Induction of light emission by luminescent bacteria treated with UV light and chemical mutagens

Intensity of light emission by luminescent bacteria in response to UV irradiation and chemical mutagens was tested. We demonstrated that luminescence of six strains of marine bacteria (belonging to four species: Photobacterium leiognathi, P. phosphoreum, Vibrio fischeri and V. harveyi) is significantly increased by UV irradiation relatively shortly after dilution of cultures. Such a stimulation of luminescence was abolished in cells treated with chloramphenicol 15 min before UV irradiation, indicating that effective gene expression is necessary for UV-mediated induction of light emission. These results suggest that stimulation of luminescence in UV-irradiated bacterial cells may operate independently of the quorum sensing regulation. A significant induction of luminescence was also observed upon treatment of diluted cultures of all investigated strains with chemical mutagens: sodium azide (SA), 2-methoxy-6-chloro-9-(3-(2-chloroethyl)aminopropylamino)acridine x 2HCl (ICR-191), 4-nitro-o-phenylenediamine (NPD), 4-nitroquinolone-N-oxide (NQNO), 2-aminofluorene (2-AF), and benzo[alpha]pyrene. These results support the proposal that genes involved in bioluminescence belong to the SOS regulon. The use of bacterial luminescence systems in assays for detection of mutagenic compounds is discussed in the light of this proposal.     

The action of the tumour promoter, TPA, on mutagenesis induced by different agents (UV light, chemical and viral mutagens)

The present paper deals with effects of 12-O-tetradecanoylphorbol-13-acetate (TPA) on the frequency of induced mutations to 6-mercaptopurine (6MP) and ouabain resistance in Chinese hamster and mouse cells. UV light, bovine adenovirus 3(BAV-3) and 5-bromodeoxyuridine (BrdU) were used as mutagens. TPA was shown to raise the frequency of gene mutations induced by UV light and BAV-3 but it did not enhance the mutagenic effect of BrdU. We also examined the ability of BAV-3 and BrdU to induce tumours in mice. BrdU was shown to have no carcinogenic effect. The results suggest that TPA enhances the mutagenic effect only for carcinogenic mutagens.     

Frequency and spectrum of chlorophyll mutants induced in rice by chemical mutagens

Summary Dry seeds of rice varieties T(N)1, IR 8 and Sona, with stabilised moisture content and presoaked in distilled water, were treated with chemical mutagens MMS, dMS, dEMS and dES with the purpose of evaluating chlorophyll mutation frequency and spectrum. In the M₂ generation, mutants occurred in 24 lines of 'T(N)1; 94 lines of IR 8 but only in six of Sona. They include albino, viridis, xantha and other categories of which viridis was predominant. dES was found to be most effective of all mutagens used in all the three varieties and varietal differences were observed.     

Induction of SOS function in Escherichia coli after exposure to various types of chemical mutagens

On the basis of the SOS-chromotest which was developed by the authors earlier, the minimum time required for expression of the SOS-response is shown to be 15 min, the maximum being recorded 2 h later. An assay of induction of the SOS-response to the mutagens which act on DNA via various mechanisms (e. g., UV-irradiation, mitomycin C, nalidixic acid, nitroso-methylurea and acridine orange) revealed that all the mutagens under study caused induction of the SOS-response. Analysis of efficiency of SOS induction under the action of a mixture of formaldehyde with various amino acids has shown that arginine, asparagine and, especially, cysteine decrease the level of the SOS-response induction. This fact suggests an opportunity for using the SOS-chromotest not only to identify the mutagens and cancerogens, but also to screen the agents for their antimutagenic activity. The study of the SOS-response in the cells which are deficient in genes for repair and recombination has shown that induction is significantly suppressed in the mutants recA, lexA and recF; it is not modified in sbcB mutants and is significantly increased in the mutant lines recBC, uvrB and, particularly, in the double mutant recBCsbcB.     

Cytological analysis of storage effects on various types of complete and mosaic change induced in drosophila chromosomes by some chemical mutagens

Structural chromosomal changes induced by ethyleneimine (EI) in Drosophila spermatozoa and the effect of storage on the relative frequencies of mosaic and complete changes were studied cytologically, using salivary gland chromosomes. The pattern of EI-induced changes in unstored spermatozoa differes from that induced by X-rays by (1) a higher proportion of mosaics, (2) a higher proportion of repeats and deficiencies and a lower one of translocations and inversions, (3) a lower proportion of interchromosomal changes and a lower proportion of breaks located in heterochromatin. All of these characteristic feautures that distinguish mutagenic effects of EI from those of X-rays are present also after treatment with triethylene melamine (TEM) and formaldehyde food (FF), but the differences between EI and X-rays are on the whole smaller than those between X-rays and TEM or FF.Effect of storage on the frequencies of EI-induced changes is similar to that found when TEM of FF were used as mutagens: the whole pattern of changes became more like that found after irradiation. The only qualitative difference between EI and TEM of FF is the way in which storage affects the frequencies of mosaics.The peculiar pattern of EI-, TEM-, or FF-induced changes and the effect of storage is attributed to the high proportion of pre-breakage lesions with delayed fixation of breaks.Residual-mutagen hypothesis, as the possible cause of storage effects is also discussed.     

A search for chromosome aberrations induced in mouse spermatogonia by chemical mutagens

Two established chemical mutagens—ethylmethanesulphonate (EMS) and triethylenemelamine (TEM)—were tested for the ability to induce chromosome aberrations in mouse spermatogonia. While not a single aberration was detected following the EMS treatment, a low frequency of translocations and fragments was found in the TEM groups. These findings are in agreement with the data obtained with the specific locus mutation test as applied to male mouse premeiotic germ cells but contrast with the effectiveness of these chemicals in breaking chromosomes in male mouse postmeiotic germ cells. A differential sensitivity of post- and premeiotic germ cells to any kind of genetic damage by these chemical mutagens is most likely to be the correct interpretation of all the data. However, it is also suggested that a high proportion of translocations induced in spermatogonia by chemical mutagens may not be detectable by present methods.     

Effects of antimutagenic flavourings on SCEs induced by chemical mutagens in cultured Chinese hamster cells

Effects of antimutagenic flavourings such as vanillin, ethylvanillin, anisaldehyde, cinnamaldehyde, coumarin and umbelliferone on the induction of SCEs by MMC were investigated in cultured Chinese hamster ovary cells. None of these 6 flavourings showed any SCE-inducing activity by themselves. However, an obvious increase in the frequencies of SCEs was observed when MMC-pretreated cells were cultured in the presence of each flavouring. All these compounds have either an alpha, beta-unsaturated carbonyl group or a carbonyl functionality neighbouring the phenyl group which may react with an enzyme SH-group and cause higher-order structure changes. SCE-enhancing effects of vanillin were further investigated on 6 other kinds of mutagens. Vanillin was also effective on SCEs induced by EMS, ENNG, ENU or MNU. On the other hand, MMS- or MNNG-induced SCEs were not influenced at all by vanillin. SCE-enhancing effects of vanillin seemed to be dependent on the quality of lesions in DNA.     

Studies of DNA-strand induced in human fibroblasts by chemical mutagens/carcinogens.

A method for the study of DNA-strand breaks using alkaline denaturation followed by hydroxylapatite chromatography has been modified and used for the detection of chemically induced DNA-strand breaks. A new procedure for the incubation of human fibroblasts with a metabolizing system and the detection of DNA-strans breaks is presented. With this method the induction and repair of DNA-strand breaks have been studied in human fibroblasts exposed to methyl methanesulphonate, melphalan, benzo[a]pyrene and cyclophosphamide. These agents all give rise to DNA-strand breaks. In cells exposed to methyl methanesulphonate, melphalan or benzo[a]pyrene these breaks disappeared within 21 h after re moval of the drug. In cells exposed to the bifunctional alkylating agent cyclophosphamide, studies of DNA-strand breaks suggest the presence of inter-strand cross links.     

Revision of th distribution of chromosome aberrations induced by chemical mutagens using the BUDR label

Cell distribution was analysed with the help of the BrDU label for the number of chromosome aberrations and breaks induced by one-center (thiophosphamide and phosphamide) and two-center (dipine and fotrine) mutagens at the stage G0 in the Ist mitosis of human lymphocytes harvested at different times of culturing (from 56 to 96 h). The comparison was made between the type of aberration distribution in cells and the dependence of their frequency on the harvesting point for various mutagens. Poisson aberration distribution in cells for two-center mutagens was found to correspond to their constant frequency observed at different times of harvesting. On the other hand, for one-center mutagens, a geometrical distribution of chromosome breaks corresponded to an exponential decrease in their frequency in time. It is suggested that two-center chemical mutagens and ionizing radiation cause largely short-live damages which are realized into chromosome aberrations rather quickly (during one cell cycle). One-center mutagens, however, cause such damages that the probability of their transformation into chromosome aberrations is decreasing rather slowly in time, under the exponential law, and their realization into chromosome aberrations can occur in subsequent cell cycle.     

Attenuation of protein-nuclein interactions induced by chemical mutagens in a human fibroblast culture

Using nucleoprotein celite chromatography, it has been shown that DNA of human cultured fibroblasts was strongly bound to the proteins of the nuclear matrix. N-methyl-N-nitrosourea and prospidin-active antitumor agents with marked mutagenic action--were shown to attenuate the interactions, which appeared to be partially sensitive in cultured fibroblasts from patients with Down's syndrome.     

Comparison of the levels of chromosome aberration and sister chromatid exchange induced by chemical mutagens in vitro

Dose dependencies of the induction of sister chromatid exchanges (SCEs) and chromosome aberrations were studied under in vivo exposure of mouse bone marrow cells to 5 alkylating agents. The efficacy of the induction of SCEs for all the substances was 20 to 60 times higher than that of the induction of chromosome aberrations. It was demonstrated that SCEs induced by chemical mutagens in vivo and in vitro are more sensitive tests than chromosome aberrations.     

Correlation of the sister chromatid exchange level with chromosome aberrations induced by chemical mutagens in vivo

The data on the dose dependencies of the induction of sister chromatid exchanges (SCE) and chromosomal aberrations during exposure of mouse bone marrow cells in vivo to 5 alkylating substances are provided. The efficacy of SCE induction was found to be higher than that of chromosomal aberrations. It was established that SCE induced by chemical mutagens in vivo and in vitro are more sensitive and stable tests than chromosomal aberrations.     

The roles of different excision-repair mechanisms in the resistance of Micrococcus luteus to UV and chemical mutagens

M. luteus mutants showing increased sensitivity to both UV and 4-NQO were isolated after the treatment of parental ATCC4698 strain with MNNG. The mutants were also highly sensitive to mitomycin C, cis-platinum, 8-methoxypsoralen (8-MOP) plus near-UV and angelicin plus near-UV in various degrees. The endonuclease activity specific for pyrimidine dimers in UV-irradiated DNA was normally detected in extract of the mutants. With regard to host-cell reactivation ability the mutants fell into two groups. The hcr- mutants lacked the ability to reactivate UV-damaged N6 phage and were resistant to X-rays. The incision of DNA did not occur during incubation after the treatment with angelicin plus near-UV in the hcr- mutants, whereas it occurred in the parental strain. The facts indicate that the hcr- mutants are defective in the incision mechanism which has a wide substrate specificity, similar to the UVRABC nuclease of E. coli. On the other hand, the incision of DNA and the removal of UV-induced thymine dimers from DNA occurred in the hcr- mutants as well as in the parental strain, which is ascribed to the UV endonuclease activity. Compared with the hcr- mutants, hcr+ mutants were highly sensitive to X-rays, like recA- mutants of E. coli.     

Cytogenetic effects in the mouse of 17 chemical mutagens and carcinogens evaluated by the micronucleus test.

2 dialkylnitrosamines, 4 oxazaphosphorines, 6 aryldialkyltriazenes, urethane, N-hydroxyurethane, 4-nitroquinoline-1-oxide, procarbazine (natulan) and the inorganic carcinogen potassium chromate were studied for cytogenetic activity in the micronucleus test on mouse bone marrow. Except diethylnitrosamine, all chemicals were active. The results are compared with those known from studies in other mammalian and sub-mammalian test systems. The results of the micro nucleus test correlate well with results from other mutagenicity tests and with the carcinogenicity of the chemicals. The lack of an effect on N-nitrosodiethylamine (DENA) is discussed with regard to the short life-time of the ultimate mutagen.     

Suppressive effect of coffee on lipopolysaccharide-induced hepatitis in D-galactosamine-sensitized rats

A coffee extract significantly suppressed lipopolysaccharide (LPS)-induced hepatitis in D-galactosamine-sensitized rats, as assessed by the plasma alanine and aspartate aminotransferase activities, when it was added to the diet (30 g/kg) and fed to rats for 14 days. Its effect was as strong as that of a green tea extract. The coffee extract suppressed LPS-induced hepatitis when singly force-fed (1.2 g/kg) 1.5 h prior to the injection of the drugs, whereas a decaffeinated coffee extract had no significant effect. The hepatoprotective effect of caffeine was stronger than that of theobromine. These results indicate that coffee can protect animals from LPS-induced hepatitis, and that the effect of coffee might be mainly due to caffeine.