In vitro effects of pulsed near-ultraviolet laser exposure on human larynx carcinoma cells.

Effects of pulsed near-ultraviolet laser beam on structural characteristics and macromolecular synthesis of carcinoma HEp2 cells were investigated. Laser irradiation damage induced in these eukaryotic cells could be characterized by two development stages: a) a reversible stage with minor morphological damages (1.5 kJ/m2) and 2) an irreversible one, at higher fluences, characterized by cellular membrane damage, necrobiosis and cells detachment from the substrate (4.5 kJ/m2). A. Studies performed referring to macromolecular syntheses of low laser fluences (1.5 kJ/m2)--irradiated HEp2 cells showed the following aspects: a) syntheses inhibiton phase in the first cycles of cellular replication and b) syntheses stimulation phases in the following cycle with total repair of laser-induced molecular lesions. B. At high laser fluences (3-4.5 kJ/m2), metabolic lesions repair was partially or totally blocked after prolonged culturing at 37 degrees C. Ths paper suggests some mechanisms of laser action on macromolecular synthesis and correlates them with morphological changes induced by laser exposure of carcinoma cells.