Radiocalcium was injected to adult animals at the doses of 0.5 and 1.0 μCi/g body weight. Animals were sacrificed at intervals of 1, 3, 5, 7 and 14 days after injection. Cytologic and quantitative study of erythroid cells (pronormoblasts and normoblasts) granuloid cells and lymphoid cells was made. Cytologic abnormalities were more pronounced in myeloid cells than in erythroid cells. The number of granuloid cells in the bone marrow decreased drastically with some signs of recovery at day 14 while that of lymphoid cell increased. The number of erythroid cells decreased upto day 3 followed by an increase upto day 7. By day 14, the erythroid cells nearly recovered fully. The importance of such a study on a wild species has been discussed and emphasized.

View full abstract

The present investigation was undertaken with the hope for elucidating the effect of a radiosensitizer on mouse L cells in culture following X-irradiation. Under the aerobic condition, a survival curve of irradiated cells showed a shoulder region with the extrapolation number of 6.4 and mean lethal dose (D₀ value) of 126 rad. On the other hand, under the extremely hypoxic condition prepared with nitrogen gas using a stainless steel apparatus, a survival curve was found to show no shoulder region, having extrapolation number of 1.1 and D₀ value of 629 rad. Thus, the oxygen enhancement ratio (o. e. r.) was calculated as a factor 5. An electron affinic radiosensitizer, Ro-07-0582 revealed a pronounced sensitizing effect under the extremely hypoxic condition by an enhancement ratio 3.9 at a concentration of 10 mM. The sensitizer reduced D₀ value with increasing concentration of the drug. The evidence obtained suggests that Ro-07-0582 acts as oxygen-mimic, although the drug shows no radiosensitizing effect at low concentration and low irradiation doses.

View full abstract

The interaction of heat with ionizing radiation in normal and cancer cells is analyzed. The factors affecting the thermal enhancement ratio (TER) are discussed. From the data available in the literature it is concluded that heat could selectively inhibit repair of radiationinduced sublethal damage in cancer cells. Using appropriate fractionation schedules this could be utilized to improve the current efficacy of tumor control by radiotherapy.

View full abstract

The function of reticuloendothelial system (RES) to sequestrate ⁵¹Cr labelled heat damaged erythrocytes was investigated in male CF#1 mice after intravenous injection of polymeric plutonium at the dose levels of 15 μCi/kg, 10μCi/kg and 5μCi/kg. Effect of splenectomy on erythrocyte life span was also examined. Total blood volume, red cell volume and plasma volume were also determined so as to study the possible cause of anemia induced by polymeric plutonium. It was observed that polymeric plutonium depressed RES function of the spleen to sequestrate ⁵¹Cr labelled heat damaged erythrocytes, but disappearance of ⁵¹Cr labelled heatdamaged erythrocytes from the circulation of plutonium-exposed mice was within normal range. Erythrocyte life span was unchanged after splenectomy. Normal disappearance rate of ⁵¹Cr labelled heat-damaged erythrocytes from the circulation with depressed RES function of the spleen by polymeric plutonium was considered to be the result of increased function of the other parts of RES. In higher dose groups, red cell volume was decreased but no change in plasma volume was observed in any group studied. From these results, the possible cause of the shortened erythrocyte life span and anemia induced by extracorpuscular effect of polymeric plutonium are discussed. It is concluded at this time that decreased RES function of the spleen may not play an important role in shortened erythrocyte life span.

View full abstract