Unit 3 (Cell Response to Radiation)

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nenyabrooke
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204159
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Unit 3 (Cell Response to Radiation)
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2013-03-03 19:30:23
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Radiation Biology
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Unit 3: Cell and Tissue Response to Radiation (Chapter 6)
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  1. A(n) ____________ cell is one that is specialized functionally and/or morphologically (structurally).
    differentiated/mature (end cell in a population)
  2. A(n) _______________ cell is not specialized whose primary function is to divide.
    undifferentiated/immature
  3. name the three main categories of cells:
    • stem cells (precursor cells)
    • transit cells
    • static cells (mature)
  4. what are the two main reasons that a stem cell's primary purpose is to divide?
    • first to maintain its own population
    • to produce cells for another population
  5. are stem cells differentiated or undifferentiated?
    undifferentiated
  6. name four examples of stem cells:
    • basal cells of epidermis
    • myleoblast of bone marrow
    • osteoblast in the bone
    • intestinal crypt cells
  7. cells that are on their way from the stem cell compartment to the mature cell compartment:
    transit cells
  8. give an example of a static cell:
    nerve cell
  9. list the 5 cell populations (defined by Rubin and Casarett):
    • 1 - Vegetative Intermitotic Cells (VIM)
    • 2 - Differentiating Intermitotic Cells (DIM)
    • 3 - Multipotential Connective Cells
    • 4 - Reverting Postmitotic Cells (RPM)
    • 5 - Fixed Postmitotic Cells (FPM)
  10. in the 5 cell populations, which is the least mature, and which is the most mature?
    • least: vegetative intermitotic cells - VIM (1)
    • most: fixed postmitotic cells - FPM (5)
    • from least to most, moving from 1 to 5
  11. a category of rapidly dividing undifferentiated cells that have a short lifetime:
    • vegetative intermitotic cells (VIM)
    • most radiosensitive
  12. name examples of vegetative intermitotic cells (VIM):
    • basal cells
    • crypt cells
    • type A spermatogonia cells
    • erythroblasts
  13. a category of cells that are produced by the division of VIM cells and are actively mitotic but more differentiated than VIM cells:
    • differentiating intermitotic cells (DIM)
    • more radioresistant than VIM
  14. name examples of differentiating intermitotic cells (DIM):
    intermediate and type B spermatogonia
  15. a category of cells that divide irregularly and are more differentiated than DIM cells:
    • multipotential connective cells
    • more radioresistant than DIM
  16. name examples of multipotential connective cells:
    • endothelial cells (line blood vessels)
    • fibroblasts (connective tissue)
  17. a category of cells that do not normally divide yet retain the ability to divide under certain circumstances, are more differentiated than previous categories, and are usually long lived:
    • reverting postmitotic cells (RPM)
    • more radioresistant than previous categories, except for lymphocytes
  18. what is noteworthy about lymphocytes' radiosensitivity?
    even though lymphocytes are very mature, they are still very sensitive (also, bone marrow)
  19. name examples of reverting postmitotic cells (RPM):
    • liver cells
    • mature lymphocytes
  20. a category of cells that do not divide and are highly differentiated, and some have long lives while others are short lived:
    • fixed postmitotic cells (FPM)
    • most radioresistant
  21. name examples of fixed postmitotic cells (FPM):
    • nerve cells
    • muscle cells
    • erythrocytes (RBC)
    • spermatozoa
  22. name six types of cell damage:
    • reproductive death
    • interphase death
    • mitotic/genetic death
    • mitotic delay
    • interference of function
    • chromosomal breakage
  23. a type of cell damage in which the cell permanently loses its ability to reproduce but the cell lives, continues to metabolize and
    synthesize nucleic acids & protein:
    reproductive death
  24. what dose range can cause reproductive death?
    • moderate doses
    • 100 to 1000 rads
    • 1 to 10 Gy
  25. what dose of radiation may commonly cause temporary sterility?
    200 rads
  26. a type of cell damage that occurs when a cell that has been irradiated dies without attempting division:
    interphase death
  27. give two alternate names for interphase death:
    • nonmitotic death
    • nondivision death
  28. what dose range can cause interphase death?
    • subjective
    • radiosensitivity of the individual cell governs the dose required
    • the more radiosensitive the cell, the smaller the dose required to cause death during interphase
  29. give various examples of interphase death occurances:
    • very sensitive cells (lymphocytes or spermatogonia): few hundred centigray (rad)
    • less radiosensitive cells (bone): average of several thousand centigray (rad). 
    • hemopoetic system would require a lower dose  than central nervous system cells
  30. a type of cell damage in which ionizing
    radiation can affect cell division adversely by retarding the mitotic process or permanently inhibiting it:
    • mitotic/genetic death
    • cell death can occur after permanent inhibition
  31. a type of cell damage that occurs when a cell dies after one or more divisions and can be caused by even small doses of radiation:
    mitotic/genetic death
  32. what dose range can cause mitotic/genetic death?
    less than the dose needed to produce interphase death in slowly dividing cells or in non-dividing cells
  33. a type of cell damage in which —the failure of the cell to start dividing on time occurs:
    mitotic delay
  34. what dose range can cause mitotic delay?
    as little as 0.01 Gy (1 rad) of ionizing radiation just before it begins dividing
  35. what usually occurs after mitotic delay?
    the cell resumes its normal mitotic function
  36. a type of cell damage in which permanent or temporary interference of cellular function, independent of the cell's ability to divide, can occur as a result of exposure to ionizing radiation:
    interference of function
  37. what can allow the cell to recover and continue to function after the interference of function due to radiation?
    if repair enzymes can fix the damage
  38. a type of cell damage that occurs when ionizing radiation interacts directly with many DNA molecules or free radicals interact with DNA with many DNA molecules:
    chromosome breakage
  39. when ionizing radiation interacts with many DNA molecules:
    direct effect (chromosome breakage)
  40. when free radicals interact with DNA with many DNA molecules:
    indirect effect (chromosome breakage)
  41. since chromosome breakage may result in a loss of genetic material this can lead to:
    genetic mutations in future generations
  42. the study of the genetics of cells, in particular cell chromosomes:
    cytogenetics
  43. concerning chromosomal breaks, when
    damage to DNA is severe (breakage of many bonds and strands), the chromosome
    may be:
    fragmented
  44. according to the target theory, for a cell to die following radiation exposure, its target molecule(s), ______, must be ___________.
    • DNA
    • inactivated
  45. in addition to radiation, the target theory can be employed equally well to describe:
    non-lethal radiation induced cell abnormalities
  46. there is no ___________ of radiation to the target molecule.
    favoritism
  47. —a method of displaying the radiation sensitivity of a particular cell type:
    cell survival curve
  48. in glassware or an artificial environment; outside the living body:
    in vitro
  49. in the living body:
    in vivo
  50. cell survival curves are plotted __________.
    in vitro
  51. a single-target, single-hit applies to:
    • enzymes
    • viruses
    • bacteria
    • other simple cells
  52. multi-target,  single-hit applies to:
    • human cells
    • mammalian cells
  53. name and label the graph:
    • typical survival curve for a mammalian cell
    • A. the surviving fraction (Y-axis)
    • B. the dose (X-axis)
    • C. extrapolation number (n)
    • D. the shoulder region (Dq)
  54. the radiation dose sufficient to kill 63% of the cells:
    D37 (with 37% surviving)
  55. according to ___________________, D37 would kill 100% of cells if there were no wasted hits (single target).
    the poison distribution law
  56. the width of the shoulder region of a cell survival curve:
    quasi-threshold dose (Dq)
  57. determined by calculation of the linear portion of the curve back to its intersection with the y axis:
    extrapolation number (n)
  58. the dose required to reduce cells surviving to
    37% on the multi-target, single hit model:
    • D0
    • an expression of radiosensitivity
    • mean lethal dose
  59. the lower the D0 the ______ radiosensitive the cell.
    more
  60. what is happening in this graph?
    • a cell survival curve showing the difference when a radiation protector (like steroids) is introduced
    • steroids decrease sensitivity, so more dose is needed to cause the same amount of damage as the curve without the drug
    • (crypt cells)
  61. what is happening in this graph?
    • a cell survival curve showing the differences in sensitivity when dealing with various types of cells
    • ex. thyroid can tolerate more radiation before cell death than mammary cells
  62. what is happening in these graphs?
    they are showing that with an increase in oxygen in a cell (aerated), sensitivity to radiation increases
  63. what is happening in this graph?
    • comparison of cell sensitivity at various dose rates
    • this graph is demonstrating that a higher absorbed dose at a higher rate will result in a decrease of cell survival
    • it also demonstrates that a higher absorbed dose at a lower rate will result in an increase of cell survival
    • fractionation to radiation helps in tolerating more radiation
  64. what is happening in these graphs?
    • the graph on the left is from low LET radiation
    • the graph on the right is from high LET radiation
  65. what is happening in this graph?
    this graph is showing that as the LET increases, the RBE increases
  66. if the curves represent high LET and low LET radiations, which is low LET?
    curve B
  67. if the curves represent different concentrations of oxygen, which curve is oxygenated?
    curve A
  68. what type of graph is this?
    single target, single hit cell survival
  69. if the curves represent different cell types, which is the most radioresistant?
    curve D
  70. name three types of factors affecting radiation response:
    • physical factors
    • biologic factors
    • chemical factors
  71. name four physical factors affecting radiation response:
    • LET (linear energy transfer)
    • RBE (radiation biologic effect)
    • protraction
    • fractionation
  72. energy transfer per length of travel:
    • LET
    • (keV/mm)
  73. how does LET affect radiation response?
    • higher LET = higher response
    • ex. apha & beta are high LET, high response
    • ex. x-ray & gamma are low LET, low response
  74. higher LET =
    ______ energy
    ______ wavelength
    ______ damage
    • lower energy
    • longer wavelength
    • more damage
  75. –dose of a standard radiation (200-250 kVp x-ray) to produce an effect compared to the dose of test radiation to produce the same effect:
    RBE (radiation biologic effect)
  76. what is the standard radiation amount used to calculate RBE?
    200-250 kVp of x-ray
  77. how does RBE affect radiation response?
    higher RBE = higher response (= higher LET)
  78. –dose delivered continuously but at a lower dose rate:
    protraction
  79. how does protraction affect radiation response?
    protraction lowers radiation response
  80. give examples of protraction:
    • HDR
    • implants
    • chronic background exposure
  81. –dose delivered at the same dose rate but in several fractions of the total dose:
    fractionation
  82. how does fractionation affect radiation response?
    • fractionation lowers radiation response
    • ex. 180 rads per day radiation treatment
  83. name seven biological factors affecting radiation response:
    • oxygen effect (OER)
    • age
    • gender
    • recovery
    • nutritional state
    • radiosensitivity
    • cell cycle
  84. concerning the oxygen effect, tissue is more sensitive to radiation when irradiated in the _________ state than when irradiated under _________ or __________ conditions.
    • oxygenated (aerobic)
    • anoxic (w/o oxygen
    • hypoxic (low-oxygen)
  85. how does oxygen affect radiation response?
    oxygen increases radiation response
  86. how do you calculate the OER?
    DIVIDE (the dose necessary under anoxic condition to produce a given effect) BY (the dose necessary under aerobic conditions to produce the same effect) TO = OER
  87. how does age affect radiation response?
    infants and geriatrics are more sensitive than middle age (if age is the only factor)
  88. how does gender affect radiation response?
    • males are more sensitive than females
    • believed to be due to feminine hormones not found in males
  89. how does recovery affect radiation response?
    • very sensitive cells need more recovery time than less sensitive cells
    • higher exposure to cells require more recovery
    • dose given in a short span of time as opposed to a longer span will require more recovery time
  90. how does nutritional state affect radiation response?
    malnourishment increases the probability of radiation response
  91. how does radiosensitivity affect radiation response?
    • undifferentiated cells are more sensitive and they divide faster (ex. erythroblast)
    • differentiated cells are less sensitive and they divide slower (ex. nerve cell)
  92. how does the cell cycle affect radiation response?
    interphase is more sensitive than the mitotic phase
  93. name two chemical factors affecting radiation response:
    • radiation-protectors
    • radiation sensitizers
  94. –drugs used to protect against ionizing radiation:
    (give example)
    • radiation-protectors
    • ex. steroids
  95. where are radiation-protectors of most interest?
    • for radiation therapy
    • but also for other uses (ex. military)
  96. –drugs used to increase the effectiveness of radiation therapy in destroying unwanted cells:
    (give examples)
    • radiation sensitizers
    • ex. cystplatnum; adriamycin
  97. according to the law of bergonie and tribondeau, ionizing radiation is more effective against cells that:
    • are actively mitotic
    • are undifferentiated
    • have a long dividing future
  98. the ______ mature a cell is, the more radioresistant it is.
    more
  99. the ___________ the tissues and organs are, the more radiosensitive they are.
    younger
  100. when the level of metabolic activity is high, radiosensitivity is _______.
    high
  101. as the proliferation rate for cells and the growth rate of tissues increase, the radiosensitivity:
    increases

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