Electron microscopic structure of the "inclusion bodies" in Pick's disease

Frontotemporal lobar degeneration with TAR DNA-binding protein 43 (TDP-43): its journey of more than 100 years

Frontotemporal lobar degeneration (FTLD) with TDP-43-immunoreactive inclusions (FTLD-TDP) is a neurodegenerative disease associated with clinical, genetic, and neuropathological heterogeneity. An association between TDP-43, FTLD and amyotrophic lateral sclerosis (ALS) was first described in 2006. However, a century before immunohistochemistry existed, atypical dementias displaying behavioral, language and/or pyramidal symptoms and showing non-specific FTLD with superficial cortical neuronal loss, gliosis and spongiosis were often confused with Alzheimer's or Pick's disease. Initially this pathology was termed dementia lacking distinctive histopathology (DLDH), but this was later renamed when ubiquitinated inclusions originally found in ALS were also discovered in (DLDH), thus warranting a recategorization as FTLD-U (ubiquitin). Finally, the ubiquitinated protein was identified as TDP-43, which aggregates in cortical, subcortical, limbic and brainstem neurons and glial cells. The topography and morphology of TDP-43 inclusions associate with specific clinical syndromes and genetic mutations which implies different pathomechanisms that are yet to be discovered; hence, the TDP-43 journey has actually just begun. In this review, we describe how FTLD-TDP was established and defined clinically and neuropathologically throughout the past century.

Microscopic studies on severing properties of actin-binding protein: its potential use in therapeutic treatment of actin-rich inclusions

Actin is an important unit of the cytoskeletal system, involved in many cellular processes including cell motility, signaling, and intracellular trafficking. Various studies have been undertaken to understand the regulatory mechanisms pertaining actin functions, especially the ones controlled by actin-binding proteins. However, not much has been explored about the molecular aspects of these proteins implicated in various diseases. In this study, we aimed to demonstrate the molecular properties of gelsolin, an actin-severing protein on the disassembly of the aggregation of actin-rich intracellular inclusions, Hirano body. We observed a decreasing tendency of actin aggregation by co-sedimentation assay and transmission electron microscopy in the presence of gelsolin. Therefore, we provide suggestive evidence for the use of actin-severing protein in novel therapeutic strategies for neurodegenerative conditions.

Structures of filaments from Pick's disease reveal a novel tau protein fold

The ordered assembly of tau protein into abnormal filamentous inclusions underlies many human neurodegenerative diseases1. Tau assemblies seem to spread through specific neural networks in each disease2, with short filaments having the greatest seeding activity3. The abundance of tau inclusions strongly correlates with disease symptoms4. Six tau isoforms are expressed in the normal adult human brain-three isoforms with four microtubule-binding repeats each (4R tau) and three isoforms that lack the second repeat (3R tau)1. In various diseases, tau filaments can be composed of either 3R or 4R tau, or of both. Tau filaments have distinct cellular and neuroanatomical distributions5, with morphological and biochemical differences suggesting that they may be able to adopt disease-specific molecular conformations6,7. Such conformers may give rise to different neuropathological phenotypes8,9, reminiscent of prion strains10. However, the underlying structures are not known. Using electron cryo-microscopy, we recently reported the structures of tau filaments from patients with Alzheimer's disease, which contain both 3R and 4R tau11. Here we determine the structures of tau filaments from patients with Pick's disease, a neurodegenerative disorder characterized by frontotemporal dementia. The filaments consist of residues Lys254-Phe378 of 3R tau, which are folded differently from the tau filaments in Alzheimer's disease, establishing the existence of conformers of assembled tau. The observed tau fold in the filaments of patients with Pick's disease explains the selective incorporation of 3R tau in Pick bodies, and the differences in phosphorylation relative to the tau filaments of Alzheimer's disease. Our findings show how tau can adopt distinct folds in the human brain in different diseases, an essential step for understanding the formation and propagation of molecular conformers.

Prion-like Spreading in Tauopathies

Tau is a microtubule-associated protein that functions in regulating cytoskeleton dynamics, especially in neurons. Misfolded and aggregated forms of tau produce pathological structures in a number of neurodegenerative diseases, including Alzheimer's disease (AD) and tauopathy dementias. These disorders can present with a sporadic etiology, such as in AD, or a familial etiology, such as in some cases of frontotemporal dementia with parkinsonism. Notably, the pathological features of tau pathology in these diseases can be very distinct. For example, the tau pathology in corticobasal degeneration is distinct from that of an AD patient. A wealth of evidence has emerged within the last decade to suggest that the misfolded tau in tauopathies possesses prion-like features and that such features may explain the diverse characteristics of tauopathies. The prion-like concept for tauopathies arose initially from the observation that the progressive accumulation of tau pathology as the symptoms of AD progress seemed to follow anatomically linked pathways. Subsequent studies in cell and animal models revealed that misfolded tau can propagate from cell to cell and from region to region in the brain through direct neuroanatomical connections. Studies in these cell and mouse models have demonstrated that experimentally propagated forms of misfolded tau can exist as conformationally distinct "strains" with unique biochemical, morphological, and neuropathological characteristics. This review discusses the clinical, pathological, and genetic diversity of tauopathies and the discoveries underlying the emerging view that the unique features of clinically distinct tauopathies may be a reflection of the strain of misfolded tau that propagates in each disease.

Propagation of Tau Aggregates and Neurodegeneration

A pathway from the natively unfolded microtubule-associated protein Tau to a highly structured amyloid fibril underlies human Tauopathies. This ordered assembly causes disease and represents the gain of toxic function. In recent years, evidence has accumulated to suggest that Tau inclusions form first in a small number of brain cells, from where they propagate to other regions, resulting in neurodegeneration and disease. Propagation of pathology is often called prion-like, which refers to the capacity of an assembled protein to induce the same abnormal conformation in a protein of the same kind, initiating a self-amplifying cascade. In addition, prion-like encompasses the release of protein aggregates from brain cells and their uptake by neighboring cells. In mice, the intracerebral injection of Tau inclusions induces the ordered assembly of monomeric Tau, followed by its spreading to distant brain regions. Conformational differences between Tau aggregates from transgenic mouse brain and in vitro assembled recombinant protein account for the greater seeding potency of brain aggregates. Short fibrils constitute the major species of seed-competent Tau in the brains of transgenic mice. The existence of multiple human Tauopathies with distinct fibril morphologies has led to the suggestion that different molecular conformers (or strains) of aggregated Tau exist.

Requirements for Hirano body formation

Hirano bodies are paracrystalline F-actin-rich structures associated with diverse conditions, including neurodegeneration and aging. Generation of model Hirano bodies using altered forms of Dictyostelium 34-kDa actin-bundling protein allows studies of their physiological function and mechanism of formation. We describe a novel 34-kDa protein mutant, E60K, with a point mutation within the inhibitory domain of the 34-kDa protein. Expression of E60K in Dictyostelium induces the formation of model Hirano bodies. The E60K protein has activated actin binding and is calcium regulated, unlike other forms of the 34-kDa protein that induce Hirano bodies and that have activated actin binding but lack calcium regulation. Actin filaments in the presence of E60K in vitro show enhanced resistance to disassembly induced by latrunculin B. Actin filaments in model Hirano bodies are also protected from latrunculin-induced depolymerization. We used nocodazole and blebbistatin to probe the role of the microtubules and myosin II, respectively, in the formation of model Hirano bodies. In the presence of these inhibitors, model Hirano bodies can form but are smaller than controls at early times of formation. The ultrastructure of model Hirano bodies did not reveal any major difference in structure and organization in the presence of inhibitors. In summary, these results support the conclusion that formation of model Hirano bodies is promoted by gain-of-function actin filament bundling, which enhances actin filament stabilization. Microtubules and myosin II contribute to but are not required for formation of model Hirano bodies.

Pick's disease: a modern approach

Pick's disease is a rare dementing disorder that is sometimes familial. The cardinal features are circumscribed cortical atrophy most often affecting the frontal and temporal poles and argyrophilic, round intraneuronal inclusions (Pick bodies). Clinical manifestations reflect the distribution of cortical degeneration, and personality deterioration and memory deficits are often more severe than visuospatial and apraxic disorders that are common in Alzheimer's disease, but clinical overlap with other non-Alzheimer degenerative disorders is increasingly recognized. Neuronal loss and degeneration are usually maximal in the limbic system, including hippocampus, entorhinal cortex and amygdala. Numerous Pick bodies are often present in the dentate fascia of the hippocampus. Less specific features include leukoencephalopathy and ballooned cortical neurons (Pick cells). Glial reaction is often pronounced in affected cerebral gray and white matter. Tau-immunoreactive glial inclusions are a recently recognized finding in Pick's disease, and neuritic changes have also recently been described. Variable involvement of the deep gray matter and the brainstem is typical, with a predilection for the monoaminergic nuclei and nuclei of the pontine base. Neurochemical studies demonstrate deficits in intrinsic cortical neurotransmitter systems (e.g., somatostatin), but inconsistent loss of transmitters in systems projecting to the cortex (e.g., cholinergic neurons of the basal nucleus). Biochemical and immunocytochemical studies have demonstrated that abnormal tau proteins are the major structural components of Pick bodies. A specific tau protein immunoblotting pattern different from that seen in Alzheimer's disease and certain other disorders has been suggested in some studies. A specific molecular marker and a genetic locus for familial cases are not known.

Tau gene mutations in frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17). Their relevance for understanding the neurogenerative process

Tau is a microtubule-associated protein that binds to microtubules and promotes microtubule assembly. Six tau isoforms are produced in adult human brain by alternative mRNA splicing from a single gene. Inclusion of a 31 amino acid repeat encoded by exon 10 of the tau gene gives rise to the three isoforms with four microtubule-binding repeats each. The other three tau isoforms have three repeats each. Abundant neurofibrillary lesions made of tau protein constitute a defining neuropathological characteristic of Alzheimer's disease. Filamentous tau protein deposits are also the defining characteristic of other neurodegenerative diseases, many of which are frontotemporal dementias or movement disorders, such as Pick's disease, progressive supranuclear palsy, and corticobasal degeneration. It is well established that the distribution of tau pathology correlates with the presence of symptoms of disease. However, until recently, there was no genetic evidence linking tau to neurodegeneration. This has now changed with the discovery of more than 15 mutations in the tau gene in frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17). The new work has shown that dysfunction of tau protein causes neurodegeneration.

From genetics to pathology: tau and alpha-synuclein assemblies in neurodegenerative diseases

The most common degenerative diseases of the human brain are characterized by the presence of abnormal filamentous inclusions in affected nerve cells and glial cells. These diseases can be grouped into two classes, based on the identity of the major proteinaceous components of the filamentous assemblies. The filaments are made of either the microtubule-associated protein tau or the protein alpha-synuclein. Importantly, the discovery of mutations in the tau gene in familial forms of frontotemporal dementia and of mutations in the alpha-synuclein gene in familial forms of Parkinson's disease has established that dysfunction of tau protein and alpha-synuclein can cause neurodegeneration.

Abnormal tau-containing filaments in neurodegenerative diseases

It has been known for some time that the neurofibrillary pathology in Alzheimer's disease consists of so-called paired helical and straight filaments made up of the microtubule-associated protein tau. The degree of dementia observed in the disease correlates better with the extent of neurofibrillary pathology than with the Abeta amyloid deposits, the other characteristic defining pathological fibrous deposit in Alzheimer's disease. However, no familial cases of Alzheimer's disease have been genetically linked to the tau protein locus. Recently a group of frontotemporal dementias with parkinsonism linked to chromosome 17 has been shown to be caused by mutations in the tau gene. Some are missense mutations giving altered tau proteins, whereas others affect the splicing of the pre-mRNA and change the balance between different tau isoforms. Histologically these diseases are all characterised by various kinds of filamentous tau protein deposits, mostly in the complete absence of Abeta deposits. The abnormal tau filaments show different morphologies, depending on the nature of the tau mutation. These diseases show that tau mutations can be a prime cause of inherited dementing illness and may throw some light on the pathological process in the much larger number of sporadic cases of Alzheimer's disease.

Filamentous nerve cell inclusions in neurodegenerative diseases: tauopathies and alpha-synucleinopathies

Alzheimer's disease and Parkinson's disease are the most common neurodegenerative diseases. They are characterized by the degeneration of selected populations of nerve cells that develop filamentous inclusions before degeneration. The neuronal inclusions of Alzheimer's disease are made of the microtubule-associated protein tau, in a hyperphosphorylated state. Recent work has shown that the filamentous inclusions of Parkinson's disease are made of the protein alpha-synuclein and that rare, familial forms of Parkinson's disease are caused by missense mutations in the alpha-synuclein gene. Besides Parkinson's disease, the filamentous inclusions of two additional neurodegenerative diseases, namely dementia with Lewy bodies and multiple system atrophy, have also been found to be made of alpha-synuclein. Abundant filamentous tau inclusions are not limited to Alzheimer's disease. They are the defining neuropathological characteristic of frontotemporal dementias such as Pick's disease, and of progressive supranuclear palsy and corticobasal degeneration. The recent discovery of mutations in the tau gene in familial forms of frontotemporal dementia has provided a direct link between tau dysfunction and dementing disease. The new work has established that tauopathies and alpha-synucleinopathies account for most late-onset neurodegenerative diseases in man. The formation of intracellular filamentous inclusions might be the gain of toxic function that leads to the demise of affected brain cells.

Ultrastructure of neurofibrillary tangles in the cerebral cortex of sheep

Recently, we reported that neurofibrillary tangles (NFTs) of the Alzheimer type develop in the cerebral cortex of aged sheep (Ovis aries). In the current study, we utilized light and electron microscopic immunocytochemistry to describe in greater detail the characteristics of sheep NFTs during early stages of neurofibrillary degeneration. We investigated neurons that were stained using the monoclonal antibody Alz-50 and that contained relatively small numbers of paired helical filaments (PHFs). Serially cut ultrathin sections were evaluated to take maximal advantage of ultrastructural resolution. At the light microscope level, we observed preferential localization of Alz-50 immunoreactive accumulations at dendritic branch points in early NFTs. A similar staining pattern was observed using the monoclonal antibody AT8 which recognizes a phosphorylated epitope on tau. Ultrastructurally, we found that Alz-50 staining at dendritic branch points was associated with clusters of ribosomes. The focal deposition of phosphorylated tau proteins at dendritic branch points may indicate a link between the initial stages of neurofibrillary pathology and specific cytoskeletal alterations that involve dendritic remodeling. Neurons that contained relatively small numbers of PHFs appeared otherwise healthy with regard to their cytoskeleton and organelles.

A case of Pick's disease with unusual neuronal inclusions

An autopsy case of unusual Pick's disease in a 61-year-old male is described. Findings included severe atrophy of the frontal and temporal lobes, pyramidal tracts and basal ganglia accompanied by numerous intraneuronal argyrophilic hyaline inclusions. His neurological symptoms were constantly progressive during the 12-year course, characterized by akinesia and emotional incontinence. The inclusions were round, well-demarcated, slightly eosinophilic and intensely argyrophilic bodies in the perikarya, and distributed mainly in the subiculum and Sommer's sector of the hippocampus, amygdala and affected gyri. Immunocytochemically, they contain antigenic determinants of both phosphorylated and nonphosphorylated neurofilaments, but were negative for ubiquitin. Ultrastructurally, they were composed primarily of skeins of neurofilaments intermingled with cell organelles. Tubular profiles studded with granular substances, previously reported as a feature of the generalized variant of Pick's disease, and Hirano body-like lattice structures were occasionally observed in the inclusions. This case represents a slowly progressive neurodegenerative disorder characterized by fronto-temporal lobar atrophy and might by categorized as a variant of Pick's disease. However, some unusual properties of neuronal inclusions may suggest a different pathogenesis from that in classical Pick's disease.

Quantitative neuropathologic analysis of Pick's disease cases: cortical distribution of Pick bodies and coexistence with Alzheimer's disease

Pick's disease is characterized morphologically by severe atrophy of the frontal and temporal lobes and the presence in the cerebral cortex of degenerative neuronal lesions referred to as Pick bodies. In the present study, we analyzed the regional and laminar distribution of Pick bodies in a series of 16 Pick's disease cases. These distribution and density patterns were compared with those observed for neurofibrillary tangles in Alzheimer's disease. Very high densities of Pick bodies were observed Ammon's horn, subiculum, entorhinal cortex, and in the granule cell layer of the dentate gyrus. In the frontal and temporal neocortex, they were preferentially distributed in layers II and VI. All of the Pick's disease cases also exhibited neurofibrillary tangles in the frontal and temporal areas and in the hippocampal formation, with higher densities in layers II-III than in layers V-VI of the neocortical regions. Interestingly, this laminar distribution of neurofibrillary tangles was strikingly different from that observed in Alzheimer's disease cases, where they were more numerous in the infragranular layers than in the supragranular layers. In addition, a few Pick's disease cases also had cortical senile plaques. These results suggest that the presence of neurofibrillary tangles in Pick's disease may be more frequent than previously reported, and that Pick's disease and Alzheimer's disease may coexist in certain cases. The lesion distribution patterns suggest that different populations of cortical neurons are affected in Pick's and Alzheimer's disease, and that alterations of select corticocortical and corticosubcortical projections may distinguish these forms of dementia. It is also possible that these two disorders share certain pathogenetic mechanisms, even though both display specific patterns of regional and neuronal vulnerability to the degenerative processes.

Abnormal Tau proteins in progressive supranuclear palsy. Similarities and differences with the neurofibrillary degeneration of the Alzheimer type

We have previously shown that abnormal Tau species are produced during the neurofibrillary degeneration of the Alzheimer type. These abnormal Tau proteins consist of a characteristic triplet named Tau 55, Tau 64 and Tau 69 which are constantly found in Alzheimer's disease (AD) and Downs syndrome brain regions with tangles. To determine if abnormal Tau species are also produced in other neurodegenerative conditions where intraneuronal filamentous Tau aggregates are observed, we have undertaken an immuno-blot study of brain homogenates from patients with progressive supranuclear palsy (PSP), a neurological disorder characterized by the presence of tangles in subcortical and cortical brain areas. We show here that abnormal Tau species are produced in PSP but that they are different from those in AD. Indeed, although Tau 64 and 69 were present in PSP brain homogenates, possibly as the result of an abnormal phosphorylation as in AD, they were detected in smaller amounts (three times lower) than in AD. In addition Tau 55 was undetected by the immunological tools, such as the absorbed anti-PHF antisera, which specifically label the abnormal Tau proteins. Also the two-dimensional analysis revealed different isoelectric properties. Our results suggest that the production of abnormal Tau species is a very important event during all types of neurofibrillary degeneration. The differences in the pathological Tau-variant profile that were observed between PSP and AD possibly reflect different etiopathogenetic pathways and might explain the formation of different types of filamentous Tau aggregates.

Eosinophilic neuronal inclusion bodies in the temporal lobe

Intracytoplasmic neuronal inclusion bodies were found in the temporal lobe of an elderly woman. The oval or rod-shaped inclusion bodies were eosinophilic, showed bright red staining with azan, and were about half the size of the nucleus of a large neuron. They were non-argyrophilic and non-congophilic. Ultrastructurally, the inclusion bodies consisted of aggregates of filamentous materials showing partial periodicity. Among inclusion bodies reported up to now, the present ones resembled some described previously as "thalamic inclusions", but were different with regard to their partial filament periodicity, and unusual in that they were located in the deep layer of the temporal lobe and not in the thalamic nuclei.

Glial cytoplasmic inclusions in the CNS of patients with multiple system atrophy (striatonigral degeneration, olivopontocerebellar atrophy and Shy-Drager syndrome)

Glial cytoplasmic inclusions (GCIs) were demonstrated by silver staining, immunocytochemistry and by electron microscopy in the central nervous system (CNS) of 11 patients with various combinations of striatonigral degeneration, olivopontocerebellar atrophy and Shy-Drager syndrome. Although their configuration in light microscope can sometimes resemble neurofibrillary tangles, their cellular localisation, measurements, ultrastructure, immunocytochemical characteristics and regional distribution all differ from these Alzheimer type changes. The majority of GCIs were localized in the white matter and appeared to be accompanied by an increase in the number of interfascicular oligodendroglial cells and pallor or loss of myelin staining. Our histological, ultrastructural and immunocytochemical findings all indicate that the cells which contain GCIs are oligodendrocytes and the inclusions themselves are composed of tubular structures. The presence of the until now unknown GCIs in all the 11 CNS, but not in age- and sex-matched control brains, indicates that GCI is a cellular change characteristic of multiple system atrophy and the three syndromes are various manifestations of the same disease.

Alz 50 recognizes abnormal filaments in Alzheimer's disease and progressive supranuclear palsy

The monoclonal antibody Alz 50 recognizes a 68-kDa protein present in large amounts in cerebral tissue of patients with Alzheimer's disease (AD). We used light and electron microscopic as well as quantitative immunochemical techniques to compare distribution, characteristics, and amount of Alz 50 antigen in the tegmental nuclei of the pons of subjects with progressive supranuclear palsy (PSP) and subjects with AD. In both conditions Alz 50 antigen was found in neurons with and without neurofibrillary tangles (NFT). In NFT-bearing neurons the antigen was located in the filamentous components of NFT in both diseases, i.e., in straight filaments forming the NFT in PSP and in paired helical filaments components of the NFT in AD. In neurons lacking NFT the antigen was associated with straight filaments of various sizes, but the straight filaments were generally thinner than those of PSP. On immunoblots of both PSP and AD tissues, Alz 50 recognized a set of bands between 68 and 35 kDa which were not present in control tissue. The amount of Alz 50 antigen in AD tissue was estimated to be 10 times higher than that present in PSP tissue. The higher amount of Alz 50 antigen in AD tissue correlates with the more severe fibrillary pathology in this disease than in PSP. We propose that the Alz 50 antigen, although possibly related to tau proteins, distinguishes neurons that are forming abnormal filaments.

Ubiquitin is associated with abnormal cytoplasmic filaments characteristic of neurodegenerative diseases

Several degenerative diseases of the nervous system are characterized by the presence of neuronal inclusions. Most of these inclusions are made of abnormal filaments and share epitopes with cytoskeletal proteins. One of these inclusions, the neurofibrillary tangle of Alzheimer disease, has recently been shown to contain ubiquitin, a regulatory protein thought to play a role in the degradation of abnormal proteins. We carried out light and electron microscopic immunocytochemistry with several polyclonal and monoclonal antibodies to investigate the presence of ubiquitin in neuronal inclusions of neurodegenerative diseases. Ubiquitin was present not only in paired helical filaments that form the neurofibrillary tangle of Alzheimer disease, but also in the filamentous components of the inclusion characteristic of Parkinson disease, Pick disease, and progressive supranuclear palsy. In contrast, ubiquitin was not detected in other neuronal inclusions often found in aging and in Alzheimer disease, such as Hirano bodies and granulovacuolar degeneration. Reactivity with monoclonal antibodies suggests differences in the ubiquitin-acceptor proteins present in the inclusions studied. It is concluded that ubiquitin is selectively present in neuronal inclusions of degenerative diseases.

Tau antisera recognize neurofibrillary tangles in a range of neurodegenerative disorders

Neurofibrillary tangles occur in a number of apparently distinct neurodegenerative diseases and in normal aging of the human brain. Antibodies raised against Alzheimer's disease paired helical filaments immunolabel the tangles seen in all other tangle-associated disorders examined to date. The neuronal microtubule-associated protein, tau, has recently been identified as an antigenic component of neurofibrillary tangles and senile plaque neurites in Alzheimer's disease. Three different polyclonal antibodies with strong tau immunoreactivity are examined in this study. These antibodies were found to immunostain tangles in normal aged brain and in brains affected by a range of neurodegenerative disorders, including Down's syndrome, Alzheimer's disease plus Parkinson's disease, progressive supranuclear palsy, and the parkinsonism-dementia complex of Guam, as well as Pick bodies in Pick's disease. The findings further illustrate the relative nonspecificity of neurofibrillary lesions in neurodegenerative disorders.

Isolation of the insoluble straight fibrils of Pick's disease

This paper describes the isolation and partial purification of the straight fibrils that occur in the neurons of Pick's disease. Pick fibrils are highly insoluble in a variety of solvents. These fibrils were shown to be sodium dodecyl sulfate insoluble even in the presence of a reducing agent at elevated temperatures. This allowed the selective isolation of the fibrils using the SDS boiling procedure and sucrose gradient centrifugation that have been described for isolation of paired helical filaments of Alzheimer's disease. The isolated fibrils retained the native morphology seen in tissue sections, but some appeared to become unraveled to yield a paired helical appearance. These results indicate that the Pick fibrils have many chemical and structural characteristics in common with Alzheimer paired helical filaments, and suggest that these two diseases may be closely related.

Cytoskeletal protein abnormalities in neurodegenerative diseases

The nervous system is a rich source of filamentous proteins that assume critical roles in determining and maintaining neuronal form and function. Neurons contain three major classes of these cytoskeletal organelles: microtubules, intermediate filaments, and microfilaments. They also contain a variety of proteins that organize them and serve to connect them with each other. Such major neurodegenerative diseases as Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis, as well as a variety of toxic neuropathies, are characterized pathologically by intraneuronal filamentous inclusions. Recent studies using biochemical and immunocytochemical techniques have established that these abnormalities represent disorganized states of the neuronal cytoskeleton and have determined some of the specific molecular constituents of these inclusions. This knowledge has led to new ways of thinking about their origins.

Identification of prion amyloid filaments in scrapie-infected brain

Extracellular collections of abnormal filaments composed of prion proteins have been identified in the brains of scrapie-infected hamsters using immunoelectron microscopy. Some of the filaments were 1500 nm in length; generally, they exhibited a uniform diameter of 16 nm. Rarely, the filaments had a twisted appearance, raising the possibility that they are flattened cylinders or are composed of helically wound protofilaments. The prion filaments possess the same diameter and limited twisting as the shorter rod-shaped particles observed in purified preparations of prions. Both the filaments and rods are composed of PrP 27-30 molecules, as determined by immunoelectron microscopy using affinity-purified antibodies. The ultrastructural features of the prion filaments are similar to those reported for amyloid in many tissues including brain. These results provide the first evidence that prion proteins assemble into filaments within the brain and that these filaments accumulate in extracellular spaces to form amyloid plaques.

Microtubule-associated protein 2: monoclonal antibodies demonstrate the selective incorporation of certain epitopes into Alzheimer neurofibrillary tangles

Neurofibrillary tangles (NFT) are the principal structural alteration of neuronal cell bodies in Alzheimer disease as well as in normal aging of the human brain. While the ultrastructure of these intraneuronal lesions has been extensively studied, the biochemical composition of the fibers comprising the NFT is unknown. We report the production of three monoclonal antibodies against the microtubule-associated protein 2 (MAP-2), one of which intensely labels Alzheimer NFT. All three antibodies specifically recognize MAP-2 on immunoblots and stain brain tissue in a characteristic dendritic pattern. The three antibodies are directed against at least two different antigenic sites on the MAP-2 molecule, and one appears to recognize a phosphorylation site on MAP-2. That only one of the three antibodies immunolabels NFT suggests that the formation of the tangle involves some modification of the MAP-2 molecule. Our findings suggest that one aspect of Alzheimer-type neurofibrillary pathology is an aggregation of MAP-2 or MAP-2 fragments with altered neurofilamentous elements present in NFT. Normal interactive function, which putatively occurs between neurofilaments and MAP-2, may thus be disrupted in Alzheimer disease.

Classic and generalized variants of Pick's disease: a clinicopathological, ultrastructural, and immunocytochemical comparative study

Six sporadic cases of dementia with lobar atrophy and neuronal cytoplasmic inclusions (Pick's disease) could be separated into two groups on the basis of the involvement of subcortical structures, the distribution and the histochemical, immunochemical, and ultrastructural characteristics of the inclusions, and possibly the age at onset. The first group (classic) was characterized by predominantly cortical atrophy and the presence in the hippocampus and neocortex of argyrophilic cytoplasmic inclusion bodies that reacted with a monoclonal antibody against neurofilament proteins and antitubulin antisera. Ultrastructurally the bodies were composed of straight fibrils of variable diameter, averaging 15 nm, and long-period constricted fibrils. The second group (generalized) showed subcortical as well as antibodies against neurofilaments and microtubules. Ultrastructurally the straight fibrils composing the bodies were coated with granular material, presumed to be derived from ribosomes. The generalized cases occurred in younger patients than did the classic cases in this series.

An ultrastructural study of Pick bodies

We report the results of an ultrastructural study of Pick bodies (PB). A histogram constructed with the maximal width of each filamentous component in PB revealed a wide range of sizes among the filaments, in contrast to the unique composition of the paired helical filaments (PHF) seen in the neurofibrillary tangle of Alzheimer type (NFT-AT). Morphologically, three groups of filaments could be distinguished. The first group consisted of straight smooth-surfaced filaments of 10-14 nm diameter, which were presumably altered neurofilaments. The second one was of straight smooth-surfaced "tubules" of 15-22 nm diameter, smaller than normal microtubules. The third one was of PHF thought to be formed by a pair of filaments of the first group. The PHF found in PB differed from PHF of NFT-AT in the distance between crossovers, and rather resembled the loosely interwinding PHF reported in NFT of progressive supranuclear palsy.

Hirano-bodies in the distal symmetric polyneuropathy of the spontaneously diabetic BB-Wistar rat

Lattice-like cytoplasmic inclusions have been demonstrated in a variety of pathologic conditions of the CNS and PNS in both man and animals. We describe 2 types of such inclusions occurring in association with the distal central-peripheral symmetric polyneuropathy of the spontaneously diabetic BB-Wistar rat. In the literature, both these lattice-like inclusions have been referred to as Hirano-bodies, but have not been separated on the basis of different measurements, locations or possible origins.

An unusual case of Pick's disease

A man aged 64, with a history of chronic trichloroethylene intoxication, presented early headache, impairment of memory, and "stehende Redensarten", later on mental deterioration with muteness and oral tendency. He died of bronchopneumonia. The brain was studied by light and electron microscopy. Numerous inflated cells, intraneuronal argentophil Pick bodies and central chromatolysis of neurons were found throughout the cerebral cortex. Widespread diffuse fibrillary gliosis was the finding bearing a striking resemblance to "progressive subcortical gliosis". Severe loss of nerve cells was observed in the temporal lobe (except the posterior of T 1) and moderate or mild loss in the gyrus rectus, insula, gyrus cinguli, and partial areas of the frontal, parietal, and occipital lobes. By electron microscopy, the argentophil Pick bodies consisted of a conglomeration of randomly arranged short 100-150 A filaments, ribosomes, vesicles, mitochondria, and scanty paired helical filaments. The present case was considered to represent a rare case of Pick's disease of the temporo-fronto-parieto-occipital type or panencephalic type.

Pick's disease: an immunocytochemical study of neuronal changes. Monoclonal antibodies show that Pick bodies share antigenic determinants with neurofibrillary tangles and neurofilaments

We used rabbit antisera to the 210,000; 155,000; and 70,000 mol. wt. neurofilament - polypeptides and monoclonal antibodies (BF 10; RT97) known to react with human neurofilaments in an immunohistochemical study of neuronal changes in Pick's disease and in senile dementia of the Alzheimer type. Pick bodies as well as neurofibrillary tangles and neurites showed strong reactivity with the monoclonal antibodies but remained unlabeled when treated with the rabbit polyclonal antisera. Our results indicate that the stained material in Pick bodies share antigenic determinants with neurofibrillary tangles and neurofilaments.

An electron microscopic study on atypical presenile dementia with numerous Lewy bodies in the cerebral cortex

A report was made of an autopsied case of presenile dementia presenting the clinically characteristic symptoms of Alzheimer's disease and Pick's disease. The neuropathological findings were senile changes, namely, numerous senile plaques, neurofibrillary tangles, granulovacuolar degeneration and Pick bodies, etc., and numerous Lewy bodies in the brain stem and in the cerebral cortex. We studied mainly the ultrastructure of Lewy bodies in the cerebral cortex in this paper. The features of ultrastructural components of Lewy bodies presented types which might correspond to the various profiles of Lewy bodies observed by a light microscope. In addition, we studied the senile changes in the cerebral cortex ultrastructurally and considered that some relationship possibly existed between Lewy bodies and senile changes.

Central nervous system pathology of tuberous sclerosis in children

Ten cases of tuberous sclerosis involving the central nervous system (CNS) in children aged 2 days to 15 years were studied. The abnormal cells found in subependymal, cortical, and white matter lesions were examined by light and electron microscopy. Histochemistry and immunohistochemistry were also employed. The results were similar in all lesions. Approximately one-third of the abnormal cells were positive by glial fibrillary acidic protein (GFAP), one-half by Nissl, and one-quarter by Holzer's stains. The intensity and pattern of GFAP staining varied from cell to cell and could not be predicted before staining. Ultrastructurally the cytoplasm of abnormal cells contained moderate to large numbers of 9- to 12-nm diameter fibrils and frequent dense bodies with crystalline appearance. Stacked rough endoplasmic reticulum was variable. Cell junctions and glycogen were rare. Nuclei were usually vesicular with a prominent nucleolus. Individual cells of tuberous sclerosis have features of both neurons and astrocytes. The disease may affect cells before differentiation. The predominant abnormal features of the cells in tuberous sclerosis are a great increase in fibrils and the presence of dense bodies, which may be a nonspecific reaction or result from a metabolic defect affecting the cells.

A new case of Pick's disease. Anatomical and ultrastructural studies

The fine structure of a cortical frontal biopsy of Pick's disease is described. Pic bodies appear made of unbranched 120 A neurofilaments, sometimes clustered in geometrical pattern. Post-mortem examination, performed 8 years later, reveals typical lesions. The characteristics of Pick bodies are discussed.

Morphogenesis of the Hirano body in neurons of the squirrel monkey dorsal horn

Electron microscopic investigation of laminae I-III in the lumbosacral region of the squirrel monkey spinal cord has disclosed possible stages in the morphogenesis of the Hirano body. These bodies occur occasionally in nerve cell bodies and dendrites. They are round to oval in shape, measure up to 2.2 micrometer in diameter and are composed of circular layers of 10 nm filaments. In several instances in the present study, Hirano bodies were observed in close association with the Golgi apparatus. Here Golgi-related vesicles were attached to the external surface of the Hirano bodies. In one instance a cluster of developing Hirano bodies of various sizes was observed. The smaller bodies were located nearest the Golgi apparatus while the larger were further away. In this case several short filaments, which may be precursors of the longer filaments which make up the layers of the inclusion, were observed in the cytoplasm between the Golgi cisternae and the smaller Hirano bodies. These observations suggest that the Golgi apparatus plays a major role in the production of the Hirano body. The significance of the occurrence of these inclusions is discussed.

Light and electron microscopic observations on the relationship between Hirano bodies, neuron and glial perikarya in the human hippocampus

Hippocampi from two intellectually normal and four demented subjects were examined in autopsy material. Large Hirano bodies seen by light and electron microscopy were thought to be glial in origin and not to be produced by the perikarya of neurons as has been suggested in the literature. Myelination of two Hirano bodies found in the stratum lacunosum-granulosum where neuron perikarya are rare suggests that these bodies are produced by oligodendroglia. Hirano bodies were found to be associated with neurons showing granulovaculoar degeneration. With electron microscope they were frequently seen to be divided by clefts filled with amorphous material which possibly consisted of free ribosomes.

Light and electron microscopic observations on a ganglioneuroma

This report describes some additional morphologic observations on a mediastinal ganglioneuroma. The neoplastic neurons contained argentaffin cytoplasmic granules presumably representing neurosecretory granules. Cytoplasmic inclusions resembling Pick's bodies were frequently observed in the neuronal components of the tumor. These inclusions consisted of neurofilaments mixed with a variable number of microtubules, dense core vesicles and other organelles. These findings expand the range of conditions in which Pick's bodies are found.

Electron microscopic structure of the Alzheimer's neurofibrillary changes in case of atypical senile dementia

A man aged 70, showed early disorientation, memory defects, delusions and rages at 66, later mental deterioration with muteness and dysphagia. He died of cardiac failure. The postmortem examination revealed macroscopically and light microscopically the neuropathological findings of atypical senile dementia. Moreover, it is the interesting characteristic in the presented case that there are electron microscopically two types of filaments making the neurofibrillary tangles. One showed the so-called "paired helical filaments", which were observed in the cerebral cortex. The other showed paralled "straight filaments". These "straight filaments" were found in the bilateral hippocampi.

Corticocerebellothalamic degeneration with chromatolytic neuronal swelling: a light and electron microscopic case study

A 50-year-old woman showing psychoorganic syndrome, cerebellar symptoms, choreatic involuntary movements, Romberg's sign and epileptic fits over a period of 14 years, was neuropathologically studied. The calcarine and postcentral cortex, the medio-dorsal nucleus of the thalamus and the cerebellar cortex were affected with neuronal loss and astrocytic gliosis. Neurons in various regions showed chromatolytic neuronal swelling. Ultrastructurally, these chromatolytic neurons contained a large hollow core with numerous mitochondria, dispersed rough endoplasmic reticulum, degenerated cisternal structures and a few neurofilaments. Some neuronal mitochondria showed membranous trans-somal bridges composed of about 60 A parallel filaments with a spacing of about 80 A.

Neurofibrillary accumulation in the zebra (Equus burchelli)

Two young zebra siblings from consecutive pregnancies suffered from neurological disease, characterized by ventral deviation of the neck and tetraparesis which progressed to tetraplegia within a few weeks. On histological examination widespread neuronal degeneration was observed in the ventral horns of the spinal cord and in the lower brain stem. Ultrastructurally the neuronal degeneration was characterized by accumulation of neurofibrillary material resembling neurofilaments. The findings are compared to other diseases with neurofibrillary accumulation in man and animals.

Presenile dementia with Alzheimer-, Pick- and Lewy-body changes

An autopsy case of unclassifiable presenil dementia is reported. The outstanding pathological findings were as follows; 1. presence of senile plaques, neurofibrillary changes, Pick bodies, Hirano bodies, granulovacuolar degeneration of neurons, etc. 2. numerous Lewy bodies in the brain stem and diencephalon, 3. peculiar swollen neurons with intracytoplasmic, eosinophilic and argentophilic inclusions ("Lewy-like-bodies") in the cerebral cortices. Detailed study of the last mentioned inclusions indicates that they are almost identical to Lewy bodies, though there are some minor differences, in histochemical and electronmicroscopic findings. Nosologically, this case may represent either a combination of Alzheimer's disease, Pick's disease and idiopathic Parkinsonism with "Lewy-like-bodies" in the cerebral cortices, or a single disease. As far as we know, no similar case been reported.