Abstract

Cell damage by low-power 365-nm radiation of a 50-W high-pressure mercury microscopy lamp was studied. Exposure of Chinese hamster ovary cells to ultraviolet-A radiation >10 kJ/m2 resulted in significant modifications of nicotinamide adenine dinucleotide attributed autofluorescence and inhibition of cell division. Single-cell gel electrophoresis revealed UVA-induced single-strand DNA breaks. According to these results, UVA excitation radiation in fluorescence microscopy may damage cells. This has to be considered in vital cell microscopy, e.g., in calcium measurements.