Prevention of infectious complications in patients with acute bone marrow depression]

Clinical efficacy of intravenous gentamicin in combination with oral use of gentamicin, ristomycin and nystatin was studied in 1977. In 1980-1984 two antiinfectious regimens were tested: intravenous administration of gentamicin in combination with total decontamination (oral use of gentamicin and nystatin) and selective decontamination (biseptol with nystatin of amphoglucamine). It was shown that the incidence of severe infections in the patients under the observation dropped against the controls. The incidence and spectrum of infectious complications in cases with acute myelodepressions were proved to depend on the intestinal autoflora inhibition.     

Effects of Suramin on PMN Interactions with Different Surfaces

Human polymorphonuclear leukocytes (PMN) were found to tightly adhere on endothelial (lines EAhy926 and ECV304) and collagen surfaces under the influence of the chemotherapeutic drug suramin. This was observed by scanning electron microscopy and quantitated by myeloperoxidase assays. Suramin also inhibited Ca²⁺ ionophore A23187-stimulated leukotriene (LT) synthesis in PMN interaction with endothelial cells or with collagen surface. Suramin decreased the release of radiolabeled arachidonic acid (AA) and 5-lip-oxygenase (5-LO) metabolites by prelabeled PMN stimulated with A23187. Using agents releasing the suramin-stimulated adhesion namely jasplakonolide and dextran sulfate, we observed a reversal of the suramin effect on leukotriene synthesis. Jasplakonolide released the adhesion of PMN on endothelial and collagen-coated surfaces and restored 5-LO activity. Dextran-sulfate released adhesion on collagen-coated surfaces and abolished suramin inhibition. Arachidonate could also overcome adhesion and inhibition of 5-LO. We conclude that suramin-induced tight attachment of PMN on to solid surfaces lead to decreased leukotriene synthesis during subsequent A23187 stimulation in the absence of exogenous substrates.     

Experimental evaluation of interaction between Yersinia pestis and soil infusoria and possibility of prolonged preservation of bacteria in the protozoan oocysts

The character and outcome of interactions between Y. pestis (vaccine strain and soil infusoria Tetrahymena pyriformis (axenic culture) were under experimental study. The parallel use of the bacteriological method and PCR test systems made it possible to follow the dynamics of Y. pestis cells (strain EV) with different plasmid profiles in their interaction with infusoria, as well as their passage into the protozoa cysts. The study revealed the complete utilization of Y. pestis cells lacking virulence factors by infusoria. The presence of plasmids of virulence influenced only the duration of complete bacterial phagocytosis. A drop in the temperature of cultivation to 2 degrees C induced the mass and rapid encystment of infusoria. In the PCR analysis specific DNA fragments of Y. pestis cells, preserved in the latent (uncultivable) state, were detected in the cysts of protozoa within the period of up to 14 months, while the results of bacteriological studies were negative. The data thus obtained are discussed with regard to the possible mechanisms of the existence and prolonged reservation of Y. pestis in the soils of natural foci with participation of protozoa.     

The radiation-modifying capacity of xenogenic apotransferrin for the number of endogenous colony forming units in the spleen of irradiated mice

After intraperitoneal injection of 100 or 198 mg/kg of human serum apotransferrin (apo TF) to mice 1 day before acute exposure to 6 Gy of gamma-radiation, the number of endogenous CFU in spleen (CFUs) increased 2.5 or 2.6 times respectively. At a dose fo 10 mg/kg of the protein only an increasing tendency was found, whereas a dose of 1 mg/kg was inefficient. A dose of 100 mg/kg of BSA did not show any effect suggesting that non-specific immune response to alien antigen did not contribute to apo TF radiomodifying action. The following mechanisms of the apoTF radiomodifying effect are discussed: 1) the ability of the protein to inactivate Fe3+ ions that reduces the consequences of radiation oxidative stress; 2) the stimulation of proliferation of the exposed bone marrow cells by activation of Fe3+ transport or by Ca2+ mediated mechanism of mitogen signal transduction; 3) changing in the content and ratio of cyclic nucleotides by apo TF stimulation of Ca-calmodulin-dependent phosphodiesterase.     

Burkholderia cepacia under different ecological conditions: the amount and variability of the bacterial population

In a series of prolonged experiments with the use of the bacteriological method and PCR analysis the amount and state of B. cepacia population, associated and not associated with infusoria Tetrahymena pyriformis, were dynamically evaluated under different conditions: in water, brain heart broth, soil extract and at different temperature (4 degrees C and 25 degrees C). In soil extract at 25 degrees C B. cepacia existed in the vegetative state for the period of up to 3 months, while at 4 degrees C, in the absence of protozoa, the transition of these microorganisms into the uncultivable forms occurred in 9 days, and they could be detected only with the use of PCR. Protozoa maintained the existence of the vegetative bacteria for as long as 2 months, and in 3-4 months uncultivable forms of B. cepacia cells were registered. In water at low temperature B. cepacia disappeared in 2 months, evidently, eaten up by infusoria. The population variability of B. cepacia under different conditions of their existence was established: S-R dissociation, a decrease in biochemical activity, growth deceleration. A high level of cytopathogenicity in B. cepacia pigment-forming clones was noted. In the process of transition into the uncultivable state pigment formation in B. cepacia population decreased up. The ecological plasticity and multi-pathogenicity of B. cepacia as phytopathogens and the causative agents of human diseases are discussed.     

Phosphorylation and other properties of proteins binding single-stranded DNA (SSB-proteins) from chromatin and extrachromatin fractions of Ehrlich ascites carcinoma

A comparative study of single-stranded DNA-binding proteins (SSB-proteins) isolated from chromatin and the extrachromatin fraction of Ehrlich ascites tumour cells was carried out. No differences were found either in SDS-gel electrophoretic mobility or in the single-stranded DNA-binding capacity and stimulation of the replicative synthesis of DNA. However, chromatin SSB-proteins contained 1.4-1.5 times more phosphate than extrachromatin proteins. Both preparations could be phosphorylated in vitro by protein kinase C and cAMP-dependent protein kinase, but the chromatin proteins were phosphorylated in a lesser degree. In parallel with phosphorylation the SSB-proteins displayed a higher binding affinity for ssDNA-cellulose. Phosphorylation can thus be regarded as a means of regulation of the SSB-protein function, in particular, their interaction with chromatin DNA.     

Sulfatides inhibit leukotriene synthesis in human polymorphonuclear granulocytes by a mechanism involving lipid rearrangement in intracellular membranes

Sulfatides - sulfated derivatives of galactocerebroside - are endogenous ligands for P- and L-selectins and are able to induce intracellular signaling in neutrophils through a L-selectin dependent pathway. Sulfatides are implicated in a variety of physiological functions and have been found to suppress the synthesis of 5-lipoxygenase (5-LO) metabolites and impede 5-LO translocation to the nuclear envelope in adherent human polymorphonuclear leukocytes (PMNs) [Sud'ina, G. F., Brock, T. G., Pushkareva, M. A., Galkina, S. I., Turutin, D. V., Peters-Golden, M., et al. (2001). Sulphatides trigger polymorphonuclear granulocyte spreading on collagen-coated surfaces and inhibit subsequent activation of 5-lipoxygenase. The Biochemical Journal, 359, 621-629]. In this study we investigated the mechanism of the leukotriene (LT) synthesis inhibition by sulfatides. Sulfatides neither attenuated the ionophore-induced rise in [Ca(2+)](i) nor promoted PKA activation. We demonstrated that sulfatides directly inhibited 5-LO enzyme activity in a cell-free assay. BODIPY-labeled sulfatides were able to rapidly penetrate into the cells. Sulfatides induced rearrangement and redistribution of cytoskeletal components in adherent PMNs. The lipid incorporation as well as sulfatide-induced inhibition of LT synthesis were abolished by cytochalasin D, an inhibitor of actin polymerization and endocytosis. Importantly, sulfatides caused a prominent intracellular cholesterol redistribution, increasing its abundance at the uropod region. On the basis of these data, we suggest that increased cholesterol accumulation in cell compartments represents a novel mechanism by which sulfatides abrogate 5-LO translocation and activation.