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Functional expression of the Ile693Thr Na+ channel mutation associated with paramyotonia congenita in a human cell line.

1. The Ile693Thr mutation of the skeletal muscle Na+ channel alpha-subunit is associated with an unusual phenotype of paramyotonia congenita characterized by cold-induced muscle weakness but no stiffness. This mutation occurs in the S4-S5 linker of domain II, a region that has not been previously implicated in paramyotonia congenita. 2. The Ile693Thr mutation was introduced into the human skeletal muscle Na+ gene for functional expression in human embryonic kidney (HEK) cells. The currents expressed were recorded with the whole-cell voltage-clamp technique. 3. In comparison with wild-type currents, Ile693Thr mutant currents showed a clear shift of about -9 mV in the voltage dependence of activation. 4. In contrast to other mutations of the Na+ channel known to cause paramyotonia congenita, the Ile693Thr mutation did not induce any significant change in the kinetics, nor in the voltage dependence, of fast inactivation. 5. In conclusion, this study provides further evidence of the involvement of the S4-S5 linker in the voltage dependence of Na+ channel activation. The negative shift in the voltage dependence found in this mutation must be associated to other defects, plausibly an impairment of the slow inactivation, to account for the long periods of muscle weakness experienced by the patients.

Cell Line↗

A case of severe respiratory depression due to cibenzoline overdosage induced by a transient renal dysfunction.

A 69-year-old man was transferred to our hospital because of severe general fatigue and progressive systemic muscle weakness. He had taken 300 mg/day of cibenzoline for his sustained ventricular tachycardia (VT) for years. At the end of June 2001 he began to feel general fatigue, which slowly progressed to systemic muscle weakness and walking disturbance. On 2nd July 2001, he finally could not stand up by himself. He also felt dyspnea. He was transferred to our emergency room, where he developed severe respiratory depression. Acute myocardial infarction was ruled out based on his ECG and blood chemistry data. Serum BUN and creatinine were elevated to 32 and 2.2 mg/dl, respectively, which returned to normal range 2 weeks later. What we did in our ICU were basically a replacement of cibenzoline with mexiletine and mechanical support of ventilation. As his renal function gradually improved, his spontaneous respiration and muscle power were slowly restored. He was discharged on foot after 1 month of hospitalization. His blood cibenzoline content taken 2 days after the cessation of cibenzoline was 959.6 mg/ml that was abnormally elevated. Considering metabolism and excretion for the 2 days between the cibenzoline cessation and the blood sample drawing, his cibenzoline level on the day of admission must have been extraordinary high. We should be aware of the possibility of abrupt overdosage of cibenzoline even in patients with normal kidney function in the event of a transient or an acute renal dysfunction.

Aged↗

Effects of resistive breathing on exercise capacity and diaphragm function in patients with ischaemic heart disease.

BACKGROUND: Muscle weakness has been suggested to result from the deconditioning that accompanies decreased activity levels in chronic cardiopulmonary diseases. The benefits of standard exercise programmes on exercise capacity and muscular strength in disease and health are well documented and exercise capacity is a significant predictor of survival in patients with chronic heart failure (CHF). Selective respiratory muscle training has been shown to improve exercise tolerance in CHF and such observations have been cited to support the suggestion that respiratory muscle weakness contributes to a reduced exercise capacity (despite biopsies showing the metabolic profile of a well trained muscle). AIMS: This study aimed to determine the effects of selective inspiratory muscle training on patients with chronic coronary artery disease to establish if an improved exercise capacity can be obtained in patients that are not limited in their daily activities. METHODS: Nine male patients performed three exercise tests (with respiratory and diaphragm function assessed before the third test) then undertook a 4-week programme of inspiratory muscle training. Exercise tolerance, respiratory and diaphragmatic function were re-assessed after training. RESULTS: Exercise capacity improved from 812+/-42 to 864+/-49 s, P<0.05, and velocity of diaphragm shortening increased (during quiet breathing from 12.8+/-1.6 to 19.4+/-1.1 mm s(-1), P<0.005, and sniffing from 71.9+/-9.4 to 110.0+/-12.3 mm s(-1), P<0.005). In addition, five from nine patients were stopped by breathlessness before training; whereas only one patient was stopped by breathlessness after training. CONCLUSION: The major findings in this study were that a non-intensive 4-week training programme of resistive breathing in patients with chronic coronary artery disease led to an increase in exercise capacity and a decrease in dyspnoea when assessed by symptom limited exercise testing. These changes were associated with significant increases in the velocity of diaphragmatic excursions during quiet breathing and sniffing. Patients that exhibited small diaphragmatic excursions during quiet breathing were most likely to improve their exercise capacity after the training programme. However, the inspiratory muscle-training programme was not associated with any significant changes in respiratory mechanics when peak flow rate, forced expiratory volume and forced vital capacity were measured. The resistive breathing programme used here resulted in a significant increase in the velocity of diaphragm movement during quiet breathing and sniffing. In other skeletal muscles, speed of contraction can be determined by the relative proportion of fibre types and muscle length (Jones, Round, Skeletal Muscle in Health and Disease. Manchester: University Press, 1990). The intensity of the training programme used here, however, is unlikely to significantly alter muscle morphology or biochemistry. Short-term training studies have shown that there can be increases in strength and velocity of shortening that do not relate to changes in muscle biochemistry or morphology. These changes are attributed to the neural adaptations that occur early in training (Northridge et al., Br. Heart J. 1990; 64: 313-316). Independent of the mechanisms involved, this small, uncontrolled study suggests that inspiratory muscle training may improve exercise capacity, diaphragm function and symptoms of breathlessness in patients with chronic coronary artery disease even in the absence of heart failure.

Aged↗

[A case of myopathy with ulcerative colitis].

A 41-year-old woman was admitted to a local hospital because of bloody diarrhea and diagnosed as having ulcerative colitis (UC). Despite prednisolone of 40 mg/day administration, her symptoms aggravated rapidly and she developed muscle weakness of lower limbs two weeks after steroid administration. On admission, she was bed-ridden and could not lift her knees and arms from bed. The serum CK level was increased slightly and total protein decreased markedly. She had moderate liver dysfunction, mild hyperthyroidism, mild glucose intolerance, and some results suggestive of immuno-deficiency including positive cold agglutinin and microsome tests, and positive antinuclear antibody. Her muscle biopsy showed both type 1 and 2 fiber atrophy and focal myofibrillar degeneration with autophagic phenomenon. There were a few fibers with nemaline bodies probably formed from marked degeneration of myofibrils. Although she had been on prednisolone for 2 weeks, the degenerative muscle pathology differed from that of steroid myopathy in which type 2 fiber atrophy is one of characteristic findings. Some additional factors including marked malnutrition, possible immuno-deficiency and hyperthyroidism should be considered for the pathogenesis of this particular myopathic changes. Since her general condition and muscle weakness gradually improved postoperatively, UC itself might have played an important role in inducing muscle symptoms.

Adult↗

[A case of Brown-Vialetto-van Laere (BVVL) syndrome in Japan].

Here we report a sixty-year-old woman of Brown-Vialetto-van Laere (BVVL) syndrome in Japan. She had sensorineural deafness, weakness and atrophy of her extremities from 15 years of age. Her neurological symptoms slowly progressed. She first visited our hospital in 1993 when she was 49 years old. At that time, she had distal muscle weakness and atrophy of the four extremities and bulbar palsy. Deep tendon reflexes were absent and the plantar toe reflex was flexor. EMG revealed neurogenic changes and the nerve conduction studied were normal. The vital capacity was marked decreased. On August 10, 2003, she was admitted to our hospital because of CO2 narcosis. She had III, VII, X, XI, XII cranial nerve palsy, distal muscle weakness and atrophy of the four extremities. From her neurological symptoms and signs, we made a diagnosis of BVVL syndrome. MRI revealed no high signal in pyramidal tract by FLAIR image. ABR showed no response, and VEP demonstrated delay of the P100. She was intubated, and was attached to a respirator to improve her CO2 narcosis. After treatment she improved and did not need to be assisted by a respirator during daytime. During night time, she had apnea, and her blood gas showed the retention of CO2, and she still required the respiratory assistance during her sleep. This is the first report of BVVL syndrome in Japanese literature.

Bulbar Palsy, Progressive↗

The measurement of muscle strength in patients with peripheral neuromuscular disorders.

The variability of voluntary isometric strength measurements has been assessed in normal subjects and patients with peripheral neuromuscular disorders. Knee extensor strength was measured in a muscle testing chair 13 times over 5 months in each of six normal subjects: coefficients of variation (CV) ranged from 4.5 to 14.0% (mean 8.5%) for individual legs in different subjects. Paired measurements of the strength of several clinically weak muscle groups were made 1-4 days apart in 20 patients using both a handheld dynamometer and the muscle chair technique: the test/retest correlation was high (r = 0.97, p less than 0.001). Visual biofeedback did not affect the strength recorded in most cases. Each of five patients had the strength of six or seven clinically weak muscle groups measured by five examiners within a 24 hour period: the CV for the five examiners ranged from 3.6-27.3% (mean 12.8%). A single examiner measuring the same groups on five occasions in three patients obtained a mean CV of 8.9%. Sources of variation are analysed and it is concluded that, with certain precautions, voluntary strength measurements offer a simple, reliable and acceptable method for monitoring change in patients.

Adolescent↗

Eosinophilic perimyositis as the presenting feature of a monoclonal T-cell expansion.

A 51-year-old physically active man was investigated for exertional myalgias and muscle stiffness. On examination he had mild proximal muscle weakness of the upper extremities and retraction of the digit flexors. Blood eosinophilia was present, but serum creatine kinase (CK) levels and an electromyographic study were normal. A skin-fascia-muscle biopsy of the calf revealed a macrophagic and CD4+ T-cell infiltration of the perimysium, and a T-cell expansion was observed in blood, bone marrow, and muscle. A diagnosis of eosinophilic perimyositis was made, and prednisone and azathioprine were administrated with a good clinical response. This case highlights the differential diagnosis of blood eosinophilia with muscle disorders, and underscores that eosinophilic perimyositis may be the expression of a T-cell monoclonal expansion. Although the pathogenesis behind the T-cell expansion is unclear but probably inflammatory, we suggest regular follow-up to allow early treatment of any T-cell lymphoproliferative malignancy that may develop.

Arm↗

Severe hyperkalemic type 4 renal tubular acidosis after kidney transplantation: a case report.

BACKGROUND: Hyperkalemia after transplantation is a common event, occurring in up to 70% of patients. It is usually asymptomatic but sometimes manifests as muscle weakness or cardiac arrhythmias. METHODS: Case report. RESULTS: At 102 days after a second cadaveric kidney transplantation, a 15-year-old boy, was admitted to the emergency room with severe muscle weakness. His examinations showed a serum potassium of 9.8 mEq/L; blood pH 7.1; serum bicarbonate 7.6 mmol/L; and creatinine 2.5 mg/dL. He was initially treated with sodium bicarbonate, calcium gluconate, and furosemide. Subsequent investigation showed hyperchloremic metabolic acidosis, urinary pH <5.5, positive urinary anion gap, reduced transtubular potassium gradient (TTKG, 1.5) and low levels of aldosterone (0.7 ng/mL), suggesting the presence of type 4 renal tubular acidosis (RTA). Other causes of hyperkalemia were excluded in the present case. Serum levels of potassium returned to normal when fludrocortisone was added to the bicarbonate supplementation. This case of severe hyperkalemic secondary to type 4 RTA after kidney transplantation only responded to the combination of alkali and mineralocorticoid therapies.

Acidosis, Renal Tubular↗

A personality profile of patients diagnosed with post-polio syndrome.

Post-polio syndrome (PPS) refers to the late development of new neuromuscular symptoms in previously stable poliomyelitis patients. Whether psychological disturbance plays a role in the manifestation of symptoms in these patients is unclear. We examined 22 patients fulfilling the clinical criteria for PPS with the Minnesota Multiphasic Personality Inventory-II (MMPI-II), Beck Depression Inventory, Spielberger State-Trait Anxiety Scales, Chapman and Chapman Psychosis-Proneness Scales, Fatigue Scales, a neurobehavioral rating scale, and Cognitive Symptoms Self-Report Scales. The overwhelming majority of scale scores were within normal limits, and there was no indication that psychopathologic symptoms were associated with the development or severity of new muscle weakness in PPS patients. Women with PPS had significantly more somatic complaints, but were less socially isolated than men with PPS. This study confirms that the development or severity of new muscle weakness in carefully diagnosed PPS patients is not due to, or influenced by, underlying psychopathology.

Adult↗

Triosephosphate isomerase deficiency with elevated sweat chloride test: report of a case.

A 15-month-old girl with severe hemolytic anemia and progressive respiratory failure is presented. She was well until the age of six months when she developed a pulmonary infection. During the next six months, she had frequent respiratory infections and her paleness became evident. At the age of 12 months, she was observed to have easy fatigability and muscle weakness, and she received her first blood transfusion. She was referred to our hospital at the age of 15 months. The physical examination revealed a malnourished girl with hypotonia, nystagmus, generalized muscle weakness and severe breathing difficulty requiring ventilatory support The hemoglobin (Hb) was 9.7 g/dl; hematocrit (Hct) 29%, mean corpuscular volume (MCV) 101 fl and reticulocyte count 15%. Peripheral blood smear revealed macrocytosis and stomatocytosis (30% of the red cells) and polychromasia. Sweat chloride test was 90 and 94 mEq/L on two separate occasions. The serum vitamin E level was 0.26 mg/dl (N: 0.44-0.68). She was found to be heterozygous for factor V Leiden mutation. Although malnutrition, low serum vitamin E and elevated sweat chloride test were suggestive of cystic fibrosis, this diagnosis failed to account for all the findings in the patient. A search for a red cell enzyme deficiency revealed that the red cell triosephosphate isomerase (TPI) activity was low. DNA analysis showed the 315 G-C (105 Glu-Asp) TPI mutation, thus confirming the diagnosis of TPI deficiency.

Anemia, Hemolytic, Congenital Nonspherocytic↗

[A case of dermatomyositis associated with thymic abnormalities].

A case of dermatomyositis (DM) associated with thymic cyst with lymphoid follicle formations has been reported. A 57-year-old man developed polyarthralgia, muscle weakness, heliotrope rash and Gottron's sign. Laboratory findings showed elevated values of creatine-phosphokinase, aldolase and transaminase. He was diagnosed as DM and was treated with prednisolone 50 mg/day. Muscle weakness was improved immediately, although rash persisted unchangeably. He was examined for coexistence of malignant tumor which had been reported frequently as associated with DM. Enlargement of thymus was found by computer tomography and then thymectomy was performed. In his thymus, lymphoid follicle formations, which are as often encountered in other autoimmune diseases, were found. So far, the beneficial effect of thymectomy on the improvement of immunological abnormalities not only in patients with myasthenia gravis but also in patients with other autoimmune diseases has been recognized. In this case, intractable rash in DM improved after thymectomy. Further study needs to clarify the relationships between DM and thymic abnormalities.

Dermatomyositis↗

New concepts of the reinnervated motor unit revealed by vaccine-associated poliomyelitis.

A late onset of slowly progressive muscle weakness 30-40 years after acute polio is well known. Previous studies by the author and others have demonstrated transmission abnormalities within the reinnervated motor unit. These transmission abnormalities shown by motor unit action potential (MUAP) instability in size and shape with repetitive discharges occurs in postpolio patients who are and who are not complaining of progressive muscle weakness. Although some reinnervated MUAPs do seem to stabilize their neuromuscular transmission with time in mildly affected muscles, the question arises as to whether or not some MUAPs ever stabilize after polio. Two cases of acute polio personally followed by the author, one over a 9 1/2 year period, are presented. In both cases, in muscles where there are more deinnervated muscle fibers than could possibly be reinnervated, the MUAPs have remained unstable. New concepts of function in the reinnervated motor unit following polio are presented.

Action Potentials↗

Apoptosis and ROS detoxification enzymes correlate with cytochrome c oxidase deficiency in mitochondrial encephalomyopathies.

The aim of this work was to investigate in muscle the role of apoptosis and of oxidative stress in mitochondrial disorders with dysfunction of respiratory chain. In patients with cytochrome c oxidase deficiency (COX) we found a variable number of myofibers with apoptotic nuclei that matched with the level of enzymatic reduction and roughly correlated with muscle weakness. In parallel, a positive immunostaining for apoptosis-related proteins and Mn and Cu/Zn superoxide dismutase (SOD) were mostly localized in COX-negative fibers. Moreover, glutathione peroxidase activity was increased in muscles with high number of SOD-positive myofibers and prominent apoptotic features. No signs of apoptosis were observed in patients with deficiencies of complexes I and II and without muscle weakness. These data suggest that apoptosis along with increased ROS production, revealed by anti-oxidant enzymes overexpression, may play an important role in the pathophysiology of mitochondrial diseases associated with COX deficiency.

Adult↗

Atypical presentation of multisystem disorders in two girls with mitochondrial DNA deletions.

UNLABELLED: We describe two girls with atypical presentations of multisystem disorders due to deletions in mitochondrial DNA (mtDNA). One presented with painful carpopedal spasms due to hypoparathyroidism at the age of 4 years. The disease was rapidly progressive with development of truncal and limb ataxia, spastic paraparesis, muscle weakness and wasting, pigmentary retinal degeneration and sensorineural hearing loss. She had short stature and vitiligo patches, hirsutism, anaemia, diabetes mellitus and exocrine pancreatic dysfunction. The other girl presented at the age of 6 years with polydipsia, polyuria and fatigue due to renal tubular dysfunction. The disease was insidiously progressive with poor growth and development of sensorineural hearing loss, muscle weakness and truncal and limb ataxia. Morphological, enzyme histochemical and biochemical investigations indicated mitochondrial dysfunction of skeletal muscle, liver and kidney in one patient and of skeletal muscle and liver in the other. Both patients had large proportions of mtDNA molecules with deletion in liver, kidney, skeletal muscle and blood cells. CONCLUSION: It may be concluded that symptoms from several different organs may be the first manifestation of a mtDNA deletion disorder.

Blotting, Southern↗

[A case of myotonic dystrophy showing proximal dominant muscle involvement but not myotonia].

A 45-year-old female had progressive difficulty in climbing stairs and standing from a chair for 10 years. She had binocular cataracts which were operated at the age of 42 years. On examination, she had marked muscle wasting in the proximal limbs, scapular and sternomastoid muscles. She presented as marked muscle weakness in the proximal portion of the lower extremities and moderate in the upper extremities and the legs. Deep tendon reflexes were absent in all limbs. There was no grip myotonia, or percussion myotonia of the thenar muscle and tongue. Myotonia was not elucidated even after the hands were exposed to cold water. Moreover, none of the examined muscles revealed insertion myotonic discharge on electromyography. Serum CK level was normal and IgG value decreased to 546 mg/dl. Muscle biopsy of the left biceps muscle showed the variation in fiber size, increased central nuclei and many fiber with pyknotic nuclear clumps on HE staining. Sarcoplasmic mass and ring fibers were also found on HE staining. There were a few percents of ragged-red fibers on Gomori-trichrome staining, and type 1 fiber atrophy was found on pH 4.5 ATP-ase staining. The expansion of lymphocyte CTG trinucleotide repeats in the myotonin protein kinase gene was about 733, so that she was diagnosed as having myotonic dystrophy (MD). MRI of skeletal muscles exhibited marked atrophy especially in the femoral region and the biceps muscle. This patient had the proximal dominant muscle weakness, and absent myotonia even on electromyographic examination, which are unusual clinical features of adult onset MD.

Atrophy↗

Juvenile and adult-onset acid maltase deficiency in France: genotype-phenotype correlation.

OBJECTIVE: To characterize the phenotypes of patients with juvenile and adult-onset acid maltase deficiency (AMD) in the French population and correlate them with genetic defects. BACKGROUND: AMD is an autosomal recessive disorder caused by the absence of the enzyme acid a-glucosidase (GAA). Patients are generally compound heterozygotes for various mutations in the GAA gene. The most common mutant allele is a -13T to G transversion in intron 1. METHODS: The authors performed a clinical, biochemical, and genetic study on 21 unrelated patients with juvenile and adult-onset AMD. RESULTS: Although onset of progressive muscle weakness occurred during adulthood in all cases but one, presence of mild, nonprogressive muscular symptoms appearing during childhood was detected in 16 patients. Eighteen patients had a similar clinical pattern with pelvic girdle muscle weakness predominating in glutei and thigh adductors. Restrictive respiratory insufficiency with vital capacity less than 60% was noted in eight patients, and respiratory failure was the first manifestation in two cases. All patients but one were compound heterozygotes, and 17 carried the IVS1 (-13T ---> G) transversion (one patient was homozygous for this mutation). The two mutated alleles were identified in 10 cases, with 13 different mutations detected in the GAA gene. There was no clear correlation between the type of mutation and phenotype. CONCLUSIONS: This study shows a high genetic heterogeneity of juvenile and adult AMD in the French population. The absence of genotype-phenotype correlation suggests a complex physiopathology that requires further investigations.

Adolescent↗

Enzyme therapy for Pompe disease: from science to industrial enterprise.

UNLABELLED: Pompe disease or glycogen storage disease type II (OMIM 232300) is a metabolic myopathy with a broad clinical spectrum. Generalised muscle weakness combined with cardiomegaly presents within the first 3 months after birth, if the lysosomal alpha-glucosidase (AGLU) deficiency is complete. Residual enzyme activity prevents cardiac involvement and delays onset of muscle weakness. Enzyme therapy, by intravenous administration of acid AGLU, aims to supplement the missing enzyme activity. At the SHS symposium on Glycogen Storage Diseases Type I and II, in Fulda, two interim accounts were given of studies on the efficacy of enzyme therapy for Pompe disease; one with recombinant human acid AGLU produced in Chinese hamster ovary cells and the other with the same enzyme produced in the milk of transgenic rabbits. CONCLUSION: this review focuses on the latter study, discusses the scientific, technological and commercial aspects of the enterprise, and addresses the prospects and challenges of enzyme therapy for Pompe disease.

Animals↗

Impaired ability of voluntary quadriceps activation bilaterally interferes with function testing after knee injuries. A twitch interpolation study.

Central activation deficits have been recognised to be partially responsible for quadriceps muscle weakness after knee injuries effecting the injured as well as the uninjured leg. The purpose of this study was to assess the extent of bilateral activation deficits and its effect on functional muscle tests using the uninjured leg as reference. The study included 30 patients with isolated rupture of the anterior cruciate ligament (group 1), 42 patients with rupture of the anterior cruciate ligament and accompanying joint damage (group 2) and 34 healthy volunteers as reference. The maximum isometric knee extension torque and the maximal voluntary muscle activation (VA) were measured bilaterally using a sensitive twitch-interpolation method. The measured and the true functional deficit, adjusted to a physiological VA of the uninjured side, was calculated. Isolated rupture of the anterior cruciate ligament caused a minor VA-deficit and severe knee injuries more severe VA-deficits of the quadriceps muscles of the injured (VA group 1: 83.8 +/- 1.9 %; group 2: 76.9 +/- 1.8 %) and on the uninjured side (VA group 1: 85.9 +/- 1.8 %; group 2: 77.9 +/- 1.8 %) compared to the control group (VA 91 +/- 0.64 %). Due to contralateral VA-deficits the mean underestimation of the isometric muscle-force deficit was 22 % in group 1 and 48% in group 2. Unilateral knee injuries lead to significant VA-deficits of the quadriceps muscles on both the injured and uninjured legs related to the severity of injury. The validity of tests for the assessment of muscle function is questionable when using the uninjured side as reference.

Adolescent↗