Uncharged P-selectin blockers

The blocking potency of P- and L-selectin was studied for certain small molecule mannosides and their polyacrylamide (PAA, 30 kDa) conjugates in comparison to SiaLe^x and fucoidan. Two experimental systems were used: (1) solid phase static assay based on recombinant selectins, and (2) P-selectin dependent rat peritoneal inflammation. βMan-SC₆H₄NO₂-p was four times more potent P-selectin inhibitor as compared to SiaLe^x. Docking of this molecule onto the P-selectin carbohydrate-binding site demonstrated that a nitro group enabled an electrostatic interaction with residue Lys 84, while the phenyl ring and the CH₂ at C-6 contacted the CH₂ groups of the same Lys residue. In vivo, βMan-SC₆H₄NO₂-p blocked experimental inflammation better than SiaLe^x, but significantly lower than fucoidan. In vitro Man-polyacrylic acid conjugates appeared to be very potent inhibitors comparable to fucoidan, uncharged Man-PAA proved rather active, comparable to SiaLe^x-PAA both in vitro, and in vivo, whereas mannan did not display any P-selectin blocking effect. Published in 2004. This revised version was published online in July 2006 with corrections to the Cover Date.     

Distribution of Bacteria,Picophytoplankton, and Flagellates in the Mekong Delta

Biology Bulletin - For the first time in the Mekong delta (Vietnam), the abundance and biomass of the main components of the planktonic microbial food web, and namely: bacteria, picophytoplankton,...     

Thermal instability caused by plasma-wall interaction

A one-dimensional model describing recycling of hydrogen isotopes in fusion reactors is proposed. The dispersion relation for thermal instability caused by plasma-wall interaction is derived, and conditions under which it develops are determined. It is shown analytically and numerically that this instability can develop under typical tokamak conditions.     

Microorganisms in Heat Supply Systems and Internal Corrosion of Steel Pipelines

In laboratory experiments with batch cultures of thermophilic microorganisms isolated from urban heat supply systems, the growth of sulfate-reducing, iron-oxidizing, and iron-reducing bacteria was found to accelerate the corrosion rate of the steel-3 plates used in pipelines. In the absence of bacteria and dissolved oxygen, minimal corrosion was determined. The aforementioned microorganisms, as well as sulfur-oxidizing bacteria, were found to be widespread in water and corrosion deposits in low-alloy steel pipelines (both delivery and return) of the Moscow heat networks, as well as in the corrosion deposits on the steel-3 plates in a testing unit supplied with the network water. The microorganisms were found in samples with a water pH ranging from 8.1 to 9.6 and a temperature lower than 90°C. Magnetite, lepidocrocite, goethite, and X-ray amorphous ferric oxide were the corrosion products identified on the steel-3 plates, as well as siderite, aragonite, and S⁰. The accumulation of corrosion deposits and variation in the total and local corrosion of the steel plates in a testing unit were considered in terms of the influence of microbial processes.     

Studies on the estrus cycle of the ground squirrel (Citellus citellus L.) at experimentally induced hibernation

Eighty-five ground squirrels (C. citellus L.) were examined immediately after arousal (March-June). It was established that the animals were in estrus at the end of March; in April they were pregnant; in May they were in lactation; and in June they were already at rest, a postlactation period. Fifteen ground squirrels were treated with Hibernal and then placed in a chamber for 30 days at external temperature, 8-12 degrees C. In this case the estrus cycle of hypothermic ground squirrels was not changed. A retarded involution of corpus luteum persisted for a month and cystic follicles appeared in the ovary.     

Synthesis of 1,2-trans-disaccharides via sugar thio-orthoesters

The reaction of sugar 1,2-thio-orthoesters in the d-gluco, d-galacto, d-manno, and l-rhamno series with primary and secondary trityl ethers of monosaccharides, in the presence of triphenylmethylium perchlorate as catalyst, affords, stereospecifically, derivatives of 1,2-trans-disaccharides in good yields. 4-Trityl ethers of benzyl 2-acetamido-3,6-di-O-acetyl-2-deoxy-α-d-glucopyranoside and methyl 2,3,6-tri-O-benzoyl-α-d-galactopyranoside exhibit low reactivity in glycosylation by thio-orthoesters. A reaction scheme for the glycosylation is discussed.     

Development of approaches to creation of experimental test system for evaluation of antigenic activity of synthetic oligosaccharide ligands related to fragments of the Streptococcus pneumoniae type 14 capsular polysaccharide

A conjugate of a synthetic hexasaccharide fragment of the Streptococcus pneumoniae type 14 capsular polysaccharide with bovine serum albumin (BSA) has been prepared. The antigenic activity and specificity of this conjugate are comparable with those of natural antigens of S. pneumoniae type 14. The data suggest that the resulting synthetic conjugate can be used as a coating antigen in an experimental test system (based on enzyme immunoassay) for evaluating the antigenic activity and specificity of synthetic oligosaccharide ligands and for testing specimens of natural capsular polysaccharides and immune sera.