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Basic Biological Interaction of Radiation

Basic Biological Interaction of Radiation. Ling Li September, 2000. Basic Biological Interaction of Radiation. Basic interaction of radiation in cell LET and RBE Radiation effect on cell. Basic Interaction of Radiation in Cell. Indirect action Direct action. x-rays photon

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Basic Biological Interaction of Radiation

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  1. Basic Biological Interaction of Radiation Ling Li September, 2000

  2. Basic Biological Interaction of Radiation • Basic interaction of radiation in cell • LET and RBE • Radiation effect on cell

  3. Basic Interaction of Radiation in Cell • Indirect action • Direct action x-rays photon free electron ion radicals free radicals chemical change from the breakage of bonds biological effects

  4. LET & RBE • LET • RBE Definition Factors that determine RBE Radiation dose Number of dose fractions Biological system or endpoint Radiation quality (LET) Dose rate

  5. Definition of RBE RBE is defined as the comparison of a dose of test radiation to the dose of 250 keV x-ray that produce the same biologic response. dose in Gy from 250 keV x-ray REB= dose in Gy from another radiation delivered under the condition that produces the same biologic effect

  6. Radiation dose Number of dose fractions

  7. Biological system on RBE 1. Mouse bone marrow 2. Ly.leuk.mouse L5178Y 3. Tissue cultured cell of human kidney origin 4. Rat rhabdomyosarcoma cells 5. Mouse crypt cells

  8. Radiation quality

  9. Radiation effect on cells • Radiation effect on DNA • Radiation effect on chromosomes • Radiation effect on other cellular constituents

  10. Radiationeffecton DNA • Base damage • Single-strand breaks (ssb) • Double-strand breaks (dsb) • Crosslinks

  11. Radiation effect on DNA

  12. Dsb and mammalian cell death • Dsb in Dna are the most common type of radiation lesions that lead to mammalian cell death • Dsb rejoining

  13. Radiation effects on chromosomes • General chromosomes effects • Structure changes • Changes in the sequence of genetic information: translocations and inversions

  14. General chromosome effects • The over all result: breakage of the chromosome, producing chromosomal fragments • Gross structure change: aberrations Chromosome aberration Chromatid aberration • Consequence to cell of the structure change Restitution Deletion Distorted chromosome: ring, dicentric, anaphase bridge Mutation

  15. Chromosome Structure Changes • Acentric fragments and dicentric rings • Ring chromosomes • Chromosome stickness

  16. Acentric fragments and dicentric rings

  17. Ring chromosomes

  18. Changes in the Sequence of Genetic Information:Translocation and Inversions

  19. Upper line (from left to right) • 1 chromatid lesions • 2 chromatid breaks • 3 isochromatid fragments • Translocation • Lower line (from left to right) • 1 Dicentrics • 2 Rings • 3 Quadriradius (middle) • endoreduplication (left) • triradius (right)

  20. Radiation Effects on Other Cellular Constituents • Carbohydrates • Proteins • Lipid • Enzyme • Membrane

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