Chapter 3 - Cell Survival Curves

Question 1

The term cell death means multiple things; name some.

Answer 1

Loss of function Loss of reproductive integrity

Question 2

A survivor cell that has retained its reporductive integrity and is able to proliferate indefinitely to produce a large colony is called?

Answer 2

Clonogenic

Question 3

Types of cell death?

Answer 3

Apoptosis Mitotic Autophagic Senescence Bystanders Effect

Question 4

Apoptosis occurs in what cells when exposed to radiation?

Answer 4

Lymphoid

Question 5

What is the most common type of cell death

Answer 5

Mitotic

Question 6

What is the Bystander Effect?

Answer 6

Where one cell that was exposed to radiation dies and spills toxins on to other cells. These other cells may die even though they were not exposed to radiation.

Question 7

How is the number of lethal aberrations per cell correlated with survival of that cell

Answer 7

Direct correlated`

Question 8

What is senescene?

Answer 8

Permanent cell arrest (Can’t move from G1-S)

Question 9

Even though a cancer cell has undergone senescene (permanent cell arrest) how can they continue to be destructive?

Answer 9

They continue to release mitogenic or cytokines and contribute to tumor regrowth

Question 10

Which cells are more sensitive to radiotherapy; apoptotic cells or mitotic death dominated cells?

Answer 10

Apoptotic

Question 11

Usually cells become less sensitive to radiation as the differentiate; however, in cancer what happens?

Answer 11

Stem cells are more resistant - Likely due to an increase in free radical scavengers

Question 12

Plating efficiency is what?

Answer 12

How many cells actually produce colonies on a plate. - Due to cell type - Augar used - Plating technique

Question 13

Radiation cell lethality is focused on?

Answer 13

DNA - nucleus

Question 14

Cells that die via mitotic death have a what ratio between the cell survival and avg number of lethal chromosomal aberrations?

Answer 14

Direct 1:1

Question 15

How can you tell on your gels if the cell has undergo apoptosis?

Answer 15

Fragments are all multiples of 185 base pairs

Question 16

Genes controlling what in a mammalian cell affect radiation sensitivity?

Answer 16

DSB repair

Question 17

Is there a link between sensitivity to killing by radiation and prediposition to cancer?

Answer 17

Yes

Question 18

Who are more sensitive to radiation; mammalian cells or microorganisms, and why?

Answer 18

Mammalian because the DNA complex is physically bigger so bigger target

Question 19

What is the doses of radiation will destroy nonproliferating cells? Proliferating cells?

Answer 19

100 Gy 2 Gy

Question 20

What is the equation for plating efficiency?

Answer 20

PE = #colonies counted/Number of cells seeded

Question 21

Surviving fraction equation?

Answer 21

SF = # Colonies counted/Cells seeded x (Plating efficiency/100)

Question 22

What a Do mean?

Answer 22

Dose required to reduce the survival of cells by 1 log or to 37%

Question 23

What is D10 mean?

Answer 23

Dose required to reduce the survival of cells by 90%

Question 24

What is the D10 equation?

Answer 24

D10 = 2.3 x Do

Question 25

What is the extrapolation number and quasithreshold dose?

Answer 25

A dose threshold that does not show any death of cells or “does not show a biological effect” because the repair mechanisms of the cell over comes the amount of damage

Question 26

What is the alpha/beta ratio?

Answer 26

Ratio that corresponds to the survival curve The lower the ratio the more sensitive the cell is to radiation because it cannot replicate/repair as fast (non-proliferative normal cells) vs high ratio = less sensitive because it can replicate/repair fast (tumor cells or highly proliferative normal cells)

Question 27

Why do high LET or alpha particles have straight survival curves?

Answer 27

They fuck shit up so much that the cell cannot repair so there is no curve

Question 28

What is the linear-quadratic model?

Answer 28

Uses alpha and beta to find survival fraction S= e^{-alphaD - ßDsquare}

Question 29

Most cancers are caused by a loss of function or gain of function?

Answer 29

Loss of function - usually loss of correcting mechasims

Some do gain functions through oncogenes

Question 30

What is p53?

Answer 30

The “Guardian” of the genome. It is a protein that prevents replication if mistakes are noted.

Elephants have a ton of sequences dedicated to p53 and therefore if one breaks they still have a ton left. Thus why elephants don’t get cancer much.

Question 31

High Do would mean what? What is the avg Do for mammalian cells?

Answer 31

High Do = radioresistence

Mammalian cells’ Do = 1-2gy