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Cell Death and Proliferation

Posted Sep 07 2008 8:38pm

Darlene McCord, Ph.D., FAPWCA

There are two distinct mechanisms for cell death. Apoptosis is the result of “normal” or programmed cell death. Through this physiological process cells are routinely eliminated, giving balance to the proliferation of new cells. During apoptosis the outer membrane of the cell forms “bubbles” known as blebs. The content of the cells becomes incased in the blebs. The blebs separate from the cell and are digested by nearby cells or macrophages. This orderly process greatly reduces toxicity to surrounding cells.

Necrosis is the other form of cell death. This is not a programmed event and is known as “accidental” death. This pathological process occurs when cells are exposed to extreme stress, chemical insult, and resultant free radical damage. The early stages of necrosis involve a swelling of the cell called oncosis. During oncosis the cell and its organelles begin to swell due to an exchange in the cell’s potassium to sodium ratios. Necrosis, after the oncosis stage, is an explosive event where the cells contents stream directly into the surrounding cells environment causing damage and an immune response.

Controlling necrosis during the early oncosis stage is important. Up to this point, necrosis is a reversible event. Reversal is possible when the cell’s environment is changed through the reduction of free radicals and other toxins. Wound repair is, in part, dependent upon reversing the risks associated with “accidental” cell death.

When the cell remains in the G O cell cycle stage and does not advance to the G 1 stage of proliferation, it is known as quiescence. The cellular quiescent-to-proliferation process is normal. Quiescence allows the cell to rest and await the signal to divide again as part of the cell cycle. When the cell’s environment is not conducive to cell division, the cell is given a signal(s) to wait for “instructions” that it is safe to divide. The longer a cell stays in abnormal quiescence the more likely it becomes that the cell will die via necrosis. Just as with early stage necrosis, early quiescence is a reversible event that can be corrected by changing the cell’s environment. Reduction of free radicals in the cell’s environment is critical to the reversal process.

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