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Biomedical subjects

M Gioux

Publications and source records attributed to M Gioux.

At least 19 recordsLinked to original sources
PubMed2005

Rapid protein kinase C-dependent reduction of rat skeletal muscle voltage-gated sodium channels by ciliary neurotrophic factor.

The ciliary neurotrophic factor (CNTF), known to exert long-term myotrophic effects, has not yet been shown to induce a rapid biological response in skeletal muscles. The present in vitro study gives rise to the possibility that CNTF could affect the sodium channel activity implied in the triggering of muscle fibre contraction. Therefore, we investigated the effects of an external CNTF application on macroscopic sodium current (I(Na)) in rat native fast-twitch skeletal muscle (flexor digitorum brevis, FDB) by using a cell-attached patch-clamp technique. The I(Na) peak amplitude measured at a depolarizing pulse from -100 to -10 mV is rapidly reduced in a time- and dose-dependent manner by CNTF (0.01-20 ng ml(-1)). The maximal decrease is 25% after 10 min incubation in 2 ng ml(-1) CNTF. There was no alteration in activation or inactivation kinetics, or in activation curves constructed from current-voltage relationships in the presence of CNTF. In contrast, the relative I(Na) inhibition induced by CNTF is accompanied by a hyperpolarizing shift in the midpoint of the inactivation curves: -6 and -10 mV for the steady-state fast and slow inactivation, respectively. Furthermore, CNTF induces a 5 mV hyperpolarization of the resting membrane potential of the fibres. The effects of CNTF are similar to those of 1-oleoyl-2-acetyl-sn-glycerol (OAG), a protein kinase C (PKC) activator, when no effect is observed in the presence of chelerythrine, a PKC inhibitor. These results suggest that, in skeletal muscle, CNTF can rapidly decrease sodium currents by altering inactivation gating, probably through an intracellular PKC-dependent mechanism that could lead to decreased membrane excitability. The present study contributes to a better understanding of the physiological role of endogenous CNTF.

Animals↗
PubMed1995

[Value and role of electromyography in the assessment and prognosis of disorders of laryngeal mobility].

Although it was described many years ago, laryngeal electromyography is of limited use. It can easily be performed in the doctor's surgery by the intercrico-thyroid approach. The author reports on 70 examinations, 64 for mobility disorders, 6 for abnormal spasmodic movements. 15 normal plots made it possible to correct a faulty diagnosis of palsy. The prognostic contribution is not so clear-cut and must take account of the clinical circumstances and the time elapsed before examination. EMG must be performed systematically before any irreversible therapeutic decision.

Electromyography↗
PubMed1993

Respiratory muscle function in trained and untrained adolescents during short-term high intensity exercise.

The breathing pattern and respiratory muscle function were investigated in ten trained and ten untrained adolescents (aged 15-16 years) while undergoing an incremental intensity exercise test on a cycle ergometer up to 80% maximal oxygen consumption (VO2max), maintained to exhaustion. Before and after exercise, maximal inspiratory (PImax) and expiratory (PEmax) pressures were measured at residual volume and total lung capacity, respectively. During exercise, the breathing pattern [tidal volume (VT), respiratory frequency (fR), ventilation] and the relative contribution of ribcage and abdomen to VT were assessed using inductance plethysmography. Electromyographic activities of transversus abdominis (EMGtr) and diaphragm (EMGdi) muscles were recorded and analysed during exercise. There was a difference in the change in the pattern of breathing between the trained and the untrained group; fR increased significantly (P < 0.05) at 40% VO2max for the untrained group. Before exercise there was no difference in the maximal respiratory pressures. Up to 60% and 80% VO2max, transversus abdominis and diaphragm muscle activity increased significantly in the trained adolescents. However in this group, no evidence of respiratory muscle fatigue appeared: PImax, PEmax and the frequency spectrum of EMGtr and EMGdi were not altered by exercise up to exhaustion. In the untrained group, who had high ventilatory responses, expiratory muscle function was unchanged at the end of the exercise, but signs of inspiratory muscle fatigue appeared in that PImax was significantly decreased after exercise.

Adolescent↗
PubMed1993

Properties of motor units after immobilization of cat peroneus longus muscle.

Changes in contractile properties of cat peroneus longus motor units were studied 2, 5, and 8 wk after selective immobilization of this muscle, which was achieved by fixing the distal tendon of the peroneus longus to the fibula either at the muscle minimal physiological length ("short" length) or at the length for a 90 degree ankle joint ("neutral" length). In each muscle, 75-90% of the units [slow (S), fast resistant to fatigue (FR), fast intermediate (FI), and fast fatigable (FF)] were studied. Immobilization elicited a permanent decrease in tetanic force developed by single motor units, which was larger for resistant-to-fatigue units (S, FR). In most instances this decrease was not related to the immobilization length. In all units, twitch contraction and half-relaxation times underwent a transient increase, the extent and time course of which were influenced by immobilization length. The relationship between the frequency of motor units activation and the ratio of unfused to maximal tetanic force was studied. For fast units, there was a transient shift of the relation toward low frequencies after 2 and 5 wk of immobilization at neutral and short length, respectively.

Animals↗
PubMed1993

Effects of immobilizing the cat peroneus longus muscle on the activity of its own spindles.

The peroneus longus muscle of 10 cats were immobilized by fixating the distal tendon on the fibula at one of two length: neutral (length for a 90 degrees flexion of the ankle joint; 5 cats) or short (length for a full extension of the joint; 5 cats). Spindle afferent discharges were studied after 2 (4 cats) or 5 wk (6 cats) of immobilization and compared with those of four control animals. In each muscle, the discharges of nearly all primary and one of secondary muscle spindle endings were recorded during 2-mm ramp-and-hold stretches applied at different initial muscle lengths. A very slight increase in both the static discharge and the dynamic index of primary endings was observed in passive spindles. The increase in connective tissue that occurs in immobilized muscle and reduces muscle compliance was likely the sole alteration responsible for this constant effect. The responses to stretches of primary endings during stimulation of static and dynamic gamma-axons were not altered. Muscle immobilization at short length, even if spindle properties are not altered, can be expected to reduce the overall amount of group Ia afferent impulses with possible long-term changes on motoneuron properties.

Animals↗
PubMed1991

Responses of cat muscle spindles which lack a dynamic fusimotor supply.

1. The experiments reported here support the view that some spindles in the peroneus tertius muscle of the anaesthetized cat lack a nuclear bag1 intrafusal fibre. 2. The bag1 fibre is characterized by the fact that it is innervated exclusively by dynamic fusimotor axons. A method was devised to test each spindle in peroneus tertius for a dynamic fusimotor innervation. The ventral roots containing the muscle's motor supply were subdivided into five portions, approximately equal in terms of the tension they generated, and each piece was stimulated in turn, repetitively, at fusimotor strength, during ramp stretch of the muscle, to look for a large increase in dynamic response. 3. The method allowed confirmation that the majority of spindles in peroneus tertius had a dynamic fusimotor innervation. However, where the dynamic effect was weak and accompanied by a strong static fusimotor action and extrafusal unloading, it risked being overlooked. 4. The confirmatory test for the presence of a bag1 fibre was whether or not the spindle showed a large increase in dynamic response in the presence of the drug succinyl choline (SCh) injected arterially close to the muscle in which the spindle is located. SCh is known to induce a contracture in the bag1 fibre and therefore mimics tonic dynamic fusimotor stimulation. 5. In five experiments, of a total of forty-two spindles with afferents conducting within the group I range, five examples were encountered where there was no increase in dynamic response, either with ventral root stimulation or perfusion with SCh. It was concluded that these were spindles which lacked a bag1 fibre. 6. Passive stretch of such spindles revealed no feature in the response which allowed them to be distinguished from spindles in which the bag1 fibre was present. This conclusion posed the question, what contribution, if any, does the bag1 fibre make to the stretch response? 7. It was possible to show that under some conditions the bag1 fibre did contribute to the response to stretch. If the spindle was conditioned by repetitive nerve stimulation, at fusimotor strength, at a length longer than that at which a test stretch was applied, the response to the stretch was delayed, and it began at a lower rate than after conditioning stimulation at the test length. The delayed response was attributed to the presence of slack in intrafusal fibres.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

[Electromyography of the larynx in the diagnosis of spontaneous or post-thyroidectomy laryngeal paralysis].

Electromyographic assessment (EMG) of the larynx is very important for diagnostic and prognostic in cases of unmoving larynx: definition that authors like better than larynx palsie or recurrent nerve palsie because it is impossible to know why the larynx do not move in many cases (15f for 20 cases in the experience of the authors). EMG must be realized on several muscles and not only on the vocal fold muscle. It is necessary to realize several EMG to have a good follow up. If we have the proof that it is a case of definitive recurrent palsie the authors think that it is now, indication of nervous selective anastomosis by micro-surgery.

Electromyography↗
PubMed1990

Intermittent stimulation of fusimotor fibres during slow stretch of muscle spindles in the cat.

Responses of muscle spindles of the peroneus tertius muscle of the cat were recorded during intermittent fusimotor stimulation, applied during slow stretch, after muscle conditioning by stimulation of the nerve at the test length or at a length 2.5 mm longer. Some static and all dynamic axons evoked afferent bursts whose amplitude was relatively independent of the level of stretch response. Other static axons produced bursts that grew in size with the stretch.

Action Potentials↗
PubMed1990

Slowing of the discharge of secondary endings of cat muscle spindles during fusimotor stimulation.

Responses of secondary endings of muscle spindles of the peroneus tertius muscle of the anaesthetized cat have been recorded during repetitive stimulation of functionally single fusimotor fibres that produced slowing of the discharge. In a sample of 125 pairs of single fusimotor fibres and secondary spindle afferents 5 examples of slowing were seen. The amount of slowing became less at longer muscle lengths. Conditioning the spindle by stimulating the muscle nerve at fusimotor strength, at a length 2.5 mm longer than the test length, and then returning to the test length 3 seconds later led to a greater degree of slowing of the discharge than after conditioning stimulation at the test length. With one exception, responses to muscle stretch were reduced during stimulation of a fusimotor fibre that produced slowing. On two occasions stimulating a fusimotor fibre that produced slowing of the response of one secondary ending, led to excitation of two other endings. Two possible explanations for the generation of slowing responses have been considered. The first is that the slowing is the result of contraction of the region of intrafusal fibre directly underlying the secondary sensory ending. The second, which we favour since it accounts for the facts more adequately, is that slowing is the result of shortening of the region of nuclear chain fibres on which the sensory ending lies, produced by movement in an adjacent nuclear bag fibre.

Animals↗
PubMed1990

Effects of tetanic contraction of motor units of similar type on the initial stiffness to ramp stretch of the cat peroneus longus muscle.

1. The stiffness during the initial portion of a ramp stretch was measured in cat peroneus longus muscle at rest and during maximal tetanic contractions produced by increasing numbers of motor units of the same type [slow (S), fast fatigue resistant (FR), or fast fatigable (FF)]. 2. This initial ramp stiffness was defined as the ratio between tension and length change over the limited range of constant velocity extension during which tension rose linearly with length change. This stiffness was reduced by tetanic contraction of a number of motor units while other units remained inactive. The reduction had different characteristics in contractions produced by S, FR, or FF units. 3. Two brief ramp (triangular) stretches were applied at short intervals to evaluate the contribution of stable cross bridges to the changes in ramp stiffness. When the amplitude of the first stretch exceeded the presumed elastic limits of the stable cross bridges, the second ramp stretch showed a reduction of 20-60% in initial stiffness. This was seen both in passive muscles and in muscles in which several motor units were contracting. 4. When increasing numbers of motor units of the same type were activated, the initial ramp stiffness to the second of a pair of triangular stretches delivered during contraction increased almost linearly with the developed tension. The slope of this increase was 2.5 times steeper for S units than for FR units. This reflects the fact that contraction produced by S units causes a proportionally greater resistance to stretch than that of fast units.

Animals↗
PubMed1990

[Rehabilitation of the abduction of the vocal cord by selective nerve anastomosis in dogs].

Laryngeal reinnervation procedures were performed on 15 dogs. Anastomosis was performed between a selected motor branch of the ansa hypoglossi and the posterior crico-arytenoid nerve. The results were analyzed endoscopically, electromyographically, and histologically. Results were satisfactory in 12 cases. The methods and results have been compared with those obtained using other reinnervation techniques.

Anastomosis, Surgical↗
PubMed1989

Does stimulation of sympathetic axons elicit an increase in cat spindle afferent discharge detectable by the antidromic collision technique?

Averaged antidromic action potentials of Group I and Group II fibres elicited in cats by stimulation of L7 and S1 dorsal roots were recorded from intact tibial nerves (near the ankle) either in absence of or during repetitive stimulation of the ipsilateral lumbar sympathetic chain. This was done to test the suggestion that stimulation of noradrenergic sympathetic axons may elicit, in spindles of foot muscles, a substantial increase in the firing rate of secondary endings, capable of reducing the size of afferent antidromic volleys by collision with orthodromic impulses. We found that potentials recorded during sympathetic stimulation were identical to those recorded in absence of stimulation. The reduction in size of a component of the compound action potentials led from the intact tibial nerve during stimulation at 10-20 Hz of the sciatic nerve with C strength pulses, as described by Grassi, Filippi and Passatore (Brain Research, 435 (1987) 15-23), was observed in certain conditions of stimulation. However this reduction cannot be ascribed to antidromic collision, because it is still observed after severing the tibial nerve distal to the recording electrode.

Action Potentials↗
PubMed1989

The Bereitschaftspotential is abnormal in Parkinson's disease.

The average Bereitschaftspotential (BP) preceding a rapid, self-paced voluntary extension movement of the index finger was recorded from 6 scalp locations in 14 patients with Parkinson's disease who had been withdrawn from their normal drug therapy for at least 12 h before testing. The amplitude of the potential was measured at the peak negativity (N1) and 650 ms prior to this (NS1), and compared with that recorded in a group of 12 age-matched control subjects. The N1 amplitude was the same as in the normals, but the NS1 component was smaller in the patients, especially in midline leads. As a result, the rise in the BP between the peak NS1 and N1 component (termed NS2) was larger in the patient group. The NS1 component of the BP is thought to reflect preparatory activity in the supplementary motor area (SMA) of cortex. Since the basal ganglia provide a major source of afferent input to SMA, the reduction in NS1 in the patients probably results from inadequate basal ganglia activation of SMA. The larger NS2 component may reflect extra activity in other brain areas to compensate for the reduced SMA activity.

Aged↗
PubMed1988

Neuroanatomical study of Galen's anastomosis (nervus laryngeus) in the dog.

To further knowledge of the laryngeal nerves, the nerve fibers of Galen's anastomosis were studied using two neuroanatomical methods, namely nerve degeneration and horseradish peroxidase labeling. It is demonstrated that the superior laryngeal nerve forms part of the tracheal and esophageal nervous system. The value of the results in relation to physiological laryngeal studies and to human laryngeal diseases is discussed.

Animals↗
PubMed1988

Vocal cord abduction rehabilitation by nervous selective anastomosis.

Laryngeal reinnervation procedures were performed on 15 dogs. An anastomosis was performed between a selected motor branch of the ansa hypoglossi and the posterior cricoarytenoid nerve. The results were analyzed endoscopically, electromyographically, and histologically. Results were satisfactory in 12 cases. The methods and results have been compared with those obtained using other reinnervation techniques.

Anastomosis, Surgical↗
PubMed1987

The Bereitschaftspotential, L-DOPA and Parkinson's disease.

Bereitschaftspotentials (BPs) prior to extension movements of the index finger were studied in normal subjects and in patients with Parkinson's disease. In both, BPs were studied before and after L-DOPA therapy; in addition, the normal subjects were studied after dopamine antagonists. In both patients and normal subjects, L-DOPA caused an increase in the amplitude of the early part of the BP and of the point of peak negativity, just prior to EMG onset (N1) but it did not cause an increase of the late lateralized part of the BP (NS' of Shibasaki); in normal subjects dopaminergic antagonists caused a decrease in the amplitude of the N1. Control experiments suggested that the change caused by L-DOPA was not the result of slower movement or poorer triggering when OFF drugs. For patients with Parkinson's disease there was no correlation between the change in their peak BP negativity (N1) after L-DOPA and their change in clinical mobility; in addition, there was no difference in the peak BP negativity of patients OFF therapy and that of age-matched normals, though there was a slight decrease in the amplitude of the early part of the BP for the patients with Parkinson's disease; this was the same part that had been enlarged by L-DOPA therapy. These findings suggest that the N1 is not affected by Parkinson's disease and that the effect of dopaminergic drugs on the N1 is mediated by actions on dopaminergic mechanisms elsewhere than in the striatum, perhaps in the cerebral cortex itself. The effect of L-DOPA will need to be taken into account in subsequent studies of the BP in Parkinson's disease.

Adult↗