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The authors studied the characteristics of isometric contraction in in vivo experiments and the histochemical typical composition of muscles in different forms of experimental impairments of innervation simulating clinical pathology. The results demonstrate that in different forms of neuromuscular pathology there is a general tendency toward changes in the histochemical composition of muscles whereas alterations of contractile parameters of these muscles are fairly specific for each type of investigated disorder.

The authors studied the metabolism of purine compounds in the skeletal muscle of 129 Re mice with hereditary muscular dystrophy (MD). The study showed impairment of purine metabolism which was expressed in a sharp decrease in ATP levels and an increase in the content of AMP, IMP and uric acid. No changes were revealed in the pool of purine nucleotides in murine red blood cells. A study of some physical properties of the red blood cells in mice with myopathy showed no alterations in the osmotic resistance of erythrocytes, yet there was a reduction in their pliability as compared to control. Examination of the temperature resistance revealed anomalies of red blood cells in myodystrophic mice at 50 degrees C. The detected changes of some physical properties of erythrocytes seem to be related to abnormalities of the sumbembranous contractile apparatus of these cells.

The influence of 3-week L-thyroxin administration on contractility and histochemical composition of skeletal muscles was studied in 129Rj mice of normal and dystrophic genotypes. The rise in speed characteristics of isometric contraction and percentage of type II "fast" fibers was established in both types of animals. Contractile properties in dystrophic animals, receiving L-thyroxin, showed a tendency towards normalization and were comparable to those of normal animals.

In athyreotic dystrophy of the heart muscle properties both actin- and myosin-containing fibers protein components are shown to change. Changes in actin-containing filaments become apparent in a decrease in superprecipitation value of hybrid actomyosin consisting of athyreotic actin and myosin from normal myocardium. Disturbances in myosin structure result in a decrease of both, the value and rate of hybrid actomyosin superprecipitation consisting of athyreotic myosin and normal actin. The value of Mg2+-ATPase activity of hybrid actomyosins does not practically differ from that of normal actomyosin. Native athyreotic tropomyosin loses its ability to activate Mg2+-ATPase of purified actomyosin but its Ca2+ sensitivity, as well as its ability to increase the superprecipitation rate of normal actomyosin do not change. The obtained data suggest that a decrease in a tension value developed by bundles of glycerinated muscle fibers of athyreotic myocardium results from changes in the properties of both actin and myosin, while a reduction in the rate of fiber contraction is caused by disturbances of myosin properties and may be of native tropomyosin as well.

Whole gastrocnemius muscles of rabbits, preliminarily denervated, were grafted. At the moment of grafting (60 days after the operation) the muscles were in the state of deep atrophy attended by distrophic changes. The autotransplantated muscles took at the site of grafting, their further reorganization provided progressive development of the muscle tissue within the transplant, its growth, and formation of definitive muscle fibers with nerve terminals. After a definite time some degenerative changes were observed in the transplant muscle tissue; as a result the muscle tissue was substituted by connective tissue. These data support the statement founded before on feasible free grafting of preliminary denervated whole muscles. However, deep denervation atrophy seems to influence the remote results of the transplantation.