Animal model Outlines

Animal model

 

INTRODUCTION

• Animal – Latin- soul/spirit
• Model – object of imitation- something that accurately resembles something else
• Animal model – animated object of imitation – investigate a physiological or pathological circumstance

 

ANIMAL MODEL

• Living organism – animal
• Normative biology / behaviour can be studied,
• Spontaneous / induced pathological process can be investigated,
• Phenomenon resembles humans or other species of animal

 

USE OF ANIMAL MODEL

• Assessment of pathogenic mechanisms
• Diagnostic and therapeutic procedures
• Nutrition and metabolic diseases
• Efficacy of novel drug development

 

TYPES OF ANIMAL MODELS

• Exploratory – understanding of normal / abnormal fundamental biological mechanisms.
• Explanatory – understanding of complex biological problems.
• Predictive – Discover and quantify the impact of investigative treatments whether for diseases or chemical toxicities

 

DISEASE RELATED ANIMAL MODEL

• Induced (experimental) – experimentally created either through surgical modifications, genetic modifications, or chemical injections.
• Spontaneous – genetic variants, which mimic the human condition. Variance occurs naturally through mutation and not by experimental induction.
• Transgenic – induced models in which DNA is inserted into or deleted (knockout) from the genome of the animal.

 

• Negative – negative models fail to react to a disease or chemical stimulus. Studies on the mechanism of disease resistance.
• Orphan – opposite of negative models – disease occurs but there is absence of corresponding disease in humans.
• Orphan models – become induced models when a similar disease is recognized in humans.

 

SUBCATEGORY

• Fidelity – the extent a biological structure in an animal resembles that of a human.
• Homologous – symptoms shown in the animal are identical to those shown in the human.
• Isomorphic – animal’s symptoms or anatomy are similar to those in the human but the etiology or genetic character is different.

 

SUBCATEGORY

• Partial – these models do not mimic the entire human disease but enough similarities exist to allow their use in studying aspects of the disease or treatments.
• Face validity – the degree to which there is a similar phenotypic display between the disease in the animal and the corresponding disease in the human.
• Construct validity – the degree to which there is a similar genetic display between the disease in the animal and the corresponding disease in the human.

 

CHOOSING THE RIGHT MODEL

1. Research factors
2. Animal care factors
3. Physical and environmental factors
4. Animal-related factors
5. RESEARCH FACTORS

• Appropriateness as an analogue – the part or organ being studied has function similar to target species.
• Transferability of information – define a process in a system with the hope of transferring the data gained to a more complex system.
• Generalizability of the results – the ability to generalize results to the target species.
• Ethical implications – certainly research must start with justification for using an animal.
• Numbers needed – numbers needed to provide scientific validity.
• Customary practice within a particular discipline.
• Existing body of knowledge of the problem – thorough literature search before forming basis for the research project.
• Natural versus experimentally produced models -unavailability of natural models will require the use of experimentally produced models.

2. ANIMAL CARE FACTORS

• Cost and availability
• Housing availability
• Husbandry expertise
• Stress factors – transportation, handling and manipulations, overcrowding, lack of environmental enrichment, and the research project itself.

 

3. PHYSICAL / ENVIRONMENTAL FACTORS

• Ecological consequences – ecological consequences must be considered in its removal.
• Hazardous components – use of chemicals, infectious agents, and radioisotopes.
• Environmental influences – environmental factors -physical, chemical, biological, and social may impact the physiological and behavioural. Humidity, ventilation, light cycle and quality, noise, cage size and bedding materials, diet and water, and room temperature.

4. ANIMAL-RELATED FACTORS

• Genetic aspects – uniformity of organisms may be necessary where applicable
• Background knowledge of biological properties – knowledge of biological properties – generalized and specialized function of body components is needed.
• Ease of and adaptability to experimental manipulation.
• Size of the animal – size of the animal impacts housing and husbandry availability.
• Life span and age.
• Progeny in a single birth.
• Diseases or conditions that might complicate results.
• Special features of the animal such as unique responses or micro flora. It is important to be familiar with unique anatomical or physiological features of the species.

 

EXTRAPOLATION TO HUMANS

• Key factor -animals in research -extrapolation of results to humans.
• Plurispecies approach – two species in toxicology screening, one of which has to be non rodent.
• Metabolic patterns and speed and body size must match between species.
• Experimental design and the life situation of the target species must correspond.

 

DESCRIPTION OF ANIMAL MODEL

• Genetic strain and sub strain using correct international nomenclature
• Special genetic features
• Microbial status of the animal
• Age
• Housing standards
• Maintenance procedures
• Diet