title: Defining apoptosis: players and systems.
abstract: OBJECTIVE
  To summarize the basic principles and concepts of apoptosis and some of the information to date regarding the nature of the regulation of apoptosis at the molecular level.
  
  
  METHODS
  In the past few years, research in cell and molecular biology has led to a much better understanding of the underlying mechanisms that regulate apoptosis.
  
  
  RESULTS
  Positive and negative regulatory elements that function in specific cell types to activate apoptosis have been identified. This activation involves signaling pathways that activate distinct proteolytic cascades that lead to the execution of cell death.
  
  
  CONCLUSIONS
  Homeostasis involves a delicate balance between the processes of proliferation, differentiation, and death by apoptosis. The current challenge is to understand how specific stimuli regulate the execution of programmed cell death in basic reproductive cells and how these interactions are integrated into the overall physiology and pathophysiology of reproduction during life.
authors.affiliation: Department of Reproductive Medicine, University of California, San Diego, La Jolla 92093-0674, USA.
authors.forename: G F
authors.initials: GF
authors.lastname: Erickson
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000235:genetics / Q000502:physiology*; D004247:DNA / Q000502:physiology; D006801:Humans; D015398:Signal Transduction; D016159:Tumor Suppressor Protein p53 / Q000502:physiology
chemical_list: D016159:Tumor Suppressor Protein p53; D004247:DNA