[Crystalloids in human skeletal muscle fibers].
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Biomedical subjects
Publications and source records attributed to H Schmalbruch.
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Of 185 patients with myopathy, 22 showed abnormal muscle mitochondria. In 12 of the 22 patients, all of whom had ocular myopathy or the ophthalmoplegia-plus syndrome, muscle biopsies contained 5%-25% "ragged red" fibers. In 4 patients with a facioscapulohumeral distribution of weakness, ragged red fibers were less numerous (3%-8%). In both groups, routine histology showed almost normal muscle. The remaining 6 patients were clinically heterogeneous, all without ptosis or ophthalmoplegia. The biopsies of three of these patients showed severely affected muscle. It is possible that mitochondrial changes in these muscles were nonspecific. Electromyography indicated or suggested a myogenic lesion in 21 of the 22 patients; in 10, the serum creatine kinase was increased.
Chlorphentermine interferes with the metabolism of phospholipids. When administered to the rat in daily doses for 5 days, it causes necrosis of muscle fibers that are rich in mitochondria. Before the onset of necrosis, the following characteristics of freeze-fractured muscle preparations were observed: multilayered lipid globules and single-layered lipid membranes without membrane particles; different stages of exocytosis of lipid through the plasma membrane of the muscle fibers; and areas of plasma membrane that were devoid of particles of intramembranous proteins. These latter areas may arise secondary to exocytosis, to fusion of lipid vesicles with the plasma membrane, or to a direct action of chlorphentermine on the membrane. It is not known whether these areas give rise to membrane defects and fiber necrosis.
In chronic experimental myasthenia gravis (EAMG) in rat, the decrement of electrical and mechanical responses evoked by maximal repetitive (3-167/sec) stimuli to the nerve was greater in the slow-twitch soleus (SOL) than in the fast-twitch extensor digitorum longus (EDL) muscle. Excitation-contraction coupling was impaired in moderate to severe EAMG, as evidenced by a diminished staircase phenomenon and by diminished posttetanic potentiation (PTP) of twitch tension in two EDLs. The only morphologic abnormality observed was an increase in length of the endplates in the EDLs of those animals that had had an acute phase of EAMG. The latter had more than a 90% reduction in the amplitude of the action potential and in the twitch tension of the EDL when stimuli were applied to the nerve. Stimuli applied directly to the muscle evoked a tetanic tension that was one-third of normal. The staircase and PTP were normal. Necrosis occurred in the endplate and in the adjacent segment of muscle fiber; outside the endplate region, the muscle fiber was normal.
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