Case Report of an Urgent Determination of Malignant Hyperthermia Status of a 24-Week Pregnant Patient Requiring Intrauterine Fetal Surgery.

Malignant hyperthermia (MH) is a potentially fatal disorder triggered by volatile anesthetics or succinylcholine, inducing a hypermetabolic crisis in susceptible patients. The caffeine-halothane contracture test (CHCT) remains a gold standard for MH detection. The authors describe a pregnant patient with a history of exertional rhabdomyolysis, who required urgent MH screening for administration of MH-triggering anesthetics.

Effect of Norepinephrine on Intracellular Ca Levels in Malignant Hyperthermia-Susceptible B Cells: Pilot Study in the Search for a New Diagnostic Test for Malignant Hyperthermia.

Malignant hyperthermia (MH) crises may induce morbidity or death in MH-susceptible (MHS) individuals. The only sensitive method of determining susceptibility is the caffeine-halothane contracture test, requiring muscle biopsy. Early research on MH demonstrated an abnormal response to catecholamines in MHS individuals.

ROS and RNS signaling in skeletal muscle: critical signals and therapeutic targets.

The health of skeletal muscle is promoted by optimal nutrition and activity/exercise through the activation of molecular signaling pathways. Reactive oxygen species (ROS) or reactive nitrogen species (RNS) have been shown to modulate numerous biochemical processes including glucose uptake, gene expression, calcium signaling, and contractility. In pathological conditions, ROS/RNS signaling excess or dysfunction contributes to contractile dysfunction and myopathy in skeletal muscle.

Mitochondrial redox potential during contraction in single intact muscle fibers.

Although the production of reactive oxygen species (ROS) during muscle contractile activity has been linked to both positive and negative adaptive responses, the sites for ROS generation within working muscle are not clearly defined. We assessed cytosolic ROS production and mitochondrial redox potential with a targeted redox-sensitive green fluorescent protein during repetitive field stimulation of single mature myofibers. Cytosolic ROS production increased by 94%, an effect that was abolished by pretreatment with the reducing agent dithiothreitol.

Malformed mdx myofibers have normal cytoskeletal architecture yet altered EC coupling and stress-induced Ca2+ signaling.

Skeletal muscle function is dependent on its highly regular structure. In studies of dystrophic (dy/dy) mice, the proportion of malformed myofibers decreases after prolonged whole muscle stimulation, suggesting that the malformed myofibers are more prone to injury. The aim of this study was to assess morphology and to measure excitation-contraction (EC) coupling (Ca(2+) transients) and susceptibility to osmotic stress (Ca(2+) sparks) of enzymatically isolated muscle fibers of the extensor digitorum longus (EDL) and flexor digitorum brevis (FDB) muscles from young (2-3 mo) and old (8-9 mo) mdx and age-matched control mice (C57BL10).

Enhanced excitation-coupled calcium entry in myotubes expressing malignant hyperthermia mutation R163C is attenuated by dantrolene.

Dantrolene is the drug of choice for the treatment of malignant hyperthermia (MH) and is also useful for treatment of spasticity or muscle spasms associated with several clinical conditions. The current study examines the mechanisms of dantrolene's action on skeletal muscle and shows that one of dantrolene's mechanisms of action is to block excitation-coupled calcium entry (ECCE) in both adult mouse flexor digitorum brevis fibers and primary myotubes. A second important new finding is that myotubes isolated from mice heterozygous and homozygous for the ryanodine receptor type 1 R163C MH susceptibility mutation show significantly enhanced ECCE rates that could be restored to those measured in wild-type cells after exposure to clinical concentrations of dantrolene.