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991.
The present study was carried out to evaluate the suitability of the unstable white-zeste system in Drosophila melanogaster by testing 4 organophosphorus insecticides for potential genotoxic activity: dimethoate, fenitrothion, malathion, and methyl parathion. In view of the high sensitivity to insecticides of the unstable zeste strain used in this assay and the negative results obtained in this work, the white-zeste system does not appear to be sufficiently accurate for the evaluation of the mutagenic potential of specifically toxic chemicals, like insecticides. 相似文献
992.
M van Duin J H Janssen J de Wit J H Hoeijmakers L H Thompson D Bootsma A Westerveld 《Mutation research》1988,193(2):123-130
The human DNA-excision repair gene ERCC-1 is cloned by its ability to correct the excision-repair defect of the ultraviolet light- and mitomycin-C-sensitive CHO mutant cell line 43-3B. This mutant is assigned to complementation group 2 of the excision-repair-deficient CHO mutants. In order to establish whether the correction by ERCC-1 is confined to CHO mutants of one complementation group, the cloned repair gene, present on cosmid 43-34, was transfected to representative cell lines of the 6 complementation groups that have been identified to date. Following transfection, mycophenolic acid was used to select for transferants expressing the dominant marker gene Ecogpt, also present on cosmid 43-34. Cotransfer of the ERCC-1 gene was shown by Southern blot analysis of DNA from pooled (500-2000 independent colonies) transformants of each mutant. UV survival and UV-induced UDS showed that only mutants belonging to complementation group 2 and no mutants of other groups were corrected by the ERCC-1 gene. This demonstrates that ERCC-1 does not provide an aspecific bypass of excision-repair defects in CHO mutants and supports the assumption that the complementation analysis is based on mutations in different repair genes. 相似文献
993.
E Alejandre-Durán R M Claramunt D Sanz M J Vilaplana P Molina C Pueyo 《Mutation research》1988,206(2):193-200
The mutagenicity of nifurtimox (nfx) and 8 nfx analogues has been investigated with the L-arabinose forward-mutation assay of Salmonella typhimurium. The nfx analogues tested were obtained by replacing the 3-methyl-4-yl-tetrahydro-1,4-thiazine-1,1-dioxide group of the parent compound with the following other groups: indazol-1-yl (1); pyrazol-1-yl (2); benzimidazol-1-yl (3); 1,2,4-triazol-4-yl (4); 1-methyl-3-methylthio-1,2,4-triazol-4-yl-5-thione (5); 3,5-bis(methylthio)-1,2,4-triazol-4-yl (6); 1-adamantyl (7); 4,6-diphenylpyridin-1-yl-2-one (8). The mutagenic activity of each chemical was determined by the standard plate-incorporation test, in the presence or absence of the S9 activation mixture. The 9 compounds were mutagenic and exhibited linear dose-mutagenic response relationships. They were direct-acting mutagens and showed a nearly 1000-fold range in mutagenic potency from chemical 1 to nfx. In most cases, the addition of S9 mixture to the test plates decreased the mutagenicity of compounds. This effect was particularly noticeable in the case of chemicals 1-3, 5 and 7 where a more than 70% decrease in mutagenic activity was observed in the presence of the S9 mixture. The mutagenic potency of compounds in the Ara test showed a negative linear correlation with previously reported antitrypanosomal activity. Thus, chemicals 6 and 8 with in vitro activities against Trypanosoma cruzi clearly superior to that of nfx showed 2 of the lowest mutagenic potencies in the Ara test and these were only somewhat higher than the mutagenicity of the reference drug. 相似文献
994.
Formaldehyde was tested for its killing and mutagenic activities in the ad-3 forward-mutation test in Neurospora crassa. The test was conducted in 3 two-component heterokaryons (dikaryons) of N. crassa in order to determine the effect of the uvs-2 allele, which causes a defect in nucleotide excision repair, on formaldehyde-induced killing and the induction of ad-3 mutants. These dikaryons were homokaryotic for uvs-2+ (H-12), homokaryotic for usv-2 (H-59), and heterokaryotic for uvs-2 (H-71). Formaldehyde induced killing and ad-3 mutants in H-12, but the presence of uvs-2 in the homokaryotic state (H-59) resulted in a 9-fold increase in killing and a 40-fold increase in the induction of ad-3 mutants. This increased sensitivity to formaldehyde-induced killing and mutation conferred by uvs-2 in the homokaryotic state (H-59 vs. H-12) is similar to that noted by others in Escherichia coli. Salmonella typhimurium and Saccharomyces cerevisiae. The dikaryon heterokaryotic for uvs-2 (H-71) has the same sensitivity to formaldehyde-induced ad-3 mutation as H-12, indicating that uvs-2 is recessive to uvs-2+. 相似文献
995.
Nitroso-aldicarb was tested for its ability to induce sister-chromatid exchanges (SCE) and cell-cycle delay in human peripheral blood lymphocytes in vitro. This derivative of aldicarb induced a dose-dependent increase in SCE values per cell. In addition, a slight decrease in the successive mitotic progression of cells in culture was observed. 相似文献
996.
Fanconi's anemia lymphocytes: effect of caffeine, adenosine and niacinamide during G2 prophase 总被引:1,自引:0,他引:1
In this investigation peripheral blood lymphocytes from 3 Fanconi's anemia (FA) patients, 2 FA heterozygotes and 4 normal subjects were treated with caffeine and/or adenosine, and/or niacinamide during G2 prophase. Caffeine dramatically increased breakage levels in homozygote and heterozygote cells. Niacinamide and adenosine decreased the amount of chromosomal aberrations detected in FA homozygote and heterozygote lymphocytes treated and untreated with caffeine during G2 prophase. Caffeine sensitivity of heterozygote lymphocytes is proposed as a new clinical test to explore heterozygosis in individuals of FA families. 相似文献
997.
J Doskocil H Storchová J Stokrová J Forstová J Meyer 《Molecular & general genetics : MGG》1988,214(2):343-347
Summary Natural recombinant genomes between several, phenotypically distinct forms of phages and were isolated and characterized by DNA restriction fragment mapping and electron microscopic heteroduplex analysis. The phenotypes of the recombinants were correlated with the physical maps of the genomes, and several genetic functions were therfore defined and mapped. All genes necessary for the assembly of infectious virus particles map in a contiguous tract of DNA comprising about 20 kb, or nearly one third of the genome length. No DNA homology occurs within these domains of the two genomes, so that homologous recombination does not take place here and phenotypic mixing of the phages is eo ipso excluded. Other regions of heterology contain regulatory genes responsible for the lytic or temperate character of the phages, and for exclusion of phage by . 相似文献
998.
Killing of Escherichia coli cells modulated by components of the stability system ParD of plasmid R1
Alicia Bravo Sagrario Ortega Gertrudis de Torrontegui Ramón Díaz 《Molecular & general genetics : MGG》1988,215(1):146-151
Summary The proteins P10 and P12 have been shown to be gene products of a new stability system, ParD, of plasmid R1. It is now shown that an R1 miniplasmid, pAB112, carrying a trans-complementable amber mutation in the gene of the P10 protein, is lethal for the host in the absence of suppression. This lethal effect is suppressed in a supF background and also by deletions in pAB112 that affect the gene of the P12 protein. These data indicate that the P12 protein has a lethal effect on the host and that this effect is neutralized by the P10 protein. The possibility that the stabilization conferred by the ParD system could be due to a counterselection, mediated by P12, of cells that lose the plasmid at cell division, is discussed. 相似文献
999.
Summary We have worked out conditions for the study of competence development and genetic transformation in Streptococcus oralis NCTC 11427 (type strain), a species that contains choline in the cell wall. The peak of competence was found at the early exponential phase of growth and the optimal conditions for transformation were achieved with shuttle plasmids prepared from S. pneumoniae or from Escherichia coli serving as donor DNA. Transformation with dye-bouyant density gradient purified plasmid preparations followed first-order kinetics. The pneumococcal amidase can be expressed in S. oralis harbouring a plasmid carrying the lytA gene. This enzyme lysed the cell wall of the transformed cell in the presence of detergents. 相似文献
1000.
Rats treated with chlorpromazine (CPZ) (1 mg/kg/day i.p.) experienced a marked decline in cerebral insulin levels (0.057 +/- 0.01 ng/g wet weight) with respect to a control group (0.38 +/- 0.05 ng/g wet weight), while rats given D-amphetamine bitartrate (AMPH) chronically (20 mg/kg/day p.o.) showed a rise in cerebral insulin (0.55 +/- 0.04 ng/g wet weight). Combined treatment with both drugs at the same dosages produced lower cerebral insulin levels (0.46 +/- 0.10 ng/g wet weight) than in the AMPH animals. In the groups of rats treated with CPZ and with AMPH + CPZ, there was a slight elevation in serum insulin levels. Serum glucose values did not vary. 相似文献