Apoptosis is a process of programmed cell death that occurs in multicellular organisms. Biochemical events lead to characteristic cell changes and death and these changes include blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, chromosomal DNA fragmentation, and global mRNA decay. Between 50 and 70 billion cells die each day due to apoptosis in the human adult. For an average child between the ages of 8 and 14, approximately 20 billion to 30 billion cells die a day, for example, the separation of fingers and toes in a developing human embryo occurs because cells between the digits undergo apoptosis. Because apoptosis cannot stop once it has begun, it is a regulated process. Apoptosis can be initiated through one of two pathways, in the intrinsic pathway the cell kills itself because it senses cell stress, while in the extrinsic pathway the cell kills itself because of signals from other cells. Both pathways induce cell death by activating caspases, which are proteases, the two pathways both activate initiator caspases, which then activate executioner caspases, which then kill the cell by degrading proteins indiscriminately. Research on apoptosis has increased substantially since the early 1990s, in addition to its importance as a biological phenomenon, defective apoptotic processes have been implicated in a wide variety of diseases. Excessive apoptosis causes atrophy, whereas an insufficient amount results in uncontrolled cell proliferation, some factors like Fas receptors and caspases promote apoptosis, while some members of the Bcl-2 family of proteins inhibit apoptosis. German scientist Karl Vogt was first to describe the principle of apoptosis in 1842, in 1885, anatomist Walther Flemming delivered a more precise description of the process of programmed cell death. However, it was not until 1965 that the topic was resurrected, while studying tissues using electron microscopy, John Foxton Ross Kerr at University of Queensland was able to distinguish apoptosis from traumatic cell death. Following the publication of a paper describing the phenomenon, Kerr was invited to join Alastair R Currie, as well as Andrew Wyllie, in 1972, the trio published a seminal article in the British Journal of Cancer. Kerr had initially used the term programmed cell necrosis, but in the article, Kerr, Wyllie and Currie credited James Cormack, a professor of Greek language at University of Aberdeen, with suggesting the term apoptosis. Kerr received the Paul Ehrlich and Ludwig Darmstaedter Prize on March 14,2000 and he shared the prize with Boston biologist H. Robert Horvitz. For many years, the apoptosis and programmed cell death were not highly cited. The 2002 Nobel Prize in Medicine was awarded to Sydney Brenner, Horvitz, the genes were identified by studies in the nematode C. elegans and homologues of these genes function in humans to regulate apoptosis. In Greek, apoptosis translates to the falling off of leaves from a tree, Cormack, professor of Greek language, reintroduced the term for medical use as it had a medical meaning for the Greeks over two thousand years before. Hippocrates used the term to mean the falling off of the bones, galen extended its meaning to the dropping of the scabs
Image: Apoptosis DU145 cells mosaic
John E. Sulston won the Nobel Prize in Medicine in 2002, for his pioneering research on apoptosis.
A section of mouse liver showing several apoptotic cells, indicated by arrows
A section of mouse liver stained to show cells undergoing apoptosis (orange)