Chapter Fifteen Experimental Design and Methodology

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Experimental Design and Methodology  Experimental design profoundly influences the outcome of a research study and is, therefore, extremely important.  The first step in designing an experiment is identifying and clearly defining the question or problem to be studied.  The objectives of the research study must be realistic, in other words, they must be achievable.  The next step is to choose the research model that is best suited for the experiment.  The model may be a culture of animal or bacterial cells also termed in vitro, or a whole animal of a particular type termed in vivo.

The Research Project  Identify the problem.  Select appropriate model.  Experimental plan includes these components:  literature search  model to be used  species, strain, number, and justification  the hypothesis - the problem or question  step-by-step schedule of experimental manipulation  methods for data collection & assessment  adverse reactions or potential personnel hazards  description of nursing care for animals  budget  qualifications of investigators

Experimental Groups  >1 control group  not subjected to experimental treatment  >1 test group  experimental, control & sham group  treated, non-treated & injection effect difference  Any factor or condition that can change = variable.  research manipulations  animal strain  age, gender  environmental conditions  Avoid introducing unplanned variables.  Protocol & SOPs help avoid unplanned variables.

Experimental Groups Continued  Utilize highly homogeneous animal populations  identical breed, strains, sex, age and weight  Technical errors such as:  mixing or exchanging strains  improper animal identification  errors in weighing or medicating  incorrect recording of data  variations in environment  increasing the noise level  changing or supplementing a standard diet  showing favoritism toward individual animals

Animal Models  Animals used in research = animal models  Study diseases as well as normal functions.  Model mimics situation to study in humans.  Animal models categorized as natural or induced.  Natural = a disease or entity that occurs spontaneously.  Atherosclerosis is natural disease in the squirrel monkey.  Epilepsy occurs in Mongolian gerbils.  Diabetes occurs in some strains of mice.  Induced = a disease or condition artificially produced.  Tumor cells injected into animals to study cancer.  Animals treated with chemicals to cause cancer.  Chemicals in cigarette smoke cause cancer.  Practical matters affect research study.  costs, availability, skill

Research Methodology  Dietary studies  What foods are best to eat?  What is best to feed an animal?  Nutrients & digestive fluids = complex interactions.  One nutrient decreases when another increases.  Effects of poisons reduced by addition certain nutrients.  Bioassay = determining substance activity.  Synthetic hormone compared w/ one occurs naturally.  Bioassays used to test for substances for which no in vitro test is known.

Implants & Cannulations  Device placed into living tissue.  Permanent:  cardiac pacemakers  artificial heart valves  bone pins and plates  Replacement joints  Other materials & devices implanted in animals:  electrodes into the brain or heart tissues  tubes, windows and ports for frequent sampling/injection of substances  osmotic pumps under the skin for a regulated continuous flow of medications or test substances

Implants & Cannulations II  Most common implant = cannulation.  insertion of small tube into body cavity, duct or vessel  Flexible rubber or plastic tubes used.  inserted in natural opening of body  Catheter through needle into vein  1 danger is introducing bacteria.  Aseptic procedures essential to avoid infection.  Report these difficulties to your supervisor:  excessive discharge around the implant  kinked tubing  attempts by the animal to dislodge the implant

Basic Biological Studies  < 25% components of body isolated & identified  How does the immune system fight cancer?  How to prevent birth defects of heart or spinal cord?  Why do animals develop bleeding disorders?  Why are some nutrients needed by certain species?  Why does parturition occur at end of gestation?  What makes animals get old and die?  Why are some strains > resistant to disease?  How does the brain work?  What factors are involved in mental disorders?  List of questions & potential answers is endless.

Safety Evaluations  Determine how new products affect users, environment, & future generations.  Some tests are nontraumatic.  Other tests may result in pain or death.  Important goal is to get the largest amount of information from smallest number of animals  Tests determine if material is toxic:  Provide appropriate warnings to future users.  Set production and use.  Set transportation standards.  Vaccine production  Each batch tested to ensure product is safe & effective.

Behavior Motivation Experiments  Behavior is response to environment.  Action and response to stimulation = behavior.  Psychology = science of human mind & behavior.  Ethology = scientific study of animal behavior.  Physiological psychology = structures & functions of body responsible for behavior.  functioning of nerve tissue  mechanisms of sensation  perception and learning  development of behavior in people and animals

Behavior Motivation II  Normal and abnormal behavior is common to humans and animals.  Relationship of psychological stress & immune response to infection.  Stress reduces effectiveness of immune response.  Inappropriate handling may influence results of experiments where stress is not meant to be a factor.  Animal rights advocates raise ethical & moral issues.  Questions on animal behavior that require legitimate scientific inquiry.  These questions provide motivation for further research in animal behavior.

(Image) Primate Transfer to Enrichment Cage

(Image) Primates in Enrichment Cage

Additional Reading Scher, S. “Setting Up an Animal Experiment.” Vet. Tech. 7(5):217–220, May, 1986.