The isometric responses of mammalian muscles. Contractile characteristics and innervation ratio of rat soleus motor units. Transformation of contraction speed in muscle following cross-reinnervation dependence on muscle size. Muscle fiber type composition of the rat hindlimb. Hindlimb muscle fiber populations of five mammals. A comparison of the effects of denervation on the mechanical properties of rat and guinea-pig skeletal muscle. Links to PubMed are also available for Selected References. Get a printable copy (PDF file) of the complete article (2.0M), or click on a page image below to browse page by page. Full textįull text is available as a scanned copy of the original print version. It is suggested that fast motoneurones may be transformed to slow by a trophic chemical released by slow muscle fibres such a process would be more extensive in predominantly slow twitch soleus than a fast muscle, and the resulting decrease in the proportion of fast motoneurones would account for the less extensive conversion in soleus. It is speculated that the mechanism accounting for the higher proportion of slow fibres in soleus muscle probably does not involve selective reinnervation. The effects of differing proportions of fast and slow fibres on the twitch contraction and half-relaxation times were modelled, and the experimental twitch data were found to be compatible with the proportions of fibre types in individual muscles. The proportion in the latter was similar to that predicted from random reinnervation. The proportion of type I fibres (presumed slow) was at least twice as high in soleus compared with plantaris muscles. Some of the muscles were stained for actomyosin ATPase activity. In the reinnervated muscles, isometric twitch time to peak (contraction time) and time to half-relaxation were longer in soleus than plantaris in every muscle examined. Reinnervation was observed in soleus (slow twitch) and plantaris (fast twitch) muscles for periods of 4-21 months after the initial operation. The medial popliteal nerve was sectioned in adult rats, and reinnervation was permitted after nerve reunion.
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