Polarotaxis in non-biting midges: female chironomids are attracted to horizontally polarized light

Non-biting midges (Chironomidae, Diptera) are widely distributed aquatic insects. The short-living chironomid adults swarm in large numbers above water surfaces, and are sometimes considered a nuisance. They are vectors of certain bacteria, and have a key-role in benthic ecosystems. Optical cues, involving reflection-polarization from water, were found to be important in the habitat selection by three Mediterranean freshwater chironomid species. In this work we report on our multiple-choice experiments performed in the field with several other European freshwater chironomid species. We show that the investigated non-biting midges are positively polarotactic and like many other aquatic insects their females are attracted to horizontally polarized light. Our finding is important in the visual ecology of chironomids and useful in the design of traps for these insects.     

Myosin cross-bridges do not form precise rigor bonds in hypertrophic heart muscle carrying troponin T mutations

Distribution of orientations of myosin was examined in ex-vivo myofibrils from hearts of transgenic (Tg) mice expressing Familial Hypertrophic Cardiomyopathy (FHC) troponin T (TnT) mutations I79N, F110I and R278C. Humans are heterozygous for sarcomeric FHC mutations and so hypertrophic myocardium contains a mixture of the wild-type (WT) and mutated (MUT) TnT. If mutations are expressed at a low level there may not be a significant change in the global properties of heart muscle. In contrast, measurements from a few molecules avoid averaging inherent in the global measurements. It is thus important to examine the properties of only a few molecules of muscle. To this end, the lever arm of one out of every 60,000 myosin molecules was labeled with a fluorescent dye and a small volume within the A-band (~ 1 fL) was observed by confocal microscopy. This volume contained on average 5 fluorescent myosin molecules. The lever arm assumes different orientations reflecting different stages of acto-myosin enzymatic cycle. We measured the distribution of these orientations by recording polarization of fluorescent light emitted by myosin-bound fluorophore during rigor and contraction. The distribution of orientations of rigor WT and MUT myofibrils was significantly different. There was a large difference in the width and of skewness and kurtosis of rigor distributions. These findings suggest that the hypertrophic phenotype associated with the TnT mutations can be characterized by a significant increase in disorder of rigor cross-bridges.     

用电化学方法研究IUD在人工配制液中铜的腐蚀

本文应用腐蚀电化学的极化电阻技术研究铜在人工配制液中的腐蚀行为，由测得的极化电阻可以算出相应的腐蚀电流和腐蚀速度的瞬时值，根据给定期间一系列数据积分可得出平均腐蚀速度。纯度自９９．７％至９９．９９％的几种铜管试样表现出相近的腐蚀速度，表明钢的纯度不是这种腐蚀的决定因素，而介质的ｐＨ起重要作用，ｐＨ６．３时的腐蚀速度是ｐＨ８．０时的５倍左右。这可以解释文献中铜释放率数据的分散性，因为人体宫腔液的ｐＨ有较大的差异。消炎痛对铜在人工配制液中的腐蚀没有什么影响。电化学方法应用于ＩＵＤ体外试验是可行和有效的。     

Polarization inventory diagrams

The significance in electrochemistry of the term ‘polarization’ is carefully explained. Several diverse effects contribute to the overall polarization and the magnitudes of the corresponding overvoltages may be calculated via equations that are presented. An informative graphical method of presenting data on the evolution of the individual overvoltages during voltammetry is described and exemplified. The diagram may be constructed from experimental data or as part of a predictive exercise using either digital simulation or convolutive modelling. Four examples of these polarization inventory diagrams are presented. Among the features that may be factored into the diagrams are various voltammetric protocols, electrode reactions of any degree of reversibility, arbitrary transfer coefficient, diffusion coefficient diversity, varied cell geometries, transport by diffusion and/or migration, first-order homogeneous reactions, uncompensated resistance, and multi-layered electrolyte solutions.     

Equilibrium potential of potentiometric ion sensors under steady-state current by using current-reversal chronopotentiometry

Potentiometric ion sensors based on a solvent polymeric ion-sensing membrane and a conducting polymer as the solid contact were investigated by current-reversal chronopotentiometry. The low-frequency electrochemical behavior of the electrodes resembles a series RC equivalent circuit. The resistance R was attributed primarily to the bulk resistance of the ion-sensing membrane and the capacitance C was attributed to the bulk redox capacitance of the conducting polymer layer acting as an ion-to-electron transducer. It is shown that the equilibrium potential of the ion sensors can be obtained in the presence of a steady-state current by using current-reversal chronopotentiometry (double current step chronopotentiometry).     

VitD3对Th细胞极化的调节作用研究

目的研究VitD3对Th细胞分化的影响及可能的机制。方法无菌分离BALB/c小鼠细胞脾细胞,2.5μg/ml的ConA 加入刺激脾细胞,在不同时间段加入不同剂量的VitD3,72h后收集细胞,3H-TdR掺入法测定淋巴细胞增殖活性,RT-PCR方法检测参与Th细胞分化的细胞因子的mRNA表达水平。结果VitD3呈剂量依赖抑制ConA诱导的淋巴细胞的活化,10-5mol/L的VitD3对ConA诱导的淋巴细胞活化的抑抑制作用最强;该抑制作用与作用时间的长短呈相关性,ConA活化淋巴细胞24h后加入VitD3对淋巴细胞活化的抑制作用最显著,并且淋巴细胞的活化程度越低,VitD3对其抑制作用越强。VitD3可增强经ConA活化的淋巴细胞Th2型细胞因子(IL-4、IL-6)mRNA的表达水平,而Th1型细胞因子(IFN-γ、TNF-α)的mRNA的表达水平显著性下降(P<0.05)。结论VitD3可抑制ConA刺激的淋巴细胞增殖活性,但亦可增强Th2细胞的分化。     

新型经静脉临时心脏起搏电极的研制与实验应用

我院应用永久性心内膜电极材料和生产工艺研制出带指引钢丝的临时经静脉螺旋式多层微粒铱镀复电极(简称A电极 )。随后采用自身对照设计 ,在 2 4只犬身上按随机顺序先后给予以 3种不同的电极经静脉临时起搏 ,比较其起搏参数的差异 ,了解A电极对起搏和感知功能的影响。结果 :A电极的起搏阈值分别较本院研制的经静脉螺旋式电极 (简称B电极 )及经静脉普通电极 (简称C电极 )降低 30 .30 %和 43.2 1% ,右室心内膜R波振幅分别较B及C电极升高 16 .78%和 2 8.2 9%。结论 :A电极能降低极化效应 ,从而降低了起搏阈值 ,提高了电极的感知性能