Immunocytochemical and ultrastructural evidence of dendritic degeneration in motor neurons of aluminum-intoxicated rabbits

Summary Using immunocytochemical and ultrastructural methods, we observed extensive and characteristic dendritic changes in motor neurons of rabbits inoculated intracisternally with aluminum phosphate. Anti-microtubule-associated protein 2 immunostaining revealed markedly reduced immunoreactivity in motor neuron dendrites and a reduced number of dendritic trees in aluminum phosphate-intoxicated rabbits. These dendritic changes were confirmed at the ultrastructural level; neurofilamentous accumulations, membranous inclusions and disrupted microtubules were common features of motor neuron dendrites, but less prominent in motor neuron axons. These observations suggest that dendrites are characteristically involved in aluminum intoxication in addition to the widely reported accumulation of phosphorylated neurofilament in perikarya and axons.     

泛素阳性包涵体在运动神经元病的表达

目的：探讨泛素阳性包涵体在运动神经病（MND）中枢神经系统的分布、成分及与神经细胞变性的关系。方法：对5例MND和9例非神经系统变性病对照患者脑和脊髓进行苏木素－伊红、快蓝和Bodian常规染色,抗－泛素、抗－tau蛋白、抗－胶质纤维酸性蛋白和抗－神经丝蛋白抗体免疫组化染色。结果：5例MND抗泛素免疫组化染色在其中4例细胞 质内发现单线－线团样包涵体、透明包涵体、路易体样包涵体和不规则包涵体、相应前角细胞存在轻中度变性。3例海马颗粒细胞内出现泛素阳性包涵体。1例患者脊髓前角细胞内少数泛素阳性包涵体抗神经丝蛋白染色也阳性,各种泛不阳性包涵体抗tau蛋白及胶质纤维酸性蛋白染色为阴性,结论脊髓前角细胞质内的泛素阳性包涵体是MND较为特异的免疫病理改变,不同类型包涵体之间可能存在一定的演变规律,与相应神经细胞的变性相关。少数泛素阳性包涵体含有神经丝蛋白成分,海马颗粒细胞内出现泛素阳性包涵休提示此病同时累及非运动系统,并可能 与MND临床上智能或精神异常有关。     

Ubiquitin-positive intraneuronal inclusions in the extramotor cortices of presenile dementia patients with motor neuron disease

Summary Ubiquitin-positive intraneuronal inclusions were found in the extramotor cortices of ten presenile dementia patients with motor neuron disease. There were inclusions in the hippocampal granular cells and in the small neurons of the superficial layers of the temporal and frontal cortices. Bunina bodies were present in the anterior horn cells in all cases. These results suggest that ubiquitin-related cytoskeletal abnormalities are common in cerebral non-motor small neurons in these patients.     

Role of proteasomes in the formation of neurofilamentous inclusions in spinal motor neurons of aluminum‐treated rabbits

We examined the role of the 20S proteasome in pathologic changes, including abnormal aggregation of phosphorylated neurofilaments, of spinal motor nerve cells from aluminum‐treated rabbits. Immunohistochemistry for the 20S proteasome revealed that many lumbar spinal motor neurons without intracytoplasmic neurofilamentous inclusions or with small inclusions were more intensely stained in aluminum‐treated rabbits than in controls, whereas the immunoreactivity was greatly decreased in some enlarged neurons containing large neurofilamentous inclusions. Proteasome activity in whole spinal cord extracts was significantly increased in aluminum‐treated rabbits compared with controls. Furthermore, Western blot analysis indicated that the 20S proteasome degraded non‐phosphorylated high molecular weight neurofilament (neurofilament‐H) protein in vitro. These results suggest that aluminum does not inhibit 20S proteasome activity, and the 20S proteasome degrades neurofilament‐H protein. We propose that abnormal aggregation of phosphorylated neurofilaments is induced directly by aluminum, and is not induced by the proteasome inhibition in the aluminum‐treated rabbits. Proteasome activation might be involved in intracellular proteolysis, especially in the earlier stages of motor neuron degeneration in aluminum‐treated rabbits.     

Frontotemporal lobar degeneration with motor neuron disease-type inclusions predominates in 76 cases of frontotemporal degeneration

This report presents the largest series of consecutive, neuropathologically confirmed cases of frontotemporal degeneration (FTD). Prior studies have found dementia lacking distinctive histology (DLDH) to be the most common pathology underlying the clinical diagnosis of FTD. In this series of 76 cases, 29 (38%) were found to have frontotemporal lobar degeneration with motor neuron disease-type inclusions (FTLD-MND-type) or FTLD-MND (with ALS), the most common neuropathological classification in our series. Only eight (11%) were classified as Picks disease. Several cases originally designated as DLDH could be reclassified as FTLD-MND-type based on current recommendations for classification of FTD.     

A new type of inclusion body in human spinal cord

Summary New pericapillary inclusion bodies were found in 17 cases of sporadic amyotrophic lateral sclerosis (ALS). The inclusion bodies consisted of paracrystalline arrays with 5–7 nm electron-dense subunits, were discernible with the light microscope and had the staining properties of protein. They were surrounded by capillary-wall basement membrane and were often associated with peripheral fibrils. Astrocytic fibrillary bodies, without paracrystalline material, were also found. The ultrastructure and staining of the fibrils suggests that the paracrystalline material is within pericapillary astrocytes. The nature and significance of the inclusion bodies are unknown, but their presence suggests that there may be pericapillary abnormalities in the spinal cord in ALS and possibly other disorders.Supported by the Montreal General Hospital Research Institute     

Aluminum, calcium, and iron in the spinal cord of patients with sporadic amyotrophic lateral sclerosis using laser microprobe mass spectroscopy: a preliminary study

We measured aluminum (Al), calcium (Ca), and iron (Fe) levels in neuronal cytoplasm and nucleus, capillaries, and neuropil in samples of ventral cervical spinal cord from 5 patients with sporadic amyotrophic lateral sclerosis (ALS) and 5 age-matched controls using laser microprobe mass spectrometry (LMMS). The concentration of Al was not altered in any area in the ALS samples. In contrast, Fe and Ca were increased 1.5-2-fold in the nucleus and cytoplasm of ALS neurons but not in capillaries and neuropil. These findings do not support the hypothesis that Al is enriched in spinal cord of sporadic ALS as has been reported for Guamanian ALS/Parkinson's dementia. The elevations of Fe in spinal neurons are consistent with reports of increased Fe in bulk samples of ALS spinal cord. The presence of increased Fe within spinal neurons may be significant in the pathogenesis of motor neuron degeneration by catalyzing the generation of reactive oxygen species within specific cells.     

Extending the clinicopathological spectrum of neurofilament inclusion disease

We describe features of a patient that broadens the clinical and pathological spectrum of neurofilament inclusion disease (NFID). The patient was a 52-year-old man with a 5–6 year history of progressive, asymmetrical spastic weakness of the upper and lower extremities; l-DOPA-unresponsive parkinsonism; and SPECT evidence of asymmetrical frontoparietal and basal ganglia hypoperfusion. The brain had marked frontoparietal parasagittal cortical atrophy, including the motor cortex, with histopathological evidence of neurofilament- and -internexin-immunoreactive neuronal inclusions. The corticospinal tract had degeneration, but there was minimal lower motor neuron pathology. There was also severe neuronal loss and gliosis in the posterolateral putamen and the substantia nigra, mimicking multiple system atrophy; however, glial cytoplasmic inclusions were not detected with -synuclein immunohistochemistry. This case extends the clinical and pathological spectrum of NFID to include cases with predominant parkinsonian and pyramidal features.Gerry Shaw holds equity in EnCor Biotechnology Inc., a company commercializing the alpha-internexin antibody used in this study, and may benefit by receiving royalties or equity growth.     

Expression of peripherin in ubiquinated inclusions of amyotrophic lateral sclerosis

We evaluated the expression of the type III intermediate filament (IF) protein, peripherin (PRP), in ubiquinated inclusions of motor neurons in amyotrophic lateral sclerosis (ALS). A previous study showed that overexpression of PRP in transgenic mice induces motor neuron disease with formation of PRP-containing inclusions before onset of symptoms [J. Cell Biol. 147 (3) (1999) 531]. To determine whether PRP inclusions occur in the human disease, we applied doublelabeling immunofluorescence to paraffin sections of the spinal cord obtained by autopsy of 40 ALS patients with sporadic disease and 39 controls. Inclusions that expressed immunoreactive ubiquitin and peripherin were recorded by video camera, and the sections were stained by hematoxylin and eosin (H&E) to define morphology. Lewy body-like inclusions (LBLIs) were seen in motor neuron perikarya of 9 of 40 ALS cases and none in controls; all LBLIs expressed peripherin. Skein-like inclusions (SLIs) were identified by ubiquitin, but did not express PRP with rare exceptions. Neither skein-like inclusions nor LBLIs expressed alpha B-crystallin, neurofilament protein (NF-L, NF-M and NF-H subunits), alpha-internexin, actin or alpha-synuclein. Immunoblot of the whole spinal cord exhibited a single 57-kDa band of peripherin in ALS patients and controls. Our data document the expression of peripherin in LBLIs, which may provide a clue to the pathogenesis of neurodegeneration in ALS.     

Binding of IDPN (β,β′-iminodipropionitrile) to rat spinal cord: Possible implication in the mechanism of spheroid formation in amyotrophic lateral sclerosis

β,β′-iminodipropionitrile (IDPN) produces ‘spheroids’ similar to those in certain cases of amyotrophic lateral sclerosis (ALS). Therefore, the target molecule of IDPN could be important to the understanding of the molecular mechanism of spheroid formation in ALS. Wistar rats were injected ip with ¹⁴C-labeled IDPN (¹⁴C-IDPN) and killed at 0.5, 1, 3, 6, 12 and 24 h thereafter. The radioactivity in each organ increased rapidly and reached the maximum at 0.5–1 h after ¹⁴C-IDPN injection. Thereafter, a rapid decrease occurred until 6 h, followed by a gradual decline until 24 h. The radioactivity in the cerebral cortex, diencephalon and cerebellum was higher than in the pons, medulla oblongata and spinal cord. Although high in the visceral organs and skeletal muscles, no or little radioactivity was detected in fat tissue. Autoradiography also confirmed these results. In three rats, ¹⁴C-IDPN was injected to the lumbar enlargement of the spinal cord. Six hours after injection, the segment was removed and homogenized with physiological saline (PS). After centrifugation, the supernatant was obtained (PS fraction). The pellet was resuspended with 4 mol/L urea and the supernatant was obtained (urea fraction). Each fraction was analysed by gel filtration. A peak of radioactivity was observed at the elution fraction Nos 19 and 20 (consistent with free ¹⁴C-IDPN) when PS fraction was applied. On application of urea fraction, another peak was obtained at the elution fractions Nos 8 and 9 (MW 60～80 kDa). The present study demonstrates that ¹⁴C-IDPN does not selectively accumulate to the spinal cord and suggests that an IDPN-binding molecule with an MW of 60–80 kDa is present in the spinal cord. The molecule may be related to the pathological process of spheroid formation in ALS.     

Mice with targeted disruption of neurofilament light subunit display formation of protein aggregation in motoneurons and downregulation of complement receptor type 3 alpha subunit in microglia in the spinal cord at their earlier age: a possible feature in pre-clinical development of neurodegenerative diseases

The pathogenesis of neurodegenerative diseases prior to the onset of symptoms is generally not clear. The present study has employed a mouse model with a lack of the low-molecular-weight neurofilament subunit (NFL-/-), in which formation of protein aggregates occurs in neurons, to investigate glial cellular reactions in the lumbar cord segments of NFL-/- mice at ages from 1 to 6 months. Age-matched C57BL/6 mice serve as the control. Apparent neurofilament positive aggregates in the cytoplasm of motoneurons have been observed in NFL-/- mice. However, there were no noticeable changes in microglial numbers and GFAP staining of astrocytes. Unexpectedly, a downregulation in expression of complement receptor type 3 alpha subunit (CD11b) was detected in the spinal cord of NFL-/- mice, while there was no obvious difference between NFL-/- and C57BL/6 mice in the CD11b staining intensity of macrophages from livers and spleens. In addition, retardation in morphological transformation from activated to amoeboid microglia in response to sciatic nerve injury, differential expressions of some cytokines in the lumbar cord segments and induction of Iba-1 (ionized calcium-binding adaptor molecule-1) expression in microglia were observed in NFL-/- mice. Our results suggest not only the existence of an inhibitory niche for CD11b expression in microglia in the lumbar cord segments of NFL-/- mice but also differential microglial reactions between earlier and later stages of neuropathogenesis. Although the real cause for such inhibition is still unknown, this effect might play a particular role in the survival of the abnormal protein aggregate-bearing motoneurons in the early development stage of neurodegeneration in the NFL-/- mice.     

Motor neuronal death in sporadic amyotrophic lateral sclerosis (ALS) is not apoptotic. A comparative study of ALS and chronic aluminium chloride neurotoxicity in New Zealand white rabbits

Whether diseased motor neurones in sporadic amyotrophic lateral sclerosis (ALS) die via apoptosis is unknown. Because this relates primarily to difficulties in utilizing post-mortem tissue from end-stage disease, motor neurone degeneration in ALS spinal cord was compared with that of a model of a chronic motor neurone degeneration. Degenerating motor neurones in ALS, identified by ubiquitin immunoreactivity, did not demonstrate the morphological characteristics of apoptosis and were not c-Jun immunoreactive or TUNEL positive. A temporal analysis of spinal motor neurone death in the chronic AlCl3 neurotoxicity model of motor neurone degeneration was also undertaken. AlCl3 was administered intracisternally every 4 weeks and, at intervals of 51, 107, 156 and 267 days, evidence of apoptosis was sought by morphology, TUNEL hybridization or DNA laddering. Double-labelling immunostudies were also performed with antibodies to either c-Jun, ubiquitin or high molecular weight neurofilament (NFH) with TUNEL hybridization. Although significant neurone loss was evident, apoptosis was not found. These studies demonstrate a lack of apoptosis in ALS spinal motor neurones and suggest that this observation does not relate to the utilization of post-mortem tissue in which apoptotic neurones may have been lost.