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C1 > MOLECULAR & CELLULAR RADIOBIOLOGY, EARLY EFFECTS OF RADIATION > Flashcards

MOLECULAR & CELLULAR RADIOBIOLOGY, EARLY EFFECTS OF RADIATION Flashcards

1
Q

What are point lesions in molecular radiobiology?

A

Cellular radiation damage that leads to late radiation effects.

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2
Q

What are the two processes metabolism consists of?

A

Catabolism and anabolism

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3
Q

Which molecule is considered the most radiosensitive?

A

DNA.

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4
Q

What is the principal radiation interaction in the human body?

A

Radiation interaction with water.

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5
Q

Irradiation outside of the cell or body.

A

in vitro irradiation

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6
Q

Irradiation within the cell or body.

A

in vivo irradiation

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7
Q

The breakage of the backbone of long-chain macromolecules.

A

main-chain scission

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8
Q

What does main-chain scission result in?

A

Reduction of a long molecule into many smaller ones and decreased viscosity.

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9
Q

What effect does cross-linking have on macromolecules?

A

Increases the viscosity of the solution.

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10
Q

A change that impairs or loses function at a single chemical bond.

A

point lesion

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11
Q

The reduction of nutrient molecules for energy.

A

catabolism

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12
Q

The production of large molecules for form and function.

A

anabolism

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13
Q

What is translation in protein synthesis?

A

Forming a protein molecule from messenger RNA.

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14
Q

What is transcription?

A

Constructing messenger RNA from DNA.

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15
Q

Which is more abundant, proteins or nucleic acids?

A

Proteins.

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16
Q

Which is less radiosensitive, proteins or nucleic acids?

A

Proteins.

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17
Q

Deoxyribose, phosphate, and base molecules accumulate, forming the double-helix DNA.

A

G1 portion of interphase

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18
Q

DNA unzips and forms two daughter DNA molecules.

A

S portion of interphase

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19
Q

What do chromosomes control in a cell?

A

The growth and development of the cell.

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20
Q

What are the two types of chromosome aberrations?

A

Terminal deletion and dicentric formation.

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21
Q

What is an ion pair created by radiolysis of water?

A

HOH+ and e-.

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22
Q

Uncharged molecules with an unpaired electron; short-lived.

A

free radicals

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23
Q

What toxic agent is formed by radiolysis of water?

A

Hydrogen peroxide (H2O2).

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24
Q

What is the principal damaging product of radiolysis of water?

A

Hydroperoxyl radical (HO2*).

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25
Q

When the initial ionizing event occurs on the target molecule.

A

direct effect

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26
Q

When the ionizing event occurs on a noncritical molecule and energy is transferred.

A

indirect effect

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27
Q

Theory that a cell dies if its target molecule is inactivated by radiation.

A

target theory

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28
Q

What is a radiation “hit”?

A

An ionization that inactivates the target molecule.

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29
Q

How does low-LET radiation interact in the absence of oxygen?

A

Low probability of hitting target molecules.

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30
Q

How does oxygen affect low-LET radiation?

A

Increases probability of a hit by forming free radicals.

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31
Q

What model applies to enzymes, viruses, and bacteria for cell survival?

A

Single-Target, Single-Hit Model.

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32
Q

Define D37.

A

Dose required to kill 63% of cells (37% survive); measures cell radiosensitivity.

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33
Q

Which phase is most variable in cell cycle time?

A

G1 phase.

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34
Q

Which cell survival model applies to human cells?

A

Multi-Target, Single-Hit Model.

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35
Q

What does a high D0 value indicate?

A

Radioresistant cells.

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36
Q

What does DQ represent in the multitarget model?

A

The threshold dose and cell recovery capacity.

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37
Q

Damage that must accumulate before cell death occurs.

A

sublethal damage

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38
Q

Describes the cell’s ability to recover from sublethal damage.

A

split-dose irradiation

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39
Q

What is the average cell-cycle time for human cells?

A

Approximately 24 hours.

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40
Q

Which phase in the cell cycle is the most sensitive to radiation?

A

Mitosis.

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41
Q

How does oxygen influence radiation effects?

A

Enhances the effect of low-LET radiation.

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42
Q

What type of radiation response is deterministic?

A

A response that varies in severity with radiation dose and has a threshold.

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43
Q

What is the prodromal period in acute radiation syndrome?

A

Initial symptoms like nausea and vomiting after exposure.

44
Q

What characterizes the hematologic syndrome?

A

Reduction in white, red cells, and platelets; dose range 200-1000 rad.

45
Q

What dose range causes GI syndrome?

A

1000-5000 rad.

46
Q

What symptoms are associated with CNS syndrome?

A

Ataxia, seizures, and loss of coordination.

47
Q

What does LD50/60 measure?

A

Dose causing 50% of subjects to die within 60 days.

48
Q

What tissues are most affected by local radiation exposure?

A

Skin, gonads, and bone marrow.

49
Q

Shrinkage of an organ or tissue due to cell death.

A

atrophy

50
Q

What are the three layers of skin?

A

Epidermis, dermis, and subcutaneous layer.

51
Q

What cells in the skin are most radiosensitive?

A

Basal cells in the epidermis.

52
Q

Reddening of the skin similar to sunburn.

A

erythema

53
Q

Ulceration and peeling of the skin.

A

desquamation

54
Q

What dose causes temporary epilation?

A

300 rad.

55
Q

What is the SED50?

A

Dose causing skin erythema in 50% of people, about 500 rad.

56
Q

What dose causes temporary sterility in men?

A

200 rad.

57
Q

What dose causes permanent sterility in women?

A

500 rad.

58
Q

Includes bone marrow, circulating blood, and lymphoid tissue.

A

hemopoietic system

59
Q

What cells are involved in the immune response?

A

Lymphocytes.

60
Q

rapid decrease in granulocytes.

A

granulocytopenia

61
Q

Platelets involved in blood clotting.

A

thrombocytes

62
Q

What cells are least sensitive to radiation?

A

Erythrocytes (red blood cells).

63
Q

A chromosome map used in cytogenetic analysis.

A

karyotype

64
Q

What are single-hit chromosome aberrations?

A

Chromosomal damage observed during the M phase.

65
Q

A chromosome formed by joining segments from two hits.

A

dicentric chromosome

66
Q

The study of cell genetics, particularly chromosomes.

A

cytogenetics

67
Q

How are radiation-induced point mutations detected?

A

They are undetectable even with karyotype analysis.

68
Q

What is the dose-response relationship for single-hit aberrations?

A

Linear, nonthreshold.

69
Q

What are iso-chromatid fragments?

A

chromatid fragments without centromeres.

70
Q

What causes stickiness in chromosomes?

A

Mechanism failure for chromatid joining.

71
Q

What radiation dose affects lymphocytes?

A

As little as 25 rad can cause hematologic depression.

72
Q

A rapid rise in granulocytes, typically after exposure.

A

granulocytosis

73
Q

What is the principal effect of radiation on blood cells?

A

Depression of blood cell numbers.

74
Q

Red blood cells that transport oxygen

A

erythrocytes

75
Q

How long do red blood cells live in the peripheral blood?

A

Approximately 4 months.

76
Q

What is the most radiosensitive phase of male gametogenesis?

A

Spermatogonial stem cells.

77
Q

What causes radiation-induced atrophy of the ovaries?

A

Irradiation, especially early in life.

78
Q

The development process of germ cells in testes and ovaries.

A

gametogenesis

79
Q

What type of radiation is associated with orthovoltage x-rays?

A

200-300 kVp x-rays.

80
Q

Ulceration of the skin that represents clinical intolerance.

A

moist desquamation

81
Q

What are the symptoms of prodromal radiation sickness?

A

Nausea, vomiting, and diarrhea.

82
Q

What is a ring chromosome aberration?

A

Chromosomal damage from two hits on the same chromosome.

83
Q

How long is the latent period in radiation sickness?

A

It varies based on dose, usually no symptoms present.

84
Q

What is the GI syndrome dose range?

A

1000-5000 rad.

85
Q

Define hemopoietic cell survival.

A

Decrease in circulating blood cells due to radiation.

86
Q

What is the approximate chromosome aberration frequency?

A

Two single-hit aberrations per rad per 1000 cells.

87
Q

What is the CNS syndrome’s ultimate cause?

A

Elevated fluid content in the brain.

88
Q

What is the effect of high-LET radiation on cell survival models?

A

Follows single-target, single-hit model.

89
Q

What is a reciprocal translocation?

A

A rearrangement of genes without genetic loss.

90
Q

What cells recover from radiation damage in 6 months to 1 year?

A

Erythrocytes.

91
Q

What is a lethal dose response?

A

Nonlinear, threshold for acute radiation lethality.

92
Q

What does radiation-induced thrombocytopenia cause?

A

Depletion of platelets, leading to hemorrhage risk.

93
Q

What is the primary function of lymphocytes?

A

Immune response regulation.

94
Q

What radiation dose can suppress menstruation in women?

A

As little as 10 rad.

95
Q

What cell system is similar to hemopoietic system?

A

Gametogenesis, both involve cell renewal.

96
Q

What is a bone marrow’s function in adults?

A

Produces most circulating blood cells.

97
Q

What type of radiation effect follows a threshold relationship?

A

Deterministic effects like local tissue damage.

98
Q

What are the three main effects of radiolysis?

A

Ion pair formation, free radicals, and hydrogen peroxide.

99
Q

What is the dose threshold for chromosome aberrations?

A

Approximately 5 rad.

100
Q

What is the lifespan of granulocytes in bone marrow?

A

8-10 days.

101
Q

What dose causes erythema in radiation patients?

A

Approximately 200 rad.

102
Q

What cells show a nonthreshold response to chromosome aberrations?

A

Human lymphocytes.

103
Q

What are the symptoms of CNS radiation syndrome?

A

Disorientation, seizures, loss of muscle coordination.

104
Q

What does linear energy transfer determine?

A

The magnitude of biological damage.

105
Q

What does RBE compare?

A

Effectiveness of test radiation vs. x-radiation.

C1 (9 decks)

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