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Laboratory Animals
1.
2. INTRODUCTION
Selection of animal model
Use of an animal phylogenetically closer to
man
Use of an animal in which the process under
investigation is as close as possible
3. BIOLOGICAL NAMES
• Genus: which have common characteristics and which can
be divided into subordinate kinds. E.g. Rattus
• Species: similar individuals capable of exchanging genes or
interbreeding to produce offsprings . E.g. Rattus rattus or
norvegicus
• Breed: morphological differences in form or function, and
therefore tend to be external and visible. E.g. beagles and
mongrels in dogs
• Strain: share a presumed common ancestry and have clear-
cut physiological diff. that are often internal and invisible. E.g
Wistar or Sprague Dawley rats
4.
5.
6. • They have similar reproductive and nervous systems
to humans, and suffer from same diseases such as
cancer, diabetes and even anxiety
• Adv:
– Short gestation period (19-21 days)
– Short lifespan (1.5-2.5yrs)
– Small size
– Low cost of maintenance
7. EXPERIMENTAL USES
• Toxicological studies
• Teratogenicity studies
• Bioassay of insulin, screening of analgesic and
anticonvulsant drugs
• Screening of chemotherapeutic agents
• Studies related to genetics and cancer research
8. TRANSGENIC MICE
• A transgenic animal is one that carries a foreign gene
that has been deliberately inserted into its genome
• In 1970, Palmiter introduced the human GH gene
into mouse zygotes by pronuclear microinjection and
transgenic offspring demonstrated dramatic growth
• Genetically modified mice are used extensively in
research as models of human disease
9. METHODS OF PRODUCING
TRANSGENIC MICE
• Transforming embryonic stem cells (ES cells)
growing in tissue culture with the desired DNA
• Injecting the desired gene into the pronucleus of a
fertilized mouse egg
10.
11. • Small Size
• Greater Sensitivity to
most drugs
• Sturdy, Can withstand
long periods of
experimentation under
anesthesia
13. Baby Rats vs Mice
• Baby rat – blunt & broad large head. Mice
have triangular small head.
• Baby rat has small ears, mice have larger ears.
• Baby rat hind paw: body ratio larger than
mice.
• Baby rat tail is thick, shorter than body length.
Mice have tail thin, larger/same length (to
body)
14. EXPERIMENTAL USES
• Study of analgesics and anticonvulsants
• Study of oestrus cycle, mating behaviour and lactation
• Gastric acid secretion
• Hepatotoxicity studies
• Bioassay of various hormones, such as insulin, oxytocin,
vasopressin
• Toxicology studies
• Rat brain tissue is extensively employed in radio-receptor
ligand studies
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18. EXPERIMENTAL USES
• Vaccines for diphtheria, TB, etc
• Hypersensitivity studies
• Anaphylactic shock
• Evaluation of bronchodilators
• Evaluation of local anaesthetics
• Terminal portion of ileum used for screening
spasmodic and anti spasmodic agents
• Nutritional studies (Ascorbic acid metabolism)
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27. EXPERIMENTAL USES
• Pyrogen testing
• Testing Topical agents as skin is sensitive
• Bioassay of anti-diabetic drugs , insulin, curaremimetic
drugs
• Studies related to antifertility agents
• It has simple cardiac tissue free of connective tissue
and hence is the animal of choice for cardiac studies
• Screening embryotoxic agents and teratogens
28. • TESTING OF COSMETICS USING DRAIZE TEST –
• Rabbits are commonly used in testing for cosmetics
and other chemicals
• This test involves the substance being placed on the
rabbit's eyes or skin, which are then observed for
redness, irritation or any other damage
29. PARAMETER MOUSE RAT GUINEA PIG RABBIT
Typical adult
wt. (gm)
20-40 250 800 1500-5000
Average life
span (yrs)
1.5-2.5 2-3 3-5 4-6
Avg age for
expt.
3 wks 6wks 3 mths 6mths
Gestation
period (days)
21 (3 wks) 21 (3wks) 68 (2 mths) 31 (1 mth)
Avg litter size 6-12 8-10 3-4 6-8
No. of litters
per year
8 6 4 4
HR (beats/min) 350-750 300-500 250-400 130-300
BP 113/81 116/90 77/47 110/80
BIOLOGICAL & PHYSIOLOGICAL DATA
41. • Zebra fish mutants are currently used to
model many human diseases, including
Alzheimer’s disease, congenital heart disease,
polycystic kidney disease , cancers and
development of the nervous system
42.
43. • The study of frog muscles in the 1920's led to
the discovery of neurotransmitter ACh
• Used in the study of action of drugs on CNS,
heart, neuromuscular junction
Studying embryonic development
• African clawed frog (Xenopus laevis) used for
studying early events, such as the formation
of the neural plate
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47.
48. SUMMARY
• Mice(74%) and rats(7%) being extensively
used in pharmacological research
• Use of transgenic animals will help us to
better understand human disease & improve
health care
Nude mouse – a hairless genetic mutant that lacks a thymus (Deficient in T- Lymphocytes) – less susceptible to cancer as possess normal number of natural killer cells
Beige Mouse – lack killer cells, susceptible to cancer.
1. Injection of ES cells into blastocyst-stage embryos
Embryonic stem cells (ES cells) are derived from the inner cell mass of blastocysts (early embryos). These cells are pluripotent, which means that they can develop into almost any type of tissue. ES cells are used for more precise modifications of the mouse genome. This technique makes it possible to insert as well as remove or modify DNA sequences. Knock-out, knock-in and conditional mutant mice can be produced with this method. The first step is the removal of ES cells from a blastocyst. After transfection of the ES cells, selection, cloning and screening methods make it possible to detect ES cell clones that demonstrate the desired, site-specific recombination. After microinjection of the genetically modified ES cells into blastocyst-stage embryos the ES cells divide and become part of the embryo. The following chimeric animals will subsequently transmit the recombinant genotype to their offspring, if the ES cells have contributed to their germ cells.
2.Microinjection of DNA into the pronucleus
The pronuclear microinjection method of producing a transgenic animal is based on the introduction of linear DNA sequences into the chromosomes of fertilized eggs. The foreign DNA must be integrated into the genome prior to the doubling of the genetic material that precedes the first cleavage in order for the animal to be born with a copy of this new information in every cell. For several hours following the entry of the sperm into the oocyte, the male and the female pronuclei can still be seen individually under a normal light microscope and they have not fused yet into a so called zygote. The foreign DNA may be injected into either pronuclei with no difference in results; however, the DNA is typically injected into the male pronucleus because it is slightly larger and closer to the oocyte surface. These oocytes are subsequently transferred into the uterus of pseudopregnant recipient animals. The offspring is screened to confirm a successful integration of the gene of interest for use in further studies.
Docile
Resembles man in that it has to be given Vit C exogenously
Histamine : susceptible to anaphylaxis, bronchoconstriction
Dopamine decreases blood pressure in GP
Uterus stimulated by adrenaline
Penicillin is 100 to 1000 times toxic to GP than in mouse
New Zealand white rabbits
Atropinesterase gene influences color of fur (black) – light reflex not abolished
Withdrawing blood from ear veins
Dopamine decreases blood pressure in GP
Uterus stimulated by adrenaline
The rabbit has provided an
Table from Ghosh 5th Edition
Recall 2 uses each
Used for BP, diabetes (as there is discrete pancreas)
Employed in experiments for studying blood pressure
Contractions of nictitating membrane for ganglionic blocking action of drugs
More suitable to study compounds that can cause methemoglobinemia like acetanilide.
Because they are transparent
Have short life span
Teratogenecity/ embryotoxicity studies
Otto Loewi – Vagusstoff
Other uses – retinal toxicity of drugs (prevention of resynthesis of bleached rhodopsin)