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4 common rodent species used in biomedical research
- mouse
- rat
- syrian hamster
- guinea pig
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hipsodontic
all teeth are opened rooted and grow continuously throughout life
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suborders
myomorpha
sciuromorpha
hystricomorpah
- mouse/rat like
- squirrel like
- guinea pig like
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why is the mouse so useful in research
- small
- inexpensive
- easily maintained
- reproduces rapidly
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outbred stocks
genetic lines that are bred to maximize heterozygosity (gene diversity) and minimize inbreeding
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two common outbred stocks used
- CD - 1
- Swiss webster mouse
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inbred strains
breeding to produce offspring genetically identical (95%)
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when is inbred strains used
- controlled studies, studies that need reproducibility of conclusions
- (toxicology, behavioral studies)
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inbred strain related health issues
- microphthalmia (tiny eyes/missing) blindness
- early deafness
- mammary tumors
- ulcerative dermatitis
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two common inbred strains
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immunodeficient mouse strains
- used for tumor biology research, immunology studies
- require special housing and husbandry procedures
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two immunodeficient mouse strains
- nude mouse
- SCID mouse (sever combined immunodeficiency)
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Genetically engineered mice aka "designer mice"
- Trasgenics
- targeted mutants
- created for a specific purpose
- used as animal models of human diseases
- always inbred
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mammary glands for a mouse
- female 5 sets (10 nipples)
- males none
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toes for a mouse
5 toes with claws
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thigmotaxis
whiskers for sensing
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adult mouse weight
15-40 grams
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mouse natural life span
1.5-3 years
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mouse dental formula
1i/3m x 4 = 16 teeth
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mouse gastrointestinal
- limiting ridge (cannot vomit)
- large cecum
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mouse hematopoetic system
spleen site for hematopoesis (mature RBC development)
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mouse reproductive system
- bicornuate (tow horns) uterus with one cervix
- prominent seminal vsciles
- anogenital distance varies between sexes
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temperature to keep mouse at
- 85.28 - 86.9 F
- poor regulation of body heat,
- overheat easily can't sweat, pant
- acclimatization primarily behavioral (burrowing)
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mouse estrus cycle
4 days
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Gestation period
19-21 days
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Fertile postpartum estrus
14-24 hours
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litter size mouse
6-10 pups
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mouse offspring
- blind, hairless, dependent on mother
- fully haired at 10 days eyes open and 14 days
- sexually mature at 4 weeks female, 6 weeks male
- polyestrus (breed year around)
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mouse nutrition
- ominivorous
- food intake = 1.5 g/10 g BW/day
- water intake = 1.5 ml/10 g bw/day
- linoleic acid essential (unsaturated omega 6 fatty acid)
- coprophagy
- nutritionallly balanced pelleted chow
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mouse behavior
- prey species (run hide/ freezing behavior)
- social
- nest builders
- burrowers
- nocturnal
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methods of handling
- tail hold (mouse/rat)
- scruff hold (mouse)
- body hold (rat)
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restraint devices
- plexiglas restrainer
- decapicone
- centrifuge tubes
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chemical restraint devices
pros and cons
- anesthetize rodent for procedrures
- pros
- - no movement
- - good access anywhere on body
- - short or long periods
- cons
- - monitor anesthetic depth
- - expensive
- - need DEA number
- - can cause vasoconstriction
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euthanasia
inducing a painless death
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criteria to consider with euthanasia
- painless method
- time it takes to produce unconsciousness
- time until death is accomplished
- reliablitlity of method
- repeatability of method
- personnel safety
- stress on animal
- non-reversibility
- compatible with scientific protocol
- aesthetically acceptable drug availability and abuse potential
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minimizing fear and appreahension for euthanasia
- gentle restraint and handling
- tranquilizers or sedatives
- prevent conscious animals from observing euthanasia of others
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3 modes of action of euthanasia methods
- hypoxemia of brain tissue
- depression of vital brain centers
- physical damage to brain tissue
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