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Matrix-entrapped Fibers Create Ecological Niches for Gut Bacterial Growth
Get PDFInsoluble plant cell walls are a main source of dietary fiber. Both chemical and physical fiber structures create distinct niches for gut bacterial utilization. Here, we have taken key fermentable solubilized polysaccharides of plant cell walls and fabricated them back into cell wall-like film forms to understand how fiber physical structure directs gut bacterial fermentation outcomes. Solubilized corn bran arabinoxylan (Cax), extracted to retain some ferulate residues, was covalently linked using laccase to form an insoluble cell wall-like film (Cax-F) that was further embedded with pectin (CaxP-F). In vitro fecal fermentation using gut microbiota from three donors was performed on the films and soluble fibers. Depending on the donor, CaxP-F led to higher relative abundance of recognized beneficial bacteria and/or butyrate producers—Akkermansia, Bifidobacterium, Eubacterium halii, unassigned Lachnospiraceae, Blautia, and Anaerostipes—than free pectin and Cax, and Cax-F. Thus, physical form and location of fibers within cell walls form niches for some health-related gut bacteria. This work brings a new understanding of the importance of insoluble cell wall-associated fibers and shows that targeted fiber materials can be fabricated to support important gut microbiota taxa and metabolites of health significance
Downstream Effects: Impact of Antibiotic Pollution on an Aquatic Host-parasite Interaction
Get PDFThe global increase in antibiotic use has led to contamination of freshwater environments. Despite the identified impacts of antibiotics on humans and wildlife, the effect of antibiotics on host–parasite life cycles in freshwater is relatively unexplored. In the current study, we utilize the trematode parasite Schistosoma mansoni, and its snail intermediate host, Biomphalaria glabrata, to investigate the influence of an ecologically relevant antibiotic concentration on the life history characteristics of both parasite and host. Our results demonstrate that antibiotics not only accelerate parasite development time, but also increase host reproduction and delay parasite-induced host castration. Using a mathematical model, we suggest that life history alterations associated with antibiotics are likely to increase parasite transmission and disease burden. Our study suggests that antibiotic pollution could impact freshwater ecosystems by influencing host–parasite dynamics and potentially increase the burden of schistosomiasis in endemic regions
Morphology Engineering of Hybrid Supercapacitor Electrodes from Hierarchical Stem-like Carbon Networks with Flower-like MoS2 Structures
Get PDFThere is a critical need to develop high-performance supercapacitors that can complement and even rival batteries for energy storage. This work introduces a strategy to drastically enhance the energy storage performance of a supercapacitor by engineering electrode morphologies with ternary composites offering distinct benefits for the energy storage application. The electrodes were fabricated with conductive networks of carbon nanotubes (CNTs) coated with a zeolitic imidazole framework (ZIF) for high ion diffusivity and ion-accumulating molybdenum disulfide (MoS2) with various morphologies. These include flower-like (fMoS2), stacked-plate (pMoS2), and exfoliated-flake (eMoS2) structures from topochemical synthesis. CNT-ZIF-fMoS2 demonstrates an excellent energy density, reaching almost 80 Wh/kg, and a maximum power density of approximately 3000 W/kg in a half-cell. This is far superior to the electrodes containing pMoS2 and eMoS2 and attributed to the increased surface area and the faradaic reactivity offered by fMoS2. Additionally, the CNT-ZIF-fMoS2 electrode demonstrates exceptional stability with an ∼78% of capacitance retention over 10,000 cycles. This work suggests that the electrode morphologies can dominate the energy storage behaviors and that the heteromaterial approach may be crucial in designing next-generation supercapacitors
Interpretable Machine Learning Models for Hospital Readmission Prediction: A Two-step Extracted Regression Tree Approach
Get PDFBackground
Advanced machine learning models have received wide attention in assisting medical decision making due to the greater accuracy they can achieve. However, their limited interpretability imposes barriers for practitioners to adopt them. Recent advancements in interpretable machine learning tools allow us to look inside the black box of advanced prediction methods to extract interpretable models while maintaining similar prediction accuracy, but few studies have investigated the specific hospital readmission prediction problem with this spirit. Methods
Our goal is to develop a machine-learning (ML) algorithm that can predict 30- and 90- day hospital readmissions as accurately as black box algorithms while providing medically interpretable insights into readmission risk factors. Leveraging a state-of-art interpretable ML model, we use a two-step Extracted Regression Tree approach to achieve this goal. In the first step, we train a black box prediction algorithm. In the second step, we extract a regression tree from the output of the black box algorithm that allows direct interpretation of medically relevant risk factors. We use data from a large teaching hospital in Asia to learn the ML model and verify our two-step approach. Results
The two-step method can obtain similar prediction performance as the best black box model, such as Neural Networks, measured by three metrics: accuracy, the Area Under the Curve (AUC) and the Area Under the Precision-Recall Curve (AUPRC), while maintaining interpretability. Further, to examine whether the prediction results match the known medical insights (i.e., the model is truly interpretable and produces reasonable results), we show that key readmission risk factors extracted by the two-step approach are consistent with those found in the medical literature. Conclusions
The proposed two-step approach yields meaningful prediction results that are both accurate and interpretable. This study suggests a viable means to improve the trust of machine learning based models in clinical practice for predicting readmissions through the two-step approach
Combined Effect of Albumin Deficiency and Acute Exercise in Reducing Hepatic Lipid Droplet Size in Mice
Get PDFHepatic lipid droplets (LDs) are implicated in ectopic lipid accumulation. The core of LDs, triacylglycerol (TAG), is synthesized from the esterification of fatty acids to a glycerol-3-phosphate (G-3-P) backbone. Albumin transports plasma free fatty acids, and previously albumin knockout (Alb−/−) mice were shown to exhibit lower hepatic TAG levels than wildtype (WT). Exercise is a beneficial strategy to alter hepatic metabolism, but its impacts on reducing hepatic lipids are far from satisfactory. The aim of this study was to investigate the combined effect of albumin deficiency and acute exercise on hepatic LDs. Eight-week-old male Alb−/− and WT mice were divided into sedentary and exercise groups. Exercised mice performed a 30-min high-intensity exercise bout. Results showed that sedentary Alb−/− mice had smaller hepatic LDs (P \u3c 0.0001), associated with mitochondria, while WT mice exhibited larger LDs, surrounded by glycogen granules. Following acute exercise, hepatic LDs in Alb−/− mice reduced by 40% in size, while in WT increased by 14% (P \u3c 0.0001). The maintenance of WT hepatic LDs was associated with elevated G-3-P level (P \u3c 0.05), potentially derived from glycogen (R = -0.32, %change in glycogen versus LD content, P \u3c 0.05). The reduction in Alb−/− mice LDs after exercise was possibly due to their low glycogen level. In conclusion, Alb−/− mice exhibited an enhanced capacity for reducing hepatic LD size and content in response to exercise. These findings suggest that modulating albumin’s functions combined with exercise could be a potential strategy to reduce ectopic lipid deposition in the liver
Optically Induced Electrothermal Microfluidic Tweezers in Bio-relevant Media
Get PDFNon-contact micro-manipulation tools have enabled invasion-free studies of fragile synthetic particles and biological cells. Rapid electrokinetic patterning (REP) traps target particles/cells, suspended in an electrolyte, on an electrode surface. This entrapment is electrokinetic in nature and thus depends strongly on the suspension medium’s properties. REP has been well characterized for manipulating synthetic particles suspended in low concentration salt solutions (~ 2 mS/m). However, it is not studied as extensively for manipulating biological cells, which introduces an additional level of complexity due to their limited viability in hypotonic media. In this work, we discuss challenges posed by isotonic electrolytes and suggest solutions to enable REP manipulation in bio-relevant media. Various formulations of isotonic media (salt and sugar-based) are tested for their compatibility with REP. REP manipulation is observed in low concentration salt-based media such as 0.1× phosphate buffered saline (PBS) when the device electrodes are passivated with a dielectric layer. We also show manipulation of murine pancreatic cancer cells suspended in a sugar-based (8.5% w/v sucrose and 0.3% w/v dextrose) isotonic medium. The ability to trap mammalian cells and deposit them in custom patterns enables high-impact applications such as determining their biomechanical properties and 3D bioprinting for tissue scaffolding
Behavioral Assays Reveal Mechanisms of Supercolony Formation in Odorous House Ants
Get PDFThe formation of expansive multi-nest and multi-queen supercolonies is perhaps the most important factor responsible for the ecological success of invasive ants. The odorous house ant, Tapinoma sessile, is a widespread ant native to North America. T. sessile is a challenging urban pest, but also serves as an interesting system to study ant social organization and invasion biology. This is due to its remarkable dichotomy in colony social and spatial structure between natural and urban environments. Natural colonies typically consist of a small number of workers, inhabit a single nest, and are monogyne whereas urban colonies show extreme polygyny and polydomy and form large supercolonies. The current study examined the extent to which T. sessile colonies from different habitats (natural vs. urban) and social structures (monogynous vs. polygynous) exhibit aggression toward alien conspecifics. Additionally, interactions between mutually aggressive colonies were examined in colony fusion experiments to assess the potential role of colony fusion as a mechanism leading to supercolony formation. Aggression assays demonstrated high levels of aggression in pairings involving workers from different urban colonies and workers from different natural colonies, but low aggression in pairings involving queens from different urban colonies. Colony merging tests demonstrated that urban T. sessile colonies are highly aggressive to each other, but capable of fusing under laboratory conditions when competing for limited nesting and food resources. Despite highly aggressive interactions and relatively high worker and queen mortality, all colony pairs merged in 3–5 days. Fusion occurred after most workers died and the survivors merged. This result suggests that the success of T. sessile in urban areas may be driven, at least in part, by successful colony mergers of unrelated colonies which may be determined by ecological constraints such as seasonal shortages in nest and/or food availability. In summary, two independent factors including the growth of a single colony and/or the merger of multiple colonies may be responsible for the evolution of supercolonies in invasive ants. Both processes may be happening simultaneously and may act synergistically to produce supercolonies