Whole-cell clamp study of Xenopus embryonic cholinergic neurons

Whole-cell clamped myoballs are placed into direct visible contact with the growth cones of isolated neurons in embryonic Xenopus culture to serve as probe of acetylcholine (AcCHo) release in order to determine whether these neurons are cholinergic or not. Using a G omega -seal, whole-cell recording method, the electrophysiological properties of these identified cholinergic neurons are studied. It is found that these embryonic neurons, like adult frog motor neurons, exhibit repetitive firings in a certain embryonic developing stage. A development of repetitive firings is observed simultaneously. Tracing the development of one neuron, we find that the development of repetitive firing is completed at the 48th h after fertilization. Tetrodotoxin (TTX) which blocks Na+ channels can abolish all firings; and tetraethyl ammonium chloride (TEA), the blocker of K+ channels, reverses this development, i.e. it makes the repetitive firings disappear again. These data show that the nature of the development of repetitive firings is the development of K+ channels.     

The Relationship Between New Ion Channels and Ectopic Discharges From a Region of Nerve Injury

Changes in ectopic discharges from axons in an injured nerve were examined while agents that interact with ion channels were applied to the site of the nerve injury. Tetraethylammonium (TEA) greatly facilitated spontaneous ectopic discharges or evoked ectopic firing in previously silent axons.Tetrodotoxin, an Na~+ channel blocker,completely blocked spontaneous discharges.Verapamil, La3~+, and Mn2~+, agents that interact with Ca2~+ channels,blocked spontaneous discharges and depressed the responses evoked by TEA, noradrenaline and high concentration of K~+.Increasing Ca2~+ levels facilitated ectopic discharges and this effect was blocked by La3~+ and Mn2~+. Normal axons (from uninjured nerves) were insensitive to all the effects seen in the axons from the injured nerve.These results suggest that following nerve injury the membrane of the regenerating sprout contains new ion channels, particularly Ca2~+ channels, anti that these channels are responsible for the generation of ectopic discharges.     

R-leaping: accelerating the stochastic simulation algorithm by reaction leaps

A novel algorithm is proposed for the acceleration of the exact stochastic simulation algorithm by a predefined number of reaction firings (R-leaping) that may occur across several reaction channels. In the present approach, the numbers of reaction firings are correlated binomial distributions and the sampling procedure is independent of any permutation of the reaction channels. This enables the algorithm to efficiently handle large systems with disparate rates, providing substantial computational savings in certain cases. Several mechanisms for controlling the accuracy and the appearance of negative species are described. The advantages and drawbacks of R-leaping are assessed by simulations on a number of benchmark problems and the results are discussed in comparison with established methods.     

Effects of Muscle Electrical Activity on the Transmission of Developing Neuromuscular Junction

Miniature endplate potentials (MEPPS) caused by the spontaneous release of ACh from the growth cone of cholinergic neurons, are recorded by the whole-cell patch-clamp technique on a large number of 1-day cultured myoballs which have contact neurites of co-cultured neurons. Both muscle cell and neuron are dissociated from the 1-day-old (about stage 20) Xenopus embryo. Frequency and/or amplitude of MEPPs can obviously increase after the repetitive high-level depolarization caused by the stimuli on muscle cells. No detectable changes of single ACh receptor channel property are observed by using the single-channel recording technique. These results suggest that the mechanism of the increase of MEPPs after electrical activity of postsynaptic muscle cells probably involve some alteration of presynaptic membrane.     

单向耦合Hindmarsh-Rose系统的同步

采用数值模拟方法, 研究了由两个具有不同初始条件单向耦合的Hindmarsh-Rose神经元所组成系统的动力学行为. 研究结果表明, 耦合强度对两个神经元的同步具有重要的影响. 当两个神经元的控制参数取值不同时, 即在驱动系统和响应系统均处于混沌态及驱动系统处于周期振荡态, 响应系统处于混沌态两种情况下, 随耦合强度的增加其放电活动都能从不同步达到相位同步, 最后实现近似完全同步.     

镧对大鼠海马神经元瞬时外向钾电流和延迟整流钾电流动力学的影响

利用全细胞膜片钳技术, 在急性分离的大鼠海马锥形细胞上研究了La³⁺对快速激活与失活的瞬时外向钾电流IA和平台电流IK的影响. 结果发现, 随着细胞外液中La ³⁺浓度的增加, La ³⁺对IA的抑制率逐渐增大, 而且具有电压依赖性; 10^-5 mol/L La ³⁺可改变IA激活曲线和失活曲线的半数激活电压Vh值, 使激活曲线和失活曲线左移, 但不改变其斜率因子k值. 细胞外液中 La ³⁺对IK及其激活曲线都没有明显作用. 这可能是镧导致海马神经元异常的作用机制之一.     

单柱离子色谱分析若干无机阴离子的初步研究

本文所提出的单柱离子色谱分离阴离子混合物的技术,不用抑制柱,树脂也无需再生。用国产多孔乙基苯乙烯-二乙烯苯共聚物制备了不同交换度的低容量阴离子交换树脂。以苯甲酸盐为洗脱液,F~-、Cl~-、Br~-可以分离,F~-峰尖锐,Br~-峰较宽。以邻苯二甲酸氢盐为洗脱液,保留时间均减小,但F~-峰被进样峰所掩盖,Cl~-、Br~-、SO_4~-:可满意地得到分离,洗脱液的浓度和pH对阴离子分离的保留时间和峰高有较大的影响。邻苯二甲酸氢盐中不同的阳离子,由于它们的电导背景不同(Li~+Na~+>K~+>NH_4~+。     

Ca_2Nb_2O_7 as a Novel Open-framework Anode Material for Potassium-ion Batteries

Potassium-ion batteries(KIBs)are a promising alternative to Lithium-based energy storage systems owning to the low cost and rich abundance of potassium resources,but are facing challenges in designing low-cost hosts that can reversibly accommodate large-size K⁺with fast diffusion kinetics.Herein,we report a novel 3D inorganic open framework of Ca₂Nb₂O₇(CNO)as an anode for KIBs.The open framework structure affords interstitial vacancies available for storing K⁺and allows a facile diffusion of K⁺,thus resulting in excellent structural stability and fast reaction kinetics.The CNO electrode delivers a reversible specific capacity of 65.3 and 52.2 mAh/g at 5 and 10 mA/g,respectively.Moreover,CNO exhibits excellent long-term cyclability with 92.53%capacity retention over 700 cycles at 10 mA/g.This will trigger more investigations into open-framework-based materials for stable and fast KIBs.     

Br+CH3S(O)CH3反应机理的直接动力学研究

采用直接动力学的方法，对多通道反应体系Br＋CH3S（O）CH3进行了理论研究．在BH＆H-LYP／6-311G（2d，2p）水平下获得了优化几何构型、频率及最小能量路径（MEP），能量信息的进一步确认在MC-QCISD（单点）水平下完成．利用正则变分过渡态理论，结合小曲率隧道效应校正（CVT／SCT）方法计算了该反应的两个可行的反应通道在200K～2000K温度范围内的速率常数．在整个反应区间内，生成HBr的反应通道与生成CHa的反应通道存在着竞争，前者是主反应通道，后者是次反应通道．变分效应和小曲率隧道效应对反应速率常数的计算影响都很小．理论计算得到的两个反应通道的反应速率常数与实验值符合得很好．     

非水体系高硅Na~i/K-ZSM-48的合成及其表征

高硅ZSM-48沸石分子筛在合成气转化催化剂中具有较好的催化性能,其特殊的中孔结构适宜于低碳碳氢化合物的生成。沸石的硅铝比,晶体形貌以及表面性质等不同程度地影响催化剂的性能。同时,不同无机阳离子对沸石的晶化等性能具有明显作     

阳离子交换色谱中色谱柱温度对碱金属与碱土金属离子保留的影响

研究了非抑制型阳离子交换色谱中色谱柱温度(25~50℃)对碱金属离子(Li+、Na+、K+、Rb+)和碱土金属离子(Mg2+、Ca2+、Sr2+)以及NH4+保留的影响。在Shim-pack IC-C1磺酸型阳离子交换柱上,以硝酸为流动相分离碱金属离子,以乙二胺或乙二胺-草酸(柠檬酸)为流动相分离碱土金属离子,随着色谱柱温度的升高,碱金属和碱土金属离子的保留时间均增长,其范特霍夫曲线具有良好的线性关系,斜率为负值,表明在此条件下碱金属和碱土金属离子的保留为吸热过程。在Shim-pack IC-SC1羧酸型阳离子交换柱上,以硫酸为流动相同时分离碱金属和碱土金属离子,随着色谱柱温度的升高,Mg2+、Ca2+的保留时间增长,而K+、Rb+的保留时间缩短,Li+、Na+、NH4+的保留时间基本不变。在此条件下,Mg2+、Ca2+、K+和Rb+的范特霍夫曲线具有良好的线性关系,其中Mg2+和Ca2+的曲线斜率为负值,K+和Rb+的曲线斜率为正值,表明Mg2+和Ca2+的保留表现为吸热过程,K+和Rb+的保留表现为放热过程。研究表明在不同固定相和流动相条件下,色谱柱温度对碱金属和碱土金属离子保留行为的影响不同。     

PRIMARY AMINE DRUG SELECTIVE ELECTRODES WITH SPECIAL CROWN ETHERS AS NEUTRAL CARRIERS*

Ionophores selectively sensitive to primary amines have been synthesized which display low potentiometric selectivity coefficients for K~+, Na~+ and NH_4~+ ions, secondary and tertiary amines as well as quaternary ammonium ions. These ionophores include macrocyclic polyethers with dinaphthyl subunits and azocrown ether with nitrogen donor atoms. The feasibility of these ionophores for preparing primary amine drug selective electrodes was investigated in detail. Practically usable PVC membrane electrodes sensitive to primary amine drugs, such as mexiletine, dopamine, metaraminol and tryptamine, and aliphatic primary amines have been prepared with these ionophores as neutral carriers. Direct potentiometric methods for assaying these drugs have been proposed by using the prepared electrodes. The proposed primary amine drug selective electrodes are remarkably superior to those based on ion-associates. Compared with the electrodes based on common ethers, the interference by K~+, Na~+ and NH_4~+ ions is subst     

不同助剂的硫化MoO3／ZrO2催化剂上CO加氢合成低碳混合醇的反应性能

研究了碱金属离子（Li^ 、Na^ 、K^ 、Cs^ ）和碱土金属离子（Ca^2 、Sr^2 、Ba^2 ）为助剂的硫化MoO3/ZrO2催化剂上CO加氢合成低碳混合醇的反应性。碱金属离子（Li^ ,K^ )、特别是钾离子为助剂的催化剂比之碱土金属离子助剂具有 更好的合成低碳醇的活性和选择性。从一系列的实验和分析发现，硫化K－MoO3/ZrO2的合 成低碳醇的活性和选择性强烈依赖于钾助剂的含量和反应条件。合理 选择 最佳K／Mo比（－0.5原子比）、反应压力、温度和空速可以获得较好的合成醇活性和选择性。     

新型手性双核Salen锰（III）配合物对咪唑、吡啶类客体的分子识别研究

合成并表征了新型手性双核Salen配体1及其锰（III）配合物2（主体2）。用 紫外-可见光谱滴定法研究了主体2与四种咪唑类、四种吡啶类客体在CHCl_3中的分 子识别行为。实验结果表明：对咪唑客体的缔合常数按K（Im） > K (2 - Melm) > K (N-MeIm) > K (EtMelm)顺序递减；吡啶类顺序为K （PyO） > K (4-PhPyO) > K (DMAP) > K(Py)，配位数n值均为2。测定了识别过程的Δ_rH_m，Δ_rS_m， 发现此类反应为放热、熵减小的过程，反应体系中存在焓熵补偿关系。与单核的 Salen锰（III）配合物3（主体3）进行比较，除EtMeIm与3的配位数为1外，其他唑 类客全的配位数均为2。就与客体的缔合能力而言，主体2比3大。用圆二色光谱（ CD）研究了主-客体的分子识别行为。     

Distinct Role of Mono-2-ethylhexyl Phthalate in Neuronal Transmission in Rat CA3 Hippocampal Neurons: Involvement of Ion Channels

Mono-(2-ethylhexyl) phthalate (MEHP) is one of the main active metabolites of di-(2-ethylhexyl) phthalate (DEHP). In our previous works, by using rat and Drosophila models, we showed a disruption of neural function due to DEHP. However, the exact neural effects of MEHP are still unclear. To explore the effects of MEHP on the central nervous system, the electrophysiological properties of spontaneous action potential (sAP), mini-excitatory postsynaptic currents (mEPSCs), ion channels, including Na⁺, Ca²⁺, and K⁺ channels from rat CA3 hippocampal neurons area were assessed. Our data showed that MEHP (at the concentrations of 100 or 300 μM) decreased the amplitude of sAP and the frequency of mEPSCs. Additionally, MEHP (100 or 300 μM) significantly reduced the peak current density of Ca²⁺ channels, whereas only the concentration of 300 μM decreased the peak current density of Na⁺ and K⁺ channels. Therefore, our results indicate that exposure to MEHP could affect the neuronal excitability and synaptic plasticity of rat CA3 hippocampal neurons by inhibiting ion channels’ activity, implying the distinct role of MEHP in neural transmission.     

H2O-C2H5OH-MX(NaCl等)体系中离子缔合和活度

用桥式电路测定了H_2O-C_2H_5OH-NaCl体系的摩尔电导, 并用Lee-Wheaton模型回归出H_2O-C_2H_5OH-NaCl(KCl、CsCl、KBr)体系的离子缔合常数、极限摩尔电导和距离参数, 并求出缔合反应标准自由焓。结果表明离子缔合能力的顺序为Cs~+>K~+>Na~+, Cl~->Br~-, 此四种盐在乙醇中都形成溶剂分开型离子对。并用液上空间气相色谱法测定了水-乙醇-(NaCl、KCl、KBr)体系中溶剂的活度, 用改进的Pitzer-Li公式计算了此体系的活度系数, 计算时考虑了盐在低介电常数溶剂中的离子缔合, 结果表明这种处理是合适的。还表明离子缔合程度随着乙醇浓度上升而加大, 以及盐的存在对水呈盐溶效应而对乙醇呈盐析效应。     

Improving precision for laser solid sampling for ICP emission with an array spectrometer

An Excimer laser operating at the wavelength of 308 nm has been used to ablate soil for bulk analysis. The ablated material has been transferred to an array ICP emission spectrometer. In order to avoid a degraded reproducibility due to imhomogeneity, repetitive firings along a sampling line have been done at a firing frequency of 3 Hz. Effects of line length, read delay and internal standardization have been studied.     

Improving precision for laser solid sampling for ICP emission with an array spectrometer

An Excimer laser operating at the wavelength of 308 nm has been used to ablate soil for bulk analysis. The ablated material has been transferred to an array ICP emission spectrometer. In order to avoid a degraded reproducibility due to imhomogeneity, repetitive firings along a sampling line have been done at a firing frequency of 3 Hz. Effects of line length, read delay and internal standardization have been studied.     

加压下煤的着火特性的研究 Ⅱ.煤及煤焦性质的影响

在加压条件下,研究了煤化程度、煤的岩相成分、煤焦及其制备方法、添加催化剂等与着火特性的关系。随煤化程度增加,煤的着火点和燃烧时间随之增加。所研究煤中镜质组的着火点高于丝质组的,而快速成焦后丝质组焦的着火点高于镜质组的。快速干馏焦的着火点显著地低于慢速干馏焦的,且煤焦着火温度随干馏温度增加而下降。在无烟煤及煤焦中添加催化剂K,Na碳酸盐后,可使着火点下降。