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Abnormal regeneration in larval frogs with mutagenic chemicals — possible applicability to mutagen screening
228
Cytogenetic and dominant-lethal studies on captan There was no significant increase in the number of structural and numerical aberrations of chromosomes of the human diploid fibroblast cells in vitro treated with captan at concentrations of 0.5, 1.5, 3.0 and 4.0 pg/ml for 4 or 24 h. However, an increase of stickiness and a decrease of mitotic index were revealed in the treated cells. Cytogenetic effects in vivo were also studied on the metaphase chromosomes of the bone-marrow cells of male rats, 4 weeks old, treated p.o. by a single intubation with 0, 500, 1000 and 2000 mg/kg, or by consecutive 5-day administrations with 0, 2 0 0 , 4 0 0 and 800 mg/kg/day. They were sacrificed 24 h after the last injection. There was no increase of chromosomal aberrations in the bone-marrow cells of the treated animals at all the dosage levels. Dominant-lethal studies were performed in mice. Ten-week-old male C3H mice were treated orally with captan at 0, 200 and 600 mg/kg/day for 5 consecutive days. The treated male mice were mated with untreated virgin ICR females for 6 weeks. Captan induced no significant increase in the rate of embryonic death at any spermatogenesis tested.
33 Sugiyama, T., M. Thant and Y. Kano, Department of Pathology, Kobe University School of Medicine, Kobe (Japan) Abnormal regeneration in larval frogs with mutagenic chemicals-, possible applicability to mutagen screening Effects of three typical mutagens, mitomycin C (MMC), furylfuramide (AF2), and 4-nitroquinoline-l-oxide (4NQO) on tail regeneration in larval frogs were studied. Larvae of Rana nigromaculata Hallowell and Xenopus laevis were used when they attained b o d y length of 2--4 cm. The larvae whose tails were amputated at 5 mm from the tail-tip were kept in 1--3 × 10 -6 M of the above mutagen solutions. Regeneration was accomplished within 10 days after the amputation both in the experimental and control groups. A b o u t 40--50% of the larval frogs revealed abnormal regeneration when they were kept in 2--3 × 10 -6 M solutions of these mutagens and this effect was dose-dependent. The abnormalities consisted of bending and curling upward or downward, p o c k e t formationl nodule formation, branched tails, folded fin, and inhibited growth of fin. The larvae kept in normal water showed no such abnormality. These results suggest a possible applicability of this system to the screening of environmental mutagens and teratogens. At the same time, mutagen actions on blastema cells were strongly suggested.
34 Takizawa, Y., Department Of Public Health, Akita University School of Medicine, Akita (Japan)
Cytogenetic and dominant-lethal studies on captan There was no significant increase in the number of structural and numerical aberrations of chromosomes of the human diploid fibroblast cells in vitro treated with captan at concentrations of 0.5, 1.5, 3.0 and 4.0 pg/ml for 4 or 24 h. However, an increase of stickiness and a decrease of mitotic index were revealed in the treated cells. Cytogenetic effects in vivo were also studied on the metaphase chromosomes of the bone-marrow cells of male rats, 4 weeks old, treated p.o. by a single intubation with 0, 500, 1000 and 2000 mg/kg, or by consecutive 5-day administrations with 0, 2 0 0 , 4 0 0 and 800 mg/kg/day. They were sacrificed 24 h after the last injection. There was no increase of chromosomal aberrations in the bone-marrow cells of the treated animals at all the dosage levels. Dominant-lethal studies were performed in mice. Ten-week-old male C3H mice were treated orally with captan at 0, 200 and 600 mg/kg/day for 5 consecutive days. The treated male mice were mated with untreated virgin ICR females for 6 weeks. Captan induced no significant increase in the rate of embryonic death at any spermatogenesis tested.
33 Sugiyama, T., M. Thant and Y. Kano, Department of Pathology, Kobe University School of Medicine, Kobe (Japan) Abnormal regeneration in larval frogs with mutagenic chemicals-, possible applicability to mutagen screening Effects of three typical mutagens, mitomycin C (MMC), furylfuramide (AF2), and 4-nitroquinoline-l-oxide (4NQO) on tail regeneration in larval frogs were studied. Larvae of Rana nigromaculata Hallowell and Xenopus laevis were used when they attained b o d y length of 2--4 cm. The larvae whose tails were amputated at 5 mm from the tail-tip were kept in 1--3 × 10 -6 M of the above mutagen solutions. Regeneration was accomplished within 10 days after the amputation both in the experimental and control groups. A b o u t 40--50% of the larval frogs revealed abnormal regeneration when they were kept in 2--3 × 10 -6 M solutions of these mutagens and this effect was dose-dependent. The abnormalities consisted of bending and curling upward or downward, p o c k e t formationl nodule formation, branched tails, folded fin, and inhibited growth of fin. The larvae kept in normal water showed no such abnormality. These results suggest a possible applicability of this system to the screening of environmental mutagens and teratogens. At the same time, mutagen actions on blastema cells were strongly suggested.
34 Takizawa, Y., Department Of Public Health, Akita University School of Medicine, Akita (Japan)