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Myotube Cultures (myotube + culture)
Selected AbstractsEvidence against a sexual dimorphism in glucose and fatty acid metabolism in skeletal muscle cultures from age-matched men and post-menopausal womenACTA PHYSIOLOGICA, Issue 3 2009A. Rune Abstract Aim:,In vivo whole body differences in glucose/lipid metabolism exist between men and women. Thus, we tested the hypothesis that intrinsic sex differences exist in skeletal muscle gene expression and glucose/lipid metabolism using cultured myotubes. Methods:, Myotube cultures were prepared for gene expression and metabolic studies from vastus lateralis skeletal muscle biopsies obtained from age-matched men (n = 11; 59 ± 2 years) and post-menopausal women (n = 10; 60 ± 1 years). Results:, mRNA expression of several genes involved in glucose and lipid metabolism was higher in skeletal muscle biopsies from female vs. male donors, but unaltered between the sexes in cultured myotubes. Basal and insulin-stimulated glucose uptake, as well as glucose incorporation into glycogen, was similar in myotube cultures derived from male vs. female donors. In males vs. females, insulin increased glucose uptake (1.3 ± 0.1 vs. 1.5 ± 0.1-fold respectively) and incorporation into glycogen (2.3 ± 0.3 vs. 2.0 ± 0.3-fold respectively) to the same extent. Basal fatty acid oxidation and rate of uptake/accumulation was similar between sexes. In response to the 5,AMP-activated protein kinase activator AICAR, lipid oxidation was increased to the same extent in myotubes established from male vs. female donors (1.6 ± 0.6 vs. 2.0 ± 0.3-fold respectively). Moreover, the AICAR-induced rate of uptake/accumulation was similar between sexes. Conclusion:, Differences in metabolic parameters and gene expression profiles between age-matched men and post-menopausal women noted in vivo are not observed in cultured human skeletal muscle cells. Thus, the sexual dimorphism in glucose and lipid metabolism is likely a consequence of systemic whole body factors, rather than intrinsic differences in the skeletal muscle proper. [source] Phosphorylation of the nicotinic acetylcholine receptor in myotube-cholinergic neuron coculturesJOURNAL OF NEUROSCIENCE RESEARCH, Issue 8 2006Maria A. Lanuza Abstract Acetylcholine receptor (AChR) stability in the postsynaptic membrane is affected by serine kinases. AChR are phosphorylated by protein kinase C (PKC) and PKA, and we have shown that activation of PKA and PKC have opposite effects on AChR stability and that this may play some role in the selective, activity-dependent synapse loss that occurs during development of the neuromuscular junction. Myotube cultures with and without added spinal motor neurons were probed with immunoaffinity-purified antibodies prepared against phosphorylated peptides with amino acid sequences from different AChR subunits. Different treatments activating PKC (phorbol 12-myristate 13-acetate; PMA) or PKA (dibutyryl cyclic adenosine monophosphate; cAMP) or blocking electrical activity (tetrodotoxin; TTX) of the cocultures were chosen because of their known effects, direct or indirect, on receptor stability. We asked whether the phospho-specific antibody staining in conjunction with ,-bungarotoxin (BTX) identification of AChR aggregates could provide a direct demonstration of changes in receptor phosphorylation produced by the treatments. We found that PMA treatment did increase phosphorylation of the delta subunit and cAMP increased phosphorylation of the epsilon subunit relative to total BTX labeling in muscle-nerve cocultures, but not in muscle-only cultures. Blockade of electrical activity with TTX increased the incidence of aggregates that showed no phospho-epsilon staining. Myotube cultures grown in the absence of neurons did not show the responses of myotubes in cocultures. The results show that manipulations that alter receptor stability also produce changes in receptor phosphorylation. We suggest that phosphorylation may be a mechanism mediating the changes in receptor stability. © 2006 Wiley-Liss, Inc. [source] Expression of phospholipase C beta family isoenzymes in C2C12 myoblasts during terminal differentiation,JOURNAL OF CELLULAR PHYSIOLOGY, Issue 2 2004Irene Faenza In the present work, we have analyzed the expression and subcellular localization of all the members of inositide-specific phospholipase C (PLC,) family in muscle differentiation, given that nuclear PLC,1 has been shown to be related to the differentiative process. Cell cultures of C2C12 myoblasts were induced to differentiate towards the phenotype of myotubes, which are also indicated as differentiated C2C12 cells. By means of immunochemical and immunocytochemical analysis, the expression and subcellular localization of PLC,1, ,2, ,3, ,4 have been assessed. As further characterization, we investigated the localization of PLC, isoenzymes in C2C12 cells by fusing their cDNA to enhanced green fluorescent protein (GFP). In myoblast culture, PLC,4 was the most expressed isoform in the cytoplasm, whereas PLC,1 and ,3 exhibited a lesser expression in this cell compartment. In nuclei of differentiated myotube culture, PLC,1 isoform was expressed at the highest extent. A marked decrease of PLC,4 expression in the cytoplasm of differentiated C2C12 cells was detected as compared to myoblasts. No relevant differences were evidenced as regards the expression of PLC,3 at both cytoplasmatic and nuclear level, whilst PLC,2 expression was almost undetactable. Therefore, we propose that the different subcellular expression of these PLC isoforms, namely the increase of nuclear PLC,1 and the decrease of cytoplasmatic PLC,4, during the establishment of myotube differentiation, is related to a spatial-temporal signaling event, involved in myogenic differentiation. Once again the subcellular localization appears to be a key step for the diverse signaling activity of PLC,s. © 2004 Wiley-Liss, Inc. [source] Evidence against a sexual dimorphism in glucose and fatty acid metabolism in skeletal muscle cultures from age-matched men and post-menopausal womenACTA PHYSIOLOGICA, Issue 3 2009A. Rune Abstract Aim:,In vivo whole body differences in glucose/lipid metabolism exist between men and women. Thus, we tested the hypothesis that intrinsic sex differences exist in skeletal muscle gene expression and glucose/lipid metabolism using cultured myotubes. Methods:, Myotube cultures were prepared for gene expression and metabolic studies from vastus lateralis skeletal muscle biopsies obtained from age-matched men (n = 11; 59 ± 2 years) and post-menopausal women (n = 10; 60 ± 1 years). Results:, mRNA expression of several genes involved in glucose and lipid metabolism was higher in skeletal muscle biopsies from female vs. male donors, but unaltered between the sexes in cultured myotubes. Basal and insulin-stimulated glucose uptake, as well as glucose incorporation into glycogen, was similar in myotube cultures derived from male vs. female donors. In males vs. females, insulin increased glucose uptake (1.3 ± 0.1 vs. 1.5 ± 0.1-fold respectively) and incorporation into glycogen (2.3 ± 0.3 vs. 2.0 ± 0.3-fold respectively) to the same extent. Basal fatty acid oxidation and rate of uptake/accumulation was similar between sexes. In response to the 5,AMP-activated protein kinase activator AICAR, lipid oxidation was increased to the same extent in myotubes established from male vs. female donors (1.6 ± 0.6 vs. 2.0 ± 0.3-fold respectively). Moreover, the AICAR-induced rate of uptake/accumulation was similar between sexes. Conclusion:, Differences in metabolic parameters and gene expression profiles between age-matched men and post-menopausal women noted in vivo are not observed in cultured human skeletal muscle cells. Thus, the sexual dimorphism in glucose and lipid metabolism is likely a consequence of systemic whole body factors, rather than intrinsic differences in the skeletal muscle proper. [source] | ||||||||||