Showing papers in "Mutation Research in 1987"
479 citations
276 citations
TL;DR: It is concluded that single doses of busulfan can permanently sterilize mice at nonlethal doses and cause long-term morphological damage to sperm produced by surviving stem spermatogonia.
Abstract: The alkylating agent busulfan (Myleran) adversely affects spermatogenesis in mammals. We treated male mice with single doses of busulfan in order to quantitate its cytotoxic action on spermatogonial cells for comparison with effects of other chemotherapeutic agents, to determine its long-term effects on fertility, and to assess its possible mutagenic action. Both stem cell and differentiating spermatogonia were killed and, at doses above 13 mg/kg, stem cell killing was more complete than that of differentiating spermatogonia. Azoospermia at 56 days after treatment, which is a result of stem cell killing, was achieved at doses of over 30 mg/kg; this dose is below the LD50 for animal survival, which was over 40 mg/kg. Busulfan is the only antineoplastic agent studied thus far that produces such extensive damage to stem, as opposed to differentiating, spermatogonia. The duration of sterility following busulfan treatment depended on the level of stem cell killing and varied according to quantitative predictions based on stem cell killing by other cytotoxic agents. The return of fertility after a sterile period did not occur unless testicular sperm count reached 15% of control levels. Dominant lethal mutations, measured for assessment of possible genetic damage, were not increased, suggesting that stem cells surviving treatment did not propagate a significant number of chromosomal aberrations. Sperm head abnormalities remained significantly increased at 44 weeks after busulfan treatment, however, the genetic implications of this observation are not clear. Thus, we conclude that single doses of busulfan can permanently sterilize mice at nonlethal doses and cause long-term morphological damage to sperm produced by surviving stem spermatogonia.
251 citations
TL;DR: Data is presented that some of the chemicals such as dimethyl sulfoxide, m-dioxan, 5-fluorouracil and paraquat, which have been reported to be non-mutagenic in Ames/Salmonella assay, were found to be active in inducing umu gene expression, while the known mutagenic compounds were non-genotoxic in the present assay system.
Abstract: The umu test system is a newly developed method to evaluate genotoxic activities of a wide variety of environmental carcinogens and mutagens (Oda et al., 1985). In the present study, we further examined the abilities of 151 chemicals to induce umu gene expression in Salmonella typhimurium TA1535/pSK1002. Among the chemicals examined, 72 compounds induced umu gene expression, which could be defined on a basis of increased beta-galactosidase activity by 2-fold over the background level. The potent genotoxic compounds without metabolic activation were adriamycin, bleomycin, daunorubicin, 1,3-dinitropyrene, 1,6-dinitropyrene, 1,8-dinitropyrene, N-ethyl-N'-nitro-N-nitrosoguanidine, furylfuramide, methyl methanesulfonate, N-methyl-N'-nitro-N-nitrosoguanidine, mitomycin C, 1-nitropyrene and 4-nitroquino-line-1-oxide. In the presence of S9, aflatoxin B1, 2-aminoanthracene, Glu-P-1, IQ, MeIQ, MeIQx, Trp-P-1 and Trp-P-2 also induced umu gene expression markedly. Several chemicals such as 2-acetylaminofluorene, 9-aminoacridine, azobenzene, benzanthracene, benzidine, diethyl nitrosamine, 1-nitronaphthalene, paraquat, potassium dichromate and sodium nitrite were weakly genotoxic and the induction by these compounds could be detected only when the incubation time was prolonged from 2 h to 5 h. Data are also presented that some of the chemicals such as dimethyl sulfoxide, m-dioxan, 5-fluorouracil and paraquat, which have been reported to be non-mutagenic in Ames/Salmonella assay, were found to be active in inducing umu gene expression, while the known mutagenic compounds including acrylonitrile, 4,4'-dinitrobiphenyl, furfural, methylene chloride, 1-naphthylamine, sodium azide, o-tolidine and o-toluidine were non-genotoxic in the present assay system.
233 citations
TL;DR: The V79-4 Chinese hamster line was mutagenized and surviving clones screened for X-ray sensitivity using a replica microwell technique, and 3 clearly sensitive clones were isolated from approximately 5000 screened, and designated irs 1 to irs 4.
Abstract: The V79-4 Chinese hamster line was mutagenized and surviving clones screened for X-ray sensitivity using a replica microwell technique. One slightly sensitive clone and 3 clearly sensitive clones were isolated from approximately 5000 screened, and designated irs 1 to irs 4. The 3 more sensitive clones showed different responses to the genotoxic agents mitomycin C (MMC), ethyl methanesulphonate (EMS) and ultraviolet light (UV). irs 1 showed considerable sensitivity to all the agents tested, in the order MMC much greater than EMS greater than UV. irs 2 and irs 3 had similar sensitivities to EMS and to UV (EMS greater than UV) but irs 3 was more sensitive than irs 2 to MMC. None of these mutants is identical in phenotype to previously published mutants.
210 citations
TL;DR: Results suggest that MX is formed during water chlorination as a result of reaction of chlorine with humic substances, and that a substantial fraction of the MX formed is likely to persist throughout the distribution system.
Abstract: 3-Chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX) was detected by gas chromatography/mass spectrometry in drinking water samples from 3 locations in the U.S.A., and also in a chlorinated humic acid solution. MX appears to account for a significant proportion of the mutagenicity of these samples, as measured in the Ames test using strain TA100 without metabolic activation. Studies on recovery of MX from spiked water samples by XAD-2/8 resin adsorption/acetone elution indicated that sample acidification prior to resin adsorption was essential to the effective recovery of MX. The stability of MX in aqueous solution was pH and temperature dependent. At 23 degrees C the order of stability, based on persistence of mutagenic activity was found to be: pH 2 greater than pH 4 greater than pH 8 greater than pH 6. The half-life at pH 8 and 23 degrees C was 4.6 days. One of the degradation products has been tentatively identified as 2-chloro-3-(dichloromethyl)-4-oxo-2-butenoic acid, an open form of MX which appears to be in the "E" configuration. Overall, these results suggest that MX is formed during water chlorination as a result of reaction of chlorine with humic substances, and that a substantial fraction of the MX formed is likely to persist throughout the distribution system.
170 citations
153 citations
TL;DR: The data on cell growth inhibition suggest that this is the result of increased incorporation of bromodeoxyuridine per cell due to decreased numbers of growing cells, although other mechanisms cannot be ruled out.
Abstract: Substantial increases in chromosome aberrations were induced in Chinese hamster ovary cells by medium made hyperosmotic with NaCl, KCl, sucrose, sorbitol or dimethyl methylphosphonate. The increases were associated with cytotoxicity but occurred in the range (e.g., 70% survival) commonly included in in vitro tests for 'genotoxicity'. The relation between increased osmotic pressure and chromosome aberrations is compound-dependent, e.g., some compounds may have a direct effect in addition to an effect mediated by osmotic pressure/ionic strength. Also, glycerol at high osmolality was not toxic and did not induce aberrations, probably because rapid equilibration across the cell membrane precluded severe osmotic stress to the cells. Weak increases in DNA single-strand breaks (NaCl and KCl) and double-strand breaks (NaCl) were also detectable, at higher concentrations and more toxic levels than those required to produce aberrations. Slight elevations in sister-chromatid exchange frequencies caused by hyperosmotic medium were found in the presence of toxicity and severe cell cycle delay. Our data on cell growth inhibition suggest that this is the result of increased incorporation of bromodeoxyuridine per cell due to decreased numbers of growing cells, although other mechanisms cannot be ruled out. The observations on chromosome aberrations demonstrate the need for keeping in vitro test conditions in the physiological range, and provide a means for investigation of indirect DNA damage.
138 citations
TL;DR: The cross-resistance study revealed that the 3H-adapted cells were resistant to SCE induction but not to the micronucleus inductions by the challenge doses of reactor radiations.
Abstract: When Chinese hamster V79 cells were internally exposed to low level chronic beta-rays from incorporated tritiated thymidine (3H-dThd), they showed an "adaptive" response to the induction of chromosomal damage by subsequent higher acute doses of gamma-rays. The yield of sister-chromatid exchanges (SCEs) in the 3H-dThd pretreated cells was less than the yield induced by gamma-rays alone (protective effects), and the micronucleus frequency was less than the sum of the induced frequencies by 3H-dThd and gamma-rays separately (below-additivity effects). No adaptation to the micronucleus induction by gamma-rays was observed after the 3H-adapted cells had divided once and when 3-aminobenzamide (3AB) was given before the challenge doses. The cross-resistance study revealed that the 3H-adapted cells were resistant to SCE induction but not to the micronucleus inductions by the challenge doses of reactor radiations. The results suggest that the SCE adaptation and the micronucleus adaptation or clastogenic adaptation are probably caused by different, inducible adaptive repair pathways.
128 citations
TL;DR: A typical procedure and guidelines for conducting the rat in vitro hepatocyte DNA-repair assay for assessing the genotoxic activity of chemical agents are provided.
Abstract: The in vitro rat-hepatocyte DNA-repair assay is a valuable tool in assessing the genotoxic activity of chemical agents. An advantage of the assay is that the target cells themselves are metabolically competent, so that the patterns of metabolic activation and detoxification closely reflect those in the whole animal. This article provides a typical procedure and guidelines for conducting the rat in vitro hepatocyte DNA-repair assay.
115 citations
TL;DR: The purpose is to provide a guide for people who perform or evaluate microbial mutagenesis tests, but it is not intended for these recommendations to replace or diminish the usefulness of presently available protocols and procedures.
Abstract: Since its development by Dr. Bruce Ames and his coworkers, the Salmonella typhimurium/mammalian microsome mutagenicity assay has been used widely throughout the world. Many authors have suggested various modifications and made recommendations in regards to this assay. Although the recommendations of a panel of experts was published in 1979 by de Serres and Shelby, a committee of members of the Environmental Mutagen Society (EMS) initiated this effort in response to the encouragement by the American Society of Testing and Materials (Committee E47.09.01) and because of new developments within the field of microbial mutagenesis testing. Its purpose is to provide a guide for people who perform or evaluate microbial mutagenesis tests, but it is not intended for these recommendations to replace or diminish the usefulness of presently available protocols and procedures.
TL;DR: The results suggest that cadmium can induce a prooxidant state in cultured mammalian cells and the mechanism by which Cadmium induces a pro oxidantState was investigated by measuring the effect of cad mium on those enzymes which constitute a cellular defense against active oxygen and on the level of the intracellular antioxidant, glutathione (GSH).
Abstract: The effects of scavengers of active oxygen species on cadmium chloride (CdCl 2 )-induced inhibition of cell growth and DNA synthesis and on the metal-induced clastogenesis were investigated to evaluate whether cadmium could induce a prooxidant state in cultured Chinese hamster V79 cells. Inhibition by CdCl 2 of cell growth and [ 3 H]thymidine incorporation into the acid-insoluble fraction of cells and the metal-induced clastogenesis were suppressed in part by the presence of the diffusible radical scavenger, butylated hydroxytoluene (BHT). The action of BHT was concentration-dependent and did not affect the intracellular level of cadmium. d -Mannitol, a hydroxyl radical scavenger, also significantly suppressed Cd-induced inhibition of cell growth and [ 3 H]thymidine incorporation. Catalase was marginally suppressive on Cd-induced inhibition of cell growth. These results suggest that cadmium can induce a prooxidant state in cultured mammalian cells. The mechanism by which cadmium induces a prooxidant state was investigated by measuring the effect of cadmium on those enzymes which constitute a cellular defense against active oxygen and on the level of the intracellular antioxidant, glutathione (GSH). 2-h treatments with CdCl 2 over a concentration range of 2–10 × 10 −5 M did not influence superoxide dismutase, catalase, GSH peroxidase or GSSG reductase. In contrast, the level of glutathione was decreased to approximately 40% by treatment with 2 × 10 −5 M cadmium. The decrease in glutathione level may be responsible for a role by active oxygen in Cd-induced inhibition of cell growth and DNA synthesis and the metal-induced clastogenesis.
TL;DR: In the present investigation, the SOS chromotest with E. coli PQ37 was evaluated and the potential to identify different kinds of bacterial mutagens was examined.
Abstract: In the present investigation, the SOS chromotest with E. coli PQ37 was evaluated. The potential to identify different kinds of bacterial mutagens was examined. 124 chemicals of different chemical classes were tested. Their responses in the SOS chromotests were compared to reported test results obtained with the Ames test.
TL;DR: The observed high frequency of mutagen-sensitive mutants in V79 cells, although unexpected and substantially higher than those published for CHO cells and L5178Y cells, can still be explained by the presence of functionally hemizygous loci.
Abstract: A replica-plating technique has been adopted for the isolation of mutagen-sensitive mutants of Chinese hamster V79 and CHO cell lines. After the mutagenic treatment (ENU) clones derived from these cell lines were replica plated into micro wells and replicas were treated with UV (254 nm), X-ray, MMC, EMC or MMS. Clonal cell lines which demonstrated mutagen sensitivity were retested by the determination of survival. Only one UV-sensitive line was obtained in 1500 clonal lines derived from CHO cells. This mutant appeared also sensitive to 4NQO and MMC. The sensitivity to UV and MMC was 2-3-fold enhanced, while the increase in sensitivity to 4NQO was 4-5-fold. In V79 cells 9 mutagen-sensitive lines were found after screening of 500 clonal lines; six of them showed increased sensitivity towards UV, two towards MMC, and one cell line was found to be X-ray sensitive. A considerable cross-sensitivity for the various agents was found among the isolated mutants. When a 2-fold increase is taken as a minimum to indicate mutagen sensitivity 6 mutants were sensitive to UV, 8 mutants were sensitive to MMC, 6 mutants were sensitive to 4NQO and 4 mutants were sensitive to X-rays. The difference in sensitivity to UV versus 4NQO makes it unlikely that 4NQO can be considered as a UV-mimetic agent. The sensitivity to MMC appears to fall into 2 classes: a class with moderate sensitivity (2-8-fold) and a class with high sensitivity (30-100-fold). The presence of similar classes is indicated for UV. Except for the two lines V-E5, V-B7 and the two lines V-H11, V-H4 all obtained mutants have a different spectrum of mutagen sensitivities which suggests that different genetic alterations underly these effects. The observed high frequency of mutagen-sensitive mutants in V79 cells, although unexpected and substantially higher than those published for CHO cells and L5178Y cells, can still be explained by the presence of functionally hemizygous loci.
TL;DR: The model presented in this study should be useful as DNA-sequence analysis becomes more commonly applied to the study of mutagenesis, and as DNA structure at and surrounding ionized base pairs may be altered.
Abstract: The nature of hydrogen bonding between normal and modified bases has been re-examined. It is proposed that hydrogen-bonding schemes may involve tautomeric, ionized or conformational forms (syn, anti and wobble). Several important cases are presented or reviewed in which physical evidence indicates the existence of ionized base pairs. When thermodynamic values determined in aqueous solution under physiological conditions are considered, it can be argued that base ionization will contribute substantially to the stability of many biologically relevant base pairs containing modified bases. A significant incidence of ionized bases in DNA may have important kinetic ramifications for the further chemical reactivity of both the modified base and its cross-strand pairing partner. Moreover, DNA structure at and surrounding ionized base pairs may be altered. For this reason, the model presented in this study should be useful as DNA-sequence analysis becomes more commonly applied to the study of mutagenesis.
TL;DR: Observations indicate that the treatments and manipulations to which sperm nuclei are subjected during flow sorting cause chromosomal aberrations, and that exposure of the cells to UV-laser irradiation contributes substantially to the chromosome damage observed.
Abstract: The separation of two sperm populations is possible using the technique of flow sorting, provided that a significant difference exists in the DNA content of X- and Y-bearing sperm. In order to ascertain whether or not chromosome damage was induced in sorted sperm, chromosome preparations were made from isolated sperm that had been microinjected into hamster eggs. While egg chromosomes exhibited a low frequency of chromosome aberrations, ranging from 4 to 7%, a large proportion of sperm cells exhibited chromosome damage. Between 29% of unstained and unsorted sperm and 38% of stained and unsorted sperm exhibited some type of chromosomal abnormality and this proportion increased to 50% in sorted sperm. If only damaged sperm nuclei are considered, the two unsorted sperm groups had a mean of 0.6 breaks, 0.8 triradial exchanges, and 0.2 quadriradial exchanges per nucleus. However, sorted sperm, which were stained with a fluorochrome and exposed to UV-laser irradiation, exhibited a mean of 2.9 breaks, 2.6 triradial, and 1.9 quadriradial exchanges per nucleus in which damage occurred. These observations indicate that the treatments and manipulations to which sperm nuclei are subjected during flow sorting cause chromosomal aberrations, and that exposure of the cells to UV-laser irradiation contributes substantially to the chromosome damage observed.
TL;DR: It is suggested that cells that have been sublethally damaged and that can repair these damages and survive could become transformed by the DNA-damaging mechanisms associated with carcinogenesis.
Abstract: Certain chemicals that are either weak or non-carcinogens had been previously shown to induce DNA single-strand breaks in rat hepatocytes, but only at cytotoxic doses. In contrast, stronger carcinogens induced DNA single-strand breaks at non-toxic doses. This report shows that the strong carcinogens and mutagens cadmium sulfate, sodium dichromate, dimethyl sulfate, and N -methyl- N ′-nitro- N -nitrosoguanidine all induce DNA single-strand breaks at non-toxic concentrations, but that they also induce DNA double-strand breaks at concentrations that are closely correlated with cytotoxicity. Some weak carcinogens produced DNA single- and double-strand breaks, but only at acutely cytotoxic concentrations. We suggest that the DNA double-strand breaks result from a cell-mediated process such as release of DNAase from lysosomes or other cellular compartments, that might occur during cellular response to acutely toxic damage. Experiments with N -dodecyl imidazole (NDI), a lysosomal detergent, show that lysosomal breakdown alone is only a weak inducer of DSBs, but that lysosomal breakdown in combination with prior chemical damage produced by MNNG synergistically induces DNA DSBs in BHK cells. N -Dodecyl imidazole also induces chromosomal aberrations in CHO cells at concentrations which cause cytotoxicity, cell cycle delay, and lysosomal breakdown. These results all suggest that chemical toxicity leads to limited lysosomal breakdown that induces DNA DSBs and chromosomal aberrations. Cells that have been sublethally damaged and that can repair these damages and survive could become transformed by the DNA-damaging mechanisms associated with carcinogenesis.
TL;DR: The survival experiments showed that mutants are very sensitive to X-rays, the D0, for the wild-type CHO-K1 was 6-fold higher than D0 value for the mutants, and possible reasons for the increased radiosensitivity of xrs mutants are discussed.
Abstract: We have studied two X-ray-sensitive mutants xrs 5 and xrs 6 (derived from the CHO-K1 cell line), known to be defective in repair of double-strand breaks, for cell killing and frequency of the chromosomal aberrations induced by X-irradiation. The survival experiments showed that mutants are very sensitive to X-rays, the D0, for the wild-type CHO-K1 was 6-fold higher than D0 value for the mutants. The modal number of chromosomes (2 n = 23) and the frequency of spontaneously occurring chromosomal aberrations were similar in all 3 cell lines. X-Irradiation of synchronized mutant cells in G1-phase significantly induced both chromosome- and chromatid-type of aberrations. The frequency of aberrations in xrs mutants was 12-fold more than in the wild-type CHO-K1 cells. X-Irradiation of G2-phase cells also yielded higher frequency of aberrations in the mutants, namely 7–8 fold in xrs 5 and about 3.5-fold in xrs 6 compared to the wild-type CHO-K1 cells. There was a good correlation between relative inability to repair of DNA double-strand breaks and induction of aberrations. The effect of 3-aminobenzamide (3AB), an inhibitor of poly(ADP-ribose) synthetase on the frequency of X-ray-induced chromosomal aberrations in these 3 cell lines was also studied. 3AB potentiated the frequency of aberrations in G1 and G2 in all the cell types. In the mutants, 3AB had a potentiating effect on the frequency of X-ray-induced chromosomal aberrations only at low doses. X-Ray-induced G2 arrest and its release by caffeine was studied by cytofluorometric methods. The relative speed with which irradiated S-G2 cells progressed into mitosis in the presence of caffeine was CHO-K1 > xrs 5 > xrs 6. Caffeine could counteract G2 delay induced by X-rays in CHO-K1 and xrs 5 but not in xrs 6. Large differences in potentiation by caffeine were observed among these cells subjected to X-rays and caffeine post-treatment for different durations. These responses and possible reasons for the increased radiosensitivity or xrs mutants are discussed and compared to ataxia telangiectasia (A - T) cells and a radiosensitive mutant mouse lymphoma cell line.
TL;DR: The random types of congenital abnormality observed and the remarkable stage-dependent sensitivity suggest a genetic basis for the response, both from genetic damages induced in premating germ cells and from teratogenic damage, which leads to malformations only when exposure of embryos occurs during the period of major organogenesis.
Abstract: When previously mated female mice were exposed to inhaled ethylene oxide at the time of fertilization of their eggs or during early pronuclear stage of the zygote (before DNA synthesis), a high incidence of mortality among conceptuses and of congenital abnormalities among both the dead and the surviving fetuses was observed. The developmental stage at which death occured ranged from near the time of implantation to day 17 of gestation when examination of the uterine contents was performed. In comparison, midgestation and late fetal deaths were absent or minimal when the females were exposed either before mating or when conceptuses were in later zygotic stages (pronuclear DNA synthesis) or had reached the early two-cell stage. The random types of congenital abnormality observed and the remarkable stage-dependent sensitivity suggest a genetic basis for the response. The effects differ, both from genetic damages induced in premating germ cells, which lead only to death near the time of implantation, and from teratogenic damage, which leads to malformation only when exposure of embryos occurs during the period of major organogenesis.
TL;DR: The genetic and embryotoxic effects of bis(tri-n-butyltin)oxide (TBTO) were evaluated in multiple in vivo and in vitro short-term tests preparatory to its potential wide use as a molluscicide in control of schistosomiasis.
Abstract: The genetic and embryotoxic effects of bis(tri-n-butyltin)oxide (TBTO) were evaluated in multiple in vivo and in vitro short-term tests preparatory to its potential wide use as a molluscicide in control of schistosomiasis. When tested in the rec assay in Bacillus subtilis, TBTO was not mutagenic and it did not induce reverse mutations in Klebsiella pneumoniae. Neither in the presence nor in the absecne of rat liver activation system did TBTO produce point mutations in Salmonella typhimurium strains TA1530, TA1535, TA1538, TA97, TA98 or TA100. TBTO was matagenic in strain TA100 in a fluctuation test, but only in the presence of rat liver S9 (Aroclor-induced). TBTO did not induce gene mutations in the yeast Schizosaccharomyces pombe, mitotic gene conversions in the yeast Saccharomyces cerevisiae, nor sister-chromatid exchange in Chinese hamster ovary cells in the presence or absence of rat or mouse liver S9. In the latter cells, structural chromosomal aberrations, endoreduplicated and polyploid cells were induced. TBTO did not induce gene mutations in V79 Chinese hamster cells (to 8-azaguanine-, ouabain- or 6-thioguanine-resistance) in the presence of a rat liver postmitochondrial fraction or in cell (hamster embryo cells and human and mouse epidermal keratinocyte)-mediated assays. In mouse lymphoma cells, TBTO did not induce 6-thioguanine- or BUdR-resistant mutations. As many tumour promoters inhibit metabolic cooperation between V79 Chinese hamster 6-thioguanine-resistant/-sensitive cells, TBTO was tested but showed no such activity. TBTO was examined for the induction of recessive lethal mutations in adult Berlin K male Drosophila melanogaster, either by feeding or by injection. Doses of 0.37 or 0.74 mM did not increase the number of X-linked recessive lethal mutations. An increased number of micronuclei was observed in the polychromatic erythrocytes of male BALB/c mice 48 h after a single oral dose of TBTO (60 mg/kg bw), while a lower dose (30 mg/kg bw) was ineffective. Neither of the two doses had induced micronuclei 30 h after treatment. The reproductive toxicity of TBTO was studied in NMRI mice. In a 10-day toxicity study, the LD50 and LD10 were 74 and 34 mg/kg bw, respectively. An increased frequency of cleft palates was seen in the fetuses of mice (compared with controls, 0.7%) treated orally during pregnancy with 11.7 mg/kg TBTO (7%), 23.4 mg/kg (24%) or 35 mg/kg (48%).(ABSTRACT TRUNCATED AT 400 WORDS)
TL;DR: 4-Hydroxynonenal induced a dose-dependent increase in the number of mutations to 6-thioguanine resistance, which reached the level of 4.7X baseline at the highest concentration tested.
Abstract: 4-Hydroxynonenal (HNE), a major product of the peroxidation of liver microsomal lipids, was examined for mutagenic activity at the hypoxanthine-quanine phosphoribosyltransferase locus in V79 Chinese hamster lung cells. At concentrations ranging from 10 to 45 μM/, HNE induced a dose -presiden inceases in the number of mutations to 6-thioguanine resistance, which reached the level of 4.7 × baseline at the highest concentrated tested.
TL;DR: Among these 48 inorganic derivatives, only the two Cr(VI) compounds and the Sn(II) compounds gave positive results.
Abstract: The genotoxic potential of 48 inorganic derivatives was studied using the bacterial colorimetric assay: the SOS Chromotest. Some of these compounds are known as carcinogens (As, Cr(VI), Cd, Ni) or suspected carcinogens for human beings (Hg, Pb), others are known as non-carcinogens. Among these 48 derivatives, only the two Cr(VI) compounds and the Sn(II) compounds gave positive results.
TL;DR: To investigate the mechanism by which the 8-hydroxyguanine residue in DNA affects the fidelity of DNA replication, the intrinsic properties of this modified base were investigated using an ab initio molecular orbital method.
Abstract: To investigate the mechanism by which the 8-hydroxyguanine residue in DNA affects the fidelity of DNA replication, the intrinsic properties of this modified base were investigated using an ab initio molecular orbital method. The most stable 8-hydroxyguanine form was revealed to be 6,8-diketo. The addition of an oxygen atom to the 8 position of a guanine base was shown to change the electrostatic potential of the molecule entirely and to give it a negative character. This effect may influence the local structure of 8-hydroxyguanine-containing DNA and the interaction with DNA polymerase, thereby resulting in infidelity of DNA replication.
TL;DR: The Fenton reaction, i.e., the iron-catalyzed Haber-Weiss reaction, provides an explanation for the active oxygen species-induced SCE: H2O2 + O2(-)----OH- + OH0 +O2, according to this view, the OH radical thus produced is the agent which ultimately causes SCE.
Abstract: When Chinese hamster fibroblasts were exposed to hydrogen peroxide or to a system consisting of xanthine oxidase and hypoxanthine, which generates superoxide anion plus hydrogen peroxide, sister-chromatid exchanges (SCEs) were formed in a dose-dependent manner. When the iron-complexing agent o-phenanthroline was present in the medium, however, the production of these SCEs was completely inhibited. This fact indicates that the Fenton reaction: Fe2+ + H2O2 → OH0 + OH− + Fe3+ is responsible for the production of SCEs. When O2− and H2O2 were generated inside the cell by incubation with menadione, the production of SCE was prevented by co-incubation with copper diisopropylsalicylate, a superoxide dismutase mimetic agent. The most likely role of O2− is as a reducing agent of Fe3+: O2− + Fe3+ → Fe2+ + O2, so that the sume of this and the Fenton reaction, i.e., the iron-catalyzed Haber—Weiss reaction, provides and explanation for the active oxygen species-induced SCE: SCE: H2O2 + O2− → OH− + OH0 + O2. Accorrding to this view, the OH radical thus produced is the agent which ultimately causes SCE. These results are discussed in comparison with other mechanisms previously proposed for induction of SCE by active oxygen species.
TL;DR: In this paper, a mixture of creatinine, phenylalanine and glucose in diethylene glycol-water solution was heated for 2 h at 128 degrees C, and a mutagen, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), was found to be produced, identified by highperformance liquid chromatography, and UV-visible and mass spectrometries.
Abstract: When a mixture of creatinine, phenylalanine and glucose in diethylene glycol-water solution was heated for 2 h at 128 degrees C, a mutagen, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), was found to be produced, identified by high-performance liquid chromatography, and UV-visible and mass spectrometries. The yield of PhIP was 3.6 nmoles/mmole original creatinine. PhIP was originally isolated from cooked beef, and this study shows creatinine, phenylalanine and glucose to be the probable precursors of PhIP in beef.
TL;DR: Results predict that 32P-postlabeling methodology is suitable to monitor and quantify DNA adducts in tissue biopsies of patients receiving MMC chemotherapy.
Abstract: Mitomycin C (MMC) is clinically used drug with mutagenic and antitumor activities, presumably elicited through its covalent binding to DNA, however, little is known about MMC binding to DNA in vivo. A 32 P-postlabeling method that does not require radiolabeled test compounds was employed here to study the formation of DNA adducts in somatic and reproductive tissues of rats 24 h after an i.p. dose of 9 mg/kg MMC. Among 14 tissues studied in female rats, MMC-DNA adduct levels were within a 2-fold range in 11 tissues, i.e. bladder, colon, esophagus, heart, kidney, liver, lung, ovary, pancreas, small intestine and stomach (minimum levels of 9.6–21.9 adducts per 10 7 ). Three other tissues, i.e. brain, spleen and thymus, exhibited lower adduct levels (0.2, 5.4 and 1.4 adducts, respectively, per 10 7 N). Liver DNA adduct levels were 32% lower in male than in female rats. Testicular DNA contained 2.5 adducts per 10 7 N, i.e. 5.3. times less than ovarian DNA. 32 P-labeled adduct patterns were qualitatively similar among the different tissues and consisted of 10 adducts, one of which comprised 71 (±5)% of the total. All these adducts were chromatographically identical to adducts formed by the reaction of chemically reduced MMC with DNA in vitro, demonstrating that metabolic activation of MMC occured via reduction. Using homopolydeoxyribonucleotides modified with MMC, in vivo adducts were shown to be mostly (>90%) gaunine derivatives and small amounts of adenine, cytosine and thymine products. Most of the adducts appeared to be monofunctional derivatives of DNA nucleotides. Dose-dependent MMC-DNA adduct formation was determined in rat liver over an 82-fold range of MMC administered (0.11–9.0 mg/kg). The lowest dose level studied was 4.5 times lower than the recommended single dose for human cancer chemotherapy (20 mg/m 2 ). Thus, these results predict that 32 P-postlabeling methodology is suitable to monitor and quantify DNA adducts in tissue biopsies of patients receiving MMC chemotherapy.
TL;DR: These results correlate with survival as well as with rates of DNA semi-conservative synthesis after 8-MOP photoaddition, the kinetics and extent of which being, however, different from that of normal or heterozygote cells.
Abstract: The fate of 8-methoxypsoralen (8-MOP)-photoinduced DNA interstrand crosslinks was followed by alkaline elution in Fanconi's anemia (FA) fibroblasts belonging to complementation groups A (FA 150 and FA 402) and B (FA 145) in comparison to a normal (1 BR/3) and a heterozygote (F 311) cell line. Clonogenic cell survival to 8-MOP photoaddition was established in parallel for all cell lines. In comparison to normal cells, group A FA cells demonstrated a higher photosensitivity than group B cells (sensitivity index 2.3 and 1.5, respectively), the heterozygote cell line being only slightly more sensitive. FA cells from both groups A and B demonstrated an incision capacity of crosslinks, the kinetics and extent of which being, however, different from that of normal or heterozygote cells. The incision is slower in FA cells and, at 24 h of post-treatment incubation, the amount of crosslinks incised is clearly lower than that observed in normal cells for group A cells, whereas in group B cells incision approaches the level of normal cells. These results correlate with survival as well as with rates of DNA semi-conservative synthesis after 8-MOP photoaddition.
TL;DR: The micronucleus test was validated in urothelial exfoliated cells obtained from urine samples of cigarette smokers for detecting genotoxic effects produced by mutagens/carcinogens in some human target tissues.
Abstract: The use of the micronucleus test on human exfoliated cells has recently been proposed (Stich et al., 1983a) for detecting genotoxic effects produced by mutagens/carcinogens in some human target tissues. So far, increased frequencies of micronucleated cells have been reported only in exfoliated cells of the buccal mucosa from individuals at risk of oral cancer, such as chewers of betel quid, nut and leaf, smokers and alcohol drinkers (Stich et al., 1982a,b, 1983b). As mutagens are present in large quantities in the urine of habital cigarette smokers, their urothelial ceils may represent a possible target for absorbed and excreted mutagens. This is supported by some recent reports on a significant increase in the risk of bladder cancer related to smoking habits (Cartwright et al., 1981; Mommsen and Aagaard, 1983; Vineis et al., 1984). Since an increase in micronucleated exfoliated ceils from the bladder mucosa of therapeutically irradiated patients has also been reported (Stich et al., 1983a), we decided to validate the micronucleus test in urothelial exfoliated cells obtained from urine samples of cigarette smokers. The urinary mutagenicity test (Ames test) was
TL;DR: A set of reference compounds can be used in attempts to identify compounds that act by a more specific (chemical) mechanism to disturb the spindle function and the results suggest that there is a good qualitative coupling in these cells between c-mitosis and aneuploidy with chemical treatment.
Abstract: Early investigations have shown that many chemically different compounds can cause disturbances of the spindle function (c-mitosis) in eukaryotic cells and that there is an unspecific (physical) mechanism based on the partitioning of the compound into cellular hydrophobic compartments. This suggests that the approach should be quantitative when testing compounds for this type of activity in vitro; effect/no effect is not the most pertinent question. The present study demonstrates how a set of reference compounds can be used in attempts to identify compounds that act by a more specific (chemical) mechanism to disturb the spindle function. All experiments were performed with an established cell line (V79 Chinese hamster). The results suggest that there is a good qualitative coupling in these cells between c-mitosis and aneuploidy with chemical treatment. Among compounds that are particularly active in relation to their lipophilic character are some chlorophenols, caffeine, diamide, diethyl maleate, 1-chloro-2,4-dinitrobenzene and tertiary butylhydroperoxide. This points to Ca2+-sequestering by mitochondria and/or cellular pH regulation (chlorophenols), Ca2+ release and sequestering by the endoplasmic reticulum (caffeine), enzymatic conjugation to glutathione (diethyl maleate, chlorodinitrobenzene) and hydroperoxide metabolism (t-butylhydroperoxide) as important target functions for specific activity.
TL;DR: An experiment sponsored by the International Atomic Energy Agency was undertaken to compare dose estimation by cytogenetic analysis on aliquots of samples of irradiated blood sent by air to participating laboratories, and most participants consistently obtained results acceptably close to the true values.
Abstract: An experiment sponsored by the International Atomic Energy Agency was undertaken to compare dose estimation by cytogenetic analysis on aliquots of samples of irradiated blood sent by air to participating laboratories. Accidental acute whole-body irradiations to 0.7 and 2.34 Gy and half-body irradiations to 3.5 Gy were simulated with X- and gamma-rays. For the partial irradiations the size of the irradiated fraction and its dose were estimated by the Qdr and contaminated Poisson techniques. Each laboratory's in vitro dose-response data were fitted to the quadratic model by the iteratively reweighted least squares method. Interlaboratory variations in dose-response curves, and in the aberration yields and dose estimates for the simulated accidents were noted. However, in general, most participants consistently obtained results acceptably close to the true values.