The results of the histological and electron microscopic investigation of adipose and reticular cells and their interconnections with blood cells are presented in the material of trephine biopsies of the iliac bone. A possibility for development of adipocytes from the adventitial reticular cells is demonstrated. Close contacts are revealed between pre-adipocytes and young hemopoietic cells. Two types of the reticular cells are characterized, they differ in their position, structural organization and interconnection with the young hemopoietic elements. The peculiarities revealed in the morphofunctional state of the microenvironmental structures demonstrate functional variegation of the stromal elements, and also attest an essential importance of intercellular contacts of the hemopoietic predecessors and the stromal cells in maintaining the hemopoietic function of the bone marrow.

Forty seven individual haemopoietic cell clones bearing unique radiation markers were studied in long-term bone marrow cultures. Throughout cultivation, clones appeared at different times, 1 to 12 weeks after explanation, survived during 1-10 weeks and markedly varied in size. Usually, the number of metaphases characteristic of an individual clone rapidly increased, achieved a maximum and declined. The cells of disappeared clones were never seen again. The experimental results provide further evidence for the model of haemopoiesis by clonal succession. The data obtained are discussed with respect to the functioning of haemopoietic stem cell population.

The recovery of a population of granulopoietic-monocytic colony-forming units of mouse bone marrow was only slightly inhibited during the first two weeks after exposure to a mixture of radiation (4 Gy) and heat (burn of 10 per cent of the skin). In the interval between days 14 and 28 following the effect, their number reached the control level, then it decreased again.

With the aim to use a previously elaborated method of extracorporeal fertilization of human ova for treating sterility, resulted from obstruction or absence of the uterine tubes, ova were obtained at laparoscopy after a previous hormonal stimulation of women. From 119 women 159 ova were obtained. Fertilization of the ova was performed in the medium Ham F-10 previously capacitated with the husband's spermatozoa. Fertilization rate was 66%. Embryos at the stage of 2-8 blastomeres were implanted transcervically into the uterine cavity with a special catheter. The embryo transfer was performed in 37 women with tubular infecundity. Menoschesis up to 3 weeks was noted in 5 women. In one woman on the 35th day after implantation, by means of hormonal-biological reaction and ultrasound investigation, pregnancy was diagnosed, it terminated in timely birth of a boy with body mass 3,500 gr. A conclusion was made that the main cause of failures at the embryo transfer was an inadequate preparation of the uterine mucosa (resulted from the main disease) to accept the fertilized ovum.

The effect of bacterial polysaccharide prodigiozan on recovery after single acute blood loss (2.5 per cent of the body weight) was studied on female mice CBA x C57Bl (F1). When administered intravenously in a dose of 0.5 mg/kg to healthy animals without blood loss prodigiozan had no significant effect on erythropoiesis. Prophylactic administration of the drug 24 hours before blood loss promoted more rapid and intensive mobilization of erythropoiesis: increasing of the levels of 59Fe incorporation into the bone marrow erythroid cells and the number of erythroid cells in the spleen as compared to those in nonstimulated animals. This is probably connected with prodigiozan-mediated stimulation of stem hemopoietic cell proliferation.

The colony formation in spleen of lethally irradiated syngeneic or hybrid recipients was studied after transplantation of bone marrow cells, with or without macrophages from lymph nodules or from peritoneal cavity of mice, cells of macrophage-like cell line J-774, and monocytes from peripheral blood of healthy donors. The direction of stem cell differentiations in the presence of all the types of mononuclear phagocytes was seen to change from mainly erythroid to mainly myeloid one. The ratio of erythroid to myeloid colonies became equal to 0.5-0.9 instead of 2.0, when bone marrow cells were injected with equivalent quantity of mononuclear phagocytes. This new regulatory function of mononuclear phagocytes is discussed.

Peptidoglycan from Lactobacillus bulgaricus converts mouse pre-T-cells into theta-positive cells and activates the complement. It has been observed that the effect depends on serum peptidoglycan concentration and the time of the interaction of the activated complement with mouse pre-T-cells. The action of peptidoglycan was replaced by C3a complement component.

A study was made of the radioprotective effect of Adeturon, a protective agent obtained in Bulgaria, on mice with Luis lung tumors exposed to fractionated radiation. The effect of the radioprotector on a radiation-induced injury to normal tissue was estimated by the number of leucocytes in the peripheral blood and its count, cellularity of bone marrow and spleen and the mass of the latter, and by the number of exogenous and endogenous CFUs. A pronounced radioprotective effect of Adeturon was implemented through maintaining or normalizing the indices under study impaired by tumor inoculation or irradiation.

A study was made of the clonogenic capacity of cells from central and peripheral zones of NKLy solid tumors of mice after heating up to 42 degrees C and after the combined effect of hyperthermia and local irradiation of the tumor. Hyperthermia markedly increased the rate of radiation death of cell populations from central tumor zones, having low oxygen tension, and had no effect on radiosensitivity of cells from peripheral well oxygenated zones. In heated tumors, the repair of potentially lethal radiation damages to cells from the peripheral zones was inhibited while in conventional irradiation conditions these damages could be restored.

The clonogenic capacity of cells from peripheral and central zones of solid NKLy tumors of mice treated with metronidazole, a sensitizer of hypoxic cells, and with a mixture of metronidazole and radiation was studied by cloning in diffusion chambers. The cytotoxic effect of metronidazole was only noted during the prolonged interaction with cells under acute hypoxia that was observed in central tumor zones. Metronidazole increased by more than two times the radiosensitivity of cells from the central zones of the tumor and did not influence the radiation response of cells from the peripheral zones. Metronidazole was shown to inhibit the repair of potentially lethal radiation damages.

An analysis of the data on the effect of lymphoid cells on the proliferation and differentiation of hemopoietic stem cells has led to a conclusion that radiation injury of lymphocytes plays an important role in the pathogenesis of the cerebrospinal syndrome. The molecular mechanisms of lymphocyte interphase death were considered. It was shown that due to some peculiarities in the energy supply of these cells the appearance of breaks in DNA causes the development of biochemical processes resulting in a decrease in NAD, an increase in the activity of nucleases, a decrease in ATP, and the accumulation of active metabolites of glycolysis. These reactions result in an increase in the disintegration of DNA, chromatin and pyknosis of lymphocyte nuclei.

In studying the influence of thymocytes fractionated by their size in the ficoll density gradient on the CFUs content of the irradiated mouse bone marrow, two subpopulations of T-cells were isolated: the administration of the first thymocyte subpopulation decreased the CFUs content during the postirradiation recovery period while thymocytes of the second subpopulation increased the content of CFUs in the bone marrow. When thymocytes of mice exposed to low-level radiation were separated a considerable stimulatory effect was produced by certain thymus cell fractions on the number of CFUs in the bone marrow of exposed recipients; no inhibitory effect was registered.