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Objective To investigate whether microtubule disassembly plays an important role in the pathogenesis of the opening of mitochondria permeability transition pore (MPTP) in hypoxic cardiomyocytes and the decrease of its activity, resulting in its hypoxic injury. Methods Neonatal rat cardiomyocytes in primary culture were randomized as normoxia group (A), hypoxic group (B), normoxia treated with microtubule destabilizing agent (Colchicine) group (C), hypoxia treated with microtubule stabilizing agent (Taxol) group (D). At 0.5, 1, 3, 6, 12 h after treatment, polymeric tubulin was detected by immunofluorescence and Western blotting, mitochondria permeability transition pore (MPTP) open by coloading with calcein AM and cobalt chloride, and the activity of cells by measuring the mitochondrial-dependent reduction of MTT to formazan. Results Early microtubule disassembly, MPTP open and activity decrease of cardiomyocytes in both groups B and C were observed at 0.5 h after treatment. These phenomena all became more and more significant with the prolongation of treatment. However, microtubule disassembly, MPTP open and activity decrease of cardiomyocytes of group D were significantly lower than those of group B. Conclusion Microtubule disassembly happened at 0.5 h after hypoxic treatment. Microtubule stabling agent Taxol and destabilizing agent Colchicine can regulate microtubule integrity efficiently. The microtubule damage plays an important role in the hypoxic injury of cardiomyocytes.
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AIM: To study the role of mitochondrial nitric oxide synthase (mtNOS) in the damages of myocardial mitochondria during the early stage after severe burns.METHODS: An experimental model of 30% TBSA full-thickness skin scalding was reproduced in rats. Myocardial mitochondria were isolated from control and burned rats at 1, 3, 6, 12 and 24 h postburn. The mitochondrial respiratory function, content of mitochondrial calcium([Ca 2+ ] m) and activities of mtNOS and cytochrome c oxidase were determined. RESULTS: (1) Myocardial mitochondrial respiratory control rate(RCR) at 1 h was evidently higher than that of control, but at 3, 6, 12 and 24 h postburn, it was significantly lower than that of the control. The changes in ST 3 is parallel to those of RCR, and ST 4 was evidently increased only at 3 h postburn. (2) [Ca 2+ ] m was higher at all time points postburn and the activity of mtNOS was higher significantly only at 3, 6, 12 and 24 h than that of the control. The activity of cytochrome c oxidase at the 3, 6, 12 and 24 h was low comparing to the control. (3) After severe burns, RCR was negatively correlated with mtNOS activity( r=0.9347, P
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AIM:To investigate the change in myocardial mitochondrial Ca 2+ concentration ([Ca 2+ ] m) and its mechanism in the early stage of severe burn. METHODS:An experimental model of 30%TBSA full-thickness skin scalding was reproduced in rats. [Ca 2+ ] m, cytosolic Ca 2+ concentration ([Ca 2+ ] c) and mitochondrial Ca 2+ transport velocity were determined. RESULTS: ① [Ca 2+ ] m increased evidently at 1st hour postburn, and continuously at 3rd hour, reached the peak at 6th hour postburn, then, it decreased at 12th and 24th hour, but remained in higher level than that of the control. ② There was no significant difference in [Ca 2+ ] c between 1st hour postburn and the control, but [Ca 2+ ] c increased evidently at 3rd, 6th, 12th, 24th hour postburn. ③ mitochondrial Ca 2+ uptake velocity at 1st hour postburn was higher than that of control, and Ca 2+ release velocity didn't change obviously, but both of them were decreased at 3rd, 6th, 12th, 24th hour postburn. ④ [Ca 2+ ] m was positive correlated with [Ca 2+ ] c after burn, and negative correlated with mitochondrial Ca 2+ release velocity at 3rd, 6th, 12th, 24th hour postburn, respectively. CONCLUSION: There was obvious Ca 2+ overload in myocardial mitochondria after severe burn, the mechanism of which might include ascent of [Ca 2+ ] c and disorder of Ca 2+ transport in mitochondria. [
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To elucidate apoptosis of polymorphonuclear leukocytes (PMN) in early postburn stage and the effects of burn sera and subeschar tissue fluid (STF) on apoptosis of PMNs, 24 Wistar rats were divided into scald group and control group (no scald group) randomly. PMNs were harvested at 0, 12, 24h after scald injury,and percentage of apoptotic PMNs was measured by flow cytometry.Apoptosis of PMNs was again assayed with flow cytometer after being incubated with burn sera or STF harvested from scalded rats. The result showed that the percentage of apoptotic PMNs in scalded group were lower than that in control group,indicating burn sera and STF could inhibit apoptosis of PMNs in a dose dependent manner. It suggested that spontaneous apoptosis of PMNs is inhibited in early postburn stage, and burn sera and STF play an important role in this process.