Validation of the BodyGem hand-held calorimeter.

OBJECTIVE: To assess the validity and reliability of a hand-held indirect calorimeter. DESIGN: Resting metabolic rate (RMR) was measured on two separate mornings. SUBJECTS: A heterogeneous sample of 41 healthy adults. MEASUREMENTS: RMR using both a metabolic cart (Sensormedics 2900, SM-2900) and a hand-held indirect calorimeter (BodyGem, BG). RESULTS: There were no trial-to-trial differences in RMR measured by the BG (6756+/-163 vs 6697+/-163 kJ/day) or the SM-2900 (6400+/-163 vs 6396+/-167 kJ/day). RMR measured by the BG was significantly higher than that measured by the SM-2900 during both trials. In a sample of 10 subjects, the energy cost of holding the BG in position was determined to be (0.17+/-0.04 kJ/min, or 255+/-84 kJ/day). After applying this adjustment, the differences between systems were no longer significant during trial 1 (mean difference=101+/-67 kJ/day) or trial 2 (46+/-75 kJ/day). In overweight and obese individuals, RMR measured by the BodyGem was more accurate than that estimated by the Harris-Benedict equations. CONCLUSION: The BodyGem provides valid and reliable measurements of RMR. The BodyGem produces significantly higher values than the Sensor Medics 2900 indirect calorimeter, with the increase largely due to an increased energy demand required to hold the BG in position.

Androgen receptor YAC transgenic mice carrying CAG 45 alleles show trinucleotide repeat instability.

X-linked spinal and bulbar muscular atrophy (SBMA) is caused by a CAG repeat expansion in the first exon of the androgen receptor (AR) gene. Disease-associated alleles (37-66 CAGs) change in length when transmitted from parents to offspring, with a significantly greater tendency to shift size when inherited paternally. As transgenic mice carrying human AR cDNAs with 45 and 66 CAG repeats do not display repeat instability, we attempted to model trinucleotide repeat instability by generating transgenic mice with yeast artificial chromosomes (YACs) carrying AR CAG repeat expansions in their genomic context. Studies of independent lines of AR YAC transgenic mice with CAG 45 alleles reveal intergenerational instability at an overall rate of approximately 10%. We also find that the 45 CAG repeat tracts are significantly more unstable with maternal transmission and as the transmitting mother ages. Of all the CAG/CTG repeat transgenic mice produced to date the AR YAC CAG 45 mice are unstable with the smallest trinucleotide repeat mutations, suggesting that the length threshold for repeat instability in the mouse may be lowered by including the appropriate flanking human DNA sequences. By sequence-tagged site content analysis and long range mapping we determined that one unstable transgenic line has integrated an approximately 70 kb segment of the AR locus due to fragmentation of the AR YAC. Identification of the cis -acting elements that permit CAG tract instability and the trans -acting factors that modulate repeat instability in the AR YAC CAG 45 mice may provide insights into the molecular basis of trinucleotide repeat instability in humans.