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Rad Biology Unit 3

How is the extrapolation number found on a sigmoid dose curve? N is found by extrapolatial segment of a sigmoidal dose survival curve to intercept at the ordinate axis
What two factors effect progrssion delay? 1. The phase in which radiation occurs and 2. the radiation dose
Explain the effect that oxygen has on the survival of cell include relationship with LET, explain the extrapolation number, and problems that a rise in tissue in mixed oxygenation The more oxygen the more radiosensitive; as LET increases OER decreases; ex# of cells cannot be related; a variety of mixed sensitivity that cant be overcome
Be able to Draw expoential curve then it explain it Exponetial Curve Single-Hit: Single Target Model This suggest damage for radiation is not accumulating
Be able to Draw the sigmoidal curve and then explain it Sigmoidal Curve Mutliple-Hit/Multiple Target Model This suggest radiation is accumulating damage
In intracellular reponse, radiation of differing LET will have what effect on the survival cellls different effects
High LET = ____ ______ more ionization
This refers to the capacity of the cell to reproduce survival of the cells
If a cell can not reproduce then what happens extinction
This is the survival relationship of any given quantity of radiation dose kills the same proportion of cells as every other quantity exponential dose(all of nothing; survive or die)
The same number of cells die between 0-100R as will between____-____ 700R-800R
cells obeying by an exponential dose is the survival reponse has___ critical targe governing reproductive capacity and __ critcal change to be made for the target to inactivate 1: and single
What are the three parts to a sigmoidal curve 1.a slight negative slpoe from theorigin through very low dose range 2.An inflection called the shoulder 3. An exponential survival response through the remaining higher dose range
This is the reponse relationship that more than a single critical change must be made before reproductive capacity falls A sigmoidal dose
Cells demonstrating the sigmoidal dose curve must have ______ and these targets must_____ more than one target; be inactivated
The amount of radiation necessary to destry targets governing cellular reproductive capacity Radiation sensitivity
In cell populations that have more than one target, there is less damage to the reproductive capacity after exposure to radiation doses given in___ than from the same dose given in _____ fractions; single exposures
Unless multi-targeted cells are killed by radiation, they are able to do what and what is likely to occur recover from some or all the damage; full recovery of the cells is likely to occur because enough time will elapse between radiation
What is progression delay When the cells are irriated, progression through the life cycle stops and resumes later
What is the most sensitive phase of a cell life cycle... what comes next mitosis or M phase; G1-S transition
What is the most resistant phase of a cell life cycle S phase
What makes cells sensitive to radiation oxygen
The affect of sensitization is most profound with lower LET
As LET is increased oxygenation males less of a differnce
What is the oxygens role in indirect action Reactions between free radicals and oxygen increase the probability that target molecules will be changed and lose function
This is the expression for degree of oxygens enhancement of radiation affects oxygen enhancement ratio(OER)
How is OER determined by measuring the radiation dose required to produce a specific effect under conditions of FULL OXYGENATION and the fullest possible HYPOXIA and expressing the result as a ratio
The OER for mammalian cells is between 2 and 3 for x and gamma ray
What two things does the oxygen and survival curves show hypoxic cells become resistant to radiation and a drop in extrapolation # which means less targets so less recovery is possible under hypoxia
What does "in vitro" mean? test tube
Cells populations of varying sensitivity to radiation mixed oxygenation
Most, if not all, ____ contain groups of severly hypoxic cells cancer
Cancer cells are radioresistant as compared to more senitive normal cells
How do you overcome the resistance of the cancer cells try to increase the oxygen level of cancer and not healthy cells and use higher LET radiation to minimize the Oxygen effect
LET increases- OER ____ decreases
Explain Recovery time lesser effects will be produced by any given dose of radiation if the radiation is given slowly, over long periods of time than given rapidly
OER decreases as dose rate_____ decreases
these may react differently when they are not independent entitles in vivo cells
How do "in vivo" and "in vitro" cells relate for the most part the experiments were the same;survivle comes however the expo# for in vivo was higher which tells that this cell repairs itself better when part of a tissue and not individuals in artifical medium
Created by: atesta0824