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U Rannug

Publications and source records attributed to U Rannug.

At least 37 records · Page 2Linked to original sources
PubMed1994

Chemically induced changes in the spectrum of amplifications of the human minisatellite MS1 integrated in chromosome III of a haploid yeast strain.

To study chemically induced DNA amplifications we used the haploid Saccharomyces cerevisiae strain TR(MS1)-1 carrying an integrated chromosomal copy of the human minisatellite. MS1. Chemicals with different mechanisms of action were tested in this strain: methyl methanesulphonate, ethylene oxide (EO), propylene oxide (PO), camptothecin, 2,3,7,8-tetrachlorodibenso-p-dioxin (TCDD) and reserpine. No increase in frequency of new MS1 length alleles was seen with any of the tested chemicals relative to the spontaneous frequency of approximately 30%. EO and TCDD induced changes in the amplification spectrum, i.e., the frequency distribution of MS1 length alleles longer than the original 1.42 kb allele. PO and camptothecin increased the frequency of plasmid "pop-out" events. It seems likely that several mechanisms e.g. unequal exchanges, replication slippage and loop formation leading to deletion of a ring of tandem repeats, are involved in the generation of new MS1 length alleles. A loop-forming deletion mechanism is supported by the tendency to multimodality shown in the deamplification (loss of repeat units) spectra, i.e. the frequency distribution of new MS1 length alleles shorter than the original allele. EO and TCDD induced "longer" MS1 length alleles as compared to the control. The frequent generation of new MS1 length alleles in this haploid yeast strain further demonstrates the instability of such sequences and their possible relevance to genetic toxicology and the mechanisms of induction of cancer as well as other diseases. This study is a first step towards the development of an assay for DNA amplification without the use of a selective agent.

Alleles↗
PubMed1994

Mutagenicity of tryptophan photoproducts in the Ames Salmonella assay.

During the photolysis of tryptophan a large number of products is formed. In this study, aqueous solutions of tryptophan were irradiated by ultraviolet light during 5, 20 or 40 h. Each of the irradiated batches was divided into two aliquots, which were freeze-dried or extracted with chloroform. For each batch the latter extract was subsequently divided into a purified chloroform extract and a methanol extract. Aliquots of the purified chloroform extracts were fractionated and pooled, peakwise, into seven fractions. A recombined sample was also constructed. All extracts and samples were tested for mutagenicity using the standard Ames Salmonella assay. The results indicate an exposure time dependent increase in mutagenicity of the extracts, as seen with tester strain TA100 both with and without metabolic activation. The mutagenicity of the freeze-dried extracts well approximated the mutagenicity of the chloroform extracts, indicating that most mutagenicity can be extracted with chloroform. With the fractions the highest mutagenic responses were seen in the late, i.e., less lipophilic fractions. This response pattern seen in TA98 and TA100, mainly with S9 activation, was in contrast to the response of TA102 without S9, which was highest to the more lipophilic fractions. On a fraction level, no general exposure dependent increase of mutagenicity was observed. The results also show that photooxidation of tryptophan gives rise to a different spectrum of products compared to pyrolysis. Both processes result in compounds with strong biological effects. Photooxidation results in compounds with low genotoxicity and high Ah receptor affinity while pyrolysis generates compounds with high genotoxicity and low or no Ah receptor affinity.

Biotransformation↗
PubMed1994

Chemical analysis and biological testing of a polar fraction of ambient air, diesel engine, and gasoline engine particulate extracts.

Extracts of gasoline and diesel vehicle exhaust and ambient air particles were fractionated into five fractions according to polarity on a silica gel column. Two medium polar fractions showing high genotoxic activity in the Ames test were further subfractionated, using normal-phase high-performance liquid chromatography. Chemical analyses were performed by means of gas chromatography combined with mass spectrometry and flame ionization and detection. The crude extracts, fractions, and subfractions were assayed with the Ames test, with and without S9, and the most abundant compounds in the subfractions are reported.

Air Pollutants↗
PubMed1993

Amplification and loss of repeat units of the human minisatellite MS1 integrated in chromosome III of a haploid yeast strain.

Minisatellites comprise arrays of tandemly repeated short DNA sequences which show extensive variation in repeat unit number. The mechanisms that underlie this length variation are not understood. In order to study processes influencing length changes of minisatellites, we integrated the human minisatellite MS1 into a haploid strain of the yeast Saccharomyces cerevisiae. Frequent spontaneous generation of MS1 alleles with new lengths were observed in this yeast strain. Hence it is concluded that recombination between members of a pair of homologous chromosomes is not a prerequisite for the generation of length changes in MS1 in yeast.

Base Sequence↗
PubMed1992

Detection of DNA alterations in human bladder tumors by DNA fingerprint analyses.

DNA fingerprint analyses were used to examine the constitutional and tumor DNA from 22 bladder tumor patients. DNA alterations, such as loss of bands, new bands, and intensity shifts were observed in 10 of the 22 patients. The most frequent DNA alteration, occurring in 80% of the patients, was a complete loss of one or several bands. Fingerprint abnormalities were present both in low-malignant superficial tumors and in high-malignant invasive tumors, but were also lacking in the latter group. Apparently no relationship exists between fingerprint abnormalities and gross chromosomal aberrations or the proportion of S-phase cells as measured by flow cytometry or development of recurrent tumors during a limited observation period. Thus, whether fingerprint aberrations express genetic alterations directly involved in the malignancy potential of bladder carcinoma remains an open question.

Adult↗
PubMed1992

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.

Alkaloids↗
PubMed1992

On the bioactivation and genotoxic action of fluoranthene.

Fluoranthene (FA) was studied with respect to possible mechanisms of its high mutagenicity but low carcinogenicity, in comparison with the corresponding properties of benzo[a]pyrene (BaP), and with regard to the synergism of these two compounds shown by van Duuren and Goldschmidt (J Natl Cancer Inst 56, 1976, 1237). FA and BaP activated by S9 from Aroclor 1254 (PCB)-treated rats induce HPRT mutations in CHO cells with about equal effectiveness at the same exposure doses, which also lead to the same frequencies of repairable DNA adducts, enzyme-induced strand breaks being used as an indirect measure of adducts to DNA. FA was also shown to be an efficient inducer of SCE in human peripheral lymphocytes cocultivated with PCB-treated HepG2 cells or with liver cells from PCB-pretreated rats. For the induction of SCE, FA and BaP were shown to act additively. From metabolic studies with liver microsomes from C57Bl/6 mice it is concluded that, whereas BaP induces the metabolism of BaP to the mutagenic epoxide, neither BaP nor FA is able to induce the metabolism of FA. In mutation experiments with V79 cells (XEM2) constitutive for P450 IA1 activity, BaP 7,8-diol but not FA 2,3-diol provokes a high frequency of HPRT mutations. In cells constitutive for P450 IA2 enzymatic activity FA and BaP are but weakly mutagenic and practically nonmutagenic, respectively. Due to the additivity of the genotoxic effects of FA and BaP, induction of an error-prone condition by the latter compound seems to be excluded.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

The presence of genotoxic and bioactive components in indigo dyed fabrics--a possible health risk?

Extracts of pure cotton and jeans fabrics were tested for mutagenicity in Salmonella typhimurium strains TA98 and TA100. The vat dye indigo, technical grade as well as 98% and greater than 99.5% pure, was also tested for mutagenicity. Synthetic indigo, indirubin and isatin were tested for TCDD receptor affinity in competition experiments in vitro. The mutagenicity of the extracts was associated with the cotton denim and nondyed cotton gave only marginal effects. The mutagenicity of the indigo dyed fabrics was dependent on type and treatment of the fabrics. Extracts of both bleached and nonbleached jeans gave mutagenic effects on TA98 +/- S9 and TA100 +/- S9. The greatest effects were seen in the presence of S9. Bleaching gave an additional increase in the mutagenicity in the absence of S9. Normal washing of the fabrics after bleaching reduced the mutagenicity. Synthetic indigo of technical grade or 98% pure showed mutagenic effects, especially on TA98 + S9. Further purification to 99.5% reduced the mutagenicity to 24 revertants/mg (6.2 rev/mu mole). Considering the amount of indigo in the extracts and its low mutagenicity, the genotoxicity of jeans extracts must be caused by other unknown components. However, indigo showed a high (Kd = 1.9 nM) affinity for the Ah or TCDD receptor. Indigo can therefore still be a potential health risk either by eliciting toxic effects of other compounds or by being a nongenotoxic carcinogen. The worldwide use of jeans with a possible exposure of a large population to genotoxic and biologically active components emphasizes the need for a more thorough characterization of these effects.

Animals↗
PubMed1991

Use of artificial intelligence in structure-affinity correlations of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) receptor ligands.

The Computer-Automated Structure Evaluation (CASE) Program, an expert system that automatically selects relevant descriptors for structure-activity relationships, has been used to analyze the binding of various ligands to the tetrachloro-dibenzo-p-dioxin (TCDD) receptor or Ah receptor. Two databases were analyzed. One database contained 136 polycyclic aromatic hydrocarbons (PAH), substituted dibenzo-p-dioxins, dibenzofurans and biphenyls whose binding affinities were measured by a sucrose density gradient technique. The other 87 compound database contained PAH, nitro-PAH, halo-PAH and N-heterocycles. Their binding affinities were measured by the electrofocusing assay. Within each training set significant correlations between the affinity for the TCDD receptor and relevant molecular fragments identified by the CASE program were observed. Among the halogenated aromatic hydrocarbons, fragments containing lateral halogens and a longitudinal hydrogen appeared important for TCDD receptor binding. The fragments of PAH and heterocyclic compounds that were most activating with respect to TCDD receptor binding were found to contain the classical 'bay' region and were in fact identical to the fragments found previously to be related to carcinogenicity. It was found that the activating fragments from PAH and heterocyclic compounds were different from those found within the halogenated compounds such as dibenzo-p-dioxins, dibenzofurans and biphenyls. One interpretation of the data is that two different recognition sites may be involved in Ah receptor binding.

Artificial Intelligence↗
PubMed1990

3,3',4,4'-tetrachlorobiphenyl: metabolism by the chick embryo in ovo and toxicity of hydroxylated metabolites.

The metabolism of 3,3',4,4'-tetrachlorobiphenyl (TCB) has been studied in the chicken in ovo by analysis of bile from chick embryos. Four percent of the [14C]TCB dose injected into the air sac on day 13 of incubation was detected in the bile by day 19. An increase of more lipophilic TCB metabolites was observed by HPLC analysis after hydrolysis of the bile. TCB and three phenolic TCB metabolites were identified and quantified in the hydrolyzed bile: TCB (14 ng/gall bladder), 5-hydroxy-3,3',4,4'-tetrachlorobiphenyl (234 ng/gall bladder), 4-hydroxy-3,3',4',5-tetrachlorobiphenyl (45 ng/gall bladder) and 2-hydroxy-3,3',4,4'-tetrachlorobiphenyl (3 ng/gall bladder). The presence of two other TCB metabolites in the bile, a dihydroxy-tetrachlorobiphenyl and a dihydroxy-trichlorobiphenyl was also indicated. The method used in the present study is well suited for studies of metabolism in avian embryos in ovo. The three TCB metabolites identified all proved to be at least two orders of magnitude less toxic than TCB in a chick embryo test. These metabolites were also shown to bind with significantly lower affinity than TCB to the Ah receptor. TCB, 5-hydroxy-3,3',4,4'-tetrachlorobiphenyl, 4-hydroxy-3,3',4',5-tetrachlorobiphenyl and 2-hydroxy-3,3',4,4'-tetrachlorobiphenyl gave Kd values of 16, 33, 45 and 37 nM, respectively, in the Ah receptor test.

Animals↗
PubMed1987

Certain photooxidized derivatives of tryptophan bind with very high affinity to the Ah receptor and are likely to be endogenous signal substances.

The purpose of the present study was to determine whether ultraviolet light (UV) irradiation of amino acids produces compounds with affinity for the Ah receptor. Aqueous solutions of L-tryptophan were exposed to radiation from an unfiltered high-pressure mercury lamp. The photoproducts formed were solvent-extracted or concentrated on Sep-Pak C18 cartridges. The concentrated extracts or eluants were treated for their ability to compete with 3H-labeled 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Binding was assayed in liver cytosolic preparations from Sprague-Dawley rats using a technique based on hydroxylapatite separation. Photoproducts with receptor affinity were formed in a time-dependent manner. Histidine and tryptamine also gave products upon UV irradiation that competed with TCDD. Commercial tryptophan, at least aged, contained trace amounts of impurities with receptor affinity. Analysis by TLC and high-pressure liquid chromatography of the photo-products of tryptophan showed a minimum of three different binding compounds. Two of the products were studied in greater detail. One of them, showing UV absorbance and yellow fluorescence, gave a molecular ion (M+) of 284 and the other gave M+ 312 but showed little UV absorption and fluorescence. The concentration, based on mass spectrometry quantifications, of the two compounds that displaced more than 50% of TCDD was found to be extremely low, giving Kd values of 0.44 nM (M+ 312) and 0.07 nM (M+ 284). The existence of high affinity receptors for oxidized amino acids is postulated and their possible role in the proliferative cellular responses to TCDD and tryptophan is discussed briefly.

Amino Acids↗
PubMed1984

Enzyme inhibition as a possible mechanism of the mutagenicity of dithiocarbamic acid derivatives in Salmonella typhimurium.

In recent years data have accumulated regarding genotoxic properties of dithiocarbamic acid derivatives. The results from the present work indicate that the mutagenicity of these compounds depends on an indirect effect via oxygen radicals. Mutagenicity of tetramethylthiuram disulfide ( TMTD ), that was used as a model substance, was established with both frameshift and base substitution sensitive strains of Salmonella typhimurium. Addition of copper ions resulted in a decreased survival at low dithiocarbamate doses. The dose response curves seem to correlate with the formation of two types of metal dithiocarbamate complexes. At low doses charged complexes are formed, while the formation of uncharged complexes is favoured at higher dosages. The data suggest that this formation of uncharged metal complexes implies a decreased toxicity but at the same time an increased mutagenicity. The mutagenicity of both TMTD and its ethyl analogue TETD was enhanced by oxygen. Furthermore, TMTD potentiates the mutagenic action of menadione, a substance that produces O(2) and H2O2 by redox cycling with molecular oxygen. Interaction of uncharged metal dithiocarbamate complexes with both production and detoxification of reactive forms of oxygen is suggested to be responsible for the direct mutagenic effects via oxidative damage to DNA. A further enhancement of the oxygen radical content of the cells by adding microsomes that produce oxygen radicals via autoxidation of cytochrome P-450 is proposed as the mechanism for the 'metabolic activation of TMTD '.

Animals↗
PubMed1984

Some chloro derivatives of polynuclear aromatic hydrocarbons are potent mutagens in Salmonella typhimurium.

A series of chlorinations of some polynuclear aromatic hydrocarbons (PAH) were carried out and the products were tested for mutagenicity on Salmonella typhimurium TA98 and TA100. We conclude that the chlorination of certain PAHs with low mutagenicity, such as pyrene and benzo[e]pyrene, resulted in the formation of two types of product. The chlorination of pyrene was studied in some detail. The major products of this chlorination were chloro-substituted pyrenes. These compounds showed an S9-dependent mutagenicity and were identified as 1-chloro-, 1,6-dichloro-, 1,8-dichloro- and 1,3-dichloropyrene. On tester strain TA100 the mutagenic effect ranged from 1.4 to 14 revertants/nmol, 1,3-dichloropyrene being the most potent of the isomers. Minor products eluting from a chromatograph in a more polar fraction than the major products were also formed. These compounds were less stable than the major products and were identified as pyrene with chloro additions in the 4- and 5-positions, with various chloro substituents at other positions. These minor products showed a high mutagenic effect on Salmonella in the absence of S9. The mutagenic effect on strain TA100 ranged from 10 to 15 revertants per ng which is at least 40 and 4000 times higher than for 1-nitropyrene and pyrenequinones, respectively. These unstable chloro derivatives of pyrene are difficult to analyse chemically because they are easily degraded and give rise to the more stable 4-chloropyrene.

Mass Spectrometry↗
PubMed1983

Mutagenicity of methyl nitrite in Salmonella typhimurium.

Methyl nitrite was tested for mutagenicity in Salmonella typhimurium TA1535. In the first set of experiments, plated bacteria were exposed to methyl nitrite in desiccators both in the absence and presence of a metabolizing system (S9 from Aroclor-pretreated Sprague-Dawley rats). Initial concentrations from 125 to 500 ppm were tested. In all experiments an increased initial concentration gave an increased mutagenic response. The mutagenic effect in the presence of S9 was similar to that in the absence of S9. Owing to difficulties in dose determinations in this type of experiment it could not be decided, unequivocally, whether the mutagenic effect was caused by methyl nitrite or its hydrolysis products. Experiments were therefore carried out in suspension, and the concentrations of methyl nitrite and inorganic nitrite were determined. Treatments with inorganic nitrite were also carried out under similar conditions. From the results of these experiments we concluded that methyl nitrite is mutagenic. Possible mechanisms of action of methyl nitrite are discussed, and it is suggested that mutagenicity may be a general property of alkyl nitrites.

Animals↗
PubMed1983

Data from short-term tests on motor vehicle exhausts.

The mutagenicity of motor vehicle exhausts has been studied by using Salmonella typhimurium strains TA 98 and TA 100. Acetone extracts of the particulate phase and the gas phase have been tested in the presence and absence of a metabolizing system (S9). The particulate phases from medium- and heavy-duty diesel vehicles were tested. The vehicles were driven according to a modified 13 mode test, and the particulate phase was sampled at mode 6 (maximum load and intermediate engine speed) and mode 12 (10% load and rated speed). In mode 6 all vehicles gave approximately the same mutagenicity in strain TA 98 (50,000-90,000 revertants/kW-hr) as well as in TA 100 (200,000-360,000 revertants/kW-hr). A higher mutagenic effect, in some cases up to 10 times, was seen with mode 12.Light-duty vehicles of different year models were tested using different fuel/engine combinations. The vehicles were driven according to FTP 72 or ECE driving cycle. Cold starts at two different temperature levels, approx. 0 degrees C and 23 degrees C, respectively, were also compared. Based on the mutagenicity of the particulate extracts (given as revertants per km), the light-duty vehicles could be divided into three main groups. The first group, the high mutagenicity group, giving 100,000-700,000 revertants/km, consists only of diesel cars. In the medium mutagenicity group, giving between 20,000 and 100,000 revertants/km, different gasoline fuels are placed, i.e., leaded and lead-free gasoline as well as alcohol/gasoline fuels. Two other fuels, methanol (M95) and propane (LPG), constitute the low mutagenicity group, giving less than 20,000 revertants/km. Fuels from the medium effect group will produce a particulate phase with low mutagenicity if the vehicle is equipped with a three way catalyst with closed loop, or fuel injection. The cold start temperature did not change this classification, since all samples gave a somewhat higher mutagenic effect at the low temperature. With the ECE driving cycle, much lower mutagenicity was noted with the diesel cars than in the tests with the FTP-72 driving cycle, at least with tester strain TA 98. On strain TA 100 the diesel exhaust samples still showed a much higher mutagenicity than other samples. Acetone extracts of the gas phase from diesel and gasoline exhaust (trapped in ice/water condensers and CO(2)/ethanol condensers) also gave mutagenic effects. The contribution of the gas phase to the mutagenic effects seems to be more important in the absence of S9 and more important in the case of gasoline exhausts.

Air Pollutants↗
PubMed1982

Formation of mutagenic metabolites from benzo(a)pyrene and 2-aminoanthracene by the s-9 fraction from the liver of the Northern pike (Esox lucius): inducibility with 3-methylcholanthrene and correlation with benzo[a]pyrene monooxygenase activity.

The mutagenicity of benzo[a]pyrene and 2-aminoanthracene in the Ames test using the S-9 fraction from the liver of the Northern pike (Esox lucius) was tested. S-9 fractions were prepared both from fish injected intraperitoneally with 3-methylcholanthrene and from control animals. In addition benzo[a]pyrene monooxygenase activity was assayed in the same S-9 fractions used in the Ames test. S-9 fractions from the liver of the Northern pike were found to convert benzo[a]pyrene and 2-aminoanthracene to mutagenic metabolites. The number of revertants obtained was increased 2--4-fold in the case of 2-aminoanthracene and 3--14-fold in the case of benzo[a]pyrene by pretreatment of the pike with a single intraperitoneal injection of 3-methylcholanthrene. This injection also caused a 2--6-fold increase in the benzo[a]pyrene monooxygenase activity of the S-9 fractions used. These increases in mutagenicity and activity of the S-9 fractions used. these increases in mutagenicity and activity occur mainly during the first 4--12 days after the injection, but further small increases are observed for as long as 60 days. A strong positive correlation was found between the benzo[a]pyrene monooxygenase activity of the S-9 fractions used and their ability to give rise to revertants in the Ames test using 2-aminoanthracene or benzo[a]pyrene. This indicates that the major determining factor in the production of reactive metabolites which attack DNA in this in vitro system is the activity of the phase I cytochrome P-450 system.

Animals↗