Genotoxicity of chromium in vitro on yeast: Interaction with DNA†

The genotoxicity of chromium chloride was investigated in cells of D₇ strain of Saccharomyces cerevisiae harvested either from logarithmic or stationary growth phase.

A weak induction of mifotic gene conversion and point reverse mutation was obtained when the incubations were performed using phosphate buffer. No genetic effect was observed when the incubations were performed using Tris‐HCl buffer.

The experiments with ⁵¹Cr radiotracer demonstrated that Cr³⁺ ion enters the yeast cells and binds to DNA even if the incubation mixture was performed with Tris HCl buffer. This behaviour could be due to the highest concentration of CrCl₃ that cause some damages to cytoplasmatic membrane.     

Effect of Grazing and Climatic Changes on Alpine Vegetation of Tungnath,Garhwal Himalaya,India

Effect of grazing and changing climate on vegetation composition of alpine pasture at Tungnath, Garhwal Himalaya was observed. Growth form pattern and phytosociological attributes were analyzed during 1988 under grazed (exposed to extensive grazing) and ungrazed (protected from grazing) conditions. These observations were repeated during 1998. It was observed that number of early growing species and long vegetative growth cycle species had increased at both sites in 1998 in comparison to 1988. Further, some species, viz., Poa alpina, Polygonum spp., Ranunculus hirtellus, Anemone spp., are predominantly found near the timberline-subalpine region. These species are less palatable and were present at both sites with higher dominance (TBC) and niche width in 1998 indicating wide distribution of the species along an altitudinal gradient. These observations indicated the migration of these species towards upper slopes of alpine. Species diversity was also higher after ten years. However, it is clear that climatic changes alone are not responsible for these vegetational shifts. In fact, human-induced changes are the main reason for habitat destruction and changes in vegetation composition of the alpine region of Garhwal Himalaya. Before final conclusions can be made, long-term studies on vegetation composition and changes are needed, especially in Himalayan region.     

The centers of gravity and dynamic types of body shape of terrestrial invertebrates

In the framework of dynamic morphology theory, the centers of gravity and geometric centers of projections have been determined for the bodies of more than 182 forms of invertebrates, and these data have been used to distinguish four types of dynamic body shapes. It has been demonstrated that specific dynamic types of body shape are characteristic of individual taxa. In addition, there are a group of “transformers,” which may assume any dynamic type of shape, and a group of invertebrates with one predominant dynamic type.     

秦淮河干流沉积物磷形态沿程分布特征

应用化学连续提取法,分析了秦淮河干流14个表层沉积物样品的磷形态沿程变化特征及其影响因素.结果发现,秦淮河干流由上游至南京市区段,随城市化程度的提高,河流沉积物总磷和各种形态磷沿程增加的趋势十分明显.Ca-P和Fe-P平均含量分别占TP的26.8%和25.7%,是主要的磷形态.易吸附态磷(L-P)在TP中的比例最低,但在城区由于TP的高度富集,其含量均超过15 mg·kg-1.沉积物中的总磷含量在城区河段显著增加,但只有很少部分转化为稳定形态的磷,人口密集区生活污水等各种来源排放的磷仍然深刻影响着城市河流的水环境质量.随城市化程度的提高,秦淮河中下游沉积物样品中钙富集的趋势明显,与之相对应的是沉积物Ca-P含量均超过200 mg·kg-1,相关分析和通径分析结果表明,二者之间存在成因上的联系.钙的富集提高了沉积物的固磷能力,将上覆水体中的磷转化为钙结合态磷.城区河流沉积物中钙含量的升高,对于河流生态系统磷的迁移转化有重要影响.     

不同退耕年限下菜子湖湿地土壤铁形态变化

选取菜子湖区不同退耕年限(3、5、7、9、11、21 a)湿地为研究对象,以仍耕作油菜地和原始湿地为参照,分别采用王水消解法和Tessier连续提取法,分析了退耕还湖后湿地土壤全铁和铁的赋存形态特征,探讨退耕还湖后湿地土壤铁组分特征变化规律.结果表明:研究区土壤铁各形态含量大小顺序为:残渣态(RES-Fe:17.09~30.84 g·kg-1)铁锰氧化态(RED-Fe:3.66~4.48 g·kg-1)有机结合态(OM-Fe:0.87~3.09g·kg-1)碳酸盐结合态(CARB-Fe:0.01~0.37 g·kg-1)可交换态(EXC-Fe:0.01~0.15 g·kg-1).占全铁均小于1.5%的EXC-Fe和CARB-Fe均在退耕3 a和5 a期间含量快速升高,而后降低再升高,最低值出现在退耕11 a;RED-Fe在退耕3~9 a比较稳定,随后缓慢增加;而OM-Fe随退耕年限增加整体上呈增加趋势;占土壤铁形态总量73.91%~85.42%的RES-Fe在退耕3a时含量下降,在3~9 a间呈现逐渐增加的趋势,9~21 a又逐渐下降;研究区全铁(Tot-Fe)平均含量在18.50~38.41 g·kg-1之间,变化趋势与RES-Fe基本一致.讨论结果表明退耕还湖后水文条件和植被状况的改变导致了土壤环境发生变化,从而不仅影响退耕后湿地土壤全铁含量变化,也影响土壤铁形态组分特征,进而影响土壤铁的有效性.     

城市河网区河流沉积物磷形态分布特征及释放贡献

以嘉兴城市河网区为研究区域,在调查区域水质和沉积物磷空间变化特征的基础上,分析沉积物中各形态磷的垂直与空间赋存状态,通过吸附释放参数计算EPC₀值,明确了沉积物-水界面磷迁移影响因素和沉积物中活跃磷素的释放风险和贡献.结果表明,研究区域水质氮磷污染较为严重,沉积物TP含量均值呈北部河网区>西部河网区>南部河网区,基于单因子指数法的生态风险评价为Ⅱ、Ⅲ和Ⅳ级的样本比例分别为10.91%、25.45%和63.64%.沉积物各形态磷整体呈现TP>IP>HCl-P>NaOH-P>OP,沉积物生物有效磷（BAP）整体呈现Olsen-P>AAP>WSP>RDP;在沉积物垂直剖面中,部分位点受到外界因素的强烈影响垂向波动较大,整体上是随深度的递增而减小,这与近年来研究区域接收的外源磷积累过程在加重有关.相关性分析表明,沉积物磷吸附容量（Q_max）与铁铝氧化物呈显著相关性 （p<0.05）;释放参数EPC₀与TP、IP与HCl-P呈显著相关性 （p<0.05）.结合BAP形态,研究区域河流沉积物NaOH-P、HCl-P、AAP、Olsen-P及WSP存在较高的释放潜力.南部河网区沉积物主要呈现磷“源”角色,西部和北部河网区部分区域沉积物充当磷“源”角色.南部河网区在长短时间尺度下的磷主要释放形态为NaOH-P、HCl-P和OP,北部河网区在长时间尺度下主要释放磷形态为NaOH-P、HCl-P,西部河网区在短时间尺度下主要释放形态以HCl-P为主,在长时间尺度下3种磷形态的释放风险仍然较高.     

铁基硅盐对土壤环境镉砷赋存形态及转化影响

为探明铁基硅盐对土壤镉砷赋存形态影响及各形态间转化规律,采用室内长期淹水培养吸附实验,研究不同比例铁硅材料对土壤离子态镉砷活性影响;筛选适宜铁基硅盐(FS)配比同时添加腐殖酸(FSC)和金属氧化物(FSCa),明确复配处理土壤中镉砷分级形态转化程度.结果显示,铁:硅比值增加10%,土壤pH值平均降低0.35;F₂-S₈处理土壤离子态镉降幅71%;F₁₀-S₀处理土壤离子态砷降低59.9%,离子态镉砷含量与硅酸盐-铁盐施用量互呈反比;处理F₄-S₆和F₆-S₄之间镉、砷钝化率产生交点,约为25%~30%.土壤中镉主要以可溶态为主,占比58%;砷主要以铁铝氧化态和钙结合态为主,占比40%和23%.铁硅比例为5:5或5.5:4.5左右复配能有效将铝结合态砷和铁铝氧化态砷转变为钙结合态砷和残渣态砷,可溶态镉转化为碳酸盐结合态镉以及铁锰氧化态镉,同步降低土壤中镉砷的活性.     

The Influence of Varying Algal Biomass On Contaminant Exposure in Benthic-Planktonic Mesocosms: Copper (Ii)

A series of mesocosms was exposed to a suite of light treatments and nutrient enrichment in order to generate algal communities of varying biomass. the influence of this biomass on the speciation of copper (II) was studied. Distribution coefficients (_Kd,Lkg-1) were relatively high (log_Kd = 5 to 7), indicative of robust trace metal sequestration, and were likely controlled by the particulate organic carbon content (foc). Differences in _Kd over time and among treatments were significant, as was the relationship between _Kd and foc. Fluorescence quenching was used to determine binding capacities (_Lt, M) and their associated binding constants (_Kcond,M^-1) in order to model the solid phase copper speciation. the _Kcond ranged between 2.1 and 5.2 × 10¹²M^-1, indicating a very strong copper-ligand complex, and was higher in mesocosms that received more light. the light _Lt increased over time, dramatically after the nutrient enrichment, but did not vary systematically among light treatments. _Lt ranged from 7.2 × 10- 7 to 4.9 × 10- 5 M. the large magnitudes of _Kd, _Kcond and _Lt ensured that greater than 97% of total copper in the mesocosms was complexed by organic matter. the total copper concentration ([Cu]_T, M) needed to reach a target dissolved copper concentration of 10^-12.5 M (pCu = 12.5) was determined for each mesocosm over time. [Cu]_T was between 8.02 × 10^-5 and 3.41 × 10^-2 M, and increased over time. the [Cu]_T normalized to the target pCu (Effective Dose Ratio, EDR) increased directly with increases in algal biomass, indicating a direct link between system productivity and copper exposure. Approximately 45% of the variance in EDR was explained by variance in total biomass, while the residual variance in EDR was due likely to differences in the strengths of particle associations and magnitude of binding capacities.     

Interactions Among the Copper Species and Forms in Sea Water/Sediments and Copper Bioaccumulation in Oysters

Abstract

Earlier papers indicated that the first incident of green discoloration in oysters (Crassostrea gigas) and the mass mortality observed in 1986 along the Taiwan Erhjin Chi coastal area were caused by the higher contents of total copper and copper species (mainly bioavailable and free ion) in sea water. the copper in sea water would be sorbed by suspended matter and transferred to sediments, and the copper in the sediments would also be desorbed to sea water. Processes of copper adsorption and desorption are the major factors influencing the contents of total copper and copper species in sea water and sediments. in this study, the Erhjin Chi sediments were mixed with sea water by a shaker technique. When the mixture was shaken for one hour, analogous to tidal mixing in estuaries, only copper desorption from sediments was observed. If the shaking time is increased for more than 3 hours, the copper released from the sediments was resorbed to the remaining solid phases. the higher the contents of mud (91.71%) and total copper (701 mg kg^?1) in sediments, the higher the copper desorption rate (1.86 ppm hr^?1) and copper adsorption rate (0.50 ppm hr^?1) were observed. in sediments containing lower mud (0.80%) and lower copper (43.5 mg kg^?1), the copper desorption and adsorption rates were 0.83 ppm hr^?1 and 0.22 ppm hr^?1, respectively. the interactions among the total copper and copper species in sea water and sediments, chemical and ecological parameters, and copper bioaccumulation in oysters in the Erhjin Chi estuarine and coastal area are also discussed.     

Evaluation of Saccharomyces cerevisiae strains as probiotic agent with aflatoxin B1 adsorption ability for use in poultry feedstuffs

In this study the aflatoxin B₁ (AFB₁) removal capacity, the tolerance to salivary and gastrointestinal conditions, autoaggregation and coaggregation with pathogenic bacteria of Saccharomyces cerevisiae strains isolated from broiler feces, were evaluated. Only four of twelve isolated strains were identified as Saccharomyces cerevisiae using molecular techniques. The results obtained in AFB₁ binding studies indicated that the amount of AFB₁ removed was both strain and mycotoxin-concentration dependent. Therefore, a theoretical model was applied in order to select the most efficient strain to remove AFB₁ in a wide range of mycotoxin concentration. The results indicated that S. cerevisiae 08 and S. cerevisiae 01 strains were the most efficient microorganisms in the mycotoxin removal. Viability on simulated salivary and gastrointestinal conditions was investigated and S. cerevisiae 08 strain showed the best results, achieving 98% of total survival whereas S. cerevisiae 01 reached only 75%. Autoaggregation and coaggregation assays showed S. cerevisiae 08 as the most appropriate strain, mainly because it was the unique strain able to coaggregate with the four bacterial pathogens assayed. Consequently, S. cerevisiae 08 is the best candidate for future in vivo studies useful to prevent aflatoxicosis. Further quantitative in vitro and in vivo studies are required to evaluate the real impact of yeast-binding activity on the bioavailability of AFB₁ in poultry. However, this study could be useful in selecting efficient strains in terms of AFB₁ binding and provide an important contribution to research into microorganisms with potential probiotic effects on the host.