Biological effects of pulsed near-ultraviolet laser irradiation in mouse lymphoma cells (EL-4)

Murine lymphoma EL-4 cells were exposed to different pulsed near-ultraviolet laser doses (337.1 nm), generated by light, to investigate some effects of this radiation on tumor cells using biophysical, biochemical, and cytogenetic methods. Our results reveal a good correlation between the growth rate of EL-4 cells and the interrogation irradiation, from 89.7% at 1.5 kJ/m(2) to 17.8% at 4.5 kJ/m(2). Nucleic acid synthesis was found to be inhibited at any laser irradiation dose. The morphological changes induced by laser irradiation of EL-4 cells and revealed by phase contrast and scanning electron microscopy (SEM) indicate a partial or total (depending on dose) loss of cellular microviliosities, the appearance of different kinds of buds and bleaching all over the cellular membrane, and also numerous necrotic lesions. By reversion of irradiated EL-4 cells, the presence of cells having morphological characteristics of lymphoid dendritic cells was observed by phase contrast and SEM. The cytogenetic analysis showed the presence of different chromosomal abnormalities: chromatidin and chromosomal fractures, rings, chromosomal markers, polyploids, and premature chromatid condensation. Our experimental results suggest the existence of morphological lesions as well as biochemical and genetic lesions induced by pulsed near-ultraviolet laser doses in mouse lymphoma EL-4 cells. (C) 1996 Society of Photo-Optical Instrumentation Engineers.