4.2. Centrifugation Experiment

The mice were exposed to short-term hypergravity at +9 Gx for 1 h using a small animal centrifuge at the Aerospace Medicine Research Center (Cheongju, Korea). The mice were placed inside a cylindrical plastic restraint device that allowed +9 Gx to be delivered along the rostrocaudal axis when mounted in the centrifuge. A cage-mounting module was attached at the end of an arm that allowed for one degree of freedom, thereby ensuring that the net gravity field was perpendicular to the floor of the restraint device [6]. The mice were sacrificed 6 h after exposure to hypergravity with or without a single dose of APAP (i.p., 500 mg/kg BW, i.p.) treatment [42]. The dose of APAP was chosen to induce oxidative stress and ER stress. Different sets of animals were submitted to daily hypergravity exposure for three days, after which the tissue samples were obtained 6 h after the last load (Figure 3A). The behavior of the mice throughout the centrifugation experiments was monitored with a charge-coupled device (CCD) camera.