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The transmission of excitation from motor neurones to muscle fibers at the neuromuscular junction is made through liberation of acetylcholine. This is concentrated into vesicles according to an exchange with H+ ions. Increase of intracellular calcium concentration leads some vesicles to mobilise and target with the neuron plasma membrane, where they are docked and preconditionned via the formation of a SNARE complex between vesicular proteins and plasma membrane proteins. Energy and control of these transports and reactions are provided by several kinds of enzymes and chaperonne molecules. Arrival of an action potential causes depolarisation of the motorneurone axon terminal and opening of large conductance calcium channels. The last step, directly linked to calcium input, leads the membranes to fuse and acetylcholine to immediately leave the neuron towards the synaptic space. [Copyright &y& Elsevier]

The excitability of the monosynaptic reflex pathway was tested in infants and children from birth to four years of age during waking and sleeping. The H reflex, evoked in the soleus muscle, was used to calculate the ratio, maximal H to maximal M, construct recruitment curves and test reflex excitability by the paired stimulus method. The excitability of the monosynaptic reflex pathway during the waking state is greatest at birth; it diminishes gradually during the first years of life without reaching the average level observed in adults by the end of the fourth year of age. From birth, regardless of age, sleep always depresses excitability. The mechanism that underlie this change with age, and with waking or sleeping, are discussed. [ABSTRACT FROM AUTHOR]

Hoffman's reflex was evoked in the soleus muscle of 105 normal children from birth to age 5 years. This technique made it possible to determine conduction time and to estimate conduction velocity over the reflex arc. For 59 children, proprioceptive and motor distal nerve conduction velocities were calculated for the tibial nerve trunk. These measurements enabled the common changes for these three velocities to be described in terms of an exponential curve. Proximal conduction velocity has similar values to those of proprioceptive distal nerve fibres: it is always higher than motor nerve conduction velocity, but the difference gradually diminishes, remaining constant after the eighteenth month. Conduction time diminishes between birth and one year of age, whereas height increases. Then conduction time increases slowly, reaching at about age 5 years, when average height is 1050 mm, the value it had just after birth. For the child born at term, maturation of the nervous system is thus especially rapid during the first year of life. [ABSTRACT FROM AUTHOR]

P0 is a transmembrane protein of the immunoglobulin superfamily that plays a role in myelin structure and function. Myelin protein zero gene (MPZ) mutations usually cause a demyelinating variant of Charcot-Marie-Tooth disease type 1B (CMT1B), but there is a wide spectrum of phenotypic manifestation of these mutations. We describe three patients from one family and one separate patient who presented with a demyelinating neuropathy. Some had recurrent lesions at compression sites mimicking hereditary neuropathy with liability to pressure palsies (HNPP). A heterozygous nonsense mutation (Tyr145Stop) corresponding to a T-to-A transition at nucleotide position 435 in exon 3 of the MPZ gene was identified in all patients. This mutation leads to an extracellular truncated protein, which may explain the mild phenotype. Therefore, such MPZ gene mutations should be searched for in cases of demyelinating neuropathy with acute nerve compression as well as in cases of the HNPP phenotype associated with normal the PMP22 gene.

Although myasthenia gravis (MG) has frequently been associated with other autoimmune disorders, it has only rarely been reported in conjunction with diseases of the nervous system. A 74-year-old patient with hypertension suddenly presented left unilateral ptosis and mastication disorders. Clinical examination showed a concomitant loss of strength distally and reduced deep tendon reflex. Electrophysiologic data indicated a diagnosis of MG and chronic inflammatory demyelinating polyneuropathy; acetylcholine receptor antibody was elevated at 4.1 nmol/L (normal < 2 nmol/L). Improvement was rapid after initiation of pyridostigmine in association with corticosteroid (1 mg/kg/day). One month later, the cranial nerve deficit disappeared and strength was normal. It is likely that a basic abnormality of immune regulation was responsible for the emergence of diseases with different clinical presentations, but similar immunopathogenesis. Corticosteroid seemed to be the most effective treatment.

Automatic analysis of electromyography (EMG), signals, first operated in 1950 with analogic machines, steeply expanded from 1980 when fast computers and worthwhile programs became available. On-line measurement of response area and latency, averaging of low amplitude waves, fast sorting of motor unit potential shape parameters, computation of the "jitter" between two muscle fibers, turns/amplitude and spectral analysis of interferential pattern records, are some examples of programs currently offered in modern EMG machines. Other techniques are still reserved for research purposes: scanning EMG, decomposition of nerve and muscle compound potentials, measurement of the threshold and firing rate of motor units, trace analysis using tracking models. Finally, the credit for artificial intelligence systems (knowledge based systems, fuzzy logic, neuronal networks) is still not clearly stated.

Needle electromyography, nerve conduction velocity measurement and recording of T, H or F waves, are the most commonly used methods to investigate patients with polyneuropathies. The grade, distribution, and functional type of the lesions are to be determined. A classification is proposed according to acute or chronic character of the neuropathy course and to prevailing signs of demyelination or axonal degeneration.

(1) The sympathetic skin response (SSR) is a slow wave, generated in deep layers of the skin, resulting from reflex activation of the sudomotor sympathetic efferent fibres. The aim of this study was to define experimental conditions, best stimulation and recording procedures, and the criteria for validation of the responses. (2) Thirty normal subjects (aged 25-56) were tested. The stimulation was an electrical pulse train applied to the median nerve at the wrist, a binaural tone burst, or both simultaneously. Records were made with surface electrodes on hand and foot contralateral to the stimulated median nerve. (3) Response shape was most often biphasic in feet, biphasic or triphasic in hands. SSR amplitude was 3.1 +/- 1.8 mV in hands, 1.4 +/- 0.8 mV in feet. Normal mean onset latency was 1.5 +/- 0.08 sec for hand response, 2.05 +/- 0.10 sec for foot response. The mean conduction velocity along peripheral sympathetic nerve fibres was 1.40 +/- 0.14 m/sec in lower limbs. (4) Bimodal stimulation (burst + median) provided responses of larger amplitude. The influence of stimulation intensity was also investigated. A decrease in amplitude and lengthening of latencies were observed after 15-20 min of testing. (5) The criteria for validation of responses are discussed. The importance of central processing time in the response delay is pointed out. In good methodological conditions, SSR would appear to be a simple, effective means of assessing sympathetic sudomotor outflow in central and peripheral nervous system disorders.

Workers using vibrating tools are exposed to vascular and nervous symptoms called vibration syndrome (VS); moreover, the same subjects show increased prevalence of possible carpal tunnel syndrome (CTS). To determine the diagnostic criteria of both syndromes, we studied clinical and neurophysiological signs and differences in 18 patients with VS and in 18 with CTS; neither group had any other pathologic symptoms. Clinical symptoms clearly distinguished the 2 groups of patients: Raynaud's phenomena were mainly observed in patients with VS (83% of cases), whereas Tinel's sign was found exclusively in patients with CTS (56% of cases). Neurophysiological results were qualitatively similar in both patients groups compared to control group results, showing a significant decrease in median motor and sensory nerve conduction velocities (NCV), a significantly higher motor distal latency and a lower nerve action potential amplitude. These group results and the scattering of interindividual results did not allow us to classify any given patient in one group or the other. Nevertheless, statistical analysis showed differences between the 2 patient groups: median abnormalities were more severe, especially as revealed by the abductor pollicis brevis electromyogram, in patients with CTS, whereas ulnar motor distal latency and motor and sensory NCV were abnormal, exclusively in 50% of patients with VS. These results lend support to the assumption that the mechanical and vascular mechanisms responsible for lesions in both groups of patients may differ in nature or occur in a different sequence.

Twelve patients with chronic renal failure, on maintenance hemodialysis have a stereotyped illness. The dialysate was made up from a high level aluminium tap water. After having been on haemodialysis for 10 to 12 months, they suffer from more and more acute osteodystrophic, osteomalacic symptoms. Then, distinctive EEG abnormalities appear. These first symptoms allow an early diagnosis of the progressive dialytic encephalopathy. The neurological symptoms appear some months later. Eight patients died from this encephalopathy. Four patients are still alive and are, from at least two years, on maintenance haemodialysis with a free aluminium water. In these 4 cases, the evolution of the disease is good: osteomalacic symptoms disappear in a year; the neurological symptoms are still present though transient. EEG abnormalities remain and blood aluminium level is about 100 micrograms/L. These cases show, once more, the significant role of aluminium as an aetiological factor in "progressive dialysis encephalopathy".

Studies were carried out on 17 male workers with clinical vibration disease who had been working with different vibrating tools (compressed-air hammers, chain-saws, rock drills, grinders) for 2 to 39 years. Their neurophysiological results were compared with those of 20 healthy men (control group). Median motor nerve conduction velocity (NCV) between elbow and wrist was significantly reduced and motor distal latency (DL) significantly longer in 43% cases. A distinct decrease of the conduction velocity of distal (finger-wrist) median sensory fibers (in 56% of cases) as well as reduced amplitude of the sensory evoked potential (62% of cases) were found. EMG showed alterations only in patients with NCV abnormalities. These electrophysiological findings point to distal axonal as well as to demyelination damage. The results, which are discussed in relation to previously published work in this field and according to a pathogenetic hypothesis of this syndrome, allowed us to draw practical conclusions for the neurophysiological examination of patients with vibration disease.

We compared plasma-membrane proteins of dystrophic and normal mouse skeletal muscle. The membrane protein concentrations were higher in dystrophic muscle than in normal muscle. The percentages of two of the protein bands on an SDS gel were different in normal and dystrophic muscle. Isaxonine (N-isopropyl-amino-2 pyrimidine) phosphate significantly increased plasma-membrane proteins in dystrophic muscle but not in normal muscle. The relative proportions of these two protein bands of dystrophic plasma membrane were modified by isaxonine phosphate. There was no change in the membrane proteins of normal muscle.