A morphological analysis of senile plaques in the brains of non-demented persons of different ages using silver, immunocytochemical and lectin histochemical staining techniques

Basal forebrain cholinergic system in the dementias: Vulnerability, resilience, and resistance

The basal forebrain cholinergic neurons (BFCN) provide the primary source of cholinergic innervation of the human cerebral cortex. They are involved in the cognitive processes of learning, memory, and attention. These neurons are differentially vulnerable in various neuropathologic entities that cause dementia. This review summarizes the relevance to BFCN of neuropathologic markers associated with dementias, including the plaques and tangles of Alzheimer's disease (AD), the Lewy bodies of diffuse Lewy body disease, the tauopathy of frontotemporal lobar degeneration (FTLD-TAU) and the TDP-43 proteinopathy of FTLD-TDP. Each of these proteinopathies has a different relationship to BFCN and their corticofugal axons. Available evidence points to early and substantial degeneration of the BFCN in AD and diffuse Lewy body disease. In AD, the major neurodegenerative correlate is accumulation of phosphotau in neurofibrillary tangles. However, these neurons are less vulnerable to the tauopathy of FTLD. An intriguing finding is that the intracellular tau of AD causes destruction of the BFCN, whereas that of FTLD does not. This observation has profound implications for exploring the impact of different species of tauopathy on neuronal survival. The proteinopathy of FTLD-TDP shows virtually no abnormal inclusions within the BFCN. Thus, the BFCN are highly vulnerable to the neurodegenerative effects of tauopathy in AD, resilient to the neurodegenerative effect of tauopathy in FTLD and apparently resistant to the emergence of proteinopathy in FTLD-TDP and perhaps also in Pick's disease. Investigations are beginning to shed light on the potential mechanisms of this differential vulnerability and their implications for therapeutic intervention.

Chronic traumatic encephalopathy: neurodegeneration following repetitive concussive and subconcussive brain trauma

Chronic Traumatic Encephalopathy (CTE) is a neurodegenerative disease thought to be caused, at least in part, by repetitive brain trauma, including concussive and subconcussive injuries. It is thought to result in executive dysfunction, memory impairment, depression and suicidality, apathy, poor impulse control, and eventually dementia. Beyond repetitive brain trauma, the risk factors for CTE remain unknown. CTE is neuropathologically characterized by aggregation and accumulation of hyperphosphorylated tau and TDP-43. Recent postmortem findings indicate that CTE may affect a broader population than was initially conceptualized, particularly contact sport athletes and those with a history of military combat. Given the large population that could potentially be affected, CTE may represent an important issue in public health. Although there has been greater public awareness brought to the condition in recent years, there are still many research questions that remain. Thus far, CTE can only be diagnosed post-mortem. Current research efforts are focused on the creation of clinical diagnostic criteria, finding objective biomarkers for CTE, and understanding the additional risk factors and underlying mechanism that causes the disease. This review examines research to date and suggests future directions worthy of exploration.

Mild traumatic brain injury: a risk factor for neurodegeneration

Recently, it has become clear that head trauma can lead to a progressive neurodegeneration known as chronic traumatic encephalopathy. Although the medical literature also implicates head trauma as a risk factor for Alzheimer's disease, these findings are predominantly based on clinical diagnostic criteria that lack specificity. The dementia that follows head injuries or repetitive mild trauma may be caused by chronic traumatic encephalopathy, alone or in conjunction with other neurodegenerations (for example, Alzheimer's disease). Prospective longitudinal studies of head-injured individuals, with neuropathological verification, will not only improve understanding of head trauma as a risk factor for dementia but will also enhance treatment and prevention of a variety of neurodegenerative diseases.

Neuronal and axonal loss are selectively linked to fibrillar amyloid-{beta} within plaques of the aged primate cerebral cortex

The amyloid-beta peptide (Abeta) deposited in plaques in Alzheimer's disease has been shown to cause degeneration of neurons in experimental paradigms in vivo and in vitro. However, it has been difficult to convincingly demonstrate toxicity of native amyloid deposits in the aged and Alzheimer brains. Here we provide evidence that the fibrillar conformation of Abeta (fAbeta) deposited in compact plaques is associated with the pathologies observed in Alzheimer brains. fAbeta containing compact but not diffuse plaques in the aged rhesus cortex contained activated microglia and clusters of phosphorylated tau-positive swollen neurites. Scholl's quantitative analysis revealed that the area adjacent to fAbeta, containing compact but not diffuse plaques in aged rhesus, aged human, and Alzheimer's disease cortex, displays significant loss of neurons and small but statistically significant reduction in the density of cholinergic axons. These observations suggest that fAbeta toxicity may not be restricted to cultured cells and animal injection models. Rather, fAbeta deposited in native compact plaques in aged and AD brains may exert selective toxic effects on its surrounding neural environment.

Cortical PIB binding in Lewy body disease is associated with Alzheimer-like characteristics

About one fourth of Lewy body disease (LBD) patients show cortical beta-amyloid load, basically a hallmark of Alzheimer disease (AD). Using [11C]PIB-PET, we tested whether LBD patients with beta-amyloid burden differ from those without with respect to demographic, clinical, biochemical and genetic parameters. Thirty-five LBD subjects (9 patients with Lewy body dementia, DLB; 12 demented Parkinson patients, PDD; 14 non-demented PD, PDND) underwent [11C]PIB-PET, and were classified as either PIB(+) or PIB(-) according to cortical PIB uptake. PIB+ and PIB(-) patients were then compared according to demographic, clinical, biochemical and genetic parameters. None of the PDND, but four PDD and four DLB subjects were PIB+. In PIB+ subjects, ApoE4 prevalence was higher, CSF Abeta42 levels were lower and, among demented patients, PIB-binding was associated with a lower MMSE score. Motor symptoms were not associated with PIB binding. Thus, LBD patients with cortical beta-amyloid show characteristics usually observed in AD.

Specific mechanism for blood inflow stimulation in brain area prone to Alzheimer's disease lesions

The present study describes the specific two-stage mechanism that intensifies blood supply to the brain area comprising amygdala, hippocampus, olfactory bulb, entorhinal cortex, and neocortex (AHBC). Cholinergic neurons from the nuclei of basal forebrain induce vasodilatory effect through release of acetylcholine. In physiological aging the efficacy of this neuronal system declines, while intensive formation of amyloidogenic peptides starts. These peptides at low, picomolar concentrations activate alpha7 nicotinic acetylcholine receptors, thus enhancing angiogenesis and in so doing restoring blood supply to the AHBC area.

Mutations in TTBK2, encoding a kinase implicated in tau phosphorylation, segregate with spinocerebellar ataxia type 11

The microtubule-associated protein tau (encoded by MAPT) and several tau kinases have been implicated in neurodegeneration, but only MAPT has a proven role in disease. We identified mutations in the gene encoding tau tubulin kinase 2 (TTBK2) as the cause of spinocerebellar ataxia type 11. Affected brain tissue showed substantial cerebellar degeneration and tau deposition. These data suggest that TTBK2 is important in the tau cascade and in spinocerebellar degeneration.

Nitric oxide synthase-containing neurons in the amygdaloid nuclear complex of the rat

The nitric oxide-producing neurons in the rat amygdala (Am) were studied, using reduced nicotinamide adenine dinucleotide phosphate diaphorase (NADPHd) histochemistry. Almost all nuclei of the Am contained NADPHd-positive neurons and fibers, but the somatodendritic morphology and the intensity of staining of different subpopulations varied. The strongly stained neurons displayed labeling of the perikaryon and the dendritic tree with Golgi impregnation-like quality, whilst the dendrites of the lightly stained neurons were less successfully followed. Many strongly positive neurons were located in the external capsule and within the intraamygdaloid fiber bundles. A large number of small, strongly stained cells was present in the amygdalostriatal transition area. In the Am proper, a condensation of deeply stained cells occurred in the lateral amygdaloid nucleus. In the basolateral nucleus, the strongly NADPHd-positive neurons were few, and were located mainly along the lateral border of the nucleus. These cells clearly differed from the large, pyramidal, and efferent cells. The basomedial nucleus contained numerous positive cells but most of them were only lightly labeled. A moderate number of strongly stained neurons appeared in the medial division of the central nucleus, and a larger accumulation of strongly positive cells was present in the lateral and the capsular divisions. The medial amygdaloid nucleus contained numerous moderately stained neurons and displayed the strongest diffuse neuropil staining in Am. In the nucleus of the lateral olfactory tract, the first layer contained only NADPHd-stained axons, in the second layer, there were numerous moderately stained cells, and in the third layer, a few but deeply stained neurons. From the cortical nuclei, the most appreciable number of stained neurons was seen in the anterior cortical nucleus. The anterior amygdaloid area contained numerous NADPHd-positive neurons; in its dorsal part the majority of cells were only moderately stained, whereas in the ventral part the neurons were very strongly stained. The intercalated amygdaloid nucleus lacked NADPHd-positive neurons but an appreciable plexus of fine, tortuous axons was present. In the intra-amygdaloid part of the bed nucleus of the stria terminalis (st) some lightly stained cells were seen but along the entire course of st strongly stained neurons were observed. Some Am nuclei, and especially the central lateral nucleus and the intercalated nucleus, display considerable species differences when compared with the primate Am. The age-related changes of the nitrergic Am neurons, as well as their involvement in neurodegenerative diseases is discussed.

Loss of calbindin-D28K from aging human cholinergic basal forebrain: relation to plaques and tangles

Reports from our laboratory have indicated a substantial and specific loss of the calcium binding protein calbindin-D28K (CB) from the human basal forebrain cholinergic neurons (BFCN) in the course of normal aging. In the present set of experiments we determined the relationship between the age-related loss of CB and the presence and density of plaques and tangles in the brains of normal elderly. In 23 cases ranging in age from 20 to 93 years of age we observed plaques and tangles in the BFCN region and the cerebral cortex in a subset of cases. Plaques were seen in the basal forebrain in very few cases above 65 years. Plaque density in the basal forebrain and cortex displayed a significant negative correlation with the proportion of the BFCN, which contained CB immunoreactivity. However, the brains of 2 elderly cases that displayed a substantial loss of CB from the BFCN did not contain any plaques. Tangles were observed in the BFCN as early as 26 years of age. Only tangles in the entorhinal cortex showed a significant negative correlation with the loss of CB from the BFCN. It is likely that loss of CB from the BFCN and formation of plaques and tangles are part of general age-related processes that occur in parallel rather than being causally related.

Early amyloid deposition in the medial temporal lobe of young Down syndrome patients: a regional quantitative analysis

The presence of the neuropathological alterations of Alzheimer's disease (AD) in essentially all older Down syndrome (DS) patients suggests that the examination of younger DS patients may clarify the early pathological progression of AD. We examined the hippocampus and parahippocampal-inferior temporal gyri of 42 DS patients (ages 4 days to 38 years) for the deposition of amyloid beta protein (Abeta) using both a modified Bielschowsky stain and immunohistochemistry for Abeta protein. The parahippocampal and inferior temporal gyri demonstrated Abeta staining in cases as young as 8 years of age. As age and degree of Abeta deposition increased, staining included the CA-1/subiculum and dentate molecular layer followed then by the remainder of the CA hippocampal regions. The first neuritic plaques were observed in the CA-1/subiculum, despite this being a later region of Abeta deposition. Although Abeta staining increased with age, there was substantial variability in the severity of Abeta deposition within age groups. These results suggest that within the hippocampal/parahippocampal region there is a progressive stereotypic deposition of Abeta. The variable severity of Abeta deposition within age groups suggests that other factors, besides DS, may be contributing to the timing and severity of Abeta deposition.

Cerebral cortex pathology in aging and Alzheimer's disease: a quantitative survey of large hospital-based geriatric and psychiatric cohorts

In order to explore the relationships between the involvement of specific neuronal populations and cognitive deterioration, and to compare the hierarchical patterns of cortical involvement in normal brain aging and Alzheimer's disease, over 1200 brains from elderly subjects without cognitive deficits, as well as from patients with age-associated memory impairment and Alzheimer's disease, were examined. Our results suggest that the neuropathological changes associated with normal brain aging and Alzheimer's disease affect select cortical circuits at different points in time. Extensive hippocampal alterations are correlated with age-associated memory impairment, whereas substantial neurofibrillary tangle formation in neocortical association areas of the temporal lobe is a prerequisite for the development of Alzheimer's disease. Despite several lines of evidence involving amyloid deposit in the pathogenesis of Alzheimer's disease and Down's syndrome, our observations indicate that there is no correlation between senile plaque densities and degree of dementia in both disorders. In contrast to younger elderly cases, in the ninth and tenth decades of life, there is a differential cortical involvement in that parietal and cingulate areas are early affected in the course of Alzheimer's disease, and neocortical senile plaques densities are strongly correlated with the severity of dementia. Moreover, Alzheimer's disease symptomatology is characterized in these very old patients by high neurofibrillary tangle densities in the anterior CA1 field, but not in the entorhinal cortex and inferior temporal cortex. These observations are discussed in the light of the hypothesis of global corticocortical disconnection and with respect to the notion of selective neuronal vulnerability in Alzheimer's disease.

Diagnostic criteria for the neuropathological assessment of Alzheimer's disease: current status and major issues

A Consensus Conference focusing on Alzheimer's disease (AD) took place in November 1996 to recommend uniform evaluation procedures and diagnostic criteria, co-sponsored by the National Institute on Aging and the Reagan Institute of the Alzheimer's Association. In conjunction with this conference, we reviewed diagnostic practices in current use, together with various neuropathological criteria proposed since 1985. Difficulties were identified in developing "gold standard" criteria for diagnosis and case classification of AD based upon the current state of knowledge. Working criteria for use within research contexts were proposed that acknowledged the realities of scientific limitations by inclusion of a broad and heterogeneous category of "uncertain" cases. (Eventually, methods will be developed for identifying these cases as preclinical AD, dementia due to multiple causes or non-AD, but this is not now possible.) Within applied contexts, the use of CERAD guidelines was supported. Finally, recommendations generated at the Consensus Conference were discussed, emphasizing the rapid pace of recent scientific advancement and the need for ongoing empirical reevaluation and modification of the Group's proposal.

Neuropathological changes in chronic adult hydrocephalus: cortical biopsies and autopsy findings

BACKGROUND

The cortical changes resulting from chronic hydrocephalus in adults are not well defined.

METHODS

Retrospective analysis of twenty-one patients (age 64-88 years) with a clinical diagnosis of "normal pressure hydrocephalus" who underwent cortical biopsy at the time of intracranial pressure monitoring or shunt insertion, and eight patients who were biopsied but not shunted. Eleven brains (age 26-92 years), seven from patients who could be considered to have "normal pressure hydrocephalus", were also examined following autopsy. Age- and sex-matched control brains with small ventricles and no history of dementia were compared to the hydrocephalic brains. Senile plaques and neurofibrillary tangles were assessed semiquantitatively and a non-parametric statistical analysis was employed.

RESULTS

Five biopsies exhibited both senile plaques and rare neurofibrillary tangles, while two had only neurofibrillary tangles. Neurofibrillary tangles were more prevalent in hydrocephalic brains than in controls. There was no difference in the prevalence of senile plaques between the two groups. Grumose bodies in the substantia nigra were identified in five autopsy brains, a prevalence higher than in control brains.

CONCLUSIONS

These pathological features are not specific for hydrocephalus; however, they suggest that long-standing ventriculomegaly is associated with degenerative brain changes in sites beyond the periventricular white matter. The presence of senile plaques in cortical biopsies from hydrocephalic patients does not appear to be a contraindication to shunting; however a prospective study in patients undergoing intracranial pressure monitoring would better address the issue.

Alzheimer-type of pathological changes in Chinese

There has been no previous description of the pathological features of Alzheimer's disease and little description of Alzheimer-type changes in Chinese brains. In this study, we examined the brains of 17 cases of Alzheimer's disease and concurrently 95 consecutive autopsy cases of non-demented patients aged above 60. Six standard regions of the brains were stained for beta-amyloid immunostaining, Bielschowsky and Bodian. Neuritic plaques, neurofibrillary tangles and diffuse plaques were quantified as per mm2. The Alzheimer's disease brains exhibited a marked increase of neurodegenerative changes over the non-demented brains. Plaque counts were similar to those proposed by Khachaturian (1985; Arch. Neurol. 42: 1097-1105) and CERAD, although the distribution of tangles was more variable with some regions of the neocortex containing few or no tangles. For the non-demented brains, overall neuritic plaques were seen in 31% and neurofibrillary tangles were seen in 42% of cases, with the overall plaque score being 1.8 per mm2 and tangle score being 0.7 per mm2. No age-dependent variation of plaque count and tangle count could be demonstrated in this group of elderly brains. Comparison with similar studies of Caucasians suggests that neuritic plaques and neurofibrillary tangles were less frequently encountered in aging Chinese brains than among the western populations.

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.

Early association of reactive astrocytes with senile plaques in Alzheimer's disease

The fibrillar beta-amyloid protein (A beta) plaques of Alzheimer's disease (AD) are associated with reactive astrocytes and dystrophic neurites and have been suggested to contribute to neurodegenerative events in the disease. We recently reported parallel in vitro and in situ findings, suggesting that the adoption of a reactive phenotype and the colocalization of astrocytes with plaques in AD may be mediated in large part by aggregated A beta. Thus, A beta-mediated effects on astrocytes may directly affect disease progression by modifying the degenerative plaque environment. Alternatively, plaque-associated reactive astrocytosis may primarily represent a glial response to the neural injury associated with plaques and not significantly contribute to AD pathology. To investigate the validity of these two positions, we examined the differential colocalization of reactive astrocytes and dystrophic neurites with plaques. Hippocampal sections from AD brains--ranging in neuropathology from mild to severe--were triple-labeled with antibodies recognizing A beta protein, reactive astrocytes, and dystrophic neurites. We observed not only plaques containing both or neither cell type, but also plaques containing (1) reactive astrocytes but not dystrophic neurites and (2) dystrophic neurites but not reactive astrocytes. The relative proportion of plaques colocalized with reactive astrocytes in the absence of dystrophic neurites is relatively high in mild AD but significantly decreases over the course of the disease, suggesting that plaque-associated astrocytosis may be an early and perhaps contributory event in AD pathology rather than merely a response to neuronal injury. These data underscore the potentially significant contributions of reactive astrocytosis in modifying the plaque environment in particular and disease progression in general.

The morphologic and neurochemical basis of dementia: aging, hierarchical patterns of lesion distribution and vulnerable neuronal phenotype

Alzheimer's disease is the most common form of dementia in elderly individuals. Approximately 11% of the population older than 65, and up to 50% of individuals over 85 qualify as having "probable Alzheimer's disease" on the basis of clinical evaluation. Since the early description of the clinical symptoms and neuropathologic features of Alzheimer's disease, there has been an extraordinary growth in the knowledge of the morphologic and molecular characteristics of Alzheimer's disease. Although the pathogenetic events that lead to dementia are not yet fully understood, several hypotheses regarding the formation of the hallmark pathologic structures of Alzheimer's disease have been proposed. In this context, the use of specific histochemical techniques in the primate brain has greatly expanded our understanding of neuron typology, connectivity and circuit distribution in relation to neurochemical identity. In this respect, very specific subsets of cortical neurons and cortical afferents can be identified by their particular content of certain neurotransmitters and structural proteins. In this article, we discuss the possible relationships between the distribution of pathologic changes in aging, Alzheimer's disease, and possibly related dementing conditions, in the context of the specific elements of the cortical circuitry that are affected by these alterations. Also, evidence for links between the neurochemical phenotype of a given neuron and its relative vulnerability or resistance to the degenerative process are presented in order to correlate the distribution of cellular pathologic changes, neurochemical characteristics related to vulnerability, and affected cortical circuits.

The topographic distribution of brain atrophy in cortical Lewy body disease: comparison with Alzheimer's disease

The topographic distribution of brain atrophy was quantified by image analysis of fixed coronal brain slices from four patients dying with cortical Lewy body disease (CLBD) all with Alzheimer-type pathology and compared to that in four other patients of similar age and gender dying with Alzheimer's disease (AD) alone. The pattern of atrophy in CLBD (+AD) was broadly similar to that in AD alone, suggesting that tissue loss was due mostly to parallel Alzheimer-type pathological changes and that the presence of Lewy bodies in cortical and subcortical neurons contributed little, if anything, to the overall degree of atrophy.

Argyrophilic plaque-like deposits in children

We recently examined the brain from an 8-month-old infant with Down's syndrome and found argyrophilic plaque-like deposits throughout the neocortex and cerebellum. To ascertain the specificity of this observation, we examined 27 additional brains from the pediatric autopsy service, including 1 from another patient with Down's syndrome. To our surprise, similar argyrophilic deposits were found in 16 of these cases. The deposits were equally well stained by three different silver stains and had the same size, shape, and distribution in gray matter as the diffuse amyloid plaques commonly seen in adults. However these structures appeared to be amyloid negative. There were no obvious differences in the primary diagnoses amongst the group of patients with argyrophilic deposits and the group without them, and the origin, permanence, and functional significance of these plaque-like deposits are still unknown. Nonetheless, their recognition is important since they may represent subtle brain injury and since similar structures in adults might easily be misinterpreted as true diffuse amyloid plaques.

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.

Neuropathological changes in the cerebral cortex of 1258 cases from a geriatric hospital: retrospective clinicopathological evaluation of a 10-year autopsy population

To examine the neuropathological and clinical characteristics of cerebral aging, we evaluated retrospectively a non-selected autopsy population of 1258 patients from the Geriatric Hospital of the University of Geneva School of Medicine. The prevalence of Alzheimer's disease increased with age below 90 years of age. In the nonagenarians and centenarians, there was a decline in the number of affected cases. The distribution with age of neurofibrillary tangles and senile plaques varied among the cortical areas studied. The CA1 field of the hippocampus and the inferior temporal cortex displayed increasing densities of neurofibrillary tangles with age, whereas the superior frontal and the occipital cortex were relatively spared, especially in patients in their tenth and eleventh decade. The percentage of cases presenting with senile plaques in the neocortex and hippocampal structure increased with age with a marked predominance of cases with moderate to high senile plaque densities. Neurofibrillary tangles were often observed in the CA1 field and the inferior temporal cortex of non-demented individuals and were present in most cases with Alzheimer's disease. Conversely, the involvement of the superior frontal and occipital cortex was moderate even in demented patients. The distribution of senile plaques was homogeneous in all of the neocortical areas independently of the clinical diagnosis. Moreover, there was no correlation between the presence of neurofibrillary tangles and senile plaques in the cerebral regions studied. These results indicate a differential topography of neurofibrillary tangles and senile plaques, and suggest that overt clinical signs of Alzheimer's disease are linked to the progression of the neurodegenerative process in neocortical areas.

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.

Neuron loss and shrinkage in the amygdala in Alzheimer's disease

Total neuron numbers in the amygdala and in eight of its subnuclei were determined in 9 cases of Alzheimer's disease (AD) and in 6 age-matched controls (AMC). Total neuron numbers were obtained using the fractionator. A neuron loss of 56.3% for the left amygdala and 50.5% for the right amygdala in AD was found, being more severe than previously reported. The subdivisions showed a differential neuron loss ranging from 35.5% in nucleus lateralis of the right amygdala to 70.4% in the nucleus basalis accessorius of the right amygdala. Moreover, a shift in size distribution to smaller neurons could be demonstrated. No left-right hemispheric differences were detected in total neuron numbers in AD and AMC.

Immunocytochemical distribution of peptidergic and cholinergic fibers in the human amygdala: their depletion in Alzheimer's disease and morphologic alteration in non-demented elderly with numerous senile plaques

As part of an ongoing investigation devoted to understanding the pathogenesis of senile plaques, we employed histochemical and immunocytochemical techniques to examine the distribution and cytologic features of acetylcholinesterase (AChE), choline acetyltransferase (ChAT), somatostatin (SOM), neurotensin (NT) and substance P (SP) containing fibers and neurons within the amygdala of: (1) patients with Alzheimer's disease (AD); (2) age-matched non-demented controls (NC); and (3) a group of non-demented cases, who upon postmortem neuropathologic examination exhibited sufficient numbers of senile plaques to be classified as AD. This latter group was referred to as high plaque non-demented (HPND). For every case, the distribution of immunolabeled fibers and neurons were determined for each transmitter throughout the various subnuclei of the amygdala. In addition, in the AD and HPND cases the topographic distribution of senile plaques was determined throughout the amygdala using thioflavine-S and Bielschowsky silver methods. In the amygdala, the distribution and density of senile plaques were not bound by conventional cytoarchitectural groupings but rather were most dense in the ventromedial regions of the amygdala with decreasing density in dorsal and lateral directions. Importantly, the density and distribution of senile plaques failed to correlate with the normal topography and/or density of the various peptidergic or cholinergic fibers within the amygdala. The finding that plaques do not correlate with the topographic distribution of any specific transmitter system suggests that plaques likely do not arise from the degeneration of a single neurotransmitter system (i.e., the cholinergic system). However, the finding that in AD a transmitter is most markedly depleted in regions of greatest plaque density, suggests certain constituents of the plaque (e.g. beta-amyloid) may be contributing to the degeneration of local fibers. The extent to which a transmitter was depleted in AD patients varied considerably among those four investigated with the cholinergic and NT systems displaying the most dramatic reductions, followed by SP and SOM. Despite these differential reductions in fiber density, all four neurotransmitters were found localized within dystrophic neurites and in most instances these dystrophic neurites were associated with thioflavine-positive senile plaques. In contrast to the AD cases, the HPND cases were characterized by no significant reductions in immunolabeled fibers, although immunostained dystrophic neurites were very prevalent in the HPND cases. These data suggest that dystrophic neurites occur very early in the disease process and likely precede the actual loss of fibers when or if it occurs.(ABSTRACT TRUNCATED AT 400 WORDS)

Evidence that transmitter-containing dystrophic neurites precede those containing paired helical filaments within senile plaques in the entorhinal cortex of nondemented elderly and Alzheimer's disease patients

Within the amygdala of elderly subjects and patients with Alzheimer's disease (AD), we recently found evidence suggesting amyloid beta-protein (A beta P) deposition occurs before the appearance of dystrophic neurites. Moreover, these data suggested dystrophic neurites initially lack evidence of cytoskeletal pathology although with time and further maturation, the dystrophic neurites display an altered cytoskeleton as evidenced by their immunoreactivity to Alz-50 and paired-helical filaments (PHF). These findings are of particular relevance to our understanding of the sequence of pathologic events in AD and thus it has become important to determine whether these events are unique to the amygdala or are representative of a more general pattern which can be found throughout the brain. Using a battery of antibodies to markers that are characteristic of AD pathology (i.e., A beta P, PHF, and Alz-50), three peptidergic neurotransmitters (neurotensin, somatostatin, and substance P), and one neurotransmitter biosynthetic enzyme (choline acetyltransferase), we examined the entorhinal cortex (EC) of three groups of subjects (AD, normal elderly, and a group of nondemented elderly with numerous senile plaques). The EC was studied, in part, because it is well recognized as a brain region displaying severe and, most importantly, early pathologic changes. Like the amygdala, we found evidence that amyloid beta-protein immunoreactive (A beta P-IR) and thioflavine-S-positive senile plaques occur within the EC prior to the appearance of transmitter-, Alz-50-, or PHF-immunoreactive dystrophic neurites. We also observed transmitter-immunoreactive dystrophic neurites in the absence of Alz-50 or PHF-immunolabeled dystrophic neurites and transmitter- and Alz-50-IR dystrophic neurites in the absence of those containing PHF. Collectively, these findings were similar to those seen within the amygdala and thus reinforced the concept that A beta P deposition is the primary event in plaque pathology, and this deposition is subsequently followed by the appearance of dystrophic neurites which retain their transmitter phenotype yet lack an altered cytoskeleton. With time, these dystrophic neurites develop cytoskeletal alterations and become immunoreactive to Alz-50 and PHF.

Dementia of frontal lobe type: neuropathology and immunohistochemistry

Brains from 12 patients dying with a clinical diagnosis of frontal lobe dementia have been examined at post mortem. In pathological terms four groups were encountered. Groups A and B showed severe frontal and temporal lobe atrophy characterised histologically in group A by severe neuronal loss, spongiform change of the superficial laminae, and mild astrocytosis; in group B severe neuronal loss was accompanied by intense gliosis but with little or no spongiform change. Two patients in this latter group also showed inclusions in frontal cortex and hippocampus typical of "Pick bodies"; such patients were considered as having classic "Pick's disease". Group C patients showed severe striatal atrophy with variable cortical (frontal or temporal) involvement, with histological changes similar to patients in groups A and B. The single patient in group D showed mild frontotemporal atrophy with spongiform degeneration of the superficial laminae of the cortex and nigral damage, and was considered to have motor neuron disease with dementia. This study is consistent with previous reports showing that the clinical syndrome of frontal lobe dementia is pathologically heterogeneous. However, the nosological relationships within these pathological variants, and between them and conditions such as progressive aphasia were similar histopathological changes are present, remain uncertain.

The topographic distribution of brain atrophy in frontal lobe dementia

The topographic distribution of brain atrophy was quantified by image analysis of fixed brain slices from ten patients dying with dementia of frontal type (DFT) and from six other patients dying with dementia of frontal type with motor neurone disease (DFT + MND). In both groups the atrophy was maximal within frontal, anterior temporal and anterior parietal regions of cortex, although other structures such as the amygdala, caudate nucleus, thalamus and hippocampus were also affected. The magnitude of the atrophy was much greater, in all affected regions, in DFT alone than in DFT + MND. Grey and white matter were affected equally in DFT alone although in DFT + MND a preferential white matter involvement was noted. No differences in the topographic distribution of the atrophy was observed in cases of DFT showing a spongiform degeneration of the cortex compared to those showing a gliotic degeneration with, or without, Pick cells and Pick bodies.

Primary or depressive dementia: mental status screening

In the course of interviewing a patient, several aspects of everyday functioning must be covered to provide a range of observations necessary to suggest a provisional diagnosis. First organized by Adolf Meyer, the mental status examination consists of several techniques which, in recent times, have been shortened, structured and standardized to cover maximal ground in minimal time. In this article, the most popular scales are reviewed psychometrically for their capacity to detect, as first-stage instruments, cognitive impairment suggestive of primary dementia in the context of varying prevalence rates and confounding factors like sensory impairments, sociodemographics and depressive states. Several of the measures are found adequate in some respects though not in others, but all of the better ones, when used as front line implements during clinical intake, regularly improve detection over base rates. An analytical method modelled on ROC procedures is then described contrasting two of them before newer instruments are considered which aim to improve sensitivity at relatively little cost to specificity.

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.

Lectin histochemistry of cerebral microvessels in ageing, Alzheimer's disease and Down's syndrome

A panel of 14 lectins was used to investigate the expression of saccharides by cerebral microvessels (MBV) in ageing, Alzheimer's disease (AD) and Down's syndrome (DS). Broad increases in lectin binding with age may reflect changes in amount and diversity of glycoproteins due to the thickening of the basement membrane (BM) common in older persons. In AD, and in persons over 50 years of age with DS, binding of e-PHA, 1-PHA and PAA was increased beyond that of age alone, as was that of UEA-I and BSA-1B4 in AD, but not in DS. Persons under 50 years of age with DS showed no changes inappropriate to their age. These specific increases in AD and DS may reflect selective disease-related changes in BM and could indicate an impaired blood-brain barrier (bbb) function or integrity. However, because they occur (in DS) after the deposition of amyloid (A4) protein and onset of neurofibrillary degeneration, it is unlikely they induce plaque and tangle formation. Such changes in MBV could stem from the loss of neurones from locus caeruleus, raphe and nucleus basalis (which are thought to innervate MBV and exert control over blood flow and permeability) that occurs in DS after 50 years of age.

The topographic distribution of brain atrophy in Alzheimer's disease

The extent of regional atrophy in ten patients, aged 52-74 years, dying with Alzheimer's disease uncomplicated pathologically by the effects of advanced old age or cerebrovascular disease, was quantified by image analysis of fixed coronal brain slices. Atrophy of the cerebral cortex was globally distributed, although the temporal lobe was most severely affected. Grey and white matter was in general affected equally. Atrophy was also present within the basal ganglia, particularly the caudate nucleus and putamen. Cerebral cortical atrophy is probably due mostly to neurofibrillary degeneration and loss of intrinsic pyramidal cells and their processes (grey matter) and axons (white matter) although loss of ascending subcortical fibres from regions such as nucleus basalis and locus caeruleus will contribute. Atrophy of the basal ganglia may relate to loss of descending cortical projections.

Neuropathological features of Alzheimer's disease in non-demented parkinsonian patients

Two patients with levodopa-responsive Parkinson's syndrome had numerous cortical and striatal senile plaques and some neurofibrillary tangles at necropsy. In addition neurons in the pars compacta of the substantia nigra were severely depleted but there were no Lewy bodies or other neuropathological changes to account for parkinsonism. Neither patient was demented. These pathological findings have not previously been described as a cause of Parkinson's syndrome without associated dementia of Alzheimer's disease type.

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.

Senile plaque neurites in Alzheimer disease accumulate amyloid precursor protein

Senile plaques are polymorphous beta-amyloid protein deposits found in the brain in Alzheimer disease and normal aging. This beta-amyloid protein is derived from a larger precursor molecule of which neurons are the principal producers in brain. We found that amyloid precursor protein (APP)-immunoreactive neurites were involved in senile plaques and that only a subset of these neurites showed markers for the abnormal filaments characteristic of neurofibrillary pathology. In the neocortex of nondemented individuals with senile plaques but spared of neurofibrillary pathology, dystrophic neurites in senile plaques showed only APP accumulation. In contrast, in the brains of Alzheimer patients, virtually all APP-immunoreactive neurites also showed immunoreactivity with ubiquitin, tau, and phosphorylated neurofilaments. The presence of tau and neurofilament epitopes in dystrophic neurites in senile plaques was correlated with the extent of neurofibrillary pathology in the surrounding brain tissue. Accumulation of APP and the formation of neurofibrillary pathology in senile plaque neurites are therefore distinct phenomena. Our findings suggest that APP accumulation in senile plaque neurites occurs prior to tau accumulation and is therefore more closely related to appearance of neuritic dystrophy.

Subtypes and differential laminar distributions of beta A4 deposits in Alzheimer's disease: relationship with the intellectual status of 26 cases

beta A4 immunoreactivity was studied in temporal neocortex, area 22, of 26 cases with graded intellectual status. Sampling was performed in psychometrically assessed women over 75 years, either intellectually normal or affected by senile dementia of Alzheimer type of various degrees of severity. beta A4 antibodies labelled various types of beta A4 deposits in 22/26 cases: (1) small, stellate deposits; (2) diffuse deposits, (3) primitive, (4) classic and (5) compact, or burn-out, plaques. The densities of the stellate deposits, primitive and classic plaques were always positively linked with the severity of the intellectual status, whereas those of the diffuse deposits were not. This was due to a single case with normal mental status and numerous beta A4 deposits. Densities of stellate and diffuse deposits were higher in layers I, III and IV, whereas densities of primitive, classic, and neuritic plaques observed with Bodian's technique were higher in layers II and III. Topographical distribution of each subtype did not vary as a function of the severity of the intellectual status. These data suggest that deposits of beta A4 protein appear a necessary but not a sufficient condition for inducing neuritic plaque formation, in the neocortex as in other brain areas. beta A4 proteins could accumulate either as diffuse deposits, which do not cause an intellectual deficit, or as dense deposits, associated with argyrophilic neurites, i.e., classic neuritic plaques, highly correlated to the intellectual impairment. This evolution could depend on factors which are laminarily distributed in the neocortex.

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)