1 Morphological changes in apoptosis Morphological alterations of apoptotic cell death that concern both the nucleus and the cytoplasm are remarkably similar across cell types and species [11, 12]. Usually several hours are required from the initiation of cell death to the final cellular fragmentation. However, the time taken depends on the cell type, the stimulus and the apoptotic pathway [13]. Morphological hallmarks of apoptosis in the nucleus are chromatin condensation and nuclear Ro-3306 purchase fragmentation, which are accompanied by rounding up

of the cell, reduction in cellular volume (pyknosis) and retraction of pseudopodes [14]. Chromatin condensation starts at the periphery of the nuclear membrane, forming a crescent or ring-like structure. The chromatin further condenses until it breaks up inside a cell with an intact membrane, a feature described as karyorrhexis [15]. The plasma membrane is intact throughout the total process. At the later stage of apoptosis some of the morphological features include

membrane blebbing, ultrastrutural modification of cytoplasmic organelles and a Selleck Tucidinostat loss of membrane integrity [14]. Usually phagocytic cells engulf apoptotic cells before apoptotic bodies occur. This is the reason why apoptosis was discovered very late in the history of cell biology in 1972 and apoptotic bodies are seen in vitro under special conditions. If the remnants of apoptotic cells are not phagocytosed such as in the case of an artificial cell culture environment, they will undergo degradation that resembles necrosis and the

condition is termed secondary necrosis [13]. 2.2 Biochemical changes in apoptosis Broadly, three main types of biochemical changes can be observed in apoptosis: 1) activation of caspases, 2) DNA and protein breakdown and 3) membrane changes and recognition by phagocytic cells [16]. Early in Tangeritin apoptosis, there is expression of phosphatidylserine (PS) in the outer layers of the cell membrane, which has been “”flipped out”" from the inner layers. This allows early recognition of dead cells by macrophages, resulting in phagocytosis without the release of BACE inhibitor pro-inflammatory cellular components [17]. This is followed by a characteristic breakdown of DNA into large 50 to 300 kilobase pieces [18]. Later, there is internucleosomal cleavage of DNA into oligonucleosomes in multiples of 180 to 200 base pairs by endonucleases. Although this feature is characteristic of apoptosis, it is not specific as the typical DNA ladder in agarose gel electrophoresis can be seen in necrotic cells as well [19]. Another specific feature of apoptosis is the activation of a group of enzymes belonging to the cysteine protease family named caspases. The “”c”" of “”caspase”" refers to a cysteine protease, while the “”aspase”" refers to the enzyme’s unique property to cleave after aspartic acid residues [16].