Slow-tonic Mhc Expression In Paralyzed Hindlimbs Of Fetal Rats

Title

Slow-tonic Mhc Expression In Paralyzed Hindlimbs Of Fetal Rats

Creator

Kucera J; Walro J M

Publisher

Histochemistry

Date

1991
1991

Description

Whether nerve activity and active contraction of myotubes are essential for the assembly and initial differentiation of muscle spindles was investigated by paralyzing fetal rats with tetrodotoxin (TTX) from embryonic day 16 (E16) to E21, prior to and during the period when spindles typically form. TTX-treated soleus muscles were examined by light and electron microscopy for the presence of spindles and expression of myosin heavy chain (MHC) isoforms by the intrafusal fibers. Treatment with TTX did not inhibit the formation of a spindle capsule or the expression of a slow-tonic MHC isoform characteristic of intrafusal fibers, but did retard development of spindles. Spindles of TTX-treated E21 muscles usually consisted of one intrafusal fiber (bag2) only rather than two fibers (bag1 and bag2) typically present in untreated (control) E21 spindles. Intrafusal fibers of TTX-treated spindles also had only one sensory region supplied by multiple afferents, and were devoid of motor innervation. These features are characteristic of spindles in normal E18-E19 muscles. Thus, nerve and/or muscle activity is not essential for the assembly of muscle spindles, formation of a spindle capsule, and transformation of undifferentiated myotubes into the intrafusal fibers containing spindle-specific myosin isoforms. However, activity may promote the maturation of intrafusal bundles, as well as the maturation of afferent and efferent nerve supplies to intrafusal fibers.

Subject

Cell Biology; heavy-chain isoforms; innervation; intrafusal muscle-fibers; numbers; spindles

Identifier

Format

Journal Article or Conference Abstract Publication

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Rights

Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).

Pages

51-57

Issue

1

Volume

96

Citation

Kucera J; Walro J M, “Slow-tonic Mhc Expression In Paralyzed Hindlimbs Of Fetal Rats,” NEOMED Bibliography Database, accessed January 15, 2021, https://neomed.omeka.net/items/show/10582.

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