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Small Animal Phenotyping Subcore


Lunar Prodigy DXA


Lunar PIXImus and Norland pDEXA
Sabre small animal DXA’s


3-in-1 quantitative magnetic
resonance (QMR) instrument


Rat QMR instrument


Imtek uCT
 

Introduction

This core provides state-of-the-art instrumentation and methodology for the determination of energy balance and body composition in small animals.  This includes the measurement of energy expenditure, via indirect calorimetry; food intake, activity and core body temperature.  Body composition techniques involve both ex vivo, via chemical carcass analysis and in vivo methods using dual energy x-ray absorptiometry (DXA), quantitative magnetic resonance (QMR) and micro computed tomography.

Services:

Chemical carcass analysis has long been the “gold standard” for the determination of body composition and the SAPC still uses this as the standard for validating new instruments and techniques.  Although useless for longitudinal studies, it is useful when an investigator’s animals have been killed and frozen.  The carcasses/samples are dried (for water content), fat extracted, and then burnt at 600 degrees Celsius to get ash content.

Dual energy x-ray absorptiometry (DXA) uses two different X-rays to measure fat, soft-lean tissue and bone in vivo.  Animals are anesthetized (Isoflurane) and placed prostrate in the imaging area with the front and back legs extended away from the body.  The DXA machines in the core can measure animals from 12g to 80g and also from 250g to 120kg. A typical scan takes approximately 5 minutes.

Quantitative magnetic resonance (QMR) is used to measure fat and lean mass as well as water content in vivo with no need for anesthesia. The core is able to use QMR to measure body composition in groups of 10 fruit flies, tissue samples (1g-10g), mice (15-100g), and rats (up t0 900g). Scans take approximately 2 minutes for mice and rats, up to 9 minutes for the fruit flies.

Micro computed tomography can be used to identify and quantify regional distribution of body fat and lean tissue. Mice are anesthetized during the scan which takes 15-25 minutes. Unlike, DXA which gives a two dimensional image, microCT provides a three dimensional reconstruction of the mouse. Different tissues can be identified and outlined based on differences in density. Fat content of the liver can also be determined based on the lower density of the tissue with higher amounts of fat. Although labor intensive, subcutaneous and visceral fat can be identified, as well as individual fat pads.

The TSE indirect calorimetry system collects data on oxygen consumption, carbon dioxide production, food consumption and locomotor activity in up to 8 animals at a time. Mice are acclimated in 16 cages for 2 days, before the measurement period of at least one day. Total and resting energy expenditure are calculated for the measurement period. Locomotor activity is measured in the x-y planes using a system of infra-red beams surrounding the cage and is collected continuously during the measurement. Data on meal size and the timing of meals is obtained from the food hoppers attached to transducers. Body composition is always assessed between the acclimation and measurement periods, using QMR, to allow for the energy expenditure measurements to be normalized appropriately for body composition.

The E-Mitter transponder/receiver system comprises of battery-free transponders that are implanted into the abdominal cavity and a receiver base that the cage sits on. The transponders transmit information on core body temperature via the base to a computer. Locomotor activity is assessed as the mouse moves over the top of the receiver. Thus activity and body temperatures can be measured continuously while the animal is in its home cage.

The core currently has two wheel running systems for mice and rats in which the wheel in the cage sends information to a computer as to the number of revolutions and the timing of the revolutions. This allows for investigators to assess voluntary physical activity.

For investigators interested in the effect of forced exercise, the core has a system of running wheels on a rolling bed, for which the speed and time of the exercise can be determined and changed by the investigator.

Digestive efficiency can be assessed by measuring food intake, weight of feces produced and then measuring the energy content of both using a bomb calorimeter. By measuring the weight of food consumed and the energy content of that food, energy intake can be calculated. The weight and energy content of the feces can be measured to give an estimate of energy lost, and together these give an indication of how much energy the animals are absorbing from the food.

Resources:

  • 3 DXA systems to measure in vivo body composition in animals from 12-100g and 250g to 120kg.
  • 2 QMR systems to measure in vivo body composition in mice and rats (or similar sized animals)
  • 8-cage TSE indirect calorimetry system with oxygen and carbon dioxide analyzers, and infra-red beam break activity system
  • 16-cage acclimation system for the indirect calorimetry system
  • 2 isoflurane anesthesia carts
  • 32 wheel running cages: 16 for rats, 16 for mice
  • 20 walking wheel forced exercise system (Lafeyette Instruments)
  • 1 Imtek microCAT II computed tomography system
  • 12 receiver bases; 12 PDT-4000 (rats) and 20 G2 (mice) implantable transponders to measure temperature and activity in home cages.
  • 1 rectal probe for measurement of rectal body temperature in mice
  • 1 bomb calorimeter for the measurement of the energy content of food and feces
  • 2 drying ovens
  • 12 Soxhlet fat extractors
  • 1 muffle furnace
  • 3 industrial blenders
  • 3 environmental chambers to measure indirect calorimetry of mice at different temperatures and light cycles
  • 1 peripheral quantitative computed tomography machine.

Fees:

DXA small (for mice) $7.50
DXA large (250g to 120kg) $12.50
QMR (any size) $5
MicroCT or pQCT $75 per hour of scan time
Indirect calorimetry $5 per animal per day (min. $15 for 2 day acclimation & 1 day measurement)
Carcass analysis (mice) $25 per animal
Carcass analysis (rats) $35 per animal
Wheel running cages $2 per animal per day
Forced exercise wheels $2 per animal per day
Temperature/activity transponders (Implantation) $15 per animal
Activity/body temperature measurements $2 per animal per day; $25 per surgery for implantation
Bomb calorimetry $17.50 per sample


TSE Lab animal system

Contact:

Tim R. Nagy, Ph.D.
Professor,
Department of Nutrition Sciences
Phone: (205) 934-4088
Email: tnagy@uab.edu
  Maria S. Johnson, Ph.D.
Research Associate,
Department of Nutrition Sciences,
Phone: (205) 934-4008
Email: mariajoh@uab.edu

 

Publications:

  • Johnson MS, Smith DL Jr, Nagy TR 2009. Validation of quantitative magnetic resonance (QMR) for determination of body composition in rats. Int J Body Compos Res. 7(3):99-107. [PMID: 20686636]
  • Jones AS, Johnson MS, Nagy TR 2009. Validation of quantitative magnetic resonance for the determination of body composition of mice. Int J Body Compos Res. 7(2):67-72. [PMID: 20467582]
  • Johnson MS, Landy NM, Potter EP, Nagy TR 2005. Comparison of software versions for body composition analysis using the PIXImus dual-energy X-ray absorptiometer. Int J Body Compos Res. 3(2):69-72. [PMID: 21552433]
  • Nagy TR, Johnson MS 2004. Measurement of body and liver fat in small animals using peripheral quantitative computed tomography. Int J Body Compos Res. 1(4):155-160. [PMID: 21546985]
  • Hunter HL, Nagy TR 2002. Body composition in a seasonal model of obesity: longitudinal measures and validation of DXA. Obes. Res. 10(11):1180-7. [PMID: 12429883]
  • Nagy TR, Prince CW, Li J 2001. Validation of peripheral dual-energy X-ray absorptiometry for the measurement of bone mineral in intact and excised long bones of rats. J Bone Miner Res. 16(9):1682-7. [PMID: 11547838]
  • Nagy TR, Clair AL 2000. Precision and accuracy of dual-energy X-ray absorptiometry for determining in vivo body composition of mice. Obes Res. 8(5):392-8. [PMID: 10968731]