Factors influencing hematopoietic spleen colony formation in irradiated mice. 3. The effect of repetitive irradiation upon proliferative ability of colony-forming cells.

Mice were irradiated repetitively at 6 wk intervals. The proliferative capacity of the hematopoietic stem cell compartment was studied after each irradiation and compared to that of age-matched controls which had been irradiated only once. Hematopoietic proliferation capacity was measured by determining the number of spleen colonies, splenic iron uptake, spleen weight, and volume of packed red cells 10 days after irradiation. 6 wk after the first irradiation, the hematopoietic compartment was apparently supranormal in size for, when such mice were again irradiated, their postirradiation hematopoiesis was in excess of that of the controls. Thereafter, there was a steady decline in regenerative capacity with each sequential irradiation. After the sixth irradiation, the number of spleen colonies and iron uptake were reduced to one-fifth of that of singly irradiated controls. A decline in body weight and an increase in irradiation mortality accompanied the decline in postirradiation hematopoiesis. The degree of measured decline in hematopoietic proliferative ability was less than that observed by other investigators who studied the effect of serial transplantation of cells upon their ability to proliferate. Furthermore, even after the sixth irradiation, a marked stimulation of postirradiation hematopoiesis was induced by bleeding the animals before irradiation.

Factors influencing hematopoietic spleen colony formation in irradiated mice. II. The effect of foreign materials.

Normal dog plasma and serum, human, rat, and Swiss-Webster mouse plasma, phytohemagglutinin, sheep red cells, mumps and influenza vaccine, fibrinogen, and endotoxin injected before irradiation led to an increased number of endogenously derived spleen colonies in irradiated mice. Spleen weight and uptake of radioactive iron and iododeoxyuridine into such spleens were also increased. The relationship between these parameters of splenic hematopoiesis was unchanged by plasma injection suggesting that, while the number of colonies was increased, the composition of individual colonies was unchanged. This conclusion was supported by studies on plethoric mice in which splenic erythropoiesis is abolished. Increased splenic hematopoiesis was accompanied by an increase in the volume of packed red blood cells 10 days after irradiation. The total volume of plasma injected, the number of days of plasma injection preceding irradiation, and the route of administration were all important variables influencing the effect of plasma injections. Crude fractions of human albumin and gamma globulin, cortisol, C57BL (maternal) and DBA (paternal) mouse plasma, and isogeneic plasma were without effect. The ineffectiveness of isogeneic and closely related allogeneic plasma rendered unlikely the hypothesis that this effect represented the presence of homeostatic hematopoietic regulating factors in plasma. The increased hematopoiesis induced with plasma appeared to be limited to the spleen, for increased bone marrow hematopoiesis was not detected. Certain observations suggested that the effect of plasma may not be due to an antigenic or an inflammatory effect. From current observations, it was unclear whether the increased colonies induced by plasma were representative of expansion of the colony-forming cell pool or of increased efficiency of growth of the fraction surviving irradiation.

Factors influencing hematopoietic spleen colony formation in irradiated mice. I. The normal pattern of endogenous colony formation.

Data pertaining to the endogenous mouse spleen colony system, 10 days postirradiation, are presented. The D(o) for visible colonies is 78 R, while that for 6 hr iron uptake over a range of 600-800 R is 50 R. The D(o) for spleen weight is 196 R and that for IUdR uptake is 193 R. These measurements increase with the age of the mouse. Hypertransfusion decreases spleen iron uptake and colony number. DF-(32)P and sodium sulfate-(35)S are not useful indicators of splenic hematopoiesis in this system. Visible hematopoietic colonies in the spleen are not produced by vinblastine, nitrogen mustard, methotrexate, or cyclophosphamide.

Neutrophil kinetics in acute infection.

Neutrophil kinetics of acute experimental infection were studied with diisopropylfluorophosphate-(32)P labeling in 31 dogs inoculated intrabronchially with pneumococci. In vitro neutrophil labeling indicated a rapid transit time through the blood in early infections, with an elevated marginal granulocyte pool sometimes preceding an elevation of the circulating granulocyte pool. 13 hr after infection, the circulating and total blood granulocyte pools were increased but the rate of neutrophil transit through the blood was normal. During the recovery from infection there was a marked prolongation of neutrophil blood transit time, suggesting virtually complete cessation of bone marrow release of neutrophils into the blood. Labeling of neutrophils in vivo indicated an increased rate of emptying of the bone marrow storage pool proportional to the severity of infection as measured by the fever index. The change in the blood ratio of nonsegmented to segmented neutrophils was a much more accurate index of the severity of infection than the blood granulocyte concentration, correlating significantly with the fever index.

Leukokinetic studies. 13. A non-steady-state kinetic evaluation of the mechanism of cortisone-induced granulocytosis.

The mechanism by which adrenocortical steroids induce granulocytosis in man has been investigated using granulocytes labeled with radioactive diisopropylfluorophosphate. After an intravenous injection of 200 mg of cortisol was given to five normal subjects, the mean value for the total blood granulocyte pool increased from 79 to 138 x 10(7) cells per kg of body weight and reflected an increase in the size of both the circulating granulocyte pool and the marginal granulocyte pool. When granulocytes in the circulation were labeled with diisopropylfluorophosphate and granulocytosis was induced later by the intravenous administration of cortisol, the rate of decline of granulocyte specific activity was increased, indicating that the blood pool was being diluted at an accelerated rate by unlabeled cells entering from the bone marrow. The rate of egress of granulocytes from the blood pool to an inflammatory exudate was studied by the "skin window" technique. After the administration of cortisol, there was a mean reduction in the cellularity of induced inflammatory exudates of 75%. However, this reduction in cellularity varied considerably from subject to subject (45-98%). From these studies we can infer that steroids induce an absolute granulocytosis by decreasing the rate of egress of cells from the total blood granulocyte pool as well as by increasing the influx of cells from the bone marrow. By model simulation studies of the non-steady state induced by cortisol injection, it has been possible to quantitate these rate changes. In the present studies cortisol injection resulted in a mean decrease in blood granulocyte egress of 74% (1-99%) and a mean increase in cell inflow of 450% (300-750%).

Idiopathic refractory sideroblastic anemia: incidence and risk factors for leukemic transformation.

The clinical course of 29 patients with idiopathic refractory sideroblastic anemia studied by us was reviewed. Four patients developed acute leukemia. We were able to find 27 out of 268 cases of idiopathic refractory sideroblastic anemia reported in the literature which terminated in acute leukemia. Nine of these were well described. The overall incidence of acute leukemia is 10%. In an attempt to identify the risk factors for the development of acute leukemia, the clinical and laboratory features of this group of thirteen well-described cases which terminated in acute leukemia were compared to the remaining 25 of our cases which did not undergo leukemic transformation. The patients who died of acute leukemia tended to have a more severe anemia, a lower reticulocyte count, and increased transfusion requirement, and thrombocytopenia. Thrombocytosis appears to be a relatively good prognostic sign.

Folate-induced remission in aplastic anemia with familial defect of cellular folate uptake.

Severe aplastic anemia developed in a young man with an extensive family history of leukemia, pancytopenia, and neutropenia. Megaloblastic changes became evident, and treatment with high doses of folic acid resulted in striking clinical improvement. However, red-cell folate levels remained persistently low despite high serum folate levels. A defect in cellular folate uptake was suspected, and, indeed, uptake of 5-14CH3-H4-folate by stimulated lymphocytes and by bone-marrow cells from the patient was significantly reduced (P less than 0.05 as compared to normal cells. Further characterization of folate metabolism showed that intestinal absorption of the vitamin, membrane transport of 5-14CH3-H4-folate by mature red cells, folate utilization in the conversion of deoxyuridylate to thymidylate and polyglutamate formation were all normal. At least five other family members manifest decreased uptake of 5-14CH3-H4-folate by stimulated lymphocytes. These studies suggest that a genetically induced abnormality of folate uptake contributed to this patient's severe, but reversible, aplasia.