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901.
Antigen-dependent increase in cytosolic free calcium in specific human T-lymphocyte clones 总被引:2,自引:0,他引:2
Calcium has been implicated as an intracellular messenger in the cellular response to various external stimuli. Exposure of lymphocytes to various mitogens and lectins results in rapid transmembrane calcium fluxes and increased cytoplasmic calcium concentrations ([Ca2+]i). It is not clear, however, whether the mechanisms by which these non-physiological stimuli activate cells are related to those involved in antigen-specific activation. We have now used antigen-specific T-cell clones to study changes in [Ca2+]i associated with specific activation and show here that these cells respond specifically in the presence of antigen and antigen-presenting cells (APC) with increased [Ca2+]i and that this increased [Ca2+]i shows the same genetic restrictions as are seen in the proliferation assay. The kinetics of the [Ca2+]i response to antigen indicate that antigen undergoes a time-dependent processing step as a prerequisite for recognition by T cells, as has been shown for T-cell proliferative responses, but that the [Ca2+]i response to processed antigen is extremely rapid. The close correlation between changes in [Ca2+]i and cell activation resulting in proliferation suggests that Ca2+ may act as an intracellular messenger in antigen-specific responses. 相似文献
902.
研究了一种用于发动机混合支承的智能控制的在频域内设计一线性多变量控制的方法。该设计使用了优化控制理论。对典型的四缸四冲程发动机的干扰力和力矩进行了分析并将其用于优化控制系统。对未使用和使用控制器的结果进行比较后表明 ,发动机混合支承系统在很大的频率范围内可以减小发动机的振动 相似文献
903.
A genomic view of alternative splicing. 总被引:55,自引:0,他引:55
Recent genome-wide analyses of alternative splicing indicate that 40-60% of human genes have alternative splice forms, suggesting that alternative splicing is one of the most significant components of the functional complexity of the human genome. Here we review these recent results from bioinformatics studies, assess their reliability and consider the impact of alternative splicing on biological functions. Although the 'big picture' of alternative splicing that is emerging from genomics is exciting, there are many challenges. High-throughput experimental verification of alternative splice forms, functional characterization, and regulation of alternative splicing are key directions for research. We recommend a community-based effort to discover and characterize alternative splice forms comprehensively throughout the human genome. 相似文献
904.
Characterization and relative abundance of maxi-chloride channels in Epstein-Barr virus (EBV) producer: B95-8 cells 总被引:2,自引:0,他引:2
T. H. Yeh M. C. Tsai S. Y. Lee M. M. Hsu 《Cellular and molecular life sciences : CMLS》1996,52(8):818-826
Several Epstein-Barr virus (EBV)-transformed cell lines were used to investigate the pathogenesis of lymphoproliferative diseases and nasopharyngeal carcinoma. The studies focus on the events occurring inside the membrane. On only one occasion, the cell membrane of EBV-transformed B lymphocytes from a cystic fibrosis patient was found to express defective Cl channels (CFTR; Cystic Fibrosis Transmembrane conductance Regulator), as in the airway epithelial cell. No other type of channel in EBV-transformed cells has so far been investigated. In this study, the cell membrane of the B95-8 cell was examined by the patch-clamp technique and compared to the non-EBV-infected BJAB cell. The high conductance (300 pS) maxi-chloride (Cl) channel activity was the most frequently observed event in inside-out configurations. Under similar experimental conditions, we have found a significantly higher probability of detecting maxi-Cl channel activity on the cell membrane of B95-8 cells (69%) than on BJAB cells (27%), or as previously reported on resting murine B lymphocytes (38%) or intact human T lymphocytes (37%). The relative abundance of the maxi-Cl channel on B95-8 cells may be linked to EBV infection and/or secretory ability. 相似文献
905.
Seong Keon Lee 《Journal of Classification》2006,23(1):123-141
In many application fields, multivariate approaches that simultaneously consider the correlation between responses are needed.
The tree method can be extended to multivariate responses, such as repeated measure and longitudinal data, by modifying the
split function so as to accommodate multiple responses. Recently, researchers have constructed some decision trees for multiple
continuous longitudinal response and multiple binary responses using Mahalanobis distance and a generalized entropy index.
However, these methods have limitations according to the type of response, that is, those that are only continuous or binary.
In this paper, we will modify the tree for univariate response procedure and suggest a new tree-based method that can analyze
any type of multiple responses by using GEE (generalized estimating equations) techniques. To compare the performance of trees,
simulation studies on selection probability of true split variable will be shown. Finally, applications using epileptic seizure
data and WWW data are introduced. 相似文献
906.
采用不同的微波消解程序和不同混合酸消解近海沉积物标准参考物(GBW0 7314 ) ,用ICP -MS测定16种金属元素(Al,Ba ,Cd ,Co ,Cr,Cu ,Fe ,K ,Mn ,Mo ,Ni,Pb ,V ,Zn ,Ca和Mg)的含量.依据回收率,比较了消解程序、混合酸组成、用量对GBW0 7314的消解效果.结果表明,由6mLHNO3 - 2mLHF/2mLH2 O2 组成的混合酸对沉积物具有很好的消解能力,微波加热2 0min能迅速有效消解沉积物;除Al外,GBW 0 7314中各元素的测定值与推荐值相符 相似文献
907.
薄层色谱指纹图谱在丹参药材质量评价中的应用研究 总被引:4,自引:0,他引:4
利用薄层色谱(TLC)技术对中药材丹参的有效成分进行了指纹图谱分析.以不同等级的中江丹参和不同采收期的丹参、南丹参为分析对象,采用适宜的水溶性及脂溶性成分提取方法和TLC分析条件,可获得其相应的TLC图像及色谱图.通过对不同丹参药材的色谱图像的分析,结合化学计量学方法对其各主要指标成分的信息进行提取,初步构建了丹参的TLC指纹图谱.结果表明,在254nm波长下获取脂溶性和水溶性成分共7个共有指纹峰,各峰相对比移值(R1)和峰面积的相对标准偏差分别小于1.7%和4.0%.通过对薄层色谱斑点的RI值、斑点颜色和大小的比较。并进行主成分分析和聚类分析,实现了对不同等级的丹参进行归属,并确立了最佳采收期.本实验建立的薄层色谱指纹图谱方法具有较高的稳定性、良好的精密度和重现性,可用于丹参药材的质量评价和控制. 相似文献
908.
This paper presents FFT and PLL based GPS signal acquisition and tracking algorithms for a software GPS receiver. Conventional hardware based acquisition and tracking have some restrictions in processing signal with poor signal to noise ratio. The FFT of digitized local signals of multiple carrier frequencies for a specified Doppler band are pre-computed and are circular correlated with the digitized incoming signal from RF-front-end in an organized computational order. The global maximum of the correlation is associated with the closest estimates of the Doppler shift and the code shift. PLL refines the estimates to track the signal. Doppler information from an external source can readily be integrated to narrow down the frequency band for correlation and is especially useful for tracking in a high dynamic navigation situation. The performance of the proposed algorithms is evaluated through post processing of the IF signals acquired from a commercial hardware GPS receiver. 相似文献
909.
马立克氏病病毒meq基因功能研究 总被引:8,自引:0,他引:8
从马立克氏病病毒(MDV)不同致病型毒株meq基因序列,meq基因产物及其细胞内表达特性和meq蛋白生物学功能的研究探讨马立克氏病病毒致瘤基因meq功能。完成了648A,CV1988/Rispens,814,广西地方毒株G2,N,0093,0095,0297,0304共9个MDV毒株meq基因的序列测定。MDV不同致病型毒株的meq基因序列相对比较保守,它们相互间核苷酸和氨基酸序列的同源性均很高;与所有7个致瘤的MDV毒株相比,在2个MDV-1弱毒疫苗CV1988/Rispens株和814株发现有二个特征性位点突变。此外,还在其ORF中首次发现含15个氨基酸残基(EELCAQLCSTPPPPI)的2个重复和含6个氨基酸残基(PPICTP)的4个重复,全分布在MEQ蛋白C-端的转录激活域内。MEQ蛋白的表达仅局限于感染细胞的核内,而且随感染时间增加。具有从核质向核仁和核膜转移趋向;Western Blotting和免疫沉淀试验证实重组杆状病毒感染细胞裂解物中有大小约为60kD的特异带,利用表达的MEQ蛋白产物免疫BALB/c小鼠,获得的杂交瘤细胞被克隆并与MDV感染的鸡胚成纤维细胞(CEF)做免疫荧光试验(FA),获得4株稳定产生抗MEQ蛋白单克隆抗体(McAb)的杂交瘤细胞,其中3G12E6单克隆抗体能够检测到MDV致瘤株感染的CEF及自然MD肿瘤细胞中表达的meq基因产物,而CV1988/Rispens感染的细胞则未检测到,发现细胞内表达的meq基因产物可明显促进MDVGA株对体外培养细胞的感染及增殖。研究结果表明,meq基因在感染细胞内的表达水平是MDV增殖和致病,致瘤的分子基因。 相似文献
910.