Amyotrophic lateral sclerosis is a multifactorial disease

Motor neurone disease in South Estonia. Diagnosis and incidence rate

The current study evaluated the diagnostic standards of MND and epidemiological markers of MND in Estonia. A total of 108 patients were referred to the University Hospital from 1986 to 1995 with the first suggested diagnosis or final diagnosis of amyotrophic syndrome, amyotrophic lateral sclerosis (ALS), progressive bulbar paralysis (PBP) or progressive muscular atrophy (PMA). In addition neurologists of the region and the National Society of Neuromuscular disorders were contacted. Some 94 patients satisfied the diagnostic criteria. The annual incidence rate in South Estonia and in the city of Tartu ranged from 0.5 to 2.8 per 100,000. The mean annual incidence rate in Tartu is 1.98 and in South Estonia in general 1.3. The highest incidence rate was 8.3 for men in the age group 60 to 64 years and 7.49 in the age group 70-74; among female patients the highest incidence rate -4.6 was in the age group from 65 to 69.

Functional significance of upper and lower motor neuron impairment in amyotrophic lateral sclerosis

The objective of this study was to examine the contribution of lower motor neuron (LMN) and upper motor neuron (UMN) dysfunction to weakness and impaired motor control in 27 patients with amyotrophic lateral sclerosis (ALS). Isometric strength was measured by dorsiflexor maximum voluntary contraction force (MVC). LMN function was measured by tetanic force, twitch force, and the amplitude of the compound muscle action potential. UMN function was measured by the speed of rapid foot taps, the maximum rate of rise of voluntary force, and the central activation ratio [CAR = MVC/(MVC + superimposed tetanic force)]. The results suggest that (1) LMN loss appears to be the primary cause of progressive weakness in ALS; while (2) UMN impairment in ALS leads to slowing of contraction speed and rapid movements, and modest decreases in central activation; and (3) during 6 months of progression, LMN changes were greater than UMN changes.

Oxidative stress and superoxide dismutase in development, aging and gene regulation

Free radicals and other reactive oxygen species are produced in the metabolic pathways of aerobic cells and affect a number of biological processes. Oxidation reactions have been postulated to play a role in aging, a number of degenerative diseases, differentiation and development as well as serving as subcellular messengers in gene regulatory and signal transduction pathways. The discovery of the activity of superoxide dismutase is a seminal work in free radical biology, because it established that free radicals were generated by cells and because it made removal of a specific free radical substance possible for the first time, which greatly accelerated research in this area. In this review, the role of reactive oxygen in aging, amyotrophic lateral sclerosis (a neurodegenerative disease), development, differentiation, and signal transduction are discussed. Emphasis is also given to the role of superoxide dismutases in these phenomena.

Comparison of corticomotoneuronal EPSPs and macro-MUPs in amyotrophic lateral sclerosis

We correlated the size of the corticomotoneuronal excitatory postsynaptic potential (CM-EPSP) arising in a single spinal motor neuron with the function of the target motor unit as measured by conventional and macro EMG in early amyotrophic lateral sclerosis (ALS). Macro motor unit potentials (macro-MUPs) were recorded from a surface electrode after spike-triggered averaging in the extensor digitorum communis muscle. The size of the CM-EPSP projecting to the same motor unit was measured from changes in the firing probability of single motor units induced by transcranial magnetic stimulation using peristimulus time histograms. In controls, the amplitudes of CM-EPSPs and macro-MUPs correlated inversely, probably reflecting a lower input resistance of larger spinal motoneurons. In ALS the amplitude of macro-MUPs did not correlate with that of CM-EPSPs and one third of normal ALS motor units had a reduced or temporally dispersed CM-EPSP. The findings indicate primary dysfunction of the corticomotoneuronal projection system in ALS that is independent of functional changes of spinal motoneurons.

Diverse abnormalities of corticomotoneuronal projections in individual patients with amyotrophic lateral sclerosis

Using peristimulus time histograms (PSTHs), abnormalities of composite excitatory postsynaptic potentials (EPSPs) induced by transcranial magnetic stimulation were studied in multiple motor units from individuals with amyotrophic lateral sclerosis (ALS) and normal subjects. We studied 97 motor units in the extensor digitorum communis muscle of 22 patients with sporadic ALS and 47 motor units of 10 healthy control subjects. Four or five motor units were studied in each patient and normal subject. For each unit, macro motor unit potentials (Macro-MUPs) were simultaneously recorded from a surface electrode after spike-triggered averaging. The composite EPSPs in ALS showed a generally bi-directional deviation from the normal curve, with small EPSPs at one end, and larger amplitude EPSPs with a prolonged rise time at the other end. The variability of EPSPs from adjacent motor units in the same individual was significantly larger in ALS than in controls. In normal subjects there is a significant negative correlation between the amplitude of composite EPSPs and the Macro-MUPs. In ALS, the trend is reversed (positive) suggesting that the abnormalities of composite EPSPs are supraspinal in origin. A combination of partial attrition of the corticomotoneuronal core and hyper-excitability of surviving corticomotoneurons projecting to a given spinal motoneuron pool best explains the diversity of the composite EPSP in individuals with ALS.

Expression of a Cu,Zn superoxide dismutase typical of familial amyotrophic lateral sclerosis induces mitochondrial alteration and increase of cytosolic Ca2+ concentration in transfected neuroblastoma SH-SY5Y cells

We have set up a model system for familial amyotrophic lateral sclerosis (FALS) by transfecting human neuroblastoma cell line SH-SY5Y with plasmids directing constitutive expression of either wild-type human Cu,Zn superoxide dismutase (Cu,ZnSOD) or a mutant of this enzyme (G93A) associated with FALS. We have tested mitochondrial function and determined cytosolic Ca2+ concentration in control cells (untransfected) and in cells expressing either wild-type Cu,ZnSOD or G93A. We report that G93A induces a significant loss of mitochondrial membrane potential, an increased sensitivity toward valinomycin and a parallel increase in cytosolic Ca2+ concentration. The above phenomena are not related to total Cu,ZnSOD content and activity in the cell.

Transgenic animals as models of neurodegenerative diseases in humans

Neurodegenerative diseases are of major socioeconomic importance and represent an enormous challenge for the scientific and medical communities. Advances in molecular genetics during the past decade have begun to provide approaches for the establishment of animal models for these disorders using transgenic technology. Their analysis will lead to better understanding of disease pathogenesis and will be invaluable for the identification of novel diagnostic and therapeutic agents. With the current pace of genomic research, the generation of transgenic animal models, reproducing in full the pathology and symptoms of even complex disorders such as Alzheimer's disease, must now be considered achievable.

Intracellular calcium chelator BAPTA protects cells against toxic calcium overload but also alters physiological calcium responses

The effect of the membrane-permeant calcium chelator 1,2-bis-(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetra(acetoxymethyl) ester (BAPTA/AM) on ionomycin-induced cellular calcium overload was studied in single differentiated NH15-CA2 neuroblastoma x glioma hybrid cells. To monitor [Ca2+]i we used the fluorescent indicator Fura-2. Preincubation of the cells with 3 microM BAPTA/AM reduced the number of cells showing deregulation of [Ca2+]i during ionomycin-induced calcium influx. The calcium transients elicited by application of KCl were also severely affected by the chelator. These transients, although varying from cell to cell in shape, amplitude and duration, are well reproducible in individual cells. After incubation of cells for 1 h with 0.3-30 microM BAPTA/AM the time course of these cellular transients was markedly slowed. At 1 microM BAPTA/AM, the time constant of decline of [Ca2+]i was increased by a factor of 4.1 +/- 2.4 (n = 14) and the amplitude was reduced to about 50%. With 30 microM BAPTA/AM, the K(+)-induced calcium transients were almost completely inhibited. We conclude that intracellularly loaded calcium chelators may be used for the prevention of [Ca2+]i-induced cell damage, however, at the expense of a disturbed calcium signalling.

Evaluation of antioxidants, protein, and lipid oxidation products in blood from sporadic amyotrophic lateral sclerosis patients

Several parameters indicators of oxidative stress were evaluated in blood from individuals with the sporadic form of amyotrophic lateral sclerosis (SALS) and compared to healthy controls. Plasma levels of 2-thiobarbituric-reactive substances (TBARS), products of lipid peroxidation, were significantly higher (p < 0.03) in the SALS patients compared to controls. The concentration of plasma antioxidants (alpha-tocopherol, beta-carotene, ubiquinol-10 and glutathione) and the activity of red blood cell CuZn superoxide dismutase were not significantly different between the groups. The ratio TBARS/alpha-tocopherol was 47% higher in the SALS individuals than in controls. Protein thiols and protein-associated carbonyls in red blood cell membranes and supernates were similar for both groups. A positive correlation (r2 = 0.91) was found between the concentration of protein-associated carbonyls in red blood cells and the onset of clinical symptoms. These findings are in agreement with several reports showing higher levels of oxidative damage to cell components in ALS.

Aberrant stress-induced phosphorylation of perikaryal neurofilaments

The aberrant phosphorylation of the neurofilament high molecular weight subunit (NFH) in the neuronal perikaryon is a common feature of several neurological diseases. We demonstrated a strong correlation between hyperphosphorylation of the NFH carboxyl-terminal domain and activation of stress-activated protein kinase (SAPK) -gamma in PC12 cells. Agents that activated SAPKgamma in PC12 cells also caused the hyperphosphorylation of perikaryal NFH in cultured dorsal root ganglion neurons. The NFH carboxyl-terminal domain was phosphorylated by SAPKgamma in vitro, and the use of peptide substrates indicated that this event occurred preferentially at KSPXE motifs. We propose that SAPKgamma, perhaps in concert with other SAPKs, is involved in the abnormal phosphorylation of perikaryal NFH. This finding could lead to new insights into the etiology of several neurological diseases.

A new hypothesis of neurodegenerative diseases: the deleterious network hypothesis

Growing evidence has indicated the existence of deleterious networks in the brains of neurodegenerative disorders, including Alzheimer's disease. Parkinson's disease, amyotrophic lateral sclerosis and Huntington's disease. The deleterious networks are formed on the basis of the intimate interactions among the key pathogenic factors, including oxidative damage, aberrant calcium homeostasis, metabolic compromise and, under certain circumstances, amyloid precursor protein mismetabolism. Based on the novel concept, deleterious network, a unifying hypothesis, the deleterious network hypothesis of neurodegenerative diseases, is proposed. This new theory stresses that the deleterious network is just the common pathway of the degenerative disorders, triggering of which by aging, certain genetic or environmental factors leads to a cascade of pathological alterations of the illnesses. It appears that this new theory has synthesized some most appealing hypotheses about neurodegenerative illnesses, providing consistent explanations to a larger number of observations about those diseases than other hypotheses. Because the disorders appear to result from the interactions among the key detrimental factors, it is suggested that the patients of the neurodegenerative diseases should be treated by combinative application of the drugs which can diminish peroxidative damage, calcium mismetabolism, and metabolic compromise.

Reactive astrogliosis of the spinal cord in amyotrophic lateral sclerosis

Many observations have been carried out on astrogliosis in the cerebral cortex in amyotrophic lateral sclerosis (ALS), whereas little attention has been paid to astrogliosis in the spinal cord. Twenty autopsy cases of sporadic, common form of ALS have been studied. Spinal cords have been examined at the cervical, thoracic and lumbar levels by histological methods and immunohistochemistry for GFAP, Vimentin, Tau-protein, Neurofilaments, PCNA. A gliosis was found in the ventral horns, in dorsal horns and at the transition between gray matter and anterior and lateral funiculi, especially close to laminae VII, VI and V as being due to secondary gliosis. The findings cannot be interpreted on the only basis of the substitutive role of reacting glia. The proposed pathogenetic mechanisms of ALS are evaluated as possible responsible stimuli; the coincidence of the distribution of reactive astrocytes with the entering points of the corticospinal tracts into the gray matter is considered of primary importance. Of special interest are reactive astrocytes at the transition between laminae VII, VI and V and the lateral funiculus, where dystrophic neurites are known to concentrate.

Clinical epidemiology of amyotrophic lateral sclerosis

The introduction of palliative therapies in amyotrophic lateral sclerosis (ALS) will alter the epidemiology of ALS as it is known now. Although incidence rates will remain unchanged in the near future, prevalence rates will likely increase dramatically. Better understanding of the age-specific presentation of motor neuron diseases worldwide will shed light on the vexing questions concerning the variable incidence rates in some countries and apparent incidence gradients in North America and Europe.