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.
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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.
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3. The intestinal epithelium cells are:
a. early-responding tissues.
b. late-responding tissues.
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4. The kidney tissue is:
a. early-responding.
b. late-responding.
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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.
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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.
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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.
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8. The most radiosensitive cells are:
a. the bone-marrow cells.
b. the mammary cells.
c. the thyroid cells.
d. the ataxia telangiectasia cells.
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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.
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