Light scattering measurements made at visible wavelengths have the ability to quantify subcellular morphology. Apoptosis, or programmed cell death, is associated with distinct morphological signatures such as mitochondrial swelling and nuclear condensation as well as characteristic biochemical signaling pathways, many of which are initiated by the release of cytochrome c from the mitochondria into the cytosol. In this Letter, we examine the time course of mitochondrial morphology changes as reported by light scattering and the subcellular location of cytochrome c measured by immunofluorescence microscopy in response to intracellular cell death signaling induced by photodynamic damage to lysosomes. We report that within this system, release of cytochrome c from the mitochondria into the cytosol occurs approximately simultaneously with mitochondrial-morphology-induced light scattering changes, providing further evidence that light scattering has the potential to play an important role in future studies of cell death biology.
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