Data/hora: 08/06/2024 03:59:04

Biblioteca(s): 	Embrapa Pantanal.	
Data corrente: 	18/03/1999	
Data da última atualização: 	18/03/1999	
Autoria: 	GAUTHIER, G. F.; BURKE, R. E.; LOWEY, S.; HOBBS, A. W.	
Título: 	Myosin isozymes in normal and cross-reinnervated cat skeletal muscle fibers.	
Ano de publicação: 	1983	
Fonte/Imprenta: 	Journal of Cell Biology, v.97, p.756-771, Sept. 1983.	
Idioma: 	Inglês	
Conteúdo: 	Immunocytochemical characteristics of myosin have been demonstrated directly in normal and cross-reinnervated skeletal muscle fibers whose physiological properties have been defined. Fibers belonging to individual motor units were identified by the glycogen depletion method, which permits correlation of cytochemical and physiological data on the same fibers. The normal flexor digitorum longus (FDL) of the cat is composed primarily of fast-twitch motor units having muscle fibers with high myosin ATPase activity. These fibers reacted with antibodies specific for the two light chains characteristic of fat myosin, but not with antibodies against slow myosin. Two categories of fast fibers, corresponding to two physiological motor unit types (FF and FR), differed in their immunochemical  responde  from which it can be concluded that their myosin are distinctive. The soleus (SOL) consists almost entirely of slow-twitch motor units having muscle fibers with low myosin ATPase activity. These fibers reacted with antibodies against slow myosin, but not with antibodies specific for fast myosin. When the FDL muscle was cross-reinnervated by the SOl nerve, twhich contraction times were slowed about twofold, and motor units resembled SOL units in a number of physiological properties. The corresponding muscle fibers had low ATPase activity, and they reacted with antibodies against slow myosin only. The myosin of individual cross-reinnervated FDL muscle units was therefore transformed, apparently completely, to a slow type. In contrast, cross-reinnervation of the SOL muscle by FDL motoneurons did not effect a complete converse transformation. Although cross-reinnervated SOL motor units had faster than normal twich contraction times (about twofold), other physiological properties chracteristics of types S motor units were unchanged. Despite the change in contraction times, cross-reinnervated SOL muscle fibers exhibited no change in ATPase activity. They also continued to react with antibodies against slow myosin, but in contrast to the normal SOL, they now showed a positive response to an antibody specific for one of the light chains of fast myosin. The myosin of both fast and slow muscles were thus converted by cross-reinnervation, but in the SOL, the newly synthesized myosin was not equaivalent to thet normally present in either the FDL or SOL. This suggests that, in the SOL, alteration of the nerve supply and the associated dynamic activity pattern are not sufficient to completely respecify the type of myosin expressed. 	
Palavras-Chave: 	Cat skeletal muscle fiber; Cross-reinnervated; Fibra de musculo; Myosin isozymes.	
Thesagro: 	Esqueleto; Gato.	
Categoria do assunto: 	--	
Registro original: 	Embrapa Pantanal (CPAP)	
Exemplares: 	CPAP - (37469-1) - ADD - SP - -- - SP4130 -  - 4130 - DIS