Posted in Histopathology, Neuropathology, pathology

CENTRAL CHROMATOLYSIS

Central chromatolysis is a condition seen in neurons with axonal reaction.

Lets look at the details now.

  1. Axonal reaction is a change observed in the cell body during regeneration of the axon; it is best seen in anterior horn cells of the spinal cord when motor axons are cut or seriously damaged.
  2. The increase in protein synthesis that occurs in response to the injury is reflected in enlargement and rounding up of the cell body, peripheral displacement of the nucleus, enlargement of the nucleolus, and dispersion of Nissl substance from the center to the periphery of the cell (central chromatolysis).

Below is a pictorial difference between normal neurons and neurons with axonal reaction.

REVIEW QUESTIONS

1. Axonal reaction is visible in which of the which of the following regions of the central nervous system?

A. Posterior horn cells of the spinal cord

B. Anterior horn cells of the spinal cord

C. Cerebral cortex

D. Cerebellum

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Answer is B: Axonal reaction is a change observed in the cell body during regeneration of the axon; it is best seen in anterior horn cells of the spinal cord when motor axons are cut or seriously damaged

2. Dispersion of nissil substance to the periphery of a neuron is characteristic of which of the following?

A. Axonal reaction

B. Wallerian degeneration

C. Neuronal degeneration

D. Red neurons.

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Answer is A:

The process described in the question is central chromatolysis and is associated with axonal reaction.

Posted in pathology

PARTHANATOS- A form of cell death

Parthanatos is a PARP1-dependent, caspase-independent, cell-death pathway that is distinct from apoptosis, necrosis, or other known forms of cell death. 

Here are a few key points to be remembered regarding parthanatos.

  1. The parthanatos pathway is activated by DNA damage. This damage is causes the activation of PARP- 1( Poly(ADP-ribose) polymerase-1 ) enzyme which activates PAR poly(ADP-ribose).
  2. Parthanatos is a caspase-independent pathway.
  3. Unlike apoptosis, parthanatos causes large scale DNA fragmentation (apoptosis only produces small scale fragmentation).
  4. Necrosis is not a regulated pathway and does not undergo any controlled nuclear fragmentation. While parthanatos does involve loss of cell membrane integrity like necrosis, it is not accompanied by cell swelling.

REVIEW QUESTION

1.All of the following starements are true regarding parthanatos except?

A. It is a caspase dependent pathway like apoptosis

B. Significant DNA fragmentation is a striking feature of parthanatos.

C. Cellular swelling is a characteristic feature of parthanatos similar to necrosis

D. All of the above.

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Answer is B

Significant DNA fragmentation is a striking feature of parthanatos

Posted in pathology

PARAPTOSIS- A form of cell death

Paraptosis was recently described as a form of cell death characterized by extensive cytoplasmic vacuolation involving swelling of mitochondria and endoplasmic reticulum.

Paraptosis is thought to have some relationship with autophagy because of the presence of cytoplasmic vacuolation.

It is closely related to both necrosis and apoptosis.

Here are some key points to remember regarding paraptosis.

  1. CASPASE INDEPENDENT: This form of cell death was not inhibited by the caspase inhibitors but is inhibited by translation and transcription inhibitors, cycloheximide and actinomycin D, suggesting a requirement for new protein synthesis.
  2. Paraptosis has been shown to be triggered by the tumor necrosis factor (TNF) receptor family TAJ/TROY and insulin-like factor I receptor. TAJ/TROY-induced paraptotic cell death was enhanced by overexpression of programmed cell death 5 (PDCD5).
  3. Glucocorticoids were shown to induce retinal toxicity by mechanisms associated with paraptosis. Although this form of cell death has been shown to be evoked by a variety of reagents, the exact molecular mechanism is far from clear.
  4. CYTOPLASMIC VACUOLATION, as seen in paraptosis, has been shown to occur in a wide range of cell lines either spontaneously or as induced by a variety of stimuli. The extent to which a cell becomes vacuolated depends on the cell type. The process of vacuolation seems to follow a definite pattern, with the vacuole number and size increasing gradually. Cells can recover from vacuolation up to a certain threshold, beyond which they succumb to death.
  5. The most studied cytoplasmic vacuolation-induced cell death is autophagy.

REVIEW QUESTION

1. Which of the following statements is true regarding paraptosis?

A. It is unrelated to necrosis and apoptosis

B. It is a caspase dependent pathway

C. Paraptosis is known to be triggered by TGF-beta related pathways.

D. Cytoplasmic vacuolation is a key feature of paraptosis.

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ANSWER IS C:

Cytoplasmic vacuolation is key to paraptosis.

It is related to both necrosis and apoptosis. Paraptosis is known to be triggered by TNF.

Posted in pathology

Autoschizis- A form of cell death

Autoschizis- A new form of cell death, which has been shown to be triggered by oxidative stress.

Here are some key points to remember regarding autoschizis and ways to differentiate it from necrosis and apoptosis.

  1. Autoschizis differs from apoptosis and necrosis and is characterized by reduction of cytoplasm to a narrow rim around the nucleus with chromatin marginating the entire nucleus from inside.
  2. Mitochondria and other organelles aggregate around the nucleus as a consequence of cytoskeletal damage and loss of cytoplasm.
  3. Interestingly, the rough endoplasmic reticulum is preserved until the late stages of autoschizis, in which cells fragment and the nucleolus becomes condensed and breaks into smaller fragments.
  4. The nuclear envelope dissipates eventually with the remaining organelles after cell death. In this type of death, cells lose cytoplasm by self-morsellation or self-excision.
  5. Autoschizis usually affects contiguous groups of cells both in vitro and in vivo but can also occasionally affect scattered individual cells trapped in subcapsular sinuses of lymph nodes.
  6. Autoschizis can be initiated via in vivo treatment with Vitamin C (VC), synthetic Vitamin K (VK3) or, better, a combination of both.

REVIEW QUESTION

1.Which of the following is true regarding autoschizis?

A. It is similar to apoptosis

B. Only occurs in vivo

C. Can be induced in vivo via Vitamin C treatment

D. None of the above

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Answer C: Autoschizis can be induced in vivo using Vitamin C and Vitamin K.