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Comparative studies of the properties of murine haemopoietic stem cells from different sources revealed that the peripheral haemopoietic stem cell is relatively weaker than the haemopoietic stem cell from bone marrow in promoting the recovery of hemopoiesis in the irradiated animals. This is due to the heterogenity of stem cell population in which some aged cellsubpopulations are co-existing. The modified potential in proliferation and differentiation of haemopoietic stem cells in the peripheral blood seems to be irreversible under normal physiological conditions. In a preliminary experiment, the use of an anti-thymocyte immunoglobulin to eliminate immunocompetent cells proved effective in reducing the severity and incidence of secondary diseases and in increasing the number of survivors of lethally irradiated semi-isologous mice after transplantation of parental peripheral mononuclear cells.

Mice irradiated continuously at a low dose rate of 70 rad/day showed not only a drop of CFU-S content in the bone marrow but also an apparent functional disturbance of haemopoietic stem cells. With increase in accumulated dose of radiation, the damage of the haemopoietic microenvironment becomes evident. From the changes caused by chronical irradiation, it is believed that haemopoietic stem cells is more sensitive than haemopoietic microenvironment, and the radiation injury by hemopoiesis involves both damage of haemopoietic stem cells and microenvironment. Furthermore, in the course of recovery of hemopoietic injury, microenvironment plays as important role. In comparison of the growth curves of CFU-S from normal and irradiated bone marrow cells in irradiated recipient spleens or cultured in diffusion chambers, it is suggested that the nature of radiation damage of haemopoietic stem cells in continuous irradiation at low dose rate is mainly attributed to the deterioration of self replicative capacity of CFU-S.

Fourteen patients with severe aplastic anemia were treated with antilymphocyte globulin (ALG). Eight were studied with co-culture of patient's lymphocytes with normal bone marrow cells. Suppression of CFU-C was prevented by pretreatment of T lymphocytes with anti-T lymphocyte McAb in four patients and concordance with clinical outcome was observed only in two patients. Conclusive in vivo therapy result for this correspondence are lacking. Seven patients received fetal liver cell suspension infusion 24-36 hours after completing ALG therapy and remission were "more complete" in three cases with good response. Response of treatment in the fourteen patients was as follows: eight had complete or partial responses and the remaining did not respond or died (42.8%).

The dynamic changes in blood gases in 34 dogs suffering severe steam inhalation injury were studied during the first 14 days post-burn to determine the effects of inhalation injury on lung function. Nineteen dogs received only severe steam inhalation injury, while 15 other dogs received both 30 per cent total body surface area (TBSA) deep burns and steam inhalation injury. The results showed marked reductions of PaO2, PaCO2, AB, SBE, T-CO2, SB, BBp, pHNR and SatO2 (P less than 0.05 approximately 0.01), whereas the P(A-a)O2 increased (P less than 0.05 approximately 0.01) within week 1 post-burn in both groups. These data suggest that the injured animals were suffering from hypoxaemia and respiratory alkalosis induced by disturbance of the gas-exchange function of the lungs. There was also metabolic acidosis, which was closely related to high fever, excessive catabolism, and particularly to hypoxaemia in week 1 post-burn. If the animals survived through the critical period (1-7 days post-burn), most of the abnormal gas parameters then gradually returned to the pre-burn levels. It is clear, therefore, that blood gas monitoring in patients with inhalation injury is not only of diagnostic importance but also of prognostic value.