Omega Loop Research Articles

Internal hernia after omega loop gastric bypass: Beware of ischemic stenosis of small intestine!

Internal hernia after omega loop gastric bypass: Beware of ischemic stenosis of small intestine!

Ceftazidime/avibactam resistance associated with L169P mutation in the omega loop of KPC-2.

Ceftazidime/avibactam resistance due to mutation in the omega loop of KPC-2 has been documented in vitro and in vivo. This study evaluated the mechanism of ceftazidime/avibactam resistance in a KPC-2-expressing Klebsiella pneumoniae isolated from a patient following ceftazidime/avibactam combination therapy with gentamicin for the treatment of ventilator-associated pneumonia. Ceftazidime/avibactam-susceptible and -resistant isolates of K. pneumoniae were evaluated by broth microdilution and WGS. The KPC-2 gene was cloned from the ceftazidime/avibactam-resistant isolate and evaluated for susceptibility to ceftazidime/avibactam, in an Escherichia coli background. A single L169P mutation was identified in the KPC-2 gene between the ceftazidime/avibactam-resistant and -susceptible isolates. The novel KPC-2 allele, designated KPC-35, was shown to confer reduced susceptibility to ceftazidime/avibactam and increased susceptibility to carbapenems, as compared with KPC-2. A novel L169P mutation was identified in KPC-2 and was shown through cloning experiments to confer reduced susceptibility to ceftazidime/avibactam.

The Mini-Gastric Bypass original technique

IntroductionMini-Gastric Bypass (MGB) is becoming more and more popular as shown by the numerous articles published over the past 15 years, supporting the operation as a short and simple procedure with excellent outcomes and low complication rates. There is still confusion amongst surgeons on the technique of the operation. The purpose of this paper is to review and describe the technique of MGB by its originators. MethodsWith 20 years of experience of performing the original MGB, the authors present the details of the MGB. ResultsThe MGB consists of a long conduit from below the crow's foot extending up to the left of the angle of His. It is similar to, but importantly, not the same as the pouch of the Sleeve Gastrectomy. MGB has a wide gastro-jejunal anastomosis to an anti-colic loop of jejunum 150–200 cm distal to the ligament of Trietz. The power of MGB comes from the fact that it is both a “Non-Obstructive” restrictive procedure and it also has a significant fatty food intolerance component with minimal malabsorption. ConclusionIn this article we describe the original Rutledge technique of Mini-Gastric Bypass. Notably this is neither a “Single Anastomosis bypass”, nor an “Omega Loop Bypass” and also not the “One Anastomosis Bypass of Carbajo”. It is a particular technique first created by Rutledge in 1997 and associated with low risk and excellent outcomes. The goal of this manuscript is to help avoid complications and problems seen when the operation deviates from some of the basic principles of general surgery used in the original operation.

Chemical Crosslinking Mass Spectrometry Reveals the Conformational Landscape of the Activation Helix of PPARγ; a Model for Ligand-Dependent Antagonism

Peroxisome proliferator-activated receptors (PPARs) are pharmacological targets for the treatment of metabolic disorders. Previously, we demonstrated the anti-diabetic effects of SR1664, a PPARγ modulator lacking classical transcriptional agonism, despite its poor pharmacokinetic properties. Here, we report identification of the antagonist SR11023 as a potent insulin sensitizer with significant plasma exposure following oral administration. To determinethe structural mechanism of ligand-dependent antagonism of PPARγ, we employed an integrated approach combining solution-phase biophysical techniques to monitor activation helix (helix 12) conformational dynamics. While informative on receptor dynamics, hydrogen/deuterium exchange mass spectrometry and nuclear magnetic resonance data provide limited information regarding the specific orientations of structural elements. In contrast, label-free quantitative crosslinking mass spectrometry revealed that binding of SR11023 to PPARγ enhances interaction with co-repressor motifs by pushing H12 away from the agonist active conformation toward the H2-H3 loop region (i.e., the omega loop), revealing the molecular mechanism for active antagonism of PPARγ.

Short communication: Extended-spectrum AmpC–producing Escherichia coli from milk and feces in dairy farms in Brazil

The AmpC enzyme is normally expressed constitutively in Escherichia coli, and its overproduction confers resistance to cefoxitin. A newly reported AmpC, the extended-spectrum AmpC (ESAC), is related to resistance to cefepime, a fourth-generation cephalosporin. This enzyme presents more flexibility in the active site due to insertions, replacements, and deletions on AA sequences. Many isolates producing ESAC were reported in human clinical isolates, but E. coli ESAC producers were reported in animals only in France. The animal E. coli strains can produce this enzyme and possibly disseminate it to human and production environments. In our study, 3 strains of E. coli from milk and feces bovine samples, collected in Rio de Janeiro, Brazil, were suspected to produce ESAC. After excluding other mechanisms of resistance, the gene was sequenced to verify ESAC characteristics. These strains presented replacement of AA in omega and R2 loops, suggesting ESAC production. This is the first report to study ESAC E. coli in dairy farms in Brazil.

Esthetic Rehabilitation of Primary Anterior Teeth using Double Omega Loop Post: A Report of Two Cases

The most common chronic disease that affects children is dental caries. In particular, maxillary anterior teeth are grossly destructed in early childhood caries. This leads to difficulty in speech, decreased masticator efficiency, development of abnormal tongue habits, and potentially subsequent malocclusion and psychological problems if esthetics is compromised. Restoration of severely decayed primary incisors is often a challenging procedure to pediatric dentists. This case series documents the esthetic rehabilitation of primary anterior teeth using double omega loop post.

Venous Omega Loops in Diabetic Retinopathy

Venous Omega Loops in Diabetic Retinopathy

Evaluation of Biomechanical Properties of Four Loops at Different Activation: A Finite Element Method Study

The aim of the study was to evaluate the force, moment, and moment/force ratio (M/F) generated by activating T loop, Kalra Simultaneous Intrusion and Retraction (KSIR) loop, Omega loop, and Teardrop loop made of titanium molybdenum alloy (TMA) wire with different preactivation bends at 1, 2, and 4 mm activation. Finite element method (FEM) models of the four loops were created and different preactivation bends were placed. The loops were then activated and analyzed for force, moment, and M/F ratio using ANSYS software. In loops without preactivation bends, highest force values were generated by Omega loop, whereas T loop had the least force value. The mean value for the M/F in the alpha segment was almost similar. In loops with preactivation bend, the force was highest in Teardrop loop, whereas T loop had the least force value. The mean value for the M/F in the alpha segment was almost similar in all the loops. T loop with preactivation bend shows the most favorable properties. T loop is comparatively reliable for the frictionless mechanics for the space closure than the other loops evaluated in clinical use.

Molecular dynamics simulation approach to explore atomistic molecular mechanism of peroxidase activity of apoptotic cytochrome c mutants

Abstract Mutations in cytochrome c (Cyt c) have been reported in tuning peroxidase activity, which in-turn cause Cyt c release from mitochondria and early apoptosis. However, the molecular tuning mechanism underlying this activity remains elusive. Herein, multiple 20 ns molecular dynamics (MD) simulations of wild type (WT), Y67F and K72W mutated Cyt c in aqueous solutions have been carried out to study how the changes in structural features alters the peroxidase activity of the protein. MD simulation results indicate that Y67F mutation caused, (i) increased distances between critical electron-transfer residues, (ii) higher fluctuations in omega loops, and (iii) weakening of intraprotein hydrogen bonds result in open conformation at heme crevice loop in Cyt c leading to an enhanced peroxidase activity. Interestingly, the aforementioned structural features are strengthened in K72W compared to WT and Y67F, which triggers K72W mutated Cyt c into a poor peroxidase. Essential dynamics results unveil that first two eigenvectors are responsible for overall motions of WT, Y67F and K72W mutated Cyt c. This study thus provides atomic level insight into molecular mechanism of peroxidase activity of Cyt c, which will help in designing novel Cyt c structures that is more desirable than natural Cyt c for biomedical and industrial processes.

Identification and characterization of ace1-type acetylcholinesterase in insecticide-resistant and -susceptible Propylaea japonica (Thunberg).

Characterization and gene cloning of acetylecholinesterase (AChE) in the insecticide-resistant (R) and -susceptible (S) insects have been reported in the past. However, the studies focused mostly on herbivorous pests, rather than predacious species, such as ladybird beetles. Using R and S Propylaea japonica (thunberg), a full-length cDNA sequence (2928 bp) of the ace1-type AChE gene was determined for the first time. The ace1 encoding a protein of 645 amino acids contained typical conserved motifs, such as FGESAG domains, catalytic triad, acyl pocket, oxyanino hole, choline binding site, peripheral anionic site, omega loop and conserved aromatic residues. R P. japonica displayed 50-times greater resistance to chlorpyrifos or mathamidophos with a significantly lower AChE sensitivity to paraoxon, malaoxon, chlorpyrifos or methamidophos than its S counterpart. Five amino acids in the ace1 of R P. japonica differed from those found in S P. japonica. One of them, F358S, located in the acyl-binding pocket, might play a crucial role in the resistance of the insect to organophosphates (OPs). Whereas, K493E and I538V, which were close to some of the conserved aromatic amino acids (i.e., H509, Y511, and W499) in the gorge, and G571R and T576A near C593 that formed the disulfide bonds with C471, might also involve in the change of insecticide resistance in P. japonica. AChE insensitivity and amino acid replacements, particularly F358S, might be the determining factors in the alteration of OPs-resistance in P. japonica.

Exploring the Landscape of Diazabicyclooctane (DBO) Inhibition: Avibactam Inactivation of PER-2 β-Lactamase.

PER β-lactamases are an emerging family of extended-spectrum β-lactamases (ESBL) found in Gram-negative bacteria. PER β-lactamases are unique among class A enzymes as they possess an inverted omega (Ω) loop and extended B3 β-strand. These singular structural features are hypothesized to contribute to their hydrolytic profile against oxyimino-cephalosporins (e.g., cefotaxime and ceftazidime). Here, we tested the ability of avibactam (AVI), a novel non-β-lactam β-lactamase inhibitor to inactivate PER-2. Interestingly, the PER-2 inhibition constants (i.e., k2/K = 2 × 103 ± 0.1 × 103 M-1 s-1, where k2 is the rate constant for acylation (carbamylation) and K is the equilibrium constant) that were obtained when AVI was tested were reminiscent of values observed testing the inhibition by AVI of class C and D β-lactamases (i.e., k2/K range of ≈103 M-1 s-1) and not class A β-lactamases (i.e., k2/K range, 104 to 105 M-1 s-1). Once AVI was bound, a stable complex with PER-2 was observed via mass spectrometry (e.g., 31,389 ± 3 atomic mass units [amu] → 31,604 ± 3 amu for 24 h). Molecular modeling of PER-2 with AVI showed that the carbonyl of AVI was located in the oxyanion hole of the β-lactamase and that the sulfate of AVI formed interactions with the β-lactam carboxylate binding site of the PER-2 β-lactamase (R220 and T237). However, hydrophobic patches near the PER-2 active site (by Ser70 and B3-B4 β-strands) were observed and may affect the binding of necessary catalytic water molecules, thus slowing acylation (k2/K) of AVI onto PER-2. Similar electrostatics and hydrophobicity of the active site were also observed between OXA-48 and PER-2, while CTX-M-15 was more hydrophilic. To demonstrate the ability of AVI to overcome the enhanced cephalosporinase activity of PER-2 β-lactamase, we tested different β-lactam-AVI combinations. By lowering MICs to ≤2 mg/liter, the ceftaroline-AVI combination could represent a favorable therapeutic option against Enterobacteriaceae expressing blaPER-2 Our studies define the inactivation of the PER-2 ESBL by AVI and suggest that the biophysical properties of the active site contribute to determining the efficiency of inactivation.

X-ray crystal structure of rivoglitazone bound to PPARγ and PPAR subtype selectivity of TZDs

Thiazolidinedione (TZD) compounds targeting the nuclear receptor peroxisome proliferator-activated receptor gamma (PPARγ) demonstrate unique benefits for the treatment of insulin resistance and type II diabetes. TZDs include rosiglitazone, pioglitazone and rivoglitazone, with the latter being the most potent. The TZDs are only marginally selective for the therapeutic target PPARγ as they also activate PPARα and PPARδ homologues to varying degrees, causing off-target effects. While crystal structures for TZD compounds in complex with PPARγ are available, minimal structural information is available for TZDs bound to PPARα and PPARδ. This paucity of structural information has hampered the determination of precise structural mechanisms involved in TZD selectivity between PPARs. To help address these questions molecular dynamic simulations were performed of rosiglitazone, pioglitazone and rivoglitazone in complex with PPARα, PPARδ, and PPARγ in order to better understand the mechanisms of PPAR selectivity. The simulations revealed that TZD interactions with residues Tyr314 and Phe318 of PPARα and residues Phe291 and Thr253 of PPARδ as well as the omega loop, are key determinants of TZD receptor selectivity. Notably, in this study, we solve the first X-ray crystal structure of rivoglitazone bound to any PPAR. Rivoglitazone forms a unique hydrogen bond network with the residues of the PPARγ co-activator binding surface (known as AF2) and makes more extensive contacts with helix 3 and the β-sheet as compared to model TZD compounds such as rosiglitazone.

Laparoscopic Conversion of Omega Loop Gastric Bypass into Roux-en-Y Gastric Bypass.

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Incidence of Biliary Reflux Esophagitis After Laparoscopic Omega Loop Gastric Bypass in Morbidly Obese Patients.

Omega loop gastric bypass is a successful bariatric surgery with numerous favorable circumstances as being basic, effective on weight reduction and treatment of obesity associated metabolic disorder, the short expectation to learn and adapt, and the simplicity of correction and inversion. However, there are arguments about the possibility of biliary reflux and/or the potential danger of gastroesophageal malignancy after the procedure. Fifty patients experiencing morbid obesity with body mass index >40 or >35 kg/m2 with two related comorbidities, for example, diabetes type II, hypertension, or dyslipidemia, underwent omega loop gastric bypass with a follow-up period up to 18 months, investigating for any symptom of reflux infection by upper gastrointestinal tract endoscopy and pH metry. Reflux esophagitis (a gastroesophageal reflux disease) was detected in 3 patients (6%); 2 cases (4%) showed (Grade A) acidic reflux esophagitis at 6 and 12 months postoperatively. Just 1 case (2%) had experienced gastroesophageal biliary reflux esophagitis (Grade A) at 12 months. No metaplasia or dysplasia was detected in the endoscopic biopsies. Omega loop gastric bypass is a safe and effective bariatric procedure with low incidence of postoperative biliary reflux, metaplasia, or dysplasia at the esophagogastric junction, confirmed 18 months after the operation.

Wing-bib multi helix maxillary expander

An orthodontic appliance for maxillary expansion is presented, which consists of a wire assembly fabricated from 0.032” round straight length beta-titanium wire. Posterior active portion of the appliance consists of a trihelix omega loop parallel to palatal surface, providing transverse expansion and distalizing forces on the first molars. Anterior active portion consisting of an acrylic apron (bib) over a (wing-like) wire framework, provides transverse expansion at the anterolateral slopes of the palate including the depths; lying directly over the envisioned canine- first premolar root area of the palatal vault surface.

High adaptability of the omega loop underlies the substrate-spectrum-extension evolution of a class A β-lactamase, PenL.

The omega loop in β-lactamases plays a pivotal role in substrate recognition and catalysis, and some mutations in this loop affect the adaptability of the enzymes to new antibiotics. Various mutations, including substitutions, deletions, and intragenic duplications resulting in tandem repeats (TRs), have been associated with β-lactamase substrate spectrum extension. TRs are unique among the mutations as they cause severe structural perturbations in the enzymes. We explored the process by which TRs are accommodated in order to test the adaptability of the omega loop. Structures of the mutant enzymes showed that the extra amino acid residues in the omega loop were freed outward from the enzyme, thereby maintaining the overall enzyme integrity. This structural adjustment was accompanied by disruptions of the internal α-helix and hydrogen bonds that originally maintained the conformation of the omega loop and the active site. Consequently, the mutant enzymes had a relaxed binding cavity, allowing for access of new substrates, which regrouped upon substrate binding in an induced-fit manner for subsequent hydrolytic reactions. Together, the data demonstrate that the design of the binding cavity, including the omega loop with its enormous adaptive capacity, is the foundation of the continuous evolution of β-lactamases against new drugs.

Delayed Graft Duodenal Perforation Due to Food Impaction at 5 Years After Simultaneous Pancreas-Kidney Transplantation: A Case Report

Introduction: Pancreas transplantation is the best treatment option in selected patients with type 1 diabetes mellitus. Although complications including graft thrombosis, graft pancreatitis, and rejection are well documented, graft duodenal perforation is very rare. Here we report a case of nonmarginal duodenal perforation at five years after a simultaneous pancreas-living donor kidney transplantation (SPLKT). The perforation may have been caused by impacted food and possible underlying chronic rejection. Case report: A 31-year old male who underwent SPLKT five years ago presented with severe abdominal pain. His past surgical history includes SPLKT initially with bladder drainage, then converted to enteric drainage one year later due to recurrent urinary tract infections. At that time, a side-to-side duodenoileostomy was performed and an omega loop created to minimize reflux. He had a marginal duodenal perforation four years later, treated by primary closure and drainage. Biopsy of pancreas and duodenum graft showed chronic rejection in the pancreas and acute inflammation with ulcer in the duodenum. At presentation, computerized tomography scan showed mesenteric pneumatosis with enteric leak and ileal dilatation proximal to the anastomotic site including the omega loop. We performed emergent laparotomy and found a 1.0cm perforation at the nonmarginal, posterior wall of the duodenum. Undigested fiber-rich food was extracted from the site and an omental patch placed over the perforation. An ileostomy was created proximal to the omega loop for decompression and a drain placed nearby. The postoperative course was unremarkable. Discussion: There are only seven previous cases of graft duodenal perforation in the literature. Duodenal graft perforation can occur immediately after transplantation or later on. Fiber-rich food residue passing through the anastomosis with impaction may have led to this perforation. The omega loop may contribute to increased pressure in the graft duodenum by luminal congestion. Patients suspected to have chronic rejection, may need modification of their diet.

Comparison of compressive strength among three different intracanal post materials in primary anterior teeth: An in vitro study.

Objective:The objective of our study was to compare the fracture resistance and the mode of failure among three different post materials in primary anterior teeth.Materials and Methods:A total of sixty extracted primary anterior teeth were selected for the study. The samples were divided into three groups of twenty teeth each: Group I (Ribbond), Group II (Omega loop), and Group III (Glass fiber post). Pulp therapy was followed by intracanal post and crown buildup. The samples were mounted in self-cure acrylic and subjected to compressive strength test using universal testing machine (Instron). The maximum force at which the tooth fractured was recorded.Results:The values were subjected to one-way analysis of variance. The mean compressive strength values of Ribbond, omega loop, and glass fiber post were found to be 83.25 N, 61.60 N, and 75.55 N, respectively. The P value was found to be 0.220.Conclusion:Group I (Ribbond) showed the highest fracture resistance values followed by Group III (Glass fiber post) and Group II (Omega loop). Although there is difference in mean values, they were nonsignificant.

A156 - Omega Loop Duodenal Switch with Linear Stapled Duodenoileostomy Peter C Ng, MD, Lindsey S. Sharp, MD, and Dustin M Bermudez, MD

A156 - Omega Loop Duodenal Switch with Linear Stapled Duodenoileostomy Peter C Ng, MD, Lindsey S. Sharp, MD, and Dustin M Bermudez, MD

Single-Anastomosis Pylorus-Preserving Bariatric Procedures: Review of the Literature.

Single-anastomosis pylorus-preserving procedures (SAPPP) were recently introduced into bariatric surgery in order to combine the physiologic advantages of a post-pyloric reconstruction with the technical advantages of an omega loop. Surgery consists of a sleeve gastrectomy that is performed first, followed by a duodeno-enterostomy. Two main variants exist: proximal and distal SAPPP, with duodeno-jejunostomy and duodeno-ileostomy, respectively. This review describes the SAPPP reported in the literature and analyzes their outcomes in comparison with the most frequently performed bariatric techniques. Preliminary results appear as promising in terms of both safety and effectiveness on weight loss and comorbidities improvement.