Growth of oral Streptococcus species and Actinomyces viscosus in human saliva.

Microorganisms in dental plaque live in constant association with saliva. The role of saliva in the adherence of bacteria to the teeth and the antibacterial properties of saliva have been well investigated; less interest has been shown in the possible role of saliva as a substrate for oral microorganisms. In this study it was shown that saliva can serve as a growth medium for oral Streptococcus spp. and Actinomyces viscosus. The cell production of these organisms on saliva was carbohydrate limited. The doubling times for growth on glucose-supplemented saliva (4 to 5 mmol/liter) ranged from 1.6 to 4.0 h. The availability of carbohydrate sources for the oral microflora is discussed in relation to microbial growth in the oral cavity.     

The role of adhesive interactions and extracellular matrix fibronectin from human polymorphonuclear leukocytes in the respiratory burst

The Arg-Gly-Asp (RGD) tripeptide and ajoene were used for studying the role of adhesive receptors in the respiratory burst. Activation of the respiratory burst was examined by using luminol-dependent and lucigenin-dependent chemiluminescence. Recently, it was shown that ajoene, (E, Z)-4,5,9-trithiadodeca-1,6,11-trien-9-oxide, a substance isolated from garlic extract, inhibits the binding of fibrinogen to activated platelets by direct interaction with fibrinogen receptor (Apitz-Castro, R., Lederma, E., Escalante, J. and Jain, M.K. (1986) Biochem. Biophys. Res. Commun. 141, 145-150). Taking into consideration the structural and functional similarity of integrins, it would be reasonable to assume that ajoene as well as RGD can inhibit adhesive interactions of human neutrophils. We have shown that the effect of various activators on the respiratory burst was abolished by ajoene or RGD treatment. The inhibitory effect of RGD and ajoene was dose-dependent. The treatment of neutrophils with antiserum against human plasma fibronectin inhibited the respiratory burst in response to formyl-methionyl-leucylphenylalanine (fMLP) and phorbol 12-myristate 13-acetate (PMA). This effect is dose-dependent and reversible with the addition of fibronectin. These data indicate that the respiratory burst in human neutrophils is mediated by the integrin family of receptors and that interactions between the extracellular matrix fibronectin and cells are necessary for the respiratory burst.     

Proteins in the insulin-secreting cell line MIN6 bind the imidazoline compound BL11282

The imidazoline BL11282 stimulates insulin release and alters islet proteomes. Subcellular fractions of MIN6 cells showed that the membrane fraction exhibited binding to BL11282 on a Biacore chip and to BL11282-labelled magnetic beads. Bound material extracted from the beads showed a 50 kDa differential band upon SDS–PAGE and a weaker 100 kDa band. The former was sensitive to competitive removal by preincubation of the fraction with BL11282, then highlighting the 100 kDa band. Masspectrometric analysis revealed the 50 kDa band to be EF1A and the 100 kDa band to be glucose regulated P94, both of interest in insulin synthesis and secretion.     

Effects of boron and calcium nutrition on the establishment of the Rhizobium leguminosarum–pea (Pisum sativum) symbiosis and nodule development under salt stress

The effects of modifying boron (B) and calcium (Ca²⁺) concentrations on the establishment and development of rhizobial symbiosis in Pisum sativum plants grown under salt stress were investigated. Salinity almost completely inhibited the nodulation of pea plants by Rhizobium leguminosarum bv. viciae 3841. This effect was prevented by addition of Ca²⁺ during plant growth. The capacity of root exudates derived from salt‐treated plants to induce Rhizobium nod genes was not significantly decreased. However, bacterial adsorption to roots was highly inhibited in plants grown with 75 mM NaCl. Moreover, R. leguminosarum 3841 did not grow in minimal media containing such salt concentration. High Ca²⁺ levels enhanced both rhizobial growth and adsorption to roots, and increased nodule number in the presence of high salt. Nevertheless, the nodules developed were not functional unless the B concentration was also increased. Because B has a strong effect on infection and cell invasion, these processes were investigated by fluorescence microscopy in pea nodules harbouring a R. leguminosarum strain that expresses green fluorescent protein. Salt‐stressed plants had empty nodules and only those treated with high B and high Ca²⁺ developed infection threads and exhibited enhanced cell and tissue invasion by Rhizobium. Overall, the results indicate that Ca²⁺ promotes nodulation and B nodule development leading to an increase of salt tolerance of nodulated legumes.     

Biosensor for the detection of bacteriophages based on a super-high-frequency resonator

Azospirillum lipoferum Sp59b microbial cells were immobilized on the surface of thin polystyrene films modified in plasma from a high-frequency discharge of argon (13.56 MHz). The optimal conditions for immobilization, under which cell activity was maintained with respect to specific bacteriophages, were established. It was shown that it is possible to record the interaction of immobilized microbial cells and bacteriophages with a microwave-based resonant system (5–8.5 GHz). It was found that the biosensor made it possible to distinguish the interaction of bacterial cells with specific bacteriophages from the control, in which such interaction was absent. With the obtained super-high-frequency sensor, it was possible to determine the content of ΦAl-Sp59b bacteriophages in a suspension containing ~106 phages/mL. The analysis time was about 10 min. The viability of microbial cells after immobilization was also determined with this sensor. The results obtained with the use of the sensor on the basis of a super-high-frequency resonator have shown that it is promising for the development of methods to determine viral particles and the viability of microbial cells.     

A method of acoustic analysis for detection of bacteriophage-infected microbial cells

The dependence of the changes of physical parameters of the suspension of Azospirillum brasilense Sp7 cells infected by FAb-Sp7 bacteriophage on their number and exposure time was studied using a biological sensor based on a piezoelectric resonator with a lateral electric field. The change in the value of the analytical signal was recorded at 1 minute from the beginning of the infection of the cells by bacteriophage. The selectivity of the action of the FAb-Sp7 bacteriophage was studied for Azospirillum brasilense (strains Cd, Sp107, Sp245, Jm6B2, Br14, KR77, S17, S27, SR55, and SR75), A. lipoferum (strains Sp59b, SR65, and RG20a), A. halopraeferans Au4, Nitrospirillum amazonense Am14, Niveispirillum irakense (strains KBC1 and KA3) bacteria, as well as for heterologous bacteria of the genera Escherichia coli (strains XL-1 and B-878), Pseudomonas putida (strains C-11 and BA-11), and Acinetobacter calcoaceticum A-122. The limit of the reliable determination of the concentration of microbial cells during bacteriophage infection process was found: ~10⁴ cells/mL. At the same time, the presence of heterologous cell cultures (E. coli XL-1 cells) did not complicate the detection. It was shown that the method of electroacoustical analysis of cell suspensions can be used for the detection of microbial cells of Azospirillum infected by the FAb-Sp7 bacteriophage. The results are promising for the development of methods for determining and controlling the number of soil microorganisms.     

Pharmacological correction of microcirculation in rats suffering from traumatic brain injury

We investigated the effect of mexicor on functional indices of erythrocytes and the structure of myocardial microcirculation in rats suffering from traumatic brain injury (TBI). At 3, 7, and 12 days after TBI, we measured the concentration of 2,3-diphosphoglycerate (2,3-DPG) and the degree of erythrocyte aggregation and their electrophoretic mobility (EPME) in the blood of rats, as well as analyzing sections of the left ventricular myocardium. The first day after the TBI, we observed a decrease in EPME, an increase of erythrocyte aggregation, and an increase of 2,3-DFG concentration in erythrocytes as compared with intact animals. Intraperitoneal injection of mexicor led to an increase of EPME and 2,3-DPG level and reduced the aggregation of erythrocytes, which was most pronounced during the 3–7 days of the post-traumatic period. Improved functional parameters of erythrocytes were accompanied by the dynamics of regenerative processes in the heart. Intraperitoneal injection of mexicor restrained architectonic damage of microvasculature and cardiomyocytes ultrastructure of the left ventricular myocardium of the heart.     

Regulation of TrkB receptor tyrosine kinase and its internalization by neuronal activity and Ca2+ influx

Internalization of the neurotrophin-Trk receptor complex is critical for many aspects of neurotrophin functions. The mechanisms governing the internalization process are unknown. Here, we report that neuronal activity facilitates the internalization of the receptor for brain-derived neurotrophic factor, TrkB, by potentiating its tyrosine kinase activity. Using three independent approaches, we show that electric stimulation of hippocampal neurons markedly enhances TrkB internalization. Electric stimulation also potentiates TrkB tyrosine kinase activity. The activity-dependent enhancement of TrkB internalization and its tyrosine kinase requires Ca2+ influx through N-methyl-d-aspartate receptors and Ca2+ channels. Inhibition of internalization had no effect on TrkB kinase, but inhibition of TrkB kinase prevents the modulation of TrkB internalization, suggesting a critical role of the tyrosine kinase in the activity-dependent receptor endocytosis. These results demonstrate an activity- and Ca2+-dependent modulation of TrkB tyrosine kinase and its internalization, and they provide new insights into the cell biology of tyrosine kinase receptors.     

Successional changes of Collembola and soil microbiota during forest rotation

Dynamic approaches to forest ecosystems are surprisingly rare. Here we report about successional changes in collembolan community structure and microbial performances during forest rotation. The study was carried out in a chronosequence of four spruce forest stands (5-, 25-, 45-, and 95 years old; Tharandter forest, Germany). CO₂ release significantly increased after clear-cutting and the amount of C stored in the organic layer subsequently declined. The early phase of forest rotation was characterized by a very active decomposer microflora, stimulation of both fungi and bacteria as well as by a high abundance of surface-oriented Collembola. In addition, collembolan species turnover was accelerated. While the biomass of fungi further increased at intermediate stages of forest rotation, the metabolic activity of the microflora was low, the functional diversity of bacteria declined and the collembolan community became impoverished. Euedaphic species dominated during this stage of forest development. These changes can be explained by both reduction in microhabitat diversity and depletion of food sources associated with an accumulation of recalcitrant soil organic matter. Results of the General Regression Model procedure indicate a shift from specific associations between collembolan functional groups and microbiota at the early stage of forest rotation to a more diffuse pattern at intermediate stages. Though the hypothesis that Collembola are relatively responsive to changes in environmental conditions is confirmed, consistently high community similarity suggests a remarkable persistence of some components of microarthropod assemblages. Our study provides evidence for substantial ecosystem-level implications of changes in the soil food web during forest rotation. Moreover, correlations between bacterial parameters and Collembola point to the overarching impact of differences in the composition of the microbial community on microarthropods.     

Structure of transfection-active histone H1/DNA complexes

Relationships between the structure of transfecting complexes of histone H1 and DNA and their transfection efficiency were studied. Transfection activity proved to be connected to complex aggregates. Low speed centrifugation of the complexes resulted in loss of the transfection activity. The complexes/aggregates were active with high efficiency in a broad range of weight input ratios r _i (0.1<r _i<30). Using atomic force microscopy (AFM), the complexes were imaged at negative, nearly electroneutral and positive charge conditions. Electroneutral complexes at r _i=1 showed a multitude of different complex forms. Fibrillar, network-like and branched structures were frequently present in one complex. Strongly positive charged complexes had a toroidal appearance. All these different forms contributed to the high transfection efficiency. Cellular uptake is supposed to be by phagocytosis.