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Effects of previous γ-irradiation on sister-chromatid exchanges in Vicia faba cells induced by chemical mutagens
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rescences treated for Trad-SHM studies were scored for pink mutation frequencies in the stamen hairs on days 8-12 after TA (1.0 mM) treatment. The results of Trad-MCN studies indicated that X-irradiation (35 R) alone yielded 51.1 MCN/100 tetrads, and 1.0 mM TA alone yielded 8.5 MCN/100 tetrads, while the combined treatment of X-rays and TA with the same dosages yielded 126.2 MCN/100 tetrads. The negative control was 4.1 MCN/100 tetrads. This kind of synergism was exhibited through all the increasing dosages of TA except the highest dosage (1.5 raM) in which the MCN frequency declined. A linear regression dose response was obtained.
79 Angelova, E., M. Krsnik-Rasol, M. Biru~ and D. Paper, Department of Molecular Biology, Faculty of Sciences, Zagreb University, Rooseveltov trg 6/111, YU-41000 Zagreb (Yugoslavia) Methotrexate effects on plant cells Methotrexate is an analogue of folic acid and it binds specifically to the enzyme dihydrofolate reduetase (DHFR) inhibiting the reduction of dihydrofolate to tetrahydrofolate, which is the essential co-factor in the synthesis of nucleic acids and proteins. Animal cells are sensitive to methotrexate, which kills them even at low concentrations. However, cells can be found which are resistant even to high concentrations of this cytostatic. The cytotoxicity of methotrexate was tested in the root cells of Allium cepa L. var. aggregatum and Vicia faba L. It exhibited cytological and chromosomal effects: mitosis inhibition, nonfunctional spindle, chromosomal breakage and stickiness. In Vicia faba seedlings, methotrexate-treated root and shoot tissue extracts had lower protein content than untreated ones. Compared to the control, peroxidase activity was lower in the shoot but higher in the treated root fragments. SDS polyacrylamide gel electrophoresis of total soluble proteins showed only slight differences in polypeptide patterns. The synthesis of a 68-kD
polypeptide seems to be induced in the treated roots.
8O Kugllk, P., and J. Slotovfi, Institute of Biophysics, Brno (Czechoslovakia) Effects of previous y-irradiation on sister-chromatid exchanges in Vicia faba cells induced by chemical mutagens Primary root meristem cells of Vicia faba were exposed to doses of 0.5, 1.5 or 3.0 Gy of y-radiation. Subsequently, after BrdU incorporation into chromosomal DNA the roots were treated for 1 h with chemical mutagens (cis-diamminedichloroplatinum II, maleic hydrazide, methyl methanesulphonate) and the incidence of SCEs was studied. The results showed that, in some cases, the mutagen-induced frequency of SCEs in preirradiated cells was lower than expected on the basis of additivity of the effects of the individual treatments. The magnitude of the reduction of SCEs, however, was found to be dependent both on the dose of the pre-irradiation and on the kind of mutagen used. These results suggest that the pretreatment with ionizing radiation can influence the level of induction of SCEs in mutagentreated plant cells.
81 Ma, T.-H. i, K.-C. Chu 2 and C. Xu 1, l Department of Biological Sciences and 2 Department of Physics, Western Illinois University, Macomb, IL 61455 (USA) Clastogenic effect of electromagnetic field (EMF) on chromosomes of Tradescantia Electromagnetic fields (EMF) have been considered to be a possible health hazard in recent years. Conflicting reports on its carcinogenic, clastogenic, physiologic and behavioral effects created social hysteria among residents in the path of high power lines, computer operators and electronic and electrical technicians. Most of the studies in the past two decades yielded inconclu-
rescences treated for Trad-SHM studies were scored for pink mutation frequencies in the stamen hairs on days 8-12 after TA (1.0 mM) treatment. The results of Trad-MCN studies indicated that X-irradiation (35 R) alone yielded 51.1 MCN/100 tetrads, and 1.0 mM TA alone yielded 8.5 MCN/100 tetrads, while the combined treatment of X-rays and TA with the same dosages yielded 126.2 MCN/100 tetrads. The negative control was 4.1 MCN/100 tetrads. This kind of synergism was exhibited through all the increasing dosages of TA except the highest dosage (1.5 raM) in which the MCN frequency declined. A linear regression dose response was obtained.
79 Angelova, E., M. Krsnik-Rasol, M. Biru~ and D. Paper, Department of Molecular Biology, Faculty of Sciences, Zagreb University, Rooseveltov trg 6/111, YU-41000 Zagreb (Yugoslavia) Methotrexate effects on plant cells Methotrexate is an analogue of folic acid and it binds specifically to the enzyme dihydrofolate reduetase (DHFR) inhibiting the reduction of dihydrofolate to tetrahydrofolate, which is the essential co-factor in the synthesis of nucleic acids and proteins. Animal cells are sensitive to methotrexate, which kills them even at low concentrations. However, cells can be found which are resistant even to high concentrations of this cytostatic. The cytotoxicity of methotrexate was tested in the root cells of Allium cepa L. var. aggregatum and Vicia faba L. It exhibited cytological and chromosomal effects: mitosis inhibition, nonfunctional spindle, chromosomal breakage and stickiness. In Vicia faba seedlings, methotrexate-treated root and shoot tissue extracts had lower protein content than untreated ones. Compared to the control, peroxidase activity was lower in the shoot but higher in the treated root fragments. SDS polyacrylamide gel electrophoresis of total soluble proteins showed only slight differences in polypeptide patterns. The synthesis of a 68-kD
polypeptide seems to be induced in the treated roots.
8O Kugllk, P., and J. Slotovfi, Institute of Biophysics, Brno (Czechoslovakia) Effects of previous y-irradiation on sister-chromatid exchanges in Vicia faba cells induced by chemical mutagens Primary root meristem cells of Vicia faba were exposed to doses of 0.5, 1.5 or 3.0 Gy of y-radiation. Subsequently, after BrdU incorporation into chromosomal DNA the roots were treated for 1 h with chemical mutagens (cis-diamminedichloroplatinum II, maleic hydrazide, methyl methanesulphonate) and the incidence of SCEs was studied. The results showed that, in some cases, the mutagen-induced frequency of SCEs in preirradiated cells was lower than expected on the basis of additivity of the effects of the individual treatments. The magnitude of the reduction of SCEs, however, was found to be dependent both on the dose of the pre-irradiation and on the kind of mutagen used. These results suggest that the pretreatment with ionizing radiation can influence the level of induction of SCEs in mutagentreated plant cells.
81 Ma, T.-H. i, K.-C. Chu 2 and C. Xu 1, l Department of Biological Sciences and 2 Department of Physics, Western Illinois University, Macomb, IL 61455 (USA) Clastogenic effect of electromagnetic field (EMF) on chromosomes of Tradescantia Electromagnetic fields (EMF) have been considered to be a possible health hazard in recent years. Conflicting reports on its carcinogenic, clastogenic, physiologic and behavioral effects created social hysteria among residents in the path of high power lines, computer operators and electronic and electrical technicians. Most of the studies in the past two decades yielded inconclu-