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Interpretations on chromium mutagenicity and carcinogenicity
292 An automated method for detection of AG r or TG r lymphocytes in human peripheral blood
In order to assess the genetic risk to exposed individuals there is a clear requirement for techniques that measure the frequency of induced mutations in some readily available somatic tissue such as blood lymphocytes. Strauss and Albertini (Mutation Res., 61 (1979) 353) used [3H]TdR labelling and autoradiography to identify lymphocytes resistant to the cytotoxic effect of 6-thioguanine (TG) but due to the paucity of these variant cells ( - 1.3 x 10 -4 in control individuals)'a very large total number of cells must be analysed, and therefore this technique is limited to comparatively small surveys. This presentation describes the use of a fast slide scanning device, the Fast Interval Processor or FIP (Shippey G.A. et al., Pattern Recog., 14 (1981) 345), to analyse slide preparations of separated lymphocytes. Preliminary results have demonstrated a strong correlation between nuclear DNA values measured by FIP and by conventional microdensitometry. Development so far allows estimation of the total cell number and identification of cells that are undergoing DNA synthesis by the presence of enhanced nuclear stain uptake and/or the presence of autoradiographic silver grains.
117 Petrilli, F.L., and S. De Flora, Institute of Hygiene, University of Genoa, 16132 Genoa (Italy) Interpretations on chromium mutagenicity and carcinogenicity
12 Cr(VI) compounds were positive in the Ames test (S. typhimurium TAI00, TA97, TA92, TA1978, TA98, TA1538 and TA1537), while 1 compound with oxidation state 0 and 7 Cr(III) compounds (unless contaminated) were negative. Soluble or artificially solubilized (alkali) Cr(VI) compounds had a similar mutagenic potency. Cr(VI) also reverted trp- E. coli (WP2, WP2uvrA) and preferentially inhibited strains lacking multiple DNA-repair mechanisms, i.e. TM 1080 (polA, lexA, R391) and CM871 (uvrA, lexA, recA). Thus, just below toxic levels, only Cr(VI) seems to elicit both frameshift errors and base-pair substitutions, amplified through an inaccurate DNA repair. Various interactions of Cr were also investigated (e.g. with BaP, cigarette smoke condensate, EDTA, ether, soda ash, crude oil, prostaglandins, oxidizing or reducing chemicals or metabolites). The effects of 37 metabolic systems, including preparations from variously treated animals (rats, mice, trout) or from humans (also under pathological conditions), were investigated. The resulting findings may contribute to interpret carcinogenicity and epidemiologic data. For instance, reduction of Cr(VI) to Cr(III) by human gastric juice is consistent with its lack of oral carcinogenicity. Also, reversal of Cr(VI) mutagenicity by erythrocyte lysates is consistent with Cr detoxication in the blood and justifies
293 the development of tumors exclusively at implant sites. Conversion of Cr(III) into mutagenic Cr(VI) was artificially afforded only by oxidizing chemicals and not by any of the metabolic systems tested. Conversely, Cr(VI) mutagenicity was decreased by $9 fractions from various tissues through NADPH-requiring pathways. Since Cr(III) is readily trapped by cytoplasmic ligands, this phenomenon is likely to indicate an intracellular detoxication. This suggests the existence of a threshold, affecting the ability of Cr(VI) in entering the nucleus and interacting with DNA, probably as Cr(III). On this basis, the slight efficiency of human lung preparations in decreasing Cr(VI) mutagenicity suggests that the development of lung cancer may depend on a quantitative balance between Cr(VI) entering these cells and their cytoplasmic defense mechanisms. Interestingly, the daily i.t. administration of dichromate in rats was found to enhance lung cell defense mechanisms. Conversely, $9 fractions from striated muscle had no detectable activity in reducing Cr(VI) mutagenicity, which may explain the development of tumors following local administration of Cr(VI) compounds.
118 Poma, K., and C. Susanne, Vrije Universiteit Brussel, Laboratorium voor Antropogenetika, Pleinlaan 2, 1050 Brussels (Belgium) Comparative cytogenetic analysis in mice chronically treated with arsenic alone and with arsenic in combination with ethyl methanesuifonate Humans exposed to arsenic show an increased chromosomal aberration rate. An experiment with mice was performed to determine the mutagenic activity of chronic arsenic. Swiss albino mice were given inorganic arsenic (250 mg As/l) in drinking water during 8 weeks. The mice were killed at several periods of the treatment (2, 4, 6 and 8 weeks); bone-marrow cells and spermatogonia were analysed for chromosomal aberrations. A significant increase of gaps was observed in bone-marrow cells when compared with controls but no breaks and exchanges were found. Chronically administered arsenic caused no chromosomal aberrations in spermatogonia. Although it seems that arsenic is not a strong mutagen, it may modify the mutagenic action of agents such as alkylating compounds because of its thiol-inhibiting capacity. Swiss albino mice were given inorganic arsenic (250 mg As/l) in drinking water during several weeks (2, 4, 6 and 8 weeks) and were injected with ethyl methanesulfonate (200 mg EMS/kg b.w.) 24 h before killing. Although significantly more gaps and breaks were found in the bone-marrow cells when the combined treatment is compared with the control group, a non-significant increase of aberrations was observed, when the combined treatment is compared with the EMS treatment alone (significant increase alone for gaps 2 weeks after administration). No chromosomal aberrations were observed in spermatogonia. Arsenic inter-
In order to assess the genetic risk to exposed individuals there is a clear requirement for techniques that measure the frequency of induced mutations in some readily available somatic tissue such as blood lymphocytes. Strauss and Albertini (Mutation Res., 61 (1979) 353) used [3H]TdR labelling and autoradiography to identify lymphocytes resistant to the cytotoxic effect of 6-thioguanine (TG) but due to the paucity of these variant cells ( - 1.3 x 10 -4 in control individuals)'a very large total number of cells must be analysed, and therefore this technique is limited to comparatively small surveys. This presentation describes the use of a fast slide scanning device, the Fast Interval Processor or FIP (Shippey G.A. et al., Pattern Recog., 14 (1981) 345), to analyse slide preparations of separated lymphocytes. Preliminary results have demonstrated a strong correlation between nuclear DNA values measured by FIP and by conventional microdensitometry. Development so far allows estimation of the total cell number and identification of cells that are undergoing DNA synthesis by the presence of enhanced nuclear stain uptake and/or the presence of autoradiographic silver grains.
117 Petrilli, F.L., and S. De Flora, Institute of Hygiene, University of Genoa, 16132 Genoa (Italy) Interpretations on chromium mutagenicity and carcinogenicity
12 Cr(VI) compounds were positive in the Ames test (S. typhimurium TAI00, TA97, TA92, TA1978, TA98, TA1538 and TA1537), while 1 compound with oxidation state 0 and 7 Cr(III) compounds (unless contaminated) were negative. Soluble or artificially solubilized (alkali) Cr(VI) compounds had a similar mutagenic potency. Cr(VI) also reverted trp- E. coli (WP2, WP2uvrA) and preferentially inhibited strains lacking multiple DNA-repair mechanisms, i.e. TM 1080 (polA, lexA, R391) and CM871 (uvrA, lexA, recA). Thus, just below toxic levels, only Cr(VI) seems to elicit both frameshift errors and base-pair substitutions, amplified through an inaccurate DNA repair. Various interactions of Cr were also investigated (e.g. with BaP, cigarette smoke condensate, EDTA, ether, soda ash, crude oil, prostaglandins, oxidizing or reducing chemicals or metabolites). The effects of 37 metabolic systems, including preparations from variously treated animals (rats, mice, trout) or from humans (also under pathological conditions), were investigated. The resulting findings may contribute to interpret carcinogenicity and epidemiologic data. For instance, reduction of Cr(VI) to Cr(III) by human gastric juice is consistent with its lack of oral carcinogenicity. Also, reversal of Cr(VI) mutagenicity by erythrocyte lysates is consistent with Cr detoxication in the blood and justifies
293 the development of tumors exclusively at implant sites. Conversion of Cr(III) into mutagenic Cr(VI) was artificially afforded only by oxidizing chemicals and not by any of the metabolic systems tested. Conversely, Cr(VI) mutagenicity was decreased by $9 fractions from various tissues through NADPH-requiring pathways. Since Cr(III) is readily trapped by cytoplasmic ligands, this phenomenon is likely to indicate an intracellular detoxication. This suggests the existence of a threshold, affecting the ability of Cr(VI) in entering the nucleus and interacting with DNA, probably as Cr(III). On this basis, the slight efficiency of human lung preparations in decreasing Cr(VI) mutagenicity suggests that the development of lung cancer may depend on a quantitative balance between Cr(VI) entering these cells and their cytoplasmic defense mechanisms. Interestingly, the daily i.t. administration of dichromate in rats was found to enhance lung cell defense mechanisms. Conversely, $9 fractions from striated muscle had no detectable activity in reducing Cr(VI) mutagenicity, which may explain the development of tumors following local administration of Cr(VI) compounds.
118 Poma, K., and C. Susanne, Vrije Universiteit Brussel, Laboratorium voor Antropogenetika, Pleinlaan 2, 1050 Brussels (Belgium) Comparative cytogenetic analysis in mice chronically treated with arsenic alone and with arsenic in combination with ethyl methanesuifonate Humans exposed to arsenic show an increased chromosomal aberration rate. An experiment with mice was performed to determine the mutagenic activity of chronic arsenic. Swiss albino mice were given inorganic arsenic (250 mg As/l) in drinking water during 8 weeks. The mice were killed at several periods of the treatment (2, 4, 6 and 8 weeks); bone-marrow cells and spermatogonia were analysed for chromosomal aberrations. A significant increase of gaps was observed in bone-marrow cells when compared with controls but no breaks and exchanges were found. Chronically administered arsenic caused no chromosomal aberrations in spermatogonia. Although it seems that arsenic is not a strong mutagen, it may modify the mutagenic action of agents such as alkylating compounds because of its thiol-inhibiting capacity. Swiss albino mice were given inorganic arsenic (250 mg As/l) in drinking water during several weeks (2, 4, 6 and 8 weeks) and were injected with ethyl methanesulfonate (200 mg EMS/kg b.w.) 24 h before killing. Although significantly more gaps and breaks were found in the bone-marrow cells when the combined treatment is compared with the control group, a non-significant increase of aberrations was observed, when the combined treatment is compared with the EMS treatment alone (significant increase alone for gaps 2 weeks after administration). No chromosomal aberrations were observed in spermatogonia. Arsenic inter-