Experimental Design Animal Models

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Experimental Design Animal Models
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Experimental Design and Methodology

• Experimental design profoundly influences the
  outcome of a research study
• Clearly define the question or problem being
  studied
• Realistic objectives (achievable)
• Choose the best research model

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Research Project

• Review current literature
• Identify the model to be used
• Develop an hypothesis
• Concise step-by-step plan for the experiment
• Description of the methods to be used
• Description of the adverse reactions or potential
  personnel hazards
• Budget

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Control and Experimental Groups

• Variables
• Any factor or condition that can change
• Specific research manipulation
• Animal strain
• Age
• Gender
• Environmental conditions

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Common Errors in Experimental Design

• Mixing or exchanging strains of animals
• Improper animal identification
• Errors in weighing or medicating animals
• Incorrect recording of data
• Variations in room temperature, lighting diet,
  bedding, or cage type
• Increase in noise level
• Changing the diet

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Animal Models

• Experimental Models (induced)
• Model in which the experimentally reproduced
  condition mimics a human condition
• Rats induce diabetes with streptozootocin
• Primates induce Parkinsons like disease by
  administration of MPTP

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Animal Models

• Negative Models (non-model)
• Models where a particular disease can not be
  produced
• Opossum resistant to rabies
• Rhesus monkeys resistant to hepatitis B
• Wood rat immune to snake bites
• Sharks are resistant to cancer
• Gerbils are resistant to radiation

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Animal Models

• Spontaneous Models (Natural)
• Model where the animal naturally acquires a
  disease which mimics a human disease
• Doberman Pincher von Willebrands disease
• NZW x NZB F1 autoimmune disease
• Hamster, mouse, Golden Retrievers muscular
  dystrophy
• BB rat and NOD mouse diabetes mellitus

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Immunodeficiency Models

• Animals that have some defect in their normal
  immune system.
• Used as models in immunology and oncology
  research.
• Understand the role the immune system plays in
  disease.
• Maintenance of tumor cell lines.

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Spontaneous Immunodeficiency

• Genetic manipulation is the most common method
  for inducing immunodeficiency.
• Deficiencies are found in lymphocytes,
  macrophages, or hematologic factors.

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Nude Mice

• Mutation results in hairlessness and lack of a
  thymus gland.
• Lack T-cells
• Need to be maintained in barrier facilities due
  to their susceptibility to disease.

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Other Immunodeficient Animal Models

• B-cell hereditary defects
• CBA/N
• Xid
• Asplenic mice
• B T-cell defects
• SCID (severe combined immunodeficiency)
• Natural Killer cell defect
• Beige

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Induced Immunodeficiency

• Surgery
• Removal of Thymus gland

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Induced Immunodeficiency

• Chemical
• Interrupt RNA and DNA synthesis
• Toxic
• Occupation health issues

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Induced Immunodeficiency

• Irradiation
• Sources
• Gamma irradiators
• Cobalt Isotope
• Cesium Isotope
• Types of Radiation Exposure
• Single Exposure
• Low level protracted semicontinuous radiation
• Partial body radiation

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Induced Immunodeficiency

• Transgenic and Knockout Technology
• Production of animals with specific, genetic
  immune deficiencies is almost limitless with the
  ability to manipulate DNA.

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Antibody Production

• Classic Vaccination
• Composed of disease organism or components,
  inoculation results in recipient producing
  antibodies to the disease.

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Antibody Production

• Polyclonal Antibodies
• Rabbits, sheep, and goats are commonly used
• SC, ID, or IM injections of antigen preparation
• Serum collected approximately 3 weeks after
  injections to test serum for presence of antibody
• Adjuvants may be used to stimulate antibody
• Directly stimulate immune system
• Prolong absorption of the antigen

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Cancer Models

• Induced Cancer Models
• Many causes of cancer are under investigation,
  including toxins, viruses, and pollutants.
• Inject cancer cells directly into animal.
• Topical application of cancer-causing chemicals.
• Transplantation of spontaneous tumors from one
  inbred animal to another inbred animal of the
  same strain.

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Cancer Models

• Spontaneous Cancer Models
• Some strains of inbred rodents have high
  incidence of naturally occurring cancers.
• 80 AKR mice develop leukemia before one year of
  age
• Evaluate animals frequently for changes in tumor
  size or metastasis.
• Animals should be euthanized if they are
  clinically ill, tumors are excessive size, or
  ulcerated.