Activation of murine macrophages by hydrogen peroxide

Hydrogen peroxide at concentrations from 0.1 to 20 μM enhances phagocytosis and oxidative burst of murine peritoneal macrophages. The activation of these macrophage functions is paralled by prolonged hyperpolarization and a transient increase in cytoplasmic free calcium concentration. All the effects are dose- and time-dependent. The results obtained for H₂O₂ are compared with those for a natural activator, peptide N-formyl-methionyl-leucly-phenylalanine. The data demonstrate the ability of small doses of hydrogen peroxide to stimulate macrophages through the intracellular mechanisms of ion transduction.     

Heterologous Expression Screens in Nicotiana benthamiana Identify a Candidate Effector of the Wheat Yellow Rust Pathogen that Associates with Processing Bodies

Rust fungal pathogens of wheat (Triticum spp.) affect crop yields worldwide. The molecular mechanisms underlying the virulence of these pathogens remain elusive, due to the limited availability of suitable molecular genetic research tools. Notably, the inability to perform high-throughput analyses of candidate virulence proteins (also known as effectors) impairs progress. We previously established a pipeline for the fast-forward screens of rust fungal candidate effectors in the model plant Nicotiana benthamiana. This pipeline involves selecting candidate effectors in silico and performing cell biology and protein-protein interaction assays in planta to gain insight into the putative functions of candidate effectors. In this study, we used this pipeline to identify and characterize sixteen candidate effectors from the wheat yellow rust fungal pathogen Puccinia striiformis f sp tritici. Nine candidate effectors targeted a specific plant subcellular compartment or protein complex, providing valuable information on their putative functions in plant cells. One candidate effector, {"type":"entrez-protein","attrs":{"text":"PST02549","term_id":"1371656274"}}PST02549, accumulated in processing bodies (P-bodies), protein complexes involved in mRNA decapping, degradation, and storage. {"type":"entrez-protein","attrs":{"text":"PST02549","term_id":"1371656274"}}PST02549 also associates with the P-body-resident ENHANCER OF mRNA DECAPPING PROTEIN 4 (EDC4) from N. benthamiana and wheat. We propose that P-bodies are a novel plant cell compartment targeted by pathogen effectors.     

A protocol for isolation and visualization of yeast nuclei by scanning electron microscopy (SEM)

This protocol details methods for the isolation of yeast nuclei from budding yeast (Saccharomyces cerevisiae) and fission yeast (Schizosaccharomyces pombe), immuno-gold labeling of proteins and visualization by field emission scanning electron microscopy (FESEM). This involves the removal of the yeast cell wall and isolation of the nucleus from within, followed by subsequent processing for high-resolution microscopy. The nuclear isolation step can be performed in two ways: enzymatic treatment of yeast cells to rupture the cell wall and generate spheroplasts (cells that have partially lost their cell wall and their characteristic shape), followed by isolation of the nuclei by centrifugation or homogenization; and whole cell freezing followed by manual cell rupture and centrifugation. This protocol has been optimized for the visualization of the yeast nuclear envelope (NE), nuclear pore complexes (NPCs) and associated cyto-skeletal structures. Samples once processed for FESEM can be stored under vacuum for weeks, allowing considerable time for image acquisition.     

Purification and properties of an enantioselective and thermoactive amidase from the thermophilic actinomycete <Emphasis Type="Italic">Pseudonocardia thermophila</Emphasis>

A constitutively expressed thermoactive amidase from the thermophilic actinomycete Pseudonocardia thermophila was purified to homogeneity by applying hydrophobic interaction, anion exchange and gel filtration chromatography, giving a yield of 26% and a specific activity of 19.5 units mg^–1. The purified enzyme has an estimated molecular mass of 108 kDa and an isoelectric point of 4.2. The amidase is active at a broad pH range (pH 4–9) and temperature range (40–80°C) and has a half-life of 1.2 h at 70°C. Inhibition of enzyme activity was observed in the presence of metal ions, such as Co²⁺, Hg²⁺, Cu²⁺, Ni²⁺, and thiol reagents. The amidase has a broad substrate spectrum, including aliphatic, aromatic and amino acid amides. The presence of a double bond or a methyl group near the carboxamide group of aliphatic and amino acid amides enhances the enzymatic activity. Among aromatic amides with substitutions at the o-, m-, or p-position, the p-substituted amides are the preferred substrates. The highest acyl transferase activity was detected with hexanoamide, isobutyramide and propionamide. The K_m values for propionamide, methacrylamide, benzamide and 2-phenylpropionamide are 7.4, 9.2, 4.9 and 0.9 mM, respectively. The amidase is highly S-stereoselective for 2-phenylpropionamide; and the racemic amide was converted to the corresponding S-acid with an enantiomeric excess of >95% at 50% conversion of the substrate. In contrast, the d,l-tryptophanamide and d,l-methioninamide were converted to the corresponding d,l-acids at the same rate. This thermostable enzyme represents the first reported amidase from a thermophilic actinomycete.     

Dominance of parental genomes in embryonic stem cell/fibroblast hybrid cells depends on the ploidy of the somatic partner

Two dozen hybrid clones were produced by fusion of diploid embryonic stem (ES) cells positive for green fluorescent protein (GFP) with tetraploid fibroblasts derived from DD/c and C57BL-I(I)1RK mice. Cytogenetic analysis demonstrated that most cells from these hybrid clones contained near-hexaploid chromosome sets. Additionally, the presence of chromosomes derived from both parental cells was confirmed by polymerase chain reaction (PCR) analysis of polymorphic microsatellites. All hybrid cells were positive for GFP and demonstrated growth characteristics and fibroblast-like morphology. In addition, most hybrid cells were positive for collagen type I, fibronectin, and lamin A/C but were negative for Oct4 and Nanog proteins. Methylation status of the Oct4 and Nanog gene promoters was evaluated by bisulfite genomic sequencing analysis. The methylation sites (CpG-sites) of the Oct4 and Nanog gene promoters were highly methylated in hybrid cells, whereas the CpG-sites were unmethylated in the parental ES cells. Thus, the fibroblast genome dominated the ES genome in the diploid ES cell/tetraploid fibroblast hybrid cells. Immunofluorescent analysis of the pluripotent and fibroblast markers demonstrated that establishment of the fibroblast phenotype occurred shortly after fusion and that the fibroblast phenotype was further maintained in the hybrid cells. Fusion of karyoplasts and cytoplast derived from tetraploid fibroblasts with whole ES cells demonstrated that karyoplasts were able to establish the fibroblast phenotype of the reconstructed cells but not fibroblast cytoplasts. Thus, these data suggest that the dominance of parental genomes in hybrid cells of ES cell/somatic cell type depends on the ploidy of the somatic partner.     

Occurrence of aminoglycoside transpherase genes in methicillin-resistant strains of Staphylococcus aureus

Fifty MRSA strains originated from clinical specimens were examined by the PCR method, for the presence of three genes: aacA-aphD, aadD oraz aph(3")-IIIa. The obtained results were correlated with the susceptibility of the strains to gentamicin, tobramicin, kanamicin, neomicin, amikacin and netilmicin. The susceptibility results were interpreted according with CLSI and EUCAST guidelines. aacA-aphD gene was found in 34 strains, aadD in 27 strains and aph(3")-IIIa was present in 22 strains. In 19 strains (38%) was present one of the investigated genes, in 29 (58%) strains two genes and in two strains (4%) all three genes were found. The most frequent variant was combination of aacA-aphD and aadD genes.     

Immobilized cytochrome P-450LM2: Dissociation and reassociation of oligomers

Subunit interactions in the purified hexameric cytochrome P-450_LM2 have been studied using covalent binding of one of the 6 protomers to an insoluble matrix. High ionic strength, large-scale pH changes, guanidine chloride and sodium cholate taken at membrane-solubilizing concentrations, had no effect on the aggregation state of the immobilized hemoprotein. SDS caused a 6-fold decrease in the amount of the bound cytochrome. Non-ionic detergents (Emulgen 913, octylglucoside, Tritons) induced hexamer dissociation. In the presence of Emulgen 913 (> 0.2%), monomers and immobilized dimers were obtained as cytochrome P-450 was studied in an aqueous medium and in the immobilized state, respectively. Immobilized dimers could be reconstituted to hexamers by treatment with an excess of solubilized monomers after removal of the detergent. In the presence of various phospholipids, which increased the immobilized cytochrome P-450_LM2 demethylase activity and induced characteristic spectral changes, no hexamer dissociation was shown. The data obtained are thus in agreement with the suggestion that hexameric arrangement is inherent in the cytochrome P-450 when it is bound to the native membranes.     

Alginate/chitosan hydrogels as perspective transport systems for cefotaxime

This work reports synthesis of pH-responsive alginate/chitosan hydrogel spheres with the average diameter of 2.0 ± 0.05 mm, which contain cefotaxime that is an antibiotic of the cefalosporine group. The spheres provided the cefotaxime encapsulation efficiency of 95 ± 1%. An in vitro release of cefotaxime from the spheres in the media that simulate human biological fluids in peroral delivery conditions was found to be a pH-dependent process. The analysis of cefotaxime release kinetics by the Korsmeyer–Peppas model revealed a non-Fickian mechanism of its diffusion, which may be related to intermolecular interactions occurring between the antibiotic and chitosan. Conductometry, UV spectroscopy, and IR spectroscopy were used to study complexation of chitosan with cefotaxime in aqueous media with varied pH, characterize the composition of the complexes, and calculate their stability constants. The composition of the cefotaxime–chitosan complexes was found to correspond to the 1.0:4.0 and 1.0:2.0 molar ratios of the components at pH 2.0 and 5.6, respectively. Quantum chemical modeling was used to evaluate energy characteristics of chitosan–cefotaxime complexation considering the influence of a solvent.