Cationic dyes reveal proteoglycans structurally integrated within the characteristic lesions of Alzheimer's disease

Summary The cationic dyes ruthenium red (RR) and cuprolinic blue (CB) were used to preserve proteoglycans (PGs) for visualization at the ultrastructural level in brain tissue from seven cases of Alzheimer's disease (obtained at autopsy within 3–4 h after death). PGs were visualized as RR-positive granules specifically localized to the amyloid fibrils in neuritic plaques. In neurofibrillary tangles, RR granules were localized to the paired helical filaments and straight filaments usually at a consistent periodicity of 40–70 nm. CB, known to preserve PGs as short punctate filaments, also demonstrated PGs specifically localized to the amyloid fibrils in neuritic plaques and in association with paired helical filaments and straight filaments in neurofibrillary tangles. Persistent staining with CB at magnesium chloride concentrations of 0.3 and 0.7 M in the neuritic plaques suggested the presence of highly sulfated PGs, whereas abolishment of CB staining at 0.7 M magnesium chloride in the neurofibrillary tangles implied that different PGs and/or glycosaminoglycans were present in the neurofibrillary tangles. The specific ultrastructural localization of PGs to the characteristic lesions in Alzheimer's disease suggests that PGs are part of a complex structural network with amyloid fibrils in neuritic plaques and the filamentous structures present in neurofibrillary tangles.Supported by the Alzheimer's Disease Research Program of the American Health Assistance Foundation, The Alzheimer's Disease and Related Disorders Association Pilot Grant 87-019 and the Friends of Alzheimer's Research in conjunction with the University of Washington Alzheimer's Disease Research Center     

Ultrastructural localization of butyrylcholinesterase on neurofibrillary degeneration sites in the brains of aged and Alzheimer's disease patients

Butyrylcholinesterase histochemical techniques were applied to vibratome sections of several cortical areas from the brains of non-demented aged and of Alzheimer's disease patients. At the light microscope level, all the senile plaque types and all the structures with neurofibrillary degeneration showed butyrylcholinesterase reaction product, whereas nearby neuronal perikarya and axons on the same slides remained unstained. Areas containing stained elements were selected, re-sectioned, and finally observed under the electron microscope. Focusing on the sites of neurofibrillary degeneration, butyrylcholinesterase reaction product was found in both intra- and extracellular neurofibrillary tangles, in neurites associated with plaques, and in neuropil threads that were either axons or dendrites. This reaction product was exclusively located over filament bundles, and sometimes covered them so completely that they could not be identified. When the filaments were only partially covered, it was possible to identify them as either paired helical filaments or straight filaments. Occasionally, neurofibrillary tangles, neuropil threads and plaque-associated neurites, all of them containing either paired helical filaments or straight filaments, were found to be completely free of butyrylcholinesterase reaction product. The origin and possible role of butyrylcholinesterase, which is ultrastructurally localized over elements presenting neurofibrillary degeneration, is discussed.     

Ultrastructure of the neuropil threads in the Alzheimer brain: their dendritic origin and accumulation in the senile plaques

Summary Thread-like structures immunoreactive with paired helical filaments and tau antisera were demonstrated as mesh-works in the neocortices of five brains with Alzheimer-type dementia, but not in those of five normal aged control brains. The ultrastructure of the threads was examined using paired routine electron microscopic ultrathin sections and adjacent 0.4-m-thick semithin sections, immunostained for protein. Outside the protein-positive senile plaques, neuropil threads appeared sporadically as small slender neurites, containing either regularly constricted or straight filaments. These neurites often showed dendritic profiles. Similar threads were also seen within the senile plaques. The threads were accumulated in amyloid fibril-rich primitive plaques, but not in amyloid fibril-poor diffuse plaques. The presence of these threads was closely associated with neurofibrillary tangle formation. Our findings suggest that wide-spread change of the neuropil neurites, neuropil threads or curly fibers, both outside and inside of the senile plaques are dendritic in origin and play an important role in the clinical manifestation of dementia.Supported by a Grant-in-aid for Scientific Research from the Japanese Ministry of Education, Science and Culture     

Comparison of the neurofibrillary pathology in Alzheimer’s disease and familial presenile dementia with tangles

Alzheimer’s disease (AD) is characterised neuropathologically by the presence of abundant extracellular β-amyloid deposits and intracellular neurofibrillary lesions consisting of neurofibrillary tangles, neuropil threads and senile plaque neurites which contain paired helical filaments (PHFs) made of hyperphosphorylated microtubule-associated protein tau. A new familial form of presenile dementia with neurofibrillary pathology and no β-amyloid deposits has been described recently [Sumi et al. (1992) Neurology 42: 120–127]. We have compared the tau pathology in this familial form of presenile dementia with that of AD. To this end we have used electron microscopy, immunoblotting and immunohistochemistry with phosphorylation-dependent (PHF1, AT8, AT100, AT180, AT270, 12E8) and phosphorylation-independent (BR133, BR134) anti-tau antibodies. We show that in the two diseases dispersed PHFs are structurally, biochemically and immunologically identical; they are stained by all anti-tau antibodies used and on immunoblots PHF-tau appears as three major bands of 60, 64 and 68 kDa. However, while the anti-tau antibodies stain neurofibrillary tangles, neuropil threads and neuritic plaques in AD brain, no neuritic plaques are found in familial presenile dementia. These results indicate that in the two diseases tau undergoes the same modifications; they confirm that neurofibrillary tangles and neuropil threads like those in AD can exist independently of β-amyloid deposits and that their presence is associated with dementia.     

Cholinesterases colocalize with sites of neurofibrillary degeneration in aged and Alzheimer's brains

Acetylcholinesterase and butyrylcholinesterase have been associated with structures undergoing neurofibrillary degeneration, as well as with all types of senile plaques, in non-demented aged and Alzheimer's brains. At the electron microscope level, the reaction product of both enzymes, appeared to decorate paired helical filaments, straight filaments and A4 amyloid fibrils. Recent studies showed that cholinesterases were associated with amyloid at early stages, e.g., in diffuse plaques. In the present study, the interrelationship of cholinesterases to structures undergoing neurofibrillary degeneration was analyzed further. Tau immunoreactivity was compared to the staining pattern observed with the two esterases. Double protocols consecutively performed on the same sections, and counterstaining with thioflavin-S, confirmed the presence of cholinesterases in all structures with neurofibrillary degeneration. The conclusion that cholinesterases consistently colocalize with both neurofibrillary bundles and A4 amyloid fibrils at all stages of their accumulation, allows us to speculate on the possible role that these enzymes may play in either the formation or the consolidation of fibrillary aggregates.Supported by Fondo de Investigaciones Sanitarias de la Seguridad Social No. 93/0198, Spain     

Abnormal phosphorylation of tau precedes ubiquitination in neurofibrillary pathology of Alzheimer disease

On tissue sections of Alzheimer brain, 4 antibodies to tau immunolabel not only neurofibrillary tangles, neuritic plaques and neuropil threads but also the tangle-free cytoplasm of a subset of hippocampal and cortical neurons we believe to be at a stage of alteration preceding the formation of paired helical filaments (PHF). Pretreatment of tissue sections with alkaline phosphatase leads to an increase in staining intensity and in number of immunoreactive lesions with antibodies directed to an amino terminal and to a mid-region of the tau molecule. The diffuse neuronal staining could not be observed with any of 7 monoclonal antibodies recognizing ubiquitin. We conclude (1) that abnormal phosphorylation of tau occurs prior to its incorporation into PHF and leads to its accumulation in the nerve cell body and (2) that ubiquitin is seen associated only when a neurofibrillary tangle is already formed.     

Immunohistochemical study of the hippocampus in parkinsonism-dementia complex on Guam

This investigation concerns the expression of paired helical filaments, tau protein, ubiquitin, beta-amyloid protein, and synaptophysin in the hippocampus of patients with parkinsonism-dementia complex on Guam (PDC) and Alzheimer's disease. Alzheimer's neurofibrillary tangles (NFTs) were identified in all cases of PDC and Alzheimer's disease by the modified Bielschowsky method, with which they were readily detected, and by immunohistochemical procedures using antibodies to paired helical filaments, tau protein, and ubiquitin. Observations regarding the different morphological stages indicated that NFTs were similar in PDC and Alzheimer's disease. The same markers were also useful for detecting neuropil threads, abundant in the CA1 field and the subiculum in both diseases. In the CA4 region of some PDC cases, prominent threads were noted. No senile plaques or amyloid angiopathies were seen in the hippocampus of the PDC cases examined. There was a significant decrease in synaptophysin immunoreactivity, most pronounced in the subfield CA1 and the subiculum, as well as in the outer molecular layer of the dentate gyrus, in both disorders.     

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

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

Reappraisal of the fine structure of Alzheimer's neurofibrillary tangles

Summary Alzheimer's neurofibrillary tangles were studied by electron microscopy. The study includes four cases of Alzheimer's disease, two cases of atypical senile dementia, and one case of progressive supranuclear palsy. In Alzheimer's disease the tangles were composed of either straight filaments or paired helical filaments. In progressive supranuclear palsy the tangles were composed of 15 nm straight filaments or helical filaments. A few straight filaments were mixed with paired helical filaments. In atypical senile dementia, both straight and paired helical filaments comprised the tangles and one type of filaments appeared to intermingle with the other in the same neurons.     

Neuropil threads of Alzheimer's disease show a marked alteration of the normal cytoskeleton

Abnormal neurites, neuropil threads, are a widespread and characteristic lesion of Alzheimer's disease likely to play a major role in the cognitive impairment of this disease. Contrary to normal neurites, neuropil threads contain straight and paired helical filaments that contain the microtubule-associated protein tau and ubiquitin. It is not known whether these abnormal filaments are added to or replace the normal cytoskeleton. In this study, we examined the fine structure of neuropil threads and carried out a morphometric analysis of the neurofilaments and abnormal filaments contained in the neuropil threads by using an antiserum to tau and colloidal gold immuno-electron microscopy. Almost 70% of the neuropil threads contained straight or paired helical filaments with no neurofilaments. The total number of filaments in each neuropil thread remained essentially unchanged either when straight or paired helical filaments were present alone or when they coexisted either together or with neurofilaments. When the three types of filaments were expressed as a proportion of the total, a linear inverse correlation was found between neurofilaments and straight filaments as well as between straight and paired helical filaments. Approximately 10% of the neuropil threads were found to be myelinated axons. It is concluded that straight filaments are likely to replace neurofilaments, that they in turn might be replaced by paired helical filaments, and that this process occurs in axons as well as dendrites.     

Alzheimer's disease: areal and laminar pathology in the occipital isocortex

Summary Sensitive and specific silver methods for demonstration of (1) amyloid and/or precursors of amyloid and (2) neurofibrillary changes were applied to examine the pathology revealed by the occipital isocortex in cases of Alzheimer's disease and age-matched controls. In general, amyloid and/or precursors of amyloid are encountered in plaque-like formations. Large numbers of amyloid plaques occur in layers that only occasionally harbor neuritic plaques. Amyloid deposits can be found in abundance in the occipital cortex of demented individuals exhibiting an only sparse number of neuritic plaques. In demented individuals the striate area contains almost as much amyloid as the parastriate area or the peristriate region. Neurofibrillary changes are encountered in neuritic plaques, neurofibrillary tangles, and neuropil threads. Neuritic plaques are predominantly found in layers II and III. Their density changes even within the boundaries of architectonic units. Large numbers of plaques are found in the cortex covering the depth of the sulci. The number of neurofibrillary tangles increases abruptly when passing the striate/parastriate and the parastriate/peristriate boundaries. The neuropil threads may densely fill a layer without the presence of neurofibrillary tangles (layer V of the striate area). Neuropil threads contribute a substantial part to the total amount of the intraneuronally deposited pathological material.Supported by the Deutsche Forschungsgemeinschaft     

Transformation of degenerating neurofibrils into amyloid substance in Alzheimer's disease: histochemical and immunohistochemical studies

Degenerating neurofibrils (DNF), which are composed of paired helical filaments (PHF) and amyloid fibrils (AF), are the 2 characteristic pathological fibrillar deposits in Alzheimer cortex. These fibrils were simultaneously studied by 2 techniques: The immunolabelling with a specific antiserum raised against PHF and elective thioflavine S staining of AF. In neuronal perikaryons, neurofibrillary tangles (NFT) consist of 3 populations: firstly, strongly immunolabelled tangles were weakly thioflavine-stained. Secondly, less dense tangles were weakly immunolabelled but strongly thioflavine-stained. Thirdly, ghost tangles which correspond to extracellular NFT were exclusively thioflavine-stained. Thus, it is likely that NFT are degraded to form extracellular AF. Around neuritic plaques and some vessels with amyloid angiopathy, immunolabelled neurites, thioflavine-stained neurites and transition figures were also observed. On the other hand, the central core of plaques and pathological vessel walls were strongly thioflavine-stained but were never immunoreactive. In conclusion, these observations favour catabolism of PHF bundles found in NFT and in degenerating neurites into an amyloid substance. This amyloid substance seems different from other amyloid deposits found in the central core of neuritic plaques and vessel walls.     

Immunohistochemical localization of beta-amyloid precursor protein sequences in Alzheimer and normal brain tissue by light and electron microscopy.

Immunohistochemical staining with antibodies directed against four segments of the amyloid precursor protein (APP) was studied by light and electron microscopy in normal and Alzheimer (AD) brain tissue. The segments according to the Kang et al. sequence were: 18-38 (T97); 527-540 (R36); 597-620 (1-24 of beta-amyloid protein [BAP], R17); and 681-695 (R37) (Kang et al. [1987]: Nature 325:733-736). The antibodies recognized full length APP in Western blots of extracts of APP transfected cells. They stained cytoplasmic granules in some pyramidal neurons in normal appearing tissue from control and AD cases. In AD affected tissue, the antibodies to amino terminal sections of APP stained tangled neurons and neuropil threads, and intensely stained dystrophic neurites in senile plaques. By electron microscopy, this staining was localized to abnormal filaments. The antibody to the carboxy terminal segment failed to stain neurofibrillary tangles or neuropil threads; it did stain some neurites with globular swellings. It also stained globular and elongated deposits in senile plaque areas. The antibody against the BAP intensely stained extracellular material in senile plaques and diffuse deposits. By electron microscopy, the antibodies all stained intramicroglial deposits. Some of the extracellular and intracellular BAP-positive deposits were fibrillary. Communication between intramicroglial and extracellular fibrils was detected in plaque areas. These data suggest the following sequence of events. APP is normally concentrated in intraneuronal granules. In AD, it accumulates in damaged neuronal fibers. The amino terminal portion binds to abnormal neurofilaments. Major fragments of APP are phagocytosed and processed by microglia with the BAP portion being preserved. The preserved BAP is then extruded and accumulates in extracellular tissue.     

Alzheimer disease: curly fibers and tangles in organs other than brain.

The filamentous brain lesions that define Alzheimer disease (AD) consist of senile plaques and neurofibrillary tangles. Undulated pathological filaments--curly fibers or neuropil threads--also occur in the neuropil. Beta-amyloid precursor proteins are synthesized by many cells outside the central nervous system and recently, deposition of beta-amyloid-protein was reported to occur in non-neuronal tissues. In addition, increasing data claim the importance of chronic inflammation in the pathogenesis of AD. These observations suggest that AD may be a widespread systemic disorder. Here we report that pathological argyrophilic filaments with histochemical properties of amyloid showing striking morphological similarity to curly fibers and/or tangles accumulate not only in ependymal layer and in epithelial cells of choroid plexus, but also in several other organs (e.g. liver, pancreas, ovary, testis, thyroid) in AD. The ependyma, choroid plexus, and various organs of 39 autopsy cases were analyzed. In search of curly fiber and tangle-like changes in organs other than brain, 395 blocks from 21 different tissues of 24 AD cases, 5 cases with discrete or moderate AD-type changes, and 10 control cases were investigated. We found in non-neuronal cells "curly fibers" or "tangles" immunoreactive with antibodies to P component, Tau-protein, ubiquitin, fibronectin, and Apolipoprotein-E, but lacking immunoreactivity with antibodies to neurofilament proteins. Ultrastructurally they consist of densely packed straight and paired helical filaments and closely resemble neurofibrillary tangles and neuropil threads. These observations indicate that the formation of "curly fibers" and "tangles" is not unique to the central nervous system. The results suggest that AD might be a systemic disorder or that similar fibrillary changes to tangles and curly fibers may also be associated with other amyloidosis than beta-amyloidosis. Further investigations are necessary to understand the pathogenetic interest of these fibrillary changes outside the CNS.     

Progressive supranuclear palsy-like syndrome in two siblings of a consanguineous marriage.

Two siblings of a consanguineous marriage showed identical clinical features consisting of supranuclear vertical ophthalmoplegia, bradykinesia, rigidity, stooped posture, pseudobulbar palsy, and dementia, all beginning in the sixth decade. There was no history of encephalitis or of exposure to known chemicals. L-Dopa therapy was only partially and temporarily effective. Autopsy of one patient revealed extensive neurofibrillary degeneration with prominent involvement of the limbic system. There were no senile plaques or Lewy bodies. Under electron microscopy, there were paired helical filaments as well as 15-nm-wide straight tubules. The diffuse appearance of neurofibrillary tangles, predominant in the limbic system, and familial occurrence are unusual in progressive supranuclear palsy; these cases may, therefore, constitute a different, distinctive clinicopathologic disease.     

Alzheimer's disease and the zinc theory

In Alzheimer's disease, the Primum Movens is amyloid production on precapillaries: dysphoric angiopathy, and capillaries: senile plaques. Cerebral amyloid alone may be asymptomatic. Clinical symptoms of amnesia appear when amyloid induces neighbouring neuritic alterations: paired helical filaments and distant neuronal body lesions: neurofibrillary tangles. Hypothesis: the amyloid induces zinc deficiency which produces the tangles. In Alzheimer's disease, cerebral zinc decreases particularly in the hippocampus. Without amyloid, neurofibrillary tangles are produced by metalotoxicity and therefore probably brain zinc displacement: by lead: encephalopatia saturnica, by calcium deficiency: Guam's encephalopathy, by aluminium, by blood-brain-barrier disturbances probably leading to an abnormal entry of metals in the brain (dementia pugilistica, viral encephalitides). Neurofibrillary tangles may be produced by deficiency of the following zinc enzymes: 1) those of DNA metabolism inducing abnormal DNA and therefore abnormal protein synthesis: paired helical filaments and neurofibrillary tangles; 2) of glutamate-dehydrogenase resulting in an excitotoxic increase of glutamate, which may produce neurofibrillary tangles, particularly in the hippocampus rich in glutamate pathways; 3) those of neuronal detoxication: superoxide-dismutase, carbonic anhydrase, lactate-dehydrogenase leading to neuronal toxicity particularly in the hippocampus normally rich in superoxide dismutase; 4) those of neurotransmitters metabolisms (opioid peptides, GABA, acetylcholine). Therapeutic implication: a non-toxic zinc complex crossing the Blood-Brain-Barrier should be useful.     

Late onset dementia with argyrophilic grains and subcortical tangles or atypical progressive supranuclear palsy?

Most clinically demented elderly patients are found at autopsy to have Alzheimer's disease, multi-infarct dementia, Parkinson's disease, Pick's disease, or Creutzfeldt-Jakob disease. We studied 5 patients clinically characterized by late onset dementia whose brains showed no pathological evidence of Alzheimer's disease, or any other specific neuropathological diagnosis. We found argyrophilic grains, coiled bodies, abundant Alz-50-positive and thioflavine S-negative neurofibrillary tangles, and neuropil threads in the hippocampus, entorhinal cortex, locus ceruleus, substantia nigra, subthalamic nucleus, and inferior olives. Ultrastructurally, the grains, threads, and tangles were composed of straight tubulofilamentous structures, 25 nm in diameter, similar to those found in patients with progressive supranuclear palsy but different from the paired helical filaments of patients with Alzheimer's disease. These findings suggest that the late onset dementia with argyrophilic grains syndrome is also characterized by the presence of tangles and threads with the topographical distribution of progressive supranuclear palsy.     

Ultrastructural characteristics of tau filaments in tauopathies: Immuno‐electron microscopic demonstration of tau filaments in tauopathies

The microtubule‐associated protein tau aggregates into filaments in the form of neurofibrillary tangles, neuropil threads and argyrophilic grains in neurons, in the form of variable astrocytic tangles in astrocytes and in the form of coiled bodies and argyrophilic threads in oligodendrocytes. These tau filaments may be classified into two types, straight filaments or tubules with 9–18 nm diameters and “twisted ribbons” composed of two parallel aligned components. In the same disease, the fine structure of tau filaments in glial cells roughly resembles that in neurons. In sporadic tauopathies, individual tau filaments show characteristic sizes, shapes and arrangements, and therefore contribute to neuropathologic differential diagnosis. In frontotemporal dementias caused by tau gene mutations, variable filamentous profiles were observed in association with mutation sites and insoluble tau isoforms, including straight filaments or tubules, paired helical filament‐like filaments, and twisted ribbons. Pre‐embedding immunoelectron microscopic studies were carried out using anti‐3‐repeat tau and anti‐4‐repeat tau specific antibodies, RD3 and RD4. Straight tubules in neuronal and astrocytic Pick bodies were immunolabeled by the anti‐3‐repeat tau antibody. The anti‐4‐repeat tau antibody recognized abnormal tubules comprising neurofibrillary tangles, coiled bodies and argyrophilic threads in progressive supranuclear palsy (PSP) and corticobasal degeneration. In the pre‐embedding immunoelectron microscopic study using the phosphorylated tau AT8 antibody, tuft‐shaped astrocytes of PSP were found to be composed of bundles of abnormal tubules in processes and perikarya of protoplasmic astrocytes. In this study, the 3‐repeat tau or 4‐repeat tau epitope was detected in situ at the ultrastructural level in abnormal tubules in representative pathological lesions in Pick’s disease, PSP and corticobasal degeneration.     

Mechanisms of tau-induced neurodegeneration

Alzheimer disease (AD) and related tauopathies are histopathologically characterized by a specific type of slow and progressive neurodegeneration, which involves the abnormal hyperphosphorylation of the microtubule associated protein (MAP) tau. This hallmark, called neurofibrillary degeneration, is seen as neurofibrillary tangles, neuropil threads, and dystrophic neurites and is apparently required for the clinical expression of AD, and in related tauopathies it leads to dementia in the absence of amyloid plaques. While normal tau promotes assembly and stabilizes microtubules, the non-fibrillized, abnormally hyperphosphorylated tau sequesters normal tau, MAP1 and MAP2, and disrupts microtubules. The abnormal hyperphosphorylation of tau, which can be generated by catalysis of several different combinations of protein kinases, also promotes its misfolding, decrease in turnover, and self-assembly into tangles of paired helical and or straight filaments. Some of the abnormally hyperphosphorylated tau ends up both amino and C-terminally truncated. Disruption of microtubules by the non-fibrillized abnormally hyperphosphorylated tau as well as its aggregation as neurofibrillary tangles probably impair axoplasmic flow and lead to slow progressive retrograde degeneration and loss of connectivity of the affected neurons. Among the phosphatases, which regulate the phosphorylation of tau, protein phosphatase-2A (PP2A), the activity of which is down-regulated in AD brain, is by far the major enzyme. The two inhibitors of PP-2A, I₁^PP2A and I₂^PP2A, which are overexpressed in AD, might be responsible for the decreased phosphatase activity. AD is multifactorial and heterogeneous and involves more than one etiopathogenic mechanism.     

Cytoskeletal pathology in familial cerebral amyloid angiopathy (British type) with non-neuritic amyloid plaque formation

The histological features of familial cerebral amyloid angiopathy (British type) with non-neuritic amyloid plaque formation (FAB) include deposition of amyloid, (supposedly associated with the C-terminal fragments of both α- and β-tubulin), in small cerebral and spinal arteries, hippocampal amyloid plaques and neurofibrillary tangles (NFTs) as well as ischaemic white matter changes. In the present study we report on the cytoskeletal pathology that occurs in association with FAB. Sections from the hippocampus and cerebellum of three cases from three unrelated families were stained with silver impregnation methods and antibodies to antigens including tau, neurofilaments, ubiquitin and glial fibrillary acidic protein. Electron microscopic examination of the hippocampus was carried out in one case. All hippocampal subregions contained large numbers of NFTs and neuropil threads (NT), which were stained with both phosphorylation-dependent and phosphorylation-independent tau antibodies and ultrastructurally were found to be composed of paired helical filaments (PHFs). Although the majority of the amyloid plaques were of the non-neuritic type, distended PHF-containing and tau-positive neurites were seen in close proximity of a minority of the hippocampal plaques. The perivascular amyloid deposits of the cerebellum contained numerous ubiquitin-positive granular elements similar to those seen in cerebellar Aβ amyloid plaques in Alzheimer’s disease. In FAB severe cytoskeletal pathology is present in areas most affected by amyloid plaque deposits, thus suggesting a localised neurotoxic effect of the poorly characterised amyloidogenic peptide characteristic of this condition. Received: 2 June 1998 / Revised, accepted: 11 August 1998