The tight control of autolysis by Streptococcus mutans is critical for proper virulence gene expression and biofilm formation. A pair of dicistronic operons, SMU.575/574 (lrgAB) and SMU.1701/1700 (designated cidAB), encode putative membrane proteins that share structural features with the bacteriophage-encoded holin family of proteins, which modulate host cell lysis during lytic infection. Analysis of S. mutans lrg and cid mutants revealed a role for these operons in autolysis, biofilm formation, glucosyltransferase expression and oxidative stress tolerance. Expression of lrgAB was repressed during early exponential phase and was induced over 1000-fold as cells entered late exponential phase, whereas cidAB expression declined from early to late exponential phase. A two-component system encoded immediately upstream of lrgAB (LytST) was required for activation of lrgAB expression, but not for cid expression. In addition to availability of oxygen, glucose levels were revealed to affect lrg and cid transcription differentially and significantly, probably through CcpA (carbon catabolite protein A). Collectively, these findings demonstrate that the Cid/Lrg system can affect several virulence traits of S. mutans, and its expression is controlled by two major environmental signals, oxygen and glucose. Moreover, cid/lrg expression is tightly regulated by LytST and CcpA.

Streptococcus mutans is widely recognized as one of the key etiological agents of human dental caries. Despite its role in this important disease, our present knowledge of gene content variability across the species and its relationship to adaptation is minimal. Estimates of its demographic history are not available. In this study, we generated genome sequences of 57 S. mutans isolates, as well as representative strains of the most closely related species to S. mutans (S. ratti, S. macaccae, and S. criceti), to identify the overall structure and potential adaptive features of the dispensable and core components of the genome. We also performed population genetic analyses on the core genome of the species aimed at understanding the demographic history, and impact of selection shaping its genetic variation. The maximum gene content divergence among strains was approximately 23%, with the majority of strains diverging by 5-15%. The core genome consisted of 1,490 genes and the pan-genome approximately 3,296. Maximum likelihood analysis of the synonymous site frequency spectrum (SFS) suggested that the S. mutans population started expanding exponentially approximately 10,000 years ago (95% confidence interval [CI]: 3,268-14,344 years ago), coincidental with the onset of human agriculture. Analysis of the replacement SFS indicated that a majority of these substitutions are under strong negative selection, and the remainder evolved neutrally. A set of 14 genes was identified as being under positive selection, most of which were involved in either sugar metabolism or acid tolerance. Analysis of the core genome suggested that among 73 genes present in all isolates of S. mutans but absent in other species of the mutans taxonomic group, the majority can be associated with metabolic processes that could have contributed to the successful adaptation of S. mutans to its new niche, the human mouth, and with the dietary changes that accompanied the origin of agriculture.

Key pointsr Endothelial inwardly rectifying K + (Kir2.1) channels regulate flow-induced vasodilatation via nitric oxide (NO) in mouse mesenteric resistance arteries.r Deficiency of Kir2.1 channels results in elevated blood pressure and increased vascular resistance.r Flow-induced vasodilatation in human resistance arteries is also regulated by inwardly rectifying K + channels.r This study presents the first direct evidence that Kir channels play a critical role in physiological endothelial responses to flow.Abstract Inwardly rectifying K + (Kir) channels are known to be sensitive to flow, but their role in flow-induced endothelial responses is not known. The goal of this study is to establish the role of Kir channels in flow-induced vasodilatation and to provide first insights into the mechanisms responsible for Kir signalling in this process. First, we establish that primary endothelial cells isolated from murine mesenteric arteries express functional Kir2.1 channels sensitive to shear stress. Then, using the Kir2.1 +/− heterozygous mouse model, we establish that downregulation of Kir2.1 results in significant decrease in shear-activated Kir currents and inhibition of endothelium-dependent flow-induced vasodilatation (FIV) assayed in pressurized mesenteric arteries pre-constricted with endothelin-1. Deficiency in Kir2.1 also results in the loss of flow-induced phosphorylation of eNOS and Akt, as well as inhibition of NO generation. All the effects are fully rescued by endothelial cell (EC)-specific overexpression of Kir2.1. A component of FIV that is Kir independent is abrogated by blocking Ca 2+ -sensitive K + channels. Kir2.1 has no effect on endothelium-independent and K + -induced vasodilatation in denuded arteries. Kir2.1 +/− mice also show increased mean blood pressure measured by carotid artery cannulation and increased microvascular resistance measured using a tail-cuff. Importantly, blocking Kir channels also inhibits flow-induced vasodilatation in human subcutaneous adipose microvessels. Endothelial Kir channels contribute to FIV of mouse mesenteric arteries via an NO-dependent mechanism, whereas Ca 2+ -sensitive K + channels mediate FIV via an NO-independent pathway. Kir2 channels also regulate vascular resistance and blood pressure. Finally, Kir channels also contribute to FIV in human subcutaneous microvessels.

This study focuses on perceived value, which is not mentioned in previous internet-only bank studies, to analyze the popularity of internet-only banks. It does this by exploring the relationships between the perceived value and usage intention of customers. The purpose of this study is to help us understand customers’ decision making to accept innovative services by finding factors that affect consumer acceptance of internet-only banks. Using multiple regression, this study analyzes data gathered from college students in their 20s who are familiar with IT services and are interested in internet-only banks. The results show that all three components of perceived value (economical value, convenience value, and emotional value) increase usage intention. Convenience value is the most important factor in the acceptance of internet-only banking services. The findings indicate that perceived value is an attractive factor in using internet-only banks and suggest that managing and developing perceived value is an important marketing strategy.

BackgroundHypercholesterolemia‐induced decreased availability of nitric oxide (NO) is a major factor in cardiovascular disease. We previously established that cholesterol suppresses endothelial inwardly rectifying K+ (Kir) channels and that Kir2.1 is an upstream mediator of flow‐induced NO production. Therefore, we tested the hypothesis that suppression of Kir2.1 is responsible for hypercholesterolemia‐induced inhibition of flow‐induced NO production and flow‐induced vasodilation (FIV). We also tested the role of Kir2.1 in the development of atherosclerotic lesions.Methods and ResultsKir2.1 currents are significantly suppressed in microvascular endothelial cells exposed to acetylated–low‐density lipoprotein or isolated from apolipoprotein E–deficient (Apoe −/−) mice and rescued by cholesterol depletion. Genetic deficiency of Kir2.1 on the background of hypercholesterolemic Apoe −/−mice, Kir2.1 +/− /Apoe −/− exhibit the same blunted FIV and flow‐induced NO response as Apoe −/−or Kir2.1 +/− alone, but while FIV in Apoe −/− mice can be rescued by cholesterol depletion, in Kir2.1 +/− /Apoe −/− mice cholesterol depletion has no effect on FIV. Endothelial‐specific overexpression of Kir2.1 in arteries from Apoe −/− and Kir2.1 +/− /Apoe −/− mice results in full rescue of FIV and NO production in Apoe −/− mice with and without the addition of a high‐fat diet. Conversely, endothelial‐specific expression of dominant‐negative Kir2.1 results in the opposite effect. Kir2.1 +/− /Apoe −/−mice also show increased lesion formation, particularly in the atheroresistant area of descending aorta.ConclusionsWe conclude that hypercholesterolemia‐induced reduction in FIV is largely attributable to cholesterol suppression of Kir2.1 function via the loss of flow‐induced NO production, whereas the stages downstream of flow‐induced Kir2.1 activation appear to be mostly intact. Kir2.1 channels also have an atheroprotective role.

Vertebrate tissues exhibit mechanical homeostasis, showing stable stiffness and tension over time and recovery after changes in mechanical stress. However, the regulatory pathways that mediate these effects are unknown. A comprehensive identification of Argonaute-2(AGO2)-associated microRNAs and mRNAs in endothelial cells identified a network of 122 microRNA families that target 73 mRNAs encoding cytoskeletal, contractile, adhesive and extracellular matrix (CAM) proteins. These microRNAs increased in cells plated on stiff vs. soft substrates, consistent with homeostasis, and suppressed targets via microRNA recognition elements (MREs) within the 3’UTRs of CAM mRNAs. Inhibition of DROSHA or AGO2, or disruption of MREs within individual target mRNAs such as Connective Tissue Growth Factor (CTGF), induced hyper-adhesive, hyper-contractile phenotypes in endothelial and fibroblast cells in vitro, and increased tissue stiffness, contractility and extracellular matrix (ECM) deposition in the zebrafish fin-fold in vivo . Thus, a network of microRNAs buffers CAM expression to mediate tissue mechanical homeostasis.

This study reports depigmenting potency of selenium-containing carbohydrates, which would be based upon the finding of direct inhibition to mushroom tyrosinase. Two selenoglycosiede, SG-3 (bis(2,3,4-tri-O-acetyl-b b-Darabinopyranosyl) selenide) and SG-8 (4-methylbenzoyl 2,3,4,6-tetra-O-acetyl-D-selenomanopyranoside) among eleven selenium-containing compounds examined, were discovered to be effective depigmenting compounds on a mushroom tyrosinase inhibitory assay. SG-3 exhibited a competitive inhibition effect that was similar to kojic acid, well-known tyrosinase inhibitor. At 100 m mM and 150 m mM, SG-8 had an uncompetitive inhibitory effect that was higher than kojic acid. A study of a melan-a cell originated-tyrosinase inhibition assay showed that SG-8 had a lower inhibitory effect than kojic acid. SG-3 showed a similar inhibition effect to kojic acid on the melan-a celloriginated tyrosinase inhibitory assay. SG-8 showed dose-dependently cytotoxicity in a study of inhibition melanin synthesis by melan-a cells. Most melan-a cells did not survive after being treated with 20 m mM of SG-8. At 10 m mM, SG-3 inhibited melanin synthesis in the melan-a cells, and the effect was similar to phenylthiourea, which is a well-known inhibitor of melanin synthesis. Therefore, SG-3 is a new candidate for depigmenting reagents.

The dental caries pathogen is continually exposed to several types of stress in the oral biofilm environment. Oxidative stress generated by reactive oxygen species has a major impact on the establishment, persistence, and virulence of Here, we combined fluorescent reporter-promoter fusions with single-cell imaging to study the effects of reactive oxygen species on activation of genetic competence in Exposure to paraquat, which generates superoxide anion, produced a qualitatively different effect on activation of expression of the gene for the master competence regulator, ComX, than did treatment with hydrogen peroxide (HO), which can yield hydroxyl radical. Paraquat suppressed peptide-mediated induction of in a progressive and cumulative fashion, whereas the response to HO displayed a strong threshold behavior. Low concentrations of HO had little effect on induction of or the bacteriocin gene, but expression of these genes declined sharply if extracellular HO exceeded a threshold concentration. These effects were not due to decreased reporter gene fluorescence. Two different threshold concentrations were observed in the response to HO, depending on the gene promoter that was analyzed and the pathway by which the competence regulon was stimulated. The results show that paraquat and HO affect the competence signaling pathway differently, and that some portions of the competence signaling pathway are more sensitive to oxidative stress than others. inhabits the oral biofilm, where it plays an important role in the development of dental caries. Environmental stresses such as oxidative stress influence the growth of and its important virulence-associated behaviors, such as genetic competence. competence development is a complex behavior that involves two different signaling peptides and can exhibit cell-to-cell heterogeneity. Although oxidative stress is known to influence competence, it is not understood how oxidative stress interacts with the peptide signaling or affects heterogeneity. In this study, we used fluorescent reporters to probe the effect of reactive oxygen species on competence signaling at the single-cell level. Our data show that different reactive oxygen species have different effects on competence, and that some portions of the signaling pathway are more acutely sensitive to oxidative stress than others.