Ultrastructure of the Invasion of Eimeria magna Sporozoites into Cultured Cells*†‡

SYNOPSIS. Monolayers of bovine kidney cells were overlaid with Eimeria magna sporozoites and observed with phase-contrast optics until penetration of the cells by the parasites had begun. Cells and penetrating parasites were fixed with glutaraldehyde and OsO₄-containing ruthenium red, dehydrated, and embedded in situ. Cells being penetrated were selected for study in the electron microscope. The lack of intracellular staining with ruthenium red and intact plasmalemmas of cells being penetrated, was accepted as evidence that the sporozoites did not disrupt the plasma membranes. The sporozoite caused invagination of the host cell plasmalemma until the parasite was entirely within the cell, after which the invagination was sealed off by short pseudopodia enclosing the sporozoite within a membrane-lined vacuole inside the cell. Often myelin-forms, apparently of host cell origin, were seen in the space between the sporozoite and the cell.     

Métabolisme du chloro-2 (p-chlorophényl)-3 propionate de méthyle et problème de sélectivité

The product of hydrolysis of the active principle of the herbicide Bidisine® is degraded in at least two different ways. One way gives p-chlorobenzoic acid. The other, more important one, gives a conjugate with l-cysteine, which is further oxidized. The ability to oxidize the conjugate provided a means of distinguishing between susceptible and resistant plant species.     

加拿大引进的二倍体燕麦种质的核型鉴定

采用常规压片法对砂燕麦、西班牙燕麦和短燕麦3个二倍体燕麦种进行了核型研究。结果表明:砂燕麦染色体核型公式为2n=2x=14=10m+4sm(2SAT),具近中部和中部着丝点染色体,第4对染色体组的短臂上有1对随体,核不对称系数为68.17%;西班牙燕麦染色体核型公式为2n=2x=14=10m+4sm(2SAT),具近中部和中部着丝点染色体,第7对染色体短臂上有1对随体,核不对称系数为59.31%;短燕麦染色体核型公式为2n=2x=14=6m+4sm+4st(2SAT),具近端部、近中部和中部着丝点染色体,第6对染色体组的短臂上有1对随体,核不对称系数为63.91%。虽然3个燕麦种的核型均为2A,但它们的染色体形态有明显不同,比较认为砂燕麦相对进化,短燕麦次之,西班牙燕麦较原始。本研究对燕麦种质资源的核型分析及进化地位研究具有参考价值。     

Genome-Wide Association Analysis Identifies a Genetic Basis of Infectivity in a Model Bacterial Pathogen

Knowledge of the genetic architecture of pathogen infectivity and host resistance is essential for a mechanistic understanding of coevolutionary processes, yet the genetic basis of these interacting traits remains unknown for most host–pathogen systems. We used a comparative genomic approach to explore the genetic basis of infectivity in Pasteuria ramosa, a Gram-positive bacterial pathogen of planktonic crustaceans that has been established as a model for studies of Red Queen host–pathogen coevolution. We sequenced the genomes of a geographically, phenotypically, and genetically diverse collection of P. ramosa strains and performed a genome-wide association study to identify genetic correlates of infection phenotype. We found multiple polymorphisms within a single gene, Pcl7, that correlate perfectly with one common and widespread infection phenotype. We then confirmed this perfect association via Sanger sequencing in a large and diverse sample set of P. ramosa clones. Pcl7 codes for a collagen-like protein, a class of adhesion proteins known or suspected to be involved in the infection mechanisms of a number of important bacterial pathogens. Consistent with expectations under Red Queen coevolution, sequence variation of Pcl7 shows evidence of balancing selection, including extraordinarily high diversity and absence of geographic structure. Based on structural homology with a collagen-like protein of Bacillus anthracis, we propose a hypothesis for the structure of Pcl7 and the physical location of the phenotype-associated polymorphisms. Our results offer strong evidence for a gene governing infectivity and provide a molecular basis for further study of Red Queen dynamics in this model host–pathogen system.     

A wingless alpine stonefly from New Zealand,and further information on genus Holcoperla (Plecoptera: Gripopterygidae)

Abstract

Holcoperla magna n.sp. is described and figured from material collected on Headlong Peak, Mt Aspiring National Park. New information is given on H. angularis (Wisely) and H. jacksoni McLellan, and the 3 species are compared. Larvae designated as type specimens of H. angularis are shown to be Apteryoperla monticola Wisely.     

The use of biomarkers in the antioxidant responses of Daphnia magna to the acute and chronic exposure to no. 20 diesel oil and 2,4-dichlorophenol

Abstract

The effects of no. 20 diesel oil exposure, 2,4-dichlorophenol (2,4-DCP) exposure and combined exposure on the antioxidant defences of Daphnia magna have been studied systematically for the first time. Daphnia magna was exposed for 1 day or 10 days to several concentrations of 0, 0.005, 0.01, 0.05, 0.1, 0.5 or 1.0 mg L^?1 solutions. Antioxidant defences consisting of the levels of reduced glutathione (GSH) and glutathione disulfide (GSSG) and activities of superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), selenium dependent glutathione peroxidase (Se-GPx) and glutathione S-transferase (GST) of daphnids were determined to evaluate their protective roles and to analyse the occurrence of oxidative stress. The possible antioxidant defence mechanisms are discussed. Furthermore, GST can be a potential biomarker and an early-warning index for the pollutants in waters in that GST responded sensitively to 1 day and 10 days of exposure to diesel oil and 2,4-DCP and 10 days of combined exposure. Crossover comparisons showed an antagonistic action about the no-observed-effect concentration (NOEC) against Daphnia magna, which needs further studies.     

燕麦种质资源重要农艺性状适应性和稳定性评价

为客观评价燕麦种质资源重要农艺性状的适应性和稳定性,本研究利用加权隶属函数法分析了81份燕麦种质材料在7个试验点的株高等7个重要农艺性状的遗传差异,以加权隶属函数值(D值)构建基因型×环境的GGE双标图,分析裸燕麦、皮燕麦在不同试验点的适应性和稳定性。结果表明:主穗粒重是裸燕麦材料在所有试验点中变异程度最大的性状,有效分蘖数是皮燕麦中变异程度最大的性状,其余5个性状的变异程度与皮裸性几乎无关;加权隶属函数法结合GGE双标图在对燕麦农艺性状进行综合分析时具有很好的应用价值;坝莜三号、73014-336、二莜麦、Bauntebue、坝燕一号等材料可用于实际生产,其中的坝莜三号、坝燕一号已是当下河北等地区的主栽品种;晋8609-1、LY03-02、二秋莜麦、64燕麦、品16、Banner、LY01-12等可作为杂交育种的亲本材料。     

上海滴水湖两种枝角类牧食对浮游植物群落影响的模拟研究

于2012年9月通过浮游动物添加实验,研究了大型溞(Daphnia magna)和隆腺溞(Daphnia carinata)对上海滴水湖浮游植物群落结构的影响.结果表明,实验组氨氮和可溶性活性磷浓度与空白组相比显著增加,大型溞组浮游植物密度较空白组降低了70.3％,隆腺溞组浮游植物密度较空白组降低了80.0％,叶绿素a浓度分别下降了80.4％和75.2％,叶绿素a与氨氮、可溶性活性磷呈显著相关性.浮游植物的群落结构较空白组也发生较大变化,硅藻、蓝藻和绿藻密度比例明显降低,隐藻、裸藻和甲藻在实验结束时没有检出,说明大型溞和隆线溞能有效控制水体中浮游植物密度,并能够对浮游植物群落结构产生影响.同时,附着藻类密度较空白组也有明显减少,说明大型溞和隆线溞对附着藻类也有一定的牧食作用.     

Migratory patterns and connectivity of two North American grassland bird species

Effective management and conservation of migratory bird populations require knowledge and incorporation of their movement patterns and space use throughout the annual cycle. To investigate the little‐known migratory patterns of two grassland bird species, we deployed 180 light‐level geolocators on Grasshopper Sparrows (Ammodramus savannarum) and 29 Argos‐GPS tags on Eastern Meadowlarks (Sturnella magna) at Konza Prairie, Kansas, USA, and six US Department of Defense (DoD) installations distributed across the species' breeding ranges. We analyzed location data from 34 light‐level geolocators and five Argos‐GPS tags attached for 1 year to Grasshopper Sparrows and Eastern Meadowlarks, respectively. Grasshopper Sparrows were present on the breeding grounds from mid‐April through early October, substantially longer than previously estimated, and migrated on average ~2,500 km over ~30 days. Grasshopper Sparrows exhibited strong migratory connectivity only at a continental scale. The North American Great Lakes region likely serves as a migratory divide for Midwest and East Coast Grasshopper Sparrows; Midwest populations (Kansas, Wisconsin, and North Dakota; n = 13) largely wintered in Texas or Mexico, whereas East Coast populations (Maryland and Massachusetts, n = 20) wintered in the northern Caribbean or Florida. Our data from Eastern Meadowlarks provided evidence for a diversity of stationary and short‐ and long‐distance migration strategies. By providing the most extensive examination of the nonbreeding movement ecology for these two North American grassland bird species to date, we refine information gaps and provide key insight for their management and conservation.     

外源硫化氢对盐碱胁迫下裸燕麦叶片有机酸和激素含量的影响

为探讨外源硫化氢(H₂S)对盐碱胁迫下植物有机酸和激素水平的调控效应,以裸燕麦(Avena nuda)为材料,研究喷施50μmol·L^-1H₂S供体硫氢化钠(NaHS)溶液对3.00 g·kg^-1盐碱胁迫下叶片有机酸、激素含量和产量性状的影响。结果表明：盐碱胁迫显著提高了琥珀酸、丁烯二酸、苹果酸、葡萄糖醛酸和总有机酸含量,显著降低了焦谷氨酸、茉莉酸-异亮氨酸(JA-Ile)、反式-玉米素(tZ)和N⁶-(Δ²-异戊烯)腺嘌呤(iP)含量。喷施NaHS溶液显著提高盐碱胁迫下裸燕麦叶片中3-羟基-3-甲基谷氨酸、吲哚乙酸(IAA)、赤霉素A₇(GA₇)、茉莉酸甲酯(MJA)、iP含量和IAA/ABA比值,显著降低葡萄糖醛酸、赤霉素A₃(GA₃)、赤霉素A₄(GA₄)、总赤霉素(GA_S)、1-氨基环丙烷羧酸(A...