title: Light-induced Ca(2+) transients observed in widefield epi-fluorescence microscopy of excitable cells.
abstract: We have investigated the possibility that variations in the level of intracellular Ca(2+) in excitable cells might be induced as an artifact of the incoherent illumination that is being used to monitor transient responses. In order to avoid the fluctuations in power of an arc lamp source, a microscope using a light emitting diode that was calibrated accurately at low power levels, was constructed to provide good control over the dose of light applied to the biological specimen. We report here that higher powers of illumination increased the probability of occurrence of Ca(2+) transients even in the sub-mW range normally used to measure such transients in epi-fluorescence work, suggesting that caution should be exercised when designing experiments and interpreting data.
authors: Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 161 Cathedral Street, Glasgo, G4 ORE,  UK.
authors: Alison
authors: A
authors: McDonald
authors: John
authors: J
authors: Harris
authors: Debbi
authors: D
authors: Macmillan
authors: John
authors: J
authors: Dempster
authors: Gail
authors: G
authors: McConnell