OBJECTIVE Eurycoma longifolia is a tropical medicinal plant belonging to Simaroubaceae distributed in South East Asia.The aim of this study is to explore the effect and mechanism of E.longifolia stem 70%ethanol extrac...OBJECTIVE Eurycoma longifolia is a tropical medicinal plant belonging to Simaroubaceae distributed in South East Asia.The aim of this study is to explore the effect and mechanism of E.longifolia stem 70%ethanol extract(EL)and its active com⁃poundson uric acid excretion.METHODS Potassium oxonate(PO)induced hyperuricemia rats and adenine-PO induced hyperuricemia mouse model were used to evaluate the effects of EL.Ultra Performance Liquid Chromatography was used to determine the levels of plasma or serum uric acid and creatinine.Hematoxylin-eosin staining was applied to observe kidney pathological changes,Western blot⁃ting was applied to detect protein expression levels of uric acid transporters.Effects of constituents on urate uptake were tested in hU⁃RAT1-expressing HEK293T cells.RESULTS EL significantly reduced serum and plasma uric acid levels at dosages of 100,200 and 400 mg·kg^-1 in hyperuricemia rats and mice,and increased the clearance rate of uric acid and creatinine,improved therenal pathological injury.The protein expression levels of urate reabsorption transporter 1(URAT1)and glucose transporter 9 were down-regulated while sodium-dependent phosphate transporter 1 and ATP-binding cassette transporter G2 were up-regulated in the kidney after EL treat⁃ment.The diterpenes(50μmol·L^-1)isolated from EL showed inhibitory effects on urate uptake in hURAT1-expressing HEK293T cells,and the effect of eurycomanol was further confirmed in vivo.CONCLUSION EL significantly reduced blood uric acid levels and prevented pathological changes of kidney in PO induced hyperuricemia animal model,improved renal urate transports.We partly clarified the mechanism was related to suppressing effect of URAT1 by diterpene in EL.This study is the first to demonstrate that EL plays a role in hyperuricemia by promoting renal uric acid excretion.展开更多
模块化多电平直流变压器(modular multilevel DC transformer, MMDCT)原边侧串联的子模块电容、桥臂电感及寄生电阻之间存在欠阻尼特性,实际运行中易引发频繁且持续的欠阻尼振荡,给系统的安全可靠运行带来挑战。为改善系统的欠阻尼特性...模块化多电平直流变压器(modular multilevel DC transformer, MMDCT)原边侧串联的子模块电容、桥臂电感及寄生电阻之间存在欠阻尼特性,实际运行中易引发频繁且持续的欠阻尼振荡,给系统的安全可靠运行带来挑战。为改善系统的欠阻尼特性,首先,建立了模块化多电平直流变压器原边侧的环流等效模型,揭示系统欠阻尼振荡产生的机理。其次,引入小量修正角实现每隔半个开关周期对环流抑制电压的修正,主动控制环流变化趋势,有效增强系统内部阻尼,从而抑制了暂态过程中的欠阻尼振荡。然后,采用功率前馈-电容电压环流双闭环控制策略,通过合理的参数设计,确保系统在多场景多工况下具备良好的动态响应性能。最后,通过仿真和实验验证了所提控制策略对MMDCT欠阻尼特性的改善作用。展开更多
文摘OBJECTIVE Eurycoma longifolia is a tropical medicinal plant belonging to Simaroubaceae distributed in South East Asia.The aim of this study is to explore the effect and mechanism of E.longifolia stem 70%ethanol extract(EL)and its active com⁃poundson uric acid excretion.METHODS Potassium oxonate(PO)induced hyperuricemia rats and adenine-PO induced hyperuricemia mouse model were used to evaluate the effects of EL.Ultra Performance Liquid Chromatography was used to determine the levels of plasma or serum uric acid and creatinine.Hematoxylin-eosin staining was applied to observe kidney pathological changes,Western blot⁃ting was applied to detect protein expression levels of uric acid transporters.Effects of constituents on urate uptake were tested in hU⁃RAT1-expressing HEK293T cells.RESULTS EL significantly reduced serum and plasma uric acid levels at dosages of 100,200 and 400 mg·kg^-1 in hyperuricemia rats and mice,and increased the clearance rate of uric acid and creatinine,improved therenal pathological injury.The protein expression levels of urate reabsorption transporter 1(URAT1)and glucose transporter 9 were down-regulated while sodium-dependent phosphate transporter 1 and ATP-binding cassette transporter G2 were up-regulated in the kidney after EL treat⁃ment.The diterpenes(50μmol·L^-1)isolated from EL showed inhibitory effects on urate uptake in hURAT1-expressing HEK293T cells,and the effect of eurycomanol was further confirmed in vivo.CONCLUSION EL significantly reduced blood uric acid levels and prevented pathological changes of kidney in PO induced hyperuricemia animal model,improved renal urate transports.We partly clarified the mechanism was related to suppressing effect of URAT1 by diterpene in EL.This study is the first to demonstrate that EL plays a role in hyperuricemia by promoting renal uric acid excretion.
文摘模块化多电平直流变压器(modular multilevel DC transformer, MMDCT)原边侧串联的子模块电容、桥臂电感及寄生电阻之间存在欠阻尼特性,实际运行中易引发频繁且持续的欠阻尼振荡,给系统的安全可靠运行带来挑战。为改善系统的欠阻尼特性,首先,建立了模块化多电平直流变压器原边侧的环流等效模型,揭示系统欠阻尼振荡产生的机理。其次,引入小量修正角实现每隔半个开关周期对环流抑制电压的修正,主动控制环流变化趋势,有效增强系统内部阻尼,从而抑制了暂态过程中的欠阻尼振荡。然后,采用功率前馈-电容电压环流双闭环控制策略,通过合理的参数设计,确保系统在多场景多工况下具备良好的动态响应性能。最后,通过仿真和实验验证了所提控制策略对MMDCT欠阻尼特性的改善作用。
