Pyknosis

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Pyknosis is a term used in cell biology to describe the irreversible condensation of chromatin in the nucleus of a cell undergoing apoptosis or necrosis. This process is a hallmark of cell death and is often observed in cells that are no longer viable.

Characteristics

During pyknosis, the chromatin condenses into a dense, compact mass. This is typically followed by the fragmentation of the nucleus, a process known as karyorrhexis. Pyknosis is one of the key morphological changes that occur during apoptosis, along with cell shrinkage, membrane blebbing, and the formation of apoptotic bodies.

Causes

Pyknosis can be triggered by various factors, including:

• DNA damage
• Oxidative stress
• Hypoxia
• Toxins
• Infection

Detection

Pyknosis can be detected using various staining techniques in histology, such as H&E staining. Under a microscope, pyknotic nuclei appear as small, darkly stained masses within the cell.

Significance

The presence of pyknotic nuclei is an important indicator of cell death and is used in both clinical pathology and research to assess the extent of tissue damage or the effectiveness of therapeutic interventions.

Related Processes

• Apoptosis
• Necrosis
• Karyorrhexis
• Karyolysis

See Also

• Chromatin
• Nucleus (cell)
• Cell death
• Histology