Techniques for Distinguishing Apoptosis from Necrosis in Cerebrocortical and Cerebellar Neurons

Apoptosis is a form of regulated cell death, characterized by a series of morphological alterations including cell shrinkage, chromatin condensation, pyknosis of the nucleus, and multistep chromatin degradation (see references in Bonfoco et al., 1995 and in Ankarcrona et al., 1995). The latter includes the cleavage of DNA into high (700–50 kbp) and low (oligonucleosomal) fragments. Despite the exponential growth of research on apoptosis during the past few years, the detection of this form of cell death both in vitro and in vivo has primarily relied on morphological criteria. Thus, electron and light microscopy have been the techniques of choice to identify apoptotic cells. Nevertheless, detection of apoptosis based on purely morphological criteria has some limitations. It cannot be utilized to efficiently screen large numbers of samples. Further, it is becoming increasingly clear that different cell types may adopt different morphological patterns of involution, and even the same cell type may vary in appearance in response to disparate apoptotic stimuli. For example, the morphological appearance of immature T-lymphocytes undergoing apoptosis after treatment with dexamethasone differs from that of T-cells killed by FAS/APO1.