Heat shock protein expression in corpora amylacea in the central nervous system: clues to their origin

Corpora amylacea negatively correlate with hippocampal tau pathology in Alzheimer's disease

Introduction

Severity and distribution of aggregated tau and neurofibrillary tangles (NFT) are strongly correlated with the clinical presentation of Alzheimer's disease (AD). Clearance of aggregated tau could decrease the rate of NFT formation and delay AD onset. Recent studies implicate corpora amylacea (CA) as a regulator of onset or accumulation of tau pathology. Normally, CA clear brain waste products by amassing cellular debris, which are then extruded into the cerebrospinal fluid to be phagocytosed. The proper functioning of CA may slow progression of AD-associated NFT pathology, and this relationship may be influenced by amount and distribution of phospho-tau (pTau) produced, age, sex, and genetic risk.

Objective

The goal of this study was to determine if CA size and number are associated with hippocampal location and local pTau severity while accounting for variations in age, sex, and genetic risk.

Methods

Postmortem brain hippocampal tissue sections from 40 AD and 38 unaffected donors were immunohistochemically stained with AT8 (pTau) and counter stained with periodic acid Schiff (PAS). Stained sections of the CA1 and CA3 regions of the hippocampus were analyzed. The percent area occupied (%AO) of CA, pTau, and NFT was calculated. Pairwise comparisons and regression modeling were used to analyze the influence of age, pTau %AO, and genetic risk on %AO by CA in each region, separately in donors with AD and unaffected donors.

Results

CA %AO was significantly higher in the CA3 region compared to CA1 in both groups. A significant negative correlation of CA %AO with both pTau %AO and neurofibrillary tangle %AO in the CA3 region of AD brain donors was found. Regression analysis in the CA3 region revealed a significant negative association between CA with both pTau and age.

Conclusion

We found an increase of CA in the CA3 region, compared to CA1 region, in AD and unaffected donors. This may suggest that the CA3 region is a hub for waste removal. Additionally, the negative correlation between %AO by CA and NFT in the CA3 region of the hippocampus in donors with AD suggests CA could play a role in AD pathologic progression by influencing tau clearance.

Uncovering tau in wasteosomes (corpora amylacea) of Alzheimer’s disease patients

Brain corpora amylacea, recently renamed as wasteosomes, are polyglucosan bodies that appear during aging and some neurodegenerative conditions. They collect waste substances and are part of a brain cleaning mechanism. For decades, studies on their composition have produced inconsistent results and the presence of tau protein in them has been controversial. In this work, we reanalyzed the presence of this protein in wasteosomes and we pointed out a methodological problem when immunolabeling. It is well known that to detect tau it is necessary to perform an antigen retrieval. However, in the case of wasteosomes, an excessive antigen retrieval with boiling dissolves their polyglucosan structure, releases the entrapped proteins and, thus, prevents their detection. After performing an adequate pre-treatment, with an intermediate time of boiling, we observed that some brain wasteosomes from patients with Alzheimer’s disease (AD) contained tau, while we did not detect tau protein in those from non-AD patients. These observations pointed the different composition of wasteosomes depending on the neuropathological condition and reinforce the role of wasteosomes as waste containers.

Wasteosomes (corpora amylacea) of human brain can be phagocytosed and digested by macrophages

Background

Corpora amylacea of human brain, recently renamed as wasteosomes, are granular structures that appear during aging and also accumulate in specific areas of the brain in neurodegenerative conditions. Acting as waste containers, wasteosomes are formed by polyglucosan aggregates that entrap and isolate toxic and waste substances of different origins. They are expelled from the brain to the cerebrospinal fluid (CSF), and can be phagocytosed by macrophages. In the present study, we analyze the phagocytosis of wasteosomes and the mechanisms involved in this process. Accordingly, we purified wasteosomes from post-mortem extracted human CSF and incubated them with THP-1 macrophages. Immunofluorescence staining and time-lapse recording techniques were performed to evaluate the phagocytosis. We also immunostained human hippocampal sections to study possible interactions between wasteosomes and macrophages at central nervous system interfaces.

Results

We observed that the wasteosomes obtained from post-mortem extracted CSF are opsonized by MBL and the C3b complement protein. Moreover, we observed that CD206 and CD35 receptors may be involved in the phagocytosis of these wasteosomes by THP-1 macrophages. Once phagocytosed, wasteosomes become degraded and some of the resulting fractions can be exposed on the surface of macrophages and interchanged between different macrophages. However, brain tissue studies show that, in physiological conditions, CD206 but not CD35 receptors may be involved in the phagocytosis of wasteosomes.

Conclusions

The present study indicates that macrophages have the machinery required to process and degrade wasteosomes, and that macrophages can interact in different ways with wasteosomes. In physiological conditions, the main mechanism involve CD206 receptors and M2 macrophages, which trigger the phagocytosis of wasteosomes without inducing inflammatory responses, thus avoiding tissue damage. However, altered wasteosomes like those obtained from post-mortem extracted CSF, which may exhibit waste elements, become opsonized by MBL and C3b, and so CD35 receptors constitute another possible mechanism of phagocytosis, leading in this case to inflammatory responses.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13578-022-00915-2.

Corpora Amylacea in the Human Brain Exhibit Neoepitopes of a Carbohydrate Nature

Corpora amylacea (CA) in the human brain are polyglucosan bodies that accumulate residual substances originated from aging and both neurodegenerative and infectious processes. These structures, which act as waste containers, are released from the brain to the cerebrospinal fluid, reach the cervical lymph nodes via the meningeal lymphatic system and may be phagocytosed by macrophages. Recent studies indicate that CA present certain neoepitopes (NEs) that can be recognized by natural antibodies of the IgM class, and although evidence of different kinds suggests that these NEs may be formed by carbohydrate structures, their precise nature is unknown. Here, we adapted standard techniques to examine this question. We observed that the preadsorption of IgMs with specific carbohydrates has inhibitory effects on the interaction between IgMs and CA, and found that the digestion of CA proteins had no effect on this interaction. These findings point to the carbohydrate nature of the NEs located in CA. Moreover, the present study indicates that, in vitro, the binding between certain natural IgMs and certain epitopes may be disrupted by certain monosaccharides. We wonder, therefore, whether these inhibitions may also occur in vivo. Further studies should now be carried out to assess the possible in vivo effect of glycemia on the reactivity of natural IgMs and, by extension, on natural immunity.

Cerebral Corpora amylacea are dense membranous labyrinths containing structurally preserved cell organelles

Corpora amylacea are cell-derived structures that appear physiologically in the aged human brain. While their histological identification is straightforward, their ultrastructural composition and microenvironment at the nanoscale have remained unclear so far, as has their relevance to aging and certain disease states that involve the sequestration of toxic cellular metabolites. Here, we apply correlative serial block-face scanning electron microscopy and transmission electron tomography to gain three-dimensional insight into the ultrastructure and surrounding microenvironment of cerebral Corpora amylacea in the human brainstem and hippocampal region. We find that cerebral Corpora amylacea are composed of dense labyrinth-like sheets of lipid membranes, contain vesicles as well as morphologically preserved mitochondria, and are in close proximity to blood vessels and the glymphatic system, primarily within the cytoplasm of perivascular glial cells. Our results clarify the nature of cerebral Corpora amylacea and provide first hints on how they may arise and develop in the aging brain.

Exploring the elusive composition of corpora amylacea of human brain

Corpora amylacea (CA) are polyglucosan bodies that accumulate in the human brain during ageing and are also present in large numbers in neurodegenerative conditions. Theories regarding the function of CA are regularly updated as new components are described. In previous work, we revealed the presence of some neo-epitopes in CA and the existence of some natural IgM antibodies directed against these neo-epitopes. We also noted that these neo-epitopes and IgMs were the cause of false staining in CA immunohistochemical studies, and disproved the proposed presence of β-amyloid peptides and tau protein in them. Here we extend the list of components erroneously attributed to CA. We show that, contrary to previous descriptions, CA do not contain GFAP, S100, AQP4, NeuN or class III β-tubulin, and we question the presence of other components. Nonetheless, we observe that CA contains ubiquitin and p62, both of them associated with processes of elimination of waste substances, and also glycogen synthase, an indispensable enzyme for polyglucosan formation. In summary, this study shows that it is imperative to continue reviewing previous studies about CA but, more importantly, it shows that the vision of CA as structures involved in protective or cleaning mechanisms remains the most consistent theory.

New perspectives on corpora amylacea in the human brain

Corpora amylacea are structures of unknown origin and function that appear with age in human brains and are profuse in selected brain areas in several neurodegenerative conditions. They are constituted of glucose polymers and may contain waste elements derived from different cell types. As we previously found on particular polyglucosan bodies in mouse brain, we report here that corpora amylacea present some neo-epitopes that can be recognized by natural antibodies, a certain kind of antibodies that are involved in tissue homeostasis. We hypothesize that corpora amylacea, and probably some other polyglucosan bodies, are waste containers in which deleterious or residual products are isolated to be later eliminated through the action of the innate immune system. In any case, the presence of neo-epitopes on these structures and the existence of natural antibodies directed against them could become a new focal point for the study of both age-related and degenerative brain processes.

Corpora Amylacea of Brain Tissue from Neurodegenerative Diseases Are Stained with Specific Antifungal Antibodies

The origin and potential function of corpora amylacea (CA) remains largely unknown. Low numbers of CA are detected in the aging brain of normal individuals but they are abundant in the central nervous system of patients with neurodegenerative diseases. In the present study, we show that CA from patients diagnosed with Alzheimer's disease (AD) contain fungal proteins as detected by immunohistochemistry analyses. Accordingly, CA were labeled with different anti-fungal antibodies at the external surface, whereas the central portion composed of calcium salts contain less proteins. Detection of fungal proteins was achieved using a number of antibodies raised against different fungal species, which indicated cross-reactivity between the fungal proteins present in CA and the antibodies employed. Importantly, these antibodies do not immunoreact with cellular proteins. Additionally, CNS samples from patients diagnosed with amyotrophic lateral sclerosis (ALS) and Parkinson's disease (PD) also contained CA that were immunoreactive with a range of antifungal antibodies. However, CA were less abundant in ALS or PD patients as compared to CNS samples from AD. By contrast, CA from brain tissue of control subjects were almost devoid of fungal immunoreactivity. These observations are consistent with the concept that CA associate with fungal infections and may contribute to the elucidation of the origin of CA.

Parahippocampal corpora amylacea: case report

OBJECTIVE

Corpora amylacea (CA) normally accumulate within perivascular, subpial, and subependymal astrocytic processes. CA are associated with a number of conditions including normal aging, hippocampal sclerosis associated with temporal lobe epilepsy, multiple sclerosis, Lafora-type progressive myoclonic epilepsy, and adult polyglucosan body disease. Reports of massive localized accumulation of CA in the brain outside of these conditions are rare.

CLINICAL PRESENTATION

A 49-year-old woman, with a long-standing history of migraine headaches, presented to her primary care provider for increased headache duration. Brain magnetic resonance imaging (MRI) revealed a left parahippocampal lesion, suggestive of low-grade glioma.

INTERVENTION

Given the MRI suggestive of left parahippocampal glioma, left-sided frontotemporal craniotomy was performed for resection of the lesion. Specimens obtained during the operation revealed focal high-density accumulation of CA with no evidence of neoplasm, ischemia, or hypoxic injury.

CONCLUSION

This case illustrates the possibility that localized high-density CA accumulation can present as an intrinsic lesion on brain MRI. CA should be included in the differential diagnosis for patients presenting with brain MRI suggestive of nonenhancing space-occupying lesions.

Novel role of transglutaminase 1 in corpora amylacea formation?

Corpora amylacea (CA) are both age and neurodegeneration-related spherical bodies, consisting of polymerized proteins, often thought to be involved in sequestration of hazardous products of cellular metabolism in brain. Although CA formation is associated with cellular stress, the process underlying their formation remains obscure. Transglutaminases (TGs) are stress associated enzymes that induce molecular cross-links, leading to polymerization of substrate proteins. TG expression and activity are elevated in Alzheimer's disease (AD) and Parkinson's disease (PD), and TG-catalyzed cross-links are present in their lesions. Considering the nature of CA, the aim of this study was to investigate the presence of TGs and TG cross-links in CA of healthy aging brain, AD and PD brain, using immunohistochemistry. We observed TG1 and TG cross-links in CA, together with typical cytoskeletal proteins. Furthermore, the presence of proteins associated with AD or PD pathogenesis was not altered in CA of disease brain compared to controls. We propose that TG1-catalyzed cross-linking and consequent polymerization of cytoskeletal and cytoskeleton-associated proteins may underlie CA formation.

Localization of blood proteins thrombospondin1 and ADAMTS13 to cerebral corpora amylacea

Corpora amylacea (CA) have long been described in aging brains and in patients with neurodegenerative conditions, but their origins have been debated. It has been proposed that CA represent collections of nervous system breakdown products that accumulate within astrocytic cytoplasm. In support of this, studies have shown that CA include glycosylated material, ubiquitin, and an assortment of proteins derived from neuronal cytoplasm. On the other hand, many of these proteins are not specifically localized to neurons or astrocytes; some components of CA, such as complement proteins, are most abundantly expressed outside the central nervous system. The characteristic predilection for CA to accumulate near vessels and ependyma suggests that proteins extravasated from blood or transudated from CSF may form a component of these structures. In this study, we report the immunohistochemical localization of blood and platelet proteins thrombospondin1 and ADAMTS13 in CA from aged individuals and patients with vascular dementia. Thrombospondin1 localized to neurons, but was most prominently localized to CA. An independent serum and platelet expressed protein, ADAMTS13, was found in CA in the same brain regions. In vitro analysis shows that thrombospondin1 and ADAMTS13 form complexes together in cells and in direct protein binding assays. We speculate that CA could result from a conglomeration of interacting proteins from degenerating neurons and from extravasated blood elements released after transient breakdown of the blood-brain barrier.

Temporal lobe epilepsy and corpora amylacea in the hippocampus: clinicopathologic correlation

Corpora amylacea (CoA) have been found in about 60% of neurosurgical specimens showing hippocampal sclerosis (HS). To determine clinical and neuroimaging differences between HS with and without CoA, we studied 29 patients (21 male, 8 female; age at surgery, 12 to 49 years) who underwent anterior temporal lobectomy for intractable medial temporal lobe epilepsy. No CoA were noted in the hippocampus of 11 cases, and deposition of CoA was mild and limited to the subependymal and vestigial hippocampal sulcus regions in nine cases; in nine cases, moderate to marked deposition was noted in the pyramidal cell layer, accompanying severe neuronal loss. No significant differences were evident between these three groups for age at onset, frequency and duration of epileptic seizures, the average age at surgery, or surgical results. Hippocampal hyperintensity in fluid-attenuated inversion recovery magnetic resonance images tended to increase with increasing hippocampal deposition of CoA. Formation of CoA appears to be a response to neuronal loss in the pyramidal cell layer, being related to the epileptogenic process as a consequence rather than a cause.

Nestin-like immunoreactivity of corpora amylacea in aged human brain

Corpora amylacea (CA) are spherical bodies routinely observed throughout the aged human brain, normally found at high frequencies under the ependymal lining of the ventricles. We identified clusters of CA under the ependyma of the lateral and fourth ventricles in post-mortem brain material from Parkinson patients as well as age-matched controls. Using a monoclonal antibody we found CA to be immunoreactive for nestin, a marker of neural stem cells, while no other structures in the investigated brain areas were labeled by this antibody. Nestin filaments are therefore possible structural components of CA, a finding which may trigger new hypotheses regarding their biogenesis and function.

Heat shock protein 60 in corpora amylacea

Heat shock protein 60 representation in the corpora amylacea of the brain was investigated in five different neurological diseases. In the cases with cerebral infarct, amyotrophic lateral sclerosis, multiple sclerosis, acute disseminated encephalomyelitis and primary tumors of the nervous system the corpora amylacea showed similar appearance with strong HSP-60 positivity in all investigated disorders at the predilection sites. In the inflammatory diseases, besides corpora amylacea, several cellular elements exhibited HSP-60 immunostaining too. In these cases, the widespread HSP-60 immunoreactivity associated with relative moderate corpora amylacea production as compared to other diseases. From this contradiction we concluded the corpora amylacea participate in the cellular stress reaction but stress protein synthesis certainly is not the primary event in corpora amylacea formation. In the development of the corpora amylacea the incipient process is most probably degenerative in nature, which later on is accompanied by stress protein synthesis and slow growing of these round structures designated for a protective role in the brain. However, the role of the stress protein synthesis in the corpora amylacea formation and growth was not unequivocally answered in this study. It is necessary to perform further comparative investigations of the stress protein representation and corpora amylacea formation in different diseases which may help in discovering useful pathogenetic data and the biological role of this degenerative structure.

Corpora amylacea and heat shock protein 27 in Ammon's horn sclerosis

Increased numbers of corpora amylacea have been observed in the resected mesial temporal lobe of many patients with complex partial seizures (CPS) and Ammon's horn sclerosis (AHS). Several heat shock proteins (HSPs) are induced by seizures and have been suggested as an etiologic factor in the formation corpora amylacea. We quantified corpora amylacea and HSP27-immunoreactive astrocytes in temporal lobe specimens from patients with CPS (28 AHS; 10 non-AHS) and in 5 autopsy controls. Corpora amylacea were increased in each sector of Ammon's horn in the AHS group, significantly so in CA1 and CA3 (p < 0.0001 and p = 0.0097, respectively), compared with the non-AHS group, although there was considerable variability among the specimens. We found HSP27 to be significantly but nonspecifically increased in the resected temporal lobe specimens from all patients with CPS, regardless of the underlying pathology. HSP27 was not, however, expressed within the corpora amylacea, and did not correlate with the number of corpora amylacea in any of the 9 mesial and lateral temporal lobe areas examined.

Corpora-amylacea and the family of polyglucosan diseases

The history, characters, composition and topography of corpora amylacea (CA) in man and the analogous polyglucosan bodies (PGB) in other species are documented, noting particularly the wide variation in the numbers found with age and in neurological disease. Their origins from both neurons and glia and their probable migrations and ultimate fate are discussed. Their presence is also noted in other organs, particularly in the heart. The occurrence in isolated cases of occasional 'massive' usually focal accumulations of similar polyglucosan bodies in association with certain chronic neurological diseases is noted and the specific conditions Adult Polyglucosan body disease and type IV glycogenosis where they are found throughout the nervous system in great excess is discussed. The distinctive differences of CA from the PGB of Lafora body disease and Bielschowsky body disease are emphasised. When considering their functional roles, a parallel is briefly drawn on the one hand between normal CA and the bodies in the polyglucosan disorders and on the other with the lysosomal system and its associated storage diseases. It is suggested that these two systems are complementary ways by which large, metabolically active cells such as neurons, astrocytes, cardiac myocytes and probably many other cell types, dispose of the products of stressful metabolic events throughout life and the continuing underlying process of aging and degradation of long lived cellular proteins. Each debris disposal system must be regulated in its own way and must inevitably, a priori, be heir to metabolic defects that give rise in each to its own set of metabolic disorders.

Spinal corpora amylacea and motor neuron disease: a quantitative study

OBJECTIVE

To test the hypothesis that as there is growing evidence that corpora amylacea, or amyloid bodies, in the CNS are derived primarily from neurons, it might be expected that their numbers in the spinal cord would decline with loss of neurons in motor neuron degeneration as they do in the retina on destruction of ganglion cells by glaucoma.

METHODS

The numbers of corpora amylacea were counted in PAS stained transverse sections of the lumbar cord from 27 patients with motor neuron disease and 21 control subjects of similar age and sex mix. The numbers and sizes of corpora amylacea were determined both in the anterior horn grey matter and in the submeningeal white matter regions in each case.

RESULTS

In both groups the total numbers in the white matter and submeningeal regions ranged from 160 to more than 5000/section and there was minimal significant difference between the two groups. No relation with age was found in this narrow age range. The mean diameters of the corpora amylacea were significantly less in the grey matter of both groups than in the submeningeal regions. However, their densities in the grey matter of the anterior horn were significantly reduced in the spinal cord sections in the motor neuron disease group, but only where few motor neurons remained.

CONCLUSIONS

These findings support the view that corpora amylacea may arise from neurons, and suggest that that there may be two compartments, one mobile and one static, the second most likely remaining in the periphery of the spinal cord for prolonged periods.

Distribution of amyloid bodies in the aged human vestibulocochlear nerve

We tried to elucidate the localization and distribution of amyloid bodies (Corpora amylacea) in the human vestibulocochlear nerve stained with luxol fast blue-periodic acid Schiff-hematoxylin using of a combination of an image analyzing computer system and a microscope fitted with a drawing tube. After having observed each section of the vestibulocochlear nerve from the brain stem to the fundus of the internal auditory meatus, we counted the numbers of amyloid bodies in three different parts for each of three corpses, and measured the areas. We found that amyloid bodies of the vestibulocochlear nerve are concentrated to the limiting glial portion of the nerve more than to the nerve parenchyma, and amyloid bodies are not seen in the vestibulocochlear nerve peripheral to the transitional zone. Our quantitative trial proved that the amyloid body was larger in the 8th decade than in the 6th or 7th decade of life.

Experimental induction of corpora amylacea-like inclusions in rat astroglia

Corpora amylacea (CA) are glycoproteinaceous inclusions that accumulate in the human central nervous system during normal ageing, and to an even greater extent in Alzheimer's disease and other neurodegenerative disorders. They are particularly prominent in subpial and subependymal regions, and are most commonly located within astrocytes and their processes. We previously demonstrated that human CA share many tinctorial and histochemical properties in common with Gomori-positive cytoplasmic granules which accumulate in periventricular astrocytes of the ageing vertebrate brain and in rat astroglial cultures exposed to the sulphydryl agent, cysteamine (CSH). In the present study, long-term exposure of neonatal rat astrocyte cultures to CSH resulted in the formation of large spherical, PAS-positive cytoplasmic inclusions which are highly reminiscent of, if not identical to, human CA. As in the case of human CA and Gomori-positive astrocyte granules, the CSH-induced CA-like inclusions exhibit non-enzymatic peroxidase activity and consistent immunolabelling with antibodies directed against the mitochondrial protein, sulphite oxidase. Taken together, our findings suggest that progressive mitochondrial damage and macroautophagy play an important role in the biogenesis of CA (and Gomori-positive granules) in astrocytes of the ageing periventricular brain.

A functional role for corpora amylacea based on evidence from complement studies

Few theories have been advanced for the production of corpora amylacea (CA) by the normal ageing brain and by the CNS under various neurological conditions. Proteins derived from neurons and oligodendrocytes are found in CA and to understand their origins brain tissue from patients with Alzheimer's disease (AD), multiple sclerosis (MS) and Pick's disease (PD) were tested for complement activity. All CA were immunopositive for antisera to classical pathway-specific components, the activation products C3d and the terminal complement complex (TCC), the C3 convertase regulator membrane cofactor protein (MCP) and the fluid phase regulators S-protein and clusterin. CA were immunonegative for the alternative complement pathway proteins and the complement regulators, decay accelerating factor (DAF) and CD59. Western immunoblotting of isolated solubilized CA from the same tissues demonstrated a weak band for MCP but TCC was more easily shown by immunoprecipitation. A filamentous fringe around CA, probably of astrocytic origin, was also immunopositive for complement factors. CA consist of an inert mucopolysaccharide matrix encasing ubiquitinated proteins, resulting from death of and damage to neurons, myelin and oligodendrocytes. A function of CA, therefore, could be to prevent the recognition of these immunogenic proteins by lymphocytes and microglia and thus protect the CNS from further injury.

X-ray microprobe analysis of corpora amylacea

Since corpora amylacea is concentrated in the high density fraction in the subcellular fractionation of autopsy brain. It is suspected that inorganic materials accumulate in corpora amylacea. Therefore, elemental analyses of partially purified corpora amylacea from autopsy brain from a patient with Alzheimer's disease and those from brain of a non-demented patient were performed by the X-ray microprobe method. Prominent peaks of sodium, phosphorus, sulphur and chloride were observed, and mapping analyses confirmed that these elements were actually contained within the corpora amylacea. A similar result was obtained using cryostat sections. Corpora amylacea are characteristically distributed along the margin of blood vessels, beneath the pial border of the hippocampus and in the subependymal zones of ventricles of aged brains, namely in the vicinity of blood and cerebrospinal fluid. From this distribution and from the results of the present paper, we suggest that corpora amylacea play a role in the absorption and accumulation of inorganic materials which have been extravasated from blood and cerebrospinal fluid (CSF) and taken up by astrocytes. This may reflect alteration of the blood-brain and blood-CSF barriers in the ageing brain.

Ubiquitinated dystrophic neurites suggest corticospinal derangement in patients with amyotrophic lateral sclerosis

Pathologic changes affecting the upper motoneuron (UMN) were studied in 37 cases of amyotrophic lateral sclerosis (ALS) by histology and immunohistochemistry and by electron and immunoelectron microscopy. The most striking finding was represented by ubiquitin-positive dot-like structures related to (1) glial lipofuscin granules, (2) small polyglucosan bodies and (3) dystrophic neurites. Their distribution areas did not overlap. In ALS cases, ubiquitinated dystrophic neurites were twice as frequent as in controls in the arcuate region of motor cortex; moreover, in ALS cases they were twice as frequent in the spinal cord at the end of corticospinal tracts, compared with the motor cortex. These findings may indicate the presence in ALS of a 'dying-back' of the corticospinal motoneuron, independently of its primary or secondary involvement.

Expression of the human groEL stress-protein homologue in the brain and spinal cord

A monoclonal antibody (ML30), previously shown to identify a human mitochondrial protein epitope homologous with the groEL heat-shock protein of bacteria (hsp60), was used in an immunohistochemical survey of the central nervous system in patients dying with no evidence of neurological disease and in tissue from patients dying with various neurological disorders. Staining was performed on frozen tissue sections and on formalin fixed, paraffin embedded tissue. Astrocytes in all areas showed a strong pattern of punctate granular staining, which was increased in astrocytes showing reactive changes. Oligodendrocytes stained lightly in a diffuse granular pattern as did most neurons. Ependymal cells showed apical granular positivity. Expression of the hsp60 epitope recognised by ML30 was not seen in ubiquitinated inclusion bodies in motor neuron disease, neurofibrillary tangles in Alzheimer's disease or Lewy bodies in Parkinson's disease. The epitope recognised by ML30 was stable after formalin fixation and in post mortem tissue up to 96 h after death. Expression of the human groEL stress-protein homologue in brain and spinal cord is consistent with a mitochondrial location and may provide a morphological indicator of the functional or metabolic state of cells, especially glial cells.