*RPB L5- Cell Survival Curves

Question 1

What does “clonogenic” mean?

Answer 1

Think of it as “Clone”- means that a cell is able to replicate itself… proliferate indefinitely

Question 2

What does “reproductive death” mean?

Answer 2

For cells that can no longer grow - they are technically still ‘alive’, however they are DEAD as they cannot replicate anymore

Question 3

What does “proliferate” mean?

Answer 3

Able to divide (in this case, replicate) indefinitely

Question 4

What factors affect the shape of the curve?

Answer 4

OER, LET, cell cycle, cell type, total dose, dose rate…

Question 5

What is the x and y axis on the cell survival curve?

Answer 5

x: dose rate, y is cell survival in LOG (so we can get a linear line)

Question 6

Why is the cell survival semi-log??

Answer 6

Semi-log scale because we want our line to be linear - easier for calculations

Question 7

How much dose do you need to destroy
1. non-proliferating cells
2. proliferating cells
Explain why

Answer 7

1. 100Gy
2. 2Gy
   Because dividing/growing cells are more radiosensitive than non-growing cells

Question 8

You saw how when there is DNA damage, you can have the sticky ends joining, or you can have diccentric rings; can these still replicate?

Answer 8

NO!

Question 9

What is the difference between in vitro and in vivo?

Answer 9

Vivo is inside organism, vitro is like in petri dish

Question 10

What is the relationship between dose and survival? (i.e. linear, cubic, quad, log…)

Answer 10

LINEAR: Increase dose, decrease cell survival

Question 11

What is “plating efficiency”?

Answer 11

Exactly what it sounds like - how efficient the ‘plate’ is - glass plate maybe?

Question 12

What is surviving fraction?

Answer 12

How many cells survived after radiation (on the petri disk); there is a formula for this

Question 13

What are the three types of results of radiation damage?

Answer 13

1. Sublethal
2. Lethal
3. Potentially lethal

Question 14

What is lethal DNA damage?

Answer 14

Cannot be reversed. It’s gone!

Question 15

Where does radiation usually target?

Answer 15

DNA

Question 16

What is mitotic death?

Answer 16

Death of the cell when it tries to divide - has lost its proliferative ability

Question 17

What is sub-lethal damage?

Answer 17

Damage that can be repaired, if given time

Question 18

What is potentially lethal damage?

Answer 18

Depends on environment - depends on the post-environmental conditions i.e. Giving oxygen

Question 19

What is the shape of the survival curve for densely ionising radiation and sparsely ionising radiation?

Answer 19

Dense would be very steep, no shoulder, straight down. Sparse would have a shoulder, mix of quadratic and linear line

Question 20

What is Dq?

Answer 20

QUASITHRESHOLD - the ‘threshold’ where no damaging is taking place up until this dose threshold

Question 21

Cell survival curve: It is both linear and quadratic. What do they represent?

Answer 21

Linear part is when there is 1 irradiation event that breaks both DNA strand. Quadratic is related to breaks due to 2 separate events - Think of it as like Linear = alpha, str8 kill

Question 22

Is high or low LET curve a straight line? Why?

Answer 22

High - More Linear Energy Transfer means more damage done = i.e. alpha particle is linear line

Question 23

Does sparse or dense ionising radiation have a linear curve?

Answer 23

DENSE

Question 24

If you were given x-rays, neutrons and alpha particles, which one would be steepest to least steep in survival curve?

Answer 24

alpha steepest, neutrons middle, x-rays least steep

Question 25

In the survival curve formula, can you actually tell which DNa is getting hit by alpha/which getting hit by beta?

Answer 25

No, this formula is kinda just a mathematical formula for us to use

Question 26

Define Quasithreshold

Answer 26

Dq is the dose at which the linear portion of the survival curve, extrapolated backward, cuts the dose axis drawn through a survival fraction of unity (100%)

Question 27

What is extrapolation number?

Answer 27

this is 'n'; tells us about the shoulder of the curve. It is the width of the shoulder. If n is large, shoulder is broad

Question 28

How do you find D0 on graph?

Answer 28

CHOOSE A LINEAR PART!! Doesn't matter where, just choose a part and go to approx 37%

Question 29

What does it mean if you see the cell survival curve with lots of repeated shoulders?

Answer 29

FRACTIONATION of dose

Question 30

What is the "bystander effect"?

Answer 30

It is when cells closeby to those cells that are directly irradiated by a charged particle gets damaged

Question 31

When is the bystander effect most pronounced?

Answer 31

When the cells are joined by gap-junctions: 30% bystander cells will die

Question 32

What is apoptosis and mitotic death?

Answer 32

You know this already!

Question 33

What is AUTOPHAGY? How is it different from apoptosis?

Answer 33

AUTOPHAGY - self eating: using lysosomes. apoptosis is programmed cell death. Autophagy is a type (2) of apoptosis

Question 34

What is senescence? What protein is involved?

Answer 34

A type of cell death - when the cell is stressed out... p53 and Rb (Rubbish bin... lol) and 53kg...

Question 35

If a response to radiation is expected, no matter how small the dose, then that dose-response is _____. Threshold or non-threshold?

Answer 35

non-threshold; like alpha particles?

Question 36

Radiation induced genetic damage follows a _____ dose-response relationship. Linear-non-threshold or linear-threshold

Answer 36

Linear non-threshold

Question 37

In a linear qudratic model, is alpha or beta constant smaller?

Answer 37

Beta- because alpha is more steep

Question 38

The mean probability of one particle causing a lesion is linearly proportional to dose

Answer 38

True