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Issues in Risk Assessment (1993) / Chapter Skim
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QUALITATIVE INFORMATION
Pages 43-48

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From page 43...
... Please use the print version of this publication as the authoritative version for attribution. 3 Advantages and Disadvantages of Bioassays that Use the MTD QUALITATIVE INFORMATION The current animal bioassay was designed as a qualitative screen for carcinogenicity and noncarcinogenicity.
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From page 44...
... If a chemical alters physiologic processes the alterations can influence delivery of the chemical or its metabolites to a target site or its clearance from a target site. An example is the effect of large lung burdens of particles on clearance of particles inhaled later (Lee et al., 1985)
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From page 45...
... , exposures of animals to high doses of the chemical, particularly in bolus doses, can lead to an underestimation of the potential for tumor production at lower doses. If the high-affinity low-capacity metabolic enzymes play a protective role in an organism, and the low-affinity high-capacity enzymes produce reactive, potentially toxic intermediates, then administration of high doses might cause a shift in metabolism to the more toxic pathway.
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From page 46...
... . Reserpine has been reported to produce adrenal medullary tumors in male rats, mammary tumors in female mice, and seminal vesicle tumors in male mice (DHEW, 1979)
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From page 47...
... The specificity and sensitivity of animal bioassays are also important considerations for evaluating the predictability of bioassay results for humans. Sensitivity refers to the ability of bioassays to detect true human carcinogens, and specificity refers to their ability to avoid mistaking substances that do not cause cancer in humans for carcinogens.
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From page 48...
... Please use the print version of this publication as the authoritative version for attribution. might be an overestimate or underestimate of the true MTD, that the fractions of the highest dose that are tested are still high doses, and that, as the dose is reduced, the statistical power to detect an effect is also reduced.
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Key Terms

  • lower doses
  • animal bioassays
  • animal studies
  • thyroid hormone
  • human carcinogens

  • low doses
  • operational definition
  • hormonal imbalance
  • animal data
  • evidence supporting

  • serum prolactin
  • mtd provides
  • tumor production
  • microsomal enzyme
  • response element

  • current bioassay
  • hepatic microsomal
  • lungs rapidly
  • male rat
  • dose exposures

  • adrenal gland
  • increase serum
  • bioassays conducted
  • designing followup
  • designs usually

  • decreased serum
  • produce thyroid
  • hormone concentrations
  • tumor incidences
  • increased tumor


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