[A computer method for assessing the average rate of movement of Paramecium caudatum by a cross-sectional light beam]

The possibility of using the motility of Paramecium caudatum for computer biotesting of toxic substances was studied. The method is based on measuring the number and duration of impulses that arise when protozoa chaotically moving in a layer 0.5 mm thick cross a red light beam (1 mm in diameter). It was found that, in the presence of Cu2+ ions and menadione bisulfite, a compound having prooxidant properties, the number of impulses decreased with a concurrent increase in the duration of impulses. The high correlation between the number of impulses and the reciprocal of impulse duration indicates that the motility of paramecium by the action of Cu2+ ions and menadione slow down, and even an immobilization of some of them occurs. The mean swimming velocity of protozoa was reduced by half within 20 min by the action of Cu2+ at a concentration of 90 microM (6 mg/l of Cu2+ ions) and within 80 min by the action of menadione bisulfite at a concentration of 50 microM. It was shown that the slowing down of motility, which indicates the presence of a toxicant in the medium, is a faster physiological reaction than cell death.