Cell Cycle - Methods to study Histology

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Cell Cycle - Methods to study Histology Powered By Docstoc
					Dr.T.Krishna MD,
www.mletips.com    1
   Cell Renewal
   Phases
   Check Points
   Regulation




                   Dr.T.Krishna MD,
                   www.mletips.com    2
   Classification of adult somatic cells ( based on mitotic activity)
    ◦ 1. Static = terminally differentiated, post mitotic cells, can’t
      divide, CNS, striated muscle (Striated and Cardiac), G ₀ phase
    ◦ 2. Stable = divide following stimulus ( injury), periosteal cells,
      SMC, EC of blood vessels
    ◦ 3. Renewing
       A) Slowly Renewing= have stem cells, hallow organs,
        fibroblasts of uterine wall
       B) Rapidly Renewing= Skin, GIT mucosa, Bone marrow




                                            Dr.T.Krishna MD,
                                            www.mletips.com                3
   Two principal phases
    ◦ Interphase (with G1, S, G2 )
    ◦ M phase (mitosis)
   Check points = control transition
    form one phase to another
   G1 phase
    ◦ Longest phase
    ◦ Begins at the end of M phase
    ◦ Two check points
        Restriction checkpoint – very important,
         mediated by Rb protein-E2F factor
        G1 DNA-damage checkpoint – p53 has
         role
   S phase
    ◦ DNA synthesis and doubling of DNA
    ◦ DNA-damage checkpoint
   G2 phase
    ◦ Cell is ready for division
   M phase
    ◦ Mitosis (Karyo & cytokinesis) takes place
    ◦ Spindle –assembly checkpoint                  Dr.T.Krishna MD,
    ◦ Chromosome-segregation checkpoint             www.mletips.com    4
   Mitotic catastrophe = failure to arrest the cell cycle
    before or at mitosis
   Result  abnormal chromosomal segregation
   Lead to aneuploidy = oncogenesis ( tumor
    formation)
   Restriction checkpoint defects
    ◦ Lead to loss of contact inhibition
    ◦ Promoted by vial proteins (SV40)
    ◦ Mesothelioma, osteosarcoma and Ependymoma




                                    Dr.T.Krishna MD,
                                    www.mletips.com          5
   Specific cytoplasmic
    proteins produced and
    degraded at specific phase
    of cell cycle
   Cyclin-Cdk complexes
   These proteins regulate cell
    cycle
   The first Cyclin produced
    is Cyclin D at G1 phase




                                   Dr.T.Krishna MD,
                                   www.mletips.com    6

				
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posted:12/26/2010
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