EXAM #6 ( Lectures 3 + 4)

Question 1

What is Programmed cell death (apoptosis and autophagy)

Answer 1

Requires energy, activation of caspases (proteolysis) and nucleases (chromatin fragment)

Question 2

What is Necrotic death

Answer 2

Loss of energy leads to ion imbalance across the plasma membrane (Na/K ATPase)

Question 3

What is Mitotic death

Answer 3

Acute mitotic catastrophe, or loss of essential genetic material.

Question 4

_____ shows cell swelling and rupture of cell membrane while apoptosis
shows chromatin condensation, DNA fragmentation and cell shrinkage.

Answer 4

Necrosis shows cell swelling and rupture of cell membrane while apoptosis
shows chromatin condensation, DNA fragmentation and cell shrinkage.

Question 5

_____ and _____ therapies have been used to induce apoptosis in some types of cancers.

Answer 5

Radiation and chemical therapies have been used to induce apoptosis in
some types of cancers.

Question 6

What’s a sublethal dose?

Answer 6

0.25-2 Sv

Question 7

What’s a lethal dose?

Answer 7

2-5 Sv

Question 8

What is a Deterministic (non-stochastic) effect ?

Answer 8

There is a threshold dose below which the health effect does not occur. The severity
of the health effect can increase as the radiation dose increases above the threshold.

Question 9

What is a Stochastic effect ?

Answer 9

Occur by chance and consist primarily of cancer and genetic effects.
SEVERITY is INDEPENDENT of absorbed dose.

Question 10

What is the law of bergonie and tribondeau?

Answer 10

Radiosensitivity of a cell is directly proportional to it’s reproductive capacity and
inversely proportional to it’s degree of differentiation. Mature (well-differentiated) cells are radioresistant.

Question 11

The LD__/__ is the dose necessary to kill 50% of the exposed population in 60 days

Answer 11

The LD50/60 is the dose necessary to kill 50% of the exposed population in 60 days

Question 12

In general, the radiation sensitivity of a tissue is proportional to the rate of proliferation of its cells and inversely proportional to the degree of cell _____.

Answer 12

In general, the radiation sensitivity of a tissue is proportional to the rate of proliferation of its cells and inversely proportional to the degree of cell differentiation.

Question 13

The objectives of radiation protection are to keep doses below the
practical threshold, preventing clinically significant deterministic (tissue) effects and limiting stochastic effects to a reasonable level in relation to benefits gained.

Answer 13

The objectives of radiation protection are to keep doses below the
practical threshold, preventing clinically significant deterministic (tissue) effects and limiting stochastic effects to a reasonable level in relation to benefits gained.

Question 14

In general, when radiation doses are fractionated, radiation damage to somatic tissues is __% reparable.

Answer 14

In general, when radiation doses are fractionated, radiation damage to somatic tissues is 90% reparable.

Question 15

Increasing treatment time allows for increased dose delivery to result in a…?

Answer 15

Increasing treatment time allows for increased dose delivery to result in a
comparable biologic outcome.

Question 16

To achieve an increase in tolerance of late-responding tissues through dose
fractionation, the time interval between the dose fractions must be long enough
(~__ hours) to allow cellular repair to approach completion.

Answer 16

To achieve an increase in tolerance of late-responding tissues through dose
fractionation, the time interval between the dose fractions must be long enough
(~6 hours) to allow cellular repair to approach completion.

Question 17

_____: The MINIMUM amount of radiation at which a biological
response can be observed. BELOW this dose a person has a negligible chance
of sustaining biologic damage.

Answer 17

Threshold Dose: The MINIMUM amount of radiation at which a biological
response can be observed. BELOW this dose a person has a negligible chance
of sustaining biologic damage.

Question 18

Death from acute whole body irradiation follows the _____ curve.

Answer 18

Death from acute whole body irradiation follows the non-linear threshold curve.

Question 19

Repopulation of tumors during and after radiation treatment is one of the main
reasons for failure of conventional fractionated radiotherapy.

Answer 19

Repopulation of tumors during and after radiation treatment is one of the main
reasons for failure of conventional fractionated radiotherapy.

Question 20

_____ and _____ can make tissue more sensitive to a second

dose of radiation.

Answer 20

Reassortment and reoxygenation can make tissue more sensitive to a second
dose of radiation.

Question 21

_____ and _____ make tissue more resistant to a second dose of radiation.

Answer 21

Repair and repopulation make tissue more resistant to a second dose of radiation.