Our research covers two related areas: cellular responses to localized oxidative stress and mechanisms for stress-induced bystander effects. The studies on localized oxidative stress involve a team approach for use of state-of-the-art methods such as ionizing radiation microbeams, in collaboration with a group in the UK, and subcellularly localized photosensitizers to study biochemical pathways involved in triggering of apoptosis, mutagenesis, and DNA damage and repair after subcellularly localized stress induction, e.g., in nuclear versus non-nuclear regions including plasma membranes and mitochondria. Cells containing genetic mutations or knock-downs in apoptosis and DNA repair pathways are used, and cellular responses are followed, among other approaches, by use of sophisticated time-lapse microscopy. The studies on stress-induced bystander effects involve investigation of the signaling pathways whereby a cell that is damaged by ionizing radiation, photosensitizers or other oxidative stresses sends a signal to neighboring undamaged cells which then show a biological response. These studies include use of a unique heavy ion irradiation facility at Brookhaven National Laboratory.