Negative chronotropic and inotropic effects exerted by diadenosine hexaphosphate (AP6A) via A1-adenosine receptors

1. Diadenosine hexaphosphate (AP6A) exerts vasoconstrictive effects. The purpose of this study was to investigate whether AP6A has any effect on cardiac function. 2. The effects of AP6A (0.1-100 microM) on cardiac contractility and frequency were studied in guinea-pig and human isolated cardiac preparations. Furthermore, the effects of AP6A on the amplitude of the L-type calcium current, on the adenosine 3':5'-cyclic monophosphate (cyclic AMP) content and on the phosphorylation of regulatory phosphoproteins, i.e. phospholamban and troponin inhibitor, were investigated in guinea-pig isolated ventricular myocytes. 3. In isolated spontaneously beating right atria of the guinea-pig AP6A exerted a negative chronotropic effect and reduced the rate of contraction maximally by 35% (IC20 = 35 microM). 4. In isolated electrically driven left atria of the guinea-pig AP6A exerted a negative inotropic effect and reduced force of contraction maximally by 23% (IC20 = 70 microM). 5. In isolated electrically driven papillary muscles of the guinea-pig AP6A alone was ineffective, but attenuated isoprenaline-stimulated force of contraction maximally by 23% (IC20 = 60 microM). Furthermore, AP6A attenuated the relaxant effect of isoprenaline. 6. In human isolated electrically driven ventricular preparations AP6A alone was ineffective, but attenuated isoprenaline-stimulated force of contraction by maximally 42% (IC20 = 18 microM). Moreover, AP6A attenuated the relaxant effect of isoprenaline. 7. All these effects of AP6A were abolished by the selective A1-adenosine receptor antagonist 1,3-dipropyl-cyclopentyl-xanthine (DPCPX, 0.3 microM), whereas the M-cholinoceptor antagonist atropine (10 microM) and the P2-purinoceptor antagonist suramin (300 microM) failed to abolish the effects of AP6A. 8. AP6A 100 microM had no effect on the amplitude of the L-type calcium current, but attenuated isoprenaline-stimulated L-type calcium current. The maximum of the current-voltage relationship (I-V curve) was shifted to the left by isoprenaline and additional application of AP6A shifted the I-V curve back to the right to the control value. The phosphorylation state of phospholamban and the troponin inhibitor was unchanged by AP6A alone, but was markedly attenuated by AP6A in the presence of isoprenaline. Cyclic AMP levels remained unchanged by AP6A, even after stimulation with isoprenaline. 9. In summary, AP6A exerts negative chronotropic and inotropic effects in guinea-pig and human cardiac preparations. These effects are mediated via A1-adenosine receptors as all effects were sensitive to the selective A1-adenosine receptor antagonist DPCPX. Furthermore, the effects of AP6A on cyclic AMP levels, protein phosphorylation and the L-type calcium current are in accordance with stimulation of A1-adenosine receptors.     

Unexpected return of spontaneous circulation after cessation of resuscitation (Lazarus phenomenon)

The heterocyclic amine 2-amino-1-methyl-6-phenylimidazo[4,5-beta]pyridine NPhIP) is a major dietary component in individuals eating cooked meats or fish. This heterocyclic amine requires biochemical activation, mainly through cytochrome P4501A2, and can be detoxified chiefly by 4'hydroxylation through other cytochromes, and be in turn converted through phase 2 enzymes to readily excreted conjugates. The active form of PhIP is mutagenic in Salmonella typhimurium TA98 and is a useful substrate to study the possible chemoprotective action of phytochemicals. We found that black and green tea depressed the mutagenicity of PhIP in dose-related fashion, and decaffeinated tea was less powerful an inhibitor. This led to the study of caffeine, that displayed effective dose-related inhibition of the mutagenicity of PhIP. Other antioxidants such as lycopene, the active antioxidant from tomatoes, and daidzein and genistein from soy products, also had a dose-related inhibition of the mutagenicity of PhIP. We conclude that PhIP is a good substrate found in several human foods to determine the protective effect of phytochemicals from vegetables, and beverages.     

浓缩~(235)U诱发免疫细胞凋亡的电镜和琼脂糖凝胶电泳研究

研究了浓缩235U内照射诱发人淋巴细胞白血病细胞株Molt－4细胞和巨噬细胞株Ana－1细胞的细胞调亡。估算了浓缩235U在不同阶段培养细胞中的辐射累积吸收剂量。通过电镜对免疫细胞的形态观察，发现Molt－4和Ana－1细胞在受235U内照射作用下可呈现核染质边聚，DNA链断裂和膜包裹的凋亡小体形成。对Molt－4和Ana－1细胞的DNA抽提，进行DNA琼脂糖凝胶电泳也显示出阶梯状条带形成的细胞调亡特征。从而证实了浓缩235U内照射可导致免疫细胞Molt－4和Ana－1细胞的凋亡发生。     

异步交叉轧制能耗特性研究

对异步交叉轧制的能耗特性进行了分析与实验验证.研究表明,随交叉角增大,轧制能耗下降,当交叉角(θ)增至临界值(θcr)时,能耗最小,交叉角θ＞θcr后,能耗基本不变;随异步比增大,能耗亦下降,当异步比(i)增至临界值(icr)时,能耗最小, i＞icr后,能耗则上升,且θ愈大, icr亦愈大.即当交叉角为θcr且异步比亦为icr时,异步交叉轧制综合能耗最小.     

基于小波分析的光纤陀螺信号处理

文章对光纤陀螺仪的实测信号进行了分析。为了抑制光纤陀螺随机噪声,利用五点三次平滑、数字滤波、小波变换分析法对光纤陀螺静态输出数据进行了滤波处理,通过对比滤波前后陀螺的输出曲线、标准差以及频谱图,可以发现:小波阈值滤波和五点三次平滑相结合的方法能够有效的补偿光纤陀螺的随机误差。     

基于COM＋技术的Web服务封装研究

早期的信息管理系统都是用于实现企业特定的业务功能而建立的,包括对企业生产、供应、销售以及客户服务等的控制和管理。企业按照职能部门建立了各种企业信息系统,这些信息管理系统被其所在部门所使用,并在实际的工作生产中发挥了巨大作用。该文从整体考虑各个企业信息管理系统,并根据具体业务的需求对这些系统进行统一编排,通过一个合适的集成平台把现有企业信息管理系统进行有机的整合起来,使各＂信息孤岛＂联系起来。     

DKNNS:面向延迟敏感型应用的可扩展精确分布式K近邻搜索算法研究

为了降低用户访问延迟,延迟敏感型网络应用需要选择合适的邻近服务节点响应用户访问请求.分布式K近邻搜索通过可扩展的选择距任意用户节点邻近的K个服务节点,可以有效满足网络应用延迟优化的目的.已有工作在精确度以及可扩展性等方面存在不足.针对可扩展精确的K近邻搜索问题,文中提出了分布式K近邻搜索方法DKNNS(distributed K nearest neighbor search).DKNNS将大量的服务节点组织为邻近性感知的多级环,通过最远节点搜索机制选择优化的K近邻搜索初始化节点,然后基于回退方式快速的在目标节点邻近区域发现K个近邻.基于理论分析,模拟测试以及真实环境下的部署实验发现,在不同规模的节点集合下,DKNNS算法能够确定近似最优的K个服务节点.且DKNNS的查询延迟,查询开销均显著低于Meridian算法.最后,DKNNS的返回结果相对于Meridian具有较高的稳定性.     

基于ADV7120的嵌入式VGA接口设计与实现

介绍了一种基于ADV7120的嵌入式VGA接V1设计与实现的方法,对扫描式TFT-LCD接口时序与VGA接口时序进行了分析对比,利用S3C2440A的LCD控制器和高性能视频D／A芯片ADV7120将扫描式TFT-LCD接口转换成VGA接口,给出了转换电路原理图和LCD控制寄存器的配置方法。实验结果表明：采用这种方法可以正确输出VGA同步信号和图像数据信号,VGA显示器图像清晰稳定,满足系统要求。     

一种从组织业务数据中获取软件需求的方法

针对隐藏于组织业务海量数据中的隐性软件需求获取提出一种方法。该方法的基本思想是：组织业务海量数据中隐含软件需求,它是以隐性知识形式存在于海量数据中的,隐性知识利用的解决方案就是组织及利益相关者对待开发软件系统的要求（软件需求）。首先,构建一个完整的、无冲突的、正确的待开发软件系统目标及其关系模型,并在待开发系统目标指导下,利用数据挖掘技术对数据进行挖掘,从中发现隐性知识;然后,识别知识的有用性和可用性;最后为可用性知识的利用提供解决方案。进而获取隐藏于大量数据中的隐性软件需求．     

8位模型计算机自动测试系统的设计与实现

描述基于MCS-51的自动测试系统的设计,实现对8位模型计算机的自动测试过程。对8位模型计算机的测试流程进行详细分析,绘出模型机的存储器模块、运算器模块和控制器模块的测试流程图,编写各模块的C语言测试程序。通过大量实验。完成时8位模型计算机的自动测试,整机测试执行时间不超过10秒钟。