Signaling versus punching hole: How do Bacillus thuringiensis toxins kill insect midgut cells?

Cry proteins, produced by Bacillus thuringiensis (Bt), are widely used for the control of insect pests in agriculture as spray products or expressed in transgenic crops, such as maize and cotton. Little was known regarding the mechanism of action of these toxins when the first commercial Bt product was introduced fifty years ago. However, research on the mechanism of action over the last two decades has enhanced our knowledge of toxin interaction with membrane receptors and their effects in insect midgut cells. All this information allowed for the rational design of improved toxins with higher toxicity or toxins that overcome insect resistance, which could compromise Bt use and effectiveness in the field. In this review we discuss and evaluate the different models of the mode of action of Cry toxins, including a discussion about the role of various receptors in toxin action. Received 13 June 2008; received after revision 05 November 2008; accepted 11 November 2008     

Use of aggregating cell cultures for toxicological studies

Summary Relatively simple techniques are now available which allow the preparation of large quantities of highly reproducible aggregate cultures from fetal rat brain or liver cells, and to grow them in a chemically defined medium. Since these cultures exhibit extensive histotypic cellular reorganization and maturation, they offer unique possibilities for developmental studies. Therefore, the purpose of the present study was to investigate the usefulness of these cultures in developmental toxicology. Aggregating brain cell cultures were exposed at different developmental stages to model drugs (i.e., antimitotic, neurotoxic, and teratogenic agents) and assayed for their responsiveness by measuring a set of biochemical parameters (i.e., total protein and DNA content, cell type-specific enzyme activities) which permit a monitoring of cellular growth and maturation. It was found that each test compound elicited a distinct, dose-dependent response pattern, which may ultimately serve to screen and classify toxic drugs by using mechanistic criteria. In addition, it could be shown that aggregating liver cell cultures are capable of toxic drug activation, and that they can be used in co-culture with brain cell aggregates, providing a potential model for complementary toxicological and metabolic studies.     

Implications of toxins in the ecology and evolution of plant pathogenic microorganisms: Bacteria

This review attempts to rationalise what is known about bacterial phytotoxins and associate it with the ecology and possible evolution of the producing organisms. Study of non-toxin producing variants gives insight into the ecological role of the toxin. Elucidation of chemical structures of phytotoxins has shown that many exist as families of analogous compounds. Studies on the variation of chemical structures and how they are distributed across species and genera can lead to development of hypotheses on evolutionary relationships. Knowledge on biosynthetic pathways to tosins allows recognition of specific enzymatic steps involved in developing the characteristic features of the structures. Phytotoxins often have a potent biochemical activity, and in some cases the producing organism has associated mechanisms to prevent action of the toxin upon itself; in such cases toxigenesis is clearly not a chance event. The various aspects of bacterial toxigenesis indicate that bacterial phytotoxins are special secondary metabolic products that play beneficial roles to the producing organisms in their various ecological niches.     

蛔虫病导致昏迷的诊治

通过两例蛔虫寄生于人体后导致昏迷的病例,探讨其机理主要是毒素作用于中枢神经系统.及时诊断与治疗,可获痊愈。     

短链蝎毒素BmK38的1H-NMR谱峰归属、二级结构分析及溶液构象

BmK38是最近从东亚钳蝎（Buthus martensi Karsch，BmK）中分离纯化得到的一种短链蝎毒素．应用2D-NMR技术研究BmK38的溶液构象，通过分析其在水溶液中的DQF-COSY、TOCSY和NOESY等1^H—NMR谱，识别了BmK38全部40个氨基酸残基的自旋体系，并通过分析NOESY谱图中dαN、dNN、dβN的联系，完成了序列专一性谱峰归属，标定了全部主链质子和绝大部分侧链质子的化学位移．根据谱峰归属的结果和NMR数据分析了BmK38的二级结构组成并且计算出BmK38的溶液构象．结构计算的结果与前述二级结构的分析是一致的．结果表明，肽段Gln8-Arg17形成α螺旋，而肽段Gly22-Glu29以及Leu32-CYS39构成反平行的口折叠，属于典型的短链蝎毒素的折叠形式．通过与其他OUKTx短链蝎毒素的结构比较，讨论了BmK38的结构特异性以及结构功能的相互关系．     

水产养殖动物补偿生长的研究进展

综述了水产养殖动物补偿生长的初步研究进展,包括水产养殖动物补偿生长的理论假说、类型、影响因素、实验方法和生理机制.初步探讨了补偿生长的研究价值及应用情况,提出了当前补偿生长研究存在的问题及今后的研究方向.     

蝎毒素成分、应用价值及其研究进展

对蝎子的分类、蝎毒素的组成成分及其性质、蝎毒素应用价值、蝎毒素研究进展及蝎毒素研究方向四个方面进行了阐述，说明蝎毒素是一种进行分子生物学研究的良好材料。     

多位点生物杀虫毒素BtA对小菜蛾的作用方式

Bt A是由 Bt伴孢晶体和阿维菌素制成的 ,对小菜蛾幼虫作用方式与阿维菌素相似 ,主要表现为胃毒和触杀作用 ,但效果比阿维菌素好。当用 1mg/m L溶液触杀处理小菜蛾 4龄幼虫背板 72小时后 ,Bt A引起的小菜蛾死亡率为 36 .7% ,显著高于阿维菌素的 2 0 .0 % ,而 Bt伴孢晶体几乎没有触杀作用。 Bt A、Bt伴孢晶体和阿维菌素对小菜蛾胃毒 4 8h的 LC50 分别为 :0 .0 136 mg/m L、0 .0 0 5 9mg/m L、0 .72 74 mg/m L。     

稻瘟病菌粗毒素对水稻幼胚愈伤组织的影响及抗性筛选

利用目前稻瘟病不同的优势小种菌株的液体培养提取的粗毒素对水稻幼胚进行处理,稻瘟病菌粗毒素提取液对水稻幼胚的愈伤的诱导和分化的有明显的抑制效应.随着毒素浓度的增加,水稻胚性愈伤获得率和分化能力显著降低.在诱导培养基中加入毒素对幼胚的筛选取效果较好,可以获得较多的胚性愈伤和较多的分化苗.培养基中毒素的浓度处理以30%效果好.水稻幼胚的抗性筛选过程中胚性愈伤获得和分化苗数较高,是很好的培养材料;而且不同的水稻品种产生的耐性不同,并可以同时筛选出抗稻瘟病的突变体.