Apoptosis morphological features

Annexin V PT UOS staining is another procedure which allows to label the cells by allowing the observation of the morphological features of apoptosis. 

Although taxanes bind to p-tubulin promoting microtubule polymerization and stabilization of the spindle complex, they serve to cause a sustained mitotic block at the metaphase/anaphase boundary. This block will occur at a lower concentration than that which is required to increase the microtubule mass (10). However, it is not completely clear how this interaction with microtubules translates into cell death. Morphologic features and the characteristic DNA fragmentation patterns seen in the setting of apoptosis have been documented in tumor cells after therapy with taxanes (10). These observations are accompanied by the phosphorylation of Bcl-2, an anti-apoptotic protein, changing the cellular balance between Bax and Bcl-2 to a status that favors apoptosis (11). 

Morphological features of apoptosis following retinal ischemia, such as DNA fragmentation, nuclear condensation, and chromatin marginalization have been... 

When AIF and endonuclease G are released into the cytoplasm, they directly translocate to the nucleus and induce DNA fragmentation and subsequent chromosomal condensation, a remarkable morphological feature of the apoptotic process. AIF induces chromatin digestion into large fragments of approximately 50 kb, probably by activating a nuclear DNAse. Therefore, these proteins are important for the caspase-indepen-dent apoptosis pathway. 

Despite extensive research, identification of apoptotic cells remains an important unresolved issue. Apoptosis can be recognized by characteristic morphological features, which are difficult to be found in the heart. Furthermore, morphology alone does not enable recognition of cells early in the apoptotic pathway. Detection of activated caspases appears to be a reasonable way to detect apoptotic cells, given the central role of caspases in the process of apoptosis. It must be kept in mind, however, that caspases may contribute to necrotic cell death [80, 81] and caspase-independent apoptosis does occur [80]. 

Immunohistochemistry, on the other hand, enables identification of activated caspases or their cleaved products in fixed archival tissue sections. This technique allows identification of cell(s) undergoing caspase activation, as well as analysis of the distribution of cell(s) in the tissue. Specific antibodies to various caspases are now commercially available, the most frequently studied being caspase-3. Studies in various human tissues and cells have shown that immunohistochemical detection of activated caspase-3 is a useful tool for identifying apoptotic cells in archival material, even before all of the morphological features of apoptosis occur [84-86]. Several target proteins cleaved by caspases can also be detected by immunohistochemistry for example PARP [87], actin [88, 89], and lamin B [90]. 

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. 

Using conventional histology, it is not always easy to distinguish apoptosis from necrosis they can occur simultaneously, depending on the intensity and duration of the stimulus, the extent of ATP depletion, and so on. Table 16.2 compares some of the major morphological features of apoptosis and necrosis. 

TABLE 16.2. Comparison of Morphological Features of Apoptosis and Necrosis... 

Ueda N, Walker P, Flsu S, Shah SV. Activation of a 15-kDa endonuclease in hypoxia/reoxygenation injury without morphologic features of apoptosis. Proc Natl Acad Sci USA 1995 92 7202-7206. 

Biochemical and morphological features of cell death during apoptosis and necrosis... 

Although the morphologic features of apoptosis are the gold standard for definitive identification of apoptotic cells, there are often limitations to the... 

Furuya, T., Kamada, T Murakami, T Kurose. A., and Sasaki, K. (1997) Laser scanning cytometry allows detection of cell death with morphological features of apoptosis in cells stained with PI. Cytometry 29, 173-177. 

Accurately applied, apoptosis is therefore a descriptive term which refers to a widely occurring phenomenon of cell death, characterized by a distinct set of morphological features. These are ... 

It is clear that the effector pathways leading to apoptosis can differ between cells and even within cells when triggered by different stimuli. What is not clear at present is whether these eventually converge into one common pathway. The fact that the morphological features of apoptosis are similar in a wide variety of cases suggests that the down-... 

Cohen GM, Sim X-M, Snowden RT, Disndale D, Skilleter DN Key morphological features of apoptosis may occur in the absence of DNA fragmentation. Biochem J 1992 286 331-334. 

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