Effects of inactivity on myosin heavy chain composition and size of rat soleus fibers

Grossman, Elena J.; Roy, Roland R.; Talmadge, Robert J.; Zhong, Hui; Edgerton, V. Reggie

doi:10.1002/(sici)1097-4598(199803)21:3<375::aid-mus12>3.0.co;2-z

Cited by 95 publications

(126 citation statements)

References 33 publications

(44 reference statements)

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“…First, the hierarchies in ®ber size and ®ber type percentage agree with existing literature. 16 Likewise, the reduction in ®ber size, SDH activity and percentage of type I ®bers as well as the increase in GPDH activity resulting from SCI are within the range of reported values for animals of similar age and duration of injury. 16,17,18 The most important ®nding of this study was that TRT ameliorated the decrease in ®ber CSA resulting from SCI.…”

Section: Discussionsupporting

confidence: 76%

Effects of testosterone replacement therapy on skeletal muscle after spinal cord injury

Gregory

Vandenborne

Huang³

et al. 2002

Spinal Cord

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Study design: Randomized control. Objective: To examine the e ects of testosterone replacement therapy (TRT) on skeletal muscle 11 weeks after complete SCI. Setting: Athens, Georgia USA. Methods: Soleus (SOL), gastrocnemius (GA), tibialis anterior (TA), vastus lateralis (VL) and triceps brachii (TRI) muscles were taken from twelve young male Charles River rats 11 weeks after complete SCI (T-9 transection, n=8) or sham surgery (n=4). Rats received either TRT (two 5 cm capsules, n=4) or empty capsules (n=8) implanted at surgery. Muscle samples were sectioned and ®bers analyzed qualitatively for myosin ATPase and quantitatively for succinate dehydrogenase (SDH), a-glycerol-phosphate dehydrogenase (GPDH) and actomyosin ATPase (qATPase) activities using standard techniques. Results: SCI decreased average ®ber size (49+4%) in a ected muscles and the percentage of slow ®bers in SOL (93+3% to 17+2%). In addition, there was a decrease in SDH and an increase in GPDH and qATPase activities across the four hind-limb muscles of the SCI animals. Fiber size in the TRI was increased (31+2%) by SCI while enzyme activities were not altered. Average ®ber size across the four hind limb muscles was decreased by only 30% in TRT SCI animals and their SOL contained 39+2% slow ®bers. TRT also attenuated changes in enzyme activities. There was no e ect of TRT on the TRI relative to SCI.

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Section: Discussionsupporting

confidence: 76%

Effects of testosterone replacement therapy on skeletal muscle after spinal cord injury

Gregory

Vandenborne

Huang³

et al. 2002

Spinal Cord

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“…2 In contrast, models of SCI involving transection of the spinal cord have shown little spontaneous recovery in muscle size. 25 This is probably due to the fact that communication between the supraspinal centers and caudal region of the spinal cord is eliminated. In addition, the restoration in muscle size in the moderate contusion injury model appears to mirror the spontaneous improvement in locomotor function.…”

Section: Discussionmentioning

confidence: 99%

A longitudinal study of skeletal muscle following spinal cord injury and locomotor training

et al. 2008

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Study design: Experimental rat model of spinal cord contusion injury (contusion SCI).Objective: The objectives of this study were (1) to characterize the longitudinal changes in rat lower hindlimb muscle morphology following contusion SCI by using magnetic resonance imaging and (2) to determine the therapeutic potential of two types of locomotor training, treadmill and cycling. Setting: University research setting. Methods: After moderate midthoracic contusion SCI, Sprague-Dawley rats were assigned to either treadmill training, cycle training or an untrained group. Lower hindlimb muscle size was examined prior to SCI and at 1-, 2-, 4-, 8-, and 12-week post injury. Results: Following contusion SCI, we observed significant atrophy in all rat hindlimb muscles with the posterior muscles (triceps surae and flexor digitorum) showing greater atrophy than the anterior muscles (tibialis anterior and extensor digitorum). The greatest amount of atrophy was measured at 2-week post injury (range from 11 to 26%), and spontaneous recovery in muscle size was observed by 4 weeks post-SCI. Both cycling and treadmill training halted the atrophic process and accelerated the rate of recovery. The therapeutic influence of both training interventions was observed within 1 week of training and no significant difference was noted between the two interventions, except in the tibialis anterior muscle. Finally, a positive correlation was found between locomotor functional scores and hindlimb muscle size following SCI. Conclusions: Both treadmill and cycle training diminish the extent of atrophy and facilitate muscle plasticity after contusion SCI.

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“…Slow muscle MHC remodeling was induced by SI. For the SI procedure the spinal cords of six animals were transected at both a mid-thoracic and the high sacral level, and a bilateral dorsal rhizotomy was performed between the two transection sites as described previously (9). The unique feature of the SI model is that the surgical treatment renders the motor neuron pools in the isolated region of the spinal cord inactive while maintaining an intact connection to the muscles of the leg.…”

Section: Methodsmentioning

confidence: 99%

“…Age-matched normal control rats were used for the control muscles (CON, n ϭ 6). A majority of the muscle atrophy during SI occurs during the first 7 days, and significant changes in MHC mRNA expression are also detected during this time period (8,9). This study followed the National Institutes of Health Animal Care Guidelines and was approved by the University of California, Los Angeles, Animal Care and Use Committee.…”

Section: Methodsmentioning

confidence: 99%

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Dynamics of Myosin Heavy Chain Gene Regulation in Slow Skeletal Muscle

Pandorf

Haddad

Roy

et al. 2006

Journal of Biological Chemistry

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The evolutionarily conserved order of the skeletal muscle myosin heavy chain (MHC) genes and their close tandem proximity on the same chromosome are intriguing and may be important for their coordinated regulation. We investigated type II MHC gene regulation in slow-type muscle fibers undergoing a slow to fast MHC transformation in response to inactivity, 7 days after spinal cord isolation (SI) in rats. We examined the transcriptional products of both the sense and antisense strands across the IIa-IIx-IIb MHC gene locus. A strand-specific reverse transcription (RT)-PCR approach was utilized to study the expression of the mRNA, the primary transcript (pre-mRNA), the antisense RNA overlapping the MHC genes, and both the intergenic sense and antisense RNAs. Results showed that the mRNA and pre-mRNA of each MHC had a similar response to SI, suggesting regulation of these genes at the transcriptional level. In addition, we detected previously unknown antisense strand transcription that produced natural antisense transcripts (NATs). RT-PCR mapping of the RNA products revealed that the antisense activity resulted in the formation of three major products: aII, xII, and bII NATs (antisense products of the IIa, IIx, and IIb genes, respectively). The aII NAT begins in the IIa-IIx intergenic region in close proximity to the IIx promoter, extends across the 27-kb IIa MHC gene, and continues to the IIa MHC gene promoter. The expression of the aII NAT was significantly up-regulated in muscles after SI, was negatively correlated with IIa MHC gene expression, and was positively correlated with IIx MHC gene expression. The exact role of the aII NAT is not clear; however, it is consistent with the inhibition of IIa MHC gene transcription. In conclusion, NATs may mediate cross-talk between adjacent genes, which may be essential to the coordinated regulation of the skeletal muscle MHC genes during dynamic phenotype shifts.Skeletal muscle is highly adaptable when subjected to altered loading and hormone states. Its size, metabolic makeup, and contractile properties can all be altered to optimize function (1). Variability in contractile properties is achieved mainly by diversification in the motor protein myosin heavy chain (MHC), 2 where different isoforms are encoded by distinct genes (1, 2). Of this family of eight MHC genes, six are tandemly linked and span ϳ420 kb in the rat on chromosome 10, with embryonic MHC situated at the most 5Ј end, sequentially followed by IIa, IIx, IIb, neonatal, and extraocular MHC. ␤ (or type I) and ␣ MHCs are located tandemly on separate chromosomes (chromosome 14 in the rat); they span ϳ50 kb and are separated by 4.5 kb. Interestingly, the genomic order and orientation on the chromosomes of the MHC genes are conserved in all mammalian species, leading researchers to suspect that this organization might be an important feature in the strategy for the coordinated regulation of these genes (2-5).Types I, IIa, IIx, and IIb, in respective order of increasing ATPase activity, are the four predominately exp...

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Effects of inactivity on myosin heavy chain composition and size of rat soleus fibers

Cited by 95 publications

References 33 publications

Effects of testosterone replacement therapy on skeletal muscle after spinal cord injury

Effects of testosterone replacement therapy on skeletal muscle after spinal cord injury

A longitudinal study of skeletal muscle following spinal cord injury and locomotor training

Dynamics of Myosin Heavy Chain Gene Regulation in Slow Skeletal Muscle

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