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A study on cytoskeleton

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Shaharu B.
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  1. Introduction
  2. Functions of cytoskeleton
  3. External cell movement
    1. Cellular movement
    2. Internal cell movement
  4. Cellular motors
  5. Broken motors
  6. Study of cytoskeleton
    1. The use of fluoresce microscopy
    2. The use of video microscopy
    3. The use of genetically engineered cells
  7. Cytoskeleton elements
    1. Microtubules
    2. Biochemical composition
    3. Microtubular associated proteins (maps)
    4. Microtubules-organizing centers (mtocs)
    5. Centrosome
  8. Assembly and disassembly of microtubules
  9. Microtubular organelles
  10. Functions of microtubules
  11. Microfilament assembly and disassembly
  12. Myosin: The molecular motor for acting filaments
  13. Intermediate filament assembly and disassembly
  14. Conclusion

The skeleton of the vertebrate is a familiar organ system consisting of hardened elements supporting the soft tissues of the body and play a key role in mediating bodily movements. Eukaryotic cells also posses a ?skeletal system?, which is of proteinecous network and composed of three well defined filamentous structures ? in the form of microtubules, microfilament and intermediate filaments.

The name cytoskeleton was coined many years ago, but it was abandoned because many of the structures observed in the cytoplasm with the light microscope were considered to be fixation artifacts.

In 1928, Koltzoff proposed the presence of an organized fibrous array in the structure of the protoplasm. He concluded that ?Each cell is a system of liquid components and rigid skeletons, which generate the shape, and even though we rarely see the skeletal fibrils in living and fixed cells which only means that these fibrils are very thin or that they are not distinguished by their refractive index form the surrounding colloidal solution?.

Electron micrograph has confirmed his assumption and reveals the presence of cytoskeleton fabric formed of microtubules, microfilaments and intermediate filaments. The main protein which are present in cytoskeleton are tubulin, actin, myosin, tropomyosin, keratin, vimentin, desmin, lamin and others protein.

[...] In many they maintain cell shape, a property based on the distribution and orientation of microtubules. This is specifically found in the axon and dendrites of neurons. The role of microtubules as skeleton elements is evident in certain highly elongated processes such as the axons of nerve cell and the axopods of heliozoan protests. In mature axons, these microtubules nerve as tracks for the movement of vesicles. In developing embryo, microtubules play a key role in maintaining the extended shape of the axon as it slowly goes of the CNS into the peripheral embryonic tissues. [...]


[...] In one approach, the protein subunits of cytoskeleton structure (e.g. tubulin or keratin) are made fluorescent by covalent linkage to a small fluorescent dye. Unlike other high-resolution techniques, the cell remains alive during observation. It is also useful to reveal the location within a cell of a protein present in very low concentration. II. The use of Video Microscopy: Microscope can be greatly increased using a video camera, tape recorder and television monitor. For example, Video microscopy can be used to observe the growth or shrinkage of individual microtubules as they gain or lose subunits in vivo. [...]


[...] Origin of microtubules of the cytoskeleton of a cultured animal cell can be best studied by depolymerising the microtubules with cold temperature or chemicals, such as nocodazole or colchicines. MTOCs occurs in basal bodies (of cilia and flagella) centrioles At poles of mitotic spindles In dividing cells that do not have centrioles On chromosomes In membranes and many other places. Not all the microtubules of an animal cell are associated with centrosome. The microtubules of an axon are not associated with the centrosome, which is located in the neuron's cell body. [...]

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