Effect of ankle joint position on electrically evoked surface myoelectric signals of the tibialis anterior muscle.

The relationship between surface myoelectric signal variables and ankle joint angle is studied in the tibialis anterior muscle of ten normal subjects during electrical stimulation of the main muscle motor point in isometric conditions. Rectangular current pulses of 0.1 ms width and 20Hz repetition rate were applied for 10s with a monopolar technique using a stimulation/detection system providing stimulation artifact suppression. Electrically evoked responses (M-waves) were detected with a four-bar electrode placed on the skin below the lowest motor point near the tendon end of the muscle. Average rectified value, root mean square value, mean and median spectral frequency, conduction velocity, and latency of the surface signal were computed for ankle angles of 15 degrees dorsal flexion (-15 degrees), 0 degrees, 15 degrees, 30 degrees and 45 degrees of plantar flexion. All variables were considerably affected by the joint angle. Spectral variables and latency showed a statistically significant decrement as angle increased from -15 degrees to 45 degrees whereas conduction velocity and amplitude variables had a less regular behavior. The evoked response showed a latency decrement and a change of shape (mostly a widening of the second phase), as ankle joint angle increased from -15 degrees to 45 degrees. In most subjects conduction velocity appeared to be over estimated at -15 degrees and 45 degrees, a fact attributed to the small distance between the electrodes and either the tendon or the innervation zone at these two angles.(ABSTRACT TRUNCATED AT 250 WORDS)

Intrathymic lymphoid cell differentiation in myasthenia gravis: an immunophenotypic study.

Thymocytes express multiple different surface antigens according to their stage of maturation. We studied lymphocyte surface differentiation antigens using direct immunofluorescence technique in the thymus of 20 patients with myasthenia gravis (MG) and 10 controls undergoing cardiac surgery. Fluorescein isothiocyanate-conjugated monoclonal antibodies were used to stain thymic cell surface antigens. We found a decrease in the percent expression of CD1, CD5, and CD7 surface antigens and a significant increase of CD20+ cells in myasthenic thymus compared with the controls. The changes in the percent expression of CD3, CD4, and CD8 antigens were not significant. These data suggest both the decrease in the immunophenotypes corresponding to cortical thymocytes (probably reflecting the cortical atrophy of the MG thymus) and the increase of mature B Cells (CD20+), which may participate in an active immune response.

Increased thymocyte differentiation in myasthenia gravis: a dual-color immunofluorescence phenotypic analysis.

Thymocytes express multiple, different surface antigens according to their stage of maturation. Surface differentiation antigens have been studied with the technique of simultaneous dual-color, direct immunofluorescence in the thymuses of 20 patients with myasthenia gravis (MG) and 10 control subjects with cardiac diseases. Fluorescein isothiocyanate-conjugated and phycoerythrin-conjugated monoclonal antibodies were used to stain thymic cell suspensions. A significant decrease in the percentage of immature and common thymocyte phenotypes (CD1+,3+ and CD4+,8+) and a significant increase in the percentage of mature thymocyte phenotypes (CD1-,3+; CD4+,8-; and CD4-,8+) and of B cells (CD20+) were found in MG thymuses compared with controls. These data, indicating an increased availability of mature, fully immunocompetent T and B cells, indirectly suggest the occurrence of an active immune response in MG thymus.

Carbamazepine toxicity and poisoning. Incidence, clinical features and management.

Carbamazepine is the drug of first choice in the treatment of simple and complex partial seizures and trigeminal and glossopharyngeal neuralgias. It is usually preferred to phenobarbitone or phenytoin because of its powerful antiepileptic activity combined with a relative lack of adverse effects. In this article the mechanisms of action and pharmacological properties of carbamazepine are outlined in order to explain the pathogenesis of most side and toxic effects. Most of these effects, namely those affecting the nervous or cardiovascular systems, correlate well with an increased concentration of the drug in plasma and disappear spontaneously upon discontinuation of therapy. Other, less frequent toxic effects, namely aplastic anaemia or fatal hepatitis, may be ascribed to unforeseeable idiosyncratic reactions. Carbamazepine poisoning, usually accidental and sometimes secondary to the coadministration of other drugs, yields a clinical picture with neurological and cardiovascular signs. The outcome is usually favourable, sometimes with spontaneous improvement, and death is a distinct rarity. No specific antidotes are available. The oral administration of activated charcoal has been shown to be an effective therapeutic measure significantly reducing the plasma half-life of the drug.

[Homo- and contralateral changes in muscle cholinergic enzymes following immobilization in the rabbit]. / Modifications homo- et contro-latérales des enzymes cholinergiques dans les muscles après immobilisation, chez le lapin.

Changes in ChAc and AChE activity were observed in the caput longum of the triceps of both forelimbs of 45-day-old rabbits when the left antebrachium was immobilized in total extension on the brachium for periods of up to 60 days. Enzyme determination on the proximal, ventral and distal portions showed a correlation between quantitative changes in AChE activity, and reappearance of its terminal activity demonstrated histochemically by other workers with the same experimental model.

Omo- and contralateral changes in cholinergic enzymes in muscles following immobilization, in the rabbit.

Changes in ChAc and AChE activity were observed in the caput longum of the triceps of both forelimbs of 45-day-old rabbits when the left antebrachium was immobilized in total extension on the brachium for periods of up to 60 days. Enzyme determinations on the proximal, ventral and distal portions showed a correlation between quantitative changes in AChE activity, and the reappearance of its terminal activity demonstrated histochemically by other workers with the same experimental model.