Mechanical and biochemical characterization of the contraction elicited by a calcium-independent myosin light chain kinase in chemically skinned smooth muscle

Summary The contraction induced by a Ca²⁺-independent myosin light chain kinase (MLCK-) was characterized in terms of isometric force (F_o), immediate elastic recoil (SE), unloaded shortening velocity (V_us), shortening under a constant load and ATPase activity of chemically skinned smooth muscle preparations. These parameters were compared to those measured in a Ca²⁺-induced contraction to assess the nature of cross bridge interaction in the MLCK-induced contraction. F_o developed in chicken gizzard fibers as well as SE were similar in contractions elicited by either agent. V_us in the contraction induced by MLCK-(0.36 mg/ml) was similar though averaged 39.3±8.9% less than V_us induced by Ca²⁺ (1.6x10^–6M) in the control fibers. Addition of Ca²⁺ (1.6x10^–6M) to a contraction induced by MLCK-resulted in small increases in both F_o and V_us. Shortening under a constant load was similar for both types of contractions. The contraction induced by MLCK-was accompanied by an increased rate of ATP hydrolysis. The MLCK-induced contraction is thus kinetically similar though not identical to a contraction induced by Ca²⁺. We conclude that with respect to actin-myosin interaction, MLCK- and Ca²⁺-induced contractions are similar.     

Molecular mechanisms in therapy of acid-related diseases

Inhibition of gastric acid secretion is the mainstay of the treatment of gastroesophageal reflux disease and peptic ulceration; therapies to inhibit acid are among the best-selling drugs worldwide. Highly effective agents targeting the histamine H2 receptor were first identified in the 1970s. These were followed by the development of irreversible inhibitors of the parietal cell hydrogen-potassium ATPase (the proton pump inhibitors) that inhibit acid secretion much more effectively. Reviewed here are the chemistry, biological targets and pharmacology of these drugs, with reference to their current and evolving clinical utilities. Future directions in the development of acid inhibitory drugs include modifications of current agents and the emergence of a novel class of agents, the acid pump antagonists. Received 30 May 2007; received after revision 15 August 2007; accepted 13 September 2007     

The plasma membrane calcium pump: Recent developments and future perspectives

The Ca²⁺ pump of the plasma membrane (PMCA) is regulated by a number of agents. The most important is calmodulin (CaM), which binds to a domain located in the C-terminal portion of the pump, removing it from an autoinhibitory site next to the active site. The CaM-binding domain is preceded by an acidic sequence which contains a hidden signal for endoplasmic reticulum (ER) retention. Chimeras of the PMCA and endoplasmic reticulum (SERCA) pumps have revealed the presence of a strong signal for ER retention in the first 45 residues of the SERCA pump. Four gene products of the PMCA pump are known: two of them (1 and 4) are ubiquitously expressed, two (2 and 3) are specific for nerve cells and may be induced by their activation. Mutagenesis work has identified four residues in three of the transmembrane domains of the pump which may be components of the trans-protein Ca²⁺ path. The mutation of two of these residues alters the membrane targeting of the pump.     

铜胁迫对甜菜幼苗生长和光合特性的影响

以甜菜品种KWS3418为实验材料,研究了铜胁迫对甜菜幼苗生长及光合作用特性的影响．结果表明：当Cu2＋≤250μmol·L-1时,甜菜幼苗生长良好,与对照（0．3μmol·L-1）相比,各生长指标没有显著差异．但是,随着Cu2＋浓度的增加（Cu2＋〉250μmol·L-1）,甜菜幼苗生长受到显著抑制,其单株干、鲜重和叶面积均显著下降．Cu2＋为250μmol·L-1时,净光合速率（pn）、气孔导度（Gs）与叶绿索含量显著低于对照组,随着Cu2＋浓度的增加,净光合速率（Pn）、气孔导度（Gs）与叶绿素含量急剧下降．这些结果表明,甜菜有一定的耐铜性,但是高铜处理可能通过引起叶绿素含量和气孔导度下降来抑制光合作用进而抑制生长．     

CseNaYC16：Sm3＋晶体的光学与磁学性质研究

掺杂三价稀土离子（Re3＋的Cs3NaYC16晶体,因具有优良的光学和磁学性质而得到了高度的重视。本文利用晶体场理论和自旋哈密顿理论分别对Cs2NaYCl6：Sm3＋晶体的光谱和电子顺磁共振谱（EPR）进行分析和计算。在叠加模型的基础上,通过对角化24x24能量矩阵研究cs2NaYCl6：Sm3＋时的能级、电子顺磁共振参数和超精细结构常数。计算结果与观测值能够较好的吻合并对结果进行讨论。     

基于Winsock的局域网聊天系统的设计与实现

设计并实现了一种基于Socket的局域网聊天系统.利用Winsock编程技术,使用底层的API函数实现Winsock平台的即时通信接口,开发了多线程局域网聊天系统.基于Winsock的局域网聊天系统的实现无需对企业原有的局域网硬件进行任何改动,且实现成本低,为原有的局域网提供一种良好、安全、快速的通信机制.     

新型杯[5]芳烃衍生物的合成及发光行为

本文合成了一种新型杯[5]芳烃衍生物5,11,17,23,29-五叔丁基-37,38,39,40,41-五羧甲氧基杯[5]芳烃,通过荧光光谱研究了其与铽（Ⅲ）离子形成1：1配合物的发光行为.结果表明,配合物的发光行为基于分子间能量转移,pH=8～10范围内荧光强度几乎没有变化,溶剂极性明显影响荧光的强度;通过紫外滴定和荧光滴定确定了体系的稳定常数.该主体化合物、铕（Ⅲ）离子和邻菲罗琳在无水乙腈中,于321nm激发波长下检测到铕（Ⅲ）的特征荧光.     

关于否定“3n＋1”猜想的一个证明

按照“3n＋l”法则,利用“4m＋3”迭代,提出了一个构建一个无限单调增值序列的方法,从而否定了“3n＋1”猜想。     

基于MapX的分层路网拓扑结构的构建方法

最优路径规划是车载导航系统最主要的功能之一,而实现这一功能的关键在于构建道路网络的拓扑结构.针对这一问题,首先利用MapInfo对道路网络进行分层处理,添加道路的等级、方向等与导航密切相关的属性信息;再通过MapX控件及其基本分析函数,在Visual C++6.0平台上完成道路网络的预处理;最后按层次提取道路的交叉口、路段的拓扑信息和属性信息,并自动存储于Access数据库中,以便供最优路径规划计算所用.实验结果表明,经过分层抽象处理之后,重建的高层路网数据规模骤减,这为路径规划的实时性提供了良好的基础.     

LaP04：Eu3＋^纳米晶的溶剂热合成及下转换荧光性质研究

采用溶剂热法,在乙醇和乙二醇的混合溶剂中,pH=8．5条件,150℃,反应12h,一步合成了LaPO4Eu3＋^晶体．室温下,用x射线衍射对材料的组成进行了表征,XRD数据表明,成功合成了LaPO4Eu^3＋^晶体．荧光光谱分析表明,在352nm紫外光激发下,其发射峰在531nm、640nm,分别对应着Eu^3＋的。Do3＋^→VF^3＋和5^D0→7^F3能级跃迁．并讨论了离子La3＋^：Eu3＋^不同浓度掺杂比对荧光性质的影响,结果表明,Eu3＋^的最佳掺杂浓度比为10％．