| 1. |
- Carlsson, Lena, et al.
(författare)
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Myotilin - a prominent marker of myofibrillar remodelling
- 2007
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Ingår i: Neuromuscular Disorders. - : Elsevier BV. - 0960-8966 .- 1873-2364. ; 17:1, s. 61-68
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Tidskriftsartikel (refereegranskat)abstract
- Myofibrillar remodelling with insertion of sarcomeres is a typical feature of biopsies taken from persons suffering of exercise-induced delayed onset muscle soreness. Here we studied the presence of the sarcomeric protein myotilin in eccentric exercise related lesions. Myotilin is a component of sarcomeric Z-discs and it binds several other Z-disc proteins, i.e. alpha-actinin, filamin C, F-actin and FATZ. Myotilin has previously been shown to be present in nemaline rods and central cores and to be mutated in limb girdle muscular dystrophy 1A (LGMD1A) and in a subset of myofibrillar myopathies, indicating an important role in Z-disc maintenance. Our findings on non-diseased muscle affected by eccentric exercise give new information on how myotilin is associated to myofibrillar components upon remodelling. We show that myotilin was present in increased amount in lesions related to Z-disc streaming and events leading to insertion of new sarcomeres in pre-existing myofibrils and can therefore be used as a marker for myofibrillar remodelling. Interestingly, myotilin is preferentially associated with F-actin rather than with the core Z-disc protein alpha-actinin during these events. This suggests that myotilin has a key role in the dynamic molecular events mediating myofibrillar assembly in normal and diseased skeletal muscle.
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| 2. |
- Carlsson, Lena, et al.
(författare)
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New aspects of obscurin in human striated muscles.
- 2008
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Ingår i: Histochemistry and Cell Biology. - : Springer Science and Business Media LLC. - 0948-6143 .- 1432-119X. ; 130:1, s. 91-103
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Tidskriftsartikel (refereegranskat)abstract
- Obscurin is a giant protein (700-800 kDa) present in both skeletal muscles and myocardium. According to animal studies, obscurin interacts with myofibrillar Z-discs during early muscle development, but is translocalised to be predominantly associated with the M-bands in mature muscles. The proposed function for obscurin is in the assembly and organisation of myosin into regular A-bands during formation of new sarcomeres. In the present study, the precise localisation of obscurin in developing and mature normal human striated muscle is presented for the first time. We show that obscurin surrounded myofibrils at the M-band level in both developing and mature human skeletal and heart muscles, which is partly at variance with that observed in animals. At maturity, obscurin also formed links between the peripheral myofibrils and the sarcolemma, and was a distinct component of the neuromuscular junctions. Obscurin should therefore be regarded as an additional component of the extrasarcomeric cytoskeleton. To test this function of obscurin, biopsies from subjects with exercise-induced delayed onset muscle soreness (DOMS) were examined. In these subjects, myofibrillar alterations related to sarcomerogenesis are observed. Our immunohistochemical analysis revealed that obscurin was never lacking in myofibrillar alterations, but was either preserved at the M-band level or diffusely spread over the sarcomeres. As myosin was absent in such areas but later reincorporated in the newly formed sarcomeres, our results support that obscurin also might play an important role in the formation and maintenance of A-bands.
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| 3. |
- Eriksson, Anders, et al.
(författare)
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Hypertrophic muscle fibers with fissures in power-lifters; fiber splitting or defect regeneration?
- 2006
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Ingår i: Histochemistry and Cell Biology. - : Springer Science and Business Media LLC. - 0948-6143 .- 1432-119X. ; 126:4, s. 409-417
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Tidskriftsartikel (refereegranskat)abstract
- Power-lifters have hypertrophic muscle fibers with fissures seen in cross-sections, called as fiber splitting.Whether this phenomenon is due to real splitting or defective regeneration has not been settled. To elucidate this matter,we have examined biopsies from the trapezius and vastus lateralis of power lifters (P group) and power lifters self-administrating anabolic steroids (PAS group). For this purpose, immunohistochemical staining of serial cross -sections was used. The PAS group had significantly more fibers with fissures than the P group in the vastus lateralis (1.2%+/-0.95% vs 0.35+/-0.34, P < 0.05) but not in the trapezius muscle (1.7% in both groups). Serial sections revealed that the fibers with fissures changed their profile profoundly over short distances. Some such fibers had a mature staining profile, whereas other fibers indicated recent degeneration and/or regeneration. Activation of satellite cells and formation of aberrant segments were also evident. We conclude that the so-called split fibers are due to defect regeneration. Some fibers with fissures are the results of old events of segmental muscle fiber damage, whereas the others reflect an ongoing process. The normal regenerative process is most likely disturbed in power-lifters by their continuous training with repeated high mechanical stress on the muscles.
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