Biosensor based on acetylcholinesterase immobilized onto layered double hydroxides for flow injection/amperometric detection of organophosphate pesticides

We developed a highly sensitive flow injection/amperometric biosensor for the detection of organophosphate pesticides (OPs) using layered double hydroxides (LDHs) as the immobilization matrix of acetylcholinesterase (AChE). LDHs provided a biocompatible microenvironment to keep the bioactivity of AChE, due to the intrinsic properties of LDHs (such as a regular structure, good mechanical, chemical and thermal stabilities, and swelling properties). By integrating the flow injection analysis (FIA) with amperometric detection, the resulting AChE-LDHs modified electrode greatly catalyzed the oxidation of the enzymatically generated thiocholine product, and facilitated the detection automation, thus increasing the detection sensitivity. The analytical conditions for the FIA/amperometric detection of OPs were optimized by using methyl parathion (MP) as a model. The inhibition of MP was proportional to its concentration ranging from 0.005 to 0.3μgmL(-1) and 0.3 to 4.0μgmL(-1) with a detection limit 0.6ngmL(-1) (S/N=3). The developed biosensor exhibited good reproducibility and acceptable stability.     

温度和盐分胁迫对新疆鼠尾草种子萌发的影响

利用控制实验研究了温度和盐分胁迫对新疆鼠尾草种子萌发的影响.结果显示:新疆鼠尾草种子萌发的最适温度为25℃.盐胁迫对新疆鼠尾草种子的萌发均有明显的抑制作用,随着盐浓度的增加,萌发率和萌发速率下降.在适宜萌发温度下,新疆鼠尾草耐盐极限值0.2 mmol/L.     

Manipulation of kynurenine pathway for enhanced daptomycin production in Streptomyces roseosporus

Daptomycin is a cyclic lipopeptide natural product produced by Stretptomyces roseosporus, displaying good bactericidal activity against a wide range of gram‐positive pathogens. Daptomycin contains a 13 amino acid and kynurenine (Kyn) is essential for optimal activity of daptomycin. In this study, we characterized the Kyn pathway in S. roseosporus and investigated its role in supplying precursor for daptomycin biosynthesis. Two genes (dptJ and tdo) coding for tryptophan‐2,3‐dioxgenase existed in the chromosome. dptJ is located in the daptomycin biosynthetic gene cluster, while tdo is in other locus. Disruption of dptJ or tdo resulted in reduced yield by ～50%. The introduction of an additional copy of dptJ but not tdo led to enhanced production of daptomycin by 110%. Furthermore, disruption of kyn encoding kynureninase showed improved daptomycin productivity by 30%. Our results demonstrated that the enhancement of Kyn supply through metabolic engineering approach is an efficient way to increase daptomycin production. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29:847–852, 2013     

Expression and signal regulation of the alternative oxidase genes under abiotic stresses

Plants in their natural environment frequently face various abiotic stresses, such as drought, high salinity, and chilling. Plant mitochondria contain an alternative oxidase （AOX）, which is encoded by a small family of nuclear genes. AOX genes have been shown to be highly responsive to abiotic stresses. Using transgenic plants with varying levels of AOX expression, it has been confirmed that AOX genes are im- portant for abiotic stress tolerance. Although the roles of AOX under abiotic stresses have been extensively studied and there are several excellent reviews on this topic, the differential expression patterns of the AOX gene family members and the signal regulation of AOX gene（s） under abiotic stresses have not been extensively summarized. Here, we review and discuss the current progress of these two important issues.     

The Mitochondrial Genome of Raphanus sativus and Gene Evolution of Cruciferous Mitochondrial Types

To explore the mitochondrial genes of the Cruciferae family, the mitochondrial genome of Raphanus sativus (sat) was sequenced and annotated. The circular mitochondrial genome of sat is 239,723 bp and includes 33 protein-coding genes, three rRNA genes and 17 tRNA genes. The mitochondrial genome also contains a pair of large repeat sequences 5.9 kb in length, which may mediate genome reorga-nization into two sub-genomic circles, with predicted sizes of 124.8 kb and 115.0 kb, respectively. Furthermore, gene evolution of mitochondrial genomes within the Cruciferae family was analyzed using sat mitochondrial type (mitotype), together with six other re-ported mitotypes. The cruciferous mitochondrial genomes have maintained almost the same set of functional genes. Compared with Cycas taitungensis (a representative gymnosperm), the mitochondrial genomes of the Cruciferae have lost nine protein-coding genes and seven mitochondrial-like tRNA genes, but acquired six chloroplast-like tRNAs. Among the Cruciferae, to maintain the same set of genes that are necessary for mitochondrial function, the exons of the genes have changed at the lowest rates, as indicated by the numbers of single nucleotide polymorphisms. The open reading frames (ORFs) of unknown function in the cruciferous genomes are not conserved. Evolutionary events, such as mutations, genome reorganizations and sequence insertions or deletions (indels), have resulted in the non- conserved ORFs in the cruciferous mitochondrial genomes, which is becoming significantly different among mitotypes. This work represents the first phylogenic explanation of the evolution of genes of known function in the Cruciferae family. It revealed significant variation in ORFs and the causes of such variation.     

Reduction of In-Stent Restenosis Risk on Nickel-Free Stainless Steel by Regulating Cell Apoptosis and Cell Cycle

High nitrogen nickel-free austenitic stainless steel (HNNF SS) is one of the biomaterials developed recently for circumventing the in-stent restenosis (ISR) in coronary stent applications. To understand the ISR-resistance mechanism, we have conducted a comparative study of cellular and molecular responses of human umbilical vein endothelial cells (HUVECs) to HNNF SS and 316L SS (nickel-containing austenitic 316L stainless steel) which is the stent material used currently. CCK-8 analysis and flow cytometric analysis were used to assess the cellular responses (proliferation, apoptosis, and cell cycle), and quantitative real-time PCR (qRT-PCR) was used to analyze the gene expression profile of HUVECs exposed to HNNF SS and 316L SS, respectively. Flow cytometry analysis revealed that 316L SS could activate the cellular apoptosis more efficiently and initiate an earlier entry into the S-phase of cell cycle than HNNF SS. At the molecular level, qRT-PCR results showed that the genes regulating cell apoptosis and autophagy were overexpressed on 316L SS. Further examination indicated that nickel released from 316L SS triggered the cell apoptosis via Fas-Caspase8-Caspase3 exogenous pathway. These molecular mechanisms of HUVECs present a good model for elucidating the observed cellular responses. The findings in this study furnish valuable information for understanding the mechanism of ISR-resistance on the cellular and molecular basis as well as for developing new biomedical materials for stent applications.     

In Vivo Validation of Simultaneous Non-Contrast Angiography and intraPlaque Hemorrhage (SNAP) Magnetic Resonance Angiography: An Intracranial Artery Study

Objectives

Simultaneous Non-contrast Angiography and intraPlaque hemorrhage (SNAP) technique was recently proposed for joint MRA and intraplaque hemorrhage (IPH) imaging. The purpose of this study is to validate SNAP’s MRA performance in patients with suspected intracranial artery disease.

Methods

SNAP and time-of-flight (TOF) techniques with matched field of view and resolution were applied on 15 patients with suspected intracranial artery disease. Both techniques were evaluated based on their detection of luminal stenosis of bilateral middle cerebral arteries (MCA) and the delineation of smallest visible branches (SVB) of the MCA. Statistical analysis was conducted on the artery level.

Results

The SNAP MRA was found to provide similar stenosis detection performance when compared with TOF (Cohen’s κ 0.79; 95% Confidence Interval: 0.56–0.99). For the SVB comparison, SNAP was found to provide significantly better small artery delineation than TOF (p = 0.017). Inter-reader reproducibility for both measurements on SNAP was over 0.7. SNAP also detected IPH lesions on 13% of the patients.

Conclusions

The SNAP technique’s MRA performance was optimized and compared against TOF for intracranial artery atherosclerosis imaging and was found to provide comparable stenosis detection accuracy. Along with its IPH detection capability, SNAP holds the potential to become a first-line screening tool for high risk intracranial atherosclerosis disease evaluation.     

Fibroblast Growth Factor 21 (FGF21) Protects against High Fat Diet Induced Inflammation and Islet Hyperplasia in Pancreas

Fibroblast growth factor 21 (FGF21) is an important endocrine metabolic regulator expressed in multiple tissues including liver and adipose tissue. Although highest levels of expression are in pancreas, little is known about the function of FGF21 in this tissue. In order to understand the physiology of FGF21 in the pancreas, we analyzed its expression and regulation in both acinar and islet tissues. We found that acinar tissue express 20-fold higher levels than that observed in islets. We also observed that pancreatic FGF21 is nutritionally regulated; a marked reduction in FGF21 expression was noted with fasting while obesity is associated with 3–4 fold higher expression. Acinar and islet cells are targets of FGF21, which when systemically administered, leads to phosphorylation of the downstream target ERK 1/2 in about half of acinar cells and a small subset of islet cells. Chronic, systemic FGF21 infusion down-regulates its own expression in the pancreas. Mice lacking FGF21 develop significant islet hyperplasia and periductal lymphocytic inflammation when fed with a high fat obesogenic diet. Inflammatory infiltrates consist of TCRb+ Thy1+ T lymphocytes with increased levels of Foxp3+ regulatory T cells. Increased levels of inflammatory cells were coupled with elevated expression of cytokines such as TNFα, IFNγ and IL1β. We conclude that FGF21 acts to limit islet hyperplasia and may also prevent pancreatic inflammation.