The Death Spectrum

As your doctor, your local sherrif or Gil Grissom will tell you, there are an infinite number of ways to die. And when it comes to cellular death, there is an entire spectrum of "death morphologies." This spectrum is anchored at the extremes by two modes of cellular death that are as different as night and day: necrosis and apoptosis.

The Death Spectrum. Necrosis is messy. Apoptosis is orderly.

Necrosis is your basic thermodynamic splat. The cell has suffered an overwhelming insult to its metabolic and structural integrity, and immediately (or very rapidly) loses its ability to partition ions. It spills lysosomal contents like hydrolases to digest itself from the inside out, swells up, and oozes all over the place. This doesn't look very orderly or regulated. It's a mess. In focal ischemia, this is the type of cell death that is associated with the densely ischemic ("necrotic") core of the infarct, and it's classically associated with calpain activity. Necrosis comes in a variety of morphological flavors: pale cell change,, ischemic cell change, and ghosts. 

Apoptosis is another story. Again, the cell has sustained an insult, but in this case it has maintained enough of its metabolic and structural integrity to keep limping along. It's still respiring, and it's working hard to maintain at least some of its electrochemical gradients. The cell looks like it might live. But in reality, the cell has taken the biomolecular equivalent of the Five-Point Palm Exploding Heart Technique. It might look okay now, but the hit has triggered a cascade of processes that are going to slowly, methodically and inexorably take the cell apart. The process is deliberate, orderly, and regulated. This is the type of cell death that is associated with the "penumbra" of the infarct, with delayed neuronal death, and with the activity of caspases. Apoptosis is characterized by the formation of  apoptotic blebs , the absence of inflammatory lysis, and the formation of DNA ladders.

 

 

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