Coordination of agonist-induced Ca2+-signalling patterns by NAADP in pancreatic acinar cells

Many hormones and neurotransmitters evoke Ca2+ release from intracellular stores, often triggering agonist-specific signatures of intracellular Ca2+ concentration. Inositol trisphosphate (InsP3) and cyclic adenosine 5'-diphosphate-ribose (cADPR) are established Ca2+-mobilizing messengers that activate Ca2+ release through intracellular InsP3 and ryanodine receptors, respectively. However, in pancreatic acinar cells, neither messenger can explain the complex pattern of Ca2+ signals triggered by the secretory hormone cholecystokinin (CCK). We show here that the Ca2+-mobilizing molecule nicotinic acid adenine dinucleotide phosphate (NAADP), an endogenous metabolite of beta-NADP, triggers a Ca2+ response that varies from short-lasting Ca2+ spikes to a complex mixture of short-lasting (1-2s) and long-lasting (0.2-1 min) Ca2+ spikes. Cells were significantly more sensitive to NAADP than to either cADPR or InsP3, whereas higher concentrations of NAADP selectively inactivated CCK-evoked Ca2+ signals in pancreatic acinar cells, indicating that NAADP may function as an intracellular messenger in mammalian cells.     

Chaperone-like activity of the AAA domain of the yeast Yme1 AAA protease

The AAA domain, a conserved Walker-type ATPase module, is a feature of members of the AAA family of proteins, which are involved in many cellular processes, including vesicular transport, organelle biogenesis, microtubule rearrangement and protein degradation. The function of the AAA domain, however, has not been explained. Membrane-anchored AAA proteases of prokaryotic and eukaryotic cells comprise a subfamily of AAA proteins that have metal-dependent peptidase activity and mediate the degradation of non-assembled membrane proteins. Inactivation of an orthologue of this protease family in humans causes neurodegeneration in hereditary spastic paraplegia. Here we investigate the AAA domain of the yeast protein Yme1, a subunit of the iota-AAA protease located in the inner membrane of mitochondria. We show that Yme1 senses the folding state of solvent-exposed domains and specifically degrades unfolded membrane proteins. Substrate recognition and binding are mediated by the amino-terminal region of the AAA domain. The purified AAA domain of Yme1 binds unfolded polypeptides and suppresses their aggregation. Our results indicate that the AAA domain of Ymel has a chaperone-like activity and suggest that the AAA domains of other AAA proteins may have a similar function.     

测井资料分析系统接口电路设计

从一种超声模拟测井记录的井下信号、深度信号送微机处理的实际要求出发，分析井下信号数据采集的工作原理，阐述了与１２位Ａ／Ｄ转换器实时配套工作的双存储体工作时序。通过对深度信号的解调，提出了一种解决４ＦＳＫ解调的有效方法。     

BP网络的抗干扰性研究及误差分析

从ＢＰ网络对信息存储的分布式特点出发，分析了连接权系数及输入变化对输出的影响，探讨了ＢＰ网络的容错性及抗干扰特性，得出了一些有益的结论。     

任意波形合成系统硬件设计

提出并分析了任意波形合成系统（ＡＷＳ）──一种高度智能化的计算机仪器的几种典型结构及其特点，着重讨论了ＰＣ总线式任意波形合成系统的系统组成及各部分硬件电路设计的关键技术     

Monoclonal antibodies to L-asparaginase

Five hybridomas secreting monoclonal antibody to E. coli L-asparaginase were isolated. These monoclonal antibodies were classified into 3 different subclasses; Ig G1 (1 clone), Ig G2 (2 clones) and Ig G3 (2 clones). One of them possessed anti-L-asparaginase neutralizing activity. Four antibodies examined demonstrated a linear Langmuir binding plot and binding affinities, with equilibrium dissociation constant (Kd) ranging between 2.5 X 10(-9) M and 6.3 X 10(-10) M. The monoclonal antibodies should be useful probes for investigation of the enzyme activity.