RESUMO
UNLABELLED: Iron availability functions as an environmental cue for enteropathogenic bacteria, signaling arrival within the human host. As enterotoxigenic Escherichia coli (ETEC) is a major cause of human diarrhea, the effect of iron on ETEC virulence factors was evaluated here. ETEC pathogenicity is directly linked to production of fimbrial colonization factors and secretion of heat-labile enterotoxin (LT) and/or heat-stable enterotoxin (ST). Efficient colonization of the small intestine further requires at least the flagellin binding adhesin EtpA. Under iron starvation, production of the CFA/I fimbriae was increased in the ETEC H10407 prototype strain. In contrast, LT secretion was inhibited. Furthermore, under iron starvation, gene expression of the cfa (CFA/I) and etp (EtpBAC) operons was induced, whereas transcription of toxin genes was either unchanged or repressed. Transcriptional reporter fusion experiments focusing on the cfa operon further showed that iron starvation stimulated cfaA promoter activity in ETEC, indicating that the impact of iron on CFA/I production was mediated by transcriptional regulation. Evaluation of cfaA promoter activity in heterologous E. coli single mutant knockout strains identified IscR as the regulator responsible for inducing cfa fimbrial gene expression in response to iron starvation, and this was confirmed in an ETEC ΔiscR strain. The global iron response regulator, Fur, was not implicated. IscR binding sites were identified in silico within the cfaA promoter and fixation confirmed by DNase I footprinting, indicating that IscR directly binds the promoter region to induce CFA/I. IMPORTANCE: Pathogenic enterobacteria modulate expression of virulence genes in response to iron availability. Although the Fur transcription factor represents the global regulator of iron homeostasis in Escherichia coli, we show that several ETEC virulence factors are modulated by iron, with expression of the major fimbriae under the control of the iron-sulfur cluster regulator, IscR. Furthermore, we demonstrate that the apo form of IscR, lacking an Fe-S cluster, is able to directly fix the corresponding promoter region. These results provide further evidence implicating IscR in bacterial virulence and suggest that IscR may represent a more general regulator mediating the iron response in enteropathogens.
Assuntos
Escherichia coli Enterotoxigênica/metabolismo , Proteínas de Escherichia coli/metabolismo , Proteínas de Fímbrias/metabolismo , Regulação Bacteriana da Expressão Gênica/fisiologia , Ferro/farmacologia , Fatores de Transcrição/metabolismo , Toxinas Bacterianas/genética , Toxinas Bacterianas/metabolismo , Sítios de Ligação , Enterotoxinas/genética , Enterotoxinas/metabolismo , Proteínas de Escherichia coli/genética , Proteínas de Fímbrias/genética , Regulação Bacteriana da Expressão Gênica/efeitos dos fármacos , Regiões Promotoras Genéticas , Fatores de Transcrição/genética , Fatores de Virulência/genética , Fatores de Virulência/metabolismoRESUMO
BACKGROUND: The acoustic assessment of phonation after total laryngectomy is challenged by signal aperiodicity which makes frequency-based acoustic measures less reliable. This is important for patients who use esophageal voice since voice samples mostly include type III (highly aperiodic) and 4 (chaotic) signals. As such, using non-linear measures, which are better suited for aperiodic phonation, may be useful to investigate the relationship between acoustic signal characteristics and perception of esophageal voice quality. OBJECTIVES: This study aimed to investigate whether nonlinear dynamic acoustic methods, nonlinear energy difference Ratio (NEDR) and spectrum convergence ratio (SCR), were correlated with perceptual measures in subjects who used esophageal phonation. METHODS: Thirty-one subjects who had undergone total laryngectomy and use esophageal voice as a rehabilitation method were included in this study. Expert and non-expert raters listened to the esophageal voice samples from the subjects and rated vowels and connected speech samples on a scale from 1 to 7 on dysphonia severity and intelligibility. In addition, non-linear acoustic analysis was performed to calculate NEDR and SCR. Analysis from the raters was compared to the non-linear acoustic analysis to find the correlation between the variables. RESULTS: There were no significant correlations between any of the non-linear acoustic measures NEDR and SCR and the perceptual ratings at the significance level of 0.05. Correlations were calculated for each acoustic measure among the expert raters and among the non-expert raters in both connected speech samples and sustained vowel fragments. CONCLUSIONS: In conclusion, the nonlinear dynamic acoustic analyses of spectrum convergence ratio and nonlinear energy difference ratio do not have a significant correlation with perceptual measures of esophageal voice.
RESUMO
To study the effects of cytokinin O-glucosylation in monocots, maize (Zea mays L.) transformants harbouring the ZOG1 gene (encoding a zeatin O-glucosyltransferase from Phaseolus lunatus L.) under the control of the constitutive ubiquitin (Ubi) promoter were generated. The roots and leaves of the transformants had greatly increased levels of zeatin-O-glucoside. The vegetative characteristics of hemizygous and homozygous Ubi:ZOG1 plants resembled those of cytokinin-deficient plants, including shorter stature, thinner stems, narrower leaves, smaller meristems, and increased root mass and branching. Transformant leaves had a higher chlorophyll content and increased levels of active cytokinins compared with those of non-transformed sibs. The Ubi:ZOG1 plants exhibited delayed senescence when grown in the spring/summer. While hemizygous transformants had reduced tassels with fewer spikelets and normal viable pollen, homozygotes had very small tassels and feminized tassel florets, resembling tasselseed phenotypes. Such modifications of the reproductive phase were unexpected and demonstrate a link between cytokinins and sex-specific floral development in monocots.
Assuntos
Expressão Gênica , Glucosiltransferases/metabolismo , Phaseolus/enzimologia , Proteínas de Plantas/metabolismo , Sementes/química , Zea mays/crescimento & desenvolvimento , Zeatina/metabolismo , Clorofila/metabolismo , Regulação da Expressão Gênica de Plantas , Glucosídeos/metabolismo , Glucosiltransferases/genética , Folhas de Planta/química , Folhas de Planta/genética , Folhas de Planta/crescimento & desenvolvimento , Folhas de Planta/metabolismo , Proteínas de Plantas/genética , Estômatos de Plantas/química , Estômatos de Plantas/citologia , Plantas Geneticamente Modificadas/química , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/crescimento & desenvolvimento , Plantas Geneticamente Modificadas/metabolismo , Sementes/genética , Sementes/crescimento & desenvolvimento , Sementes/metabolismo , Zea mays/química , Zea mays/genética , Zea mays/metabolismoRESUMO
The kinetic energy in ocean currents, or marine hydrokinetic (MHK) energy, is a renewable energy resource that can help meet global energy requirements. An ocean circulation model-based census shows that subtropical surface western boundary currents (WBCs) are the only nearshore, large-scale currents swift enough to drive large electricity-generating ocean turbines envisioned for future use. We review several WBCs in the context of kinetic energy extraction. The power density in the Gulf Stream off North Carolina at times reaches several thousand watts per square meter at 75 m below the surface, and the annual average power is approximately 500-1,000 W m-2. Significant fluctuations occur with periods of 3-20 days (Gulf Stream meanders) and weeks to months (Gulf Stream path shifts). Interannual variations in annual average power occur because of year-to-year changes in these WBC motions. No large-scale turbines presently exist, and the road to establishing MHK facilities in WBCs will encounter challenges that are similar in many aspects to those associated with the development of offshore wind power.
Assuntos
Conservação de Recursos Energéticos , Eletricidade , Oceanos e Mares , Movimentos da Água , Previsões , VentoRESUMO
Colonization factors (CFs) mediate early adhesion of Enterotoxigenic Escherichia coli (ETEC) in the small intestine. Environmental signals including bile, glucose, and contact with epithelial cells have previously been shown to modulate CF expression in a strain dependent manner. To identify novel components modulating CF surface expression, 20 components relevant to the intestinal environment were selected for evaluation. These included mucin, bicarbonate, norepinephrine, lincomycin, carbon sources, and cations. Effects of individual components on surface expression of the archetype CF, CFA/I, were screened using a fractional factorial Hadamard matrix incorporating 24 growth conditions. As most CFs agglutinate erythrocytes, surface expression was evaluated by mannose resistant hemagglutination. Seven components, including porcine gastric mucin, lincomycin, glutamine, and glucose were found to induce CFA/I surface expression in vitro in a minimal media while five others were inhibitory, including leucine and 1,10-phenanthroline. To further explore the effect of components positively influencing CFA/I surface expression, a response surface methodology (RSM) was designed incorporating 36 growth conditions. The optimum concentration for each component was identified, thereby generating a novel culture media, SP1, for CFA/I expression. CFs closely related to CFA/I, including CS4 and CS14 were similarly induced in SP1 media. Other epidemiologically relevant CFs were also induced when compared to the level obtained in minimal media. These results indicate that although CF surface expression is complex and highly variable among strains, the CF response can be predicted for closely related strains. A novel culture media inducing CFs in the CF5a group was successfully identified. In addition, mucin was found to positively influence CF expression in strains expressing either CFA/I or CS1 and CS3, and may function as a common environmental cue.
Assuntos
Meios de Cultura/farmacologia , Escherichia coli Enterotoxigênica/efeitos dos fármacos , Proteínas de Escherichia coli/biossíntese , Proteínas de Fímbrias/biossíntese , Regulação Bacteriana da Expressão Gênica/efeitos dos fármacos , Adesinas Bacterianas/biossíntese , Adesinas Bacterianas/genética , Animais , Aderência Bacteriana , Toxinas Bacterianas/análise , Técnicas Bacteriológicas , Bovinos , Parede Celular/química , Meios de Cultura/química , Escherichia coli Enterotoxigênica/genética , Escherichia coli Enterotoxigênica/metabolismo , Escherichia coli Enterotoxigênica/patogenicidade , Enterotoxinas/análise , Ensaio de Imunoadsorção Enzimática , Proteínas de Escherichia coli/análise , Proteínas de Escherichia coli/genética , Proteínas de Fímbrias/genética , Glutamina/farmacologia , Testes de Hemaglutinação , Humanos , Intestinos/química , Intestinos/microbiologia , Lincomicina/farmacologia , Mucinas/farmacologia , Sus scrofa , Suínos , Virulência/efeitos dos fármacosRESUMO
PURPOSE/BACKGROUND: To develop a consensus on the critical constructs necessary to be included in a physical performance assessment checklist (PPAC) to assess an athlete's ability for return to sport following a lower extremity injury. METHODS: The study used a 3-round Delphi method to finalize the PPAI originally developed by a panel of experts. Fourteen Delphi representative sample participants were randomly derived from the authors of peer-reviewed publications of lower extremity injuries. Nine participants completed all 3 rounds. RESULTS: Throughout the 3 rounds, the 10 initial constructs were modified and revised to produce the finalized PPAC consisting of 12 constructs necessary to consider for an athlete's return to sport after a lower extremity injury. CONCLUSIONS: This instrument can be used as a checklist to advocate for prospective batteries of physical performance tests to incorporate the elements identified by this study. LEVEL OF EVIDENCE: 5.