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Model Organisms for Human Research
Rationale for Model Organisms: Model organisms are used to study aspects of human physiology or pathophysiology that are not feasible to investigate directly in humans. This allows for invasive or longitudinal studies that would otherwise be impossible or unethical.
Zebrafish (Danio rerio):
Advantages: Their transparent eggs and embryos allow for continuous, non-invasive observation of embryonic development under a microscope without harming the organism. This is a significant ethical and practical advantage.
Physiological Similarities: Possess a central nervous system, hormonal regulation, and a circulatory system with hemoglobin, allowing modeling of most human systems, despite differences in heart structure.
Limitations: Lack lungs, arms, and legs.
Rearing: Easy to breed and maintain in aquariums through multiple cycles.
House Mouse (Mus musculus):
Primary Mammalian Model: The most widely used model organism for vertebrate and human physiology, particularly for genetics (compared to fruit flies for animal genetics).
Physiological Similarities: Possesses an immune system, four limbs, breathes air, and shares most human features, with minor differences that facilitate their growth.
Limitations: Their relatively short lifespan means their immune systems are less developed compared to long-lived species like humans. For example, they may not develop immunity for future seasonal illnesses if their lifespan doesn't extend to the next season.
Phenomics Facilities: Large facilities (e.g., at ANU, the largest in the Southern Hemisphere) breed mice with specific individual gene mutations. This allows researchers to study the effects of particular drugs or treatments on individuals compromised in specific metabolic, immune, neural, or cardiovascular pathways, by selecting appropriate mouse strains.
Historical Context/Practicalities: Historically, transporting specific mutant mouse strains (e.g., from Switzerland) was extremely expensive and complicated, sometimes involving special treatment for the mice during transit. Modern facilities, like ANU's, make these resources more accessible locally.
Tamar Wallabies (Macropus eugenii) / Marsupials:
Unique Embryonic Development Model: Offer an alternative for studying mammalian embryonic development without invasive procedures like C-sections required for placental mammals (e.g., mice).
Mechanism: Marsupials give birth to a highly undifferentiated young, often referred to as a 'joey', which then completes its remarkable development ex utero in a pouch. This allows for direct, non-invasive observation and manipulation of post-natal embryonic development, including organogenesis and neurological development, as the joey is accessible within the pouch for study.