Die Belastung von Wässern mit gentoxischen Substanzen

Assessment of genotoxicity in gonads, liver and gills of zebrafish (Danio rerio) by use of the comet assay and micronucleus test after in vivo exposure to methyl methanesulfonate

Since generative tissues are a link between the generations, the detection of genetic damage in testis and ovary of fish is conductive to elucidating the relationship between genotoxicity and impairment of reproduction. In the current study, exposure of zebrafish to methyl methanesulfonate over two weeks caused concentration dependent genotoxic effects in gonads, liver and gills using the alkaline comet assay. Likewise, the micronucleus frequency was elevated in all of these organs. Thus, the comet assay and the micronucleus test proved appropriate for the detection of genotoxicity in primary male and female gonad cells and histological sections of the gonads from zebrafish, respectively.

Reproductive and genotoxic effects in zebrafish after chronic exposure to methyl methanesulfonate in a multigeneration study

There is still controversy whether adverse effects by genotoxic anthropogenic pollutants are linked to the decline of fish populations. Further investigations into the relationship between genotoxic stress and detrimental effects on development and reproduction in fish are required. For this end, zebrafish (F0 generation) were exposed in vivo to the alkylating model genotoxin methyl methanesulfonate (MMS) from fertilization to the age of 1 year. F0 fish were mated over 6 months to check for reproductive capacities. F1 fish grew up without exposure in order to allow for regeneration. Mortality of F0 fish depended on MMS concentrations. In MMS-exposed F0 fish, times of first spawning were delayed and fertility was reduced. Using the alkaline comet assay and the micronucleus test, significant genotoxic effects were found in the livers, gills and gonads of either sex in the F0 generation. No detrimental effects on growth were found. In F1 fish with parental exposure, teratogenic effects were increased, and larval survival was reduced. However, fertility capacities of the non-exposed F1 generation had recovered. Development and survival rates further recovered in the F2 generation. Anthropogenic genotoxicants may thus play a considerable role in the decline of wild fish populations.

Tail moment versus tail length--application of an in vitro version of the comet assay in biomonitoring for genotoxicity in native surface waters using primary hepatocytes and gill cells from zebrafish (Danio rerio)

In order to investigate the suitability of an in vitro version of the comet assay with primary hepatocytes and gill cells from zebrafish (Danio rerio), cells were isolated by immersion in trypsin/EDTA solution after whole-body perfusion with phosphate-buffered saline. Within the scope of an 18-month biomonitoring study, primary cells were used to identify the genotoxic potential of native water samples from different sites along the major German rivers, Rhine and Elbe, and to evaluate the sensitivity and practicability of the chosen assay. Depending on the endpoint measured, considerable differences were detected with respect to the number of genotoxic surface water samples: Whereas no differences could be recorded for tail moment and relative DNA contents of head and tail, the number of positively tested native surface water samples significantly increased with tail length as endpoint.

Assessment of the genotoxicity of mine-dump material using the Tradescantia-stamen hair (Trad-SHM) and the Tradescantia-micronucleus (Trad-MCN) bioassays

The Tradescantia-stamen hair (Trad-SHM) and -micronucleus (Trad-MCN) bioassays were used to determine the genotoxicity of two eluates derived from mine tailings. The goal was to test the suitability of the Tradescantia bioassays as screening tools for this kind of waste material. Leachates obtained using the current standard German leaching test methods (S4 eluate) as well as leachates obtained using a new eluation method (pHstat4) were tested and compared. Concentration of heavy metals in the pHstat4 eluate were much higher than in the S4 eluate. The chemical analysis corresponded well with the results of the bioassays. Exposure to solutions containing more than 1% pHstat4 eluate caused a significantly higher number of micronuclei. The Trad-SHM bioassay also showed an increased pink mutation rate when plants were exposed to 8 or 16% eluate solutions. In contrast, the S4 eluate only caused increased mutation rates when solutions containing more than 32% eluate were used. The low pH of the pHstat4 eluate was not responsible for the genotoxicity observed using both bioassays, as indicated by the lack of significant mutation rates in the nitric acid controls. This demonstrates that the Tradescantia bioassays can be used as tools to assess the genotoxic potential of environmental samples with a wide range of pH values, without the need for sample modification.

Tradescantia-micronucleus assay for the assessment of the clastogenicity of Austrian water

Seven water samples collected from Vienna and Salzburg areas in Austria were tested for their clastogenicity with the Tradescantia-micronucleus (Trad-MCN) assay. There was no indication of clastogenic activity in two drinking water samples; likewise, samples from two major rivers (Danube and Salzburg) and of a river that received effluents from a paper mill also gave negative results. Urban river water as well as ground water samples which were collected near an industrial waste dump site caused a statistically significant and dose dependent increase of the MCN frequencies.

Detection of genotoxic effects of heavy metal contaminated soils with plant bioassays

Aim of the present study was the development of a bioassay which enables the detection of genotoxic effects of heavy metal contaminated soils. In the first part of the present study, the data base on metal effects in plant bioassays was extended. Four metal salts, namely Cr(VI)O3, Cr(III)Cl3, Ni(II)Cl2 and Sb(III)Cl3 were tested comparatively in MN tests with pollen tetrad cells of Tradescantia clone #4430 and in meristematic root tip cells of Vicia faba. With Cr6+ and Ni2+, clear-cut dose-effects were observed in a range between 0.75 and 10.0 mM, whereas this was not the case with Cr3+ (range tested 1.25-10 mM) and Sb3+ (range 0.30-5.25 mM). In Vicia, negative results were obtained with the four metal salts under all conditions of test. To compare the mutagenic potencies of the metals, the increases of the regression curves (k-values) were calculated, they indicate the number of MN induced per mM in 100 tetrad cells. The corresponding values for Cr6+ and Ni2+ are 0.87 and 1.05, respectively. It appears that the Tradescantia system is in particular sensitive towards those metal species which cause DNA damage in animals and man such as Cr6+, Cd2+, Ni2+, and Zn2+, whereas no clear positive results were obtained with less harmful metal ions such as Cu2+, Cr3+ or Sb3+. In the second part of the study, the mutagenic effects of four metal contaminated soils and two types of standardized leachates (pH 4.0 and pH 7.0) of these soils were tested in Tradescantia and in Vicia. In addition, chemical analyses were carried out to determine the metal concentrations in the soils and in the extracts. Two of the samples contained highly elevated levels of a number of metals (Zn, Pb, Cu, Cd, Sb, As), one soil came from the Central Austrian Alps and contained high As levels only. Direct exposure of the Tradescantia plants in the soils resulted in a drastic increase of the MN frequencies over the background. The lowest effect was seen with the Slovakian soil which contained in particular Sb and As (4.5-fold increase over the background), with the other soils, the induced frequencies were 11-15-fold over the control values. On the contrary, negative results were obtained upon exposure of Tradescantia cuttings in the leachates and upon implantation of germinated Vicia beans in the soils. The results of the present study indicate that Trad-MN assays with direct exposure of intact plants is an appropriate method which enables to detect genotoxic effects of metal contaminated soils in situ. This simple and fast biomonitoring assays might be a valuable supplement to analytical analyses of contaminated soils.