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 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 NATURE 2)RADIATION INTERACTS AT CELLULAR LEVEL 3)FACTORS THAT ALTER THESE INTERACTIONS