Gut Commensal Bacteroidetes Encode a Novel Class of Vitamin B12-Binding Proteins.

Human gut commensal Bacteroidetes rely on multiple transport systems to acquire vitamin B12 and related cobamides for fitness in the gut. In addition to a set of conserved transport proteins, these systems also include a diverse repertoire of additional proteins with unknown function. Here, we report the function and structural characterization of one of these proteins, BtuH, which binds vitamin B12 directly via a C-terminal globular domain that has no known structural homologs. This protein is required for efficient B12 transport and competitive fitness in the gut, demonstrating that members of the heterogeneous suite of accessory proteins encoded in Bacteroides cobamide transport system loci can play key roles in vitamin acquisition. IMPORTANCE The gut microbiome is a complex microbial community with important impacts on human health. One of the major groups within the gut microbiome, the Bacteroidetes, rely on their ability to capture vitamin B12 and related molecules for fitness in the gut. Unlike well-studied model organisms, gut Bacteroidetes genomes often include multiple vitamin B12 transport systems with a heterogeneous set of components. The role, if any, of these components was unknown. Here, we identify new proteins that play key roles in vitamin B12 capture in these organisms. Notably, these proteins are associated with some B12 transport systems and not others (even in the same bacterial strain), suggesting that these systems may assemble into functionally distinct machines to capture vitamin B12 and related molecules.

De novo synthesis of alkyne substituted tryptophans as chemical probes for protein profiling studies.

De novo synthesis of alkynalted tryptophan moieties as chemical probes for protein profilling studies, via an unexpected synthesis of Michael acceptor 12 is reported. Friedel Craft's alkylation of 12 and alkyne substituted indoles gave alkynalated tryptophan moieties, which perform as chemical probe by incorporating into actively translating Escherichia coli cells, whereby the alkyne moiety enables multimodal analyses through click chemistry mediated attachment of reporting groups.

Caveolae in ventricular myocytes are required for stretch-dependent conduction slowing.

Mechanical stretch of cardiac muscle modulates action potential propagation velocity, causing potentially arrhythmogenic conduction slowing. The mechanisms by which stretch alters cardiac conduction remain unknown, but previous studies suggest that stretch can affect the conformation of caveolae in myocytes and other cell types. We tested the hypothesis that slowing of action potential conduction due to cardiac myocyte stretch is dependent on caveolae. Cardiac action potential propagation velocities, measured by optical mapping in isolated mouse hearts and in micropatterned mouse cardiomyocyte cultures, decreased reversibly with volume loading or stretch, respectively (by 19±5% and 26±4%). Stretch-dependent conduction slowing was not altered by stretch-activated channel blockade with gadolinium or by GsMTx-4 peptide, but was inhibited when caveolae were disrupted via genetic deletion of caveolin-3 (Cav3 KO) or membrane cholesterol depletion by methyl-ß-cyclodextrin. In wild-type mouse hearts, stretch coincided with recruitment of caveolae to the sarcolemma, as observed by electron microscopy. In myocytes from wild-type but not Cav3 KO mice, stretch significantly increased cell membrane capacitance (by 98±64%), electrical time constant (by 285±149%), and lipid recruitment to the bilayer (by 84±39%). Recruitment of caveolae to the sarcolemma during physiologic cardiomyocyte stretch slows ventricular action potential propagation by increasing cell membrane capacitance.

Successful management of lipid-lowering programs.

Health improvement programs must today face the hurdle of demonstrating their value to the business professionals in managed care organizations. These individuals have vast fiscal responsibilities but often lack a medical background. It is imperative that program advocates not only identify these key decision makers, but present an argument for program adoption by using data these decision-makers are most familiar with: grounded, quantitative results. This tactic can enhance the likelihood of a program being implemented. To validate the proposed program to the MCO business sector, it must address a disease or condition that is characterized by wide variation in physician practice, high cost, high volume, and an evidence base that supports the proposed intervention.

Effect of a legislative mandate on mammography use and coding practices in Maryland.

PURPOSE: To analyze the effect of the 1991 Maryland legislative mandate of screening mammography benefits. MATERIALS AND METHODS: Claims submitted between January 1991 and December 1993 for outpatient mammograms obtained in women covered under Blue Cross Blue Shield of Maryland insurance indemnity contracts were analyzed for the distribution of services and charges. RESULTS: For 184,723 women, 285,241 claims were submitted by 851 Maryland providers. Claims for "mammography bilateral," which were considered "diagnostic," represented 67%; 24% were submitted for "screening mammography bilateral," and 9% were submitted for "mammography unilateral." Mammography claims increased only 25% during the 3 years, despite an estimated fivefold increase in the number of women with the screening mammography benefit. Mammography coding shifted from bilateral to screening. CONCLUSION: The number of mammograms obtained increased only modestly after the mandate, but claims coded for mammography bilateral declined dramatically. Removal of financial barriers appears to be insufficient to increase appropriate use of screening mammography.