[The effect of microgravity and head down immobilization on hemopoiesis in primates]

Objects of the investigation were peripheral blood and bone marrow cytology in 6 primates during readaptation following the 2-wk. space flights (SF) aboard biosatellites BION-9, 10 and 11, and ground-based simulations of 17-d sitting in the chairs of the Bios-primat capsule (4 primates) and 4-wk. head-down immobilization (-5 degrees, 12 primates). On completion of each of the three experiments, the hemopoietic system was characterized by a distinct nonspecific stress-reaction, i.e. neutrophilous leukocytosis against reductions of the lymphocyte and eosinophil counts. After SF and HD immobilization, the blood profile carried signs of a specific reaction which consisted of a hemoconcentration (hematocrit and hemoglobin) reduction during early readaptation and recovery as a result of erythropoiesis activation due to, primarily, blood redistribution and a decreased weight-bearing load. The specific reactions to HD immobilization were less significant and did not reveal themselves at all in the chaired primates.