Effect of vanillin on toxicant-induced lethality in the Drosophila melanogaster DNA repair test

Vanillin (VA) modulates the genotoxicity of chemical and physical agents in a complex manner. Previous studies indicate that VA inhibits the mutagenicity but increases the mitotic homologous recombination caused by at least some genotoxic agents. In the present study, we have evaluated the effects of VA on the repair of lethal damage produced by three genotoxins, N-ethyl-N-nitrosourea (ENU), ethyl methanesulfonate (EMS), and mitomycin C (MMC), using the DNA repair test (DRT) in Drosophila melanogaster. VA, 0.25% and 0.5% (w/v), increased the toxicity of MMC and EMS in repair-deficient flies, as measured by a decrease in the proportion of male to female progeny in the DRT; sex ratios decreased from 18-48% for MMC and 21-97% for EMS. These effects may be caused by the inhibition of nonhomologous DNA end joining caused by VA. In contrast to the results with MMC and EMS, VA protected against the lethality of ENU in repair-defective flies, as measured by a 43-207% increase in the survival of male flies in the DRT. It was inferred that the protective effect was due to VA modulating stages prior to the induction of ENU lesions in DNA, including modulating the antioxidant properties of VA and/or to its interference with the metabolic activation and/or detoxification of specific genotoxins. The results from this study indicate that the characterization of VA as a promising agent for preventing damage to genes and chromosomes should be tempered by observations that VA can increase the toxicity of chemical agents.     

Genotoxicity testing of Plantago major extracts in somatic cells of Drosophila melanogaster

Plantago major is used in many parts of the world for the treatment of diseases and to promote the healing of wounds. In the present study, the somatic mutation and recombination test (SMART) in Drosophila melanogaster was used to evaluate the genotoxic activity of an aqueous extract of P. major. The following Drosophila crosses were made: standard (ST) cross, in which virgin flare females (flr3/TM3, Bds) were mated with mwh/mwh males, and high-bioactivation (HB) cross, in which virgin ORR females (ORR/ORR; flr3/TM3, Bds) were mated with mwh/mwh males. Each cross produced two types of descendents, marker-transheterozygous (MH) (mwh +/+ flr3) and balancer-heterozygous (BH) (mwh +/+ TM3, Bds) flies. Three-day-old larvae of both types of descendents were treated with undiluted and diluted (1:1 and 1:2 in water) aqueous extracts of P. major. The extracts were genotoxic in both crosses, producing similar induced frequencies in ST and HB flies. Comparison of the frequencies of wing spots in the BH and MH descendents indicated that recombination was a major response. The results indicate that, under these experimental conditions, aqueous extracts of P. major are genotoxic (recombinagenic).     

Genotoxicity of vesicular fluid and saline extract of Taenia solium metacestodes in somatic cells of Drosophila melanogaster

Neurocysticercosis, the most common parasitic disease of the central nervous system, is caused by cysticerci of the helminth Taenia solium, which is prevalent in developing countries and is reemerging in affluent societies. This helminth is associated with brain tumors and hematological malignancies in humans. In the present study, we analyzed the genotoxicity of vesicular fluid (VF) and a saline extract (SE) of T. solium metacestodes in the Drosophila melanogaster wing somatic mutation and recombination test (SMART). Third-instar larvae derived from standard and high bioactivation crosses were treated for approximately 48 hr with 12.5, 25.0, and 50.0 microg/ml of VF and SE of T. solium metacestodes. Negative (phosphate buffered saline) and positive (10 mM urethane) controls were also included. The results showed that the two test compounds were genotoxic in both crosses of Drosophila. Nevertheless, further research is needed to determine the genotoxic potential of specific compounds present in VF and SE and their role in the development of cancer.     

The somatic white-ivory eye spot test does not detect the same spectrum of genotoxic events as the wing somatic mutation and recombination test in Drosophila melanogaster

A group of six chemical compounds was tested in parallel in two different somatic genotoxicity assays in Drosophila melanogaster, the wing somatic mutation and recombination test (SMART) and the white-ivory eye spot test. The wing spot test makes use of the wing cell markers multiple wing hairs (mwh) and flare (flr) and detects both mitotic recombination and various types of mutational events. The white-ivory eye spot test makes use of the white-ivory (w′) quadruplication and detects the somatic reversion of the recessive eye color mutation w′ to the wild-type (w⁺). Three- or two-day-old larvae were fed chronically with the compounds ethylnitrosourea (ENU), N-nitrosopyrrolidine (NNP), caffeine (CAF), chromium (VI) oxide (CRO), potassium chromate (POC), and 2,4-dichlorophenoxyacetic acid (2,4-D). All six compounds are genotoxic to various degrees in the wing spot test. The percentage of the genotoxic activity that is due to mitotic recombination was between 84% and 91% for the hexavalent chromium compounds CRO and POC and about 68% for 2,4-D. In contrast, ENU and NNP showed only 46% and 25% recombinagenic activity, respectively. In the white-ivory eye spot test, the three compounds [CRO, POC, and 2,4-D] with high recombinagenic activity and CAF were clearly nongenotoxic, whereas only ENU and NNP gave a positive response. From these results, it is concluded that the spectrum of genotoxic events detected by the two assays is different. In particular, the white-ivory eye spot test appears not to detect mitotic recombination the way the wing spot test does. © 1996 Wiley-Liss, Inc.     

Genotoxicity of two arsenic compounds in germ cells and somatic cells of Drosophila melanogaster

Two arsenic compounds, sodium arsenite (NaAsO₂) and sodium arsenate (Na₂HAsO₄), were tested for their possible genotoxicity in germinal and somatic cells of Drosophila melanogaster. For germinal cells, the sex-linked recessive lethal test (SLRLT) and the sex chromosome loss test (SCLT) were used. In both tests, a brood scheme of 2–3–3 days was employed. Two routes of administration were used for the SLRLT: adult male injection (0.38, 0.77 mM for sodium arsenite; and 0.54, 1.08 mM for sodium arsenate) and larval feeding (0.008, 0.01, 0.02 mM for sodium arsenite; and 0.01, 0.02 mM for sodium arsenate). For the SCLT the compounds were injected into males. Controls were treated with a solution of 5% sucrose which was employed as solvent. The somatic mutation and recombination test (SMART) was run in the w⁺/w eye assay as well as in the mwh +/+ flr³ wing test, employing the standard and insecticide-resistant strains. In both tests, third instar larvae were treated for 6 hr with sodium arsenite (0.38, 0.77, 1.15 mM), and sodium arsenate (0.54, 1.34, 2.69 mM). In the SLRLT, both compounds were positive, but they were negative in the SCLT. The genotoxicity of both compounds was localized mainly in somatic cells, in agreement with reports on the carcinogenic potential of arsenical compounds. Sodium arsenite was an order of magnitude more toxic and mutagenic than sodium arsenate. This study confirms the reliability of the Drosophila in vivo system to test the genotoxicity of environmental compounds. © 1995 Wiley-Liss, Inc.     

Absence of genotoxicity of a phytotherapeutic extract from Stryphnodendron adstringens (Mart.) Coville in somatic and germ cells of Drosophila melanogaster

Stryphnodendron adstringens (Mart.) Coville, a medicinal plant that grows in the “cerrados” (a savanna ecosystem) of Brazil, popularly known as “Barbatimão,” is an important source of tannins (polyphenols). In Brazil, it is used in industry (mainly as vegetable tanning) and also in traditional medicine for the treatment of various diseases. In the present study, a phytotherapeutic extract from S. adstringens stem bark was evaluated for mutagenic and recombinagenic effects using the wing spot test of Drosophila melanogaster (somatic mutation and recombination test, SMART), and for chromosome damage in germ cells using the Drosophila sex‐chromosome loss test (ring‐X loss). For SMART, the standard as well as the high bioactivation fly crosses were used; the latter cross is characterized by a high sensitivity to promutagens and procarcinogens. Third‐instar larvae from these two crosses were treated for 48 hr with different concentrations (66%, 75%, and 100%) of the phytotherapeutic extract. The wings of the emerging adults were analyzed for the occurrence of different types of mutant spots. No statistically significant differences in spot frequencies between controls and treated series were observed. For the ring‐X loss test, adult males were fed with the same concentrations of the extract as in the wing spot test. No statistically significant increases in ring‐X losses were observed. The results of our experiments suggest that the phytotherapeutic extract from S. adstringens stem bark is not genotoxic in somatic and germ cells of D. melanogaster. Environ. Mol. Mutagen. 41:293–299, 2003. © 2003 Wiley‐Liss, Inc.     

On the use of excision repair defective cells in the wing somatic mutation and recombination test in Drosophila melanogaster

Ten chemical mutagens were tested in the wing somatic mutation and recombination test in Drosophila melanogaster. This assay makes use of genetic markers expressed on the wing of adult flies. Larvae which are trans-heterozygous for mwh (multiple wing hairs) and flr (flare) were fed with the compounds either acutely (2, 4, or 6 hr) or chronically (48 or 72 hr), or were treated by inhalation (1 hr). Genetic changes induced in the somatic cells of the wing imaginal discs lead to the formation of mutant clones on the wing (mwh and/or flr). Single spots are produced by point mutation, chromosome breakage, and mitotic recombination; twin spots are produced exclusively by mitotic recombination. All 10 mutagens belonging to different chemical classes were clearly positive in this assay. However, the choice of the optimal treatment conditions (concentration of compound, duration of treatment, age of larvae at treatment) is essential. Eight of the compounds were also tested in excision repair defective cells by introducing the mei-9L1 mutation into the test system. This seems not to improve the detection capacity of the assay, mainly because only small spots are found in excision repair defective wings. In addition, the frequencies of spots in these wings are enhanced four to five times, which makes the scoring more tedious. For these and other practical reasons the use of this specific cross is not recommended in the wing spot test for routine screening purposes.     

Genotoxic effects of cisplatin in somatic tissue of Drosophila melanogaster

Third instar larvae of Drosophila melanogaster transdihybrid for mwh and flr were exposed to varying concentrations of cisplatin by feeding on dry media wetted with aqueous solutions of the test compound. Larval feeding continued until pupation, and surviving transdihybrid adults were collected seven days following commencement of feeding. Wings of adults were removed and scored under 400X magnification for the presence of twin spots and single spots comprised of clones of cells possessing malformed wing hairs. Cisplatin was found to induce both twin spots and single spots, and significant (p less than 0.05) linear concentration-response relationships were obtained with respect to the induction of all endpoints. Induction of twin spots demonstrates that cisplatin induces mitotic recombination in the somatic tissue of Drosophila larvae. This capacity to induce mitotic exchange in the somatic tissue of Drosophila compares well with the compound's reported ability to induce chromosome breaks in Drosophila germ cells [Brodberg et al. 1983]. However, not all compounds possess similar genotoxic profiles in the somatic and germ tissue of Drosophila.     

Genotoxic activity of different chromium compounds in larval cells of Drosophila melanogaster, as measured in the wing spot test.

Two chromium(VI) compounds (potassium chromate and potassium dichromate) and one chromium(III) compound, chromium chloride, were evaluated for genotoxic effects in the wing spot test of Drosophila melanogaster following standard procedures. This assay detects both somatic recombination and mutational events. The genotoxic effects were determined from the appearance of wing spots in flies transheterozygous for the third chromosome recessive markers multiple wing hairs (mwh) and flare-3 (flr(3)), as well as in flies heterozygous formwh and the multiply inverted TM3 balancer chromosome. Genetic changes induced in somatic cells of the wing's imaginal discs lead to the formation of mutant clones on the wingblade. Single spots are due to different genotoxic mechanisms: point mutation, deletion, chromosome breakage, and mitotic recombination; while twin spots are produced only by mitotic recombination. From our results it appears that both chromium(VI) compounds clearly increase the incidence of mutant clones by inducing high increases in the frequency of all types of clones recorded. On the contrary, chromium(III) did not increase the frequency of mutant clones. A high proportion of the total spot induction was due to mitotic recombination, confirming previously reported data on the strong recombinogenic activity of chromium(VI) compounds.     

Recombinagenic activity of integerrimine,a pyrrolizidine alkaloid from Senecio brasiliensis,in somatic cells of Drosophila melanogaster

Integerrimine (ITR), a pyrrolizidine alkaloid from Senecio brasiliensis, was tested for genotoxicity using the wing somatic mutation and recombination test (SMART) in Drosophila melanogaster. The compound was administered by chronic feeding (48 hours) of 3-day-old larvae. Two different crosses involving the markers flare (flr) and multiple wing hairs (mwh) were used, that is, the standard (ST) cross and the high bioactivation (HB) cross, which has a high cytochrome P450-dependent bioactivation capacity. In both crosses, the wings of two types of progeny were analyzed, that is, inversion-free marker heterozygotes and balancer heterozygotes carrying multiple inversions. ITR was found to be equally potent in inducing spots in a dose-related manner in the marker heterozygotes of both crosses. This indicates that the bioactivation capacity present in larvae of the ST cross is sufficient to reveal the genotoxic activity of ITR. In the balancer heterozygotes of both crosses, where all recombinational events are eliminated due to the inversions, the frequencies of induced spots were considerably reduced which documents the recombinagenic activity of ITR. Linear regression analysis of the dose response relationships for both genotypes shows that 85% to 90% of the wing spots are due to mitotic recombination. Environ. Mol. Mutagen 29:91–97, 1997 © 1997 Wiley-Liss, Inc.     

Effect of nucleotide excision repair on ENU-induced mutation in female germ cells of Drosophila melanogaster

The role of nucleotide excision repair (NER) in the repair of alkylation damage in the germ cells of higher eukaryotes has been studied mainly by treating postmeiotic male germ cells. Little is known about repair in actively repairing female germ cells. In this study, we treated NER-deficient (ner(-)) mus201(D1) Drosophila females with N-ethyl-N-nitrosourea (ENU) and determined both the mutant frequencies in the multiple locus recessive lethal (RL) test and in the single locus vermilion gene and determined the ENU mutation spectrum in the vermilion gene. The results show that ENU is mutagenic in all cell stages and that the induced frequencies increase with cell maturation, from oogonia to mature oocytes. In addition, the induced spectrum consists mainly of A:T-->T:A transversions (43.8%), A:T-->G:C transitions (21.9%), and A:T-->C:G transversions (15.6%). G:C-->A:T (3.1%) transitions, other transversions (9.4%), frameshifts (3.1%), and deletions (3.1%) were also found. Comparison of these results with those previously obtained for repair-proficient (ner(+)) female germ cells reveal: 1) Differences in the RL and vermilion mutation frequencies for ner(+) and ner(-) germ cells, indicating that NER is involved in the repair of ENU-induced damage to these cells. 2) At least 15.6% of mutations in ner(-) cells may be the consequence of N-ethylation damage and mutations of this type were not detected in ner(+) cells. 3) Although differences were found in transition frequencies between ENU-treated ner(+) and ner(-) germ cells (52.2% vs. 25%), suggesting that a functional NER is involved in processing O-ethylated damage, the role of NER in repairing O-ethylated adducts is uncertain.     

Analysis of UV-stimulated recombination in the Drosophila SMART assay

The UV component of solar radiation is classified into UVA (320-400 nm), UVB (290-320 nm), and UVC (200-290 nm). Although all three types of UV light are capable of damaging biological systems, the earth's atmosphere filters out UVC, and a portion of UVB. In this study, we evaluated the induction of mutation and recombination by different wavelengths of UV light in the wing spot test of Drosophila melanogaster (Somatic Mutation and Recombination Test, SMART). Third-instar larvae that were trans-heterozygous for the third chromosome recessive markers, multiple wing hairs (mwh) and flare-3 (flr(3)), were exposed to different doses of UVA (at 365 nm), UVB (at 312 nm) or UVC (at 254 nm), and transferred to standard Drosophila culture medium. Feeding ended with pupation of the surviving larvae, and the genetic changes induced in the 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 500-4,000 J/cm(2) UVA did not increase the frequency of mutant spots. UVB doses of 200, 250, 300, 350, and 400 J/cm(2) increased the frequency of all categories of spots, indicating that UVB was potentially both mutagenic and recombinogenic. Assays run in balancer-heterozygous flies (which are insensitive to recombination) indicated that the fraction of mutants in trans-heterozygous flies due to recombination increased from 48.57% at 200 J/cm(2) UVB to 98.30% at 400 J/cm(2) UVB. While 140-480 J/cm(2) of UVC was not genotoxic, UVC produced a strong toxic response at doses higher than 140 J/cm(2). The results of this study indicate that UVB was much more active than UVC or UVA in the SMART assay, and that UVB was highly recombinogenic.     

Somatic mutation and recombination test in Drosophila melanogaster

A novel test system for the detection of mutagenic and recombinogenic activity of chemicals is described in detail. Drosophila melanogaster larvae trans-heterozygous for the mutations multiple wing hairs (mwh) and flare (flr) are exposed to the test compounds for various periods of time ranging from 96 hr to 1 hr. Induced mutations are detected as single mosaic spots on the wing blade of surviving adults that show either the multiple wing hairs or flare phenotype. Induced recombination leads to mwh and flr twin spots and also to a certain extent, to mwh single spots. Recording of the frequency and the size of the different spots allows for a quantitative determination of the mutagenic and recombinogenic effects. This and earlier studies with a small set of well-known mutagens indicate that the test detects monofunctional and polyfunctional alkylating agents (ethyl methanesulfonate, diepoxybutane, mitomycin C, Trenimon), mutagens forming large adducts (aflatoxin B1), DNA breaking agents (bleomycin), intercalating agents (5-aminoacridine, ICR-170), spindle poisons (vinblastine), and antimetabolites (methotrexate). In addition, the test detects mutagens unstable in aqueous solution (beta-propiolactone), gaseous mutagens (1,2-dibromoethane), as well as promutagens needing various pathways of metabolic activation (aflatoxin B1, diethylnitrosamine, dimethylnitrosamine, mitomycin C, and procarbazine). The rapidity and ease of performance as well as the low costs of the test necessitate a high priority for validation of this promising Drosophila short-term test.     

Genotoxic Assessment of the Dry Decoction of Myracrodruon urundeuva Allemão (Anacardiaceae) Leaves in Somatic Cells of Drosophila melanogaster by the Comet and SMART Assays

Medicinal plants are worldwide used as an efficient treatment of many diseases. Myracrodruon urundeuva Allemão (Anacardiaceae) is widely used Brazilian folk medicine to treat inflammations and infections of the female genital tract, conditions of the stomach and throat, and to heal wounds on the skin and mucous membranes. Several pharmacological properties of extracts and compounds isolated from M. urundeuva are found in the literature, corroborating its uses as antiulcer and gastroprotective, anti-inflammatory and analgesic, as well as antimicrobial. Despite these many uses in traditional herbal medicine, there are few reports of its toxic-genetic effect. This work aimed to investigate the genotoxic and mutagenic potential in vivo of the dry decoction of M. urundeuva leaves on somatic cells of Drosophila melanogaster, through the Comet assay and somatic mutation and recombination test (SMART). Six concentrations (0.5, 1.0, 2.0, 4.0, 8.0, and 16.0 mg/mL) were studied after feeding individuals for 24 hr in culture medium hydrated with extracts of M. urundeuva. In the Comet assay, all concentrations showed a genotoxic effect significantly higher than the negative control group, treated with distilled water. The two highest concentrations were also superior to the positive control group, treated with cyclophosphamide (1 mg/mL). In the SMART, there was a mutagenic effect at all concentrations tested, with a clear dose-dependent relationship. Both recombination and mutation account for these mutagenic effects. The set of results indicate that the dry decoction of M. urundeuva leaves is genotoxic and mutagenic for D. melanogaster under the experimental conditions of this study. Environ. Mol. Mutagen. 61:329–337, 2020. © 2019 Wiley Periodicals, Inc.     

V(D)J recombination,somatic hypermutation and class switch recombination of immunoglobulins: mechanism and regulation

Immunoglobulins emerging from B lymphocytes and capable of recognizing almost all kinds of antigens owing to the extreme diversity of their antigen-binding portions, known as variable (V) regions, play an important role in immune responses. The exons encoding the V regions are known as V (variable), D (diversity), or J (joining) genes. V, D, J segments exist as multiple copy arrays on the chromosome. The recombination of the V(D)J gene is the key mechanism to produce antibody diversity. The recombinational process, including randomly choosing a pair of V, D, J segments, introducing double-strand breaks adjacent to each segment, deleting (or inverting in some cases) the intervening DNA and ligating the segments together, is defined as V(D)J recombination, which contributes to surprising immunoglobulin diversity in vertebrate immune systems. To enhance both the ability of immunoglobulins to recognize and bind to foreign antigens and the effector capacities of the expressed antibodies, naive B cells will undergo class switching recombination (CSR) and somatic hypermutation (SHM). However, the genetics mechanisms of V(D)J recombination, CSR and SHM are not clear. In this review, we summarize the major progress in mechanism studies of immunoglobulin V(D)J gene recombination and CSR as well as SHM, and their regulatory mechanisms.     

Antigenotoxicity of coffee in the Drosophila assay for somatic mutation and recombination

The somatic mutation and recombination test (SMART) in Drosophilamelanogaster was carried out to investigate whether or not coffeecan modulate the genotoxicity of the well-established mutagenic/carcinogenicchemicals cyclophosphamide (CPH), diethylnitrosamine (DEN),mitomycin C (MMC), procarbazine (PRO) and urethane (URE). Forthis purpose, 3-day-old larvae, trans-heterozygous for the winghair markers mwh (multiple wing hairs) and flr³ (flare³), wereraised on instant medium containing either the genotoxin aloneor in combination with instant coffee. From the results obtained,it was evident that the chronic co-administration of coffeewas effective in significantly reducing the frequencies of singleand twin spots induced by CPH, DEN, MMC and URE but not PRO.The maximum reduction was observed in the frequencies of twinspots (produced by mitotic recombination) after feeding larvaeon medium containing coffee in combination with the compoundsCPH or URE. ¹C-4/48 (second floor), Safdarjung Development Area, New Delhi - 110 016, India     

Detection of mitotic recombination and sex chromosome loss induced by adriamycin, chlorambucil, demecolcine, paclitaxel and vinblastine in somatic cells of Drosophila melanogaster in vivo

The conventional w/w+ eye assay in Drosophila has been used for the last 10 years for genotoxic evaluation of a broad number of chemicals with different mechanisms of action. Although chemicals that induce genotoxic effects by mechanisms other than covalent binding to DNA are difficult to detect. The aim of this study was the parallel detection of both mitotic recombination and X chromosome loss induced by five chemical compounds used worldwide as antineoplastic drugs using the w/w+ somatic assay in Drosophila melanogaster. The compounds tested were the intercalating agent adriamycin (AD), the alkylating compound chlorambucil (CAB) and the spindle poisons demecolcine (DEM), paclitaxel (taxol, TX) and vinblastine (VBL). We used a cross between heterozygous females with a rod-X and a ring-X chromosome mated with ywf males. All four genotypes in the next generation are heterozygous or hemizygous for the w+ reporter gene and were inspected for the occurrence of white clones in their compound eyes. We found differences in the induction of mitotic recombination when compared with chromosome loss. Genotoxic profiles obtained for the antineoplastic drugs studied indicate direct and indirect effects. While AD seems to be clastogenic due to its induction of X chromosome loss in XrX females; DEM, CAB and TX produced both structural chromosome aberrations through clastogenic activities and mitotic recombination through DNA interactions; the cytotoxic VBL induced rX loss only in XrY and intra-chromosomal recombination (XY) males, probably due to sister strand recombination, generating a w+w+ duplication and a w- deletion, forward mutations or small deletions at the white locus.     

Use of the Drosophila wing spot test in the genotoxicity testing of different herbicides

Four herbicides, namely propanil, maleic hydrazide, glyphosate, and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), were investigated for genotoxicity in the wing spot test of Drosophila melanogaster. The herbicides were administered by chronic feeding to 3-day-old larvae. Two different crosses, a standard (ST) and a high-bioactivation (HB) cross, involving the flare-3 (flr(3)) and the multiple wing hairs (mwh) markers, were used. The HB cross uses flies characterized by an increased cytochrome P-450-dependent bioactivation capacity, which permits a more efficient biotransformation of promutagens and procarcinogens. In both crosses, the wings of the two types of progeny, which are inversion-free marker heterozygotes and balancer heterozygotes, were analyzed. Maleic hydrazide and glyphosate proved to be more genotoxic in the ST cross, whereas propanil appeared to be slightly more genotoxic in the HB cross. On the other hand, the herbicide 2,4,5-T increased the mutation frequency for only the small single spots in the ST cross.     

Induction of somatic mutation and recombination by four inhibitors of eukaryotic topoisomerases assayed in the wing spot test of Drosophila melanogaster

Four inhibitors of eukaryotic topoisomerases were investigatedfor genotoxic effects in the wing spot test of Drosophila melanogaster.As a somatic mutation and recombination test (SMART) this assayassesses mitotic recombination and mutational events of variouskinds. We studied camptothecin as a topoisomerase I inhibitor,as well as ellipticine as an intercalating inhibitor and teniposideand etoposide as two non-intercalating inhibitors of topoisomeraseII. Wing spots were induced in flies trans-heterozygous forthe recessive wing cell markers multiple wing hairs (mwh) andflare (flr³) as well as in flies heterozygous for mwh and themultiply inverted TM3 balancer chromosome. All four compoundsproved significantly genotoxic in this test The spot inductionfrequencies formally standardized to the millimolar unit ofexposure dose decreased in the order camptothecin > teniposide> ellipticine