Cell Death (PowerPoint)

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					Cell Death


    Hoon Lee
Cell Death

   Within each cell line, the control of cell number
    is regulated by a balance of cell proliferation
    and cell death.
   There are two principle patterns of cell death
     1. Necrosis (death by injury)

    2. Apoptosis (death by suicide)
Necrosis


   Refer to cell death in an organ or tissue.
   Caused by infarction, infectious disease,
    poisoning etc.
   Affects contiguous groups of cell.
   Usually precipitates an inflammatory response.
Cytological characteristics of
Necrosis


   Initial swelling of the cell.

   Rupture of the plasma
    membrane.

   Cytoplasm is spilled to
    the extracellular
    environment.
Types of Necrosis

   Coagulation Necrosis (seen in infarcted organs,
    e.g.myocardial infarct).

   Liquefaction Necrosis (softening of the center of an
    abscess)

   Caseous Necrosis (cheesy, crumbly appearance, e.g.
    Tuberculosis lesion in the lung)
Apoptosis

   Responsible for Programmed Cell Death
    (PCD)
   Plays an important role in multicellular
    development.
   Cause deletion of individual cells in the midst
    of others.
   No inflammatory response but rapid
    phagocytosis
Cytological characteristics of
Apoptosis

   Nucleus condensation.
   Membranes preserved.
   Fragmentation.
   phagocytosis
Examples of Programmed Cell
Death
  Phylogenic: the loss of the vertebrate tail during human
   fetal development.
 Morphogenic: the loss of mesenchyme between the
   digit.
 Histogenic: the reduction of numbers of neurons in the
   developing brain.
*(PCD occurs during embryonic development as mitosis)
 Normal maintenance.
 Suicide cell death: virtually infected cells.
Mechanism of Apoptosis

   Internal signals: Mitochondrial pathway.

   External signals: Death receptor pathway.

   Apoptosis-Inducing Factor.
Internal signals: Mitochondrial
pathway
External signals: Death receptor
pathway
Apoptosis-Inducing Factor (AIF)

   Release from the mitochondria.
   Migrates into the nucleus.
   Bind to DNA.
   Destruction of the DNA
   Cell death.

				
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