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- Sterner, O., et al.
(author)
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Mutagens in larger fungi II. The mutagenicity of commercial pickled Lactarius necator in the Salmonella assay
- 1982
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In: Mutation Research Letters. - 0165-7992. ; 104:4-5, s. 233-237
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Journal article (peer-reviewed)abstract
- In the course of an ongoing screening of larger mushrooms for the occurrence of chemical mutagens, 33 out of 48 species tested exhibited a significant direct mutagenic activity in the Salmonella/microsome assay (Sterner et al., 1982). (No mutagens requiring metabolic activation were indicated.) These findings are of some concern, since mushrooms are used extensively as food in many areas, and there are strong indications that carcinogens in food are of considerable importance in cancer aetiology (Sugimura, 1979). A recent communication by Knuutinen and von Wright (1982) on the mutagenicity of 4 Lactarius species collected in Finland prompts us to report our own results from mutagenicity tests with commercially preserved (pickled) Lactarius necator.
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| 4. |
- Levan, G, et al.
(author)
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Gene amplification in the murine SEWA system.
- 1992
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In: Mutation research. - : Elsevier BV. - 0027-5107. ; 276:3, s. 285-290
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Journal article (peer-reviewed)abstract
- Considerable work with DNA amplification has been carried out in the murine SEWA ascites tumor cell system. In SEWA cells there is 'spontaneous' amplification of the c-myc oncogene, and transitions between different cytogenetic expressions of gene amplification such as DM (double minutes), CM (C-bandless chromosomes) and HSR (homogeneously staining regions) of the amplified DNA have been recorded during serial in vivo transplantations. In SEWA cells it has also been shown that the c-myc-containing DM will he lost under in vitro conditions, but are rapidly recovered if the cells are reinjected into animals. Additional gene amplification has been superimposed on the c-myc amplification in SEWA cells by stepwise selection in vitro, leading to resistance to different drugs, such as methotrexate, actinomycin D, colcemid and vincristine. Cytogenetically, DNA amplification is multifaceted and, in addition to the structures mentioned, it may also take the form of CB (chromatin bodies), which have been shown to be the carriers of resistance genes in hybrids between multidrug-resistant SEWA cells and Chinese hamster CHO cells. In most instances, DM are noncentromeric and distributed by a 'hitch-hiking' mechanism at mitosis; in one colcemid-resistant SEWA line, however, we have shown that the DM carry active centromeres. The molecular mechanism behind DNA amplification appears to be complex. We have shown that in four independently derived multidrug-resistant SEWA sublines the amplicons resided on circular molecules which were about 2500 kb long and carried at least five genes, including the three mouse mdr genes. Within the circles the DNA was unrearranged compared to the organization of the DNA in sensitive cells.
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