Genetic analysis of X-linked mutagen-sensitive mutants of Drosophila melanogaster

Mutants at 2 new loci which control mutagen-sensitivity are described. Mutants at both loci are female-sterile and are hypersensitive to killing by MMS; neither increases the frequency of sex-linked recessive lethals. A screen of previously described female-sterile and meotic mutants has revealed that a number of these are also sensitive to mutagens. In addition, several new mutants have been identified on the basis of sensitivity to either HN2 or MMS. An anlysis of complementation data suggests that all of the X-linked genes controlling sensitivity to MMS may now have been identified. Among the new mei-41 alleles are mutants which show verly little meiotic nondisjunction or loss. Cytogenetic mapping of previously known mutants is also described. The mutants mus(1)104^D1 and mei-41^D5 are located in th eregion 14B13±?14D1,2 on the polytene chromosome map, and they map very close to each other genetically. Cytogenetically mus(1)101^D1 is between salivary chromosome bands 12A6,7 and 12D3, mus(1)103^D1 is between bands 12A1,2 and 12A6,7, and mus(1)-109^A1 is in section 8F3-9A2.     

Mutagenic activity of antibiotics alone and in conjunction with alkanesulfonates

Differential and combined effects of 0.25 and 0.50% antibiotics (ampicillin, neomycin, furadentine) and alkylating agents (ethyl methanesulfonate, methyl ethanesulfonate, methyl methanesulfonate) were assayed on Phaseolus vulgaris L. (2 n = 22) at the M₂ generation for chlorophyll mutations. The general types scored were Albino, Xantha, Virescens and Maculata. Yellowish-green leaves having red mid-veins and veinlets were observed only amongst the progeny raised after treatment with 0.25% ethyl methanesulfonate or 0.25% methyl ethanesulfonate + 0.25% ampicillin. The frequency of chlorophyll mutation after combined treatments in general was higher than after differential treatments. Methyl methanesulfonate among alkanesulfonates and neomycin among antibiotics induced higher frequencies of chlorophyll mutations. No chlorophyll mutant was produced by ampicillin.Although antibiotics induced a lower frequency of chlorophyll mutation than alkylating agents, the frequency and pattern of spectra of chlorophyll mutants showed an action of antibiotics in inducing mutation similar to that of alkylating agents. Therefore, it is considered that antibiotics are potential mutagens.     

Mutagenesis at the ad-3A and ad-3B loci in haploid UV-sensitive strains of Neurospora crassa. IV. Comparison of dose-response curves for MNNG, 4NQO and ICR-170 induced inactivation and mutation-induction

The genetic effects of MNNG, 4NQO and ICR-170 have been compared on 5 different UV-sensitive strains and a standard wild-type strain of Neurospora crassa with regard to inactivation and the induction of forward-mutations at the ad-3A and ad-3B loci. Whereas all UV-sensitive strains (upr-1, uvs-2, uvs-3, uvs-5 and uvs-6) are more sensitive to inactivation by MNNG and ICR-170 than wild-type, only uvs-5 shows survival comparable to wild-type after 4NQO treatment, all other strains are more sensitive to 4NQO. In contrast to the effects on inactivation, a wide variety of effects were found for the induction of ad-3A and ad-3B mutations: higher forward-mutation frequencies than were found in wild-type were obtained after treatment with MNNG or 4NQO for upr-1 and uvs-2, no significant increase over the spontaneous mutation frequency was found with uvs-3 after MNNG, 4NQO or ICR-170 treatment; mutation frequencies comparable to that found in wild-type were obtained with uvs-6 after MNNG, 4NQO or ICR-170 treatment and with upr-1 after ICR-170 treatment. Lower forward-mutation frequencies than were found in wild-type were obtained with uvs-2 after ICR-170 treatment and with uvs-5 after MNNG, 4NQO or ICR-170 treatment. These data clearly show that the process of forward-mutation at the ad-3A and ad-3B loci is under genetic control by mutations at other loci (e.g. upr-1, uvs-2, uvs-3, uvs-5 and uvs-6) and that the effect is markedly mutagen-dependent.     

Induction,ultrastructure, isolation,and tissue culture of chlorophyll mutants in carrot

Summary Seeds ofDaucus carota “Danvers” were treated with ethyl methanesulfonate (EMS) for 6-hr periods at concentrations of 0.01, 0.03, 0.1, 0.3, 1.0, and 3.0% to induce plastid mutants. In these treatments, there was a gradual decrease in percent germination from control up to 1.0% EMS and no germinations at 3.0%. The number of chlorophyll mutants increased with dose of mutagen. One mutant plant was isolated from the 0.1% treatment and it had leaf sections of green, white layered on green and pure white; and white and green striped petioles. Histogenic analysis of this mutant showed it to be a GGW chimera, the “all-white” sectors being GWW, arising from displacement of L-II by L-III. Electron micrographs of the white sections showed plastids that had dilated thylakoids typical of PS-I mutants. So called “mixed cells” of normal and mutant plastids were found, suggesting a plastome mutation. Leaf and petiole sections have been successfully cultured through the development of callus, and both green and white plants have been regenerated. Regenerated white plantlets were insensitive to 10 mM methyl viologen (paraquat), whereas green tissues were killed by the herbicide. Support for some of this work was provided by the Miami University Faculty Research Committee and the Comprehensive Employment and Training Act (CETA). This paper will be included as part of the dissertation work of P. D. Miller.     

The sulfhydryl groups of the thiol-dependent cytolytic toxin from Bacillus alvei evidence for one essential sulfhydryl group

Alveolysin, an extracellular protein toxin (M_r ? 63,000) excreted by Bacillus alvei and purified to homogeneity was shown to contain four cysteine residues. All thiol groups of the hemolytically active toxin preparation were free as found by direct titration by 5,5′-dithiobis (2-nitrobenzoic acid) and confirmed by the absence of disulfide bond. Toxin alkylation with tosyl lysine chloromethyl ketone resulted in the complete loss of hemolytic activity and the disappearance of only one thiol group with no modification of histidine residues. These results support the conclusion that one essential thiol group is implicated in the membrane-disrupting activity of alveolysin.     

Effects of metabolic inhibitors on cell lethality and mutation induction in Chinese hamster cells. I. Inhibitors of de novo purine synthesis and a comparison with the effects of caffeine

The effect of pre- and posttreatment incubation of UV-irradiated and ethyl methanesulphonate (EMS) treated cells with non-toxic concentrations of inhibitors of de novo purine synthesis (dnPS) on expression of potentially lethal and premutational damage at the hypoxanthine-guanine phosphoribosyl transferase (HGPRT) locus in V79 cells has been examined. The concentrations of inhibitors used were shown to profoundly perturb de novo DNA synthesis, by measurements of [¹⁴C]formate uptake, and cell cycle progression by flow cytofluorimetry. Postincubation in 6-methyl mercaptopurine ribonucleoside (MMPR) usually but not invariably potentiated the cytotoxic effects of UV and EMS but azaserine (AZS) and methotrexate (MTX) were without effect. No effects on mutant frequencies were observed on posttreatment with any of these agents. Caffeine produced the least effect on dnPS, but invariably potentiated lethal damage. This potentiation of lethal damage is not mediated by dnPS inhibition as has been suggested for Chinese hamster ovary (CHO) cells.     

Affinity labeling of phosphoenolpyruvate carboxykinase with 1, 5-I-AEDANS.

The concentrations of zinc thionein and cytosolic zinc in rat liver were examined in male rats five days after bilateral adrenalectomy. Zinc in metallothionein increased 10 fold, as compared with control animals. Cytosolic zinc increased 79% as compared with controls. 65% of this increase could be accounted for bound to metallothionein. Sham operated animals after five days showed a 4 fold increase in hepatic zinc thionein and a 23% increase in cytosolic zinc, 71% of this increase being bound to metallothionein. Adrenalectomized rats, maintained on daily injections of corticosterone (4mg/100g b.w.), exhibited the same levels of zinc thionein and cytosolic zinc as adrenalectomized rats receiving no treatment. Adrenalectomized rats, maintained on daily injections of aldosterone (5μg/100g b.w.), exhibited the same levels of zinc thionein as the sham operated rats, but the cytosolic zinc remained elevated at the level found in adrenalectomized rats receiving no treatment. These results indicate that there is adrenal involvement in the control of hepatic zinc and zinc thionein levels in the rat.     

Inhibition by polyamines of lipid peroxide formation in rat liver microsomes.

Both NADPH- and ascorbic acid-dependent lipid peroxidations were inhibited by spermine, the degree of inhibition being greater with the former peroxidation. The effective concentration of spermine required for inhibition was higher when larger amounts of microsomes were used. However, the activities of NADPH-cytochrome c reductase and NADPH-peroxidase were not influenced by spermine. These results suggest that spermine inhibits lipid peroxidation by binding to phospholipids in the microsomes.     

Relationship between acute and chronic exposures in mutagenicity studies in mice

The relationship between acute and chronic exposures in mutagenicity studies on mammals still lacks experimental data that might permit the decision whether or not the long-term exposures are of significance in mutagenicity testing.Fractional application of TEPA, THIOTEPA, EMS cyclophosphamide and sodium arsenite was made in experiments with mice, by using the dominant-lethal test and cytogenetic analysis of bone marrow. In most experiments the repeated application yielded the same or higher genetic injury than the same total dose at a single application. Negative results are discussed in relation to the threshold dose and the different sensitivity of the germ-cell stage.Possible interaction of mutagens was also studied by analyzing the combined effect of a long-term exposure to sodium arsenite, which probably affected the repair mechanism, and of a single dose of TEPA. It is concluded that the present stage of knowledge requires acceptance of the opinion that the genetic risk induced by chronic exposure to a chemical is as serious as that induced by an acute exposure.