[Role of dynamic factors of space flight in the pathogenesis of lymphoid organ involution (experimental morphologic...

The role of the dynamic factors in accidental involution of lymph organs has been investigated in a ground-based study simulating a 20-day space flight. It has been inferred from the study that lymph organ involution observed in rats exposed to prolonged space flights is caused by chronic and acute stresses. Chronic stress is associated with weightlessness and leads to hypoplasia of lymph organs; acute stress is connected with the transition from weightlessness to normal gravity (gravity stress), thus enhancing chronic stress induced lymph tissue hypoplasia. Spleens of both weightless and hypokinetic rats show inhibition of erythropoiesis and accumulation of hemosiderine due to accelerated erythrocyte degradation caused by diminished motor activity.