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Objective To evaluate the role of mitochondrial ATP-sensitive potassium (mito-KATP) channels in urocortin postconditioning-induced protection of rat cardiomyocytes.Methods Clean-grade healthy male Sprague-Dawley rats,aged 16-20 weeks,weighing 200-250 g,were used in this study.Cardiomyocytes of rats were isolated,cuhured and divided into 4 groups (n =28 each) using a random number table method:control group (group C),H/R group (group HR),urocortin postconditioning group (group U) and 5-hydroxydecanoate (5-HD,mito-KAw channel blocker) plus urocortin postconditioning group (group HU).In group C,the cells were continuously cultured for 150 min in an incubator filled with 95％ O2-5％ CO2 at 37 ℃.In group HR,the cells were exposed to 40-min hypoxia in an incubator filled with 95％ N2-5％ CO2 at 37 ℃,followed by 110-min reoxygenation.In group U,the cells were exposed to 40-min of hypoxia,followed by 10-min reoxygenation,and then cultured in a cuhure medium containing 10-8mmol/L urocortin for 30 min,followed by 70-min reoxygenation.In group HU,the cells were cultured for 10 min in a culture medium containing 10-4mmol/L 5-HD,and the other treatments were similar to those previously described in group U.At the end of reoxygenation,the opening of mitochondrial permeability transition pore (mPTP) and mitochondrial membrane potential (MMP) were measured by fluorescence spectrophotometry.The expression of Bax and Bcl-2 was determined by Western blot,and the cell viability was measured by CCK-8 assay.Results Compared with group C,the viability of cardiomyocytes and MMP were significantly decreased,the opening of mPTP was increased,the expression of Bcl-2 was down-regulated,and the expression of Bax was up-regulated in the other 3 groups (P＜0.05).Compared with group HR,the viability of cardiomyocytes and MMP were significantly increased,the opening of mPTP was decreased,the expression of Bcl-2 was up-regulated,and the expression of Bax was down-regulated in group U,and the opening of mPTP was decreased (P ＜ 0.05),and no significant change was found in the other parameters in group HU (P＞0.05).Compared with group U,the viability of cardiomyocytes and MMP were significantly decreased,the opening of mPTP was increased,the expression of Bcl-2 was down-regulated,and the expression of Bax was up-regulated in group HU (P＜0.05).Conclusion The mechanism by which urocortin postconditioning attenuates H/R-induced damage to rat cardiomyocytes is associated with promoting mito-KATP channel opening and inhibiting mPTP opening.
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Objective To investigate the effect of Urocortin I pretreatment on heart function and ATP in rat heart during myocardial ischemia-reperfusion injury. Methods Part I. 48 SD rats were randomly divided into four groups(n=12):normal group(group N1),ischemia-reperfusion group(group IR),urocortin I pretreatment group (group U1),and 5-HD+urocortin I group (group HU1). Group N1 received continuous perfusion for 155 min ,group IR experienced 40 min ischemia and 60 min reperfusion ,group U1 received urocortin I for 30 min before ischemia,and group HU1 received 5-HD for 5 min before urocortin I pretreatment. Changes of heart rate (HR),left ventricular end-diastolic pressure(LVEDP),left ventricular developed pressure(LVDP),maximum dp/dt(dp/dtmax)and microstructure of myocardium were evaluated. Part Ⅱ. The isolated and cultivated myocytes were randomly divided into four groups:group N2,HR,U2 and HU2. Group N2 was cultured continuously for 155 min,while other groups experienced 40 min-anoxia and 60 min reoxygenation. Urocortin I was added to group U2 for 30 min before anoxia. 5-HD was added to group HU2 before adding urocortin I. The content of ATP at the end of reoxygenation was detected. Results Urocortin I pretreatment restrained the decline in HR,LVDP,and dp/dt and the rise in LVEDP during ischemia-reperfusion injury. Furthermore ,the content of ATP was preserved and the microstructure of myocardium was sustained during anoxia/reperfusion. Conclusions Urocortin I pretreatment can not only enhance cardiac contractility of the isolated heart ,but also preserve the content of ATP through the opening of mitoKATP channel,thus maintaining the microstructures of myocytes and improving heart function after ischemia-reperfusion injury.
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Objective To investigate the effect of Urocortin I pretreatment on heart function and ATP in rat heart during myocardial ischemia-reperfusion injury. Methods Part I. 48 SD rats were randomly divided into four groups(n=12):normal group(group N1),ischemia-reperfusion group(group IR),urocortin I pretreatment group (group U1),and 5-HD+urocortin I group (group HU1). Group N1 received continuous perfusion for 155 min ,group IR experienced 40 min ischemia and 60 min reperfusion ,group U1 received urocortin I for 30 min before ischemia,and group HU1 received 5-HD for 5 min before urocortin I pretreatment. Changes of heart rate (HR),left ventricular end-diastolic pressure(LVEDP),left ventricular developed pressure(LVDP),maximum dp/dt(dp/dtmax)and microstructure of myocardium were evaluated. Part Ⅱ. The isolated and cultivated myocytes were randomly divided into four groups:group N2,HR,U2 and HU2. Group N2 was cultured continuously for 155 min,while other groups experienced 40 min-anoxia and 60 min reoxygenation. Urocortin I was added to group U2 for 30 min before anoxia. 5-HD was added to group HU2 before adding urocortin I. The content of ATP at the end of reoxygenation was detected. Results Urocortin I pretreatment restrained the decline in HR,LVDP,and dp/dt and the rise in LVEDP during ischemia-reperfusion injury. Furthermore ,the content of ATP was preserved and the microstructure of myocardium was sustained during anoxia/reperfusion. Conclusions Urocortin I pretreatment can not only enhance cardiac contractility of the isolated heart ,but also preserve the content of ATP through the opening of mitoKATP channel,thus maintaining the microstructures of myocytes and improving heart function after ischemia-reperfusion injury.
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Objective To investigate the effect of hypoxic postconditioning and diazoxide postconditioning on the calreticulin expression during hypoxia/reoxygenation (H/R) in rat cardiomyocytes. Methods Primary cultured male SD rat cardiomyocytes were randomly divided into 6 groups (n = 8 each): control group (group C),H/R group; hypoxic postconditioning group (group HP) and diazoxide postconditioning group (group DP). Group C were cultured continuously for 2 h. Group H/R, Hp and DP were exposed to 45 min hypoxia (95% N2-5% CO2)followed by 1 h reoxygenation. In group HP, the cells were subjected to three cycles of 3 min hypoxia at 3 min intervals at the end of 45 min hypoxia before 1 h reoxygenation. In group DP, diazoxide 50 μmol/L was giyen at the end of hypoxia. Caspase-3 activity, calreticulin expression and intracellular free calcium ion concentrations were determined. Results Compared with group C, caspase-3 activity was significantly increased in the other groups,the calreticulin expression was up-regulated in group HP and DP, and the free calcium ion concentrations were increased in group H/R (P ＜ 0.05 or 0.01). Compared with group H/R, caspase-3 activity was significantly decreased in HP and DP, the calreticulin expression was up-regulated and the free calcium ion concentrations were decreased in group HP and DP (P ＜ 0.01). Conclusion Hypoxic postconditioning and diazoxide postconditioning attenuate H/R injury in rat cardiomyocytes through up-regulating the expression of calreticulin and reducing intracellular calcium overload.
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Objective To investigate the effect of hydrogen sulfide postconditioning on the systolic function of left ventricle during myocardial ischemia-reperfusion (IR) in rats. Methods Part Ⅰ Adult male SD rats weighing 200-250 g were anesthetized with pentobarbital 40 mg/kg and heparin 250 U/kg. Their hearts were excised and perfused in a Langendorff apparatus with K-H solution saturated with 95% O2-5% CO2 at 37 ℃. Forty isolated rat hearts were randomly divided into 5 groups ( n = 8 each) after 20 min of equilibration: control group (group C); IR group; sodium hydrosulfide 1,10, 100 μmol/L postconditioning group (group SP1, SP10, SP100 ).In group Cthe hearts were perfused continuously for another 100 min. In group IR, the hearts were reperfused for 60 min after 40 min ischemia induced by 10 ml/kg ST. Thomas solution. In group SP1 , SP10 and SP100 the hearts were perfused with K-H solution containing sodium hydrosulfide 1, 10, 100 μmol/L for 2 min before reperfusion.LVDP and ± dp/dtmax were recorded at the end of equilibration and reperfusion. Part Ⅱ Cardiomyocytes were isolated from the male SD rats (weighing 200-250 g) and then cultured in CO2 incubator for 4 h. Sixty-four dishes of cultured myocytes were randomly divided into 4 groups( n = 16 each): control group (group C), hypoxia/reoxygenation group (group HR), hydrogen sulfide postconditioning group (group SP) and hypoxia postconditioning group (group HP). Group C were cultured continuously for 2 h. Group HR, SP and HP were exposed to 1 h hypoxia (95%N2-5%CO2 ) followed by 1 h reoxygenation. In group SP 10 μmol/L sodium hydrosulfide was added and the myocytes were then incubated for 2 min before reoxygenation. In group HP the cultured myocytes were expased to 3 min reoxygenation followed by 3 min hypoxia for 3 times before the 1 h reoxygenation. Mitochondrial membrane potential and F-actin expression were determined. Results Part Ⅰ Compared with group C, LVDP and ± dp/dtmax were significantly decreased at the end of reperfusion in group IR (P ＜ 0.05), while no significant difference was found in group SP1 , SP10 and SP100(P ＞0.05). Compared with group IR, LVDP and ± dp/dtmax were significantly increased in group SP ( P ＜ 0.05). There was no significant difference in LVDP and ± dp/dtmax among group SP1, SP10 and SP100(P ＞0.05). Part H Compared with group C, the mitochondrial membrane potential was significantly decreased in group HR and HP, and the expression of F-actin was significantly up-regulated in group HR, SP and HP ( P ＜ 0.05). Compared with group HR, the mitochondrial membrane potential was significantly increased and the expression of F-actin up-regulated in group SP and HP ( P ＜ 0.05 ). There were no significant difference in the mitochondrial membrane potential and expression of F-actin between group SP and HP ( P ＞0.05).Conclusion Hydrogen sulfide postconditioning can improve left ventricular systolic function during IR in rats by stabilizing mitochondrial membrane potential and promoting aggregation of F-actin.
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To intensify the medical students' clinical skills training is the main objective of medical education,and it can promote the reform of clinical teaching.In the whole process of clinical practice,we have adopted means of teaching before receiving clinical practical training,estimating indexes of examine,making use of diversified clinical skill training,supervising clinical practical quality.The operation ability of medical students has greatly increased.
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Objective To investigate the effect of ischemic preconditioning ( IP) on the content of myocardial mitochondria cardiolipin and the heart function in isolated rat hearts. Methods Seventy-two healthy SD rats of both sexes ( 36 males,36 females) weighing 200 to 300 g were randomly divided into 4 groups ( n =18 for each group) : normal group,control group,IP group ( IP) and 5-hydroxydecanoate ( 5-HD) plus IP group ( HD) . Langendorff apparatus were used to establish the model of ischemia/reperfusion in isolated rat hearts. The hearts were perfused for 20 min to get stabilization followed by continuous perfusion in normal group for 100 min. In control group,after perfusing of 20 min for stabilization followed by continuous perfusion for 30 min,the hearts were then reperfused for 30 min after 40 min ischemia. In IP group,the hearts were given a 5-minute ischemia and 5-minute reperfusion for twice in order within a brief intermittent period,and ischemia reperfusion was carried out in the same way as that in control group. In HD group,the hearts were perfused with 100 ?mol/L 5-HD before IP,and the following procedures were carried out as those in IP group. HR,left ventricular end-diastolic pressure ( LVEDP) ,left ventricular developed pressure ( LVDP) were recorded at the end of stable perfusion ( T1) ,immediately before ischemia ( T2) and at the end of reperfusion ( T3) in all the groups. The content of myocardial mitochondria cardiolipin was measured with HPLC. Results When theparameters at T3 were compared with those at T1 and T2,HR and LVDP were decreased,LVEDP was increased and the content of myocardial mitochondria cardiolipin was decreased. All these changes were significant ( P
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Objective Structured Clinical Examination(OSCE) is a model of clinical skills examination.We have applied OSCE in the graduate examination of medical colleges for three years.There are different requests for training teachers and Standardized Patients(SP),setting exam place,examiners and students and so on.OSCE is worth spreading as clinical ability examination in other medical education.