Systematic Review of the Management of Ureteroarterial Fistulas After Ileal Conduit Urinary Diversion.

OBJECTIVE. No studies or guidelines exist to direct management of ureteroarterial fistula (UAF) after ileal conduit urinary diversion in which the possible risks and complications associated with stent-graft infection from the conduit flora must be reconciled with those of open surgical repair. This study seeks to characterize the clinical presentation, pathogenesis, and optimal diagnostic and therapeutic management of this entity through a systematic review of the literature. MATERIALS AND METHODS. A systematic search of the English-language literature using the PubMed, Scopus, and ScienceDirect databases was performed: 264 abstracts were identified. From those abstracts, 32 studies comprising 40 patients with 43 UAFs were selected for analysis. Data points including demographics, clinical presentation, UAF specifications, procedural details, postprocedural complications, and clinical outcomes were reviewed. RESULTS. Predisposing factors included female sex, chronic ureteral stent placement, and past surgical intervention and irradiation for pelvic malignancy. Fistulization was overwhelmingly unilateral (95.0% of patients) and included the common iliac artery (90.7% of UAFs). Combined endovascular and endoureteral modalities presented similar outcomes compared with surgical approaches in terms of UAF-related mortality (7.1% vs 13.3%, respectively) and complication rates (28.6% vs 26.7%) during a similar median follow-up period (9.5 vs 14.0 months). Endovascular stent-graft infections were present in 14.3% of cases and represented a leading indication for reintervention after endovascular management (50.0%). CONCLUSION. Short- and intermediate-term outcomes of combined endovascular and endoureteral techniques compare favorably with those of surgical approaches in the treatment of UAF after ileal conduit urinary diversion. Although there is a relatively low stent-graft infection rate, close follow-up within the first year after the procedure is required given the propensity of complications to develop during this window. The use of postprocedural antibiotics is uncertain but is likely prudent.

Imaging features of gastrointestinal toxicity in non-small cell lung cancer patients treated with erlotinib: A single institute 13-year experience.

OBJECTIVES: To investigate the imaging features of erlotinib-associated gastrointestinal toxicity (GT) in patients with non-small cell lung cancer (NSCLC). MATERIALS AND METHODS: The electronic medical records of 157 patients with NSCLC who received erlotinib between 2005 and 2018 were retrospectively reviewed to identify patients with GT. Clinical and radiologic evidence of erlotinib-associated GT was evaluated. Imaging findings were cross-referenced with clinical presentation, management, and outcomes. RESULTS: 24 (15%) patients (16 women; median age, 68 years) with radiologic evidence of GT were identified. The median time to detection of GT on imaging was 4.5 months (range: 0-58 months). 3/24 (12.5%) patients had no clinical symptoms, but GT was radiologically identified. Erlotinib-associated GT manifested in the large bowel in either a diffuse (42%) or segmental (58%) pattern. The most common imaging finding was fluid-filled bowel (23/24, 96%). CONCLUSION: Erlotinib-associated GT was identified in 15% patients with NSCLC. Fluid-filled colon and segmental involvement were the most common imaging manifestations.

Catheter directed interventions for inferior vena cava thrombosis.

Inferior vena cava (IVC) thrombosis, although similar in many aspects to deep venous thrombosis (DVT), has distinct clinical implications, treatments and roles for endovascular management. Etiologies of IVC thrombosis vary from congenital malformations of the IVC to acquired, where indwelling IVC filters have been implicated as a leading cause. With an increasing incidence of IVC thrombosis throughout the United States, clinicians need to be educated on the clinical signs and diagnostic tools available to aid in the diagnosis as well as available treatment options. Untreated IVC thrombus can result in serious morbidity and mortality, both in the acute phase with symptoms related to venous outflow occlusion and embolism, and in the long-term, sequelae of post-thrombotic syndrome (PTS) related to chronic venous occlusion. This manuscript will discuss the clinical presentation of IVC thrombosis, diagnostic and treatment options, as well as the role of endovascular management.

Molecular interactions between general anesthetics and the 5HT2B receptor.

BACKGROUND: Serotonin modulates many processes through a family of seven serotonin receptors. However, no studies have screened for interactions between general anesthetics currently in clinical use and serotonergic G-protein-coupled receptors (GPCRs). Given that both intravenous and inhalational anesthetics have been shown to target other classes of GPCRs, we hypothesized that general anesthetics might interact directly with some serotonin receptors and thus modify their function. METHODS: Radioligand binding assays were performed to screen serotonin receptors for interactions with propofol and isoflurane as well as for affinity determinations. Docking calculations using the crystal structure of 5-HT2B were performed to computationally confirm the binding assay results and locate anesthetic binding sites. RESULTS: The 5-HT2B class of receptors interacted significantly with both propofol and isoflurane in the primary screen. The affinities for isoflurane and propofol were determined to be 7.78 and .95 µM, respectively, which were at or below the clinical concentrations for both anesthetics. The estimated free energy derived from docking calculations for propofol (-6.70 kcal/mol) and isoflurane (-5.10 kcal/mol) correlated with affinities from the binding assay. The anesthetics were predicted to dock at a pharmacologically relevant binding site of 5HT2B. CONCLUSIONS: The molecular interactions between propofol and isoflurane with the 5-HT2B class of receptors were discovered and characterized. This finding implicates the serotonergic GPCRs as potential anesthetic targets.

Characterization of a computationally designed water-soluble human µ-opioid receptor variant using available structural information.

BACKGROUND: The recent X-ray crystal structure of the murine µ-opioid receptor (MUR) allowed the authors to reengineer a previously designed water-soluble variant of the transmembrane portion of the human MUR (wsMUR-TM). METHODS: The new variant of water-soluble MUR (wsMUR-TM_v2) was engineered based on the murine MUR crystal structure. This novel variant was expressed in Escherichia coli and purified. The properties of the receptor were characterized and compared with those of wsMUR-TM. RESULTS: Seven residues originally included for mutation in the design of the wsMUR-TM were reverted to their native identities. wsMUR-TM_v2 contains 16% mutations of the total sequence. It was overexpressed and purified with high yield. Although dimers and higher oligomers were observed to form over time, the wsMUR-TM_v2 stayed predominantly monomeric at concentrations as high as 7.5 mg/ml in buffer within a 2-month period. Its secondary structure was predominantly helical and comparable with those of both the original wsMUR-TM variant and the native MUR. The binding affinity of wsMUR-TM_v2 for naltrexone (K(d) approximately 70 nM) was in close agreement with that for wsMUR-TM. The helical content of wsMUR-TM_v2 decreased cooperatively with increasing temperature, and the introduction of sucrose was able to stabilize the protein. CONCLUSIONS: A novel functional wsMUR-TM_v2 with only 16% mutations was successfully engineered, expressed in E. coli, and purified based on information from the crystal structure of murine MUR. This not only provides a novel alternative tool for MUR studies in solution conditions but also offers valuable information for protein engineering and structure-function relations.

Scalable production of highly sensitive nanosensors based on graphene functionalized with a designed G protein-coupled receptor.

We have developed a novel, all-electronic biosensor for opioids that consists of an engineered µ-opioid receptor protein, with high binding affinity for opioids, chemically bonded to a graphene field-effect transistor to read out ligand binding. A variant of the receptor protein that provided chemical recognition was computationally redesigned to enhance its solubility and stability in an aqueous environment. A shadow mask process was developed to fabricate arrays of hundreds of graphene transistors with average mobility of ∼1500 cm(2) V(-1) s(-1) and yield exceeding 98%. The biosensor exhibits high sensitivity and selectivity for the target naltrexone, an opioid receptor antagonist, with a detection limit of 10 pg/mL.

n-Dodecyl ß-D-maltoside specifically competes with general anesthetics for anesthetic binding sites.

We recently demonstrated that the anionic detergent sodium dodecyl sulfate (SDS) specifically interacts with the anesthetic binding site in horse spleen apoferritin, a soluble protein which models anesthetic binding sites in receptors. This raises the possibility of other detergents similarly interacting with and occluding such sites from anesthetics, thereby preventing the proper identification of novel anesthetic binding sites. n-Dodecyl ß-D-maltoside (DDM) is a non-ionic detergent commonly used during protein-anesthetic studies because of its mild and non-denaturing properties. In this study, we demonstrate that SDS and DDM occupy anesthetic binding sites in the model proteins human serum albumin (HSA) and horse spleen apoferritin and thereby inhibit the binding of the general anesthetics propofol and isoflurane. DDM specifically interacts with HSA (Kd = 40 µM) with a lower affinity than SDS (Kd = 2 µM). DDM exerts all these effects while not perturbing the native structures of either model protein. Computational calculations corroborated the experimental results by demonstrating that the binding sites for DDM and both anesthetics on the model proteins overlapped. Collectively, our results indicate that DDM and SDS specifically interact with anesthetic binding sites and may thus prevent the identification of novel anesthetic sites. Special precaution should be taken when undertaking and interpreting results from protein-anesthetic investigations utilizing detergents like SDS and DDM.

A computationally designed water-soluble variant of a G-protein-coupled receptor: the human mu opioid receptor.

G-protein-coupled receptors (GPCRs) play essential roles in various physiological processes, and are widely targeted by pharmaceutical drugs. Despite their importance, studying GPCRs has been problematic due to difficulties in isolating large quantities of these membrane proteins in forms that retain their ligand binding capabilities. Creating water-soluble variants of GPCRs by mutating the exterior, transmembrane residues provides a potential method to overcome these difficulties. Here we present the first study involving the computational design, expression and characterization of water-soluble variant of a human GPCR, the human mu opioid receptor (MUR), which is involved in pain and addiction. An atomistic structure of the transmembrane domain was built using comparative (homology) modeling and known GPCR structures. This structure was highly similar to the subsequently determined structure of the murine receptor and was used to computationally design 53 mutations of exterior residues in the transmembrane region, yielding a variant intended to be soluble in aqueous media. The designed variant expressed in high yield in Escherichia coli and was water soluble. The variant shared structural and functionally related features with the native human MUR, including helical secondary structure and comparable affinity for the antagonist naltrexone (Kd = 65 nM). The roles of cholesterol and disulfide bonds on the stability of the receptor variant were also investigated. This study exemplifies the potential of the computational approach to produce water-soluble variants of GPCRs amenable for structural and functionally related characterization in aqueous solution.