Radiosensitivity & Radiolysis Flashcards
Which is the cytoplasmic organelle containing digestive enzymes that break down organic compounds and eliminate wastes
lysosomes
What is the most important component of the nucleolus?
RNA
As a result of the second meiotic division, the daughter cells each contain how many chromosomes?
23
When oxygen is present, the probability of biologic damage increases with high or low LET?
increases with low LET
What are the membranes of the cell nucleus and cytoplasm organelles composed of?
Lipids and proteins
When the process of cellular division stops and the cell does not divide further
Late in the G1 phase
What is the chance of a master molecule being struck by radiation?
The same as any other molecule
Which phase of mitosis does actual cell division occur?
Telophase
How many functional ootid are produced during the process of meiosis?
One
What is cell death that occurs after cell reproduction has occurred called?
Mitotic death
What structures with identical DNA are formed in the S phase?
Two pairs of chromatids
When does most cell damage occur in relation to the master molecule and radiation?
When a molecule other than a master molecule interacts with radiation
When does radiolysis of water occur?
when water is ionized
When an electron is dislodged from an atom, the atom’s charge changes from ____ to ____
neutral to positive
A positively charged water molecule separates into what 2 byproducts?
hydrogen ion H+ and hydroxyl radical OH*
The S phase of mitosis is the
actual DNA synthesis period
Which is the most radiosensitive portion of the cell cycle?
mitosis
What molecule is a potentially harmful by-product of the radiolysis of water?
H*
Which chromosomal aberration is most often responsible for a significant biologic response from ionizing radiation exposure?
double strand break
What is the primary mechanism of biologic harm from radiation on humans?
indirect effects
The study of a response to radiation or other stimulus occurring to the tissues outside the body (test tube) is termed
in vitro
What is considered to be a low-LET radiation?
gamma ray and x-ray
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
RBE
When internal contamination is possible, high LET radiation is of greatest concern because
the potential exists for irreparable damage because multiple strand breaks in DNA are possible
Free radicals behave as an extremely reactive single entity as a result of the presence of
unpaired valence electrons
Which action of ionizing radiation is most harmful to the human body?
indirect action
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
When does ionizing radiation cause complete chromosome breakage?
when 2 direct hits occur in the same rung of the DNA macromolecule
In a DNA macro molecule, the sequence of ___ determines the characteristics of every living thing
nitrogenous organic bases
how many base pairs are there in the human genome?
2.9 billion
which cells produce antibodies?
lymphocytes
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
What governs the radiation dose required to cause apoptosis?
radiosensitivity of the cell
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
What do basal cells of the skin, intestinal crypt cells, and reproductive cells all have in common?
all cells are radiosensitive
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
Which organ system is most radiosensitive in human beings?
hematopoietic (blood production)
Radiation induced leukemia and solid tumors are attributed predominantly to which type of radiations exposure
gamma radiation exposure
Early demise of experimental animals exposed to nonlethal doses of radiation resulted from
induction of cancer
components of the hematopoietic system?
bone marrow, circulating blood, lymphoid organs
The linear dose response model accurately reflects the effects of
low-LET radiation at higher doses
Epilation is another term for
hair loss
A positively charged water molecule separates into what 2 by products?
hydrogen ion H+ and hydroxyl radical OH*
Water is an organic or inorganic compound?
inorganic- it does not contain carbon
When oxygen is present, the probability of biological damage increases with low or high LET?
LOW
Greater RBE and LET create a greater or lesser response to radiation?
GREATER
Instant death of cell occurs at how many rads?
100,000
Biological effects from expsure to ionizing radiation can be observed at a __________, ____________, and __________ level.
molecular, cellular, organic
Reproductive and Interphase death of a cell occurs at how many rads?
100-1,000
Mitotic/Genetic death occurs at how many rads?
amount varies
Mitotic delay occurs after how many rads of radiation?
1 rad
Interference of cellular function occurs after how many rads?
amount varies- cells may not produce as many proteins or break down glycoproteins
Why are cells more sensitive in their natural state (in vivo)?
increased oxygenation and metabolic state
Main Chain Scission (Macromolecules)
chain breaks into smaller molecules- easier to metabolize- DECREASES viscosity
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
Point Lesions (Macromolecules)
photons weaken chain- late effects at WHOLE body level- sugar/phosphate bonds weakened and may break apart DECREASING viscosity
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
DNA Irradiation: Main Chain Scission 1 Rail Severed
1 side rail severed - sugar from elsewhere can come in and repair
DNA Irradiation: Main Chain Scission 2 Rails Severed
2 side rails severed- sugars can come from elsewhere and repair
DNA Irradiation: Main Chain Scission & Cross Linking
main chain broken but macromolecule reattaches creating new appendages
DNA Irradiation: Rung Breakage
rung broken containing purines and pyrimidines (genetic code)- repairable if DNA code has not been altered
DNA Irradiation: Change or Loss of Base Pair
genetic code can not be repaired - genetic mutation would occur
What type of DNA irradiation can cause permanent damage?
Change or loss of base pair
What 3 things can result from DNA irradiation?
Cell death, malignant disease, genetic damage
How is dose and cell survival related?
Inversely proportional
Fractionated or protracted dose has better survival rate?
Fractionated
Indirect vs direct effect, greater effect?
Indirect effect
Cell types are classified by what 2 things?
Reproductablity/proliferation rate & stage of development (immature vs mature)
Radiosensitivity is _______ proportional to their reproductive activity.
directly
Radiosensitivity is ______ proportional to their degree of differentiation.
inversely
Blood cells have a _____ proliferation rate with ____ differentiation.
High, low
Nerve cells are ______ specialized with a _____ reproductability rate.
highly, low
Immature Blood Cells: High sensitivity to lower sensitivity (3)
Erythroblasts (red stem cells)
Myeloblasts (white stem cells)
Megakaryoblasts (platelet stem cells)
High metabolic activity creates high or low radiosensitivity?
high
Mature Blood Cells: High sensitivity to lower sensitivity (6)
Lymphocytes
Erythrocytes
Leukocytes
Neutrophils
Granulocytes
Thrombocytes (platelets)
Epithelial Cells: High sensitivity to lower sensitivity (3)
Connective Tissue (blood, cartilage)
Muscle (high protein count)
Nervous Tissue (connective tissue)
Cell Sensitivity: 8 Categories from MOST radiosensitive to LEAST Radiosensitive
- Immature Blood Cells
- Other Somatic Cells
- Mature Blood Cells
- Epithelial Cells
- Muscle Cells
- Reproductive Cells
- Specialized Cells (liver, renal, pancreatic, splenic)
- Nerve Cells
What type of dose produces acute effects?
protracted
What type of dose produces late effects?
fractionated
What are the 5 factors that affect cell radiosensitivity?
Dose Rate
Oxygen Content
Age
Sex
Chemical Agent
The Oxygen Enhancement Ratio is greatest with low or high LET radiation?
low
OER is dependent upon what factor?
linear energy transfer
At what stage of fetal development is radiosensitivity the highest?
Embryonic
Permanent sterility for females occurs with a dose of how many rads (gray)?
500 rads (5gray)
Permanent sterility for males occurs with a dose of how many rads (gray)?
500-600 rads (5-6gray)
Halogenated Pyridimes: Radiosensitizer or Radioprotector?
Radiosensitizer
Methotrexate: Radiosensitizer or Radioprotector?
Radiosensitizer
Actinomycin D: Radiosensitizer or Radioprotector?
Radiosensitizer
Hydroxyurea: Radiosensitizer or Radioprotector?
Radiosensitizer
Vitamin K: Radiosensitizer or Radioprotector?
Radiosensitizer
Aminothols: Radiosensitizer or Radioprotector?
Radioprotector
Heroine: Radiosensitizer or Radioprotector?
Radioprotector
Sulfhydrol (sulphur & hydrogen) Radiosensitizer or Radioprotector?
Radioprotector
Cysteine: Radiosensitizer or Radioprotector?
Radioprotector
Cysteamine: Radiosensitizer or Radioprotector?
Radioprotector
Organ radiosensitivity is determined by what 4 factors?
- function of organ in the body
- rate at which cells mature
- inherent radiosensitivity of cell type
- dosage of specific area or whole body
As LET increases, the biological effect of organs increases or decreases?
increases
As RBE increases, the biological effect of organs increases or decreases?
increases
What type of interaction causes a DNA chain to become less viscous and easier to metabolize?
Main Chain Scission & Point Lesions
What type of interaction causes a DNA chain to become more viscous and harder to metabolize?
Cross-Linking “Spurring”
Sensitivity of Nucleotides: Most sensitive to less sensitive
Nucleic Acids
DNA
RNA
Proteins
What stage of DNA synthesis is the MOST sensitive?
G1 (pre-synth)
DNA Irradiation may cause what 3 things?
Abberations (mutations), amnormal metabolic activity (cancer), genetic mutations in next generation (germ cells)
Cell Survival depends on what 4 traits?
- Dose- amount of energy absorbed
- Exposure rate- fractionated or protracted
- Type of molecule and sensitivity
- Number of targets- individual vs multi
Enzymes, Viruses, Bacteria and simple cells provide an individual or multiple target?
individual- cell survival is lowest
single target- single hit
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
What type of charge do free radicals have?
no charge
Photons interact with water molecules creating what 2 possible by-products?
Free radicals
New Molecules
The initial chemical reaction of a photon and water molecule will produce what?
Positive HOH+ water molecule
free electron e-
If an unstable positive HOH+ water molecule and a e- free electron attach, what is created?
water molecule
An HOH+ may disassociate into what 2 things?
positive hydrogen molecule H+
Hydroxyl Free Radical OH*
A HOH- may disassociate into what 2 things?
Negative hydroxyl molecule OH-
Hydrogen Free Radical H*
What is the reaction of the combination of 2 hydroxyl free radicals OH*?
Hydrogen peroxide molecule H2O2
What are the byproducts of the combination of a hydrogen free radical H* and oxygen O2?
Hydroperoxyl Free radical HO2*
Why is oxygen combined with a free radical extra harmful?
oxygen is an excellerent, creates a stronger reaction
What are the byproducts of 2 hydroperoxyl free radicals HO2*? (reactions)
Hydrogen Peroxide H2O2
Oxygen O2
What is the byproduct of a photon and RH+ interaction?
RH* free radical
What are the byproducts of an RH* disassociation?
Hydrogen free radical H*
Reesis Free radical R*
What are the byproducts of a R* reesis free radical and O2 molecule?
Reesis Oxygen Free Radical RO2*
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
What unit of measure have scientists developed to compare different types of radiation and the biologic effects at different doses
RBE
What happens when a free electron combines with another water molecule?
An unstable, negatively charged molecule results
Why do hydrogen and hydroxyl ions present minimal danger of biologic damage?
They can easily recombine to form a molecule of water.
What is cell death that occurs after cell reproduction has occurred called?
mitotic death
What causes main-chain scission?
Breakage in a thread or backbone of a long-chain molecule
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
When do molecular lesions or point lesions occur?
When single chemical bonds of molecules are disrupted
What can happen when the metabolic activity of cells increases as a result of irradiation?
Cells reproduce more rapidly.
What is the process called when DNA is irradiated in solution and breakage occurs in the long-chain molecule?
main chain scission
When DNA is irradiated in solution, when does cross-linking occur?
When molecule fragments attach to other molecules or fragments
What causes a decrease in the viscosity of the fluid in a cell?
main chain scission
RBE Formula
Standard dose necessary to produce desired effect
_____________________________
test dose necessary to produce same effect
Temporary sterility in females occurs after how many rads/gy of exposure?
200rads (2gy)
Menstrual irregularities occur after what dose?
10rads (.1gy)
Temporary sterility in males occurs after how many rads/gy of exposure?
250rads (2.5gy)
Sperm count reduction occurs after what dose of radiation?
10 rads (.1gy)
