bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental study of CO2 dissociation in an expanding dc arc discharge at atmospheric pressure with multiple pin-to-pin electrodes
Authors: Lazarova S , Kolev St , Paunska Ts
Published: February 2024

In the following study, we examine the performance of a new design of the classic gliding arc discharge (GAD) with diverging electrodes between dielectric walls at atmospheric pressure. In the present design, a tungsten pin-to-pin electrode pair ladder replaces the standard curved diverging electrodes. A major problem with the classic GAD design is the surface erosion of the electrodes, which leads to bad repeatability and issues with long-term usage. The new construction provides controlled electrode wear at well-defined points of arc attachment. This ensures stable operation while retaining the arc expansion effect. This new configuration of the discharge is being developed for gas treatment. In the current work, the device was applied for CO2 dissociation. The most significant quantities for this application of the GAD, the CO2 conversion rate and energy efficiency, are measured at different gas flow rates (2–12 Ln/min) and arc currents (50–210 mA). The results are analyzed and compared with previous measurements using the classic GAD at the same conditions.
One-dimensional multi-fluid model of the plasma wall transition
Authors: Gyergyek Tomaž , Kovačič Jernej , Costea Stefan , Kos Leon
Published: February 2024

A one-dimensional multi-fluid model of the plasma wall transition is presented. The plasma is composed of singly charged positive ions, electrons and negative ions. Positive ions are assumed to obey the continuity, momentum transfer and energy transport equation, while the electrons and negative ions are treated by the continuity and momentum transfer equation. For the positive ions the closure is done by assuming that heat flux in the plasma is zero, while both negative species are treated as isothermal, with the pressure gradient term being proportional to the density gradient. The potential drop in the pre-sheath can be determined either by the electrons or the negative ions – depending on their densities in the unperturbed plasma. It is shown how the boundary density of both particle species can be in some cases determined very precisely.
Model of slot antenna for MPECVD of carbon nanostructure
Authors: Vachkov V , Kiss’ovski Zh
Published: February 2024

A model of a slotted waveguide antenna for microwave plasma enhanced chemical vapor deposition (MPECVD) of carbon nanostructures at low pressure is developed. The performance of two slot applicator for the production of dense plasma in the working gas (argon) at a frequency of 2.45 GHz is investigated by EM field simulator. Results show that dimensions of the symmetrical slots (length l ≤ λg/2, width of d = 6-10 mm) and optimized angle (φ=32° with respect to the waveguide central line) have a strong influence on the impedance matching of the waveguide to the dielectric window and plasma column (1.5 < SWR < 2.5), and on the radiation efficiency. The dielectric plate and plasma column density were taken into account in the model in the optimisation of the dimensions of the slots. The mode structure of standing surface waves in the plasma column is investigated at three values of plasma density and results for the radial (n=1) and azimuthal wave numbers (m=3, 4, 5) are in agreement with experimental results.
Application programming interface for electron beam welding of Inconel 718 thin plates
Authors: Koleva L , Koleva E
Published: February 2024

In this paper the simulation of electron beam welding of Inconel 718 thin plates by a moving linear heat source is considered. Neural network models are developed and used for the description of the dependence of the molten pool geometry characteristics on the process parameters - electron beam power, welding velocity, and the plate thickness. Neural network models, based on a multi-layered feedforward neural network, trained with Levenberg-Marquardt error backpropagation algorithm are compared with estimated regression models. The neural networks are trained, tested and validated using a set of experimental data. The resulting models are implemented for developing of an application programming interface for electron beam welding of Inconel 718 thin plates, which is used for prediction, investigation and graphical optimization of the molten pool geometry characteristics of the obtained electron beam welds.
A global centralized magnetic flux leakage small defect detection network
Authors: Chen Yufei , Lang Xianming , Liu Mingyang
Published: February 2024

To solve the problem that magnetic-flux-leakage (MFL) small defects are difficult to accurately detect by machine learning methods, a global centralized magnetic flux leakage small defect detection network (RCFPNet) is proposed. RCFPNet consists of simulation data enhancement, improved feature extraction (backbone), an improved centralized feature pyramid (CFP) and a detection head network. The MFL defect data of various scales and shapes are simulated by ANSYS simulation software and superimposed with the actual detected MFL defects to expand the dataset. The Repvgg module is used to replace the 3*3 convolution of the backbone to improve the detection speed. An improved spatially explicit vision center scheme (EVC) and a global centralized regulation rule (GCR) for feature fusion networks are proposed for feature fusion networks. RCFPNet is based on an improvement of the YOLOv5 network. Experiments have proven that RCFPNet has improved detection speed and accuracy and has achieved good results in the detection of magnetic leakage small defects. Experiments show that when the IOU = 0.5, the accuracy rate of this algorithm is 96.1%, and the reasoning time is 8.9 ms.
The Weight of Tradition at the Beginning of the European Middle Ages
Authors: Gabriele Matthew
Published: February 2024

This chapter confronts how early Christians, especially after the conversion of Constantine, dealt with the problem of time. The work of biblical commentary (exegesis) in this period was often focused on discerning a pattern within sacred history. Here too, however, in order to get back to the past itself, we must work though the historiography, which is heavily shaped by anti-fascist Roman Catholicism of the mid-twentieth century. But once we do, we can see how Augustine built from earlier thinkers, looked around, and saw a world in stasis—an Augustinian Atemporality—with no end in sight.
Epilogue
Authors: Gabriele Matthew
Published: February 2024

This brief epilogue begins with a case study of the historical writing of Fulcher of Chartres, who participated in the so-called First Crusade and then stayed on in Jerusalem under its new Latin kings. After the conquest of Jerusalem by the Christians in 1099, the surety of knowing the pattern of sacred history that developed across the eleventh century seemed to be confirmed. The chapter suggests we see evidence of this in various new currents across twelfth-century Europe. But that surety faded quickly and the intellectual cycle returned, with medievals again looking to the past for answers.
Selective conformal inference with false coverage-statement rate control
Authors: Bao Yajie , Huo Yuyang , Ren Haojie , Zou Changliang
Published: February 2024

Conformal inference is a popular tool for constructing prediction intervals. We consider here the scenario of post-selection/selective conformal inference, that is, prediction intervals are reported only for individuals selected from unlabelled test data. To account for multiplicity, we develop a general split conformal framework to construct selective prediction intervals with the false coverage-statement rate control. We first investigate the false coverage rate–adjusted method of Benjamini & Yekutieli (2005) in the present setting, and show that it is able to achieve false coverage-statement rate control, but yields uniformly inflated prediction intervals. We then propose a novel solution to the problem called selective conditional conformal prediction. Our method performs selection procedures on both the calibration set and test set, and then constructs conformal prediction intervals for the selected test candidates with the aid of the conditional empirical distribution obtained by the post-selection calibration set. When the selection rule is exchangeable, we show that our proposed method can exactly control the false coverage-statement rate in a model-free and distribution-free guarantee. For nonexchangeable selection procedures involving the calibration set, we provide non-asymptotic bounds for the false coverage-statement rate under mild distributional assumptions. Numerical results confirm the effectiveness and robustness of our method under false coverage-statement rate control and show that it achieves more narrowed prediction intervals over existing methods across various settings.
Resting-state electroencephalography microstates as a marker of photosensitivity in juvenile myoclonic epilepsy
Authors: Mazzeo Adolfo , Cerulli Irelli Emanuele , Leodori Giorgio , Mancuso Marco , Morano Alessandra , Giallonardo Anna Teresa , Di Bonaventura Carlo
Published: February 2024

Juvenile myoclonic epilepsy is an idiopathic generalized epilepsy syndrome associated with photosensitivity in approximately 30–40% of cases. Microstates consist of a brief period of time during which the topography of the whole resting-state electroencephalography (EEG) signal is characterized by a specific configuration. Previous neurophysiological and neuroimaging studies have suggested that Microstate B may represent activity within the visual network. In this case-control study, we aimed to investigate whether anatomical and functional alterations in the visual network observed in individuals with photosensitivity could lead to changes in Microstate B dynamics in photosensitive patients with juvenile myoclonic epilepsy. Resting-state electroencephalography microstate analysis was performed on 28 patients with juvenile myoclonic epilepsy. Of these, 15 patients exhibited photosensitivity, while the remaining 13 served as non-photosensitive controls. The two groups were carefully matched in terms of age, sex, seizure control and anti-seizure medications. Multivariate analysis of variance and repeated-measures analysis of variance were performed to assess significant differences in microstate metrics and syntax between the photosensitive and the non-photosensitive group. Post hoc false discovery rate adjusted unpaired t-tests were used to determine differences in specific microstate classes between the two groups. The four classical microstates (Classes A, B, C and D) accounted for 72.8% of the total electroencephalography signal variance in the photosensitive group and 75.64% in the non-photosensitive group. Multivariate analysis of variance revealed a statistically significant class–group interaction on microstate temporal metrics (P = 0.021). False discovery rate adjusted univariate analyses of variance indicated a significant class–group interaction for both mean occurrence (P = 0.002) and coverage (P = 0.03), but not for mean duration (P = 0.14). Post hoc false discovery rate adjusted unpaired t-tests showed significantly higher coverage (P = 0.02) and occurrence (P = 0.04) of Microstate B in photosensitive patients compared with non-photosensitive participants, along with an increased probability of transitioning from Microstates C (P = 0.04) and D (P = 0.02) to Microstate B. No significant differences were found concerning the other microstate classes between the two groups. Our study provides novel insights on resting-state electroencephalography microstate dynamics underlying photosensitivity in patients with juvenile myoclonic epilepsy. The increased representation of Microstate B in these patients might reflect the resting-state overactivation of the visual system underlying photosensitivity. Further research is warranted to investigate microstate dynamics in other photosensitive epilepsy syndromes.
A visual, rapid, and sensitive detection platform for Vibrio parahaemolyticus based on RPA-CRISPR/Cas12a and an immunochromatographic test strip
Authors: Wang Jinbin , Xu Danhong , Liu Hua , Liu Juan , Zhu Lemei , Zeng Haijuan , Wu Wenhui
Published: February 2024

Objectives

Vibrio parahaemolyticus is the primary species that causes vibriosis. In this study, a point-of-care detection method was developed for V. parahaemolyticus.

Materials and Methods

The detection platform targeted the thermolabile haemolysin (tlh) gene of V. parahaemolyticus based on recombinant polymerase amplification (RPA) and clustered regularly spaced short palindromic repeat (CRISPR/Cas) systems. The platform was combined with an immunochromatographic test strip (ICS) that enables low-cost, simple, visual detection of V. parahaemolyticus.

Results

The detection limit was 2.5×102 fg/µL for plasmids and 1.4×102 CFU/mL for V. parahaemolyticus. In addition, V. parahaemolyticus in salmon sashimi could be detected at a concentration of 154 CFU/g without enrichment, and the entire detection time was around 30 min. After enrichment for 6 h, 2 CFU/g V. parahaemolyticus could be detected.

Conclusions

Consequently, the proposed RPA-CRISPR/Cas12a-ICS platform could detect V. parahaemolyticus in seafood intuitively, quickly, and sensitively, leading to high practical application value.
An Emerging 21st-Century Midlife Sleep Crisis? Cohort Differences in Sleeping Patterns Among Americans in Midlife and Older Adulthood
Authors: Sheehan Connor M , Infurna Frank J
Published: February 2024

Objectives

To descriptively document birth cohort differences in sleeping patterns, self-reported age-specific sleep duration, and insomnia symptoms among adults aged 50+ from the National Health Interview Survey (NHIS) and the Health and Retirement Study (HRS).

Methods

We analyzed respondents aged 50+ (born 1920–1969) from the 2006–2018 NHIS (n = 162,400) and HRS (n = 28,918). We fit multinomial models among the NHIS sample predicting age-specific optimal sleep duration (optimal for age vs short for age, and optimal for age vs long for age). For the HRS sample, we fit growth curve models predicting age-based insomnia symptom trajectories. The models for both samples adjusted for age, gender, race/ethnicity, and educational attainment.

Results

Results regarding sleep duration in the NHIS, suggested that cohorts born in the 1950s and 1960s had significantly higher odds of reporting short sleep duration than cohorts before them. Results from the HRS similarly illustrated that cohorts born in the 1950s and 1960s had significantly higher levels of insomnia symptoms than those born before them. The worsening sleep among cohorts entering midlife was consistent regardless of alternative cohort specification, when age groups or periods were analyzed, and when more extensive covariates were modeled.

Discussion

We observe a pronounced decline in healthy sleeping patterns among American cohorts in midlife, with consistent and striking results across data sets, methods, and measures. These findings have important implications for the well-being and longevity of Americans who have entered midlife in the 21st century.
A framework for multidisciplinary science observations from commercial ships
Authors: Macdonald Alison M , Hiron Luna , McRaven Leah , Stolp Laura , Strom Kerry , Hudak Rebecca , Smith Shawn R , Hummon Julia , Andres Magdalena
Published: February 2024

Science Research on Commercial Ships (Science RoCS) is a grassroots multi-institution group of scientists, engineers, data managers, and administrators seeking to further research opportunities by equipping commercial vessels with suites of maritime appropriate scientific sensors operated autonomously on regular ship routes with minimal crew intervention. Science RoCS aims to foster cooperation between the shipping industry and scientific community at a level that will be transformative for societally relevant ocean science, promote cross-disciplinary ocean science through simultaneous observation of the air/sea interface and water column, and spur a technological revolution in observational oceanography by developing new turnkey, maritime-industry-appropriate scientific equipment whose data streams can be used to stimulate innovations in oceanic (physical, chemical, and biological) understanding and forecasting. We envision a future where scientific data collection on commercial ships is the new industry standard, providing repeat measurements in undersampled, remote regions, on scales not otherwise accessible to the scientific community.
Shark and odontocete depredation on the catch of the tuna longline fishery in New Caledonia (South Pacific Ocean)
Authors: Mollier Margaux , Mazé Camille , Prioul François , Hamer Paul , Hosken Malo , McKechnie Sam , Tixier Paul
Published: February 2024

Large marine predators feeding on fish caught on fishing gear, referred to as ‘depredation’, occur in a wide range of fisheries worldwide. Depredation can result in negative ecological and socio-economic impacts, leading to conflict between fishers and depredating species. However, depredation remains understudied in many fisheries, and this hampers the development of effective mitigation solutions. In this study, 21 years of fishing data (2002–2022) were used to assess shark and odontocete depredation in the pelagic tuna longline fishery of New Caledonia. Using generalized linear models, the year, season, effort, soaking time, and vessel were identified as variables significantly influencing the probability of depredation to occur. Results showed that while shark depredation occurred more frequently than odontocete depredation (58.5% vs. 9.2% of the longline sets), they damaged a lower proportion of fish (3.9% vs. 12.3%) over the study period. Unlike sharks, odontocetes selectively depredate tuna, with their highest occurrence during periods of high tuna catch rates, suggesting a co-occurrence with fishing activities. Together, these results indicate that depredation in the New Caledonian fishery is high compared to other regions and provide essential information on the dynamics and impacts of the issue as a basis for considering management and mitigation options.
Tangential tensor fields on deformable surfaces—how to derive consistent L2-gradient flows
Authors: Nitschke Ingo , Sadik Souhayl , Voigt Axel
Published: February 2024

We consider gradient flows of surface energies that depend on the surface by a parameterization and on a tangential tensor field. The flow allows for dissipation by evolving the parameterization and the tensor field simultaneously. This requires the choice of a notation for independence. We introduce different gauges of surface independence and show their consequences for the evolution. In order to guarantee a decrease in energy, the gauge of surface independence and the time derivative have to be chosen consistently. We demonstrate the results for a surface Frank–Oseen–Helfrich energy.
One Man, Two Guvnors: Revisiting the Principle Against Two Employers
Authors: Wynn-Evans Charles
Published: February 2024

This case note reviews the detail of, rationale for, and issues arising in relation to the longstanding principle that in general terms an employee cannot simultaneously have two employers in the context of its impact on the scope and application of labour law protections and its recent consideration by the Employment Appeal Tribunal in its Embery and United Taxis decisions. It is argued that this principle is ripe for reconsideration and restatement, not least in the light of the arguments in favour of the adoption of a joint employment model in order, where appropriate, to ensure the effective application of labour standards.
A5 DEVELOPMENT OF A PRE-CLINICAL MOUSE MODEL TO INVESTIGATE ADVERSE FOOD REACTIONS IN INTESTINAL INFLAMMATION
Authors: Barbosa da Luz B , Rondeau L , Dang R , Caminero A
Published: February 2024

Background

Patients with chronic intestinal conditions, including inflammatory bowel disease (IBD), experience diverse food-related adverse reactions. However,, the precise mechanisms of food intolerances in IBD remains unclear. Emerging evidence suggests that altered diet-microbiota interactions can contribute to the development of IBD. Previously we shown that intestinal microbiota plays an important role in the development of food intolerances. We hypothesize that microbial alterations in IBD patients facilitate adverse reactions to foods.

Aims

To establish a preclinical mouse model to study adverse food reactions in intestinal inflammation.

Methods

Eight-week-old C57BL/6 mice were treated with 3% dextran sodium sulfate (DSS) for 5 days, then divided into three groups. The first group was sensitized to dairy protein (3% casein and 3% whey), using 4 oral administrations of cholera toxin over 2 weeks, without any further diet intervention. The second group was also sensitized to casein and whey, then after 1 week of recovery, the mice were subsequently place on a chow containing casein and whey. Finally, the third group was subjected to diet intervention without sensitization. The same experiment was repeated in a different subset of C57BL/6 mice which included a second cycle of DSS (1.5%) during the dietary interventions. Markers of intestinal inflammation (disease activity index (DAI), histological damage, cell infiltration and pro-inflammatory genes expression (NanoString)) and intestinal microbiota were analysed after 1 week of the diet intervention.

Results

Mice previously sensitized on the dairy diet exhibited an enhanced activation of immune cells after intestinal inflammation. While the histological damage score did not reveal significant differences among experimental groups, the sensitized group under dairy intervention exhibited an elevated level of immune cell infiltration, increasing the polymorphonuclear, CD3+ and mast cells. Gene expression also revealed that dairy induced the expression of inflammatory genes, such as C6, Arg1, Tnf, Il6, Cxcl9 and Cxcl10. When animals are subjected to a second DSS-cycle, dairy worsen colitis in mice previously sensitized, as shown by higher DAI compared to group with control diet and dairy diet without sensitization.

Conclusions

In the context of intestinal inflammation, dairy protein leads to immune activation characterized by an increase in polymorphonuclear cells, mast cells and lymphocytes, as well as worsening colitis. Future studies using this model will provide valuable insights into the role of intestinal microbiota in food intolerances associated with intestinal inflammation.

Funding Agencies

CCC
A7 CANNABINOID 1 AND 2 RECEPTOR AGONISTS AND MU-OPIOID RECEPTOR AGONISTS SYNERGISTICALLY INHIBIT COLONIC NOCICEPTION DURING ACUTE COLITIS
Authors: Tsang Q K , Lomax A E , Vanner S , Reed D E
Published: February 2024

Background

Abdominal pain is a debilitating symptom in patients with inflammatory bowel disease. Previously we have shown that combining sub-analgesic doses of cannabinoid 1 receptor (CB1R), but not cannabinoid 2 receptor (CB2R), and mu-opioid receptor (MOR) agonists synergistically inhibits colonic nociception in healthy mice. However, it is unknown whether this combination has analgesic efficacy in a pre-clinical model of colitis.

Aims

To determine the effects of combining sub-analgesic doses of CBR and MOR agonists on colonic nociception during acute colitis.

Methods

Colitis was induced in male and female C57BL/6 mice with 2.5% dextran sulfate sodium in drinking water. Extracellular afferent nerve recordings were obtained from ex vivo flat sheet preparations of mouse distal colon. Mechanosensitivity of single afferent axons was assessed via probing of the colon with a 1g von Frey hair before and after superfusion of agonists of CB1R or CB2R plus MOR. To examine effects in vivo, visceromotor response (VMR) to colorectal distention (volume range 20-80 µL) was measured via electromyography. Mice were injected intraperitoneally with vehicle, or a combination of CB1R or CB2R agonist plus morphine 30-minutes prior to VMR experiment. Data were analyzed using a one or two-way ANOVA with Bonferroni test. N denotes number of mice; n denotes number of single afferent axons.

Results

In afferent nerve recordings, in contrast to healthy mice, the CB2R agonist HU-308 (1 µM and 3 µM) inhibited colonic mechanosensitivity in mice with colitis (1 µM: p<0.01, N=5, n=12; 3 µM: p<0.01, N=7, n=10); a lower concentration (300 nM) had no effect (p=0.52, N=6, n=10). The CB1R agonist ACEA (10 µM) reduced mechanosensitivity during acute colitis (p<0.05, n=11, N=6), whereas 100 nM (p>0.99, n=7, N=5) and 1 µM (p=0.25, n=10, N=6) had no effect. A combination of sub-analgesic concentrations of ACEA (100 nM) and DAMGO (MOR agonist, 1 nM) inhibited colonic mechanosensitivity in healthy mice (p<0.01, N=4, n=8) and during acute colitis (p<0.05, N=6, n=8). While a combination of sub-analgesic concentrations of HU-308 (300 nM) and DAMGO (1 nM) had no effect in healthy mice (p=0.70, N=4, n=8), it inhibited colonic mechanosensitivity during acute colitis (p<0.01, N=8, n=15). In VMR experiments, a combination of a sub-analgesic dose of ACEA (0.3 mg/kg) with morphine (0.3 mg/kg) reduced VMR (p<0.01, N=7) during acute colitis. Similarly, a combination of a sub-analgesic dose of HU-308 (1 mg/kg) and morphine (0.3 mg/kg) reduced VMR (p<0.01, N=6) during acute colitis.

Conclusions

A CB2R agonist inhibits colonic nociception during acute colitis, but not in healthy mice. A sub-analgesic combination of CB1R and MOR agonists can inhibit pain in healthy and inflamed mice, while combining sub-analgesic CB2R and MOR agonists is only inhibitory during acute colitis.

Funding Agencies

NRC
A11 TELOCYTES-FOXL1+ REGULATES THE EXTRACELLULAR MATRIX NETWORK IN COLITIS-ASSOCIATED CANCER
Authors: Reyes Nicolas V , Alfonso A B , Raisch J , Boisvert F , Lauzon M A , Perreault N
Published: February 2024

NOT PUBLISHED AT AUTHOR’S REQUEST

Please acknowledge all funding agencies listed below

Funding Agencies

CIHRDoctoral Scholarship Fonds de recherche du Québec (FRQS)
A15 LEVERAGING CULTURE-DEPENDENT AND -INDEPENDENT METAGENOMICS TO IDENTIFY ENTEROBACTERIACEAE GENES ASSOCIATED WITH ACTIVE ULCERATIVE COLITIS
Authors: Tertigas D , Rinawi F , Moayyedi P , Griffiths A , Surette M
Published: February 2024

Background

Ulcerative colitis (UC) is a type of inflammatory bowel disease (IBD) that is restricted to the large intestine and is characterized by mucosal inflammation. There is evidence that pathogenic bacteria contribute to UC pathogenesis in at least some patients and the bacterial family Enterobacteriaceae are prime suspects. Some strains of Enterobacteriaceae carry virulence genes important for colonizing the gut (e.g. fimH) and disrupting the intestinal epithelium (e.g. hemolysins). We hypothesize that key virulence genes carried by strains of many Enterobacteriaceae species contribute to disease activity in some UC patients. As we predict virulence genes are strain-specific, the detection of the species alone (e.g. Escherichia coli) is insufficient to predict pathogenic potential and this has confounded previous studies to identify infectious agents in UC.

Aims

We aim to use culture-dependent and -independent sequencing approaches to identify Enterobacteriaceae genes in the UC gut microbiome associated with active disease.

Methods

UC patient stool samples collected throughout enrolment in randomized control trials of fecal microbiota transplantation (FMT) for adult UC (n=10) and microbiome studies in early-onset pediatric UC (n=25) were cultured on MacConkey (MAC) agar to enrich for Enterobacteriaceae. Strains were isolated from baseline stool samples cultured on MAC agar for whole genome sequencing and virulence gene characterization. Baseline and post-treatment stool samples cultured on MAC agar were sent for metagenomic sequencing. Using a subset of 11 pediatric patients, I developed a metagenomic pipeline to identify Enterobacteriaceae genes enriched during active UC compared to periods of remission or milder disease.

Results

Known virulence genes, including fimH and hemolysins, were present in some strains across multiple Enterobacteriaceae species. Using an unbiased metagenomic approach with the pediatric cohort, we identified 42 genes enriched at baseline with the criteria they must be elevated in at least three of the 11 patients. The majority of the 42 genes were distributed into six gene clusters, including a small plasmid.

Conclusions

Our approach allows us to identify genes enriched in active UC that have not been previously described in the literature and our analysis will be repeated with our adult cohort. Genes that are enriched in active UC in the pediatric and/or adult cohort will be validated in publicly available metagenomic datasets that consist of both IBD patients and healthy controls. Furthermore, culture-dependent approaches allow us to test mechanisms in vivo that are informed by our bioinformatics. Leveraging microbiome and clinical data provides a unique window to guide future diagnostics and treatments to improve outcomes for UC patients.

Funding Agencies

CIHROGS
A41 IDENTIFICATION OF MICROBIAL LYSOPHOSPHATIDYLCHOLINE (LPC) AND LYSOPHOSPHATIDIC ACID (LPA) PRODUCERS AND THEIR EFFECTS ON THE HOST
Authors: Hall-Bruce M , Pujo J , De Palma G , Mohan V , Lu J , Collins S , Bercik P
Published: February 2024

Background

Gut microbiota plays a key role in shaping our immune system, producing a myriad of molecules with neuro- and immunomodulatory properties. Many of these bioactive molecules are generated by bacterial metabolism of common dietary components. We have recently found that fecal samples of patients with chronic abdominal pain contain high levels of inflammatory phospholipids, lysophosphatidylcholine (LPC) and its active metabolite lysophosphatidic acid (LPA). Both phospholipids have been previously linked to genesis and maintenance of chronic neuropathic pain. In addition, they appear to have pro-inflammatory properties.

Aims

To investigate whether gut bacteria can produce LPC and LPA from dietary precursor phosphatidylcholine (PC), and whether these phospholipids can induce inflammatory responses in the host.

Methods

Fecal samples from patients with chronic abdominal pain were analyzed for microbial profiles using 16S rRNA (Illumina) analysis, and abundance of individual bacteria was correlated with fecal LPC and LPA levels as measured by ELISA. To confirm ability to produce these lipids, identified bacteria were incubated with either phosphatidylcholine (PC) or LPC (the immediate precursors of LPC and LPA, respectively) and LPC and LPA levels measured using liquid chromatography-mass spectrometry. To investigate pro-inflammatory effect of LPC and LPA, mouse splenocytes were incubated with LPC and/or LPA in vitro, and tested for cytokine production.

Results

Higher abundance of several bacterial species was associated with higher fecal levels of LPC and LPA. Among them, a bacterium from family Oscillospiraceae was identified as the most likely producer of both LPA and LPC; its abundance also correlated with high pain scores. Culturing and incubating this bacterium with PC and LPC resulted in a significant production of LPC and LPA. Additionally, LPA, but not LPC, resulted in increased levels of IL-6 production by splenocytes in vitro compared to the PBS only control. Interestingly, LPA induced IL-6 secretion was inhibited in the presence of LPC.

Conclusions

We have identified several bacterial producers of LPC and LPA, among them a bacterium from family Oscillospiraceae, which was also associated with high abdominal pain scores. LPA, but not LPC, seems to induce proinflammatory responses in the host. Further experiments are needed to identify the specific mechanisms by which these bioactive phospholipids induce abdominal pain and immune responses in the host.

Funding Agencies

CIHRFarncombe Family Digestive Health Research Institute
A43 MECHANISMS OF UNIQUE COLONIZATION DYNAMICS AND IMMUNE RESPONSES TO MURIBACULACEAE
Authors: Popple S , Pepin D , Ghezzi H , Tropini C , Osborne L
Published: February 2024

Background

Commercially available probiotics have a limited ability to alter the gut microbiome and establish within a pre-existing microbial community. Increases in osmolality, a condition prevalent in intestinal diseases, depletes the highly abundant bacterial family Muribaculaceae (Mb) from the gut microbiome in a mouse model of short-term osmotic laxative use. Excitingly, despite microbial community re-equilibration in its absence, Mb supersedes other bacterial colonizers to its original abundance if reintroduced, suggesting unique colonization attributes and a potential privileged immune interaction.

Aims

We aimed to investigate whether and how Mb colonization affects intestinal innate and adaptive immune homeostasis, including the generation of Mb-specific antibodies.

Methods

To examine interactions between Mb and the immune system that allows for efficient colonization, we used the osmotic laxative polyethylene glycol (PEG) to clear Mb and then generated mice with complex microbiomes that either lack Mb completely (Mb naïve) or were introduced to 8 murine-derived Mb strains (Mb+). The same strains were then introduced to Mb naïve mice (primary exposure to the immune system). To model secondary exposure, Mb+ mice were treated with PEG, and Mb re-introduced 3 weeks later. Leukocytes from the small and large intestinal lamina propria and gut-draining mesenteric lymph nodes (mLNs) were profiled over 21 days to characterize colonization and recolonization dynamics.

Results

High-throughput 16SrRNA sequencing showed no significant difference between relative abundance of Mb isolates during colonization or recolonization, indicating that Mb is capable of establishing in mice that have never been colonized with it before, making up to 20% of the relative abundance. Broad immunophenotyping demonstrated robust CD11b-CD103+ dendritic cell and Germinal Centre B cell responses in the mLNs of mice seeing Mb for the first time, yet no subsequent plasmablast accumulation in the mLN or lamina propria. We also observed significantly increased type two innate lymphoid cells in the small intestine upon primary exposure to Mb. Recolonization elicited no detectable changes in the monitored populations.

Conclusions

The lack of immune reactivity upon reintroduction to Mb suggests Mb may evade immune detection upon repeat exposure and contribute to its robust colonization abilities. Determining mechanisms involved in Mb colonization and its impact on host immune responses could increase our understanding of colonization dynamics and highlights the potential of Mb as a model for microbiota reintroduction in therapeutic applications.

Funding Agencies

Weston Family Foundation
A52 THE LGR5 ACTIVITY MODULATES CELL METABOLISM TO FAVOR WOUND HEALING
Authors: Acosta Montalvo J A , Arguin G , Dagenais Bellefeuille S , Gendron F
Published: February 2024

Background

The stem cell marker leucine-rich G-protein-coupled receptor-5 (LGR5) acts as an R-spondin (RSPO) signal transducer, facilitating WNT signaling to support tissue development and renewal. In GI diseases, LGR5+intestinal stem cells play a critical role in wound healing, while its expression by cancer stem cells correlates with cancer progression and chemoresistance. Surprisingly, only a handful of studies have investigated the functional role of LGR5 as a receptor. Demonstrating LGR5 receptor function and identifying signaling determinants will be a significant breakthrough in understanding stem cell biology under normal and pathological conditions. The project hypothesis is that LGR5 scaffolds the assembly of signaling complexes that modulate cell metabolism to accommodate cell fate, growth, and migration.

Aims

The project aims to characterize the molecular determinants linking LGR5 to cell metabolism and wound healing.

Methods

As a working model, recombinant LGR5 and mutant constructs were expressed in HEK293 cells. Wound healing was determined using scratch and single-cell tracking assays to measure cell migration. Cellular metabolism was measured using Seahorse assays complemented by metabolomic studies.

Results

Proteomic analysis revealed a rich LGR5 protein interactome associated with amino acid, glucose, purine metabolism, scaffold proteins (e.g., 14-3-3), and GPCR signaling. Using Seahorse assays, we showed that oxygen consumption and glycolysis were increased in LGR5-expressing cells, while metabolic profiling revealed enrichment in metabolites associated with glutamate, purine, pyrimidine metabolism, pentose phosphate pathway, glycolysis, and TCA cycle, among others. Finally, LGR5 expression promoted wound healing and a single cell's migration distance.

Conclusions

The results describe for the first time a functional role of LGR5 as a receptor, but foremost as an effector modulating cell metabolism. The findings may pave the way for new therapeutics targeting the LGR5 interactome to restore tissue homeostasis in diseases such as inflammatory bowel disease or to block cell adaptation and dissemination in the context of cancer.

Funding Agencies

CCCNSERC
A58 UTILIZATION OF HYPOXIA-TOLERANT ORGANISMS AS A MODEL IN THE STUDY OF ISCHEMIC-REPERFUSION INJURY IN TRANSPLANT HEPATOLOGY
Authors: Hossein-Javaheri N , Buck L
Published: February 2024

Background

Ischemic-reperfusion injury (IRI) is a barrier to successful liver transplantation. This complex process is initiated by an episode of hypoxia and decreased adenosine triphosphate (ATP) production. Mammalian hepatocytes are susceptible to prolonged hypoxia and may experience irreversible damage with ATP depletion. Yet, facultative anaerobes have developed physiological hepatoprotective strategies to tolerate hypoxic stress. The painted turtle (Chrysemys picta belli) and the common goldfish (Carassius auratus) are able to survive under severe hypoxia for weeks to months.

Aims

Introducing hypoxia-tolerant organisms as a suitable animal model for studying IRI in transplant hepatology.

Methods

A comprehensive search of PubMed, OVID, CINAHL, and Cochrane databases up to May 2023 was conducted to identify all studies reporting experimental evidence and hepatoprotective pathways in hypoxia-tolerant organisms (HTOs). Each article was qualitatively assessed. The primary focus was on cell death, intracellular ion gradient, mitochondrial function, and reactive oxygen species (ROS) with hypoxia and IRI.

Results

HTOs have increased glycogen storage with a greater ATP yield from anaerobic metabolism (glycolysis). Approximately 15-30% of liver mass in HTOs is composed of glycogen which is massive compared to 5-6% in mammals. Turtle isolated hepatocytes can tolerate 10 hours of anoxia by reducing cellular metabolic demand by 90% through decreased protein synthesis and ion channel activity. Goldfish hepatocytes can tolerate 6 hours of anoxia via similar strategies. In mammals, mitochondria undergo depolarization, Ca2+ efflux, cellular swelling, and apoptosis with anoxia. Yet, a depolarized mitochondrial membrane potential is regulated to provide cellular protection in HTOs. The ability to preserve mitochondrial function and electrochemical gradients with oxygen lack is an important contributor to cellular survival. Even in mammalian hepatocytes, if the mitochondrial integrity is maintained, cells are better able to tolerate ischemic insults. Finally, formation of radicals with reperfusion leads to hepatocyte apoptosis and necrosis in the mammalian model. Meanwhile, regulated ROS levels in turtles and goldfish cells, prevent cell death and IRI.

Conclusions

IRI is of significant interest in transplant hepatology. Although extremely valuable, the traditional mammalian models are vulnerable to hypoxia. Meanwhile, HTOs have undergone years of adaptation with thousands of genes dedicated to hypoxia tolerance. Utilizing these organisms can provide a broader understanding of IRI and avoid irreversible tissue damage in transplant hepatology.

Funding Agencies

CIHR
A60 INVESTIGATING THE ROLE OF NUCLEOTIDE-BINDING OLIGOMERIZATION DOMAIN (NOD) PROTEINS DURING BACTERIAL INFECTIONS IN INTESTINAL EPITHELIAL CELLS
Authors: Nissan M , Girardin S E
Published: February 2024

Background

Inflammatory bowel disease (IBD) is a collection of conditions that result in the inflammation of the gastrointestinal tract causing diarrhea, abdominal pain, weight loss, nausea, and vomiting. With its prevalence a whopping 0.6% in Canada, there is a need to understand the targets of therapy for the disease. Crohn’s disease, which is one of the two main conditions implicated in IBD, is most often associated with polymorphisms in the NOD2 gene. NOD2 is integral to the innate immune system of mammals, and functions as a pattern recognition receptor within the cytosol of cells. It detects conserved bacterial peptidoglycans to elicit an anti-microbial response by activating the nuclear factor kappa B pathway. NOD proteins also tackle infections upon bacterial recognition by recruitment of autophagy proteins allowing for the degradation of invading bacteria. Given their roles in bacterial clearance, it is unsurprising that mice deficient for NOD1 or NOD2 show increased susceptibility to pathogens, which is also what is thought to occur with Crohn's disease patients.

Aims

Although NOD1 and NOD2 have been well characterized in immune cells, little research has been done to interrogate their role during bacterial dysbiosis in intestinal epithelial cells. This research aims to elucidate the global signaling landscape that these proteins modulate in intestinal epithelial cells post-infection. We hypothesize that NOD1 and NOD2 play a critical role in host defense against intracellular bacterial pathogens in intestinal epithelial cells.

Methods

Intestinal crypts were harvested from WT, Nlrc4-/-, and Nlrc4-/- Ripk2-/- C57BL/6 mice to generate primary ileal organoids. Organoids infected with Shigella flexneri were harvested for protein and RNA. Downstream western blot, qPCR, Immunohistochemistry, and CFU analyses were performed to ensure the efficacy of the infection.

Results

Upon Shigella flexneri infection, CFU counts were only able to be recorded in a non-pyroptotic background (Nlrc4-/-). When examining the organoids by Immunohistochemistry, Shigella was well visualized in the Nlrc4-/- enteroids and was absent in WT controls 4 hours post-infection. Additionally, an increase in pro-inflammatory and stress genes was seen only in Nlrc4-/- organoids compared to WT controls. Finally, Nlrc4-/- Ripk2-/- organoids experience higher bacterial loads by CFU analysis compared to Nlrc4-/-Ripk2+/+ organoids.

Conclusions

Our research has shown that NOD1 and NOD2 deficiencies in primary mouse epithelial cells have increased bacteria loads compared to WTs upon infections showcasing a novel epithelial-intrinsic role for NOD1 and NOD2. This new insight into an epithelium-intrinsic role may be a step towards understanding the mechanism behind NOD2-associated Crohn's disease pathogenesis.

Funding Agencies

CIHRCrohn's and Colitis Canada
A70 INABILITY TO AMBULATE FOLLOWING COLONOSCOPY: AN UNEXPECTED COMPLICATION
Authors: Balbaa A , Brackenridge E , Tarnopolsky M , Sherlock M
Published: February 2024

Background

The peroneal nerve innervates the lower extremities. Compression injury has been documented in the adult patients following the lithotomy position perioperatively, but has rarely been described in pediatric patients following colonoscopy.

Aims

To report a rare complication following colonoscopy and discuss possible aetiologies.

Methods

A chart review of a post-colonoscopy peroneal nerve injury in a pediatric patient was conducted along with a literature review.

Results

A 12 year old boy with ulcerative colitis underwent a colonoscopy for flare symptoms. He was in the left lateral decubitus position for 60 minutes. Immediately after the procedure, he experienced loss of sensation from the left knee to the plantar aspect of the foot, and left foot drop. He had no symptoms of weakness or paresthesia in the right lower extremity or the upper extremities. Prior to the procedure, he reported normal strength, function, and sensation of all extremities. He had no history of injury, joint inflammation or previous surgery affecting his left leg. He had no recent history of steroid use or systemic illness.

Two months post procedure he had some symptom improvement and could independently ambulate. He had normal range of motion, strength, and sensation in the upper extremities and right lower extremity. His left leg had 4/5 strength on dorsiflexion and decreased pinprick and light touch sensation. He had difficulty with heel-toe walking.

Reflexes were normal.

Left leg X-ray and spine MRI were normal. Electrodiagnostic evaluation supported a left common peroneal nerve injury, predominantly demyelinating in nature with minimal axonal contribution, likely secondary to compression around the fibular head during the time of the colonoscopy. He showed full recovery and returned to baseline by 7 months.

Conclusions

Peroneal nerve injury post colonoscopy is very rare. A study focusing on pediatric colonoscopy found that 3 of 746 patients experienced postoperative neuropathies in their lower extremities. Procedure times were between 70-120 minutes. Presentations and recovery periods were variable, lasting several days to 3 months.

The mechanisms of this injury are unclear and felt unlikely to be secondary to positioning alone. It is speculated that BMI, procedure length, frog leg position and position changes, as well as systemic inflammation may be contributory. Factors such as hypothermia, dehydration, hypotension, hypoxia, and electrolyte disturbances may further place patients at risk. Awareness of this rare event and potential modifiable risk factors is important.

Funding Agencies

None