Questions, answers and discussions regarding general pathology
HomeQ: Karyorrhexis, pyknosis & karyolysis… WHEN DOES WHAT HAPPEN?! What is associated with apoptosis (I thought pyknosis followed by karyorrhexis, but my teacher said pyknosis by definition was oncosis.), and what is oncosis?
Q: Karyorrhexis, pyknosis & karyolysis… WHEN DOES WHAT HAPPEN?! What is associated with apoptosis (I thought pyknosis followed by karyorrhexis, but my teacher said pyknosis by definition was oncosis.), and what is oncosis?
10 thoughts on “Q: Karyorrhexis, pyknosis & karyolysis… WHEN DOES WHAT HAPPEN?! What is associated with apoptosis (I thought pyknosis followed by karyorrhexis, but my teacher said pyknosis by definition was oncosis.), and what is oncosis?”
There exists some confusion in the nomenclature of cell death and disagreement on whether karyorhexis, pyknosis and karyolysis succeed eachother chronologically, or whether they can exist individually. However, the consensus seems to be that karyrrhexis follows pyknosis (see the latest (8th) edition of Robbins and Cotran’s Pathologic Basis of Diseases. Pyknosis and karyorrhexis is seen in apoptotic cells, not karyolysis. Oncosis is a word for necrosis. Actually, it means “swelling necrosis” (onkos = swelling in Greek). Pyknosis is seen both in apoptotic cells and in necrotic (oncotic) cells, which is also described in Robbins and Cotran’s textbook (8th edition, p. 14).
Oncosis =
Years ago, cell death was divided into apoptosis and necrosis. Today, however, many cell death types are recognized: Oncosis is a form of necrosis characterized by cell swelling. In general terms, one can say that oncosis and necrosis describe the same morphological type of cell death.
Karyorhexis – pyknosis – karyolysis =
Cell death is always related to a specific pathological insult and therefore each disease has its own characteristics when it comes to the order of morphological and biochemical changes. Typical nuclear morphological changes are – in the ideal world – described as pyknosis (nuclear condensation) followed by karyorhexis (nuclear fragmentation) followed by karyolysis (complete dissolution of the nuclear fragments), but you need to be aware that this will not always be the case in the real world when you focus on specific diseases. The typical pathologic insult leading to pyknosis, karyorhexis and karyolysis is ischemia in the heart and/or brain.
You might say that apoptosis is associated with pyknosis and karyorhexis. However, the classical description of nuclear fragmentation during apoptosis is crescent condensation of the nuclear chromatin beneath the nuclear membrane. Finally, it should be noted that pyknosis following e.g. ischemia in the brain is a potential reversible process as neurons with these nuclear changes are not TUNEL positive.
TUNEL (Terminal deoxynucleotidyl transferase dUTP Nicked End Labeling) is a staining method used to stain cells which contain fragmented DNA, i.e. apoptotic cells. It should be noted that even though this is an accepted method of staining apoptotic cells, some controversy as to whether TUNEL can also stain necrotic cells persists (for example: http://www.sciencedirect.com/science/article/pii/S030439409700445X).
Therefore, when Flemming states that neurons are not TUNEL positive he simply refers to the fact that they have not undergone apoptosis.
For more information on the TUNEL assay: http://en.wikipedia.org/wiki/TUNEL_assay
i want to do a research about analyzing the frequence of pyknotic cells in human bucal mucosa. but i still confuse about how to differentiate between pyknotic cells in apoptosis and necrosis. do they have different characteristic to differentiate, between ‘this pyknotic cells is because of apoptosis’ and ‘this pyknotic cells is because of necrosis’ as they have the same name ‘pyknotic’? thanks before.
You ask how to differentiate between pyknotic cells in apoptosis and necrosis. In my experience, pyknosis occurs before the cell has “decided” wether it turns into an apoptotic or necrotic process. As mentioned above, the pyknotic cells we investigated, were not TUNEL positive. When we in our previous work differentiated between nekrotic and apoptotic pathways, we combined nuclear fragmentation with the presence or absence of activated caspase 3 inside the cytosol. However this is more likely to happen, when the nucleus fragmentates. The best morphological sign of apoptosis, is clumping of nuclear chromatin on the inside of a intact nuclear membrane.
Read more in this article: http://www.ncbi.nlm.nih.gov/pubmed/15605989
i wanna ask another question, if so pyknosis happened in the term before wether it turns into an apoptotic or necrotic process, does the cell itself has ability to repair or adapt in order when pyknotic happened? if so, how? thanks again.
Ischemia in the brain can be reversible or irreversible depending on the load of damage. According to the above mentioned investigation the morphological form of pyknosis is a reversible reaction following brain ischemia and thus could be classified as a form of adaption – although this is not generally accepted or found in textbooks.
The impact of ischemic brain damage depends on the strength and duration of the ischemia when performed under strictly controlled standard physiological conditions. In this context mild reversible ischemic damage can induce tolerance or what is also known as conditioning. This means that a mild reversible ischemic insult can lead to protection of brain tissue from a later severe ischemic insult that without conditioning would be lethal to the cells. The molecular basis for this is not fully elucidated, but is hypothesized to involve bradykinin and the ATP dependent potassium pump in mitochondria.
There exists some confusion in the nomenclature of cell death and disagreement on whether karyorhexis, pyknosis and karyolysis succeed eachother chronologically, or whether they can exist individually. However, the consensus seems to be that karyrrhexis follows pyknosis (see the latest (8th) edition of Robbins and Cotran’s Pathologic Basis of Diseases. Pyknosis and karyorrhexis is seen in apoptotic cells, not karyolysis. Oncosis is a word for necrosis. Actually, it means “swelling necrosis” (onkos = swelling in Greek). Pyknosis is seen both in apoptotic cells and in necrotic (oncotic) cells, which is also described in Robbins and Cotran’s textbook (8th edition, p. 14).
Oncosis =
Years ago, cell death was divided into apoptosis and necrosis. Today, however, many cell death types are recognized: Oncosis is a form of necrosis characterized by cell swelling. In general terms, one can say that oncosis and necrosis describe the same morphological type of cell death.
Karyorhexis – pyknosis – karyolysis =
Cell death is always related to a specific pathological insult and therefore each disease has its own characteristics when it comes to the order of morphological and biochemical changes. Typical nuclear morphological changes are – in the ideal world – described as pyknosis (nuclear condensation) followed by karyorhexis (nuclear fragmentation) followed by karyolysis (complete dissolution of the nuclear fragments), but you need to be aware that this will not always be the case in the real world when you focus on specific diseases. The typical pathologic insult leading to pyknosis, karyorhexis and karyolysis is ischemia in the heart and/or brain.
You might say that apoptosis is associated with pyknosis and karyorhexis. However, the classical description of nuclear fragmentation during apoptosis is crescent condensation of the nuclear chromatin beneath the nuclear membrane. Finally, it should be noted that pyknosis following e.g. ischemia in the brain is a potential reversible process as neurons with these nuclear changes are not TUNEL positive.
What does it mean that neurons are not TUNEL positive?
TUNEL (Terminal deoxynucleotidyl transferase dUTP Nicked End Labeling) is a staining method used to stain cells which contain fragmented DNA, i.e. apoptotic cells. It should be noted that even though this is an accepted method of staining apoptotic cells, some controversy as to whether TUNEL can also stain necrotic cells persists (for example: http://www.sciencedirect.com/science/article/pii/S030439409700445X).
Therefore, when Flemming states that neurons are not TUNEL positive he simply refers to the fact that they have not undergone apoptosis.
For more information on the TUNEL assay: http://en.wikipedia.org/wiki/TUNEL_assay
i want to do a research about analyzing the frequence of pyknotic cells in human bucal mucosa. but i still confuse about how to differentiate between pyknotic cells in apoptosis and necrosis. do they have different characteristic to differentiate, between ‘this pyknotic cells is because of apoptosis’ and ‘this pyknotic cells is because of necrosis’ as they have the same name ‘pyknotic’? thanks before.
Dear Intan
You ask how to differentiate between pyknotic cells in apoptosis and necrosis. In my experience, pyknosis occurs before the cell has “decided” wether it turns into an apoptotic or necrotic process. As mentioned above, the pyknotic cells we investigated, were not TUNEL positive. When we in our previous work differentiated between nekrotic and apoptotic pathways, we combined nuclear fragmentation with the presence or absence of activated caspase 3 inside the cytosol. However this is more likely to happen, when the nucleus fragmentates. The best morphological sign of apoptosis, is clumping of nuclear chromatin on the inside of a intact nuclear membrane.
Read more in this article:
http://www.ncbi.nlm.nih.gov/pubmed/15605989
Best wishes FF
i wanna ask another question, if so pyknosis happened in the term before wether it turns into an apoptotic or necrotic process, does the cell itself has ability to repair or adapt in order when pyknotic happened? if so, how? thanks again.
the information which you are giving is very interesting.how is the ischemia of brain is reversible?please mention the adaptations.
Ischemia in the brain can be reversible or irreversible depending on the load of damage. According to the above mentioned investigation the morphological form of pyknosis is a reversible reaction following brain ischemia and thus could be classified as a form of adaption – although this is not generally accepted or found in textbooks.
The impact of ischemic brain damage depends on the strength and duration of the ischemia when performed under strictly controlled standard physiological conditions. In this context mild reversible ischemic damage can induce tolerance or what is also known as conditioning. This means that a mild reversible ischemic insult can lead to protection of brain tissue from a later severe ischemic insult that without conditioning would be lethal to the cells. The molecular basis for this is not fully elucidated, but is hypothesized to involve bradykinin and the ATP dependent potassium pump in mitochondria.
What’s the main difference between necrosis and apoptosis. Both are cell death but how we are recogniz that these are the necrosis or apoptosis.