Unit 4 (Radiation Effect)

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nenyabrooke
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Unit 4 (Radiation Effect)
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2013-04-24 22:29:32
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Radiation Biology
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Unit 4: Radiation Effect on Organ Systems
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  1. results that are demonstrated in future generations of the individual exposed:
    genetic effects
  2. results that are seen in the exposed individual in his/her lifetime:
    somatic effects
  3. effects that become evident months or years after exposure:
    long term (late; delayed; latent) effects
  4. results that are evident within minutes to weeks of the exposure:
    short term (early) effects
  5. —“random in nature”
    stochastic effects
  6. odds of interaction will increase with ________ in dose:
    • increase
    • (stochastic effects)
  7. an effect that generally does not have a threshold dose:
    stochastic effect
  8. give examples of stochastic effect:
    • cancer
    • embrylogic effects (birth defects)
  9. radiation effects which increase with increase in dose:
    nonstochastic (deterministic) effects
  10. effects that usually have a threshold:
    nonstochastic (deterministic) effects
  11. give examples of nonstochastic effects:
    • skin erythema
    • cataracts
    • sterility          
    • reduced fertility
    • loss of parenchymal cells
    • organ atrophy
    • fibrosis
  12. threshold or nonthreshold:
    nonthreshold
  13. damage to chromosomes that can occur post irradiation:
    • nonthreshold
    • (stochastic)
  14. threshold or nonthreshold:
    threshold
  15. point at which a stimulus begins to produce a sensation;  lower limit of perception of a stimulus:
    threshold
  16. acute radiation symptoms do not appear at low-dose radiation exposures, giving rise to a concept known as a _______________ that is below a certain radiation dose, no acute symptoms occur.
    threshold dose
  17. the concept that any radiation dose will produce a biologic effect:
    nonthreshold relationship
  18. —no radiation dose is believed to be:
    absolutely safe
  19. —small doses of radiation delivered over a long period of time:
    chronic radiation exposure
  20. —a large dose of radiation delivered in a short period of time:
    acute radiation exposure
  21. give three examples of acute radiation exposure:
    • –atomic bombs at Nagasaki, Hiroshima, and 3-Mile Island 1954
    • –1986 Chernobyl nuclear radiation accident
    • total body irradiation with radiation therapy patients
  22. LD 50/30 signifies:
    the amount of radiation that can be lethal to 50% of the exposed population within 30 days
  23. —LD 50/60 signifies:
    the amount of radiation that can be lethal to 50% of the exposed population within 60 days
  24. methods of measuring lethality, other than LD 50/30 and LD 50/60:
    • –LD 10/30
    • LD 50/60
    • LD 100/60
  25. acute radiation induced lethality is only of academic interest in:
    • diagnostic radiology
    • (acute radiation syndrome: no recorded cases)
  26. the sequence of events after high-level radiation exposure that usually leads to death within:
    • acute radiation syndrome (ARS)
    •  within a few days or weeks of the exposure
  27. major response stages of ARS:
    • —prodromal syndrome
    • latent period
    • manifest illness
    • recovery or death
  28. “running before”
    prodromal
  29. give the exposure, symptoms, and length of the prodromal stage of ARS:
    • exposure: 50 rads & above whole body produce initial symptoms within minutes to hours of the exposure
    • symptoms: nausea, vomiting, diarrhea, and leukopenia (NVD syndrome)
    • length: few hours to 2 days
  30. give the symptom and length of the latent period of ARS:
    • during this time the subject is free of visible symptoms, but there is the beginning of recovery and death
    • length: few hours to weeks (period is shorter at  higher doses)
  31. give the symptoms and examples of the manifest illness stage of ARS:
    • this stage follows the latent period and symptoms vary according to the body system affected
    • example: the hematopoietic system is   more sensitive than the skeletal system or   CNS system. Symptoms will vary due to the   systems sensitivity to radiation exposure
  32. forms of ARS in the body:
    • —hematopoietic syndrome
    • gastrointestinal syndrome
    • central nervous syndrome
  33. give the following for hematologic syndrome:
    alternate names
    dose and survival time
    prodromal stage
    latent stage
    manifest stage
    cause of death
    • aka: bone marrow syndrome;hematopoietic syndrome
    • dose & survival time: 100-1000 rads; 200 rads may die within 6-8 weeks; 200-1000 rads will die sooner; 100-200 rads considered non-lethal and may recover within 3 weeks to 6 months post irradiation
    • prodromal: within a few hours of irradiation and may last several days
    • latent: may last up to four weeks
    • manifest: severe NVD; decrease in RBC, WBC, and platelets in the circulating blood, hemorrhage, infection
    • cause of death: generalized infection, electrolyte imbalance, dehydration
  34. give the following for gastrointestinal syndrome:
    survival time
    prodromal stage
    latent stage
    manifest stage
    cause of death
    • survival time: with doses of 600-1000 rads may die within 3-10 days
    • prodromal: severe nausea, vomiting, and diarrhea for as long as 24 hours
    • latent: 5 days
    • manifest: severe nausea, vomiting, may induce fever, fatigue, loss of appetite, lethargy, anemia, leukopenia, hemorrhage, infection, electrolyte imbalance, and emaciation
    • cause of death: damage to cells lining the GI tract; these crypt cells are very sensitive to radiation because they have a high turnover rate of 3-5 days
  35. give the following for central nervous syndrome:
    dose and survival
    prodromal stage
    latent stage
    manifest stage
    cause of death
    • dose & survival: above 5000 rads; 3-5 days
    • prodromal: begins within minutes of exposure and may include confusion and nervousness
    • latent: lasts up to 12 hours
    • manifest: disorientation, shock, periods of agitation alternating with stupor, ataxia, edema in the cranial vault, loss of equilibrium, fatigue, lethargy, convulsive seizures, electrolyte imbalance, meningitis, prostration, respiratory distress, vasculitis, and coma
    • cause of death: unknown, thought to be due to increased intracranial pressure
  36. effects that appear months or years after exposure to ionizing radiation:
    late somatic effects
  37. effects that can be directly related to the dose received and occur months to years after exposure to high-level radiation:
    late nonstochastic (deterministic) somatic effects
  38. effects that do not have a threshold, are unpredictable, and do not increase with severity when dose increases, with results that occur months or years after exposure to high-level or low-level radiation exposure:
    late stochastic (probabilistic) somatic effects
  39. three major types of late somatic effects:
    • carcinogenesis
    • cataractogenesis
    • embryologic effects (birth defects)
  40. how is the risk measurable for carcinogenesis, for both high doses and low doses?
    • at high doses, like that seen in atomic bomb survivors, the risk is measurable in human populations
    • at low doses, like that seen in occupational exposure or diagnostic studies, the risk is not directly measurable in population studies (risk is overshadowed by the naturally occurring cancers)
  41. in carcinogenesis, predicts that a specific number of excess cancers will occur as a result of exposure:
    absolute risk model
  42. in carcinogenesis, predicts that the number of excess cancers will increase as the natural incidence of cancer increases with advancing age in a population:
    relative risk model
  43. absolute or relative risk model:
    absolute risk model
  44. absolute or relative risk model:
    relative risk model
  45. list seven examples of human evidence of radiation carcinogenesis:
    • radium watch dial painters (1920s-1930s)
    • uranium miners (1950s-1960s)
    • early medical radiation workers (1896-1910)
    • patients injected with thorotrast (1925-1945)
    • infants irradiated for large thymus glands(1954)
    • japanese atomic bomb survivors (1945)
    • evacuees of Chernobyl nuclear power disaster (1986)
  46. describe the chemicals and reactions involved with the watch dial painters from the 1920s:
    • paint consisted of zinc sulfide (ZnS) mixed with radium (226Ra)
    • radium is an alpha-particle emitter that is chemically similar to calcium, and is therefore a 'bone seeker' 
    • 226Ra that accumulated in the bone marrow irradiated nearby tissue, and produced bone cancer and other genetic damage
  47. who's death caused the medical community to seriously consider the idea that xrays could prove fatal?
    • thomas edison's assistant, clarence dally, who died in 1904
    • after documentation of his struggle with burns, serial amputations, and extensive lymph node involvement
  48. in the bombing of nagasaki and hiroshima, what was one of the important clues for establishing the location of the epicenter:
    —the shadows of the parapets were imprinted on the road surface of the Yorozuyo Bridge, 1/2 a mile south-south-west of the hypocenter
  49. the chance a single dose of __________ will induce the formation of cataracts is high.
    200 rads
  50. a neutron dose as low as _______ has been known to cause cataracts in mice.
    1 rad
  51. name two examples of those who are among small groups who unknowingly received high doses of radiation exposure:
    • physicist who worked on the cyclotron
    • japanese atomic bomb survivors
  52. name the three embryologic stages and their lengths:
    • preimplantation: 0-9 days after conception
    • organogenesis: 10 days to 6 weeks (after conception)
    • fetal: 6 weeks (after conception) to term
  53. describe the effects of radiation in the different embryologic stages:
    • first eight weeks: equivalent doses in excess of 20 rem frequently results in death
    • preimplantation: 5 to 15 rads can cause embryonic death
    • organogenesis: very susceptible to radiation-induced congenital abnormalities
    • third trimester: fetus less sensitive to radiation, but this later stage can still experience congenital abnormalities and functional disorders such as sterility
  54. most radiologic procedures performed during pregnancy result in an equivalent dose of ___________.
    • only 1 rem
    • not considered dangerous to the unborn
  55. —biologic effects of ionizing radiation on future generations:
    "genetic effects"
  56. how is the damage of genetic effects brought on and what does it allow?
    • brought on by damage to the DNA in the sperm or ova
    • allows for faulty genetic information to be carried on to the offspring.
  57. genetic effects that occur spontaneously with no known cause:
    natural spontaneous mutations
  58. conditions that can be caused from natural spontaneous mutations:
    • hemophilia
    • huntington's chorea
    • down's syndrome (mongolism)
    • duchenne's muscular dystrophy
    • sickle cell anemia
    • cystic fibrosis
    • hydrocephalus
  59. ________ of all births in the U.S. have a genetic disorder.
    10%
  60. mutagens responsible for genetic mutations:
    • elevated temperature
    • ionizing radiation
    • viruses
    • chemicals
  61. what happens with —radiation interaction with DNA macromolecules?
    after radiation interacts with DNA, the molecules can experience chromosomal breakage or change in the amount of DNA belonging to the cell or an alteration in the sequence of nitrogenous bases.  All of which can lead to genetic mutations in subsequent generations
  62. what happens with —cellular damage repair by enzymes?
    • if the enzymes are able to repair, the cells function as normal
    • if the enzymes are unable to repair, the cells may suffer functional impairment or die
  63. ______________ cannot govern the cell’s normal chemical reactions or properly control the sequence of amino acids in the formation of specific proteins.
    mutant genes
  64. arises from the defective synthesis of the protein hemoglobin:
    sickle cell anemia
  65. a condition caused by the omission of only one vital amino acid:
    sickle-cell anemia
  66. genetic mutations at the molecular level that may be either dominant (probably expressed in off-spring) or recessive (probably not expressed for several generations):
    points mutations
  67. radiation is thought to cause ____________ mutations, if any.
    recessive
  68. what must happen for a recessive mutation to appear in the off-spring?
    both parents must have the same genetic defect
  69. recessive point mutations appear as:
    • –allergies
    • slight alteration in metabolism
    • decreased intelligence
    • predisposition of certain diseases
  70. with the increase of radiation exposure to patients, the chance of two people carrying out a recessive point mutation:
    may be rising
  71. experiments studying ionizing radiation as a cause of genetic effects come from studies of:
    fruit flies and mice
  72. experiments ionizing radiation as a cause of genetic effects have determined that:
    • genetic effects do not have a threshold
    • implies no such thing as a safe dose of radiation
  73. what do we know about radiation-induced genetic effects in humans?
    • the information is contradictory and inconclusive
    • test groups include children conceived after exposure at Nagasaki and Hiroshima.  As of third generation, no radiation-induced genetic effects are known
    • Crow, a geneticist, states genetic induced effects may include higher embryonic death, shorter life-span, increase in disease and decreased fertility
  74. the idea that the radiation dose that causes the number of spontaneous mutations occurring in a given generation to increase to two times their original number:
    doubling dose concept
  75. nagasaki and hiroshima atomic bomb survivors' mean value is ________ based on the genetic indicators of untoward pregnancy outcome.
    • 156 rem
    • (–stillbirths, childhood mortality, sex chromosome aneuploidy)

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