The effect of granulocyte-macrophage colony-stimulating factor on hemopoiesis recovery and the survival of irradiated mice

A human recombinant granulocytic-and-macrophagic colony-stimulating factor (rGM-CSF) administered repeatedly to irradiated (10 Gy) CBA mice increased CFUs and CFU-GM content, the number of bone marrow granulocytes and erythronormoblasts, and spleen and peripheral blood cellularity. The survival rate of exposed (9.7 Gy) mice repeatedly injected with rGM-CSF increased from 25% (control) to 90%.     

Thymidine excretion from thymocytes in irradiated and nonirradiated rats during endonucleolysis

The concentration of free thymidine (dT), excreted from thymocytes of irradiated and nonirradiated rats, was determined after incubation of cells in various digestive buffers. The release of dT from thymocytes depended upon the rate of DNA fragmentation in conditions of chromatin endonucleolysis. The increase in the thymidine content, in conditions of chromatin endonucleolysis in buffers containing no calcium ions, was only noted in thymocytes of exposed rats: this was the consequence of chromatin DNA damages already available in these cells.     

Stimulation of hemopoiesis in irradiated mice using horse immunoglobulin G

The injection of heterologous polyclonal immunoglobulin G promotes the recovery of CFUs pool and increases the amount of myelokaryocytes in irradiated mice, while in nonirradiated mice, it activates differentiation of bone marrow CFUs and enhances their migration.     

Synthesis of lipids in the thymocytes of irradiated rats

During the first two hours following whole-body gamma-irradiation of rats with a dose of 7.5 Gy, the content of free cholesterol, phosphatidylcholine and phosphatidylethanolamine in the thymus decreases. Incorporation of 2-14C-acetate into cholesterol and fatty acids of thymus phospholipids in vitro is inhibited. At a dose of 4 Gy, incorporation of 2-14C-acetate into cholesterol and total lipids of thymocytes is activated.     

Mechanism of changes in irradiated thymocytes detected by anilinonaphthalenesulfonate

In experiments on rat thymocytes obtained 15 min, 2 h and 4 h after irradiation of animals with the dose of 10 Gy it was found that 15 min and 4 h following irradiation changes occurred in their membranes increasing the lifetime of the excited state of anilinonaphthalene sulfonate and hydrofobicity and viscosity of its microenvironment. The indicated parameters did not vary from the controls 2 h following irradiation. The analysis of the data obtained prompted a suggestion that the observed changes were associated with the structural rearrangements in the plasma membrane rather than with its destruction. Model experiments on irradiated thymocyte suspensions showed that there was a correlation between changes in the cell membrane and meabolic processes.     

Modulating effect of opioid peptides on hemopoiesis in stress

The influence of leu-enkephalin and dalargin on the blood system was studied during immobilization stress in mice. The early transmitted reactions of the peripheral blood were shown to decrease upon single drug infusions after immobilization. At later terms the activation of bone marrow hematopoiesis was not registered in mice receiving opioid peptides in contrast to the control animals. It correlates with drug-induced decrease in the mitotic activity of bone-marrow cells. Suppressive effect of opioids on hematopoiesis during stress was connected with their decreasing effect on corticosteroid level in the animal plasma. The latter can suggest indirect influence of enkephalins on bone marrow hematopoiesis in immobilization stress.     

Biosynthesis of chromatin proteins in the thymocytes of irradiated rats

Biosynthesis of chromatin proteins in thymus cells of irradiated rats has been studied. During the period immediately preceding DNA degradation, new proteins, which are not found in the chromatin of the control cells, are synthesized in the exposed thymocytes and enter the chromatin. Besides, the rate of biosynthesis of a large number of other chromatin proteins decreases. The data obtained indicate that interphase death of lymphoid cells is an active, genetically programmed process.     

Endonucleolysis of chromatin in thymocytes of irradiated and non-irradiated rats

It was shown that in conditions optimal for Ca/Mg endonuclease, chromatin endonucleolysis in the nuclei and thymocytes occurs due to internucleosome fragmentation of DNA. Irradiation activates chromatin degradation in thymocytes washed by a buffer containing 0.25 M sucrose, 10 mM tris-HCl, pH 7.2, 3 mM MgCl2, and does not influence this process in thymocytes washed by 10 mM tris-HCl, pH 7.2, 3 mM MgCl2.     

Postirradiation changes in the chromatin structure of thymocytes in irradiated rats

In this work the antibodies were obtained against chromatin isolated from thymocytes of intact and irradiated rats (2 h after exposing to 10 Gy) and against polydeoxyribonucleotides (PDN) extracted from thymus nuclei 6 h following irradiation. All the antibodies under study reacted more readily with the chromatin obtained from the thymus of exposed rats than with the control chromatin. The complexes of DNA with the most firmly bound non-histone proteins, obtained from the three objects under study, reacted with the antibodies with equal efficiency. Thus, a higher reactivity of PDN and chromatin from thymocytes of exposed rats was associated with the decondensation of the latter leading to an increase in availability of a part of antigenic determinants. Using the immunoblotting method we failed to discover any qualitative differences in the protein composition of the chromatin from control and exposed rats.     

Effect of mitochondrial energetic state on radiation-induced DNA internucleosomal fragmentation in irradiated thymocytes

One of the earliest features of apoptosis is a decrease of mitochondrial membrane potential. Here we show that when apoptosis is induced in thymocytes by ionizing radiation, inhibitors of mitochondrial energy production suppress DNA internucleosomal fragmentation. The suppression of fragmentation by inhibitors does not correlate with their effect on mitochondrial membrane potential, as it was observed when membrane potential was decreased (in the presence of inhibitors of respiratory chain, uncouplers of oxidative phosphorylation) or non affected (in the presence of oligomycin, inhibitor of mitochondrial ATPase).     

Biosynthesis of nuclear sap proteins in the thymocytes of irradiated rats

A study was made of biosynthesis of nuclear sap proteins in rat thymus cells exposed to 8 Gy gamma-radiation. Four hours following irradiation, changes were observed in the nuclear sap protein spectrum which were not associated with proteolysis.     

The intercellular interactions in the interphase death of irradiated thymocytes. A study of the nature of the mediator of the interaction of irradiated thymocytes]

A study was made of the influence of cytosol and conditioned medium, obtained at different times of incubation of irradiated thymocytes, on native thymocytes, as well as of the influence of mixing the suspension and changing the medium and the enzyme inhibitors, involved in metabolism of arachidonic acid, on the radiation injury to thymocytes. Cytosol of thymocytes, incubated for 60 min after irradiation, was shown to exert an insignificant toxic effect on native thymocytes. The conditioned medium of irradiated thymocytes is virtually ineffective. The mixing of the suspension upon incubation and the changing of the medium reduced the damage to exposed thymocytes while inhibitors of phospholipase A2 and lipoxygenase prevented completely the radiation-induced pyknosis of nuclei, whereas a inhibitor of cyclooxygenase did not influence it. It is inferred from the data obtained that unstable lipoxygenase products may serve as mediators of intercellular interactions of exposed thymocytes.