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Retention of some properties of fast muscle in the regenerated muscle grown from fast muscle slices in spite of flow motor innervation in chick

Wu Wangyuan, Lu Daxing, Zhu Dexing

Shanghai Institute of Physiology, Academia Sinica. Shangkai, China

Abstract

The determination of muscle types has been ascribed to motor innervation by many authors. In the attempt to further study the gene expression of skeletal muscle, two hypotheses have been raised, which, though different from each other, are all based on the assumption that myoblasts are bipotent and the choice of one from the two options of development is dictated by the nerve, but his assumption is not supported by the present work which, conversely, has to be interpreted otherwise at least in chick. The right anterior Latissimus Dorsi (slow) of 3-week-old chick is extirpated, the vacant place is either occupied by 1 mm slices of fast muscle (left posterior Latissimus Dorsi) in the first group of animals, or occupied by slices of slow muscle (right ALD) in the second group of animals. The muscle slices are consolidated by blood clot and left waiting for the sequential events of necrosis, regeneration and re-innervation by the remaining slow nerve to happen. After 2-17 mo (mostly 2-6 mo) the muscle contraction is recorded with isometric lever by stimulating the slow nerve. All regenerated muscles of the 15 animals of the first group and 14 animals of the second group exhibit tetanic contractions when tetanically stimulated but 12 in the first group and 8 in the second group exhibit single twitch when single shock is given. The single twitches are significantly faster in the first group, than in the second as shown in the table. Still different are the responses to high frequency shocks applied to the slow nerve that the muscles grown from minced fast (first group) all exhibit Wedensky inhibition as the normal PLD do, while muscles of the other group exhibit no inhibition even at 460/s as the normal ALD do. Wedensky inhibition has been claimed to be due to changes on the post-synaptic membrane rather than changes on the nerve terminal. The above result again proves its irrelevance to nerve and that the retention of some properties of the fast muscle in the newlv rezenerated muscle is verv nrobablv through satellite cells (presumptive myowast in muscle) in spite of incompatible innervation. H previous work with histochemical observations by the present authors leads to the same conclusion that the commitment of a muscle to be fast or slow does not necessarily take place after innervation. Since the tetanic contractions of the muscles of the two groups are all like that of the ALD, the exogenous neural factor seems to be reasonably involved.

Key words: Cross-flnnervation;Muscle transplantation;Wedensky inhibition

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Citing This Article：

Wu Wangyuan, Lu Daxing, Zhu Dexing. Retention of some properties of fast muscle in the regenerated muscle grown from fast muscle slices in spite of flow motor innervation in chick. Acta Physiol Sin 1985; 37 (1): (in Chinese with English abstract).