Influence of parabolic flight on the ROS production visualized by luminol kinetics in the PMT clinostat (non-rotating) during the parabolic flights. Cells were stimulated by opsonized zymosan as indicated. Luminescence was measured in counts per second (CPS). Two independent measurements during one flight day are shown in blue (stimulation before parabola 0) and green (before parabola 16). 1 g control experiment was performed on ground after each flight using the same experiment hardware, in flight-analogueconditions. Unstimulated control cells (PBS control) were not activated with zymosan.