Inhibitory effects of phenolic ecotoxicants on photobacteria at various pH values

Kinetic characteristics of light emission by intact cells of the photobacteria Photobacterium phosphoreum and Vibrio harveyi at pH 5.5, 7.0, and 8.0 were studied as well as specific features of inhibitory effects of 2,4-di- and 2,4,5-triphenoxyacetic acids (2,4-D and 2,4,5-T), pentachlorophenol (PCP), and 2,6-dimethylphenol (2,6-DMP) at the same pH values. Nonstationarity of emission kinetics was observed at all the pH values studied. Exponential luminescence decay in a 60-sec range was observed at pH 5.5; a 5-min luminescence activation, at pH 7.0 and 8.0. The cell respiratory activity drops by over one order of magnitude at pH 5.5 compared with the activities at pH 7.0 and 8.0. The inhibitory effects of 2,4-D, 2,4,5-T, and PCP differ by one-two orders of magnitude depending on pH. The maximal cell sensitivity to these compounds appears at pH 5.5; the minimal, at pH 8.0. The effect of 2,6-DMP is independent of pH. As is demonstrated, it is hydrophobicity of the molecule and pK values of the toxicants that determine the inhibitory effect. Characteristic of the substrate-starved photobacterial cells are higher sensitivity to chlorophenolic compounds compared with the cells provided with high energy supply at all the pH values.     

Mechanosensitivity of gramicidin A channels in semispherical bilayer membranes at constant tension

Mechanoelectrical transduction in gramicidin A channels was studied in macroscopic planar lipid bilayer membranes bulged at constant tension. We found a supralinear increase in the single channel activity, which was proportional to the square of membrane radius but could not be accounted for by the increase in membrane surface area or by recruitment of new channels. When being extrapolated to biological membranes, these observations may suggest that the activity of permeability of ion channels can be influenced simply by changing the shape of the membrane, with or without stretching.     

The accuracy of several multiple sequence alignment programs for proteins

Background  

There have been many algorithms and software programs implemented for the inference of multiple sequence alignments of protein and DNA sequences. The "true" alignment is usually unknown due to the incomplete knowledge of the evolutionary history of the sequences, making it difficult to gauge the relative accuracy of the programs.     

Compression or tension? The stress distribution in the proximal femur

Background  

Questions regarding the distribution of stress in the proximal human femur have never been adequately resolved. Traditionally, by considering the femur in isolation, it has been believed that the effect of body weight on the projecting neck and head places the superior aspect of the neck in tension. A minority view has proposed that this region is in compression because of muscular forces pulling the femur into the pelvis. Little has been done to study stress distributions in the proximal femur. We hypothesise that under physiological loading the majority of the proximal femur is in compression and that the internal trabecular structure functions as an arch, transferring compressive stresses to the femoral shaft.     

KCa1.1 potassium channels regulate key proinflammatory and invasive properties of fibroblast-like synoviocytes in rheumatoid arthritis

Fibroblast-like synoviocytes (FLS) play important roles in the pathogenesis of rheumatoid arthritis (RA). Potassium channels have regulatory roles in many cell functions. We have identified the calcium- and voltage-gated KCa1.1 channel (BK, Maxi-K, Slo1, KCNMA1) as the major potassium channel expressed at the plasma membrane of FLS isolated from patients with RA (RA-FLS). We further show that blocking this channel perturbs the calcium homeostasis of the cells and inhibits the proliferation, production of VEGF, IL-8, and pro-MMP-2, and migration and invasion of RA-FLS. Our findings indicate a regulatory role of KCa1.1 channels in RA-FLS function and suggest this channel as a potential target for the treatment of RA.     

Temporal Variation in Seed Predation by Insects in a Population of Syagrus romanzoffiana (Arecaceae) in Santa Catarina Island, SC, Brazil

Insect seed predation may vary depending on seed production. The present study considers the hypothesis that the rates of seed predation tend to be smaller in years of higher fruit production. Thus, we monitored the production of fruits and predation of seeds of the palm Syagrus romanzoffiana over 2?years in the Atlantic Forest (Parque Municipal da Lagoa do Peri, Florianópolis, SC, Brazil), between July 2006 and June 2008. Plots of 0.25?m² were fitted under 20 mother plants and fruits were monthly collected for assessment of abundance and seed predation. There was variation in fruit production between the 2?years and among reproductive plants. Predation rates were high and occurred in the predispersal phase by the Curculionidae Revena rubiginosa Boheman, Anchylorhynchus aegrotus Fahraeus, and Anchylorhynchus variabilis Gyllenhal. Seed predation by these species of Anchylorhynchus is first registered in the present study. In average, about 60% of the seeds monthly produced in the population tend to escape insect predation in year of high or low production, becoming available for recruitment. The predation rate was not related to the amount of fruits produced per reproductive plant. Also, different than expected, there was a positive relation between the rates of seed predation and the total of fruits produced monthly on the plots. Thus, no evidence for the satiation of insect seed predators was found in this study with S. romanzoffiana.     

Characteristics of the het mutations in the Escherichia coli chromosome causing an increase in Tn1 transposition frequency

Four mutations were studied which lead to increasing the frequency of transposon Tn1 translocation into different replicons. These mutations (het1, het2, het3 and het4) increase the frequency of Tn1 translocation 10-20-fold. The het1 mutation is recessive and has been localized in the 90-94.5 min region of the bacterial chromosome. The mutation effects Tn1 transposition in the presence of F plasmid only. As we have demonstrated recently, F-plasmid inhibits Tn1 transposition in Escherichia coli cells. The het1 mutation eliminates this inhibition. Unlike het2, het3 and het4 mutations, het1 is responsible for resistance to male phages f1, f2, MS2 and inhibition of conjugative transfer in F+ bacteria.     

Mathematical model of blunt injury to the vascular wall via formation of rouleaux and changes in local hemodynamic and rheological factors. Implications for the mechanism of traumatic myocardial infarction

Background  

Blood viscosity is fundamentally important in clinical practice yet the apparent viscosity at very low shear rates is not well understood. Various conditions such as blunt trauma may lead to the appearance of zones inside the vessel where shear stress equals zero. The aim of this research was to determine the blood viscosity and quantitative aspects of rouleau formation from erythrocytes at yield velocity (and therefore shear stress) equal to zero. Various fundamental differential equations and aspects of multiphase medium theory have been used. The equations were solved by a method of approximation. Experiments were conducted in an aerodynamic tube.