Abiotic Environmental Factors Affecting the Formation of Microbial Biofilms

Biofilms are aform of existence of bacteria in the environment, due to which bacteria can expand the boundaries of their habitats during contamination of different surfaces under diverse conditions. The most important environmental factors affecting biofilms are discussed. These factors include temperature, osmolarity, the concentration of ferrous iron ions, the availability of nutrients, the quality of materials on which biofilms are formed, and light and theambient acidity.     

The dynamics of the direct current potentials of the brain during sustained attention in 10-11-year-old children

The dynamics of direct current potentials of the brain was studied in 10-11-year-old children during sustained attention to successive presentation of series of Shulte tables. Children were examined twice: before and after the series of training to fast reading. A gradual increase in the level of direct current potentials during sustained attention was observed. The increase was more pronounced in children with excessive than in children with moderate reactions to the loading. After the series of training to fast reading, the increase in the level of direct current potentials was reduced in both groups. This aftertraining neurophysiological phenomenon was combined with a transformation of psychophysiological characteristics: a decrease in the time of viewing of Shulte tables and increase in the speed of reading. It is suggested that the shifts of direct current potentials reflects the dynamics of intensity of the cerebral energy metabolism.     

Photochromic Modulation of Cys-loop Ligand-gated Ion Channels

Journal of Evolutionary Biochemistry and Physiology - Advances in molecular and cellular biology, as well as the development of chemical synthesis and modern technologies, enriched the contemporary...     

Concomitant loss of cell surface fibronectin and laminin from transformed rat kidney cells

Both fibronectin and laminin were found by immunofluorescence as a matrix at the surface of normal rat kidney cells. These matrices were absent from the surface of virally transformed rat kidney cells. Soluble fibronectin and laminin were detected in the culture media of the transformed as well as the normal cells. Culture supernates of the transformed cells contained even more fibronectin than the supernates of the transformed cells contained even more fibronectin than the supernates of the normal cells while laminin was present in similar amounts in both culture media. This shows that the loss of fibronectin and laminin from the surface of the transformed cells is caused by failure of the cells to deposit these proteins into an insoluble matrix and not caused by inadequate production. Fibronectins isolated from culture media of the normal and transformed cells were similar in SDS polyacrylamide gel electrophresis. Laminin isolated from culture media by affinity chromatography on heparin-Sepharose followed by immunoprecipitation was composed of three main polypeptides, one with a molecular weight of 400,000 and two with a molecular weight close to 200,000 in both cell types. Fibronectins from both cell types were equally active in promoting cell attachment. Rat fibronectin from transformed cells, like normal cells, when applied to culture dishes coated with fibronectin, readily attached and spread on the substratum, requiring approximately the same amount of fibronectin as the normal cells. On the basis of these results it seem that the failure of the transformed cells to incorporate fibronectin into an insoluble cell surface matix is not a consequence of a demonstrable change in the functional characteristics of the fibronectin molecule or in the ability of the cells to interact with fibronectin. It may depend on as yet unidentified interactions of the cell surface. Similar interactions may be needed for the deposition of laminin into the matrix, because laminin was also absent from the surface of transformed cells, despite its being synthesized by these cells.     

Dissociation of intracellular lysosomal rupture from the cell death caused by silica

The relationship between intracellular lysosomal rupture and cell death caused by silica was studied in P388d(1) macrophages. After 3 h of exposure to 150 μg silica in medium containing 1.8 mM Ca(2+), 60 percent of the cells were unable to exclude trypan blue. In the absence of extracellular Ca(2+), however, all of the cells remained viable. Phagocytosis of silica particles occurred to the same extent in the presence or absence of Ca(2+). The percentage of P388D(1) cells killed by silica depended on the dose and the concentration of Ca(2+) in the medium. Intracellular lyosomal rupture after exposure to silica was measured by acridine orange fluorescence or histochemical assay of horseradish peroxidase. With either assay, 60 percent of the cells exposed to 150 μg silica for 3 h in the presence of Ca(2+) showed intracellular lysosomal rupture, was not associated with measureable degradation of total DNA, RNA, protein, or phospholipids or accelerated turnover of exogenous horseradish peroxidase. Pretreatment with promethazine (20 μg/ml) protected 80 percent of P388D(1) macrophages against silica toxicity although lysosomal rupture occurred in 60-70 percent of the cells. Intracellular lysosomal rupture was prevented in 80 percent of the cells by pretreatment with indomethacin (5 x 10(-5)M), yet 40-50 percent of the cells died after 3 h of exposure to 150 μg silica in 1.8 mM extracellular Ca(2+). The calcium ionophore A23187 also caused intracellular lysosomal rupture in 90-98 percent of the cells treated for 1 h in either the presence or absence of extracellular Ca(2+). With the addition of 1.8 mM Ca(2+), 80 percent of the cells was killed after 3 h, whereas all of the cells remained viable in the absence of Ca(2+). These experiments suggest that intracellular lysosomal rupture is not causally related to the cell death cause by silica or {"type":"entrez-nucleotide","attrs":{"text":"A23187","term_id":"833253","term_text":"A23187"}}A23187. Cell death is dependent on extracellular Ca(2+) and may be mediated by an influx of these ions across the plasma membrane permeability barrier damaged directly by exposure to these toxins.     

Regulation of aspartate-derived amino-acid metabolism in Zygosaccharomyces rouxii compared to Saccharomyces cerevisiae

To elucidate the growth inhibitory effect of threonine, the regulation of the aspartate-derived amino-acid metabolism in Zygosaccharomyces rouxii, an important yeast for the flavor development in soy sauce, was investigated. It was shown that threonine inhibited the growth of Z. rouxii by blocking the methionine synthesis. It seemed that threonine blocked this synthesis by inhibiting the conversion of aspartate. In addition, it was shown that the growth of Z. rouxii, unlike that of Saccharomyces cerevisiae, was not inhibited by the herbicide sulfometuron methyl (SMM). From enzyme assays, it was concluded that the acetohydroxy acid synthase in Z. rouxii, unlike that in S. cerevisiae, was not sensitive to SMM. Furthermore, the enzyme assays demonstrated that the activity of threonine deaminase in Z. rouxii, like in S. cerevisiae, was strongly inhibited by isoleucine and stimulated by valine. From this work, it is clear that the aspartate-derived amino-acid metabolism in Z. rouxii only partly resembles that in S. cerevisiae.     

An in vivo control map for the eukaryotic mRNA translation machinery

Rate control analysis defines the in vivo control map governing yeast protein synthesis and generates an extensively parameterized digital model of the translation pathway. Among other non‐intuitive outcomes, translation demonstrates a high degree of functional modularity and comprises a non‐stoichiometric combination of proteins manifesting functional convergence on a shared maximal translation rate. In exponentially growing cells, polypeptide elongation (eEF1A, eEF2, and eEF3) exerts the strongest control. The two other strong control points are recruitment of mRNA and tRNA_i to the 40S ribosomal subunit (eIF4F and eIF2) and termination (eRF1; Dbp5). In contrast, factors that are found to promote mRNA scanning efficiency on a longer than‐average 5′untranslated region (eIF1, eIF1A, Ded1, eIF2B, eIF3, and eIF5) exceed the levels required for maximal control. This is expected to allow the cell to minimize scanning transition times, particularly for longer 5′UTRs. The analysis reveals these and other collective adaptations of control shared across the factors, as well as features that reflect functional modularity and system robustness. Remarkably, gene duplication is implicated in the fine control of cellular protein synthesis.     

Contractile properties, transversal stiffness and cytoskeletal protein content in Mongolian gerbils soleus fibers under long-term hindlimb suspension

Structural and functional changes in Mongolian gerbil soleus fibers were analyzed after a 31-day hindlimb suspension. Contractile properties of muscle fibers were studied by means of tensometry; the transversal stiffness of different parts of the contractile apparatus was measured by atomic force microscopy, resting calcium level was estimated by fluorescence microscopy by using Fluo-4-AM; cytoskeletal protein content was determined by western blotting. It was shown that after gravitational unloading the maximal force of contraction and specific tension of fiber were significantly reduced, as well as calcium sensitivity actually lowered. At the same time, the transversal stiffness of Z-disk in the relaxed and activated state was decreased significantly compared to the control group. Desmin content was at the control level, but alpha-actinin-2, main structural protein of Z-disk, became considerably less after a 31-day hindlimb suspension. Besides, resting calcium level remained at control values during the simulated gravitational unloading. The data suggest that Z-disk destruction, as a result of alpha-actinin-2 content reduction, leads to changes in the lattice spacing and decreases contractile properties.     

Phenol oxidase activity in bacteria of the genus <Emphasis Type="Italic">Azospirillum</Emphasis>

Phenol oxidase activity was detected for the first time in a number of strains belonging to various Azospirillum species. Both extracellular and intracellular activities of laccase, Mn-peroxidase, lignin peroxidase, and tyrosinase were observed. Extracellular enzymes were found to have higher activity. Significant differences in phenol oxidase activities were observed between species and strains.