Unit 3 Cell and Tissue Response to Radiation

a cell that is specialized functionally and/or morphologically
can be mature cell or end cell in a population

cell that is not specialized.
immature cell whose primary function is to divide

three categories of cells

-cyte =
-blast =

stem cells primary function is to divide to:

stems cells are

basal cells of epidermis
myoblast of bone marrow
osteoblast in the bone
intestinal crypt cells

used to treat severely burned patients

cells that are on their way from the stem cell compartment to the mature cell compartment

5 cell populations

cell populations were defined by

rapidly dividing undifferentiated cells that have a short lifetime
most radiosensitive

examples of VIM

cells produced by the division of VIM cells.
actively mitotic but more differentiated than VIM.
more radioresistant thatn VIM

examples of DIM

cells divide irregularly and are more differentiated than DIM cells
more radioresistant than DIM

examples of multipotential connective cells

cells that do not normally divide, however, they retain the ability to divide under certain circumstances.
more differentiated and usually long lived

reverting postmitotic cells are more radioresistant except

examples of RPM

cells do not divide and are highly differentiated
most radioresistant

examples of FPM

types of cell damage

cell permanently loses it ability to reproduce
cells lives continuing to metabolize and synthesize nucleic acids and protein
100-1000 rads (1-10 Gy)

when a cell has been irridated and dies without attempting division
governed by radiosensitivity of cell
more radiosensitive=smaller dose required

interphase death for cells in hemopoetic system would require                        than central nervous system cells

interphase death for radiosensitive cells such as lymphocytes or spermatogonia requires                    cGy (rad), where interphase death for more radioresistant cells such as those in bone requires                   cGy (rad)

occurs when a cell dies after one or more divisions. can be caused by small doses of radiation. mitotic process is slowed or permanently inhibited. cell death can occur after permanent inhibition

the radiation dose required to produce mitotic death is            than the dose needed to produce interphase death in slowl dividing cells or in non-dividing cells

failure of a cell to start dividing on time.
can result from as little as         Gy (rad)

permanent or temporary                                      idependent of the cell's ability to divide can occur as a result of exposure to ionizing radiation.
if repair enzymes can fix the damage. the cell can recover and continue to function.

                     occurs when:
ionizing radiation interacts directly with many DNA molecules (direct effect)
free radicals interact with DNA with many DNA molecules (inderect effect)

since chromosome breakage may result in a loss of genetic material this can lead to                                in the future generations

the study of genetics of cells in particular cell chromosomes

when damage to DNA is severe (breakage of many bonds and strands) the chromosome may be fragmented

for a cell to die following radiation exposure, its target molecule must be inactivated

experimental evidence suggests that the target molecule is         and that there is                            of radiation to the target molecule

Effect
 Blood count changes

Vomiting (threshold)

Mortality (threshold)
 
LD50/60 (with minimal supportive care)

LD50/60 (with supportive medical treatment)
 
100% mortality (with best available treatment)

a method of displaying th eradiation sensitivity of a particular cell type                  and are plotted            

in glassware or an artificial environment, outisde the living body

in the living body

in vitro assays:

single target, single hit applies to:

multi target, single hit applies to:

the radiation dose sufficient to kill 63% of the cells. (37% surviving).

quais-threshold dose. the width of the shoulder region of a cell survival curve

determined by extrapolation of the linear portion of the curve back to its intersection with the y axis

an expression of radiosensitivitym, mean lethal dose. dose required to reduce cells surviving to 37% o nthe multi target single hit model.

the lower the D₀ the more               the cell

factors affecting radiation response.

energy transfer per length of travel (keV/micrometer)
higher LET produces higher response

alpha and beta are               LET
xray and gamma are                  LET

dose of standard radiation (200-250 kvp) to produce an effect compared to the dose of test radiation to produce the same effect
Higher           = greater response

dose delivered continuously but at a lower dose rate
allows for higher overall doses to be achieved which is helpful when treating cancer

dose delivered approx the same time each day but over a course of several days or weeks.
lowers radiation response but allow for good cells to repair

the vast majority of intracellular repair is finished by           post irridation

tissue is more sensitive to radiation when irridated in the oxygenated state than when irridated under anoxic or hypoxic conditions

dose necessary under anoxic condition to produce a given effect divided by dose necessary under aerobic conditions to produce the same effect

oxygen            radiation response

                        are more sensitive than middle age if considering age only

          are more sensitive than               
this high tolerance is thought to be contributed to what?

very sensitive cells need                        time than less sensitive cells

dose given in a short span of time as oppesed to a long span will require                time

malnourishment                  the probabiblity of radiation response

undifferentiated cells are            sensitive and divide                

differentiated cells are                sensitive and divide               

                     is more sensitive than mitotic

drugs used to protect against ionizing raditation:

drugs used to increase the effectiveness of radiation therapy in destroying unwanted cells

ionizing radiation is more effective against cells that are actively mitotic, undifferentiated, and have a long dividing future

cells with high radiosensitivity

cells with fairly high radiosensitivity

cells with moderate radiosensitivity

cells with fairly low radiosensitivity

cells with low radiosensitivity