Action of powerful ultrashort laser impulses on the permeability of the outer membrane of HeLa cells

It was shown that in HeLa cells, at the stationary growth phase, the permeability of the outer membrane for thymidine increased 1 h after irradiation with two ultrashort impulses (Nd3+: YAG laser, lambda = 266, 532 or 1064 nm, the impulse duration of 3 X 10(-11) s, I = 2 or 20 MW/cm2). The effect was dependent on the time interval between the impulses and virtually independent of the radiation wave-length. The maximum increase in the membrane permeability (by approximately 3 times) was noted after irradiation at 4-6 s intervals between the impulses.