Biological action of low-intensity visible light on HeLa cells as a function of the coherence, dose, wavelength, and irradiation regime

An investigation was made of the action of λ = 633 nm low-intensity red light (He–Ne laser, incandescent lamp with light filters, dye laser pumped by a copper laser) on the rate of nucleic acid synthesis in HeLa cells 1.5 h after irradiation. It was found that DNA synthesis is stimulated almost equally by irradiation with an He–Ne laser and with a conventional source; the rate of RNA synthesis remains the same in both cases. On exposure to λ = 633 nm pulse-periodic radiation, RNA synthesis is stimulated and DNA synthesis is unaffected. Spectra of the stimulating effect of cw light in the 570–693 nm range on DNA and RNA synthesis are presented.