title: Non-invasive measurement of organ density in a rat simulated microgravity model.
abstract: BACKGROUND
  Spaceflight has caused serious concerns to the health and well-being of astronauts, both while in space and post-mission on Earth. The deleterious health effects due to microgravity are not well understood and though these effects may be caused by multiple factors, fluid shifts within the body may play a major role.
  
  
  OBJECTIVE
  We believe that 45 degrees C HDT will cause significant changes in organ density as measured by spiral computed tomography in a 1-h experimental time period.
  
  
  METHODS
  There were 20 male Fischer 344 rats that were randomly selected to be in an experimental or control group. The experimental group (n = 12) was subjected to a 45 degrees head down tilt microgravity exposure (45 degrees HDT) for 1 h, and the control group (n = 8) remained in the prone position for the same amount of time. At the end of 1 h, the density of the brain, lungs, heart, liver, and left and right kidneys were measured using spiral computed tomography (SCT) while the rats remained in their experimental positions.
  
  
  RESULTS
  With the exception of the right kidney, we demonstrated that there was a significant change (p < 0.05) in the densities of all tested organs in the 45 degrees HDT group when compared with the control group. The brain showed the largest percent increase at 45.6% while the lungs showed the least amount of change at 8.7%.
  
  
  CONCLUSIONS
  We conclude there are significant increases in organ density, as measured by SCT, in male 45 degrees HDT rats compared with prone controls.
authors.affiliation: Department of Pediatrics, Steele Memorial Children's Research Center, University of Arizona College of Medicine, Tucson, USA.
authors.forename: J M
authors.initials: JM
authors.lastname: Nathan
authors.forename: B A
authors.initials: BA
authors.lastname: Bradshaw
authors.forename: N
authors.initials: N
authors.lastname: Bartoletti
authors.forename: M L
authors.initials: ML
authors.lastname: Witten
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D018495:Fluid Shifts / Q000502:physiology*; D008297:Male; D023421:Models, Animal; D009929:Organ Size / Q000502:physiology*; D011897:Random Allocation; D051381:Rats; D011916:Rats, Inbred F344; D014057:Tomography, X-Ray Computed; D014781:Viscera / Q000033:anatomy & histology*; D018474:Weightlessness Simulation