Saccharomyces Cerevisiae Strain D7 Research Articles

Nutraceutical potential of hemp (Cannabis sativa L.) seeds and sprouts

In this study the antioxidant effect of Cannabis sativa L. seeds and sprouts (3 and 5 days of germination) was evaluated. Total polyphenols, flavonoids and flavonols content, when expressed on dry weight basis, were highest in sprouts; ORAC and DPPH (in vitro assays), CAA-RBC (cellular antioxidant activity in red blood cells) and hemolysis test (ex vivo assays) evidenced a good antioxidant activity higher in sprouts than in seeds. Untargeted analysis by high resolution mass spectrometry in negative ion mode allowed the identification of main polyphenols (caffeoyltyramine, cannabisin A, B, C) in seeds and of ω-6 (linoleic acid) in sprouts. Antimutagenic effect of seeds and sprouts extracts evidenced a significant decrease of mutagenesis induced by hydrogen peroxide in Saccharomyces cerevisiae D7 strain. In conclusion our results show that C. sativa seeds and sprouts exert beneficial effects on yeast and human cells and should be further investigated as a potential functional food.

Adaptive response to hydrogen peroxide in yeast: Induction, time course, and relationship to dose–response models

The assay for trp5 gene conversion and ilv1-92 reversion in Saccharomyces cerevisiae strain D7 was used to characterize the induction of an adaptive response by hydrogen peroxide (H(2)O(2)). Effects of a small priming dose on the genotoxic effects of a larger challenge dose were measured in exponential cultures and in early stationary phase. An adaptive response, indicated by smaller convertant and revertant frequencies after the priming dose, occurred at lower priming and challenge doses in young, well-aerated cultures. Closely spaced priming doses from 0.000975 to 2 mM, followed by a 1 mM challenge, showed that the induction of the adaptive response is biphasic. In exponential cultures it was maximal with a priming dose of 0.125-0.25 mM. Very small priming doses were insufficient to induce the adaptive response, whereas higher doses contributed to damage. A significant adaptive response was detected when the challenge dose was administered 10-20 min after the priming exposure. It was fully expressed within 45 min, and the yeast began to return to the nonadapted state after 4-6 hr. Because of the similarity of the biphasic induction to hormetic curves and the proposal that adaptive responses are a manifestation of hormesis, we evaluated whether the low doses of H(2)O(2) that induce the adaptive response show a clear hormetic response without a subsequent challenge dose. Hormesis was not evident, but there was an apparent threshold for genotoxicity at or slightly below 0.125 mM. The results are discussed with respect to linear, threshold, and hormesis dose-response models.

A multivariate analysis approach to the study of chemical and functional properties of chemo‐diverse plant derivatives: lavender essential oils

ABSTRACTSix lavender essential oils, L. angustifolia and five Lavandula x hybrida cultivars (Super Z, Abrialis, R.C., Alardii and Ordinario), were evaluated from a phytochemical and biological standpoint, and the results were computed by using multivariate data analysis. The essential oils were analysed by gas chromatography, gas chromatography–mass spectrometry and headspace gas‐chromatography. Multivariate analyses (principal component analysis) identified three main phytochemical clusters among lavender essential oils, represented by 1,8‐cineole, linalyl acetate and linalool. Functional properties of the essential oils were checked by (1) estimating cytotoxicity and genotoxicity using the Saccharomyces cerevisiae D7 strain; (2) determining antifungal activity against three common phytopathogens (Pythium ultimum, Magnaporthe grisea and Botrytis cinerea), by performing an agar vapour bioassay; and (3) calculating the antioxidant capacity by using the 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) and β‐carotene bleaching tests. No mutagenic effects were detected, but multivariate analyses (PLS, partial least squares regression) showed that the essential oils belonging to the linalool cluster were the most cytotoxic. Antifungal activity against phytopathogens confirmed the predictive results of PLS. The differences among lavender essential oils regarding weak antioxidant capacity showed a positive relationship between the high polarity compounds and the DPPH method, as determined by PLS. The opposite effect was shown for the same type of compound and β‐carotene. Ketones and esters did not exert any significant antioxidant activity. In conclusion, taking lavender essential oils as a model and computing multivariate data of a reduced number of parameters, the proposed approach assured the description of the relationship between a phytocomplex, its constituents and bioactivities, and allowed a comprehensive, predictive approach to be defined, for which the chemical profile provides a possible synergic overall effort in terms of applicative perspectives. Copyright © 2013 John Wiley & Sons, Ltd.

Potentiation of the mutagenicity and recombinagenicity of bleomycin in yeast by unconventional intercalating agents

Interactions between bleomycin (BLM) and conventional or unconventional intercalating agents were analyzed in an assay for mitotic gene conversion at the trp5 locus and reversion of the ilv1-92 allele in Saccharomyces cerevisiae strain D7. BLM is a potent recombinagen and mutagen in the assay. Various chemicals modulate the genetic activity of BLM, producing either antimutagenic effects or enhanced genotoxicity. Effects of cationic amino compounds include enhancement of BLM activity by aminoacridines and protection against BLM by aliphatic amines. The potentiation of BLM is similar to findings in a micronucleus-based BLM amplification assay in Chinese hamster V79 cells. In this study, the amplification of BLM activity was explored in yeast using known intercalators, compounds structurally related to known intercalators, and unconventional intercalators that were identified on the basis of computer modeling or results in the Chinese hamster BLM amplification assay. As shown in previous studies, the classical intercalator 9-aminoacridine (9AA) caused dose-dependent enhancement of BLM activity. Other compounds found to enhance the induction of mitotic recombination and point mutations in strain D7 were chlorpromazine, chloroquine, mefloquine, tamoxifen, diphenhydramine, benzophenone, and 3-hydroxybenzophenone. The increased activity was detectable by cotreatment of yeast with BLM and the modulator compound in growth medium or by separate interaction of the intercalator with DNA followed by BLM treatment of nongrowing cells in buffer. The data support the interpretation drawn from micronucleus assays in mammalian cells that BLM enhancement results from DNA intercalation and may be useful in detecting noncovalent interactions with DNA. Environ.

Chemical fingerprinting and bioactivity of Amazonian Ecuador Croton lechleri Müll. Arg. (Euphorbiaceae) stem bark essential oil: A new functional food ingredient?

Croton lechleri essential oil has been obtained by steam distillation of fresh stem bark from Amazonian Ecuador adult plants (yield: 0.61ml/kg [0.061%]; density: 1.01g/ml), and then chemically characterised by GC (Gas Chromatography) and GC–MS (gas chromatography–mass spectrometry). Seventy-four chemicals were detected and identified; the most abundant in descending order, were the sesquiterpenes sesquicineole (17.29%), α-calacorene (11.29%), 1,10-di-epi-cubenol (4.75%), β-calacorene (4.34%) and epi-cedrol (4.09%). Monoterpenes checked with a relative peak area higher than 2.0% were α-pinene (2.01%), p-cymene (2.61%), limonene (4.20%) and borneol (2.67%). The structure of the main chemicals were confirmed by GC–MS and 1H NMR analyses. Spectrophotometric 1,1-diphenyl-2-picrylhydrazyl (DPPH) and DPPH-(high performance) thin layer chromatography (DPPH-(HP)TLC) bioautographic assays showed a lower radical scavenging capacity (IC50) with respect to commercial thyme essential oil and BHA (butylated hydroxyl anisole), pointing out, however, that the C. lechleri essential oil fraction, characterised by α-calacorene, β-calacorene and δ-cadalene, was the most involved in the bioactivity. Similar results were obtained with β-carotene bleaching assay, where the IC50 values were 0.291±0.024mg/ml for C. lechleri essential oil, 0.164±0.013 and 1.34×10−4±10−5mg/ml for thyme essential oil and BHA, respectively. (HP)TLC-bioautographic assay performed with Gram positive and Gram negative bacteria revealed a minimum inhibitory concentration (MIC) values comprised between 0.10mg/ml (Escherichia coli) and 10.10mg/ml (for e.g. Pseudomonas aeruginosa), and the fraction mainly characterised by sesquicineole (97.38%) as the most involved in antibacterial capacity. Ames test employing Salmonella typhimurium TA98 and TA100 with and without a metabolic activation mixture (S9 mix) demonstrated the absence of mutagenicity of the C. lechleri essential oil between a concentration range of 10−2 and 100mg/plate. The same results were achieved by Saccharomyces cerevisiae D7 strain assay. An interesting mutagen-protective efficacy was evidenced by a 30% and 33% revertants reduction of TA98 strain treated with 2-aminoanthracene and nitrofluorene (2μg/plate), suggesting, above all, the possibility to employ C. lechleri essential oil as a new flavouring protective ingredient for foods or dietary supplements against potential mutagens formed during cooking and/or processing in general.

Ecuadorian stingless bee (Meliponinae) honey: A chemical and functional profile of an ancient health product

Stingless bee honey samples from west Amazonian Ecuador were studied for their physiochemical, chemical and functional properties. Reducing sugars (44.9 ± 5.72 g/100 g), water (34.1 ± 4.34 g/100 g), free acidity (31.8 ± 4.05 meq/100 g), diastase activity (1.60 ± 0.20 u.d./g), hydroxymethylfurfural (15.0 ± 1.91 mg/kg), electrical conductivity (0.48 ± 0.06 mS/cm), ash (0.28 ± 0.04 g/100 g), colour (150 mm Pfund) were determined as physicochemical parameters. Melissopalynological analyses were processed evidencing pollen belonging to 14 plant families. Glucose (25.5 ± 3.41 g/100 g), fructose (25.2 ± 3.37 g/100 g) and sucrose (3.72 ± 0.49 g/100 g) contents were determined by HPLC, evidencing equal concentrations between fructose and glucose. Coumarins and flavonoids were determined by densitometric HPTLC: fraxin and bergamotin (0.065 ± 0.009; 0.035 ± 0.005 μg/g) among coumarins; luteolin (0.045 ± 0.006 μg/g), quercitrin (0.020 ± 0.003 μg/g), isoramnetin (0.015 ± 0.002 μg/g) among flavonoids. Among the vitamin E isomers, evaluated by HPLC, the occurrence of the only β-tocopherol (1.12 ± 0.15 μg/g) was noted. All these results were compared with those acquired for two multifloral Apis mellifera honeys. DPPH and β-carotene bleaching tests were performed, showing interesting values for Ecuadorian honey samples, higher than those shown by multifloral A. mellifera honeys (88.1 ± 11.1 DPPH inhibition%; 70.8 ± 8.90 β-carotene inhibition%). Antibacterial activity, against both Gram positive and Gram negative bacteria, revealed MIC values (10–50 μg/ml) always lower than those of A. mellifera honeys. Ecuadorian Meliponinae honey samples also showed anti-mutagenic activity assayed with Saccharomyces cerevisiae D7 strain, inhibiting back mutation over the entire range of concentrations.

Modulation of the genotoxicity of bleomycin by amines through noncovalent DNA interactions and alteration of physiological conditions in yeast

The effects of amines on the induction of mitotic gene conversion by bleomycin (BLM) were studied at the trp5 locus in Saccharomyces cerevisiae strain D7. BLM induces double-strand breaks in DNA and is a potent recombinagen in this assay. The polyamine spermidine causes concentration-dependent protection against the genotoxicity of BLM, reducing the convertant frequency by over 90% under the most protective conditions. Spermine, diethylenetriamine, ethylenediamine, putrescine, and ethylamine were also antigenotoxic in combined treatments with BLM. There was a general correspondence between the protective effect and the number of amino groups, suggesting that more strongly cationic amines tend to be stronger antirecombinagens. Electrostatic association of the amines with DNA probably hinders BLM access to the 4′ position of deoxyribose where it generates a free radical. Other amines interact with BLM differently from these unbranched aliphatic amines. The aminothiol cysteamine inhibits the genotoxicity of BLM under hypoxic conditions but increases it under euoxic conditions. In contrast, pargyline potentiates the genotoxicity of BLM under hypoxic conditions but not under euoxic conditions. The antirecombinagenic effect of cysteamine apparently involves DNA binding and depletion of oxygen needed for BLM activity, whereas its potentiation of BLM entails its serving as an electron source for the activation of BLM. Pargyline may enhance BLM indirectly by preventing the depletion of oxygen by monoamine and polyamine oxidase. The planar 9-aminoacridine weakly induces gene conversion in strain D7, but it is strongly synergistic with BLM. Enhancement of BLM activity by this compound and by the related nitroacridine Entozon is apparently mediated by intercalation of the acridine ring system into DNA. Thus, the influence of amines on the genotoxicity of BLM in yeast encompasses antigenotoxic, potentiating, and synergistic interactions. The underlying mechanisms involve noncovalent association with DNA, altered BLM access to DNA, and modulation of physiological conditions.

Detection of mutagens in water-distribution systems after disinfection

This research examined the quality of water—before and after distribution—of four drinking-water production plants located in Northern Italy, two of which collected water from local aquifers and two from the River Po. A battery of genotoxicity assays for monitoring drinking-water was performed to assess the quality of the water produced by the treatment plants under study. Three different sampling stations were selected at each plant, one right at the outlet of the treatment plant and two along with the distribution pipelines. Raw river water was also sampled and analysed as a control. The water samples (500 l) were concentrated on silica C 18 cartridges and the extracts were tested in in vitro mutagenicity assays ( Salmonella/microsome assay with strains TA 98 and TA 100; SOS Chromotest with Escherichia coli strain PQ37); gene conversion, point mutation and mitochondrial DNA mutability assays with the diploid Saccharomyces cerevisiae strain D7 and a toxicity test using the bioluminescent bacterium Vibrio fischeri (Microtox ™). The Microtox ™ test and the mitochondrial DNA mutability assay showed the greatest sensitivity towards toxic or mutagenic substances in the water extracts considered. The results show that this battery of short-term tests is applicable in the routine monitoring of drinking-water quality before and after distribution.

Sodium hypochlorite-, chlorine dioxide- and peracetic acid-induced genotoxicity detected by the Comet assay and Saccharomyces cerevisiae D7 tests.

Mutagenicity of drinking water is due not only to industrial, agricultural and urban pollution but also to chlorine disinfection by-products. Furthermore, residual disinfection is used to provide a partial safeguard against low level contamination and bacterial re-growth within the distribution system. The aims of this study were to further evaluate the genotoxic potential of the world wide used disinfectants sodium hypochlorite and chlorine dioxide in human leukocytes by the Comet assay and in Saccharomyces cerevisiae strain D7 (mitotic gene conversion, point mutation and mitochondrial DNA mutability, with and without endogenous metabolic activation) and to compare their effects with those of peracetic acid, proposed as an alternative disinfectant. All three disinfectants are weakly genotoxic in human leukocytes (lowest effective dose 0.2 p.p.m. for chlorine dioxide, 0.5 p.p.m. for sodium hypochlorite and peracetic acid). The results in S.cerevisiae show a genotoxic response on the end-points considered with an effect only at doses higher (5- to 10-fold) than the concentration normally used for water disinfection; sodium hypochlorite and peracetic acid are able to induce genotoxic effects without endogenous metabolic activation (in stationary phase cells) whereas chlorine dioxide is effective in growing cells. The Comet assay was more sensitive than the yeast tests, with effective doses in the range normally used for water disinfection processes. The biological effectiveness of the three disinfectants on S.cerevisiae proved to be strictly dependent on cell-specific physiological/biochemical conditions. All the compounds appear to act on the DNA and peracetic acid shows effectiveness similar to sodium hypochlorite and chlorine dioxide.

Cytotoxic and genotoxic effects of megazol, an anti-Chagas’ disease drug, assessed by different short-term tests

Cyto- and genotoxicity induced by drugs can limit the dose and duration of treatment, can adversely affect patient quality of life, and may be life-threatening. Two drugs are currently being used for treatment of the acute phase of Chagas’ disease and both have serious undesirable effects. In this research, cyto- and genotoxic activity of the nitroimidazole-tiadiazole derivative CL 64855 2-amino-5-(1-methyl-5-nitro-2-imidazolyl)-1,3,4-thiadiazole (megazol), a promising alternative drug, was evaluated in vitro with different short-term tests: (a) induction of recombination events and mutation in the yeast Saccharomyces cerevisiae D7 strain, with and without induction of cytochrome P-450; DNA damage (single and double strand breaks, alkali-labile sites, etc.) by the Comet assay in different mammalian cells. S. cerevisiae did not show a significant increase of mutant and recombinant event frequency, both with and without cytochrome P-450. On the other hand, the cytochrome complex appeared to detoxify the drug with respect to cytotoxicity. Results in rat and mouse fresh leukocytes showed a dose–response relation of drug-induced DNA damage. Findings in treated VERO cells suggested a complex treatment time–DNA damage relationship and the possible induction of repair mechanisms. Furthermore, bleomycin effects were increased in rat cells by simultaneous administration of megazol. Megazol shows different biological activity in relation to cellular types and experimental conditions (with or without cytochrome P-450, short/long time of exposure, with or without other genotoxins), thus suggesting a modulation of effectiveness by different physiological/biochemical conditions of cells. The findings could be useful to evaluate new megazol-derived compounds and to assess the risks/benefits relationship for each drug.

Urban airborne particulate: genotoxicity evaluation of different size fractions by mutagenesis tests on microorganisms and comet assay

The genotoxic effects of different size fractions of airborne particulate (Total, PM 10 and PM 2.5), extracted with acetone or toluene, were evaluated by: the Ames plate test (TA98 and TA100 strains, w/o S9), gene conversion and reversion (w/o endogenous metabolic activation) in the Saccharomyces cerevisiae D7 strain, and the comet assay on human leukocytes. The data on human leukocytes confirm the sensitivity of the comet assay and its applicability to assess genotoxicity in environmental samples. The PM 2.5 fraction of airborne particulate generally shows the highest concentration of DNA-damaging compounds. Genotoxic response, in all the test systems applied, is highly dependent on extraction solvent used. Acetone seems to extract compounds with more similar genotoxic responses in the three test systems used than toluene extracts. Toluene appears to extract air pollutants genotoxic on yeast and leukocytes but is mainly cytotoxic on Salmonella.

Biological Activity of Four Thiophene Compounds in Resting Saccharomyces cerevisiae Cells

Biological activity (mortality and genotoxicity) of four thiophene compounds [a-terthienyl (a-T); 5-(4-hydroxy-1-butinyl)-2,2'-bithienyl (BBTOH); 5-(3-buten-1-ynyl)-2,2'-bithienyl (BBT); 5-(4-acetoxy-1-butinyl)-2,2'-bithienyl (BBTOAc)] was evaluated on Saccharomyces cerevisiae D7 strain cells. An high percentage of mortality was found with BBTOAc at all concentrations tested. A significant effect was also detected with a-T but only at the highest concentration. BBTOH stimulated colonies growth only at the lowest concentration, while BBT showed no effects. None of the tested compounds presented genotoxic activity.

Two mechanisms of antimutagenicity of the aminothiols cysteamine and WR-1065 in Saccharomycescerevisiae

The aminothiols cysteamine (CSM) and 2-[(aminopropyl)amino] ethanethiol (WR-1065) are radioprotectors, in that they reduce the mutagenic and potentially lethal consequences of ionizing radiation. We have studied the effects of these compounds on the induction of gene conversion at the trp5 locus in Saccharomyces cerevisiae strain D7 by two chemical mutagens: bleomycin (BLM) and β-propiolactone ( β-PL). Both mutagens are potent recombinagens in this assay, giving rise to trp5 convertant frequencies greater than 10 −3. CSM and WR-1065 are effective antimutagens, reducing the recombinagenic effect of β-PL by about 95%. The maximum reduction in the recombinagenic activity of BLM was 91% with CSM and 89% with WR-1065. Although the antimutagenic effects of the aminothiols against β-PL and BLM appear to be similar, they stem from different underlying mechanisms. Aminothiols protect against the recombinagenicity of β-PL through direct inactivation of the electrophilic mutagen by the nucleophilic antimutagen. They protect against that of BLM through modification of physiological conditions, most notably by depletion of oxygen required for BLM activity.

Occupational genotoxicity assessment by mutagenicity assays

Mutagenic activity measured by Ames test and by gene conversion, point mutation and mitochondrial mutability in Saccharomyces cerevisiae D7 strain was determined in the indoor environment of a glass factory. The results suggest that the increase in mutagenicity of air sample collected near the machinery is due to the thermal decomposition of oils. Modified assays were therefore compared for their ability to detect mutagens contained in urinary concentrates of exposed workers. The bacterial tests were performed by microsuspension assay in TA98, TA100 strains and in YG1024, YG1029 strains which overproduce O-acetyltransferase. Significant differences are evidenced both in the eukaryotic and prokaryotic systems.

Mutagenic activity of phosmet, the active component of the organophosphorus insecticide Decemtione EK 20 in Salmonella and Saccharomyces assays

Phosmet, the active component of the organophosphorus insecticide Decemtione EK 20, was shown to be mutagenic in the standard Ames Salmonella/mammalian microsome assay in the absence and presence of metabolic activation. It appears to be a direct mutagen inducing base substitution mutations (TA100) as well as a weak frameshift mutagen (TA97). This compound was genotoxic in the Saccharomyces cerevisiae D7 strain. It significantly increase reverse mutation, mitotic crossing-over and slightly, but not significantly, increased gene conversion at the highest concentration used.

Urban air pollution: Use of different mutagenicity assays to evaluate environmental genetic hazard

The genotoxic activities associated with airborne particulate matter collected in Parma (northern Italy) have been determined. The airborne particle extracts were tested for mutagenicity using Salmonella frameshift (TA98) and base-substitution (TA100) tester strains with and without S9 microsomal activation and Saccharomyces cerevisiae strain D7 in order to determine the frequency of mitotic gene conversion and i[v]-92 mutant reversion in cells harvested at stationary and logarithmic growth phase. The relationship between mitochondrial DNA mutations and ageing, degenerative diseases and cancer prompted us to take into account the mitochondrial informational target, i.e., the respiratory-deficient (RD) mutants. The results obtained show a variability in the response for the different test systems during different months. The Salmonella mutagenicity trend was directly correlated with carbon monoxide, nitrogen oxides (NO x ) and Pb concentration in airborne particulates and inversely correlated with temperature, whereas the mitochondrial genotoxic effect was higher during spring and late summer. These data suggest that the genotoxic risk assessment is a time-dependent value strictly correlated with the evaluation system being tested.

Evaluation of genotoxicity of tert.-butylhydroquinone in an hepatocyte-mediated assay with V79 Chinese hamster lung cells and in strain D7 of Saccharomyces cerevisiae

tert.-Butylhydroquinone (TBHQ) has been reported to be genotoxic in some short-term assays but non-genotoxic in others. We have examined cytotoxicity and genotoxicity of TBHQ, a principal metabolite of the phenolic antioxidant 2(3)- tert.-butyl-4-hydroxyanisole (BHA), in an hepatocyte-mediated assay with V79 Chinese hamster lung cells including both sister-chromatid exchange (SCE) and thioguanine-resistance (TG R) endpoints. The ability of BHA and of TBHQ to elicit a genotoxic response in Saccharomyces cerevisiae strain D7 was also investigated. In V79 cytotoxicity tests, TBHQ without hepatocytes produced a 50% reduction in colony formation at 4.2 μg/ml and was lethal to 100% of the cells at concentrations above 5 μg/ml. At partially cytotoxic dose levels, (0.17–3.4 μg/ml of medium), TBHQ sometimes increased significantly the frequency of SCE. TBHQ also produced sporadic statistically significant increases in the mutation frequency at the HGPRTase (TG R) gene locus when tested alone or with activation by rat or hamster hepatocytes. Mitotic gene conversion and reverse mutation were not induced in strain D7 of Saccharomyces cerevisiae by exposure to BHA or to TBHQ for 4 h at concentrations as high as 200 μg/ml for BHA or 500 μg/ml for TBHQ, either alone or with activation by rat-liver S9. Incubation of the yeast cells with BHA or TBHQ for 24 h in growth medium without activation also did not induce genotoxic activity. The slight and sporadic response to TBHQ in the V79 test system may indicate weak genotoxicity which is sensitive to slight differences in test conditions. The classification and test strategies adopted for compounds such as TBHQ could have important implications for regulatory decisions and for the validation of short-term tests.

Genotoxic potential of waste waters from a leather industry

The genotoxic potential of tannery waste water was evaluated by means of the induction of gene conversion and point mutation in Saccharomyces cerevisiae D7 strain. Neither a toxic nor a genotoxic response was obtained after a 2 hr incubation of raw water samples with the strain. A dose-related increase in the induced gene conversion and mitotic reversion was obtained when dilutions of the raw effluent were incubated for 24 hr. Samples of the waste water were also passed through an XAD2 resin column. The column was sequentially eluted with ethyl ether, chloroform and methanol. The ether and methanol fractions showed a positive genotoxic response.

Certain tryptophan photoproducts are inhibitors of cytochrome P450-dependent mutagenicity.

Two photoproducts, derived from UV-irradiation of the amino acid L-tryptophan and with high Ah (TCDD) receptor binding affinity, were tested for genotoxic and antimutagenic effects. The two indolo[3,2-b]carbazole derivatives, with the molecular weights of 284 and 312, respectively, were tested in Saccharomyces cerevisiae strain D7 for mitotic gene conversion and reverse mutation and in strain RS112 for sister chromatid conversion and gene conversion. No significant (P > 0.05) genotoxic effects were found in strain D7, while strain RS112 showed a small but significant increase in the frequency of sister chromatid conversions. In Chinese hamster ovary (CHO) cells the two compounds induced a statistically significant but less than twofold increase in the frequency of sister chromatid exchanges (SCE). No mutations were detected when the compounds were tested in Salmonella typhimurium strains TA98 and TA100. However, both 284 and 312 acted as antimutagens on strain TA100 + S9 in the presence of benzo(a)pyrene. The decrease in mutagenicity by the most potent compound 284 was 20 revertants/nmol. This effect could be explained by an inhibitory effect on the cytochrome P450-dependent ethoxyresorufin O-deethylase (EROD) activity as seen in rat hepatocytes. The two compounds were also tested with hamster cells expressing rat cytochrome P-450IA1. The results support the conclusion that this cytochrome P-450 isozyme is inhibited by the tryptophan photoproducts. Similar results were also seen with two other high affinity Ah receptor ligands the quinazolinocarboline alkaloids rutaecarpine and dehydrorutaecarpine.

Polluted water concentrates: Induction of genetic alterations inSaccharomyces cerevisiae D7 strain

In a previous paper the authors showed that samples of raw water obtained from the Riachuelo (a heavily polluted watercourse) induced genetic effects in Saccharomyces cerevisiae D7 strain. In those tests the raw water samples were assayed within 24 hr and only the mutagenic activity of the non-volatile, water soluble constituents could be detected. The detection and quantitation of genetic toxicity in the organic water-insoluble fraction becomes much more difficult. This organic material consists of thousands of unidentified compounds in dilute mixtures which are not amenable to current analytical technology. Consequently, concentration of organic compounds is required before performance of biological tests. The development of analytical methods involving XAD resins for the isolation and identification of pesticides and other compounds led to the use of XAD resins in the concentration of organics in water. In the experiments reported here the genotoxic potential of XAD2 concentrates, obtained from samples of a heavily polluted stream, were evaluated by the induction of gene conversion and point mutation in Saccharomyces cerevisiae D7 strain.