Apoptosis Apoptotic bodies

Figure 20.34 A simple representation of the processes of necrosis and apoptosis leading to the death of cells. Necrosis is initiated by a decrease In the ATP/ADP concentration ratio, which slows ion pumps, which leads to cation imbalance (e.g. ca ion entry into the cytosol) and hence intracellular damage, entry of water and lysis which can lead to local inflammation. Apoptosis is initiated by specific extracellular or intracellular factors, which lead to cell shrinkage and disruption into apoptotic bodies which are removed by phagocytes.

Fig. 15.1. Schematic representation of morphologic changes in a cell during apoptosis. On reception of an apoptotic signal, an adhesive cell (a) begins to become rounded (b) and the nuclear DNA condenses (c). The DNA is fragmented and the nucleus begins to break down into discrete chromatin bodies (d). Finally, the cell disintegrates into several vesicles (apoptotic bodies) (e), which are phagocytozed by neighboring cells (f).

Further study demonstrated that THS significantly inhibited hepatic DNA fragmentation, the emergence of apoptotic bodies and chromatin condensation in D-GalN/LPS-induced liver injury in mice. The extent of the inhibitory effect of THS on hepatocyte apoptosis at 5 hr paralleled that on serum ALT elevation at 8 hr [87]. As mentioned above, in this model, a large number of hepatocytes undergoing apoptotic cell death can... 

In contrast to cell necrosis, apoptosis is a process by which cells are systematically destroyed and removed. The nuclear body and organelles within the cell become enclosed in a membrane to form residues called apoptotic bodies. These are then said to be phagocytosed as they are enclosed within membranes and actively removed from the site of the injury. Apoptosis is an active process for eliminating dead cellular material. 

Translocation of the phosphatidylserine from the inner to the outer leaflet of the plasma membrane is an initial event related to the apoptotic process and possibly serves as a signal for the removal of apoptotic bodies by phagocytic cells (Martin et al., 1995). The exposure of this phospholipid has been largely used as a specific apoptosis marker. 

Apoptotic features have been occasionally found in other cardiac disorders in humans [128-131] and experimental models [107, 132-135]. Takemura et al. [135] studied Fas-induced cardiomyocyte apoptosis by electron microscopy, and found extensive condensation of nuclear chromatin and shriveled cytoplasm, fragmented nuclei, and apoptotic bodies. Apoptotic features correlated with positivity for TUNEL and caspase-3. A distinct morphological feature was the abundance of lipid-like structures in the cytoplasm at the early phase and high incidence of plasma membrane rupture at the later phase. Apoptotic bodies were observed to be phagocytosed by neighboring cardiomyocytes. 

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