Direct evidence of lead contamination in wheat tissues from atmospheric deposition based on atmospheric deposition exposure contrast tests.

A field experiment was conducted to assess the atmospheric deposition effects on lead (Pb) contamination in wheat by two contrasting treatments: wheat exposed or not to atmospheric deposition. Plants were housed in a shed during wheat greening for the non-exposed treatment. The Pb contents of wheat during different growth stages, of soil and of atmospheric deposits were analysed and combined with Pb stable isotope data to quantify the contribution of atmospheric deposition and soil to Pb in wheat tissue. The Pb content in atmospheric deposits was significantly higher than those in soil and wheat tissue, and the Pb content in wheat tissue exposed to atmospheric deposition was significantly higher than the Pb content in non-exposed tissue (p < 0.05). The 206Pb/207Pb of soil was significantly higher than the 206Pb/207Pb of atmospheric deposits (p < 0.05), and soil and atmospheric deposition were the two sources of Pb in wheat tissue. Atmospheric deposition was the main source of wheat tissue Pb in the exposed treatment, and most of the wheat tissue Pb, except for that in the stem, also came from atmospheric deposition in the maturing stage. The proportion of Pb from atmospheric deposition in roots, stems and leaves evidently decreased after the shed was erected, and the contribution of Pb from atmospheric deposition to wheat tissue was significantly higher in the exposed treatment than in the non-exposed treatment (p < 0.05). This contrast test directly confirmed that atmospheric deposition was the main source of Pb in the wheat tissues. Therefore, taking measures to reduce the absorption of Pb by wheat from atmospheric deposition can effectively ensure food safety.

Influence of matured compost inoculation on sewage sludge composting: Enzyme activity, bacterial and fungal community succession.

The influence of matured compost inoculation during sewage sludge with sawdust composting was assessed. Mature compost reduced the heating rate, thermophilic phase, peak temperature, and volatile solid degradation rate, with no significant effect on pH and germination index. Matured compost addition also increased the cellulase, peroxidase, arylsulfatase, and urease contents during the mesophilic phase, and increased the urease content but decreased the cellulase, peroxidase, protease, and arylsulfatase contents during the cooling phase, with no significant effect on enzyme activities at the thermophilic phase. Matured compost increased the diversity of bacteria during the mesophilic and thermophilic phases, but reduced the fungal diversity throughout composting. Matured compost significantly improved uniformity of the bacterial community and affected the structure of the bacterial and fungal communities, while changing the correlation between some functional microorganisms and enzyme activities. These results provide guidance for optimizing the composting process when matured compost as bulking agent.

[Study on the application of absorption spectrum to the treatment of landfill leachate by membrane technology].

Molecular weight (MW) distributions of organics in the Bei Shenshu landfill leachate and their permeation from membranes were determined and studied by absorption spectrum, and the removal rates of organics with various molecular weight were measured. A new FTIR preparation method of wastewater sample used in the determination of landfill leachate was proposed in the present paper. The results showed that the aromatics in landfill leachate were mainly related to the organics with MW < 2 500, whereas the distribution of total organics was dispersal comparatively. The removal rates of various humic compounds and oils in landfill leachate were estimated in accordance with the change in FTIR absorbance of permeation from membranes at three characteristic wave numbers 2 930, 2 960 and 3 030 cm(-1), indicating that the defined membrane treatment process can removed organics with relevant MW fractions effectively.

Effect of disruption of Staphylococcus aureus PBP4 gene on resistance to beta-lactam antibiotics.

Penicillin-binding proteins (PBPs) mediate susceptibility to beta-lactam antibiotics. PBP 4, although not essential for survival, has been associated with low-level resistance to beta-lactam antibiotics. To determine its contribution to survival of Staphylococcus aureus cells exposed to beta-lactams, the PBP 4 gene (pbp4) was disrupted and then complemented in the methicillin-susceptible strain RN4220 and the homogeneous methicillin-resistant strain COL. Depending on the antibiotic tested, the presence or absence of an intact pbp4 has no effect or only a modest effect on growth measured by population analysis. These data indicate that PBP 4 is a relatively unimportant target of beta-lactams not only in methicillin-susceptible but also methicillin-resistant S. aureus.

[QSAR/QSPR for predicting the toxicity of imidazolium ionic liquids].

Ionic liquids have received lots of attention due to their physical and chemical characteristics. They are honoured the sustainable "Green Solvent". In this paper, the QSPR/QSAR (quantitative structure-property/activity relationships) method was used to study the quantitative relationship between the toxicity and structure of 43 kinds of imidazolium ionic liquids, 10 kinds of substances were used to carry out the external test. The model contains six structural descriptors selected from heuristic method, and R2, R2(CV), F and S2 of the model were 0.921, 0.894, 70.35, 0.098 respectively. Test set was used to conduct external validation, and the R2 was 0.952. The result showed that this model had good reliability, and can be used to predict the toxicity of imidazolium ionic liquids.

[Prevalence of food allergy in children under 2 years of age in three cities in China].

OBJECTIVE: To estimate the prevalence and clinical features of food allergy in children aged 0 - 2 years. METHOD: From January to February, 2009 and January to May, 2010, all well-infants and young children between the age of 0 and 2 years attending routine health visits at the Department of Primary Child Care, in Chongqing, Zhuhai and Hangzhou were invited to participate in the study. Parents completed questionnaires and all children were skin prick tested (SPT) to a panel of 10 foods (egg white, egg yolk, cow's milk, soybean, peanut, wheat, fish, shrimp, orange and carrot). Based on the results of SPT and medical history, the subjects under went the suspected food elimination and oral food challenge under medical supervision. Food allergy was confirmed by the food challenge test. RESULT: Totally 1687 children were recruited by the consent of their parents. Of 1687 children approached, 1604 (550 of Chongqing, 573 of Zhuhai and 481 of Hangzhou) fulfilled the study criteria for diagnosing food allergy. One hundred children were confirmed to have challenge-proven food allergy in 3 cities (40 of Chongqing, 33 of Zhuhai and 27 of Hangzhou). The prevalence of food allergy in 0-2 years old children in Chongqing was 7.3%, in Zhuhai was 5.8% and in Hangzhou was 5.5%. There was no significant difference in the prevalence of food allergy in children under 2 years among the three cities, and the average prevalence for food allergy in children under 2 years was 6.2%. Egg (3.0% - 4.4%) was the most common allergen, followed by cow's milk (0.83% - 3.5%), shrimp (0.17% - 0.42%) and fish (0.17% - 0.21%). CONCLUSION: The prevalence of food allergy in 0 - 2 years old children in China was 5.5% - 7.3%. There was no significant difference in the prevalence of food allergy in children under 2 years of age among the three cities. Egg was the most common allergen, followed by cow's milk, shrimp and fish.

[Comparative evaluation of Hebei HIV-1 p24 kit for the detection of human immunodeficiency virus].

OBJECTIVE: To probe into the feasibility of screening anti-HIV compounds by using HIV-1 p24 detection kit made by Hebei Medical University. METHODS: The sensitivity, reproducibility and efficacy of the Hebei p24 kit were evaluated compared with the commercially available Vironostika HIV-1 Antigen Microelisa System (Biomerieux). RESULTS: Hebei p24 kit had high sensitivity and good reproducibility. In vitro screening demonstrated that there was no statistically significant difference (P greater than 0.05) between these two kits in assessing anti-HIV compounds. CONCLUSION: Hebei p24 kit could be used as an easily affordable alternative method for detection of HIV-1 in screening anti-HIV compounds.

Characterization of a human rhomboid homolog, p100hRho/RHBDF1, which interacts with TGF-alpha family ligands.

The activity of the TGF-alpha-like ligand Spitz in Drosophila depends on Rhomboid, a seven-transmembrane spanning protein that resides in the Golgi and acts as a serine protease to cleave Spitz, thereby releasing the soluble ligand. Several rhomboids in Drosophila have been implicated in the processing of TGF-alpha-like ligands, and consequent EGF receptor activation. The larger number of TGF-alpha-like ligands in vertebrates raises the possibility that they too might be subject to regulation by rhomboid-like proteins. We present the cDNA cloning and polypeptide sequence of an atypically long human rhomboid, which, based on the absence of critical residues for serine protease activity, is not predicted to act as a serine protease. We examined its tissue distribution, in comparison with TGF-alpha and the TGF-alpha-related protein HB-EGF, and the EGF/TGF-alpha receptor, in mouse embryo. This rhomboid, named p100(hRho) or RHBDF1, is a seven-transmembrane protein with a long N-terminal cytoplasmic extension that comprises half of the polypeptide sequence, and is found in the endoplasmic reticulum and Golgi, but not on the cell surface. It is expressed as two forms with different lengths, forms dimers and interacts with TGF-alpha ligands through a luminal interaction with the EGF core ectodomain. Finally, we evaluated the function of p100(hRho)/RHBDF1 in Drosophila, demonstrating that the short, but not the full-length form has functional activity. The characterization of this protein extends our understanding of the rhomboid family of regulatory proteins.

PBP 2a mutations producing very-high-level resistance to beta-lactams.

Resistance to the beta-lactam class of antibiotics in methicillin-resistant Staphylococcus aureus (MRSA) is mediated by PBP 2a, a synthetic bacterial cell wall penicillin-binding protein with a low affinity of binding to beta-lactams that is encoded by mecA. Beta-lactams that bind to PBP 2a with a high affinity and that are highly active against MRSA are under development. The potential for the emergence of resistance to such compounds was investigated by passage of homogeneous MRSA strain COL in L-695,256, an investigational carbapenem. A highly resistant mutant, COL52, expressed PBP 2a in which a two-amino-acid deletion mutation and three single-amino-acid substitution mutations were present. To examine the effects of these mutations on the resistance phenotype and PBP 2a production, plasmids carrying (i) PBP 2a with two or three of the four mutations, (ii) wild-type PBP 2a, or (iii) COL52 PBP 2a were introduced into methicillin-susceptible COL variants COLnex and COL52ex, from which the staphylococcus cassette chromosome mec (SCCmec) has been excised, as indicated by the "ex" suffix. Two amino acids substitutions, E-->K(237) within the non-penicillin-binding domain and V-->E(470) near the SDN(464) conserved penicillin-binding motif in the penicillin-binding domain in COL52, were important for high-level resistance. The highest level of resistance was observed when all four mutations were present. The emergence of PBP 2a-mediated resistance to beta-lactams that bind to PBP 2a with a high affinity is likely to require multiple mutations in mecA; chromosomal mutations appear to have a minor role.

Jumping the barrier to beta-lactam resistance in Staphylococcus aureus.

Although the staphylococcal methicillin resistance determinant, mecA, resides on a mobile genetic element, staphylococcus cassette chromosome mec (SCCmec), its distribution in nature is limited to as few as five clusters of related methicillin-resistant Staphylococcus aureus (MRSA) clones. To investigate the potential role of the host chromosome in clonal restriction of the methicillin resistance determinant, we constructed plasmid pYK20, carrying intact mecA, and introduced it into several methicillin-susceptible Staphylococcus aureus strains, five of which were naive hosts (i.e., mecA not previously resident on the host chromosome) and five of which were experienced hosts (i.e., methicillin-susceptible variants of MRSA strains from which SCCmec was excised). We next assessed the effect of the recipient background on the methicillin resistance phenotype by population analysis, by assaying the mecA expression of PBP2a by Western blot analysis, and by screening for mutations affecting mecA. Each experienced host transformed with pYK20 had a resistance phenotype and expressed PBP2a similar to that of the parent with chromosomal SCCmec, but naive hosts transformed with pYK20 selected against its expression, indicative of a host barrier. Either inducible beta-lactamase regulatory genes blaR1-blaI or homologous regulatory genes mecR1-mecI, which control mecA expression, acted as compensatory elements, permitting the maintenance and expression of plasmid-carried mecA.

[Preparation of bispecific monoclonal antibody against HIV p24 and human group A erythrocytes].

AIM: To prepare bispecific monoclonal antibody (bsmAb) against HIV p24 and human group A erythrocytes, and set up an indirect hemagglutination test for detecting HIV p24. METHODS: Hybridoma cells 2-E(4) secreting anti-HIV p24 mAb and hybridoma cells S(2) secreting anti-human group A erythrocyte mAb were naturalized with 8-Ag and 5-BrdU respectively, making them sensitive to HAT. Then the two hybridoma cells sensitive to HAT were fused by routine method and hybrid-hybridoma cells secreting the bsmAb against HIV p24 and human group A erythrocytes were screened. The bsmAb was used to establish an indirect hemagglutination test for detecting HIV p24. RESULTS: 6 hybrid-hybridoma cell lines were obtained. An indirect hemagglutination test for detecting HIV p24 was set up by using the bsmAb, and its sensitivity reached 400 ng/L. CONCLUSION: The bsmAb against HIV p24 and human group A erythrocytes is prepared and a rapid indirect hemagglutination test for detecting HIV p24 is developed by using the purified bsmAb.

Crystal structures of the Apo and penicillin-acylated forms of the BlaR1 beta-lactam sensor of Staphylococcus aureus.

Staphylococcus aureus is among the most prevalent and antibiotic-resistant of pathogenic bacteria. The resistance of S. aureus to prototypal beta-lactam antibiotics is conferred by two mechanisms: (i) secretion of hydrolytic beta-lactamase enzymes and (ii) production of beta-lactam-insensitive penicillin-binding proteins (PBP2a). Despite their distinct modes of resistance, expression of these proteins is controlled by similar regulation systems, including a repressor (BlaI/MecI) and a multidomain transmembrane receptor (BlaR1/MecR1). Resistance is triggered in response to a covalent binding event between a beta-lactam antibiotic and the extracellular sensor domain of BlaR1/MecR1 by transduction of the binding signal to an intracellular protease domain capable of repressor inactivation. This study describes the first crystal structures of the sensor domain of BlaR1 (BlaRS) from S. aureus in both the apo and penicillin-acylated forms. The structures show that the sensor domain resembles the beta-lactam-hydrolyzing class D beta-lactamases, but is rendered a penicillin-binding protein due to the formation of a very stable acyl-enzyme. Surprisingly, conformational changes upon penicillin binding were not observed in our structures, supporting the hypothesis that transduction of the antibiotic-binding signal into the cytosol is mediated by additional intramolecular interactions of the sensor domain with an adjacent extracellular loop in BlaR1.