Cell Survival Curves

Question 1

Reproductive Death

Answer 1

Loss of the ability to divide indefinitely

Question 2

Relevant Doses

Answer 2

100 Gy - destroys cell function in non-proliferating systems

2 Gy - mean lethal dose for loss of proliferative capacity

Question 3

In-Vitro

Answer 3

Studies performed on cells outside of their biological context (in petri-dishes)

Question 4

Clonogenic Cells

Answer 4

Cells that have retained reproductive integrity and is able to proliferate indefinitely

Question 5

Survival Curve

Answer 5

Describes the relationship between radiation dose and the fraction of cells that survive that dose

Question 6

Plating Efficiency

Answer 6

Percentage of cells, in the control batch, that grow into colonies

Question 7

Surviving Fraction

Answer 7

Fraction of cells that plate successfully and survive irradiation

(Colonies Counted) / (Cells Seeded x Plating Efficiency/100)

Question 8

Relationship between survival curves and LET

Answer 8

As LET increases:

• Slope of curve increases
• Curve becomes more linear on semi-log plot
• Shoulder disappears

Question 9

2 General Cell Survival Models

Answer 9

Linear Quadratic Model

Multi-target Model

Question 10

Linear Quadratic Model

Answer 10

First component - cell killing is proportional to dose for damage caused by a single event

Second component - cell killing is proportional to dose squared for damage caused by multiple events

Question 11

Multi-target Model

Answer 11

Based on the probability of hitting the target

Initial slope is due to single-event killing and final slope is due to multiple-event killing

Question 12

Bystander Effect

Answer 12

Induction of biological effects in cells not directly traversed by a charged particle but in close proximity to the charged particle

Appears mainly at low doses

Question 13

Cause of Bystander Effect

Answer 13

Cytotoxic materials produced in irradiated cell is released into bystander cells via gap-junction communication medium and cause bystander cell death

Question 14

Apoptotic (Programmed) Cell Death

Answer 14

Cell ceases to communicate with neighbors
Cell detaches from neighbors
Chromatin condenses at nuclear membrane
Fragmentation of nucleus
Cell shrinks and separates into membrane bound fragments
Little or no dose-rate effect

Question 15

Mitotic Cell Death

Answer 15

Most common form of cell death following radiation exposure
Results from exchange type aberrations
Cells die attempting to divide with damaged chromosomes
Substantial Dose Rate Effect

Question 16

Fixed Post-Mitotic Cells

Answer 16

Do not divide, highly differentiated

-skin, red blood cell, muscle, nerve

Question 17

Reverting Post-Mitotic Cells

Answer 17

Don’t divide regularly, but can if needed

-Liver Cells

Question 18

Differentiating Inter-Mitotic

Answer 18

Divide regularly, some differentiation

-Spermatocytes

Question 19

Vegetative Inter-Mitotic

Answer 19

Produce cells like themselves, go through mitosis regularly

-Intestinal crypt cells

Question 20

Cell Classifications from least radiosensitivity to highest radiosensitivity

Answer 20

Fixed Post-Mitotic

Reverting Post-Mitotic

Differentiating Inter-Mitotic

Vegetative Inter-Mitotic