Chapter 18
Dose-response relationships for model normal tissues



1. Which of the following statements is false?

a. Most cells in vitro die a mitotic death after irradiation.

b. Apoptosis (programmed death) occurs both in normal tissue cells and in neoplasm cells.

c. Irradiated cells cannot die by apoptosis.



2.There is a number of techniques available to determine the dose-response relationship of normal tissues. Amongst them, the clonogenic assays are techniques in which:

a. the endpoint observed depends directly on the reproductive integrity of individual cells (either in situ or in a different tissue where the cells are transplanted after irradiation.)

b. functional endpoints are studied (which tend to reflect the minimum number of functional cells remaining in a tissue).

c. one infers the dose-response curve for a tissue in which it cannot be directly observed by performing a number of multifraction experiments.



3. The intestinal epithelium cells are:

a. early-responding tissues.

b. late-responding tissues.



4. The kidney tissue is:

a. early-responding.

b. late-responding.



5. The radiation response of all tissues (early-responding and late-responding) results from a depletion of the critical parenchymal cells.

a. True.

b. False.



6. Which of the following statements referring to clonogenic assays in situ is false?

a. The survival curves of mouse skin colonies were studied for single-dose and double-dose exposures. The study resulted in a D0 value of 1.35 Gy and a Dq value of 3.5 Gy.

b. To obtain the survival curve for the jejunal crypt cells in mice, groups of animals were exposed to graded total-body doses (at different fractionations) and the number of regenerating (i.e. surviving) crypt cells were subsequently measured. The study resulted in a D0 value of 1.3 Gy and a Dq value in the range 4 - 4.5 Gy.

c. In testes stem cells studies, it was found that D0 has the value of 1.7 Gy and Dq is equal to 2.7 Gy.

d. The radiosensitivity of kidney tissue was found to be very different from the radiosensitivities of skin, crypt cells and testes.



7. Which of the following statements about clonogen transplant assays is false?

a. In clonogen assays, the survival curve is extracted by measuring the ratio of irradiated to unirradiated cells that are required to produce a colony (as a function of dose).

b. Bone-marrow stem cells in mice are the most sensitive mammalian cells to die a mitotic death (D0=0.95 Gy) and they have a little shoulder in the survival curve.

c. The D0 for mammary cells has the value 1.27 Gy.

d. The D0 value for thyroid gland cells is a little higher than the D0 value for mammary cells, which shows that the thyroid cells are more sensitive than the mammary cells.



8. The most radiosensitive cells are:

a. the bone-marrow cells.

b. the mammary cells.

c. the thyroid cells.

d. the ataxia telangiectasia cells.



9. Which of the following statements (regarding dose-response observations for functional endpoints) is false?

a. Skin cells show both an early and a late reaction to radiation.

b. Experiments on skin reaction with pigs and mice have shown similar results.

c. The lung shows both early and late response to radiation.

d. Experiments on rats have shown that the spinal cord has a late response to radiation.