Paxilline Prevents the Onset of Myotonic Stiffness in Pharmacologically Induced Myotonia: A Preclinical Investigation.

Reduced Cl conductance causes inhibited muscle relaxation after forceful voluntary contraction due to muscle membrane hyperexcitability. This represents the pathomechanism of myotonia congenita. Due to the prevailing data suggesting that an increased potassium level is a main contributor, we studied the effect of a modulator of a big conductance Ca- and voltage-activated K channels (BK) modulator on contraction and relaxation of slow- and high-twitch muscle specimen before and after the pharmacological induction of myotonia.

Correction to: Preclinical pharmacological in vitro investigations on low chloride conductance myotonia: effects of potassium regulation.

The original article contains an error during online publication. Table 2 was included during production round and now deleted. The Original article has been corrected.

Preclinical pharmacological in vitro investigations on low chloride conductance myotonia: effects of potassium regulation.

In myotonia, reduced Cl conductance of the mutated ClC-1 channels causes hindered muscle relaxation after forceful voluntary contraction due to muscle membrane hyperexcitability. Repetitive contraction temporarily decreases myotonia, a phenomena called "warm up." The underlying mechanism for the reduction of hyperexcitability in warm-up is currently unknown.

Infantile-Onset Paroxysmal Movement Disorder and Episodic Ataxia Associated with a TBC1D24 Mutation.

Mutations that disrupt the presynaptic protein have been implicated in various neurological disorders including epilepsy, chronic encephalopathy, DOORS (deafness, onychodystrophy, osteodystrophy, mental retardation, and seizures) syndrome, nonsyndromic hearing loss, and myoclonus. We present the case of a 22-month-old male with infantile-onset paroxysmal episodes of facial and limb myoclonus. The episodes were linked to biallelic variants in exon 2 of the gene that lead to amino acid changes (c.

Strength and muscle structure preserved during long-term therapy in a patient with hypokalemic periodic paralysis (Cav1.1-R1239G).

We report a young wheelchair-dependent patient with an unclear proximal myopathy and a heterozygous, de-novo Cav1.1-R1239G mutation suggesting hypokalemic periodic paralysis (HypoPP). Sonography showed a loss of the pennate pattern indicative of an edema, whereas fatty degeneration was excluded.

Kir2.2 p.Thr140Met: a genetic susceptibility to sporadic periodic paralysis.

Introduction: Periodic paralyses (PP) are recurrent episodes of flaccid limb muscle weakness. Next to autosomal dominant forms, sporadic PP (SPP) cases are known but their genetics are unclear.

Methods: In a patient with hypokalemic SPP, we performed exome sequencing to identify a candidate gene.

Elevation of extracellular osmolarity improves signs of myotonia congenita in vitro: a preclinical animal study.

Key Points: During myotonia congenita, reduced chloride (Cl ) conductance results in impaired muscle relaxation and increased muscle stiffness after forceful voluntary contraction. Repetitive contraction of myotonic muscle decreases or even abolishes myotonic muscle stiffness, a phenomenon called 'warm up'. Pharmacological inhibition of low Cl channels by anthracene-9-carboxylic acid in muscle from mice and ADR ('arrested development of righting response') muscle from mice showed a relaxation deficit under physiological conditions compared to wild-type muscle.

Na1.4 DI-S4 periodic paralysis mutation R222W enhances inactivation and promotes leak current to attenuate action potentials and depolarize muscle fibers.

Hypokalemic periodic paralysis is a skeletal muscle disease characterized by episodic weakness associated with low serum potassium. We compared clinical and biophysical effects of R222W, the first hNa1.4 domain I mutation linked to this disease.

Myotonia permanens with Nav1.4-G1306E displays varied phenotypes during course of life.

Introduction: Myotonia permanens due to Nav1.4-G1306E is a rare sodium channelopathy with potentially life-threatening respiratory complications. Our goal was to study phenotypic variability throughout life.

Na MRI and myometry to compare eplerenone vs. glucocorticoid treatment in Duchenne dystrophy.

In this pilot study we tested whether a low dose application of a mild diuretic substance such as eplerenone is beneficial in early stages of Duchenne muscular dystrophy using Na und H imaging, myometry, and clinical testing versus the glucocorticoid gold standard. Two 7-years old patients with DMD were examined on a 3T MRI system. H MRI and Na density-adapted 3-dimensional radial MRI sequences were performed both before and 1, 3 and 6 months after therapy with eplerenone respectively cortisone.

Successful treatment of periodic paralysis with coenzyme Q10: two case reports.

Primary periodic paralyses (PPs) are autosomal dominant ion channel disorders characterized by episodic flaccid weakness associated with variations in serum potassium level. The main prophylactic therapy of choice for PPsis carbonic anhydrase inhibitors that are not always effective. In this report, we described two PP patients who were successfully treated with coenzyme Q10.

Eplerenone repolarizes muscle membrane through Na,K-ATPase activation by Tyr10 dephosphorylation.

Eplerenone, an aldosterone antagonist, repolarizes muscle membrane in-vitro and increases strength in-vivo in channelopathies. In Duchenne dystrophy, it is administered for cardiomyopathy. We studied its mechanism of action on skeletal muscle to test its suitability for increasing strength in Duchenne dystrophy.

Effects of S906T polymorphism on the severity of a novel borderline mutation I692M in Na 1.4 cause periodic paralysis.

Hyperkalemic periodic paralysis (HyperPP) is a dominantly inherited muscle disease caused by mutations in SCN4A gene encoding skeletal muscle voltage gated Na 1.4 channels. We identified a novel Na 1.

Hypermetabolism in B-lymphocytes from malignant hyperthermia susceptible individuals.

Malignant hyperthermia (MH) is a pharmacogenetic disorder of skeletal muscle metabolism which is characterized by generalized muscle rigidity, increased body temperature, rhabdomyolysis, and severe metabolic acidosis. The underlying mechanism of MH involves excessive Ca(2+) release in myotubes via the ryanodine receptor type 1 (RyR1). As RyR1 is also expressed in B-lymphocytes, this study investigated whether cellular metabolism of native B-lymphocytes was also altered in MH susceptible (MHS) individuals.

7-T (35)Cl and (23)Na MR Imaging for Detection of Mutation-dependent Alterations in Muscular Edema and Fat Fraction with Sodium and Chloride Concentrations in Muscular Periodic Paralyses.

Purpose To determine whether altered sodium (Na(+)) and chloride (Cl(-)) homeostasis can be visualized in periodic paralyses by using 7-T sodium 23 ((23)Na) and chlorine 35 ((35)Cl) magnetic resonance (MR) imaging. Materials and Methods Institutional review board approval and informed consent of all participants were obtained. (23)Na (repetition time msec/echo time msec, 160/0.

Early-onset familial hemiplegic migraine due to a novel SCN1A mutation.

Introduction Familial hemiplegic migraine (FHM) is a rare autosomal dominant subtype of migraine with aura. The FHM3 subtype is caused by mutations in SCN1A, which is also the most frequent epilepsy gene encoding the voltage-gated Na channel Na1.1.

Painful cramps and giant myotonic discharges in a family with the Nav1.4-G1306A mutation.

Introduction: Two previously reported Norwegian patients with painful muscle cramps and giant myotonic discharges were genotyped and compared with those of members of 21 families harboring the same mutation.

Methods: Using primers specific for SCN4A and CLCN1, the DNA of the Norwegian family members was amplified and bidirectionally sequenced. Clinical and neurophysiological features of other families harboring the same mutation were studied.

Rare KCNJ18 variants do not explain hypokalaemic periodic paralysis in 263 unrelated patients.

Objective: To examine rare KCNJ18 variations recently reported to cause sporadic and thyrotoxic hypokalaemic periodic paralysis (TPP).

Methods: We sequenced KCNJ18 in 474 controls (400 Caucasians, 74 male Asians) and 263 unrelated patients with periodic paralysis (PP), including 30 patients with TPP without mutations in established PP genes.

Results: In 10 patients without TPP, we identified 9 heterozygous, novel variations (c.

Domain III S4 in closed-state fast inactivation: insights from a periodic paralysis mutation.

Heterologous expression of sodium channel mutations in hypokalemic periodic paralysis reveals 2 variants on channel dysfunction. Charge-reducing mutations of voltage sensing S4 arginine residues alter channel gating as typically studied with expression in mammalian cells. These mutations also produce leak currents through the voltage sensor module, as typically studied with expression in Xenopus oocytes.

Contractile elements in muscular fascial tissue - implications for in-vitro contracture testing for malignant hyperthermia.

Malignant hyperthermia is a dreaded complication of general anaesthesia. Predisposed individuals can be identified using the standardised caffeine/halothane in-vitro contracture test on a surgically dissected skeletal muscle specimen. Skeletal muscle is composed of muscle fibres and interwoven fascial components.

A gating model for wildtype and R1448H Nav1.4 channels in paramyotonia.

We studied the consequences of the Nav1.4 mutation R1448H that is situated in the fourth voltage sensor of the channel and causes paramyotonia, a cold-induced myotonia followed by weakness. Previous work showed that the mutation uncouples inactivation from activation.

Towards the automated generation of expert profiles for rare diseases through bibliometric analysis.

For patients suffering from rare diseases it is often hard to find an expert clinician. Existing registries rely on manual registration procedures and cannot easily be kept up to date. A prototype data collection system for discovering experts on rare diseases using MEDLINE has been successfully deployed.

NaV1.4 mutations cause hypokalaemic periodic paralysis by disrupting IIIS4 movement during recovery.

Hypokalaemic periodic paralysis is typically associated with mutations of voltage sensor residues in calcium or sodium channels of skeletal muscle. To date, causative sodium channel mutations have been studied only for the two outermost arginine residues in S4 voltage sensor segments of domains I to III. These mutations produce depolarization of skeletal muscle fibres in response to reduced extracellular potassium, owing to an inward cation-selective gating pore current activated by hyperpolarization.