Persistence of myosin heavy chain-based fiber types in innervated but silenced rat fast muscle

Roy, Roland R.; Kim, Jung A; Grossman, Elena J.; Bekmezian, Arpi; Talmadge, Robert J.; Zhong, Hui; Edgerton, V. Reggie

doi:10.1002/(sici)1097-4598(200005)23:5<735::aid-mus11>3.0.co;2-t

Cited by 26 publications

(41 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Moreover, a small but significant proportion of hybrid type I/IIA myofibers does emerge in tail muscles after spinal isolation. This is consistent with the idea that the sacrocaudal spinal isolation (sacral spinal cord transection combined with bilateral sacrocaudal deafferentation) results in a drastic long-term reduction of neuromuscular activity among tail motor units, just as a more rostral lumbar spinal isolation (bilateral lumbar deafferentation between transections at low thoracic and high sacral levels) dramatically reduces muscle activity in rats and cats (Pierotti et al 1991;Roy et al 2000). No antibody specific for MyHC IId(x) was available; thus it is not known if there are hybrid tail myofibers coexpressing the MyHC IId(x) isoform (e.g., type IIA/D(X) or type IID(X)/B myofibers).…”

Section: Rat Segmental Tail Muscles Can Be Reliably Assessed With Rousupporting

confidence: 87%

“…Our results also demonstrate that early after spinal cord transection, tail muscles in young chronic spinal rats undergo a modest transformation in their myofiber types toward faster MyHC isoforms compared with in young normal rats, with smaller proportions of slow type I myofibers and larger proportions of fast type IID(X) myofibers, consistent with the classic effects of reduced muscle activity (Roy et al 2000;Talmadge et al 1999). Again, after 4 mo of complete spasticity in older chronic spinal rats, these proportions recover to no different from in age-matched older normal rats.…”

Section: Spasticity Opposes Transformation Of Myofiber Types After Chsupporting

confidence: 71%

“…Unexpectedly after spinal isolation, within the fast type II myofiber population, there is a large decrease in the proportion of type IID(X) myofibers and a large increase in the proportion of type IIA myofibers, which is not consistent with observations of other muscles after spinal isolation (Roy et al 2000) FIG. 7.…”

Section: Spasticity Opposes Transformation Of Myofiber Types After Chmentioning

confidence: 59%

“…After spinal cord injury (SCI, transection or partial injury), reduced neuromuscular activity leads to myofiber atrophy in muscles innervated below the level of the lesion (DupontVersteegden et al 1998;Lotta et al 1991) especially when muscle activity is further reduced by spinal cord transections combined with bilateral deafferentation (i.e., spinal isolation) (Roy et al 2000). These muscles typically also undergo transformations in myofiber types and isoforms of the associated myosin heavy chain (MyHC) proteins from slower, fatigueresistant myofibers to faster, more fatigable myofibers (Dupont-Versteegden et al 1998;Hartkopp et al 2003;Lieber et al 1986a;Roy et al 2000).…”

Section: Introductionmentioning

confidence: 99%

“…These muscles typically also undergo transformations in myofiber types and isoforms of the associated myosin heavy chain (MyHC) proteins from slower, fatigueresistant myofibers to faster, more fatigable myofibers (Dupont-Versteegden et al 1998;Hartkopp et al 2003;Lieber et al 1986a;Roy et al 2000). Consequently, faster, weaker, and more fatigable muscle contractile properties often result (Cope et al 1986;Hartkopp et al 2003;Lieber et al 1986b;Roy et al 1999Roy et al , 2002b.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Spastic Tail Muscles Recover From Myofiber Atrophy and Myosin Heavy Chain Transformations in Chronic Spinal Rats

Harris¹,

Putman²,

Rank³

et al. 2007

Journal of Neurophysiology

View full text Add to dashboard Cite

Harris RL, Putman CT, Rank M, Sanelli L, Bennett DJ. Spastic tail muscles recover from myofiber atrophy and myosin heavy chain transformations in chronic spinal rats. J Neurophysiol 97: 1040 -1051, 2007. First published November 22, 2006; doi:10.1152/jn.00622.2006. Without intervention after spinal cord injury (SCI), paralyzed skeletal muscles undergo myofiber atrophy and slow-to-fast myofiber type transformations. We hypothesized that chronic spasticity-associated neuromuscular activity after SCI would promote recovery from such deleterious changes. We examined segmental tail muscles of chronic spinal rats with longstanding tail spasticity (7 mo after sacral spinal cord transection; older chronic spinals), chronic spinal rats that experienced less spasticity early after injury (young chronic spinals), and rats without spasticity after transection and bilateral deafferentation (spinal isolated). These were compared with tail muscles of age-matched normal rats. Using immunohistochemistry, we observed myofiber distributions of 15.9 Ϯ 3.5% type I, 18.7 Ϯ 10.7% type IIA, 60.8 Ϯ 12.6% type IID(X), and 2.3 Ϯ 1.3% type IIB (means Ϯ SD) in young normals, which were not different in older normals. Young chronic spinals demonstrated transformations toward faster myofiber types with decreased type I and increased type IID(X) paralleled by atrophy of all myofiber types compared with young normals. Spinal isolated rats also demonstrated decreased type I myofiber proportions and increased type II myofiber proportions, and severe myofiber atrophy. After 4 mo of complete spasticity (older chronic spinals), myofiber type transformations were reversed, with no significant differences in type I, IIA, IID(X), or IIB proportions compared with age-matched normals. Moreover, after this prolonged spasticity, type I, IIA, and IIB myofibers recovered from atrophy, and type IID(X) myofibers partially recovered. Our results indicate that early after transection or after long-term spinal isolation, relatively inactive tail myofibers atrophy and transform toward faster myofiber types. However, long-term spasticity apparently produces neuromuscular activity that promotes recovery of myofiber types and myofiber sizes.

show abstract

Section: Rat Segmental Tail Muscles Can Be Reliably Assessed With Rousupporting

confidence: 87%

Section: Spasticity Opposes Transformation Of Myofiber Types After Chsupporting

confidence: 71%

Section: Spasticity Opposes Transformation Of Myofiber Types After Chmentioning

confidence: 59%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Spastic Tail Muscles Recover From Myofiber Atrophy and Myosin Heavy Chain Transformations in Chronic Spinal Rats

Harris¹,

Putman²,

Rank³

et al. 2007

Journal of Neurophysiology

View full text Add to dashboard Cite

show abstract

Mechanical properties of the electrically silent adult rat soleus muscle

et al. 2002

Self Cite

View full text Add to dashboard Cite

The isometric and isotonic in situ mechanical properties of the soleus muscle of adult female rats were determined after 60 days of inactivity induced by spinal cord isolation (SI). Compared to control, the absolute muscle mass, physiological cross-sectional area, and maximum tetanic tension of the soleus in SI rats were reduced by 69%, 66%, and 77%, respectively. Isometric twitch time-to-peak-tension and half-relaxation times were 41% and 60% shorter in SI than control rats. The maximum velocity of shortening (mm/s), as determined using the afterloaded technique, was 66% faster in SI than control rats, whereas unloaded shortening velocity was similar in the two groups (9% faster in SI rats). Peak power was 48% lower in SI than control rats. The SI soleus was 39% more fatigable than control. Thus, the soleus became a smaller, faster, and more fatigable muscle following 60 days of inactivity. In general, the results indicate that the adaptations are of a lesser magnitude than those reported previously following denervation for the same duration. These data provide a baseline for future efforts to experimentally define the mechanisms of neurally mediated, but activity-independent, regulation of the mechanical properties of the rat soleus muscle.

show abstract

Temporal effects of inactivty on myosin heavy chain gene expression in rat slow muscle

et al. 2001

Self Cite

View full text Add to dashboard Cite

Myosin heavy chain (MHC) mRNA and protein profiles in adult rat soleus and adductor longus were determined after 4, 8, 15, 30, 60, and 90 days of spinal cord isolation (SI). SI results in complete neuromuscular inactivity while leaving the motoneuron-muscle fiber connections intact. From 15 to 90 days, type I MHC mRNA was significantly decreased, whereas type I MHC protein did not significantly decrease until 30 and 60 days in the soleus and adductor longus, respectively. However, in both muscles, slow MHC downregulation was offset by significant upregulation of the faster MHC isoforms, primarily IIx. From 60 to 90 days, type I MHC was almost completely replaced with faster isoforms at the mRNA and protein levels. Thus, chronic inactivity and unloading of slow rat hindlimb muscles shifted the MHC profile from predominately type I to type IIx MHC mRNA and protein.

show abstract

Persistence of myosin heavy chain-based fiber types in innervated but silenced rat fast muscle

Cited by 26 publications

References 35 publications

Spastic Tail Muscles Recover From Myofiber Atrophy and Myosin Heavy Chain Transformations in Chronic Spinal Rats

Spastic Tail Muscles Recover From Myofiber Atrophy and Myosin Heavy Chain Transformations in Chronic Spinal Rats

Mechanical properties of the electrically silent adult rat soleus muscle

Temporal effects of inactivty on myosin heavy chain gene expression in rat slow muscle

Contact Info

Product

Resources

About