Total numbers of limb motor neurones in the human lumbosacral cord and an analysis of the accuracy of various sampling procedures

Severe and progressive neuronal loss in myelomeningocele begins before 16 weeks of pregnancy

BACKGROUND

Despite undisputable benefits, midtrimester prenatal surgery is not a cure for myelomeningocele (MMC): residual intracranial and motor deficits leading to lifelong handicap question the timing of prenatal surgery. Indeed, the timing and intensity of intrauterine spinal cord injury remains ill defined.

OBJECTIVE

We aimed to describe the natural history of neuronal loss in MMC in utero based on postmortem pathology.

STUDY DESIGN

Pathology findings were analyzed in 186 cases of myelomeningocele with lesion level between S1 and T1. Using a case-control, cross-sectional design, we investigated the timewise progression and topographic extension of neuronal loss between 13 and 39 weeks. Motor neurons were counted on histology at several spinal levels in 54 isolated MMC meeting quality criteria for cell counting. These were expressed as observed-to-expected ratios, after matching for gestational age and spinal level with 41 controls.

RESULTS

Chiari II malformation increased from 30.7% to 91.6% after 16 weeks. The exposed spinal cord displayed early, severe, and progressive neuronal loss: the observed-to-expected count dropped from 17% to ≤2% after 16 weeks. Neuronal loss extended beyond the lesion to the upper levels: in cases <16 weeks, the observed-to-expected motor neuron count was 60% in the adjacent spinal cord, decreasing at a rate of 16% per week. Progressive loss was also found in the upper thoracic cord, but in much smaller proportions. The observed-over-expected ratio of motor neurons was not correlated with the level of myelomeningocele.

CONCLUSIONS

Significant neuronal loss is present ≤16 weeks in the exposed cord and progressively extends cranially. Earlier prenatal repair (<16 weeks) could prevent Chiari II malformation in 69.3% of cases, rescue the 17% remaining motor neurons in the exposed cord, and prevent the extension to the upper spinal cord.

Role of Human-Induced Pluripotent Stem Cell-Derived Spinal Cord Astrocytes in the Functional Maturation of Motor Neurons in a Multielectrode Array System

The ability to generate human‐induced pluripotent stem cell (hiPSC)‐derived neural cells displaying region‐specific phenotypes is of particular interest for modeling central nervous system biology in vitro. We describe a unique method by which spinal cord hiPSC‐derived astrocytes (hiPSC‐A) are cultured with spinal cord hiPSC‐derived motor neurons (hiPSC‐MN) in a multielectrode array (MEA) system to record electrophysiological activity over time. We show that hiPSC‐A enhance hiPSC‐MN electrophysiological maturation in a time‐dependent fashion. The sequence of plating, density, and age in which hiPSC‐A are cocultured with MN, but not their respective hiPSC line origin, are factors that influence neuronal electrophysiology. When compared to coculture with mouse primary spinal cord astrocytes, we observe an earlier and more robust electrophysiological maturation in the fully human cultures, suggesting that the human origin is relevant to the recapitulation of astrocyte/motor neuron crosstalk. Finally, we test pharmacological compounds on our MEA platform and observe changes in electrophysiological activity, which confirm hiPSC‐MN maturation. These findings are supported by immunocytochemistry and real‐time PCR studies in parallel cultures demonstrating human astrocyte mediated changes in the structural maturation and protein expression profiles of the neurons. Interestingly, this relationship is reciprocal and coculture with neurons influences astrocyte maturation as well. Taken together, these data indicate that in a human in vitro spinal cord culture system, astrocytes support hiPSC‐MN maturation in a time‐dependent and species‐specific manner and suggest a closer approximation of in vivo conditions. stem cells translational medicine2019;8:1272&1285

We describe a fully human, spinal cord‐specific, coculture platform with human‐induced pluripotent stem cell‐derived motor neurons and astrocytes for multielectrode array recording. We show that human‐induced pluripotent stem cell‐derived motor neurons/human‐induced pluripotent stem cell‐derived astrocytes bidirectional morphological and molecular maturation is reflected by electrophysiological recordings with multielectrode array recording.

Neuromuscular Junction as an Entity of Nerve-Muscle Communication

One of the crucial systems severely affected in several neuromuscular diseases is the loss of effective connection between muscle and nerve, leading to a pathological non-communication between the two tissues. The neuromuscular junction (NMJ) represents the critical region at the level of which muscle and nerve communicate. Defects in signal transmission between terminal nerve endings and muscle membrane is a common feature of several physio-pathologic conditions including aging and Amyotrophic Lateral Sclerosis (ALS). Nevertheless, controversy exists on whether pathological events beginning at the NMJ precede or follow loss of motor units. In this review, the role of NMJ in the physio-pathologic interplay between muscle and nerve is discussed.

Age-related changes in the structure and function of mammalian neuromuscular junctions

As mammals age, their neuromuscular junctions (NMJs) change their form, with an increasingly complex system of axonal branches innervating increasingly fragmented regions of postsynaptic differentiation. It has been suggested that this remodeling is associated with impairment of neuromuscular transmission and that this contributes to age-related muscle weakness in mammals, including humans. Here, we review previous work on NMJ aging, most of which has focused on either structure or function, as well as a new study aimed at seeking correlation between the structure and function of individual NMJs. While it is clear that extensive structural changes occur as part of the aging process, it is much less certain how, if at all, these are correlated with an impairment of function. This leaves open the question of whether loss of NMJ function is a significant cause of age-related muscle weakness.

Sarcopenia: Relocating the Forest among the Trees

As life expectancy continues to rise worldwide, health concerns associated with advanced age are increasingly becoming prominent public health concerns. Among these concerns, nearly 30 years of discussion and research have yielded a wealth of information regarding the pathophysiology, biologic etiology, and clinical implications of age-related declines in skeletal muscle mass and function (i.e., sarcopenia). Recent years have yielded several debates surrounding both the definition and terminology of sarcopenia, yet many questions remain regarding interventions to treat the condition. Among major future challenges in the area will be to design and conduct high-quality clinical trials to ultimately provide new therapeutic strategies for the treatment of sarcopenia.

Acute Elevated Glucose Promotes Abnormal Action Potential-Induced Ca2+ Transients in Cultured Skeletal Muscle Fibers

A common comorbidity of diabetes is skeletal muscle dysfunction, which leads to compromised physical function. Previous studies of diabetes in skeletal muscle have shown alterations in excitation-contraction coupling (ECC)-the sequential link between action potentials (AP), intracellular Ca²⁺ release, and the contractile machinery. Yet, little is known about the impact of acute elevated glucose on the temporal properties of AP-induced Ca²⁺ transients and ionic underlying mechanisms that lead to muscle dysfunction. Here, we used high-speed confocal Ca²⁺ imaging to investigate the temporal properties of AP-induced Ca²⁺ transients, an intermediate step of ECC, using an acute in cellulo model of uncontrolled hyperglycemia (25 mM, 48 h.). Control and elevated glucose-exposed muscle fibers cultured for five days displayed four distinct patterns of AP-induced Ca²⁺ transients (phasic, biphasic, phasic-delayed, and phasic-slow decay); most control muscle fibers show phasic AP-induced Ca²⁺ transients, while most fibers exposed to elevated D-glucose displayed biphasic Ca²⁺ transients upon single field stimulation. We hypothesize that these changes in the temporal profile of the AP-induced Ca²⁺ transients are due to changes in the intrinsic excitable properties of the muscle fibers. We propose that these changes accompany early stages of diabetic myopathy.

Sarcopenia in older mice is characterized by a decreased anabolic response to a protein meal

Ageing is associated with sarcopenia, a progressive decline of skeletal muscle mass, muscle quality and muscle function. Reduced sensitivity of older muscles to respond to anabolic stimuli, i.e. anabolic resistance, is part of the underlying mechanisms. Although, muscle parameters have been studied in mice of various ages/strains; the aim was to study if mice display similar deteriorating processes as human ageing. Therefore, 10,16,21 and 25 months-old C57BL6/6J male mice were studied to measure parameters of sarcopenia and factors contributing to its pathophysiology, with the aim of characterizing sarcopenia in old mice. Muscle mass of the hind limb was lower in 25 as compared to 10 month-old mice. A significant decrease in physical daily activity, muscle grip strength and ex vivo muscle maximal force production was observed in 25 compared to 10 month-old mice. The muscle anabolic response to a single protein meal showed increased muscle protein synthesis in young, but not in old mice, indicative to anabolic resistance. However, by increasing the protein content in meals, anabolic resistance could be overcome, similar as in human elderly. Additionally, aged mice showed higher fasted insulin and hepatic malondialdehyde (MDA) levels (=marker oxidative stress). This study shows clear characteristics of sarcopenia that coincide with anabolic resistance, insulin resistance and oxidative stress in 25 month-old C57/BL6 male mice, similar to human ageing. Furthermore, similar decline in muscle mass, strength and function was observed in this aged-mice-model. These observations offer potential for the future to explore in old mice the effects of interventions targeting sarcopenia.

Troponin T nuclear localization and its role in aging skeletal muscle

Troponin T (TnT) is known to mediate the interaction between Tn complex and tropomyosin (Tm), which is essential for calcium-activated striated muscle contraction. This regulatory function takes place in the myoplasm, where TnT binds Tm. However, recent findings of troponin I and Tm nuclear translocation in Drosophila and mammalian cells imply other roles for the Tn-Tm complex. We hypothesized that TnT plays a nonclassical role through nuclear translocation. Immunoblotting with different antibodies targeting the NH2- or COOH-terminal region uncovered a pool of fast skeletal muscle TnT3 localized in the nuclear fraction of mouse skeletal muscle as either an intact or fragmented protein. Construction of TnT3-DsRed fusion proteins led to the further observation that TnT3 fragments are closely related to nucleolus and RNA polymerase activity, suggesting a role for TnT3 in regulating transcription. Functionally, overexpression of TnT3 fragments produced significant defects in nuclear shape and caused high levels of apoptosis. Interestingly, nuclear TnT3 and its fragments were highly regulated by aging, thus creating a possible link between the deleterious effects of TnT3 and sarcopenia. We propose that changes in nuclear TnT3 and its fragments cause the number of myonuclei to decrease with age, contributing to muscle damage and wasting.

Models of accelerated sarcopenia: critical pieces for solving the puzzle of age-related muscle atrophy

Sarcopenia, the age-related loss of skeletal muscle mass, is a significant public health concern that continues to grow in relevance as the population ages. Certain conditions have the strong potential to coincide with sarcopenia to accelerate the progression of muscle atrophy in older adults. Among these conditions are co-morbid diseases common to older individuals such as cancer, kidney disease, diabetes, and peripheral artery disease. Furthermore, behaviors such as poor nutrition and physical inactivity are well-known to contribute to sarcopenia development. However, we argue that these behaviors are not inherent to the development of sarcopenia but rather accelerate its progression. In the present review, we discuss how these factors affect systemic and cellular mechanisms that contribute to skeletal muscle atrophy. In addition, we describe gaps in the literature concerning the role of these factors in accelerating sarcopenia progression. Elucidating biochemical pathways related to accelerated muscle atrophy may allow for improved discovery of therapeutic treatments related to sarcopenia.

Involvement of Onuf's nucleus in Machado-Joseph disease: a morphometric and immunohistochemical study

Machado-Joseph disease (MJD) is an autosomal dominant neurodegenerative disease caused by an expansion of CAG repeats in the MJD1 gene, in which lower urinary tract dysfunction is known to be the most commonly encountered autonomic failure. However, it remains unclear whether Onuf's nucleus (ON), which plays major roles in the micturition reflex and voluntary continence, degenerates during the disease process. In the present study, we conducted a morphometric and immunohistochemical study of ON, together with the lateral nuclear group (LNG) of the sacral anterior horns, in seven patients with MJD. When compared with controls, the number of lower motor neurons in both ON and LNG was significantly smaller in the MJD patients, the former being inversely correlated with the size of the expanded CAG repeats. Notably, MJD patients with a large CAG-repeat expansion showed an ON-predominant pattern of neuronal loss, while in the remaining patients, ON and LNG were affected to a similar degree, or rather an LNG-predominant pattern of neuronal loss was evident. Moreover, when adjusted for age, the degree of neuronal loss in both ON and LNG was significantly correlated with the extent of expansion of the CAG repeats. In MJD, the remaining lower motor neurons in ON often exhibited ataxin-3- or 1C2-immunoreactive (ir) neuronal intranuclear inclusions, while no pTDP-43-ir neuronal cytoplasmic inclusions were present in these neurons. In conclusion, the present findings strongly suggest that neuronal loss in ON, the degree of which is highly influenced by the extent of expansion of CAG repeats, is a consistent feature in MJD.

Morphometric and topographical studies of small neurons in sporadic amyotrophic lateral sclerosis spinal gray matter

Little attention has been paid to the degeneration of small neurons in ALS spinal gray matter. The purpose of the present paper was to undertake morphometric and quantitative analysis of the spinal gray matter of 15 ALS patients and compare findings to those of five controls. A significant reduction of small neurons in the anteromedial and intermediate parts of the gray matter were detected in ALS spinal cords with diffuse myelin pallor in the ventral aspects of the anterolateral columns outside the corticospinal tracts, and the number of small neurons in these areas was decreased significantly depending on the intensity of the myelin pallor. There were no significant alterations in the number of small neurons in the corresponding areas of ALS spinal cords without diffuse myelin pallor or in those of controls. In the posterior parts of the gray matter, there were no significant differences in the number of small neurons among ALS patients and controls. These findings strongly suggest that diffuse myelin pallor in the ventral aspects of anterolateral columns in ALS spinal cords is derived from the degeneration of small neurons in the anteromedial and intermediate parts of the gray matter.

Age-related changes in histogram pattern of anterior horn cells in human cervical spinal cord

The purpose of the present study was to clarify age-related changes in histograms of spinal anterior horn cells. The study examined Rexed lamina IX of the C7 spinal cord segment in 22 men who had died of non-spinal disease (age range, 0-85 years). First, we confirmed that the size of nucleoli exhibited a linear relationship to the diameter of spinal anterior horn cells by preparing histograms of nucleoli. Second, this formula was used to create histograms of cervical anterior horn cells. Results were as follows: (i) diameter of nucleoli ranged from 2.0 microm to 6.0 microm; (ii) in each subject, no changes were seen in histogram patterns among ventral, intermediate, dorsal and overall sections; (iii) at < or =20 years of age, histograms displayed a single peak for the diameter of nucleoli at about 4.0-4.5 microm; (iv) at 21-60 years of age, histograms displayed two peaks, at about 3.5-4.0 microm and 5.0-5.5 microm; and (v) at 61-85 years of age, histograms displayed a single peak at about 5.0-5.5 microm.

Widespread loss of neuronal populations in the spinal ventral horn in sporadic motor neuron disease. A morphometric study

The cytopathology and loss of neurons was studied in 7670 neurons from the ventral horn of the third lumbar segment of the spinal cord of six sporadic motor neuron disease (MND) patients compared with 7568 neurons in seven age matched control subjects. A modified Tomlinson et al. [Tomlinson BE, Irving D, Rebeiz JJ. Total numbers of limb motor neurones in the human lumbosacral cord and an analysis of the accuracy of various sampling procedures. J Neurol Sci 1973;20:313-27] sampling procedure was used for neuronal counts. The ventral horn was divided in quadrants. Neuronal populations were also classified by the maximum cell diameter through the nucleolus. There was widespread loss of neurons in all quadrants of the ventral horn in MND. Size distribution histograms showed similar neuron loss across all populations of neurons. The dorsomedial quadrant contains almost exclusively interneurons and the ventrolateral quadrant mostly motor neurons. The cytopathology of neurons in the dorsomedial quadrant and of large motorneurons in the ventrolateral quadrant MND was similar. In the dorsomedial quadrant, neuron loss (56.7%) was similar to the loss of large motor neurons in the ventrolateral quadrant (64.4%). The loss of presumed motor neurons and interneurons increased with increased disease duration. There was no evidence that loss of presumed interneurons occurred prior, or subsequent, to loss of motor neurons. We conclude that, in sporadic MND, all neuronal populations in the ventral horn are affected and that interneurons are involved to a similar extent and in parallel with motor neurons, as reported in the G86R transgenic mouse model of familial MND. The increasing evidence of loss of neurons other than motor neurons in MND suggests the need for revising the concept of selective motor neuron vulnerability.

Transferrin as a muscle trophic factor

Muscle cells grow by proliferation and protein accumulation. During the initial stages of development the participation of nerves is not always required. Myoblasts and satellite cells proliferate, fusing to form myotubes which further differentiate to muscle fibers. Myotubes and muscle fibers grow by protein accumulation and fusion with other myogenic cells. Muscle fibers finally reach a quasi-steady state which is then maintained for a long period. The mechanism of maintenance is not well understood. However, it is clear that protein metabolism plays a paramount role. The role played by satellite cells in the maintenance of muscle fibers is not known. Growth and maintenance of muscle cells are under the influence of various tissues and substances. Among them are Tf and the motor nerve, the former being the main object of this review and essential for both DNA and protein synthesis. Two sources of Tf have been proposed, i.e., the motor nerve and the tissue fluid. The first proposal is that the nervous trophic influence on muscle cells is mediated by Tf which is released from the nerve terminals. In this model, the sole source of Tf which is donated to muscle cells should be the nerve, and Tf should not be provided for muscle fiber at sites other than the synaptic region; otherwise, denervation atrophy would not occur, since Tf provided from TfR located at another site would cancel the effect of denervation. The second proposal is that Tf is provided from tissue fluid. This implies that an adequate amount of Tf is transferred from serum to tissue fluid; in this case TfR may be distributed over the entire surface of the cells. The trophic effects of the motor neuron have been studied in vivo, but its effects of myoblast proliferation have not been determined. There are few experiments on its effects on myotubes. Most work has been made on muscle fibers, where innervation is absolutely required for their maintenance. Without it, muscle fibers atrophy, although they do not degenerate. In contrast, almost all the work on Tf has been performed in vitro. Its effects on myoblast proliferation and myotube growth and maintenance have been established; myotubes degenerate following Tf removal. But its effects on mature muscle fibers in vivo are not well understood. Muscle fibers possess TfR all over on their cell surface and contain a variety of Fe-binding proteins, such as myoglobin. It is entirely plausible that muscle fibers require an amount of Tf, and that this is provided by TfR scattered on the cell surface.(ABSTRACT TRUNCATED AT 400 WORDS)

Expression and localization of cyclooxygenase-1 and -2 in human sporadic amyotrophic lateral sclerosis

Prostaglandins (PGs) are critical mediators of physiologic processes and inflammation. They are produced by two different isoforms of the cyclooxygenase (COX) enzyme, namely COX-1 and COX-2. In particular COX-2 was demonstrated to be crucial for PG-synthesis in inflammation. Recently, inhibition of COX-2 was shown to prevent the loss of motor neurons in a model of amyotrophic lateral sclerosis (ALS). Furthermore, spinal COX-2 expression was shown to be increased in transgenic mice that produce an ALS-like syndrome. Therefore, we investigated the expression of COX-1 and COX-2 in the spinal cord of seven human sporadic ALS patients by means of immunohistochemistry. Specimens from seven patients without any neurological disease served as controls. COX-2 expression was dramatically increased in the spinal cord of patients with ALS. Its protein was found in motor neurons, interneurons and glial cells. Statistical analysis showed a significantly higher expression of COX-2 in ALS for both neurons and glia. In contrast, COX-1 expression was predominantly confined to microglia and no apparent difference was detected between controls and ALS. In addition, we studied the concentration of prostaglandin E2 (PG E2) as a marker for COX activity in the cerebrospinal fluid of nine patients diagnosed for ALS and compared the results with those from nine patients without motor neuron disease. PG E2 levels were markedly increased in ALS cases (45.8 +/- 35.1 pg/mL) compared to the non-ALS specimens (15.8 +/- 3.7 pg/mL). The results of our study corroborate a potential role for COX-2 in the pathogenesis of motor neuron death in ALS. Selective COX-2 inhibition might therefore offer a new possibility in the treatment of human ALS. However, to determine the exact role of COX-2 in human ALS will require further research.

Ubiquitin immunoreactivity in presumed spinal interneurones in motor neurone disease

Previous studies have demonstrated the presence of ubiquitin-immunoreactivity (Ub-IR) as inclusions and skeins in motor neurones of both the familial and sporadic forms of motor neurone disease (MND). There is evidence that interneurones also degenerate in MND, but Ub-IR in ventral horn spinal interneurones has not been studied previously. Here, Ub-IR was investigated in 1445 presumed interneurones and 1086 presumed motor neurones counted in three random 20-microm sections of the ventral horn of the third lumbar segment of the spinal cord of each of seven controls and seven patients with MND. The ventral horn was divided into four quadrants; the dorsomedial quadrant contains almost exclusively interneurones and the ventrolateral quadrant largely motor neurones. The neurones were also classified by morphological and size criteria into presumed interneurones (< 25 microm) and presumed motor neurones (>or= 25 microm). Ub-IR was classified as inclusions, skeins and dispersed cytoplasmic and nuclear staining. Ub-IR inclusions or skeins were not observed in the controls but 6.6% of neurones (motor neurones and interneurones) showed the presence of dispersed cytoplasm staining and nuclear staining. The incidence of Ub-IR cytoplasmic and nuclear staining was significantly greater in both motor neurones and interneurones of MND patients than controls. Ub-IR was less frequent in MND cases in which a great loss of neurones was observed. Ub-IR was significantly more frequent in motor neurones than interneurones, both in patients and controls. Ub-IR inclusions and skeins were only observed in motor neurones from MND patients. Ub-IR inclusions were not observed in presumed spinal interneurones, while skeins were only seen in three out of 565 of these cells (two of them in the dorsomedial quadrant) in two out of seven patients. Thus, although presumed spinal interneurones occasionally revealed Ub-IR features similar to motor neurones, the rare staining of Ub-IR skeins and the lack of Ub-IR inclusions in interneurones in MND suggests that these neurones only occasionally form ubiquitin-protein conjugates. Neuronal size, rather than type, may be important in determining whether ubiquitin-protein conjugates form in the ventral horn neurones in MND.

Gene therapy for amyotrophic lateral sclerosis and other motor neuron diseases

There are several incurable diseases of motor neuron degeneration, including amyotrophic lateral sclerosis (ALS), primary lateral sclerosis, hereditary spastic hemiplegia, spinal muscular atrophy, and bulbospinal atrophy. Advances in gene transfer techniques coupled with new insights into molecular pathology have opened promising avenues for gene therapy aimed at halting disease progression. Nonviral preparations and recombinant adenoviruses, adeno-associated viruses, herpesviruses, and lentiviruses may ultimately transduce sufficient numbers of cerebral, brainstem, and spinal cord neurons for therapeutic applications. This could be accomplished by direct injection, transduction of lower motor neurons via retrograde transport after intramuscular injection, or cell-based therapies. Studies using transgenic mice expressing mutant superoxide dismutase 1 (SOD1), a model for one form of ALS, established that several proteins were neuroprotective, including calbindin, bcl-2, and growth factors. These same molecules promoted neuronal survival in other injury models, suggesting general applicability to all forms of ALS. Potentially correctable genetic lesions have also been identified for hereditary spastic hemiplegia, bulbospinal atrophy, and spinal muscular atrophy. Finally, it may be possible to repopulate lost corticospinal and lower motor neurons by transplanting stem cells or stimulating native progenitor populations. The challenge ahead is to translate these basic science breakthroughs into workable clinical practice.

Quantitative assessment of motor neuron loss in equine motor neuron disease (EMND)

The mean number of motor neurons was assessed in the C7 spinal cord segment of 5 EMND and 5 control horses. Mean number per section in EMND horses was reduced significantly (P<0.001). The mean neuronal loss was estimated at 31%. Each of the 5 affected horses had a mean neuronal count below the 95% confidence interval for control horses. The statistically significant difference between the 2 groups was consistent in the cranial, middle and caudal thirds of the C7 segment (P<0.001). The results of regression analysis indicated an association between neuronal reduction in EMND horses and the duration of the disease when adjusted for age (P<0.001). This is the first quantitation of the neurodegenerative loss in EMND and it provides a clearer explanation for residual deficits in horses that survive EMND.

Morphological and morphometric characterisation of Onuf's nucleus in the spinal cord in man

In the absence of a systematic morphometric study of Onuf's nucleus in man, this investigation defines the limits of variation of segmental position and the range of length and volume of Onuf's nucleus in 6 normal humans displaying no neurological disease (2 males, 4 females). Serial section reconstruction methods in conjunction with the disector method provided information on the numbers, sizes and shapes of the constituent motor neurons of Onuf's nucleus. In contrast to previous descriptions, the cranial origin of Onuf's nucleus occurred in rostral S1 in 50% of subjects, and midcaudal S1 in the remaining subjects. Onuf's nucleus varied in length between 4 and 7 mm, and was 0.2-0.37 mm3 in volume. Differences in length or volume between males or females, or between the left and right side of the cord were not statistically significant. Neurons in Onuf's nucleus varied in diameter between 10 microns and 60 microns (mean 26 microns) and their mean number was 625 +/- 137. A higher density of neurons occurred at the cranial and caudal ends of the nucleus relative to the middle. While 37% of neurons were approximately spherical (shape index approximately 1), 44% were ellipsoid and 19% fusiform (shape indices varying between 0.26 and 0.8). These findings are compared with previous studies of Onuf's nucleus in man and animals. The results form a basis for further studies on Onuf's nucleus in normality and neurodegenerative diseases.

Immunohistochemical study on choline acetyltransferase in the spinal cord of patients with amyotrophic lateral sclerosis

The authors developed a polyclonal antibody against a fusion protein containing 598 amino acids from a human choline acetyltransferase (ChAT) cDNA and 12 amino acids derived from an expression vector, and examined immunohistochemical reactivity for ChAT in large motor neurons (30 microns and more in somal minimal diameter) of the lumbar spinal cords of four patients with amyotrophic lateral sclerosis (ALS) and of four control cases. In controls, the number of large neurons included in the tissue with a total thickness of 100 microns ranged from 74 to 105 (average 87). About 60-90% (average 80%) of the neurons were positively stained in their perikarya with an anti-human ChAT antibody. In the cases of ALS, the number of large motor neurons was greatly reduced (25-60, average 38). About 4-13% (average 8%) were positively stained. These results indicate that not only large neurons are reduced in number, but also their positivity for ChAT is decreased in the anterior horn of ALS spinal cord.

N-methyl-D-aspartate (NMDA) receptors in the spinal cord and motor cortex in motor neuron disease: a quantitative autoradiographic study using [3H]MK-801

The distribution and density of NMDA receptors in spinal cord and motor cortex was compared in motor neuron disease (MND; 10 cases) and controls (8 cases) using [3H]MK-801 autoradiography. In the spinal ventral horn of MND cases, [3H]MK-801 binding was reduced and there were fewer focal hot spots of binding. These changes are likely to reflect loss of motor neurons (MN) bearing NMDA receptors. [3H]MK-801 binding was increased in intermediate spinal grey matter and deeper layers of the motor cortex in MND cases compared to controls. This may represent either an adaptive response to MN loss or a pathophysiological phenomenon contributing to MN degeneration.

Disease-specific patterns of neuronal loss in the spinal ventral horn in amyotrophic lateral sclerosis, multiple system atrophy and X-linked recessive bulbospinal neuronopathy, with special reference to the loss of small neurons in the intermediate zone

The ventral horn cells of the fourth lumbar segment were morphometrically analysed in six cases of amyotrophic lateral sclerosis (ALS; there common forms and three pseudopolyneuritic forms), six of multiple system atrophy (MSA) with autonomic failure, four of X-linked recessive bulbospinal neuronopathy (X-BSNP), and seven age-matched autopsy cases of non-neurological disorders. In the common form of ALS, large and medium-sized neurons of the medial and lateral nuclei were markedly lost; small neurons in the intermediate zone were slightly diminished but fairly well preserved. In the pseudopolyneuritic form of ALS, marked loss was present in the large and medium-sized neurons, and in the small neurons located in the intermediate zone as well. In the MSA, in contrast to ALS, there was a marked reduction in small neurons in the intermediate zone, and large and medium-sized neurons of the medial and lateral nuclei tended to be preserved. In X-BSNP, large and medium-sized neurons were almost completely lost and small neurons were also markedly depopulated. These findings indicated that the pattern of neuron loss in the ventral horn is distinct among these diseases depending on size, location and function of the ventral horn cell population. These disease-specific patterns of neuron loss suggest a difference in the process of neuronal degeneration of ventral horn cells among the disease examined.

Effects of ageing on the motor unit: a brief review

This review briefly summarizes the current state of knowledge regarding age related changes in skeletal muscle, followed by a more in-depth review of ageing effects on animal and human motor units (MUs). Ageing in humans is generally associated with reductions in muscle mass (atrophy), leading to reduced voluntary and electrically evoked contractile strength by the 7th decade for most muscle groups studied. As well, contraction and one-half relaxation times are typically prolonged in muscles of the elderly. Evidence from animal and human studies points toward age associated MU loss as the primary mechanism for muscle atrophy, and such losses may be greatest among the largest and fastest MUs. However, based on studies in animals and humans, it appears that at least some of the surviving MUs are able to partially compensate for MU losses, as indicated by an increase in the average MU size with age. The fact that muscles in the elderly have fewer, but on average larger and slower, MUs has important implications for motor control and function in this population.

Acetylcholinesterase-containing neurons, substance P and enkephalin fibers in the ventral horns of developing human embryos and fetuses

The presence of the acetylcholinesterase neurons and substance P-like and enkephalin-like fibers in the various nuclear columns of the ventral horns of the spinal cords was studied in the developing human by acetylcholinesterase histochemistry and substance P and enkephalin immunohistochemistry. Acetylcholinesterase-positive neurons initially appeared in the lateral neuronal columns and eventually were also observed in the medial columns as well as the median columns at various levels of the spinal cord by 10 weeks' gestation. Acetylcholinesterase-positive neurons in the lower sacral levels were not detected until 11-12 weeks' gestation. Diffused substance P- and enkephalin-like fibers were demonstrated as early as 10 weeks' gestation but did not align with any particular nuclear column until after 15 weeks' gestation. These fibers further increased in length and adopted reticular branching patterns and many of these tended to surround the cell bodies of the nuclear columns. Possible interaction of acetylcholinesterase neurons and substance P and enkephalin fibers would commence by 15 weeks' gestation.

Cholinergic markers in ALS spinal cord

We analyzed binding sites for quinuclidinyl benzilate (QNB) and hemicholinium-3 (HC-3) by quantitative slice autoradiography and the activities of choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) in spinal cord of 5-7 patients with amyotrophic lateral sclerosis (ALS). In the ventral horn, QNB binding sites were markedly reduced (38% of controls; P less than 0.001), whereas HC-3 binding sites were only moderately affected (76%, P less than 0.01). Losses in cholinergic marker enzymes were inconsistent. The loss of muscarinic binding sites in the ventral horn was the most reliable cholinergic disease marker in ALS.

A histometrical and comparative study on Purkinje cell loss and olivary nucleus cell loss in multiple system atrophy

We examined pathologically 21 cases of multiple system atrophy (MSA). Density of Purkinje cell in 16 cases and of olivary nucleus cell in 20 cases was quantitatively measured, and their distribution as well as degree were studied. Contrary to the findings of previous reports, Purkinje cell loss was more pronounced in the vermis than in the hemispheres. Olivary nucleus cell loss was more outstanding in the accessory nucleus than in the inferior nucleus. A topographical characteristic of cell degeneration exists between the Purkinje layer and the olivary nucleus. Significant sparing of the nodulus apparently related to that of the vestibular system was found. While the common distribution of cell loss was seen, its degree varied considerably case by case. The degree was related to both duration of illness and, to some extent, clinical subtypes of MSA.

An investigation of possible transynaptic neuronal degeneration in human spinal cord injury

Neurophysiological studies suggested that transynaptic neuronal degeneration of the anterior horn cells (AHC) may occur after an upper motoneuron lesion as the result of "deafferentation". To test this observation anatomically, patients with spinal cord injury (SCI) who had come to post mortem were investigated. Four patients with longstanding clinically and pathologically "complete" SCI were selected for comparison with 4 age-matched normal controls and with 2 patients who died of motoneuron disease (MND). The total number of AHCs in the L3 spinal cord segment was counted in each of the cases. The lesions in the traumatic group were all above the L3 segment. No significant differences in the number of AHC between the test cases and the normal controls was found. There was, as expected, a highly significant difference between the test cases and those with MND. The conclusion drawn from the study is that transynaptic neuronal degeneration of AHCs does not occur following complete transection of the human spinal cord. Thus the neurophysiological hypothesis is not supported anatomically.

The morphological relationships between substance P immunoreactive processes and ventral horn neurons in the human and monkey spinal cord

The distribution of substance P (SP)-containing neural processes in the ventral horn region of the human and monkey spinal cord was studied by staining for SP by the indirect antibody peroxidase-antiperoxidase technique and by light and electron microscopic examination of stained material. Immunoreactive fibers and terminals were found in all major cell columns of the ventral horn in the human and monkey spinal cord, with the immunoreactive profiles in close apposition to motoneurons. The immunoreactivity was contained in synaptic knoblike (bouton) structures, in which the label was associated with small agranular vesicles, dense-core vesicles, and mitochondria. The immunoreactive synaptic knobs formed synaptic junctions predominantly with dendrites. The labeled knobs were similar to "S" (agranular spheroid vesicles) and "G" (dense-core vesicles) type bulbs described previously in the monkey ventral horn. Their location, mainly on the neuron dendrites and soma supports the physiological evidence that SP-produced membrane depolarization is mediated primarily by a direct action of the neurochemical on the neuron rather than by a transynaptic mechanism.

Morphometric quantification of the cervical limb motor cells in various neuromuscular diseases

The number of motor cells was significantly reduced in the C8 segment of the cervical spinal cord in all 12 cases of amyotrophic lateral sclerosis (ALS), in the C6 and/or C8 segments in 1 case of adult onset spinal muscular atrophy, 2 cases of Werdnig-Hoffmann (W-H) disease, 3 of 4 cases of chronic polyneuropathy and in 1 case of poliomyelitis and 1 of ossification of the posterior longitudinal ligament in the cervical spine (OPLL). The numbers of motor cells were normal in the C6 or C8 segment in 6 cases of muscular dystrophy, except in one case of congenital muscular dystrophy, who showed reduced numbers of the motor cells. Examination of the distribution of motor cells per 500 micrometers thickness in serial sections revealed that reduction in numbers of the motor cells was diffuse and symmetrical in half the cases of ALS and W-H disease and in the cases of chronic polyneuropathy and congenital dystrophy; diffuse but asymmetrical in the other ALS and W-H disease cases and in a case of adult spinal muscular atrophy, and localized and asymmetrical in the cases of poliomyelitis and OPLL. In muscular dystrophy the distribution of motor cells showed segmental variations similar to controls.

Morphometric quantification of the cervical limb motor cells in controls and in amyotrophic lateral sclerosis

The limb motor cells of the C6 segment of the spinal cord were counted and correlated with quantified histological findings of biceps brachii muscles in controls and in cases of amyotrophic lateral sclerosis (ALS). In 12 controls the motor cells were divided into larger ones with a minimum diameter greater than 20 micron, and smaller cells. Total numbers of the larger motor cells decreased significantly in 11 of 12 cases of ALS and of the smaller cells in 4 cases. In 4 controls most of the constituents of the biceps brachii muscle were normal-sized fibers, while in ALS smaller fibers and interstitial connective tissue increased and hypertrophic fibers decreased in association with a decrease of normal-sized fibers. The correlation coefficients between total numbers of the larger or smaller motor cells and normal-sized fibers in ALS were 0.92 and 0.65 respectively, and the larger motor cells, correlating with muscular atrophy of the upper arm, were considered to be alpha motor cells. Although in ALS the larger motor cells decreased almost diffusely, there were segmental variations, similar to controls, in numbers of the motor cells per 500 micron thickness.

Spinal cord limb motor neurons in dystrophia myotonica

The total numbers of limb motor neurons have been counted in 20 micron sections of the lumbosacral spinal cord obtained a autopsy from 5 control subjects who showed no evidence of neuromuscular disease and from 5 patients with dystrophia myotonica ranging in age from 42 to 64 years. No significant reduction in the total number or distribution of such neurons was found in the cases of myotonic dystrophy and the quantity of lipofuscin present in the cells was similar to that in controls. Glial cell numbers were, however, significantly increased in the cases of dystrophia myotonica and this increase was not due to shortening or "crowding" of the relevant cord segments; in 2 patients with dystrophia myotonica the cell body area of the motor neurons was reduced by comparison with normal controls.

The numbers of limb motor neurons in the human lumbosacral cord throughout life

Forty-seven spinal cords from subjects between 13 and 95 years of age have been examined; in the majority death occurred suddenly or rapidly from a state of previous good health. The limb motor neurons in the lumbospinal segments have been estimated by counting nucleoli in characeteristic cells in every fifth group of 10 serial sections from the entire lumbosacral cord. No evidence exists of loss of motor neurons up to the age of 60 years, but beyond that age, although individual counts vary considerably, there is increasing evidence of a diminishing motor neuron pupulation; above 60 years, several cases showed motor neuron counts of only 50% of the counts in early adult life or middle age. Cell loss appeared to be uniform throughout all the segments and was unaccompanied by any other striking morphological change.

Hereditary hypertrophic neuropathy in the trembler mouse. Part 1. Histopathological studies: light microscopy

The Trembler mouse suffers from a dominantly inherited chronic hypertrophic neuropathy. Quantitative light-microscopic studies have been performed on Trembler peripheral nerves from birth to adulthood, and compared with the findings in age-matched control mice. Teased fibres of Trembler nerves contained virtually no myelin, nodes of Ranvier were difficult to identify, and supernumerary Schwann cells were prominent. Results of quantitative studies performed on the dorsal root ganglia and spinal cord of Trembler mice did not differ from those in controls. The density of myelinated fibres in the case of Tremblers was reduced at all ages when compared with controls, and there was a predominant loss of large diameter fibres.

On the pathogenesis of duchenne muscular dystrophy

The relative merits of the three presently most active hypotheses (vascular, neurogenic, and myogenic) concerning the pathogenesis of Duchenne muscular dystrophy are analysed and discussed and the literature is comprehensively reviewed.

Myoglobin in primary muscular disease. I. Duchenne muscular dystrophy. II. Muscular dystrophy of distal type

Skeletal myoglobin from two cases of muscular dystrophy, one of Duchenne muscular dystrophy, and one of muscular dystrophy of distal type, have been examined and no differences from normal human myoglobin were found. The opportunity has been taken to discuss the nature of minor fractions of myoglobin-like material which are found when human skeletal myoglobin is isolated. Those which have been observed in the present study have been artefacts and it was possible to demonstrate that they were due to deamidation of certain glutamine and asparagine residues.