SISTER-CHROMATID EXCHANGE INDUCTION IN SHEEP PERIPHERAL-BLOOD MONONUCLEAR-CELLS BY HELIO-NEON LASER-RADIATION

The effects of laser light on the cellular DNA have not been extensive ly characterized. Low-power laser sources, such as the helium-neon (He -Ne) laser with a wavelength of 632.8 nm, have been found to produce p hotobiological and photodamage effects with evidence of interference w ith cell replication. We have investigated the effects of He-Ne laser irradiation on sister chromatid exchange (SCE) frequencies in sheep pe ripheral blood mononuclear cells (PBMC). Cultured cells were irradiate d once at 6 selected energy intensities of laser irradiation and then stimulated with pokeweed mitogen and cultured in the presence of 5-bro modeoxyuridine (BrdUrd). The frequency of SCEs of both irradiated and non-irradiated cells were analyzed. The mean SCE of irradiated cells s ignificantly increased with growing energy density up to a laser dose of 24 J/cm(2), whereas after an energy density of 24 J/cm(2), the SCE frequency decreased with increasing energy densities. We concluded tha t the application of He-Ne laser irradiation at energy densities rangi ng from 2 to 96 J/cm(2) produced a different effect on SCE frequency i n sheep PBMC in vitro.