Histochemistry of rat intrafusal muscle fibers and their motor innervation.

Abstract

Muscle spindles were followed in serial transverse sections of freshly frozen rat soleus muscles. Adenosine triphosphatase (ATPase) histochemical staining reaction was used to identify nuclear bagi, nuclear bag2 and nuclear chain intrafusal muscle fibers. Regional differences in ATPase staining occurred along bagi and bag2 fibers but not along chain fibers. Bag1 fibers displayed ultrastructural heterogenity when their intra-and extracapsular regions were compared. Simple "diffuse" and more elaborate "plate" motor nerve terminals were demonstrated histochemically along the poles of bagi and bagl fibers by staining for cholinesterase. One motor terminal of the "plate" appearance was present on a chain fiber pole. There was no consistent spatial correlation between the intensity of regional ATPase staining along the nuclear bag fibers and the location, number and type of motor endings. Other factors, such as intrafusal fiber sensory innervation and regional differences in active and passive functional recruitment of nuclear bag fibers during muscle activity, may contribute to the ATPase staining variability along the intrafusal fibers.

Influence du type d'innervation des fibres musculaires sur l'acquisition des propriétés de l'ATPase myofibrillaire

“…Moreover, we report that a regional variation of the acid stability of myofibrillar ATPase may occur in the polar zone of intrafusal fibres in chick PLD muscle spindles, a zone devoid of innervation. This observation is related to a similar variation in the polar zone of rat intrafusal fibres (Kucera et al, 1978). New examples are presented supporting the conclusion that the differentiation of the properties of ATPase activity, and thus of fibre types, takes place, at least in some cases, independently of the type of innervation received.…”

“…Ces variations longitudinales sont souvent sans rapport avec la localisation des terminaisons fusimotrices (Kucera et al, 1978 (Koenig et Fardeau, 1973 ;Toutant et al, 1979 …”

Motor innervation of intrafusal fibers in rat muscle spindles: Incomplete separation of dynamic and static systems

“…Rat spindles that contain two bag fibers invariably contain one bag, fiber and one bag2 fiber (Kucera et al, 1978). Spindles that contain two baga and no bagl, or two bagl and no baga fibers, are not known to occur in spindles of mammals (Kucera et al, 1978;Kucera, 1983). The fiber identified as bagl had more motor endings than did the fiber identified as bag2 in the same spindle pole.…”

“…Sectioning began or terminated in the extreme polar region of another six spindle poles. No motor endings are present in this region (Kucera et al, 1978); thus few, if any, motor endings were omitted from analysis. Sectioning began at the limit of the capsule of one spindle pole; hence the motor innervation to the extracapsular region of this spindle pole could not be traced.…”

Ultra-High-Resolution Scanning Electron Microscopic Studies on the Sarcoplasmic Reticulum and Mitochondria of the Rat Intrafusal Muscle Fibers. Part I. The Capsular Sleeve Region

“…Arrowhead shows a hollow. x99,000 DISCUSSION Mammalian intrafusal fibers have been classified histochemically into three types according to their patterns of staining with oxidative enzymes, myofibrillar ATPase and phosphorylase (OGATA andMORI, 1962, 1964;OVALLE and SMITH, 1972;BARKER, 1974;BANKS et al, 1977;KUCERA et al, 1978). Ultrastructurally they can be distinguished by the characteristic structure of their Z-and M-lines and mitochondria; that is, chain fibers have distinct M-lines and well developed mitochondria, bag, fibers have thick Z-lines and faint, thin double M-lines and small mitochondria, and bag2 fibers have thin Z-lines, vague M-lines and medium size mitochondria (OVALLE, 1971(OVALLE, , 1972BARKER, 1974;BANKS et al, 1977).…”