NanR Regulates Sporulation and Enterotoxin Production by Clostridium perfringens Type F Strain F4969.

Clostridium perfringens type F strains, which produce C. perfringens enterotoxin (CPE), are a major cause of gastrointestinal infections, including the second most prevalent bacterial foodborne illness and 5 to 10% cases of antibiotic-associated diarrhea. Virulence of type F strains is primarily ascribable to CPE, which is synthesized only during sporulation. Many type F strains also produce NanI sialidase and carry a nan operon that likely facilitates uptake and metabolism of sialic acid liberated from glycoconjugates by NanI. During vegetative growth of type F strain F4969, NanR can regulate expression of nanI Given their importance for type F disease, the current study investigated whether NanR can also influence sporulation and CPE production when F4969 or isogenic derivatives are cultured in modified Duncan-Strong sporulation (MDS) medium. An isogenic F4969 nanR null mutant displayed much less sporulation and CPE production but more NanI production than wild-type F4969, indicating that NanR positively regulates sporulation and CPE production but represses NanI production in MDS. Results for the nanR mutant also demonstrated that NanR regulates expression of the nan operon. A nanI nanR double null mutant mirrored the outcome of the nanR null mutant strain but with a stronger inhibition of sporulation and CPE production, even after overnight incubation. Coupled with results using a nanI null mutant, which had no impairment of sporulation or CPE production, NanR appears to carefully modulate the availability of NanI, nan operon-encoded proteins and sialic acid to provide sufficient nutrients to sustain sporulation and CPE production when F4969 is cultured in MDS medium.

Myofibroblast senescence promotes arrhythmogenic remodeling in the aged infarcted rabbit heart.

Progressive tissue remodeling after myocardial infarction (MI) promotes cardiac arrhythmias. This process is well studied in young animals, but little is known about pro-arrhythmic changes in aged animals. Senescent cells accumulate with age and accelerate age-associated diseases. Senescent cells interfere with cardiac function and outcome post-MI with age, but studies have not been performed in larger animals, and the mechanisms are unknown. Specifically, age-associated changes in timecourse of senescence and related changes in inflammation and fibrosis are not well understood. Additionally, the cellular and systemic role of senescence and its inflammatory milieu in influencing arrhythmogenesis with age is not clear, particularly in large animal models with cardiac electrophysiology more similar to humans than previously studied animal models. Here, we investigated the role of senescence in regulating inflammation, fibrosis, and arrhythmogenesis in young and aged infarcted rabbits. Aged rabbits exhibited increased peri-procedural mortality and arrhythmogenic electrophysiological remodeling at the infarct border zone (IBZ) compared to young rabbits. Studies of the aged infarct zone revealed persistent myofibroblast senescence and increased inflammatory signaling over a 12-week timecourse. Senescent IBZ myofibroblasts in aged rabbits appear to be coupled to myocytes, and our computational modeling showed that senescent myofibroblast-cardiomyocyte coupling prolongs action potential duration (APD) and facilitates conduction block permissive of arrhythmias. Aged infarcted human ventricles show levels of senescence consistent with aged rabbits, and senescent myofibroblasts also couple to IBZ myocytes. Our findings suggest that therapeutic interventions targeting senescent cells may mitigate arrhythmias post-MI with age.

Characterization of NanR Regulation of Sialidase Production, Sporulation and Enterotoxin Production by Clostridium perfringens Type F Strains Carrying a Chromosomal Enterotoxin Gene.

Clostridium perfringens type F food poisoning (FP) strains produce C. perfringens enterotoxin (CPE) to cause a common bacterial food-borne illness in the United States. During FP, CPE is synthesized in the intestines when C. perfringens sporulates. Besides CPE, FP strains also produce sialidases. Most FP strains carry their cpe gene on the chromosome and all surveyed chromosomal cpe (c-cpe) FP strains produce NanH sialidase or both NanJ and NanH sialidases. NanR has been shown previously to regulate sialidase activity in non-FP strains. The current study investigated whether NanR also regulates sialidase activity or influences sporulation and CPE production for c-cpe FP strains SM101 and 01E809. In sporulation medium, the SM101 nanR null mutant showed lower sialidase activity, sporulation, and CPE production than its wild-type parent, while the 01E809 nanR null mutant showed roughly similar sialidase activity, sporulation, and CPE production as its parent. In vegetative medium, the nanR null mutants of both strains produced more spores than their parents while NanR repressed sialidase activity in SM101 but positively regulated sialidase activity in 01E809. These results demonstrate that NanR regulates important virulence functions of c-cpe strains, with this control varying depending on strain and culture conditions.

Augmented reality in medical education: a systematic review.

INTRODUCTION: The field of augmented reality (AR) is rapidly growing with many new potential applications in medical education. This systematic review investigated the current state of augmented reality applications (ARAs) and developed an analytical model to guide future research in assessing ARAs as teaching tools in medical education. METHODS: A literature search was conducted using PubMed, Embase, Web of Science, Cochrane Library, and Google Scholar. This review followed PRISMA guidelines and included publications from January 1, 2000 to June 18, 2018. Inclusion criteria were experimental studies evaluating ARAs implemented in healthcare education published in English. Our review evaluated study quality and determined whether studies assessed ARA validity using criteria established by the GRADE Working Group and Gallagher et al., respectively. These findings were used to formulate an analytical model to assess the readiness of ARAs for implementation in medical education. RESULTS: We identified 100,807 articles in the initial literature search; 36 met inclusion criteria for final review and were categorized into three categories: Surgery (23), Anatomy (9), and Other (4). The overall quality of the studies was poor and no ARA was tested for all five stages of validity. Our analytical model evaluates the importance of research quality, application content, outcomes, and feasibility of an ARA to gauge its readiness for implementation. CONCLUSION: While AR technology is growing at a rapid rate, the current quality and breadth of AR research in medical training is insufficient to recommend the adoption into educational curricula. We hope our analytical model will help standardize AR assessment methods and define the role of AR technology in medical education.

CONTEXTE: Le domaine de la réalité augmentée (RA) est en pleine émergence et dispose de plusieurs nouvelles applications potentielles en éducation médicale. Cette revue systématique a évalué l'état actuel des applications de réalité augmentée (ARA) afin d'et élaboré un modèle analytique pour orienter les futures recherches sur l'évaluation des ARA comme outils pédagogiques en éducationmédicale. MÉTHODES: Une recherche documentaire a été menée à l'aide de PubMed, Web of Science, Cochrane Library et Google Scholar. Cette revue a suivi les directives de la méthode PRISMA et contenait les publications du 1er janvier 2000 au 18 juin 2018. Les études étaient retenues si elles avaient un devis expérimental et qu'elles avaient été publiées en anglais et qu'elles évaluaient des ARA mises en place dans l'enseignement des soins de santé. Notre revuea évalué la qualité des études et déterminé si les études ont pu évaluer la validité des ARA en utilisant les critères établis par le GRADE Working Group et Gallagher et coll., respectivement. À partir de ces conclusions, nous avons formulé un modèle analytique afin d'évaluer si les ARA peuvent être mises en place dans la formation médicale. RÉSULTATS: Nous avons trouvé 100 807 articles lors de la recherche documentaire initiale; 36 ont satisfait aux critères d'inclusion pour l'examen final et ont été classés dans trois catégories : chirurgie (23), anatomie (9) et autre (4). La qualité globaledes études était de mauvaise et aucune ARA n'a été testée pour toutes les cinq étapes de validité. Notre modèle analytique évalue l'importance de la qualité des recherches, du contenu des applications, des résultats, et de la faisabilité d'une ARA pour déterminer si elle est prête à être mise en place. CONCLUSION: Bien que la technologie de la RA progresse rapidement, la qualité et l'étendue actuelles de la recherche sur la RA en éducationmédicale sont insuffisantes pour recommander son adoption dans le cursus de formation. Nous espérons que notre modèle analytique aidera à uniformiserles méthodes d'évaluations de la RA et à déterminer le rôle de la technologie liée à la RA en éducation médicale.

Identification of an Important Orphan Histidine Kinase for the Initiation of Sporulation and Enterotoxin Production by Clostridium perfringens Type F Strain SM101.

Clostridium perfringens type F strains cause a common human foodborne illness and many cases of nonfoodborne human gastrointestinal diseases. Sporulation plays two critical roles during type F enteric disease. First, it produces broadly resistant spores that facilitate type F strain survival in the food and nosocomial environments. Second, production of C. perfringens enterotoxin (CPE), the toxin responsible for causing the enteric symptoms of type F diseases, is restricted to cells in the process of sporulation. While later steps in the regulation of C. perfringens sporulation have been discerned, the process leading to phosphorylation of Spo0A, the master early regulator of sporulation and consequent CPE production, has remained unknown. Using an insertional mutagenesis approach, the current study identified the orphan histidine kinase CPR0195 as an important factor regulating C. perfringens sporulation and CPE production. Specifically, a CPR0195 null mutant of type F strain SM101 made 103-fold fewer spores than its wild-type parent and produced no detectable CPE. In contrast, a null mutant of another putative C. perfringens orphan histidine kinase (CPR1055) did not significantly affect sporulation or CPE production. Studies using a spoIIA operon promoter-driven reporter plasmid indicated that CPR0195 functions early during sporulation, i.e., prior to production of sporulation-associated sigma factors. Furthermore, in vitro studies showed that the CPR0195 kinase domain can autophosphorylate and phosphorylate Spo0A. These results support the idea of CPR0195 as an important kinase that initiates C. perfringens sporulation by directly phosphorylating Spo0A. This kinase could represent a novel therapeutic target to block C. perfringens sporulation and CPE production during type F disease.IMPORTANCEClostridium perfringens type F enteric diseases, which include a very common form of food poisoning and many cases of antibiotic-associated diarrhea, develop when type F strains sporulate and produce C. perfringens enterotoxin (CPE) in the intestines. Spores are also important for transmission of type F disease. Despite the importance of sporulation for type F disease and the evidence that C. perfringens sporulation begins with phosphorylation of the Spo0A transcriptional regulator, the kinase phosphorylating Spo0A to initiate sporulation and CPE production had not been ascertained. In response, the current report now provides identification of an orphan histidine kinase named CPR0195 that can directly phosphorylate Spo0A. Results using a CPR0195 null mutant indicate that this kinase is very important for initiating C. perfringens sporulation and CPE production. Therefore, the CPR0195 kinase represents a potential target to block type F disease by interfering with intestinal C. perfringens sporulation and CPE production.

Extracellular Ubiquitin(1-76) and Ubiquitin(1-74) Regulate Cardiac Fibroblast Proliferation.

SDF-1α (stromal cell-derived factor-1α) is a CXCR4-receptor agonist and DPP4 (dipeptidyl peptidase 4) substrate. SDF-1α, particularly when combined with sitagliptin to block the metabolism of SDF-1α by DPP4, stimulates proliferation of cardiac fibroblasts via the CXCR4 receptor; this effect is greater in cells from spontaneously hypertensive rats versus Wistar-Kyoto normotensive rats. Emerging evidence indicates that ubiquitin(1-76) exists in plasma and is a potent CXCR4-receptor agonist. Therefore, we hypothesized that ubiquitin(1-76), similar to SDF-1α, should increase proliferation of cardiac fibroblasts. Contrary to our working hypothesis, ubiquitin(1-76) did not stimulate cardiac fibroblast proliferation, yet unexpectedly antagonized the proproliferative effects of SDF-1α combined with sitagliptin. In this regard, ubiquitin(1-76) was more potent in spontaneously hypertensive versus Wistar-Kyoto cells. In the presence of 6bk (selective inhibitor of insulin-degrading enzyme [IDE]; an enzyme known to convert ubiquitin(1-76) to ubiquitin(1-74)), ubiquitin(1-76) no longer antagonized the proproliferative effects of SDF-1α/sitagliptin. Ubiquitin(1-74) also antagonized the proproliferative effects of SDF-1α/sitagliptin, and this effect of ubiquitin(1-74) was not blocked by 6bk and was >10-fold more potent compared with ubiquitin(1-76). Neither ubiquitin(1-76) nor ubiquitin(1-74) inhibited the proproliferative effects of the non-CXCR4 receptor agonist neuropeptide Y (activates Y1 receptors). Cardiac fibroblasts expressed IDE mRNA, protein, and activity and converted ubiquitin(1-76) to ubiquitin(1-74). Spontaneously hypertensive fibroblasts expressed greater IDE activity. Extracellular ubiquitin(1-76) blocks the proproliferative effects of SDF-1α/sitagliptin via its conversion by IDE to ubiquitin(1-74), a potent CXCR4 antagonist. Thus, IDE inhibitors, particularly when combined with DPP4 inhibitors or hypertension, could increase the risk of cardiac fibrosis.