Apoptosis refers to the orderly death of cells that are controlled by genes to maintain homeostasis. 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 kind of autologous injury under pathological conditions. Phenomenon, but a death process that is actively pursued to better adapt to the living environment.
Figure 1. Labelled diagram of a cell undergoing apoptosis.
The cells in the human body are destined to die, some deaths are physiological, and some deaths are pathological. Research on the process of cell death has become a hot spot in biology and medical research. It is known that there are at least two ways of cell death, namely cell necrosis and apoptosis. Cell necrosis is a cell death pattern that has long been recognized, and apoptosis is a form of cell death that is gradually recognized. Apoptosis is a fundamental biological phenomenon of cells that plays a necessary role in the removal of unwanted or abnormal cells by multicellular organisms. It plays an important role in the evolution of organisms, the stability of the internal environment, and the development of multiple systems. Apoptosis is not only a special type of cell death, but also has important biological significance and complex molecular biological mechanisms. Apoptosis is a process in which multiple genes are strictly controlled. These genes are very conserved among species, such as the Bcl-2 family, the caspase family, oncogenes such as C-myc, and the tumor suppressor gene P53. With the development of molecular biology techniques, there are many processes for apoptosis. Quite understanding, but the exact mechanism of the apoptotic process to date is not fully understood. The disorder of the apoptotic process may be directly or indirectly related to the occurrence of many diseases. Such as tumors, autoimmune diseases, etc., there are many factors that can induce apoptosis, such as radiation, drugs and so on. Part of the human physiological structure belongs to natural apoptosis, such as the human tail stage, and the tail is automatically apoptotic during development.
Programmed cell death (PCD)
Programmed cell death (PCD) is quite different from apoptosis. The concept of programmed cell death was proposed in 1956. PCD is a functional concept that describes certain cell deaths in a multicellular organism as a predetermined, and strictly controlled, normal component of ontogeny. For example, cockroaches become frogs, and the disappearance of the tail during metamorphosis is accompanied by a large number of cell deaths. The disappearance of sputum in the higher mammals, the fusion of sputum, the development of the retina, and the normal development of the immune system must involve cell death. These various kinds of cell deaths that occur during the development of the body have a common feature: they are scattered, one by one, die and disappear from normal tissues, the body has no inflammatory reaction, and it is beneficial and necessary for the development of the whole body. Therefore, it is believed that the programmed cell death in animal development is a concept of development, and apoptosis is a morphological concept, describing a form of cell death that is completely different from necrosis with a complete set of morphological features. However, it is generally believed that the two concepts of apoptosis and programmed death can be used interchangeably and have equal meaning.
The difference between apoptosis and necrosis
Although the final results of apoptosis and necrosis are very similar, their processes and performance are very different.
Necrosis is the process of death in which cells undergo a strong physical or biological influence to cause disordered changes in cells. It is characterized by swelling of the cells, rupture of the cell membrane, spillage of cell contents, slow nuclear changes, insufficient DNA degradation, and local severe inflammatory reactions.
Apoptosis is a physiological pathological stimulus signal of the environment to the environment, a change in environmental conditions or a death process in response to an orderly change in response to mitigation. The changes in cells and tissues are significantly different from necrosis.
1. Apoptosis initiation
2, apoptotic body formation
3. The apoptotic bodies are gradually engulfed by neighboring cells or phagocytic cells in the body, and the residual substances of the apoptotic cells are digested and reused.
Apoptotic cell disassembly
Disassembly is required before treatment of apoptotic cells. There are three recognized steps in the breakdown of apoptotic cells:
Membrane foaming: There are irregular buds on the cell membrane called blistering. Initially, these are smaller surface bubbles. Later these can grow into larger so-called dynamic bubbles. An important regulator of apoptotic cell membrane blebbing is ROCK1 (rho-associated coiled-coil kinase 1).
Formation of membrane protrusions: Under certain conditions, certain types of cells may form long and thin extensions of different types of cell membranes, called membrane protrusions. Three types have been described: microtubule spikes, apoptosis (dead foot) and bead cell apoptosis (the latter having a beaded appearance). Pannexin 1 is an important component of the cell membrane channel and is involved in the formation of apoptosis and beaded cell apoptosis.
Fragmentation: Cells divide into multiple vesicles called apoptotic bodies and undergo phagocytosis. Plasma membrane processes can help bring apoptotic bodies closer to phagocytic cells.
Figure 2. Different steps in apoptotic cell disassembly.
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