The fraction of the survived intestinal crypts associated with patches of Peyer is higher to those non-patch-associated crypts of mice for three inbred strains. The difference in the survival between associated and non-patch-associated crypts increases with dose of gamma-irradiation. This difference for old mice is less than for young mice. Pre-irradiation (5 Gy) of mice one week before the conditioned gamma-irradiation cannot modify the difference in the survival between associated and non-patch-associated crypts. Radioprotection of mice by hypoxic gas mixture (10% O2) cannot modify this difference. Pre-treatment of mice by dextran-sulfate alone or in combination with hypoxic gas mixture decreased the survival of intestinal crypts associated with patches of Peyer to the level of non-path-associated crypts. The difference in the survival between two subpopulation of intestinal stem cells is less after neutron irradiation than after gamma-irradiation.

Human intrathymic precursors are characterized by mitogenic reaction on thymic hormone, lacking the cortical and medullar thymic membrane markers (CD3, CD4 and/or CD8) and expressing of the common T-cell CD7 and CD5 antigens. Fraction 1.062 g/cm3 of peripheral white blood cells contains cells with analogous characteristics. The cell fraction of blood from men participated in amelioration after the Chernobyl accident is enriched with hemopoietic precursors (CD4+), pre-T-cells, reacting to thymosin (CD5+CD3-), and CD3+CD4-CD8- T-cells in a greater extent than the cell fraction from donors blood. Defects of T-cell and hemopoietic differentiation in children migrated from the Chernobyl area to Moscow Region were more substantial than in "ameliorators" and correlated with drop of thymic serum activity level. Research substantiates the approach to analysis of radiation-induced defects in early stages of lympho- and hemopoiesis.

The agent HC-1539, an analogue of tamoxifen, was studied for its effects on the blood system of intact animals and on the time course of postradiation recovery of hemopoiesis. HC-1539 given to the mice unexposed to radiation reduced bone marrow levels of CFUs (a colony of forming units in the spleen) and CFU-GM (that in the granulocyte-macrophages) and increased splenic counts of granulocyte-macrophage precursors. There was also a decrease in the proliferative activity of CFU-GM 1 and 5 days after the drug administration and an increase in serum GM-CCP levels when the agent showed the peak of its radioprotective effect. In the HC-1539-treated mice, there was a more intensive normalization of the CFUs of CFU-GM myeloid and erythroid hemopoietic populations than in the radiation-exposed ones. Thus, the mechanisms responsible for the radioprotective action of HC-1539 may be associated both with its direct effects on the proliferation and differentiation of hemopoietic cellular precursors and with the stimulation of release of growth-differential factors by hemopoietic microenvironmental elements.

The main bulk of corneal endothelial cells is formed during early embryonic development. In the course of development, two-layered endothelium becomes single-layered; the cell layer consists of rosette-like structures formed of a central cell (9 to 10% of all endothelial cells) surrounded by peripheral cells. The central cell is not a stem cell, and the peripheral cells are not its descendants. The presence in corneal endothelium of a constant number of peripheral cells surrounding the central cell, as in other epithelia with different proliferative potential, is evidence that the central cells can organize the peripheral cells and exercise control over them.

The effect of stem cell proliferation inhibitor (PIF) on hemopoietic stem cell and committed precursor cell subpopulations in aged mice was studied. The following parameters were analyzed: the number of CFUs-5, CFUs-8, and CFUs-12 in bone marrow and spleen, the number of BFUe, CFUs-GM, CFUs-M, and the ability of bone marrow cells of aged mice to repopulate bone marrow of lethally irradiated recipients (MRA). Characteristic of aged mice were an increased number of precursors (mainly in bone marrow), changes in their erythropoietic differentiation, and a decreased MRA of bone marrow cells. The suppression of stem cell proliferation by PIF was accompanied by a decrease in the total number of precursors and led to changes in their migration and differentiation, which might provide for restoration of hemopoiesis in aged mice to the level characteristic of young mice.

It was shown using the micronucleus test and estimating the defects of sperm heads that premeiotic and meiotic mammalian cells are genetically very sensitive to Dipin and nitrosomethylurea. In rats, unlike mice, the stem and differentiating spermatogonia with serious chromosomal defects are not eliminated and pass through a "sieve" of mitotic and meiotic divisions reaching the stage of round spermatids. Our observations suggest long-term preservation Dipin-induced, rather than nitrosomethylurea-induced, mutations in the stem cells of both mice and rats.

The effects of activated neutrophilic secretory products on marrow erythroblastic islet erythropoiesis and peripheral blood parameters were studied after experimental blood loss. The supernatant of activated neutrophils was demonstrated to potentiate erythrodieresis in early post-loss period. At the same time the supernatant had a high stimulant effect on erythroblastic islet erythropoiesis. The erythroblastic islets showed increases in new formation and reconstitution, acceleration of amplification wave, which results in peripheral blood reticulocytosis. Thus, neutrophilic secretory products stimulates the synthesis and secretion of central macrophage products, which promotes accelerated maturation of erythroblasts in the erythroblastic islet crown.

The production of haemopoietic factors (IL-1, IL-3, CSA) by adherent and nonadherent cells of lethally irradiated CBA mice bone marrow and after syngenic myelokaryocyte transplantation was studied. Radioresistant myelokaryocytes capable to produce haemopoietic factors IL-1, CSA as early as 24 hr after irradiation were found in adherent cell fraction. The synthesis of humoral factors (IL-3, CSA) by nonadherent bone marrow elements was realised in a late terms of experiment (3-6 days) that was connected with forming of functionally valuable cell forms from transplanted or viable stem cells.

Hematopoiesis is regulated by a tiny population of cells, the stem cells and committed progenitors. These cells are under the influence of hematopoietic growth factors most of which are produced immediately in their environments. Their fates are strongly influenced by those growth factors. The growth factors interact with specific receptors that are present on progenitor surfaces and may in fact induce changes in the levels of those receptors. The receptors form dimers or heterodimers to pass proliferative and differentiation signals into the cell. We do not yet know exactly how that signalling is accomplished, but will probably known much more about it in the next year or so.

The study of clonogenic properties of granulomonocytopoiesis cell-precursors (CFU-GM) in 47 multiple myeloma patients revealed that the lowest clonogenic activity of the bone marrow occurs in the initial stage of multiple myeloma and in the development of the disease relapse. In remission the pool of normal CFU-GM seemed much improved due to suppression of the tumor cell pool by cytostatic drugs. Clonogenic properties of the above cell-precursors may serve a valuable marker of the multiple myeloma treatment efficacy.

Mice were irradiated in dose of 2 Gy in 14 or 17 days of gestation. Irradiation retarded the increase of cell number in developing thymuses but in the day of birth the number of thymocytes was normalized. In normal development SC-1+ cells (T cell precursors) disappeared from the thymus immediately before the birth. After the irradiation they persisted in the newborn thymus. Mitogenic responses of newborn thymocytes on the action of thymic peptides and T cell mitogens were decreased after the fetal irradiation (adult irradiation enhances mitogenic response of thymocytes). The helper activity of thymocytes in humoral immunity was decreased after the fetal irradiation in more degree and helper activity in splenic colony-formation--in less degree than after the adult irradiation. The consequences of the irradiation in 14 and 17 days of gestation were similar.

The dynamic of granulocytic macrophages and erythroid precursors content in bone marrow of CBA mice, irradiated by 2.0 Gy and the level of colony-stimulating and erythropoietic activities in supernatant of bone marrow myelocariocytes and blood serum were studied. The process of haemopoiesis regeneration was accompanied by increasing of the values of these indexes in bone marrow and peripheral blood. The treatment of bone marrow cells by monoclonal antibodies to Thy 1.2 antigens resulted in decreasing of myeloid precursors and diminishing of colony-stimulating activity of bone marrow cells supernatant.

Conditions for isolation of pluripotent inner cell masses (ICM) from rabbit blastocysts are described. The rabbit intact embryos were collected on day 4 post coitus, zona pellucida was removed from embryos by pronase treatment, and rabbit blastocysts were plated on different monolayers of somatic cells. The differences in attachment and proliferation of ICM of rabbit embryos were determined in dependence on the feeder layer type on their long culturing in vitro. Among the tested monolayers of somatic cells a feeder layer of rabbit embryonic fibroblasts, derived from fetuses on day 16-18 pregnancy, appeared more effective for isolation of ICM and for receipt of rabbit embryonic stem cells (with ES-like morphology).

The role of adrenergic structures in mechanisms of erythro- and granulomonocytopoiesis precursor cell proliferation and differentiation under immobilization stress was antagonist administration inhibited stress-induced rise of erythroid, erythrogranulocyte and granulocyte hemopoietic islets erythrogranulocyte and granulocyte hemopoietic islets forming in the bone marrow. In vitro the alpha-adrenergic agonist had a direct activating effect on CFU-GM but on CFU-E growth in normal state (10(-5) M) and after immobilization (10(-9), 10(-7) M). At the same time beta-adrenergic agonist (10(-5) M) increased exclusively CFU-E growth after extreme influence. Thus, adrenergic mechanisms are of great importance in direct (receptor) and microenvironmental hemopoiesis-induced stimulation of the processes of proliferation and differentiation of hemopoietic precursors during stress.

The data concerning the reasons of CFU-S radioresistance increase after low dose irradiation of mice were obtained; the reparation processes in CFU-S adapted by low dose irradiation were shown to be more active than in intact ones. Colony formation increase was demonstrated to be more pronounced in adapted animals when they had been injected by 50 mcg of synthetic polyribonucleotide PolyI-PolyC two days before irradiation in challenge dose. The thymogen immunomodulator administration to adapted and intact donor animals leads to the increase of colony yield in equal extent.