Lei Zhang
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Lei Zhang
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Optimized negative-staining electron microscopy for lipoprotein studies.
Journal: Biochimica et biophysica acta
February/14/2013
Description

BACKGROUND

Negative-staining (NS), a rapid, simple and conventional technique of electron microscopy (EM), has been commonly used to initially study the morphology and structure of proteins for half a century. Certain NS protocols however can cause artifacts, especially for structurally flexible or lipid-related proteins, such as lipoproteins. Lipoproteins were often observed in the form of rouleau as lipoprotein particles appeared to be stacked together by conventional NS protocols. The flexible components of lipoproteins, i.e. lipids and amphipathic apolipoproteins, resulted in the lipoprotein structure being sensitive to the NS sample preparation parameters, such as operational procedures, salt concentrations, and the staining reagents.

METHODS

The most popular NS protocols that have been used to examine lipoprotein morphology and structure were reviewed.

CONCLUSIONS

The comparisons show that an optimized NS (OpNS) protocol can eliminate the rouleau artifacts of lipoproteins, and that the lipoproteins are similar in size and shape as statistically measured from two EM methods, OpNS and cryo-electron microscopy (cryo-EM). OpNS is a high-throughput, high-contrast and high-resolution (near 1nm, but rarely better than 1nm) method which has been used to discover the mechanics of a small protein, 53kDa cholesterol ester transfer protein (CETP), and the structure of an individual particle of a single protein by individual-particle electron tomography (IPET), i.e. a 14Å-resolution IgG antibody three-dimensional map.

CONCLUSIONS

It is suggested that OpNS can be used as a general protocol to study the structure of proteins, especially highly dynamic proteins with equilibrium-fluctuating structures.

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Pharmacokinetic assessment in patients receiving continuous RRT: perspectives from the Kidney Health Initiative.
Journal: Clinical journal of the American Society of Nephrology : CJASN
September/8/2015
Description

The effect of AKI and modern continuous RRT (CRRT) methods on drug disposition (pharmacokinetics) and response has been poorly studied. Pharmaceutical manufacturers have little incentive to perform pharmacokinetic studies in patients undergoing CRRT because such studies are neither recommended in existing US Food and Drug Administration (FDA) guidance documents nor required for new drug approval. Action is urgently needed to address the knowledge deficit. The Kidney Health Initiative has assembled a work group composed of clinicians and scientists representing academia, the FDA, and the pharmaceutical and dialysis industries with expertise related to pharmacokinetics, AKI, and/or CRRT. The work group critically evaluated key considerations in the assessment of pharmacokinetics and drug dosing in CRRT, practical constraints related to conducting pharmacokinetic studies in critically ill patients, and the generalizability of observations made in the context of specific CRRT prescriptions and specific patient populations in order to identify efficient study designs capable of addressing the knowledge deficit without impeding drug development. Considerations for the standardized assessment of pharmacokinetics and development of corresponding drug dosing recommendations in critically ill patients with AKI receiving CRRT are proposed.

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2-Deoxy-d-glucose attenuates sevoflurane-induced neuroinflammation through nuclear factor-kappa B pathway in vitro.
Journal: Toxicology in vitro : an international journal published in association with BIBRA
March/30/2015
Description

OBJECTIVE

Sevoflurane, one of the most commonly used anesthetics in clinic, induced neuroinflammation and caused cognitive impairment. 2-deoxy-d-glucose (2-DG) is a synthetic analogue of glucose and is clinically used in medical imaging safely.

METHODS

We examined the effect of 2-DG on sevoflurane-induced neuroinflammation in the mouse primary microglia cells. Mouse microglia cells were treated with 4.1% sevoflurane for 6h to examine the expression of interleukin (IL)-6 and tumor necrosis factor (TNF-α) and activation of nuclear factor-kappa B (NF-κB). Pyrrolidine dithiocarbamate (PDTC) or 2-DG was used 1h before sevoflurane treatment.

RESULTS

In the present study, we found that sevoflurane increased level of IL-6 and TNF-α through activating NF-κB signaling, and that 2-DG reduced sevoflurane-induced increase in IL-6 and TNF-α and nuclear NF-κB in microglia cells.

CONCLUSIONS

Our data suggests that NF-κB signaling pathway could be a target for sevoflurane-induced neuroinflammation and 2-DG might be a potential therapy to prevent or treat sevoflurane-induced neuroinflammation.

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Pubmed
Uncoupling protein-1 is protective of bone mass under mild cold stress conditions.
Journal: Bone
November/17/2017
Description

Brown adipose tissue (BAT), largely controlled by the sympathetic nervous system (SNS), has the ability to dissipate energy in the form of heat through the actions of uncoupling protein-1 (UCP-1), thereby critically influencing energy expenditure. Besides BAT, the SNS also strongly influences bone, and recent studies have demonstrated a positive correlation between BAT activity and bone mass, albeit the interactions between BAT and bone remain unclear. Here we show that UCP-1 is critical for protecting bone mass in mice under conditions of permanent mild cold stress for this species (22°C). UCP-1-/- mice housed at 22°C showed significantly lower cancellous bone mass, with lower trabecular number and thickness, a lower bone formation rate and mineralising surface, but unaltered osteoclast number, compared to wild type mice housed at the same temperature. UCP-1-/- mice also displayed shorter femurs than wild types, with smaller cortical periosteal and endocortical perimeters. Importantly, these altered bone phenotypes were not observed when UCP-1-/- and wild type mice were housed in thermo-neutral conditions (29°C), indicating a UCP-1 dependent support of bone mass and bone formation at the lower temperature. Furthermore, at 22°C UCP-1-/- mice showed elevated hypothalamic expression of neuropeptide Y (NPY) relative to wild type, which is consistent with the lower bone formation and mass of UCP-1-/- mice at 22°C caused by the catabolic effects of hypothalamic NPY-induced SNS modulation. The results from this study suggest that during mild cold stress, when BAT-dependent thermogenesis is required, UCP-1 activity exerts a protective effect on bone mass possibly through alterations in central NPY pathways known to regulate SNS activity.

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Hydrolytic cationic ester microparticles for highly efficient DNA vaccine delivery.
Journal: Small (Weinheim an der Bergstrasse, Germany)
June/10/2014
Description

DNA vaccination holds great potential to be a safer and more efficient alternative to traditional vaccination strategies, but the current lack of nontoxic and effective delivery systems is the greatest impediment to its clinical implementation. In this work, a convenient one-step method is used to prepare a degradable "microgel" delivery platform, featuring hydrolytic esters. Prior to hydrolysis, these micrometer-sized gel particles can effectively condense DNA due to their positive surface charge. Upon entering antigen-presenting cells (APCs), the microgels can be hydrolyzed to nontoxic zwitterionic polymers, consequently releasing the DNA and inducing phagosomal escape. Surface charge, DNA loading, cytotoxicity, and gene transfection efficiency of the hydrolysable microparticles with different tertiary to quaternary amine ratios are systematically studied. Nonhydrolysable counterparts and commercially developed PLGA-CTAB particles are used as the control. The passive targeting effect is further evaluated by blocking the phagocytosis pathway of the cells. The hydrolytic microgels prepared in this study possess great potential to become a platform for DNA vaccine delivery.

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Simultaneous determination of triptolide, tripterifordin, celastrol and nine sesquiterpene alkaloids in Tripterygium preparations using high-performance liquid chromatography-triple quadrupole mass spectrometry.
Journal: Journal of pharmaceutical and biomedical analysis
August/25/2016
Description

Tripterygium wilfordii tablet (TWT) and Tripterygium hypoglaucum tablet (THT), the preparations of the two Tripterygium herbs, are well known for the treatment of rheumatoid arthritis and other related inflammatory diseases clinically. In the present study, a high performance liquid chromatography (HPLC) coupled with electrospray ionization (ESI) tandem triple quadrupole mass spectrometry (QQQ/MS) method was developed for simultaneous quantification of 12 chemical components in Tripterygium preparations. The fragmentation patterns of analytes using ESI and collision-induced dissociation (CID) techniques were reported. This assay method was validated with respect to linearity (r(2)>0.9991), precision, repeatability, and accuracy (recovery rate between 97.2 and 104.2%). The proposed method was successfully applied for simultaneous quantification of the 12 compounds in Tripterygium preparations from the different manufactures. In addition, to evaluate the quality of Tripterygium preparations, partial least square discrimination analysis (PLS-DA) was performed to differentiate the contents of 12 compounds. In conclusion, the established HPLC/QQQ/MS method was proven to be useful and efficient for quality control of Tripterygium preparations.

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Genetic Regulation of Fate Decisions in Therapeutic T Cells to Enhance Tumor Protection and Memory Formation.
Journal: Cancer research
September/29/2015
Description

A key challenge in the field of T-cell immunotherapy for cancer is creating a suitable platform for promoting differentiation of effector cells while at the same time enabling self-renewal needed for long-term memory. Although transfer of less differentiated memory T cells increases efficacy through greater expansion and persistence in vivo, the capacity of such cells to sustain effector functions within immunosuppressive tumor microenvironments may still be limiting. We have therefore directly compared the impact of effector versus memory differentiation of therapeutic T cells in tumor-bearing mice by introducing molecular switches that regulate cell fate decisions via mTOR. Ectopic expression of RAS homolog enriched in brain (RHEB) increased mTORC1 signaling, promoted a switch to aerobic glycolysis, and increased expansion of effector T cells. By rapidly infiltrating tumors, RHEB-transduced T cells significantly reduced the emergence of immunoedited escape variants. In contrast, expression of proline-rich Akt substrate of 40 kDa (PRAS40) inhibited mTORC1, promoted quiescence, and blocked tumor infiltration. Fate mapping studies following transient expression of PRAS40 demonstrated that mTORC1(low) T cells made no contribution to initial tumor control but instead survived to become memory cells proficient in generating recall immunity. Our data support the design of translational strategies for generating heterogeneous T-cell immunity against cancer, with the appropriate balance between promoting effector differentiation and self-renewal. Unlike pharmacologic inhibitors, the genetic approach described here allows for upregulation as well as inhibition of the mTORC1 pathway and is highly selective for the therapeutic T cells without affecting systemic mTORC1 functions.

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Signaling cascades implicated in muscarinic regulation of proliferation of neural stem and progenitor cells.
Journal: Drug news & perspectives
September/19/2004
Description

Muscarinic acetylcholine receptors (mAChRs) belong to the G-protein-coupled receptor superfamily that transduces signals through multiple intracellular signaling cascades to regulate a wide variety of physiological responses. Recently, it has been discovered that subtypes of mAChRs are expressed in proliferative neuroepithelial cells of the ventricular zone and in basic fibroblast growth factor-expanded neural stem and progenitor cell cultures. Activation of the mAChRs by ACh or its analogue carbachol leads to increased DNA synthesis and neurogenesis. The mitogenic effects of muscarinic agonists are likely mediated via mAChR-activated multisignaling pathways. The exact intracellular mechanisms underlying mAChR-modulated DNA synthesis and neurogenesis are not fully understood. However, several pathways through Ras-mitogen-activated protein kinase, phosphatidylinositol 3-kinase-Akt, protein kinase C, c-Src and Ca(2+) signaling have been shown to play roles in this dynamic process. These novel signaling cascades may improve our understanding of the intracellular mechanisms underlying mAChR-stimulated neural progenitor proliferation and provide insights for therapeutic drug development.

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Icariin promotes extracellular matrix synthesis and gene expression of chondrocytes in vitro.
Journal: Phytotherapy research : PTR
January/2/2013
Description

To effectively treat articular cartilage defect with tissue engineering there is an urgent need to develop safe and cheap drugs that can substitute or cooperate with growth factors for chondrogenesis promotion. Here, we demonstrate the chondrogenic effect of icariin, the major pharmacological active constituent of Herb Epimedium (HEP). Rabbit chondrocytes were isolated from articular cartilage and cultured in vitro with different concentrations of icariin. Icariin at concentrations under 1 × 10⁻⁵ M showed low cytotoxicity toward chondrocytes, but icariin at 5 × 10⁻⁵ M inhibited the proliferation of chondrocytes. Icariin hardly affected the cell morphology with concentrations ranging from 1 × 10⁻⁷ M to 5 × 10⁻⁵ M. However, the higher concentration of icariin produced more extracellular matrix (ECM) synthesis and expression of chondrogenesis genes of chondrocytes. Indeed, the promotion of icariin on the synthesis of glycosaminoglycans (GAGs) and collagen of chondrocytes, and finally exerting a potent chondrogenic effect, might be due to its ability to up-regulate the expression of aggrecan, collagen II and Sox9 genes and to down-regulate the expression of the collagen I gene of chondrocytes. These preliminary results imply that icariin might be an effective accelerant for chondrogenesis and that icariin-loaded biomaterials might have the potential for cartilage tissue engineering. 1 × 10⁻⁵ M may be a suitable concentration of icariin with chondrogenic effect for tissue engineering.

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Increasing imipenem resistance and dissemination of the ISAba1-associated blaOXA-23 gene among Acinetobacter baumannii isolates in an intensive care unit.
Journal: Journal of medical microbiology
April/3/2011
Description

The antibiotic susceptibility of Acinetobacter calcoaceticus-Acinetobacter baumannii complex strains recovered from the intensive care unit (ICU) of West China Hospital, Sichuan, PR China, from 2006 to 2009 was investigated. The identification of A. baumannii and analysis of carbapenemase-encoding genes and their relationship with ISAba1 were performed by PCR. Furthermore, a DiversiLab repetitive extragenic palindromic sequence-based PCR (rep-PCR) microbial typing system and a multilocus sequence typing (MLST) scheme were applied to assess the genetic relationship of the isolates. The results showed that the antibiotic susceptibility of the A. calcoaceticus-A. baumannii complex isolates changed and imipenem resistance increased rapidly between 2006 and 2009. The blaOXA-51-like and ISAba1-associated blaOXA-23 genes were prevalent in the imipenem-resistant A. baumannii isolates. However, the blaOXA-58-like gene was found in only one isolate and no metallo-β-lactamase genes were detected. The representative multidrug-resistant A. baumannii isolates were identified as one cluster by rep-PCR fingerprinting and belonged to the clonal complex 92 (CC92) according to MLST. These findings indicate a situation of increasing resistance and wide distribution of class D β-lactamase genes, especially the acquired ISAba1-associated blaOXA-23 gene, in A. baumannii isolates in the ICU of West China Hospital, probably caused by expansion of the CC92 clone.

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