DNA staining with the fluorochromes EtBr, DAPI and YOYO-1 in the comet assay with tobacco plants after treatment with ethyl methanesulphonate, hyperthermia and DNase-I

Evaluation of the antioxidant activity, genotoxic, and cytotoxic effects of the ethanolic leaves extract of Abutilon hirtum (Lam.) Sweet using in vitro assays

Abutilon hirtum (Lam.) Sweet belongs to the Malvaceae family and is a perennial shrub commonly known as Indian mallow, which is distributed in tropical regions and many different areas in Saudi Arabia. A. hirtum is an economically and a medicinally useful plant in different zones of the world for healing various diseases. The current research explores the in vitro antioxidant characteristics and cytotoxic and genotoxic potential effects of the ethanolic leaf extract of A. hirtum (LEAH). Mitotic index (MI), micronucleus (MN), and chromosomal aberration (CA) tests were performed in Allium cepa, and MTT assays were performed using human dermal fibroblast, adult (HDFa) and breast cancer (MCF7) cell lines. The comet assay was used to assess the genotoxic effect of LEAH. The antioxidant activity of LEAH was evaluated by DPPH and superoxide anion free radical scavenging assays. The results revealed that the cytotoxic effects of LEAH on Allium cepa were significantly changed in an inverse relationship with MI (general average for 3 times 0.275) and a direct relationship with MNs and CAs against concentration and treatment time, for highest concentration 1.351 mg/ml were 0.74 and 1.81 respectively. In addition, the MTT test revealed a dose-dependent cytotoxic impact, with the % cell viability decreasing as the concentration of LEAH increased, the lowest % cell viability (19.54) and highest inhibition (80.46) were obtained with 4.40 mg/ml of LEAH. In general, the results indicated that A. hirtum has a damaging effect at high doses; however, a cell safe effect, and a strong antioxidant and DNA protective effect at carefully calculated doses was observed. This provides credibility to justify its general therapeutic activity. Moreover, future studies should identify bioactive molecules and their molecular mechanisms responsible for potential therapies.

Role of Gemini Surfactants with Variable Spacers and SiO2 Nanoparticles in ct-DNA Compaction and Applications toward In Vitro/In Vivo Gene Delivery

Compaction of calf thymus DNA (ct-DNA) by two cationic gemini surfactants, 12-4-12 and 12-8-12, in the absence and presence of negatively charged SiO₂ nanoparticles (NPs) (∼100 nm) has been explored using various techniques. 12-8-12 having a longer hydrophobic spacer induces a greater extent of ct-DNA compaction than 12-4-12, which becomes more efficient with SiO₂ NPs. While 50% ct-DNA compaction in the presence of SiO₂ NPs occurs at ∼77 nM of 12-8-12 and ∼130 nM of 12-4-12, but a conventional counterpart surfactant, DTAB, does it at its concentration as high as ∼7 μM. Time-resolved fluorescence anisotropy measurements show changes in the rotational dynamics of a fluorescent probe, DAPI, and helix segments in the condensed DNA. Fluorescence lifetime data and ethidium bromide exclusion assays reveal the binding sites of surfactants to ct-DNA. 12-8-12 with SiO₂ NPs has shown the highest cell viability (≥90%) and least cell death in the human embryonic kidney (HEK) 293 cell lines in contrast to the cell viability of ≤80% for DTAB. These results show that 12-8-12 with SiO₂ NPs has the highest time and dose-dependent cytotoxicity compared to 12-8-12 and 12-4-12 in the murine breast cancer 4T1 cell line. Fluorescence microscopy and flow cytometry are performed for in vitro cellular uptake of YOYO-1-labeled ct-DNA with surfactants and SiO₂ NPs using 4T1 cells after 3 and 6 h incubations. The in vivo tumor accumulation studies are carried out using a real-time in vivo imaging system after intravenous injection of the samples into 4T1 tumor-bearing mice. 12-8-12 with SiO₂ has delivered the highest amount of ct-DNA in cells and tumors in a time-dependent manner. Thus, the application of a gemini surfactant with a hydrophobic spacer and SiO₂ NPs in compacting and delivering ct-DNA to the tumor is proven, warranting its further exploration in nucleic acid therapy for cancer treatment.

Identification of a Small Molecule That Inhibits the Interaction of LPS Transporters LptA and LptC

The need for novel antibiotics has become imperative with the increasing prevalence of antibiotic resistance in Gram-negative bacteria in clinics. Acting as a permeability barrier, lipopolysaccharide (LPS) protects Gram-negative bacteria against drugs. LPS is synthesized in cells and transported to the outer membrane (OM) via seven lipopolysaccharide transport (Lpt) proteins (LptA-LptG). Of these seven Lpt proteins, LptC interacts with LptA to transfer LPS from the inner membrane (IM) to the OM, and assembly is aided by LptD/LptE. This interaction among the Lpt proteins is important for the biosynthesis of LPS; therefore, the Lpt proteins, which are significant in the assembly process of LPS, can be a potential target for new antibiotics. In this study, a yeast two-hybrid (Y2H) system was used to screen compounds that could block LPS transport by inhibiting LptA/LptC interaction, which finally disrupts the biosynthesis of the OM. We selected the compound IMB-0042 for this study. Our results suggest that IMB-0042 disrupts LptA/LptC interaction by binding to both LptA and LptC. Escherichia coli cells, when treated with IMB-0042, showed filament morphology, impaired OM integrity, and an accumulation of LPS in the periplasm. IMB-0042 inhibited the growth of Gram-negative bacteria and showed synergistic sensitization to other antibiotics, with low cytotoxicity. Thus, we successfully identified a potential antibacterial agent by using a Y2H system, which blocks the transport of LPS by targeting LptA/LptC interaction in Escherichia coli.

A comprehensive investigation of toxicity and pollution potential of municipal solid waste landfill leachate

It is evident from the literature that research on the treatment of leachate generated from municipal solid waste (MSW) landfills has been a focus area of environmental management. However, the available information is discrete because most studies have reported only one or a couple of aspects of either closed or active MSW landfill leachate treatment. Hence, this investigation has focused on comprehensive attributes of both closed landfill leachate (CLL) and active landfill leachate (ALL), including generation, characterisation, and toxicity assessment to quantify and establish their pollution potential. The results indicated that CLL generation is higher (188.59 m³/d) than ALL (49.53 m³/d). The concentrations of principal physical, chemical, and biological constituents and concomitant leachate pollution index were higher in CLL (33.20) than in ALL (26.65). Furthermore, the germination indices of CLL (57.48) and ALL (79.14) and tail DNA damage of CLL (56.49%) and ALL (23.8%) ratified greater phytotoxicity and genotoxicity potential, respectively of CLL over ALL. The reasons for the variations in the generation, characteristics, and toxicity of CLL and ALL were discussed in detail. Evaluation of the commonly used landfill leachate treatment methods through the analytical hierarchy process confirmed that the activated sludge process and Fenton oxidation process are the most and least preferred treatment methods. The comprehensive investigation of CLL and ALL have established their pollution potential and the inevitable necessity for their treatment. The findings of this investigation will serve as a ready reference for researchers from academia and industry who work on the monitoring, treatment, and management of landfill leachate.

Green synthesized silver nanoparticles induced cytogenotoxic and genotoxic changes in Allium cepa L. varies with nanoparticles doses and duration of exposure

This study aimed to test the ability of aqueous leaf extract of Eichhornia crassipes (Mart.) Solms-Laubach to synthesize silver nanoparticles (AgNPs) and to estimate the cytotoxicity and genotoxicity of AgNPs using Allium cepa assay. Fresh Eichhornia crassipes plants were collected from the Nile River of Egypt. The mixed-shaped structures of the biogenic AgNPs were qualitatively characterized by UV-vis spectroscopy, scanning electron microscopy and transmission electron microscopy. Selected area electron diffraction confirmed the crystalline structure of AgNPs and energy dispersive X-ray analysis clarified the presence of the elemental silver in a percentage of 83.29%. The biogenic AgNPs were quite stable (0.316) and negatively charged (-18.5 mV) based on the polydispersity index values. Allium cepa L. roots were exposed to several AgNPs concentrations (0, 5, 10, 20, 40 and 80 mg L^-1) for different time intervals 2, 4 and 6 h. Cytotoxicity measured by both the spectrophotometric and macroscopic techniques recorded the maximum cell death of root tips of A. cepa after 20 mg L^-1 treatment. The analysis of comet assay output images showed an alteration of DNA repair kinetics. The use of aqueous leaf extract of E. crassipes (Mart.) Solms-Laubach in the large-scale production of AgNPs by the method proposed in this study may be a step in improving the water loss in the Nile River. At the same time, a sensitive approach to the cytogenotoxicity of AgNPs must be considered.

An investigation of some Schiff base derivatives as chemosensors for Zn(II): The performance characteristics and potential applications

The fluorescence properties of four simple Schiff bases (LH₂, LDMH₂, LH₂^H and LDM^HH₂) and their potential application as chemosensors for the detection of zinc ion in aqueous solution have been investigated. While LH₂ and LDMH₂ have displayed specific recognition to Zn(II), the reduced derivatives (LH₂^H and LDM^HH₂) of these ligands have shown no fluorescence response due to the lack of CN group. The Job plots, fluorescence titration experiments and ESI-MS results indicate the formation of 1:1 complexes between sensors and Zn(II). The analytic methods based on LH₂ and LDMH₂ as chemosensors have been proposed and optimized to detect Zn(II) ions in aqueous solution. The optimized methods have shown a good range of linearity, high precision, good accuracy and low detection limit. As an alternative to these methods, LH₂ and LDMH₂ have the capability to detect Zn(II) ions by naked eye under UV lamp. Moreover, LH₂-Zn and LDMH₂-Zn complexes have the ability to be a staining agent for identifying the radiation treatment of food by DNA comet assay.

Are CuO nanoparticles effects on hemocytes of the marine scallop (Chlamys farreri) caused by particles and/or corresponding released ions?

Manufactured nanoparticles (NPs) have become emerging pollutants and attracted extensive concern about their potential effects on the marine environment. However, the contribution of particles and their corresponding released ions to the overall toxicity of CuO NPs is poorly understood. In this study, we investigated the toxicological effects of CuO NPs and their corresponding released ions on the hemocytes of Chlamys farreri. Both copper species induced membrane damage, and increased lysosome contents in hemocytes. Based on the integrated biomarker responses method, the relative contributions of particles (NP_particle) and dissolved ions (NP_ion) to the toxicity of CuO NPs after 2h of exposure were 62.07% and 37.93%, respectively, indicating that the particles rather than the dissolved ions were the dominant source of NP toxicity. Transmission/scanning electron microscopy analysis confirmed the greater histopathological effects exerted by particles than Cu ions. Higher reactive oxygen species (ROS) generation induced by NP_particle than by NP_ion suggested that the intracellular ROS production might be responsible for the NP toxicity. Our findings suggest that particles effects play a key role in risk assessment of CuO NPs on the marine ecosystem.

Marine pollution risk in a coastal city: use of an eco-genotoxic tool as a stress indicator in mussels from the Eastern Aegean Sea

Coastal areas, such as bays, estuaries, and harbors, are heavily polluted since these areas are the settlements to which toxic chemicals from industrial and domestic wastes are discharged. The genetic damage was evaluated using bioindicator mussel Mytilus galloprovincialis caused by toxic chemicals (metals and polycyclic aromatic hydrocarbons) in İzmir and Çandarlı Bays (the Eastern Aegean Sea) through comet assay. Three sampling sites from the two bays were selected and the study was conducted during the spring and autumn periods. The highest levels of DNA damage expressed as %Tail-DNA were observed in İzmir Bay (34.60 % Tail-DNA) in the spring. Analysis of the correlation between PAHs and metals in mussels and %T-DNA in the hemolymph and gill cells showed a statistically significant positive correlation between %T-DNA and ∑PAH, chromium (p < 0.05). This study determined the pollution level of the İzmir and Çandarlı Bays by using the DNA damage to the mussel, which can identify the effects of environmental pollutants at the cellular levels. These results confirm that comet assay can be used to determine the temporal and spatial differences of DNA damage, and as a suitable tool for the measurement of genotoxicity in regions with low pollutant concentrations.

The comet assay in higher terrestrial plant model: Review and evolutionary trends

The comet assay is a sensitive technique for the measurement of DNA damage in individual cells. Although it has been primarily applied to animal cells, its adaptation to higher plant tissues significantly extends the utility of plants for environmental genotoxicity research. The present review focuses on 101 key publications and discusses protocols and evolutionary trends specific to higher plants. General consensus validates the use of the percentage of DNA found in the tail, the alkaline version of the test and root study. The comet protocol has proved its effectiveness and its adaptability for cultivated plant models. Its transposition in wild plants thus appears as a logical evolution. However, certain aspects of the protocol can be improved, namely through the systematic use of positive controls and increasing the number of nuclei read. These optimizations will permit the increase in the performance of this test, namely when interpreting mechanistic and physiological phenomena.

Interaction of YOYO-1 with guanine-rich DNA

The oxazole homodimer YOYO-1 has served as a valuable tool for the detection and quantification of nucleic acids. While the base specificity and selectivity of binding of YOYO-1 has been researched to some extent, the effect of unorthodox nucleic acid conformations on dye binding has received relatively less attention. In this work, we attempt to correlate the quadruplex-forming ability of G-rich sequences with binding of YOYO-1. Oligonucleotides differing in the number of tandem G repeats, total length, and length of loop sequence were evaluated for their ability to form quadruplexes in presence of sodium (Na(+)) or potassium (K(+)) ions. The fluorescence behavior of YOYO-1 upon binding such G-rich sequences was also ascertained. A distinct correlation was observed between the strength and propensity of quadruplex formation, and the affinity of YOYO-1 to bind such sequences. Specifically, as exemplified by the oligonucleotides 5'-G4T2G4-3' and 5'-G3TG3TG3-3', sequences possessing longer G-rich regions and shorter loop sequences formed stronger quadruplexes in presence of K(+) which translated to weaker binding of YOYO-1. The dependence of binding of YOYO-1 on sequence and structural features of G-rich DNA has not been explored previously and such studies are expected to aid in more effective interpretation of applications involving the fluorophore.

In vitro and in vivo genotoxicity of silver nanoparticles

The biocidal effect of silver nanoparticles (Ag-np) has resulted in their incorporation into consumer products. While the population exposed to Ag-np continues to increase with ever new applications, Ag-np remains a controversial research area with regard to their toxicity in biological systems. Here a genotoxic and cytotoxic approach was employed to elucidate the activity of Ag-np in vitro and in vivo. Characterization of Ag-np using scanning electron microscopy revealed a size range of 90-180nm. Cytotoxic potential of Ag-np was evaluated in human lymphocytes via cell viability assay (Trypan blue dye exclusion method, MTT and WST assay). The uptake and incorporation of Ag-np into the lymphocytes was confirmed by flow cytometry. Additionally apoptosis (AnnexinV-FITC-PI staining) and DNA strand breaks (comet assay) in human lymphocytes revealed that Ag-np at concentration 25μg/ml can cause genotoxicity. In vivo experiments on plants (Allium cepa and Nicotiana tabacum) and animal (Swiss albino male mice) showed impairment of nuclear DNA. Induction of oxidative stress was also studied. The DNA damage and chromosomal aberrations raise the concern about the safety associated with applications of the Ag-np. A single ip administration of Ag-np gave a significant (P≤0.05) increase in the frequency of aberrant cells and Tail DNA percent at concentrations 10mg/kg body weight and above. Results of comet assay in A. cepa and N. tabacum demonstrated that the genotoxic effect of Ag-np was more pronounced in root than shoot/leaf of the plants. The present study indicated a good correlation between the in vitro and in vivo experiments. Therefore the biological applications employing Ag-np should be given special attention besides adapting the antimicrobial potential.

The use of FISH-comet to detect c-Myc and TP 53 damage in extended-term lymphocyte cultures treated with terbuthylazine and carbofuran

Terbuthylazine and carbofuran are suspected to cause non-Hodgkin's lymphoma and lung cancer. We evaluated the effects of prolonged exposure to low concentrations on primary DNA damage by comet assay, and on the structural integrity of c-Myc and TP 53 genes by FISH-comet. Another novelty in studying these pesticides' genotoxicity is the use of 14-day extended-term human lymphocyte cultures. Concentrations corresponded to values of ADI and OEL: for terbuthylazine 0.58 ng/ml and 8 ng/ml; for carbofuran 8 ng/ml and 21.6 ng/ml, respectively. A possible effect of metabolic activation (S9) was also considered. Carbofuran treatment induced a significant migration of DNA into the tail in a concentration-dependent manner, while for terbuthylazine the effect was significant only at the higher concentration. Terbuthylazine caused migration of both c-Myc signals into the comet tail. A significant occurrence of TP 53 signals in the tail was observed at 8 ng/ml. Prolonged carbofuran treatment significantly elevated the migration of a single c-Myc signal into the tail in a concentration-dependent manner. With S9, distribution of signals shifted toward increased presence of both signals in tail. Our results showed impaired structural integrity of c-Myc and TP 53 due to prolonged exposure to terbuthylazine and carbofuran.

Technical note: Vetiver can grow on coal fly ash without DNA damage

Fly ash is a by-product of coal-fired electricity generation plants. The prevalent practice of disposal is as slurry of ash and water to open lands or ash ponds located near power plants and this has lain to waste thousands of hectares all over the world. Wind and leaching are often the causes of off-site contamination from fly ash dumpsites. Vetiver (Vetiveria zizanioides) grown on fly ash for three months showed massive, mesh-like growth of roots which could have a phytostabilizing effect. The plant achieved this without any damage to its nuclear DNA as shown by comet assay done on the root nuclei, which implies the long-term survival of the plant on the remediation site. Also, when Vetiver is used for phytoremediation of coal fly ash, its shoots can be safely grazed by animals as very little of heavy metals in fly ash were found to be translocated to the shoots. These features make planting of Vetiver a practical and environmentally compatible method for restoration of fly ash dumpsites. Lack of DNA damage in Vetiver has been compared to that in a sensitive plant i.e. Allium cepa. Our results suggested that apart from traditional end-points viz. growth parameters like root length, shoot length and dry weight, comet assay could also be included in a battery of tests for initial, rapid and effective selection of plants for restoration and phytoremediation of polluted sites.

Evaluation of 2,4-D and Dicamba genotoxicity in bean seedlings using comet and RAPD assays

The present study was undertaken to evaluate genotoxic potential of two auxinic herbicides [2,4-dicholorophenoxy acetic acid (2,4-D) and 3,6-dichloro-2-methoxybenzoic acid (Dicamba)] in the roots of common bean (Phaseolus vulgaris L.) seedlings. Two-day-old etiolated seedlings were treated with 10 ppm methyl methanesulfonate (MMS, positive control) or 0.1, 0.2, or 0.3 ppm of either 2,4-D or Dicamba. At the end of a 96 h growth period, root growth, total soluble protein content, DNA damage in individual cells (comet assay scores) and randomly amplified polymorphic DNA (RAPD) profiles were used as endpoints of genotoxicity. 2,4-D and Dicamba were clearly dose-dependent root growth inhibitors. Total soluble protein content was significantly decreased in the positive control and at high concentrations (0.2 and 0.3 ppm) of Dicamba. Soluble protein content increased significantly only at 0.3 ppm 2,4-D (P<0.05). In the comet assay, DNA fragmentation increased in a dose-dependent manner. The diagnostic and phenetic analyzes of appeared and/or disappeared RAPD bands indicated that dose-dependent DNA polymorphism was induced by both herbicides. Genomic template stability was significantly affected at all 2,4-D and Dicamba doses tested. Overall 2,4-D and Dicamba have similar effects on DNA damage detected by comet and RAPD assays.

Modelling the comet assay

The single-cell gel electrophoresis technique or comet assay is widely regarded as a quick and reliable method of analysing DNA damage in individual cells. It has a proven track record from the fields of biomonitoring to nutritional studies. The assay operates by subjecting cells that are fixed in agarose to high salt and detergent lysis, thus removing all the cellular content except the DNA. By relaxing the DNA in an alkaline buffer, strands containing breaks are released from supercoiling. Upon electrophoresis, these strands are pulled out into the agarose, forming a tail which, when stained with a fluorescent dye, can be analysed by fluorescence microscopy. The intensity of this tail reflects the amount of DNA damage sustained. Despite being such an established and widely used assay, there are still many aspects of the comet assay which are not fully understood. The present review looks at how the comet assay is being used, and highlights some of its limitations. The protocol itself varies among laboratories, so results from similar studies may vary. Given such discrepancies, it would be attractive to break the assay into components to generate a mathematical model to investigate specific parameters.

Evaluation of genotoxicity of coal fly ash in Allium cepa root cells by combining comet assay with the Allium test

Fly ash is a by-product of coal-fired electricity generation plants. Its utilization and disposal is of utmost importance. Using onion (Allium cepa) root tip system, the present study was carried out to evaluate the potential toxic and genotoxic effects of fly ash, collected from a thermal power plant in West Bengal, India. Prior to testing, the collected fly ash sample was mixed with sand in different proportions. Allium bulbs were allowed to germinate directly in fly ash and after five days the germinating roots were processed for the Allium test. Additionally, the Allium test was adapted for detecting DNA damage through comet assay. The results from the Allium test indicate that fly ash at 100% concentration inhibits root growth and mitotic indices; induces binucleated cells as a function of the proportion, but is not toxic at very low concentration. In the comet assay, a statistical increase for DNA strand breaks was found only at higher concentrations. The sample was analyzed by flame atomic absorption spectrometer for Zn, Pb, Cu, Ni, Cd and As, whose presence could partly be responsible for the toxicity of fly ash. The study concludes that the classical Allium test can give a more comprehensive data when done in combination with the comet assay, which is faster, simpler and independent of mitosis. Also when fly ash is used for other purposes in combination with soils, it should be judiciously used at very low concentrations in order to protect the ecosystem health from any potential adverse effects.

Mutagenicity and genotoxicity of coal fly ash water leachate

Fly ash is a by-product of coal-fired electricity generation plants. The prevalent practice of disposal is as slurry of ash and water to storage or ash ponds located near power stations. This has lain to waste thousands of hectares of land all over the world. Since leaching is often the cause of off-site contamination and pathway of introduction into the human environment, a study on the genotoxic effects of fly ash leachate is essential. Leachate prepared from the fly ash sample was analyzed for metal content, and tested for mutagenicity and genotoxicity. Analyses of metals show predominance of the metals-sodium, silicon, potassium, calcium, magnesium, iron, manganese, zinc, and sulphate. The Ames Salmonella mutagenicity assay, a short-term bacterial reverse mutation assay, was conducted on two-tester strains of Salmonella typhimurium strains TA97a and TA102. For genotoxicity, the alkaline version of comet assay on fly ash leachate was carried in vitro on human blood cells and in vivo on Nicotiana plants. The leachate was directly mutagenic and induced significant (P<0.05) concentration-dependent increases in DNA damage in whole blood cells, lymphocytes, and in Nicotiana plants. The comet parameters show increases in tail DNA percentage (%), tail length (mum), and olive tail moment (arbitrary units). Our results indicate that leachate from fly ash dumpsites has the genotoxic potential and may lead to adverse effects on vegetation and on the health of exposed human populations.

Genomic damage induced in tobacco plants by chlorobenzoic acids--metabolic products of polychlorinated biphenyls

Tobacco seedlings (Nicotiana tabacum var. xanthi) were treated for 24 h with mono-(2- and 3-CBA), di-(2,5- and 3,4-CBA), and tri-(2,4,6- and 2,3,5-CBA)-chlorobenzoic acids (CBAs) and with the mixture of polychlorinated biphenyls--Delor 103, or cultivated for 1 or 2 weeks in soil polluted with the CBAs. DNA damage in nuclei of leaves and roots was evaluated by the comet assay. A significant increase in DNA damage was observed only at concentrations of CBAs that caused withering of leaves or had lethal effects within 2-4 weeks after the treatments. As the application of CBAs did not induce somatic mutations, the induced DNA migration is probably caused by necrotic DNA fragmentation and not by DNA damage resulting in genetic alteration. In contrast, the application of the monofunctional alkylating agent ethyl methanesulphonate as a positive control resulted in a dose-response increase of DNA damage and an increase of somatic mutations. Thus, the EMS-produced DNA migration is probably associated with genotoxin-induced DNA fragmentation. The data demonstrate that the comet assay in plants should be conducted together with toxicity studies to distinguish between necrotic and genotoxin-induced DNA fragmentation. The content of 2,5-CBA in tobacco seedlings was measured by reverse-phase high pressure liquid chromatography.

Monitoring toxicity, DNA damage, and somatic mutations in tobacco plants growing in soil heavily polluted with polychlorinated biphenyls

Heterozygous tobacco (Nicotiana tabacum var. xanthi) plants were cultivated in soil from a dump site highly polluted with polychlorinated biphenyls (PCBs) at Lhenice in South Bohemia, Czech Republic. The total amount of PCBs in the polluted soil, measured by gas chromatography varied from 165 to 265mgkg(-1) of soil. In tobacco plants cultivated for 8 weeks in the polluted soil the amount of PCB in the leaves varied from 11 to 28 and in the roots from 104 to 308mgkg(-1) dry mass. The average leaf area of tobacco plants growing in the PCB-polluted soil was significantly reduced and the DNA damage in leaf nuclei, measured by the comet assay, was slightly but significantly increased compared with controls. The tobacco plants with increased DNA damage showed reduced growth and had distorted leaves. No increase in the frequency of somatic mutations was detected in tobacco plants growing in the PCB-polluted soil.

Alcian Blue Staining Method to Visualize Bonghan Threads Inside Large Caliber Lymphatic Vessels And X-Ray Microtomography to Reveal Their Microchannels

BACKGROUND

Novel threadlike structures, so-called Bonghan threads, inside large caliber lymphatic vessels were recently observed by using the Janus Green B staining in the case of rabbits, and by using fluorescent magnetic nanoparticles for rats. They are thought to have channels through which some liquid with abundant hyaluronic acid (HA) flows. In the present work, the authors put forward a hypothesis to test that the Bonghan threads can be visualized in vivo by HA-staining dye, Alcian blue, and that the channels may be revealed by using X-ray microtomography.

METHODS AND RESULTS

Alcain blue was injected into a lymph vessel near the caudal vena cava of a rat to make the Bonghan threads visible. Specimens were stained with YoYo-1 and Masson's trichrome. They were also examined by confocal microscopy and X-ray microtomography. A Bonghan thread was well stained by Alcian blue and was about 50 microm thick and 10-20 times thinner than the surrounding lymphatic vessel. It had a broken line shape, with a distribution of rod-shaped nuclei, which is the characteristic of Bonghan threads in general. Whereas lymphatic vessels are surrounded by a collagenous matrix, Bonghan threads do not contain any collagenous component. X-ray microtomography revealed continuous microchannels inside the Bonghan threads.

CONCLUSIONS

Bonghan threads contain HA abundantly, harbor continuous microchannels, and have characteristic distribution of the rod-shape nuclei. Thus, they are novel anatomical structures with liquid-carrying microchannels.