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Pyknosis, or the irreversible nuclear condensation (a nuclear morphology) in a cell (generally old vertebrate leukocyte cells) is the result of a cell undergoing either apoptosis or necrosis. [3] There are two types of pyknosis: nucleolytic pyknosis and anucleolytic pyknosis.
Karyolysis (from Greek κάρυον karyon—kernel, seed, or nucleus), and λύσις lysis from λύειν lyein, "to separate") is the complete dissolution of the chromatin of a dying cell due to the enzymatic degradation by endonucleases.
During apoptosis, a cell goes through a series of steps as it eventually breaks down into apoptotic bodies, which undergo phagocytosis.In the context of karyorrhexis, these steps are, in chronological order, pyknosis (the irreversible condensation of chromatin), karyorrhexis (fragmentation of the nucleus and condensed DNA) and karyolysis (dissolution of the chromatin due to endonucleases).
The stages of cellular necrosis include pyknosis, the clumping of chromosomes and shrinking of the nucleus of the cell; karyorrhexis, the fragmentation of the nucleus and break up of the chromatin into unstructured granules; and karyolysis, the dissolution of the cell nucleus. [10]
Affected cells then proceed to blebbing, and this is followed by pyknosis, in which nuclear shrinkage transpires. [21] In the final step of this pathway cell nuclei are dissolved into the cytoplasm, which is referred to as karyolysis. [21] The second pathway is a secondary form of necrosis that is shown to occur after apoptosis and budding. [21]
From 4-24 hours coagulative necrosis begins to be seen, which is characterized by the removal of dead cardiomyocytes through heterolysis and the nucleus through karyorrhexis, karyolysis, and pyknosis. [3] On gross examination, coagulative necrosis shows darkened discoloration of the infarcted tissue.
Overview of signal transduction pathways involved in apoptosis. Cell death is the event of a biological cell ceasing to carry out its functions. This may be the result of the natural process of old cells dying and being replaced by new ones, as in programmed cell death, or may result from factors such as diseases, localized injury, or the death of the organism of which the cells are part.
The Azzopardi phenomenon, or Azzopardi effect, is the presence of DNA in necrotic venules. [1] It can occur in small cell carcinomas and in some high-grade malignant neoplasms.