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Featured researches published by Heiji Maizumi.


Mutation Research Letters | 1984

Cytotoxicity, chromosome aberrations and unscheduled DNA synthesis in cultured human diploid fibroblasts induced by sodium fluoride

Takeki Tsutsui; Nobuko Suzuki; Manabu Ohmori; Heiji Maizumi

The effects of exposure of cultured human diploid fibroblasts (JHU-1 cells) to sodium fluoride have been studied with respect to cytotoxicity and induction of chromosome aberrations and unscheduled DNA synthesis (UDS) Cytotoxicity of NaF on JHU-1 cells, as determined by a decrease in colony-forming ability, linearly increased with increasing dose of NaF (50-150 micrograms/ml) or exposure time (1-24 h). Treatment of the cells with 50 micrograms/ml NaF for 24 h resulted in a lethality (approximately 70%) similar to that obtained with 100 micrograms/ml for 12 h. A linear increase in cytotoxicity was observed as a fraction of the product of NaF treatment time and dose. JHU-1 cells treated with 20-50 micrograms/ml NaF for 12 or 24 h were analyzed for chromosome aberrations. A significant increase in the frequency of chromosome aberrations at the chromatid level was observed in treated cells in a dose-dependent manner. For detection of UDS, confluent JHU-1 cells were cultured with medium containing low serum and then exposed to NaF in the presence of 10 mM hydroxyurea. Treatment with 100-400 micrograms NaF/ml for 4-24 h reproducibly elicited UDS in a dose-related fashion as determined by direct scintillation counting of [3H]thymidine incorporated into DNA during repair synthesis. These results suggest that NaF causes DNA damage in human diploid fibroblasts in culture.


Mutation Research Letters | 1984

Induction of unscheduled DNA synthesis in cultured human oral keratinocytes by sodium fluoride

Takeki Tsutsui; Koichi Ide; Heiji Maizumi

The effect of treatment of cultured human oral keratinocytes with sodium fluoride (NaF) has been investigated with respect to induction of unscheduled DNA synthesis (UDS). Oral keratinocytes were isolated from excised buccal mucosa of normal individuals by trypsinization at 4 degrees C overnight, followed by separation of the epithelium of mucosa from lamina propria mucosae with forceps. Isolated cells were cultured in vitro and all experiments were performed with secondary cultures. For detection of UDS, the keratinocytes were cultivated with medium containing 1% fetal calf serum (FCS) for 2 days and then treated with 100-300 micrograms/ml NaF for 4 h in medium containing 1% FCS and 10 mM hydroxyurea (1% FCS-HU medium). Following treatment with NaF, UDS was measured by direct scintillation counting of [3H]thymidine incorporated into DNA of the cells in 1% FCS-HU medium. Significant levels of UDS were induced in a dose-related fashion by NaF treatment. The results suggest that NaF causes DNA damage in cultured human oral keratinocytes.


Mutation Research Letters | 1984

Amitrole-induced cell transformation and gene mutations in Syrian hamster embryo cells in culture

Takeki Tsutsui; Heiji Maizumi; J. Carl Barrett

Amitrole, a widely used herbicide, is an animal carcinogen and an inducer of cell transformation. However, it is inactive as a mutagen in bacterial test systems. Thus, it has been suggested that amitrole is a non-mutagenic carcinogen. Over the dose range that induces morphological transformation of Syrian hamster embryo cells in culture, amitrole induced gene mutations at the Na+/K+ ATPase and hypoxanthine phosphoribosyl transferase loci measured concomitantly in the same cells. These results indicate that amitrole may act via a mutational mechanism.


Mutation Research | 1985

Induction by modified purines (2-aminopurine and 6-N-hydroxylaminopurine) of chromosome aberrations and aneuploidy in Syrian hamster embryo cells.

Takeki Tsutsui; Heiji Maizumi; J. Carl Barrett

The modified purines, 2-aminopurine and 6-N-hydroxylaminopurine, are known point mutagens in prokaryotic organisms. 2-Aminopurine is much less potent than 6-N-hydroxylaminopurine in inducing gene mutation in mammalian cells in culture and this corresponds to the relative activity of these two compounds in inducing tumors in rats and neoplastic transformation of Syrian hamster embryo cells in culture. We report here that these modified purines can induce chromosome aberrations, including chromatid gaps, breaks, and exchanges, as well as numerical chromosome changes in Syrian hamster embryo cells. These chromosome mutations occur over the concentration range of chemical needed to induced morphological transformation of the same cells. It is not known how nucleic base analogs induce chromosome mutations; however, this activity must be considered in attempting to understand the mechanism by which these agents induce neoplastic transformation of cells.


Cancer Research | 1983

Aneuploidy Induction and Cell Transformation by Diethylstilbestrol: A Possible Chromosomal Mechanism in Carcinogenesis

Takeki Tsutsui; Heiji Maizumi; John A. McLachlan; J. Carl Barrett


Carcinogenesis | 1984

Colcemid-induced neoplastic transformation and aneuploidy in Syrian hamster embryo cells

Takeki Tsutsui; Heiji Maizumi; J. Carl Barrett


Cancer Research | 1984

Dependence on Exogenous Metabolic Activation for Induction of Unscheduled DNA Synthesis in Syrian Hamster Embryo Cells by Diethylstilbestrol and Related Compounds

Takeki Tsutsui; Gisela H. Degen; Dietmar Schiffmann; Annette Wong; Heiji Maizumi; John A. McLachian; J. Carl Barrett


Carcinogenesis | 1986

alteration in diethylstilbestrol-induced mutagenicity and cell transformation by exogenous metabolic activation

Tsutsui T; Nobuko Suzuki; Heiji Maizumi; John A. McLachlan; J. Carl Barrett


Journal of Cellular Physiology | 1984

Dependence of lethality induced by a direct DNA perturbation of synchronized human diploid fibroblasts on different periods of the DNA synthetic period (S phase)

Takeki Tsutsui; Manabu Ohmori; Nobuko Suzuki; Heiji Maizumi


Japanese journal of medical science & biology | 1973

LONG-TERM CULTIVATION OF FIBROBLASTS DERIVED FROM NORMAL GINGIVAL TISSUES OF HUMAN ADULTS

Takeki Tsutsui; Yasuko Hirokawa; Heiji Maizumi

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Takeki Tsutsui

The Nippon Dental University

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Nobuko Suzuki

The Nippon Dental University

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Tsutsui T

National Institutes of Health

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Gisela H. Degen

National Institutes of Health

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