Radiofrequency radiation at 2.856 GHz does not affect key cellular endpoints in neuron-like PC12 cells

To investigate the potential cytotoxicity of radiofrequency (RF) radiation on central nervous system, rat pheochromocytoma (PC12) cells were exposed to 2.856 GHz RF radiation at a specific absorption rate (SAR) of 4 W/kg for 8 h a day for 2 days in 35 mm Petri dishes. During exposure, the real-time variation of the culture medium temperature was monitored in the first hour. Reactive oxygen species (ROS) production, intracellular Ca²⁺ concentration, and cell apoptosis rate were assessed immediately after exposure by flow cytometry. The results showed that the medium temperature raised about 0.93 °C, but no significant changes were observed in apoptosis, ROS levels or intracellular Ca²⁺ concentration after treatment. Although several studies suggested that RF radiation does indeed cause neurological effects, this study presented inconsistent results, indicating that 2.856 GHz RF radiation exposure at a SAR of 4 W/kg does not have a dramatic impact on PC12 cells, and suggests the need for further investigation on the key cellular endpoints of other nerve cells after exposure to RF radiation.     

Growth, structure and spectroscopic characterization of Nd3+-doped KBaGd(WO4)3 crystal with a disordered structure

The undoped and the Nd(3+):KBaGd(WO(4))(3) crystals were grown by the top seeded solution growth (TSSG) method from a flux of K(2)W(2)O(7). The structure of the pure crystal was determined by the single-crystal X-ray diffraction method. It crystallizes in the monoclinic symmetry with space group C2/c. In the structure, K(+) and Ba(2+) ions share the same 8f site with occupancy of 0.464 and 0.536, respectively. The investigation of spectral properties of Nd(3+):KBaGd(WO(4))(3) crystal indicates that it exhibits broad absorption and emission bands, which are attributed to locally disordered environments around the Nd(3+) centers. The broad absorption band is suitable for diode laser pumping.     

Construction of a trivalent candidate vaccine against Shigella species with DNA recombination

In this work asd gene of Shigella flexneri 2a strain T32 was replaced by Vibrio cholerae toxin B subunit (ctxB) gene with DNA recombination in vivo and in vitro. The resulting derivative of T32, designed as FWL01, could stably express CtxB, but its growth in LB medium depended on the presence of diaminopimelic acid (DAP). Then form I plasmid of Shigella sonnei strain S7 was labeled with strain T32 asd gene and mobilized into FWL01. Thus a trivalent candidate oral vaccine strain, designed as FSW01, was constructed. In this candidate strain, a balanced-lethal system was constituted between the host strain and the form I plasmid expressing S, sonnei O antigen. Therefore the candidate strain can express stably not only its own O antigen but also CtxB and O antigen of S. sonnei in the absence of any antibiotic. Experiments showed that FSW01 did not invade HeLa cells or cause keratoconjunctivitis in guinea pigs. However, rabbits immunized FSW01 can elicit significant immune responses. In mice and rhesus monkey     

Screening and identification of receptor antagonist for shiga toxin from random peptides displayed on filamentous bacteriophages

The bacteriophage clones which can bind with shiga toxin B subunit (StxB) and inhibit cytotoxicity of shiga toxin were obtained by using antibody capturing method from a 15-mer random peptide library displayed on the surface of bacteriophage fd. Among them, one peptide encoded by the random DNA region of a selected bacteriophage (A12) was synthesized and testedin vitro andin vim, where the peptide competed with the receptor of shiga toxin to bind StxB, and inhibited the cytotoxicity and enterotoxicity of shiga toxin. The peptide can also block other apparently unrelated StxB binding bacteriophage (A3), which suggests that there are overlapping StxB interaction sites for those ligands with different sequences. The results provide a demonstration of bacteriophage display to screen peptide ligands for a small and/or unable biotinylated molecule by antibodies-capturing strategy, and take the lead for the development of receptor antagonists for shiga toxin.     

赤潮过程中“藻-菌”关系研究进展

微生物对促进海洋物质循环,维持水生环境的生态平衡具有重要作用。在赤潮事件中,基于微生物(尤其是细菌)的多样性和重要性,它们与藻类之间的相互关系成为了研究的热点。过去20年里,人们从不同角度对"藻-菌"间的关系进行了探索,包括物理学过程、生物学过程、环境过程以及化学过程。就化学过程而言,它作为一种较早出现的技术,在以往的研究中带给人们许多认识藻菌关系的方法。随着学科的渗透,化学法有了拓展与延伸,为人们认识藻菌关系带来了新的契机。从化学生态学领域来梳理"藻-菌"关系中涉及的现象和行为,包括菌对藻的有益面、菌对藻的有害面、以及藻类应答细菌行为的化学途径;并从信号语言(群体感应、化感作用)的角度来阐释两者之间的互生或克生关系。通过文献综述的方式来解读藻菌关系的互作过程和机理,为认识赤潮的发生和防控方法提供借鉴。     

宋内Ⅰ相抗原和霍乱CT-B共表达的免疫保护效果观察

将编码宋内氏痢疾菌(Shigella sonnei)I相O抗原的基因和霍乱弧菌(Vibrio choler-ae)的CT-B基因克隆至带asd基因的质粒PYA248,得重组质粒PMGL105。将该重组质粒转入asd基因缺失的减毒伤寒沙门氏菌X4072,构成了一个不带抗药性基因的载体-宿主平衡致死系统。一系列实验表明,该重组菌X4072(PMGL105)能稳定地表达宋内I相O抗原和霍乱弧菌的CT-B抗原。小鼠免疫保护实验表明,该重组菌对有毒的宋内氏I相痢疾杆菌及霍乱弧菌的攻击均具有良好保护作用。     

Construction of a trivalent candidate Shigella vaccine strain with host-vector balanced-lethal system

A trivalent live Shigella vaccine candidate FSD01 against S. flexneri 2a, S. sonnei and S. dysen-teriae I was constructed. This candidate strain was based on the S. flexneri 2a vaccine T32. By homologous recombi-nation exchange, the chromosomal asd gene of T32 was site-specifically inactivated, resulting in the strain unable to grow normally in LB broth, while another asd gene of S. mutans was employed to construct an Asd complementary vector. This combination of asd 'host/ Asd vector formed a balanced-lethal expression system in T32 strain. By use of this system, two important protective antigen genes coding for S. sonnei Form I antigen and Shiga toxin B subunit were cloned and expressed in T32, which led to the construction of trivalent candidate vaccine FSD01. Experimental results showed that this strain was genetically stable, but its recombinant plasmid was non-resistant. Moreover, it was able to effectively express trivalent antigens in one host and induce protective responses in mice against the     

基于景观连接度的森林景观恢复研究——以巩义市为例

景观连接度是研究景观促进或阻碍生物体或某种生态过程在斑块间运动的程度。基于景观连接度原理,借用景观连接度指数,在地理信息系统支持下,探讨了巩义市丘陵和低山地区森林景观在不同景观距离阈值下连接度的变化,确定了分析森林景观连接度的合适距离阈值。在此基础上分析了要恢复为森林景观的农业斑块的重要值的大小,确定了对要恢复为森林景观的每一农业景观斑块对新形成的森林景观的连接度贡献大小,并结合区域地形特征,明确了森林恢复之初的重要斑块的选取及恢复的先后次序。结果显示,在不同的距离阈值下,低山地区森林景观的整体连通性指数值(IIC)都大于丘陵地区森林景观的IIC值;森林景观的适宜距离阈值,在丘陵地区可选择750 m,在低山地区可选择500 m,或者更小尺度;通过农业景观斑块重要值(dIIC)确定的对森林景观连接度作用起"非常高"和"高"的斑块的数量非常少,但对森林景观连接度的贡献作用却比较大。提出的基于景观连接来分析在森林恢复时重要斑块的选取的方法,具有一定的可操作性与实用性,对区域生态恢复和生态建设具有重要意义。     

稳定、无抗药的痢疾福氏2a和宋内双价菌苗候选株的构建

通过体内外基因重组,将大肠杆菌粘附因子cs3基因定位整合到痢疾杆菌福氏2a疫苗株T32菌染色体的asd基因内,使asd基因灭活;将来内O抗原基因克隆至无抗药性表达载体pXL378,获得重组质粒pXL390,将其转化asd-的T32受体菌,构建成福氏2a和宋内双价苗苗株FS01。实验表明:重组质粒pXL390在不带任何抗菌素基因的情况下,在asd-的T32受体菌内是稳定的。FS01株遗传稳定,能表达两种痢疾菌的PLS-O抗原,无明显毒性作用。动物试验表明,以FS01株皮下免疫的小鼠对福氏2a和宋内有毒株的腹腔攻击有100％的保护。