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

A microculture technique was applied to the study of lymphocytes of Umbra limi, which have a low number of large meta- and submetacentric chromosomes (2n = 22). On the 5th day (90h) and later after initiation of culture at 20 degrees C, some cultures provided well spread metaphase chromosomes for analyses. After initiation, cultures were irradiated with 50, 100, 150 and 200 R of 200 kVp X-rays. The cultures were harvested on the 5th day, at which time all arrested metaphase chromosomes were in their first division. The dicentric yields induced in X-irradiated Umbra lymphocytes were observed to be significantly (P = 0.05) lower than those in human lymphocytes. The resulting dose-response relationship for dicentric yield was described by the quadratic equation Y = aD + bD2. The advantage of this method lies in the fact that small amounts (0.1 ml) of blood can be repeatedly withdrawn from the fish after a minimal interval of 2 weeks. The microculture technique with Umbra lymphocytes is thought to have a wide range of applications in studies of the potential genotoxic effects of clastogenic agents in the aquatic environment.