Lactobacilli isolated from kefir grains: evidence of the presence of S-layer proteins

In the present study we report for the first time the presence of S-layer proteins in Lactobacillus kefir and Lactobacillus parakefir isolated from kefir grains. Soluble whole-cell protein profile obtained either by mechanical disruption (X-press) or by a combined treatment with lysozyme and SDS on whole cells, showed a significant band of apparent molecular mass of 66-71 kDa as measured by SDS-PAGE. The intensity of this band was considerably reduced when cells were treated with 5 M-LiCl. The above mentioned proteins were recovered in the LiCl extracts. After dialysis and concentration, the proteins extracted were able to reassemble in a regular array. Negative staining of these protein preparations were analysed by transmission electron microscopy and a paracrystalline arrangement was seen. Thin sections of bacteria analysed by transmission electron micrographs showed an outermost layer over the bacterial cell wall, that was lost after the LiCl treatment. The production of this surface structure under different culture conditions was also evaluated. Finally, the relationship between the presence of S-layer proteins and surface properties (e.g. adhesion to Caco-2 cells, autoaggregation, and hemagglutination) was investigated.     

Free iron in pale, dark and alcohol-free commercial lager beers

BACKGROUND: A highly sensitive, selective, rapid, reliable and inexpensive method has been developed for the direct analysis of free iron in 40 samples of bottled lager beer. RESULTS: A differential pulse adsorptive stripping voltammetry technique at a hanging mercury drop electrode without any sample digestion was performed. The iron content in the analysed samples was in the range of 41 to 165 ppb. CONCLUSIONS: The results point out that dark beers keep the highest free iron concentrations, which may be related to the highest amounts of minor ingredients in dark beers. Meanwhile, alcohol‐free beers present the lowest free iron concentrations. Some discussion is presented regarding the basis of the free and complexed iron in beer and its participation as an essential element in the human diet. Copyright © 2011 Society of Chemical Industry     

Antifungal activity of natural and enzymatically-modified flavonoids isolated from citrus species

The antifungal activity of isolated flavonoids from Citrus species, such as naringin, hesperidin and neohesperidin, and enzymatically-modified derivatives of these compounds, was studied on four fungi often found as food contaminants: Aspergillus parasiticus, Aspergillus flavus, Fusarium semitectum and Penicillium expansum. Although all the flavonoids showed antifungal activity, the intensity of this activity depended on the type of fungus and compound used. The hesperetin glucoside laurate strongly inhibited the mycelial growth of P. expansum, while prunin decanoate was the most inhibiting flavonoid for A. flavus, A. parasiticus, and F. semitectum.     

Usability evaluation of virtual reality interaction techniques for positioning and manoeuvring in reduced, manipulation-oriented environments

This paper introduces some novel interaction techniques based on the concepts of composite positioning and composite manoeuvring (described in the paper). In contrast with other previous proposals, these techniques have been designed and evaluated in the context of a user centred process. The results of this evaluation and some relevant findings for the field of human computer interaction are also described.     

Morphological characterization of the growing front of Rhizopus oligosporus in solid media

Rhizopus oligosporus is used to prepare tempeh and is formed by hyphae which grow as a complex branched structure with irregular borders. The objective of this research was to characterize the macro and micro structural development of R. oligosporus colonies growing on solid media in Petri dishes through image processing and fractal dimension. Stereomicroscope images of the colony were used to detecting the zone in which the fractal dimension (FDE) of the edge (growing front) of the colony represented 97% of the maximum FDE for the 80% of the image of the border. Evaluated characteristics were: radial growth, number of tips in the growing front and the average length of hypha. Two simultaneous events of different and oscillating magnitude were detected in the growing front: branching and increase of the average hypha length. Biomass had a good correlation with radius of the colony, fractal dimension of texture (FDT) and number of tips in the border.     

Particulate matter air pollution disrupts endothelial cell barrier via calpain-mediated tight junction protein degradation

ABSTRACT: BACKGROUND: : Exposure to particulate matter (PM) is a significant risk factor for increased cardiopulmonary morbidity and mortality. The mechanism of PM-mediated pathophysiology remains unknown. However, PM is proinflammatory to the endothelium and increases vascular permeability in vitro and in vivo via ROS generation. OBJECTIVES: We explored the role of tight junction proteins as targets for PM-induced loss of lung endothelial cell (EC) barrier integrity and enhanced cardiopulmonary dysfunction. METHOD: S: Changes in human lung EC monolayer permeability were assessed by Transendothelial Electrical Resistance (TER) in response to PM challenge (collected from Ft. McHenry Tunnel, Baltimore, MD, particle size >0.1 um). Biochemical assessment of ROS generation and Ca2+ mobilization were also measured. RESULTS: : PM exposure induced tight junction protein ZO-1 relocation from the cell periphery, which was accompanied by significant reductions in ZO-1 protein levels but not in adherens junction proteins (VE-cadherin and beta-catenin). N-acetyl-cysteine (NAC, 5mM) reduced PM-induced ROS generation in ECs, which further prevented TER decreases and atteneuated ZO-1 degradation. PM also mediated intracellular calcium mobilization via the transient receptor potential cation channel M2 (TRPM2), in a ROS-dependent manner with subsequent activation of the Ca2+-dependent protease calpain. PM-activated calpain is responsible for ZO-1 degradation and EC barrier disruption. Overexpression of ZO-1 attenuated PM-induced endothelial barrier disruption and vascular hyperpermeability in vivo and in vitro. CONCLUSIONS: : These results demonstrate that PM induces marked increases in vascular permeability via ROS-mediated calcium leakage via activated TRPM2, and via ZO-1 degradation by activated calpain. These findings support a novel mechanism for PM-induced lung damage and adverse cardiovascular outcomes.     

Antibacterial activity of silver-doped hydroxyapatite nanoparticles against gram-positive and gram-negative bacteria

Ag-doped nanocrystalline hydroxyapatite nanoparticles (Ag:HAp-NPs) (Ca_10-xAg_x(PO₄)₆(OH)₂, x_Ag = 0.05, 0.2, and 0.3) with antibacterial properties are of great interest in the development of new products. Coprecipitation method is a promising route for obtaining nanocrystalline Ag:HAp with antibacterial properties. X-ray diffraction identified HAp as an unique crystalline phase in each sample. The calculated lattice constants of a = b = 9.435 Å, c = 6.876 Å for x_Ag = 0.05, a = b = 9.443 Å, c = 6.875 Å for x_Ag = 0.2, and a = b = 9.445 Å, c = 6.877 Å for x_Ag = 0.3 are in good agreement with the standard of a = b = 9.418 Å, c = 6.884 Å (space group P6₃/m). The Fourier transform infrared and Raman spectra of the sintered HAp show the absorption bands characteristic to hydroxyapatite. The Ag:HAp nanoparticles are evaluated for their antibacterial activity against Staphylococcus aureus, Klebsiella pneumoniae, Providencia stuartii, Citrobacter freundii and Serratia marcescens. The results showed that the antibacterial activity of these materials, regardless of the sample types, was greatest against S. aureus, K. pneumoniae, P. stuartii, and C. freundii. The results of qualitative antibacterial tests revealed that the tested Ag:HAp-NPs had an important inhibitory activity on P. stuartii and C. freundii. The absorbance values measured at 490 nm of the P. stuartii and C. freundii in the presence of Ag:HAp-NPs decreased compared with those of organic solvent used (DMSO) for all the samples (x_Ag = 0.05, 0.2, and 0.3). Antibacterial activity increased with the increase of x_Ag in the samples. The Ag:HAp-NP concentration had little influence on the bacterial growth (P. stuartii).     

Effect of the support on the selective hydrogenation of benzeneover ruthenium catalysts. 1. Al2O3 and SiO2

The effect of the support on the liquid phase selective hydrogenation of benzene to cyclohexene over Ru catalysts was studied. Catalysts were prepared using RuCl₃ as precursor and characterized by hydrogen chemisorption, XPS and TPR. The reaction was carried out at 373 K and 2 MPa using a stirred tank reactor. It was found that the catalytic activity is not influenced by the Ru dispersion. More electron-deficient Ru species are present on Al₂O₃ than on SiO₂. The electronic state of Ru affects the selectivity to cyclohexene.     

An evaluation of the Diamat HPLC analyser for simultaneous determination of haemoglobins A2 and F

The authors describe a modification of the instrumental parameters of the Diamat fully automated HPLC system for Hb A₂ assay (Bio-Rad Laboratories, Milan, Italy) in order to obtain simultaneous determination of Hb A₂ and Hb F.Hb A₂ and Hb F measurements are reproducible (within-run CV 2.6%, with Hb A₂2.7%; 5.1%, with Hb F 1.3%) and accurate (from a comparison with two microchromatographic techniques for Hb A₂: r = 0.9639 and 0.9755; with two alkali denaturation procedures for Hb F: r = 0.9990 and 0.9952; with radial immunodiffusion, r = 0.9877). Assay linearity has been confirmed for Hb A₂ concentrations between 0 and 6.0%, and for Hb F between 0 and 60%. The data obtained from the analysis of some pathological samples for Hb Bart''s, Hb H, Hb J Sardegna, Hb Lepore and Hb S are in agreement with cellulose acetate electrophoresis analysis.The Hb A₂ reference intervals for normals (N = 597) and Beta-thalassemia carriers (N = 200) are respectively (95% limits) 2.02-3.27 and 3.92-5.90 in % units. Hb F values measured in normals (N = 968), in β-thal carriers (N = 302) and in δβ-thal carriers (N =3) have been found to be consistent with the usual diagnostic parameters.Some minor limitations emerged: the most relevant concerns Hb A_1c, which is overestimated with respect to a reference method (y = 1.217x + 0.16; N = 79; r = 0.9235). A probable interference from labile fractions is responsible for this Hb A_1c inaccuracy.