Electric field-induced changes in agonist-stimulated calcium fluxes of human HL-60 leukemia cells

The mechanism of biological effects of extremely-low-frequency electric and magnetic fields may involve induced changes of Ca2+ transport through plasma membrane ion channels. In this study we investigated the effects of externally applied, low-intensity 60 Hz electric (E) fields (0.5 V/m, current density 0.8 A/m2) on the agonist-induced Ca2+ fluxes of HL-60 leukemia cells. The suspensions of HL-60 cells received E-field or sham exposure for 60 min and were simultaneously stimulated either by 1 microM ATP or by 100 microM histamine or were not stimulated at all. After E-field or sham exposure, the responses of the intracellular calcium levels of the cells to different concentrations of ATP (0.2-100 microM) were assessed. Compared with control cells, exposure of ATP-activated cells to an E-field resulted in a 20-30% decrease in the magnitude of [Ca2+]i elevation induced by a low concentration of ATP (<1 microM). In contrast, exposure of histamine-activated HL-60 cells resulted in a 20-40% increase of ATP-induced elevation of [Ca2+]i. E-field exposure had no effect on non-activated cells. Kinetic analysis of concentration-response plots also showed that compared with control cells, exposure to the E-field resulted in increases of the Michaelis constant, Km, value in ATP-treated cells and of the maximal [Ca2+]i peak rise in histamine-treated HL-60 cells. The observed effects were reversible, indicating the absence of permanent structural damages induced by acute 60 min exposure to electric fields. These results demonstrate that low-intensity electric fields can alter calcium distribution in cells, most probably due to the effect on receptor-operated Ca2+ and/or ion channels.     

钛酸锶粉体的制备及超声降解性能的研究

以硝酸锶和钛酸四丁酯为前驱物,采用溶胶-凝胶法制备了钛酸锶粉体.采用傅里叶红外光谱、X射线粉末衍射和扫描电镜等测试手段,对钛酸锶粉体进行了表征,并对其超声降解甲基橙性能进行了研究.结果表明:在锻烧温度为700℃,锻烧时间为2.0 h时生成的钛酸锶超声降解甲基橙效率最高;掺杂五氧化二钒可显著提高钛酸锶催化活性,掺杂三氧化...     

稀土异戊橡胶与天然橡胶共混胶性能的研究

对不同共混比的稀土异戊橡胶（NdIR）/天然橡胶（NR）共混胶的硫化特性及物理机械性能进行了系统研究,并与俄罗斯钛体系异戊橡胶（SK-3）及SK-3/NR共混胶的性能进行了对比。结果表明,NdIR/NR的相容性好于SK-3/NR;NdIR/NR共混胶较好地保持了NR原有的高拉伸、高抗撕裂性能,并能有效提高交联密度和拉断伸长率,其焦烧时间得到适当延长;NdIR/NR共混胶没有出现炭黑团聚和微相分离现象,NdIR在某些领域可替代天然橡胶。     

电厂热力系统分析方法的研究现状及发展趋势

本文系统介绍了当前国内热力系统热经济性分析方法的研究现状,回顾了国内在该领域的发展过程。根据掌握的文献资料客观地评价了几种目前较典型的热经济性分析方法的优点与不足,最后在总结已分析的基础上提出了对于热力系统分析方法研究趋势的新观点。     

基于EKF的低速永磁电机控制系统建模与分析

为了实现大转矩、低转速永磁电机的变频控制,提出了一种基于卡尔曼滤波原理的调速系统。在系统中,采用卡尔曼滤波算法对电机位置、转速和d—q轴电流进行了估计。在广义卡尔曼滤波（EKF）的基础上,系统的电流环和速度环采用PI控制,电机采用空间矢量脉宽调制（SVPWM）矢量控制方法。利用Matlab／Simulink对整个系统进行了仿真建模,并对仿真结果进行了分析。通过对误差的分析以及参数鲁棒性的分析,可以证明卡尔曼滤波算法适用于低速的永磁电机调速系统。     

PRO/E在翻罐卷扬机设计中的应用

叙述了在翻罐卷扬机的设计中用PRO/E进行铁水罐的三维实体造型工作,并模拟了铁水罐的倾翻过程,进而精确地计算出了在这一进程中铁水罐地倾翻特性,为翻罐卷扬机地设计提供了准确地数据。     

The ontogeny of 11 beta-hydroxysteroid dehydrogenase type 2 and mineralocorticoid receptor gene expression reveal intricate control of glucocorticoid action in development

Glucocorticoids play important roles in development and 'fetal programming'. Fetal exposure to excess glucocorticoids reduces birth weight and causes later hypertension. To investigate these processes further we have determined the detailed category of 11 beta-hydroxysteroid dehydrogenase type2 (11 beta-HSD2, which potently inactivates glucocorticoids) and the mineralocorticoid receptor (MR) by in situ hybridisation from embryonic day 9.5 (E9.5, term = E19) until after birth in the mouse. Widespread abundant 11 beta-HSD2 mRNA expression from E9.5-E12.5 changes dramatically at approximately E13 to a limited tissue-specific pattern (kidney, hindgut, testis/bile ducts, lung and a few brain regions (later seen in cerebellum, thalamus, roof of midbrain, neuroepithelial regions in pons and near the subicular hippocampus)). Placenta (labyrinthine zone) and extra-embryonic membranes express abundant 11 beta-HSD2 mRNA until E15.5 but this ceases = E16.5. It is unclear to what extent rodent term placental 11 beta-HSD activity is due to persisting 11 beta-HSD2 protein. Convincing MR mRNA expression is seen from E13.5 and includes pituitary, heart, muscle and meninges with expression later in gut, kidney, thymus, discrete areas of lung and several brain regions (including hippocampus, rhinencephalon and hypothalamus). 11 beta-HSD2 and MR clearly co-localise = E18.5 in kidney and colon and might do so in discrete areas of lung (E14-15) and neuroepithelia near the subicular hippocampus. Probably elsewhere MR are non-selective and 11 beta-HSD2 is involved in protecting glucocorticoid receptors in fetal fetal tissues. Comparison with previous enzymology studies suggest the changing pattern of 11 beta-HSD2 mRNA is likely to be translated into enzyme activity and have significant parallels in human development.