Apoptosis in Action:
The steps leading to apoptosis are diagrammed below. Normal, healthy cells only undergo apoptosis when subjected to genetic errors or cell injury. In some cases the cell can repair all the errors or injuries, however if the damage is extensive, than apoptosis occurs. In this way, the cell protects the organism as a whole from continuing to duplicate genetically damaged information, which could result in disease or even cancer.
This is a simplified view of the steps a cell would take before undergoing apoptosis. The following pictures show the programmed cell death (apoptosis) of a trophoblast, which is a placental cell that helps to maintain pregnancy by secreting hCG, human chorionic gonadotropin to maintain progesterone.
In picture A, the cytoplasm of the cell is shrinking due to lamin and actin filament cleavage. The cytoskeleton is a critical factor in the integrity of any cell, and so cleavage of these filaments causes the cell’s cytoskeleton to breakdown, thereby causing it to shrink. In picture B, the nucleus is condensing as the nuclear structural proteins and chromatin (DNA) break down slowly. As you can see, the nucleus takes on a horseshoe shape, which is common among apoptotic cells. In picture C, the cell is condensing itself into a form that is easily identifiable and destroyed by macrophages, which are cells responsible for cleaning tissues of apoptotic cells or other debris. In picture D, you can see membrane blebs, which are blisters associated with the membrane of an apoptotic cell. Other membrane changes that can occur in an apoptotic cell is the translocation of phosphatydylserine to the outer membrane. Also, as indicated by the arrow, apoptotic bodies can appear, which are small vesicles.
Please visit the following webpage for a video clip of apoptosis.
You will need QuickTime to view the video:
http://www.sgul.ac.uk/depts/immunology/%7Edash/apoptosis/apoptosisvideo.html
As previously stated, the end of apoptosis involves the packaging of an apoptotic
cell into a distinct shape that makes it available for macrophage phagocytosis. This can be seen in the next picture
where the white blood cell represents the macrophage and the apoptotic cell is seen
packaging itself into apoptotic bodies..
References
“Apoptosis”. Reproductive and Cardiovascular Disease Research Group.(online). Retrieved April 25, 2006 from: http://www.sgul.ac.uk/depts/immunology/~dash/apoptosis/
“Apoptosis” Oct 2005. Retrieved from: http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/Apoptosis.html#CTL
“Caspase 7” Retrieved from: http://www.caspases.org/
Image Gallery, Clinical Tools (online). Retrieved from: http://www1.geneticsolutions.com/PageReq?id=3844:1873
“Apoptosis Glossary Version 1.3” Retrieved from: http://www.biosource.com/content/apop/glossary.html
“Apoptosis” Neuromuscular (online). Retrieved from: http://www.neuro.wustl.edu/neuromuscular/mother/apoptosis.htm