[Properties of eeythropoietin-independent mouse bone marrow precursor cells of the erythroid series].

The properties of early (BFUen) and late (CFUen) erythropoietin-independent progenitors were studied in bone marrow plasma clot cultures of mice. Syngeneic serum was used as a stimulant of colony formation. It was revealed that serum from polycytemic mice did not alter the efficacy of cloning the erythroid progenitors.

[Erythroid precursors studied by mouse bone marrow cultivation in a plasma clot].

Two types of erythroid precursors were found by cultivation of the mouse bone marrow in the plasma clot with mouse serum and without adding exogenic erythropoietin to the culture medium. The first precursor had properties similar to the erythroid colony-forming unit (CFUe) previously described while the second resembles in its properties the erythroid burst-forming unit (BFUe). Optimal concentration of mouse serum in the culture medium was 10-15%.

[Mechanism of inhibition of erythropoiesis during post-transfusion polycythemia].

In mouse with posttransfusion polycytemia, depression of erythropoiesis suggests that, in response to erythrocytes transfusion, not only the differentiation of erythropoietin-sensitive cells is interrupted (cessation of inflow of the labelled erythrocytes into the circulation on the 8th day), but the proligeration of differentiated erythroid precursors is also inhibited (fall of amount of labelled erythrocytes during first days). This was corroborated by analysis of the experimental data with the aid of mathematical model of erythropoiesis. The model revealed that, in posttransfusion polycytemia, division of 40 percent of all divisionable erythroid precursors was halted.