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bioRxiv2026

Rapid phase resetting of Aedes aegypti circadian rhythms by transient alterations in light exposure

Circadian clocks enable mosquitoes to anticipate recurring environmental variations and coordinate behaviors critical for survival and disease transmission, such as locomotion, reproduction, host-seeking, and blood-feeding, with times of day when performance is maximal. In Aedes aegypti, locomotor activity follows a robust diurnal rhythm shaped by endogenous circadian clocks and environmental cues, among which light has been shown to be the primary source of temporal information. While early studies established the role of light in regulating locomotor activity, behavior, oviposition and pupation, it remains unclear which features of a light cycle drive changes in circadian rhythms. This question is increasingly relevant as Ae. aegypti is frequently exposed to artificial and dynamic lighting conditions in urban environments. Here, we investigated how transient changes in light schedules influence circadian rhythms in locomotor activity by systematically manipulating the timing, duration, and direction of light exposure. Using a high-throughput assay, we tested over 1900 individuals, including wild-type and timeless knockout mutants, and showed that a single day of al tered lighting is sufficient to induce robust phase shifts, with no evidence of masking effects. A 6-hour light pulse was sufficient to re-entrain mosquitoes regardless of the timing of the pulse, and phase shifts were primarily driven by the offset time of the light pulse, indicating that light-offset acts as a major zeitgeber. Together, these findings challenge conventional assumptions about the timescale of circadian synchronization and highlight the remarkable plasticity of mosquito behavior in response to anthropogenic light. Eventually, these effects could explain the rapid adaptation of the species to urban environments and have potential consequences for disease transmission dynamics.

animal behavior and cognition↗

bioRxiv2026

Stop codon readthrough in Trichomonas is a mechanism for gene expression regulation and expanding protein function

Trichomonas vaginalis is the causative agent of trichomoniasis, a common sexually transmitted infection among women of reproductive and peri-menopausal age. The parasite has an unusually large genome, rich in complex repeats, including a vast repertoire of transposable elements and multi-copy gene families. Since very few T. vaginalis genes have introns, gene expression is usually straightforward, with ribosomal translational machinery proceeding from a start codon to the next in-frame stop codon of an unspliced poly(A)denylated mRNA. However, our previous studies raised the possibility of T. vaginalis gene expression involving stop codon readthrough (SCR), where transcription through in-frame stop codons produces longer-than-predicted mRNAs that translate to fully functional proteins. Here, we leverage long-read RNA-seq and new chromosome-scale assemblies of two T. vaginalis strains and two avian sister species to investigate and characterize ~1,400 long, mature mRNAs that contain more than one predicted protein-coding gene transcribed from what we call '' RT genes '', composites of adjacent predicted genes. We first identify RT genes in a second T. vaginalis strain and in close relatives T. vaginalis-like and T. stableri, indicating that this phenomenon is conserved among Trichomonas species and strains. Second, we find transcripts of RT genes to be more abundant by many orders of magnitude than monocistronic genes. Third, we found the distance between predicted genes within RT genes to be significantly shorter than between adjacent independent predicted genes. Fourth, functional annotation revealed that RT genes encode at least 50 distinct protein functions, suggesting that this unusual transcriptional mechanism has a role in an array of biological processes in Trichomonas. Our results from two Trichomonas species suggest that SCR is an important mechanism controlling gene expression and the diversity of protein function in this parasite.

molecular biology↗

bioRxiv2026

A geometric anthropomorphic phantom for quantitative susceptibility mapping: accuracy and repeatability

Quantitative Susceptibility Mapping (QSM) relies on a tissue's underlying macroscopic geometry to lead to measurable orientation-dependent field perturbations. To understand and assess QSM error in vivo, anthropomorphic phantoms provide a useful model that mimic the electromagnetic properties and morphology of underlying tissue. Herein, we designed and manufactured an MRI compatible anthropomorphic phantom with cylindrical and spheroid compartments containing realistic susceptibilities to mimic hemorrhages, calcifications, and blood vessels. We estimated accuracy ({epsilon}, bias, RMSE) and repeatability (RC) of MEDI-susceptibility measurements within ROIs. We evaluated voxel-based agreement to validate susceptibility mapping under different acquisition conditions (3T versus 7T) and reconstruction algorithms (COSMOS versus MEDI). Reliable MEDI-based susceptibility measurements were obtained from ellipsoids but not from straws. The ellipsoids (|{epsilon}| = 0.007 to 0.083 ppm at 3T; 0.050 to 0.118 ppm at 7T) were more accurate than the straws (|{epsilon}| = 0.084 to 0.190 ppm at 3T; 0.105 to 0.160 ppm at 7T). The repeatability coefficient across all 6 ROIs (RC = 0.652 ppm at 3T; 0.459 ppm at 7T) was substantially larger than across the 4 ellipsoid ROIs only (RC' = 0.168 ppm at 3T; 0.141 ppm at 7T). The accuracy at 3T (bias = -0.002 ppm, RMSE = 0.082 ppm) was better than the accuracy at 7T (bias = -0.056 ppm, RMSE = 0.092 ppm). Using voxels from the 4 ellipsoid ROIs, we observed excellent agreement between COSMOS and MEDI susceptibility maps at 3T, with linear regression of y=1.00x-0.01 (r=0.99). We observed some underestimation of MEDI susceptibility maps relative to COSMOS at 7T, with linear regression and y=0.93x-0.04 (r=0.99). The results imply that QSM reconstructions are reliable with 3T scanners but can be challenging with 7T scanners at high magnetic susceptibilities.

biophysics↗

bioRxiv2026

Single-Cell Analytics for Dose Response (SCADR) discriminates PTEN missense variants by lipid and protein phosphatase dysfunction

The proliferation of sequencing efforts has revealed a vast and expanding catalog of single nucleotide gene variants, many associated to, but with unclear roles in disease. Fully charactering variant impacts and linking specific protein dysfunctions to disease are challenging due to the multi-functional nature of many proteins and varying degree of variant effects on these functions. Lagging are sensitive approaches to empirically assess the impact of missense variant-induced single amino acid changes on a wide range of protein functions. To address these issues, we have developed an open-source computational analysis tool called SCADR (Single-Cell Analytics for Dose Response) for simultaneously measuring and comparing impacts of exogenously-expressed variants on multiple signaling pathways using multiplex phospho-antibody spectral flow cytometry in human cell lines. SCADR retains and correlates single-cell measures of signal protein activity states along with expression levels of exogenously-expressed variants, providing rich characterization of multiple protein functions, signaling protein interactions, and enhanced discrimination of variant impacts on different signaling pathways, highlighting each variants unique dysfunction profile. Here, we apply SCADR for analyses of the impact of 6 variants of the tumor-suppressor protein PTEN (P38H, C124S, G129E, Y138L, D268E, 4A) expressed in HEK293 cells on the phosphorylation states of the canonical and noncanonical downstream signaling proteins Akt, S6, CREB, ERK, and p38 detected with fluorophore-conjugated phospho-antibodies, along with an antibody detecting an N-terminal HA tag on PTEN variants allowing measures of dose-response effects of each variants expression on signaling cascades. Results identify variant-specific impacts on downstream signaling cascades.

genomics↗

bioRxiv2026

From Prompt to Provenance: BloClaw, a Capability-Gated AI4S Workstation for Auditable Computational Biology

Scientific agents can produce plausible answers while remaining unable to establish whether the computation behind an answer is executable, recoverable, or reproducible. We present BloClaw, an AI4S workstation built around a simple principle: a scientific agent should know what it can do, show how it did it, and state what remains unvalidated. Each capability declares an execution state, input constraints, dependencies, expected outputs, and scientific limitations. Natural-language requests are translated into structured tasks, validated against this registry, executed through scientific tools, and recorded in a provenance-aware Living Lab Notebook. The system is designed to detect invalid inputs, failed tool calls, missing dependencies, and remote timeouts, and to route them to repair, retry, or escalation. The implemented and tested scope comprises RDKit-based molecular property and rule screening, protein structure analysis, docking-pose inspection, 3D visualization, and structured reporting. We demonstrate the workflow on a PubChem-retrieved osimertinib structure and a supplied 6LU7 docking artifact: the former yields deterministic descriptors (molecular weight 499.619 Da, cLogP 4.5098, TPSA 87.55 A^2), while the latter contains 2,387 protein ATOM records, 309 residues, and nine pose records. These examples are workflow demonstrations, not efficacy or affinity studies. Beyond retrospective prediction, the manuscript specifies a prior-minimized constructive mode in which a desired function is compiled into explicit physical, chemical, and systems constraints, candidate mechanisms are simulated, and observations are reintroduced for calibration and falsification; this is a proposed extension rather than a result of the present case studies. We describe an evaluation protocol that compares BloClaw with a standard single-agent workflow and fixed-script execution using task completion, scientific correctness, recovery success, provenance completeness, reproducibility, human review time, latency, and cost. This manuscript reports the system design, verified capability boundary, deterministic software artifacts, and a reproducible evaluation protocol; it does not claim benchmark improvements before those experiments are run. BloClaw is an execution and accountability layer for AI-assisted research, complementing expert review and experimental validation rather than replacing them.

bioinformatics↗

bioRxiv2026

Melanophilin, a Myosin Va Adapter Protein, Biases Track Selection of Myosin Va-and Kinesin-1-Transported Liposomes at Actin-Microtubule Intersections In Vitro

Secretory vesicle transport from the Golgi to the cell membrane involves kinesin and myosin Va motors on the vesicle surface cooperatively navigating their shared cargo through numerous actin-microtubule (MT) intersections. How the track on which the cargo exits the intersection is selected so that vesicles are delivered to their destination with spatial and temporal fidelity remains unclear. Here we hypothesized that melanophilin -- the adapter that links myosin Va to pigmented melanosomes and can bind to both actin and MTs -- acts as a phosphorylation-dependent switch to bias track preference at actin-MT intersections. To test this, we modeled melanosome transport in vitro using 350-nm liposomes with ~5 surface-bound molecules each of constitutively active myosin Va, kinesin-1, and full-length melanophilin with varying phosphorylation levels. Liposomes were then challenged with actin-MT intersections. Regardless of the track the liposomes entered the intersection on, liposomes with phosphorylated melanophilin were biased towards exiting the intersection on actin filaments while those with dephosphorylated melanophilin were biased to exit on MTs. Consistent with this, phosphorylated melanophilin showed a 2-fold preference to bind actin over MTs, and slowed liposome transport by myosin Va along actin filaments by ~40% by effectively acting as an anchor. Conversely, dephosphorylated melanophilin preferentially bound (2-fold) MTs over actin and, by acting as a tether, increased the kinesin-1 liposome transport distance on MTs. Therefore, melanophilin, based on its phosphorylation state, can bias track selection of cargo transported by kinesin-1 and myosin Va through the cell's complex cytoskeletal network with its numerous actin-MT intersections.

biophysics↗

bioRxiv2026

Functional plasticity of AIF revealed by dimerization and CHCHD4 interaction states

Apoptosis-inducing factor is a mitochondrial flavoprotein that links redox metabolism to mitochondrial homeostasis through its interaction with the disulfide relay protein CHCHD4. Although NADH-dependent AIF dimerization has been proposed as the activated state mediating CHCHD4 engagement, whether it is strictly required for productive AIF-CHCHD4 function remains unclear. Here, combining cellular, biochemical and biophysical approaches, we show that disruption of the AIF dimer interface compromises oxidative phosphorylation, respiratory-chain organization and CHCHD4-dependent mitochondrial homeostasis, yet preserves partial AIF function. Our data reveal that the AIF-CHCHD4 system operates as a conformational dynamic redox module in which distinct AIF oligomeric and redox states sustain CHCHD4 activity with different efficiencies. Mechanistically, dimerization is coupled to NADH-dependent conformational changes that regulate coenzyme binding, charge-transfer complex stabilization and catalytic efficiency. In turn, CHCHD4 binding remodels AIF conformational and redox properties, partially compensating for defects in dimer stabilization or redox coupling. Consistently, a peptide derived from the CHCHD4 N-terminus partially restores redox function in a pathogenic AIF variant defective in dimer stabilization, supporting partner-assisted allosteric regulation as a potential therapeutic strategy.

biochemistry↗

bioRxiv2026

Comparison of evolutionary rescue via biological and cultural evolution

Rapid evolution allows populations to persist in environments where they would otherwise go extinct. This phenomenon, known as evolutionary rescue, is typically studied in the framework of biological evolution, yet adaptive traits can also arise and spread through cultural evolution. The present study developed a stochastic eco-evolutionary model to compare rescue probabilities through biological and cultural evolution. Transmission bias governed the rescue probability under cultural evolution by setting how readily a rare adaptive trait was copied. Conformity bias suppressed population persistence because a rare trait was the least likely to be copied. Content bias toward the adaptive trait enabled evolutionary rescue when social learning was rapid, but it typically yielded a lower rescue probability than biological evolution. Only anticonformity bias, together with a high social learning rate, exceeded the rescue probability of biological evolution by enabling the adaptive trait to be established more rapidly. These results demonstrate that transmission bias alters the demographic consequences of cultural evolution and highlight the importance of transmission processes in evolutionary rescue theory. Understanding how adaptive behaviours are socially transmitted may also improve predictions of animal population persistence and inform conservation efforts in rapidly changing environments.

evolutionary biology↗

bioRxiv2026

Initial tumor composition shapes resistance evolution and treatment outcomes in non-small cell lung cancer

Drug resistance is a leading cause of treatment failure in non-small cell lung cancer (NSCLC), yet how resistance evolves during treatment and whether its fitness consequences depend on tumor composition remains poorly understood. Using a game-theoretic mathematical model fitted to longitudinal in-vitro data from alectinib-sensitive and alectinib-resistant H3122 NSCLC cells grown under different treatment and microenvironmental conditions, we found that the fitness effect of evolving resistance depended critically on the initial proportion of resistant cells in the tumor. When resistant cells were initially rare, resistance evolved faster and increasing resistance was associated with a growth advantage. When resistant cells were initially frequent, increasing resistance was associated with a fitness cost. In both cases, increasing resistance eroded treatment efficacy. In the gain-of-resistance regime, stabilization therapy could maintain a stable tumor equilibrium only if resistant cells were excluded. Maximum tolerated dosing was not always optimal for maximizing time to progression; intermediate doses performed better when they kept the initial tumor growth rate close to zero. These results suggest that evolutionary therapy for NSCLC should account not only for the abundance of resistant cells, but also for how resistance is evolving and what fitness consequences it currently carries in individual patients.

cancer biology↗

bioRxiv2026

Anxiety-Related Traits Are Associated with Subjective Biases but not Altered Threat-Safety Discrimination

Anxiety-related traits (ARTs) have been linked to altered fear learning, but previous studies have typically examined different experimental phases and response systems, limiting the comparability of findings and the accumulation of consistent evidence. Here, we comprehensively examined associations between ARTs and fear conditioning across acquisition, extinction and renewal and across subjective, physiological and neural response systems in a well-powered sample (N = 267) using a two-day differential conditioning paradigm. ARTs were operationalized as a composite of trait anxiety, neuroticism, and intolerance of uncertainty and conditioned responding was assessed using skin conductance responses, fear-potentiated startle, US expectancy ratings, fear ratings, and functional magnetic resonance imaging. Higher ARTs were consistently associated with elevated subjective fear and US expectancy to both threat and safety cues during extinction and renewal, without corresponding elevations in physiological responding. At the same time, ARTs were not associated with threat-safety discrimination in subjective or physiological measures across phases, while neural associations were limited to reduced dorsal anterior cingulate cortex discrimination during early renewal. These findings suggest that ARTs are characterized by a CS unspecific cognitive bias toward heightened threat expectancy and evaluation rather than altered associative fear learning, highlighting the importance of distinguishing conditioned discrimination from general levels of responding across response systems.

neuroscience↗

bioRxiv2026

Human Osteocytes Express MHC ClassII and Act as Non-classical Antigen-Presenting Cells During Bacterial Infection

Osteocytes are the most abundant cells in bone and are increasingly recognised not only for their role in skeletal remodelling and inflammatory signalling but also for their potential involvement in immune responses. In this study, we searched available gene expression datasets of human primary osteocyte-like cells exposed acutely to Staphylococcus aureus and identified significantly induced expression of key genes related to antigen processing and presentation. We then confirmed that human bone explant-derived osteoblastic cells, representative of a mature osteoblast-pre-osteocyte stage, expressed, as expected, high cell surface levels of major histocompatibility complex (MHC) Class I but also, low basal levels of the MHC Class II family member, HLA-DR. However, confocal imaging revealed high expression of MHC Class II molecules and the peptide-loading chaperone HLA-DM within the lysosomal compartments, consistent with canonical antigen-processing machinery. Differentiation towards a mature osteocyte phenotype increased MHC Class II protein levels and maintained expression of intracellular HLA-DM. Exposure of mature osteocyte-like cells to S. aureus further up-regulated both intracellular and cell surface MHC Class II expression. Demonstrative of antigen presenting cell functionality, S. aureus-exposed osteocytes induced autologous CD4+ T cell proliferation. Furthermore, MHC Class II expression in osteocytes was detected in bone sampled from patients with periprosthetic joint infections, providing evidence that these mechanisms operate in vivo. Together, our findings reveal that human osteocytes are capable of inducible MHC Class II-associated antigen presentation in response to bacterial challenge, pointing to a novel role for osteocytes in adaptive immune surveillance within bone.

immunology↗

bioRxiv2026

Beyond Equilibrium Ensembles: Time Rescaling in Coarse-Grained Simulations across Single-Molecule and Condensate Regimes

Residue-level coarse-grained simulations provide a powerful route for modeling biomolecular condensates over length and time scales that are difficult to access with atomistic molecular dynamics. Coarse-grained models have been shown to reproduce many aspects of equilibrium phase behavior. However, it remains unclear to what extent such models can reproduce the relative timescales of molecular dynamics. Here, we examine this question for complex coacervates with markedly different dynamics, formed by the highly acidic intrinsically disordered protein prothymosin with four cationic partners: linker histone H1, protamine, polylysine, and polyarginine. Coexistence simulations using a residue-level coarse-grained model reproduce key equilibrium observables from experiments, including dense-phase concentrations, ionic-strength-dependent phase behavior, and chain dimensions in the dense and dilute phases. Dynamics are accelerated in these simulations, but a composition-specific time-rescaling factor captures the ionic-strength dependence of chain reconfiguration times within a given complex coacervate. In contrast, time rescaling is not transferable between dense and dilute phases or across condensate compositions and can depend on the chosen observable. These results show that agreement with measured equilibrium observables does not imply a universally transferable timescale for conformational dynamics in residue-level coarse-grained simulations. However, we find that the required time rescaling strongly correlates with the interaction energy of the protein chains, suggesting that the missing frictional effects arise from protein-protein interactions rather than solely from protein-solvent interactions, reminiscent of internal friction. Our findings highlight the need to combine thermodynamic validation with kinetic calibration when interpreting chain relaxation, molecular diffusion, and material properties from residue-level coarse-grained simulations of biomolecular condensates.

biophysics↗

bioRxiv2026

From Public Archive to Reusable Resource: Characterizing Gut Microbiome Metadata in the NCBI SRA

Public sequencing repositories contain large amounts of gut microbiome data that could support cross-study comparison, reproducibility analysis, and microbiome foundation model development. However, the extent to which these data are structured, harmonized, and reusable at archive scale remains unclear. Here, we characterized publicly available gut microbiome sequencing metadata from the NCBI Sequence Read Archive using Google BigQuery, focusing on human gut metagenome, mouse gut metagenome, and broadly annotated gut metagenome records. We evaluated temporal growth, sequencing depth, BioSample and BioProject structure, platform and instrument use, metadata completeness, host attribution, publication linkage, and research themes from linked literature. Public gut microbiome data increased substantially over time and were dominated by human-associated datasets and Illumina sequencing platforms. Core technical metadata fields were highly complete, but biological context needed for reuse, including host identity, phenotype, study design, and disease status, was often inconsistently encoded or required recovery from BioSample attributes and linked publications. In the generic "gut metagenome" cohort, host identity could be assigned for only 13.00% of BioSamples, highlighting the limitations of broad organism annotations for automated cohort construction. Publication linkage was also incomplete at the archive level, although usable text was recovered for most linked publications. Topic modeling of SRA-linked literature showed persistent emphasis on core gut microbiota composition and increasing representation of human cohort and infant microbiome studies. Overall, these findings show that public gut microbiome data are extensive and technically rich but not uniformly analysis ready. Improved metadata harmonization, publication linkage, and biological context recovery will be necessary to support reliable large-scale reuse and AI-ready microbiome data resources.

bioinformatics↗

bioRxiv2026

Hyperglycemia Activates Retinal Photoreceptors to Induce Neuroglial Inflammation

Abstract Diabetic retinopathy (DR) is a major cause of vision loss in working-age adults. Accumulating evidence suggests that retinal photoreceptors contribute to the initiation and progression of diabetic retinopathy. In this study, we investigated whether hyperglycemia directly alters photoreceptor signaling and whether photoreceptor-derived inflammatory mediators activate downstream Muller glial cells. Primary photoreceptors were isolated from adult mice and cultured with normal glucose, high D-glucose, or high L-glucose as an osmotic control. Photoreceptorconditioned media were analyzed for inflammatory and growth factors and used to stimulate primary Muller glia. High glucose exposure increased photoreceptor production of TNF-a, IL-6, and VEGF. Photoreceptorconditioned media from high glucose-treated photoreceptors induced Muller glial expression of IL-1b, TNF-a, and IL-6. Muller glia exposed to photoreceptor-conditioned media increased VEGF expression and secretion and enhanced MMP-9 expression, secretion, and gelatinase activity. Together, these findings support a direct role for photoreceptors as glucose-responsive neuronal cells that can initiate and amplify neuroglial inflammatory signaling in hyperglycemic conditions.

neuroscience↗

bioRxiv2026

Microglia drive demyelination via multiple sclerosis antibodies and BTK signaling

Microglia are the predominant immune cells in multiple sclerosis (MS) demyelinating lesions, where they phagocytose myelin, but whether they destroy myelin or merely scavenge its debris is unknown. Here, we explore whether pathogenic autoantibodies found in MS may induce the phagocytic destruction of myelin by microglia. Applying patient-derived, myelin-targeting antibodies to the mouse cortex, we developed an in vivo model of MS with focal demyelination that depended on epitope specificity and Fc gamma receptor and complement binding. Longitudinal monitoring of microglia-myelin interactions using in vivo two-photon microscopy revealed rapid microglial envelopment of intact myelin driving myelin loss, while single-cell RNA sequencing identified a demyelination-associated microglial signature. Parallel changes were observed in human MS lesions, where microglia enveloped intact myelin and similar genes were upregulated. Inhibition of Brutons tyrosine kinase (BTK) limited microglial transcriptional changes and prevented myelin loss following microglial envelopment. These findings directly implicate microglia in pathological myelin loss and support BTK inhibition as a therapeutic strategy to prevent demyelination by modulating microglia behavior.

neuroscience↗

bioRxiv2026

Elucidating the functional domain architecture of ArCS1, a biomineralizing myosin chitin synthase: I. The role of lipids

In molluscs, chitin synthases are essential for biologically controlled biomineralization, with some variants possessing a myosin motor domain that may link polymer synthesis to the cytoskeleton. Experimentally, we established a reliable workflow for expressing ArCS1_E22TM in Dictyostelium discoideum and developed effective purification methods to reconstitute ArCS1_E22TM in nanodiscs using MSPs and specific lipid composition. MSP1D1deltaH5 proved optimal for nanodisc formation, yielding homogeneous, monodisperse discs (~8.2 nm). Lipids were refined to POPC:POPE:POPG (3:1:1) with 20% cholesterol, improving nanodisc quality and uniformity as observed by negative-stain EM. The full-length ArCS1 and its subdomains were modeled using AlphaFold3; the myosin motor, glycosyltransferase, and transmembrane regions are well-defined internally but loosely constrained relative to one another, suggesting flexible linking and conformational coupling. Modelling with Mg2+ and oleic acid as ligands and comparative analyses with bacterial cellulose synthase and yeast chitin synthase 1 provided insights into substrate binding and a potential mechanism for chitin polymerization and translocation. This research establishes a standard procedure for comprehensive structural analyses of recombinant molluscan chitin synthase in near-native or biomimetic membranes. This sets the stage for high-resolution cryo-electron microscopy to determine the first experimentally resolved structure of a molluscan chitin synthase and to provide insight into the enzyme's architecture and the regulatory mechanisms of biomineralization.

molecular biology↗

bioRxiv2026

Sympathetic activation and the force-frequency relationship in heart failure with reduced ejection fraction

Background Limited heart rate rise contributes to reduced exercise tolerance for people who have heart failure with reduced ejection fraction (HFrEF), yet rate-adaptive pacing does not improve functional capacity due to an attenuated force-frequency relationship (FFR). How the FFR relates to total peripheral resistance and sympathetic tone in HFrEF is unknown. Methods In a prospective, observational study, participants with HFrEF and controls underwent an incremental pacing protocol, during which heart rate was increased from 50 to 140 beats per minute. At each heart rate increment LV contractility was measured by echocardiography to determine the FFR, as well as continuous beat-to-beat measurement of systolic and diastolic blood pressures with a plethysmography device to determine cardiac output, total peripheral resistance and blood pressure variability (BPV). A microneurography study was then conducted to measure muscle sympathetic nerve activity (MSNA) during incremental pacing. Results A total of 157 participants with HFrEF and 55 controls (mean age 71.1{+/-}1.4 years, 172 (81.1%) male) underwent the pacing protocol. We observed single units in seven of 11 participants who participated in the microneurography study. In both groups, LV contractility and cardiac output increased until the peak of the FFR, after which these declined. We observed a reduction in total peripheral resistance, blood pressure variability, MSNA frequency and incidence coinciding with the peak of the FFR, beyond which these increased. Whilst these relationships were present in both groups, they were more evident in participants with HFrEF. Conclusions For people with HFrEF there is a bidirectional relationship between heart rate and sympathetic activation, with a nadir of sympathetic tone occurring at the peak of the FFR. Both excessively low and high heart rates are accompanied by greater sympathetic activation. Taken together, these data suggest that optimal heart rate targets for HFrEF are likely to be individual.

physiology↗

bioRxiv2026

EcoEnamel: Development of a Gelatin-Pectin Film for S. mutans Inhibition and Enamel Preservation in an In Vitro Model

Rinsing-dependent dental hygiene presents a significant public health challenge in water-scarce environments. This study investigated combinations of xylitol (Xyl), chitosan (Chi), glycyrrhizin (Gly), epigallocatechin gallate (EGCG), dicalcium phosphate (DCP), and nano-hydroxyapatite (nHA) on the primary bacteria behind dental caries, S. mutans. These combinations were assessed for markers of dental caries by biofilm reduction, bacterial killing, and acid buffering against S. mutans when applied to an in vitro simulated enamel model using glass bead surfaces for biofilm formation, and gene expression was subsequently examined via RT-qPCR. Separately, mineral retention was also quantified. The EGCG-DCP-Xyl film demonstrated the highest overall efficacy, achieving a significant reduction in biofilm concentration compared to the untreated control and performing similarly in magnitude to the positive toothpaste control. Dead fluorescence staining confirmed that the EGCG-DCP-Xyl film induced the highest rate of non-viable cells, followed by the Chi-Gly film and the Gly-Xyl film. During 10-day pH cycling, the EGCG-DCP-Xyl and DCP-Xyl formulations buffered pH the most, consistently maintaining mean pH levels safely above the demineralization threshold of pH 5.5. The EGCG-DCP-Xyl also optimized mineral stability with the highest retained calcium concentration, significantly outperforming the Chi-Xyl film. At the transcript level, the EGCG-DCP-Xyl film induced substantial downregulation of key virulence genes, yielding decreases in expression for glucosyltransferase B (gtfB), associated with biofilm synthesis, collagen-binding protein (cnm), associated with tissue invasion, and lactate dehydrogenase (ldh), associated with lactic acid production, compared to the untreated control, with effects comparable in magnitude to the positive toothpaste control. This research suggests that targeting bacterial pathways and mineral loss through a portable film may have potential for preventing dental caries, especially in environments where water is limited. However, additional studies are necessary to evaluate real-world effectiveness.

microbiology↗