Memory

Our understanding of the cellular and molecular mechanisms underlying learning and memory formation derives from studies of species as diverse as worms, mollusks, insects, birds and mammals. Despite the quite different brain structures and neuronal networks, the studies support the current notion that neuronal activity leads to changes in synaptic connections as the neural substrate of behavioral plasticity. The analysis of the mechanisms underlying learning and memory formation reveals a surprisingly high conservation between invertebrates and mammals, both at the behavioral as well as the molecular level. This special issue provides an overview of the current knowledge on cellular and molecular processes underlying memory formation. The contributing reviews summarize the findings in different organisms, such as Aplysia, Drosophila, honeybees and mammals, and discuss new approaches, developments and hypotheses all aimed at understanding how the nervous system acquires, stores and retrieves information.     

Role of ethylene signaling in the production of rice volatiles induced by the rice brown planthopper Nilaparvata lugens

In response to herbivory, plants release volatiles to attract the natural enemies of herbivores[1,2]. This phe- nomenon has been reported in more than 23 plant spe- cies[3―6], and several field studies have shown that these herbivore-induced volatiles en…     

一种基于IP的超微蜂窝系统传输控制协议

提出一种基于IP的超微蜂窝系统中BSSMAP(BSS Mobile Application Part)信令和话音的传输控制协议———BSTP(BSSMAP Simplified Transport Protocol).采用基于BSTP的传输系统,可以实现在无路由、交换式IP网络上简便、高效地传输话音业务.相对于传统SS7系统的SC-CP(Signaling Connection Control Part)和IP电话系统的RTP(Real-time Transport Protocol),BSTP协议更易于实现,并可在保证性能的前提下极大地降低系统成本.仿真分析和实际系统的话音业务试验结果均表明,BSTP协议及其传输架构是有效可行的.     

纵向型企业集团R&D决策的两阶段信号博弈模型

为了研究动态环境下企业集团的最优 R& D战略 ,建立了一个基于熊彼特的创造性毁灭过程的纵向型集团两阶段 R& D决策的信号博弈模型 .该模型是一个综合的内生增长模型 ,综合了新增长理论中基于资本和基于思想的两类模型 .经过分析 ,给出了集团成员企业的最优 R& D和资本投资战略 .从模型可以推得 ,上游企业的创新大小越大 ,下游企业的最优创新大小越小 ;第 1阶段的创新大小越大 ,第 2阶段的最优创新大小越小     

通过改变代谢途径选育赖氨酸生产菌株

经化学诱变,通过改变谷氨酸棒杆菌B1代谢途径,筛选出以甘油、丙酮酸和高丝氨酸为碳源的营养缺陷型,该突变菌株B10的产酸率和转化率分别比出发菌株高18.097%和15.56%.     

柑橘香橙素生成途径关键酶黄烷酮-3-羟化酶特性分析及原核表达

香橙素是柑橘类黄酮的重要组成,黄烷酮-3-羟化酶是香橙素生成途径中的关键作用酶。对黄烷酮-3-羟化酶的特点进行总结与分析并在大肠杆菌中进行表达。首先从NCBI数据库筛选了来自柑橘、陆地棉、玉米、水母雪莲和欧芹的5种f3h,对其进行理化性质、蛋白质二三级结构、序列比对等生物信息学分析并以大肠杆菌为宿主进行表达。发现5种来源的f3h,其基因开放阅读框为1032~1119bp,编码343~372个氨基酸,蛋白分子质量为38.89~41.45kDa,理论等电点在5.43~5.96,且不同物种F3H的理化性质、结构域和蛋白质结构也有一定的相似性。通过构建大肠杆菌表达体系发现:黄烷酮-3-羟化酶均能进行原核表达,除去来源于水母雪莲的F3H未检测到香橙素的生成,其余4种F3H均能将柚皮素转化为香橙素且产物生成量不同,其中ZmF3H生成量最高达20.12mg/L。     

CDMA网络Abis接口信令解码方案设计

为实现码分多址(code division multiple access,CDMA)网络Abis接口的信令监测,分析了Abis接口协议栈,阐述了信令信道和业务信道上消息的透传方式,提出了Abis接口信令解码方案。基于Abis接口业务信道承载层3信令这一特性,给出了业务信道上识别信令数据的方法,同时采用遍历法完成信息元素的解码,以此实现消息在信令监测平台的回放,为设计详细呼叫记录(call detail record,CDR)合成、出表、统计等功能模块奠定基础。经现网测试,验证了该解码方案的正确性与可行性,有效解决了CDMA网络Abis接口不同信道上各类消息的解码。     

Amelogenin gene splice products: potential signaling molecules

The amelogenins, the major proteins of the developing tooth enamel matrix, are highly conserved throughout most species studied. The gene structure is similar, with a set of seven exons and intervening introns, and remarkable conservation of particular exon sizes over divergent species. Studies of exon skipping and consequent alternative gene splicing suggest that, in vertebrates, exon definition is crucial. In this mechanism, exon size is important. If too small, an exon can be readily skipped, if too large, internal cryptic splice sites may be utilized. Other factors, such as intron length and specific nucleotide sequences at the splice boundaries also modulate splicing efficiency, but amelogenin gene splicing conforms well to the generalized exon length model. Exons 1, 2 and 7 are not subject to splicing that affects the secreted protein product, but exons 3, 4 and 5 are at the lower boundary of exon size, rendering them, 4 and 5 especially, subject to skipping. On the other hand, exon 6 is very long and has cryptic splicing sites that can be used. In the mouse, nine distinct splice product proteins have been detected. The question now is the functions of these products. The larger forms, those that contain the intact proline-rich, hydrophobic exon 6 domains, are important for enamel mineralization. Recent work suggests that the small proteins resulting from deletion of a major part of amelogenin gene exon 6 via utilization of a cryptic site may have signal transduction functions during tooth development. Furthermore, new work also suggests that odontoblasts transiently express the small amelogenins during the period that epithelial-mesenchymal signaling between preodontoblasts and preameloblasts determines the course of tooth development. The same peptides have been demonstrated to act on non-odontogenic cells and effect their phenotypic expression patterns in vitro, and to induce bone formation in implants in vivo. Received 20 March 2002; received after revision 2 July 2002; accepted 3 July 2002     

The odd couple: signal transduction and endocytosis

Cell surface receptors are used to transmit extracellular information. The activation of cell surface receptors initiates signal transduction and receptor endocytosis. Signal transduction and the endosomal transport of activated receptors require precise regulation. New concepts for the integration of endocytosis and signaling arise from recent findings that suggest bidirectional interplay of these two processes. This review discusses the following questions: (i) do activated cell surface receptors modify the endosomal system to promote internalization and endosomal traffic, and (ii) do internalized cell surface receptors use specifically localized signaling complexes to generate specific biological signals?