Mechanism and Principle

Question 1

1. Aldrin and heptachlor are metabolized by MFO systems to corresponding intermediates which are more toxic than the parent compounds.  One such class of intermediates is
A) aldehydes
B) epoxides
C) ketones
D) none of the above

Answer 1

B

Question 2

2. Considerable evidence indicates that benzo(a)pyrene is metabolically activated to an electrophilic carcinogenic
A) K region arene oxide
B) free radical
C) quinine
D) diol epoxide
E) superoxide

Answer 2

D

Question 3

3. NADPH (TPNH) is required as a cofactor for
   1) the microsomal pathway of drug oxidation
   2) conjugation by acetylation
   3) the microsomal pathway of drug reduction
   4) oxidation or reduction by liver alcohol dehydrogenase
   Choose: A if 1, 2 and 3 are correct; B if 1 and 3 are correct; C if 2 and 4 are correct; D if only 4 is correct; E if all are correct

Answer 3

B

Question 4

4. The formation of oxygen radicals as a mechanism of action applies to which of the following?
   1) paraquat
   2) adriamycin
   3) bleomycin
   4) nitrofurantoin
   Choose: A if 1, 2 and 3 are correct; B if 1 and 3 are correct; C if 2 and 4 are correct; D if only 4 is correct; E if all are correct

Answer 4

E

Question 5

5. Which of the following is/are correct?
   1) oxidation of cytochrome P450 results in “active oxygen”
   2) “active oxygen” is required for metabolism of all drugs
   3) cytochrome P450 will complex with carbon monoxide
   4) cytochrome P450 is required for metabolism of all drugs
   Choose: A if 1, 2 and 3 are correct; B if 1 and 3 are correct; C if 2 and 4 are correct; D if only 4 is correct; E if all are correct

Answer 5

B

Question 6

6. High molybdenum content in the soil may lead to defective myelination in young ruminants by
   A) a direct destructive effect on myelin
   B) damaging the cells that produce and maintain myelin
   C) interfering with copper absorption to produce a copper deficiency which causes demyelination
   D) activation of a virus which produces demyelination
   E) stimulation of the immune system to produce antibodies against the basic myelin protein

Answer 6

C

Question 7

7. Which of the following substances prevents the release of acetylcholine from the axon terminal?
A) curare
B) parathion
C) carbaryl
D) botulinum toxin
E) DDT

Answer 7

D

Question 8

8. Which of the following has a mechanism of toxic action related to hepatic microsomal free radical formation?
A) carbon monoxide
B) methane
C) kerosene
D) carbon tetrachloride
E) carbon disulfide

Answer 8

D

Question 9

9. Which of the following is the molecular basis for the acute effects of cyanide poisoning?
A) formation of methemoglobin
B) formation of carboxyhemoglobin
C) inhibition of sulfydryl enzymes
D) inhibition of cytochrome oxidase
E) inhibition of hydrolytic enzymes

Answer 9

D

Question 10

10. Which of the following is characteristic of ethylene glycol?
    A) it uncouples oxidative phosphorylation
    B) it is metabolized to formic acid
    C) it is metabolized to oxalic acid
    D) it inhibits aconitase
    E) it inhibits the effect of vitamin K

Answer 10

C

Question 11

11. In antagonizing methemoglobinemia, methylene blue
    A) serves as an artificial oxygen transporting system in blood
    B) is converted from its oxidized form to its reduced form by NADPH
    C) facilitates the reduction of iron in hemoglobin from Fe+++ to Fe++
    D) displaces the toxicant from hemoglobin
    E) is oxidized by methemoglobin reductase

Answer 11

C

Question 12

12. Which of the following is a potent inhibitor of cytochrome oxidase?
A) acetazolamide
B) hydrocyanic acid
C) iproniazid
D) physostigmine
E) para-aminosalicylic acid

Answer 12

B

Question 13

13. Which of the following chemical pair interactions are appropriate?
    1) propanol - carbon tetrachloride: potentiation
    2) morphine - naloxone: synergism
    3) mercury - BAL: chemical antagonism
    4) propoxyphene - amytal: dispositional antagonism
    Choose: A if 1, 2 and 3 are correct; B if 1 and 3 are correct; C if 2 and 4 are correct; D if only 4 is correct; E if all are correct

Answer 13

B

Question 14

14. For a toxic effect to occur, it is necessary that the toxic agent or its metabolites
    1) reach an appropriate receptor
    2) be present at sufficiently high concentrations
    3) be present for enough time to produce an effect
    4) exhibit bioaccumulation
    Choose: A if 1, 2 and 3 are correct; B if 1 and 3 are correct; C if 2 and 4 are correct; D if only 4 is correct; E if all are correct

Answer 14

A

Question 15

15. Hyalin droplet nephropathy induced by unleaded gasoline (trimethylpentane) or d-limonene is characterized by which of the following?
    1) activation of these agents by proximal tubular (P-2 segment) cytochrome P450
    2) a male-specific response in the rat
    3) binding of activated metabolites to basement proteins in the glomerulus
    4) binding of the agents to alpha-2-microglobulin and subsequent accumulation in P-2 segment proximal tubular cells
    Choose: A if 1, 2 and 3 are correct; B if 1 and 3 are correct; C if 2 and 4 are correct; D if only 4 is correct; E if all are correct

Answer 15

C

Question 16

16. Pyrethroid insecticides appear to affect the nervous system by
    A) interfering with sodium conductance in individual neurons
    B) reversibly binding to cholinesterase enzymes
    C) irreversibly binding to brain acetylcholinesterase
    D) inhibiting the TCA (Krebs) cycle
    E) displacing oxygen from receptors in hemoglobin

Answer 16

A

Question 17

17. The distinction between genotoxic and epigenetic carcinogens
    A) has been useful for regulatory decision making since the early 1960’s
    B) is unimportant
    C) is that genotoxic carcinogens produce an observable change in genetic material but epigenetic carcinogens do not
    D) cannot be made on the basis of current knowledge
    E) is crucial because humans are not susceptible to cancers produced in animals by epigenetic carcinogens

Answer 17

C

Question 18

19. A known example of drug action which is dependent upon individual heredity is
    A) antibacterial effects of sulfadiazine – dependent on rates of acetylation of the drug
    B) analgesic effects of meperidine – dependent on rates of hydrolysis of the drug by liver and plasma enzymes
    C) anticonvulsant effects of phenobarbital – dependent on rates of penetration of the drug into the CNS
    D) neuromuscular blocking effects of succinylcholine – dependent on rate of hydrolysis by plasma esterases
    E) antihistaminic effects of chloroquine – dependent on rates of absorption from the GI tract

Answer 18

D

Question 19

20. If the compound 1,2-bis(2-chloroethyl)-1-nitrosourea (BCNU) is added to hepatocytes which are being subjected to an oxidative stress, what will likely happen to the GSH levels of these cells, compared to an identical hepatocyte incubation without BCNU?
    A) GSH levels will be zero in cells with BCNU because BCNU catalytically destroys GSH
    B) GSH levels will be similar in cells with and without BCNU
    C) GSH levels will be-higher in cells with added BCNU
    D) GSH levels will be lower in cells with added BCNU

Answer 19

D

Question 20

21. Which of the following accurately describes hydrogen sulfide?
    A) can bind to methemoglobin
    B) inhibits cytochrome P-450 reductase
    C) requires thiosulfate as an antidote
    D) is much less toxic than hydrogen cyanide
    E) all are correct

Answer 20

A