| Autor: |
Mehta, Rahul, Freyaldenhoven, Sidney G., Heacox, Hayley N., Hill, Brent J. F., Chowdhury, Parimal |
| Předmět: |
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| Zdroj: |
AIP Conference Proceedings; 2019, Vol. 2160 Issue 1, p060006-1-060006-7, 7p |
| Abstrakt: |
This research studies rat femur and tibia bones from live rats that were exposed to hind-limb suspension (HLS) (to simulate microgravity) and/or x-ray irradiation (HLS/IR) (to simulate space radiation). It is hypothesized that space conditions will produce weakened bones, lower elastic moduli and abnormal concentrations of calcium and phosphorus, as compared to bones not subject to these conditions. In the experiment, male rats were suspended by tail for two to four weeks. The radiation was given over a two-week period with dosage varying from 0.5 to 2.0 gray (Gy). The tibia and femur bones of euthanized rats were measured for elasticity and then cross sectioned to study elemental changes. Elasticity measurements were done by using three-point bending. A stress vs. strain graph allowed for the estimation of the elastic modulus of a leg bone for control, HLS and HLS-IR samples. The relative percentages of elements in the bone mineral hydroxyapatite [Ca10(PO4)6(OH)2] were determined using Energy Dispersive Spectroscopy (EDS) - from an electron beam in a Scanning Electron Microscope (SEM). The electron beam energy ranged from 10-20 keV. X-rays emitted from the sample during electron bombardment were measured using a Peltier cooled SD X-ray detector. Kα- x-rays from carbon, oxygen, phosphorus and calcium formed the major peaks in the spectrum. Relative percentages of these elements were determined using a software that could also correct for Z (atomic number), A (X-ray absorption) and F(fluorescence yield). The elemental composition of femur and tibia indicated a strong relationship between the compositional ratios of calcium, phosphorus and oxygen with the location on the leg. The chemical analysis of bone suggests that there must be some change in the hydroxyl or phosphate group of the main component of bone structure, due to hind limb suspension. The effect of radiation could be seen with dosage as low as 0.5 Gy. No statistically significant difference in elastic modulus was found between control and irradiated rats or in control and hind-limb suspended and irradiated rats; however, a significant difference was demonstrated between control and hind-limb suspended rat in femurs only. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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