Using an enrichment protocol, we isolated 16 gram-negative, multidrug-resistant strains of known or opportunistic bacterial pathogens from the Salmon River in south-central British Columbia from 2005 to 2009, and investigated the genetic basis of their resistance to a variety of antibiotics. Of the 16 strains, 13 carried class 1 integrons and three carried class 2 integrons. Genes found in cassettes associated with the integrons included those for dihydrofolate reductases (dfrA1, dfrA12, dfrA17, and dfrB7), aminoglycoside adenyltransferases (aadA1, aadA2, aadA5, and aadB), streptothricin acetyltransferase (sat), and hypothetical proteins (orfF and orfC). A new gene cassette of unknown function, orf1, was discovered between dfrA1 and aadA5 in Escherichia sp. Other genes for resistance to tetracycline, chloramphenicol, streptomycin, and kanamycin (tetA, tetB, tetD; catA; strA-strB; and aphA1-Iab, respectively) were outside the integrons. Several of these resistance determinants were transferable by conjugation. The detection of organisms and resistance determinants normally associated with clinical settings attest to their widespread dispersal and suggest that regular monitoring of their presence in aquatic habitats should become a part of the overall effort to understand the epidemiology of antibiotic resistance genes in bacteria.

In the present study, we analyzed the oxidative stress related indices and immune related gene expression of zebrafish embryos after a short-term exposure to various concentrations of di-n-butyl phthalate (DBP), diethyl phthalate (DEP) and their mixture (DBP-DEP) from 4 h post-fertilization (hpf) to 96 hpf. Exposure to the chemicals was found to enhance the production of reactive oxygen species (ROS) and lipid peroxidation (LPO) in a concentration-dependent manner. Simultaneously, adaptive responses to DBP/DEP-induced oxidative stress were observed. The activity of antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) were all increased in a concentration-dependent manner. The transcription of innate immune related genes including interferon gamma (IFN gamma), interleukin-1 beta (1L1 beta), Myxovirus resistance (Mx), tumor necrosis factor a (TNF alpha), CC-chemokine, CXCL-clc, lysozyme (Lyz) and complement factor C3B (C3) were up-regulated upon DBP, DEP and their mixture exposure, suggesting the induction of immune response. In addition, co-exposure to DBP-DEP also induced antioxidant defense and immune response in zebrafish embryo. The results demonstrat that DBP/DEP exposure could induce the antioxidant and immune responses in zebrafish embryos. (C) 2013 Elsevier Inc. All rights reserved.

Petroporphyrins were extracted from two typical Chinese heavy crude oils, Tahe and Du84, and then purified by silica gel chromatography, followed by demetallization by methyl sulfonic acid. The extraction and purification were monitored using ultraviolet-visible spectroscopy, and the final petroporphyrins were analyzed using laser desorption ionization time-of-flight mass spectrometry. The soft ionization mass spectrometric technique proved to be effective for the characterization of petroporphyrins. The results show that, in Tahe crude oil, vanadium is more abundant than nickel and 75% of the vanadyl porphyrins are of the etioporphyrin (ETIO) type, with remaining fractions attributed to deoxophylloerythroetioporphyrin (DPEP) and benzo types. The Sigma DPEP/Sigma ETIO ratio was found to be 0.18. In contrast, the Du84 heavy crude oil contains more abundant nickel than vanadium, with its nickel porphyrins comprising mainly DPEP and ETIO types, with each occupying 45%, and the tetrahydrobenzo-DPEP and benzo types attributed to the remaining 10%. The Sigma DPEP/Sigma ETIO ratio is similar to 1.1. These results suggest that the Tahe crude oil has higher thermal maturity than the Du84 crude oil, and the former is in its mature stage, whereas the latter is in its evolution stage.

Conformational orientations of a mouse monoclonal antibody to the, unit of human chorionic gonadotrophin (anti-beta-hCG) at the hydrophilic silicon oxide/water interface were investigated using atomic force microscopy (AFM) and neutron reflectivity (NR). The surface structural characterization was conducted with the antibody concentration in solution ranging from 2 to 50 mg center dot L(-1) with the ionic strength kept at 20 mM and pH = 7.0. It was found that the antibody adopted a predominantly "flat-on" orientation, with the Fc and two Fab fragments lying flat on the surface. The AFM measurement revealed a thickness of 30-33 angstrom of the layer formed in contact with 2 mg, L(-1) antibody in water, but, interestingly, the flat-on antibody molecules formed small nonuniform clusters equivalent to 2-15 antibody molecules. Parallel AFM scanning in air revealed even larger surface clusters, suggesting that surface drying induced further aggregation. The AFM study thus demonstrated that the interaction between protein and the hydrophilic surface is weak and indicated that surface aggregation can be driven by the attraction between neighboring protein molecules. NR measurements at the solid/water interface confirmed the flat-on layer orientation of adsorbed molecules over the entire concentration range studied. Thus, at 2 mg, L(-1), the adsorbed antibody layer was well represented by a uniform layer with a thickness of 40 angstrom. This value is thicker than the 30-33 angstrom observed from AFM, suggesting possible layer compression caused by the tip tapping. An increase in the antibody concentration to 10 mg, L(-1) led to increasing surface adsorption. The corresponding layer structure was well represented by a three-layer model consisting of an inner sublayer of 10 angstrom, a middle sublayer of 30 angstrom, and an outer sublayer of 25 angstrom, with the protein volume fractions in each sublayer being 0.22, 0.42, and 0.10, respectively. The structural transition can be interpreted as a twisting and tilting of segments of the adsorbed molecules, driven by an electrostatic repulsion between them that increases with the surface packing density. Hindrance of antigen access to antibody binding sites, resulting from the change in surface packing, can account for the decrease in antigen binding capacity (AgBC) with increasing surface density of the antibody that is observed.