MECHANISMS OF NEURONAL CELL-DEATH

Apoptosis is a mechanism of cell death that plays a fundamental role d uring the development of many tissues, including the central nervous s ystem. Apoptosis has traditionally been distinguished in developing ti ssues on the basis of specific morphological criteria, including perin uclear chromatin condensation, cell shrinkage, and endonuclease-mediat ed internucleosomal DNA fragmentation into a ''ladder'' pattern. More recently, the term ''apoptosis'' has been used to describe the prog ra mm ed biochemical pathways of ce I I death that accompany development , tissue injury, and degeneration. In the context of this review, apop tosis will refer to the biochemical pathways of cell death. There is a ccumulating evidence that acutely injured and degenerating neurons may die by a process of apoptosis, contributing to the loss of neurons ob served under these conditions. The possibility that neurons may succum b under some circumstances by an active mechanism of cell death has ra ised interest in the regulatory pathways governing these processes. In this review, we examine recent evidence pertaining to the presence an d activation of these regulatory pathways in nervous system injury and degeneration. (C) 1998 Wiley-Liss, Inc.