Leon O. Jacobson

Studies on erythropoiesis. III. Factors controlling erythropoietin production.

Summary and Conclusion 1. We studied the erythropoietic response to anemic plasma of a variety of experimental conditions in the rat. Rats subjected to hypophysectomy, an atmosphere of high O2, starvation, and transfusion-induced polycythemia have a decreased rate of erythropoiesis and an exaggerated response to the administration of anemic plasma. 2. Treatment with dinitrophenol increases the rate of erythropoiesis and decreases the response to anemic plasma. 3. These findings are in agreement with the hypothesis that the rate of erythropoiesis is determined by the amount of erythropoietin, the production of which is regulated by the relationship between O2 supply and demand, not by either factor alone.

The role of the spleen in radiation injury.

Summary and Conclusions These hematologic and histologic data indicate that: 1) Severe anemia, leucopenia, and thrombocytopenia develop in mice after a single dose of 600 r whole-body X radiation. 2) Ectopic erythrocytopoiesis, in the lead-protected spleens of mice given 600 r whole-body X radiation (exclusive of spleens) compensates with such rapidity and so extensively for the destruction and interruption of this activity in the marrow spaces that no anemia of significance becomes apparent. Ectopic granulocytopoiesis and megakaryocytopoiesis in the lead-protected spleens compensates significantly but at a slower pace and less completely for the bone marrow destruction. 3) A marked and sustained decrease in the amount of lymphatic tissue is produced in the lead-protected spleens of animals given 600 r whole-body X radiation. This decrease in lymphatic tissue may perhaps be a result of (a) unsuccessful competition of the lymphatic tissue with the ectopic hematopoiesis for nutritional requirements, (b) actual indirect effect of radiation and (c) a differential humoral suppression from some unknown site. The rapidity with which erythrocytopoiesis transfers from the X-ray damaged bone marrow to the lead-protected spleen in the absence of anemia suggests that the mechanism of stimulation of erythrocytopoiesis under the conditions of this experiment may involve some factor or factors other than, or in addition to, the accepted hemoglobin-oxygen relationship. This technic permits more or less exclusive protection of the spleen or the appendix or other visceral tissues from irradiation while applying various dosages to the remainder of the body. It provides a method of studying potential sites and mechanism of the production of ectopic blood formation, possible secondary effects of radiation as well as offering possibilities for determining the potential role of such sites in immune reactions, in preventing or alleviating radiation-induced hemorrhagic phenomena and in the study of survival or recovery from radiation injury.

Studies on Erythropoiesis. Part IV. Reticulocyte Response of Hypophysectomized and Polycythemic Rodents to Erythropoietin

Summary and Conclusions 1. Following hypophysectomy of rats, reticulocytes in the peripheral blood fall to a minimal level within a period of 3 to 4 weeks. This reduction represents a 5- to 10-fold decrease from the prehypophysectomy control. This reticulocyte decline is more rapid in 8-week-old rats than in younger animals. 2. Administration of anemic plasma to hypophysectomized rats produces a reticulocyte rise that is many fold greater than that produced by normal plasma or saline. 3. Erythropoiesis, as measured by the number of reticulocytes in peripheral blood, falls to zero in 6 days in mice made polycythemic by repeated intraperitoneal injections of homologous red cells. Anemic plasma obtained from rats or rabbits, when injected intravenously or intra-peritoneally into polycythemic mice, produces a reticulocytosis many times greater than that observed from normal plasma. Normal saline produces no increase in reticulocytes. 4. In polycythemic mice and hypophysectomized rats, reticulocyte determinations in the peripheral blood and Fe59 red cell incorporation studies are of about equal sensitivity in measuring the response to anemic plasma.

The Hematological Effects of Ionizing Radiations

The objectives of the Health Division of the Plutonium Project were essentially (a) to study the fundamental and comparative biological action of external radiations and internally administered radioactive materials, (b) to apply the findings for the protection of individuals who worked in the Project, and (c) to use the findings generally for the protection of the public which was potentially in danger of exposure to these physical hazards. The hematologic studies2 conducted on the Plutonium Project were divided into four main categories, namely, the effects of acute3 whole-body exposure to externally administered penetrating radiation, the effects of chronic4 whole-body exposure to externally administered penetrating radiations, acute toxicity of parenterally and enterally administered radioactive compounds, and chronic toxicity of parenterally and enterally administered radioactive isotopes. In order to correlate properly studies on the peripheral blood effects with those occurring in the hemopoietic t...

Studies of erythropoietin: the hormone regulating red cell production.

There is mounting evidence that erythropoiesis is controlled by a humoral factor or factors. Since Carnot and DCflandrel first published this thesis in 1906, many investigators have attempted to substantiate their work, but it has been largely in the last twenty years that such investigators as Reissmann,Z Erslevj3 Gordon and his co-~orkers ,~ Borsook et u Z . , ~ and Stohlman et aL6 have succeeded in bringing the problem to the point of serious study and acceptance. In 1952 Grant and Root7 wrote a comprehensive review of the literature on the subject. The first convincing support of Carnot’s hypothesis is found in the work of Reissmann,2 and Stohlman et uL6 Reissmann demonstrated that increased erythropoiesis occurred in both parabionts even though only one of the pair was maintained in low O2 tension. Stohlman and Rath found that erythroblastic hyperplasia was not confined to the areas of regional hypoxia in a human being with regional hypoxia secondary to a patent ductus arteriosus. Hyperplasia was also observed in the bone marrow that was supplied by blood with a normal 0 2 saturation. Of necessity, the relationship of the humoral factor that is present in anemic plasma to the maintenance of a normal amount of red blood cells and hemoglobin has been one of conjecture until recently, when Gurney and his associates demonstrated its presence in normal plasma.* The exact relationship of arterial oxygen saturation to the production of circulatory erythropoietint and, thus, to erythropoiesis has likewise not been established. During the past several years we have been concerned with: (1) applying the technique of Fe69 incorporation as a measure of red cell production; (2) finding more sensitive assay preparations for erythropoietin; (3) elucidating the role of erythropoietin in maintaining the dynamic equilibrium of erythropoiesis; (4) determining the basic conditions that control erythropoietin blood levels and, thus, the rate of erythropoiesis; (5) studying the effect of cobaltous ion on erythropoietin production; (6) searching for the site of erythropoietin production; and, of course, (7) using the information obtained to solve certain clinical problems. A brief discussion of our research and some interpretations of the data are the subjects of this paper.

Erythropoiesis. II. Assay of erythropoietin in hypophysectomized rats.

Summary and Conclusions Using incorporation of Fe59 into newly-formed red cells as index of red cell production, it has been shown that erythropoiesis is gradually reduced, reaching a minimum in rats at 8 to 13 days after hypophysectomy. A factor of 10 exists between incorporation of Fe59 into red cells of normal control (37 ± 4) and the hypophysectomized rat (4 ± 2) at this interval. We have also found that the hypophysectomized rat is an extremely sensitive preparation for assay of factor(s) in anemic plasma that stimulates or mediates erythropoiesis. Our observations may be summarized as follows: 1. Administration of anemic plasma to hypophysectomized assay animal increases incorporation of Fe59 3- to 7-fold. 2. Plasma from hypophysectomized animals and un-operated controls made anemic by repeated phlebotomy increases Fe59 red cell incorporation to the same extent when administered to the hypophysectomized assay animal. 3. A single injection of 2 ml of anemic plasma to the hypophysectomized assay animal elicits a 2- to 3-fold increase in Fe59 incorporation. The mechanism of rapid reduction of erythropoiesis that follows hypophysectomy in rats and its relationship to increased sensitivity of the hypophysectomized animal to anemic plasma are discussed briefly.

THE PHYSIOLOGIC AND CLINICAL SIGNIFICANCE OF ERYTHROPOIETIN

Excerpt Until recently it was generally agreed that low oxygen tension in the bone marrow constituted a direct stimulus for red cell production. This view was challenged by many investigators whose...

Biological Studies with Arsenic76 II. Excretion and Tissue Localization

Summary 1. Arsenic excretion was studied in man, rats, and rabbits. Less than 10% of the excreted arsenic is found in feces in any of these species; rats have by far the slowest rate of excretion. 2. Data are given for arsenic distribution in various organs in man, the rat, the rabbit, and 2 strains of mouse. 3. The degree of individual variation within each species was very great; in contrast to man and to other animals studied, the rat retains most of the injected dose in the blood for a considerable length of time. 4. The ratio of arsenic concentration in kidney, liver, and spleen of healthy inbred mice was found to be fairly constant for a given time after administration, and this ratio is suggested as a criterion for effects of various types of treatment. 5. Using this ratio as criterion, it was found that arsenic distribution is altered by the presence of transplanted tumors. 6. Factors changing arsenic distribution are discussed in relation to effects on levels of sulfhydryl-containing substances.

Immune Response in Irradiated Mice with Peyer's Patch Shielding.∗

Summary 1. Shielding one Peyers patch of a mouse during lethal x-irradiation protects a sufficient number of cells to cause rejection of a heterologous or homologous bone marrow graft. 2. Shielding 11 mm of the small intestine results in a similar but less violent reaction. 3. A dosage of 650 r or more to the protected Peyers patch is necessary to impair the capacity of the lymphatic tissue to reject the graft. 4. Regeneration of lymphatic tissue is evident in the spleen, mesenteric lymph node and thymus in Peyers patch-shielded mice 6 days post-irradiation. On the other hand no bone marrow regeneration was observed nor was there evidence of granulocytic, megakaryocyte, or erythrocytic regeneration elsewhere.

The Influence of the Spleen on Hematopoietic Recovery After Irradiation Injury

Summary and Conclusions Young adult female mice were exposed to 1025 r whole-body X radiation. The spleens of these mice were mobilized surgically through an abdominal incision and lead protected during irradiation in one group and mobilized but not lead protected during irradiation in another group. The bone marrow and lymphatic tissues were destroyed and no regeneration was as yet apparent on the tenth day in the animals irradiated without lead protection of the spleen. In the animals with lead protection of the spleen during irradiation, these tissues were never depleted of free hematopoietic cells and the bone marrow and the lymph nodes were normal in cellularity by the eighth day after irradiation. Several possible interpretations of the role of the spleen under the conditions of these experiments are discussed.