No abstract

Large-scale expression of β-adrenergic receptor (β-AR) in functional form is necessary for establishment of receptor assays for detecting illegally abused β-adrenergic agonists (β-agonists). Cell-based heterologous expression systems have manycritical difficulties in synthesizing this membrane protein, such as low protein yields and aberrant folding. To overcome these challenges, the main objective of the present work was to synthesize large amounts of functional β-AR in a cell-free system based on Escherichia coli extracts. A codon-optimized porcine β-AR gene (codon adaptation index: 0.96) suitable for high expression in E. coli was synthesized and transcribed to the cell-free system, which contributed to increase the expression up to 1.1 mg/ml. After purification using Ni-affinity chromatography, the bioactivity of the purified receptor was measured by novel enzyme-linked receptor assays. It was determined that the relative affinities of the purified β-AR for β-agonists in descending order were as follows: clenbuterol > salbutamol > ractopamine. Moreover, their IC values were 45.99, 60.38, and 78.02 µg/liter, respectively. Although activity of the cell-free system was slightly lower than activity of systems based on insect and mammalian cells, this system should allow production of β-AR in bulk amounts sufficient for the development of multianalyte screening methods for detecting β-agonist residues.

Background: Pneumomediastinum is an emergency pediatric disease. A severe tension pneumomediastinum can result in respiratory and circulatory dysfunction. However, few papers describe surgical methods to treat tension pneumomediastinum in a normative manner.Methods: We did a case-control study of 104 pediatric patients with tension pneumomediastinum and comorbid type II respiratory failure. Fifty-two patients were treated with a drainage strip being inserted into the pre-tracheal space while other 52 patients were treated without drainage. Arterial blood pO2 and pCO2 after 30 minutes and 12 hours of mechanical ventilation, chest radiography results after 12 hours of mechanical ventilation, and the length of stay in PICU of the two groups were analyzed by paired t-tests and Chi-square.Results: Chest radiography after 12 hours of mechanical ventilation showed that the pneumomediastinum basically disappeared in the surgery group but did not decrease significantly in the control group. The arterial blood pCO2 after 12 hours of mechanical ventilation and the length of stay in PICU were significantly lower in the surgery group than in the control group (p<0.001, p<0.001), while the arterial blood pO2 after 12 hours of mechanical ventilation was significantly higher in the surgery group than in the control group (p<0.001). There were no significant intergroup differences in other variables. No recurrence occurred in either group during 7–14 days after discharge, and all patients recovered.Conclusions: Our method for draining tension pneumomediastinum improved respiratory function and shortened the length of stay in PICU.Trial registration: ChiCTR2000039496. Date of registration: 2021/2/25 (retrospectively registered).

Molecular imprinting polymer (MIP) has been increasingly employed for sulfonylurea herbicides (SUHs) detection in different matrices. A novel MIP that was effective as a highly class-selective sorbent in molecularly imprinted solid-phase extraction (MISPE) was successfully prepared for isolation and purification of SUHs, namely, metsulfuron-methyl, chlorsulfuron, chlorimuron-ethyl, prosulfuron, and pyrazosulfuron-ethyl, in rice, corn and soybean samples. The MIP was synthesized by precipitation polymerization using metsulfuron-methyl as the template, 4-vinylpyridine as the functional monomer, ethylene glycol dimethacrylate as the crosslinker, and MeCN as the porogen. The polymerization system of the MIP was optimized, and its adsorption performances were evaluated by comparing its adsorption isotherms and adsorption kinetics with those of a non-imprinted polymer (NIP). Following MISPE for extracting and enriching SUHs from rice, corn and soybean samples, high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was performed. Acceptable recoveries were observed at SUHs contaminant concentrations of 10, 20 and 40 μg/L: from 77.56 to 99.81%, with relative standard deviations of <13.8% (n = 5) for all samples. The limits of detection for the five SUHs were 0.21-0.26 μg/L. The results demonstrated that the proposed MISPE-HPLC-MS/MS method is an effective approach for the simultaneous and sensitive determination of the five SUHs in rice, corn and soybean samples.