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Xylooligosaccharides (XOS) have been employed as prebiotics containing oligomers of varying sizes or molecular ratios. XOS with a low degree of polymerization (DP) has been demonstrated to have high prebiotic potential. However, there is limited information regarding the specific chain length of XOS required to elicit distinct responses in the gut microbiota. In this study, we aimed to explore whether variations in XOS DP could alter the fate of colonic fermentation. Five XOS fractions (BWXFs) with DP ranges of >40, 20-40, 10-20, 5-10, and 2-4 were prepared by beechwood xylan autohydrolysis and tested on human gut microbiota. Extracellular XOS degradation was observed for molecules with a DP exceeding 5. BWXF treatments altered the microbial community structures, and substrate size-dependent effects on the microbial composition and metabolic outputs were observed. Bacteroidaceae were specifically enriched by xylan. Lachnospiraceae were particularly stimulated by XOS with a DP of 20-40 and 2-4. Bifidobacteriaceae were notably enriched by XOS with a DP of 5-20. High butyrate yields were obtained from cultures containing long-chain BWXFs. Microbiota responses differed with XOS DP composition changes, and microbial competition with XOS with a DP of 2-4 requires further exploration.
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Prebióticos , Xilanos , Humanos , Fermentación , Xilanos/metabolismo , Colon/metabolismo , Oligosacáridos/metabolismo , Glucuronatos/metabolismoRESUMEN
Butyrate, a physiologically active molecule, can be synthesized through metabolic interactions among colonic microorganisms. Previously, in a fermenting trial of human fecal microbiota, we observed that the butyrogenic effect positively correlated with the increasing Bifidobacterium population and an unidentified Megasphaera species. Therefore, we hypothesized that a cross-feeding phenomenon exists between Bifidobacterium and Megasphaera, where Megasphaera is the butyrate producer, and its growth relies on the metabolites generated by Bifidobacterium. To validate this hypothesis, three bacterial species (B. longum, B. pseudocatenulatum, and M. indica) were isolated from fecal cultures fermenting hydrolyzed xylan; pairwise cocultures were conducted between the Bifidobacterium and M. indica isolates; the microbial interactions were determined based on bacterial genome information, cell growth, substrate consumption, metabolite quantification, and metatranscriptomics. The results indicated that two Bifidobacterium isolates contained distinct gene clusters for xylan utilization and expressed varying substrate preferences. In contrast, M. indica alone scarcely grew on the xylose-based substrates. The growth of M. indica was significantly elevated by coculturing it with bifidobacteria, while the two Bifidobacterium species responded differently in the kinetics of cell growth and substrate consumption. Coculturing led to the depletion of lactate and increased the formation of butyrate. An RNA-seq analysis further revealed the upregulation of M. indica genes involved in the lactate utilization and butyrate formation pathways. We concluded that lactate generated by Bifidobacterium through catabolizing xylose fueled the growth of M. indica and triggered the synthesis of butyrate. Our findings demonstrated a novel cross-feeding mechanism to generate butyrate in the human colon.IMPORTANCEButyrate is an important short-chain fatty acid that is produced in the human colon through microbial fermentation. Although many butyrate-producing bacteria exhibit a limited capacity to degrade nondigestible food materials, butyrate can be formed through cross-feeding microbial metabolites, such as acetate or lactate. Previously, the literature has explicated the butyrate-forming links between Bifidobacterium and Faecalibacterium prausnitzii and between Bifidobacterium and Eubacterium rectale. In this study, we provided an alternative butyrate synthetic pathway through the interaction between Bifidobacterium and Megasphaera indica. M. indica is a species named in 2014 and is indigenous to the human intestinal tract. Scientific studies explaining the function of M. indica in the human colon are still limited. Our results show that M. indica proliferated based on the lactate generated by bifidobacteria and produced butyrate as its end metabolic product. The pathways identified here may contribute to understanding butyrate formation in the gut microbiota.
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Bifidobacterium , Ácido Láctico , Humanos , Ácido Láctico/metabolismo , Bifidobacterium/metabolismo , Xilanos/metabolismo , Xilosa/metabolismo , Butiratos/metabolismo , Megasphaera/metabolismo , FermentaciónRESUMEN
Background: Numerous studies have confirmed that skilled readers can benefit from a semantically related preview word (i.e., semantic preview benefit, SPB), suggesting that readers can extract semantic information from the parafovea to achieve efficient reading. It is still under debate whether the occurrence of this benefit is because of the semantic association between the preview and target words or because of the contextual fit of the preview word in the sentence context. Methods: Two independent factors, preview plausibility (preview plausible/implausible) and semantic relatedness (semantically related/unrelated), were manipulated, and we further strictly controlled for syntactic plausibility in the present study. Results: The results showed that the first-pass reading times of the target words were significantly shorter in the plausible preview condition than in the implausible preview condition. However, the main effect of semantic relatedness was found only in the gaze duration measure. Discussion: The pattern of results revealed that semantic plausibility affects the semantic preview benefit preferentially in Chinese reading, supporting the contextual fit account. Our findings have implications for a better understanding of parafoveal processing and provide empirical support for the eye-movement control model.
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Pueblos del Este de Asia , Semántica , Humanos , Pueblo Asiatico , Movimientos Oculares , China , LecturaRESUMEN
Background/purpose: Periodontitis is a chronic inflammatory disease, and periodontal ligament cells (PDLCs) are pivotal for osteogenesis. Circular RNAs (circRNAs) can regulate disease progression via targeting miRNA/mRNA axis. The purposes of this study were to explore the function and mechanism of circ_0138959 in periodontitis. Materials and methods: Periodontitis cell model was established by lipopolysaccharide (LPS) treatment in PDLCs. RNA expression was determined by quantitative reverse transcription-polymerase chain reaction assay. Cell proliferation was detected using 3-(4, 5-dimethylthiazol-2-y1)-2, 5-diphenyl tetrazolium bromide assay. Wound healing and cell apoptosis were examined by wound healing assay and flow cytometry. Inflammatory cytokines were measured via Enzyme-linked immunosorbent assay. Osteogenic differentiation was assessed by Alkaline phosphatase and Alizarin red S staining assays. Western blot was used for protein detection. The target interaction was validated by dual-luciferase reporter assay. Results: Circ_0138959 was overexpressed in periodontitis tissues and LPS-treated PDLCs. Downregulation of circ_0138959 attenuated LPS-induced inhibition of proliferation, wound healing and osteogenic differentiation but promotion of apoptosis and inflammation. Circ_0138959 acted as a miR-495-3p sponge, and the regulatory role of circ_0138959 in LPS-induced cell injury was achieved by sponging miR-495-3p. Additionally, miR-495-3p targeted TNF Receptor Associated Factor 6 (TRAF6) and miR-495-3p protected against LPS-induced cell dysfunction by targeting TRAF6. Circ_0138959 upregulated TRAF6 level via inhibiting miR-495-3p. Conclusion: This study suggested that circ_0138959 upregulated the TRAF6 expression by binding to miR-495-3p, consequently aggravating LPS-induced cell damages in PDLCs. Circ_0138959 might be a probable target for treatment of periodontitis.
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An exopolysaccharide (EPS) synthesizing potentially probiotic Gram-positive bacterial strain was isolated from fish (Tor putitora) gut, and its EPS was structurally characterized. The isolate, designated as FW2, was identified as Lactobacillus reuteri through 16S rRNA gene sequencing and phylogenetic analysis. This isolate produces fructan-type EPS using sucrose as a substrate. Based on 13C-NMR spectroscopy, methylation analysis and monosaccharide composition, the EPS was identified as a linear levan polymer with fructose as main constituent linked via ß(2 â 6) linkages. Based on molecular weight (MW) distribution, two groups of levan were found to be produced by the isolate FW2: one with high MW (4.6 × 106 Da) and the other having much lower MW (1.2 × 104 Da). The isolate yielded about 14 g/L levan under optimized culturing parameters including aeration conditions, pH, temperature and substrate concentration. The obtained bimodal molecular weight linear levan is the first of its type to be synthesized by a L. reuteri isolate from fish gut. Bimodal molecular weight prebiotic levan together with the probiotic potential of the producing strain would provide a new promising synbiotic combination for use in aqua culture.
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Limosilactobacillus reuteri , Animales , Fructanos , Limosilactobacillus reuteri/genética , Peso Molecular , Filogenia , ARN Ribosómico 16S/genéticaRESUMEN
Autohydrolysis is used for producing xylan-derived oligosaccharides from lignocellulosic biomass. Although numerous studies report optimized autohydrolysis conditions for various plants, few of these studies correlate process parameters with the resulting structural properties to their impact on intestinal bacterial communities. Thus, to further clarify these relationships, beechwood xylan (BWX)-derived substrates, processed under five conditions, were fermented in vitro by human gut microbiota. Autohydrolysis reduced the mean molecular size and substitutions of BWX. Distinct fermentation kinetics were observed with differing processing of BWX substrates, which correlated with impacts on community species evenness. The relative abundances of Bacteroides, Fusicatenibacter, Bifidobacterium, and Megasphaera within the fermentations varied with processing conditions. While the total short-chain fatty acid concentrations were the same among the treatments, processing conditions varied the extent of propionate and butyrate generation. Autolysis parameters may be an important tool for optimizing beneficial effects of xylan-derived fibers on human gut microbiota structure and function.
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Microbioma Gastrointestinal/efectos de los fármacos , Oligosacáridos/farmacología , Xilanos/farmacología , Bacterias/efectos de los fármacos , Bacterias/metabolismo , Fagus/química , Ácidos Grasos Volátiles/metabolismo , Fermentación , Hidrólisis , Oligosacáridos/química , Oligosacáridos/metabolismo , Xilanos/química , Xilanos/metabolismoRESUMEN
Gene feoA plays an important role in cell growth because of its function of transport Fe2+ which is a necessary element for cells. In this study, the recombinant plasmid pUC19-feoA-Tet was successfully constructed using the inserted gene inactivation method. Using the homologous recombination technique, the tet gene was used as a resistance screening marker to knock out the feoA gene of Lactobacillus delbrueckii subsp. bulgaricus 34.5 (strain 34.5). Comparative analysis of growth curves revealed the growth changes in the absence of feoA gene in strain 34.5. The results showed that the growth of the bacteria was prolonged by 2 h and could be restored in the stationary phase. To further study whether feoA is related to the cell division of strain 34.5, the qPCR experiment was carried out. The results showed that, compared with the wild-type strain, the expression of genes related to cell division in the mutant strain was up-regulated in the pre-log phase, down-regulated in the late-log phase, and returned to the original level in the stationary phase. These findings provide ideas for Lactobacillus delbrueckii subsp. bulgaricus to control division and cell cycle.
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Ciclo Celular , Regulación Bacteriana de la Expresión Génica , Proteínas de Unión a Hierro , Lactobacillus delbrueckii , Ciclo Celular/genética , Técnicas de Inactivación de Genes , Proteínas de Unión a Hierro/genética , Proteínas de Unión a Hierro/metabolismo , Lactobacillus delbrueckii/genética , Lactobacillus delbrueckii/crecimiento & desarrollo , Plásmidos/genéticaRESUMEN
Older adults are thought to compensate for slower lexical processing by making greater use of contextual knowledge, relative to young adults, to predict words in sentences. Accordingly, compared to young adults, older adults should produce larger contextual predictability effects in reading times and skipping rates for words. Empirical support for this account is nevertheless scarce. Perhaps the clearest evidence to date comes from a recent Chinese study showing larger word predictability effects for older adults in reading times but not skipping rates for two-character words. However, one possibility is that the absence of a word-skipping effect in this experiment was due to the older readers skipping words infrequently because of difficulty processing two-character words parafoveally. We therefore took a further look at this issue, using one-character target words to boost word-skipping. Young (18-30 years) and older (65+ years) adults read sentences containing a target word that was either highly predictable or less predictable from the prior sentence context. Our results replicate the finding that older adults produce larger word predictability effects in reading times but not word-skipping, despite high skipping rates. We discuss these findings in relation to ageing effects on reading in different writing systems.
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Atención , Anciano , Envejecimiento , China , Movimientos Oculares , Humanos , LenguajeRESUMEN
Several eye-movement studies have revealed flexibility in the parafoveal processing of character-order information in Chinese reading. In particular, studies show that processing a two-character word in a sentence benefits more from parafoveal preview of a nonword created by transposing rather than replacing its two characters. One issue that has not been investigated is whether the contextual predictability of the target word influences this processing of character order information. However, such a finding would provide novel evidence for an early influence of context on lexical processing in Chinese reading. Accordingly, we investigated this issue in an eye-movement experiment using the boundary paradigm and sentences containing two-character target words with high or low contextual predictability. Prior to the reader's gaze crossing an invisible boundary, each target word was shown normally (i.e. a valid preview) or with its two characters either transposed or replaced by unrelated characters to create invalid nonword previews. These invalid previews reverted to the target word once the reader's gaze crossed the invisible boundary. The results showed larger preview benefits (i.e. a decrease in fixation times) for target words following transposed-character than substituted-character previews, revealing a transposed-character effect similar to that in previous research. In addition, a word predictability effect (shorter fixation times for words with high than low predictability) was observed following both valid and transposed-character previews, but not substituted-character previews. The findings therefore reveal that context can influence an early stage of lexical processing in Chinese reading during which character order is processed flexibly.
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Atención , Movimientos Oculares , Lectura , Pueblo Asiatico , Fijación Ocular , Fóvea Central , Humanos , Lenguaje , Reconocimiento Visual de ModelosRESUMEN
Substantial progress has been made in understanding the mostly detrimental effects of normative aging on eye movements during reading. This article provides a review of research on aging effects on eye movements during reading for different writing systems (i.e., alphabetic systems like English compared to non-alphabetic systems like Chinese), focused on appraising the importance of visual and cognitive factors, considering key methodological issues, and identifying vital questions that need to be addressed and topics for further investigation.
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Research suggests that pattern complexity (number of strokes) limits the visual span for Chinese characters, and that this may have important consequences for reading. With the present research, we investigated age differences in the visual span for Chinese characters by presenting trigrams of low, medium or high complexity at various locations relative to a central point to young (18-30 years) and older (60+ years) adults. A sentence reading task was used to assess their reading speed. The results showed that span size was smaller for high complexity stimuli compared to low and medium complexity stimuli for both age groups, replicating previous findings with young adult participants. Our results additionally showed that this influence of pattern complexity was greater for the older than younger adults, such that while there was little age difference in span size for low and medium complexity stimuli, span size for high complexity stimuli was almost halved in size for the older compared to the young adults. Finally, our results showed that span size correlated with sentence reading speed, confirming previous findings taken as evidence that the visual span imposes perceptual limits on reading speed. We discuss these findings in relation to age-related difficulty reading Chinese.
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An influential account of normative aging effects on reading holds that older adults make greater use of contextual predictability to facilitate word identification. However, supporting evidence is scarce. Accordingly, we used measures of eye movements to experimentally investigate age differences in word predictability effects in Chinese reading, as this nonalphabetic language has characteristics that may promote such effects. Word-skipping rates were higher and reading times lower for more highly predictable words for both age groups. Effects of word predictability on word skipping did not differ across the 2 adult age groups. However, word predictability effects in reading time measures sensitive to both lexical identification (i.e., gaze duration) and contextual integration (i.e., regression-path reading times) were larger for the older than younger adults. Our findings therefore reveal that older Chinese readers make greater use of a word's predictability to facilitate both its lexical identification and integration with the prior sentence context. (PsycINFO Database Record (c) 2019 APA, all rights reserved).
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Envejecimiento/fisiología , Atención/fisiología , Envejecimiento Cognitivo/psicología , Movimientos Oculares/fisiología , Lenguaje , Lectura , Adolescente , Anciano , Anciano de 80 o más Años , Envejecimiento/psicología , Pueblo Asiatico , Femenino , Humanos , Masculino , Persona de Mediana Edad , Percepción Visual/fisiología , Adulto JovenRESUMEN
Kefir is a natural fermentation agent composed of various microorganisms. To address the mechanism of kefir grain formation, we investigated the microbial role in forming kefir biofilms. The results showed that a biofilm could be formed in kefir-fermented milk and the biofilm forming ability reached the maximum at 13 days. The strains Kluyveromyces marxianus, Lactococcus lactis, Leuconostoc mesenteroides, Lactobacillus kefiri, Lactobacillus sunkii and Acetobacter orientalis were isolated from kefir biofilms by the streak-plate method. These microorganisms were analysed with respect to biofilm forming properties, including their surface characterisation (hydrophobicity and zeta potentials) and the microbial aggregation. The results indicated that Klu. marxianus possessed the strongest biofilm forming properties with the strongest hydrophobicity, lowest zeta potential and greatest auto-aggregation ability. When Klu. marxianus and Ac. orientalis were co-cultured with kefir LAB strains respectively, it was found that mixing Klu. marxianus with Lb. sunkii produced the highest co-aggregation ability. These results elucidated the mechanism of kefir biofilm formation and the microorganisms involved.
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Acetobacter/química , Biopelículas/crecimiento & desarrollo , Kéfir/microbiología , Kluyveromyces/química , Lactobacillus/química , Lactococcus lactis/química , Leuconostoc/química , Acetobacter/genética , Acetobacter/aislamiento & purificación , Acetobacter/metabolismo , Adhesión Bacteriana , ADN Bacteriano/genética , ADN de Hongos/genética , Fermentación , Microbiología de Alimentos , Interacciones Hidrofóbicas e Hidrofílicas , Kluyveromyces/genética , Kluyveromyces/aislamiento & purificación , Kluyveromyces/metabolismo , Lactobacillus/genética , Lactobacillus/aislamiento & purificación , Lactobacillus/metabolismo , Lactococcus lactis/genética , Lactococcus lactis/aislamiento & purificación , Lactococcus lactis/metabolismo , Leuconostoc/genética , Leuconostoc/aislamiento & purificación , Leuconostoc/metabolismo , Consorcios Microbianos/genética , Electricidad EstáticaRESUMEN
Candida albicans is an important opportunistic fungus causing both disseminated and local infections. The discovery of neutrophil extracellular traps (NETs) has presented a new strategy to kill microorganisms in host's innate immune response. Although it has been reported that NETs can trap and kill both yeast and hyphal forms of C. albicans, the mechanism by which C. albicans escape from NETs has not been fully understood. In this study, the ability of two strains of C. albicans SC5314 and 3683 to escape NETs-mediated killing was compared. It was found that SC5314 induced higher levels of reactive oxygen species (ROS) and expressions of Rac1/2 and more NETs formation by neutrophils, and also generated more deoxyribonucleases (DNase) than 3683 did. However, resistance to neutrophils killing was greater in SC5314 than that of 3683. When extracellular traps were degraded by exogenous DNase I or catalase, and neutrophil phagocytic activity blocked by cytochalasin D, the killing capacity of neutrophils co-cultured with either C. albicans SC5314 or 3683 was significantly decreased. This study indicates that C. albicans can escape from the trapping and killing of NETs by secreting DNase, which offers further insights into the basis for differences in virulence of different strains of C. albicans.
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In this study, differences between two strains of inbred mice in aspects of neutrophil function, namely Rac1 expression, chemotaxis, nicotinamide adenine dinucleotide phosphate oxidase activity and formation of neutrophil extracellular traps (NETs), were determined. Neutrophils from CBA/CaH mice exhibited weaker Rac1 expression and a slower chemotactic gradient than BALB/c mice. Furthermore, PMA- or fMLP-stimulated neutrophils from CBA/CaH mice generated much less superoxide and NETs than similarly stimulated neutrophils from BALB/c mice. These findings suggest that neutrophils from BALB/c mice are functionally more efficient than those from CBA/CaH mice.
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Ratones/clasificación , Ratones/fisiología , Neutrófilos/inmunología , Animales , Quimiotaxis , Trampas Extracelulares/metabolismo , Perfilación de la Expresión Génica , Ratones Endogámicos BALB C , Ratones Endogámicos CBA , NADPH Oxidasas/análisis , Neuropéptidos/biosíntesis , Neuropéptidos/genética , Neutrófilos/enzimología , Neutrófilos/metabolismo , Neutrófilos/fisiología , Especificidad de la Especie , Superóxidos/metabolismo , Proteína de Unión al GTP rac1/biosíntesis , Proteína de Unión al GTP rac1/genéticaRESUMEN
Application of solar collectors for hot water supply, space heating, and cooling plays a significant role in reducing building energy consumption. For conventional solar collectors, solar radiation is absorbed by spectral selective coating on the collectors' tube/plate wall. The poor durability of the coating can lead to an increased manufacturing cost and unreliability for a solar collector operated at a higher temperature. Therefore, a novel nanofluid-based direct absorption solar collector (NDASC) employing uncoated collector tubes has been proposed, and its operating characteristics for medium-temperature solar collection were theoretically and experimentally studied in this paper. CuO/oil nanofluid was prepared and used as working fluid of the NDASC. The heat-transfer mechanism of the NDASC with parabolic trough concentrator was theoretically evaluated and compared with a conventional indirect absorption solar collector (IASC). The theoretical analysis results suggested that the fluid's temperature distribution in the NDASC was much more uniform than that in the IASC, and an enhanced collection efficiency could be achieved for the NDASC operated within a preferred working temperature range. To demonstrate the feasibility of the proposed NDASC, experimental performances of an NDASC and an IASC with the same parabolic trough concentrator were furthermore evaluated and comparatively discussed.
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Candida albicans is an opportunistic human fungal pathogen that continues to be a leading cause of candidal infections in immunocompromised hosts. Enolase, an important glycolytic enzyme located on the cell wall of C. albicans, was cloned, purified, and characterized by molecular cloning, affinity chromatography and Western blotting. C57BL/6J mice were immunized with recombinant enolase subcutaneously every two weeks, and the protective effect against systemic challenge evaluated by fungal burdens in target organs, titres of specific antibodies to enolase, and by levels of Th1/2 cytokines in serum. After challenge with C. albicans strains SC5314 and 3630, fungal burdens in the liver, kidney, brain, spleen and lung were significantly decreased in immunized mice. Histopathological assessment demonstrated that enolase protected the tissue structure, and decreased the infiltration of inflammatory cells. The titres of enolase-specific IgG1 and IgG2a in the immune serum reached up to 1:51200. Furthermore, opsonization with immune serum resulted in enhanced killing of both 3630 and SC5314 by murine neutrophils. Levels of IL-12 and IL-8 in the immune serum increased, whereas the concentration of the Th2 cytokine, IL-10, was significantly higher in immunized mice compared to the control group. It was concluded that recombinant enolase effectively protected mice against disseminated candidiasis, and may be a promising target for vaccination against different strains of C. albicans.