KATP通道对缺血性心肌电平衡的维护作用及机制

目的：利用异丙肾上腺素（ISO）诱导大鼠心肌缺血性损伤模型和心肌细胞损伤模型,并对其进行药物干预,探讨心肌ATP敏感性钾 通道（KATP通道）维持缺血性心肌电平衡的作用与机制。方法：在动物实验中,将雄性SD大鼠,随机分为5组,正常对照组大鼠皮下注射0.9% 氯化钠溶液,其余各组大鼠均皮下注射等量1 g ? L -1 ISO（qd）,连续9 d,其间,在第7~9 d,除了正常对照组和模型组外,其他3组大鼠还 分别灌胃给予1.75 g ? L -1 普萘洛尔（PRO）2 mL ? kg -1 ? d -1 、5 g ? L -1 曲美他嗪（VAS）2 mL ? kg -1 ? d -1 或腹腔注射给予5 g ? L -1 二苯基碘（DPI） 1 mL ? kg -1 ? d -1 。在造模期间不同时间点,对各组大鼠进行心电图检查,并制备心肌标本,检测其中KATP通道亚基KIR6.2蛋白表达水平。 在细胞实验中,将H9C2心肌细胞分成对照组（不给药）、ISO组、ISO+ PRO组、ISO+DPI组和ISO+VAS组,后3组细胞均在1 μmol ? L -1 ISO加入前30 min,分别给予2 μmol ? L -1 PRO、10 μmol ? L -1 DPI和10 μmol ? L -1 VAS,且在加入ISO后,与ISO组细胞一样,再孵育1 和24 h,采用实时荧光定量 PCR法测定各组细胞中KATP通道亚基KIR6.2和SUR2A基因表达水平。结果：大鼠实验显示,与正常对照组相比, 模型组大鼠在造模的第3、7 d,心电图参数QTc明显缩短,心率加快（P ＜0.05）,且心肌中KIR6.2蛋白表达明显增多（P ＜0.01）,而造 模9 d后,其QTc明显延长（P ＜0.01）,心率减慢（P ＜0.05）,心肌中KIR6.2蛋白表达显著降低（P ＜0.01）;ISO+ PRO、ISO+DPI 和ISO+VAS各组大鼠在持续3 d分别接受3种药物治疗后,其QTc较模型组明显缩短,心率升高,均趋于恢复正常水平。细胞实验显示, 与对照组相比,ISO组H9C2细胞经ISO孵育1 h后,KIR6.2和SUR2A的mRNA表达显著上调（P ＜0.05）,而在ISO孵育24 h后, KIR6.2和SUR2A的mRNA表达显著下调（ P ＜0.01）;与ISO组相比,各给药组细胞经ISO孵育1 h后,KIR6.2和SUR2A的mRNA表 达均有不同程度下调,而在ISO孵育24 h后,KIR6.2和SUR2A的mRNA表达均显著上调（P ＜0.05或P ＜0.01）。结论：KATP通道对 维护缺血性心肌电平衡起重要作用。持续性激动β受体、氧化应激或能量供应不足等体内多条途径都会影响KATP通道的表达和功能,而保护 KATP通道功能,对于维持心电平衡,抑制心律失常基质形成,意义重大。     

Asymmetric somatic cell hybridization in plants

As part of an investigation into whether it would be possible to use UV radiation as a suitable pretreatment of the donor cells in asymmetric hybridization experiments, the effects of this treatment on sugarbeet (Beta vulgaris L.) protoplast DNA have been determined and compared with those of gamma radiation. Both nuclear and mitochondrial DNAs have been examined. The dose ranges chosen had previously been determined to be potentially applicable for fusion experiments. Pulsed field gel electrophoresis and standard agarose gel electrophoresis have been used in combination with laser scanning densitometry to gain an insight into the precise nature and degree of DNA damage resulting from irradiation. It was observed that UV radiation introduced substantial modifications to sugarbeet DNA. Double-strand breaks were detected, the number of which was found to be directly proportional to the dose applied. Such breaks indicate that UV radiation results in substantial chromosome/chromatid fragmentation in these cells. Chemical modifications to the DNA structure could be revealed by a significant reduction in DNA hybridization to specific mitochondrial and nuclear DNA probes. Following gamma irradiation at equivalent biological doses (i.e. those just sufficient to prevent colony formation) much less damage was detected. Fewer DNA fragments were produced indicating the presence of fewer double-strand breaks in the DNA structure. In comparison to UV treatments, DNA hybridization to specific probes following gamma radiation was inhibited less. For both treatments, mitochondrial DNA appeared more sensitive to damage than nuclear DNA. The possibility that DNA repair processes might account for these differences has also been investigated. Results indicate either that repair processes are not involved in the effects observed or that DNA repair occurs so fast that it was not possible to demonstrate such involvement with the experimental system used. The general relevance of such processes to asymmetric cell hybridization is discussed.     

RNA-Puzzles Round II: assessment of RNA structure prediction programs applied to three large RNA structures

This paper is a report of a second round of RNA-Puzzles, a collective and blind experiment in three-dimensional (3D) RNA structure prediction. Three puzzles, Puzzles 5, 6, and 10, represented sequences of three large RNA structures with limited or no homology with previously solved RNA molecules. A lariat-capping ribozyme, as well as riboswitches complexed to adenosylcobalamin and tRNA, were predicted by seven groups using RNAComposer, ModeRNA/SimRNA, Vfold, Rosetta, DMD, MC-Fold, 3dRNA, and AMBER refinement. Some groups derived models using data from state-of-the-art chemical-mapping methods (SHAPE, DMS, CMCT, and mutate-and-map). The comparisons between the predictions and the three subsequently released crystallographic structures, solved at diffraction resolutions of 2.5–3.2 Å, were carried out automatically using various sets of quality indicators. The comparisons clearly demonstrate the state of present-day de novo prediction abilities as well as the limitations of these state-of-the-art methods. All of the best prediction models have similar topologies to the native structures, which suggests that computational methods for RNA structure prediction can already provide useful structural information for biological problems. However, the prediction accuracy for non-Watson–Crick interactions, key to proper folding of RNAs, is low and some predicted models had high Clash Scores. These two difficulties point to some of the continuing bottlenecks in RNA structure prediction. All submitted models are available for download at http://ahsoka.u-strasbg.fr/rnapuzzles/.     

Inactivation of E. coli in Cranberry Juice by a High Voltage Pulsed Electric Field

The aim of this work was to study the effect of a high voltage pulsed electric field (PEF) on the inactivation of E. coli in cranberry juice to achieve the regulatory requirement of a 5‐log reduction in the microbial count. PEF processing involved the application of high voltage pulses to liquid or semi‐solid materials, placed between two electrodes at ambient, sub‐ambient, or supra‐ambient temperature. In this work, cranberry juice, inoculated with E. coli was subjected to 60 pulses in the voltage range of 5 to 40 kV/cm. The experiments were carried out at 20 °C. The temperature rise was less than 2 °C at the average treatment time of 80 s. PEF is an emerging non‐thermal technology for food preservation that retains the natural taste of food. It has mainly been applied to improve the shelf life of such foods as milk, liquid eggs and fruit juices.     

脑部磁刺激场的理论模型

作为脑部磁刺激研究的一项基础工作,建立了刺激磁场中的球形头模型、对方形线圈在其内产生的时变磁场和感应电场进行了理论研究.导出(?).(?).(?)的解析表达式,分析了场的特性和刺激强度的分布规律.为进一步探索时变磁场对人脑的最佳刺激方式和作用机理提供了初步的理论基础.     

南京地区12种常绿阔叶树种冬季抗寒性动态变化

选取南京地区露地引种的12种常绿阔叶树种,借助电导法对其抗寒性进行研究,结果表明:12种常绿树种在2003年与2005年冬季期间,抗寒能力高低排序具有很好的一致性与重复性.12种常绿树种在2005年10月至2006年3月期间随冬季低温诱导进行其抗寒能力呈逐渐增强趋势,其中在1月中旬树种抗寒能力均达到最强,而通常在10月份或3月份期间树种抗寒能力最弱.比较而言,12种常绿阔叶树种对冬季低温条件响应的快慢程度各有差异,其中樟科的香樟(Cinnamomum camphora)、浙江樟(Cinnamomum japonicum)属于低温快速响应型,而冬青科的冬青(Ilex purpurea)、大叶冬青(Ilex latifolia)属于低温滞缓响应型,其余树种为正常响应型.12种常绿阔叶树种试验所得抗寒能力结果与引种地冬季观察结果具有很好的对应性.研究结果可为常绿阔叶树种进一步向较高纬度地区的引种与栽培管理工作提供重要的参考.     

Investigating the permanent electric dipole moment of beta-lactoglobulin fibrils, using transient electric birefringence

Amyloid fibrils, which are polymeric assemblies of protein molecules, have been intensively studied on a structural level, yet due to complications such as the disorder within the molecules, several aspects of their structure remain mysterious. Similarly, the kinetics of assembly are not well understood. Here we investigate the electric dipole moment of beta-lactoglobulin fibrils, a model amyloid fibril system, by applying the technique of transient electric birefringence. This moment appears to be large, and comparable to the total moment of the constituent protein monomers if they were joined in a chain, head-to-tail, without changing conformation, suggesting an ordered joining of monomers in the fibril. Such an ordered assembly may have implications for the assembly mechanism of beta-lactoglobulin fibrils in particular, and amyloid fibrils in general.     

Computer simulation of synchronization of Na/K pump molecules

The behavior of Na/K pump currents when exposed to an oscillating electric field is studied by computer simulation. The pump current from a single pump molecule was sketched based on previous experimental results. The oscillating electric field is designed as a symmetric, dichotomous waveform varying the membrane potential from −30 to −150 mV around the membrane resting potential of −90 mV. Based on experimental results from skeletal muscle fibers, the energy needed to overcome the electrochemical potentials for the Na and K-transports are calculated in response to the field’s two half-cycles. We found that a specially designed oscillating electric field can eventually synchronize the pump molecules so that all the individual pumps run at the same pumping rate and phase as the field oscillation. They extrude Na ions during the positive half-cycle and pump in K ions during the negative half-cycle. The field can force the two ion-transports into the corresponding half-cycles, respectively, but cannot determine their detailed positions. In other words, the oscillating electric field can synchronize pumps in terms of their pumping loops but not at a specific step in the loop. These results are consistent with our experimental results in measurement of the pump currents.