title: Spaceflight and hind limb unloading induce similar changes in electrical impedance characteristics of mouse gastrocnemius muscle.
abstract: OBJECTIVE
  To assess the potential of electrical impedance myography (EIM) to serve as a marker of muscle fiber atrophy and secondarily as an indicator of bone deterioration by assessing the effects of spaceflight or hind limb unloading.
  
  
  METHODS
  In the first experiment, 6 mice were flown aboard the space shuttle (STS-135) for 13 days and 8 earthbound mice served as controls. In the second experiment, 14 mice underwent hind limb unloading (HLU) for 13 days; 13 additional mice served as controls. EIM measurements were made on ex vivo gastrocnemius muscle. Quantitative microscopy and areal bone mineral density (aBMD) measurements of the hindlimb were also performed.
  
  
  RESULTS
  Reductions in the multifrequency phase-slope parameter were observed for both the space flight and HLU cohorts compared to their respective controls. For ground control and spaceflight groups, the values were 24.7±1.3°/MHz and 14.1±1.6°/MHz, respectively (p=0.0013); for control and HLU groups, the values were 23.9±1.6°/MHz and 19.0±1.0°/MHz, respectively (p=0.014). This parameter also correlated with muscle fiber size (ρ=0.65, p=0.011) for spaceflight and hind limb aBMD (ρ=0.65, p=0.0063) for both groups.
  
  
  CONCLUSIONS
  These data support the concept that EIM may serve as a useful tool for assessment of muscle disuse secondary to immobilization or microgravity.
authors.affiliation: Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA.
authors.forename: M
authors.initials: M
authors.lastname: Sung
authors.forename: J
authors.initials: J
authors.lastname: Li
authors.forename: A J
authors.initials: AJ
authors.lastname: Spieker
authors.forename: J
authors.initials: J
authors.lastname: Spatz
authors.forename: R
authors.initials: R
authors.lastname: Ellman
authors.forename: V L
authors.initials: VL
authors.lastname: Ferguson
authors.forename: T A
authors.initials: TA
authors.lastname: Bateman
authors.forename: G D
authors.initials: GD
authors.lastname: Rosen
authors.forename: M
authors.initials: M
authors.lastname: Bouxsein
authors.forename: S B
authors.initials: SB
authors.lastname: Rutkove
mesh_terms: D000818:Animals; D001823:Body Composition / Q000502:physiology*; D017097:Electric Impedance; D019417:Hindlimb Suspension / Q000502:physiology*; D051379:Mice; D018482:Muscle, Skeletal / Q000502:physiology*; D013026:Space Flight; D014893:Weightlessness