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A review of in vitro mutagenesis assessment of metal compounds in mammalian and nonmammalian test systems has been compiled.
Prokaryotic assays are ineffective or inconsistent in their detection of most metals as mutagens, with the notable exception
of hexavalent chromium. Mammalian assay systems appear to be similarly inappropriate for the screening of metal compounds
based upon the limited number of studies that have employed those compounds having known carcinogenic activity. Although of
limited value as screening tests for the detection of potentially carcinogenic metal compounds, the well-characterized in
vitro mutagenesis systems may prove to be of significant value as a means to elucidate mechanisms of metal genotoxicity. 相似文献
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Georg Steinhauser Johannes H. Sterba Karin Poljanc Max Bichler Karl Buchtela 《Journal of trace elements in medicine and biology》2006,20(3):119-153
In this study, 18 partly commercially available samples of rock salt from Austria, Germany, Pakistan, Poland, Switzerland, and Ukraine were investigated with respect to their content of trace elements using instrumental neutron activation analysis. Elements detected were Al, Ba, Br, Ca, Ce, Cl, Co, Cr, Cs, Eu, Fe, Hf, La, Mn, Na, Rb, Sb, Sc, Sm, Sr, Ta, Tb, Th, and Zn, some of them only in individual cases. An estimation of the bioavailability of these trace elements was performed by dissolving an equivalent of the sodium chloride samples in diluted hydrochloric acid (simulating stomach acid), filtering off the insoluble components, and analyzing the evaporated filtrate. It could be shown that in most cases bioactive trace elements like Fe can be found in rock salt in the form of almost insoluble compounds and are therefore not significantly bioavailable, whereas thorium, for example, was partly bioavailable in two cases. A significant contribution to the recommended daily intake of metal trace elements by using rock salt for nutrition can be excluded. 相似文献
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Genetic mapping of a mutation conferring sensitivity to bacteriophage Mu in Salmonella typhimurium LT2. 总被引:8,自引:5,他引:3
Two strains of Salmonella typhimurium LT2, SA1475 and MA411, were fortuitously found to be sensitive to bacteriophage Mu. The Mu-sensitivity allele of SA1475 was called musA1 and shown to be linked to the histidine operon both in conjugation and transduction experiments. The Mus allele of MA411 was unlinked to the his region and was tentatively designated musB2. Strains carrying large deletions of the his operon were also tested for Mu sensitivity; those of which the his-rib region is deleted were also sensitive to Mu. Transduction data led to the order zee-2 hisOGDCBAHFIE gnd musA. An Hfr injecting the his operon early (HfrK9) an carrying hisG9424::Tn10 delta 4 delta 11 and musA1 was isolated; this Hfr made it possible to introduce the Mus character into most derivatives of S. typhimurium LT2. Since strain SA1475 is resistant to bacteriophage P1, it could be used to select a new P1-Mu hybrid which has the host range of Mu and the transduction properties of P1. 相似文献
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Protein of the tobacco mosaic virus mutant E66 has lysine replacing asparagine of the type strain, vulgare, at position 140. Thus, E66 protein should have one more positive or one less net negative charge than vulgare at pH 6 to 7. To investigate the effect of charge, a comparative study of the polymerization of E66 and vulgare proteins at pH 6.0, 6.2, 6.4, 6.6, and 6.8 at ionic strengths 0.15, 0.10, and 0.05 was made by turbidimetry. Polymerization of E66 protein always proceeded at a lower temperature than vulgare. However, the extent of polymerization was much lower in E66, especially at the higher ionic strengths. Sedimentation velocity results paralleled those from turbidity measurements in that E66 protein polymerizes at lower temperatures than vulgare; the 20 S component is more abundant in E66 protein. Osmotic pressure measurements also show that E66 protein is more polymerized than vulgare, especially at lower pH values. Hydrogen ion titrations of E66 protein were carried out from pH 8 to 5 and back to pH 8 in 0.10 m KCl at three temperatures, 4, 10, and 15 °C. These titrations were reversible when carried out slowly. The isoionic point is near pH 5; thus the charge at pH 7.5 is ?3. The reversible titration results were correlated with the aggregates present at the various pH values and temperatures, determined from the areas under the schlieren peaks in sedimentation velocity experiments. It is found that hydrogen ion binding at the three pH values is correlated with the disappearance of the smallest aggregates and is independent of the type of higher polymer formed. To investigate the effect of ionic strength and pH on the characteristic temperature corresponding to an optical density increment of 0.01 by the method used previously for vulgare, two sets of turbidity measurements were carried out. In the first one the ionic strength was changed from 0.025 to 0.15 in increments of 0.025 at pH 6.0 and 6.4. In the other set, the ionic strength was kept constant at 0.10 and the pH changed from 5.9 to 6.7 in increments of 0.1 pH units. When the analysis of these data was carried out, was obtained. For the salting out constant a value of 1.7 was found, compared to 2.2 for vulgare, a result consistent with the fact that E66 should be less hydrophobic than vulgare. The electrical work term ΔWel also turns out to be about one-half that for vulgare, which is expected from the lower net negative charge on E66 protein. 相似文献
7.
Xiuling Li Songbai Yang Zhonglin Tang Kui Li Max F. Rothschild Bang Liu Bin Fan 《Animal genetics》2014,45(3):329-339
Due to the direction, intensity, duration and consistency of genetic selection, especially recent artificial selection, the production performance of domestic pigs has been greatly changed. Therefore, we reasoned that there must be footprints or selection signatures that had been left during domestication. In this study, with porcine 60K BeadChip genotyping data from both commercial Large White and local Chinese Tongcheng pigs, we calculated the extended haplotype homozygosity values of the two breeds using the long‐range haplotype method to detect selection signatures. We found 34 candidate regions, including 61 known genes, from Large White pigs and 25 regions comprising 57 known genes from Tongcheng pigs. Many selection signatures were found on SSC1, SSC4, SSC7 and SSC14 regions in both populations. According to quantitative trait loci and network pathway analyses, most of the regions and genes were linked to growth, reproduction and immune responses. In addition, the average genetic differentiation coefficient FST was 0.254, which means that there had already been a significant differentiation between the breeds. The findings from this study can contribute to further research on molecular mechanisms of pig evolution and domestication and also provide valuable references for improvement of their breeding and cultivation. 相似文献
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A new technique has been developed for the isolation of membrane vesicles from the vitamin D-deficient and vitamin D-treated chick intestinal brush border membrane. The technique involves removal of nuclei from a low speed pellet by discontinuous sucrose gradient centrifugation. The resulting intact brush borders are then homogenized in 0.5 M Tris and the membrane fragments purified on a glycerol gradient. This preparation represents a 20-fold purification of the brush border marker sucrase. After 1α-hydroxyvitamin D3 treatment there is a significant increase in membrane phospholipid phosphorous, an alteration in the fatty acid composition of the phosphatidylcholine fraction of membrane phospholipid, and a decrease in sucrase specific activity. 相似文献