Cytogenetic effects of silver and gold nanoparticles on Allium cepa roots

The present study evaluates the cytogenetic effects of both silver and gold nanoparticles on the root cells of Allium cepa. In this study, the root cells of Allium cepa were treated with both gold and silver nanoparticles of different concentrations (1?mg/L, 5?mg/L and 10?mg/L) along with control for 72?h. Experimental results revealed that after 72?h of exposure, a significant decrease in mitotic index (MI) from 68% (control) to 52.4% (1?mg/L), 47.3% (5?mg/L) and 41.4% (10?mg/L) for gold nanoparticles and 57.1% (1?mg/L), 53% (5?mg/l), 55.8% (10?mg/L) for silver nanoparticles. Through minute observation of the photograph, it was recorded that some specific chromosomal abnormalities such as stickiness of chromosome, chromosome breaks, nuclear notch, and clumped chromosome at different exposure conditions. Therefore, present results clearly suggest that Allium cepa root tip assay could be a viable path through which negative impact of both gold and silver nanoparticles can be demonstrated over a wide range of concentrations.     

Potential cytotoxic effect of Anilofos by using Allium cepa assay

Cytogenetic effects of Anilofos which was widely used in agriculture, was evaluated in Allium cepa root meristematic cells. In the Allium root growth inhibition test EC₅₀ value was determined 50 ppm and 1/2× EC₅₀ (25 ppm), EC₅₀ (50 ppm) and 2 × EC₅₀ (100 ppm) concentrations of Anilofos were applied to onion roots. A negative and positive control were used in the experiment in parallel. According to results mitotic index decreased with increasing the Anilofos concentrations in all application groups and each exposure time, while disturbed anaphase–telophase, choromosome laggard(s), stickiness and anaphase bridge(s) were observed. In anaphase–telophase cells, c-metaphase, disturbed nucleus and binuclear cells were observed in other anomalies. The results were also analyzed statistically by using Dunnett t test (2-tailed) and all concentrations of Anilofos were found significant.     

Analysis of chromosomal aberrations in men occupationally exposed to cement dust

Cement industry is considered as a major pollution problem on account of dust and particulate matter emitted at various steps of cement manufacture. Cement dust consists of many toxic constituents. The workers who are employed in cement industries are exposed to cement dust for long periods. Therefore, it is mandatory to evaluate the mutagenic effects of occupational exposure to cement dust in such workers. In the present study, we analyzed the samples of 124 male workers including 59 smokers and 65 non-smokers who were employed in cement industry for a period of 1–17 years. For comparison, 106 controls (including 47 smokers and 59 non-smokers) of the same age group and socio-economic status were also studied. Controls had no exposure to cement dust or any known physical or chemical agent. A significant increase in the incidence of chromosomal aberrations was observed in the exposed group when compared to the control group. The results were analyzed separately for non-smokers and smokers. The chromosomal damage was more pronounced in the smokers when compared with the non-smokers both in control and exposed groups. A significant increase in the frequency of chromosomal aberrations was also observed with increase in age in both control and exposed subjects.     

Hypersensitivity of lymphoblastoid lines derived from ataxia telangiectasia patients to the induction of chromosomal aberrations by etoposide (VP-16)

Mammalian DNA topoisomerase II represents the cellular target of many antitumor drugs, such as epipodophyllotoxin VP-16 (etoposide). The mechanism by which VP-16 exerts its cytotoxic and antineoplastic actions has not yet been firmly established, although the unique correlation between sensitivity to ionizing radiation and to topoisomerase II inhibitors suggest the involvement of DNA double-strand breaks. In the present study we analyzed the chromosomal sensitivity of lymphoblastoid cell lines derived from ataxia telangiectasia (AT) patients to low concentrations of the drug. Our results indicate that AT derived cells are hypersensitive to the clastogenic activity of VP-16 either when the drug is present for the whole duration of the cell cycle or specifically in the G2 phase, confirming that the induction of DNA double strand breaks, to which AT cells seem typically sensitive, could have an important role in the biological activity of VP-16.     

Influence of PAHs in ambient air on chromosomal aberrations in exposed subjects: international study - EXPAH

The aim of this study was to determine the influence of carcinogenic polycyclic aromatic hydrocarbons (c–PAHs) in complex mixtures in ambient air on DNA damage (chromosomal aberrations) in occupationally exposed subjects measured as percent of aberrant cells (% AB.C.).

There were in total 203 exposed subjects and 150 respective controls in the whole project, allocated in three different European cities – Kosice (Slovakia), Prague (Czech Republic) and Sofia (Bulgaria). The studied population from Kosice (Slovakia) consisted of 106 subjects. From these 51 were exposed policemen and 55 were controls. The Czech population comprised 52 exposed policemen and 50 controls. In Bulgaria, there were two equally numerous exposed groups: 50 policemen and 50 professional bus drivers together with 45 controls. According to personal monitoring, policemen and bus drivers in the Bulgarian capital Sofia were exposed to the highest levels of c-PAHs amongst the exposed subject groups in the cities (45.3 ± 25.9 ng/m³ in policemen resp. 36.1 ± 31.6 ng/m³ in bus drivers in Sofia, 26.8 ± 39.8 ng/m³ for policemen in Kosice and 11.9 ± 11.2 ng/m³ for policemen in Prague), compared to the respective controls (24.9 ± 17.7 ng/m³ for controls in Sofia, 7.9 ± 3.8 ng/m³ for controls in Kosice and 6.2 ± 3.6 ng/m³ for controls in Prague).

We observed the following frequency of % AB.C. scored by conventional method: 2.60 ± 2.64 in exposed policemen and 2.14 ± 1.61 in controls in Kosice (p = n.s.); 2.33 ± 1.53 in exposed policemen and 1.94 ± 1.28 in controls in Prague (p = n.s.); 3.04 ± 1.64 in exposed policemen, respectively, 3.60 ± 1.63 in exposed bus drivers and 1.79 ± 0.77 in the control group in Sofia (p < 0.05, respectively, p < 0.05).

According to data from multiple regression analysis, and group comparison of smokers versus nonsmokers in Sofia also cigarette smoking (p = 0.055) and the age (p = 0.020) seem to play an important role within the aberrant cell formation in addition to the occupational c-PAHs exposure (p = 0.000). Smoking status was the modifying factor for % AB.C. in Kosice (p = 0.020) after multiple regression approach was employed.

In summary, we can say that subjects occupationally exposed to higher levels of c-PAHs in ambient air in Sofia are at greater genotoxic risk compared to those working indoors.     

Methyl mercury uptake and associations with the induction of chromosomal aberrations in Chinese hamster ovary (CHO) cells

In order to evaluate possible health effects of environmental exposure of humans towards methyl mercury species, relevant exposure experiments using methyl mercury chloride in aqueous solution and Chinese hamster ovary (CHO) cells were performed. The solution was monitored for the presence of monomethyl, dimethyl and elemental mercury by several analytical techniques including chromatographic as well as atomic absorption and mass spectrometric methods. Methyl mercury induces structural chromosomal aberrations (CA) and sister chromatid exchanges (SCE) in CHO cells. At a concentration of methyl mercury in the culture medium of 1.0 x 10(-6) M where the frequencies of CA and SCE are significantly elevated, the intracellular concentration was 1.99 x 10(-16) mol/cell. Possible biochemical processes leading to the cytogenetic effects are discussed together with toxicological consequences, when humans (e.g. workers at waste deposits) are exposed to environmental concentrations of methyl mercury.     

Biosynthesis of copper nanoparticles and its effect on actively dividing cells of mitosis in Allium cepa

Nanobiotechnological application of copper nanoparticles has paved the way for advancement in agriculture owing to its bactericidal and fungicidal activities. Recently, researchers have focussed on bioinspired synthesis of copper nanoparticles as a viable alternative to existing physicochemical techniques. For the commercialization of nanocopper, the toxicity evaluation is a major issue. In this context, Citrus medica (L.) fruit extract‐mediated copper nanoparticles were synthesized and its different concentrations (10, 20, 40, 60, 80, and 100 µg mL^?1) were evaluated for its effect on actively dividing cells of Allium cepa. The study clearly revealed that copper nanoparticles increased mitotic index up to the concentration of 20 µg mL^?1. In addition, a gradual decline in mitotic index and increase in abnormality index was observed as the concentration of copper nanoparticles and treatment duration were increased. Aberrations in chromosomal behavior such as sticky and disturbed chromosomes in metaphase and anaphase, c‐metaphase, bridges, laggard, disturbed telophase, and vacuolated nucleus were also observed. © 2015 American Institute of Chemical Engineers Biotechnol. Prog., 31:557–565, 2015     

The nonhistone chromosomal proteins of vertebrate liver and kidney: A comparative study by gel electrophoresis

Summary The nonhistone chromosomal proteins (NHC proteins) probably include enzymes of chromosomal metabolism, general structural proteins, and possibly control elements. In theory, these proteins may have been strongly conserved during evolution, as the histones have. We have used sodium dodecyl sulfate (SDS) disc gel electrophoresis to analyze and compare the NHC proteins of two tissues, liver and kidney, from rat, cat, cow, chicken, turtle, and frog. The gel patterns indicate that the NHC proteins have changed much more during evolution than have the histones; the total pattern of NHC proteins has not been conserved. However, there does appear to be a conservation of a subset of bands for each tissue investigated. Further chemical analysis will be required to establish the significance of the results.Recipient of NIH Career Development Award NIH AI-20388     

An improved system for exposure of cultured mammalian cells to gaseous compounds in the chromosomal aberration assay

A gas exposure system using rotating vessels was improved for exposure of cultured mammalian cells to gaseous compounds in the chromosomal aberration assay. This system was composed of 12 square culture vessels, a device for preparation of air containing test gas, and positive and negative control gases at target concentrations and for supplying these gases to the culture vessels, and a roller apparatus in an incubator. Chinese hamster lung cells (CHL/IU) were grown on one side of the inner surface of the square culture vessel in the MEM medium. Immediately prior to exposure, the medium was changed to the modified MEM. Air in the culture vessel was replaced with air containing test gas, positive or negative control gas. Then, the culture vessels were rotated at 1.0 rpm. The monolayered culture cells were exposed to test gas during about 3/4 rotation at upper positions and alternatively immersed into the culture medium during about 1/4 rotation at lower positions. This system allowed the chromosomal aberration assay simultaneously at least at three different concentrations of a test gas together with positive and negative control gases with and without metabolic activations, and duplicate culture at each exposure concentration. Seven gaseous compounds, 1,3-butadiene, chlorodifluoromethane, ethyl chloride, methyl bromide, methyl chloride, propyne, and vinyl chloride, none of which has been tested to date, were tested on CHL/IU for the chromosomal aberration assay using this gas exposure system. All the compounds except chlorodifluoromethane showed positive responses of the structural chromosomal aberrations, whereas polyploidy was not induced by any of these gases. This improved gas exposure system proved to be useful for detecting chromosomal aberrations of gaseous compounds.     

Structure-activity relationship in the induction of chromosomal aberrations and spindle disturbances in Chinese hamster epithelial liver cells by regioisomeric phenanthrene quinones

Four regioisomeric phenanthrene (PH) quinones (Q) were investigated for their ability to induce chromosomal damage and spindle disturbances. PH 1,4-Q and PH 1,2-Q induced structural as well as numerical chromosomal aberrations, whereas the isomers PH 9,10-Q and PH 3,4-Q were virtually inactive in this respect. However, all four compounds enhanced the frequency of c-mitoses.     

Metal accumulation and sublethal effects in the sea anemone, Aiptasia pallida, after waterborne exposure to metal mixtures

The marine environment is subjected to contamination by a complex mixture of metals from various anthropogenic sources. Measuring the biological responses of organisms to a complex mixture of metals allows for examination of metal-specific responses in an environmentally realistic exposure scenario. To address this issue, the sea anemone, Aiptasia pallida was exposed to a control and a metal mixture (copper, zinc, nickel, and cadmium) at three exposure levels (10, 50, and 100 μg/L) for 7 days. Anemones were then transferred to metal-free seawater for an additional 7 days after the metal exposure to assess metal depuration and recovery. Metal accumulation, activity of the enzymes catalase, glutathione reductase, and carbonic anhydrase, as well as, cell density of the symbiotic zooxanthellae were measured over 14 days. Metal accumulation in A. pallida occurred in a concentration dependent manner over the 7-day exposure period. Altered enzyme activity and tentacle retraction of the host, as well as decreased zooxanthellae cell density were observed responses over the 7 days, after exposure to a metal concentration as low as 10 μg/L. Metal depuration and physiological recovery were dependent on both the metal and the exposure concentration. Understanding how A. pallida and their symbionts are affected by metal exposures in the laboratory may allow better understanding about the responses of symbiotic cnidarians in metal polluted aquatic environments.     

Comparison of heavy metal accumulation in a natural wetland and constructed wetlands receiving acid mine drainage

Metal accumulations in sediments and plants of constructed and natural wetlands were compared in two wetlands constructed by the Tennessee Valley Authority (TVA) for the treatment of acid mine drainage and a natural wetland. Load rates and removal efficiencies of most metals were generally greater in the constructed wetlands than in the natural wetland. There were similar sediment and plant metal concentrations between one constructed wetland and the natural wetland and greater metal concentrations in the sediments and plants in the other constructed wetland compared to the natural wetland. Data indicate that Mn, Zn, Cu, Ni, B, and Cr are being accumulated in the plants at all three wetlands, although accumulation of metals by these plants accounts for only a small percentage of the removal of the annual metal load supplied to each wetland.     

Assessing the ecological health risk in a conserved mangrove ecosystem due to heavy metal pollution: A case study from Sundarbans Biosphere Reserve,India

Sundarbans Biosphere Reserve (SBR) is the world's largest contiguous conserved mangrove forest with unique flora and fauna, but it still has to bear the brunt of anthropogenic disturbances due to huge population pressure. This study aimed to identify the sources, extent of metal pollution (Cd, Cr, Mn, Ni, Pb, and Zn), and their potential ecological risk in this fragile ecosystem. Sediments were collected from 10 locations with varied levels of anthropogenic pressure from the fringe of the reserve forest. Cluster analysis (CA) and factor analysis (FA) identified Ni, Cd, and Pb as the major anthropogenic pollutants in this area. Concentrations of Pb (27.79–47.07 mg/kg) and Cd (0.8–3.3 mg/kg) were found to be higher in areas reliant on fossil fuel-operated motorboats for transport and dependent on rechargeable batteries to cope with the shortage of electricity. The contamination factor (C_f), geoaccumulation index (I_geo), and ecological risk index (ERI) highlight that populated areas are mostly exposed to Cd, Pb, and Cr contamination. Interpolation maps identified that the central part of the area is acutely affected by Cd pollution, whereas the main ecotourism routes within the reserve forest have high Pb concentrations. This study concludes that conservation-friendly ecotourism and improper disposal of batteries can also pose a threat to this ecosystem and these possibilities could be considered during formulation of conservation plans.     

GISH study of advanced generation of the interspecific hybrids between Allium cepa L. and Allium fistulosum L. with relative resistance to downy mildew

Genomic in situ hybridization (GISH) was used for a chromosomal composition study of the later generations of interspecific hybrids between A. cepa L. and A. fistulosum L., which are relatively resistant to downy mildew (peronosporosis). GISH revealed that F₂ hybrids, which did not produce seeds, were triploids (2n = 3x = 24) with 24 chromosomes and possessed in their complements 16 chromosomes of A. fistulosum L. and eight chromosomes of A. cepa L. or eight chromosomes of A. fistulosum L. and 16 chromosomes of A. cepa L. The advanced F₅ hybrid, which produced few seeds, was amphidiploid with 32 chromosomes. BC₁F₅ hybrid was triploid with eight chromosomes of A. fistulosum L. and 16 chromosomes of A. cepa L., which did not produce seeds. BC₂ (BC₁F₅) plant was amphidiploid that possessed 4 recombinant chromosomes and produced few seeds. GISH results point to 2n-gametes formation in macro- and microsporogenesis of the hybrids. The mechanism of 2n-gametes formation and the possibility of apomixes events in the backcrossing progeny are discussed.     

Attachment of origins of replication to the nuclear matrix and the chromosomal scaffold

We have investigated the attachment of DNA to the nuclear matrix and chromosomal scaffold in synchronized bovine liver cells. Label incorporated at the onset of the S phase remained preferentially associated with the matrix during the subsequent G1 phase and with a residual protein structure from dehistonized chromosomes during mitosis. On the other hand label incorporated during mid or late S phase was about equally distributed over the DNA molecule after a chase into the G1 phase. These results suggest that DNA is attached to the nuclear matrix and chromosome scaffolds by the origins of replication.     

Morphological and physiological alterations in the diatom Gomphonema pseudoaugur due to heavy metal stress

Periphytic diatom communities were analyzed from several heavy metal contaminated water bodies of Haryana, India. Among the analyzed sites, site HO3 (Saraswati Dham, Kurukshetra, Pehowa) showed significant response in the periphytic diatom community in terms of community shift (dominance of Gomphonema pseudoaugur) and lower biodiversity indices (species richness and Shannon index). Gomphonema pseudoaugur responded more specifically through induction of lipid bodies and occurrence of deformities in diatom frustules. PCA analysis showed that site HO3 is contaminated with heavy metals, especially Pb and Se. Pearson's correlation analysis showed a positive and statistically strong relationship between induction of lipid bodies and deformities with heavy metals (Pb and Se). Finally, from the present study, we concluded that heavy metal stress induces increased lipid body (LBs) size and deformities in the diatom species Gomphonema pseudoaugur, which could be a valuable indicator species for biomonitoring and a consideration in biofuel production.     

超富集植物对重金属耐受和富集机制的研究进展

超富集植物对重金属耐受和富集机制的研究成为近年来植物逆境生理研究的热点,在简要总结细胞壁沉淀、重金属螯合效应、酶活性机制和细胞区室化作用的基础上,概述了超富集植物对重金属的耐受机制,讨论了重金属跨根细胞质膜运输,共质体内运输、木质部运输和跨叶细胞膜运输的富集过程。     

Influence of DNA repair gene polymorphisms of hOGG1, XRCC1, XRCC3, ERCC2 and the folate metabolism gene MTHFR on chromosomal aberration frequencies

We have studied the effect of genetic polymorphisms in the DNA repair genes hOGG1, XRCC1, XRCC3, ERCC2 and the MTHFR gene in the folate metabolism on the frequencies of cells with chromosomal aberrations (CA), chromosome-type aberrations (CSA), chromatid-type aberrations (CTA), chromatid breaks (CTB) and chromatid gaps (CTG) scored in peripheral blood lymphocytes from 651 Norwegian subjects of Caucasian descendant. DNA was extracted from fixed cell suspensions. The log-linear Poisson regression model was used for the combined data which included age, smoking, occupational exposure and genotype for 449 subjects.

Our results suggest that individuals carrying the hOGG1 326Cys or the XRCC1 399Gln allele have an increased risk of chromosomal damage, while individuals carrying the XRCC1 194Trp or the ERCC2 751Gln allele have a reduced risk regardless of smoking habits and age.

Individuals carrying the XRCC1 280His allele had an increased risk of CSA which was only apparent in non-smokers. This was independent of age.

A protective effect of the XRCC3 241Met allele was only found in the older age group in non-smokers for CA, CSA and CTA, and in smokers for CSA. In the youngest age group, the opposite effect was found, with an increased risk for CA, CTA and CTG in smokers. Carrying the MTHFR 222Val allele gave an increased risk for chromosome and chromatid-type aberrations for both non-smokers and smokers, especially for individuals in the older age group, and with variable results in the youngest age group. The variables included in the different regression models accounted, however, for only 4–10% of the variation. The frequency ratio for CTG was significantly higher than for CTA and CTB for only 7 of the 43 comparisons performed. Some of the gap frequencies diverge from the trend in the CA, CSA, CTA and CTB results.     

A comparative study of the wild and mutated heavy metal resistant Klebsiella variicola generated for cadmium bioremediation

Ten indigenous heavy metals resistant bacteria were isolated from the discharged effluent of Biological Sciences building at Obafemi Awolowo University, Ile-Ife, Osun State, Nigeria. The bacterial strains were isolated using enrichment method in tryptone soya agar (TSA) supplemented with 100 mg/L of Pb, Cd, As, and Ni. All the isolated bacteria showed multiple tolerances to the heavy metals; however, strain GBB 220, which showed a maximum tolerable concentrations (MTCs) of 2000, 1200, 4700, and 1000 mg/L for Pb, Cd, As, and Ni, respectively, was selected for further studies. The bacterium was identified by 16S rRNA sequences as Klebsiella variicola and was subjected to mutational enhancement by acridine orange and ethidium bromide. Eight mutants were recovered, strains K. variicola MutAa–Ad showed improvement in their MTCs of 2500, 2200, and 5000 mg/L for Pb, Cd, and As whereas K. variicola MutEa–Ed had same MTCs as the wild type except for cadmium which increased from 1200 to 1500 mg/L. The antibiotic susceptibility patterns showed that all the strains of K. variicola had multiple resistances to some of the antibiotics. The K. variicola mutants had their optimum pH at 5 and 8 while the wild type had optimum pH at 7 and 8. The cadmium removal efficiency of 97.9% at pH 7, 97.7% at pH 8, and 99.4% at pH 7 was observed for K. variicola Wt, K. variicola Mut Eb, and K. variicola Mut Ac, respectively. These findings suggested that the artificially mutated strains of K. variicola may be applied to remove cadmium from polluted environment.     

Genetic and biochemical analysis of high iron toxicity in yeast: iron toxicity is due to the accumulation of cytosolic iron and occurs under both aerobic and anaerobic conditions

Iron storage in yeast requires the activity of the vacuolar iron transporter Ccc1. Yeast with an intact CCC1 are resistant to iron toxicity, but deletion of CCC1 renders yeast susceptible to iron toxicity. We used genetic and biochemical analysis to identify suppressors of high iron toxicity in Δccc1 cells to probe the mechanism of high iron toxicity. All genes identified as suppressors of high iron toxicity in aerobically grown Δccc1 cells encode organelle iron transporters including mitochondrial iron transporters MRS3, MRS4, and RIM2. Overexpression of MRS3 suppressed high iron toxicity by decreasing cytosolic iron through mitochondrial iron accumulation. Under anaerobic conditions, Δccc1 cells were still sensitive to high iron toxicity, but overexpression of MRS3 did not suppress iron toxicity and did not result in mitochondrial iron accumulation. We conclude that Mrs3/Mrs4 can sequester iron within mitochondria under aerobic conditions but not anaerobic conditions. We show that iron toxicity in Δccc1 cells occurred under both aerobic and anaerobic conditions. Microarray analysis showed no evidence of oxidative damage under anaerobic conditions, suggesting that iron toxicity may not be solely due to oxidative damage. Deletion of TSA1, which encodes a peroxiredoxin, exacerbated iron toxicity in Δccc1 cells under both aerobic and anaerobic conditions, suggesting a unique role for Tsa1 in iron toxicity.