CRISPR/Cas13b系统对猪流行性腹泻病毒增殖的抑制作用

【目的】猪流行性腹泻是由猪流行性腹泻病毒(Porcine epidemic diarrhea virus,PEDV)引起的一种对养猪业造成巨大损失的高致死率的传染性疫病。CRISPR/Cas13b系统精准切割和编辑RNA的功能提供了一种靶向抑制RNA病毒的策略。本研究尝试利用CRISPR/Cas13b的RNA干扰功能对PEDV的基因组RNA进行切割,以探索一种新型的PEDV病毒抑制策略。【方法】设计了4对靶向PEDV基因组不同区域的CRISPR RNA(crRNA)位点,构建了CRISPR/Cas13b打靶载体,以打靶载体转染Vero细胞,并利用PEDV感染转染细胞,检测PEDV在CRISPR/Cas13b转染细胞内的增殖情况。【结果】CRISPR/Cas13b系统对PEDV在Vero细胞的增殖具有明显的抑制作用。打靶载体U6-crRNA3和U6-crRNA4转染组相较于正常细胞组,病毒免疫荧光试验中荧光团明显减少;定量PCR结果显示,打靶载体转染组在细胞水平抑制50%以上病毒增殖量。【结论】本研究构建的CRISPR/Cas13b系统能有效抑制PEDV增殖,为开发有效的RNA病毒防控手段、建立抗病动物模型提供了新的研究策略。     

Noise propagation in gene networks

Accurately predicting noise propagation in gene networks is crucial for understanding signal fidelity in natural networks and designing noise-tolerant gene circuits. To quantify how noise propagates through gene networks, we measured expression correlations between genes in single cells. We found that noise in a gene was determined by its intrinsic fluctuations, transmitted noise from upstream genes, and global noise affecting all genes. A model was developed that explains the complex behavior exhibited by the correlations and reveals the dominant noise sources. The model successfully predicts the correlations as the network is systematically perturbed. This approach provides a step toward understanding and manipulating noise propagation in more complex gene networks.     

PAMELA measurements of cosmic-ray proton and helium spectra

Protons and helium nuclei are the most abundant components of the cosmic radiation. Precise measurements of their fluxes are needed to understand the acceleration and subsequent propagation of cosmic rays in our Galaxy. We report precision measurements of the proton and helium spectra in the rigidity range 1 gigavolt to 1.2 teravolts performed by the satellite-borne experiment PAMELA (payload for antimatter matter exploration and light-nuclei astrophysics). We find that the spectral shapes of these two species are different and cannot be described well by a single power law. These data challenge the current paradigm of cosmic-ray acceleration in supernova remnants followed by diffusive propagation in the Galaxy. More complex processes of acceleration and propagation of cosmic rays are required to explain the spectral structures observed in our data.     

基于复杂网络的风险传播模型及有效算法

提出一种基于复杂网络的风险传播模型及有效算法，通过结合复杂网络中传播蔓延现象的推广模型，将风险传播模型划分为两种：主动型风险传播模型与被动型风险传播模型。并对已有风险传播算法进行改进，实验表明，该模型及算法能健全风险传播机制，提高传播速度与精确度。     

Structural heterogeneity and functional domains of murine immunoglobulin G Fc receptors

Binding of antibodies to effector cells by way of receptors to their constant regions (Fc receptors) is central to the pathway that leads to clearance of antigens by the immune system. The structure and function of this important class of receptors on immune cells is addressed through the molecular characterization of Fc receptors (FcR) specific for the murine immunoglobulin G isotype. Structural diversity is encoded by two genes that by alternative splicing result in expression of molecules with highly conserved extracellular domains and different transmembrane and intracytoplasmic domains. The proteins encoded by these genes are members of the immunoglobulin supergene family, most homologous to the major histocompatibility complex molecule E beta. Functional reconstitution of ligand binding by transfection of individual FcR genes demonstrates that the requirements for ligand binding are encoded in a single gene. These studies demonstrate the molecular basis for the functional heterogeneity of FcR's, accounting for the possible transduction of different signals in response to a single ligand.     

Subunit communication in the anthranilate synthase complex from Salmonella typhimurium

The anthranilate synthase-phosphoribosyl transferase complex of the tryptophan biosynthetic pathway in Salmonella typhimurium is an allosteric, heterotetrameric (TrpE2-TrpD2) enzyme whose multiple activities are negatively feedback-regulated by L-tryptophan. A hybrid complex containing one catalytically active, feedback-insensitive and one catalytically inactive, feedback-sensitive mutant TrpE subunit was assembled in vitro and used to investigate communication between regulatory and catalytic sites located on different subunits. The properties of the hybrid complex demonstrate that the binding of a single inhibitor molecule to one TrpE subunit is sufficient for the propagation of a conformational change that affects the active site of the companion subunit.     

Complex multicolor tilings and critical phenomena in tetraphilic liquid crystals

T-shaped molecules with a rod-like aromatic core and a flexible side chain form liquid crystal honeycombs with aromatic cell walls and a cell interior filled with the side chains. Here, we show how the addition of a second chain, incompatible with the first (X-shaped molecules), can form honeycombs with highly complex tiling patterns, with cells of up to five different compositions ("colors") and polygonal shapes. The complexity is caused by the inability of the side chains to separate cleanly because of geometric frustration. Furthermore, a thermoreversible transition was observed between a multicolor (phase-separated) and a single-color (mixed) honeycomb phase. This is analogous to the Curie transition in simple and frustrated ferro- and antiferromagnets; here spin flips are replaced by 180° reorientations of the molecules.     

某些培养条件对甘蓝夜蛾核型多角体病毒离体增殖的影响

不同培养条件对甘蓝夜蛾核型多角体病毒 （ Ｍｂ Ｎ Ｐ Ｖ） 在同源寄主细胞系 Ｍｂ９３１１０４ 中增殖的研究。结果表明, 培养基种类、细胞密度和细胞龄期影响 Ｍ ｂ Ｎ Ｐ Ｖ 在细胞系中的增殖, 引起细胞感染率和多角体产量显著的差异。使用 Ｔ Ｃ—１００ 昆虫组织培养基, 细胞密度为３×１０５ｃｅｌｌｓ／ｍ Ｌ的对数生长期的细胞接毒最适于 Ｍ ｂ Ｎ Ｐ Ｖ 的增殖, 条件培养基对该病毒在细胞系中的增殖没有显著影响。     

光照和温度对蓝莓组织培养快速繁殖的影响

[目的]筛选出几个主要蓝莓品种的最佳培养条件.[方法]研究了光照和温度对5个蓝莓品种快速增殖的影响.[结果]较低的温度和光强有利于蓝丰品种的快速增殖;较高的温度和光强有利于埃利奥特的快速增殖;低温和常光强有利于布里吉塔的快速增殖;常温和常光强有利于力格西的快速增殖;高温和常光强有利于密斯蒂的快速增殖.[结论]温度和光强对蓝莓组织培养快速繁殖有很大影响,不同蓝莓品种所需的最佳培养温度和光强也不尽相同,所以应根据不同品种设置不同的培养条件.     

压力容器内外壁轴向双裂纹相互作用

压力容器在制造过程、疲劳与复杂应力状态下会产生裂纹,这些裂纹的存在将影响到容器的安全使用,有必要对容器内外壁同时存在轴向双内外裂纹相互作用对应力强度因子的影响进行深入研究。利用ANSYS、FRANC 3D有限元软件建立含内外壁轴向裂纹的柱形压力容器模型,分析不同裂纹深长比的内外裂纹在静、动态下的相互作用对应力强度因子的影响,拟合得到不同裂纹深长比下名义应力强度因子的变化曲线,发现裂纹相互作用对深长比小的初始裂纹的扩展有促进作用,而对深长比大的初始裂纹的扩展则有抑制作用。研究结果对于不同深长比多裂纹相互作用下的裂纹扩展机理及多裂纹断裂失效评定问题的研究具有借鉴作用。     

URF6, last unidentified reading frame of human mtDNA, codes for an NADH dehydrogenase subunit

The polypeptide encoded in URF6, the last unassigned reading frame of human mitochondrial DNA, has been identified with antibodies to peptides predicted from the DNA sequence. Antibodies prepared against highly purified respiratory chain NADH dehydrogenase from beef heart or against the cytoplasmically synthesized 49-kilodalton iron-sulfur subunit isolated from this enzyme complex, when added to a deoxycholate or a Triton X-100 mitochondrial lysate of HeLa cells, specifically precipitated the URF6 product together with the six other URF products previously identified as subunits of NADH dehydrogenase. These results strongly point to the URF6 product as being another subunit of this enzyme complex. Thus, almost 60% of the protein coding capacity of mammalian mitochondrial DNA is utilized for the assembly of the first enzyme complex of the respiratory chain. The absence of such information in yeast mitochondrial DNA dramatizes the variability in gene content of different mitochondrial genomes.     

无土基质立体栽培条件下半夏生物量分配格局

在大棚内3层4组立体设施条件下,分上、中、下各层次随机设置无土基质:沙 沙、谷壳 沙、树叶 沙、锯末 沙4种处理.研究不同基质对半夏(Pinellia ternate)各器官生物量分配的影响,探讨半夏总生物量在无性繁殖、有性生殖及营养器官中的分配规律.结果表明,不同基质中,设施上层沙 沙基质中根的生物量最高;谷壳 沙基质是半夏块茎生长较适宜的基质;树叶 沙基质不利于半夏块茎生物量的积累,却有利于珠芽形成及叶片的生长;花序的生物量只是在设施中层谷壳 沙基质中较高;不同基质对总生物量的影响与对块茎生物量的影响表现基本一致.单株半夏总生物量用于无性繁殖(块茎、珠芽)的生物量投入比例在设施下层锯末 沙基质中最高;树叶 沙基质中的有性生殖投入比例与其它基质比较,其生殖分配相对较高;用于总繁殖(无性繁殖、有性繁殖)的投入比例在锯末 沙基质中排序第一;在树叶 沙基质中,与同一层次的其它基质相比较,用于营养器官(根、叶)的生物量投入比例都处于最高水平.     

兜兰属植物繁殖生物学研究进展

兜兰属植物为兰科植物的珍品,具有极高的观赏价值。由于人为破坏,许多兜兰种濒临灭绝。近年来,兜兰的保育学研究兴起,特别是兜兰的大规模扩繁研究,为兜兰属植物的保护提供了理论指导。从兜兰属植物的分株繁殖、组织培养、有菌播种以及无菌播种4个方面综述了兜兰的繁殖生物学研究进展。     

Cell migration: integrating signals from front to back

Cell migration is a highly integrated multistep process that orchestrates embryonic morphogenesis; contributes to tissue repair and regeneration; and drives disease progression in cancer, mental retardation, atherosclerosis, and arthritis. The migrating cell is highly polarized with complex regulatory pathways that spatially and temporally integrate its component processes. This review describes the mechanisms underlying the major steps of migration and the signaling pathways that regulate them, and outlines recent advances investigating the nature of polarity in migrating cells and the pathways that establish it.     

基于BP神经网络的竹林遥感监测研究

竹林信息提取对利用遥感技术估算竹林碳储量至关重要,高精度地提取竹林信息将有利于降低碳储量估算误差。借助Matlab神经网络模块．采用BP神经网络（back propagation neural network）对ETM＋（enhanced themativ mapper plus）遥感影像提取竹林信息,得到了较高的精度,生产精度和用户精度分别为84．04％和98．75％;同时比较了Levenberg-Marquardt BP算法函数（Trainlm）、自适应学习率BP的梯度递减函数（Traingda）和梯度下降动量BP算法函数（Traingdm）等3种训练函数在分类中的差异。分析表明,Traingda算法函数分类精度最高,而Trainlm算法函数的训练时间最短。     

甘薯脱毒试管苗高效快繁体系研究

选择具有不同蔓长特性的铁丝藤、海白、北京553等6个甘薯品种试管脱毒苗为材料,切段后分别接种在添加IAA、NAA、GA3、NAA/KT和NAA/6-BA不同处理的MS培养基和无激素的不同无机盐浓度MS培养基上,研究试管苗快繁技术.试验结果表明:不同蔓长特性甘薯品种的快繁最佳培养基为添加NAA/6-BA分别为0.01～0.05 mg·L-1和1.0 mg·L-1的MS培养基.中、短蔓品种快繁最佳激素组合和激素为NAA/6-BA分别为0.01～0.05 mg·L-1和1.0 mg·L-1的MS培养基.     

栝楼无土育苗技术研究

从育苗基质和根粗两个因素研究栝楼育苗技术,结果表明：选用直径1.5-3 cm段的块根,以煤渣、棉籽壳、河沙等体积配比作基质进行无土育苗,苗壮且根系发达,但考虑到成本因素,选河沙作基质也较好。     

栝楼无土育苗技术研究

从育苗基质和根粗两个因素研究栝楼育苗技术,结果表明：选用直径1．5—3cm段的块根,以煤渣、棉籽壳、河沙等体积配比作基质进行无土育苗,苗壮且根系发达,但考虑到成本因素,选河沙作基质也较好。     

鸡血藤扦插繁殖技术研究

[目的]研究鸡血藤快速繁殖方法,为进行其人工栽培提供科学参考与技术依据。[方法]选择生根剂丰叶宝、吲哚丁酸和ABT1号生根粉作为扦插穗的化学促进剂;选择3个不同木质化程度的插条类型;选择河沙、泥炭土、珍珠岩进行单因素试验优选鸡血藤扦插繁殖技术。[结果]最佳条件为以300mg/L的ABT1号浸泡2h,选用具有2～3个芽体的木质化硬枝,于春季扦插于珍珠岩或砂壤质黄心土,其生根效果较好。[结论]鸡血藤扦插快繁可行性良好。     

杂交兰原球茎增殖及分化研究

[目的]对杂交兰原球茎的增殖及分化进行研究。[方法]采用L9(34)正交试验设计,研究培养基、6-BAI、BA和AC对杂交兰原球茎增殖的影响;设置几种不同培养基对原球茎的分化进行探讨。[结果]培养基和6-BA对原球茎的增殖影响不大,IBA浓度为0.1 mg/L、AC浓度为1.0 mg/L时,原球茎增殖效果最好;1/2 MS+6-BA 1.0 mg/L+NAA 0.5 mg/L对原球茎的分化效果最好。[结论]在培养基中添加NAA有利于原球茎的分化。