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Understanding Ionizing Radiation: Its Effects on Human Cells and the Mechanisms of Biologic Damage

This chapter delves into the intricate relationship between ionizing radiation and the human body, focusing on biologic damage caused by different types of radiation including X-rays, gamma rays, and high-energy particles. Key concepts such as Linear Energy Transfer (LET), Relative Biological Effectiveness (RBE), and Oxygen Enhancement Ratio (OER) are explored. The interaction of radiation with cellular structures, particularly DNA, leads to various forms of damage, including single and double strand breaks, mutations, and chromosomal anomalies. Understanding these effects is crucial for evaluating radiation risk in medical and environmental contexts.

walter-trevino
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Understanding Ionizing Radiation: Its Effects on Human Cells and the Mechanisms of Biologic Damage

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  1. CHAPTER 6 Molecular and Cellular Radiation biology Ionizing Radiation and the Human body

  2. Biologic damage • From x-rays, gamma, or high energy particulate radiation • ALPHA, BETA • Alpha=two protons and two neutrons attracts negatively charged electrons • Ionized atoms will not bond properly in molecules

  3. Biologic Damage and relationship to • LET • RBE • OER

  4. Low LET VS High LET • X-ray/gamma rays • Streams of particles with no mass or charge • Penetrating • Sparsely ionizing • Interacts randomly • Damage via indirect action • Sublethal damage • Particles of mass and charge • Alpha, neutrons • What other characteristics?

  5. LET RBE • 250 kVp of known radiation (usually x-ray) over dose of test radiation=biologic effect (Box 5-2) • Used in animals • Weighting factor of radiation used to determine biologic damage • Low • Risk of damage to DNA/Probability of interaction with DNA • What radiations are considered low LET? • High • Risk of damage to DNA/ DNA/Probability of interaction with DNA • Internal contamination • What radiations are considered high LET?

  6. OER • DOSE REQUIRED TO PRODUCE AN EFFECT IN AN OXYGEN DEPRIVED ENVIRONMENT VS A NORMAL OXYGEN ENVIRONMENT • OER IS HIGH FOR LOW LET • THE OPPOSITE FOR HIGH LET • THE DIFFERENCE IS DUE TO DIRECT AND INDIRECT EFFECT

  7. DIRECT EFFECT INDIRECT EFFECT BOTTOM LINE…..IF IONIZATION FROM EITHER EFFECTS DISTURBS THE CHEMICAL BALANCE OF THE CELL, THE CELLULAR ACTIVITY BECOMES ABNORMAL OR THE CELL CAN EVEN CEASE TO FUNCTION

  8. DIRECT INDIRECT • INTERACTS WITH WATER • OCCURS MORE OFTEN WITH LOW LET • RADIOLYSIS OF WATER/FREE RADICALS • IMPACTS THE DNA • OCCURS MORE OFTEN WITH HIGH LET

  9. SINGLE STRAND BREAK figure 6.6 • DOUBLE STRAND BREAK figure 6-7/IN SAME RUNG figure 6-8 • MUTATION figure 6-9 • COVALENT CROSS LINKS figure 6-10 • CHROMOSOME BREAKS • CHROMOSOMAL FRAGMENTS • CHROMOSOME ANOMALIES • Structural changes

  10. MALIGNANT CELLS • HIGHLY MITOTITIC • ABNORMALLY DIVIDE • LARGE NUCLEUS • Relate this to Bergonie and Tribondeau (pg 102) and direct/indirect effects

  11. TARGET THEORY THE MASTER MOLECULE PG 125

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