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Fujimoto, K.

Publications and source records attributed to Fujimoto, K..

At least 19 recordsLinked to original sources

Modeling the Impact of Dynamic Gastric pH on Helicobacter pylori Eradication and Antibiotic Resistance Emergence

Helicobacter pylori infections present a persistent global health challenge due to increasing antibiotic resistance and the bacteriums ability to survive in the acidic gastric environment. Existing within-host models of H. pylori infection neglect the gastric pH fluctuation, despite its role in modulating bacterial growth and antibiotic efficacy. To address this gap, we extend a published in-host model by explicitly incorporating gastric pH as a dynamic state variable, influenced by three key physiological processes (i) bacteria urease which neutralizes gastric acid to create a protective niche; (ii) host acid secretion response, which attempts to restore baseline acidity; and (iii) dietary perturbations, which induce temporary pH changes. Equilibrium and stability analysis reveal pH-dependent reproductive thresholds [R]s(H) and [R]r(H) that determine the conditions for bacterial persistence and treatment outcome. Successful eradication requires driving both thresholds below unity. Numerical simulations validate distinct clinical scenarios including complete bacterial clearance, resistant strain dominance, stable bacterial coexistence, and oscillatory persistence. These outcomes emerge from the coupled interplay between antibiotic pressure, immune response, and pH regulation. Our model provides a comprehensive theoretical framework for understanding H. pylori treatment failures and highlights how adjuvant pH-modulation strategies could enhance antibiotic efficacy against resistant infections.

microbiology↗

3D geometry and mechanics of a single apical stem cell ensure helically symmetric plant body in multicellular models

Self-renewing divisions of stem cells at the growing tip universally govern plant development. In basal land plants, a single apical stem cell (AC) undergoes successive 120-degree rotational divisions while maintaining a self-similar tetrahedral geometry with three division walls, recapitulating the helically symmetric body architecture. The mechanisms by which AC geometry and mechanics determine the division axis and its rotation are largely unknown. Here, we develop two 3D multicellular mathematical models to address these questions. Our geometrical model reveals that the least area rule, coordinated with the AC surface curvature, is sufficient to drive rotational divisions by rotating the geometric proportion of the AC. Furthermore, by incorporating biologically plausible cell growth mechanics, we show that the tetrahedral AC and its rotational division spontaneously emerge from a spherical cell. Notably, the maximal tension rule confers superior robustness against stochastic fluctuations in division orientation compared to the least area rule, because the sequential formation of division walls continuously updates the tension distribution to guide subsequent orientation. These results suggest that the tetrahedral AC and the helically symmetric body plan are natural consequences of self-renewing cell divisions, imposed by 3D geometry and/or mechanics.

plant biology↗

Functional impact of pathogenic Runt domain mutations in Runx2 in vivo: Insights into the skeletal and dental anomalies of cleidocranial dysplasia

Runt-related transcription factor 2 (RUNX2) is essential for skeletogenesis, and mutations in its gene cause cleidocranial dysplasia (CCD), an autosomal dominant skeletal disorder. The evolutionarily conserved 128-amino acid Runt homology domain (RHD) of human RUNX2 is essential for DNA binding and heterodimerization, and serves as a mutation hotspot associated with severe CCD phenotypes. To elucidate the functional impact of pathogenic RHD mutations in vivo, we generated two novel mouse lines: one carrying a missense mutation, c.695G>A (p.R232Q) (Runx2m/+), corresponding to the human RUNX2 c.674G>A (p.R225Q), and the other harboring a frameshift mutation, c.697_698delGA (p.E233TfsTer9) (Runx2112/+), causing a premature stop codon. Homozygous Runx2m/mand Runx2112/112 mice lacked membranous ossification, whereas heterozygous Runx2m/+ and Runx2112/+ mice displayed typical CCD-like skeletal features, including an open anterior fontanelle and clavicle hypoplasia. Unexpectedly, heterozygotes carrying pathogenic mutations in RHD developed an accessory root-like protrusion at the furcation of three-rooted maxillary first molars, representing a previously unrecognized dental phenotype during root development. Dual luciferase assays revealed impaired transactivation of the p.R232Q mutant Runx2 on the osteocalcin enhancer/promoter. Wild-type Runx2 was robustly expressed in osteoblasts and hypertrophic chondrocytes during bone formation, but the mutant Runx2 exhibited reduced expression in hypertrophic chondrocytes and partially impaired nuclear localization, resulting in arrested osteoblast and chondrocyte maturation. Our mutant mouse model provides a valuable in vivo platform to study CCD pathogenesis, mechanisms of tooth root furcation, and therapeutic interventions targeting dysfunctional RHD.

genetics↗

HD-ZIP IV genes are essential for embryo initial cell polarization in the radial axis initiation in Arabidopsis

Plants develop along apical-basal and radial axes. In Arabidopsis thaliana, the radial axis becomes evident when the cells of the eight-cell proembryo divide periclinally, forming inner and outer cell layers. Although changes in cell polarity or morphology likely precede this oriented cell division, the initial events and the factors regulating radial axis formation remain elusive. Here, we report that three transcription factors belonging to class IV homeodomain-leucine zipper (HD-ZIP IV) family redundantly regulate radial pattern formation: HOMEODOMAIN GLABROUS11 (HDG11), HDG12, and PROTODERMAL FACTOR2 (PDF2). The hdg11 hdg12 pdf2 triple mutant failed to undergo periclinal division at the eight-cell stage and cell differentiation along the radial axis. Live-cell imaging revealed that this failure in radial axis formation can be traced back to the behavior of the embryo initial cell (apical cell), which is generated by zygote division. In the wild type, the apical cell grows longitudinally and then radially and its nucleus remains at the bottom of the cell, where the vertical cell plate emerges. By contrast, the mutant apical cell elongates longitudinally and its nucleus releases from its basal position, resulting in a transverse division. Computer simulations based on the live-cell imaging data confirmed the importance of the geometric rule (the minimal plane principle and nucleus-passing principle) in determining the cell division plane. We propose that HDG11, HDG12, and PDF2 promote apical cell polarization, i.e., radial cell growth and basal nuclear retention, as the initial event of radial axis formation during embryogenesis.

plant biology↗

Isogenic iPSC-derived proximal and distal lung-on-chip models: Tissue- and virus-specific immune responses in human lungs

Micro-physiological systems (MPS) are set to play a vital role in preclinical studies, particularly in the context of future viral pandemics. Nonetheless, the development of MPS is often impeded by the scarcity of reliable cell sources, especially when seeking various organs or tissues from a single patient for comparative analysis of the host immune response. Herein, we developed human airway-on-chip and alveolus-on-chip models using induced pluripotent stem cell (iPSC)-derived isogenic lung progenitor cells. Both models demonstrated the replication of two different respiratory viruses, namely SARS-CoV-2 and Influenza, as well as related cellular damage and innate immune responses-on-chip. Our findings reveal distinct immune responses to SARS-CoV-2 in the proximal and distal lung-on-chip models. The airway chips exhibited a robust interferon (IFN)-dependent immune response, whereas the alveolus chips exhibited dysregulated IFN activation but a significantly upregulated chemokine pathway. In contrast, Influenza virus infection induced a more pronounced immune response and cellular damage in both chip models compared to SARS-CoV-2. Thus, iPSC-derived lung-on-chip models may aid in quickly gaining insights into viral pathology and screening potential drugs for future pandemics.

bioengineering↗

Pulsation waves along the Ciona heart tube reverse by bimodal rhythms expressed by a remote pair of pacemakers

The heart of ascidians, marine invertebrate chordates, exhibits a tubular structure, and heartbeats propagate from one end to the other. The direction of pulsation waves intermittently reverses in the heart of ascidians and their relatives; however, the underlying mechanisms remain unclear. We herein performed a series of experiments to characterize the pacemaker systems in isolated hearts and their fragments and applied a mathematical model to examine the conditions leading to heart reversals. The isolated heart of Ciona sufficiently performed heart reversals, and experimental bisections of isolated hearts revealed that independent pacemakers resided on each side and also that their beating frequencies periodically changed as they expressed bimodal rhythms. Only fragments including 5% or shorter terminal regions of the heart tube maintained autonomous pulsation rhythms, whereas other regions did not. Our mathematical model, based on FitzHugh-Nagumo equations applied to a one-dimensional alignment of cells, demonstrated that the difference between frequencies expressed by the two independent terminal pacemakers determined the direction of propagated waves. Changes in the statuses of the terminal pacemakers between the excitatory and oscillatory modes as well as in their endogenous oscillation frequencies were sufficient to lead to heart reversals. These results suggest that the directions of pulsation waves in the Ciona heart reverse according to the changing rhythms independently expressed by remotely coupled terminal pacemakers. Summary statementPulsation waves traveling along the heart tube of the ascidian Ciona intermittently reverse because of autonomous and periodical changes in beating frequencies at a pair of terminal pacemakers.

physiology↗

Size-Correlated Polymorphisms in Phyllotaxis-Like Periodic and Symmetric Tentacle Arrangements in Hydrozoan Polyps

IntroductionPeriodic organ arrangements occur during growth and development and are widespread in animals and plants. In bilaterian animals, the organs can be interpreted as being periodically arranged along the two-dimensional space and defined by two body axes; on the other hand, in radially symmetrical animals and plants, organs are arranged in the three-dimensional space around the body axis and around plant stems, respectively. The principles of periodic organ arrangement have primarily been investigated in bilaterians; however, studies on this phenomenon in radially symmetrical animals are scarce. MethodsIn the present study, we combined live imaging, quantitative analysis, and mathematical modeling to elucidate periodic organ arrangement in a radially symmetrical animal, Coryne uchidai (Cnidaria, Hydrozoa). ResultsThe polyps of C. uchidai simultaneously formed multiple tentacles to establish a regularly angled, ring-like arrangement with radial symmetry. Multiple rings periodically appeared throughout the body and mostly maintained symmetry. Furthermore, we observed polymorphisms in symmetry type, including tri-, tetra-, and pentaradial symmetries, as individual variations. Notably, the types of radial symmetry were positively correlated with polyp diameter, with a larger diameter in pentaradial polyps than in tetra- and triradial ones. Our mathematical model suggested the selection of size-correlated radial symmetry based on the activation-inhibition and positional information from the mouth of tentacle initiation. DiscussionOur established quantification methods and mathematical model for tentacle arrangements are applicable to other radially symmetrical animals, and will reveal the widespread association between size-correlated symmetry and periodic arrangement principles.

developmental biology↗

An In-Silico Testbed for Fast and Accurate MR Labeling of Orthopaedic Implants

AO_SCPLOWBSTRACTC_SCPLOWOne limitation on the ability to monitor health in older adults using Magnetic Resonance (MR) imaging is the presence of implants, where the prevalence of implantable devices (orthopedic, cardiac, neuromodulation) increases in the population, as does the pervasiveness of conditions requiring MRI studies for diagnosis (musculoskeletal diseases, infections, or cancer). The present study describes a novel multiphysics implant modeling testbed using the following approaches with two examples: - an in-silico human model based on the widely available Visible Human Project (VHP) cryo-section dataset; - a finite element method (FEM) modeling software workbench from Ansys (Electronics Desktop/Mechanical) to model MR radio frequency (RF) coils and the temperature rise modeling in heterogeneous media. The in-silico VHP Female model (250 parts with an additional 40 components specifically characterizing embedded implants and resultant surrounding tissues) corresponds to a 60-year-old female with a body mass index (BMI) of 36. The testbed includes the FEM-compatible in-silico human model, an implant embedding procedure, a generic parameterizable MRI RF birdcage two-port coil model, a workflow for computing heat sources on the implant surface and in adjacent tissues, and a thermal FEM solver directly linked to the MR coil simulator to determine implant heating based on an MR imaging study protocol. The primary target is MR labeling of large orthopaedic implants. The testbed has very recently been approved by the US Food and Drug Administration (FDA) as a medical device development tool (MDDT) for 1.5 T orthopaedic implant examinations.

biophysics↗

Diffusive mediator feedback explains the health-to disease transition of skin inflammation

The spatiotemporal dynamics of inflammation provide vital insights into the understanding of skin inflammation. Skin inflammation primarily depends on the regulatory feedback between pro- and anti-inflammatory mediators. Healthy skin exhibits faded erythema. In contrast, diseased skin exhibits expanding erythema with diverse patterns, clinically classified into five types: circular, annular, arcuate, gyrate, and polycyclic. Inflammatory diseases with expanding erythema are speculated to result from the overproduction of pro-inflammatory mediators. However, the mechanism by which feedback selectively drives the switch from a healthy fading erythema to each of the five types of diseased expanding erythema remains unclear. This study theoretically elucidates the imbalanced production between pro- and anti-inflammatory mediators and prospective treatment strategies for each expansion pattern. Our literature survey showed that eleven diseases exhibit some of the five expanding erythema, suggesting a common spatiotemporal regulation underlying different patterns and diseases. Accordingly, a reaction-diffusion model incorporating mediator feedback reproduced the five observed types of diseased expanding and healthy fading patterns. Importantly, the fading pattern transitioned to the arcuate, gyrate, and polycyclic patterns when the productions of anti-inflammatory and pro-inflammatory mediators were lower and higher, respectively, than in the healthy condition. Further depletion of anti-inflammatory mediators caused a circular pattern, whereas further overproduction of pro-inflammatory mediators caused an annular pattern. Mechanistically, the bistability due to stabilization of the diseased state exhibits circular and annular patterns, whereas the excitability exhibits the gyrate, polycyclic, arcuate, and fading patterns as the threshold of pro-inflammatory mediator concentration relative to the healthy state increases. These dynamic regulations of diffusive mediator feedback provide effective treatment strategies for mediator production wherein skins recover from each expanding pattern toward a fading pattern. Thus, these strategies can estimate disease severity and risk based on erythema patterns, paving the way for developing noninvasive and personalized treatments for inflammatory skin diseases.

biophysics↗

Geodesic theory of long association fibers guidance on the human fetal cortex

Association fibers connect different areas of the cerebral cortex over long distances and integrate information to achieve higher brain functions, particularly in humans. Prototyped association fibers are developed to the respective tangential direction throughout the cerebral hemispheres in the subplate layer during the fetal period. However, the directional guidance principle for forming association fibers is unknown. Because the subplate is located below the cortical surface, the tangential direction of the fibers may be biased by the curved surface geometry due to Sylvian fissure and cortical poles. The fiber length can be minimized if the tracts follow the shortest paths (geodesics) of the curved cortical surface. Here, we propose and examine a theory that geodesics guide the tangential direction of long association fibers by analyzing how geodesics are spatially distributed on the fetal human brains. Unlike the homogeneous distribution on spherical surfaces, we found that the geodesics were dense on the saddle-shaped surface of the perisylvian region and sparse on the dome-shaped cortical poles. The geodesics corresponded with the positions of five typical association fibers, supporting the geodesic theory. Thus, the geodesic theory provides directional guidance and suggests that long association fibers emerge from minimizing their tangential length on fetal brains.

neuroscience↗

Spatio-temporal remodeling of extracellular matrix orients epithelial sheet folding

Biological systems are inherently noisy; however, they produce highly stereotyped tissue morphology. Drosophila pupal wings show a highly stereotypic folding through uniform expansion and subsequent buckling of wing epithelium within a surrounding cuticle sac. The folding pattern produced by buckling is generally stochastic; it is thus unclear how buckling leads to stereotypic tissue folding of the wings. We found that the extracellular matrix (ECM) protein, Dumpy, guides the position and direction of buckling-induced folds. Dumpy anchors the wing epithelium to the overlying cuticle at specific tissue positions. Tissue-wide alterations of Dumpy deposition and degradation yielded different buckling patterns. In summary, we propose that spatio-temporal ECM remodeling shapes stereotyped tissue folding through dynamic interactions between the epithelium and its external structures. One-Sentence SummaryRemodeling of extracellular matrix protein, Dumpy, guides epithelial tissue folding during Drosophila wing development.

developmental biology↗

Diagnosis of type 2 Diabetes Mellitus (T2DM) using Paired microRNAs

Type 2 Diabetes mellitus (T2DM) is one of the most common diseases in the world and its prevalence ratio is still increasing. Patients with T2DM have diverse pathophysiological changes like as macrovascular, microvascular diseases, cancers as well as abnormal glucose metabolism. Thus, there are urgent needs to develop relevant biomarkers for the broad range of pathophysiology in patients with T2DM. We analyzed the signatures of serum miRNAs with the miRNA array analysis and reverse-transcription based quantitative polymerase chain reaction (RT-qPCR) in 50 patients with type 2 DM (T2DM) and 15 normal subjects. Array analysis showed that 19 miRNAs were up-regulated more than 2-fold and 71 miRNAs were down-regulated less than 0.5 in T2DM in comparison with normal subjects. Top 5 of up-regulated miRNAs were miR-3619-3p, miR-557, miR-6850-5p, miR-3648, miR-4730, and 5 of most down-regulated miRNAs were miR-5100, miR-4454, miR-1260b, miR-7975, miR-6131. We selected 4 miRNAs for validation analysis with RT-qPCR based on the abundance enough for reliable analyses and disease-specificities reported in previous reports. Serum miR-126-3p was down-regulated (3.21-fold, p<0.05) in T2DM, and miR-10a up-regulated (1.94-fold, p<0.05). However, none of single miRNA had significant correlation with clinical data and state. Data of the paired miRNAs: miR-10a and miR-200c, or miR-126 and miR-10a, clearly differentiated T2DM patients from normal subjects (p<0.05). Our study showed the paired-miRNA analyses as the more effective diagnostics for T2DM than the single miRNA analysis.

molecular biology↗

Single-molecule tracking of Nanog and Oct4 in mouse embryonic stem cells

Nanog and Oct4 are core transcription factors in a gene regulatory network that regulate hundreds of target genes for pluripotency maintenance in mouse embryonic stem cells. To understand their function as a gatekeeper or a pioneer factor at the molecular scale, we quantified the residence time on target loci, fluctuation at the loci, and interaction clustering by visualizing single molecules of Nanog and Oct4 in a living nucleus during the pluripotency loss. Interestingly, Nanog interacted longer with its target loci in the lower Nanog expression state or at the onset of differentiation, indicating the possibility of a new feedback mechanism to maintain Nanog expression. The interaction time of Nanog and Oct4 corresponded to their fluctuation and interaction clustering, which depended on their expression or differentiation state, respectively. The DNA viscoelasticity near the Oct4 target locus remained flexible during the differentiation, reflecting its role as a pioneer factor. Based on these results, we propose a new feedback mechanism for pluripotency maintenance in which Nanog function is prolonged, corresponding to chromatin condensation, and Oct4 reopens the condensation.

biophysics↗

Phylogeny and Metadata Network Database for Epidemiologic Surveillance

AO_SCPLOWBSTRACTC_SCPLOWThe ongoing SARS-CoV-2 pandemic has highlighted the difficulty in integrating disparate data sources for epidemiologic surveillance. To address this challenge, we have created a graph database to integrate phylogenetic trees, associated metadata, and community surveillance data for phylodynamic inference. As an example use case, we divided 22,713 SARS-CoV-2 samples into 5 groups, generated maximum likelihood trees, and inferred a potential transmission network from a forest of minimum spanning trees built on patristic distances between samples. We then used Cytoscape to visualize the resultant graphs.

evolutionary biology↗

Neural mechanism of experience-dependent sensory gain control in C. elegans

Animals sensory systems adjust their responsiveness to environmental stimuli that vary greatly in their intensity. Here we report the neural mechanism of experience-dependent sensory adjustment, especially gain control, in the ASH nociceptive neurons in Caenorhabditis elegans. Using calcium imaging under gradual changes in stimulus intensity, we find that the ASH neurons of naive animals respond to concentration increases in a repulsive odor 2-nonanone regardless of the magnitude of the concentration increase. However, after preexposure to the odor, the ASH neurons exhibit significantly weak responses to a small gradual increase in odor concentration while their responses to a large gradual increase remain strong. Thus, preexposure changes the slope of stimulus-response relationships (i.e., gain control). Behavioral analysis suggests that this gain control contributes to the preexposure-dependent enhancement of odor avoidance behavior. Mathematical analysis reveals that the ASH response consists of fast and slow components, and that the fast component is specifically suppressed by preexposure. In addition, genetic analysis suggests that G protein signaling is required for the fast component. Thus, our integrative study demonstrates how prior experience dynamically modulates stimulus-response relationships in sensory neurons, eventually leading to adaptive modulation of behavior.

neuroscience↗

Lipid nanodiscs facilitate the identification of a fragment compound inhibiting the enzymatic activity of the bacterial membrane protein MsbA.

Membrane proteins are critical elements of numerous therapeutic approaches ranging from cancer to bacterial infections. MsbA is a bacterial membrane protein that has received increasing attention as an antibacterial target for its role in the processing of Lipid A, a key precursor of lipopolysaccharide that is essential for bacterial growth. When employing nanodiscs it is possible to stabilize MsbA by providing a membrane-like environment that enhances its enzymatic activity. Taking advantage of this property we have carried out a fragment screening using the biophysical method of surface plasmon resonance. This approach identified several compounds that bind specifically to MsbA. In particular, one of these fragment molecules not only binds to the target, but also inhibits the ATPase activity of the MsbA protein. The similarity of this fragment to the adenine moiety of ATP points at a route to generate stronger and more potent inhibitors for MsbA and even other proteins of its family of ABC transporters. Collectively, our study reveals biophysical approaches that facilitate the identification of fragment candidates inhibiting the activity of membrane proteins.

biophysics↗

Establishing defined daily doses (DDDs) for antimicrobial agents used for pigs, cattle and poultry in Japan and comparing them with European DDD values

Monitoring of antimicrobial use is essential to manage the development and selection of antimicrobial resistance. A variety of indicators has become available to monitor antimicrobial use in human and animal medicine. One of them is an indicator based on defined daily dose (DDD). By using the number of DDDs used and normalizing it by the population at risk of being treated in a defined period, one can estimate the number of treatment days with antimicrobial agents in a population. For veterinary medicine, the European Medicines Agency (EMA) has published the European values of DDD (DDDvet) for food-producing animals. In this study, we defined Japanese defined daily doses for antimicrobial agents (DDDjp) using DDD values that we previously assigned for antimicrobial products approved for use in pigs, cattle and poultry in Japan and compared them with DDDvet values. For the comparison, the quotient of Japanese and European values (QDDD) was calculated and the effect of the administration route and the number of active substances contained in the preparation was investigated. A total of 59, 51 and 27 DDDjp values were defined for 43, 32 and 25 antimicrobial agents using the data of 269, 195 and 131 products approved for use in pigs, cattle and poultry respectively. A comparison was possible for 44, 27 and 17 pairs of DDDjp and DDDvet values for antimicrobial agents used for pigs, cattle and poultry respectively. The comparison showed median QDDD value of 0.66 and 0.63 for antimicrobial agents used for pigs and cattle respectively (P<0.01), indicating that the Japanese daily doses are significantly lower than the corresponding EMA values in these species. For the antimicrobial agents used for poultry, no siginificant difference was observed between DDDjp and DDDvet values with median QDDD value of 1.17. The difference between DDDvet and DDDjp values and absence of DDDvet values for some antimicrobial agents marketed in Japan indicate that DDDjp rather than DDDvet should be used as the basis for the calculation of antimicrobial use monitoring in farm animals in Japan.

bioinformatics↗

A Software Toolkit for TMS Electric-Field Modeling with Boundary Element Fast Multipole Method: An Efficient MATLAB Implementation

BackgroundTranscranial magnetic stimulation (TMS) is currently the only non-invasive neurostimulation modality that enables painless and safe supra-threshold stimulation by employing electromagnetic induction to efficiently penetrate the skull. Accurate, fast, and high resolution modeling of the electric fields (E-fields) may significantly improve individualized targeting and dosing of TMS and therefore enhance the efficiency of existing clinical protocols as well as help establish new application domains. ObjectiveTo present and disseminate our TMS modeling software toolkit, including several new algorithmic developments, and to apply this software to realistic TMS modeling scenarios given a high-resolution model of the human head including cortical geometry and an accurate coil model. MethodThe recently developed charge-based boundary element fast multipole method (BEM-FMM) is employed as an alternative to the 1st order finite element method (FEM) most commonly used today. The BEM-FMM approach provides high accuracy and unconstrained field resolution close to and across cortical interfaces. Here, the previously proposed BEM-FMM algorithm has been improved in several novel ways. Results and ConclusionsThe improvements resulted in a threefold increase in computational speed while maintaining the same solution accuracy. The computational code based on the MATLAB(R) platform is made available to all interested researchers, along with a coil model repository and examples to create custom coils, head model repository, and supporting documentation. The presented software toolkit may be useful for post-hoc analyses of navigated TMS data using high-resolution subject-specific head models as well as accurate and fast modeling for the purposes of TMS coil/hardware development.

bioengineering↗