LATG Chapters 16-18
Unique Anatomy of Lab Animal Species
Gnotobiology
Statistics
Mus musculus
• Rapid heart rate (300+/min) and respiration rate
(100+/min)
• Calcification of the costochondral cartilage
• Functional marrow in long bones for life
• Extensive mammary tissue going over back and
shoulders
• Esophagus lacks glands, has stratified squamous
epithelium and enters stomach in the middle
Mus musculus
• The pancreas is diffusely spread through the
mesentery ( the same is true for rats and hamsters)
• The spleen of males is 50% larger than that of
females
• The thymus is thinner than that of other species
• There is a Harderian gland and two accessory lacrimal
glands
• Brown fat can be found on the back, neck, and by
the kidneys and thymus
Rattus norvegicus
• Rat skeletons continue to grow throughout their life
• Like mice and hamsters, rats have a diffuse pancreas
• The liver has no gall bladder to store bile
• Accessory sex glands include 2 pairs of prostates, paired
seminal vesicles, coagulating glands, ampullary glands,
and bulbourethral glands
Rattus norvegicus
• Rats have an os penis and open inguinal
canals
• Like the mouse, the rat uterus has 2 horns and 2
cervices
• Mature males have larger pituitary and adrenal glands
than females
• Like the mouse and hamster, the rat has Harderian
glands that can cause chromodachyrrhea
Mesocricetus auratus
Hamsters have large cheek pouches that are
immunologically tolerant sites
They have sebaceous glands on each flank, behind the
rib cage - these are more prominent in males
Hamsters have a pre-gastric pouch or diverticulum
The adrenal glands of the male are larger than the
female, and the male’s spleen is smaller
Mesocricetus auratus
Male accessory sex glands similar to mice and rats
Males have open inguinal canals like mice and rats
Females have duplex uterine horns with 2 cervices like
mice and rats
Harderian gland present like mice and rats
Some hamster lines have V-shaped tracheal rings
Cavia porcellus
Young are precocious with eyes open, teeth erupted,
fully furred, able to walk and eat solid food
All teeth are open rooted and grow continuously
Very large cecum compared to other rodents, ends in
cecal appendix
Left adrenal long and thin, right one shorter and flat
Male penis has papillae and two erectile spines
Sex glands, inguinal canal, uterus similar to other
rodents
Females have ligament allowing separation of pubic
syphysis
Presence of Kurlhoff bodies in some lymphocytes,
and heterophils instead of the normal neutrophils
Guinea pig
Palatial ostium covers posterior pharynx
Intact vaginal closure membrane
Pubic symphsis under control of relaxin
Sow must be bred before 8-9 months of age
Oryctolagus cuniculus
Two “peg teeth” behind primary incisors
Very light weight skeleton (8% BW)
Open rooted teeth like guinea pig
Cleft lip, papillae on tongue
GI tract unique
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Peyer’s patches
Sacculus rotundus
cecum ends in vermiform process
colon has haustra and taenia coli
colon has fusus coli for production of night feces = cecotrophs
Oryctolagus cuniculus
Highly vascularized ears - used for thermoregulation and
access for bleeding/injection
Right and left AV valves bicuspid
Heterophils present as in the guinea pig
Male accessory glands include prostate, seminal
vesicles, bulbourethral, and ampullary. No coagulating
gland, no os penis. Testes in inguinal pouch not in
scrotal sac.
Each uterine horn has its own cervix, like rodents
Rabbits, rats and horses can’t vomit
Rabbit
Lagomorphs have two peg teeth
Rabbit skeleton is 8% body weight
sacculus rotundus located at juncture of cecum
and ileum
Cecal appendix = vermiform appendix
Neutrophils= heterophils
Felis catus
Cats have 2 additional salivary glands - molar and
infraorbital
No appendix
Anal glands present, as in dogs
Kidneys have high fat content making them yellowish in
appearance
Closed inguinal rings, papillae on penis, only prostate
and bulbouretheral glands present in males
Single cervix in females
Canis familiaris
Cartilaginous clavicles like cats
Esophagus has numerous mucus glands
Anal glands
Closed inguinal ring, prostate and ampullary gland
Small ovaries
Nonhuman Primates
Prosimians and simians
Prosimians include tree shrews, bush babies, lemurs,
lorises, and tarsiers
Both groups have articulating clavicles, deciduous and
permanent teeth, bony eye sockets, a pendulous penis,
scrotal testicles, and an opposable thumb
Nonhuman Primates
Catarrhinni
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32 permanent teeth
flat skulls, brow ridges,
narrow nasal septum, long
nostrils
cheek pouches
ischial callosities
non-prehensile tails
better developed
opposable thumbs
need Vit C but not D3
Platyrrhini
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36 permanent teeth
rounded skulls, no brow
ridges, wide nasal septum,
oval nostrils
no cheek pouches
no ischial callosities
prehensile tails
less developed opposable
thumbs
need Vit C and Vit D3
Gnotobiology
Introduction/History
Gnotobiotics= “known life”
Science of keeping animals in a controlled environment;
organisms that inhabit body are known
Pasteur experiments over 90 years ago (guinea pigs)
1946- first germ-free rat colony
1957-Trexler isolator created
Use in Research
Source of foundation stock to be used in the
production of barrier- bred animals ie. SPF, GF,
DF
Carcinogenesis/mutagenesis
Infections/Immunity
Nutrition
Toxicology, Pharmacology, and Physiology
Terminology
Defined Flora (DF): microflora is totally
known
Axenic=Germ-free (GF): free of all known
organisms; except for its’ own living cells
Specific Pathogen Free (SPF): animals
free from specified organisms considered
pathogenic
Conventional: Harboring undefined
microfauna
The Isolator
Components: body, air handling system, entry/exit,
operator access
Types: Rigid and flexible
Must provide
- temperature control
- # of hours of light/darkness
- source of sterile air
- means of air exhaust
Laminar Flow Cabinet
Provide slow-moving, linear-flowing, filtered, sterile air
Use: Removes airborne microbes, prevents
contamination
HEPA filtered
Sterilization Techniques
Steam autoclaving
Dry heat
Ethylene oxide
Gamma irradiation
Membrane filtration
Gnotobiotic
Physiologic and Anatomic Characteristics
Intestinal walls are thin
poor muscle development
enlarged cecum
longer lifespan
higher nutritional requirement
higher blood cholesterol
generally smaller internal organs
Caesarian Derivation or Embryo Transfer
Entry of disease free breeders into barrier facility
Surgical removal of uterus from time-mated
donor animal
Uterus passed through dip tank containing
germicide into isolator
Fetuses removed from uterus
Adopted onto donor female-axenic foster mother
Microbiologic monitoring of fostered offspring
Adm. of normal non-pathogenic intestinal flora” Schaedler’s cocktail”
Why the Need for
Statistics/Statistical Calculations?
To draw valid conclusions from data
To distinguish differences from random variability
To make the strongest possible conclusion from
the least amount of data
Limitations: No statistical extrapolation
Key Words
Hypothesis: assumption of truth
Variables (experimental)
- dependent: weight, sex , age
- independent
Randomization
Mean- average number
Distribution
Distribution= “normal variation”
Bell shaped Curve or Gaussian curve
Most of the examples in a set of data are close to
average, while few examples are extreme
Statistical Significance
Populations are the same or different
Accepted margin of error: Results occur less than 5% of
time if the populations were really identical.
Researcher is 95% sure that results are due to
measured data and not normal variation ( 95%
confidence level)
Minimum number of animals should be used
(SS ) does not = biological or clinical significance
Standard Deviation
How close the various examples are to the mean
in a set of data.
Expressed as plus or minus
Steep bell shaped curve= small S.D.
Wide bell shaped curve= large S.D.