Rad Bio Final Exam

What type of radiation is more likely to cause biological damage (between gamma and alpha)?

alpha

Characteristics of double strand DNA breaks

1. caused by high LET radiation

2. Repair is difficult (results in broken nitrogen bases which may cause the break of a chromosome)

3. High probability of gene abnormality/late effects

4. Requires more than one interaction

What kinds of radiation are considered low LET?

x-ray, gamma

What is the LET of an alpha particle?

100

Low LET means what for OER?

High OER

As LET increases, what happens to RBE?

decreases

How radiosensitive are muscles (sensitive/resistant/etc)

resistant

What is a lethal dose of radiation without medical treatment?

3-4 Gy

LET for diagnostic x-rays

3 keV/micrometer

Anoxic cells are how many more times resistant to radiation than oxygenated cells?

x3

How much (fraction) of radiation induced damage is caused by free radicals?

2/3

What are adult nerve cells radiosensitivity?

very low

When LET increases, the chance of a significant biological response in radiosensitive DNA _______

also increases

What is the radiosensitivity of lymphocytes

Highlight radiosensitive

Chromosomal abberations happen BEFORE or AFTER DNA synthesis?

before

When is an embryo-fetus most radiosensitive

8th-15th week after gestation

Do muscle/adult nerve cells divide frequently?

no

If the master molecule is “hit” multiple times and the cell deactivates, what results for the cell?

normal cell functions cease — cell dies

What Gy will cause permanent sterility in males and females

5-6 Gy

Are free radicals formed by direct interactions?

no

What are the layers of the skin?

1. epidermis

2. dermis

3. hypodermis

Grenz rays were once used to treat and cure

skin diseases like ringworm

What form of ARS syndrome causes intercranial pressure

Cerebrovascular syndrome

Are early somatic effects a concern for those working with diagnostic x-rays?

no

When does the prodromal stage of ARS occur?

in the beginning

ARS syndrome that will most likely occur at 3 Gy

Hematopoietic syndrome

What are the forms of ARS?

1. Hematopoietic

2. Gastrointestinal

3. Cerebrovascular

Order of female germ cell development

1. primordial follicle

2. mature follicle

3. corpus luteum

4. ovum

What is the period of ARS where a false calm occurs for several days called?

latent period

What dose is considered fatal regardless of medical treatment?

12 Gy

Spermatogonia take how many weeks to mature?

3-5 weeks

What does LD 50/30 mean?

lethal dose in 50% of exposed population in 30 days

For someone with hematopoietic syndrome, survival time shortens as ________

dose increases

Name tissues that suffer immediate consequences from high radiation dose

1. Bone marrow

2. female/male reproductive organs

3. skin

What Gy will produce skin erythema in 24-48 hours

2 Gy

What is the typical cause of death if a pt has gastrointestinal syndrome

damage to epithelial cells in the digestive tract

How does increasing dose effect early tissue reactions?

severity increases with dose

LD 50/30 for an adult

3-4 Gy

Factors that organ and tissue responses to radiation depend on

1. Reproductive characteristics

2. Radiosensitivity

3. Cell growth rate

What is atrophy?

shrinkage of organs and tissues after high radiation dose

Has the incidence of leukemia increased or decreased since the late 1940s?

decreased

What does linear non-threshold mean?

response to dose is directly proportional all the way down to zero

Examples of mutagens that increase frequency of mutations

1. chemicals

2. viruses

3. ionizing radiaiton

What period of time is the organogenesis stage of pregnancy?

day 10 to 12 weeks

Why can radium be incorporated into bone?

it is chemically similar to calcium

What are genetic mutations at the molecular level called

point mutations

What are spontaneous mutations

mutations that occur at random as a natural phenomena

Genetic effects do not have a threshold dose (T/F)

true

experiments with mice conclude that cataracts can be formed with doses as low as

0.1 Gy

What is the mean value of radiation doubling dose for humans

1.56 Sv

What model dose radiation induced cataracts follow?

threshold, nonlinear

How did physicians attempt to reduce thyroid cancer in children in Poland following Chernobyl?

administration of potassium iodide to prevent uptake of the radioactive isotope iodine-131

What is reduced birth weight due to radiation exposure an example of

Teratogenic effect

Equivalent dose of most diagnostic procedures

less than 0.1 Sv

Radium half life

1622 years

What is the most significant late stochastic effect of radiation exposure

cancer

What percent of all live births in the US have genetic mutations?

10%

When the Navajo people mined uranium and developed lung cancer years later, this is an example of

a late stochastic effect

When a prediction is made that the number of excess cancers will increase as the natural incidence of cancer increases with the advancing age of a population, the risk is considered

relative

How does ionizing radiation damage biological structures

removes electrons from molecular structures

What is the charge of an alpha particle

+2

What determinants influence extent to which radiation modalities transfer energy to tissues?

1. Charge

2. Mass

3. Energy

What does LET stand for?

Linear Energy Transfer

What is LET?

how radiation interacts and loses energy to the medium its traveling inside of

measured in energy deposited per unit traveled

What is the LET of x-rays?

3 keV/micrometer (relatively low)

LET is an essential factor in assessing what?

potential organ/tissue damage

High LET means what for biological response from tissues?

high chance of significant response

How do x-rays/gamma cause damage primarily?

indirectly (in the form of free radicals)

High LET radiation has substantial

1. mass

2. charge

Examples of high LET radiation

1. Alpha particles

2. ions of heavy nuclei

3. neutrons

4. certain charged particles from interactions with neutrons and atoms

High LET radiation travels (far/not far) and travels (slow/fast)

1. not far (stopped easily once colliding)

2. slow

Why is x-ray able to travel farther through matter?

interacts less with surrounding matter

Since high LET radiation causes so much damage, what irreparable damage is possible?

multiple strand breaks in DNA —> complete chromosomal breakage (cell death)

What is Relative Biological Effectiveness (RBE)?

“comparable capabilities of radiation with differing LETs to produce a particular biologic reaction”

not in itself able to identify rad protection dose (needs weighting factors)

What is Oxygen Enhancement Ratio? (OER)

the therapeutic or detrimental effect of radiation dependent on the presence of oxygen

Are tissues more or less sensitive to radiation with a higher presence of oxygen?

more sensitive

How do high LET particles effect cells when there is a high presence of oxygen?

unaffected— high LET particles kill the cells regardless of the presence of oxygen due to their destructiveness

(OER of 1)

What is the OER of X-ray/gamma

3

Why does the presence of oxygen make cells more sensitive to radiation?

free radicals interact with oxygen to produce peroxides —> harmful for cell

What is the oxygen fixation hypothesis?

radiation damage in the presence of oxygen makes the damage permanent

What are the 3 levels biological damage can occur?

1. molecular

2. cellular

3. organ systems

If radiation damages germ cells, what can potentially happen?

damage can be passed onto offspring

Interaction from radiation is classified as _______ or _______

indirect or direct

Which kind of LET radiation is more likely to cause direct damage?

high LET

What two products can form when radiation ionizes water?

HOH+ —> may form water again with no damage
HOH- —> causes damage

What is a point lesion?

altered area caused by a single chemical bond change

Because the body is 80% water, most damage from low LET radiation is _______

indirect

Is a single strand break more common with high or low LET?

low LET

What kind of radiation causes noticeable changes to chromosomal structure (visible)

high LET

When are chromosomal mutations/damage able to be viewed?

during metaphase

when do solitary chromatid abberations occur?

after DNA synthesis in interphase

Restitution

break reforms as it was before, no damage sustained

Deletion

part of chromosome is lost in cell division

Broken End Rearrangement

results in grossly misshapen chromosomes

What is target theory

there is a master molecule in cells that, once hit multiple times by radiation, results in serious effects (cell death)

most likely DNA

What dose is required for permanent cell reproductive death

1-10 Gy

What is the difference between survival curves for mammalian cells with high vs low LET radiaiton?

low - shoulder is present, then a linear drop off —> repair at low doses

high - no shoulder —> indicates the cell is unable to repair

Do specialized or non-specialized cells undergo more rapid cell division?

nonspecialized

Oxygen Enhancement Effect — Cancer Treatment

Cancer cells are typically less oxygenated than healthy cells, so oxygenating them through hyperbaric oxygenation can make them more sensitive to radiation therapy treatments

Radiosenstivity in cells is directly proportional to _________ and inversely proportional to ________

1. Reproductive Activity

2. Degree of Differentiation