[Duchenne-type muscular dystrophy: problems, early diagnosis, early treatment (author's transl)]

The aetiology and pathogenesis of the Duchenne-type muscular dystrophy (pseudohypertrophic muscular dystrophy) are still largely unknown. The possibilities of treating the disease are rather limited. Treatment is the more successful, the earlier diagnosis was possible, and the earlier treatment is initiated. The CK-Screening Test is an important aid for early diagnosis. The CK-Screening Test is also valuable for genetic consultation and advice, because it helps to identify women who are conductors or carriers of the disease. Current hypotheses on aetiology and pathogenesis are mentioned. Progress made in the fields of biochemistry, including enzyme histochemistry, and electron microscopy, raise hopes of finding more efficient therapeutic possibilities in the future. The many interests of patients with muscular diseases are being looked after by the European Alliance of Muscular Dystrophy Associations (EAMDA). Thirteen European associations are members of this organisation, including the German association "Bekämpfung der Muskelkrankheiten e.V." The number of sponsoring members of the EAMDA is at present about 300,000. 3 international congresses have already been held on the problems of muscular diseases. The fourth congress is scheduled to take place in Montreal in 1978.

Experimental progressive muscular dystrophy and its treatment with high doses anabolizing agents

We are still a long way from discovering an unequivocal pathogenetic interpretation of progressive muscular dystrophy in man. Noteworthy efforts have been made in the experimental field; a recessive autosomic form found in the mouse seems to bear the closest resemblance to the human form from the genetic point of view. Myopathy due to lack of vitamin E and myopathy induced by certain viruses have much in common anatomically and pathologically with the human form. The authors induced myodystrophy in the rat by giving it a diet lacking in vitamin E. The pharmacological characteristics of vitamin E and the degenerative changes brought about by its deficiency, especially in the muscles, are illustrated. It is thus confirmed that the histological characteristics of myopathic rat muscle induced experimentally are extraordinarily similar to those of human myopathy as confirmed during biopsies performed at the Orthopaedic Traumatological Centre, Florence. The encouraging results obtained in various authoratative departments in myopathic patients by using anabolizing steroids have encouraged the authors to investigate the beneficial effects of one anabolizing agent (Dianabol, CIBA) at high doses in rats rendered myopathic by a diet deficient in vitamin E. In this way they obtained appreciable changes in body weight (increased from 50 to 70 g after forty days at a dose of 5 mg per day of anabolizing agent), but most of all they found histological changes due to "regenerative" changes in the muscle tissue, which however maintained its myopathic characteristics in the control animals that were not treated with the anabolizing agent. The authors conclude by affirming the undoubted efficacy of the anabolizing steroids in experimental myopathic disease, but they have reservations as to the transfer of the results into the human field, where high dosage cannot be carried out continuously because of the effects of the drug on virility; because the tissue injury too often occurs at an irreversible stage vis-a-vis the "regeneration" of the muscle tissue; and finally because the dystrophic injurious agent is certainly not the lack of vitamin E but something as yet unknown.

[The Schwartz-Jampel syndrome (myotonia chondrodystrophica)]

Report on three siblings with typical features of Schwartz-Jampel's syndrome which is transmitted by a rare autosomal recessive gene: odd facies, stiff posture, high pitched voice, myotonic reaction, Perthes-like dysplasia of the femoral head. Biochemical and histological findings are minimal and nonspecific.

Experimental serotonin myopathy

One hundred and eight Wistar rats were injected with serotonin (20 mg per kilogram of body weight intraperitoneally) or imipramine hydrochloride (20 mg per kilogram intraperitoneally), or both, in a single cycle or in multiple (up to 18 weeks) weekly cycles. In contrast to previous reports, a characteristic myopathy was produced with serotonin alone, identical to that produced by serotonin and imipramine in combination. Imipramine alone produced no significant change. The myopathy produced was characterized by (1) preferential damage to myofibers with high oxidative capacity (types I and IIA), (2) prominent regenerative activity occurring as early as 48 hours, and (3) degeneratio of capillary endothelium (thickening, vacuolar degeneration, proliferation of marginal folds, dissolution of mitochondria). Small groups of degenerating fibers and increased connective tissue were not observed. There was no loss of myofibers or fat replacement. The changes suggested repeated acute insults followed the complete recovery. These observations suggest that although the pathogenesis of serotonin and serotonin-imipramine myopathy is primarily ischemic, it is not a satisfactory model of human Duchenne muscular dystrophy.

[Human myopathy and animal muscular dystrophy]

Two hereditary muscular dystrophies similar to human progressive muscular dystrophy (P.M.D. Duchenne type) have been isolated in animals, one in mouse, the other in chicken. The decrease in the activity of glycogenolytic enzymes is similar to that observed in denervated muscle. Isozymic fetal types for several muscular enzymes have been observed as well in chicken as in man, but this fetal type may also be found in neurogenic atrophy. The release in circulation of muscle enzymes seems more specific. But the origin of the genetic lesion is still unknown. We describe here the three different theories about this problem: i.e. neurogenic, vascular, or myogenic. This last theory implies a trouble of membrane permeability.

A comparison of the fine structure of motor end-plates in Duchenne dystrophy and in human neurogenic diseases

With the aim of investigating the pathogenesis of Duchenne dystrophy, and in particular the role of denervation, the fine structural features of motor end-plates in the limb muscles of 13 patients with Duchenne dystrophy were compared with those in 26 controls and 50 patients suffering from known neurogenic diseases. The wide variation in control end-plates es emphasised. The sole plates in Duchenne dystrophy tended to retract from the end-plate, and shared only sprout formation, enclodure of terminals in Schwann cell cytoplasm and (in one instance) close packing of neurofilaments in the terminal with the changes in denervating end-plates. In these latter, withdrawal of terminals from the sole and various degenerative figures were the rule. It was concluded that there is no adequate morphological evidence in motor end-plates to support the concept of Duchenne dystrophy as a neurogenic disease.

Mitochondrial calcium overload: A general mechanism for cell-necrosis in muscle diseases

It is suggested that the mechanism of muscle-cell necrosis in various muscle diseases is explained by an increased net influx of calcium into cells which triggers a "vicious cycle" of mitochondrial calcium overloading and energy depletion. If correct, this hypothesis may offer the basis of a more rational treatment of some muscle diseases even before their primary aetiology is known.

Myofibrillar incorporation of 3H (G) L-leucine in pgrogressive muscular dystrophy and motor neuron disease

A study of the incorporation of hydrogen 3 (3H) leucine into skeletal muscle in patients with human muscular dystrophy and motor neuron disease showed uptake in cytoplasm and myofibrils. The techniques used were light and electron microscopy and autoradiography before and after glycerination (Szent-Gyorgyi). The results indicated an increase of 3H leucine uptake into cytoplasm of the dystrophic muscle and a marked drop in incorporation into structural protein. In the patients with motor neuron disease, the normal incorporation into cytoplasm was seen, with reduced uptake into structural protein. These results showed a different protein synthesis pattern in dystrophic and denervated muscle.

Hypotheses and recent findings concerning aetiology and pathogenesis of the muscular dystrophies

The survey reports recent findings and current hypotheses on the aetiology and pathogenesis of the muscular dystrophies. Briefly presented are (1) biochemical anomalies of structure and metabolism, (2) membrane defects, (3) the neural hypothesis, (4) the vascular hypothesis, and (5) the connective tissue hypothesis. At present, research interest is focused primarily on membrane structure and biochemistry, on neural muscle trophism, and on the genetic aspects of abnormalities in molecular biology. Whether the progressive muscular dystrophies are primary disorders of voluntary muscle or whether the primary alteration is located outside of the muscle still remains unknown.

Duchenne dystrophy: electron microscopic findings pointing to a basic or early abnormality in the plasma membrane of the muscle fiber

In seven patients with Duchenne dystrophy, high-resolution phase microscopy demonstrated a population on non-necrotic fibers with one or more focal lesions. The typical lesion was wedge-shaped, with the base resting on the fiber surface. In the electron microscope, the plasma membrane overlying the lesion was either absent or disrupted, while the basement membrane was always preserved. Within the lesion, there were cytoplasmic abnormalities, and in the neighboring fiber region, the myofibrils were usually highly contracted. The structural defect in the plasma membrane suggested that this site was an ineffective cellular barrier. This was confirmed by the frequent ingress of peroxidase-containing extracellular fluid into the lesions. In two control subjects, peroxidase penetration into fibers was seen only rarely and only with other evidence of mechanical injury to the specimen. The findings point to an early and possibly basic abnormality in the plasma membrane of the muscle fiber in Duchenne's dystrophy.

A comparison of the structure of small blood vessels in normal, denervated and dystrophic human muscle

A light- and electron-microscopic study of the small arterial vessels and capillaries in muscle from 20 patients with Duchenne muscular dystrophy failed to adduce any direct morphological evidence that the necrobiotic muscle lesions in this disease are produced by muscle ischaemia. However the electron-microscopic studies showed that the basement membrane width in 3 out of 4 cases of Duchenne dystrophy so studied was significantly less than that or normal control material. In further case of Duchenne dystrophy, selected for study because some vessels in the biopsy muscle were surrounded by small round cell infilitrates, the basement membrane width was significantly greater than that in the normal control material. In the single case of spinal muscular atrophy studied, the basement membrane width was also significantly less than the control measurements. The possible relationship of these observations to the "ischaemic" theory of the pathogenesis of muscular dystrophy is discussed.

Failure to confirm a vascular cause of muscular dystrophy

The vascular hypothesis of the cause of muscular dystrophy suggests that ischemia is responsible for the muscle fiber necrosis. A xenon 133 clearance study of muscle blood flow in Duchenne and other muscular dystrophies showed no obvious difference between the response to exercise and arterial occlusion compared with control subjects. Radioautographic study of distribution of 4-125l-antipyrine in skeletal muscle of mice with muscular dystrophy showed no abnormal areas of ischemia. A statistical examination was also made of the grouping of damaged fibers, one of the observations on which the vascular hypothesis was based. Only 0.9% of fibers undergoing phagocytosis occurred in groups of four or more fibers in greater frequency than would have been expected by chance, and 70% of such fibers were isolated. These studies argue strongly against the vascular hypothesis of the cause of muscular dystrophy.

Effects of microembolization on the skeletal muscle blood flow. A critique of the microvascular occlusion model of Duchenne dystrophy

Muscle blood flow (MBF) during exercise was determined in both anterior tibial muscles of 12 rabbits by the local 133-Xe method before and after embolization of 20 to 80 mum dextran particles into the right femoral artery. With a relatively low dose of particles (dry weight: 8.7 mg), MBF was significantly decreased up to 4 days after each embolization, and mild histologic abnormalities were observed in the embolized muscles. A four-fold higher dose resulted in a marked and permanent decrease of the MBF, ischemic necrosis of the distal leg muscles and toe gangrene. In the light of these findings and the previously demonstrated normal MBF in Duchenne dystrophy, the validity of the assumption that Duchenne dystrophy is caused by small vessel occlusions is questioned.

Neuromuscular disorders in childhood. Old dogmas, new concepts

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Preliminary results of examinations of rats after a 22-day flight aboard the Cosmos-605 biosatellite

The results of biomedical investigations carried out in flights of the Salyut and Skylab orbital stations give evidence that during prolonged weightlessness cosmonauts and astronauts remain in a good physical and mental condition. They fill specialists with optimism in regards to a further increase of the duration of manned space flights. In order to make reliable plans for such missions, it is necessary to accumulate detailed knowledge about the mechanism of the effect of weightlessness on different functions of the human body. In addition to manned experiments, of great interest are animal experiments. They may yield data that cannot be obtained in human studies, which is obviously very important from the point of view of space medicine. This was the purpose of the experiment carried out in November 1973 on the biosatellite Cosmos-605; 45 rats aboard the biosatellite flew for 22 d. Preliminary results of examinations of rats after a 22-d space flight in the Cosmos-605 satellite demonstrated not only physiological and biochemical but also morphological changes in the animal body due to prolonged weightlessness. These changes were reversible.

Comparison of the turnover patterns of total and individual muscle proteins in normal mice and those with hereditary muscular dystrophy

1. The incorporation of amino acids into hindleg muscle proteins of normal and dystrophic mice was measured (1/2)h to 16 days after administration of the radioactive pulse. 2. Dystrophic animals showed a faster initial rate of incorporation into total and soluble proteins in the first few hours after injection, but the extent of incorporation relative to the size of the amino acid pool was similar in both. There was little difference between the overall degradation rates although this started later in the dystrophic proteins. An initial fast phase of degradation reached a plateau after 3 days whereupon the residual label in the protein remained constant up to 16 days after injection. 3. Analyses of individual radioactive proteins fractionated by polyacrylamide-gel electrophoresis showed that the distribution of label was similar in all the soluble proteins from normal and dystrophic muscle. Time-course experiments revealed that in dystrophic mice the two major soluble proteins of the muscle, creatine kinase and adenylate kinase, initially incorporated 2-3 times more label relative to the initial size of the precursor pool. This label was then lost equally rapidly and the final plateau value was much less than that in normal mice. This initial peak of activity was not observed in normal mice. 4. A group of dehydrogenases showed similar initial turnover patterns in both dystrophic and normal mice but the final plateau value was much higher in the former. 5. The results provide support for the hypothesis that there is no obvious defect in the protein synthetic machinery of dystrophic muscle. However, certain proteins do show anomalous turnover patterns relative to those in normal animals. A single structural gene mutation giving rise to one particularly unstable and readily degradable muscle protein is excluded as the cause of the dystrophy.