沙漠腹地达理雅博依绿洲浅层地下水水化学特征分析

为了评价塔克拉玛干沙漠腹地达理雅博依绿洲地下水水化学特征与演化规律及对当地生态环境的影响。在研究区的生态井位观测点采集了19组地下水样品进行检测。综合运用数理统计、相关性分析、Piper三线图、Gibbs模型、Schoeller图和离子比等方法,分析地下水水化学特征和克里雅河尾闾绿洲的水化学演化规律。研究表明:研究区地下水阳离子以Na⁺、Mg⁺离子为主,阴离子以Cl^-、SO₄^2-,为主,Mg⁺、Cl^-、SO₄^2-表现为强变异性,K⁺、Ca⁺、Na⁺、HCO-3表现为中等变异;TDS介于1000mg/L-18620mg/L范围内,平均值为4366.408mg/L,矿化度较高;水化学类型以Cl^--Na⁺为主;地下水样品主要分布于Gibbs图的右上部分,表明研究区地下水主要受蒸发浓缩作用控制,岩石风化和大气降水影响较小;主要离子比表明碳酸盐、蒸发岩和硅酸盐是离子的主要来源,且处于沙漠腹地的独特地理因素,地下水中的离子交换作用较弱。     

Widespread translational inhibition by plant miRNAs and siRNAs

High complementarity between plant microRNAs (miRNAs) and their messenger RNA targets is thought to cause silencing, prevalently by endonucleolytic cleavage. We have isolated Arabidopsis mutants defective in miRNA action. Their analysis provides evidence that plant miRNA-guided silencing has a widespread translational inhibitory component that is genetically separable from endonucleolytic cleavage. We further show that the same is true of silencing mediated by small interfering RNA (siRNA) populations. Translational repression is effected in part by the ARGONAUTE proteins AGO1 and AGO10. It also requires the activity of the microtubule-severing enzyme katanin, implicating cytoskeleton dynamics in miRNA action, as recently suggested from animal studies. Also as in animals, the decapping component VARICOSE (VCS)/Ge-1 is required for translational repression by miRNAs, which suggests that the underlying mechanisms in the two kingdoms are related.     

Indicators of unsustainable fishery in the Middle Danube

Fishery in the Danube River basin has been characterised over the past century by increasing fishing levels, illegal fishing practices and poor regulations. However, there is a remarkable lack of available information on the actual status of fish stocks, as well as on the trends and sustainability of fisheries, which poses a problem for the development of adequate policy and management measures. In this study, we assessed the trends in the commercial fishery in the Middle Danube in Serbia during 1969–1989 and 2006–2010 by evaluating the temporal changes in life history‐related indicators that might point out unsustainable fishing pressures. Moreover, we present the approach of using the catch‐weighted mean egg‐per‐recruit (EPR) index as a proxy for the overall resilience of fish stocks to fishing. Results indicated a marked shift towards smaller fish that mature earlier and have a shorter lifespan. Landings also shifted towards species at lower trophic levels, with a mean trophic level decline at a rate of approximately 0.16 per decade. Results indicated likely presence of the ‘fishing through the food web’ phenomenon. At the same time, catch‐weighted community mean of the 20% EPR threshold ratio (EPR_20%) increased by 4.2%, indicating the increase of the overall resilience to fishing of the exploited species. Obtained results indicated the importance of using such metrics for the assessments of trends in fishery. The approach and results presented here could be of interest for the scientific community and stakeholders involved in fishery management.     

Effect of the Simultaneous Action of Zinc and Chromium on <Emphasis Type="Italic">Arthrobacter</Emphasis> spp.

Bacteria are regarded as the most effective in the detoxification of heavy metals, being environmental compatible. Metalloresistant bacteria are usually found in nature in highly contaminated environment where they interact with a combination of several toxic metals. For the present research, Arthrobacter oxydans and Arthrobacter globiformis have been isolated from the soil samples of the most polluted regions of Georgia, rich with manganese and iron, and contain co-produced toxic metals such as Cr, V, Zn, Ni, Pb, and Mo. We have studied the effects of the metals with different valence/charge on the metalloresistant Arthrobacter spp., the divalent cation—Zn(II) and the hexavalent anion—Cr(VI). The permanent presence of a nontoxic concentration of zinc alone or zinc together with the subtoxic concentration of chromium at the growth of A. oxydans and A. globiformis as batch culture causes the activation of the zinc primary uptake system transporters from the ZIP family (Zrt1). Chromium does not affect the process. The studied Arthrobacter spp. differ by the character of the activation of the antioxidant defense system. Chromium and zinc concomitant action causes the strongest oxidative stress in the case of A. globiformis that is demonstrated by the increased activity of superoxide dismutase (SOD) and catalase. In the case of A. oxydans, the zinc separate action, and the joint action of zinc and chromium decreases the activity of SOD and catalase. The antioxidant system is active in A. globiformis at the prolonged action of metals (96 h), whereas the cells of A. oxyidans activate the other defense mechanisms to survive.     

Bt与硫丹、氟铃脲对棉铃虫的联合作用

通过室内和田间试验，研究了Bt与硫丹、氟铃脲对棉铃虫的联合作用。结果表明：(1)Bt与硫丹无论以何种比例相混，对敏感品系和氰戌菊脂中抗品系均增效。(2)Bt与氟铃脲只有以1:60相混才明显增效；Bt中加入少量氟铃脲和氟铃脲中加入少量Bt则明显拮抗。（3）Bt与硫丹和氟铃脲混用，明显加快了2龄幼虫的死亡速度，混剂在处理后第3d，死亡率便明显高于Bt，而与硫丹或氟铃脲单用接近。（4）田间试验中，Bt和硫丹的混剂显著增效，Bt与氟铃脲的混剂在药后4d表现出一定的增效作用，但药后7d明显拮抗。     

Postnatal development of metallophilic macrophages in the rat thymus

Metallophilic macrophages (MMs) are a distinct cell type of the rodent thymus. Our previous research has focused on the morphological characteristics of MMs, as well as on the molecular mechanisms involved in the development and tissue positioning of these cells. However, the postnatal development of MMs has not been sufficiently studied. In the present study, we investigated the positioning of MMs in the rat thymus between postnatal day 0 (P0) and P30. On P0, MMs were evenly distributed all over the thymic tissue—that is, the cortex, cortico-medullary zone and medulla. From P0 to P15, the number of MMs in the thymic cortex significantly decreased, and after P15, this number did not change. Thus, the present study shows that on P15, MMs almost completely disappear from the thymic cortex and show their adult position in the cortico-medullary zone and in the medulla.