The content of Ig-bearing lymphocytes and their precursors in the mouse bone marrow was investigated 6 and 36 hours after the hydroxyurea treatment. Some increase of the B-cell content takes place in the trated bone marrow. Dividing and non-dividing B-cell precursors, except the stem cells, were practically absent.

The reproductive power of the blood forming tissue of irradiated rats (450 rad), cultured in diffusional chambers in vivo, has been followed for 30 days. The cultivation of bone marrow of the control donors did not change the intensity of ultra-violet fluorescence, compared to the similar cells in situ. The differentiation capacity of bone marrow, taken from animals irradiated half a year before, became weaker in diffusion culture conditions. These changes coincided in time with the appearance of some abnormalities in blood forming tissue of the irradiated animals.

Paralytical form of chronic intoxication was caused by single intracutaneous administration of tri-O-cresyl phosphate (TOCP)/2=2.2 ml/kg/ into guinea pigs. Within the first 27--33 days after the treatment, the animals with pronounced symptoms of neurotoxic effect of TOCP were subcutaneously administered with 2-14C-acetate/100 mu Ci per 100 g of body weight/2 hrs before decapitation. Purified cerebrosides, gangliosides and acid-soluble fraction, containing 14C-precursors, were isolated and their specific radiactivity was measured in a gas-flow counter. The rate of 14C incorporation into cerebrosides and gangliosides in spinal cord was found to exceed that in brain stem. In paralytical stage of disease, caused by TOCP, synthesis of cerebroside was depressed in spinal cord and in brain stem, according to calculated value for relative specific radioactivity. In spinal cord the rate of 14C incorporation into gangliosides was also decreased. These data suggest that neurtoxic drug TOCP affects metabolic processes both in oligodendroglial cells and in neurons, where ganglioside biosynthesis occurs.

The migration activity of the spleen cells from intact mice is inhibited by the stem cell inhibitory factor (SCIF) released by lymphocytes treated with antilymphocytic globulin. The degree of the migration inhibition is proportional to the activity of SCIF in the colony-formation inhibition. The macrophage-migration inhibitory factor (MIF), obtained in the H-2 system exhibited a stimulating effect on the colony formation in mice when used in vitro for the treatment of bone marrow transplants. This activity of MIF corresponds to its migration-inhibitory effect on the spleen cells. Incubation of the bone marrow cells with MIF for 30 minutes is more effective than the 2-hour treatment. The observed effects are interpreted as an indication of non-identity of SCIF and MIF.

Blood serum leukopoietic activity after the injection to intact Wistar rats of products of 12 and 60 million homologous granulocytes lysis per 100 g of animal body weight, and the character of the serum action on the proliferation and differentiation of stem hematopoietic cells in the spleen of lethally irradiated mice were studied. Accumulation in the blood of granulocytopoietins resulting from the action of the products of granulocytes lysis was noted. Granulocytopoietins stimulated the proliferating activity of stem cells and their differentiation into granulocytes in the spleen of the lethally irradiated mice. A conclusion was drawn on the stimulating action of granulocyte lysis products on the hemopoiesis through the granulocytopoietins.

It was shown that treatment of the bone marrow with the serum reacting with the theta-antigen, irrespective of the presence of the complement, sharply decreases the capacity of its cells to form splenic colonies. Administration of the thymus cells together with the bone marrow to the recipient largely elminates the effect of this system, significantly increasing the splenic colony formation. It is supposed that the antiserum in the bone marrow inactivates the population of cells necessary for the formation of the colonies in the spleen, but differing from the pluripotent stem cells, possibly the population of T-cells.

Lymph node cells of normal CBA mice, syngeneic radiation chimerae CBA leads to CBA and B-mice after incubation with thymosin (fraction 5) were transplanted to sublethally irradiated recipients (CBA X C57BL) F1; the number of endogenic colonies in the recipient's spleen was then recorded. Thymosin was shown to increase the killer activity of the lymph node cells of normal mice CBA, syngeneic chimerae CBA leads to CBA, but not of B-mice. As suggested, TU-cells' subpopulation served as target cells for thymosin.

In combined administration of cyclophosphamide and lymphocytes of mice (CC57BR XX C3H) F1 to mice CC57BR there was observed a tolerance to alloantigens of mice C3H. Immunization of the tolerant mice with the vaccines of streptococcus, group A, and Candida albicans, containing antigens similar to the transplantation ones, led, to the partial destruction of the tolerance. This was expressed in the reduction in the CC57BR mice of the survival of skin allotransplants of mice C3H and the appearance in the lymphoid organs of lymphocytes with the cytotoxic activity against the allogenic target cells. In case of the tolerance destruction the amount of the recipient's lymphocytes forming rosettes with the erythrocytes of mice C3H remained unchanged, but the stem cell count fell in the spleen and the lymph nodes. The total amount of the T- and B-lymphocytes in the lymphoid organs was unchanged in destruction of the tolerance.

A series of mathematical models of cell population is analysed. The mitotic activity of stem cells of this population is controlled by population density. The effect of different factors on autooscillation regimes has been studied. The effect of reversible stages of cell differentiation is analysed, as well as that of cell losses at each stage of differentiation. The behaviour of cell population under the conditions of a limited supply of the limiting substrate was analysed. The effect of cell doubling at each differentiation stage on the stability of the population was studied too.

Bone marrow cells together with allogeneic cortisone-resistant thymocytes or the lymph node cells of intact mice treated with antilymphocytic T or O-antisera were transplanted to the lethally irradiated mice. The antisera eliminated the capacity of T lymphocytes to inactivate allogeneic stem cells. Cortisone-resistant thymocytes displayed a strong inactivating action. The principal role in the processes of inactivation of genetically foreign stem cells was played by T lymphocytes. B lymphocytes possessed no properties of killer cells. The presence of B lymphocytes in the population of killer cells apparently failed to serve as a determinant one for the development of inactivation processes.