Limited fiber type grouping in self-reinnervation cat tibialis anterior muscles.
The percent and distribution patterns of three immunohistochemically identified fiber types within the anterior compartment of the cat tibialis anterior were determined 6 months after denervation and self-reinnervation. After self-reinnervation, mean frequencies of slow (9%) and fast (91%) fibers were similar to those in control (12% and 88%, respectively) muscles. However, a lower proportion of fast-1 (26%) and a higher proportion of fast-2 (65%) fibers were observed in self-reinnervated than control (32% and 56%) muscles. Quantitation of adjacencies between fibers of similar myosin heavy chain (MHC) phenotype, a measure of type grouping, revealed that the frequencies of two slow or two fast-1 fibers being adjacent in self-reinnervated muscles were similar to control. In contrast, the frequency of fast-2/fast-2 fiber adjacencies found in self-reinnervated muscles (45%) was significantly higher than in control muscles (37%). In both groups, the frequency of adjacencies between slow, fast-1, or fast-2 fibers was largely attributable to the number of each fiber type present. These data show that the incidence of grouping within each fiber type present was not altered after 6 months of self-reinnervation. Minimal changes in the spatial distribution of fiber types following self-reinnervation in adults suggests a limited degree of conversion of muscle fibers to a MHC phenotype matching the motoneuron characteristics.
Unguez
G A
GA
Department of Physiological Science, UCLA, Los Angeles, California 90095-1761, USA.
Roy
R R
RR
Bodine-Fowler
S
S
Edgerton
V R
VR
D000818:Animals; D002415:Cats; D003714:Denervation; D005260:Female; D005528:Foot; D007150:Immunohistochemistry; D018485:Muscle Fibers, Skeletal / Q000145:classification* / Q000648:ultrastructure*; D018482:Muscle, Skeletal / Q000294:innervation* / Q000648:ultrastructure*; D009416:Nerve Regeneration