Lola S. Kelly

Cell division and phagocytic activity in liver reticulo-endothelial cells.

Summary Radioautographs of liver sections from mice given tritiated thymidine were used to identify the cells which were preparing for division and colloidal saccharated iron oxide was used to identify the active phagocytic cells. In livers of mice whose reticulo-endothelial system was stimulated by estradiol, it was established that the cells preparing for division and those which had recently divided were actively phagocytic. In livers of mice whose reticulo-endothelial system had been “blockaded” with saccharated iron oxide, it was established that the cells which had phagocytized colloid were able to divide in the process of recovery from “blockade.” No evidence was found for a stem cell which proliferates and differentiates to provide the active phagocytic population.

Autoradiographic Studies of Leukocyte Formation.

Summary 1. Twenty-four hours are required for maturation of the neutrophil from the last division stage in the marrow. 2. The data are best explained by a finite life of 2/3 day for mature neutrophils in marrow, followed by a peripheral life span of 1 to 1 1/3 days. 3. Lymphocytes fall into two classes—medium and large cells, which are rapidly renewed, and small cells, which live at least a week.

SOME PROBLEMS OF LYMPHOCYTE PRODUCTION

Though lymphocyte production has been studied for many years, it still presents a number of unsolved problems. One of the first, perhaps, is to define what a lymphocyte really is. Having done this, we should like to know (1) where lymphocytes are produced, and (2) in what numbers. Furthermore, the questions of the role of the lymphocyte and its ultimate destination also become involved in the study of lymphocyte production.

Effects of Irradiation on Nucleic Acid Formation.

Summary Mice of the A strain bearing bilateral transplants of mammary carcinoma were used to demonstrate an indirect effect of irradiation on the desoxypentose nucleic acid turnover rate. In 2 experiments the animals were irradiated by means of radioyttrium colloids which localize in the liver when injected intravenously and remain at the site of injection when given intramuscularly. The nucleic acid turnover rate was measured by giving a tracer dose of radioactive sodium phosphate, sacrificing the animals after 2 hours, and isolating the desoxypentose nucleic acid from their tumors and livers. The specific activity of the nucleic acid phosphorus was measured and considered to be an index of the turnover rate. It was found necessary to purify the nucleic acid much more carefully than is done in standard methods in order to obtain a constant specific activity upon successive reprecipitations. The animals whose livers were irradiated with 4.25 × 105 ergs showed only 66% of the tumor nucleic acid specific activity of the control group. The animals whose muscles were irradiated with 5.25 × 105 ergs showed 84% of the tumor nucleic acid specific activity of the control group. Both these experiments definitely confirm the existence of an indirect effect of radiation on the desoxypentose nucleic acid turnover rate. One group of animals received 60 r (1.4 × 105 ergs) total body X-irradiation with 180 KV X-rays and both the tumors and livers showed a significant depression in the turnover rate.

Effect of Total-Body X-Irradiation on Relative Turnover of Nucleic Acid Phosphorus.∗:

Summary The incorporation of P32 into DNA; nuclear PNA (nPNA), and cytoplasmic PNA (cPNA) of liver was measured in rats which had been exposed to 2500r total body X-irradiation and in mice which had been exposed to 600r total body X-irradiation. It was found that the incorporation of P32 into cPNA was increased in all cases, while into DNA and nPNA it was depressed. In the Sprague-Dawley rats an increase in the weights of the liver was observed concurrent with the increase in cPNA specific activity. A possible interrelationship between protein and cPNA synthesis has been discussed.

DNA synthesis and incorporation of P32 in irradiated Ehrlich ascites cells.

Summary Experiments were carried out 4 to 6 days after inoculation of approximately 2 × 107 Ehrlich ascites tumor cells in mice. When the 2-hour incorporation of P32 into DNA was measured at various times after irradiation (800 r total body x-irradiation), no significant depression in DNA specific activity was observed until 1 day. Measurements of mean cell volume, mean DNA content per cell, and mean total nucleic acid content per cell at 13 and 20 hours revealed that all 3 quantities increased at approximately the same rate, closely matching the growth rate of the unirradiated tumor and rate of DNA formation estimated from the incorporation data. The increased DNA content per nucleus after radiation was confirmed by Feulgen microspectrophotometry. At 48 hours after irradiation cell volume and total nucleic acid per cell had risen even higher while DNA per cell showed little further increase. The data suggest that the irradiated cells continue to synthesize DNA until they reach the premitotic DNA content (octoploid in Ehrlich cells) and are arrested there because they are unable to go through mitosis.

The design of an experiment to study leukemogenesis in mice irradiated by energetic heavy ions.

The design of an experiment to study the incidence of cancer and hematological effects in mice irradiated by heavy ions is described. A beam of fully stripped

Proliferation of the reticuloendothelial system in the liver

{\rm C}^{6+}

Post-Irradiation Time and Dose-Response Studies on the Incorporation of P32 into DNA of Mouse Tissues

ions of energy 250 MeV/amu was produced by the Bevatron. Mice were irradiated in groups of 12 by rotating them in a wide beam (11.4 cm FWHM) once per minute. At a beam intensity of 108 ions per pulse irradiations of 250 animals to absorbed doses of 200 rad were completed in a few hours, an efficient use of accelerator beam time. The average LET of the radiation was 16.6 keV/μm with a spread in the animal of ±2 keV/μm. Radial and longitudinal variations in absorbed dose were less than 30% and 15%, respectively. Estimates of tissue-entrance absorbed doses with an ionization chamber and with thermoluminescent dosimeters differed by less than 3%.