Biomedical subjects

C W Moore

Publications and source records attributed to C W Moore.

43 records · Page 3Linked to original sources

PubMed1980

Isolation and partial characterization of mutants of Saccharomyces cerevisiae altered in sensitivities to lethal effects of bleomycins.

Two of eight mutants (bmr) isolated in Saccharomyces cerevisiae on the basis of their increased resistance to lethal effects of antitumor bleomycins (BM), and about two-thirds of 180 yeast mutants (bms) isolated on the basis of their increased sensitivities to cell-killing by phleomycins (PM) or BM were sensitive to one or more of the agents UV, X-rays or hydrogen peroxide, Thus these mutants are likely to be altered in processes acting directly or indirectly on DNA damage. The remaining six bmr mutants and approximately 60 bms mutants appear as resistant as the parent strain to cell-killing by UV or X-rays, and are likely therefore, to be altered in cell wall or membrane function. A genetic basis for the phenotypes of some of the bmr and bms mutants has been established.

Bleomycin↗

PubMed1979

Genetic effects of impure and pure saccharin in yeast.

Yeast cells were grown in media containing impure or purified saccharin preparations. Dose-dependent increases in frequencies of cells possessing aberrant cell morphologies were revealed by light microscopy. At each test dose, cells grown in impure saccharin exhibited up to sevenfold higher frequencies of mitotic crossing-over or gene conversion in three of four assays for genetic recombination than cells grown in purified saccharin from the same lot. With one exception, the sweetener produced by the Maumee process caused larger increases in recombination and gene reversion than the sweetener produced by the Remsen-Fahlberg process. The several test markers did not respond equally to any test saccharin. Cells grown in liquid media containing no saccharin or two of three test concentrations of saccharin produced cell titers that were approximately equivalent.

Cell Division↗

PubMed1979

Recombinogenicity and mutagenicity of saccharin in Saccharomyces cerevisiae.

Diploid yeast grown in the presence of a commercial lot of saccharin exhibited reproducible, dose-dependent increases in intergenic and intragenic recombination, and mutation. Cells grew to nearly the same titer in media without saccharin and containing 2 or 20 mg saccharin/ml, although cell viability was somewhat reduced in saccharin-containing media. At the high test dose of 100 mg/ml, titers and cell viability were more markedly lowered. Differences between this study and previous (negative) tests of saccharin in yeast are described.

Dose-Response Relationship, Drug↗

PubMed1978

Bleomycin-induced mutation and recombination in Saccharomyces cerevisiae.

Clinical preparations of bleomycins (BM) were tested for their recombinogenicity and mutagenicity at relatively high survival levels in the simple eucaryote, Saccharomyces cerevisiae. More than a dozen test loci or genetic intervals were assayed for bleomycin-induced mutation or recombination. Treatments of stationary phase diploid yeast routinely results in 25--75% inactivation. The antibiotic was mildly to very highly recombinogenic and mutagenic, with one exception. The amount of bleomycin-induced mutation, gene conversion or crossing-over depended upon the particular genetic markers assayed. The drug was also potently recombinogenic in yeast cells growing in the presence of BM. These results contrast with the finding that this antitumor agent was not mutagenic in the Salmonella/mammalian microsome mutagenicity test; possible explanation of this difference are given.

Bleomycin↗

PubMed1978

Responses of radiation-sensitive mutants of Saccharomyces cerevisiae to lethal effects of bleomycin.

Haploid and diploid strains of yeast containing genes conferring radiation-sensitivity were studied under growing and nongrowing experimental conditions for their relative sensitivities to growth-inhibitory effects of bleomycin (BM). The rad1, rad2, rad3, rad4, rad5 (and allelic rev2), rad7, rad10, rad11, rad 12, rad14, rad15, rad16 and rev3 strains exhibited responses similar to normal (Rad+) yeast strains. It is concluded from these findings that the excision-repair function deficient in several of these mutant strains is not important for repair of bleomycin-induced damages in yeast. The sensitive strains contained rad6, rad9, rad18, rad22, rad50, rad51, rad52, rad53, rad54, rad55, rad56, rad57 and rs1. Strains bearing rad8 or rad19 could not be classified unambiguously. With one exception, all rad mutants found very sensitive to BM were sensitive to X-rays, suggesting that some aspect of the repair of BM- and X-ray-induced damages in yeast may be similar. Sensitivities to BM and radiation co-segregated in pedigrees following meiosis, and several BM-resistant revertants isolated from two rad6 mutant strains sensitive to BM, X-rays and UV were cross-resistant to all three agents. These results confirm that the rad mutants were responsible for the cross-sensitivities in the original strains.

Bleomycin↗

PubMed1977

Role of DNA sequences in genetic recombination in the iso-1-cytochrome c gene of yeast. II. Comparison of mutants altered at the same and nearby base pairs.

X-ray-induced mitotic recombination rates and spontaneous meiotic recombination rates have been determined in two-point crosses of various defined cyc1 mutants of the yeast Saccharomyces cerevisiae. All but one of the 17 cyc1 mutants chosen for this study contained either the addition, deletion or substitution of single base-pairs located within a defined segment of the gene that corresponds to the 11 amino acid residues at the amino terminus of iso-1-cytochrome c; approximately half of these mutants had alterations of the AUG initiation codon, some at the same base pair. Up to 66-fold differences in X-ray-induced recombination rates were observed when the same cyc1 mutant was crossed to cyc1 mutants having different alterations in the AUG initiation codon; over a ten-fold difference was observed in series of homologous crosses involving mutants with different changes at the same base-pair. Recombination rates that were associated with specific cyc1 mutants co-segregated with the particular alleles following meiosis, and comparable recombination patterns were also observed for independently isolated, identical mutations. With the mutants used in this study, the frequencies of meiotic recombination did not differ as markedly, suggesting a dissimilar dependence on specific DNA sequences for these two modes of recombination. These disproportionalities of recombination rates suggest that the nature of the mismatched bases influences the recombination process, but not in a way that can be simply interpreted.

Base Sequence↗

PubMed1975

Role of DNA sequences in genetic recombination in the iso-1-cytochrome c gene of yeast. I. Discrepancies between physical distances and genetic distances determined by five mapping procedures.

Recombination rates have been examined in two-point crosses of various defined cyc1 mutants using five mapping methods. Nucleotide sequences of mutant codons were identified in previous studies from alterations in functional iso-1-cytochromes c produced by intragenic revertants. Heteroallelic diploids were analyzed for rates of mitotic recombination that occurred spontaneously and that were induced with x-rays, ultraviolet light and the near-ultraviolet light emitted by sunlamps, as well as rates of meiotic recombination that occur after sporulation. Frequencies of both mitotic and meiotic recombination do not necessarily correspond with physical distances separating altered nucleotides. The most extreme discrepancy involved two adjacent intervals of thirteen basepairs which differed approximately thirty-fold in their spontaneous and X-ray-induced recombination rates. Marked disproportions between genetic and physical distances appear to be due to the interaction of the two nucleotide sequences in the heteroallelic combination and not to the sequences of the mutant codons alone. Recombination values that were obtained by all five methods could not be used to establish to correct order of mutant sitesmrelationships of the recombination rates for the various pairwise crosses are different after mitosis from those after meiosis, suggesting that these two recombinational processes are to some extent different in their dependence on particular nucleotide configurations. On the other hand, the relationships of the rates induced by UV-, sunlamp- and X-irradiation were identical or very similar. In addition to the intrinsic properties of the alleles affecting frequencies of mitotic and meiotic recombination rates, two- to threefold variations in recombination rates could be attributed to genetic backgrounds.

Base Sequence↗