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- Degens, H, et al.
(författare)
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Post-operative effects on insulin resistance and specific tension of single human skeletal muscle fibres
- 1999
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Ingår i: Clinical science (London, England : 1979). - : Portland Press Ltd.. - 0143-5221 .- 1470-8736. ; 97:4, s. 449-455
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Tidskriftsartikel (refereegranskat)abstract
- Surgery and accidental trauma are associated with a transient period of insulin resistance, substrate catabolism and muscle weakness. In the present study, we evaluated the changes in the force-generating capacity of chemically skinned single muscle fibres following abdominal surgery. Biopsies of the m. vastus lateralis were obtained in three patients 1 day before and 3 or 6 days after surgery. Part of the biopsy was frozen for histochemical analysis of the fibre cross-sectional area (FCSA) and myofibrillar protein content, and another part was used for single-fibre contractile measurements. All patients developed insulin resistance following surgery. The maximum velocity of unloaded shortening of single muscle fibres did not change following surgery. The FCSA did not decrease after surgery, as determined either from histochemical sections or from single fibres measured at a fixed sarcomere length of 2.76±0.09 μm (mean±S.D.). Further, the force-generating capacity of the single fibres, measured as maximal Ca2+-activated force (P0) or as P0 normalized to FCSA (specific tension), remained unchanged, as did the myofibrillar protein content of the muscle. In conclusion, the muscle weakness associated with post-operative insulin resistance is not related to a decreased specific tension or a loss of myofibrillar proteins. Other potential cellular mechanisms underlying post-operative weakness are discussed.
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- Prasthofer, T, et al.
(författare)
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Protein kinase C phosphorylates two of the four known syndecan cytoplasmic domains in vitro
- 1995
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Ingår i: Biochemistry and Molecular Biology International. - 1039-9712. ; 36:4, s. 793-802
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Tidskriftsartikel (refereegranskat)abstract
- The transmembrane heparan sulfate proteoglycans of the syndecan family are implicated to participate in several cellular reactions which are dependent on protein kinase C. We have used an in vitro assay to assess whether any of the Peptides corresponding to the complete cytoplasmic domains of rat syndecans 1 through 4 were used as substrates for the enzyme. The syndecan-2 (fibroglycan) and syndecan-3 (N-syndecan) peptides were both found to be phosphorylated by protein kinase C with Kms of 15 +/- 3 microM and 85 +/- 25 microM, respectively, while the syndecan-1 and -4 peptides were not phosphorylated under the conditions used. The sites of in vitro phosphorylation for syndecans-2 and -3 were localized to ser-197 and ser-339, respectively. Thus, among 13 available sites (serines and threonines) in the four peptides, two were selectively modified by the enzyme. The specificity and the kinetics of the reactions indicate that the cytoplasmic domains of syndecan-2 and -3 are likely to be physiological substrates for protein kinase C.
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