3种酰胺类稻田除草剂对克氏原螯虾的急性毒性

[目的] 研究稻虾共作模式条件下,稻田封闭除草剂对克氏原螯虾产生的急性毒性。[方法] 采用半静态试验方法,研究3种酰胺类除草剂（乙草胺、丙草胺和丁草胺）对克氏原螯虾的急性毒性,计算3种酰胺类除草剂对克氏原螯虾的安全浓度,并分析其LC₅₀衰减规律。[结果] 随着暴露时间和除草剂浓度的增加,虾体侧躺,步行足和游泳足活动频率降低,最终死亡。乙草胺对克氏原螯虾的96 h半致死浓度（LC₅₀）和安全浓度（SC）分别为0.0707和0.0146 mL·L^-1;丙草胺对克氏原螯虾的96 h LC₅₀和SC分别为0.0119和0.0021 mL·L^-1;丁草胺对克氏原螯虾的96h LC₅₀和SC分别为0.0073和0.0014 mL·L^-1。乙草胺、丙草胺及丁草胺除草剂LC₅₀随着暴露时间延长呈下降趋势,符合双曲线衰减模型,回归方程分别为：① y₁=2.0840x^-0.7380（R²=0.9973）;② y₂=0.1106x^-0.4930（R²=0.9872）;③ y₃=0.2236x^-0.7480（R²=0.9990）。克氏原螯虾对3种除草剂的敏感性由高到低依次为：丁草胺 > 丙草胺 > 乙草胺。[结论] 乙草胺和丙草胺可在稻田综合种养生产过程中按常规剂量使用,而丁草胺按常规剂量使用可能存在较大的风险。     

Gc、Pi蛋白亚型的快速微量电泳分析

用快速微量等电聚焦技术对190名北京地区汉族健康人血清Gc蛋白亚型、Pi蛋白亚型进行分型鉴定和基因频率调查.上样量为1.5μl,电泳和染色各0.5h.Gc^1F=0.4891,Gc^1S=0.2432,Gc²=0.2678.观察值与期望值吻合良好.(∑X²=1.404,0.7<P<0.8).Pi^M₁=0.7542,Pi^M₂=0.1808,Pi^M₃=0.0650,观察值与期望值吻合也良好,(∑X²=1.1233,0.7<P<0.8).     

Evaluation of the maximum specific growth rate of a yeast indicating non-linear growth trends in batch culture

The maximum specific growth rate (μ_max) of an ethanolic D-xylose-fermenting yeast, Pichia stipitis, showing non-linear growth trends in batch culture, was calculated using the rate equation μ₂ = (1/Δt) ln(x ₂/x ₁). The absolute error Δμ, affecting μ₂, was derived using an equation given by Borzani (1994). Based on the assumption of linearity of growth curves between two closest time points, the relation between the two rate formulae, μ₁ = (1/xˉ)dx _t /dt and μ₂ = (1/Δt) ln(x ₂/x ₁) was established. In a particular condition, when μ₁ = μ₂, an equation has been developed, the roots of which are the specific growth rates at different time points. This revised version was published online in July 2006 with corrections to the Cover Date.     

西藏双须叶须鱼年龄与生长特点研究

双须叶须鱼（Ptychobarbus dipogon Regan）隶属裂腹鱼亚科（Schizothoracinae）叶须鱼属（Ptychobarbus）,是西藏特有经济鱼类,2016年被列入中国脊椎动物红色名录,必须加快推动该鱼的养护工作。2013年2~3月份及2014年2~6月份,在雅鲁藏布江谢通门段与支流拉萨河上游段采集1 030尾双须叶须鱼样本,以脊椎骨作为年龄鉴定材料进行年龄与生长特点研究,以期分析和评价该类群鱼类资源情况。研究结果如下：双须叶须鱼样本中最大年龄为49龄,最小年龄为4龄;体重与体长关系是样本总体W=4.4×10^-5?SL^2.7688、雌鱼W_♀=5.0×10^-4?SL^2.3474、雄鱼W_♂=2.8×10^-5?SL^2.8414;体长生长方程为雌鱼L_t（♀）=431.8［1-e^-0.19（t+1.19）］,渐进体长L∞_（♀）=431.8 mm,拐点年龄为3.3龄,雄鱼L_t（♂）=367.6［1-e^-0.42（t+3.37）］,渐进体长L∞_（♂）=367.7 mm;体重生长方程为雌鱼W_t（♀）=767.40［1-e^-0.19（t+1.19）］^2.3474,雄鱼W_t（♂）=545.02［1-e^-0.42（t+3.37）］^2.8414;群体异速生长指数b=2.768 8与匀速生长指数3存在显著性差异,即P<0.05。研究表明双须叶须鱼体趋向低龄化,应当予以充分关注。     

西南地区野生刺梨的遗传多样性和遗传结构研究

为了探究西南地区野生刺梨(Rosa roxburghii)的遗传多样性和起源演化,该研究基于2段单拷贝核基因(GAPDH和ncpGS)和3段叶绿体基因(atpF-trnH、trnL-trnF和trnG-trnS)的拼接序列,对刺梨27个野生居群共320个个体进行PCR扩增和测序,并用相关软件对测序结果进行分析。结果表明:(1)在单拷贝核基因和叶绿体基因水平上刺梨均表现出较低的遗传多样性(scnDNA: Hd=0.469 2, π=0.000 49; cpDNA: Hd=0.653 4, π=0.000 65),并且不同居群间存在较大差异。(2)分子方差分析(AMOVA)结果均显示,遗传变异主要发生在居群内,表明居群内的变异是野生刺梨遗传变异的主要来源,居群间存在明显的遗传分化( cpDNA:F_ST=0.336 47,G_ST=0.273,N_ST= 0.308; scnDNA:F_ST=0.094 87,N_ST=0.076,G_ST=0.056),刺梨的分布不具有明显的谱系地理结构(P>0.05)。(3)中性检验 Tajima''s D值均为不显著负值,符合中性进化模型。Fu''s Fs值均为显著负值,结合失配分析曲线,推测刺梨种群在小范围内经历过扩张,但总体上维持稳定状态。(4)根据单倍型多样性得出,毕节地区的居群遗传多样性水平较高并且拥有丰富的单倍型,推测可能为冰期避难所,因此应对其实施就地保护。对于拥有特殊性状和特有单倍型的居群也应采取优先保护措施。该文为野生刺梨资源保护和遗传育种提供了一定的参考价值。     

不同CO2浓度升高和氮肥水平对水稻叶绿素荧光特性的影响

为研究不同CO₂浓度升高和氮肥水平对水稻叶绿素荧光特性的影响,利用由开顶式气室（OTC）组成的CO₂浓度自动调控平台开展田间试验。以粳稻9108为试验材料,CO₂浓度设置CK（对照,环境大气CO₂浓度）、C₁（CO₂浓度比CK增加160 μmol/mol）和C₂（CO₂浓度比CK增加200 μmol/mol）3个水平;氮肥设置低氮（N₁：10 g/m²）、中氮（N₂：20 g/m²）和高氮（N₃：30 g/m²）3个水平。结果表明,在低氮条件下,与CK相比,C₁处理使拔节期的F_o上升4.8%（P=0.031）;C₂处理使拔节期的F_o上升6.3%（P=0.015）,F_v/F_m下降4.8%（P=0.003）,使孕穗期的F_o上升12.7%（P=0.039）,F_v/F_o下降18.2%（P=0.039）。在高氮条件下,与CK相比,C₂处理使灌浆期的F_m、F_v和F_v/F_m分别下降3.6%（P=0.039）、4.9%（P=0.013）和1.3%（P=0.039）。在中氮条件下,与CK相比,C₁和C₂处理的影响不明显。在整个生育期内,CO₂浓度升高与施氮处理交互作用对水稻叶绿素荧光特性的影响未到达显著水平。研究表明,大气CO₂浓度升高使水稻叶片光系统Ⅱ受损,抑制其电子传递能力、电子受体Q_A氧化还原情况、最大光化学效率和潜在活性,通过适量施氮可以有效地缓解其负面效应。     

利用黄毛草莓创制蜜桃香味草莓新株系

为创制具有蜜桃香味的草莓新株系,用栽培品种‘红颊’（‘Benihoppe’,2n=8x）与黄毛草莓（Fragaria nilgrrensis,2n=2x）为亲本进行杂交,得到种间杂种五倍体（2n=5x）,再经秋水仙素诱导后获得十倍体（2n=10x）,收获该十倍体的种子进行实生选种,选育出4个具有蜜桃香味的草莓新株系。结果表明,‘红颊’×黄毛草莓的杂交组合结实率和出苗率分别为39.58%和28.11%,适宜草莓十倍体诱导的秋水仙素浓度在200 mg/L左右,处理时间30~40 d,4个草莓新株系均具有蜜桃香味,抗氧化物质含量显著提高,但果肉质地较松软,平均单果重和株产稍低。这为野生草莓资源的利用和种质创新提供了科学参考。     

秃病蚤蒙冀亚种与长爪沙鼠密度的状态空间模型

 给出了一个描述秃病蚤蒙冀亚种Nosopsyllus laeviceps kuzenkovi与长爪沙鼠M eriones unguiculatus密度的状态空间模型,模型为x_t+1=-0.336x_t+0057y _t+0107z_t, y_t+1=0.586x_t-0369y_t-0274z_t, z_t+1=0.189x _t+0247y_t-0309z_t, 其中x_t,y_t和z_t分别为t月份的沙鼠密度, 巢秃病蚤 和体秃病蚤指数。结果表明,模型能够较好地描述野外秃病蚤蒙 冀亚种与长爪沙鼠间的关系,并发现沙鼠密度显著地影响巢秃病蚤指数。     

光枝勾儿茶内生真菌多样性及抑菌活性研究

为探索贵州苗药光枝勾儿茶内生真菌类群特征、分布部位及其抑菌活性,该研究采用传统方法对贵州省贵阳市和黔西市光枝勾儿茶内生真菌进行分离,并基于分子生物学及统计学对其分类地位进行鉴定及多样性评价,最后通过微量肉汤倍比稀释法筛选具有抑菌活性的菌株。结果表明:(1)从光枝勾儿茶中分离到191 株内生真菌,隶属于3 个门5 个纲10 个目15 个科19 个属,优势属为叶点霉属(Phyllosticta)、间座壳属(Diaporthe)、葡萄座腔菌属(Botryosphaeria)和刺盘孢属(Colletotrichum)。(2)黔西光枝勾儿茶内生真菌香农-维纳多样性指数(H''_Q=2.112)较贵阳(H''_G=1.801)高,索伦森相似性指数Cs_G-Q为0.923,不同组织香农-维纳多样性指数为茎(H''_S=2.004)>根(H''_R=1.764)>叶(H''_L=1.654)>果实(H''_F=1.473),茎和叶内生真菌的索伦森相似性最高(Cs_S-L=0.667)。(3)筛选出的21株内生真菌对供试菌大肠杆菌(Escherichia coli)、金黄色葡萄球菌(Staphylococcus aureus)和沙门氏菌(Salmonella enterica)具有抑菌效果,其中Diaporthe sp. QX4G6对大肠杆菌、金黄色葡萄球菌和沙门氏菌的最小抑菌浓度分别为12.5、6.25、12.5 mg·mL^-1,最小杀菌浓度分别为12.5、6.25、12.5 mg·mL^-1。以上研究结果揭示了光枝勾儿茶蕴藏丰富的内生真菌资源,不同地区及组织内生真菌类群组成有差异,多个分离菌株具有抗菌活性,为光枝勾儿茶内生真菌天然抗菌药物或药源研发奠定了基础。     

蝎毒素BmkTXKβ对家兔心房肌细胞瞬间外向钾电流的抑制作用

为研究蝎毒素BmkTXKβ对家兔心房肌细胞瞬间外向钾电流(I_to)的影响,采用全细胞膜片钳技术记录应用BmkTXKβ前后的I_to电流. 结果显示BmkTXKβ（1 μmol/L）使心房肌细胞I_to（刺激电压为+50 mV）从（13.63±0.87）pA/pF减少到（7.98±0.78）pA/pF,抑制率为41.4% (n=16, P＜0.001).冲洗后, I_to部分恢复至(11.18±0.82)pA/pF (n=6, P＜0.01,与给药后比较).在0.01～100 μmol/L范围内BmkTXKβ呈浓度依赖性地抑制I_to,IC₅₀的均值为0.95 μmol/L (n=10, P＜0.01),但无频率依赖性(n=6,P＞0.05). 1 μmol/L的BmkTXKβ可使I_to通道的失活动力学曲线明显左移,V_1/2分别为（－23.6±2.7） mV和（－35.3±3.6） mV（n=8,P＜0.05）,曲线斜率基本不变.同时可使I_to通道的恢复过程明显减慢,恢复曲线右移,τ值从（51.2±8.5） ms延长至（93.5±13.4） ms（n=9,P＜0.01）,但不影响其激活过程.据此推断BmkTXKβ对家兔心房肌细胞I_to具有显著的抑制作用,主要作用于失活过程,延长该通道的恢复时间.     

Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

The structure, reproduction and taxonomy of Vidalia and Osmundaria (Rhodophyta, Rhodomelaceae)

Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.     

New or rare chromosome counts in Artemisia L. (Asteraceae, Anthemideae) and related genera from Kazakhstan

Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted.