Marrow distribution in rat femurs determined by cell enumeration and Fe59 labeling

The proportion of erythroid mitoses in normal human bone marrow in short-term culture systems

The proportion of erythroid cells in mitosis was determined in direct preparations and in synchronized and unsynchronized short-term cultures from normal human bone marrow. The stimulating effect on the proportion of erythroid mitoses of bovine serum albumin (BSA), erythropoietin (EP) and human leucocyte conditioned medium (HLC) derived from stimulated lymphocytes, was also analyzed in short-term marrow cultures. In synchronized and unsynchronized cultures, the proportion of erythroid mitoses was markedly lower than in direct preparations, with a mean of 75% in the direct compared to 11% in the unsynchronized cultures and 7% in synchronized. Statistical analysis showed that EP had a substantial influence on the erythroid cells while HCL had a minor effect.

Sustained hypertransfusion and induction of a transplantable myeloid leukemia in RLV-A-infected BALB/c mice

Infection of BALB/c mice with the RLV-A virus typically results in an erythropoietic dysplasia characterized by hepatosplenomegaly, erythroblastosis, erythroblastemia and severe anemia without reticulocytosis. Mice hypertransfused weekly with 75%-packed red cells for 42 days prior to RLV-A infection and viral potency controls manifested this typical RLV-A response. Mice that were hypertransfused prior to and following RLV-A infection never developed the "typical" RLV-A pathogenesis. Instead, a transplantable myeloid leukemia was established. Although the reason for altered pathogenesis remains uncertain, it seems plausible that continued hypertransfusion, presumably after establishment of an altered granulopoietic microenvironment, resulted in a completely different viral expression and development of the transplantable myeloid leukemia.

Variations in the histologic distribution of rat bone marrow cells with respect to age and anatomic site

Bone marrow cellularity in untreated Fischer 344/N rats was subjectively evaluated in hematoxylin and eosin (H & E)-stained histologic sections from femur, tibia, humerus, sternum, lumbar vertebrae, ribs, pelvis, and skull of 2-, 4-, 7-, 16-, and 24-month-old males. Marrow cellularity varied with age of the rat and bone site sampled. Hematopoietic cellularity was consistently higher in rats less than 4 months of age and less consistently higher in 24-month-old rats versus intermediate age groups examined. The 24-month-old rats had the greatest animal-to-animal variation in cellularity. Site differences in bone marrow cellularity were present and similar at 4, 7, and 16 months. Mean percentage of marrow space occupied by hematopoietic cells ranged from 33-75%. Categories for histologic grading of bone marrow cellularity are presented. Sternum, femur, and humerus are recommended sites for histologic evaluation of bone marrow cellularity from conventional H & E-stained sections. Definitive evaluation and assessment of hematopoietic perturbations should not be solely based on subjective evaluation of routine histologic sections.

Pathogenesis of the anemia of Shay Chloroleukemia

The pathogenesis of anemia of the Shay chloroleukemia (SCL) was studied in rats following SC, IP and IV inoculation of chloroma cells. Little difference in survival was noted regardless of the route of inoculation. A decrease in hamatocrit occurred in all SCL rats during approximately the final 48 hours of the disease; however, the anemia was more severe in SC- and IP-inoculated terminal rats than in SCL rats inoculated IV. A reduction in the numbers of normal cellular elements was noted in the femoral bone marrow of most terminal rats studied which was found to correlate inversely with the leukemic blast cell content of the marrow. No correlation was observed between the erythroblast content of the marrow and the degree of anemia. The number of erythroblasts varied from greatly reduced to normal in terminal SCL rats despite severe anemia. Moreover, the greatest reduction of both normal marrow cellularity and erythroblast numbers was observed in IV inoculated rats which consistently displayed the highest hematocrits in the terminal stage of the disease. Thus, the terminal anemia appears to be due primarily to excessive red cell loss. The decrease in erythroblasts, when observed, was most striking in the orthochromatophilic and polychromatophilic stages of erythroid maturation.

Effect of erythropoietin on anemia of peritoneally dialyzed anephric rats

The effect of erythropoietin on anemia was studied in anephric rats undergoing peritoneal dialysis. Both the number of bone marrow red cell precursors and plasma iron turnover were markedly depressed in untreated peritoneally dialyzed anephric animals when compared to peritoneally dialyzed sham-operated control rats. Anephric rats receiving 2 U of erythropoietin per day for 12 days had greater than threefold more bone marrow red cell precursors and a twofold larger plasma iron turnover than did the saline injected anephric rats. There was no significant difference in either bone marrow red cell precursors or plasma iron turnover in the erythropoietin-treated anephric rats when compared to the nonuremic controls. Although the rats receiving erythropoietin for 12 days had a significantly higher hematocrit (29.5%) than the saline injected uremic rats did (19.0%), the hematocrit was significantly lower than that found in nonuremic control animals, either receiving erythropoietin (48.1%) or not receiving erythropoietin (41.6%). Our data suggests that erythropoietin is potentially a useful agent for the treatment of anemia of chronic renal failure.

Effect of hypertransfusion on granulopoiesis in bone marrow depression: studies in the irradiated mouse

The response of granulopoietic activity in bone marrow depression to a reduction in the demand for erythropoiesis has been examined by means of hypertransfusing C-57B mice which had been exposed to sublethal whole body irradiation. Multiple intraperitoneal injections of 0.5 ml packed red cells from irradiated donors were employed to maintain the haematocrit sufficiently above the normal range to produce significant suppression of erythropoietic activity for the duration of the bone marrow depression. This was associated with elevation above control values of 32--102% in the blood granulocyte count, 22--78% in total cells of the granulocytic series per femur, and up to 44% in total agar colony forming units per femur. Restoration of essentially normal values occurred 13 d after irradiation in contrast to 17--18 d in controls. Single transfusions which produced less suppression of erythroblast numbers per femur resulted in an intermediate degree of improvement in these parameters. Such changes in the granulocyte compartment indicate improved granulopoietic capacity in the hypertransfused group. It is suggested that this effect reflects increased production of granulocyte progenitors due to the reduction in competing demands on the compromised multipotential stem cell compartment for progenitors of the erythroid series. The findings raise the possibility that hypertransfusion might be capable of producing a beneficial effect on granulopoiesis in human bone marrow depression.

Globin messenger-RNA induction during erythroid differentiation of cultured leukemia cells

A cloned line of murine proerythroblastoid cells (T-3-Cl-2), transformed by Friend leukemia virus, undergoes changes associated with erythroid differentiation when treated with dimethylsulfoxide in culture. This line, which does not undergo spontaneous differentiation, develops specific erythrocyte-membrane antigen and accumulates detectable amounts of heme within four days of dimethylsulfoxide treatment. In the present study, we have followed the phenotypic expression of the globin genes by measuring globin mRNA in differentiating cells. Our hybridization probe for this purpose is [(3)H]DNA, which is complementary to purified globin mRNA, synthesized by viral RNA-directed DNA polymerase. This probe is sufficiently sensitive to detect less than 1 ng of globin mRNA. Using it, we find little or no hybridizable globin mRNA in either uninduced cells or in treated control lymphoid cells. In contrast, globin mRNA can be detected in T-3-Cl-2 cell 2 days after induction by dimethylsulfoxide; it reaches a maximum concentration four days after induction. At this time, cells that stain positively for heme appear. The hybridizable cytoplasmic RNA induced in these cells has the sedimentation properties of 9S globin mRNA. Considering the stable character of globin mRNA, our results are most readily explained in terms of a transcriptional activation of the globin genes.

Hemoglobin synthesis in murine virus-induced leukemic cells in vitro: stimulation of erythroid differentiation by dimethyl sulfoxide

Cells of a cloned line of murine virus-induced erythroleukemia were stimulated to differentiate along the erythroid pathway by dimethyl sulfoxide at concentrations that did not inhibit growth. A rise in the number of benzidine-positive normoblasts was accompanied by increased synthesis of heme and hemoglobin and a decrease in the malignancy of the cells. This action of dimethyl sulfoxide, which was reversible, may represent the derepression of leukemic cells to permit their maturation.

Nucleoside deaminase: an enzymatic marker for stress erythropoiesis in the mouse

The level of nucleoside deaminase was determined in extracts of mouse tissues obtained during a period of accelerated erythropoiesis induced by hypoxia, hemorrhage, or the injection of phenylhydrazine. Under these conditions a striking (10- to 100-fold) elevation of the enzyme activity occurred in the spleen. Similar results were obtained with the injection of purified erythropoietin. In control animals, only a trace of nucleoside deaminase activity was detected in the blood. During the reticulocyte response which followed erythropoietic stimulation, there was a sharp increase in the blood level of nucleoside deaminase, which rose up to 120 times that of control animals. By differential centrifugation, the enzyme was localized to the reticulocyte-rich fraction. Erythrocyte nucleoside deaminase remained elevated even after the reticulocyte count had fallen to normal in the phenylhydrazine-treated mice or to zero after the cessation of hypoxia. There was a very gradual decline in the enzyme activity in the blood which fell to the barely detectable control levels about 45 days after the initial reticulocyte response, a time period which corresponds to the survival of the mouse red blood cell. The persistence of high levels of nucleoside deaminase for the full life span of a generation of erythrocytes formed during stress, viewed in contrast to the virtual absence of the enzyme from normal erythrocytes of all ages, represents an enzymatic difference between the normal red blood cell and the cell produced under conditions of accelerated erythropoiesis.

Erythropoiesis in the rat: differential rates of DNA synthesis and cell proliferation

Direct in vivo estimates of DNA synthesis time in early and late erythroblasts were obtained by using the H(3)- and C(14)-thymidine double-la-beling technique. A double-emulsion autoradiographic procedure was used to resolve the two isotopes. Early erythroblasts were found to proliferate at a rate about five times that of late cells. This results primarily from a shorter mean DNA synthesis time in early cells (2.5 hours) than in late cells (6.5 hours).