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Biomedical subjects

P Guiheneuc

Publications and source records attributed to P Guiheneuc.

At least 19 recordsLinked to original sources
PubMed2003

[Neuromuscular synapse: molecular mechanisms of acetylcholine vesicular exocytosis].

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 preconditioned 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 chaperone molecules. Arrival of an action potential causes depolarisation of the motoneurone 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.

Acetylcholine↗
PubMed2002

Partial return of motor function in paralyzed legs after surgical bypass of the lesion site by nerve autografts three years after spinal cord injury.

Spinal cord injuries often result in irreversible loss of motor and somatosensory functions below the lesion level. Treatment is limited to physiotherapy aimed at compensating disability. We previously showed that re-establishment of tissue continuity can be achieved in animal models through nerve autografts implanted between the rostral spinal ventral horn and the caudal ventral roots. Rostral motor neuron axons could thus reach peripheral targets, leading to some return of motor function. We used a similar approach in a paraplegic patient with stabilized clinical states three years after spinal cord traumatic damage at the T9 level. Three segments from autologous sural nerves were implanted into the right and left antero-lateral quadrant of the cord at T7-8 levels, then connected to homolateral L2-4 lumbar ventral roots, respectively. Eight months after surgery, voluntary contractions of bilateral adductors and of the left quadriceps were observed. Muscular activity was confirmed by motor unit potentials in response to attempted muscle contraction. Motor-evoked potentials from these muscles were recorded by transcranial magnetic stimulation. These data support the hypothesis that muscles have been re-connected to supra-spinal centers through motor neurons located in the rostral stump of the damaged cord. They suggest that delayed surgical reconstruction of motor pathways may contribute to partial functional recovery.

Electromyography↗
PubMed2002

[Ptosis and mastication disorders revealing concurrent myasthenia gravis and chronic polyradiculoneuritis].

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.

Adrenal Cortex Hormones↗
PubMed1997

Load compensation tasks evoke tremor in cerebellar patients: the possible role of long latency stretch reflexes.

'Tremor' is one of the clinical signs of cerebellar dysfunction. Its nature remains subject to debate, one hypothesis being that of a predominant role of peripheral afferences in its genesis. This study was designed to study whether load compensating tasks, evoking sudden stretch, and thus stimulation of peripheral afferences induced tremor in cerebellar patients. We study the kinematics and EMG pattern of a load compensating task which consists of maintaining a constant elbow position despite the onset and cessation of a 2 Nm torque loading the elbow flexors in eight cerebellar patients and six controls. Angular position and velocity, and EMG of the biceps and triceps are recorded at a sampling rate of 1 kHz. In normal subjects, trajectories are simple with little overshoot of the aimed position. EMG analysis shows a long latency stretch response (LLSR) which initiates a phasic and then tonic voluntary activity. In cerebellar patients, the two prominent cinematic features are hypermetria and tremor. The stretch response is of the same latency, but the EMG pattern is modified with bursts of activity related to the tremor. These results show severe perturbations of load compensating tasks in cerebellar patients. We discuss the possible role of the exaggeration of LLSR in both hypermetria and tremor.

Case-Control Studies↗
PubMed1997

[Signal processing in electromyography: a review].

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.

Artifacts↗
PubMed1992

[Electrophysiological investigation of polyneuropathies].

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.

Adult↗
PubMed1990

Sympathetic skin response: normal results in different experimental conditions.

(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.

Acoustic Stimulation↗
PubMed1989

[Phrenic stimulation in C1-C2 tetraplegia. Apropos of a case].

The authors report a case of post traumatic tetraplegia at the C1-C2 level in a young man of 16 with total respiratory paralysis treated with mechanical ventilation and a tracheotomy. Thirty months after the accident, an Avery S 232(1) diaphragmatic pacemaker was surgically implanted by the mediastinal approach. The technique was rapidly successful and enabled satisfactory ventilation and phonation two months after the implantation. The patient is currently treated at home with no signs of diaphragmatic fatigue 20 months after the implantation of the stimulator.

Adolescent↗
PubMed1989

[Are intraluminal electrodes reliable for recording myoelectric activity of the small intestine?].

In humans except for the postoperative state, electromyographic activity of the small bowel can only be recorded with intraluminal electrodes. The aim of this study was to validate the use of intraluminal electrodes in pigs by comparing the signal recorded from such electrodes to those recorded with surgically implanted electrodes. A polyethylene probe equipped with bipolar ring-shaped electrodes was placed in the lumen of the proximal jejunum of 6 pigs, at the same level as intramuscular implanted electrodes. The signals were recorded in conscious pigs fed normally. By comparison to the myoelectric activity recorded from the intramuscular implanted electrodes, the intraluminal electrodes provided reliable spike burst detection (sensitivity 85 p. 100; positive predictive value 91 p. 100) in the fasted and fed state, and good identification of migrating myoelectric complexes. Spectral analysis showed the same frequency patterns for signals obtained with both types of electrodes. In conclusion, intraluminal ring-shaped electrodes allow reliable detection of small bowel myoelectric activity and may represent a useful tool for motility studies in man.

Animals↗
PubMed1988

[Digital vibration syndrome and carpal tunnel syndrome: possible neurophysiological differences?].

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.

Adult↗
PubMed1986

[Digital vibration syndrome: neuro-physiologic study in 17 patients].

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.

Adult↗
PubMed1984

[Motor nerve conduction velocity in children: normal values and application to a few pathologic cases].

Nerve conduction velocity (NCV), according to age, was studied in normal children. Motor distal ulnar NCV (in 63 children, from 1 day to 4 years of age), motor distal tibial NCV (in 93 children, from birth to 15 years of age), proprioceptive tibial NCV (in 59 children, from birth to 5 years of age) and proximal CV (in 133 children from birth to 15 years of age), as well as VIIth superior branch CV (in 67 children) and XIIth CV (in 56 children) from birth to 3 years of age, were measured. These measurements showed that NCV changes were similar; NCV was 45-50% of the adult value during the first month of life. Then NCV increased very quickly, the progression being 90% of the first month's value during the first 18 months of life. The adult value was reached between 2 and 5 years of age. Proprioceptive NCV was 8-13 m/sec higher than motor NCV; proximal NCV was also 10-13 m/sec higher than distal motor tibial NCV. Ulnar NCV remained higher than tibial NCV, although changes in velocity as a function of age remained parallel. These NCV measurements proved significant in some diseases. The were useful for diagnosis of Krabbe's disease or of metachromatic leucodystrophy and to calculate the degree of disturbance in toxic polyneuritis, polyradiculoneuritis and some cranial nerve injuries; they were also useful in following up children undergoing chronic haemodialysis. In each case, NCV was only one aspect of a more complete neurophysiological study.

Adolescent↗
PubMed1984

Maturation of the blink reflex in infants.

The blink reflex was elicited in 50 children from birth to 3 years of age. In the awake state, the R1 response was always obtained; R2 responses, especially contralateral ones, were more difficult to elicit under 9 months of age. R1 latency and VIIth motor nerve conduction variations were a good witness of the peripheral nervous system maturation. The influence of the different states of waking and sleeping on these reflex responses was studied. These results and some of the mechanisms that underlie these changes are discussed.

Blinking↗
PubMed1983

[New method of iterative measurement of muscular force in normal and dystrophic mice].

A new method is described, to perform repeated measures of twitch and tetanic tensions during isometric contractions of the tail's extensor muscles, in anesthetized mice. The results obtained from 20 normal and 15 dystrophic (S57 BL/6J dy/dy) mice are presented. This method may be a good tool for long term therapeutic trials in dystrophic mice.

Animals↗
PubMed1982

[Study of membrane proteins in skeletal muscle of normal or dystrophic mice. Effects of isaxonine phosphate (author's transl)].

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.

Animals↗
PubMed1982

[Study of the effects of isaxonine on retrograde axon degeneration induced by vincristine in man (author's transl)].

Fifteen patients with Hodgkin's disease were examined before and after each administration of vincristine sulfate (2 intravenous injections of 1.4 mg/m2 of body surface, during the first week of each month for 3 months). Moreover, each patient received daily, according to a double blind protocol, either 4 capsules of 375 mg of isaxonine, either 4 capsules filled with lactose used as placebo. At the end of treatment, analysis revealed that 8 subjects were given isaxonine and 7 the placebo. Motor, sensory and reflex conduction velocities, amplitudes of potentials evoked by stimulating motor, cutaneous sensory, or primary afferent fibres, were determined in each electrophysiological examination session. The data and pecularly those obtained from reflex studies, show a significant lesser degree of distal axonal degeneration, in patients receiving a placebo. These results support evidence for a protective effect of the drug against vincristine induced peripheral nerve lesions.

Double-Blind Method↗