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  • Rights: University of Waikato. All Rights Reserved.
    Published 4 September 2012 Referencing Hub media
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    Paul McNabb explains LD50 – a lethal dose1 given to animals to determine the toxicity2 of a toxin3. The graph in the clip shows the cumulative4 population5 response to increasing doses of a toxin.

    Transcript

    Paul McNabb

    One of the first things we do if we discover a new toxin is do something called an LD50, so it’s a lethal6 dose7 which kills 50% of the test animals. And that’s usually done initially by injection of a toxin into the mouse and then that would be followed by feeding the toxin to the mouse. It would be most common for toxins to be more potent when injected than when fed, and the difference between those different types of LD50 can tell us about the toxin, how much of a risk it may be.

    And we’ve certainly had examples in the past where toxins that are very potent by injection are a lot less potent by feeding. And that means that, if we’re doing our mouse bioassays to check our food is safe by injection, we’re often overestimating the risk because the risk when the toxin is eaten is a lot less. So we incorporate that information about each toxin into our LC-MS test, and then that helps us assess by the LC-MS whether the food is safe or unsafe.

    1. lethal dose (LD50): Also written as LD50. This is the amount of or length of exposure to a substance that causes death in 50% of the species studied under experimental conditions.
    2. toxicity: The level of harm a toxin can cause.
    3. toxin: A poisonous substance that is a specific product of the metabolic activities of a living organism.
    4. cumulative: Gradually building up.
    5. population: In biology, a population is a group of organisms of a species that live in the same place at a same time and that can interbreed.
    6. lethal: Capable of causing death.
    7. dose: The amount of a substance that comes into contact with a living organism or some part of a living organism.
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      lethal dose (LD50)

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    2. Also written as LD50. This is the amount of or length of exposure to a substance that causes death in 50% of the species studied under experimental conditions.

      cumulative

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    4. Gradually building up.

      dose

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    6. The amount of a substance that comes into contact with a living organism or some part of a living organism.

      toxicity

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    8. The level of harm a toxin can cause.

      population

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    10. In biology, a population is a group of organisms of a species that live in the same place at a same time and that can interbreed.

      toxin

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    12. A poisonous substance that is a specific product of the metabolic activities of a living organism.

      lethal

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    14. Capable of causing death.