Impact of microgravity on radiobiological processes and efficiency of DNA repair

Three major plant bioassays, i.e., the Allium root anaphase aberration (Allium-AA), the Tradescantia-micronucleus (Trad-MCN) and the Tradescantia stamen hair mutation (Trad-SHM) tests, were utilized in soil solutions or shallow well water samples to determine the degree of their genotoxicity. Shallow well water samples were collected from five different farms, and soil solutions were extracted with distilled water or dimethyl sulfoxide (DMSO) from pesticide-contaminated (metolachlor, atrazine, extrazine, and 2, 4-D) and pesticide-free soil samples. Genotoxicity was expressed in terms of anaphase aberration (AA) frequencies in the Allium-AA test, in terms of micronuclei frequencies in the Trad-MCN test, and in terms of pink mutation events in the Trad-SHM test. On average, results of Allium-AA tests showed a 2.78-3.01 fold increase in anaphase aberration frequencies in contaminated soil solution samples and well water samples as compared with the negative control. Results of Trad-MCN tests showed a 1.66-4.75 fold increase of MCN frequencies in contaminated soil solution samples and shallow well water samples as compared with the frequencies of the controls. Results of Trad-SHM tests showed a 2.7-2.86 fold increase of pink mutation events in the contaminated soil solution samples over that of the controls. Control groups of the Allium-AA tests had an average of 0.75/1000 anaphase figures, and control groups of the Trad-MCN tests had an average of 3.2 MCN/100 tetrads, while control groups of the Trad-SHM tests had an average of 1.4 mutation events/1000 hairs. In general, soil solutions of DMSO extracts showed higher genotoxicity than that of distilled water extracts. Among these three plant bioassays, the Trad-MCN test has the highest efficiency. The highest toxicity, based upon the Trad-MCN test results, was found in the pesticide contaminated soil samples from Monroe's farm. Water samples from the Fountain Green/Bushnell area ranked second in genotoxicity.     

Assessment of the genotoxicity of contaminated soil with the Allium/Vicia-micronucleus and the Tradescantia-micronucleus assays.

The present study concerns the genotoxicity of contaminated soil near Metz, France. Three plant bioassays, the Vicia faba (broad bean), the Allium cepa (white onion) and the Tradescantia (spiderwort) micronuclei tests were used to evaluate for genotoxicity. Two soil samples were tested: soil sample A (from an industrial waste site) and soil sample B (from a cokeworks waste site). Maleic hydrazide was used as the positive control. Aqueous extracts of the soil samples were used to treat the roots of Vicia and Allium, and plant cuttings of Tradescantia according to the standard protocol for these plant assays established by the International Program on Chemical Safety and the World Health Organization. The results of these tests showed differential sensitivity in the three different bioassays. Soil sample A was more toxic than soil sample B.     

Vicia root-micronuclei assays on the clastogenicity of water samples from the Kui River near Xuzhou city, People's Republic of China.

The Vicia root-micronucleus (VR-MCN) bioassay was used to determine the genotoxicity of water samples collected from the Kui River near Xuzhou city, China. Results show that all water samples induced elevated MCN frequencies over background. This indicates that the river water was polluted with genotoxic material. The source of pollutants in this river is discussed.     

Evaluation of genotoxicity of combined soil pollution by cadmium and imidacloprid

Cadmium (Cd) is one of the important pollutants of soil and the genotoxicity of Cd-contaminated soil was studied in combination with imidacloprid. The single cell gel electrophoresis or comet assay was used to quantify DNA strand breaks as a measure of DNA damage induced by Cd and imidacloprid contamination in soil. The soil was artificially contaminated by Cd (0.0, 0.2, 0.5, 1.0, 2.0 mg· kg^?1 dry soil) or Cd (0.0, 0.2, 0.5, 1.0, 2.0 mg · kg^?1 dry soil) and imidacloprid (0.5 mg · kg^?1 dry soil). Roots ofVicia faba were exposed to the contaminated soil for 2 h at 25°C and were used in the comet assay. DNA damage was measured as the values of percentage of nuclei with tails, tail length, tail DNA, tail moment (TM), and Olive tail moment (OTM). DNA damages of root tips ofVicia faba increased after Cd treatment and there were dose-related increases in DNA damage measured as these parameters. However, the addition of imidacloprid further increased the DNA damage. These data confirmed the genotoxic effect of Cd to plants, and that the combined pollution with imidacloprid can enhance the genotoxicity of Cd.     

Genotoxicity of hydrated sulfur dioxide on root tips of Allium sativum and Vicia faba

Genotoxicity of sulfur dioxide (SO(2)) and its hydrates (bisulfite and sulfite) in human lymphocytes and other mammalian cells have been found earlier in our laboratory. In the present studies, we used Allium stavium and Vicia faba cytogenetic tests, which are the highly sensitive and simple plant bioassays. A mixture of sodium bisulfite and sodium sulfite (1:3), at various concentrations from 1 x 10(-4) to 2 x 10(-3)M was used for the treatment. Genotoxicity was expressed in terms of anaphase aberration (AA) frequencies in the Vicia-AA test and in terms of micronuclei (MCN) frequencies in both Vicia-MCN test and Alllium-MCN test. On average, the results showed a 1.7-3.9-fold increase of AA frequencies and a 3.5-4.5-fold increase of MCN frequencies in Vicia root tips as compared with the negative control. Similarly, results of Allium-MCN test also showed a significant increase in MCN frequencies in the treated samples. In addition, pycnotic cells (PNC) appeared in Allium root tips of treated groups. The frequencies of MCN, AA and PNC increased dose-dependently and the cell cycle delayed at the same time in bisulfite treated samples. Results of the present study suggest that the Vicia and Allium cytogenetic bioassays are efficient, simple and reproducible in genotoxicity studies of bisulfite.     

Evaluation of genotoxicity of combined soil pollution by cadmium and imidacloprid

Cadmium (Cd) is one of the important pollutants of soil and the genotoxicity of Cd-contaminated soil was studied in combination with imidacloprid. The single cell gel electrophoresis or comet assay was used to quantify DNA strand breaks as a measure of DNA damage induced by Cd and imidacloprid contamination in soil. The soil was artificially contaminated by Cd 2 h at 25℃ and were used in the comet assay. DNA damage was measured as the values of percentage of nuclei with tails, tail length, tail DNA, tail moment (TM), and Olive tail moment (OTM). DNA damages of root tips of Vicia faba increased after Cd treatment and there were dose-related increases in DNA damage measured as these parameters. However, the addition of imidacloprid further increased the DNA damage. These data confirmed the genotoxic effect of Cd to plants, and that the combined pollution with imidacloprid can enhance the genotoxicity of Cd.     

A comparison between short-term evolution of micronuclei induced by X-rays and colchicine in root tips of Vicia faba

The short-term evolution of micronuclei derived from acentric fragments and whole chromosomes was studied in root tips of Vicia faba. Micronuclei were induced by X-rays (30 cGy and 120 cGy) and colchicine (10(-5) M and 3 X 10(-4) M). Frequencies of chromosome breakage or loss of micronuclei in interphase and mitotic cells were studied. The DNA content of micronuclei in interphase cells was also measured. Micronuclei derived from whole chromosome showed a higher probability to survive and to undergo mitotic condensation in synchrony with main nuclei than micronuclei derived from an acentric fragment. PCC (Premature Chromosome Condensation) was not observed for both types of micronuclei in Vicia faba, in contrast to the ones reported in mammalian cells in culture.     

Genotoxicity of water samples from Dianchi lake detected by the Vicia faba micronucleus test.

Dianchi Lake covers about a 300 km2 area. Kunming city on the edge of the lake is surrounded by industrial establishments. Farm land surrounds the remaining areas of the lake. The lake water is polluted by the Kunming city municipal sewage from 3 million inhabitants, the industrial effluent and farm runoff. Water samples were collected from 12 sites along the shore of the lake during the dry (May) and rainy (August) seasons for genotoxicity testing with the Vicia micronucleus assay during the year 1995. Genotoxicity in terms of micronuclei (MCN) frequencies in the root tip cells of Vicia showed a consistent elevated frequency of MCN over the control sample at the 0.05-0.01 levels of significance in both seasons. The MCN frequencies of sites A (Daguanhe), B (Gaoqiao) and C (Xiyuan) were 3.5-4 times as high as the control values (5.25/1000 cells) in the dry season. In the rainy season, the MCN frequencies of water samples from most of the 12 sites were relatively lower than those of the dry season except sites J (Haikou), and K (Kunyang). The average MCN frequency of the dry season samples was 14.97 per 1000 cells and that of the rainy season samples was 12.24 per 1000 cells while the average control value was around 5.00/1000 cells.     

死鱼事件中污染源废水对鱼类急性毒性及诱变微核的研究

为了研究2006年9月广州郊区某鱼塘因化工企业污染源废水进入而导致大量死鱼事件中鱼类死亡原因,用斑马鱼(Brachydanio rerio)和蚕豆(Vicia faba)根尖对污染源废水及鱼塘水分别进行了鱼类急性毒性试验和蚕豆根尖微核试验。污染源废水和鱼塘水的96hLC₅₀分别为1.69%、23.95%,污染源废水和鱼塘水的微核率分别为27.8‰、13.7‰,污染源废水和鱼塘水的COD、BOD、石油类、氨氮、总磷等均出现超标情况,其中氨氮、苯胺、石油类污染物严重超标。监测结果表明,以氨氮污染为主的污染源废水是导致死鱼事件的主要原因,废水对蚕豆根尖微核率的形成具有显著性影响,可能存在潜在的致突变性危险。     

Exposure of Vicia faba and Pisum sativum to copper-induced genotoxicity

The potential genotoxicity of Cu(2+) was investigated in Vicia faba and Pisum sativum seedlings in hydroponic culture conditions. Cu(2+) caused a dose-dependent increase in micronuclei frequencies in both plant models. Cytological analysis of root tips cells showed clastogenic and aneugenic effects of this heavy metal on V. faba root meristems. Cu(2+) induced chromosomal alterations at the lowest concentration used (2.5 mM) when incubated for 42 h, indicating the potent mutagenic effect of this ion. A spectrum of chromosomal abnormalities was observed in V. faba root meristems, illustrating the genotoxic events leading to micronuclei formation.     

Vicia root-mirconucleus and sister chromatid exchange assays on the genotoxicity of selenium compounds

Selenium (Se) is an important metalloid with industrial, environmental, biological and toxicological significance. Excessive selenium in soil and water may contribute to environmental selenium pollution, and affect plant growth and human health. By using Vicia faba micronucleus (MN) and sister chromatid exchange (SCE) tests, possible genotoxicity of sodium selenite and sodium biselenite was evaluated in this study. The results showed that sodium selenite, at concentrations from 0.01 to 10.0mg/L, induced a 1.9-3.9-fold increase in MN frequency and a 1.5-1.6-fold increase in SCE frequency, with a statistically significantly difference from the control (P<0.05 and 0.01, respectively). Sodium selenite also caused mitotic delay and a 15-80% decrease in mitotic indices (MI), but at the lowest concentration (0.005mg/L), it slightly stimulated mitotic activity. Similarly, the frequencies of MN and SCE also increased significantly in sodium biselenite treated samples, with MI decline only at relatively higher effective concentrations. Results of the present study suggest that selenite is genotoxic to V. faba root cells and may be a genotoxic risk to human health.     

铬渣堆场渗滤液对蚕豆根尖细胞微核的影响

利用蚕豆根尖微核技术监测化工铬渣堆场渗出液的遗传毒性,结果表明,化工铬渣渗出液含有较高浓度的Cr6+,能明显诱导蚕豆根尖细胞微核的形成,具有较强的遗传毒性。当铬渣渗出液中Cr6+浓度为186.6460 mg/L时,微核率达到最大。铬渣渗出液所诱导的微核率与阴性对照组相比有极显著差异。     

Soil chromium bioremediation: Synergic activity of actinobacteria and plants

The aim of this work was to evaluate a strategy to reduce the bioavailable chromium fraction in soil, using a Cr(VI) resistant microorganism, Streptomyces sp. MC1, under non sterile conditions, with maize plants as bioindicator and/or bioremediator.Soil samples were contaminated with 100, 200 and 400 mg kg⁻¹ of Cr(VI) or Cr(III). Bioavailable chromium (35%) was only detected in samples with Cr(VI). Soil samples with Cr(VI) 200 mg kg⁻¹ were inoculated with Streptomyces sp. MC1, and bioavailable chromium decreased up to 73%.Zea mays seedlings were planted in soil samples contaminated with chromium. Plantlets accumulated chromium mainly as Cr(III), and biomass decreased up to 88%. Streptomyces sp. MC1 was inoculated in soil samples contaminated with 200 mg kg⁻¹ of Cr(VI) and Z.mays seedlings were planted.Streptomyces sp. MC1 caused Z.mays biomass increase (57%), chromium accumulation and bioavailable chromium decreased up to 46% and 96%, respectively.This work constitutes the first contribution of cooperative action between actinobacteria and Z.mays in the bioremediation of Cr(VI) contaminated soil. The large removal capacity of bioavailable chromium by Streptomyces sp. MC1 and Z.mays infers that they could be successfully applied together in bioremediation of soils contaminated with Cr(VI).     

Gene transfer in bacteria from soils contaminated with heavy metals

Transfer of metal resistance plasmids into two pseudomonad recipients, Pseudomonas aureofaciens and Ps. putida , from soil bacteria donor populations, was investigated in agricultural soil contaminated predominantly with Zn and Cu. The putative donor and recipient numbers on selective agar were not affected by the concentration of metals in the soils, nor were the number of transconjugants. However, there were differences in transfer frequencies of Hg and Cu resistance from the different soil samples. This is the first time that transfer of Cu resistance has been observed from native bacteria present in agricultural soils.     

Dielectric Properties Based Detection of Heavy Metal Contaminated Soil in the Frequency Range from 10 MHz to 1 GHz

Physical parameters based electromagnetic methods are promising technologies to detect contaminated sites. In these methods, the dielectric property is a key parameter. In this paper, we studied the dielectric characteristics of heavy metal contaminated soil. The chromium contaminated soil was made into samples, and the open-ended coaxial line was adopted as the measurement method. Experiments were conducted in the frequency band between 10 MHz and 1 GHz. The results showed that the complex permittivity, including the real part and the imaginary part, changes as the ionic content changes. Especially, at low frequencies (<50 MHz), the complex permittivity increases significantly with the increase of ionic content. In addition, it also could be seen that the water content of the soil also affects the complex permittivity. We proposed to adopt the drying method or the Time Domain Reflection method to determine the water content. The dielectric parameters are most affected by the ionic content after knowing the water content. Therefore, it is feasible to detect heavy metal contaminated sites based on dielectric properties.     

氯苯胁迫对蚕豆幼苗生长和细胞分裂的影响

研究了1,2,4-三氯苯(TCB)对蚕豆幼苗生长、根尖细胞分裂及染色体畸变的影响．结果表明,随TCB浓度增加和处理时间延长,蚕豆幼苗根长的生长及根尖细胞有丝分裂指数降低甚至停止．TCB诱发蚕豆根尖细胞有丝分裂过程中染色体数目畸变和结构畸变．50-100μg.g^-1TCB胁迫12-24h,蚕豆根尖染色体的主要损伤形式为c-有丝分裂、染色体桥和不均匀排列,其出现百分率达1．0％--10.3％．300μg.g^-1TCB胁迫12-96h,蚕豆根尖细胞中染色体粘连(S)、S+染色体断裂(S+B)、S+染色体环(S+R)、S+染色体不均匀排列(S+A)及S+染色体桥(S+Be)出现的百分率达47．9％--88.9％,各种类型染色体断裂出现的百分率仅为18．1％--29．6％,说明蚕豆根尖细胞染色体畸变分析可作为TCB土壤污染监测的敏感生物监测指标．     

甲硝唑诱导蚕豆根尖细胞微核的研究

本实验研究了甲硝唑诱导蚕豆根尖细胞微核的效应。实验表明：(1)浓度为0.1、6、12、40和500 mg/L甲硝唑均能使蚕豆根尖细胞微核率显著增加,且蚕豆根尖细胞微核率和甲硝唑浓度之间存在明显的剂量-效应关系;(2)甲硝唑能引起DNA损伤,具有分子诱变剂的性能。     

Vicia root-mirconucleus and sister chromatid exchange assays on the genotoxicity of selenium compounds

Selenium (Se) is an important metalloid with industrial, environmental, biological and toxicological significance. Excessive selenium in soil and water may contribute to environmental selenium pollution, and affect plant growth and human health. By using Vicia faba micronucleus (MN) and sister chromatid exchange (SCE) tests, possible genotoxicity of sodium selenite and sodium biselenite was evaluated in this study. The results showed that sodium selenite, at concentrations from 0.01 to 10.0 mg/L, induced a 1.9–3.9-fold increase in MN frequency and a 1.5–1.6-fold increase in SCE frequency, with a statistically significantly difference from the control (P < 0.05 and 0.01, respectively). Sodium selenite also caused mitotic delay and a 15–80% decrease in mitotic indices (MI), but at the lowest concentration (0.005 mg/L), it slightly stimulated mitotic activity. Similarly, the frequencies of MN and SCE also increased significantly in sodium biselenite treated samples, with MI decline only at relatively higher effective concentrations. Results of the present study suggest that selenite is genotoxic to V. faba root cells and may be a genotoxic risk to human health.     

Genotoxicity Assessment of Wood-Preserving Waste-Contaminated Soil Undergoing Bioremediation

Bioremediation represents one of the most cost-effective technologies for treatment of petroleum hydrocarbons in contaminated surface soils. A major concern for regulatory agencies when evaluating bioremediation is how to determine acceptable levels for residual organics in soil. Although guidelines have been developed for some organics in soil, limited information is available to define acceptable levels of the metabolites of biological degradation. The products of oxidative degradation are likely to be more water soluble and may also be more toxic. The purpose of the current study was to monitor changes in compound concentration and genotoxicity in soils undergoing bioremediation. The site selected for this study was a former wood-preserving site in the northwestern United States. Soil samples were collected over a 4-year period from two 6075-m² land treatment units. Conditions for biodegradation were enhanced by the addition of water and nutrients, as well as by frequent tilling to add oxygen. Due to the location of the facility, the temperature was conducive to a more rapid rate of biodegradation for approximately 6 months per year. Soil samples were collected using a grid system and solvent extracted. Polycyclic aromatic hydrocarbons were quantified in soil extracts using gas chromatography-mass spectrometry (GC/MS), and genotoxicity measured using the Salmonella/microsome assay. After 2 years of treatment, concentrations of total and carcinogenic polycyclic aromatic hydrocarbons (PAHs) were reduced to approximately 10% the concentration in the untreated soil. However, the mean weighted activity of the untreated soil was 293 net revertants per g soil, whereas the extracts of soil collected after 2 years induced a mean weighted activity of 325 net revertants per g soil. Thus, although biodegradation clearly reduced the concentration of total and carcinogenic PAHs in the surface soils, the results from the genotoxicity bioassay indicate that there was a lag in the reduction of mutagenicity in treated soils.     

电子垃圾拆解地区土壤和植物中邻苯二甲酸酯分布特征

近年来,电子垃圾不当拆解带来的环境问题引起国际社会的极大关注.本研究对浙江省台州市不同电子垃圾拆解地区土壤和植物样品中5种邻苯二甲酸酯类（PAEs）污染物进行了测定分析.结果表明：土壤（以干质量计）中PAEs类污染物的浓度为12.566~46.669 mg·kg^-1,其中邻苯二甲酸二异辛酯（DEHP）、邻苯二甲酸二丁酯（DBP）和邻苯二甲酸二乙酯（DEP）相对含量较高,约占PAEs总量的94%以上.拆解地区蚕豆（Vicia faba L.）中PAEs总量明显高于同地区其他植物,且土壤和所有植物体内PAEs浓度相关性均不显著(P>0.05).与美国国家环保局制定的土壤PAEs治理标准比较,台州电子垃圾拆解地区土壤PAEs污染较为严重.