Resonant formation of DNA strand breaks by low-energy (3 to 20 eV) electrons

Most of the energy deposited in cells by ionizing radiation is channeled into the production of abundant free secondary electrons with ballistic energies between 1 and 20 electron volts. Here it is shown that reactions of such electrons, even at energies well below ionization thresholds, induce substantial yields of single- and double-strand breaks in DNA, which are caused by rapid decays of transient molecular resonances localized on the DNA's basic components. This finding presents a fundamental challenge to the traditional notion that genotoxic damage by secondary electrons can only occur at energies above the onset of ionization, or upon solvation when they become a slowly reacting chemical species.     

Recent findings on certain bioactive components in whole grain wheat and rye

Whole grain wheat and rye are important sources of many bioactive compounds and contribute significantly to the total intake of cereals in many countries. Alkylresorcinols, benzoxazinoids, lignans, phenolic acids, phytosterols and tocols are common bioactive compounds present in these cereals. In this review, we report recent findings (mainly from 2010 onwards) regarding their content, composition, effects of food processing and their uptake, elimination and bioactivities with implications for health.     

High-throughput screening reveals small molecule modulators inhibitory to Acidovorax citrulli

Acidovorax citrulli is a seed-transmitted gram-negative bacterium that can cause substantial economic yield loss in watermelon and melon production worldwide. Four small-molecule libraries containing 4,952 compounds were selected for high-throughput screening against A. citrulli wild-type strain Xu3-14 by evaluation of growth inhibition. One hundred and twenty-seven molecules (2.5% hit rate) were identified as bactericidal or bacteriostatic against A. citrulli at 100 μM. Secondary screens indicated that 27 candidate compounds were more effective against A. citrulli Group II strains than Group I strains (classified using repetitive element PCR). Several compounds were inhibitory to other pathogenic bacteria, including Clavibacter michiganensis subsp. michiganensis and Xanthomonas campestris pv. campestris, but did not affect the growth of plant beneficial bacteria Pseudomonas fluorescens and Bacillus subtilis. More than half of the compounds did not inhibit germination of Arabidopsis or watermelon seeds. The effect of small molecules on A. citrulli seed-to-seedling transmission was evaluated by applying each compound to inoculated watermelon seeds and assessing seedling infection. Nine compounds were chosen for further investigation based on their reduction of percentage seedling infection and compiling scores on their specificity, sensitivity, and phytotoxicity obtained in the secondary screens. The five best compounds were selected (thiamphenicol, nadifloxacin, pipemidic acid, ciclopirox, and zinc pyrithione) for greenhouse tests and were found to effectively reduce the seed-to-seedling transmission of A. citrulli in both artificially and naturally infested seeds. These top five compounds provide a basis for future development of an A. citrulli-specific bactericide.     

Differential distribution and response to experimental sexual maturation of two forms of brain gonadotropin-releasing hormone (GnRH) in the European eel,Anguilla anguilla

Using specific radioimmunoassays for the two GnRH molecular forms present in the European eel, Anguilla anguilla, (mGnRH and cGnRH II), we compared their distributions in the pituitary and different parts of the brain of female silver eels, as well as the modifications of their levels in experimentally matured female eels (treated with carp pituitary extract). In control eels, mGnRH levels were higher than cGnRH II levels in the pituitary, olfactory lobes and telencephalon, di- and mesencephalon, while the opposite was found in the posterior part of the brain (met- and myelencephalon). Experimental sexual maturation of the gonads significantly increased mGnRH levels in the pituitary and anterior parts of the brain; such a positive effect was not observed on the low cGnRH II levels, which were, in contrast, reduced. These data indicate that the positive feedback of gonadal hormones on GnRH, that we previously demonstrated, would specifically affect the mGnRH form. The differential distribution and control of mGnRH and cGnRH II suggest that these two forms have different physiological roles in the eel. The large increase in mGnRH during sexual maturation suggests the prime implication of this form in the neuroendocrine control of reproduction.     

Residential runoff – The role of spatial density and surface cover,with a case study in the Höjeå river catchment,southern Sweden

Depending on the spatial density of built cover and location within a catchment, residential areas make varying contributions to surface runoff throughout different rainfall events. This study examined these contributions and the associated effect of different surface covers and sustainable drainage systems on runoff generation. The Soil Conservation Service curve number (SCS-CN) method was applied to analyse urban development in the Höjeå river catchment in southern Sweden.The results indicated that identical amounts of surface runoff are generated by low-density residential areas on heavy clay soils and high-density residential areas on sandy soils. However, increasing the density of built-up areas on sandy soils is likely to be more disruptive to the hydrological balance and to generate a greatly increasing difference in runoff as building density and impermeable surface area increase. A similar pattern is likely to occur if rainfall intensity increases. It may therefore be appropriate to apply different planning considerations to residential developments depending on the existing soil group, e.g. conserving existing vegetated surfaces on sandy soil and incorporating permeable paving materials and sub-surface infiltration beds in development on clayey soils. Increased area of impermeable surface cover will increase surface runoff in all residential areas, irrespective of building density, soil group and rainfall intensity. However, adapting a systems approach in combining vegetative structures and permeable paving materials with subsurface infiltration beds can help mitigate the impact of surface runoff, particularly in urban developments on clay-rich soils.     

Genesis of light-colored acid eluvial horizons in soil profiles

General ideas concerning the formation of light-colored acid eluvial horizons in soil profiles are considered. In Russia, the current concept is related to the polygenetic origin of these horizons due to processes of acid hydrolysis, lessivage, and gley. Based on the original and literature data summarized by the author, the conclusion was drawn that the acid hydrolysis cannot provide the reduction of Fe (III) to Fe (II) under aerobic conditions or its further transfer to the soil solution. Lessivage, which governs the formation of light-colored acid eluvial horizons, is not an obligatory factor, as its features are often absent in the profile of these soils. Under conditions of a stagnant-percolative water regime, gley may be considered to be the only process responsible for the eluviation of Fe, Mn, and Al and removal of iron hydroxide and iron oxide coatings from mineral grains, resulting in an increase in the relative Si content and the appearance of a whitish color. This factor is the only cause for the formation of light-colored eluvial (podzolic) horizons. Therefore, they are monogenetic in origin.     

镉对油菜叶细胞膜的损伤及细胞自身保护机制初探

砂基培养 50 d的油菜幼苗，用不同浓度的 CdCl2溶液灌溉后，研究叶细胞膜结构与功能及细胞保护系统的变化。结果表明， 0.1 mg· L－ 1 Cd污灌，叶细胞膜结构与功能及细胞保护系统未见明显变化；浓度大于 1 mg· L－ 1时，叶组织细胞膜脂质过氧化水平升高，膜结构损伤，膜透性增大。 1— 20 mg· L－ 1 Cd污灌， SOD、 POD、 CAT活性表现出不同程度的升高，细胞呈现出积极性自身保护机制； 50 mg· L－ 1 Cd污灌， SOD、 POD、 CAT活性下降，细胞自身积极性保护作用消失。说明细胞自身保护系统只能在一定范围内起积极作用。     

Multiple glassy states in a simple model system

Experiments, theory, and simulation were used to study glass formation in a simple model system composed of hard spheres with short-range attraction ("sticky hard spheres"). The experiments, using well-characterized colloids, revealed a reentrant glass transition line. Mode-coupling theory calculations and molecular dynamics simulations suggest that the reentrance is due to the existence of two qualitatively different glassy states: one dominated by repulsion (with structural arrest due to caging) and the other by attraction (with structural arrest due to bonding). This picture is consistent with a study of the particle dynamics in the colloid using dynamic light scattering.     

Erratum to Variation in aggressiveness of Plasmopara halstedii (sunflower downy mildew).

Journal of Plant Diseases and Protection -