ASRB NET and ARS / SMS / STO (Agricultural Scientists Recruitment Board) · India · Agricultural Scientists Recruitment Board
Original practice questions written to the published syllabus · not past papersBiology, housing and health monitoring of laboratory animals, their common diseases, the 3Rs, ethics committees and experimental techniques.
In the exams: EAEVE Day One competence on the 3Rs; ACLAM and ECLAM specialist colleges
How our questions for ASRB NET and ARS / SMS / STO spread across the units of Laboratory Animal Science & Medicine. Difficulty: 22 easy, 18 medium, 2 hard.
| Biology of laboratory species | 9 | |
| Housing of laboratory animals | 6 | |
| Health monitoring | 5 | |
| Tyzzer's disease | 5 | |
| Murine respiratory mycoplasmosis | 4 | |
| Experimental techniques | 4 | |
| Pasteurellosis | 3 | |
| The 3Rs: replacement, reduction and refinement | 3 | |
| Animal ethics committees: CPCSEA, IACUC and EU Directive 2010/63 | 3 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
Which of these common laboratory rodents has the shortest gestation, at about 16 days?
B. Syrian hamster
The Syrian hamster's gestation is about 16 days. The mouse is about 19 to 21 days, the rat about 21 to 23 days and the gerbil about 24 to 26 days, so a student who remembers the mouse as 'shortest' is thinking only of the two commonest species.
Further reading: Standard laboratory animal science texts
Which rat is the classic spontaneous model of central diabetes insipidus because it cannot produce vasopressin?
A. Brattleboro rat
The Brattleboro rat has a vasopressin gene mutation causing central diabetes insipidus. The Gunn rat models unconjugated hyperbilirubinaemia, the Zucker rat obesity from a leptin receptor mutation, and the SHR essential hypertension.
Further reading: Standard laboratory animal science texts
A room measures 4 m x 5 m x 3 m and receives 900 cubic metres of fresh air per hour. How many air changes per hour does it receive?
C. 15
Room volume = 4 x 5 x 3 = 60 cubic metres. Air changes per hour = 900 / 60 = 15. 45 comes from dividing by the floor area of 20 square metres and forgetting the height; 0.25 is 15 divided by 60, a per-minute figure; 5 comes from multiplying the height in again (900 / 180).
Further reading: NRC Guide, 8th ed.
Using n = log(1 - C) / log(1 - p), how many animals must be sampled to have 95% confidence of detecting at least one infected animal when the prevalence is 30%, assuming a large population, random sampling and a perfect test?
C. 9
n = log(0.05) / log(0.70) = 8.40, which rounds up to 9 because you cannot sample part of an animal and must not fall below the confidence target. 8 comes from rounding down; 3 from multiplying 0.3 by 10; 30 confuses prevalence with sample size.
Further reading: ILAR/FELASA health-monitoring sampling principles
Which test is the method of choice for detecting the mouse pinworm Syphacia obvelata?
A. Perianal cellophane tape test
Syphacia females lay eggs on the perianal skin, so the tape test finds them; eggs are seldom in faeces. Faecal flotation is used for Aspiculuris, whose eggs are passed in faeces; pelage examination is for fur mites.
Further reading: Fox et al., Laboratory Animal Medicine
Why does a negative routine bacterial culture of liver lesions not exclude Tyzzer's disease?
D. Clostridium piliforme is obligately intracellular and does not grow on cell-free media
C. piliforme can be propagated only in embryonated eggs, cell culture or animals, so diagnosis relies on histology with special stains, PCR and serology. It is a bacterium, not a virus, and incubation temperature is not the issue.
Further reading: Fox et al., Laboratory Animal Medicine
Which form of pasteurellosis results from spread of Pasteurella multocida up the Eustachian tube in rabbits?
A. Otitis media and otitis interna with torticollis
Ascent of the Eustachian tube leads to otitis media and, by extension, otitis interna with head tilt. Spread along the nasolacrimal duct gives dacryocystitis and conjunctivitis; genital forms arise from venereal or haematogenous spread.
Further reading: Fox et al., Laboratory Animal Medicine
A study uses liver cells taken from rats humanely killed for another purpose instead of dosing live rats. In Russell and Burch's terms, what kind of replacement is this?
D. Relative replacement
Relative replacement still uses animals or their tissues but avoids procedures on living sentient animals. Absolute replacement uses no animal material, such as human cells or computer models. Tissue sharing also reduces numbers, but the method itself is classed as relative replacement.
Further reading: Russell and Burch, 1959
Which member is required on an Indian Institutional Animal Ethics Committee to represent the central committee (CCSEA, formerly CPCSEA)?
B. A nominee of the central committee
The IAEC includes a nominee of the central committee, alongside scientists, a veterinarian, the scientist in charge of the animal house, an outside scientist and a socially aware non-scientist. The other officials are not required members.
Further reading: CCSEA (formerly CPCSEA) guidelines
A test compound is to be given by oral gavage to mice at 20 mg/kg in a dose volume of 10 mL/kg. What concentration should the dosing solution have, and what volume does a 25 g mouse receive?
B. 2 mg/mL; 0.25 mL
Concentration = dose / volume = 20 mg/kg / 10 mL/kg = 2 mg/mL. Volume = 10 mL/kg x 0.025 kg = 0.25 mL. 2.5 mL mistakes 25 g for 0.25 kg; 0.2 mg/mL and 20 mg/mL are factor-of-ten slips.
Further reading: Diehl et al., 2001
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