Apoptosis Research Tools Caspase Inhibitors Caspase Activity Assays Mitochondrial  Permeability Assays CytoGlo Annexin V-FITC Apoptosis Kit Serine Protease Activity Assays

Cell death is a fundamental aspect of the life cycle of the eukaryotic cell. Homeostasis implies a balance between cell proliferation and cell death, and this balance is essential for the development and maintenance of multicellular organisms. Dysregulation of either cell death or proliferation leads to a wide range of pathologies including cancer, neurodegenerative disease, and aberrant embryogenesis. During the 1990’s research in the field of cell death grew exponentially, and fundamental aspects regarding the molecular nature and physiological regulation of the dying process were elucidated. By the end of the decade, it was recognized that cell death occurs through a network of mechanisms. These mechanisms act in series or in parallel, each of which can be variably expressed in different eukaryotic species and within the same species, among distinct cell types. By the early 2000’s assays to analyze cell death had become essential research and diagnostics tools in laboratories worldwide.

Apoptosis Concepts and Cell Death Assays
The main goal of the cell death field is to determine the mechanisms and regulation of cell death, whether it occurs in prokaryotes, eukaryotes, single celled or multicellular organisms, animals or plants. Traditionally, many cell death assays have been referred to as apoptosis assays. However, apoptosis was originally defined purely on morphological terms in a now classic paper by Kerr et al. in 1972 to designate a morphologically distinct form of cell death associated with normal physiology. Apoptosis was distinguished from necrosis, which is associated with acute injury to cells. Apoptosis is characterized by nuclear chromatin condensation, cell shrinking, dilated endo-plasmic reticulum, and membrane blebbing.

As the cell death field matured, focus shifted away from describing the morphological aspects of cell death to assessing the underlying biology. As a result, today’s assay methodologies are based on detecting specific biological aspects of the cell death process including caspase activation, protein cleavage, mitochondrial functioning, loss of phospholipid membrane asymmetry, and DNA fragmentation.

Many different models of cell death have emerged including necrosis, apoptosis, anoikis, caspase-independent apoptosis, autophagy, endoplasmic reticulum stress, Wallerian degeneration, excitotoxicity, erythropoiesis, platelets, cornification and lens (reviewed in Melino et al. 2005). However, apoptosis continues to be a popular, although loosely defined term that is used differently by different investigators to measure and describe cell death. In general, anything that looks like apoptosis has been called apoptosis which has contributed to the complexity of the cell death literature (Vaux et al. 1999). Researchers should keep in mind that cell death assays detect a biological aspect or mechanism of cell death versus being exclusive to a particular type of cell death such as apoptosis or necrosis.

IMGENEX offers a wide range of products and assays for detecting and analyzing cell death. Collectively, these products encompass a variety of techniques including flow cytometry, western blot analysis, immunohistochemisty, fluorescence microscopy, and ELISA. As cell death occurs through different mechanisms, which may be present in various combinations, the Nomenclature Committee on Cell Death (NCCD) encourages investigators studying cell death to use more than one assay whenever possible (Kroemer et al. 2005).

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