radiobiology: part two. cellular effects of irradiation instant death reproductive death apoptosis,...

RADIOBIOLOGY: PART TWO

CELLULAR EFFECTS OF IRRADIATION

Instant death

Reproductive death

Apoptosis, programmed cell death(interphase death)

Mitotic or genetic death

Mitotic Delay

Interference of Function

Chromosome Breakage

Survival curves for Mammalian Cells

• Shoulder indicates an area of cellular repair with Low LET exposures

Cell radiosensisitivy and Law of Bergonie and Tribondeau

• Blood cells

• Epithelial tissue

• Muscle Tissue

• Nervous Tissue

• Reproductive cells

• Blood Cells ???• Find the dose for• Whole body hematologic

depression• What are stem or

precursor cells?• What dose moderately to

severely deplete bone marrow cells?

• What are the most sensitive stems cells of human tissue?

Blood Cells -MORE QUESTIONS

• Is death caused from high doses to red blood cells or white blood cells or platelets?Why?

• What is the lethal dose for humans?

• What dose level can impact lymphocytes and why is it so low?

• Why are radiation patients monitored

• Epithelial tissue

• Muscle Tissue

• Nervous Tissue

• Radiosensitive

• Insenstive

• When are nerve cells most sensitive?

Reproductive cells

• Mature spermatogonia-sensitive or insensitive? Why?

• What dose can cause temporary sterility in male? In female?

• What dose can cause permanent sterility in male? In female?

• Mature ova sensitive or insensitive?

• What dose may suppress male sperm population?

• When are a woman’s ovaries most sensitive?

STOCHASTIC

• Random

• “all or nothing”

• linear,nonthreshold

• playing the lottery

Deterministic Effect

• AKA nonstochastic or certainty effect

• Nonlinear threshold curve

• threshold assumed

• increases with severity of dose

Dose Linear Curves (PG 112 in Sherer, Pg.498-499 Bushong)

• Linear, non-threshold

• Linear threshold

• Nonlinear (Curvilinear, Sigmoid) Threshold curve

• Non-linear, non threshold curve

• Linear Quadratic Non threshold

•

AGE

• The age of the biological structure determines sensitivity

• Bergonie and Tribondeau

• Embryo-fetus-newborn-young child

• Decreases in late teens

• Stabilizes until old age

• increases in old age

GENDER

• Females tolerate 5-15% more

RECOVERY

• Cell can recover if sufficient time is given between irradiation

• some cells have greater capacity for repair

• Sufficient radiation causes atrophy

REVIEW

PRINCIPLES OF RADIOBIOLOGY ARE BUILT ON THE FOLLOWING:

1)RANDOM NATURE2)RADIATION INTERACTS AT

CELLULAR LEVEL3)FACTORS THAT ALTER THESE

INTERACTIONS