cell death apoptosis Energy dependent cell death induced by intrinsic genetic or developmental programme, or external stimuli such as addition or withdrawal of cytokines or trophic factors, radiation, chemotherapeutic agents etc. Characterised by cell shrinkage, increases in membrane permeability, endonucleolyis and nuclear fragmentation resulting in the formation of rapidly endocytosed apoptotic bodies. MPATH:3 mouse_pathology.ontology programmed cell death