Antigenic affinity of meningococci and human A- and B-group erythrocytes

The use of the modified method of isohemagglutinin adsorption by microbial antigens in experiments with the causative agent of meningococcal infection has led, for the first time, to the detection of meningococcal antigens affined to the antigens of human erythrocytes, groups A and B. The antigenic affinity of group A erythrocytes and meningococci has proved to be more pronounced in meningococcal strains isolated from the spinal fluid of patients than in cultures obtained from the nasopharynx of healthy persons. The detection of the affinity of these antigens makes it possible to explain the mechanism of differences in the susceptibility of persons with different blood groups to meningococcal infection by "antigenic mimicry".     

Lipid composition determines interaction of liposome membranes with Pluronic L61

Triblock copolymers of ethylene oxide (EO) and propylene oxide (PO) of EO(n/2)PO(m)EO(n/2) type (Pluronics) demonstrate a variety of biological effects that are mainly due to their interaction with cell membranes. Previously, we have shown that Pluronics can bind to artificial lipid membranes and enhance accumulation of the anti-tumor drug doxorubicin (DOX) inside the pH-gradient liposomes and transmembrane migration (flip-flop) of NBD-labeled phosphatidylethanolamine in the liposomes composed from one component-lecithin. Here, we describe the effects caused by insertion of other natural lipids in lecithin liposomes and the significance of the lipid composition for interaction of Pluronic L61 with the membrane. We used binary liposomes consisting of lecithin and one of the following lipids: cholesterol, phosphatidylethanolamine, ganglioside GM1, sphingomyelin, cardiolipin or phosphatidic acid. The influence of the additives on (1) membrane microviscosity; (2) binding of Pluronic L61; (3) the copolymer effect on lipid flip-flop and membrane permeability towards DOX was studied. The results showed that insertion of sphingomyelin and cardiolipin did not influence membrane microviscosity and effects of Pluronic on the membrane permeability. Addition of phosphatidic acid led to a decrease in microviscosity of the bilayer and provoked its destabilization by the copolymer. On the contrary, cholesterol increased microviscosity of the membrane and decreased binding of Pluronic and its capacity to enhance flip-flop and DOX accumulation. Analogous tendencies were revealed upon incorporation of egg phosphatidylethanolamine or bovine brain ganglioside GM1. Thus, a reverse dependence between the microviscosity of membranes and their sensitivity to Pluronic effects was demonstrated. The described data may be relevant to mechanisms of Pluronic L61 interaction with normal and tumor cells.     

Evaluation and comparison of the genetic structure of <Emphasis Type="Italic">Bunias orientalis</Emphasis> populations in their native range and two non-native ranges

We studied the invasive warty cabbage Bunias orientalis (Brassicaceae) in three geographically distinct areas. Using inter-simple sequence repeat fingerprinting, we analyzed warty cabbages, including non-native populations, from the eastern Baltic and western Siberian regions and native populations from southwestern Russia. The eastern Baltic region and western Siberia represent the two opposite directions of B. orientalis spread in climatically different zones. The genetic structures of the native and non-native B. orientalis populations were assessed through analysis of molecular variance (AMOVA) and the Bayesian clustering method and by determining the main measures of genetic diversity. AMOVA revealed considerable population differentiation in both the native and invasive ranges. Our results did not indicate a decrease in genetic diversity in the non-native populations of B. orientalis. Similar measures of genetic diversity and genetic structure were determined in the invasive populations in two geographically and ecologically distinct, non-native regions located in Europe and Asia. In both of these regions, higher genetic diversity was detected in the non-native populations than in the native region populations, which may be due to multiple introductions. However, Bayesian clustering analysis revealed slightly different sources of invasive populations in the two non-native regions. Genetic diversity patterns revealed the lack of isolation by distance between populations and confirmed the influence of anthropogenic factors on the spread of B. orientalis. The significance of native populations as germplasm resources for breeding is discussed.     

Potential use of the monosaccharide composition of bacteria for their identification

The monosaccharide composition of cell hydrolysates can be used as a criterion for the chemical differentiation of gram-positive bacteria. The monosaccharide composition of six bacterial species belonging to the genus Bacillus has been determined using gas chromatography, mass spectrometry and computers. The qualitative composition was similar, glucose, galactose, ribose and glucosamine being the main components in all of the species. Some Bacillus species differed in their minor components. Although the monosaccharide composition appeared to be homogeneous, bacteria can be identified in terms of their carbohydrate profile using computers. To this end, the monosaccharide composition of bacterial cells is represented as a two-dimensional data file including the qualitative composition of components and the quantity of each component.