HB Cross Research Articles

Mutagenic and genotoxic activities of Phospholipase A2 Bothropstoxin-I from Bothrops jararacussu in Drosophila melanogaster and human cell lines

Phospholipase A2 Bothropstoxin-I (PLA2 BthTX-I) is a myotoxic Lys49-PLA2 from Bothrops jararacussu snake venom. In order to evaluate the DNA damage caused by BthTX-I, we used the Somatic Mutation and Recombination Test (SMART) in Drosophila melanogaster and Comet assay in HUVEC and DU-145 cells. For SMART, different concentrations of BthTX-I (6.72 to 430 μg/mL) were used and no significant changes in the survival rate were observed. Significant frequency of mutant spots was observed for the ST cross at the highest concentration of BthTX-I due to recombinogenic activity. In the HB cross, BthTX-I increased the number of mutant spots at intermediate concentrations, being 53.75 μg/mL highly mutagenic and 107.5 μg/mL predominantly recombinogenic. The highest concentrations were neither mutagenic nor recombinogenic, which could indicate cytotoxicity in the wing cells of D. melanogaster. In vitro, all BthTX-I concentrations (1 to 50 μg/mL) induced decrease in HUVEC cell viability, as well as in DU-145 cells at concentrations of 10, 25, and 50 μg/mL. The comet assay showed that in HUVEC and DU-145 cells, all BthTX-I concentrations promoted increase of DNA damage. Further studies should be performed to elucidate the mechanism of action of PLA2 BthTX-I and its possible use in therapeutic strategies against cancer.

English

The study was conducted from December 2019 to May 2020 to evaluate the efficiency of local convectional semen and imported sexed semen on in vivo produced bovine embryo quality in Boran and HB cross breed donor cows in Bishoftu, Ethiopia. In this study, it was hypothesized that the breed of donor cows and types of semen can influence the quality of in vivo produced embryo as well as the number of transferable embryos. Randomized experimental design was employed, and a total of 20 donor cows (10 Boran and 10H*B cross) were superovulated and flushed excluding non-responsive donor cows. Donor cows were randomly assigned to two groups: Group-1- five donors inseminated with sexed semen and group-2- five other cows inseminated with convectional semen from each breed. The results of study showed that the embryo recovery rate was 68% in H*B crossbreds and 53% in Boran donor cows. A total of 121 embryos were produced of which, 60 were transferable embryos (36 from H*B crossbreds and 24 from Boran), 39 UFOs (31 from H*B crossbreds and 8 from Boran) and 22 degenerated embryos (12 from HB cross and 10 from Boran). The results of this study showed that the number of transferable embryos produced from donors inseminated with sexed semen and convectional semen was nearly similar. However, the number of defective embryos tended to be higher with sexed semen and the number of unfertilized oocytes is significantly (p<0.05) higher in crossbred cows. This finding suggests that farmer can use sexed semen to get sex specific dairy calves in both cattle genotypes. Key words: Breed, donor cows, superovulation.

Modulating effect of vitamin D3 on the mutagenicity and carcinogenicity of doxorubicin in Drosophila melanogaster and in silico studies

Vitamin D3 (VD3) deficiency increases DNA damage, while supplementation may exert a pro-oxidant activity, prevent viral infections and formation of tumors. The aim of this study was to investigate the mutagenicity and carcinogenicity of VD3 alone or in combination with doxorubicin (DXR) using the Somatic Mutation and Recombination Test and the Epithelial Tumor Test, both in Drosophila melanogaster. For better understanding of the molecular interactions of VD3 and receptors, in silico analysis were performed with molecular docking associated with molecular dynamics. Findings revealed that VD3 alone did not increase the frequency of mutant spots, but reduced the frequency of mutant spots when co-administered with DXR. In addition, VD3 did not alter the recombinogenic effect of DXR in both ST and HB crosses. VD3 alone did not increase the total frequency of tumor, but significantly reduced the total frequency of tumor when co-administered with DXR. Molecular modeling and molecular dynamics between calcitriol and Ecdysone Receptor (EcR) showed a stable interaction, indicating the possibility of signal transduction between VD3 and EcR. In conclusion, under these experimental conditions, VD3 has modulatory effects on the mutagenicity and carcinogenicity induced by DXR in somatic cells of D. melanogaster and exhibited satisfactory interactions with the EcR.

Betulinic acid modulates urethane-induced genotoxicity and mutagenicity in mice and Drosophila melanogaster

Betulinic acid (BA) is a pentacyclic triterpenoid found in several plant species. Urethane (URE) is a known promutagen. Here, we examine the genotoxicity and mutagenicity of BA alone or in combination with URE using the bone marrow micronucleus assay in mice bone marrow cells and the Somatic Mutation and Recombination Test in Drosophila melanogaster. Findings revealed that BA alone was not genotoxic, but reduced the frequency of micronucleus when compared to the positive control. No significant differences were observed in the cytotoxicity. Biochemical analyzes showed no significant differences for liver (AST and ALT) or renal (creatinine and urea) function parameters, indicating the absence of hepatotoxic and nephrotoxic effects. BA alone did not increase the frequency of mutant spots, but reduced the total frequency of mutant spots when co-administered with URE in both ST and HB crosses. In addition, BA reduced the recombinogenic effect of URE at the highest concentrations of both crosses. In conclusion, under experimental conditions, BA has modulatory effects on the genotoxicity induced by URE in mice, as well as in somatic cells of D. melanogaster. We suggest that the modulatory effects of BA may be mainly due to its antioxidant and apoptotic properties.

HERBICIDE GENOTOXICITY REVEALED WITH THE SOMATIC WING SPOT ASSAY OF Drosophila melanogaster

The genotoxicity of the herbicides clomazone, linuron and simazine was detected using the somatic wing spot assay of Drosophila melanogaster . For the evaluation of the mutagenic and recombinogenic activities induced by the herbicides two crosses were used: the standard cross (ST) which expresses basal levels of cytochrome P450 enzymes and the high bioactivation cross (HB) with overexpression of P450 genes conferring increased sensitivity to promutagens and procarcinogens. Third-instar larvae were exposed by chronic feeding (48 h) to three different concentrations of each herbicide. The frequencies of spots per individual in the treated series were compared to the negative concurrent control series (water or 5 % ethanol solution depending on the herbicide). Clomazone showed positive results for small and total spots in both the ST and the HB crosses. Linuron was positive at all concentrations tested for small and total spots in the ST cross while only positive for small and total spots at the highest concentration assayed in the HB cross. Simazine did not produce positive results in the ST cross while it was positive in the HB cross. The bifunctional cross-linking agent mitomycin C (MMC – 0.15 mM) was used as positive control and produced as expected a significant increase of all types of spots in both crosses. In conclusion, the positive results were due to induced mutations and not by recombinogenic activity, furthermore the significant increase in the frequency of total spots was mainly due to the induction of small single spots.

Evaluation of the genotoxic properties of nickel oxide nanoparticles in vitro and in vivo

Nickel-based nanoparticles (NPs) are new products with an increasing number of industrial applications that were developed in recent years. NiO NPs are present in several nanotechnological industrial products, and the characterization of their genotoxic potential is essential. The present study assessed the genotoxicity of NiO NPs in vivo and in vitro using the somatic mutation and recombination test in somatic cells of Drosophila melanogaster (SMART), the cytokinesis – block micronucleus assay (CBMN), and the comet assay in a V79 cell line. The NiO NPs used in this study were about 30 nm in mean size. Larvae of Drosophila melanogaster were exposed to 5 mL of five different concentrations (1.31, 2.62, 5.25, 10.5, and 21 mg/mL) of NiO NPs. In turn, V79 cells were treated with a concentration range of 15–2000 μg/mL NiO NPs. The SMART showed that all concentrations of NiO NPs are genotoxic to the standart (ST) cross when compared to the negative control. On the other hand, only the highest concentration (21 mg/mL) was genotoxic to the HB cross. Somatic recombination was the preferential mechanism lesions were induced in D. melanogaster. The results show that NiO NPs were mutagenic to V79 cells as assessed by the CBMN assay. Significant differences in the frequencies of micronuclei (MN) were observed using the highest NiO NP concentrations (250 and 500 μg/mL) in the 4- and 24-h treatments, but when 125 μg/mL NiO NPs was used, such difference was observed only in the 4-h exposure time. The comet assay revealed that 62, 125, 250 and 500 μg/mL NiO NPs induced a significant increase in DNA damage. The results observed in this study indicate that NiO NPs are genotoxic and mutagenic in vitro and in vivo.

Evaluation of toxicity, mutagenicity and carcinogenicity of samples from domestic and industrial sewage

Physico-chemical and toxicological analyses are of fundamental importance to determine water quality. The objectives of the present study were to evaluate the toxicity, mutagenicity and carcinogenicity of samples from the Mumbuca Stream and the Perdizes River, through both SMART and the wts test, respectively, in somatic cells of Drosophila melanogaster and to quantify the amount of heavy metals and other pollutants, which are indicative of environmental quality. Water samples were collected (M1, M2, P1, P2 and MP) and submitted to physico-chemical analysis, calculating the water quality index for each sampling site. In order to evaluate the toxicity, mutagenicity and carcinogenicity of the samples, third instar larvae descended from the crossing between virgin female wts/TM3, sb1 and mwh/mwh males (wts test) and ST and HB (SMART) crosses were treated with samples from P1, P2, M1, M2 and MP sites. The physico-chemical analysis and the biological assay allowed us to conclude that undetected values for heavy metals and the low frequency of mutant spots (SMART) and epithelial tumor (wts) in treated flies from the Mumbuca Stream and Perdizes River may be due to the reduction of ceramic activities in the municipality. The physico-chemical analyzes identified altered the environmental quality parameters, which directly influenced the survival of D. melanogaster treated with samples of M2 and MP, which according to the WQI were classified as regular and poor environmental quality, respectively. The altered parameters may be due to clandestine domestic sewage sent downstream of the effluent.

Assessment of mutagenic, recombinogenic and carcinogenic potential of titanium dioxide nanocristals in somatic cells of Drosophila melanogaster

Nanoparticles have been widely used in several sectors and their long-term effect on the body and environment remains unknown. To evaluate the mutagenic, recombinogenic and carcinogenic potential of 11 nm titanium dioxide nanocrystals (TiO2 NCs), the Somatic Mutation and Recombination Test (SMART) and the Test for Detection of Epithelial Tumors Clones (Warts-Wts) were used, both in Drosophila melanogaster. Third-instar larvae (72 + 4 h), obtained in both tests, were treated with different concentrations of TiO2 NCs ranging from 6.25 to 100 mM. Ultrapure water and urethane were used as negative and positive controls, respectively. At ST cross, all concentrations of TiO2 NCs showed a significant increase in the frequencies of mutant spots, demonstrating higher recombination rates. At the HB cross, only the 50 mM concentration showed a negative result. In the Wts Test, all used concentrations were carcinogenic, except for the 100 mM one, which was toxic. No relationship was demonstrated between the used concentrations and the obtained responses. There was no interference of the cytochrome P450 enzyme complex in the induction of mutant spots.

Evaluation of mutagenic, recombinogenic and carcinogenic potential of (+)-usnic acid in somatic cells of Drosophila melanogaster

The main of this study was to evaluate the mutagenic and carcinogenic potential of (+) – usnic acid (UA), using Somatic Mutation and Recombination Test (SMART) and the test for detecting epithelial tumor clones (wts) in Drosophila melanogaster. Larvae from 72 ± 4 h from Drosophila were fed with UA (5.0, 10.0 or 20.0 mM); urethane (10.0 mM) (positive control); and solvent (Milli-Q water, 1% Tween-80 and 3% ethanol) (negative control). ST cross produced increase in total mutant spots in the individuals treated with 5.0, 10.0 or 20.0 mM of UA. HB cross produced spot frequencies in the concentration of 5.0 mM that were higher than the frequency for the same concentration in the ST cross. In the highest concentrations the result was negative, which means that the difference observed can be attributed, in part, to the high levels of P450, suggesting that increasing the metabolic capacity maximized the toxic effect of these doses. In the evaluation of carcinogenesis using the wts test, the results obtained for the same concentrations of UA show a positive result for the presence of tumors when compared to the negative control. We conclude that UA has recombinogenic, mutagenic and carcinogenic effects on somatic cells in D. melanogaster.

Modulating effect of synthetic statins against damage induced by doxorubicin in somatic cells of Drosophila melanogaster

The competitive inhibitors of HMG-CoA reductase, popularly known as statins, exert pleiotropic effects, which result from the ability of statins to inhibit the synthesis of isoprenoids, which are fundamental for the functioning of proteins responsible for intracellular signaling. Some recent studies suggest an important role associated with the use of antineoplastic atorvastatin and rosuvastatin, the statins most widely used today. In this study, the Drosophila wing spot test was used to evaluate possible protective effects of atorvastatin and rosuvastatin against damage induced by DXR. Larvae were chronically treated with negative control (ethanol 5%), positive control (DXR 0.125 mg/mL) and five different concentrations of atorvastatin and rosuvastatin. The results demonstrated absence of a mutagenic effect for the two statins tested. The analysis of the descendants co-treated with DXR and atorvastatin/rosuvastatin revealed a modulatory effect of these statins on damage induced by DXR. This effect was verified in all concentrations tested in the descendants of the ST and HB crosses treated with rosuvastatin, and only in descendants of the HB cross treated with atorvastatin. Induction of apoptosis and antioxidant activity appear to be the main mechanisms involved in reducing the frequency of mutant spots and consequent modulation of the damage induced by DXR.

Genotoxic evaluation of bupivacaine and levobupivacaine in the Drosophila wing spot test.

Bupivacaine and levobupivacaine are amino amide local anesthetics commonly used in medical practice. Although bupivacaine consists of a racemic mixture of S (-)-bupivacaine and R (+)-bupivacaine enantiomers, levobupivacaine is comprised of pure S (-)-bupivacaine. It has been known that levobupivacaine is preferable to bupivacaine since it may cause cardiovascular and nervous system toxicity. For determining genotoxicity of these anesthetics, we used the wing somatic mutation and recombination test in Drosophila melanogaster. Three-day-old trans-heterozygous larvae were treated with bupivacaine and levobupivacaine. Analysis of the standard crosses indicated that bupivacaine and levobupivacaine did not exhibit mutagenic or recombinogenic activity until toxic doses have been reached at the larval stage. When we examined bupivacaine and levobupivacaine in the HB cross, bupivacaine did not exhibit any genotoxicity at high concentrations (500µg/mL), but levobupivacaine did exert genotoxicity at high concentrations (1000µg/mL)-depending on the substantial recombinogenic effect.

Lack of mutagenic effect by multi-walled functionalized carbon nanotubes in the somatic cells of Drosophila melanogaster

Carbon nanotubes (CNTs) are formed by rolling up a single graphite sheet into a tube. Among the different types of CNTs, the multi-walled carbon nanotubes (MWCNTs) comprise a set of concentric nanotubes with perfect structures. Several uses for MWCNTs have been suggested to be included in biological applications such as manufacturing of biosensors, carriers of drugs. However, before these materials can be put on the market, it is necessary to know their genotoxic effects. Thus, this study aims to evaluate the mutagenicity of multi-walled carbon nanotubes (MWCNTs) functionalized in somatic cells of Drosophila melanogaster, using the somatic mutation and recombination test (SMART). This assay detects the loss of heterozygosity of marker genes expressed phenotypically on the wings of the fly. Larvae of three days were used, resulting from ST cross, with basal levels of the cytochrome P450 and larvae of high metabolic bioactivity capacity (HB cross). They were treated with different concentrations of MWCNTs functionalized. The MH descendants, analyzed in both ST and HB crosses, had no significant effects on the frequency of mutant. Based on the results and on the experimental conditions mentioned in this study, it was concluded that MWCNTs were not mutagenic in D. melanogaster.

Interactions of sulforaphane and dimethyl sulfoxide with methyl methanesulfonate, urethane, 4-nitroquinoline-1-oxide and hydrogen peroxide in the Drosophila melanogaster wing spot test

Sulforaphane (SF) is an isothiocyanate present in Brassicaceae, vegetables that induce the detoxification of electrophiles and reactive oxygen species. SF has been correlated with chemoprevention mechanisms against degenerative diseases. We tested if the SF had an effect against methyl methanesulfonate (MMS), urethane (URE), 4-NQO and H2O2. SF (>95% purity, 0.14, 0.28, 0.56mM) was diluted in a DMSO/Tw80/EtOH mixture (DTE) corresponding to 25, 50, 100% of lyophilized broccoli. The SF treatment (0.14mM) was positive for small spots in the ST cross and negative in the HB cross. In the HB cross, SF (0.28mM) was genotoxic. In the ST cross, the SF treatments showed a tendency to reduce the genotoxic damage caused by MMS, which could be explained by the radical scavenging action of the DTE mixture. In the ST cross, the frequency of small spots in the SF 0.14mM/URE treatment was similar to that of Water/URE, which can be explained by a DTE and SF scavenger action. In both crosses, the results for the direct oxidants, 4-NQO and H2O2, were different and must be related to differential modulation of CYPs expression and the SF and DTE scavenger properties.

Electrophoresis release of hemoglobin from living red blood cells

Nowadays, proteomics research is almost always made by lysing cells to release protein first and then to analyze the protein solution in many ways, the lytic product of red blood cells is also called hemolysate, the main components of which are hemoglobin A 1 , A 2 , A 3 and carbonic anhydrase (CA), etc. In our laboratory, intact (unlysed) living red blood cells are used for direct electrophoresis so as to observe the released hemoglobin (Hb). Thus an electophoresis release experiment has been established with starch-agarose mixed gel. Electrophoresis release can be classified as initial release and re-release. In the former, the electropheresis is completed by switching on once when the release of Hb can be seen. In the latter, the electrophoresis is switched off and then switched on, when Hb release can be seen again. In our laboratory, HbA 2 phenomenon was observed in the initial release experiment and HbA 2 and HbA 1 interaction was seen in Hb cross eletrophoresis. In a two-way diagonal electrophoresis of the initial release type, HbA 2 and HbA 1 were found to exist in binding in the red blood cells. SDS-PAGE and mass spectrometry were conducted for the released products in the HbA 2 phenomenon of the electrophoresis and it was found that Prx-2 (peroxiredoxin-2) may be involved in the formation of HbA 2 phenomenon. In the re-release experiment, it was found that Hb mostly had “multi-band re-release phenomenon”. Based on this research, we designed a series of relevant experiments such as isotonic re-release, hypotonic re-release, full re-release from isolonic to hypotonic, two-way diagonal electrophoresis of re-release type, as well as comparative study of re-release of two kinds of red blood cells (red blood cells in whole blood and those isolated from it) and the influence of plasma elements on the re-release of Hb in the red blood cells. These methods have provided certain bases for research into the existence states of in vivo intracellular proteins and opened up new approaches and new fields of research.

Ausência de mutagenicidade de Solanum paniculatum L. em célula s somáticas de Drosophila melanogaster: SMART/asa

The lyophilized aqueous extract of Solanum paniculatum L. (jurubeba) leaves, a medicinal plant widely used by people as diuretic, in liver and spleen treatments, against fever and inflammation, underwent the SMART/wing test in somatic cells of Drosophila melanogaster for the evaluation of its mutagenic potential. We used three different concentrations of the leaf extract (2.5 mg.mL-1, 6.25 mg.mL-1, and 10 mg.mL-1), doxorubicin (DXR) as positive control, and distilled water with  5% sucrose as negative control. We employed three lineages of Drosophila in this experiment, flr³, ORR, and mwh. The  larvae derived from the standard cross (ST: flr³ females x mwh males) and the high bioactivation cross (HB: ORR females x mwh males) were chronically treated and the wings of the  emerging adults were analyzed. Our results showed no  mutagenic activity of S. paniculatum L. ST or HB crosses.

Measurement of theb-hadron production cross section using decays toμ−D0Xfinal states inpp¯collisions ats=1.96 TeV

We report a measurement of the production cross section for b hadrons in pp¯ collisions at s=1.96 TeV. Using a data sample derived from an integrated luminosity of 83 pb−1 collected with the upgraded Collider Detector (CDF II) at the Fermilab Tevatron, we analyze b hadrons, Hb, partially reconstructed in the semileptonic decay mode Hb→μ−D0X. Our measurement of the inclusive production cross section for b hadrons with transverse momentum pT>9 GeV/c and rapidity |y|<0.6 is σ=1.30 μb±0.05 μb(stat)±0.14 μb(syst)±0.07 μb(B), where the uncertainties are statistical, systematic, and from branching fractions, respectively. The differential cross sections dσ/dpT are found to be in good agreement with recent measurements of the Hb cross section and well described by fixed-order next-to-leading logarithm predictions.3 MoreReceived 11 March 2009DOI:https://doi.org/10.1103/PhysRevD.79.092003©2009 American Physical Society

Mutagenic and recombinagenic activity of airborne particulates, PM10 and TSP, organic extracts in the Drosophila wing-spot test

The genotoxicity associated with air pollution in the city of Canoas, Rio Grande do Sul (Brazil), was assessed in November (spring) and January (summer). We applied the somatic mutation and recombination test (SMART) in Drosophila melanogaster in its standard version with normal bioactivation (ST) and in its variant with increased cytochrome P450-dependent biotransformation capacity (HB). The data indicated the genotoxicity of TSP and PM10 collected in November, in both ST and HB crosses. The genotoxic activity of the PM10 material in the spring sample was exclusively associated with the induction of mitotic recombination, whereas the TSP genetic toxicity was due to both recombinational as well as point and/or chromosomal mutation events. Considering PM10 collected in January, a positive response—100% (17.10 m 3/ml) concentration—was observed in the HB cross, which was not detected in the ST cross.

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.

Analysis of the in vivo nitrosation capacity of the larvae used in the wing somatic mutation and recombination test of Drosophila melanogaster

The in vivo nitrosation capacity of third-instar larvae of Drosophila melanogaster was assessed using the wing somatic mutation and recombination test (SMART). Larvae derived from two different crosses, the standard cross (ST) and the high bioactivation cross (HB) both involving the recessive wing cell markers multiple wing hairs ( mwh) and flare ( flr 3), were used. The HB cross is characterised by an increased cytochrome P450-dependent bioactivation capacity for promutagens and procarcinogens. The larvae were treated either with methyl urea, sodium nitrite or its combination. N-Nitrosomethylurea was used as a positive control. The wings of the resulting flies were analysed for the occurrence of mutant spots produced by various types of mutational events or by mitotic recombination. Methyl urea is negative in the ST and the HB cross, whereas sodium nitrite is weakly genotoxic in both crosses. However, the combination of both compounds produces highly increased frequencies of mutations and recombinations predominantly in the HB cross. The genotoxic effects produced by the combined treatments were considerably increased when mashed potatoes or an agar–yeast medium were used for the treatment instead of the standard instant medium. Treatment of larvae with the mixture resulting from the in vitro reaction of nitrosation precursors also resulted in high frequencies of induced spots comparable to those recorded with the potent genotoxin N-nitrosomethylurea. Further experiments showed that the genotoxic effect resulting from the in vivo exposure to nitrosation precursors can be reduced by co-treatment with catechin, a known nitrosation inhibitor. The present study demonstrates that the wing spot test is well suited for the determination of genotoxicity produced by in vivo nitrosation processes and for the study of their modulation by individual compounds or dietary complex mixtures.

Genotoxic activity of environmentally important polycyclic aromatic hydrocarbons and their nitro derivatives in the wing spot test of Drosophila melanogaster

The genotoxicity of three polycyclic aromatic hydrocarbons (PAHs) and of three of their nitro derivatives was evaluated in the wing Somatic Mutation And Recombination Test (SMART) in Drosophila melanogaster. Two crosses were used, i.e. the standard cross (ST) and the improved high bioactivation cross (HB) which is characterised by an increased sensitivity to the genotoxic effects of promutagens and procarcinogens. Larvae trans-heterozygous for the two recessive wing cell markers multiple wing hairs ( mwh) and flare ( flr 3 ) were fed with the test compounds for 48 h. The wings of the surviving flies were analysed for the occurrence of single and twin spots. Naphthalene, 1-nitronaphthalene and 1,5-dinitronaphthalene proved to be more genotoxic in the HB cross than in the ST cross. Anthracene showed a clear genotoxic activity only in the HB cross whereas it was negative in the ST cross. 9-Nitroanthracene gave inconsistent results in both crosses. Phenanthrene was negative in the ST cross, but weakly positive in the HB cross. These results demonstrate that the genotoxic activity of these PAHs and their nitro derivatives can be detected with the somatic cells of the wing imaginal discs of larvae with high bioactivation capacity.