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| 2. |
- Yu, F, et al.
(författare)
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Human single masseter muscle fibers contain unique combinations of myosin and myosin binding protein C isoforms
- 2002
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Ingår i: Journal of Muscle Research and Cell Motility. - 0142-4319 .- 1573-2657. ; 23, s. 317-
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Tidskriftsartikel (refereegranskat)abstract
- Striated craniofacial and limb muscles differ in their embryological origin, regulatory program during myogenesis, and innervation. In an attempt to explore the effects of these differences on the striated muscle phenotype in humans, the expression of myosin and myosin-associated thick filament proteins were studied at the single fiber level both in the human jaw-closing masseter muscle and in two limb muscles (biceps brachii and quadriceps femoris muscles). In the masseter, unique combinations of myosin heavy chain (MyHC) and myosin binding protein C (MyBP-C) isoforms were observed at the single fiber level. Compared to the limb muscles, the MyHC isoform expression was more complex in the masseter while the opposite was observed for MyBP-C. In limb muscles, a coordinated expression of three MyHC and three MyBP-C isoforms were observed, i.e., single fibers contained one or two MyHC isoforms, and up to three MyBP-C isoforms. Also, the relative content of the different MyBP-C isoforms correlated with the MyHC isoform expression. In the masseter, on the other hand, up to five different MyHC isoforms could be observed in the same fiber, but only one MyBP-C isoform was identified irrespective MyHC isoform expression. This MyBP-C isoform had a migration rate similar to the slow MyBP-C isoform in limb muscle fibers. In conclusion, a unique myofibrillar protein isoform expression was observed in the human masseter muscle fibers, suggesting significant differences in structural and functional properties between muscle fibers from human masseter and limb muscles.
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| 3. |
- Yu, Ji-Guo, et al.
(författare)
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Desmin and actin alterations in human muscles affected by delayed onset muscle soreness : a high resolution immunocytochemical study.
- 2002
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Ingår i: Histochemistry and Cell Biology. - : Springer. - 0948-6143 .- 1432-119X. ; 118:2, s. 171-9
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Tidskriftsartikel (refereegranskat)abstract
- Lack of staining for desmin in muscles in animal models of eccentric exercise has been suggested to reflect disruption of the desmin intermediate filament network and proposed to cause disruption of the myofibrillar apparatus and deterioration of muscle fibers. In a recent study, we examined muscle biopsies from persons who had performed different eccentric exercise protocols, which induced delayed onset muscle soreness (DOMS). We were unable to verify that loss of staining for desmin was a feature of sore muscles. Nevertheless, we observed changes in the desmin cytoskeleton, but the meaning of the observations was not conclusive. In the present study, a high resolution immunocytochemical method was used to investigate the changes of desmin and actin in human muscles following a bout of eccentric exercise that lead to DOMS 2-3 days post-exercise. Biopsies were taken before exercise and 1 h and 2-3 and 7-8 days after exercise. Phalloidin, a ligand that labels filamentous actin, and anti-desmin antibodies were used to stain semithin (approximately 0.5 micro m) cryosections. At 1 h post-exercise, the staining of actin and desmin did not differ from the controls, whereas in biopsies taken 2-3 and 7-8 days after exercise, 12.5% (SD 5.8%) and 6.1% (SD 2.3%) fibers showed areas of increased staining for actin. Corresponding values for fibers with increased staining for both actin and desmin were 8.7% (SD 3.9%) and 11.4% (SD 4.6%), respectively. We suggest that the increased staining of actin and desmin reflects an increased synthesis of these proteins as part of an adaptation process following the unaccustomed eccentric exercise.
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| 5. |
- Yu, Ji-Guo, et al.
(författare)
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Eccentric contractions leading to DOMS do not cause loss of desmin nor fibre necrosis in human muscle.
- 2002
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Ingår i: Histochemistry and Cell Biology. - : Springer. - 0948-6143 .- 1432-119X. ; 118:1, s. 29-34
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Tidskriftsartikel (refereegranskat)abstract
- High force eccentric muscle contractions can result in delayed onset muscle soreness (DOMS), prolonged loss of muscle strength, decreased range of motion, muscle swelling and an increase of muscle proteins in the blood. At the ultrastructural level Z-line streaming and myofibrillar disruptions have been taken as evidence for muscle damage. In animal models of eccentric exercise-induced injury, disruption of the cytoskeleton and the sarcolemma of muscle fibres occurs within the first hour after the exercise, since a rapid loss of staining of desmin, a cytoskeletal protein, and the presence of fibronectin, a plasma and extracellular protein, are observed within the muscle fibres. In the present study, biopsies from subjects who had performed different eccentric exercises and had developed DOMS were examined. Our aim was to determine whether eccentric exercise leading to DOMS causes sarcolemmal disruption and loss of desmin in humans. Our study shows that even though the subjects had DOMS, muscle fibres had neither lost staining for desmin nor contained plasma fibronectin. This study therefore does not support previous conclusions that there is muscle fibre degeneration and necrosis in human skeletal muscle after eccentric exercise leading to DOMS. Our data are in agreement with the recent findings that there is no inflammatory response in skeletal muscle following eccentric exercise in humans. In combination, these findings should stimulate the search for other mechanisms explaining the functional and structural alterations in human skeletal muscle after eccentric exercise.
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| 6. |
- Yu, Ji-Guo, et al.
(författare)
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Evidence for myofibril remodeling as opposed to myofibril damage in human muscles with DOMS : an ultrastructural and immunoelectron microscopic study.
- 2004
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Ingår i: Histochemistry and Cell Biology. - : Springer Science and Business Media LLC. - 0948-6143 .- 1432-119X. ; 121:3, s. 219-227
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Tidskriftsartikel (refereegranskat)abstract
- The myofibrillar and cytoskeletal alterations observed in delayed onset muscle soreness (DOMS) caused by eccentric exercise are generally considered to represent damage. By contrast our recent immunohistochemical studies suggested that the alterations reflect myofibrillar remodeling (Yu and Thornell 2002; Yu et al. 2003). In the present study the same human muscle biopsies were further analyzed with transmission electron microscopy and immunoelectron microscopy. We show that the ultrastructural hallmarks of DOMS, Z-disc streaming, Z-disc smearing, and Z-disc disruption were present in the biopsies and were significantly more frequent in biopsies taken 2-3 days and 7-8 days after exercise than in those from controls and 1 h after exercise. Four main types of changes were observed: amorphous widened Z-discs, amorphous sarcomeres, double Z-discs, and supernumerary sarcomeres. We confirm by immunoelectron microscopy that the main Z-disc protein alpha-actinin is not present in Z-disc alterations or in the links of electron-dense material between Z-discs in longitudinal register. These alterations were related to an increase of F-actin and desmin, where F-actin was present within the strands of amorphous material. Desmin, on the other hand, was seen in less dense regions of the alterations. Our results strongly support that the myofibrillar and cytoskeletal alterations, considered to be the hallmarks of DOMS, reflect an adaptive remodeling of the myofibrils
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| 7. |
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| 8. |
- Yu, Ji-Guo, et al.
(författare)
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The mode of myofibril remodelling in human skeletal muscle affected by DOMS induced by eccentric contractions.
- 2003
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Ingår i: Histochemistry and Cell Biology. - : Springer-Verlag New York. - 0948-6143 .- 1432-119X. ; 119:5, s. 383-93
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Tidskriftsartikel (refereegranskat)abstract
- Myofibrillar Z-disc streaming and loss of the desmin cytoskeleton are considered the morphological hallmarks of eccentric contraction-induced injury. The latter is contradicted by recent studies where a focal increase of desmin was observed in biopsies taken from human muscles with DOMS. In order to determine the effects of eccentric contraction-induced alterations of the myofibrillar Z-disc, we examined the distribution of alpha-actinin, the Z-disc portion of titin and the nebulin NB2 region in relation to actin and desmin in DOMS biopsies. In biopsies taken 2-3 days and 7-8 days after exercise, we observed a significantly higher number of fibres showing focal areas lacking staining for alpha-actinin, titin and nebulin than in biopsies taken from control or 1 h after exercise. None of these proteins were part of Z-disc streamings but instead they were found in distinct patterns in areas characterised by altered staining for desmin and actin. These were preferentially seen in regions with increased numbers of sarcomeres in parallel myofibrils. We propose that these staining patterns represent different stages of sarcomere formation. These findings therefore support our previous suggestion that muscle fibres subjected to eccentric contractions adapt to unaccustomed activity by the addition of new sarcomeres.
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