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The effects of caffeine on thiotepa-induced chromosomal aberrations in Vicia faba and in human lymphocytes
260 trypsinized and exposed in suspension culture before being plated. The modified procedure ensures reproducible results and a constant, low number of spontaneous transformations (3.9 + 2.3; n = 22). So far the cells have been exposed to Ni3S2, NiO, Ni203 and Ni-acetate in concentrations including the 50% toxicity level. Particles ( < 4 ~tm) were phagocytized by the BHK cells, whereas the soluble Ni-acetate entered the cells by a different mechanism. At the 50% toxicity level all the compounds showed the same transforming activity. However, the 50% toxicity level was 10 times lower in the case of Ni3S 2 and Ni203 as compared to NiO and Ni-acetate.
64 Hansson, K., H.C. Andersson and B.A. Kihlman, Department of Genetics, University of Uppsala, Box 7003, S-750 07 Uppsala (Sweden) The effects of caffeine on thiotepa-induced chromosomal aberrations in Vicia faba and in human lymphocytes
One of the well documented effects of caffeine is its ability to potentiate mutagen-induced chromosome damage and cell killing. Experiments with both plant and mammalian cells have indicated that in order to be effective caffeine has to be present during the first S phase after treatment with S-dependent mutagens. However, results obtained during the last year demonstrate that in human lymphocytes, caffeine is even more effective as a potentiating agent when present during late G 2. We have compared the effects of post-treatments with caffeine on the frequencies of chromosomal aberrations induced by the trifunctional alkylating agent thiotepa in human lymphocytes and in root tips of Vicia faba. In lymphocytes the frequency of aberrations induced in G O or G~ was most strongly increased when caffeine was given during G 2. In Vicia, on the other hand, the frequency of aberrations induced in early interphase was unaffected by post-treatments with caffeine during G 2, but strongly increased when the root tips were exposed to caffeine during the S phase.
65 Harnasch, D., and R. Stumpf, Zentrallabor for Mutagenit~itspriafung der Deutschen Forschungsgemeinschaft, D-78 Freiburg (F.R.G.) Long-term treatment of mice with procarbazine leads to reduced frequencies of H mutants with time
The report of a higher frequency of specific-locus mutants after treatment with 600 m g / k g procarbazine in comparison to treatment with a dose of 800 m g / k g [1]
64 Hansson, K., H.C. Andersson and B.A. Kihlman, Department of Genetics, University of Uppsala, Box 7003, S-750 07 Uppsala (Sweden) The effects of caffeine on thiotepa-induced chromosomal aberrations in Vicia faba and in human lymphocytes
One of the well documented effects of caffeine is its ability to potentiate mutagen-induced chromosome damage and cell killing. Experiments with both plant and mammalian cells have indicated that in order to be effective caffeine has to be present during the first S phase after treatment with S-dependent mutagens. However, results obtained during the last year demonstrate that in human lymphocytes, caffeine is even more effective as a potentiating agent when present during late G 2. We have compared the effects of post-treatments with caffeine on the frequencies of chromosomal aberrations induced by the trifunctional alkylating agent thiotepa in human lymphocytes and in root tips of Vicia faba. In lymphocytes the frequency of aberrations induced in G O or G~ was most strongly increased when caffeine was given during G 2. In Vicia, on the other hand, the frequency of aberrations induced in early interphase was unaffected by post-treatments with caffeine during G 2, but strongly increased when the root tips were exposed to caffeine during the S phase.
65 Harnasch, D., and R. Stumpf, Zentrallabor for Mutagenit~itspriafung der Deutschen Forschungsgemeinschaft, D-78 Freiburg (F.R.G.) Long-term treatment of mice with procarbazine leads to reduced frequencies of H mutants with time
The report of a higher frequency of specific-locus mutants after treatment with 600 m g / k g procarbazine in comparison to treatment with a dose of 800 m g / k g [1]