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- NEW SET
- A
- The principal protector of the horseshoe crab's internal environment is
- a primitive white blood cell called the amebocyte. Like the free-living
- amebas for which it is named, it appears self-directed as it perambulates
- the blood-stream in search of endotoxin-producing bacterial invaders,
- including coliforms and other fecal bacteria. When it finds such a
- bacterium, the amebocyte releases an enzyme and a clotting substance, which
- reacts to transform the liquid blood around the bacterium into a sticky gel.
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- 1
- 1. As used in the above paragraph, the best definition for "perambulates" is:
-
- A. strolls
- B. rambles
- C. travels through
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- c
- 0
- B
- Correct.
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- wrong answer explanation
- B
- (C) The amebocyte travels through the bloodstream.
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- B
- The bacterium is immobilized and dies, like a tiger in a tar pit.
- Usually only a tiny bit of gel is formed, but in a massive bacterial
- infection, much of a horseshoe crab's blood turns to jelly - and the animal
- may die as a result.
- The active ingredients in this response can be extracted from the
- amebocytes; the purified extract is called LAL, for limulus amebocyte
- lysate. LAL is incredibly sensitive: It will detect as little as a
- billionth of a gram of endotoxin in an eyedropper of water.
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- 1
- 1. Endotoxins are:
-
- A. poisons released from bacteria
- B. part of the crab's protective system
- C. amebocytes
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- a
- 0
- C
- Correct.
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- wrong answer explanation
- C
- (A) They are poisons which are released by bacteria.
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- C
- The present test for endotoxin requires injecting the drug product
- into three to eight rabbits, then monitoring them carefully for several
- hours to see if they become feverish. This is expensive and slow, and
- takes many rabbits' lives. Blood specialist Levin decided that the same
- information might be obtained more expeditiously using horseshoe crab
- blood. Dr. Levin and his colleague, Dr. Frederick Bang, demonstrated that
- the crab's blood could detect endotoxin.
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- 1
- 1. Based on this paragraph, it appears that:
-
- A. Endotoxin is an ingredient used to manufacture drugs.
- B. Endotoxin contaminates drugs.
- C. Rabbits are immune to endotoxins.
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- b
- 0
- D
- Correct.
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- wrong answer explanation
- D
- (B) Endotoxins contaminate drugs.
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- D
- Producers of LAL test kits freeze-dry the lysate extract. It is
- then reconstituted with sterile water and added to a sample of the drug
- or antibiotic or biological product to be tested or, in the case of a
- medical device, to the saline solution in which the device has been
- washed. If endotoxin is present in a sample, a firm clot will form.
- In this way manufacturers can withhold from distribution products
- contaminated with endotoxin levels that could cause serious reactions.
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- 1
- 1. The lysate extract is freeze-dried:
-
- A. to make it edible
- B. to make it sensitive to endotoxins
- C. for ease of handling
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- c
- 0
- E
- Correct.
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- wrong answer explanation
- E
- (C) The extract is freeze-dried for shipping.
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- E
- "The test is now generally accepted as the best assay for
- endotoxin," hematologist Peter A. Tomasulo told a Woods Hole conference
- on horseshoe crabs and medicine. "The test is simple and easy to learn,
- and requires no sophisticated equipment."
- The test's principal users thus far are drug companies, for whom,
- Levin says, it provides a far more sensitive endotoxin assay than
- the rabbits.
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- 1
- 1. An endotoxin assay is:
-
- A. a substance used to eliminate endotoxins
- B. a method of producing endotoxins
- C. a chemical test to determine if endotoxins are present
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- c
- 0
- F
- Correct.
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- wrong answer explanation
- F
- (C) This is a test used for determining endotoxin presence.
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- F
- The LAL test also is being used to detect endotoxin in the body fluid
- specimens withdrawn from critically ill patients, although FDA has not
- specifically approved it for this purpose. It is particularly valuable,
- Levin reports, in the diagnosis of bacterial meningitis, a dangerous
- infection of the brain's membranes.
- "Of all the infectious diseases we treat," Levin says, "meningitis is
- the one in which rapid diagnosis and treatment are particularly critical.
- The difference between treating now and in six hours may be life and death."
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- 1
- 1. The LAL test is the fastest way to detect endotoxin.
-
- A. True
- B. False
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- a
- 0
- G
- Correct.
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- G
- (A) The LAL test is much faster than testing with rabbits.
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- G
- The standard tests are complicated and time-consuming. Using the
- experimental LAL test and a single drop of spinal fluid from the patient,
- meningitis due to gram-negative bacteria can be diagnosed in an hour,
- speeding the start of appropriate antimicrobial therapy.
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- 1
- 1. The LAL test can be used to diagnose meningitis due to gram-negative
- bacteria.
-
- A. True
- B. False
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- a
- 0
- H
- Correct.
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- wrong answer explanation
- H
- The LAL test can be used to test for meningitis due to gram-negative
- bacteria.
- end