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The cycling characteristics of human peripheral blood lymphocytes in phytohemagglutinin-stimulated cultures were examined by means of a new technique employing radioautographic methods which assay the fraction of cells whose nuclei contain DNA polymerase utilizing exogenous and/or endogenous DNA primer-template capability. The fraction of cells labeled by these techniques increases 5-11 hr prior to the onset of DNA synthesis. Estimates of cell cycle time, G, time, and fraction of cycling cells are made for the first 4 days in culture. Evidence is presented to support the hypothesis that daughter cells of the first divisions may be retired from cycle by virtue of loss of primer-template availability, rather than by loss of DNA polymerase.

Perchloric acid extracts of radiation-induced fibrosarcoma (RIF-1) tumors grown in mice have been analyzed by multinuclear NMR spectroscopy and by various chromatographic methods. This analysis has permitted the unambiguous assignment of the 31P resonances observed in vivo to specific phosphorus-containing metabolites. The region of the in vivo spectra generally assigned to sugar phosphates has been found in RIF-1 tumors to contain primarily phosphorylethanolamine and phosphorylcholine rather than glycolytic intermediates. Phosphocreatine was observed in extracts of these tumor cells grown in culture as well as in the in vivo spectra, indicating that at least some of the phosphocreatine observed in vivo arises from the tumor itself and not from normal tissues. In the 31P-NMR spectra of the perchloric acid extract, resonances originating from purine and pyrimidine nucleoside di- and triphosphate were resolved. HPLC analyses of the nucleotide pool indicate that adenine derivatives were the most abundant components, but other nucleotides were present in significant amounts. The 1H and 13C resonance assignments of the majority of metabolites present in RIF-1 extracts have also been made. Of particular importance is the ability to observe lactate, the levels of which may provide a noninvasive measure of glycolysis in these cells in both the in vivo and in vitro states. In addition, the aminosulfonic acid, taurine, was found in high levels in the tumor extracts.

Autologous erythrocytes were irradiated at doses of 35,000 to 200,000 rads, chromated, and red cell survival studied. The 24-hour loss of labeled cells and subsequent apparent erythrocyte survival times were found to be functions of the radiation dose. ECIB-produced red cell hemolysis of a mild degree is to be expected during courses of therapy, as demonstrated by clinical findings. However, there is no doubt that acute, severe, hemolysis could be produced by administering large doses to patients over a short period of time.

The 4-hour whole body count is found to be clinically valid as a "100 per cent value" in iron absorption studies performed with a whole body counter. Measurement of iron absorption can be made 2 weeks after ingestion of radioiron, but not prior to this period.

1. A technic for the study of fixed preparations of blood and bone marrow by means of fluorescence microscopy with acridine orange is presented. 2. The distribution of RNA and DNA within the blood cells can be demonstrated cytochemically. 3. The RNA content of the erythroid and myeloid cells decreases with maturation. Mature plasma cells contain large quantities of RNA. 4. It is possible to demonstrate cytoplasmic metachromasia between the AO-RNA complexes of the erythroid, myeloid, and plasmacytic cells.

1. Two patients with acute leukemia had considerable decreases in leukemic cells in the peripheral blood as well as reduction in size of spleen and leukemic masses after 10 injections of 3H-TDR given over a 5-day period. Each injection was 0.25 µc./Gm. body weight.

1) The rate of disappearance of 60Co-cyanocobalamin (CNCB) from the body as measured by whole-body counting was found to change continuously as a function of time after administration.2) The administration of large doses of vitamin B12(500-1,000 µg) any time after 60Co-CNCB administration caused the biologic T½ of 60Co-CNCB to decrease.3) The administration of small doses (100 µg) of vitamin B12caused no detectable change in biologic T½ of 60Co-CNCB.4) The administration of large doses of CNCB caused a decreased biologic T½ of 58Co-hydroxocobalamin (HOCB) and the administration of large doses of HOCB caused a decreased biologic T½ of 60Co-CNCB, and both analogues had similar biologic T½’s over the study period.

THE EVALUATION of iron absorption using a single crystal whole-body counter is complicated by the inherent difficulty of determining a correct ‘ x2018;100 per cent value.” Shortly after ingestion, tracer radioiron can be found in the stomach, upper small intestine, portal circulation and liver. Fourteen to 20 days later, the time at which absorption is measured most effectively,1,2the radioiron will be distributed between the red cell mass, liver, spleen, bone marrow and other storage areas. With this mixed distribution there will always be an error because of geometric factors, and hence in counting efficiency, in using the relationship of to calculate iron absorption. In a previous iron absorption study reported from this group, the radioiron retention measured 4 to 10 hours post-ingestion was used as the ‘ x2018;’100 per cent value.”1

The observation of Miller of severe immunological deficiencies in adult, thymectomized, total-body-irradiated mice,1 led to the belief that the thymus played an essential role in reestablishing immune mechanisms in adult life. Miller2 implied that after adult thymectomy the animal becomes incapable of producing new immunologically competent cells. This deficiency results in gradual decrease in the ability of the animal to produce an immune response, provided that the noncommitted immunologically competent cells normally die and disappear in time. Adult thymectomy has been added to the recognized methods of immunosuppresion in animals and in man, in an effort to prolong the survival of allografts. The results of such efforts have been conflicting.3-10We decided to investigate the influence of extracorporeal irradiation of blood (ECIB) and thymectomy on skin allograft survival in calves and to compare these results to those obtained with ECIB alone.11 It has been shown that