T. T. Odell

Implantation of Functional Erythropoietic Elements Following Total-Body Irradiation.

Summary Rats have been irradiated with doses of X-rays in the LD50 range and subsequently injected with homologous bone marrow carrying an immunogenetic marker. Erythrocytes carrying the label can be detected in the peripheral circulation of these animals within 2 to 3 weeks after administration of the marrow; unirradiated but marrow-injected controls do not show erythrocytes from the implant. Marrow implants have persisted and functioned for as long as 147 days at the time of this communication. The implanted marrow contributes as much as 80% of the peripheral erythrocytes.

Stimulation of platelet production by serum of platelet-depleted rats.

Summary Four subcutaneous injections, given during a 2-day period, of serum from platelet-depleted rats into untreated or splenectomized rats caused an increase in the number of circulating platelets to as much as 167% of the initial count. The rise in peripheral platelet count began 2 days after the first injection, reached a peak at 5 days, then declined to control values at 8 days. Equal amounts of serum from untreated donors did not produce this response. The results indicate that the active serum contains an agent (thrombopoietin) that stimulates production of blood platelets.

INFLUENCE OF AGE AT TIME OF IRRADIATION ON INDUCTION OF LEUKEMIA AND OVARIAN TUMORS IN RF MICE

Summary RF mice exposed to 100-300 r of whole-body X-rays at various ages from before birth to 180 days after birth showed age-dependent variations in susceptibility to leukemia induction. Susceptibility to induction of granulocytic leukemia was minimal when irradiation was carried out during gestation or shortly after birth, rising later to a maximum at about 70 days of age. Susceptibility to induction of thymic lymphomas was, likewise, apparently minimal during gestation but maximal shortly after birth, declining later in life at the time of thymic involution. Susceptibility to induction of ovarian tumors was relatively low in mice irradiated in utero. We are grateful to F. F. Wolff, E. S. Ledford, and W. D. Gude for technical assistance and to Dr. A. W. Kimball for statistical analysis of data.

Maturation of Rat Megakaryocytes Studied by Microspectrophotometric Measurement of DNA.

Summary The amount of DNA in the nuclei of individual megakaryocytes of male Sprague-Dawley rats was measured micro-spectrophotometrically in marrow smears stained by the Feulgen reaction. When the DNA values were arranged in a frequency distribution, the megakaryocytes fell into groups with the modal DNA content of successive groups increasing approximately by a factor of 2. Ploidy of the megakaryocyte groups was determined by comparison with DNA values of diploid cells. Frequencies of 4N, 8N, 16N, and 32N megakaryocytes were, respectively, 1.6%, 10.5%, 71.2%, and 17.1%. The results indicate synchronous division of the nucleus of polyploid megakaryocytes. The relative numbers of cells in ploidy stages may indicate the relative length of time spent in the stages. An hypothesis of megakaryocyte maturation is proposed. The method may prove useful in studies of megakaryocyte maturation and regulation. ADDENDUM: In a recent microspectrophotometric study, de Leval observed a frequency distribution pattern of DNA of polyploid megakaryocytes of guinea pigs very similar to that of rats described here (de Leval, M., Compt. Rend. Soc. Biol., 1964, vl58, 2198).

Isolation of a Sulfated Mucopolysaccharide from Blood Platelets of Rats.

Summary Most of the radiosulfate in S35-labeled rat blood platelets was recovered in an alkali extract. The extracted material stained with Alcian blue for mucopolysaccharides and was found to behave similarly to chondroitin sulfate when subjected to paper electrophoresis and paper chromatography.

Chemical Studies of Mucopolysaccharides of Rat Blood Platelets

Summary Two mucopolysaccharide fractions have been extracted from blood platelets of rats. Paper electrophoresis and paper chromatography of the intact MPS of fraction 1 and paper chromatography of its hydrolysis products show it to be similar to chondroitin sulfate. Fraction 2 is probably a uronic acid-free mucopolysaccharide.

Life Span of Mouse Blood Platelets

Summary In male BDF1 mice injected daily with Na2S35O4; radioactivity of the circulating platelets increased at a rate of 26% per day, reaching a plateau in 4 days. From the time required to attain maximum labeling of the circulating platelet population, the life span of mouse platelets is estimated to be approximately 4 days. We thank Dr. M. Asano for examining the bone marrow sections.

Stimulation of mouse megakaryocyte endomitosis by plasma from thrombocytopenic rats.

Summary Injection of plasma from thrombocytopenic donor rats resulted in an increase in the endomitotic index of megakaryocytes of recipient mice 32 hr after the initial treatment with plasma. The results suggested a dose-response relationship between the amount of plasma administered and the degree of stimulation of megakaryocytopoiesis. These findings demonstrate that an agent capable of stimulating megakaryocytopoiesis is released in response to thrombocytopenia and that this factor can be successfully transferred between species. They also substantiate the assumption that the increase in peripheral platelet numbers and in platelet labeling after administration of presumptive TSF occurs via stimulation of megakaryocytopoiesis.

The mitotic index of megakaryocytes of mice after acute thrombocytopenia.

Summary C3H mice were made severely thrombocytopenic by injection of antiplate-let serum. The peripheral platelet counts and the endomitotic index and number of marrow megakaryocytes were determined at intervals during the 6 days following treatment. Both the endomitotic index and the number of megakaryocytes increased and returned to pretreatment levels during that time, indicating a transitory stimulation of megakaryocytopoiesis in response to thrombocy topenia. We are most grateful to Dr. T. P. McDonald for supplying the antiplatelet serum that was used in these investigations.

Life Span of Rat Erythrocytes as Determined by Cr51 and Differential Agglutination Methods

Summary Survival of rat erythrocytes has been studied by simultaneous use of 2 methods, Cr51-labeling and differential agglutination. Results suggest that random destruction of rat erythrocytes did not occur and that the extinction of radioactivity of Cr51-labeled cells is a valid criterion for determination of erythrocyte life span. Both methods suggested a life span of about 65 days.