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AZT has induced a macrocytic anemia in AIDS patients on long term AZT therapy. It is generally assumed that DNA elongation is stopped by the insertion of AZT into the chain in place of thymidine thus preventing the phosphate hydroxyl linkages and therefore suppresses hemopoietic progenitor cell proliferation in an early stage of differentiation. CBA/Ca male mice started on AZT 0.75 mg/ml H2O at 84 days of age and kept on it for 687 days when dosage reduced to 0.5 mg/ml H2O for a group, another group removed from AZT to see recovery, and third group remained on 0.75 mg. At 687 days mice that had been on 0.75 mg had average platelet counts of 2.5 x 10(6). Histological examination on 9 of 10 mice with such thrombocytopenia showed changes compatible with myelodysplastic syndrome (MDS). A variety of histological patterns was observed. There were two cases of hypocellular myelodysplasia, two cases of hypersegmented myelodysplastic granulocytosis, two cases of hypercellular marrow with abnormal megakaryocytes with bizarre nuclei, one case of megakaryocytic myelosis associated with a hyperplastic marrow, dysmyelopoiesis and a hypocellular marrow and two cases of myelodysplasia with dyserythropoiesis, hemosiderosis and a hypocellular marrow. Above mentioned AZT incorporation may have induced an ineffective hemopoiesis in the primitive hemopoietic progenitor cells, which is known to be seen commonly in the myelodysplastic syndrome.

Following 200 cGy total body irradiation, 20-25% of CBA/Ca mice and their CBA/B and CBA/H sublines develop myeloid leukemia. To determine whether hematologic changes in vitro were detectable, long-term marrow cultures (LTBMCs) were established from the right and left hind limbs of 11 individual control and 11 CBA/B mice 100-114 days after 200 cGy total body irradiation. Individual cultures were studied weekly for cumulative production of nonadherent cells and colony-forming, hematopoietic progenitor cells. Control cultures produced significantly more nonadherent cells over 25 weeks in long-term marrow culture compared to those from irradiated (treated) mice. Permanent stromal cell lines were established from control and irradiated CBA/B mouse LTBMCs and clonal sublines were established. The stromal cell lines from LTBMCs of in vivo irradiated CBA/B mice had uniformly lower plating efficiencies, and only one formed a permanent clonal subline at 100-fold lower frequency compared to stromal cell lines from control mouse LTBMCs. The irradiation sensitivity of both uncloned and clonal sublines was similar by single-hit, multi-hit or by linear quadratic formula. Cocultivation of an IL-3 dependent hematopoietic progenitor cell line established from a control CBA/B, LTBMC with control of irradiated stromal cell lines derived from either a control (CC3) or the one successfully cloned in vivo irradiated (CT4) LTBMC, produced few cobblestone islands in the presence of IL-3. In contrast, formation of cobblestone islands in the presence of L cell-condition medium as a source of M-CSF was significantly greater, and these persisted for 21 days on both CC3 and CT4 stromal lines. The data provide evidence for irradiation induced changes in the bone marrow stromal cell compartment of CBA/B mice which persist and are detectable in vitro 6 months after explant of the cells to culture. These marrow stromal cell lines may provide valuable resources for analyzing the molecular biologic changes in the hematopoietic microenvironment during irradiation leukemogenesis.

Because of increasing evidence of heterogeneity in the hematopoietic stem cell compartments, the radiosensitivity of spleen colony-forming units (CFU-S) was reevaluated to ascertain whether the classical single exponential curve for a graded dose of radiation is applicable at higher doses of radiation, 400-600 cGy. Bone marrow cells (BMC) removed from mice immediately after death under anesthesia were irradiated in vitro. Great care was taken to exclude anoxic effects during irradiation and to avoid any possible effects in the recipient mice from injection of excessive numbers of BMC. By estimating the number of cells to be injected to produce numbers of colonies within the evaluation range of the assay, we obtained a radiation survival curve that appeared to have a multiphasic concave shape; the D0 value for the 400-600 cGy range was estimated to be about 275 cGy, whereas the D0 for the lower doses was 95 cGy, the same value as previously reported. The reason a single exponential survival curve was previously obtained after graded doses of radiation is discussed, and a comparison of those results with the present data from in vitro radiation is made. Lacking experimental evidence, we speculate that the major factor that determines the slope of the survival curve is the degree to which the stem cells are in their normal hematopoietic environment during the irradiation. The probable existence of a fraction surviving after an exposure to 600 cGy, estimated by the limiting dilution assay, was about 1 per 2 x 10(6) BMC. Such radio-insensitive CFU-S appear to be primitive CFU-S, which can contribute materially to the long-term survival of lethally irradiated bone marrow recipients.

On March 1, 1954, after detonation of a thermonuclear device on Bikini atoll, an unexpected wind shift resulted in the deposition of radioactive fallout on inhabited atolls. The fallout radiation caused fleeting systemic effects, dose-dependent depression of hematopoiesis and skin burns primarily due to the beta ray component of the fission radionuclides. Within a few weeks, hematopoietic recovery was substantial but slight depression of blood counts was maintained for several years. One case of fatal acute myeloblastic leukemia developed in a boy receiving 1.9 Gy as an infant. Cretinism developed in two boys exposed as infants with estimated thyroidal dose in excess of 50 Gy. Chemical hypothyroidism was detected in several persons. Thyroid adenomas and cancer commenced appearance ten years after exposure and became a major long-term medical problem. There have been no late effects attributable to the beta burns 40 years after exposure. Internal contamination from ingestion and inhalation of radionuclides is detectable. The doses are comparable to background levels in the U.S. There is no detectible decrease in longevity of the exposed Marshallese compared to an unexposed Marshallese population.

The effects of chronic low-dose irradiation on the immune system and the lymphocytes are largely unknown. The uranium miners in the former German Democratic Republic (GDR) were exposed mainly to a local low-dose irradiation in the lung by radon and its progeny, but also to some whole-body gamma irradiation. The local irradiation led to an increased rate of lung cancer and perhaps to some increase in extrapulmonary neoplasms. But little is known about the effects on the lymphocytes circulating and recirculating to the lung. As a prerequisite for the establishment of a biomathematical model to estimate lymphocyte fluxes, and to assess the radiation effects on the lymphocytic (and stem cell) populations passing through the lung, it was necessary to establish the current knowledge with respect to the physiology and pathophysiology of the lymphocytic cell renewal systems. The data concerning lymphopoiesis and lymphocyte kinetics, which are important for the development of this model, are summarized. The distribution of lymphocytes between different compartments including the lung is taken into consideration, as well as the effects of acute and chronic irradiation on the immune system. The extracorporeal irradiation of the blood (ECIB) may serve as a model of irradiation of blood in the lung. This review shows that many data necessary for development of a detailed biomathematical model are still missing, especially data concerning details on lymphocyte production rates of their different subsets and regulatory mechanisms of the lymphocytic system.

C57Bl/6 mice were given 10 Gy X rays fractionated in several ways. There was a cyclical pattern of animal survival which was correlated to the fractionation interval and which indicated a periodicity of 6 h. Ten grays given in a single dose is fatal to 100% of the mice and depresses the CFU-S to about one per leg with no evidence of proliferation during the remaining life. Ten grays given in 2.5-Gy increments at 24-h intervals causes no fatalities and results in a similar CFU-S depression but is followed by an exponential increase in CFU-S over the ensuing 12 days. Although bone marrow from survivors of such treatment was comparable to control marrow in its capacity for short-term rescue, it was clearly inferior in its capacity for long-term rescue. The periodicity of 6 h suggests that the cells responsible for survival of the mice have been synchronized into more or less radiosensitive and radioresistant stages of the cell cycle as a result of the time between the 2.5-Gy increments. Implications for the CFU-S and long-term repopulating cells are discussed.

Are the stem cells that survive graded doses of ionizing radiation as effective in restoring hematopoiesis in irradiated mice as transfused nonirradiated stem cells? This question was addressed by determining animal dose mortality and 10-day colony-forming units (CFU-S) survival curves and then replotting the percent animal survival against the number of CFU-S surviving the different doses of radiation, and by determining the number of nonirradiated CFU-S injected into fatally irradiated mice that result in a CFU-S dose mortality response curve. The number of CFU-S surviving per mouse after doses of radiation resulting in 95, 50 and 5% animal survival were calculated to be 520, 300 and 153, respectively. From the transfused CFU-S dose mortality curve of otherwise fatally irradiated mice (8.5 Gy), the number of transfused normal CFU-S required for 95, 50 and 5% animal survival was estimated to be 153, 24 and 3, respectively. The ratios of surviving CFU-S to nonirradiated, injected CFU-S are: at 95% survival (6.3 Gy), 3.4; at 50% survival (6.88 Gy), 12.5; and at 5% survival (7.4 Gy), 51.0. These data show that, in addition to a reduced number of CFU-S, as radiation dose increases, the quality of surviving CFU-S responsible for 30-day survival decreases. By implication, the long-term repopulating cell (LTRC) that is now known not to be the 10-day CFU-S must also decrease.

G-banded metaphase chromosomes prepared from 14 male CBA/Ca mice with histologically confirmed myeloid leukemia (ML) were studied in an effort to identify specific chromosomal changes associated with radiation leukemogenesis. The chromosome studies were undertaken as part of a larger investigation of radiation carcinogenesis, in which mice were exposed to radiation of several different qualities, i.e., x-rays, gamma-rays and "monoenergetic" fast neutrons of 5 mean energies ranging from 0.2 to 14 MeV. The 14 ML cases showed no histologically phenotypic differences and they were transplantable in syngeneic mice. We detected a specific chromosomal deletion in 1 copy of mouse chromosome 2 at regions D-E in all radiation-induced ML cells, regardless of radiation quality. Our results strongly implicate the involvement of genes within or close to regions D-E of chromosome 2 in radiation leukemogenesis. In addition to the specific deletion in chromosome 2, loss or gain of the Y chromosome was also detected in some cells from 6 ML cases. Because this hypo- or hyperploidy occurred in only a small fraction of leukemic cells, a causative role in radiation leukemogenesis appears unlikely.

Normal and splenectomized mice (SPLXM) were given rhG-CSF for 10 to 128 days and serial observations were made on blood counts for 128 days. After 10 days, mice were killed for histologic studies. All treatment schedules produced, in addition to elevated white blood counts, a macrocytic anemia which only partially responded to large doses of Epo. Stopping rhG-CSF treatment for 2 days resulted in the return of granulocytes, lymphocytes, monocytes, platelets and polychromatophilic erythrocytes to near normal levels, indicating a need for the continued presence of rhG-CSF to maintain peripheral blood increases. Treatment of normal and SPLXM with rhG-CSF induced marked granulocytic hyperplasia of the bone marrow with expansion of the granulocytic marrow into the adjoining muscle as in acute myelocytic leukemia. The hyperplasia is greater in the SPLXM than in the normal mouse where splenic hyperplasia occurs in all cell lines. The rhG-CSF also results in expansion of granulopoiesis into the normally fatty tail bone marrow in SPLXM. The rhG-CSF treatment produced marked increases in the assayable numbers of GM-CFU, G-CFU and M-CFU. The significance and mechanisms of induction of these changes are not clear. It is speculated that treatment with rhG-CSF has multicellular effects, suggesting that it initiates a cascade of molecular reactions that cause the effects observed.

The success of chemotherapy in leukemias in which the marrow appears entirely replaced by leukemic cells must be due to the persistence of some normal stem cells. The implied competition between leukemic and normal stem cells is thus akin to the competition between donor and host cells in irradiated animals. A review of that competition points to the importance of the quantitative relationships between the competing stem cells, even when one of the competing stem cell clones has a proliferative advantage. Pursuing that analogy, it is suggested that stimulating the surviving normal stem cells by appropriate combinations of cytokines may be of therapeutic benefit, once the tumor load has been reduced by chemotherapy. Complete eradication of leukemic cells may not be necessary, if surviving normal cells could gain ascendancy over the residual leukemic cell clones.

In view of the enormous number of base pair replications per annum in hemopoietic stem cells with the likelihood of coding errors, the rarity of the leukemogenic event at the cellular level after high doses of radiation, the infrequent occurrence of radiation events in cells at low-level exposure (large fraction of cells uninvolved), biological protective mechanisms and the realization that exposure of human populations to radiation from nuclear power plants is a very small fraction of natural radioactivity and will for the foreseeable future remain small and that populations exposed to high natural background radiation show no detectable harmful effects, it is concluded that either there is no effect, or for statistical reasons one cannot detect an effect.

Cortical thymocytes of young adult mice were labeled in situ with radioactive DNA precursors. As a result of cell emigration and cell death, total thymic radioactivity decreased within 8 days to 10% or less of that present on day 1. Accumulation of thymic migrants in peripheral lymphoid organs was estimated by computing the net thymus-derived radioactivity in these tissues. Thymic cell death was assessed by comparing values obtained with 125I-UdR to those acquired with 3H-TdR; The results indicate that cortical thymocytes migrate to the spleen, mesenteric lymph node, femurs and intestine; nevertheless, only a small fraction of the activity originally present in the thymus was recovered in these organs; the vast majority of newly formed cortical thymocytes apparently die after a relatively short life span. Exclusive of the fraction which dies in situ, evidence for thymocyte death is seen in bone marrow; however, most migrants appear to terminate in the intestine.

Autologous bone marrow (BM) cells were cultured in diffusion chambers (DC) implanted into whole-body irradiated, non-irradiated, or sham- irradiated goats. Proliferation was apparent in DC implanted in both irradiated and nonirradiated goats. However, cells in DC cultured in irradiated hosts increased in number beginning earlier, proceeded at a faster rate, and reached higher numbers than in DC in nonirradiated hosts. Growth enhancement could not have occurred as a result of radiation-induced immunosuppression in autologous hosts. The nonirradiated “target cells” in the DC therefore constituted an indicator system for stimulatory or inhibitory substances in the host. The simultaneous increase in the number of granulocytes in peripheral blood and in DC of irradiated hosts was paralleled by an initial rise in serum colony-stimulating factor (CSF). A second, prolonged period of severe granulocytopenia following irradiation of the host correlated with high levels of serum CSF. Increased numbers of megakaryocytes were seen in DC as thrombocytopenia developed in the irradiated host. DC erythropoiesis disappeared rapidly in nonirradiated goats; however, in DC of irradiated goats, the number of erythrocytic precursors increased exponentially during ablation of host erythroid marrow. Anemia did not develop in the host during the culture period. Proliferation of mononuclear cells in DC was markedly stimulated by irradiation of the host. Proliferation of macrophages appeared independent of host treatment. These observations provide strong evidence for diffusion of specific and/or nonspecific humoral hematopoietic stimulators from the host into the DC. This stimulation appears to be elicited and/or intensified by irradiation of the host.

In order to study radiation induced residual injury in hemopoietic stem cells the number and size of spleen colonies were compared to the incorporation of 125I-labeled iododeoxyuridine (125IUdR) in the spleen after transfusion of irradiated bone marrow cells in the lethally irradiated mouse. Bone marrow cells from non-irradiated or from mice that had been given 3, 000 rad in daily 50 rad increments 5 days per week were used 3 months after termination of irradiation. Marrow cells from donor mice given 50 rad immediately prior to the experiment were comparably used to study acute radiation effect. The splenic proliferation factor (PF) (ratio of 5th to 3rd day-125IUdR incorporation) of 7.3 ± 0.2 for the 3, 000 rad irradiated bone marrow is 44.2% of the control value (16.5 ± 0.9). Spleen colonies produced by stem cells from 3, 000 rad mice are 40-50% of the size of colonies produced by nonirradiated stem cells. An acute dose of 50 rad reduced the PF from 20.7 ± 0.9 for controls to 8.0 ± 0.7 for the irradiated bone marrow. This reduction is compatible with the reduction in size and number of the spleen colonies. The cytological appearance of spleen colonies formed from the 3, 000 rad and 50 rad irradiated bone marrow was different. The colonies produced by bone marrow from mice given 50 rad immediately before preparing the BM showed extensive karyorrhexis, so called apoptosis, not seen in the colonies produced by BM cells taken from mice 3 months after receiving 3, 000 rad in 50 rad increments 5 days per week for 12 weeks.

Iron loads between 0.20 microgram and 26 microgram, added to 5 mu Ci 59Fe, were followed for up to 150 days in mice. Relative organ uptake increased as a function of iron load in liver and kidneys while it decreased in bone marrow and blood. Several weeks after injection, all load-related differences disappeared.

A patient with multiple myeloma developed periodic blood neutropenia (periodicity of 15–25 days) after 3 yr of intermittent treatment with cytotoxic agents. Peaks of serum colony-stimulating activity (CSA) level coincided with valleys of blood neutrophils. Fraction of marrow neutrophils in the multiplicative pool was high during blood neutrophil valleys and low during neutrophil peaks. In contrast, the maturation storage pool exhibited the reverse pattern. An increased fraction of marrow neutrophilic cells in the multiplicative pool was in active proliferation during a blood neutrophil valley and a decreased fraction during a blood neutrophil peak. These findings suggest that the marrow granulopoiesis was regulated through CSA. The defect causing the periodicity was probably related to the reduced number of neutrophils in the marrow maturation storage pool, which in turn may be related to a reduced and/or defective granulocytic stem cell pool size consequent to the long-term administration of cytotoxic drugs and/or infiltration of the marrow by myeloma cells.

Continuous extracorporeal irradiation of the circulating blood (ECIB) of from 3 to 501/2 hr duration was used to study in the calf the differential depletion of lymphocytes from spleen, lymph nodes and thymus as compared to blood and thoracic duct lymph. The cell content of tissues was measured by planimetry and/or test point analysis. Lymphocyte depletion by ECIB from various lymphoreticular organs, and from different areas within a given organ, was less than in the circulating blood or the thoracic duct lymph and varied from one site of a lymphoreticular organ to another. The degree of depletion with time followed an exponential function with at least two components. The first component corresponded to a relatively rapid fall and the second to a very slow reduction in lymphocyte content. The former is related to the elimination of an easily mobilizable pool of lymphocytes while the latter corresponds to a more sessile mass of lymphocytes which exchange with blood lymphocytes very slowly. Elimination of the easily mobilizable pool of lymphocytes by ECIB from all tissues studied was observed within 10–15 hr, indicating that the rate of exchange with blood is similar for this group of cells in various lymphoreticular tissues. The size, however, of the easily mobilizable vs the more sessile pools of lymphocytes may vary considerably, the best estimates for the former being as follows (in per cent of total lymphocyte mass): lymph node medulla, less than 10%; lymph node cortex plus paracortical zone, 18% (depletion mainly paracortical); red pulp of the spleen, 37%; densely populated white pulp of the spleen, 55%; and loosely populated white pulp of the spleen, 60%. In comparison, the approximate fractions of lymphocytes originating fromthe easily mobilizable pools in various lymphoreticular tissues plus the cells already circulating a t the onset of EClB correspond to 64% for the thoracic duct lymph and 78% for the circulating blood respectively. These findings are discussed in relation to production, recirculation and life span of lymphocytes, and immune reactions.

Swiss Albino mice received a single i.v. injection of 3H-thymidine (TdR) or of 125I-deoxyuridine (IUdR). Bone marrow, thymus, spleen and mesenteric lymph node were examined for the efficiency of precursor incorporation into DNA, and for DNA renewal from day 1 to day 8. TdR is 5–8 times more efficiently incorporated by the different organs in vivo and in vitro than is IUdR. This indicates that the discrimination against IUdR occurs at the level of DNA synthesizing cells. A diminished DNA turnover rate measured with 3H-TdR in comparison with 125I-UdR is interpreted to indicate reutilization of TdR. TdR reutilization was observed in bone marrow and spleen from at least day 1 on, and in the thymus from day 3 on, following pulse labeling of DNA synthesizing cells. The degree of TdR reutilization appears higher in the thymus (67%) than the bone marrow (43%) and spleen (38%). The mesenteric lymph node indicates either no, or a very low efficiency of TdR reutilization. The data are also consistent with a reutilization equally efficient for TdR and IUdR. It is suggested that the TdR salvage pathway in hemopoietic tissues is largely localized to single organs which have immediate access to TdR made available by catabolism of DNA. The contribution of TdR from systemic reutilization to the organs studied falls within the limits of error of measurements. Moreover, the TdR salvage pathway especially in the lymph node may involve other DNA breakdown products than nucleosides.

Shielding of small portions of the hematopoietic system provides protection against the lethal effects of whole-body irradiation in the midlethal dose range. Transfusion of either whole blood or transplantation of hematopoietic tissues protects to some degree in every mammalian species studied.Manipulation of the radiation dose, time of transplant and recipient treatment with immune suppressors leads to some success in transplants between species. The probability of acceptance of an allograft is inversely related to the number of histocompatibility differences. Hence, in identical twins with no antigenic differences there should be 100% takes. Several investigators (1-4) have followed Atkinson (5) in attempting transplants between a normal individual and his whole-body irradiated leukemic identical twin. A logical extension of identical twin donor-recipient matching is the autologous transplant. The patient serves as donor and recipient with an interim treatment of radio or chemotherapy. This method has b...

1. The hemorrhagic syndrome of acute radiation illness in goats and swine has been described. This syndrome is predominantly a result of a combination of "increased vascular fragility" and thrombopenia. Infrequently, a blood coagulalation defect characterized by a prolonged clotting time due to a circulating anticoagulant with heparin-like properties appears, thus confirming under some conditions in goats and swine the work of Allen on "heparinemia" in irradiated dogs. 2. The prolonged blood coagulation time appeared only in fatally irradiated goats and swine. 3. Evidence was presented suggesting that serum fibrinolysins may have been activated. 4. It is concluded on the basis of this work and that of others that a hemorrhagic syndrome can develop in irradiated dogs, goats, swine, rats, chickens and guinea pigs without the appearance of a prolonged clotting time and without a detectible "heparinemia." The biologically most universal phenomena observed in the hemorrhagic syndrome of radiation illness appear to be: (a) increased vascular fragility, (b) thrombopenia, and (c) ulcerations. ACKNOWLEDGMENTS The author is highly indebted to Captain R. H. Draeger, MC, USN, officer in charge; Captain Shields Warren, MC, USNR, executive officer; Commander, John L. Tullis, MC, USN, pathologist, Naval Medical Research Section Operation Crossroads for guidance and assistance in all phases of this work, and to Dr. George V. LeRoy for having kindly edited this paper and given valuable suggestions.

The development of hypothalamic lesions due to goldthioglucose are described. The initial extensive necrotic lesion occurs in close to 100 per cent of animals injected with LD50. Within 2 weeks the necrotic material has been removed and a narrow scar results. After a lapse of several months, the scar is often difficult to visualize, especially in animals that have not developed obesity. The ventromedial nucleus is not the center of the lesion. The nucleus is preserved in some instances, and partially or completely destroyed in others, depending on the extent of the lesion. The more prominent scar in the obese animals correlates with the larger initial lesion necessary for the complete bilateral destruction of the ventromedial nucleus which is known to be a prerequisite for the development of hypothalamic obesity. Thus, contrary to earlier suggestions, goldthioglucose does not localize specifically in the cells of the ventromedial nucleus.

SummaryFollowing whole body exposure to sublethal doses of X-rays, erythropoiesis was depressed in both dogs and rats, but could be markedly increased by bleeding the animals shortly before or after irradiation. In rats, post-irradiation administration of PAPP resulted in a similar increase in erythropoiesis. Blood loss 24 hours after irradiation had no appreciable effect. The data indicate the reversibility or modification of injury to the erythropoietic system without similarly affecting the recovery of other bone marrow elements.

A significant proportion of lymphoid cells which leave the calf thymus by the efferent lymph or blood have thymus-specific antigen (BTA) in their cell membrane. These were found to be larger than the majority of BTA-positive cells within the thymus. Similar cells were not observed in arterial blood, thoracic duct lymph or prescapular lymph nodes.

Mouse bone marrow cells were stored for 0.5, 16 and 24 hours under one of the following four conditions; saline G at room temperature, saline G at ice temperature, CMRL 1066 at room temperature and CMRL 1066 at ice temperature. Their viability was then examined by counting CFU in the spleen of irradiated recipient mice. 1) The CFU decreased rapidly with storage time under all four conditions. Among four storage conditions, the storage in saline G at ice temperature seemed to give slightly more favorable results than others. 2) Types of micro-colonies were not significantly different under the present storage conditions. 3) Since the size of endogenous colonies were relatively small compared to exogenous colonies, the observed colonies are likely to be resulted from injected bone marrow elements and some endogenous cells. 4) It is concluded that the storage conditions in the present paper are not suitable for the storage of bone marrow cells. This emphasizes the need of exploration of a better storage method.

Post-irradiation anemia is primarily the consequence of red cell aplasia and of hemorrhage secondary to thrombocytopenia. Data have been presented which indicate that in addition there is intravascular red cell damage. Of particular interest was the observation herein presented that the damage to the red cells produced by ionizing radiations is of an indirect nature. Using the chromium technic it was possible to demonstrate red cell damage as early as the 1st-3rd post-irradiation day. In these studies tagged cells were transfused 15-55 days prior to irradiation in order to establish the elution rate of Cr51. On the 1st-3rd day following irradiation there was an abrupt increase in the rate of Cr51 loss. When normal cells were transfused immediately after irradiation there was also a striking increase in the rate of Cr51 loss above that observed in normal animals, indicating that radiation damage to the red cell was indirect. When cells were transfused from irradiated donors into normal recipients, it was not possible to demonstrate red cell damage prior to the 10th post-irradiation day, indicating that the damage was progressive. Since there was a selective loss of Cr51 it is suggested that chromium produced an additive damage to the cell. The possible implication of this observation in the use and interpretation of Cr51 survival curves is discussed. It was also determined that red cells which were recirculated following extravasation during the thrombocytopenic phase of radiation injury had a shortened survival, whereas normal cells, tagged and injected intramuscularly into normal recipients survived normally on return to the general circulation. Cells collected from dogs one day after irradiation, tagged with Cr51 and then injected intramuscularly into normal recipients, showed a striking increase in the rate of destruction. Cells collected on the 4th post-irradiation day were destroyed even more rapidly. These studies confirmed the early onset of radiation injury to the cells, its progressive nature, and demonstrated the damage incurred as a result of passage through the extravascular cycle. As might be expected there was also a shortened survival of red cells collected from the thoracic lymph of thrombopenic irradiated animals. Conclusions: 1. Ionizing radiations produce intravascular red cell damage in addition to the known loss incident to hemorrhage. This damage is evident within 24-72 hrs. of irradiation. 2. The red cell damage is an indirect and progressive effect of irradiation. 3. Those cells which are returned to the general circulation, following passage through an extravascular cycle, are damaged. The extent of injury to normal cells is such that it is not detectable by current methods. However, the addition of a second injury, such as that following irradiation, enables the detection of this damage. 4. Chromium "elution" is altered by irradiation injury.

Radiation through its biologic effects and its use as a tool in research is rapidly spreading in to all facets of science and medicine. Through the medium of the atomic bomb, radiation is extending into the fields of diplomacy, politics, and the social sciences. Since medicine reaps the profits of research in all fields and since newer weapons of warfare increase the heavy burden of the practice of medicine, it is logical and proper that the profession should take an active role in the painful adjustment of society to the realities and potential acute and chronic hazards of nuclear explosions. Accordingly this review will consider the physiologic effects of single whole body radiation on mammals, the modification of the biologic response by variou� agents given before and after irradiation, and the application of these findings to the treatment of casualties in atomic warfare. Papers on cellular physiology and radiation chemistry 3;re only occasionally referred to. Their value for the ultimate understanding of the nature of radiation injury is fundamental. However, to date, the gap between our knowledge of cellular physiology and of the clinical syndrome remains largely unbridged. We have attempted to include primarily those papers which have advanced our present concepts of the clinical manifestations of radiation i' njury. A complete list of references alone would fill the entire aUotted space.

1. Tritiated thymidine was injected into mice of pregnancy ages 6, 7, 8, 9, 10, 11, 14, and 17 days. 2. The incorporation of the thymidine into the tissues of the embryo, uterus and placenta were studied by the method of stripping film autoradiography. 3. Thymidine is incorporated into uterine cells at all stages. The greatest amount of uptake is effected by endothelial cells. Decidual cells show good uptake at the beginning, less later. 4. Embryonic tissues do not show any noticeable uptake until the ninth day, and then only in the outer membrane tissues of the trophoblast cells, giant cells and yolk sac cells. 5. On the tenth day incorporation occurs mainly in the blood and mesenchyme cells. On succeeding days more incorporation is found in other embryonic tissue. The nervous system does not incorporate the thymidine noticeably until the fourteenth day.

Summary(1) A simple method is presented for the efficient separation and concentration of platelets from human, dog, and guinea pig blood in quantities sufficient for transfusion. (2) This method depends upon the use of Sequesterene Na2 as an anticoagulant, which prevents the development of platelet stickiness and clumping in shed blood. (3) Platelets prepared by this method and transfused into the thrombopenic, irradiated dog remain in the circulation, reverse the coagulation defect, and prevent hemorrhage.

Summary(1) The rate of the incisor teeth eruption in newborn rats is markedly accelerated by thyroxine; time of eruption varying with the dosage used. (2) The use of this observation as a method of standardizing the thyrotropic hormone was unsuccessful.

SummaryThe feasibility of recirculating separated leucocytes has been demonstrated in dogs with complete bone marrow aplasia induced by x-irradiation. The transfused granulocytes were shown to migrate to sites of infection.

Summary and ConclusionsRats can survive an otherwise fatal dose of radiation if joined after radiation to non-irradiated litter mates. Such rats show accelerated bone marrow regeneration when compared with single controls. It is suggested that post-radiation parabiosis is primarily of benefit because it accelerates recovery of myelopoiesis by the transfer of some cellular or non-cellular material from the non-irradiated partner.

Conclusions1. By the criteria used there is no significant difference in the destructive effects of irradiation on normal mice or mice treated with large doses of glutathione before irradiation. 2. A striking difference is seen in the rate of regeneration of the hemopoietic tissues.

An established method for determining radioiron absorption by whole body counting was used to study six parous women with hypochromic anemia and menorrhagia, and a seventh nulliparous woman with normal blood values and normal menses. In addition to demonstrating iron deficiency by increased radioiron absorption, the method was found useful in estimating the quantity of blood lost with each menstrual period. As much as 550 ml of menstrual loss was noted in two of the patients studied. Estimates in the patient with normal menses were 59 and 33 ml. Two additional patients demonstrated patierns of blood loss found in continuous gastrointestinal hemorrhage due to hereditary hemorrhagic telangiectasia, and in severe epistaxis, as further applications of the technique. Where available, the method is to be recommended for routine investigation of hypochromic anemia when episodic or continuous blood loss such as that of menorrhagia is suspected. (auth)

Benzene is ubiquitous and accepted as a human carcinogen by regulatory agencies. Proposed regulations assume without proof that the carcinogenic response to benzene exposure is "one hit" implying a linear with no threshold. There is no solid experimental proof for this concept. This research involves exposure of CBA/Ca male mice to benzene vapor in varying concentrations. Exposure to 300 ppm 6 hrs/day, 5 days/week, for 16 weeks is highly leukemogenic. Exposure for the same time to 100 ppm is also leukemogenic. Concentrations from 25 ppm to 400 ppm 6 hrs/day, 5 days/week, for 10 exposures produce an increasing lymphopenia. Exposure to 100 ppm for the same exposure time produces anemia, decrease in stem cell content of marrow, and marrow cellularity. Further dose-effect studies are required to test the "one hit hypothesis" and to determine whether the same integral dose of benzene administered over variable exposure has the same or different biological responses. It is of concern that biologic effects are observed at 25 ppm only 2.5 times the present permissible time-weighted average exposure during a working day and research by others (see Discussion) has demonstrated an effect (noncarcinogenic) at 10 ppm.