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Ryanodine receptors (RyRs) are tetrameric Ca2+ release channels of sarcoplasmic reticulum (SR). This review attempts to detail the key mechanism of RyR channel gating and to discuss the hypothesis that skeletal muscle fatigue, defined as reduced force production, would result from functional changes in both individual RyR channel opening and coupling among RyR channels. Previous studies have shown that RyR channels in skeletal muscle open simultaneously, called coupled gating, because of physical interaction among channels. In this review, mechanisms underlying muscle fatigue are discussed with consideration of the coupling effect. Fatigue mechanisms are thought to be different between acute exercise and long-term exercise training. The impairments in individual channel opening and coupling between RyR channels can occur after acute exercise, leading to decreased SR Ca2+ release and force depression. On the contrary, during long-term exercise training, individual channel opening would be enhanced but coupling between channels would be impaired. If this were to continue for long periods, SR Ca2+ content would reduce, leading to less Ca2+ release and lower force production.
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Objective To investigate the cytopathic effect of amino acid residues 86 to 175 of rotavirus nonstructural protein 4 (NSP486-175) on rat neurons and to analyze the underlying mechanism.MethodsPrimary cultured rat neurons were treated with NSP486-175 and the morphological changes induced in rat neurons were observed.Lactate dehydrogenase (LDH) activity in the culture supernatant of NSP486-175 treated-neurons was measured.Laser scanning confocal microscope was used to detect the concentration of intracellular Ca2+ labeled with Fluo-3 AM.Results Exogenous addition of NSP486-175 induced obvious cytopathic effect on rat neurons.The LDH activity in the culture supernatant of treated-neurons was stronger than that of the control group.The intensity and the distribution of fluorescence in neurons were altered after stimulation with NSP486-175.Conclusion NSP486-175 can induce the damage of rat neurons, which may be related to its role in increasing the concentration of intracellular Ca2+.This study may provide certain theoretical basis for understanding extra-intestinal spread and pathogenesis of rotavirus infection.
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AIM:To observe the effects of hawthorn leaf polymeric procyanidins ( PPC) on calcium mobiliza-tion of vascular endothelial cells , and to study the underlying mechanism .METHODS: Free calcium in cultured human umbilical vein endothelial cells (HUVECs) was labeled with Fura-2.HUVECs were treated with ATP, a positive control drug, and PPC at concentrations of 12.5, 25 and 50 mg/L..The intracellular calcium concentrations were measured with a living cell microscope for 30 min.RESULTS:PPC concentration-dependently increased the intracellular calcium concen-tration of HUVECs .The intracellular calcium concentrations in 25 and 50 mg/L PPC groups were significantly higher than that in normal group (P<0.01).The dynamic manner of calcium concentration elevations elicited by PPC was a slow in -crease which happened after a latency time of several minutes , lasted for several minutes , and reached a plateau finally . This manner was quite different from that elicited by ATP , a typical SOC operator , hinting different mechanisms between them .Inhibiting the intracellular calcium release did not influence the effects of PPC;however , deleting extracellular calci-um, inhibiting the reverse mode of Na +-Ca2+exchange, or deleting extracellular sodium , restrained or even abolished the effects of PPC.CONCLUSION:PPC elicits calcium mobilization in vascular endothelial cells , which may be one of the mechanisms of the vascular modulatory activity of hawthorn procyanidins .This effect may be achieved through inducing the influx of sodium and then activating the reverse mode of Na +-Ca2+exchange.
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AIM:To observe the influence of erythropoietin (EPO) on eryptosis and production of reactive oxygen species (ROS) in erythrocytes under stimulation of hydrogen peroxide (H2O2),.and to explore its related mecha-nism. METHODS:The erythrocyte suspension (1%) was cultured in vitro and divided into 3 groups:control group (C group,the culture medium was PBS),H2O2group (H group,the culture medium was PBS containing H2O2at final con-centration of 100 μmol/L) and EPO group (E group,the culture medium was PBS containing H2O2at final concentration of 100 μmol/L and EPO at final concentration of 2×104U/L). The erythrocytes were collected at 24 h and 60 h. The eryptosis was detected by flow cytometry with Annexin V staining. The production of ROS and intracellular calcium ion con-centration (Ca2+]i) were also analyzed by flow cytometry. RESULTS:The eryptosis in C group was increased as the in-cubating time extended. The eryptosis in H group was higher than that in C group (P<0.01),while that in E group was lower than that in H group(P<0.01). Meanwhile,ROS production andCa2+]iwere higher in H group than those in C group (P<0.01), but those were lower in E group than those in H group (P<0.05 or P<0.01). CONCLUSION:EPO inhibits eryptosis induced by H2O2and its mechanism may be related to antioxidant effect and change of Ca2+]i.
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AIM: To observe the effect of ginkgolide B (CB) on the intracellular calcium ion concentration ( [ Ca~(2+) ]_i) and mitochondrial function of cultured rat retinal neurons in vitro. METHODS: in vitro primary culture of rat retinal neurons was used in the experiment. The apoptosis model of glutamate - induced retinal neurons was established and co - cultured with ginkgolide B. The [ Ca~(2+) ]_i and mitochondrial membrane potential of the retinal neurons were detected by laser scanning confocal microscope. RESULTS: Glutamate decreased the survival rate of retinal neurons, increased the apoptosis and the [ Ca~(2+) ]_i, lowered the mitochondrial membrane potential. The [ Ca~(2+) ]_i was clearly diminished and the mitochondrial membrane potential was significantly increased with the GB intervention, and the apoptosis decreased significantly. CONCLUSION: GB protects retinal neurons from glutamate induced neurotoxicity. The effect of GB on retinal neurons might be due to its ability to decrease the [Ca~(2+) ]_i and increase mitochondrial membrane potential.
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Objective:To observe the proliferation and the free intracellular calcium ion concentration of osteoblast under the effect of static magnetic field and discuss the possible mechanism of the static magnetic field on promoted the proliferative function. Methods: The MTT assay was used to measure the rate of the proliferation on different magnetic field intensity(0, 0.026, 0.044, 0.090 T)and action time(24, 48, 72 h).The fluorescence double wavelength spectrophotometer was used to measure the concentration of intracellular calcium ion. The data obtained were analyzed for ANOVA and t-test using SPSS 11.0 software package. Results: Osteoblasts in group 0.044 T appeared significant proliferation within 48 h(P
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AIM:To observe the effect of ginkgolide B (GB) on the intracellular calcium ion concentration ([Ca2+]i) and mitochondrial function of cultured rat retinal neurons in vitro.METHODS:in vitro primary culture of rat retinal neurons was used in the experiment. The apoptosis model of glutamate-induced retinal neurons was established and co-cultured with ginkgolide B. The [Ca2+]i and mitochondrial membrane potential of the retinal neurons were detected by laser scanning confocal microscope.RESULTS:Glutamate decreased the survival rate of retinal neurons,increased the apoptosis and the [Ca2+]i,lowered the mitochondrial membrane potential. The [Ca2+]i was clearly diminished and the mitochondrial membrane potential was significantly increased with the GB intervention,and the apoptosis decreased significantly.CONCLUSION:GB protects retinal neurons from glutamate induced neurotoxicity. The effect of GB on retinal neurons might be due to its ability to decrease the [Ca2+]i and increase mitochondrial membrane potential.