Introduction to Apoptosis (Part One)
By: Lionel Perez Valenzuela
Why cells die?
Cells die in two basic forms, die due to damage and injuries they have suffered, a process called necrosis or induced to commit "suicide" slow and regulated process known as apotosis or programmed cell death.
In Greek classic apoptosis means "fall" in analogy with the falling leaves of autumn trees or petals in flowers. This analogy reinforces the idea that cell death is an integral and necessary part of the life cycle of living beings.
Injury Death
The damage that can receive a cell can be of different types, damage mechanical, ischemia (lack of oxygen) or can be exposed toxic elements.
The cell necrosis is a passive victim. Cells that receive these attacks, suffering a series of updates feature. To break the membrane of cells and their organelles (like mitochondria) swell, as they have lost the ability to regulate the passage of ions and water. Finally, the cell ruptures, releasing its contents that may cause inflammation in surrounding tissues.
Upon inflammatory signals, macrophages and other white blood cells converge in necrotic cells and ingested. Inflammation contributes to limit the infection and remove debris, but the action and the secretions of the white blood cells can damage normal tissue.
Death by "suicide"
Apoptosis is an active process that requires Cell waste energy in their own demise. It is accompanied by specific morphological changes, cell loss volume ( shrinks), it departs from neighboring cells and appear to boil as on its surface are "bubbles."
The cell nucleus, undergoes major changes, initially chromatin condenses and drops out of the nuclear envelope. Mitochondria break down and release the c itocromo c. The plasma membrane may also undergo changes, as exposure to the outer surface of the phospholipid phosphatidylserine , normally found on the inside of the membrane (plasma membrane asymmetry).
These cells are dying and giving their Phosphatidylserines can be recognized by neighboring cells or scavenger cells that have receptors for phosphatidylserine. These phagocytic cells such as macrophages and dendritic Ceulaer, which are present in all tissues, phagocytose apoptotic cells without causing inflammatory response, and that release cytokines that inhibit inflammation (IL-10 and TGF-beta).
Other non-apoptotic cells ingested continue undergoing new changes. Chromatin and fragmented nucleus with the rest of the cell is divided into numerous apoptotic bodies, which may contain one or two fragments nuleares. These bodies in turn may be ingested by phagocytic cells without causing inflammation.
Finally we know that certain cells undergoing programmed death are not phagocytosed but may persist indefinitely. One such case is the lens of the eye, whose cells replaced most of its cytoplasm by the protein crystal, when they die, Another case of skin cells, called keratinocytes, which are generated from precursors of a deeper layer and then migrate to the surface, dying on the road. These cells cytoplasmic keratin content. These dead cells form the outer protective layer of the skin to fall off and are replaced by other keratinocytes.
events leading to programmed cell death follow a pattern ordered as specific and can be compared with those of cell mitosis.
I leave here a few videos (later will add others, as progress with the subject.) Are English and German. As I can I will put the subtitles in Castilian.
This video is just to link it, and this in German. A little patience, for the clarity of the filming of the cell into apoptosis is worth it.
http://www.youtube.com/watch?v=E5e1jbFYjD4&feature=related
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