Hisami Etoh

Survival and Photoreactivability of Ultraviolet-Irradiated Cultured Fish Cells (CAF-MM1)

The sensitivity to ultraviolet light (uv) and photoreactivating ability of cultured fish clone cells (CAF-MM1) were investigated. Dose-survival relationship curves were obtained using the colony-forming technique at various postirradiation temperatures (33, 26, and 20/sup 0/C). At 26/sup 0/C the values of D/sub 0/, D/sub q/, and the extrapolation number (n) were 1.74 J/m/sup 2/, 2.62 J/m/sup 2/, and 4.5, respectively; no marked differences in these values were found among different temperatures. Visible light illumination after uv irradiation produced a marked increase in survival. No photoreactivation effects were observed beyond about 30 h. Caffeine increased uv sensitivity of the CAF-MM1 cells, and from the results it is suggested that the cells have some caffeine-sensitive dark repair mechanisms.

Fish cell line (ULF-23HU) derived from the fin of the central mudminnow (Umbra limi): Suitable characteristics for clastogenicity assay

SummaryA cell line (ULF-23HU) from the fin of the central mudminnow (Umbra limi) was characterized and tested for its suitability to assess cytogenetic damages induced by chemicals in fish. Cells of this line exhibit a fibroblastlike appearance and grew optimal at 25°C in, TC-199 medium containing 10% fetal bovine serum, but slower growth continued down to 4°C, where they could be stored for prolonged periods. Seeding efficiency of ULF-23HU cells on the plastic substratum was approximately 85% in the above culture medium at 25°C. They had a 32-h cell cycle time taken up by a 20-h S period as determined by the autoradiographic analysis of the fraction of labeled mitosis. Cultures showed relatively high mitotic index (0.84 to 2.35%) during exponential growth phase lasting about 7 d. Karyological analysis of the cells at the different subculture passages revealed constant chromosome modal number of 23 consisting of metacentric or submetacentric chromosomes, which were primarily similar to those of in vivo cells, with one additional chromosome. The spontaneous sister chromatid exchange rate was 5.3 per metaphse. When ULF-23HU cells were exposed toN-nitroso-N-methylurea, a clastogen in the mammalian cells, dose-dependent increases both in sister chromatid exchanges and chromosome aberrations were clearly detected. These results on the growth kinetics and cytogenetic characteristics offered the high possibility of the use of this cell line as a suitable in vitro model for clastogenicity studies in fish.

Effects of tritiated water on germ cells in medaka embryos

Embryos of medaka, Oryzias latipes, were exposed to tritiated water and 137Cs gamma rays continuously from the one-cell stage until hatching (10 days at 26 degrees C). Germ cells in the gonads of newly hatched fry were counted in histological sections and compared with controls. The accumulated dose for 50% survival of germ cells was 195 rad for tritium beta rays and 350 rad for 137Cs gamma rays. Female progeny were produced using Yamamotos method. The 50% survival doses for female germ cells treated in a manner similar to that described above were 140 rad for beta rays and 305 rad for gamma rays. When embryos of medaka were irradiated with gamma rays below an accumulated dose of 475 rad or treated with tritiated water at a concentration of 0.2 mCi/ml or lower, the dose response of the germ cells showed an exponential relationship. It appeared that there was no threshold or significant dose-rate effect for either beta or gamma rays on germ cell survival, and that tritium beta rays were more effective than 137Cs gamma rays in germ cell killing.

RBE of fast neutrons for inhibition of hatchability in fish embryos irradiated at different developmental stages.

Embryos of the fish, Oryzias latipes at four different developmental stages were irradiated with various doses of 2 MeV fast neutrons from a Van de Graaff or 200 kVp x-rays. The hatchability, morta...

DAMAGE ACCUMULATION AND RECOVERY IN THE FISH ORYZIAS LATIPES EXPOSED TO FRACTIONATED OR PROTRACTED RADIATION AT DIFFERENT TEMPERATURES.

In the fish Oryzias latipes, 3 to 4 kR of X-irradiation was less lethal if applied in several separate fractions at intervals than if applied in the same total dose given by a single acute exposure...

Resistance of a cultured fish cell line (CAF-MM1) to. gamma. irradiation

Fish are generally more resistant to whole-body ionizing radiation than mammals. To study the radiosensitivity of fish in vitro, CAF-MM1 cells derived from the fin of the goldfish, Carassius auratus, were used. The survival parameters of CAF-MM1 obtained after ..gamma.. irradiation at 26/sup 0/C were 325 rad for D/sub o/, 975 rad for Dq, and 15 for n. No mammalian cell line with such a low sensitivity in the presence of O/sub 2/ has been reported. It was found that the large initial shoulder of the survival curve was paralleled by substantial repair of sublethal damage as evidenced by split-dose experiments. This low sensitivity to ..gamma.. irradiation did not change upon the administration of caffeine or postirradiation illumination, although these treatments were effective after uv irradiation. The decrease in the mitotic index in CAF-MM1 occurred immediately after irradiation, and it recovered within a very short time. This indicated that the duration of G2 arrest was shorter than that observed in mammalian cells. The data also suggest that the resistance of fish to whole-body irradiation is attributable to resistance at the cellular level.

Cytokinetics of regeneration in beta-irradiated guinea-pig epidermis.

We studied the time course of depopulation and repopulation of epidermal cells in guinea-pig skin after β irradiation from a

EFFECT OF TEMPERATURE ON THE RATE OF RECOVERY FROM RADIATION-INDUCED DAMAGE IN THE FISH ORYZIAS LATIPES

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X-ray-induced dicentric yields in lymphocytes of the teleost, Umbra limi

sealed source. Immediately after clipping, one site on each flank was locally irradiated with 1000, 2200, 3000, or 5000 rad (six sites per animal). The changes in number of basal cells, labeling index (LI), and the appearance of clusters of

Effects of Tritiated Water on Germ Cells in Medaka: II. Diminished Reproductive Capacity Following Embryonic Exposure

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