[Determination of "settling factor" (f) by the hematopoietic stem cell cloning test in mouse spleen and bone marrow]

The effect of distribution of injected colony-forming units (CFU) in the recipient's organism was studied. The distribution was assessed by the "sedimentation factor" (f) criterion. This factor was found by the number of colonies revealed on histological sections of the spleen and femoral bone marrow in comparison with the number of colonies visible on the surface of the spleen. Macroscopic count of the colonies on the spleen permits, to assess the f value both in the whole spleen volume and in the femoral bone marrow. In this case f value was independent of the character of CFU differentiation. f value could change depending on the physiological condition of CFU population. In irradiation of the bone marrow CFU in a dose of 200, 400 and 600 R f value in the spleen decreased in comparison with control, but remained unchanged in the bone marrow.