Study examining mnsod overexpression reduces fibrosis and pro-apoptotic signaling in. Cardiovascular deconditioning was observed with reduced cardiac mass and altered vascular function. Blood volume decreased by 10-15% within first weeks. Orthostatic intolerance developed in 70% of crew post-flight. Carotid artery stiffness increased during flight. Cardiac atrophy affected left ventricular mass. Cerebral blood flow regulation was impaired upon return to gravity.