Chapter 3 - Cell Survival Curves Flashcards
The term cell death means multiple things; name some.
Loss of function Loss of reproductive integrity
A survivor cell that has retained its reporductive integrity and is able to proliferate indefinitely to produce a large colony is called?
Clonogenic
Types of cell death?
Apoptosis Mitotic Autophagic Senescence Bystanders Effect
Apoptosis occurs in what cells when exposed to radiation?
Lymphoid
What is the most common type of cell death
Mitotic
What is the Bystander Effect?
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.
How is the number of lethal aberrations per cell correlated with survival of that cell
Direct correlated`
What is senescene?
Permanent cell arrest (Can’t move from G1-S)
Even though a cancer cell has undergone senescene (permanent cell arrest) how can they continue to be destructive?
They continue to release mitogenic or cytokines and contribute to tumor regrowth
Which cells are more sensitive to radiotherapy; apoptotic cells or mitotic death dominated cells?
Apoptotic
Usually cells become less sensitive to radiation as the differentiate; however, in cancer what happens?
Stem cells are more resistant - Likely due to an increase in free radical scavengers
Plating efficiency is what?
How many cells actually produce colonies on a plate. - Due to cell type - Augar used - Plating technique
Radiation cell lethality is focused on?
DNA - nucleus
Cells that die via mitotic death have a what ratio between the cell survival and avg number of lethal chromosomal aberrations?
Direct 1:1
How can you tell on your gels if the cell has undergo apoptosis?
Fragments are all multiples of 185 base pairs
Genes controlling what in a mammalian cell affect radiation sensitivity?
DSB repair
Is there a link between sensitivity to killing by radiation and prediposition to cancer?
Yes
Who are more sensitive to radiation; mammalian cells or microorganisms, and why?
Mammalian because the DNA complex is physically bigger so bigger target
What is the doses of radiation will destroy nonproliferating cells? Proliferating cells?
100 Gy 2 Gy
What is the equation for plating efficiency?
PE = #colonies counted/Number of cells seeded
Surviving fraction equation?
SF = # Colonies counted/Cells seeded x (Plating efficiency/100)
What a Do mean?
Dose required to reduce the survival of cells by 1 log or to 37%
What is D10 mean?
Dose required to reduce the survival of cells by 90%
What is the D10 equation?
D10 = 2.3 x Do
What is the extrapolation number and quasithreshold dose?
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
What is the alpha/beta ratio?
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)
Why do high LET or alpha particles have straight survival curves?
They fuck shit up so much that the cell cannot repair so there is no curve
What is the linear-quadratic model?
Uses alpha and beta to find survival fraction S= e-alphaD - ßDsquare
Most cancers are caused by a loss of function or gain of function?
Loss of function - usually loss of correcting mechasims
Some do gain functions through oncogenes
What is p53?
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.
High Do would mean what? What is the avg Do for mammalian cells?
High Do = radioresistence
Mammalian cells’ Do = 1-2gy
