Effect of temperature on frequencies of spots in Drosophila wing-spot assay

Genotoxicity Testing of Four Textile Dyes in Two Crosses of Drosophila Using Wing Somatic Mutation and Recombination Test

In this study, four textile dyes, namely Astrazon Yellow, Red, Blue, and Black, were tested for their genotoxic effects in the wing cells of Drosophila melanogaster. Two crosses were used, the standard cross (ST) and the improved high-bioactivation cross (HB), the latter being characterized by increased sensitivity to the genotoxic effects of promutagens and procarcinogens. Three-day-old larvae were exposed to different concentrations of dyes. Commonly known mutagens were applied as positive controls. All concentrations of textile dyes, ethyl methanesulfonate (EMS), and urethane caused a decrease in survival proportional to concentration used. EMS and urethane caused an increase in the number of all types of spots in both standard and high-bioactivation crosses. Compared to ST crosses, the number of induced spots in the HB cross treated with urethane was considerably high. Treatment of the standard and the high-bioactivation crosses with textile dyes gave positive results, apparent from increase in the frequency of the small single spots. Yellow and red dyes also increased the number of large single spots in both crosses, whereas the twin spots were positive only at the highest dose of yellow dye. All these results indicate that D. melanogaster wing spot test can be recommended as a suitable in vivo test for the determination of genotoxicity of textile dyes.

How reliable is the humeral pale spot for identification of cryptic species of the Minimus Complex?

The Anopheles minimus Complex Theobald (Diptera: Culicidae) is composed of the 3 sibling species A, C, and E. The malaria vectors An. minimus A and C are distributed over the Southeast Asian region, whereas species E is restricted to the Ryukyu Japanese Islands. Because species A and C can be sympatric and present specific behaviors and have a role in malaria transmission, it is important to differentiate them. The literature mentioned the presence of a presector pale spot on the wing costa of An. minimus A, whereas species C may exhibit both presector and humeral pale spots. However, the reliability of their diagnostic power has not been established over large temporal and geographic surveys. From the analyses of 9 populations throughout Southeast Asia, including published data and field populations from 2 sites in Thailand, we showed that the wing patterns present spatial and temporal variations that make these two morphological characters unreliable for the precise identification of An. minimus A and C. Therefore, molecular identification remains the most efficient method to obtain an unambiguous differentiation of these 2 species. Correct species identification is essential and mandatory for any relevant study on the Minimus Complex and for the application of successful control strategies.

Genotoxicity modulation by cadmium treatment: studies in the Drosophila wing spot test

The genotoxic activity of cadmium chloride (CC) has been evaluated in the somatic mutation and recombination test (SMART) in Drosophila melanogaster. In addition, its possible modulating effect on the genotoxicity of two known mutagenic agents, potassium dichromate (PDC) and ethyl methanesulfonate (EMS), was investigated. Three different types of combined treatments of CC with the two genotoxins were performed: pretreatment, cotreatment, and posttreatment. The SMART assay is based on the principle that loss of heterozygosity for the recessive markers, multiple wing hairs (mwh) and flare-3 (flr(3)), leads to the formation of mutant clones in the imaginal disks of larvae, which are expressed as mutant spots on the wings of adult flies. Thus, after adult emergence, the wings of the adult flies were scored for the presence of single and/or twin spots. Our results show that CC alone was not effective in increasing the frequency of any of the three categories of spots (small, large, and twin). In the cotreatment experiments, CC increased the genotoxicity of PDC but it decreased the genotoxicity of EMS. No effects of CC were observed in the pretreatment or posttreatment experiments; however, only low concentrations of CC, PDC, and EMS were tested in the pretreatment assays due to the high toxicity of the treatment. Although our results with PDC are consistent with the hypothesis that cadmium can interfere with repair mechanisms, the EMS data suggest that other modulating mechanisms are also involved in the genotoxicity of this metal.

Influence of sodium arsenite on the genotoxicity of potassium dichromate and ethyl methanesulfonate: studies with the wing spot test in Drosophila

The wing spot test in Drosophila melanogaster was used to investigate the genotoxicity of arsenic and its effects on the action of two clearly genotoxic agents: potassium dichromate (PDC) and ethyl methanesulfonate (EMS). This assay is based on the principle that the loss of heterozygosity of the suitable recessive markers multiple wing hairs (mwh) and flare-3 (flr(3)) can lead to the formation of mutant clones of larval cells, which are then expressed as spots on the wings of adult flies. These spots can be attributed to different genotoxic events: either mitotic recombination or mutation (deletion, point mutation, and specific types of translocation). Pretreatments and chronic cotreatments were comparatively used for combined treatments. From the results obtained it is evident that sodium arsenite (SA) does not increase the frequency of any of the three categories of spots recorded (small, large, and twin spots) at the concentrations tested. The effects of SA in combination with PDC, in both cotreatments and pretreatments, indicate that SA almost suppressed the clones induced by PDC. Nevertheless, no effects of arsenic were observed with respect to the pre- and cotreatments with EMS. Thus, SA does not modify the frequencies of mutant clones induced by EMS.

Genotoxicity testing of five herbicides in the Drosophila wing spot test

Four triazine herbicides: amitrole, metribuzin, prometryn and terbutryn, and the bipyridal compound diquat dibromide have been evaluated for genotoxicity in the wing somatic mutation and recombination test of Drosophila melanogaster, following standard procedures. Third-instar larvae trans-heterozygous for the third chromosome recessive markers multiple wing hairs (mwh) and flare-3 (flr(3)) were chronically fed with different concentrations of the test compounds. Feeding ended with pupation of the surviving larvae. Genetic changes induced in somatic cells of the wing's imaginal discs lead to the formation of mutant clones on the wing blade. Point mutation, chromosome breakage and mitotic recombination produce single spots; while twin spots are produced only by mitotic recombination. Exposure to 0.5 mM and 1 mM of amitrole clearly increased the frequency of small single, large single and total spots. Terbutryn, at the concentration of 5 mM, induced a slight increase in the frequency of small single and total spots, but this result could be false positive. The other three herbicides tested did not show any genotoxic effect. When heterozygous larvae for mwh and the multiple inverted TM3 balancer chromosomes were treated, significant increases in the frequency of mutant spots were only detected for amitrole. The observed spot frequencies were lower than those found in mwh/flr(3)50%) of the total spot induction was due to mitotic recombination.

Antigenotoxicity studies in Drosophila melanogaster

The fruit fly Drosophila melangaster with its well developed array of genotoxicity test systems has been used in a number of studies on antigenotoxicity of various compounds and mixtures. In recent years, the newly developed Somatic Mutation and Recombination Tests (SMART) have mainly been employed. These one-generation tests make use of the wing or eye imaginal disc cells in larvae and have proven to be very efficient and sensitive. They are based on the principle that the loss of heterozygosity of suitable recessive markers can lead to the formation of mutant clones of cells that are then expressed as spots on the wings or eyes of the adult flies. We have employed the wing spot test with the two markers multiple wing hairs (mwh,3-0.3) and flare (flr,3-38.8). Three-day-old larvae, trans-heterozygous for these markers, are treated chronically or acutely by oral administration with the test compound(s) or complex mixtures. For antigenotoxicity studies, chronic co-treatments can be used, as well as separate pre-treatments with an antigenotoxic agent followed by a chronic treatment with a genotoxin. After eclosion, the wings of the adult flies are scored for the presence of single and twin spots. These spots can be due to different genotoxic events: either mitotic recombination or mutation (deletion, point mutation, specific types of translocation, etc.). The analysis of two different genotypes (one with structurally normal chromosomes, one with a multiply inverted balancer chromosome) allows for a quantitative determination of the recombinagenic activity of genotoxins. Results of two separate studies presented: (1) instant coffee has antirecombinagenic but not antimutagenic activity in the wing spot test; and (2) ascorbic acid and catechin are able to protect against in vivo nitrosation products of methyl urea in combination with sodium nitrite.

Analysis of the relationship between age of larvae at mutagen treatment and frequency and size of spots in the wing somatic mutation and recombination test in Drosophila melanogaster

The relationship between the induction of mutant clones and the time of mutagen treatment was studied in the somatic mutation and recombination test (SMART) in wing cells of Drosophila melanogaster. Larvae trans-heterozygous for the recessive marker mutations multiple wing hairs (mwh) and flare (flr) were produced. Batches of these larvae were then treated with mutagen at different ages spanning all three larval instars. Methyl methanesulfonate was fed acutely for 2 h by immersing the larvae in a solution of the mutagen mixed with powdered cellulose. Wings of the surviving adult flies were mounted and scored for the presence of spots. The frequency and size of single and twin spots were recorded separately. Twin spots are produced exclusively by mitotic recombination, whereas single spots can result from various types of mutational and exchange events. There exists a clear correlation between time of induction and frequency as well as size of the single spots. In young larvae only few but very large spots are induced, whereas in older larvae the frequencies are considerably increased but the sizes are smaller. The twin spots show a different relationship. Practically no twin spots are found in very young and in very old larvae. The results demonstrate that in the wing spot test the optimal age of the larvae for mutagen treatment is 72 h.