Ceramides stimulate mitochondrial fission and this event is associated with early activation of cardiomyocyte apoptosis.

Skeletal muscle is one of the main physiological targets of insulin, a hormone that triggers a complex signaling cascade and that enhances the production of reactive oxygen species (ROS) in different cell types. ROS, currently considered second messengers, produce redox modifications in proteins such as ion channels that induce changes in their functional properties. In myotubes, insulin also enhances calcium release from intracellular stores. In this work, we studied in myotubes whether insulin stimulated ROS production and investigated the mechanisms underlying the insulin-dependent calcium increase: in particular, whether the late phase of the Ca 2؉ increase induced by insulin required ROS. We found that insulin stimulated ROS production, as detected with the probe 2, 7-dichlorofluorescein diacetate (CM-H 2 DCFDA). We used the translocation of p47 phox from the cytoplasm to the plasma membrane as a marker of the activation of NADPH oxidase. Insulin-stimulated ROS generation was suppressed by the NADPH oxidase inhibitor apocynin and by small interfering RNA against p47 phox , a regulatory NADPH oxidase subunit. Additionally, both protein kinase C and phosphatidylinositol 3-kinase are presumably involved in insulin-induced ROS generation because bisindolylmaleimide, a nonspecific protein kinase C inhibitor, and LY290042, an inhibitor of phosphatidylinositol 3-kinase, inhibited this increase. Bisindolylmaleimide, LY290042, apocynin, small interfering RNA against p47 phox , and two drugs that interfere with inositol 1,4,5-trisphosphate-mediated Ca 2؉ release, xestospongin C and U73122, inhibited the intracellular Ca 2؉ increase produced by insulin. These combined results strongly suggest that insulin induces ROS generation trough NADPH activation and that this ROS increase is required for the intracellular Ca 2؉ rise mediated by inositol 1,4,5-trisphosphate receptors.A transient intracellular Ca 2ϩ increase is a key component of the excitation-coupling mechanism in skeletal muscle cells. Intracellular Ca 2ϩ can also increase in response to stimuli other than membrane potential depolarization, including hormones such as insulin. We have previously reported that in myotubes, the addition of insulin produces a fast intracellular Ca 2ϩ concentration transient, which requires external Ca 2ϩ and is inhibited by the L-type Ca 2ϩ channel blocker nifedipine and by ryanodine (1). Other reports show that the Ca 2ϩ increase evoked by insulin in skeletal muscle fibers depends on Ca 2ϩ influx and is related to Glut-4 translocation (2). As steep changes in insulin concentration are unlikely to occur physiologically, we decided to explore changes in intracellular Ca 2ϩ after longer exposure to insulin. We further investigated whether ROS 3 play a role in this process. It is known that ROS modulate the activity of Ca 2ϩ release channels (3), and in particular, the activity of skeletal muscle ryanodine receptors is regulated by NADPH oxidase-dependent redox modifications (4). On the other hand, in target tissues, insulin is known ...

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In this work we examined MoS2 sheets by aberration-corrected scanning transmission electron microscopy (STEM) at three different energies: 80, 120 and 200 kV. Structural damage of the MoS2 sheets has been controlled at 80 kV according a theoretical calculation based on the inelastic scattering of the electrons involved in the interaction electron-matter. The threshold energy for the MoS2 material has been found and experimentally verified in the microscope. At energies higher than the energy threshold we show surface and edge defects produced by the electron beam irradiation. Quantitative analysis at atomic level in the images obtained at 80 kV has been performed using the experimental images and via STEM simulations using SICSTEM software to determine the exact number of MoS2 layers.