Frank E. Trobaugh

THE ASSAY OF THE TRANSPLANTATION POTENTIAL OF FRESH AND STORED BONE MARROW BY TWO IN VIVO SYSTEMS.

The transplantation of isologous mouse marrow in the fresh and thawed state was compared in two in vivo systems. Both assay techniques indicate good survival of the basic repopulating unit after storage in 15% glycerol. The spleen colony technique is more efficient and sensitive than the studies of mouse protection. Presumably, both techniques depend upon the ability of the marrow to repopulate. Itilizing this colony-assay system, dimethyl suifoxide appears iess efficient than glycerol in protecting the basic repopulating unit. (auth)

EFFECT OF CYCLOPHOSPHAMIDE ON THE HEMATOPOIETIC MICROENVIRONMENTAL FACTORS WHICH INFLUENCE HEMATOPOIETIC STEM CELL PROLIFERATION

Transplanted hematopoietic stem cells (HSC) regenerate more rapidly in the femoral marrow of lethally irradiated hosts pretreated with cyclophosphamide (CY) 4 days prior to X‐irradiation than they do in that of uninjected irradiated hosts (control). On the other hand, regeneration of HSC transplanted into irradiated hosts given CY 7 days before X‐irradiation is slower than in controls.

STUDIES OF HEMATOPOIESIS IN MURINE SPLEENS: SIGNIFICANCE OF HEMATOPOIETIC COLONIES FORMED ON THE SURFACE OF SPLEENS

Conies of hematopoietic tissue are formed in spleens of lethally irradiated mice by the injection of small numbers of hematopoietic cells. Some of these colonies appear as surface colonies, others can be identified only in serial sections of the spleen. The present studies have related the number and cellular composition of total hematopoietic colonies in the murine spleen to their visual recognition on the splenic surface. These studies demonstrate that only 50% of the total colonies in a spleen are recognized as surface colonies and that of those colonies on the surface, approximately 80% contain erythroid elements. At least four factors play important roles in the recognition of hematopoietic colonies as splenic surface colonies: (1) dose of repopulating cells or hematopoietic stem cells injected into the irradiated animal; (2) location of colonies within the spleen; (3) size of colonies; and (4) cellular content of the colonies. These studies demonstrate that surface colony formation reflects primarily erythropoiesis and not total hematopoiesis.

TRANSPLANTATION POTENTIAL OF FRESH AND STORED HEMATOPOIETIC TISSUE AS ESTIMATED BY STANDARD IN VITRO TECHNIQUES

The ability of three in vitro systems to predict marrowrepopulating potential was tested and it was found that the data do not measure this potential. The results of dyeexclusion tests are greatly influenced by the suspension medium and the prior treatment of cells. They are widely used in estimating the viability of homogeneous suspensions of cells such as lymphocytes or tumor cells, but marrow is a suspension of heterogeneous cells. In tissue culture, it was noted that the sick-looking thawed cells return to a state of apparent good health and activity, but were not able to apply these observations to study of the repopulating unit. Early in short-term tissue culture the thawed cells appear damaged. It is anticipated that any in vitro test of viability applied shontly after thawing would be greatly affected by this apparent damage. Incorporation of labeled thymidine into DNA apparently reflects the number of cells in the phase of DNA synthesis, but there is no evidence that it reflects the number of viability of the cells responsible for repopulation. (auth)

APPLICATION OF ERYTHROPOIETIN ANTISERA TO STUDIES OF ERYTHROPOIESIS

INTRODUCTION The development of antiserum to erythropoietin provides a new tool for the study of the action of this hormone, its site of formation, and its target cell, as well as for the development of an immunoassay. This paper describes some of the immunologic properties of erythropoietin antiserum, reports the results of in vivo and in vitro studies of its effect on erythropoiesis, and discusses problems associated with its production.

Effect of Sex Differences on Extrarenal Erythropoietin Production

Summary Evidence is presented to show that extrarenal as well as renal sites of Ep production are more sensitive to hypoxia in male than in female rats. However, on exposure to very intense hypoxia, the peak plasma Ep levels of both anephric and intact female rats are comparable to those of males.

The inhibitory effect of collagenase on bone marrow fibroblasts in vitro.

Abstract Collagenase added to the incubation medium of bone marrow explants in well cultures inhibits the development of “fibroblast-like cells” which ordinarily occur in these cultures. It doe not prevent the formation of primitive macrophage-like cells after one week in culture.