The size of the myofibers in mature grafts of the mouse extensor digitorum longus muscle

Thomas, Denise; Klueber, Kathleen M.; Bourke, Dianna; Ontell, Marcia

doi:10.1002/mus.880070307

Cited by 23 publications

(25 citation statements)

References 30 publications

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“…In 20 adult animals examined (2-4 months of age), no slow fibers could be demonstrated by standard histochemical techniques in the EDL muscle of 10 mice while the remaining mice had less than 10 slow fibers per muscle (table 1). Similar results have been reported by others for the same mouse strain [26] and for the EDL muscle of C57Bl mice [27]. In a total of 30 mice of 2-6 months of age, no SM muscle was found to contain slow fibers.…”

Section: Presence Of Slow Myosin-containing Fibers In Young Mouse Mussupporting

confidence: 91%

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A developmentally regulated disappearance of slow myosin in fast‐type muscles of the mouse

et al. 1984

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Histochemistry and immunocytochemistry using an antibody to adult rat slow-type myosin demonstrated that about 10% of the fibers in the mouse extensor digitorum longus and semimembranosus muscles contain slow myosin during the first month after birth. In adult animals, these muscles have only t&0.8% slow myosin-containing fibers. These results demonstrate a developmentally linked disappearance of an adult-type myosin, and show that the adult phenotype of muscle fibers is not necessarily determined before birth as previously suggested. Histochemistry Immunocytochemistry

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Section: Presence Of Slow Myosin-containing Fibers In Young Mouse Mussupporting

confidence: 91%

“…The same muscles contain no (SM) or less than 10 (EDL; table 1 and [26,27]) slow fibers at adult ages. The immunocytochemical results demonstrate therefore an age-related disappearance of an apparently adult myosin type, a situation which has not been documented previously in developing muscles.…”

Section: Discussionmentioning

confidence: 99%

A developmentally regulated disappearance of slow myosin in fast‐type muscles of the mouse

et al. 1984

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“…However, as with the endogenous MLC3F gene in adult mice, transgene activity is reduced in muscles having few type IIB fibers (Kelly et al, 1995). In the present study, relatively high transcription of the transgene could be anticipated in in vivo experiments because the muscle into which the 3FlacZ10 cells were injected is the regenerating EDL, a muscle in which 63% of the total fiber population is type IIB (Thomas et al, 1984). It could be that the rate of transcription of this gene is the factor permitting us to determine that extensive translocation of nlsb-gal (or its mRNA) from encoding to nonencoding nuclei in a myofiber can occur.…”

Section: Discussionmentioning

confidence: 72%

“…Within a week after transplantation, the entire girth of the mouse EDL muscle is filled with regenerated myofibers (formed from the muscle's myosatellite cells, which become activated by the trauma of transplantation; Thomas et al, 1984). In the present study, [3H]-thymidine-labeled 3FlacZ10 myoblasts were injected into the transplanted EDL muscle of Swiss Webster mice 2 days after transplantation.…”

Section: Transport Of B-gal Product In Myotubes In Vivomentioning

confidence: 90%

Limitations of nlsβ‐galactosidase as a marker for studying myogenic lineage or the efficacy of myoblast transfer

Yang¹,

Ontell²,

Kelly³

et al. 1997

Anat. Rec.

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Background: Nuclear localizing b-galactosidase (nlsb-gal) is used as a marker for studying myoblast cell lineage and for evaluating myoblast survival after myoblast transfer, a procedure with potential use for gene complementation for muscular dystrophy. Usefulness of this construct depends on the establishment of the extent to which nlsb-gal or its mRNA may be translocated from the nucleus that encodes it to other non-coding myonuclei in hybrid myofibers and the ease with which the encoding and non-coding myonuclei can be distinguished. Previous in vitro studies (Ralston and Hall 1989. Science, 244:1066-1068) have suggested limited translocation of the fusion protein. We re-examined the extent to which nlsb-gal is translocated in hybrid myofibers, both in vitro and in vivo, and evaluated the extent to which one can rely on histochemistry to distinguish encoding from non-coding nuclei in these myofibers.Methods: Myotubes formed in co-cultures of a myoblast line (MM14 cells), stably transfected with a construct consisting of a nlsb-gal under the control of the myosin light chain 3F promoter and 38 enhancer (3FlacZ10 cells), and [3H]-thymidine-labeled parental MM14 cells (plated at ratios of 1:6 or 1:20, respectively) were reacted with X-gal. After autoradiography, the distance over which nlsb-gal was translocated in hybrid myotubes was determined. In vivo translocation of nlsb-gal was evaluated by injecting [3H]-thymidine-labeled 3FlacZ10 myoblasts into the regenerating extensor digitorum longus muscle of immunosuppressed normal and mdx (dystrophin deficient) mice. Sections stained with X-gal and subjected to autoradiography permitted determination of the extent of nlsb-gal translocation in hybrid myofibers.Results: In vitro: All nuclei in G92% of hybrid myotubes showed evidence of nlsb-gal after exposure to X-gal, suggesting extensive translocation. Within hybrid myotubes, MM14-derived myonuclei D350 mm from a 3FlacZ10-derived myonucleus showed evidence of nlsb-gal. In vivo: Similar translocation of nlsb-gal was observed in vivo. One week after myoblast transfer, donor-derived myonuclei were distinguishable from hostderived myonuclei containing nlsb-gal by the greater accumulation of reaction product in donor myonuclei after X-gal staining. However, 2 weeks after injection, host myonuclei often contained a significant amount of nlsb-gal, and accumulation of reaction product could not be used as the criterion for identification of donor myonuclei.Conclusions: Translocation of nlsb-gal (or its mRNA) is significantly greater than previously reported (Ralston and Hall 1989), resulting in large numbers of nlsb-gal positive non-coding myonuclei in hybrid myofi-

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“…We have evaluated the accumulation of the four MRF transcripts per nanogram of total RNA in the aneural EDL (a crural muscle that in the normal, adult mouse contains 99% fast twitch fibers [Thomas et al, 1984]) and soleus (a crural muscle that in the normal adult contains 40 -60% slow twitch fibers [Wirtz et al, 1983;Wigston and English, 1992]) muscles, and we have compared these MRF mRNA levels with that in innervated developing muscles. To determine the extent to which changes in MRF proteins in aneural fetal muscle might mimic changes in transcripts, we have used Western blots to evaluate the levels of myoD protein accumulation.…”

Section: Introductionmentioning

confidence: 99%

Neuronal control of myogenic regulatory factor accumulation in fetal muscle

Washabaugh¹,

Ontell²,

Shand³

et al. 2007

Developmental Dynamics

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The lumbosacral spinal cords of 14.5-day gestation mice (E14.5) were ablated. The number of molecules of each of the four myogenic regulatory factor (MRF) mRNAs per nanogram of total RNA were evaluated in innervated and aneural fetal crural muscles. Accumulation of all four MRF mRNAs was affected in aneural muscle, but was never more than threefold different than in innervated muscles, considerably less than after adult denervation. The effect of the nerve varied with the MRF, the fetal age, and with the muscle (extensor digitorum longus muscle [EDL] vs. soleus muscle), with the nerve having multiple effects including down-regulation of certain MRF genes at specific periods (e.g., myoD and myogenin [E16.5-E18.5] and MRF4 in the EDL only [E18.5-E19.5]); limiting the up-regulation of certain genes, which occurred in the absence of innervation (e.g., myf-5 [E18.5-E19.5] and myogenin [E14.5-E16.5]); and even enhancing the accumulation of MRF4 mRNA (E14.5-E16.5). We hypothesize that factors other than nerve contribute to the down-regulation of myf-5 and myogenin mRNAs to adult levels. Innervation was required for the emergence of the slow, but not the fast, MRF mRNA profile at birth. MyoD, found in both the nuclear and cytoplasmic protein extracts of innervated fetal muscle, increased by ϳ5-fold in the nuclear extracts (ϳ2.5-fold in the cytoplasmic) of E19.5 aneural muscles, significantly less than the 12-fold increase found in the nuclear extract of 4-day denervated adult muscle. This increase in aneural fetal muscle was due primarily to an increased concentration of myoD in muscle lineage nuclei, rather than to the presence of additional myoD

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The size of the myofibers in mature grafts of the mouse extensor digitorum longus muscle

Cited by 23 publications

References 30 publications

A developmentally regulated disappearance of slow myosin in fast‐type muscles of the mouse

A developmentally regulated disappearance of slow myosin in fast‐type muscles of the mouse

Limitations of nlsβ‐galactosidase as a marker for studying myogenic lineage or the efficacy of myoblast transfer

Neuronal control of myogenic regulatory factor accumulation in fetal muscle

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