Journal of Anatomy

The peripheral auditory system of dolphins comprises specialised bony, fatty, vascular, and neural structures adapted for underwater hearing and diving physiology. These include the external ear canal, acoustic fat bodies, sinuses, and associated neurovascular networks, which together support sound conduction, protection, and possibly sensory functions. Despite advances in gross anatomical description, the detailed integration of these tissues, particularly the innervation, neurovascular organisation, and their functional implications, remains poorly understood. Previous studies have described the presence of sensory nerve formations and vascular plexuses, but their arrangement, connectivity, and relation to each other are unresolved. Here, we combine macroscopic dissection, DICE-{micro}CT, histology, and high-resolution confocal microscopy to characterise several neurovascular and sensory components of the dolphin peripheral auditory system in several delphinid species. Macroscopic dissection and DICE-{micro}CT revealed the traditional acoustic fat body distribution with detailed morphology of the posterolateral extension that is not well-known. The cranial nerve distribution, and specifically the mandibular nerve branching patterns, are described in detail. Confocal microscopy uncovered a stratified neurovascular plexus around the external ear canal with a complex sensory system comprising lamellar corpuscles, Merkel cell-neurite complexes, and intraepithelial nerve fibres. Notably, the lamellar corpuscles formed a continuous, three-dimensional neural network with frequent merging and splitting of axonal bundles, shared perineuria, and vascular integration, features not observed in previous studies. Our findings demonstrate that the dolphin external ear canal and surrounding structures form a sophisticated, multimodal somatosensory organ, integrating structural, vascular, and neural specialisations likely adapted for proprioceptive mechanosensation in the aquatic environment. This study provides insights into the integration of the various components of the peripheral hearing apparatus. Future studies integrating anatomical, electrophysiological, and biomechanical approaches are needed to fully elucidate these adaptations.

The diversity of body shapes is one of the most prominent features of phenotypic variation in mammals. Yet, mammalian body shapes are poorly quantified and the underlying components contributing to its diversity as well as its relationship to other components of the skeleton are rarely tested. Here, we use lagomorphs (hares, rabbits and pikas) as a model system to (1) investigate which components of the skeleton contributed the most to body shape diversity, (2) examine the relationships between body shape and relative limb lengths, and (3) test how body size, ecotype, burrowing behavior, and locomotor mode influenced variation in lagomorph body shape and appendicular morphology. We quantified the body shape and functional proxies of the appendicular skeleton in 40 lagomorph species from osteological specimens held at museum collections. Using phylogenetic comparative methods, we found the relative length of the ribs and elongation or shortening of the thoracic and lumbar regions contributed the most to body shape evolution across lagomorphs. Second, we found that only leporids (hares and rabbits) exhibited a significant relationship between limb length and body shape, where more elongate species exhibit relatively shorter forelimbs and hindlimbs. Lastly, we found that models incorporating body size were the best predictors of lagomorph body shape and the majority of the appendicular traits, whereas models incorporating burrowing behavior and locomotor mode were largely poor fits. Broadly, these results indicate that larger lagomorphs tend to exhibit more robust body shapes with longer, more gracile forelimbs, whereas smaller lagomorphs tend to exhibit more elongate body shapes with shorter, more robust forelimbs. Overall, this work contributes to the growing understanding of mammalian body shape evolution and demonstrates the importance of not omitting body size in ecomorphological analyses.

BACKGROUNDIn tetralogy of Fallot (ToF), changes to right ventricular (RV) function (as seen by strain or TAPSE) relate to altered myocardial structure. Direct three-dimensional anatomical evidence supporting these changes remains limited. OBJECTIVESTo non-destructively characterize myocardial architecture in pediatric ToF hearts using Hierarchical Phase-Contrast Tomography (HiP-CT) and structure tensor analysis. METHODSTwenty ToF and control pediatric hearts were imaged at the European Synchrotron, ESRF. Myocyte orientation was assessed through structure tensor analysis and distributed high-performance computing. A region-specific framework was developed for analysis of the RV. The predominant direction of myocardial aggregates (their helical angle) was compared across ventricular regions. RESULTSSignificant differences in orientation were found in all ToF segments vs controls (left ventricle, RV inlet, RV outflow tract, septum; p < 0.001). Myocytes in the ToF RV inlet were more circumferential overall, with regional heterogeneity. Contrary to traditional models, no discrete middle layer was found in the ToF RV, instead, a shift towards more circumferentially orientated myocytes and disrupted septal and outflow components was observed. RV contribution to the septum was greater in ToF (47.3% vs 34.0% ; p = 0.0026) with extension of ventricular insertion points disrupting septal architecture. There were more longitudinally oriented myocytes in the ToF RVOT, consistent with hypertrophied septo-parietal trabeculations. LV structure in ToF demonstrated a greater proportion of circumferentially oriented myocytes vs controls. CONCLUSIONSWe reveal profound alterations in ToF myocardial organization which broadly align with clinical observations and provide the first open-access HiP-CT congenital heart disease data as a basis for future computational modelling.

IntroductionHealthy and diseased placentae alike often display some degree of pathology. However, quantitative techniques to characterize common pathologies and their relationship to local maternal hemodynamics in healthy primate placentae are currently limited. MethodsPlacentae from seven rhesus macaques were imaged by MRI at three time points across mid-to late-gestation, to quantify placental blood volume, flow, and perfusion from maternal spiral arteries across pregnancy. Near term, we collected placental cotyledons, digitized hematoxylin/eosin-stained slides, then segmented and annotated sub-tissues and major pathologies (intervillous gaps, fibrin deposition, villous agglutination, inflammatory agglutination, and stromal mineralization) within each cotyledon. Individual pathologies were assessed in relation to each other and MRI perfusion metrics, in a cotyledon-specific manner. Parallel analyses were performed to investigate both basic (Spearman correlation) and animal variance-negated (dimensionality-reduction) relationships. ResultsCotyledons with increased stromal mineralization demonstrated low blood perfusion across pregnancy, alongside significant compensatory changes. Mineralization was further associated with decreased fetal weight, across all sub-tissues. Dimensionality reduction revealed maternal vascular malperfusion-associated pathologies as the largest contributor to dataset variance. Additionally, pathologies commonly associated with healthy placental function demonstrated low cotyledon blood flow and volume at all timepoints, with no evidence of compensatory changes across gestation. ConclusionsComprehensive digital annotation revealed several relationships connecting pathology and maternal blood perfusion in the healthy primate pregnancy, at the smallest functional unit of the placenta. This methodological framework embeds pathologist-refined morphological expertise into a quantitative, spatially resolved format that can ground, rather than be replaced by, unsupervised computational approaches to placental analysis.

Aortic dissection is life-threatening due to continued loss of medial integrity that may culminate in secondary rupture within hours to days. While pre-existing defects or hemodynamic loads compound structural deterioration of the aorta, pathological progression from symptomatic dissection channel to lethal transmural tear is poorly understood. We examined the structure of referent and acutely dissected ascending aortas by microscopy. Elastic, collagen, and cellular components of non-dissected media were intricately interconnected. Medial damage in dissection lesions was traced from ingress to central to peripheral areas. Entry tears broke cleanly through successive laminae leading to cavernous false lumens in which medial structure was destroyed. Nearby laminae with widening between flanking elastic lamellae (termed minor delaminations) were filled with blood and showed severe medial damage. Farther laminae without delamination but containing red blood cells (termed blood extravasation) displayed moderate medial damage. More distant, non-delaminated laminae with accumulation of albumin but not red blood cells (termed plasma extravasation) exhibited mild medial damage. Varying medial hemorrhage with scattered sloughing of laminae was observed along the entire false lumen. We conclude that hydraulic fracturing of residual dissected media by pressurized blood via communications from the false lumen contributes to further structural weakening of the aortic wall.

Idiopathic scoliosis is a common spinal disorder characterized by progressive three-dimensional curvature of unknown cause. Although biomechanical imbalance has long been proposed to contribute to scoliosis, the early physiological states that precede curvature onset remain poorly understood. Here, we investigated this problem using zebrafish uts2r3 mutants, which develop fully penetrant juvenile-onset spinal curvature following disruption of urotensin signaling. Transcriptomic analysis before curvature revealed altered expression of muscle-associated genes, suggesting that Uts2r3 influences axial muscle development or function. However, immunofluorescence, birefringence imaging, and quantitative analysis of myotome morphology showed that mutants lack overt muscle architectural defects or dystrophic pathology. By contrast, direct measurements of isolated larval trunks revealed pre-curvature biomechanical abnormalities: namely, uts2r3 mutants generated reduced active force following electrical stimulation while also exhibiting increased passive resistance to stretch. These findings identify urotensin signaling as a regulator of axial tissue biomechanics during growth and suggest that scoliosis-like curvature can arise from an early imbalance between active force generation and passive tissue stiffness. SignificanceSpinal curvature is common, but the biological events that cause the spine to bend during growth remain poorly understood. Animal models, especially zebrafish, make it possible to study these events before curvature begins. Zebrafish lacking urotensin signaling develop spinal curves that arise during juvenile growth, similar to idiopathic scoliosis in humans. Here, we demonstrate that zebrafish lacking the urotensin pathway receptor Uts2r3 develop an abnormal biomechanical state prior to curve onset. Their axial tissues generate less active force when contracting and, at the same time, show increased passive resistance to stretch--an unexpected combination that reveals a distinct pre-curvature biomechanical state. These findings suggest that spinal curvature can arise from an early imbalance in tissue mechanics during growth and identify urotensin signaling as a pathway that helps preserve spinal morphology through a biomechanical mechanism.

Silk glands have been found in two groups of amphipods: the Corophiida and the Ampeliscidae. The silk glands in Ampeliscidae, however, have yet to be examined in detail. Here we report, for the first time, the morphology and distribution of pereopodal glands in the Ampeliscidae, in non-thread producing Synopiidae, and in the Paragammaropsidae. In the Ampeliscidae we found two gland types distributed throughout all pereopods which have the ability to create threads. Pereopods three and four have additional silk extrusion morphology at the tip of the dactylus in which silk is transformed into semi-cylindrical threads used for building domiciles. Synopiid outgroup species have one of the gland types but lack silk extrusion morphology. Using ancestral state reconstruction analysis, we find that glands in the Synopiidae are likely ancestral and hypothesize that silk glands in Ampeliscidae are derived from these ancestral glands. Silk-spinning pereopods in the Paragammaropsidae had similarities with both Corophiida and Ampeliscidae but had distinctions. Ampeliscidae silk-spinning systems bear surprising resemblance to the Corophiida which presents one to reconsider the taxonomic placement of Ampeliscidae and the origins of silk-spinning in amphipods. This is the first comprehensive study on the glandular systems of Ampeliscidae, Synopiidae, and Paragammaropsidae using advanced microscopy, providing pertinent morphological data to the study of arthropod silk gland evolution and complex traits.

BackgroundThe pivot shift (PS) test is the most specific clinical examination for anterolateral rotational instability in ACL-deficient knees, yet grading remains subjective, as evidenced by poor inter-observer reliability, particularly for Grade 2. Since low-grade (Grade 1) versus high-grade (Grades 2/3) PS is the threshold for recommending lateral extra-articular augmentation, performing the test in awake clinic patients limits grading reproducibility and introduces variability in surgical decision-making. Existing methods to quantify the pivot shift usually require examiner-performed testing under general anaesthesia. No prior approach has ascertained PS grading from a separate patient-performed functional movement. PurposeTo evaluate the feasibility of a machine learning (ML) classifier, trained on kinematic ultrasound bone-tracking signals acquired during a patients sit-stand-sit (SSS) knee movement, to predict their PS grade, and to clinically validate its ability to differentiate low versus high-grade PS. MethodsUltrasound bone-tracking kinematic data were collected during SSS manoeuvres in 23 ACL-injured patients using the GATOR device, and ground truth PS grades (0-3) were assigned under general anaesthesia by fellowship-trained orthopaedic sports surgeons. From the data collected, Leave-one-out cross-validation (LOOCV) was used to train the ML classifier. Clinical SSS data from 6 ACL-deficient patients was used for independent held-out validation of their low-grade (Grade 1) versus high-grade (Grade 2/3) PS. Multiple deep learning architectures (XceptionTime, InceptionTime, FCN, ResNet, ResCNN) and training strategies (including mixup augmentation and supervised contrastive learning) were tested. Performance was measured by one-versus-rest (OVR) AUC under LOOCV and by AUC (low vs high grade PS) from the held-out patient sessions. ResultsThe ML classifier achieved a maximum OVR AUC of 0.928 {+/-} 0.084 under LOOCV. Classifier performance increased with pivot-shift severity: Grade 3 was identified most reliably (AUC ~0.81; sensitivity 0.70-0.80), whereas Grade 2 remained the most challenging boundary (sensitivity 0.20-0.75 across configurations). For the clinically relevant binary classification of low-versus high-grade pivot shift, the classifier generalised well to a completely unseen patient cohort (AUC 0.889; accuracy 0.860; sensitivity 0.850; minimum-class sensitivity 0.767). ConclusionThe study demonstrates that kinematic ultrasound bone-tracking during sit-stand-sit contains transferable information about rotational instability severity in ACL-deficient patients, and represents the first reported approach to predict pivot shift grade from a patient-performed functional movement. The strong cross-validation performance confirms that the signals contain meaningful PS grade-discriminative information, but larger datasets targeting 50-100 sessions per grade will be required to achieve patient-level generalisation and advance this novel rotational instability assessment tool toward full clinical adoption. Level of EvidenceLevel IV, diagnostic feasibility study.

Resting state networks RSNs measured through functional connectivity FC emerge in utero and are detectable within hours of birth. Although neonatal growth metrics predict later neurodevelopmental outcomes and structural brain maturation their relationship to early functional network organization remains poorly understood. We examined associations between anthropometric growth metrics and resting state FC in a cohort of healthy near term and term born neonates using functional near infrared spectroscopy fNIRS acquired during the first few days of life. Task free fNIRS data were recorded in 121 neonates 67 males 55 percent mean postnatal age equals 25.6 hours mean gestational age equals 38.63 weeks. Based on birthweight percentiles 12 9 percent newborns were small for gestational age SGA and 13 11 percent were large for gestational age LGA. Growth metrics included birth weight for gestational age z score BGZ head circumference for gestational age z score HGZ birth weight for length z score BLZ and z scored Ponderal Index PIz. Whole brain FC was calculated as the mean Fisher Z transformed correlation across valid channel pairs. Channel wise associations were examined using general linear and linear mixed effects models controlling for gestational age postnatal age and sex. Linear and quadratic terms were tested and multiple comparisons were controlled using the false discovery rate. None of the anthropometric measures were associated with global FC however significant nonlinear quadratic relationships emerged at the channel pair level. BGZ B range equals negative 0.102 to negative 0.074 FDR corrected p less than 0.005 and PIz B range equals negative 0.088 to negative 0.074 FDR corrected p less than 0.001 demonstrated negative quadratic associations with inter and intra hemispheric connectivity such that newborns with both lower SGA and higher LGA growth values showed reduced FC relative to those with average growth. In contrast HGZ demonstrated positive quadratic associations B range equals 0.051 to 0.074 FDR corrected p less than 0.001 with infants at the lower and higher ends of the head size distribution exhibiting increased FC relative to infants near the mean. BLZ showed no significant associations after correction. Results indicate that early somatic growth is reflected in the organization of neonatal functional brain networks and that deviations from average growth whether smaller or larger are associated with altered regional connectivity. Findings suggest that neonatal growth metrics may provide an accessible marker of early brain health reflected in regionally specific functional connectivity patterns.

Elite athletes exhibit sport-specific neural adaptations, yet it remains unclear whether such changes reflect general effects of training or the unique demands of individual sports. Skiing requires postural control and whole-body coordination under dynamically unstable environments, placing high demands on somatosensory processing and sensorimotor integration. The present study aimed to identify structural brain characteristics specific to elite skiers by comparing them with athletes from other sports disciplines and non-athletes. T1-weighted MRI data were analyzed using voxel-based morphometry in 13 skiers, 23 non-ski control athletes and 25 non-athletes. Whole-brain analysis comparing skiers with non-ski athletes revealed a significant cluster showing greater gray matter volume in skiers compared with non-ski athletes in the left postcentral gyrus, extending into the superior parietal lobule. The identified cluster primarily encompassed cytoarchitectonic Areas 2 and 5L. These regions are involved in higher-order somatosensory processing and multisensory integration. Importantly, region-of-interest analysis demonstrated that gray matter volume within this cluster was greater in skiers compared with non-ski athletes and non-athletes, with no difference between non-ski athletes and non-athletes. These findings highlight the relative prominence of structural adaptations within somatosensory-parietal networks, reflecting the unique integration of proprioceptive and other sensory information required for elite skiing. Overall, these findings provide evidence for sport-specific structural brain differences in elite athletes and highlight the importance of somatosensory and parietal regions in sensorimotor integration relevant to skiing. These findings may have implications for understanding neural markers of expertise and may inform future approaches to training and performance evaluation in skiing.

Importance: Foot drop impairs mobility for many children globally, causing life-long health issues. Existing treatments are costly, custom-made, and require frequent clinical visits. A new, low-cost, off-the-shelf splint (OrthoPed) could improve access and user experience. Objective: To determine the feasibility of recruiting children (4-17 years) with moderate foot drop and collecting biomechanical, clinical, and patient-reported outcomes to compare OrthoPed with existing treatments. Design: Single-centre cross-sectional feasibility and pilot study informing a future randomised clinical trial. Participants: Twelve children (target=20; mean age=10.6 {+/-} 3.5 years; 2 females) with moderate foot drop and prescribed orthotic support were recruited via physiotherapy. Intervention: The new OrthoPed splint was compared against existing treatments: ankle foot orthoses (AFOs) and Lycra socks. Main outcome measures: Primary outcome: recruitment and retention rates. Secondary outcomes: biomechanical and clinical gait measures, alongside useability and performance questionnaires. Results: Recruitment reached 22% of eligible participants (an "amber" rating for future trials). Despite four dropouts due to treatment burden, all outcome measures were successfully collected. Preliminarily, OrthoPed supported more natural gait mechanics than AFOs and offered better usability and comfort than AFOs and Lycra socks, potentially enhancing adherence. Conclusions: Recruiting children for orthotic trials is feasible, though coordinating gait testing with routine clinical appointments could improve future recruitment. Importantly, low-cost orthotic devices may provide better usability, accessibility and adherence than existing prescribed options.

Eya3 and Eya4 are two Eya genes expressed in adult myogenic stem cells, where they may act as SIX cofactors. We analyzed muscle regeneration in single and compound Eya3 and satellite cell-specific Eya4 mutant mice. A kinetic analysis of muscle regeneration after Notexin injury of the Tibialis Anterior revealed no major phenotype at 4, 14, and 30 days after injury in terms of PAX7+ cell number and myofiber cross-sectional area in Eya3 mutants, while all parameters were decreased in Eya4 mutants and further worsened in Eya3/Eya4 double mutants, in which we also observed a modification of the myofiber phenotype at 30 days after injury. Satellite cells were cultured ex vivo and Eya4 deletion was induced by Ad-Cre-mediated recombination. While single Eya3 mutant cells showed normal proliferation and differentiation, double mutant cells exhibited normal proliferation but failed to fuse. Analysis of their transcriptome revealed that the expression of Myomixer, Follistatin, and Noggin was severely downregulated specifically in double mutant cells, explaining their fusion deficiency. To gain a better understanding of the involvement of Eya genes during embryonic development and the genesis of PAX7+ myogenic stem cells, we analyzed Eya1 / ;Eya2 / , Eya3 / , Eya4 / , and Eya3 / ;Eya4 / E18.5 mutant fetuses at the limb and craniofacial levels. In Eya1 / ;Eya2 / fetuses, we confirmed the absence of distal limb muscles and observed reduced craniofacial muscles. In Eya3 / ;Eya4 / fetuses, craniofacial myogenesis appeared preserved and PAX7+ myogenic stem cells were present. BackgroundThe Eyes absent (Eya) genes encode transcriptional co-activators and phosphatases that function within the PAX-SIX-EYA-DACH (PSED) regulatory network. In skeletal muscle, EYA proteins cooperate with SIX homeoproteins to control myogenic gene expression during both embryonic development and adult regeneration. While Eya1 and Eya2 are predominantly expressed in embryonic myogenic progenitors and Eya3 and Eya4 are the dominant paralogs in adult satellite cells (SC), the specific and redundant contributions of individual family members to myogenesis remain poorly characterized. MethodsWe analyzed compound Eya mutant mice during adult Tibialis anterior muscle regeneration and during embryogenesis. We complemented this analysis by performing ex vivo myogenic stem cell cultures from compound Eya mutants and examining their fusion capacity. ResultsAnalysis of muscle regeneration following Notexin injury revealed that Eya2 and Eya3 single mutants display no major regenerative deficit. In contrast, satellite cell-specific deletion of Eya4 (Eya4sc/sc) caused a transient impairment of early regeneration, with reduced numbers of smaller regenerating MYH3+ (embryonic myosin heavy chain) myofibers and a transient decrease in SC number at 4 days post-injury (dpi). Compound Eya3-/-;Eya4sc/scdouble mutants showed a more severe and persistent phenotype, with decreased myofiber cross-sectional area, reduced myonuclear accretion, accumulation of PAX7+ cells associated with regenerated myofibers, and altered fiber-type composition at 14 and 30 dpi. Ex vivo analysis of double mutant SCs revealed a specific and complete blockade of myogenic fusion without defects in proliferation or MYOD expression. Transcriptomic analysis identified severe downregulation of Myomixer, Noggin, and Follistatin in differentiating Eya3-/-;Eya4-/- SCs. Open-access SIX1 and SIX4 ChIP-seq publicly available data confirmed direct binding at the Myomixer, Noggin, and Follistatin loci, supporting a direct SIX-EYA transcriptional mechanism. In parallel, embryonic analysis demonstrated that Eya1-/-;Eya2-/-E18.5 fetuses lack distal limb musculature and display severe craniofacial muscle hypoplasia, while in Eya3-/-;Eya4-/-fetuses limb and craniofacial musculature developed with no detectable defects. ConclusionsThese results reveal distinct temporal requirements for EYA proteins in skeletal muscle: EYA1 and EYA2 are essential SIX cofactors for embryonic myogenic fate acquisition in hypaxial and craniofacial progenitors, while EYA3 and EYA4 act redundantly in adult satellite cells to enable myogenic fusion by maintaining BMP antagonist expression and Myomixer activation downstream of the SIX-EYA transcriptional complex.

Background: Apnoea of prematurity is common and may cause desaturation and/or bradycardia. There is marked variability in infants cardiorespiratory responses to apnoea, despite standardised clinical thresholds. Factors influencing apnoea-related cardiorespiratory instability and whether instability can be predicted warrant investigation. Methods: 181,511 apnoeas >5 seconds were identified from continuous physiological recordings from 146 preterm infants <37 weeks postmenstrual age. Cardiorespiratory instability was defined as bradycardia (>30% heart rate reduction) and/or oxygen desaturation (<85%). Mixed-effects models assessed clinical, demographic and dynamic modulators of the relationship between apnoea duration and cardiorespiratory instability. Machine learning (XGBoost) was used to train models to predict apnoea-related cardiorespiratory instability. Results: Longer duration apnoeas were associated with increased instability, although variability was substantial and 3.6% of apnoeas <10 seconds were associated with cardiorespiratory instability, while 61.2% of apnoeas [&ge;]20 seconds were not. Multiple clinical/demographic (postmenstrual and gestational age, sex, weight z-score, and ventilation mode) and dynamic (baseline heart rate, oxygen saturation, and recent apnoea clustering) factors were associated with increased instability risk. Apnoea-related cardiorespiratory instability could be predicted with a balanced test accuracy of 75.8% when incorporating all features, while a model using only clinical/demographic features achieved 66.0%. Conclusions: Multiple factors influence cardiorespiratory responses to apnoea. Predictive modelling may enable personalised apnoea definitions, improving individualised care.

Abstract Purpose: MyotonPRO (MTP) and time-harmonic elastography (THE) are increasingly used to assess muscle mechanical properties, yet they operate on fundamentally different physical principles. MTP measures composite MTP stiffness (N/m) through surface oscillations, while THE quantifies intrinsic shear modulus (THE stiffness, kPa) via propagating shear waves. This study aimed at systematically compare MTP and THE measurements in the vastus lateralis muscle across different contraction intensities and examine how the skin layer and subcutaneous fat (SLSF) thickness influence their relationship. Methods: Twenty-six healthy adults (15 males, 11 females; age 25 [SD 4] years) underwent MTP and THE measurements of the vastus lateralis at rest and during isometric contractions at 15% and 30% maximal voluntary contraction (MVC). Effects of contraction intensities on tissue properties were assessed using univariate analyses of variance with repeated measures. Associations between the different outcomes of THE and MTP technologies were explored using Pearson's correlations and partial correlation coefficients separately for each contraction intensity with adjustment of the SLSF thickness of participants. Results: Both technologies detected contraction intensity-dependent stiffening across all outcomes (p < 0.001). THE stiffness increased from 5.3 [1.2] kPa at rest to 15.6 [6.1] kPa at 30% MVC; THE wave attenuation increased from 0.83 [0.19] to 1.42 [0.36] s/m while MTP stiffness increased from 337.3 [49.3] N/m at rest to 529.4 [160.7] N/m at 30% MVC. Correlations between modalities were weak and condition-dependent. THE wave attenuation did not significantly correlate with any MTP outcome across conditions. Conclusion: MTP and THE detect contraction-induced stiffening through fundamentally different physical mechanisms and should not be regarded as interchangeable. Their correlation is modest at rest and breaks down (or reverses) during active contraction, with subcutaneous fat as a key modifying factor. Clinical trial number: Not applicable.

IntroductionVagus nerve stimulation modulates laryngeal, cardiac, pulmonary, and gastrointestinal functions. Knowledge of where along the vagal trunk organ-specific branches emerge may support alternative surgical placements of stimulation devices to engage targeted functions while avoiding off-target effects. However, no quantified map of how vagal branches emerge and how they relate to surgically relevant anatomical landmarks exists in humans. MethodsFifty-eight vagus nerves (29 left, 29 right) from 29 embalmed donor bodies (15 females) were dissected from the jugular foramen through the thoracic cavity. Branches were traced to end organs and allocated to seven groups -- sympathetic, muscular, vascular, cardiac, pulmonary, esophageal, and multiple targets -- and several sub-groups. Distances between branch emergence and the jugular foramen (JF) were normalized to three anatomical landmarks: carotid bifurcation, laryngeal prominence, and superior border of clavicle. ResultsBranch emergence follows a proximal-to-distal order: sympathetic (5.28 cm from JF), muscular (9.59 cm), vascular (10.70 cm), cardiac (19.65 cm), pulmonary (25.36 cm), and esophageal (26.57 cm). Vagal branches emerge into two embryological domains separated near the clavicle: pharyngeal arch-targeting branches cluster proximally (9.34 cm) and primitive mediastinum-targeting branches cluster distally (23.74 cm), with sympathetic, muscular, and vascular sub-groups occupying distinct zones within the proximal domain. The largest branch-free intervals occur above the left clavicle (2.33 {+/-} 2.80 cm) and below the left carotid bifurcation (2.58 {+/-} 3.17 cm). Alternate placement regions separating targeted organs from off-targets: sympathetic vs. cervical visceral at 6/8 cm (L/R), cardiac vs. carotid sinus/bifurcation at 14/10 cm, and recurrent laryngeal vs. other cervical visceral at 18/13 cm from JF. Overall, no differences were found between male and female donors. ConclusionsThis study provides a quantified, landmark-registered map of cervical and thoracic vagal branch emergence, offering a standardized anatomical template that may inform strategies for more function-selective vagal neuromodulation.

Kawasaki disease (KD) is a systemic vasculitis in young children, and early diagnosis remains challenging when clinical features are incomplete or overlap with those of other febrile illnesses. Because electrocardiography (ECG) is noninvasive and widely available, we investigated whether ECG-derived features could help distinguish complete KD from pediatric patients with fevers. We conducted a single-center retrospective study of hospitalized febrile children aged 1-8 years who underwent digital 12-lead ECG recording during the initial evaluation. Five amplitude features and six timing features extracted from the ECG were used to develop a logistic regression model to distinguish between complete KD and other febrile illnesses. The model discriminated between the KD and non-KD groups in the validation dataset. The prediction score was not significantly correlated with the age and body temperature. S-wave amplitude, the RR interval, and P-and Q-wave amplitudes were suggested to contribute to discrimination. These findings suggest that ECG-derived features may provide adjunctive information for distinguishing complete KD from other febrile illnesses. Author SummaryKawasaki disease is an inflammatory illness in young children that can lead to coronary artery complications if treatment is delayed. Early diagnosis is often difficult because its initial symptoms overlap with those of many common febrile illnesses. We investigated whether a routine 12-lead electrocardiogram (ECG), which is noninvasive, rapid, and widely available, contains information that can help distinguish complete Kawasaki disease from other febrile conditions. We retrospectively analyzed digital ECGs from hospitalized febrile children and extracted waveform amplitude and timing features. Using these features, we built a logistic regression model and evaluated it in a temporally separate validation cohort. The model distinguished patients with Kawasaki disease from patients with fever. P-, Q-, and S-wave amplitudes and the RR interval were repeatedly selected as important contributors, suggesting that both waveform morphology and heart-rate-related information may be relevant. These findings indicate that ECG-derived features may provide useful adjunctive information during the clinical assessment of complete Kawasaki disease.

Plac1 is an X-linked gene essential for placental and embryonic development. A knockout (KO) mouse model was used to identify Plac1-regulated gene expression at E16.5 and E18.5 using gene expression microarray. Genes exhibiting at least 1.5-fold change in expression and FDR < .05 were considered significant. At E16.5, 717 genes were downregulated and 798 were upregulated in male KO placentas versus wild type (WT), whereas at E18.5, 1122 genes were downregulated and 1149 were upregulated. GO, KEGG, and IPA analyses revealed downregulated genes were enriched for Rho GTPase-mediated and actin-cytoskeleton based processes that transmit extracellular cues through canonical signaling pathways, including Integrin, GPCR, Wnt, Notch, VEGF, BMP and TGF-beta, documented to impact trophoblast development, vasculogenesis, vascular tone, branching morphogenesis, and immunomodulation. Furthermore, a preeclampsia-associated transcriptomic signature was induced that strengthened over time. By contrast, upregulated genes reflected immune activation and adaptations to oxidative stress resulting from impaired placental function. These findings indicate that Plac1 supports signaling required to maintain placental structure and regulatory function. Its absence disrupts essential regulatory processes and triggers cellular stress and immune activation, contributing to fetal growth restriction, increased risk for embryopathy and preeclampsia, consistent with the Developmental Origins of Health and Disease (DOHaD) framework.

The mesencephalic trigeminal nucleus (MTN) contains the proprioceptive sensory neurons that innervate mechanoreceptors in the jaw closing muscles. In the chick embryo, MTN neurons are the first neurons generated in the mesencephalon. They arise bilaterally adjacent to the roof plate and then extend their axons ventrally before projecting caudally towards the rhombencephalon. MTN axons remain in a mid - dorsoventral position and pioneer the lateral longitudinal fasciculus. Notably, MTN axons never cross the roof plate, raising the question of which mechanisms underlie this restriction. Here, we investigated the effects of tissue transplants on the guidance of MTN axons. We found that both the diencephalon and the notochord exert repulsive effects on MTN axons, which could partially explain their early trajectory. We have also analysed the potential roles of the guidance cues BMP2/4, GDF7, SLIT and NETRIN in MTN axon navigation, both in vivo and in vitro. We found no evidence for a role of BMP2/4 or GDF7 in directing MTN axons. However, SLIT-ROBO signaling was found to play a significant role. SLIT proteins are repulsive guidance cues expressed by roof and floor plate. Loss or reduced expression of ROBO2 led to aberrant axon meandering within the dorsal midbrain. Most axons eventually reoriented posteriorly, and only a small fraction crossed the roof plate. Unexpectedly, in the absence of ROBO2, MTN somata migrated into the roof plate, resulting in the loss of a defined roof plate region. Taken together, these results suggest that SLIT2-ROBO2 signaling not only prevents MTN axons from crossing the roof plate but also maintains MTN cell bodies adjacent to the roof plate. With regards to MTN neuron guidance, we conclude that additional roof plate - derived factors are likely to co-operate with SLIT proteins to prevent crossing of the roof plate. Another possibility could be that SLIT might signal through additional receptors.

BackgroundSkeletal muscle represents around 40% of total human body weight and exhibits remarkable plasticity. It can hypertrophy, atrophy, or regenerate in response to changes in activity, nutrient availability, or injury. The main component of striated muscle, the myofiber, is a post-mitotic, multinucleated cell that contains the muscles contractile unit, the sarcomere. The myonuclei within these fibers are specialized and differ in terms of gene expression and localization. Adult muscles also contain various other cell types, including adult muscle stem cells (MuSCs), macrophages, fibro-adipogenic progenitors (FAPs), and endothelial cells. MuSCs are central to muscle plasticity, and are capable of activation, proliferation, differentiation, and fusion to form new myofibers during regeneration, or to fuse with existing myofibers during hypertrophy. Muscle hypertrophy and myofibers enlargement involve increased protein synthesis and reduced protein degradation, as well as myonuclear accretion following satellite cell activation. Multiple signaling pathways, such as the mTOR pathway and the RhoA/SRF mechanotransduction pathway, are involved in these processes. MethodsWe performed single-nucleus RNA sequencing (snRNA-seq) on plantaris muscles of adult mice, comparing samples 7 days after hypertrophy induction (overload, 7OV) to non-hypertrophied controls (Ctl). RNAscope experiments on isolated myofibers identified the heterogeneity of myonuclei along the myofiber. ResultsSnRNA-seq analysis revealed a previously unknown population of myonuclei (UM). UM-Ctl, which is present only in the Ctl condition, and UM-7OV, only in the 7OV condition. These myonuclei are localised at the tips of myofibres. Furthermore, we determined that UM-7OV are not newly fused myonuclei from activated satellite cells. Trajectory analyses suggest that UM-Ctl transition into UM-7OV during hypertrophy, returning to a near-basal homeostatic state after 21 days of overload (21OV). Gene expression analysis showed that UM-Ctl and UM-7OV have distinct gene expression profiles compared to other myonuclei and respond differently to hypertrophy. ConclusionOur findings suggest the existence of a specific population of myonuclei with unique localization and gene expression profiles, which play distinct roles at baseline and during hypertrophy. These results highlight the differential properties of myonuclei in the myofiber and their potential specific functions in muscle homeostasis and adaptation.

Vestibular neurons are core elements of the pathways involved in vestibulo-motor functions, such as vestibulo-spinal and vestibulo-ocular reflexes. To meet behavioral needs, electrophysiological neuronal properties are adequately adapted to the sensory-motor computation sustaining these distinct vestibular reflexes. During frog metamorphosis, there is a complete reorganization of the posturo-locomotor system while the oculomotor system remains minimally changed, probably associated to so far unknown changes in vestibular neuronal properties. We used this unique model to investigate the central developmental mechanisms underlying such a reconfiguration of vestibular-associated behaviors. Central vestibular neurons exhibit two types of electrophysiological phenotypes: tonic neurons with a continuous discharge and phasic neurons with a transitory discharge mainly due to the activation of Kv1.1 channel. Electrophysiological recordings and Kv1.1 immunolabeling of vestibulospinal (VS) and vestibulo-ocular (VO) neurons at both larval and juvenile stages revealed that the majority of VS neurons exhibited a tonic discharge in larvae but a phasic discharge in juvenile, while VO neurons remained mainly tonic throughout development. Changes in phasic and tonic neurons proportions in VS population are partly explained by neurogenesis. But we provide evidences that an electrophysiological phenotype switch is a concomitant developmental mechanism participating in the maturation of these central vestibular neurons. All together our results showed that the maturation process in central vestibular neuronal groups is highly related to the metamorphosis-induced remodeling of vestibulo-motor functions they are involved in, with the ultimate purpose of ensuring an adequate adaptation of neuronal elements properties to the developmental changes of behavioral constrains.