Radiosensitivity & Radiolysis Flashcards
(136 cards)
1
Q
Which is the cytoplasmic organelle containing digestive enzymes that break down organic compounds and eliminate wastes
A
lysosomes
2
Q
What is the most important component of the nucleolus?
A
RNA
3
Q
As a result of the second meiotic division, the daughter cells each contain how many chromosomes?
A
23
4
Q
When oxygen is present, the probability of biologic damage increases with high or low LET?
A
increases with low LET
5
Q
What are the membranes of the cell nucleus and cytoplasm organelles composed of?
A
Lipids and proteins
6
Q
When the process of cellular division stops and the cell does not divide further
A
Late in the G1 phase
7
Q
What is the chance of a master molecule being struck by radiation?
A
The same as any other molecule
8
Q
Which phase of mitosis does actual cell division occur?
A
Telophase
9
Q
How many functional ootid are produced during the process of meiosis?
A
One
10
Q
What is cell death that occurs after cell reproduction has occurred called?
A
Mitotic death
11
Q
What structures with identical DNA are formed in the S phase?
A
Two pairs of chromatids
12
Q
When does most cell damage occur in relation to the master molecule and radiation?
A
When a molecule other than a master molecule interacts with radiation
13
Q
When does radiolysis of water occur?
A
when water is ionized
14
Q
When an electron is dislodged from an atom, the atom’s charge changes from ____ to ____
A
neutral to positive
15
Q
A positively charged water molecule separates into what 2 byproducts?
A
hydrogen ion H+ and hydroxyl radical OH*
16
Q
The S phase of mitosis is the
A
actual DNA synthesis period
17
Q
Which is the most radiosensitive portion of the cell cycle?
A
mitosis
18
Q
What molecule is a potentially harmful by-product of the radiolysis of water?
A
H*
19
Q
Which chromosomal aberration is most often responsible for a significant biologic response from ionizing radiation exposure?
A
double strand break
20
Q
What is the primary mechanism of biologic harm from radiation on humans?
A
indirect effects
21
Q
The study of a response to radiation or other stimulus occurring to the tissues outside the body (test tube) is termed
A
in vitro
22
Q
What is considered to be a low-LET radiation?
A
gamma ray and x-ray
23
Q
What defines the ratio of the quantity of a reference radiation compared to that of a tested radiation in its ability to result in biological harm
A
RBE
24
Q
When internal contamination is possible, high LET radiation is of greatest concern because
A
the potential exists for irreparable damage because multiple strand breaks in DNA are possible
25
Free radicals behave as an extremely reactive single entity as a result of the presence of
unpaired valence electrons
26
Which action of ionizing radiation is most harmful to the human body?
indirect action
27
Which molecules in the human body are most commonly directly acted on by ionizing radiation to produce molecular damage through an indirect action?
water molecules
28
When does ionizing radiation cause complete chromosome breakage?
when 2 direct hits occur in the same rung of the DNA macromolecule
29
In a DNA macro molecule, the sequence of ___ determines the characteristics of every living thing
nitrogenous organic bases
30
how many base pairs are there in the human genome?
2.9 billion
31
which cells produce antibodies?
lymphocytes
32
If only a few non-DNA cellular molecules are destroyed by radiation exposure, the cell will likely
not show any evidence of injury after irradiation
33
What governs the radiation dose required to cause apoptosis?
radiosensitivity of the cell
34
The most pronounced radiation effects occur in cells with the ____ (Law of Bergonie and Tribondeau)
greatest reproductive activity, longest mitotic phases, least maturity, least amount of specialization or differentiation
35
What do basal cells of the skin, intestinal crypt cells, and reproductive cells all have in common?
all cells are radiosensitive
36
The total radiation dose given to a somatic or genetic cell at the period of time in which that dose was delivered determine the rate of production of
chromosome aberrations
37
Which organ system is most radiosensitive in human beings?
hematopoietic (blood production)
38
Radiation induced leukemia and solid tumors are attributed predominantly to which type of radiations exposure
gamma radiation exposure
39
Early demise of experimental animals exposed to nonlethal doses of radiation resulted from
induction of cancer
40
components of the hematopoietic system?
bone marrow, circulating blood, lymphoid organs
41
The linear dose response model accurately reflects the effects of
low-LET radiation at higher doses
42
Epilation is another term for
hair loss
43
A positively charged water molecule separates into what 2 by products?
hydrogen ion H+ and hydroxyl radical OH*
44
Water is an organic or inorganic compound?
inorganic- it does not contain carbon
45
When oxygen is present, the probability of biological damage increases with low or high LET?
LOW
46
Greater RBE and LET create a greater or lesser response to radiation?
GREATER
47
Instant death of cell occurs at how many rads?
100,000
48
Biological effects from expsure to ionizing radiation can be observed at a __________, ____________, and __________ level.
molecular, cellular, organic
49
Reproductive and Interphase death of a cell occurs at how many rads?
100-1,000
50
Mitotic/Genetic death occurs at how many rads?
amount varies
51
Mitotic delay occurs after how many rads of radiation?
1 rad
52
Interference of cellular function occurs after how many rads?
amount varies- cells may not produce as many proteins or break down glycoproteins
53
Why are cells more sensitive in their natural state (in vivo)?
increased oxygenation and metabolic state
54
Main Chain Scission (Macromolecules)
chain breaks into smaller molecules- easier to metabolize- DECREASES viscosity
55
Cross Linking ("Spurring") (Macromolecules)
increase in size with new appendages -harder to metabolize- INCREASES viscosity - prevents DNA from communicating with RNA so cell may begin functioning differently
56
Point Lesions (Macromolecules)
photons weaken chain- late effects at WHOLE body level- sugar/phosphate bonds weakened and may break apart DECREASING viscosity
57
Ring Chromosome Abberation (Macromolecules
breaks apart and put back together incorrectly - lost piece called acentric fragment- broken ends create rings called dicentrics- genetic code damaged creating mutation
58
DNA Irradiation: Main Chain Scission 1 Rail Severed
1 side rail severed - sugar from elsewhere can come in and repair
59
DNA Irradiation: Main Chain Scission 2 Rails Severed
2 side rails severed- sugars can come from elsewhere and repair
60
DNA Irradiation: Main Chain Scission & Cross Linking
main chain broken but macromolecule reattaches creating new appendages
61
DNA Irradiation: Rung Breakage
rung broken containing purines and pyrimidines (genetic code)- repairable if DNA code has not been altered
62
DNA Irradiation: Change or Loss of Base Pair
genetic code can not be repaired - genetic mutation would occur
63
What type of DNA irradiation can cause permanent damage?
Change or loss of base pair
64
What 3 things can result from DNA irradiation?
Cell death, malignant disease, genetic damage
65
How is dose and cell survival related?
Inversely proportional
66
Fractionated or protracted dose has better survival rate?
Fractionated
67
Indirect vs direct effect, greater effect?
Indirect effect
68
Cell types are classified by what 2 things?
Reproductablity/proliferation rate & stage of development (immature vs mature)
69
Radiosensitivity is _______ proportional to their reproductive activity.
directly
70
Radiosensitivity is ______ proportional to their degree of differentiation.
inversely
71
Blood cells have a _____ proliferation rate with ____ differentiation.
High, low
72
Nerve cells are ______ specialized with a _____ reproductability rate.
highly, low
73
Immature Blood Cells: High sensitivity to lower sensitivity (3)
Erythroblasts (red stem cells)
Myeloblasts (white stem cells)
Megakaryoblasts (platelet stem cells)
74
High metabolic activity creates high or low radiosensitivity?
high
75
Mature Blood Cells: High sensitivity to lower sensitivity (6)
Lymphocytes
Erythrocytes
Leukocytes
Neutrophils
Granulocytes
Thrombocytes (platelets)
76
Epithelial Cells: High sensitivity to lower sensitivity (3)
Connective Tissue (blood, cartilage)
Muscle (high protein count)
Nervous Tissue (connective tissue)
77
Cell Sensitivity: 8 Categories from MOST radiosensitive to LEAST Radiosensitive
1. Immature Blood Cells
2. Other Somatic Cells
3. Mature Blood Cells
4. Epithelial Cells
5. Muscle Cells
6. Reproductive Cells
7. Specialized Cells (liver, renal, pancreatic, splenic)
8. Nerve Cells
78
What type of dose produces acute effects?
protracted
79
What type of dose produces late effects?
fractionated
80
What are the 5 factors that affect cell radiosensitivity?
Dose Rate
Oxygen Content
Age
Sex
Chemical Agent
81
The Oxygen Enhancement Ratio is greatest with low or high LET radiation?
low
82
OER is dependent upon what factor?
linear energy transfer
83
At what stage of fetal development is radiosensitivity the highest?
Embryonic
84
Permanent sterility for females occurs with a dose of how many rads (gray)?
500 rads (5gray)
85
Permanent sterility for males occurs with a dose of how many rads (gray)?
500-600 rads (5-6gray)
86
Halogenated Pyridimes: Radiosensitizer or Radioprotector?
Radiosensitizer
87
Methotrexate: Radiosensitizer or Radioprotector?
Radiosensitizer
88
Actinomycin D: Radiosensitizer or Radioprotector?
Radiosensitizer
89
Hydroxyurea: Radiosensitizer or Radioprotector?
Radiosensitizer
90
Vitamin K: Radiosensitizer or Radioprotector?
Radiosensitizer
91
Aminothols: Radiosensitizer or Radioprotector?
Radioprotector
92
Heroine: Radiosensitizer or Radioprotector?
Radioprotector
93
Sulfhydrol (sulphur & hydrogen) Radiosensitizer or Radioprotector?
Radioprotector
94
Cysteine: Radiosensitizer or Radioprotector?
Radioprotector
95
Cysteamine: Radiosensitizer or Radioprotector?
Radioprotector
96
Organ radiosensitivity is determined by what 4 factors?
1. function of organ in the body
2. rate at which cells mature
3. inherent radiosensitivity of cell type
4. dosage of specific area or whole body
97
As LET increases, the biological effect of organs increases or decreases?
increases
98
As RBE increases, the biological effect of organs increases or decreases?
increases
99
What type of interaction causes a DNA chain to become less viscous and easier to metabolize?
Main Chain Scission & Point Lesions
100
What type of interaction causes a DNA chain to become more viscous and harder to metabolize?
Cross-Linking "Spurring"
101
Sensitivity of Nucleotides: Most sensitive to less sensitive
Nucleic Acids
DNA
RNA
Proteins
102
What stage of DNA synthesis is the MOST sensitive?
G1 (pre-synth)
103
DNA Irradiation may cause what 3 things?
Abberations (mutations), amnormal metabolic activity (cancer), genetic mutations in next generation (germ cells)
104
Cell Survival depends on what 4 traits?
1. Dose- amount of energy absorbed
2. Exposure rate- fractionated or protracted
3. Type of molecule and sensitivity
4. Number of targets- individual vs multi
105
Enzymes, Viruses, Bacteria and simple cells provide an individual or multiple target?
individual- cell survival is lowest
single target- single hit
106
Human Cells provide an individual or multiple target?
multi-target, single hit or multi hit - greater chance of survival- larger area and more parts to hit
107
What type of charge do free radicals have?
no charge
108
Photons interact with water molecules creating what 2 possible by-products?
Free radicals
New Molecules
109
The initial chemical reaction of a photon and water molecule will produce what?
Positive HOH+ water molecule
free electron e-
110
If an unstable positive HOH+ water molecule and a e- free electron attach, what is created?
water molecule
111
An HOH+ may disassociate into what 2 things?
positive hydrogen molecule H+
Hydroxyl Free Radical OH*
112
A HOH- may disassociate into what 2 things?
Negative hydroxyl molecule OH-
Hydrogen Free Radical H*
113
What is the reaction of the combination of 2 hydroxyl free radicals OH*?
Hydrogen peroxide molecule H2O2
114
What are the byproducts of the combination of a hydrogen free radical H* and oxygen O2?
Hydroperoxyl Free radical HO2*
115
Why is oxygen combined with a free radical extra harmful?
oxygen is an excellerent, creates a stronger reaction
116
What are the byproducts of 2 hydroperoxyl free radicals HO2*? (reactions)
Hydrogen Peroxide H2O2
Oxygen O2
117
What is the byproduct of a photon and RH+ interaction?
RH* free radical
118
What are the byproducts of an RH* disassociation?
Hydrogen free radical H*
Reesis Free radical R*
119
What are the byproducts of a R* reesis free radical and O2 molecule?
Reesis Oxygen Free Radical RO2*
120
What are the 4 free radical byproducts of a RH+ Photon interaction?
RH* Free Radical
H* Hydrogen Free Radical
R* Reesis Free Radical
RO2* Reesis Oxygen Free Radical
121
What unit of measure have scientists developed to compare different types of radiation and the biologic effects at different doses
RBE
122
What happens when a free electron combines with another water molecule?
An unstable, negatively charged molecule results
123
Why do hydrogen and hydroxyl ions present minimal danger of biologic damage?
They can easily recombine to form a molecule of water.
124
What is cell death that occurs after cell reproduction has occurred called?
mitotic death
125
What causes main-chain scission?
Breakage in a thread or backbone of a long-chain molecule
126
What occurs when the spur-like molecules extending off a macromolecule chain attach to other parts of the chain or to other macromolecules?
Cross-linking
127
When do molecular lesions or point lesions occur?
When single chemical bonds of molecules are disrupted
128
What can happen when the metabolic activity of cells increases as a result of irradiation?
Cells reproduce more rapidly.
129
What is the process called when DNA is irradiated in solution and breakage occurs in the long-chain molecule?
main chain scission
130
When DNA is irradiated in solution, when does cross-linking occur?
When molecule fragments attach to other molecules or fragments
131
What causes a decrease in the viscosity of the fluid in a cell?
main chain scission
132
RBE Formula
Standard dose necessary to produce desired effect
_____________________________
test dose necessary to produce same effect
133
Temporary sterility in females occurs after how many rads/gy of exposure?
200rads (2gy)
134
Menstrual irregularities occur after what dose?
10rads (.1gy)
135
Temporary sterility in males occurs after how many rads/gy of exposure?
250rads (2.5gy)
136
Sperm count reduction occurs after what dose of radiation?
10 rads (.1gy)
