Action of ultrashort ultraviolet laser pulses on HeLa tumor cells

An investigation was made of the selective action of pulsed laser radiation (fourth harmonic of a YAG:Nd³⁺ laser having a wavelength of 266 nm and a pulse duration of 35 psec) on nucleic acids in HeLa tumor cells which were at the logarithmic stage of growth. It was found that by varying the radiation parameters (number of pulses and their intensity), the rate of synthesis of nucleic acids could be varied, being either accelerated or slowed down. Irradiation by a dose of between 10^–5 and 10^–3 J/cm² stimulates synthesis of DNA and RNA whilst the permeability of the cell membrane for synthesis precursors remains constant, whereas irradiation by doses between 10^–3 and 0.1 J/cm² inhibits synthesis of nucleic acids and the permeability of the cell membrane decreases.