Introduction to apoptosis and how it differs from cell necrosis

Apoptosis refers to the spontaneous and orderly death
of genes-controlled cells to maintain a stable internal environment.
Apoptosis is different from cell necrosis, apoptosis is not a passive process, but an active process, it involves the activation, expression and regulation of a series of genes, it is not a phenomenon of autologous damage under pathological conditions, but a death process
that actively strives for better adaptation to the living environment.
The difference between apoptosis and necrosis:
Although the end result of apoptosis and necrosis is very similar, their process and performance are very different
.

Necrosis :Necrosis is the process
of death in which cells undergo strong physicochemical or biological factors that cause cell disorder changes.
It is manifested by cell expansion, rupture of the cell membrane, spillage of cell contents, slow nuclear changes, insufficient DNA degradation, and a serious local inflammatory response
.

Apoptosis is the death process
of orderly changes in the response of cellular signals to the environment, changes in environmental conditions, or moderate damage.
Its cell and tissue changes are significantly different from necrosis
.

Process:
1, apoptosis onset
2, apoptosis body formation
3, apoptosis body is gradually engulfed by neighboring cells or phagocytes in vivo, and the remnants of apoptosis cells are digested and reused
.
Morphological changes:
Morphological observation of changes in apoptosis is multi-stage, and apoptosis often involves a single cell, even a small number of cells are not synchronized
。 The first thing that appears is the cell volume shrinks, the connection disappears, it detaches from the surrounding cells, then the cytoplasmic density increases, the mitochondrial membrane potential disappears, the permeability changes, the cytochrome C is released to the cytoplasm, the nuclear plast is concentrated, the nuclear membrane nucleolar is broken, and the DNA degrades into about 180bp-200bp fragments; The membrane has a small vesicle formation, the inner side of the membrane phosphatidylserine is turned outward to the membrane surface, the membrane structure is still intact, and finally the apoptosis cell remains can be divided and wrapped into several apoptotic bodies, no contents spill, so it does not cause the surrounding inflammatory response, and the apoptotic bodies can be quickly engulfed by the surrounding full-time or non-full-time phagocytes
.
Biochemical changes:
1) A significant feature of fragmentation
of DNA apoptosis is DNA degradation of cell chromosomes, which is a more common phenomenon
。 This degradation is very specific and regular, resulting in different lengths of DNA fragments of about 180-200bp integer multiples, and this is exactly the length of the entangled histone oligomer, suggesting that the chromosomal DNA is cut off at the junction of the nucleosome and the nucleosome, resulting in oligonucleosome fragments of different lengths, experiments have proved that the controlled degradation of this DNA is the result of an endogenous nucleic acid endonuclease action, the enzyme cuts off the chromosomal DNA at the junction of the nucleosome, This degradation is manifested in a specific ladder-like Lady pattern in agarose gel electrophoresis, while necrosis is diffuse in a continuous pattern
.
2) The biochemical changes of macromolecule synthesis
of apoptosis are not only the controlled degradation of DNA, but also the expression of new genes and the synthesis of certain biological macromolecules as regulators
in the process of apoptosis.
For example, TFAR-19 found in our laboratory is a molecule with high expression during apoptosis, and in the process of glucocorticoid-induced apoptosis of murine thymic cells, the addition of RNA synthesis inhibitors or protein synthesis inhibitors can inhibit the occurrence
of apoptosis.