ORCID Profile
0000-0002-6985-099X
Current Organisation
Karolinska Institutet
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Publisher: Wiley
Date: 22-12-2005
DOI: 10.1111/J.1748-1716.2005.01499.X
Abstract: This study determined whether fatigue in skeletal muscle is primarily due to the repeated elevations of myoplasmic free calcium concentration ([Ca(2+)](i)) or to metabolite accumulation. We examined the effects of N-benzyl-p-toluene sulphonamide (BTS) which is a potent and specific inhibitor of fast muscle myosin-II on the development of fatigue in mouse flexor digitorum brevis (FDB) muscle fibres. Single intact FDB fibres were micro-injected with indo-1 to monitor changes in [Ca(2+)](i) and stimulated repeatedly for a maximum of 150 tetani or until force declined to 40%. BTS markedly reduced tetanic force but had no effect on the tetanic [Ca(2+)](i) transients. When fatigue was induced in the presence of BTS, the reduction in [Ca(2+)](i) and force transients occurred much more slowly than in the absence of BTS. The extent of force depression was similar after induction of fatigue in fibres exposed to Tyrode only or to BTS and force recovered to the same extent. The results suggest that the decrease in tetanic [Ca(2+)](i) and force caused during fatigue are due mainly to accumulated metabolic changes.
Publisher: Wiley
Date: 19-10-2012
Publisher: Elsevier BV
Date: 12-2022
Publisher: Cold Spring Harbor Laboratory
Date: 30-03-2021
DOI: 10.1101/2021.03.29.437546
Abstract: Cells rapidly lose their physiological phenotype upon disruption of their extracellular matrix (ECM)-intracellular cytoskeleton interactions. Here, we investigated acute effects of ECM disruption on cellular and mitochondrial morphology, transcriptomic signatures, and Ca 2+ handling in adult mouse skeletal muscle fibers. Adult skeletal muscle fibers were isolated from mouse toe muscle either by collagenase-induced dissociation of the ECM or by mechanical dissection that leaves the contiguous ECM intact. Experiments were generally performed four hours after cell isolation. At this time, there were striking differences in the gene expression patterns between fibers isolated with the two methods 24h after cell isolation, enzymatically dissociated fibers had transcriptomic signatures resembling dystrophic phenotypes. Mitochondrial appearance was grossly similar in the two groups, but 3D electron microscopy revealed shorter and less branched mitochondria in enzymatically dissociated than in mechanically dissected fibers. Similar increases in free cytosolic [Ca 2+ ] during repeated tetanic stimulation were accompanied by marked mitochondrial Ca 2+ uptake only in enzymatically dissociated muscle fibers. The aberrant mitochondrial Ca 2+ uptake was partially prevented by the mitochondrial Ca 2+ uniporter inhibitor Ru360 and by cyclosporine A and NV556, which inhibit the mitochondrial protein Ppif (also called cyclophilin D). Importantly, inhibition of Ppif with NV556 significantly improved survival of mice with mitochondrial myopathy in which muscle mitochondria take up excessive amounts of Ca 2+ even with an intact ECM. In conclusion, skeletal muscle fibers isolated by collagenase-induced dissociation of the ECM display aberrant mitochondrial Ca 2+ uptake, which involves a Ppif-dependent mitochondrial Ca 2+ influx resembling that observed in mitochondrial myopathies.
Publisher: Springer Science and Business Media LLC
Date: 04-2005
DOI: 10.1007/S10974-005-2679-2
Abstract: We have examined the effects of N-benzyl-p-toluene sulphonamide (BTS), a potent and specific inhibitor of fast muscle myosin-II, using small bundles of intact fibres or single fibres from rat foot muscle. BTS decreased tetanic tension reversibly in a concentration-dependent manner with half-maximal inhibition at approximately approximately 2 microM at 20 degrees C. The inhibition of tension with 10 microM BTS was marked at the three temperatures examined (10, 20 and 30 degrees C), but greatest at 10 degrees C. BTS decreased active muscle stiffness to a lesser extent than tetanic tension indicating that not all of the tension inhibition was due to a reduced number of attached cross-bridges. BTS-induced inhibition of active tension was not accompanied by any change in the free myoplasmic Ca2+ transients. The potency and specificity of BTS make it a very suitable myosin inhibitor for intact mammalian fast muscle and should be a useful tool for the examination of outstanding questions in muscle contraction.
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