Deposition of amyloid (A4) protein within the brains of persons with dementing disorders other than Alzheimer's disease and Down's syndrome

Cerebellar Calcium-Binding Protein and Neurotrophin Receptor Defects in Down Syndrome and Alzheimer's Disease

Cerebellar hypoplasia is a major characteristic of the Down syndrome (DS) brain. However, the consequences of trisomy upon cerebellar Purkinje cells (PC) and interneurons in DS are unclear. The present study performed a quantitative and qualitative analysis of cerebellar neurons immunostained with antibodies against calbindin D-28k (Calb), parvalbumin (Parv), and calretinin (Calr), phosphorylated and non-phosphorylated intermediate neurofilaments (SMI-34 and SMI-32), and high (TrkA) and low (p75NTR) affinity nerve growth factor (NGF) receptors as well as tau and amyloid in DS (n = 12), Alzheimer's disease (AD) (n = 10), and healthy non-dementia control (HC) (n = 8) cases. Our findings revealed higher Aβ42 plaque load in DS compared to AD and HC but no differences in APP/Aβ plaque load between HC, AD, and DS. The cerebellar cortex neither displayed Aβ40 containing plaques nor pathologic phosphorylated tau in any of the cases examined. The number and optical density (OD) measurements of Calb immunoreactive (-ir) PC soma and dendrites were similar between groups, while the number of PCs positive for Parv and SMI-32 were significantly reduced in AD and DS compared to HC. By contrast, the number of SMI-34-ir PC dystrophic axonal swellings, termed torpedoes, was significantly greater in AD compared to DS. No differences in SMI-32- and Parv-ir PC OD measurements were observed between groups. Conversely, total number of Parv- (stellate/basket) and Calr (Lugaro, brush, and Golgi)-positive interneurons were significantly reduced in DS compared to AD and HC. A strong negative correlation was found between counts for Parv-ir interneurons, Calr-ir Golgi and brush cells, and Aβ42 plaque load. Number of TrkA and p75NTR positive PCs were reduced in AD compared to HC. These findings suggest that disturbances in calcium binding proteins play a critical role in cerebellar neuronal dysfunction in adults with DS.

Multifarious roles of mTOR signaling in cognitive aging and cerebrovascular dysfunction of Alzheimer's disease

Age-related cognitive failure is a main devastating incident affecting even healthy people. Alzheimer's disease (AD) is the utmost common form of dementia among the geriatric community. In the pathogenesis of AD, cerebrovascular dysfunction is revealed before the beginning of the cognitive decline. Mounting proof shows a precarious impact of cerebrovascular dysregulation in the development of AD pathology. Recent studies document that the mammalian target of rapamycin (mTOR) acts as a crucial effector of cerebrovascular dysregulation in AD. The mTOR contributes to brain vascular dysfunction and subsequence cerebral blood flow deficits as well as cognitive impairment. Furthermore, mTOR causes the blood-brain barrier (BBB) breakdown in AD models. Inhibition of mTOR hyperactivity protects the BBB integrity in AD. Furthermore, mTOR drives cognitive defect and cerebrovascular dysfunction, which are greatly prevalent in AD, but the central molecular mechanisms underlying these alterations are obscure. This review represents the crucial and current research findings regarding the role of mTOR signaling in cognitive aging and cerebrovascular dysfunction in the pathogenesis of AD.

Application of Machine Learning Technique to Distinguish Parkinson's Disease Dementia and Alzheimer's Dementia: Predictive Power of Parkinson's Disease-Related Non-Motor Symptoms and Neuropsychological Profile

In order to develop a predictive model that can distinguish Parkinson’s disease dementia (PDD) from other dementia types, such as Alzheimer’s dementia (AD), it is necessary to evaluate and identify the predictive accuracy of the cognitive profile while considering the non-motor symptoms, such as depression and rapid eye movement (REM) sleep behavior disorders. This study compared Parkinson’s disease (PD)’s non-motor symptoms and the diagnostic predictive power of cognitive profiles that distinguish AD and PD using machine learning. This study analyzed 118 patients with AD and 110 patients with PDD, and all subjects were 60 years or older. In order to develop the PDD prediction model, the dataset was divided into training data (70%) and test data (30%). The prediction accuracy of the model was calculated by the recognition rate. The results of this study show that Parkinson-related non-motor symptoms, such as REM sleep behavior disorders, and cognitive screening tests, such as Korean version of Montreal Cognitive Assessment, were highly accurate factors for predicting PDD. It is required to develop customized screening tests that can detect PDD in the early stage based on these results. Furthermore, it is believed that including biomarkers such as brain images or cerebrospinal fluid as input variables will be more useful for developing PDD prediction models in the future.

Brain Microbiota in Huntington's Disease Patients

One of the most important challenges facing medical science is to better understand the cause of neuronal pathology in neurodegenerative diseases. Such is the case for Huntington's disease (HD), a genetic disorder primarily caused by a triplet expansion in the Huntingtin gene (HTT). Although aberrant HTT is expressed from embryogenesis, it remains puzzling as to why the onset of disease symptoms manifest only after several decades of life. In the present study, we investigated the possibility of microbial infection in brain tissue from patients with HD, reasoning that perhaps mutated HTT could be deleterious for immune cells and neural tissue, and could facilitate microbial colonization. Using immunohistochemistry approaches, we observed a variety of fungal structures in the striatum and frontal cortex of seven HD patients. Some of these fungi were found in close proximity to the nucleus, or even as intranuclear inclusions. Identification of the fungal species was accomplished by next-generation sequencing (NGS). Interestingly, some genera, such as Ramularia, appeared unique to HD patients, and have not been previously described in other neurodegenerative diseases. Several bacterial species were also identified both by PCR and NGS. Notably, a curved and filamentous structure that immunoreacts with anti-bacterial antibodies was characteristic of HD brains and has not been previously observed in brain tissue from neurodegenerative patients. Prevalent bacterial genera included Pseudomonas, Acinetobacter, and Burkholderia. Collectively, our results represent the first attempt to identify the brain microbiota in HD. Our observations suggest that microbial colonization may be a risk factor for HD and might explain why the onset of the disease appears after several decades of life. Importantly, they may open a new field of investigation and could help in the design of new therapeutic strategies for this devastating disorder.

Genetic Variation in Genes Underlying Diverse Dementias May Explain a Small Proportion of Cases in the Alzheimer's Disease Sequencing Project

BACKGROUND/AIMS

The Alzheimer's Disease Sequencing Project (ADSP) aims to identify novel genes influencing Alzheimer's disease (AD). Variants within genes known to cause dementias other than AD have previously been associated with AD risk. We describe evidence of co-segregation and associations between variants in dementia genes and clinically diagnosed AD within the ADSP.

METHODS

We summarize the properties of known pathogenic variants within dementia genes, describe the co-segregation of variants annotated as "pathogenic" in ClinVar and new candidates observed in ADSP families, and test for associations between rare variants in dementia genes in the ADSP case-control study. The participants were clinically evaluated for AD, and they represent European, Caribbean Hispanic, and isolate Dutch populations.

RESULTS/CONCLUSIONS

Pathogenic variants in dementia genes were predominantly rare and conserved coding changes. Pathogenic variants within ARSA, CSF1R, and GRN were observed, and candidate variants in GRN and CHMP2B were nominated in ADSP families. An independent case-control study provided evidence of an association between variants in TREM2, APOE, ARSA, CSF1R, PSEN1, and MAPT and risk of AD. Variants in genes which cause dementing disorders may influence the clinical diagnosis of AD in a small proportion of cases within the ADSP.

Genetic overlap between Alzheimer's disease and Parkinson's disease at the MAPT locus

We investigated the genetic overlap between Alzheimer's disease (AD) and Parkinson's disease (PD). Using summary statistics (P-values) from large recent genome-wide association studies (GWAS) (total n=89 904 individuals), we sought to identify single nucleotide polymorphisms (SNPs) associating with both AD and PD. We found and replicated association of both AD and PD with the A allele of rs393152 within the extended MAPT region on chromosome 17 (meta analysis P-value across five independent AD cohorts=1.65 × 10(-7)). In independent datasets, we found a dose-dependent effect of the A allele of rs393152 on intra-cerebral MAPT transcript levels and volume loss within the entorhinal cortex and hippocampus. Our findings identify the tau-associated MAPT locus as a site of genetic overlap between AD and PD, and extending prior work, we show that the MAPT region increases risk of Alzheimer's neurodegeneration.

Can Alzheimer's type pathology influence the clinical phenotype of Parkinson's disease?

OBJECTIVES

Patients with clinical and pathological diagnosis of Parkinson's disease (PD) may, at death, also be found to have the pathological changes of Alzheimer's disease (AD). With this study we aim to determine the influence of AD pathology on the clinical phenotype of PD.

METHODS

We studied 64 patients who donated their brains to the University of Miami Brain Endowment Bank(TM) and fulfilled the clinical and pathological criteria for PD. For the evaluation of AD pathology we used the CERAD criteria. Dementia was diagnosed, in life, also using standard criteria. Case histories were abstracted and reviewed by one investigator (SP) who then made comparisons between patients.

RESULTS

Patients with AD pathology (PD-AD) were older both at the time of diagnosis and death. The presence of AD pathology did not seem to influence disease duration in our cohort of PD patients. As expected there was a clear relation between AD pathology and dementia but not all PD-AD patients were demented. Psychosis and depression were also found to be more prevalent in the PD-AD patients. In the comparison between demented and non-demented PD-AD patients dementia was more likely to appear in patients with PD and definite criteria for AD.

CONCLUSION

Apart from dementia AD pathology seems to be associated with a number of other clinical characteristics of PD.

Overlap between neurodegenerative disorders

Neurodegenerative disorders are characterized by the formation of distinct pathological changes in the brain, including extracellular protein deposits, cellular inclusions, and changes in cell morphology. Since the earliest published descriptions of these disorders, diagnosis has been based on clinicopathological features, namely, the coexistence of a specific clinical profile together with the presence or absence of particular types of lesion. In addition, the molecular profile of lesions has become an increasingly important feature both in the diagnosis of existing disorders and in the description of new disease entities. Recent studies, however, have reported considerable overlap between the clinicopathological features of many disorders leading to difficulties in the diagnosis of individual cases and to calls for a new classification of neurodegenerative disease. This article discusses: (i) the nature and degree of the overlap between different neurodegenerative disorders and includes a discussion of Alzheimer's disease, dementia with Lewy bodies, the fronto-temporal dementias, and prion disease; (ii) the factors that contribute to disease overlap, including historical factors, the presence of disease heterogeneity, age-related changes, the problem of apolipoprotein genotype, and the co-occurrence of common diseases; and (iii) whether the current nosological status of disorders should be reconsidered.

A grading system of Alzheimer disease lesions in neocortical areas

Progression of neuritic and Abeta pathology in the cerebral cortex during aging and Alzheimer disease is well known, but the chronology of the various types of lesions (Abeta deposition, amyloid formation, inflammation, ubiquitination, tangle formation) within a given area has not been fully elucidated. We examined these lesions in the primary visual cortex (Brodmann area 17), correlating them with the severity of the disease (as evaluated by the cognitive status and the number of cortical samples that contained neurofibrillary tangles). Four 'grades' were identified. At grade 1, only deposits of Abeta peptide were noticed. At grade 2, Congo red positive deposits, and processes containing ubiquitin and cathepsin D immunoreactivity around plaque cores could also be found. At grade 3, neuritic plaques and neuropil threads were present, and at grade 4, neurofibrillary tangles. The density of all the lesions dramatically increased at grade 4. The sequence of isocortical lesions from grade 1 to grade 4 is compatible with a cascade of events beginning with deposition of Abeta peptide and ending with neurofibrillary tangle.

Quantifying the pathology of neurodegenerative disorders: quantitative measurements, sampling strategies and data analysis

The use of quantitative methods has become increasingly important in the study of neurodegenerative disease. Disorders such as Alzheimer's disease (AD) are characterized by the formation of discrete, microscopic, pathological lesions which play an important role in pathological diagnosis. This article reviews the advantages and limitations of the different methods of quantifying the abundance of pathological lesions in histological sections, including estimates of density, frequency, coverage, and the use of semiquantitative scores. The major sampling methods by which these quantitative measures can be obtained from histological sections, including plot or quadrat sampling, transect sampling, and point-quarter sampling, are also described. In addition, the data analysis methods commonly used to analyse quantitative data in neuropathology, including analyses of variance (anova) and principal components analysis (PCA), are discussed. These methods are illustrated with reference to particular problems in the pathological diagnosis of AD and dementia with Lewy bodies (DLB).

Dementia associated with Parkinson's disease

Dementia affects about 40% of patients with Parkinson's disease; the incidence of dementia in these patients is up to six times that in healthy people. Clinically, the prototype of dementia in PD is a dysexecutive syndrome. Loss of cholinergic, dopaminergic, and noradrenergic innervation has been suggested to be the underlying neurochemical deficits. Nigral pathology alone is probably not sufficient for the development of dementia. Although there is some controversy with regard to the site and type of pathology involved, dementia is likely to be associated with the spread of pathology to other subcortical nuclei, the limbic system, and the cerebral cortex. On the basis of more recent studies, the main pathology seems to be Lewy-body-type degeneration with associated cellular and synaptic loss in cortical and limbic structures. Alzheimer's disease-type pathology is commonly associated with dementia but less predictive. Recent evidence from small studies suggests that cholinesterase inhibitors may be effective in the treatment of dementia associated with PD.

Relationship of the extended tau haplotype to tau biochemistry and neuropathology in progressive supranuclear palsy

Two extended haplotypes of the tau gene (H1 and H2) have been described. The frequency of H1 haplotype is increased in progressive supranuclear palsy (PSP). PSP is associated with filamentous tau lesions in neurons and glia, which are reportedly composed exclusively of tau isoforms with four repeats in the microtubule-binding domain (4R tau). To determine the influence of the tau haplotype on tau isoform composition and neuropathology, we studied 25 PSP cases and 6 Alzheimer's disease patients matched for age, sex, and postmortem delay. In the basal ganglia, tau and amyloid burdens were determined to see if there was an effect of concurrent Alzheimer-type pathology, and the ratio of 4R to 3R tau was measured in detergent-insoluble tau fractions. Insoluble tau from PSP was not composed exclusively of 4R tau. All brains had a mixture of 4R and 3R tau, but the ratio was different in Alzheimer's disease and PSP. In Alzheimer's disease there was less 4R than 3R tau, whereas the ratio was reversed in PSP. In PSP cases with concurrent Alzheimer-type pathology, the ratio of 4R to 3R was intermediate between Alzheimer's disease and PSP. The H1 haplotype had no effect on the 4R to 3R ratio or on tau and amyloid burdens. In summary, the H1 haplotype does not have a major influence on the pathological or biochemical phenotype of PSP.

Amyloid beta protein deposition in patients with frontotemporal lobar degeneration: relationship to age and apolipoprotein E genotype

Amyloid beta protein (Abeta) deposition was investigated in the frontal cortex of 54 autopsy cases of frontotemporal lobar degeneration (FTLD) using methenamine silver staining, and immunohistochemistry employing the monoclonal end-specific antibodies BC05 and BA27 to visualize deposits containing Abeta(42(43)) and Abeta(40), respectively. Abeta was detected in 14 (26%) patients, nearly always in the form of diffuse Abeta(42(43)) containing plaques though some cored, neuritic plaques with trace amounts of Abeta(40) were occasionally seen. The 14 patients showing Abeta deposits were significantly older at onset of illness than those 40 patients without Abeta. It was only possible to genotype 46/54 cases, 16 of whom bore at least one copy of the Apolipoprotein E (APOE) epsilon4 allele, giving an allele frequency of 20%. Possession of APOE epsilon4 allele was significantly associated with deposition of Abeta such that 10/16 epsilon4 allele bearers had Abeta deposits. Eight of these ten patients showed only mild to moderate amounts of Abeta, but in two patients, one homozygous and one heterozygous for epsilon4 allele, there was extensive neuritic plaque and neurofibrillary tangle formation. In contrast, only few non-epsilon4 allele bearers (4/30) showed minor Abeta deposits. When stratifying for APOE epsilon4 allele, both bearers and non-bearers of epsilon4 allele with Abeta deposits had a significantly later age at onset than their respective groups without Abeta deposits. We conclude that the likelihood of Abeta deposition, as a secondary and coincidental feature unrelated to the primary pathological process, within the brains of individuals with FTLD will be high if patients have a sufficiently late onset of illness or happen to be a bearer of the APOE epsilon4 allele. Indeed 9/14 patients with Abeta deposits studied here had an onset of illness after 55 years of age and bore APOE epsilon4 allele.

Reduced neuronal activity and reactivation in Alzheimer's disease

1. Alzheimer's disease is a multifactorial disease in which age and APOE-epsilon 4 are important risk factors. Various mutations and even viral infections such as herpes simplex (Itzhaki et al., 1997) may play an additional role. 2. The neuropathological hallmarks of Alzheimer's disease (AD), i.e. amorphous plaques, neuritic plaques (NPs), pretangles, neurofibrillary tangles (NFT) and cell death are not part of a single pathogenetic cascade but are basically independent phenomena. 3. Pretangles can occur in neurons from which the metabolic rate is not altered. However, in brain areas where classical AD changes, i.e. NPs and NFTs, are present, such as the CA1 area of the hippocampus, the nucleus basalis of Meynert and the tuberomamillary nucleus, a decreased metabolic rate is found. Decreased metabolic rate appears to be an independent phenomenon in Alzheimer's disease. It is not induced by the presence of pretangles, NFT or NPs. 4. Decreased metabolic rate may precede cognitive impairment and is thus an early occurring hallmark of Alzheimer's disease, which, in principle, may be reversible. The observation that the administration of glucose or insulin enhances memory in Alzheimer patients also supports the view that Alzheimer's disease is basically a metabolic disease. Moreover, several observations indicate that activated neurons are better able to withstand aging and AD, a phenomenon paraphrased by us as "use it or lose it". It is, therefore, attractive to direct the development of therapeutic strategies towards restimulation of neuronal metabolic rate in order to improve cognition and other symptoms in Alzheimer's disease. A number of pharmacological and non-pharmacological studies support the concept that activation of the brain indeed has beneficial effects on several aspects of cognition and other central functions.

Achromatic neurons in the cortex of progressive supranuclear palsy

Achromatic neurons (AN) in the cerebral cortex are a characteristic feature of several neurodegenerative conditions including Pick's disease, corticobasal degeneration and some cases of primary progressive aphasia. Although AN are occasionally seen in some other diseases, their presence in progressive supranuclear palsy (PSP) has not been previously documented. We found significant numbers of AN in the cerebral cortex of five out of seven cases which had been diagnosed pathologically as PSP. The identification of AN was greatly facilitated by the use of neurofilament immunohistochemistry. The entorhinal and transentorhinal cortices were most frequently involved, but in several cases AN were also seen throughout the neocortex. The presence and number of AN roughly correlated with a history of clinical dementia. This suggests that cortical AN may be a common and important pathological finding in PSP.

Cerebral beta amyloid deposition in patients with malignant neoplasms: its prevalence with aging and effects of radiation therapy on vascular amyloid

We examined immunohistochemically 123 autopsy brains from patients aged between 30 to 59, who died as a result of malignant neoplasms. Using antiserum to amyloid beta protein (A beta), we found that cerebral A beta deposits began in the subjects' fifth decade; its prevalence was 0%, 9.8% and 21.5% in the fourth, fifth and sixth decades, respectively. The major form of A beta deposition was diffuse-type plaques, although one third of the brains with A beta deposition showed amyloid angiopathy. Subpial A beta deposition is frequently associated with amyloid angiopathy. The prevalence of cerebral A beta deposits was about two times higher in the patients who had received brain radiation therapy (27.8%) compared to non-radiated patients (14.8%). Amyloid angiopathy was much more prominent (P < 0.05) with radiation therapy (22.2%) than without (8.0%). We found that cerebral A beta-deposition is dependent on aging, even in patients with malignant tumors and at beginning in their forties, and that brain radiation therapy is a possible risk factor of A beta deposition, especially in the form of amyloid angiopathy.

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

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

Apolipoprotein E genotype in diverse neurodegenerative disorders

While the apolipoprotein E (ApoE) epsilon 4 allele is a recognized risk factor for Alzheimer's disease (AD), an association of epsilon 4 with other neurodegenerative diseases (NDs) has not been extensively explored. We examined 51 cases of neuropathologically confirmed ND. After eliminating 18 cases exhibiting pathology sufficient to warrant an additional diagnosis of AD, three disorders characterized by tau-related cytoskeletal pathology, i.e., Pick's disease, corticobasal degeneration, and progressive supra-nuclear palsy, showed increased epsilon 4 frequencies. Since the number of cases within each category was small, these increased epsilon 4 frequencies were not statistically significant. beta-Amyloid (beta A4) immunoreactive diffuse plaques were observed in many of these cases. While we cannot eliminate the possibility that these patients were destined to develop AD, these changes may merely reflect an independent association of epsilon 4 with amyloid deposition. These preliminary data affirm the need for further study of well-characterized cases to explore the relationship of ApoE to cytoskeletal pathology and ND.

beta-Amyloid (A beta) deposition in elderly non-demented patients and patients with Alzheimer's disease

beta-amyloid (A beta) deposition in the medial temporal lobe (MTL) was studied in elderly non-demented (ND) cases and in patients with Alzheimer's disease (AD). In AD, A beta deposits were present throughout the MTL although density was less in the hippocampus than the adjacent cortical regions. In the ND cases, no A beta deposits were recorded in 6 cases and in the remaining 8 cases, A beta deposits were confined to the cortical regions adjacent to the hippocampus. The mean density of A beta deposits in the cortical regions examined was greater in AD than in the ND cases but there was a significant overlap between the two groups. The ratio of mature to diffuse A beta deposits was greater in the ND than the AD cases. In both patient groups, A beta deposits formed clusters in the cortex and many tissues exhibited a regular distribution of clusters along the cortex parallel to the pia. The mean dimension of the A beta clusters was greater in AD than in the ND cases. Hence, few aspects of A beta deposition appeared to consistently separate AD from ND cases. However, the spread of A beta pathology between modular units of the cortex and into regions of the hippocampus could be factors in the development of AD.

Dorothy Russell Memorial Lecture. The molecular pathology of Alzheimer's disease: are we any closer to understanding the neurodegenerative process?

Alzheimer's disease, the most common cause of dementia in the elderly, is rapidly becoming epidemic in the western world, with major social and economic ramifications. Thus enormous international scientific efforts are being made to increase our understanding of the pathogenesis of this disease, with the eventual goal of developing beneficial therapy. The two major neuropathological hallmarks of Alzheimer's disease (AD) are extracellular senile plaques, the principal component of which is the A beta amyloid peptide, and intraneuronal neurofibrillary tangles, which are composed of aggregated tau protein in the form of paired helical filaments (PHF). In the past decade, since the major proteinaceous components of these pathological markers have been identified, great strides have been made in elucidating the biochemical processes which may underlie their abnormal deposition and aggregation in Alzheimer's disease. Simultaneously, extensive population genetic analyses have identified mutations in the A beta amyloid precursor protein (APP) in a small number of pedigrees with familial Alzheimer's disease (FAD) whilst other FAD cases have been linked to an, as yet, unidentified marker on chromosome 14. Most recently, inheritance of the type 4 allele of apolipoprotein E has also been identified as a risk factor in sporadic AD. The challenge facing scientists now is to incorporate this wealth of exciting new biochemical and genetic data into a coherent model which can explain the long established neurochemical and histopathological lesions characteristic of AD.

Analysis of staining methods for different cortical plaques in Alzheimer's disease

This study evaluated current methods for demonstrating and categorizing cortical plaques, with the aim of establishing objective methodology for future diagnostic evaluation. Analysis of four methods of tissue processing revealed that the highest numbers of plaques were identified in formalin-fixed, paraffin-embedded tissue regardless of the stain used. Analysis of three silver stains and four immunohistochemical dilutions of an antibody to beta A4 protein revealed that the recent silver method published by Garvey et al. [(1990) J Histotechnol 14: 39-42] was equivalent to beta A4 immunohistochemistry in demonstrating the highest number of plaques. Plaque differentiation was easier and more reliable in silver compared to beta A4-stained sections, although the number of identifiable small compact plaques was significantly reduced in silver-stained sections. These studies show that plaque differentiation may be compromised by tissue processing and staining protocols. The establishment of superior methods may provide better diagnostic resolution for patients with Alzheimer's disease.

The neuropathology of progressive supranuclear palsy

The macroscopical, histological, ultrastructural and immunocytochemical features of progressive supranuclear palsy (PSP) are reviewed. Recent investigations have revealed important differences in the distribution, ultrastructure and immunocytochemical profile of neurofibrillary tangles in PSP and in Alzheimer's disease. Cortical involvement, as demonstrated by the presence of tangles and neuropil threads has extended the neuropathological spectrum of PSP. Quantitative assessments of neuronal populations show neuronal loss, not only in various nuclei of the brainstem, diencephalon and cerebellum, but also in other areas, including the nucleus basalis of Meynert, substantia nigra and neostriatum. A new classification, based on neuropathological criteria, is suggested in order to take into consideration the phenotypic heterogeneity of PSP. This new classification distinguishes three types: typical, atypical and combined cases. Typical (Type 1) cases conform to the original definition of PSP. Type 2, atypical cases are variants of the histological changes characteristic of PSP: either the severity or the distribution of abnormalities, or both of these deviate from the typical pattern. Cases with combined pathology belong to type 3 group: in these the typical pathology of PSP is accompanied by lesions characteristic of another neurodegenerative or vascular disease.

Evidence that transmitter-containing dystrophic neurites precede paired helical filament and Alz-50 formation within senile plaques in the amygdala of nondemented elderly and patients with Alzheimer's disease

Immunocytochemical techniques were employed to examine the temporal ordering whereby amyloid beta-protein (A beta P) and neuronal elements collectively come together to form senile plaques in Alzheimer's disease (AD). Specifically, we addressed three questions: (1) whether A beta P deposition precedes or follows neuritic changes; (2) whether paired helical filament (PHF) formation is an early or late event in the genesis of the dystrophic neurites which participate in plaque formation; and (3) whether the density of senile plaques displays any relationship with the prevalence of PHF or Alz-50 containing neurons. To address these questions we studied the amygdala from a group of patients with AD, a group of nondemented age-matched individuals exhibiting a sufficient number of senile plaques to be classified by neuropathological criteria as AD, and a group of age-matched controls without AD pathology. Amyloid-bearing plaques were demonstrated by A beta P immunolabeling and thioflavine-S staining. Neuritic changes in the form of dystrophic neurites were observed with the aid of antibodies against PHF, Alz-50, as well as antibodies against several neuropeptides (i.e., substance P, somatostatin, and neurotensin) and the acetylcholine biosynthetic enzyme, choline acetyltransferase. By using a graded range of pathologic changes both within and across the patient population to provide us with a means of evaluating plaque deposition from its earliest to most advanced stages of development, we observed in patients and/or regions of the amygdala displaying a mild degree of pathologic change A beta P deposition in the absence of any neuritic changes. With increasing density of A beta P, however, we began to observe dystrophic neurites within plaques. In regions of relatively few plaques, the dystrophic neurites were immunolabeled only with antibodies against the various neurotransmitters and they lacked evidence of cytoskeletal pathology (i.e., Alz-50 or PHF). Only as the density of A beta P increased further within a region, were dystrophic neurites observed that exhibited Alz-50 or PHF. In no instance did we observe a relationship between the density of A beta P deposition and the density of Alz-50 or PHF-immunoreactive neurons. Collectively, our data suggest that the deposition of A beta P is an early pathologic event in senile plaque formation. Thereafter, swollen neurites can be seen in the vicinity of A beta P. This early neuritic response, which can first be visualized by immunolabeling for one or another transmitter substance, is followed by alterations in the cytoskeleton as recognized initially by antibodies to Alz-50 and subsequently by the presence of PHF.

Amyloid beta-protein as a substrate interacts with extracellular matrix to promote neurite outgrowth

Progressive deposition of amyloid beta-protein (A beta) in brain parenchyma and blood vessels is a characteristic feature of Alzheimer disease. Recent evidence suggests that addition of solubilized synthetic A beta to medium may produce toxic or trophic effects on cultured hippocampal neurons. Because soluble A beta may not accumulate in significant quantities in brain, we asked whether immobilized A beta peptide as a substrate alters neurite outgrowth from cultured rat peripheral sensory neurons. This paradigm may closely mimic the conditions in Alzheimer disease brain tissue, in which neurites contact insoluble, extracellular aggregates of beta-amyloid. We detected no detrimental effects of A beta substrate on neurite outgrowth. Rather, A beta in combination with low doses of laminin or fibronectin enhanced neurite out-growth from these neuronal explants. Our results suggest that insoluble A beta in the cerebral neuropil may serve as a neurite-promoting matrix, perhaps explaining the apparent regenerative response of neurites observed around amyloid plaques in Alzheimer disease. Moreover, in concert with the recent discovery of A beta production by cultured neurons, our data suggest that A beta plays a normal physiological role in brain by complexing with the extracellular matrix.

Alzheimer's disease-like dystrophic neurites characteristically associated with senile plaques are not found within other neurodegenerative diseases unless amyloid beta-protein deposition is present

Swollen, bulbous-shaped (dystrophic) neurites are a common pathologic feature of Alzheimer's disease (AD) and represent one of the most abundant neuritic abnormalities within the brains of patients with this disease. In the present study, we sought to determine whether the dystrophic neurites which are observed in association with senile plaques are unique to AD or whether they are characteristic of a more generalized process of neuritic and/or neuronal degeneration which can be observed in other neurodegenerative diseases. To accomplish this, we examined post-mortem brain material from patients with AD, Parkinson's disease (PD), Parkinson's disease with associated AD, Parkinson's disease with dementia yet without AD pathology, Huntington's disease (HD), Pick's disease and normal age-matched controls (NC). Using a battery of antibodies to amyloid beta-protein (A beta P), paired-helical filaments (PHF), tyrosine hydroxylase, substance P, neurotensin, and somatostatin we found that immunolabeled dystrophic neurites of the type characteristically observed in AD, were seen only in cases and in brain regions where A beta P deposition was present. More specifically, brain areas known to display severe afferent and/or local degenerative changes such as the caudate and putamen in all three PD groups, the caudate in the HD cases, and the temporal cortex in the HD and Pick's cases were conspicuously free of these swollen neurites unless A beta P deposition was also present.(ABSTRACT TRUNCATED AT 250 WORDS)

Intermediary metabolism disturbance in AD/SDAT and its relation to molecular events

1. Early-onset dementia of Alzheimer type (EODAT; AD) and late-onset dementia of Alzheimer type (LODAT; SDAT) are heterogenous in origin. 2. A common superordinate pathobiochemical principle in the etiopathogenesis of both types of dementia is neuronal energy failure with subsequent abnormalities in cellular Ca2+ homeostasis and glucose-related amino acid metabolism. 3. These metabolic abnormalities are assumed to occur first at axodendritic terminals of the acetylcholinergic-glutamatergic circuit and to cause morphological damage at synaptic sites. 4. Metabolic stress and structural damage at synaptic sites may induce enhanced formation of APP and its cleavage product amyloid. 5. Energy-metabolism related abnormalities along with functional and structural changes at synaptic sites of the acetylcholinergic-glutamatergic circuit may precede the formation of amyloid in DAT brain.

Brain oxidative energy and related metabolism, neuronal stress, and Alzheimer's disease: a speculative synthesis

A reduction in the cerebral metabolic rate of glucose is one of the most predominant abnormalities generally found in the Alzheimer brain, whereas the cerebral metabolic rate of oxygen is diminished only slightly or not at all at the beginning of this dementive disorder. From the cerebral metabolic rates of oxidized glucose and oxygen, the cerebral adenosine triphosphate (ATP) formation rate was calculated in incipient early-onset, incipient late-onset, and stable advanced dementia of the Alzheimer type (DAT). A reduction in ATP formation by various amounts was found, ranging from at least 7% in incipient early-onset DAT, from around 20% in incipient late-onset DAT, and from 35% up to more than 50% in stable advanced dementia. The cerebral diminution in energy availability, along with a loss of functionally important amino acids, ammonia toxicity, supposed membrane damage, dysregulation of Ca2+ homeostasis, and glycogen accumulation in the incipient stages of DAT are assumed to be stress-related abnormalities capable of inducing the formation of heat shock proteins. These events may lead to an enhanced generation of amyloid precursor protein in earlier states of DAT. If abnormally cleaved, amyloid A4 protein may be produced in increased amounts. From the results discussed in this article it is deduced as a speculative synthesis that perturbations in brain oxidative energy and related metabolism may precede the generation of amyloid precursor protein and the formation of plaques in the brain affected by incipient DAT.

Beta A4 deposition in the temporal cortex of adults with Down's syndrome

The deposition of beta A4 has been quantified in the temporal cortex of 9 adults (4 male, 5 female) with Down's syndrome (DS), mean age (+/- SD) 54.7 +/- 8.8 years (range 41-67 years) at the time of death. Immunostaining with antibodies, raised to different portions of the beta A4 protein, showed a greater number of deposits than were seen with traditional silver impregnation or amyloid stains. Antibody to beta A4(1-10) identified fewer plaques than the antibody to beta A4(12-28), the mean ratio of beta A4(1-10)/beta A4(12-28) plaques being 0.30 +/- 0.10 (mean +/- SD). Morphologically, 'diffuse' and 'neuritic' deposits could be distinguished but there was no significant difference in the beta A4(1-10)/beta A4(12-28) ratio according to plaque morphology, nor did the ratio change with age. Quantitatively, the beta A4(12-28) load in the temporal cortex of DS patients was high, occupying some 14% of the field area, and it was not related to the age of the subject over the range studied. Similarly, the total beta A4(12-28) plaque count was high and not age-related. The proportion of morphological plaque types visualised by the Glees and Marsland silver impregnation and by beta A4(12-28) immunostaining were compared. In both techniques 'diffuse' plaques (D) were predominant in the younger subjects and the proportion of 'neuritic' plaques (N) increased with age. The relative proportions of cored plaques (Cp) and plaque cores (C) did not change significantly with age.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenylyl cyclase activity in postmortem human brain: evidence of altered G protein mediation in Alzheimer's disease

The effects of agonal status, postmortem delay, and age on human brain adenylyl cyclase activity were determined in membrane preparations of frontal cortex from a series of 18 nondemented subjects who had died with no history of neurological or psychiatric disease. Basal and guanosine 5'-O-(3-thiotriphosphate)-, aluminum fluoride-, and forskolin-stimulated enzyme activities were not significantly reduced over an interval from death to postmortem of between 3 and 37 h and were also not significantly different between individuals dying with a long terminal phase of an illness and those dying suddenly. Basal and aluminum fluoride-stimulated enzyme activities showed a negative correlation with increasing age of the individual. In subsequent experiments, basal and guanosine 5'-O-(3-thiotriphosphate)-, aluminum fluoride-, and forskolin-stimulated enzyme activities were compared in five brain regions from a series of eight Alzheimer's disease and seven matched nondemented control subjects. No significant differences were observed between the groups for either basal activity or activities in response to forskolin stimulation of the catalytic subunit of the enzyme. In contrast, enzyme activities in response to stimulation with guanosine 5'-O-(3-thiotriphosphate) and aluminum fluoride were significantly reduced in preparations of neocortex and cerebellum from the Alzheimer's disease cases compared with the nondemented controls. Lower guanosine 5'-O-(3-thiotriphosphate)-, but not aluminum fluoride-, stimulated activity was also observed in preparations of frontal cortex from a group of four disease controls compared with nondemented control values. The disease control group, which contained Parkinson's disease and progressive supranuclear palsy patients, showed increased forskolin-stimulated activity compared with both the nondemented control and the Alzheimer's disease groups. These findings indicate a widespread impairment of G protein-stimulated adenylyl cyclase activity in Alzheimer's disease brain, which occurs in the absence of altered enzyme catalytic activity and which is unlikely to be the result of non-disease-related factors associated with the nature of terminal illness of individuals.

Pathological changes in the brain of a patient with familial Alzheimer's disease having a missense mutation at codon 717 in the amyloid precursor protein gene

The brain of a 61-year-old patient with familial Alzheimer's disease, showing a missense (valine----glycine) mutation at codon 717 of the amyloid precursor gene, has been examined at postmortem. Sections of brain showed pathological features entirely typical of Alzheimer's disease with no unusual characteristics. It seems therefore that this particular mutation is indeed pathogenic and that the altered amyloid precursor protein resulting from expression of this mutation is processed in a way that triggers or promotes the pathological cascade of Alzheimer's disease.

Deposition of amyloid beta protein in non-Alzheimer dementias: evidence for a neuronal origin of parenchymal deposits of beta protein in neurodegenerative disease

In two elderly patients with frontal lobe dementia and in two others with progressive aphasia an inverse relationship between the severity of beta protein deposition and the principal pathology of these disorders was noted. Deposition of beta protein occurred only in areas of cortex where functional (viable) neurones were still present and was absent where neuronal decimation had taken place. Such findings suggest that the presence of functional neurones is necessary for beta protein deposition to occur and, therefore, that neurones may be the source of the amyloid protein that is deposited within brain parenchyma not only in these disorders but also in other conditions, particularly Alzheimer's disease.

A case of progressive supranuclear palsy with widespread senile plaques

A case of progressive supranuclear palsy (PSP) with frontal lobe atrophy is reported, in which many senile plaques were widely distributed in the neocortex, the entorhinal cortex, the amygdala, and, to a lesser extent, the cerebellar cortex, but not in the hippocampus. Most of the plaques were of the diffuse and primitive types. They were well visualized by beta-protein immunostaining, modified Bielschowsky staining and methenamine silver staining, but were not seen by Bodian staining. The widespread distribution of senile plaques in the cerebral and cerebellar cortices was far beyond that seen in normal aging, and was reminiscent of concomitant Alzheimer's disease (AD). Unlike AD, however, this case had neither senile changes in the hippocampus nor neurofibrillary tangles in the amygdala and entorhinal cortex. It seems that many senile plaques may appear widely in the cerebral cortex and even, to a lesser extent, in the cerebellar cortex of some patients with PSP. Additional case studies using sensitive silver and amyloid antibody preparations are required to elucidate the presence of senile plaques in the cerebral cortex of PSP.

Is the pattern of nerve cell loss in aging and Alzheimer's disease a real, or only an apparent, selectivity?

The pattern of neuronal loss from the brain in Alzheimer's disease (AD) is selective, not on the basis of neurotransmitter type, metabolic character or trophic dependence, but only in relationship to the anatomical connection of all affected cell types with the association cortex. The "selectivity" of the process of AD seems to lie with local factors within the cerebral cortex whose presence (or absence) links the processes that lead to the deposition of amyloid (A4) protein, to the neuritic response that results in the production and accumulation of abnormal tau proteins and which, ultimately, form the neurofibrillary tangle and bring about the demise of the neurone.

Proteolytic cleavage of the Alzheimer's disease amyloid A4 precursor protein

Amyloid A4 protein (beta-protein) is deposited in the brain of a patient with Alzheimer's disease (AD) as one of the main components of extracellular cerebrovascular amyloid, as well as neurofibrillary tangles. It is derived from a precursor protein, and its formation has been considered to be a rate-limiting step for brain degeneration in AD. In this article, proteolytic cleavage events that can degrade amyloid precursor protein are reviewed with respect to how the topographical distribution of the proteinase and its substrates disturbs normal processing steps in AD brain.

Constant neurofibrillary changes in the neocortex in progressive supranuclear palsy. Basic differences with Alzheimer's disease and aging

Neocortical neurofibrillary tangles (NFT) revealed by Bodian technique and anti-tau immunolabelling were seen in 5/5 cases of progressive supranuclear palsy (PSP) aged 58-76 years. These lesions differed from Alzheimer's disease or age-related changes: (1) they were most frequent in the precentral gyrus (Brodmann's area 4) whereas associative areas are predominantly lesioned in Alzheimer's disease; (2) they affected mainly large pyramidal neurons and small cells, relatively sparing the cell population selectively involved in Alzheimer's disease; (3) they predominated in layers V and VI of area 4, whereas NFT are most dense in layers III and V in Alzheimer's disease; (4) mature senile plaques (1/5 cases) and beta-amyloid diffuse deposits (3/5 cases), which usually precede or go together with NFT in Alzheimer's disease were rare or absent (2/5) in PSP. Neuropil threads and tufts of abnormal fibres were also seen. In addition, NFT and neuropil threads were found in the hippocampus. PSP is thus another example of abnormal storage of tau developing in the neocortex in the absence of beta-amyloid deposits. It might prove a useful model for the understanding of the mechanisms of localization and spreading of tau storage in the brain.

The prevalence of amyloid (A4) protein deposits within the cerebral and cerebellar cortex in Down's syndrome and Alzheimer's disease

The extent of amyloid deposition within the cerebellum and the cerebral cortex was assessed and compared, using anti-amyloid protein (A4) immunostaining and a novel methenamine silver method, in 20 patients aged between 60 and 77 years with Alzheimer's disease (AD), 29 patients aged between 13 and 71 years with Down's syndrome (DS), 26 demented patients with disorders other than AD and DS and in 20 non-demented elderly individuals of age range 60-102 years. In AD, amyloid deposits were noted in the cerebellar cortex in 90% of patients and in the meningeal vessels of the cerebellum in 80% of patients. In DS, amyloid deposits were seen in the cerebellar cortex in 82% of patients over 30 years of age and was universal in patients over 50 years of age. Overall, in DS, amyloid deposits were present in the meningeal vessels of the cerebellum in 79% of patients, but were present in 94% of those patients over 50 years of age. The sites of amyloid deposition in the cerebellar cortex were (poorly) detected by lectin histochemistry (Concanavalin A binding) in only 40% of patients with AD and 43% of all patients with DS (69% of those over 50 years of age). No amyloid deposits were seen in either the cerebellar cortex or its meningeal vessels in any of the 20 non-demented elderly individuals nor in any of the non-Alzheimer demented patients. The cerebellar amyloid deposits were never associated with a neuritic change [i.e. as characterised by the presence of (tau-positive) paired helical filaments (PHF)] and neurofibrillary tangles were seen only in a few cells of the dentate nucleus in a single patient with AD and in three of the elderly DS patients. Amyloid deposits were numerous in the cerebral cortex of all patients with AD and in all, except the 13-year-old patient, with DS. In all the AD patients and in most of the DS patients over 30 years of age, many of the cerebral cortical amyloid deposits were associated with neurites and were strongly recognised by lectin histochemistry. Amyloid deposits were present within the meningeal vessels of the cerebral cortex in 75% patients with AD and 72% of patients, over 30 years of age, with DS (82% of those over 50 years of age). These data indicate that the process of amyloidosis in AD and in elderly DS patients is not restricted to the cerebral cortex and may affect other grey matter regions, particularly the cerebellum.(ABSTRACT TRUNCATED AT 400 WORDS)