Spinal and cranial motor nerve roots in amyotrophic lateral sclerosis and X-linked recessive bulbospinal muscular atrophy: morphometric and teased-fiber study

A cellular taxonomy of the adult human spinal cord

The mammalian spinal cord functions as a community of cell types for sensory processing, autonomic control, and movement. While animal models have advanced our understanding of spinal cellular diversity, characterizing human biology directly is important to uncover specialized features of basic function and human pathology. Here, we present a cellular taxonomy of the adult human spinal cord using single-nucleus RNA sequencing with spatial transcriptomics and antibody validation. We identified 29 glial clusters and 35 neuronal clusters, organized principally by anatomical location. To demonstrate the relevance of this resource to human disease, we analyzed spinal motoneurons, which degenerate in amyotrophic lateral sclerosis (ALS) and other diseases. We found that compared with other spinal neurons, human motoneurons are defined by genes related to cell size, cytoskeletal structure, and ALS, suggesting a specialized molecular repertoire underlying their selective vulnerability. We include a web resource to facilitate further investigations into human spinal cord biology.

Selective Loss of MATR3 in Spinal Interneurons, Upper Motor Neurons and Hippocampal CA1 Neurons in a MATR3 S85C Knock-In Mouse Model of Amyotrophic Lateral Sclerosis

Simple Summary

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease affecting the motor neurons in the brain and spinal cord. Mutations in the gene Matr3 have been linked to ALS, including the autosomal dominant missense mutation S85C. We previously created a mouse model containing the S85C mutation in the Matr3 gene to understand how it causes ALS. The S85C mice exhibited MATR3 staining loss in selective populations of degenerating neurons, such as Purkinje cells in the cerebellum and α-motor neurons in the lumbar spinal cord. However, studies have shown that neurons other than motor neurons may be involved in contributing to ALS; therefore, we investigated additional neuronal cell types in the spinal cord and brain. Here, we found that MATR3 staining is selectively reduced in interneurons and α-motor neurons of the cervical and thoracic regions of the spinal cord, as well as in subsets of upper motor neurons and hippocampal neurons. These neurons did not exhibit cell body loss; however, how the MATR3 loss affects neuronal function remains to be determined. Overall, these findings demonstrate that the MATR3 S85C mutation affects other neuronal types of the brain and spinal cord in addition to motor neurons, suggesting that these additional neuronal types are involved in ALS pathogenesis.

Abstract

The neuropathological hallmark of amyotrophic lateral sclerosis (ALS) is motor neuron degeneration in the spinal cord and cortex. Accumulating studies report that other neurons in the central nervous system (CNS) are also affected in ALS. Mutations in Matr3, which encodes a nuclear matrix protein involved in RNA splicing, have been linked to ALS. Previously, we generated a MATR3 S85C knock-in (KI) mouse model that recapitulates early-stage features of ALS. We reported that MATR3 S85C KI mice exhibit defects in lumbar spinal cord motor neurons and in cerebellar Purkinje cells, which are associated with reduced MATR3 immunoreactivity. Here, we show that neurons in various other regions of the CNS are affected in MATR3 S85C KI mice. Using histological analyses, we found selective loss of MATR3 staining in α-motor neurons, but not γ-motor neurons in the cervical and thoracic spinal cord. Loss of MATR3 was also found in parvalbumin-positive interneurons in the cervical, thoracic and lumbar spinal cord. In addition, we found the loss of MATR3 in subsets of upper motor neurons and hippocampal CA1 neurons. Collectively, our findings suggest that these additional neuronal types may contribute to the disease process in MATR3 S85C KI mice.

ALS-CSF-induced structural changes in spinal motor neurons of rat pups cause deficits in motor behaviour

Amyotrophic lateral sclerosis (ALS) is a late-onset, neurodegenerative disease associated with the loss of motor neurons in the spinal cord, brain stem and primary motor cortex. Deficit in the motor function is one of the clinical features of this disease. However, the association between adverse morphological alterations in the spinal motor neurons and motor deficit in sporadic ALS (SALS) is still debated. The present study has sought to investigate the effects of serial intrathecal injections of ALS-CSF into rat pups, at post-natal (P) days 3, 9 and 14, on the motor neuronal (MN) morphology at the cervical and lumbar levels of the spinal cord at P16 and P22. The present study used Cresyl violet and Golgi-Cox staining methods to determine the progressive changes in the morphology of spinal MNs in both cervical and lumbar extensions. The study found a loss of motor neurons in the spinal cord (36% for P16 in cervical and 41.7% in P16 lumbar and 49.57% for P22 cervical and 44.63% for P22 lumbar) and reduced choline acetyl transferase (ChAT) expression after repeated infusion of ALS-CSF. Significant increase in the soma area was also found in ALS-CSF rats (around 21% in P22 cervical and 26.4% in P22 lumbar). Soma hypertrophy was associated with increased dendritic arborization of MNs at both cervical and lumbar levels of the spinal cord. The data also showed a direct correlation between ALS-CSF induced changes in the MN number in the spinal cord and motor behavioral deficits. The loss of MNs, reduced ChAT, changes in soma and dendritic morphology with declined rotarod performance, thus, confirming the pathological phenotypes as seen in ALS patients.

The Dual Nature of Onuf's Nucleus: Neuroanatomical Features and Peculiarities, in Health and Disease

Onuf's nucleus is a small group of neurons located in the ventral horns of the sacral spinal cord. The motor neurons (MNs) of Onuf's nucleus innervate striated voluntary muscles of the pelvic floor and are histologically and biochemically comparable to the other somatic spinal MNs. However, curiously, these neurons also show some autonomic-like features as, for instance, they receive a strong peptidergic innervation. The review provides an overview of the histological, biochemical, metabolic, and gene expression peculiarities of Onuf's nucleus. Moreover, it describes the aging-related pathologies as well as several traumatic and neurodegenerative disorders in which its neurons are involved: indeed, Onuf's nucleus is affected in Parkinson's disease (PD) and Shy-Drager Syndrome (SDS), whereas it is spared in Amyotrophic Lateral Sclerosis (ALS), Spinal Muscular Atrophy (SMA), Duchenne Muscular Dystrophy (DMD). We summarize here the milestone studies that have contributed to clarifying the nature of Onuf's neurons and in understanding what makes them either vulnerable or resistant to damage. Altogether, these works can offer the possibility to develop new therapeutic strategies for counteracting neurodegeneration.

Disentangling balance impairments in spinal and bulbar muscular atrophy

Spinal and bulbar muscular atrophy (Kennedy's disease) has been associated with balance dysfunction and falls. However, postural control has not been studied quantitatively. Here, we quantified upright stance and aimed to disentangle the role of vestibular, proprioceptive and oculomotor deficits. Static balance was assessed in Kennedy patients (n = 7) during quiet stance on a force platform under different visual and proprioceptive feedback conditions. Vestibular function was assessed with the video head impulse test. Sural nerve neurography was employed to evaluate the severity of peripheral neuropathy. Also, horizontal saccades were recorded and quantified by the main sequence relationship. Posturographic analyses revealed significantly increased body sway, more pronounced in conditions with closed eyes, which was also reflected in the calculated Romberg indices. Horizontal vestibulo-ocular reflex gains were normal, i.e. > 0.75. In contrast, compound sensory nerve action potentials were markedly decreased in all patients (mean = 2.4 μV). Two patients showed slow saccades with increased exponential main sequence constants. We conclude that Kennedy patients exhibit severe deficits in quiet stance. Postural instability is greatest in conditions of absent vision with reduced proprioception being the main determinant of unsteadiness. Some patients show slowed saccadic eye movements suggesting a nuclear abducens neuronopathy.

Gamma motor neurons survive and exacerbate alpha motor neuron degeneration in ALS

The molecular and cellular basis of selective motor neuron (MN) vulnerability in amyotrophic lateral sclerosis (ALS) is not known. In genetically distinct mouse models of familial ALS expressing mutant superoxide dismutase-1 (SOD1), TAR DNA-binding protein 43 (TDP-43), and fused in sarcoma (FUS), we demonstrate selective degeneration of alpha MNs (α-MNs) and complete sparing of gamma MNs (γ-MNs), which selectively innervate muscle spindles. Resistant γ-MNs are distinct from vulnerable α-MNs in that they lack synaptic contacts from primary afferent (I_A) fibers. Elimination of these synapses protects α-MNs in the SOD1 mutant, implicating this excitatory input in MN degeneration. Moreover, reduced I_A activation by targeted reduction of γ-MNs in SOD1^G93A mutants delays symptom onset and prolongs lifespan, demonstrating a pathogenic role of surviving γ-MNs in ALS. This study establishes the resistance of γ-MNs as a general feature of ALS mouse models and demonstrates that synaptic excitation of MNs within a complex circuit is an important determinant of relative vulnerability in ALS.

Wnt and extraocular muscle sparing in amyotrophic lateral sclerosis

PURPOSE

The extraocular muscles (EOM) and their motor neurons are spared in amyotrophic lateral sclerosis (ALS). In limb muscle, axon retraction from the neuromuscular junctions occurs early in the disease. Wnts, a conserved family of secreted signaling molecules, play a critical role in neuromuscular junction formation. This is the first study to examine Wnt signaling for its potential involvement in maintenance of normal morphology in EOM in ALS.

METHODS

Extraocular muscle and limb muscle axons, neuromuscular junctions, and myofibers from control, aging, and ALS subjects and the SOD1(G93A) mouse model of ALS were quantified for their expression of Wnt1, Wnt3a, Wnt5a, Wnt7a, and β-catenin.

RESULTS

All four Wnt isoforms were expressed in most axon profiles in all human EOM. Significantly fewer were positive for Wnt1, Wnt3a, and Wnt7a in the human limb muscles. Similar differential patterns in Wnt myofiber expression were also seen except in the case of Wnt7a, where expression was elevated. In the SOD1(G93A) mouse, all four Wnt isoforms were significantly decreased in the neuromuscular junctions at the terminal stage compared to values in age-matched controls. β-Catenin was activated in a subset of myofibers in EOM and limb muscle in all subjects.

CONCLUSIONS

The differences in expression of Wnts in EOM and limb muscle, particularly at the neuromuscular junction level, suggest that they play a role in the pathophysiology of ALS. Collectively, the data support a role for signaling of Wnts in the preservation of the EOM in ALS and their dysregulation and the subsequent development of pathology in the ALS limb muscles.

Characterization of thoracic motor and sensory neurons and spinal nerve roots in canine degenerative myelopathy, a potential disease model of amyotrophic lateral sclerosis

Canine degenerative myelopathy (DM) is a progressive, adult-onset, multisystem degenerative disease with many features in common with amyotrophic lateral sclerosis (ALS). As with some forms of ALS, DM is associated with mutations in superoxide dismutase 1 (SOD1). Clinical signs include general proprioceptive ataxia and spastic upper motor neuron paresis in pelvic limbs, which progress to flaccid tetraplegia and dysphagia. The purpose of this study was to characterize DM as a potential disease model for ALS. We previously reported that intercostal muscle atrophy develops in dogs with advanced-stage DM. To determine whether other components of the thoracic motor unit (MU) also demonstrated morphological changes consistent with dysfunction, histopathologic and morphometric analyses were conducted on thoracic spinal motor neurons (MNs) and dorsal root ganglia (DRG) and in motor and sensory nerve root axons from DM-affected boxers and Pembroke Welsh corgis (PWCs). No alterations in MNs or motor root axons were observed in either breed. However, advanced-stage PWCs exhibited significant losses of sensory root axons, and numerous DRG sensory neurons displayed evidence of degeneration. These results indicate that intercostal muscle atrophy in DM is not preceded by physical loss of the motor neurons innervating these muscles, nor of their axons. Axonal loss in thoracic sensory roots and sensory neuron death suggest that sensory involvement may play an important role in DM disease progression. Further analysis of the mechanisms responsible for these morphological findings would aid in the development of therapeutic intervention for DM and some forms of ALS.

Pathogenesis and molecular targeted therapy of spinal and bulbar muscular atrophy

Spinal and bulbar muscular atrophy (SBMA) or Kennedy's disease is a motor neurone disease characterized by muscle atrophy, weakness, contraction fasciculations and bulbar involvement. SBMA mainly affects males, while females are usually asymptomatic. SBMA is caused by expansion of a polyglutamine (polyQ)-encoding CAG trinucleotide repeat in the androgen receptor (AR) gene. AR belongs to the heat shock protein 90 (Hsp90) client protein family. The histopathologic hallmarks of SBMA are diffuse nuclear accumulation and nuclear inclusions of the mutant AR with expanded polyQ in residual motor neurones in the brainstem and spinal cord as well as in some other visceral organs. There is increasing evidence that the ligand of AR and molecular chaperones play a crucial role in the pathogenesis of SBMA. The success of androgen deprivation therapy in SBMA mouse models has been translated into clinical trials. In addition, elucidation of its pathophysiology using animal models has led to the development of disease-modifying drugs, that is, Hsp90 inhibitor and Hsp inducer, which inhibit the pathogenic process of neuronal degeneration. SBMA is a slowly progressive disease by nature. The degree of nuclear accumulation of mutant AR in scrotal skin epithelial cells was correlated with that in spinal motor neurones in autopsy specimens; therefore, the results of scrotal skin biopsy may be used to assess the efficacy of therapeutic trials. Clinical and pathological parameters that reflect the pathogenic process of SBMA should be extensively investigated.

Autonomic impairment in amyotrophic lateral sclerosis

PURPOSE OF REVIEW

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder characterized by progressive loss of motor neurones, but it is increasingly recognized to be a more disseminated disease. The autonomic nervous system may also be involved. Here we review the literature with specific emphasis on autonomic functions in ALS.

RECENT STUDIES

Ample evidence exists for subclinical dysfunction of cardiovascular, sudomotor, gastrointestinal, salivary and lacrimal regulation, even in early ALS cases. Autonomic disturbances may lead to circulatory collapse or sudden death in respirator dependent patients. Several studies suggest the existence of sympathetic hyperactivity in ALS. We discuss some possible pathophysiological mechanisms of the subtle abnormalities and some clinical and treatment implications.

SUMMARY

The wide range of autonomic involvement, together with results suggesting cognitive and extrapyramidal dysfunction, supports the view that ALS is a multisystem degenerative disease.

The experimental toxicology of metallic mercury on the murine peripheral motor system: a novel method of assessing axon calibre spectra using the phrenic nerve

The toxicology of metallic mercury on motor neurons and their processes requires further work to resolve controversial implications in the aetiology of human motor neuron disease (MND). The assessment of experimental neurotoxicity in the peripheral motor system is, however, technically problematic and difficult to interpret. The mean number of axons in a nerve can vary considerably due to a high degree of biological variation. Atrophy of large axons can appear as loss when, in fact, their numbers appear in smaller diameter axonal categories. We addressed these quantitative problems using the murine phrenic nerve (MPN), a mono-fascicular, predominantly motor nerve as a model system. One micrometer transverse sections of gluteraldehyde/osmium tetroxide fixed MPNs were stained for myelin using a silver technique. Axon areas were measured from digital images of the nerve in cross-section (ImagePro Plus software) and transformed to circular diameter equivalents, then displayed as frequency distributions. We found a high biological variation in the mean axon number between paired nerves within experimental groups. Therefore, axon diameter data within individuals group was pooled. Theoretical simulation of axonal degeneration, atrophy and hypertrophy of larger myelinated axons (also affected in MND) were modelled by manipulating the original data set. With this model, by comparing normal distributions, it is possible to distinguish axonal atrophy, degenerative loss, and hypertrophy as distinct pathological processes in the large calibre axon subgroup that are selectively vulnerable to metallic toxins such as mercury.

Brainstem motor nuclei respond differentially to degenerative disease in the mutant mouse wobbler

Degenerative motoneurone diseases, whether in humans, animals, or transgenic mouse models, do not affect all types of motoneurone to the same degree. Understanding the relative differences in vulnerability of certain motor pools may be the key to developing therapies. Expression of calbindin (CB) and parvalbumin (PV) immunoreactivity, which are potentially neuroprotective calcium-binding proteins, and NADPH-diaphorase (NADPH-d) histochemical reactivity, a marker for neurodegeneration, was studied in brainstem sections from mutant wobbler mice and their normal littermates during the motoneurone degeneration phase (3-8 weeks of age). The motor trigeminal and facial nuclei reacted in a manner previously observed in spinal somatic motoneurones in the wobbler. Many motoneurones expressed moderate NADPH-d reactivity, correlated with the appearance of vacuolated motoneurones in Nissl-stained sections. This was not observed in littermate controls. Motoneurone counts from Nissl-stained sections from 14-month-old wobblers and littermates revealed significantly fewer (approximately 27%) motoneurones in the trigeminal nucleus of wobblers. In contrast, the wobbler hypoglossal nucleus contained neither vacuolated nor NADPH-d reactive motoneurones. However, expression of CB immunoreactivity by the majority of wobbler hypoglossal motoneurones was observed but not in littermate controls or in any other motor nucleus. Counts in older animals showed a smaller but still significant difference in motoneurone number between wobblers and controls (approximately 9% reduction). Finally, the wobbler abducens nucleus displayed neither vacuolated neurones, nor NADPH-d reactivity nor CB immunoreactivity. Motor nuclei innervating extraocular muscles appear to be protected in many forms of motoneurone disease in man and other species. However, there were still markedly fewer abducens motoneurones in the old wobblers compared to controls (approximately 29% reduction). Sparing of oculomotor neurones in other diseases has been attributed to their relatively high PV expression, which we also observed in the abducens nucleus of both wobblers and littermates, and to a lesser extent in the other motor nuclei too. In conclusion, our results suggest that, in the wobbler mouse, motoneurone degeneration may occur without overt signs such as cell body vacuolation and NADPH-d expression. Induced CB expression may be neuroprotective but that constitutive expression of PV may not.

Maximal and minimal motor conduction velocity in amyotrophic lateral sclerosis and X-linked bulbospinal muscular atrophy measured by Harayama's collision method

Measurement of the maximal (Vmax) and minimal (Vmin) motor nerve conduction velocities was performed in amyotrophic lateral sclerosis (ALS), bulbospinal muscular atrophy (BSMA), and control subjects. The collision method as described initially by Harayama and coworkers was used. This allowed for the correction of the velocity recovery effect (VRE) in Hopf's original method. The purpose of this study is to clarify the controversial results regarding the Vmin and the difference between Vmax and Vmin (Vmax-Vmin) in ALS and to compare these results with BSMA, and clarify the usefulness of Harayama's method. In ALS, a reduction of Vmax and Vmin, and an increase of Vmax-Vmin were found in both median and posterior tibial nerve. In BSMA, a reduction of Vmin and an increase of Vmax-Vmin in the median nerve were noted. Some patients whose results of conventional nerve conduction study were entirely within normal range showed abnormal results in Vmin and/or Vmax-Vmin. These results suggest that the correction of VRE is essential to determine a Vmin, and motor fibers with abnormally slow conduction velocities were present in ALS and BSMA. Harayama's collision method is useful to detect abnormalities of motor fibers with submaximal conduction velocities.

Comparative analysis of motoneuron loss and functional deficits in PMN mice: implications for human motoneuron disease

We have investigated the correlation between functional and morphological deficits in PMN mice, an animal model of human motoneuron disease. Electrophysiologic investigations showed first abnormalities, i.e. reduction of M-response amplitudes, already at postnatal d 13 when the disease was not yet phenotypically apparent, and when motoneuron and motor axon numbers were still normal. After d 27, a loss of more than 30% of motoneuron axons and cell bodies was detectable in the phrenic nerve and facial nucleus, respectively. At that stage, PMN mice showed severe functional and electrophysiological deficits. At later stages of the disease when still more than 50% of motor axons and at least 60% of motoneuron cell bodies were present, the distal compound muscle action potential amplitude decreased by more than 95% in small foot muscles after sciatic nerve stimulation. We conclude that functional deficits precede structural deficits in this animal model of human motoneuron disease. Our findings are in agreement with the concept of the 'sick motoneuron' in this animal model of motoneuron disease rather than the idea of progressive loss of motoneurons resulting in disease only after a significant number of motoneurons has degenerated.

Sympathetic skin response in amyotrophic lateral sclerosis

OBJECTIVES

The aim of our study was to verify the usefulness of the sympathetic skin response (SSR) as an instrument for assessing autonomic involvement in amyotrophic lateral sclerosis (ALS).

MATERIAL AND METHODS

- We studied palmar and plantar SSR in 31 patients with ALS (mean age: 58.4+/-9.3 years); 48 age-matched healthy subjects constituted the control group.

RESULTS

Palmar SSR was elicitable in all patients, and its latency and amplitude did not significantly differ from that of the controls. Plantar response was evoked in all but 7 patients. The lack of response was significantly related to the functional disability and duration of the disease.

CONCLUSIONS

We conclude that SSR, even the plantar response, cannot be considered a useful tool for detecting early autonomic involvement in ALS.

Clinical aspects of CAG repeat diseases

Seven neurodegenerative disorders are known to be caused by unstable expansions of the trinucleotide CAG within human genes, and more will be discovered in the coming years. These disorders share some clinical similarities, as well as some differences, which are summarized here. These diseases have unusual clinical genetic properties related to the dynamic nature of CAG repeat expansions, including instability of the repeat expansion in meiosis, particularly male meiosis; a strong correlation between onset age and size of the repeat expansion; anticipation (earlier disease onset in succeeding generations); new mutations arising from unstable, mutable alleles with a high-normal CAG repeat number; and reduced penetrance for alleles in the low-affected range. Much more remains to be learned about the molecular biology and clinical pathophysiology of this new class of genetic diseases.

Motor nerve biopsy studies in motor neuropathy and motor neuron disease

The clinical presentation of motor neuropathy often resembles that of motor neuron disease, sometimes leading to an erroneous diagnosis. Moreover, the underlying pathological process in motor neuropathy has been rarely investigated and there are no systematic studies of the affected motor nerves. We describe a new motor nerve biopsy procedure, performed in 15 patients: 6 with motor neuropathy and 9 with motor neuron disease. The motor branch from the anterior division of the obturator nerve to the gracilis muscle in the thigh was biopsied. In both groups of patients the motor nerves exhibited depletion of myelinated nerve fibers. In motor neuropathy there was a significantly higher density of regenerative clusters of small myelinated fibers in comparison to motor nerves from patients with motor neuron disease. In addition, in 3 patients with motor neuropathy there was evidence for demyelination with thinly myelinated axons and small onion bulb formations. These pathological studies of motor nerve biopsies can help to differentiate motor neuropathy from motor neuron disease.

Changes of unmyelinated nerve fibers in sural nerve in amyotrophic lateral sclerosis, Parkinson's disease and multiple system atrophy

Quantitative changes in unmyelinated nerve fibers (UMNFs) of sural nerves in patients of amyotrophic lateral sclerosis (ALS), Parkinson's disease (PD) and multiple system atrophy (MSA) were evaluated using autopsy materials whose pathological diagnosis had been confirmed by careful postmortem examinations. Ordinary ALS cases demonstrated no involvement in cutaneous UMNFs; however, the patients with long survival due to the application of ventilatory support showed bimodality in UMNF diameter histograms, and a patient with involvement of systems other than motor pathways showed an abnormal value in two indices: a low percentage of subunits containing axon(s) and a high mean number of Schwann cell profiles per axon. A significant reduction of the mean value of UMNF density (21%) was found in PD patients. Because the density of myelinated nerve fibers did not show any significant decrease as compared with age-matched controls, the change of nerve fibers in peripheral nervous system was considered to be confined to UMNFs in PD. Elderly PD cases showed enhanced changes in the ageing process, as expressed by the two indices described above. In MSA, the mean value of UMNF density was significantly decreased (23%), and this decrease almost paralleled that of myelinated nerve fiber density. Abnormal values for the two indices described above were found and two out of four cases demonstrated bimodality in the diameter histogram of UMNFs. Unlike MSA, ALS and PD have not been included in the disorders with cutaneous UMNF involvement. Our results supply the first evidence of morphological changes in cutaneous UMNFs in PD cases. In ordinary ALS cases, the emergence of such morphological changes is suggested in cases with long survival.

Decreased heart rate variability in amyotrophic lateral sclerosis

Autoregressive spectral analysis of heart rate variability (HRV) was performed in 29 patients with amyotrophic lateral sclerosis (ALS) and 33 age-matched healthy subjects to evaluate the involvement of the autonomic nervous system. HRV analysis provides a means to recognize low (LF) and high (HF) frequency components, respectively mediated by sympathetic and parasympathetic heart control. An increase in the mean heart rate at rest (P < 0.001), a decrease in standard deviation of R-R interval as well as in PNN50 (P < 0.001), and an increase in the LF/HF component ratio (P < 0.01) were found in the ALS patients, indicating a vagal-sympathetic imbalance. These alterations were not related to the clinical features and to the duration of the disease. Our results suggest a subclinical involvement of the autonomic nervous system in ALS, particularly affecting parasympathetic cardiovascular control.

Clinicopathological study of the peripheral nervous system in Machado-Joseph disease

Three cases of histologically-proven Machado-Joseph disease (MJD) (clinically, types II and III) are described with special reference to the peripheral nervous system. We systematically and quantitatively analyzed the myelinated fiber densities in various nerves of three MJD patients and compared the results with the patients' clinical features and the pathological findings for the central nervous system (CNS). The results obtained were (1) motor system: The number of intermediate gammamotoneuron fibers was decreased prominently in all three MJD patients. In the type III MJD cases, the number of large alpha-motoneuron fibers also were decreased. (2) Sensory system: it generally was less involved than the motor system at the root level; but the large fibers of the distal portion were vulnerable. (3) Oculomotor system: the number of large oculomotor fibers was decreased markedly in all three cases, but there was relative preservation of parasympathetic fibers. (4) Autonomic system: the preganglionic sympathetic fibers from the intermediate lateral nucleus generally were preserved. These results suggest that in MJD the vulnerability of the peripheral nerves reflects the degree of loss of their original neuronal cells and varies according to the clinical phenotype. The characteristic peripheral neuropathy of MJD may be the result of axonal degeneration due to perikaryal neuronal damage in the central nervous system.

Choline acetyltransferase and NADPH diaphorase are co-expressed in rat spinal cord neurons

Phenotypic diversity underlies the complex functioning of the nervous system. One characteristic in which neurons differ from one another is the kind of molecules that they use for intercellular signalling. The classical neurotransmitter acetylcholine, synthesized by the enzyme choline acetyltransferase, is used by five groups of neurons in the rat spinal cord. Another messenger is nitric oxide, which is synthesized by nitric oxide synthase. Neurons that express nitric oxide synthase can be stained specifically by NADPH diaphorase histochemistry. In the spinal cord, approximately five groups of neurons are labeled by the diaphorase reaction, and some of these populations overlap with cholinergic groups. To determine the proportions of neurons that co-express choline acetyltransferase and nitric oxide synthase, we performed choline acetyltransferase immunocytochemistry and diaphorase histochemistry on single sections of rat spinal cord. Some cell types were single-labeled: somatic motor neurons were choline acetyltransferase-immunoreactive only, and neurons in lamina II were diaphorase-positive only. Four cell groups included double-labeled cells. Autonomic motor neurons were either double-labeled (62%) or choline acetyltransferase-only (37%), partition cells in lamina VII were double-labeled (54%) or choline acetyltransferase-only (45%), neurons in laminae III-V of the dorsal horn were double-labeled (70%) or diaphorase-only (27%), and neurons surrounding the central canal were double-labeled (56%), choline acetyltransferase-only (23%) or diaphorase-only (21%). These data indicate that certain spinal cord populations may be heterogeneous with regard to the intercellular messenger phenotypes involving acetylcholine and nitric oxide.(ABSTRACT TRUNCATED AT 250 WORDS)

Selective vulnerability of alpha motor neurons in ALS: relation to autoantibodies toward acetylcholinesterase (AChE) in ALS patients

The degenerative process in amyotrophic lateral sclerosis (ALS) concerns primarily alpha motor neurons in the spinal cord and brain stem, and neurons forming descending pathways to the cord, especially in the pyramidal tract. Some degeneration of large peripheral sensory nerve fibers often occurs too, but preganglionic autonomic neurons and gamma motor neurons are most often spared in the disease. The vulnerability of alpha motor neurons compared to other types of neurons in ALS is discussed in relation to retrograde axoplasmic transport from peripheral blood of foreign noxious macromolecules, interneuronal transport of such molecules, and neuronal surface structure properties relevant to uptake for retrograde axoplasmic transport. Certain differences in these aspects between alpha motor neurons and other neuronal types exist. Some differences concern the neuronal turnover of acetylcholinesterase (AChE), which could be of special interest in view of the recent demonstration of regular occurrence of autoantibodies towards this enzyme in ALS patients.

Somatic motor efferents in multiple system atrophy with autonomic failure: a clinico-pathological study

The myelinated fibers in the corticospinal tracts, ventral spinal roots, and the neurons in the ventral spinal horns were quantitatively examined in 8 autopsied cases of multiple system atrophy associated with autonomic failure. In these structures consisting of the somatic motor efferents, the main pathological feature was the size dependent-involvement of predominantly small-sized fibers and neurons. The small myelinated fibers were significantly depopulated, while the large myelinated fibers were well populated in the corticospinal tract. Neurons in the ventral horns were also involved, but those with a small diameter and located in the intermediate zone (Rexed's lamina VII, VIII) were markedly diminished. In the ventral spinal roots, in the fourth lumbar segments containing essentially no autonomic efferents, small myelinated fibers were also preferentially involved. These pathological changes in the small-sized fiber and neuron loss were examined in relation to the somatic and autonomic motor symptoms, particularly of pyramidal signs.

Maximal and minimal motor nerve conduction velocities in patients with motor neuron diseases: correlation with age of onset and duration of illness

We measured the maximal and minimal motor nerve conduction velocities of the ulnar nerve in 17 patients with spinal muscular atrophy (SMA), 27 patients with amyotrophic lateral sclerosis (ALS), and 40 age-matched control subjects. Crude values of the maximal and minimal motor nerve conduction velocities were reduced in both patient groups, but their difference in each patient was not statistically different from that of a control subject. The conduction velocities adjusted according to each patient's age were faster in SMA patients than in ALS patients. Among patients with either ALS or SMA, the age-adjusted conduction velocities were larger in those who had developed the disease at younger ages and suffered from it for shorter periods of time. These findings suggest that the motor nerve fibers regenerate more in younger patients in the early stages of the disease, particularly in SMA.

Nerve growth factor receptor immunostaining in the spinal cord and peripheral nerves in amyotrophic lateral sclerosis

In animal experiments, nerve transection is followed by expression of nerve growth factor receptors (NGFR) on Schwann cells of both motor and sensory nerve fibres distally to the site of the lesion. To determine whether denervated Schwann cells in amyotrophic lateral sclerosis (ALS) similarly express NGFR, a study was made of post-mortem material of peripheral nerves and ventral roots from ALS cases and age-matched controls, using immunolabelling methods. Dorsal roots and spinal cords were also examined for the presence of NGFR. In all the ALS cases and controls, NGFR immunostaining was seen in the outer layer of vessel walls, perineurial sheaths, connective tissue surrounding fascicles in nerve roots and in the substantia gelatinosa of the spinal cord. In ALS, NGFR staining was also present in the Schwann cells of degenerated nerve fibres in mixed peripheral nerves, in ventral roots and, to a lesser extent, in dorsal roots. NGFR immunoreactivity was also seen in elongated cells extending from the perifascicular connective tissue into the nerve fascicles. It is concluded that denervated Schwann cells in ALS express NGFR and that NGFR immunostaining on Schwann cells may be used as an indicator of axonal degeneration. The NGFR labelling in the dorsal roots supports the notion that ALS is not a pure motor syndrome.

Expression of nerve growth factor receptor in human peripheral neuropathies

Nerve growth factor (NGF) receptors in human sural nerve biopsies were detected immunohistochemically using a monoclonal anti-human NGF receptor antibody. NGF receptors were not visualized within the endoneurium of normal adult nerves but were readily demonstrable within the endoneurium of nerves undergoing active axonal degeneration. Immunostaining of adjacent sections for S-100 beta protein, a specific Schwann cell marker, suggested that Schwann cells expressed the NGF receptors induced by axonal degeneration. Residual Schwann cells in nerves in which axons were completely depleted also expressed NGF receptors. NGF receptors were not detected in relation to thinly myelinated regenerating axons, nor were they detected in the endoneurium of nerves that had undergone segmental demyelination and remyelination. The increased expression of NGF receptors in human axonal neuropathies may contribute to regeneration by NGF-responsive neurons in these disorders.

Motoneuron loss in the abducens nucleus of wobbler mice

The 'wobbler' mutant mouse can be recognized at about 4 weeks of age by its tremor and atrophy of forelimb muscles. In addition to degeneration of spinal motoneurons, especially in cervical spinal cord, selected bulbar motoneurons have also been reported to degenerate in the mutant. We examined a cranial motor nucleus and found a 31% loss of abducens motoneurons in 4-5-week-old wobbler mice as compared to age-matched control mice.

Morphometry of the degenerative process in the hypoglossal nerves in amyotrophic lateral sclerosis

The peripheral hypoglossal nerves in 13 cases of amyotrophic lateral sclerosis (ALS) and five control cases were examined using morphometrical methods to demonstrate the degenerative process of motor nerve degeneration. The total number of myelinated fibers and their histograms were analyzed according to the degree of severity of the degeneration. Reduction of the total number of myelinated fibers in ALS hypoglossal nerves were graded in three groups: mild 65%-75%, moderate 50%-65% and severe 30%-50% of the myelinated fibers in controls. Each histogram of the remaining myelinated fibers showed different patterns corresponding to the degree of the degeneration and disclosed that the progressive reduction of large myelinated fibers was the fundamental change. Small myelinated fibers were not reduced, but increased, especially in the group with a moderate grade of degeneration. In plastic section, there were clusters of regenerated myelinated fibers. The transient increase of small myelinated fibers may be a reflexion of myelinated fiber regeneration during the progressive degenerative process of the motor neurons. The correlation between the degree of severity of the hypoglossal nerve degeneration and the atrophy of the tongue muscle and the duration of bulbar symptoms was examined and discussed.

Light and ultrastructural studies in sural biopsies of the pseudopolyneuropathic form of ALS

The aim of this work was to study the neuropathological picture of the sural nerve in the pseudopolineuropathic form of A.L.S. Five patients were considered: in all cases the clinical and electromyographic follow-up excluded other diseases. EMG-studies were repeatedly performed: they showed the progressive evolution of the spinal anterior horn cell pathology from lower spinal to cervical levels. The sural nerve was processed according to the procedure used in our laboratory for light and ultrastructural examination. Quantitative analysis of myelinated fiber density was carried out on photographic enlargement and reported on histograms. The light and ultrastructural examination showed a severe loss of myelinated fibers; the decrease affected all types of fibers, but predominated in the largest ones. In the axons there was an increase of mitochondria, dilation of the small vesicles and increase in the number of neurofilaments. It is our opinion that all histopathologic data obtained in the sural nerve biopsy in this form of A.L.S. reveal a clear involvement of the sensory neurons of the spinal ganglia and the results can be useful for the study of precocius lesions in the A.L.S.

Peripheral nerve involvement in familial chorea-acanthocytosis

Myelinated fibers and neuronal cell bodies of the ventral spinal outflow and primary sensory neurons were histopathologically examined in a patient with familial chorea-acanthocytosis and age-matched controls. The patient exhibited a marked loss of large myelinated axons and their neuronal cell bodies in the ventral spinal outflow, while there was frequent occurrence of axonal sprouts. Large myelinated fibers in sensory afferents were also decreased in number. Segmental de- and remyelination was markedly increased in teased fiber preparations of both motor and sensory peripheral nerves.

Amyotrophic lateral sclerosis: Part 1. Clinical features, pathology, and ethical issues in management

Amyotrophic lateral sclerosis (ALS) is a progressive degenerative disease of the motor system in adults that occurs in sporadic, familial, and Western Pacific forms. Involvement of non-motor pathways has been increasingly recognized, both clinically and pathologically. Although the usual course is relentlessly progressive with death in half the cases within three years from onset, it can sometimes be protracted. Degeneration and loss of large motor neurons in the cerebral cortex, brainstem, and cervical and lumbar spinal cord are characteristic. Marked reduction in the number of large myelinated fibers is notable in the cervical and lumbar ventral roots. Peripheral nerves show reduced numbers of large myelinated fibers, acute axonal degeneration at all levels, and distal axonal atrophy. Motor end-plates reveal small or absent nerve terminals. Subclinical non-motor system involvement includes neuronal loss in Clarke's nucleus and dorsal root ganglia, degeneration of non-motor tracts in the spinal cord, loss of receptors in the dorsal horns of the spinal cord, and myelinated fiber loss with segmental demyelination in sensory and mixed nerves. The serious implications of the diagnosis of ALS make it mandatory to exclude similar potentially treatable disorders. Management should be multidisciplinary, and discussions with the patient and family members should be frank and frequent. Discussions about ventilatory support should take place early in the disease so that death from respiratory failure can be prevented, when that is desired, and conversely to obviate the discontent and anger that accompany involuntary life on a ventilator.

Autonomic function in amyotrophic lateral sclerosis: a study of cardiovascular responses

Autonomically mediated cardiovascular responses were evaluated in 15 ALS patients and compared with 15 healthy subjects. The respiratory sinus arrhythmia, the heart rate response to a Valsalva manoeuvre, to isometric handgrip and to a dive reflex test was normal, indicating a normal function of vagal nerves. The heart rate and blood pressure responses during an orthostatic test were normal, indicating a normal function of sympathetic nerves. The increase in blood pressure and blood flow in the contralateral forearm which occurs on handgrip in healthy subjects was reduced in the ALS patients. The cause of this is unclear, but could be related to decreased function of "ergoreceptors" or altered vascular reactivity in atrophic muscle.