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At least 19 recordsLinked to original sources
PubMed1993

[Myotonia congenital (Thomsen) and recessive generalized myotonia (Becker)].

Myotonia congenita (Thomsen's disease) is a muscular disorder with autosomal dominant inheritance. The main symptom is muscle stiffness caused by hyperexcitability of the muscle cell membranes. The disorder is noticeable at birth or in early childhood and is progressive. Muscle hypertrophy is a common sign. Recessive generalized myotonia (Becker) resembles myotonia congenita in many respects, but there are also differences, e.g. later onset and transient muscle weakness experienced by many patients during muscle exertion after rest. The clinical signs usually progress over several years and then remain stable. The decisive criterion for the differential diagnosis of Thomsen or Becker type myotonia is the mode of inheritance. Both disorders are caused by defects of the gene, situated on chromosome 7, that is responsible for the normal functioning of the chloride channels in the muscle cell membranes. The differences between the two types of myotonia are probably caused by different mutations of this gene. The present paper also describes two animal models of myotonia (the myotonic goat and the myotonic mouse), which simulate the dominant and recessive types of human myotonia, respectively. The models have been very helpful in research into the origins of myotonia.

Adolescent↗
PubMed1989

[Intracellular recording of myotonia in mdx mouse and the effect of Ca antagonist in myotonia].

Bulfield and others found X-linked muscular dystrophic (mdx) mouse by screening C57 BL/10 mice. The serum CK and PK are high in mdx mice, and they develop muscle degeneration 10-15 days after birth. The regeneration is vigorous in mdx mice and almost all the muscle fibers are replaced by regenerated fibers by 60 days after birth. Although mdx mice have been developed as a model for X-linked muscular dystrophy we have found that myotonic bursts are recorded when a glass microelectrode is inserted into the muscle fibers of hemidiaphragm preparations of mdx mice. Insertion myotonia is ceased by addition of the Na channel blocker tetrotoxin. Myotonia is not reduced, nor ceased by lowering the extracellular Ca to 1/15 of the volume of ordinary Tyrode's solution. Calcium antagonist, nicardipine at the dose of 10(-7), and 10(-6)M/L do not reduce myotonic bursts. Higher dose of nicardipine up to 2 x 10(-5)M/L abolished myotonic bursts. These results indicate that myotonic bursts are related to muscle membrane abnormalities, and each action potential occurs through Na channel, but not through Ca channel Higher dose of calcium antagonist can abolish myotonia by affecting Na channel in addition to their primary effects of Ca channel. The clinical effects of the Ca antagonist for myotonia was reported in one study. Since previous medications for myotonia including quinine HCl, procaine amide, diphenylhydantoin, and carbamazepine have some side effects such as tinnitus, headache, nausea, cardiac blocks, and bone marrow suppression, Ca antagonist may be used as a safe therapeutic drug for myotonia.

Animals↗
PubMed1977

Electron spin resonance studies of an animal model of human congenital myotonia: increased erythrocyte membrane fluidity in rats with 20,25-diazacholesterol-induced myotonia.

Electron spin resonance experiments have been performed on erythrocyte membranes from rats with myotonia induced by treatment with 20,25-diazacholesterol. The results suggest that erythrocyte membranes in this animal model of human congenital myotonia possess a highly significantly increased surface membrane fluidity compared to that of controls. Alterations in the physical state of membrane proteins were not apparent. These findings, also present in human congenital myotonia [Butterfield, Chesnut, Roses & Appel, 1976, Nature (London) 263:159; Butterfield, 1977 (Submitted for publication)], strengthen the concepts that increased membrane fluidity is associated with the presence of myotonia and that congenital myotonia may be a diffuse membrane disease.

Amino Acids, Sulfur↗
PubMed1991

Altered sodium channel behaviour causes myotonia in dominantly inherited myotonia congenita.

The cause of increased excitability in autosomal dominant myotonia congenita (MyC) was studied in resealed greater than 3-cm long segments of muscle fibres from eight patients. Three hours after biopsy only about 50% of the fibre segments had regained a normal resting potential. This differs from our experiences with normal muscle or other disorders of myotonia (e.g. recessive generalized myotonia) where nearly all cut fibres reseal and repolarize during this time. When the depolarized MyC fibre segments were placed in a solution containing 1 microM tetrodotoxin (TTX) they repolarized to -80 to -90 mV. In fibre segments with normal resting potential, in the absence of TTX, spontaneous myotonic runs were recorded intracellularly, occasionally with double spikes. For only one of the eight patients, the Cl- conductance was reduced (50% of the total membrane conductance vs the usual 75%), for the rest of the patients the steady-state current-voltage relationship was normal. Sodium currents through single membrane channels were recorded with a patch clamp. For every patient re-openings of the Na+ channels were observed throughout 10-ms depolarizing pulses. These are very uncommon in normal muscle. At potentials positive to the resting potential, the duration of the re-openings increased, but the current amplitude was the same. It is concluded that in myotonia congenita re-openings of Na+ channels are the major cause of hyperexcitability and that Cl- conductance is normal. If it is reduced in rare cases, it may potentiate the myotonia.

Action Potentials↗
PubMed1984

Membrane fluidity and myotonia: effects of cholesterol and desmosterol on erythrocyte membrane fluidity in rats with 20,25-diazacholesterol-induced myotonia and on phospholipid liposomes.

Previous spin-label and electromyographic experiments with rats fed 20,25-diazacholesterol, an inhibitor of the biosynthetic conversion of desmosterol to cholesterol, demonstrated an increased erythrocyte membrane fluidity and myotonia, a prolonged muscle contraction upon stimulation. The current studies with rats showed normal erythrocyte fluidity in animals fed 20,25-diazacholesterol but maintained on a high-cholesterol diet and no myotonia. Studies of model membrane systems composed of phospholipid vesicles containing desmosterol, cholesterol, or both demonstrated that desmosterol increased membrane lipid fluidity relative to cholesterol, suggesting that in 20,25-diazacholesterol-induced myotonia, in which desmosterol accounts for 85% of the plasma sterol, the increased membrane fluidity previously observed in erythrocytes and sarcolemma in this animal model of human congenital myotonia may be due to desmosterol.

Animals↗
PubMed1975

A family with dominant hereditary myotonia, muscular hypertrophy, and increased muscular irritability, distinct from myotonia congenita thomsen.

Myotonia is a symptom, which occurs in a series of hereditary diseases, and it is also seen in less frequently occurring syndromes. A summary is given of conditions with myotonia. Five cases are reported from a family with a dominant hereditary disease presenting myotonia, muscular hypertrophy and increased muscle irritability as the only symptoms. In the most affected patient, some unusual rolling muscle contractions are seen. Apart from a moderate increase of creatin kinase, supplementary examinations are normal. The clinical picture resembles myotonia congenita Thomsen, but differs from this in significant respects. Other diagnostic possibilities are also considered. It is concluded that the clinical picture is different from all previously described conditions.

Adolescent↗
PubMed1981

[The influence of several membrane stabilizing drugs on the induced hereditary myotonia--a methodic way to test the effectiveness of drugs on myotonia (author's transl)].

The therapeutic effectiveness of several membrane stabilizing drugs was investigated on experimentally induced myotonia by 2,4-Dichlorophenoxyacetate (2,4-D) and in 20 patients with myotonia congenita. Procainamide and quinine showed a better antimyotonic effect in-vitro- as well as in-vivo-experiments on the cold blood muscle and the rat than Sparteine sulfate and Tachmaline (Ajmalin). The two last-mentioned drugs had nearly the same effect. Because of these experimental results only procainamide and sparteine sulfate were clinically used. Quinine was not used because of the well known side-effects. Mention is made of the fact, that the therapeutic effect depends on the dose or the concentration. The results support not only the theoretic considerations on the pathogenesis of myotonia but also recommend to carry out further pharmacological investigations with this method.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1999

Electrical myotonia in heterozygous carriers of recessive myotonia congenita.

We investigated electrophysiologically the unaffected parents of patients with recessive myotonia congenita. We studied 18 families, in nine of which the diagnosis was confirmed by molecular genetics. Brief myotonic discharges were present in at least one parent in 67% of the families. Fathers were more likely than mothers to show these discharges. The difficulty in distinguishing very mildly affected parents with dominant myotonia congenita from the heterozygous carriers of recessive myotonia congenita is stressed.

Action Potentials↗
PubMed1977

Myotonia not aggravated by cooling. Force and relaxation of the adductor pollicis in normal subjects and in myotonia as compared to paramyotonia.

The effect of local cooling has been studied in 27 normal subjects, 8 cases of myotonia congenita, 5 of myotonic dystrophy and one of paramyotonia. Using the adductor pollicis we registered the compound muscle action potential, the isometric twitch force and the time to half relaxation, the maximum tetanic force and to time 3/4 relaxation. 1. In normal subjects the twitch force and maximum tetanic force decreased after cooling (Fig. 2). The amplitude of the action potential increased. 2. Myotonia congenita and myotonic dystrophy were not aggravated by cooling. Muscle force was reduced only in the same proportion as in normal subjects (Fig. 2). The myotonic after-contraction was made normal by cooling (Figs. 5 and 6). 3. In paramyotonia initial tonic stiffness with a pronouncedly prolonged twitch relaxation occured directly after cooling (Fig. 1 B). Paradoxical myotonia occured only after exercise and was accompained by increasing paresis (Figs. 3 and 8). The results indicate that exposure to cold has a specific effect on muscle function only in paramyotonia.

Adolescent↗
PubMed1978

Fenoterol precipitating myotonia in a minimally affected case of recessive myotonia congenita.

Fenoterol is used in patients with premature labor to delay delivery. A young women treated with fenoterol developed severe generalized myotonia. Symptoms disappeared after medication had been stopped. In a later study myotonic discharges were found electromyographically in the muscles of the patient and her brother. Both suffered from subclinical recessive myotonia congenita (Becker). A heterozygous manifestation may be supposed.

Adult↗
PubMed1981

Myotonia congenita. A histochemical and ultrastructural study in the goat: comparison with abnormalities found in human myotonia dystrophica.

Muscle biopsy specimens from the myotonic goat, an animal model of heritable myotonia, were examined histochemically and by electron microscopy. After Periodic acid-Schiff (PAS) staining with diastase digestion, there was increased PAS-positive material within myotonic goat fibers, as compared with those of normal goats. Myotonic muscle stained with alizarin red S, a histochemical stain for calcium, also had an increased staining reaction when compared with muscle from normal goats. Several ultrastructural abnormalities were found in myotonic goat muscle using routine osmium and uranyl acetate staining. These included increased density of the t-tubules, electron-dense material within t-tubules, proliferation and dilatation of sarcotubular elements, and abnormal mitochondria in the myotonic biopsy specimens. To further study muscle ultrastructure, ruthenium red and lanthanum were used as electron microscopic stains with specificity for membranes. There was increased density of the sarcolemma and t-tubules in myotonic muscle stained with ruthenium red as compared to normal, and lanthanum produced a darker staining reaction of the myotonic goat sarcolemma. The histochemical and ultrastructural differences between normal and myotonic goat muscle were interpreted to be consistent with a morphologic basis for the abnormal contraction-relaxation properties characteristic of myotonia.

Adolescent↗