Aim： To observe effects of angiotensin （Ang） II receptor antagonist （ATI） irbesartan and angiotensin-converting enzyme （ACE） inhibitor perindopril on rat myocardium calcineurin expression and sarcoplasmic retic...Aim： To observe effects of angiotensin （Ang） II receptor antagonist （ATI） irbesartan and angiotensin-converting enzyme （ACE） inhibitor perindopril on rat myocardium calcineurin expression and sarcoplasmic reticulum Ca^2＋-ATPase activity in the model of pressure-overload cardiac hypertrophy. Methods： Forty male adult Sprague Dawley rats were divided into 5 groups One group was treated by sham operation; four groups were myocardium hypertrophy cases caused by banding aortic above renal artery. Drugs were given one week after operation. Group 1： sham group, rats （n=8） were gavaged with normal saline 2 ml/（kg·d） （ig）; Group 2： control group, rats （n=8） were treated with normal saline 2 ml/（kg·d） （ig）; Group 3： rats （n=8） were given perindopril 2 mg/（kg·d） （ig）; Group 4： rats （n=8） were treated with irbesartan 20 mg/（kg·d） （ig）; Group 5： rats （n=8） were given irbesartan 20 mg/（kg·d） plus perindopril 2 mg/（kg·d） （ig）. Morphometric determination, calcineurin expression and sarcoplasmic reticulum Ca^2＋-ATPase activity were done at the end of 6 week of drug intervention. Expression of calcineurin in myocardium was detected by immunohistochemistry. Results： Left ventricular mass index （LVMI）, transverse diameter of myocardial cell （TDM）, calcineurin activity were remarkably decreased after drug intervention and this decrease was most remarkable in the combination drug therapy group. Sarcoplasmic reticulum Ca^2＋-ATPase activity was increased after drug intervention, especially in the combined drug therapy group. Calcineurin expression in myocardium was remarkably decreased after drug intervention. LVMI was positively correlated with TDM and calcineurin, negatively correlated with sarcoplasmic reticulum Ca^2＋-ATPase. Conclusion： These data suggest that irbesartan and perindopril inhibit cardiac hypertrophy through the increased activity of sarcoplasmic reticulum Ca^2＋-ATPase and decreased expression of calcineurin. Their combination had better effects on regressing of ventricular hypertrophy.展开更多
By using the finite element method,three-dimensional models of a number of periodic blunt and sharp notches subjected to tension loading are investigated.The aim of this research is to investigate the thickness effect...By using the finite element method,three-dimensional models of a number of periodic blunt and sharp notches subjected to tension loading are investigated.The aim of this research is to investigate the thickness effect on the location of maximum stress and notch stress intensity factor(NSIF)of corresponding blunt and sharp periodic notches respectively.With this aim,different number of periodic notches as well as different notch opening angles are examined.While for two-dimensional plates weakened by periodic notches some results are available in the literature,this paper first faces the problem of three-dimensional cases.A total of about 100 geometrical configurations are investigated.It is found that,the effect of plate thickness of periodic notched components can be characterized by the relative value with respect to the depth of the notch(H/t).For the blunt periodic notches with relatively higher values of H/t ratio,the value of the maximum tensile stress is located near the free surface.On the contrary for lower values of H/t,it is placed at the middle plane.The same behaviour is observed for sharp periodic notches in terms of notch stress intensity factors.展开更多
文摘Aim： To observe effects of angiotensin （Ang） II receptor antagonist （ATI） irbesartan and angiotensin-converting enzyme （ACE） inhibitor perindopril on rat myocardium calcineurin expression and sarcoplasmic reticulum Ca^2＋-ATPase activity in the model of pressure-overload cardiac hypertrophy. Methods： Forty male adult Sprague Dawley rats were divided into 5 groups One group was treated by sham operation; four groups were myocardium hypertrophy cases caused by banding aortic above renal artery. Drugs were given one week after operation. Group 1： sham group, rats （n=8） were gavaged with normal saline 2 ml/（kg·d） （ig）; Group 2： control group, rats （n=8） were treated with normal saline 2 ml/（kg·d） （ig）; Group 3： rats （n=8） were given perindopril 2 mg/（kg·d） （ig）; Group 4： rats （n=8） were treated with irbesartan 20 mg/（kg·d） （ig）; Group 5： rats （n=8） were given irbesartan 20 mg/（kg·d） plus perindopril 2 mg/（kg·d） （ig）. Morphometric determination, calcineurin expression and sarcoplasmic reticulum Ca^2＋-ATPase activity were done at the end of 6 week of drug intervention. Expression of calcineurin in myocardium was detected by immunohistochemistry. Results： Left ventricular mass index （LVMI）, transverse diameter of myocardial cell （TDM）, calcineurin activity were remarkably decreased after drug intervention and this decrease was most remarkable in the combination drug therapy group. Sarcoplasmic reticulum Ca^2＋-ATPase activity was increased after drug intervention, especially in the combined drug therapy group. Calcineurin expression in myocardium was remarkably decreased after drug intervention. LVMI was positively correlated with TDM and calcineurin, negatively correlated with sarcoplasmic reticulum Ca^2＋-ATPase. Conclusion： These data suggest that irbesartan and perindopril inhibit cardiac hypertrophy through the increased activity of sarcoplasmic reticulum Ca^2＋-ATPase and decreased expression of calcineurin. Their combination had better effects on regressing of ventricular hypertrophy.
文摘By using the finite element method,three-dimensional models of a number of periodic blunt and sharp notches subjected to tension loading are investigated.The aim of this research is to investigate the thickness effect on the location of maximum stress and notch stress intensity factor(NSIF)of corresponding blunt and sharp periodic notches respectively.With this aim,different number of periodic notches as well as different notch opening angles are examined.While for two-dimensional plates weakened by periodic notches some results are available in the literature,this paper first faces the problem of three-dimensional cases.A total of about 100 geometrical configurations are investigated.It is found that,the effect of plate thickness of periodic notched components can be characterized by the relative value with respect to the depth of the notch(H/t).For the blunt periodic notches with relatively higher values of H/t ratio,the value of the maximum tensile stress is located near the free surface.On the contrary for lower values of H/t,it is placed at the middle plane.The same behaviour is observed for sharp periodic notches in terms of notch stress intensity factors.
