[Hematopoietic functions in hypokinesia]

Materials on the state of hemopoietic organs and peripheral blood of mice and rats kept under hypokinetic conditions for from 1 to 60 days are presented. The changes occurring in the lymphoid tissue (involution of thymo-lymphatic apparatus, lymphopenia and neutrophilosis) have been shown to result from the state of stress. In the bone marrow of animals there occurs activation of erythropoiesis (erythroblasts-polychromatophilic normoblasts) at early (up to 15 days) term of hypokinesia, followed by its inhibition on the 60th day of the experiment. The study of kinetics of the amount of hemopoietic stem cells in the spleen and bone marrow of the femur of mice kept under hypokinesia for 1-45 days suggests the amount of stem cells in the spleen to decrease exponentially while in the bone marrow it changes undulatorily with the maximum on the 1st-3d and 30th-45th days of hypokinesia. Shifts in the number of the stem cell population are accompanied by changes in the direction of their differentiation. The stem cells of the bone marrow manifest higher potencies to form colonies of the erythroid type as compared with the stem cells of intact animals. Possible mechanisms underlying the inhibition of lymph-and erythropoiesis and changes of the stem cell differentiation from the myeloid way to the erythroid way under conditions of hypokinesia are discussed.