Impact of Land-Use Patterns on Chemical Properties of Trace Elements in Soils of Rural,Semi-Urban,and Urban Zones of the Niger Delta,Nigeria

The study of the concentrations of Cr, Zn, Cd, Pb, Ni, and Cu in soils under different land uses in rural, semi-urban, and urban zones in the Niger Delta was carried out with a view to providing information on the effects of the different land uses on the concentrations of trace elements in soils. Our results indicate significant variability in concentrations of these metals in soils under different land uses in rural, semi-urban, and urban zones. The maximum concentrations of metals in the examined soil samples were 707.5 mg.kg^?1, 161.0 mg.kg^?1, 2.6 mg.kg^?1, 59.6 mg.kg^?1, 1061.3 mg.kg^?1, and 189.2 mg.kg^?1 for Cr, Zn, Cd, Pb, Ni, and Cu, respectively. In the rural zone, the cassava processing mill is a potent source of Ni, Cr, Cu, and Zn while agricultural activities are a source of Cd, and automobile emissions and the use of lead oxide batteries constitute the major sources of Pb. In the urban zone, soils around the wood processing mill showed elevated concentrations of Cu, Cr, Zn, and Ni, while soils around automobile mechanic works and motor parks showed elevated levels of Pb. Elevated Cd concentrations were observed in soils under the following land uses: urban motor park, playground, welding and fabrication sheds, and metallic scrap dump. The contamination/pollution index of metals in the soil follows the order: Ni > Cd > Cr > Zn > Cu > Pb. The multiple pollution index of metals at different sites were greater than 1, indicating that these soils fit into “slight pollution” to “excessive pollution” ranges with significant contributions from Cr, Zn, Cd, Ni, and Cu.     

Hill coefficient-based stochastic switch-like signal directly governs damage-recovery dynamics in freshwater fish in response to pulse copper

Growing evidence demonstrates that fluctuating metal stressors can have profound impact on the ecophysiological responses in aquatic species. However, how environmental stochasticity affects the complex damage-recovery dynamics in organisms remains difficult to predict. The objective of this paper was to investigate the stochastic behavior in the damage-recovery dynamics in tilapia in response to pulse waterborne copper (Cu). We developed a mathematical framework that allows discrimination between damage and recovery processes in tilapia exposed to designed pulse Cu scenarios. We built deterministic nonlinear models for the damage-recovery dynamics that produce response surfaces describing killing/recovery rate–Cu-pulse interval interactions. Here we showed that the stochastic switching behavior arose from competition among killing, recovery rates, and Cu pulse frequency. This competition resulted in an ultrasensitivity appeared in whole body, gills, muscle, liver, and kidney with Hill coefficients of ≥7, 4, 7, 5, and 5, respectively, at Cu 3 mg L⁻¹, dilution rate 0.05 h⁻¹, and pulse interval 72 h, indicating that a stochastic switch-like response was generated. We argue that the role of gill-associated Hill coefficient as a direct signal of the stochastic switch-like response in the damage-recovery dynamics in response to pulse metal stressor can serve as a sensitive indicator for risk detection in fluctuating environments. Our approach constitutes a general method to identify the stochastic switch-like response for aquatic species exposed to fluctuating metal stressors, which may help to predict and, eventually, expand our understanding of the damage-recovery dynamics. Finally, we implicate that Hill coefficient-based switch-like signal and its damage with hazard response can be linked in an information theoretic framework to handle environmental stochasticity.     

The vegetation of metalliferous and non-metalliferous grasslands in two former mine regions in Central Slovakia

We investigated the composition of the vegetation in two former mining regions in Central Slovakia: Banská Štiavnica with predominant Pb-Zn contamination and Staré Hory with a very high Cu content in the soil. Old heaps rich in heavy metals are covered with specific vegetation. On the Cu-rich spoil heaps, species-poor plant communities with prevailing Agrostis stolonifera, Avenella flexuosa, Acetosella vulgaris, Arabidopsis arenosa, Silene dioica, and S. vulgaris occur. Species such as Agrostis capillaris, Acetosella vulgaris, Arabidopsis arenosa, and Thlaspi caerulescens appear frequently on Pb-Zn mine wastes. Several differences in the vegetation structure were detected between the Pb-Zn and Cu mine heaps; higher amounts of vascular plants and fewer lichen species covered the Pb-Zn mine heaps. For the Cu mine heaps, on the contrary a small number of vascular species but a high number and coverage of lichen species, especially Ceratodon purpureus and Cladonia arbuscula subsp. mitis were typical. The non-metalliferous meadows in the vicinity of the mines showed uniform structure but a higher species diversity.     

A chemically induced new pea (Pisum sativum) mutant SGECdt with increased tolerance to, and accumulation of, cadmium

BACKGROUND AND AIMS: To date, there are no crop mutants described in the literature that display both Cd accumulation and tolerance. In the present study a unique pea (Pisum sativum) mutant SGECd(t) with increased Cd tolerance and accumulation was isolated and characterized. METHODS: Ethylmethane sulfonate mutagenesis of the pea line SGE was used to obtain the mutant. Screening for Cd-tolerant seedlings in the M2 generation was performed using hydroponics in the presence of 6 microm CdCl2. Hybridological analysis was used to identify the inheritance of the mutant phenotype. Several physiological and biochemical characteristics of SGECd(t) were studied in hydroponic experiments in the presence of 3 microm CdCl2, and elemental analysis was conducted. KEY RESULTS: The mutant SGECd(t) was characterized as having a monogenic inheritance and a recessive phenotype. It showed increased Cd concentrations in roots and shoots but no obvious morphological defects, demonstrating its capability to cope well with increased Cd levels in its tissues. The enhanced Cd accumulation in the mutant was accompanied by maintenance of homeostasis of shoot Ca, Mg, Zn and Mn contents, and root Ca and Mg contents. Through the application of La(+3) and the exclusion of Ca from the nutrient solution, maintenance of nutrient homeostasis in Cd-stressed SGECd(t) was shown to contribute to the increased Cd tolerance. Control plants of the mutant (i.e. no Cd treatment) had elevated concentrations of glutathione (GSH) in the roots. Through measurements of chitinase and guaiacol-dependent peroxidase activities, as well as proline and non-protein thiol (NPT) levels, it was shown that there were lower levels of Cd stress both in roots and shoots of SGECd(t). Accumulation of phytochelatins [(PCcalculated) = (NPT)-(GSH)] could be excluded as a cause of the increased Cd tolerance in the mutant. CONCLUSIONS: The SGECd(t) mutant represents a novel and unique model to study adaptation of plants to toxic heavy metal concentrations.     

高等植物金属抗性中有机酸的作用及其机理

植物的金属抗性可通过避性和耐性途径获得。具有螯合能力的有机酸在植物的金属外部排斥(避性)机制和内部耐受(耐性)机制中均具有重要作用。在金属的外部排斥过程中,植物根系分泌有机酸,与金属离子形成稳定的复合体,降低土壤金属的移动性,达到体外解毒的目的。超积累型植物的内部耐受机制主要体现在,有机酸可与金属元素发生螯合作用,将离子态的金属转变成低毒或无毒的螯合态,从而降低细胞内金属离子的毒害效应。有机酸的种类受植物种类、金属类型等因素的影响。     

不同培养基和三种金属离子对桦褐孔菌培养菌丝体的羊毛甾醇和麦角甾醇积累的影响

Lanosterol and ergosterol are the active principles with potential pharmacological activities in Inonotus obliquus. However, the two sterols are less accumulated in cultured mycelia of the fungus. In this study, different carbon and nitrogen sources and pH levels together with three metal ions were assayed for their effects on accumulation of the two sterols in the fungus. Among the tested media the growth medium consisting of glucose (1.5%), rice powder (0.5%), yeast extract (0.4%), wheat bran (0.1%), KH2PO4 (0.01%) and MgSO4?7H2O (0.05%) with pH level at 6.5 yielded a maximum production of the two sterols, which can further be increased following the treatment of Ag+, Cu2+ and Ca2+. Supplementing Ag+ at concentrations of 0.28 and 0.35?mol partially inhibited ergosterol biosynthesis, leading to an enhanced accumulation of lanosterol, the presence of intermediates of ergosterol biosynthetic pathway and a reduced accumulation of ergosterol in cultured mycelia of I. obliquus.     

Cd2+、Cu2+胁迫对黑藻(Hydrilla verticillata)的生长及光合荧光特性的影响

以黑藻(Hydrilla verticillata)为供试材料,采用Cd2+和Cu2+等两种重金属分别在5个浓度梯度水平下的河砂水培方法,研究Cd2+或Cu2+不同浓度胁迫对黑藻株高、生物量、成活率和叶绿素含量的影响,以及对黑藻叶片最小荧光(Fo)、最大荧光(Fm),PSⅡ最大量子产率(QYmax,)、稳态下的PSⅡ反应中心关闭程度(1-Qp_Lss)、稳态下的非光化学淬灭(NPQ_Lss)等光合荧光参数及其荧光成像的影响,探讨各个参数分别随镉、铜浓度递增的变化规律。研究结果表明,Cd2+胁迫下黑藻的株高显著下降,说明Cd2+可能对黑藻叶片的维管束结构产生伤害作用;Cd2+和Cu2+胁迫对黑藻鲜重均无显著影响,说明与水生植物自由水含量存在一定关系;Cd2+和Cu2+胁迫均使黑藻干重显著下降,其中Cu2+胁迫对黑藻干重的影响更显著,说明Cu2+胁迫对黑藻累积生物量的影响远大于Cd2+;Cd2+和Cu2+胁迫下叶绿素各值均呈下降趋势,而Cu2+胁迫对叶绿素的影响更大,说明Cu2+对黑藻叶绿体的毒害比Cd2+更大。随着Cd2+或Cu2+胁迫浓度梯度的增加,黑藻的叶绿素荧光参数(Fo、Fm、QYmax)呈显著下降趋势,(1-Qp_Lss)呈上升趋势,而NPQ_Lss先上升后下降。黑藻在不同重金属胁迫下的生理指标、荧光参数及成像特征等方面所表现出的变化差异性,反映出同等浓度下黑藻受重金属胁迫的影响程度为:Cd2+胁迫Cu2+胁迫;黑藻可以在Cu2+浓度低于1 mg/L的环境下具有正常的光合活性,可推测将黑藻用于低浓度Cu污染水域的修复;在Cu2+浓度达3 mg/L以上环境下黑藻即无法长时间生存,可推测黑藻可以作为Cd污染水环境的指示种。     

A Jonah-like chymotrypsin from the therapeutic maggot Lucilia sericata plays a role in wound debridement and coagulation

Lucilia sericata larvae are used in maggot debridement therapy, a traditional wound healing approach that has recently been approved for the treatment of chronic wounds. Maggot excretion products (MEP) contain many different proteases that promote disinfection, debridement and the acceleration of wound healing, e.g. by activating the host contact phase/intrinsic pathway of coagulation. In order to characterise relevant procoagulant proteases, we analysed MEP and identified a chymotrypsin-like serine protease with similarities to Jonah proteases from Drosophila melanogaster and a chymotrypsin from Lucilia cuprina. A recombinant form of the L. sericata Jonah chymotrypsin was produced in Escherichia coli. The activated enzyme (Jonah_m) had a pH optimum of 8.0 and a temperature optimum of 37 °C, based on the cleavage of the chromogenic peptide s-7388 and casein. Jonah_m reduced the clotting time of human plasma even in the absence of the endogenous protease kallikrein, factor XI or factor XII and digested the extracellular matrix proteins fibronectin, laminin and collagen IV, suggesting a potential mechanism of wound debridement. Based on these characteristics, the novel L. sericata chymotrypsin-like serine protease appears to be an ideal candidate for the development of topical drugs for wound healing applications.     

Nickel requirement for chemolithotrophic growth in hydrogen-oxidizing bacteria

In a comparative study the requirement of several strains of autotrophic hydrogen-oxidizing bacteria for nickel was examined. Autotrophic growth was studied both in liquid media, previously freed from trace metals; and on solidified media, using a plate diffusion assay. The latter assay was based on the observation that EDTA causes complete inhibition of autotrophic growth on agar medium as a result of nickel deficiency. Nickel was shown to be required as a trace element in five strains of Alcaligenes eutrophus, in two strains of Xanthobacter autotrophicus, in Pseudomonas flava, in Arthrobacter spec. 11X and in strain 12X. In these bacteria nickel was not replaceable by cobalt, copper, manganese or zinc ions. No significant nickel requirement was detected by these methods, however, for Paracoccus denitrificans and Nocardia opaca 1b.     

水稻直链淀粉和蛋白质突变系筛选及其与主要农艺性状的关联分析

研究利用重离子辐照杂交籼稻9311创建农艺性状突变体库,使用化学方法筛选直链淀粉、蛋白质突变材料,并分析籽粒品质性状与农艺性状之间的相关性,为后续筛选直链淀粉、蛋白质突变体工作奠定基础。结果显示:在169份直链淀粉、蛋白质突变体中,直链淀粉含量变幅范围是7.64%~32.37%,其中高含量直链淀粉突变体材料有11份,低含量直链淀粉突变体材料有5份;蛋白质含量变幅范围是7.05%~13.79%,其中高蛋白突变体有34份,低蛋白突变体有3份。从169份突变体中筛选出直链淀粉、蛋白质含量都有梯度差异的突变体材料,筛选出材料的农艺性状分析结果表明:在直链淀粉、蛋白质突变体材料的农艺性状中,每穗实粒数、有效穗数、结实率和株高这四个农艺性状与籽粒品质性状间有关联,变异系数分别为37.53%、30.72%、24.70%、15.38%。相关性结果表明:直链淀粉含量和蛋白质含量呈负相关,直链淀粉含量与农艺性状呈正相关,蛋白质与农艺性状呈负相关,其中蛋白质含量和每穗实粒数、结实率呈极显著负相关,相关系数分别为-0.504、-0.592。