Biology subjects

Bonnard, T.

Publications and source records attributed to Bonnard, T..

6 recordsLinked to original sources

bioRxiv2026

Swung and spun in weightlessness : Evidence of immediate canalar underdetection of rotations in parabolic flight

Despite extensive research on vestibular function in microgravity, particularly during orbital and parabolic flight exposure, several gaps remain regarding the spontaneous behavior of vestibular organs under non-terrestrial gravitoinertial conditions. In particular, semicircular canal function, typically assessed through vestibulo-ocular reflex (VOR) recordings, has yielded inconsistent findings, with reports describing either no effect or reduced performance in microgravity. Moreover, many of these studies are limited by methodological constraints that reduce the interpretability of their conclusions. To clarify these discrepancies, we evaluated horizontal and vertical VOR responses during parabolic flights to assess semicircular canal function under transient weightlessness. Participants were passively rotated at a constant frequency and amplitude during normogravity and microgravity phases, centered along the heads vertical or inter-aural axis. Eye movements were recorded binocularly using infrared eye-tracking in darkness to eliminate visual influences, while participants were tightly restrained to minimize proprioceptive variability. Results show a reduction in VOR gain during microgravity in both axes, despite consistent rotational stimulation across gravity conditions. In addition, VOR gain remained reduced after parabolas in the horizontal plane, whereas vertical VOR performance was preserved. These are the first results to demonstrate an immediate alteration of semicircular canal function in weightlessness. Possible sources of the reduction in VOR performance in 0g are discussed. We also propose that the observed post-flight effects reflect a down-weighting of semicircular canal inputs during multisensory integration.

neuroscience↗

bioRxiv2026

Dual-action nanoconjugate for overcoming r-tPA -resistant clots

Clot resistance to pharmacological thrombolysis remains a critical challenge in ischemic stroke (IS) management. Thrombus heterogeneity, particularly the presence of thrombolysis-resistant domains composed of dense fibrin and non-fibrin components, including neutrophil extracellular traps (NETs), significantly limits the efficacy of recombinant tissue-type plasminogen activator (r-tPA) and its variant, Tenecteplase (TNK). Consequently, novel therapeutic strategies are urgently required. Emerging evidence suggests that co-administration of deoxyribonuclease I (DNase I) with r-tPA can degrade DNA fibers and enhance clot lysis. In this study, we optimized a previously developed theranostic agent--iron oxide microparticles coated with polydopamine--by dual-grafting both r-tPA and DNase to target resistant thrombi. Using functional ultrasound imaging (fUS) during the acute phase of IS, we demonstrated accelerated reperfusion with this dual-functionalized platform in a r-tPA resistant IS model. Furthermore, MRI analysis confirmed a significant reduction in lesion volume at 24 hours, correlating with improved functional recovery five days post-ischemia.

pathology↗

bioRxiv2026

Turning green in microgravity: facial color changes as best physiological indicator of space sickness

ABSTRACTMotion sickness (MS) is commonly hypothesized to arise from sensory conflicts between incongruent sources of sensory information. Different types of sensory conflicts can induce MS, yet it remains unclear whether distinct contexts produce different physiological responses. Moreover, there is a lack of reliable objective predictors of MS, particularly for space motion sickness (SMS), which appears unrelated to motion sickness susceptibility on Earth. This study examined multiple physiological measures as potential objective markers of MS, including heart rate, blood pressure, salivary cortisol, skin conductance, skin surface temperature, and facial skin colorimetry. Subjective motion sickness severity and symptomatology were assessed using standardized questionnaires (SSQ, MSAQ, MSSQ). All measures were collected before and immediately after exposure to two sensory conflict paradigms: virtual reality (visuo-vestibular conflict) and parabolic flight (otolitho-canal conflict). Post-exposure, both paradigms were associated with increased cortisol, skin conductance, and skin greeness. Notably, increased skin greenness was associated with greater MS severity in parabolic flight and strongly correlated with subjective nausea ratings in both paradigms. Skin temperature and systolic blood were affected differently by VR and parabolic flight. No robust new physiological predictors of MS were identified. Overall, our findings suggest that facial skin color -particularly skin greenness- may serve as a simple, non-invasive, and reliable objective indicator of MS severity.

neuroscience↗

bioRxiv2025

Visual and vestibular reweighting after cyber- and space-sickness

Sensory conflicts are widely recognized as the primary drivers of motion sickness (MS), though the underlying integrative processes remain poorly understood. This study investigated sensory reweighting that follows exposure to different sensory conflict paradigms. First, visual and vestibular reflexes were assessed before and after a visuo-vestibular conflict induced by purely visual stimulation in virtual reality. Second, visual and vestibular integration were evaluated before and after an otolith-canal conflict induced by gravitational changes in parabolic flight. Semi-circular canal integration was measured via the vestibuloocular reflex (VOR) suppression task, while visual weighting was assessed through optokinetic nystagmus (OKN). Our findings revealed that different sensory conflict paradigms elicit distinct sensory reweighting processes. Visuo-vestibular conflict resulted in a decreased VOR response, whereas vestibulo-vestibular conflict mainly led to a reduction in OKN following parabolic flight. Sensory down-weighting occured in the modality that did not detected displacement, likely perceived as the less reliable input, regardless of its accuracy. Additionally, visual sensitivity emerged as a potential predictor of cybersickness, while vestibular sensitivity seemed to influence MS severity in parabolic flight. Our data suggest that the sensitivity of the most stimulated sensory modality during a given conflict may determine an individuals susceptibility to MS. KEY POINTSO_LISensory reweighting occur through brief and specific exposure to motion sickness. C_LIO_LIAdaptive reweighting is modulated by the nature of the motion sickness exposure, with distinct effects observed between space-sickness and Earth-like motion sickness cues. C_LIO_LIMotionless cues are consistently downweighted, regardless of their accuracy. C_LIO_LIMotion sickness intensity depends on individuals sensitivity to the stimulated sensory sources, which varies across provocative sensory environments. C_LI

neuroscience↗

bioRxiv2025

Monitoring Whole-Body Inflammation with Gallium-68 Labeled Polydopamine Iron Oxide Particles via Hybrid Immuno-PET-MRI

Monitoring immune reactions via inflammation imaging provides valuable disease prognosis but remains limited by currently available probes and imaging capabilities. In this study, a bimodal imaging probe was developed from microsized polydopamine matrix-based magnetic particles (M3P) functionalized with antibodies that target vascular cell adhesion molecule-1 (VCAM-1) and that are radiolabeled with the radioisotope Gallium-68. This probe combines sensitive inflammation detection via Positron Emission Tomography (immuno-PET) and high-resolution mapping via Magnetic Resonance Imaging (immuno-MRI). The probe represents a powerful disease diagnosis tool to assess the status of systemic inflammation in sepsis as whole-body immuno-PET enables rapid evaluation of the situation, and immuno-MRI provides a more detailed characterization of the identified affected tissues. The elimination profile of the M3P probe is restricted to the mononuclear phagocyte system and does not undergo renal clearance, which is suitable for application in kidney disorders. The efficacy of the hybrid immuno-PET-MRI diagnosis protocol was tested in a murine model of rhabdomyolysis. Kidney inflammation was detected by whole-body immuno-PET, and vascular inflammation patterns could be revealed by high-resolution immuno-MRI. This bimodal PET-MRI probe could significantly improve inflammation monitoring in pathologies characterized by systemic inflammation or lung and kidney dysfunction.

bioengineering↗

bioRxiv2023

Subchronic alteration of vestibular hair cells in mice: implications for multisensory gaze stabilization

The functional complementarity of the vestibulo-ocular reflex (VOR) and optokinetic reflex (OKR) allows for optimal combined gaze stabilization responses (CGR) in light. While sensory substitution has been reported following complete vestibular loss, the capacity of the central vestibular system to compensate for partial peripheral vestibular loss remains to be determined. Here, we first demonstrate the efficacy of a 6-week subchronic ototoxic protocol in inducing transient and partial vestibular loss which equally affects the canal- and otolith-dependent VORs. Immunostaining of hair cells in the vestibular sensory epithelia revealed that organ-specific alteration of type I, but not type II, hair cells correlates with functional impairments. The decrease in VOR performance is paralleled with an increase in the gain of the OKR occurring in a specific range of frequencies where VOR normally dominates gaze stabilization, compatible with a sensory substitution process. Comparison of unimodal OKR or VOR versus bimodal CGR revealed that visuo-vestibular interactions remain reduced despite a significant recovery in the VOR. Modeling and sweep-based analysis revealed that the differential capacity to optimally combine OKR and VOR correlates with the reproducibility of the VOR responses. Overall, these results shed light on the multisensory reweighting occurring in pathologies with fluctuating peripheral vestibular malfunction.

neuroscience↗