In myoblasts, activity of this pathway is transiently increased, indicating that exposure time is a determinant of the effects of insulin and IGFs. Insulin and IGF-1 activate the phosphatidylinositol 3-Kinase (PI3K)–Akt–mammalian target of rapamycin (mTOR) pathway. A major reason for this is that the effects of insulin and insulin-like factors depend strongly on several other factors. The mechanisms by which insulin and IGFs stimulate the synthesis and inhibit the degradation of muscle proteins are subject of controversy (cf. Of these, insulin and insulin-like growth factors (IGFs) are key regulators of muscle protein synthesis and degradation. Many genes and physiological stimuli are involved in the regulation of adaptation of muscle size. Prevention of muscle atrophy and induction hypertrophy requires insight in the mechanisms regulating protein synthesis and breakdown. chronic heart failure, chronic obstructive pulmonary disease, cancer and HIV) are characterised by severe muscle wasting causing limited mobility of millions of patients. Furthermore, albumin is important in regulating muscle fibre adaptation by a synergistic action with growth factors like insulin.Ĭhronic catabolic conditions (e.g. We conclude that albumin prevents muscle fibre damage and preserves E–C coupling in culture. #How to use glycerin albumen histology series#P = 0.007) after 16.3 ± 1.7 days, whereas the number of sarcomeres in series remained unchanged. In contrast, muscle fibres cultured with both albumin and insulin showed an increase in tetanic force and fibre cross-sectional area of 19.6 ± 2.8% and 32.5 ± 4.9%, respectively, (means ± SEM. Muscle fibres cultured in medium with insulin or albumin exclusively did not hypertrophy or change the number of sarcomeres in series. In the presence of albumin, all cultured muscle fibres were stable for at least 10 days. Caffeine contractures of in-excitable muscle fibres produced 80.4 ± 2.4% of initial peak tetanic force, indicating impaired excitation–contraction (E–C) coupling in in-excitable fibres. In culture medium with insulin, 50% of the muscle fibres became in-excitable within 7–12 days, whereas the other 50% were stable. The medium was supplemented with (final concentrations): (1) bovine insulin (6 nmol/L or 200–600 nmol/L), (2) 0.2% bovine albumin or (3) 0.2% bovine albumin in combination with insulin (120 nmol/L). Fibres were cultured in a serum-free medium at slack length (mean sarcomere length 2.3 μm) for 8 to 22 days. iliofibularis of Xenopus laevis and attached to a force transducer in a culture chamber. Single muscle fibres were dissected from m. The aim of this study was to investigate effects of albumin and insulin separately as well as in combination on mature muscle fibres during long-term culture.
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