Immunohistochemical detection of anti-oxidative stress enzymes in the dog brain

Anti-oxidative stress enzymes were immunohistochemically detected in the brain from young to very-aged dogs. More than half of the neurons in the cerebral cortex of the young dogs (< 5 years old) were positive for copper (Cu), zinc (Zn) superoxide dismutase (SOD), and the staining intensity was strong. The number of Cu, Zn SOD-positive neurons decreased with age, and only 10–50% of neurons were positive for SOD in the aged and very aged (> 9 years old) dogs. In contrast, no glial cells were immunostained for Cu, Zn SOD in the young dogs, and the number, as well as the staining intensity, increased with age, reaching > 50% in the aged and very aged dogs. Apoptotic brain cells, which were conspicuous in the aged dog brain, were negative for Cu, Zn SOD. The Cu, Zn SOD immunoreactions were also observed in the degenerative neurites of amyloid type senile plaques, vessels affected with cerebral amyloid angiopathy (CAA) and reactive astroglia around these amyloid plaques and CAA in the aged and very aged dog brains. Diffuse type senile plaques were negative for Cu, Zn SOD. The number of catalase- or glutathione peroxidase-positive cells varied among dogs regardless of their age. An age-related decrease in number of Cu, Zn SOD-positive neurons may enhance the toxicity of oxygen free radicals, resulting in neuronal cell death.     

Niemann-Pick type C disease: accelerated neurofibrillary tangle formation and amyloid beta deposition associated with apolipoprotein E epsilon 4 homozygosity

Niemann-Pick type C disease is a neurovisceral storage disorder. Neurofibrillary tangles similar to those in Alzheimer's disease have been reported in most juvenile/adult patients without amyloid beta protein (Abeta) deposits. Recently, we found deposits of Abeta in the form of diffuse plaques in three (31- and 32-year-old sisters and a 37-year-old man) of nine Niemann-Pick type C disease patients, who presented with most severe tauopathy and with numerous neurofibrillary tangles. Abeta deposits were not detected in any of the control brains of patients younger than age 42 years. These three patients with Abeta deposit all were homozygotes of apolipoprotein E epsilon 4. Our study suggested that NPC1 gene mutations combined with homozygosity of apolipoprotein E epsilon 4 alleles could manifest neuropathology similar to that of Alzheimer's disease. Investigation of these patients may provide an important clue for understanding the pathogenesis of Alzheimer's disease.     

Diversity of senile plaques in Alzheimer's disease as revealed by a new monoclonal antibody that recognizes an internal sequence of the Abeta peptide

In order to have more specific tools available to approach amyloidogenesis in Alzheimer's disease (AD), we have produced several polyclonal and monoclonal antibodies that recognize specific sequences of the amyloid beta (Abeta) peptide. Here we present results that demonstrate that our monoclonal antibody EM5 recognizes an internal sequence (residues 11-16) of the Abeta peptide. This strategic localization of the epitope allowed us to employ this antibody, together with two previously reported polyclonal antibodies (EM2 and EM3, specific for AbetaX-40 and AbetaX-42, respectively), in an immunohistochemical study aimed at exploring the differential distribution of longer (AbetaX-40/42) and shorter (Abeta17-X) peptides along the various types of amyloid deposits of AD. This antibody panel was used in six AD brains, on sections from associative neocortex, striatum and cerebellar cortex. Single and double immunostaining revealed specific staining of vascular amyloid deposits and neuritic plaques by EM5 antibody, with high co-localization of EM2. Our results suggest that EM5 antibody recognizes pathogenic forms of Abeta deposits (amyloid angiopathy and neuritic plaques) and reveals the existence of a subset of plaques with a profile similar to vascular deposits. Additionally, our results show that diffuse plaques in AD brains may contain Abeta17-X peptides as its principal component. EM5 may be a useful tool in research both on human and transgenic mice tissue that may aid in the study of molecular heterogeneity of plaques in AD.     

Distribution of the protease inhibitor alpha 1-antichymotrypsin in cerebral and systemic amyloid.

We performed immunocytochemical staining to study the distribution of serum protease inhibitors in cerebral and systemic amyloid deposits. In beta-protein amyloid deposits in Alzheimer's disease, Down's syndrome, age-related cerebral amyloidosis, sporadic cerebral amyloid angiopathy and hereditary cerebral hemorrhage with amyloidosis of Dutch origin, antibody to alpha 1-antichymotrypsin (ACT) stains senile plaques and vascular deposits. Immature plaques or preamyloid deposits, identified by their positive staining for beta-protein and negative staining for Congo red, which represents the earliest recognizable stages of amyloid deposition, are also labeled. We did not detect ACT in other chemically different forms of cerebral and systemic amyloid. None of the other inhibitors in this study, i.e. antithrombin III and alpha 2-macroglobulin, was detected in the amyloid deposits. Neurons and glial cells throughout the central nervous system in normal and amyloid-containing brains also bind ACT antibody. The results emphasize the close association of ACT with one type of cerebral amyloid (beta-amyloid diseases) as well as the failure to detect such an association in other chemically different forms of cerebral and systemic amyloids.     

The widespread alteration of neurites in Alzheimer's disease may be unrelated to amyloid deposition

The structural changes of Alzheimer's disease (AD) include a widespread alteration of neuronal cell processes in addition to senile plaques and neurofibrillary tangles. Since the antigenic characteristics of these abnormal neurites are similar to those of the abnormal neurites associated with the senile plaques, the question has been raised as to whether the widespread neuritic alteration is secondary to the deposition of amyloid. To answer this question, we examined brains from 2 subjects with a longer-lasting form of subacute sclerosing panencephalitis (SSPE) characterized by the presence of numerous neurofibrillary tangles but no senile plaques, 3 subjects with AD, and 2 age-matched controls. Light and electron immunocytochemical analyses revealed that abnormal neurites are present diffusely in SSPE cerebral cortex in the absence of amyloid deposits. These abnormal neurites were qualitatively identical to the widespread abnormal neurites of AD. The abnormal neurites, in contrast to the neurites of control brains, immunoreacted with antibodies to tau and ubiquitin. These distinctive antigenic features were due to the presence in these abnormal neurites of straight filaments, 14 to 16 nm in diameter, mixed with a few paired helical filaments. The spatial distribution of the widespread neuritic alteration correlated with that of neurofibrillary tangles in both conditions, but not with that of senile plaques in AD. The present findings demonstrate that a diffuse alteration of neurites similar to that present in AD takes place independently of the deposition of amyloid in SSPE, and they are consistent with the hypothesis that in AD, also, this alteration is not secondary to the deposition of amyloid.(ABSTRACT TRUNCATED AT 250 WORDS)     

Iron deposits in multiple sclerosis and Alzheimer''s disease brains

Iron may contribute to the pathogenesis of neurological diseases by promoting oxidative damage. The localization of iron in multiple sclerosis (MS) and Alzheimer's disease (AD) brains was investigated to further the understanding of its pathogenic role in these disease states. Earlier studies, utilizing a standard Perls' stain, yielded conflicting reports regarding the distribution of iron deposits in MS brains, and a previous study on AD brains utilized a diaminobenzidine (DAB) enhanced version of this stain. In the present study, a modified version of the DAB-enhanced stain was used; it utilizes sodium borohydride, proteinase K, Triton X-100 and xylenes to increase the accessibility of tissue iron to histochemical reagents. This modified method can reveal iron deposits that are missed by the Perls' or DAB-enhanced Perls' stains. In addition to its normal deposition in oligodendrocytes and myelin, iron was detected in reactive microglia, ameboid microglia and macrophages in MS brains. In AD brains, three types of plaques were stained: dense core, clear core and amorphous plaques. Punctate staining was also observed in neurons in the corticies of AD brains. The structure accounting for punctate labeling may be damaged mitochondria, lipofuscin or amyloid deposits. Dense core plaques, clear plaques and punctate labeling were not detected in the previous AD study which utilized only the DAB-enhanced Perls' stain. The labeling of these additional structures illustrates the benefit of the modified method. In summary, the localization of iron deposition in MS and AD brains indicates potential sites where iron could promote oxidative damage in these disease states.     

Lysosomal proteinase antigens are prominently localized within senile plaques of Alzheimer's disease: evidence for a neuronal origin

To investigate the role of proteolysis in amyloid formation, we studied the localization of the proteolytic enzymes, cathepsin D and cathepsin B, in the prefrontal cerebral cortex and hippocampus of human postmortem brains from patients with Alzheimer's disease and from individuals free of neurological disease. In control and Alzheimer brains, cathepsin immunoreactivity within cells was localized to lysosome-related structures, which were particularly abundant in neuronal perikarya. In Alzheimer brain, cathepsin immunoreactivity was also heavily concentrated extracellularly within senile plaques. Cathepsin immunoreactivity associated with plaques was not confined to lysosomes and was distributed throughout the plaque. Isolated amyloid cores, however, were not immunostained. Cathepsin-laden perikarya of degenerating neurons were frequently seen within senile plaques and, in the more advanced stages of degeneration, cathepsin immunoreactivity was present throughout the cytoplasm. Other identified constituents of senile plaques appeared to be less significant sources of cathepsin immunoreactivity, including astrocytes, degenerating neurites, microglia and macrophages. These results demonstrate that lysosomal proteinases are major constituents of the senile plaque and that degenerating neuronal perikarya are a principal source of the cathepsin immunoreactivity. We propose that the unregulated action of extracellular cathepsins liberated from degenerating neurons may lead to abnormal processing of the amyloid precursor protein and to the formation of amyloid locally within senile plaques in Alzheimer's disease.     

Regression stage senile plaques in the natural course of Alzheimer's disease

Resolution process of cerebroparenchymal amyloid beta-protein (Abeta) deposition has become of increasing interest in the light of recent advance in the Abeta-vaccination therapy for Alzheimer's disease (AD). However, the neuropathological features of degraded and disappearing senile plaque remain poorly characterized, especially in the natural course of the disease. To clarify the natural removal processes of Abeta burden in the brain with AD, we devised a triple-step staining method: Bodian for dystrophic neurites, anti-glial fibrillary acidic protein for astrocytes, and anti-Abeta. We thus examined 24 autopsied AD brains. A novel form of senile plaques, termed 'remnant plaques', was identified. Remnant plaques were characterized by mesh-like astroglial fibrils within the entire plaque part, Abeta deposit debris exhibiting weak Abeta immunoreactivity, and only a few slender dystrophic neurites. In remnant plaques, amyloid burden was apparently decreased. The density of remnant plaques increased significantly with disease duration. Dual-labelling immunohistochemistry revealed many Abeta-immunoreactive granules in astrocytes and a modest number in microglia, both of which accumulated in senile plaques. We consider amyloid deposits of diffuse and neuritic plaques to be shredded by astrocytic processes from the marginal zone of plaques, and to gradually disintegrate into smaller compartments. Cerebroparenchymal Abeta deposits undergo degradation. After a long-standing resolution process, diffuse and neuritic plaques may finally proceed to remnant plaques. Astrocytes are actively engaged in the natural Abeta clearance mechanism in advanced stage AD brains, which may provide clues for developing new therapeutic strategies for AD.     

LRP and senile plaques in Alzheimer's disease: colocalization with apolipoprotein E and with activated astrocytes

The low density lipoprotein receptor-related protein (LRP) is a multifunctional receptor which is present on senile plaques in Alzheimer's disease (AD). It is suggested to play an important role in the balance between amyloid beta (Abeta) synthesis and clearance mechanisms. One of its ligands, apolipoprotein E (apoE), is also present on senile plaques and has been implicated as a risk factor for AD, potentially affecting the deposition, fibrillogenesis and clearance of Abeta. Using immunohistochemistry we show that LRP was present only on cored, apoE-containing senile plaques, in both PDAPP transgenic mice and human AD brains. We detected strong LRP staining in neurons and in reactive astrocytes, and immunostaining of membrane-bound LRP showed colocalization with fine astrocytic processes surrounding senile plaques. LRP was not present in plaques in young transgenic mice or in plaques of APOE-knockout mice. As LRP ligands associated with Abeta deposits in AD brain may play an important role in inducing levels of LRP in both neurons and astrocytes, our findings support the idea that apoE might be involved in upregulation of LRP (present in fine astrocytic processes) and act as a local scaffolding protein for LRP and Abeta. The upregulation of LRP would allow increased clearance of LRP ligands as well as clearance of Abeta/ApoE complexes.     

Association of apolipoprotein J-positive beta-amyloid plaques with dystrophic neurites in Alzheimer's disease brain

Apolipoprotein J (apoJ), also known as clusterin and SP-40,40, binds soluble beta-amyloid (Abeta and is up-regulated in the Alzheimer's disease (AD) brain. In the present study we classified apoJ-immunopositive Abeta deposits in AD temporal cortex, and found apoJ-immunoreactive plaques were often associated with dystrophic neurites. Quantitative immunohistochemical analysis of five AD brains showed that 29% of Abeta deposited in the parenchyma was associated with apoJ. Of Abeta deposits with apoJ immunopositivity, 71% were associated with phospho-tau-positive dystrophic neurites in the surrounding tissue. Conversely, 64% of phospho-tau-labeled neuritic deposits were labeled with apoJ. ApoJ was found at the core of these deposits, and co-localized with the amyloid staining agent thioflavine-S. To test the direct effects of apoJ on tau metabolism, we treated cells in culture with apoJ-containing conditioned media, and we injected apoJ-containing media into the rat hippocampus. Using both systems, we observed increases in levels of tau and phosphorylated tau. Our findings demonstrate that apoJ immunopositivity strongly correlates with the presence of amyloid and associated neuritic dystrophy in the neuropil of AD temporal cortex, and supports a model where extracellular apoJ facilitates the conversion of diffuse Abeta deposits into amyloid and enhances tau phosphorylation in neurites surrounding these of plaques.     

AMYLOID PLAQUES IN THE BRAINS OF MICE INFECTED WITH SCRAPIE: MORPHOLOGICAL VARIATION AND STAINING PROPERTIES

Amyloid plaques in the brains of mice infected with scrapie: morphological variation and staining properties
Cerebral amyloid deposits predominantly in the form of plaques are associated with experimental scrapie produced by particular agents in inbred mice. In this paper the staining properties and variation in the morphology of these deposits are described. At the light microscope level a discretionary classification into six types is made: shadowy plaques; amorphous plaques; stellate plaques; giant plaques; diffuse amyloid deposits; and perivascular amyloid deposits. It is shown that Masson's trichrome technique provides the most efficient staining method for identifying cerebral amyloid of all these types. A preliminary ultrastructural examination of stellate plaques confirms the presence of amyloid on the basis of characteristic fibrils and demonstrates that microglia and distended neurites are involved in the structure of the plaques. The similarities and differences between cerebral amyloid in scrapie and other forms of amyloid deposits in the brain, particularly kuru plaques and senile plaques, are discussed.     

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

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.     

Congophilia in cerebral amyloidosis is modified by inactivation procedures on slow transmissible pathogens

Cerebral tissues with amyloid deposits were treated by various chemicals which inactivated the agent of subacute spongiform encephalopathy (SSE). We discovered Congophilia in the amyloid plaques in cases of Creutzfeldt-Jakob disease (CJD) and Gerstmann-Str?ussler syndrome (GSS) correlated to the chemical inactivation profiles of SSE. After incubation with trichloroacetate, guanidine-SCN, guanidine-HCl, formic acid, phenol and autoclaving, amyloid plaques in unfixed frozen sections of human brains with CJD or GSS, lost the affinity of Congo red and green birefringence under polarized light. In formalin-fixed, paraffin-embedded tissue sections, amyloid plaques of CJD and GSS lost the affinity of Congo red after most of these treatments. On the other hand, senile plaques in the aged, patients with Alzheimer's disease and with senile dementia of the Alzheimer type did not lose the affinity of Congo red after most of these treatments. Therefore, the amyloid deposits in the amyloid plaques differ from those in senile plaques. The methods we used facilitate differentiation of amyloid and senile plaques in formalin-fixed, paraffin-embedded tissues.     

Neuropathology of mice carrying mutant APP(swe) and/or PS1(M146L) transgenes: alterations in the p75(NTR) cholinergic basal forebrain septohippocampal pathway

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.     

Current advances on different kinases involved in tau phosphorylation, and implications in Alzheimer's disease and tauopathies

Hyperphosphorylation and accumulation of tau in neurons (and glial cells) is one the main pathologic hallmarks in Alzheimer's disease (AD) and other tauopathies, including Pick's disease (PiD), progressive supranuclear palsy, corticobasal degeneration, argyrophilic grain disease and familial frontotemporal dementia and parkinsonism linked to chromosome 17 due to mutations in the tau gene (FTDP-17-tau). Hyperphosphorylation of tau is regulated by several kinases that phosphorylate specific sites of tau in vitro. GSK-3-immunoprecipitated sarcosyl-insoluble fractions in AD have the capacity to phosphorylate recombinant tau. In addition, GSK-3 phosphorylated at Ser9, that inactivates GSK-3, is found in the majority of neurons with neurofibrillary tangles and dystrophic neurites of senile plaques in AD, and in Pick bodies and other phospho-tau-containing neurons and glial cells in other tauopathies. Increased expression of active kinases, including stress-activated kinase, c-Jun N-terminal kinase (SAPK/JNK) and kinase p38 has been found in brain homogenates in all the tauopathies. Strong active SAPK/JNK and p38 immunoreactivity has been observed restricted to neurons and glial cells containing hyperphosphorylated tau, as well as in dystrophic neurites of senile plaques in AD. Moreover, SAPK/JNK- and p38-immunoprecipitated sub-cellular fractions enriched in abnormal hyperphosphorylated tau have the capacity to phosphorylate recombinant tau and c-Jun and ATF-2 which are specific substrates of SAPK/JNK and p38 in AD and PiD. Interestingly, increased expression of phosphorylated (active) SAPK/JNK and p38 and hyperphosphorylated tau containing neurites have been observed around betaA4 amyloid deposits in the brain of transgenic mice (Tg 2576) carrying the double APP Swedish mutation. These findings suggest that betaA4 amyloid has the capacity to trigger the activation of stress kinases which, in turn, phosphorylate tau in neurites surrounding amyloid deposits. Complementary findings have been reported from the autopsy of two AD patients who participated in an amyloid-beta immunization trial and died during the course of immunization-induced encephalitis. The neuropathological examination of the brain showed massive focal reduction of amyloid plaques but not of neurofibrillary degeneration. Activation of SAPK/JNK and p38 were reduced together with decreased tau hyperphosphorylation of aberrant neurites in association with decreased amyloid plaques in both Tg2576 mice and human brains. These findings support the amyloid cascade hypothesis of tau phosphorylation mediated by stress kinases in dystrophic neurites of senile plaques but not that of neurofibrillary tangles and neuropil threads in AD.     

Multiple transmitter systems contribute neurites to individual senile plaques

Senile plaques (SP), which consist largely of abnormal neuronal processes in proximity to deposits of amyloid, are a characteristic neuropathological feature of Alzheimer's disease. In lesser numbers, SP also occur in the brains of nondemented aged humans and nonhuman primates. To date, it is not known whether neurites in individual SP derive from neurons of one or several neurotransmitter systems. In aged monkeys, two strategies were used to test the hypothesis that individual SP can contain abnormal neurites arising from multiple neuronal systems. First, immunocytochemical methods were used to identify somatostatin-immunoreactive neurites in plaques, and these sections were subsequently stained with silver to visualize other neurites. Numerous plaques contained both somatostatin-positive and somatostatin-negative (i.e. argyrophilic only) neurites, suggesting that more than one transmitter system contributed neurites to each of these plaques. Second, two-color immunocytochemical techniques showed, in a small percentage of plaques, that cholinergic neurites coexist with neuropeptide Y (NPY)-containing neurites or catecholaminergic neurites. These results suggest that the formation of SP may result from events that involve abnormalities of neuronal processes arising from multiple transmitter systems.     

Distribution of amyloid beta protein precursor in the Alzheimer's disease brain

In order to clarify the distribution and pathological changes of the amyloid beta protein precursor (betaAPP), 10 Alzheimer's disease (AD) brains and seven normal control brains were examined by immunocytochemistry and in situ hybridization histochemistry. All betaAPP isoforms were distributed evenly in neuronal cell bodies and their axons and dendrites. The betaAPP-positive neuronal processes showed mesh-like networks. In AD brains, betaAPP-positive neurons and mesh-like networks were generally decreased in spite of some intensely labeled neurons. All betaAPP isoforms accumulated in neuronal processes, dystrophic neurites and senile plaques. In situ hybridization histochemistry confirmed that all isoforms of betaAPP were expressed in neurons in control brains. In AD brains, the betaAPP mRNA signal was generally decreased besides some intense signal neurons corresponding to immunostaining findings. Few astrocytes expressed betaAPP. Thus, uniform expression and distribution of betaAPP were disturbed in AD brains showing uneven decreases or increases of neuronal betaAPP expression in individual neurons and betaAPP accumulation in neurons, neuronal processes and abnormal structures including dystrophic neurites, senile plaques and neurofibrillary tangles.     

Neurodegenerative changes associated with beta-amyloid deposition in the brains of mice carrying mutant amyloid precursor protein and mutant presenilin-1 transgenes

Mutations of amyloid precursor protein (APP) and presenilin-1 (PS1) lead to an increase in beta-amyloid (Abeta) production. Despite the fact that a number of transgenic mice develop cerebral Abeta plaques, few have been subjected to ultrastructural investigation and the sequence of events leading to Abeta plaque formation is unclear. We therefore investigated the doubly transgenic (mutant APP(K670N,M671L)-mutant PS1(M146L)) mouse, which develops Abeta deposits much earlier than singly transgenic littermates. Widespread Abeta plaques with or without a distinct core were found in gray matter. Abeta plaques were also present in white matter. Astrocytosis was greater around gray matter plaques than around white matter plaques. In some plaques, Abeta cores were associated with cell profiles containing prominent endoplasmic reticulum and a homogeneous cytoplasm that appeared to be neuronal. The morphology and location of other profiles indicated them to be microglia or oligodendrocytes. Some Abeta fibrils appeared to lie within these profiles, but they may have been simply surrounded by the cell profile since the profile membrane was not always visible. Dark atrophic neurons, whose morphology suggested that they were apoptotic, were present around gray matter plaques. Cerebrovascular Abeta deposition was also observed in the brains of APP/PS1 transgenic mice. Thus, the amyloid deposition and neuropathology observed in APP/PS1 mouse brain are similar to those in Alzheimer's disease and they appear to develop earlier and become more severe than in the other transgenic models currently available.     

Cortical somatostatin, neuropeptide Y, and NADPH diaphorase neurons: normal anatomy and alterations in Alzheimer's disease

Somatostatin and neuropeptide Y are two neuropeptides that are of particular interest in Alzheimer's disease because they are reported to be depleted in cerebral cortex. In the present study we examined somatostatin, neuropeptide Y, and nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase neurons in nine cortical regions in both normal and Alzheimer's disease brains. These three neurochemical markers show a high degree of co-localization (greater than 90%) in nonpyramidal neurons that are primarily distributed in cortical layers II-III, V-VI, and, most prominently, in infracortical white matter. The highest cell density was in temporal and parietal association cortex. The major morphological abnormality in Alzheimer's disease brains was a marked pruning and distortion of fiber plexuses with an apparent reduction in fiber density. In contrast, perikaryal density was preserved except for a reduction in parietal association cortex. Approximately 10 to 15% of senile plaques in the inferior temporal gyrus contained abnormal neurites. Additional abnormal collections of neurites without plaque cores were frequently found in layers II-III and V-VI. Neuropeptide Y and somatostatin were co-localized in abnormal neurites, suggesting an origin from local intrinsic neurons in which the two peptides are co-localized. Double immunofluorescence staining for both tau protein, a major antigenic component of paired helical filaments, and either somatostatin or neuropeptide Y showed that these neurons do not contain tau-immunoreactive neurofibrillary tangles. The morphological correlate of reduced somatostatin and neuropeptide Y content in Alzheimer's disease brain therefore appears to be a distortion and reduction in fiber plexuses. In addition, it is apparent that these neurons can develop widespread morphological abnormalities in the absence of neurofibrillary tangle formation.     

Immunohistochemical study of neurons containing corticotropin-releasing factor in Alzheimer's disease

In the brains of controls and individuals with Alzheimer's disease (AD), antisera to corticotropin-releasing factor (CRF) were used to immunostain neurons and their processes. In AD, we identified abnormal CRF-immunoreactive axons as well as neurites associated with deposits of amyloid in brain regions showing senile plaques. The number of immunoreactive fibers was decreased in individuals with AD. In contrast, CRF immunoreactivity was markedly increased in some neurons located within the paraventricular nucleus (PVN) of the hypothalamus. These findings support previous neurochemical studies indicating that certain CRF systems are affected in AD.