Probing the Pore of ClC-0 by Substituted Cysteine Accessibility Method Using Methane Thiosulfonate Reagents

ClC channels are a family of protein molecules containing two ion-permeation pores. Although these transmembrane proteins are important for a variety of physiological functions, their molecular operations are only superficially understood. High-resolution X-ray crystallography techniques have recently revealed the structures of two bacterial ClC channels, but whether vertebrate ClC channel pores are similar to those of bacterial homologues is not clear. To study the pore architecture of the Torpedo ClC-0 channel, we employed the substituted-cysteine-accessibility method (SCAM) and used charged methane thiosulfonate (MTS) compounds to modify the introduced cysteine. Several conclusions were derived from this approach. First, the MTS modification pattern from Y512C to E526C in ClC-0, which corresponds to residues forming helix R in bacterial ClC channels, is indeed consistent with the suggested helical structure. Second, the ClC-0 pore is more accessible to the negatively charged than to the positively charged MTS compound, a pore property that is regulated by the intrinsic electrostatic potential in the pore. Finally, attempts to modify the introduced cysteine at positions intracellular to the selectivity filter did not result in larger MTS modification rates for the open-state channel, suggesting that the fast gate of ClC-0 cannot be located at a position intracellular to the Cl− selectivity filter. Thus, the proposal that the glutamate side chain is the fast gate of the channel is applicable to ClC-0, revealing a structural and functional conservation of ClC channels between bacterial and vertebrate species

Electrostatic Control and Chloride Regulation of the Fast Gating of ClC-0 Chloride Channels

The opening and closing of chloride (Cl−) channels in the ClC family are thought to tightly couple to ion permeation through the channel pore. In the prototype channel of the family, the ClC-0 channel from the Torpedo electric organ, the opening-closing of the pore in the millisecond time range known as “fast gating” is regulated by both external and internal Cl− ions. Although the external Cl− effect on the fast-gate opening has been extensively studied at a quantitative level, the internal Cl− regulation remains to be characterized. In this study, we examine the internal Cl− effects and the electrostatic controls of the fast-gating mechanism. While having little effect on the opening rate, raising [Cl−]i reduces the closing rate (or increases the open time) of the fast gate, with an apparent affinity of >1 M, a value very different from the one observed in the external Cl− regulation on the opening rate. Mutating charged residues in the pore also changes the fast-gating properties—the effects are more prominent on the closing rate than on the opening rate, a phenomenon similar to the effect of [Cl−]i on the fast gating. Thus, the alteration of fast-gate closing by charge mutations may come from a combination of two effects: a direct electrostatic interaction between the manipulated charge and the negatively charged glutamate gate and a repulsive force on the gate mediated by the permeant ion. Likewise, the regulations of internal Cl− on the fast gating may also be due to the competition of Cl− with the glutamate gate as well as the overall more negative potential brought to the pore by the binding of Cl−. In contrast, the opening rate of the fast gate is only minimally affected by manipulations of [Cl−]i and charges in the inner pore region. The very different nature of external and internal Cl− regulations on the fast gating thus may suggest that the opening and the closing of the fast gate are not microscopically reversible processes, but form a nonequilibrium cycle in the ClC-0 fast-gating mechanism

Perioperative Stroke Following General Surgery

AbstractPerioperative stroke is rare; however, patients undergoing cardiovascular surgery are considered to be at high risk for perioperative stroke. Here, we outline a case where perioperative stroke occurred following total hip replacement surgery. The risk factors and possible causes of the stroke in this patient are discussed. In addition, we reiterate the appropriate management approaches needed to prevent perioperative stroke. Briefly, the importance of precise preoperative evaluation and of proper intraoperative and postoperative management should not be overlooked. Finally, it is important to realize that decreasing perioperative strokes and the disabilities associated with them will lower the financial burden on families and the community

A systematic review and meta-analysis of guided tissue regeneration/osseous grafting for the treatment of Class II furcation defects

AbstractBackground/purposeThe purpose of this article was to conduct a systematic review of the clinical evidence on the efficacy of guide tissue regeneration (GTR) with/without osseous grafting (OG) in treating periodontal furcation Class II defects.Materials and methodsReports from randomized controlled clinical trials, with at least 6 months follow-up, comparing open flap debridement (OFD); GTR, and GTR + OG were located from various sources. Sources included the electronic databases of Cochrane Oral Health Group specialist trials register, MEDLINE, and PubMed; in addition, journal archives were hand-searched. Trials up to and including March 2012 were included. Using the PICO (Patient or Problem, Intervention, Comparison, and Outcome) question format, data from eligible articles were extracted and meta-analyzed. The outcomes measures were furcation closure rate, vertical/horizontal bone fill (re-entry), and vertical/horizontal attachment level gain.ResultsThe meta-analysis showed that the GTR and GTR + OG groups obtained greater furcation closure rate, vertical/horizontal bone fill, and vertical/horizontal attachment level gain than the OFD group in mandibular molars. The GTR group obtained greater vertical/horizontal bone fill and vertical attachment level gain than the OFD group in maxillary molars. The GTR + OG group achieved better clinical outcomes than the GTR group did in all the comparing outcomes in mandibular molars.ConclusionGTR technique seemed to be more effective than OFD for resolving Class II periodontal furcation defects, and the GTR + OG technique showed even better clinical results. The outcomes were better for mandibular molars than for maxillary molars

Experimental and Numerical Analysis of Stainless Steel Microtube in Flaring Process

This study, with experiments and comparisons, aims to analyze the difference of stainless (SUS316L) microtubes in the flaring forming among dies with various semicone angles (35°, 40°, 45°, 50°, and 55°). The flow rule by Prandtl-Reuss combined with the finite element deformation theory and updated Lagrangian formulation (ULF) is applied to establish the finite element analysis equation for an incremental elastoplastic deformation to simulate the microtube flaring process. The broad rmin algorithm is utilized in the forming process for the elastoplastic state and die contact. The simulation data allow acquiring the deformation traceability, the relationship between punch load and punch stroke, the distribution of stress and strain, the distribution of the thinnest thickness resulted from dies with different semicone angles, and the distribution of flaring radius caused by dies with distinct semicone angles in the forming process. The experimental result presents similar results to the relationship between punch load and punch stroke and the simulation of the coefficient of friction μ=0.05, revealing the analysis being suitable for the analysis of microtube cone angle flaring process. The analysis and experimental results show that the thinnest thickness of the microtube increases with increasing semicone angles of dies and the maximal flaring radius of microtubes increases with increasing semicone angles of dies

Impact of interleukin-28B polymorphism on HCV-1 infected patients treated with response-guided therapy

SummaryBackgroundSingle nucleotide polymorphisms (SNPs) of interleukin-28B (IL28B) were associated with sustained virological response (SVR) in hepatitis C virus genotype 1 (HCV-1) infected patients treated with a standard 48-week regimen of peginterferon and ribavirin combination. Whether IL28B SNP genotype would be the influential prognosticator for patients treated with response-guided therapy (RGT) is still not well understood.AimsTo investigate the impact of IL28B rs809917 genotype on HCV-1 infected patients treated with RGT.MethodsA total of 128 consecutive treatment-naïve HCV-1 infected patients between July 2006 and July 2011 were analyzed. For rapid virological response (RVR) patients, we allowed an abbreviated 24-week regimen regardless of baseline viral loads; otherwise, a 48-week regimen was implemented (for patients with early virological response). The IL28B rs8099917 SNP genotypes were determined accordingly.ResultsA total of 117 patients (91.4%) were of rs8099917 TT genotype and 11 (8.6%) were of GT/GG genotype. Eighty-two of the 128 (64.1%) patients achieved SVR, occurring in 54 of 67 RVR patients (80.6%) and 28 of 61 non-RVR patients (45.9%, p < 0.001). Compared to the GT/GG genotype, patients with the TT genotype had significantly higher SVR rates (67.5% vs. 27.3%; p = 0.008) and low relapse rates (28.2% vs. 70.0%; p = 0.006). The multivariate analysis showed that RVR (odds ratio, 4.51; 95% confidence interval, 1.87–10.90; p = 0.001) and rs8099917 TT genotype (odds ratio, 6.91; 95% confidence interval, 1.53–31.17; p = 0.012) were independent factors associated with SVR.ConclusionFor HCV-1 infected patients who were treated with RGT, the IL28B unfavorable genotype predicted a higher relapse rate; RVR and IL28B favorable genotype were independent factors associated with SVR in patients treated with RGT

Regulation of CLC-1 chloride channel biosynthesis by FKBP8 and Hsp90β.

Mutations in human CLC-1 chloride channel are associated with the skeletal muscle disorder myotonia congenita. The disease-causing mutant A531V manifests enhanced proteasomal degradation of CLC-1. We recently found that CLC-1 degradation is mediated by cullin 4 ubiquitin ligase complex. It is currently unclear how quality control and protein degradation systems coordinate with each other to process the biosynthesis of CLC-1. Herein we aim to ascertain the molecular nature of the protein quality control system for CLC-1. We identified three CLC-1-interacting proteins that are well-known heat shock protein 90 (Hsp90)-associated co-chaperones: FK506-binding protein 8 (FKBP8), activator of Hsp90 ATPase homolog 1 (Aha1), and Hsp70/Hsp90 organizing protein (HOP). These co-chaperones promote both the protein level and the functional expression of CLC-1 wild-type and A531V mutant. CLC-1 biosynthesis is also facilitated by the molecular chaperones Hsc70 and Hsp90β. The protein stability of CLC-1 is notably increased by FKBP8 and the Hsp90β inhibitor 17-allylamino-17-demethoxygeldanamycin (17-AAG) that substantially suppresses cullin 4 expression. We further confirmed that cullin 4 may interact with Hsp90β and FKBP8. Our data are consistent with the idea that FKBP8 and Hsp90β play an essential role in the late phase of CLC-1 quality control by dynamically coordinating protein folding and degradation

Flattening the Curve with Einstein's Quantum Elevator: Hermitization of Non-Hermitian Hamiltonians via a Generalized Vielbein Formalism

The formalism for non-Hermitian quantum systems sometimes blurs the underlying physics. We present a systematic study of the vielbein-like formalism which transforms the Hilbert space bundles of non-Hermitian systems into the conventional ones, rendering the induced Hamiltonian to be Hermitian. In other words, any non-Hermitian Hamiltonian can be "transformed" into a Hermitian one without altering the physics. Thus we show how to find a reference frame (corresponding to Einstein's quantum elevator) in which a non-Hermitian system, equipped with a non-trivial Hilbert space metric, reduces to a Hermitian system within the standard formalism of quantum mechanics.Comment: 10 pages, 2 figure