Minimally Invasive Vacuum-Assisted Closure Therapy With Instillation (Mini-VAC-Instill) for Pleural Empyema

Enthusiasm for minimally invasive thoracic surgery is increasing. Thoracoscopy plays a significant therapeutic role in the fibrinopurulent stage (stage II) of empyema, in which loculated fluid cannot often be adequately drained by chest tube alone. For some debilitated and septic patients, further procedures such as open-window thoracostomy (OWT) with daily wound care or vacuum-assisted closure (VAC) therapy are necessary. In the present article, we propose a new option of minimally invasive VAC therapy including a topical solution of the empyema without open-window thoracostomy (Mini-VAC-instill). Three patients who underwent surgery using this technique are also presented. The discussion is focused on the advantages and disadvantages of the approach

Complex pleural empyema can be safely treated with vacuum-assisted closure

<p>Abstract</p> <p>Objective</p> <p>For patients with postoperative pleural empyema, open window thoracostomy (OWT) is often necessary to prevent sepsis. Vacuum-assisted closure (VAC) is a well-known therapeutic option in wound treatment. The efficacy and safety of intrathoracal VAC therapy, especially in patients with pleural empyema with bronchial stump insufficiency or remain lung, has not yet been investigated.</p> <p>Methods</p> <p>Between October 2009 and July 2010, eight consecutive patients (mean age of 66.1 years) with multimorbidity received an OWT with VAC for the treatment of postoperative or recurrent pleural empyema. Two of them had a bronchial stump insufficiency (BPF).</p> <p>Results</p> <p>VAC therapy ensured local control of the empyema and control of sepsis. The continuous suction up to 125 mm Hg cleaned the wound and thoracic cavity and supported the rapid healing. Additionally, installation of a stable vacuum was possible in the two patients with BPF. The smaller bronchus stump fistula closed spontaneously due to the VAC therapy, but the larger remained open.</p> <p>The direct contact of the VAC sponge did not create any air leak or bleeding from the lung or the mediastinal structures. The VAC therapy allowed a better re-expansion of remaining lung.</p> <p>One patient died in the late postoperative period (day 47 p.o.) of multiorgan failure. In three cases, VAC therapy was continued in an outpatient service, and in four patients, the OWT was treated with conventional wound care. After a mean time of three months, the chest wall was closed in five of seven cases. However, two patients rejected the closure of the OWT. After a follow-up at 7.7 months, neither recurrent pleural empyema nor BPF was observed.</p> <p>Conclusion</p> <p>VAC therapy was effective and safe in the treatment of complicated pleural empyema. The presence of smaller bronchial stump fistula and of residual lung tissue are not a contraindication for VAC therapy.</p

Molecular determinants of ligand discrimination in the glutamate-binding pocket of the NMDA receptor.

Binding of glutamate to ionotropic glutamate receptors occurs within a bilobate binding pocket built from conserved S1 and S2 domains. Using the crystal structure of the binding region of the (RS)-2-amino-3-(3-hydroxy-5-methyl-4-isoxazolyl)-propionic acid (AMPA)-selective GluR2 subunit, we identified determinants of ligand selectivity and efficacy within the glutamate-binding pocket of the NR2B subunit of the N-methyl-D-aspartate (NMDA) receptor by site-directed mutagenesis. Electrophysiological analyses of mutated NR2B polypeptides revealed drastic effects on the affinity of L-glutamate but not of the co-agonist glycine. With seven out of 19 substitutions, we found differences in the potency of the full agonist L-glutamate and the partial agonist NMDA. In particular, substitutions located at the interface between the S1 and S2 domains resulted in changes of agonist efficacy, suggesting a role in transducing the ligand-binding signal. Inhibition by the competitive antagonist D-AP5 was highly sensitive to replacement of residues involved in stabilization of the closed conformation of the binding pocket, consistent with antagonists preventing closure of the binding pocket. In addition, we identified residues predicted to be important for liganding the methyl group of NMDA. Collectively our data describe specific side chain interactions that determine ligand efficacy and pharmacology at the glutamate site of the NMDA receptor

Evolution of Process Portals to Multi-Channel Architectures - A Service-Oriented Approach at ETA

This paper illustrates a typical pathway towards increasing electronic interaction with external business partners. Based on the case study of ETA SA, a Swiss manufacturer of watch movements and components, it explores current issues in portal-based B2B integration. In order to allow for tighter process integration with distinct customers, ETA conceives a multi-channel architecture which provides electronic services to customers using either direct or portal-based electronic channels. Since a multichannel approach typically is associated with major integration challenges, the paper outlines and discusses the vision of service-oriented architecture for interorganizational integration.

Disruption of interdomain interactions in the glutamate binding pocket affects differentially agonist affinity and efficacy of N-methyl-D-aspartate receptor activation.

In ionotropic glutamate receptors, agonist binding occurs in a conserved clam shell-like domain composed of the two lobes D1 and D2. Docking of glutamate into the binding cleft promotes rotation in the hinge region of the two lobes, resulting in closure of the binding pocket, which is thought to represent a prerequisite for channel gating. Here, we disrupted D1D2 interlobe interactions in the NR2A subunit of N-methyl-d-aspartate (NMDA) receptors through systematic mutation of individual residues and studied the influence on the activation kinetics of currents from NR1/NR2 NMDA receptors heterologously expressed in HEK cells. We show that the mutations affect differentially glutamate binding and channel gating, depending on their location within the binding domain, mainly by altering k(off) and k(cl), respectively. Whereas impaired stability of glutamate in its binding site is the only effect of mutations on one side of the ligand binding pocket, close to the hinge region, alterations in gating are the predominant consequence of mutations on the opposite side, at the entrance of the binding pocket. A mutation increasing D1D2 interaction at the entrance of the pocket resulted in an NMDA receptor with an increased open probability as demonstrated by single channel and whole cell kinetic analysis. Thus, the results indicate that agonist-induced binding domain closure is itself a complex process, certain aspects of which are coupled either to binding or to gating. Specifically, we propose that late steps of domain closure, in kinetic terms, represent part of channel gating

Structural determinants of calmodulin binding to the intracellular C-terminal domain of the metabotropic glutamate receptor 7A

Calmodulin (CaM) binds in a Ca2+-dependent manner to the intracellular C-terminal domains of most group III metabotropic glutamate receptors (mGluRs). Here we combined mutational and biophysical approaches to define the structural basis of CaM binding to mGluR 7A. Ca2+/CaM was found to interact with mGluR 7A primarily via its C-lobe at a 1:1 CaM:C-tail stoichiometry. Pulldown experiments with mutant CaM and mGluR 7A C-tail constructs and high resolution NMR with peptides corresponding to the CaM binding region of mGluR 7A allowed us to define hydrophobic and ionic interactions required for Ca2+/CaM binding and identified a 1-8-14 CaM-binding motif. The Ca2+/CaM·mGluR 7A peptide complex displays a classical wraparound structure that closely resembles that formed by Ca2+/CaM upon binding to smooth muscle myosin light chain kinase. Our data provide insight into how Ca2+/CaM regulates group III mGluR signaling via competition with intracellular proteins for receptor-binding sites

Mutations within the agonist-binding site convert the homomeric alpha1 glycine receptor into a Zn2+-activated chloride channel.

The divalent cation Zn2+ has been shown to regulate inhibitory neurotransmission in the mammalian CNS by affecting the activation of the strychnine-sensitive glycine receptor (GlyR). In spinal neurons and cells expressing recombinant GlyRs, low micromolar (10 microM) have an inhibitory effect. Mutational studies have localized the Zn2+ binding sites mediating allosteric potentiation and inhibition of GlyRs in distinct regions of the N-terminal extracellular domain of the GlyR alpha-subunits. Here, we examined the Zn2+ sensitivity of different mutations within the agonist binding site of the homomeric alpha(1)-subunit GlyR upon heterologous expression in Xenopus oocytes. This revealed that six substitutions within the ligand-binding pocket result in a total loss of Zn2+ inhibition. Furthermore, substitution of the positively charged residues arginine 65 and arginine 131 by alanine (alpha(1)(R65A), alpha(1)(R131A), or of the aromatic residue phenylalanine 207 by histidine (alpha(1)(F207H)), converted the alpha(1) GlyR into a chloride channel that was activated by Zn2+ alone. Dose-response analysis of the alpha(1)(F207H) GlyR disclosed an EC(50) value of 1.2 microM for Zn2+ activation; concomitantly the apparent glycine affinity was 1000-fold reduced. Thus, single point mutations within the agonist-binding site of the alpha(1) subunit convert the inhibitory GlyR from a glycine-gated into a selectively Zn2+-activated chloride channel. This might be exploited for the design of metal-specific biosensors by modeling-assisted mutagenesis

Structural model of the N-methyl-D-aspartate receptor glycine site probed by site-directed chemical coupling.

The N-methyl-d-aspartate (NMDA) receptor is a ligand-gated ion channel that requires both glutamate and glycine for efficient activation. Here, a strategy combining cysteine scanning mutagenesis and affinity labeling was used to investigate the glycine binding site located on the NR1 subunit. Based on homology modeling to the crystal structure of the glutamate binding site of the 2-amino-3-(3-hydroxy-5-methyl-4-isoxazolyl)-propionic acid receptor GluR2, cysteines were introduced into the NR1 subunit as chemical sensors for three thiol-reactive derivatives of the competitive antagonist L-701324. After coexpressing the mutant NR1 with wild-type NR2B subunits in Xenopus oocytes, agonist-induced currents were recorded to monitor irreversible receptor inactivation by the reactive antagonists. For each derivative, glycine site-specific inactivations were observed with a distinct subset of cysteine-substituted receptors. Together these inactivating substitutions identified seven NR1 residues (Ile-385, Gln-387, Glu-388, Thr-500, Asn-502, Ala-696, and Val-717) that undergo proximity-induced covalent coupling with specific regions of the bound antagonist and disclose its mode of docking in the glycine binding pocket of the NMDA receptor. Our approach may help to unravel the structural basis of distinct NMDA receptor subtype pharmacologies