A simple PCR-based macroarray system for detection of multiple gene markers in the identification of priority enterohemorrhagic Escherichia coli

Enterohemorrhagic Escherichia coli (EHEC) strains bearing the O antigenic determinants O157, O26, O111, O103, and O145 have a high rate of association with foodborne illness worldwide. To expand Canadian food inspection capability, a cloth-based hybridization array system (CHAS) was developed for the identification and characterization of priority EHEC. This method targets key virulence genes (eae, hlyA, vt1, and vt2) plus the rfbE gene specifying the O157 antigenic determinant, and the wzx genes specifying the O26, O111, O103, and O145 determinants. Multiplex PCR products incorporating a digoxigenin label were detected by hybridization with an array of specific oligonucleotide probes immobilized on a polyester cloth support, with subsequent immunoenzymatic assay of the captured amplicons. This method identified the relevant markers in 85 different strains bearing various combinations of the target genes (virulence and priority O-antigen markers). None of the target genes was detected in 26 different strains of other E. coli and non-E. coli bacteria. The CHAS demonstrated 100% inclusivity and 100% exclusivity characteristics, with respect to detection of the various markers among different bacterial strains. The CHAS demonstrated 100% inclusivity and 100% exclusivity characteristics, with respect to detection of the markers among various target and nontarget bacteria. The entire procedure could be completed in less than 5 h, and is useful for the identification of priority EHEC colonies isolated from foods by using enrichment culture techniques.     

Residual stresses in cold drawn pearlitic rods

Residual stress profiles in the three principal directions in a cold-drawn pearlitic rod were calculated by a three-dimensional finite element simulation and measured by synchrotron X-ray diffraction. It has been shown that anisotropy of cold-drawn pearlite has to be considered for accurate simulations of residual stresses of steel wires.     

Detection of Escherichia coli O157 in foods by a novel polymyxin-based enzyme-linked immunosorbent assay

An enzyme-linked immunosorbent assay (ELISA) system was developed using polymyxin immobilized in the wells of a microtiter plate as a high-affinity adsorbent for Escherichia coli O157 lipopolysaccharide (LPS) antigens. Extracts from cell suspensions were reacted with polymyxin-coated microwells followed by immunoenzymatic detection of captured LPS antigens using a commercially available anti-E. coli O157 antibody-peroxidase conjugate and a 3,3',5,5'-tetramethylbenzidine substrate. The polymyxin ELISA was highly sensitive and specific for E. coli strains bearing the O157 antigen. When this ELISA was combined with enrichment, results were in complete agreement with those of standard culture techniques for the detection of this pathogen in a variety of artificially inoculated and naturally contaminated foods. The polymyxin ELISA is a simple and inexpensive assay for E. coli O157 with a 96-well microtiter plate format, making this system ideally suited for processing large numbers of samples.     

Rapid discrimination of Salmonella isolates by single-strand conformation polymorphism analysis

A molecular typing technique was developed for the differentiation of Salmonella isolates based on single-strand conformation polymorphism (SSCP) analysis of amplicons generated by PCR. Amplicons from parts of the fimA (both the 5' and 3' ends), mdh, invA, and atpD genes were generated separately from a panel of Salmonella strains representing Salmonella bongori, and four subspecies and 17 serovars of Salmonella enterica. These amplicons were subjected to SSCP analysis for differentiation of the salmonellae on the basis of different conformational forms arising due to nucleotide sequence variations in the target genes. Several distinct SSCP banding patterns (a maximum of 14 each for atpD and fimA 3' end) were observed with this panel of Salmonella strains for amplicons generated from each target gene. The best discrimination of Salmonella subspecies and serovar was achieved from the SSCP analysis of a combination of at least three gene targets: atpD, invA, and either mdh or fimA 3' end. This demonstrates the applicability of SSCP analysis as an important additional method to classical typing approaches for the differentiation of foodborne Salmonella isolates. SSCP is simple to perform and should be readily transferable to food microbiology laboratories with basic PCR capability.     

Self-dual codes and modules for finite groups in characteristic two

Using representation theoretical methods we investigate self-dual group codes and their extensions in characteristic 2. We prove that the existence of a self-dual extended group code heavily depends on a particular structure of the group algebra KG which can be checked by an easy-to-handle criteria in elementary number theory. Surprisingly, in the binary case such a code is doubly even if the converse of Gleason's theorem holds true, i.e., the length of the code is divisible by 8. Furthermore, we give a short representation theoretical proof of an earlier result of Sloane and Thompson which states that a binary self-dual group code is never doubly even if the Sylow 2-subgroups of G are cyclic. It turns out that exactly in the case of a cyclic or Klein four group as Sylow 2-subgroup doubly even group codes do not exist.     

4-1BBL as a Mediator of Cross-Talk between Innate,Adaptive, and Regulatory Immunity against Cancer

The ability of tumor cells to evade the immune system is one of the main challenges we confront in the fight against cancer. Multiple strategies have been developed to counteract this situation, including the use of immunostimulant molecules that play a key role in the anti-tumor immune response. Such a response needs to be tumor-specific to cause as little damage as possible to healthy cells and also to track and eliminate disseminated tumor cells. Therefore, the combination of immunostimulant molecules and tumor-associated antigens has been implemented as an anti-tumor therapy strategy to eliminate the main obstacles confronted in conventional therapies. The immunostimulant 4-1BBL belongs to the tumor necrosis factor (TNF) family and it has been widely reported as the most effective member for activating lymphocytes. Hence, we will review the molecular, pre-clinical, and clinical applications in conjunction with tumor-associated antigens in antitumor immunotherapy, as well as the main molecular pathways involved in this association.     

Detection of group D salmonellae including Salmonella Enteritidis in eggs by polymyxin-based enzyme-linked immunosorbent assay

A high-throughput, rapid method was devised for the detection of Salmonella Enteritidis in egg products. For each target organism, preenrichment in nutrient broth was followed by selective enrichment in Rappaport-Vassiliadis soya peptone and tetrathionate brilliant green broths or by plating on modified semisolid Rappaport Vassiliadis (MSRV) agar medium. The presence of Salmonella Enteritidis was determined by subjecting portions of the selective broth cultures or swarming growth on MSRV medium to an enzyme-linked immunosorbent assay (ELISA) procedure using polymyxin immobilized in the wells of a microtiter plate as a high-affinity adsorbent for lipopolysaccharide (LPS) antigens. Sample extracts were reacted with polymyxin-coated microwells, and captured LPS antigens were detected immunoenzymatically with a commercially available Salmonella factor O9-specific antibody. The polymyxin-ELISA was 100% sensitive and 100% specific for Salmonella strains bearing the O9 antigen. When the ELISA was combined with enrichment using either the selective broths or plating on MSRV medium, the system was an effective means for detection of Salmonella Enteritidis in artificially inoculated egg products. The polymyxin-ELISA is a simple and inexpensive assay for group D salmonellae (including Salmonella Enteritidis) in a convenient 96-well microtiter plate format, making this system ideally suited for processing large numbers of samples.     

Is the class of cyclic codes asymptotically good?

There is the long-standing question whether the class of cyclic codes is asymptotically good. By an old result of Lin and Weldon, long Bose-Chaudhuri-Hocquenhem (BCH) codes are asymptotically bad. Berman proved that cyclic codes are asymptotically bad if only finitely many primes are involved in the lengths of the codes. We investigate further classes of cyclic codes which also turn out to be asymptotically bad. Based on reduction arguments we give some evidence that there are asymptotically good sequences of binary cyclic codes in which all lengths are prime numbers provided there is any asymptotically good sequence of binary cyclic codes.     

Retinal vascular tree morphology: a semi-automatic quantification

A semi-automatic method to measure and quantify geometrical and topological properties of continuous vascular trees in clinical fundus images is described. Measurements are made from binary images obtained with a previously described segmentation process. The skeletons of the segmented trees are produced by thinning,ff branch and crossing points are identified and segments of the trees are labeled and stored as a chain code. The operator selects a tree to be measured and decides if it is an arterial or venous tree. An automatic process then measures the lengths, areas and angles of the individual segments of the tree. Geometrical data and the connectivity information between branches from continuous retinal vessel trees are tabulated. A number of geometrical properties and topological indexes are derived. Vessel diameters and branching angles are validated against manual measurements and several derived geometrical and topological properties are extracted from red-free fundus images of ten normotensive and ten age- and sex-matched hypertensive subjects and compared with previously reported results.