the boundaries of thioflavine S cores. Remaining dendrites within plaques develop substantial morphological alterations quantitatively similar to those seen in AD. A statistically significant but smaller degree of change in geometry was seen in the immediate vicinity around plaques, suggesting a propagation of cytoskeletal disruption from the center of the plaque outward. We examined the possible physiological consequences of this change in dendritic geometry using a standard cable-theory model. We found a predicted delay of several milliseconds in about one quarter of the dendrites passing through a thioflavine S plaque. These results are consistent with previous observations in AD, and suggest that thioflavine S-positive amyloid-beta deposits have a marked effect on dendritic microarchitecture in the cortex, even in the relative absence of phosphorylated tau alterations.

Kuo, Y. M., T. A. Kokjohn, et al. (2001). "Comparative analysis of amyloid-beta chemical structure and amyloid plaque morphology of transgenic mouse and Alzheimer's disease brains." J Biol Chem 276(16): 12991-8.
We have undertaken an integrated chemical and morphological comparison of the amyloid-beta (Abeta) molecules and the amyloid plaques present in the brains of APP23 transgenic (tg) mice and human Alzheimer's disease (AD) patients. Despite an apparent overall structural resemblance to AD pathology, our detailed chemical analyses revealed that although the amyloid plaques characteristic of AD contain cores that are highly resistant to chemical and physical disruption, the tg mice produced amyloid cores that were completely soluble in buffers containing SDS. Abeta chemical alterations account for the extreme stability of AD plaque core amyloid. The corresponding lack of post-translational modifications such as N-terminal degradation, isomerization, racemization, pyroglutamyl formation, oxidation, and covalently linked dimers in tg mouse Abeta provides an explanation for the differences in solubility between human AD and the APP23 tg mouse plaques. We hypothesize either that insufficient time is available for Abeta structural modifications or that the complex species-specific environment of the human disease is not precisely replicated in the tg mice. The appraisal of therapeutic agents or protocols in these animal models must be judged in the context of the lack of complete equivalence between the transgenic mouse plaques and the human AD lesions.

Klein, W. L., G. A. Krafft, et al. (2001). "Targeting small Abeta oligomers: the solution to an Alzheimer's disease conundrum?" Trends Neurosci 24(4): 219-24.
Amyloid beta (Abeta) is a small self-aggregating peptide produced at low levels by normal brain metabolism. In Alzheimer's disease (AD), self-aggregation of Abeta becomes rampant, manifested most strikingly as the amyloid fibrils of senile plaques. Because fibrils can kill neurons in culture, it has been argued that fibrils initiate the neurodegenerative cascades of AD. An emerging and different view, however, is that fibrils are not the only toxic form of Abeta, and perhaps not the neurotoxin that is most relevant to AD: small oligomers and protofibrils also have potent neurological activity. Immuno-neutralization of soluble Abeta-derived toxins might be the key to optimizing AD vaccines that are now on the horizon.

Kiuchi, Y., Y. Isobe, et al. (2001). "Entactin-induced inhibition of human amyloid beta-protein fibril formation in vitro." Neurosci Lett 305(2): 119-22.
Amyloid beta-protein (Abeta) fibril in senile plaques may possibly be related to the pathogenesis of Alzheimer's disease (AD). Basement membrane (BM) components are localized to the plaques. Entactin binds the plaque associated BM components. We investigated the potential of entactin to prevent Abeta fibril formation. Thioflavin T fluorometric assay and electron microscopy revealed that entactin significantly inhibited Abeta1-40 (Abeta40) fibril formation at an Abeta40:entactin molar ratio of 50:1. The inhibitory effect of entactin was displayed in a dose-dependent manner. Circular dichroism spectroscopy data indicated that entactin induced a random coil structure in Abeta40. We propose that the ability of entactin to induce random structure is linked to the inhibition of Abeta fibril formation. Entactin may be related to the pathogenesis of AD by regulating Abeta40 fibril formation.

Kawarabayashi, T., L. H. Younkin, et al. (2001). "Age-dependent changes in brain, CSF, and plasma amyloid (beta) protein in the Tg2576 transgenic mouse model of Alzheimer's disease." J Neurosci 21(2): 372-81.
The accumulation of amyloid beta protein (Abeta) in the Tg2576 mouse model of Alzheimer's disease (AD) was evaluated by ELISA, immunoblotting, and immunocytochemistry. Changes in Abeta begin at 6-7 months as SDS-insoluble forms of Abeta42 and Abeta40 that require formic acid for solubilization appear. From 6 to 10 months, these insoluble forms increase exponentially. As insoluble Abeta appears, SDS-soluble Abeta decreases slightly, suggesting that it may be converting to an insoluble form. Our data indicate that it is full-length unmodified Abeta that accumulates initially in Tg2576 brain. SDS-resistant Abeta oligomers and most Abeta species that are N-terminally truncated or modified develop only in older Tg2576 mice, in which they are present at levels far lower than in human AD brain. Between 6 and 10 months, when SDS-insoluble Abeta42 and Abeta40 are easily detected in every animal, histopathology is minimal because only isolated Abeta cores can be identified. By 12 months, diffuse plaques are evident. From 12 to 23 months, diffuse plaques, neuritic plaques with amyloid cores, and biochemically extracted Abeta42 and Abeta40 increase to levels like those observed in AD brains. Coincident with the marked deposition of Abeta in brain, there is a decrease in CSF Abeta and a substantial, highly significant decrease in plasma Abeta. If a similar decline occurs in human plasma, it is possible that measurement of plasma Abeta may be useful as a premorbid biomarker for AD.

Jayasena, U. L., S. K. Gribble, et al. (2001). "Identification of structural variations in the carboxyl terminus of Alzheimer's disease-associated beta A4[1-42] amyloid using a monoclonal antibody." Clin Exp Immunol 124(2): 297-305.
The accumulation of amyloid plaques and amyloid congophilic angiopathy (ACA) in the brains of affected individuals is one of the main pathological features of Alzheimer's disease. Within these deposits, the beta A4 (Ass) polypeptide represents a major component with the C-terminal 39-43 amino acid variants being most abundant. Using a mouse IgG1 MoAb produced by hybridoma beta A4[35-43]-95.2 3B9, which reacts with the epitope is defined by the amino acid residues beta A438[GVV]40, this study has identified a unique conformation within the carboxyl terminus of human beta A4[1-42]. Although the beta A438[GVV]40 sequence is present within the C-termini of human beta A4[1-40] and beta A4[1-43] and the beta A4-containing region of human APP, the beta A4[35-43]-95.2 3B9 MoAb (designated MoAb 3B9) does not bind these polypeptides, demonstrating a high degree of specificity for the beta A438[GVV]40 epitope as presented within the beta A4[1-42] sequence. The beta A4[1-42] epitope bound by MoAb 3B9 is sensitive to heating (100 degrees C for 5 min) and is denatured by SDS but not by oxidative radio-iodination of beta A4 or by adsorption to plastic surfaces or nitrocellulose. The recognition of beta A4 plaque deposits and ACA by MoAb 3B9 within formalin-fixed sections of human AD brain demonstrates the potential of these antibodies for investigating the role of the unique beta A4[1-42] conformation in the development of Alzheimer's disease.

Janssen, J. C., P. L. Lantos, et al. (2001). "Autopsy-confirmed familial early-onset Alzheimer disease caused by the l153V presenilin 1 mutation." Arch Neurol 58(6): 953-8.
BACKGROUND: Three affected individuals are described from a small English kindred with early-onset autosomal dominant familial Alzheimer disease (FAD) caused by a leucine-to-valine change at codon 153 (L153V) of the presenilin 1 (PSEN1) gene. METHODS: Clinical information on the pedigree was collected directly from family members and from hospital records. Samples of DNA were screened by means of direct sequencing of all coding exons of PSEN1. One patient underwent neuropathological examination. RESULTS: Mean age at onset of symptoms was 35.3 years (95% confidence interval [CI], 34.6-36.0 years); at death, 44.0 years (95% CI, 39.1-48.9 years). Mean duration of illness was 8.3 years (95% CI, 4.7-11.9 years). Myoclonus was a late feature in 1 patient; seizures were not reported in any subjects. Spastic paraparesis and extrapyramidal signs were absent. The neuropsychometric profile of 1 patient showed relatively preserved naming skills in the setting of global cognitive deficits. Results of neuropathological examination demonstrated the signature lesions of Alzheimer disease and the presence of occasional cortical Lewy bodies. CONCLUSIONS: The PSEN1 L153V mutation lies in the main mutation cluster of PSEN1 in the second transmembrane domain. It causes early-onset FAD with clinical features similar to those of other reported FAD pedigrees.

Jaffar, S., S. E. Counts, et al. (2001). "Neuropathology of Mice Carrying Mutant APP(swe) and/or PS1(M146L) Transgenes: Alterations in the p75(NTR) Cholinergic Basal Forebrain Septohippocampal Pathway." Exp Neurol 170(2): 227-43.
Cholinergic basal forebrain (CBF) projection systems are defective in late Alzheimer's disease (AD). We examined the brains of 12-month-old singly and doubly transgenic mice overexpressing mutant amyloid precursor protein (APP(swe)) and/or presenilin-1 (PS1(M146L)) to investigate the effects of these AD-related genes on plaque and tangle pathology, astrocytic expression, and the CBF projection system. Two types of beta-amyloid (Abeta)-immunoreactive (ir) plaques were observed: type 1 were darkly stained oval and elongated deposits of Abeta, and type 2 were diffuse plaques containing amyloid fibrils. APP(swe) and PS1(M146L) mouse brains contained some type 1 plaques, while the doubly transgenic (APP(swe)/PS1(M146L)) mice displayed a greater abundance of types 1 and 2 plaques. Sections immunostained for the p75 NGF receptor (p75(NTR)) revealed circular patches scattered throughout the cortex and hippocampus of the APP(swe)/PS1(M146L) mice that contained Abeta, were innervated by p75(NTR)-ir neurites, but displayed virtually no immunopositive neurons. Tau pathology was not seen in any transgenic genotype, although a massive glial response occurred in the APP(swe)/PS1(M146L) mice associated with amyloid plaques. Stereology revealed a significant increase in p75(NTR)-ir medial septal neurons in the APP(swe) and PS1(M146L) singly transgenic mice compared to the APP(swe)/PS1(M146L) mice. No differences in size or optical density of p75(NTR)-ir neurons were observed in these three mutants. p75(NTR)-ir fibers in hippocampus and cortex were more pronounced in the APP(swe) and PS1(M146L) mice, while the APP(swe)/PS1(M146L) mice showed the least p75(NTR)-ir fiber staining. These findings suggest a neurotrophic role for mutant APP and PS1 upon cholinergic hippocampal projection neurons at 12 months of age. Copyright 2001 Academic Press.

Ishii, K., C. Lippa, et al. (2001). "Distinguishable effects of presenilin-1 and APP717 mutations on amyloid plaque deposition." Neurobiol Aging 22(3): 367-76.
Both APP and PS-1 are causal genes for early-onset familial Alzheimer's disease (AD) and their mutation effects on cerebral Abeta deposition in the senile plaques were examined in human brains of 29 familial AD (23 PS-1, 6 APP) cases and 14 sporadic AD cases in terms of Abeta40 and Abeta42. Abeta isoform data were evaluated using repeated measures analysis of variance which adjusted for within-subject measurement variation and confounding effects of individual APP and PS-1 mutations, age at onset, duration of illness and APOE genotype. We observed that mutations in both APP and PS-1 were associated with a significant increase of Abeta42 in plaques as been documented previously. In comparison to sporadic AD cases, both APP717 and PS-1 mutation cases had an increased density (measured as the number of plaques/mm(2)) and area (%) of Abeta42 plaques. However, we found an unexpected differential effect of PS-1 but not APP717 mutation cases. At least some of PS-1 but not APP717 mutation cases had the significant increase of density and area of Abeta40-plaques as compared to sporadic AD independently of APOE genotype. Our results suggest that PS-1 mutations affect cerebral accumulation of Abeta burden in a different fashion from APP717 mutations in their familial AD brains.

Ingram, D. K. (2001). "Vaccine development for Alzheimer's disease: a shot of good news." Trends Neurosci 24(6): 305-7.
Studies in transgenic mouse models of Alzheimer's disease suggest the potential for vaccine development for this disease. Specifically, inoculation with Abeta peptide reduces Abeta plaque formation. However, this vaccination strategy has raised safety concerns. Recent studies have reduced these concerns by demonstrating that long-term Abeta vaccination in transgenic mice does not produce detrimental behavioral effects and in fact appears to protect against age-related functional decline in spatial memory tasks.

Imamura, K., M. Sawada, et al. (2001). "Activation mechanism of brain microglia in patients with diffuse neurofibrillary tangles with calcification: a comparison with Alzheimer disease." Alzheimer Dis Assoc Disord 15(1): 45-50.
Diffuse neurofibrillary tangles with calcification (DNTC) is an atypical dementia and is characterized pathologically by diffuse neurofibrillary tangles (NFTs) without senile plaques (SPs). In this study, we investigated the distribution of human leukocyte antigen (HLA)-DR-positive activated microglia in postmortem brain tissue of six patients with DNTC and six patients with Alzheimer disease (AD). HLA-DR-positive activated microglia were observed to associate with SPs in AD. In the DNTC brain, which lacks SPs, HLA-DR-positive microglia were mainly accumulated around weakly tau-positive NFTs, which were also positive for anti-amyloid-P and anti-C3d antibodies. The results of this study suggest that the complement pathway is also activated in the DNTC brain and that immune and inflammatory responses, including microglia activation, may occur around extracellular NFTs in DNTC patients.

Head, E., B. Y. Azizeh, et al. (2001). "Complement association with neurons and beta-amyloid deposition in the brains of aged individuals with Down Syndrome." Neurobiol Dis 8(2): 252-65.
To study the link between beta-amyloid (Abeta) and neuroinflammation, we examined the levels of complement as a function of age and extent of Abeta deposition in Down Syndrome (DS) brain. C1q, the first component of the complement cascade, was visualized using immunohistochemistry in the frontal, entorhinal cortex, and hippocampus of 12 DS ranging from 31 to 69 years of age. C1q was consistently associated with thioflavine-S positive Abeta plaques in DS brain and increased with more extensive age-dependent Abeta deposition. In contrast, little or no C1q labeling was associated with diffuse or thioflavine-S negative Abeta deposits. Neurons in the hippocampus and entorhinal cortex, but less frequently in frontal cortex, were C1q positive in DS cases with sufficient neuropathology to have a diagnosis of Alzheimer's disease. C1q-positive neurons were associated with activated microglia. These results provide evidence for Abeta-mediated inflammatory factors contributing to the rapid accumulation of neuropathology in DS brain. Copyright 2001 Academic Press.

Haugabook, S. J., T. Le, et al. (2001). "Reduction of Abeta accumulation in the Tg2576 animal model of Alzheimer's disease after oral administration of the phosphatidyl-inositol kinase inhibitor wortmannin." Faseb J 15(1): 16-18.
The abnormal accumulation of the amyloid beta protein (Abeta) has been implicated as an early and critical event in the etiology and pathogenesis of Alzheimer's disease (AD). Compounds that reduce Abeta accumulation may therefore be useful therapeutically. In cell-based screens we detected a significant reduction in Abeta concentration after treatment with the phosphatidylinositol kinase inhibitors wortmannin and LY294002. To determine the effect of this class of compounds on in vivo Abeta accumulation, we administered wortmannin to the Tg2576 mouse model of AD. Oral administration of wortmannin over four months resulted in a significant, non-overlapping 40%-50% reduction in the number of senile plaques, one of the pathological hallmarks of AD. Sandwich ELISA analysis of formic acid extractable Abeta in the brain of treated animals indicates that both Abeta40 and the longer, more amyloidogenic form of the peptide, Abeta42, were significantly reduced. These data provide the first direct evidence that compounds identified by their ability to reduce Abeta concentration in vitro can reduce Abeta accumulation and deposition in the brain, thus establishing a basic paradigm for the identification and evaluation of additional compounds that lower Abeta accumulation.

Hartlage-Rubsamen, M., J. Apelt, et al. (2001). "Fibrillary beta-amyloid deposits are closely associated with atrophic nitric oxide synthase (NOS)-expressing neurons but do not upregulate the inducible NOS in transgenic Tg2576 mouse brain with Alzheimer pathology." Neurosci Lett 302(2-3): 73-6.
Transgenic mice (Tg2576) that express the Swedish double mutation of human amyloid precursor protein and develop Alzheimer-like beta-amyloid deposits in the aged brain, were used to study the effect of beta-amyloid deposition on expression of both neuronal (nNOS) and inducible nitric oxide synthase (iNOS) in cells surrounding beta-amyloid plaques. Nicotinamide adenine dinucleotide phosphate-diaphorase histochemistry and double immunofluorescent labeling revealed that most of the fibrillary, thioflavine-S-positive cortical beta-amyloid deposits in 13-, 17-, and 21-month-old transgenic animals were closely associated with dystrophic nNOS-positive neurons, while nNOS-bearing neurons located more distal to plaques appeared to be unaffected. There was no significant expression of iNOS in transgenic mouse brain. The data suggest enhanced vulnerability of nNOS-containing neocortical neurons to beta-amyloid toxicity. Alternatively, expression of nNOS may also be a response to plaque-mediated damage of neurons, consistent with a neuroprotective role of nitric oxide.

Gyure, K. A., R. Durham, et al. (2001). "Intraneuronal abeta-amyloid precedes development of amyloid plaques in Down syndrome." Arch Pathol Lab Med 125(4): 489-92.
CONTEXT: Down syndrome patients who live to middle age invariably develop the neuropathologic features of Alzheimer disease, providing a unique situation in which to study the early and sequential development of these changes. OBJECTIVE: To study the development of amyloid deposits, senile plaques, astrocytic and microglial reactions, and neurofibrillary tangles in the brains of young individuals (<30 years of age) with Down syndrome. METHODS: Histologic and immunocytochemical study of a series of autopsy brains (n = 14, from subjects aged 11 months to 56 years, with 9 subjects <30 years) examined at the Office of the Chief Medical Examiner of the State of Maryland and The Johns Hopkins Hospital. RESULTS: The principal observations included the presence of intraneuronal Abeta immunostaining in the hippocampus and cerebral cortex of very young Down syndrome patients (preceding the extracellular deposition of Abeta) and the formation of senile plaques and neurofibrillary tangles. CONCLUSIONS: We propose the following sequence of events in the development of neuropathologic changes of Alzheimer disease in Down syndrome: (1) intracellular accumulation of Abeta in neurons and astrocytes, (2) deposition of extracellular Abeta and formation of diffuse plaques, and (3) development of neuritic plaques and neurofibrillary tangles with activation of microglial cells.

Guardado-Santervas, P. (2001). "[Controversy surrounding new drugs for the treatment of dementia. an unfavourable view]." Rev Neurol 32(2): 172-175.
Currently, the important part played by the senile plaque and neurofibrillary tangles puts amyloid protein and tau hyperphosphorylation at the centre of a new direction in the investigation of the molecular biology and treatment of Alzheimer s disease. OBJECTIVE. To consider the scientific evidence regarding the limitations of anticholinesterase treatment. DEVELOPMENT. Most of the clinical trials with anticholinesterase inhibitor drugs have been too short (3-6 months in a disease lasting an average of 8.5 years). There is slight clinical improvement with a definite therapeutic ceiling. A small proportion of patients respond, but there is no way of knowing who these will be. Improvement occurs during the early stages of the illness. This means that when the illness is advanced or does not respond initially, treatment should be reconsidered. It is necessary for consensus to be reached to obtain uniformity of objectives and methodology in clinical trials, which have been heterogeneous until now, incorporating the results of epidemiological studies. CONCLUSION. Initial expectations of an analogy between the cholinergic deficit of Alzheimer s disease and the dopaminergic deficit of Parkinson s disease, with the effects on treatment implied by this, has been proved false with the passage of time and clinical, therapeutic and scientific experience.

Gouras, G. K. and M. F. Beal (2001). "Metal chelator decreases Alzheimer beta-amyloid plaques." Neuron 30(3): 641-2.
Transgenic mice developing beta-amyloid (Abeta) plaques are advancing experimental treatment strategies for Alzheimer's disease. The metal chelator, clioquinol, is reported by Cherny et al. (2001) to reduce Abeta plaques, presumably by chelation of Abeta-associated zinc and copper. This and other recent Abeta-modulating treatment approaches are discussed.

Gordon, M. N., D. L. King, et al. (2001). "Correlation between cognitive deficits and Abeta deposits in transgenic APP+PS1 mice." Neurobiol Aging 22(3): 377-85.
Doubly transgenic mAPP+mPS1 mice (15-16 months) had impaired cognitive function in a spatial learning and memory task that combined features of a water maze and a radial arm maze. Nontransgenic mice learned a new platform location each day during 4 consecutive acquisition trials, and exhibited memory for this location in a retention trial administered 30 min later. In contrast, transgenic mice were, on average, unable to improve their performance in finding the hidden platform over trials. The cognitive performance of individual mice within the transgenic group were inversely related to the amount of Abeta deposited in the frontal cortex and hippocampus. These findings imply that mAPP+mPS1 transgenic mice develop deficits in cognitive ability as Abeta deposits increase. These data argue that radial arm water maze testing of doubly transgenic mice may be a useful behavioral endpoint in evaluating the functional consequences of potential AD therapies, especially those designed to reduce Abeta load.

Gerlai, R. (2001). "Alzheimer's disease: beta-amyloid hypothesis strengthened!" Trends Neurosci 24(4): 199.

Frey, J. (2001). "[Is there sugar in the Alzheimer's disease?]." Ann Biol Clin (Paris) 59(3): 253-7.
Epidemiological and immunohistochemical studies focus the interest on the contribution of carbohydrates in the pathophysiology of Alzheimer's disease. Diabetes mellitus increases the risk. In the extracellular (senile) plaques, which contain aggregates of amyloid proteins, and in the neurofibrillary tangles within the cytoplasm of neurons, advanced glycation end products were detected. It is discussed whether it is a cause or an effect of the Alzheimer's disease. The vascular origin of the lesions is also considered.

Fraser, P. E., A. A. Darabie, et al. (2001). "Amyloid-beta interactions with chondroitin sulfate-derived monosaccharides and disaccharides. implications for drug development." J Biol Chem 276(9): 6412-9.
In Alzheimer's disease, the major pathological features are diffuse and senile plaques that are primarily composed of the amyloid-beta (A beta) peptide. It has been proposed that proteoglycans and glycosaminoglycans (GAG) facilitate amyloid fibril formation and/or stabilize the plaque aggregates. To develop effective therapeutics based on A beta-GAG interactions, understanding the A beta binding motif on the GAG chain is imperative. Using electron microscopy, fluorescence spectroscopy, and competitive inhibition ELISAs, we have evaluated the ability of chondroitin sulfate-derived monosaccharides and disaccharides to induce the structural changes in A beta that are associated with GAG interactions. Our results demonstrate that the disaccharides GalNAc-4-sulfate(4S), Delta UA-GalNAc-6-sulfate(6S), and Delta UA-GalNAc-4,6-sulfate(4S,6S), the iduronic acid-2-sulfate analogues, and the monosaccharides d-GalNAc-4S, d-GalNAc-6S, and d-GalNAc-4S,6S, but not d-GalNAc, d-GlcNAc, or Delta UA-GalNAc, induce the fibrillar features of A beta-GAG interactions. The binding affinities of all chondroitin sulfate-derived saccharides mimic those of the intact GAG chains. The sulfated monosaccharides and disaccharides compete with the intact chondroitin sulfate and heparin GAGs for A beta binding, as illustrated by competitive inhibition ELISAs. Therefore, the development of therapeutics based on the model of A beta-chondroitin sulfate binding may lead to effective inhibitors of the GAG-induced amyloid formation that is observed in vitro.

Fitzjohn, S. M., R. A. Morton, et al. (2001). "Age-related impairment of synaptic transmission but normal long-term potentiation in transgenic mice that overexpress the human APP695SWE mutant form of amyloid precursor protein." J Neurosci 21(13): 4691-8.
We have studied synaptic function in a transgenic mouse strain relevant to Alzheimer's disease (AD), overexpressing the 695 amino acid isoform of human amyloid precursor protein with K670N and M671L mutations (APP(695)SWE mice), which is associated with early-onset familial AD. Aged-transgenic mice had substantially elevated levels of Abeta (up to 22 micromol/gm) and displayed characteristic Abeta plaques. Hippocampal slices from 12-month-old APP(695)SWE transgenic animals displayed reduced levels of synaptic transmission in the CA1 region when compared with wild-type littermate controls. Inclusion of the ionotropic glutamate receptor antagonist kynurenate during preparation of brain slices abolished this deficit. At 18 months of age, a selective deficit in basal synaptic transmission was observed in the CA1 region despite treatment with kynurenate. Paired-pulse facilitation and long-term potentiation (LTP) were normal in APP(695)SWE transgenic mice at both 12 and 18 months of age. Thus, although aged APP(695)SWE transgenic mice have greatly elevated levels of Abeta protein, increased numbers of plaques, and reduced basal synaptic transmission, LTP can still be induced and expressed normally. We conclude that increased susceptibility to excitotoxicity rather than a specific effect on LTP is the primary cause of cognitive deficits in APP(695)SWE mice.

Fishman, C. E., D. J. Cummins, et al. (2001). "Statistical aspects of quantitative image analysis of beta-amyloid in the APP(V717F) transgenic mouse model of Alzheimer's disease." J Neurosci Methods 108(2): 145-52.
Cerebral beta-amyloidosis is a central part of the neuropathology of Alzheimer's disease (AD). Quantitation of beta-amyloid plaques in the human AD brain, and in animal models of AD, is an important study endpoint in AD research. Methodologic approaches to the measurement of beta-amyloid in the brain vary between investigators, and these differences affect outcome measures. Here, one quantitative approach to the measurement of beta-amyloid plaques in brain sections was analyzed for sources of variability due to sampling. Brain tissue was from homozygous APP(V717F) transgenic male mice. Sampling variables were at the mouse and microscopic slide and field levels. Results indicated that phenotypic variability in the mouse sample population was the largest contributor to the standard error of the analyses. Within each mouse, variability between slides or between fields within slides had smaller effects on the error of the analyses. Therefore, when designing studies of adequate power, in this and in other similar models of cerebral beta-amyloidosis, sufficient numbers of mice per group must be included in order for change in mean plaque burden attributable to an experimental variable to outweigh phenotypic variability.

Ferrer, I. (2001). "[Alpha-synucleinopathies]." Neurologia 16(4): 163-170.
The term a-synucleinopathy is used to name a group of disorders having in common the abnormal deposition of a-synuclein in the cytoplasm of neurons or glial cells, as well as in extracellular deposits of amyloid. In Parkinson's disease and Lewy body dementia, a-synuclein is the main component of Lewy bodies and dystrophic neurites; a-synuclein also accumulates in the cytoplasm of glial cells. In multiple system atrophy, a-synuclein conforms the cytoplasmic oligodendroglial inclusions and the neuronal inclusions which are the hallmark of this disease. Finally, the amyloidogenic fragment 61-95 amino acids of a-synuclein is the non-AB component of senile plaque amyloid in Alzheimer disease. Accumulations of a-synuclein in all these disorders have in common a fibrilar configuration, but they differ in the binding of a-synuclein to distinct proteins with the exception of ubiquitin whose binding to a-synuclein is common to all a-synuclein inclusions. The mechanisms leading to a-synuclein fragmentation and aggegation into extracellular amyloid are not known, although a-synuclein fragment and BA4 aggregates are the result of abnormal cleavage of large precursors. On the other hand, several studies have shown that a-synuclein may adopt a fibrilar conformation and give rise to insoluble forms and high molecular weight aggregates in vitro. Similar complexes have also been observed in a-synucleinopathies. Although studies in vitro and in vivo have shown toxic effects of a-synuclein, the consequence of a-synuclein deposition on cell survival in a-synucleinopathies is not known.

Ferrer, I., R. Blanco, et al. (2001). "Prion protein expression in senile plaques in Alzheimer's disease." Acta Neuropathol (Berl) 101(1): 49-56.
Prion protein (PrPC) is a glycolipid-anchored cell membrane sialoglycoprotein that localises in presynaptic membranes. Since synapses are vulnerable to Alzheimer's disease (AD), the present study examines PrPC expression in senile plaques, one of the major structural abnormalities in AD, by single- and double-labelling immunohistochemistry. Punctate PrPC immunoreactivity is found in diffuse plaques, whereas isolated large coarse PrPC-positive granules reminiscent of dystrophic neurites are observed in neuritic plaques. Finally, PrPC deposition also occurs as dense filamentous and amorphous precipitates in amyloid cores of senile plaques, but not in the walls of blood vessels with amyloid angiopathy. In contrast to PrPC, betaA4-amyloid immunoreactivity is preserved and even enhanced following incubation of the tissue sections with proteinase K prior to immunohistochemistry, thus indicating no PrPC and betaA4-amyloid cross-reactivity in dense amyloid cores of senile plaques. Punctate PrPC deposition in diffuse plaques is similar to that of synaptophysin, a synaptic vesicle-associated protein, as already reported in other studies. Immunoprecipitation, electrophoresis and Western blot studies have shown that synaptophysin, amyloid precursor protein (APP) and betaA4 do not co-precipitate with PrP. These results suggest that synaptophysin, APP and betaA4 are likely not bound to PrP. PrPC accumulation in betaA4-amyloid dense cores may be the consequence of the release of PrP into the extracellular space. Whether PrPC accumulation in the extracellular space is the result of impaired endocytosis and subsequent hydrolysis in the endosomal compartment, in contrast to normal degradation of PrPC, resulting from or occurring in parallel to abnormal APP degradation, deserves further study.

El-Agnaf, O. M., J. M. Sheridan, et al. (2001). "Effect of the disulfide bridge and the C-terminal extension on the oligomerization of the amyloid peptide ABri implicated in familial British dementia." Biochemistry 40(12): 3449-57.
Familial British dementia (FBD) is a rare neurodegenerative disorder and shares features with Alzheimer's disease, including amyloid plaque deposits, neurofibrillary tangles, neuronal loss, and progressive dementia. Immunohistochemical and biochemical analysis of plaques and vascular amyloid of FBD brains revealed that a 4 kDa peptide named ABri is the main component of the highly insoluble amyloid deposits. In FBD patients, the ABri peptide is produced as a result of a point mutation in the usual stop codon of the BRI gene. This mutation produces a BRI precursor protein 11 amino acids longer than the wild-type protein. Mutant and wild-type precursor proteins both undergo furin cleavage between residues 243 and 244, producing a peptide of 34 amino acids in the case of ABri and 23 amino acids in the case of the wild-type (WT) peptide. Here we demonstrate that the intramolecular disulfide bond in ABri and the C-terminal extension are required to elongate initially formed dimers to oligomers and fibrils. In contrast, the shorter WT peptide did not aggregate under the same conditions. Conformational analyses indicate that the disulfide bond and the C-terminal extension of ABri are required for the formation of beta-sheet structure. Soluble nonfibrillar ABri oligomers were observed prior to the appearance of mature fibrils. A molecular model of ABri containing three beta-strands, and two beta-hairpins annealed by a disulfide bond, has been constructed, and predicts a hydrophobic surface which is instrumental in promoting oligomerization.

Dickson, T. C. and J. C. Vickers (2001). "The morphological phenotype of beta-amyloid plaques and associated neuritic changes in Alzheimer's disease." Neuroscience 105(1): 99-107.
We have utilised laser confocal microscopy to categorise beta-amyloid plaque types that are associated with preclinical and end-stage Alzheimer's disease and to define the neurochemistry of dystrophic neurites associated with various forms of plaques. Plaques with a spherical profile were defined as either diffuse, fibrillar or dense-cored using Thioflavin S staining or immunolabelling for beta-amyloid. Confocal analysis demonstrated that fibrillar plaques had a central mass of beta-amyloid with compact spoke-like extensions leading to a confluent outer rim. Dense-cored plaques had a compacted central mass surrounded by an outer sphere of beta-amyloid. Diffuse plaques lacked a morphologically identifiable substructure, resembling a ball of homogeneous labelling. The relative proportion of diffuse, fibrillar and dense-cored plaques was 53, 22 and 25% in preclinical and 31, 49 and 20% in end-stage Alzheimer's disease cases, respectively. Plaque-associated dystrophic neurites in preclinical cases were immunolabelled for neurofilament proteins whereas, in end-stage cases, these abnormal neurites were variably labelled for tau and/or neurofilaments. Double labelling demonstrated that the proportion of diffuse, fibrillar and dense-cored plaques that were neuritic was 12, 47 and 82% and 24, 82 and 76% in preclinical and end-stage cases, respectively. Most dystrophic neurites in Alzheimer's disease cases were labelled for either neurofilaments or tau, however, confocal analysis determined that 30% of neurofilament-labelled bulb-like or elongated neurites had a core of tau immunoreactivity.These results indicate that all morphologically defined beta-amyloid plaque variants were present in both early and late stages of Alzheimer's disease. However, progression to clinical dementia was associated with both a shift to a higher proportion of fibrillar plaques that induced local neuritic alterations and a transformation of cytoskeletal proteins within associated abnormal neuronal processes. There data indicate key pathological changes that may be subject to therapeutic intervention to slow the progression of Alzheimer's disease.

Dandrea, M. R., P. A. Reiser, et al. (2001). "Application of triple immunohistochemistry to characterize amyloid plaque-associated inflammation in brains with Alzheimer's disease." Biotech Histochem 76(2): 97-106.
Inflammation, characterized by the presence of activated microglia and reactive astrocytes (gliosis), has been described in Alzheimer's disease (AD). We used our routine single immunohistochemical (IHC) labeling protocol to label amyloid plaques, an AD neuropathological hallmark, activated microglia, and reactive astrocytes in serial sections of AD hippocampus and entorhinal cortex of brain. Although most amyloid plaques were associated with inflammation throughout the serial sections, the extent of microglial and astrocytic activation varied among the amyloid plaques. We also observed a population of amyloid plaques that did not appear to coincide with immunolabeled microglia and astrocytes in serial sections, leading us to speculate that some amyloid plaques are not associated with inflammation. Because serial sectioning limited our ability to confirm these findings, we developed a triple IHC protocol to investigate the association of activated microglia and reactive astrocytes simultaneously with amyloid plaques in sections of AD brain entorhinal cortex and hippocampus. Unlike the potential errors of extrapolating descriptive information from routine IHC or histochemical staining methods on sectioned tissues, triple IHC allowed direct characterization of three differently colored antigens in situ. The success of the protocol depended on selection of distinguishable color schemes and resolution of other critical technical elements including the compatibility of the reagents and the sensitivity and sequence of the detection systems. The results of the triple IHC protocol clarified the spatial relation of microglia and astrocytes with amyloid plaques and provoked novel interpretations about the roles of inflammation in AD brain tissues. We categorized three distinct populations of amyloid plaques related to of inflammation: 1) Abeta42 immunoreactive (a marker of amyloid plaques) amyloid plaques without activated microglia or reactive astrocytes, 2) Abeta42-positive amyloid plaques with HLA-DR (a marker of microglia)-positive microglia and no astrocytes, 3) Abeta42-positive amyloid plaques among HLA-DR and GFAP (a marker of astrocytes) immunoreactive astrocytes. Most amyloid plaques had varying degrees of activated microglia and reactive astrocytes. Some of the amyloid plaques were not associated with inflammation while others were associated only with activated microglia. These findings suggest that amyloid plaques without associated inflammation may represent recently formed plaques and that the presence of amyloid plaques in AD brains may activate microglia prior to gliosis. Furthermore, the shape of the amyloid plaques may be altered subsequently from its typical spherical to an aspherical shape by the inflammatory cells.

D'Andrea, M. R., R. G. Nagele, et al. (2001). "Evidence that neurones accumulating amyloid can undergo lysis to form amyloid plaques in Alzheimer's disease." Histopathology 38(2): 120-34.
AIMS: Amyloid has recently been shown to accumulate intracellularly in the brains of patients with Alzheimer's disease (AD), yet amyloid plaques are generally thought to arise from gradual extracellular amyloid deposition. We have investigated the possibility of a link between these two apparently conflicting observations. METHODS AND RESULTS: Immunohistochemistry and digital image analysis was used to examine the detailed localization of beta-amyloid(42) (A beta 42), a major component of amyloid plaques, in the entorhinal cortex and hippocampus of AD brains. A beta 42 first selectively accumulates in the perikaryon of pyramidal cells as discrete, granules that appear to be cathepsin D-positive, suggesting that they may represent lysosomes or lysosome-derived structures. AD brain regions abundantly populated with pyramidal neurones exhibiting excessive A beta 42 accumulations also contained evidence of neuronal lysis. Lysis of these A beta 42-burdened neurones apparently resulted in a local, radial dispersion of their cytoplasmic contents, including A beta 42 and lysosomal enzymes, into the surrounding extracellular space. A nuclear remnant was found at the dense core of many amyloid plaques, strengthening the idea that each amyloid plaque represents the end product of a single neuronal cell lysis. The inverse relationship between the amyloid plaque density and pyramidal cell density in the AD brain regions also supports this possibility, as does the close correlation between plaque size and the size of local pyramidal cells. CONCLUSIONS: Our findings suggest that excessive intracellular accumulation of A beta 42-positive material in pyramidal cells can result in cell lysis, and that cell lysis is an important source of amyloid plaques and neuronal loss in AD brains.

Christie, R. H., B. J. Bacskai, et al. (2001). "Growth arrest of individual senile plaques in a model of Alzheimer's disease observed by in vivo multiphoton microscopy." J Neurosci 21(3): 858-64.
In Alzheimer's disease, amyloid-beta peptide aggregates in the extracellular space to form senile plaques. The process of plaque deposition and growth has been modeled on the basis of in vitro experiments in ways that lead to divergent predictions: either a diffusion-limited growth model in which plaques grow by first-order kinetics, or a dynamic model of continual deposition and asymmetrical clearance in which plaques reach a stable size and stop growing but evolve morphologically over time. The models have not been tested in vivo because plaques are too small (by several orders of magnitude) for conventional imaging modalities. We now report in vivo multiphoton laser scanning imaging of thioflavine S-stained senile plaques in the Tg2576 transgenic mouse model of Alzheimer's disease to test these biophysical models and show that there is no detectable change in plaque size over extended periods of time. Qualitatively, geometric features remain unchanged over time in the vast majority of the 349 plaques imaged and re-imaged. Intervals as long as 5 months were obtained. Nonetheless, rare examples of growth or shrinkage of individual plaques do occur, and new plaques appear between imaging sessions. These results indicate that thioflavine S-positive plaques appear and then are stable, supporting a dynamic feedback model of plaque growth.

Cho, H. S., B. T. Hyman, et al. (2001). "Quantitation of apoE domains in Alzheimer disease brain suggests a role for apoE in Abeta aggregation." J Neuropathol Exp Neurol 60(4): 342-9.
Apolipoprotein E (apoE) and apoE-derived proteolytic fragments are present in amyloid deposits in Alzheimer disease (AD) and cerebral amyloid angiopathy (CAA). In this study, we examined which apoE fragments are most strongly associated with amyloid deposits and whether apoE receptor binding domains were present. We found that both apoE2- and apoE4-specific residues were present on plaques and blood vessels in AD and CAA. We quantified Abeta plaque burden and apoE plaque burdens in 5 AD brains. ApoE N-terminal-specific and C-terminal-specific antibodies covered 50% and 74% of Abeta plaque burden, respectively (p < 0.003). Double-labeling demonstrated that the plaque cores contained the entire apoE protein, but that outer regions contained only a C-terminal fragment, suggesting a cleavage in the random coil region of apoE. Presence of N- and C-terminal apoE cleavage fragments in brain extracts was confirmed by immunoblotting. The numbers of plaques identified by the apoE N-terminal-specific antibodies and the apoE C-terminal-specific antibody were equal, but were only approximately 60% of the total Abeta plaque number (p < 0.0001). Analysis of the size distribution of Abeta and apoE deposits demonstrated that most of the Abeta-positive, apoE-negative deposits were the smallest deposits (less than 150 microm2). These data suggest that C-terminal residues of apoE bind to Abeta and that apoE may help aid in the progression of small Abeta deposits to larger deposits. Furthermore, the presence of the apoE receptor binding domain in the center of amyloid deposits could affect surrounding cells via chronic interactions with cell surface apoE receptors.

Cherny, R. A., C. S. Atwood, et al. (2001). "Treatment with a copper-zinc chelator markedly and rapidly inhibits beta-amyloid accumulation in Alzheimer's disease transgenic mice." Neuron 30(3): 665-76.
Inhibition of neocortical beta-amyloid (Abeta) accumulation may be essential in an effective therapeutic intervention for Alzheimer's disease (AD). Cu and Zn are enriched in Abeta deposits in AD, which are solubilized by Cu/Zn-selective chelators in vitro. Here we report a 49% decrease in brain Abeta deposition (-375 microg/g wet weight, p = 0.0001) in a blinded study of APP2576 transgenic mice treated orally for 9 weeks with clioquinol, an antibiotic and bioavailable Cu/Zn chelator. This was accompanied by a modest increase in soluble Abeta (1.45% of total cerebral Abeta); APP, synaptophysin, and GFAP levels were unaffected. General health and body weight parameters were significantly more stable in the treated animals. These results support targeting the interactions of Cu and Zn with Abeta as a novel therapy for the prevention and treatment of AD.

Chen, M. and H. L. Fernandez (2001). "Where do Alzheimer's plaques and tangles come from? Aging-induced protein degradation inefficiency." Front Biosci 6: E1-E11.
Amyloid plaques and neurofibrillary tangles are prominent lesions in the aging brain and they may be responsible for cell death in Alzheimer's disease. But a basic question has not been answered: why and how are plaques and tangles formed during aging? In this study, we approach this question by first examining what happens in the aging body. Plaques and tangles do not come alone, but together with many other aging markers in the body (cholesterol deposition, gallstones, hair graying, and bone loss, etc.). Because these aging markers occur to a certain extent in all elderly and at about the same time in life, it is reasonable to conceive that they originate from a common cause, that is, aging-induced metabolic inefficiency. If cholesterol and gallstone depositions are the results of inefficient degradation/clearance of lipids and minerals, then similarly plaque and tangle formation in most people would be the results of inefficient normal degradation of ?-amyloid precursor protein (APP) and tau, respectively. By this view, our studies should focus on the enzymes responsible for APP and tau normal degradation and their natural changes in aging, rather than on presumed pathological factors. Whatever precise mechanisms underlying their depositions, plaques and tangles are the natural products of aging, thus fundamentally different from pathological events such as cancer growth in concept.

Campbell, A. (2001). "beta-amyloid: friend or foe." Med Hypotheses 56(3): 388-91.
The function of the amyloid precursor protein (APP) and its product, beta-amyloid, (Abeta) is at present unknown. The deposition of Abeta in senile plaques as well as meningeal and cerebral vessels has led many researchers to discount the possibility of a beneficial protective function for the protein. Thus it is generally believed that the aberrant processing of APP leads to increased beta-amyloid secretion that in turn leads to subsequent plaque formation and Alzheimer's disease. Here, a hypothesis is presented that the protein may indeed be protective and that a potential role for beta amyloid in innate immunity may exist. Copyright 2001 Harcourt Publishers Ltd.

Callahan, M. J., W. J. Lipinski, et al. (2001). "Augmented senile plaque load in aged female beta-amyloid precursor protein-transgenic mice." Am J Pathol 158(3): 1173-7.
Transgenic mice (Tg2576) overexpressing human beta-amyloid precursor protein with the Swedish mutation (APP695SWE) develop Alzheimer's disease-like amyloid beta protein (Abeta) deposits by 8 to 10 months of age. These mice show elevated levels of Abeta40 and Abeta42, as well as an age-related increase in diffuse and compact senile plaques in the brain. Senile plaque load was quantitated in the hippocampus and neocortex of 8- to 19-month-old male and female Tg2576 mice. In all mice, plaque burden increased markedly after the age of 12 months. At 15 and 19 months of age, senile plaque load was significantly greater in females than in males; in 91 mice studied at 15 months of age, the area occupied by plaques in female Tg2576 mice was nearly three times that of males. By enzyme-linked immunosorbent assay, female mice also had more Abeta40 and Abeta42 in the brain than did males, although this difference was less pronounced than the difference in histological plaque load. These data show that senescent female Tg2576 mice deposit more amyloid in the brain than do male mice, and may provide an animal model in which the influence of sex differences on cerebral amyloid pathology can be evaluated.

Bornemann, K. D., K. H. Wiederhold, et al. (2001). "Abeta-induced inflammatory processes in microglia cells of APP23 transgenic mice." Am J Pathol 158(1): 63-73.
A microglial response is part of the inflammatory processes in Alzheimer's disease (AD). We have used APP23 transgenic mice overexpressing human amyloid precursor protein with the Swedish mutation to characterize this microglia response to amyloid deposits in aged mice. Analyses with MAC-1 and F4/80 antibodies as well as in vivo labeling with bromodeoxyuridine demonstrate that microglia in the plaque vicinity are in an activated state and that proliferation contributes to their accumulation at the plaque periphery. The amyloid-induced microglia activation may be mediated by scavenger receptor A, which is generally elevated, whereas the increased immunostaining of the receptor for advanced glycation end products is more restricted. Although components of the phagocytic machinery such as macrosialin and Fc receptors are increased in activated microglia, efficient clearance of amyloid is missing seemingly because of the lack of amyloid-bound autoantibodies. Similarly, although up-regulation of major histocompatibility complex class II (IA) points toward an intact antigen-presenting function of microglia, lack of T and B lymphocytes does not indicate a cell-mediated immune response in the brains of APP23 mice. The similar characteristics of microglia in the APP23 mice and in AD render the mouse model suitable to study the role of inflammatory processes during AD pathogenesis.

Bamberger, M. E. and G. E. Landreth (2001). "Microglial interaction with beta-amyloid: Implications for the pathogenesis of Alzheimer's disease." Microsc Res Tech 54(2): 59-70.
The etiology of Alzheimer's disease (AD) involves a significant inflammatory component as evidenced by the presence of elevated levels of a diverse range of proinflammatory molecules in the AD brain. These inflammatory molecules are produced principally by activated microglia, which are found to be clustered within and adjacent to the senile plaque. Moreover, long-term treatment of patients with non-steroidal anti-inflammatory drugs has been shown to reduce risk and incidence of AD and delay disease progression. The microglia respond to beta-amyloid (Abeta) deposition in the brain through the interaction of fibrillar forms of amyloid with cell surface receptors, leading to the activation of intracellular signal transduction cascades. The activation of multiple independent signaling pathways ultimately leads to the induction of proinflammatory gene expression and production of reactive oxygen and nitrogen species. These microglial inflammatory products act in concert to produce neuronal toxicity and death. Therapeutic approaches focused on inhibition of the microglial-mediated local inflammatory response in the AD brain offer new opportunities to intervene in the disease. Copyright 2001 Wiley-Liss, Inc.

Bach, J. H., H. S. Chae, et al. (2001). "C-terminal fragment of amyloid precursor protein induces astrocytosis." J Neurochem 78(1): 109-20.
One of the pathophysiological features of Alzheimer's disease is astrocytosis around senile plaques. Reactive astrocytes may produce proinflammatory mediators, nitric oxide, and subsequent reactive oxygen intermediates such as peroxynitrites. In the present study, we investigated the possible role of the C-terminal fragment of amyloid precursor protein (CT-APP), which is another constituent of amyloid senile plaque and an abnormal product of APP metabolism, as an inducer of astrocytosis. We report that 100 nM recombinant C-terminal 105 amino acid fragment (CT105) of APP induced astrocytosis morphologically and immunologically. CT105 exposure resulted in activation of mitogen-activated protein kinase (MAPK) pathways as well as transcription factor NF-kappaB. Pretreatment with PD098059 and/or SB203580 decreased nitric oxide (NO) production and nuclear factor-kappa B (NF-kappaB) activation. But inhibitors of NF-kappaB activation did not affect MAPKs activation whereas they abolished NO production and attenuated astrocytosis. Furthermore, conditioned media derived from CT105-treated astrocytes enhanced neurotoxicity and pretreatment with NO and peroxynitrite scavengers attenuated its toxicity. These suggest that CT-APP may participate in Alzheimer's pathogenesis through MAPKs- and NF-kappaB-dependent astrocytosis and iNOS induction.

Apelt, J. and R. Schliebs (2001). "Beta-amyloid-induced glial expression of both pro- and anti-inflammatory cytokines in cerebral cortex of aged transgenic Tg2576 mice with Alzheimer plaque pathology." Brain Res 894(1): 21-30.
To elucidate the mechanisms involved in beta-amyloid-mediated inflammation in Alzheimer's disease, transgenic Tg2576 mice containing as transgene the Swedish double mutation of human amyloid precursor protein 695, were examined for the expression pattern of various cytokines using double immunocytochemistry and laser scanning microscopy. Tg2576 mice studied at postnatal ages of 13, 16 and 19 months demonstrated an age-related accumulation of both senile and diffuse beta-amyloid plaques in neocortex and hippocampus. Reactive interleukin (IL)-1beta-immunoreactive astrocytes were found in close proximity to both fibrillary and diffuse beta-amyloid deposits detectable at very early stages of plaque development, while activated microglia appeared in and around fibrillary beta-amyloid plaques only. Subpopulations of reactive astrocytes also demonstrated immunolabeling for transforming growth factor (TGF)-beta1, TGF-beta3, and IL-10, already detectable in 13-month-old transgenic mouse brain, while a few IL-6-immunoreactive astrocytes were observed only at later stages of plaque development. The early beta-amyloid-mediated upregulation of IL-1beta, TGF-beta, and IL-10 in surrounding reactive astrocytes indicates the induction of both pro- and anti-inflammatory mechanisms. The transgenic approach used in this study may thus provide a useful tool to further disclose the in vivo mechanisms by which pro- and anti-inflammatory cytokines interact and/or contribute to the progression of Alzheimer's disease.

Akiyama, H., H. Kondo, et al. (2001). "Immunohistochemical localization of neprilysin in the human cerebral cortex: inverse association with vulnerability to amyloid beta-protein (Abeta) deposition." Brain Res 902(2): 277-81.
We investigated the immunohistochemical localization of neprilysin, a putative amyloid beta-protein (Abeta)-degrading enzyme, in postmortem human brain tissues. In the cerebral cortex, neprilysin immunoreactivity was weak, but relatively dense distribution was found in the primary somatosensory and visual cortices compared with the hippocampus and association cortices. In Alzheimer brain, neprilysin-positive dystrophic neurites occurred in senile plaques in the primary cortices, an observation that supports the relative abundance of neprilysin-positive neuronal processes. A paucity of neprilysin in the hippocampus and association cortices may contribute to the vulnerability of these areas to Abeta deposition.