Sucrase-isomaltase is an adenosine 3',5'-cyclic monophosphate–dependent epithelial chloride channel

BACKGROUND & AIMS: We previously isolated a monoclonal antibody against a Necturus gallbladder epitope that blocks native adenosine 3',5'-cyclic monophosphate (cAMP)-dependent chloride channels in intestine, gallbladder, urinary bladder, and airway epithelia in various animals. METHODS: Using this antibody, we purified a 200-kilodalton protein that, when reconstituted in lipid bilayers, forms 9-pS chloride channels that are blocked by the antibody. RESULTS: Amino acid sequencing of the purified protein showed strong homology to rabbit sucrase-isomaltase, an abundant intestinal enzyme. Western blot analysis of the in vitro-translated sucrase-isomaltase was indistinguishable from that of the protein used in the lipid bilayer studies. Expression of this protein in Chinese hamster ovary cells and in Xenopus laevis oocytes yielded cAMP-dependent chloride currents that in the latter system were blocked by the antibody. CONCLUSIONS: Because the monoclonal antibody blocks cAMP-dependent currents in epithelia as well as those produced both by the reconstituted and by the heterologously expressed protein, sucrase-isomaltase is a cAMP-dependent epithelial chloride channel. Thus an enzyme that can also function as an ion channel has been described for the first time

The certification of mass concentration of Beta-2-microglobulin in human serum: ERM-DA470k/IFCC

This report describes the additional certification of the mass concentration of Beta-2-microglobulin (B2M) in ERM-DA470k/IFCC, a human serum material. The material was certified following ISO Guide 34:2009. The material was released in 2008 and was certified for the mass concentration of 12 proteins in human serum. A full description of the processing steps can be found in the original report. Between unit-homogeneity was quantified and stability during dispatch and storage were assessed in accordance with ISO Guide 35:2006. Within-unit homogeneity was estimated to determine the minimum sample intake. The material was characterised by an intercomparison among laboratories of demonstrated competence and adhering to ISO/IEC 17025. Uncertainties of the certified values were calculated in compliance with the Guide to the Expression of Uncertainty in Measurement (GUM) and include uncertainties related to possible inhomogeneity, to instability and to characterisation. The material is intended for the calibration of immunoassay-based in-vitro diagnostic devices or control products for the proteins certified. As for any calibrator it should be verified that it is commutable. The material is produced in a similar manner as ERM-DA470, the use of which has led to a significant reduction in the between-method and between-laboratory variation for the proteins certified (B2M was not certified in this material) [ , ]. It was verified during the value assignment procedure that there were no significant matrix effects, and that different methods produced consistent results. However, when the material is used as a calibrator, the commutability should be verified for the particular assay concerned. The Certified Reference Material (CRM) is available in the lyophilised form of a 1.0 mL portion of serum with additives (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES), sodium azide, benzamidine hydrochloride, sodium chloride and aprotinin). The material is kept under nitrogen gas in threaded glass bottles with rubber stoppers and polypropylene screw caps. The water mass fraction of the sample is (4.3 ± 0.6) mg/g. The lyophilised powder has to be reconstituted with (1.00 ± 0.01) g of distilled water. The minimum amount of reconstituted sample to be used is 2 µL. The CRM was accepted as European Reference Material (ERM®) after peer evaluation by the partners of the European Reference Materials consortium.JRC.D.2-Standards for Innovation and sustainable Developmen

Generation of a New Cystatin C-Based Estimating Equation for Glomerular Filtration Rate by Use of 7 Assays Standardized to the International Calibrator.

Many different cystatin C-based equations exist for estimating glomerular filtration rate. Major reasons for this are the previous lack of an international cystatin C calibrator and the nonequivalence of results from different cystatin C assays

Interaction of cells and nanofiber scaffolds in tissue engineering

10.1002/jbm.b.30841Journal of Biomedical Materials Research - Part B Applied Biomaterials84134-48JBMR