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Biomedical subjects

C Bonciocat

Publications and source records attributed to C Bonciocat.

At least 19 recordsLinked to original sources
PubMed1975

The action of benzalkonium chloride on the activation of contraction in frog skeletal muscle.

Toe muscle was used. The changes in K contracture and in the resting potential were measured. Above 0.2 mM, benzalkonium-Cl (BAC) induced an irreversible contracture associated to a rapid depolarization which caused in few min. the abolition of K contractures. With 0.5 mM, a steady tension representing 13-40% of maximal K contractures was reached in 11-16 sec. The development of BAC rigor was delayed in K depolarized muscles. BAC rigor had similarly a slower development after destruction of transverse tubules, suggesting a direct effect on sarcoplasmic reticulum (SR) in the maintenance of the steady tension and the dependence on membrane depolarization of its rapid onset. BAC effects were not affected by 10(-4) M D-tubocurarine. Concentrations between 0.01 and 0.2 mM induced within tens of min. the irreversible depolarization and abolition of K contractures. Caffeine contracture was diminished. Pretreatment with lower concentrations favoured the development of BAC rigor in K depolarized muscles. These findings suggest that even in lower concentrations, besides the depolarizing and the uncoupling effects, BAC is still able to depress Ca uptake by SR.

Animals↗
PubMedDate not supplied

Electrical activity induced by ischemia in the skeletal muscle of patients with spasmophilia.

The incidence of spontaneous electrical activity during ischemia was studied in normal and spasmophilic subjects with a Bronk electrode inserted in the first dorsal interosseous muscle. Subjects were of both sexes, aged 16 to 65 years. The diagnosis of spasmophilia was established electromyographically by a variant of the Alajouanine test. Ischemia induced in many cases an electrical activity consisting of discharge potentials that have the amplitude, duration and morphology of motor unit potentials. The number of discharging motor units varied, sometimes leading to an electrical Trousseau associated to a carpal spasm. The discharge of individual motor units was irregular and practically uninfluenced by passive manipulations on the muscle or voluntary contraction. The activity started usually 30 sec to 1 min after the onset of ischemia, reached a maximal intensity (as to the number of motor units and frequency of discharge) in about 1 min and declined gradually in the following minutes. This activity was encountered in 55.06% of 770 cases of spasmophilia and only in 11.66% of 283 normal subjects, with a tendency to more intense discharge in spasmophilia. Its incidence in the spasmophilic group was closely related to the intensity of spontaneous repetitive discharges appearing electromyographically after the activation test, reaching 78.63% in most severe cases. The behaviour was interpreted as indicating a higher susceptibility in spasmophilia of axons to depolarization induced by hypoxia. This higher susceptibility appears as an important component of the excitability alterations leading to the complex neuromuscular disorders occurring in spasmophilia.

Adolescent↗
PubMedDate not supplied

Effect of tannic acid on excitation-contraction coupling in skeletal muscle.

Toe muscles of the frog were exposed to the action of solutions containing 60-300 micrometer tannic acid (TA). The effects of K-induced contractures of the muscle and on the resting potential of the fibres were studied. After an initial transient potentiation, K contractures are progressively slowed and depressed, the effect being irreversible. After their abolition, caffeine is still able to induce a mechanical response with a reduced amplititude and a pronounced slowing in both tension development and relaxation after withdrawal of the drug. The blocking effects on excitation-contraction coupling are independent of the presence or absence of Ca from the bath. During the initial potentiation the muscle acquires the ability to respond by a contracture to EDTA solutions. TA induces a moderate membrane depolarization with a more rapid fall in resting potential during the first tens of minutes. EDTA contracture appears to be initiated at the level of T tubules, being not associated to a rapid membrane depolarization. These results suggest that TA effects on excitation-contraction coupling are primarily due to a surface mechanism involving probably the signal transmission at the level of T system as well. These effects may be the result of its capacity to crosslink protein macromolecules, interfering with conformational changes underlying initiation and propagation of excitation from membrane to the interior of muscle fibre.

Action Potentials↗
PubMedDate not supplied

Visual size analysers and Mueller-Lyer illusions.

The characteristics of the structural components inducing a length distortion were studied in Mueller-Lyer configuration and in other similar or different configurations. When placed in a more central position both ingoing and outgoing fins induced an apparent shrinkage of the shaft. It was found that a comparable effect is obtained as well with perpendicular lines and various other forms placed slightly centrally from the ends of the shaft (when placed away from the ends, an elongation is obtained). The shrinkage effect depended primarily on the ratio of the inner extent defined by the inducing forms to the extent of the shaft. With perpendicular inducing lines the most pronounced effects were observed at ratios of about 3/4. Configurations containing instead of perpendicular lines angled fins in equivalent positions showed a slightly more pronounced effect for the ingoing fins and less pronounced for the outgoing fins with a shift of optimal positions towards the ends for the ingoing and towards the center for the outgoing fins. If the ends of the shaft are marked by vertical lines the effect of the inducing forms is drastically reduced; it becomes significant as they exceed in vertical extent the end vertical lines. The findings support the idea of an interaction between size detectors as a basis of the length distorsion associated to Mueller-Lyer and other related configurations.

Form Perception↗