New approaches to estimating the mutagenic potential of chemicals

New developments in mutagenic risk assessment have appeared in the past few years. New methods have been developed such asin vitro micronucleus assay for chromosomal alterations, comet assay for primary DNA damage, use of transgenic animals to detectin vivo gene mutations, and fluorescent in situ hybridization method to detect aneuploidy. Other new methods will be developed in the few next years, including the use of DNA chips and the use of molecular biological methods. Several micromethods have been developed to test a great number of chemical compounds. New concepts have appeared concerning interpretation of data, and particularly of thresholds especially in the case of aneugens; in some cases metabolic or mechanistic thresholds were demonstrated. Genotoxic studies are best integrated into toxicological testing: for example, some genotoxicity tests can be integrated into subacute toxicology; interpretation of data includes metabolism; and toxicokinetic data relate to other toxicological studies. Conversely, genotoxicity data can be used to interpret toxicology studies. This revised version was published online in July 2006 with corrections to the Cover Date.     

基于BAC重组酶系统构建莱航鸡多位点基因打靶载体的研究

以莱航鸡重复的rDNA基因间的间隔序列为靶位点,利用BAC重组酶系统构建含人干扰素基因的多位点基因打靶载体,为建立莱航鸡多位点基因打靶技术获得关键材料。首先构建BAC-TDN筛选载体,然后构建pYLVS-GID表达载体。将BAC-TDN筛选载体和pYLVS-GID表达载体共转化至大肠杆菌NS3529中,通过其Cre重组酶的作用形成BAC-TDN-VS-GID质粒,采用归位内切酶I-SceⅠ切除pYLVS质粒骨架,利用接头LS使之环化,构建成莱航鸡大容量多位点基因打靶载体BAC-TDN-GID。每次克隆均经酶切或PCR、测序等鉴定DNA片段的插入及插入方向。以该载体为材料的多位点基因打靶技术将提高基因定点整合效率,解决外源基因不能稳定表达、安全性等部分问题,突破了DNA重复序列不能作为外源基因整合靶位点的禁区。     

Floral synorganization and its influence on mechanical isolation and autogamy in Marantaceae

The flowers of Marantaceae (～ 550 species) exhibit a highly derived pollination mechanism within Zingiberales, with a rapid and irreversible style movement based on a close synorganization of different floral parts. Given the complexity of the structure, we assume that little variation is possible if functionality is to be maintained. To test this, we investigated how much floral diversity exists in the clade and whether this diversity potentially influences the breeding system and placement of pollen on the pollinator. Flowers of 66 species covering the five major phylogenetic clades of the family were analysed. All species are similar in their basic flower construction: the fleshy staminode forms the tunnel‐shaped roof of the flower and narrows the tube with stiff swellings, and the hooded staminode holds the style under tension and narrows the flower entrance with its trigger appendage. Despite morphological diversity of the pollination apparatus, functionality is maintained by coordinated variation of the fleshy and hooded staminodes. Autogamy is usually avoided by herkogamy. However, in a few exceptions, subtle morphological changes alter the breeding system from allogamy to autogamy. Variable floral proportions allow for differential pollen deposition potentially causing mechanical isolation between sister taxa. This study clearly illustrates that structural variation is not only present in the highly synorganized flowers of Marantaceae, but that it also creates potentially new options for evolutionary diversification. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 168 , 300–322.     

The Olfactory System as a Model to Study Axonal Growth Patterns and Morphology In Vivo

The olfactory system has the unusual capacity to generate new neurons throughout the lifetime of an organism. Olfactory stem cells in the basal portion of the olfactory epithelium continuously give rise to new sensory neurons that extend their axons into the olfactory bulb, where they face the challenge to integrate into existing circuitry. Because of this particular feature, the olfactory system represents a unique opportunity to monitor axonal wiring and guidance, and to investigate synapse formation. Here we describe a procedure for in vivo labeling of sensory neurons and subsequent visualization of axons in the olfactory system of larvae of the amphibian Xenopus laevis. To stain sensory neurons in the olfactory organ we adopt the electroporation technique. In vivo electroporation is an established technique for delivering fluorophore-coupled dextrans or other macromolecules into living cells. Stained sensory neurons and their axonal processes can then be monitored in the living animal either using confocal laser-scanning or multiphoton microscopy. By reducing the number of labeled cells to few or single cells per animal, single axons can be tracked into the olfactory bulb and their morphological changes can be monitored over weeks by conducting series of in vivo time lapse imaging experiments. While the described protocol exemplifies the labeling and monitoring of olfactory sensory neurons, it can also be adopted to other cell types within the olfactory and other systems.     

森林-农业景观格局变化的社会-生态系统模拟模型方法进展

社会-生态系统(SES)模拟模型是景观格局分析和决策的有效工具,能表征景观格局变化的社会-生态效应及景观决策的复杂反馈机制。文献综述了森林-农业景观格局的SES模型方法进展发现:(1)多数模型对景观过程与社会经济决策的反馈关系分析不足;(2)应集成多种情景模拟和景观效应分析方法,完善现有SES模型的理论方法基础;(3)通过集成格局优化模型和自主体模型会有效改进SES模型功能,具体途径包括:集成情景-生态效应的景观格局模拟方法、完善景观决策的理论基础、加强集成模型的不确定性分析、降低模型复杂性和综合定性-定量数据等。研究结果有助于理解多尺度森林-农业景观格局在社会-生态系统中的重要作用,能更好地支持跨学科集成模型开发与应用。     

铵载体（Amt）进展

铵载体是一类存在于细胞膜上分子量约为４８ｋＤａ的主动转远ＮＨ＾＋４的载体。本文在简单介绍了铵载体的研究历史和铵载体与泌铵的相互关系后,阐述了在原核和真核生物中的铵载体基因的克隆及其基因表达调控的研究进展,探讨了铵载体存在的普遍性和它在氮代谢中的作用。     

RIOK3促进了caspase-10对PAK2的酶解激活

RIO3为非典型激酶RIO家族的成员之一,仅在多细胞真核生物中出现,为研究RIOK3蛋白的功能,以其作为诱饵蛋白对成人肝cDNA文库进行酵母双杂交筛选,得到其相互作用蛋白PAK2,并通过细胞内免疫共沉淀和免疫荧光共定位实验验证了该相互作用。实时定量PCR和免疫印迹检测结果显示,RIOK3能够在蛋白水平上降低PAK2表达量。通过CCK-8和细胞凋亡检测,发现二者共表达可以抑制增殖并促进凋亡,并且这一促凋亡效应可以被caspase-10的无酶活最短剪切本caspase-10G所抑制。实验结果显示,RIOK3可能促进了caspase-10对PAK2的酶解,在PAK2的酶解激活途径中发挥重要作用。     

AtSARK互作蛋白的筛选与鉴定

植物LRR型类受体蛋白激酶在植物生命活动中发挥着重要作用。前期研究发现了一个通过生长素和乙烯的协同作用参与拟南芥叶片衰老过程正调控的类受体蛋白激酶, AtSARK。为深入研究 AtSARK 蛋白的作用机制, 文章采用酵母双杂交系统, 以AtSARK胞内域（AtSARK-CD）为诱饵蛋白, 对拟南芥均一化cDNA文库进行筛选, 得到83个AtSARK的候选互作组分, 经过复筛, 初步发现AtSARK的互作组分包括14-3-3蛋白、FKBP-型肽脯氨酰顺反异构酶、醛缩酶超家族成员、RING/U-box 超家族成员以及WRKY转录因子家族成员。我们对其中一个功能未知的醛缩酶家族基因AtFBA5 （AT4G26530）的表达模式进行了分析, 并用GST pulldown实验证实了AtSARK-CD与 AtFBA5间存在直接的相互作用。At-SARK互作组分的文库筛选及AtFBA5的分离有利于进一步研究 AtSARK 基因在衰老信号通路中的作用机制。     

Meat odour and flavour and indoles concentration in ruminal fluid and adipose tissue of lambs fed green herbage or concentrates with or without tannins

A 2 × 2 factorial experiment was carried out to evaluate the effect of herbage or concentrate feeding system and tannin addition to diet on skatole and indole in ruminal fluid and adipose tissue and meat sensory properties. Twenty-eight male lambs aged 45 days were randomly assigned to one of two feeding systems (vetch green herbage or concentrates, n = 14) and within feeding system to one supplement (quebracho tannins added to the diet or none). Animals were kept in singular pens and slaughtered at the age of 105 days. Indole (P < 0.05) and skatole (P < 0.01) concentrations in ruminal fluid were higher in lambs fed herbage compared to those given concentrates. Skatole in ruminal fluid tended to be present at lower concentrations in animals that received the tannin supplementation (P = 0.07). Indole was also higher in the caudal fat of animals fed green vetch compared to those fed concentrate (P = 0.04). Skatole concentration was lower in the fat of lambs fed concentrates compared to those given herbage (P = 0.05) and was lower in the fat of animals supplemented with tannins compared to the animals not supplemented (P = 0.01). Sheep meat odour was lower in meat from animals supplemented with tannins compared to those not supplemented (P < 0.01). It is concluded that tannins are more effective in reducing skatole formation in ruminants when they are associated with concentrate diets than green herbages.