Inhibition of DNA polymerase β activity in isolated bovine liver nuclei by captan and related compounds

The effects on DNA synthesis of the fungicide captan and several structurally related compounds were investigated in isolated bovine liver nuclei. Captan, folpet, captafol, and trichloromethanesulfenyl chloride inhibited DNA synthesis to the same degree with ID₅₀ values of approximately 50 μM in a 40-min assay. The inhibition is concentration dependent and the degree of inhibition increases with time. Studies with structural analogs of captan indicated that inhibition of DNA synthesis by captan is mediated through the trichloromethylthio moiety of the captan molecule. In addition, the data indicate thiophosgene is probably not the toxic species involved in the inhibition of DNA synthesis. The isolated nuclei used in this study were shown to exhibit only a single DNA polymerase activity which was determined to be of the β or low-molecular-weight type. In addition to its inhibition in intact nuclei, captan inhibited the activity of the β polymerase in nuclear extracts as well as in partially purified enzyme preparations. These results indicate that captan inhibits DNA synthesis in our preparation of isolated nuclei by acting directly on the DNA polymerase-catalyzed reaction rather than by causing a nonspecific or indirect effect in the nuclear system such as alterations in the nuclear membrane or aggregation of the nuclei. The site of captan's inhibitory action is the DNA polymerase molecule. The interaction of captan with the polymerase results in irreversible inhibition of the enzyme. Interaction of captan with the template, if it occurs, does not appear to be involved in mediating the inhibition.     

A modified fluorometric method to quantify the concentration effect (pI50) of photosystem II-inhibiting herbicides

Chlorophyll fluorescence induction curves of isolated thylakoids were measured in the absence and in the presence of various concentrations of photosystem II-inhibiting herbicides. A mathematical program was applied to simulate the curves. Based on these simulated curves a new method is developed to determine the concentration effect (pI₅₀) of the herbicides. The results of the new method correspond well with reported values in the literature. The method is very convenient and time-saving.     

Theileria orientalis: a review

Theileria orientalis (also known historically as T. sergenti and T. buffeli) is responsible for benign or non-transforming theileriosis, and exerts its major effect through erythrocyte destruction. The life cycle of T. orientalis is essentially similar to that of other Theileria species, except that the schizonts do not induce transformation and fatal lymphoproliferation. The pathogenesis of anaemia as a result of infection is not clearly established and may be multifaceted. Clinical signs of weakness, reluctance to walk and abortion are early but non-specific indications of disease, particularly if accompanied by a history of cattle being moved. Physical examination may reveal pallor (pale eyes, vaginal mucosa), pyrexia, and elevated heart and respiratory rates. T. orientalis is an economically important parasite of cattle in New Zealand, Australia and Japan, especially where naïve animals are introduced into an endemic area or in animals under stress. Increased awareness of the risks posed by the parasite is required to enable management practices to be implemented to minimise its impact.     

一种确定林业发展项目的有效工具(英文)

在云南省绿春县的有些村庄,由砍柴造成的森林破坏是造成环境退化的主要原因。在黑河流域的上游,不断加剧的水土流失和河床抬升对下游上百万的人们构成威胁。尽管人们对森林破坏和土地的可持续利用、社区可持续发展之间的关系不是不了解,但当生存压力存在的时候就会忽略由此造成的对未来的影响。对于村民来说,他们已经意识到了他们的生存状况,并讨论解决的有效途径,而不是单纯等待外界的援助和干预。问题的关键是如何将这些变化和影响以一种直观和形象的方式向村民解释,并且让包括文盲在内的所有人都能理解。从这方面考虑,图形的东西比文字和数字分析更有优势。本文采用MIGIS(移动交互式地理信息系统的英文缩写,它包括两部分的内容,即PLA-参与式学习和行动和GIS-地理信息系统)在云南省绿春县哈尼族村寨来协助进行村民自发的造林规划。图6表1参16。