[en] The previously reported decrease in the ratio of erythrocytic (E): granulocytic (G) spleen colonies observed 8 days after bone marrow transplantation, when the donors had been x-irradiated up to 4 hours before the marrow was taken for transfer, was confirmed. The effect of taking the marrow between 4 hours and 13 days after x-irradiation, on the E:G ratio in both spleen and femoral bone marrow colonies, has been studied in detail. The reversion to a normal E:G ratio in spleen colonies assessed at 8 or 10 days was associated with increases in this ratio of colonies in the femoral bone marrow. Transplantation of cell suspensions prepared from the spleen and femoral bone marrow of primary recipients 8 days after the initial transfer produced a histological distribution of 8-day colonies in secondary recipients which was independent of x-irradiation of the donor. The data suggest that a hypothesis involving CFU migration within the spleen and, possibly, from the bone marrow to the spleen, provides a more satisfactory explanation of the data than one involving two CFU populations with different radiosensitivities. (author)

[en] Two main aspects of the in vitro mouse foetal liver cell assay for erythroid stimulating factor (ESF) in human sera have been investigated. The haem extraction process has been shown to give specific and quantitative recovery of ⁵⁹Fe labelled haem from haemoglobin thus confirming that the material assayed in human sera is stimulating the synthesis of this protein. The extraction procedure can be simplified considerably by prior mixing of the reagents without significantly influencing the results. Several serum constituents (citrate, testosterone, B₁₂, folic acid and iron) have been investigated over a range of concentrations for possible effects on the cultures. Generally only small effects on haem synthesis were observed. It is concluded that variations in the levels of these factors in sera from treated patients will not produce any significant alterations in the estimated ESF concentrations. (author)

[en] Previous studies have shown that a decrease in red cell mass occurs in astronauts, and some studies indicate a leukocytosis occurs. A life science module housing young and mature rats was flown on shuttle mission Spacelab 3 (SL-3), and the results of hematology studies of flight and control rats are presented. Statistically significant increases in the hematocrit, red blood cell counts, and hemoglobin determinations, together with a mild neutrophilia and lymphopenia, were found in flight animals. No significant changes were found in bone marrow and spleen cell differentials or erythropoietin determinations. Clonal assays demonstrated an increased erythroid colony formation of flight animal bone marrow cells at erythropoietin doses of 0.02 and 1.0 U/ml but not 0.20 U/ml. These results agree with some but vary from other previously published studies. Erythropoietin assays performed by radioimmunoassay and clonal studies were performed for the first time