《中国生物多样性红色名录》的制定 及其对生物多样性保护的意义

早在20世纪80年代, 我国就引入IUCN红色名录原理, 对我国生物物种的濒危状况开展评估工作。但是随着经济发展和气候变化, 一些物种的数量和分布区发生了变化, 加之在以往的评估中存在一些不足, 亟需对我国生物物种的濒危状况开展一次全面的评估。2008年, 环境保护部联合中国科学院启动了《中国生物多样性红色名录》的编制工作, 《中国生物多样性红色名录——高等植物卷》和《中国生物多样性红色名录——脊椎动物卷》分别于2013年9月和2015年5月正式对外发布。本文回顾了《中国生物多样性红色名录》的编制背景、过程和取得的成果。《中国生物多样性红色名录》完成了对我国34,450种高等植物和除海洋鱼类外的4,357种脊椎动物受威胁状况的评估, 是迄今为止对象最广、信息最全、参与专家人数最多的一次评估。在评估中取得了一系列成果: 统计了中国已知高等植物和脊椎动物物种数, 确定了物种丰富度在世界上的排名; 完善了国际上所使用的IUCN红色名录评估等级标准体系; 评估分析了我国已知高等植物和脊椎动物的受威胁程度及分布差异; 评估分析了高等植物和脊椎动物濒危灭绝的原因, 其中人类活动导致的生境丧失和退化是首要因素。这些成果将对我国生物多样性保护和管理工作产生积极的影响。     

通过红色名录评估研究中国内陆鱼类受威胁现状及其成因

根据已有的基础资料, 采用IUCN评估等级和标准, 对中国目前已鉴定的1,443种内陆鱼类受威胁现状进行了评估。评估结果显示, 1,443种内陆鱼类中, 灭绝3种、区域灭绝1种、极危65种、濒危101种、易危129种、近危101种、无危454种和数据缺乏589种。同已有的IUCN评估结果相比, 本次被评估的物种数目多, 受威胁物种大幅度增加, 其数目达295种, 占已知中国内陆鱼类总数的20.44%, 低于全球平均值(29%)。属于灭绝等级的鱼类是大鳞白鱼(Anabarilius macrolepis)、异龙鲤(Cyprinus yilongensis)和茶卡高原鳅(Triplophysa cakaensis); 属于区域灭绝等级的鱼类是长颌北鲑(Stenodus nelma)。鲤科是受威胁物种数最多的科, 其中裂腹鱼亚科和鲤亚科的种类受威胁程度最高。长江上游和珠江上游受威胁物种最多, 是受威胁最严重的地区。中国内陆鱼类受威胁的主要因素为河流筑坝、生境退化或丧失、酷渔滥捕和引进外来种。列入数据缺乏等级的鱼类较多, 占中国内陆鱼类的40.82%, 表明对中国内陆鱼类物种多样性了解不充分, 需要加强野外调查以积累基础资料。     

Expression, refolding, and characterization of a novel recombinant dual human stem cell factor

A novel recombinant dual human stem cell factor (rdhSCF) gene which consisted of a full-length hSCF(1-165aa) cDNA and a truncated hSCF (1-145aa) cDNA, linked by a peptide (GGGGSGGGGSGG) coding region, was constructed and cloned into Escherichia coli expression vector pET-22b. The rdhSCF was expressed at high level in E. coli BL21(DE3) and existed mainly as inclusion bodies. The inclusion bodies were solubilized in urea and refolded by ion-exchange chromatography. After renaturation, the purity of the yielded rdhSCF was up to 90%. Cell proliferation assay showed that the specific activity of the rdhSCF was 2.86x10(5) U/mg, about 1.66 times as high as that of monomer rhSCF expressed in E. coli.     

Expression of a novel recombinant stem cell factor/macrophage colony-stimulating factor fusion protein in baculovirus-infected insect cells

A novel human stem cell factor (SCF)/macrophage colony-stimulating factor (M-CSF) fusion protein gene was constructed, in which the coding regions of human SCF cDNA (1-165aa) and the truncated M-CSF cDNA (1-149aa) were connected by a linker sequence encoding a short peptide GGGGSGGGGSGG. The SCF/M-CSF gene was cloned into baculovirus transfer vector pVL1392 under the control of polyhedrin promoter and expressed in the Sf9 cells (Spodoptera frugiperda). SDS-PAGE and Western blot analysis showed that the purified fusion protein was a homodimer with a molecular weight about 84kDa under non-reducing conditions or a monomer about 42kDa under reducing conditions. The specific activity of rhSCF/M-CSF was 17 times as high as that of monomeric rhSCF to stimulate the proliferation of TF-1 cell. The results of macrophages colony-forming (CFU-M) assay performed with human bone marrow mononuclear cells demonstrated that rhSCF/M-CSF was more potent in promoting CFU-M than the equimolar of SCF, M-CSF or that of two cytokines mixture.     

Kinetic studies on the glutathione peroxidase activity of selenium-containing glutathione transferase

Selenium-containing glutathione transferase (seleno-GST) was generated by biologically incorporating selenocysteine into the active site of glutathione transferase (GST) from a blowfly Lucilia cuprina (Diptera: Calliphoridae). Seleno-GST mimicked the antioxidant enzyme glutathione peroxidase (GPx) and catalyzed the reduction of structurally different hydroperoxides by glutathione. Kinetic investigations reveal a ping-pong kinetic mechanism in analogy with that of the natural GPx cycle as opposed to the sequential one of the wild type GST. This difference of the mechanisms might result from the intrinsic chemical properties of the incorporated residue selenocysteine, and the selenium-dependent mechanism is suggested to contribute to enhancement of the enzymatic efficiency.     

Chemical characterization and radioprotective effect of polysaccharide from <Emphasis Type="Italic">Monostroma angicava</Emphasis> (Chlorophyta)

Polysaccharide from the green alga Monostroma angicava was extracted with boiling water and was purified by ion-exchange and size-exclusion column chromatography. The radioprotective effect of the polysaccharide was investigated in mice. The results show that polysaccharide from M. angicava has a different chemical composition to other Chlorophyta having a high rhamnose – containing sulfated polysaccharide. The sulfate ester content was estimated to be 21.8%. When the polysaccharide was applied to BALB/c mice following whole-body X-ray irradiation the counts of leukocytes, thrombocytes and erythrocytes recovered more rapidly in the polysaccharide treated mice after irradiation. In the irradiated mice, the polysaccharide significantly increased the spleen index, natural killer cytostatic activity and the transformation response of splenic lymphocytes. The present observations suggest that polysaccharide from M. angicava led to leukocytogensis and hematopoetic activation in mice after irradiation and that the biological response might be caused by immune activation.     

Identification of a subversive substrate of Trichomonas vaginalis purine nucleoside phosphorylase and the crystal structure of the enzyme-substrate complex

Trichomonas vaginalis is an anaerobic protozoan parasite that causes trichomoniasis, a common sexually transmitted disease with worldwide impact. One of the pivotal enzymes in its purine salvage pathway, purine nucleoside phosphorylase (PNP), shows physical properties and substrate specificities similar to those of the high molecular mass bacterial PNPs but differing from those of human PNP. While carrying out studies to identify inhibitors of T. vaginalis PNP (TvPNP), we discovered that the nontoxic nucleoside analogue 2-fluoro-2'-deoxyadenosine (F-dAdo) is a "subversive substrate." Phosphorolysis by TvPNP of F-dAdo, which is not a substrate for human PNP, releases highly cytotoxic 2-fluoroadenine (F-Ade). In vitro studies showed that both F-dAdo and F-Ade exert strong inhibition of T. vaginalis growth with estimated IC(50) values of 106 and 84 nm, respectively, suggesting that F-dAdo might be useful as a potential chemotherapeutic agent against T. vaginalis. To understand the basis of TvPNP specificity, the structures of TvPNP complexed with F-dAdo, 2-fluoroadenosine, formycin A, adenosine, inosine, or 2'-deoxyinosine were determined by x-ray crystallography with resolutions ranging from 2.4 to 2.9 A. These studies showed that the quaternary structure, monomer fold, and active site are similar to those of Escherichia coli PNP. The principal active site difference is at Thr-156, which is alanine in E. coli PNP. In the complex of TvPNP with F-dAdo, Thr-156 causes the purine base to tilt and shift by 0.5 A as compared with the binding scheme of F-dAdo in E. coli PNP. The structures of the TvPNP complexes suggest opportunities for further improved subversive substrates beyond F-dAdo.     

Matrix-induced inhibition of membrane binding contributes to human immunodeficiency virus type 1 particle assembly defects in murine cells

Defective human immunodeficiency virus type 1 (HIV-1) assembly in murine cells is accompanied by poor plasma membrane binding and proteolytic processing of the HIV-1 Gag precursor. Here, we show that such defects are induced by the propensity of the HIV-1 MA globular head to inhibit membrane binding and particle assembly, particularly at the low expression levels observed in murine cells. Simple additions to or deletion of the MA globular head can improve the yield of infectious virions from murine cells by >50-fold. Expression level and autoinhibition can be important confounding variables in studies of HIV-1 assembly and contribute to defects encountered in murine cells.     

Burn injury promotes antigen-driven Th2-type responses in vivo

Severe injury induces detrimental changes in immune function, often leaving the host highly susceptible to developing life-threatening opportunistic infections. Advances in our understanding of how injury influences host immune responses suggest that injury causes a phenotypic imbalance in the regulation of Th1- and Th2-type immune responses. We report in this study, using a TCR transgenic CD4(+) T cell adoptive transfer approach, that injury skews T cell responses toward increased Th2-type reactivity in vivo without substantially limiting Ag-driven CD4(+) T cell expansion. The increased Th2-type response did not occur unless injured mice were immunized with specific Ag, suggesting that the phenotypic switch is Ag dependent. These findings establish that severe injury induces fundamental changes in the induction of Ag-specific CD4(+) Th cell responses favoring the development of Th2-type immune reactivity in vivo.