PREPARATION AND CHARACTERIZATION OF SELF-HEALING MAGNETORHEOLOGICAL ELASTOMERS

Magnetorheological elastomers (MREs) are a kind of active control smart material, and their critical problem is that their ferromagnetic particles are too large, which causes holes to develop and results in MREs with poor mechanical performance and fatigue resistance. In this work, liquid butadiene acrylonitrile rubber (NBR)-synthesized phenolic resin microcapsules were synthesized and applied to MREs as a self-healing agent, effectively reducing the number of holes caused by ferromagnetic particles. The structure of the self-healing agent was determined by Fourier transform infrared (FT-IR) spectroscopy, thermal gravimetric analysis (TGA), and scanning electron microscopy (SEM). The results indicated that a self-healing agent was successfully synthesized, the core of the capsule was spherical liquid nitrile rubber, and the wall of the capsule was composed of phenolic resin microspheres. Furthermore, the SEM images of the MREs showed that the number of cavities caused by ferromagnetic particles was greatly reduced after the addition of the self-healing agent, and the X-ray photoelectron spectroscopy (XPS) results of the MREs indicated the formation of a chemical bond between Fe and O. In addition, the mechanical properties and fatigue resistance of the MRE materials with the self-healing agent were improved. Under 100% strain and with the same number of cycles, the crack growth rate of MREs without self-healing agent is faster by about 329%, and the crack length is longer by about 220% than those of MREs with self-healing agent.

Lycopene protects pancreatic acinar cells against severe acute pancreatitis by abating the oxidative stress through JNK pathway

This study investigated the anti-oxidative and anti-inflammatory effects of lycopene on severe acute pancreatitis (SAP) in both in vivo and in vitro models. Utilizing a rat model, we found that lycopene administration protected against SAP, as indicated by the decreased levels of serum amylase and C-reactive protein. Pathological changes were alleviated by pretreatment with lycopene. The serum levels of tumor necrosis factor-α, interleukin-6, macrophage inflammatory protein-1α, and monocyte chemotactic protein-1 were decreased by lycopene. The decreased reactive oxygen species (ROS) content in the pancreatic tissues of the lycopene-treated group were indirectly evaluated by measuring the levels of myeloperoxidase, lipid peroxidase, and superoxide dismutase. Lycopene protected acinar cells against necrosis and apoptosis by relieving the mitochondrial and endoplasmic stress caused by ROS which was shown in electron microscopy and immunohistochemistry staining of active nuclear factor-κB p65. The protective effect was also observed in a simulated SAP model in a rat acinar cell line. ROS and apoptotic staining were compared between groups. Lycopene exerts protective effects against SAP in rats that may be related to its anti-inflammatory property through inhibiting the expression of damage-associated molecular patterns, and anti-oxidative property which can thus maintain cellular homeostasis and prevent the phosphorylation of JNK pathway.

Detection of resistance phenotype and genotype of avian Escherichia coli in Hebei Province

We investigated the resistance of avian Escherichia coli to commonly used clinical antibiotics in Hebei Province. It is of significance to reveal the extent and mechanism of drug resistance, as well as to prevent and control colibacillosis. We investigated the resistance of 132 E. coli isolates to 5 kinds of antibiotics (including β-lactams, aminoglycosides, tetracyclines, sulfonamides, and chloramphenicol) using the Kirby-Bauer drug susceptibility test, and resistance genes were detected by PCR. The results showed that the E. coli had a higher resistance rate to ampicillin, cephalotin, gentamicin, streptomycin, tetracycline, doxycycline, sulfamethoxazole trimethoprim, sulfamonomethoxine, and florfenicol, but it had higher sensitive rate to cefepime, imipenem, spectinomycin, and minocycline. Of the resistance genes, the TEM, aac(3)-IIa, tetA, Sul1, Sul2, and forl had higher positive rates. Therefore, drug resistance of avian E. coli in Hebei Province is very serious. The resistance mechanisms may include structure changes of the target enzyme mediated by multiresistance genes, and resulting in reduced affinity and increased efflux of antibiotics.

Survey on tetracycline resistance and antibiotic-resistant genotype of avian Escherichia coli in North China

The experiment was performed to investigate the tetracycline resistance and antibiotic-resistant genotype of avian Escherichia coli in North China and to analyze the correlation of genotype and phenotype. The resistance of 164 E. coli isolates (from Beijing, Tianjin, inner Mongolia, Shanxi, and Hebei regions of China) to tetracycline, doxycycline, and minocycline was investigated by using a drug susceptibility test. The results show that the rate of resistance to tetracycline antibiotics was 89.63% (147/164). The higher resistance rate was 84.76% (139/164) to tetracycline and 70.12% (115/164) to doxycycline, and the lowest resistance rate was 4.88% (8/164) to minocycline. The distribution of tetracycline resistance (Tcr) genes (tetA, tetB, tetC, and tetM) in avian E. coli isolates was detected by PCR. Of the isolates, 82.32% (135/164) carried tetracycline resistance genes. The positive rates of tetA, tetB, and tetM were 57.93% (95/164), 38.41% (63/164), and 10.97% (18/164), respectively. No tetC was amplified in avian E. coli isolates. The total positive rate of resistance genes (82.32%) was almost equal to the total rate of resistance to tetracycline antibiotics (89.63%). Thus, the positive rate of genotype was basically in line with that of phenotype for tetracycline resistance. The tetracycline resistance genes are widely distributed in E. coli and their main resistance mechanism to tetracycline is the active efflux effect mediated by tetA and tetB.

Molecular epidemiological survey on aminoglycoside antibiotics-resistant genotype and phenotype of avian Escherichia coli in North China

Monitoring drug resistance in Escherichia coli is important for prevention and treatment of colibacillosis. To choose effective drugs to prevent and control avian colibacillosis in North China, we investigated resistance of 205 E. coli isolates (from Beijing, Tianjin, inner Mongolia, Shanxi, and Hebei regions) to commonly used clinical aminoglycoside antibiotics using a drug susceptibility test. The results show that the isolates had varying degrees of resistance to kanamycin, gentamicin, streptomycin, amikacin, neomycin, and spectinomycin. Particularly, the resistance rates of the former 3 antibiotics exceeded 40%. To explore the reasons for wide drug resistance, aminoglycosides modifying enzymes (AME) genes, which are important in generation of aminoglycoside resistance, were detected by PCR. Of the isolates, 60.98% carried AME genes and 38.05% carried commensal multidrug resistance genes. Therefore, resistance of avian E. coli to aminoglycoside antibiotics is very serious in North China, perhaps due to the existence of resistance genes.

Is FCGR2A a susceptibility gene to systemic lupus erythematosus in Chinese?

Recent genome-wide association scans and replication studies reinforce that FCGR2A is a susceptibility gene in systemic lupus erythematosus (SLE) in Caucasians. However, previous case control studies denied such conclusions in Chinese people. Besides genetic heterogeneity among different ethnicities, copy number variation (CNV), non-homogenous phenotypes and insufficient power may be confounders. We performed a case control study with 1066 Chinese (589 SLE patients and 477 healthy controls) and a meta-analysis based on 2328 SLE patients and 2313 healthy controls. FCGR2A CNV and FCGR2A131H/R [rs1801274] were detected by TaqMan assays. No variation of copy numbers of FCGR2A gene was found in Chinese. A further case control study suggested a dose-response character for FCGR2A131H/R and it affected disease activity, severity and prognosis. Finally, meta-analysis indicated FCGR2A that was a susceptibility gene to SLE in Chinese with an odds ratio of 1.094 and population attributable risk proportion of (PARP) 0.031. By an integrative strategy, we validate that FCGR2A bears no population-specific CNV. FCGR2A131H/R contributes to SLE susceptibility in Chinese, and affects disease activity, severity and prognosis. The undetected association in Chinese derives from under-power rather than any methodological obstacle due to CNV or population-specific genetic effect.