AI reveals a damage signalling hierarchy that coordinates different cell behaviours driving wound re-epithelialisation.

One of the key tissue movements driving closure of a wound is re-epithelialisation. Earlier wound healing studies have described the dynamic cell behaviours that contribute to wound re-epithelialisation, including cell division, cell shape changes and cell migration, as well as the signals that might regulate these cell behaviours. Here, we use a series of deep learning tools to quantify the contributions of each of these cell behaviours from movies of repairing wounds in the Drosophila pupal wing epithelium. We test how each is altered following knockdown of the conserved wound repair signals, Ca2+ and JNK, as well as ablation of macrophages which supply growth factor signals believed to orchestrate aspects of the repair process. Our genetic perturbation experiments provide quantifiable insights regarding how these wound signals impact cell behaviours. We find that Ca2+ signalling is a master regulator required for all contributing cell behaviours; JNK signalling primarily drives cell shape changes and divisions, whereas signals from macrophages regulate largely cell migration and proliferation. Our studies show AI to be a valuable tool for unravelling complex signalling hierarchies underlying tissue repair.

Racial, Ethnic, and Age-Related Disparities in Sedation and Restraint Use for Older Adults in the Emergency Department.

OBJECTIVES: Older adults may present to the emergency department (ED) with agitation, a symptom often resulting in chemical sedation and physical restraint use which carry significant risks and side effects for the geriatric population. To date, limited literature describes the patterns of differential restraint use in this population. DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS: This retrospective cross-sectional study used electronic health records data from ED visits by older adults (age ≥65 years) ranging 2015-2022 across nine hospital sites in a regional hospital network. Logistic regression models were estimated to determine the association between patient-level characteristics and the primary outcomes of chemical sedation and physical restraint. RESULTS: Among 872,587 ED visits during the study period, 11,875 (1.4%) and 32,658 (3.7%) encounters involved the use of chemical sedation and physical restraints respectively. The populations aged 75-84, 85-94, 95+ years had increasingly higher odds of chemical sedation [adjusted odds ratios (AORs) 1.35 (95% CI 1.29-1.42); 1.82 (1.73-1.91); 2.35 (2.15-2.57) respectively] as well as physical restraint compared to the 65-74 group [AOR 1.31 (1.27-1.34); 1.55 (1.50-1.60); 1.69 (1.59-1.79)]. Compared to the White Non-Hispanic group, the Black Non-Hispanic and Hispanic/Latinx groups had significantly higher odds of chemical sedation [AOR 1.26 (1.18-1.35); AOR 1.22 (1.15-1.29)] and physical restraint [AOR 1.12 (95% CI 1.07-1.16); 1.22 (1.18-1.26)]. CONCLUSION: Approximately one in 20 ED visits among older adults resulted in chemical sedation or physical restraint use. Minoritized group status was associated with increasing use of chemical sedation and physical restraint, particularly among the oldest old. These results may indicate the need for further research in agitation management for historically marginalized populations in older adults.

Preoperative visualization of the greater occipital nerve with magnetic resonance imaging in candidates for occipital nerve decompression for headaches.

Occipital nerve decompression is effective in reducing headache symptoms in select patients with migraine and occipital neuralgia. Eligibility for surgery relies on subjective symptoms and responses to nerve blocks and Onabotulinum toxin A (Botox) injections. No validated objective method exists for detecting occipital headache pathologies. The purpose of the study is to explore the potential of high-resolution Magnetic Resolution Imaging (MRI) in identifying greater occipital nerve (GON) pathologies in chronic headache patients. The MRI protocol included three sequences targeting fat-suppressed fluid-sensitive T2-weighted signals. Visualization of the GON involved generating 2-D image slices with sequential rotation to track the nerve course. Twelve patients underwent pre-surgical MRI assessment. MRI identified four main pathologies that were validated against intra-operative examination: GON entanglement by the occipital artery, increased nerve thickness and hyperintensity suggesting inflammation compared to the non-symptomatic contralateral side, early GON branching with rejoining at a distal point, and a connection between the GON and the lesser occipital nerve. MRI possesses the ability to visualize the GON and identify suspected trigger points associated with headache symptoms. This case series highlights MRI's potential to provide objective evidence of nerve pathology. Further research is warranted to establish MRI as a gold standard for diagnosing extracranial contributors in headaches.

Generation and characterization of temperature-sensitive alleles of the glucanosyltransferase Gas1 in Schizosaccharomyces pombe.

The Schizosaccharomyces pombe Gas family of ß-1,3-glucanosyltransferases modify the cell wall by elongating ß-1,3-glucan chains. While gas1Δ cells are inviable under standard laboratory growth conditions, they are viable in the presence of an osmotic stabilizer. Even under these conditions however, gas1Δ cells are slow-growing and display cell separation and morphology defects. Here, we isolated and characterized two gas1 temperature-sensitive alleles. Our data support that Gas1 is the primary S. pombe ß-1,3-glucanosyltransferase important for cell separation and cell viability and provide useful tools for further analysis of S. pombe cell wall formation.

Formative evaluation of an emergency department clinical decision support system for agitation symptoms: a study protocol.

INTRODUCTION: The burden of mental health-related visits to emergency departments (EDs) is growing, and agitation episodes are prevalent with such visits. Best practice guidance from experts recommends early assessment of at-risk populations and pre-emptive intervention using de-escalation techniques to prevent agitation. Time pressure, fluctuating work demands, and other systems-related factors pose challenges to efficient decision-making and adoption of best practice recommendations during an unfolding behavioural crisis. As such, we propose to design, develop and evaluate a computerised clinical decision support (CDS) system, Early Detection and Treatment to Reduce Events with Agitation Tool (ED-TREAT). We aim to identify patients at risk of agitation and guide ED clinicians through appropriate risk assessment and timely interventions to prevent agitation with a goal of minimising restraint use and improving patient experience and outcomes. METHODS AND ANALYSIS: This study describes the formative evaluation of the health record embedded CDS tool. Under aim 1, the study will collect qualitative data to design and develop ED-TREAT using a contextual design approach and an iterative user-centred design process. Participants will include potential CDS users, that is, ED physicians, nurses, technicians, as well as patients with lived experience of restraint use for behavioural crisis management during an ED visit. We will use purposive sampling to ensure the full spectrum of perspectives until we reach thematic saturation. Next, under aim 2, the study will conduct a pilot, randomised controlled trial of ED-TREAT at two adult ED sites in a regional health system in the Northeast USA to evaluate the feasibility, fidelity and bedside acceptability of ED-TREAT. We aim to recruit a total of at least 26 eligible subjects under the pilot trial. ETHICS AND DISSEMINATION: Ethical approval by the Yale University Human Investigation Committee was obtained in 2021 (HIC# 2000030893 and 2000030906). All participants will provide informed verbal consent prior to being enrolled in the study. Results will be disseminated through publications in open-access, peer-reviewed journals, via scientific presentations or through direct email notifications. TRIAL REGISTRATION NUMBER: NCT04959279; Pre-results.

Isogenic hiPSC models of Turner syndrome development reveal shared roles of inactive X and Y in the human cranial neural crest network.

Modeling the developmental etiology of viable human aneuploidy can be challenging in rodents due to syntenic boundaries, or primate-specific biology. In humans, monosomy-X (45,X) causes Turner syndrome (TS), altering craniofacial, skeletal, endocrine, and cardiovascular development, which in contrast remain unaffected in 39,X-mice. To learn how human monosomy-X may impact early embryonic development, we turned to human 45,X and isogenic euploid induced pluripotent stem cells (hiPSCs) from male and female mosaic donors. Because neural crest (NC) derived cell types are hypothesized to underpin craniofacial and cardiovascular changes in TS, we performed a highly-powered differential expression study on hiPSC-derived anterior neural crest cells (NCCs). Across three independent isogenic panels, 45,X NCCs show impaired acquisition of PAX7+SOX10+ markers, and disrupted expression of other NCC-specific genes, relative to their isogenic euploid controls. In particular, 45,X NCCs increase cholesterol biosynthesis genes while reducing transcripts that feature 5' terminal oligopyrimidine (TOP) motifs, including those of ribosomal protein and nuclear-encoded mitochondrial genes. Such metabolic pathways are also over-represented in weighted co-expression gene modules that are preserved in monogenic neurocristopathy. Importantly, these gene modules are also significantly enriched in 28% of all TS-associated terms of the human phenotype ontology. Our analysis identifies specific sex-linked genes that are expressed from two copies in euploid males and females alike and qualify as candidate haploinsufficient drivers of TS phenotypes in NC-derived lineages. This study demonstrates that isogenic hiPSC-derived NCC panels representing monosomy-X can serve as a powerful model of early NC development in TS and inform new hypotheses towards its etiology.

Model-based parcellation of diffusion MRI of injured spinal cord predicts hand use impairment and recovery in squirrel monkeys.

A mathematical model-based parcellation of magnetic resonance diffusion tensor images (DTI) has been developed to quantify progressive changes in three types of tissues - grey (GM), white matter (WM), and damaged spinal cord tissue, along with behavioral assessments over a 6 month period following targeted spinal cord injuries (SCI) in monkeys. Sigmoid Gompertz function based fittings of DTI metrics provide early indicators that correlate with, and predict, recovery of hand grasping behavior. Our three tissue pool model provided unbiased, data-driven segmentation of spinal cord images and identified DTI metrics that can serve as reliable biomarkers of severity of spinal cord injuries and predictors of behavioral outcomes.

Bacterial community dynamics during distilled spirit fermentation: influence of mash recipes and fermentation processes.

IMPORTANCE: Production of ethanol from sugars and yeast is an ancient, ostensibly simple process. The source of sugars varies depending on the desired product and can include fruits, vegetables, molasses, honey, or grains, among other things. The source of yeast can be natural in the case of spontaneous ferments, but dry yeast addition is typical for large-scale fermentations. While the polymicrobial nature of some alcoholic fermentations is appreciated (e.g., for wine), most grain-based ethanol producers view microbes, apart from the added yeast, as "contaminants" meant to be controlled in order to maximize efficiency of ethanol production per unit of sugar. Nonetheless, despite rigorous cleaning-in-place measures and cooking the mash, bacteria are routinely cultured from these fermentations. We now know that bacteria can contribute to fermentation efficiency on an industrial scale, yet nothing is known about the makeup and stability of microbial communities in distilled spirit fermentations. The work here establishes the roles of mash recipes and distillery practices in microbial community assembly and dynamics over the course of fermentation. This represents an important first step in appreciating the myriad roles of bacteria in the production of distilled spirits.

An analysis of time-varying dynamics in electrically sensitive arthropod hairs to understand real-world electrical sensing.

With increasing evidence of electroreception in terrestrial arthropods, an understanding of receptor level processes is vital to appreciating the capabilities and limits of this sense. Here, we examine the spatio-temporal sensitivity of mechanoreceptive filiform hairs in detecting electrical fields. We first present empirical data, highlighting the time-varying characteristics of biological electrical signals. After which, we explore how electrically sensitive hairs may respond to such stimuli. The main findings are: (i) oscillatory signals (elicited by wingbeats) influence the spatial sensitivity of hairs, unveiling an inextricable spatio-temporal link; (ii) wingbeat direction modulates spatial sensitivity; (iii) electrical wingbeats can be approximated by sinusoidally modulated DC signals; and (iv) for a moving point charge, maximum sensitivity occurs at a faster timescale than a hair's frequency-based tuning. Our results show that electro-mechanical sensory hairs may capture different spatio-temporal information, depending on an object's movement and wingbeat and in comparison with aero-acoustic stimuli. Crucially, we suggest that electrostatic and aero-acoustic signals may provide distinguishable channels of information for arthropods. Given the pervasiveness of electric fields in nature, our results suggest further study to understand electrostatics in the ecology of arthropods and to reveal unknown ecological relationships and novel interactions between species.

Longitudinal traumatic peripheral nerve injury recovery: quantitative description, classification and prediction.

Aim: Repair of peripheral nerves is recommended following transection. Systematic evaluation of longitudinal recovery in injury models is needed to improve patient management. Gompertz function provided straightforward interpretation and prediction of recovery outcomes. Materials & methods: Behavioural sciatic function index, measured 3 days post injury, and weekly for 12 weeks following full nerve transection and repair (n = 6) as well as crush injuries (n = 6). Results: Gompertz parametrization provided early classification between types of traumatic peripheral nerve injuries following surgical repair. Results distinguished injury nerves (A: p < 0.01; Ti: p < 0.05; Ic: p < 0.05 and outcome: p < 0.01). Early prognostication of outcomes (crush: 5.5 ± 0.3 and cut/repair: 8 ± 1 weeks) preceded current methods. Conclusion: Our findings identify injury type, state of recovery and early prognostication of outcome.

Passive electrolocation in terrestrial arthropods: Theoretical modelling of location detection.

The recent discovery that some terrestrial arthropods can detect, use, and learn from weak electrical fields adds a new dimension to our understanding of how organisms explore and interact with their environments. For bees and spiders, the filiform mechanosensory systems enable this novel sensory modality by carrying electric charge and deflecting in response to electrical fields. This mode of information acquisition opens avenues for previously unrealised sensory dynamics and capabilities. In this paper, we study one such potential: the possibility for an arthropod to locate electrically charged objects. We begin by illustrating how electrostatic interactions between hairs and surrounding electrical fields enable the process of location detection. After which we examine three scenarios: (1) the determination of the location and magnitude of multiple point charges through a single observation, (2) the learning of electrical and mechanical sensor properties and the characteristics of an electrical field through several observations, (3) the possibility that an observer can infer their location and orientation in a fixed and known electrical field (akin to "stellar navigation"). To conclude, we discuss the potential of electroreception to endow an animal with thus far unappreciated sensory capabilities, such as the mapping of electrical environments. Electroreception by terrestrial arthropods offers a renewed understanding of the sensory processes carried out by filiform hairs, adding to aero-acoustic sensing and opening up the possibility of new emergent collective dynamics and information acquisition by distributed hair sensors.

Can Diffusion Tensor Imaging Apparent Diffusion Coefficient Diagnose Carpal Tunnel Syndrome? A Systematic Review and Meta-Analysis.

Magnetic resonance diffusion tensor imaging (DTI) can detect microstructural changes in peripheral nerves. Studies have reported that the median nerve apparent diffusion coefficient (ADC), a quantification of water molecule diffusion direction, is sensitive in diagnosing carpal tunnel syndrome (CTS). Five databases were searched for studies using ADC to investigate CTS. Apparent diffusion coefficient (measured in mm2/s) were pooled in random-effects meta-analyses. Twenty-two studies met criteria yielding 592 patients with CTS and 414 controls. Median nerve ADC were measured at the level of the distal radioulnar joint (CTS ADC: 1.11, 95% CI: 1.07-1.15, I2 = 54%; control ADC: 1.04, 95% CI: 1.01-1.07, I2 = 57%), pisiform (CTS ADC: 1.39, 95% CI: 1.37-1.42, I2 = 0%; control ADC: 1.27, 95% CI: 1.23-1.31, I2 = 59%), hamate (CTS ADC: 1.40, 95% CI: 1.36-1.43, I2 = 58%; control ADC: 1.27, 95% CI: 1.25-1.28, I2 = 47%), and as an combination of several measurements (CTS ADC: 1.40, 95% CI: 1.37-1.47, I2 = 100%; control ADC: 1.39, 95% CI: 1.24-1.53, I2 = 100%). Median nerve ADC is decreased in individuals with CTS compared to controls at the levels of the hamate and pisiform. ADC cut-offs to diagnose CTS should be established according to these anatomic levels and can be improved through additional studies that include use of a wrist coil.

Machine-learning-based video analysis of grasping behavior during recovery from cervical spinal cord injury.

Comprehensive characterizations of hand grasping behaviors after cervical spinal cord injuries are fundamental for developing rehabilitation strategies to promote recovery in spinal-cord-injured primates. We used the machine-learning-based video analysis software, DeepLabCut, to sensitively quantify kinematic aspects of grasping behavioral deficits in squirrel monkeys with C5-level spinal cord injuries. Three squirrel monkeys were trained to grasp sugar pellets from wells of varying depths before and after a left unilateral lesion of the cervical dorsal column. Using DeepLabCut, we identified post-lesion deficits in kinematic grasping behavior that included changes in digit orientation, increased variance in vertical and horizontal digit movement, and longer time to complete the task. While video-based analyses of grasping behavior demonstrated deficits in fine-scale digit function that persisted through at least 14 weeks post-injury, traditional end-point behavioral analyses showed a recovery of global hand function as evidenced by recovery of the proportion of successful retrievals by approximately 14 weeks post-injury. The combination of traditional end-point and video-based kinematic analyses provides a more comprehensive characterization of grasping behavior and highlights that global grasping performance may recover despite persistent fine-scale kinematic deficits in digit function. Machine-learning-based video analysis of kinematic digit function, in conjunction with traditional end-point behavioral analyses of grasping behavior, provide sensitive and specific indices for monitoring recovery of fine-grained hand sensorimotor behavior after spinal cord injury that can aid future studies that seek to develop targeted therapeutic interventions for improving behavioral outcomes.

New antioxidant lauryl-free herbal shampoo formulation with a Brazilian plant extract.

Sodium lauryl sulfate is the main cleaning ingredient in shampoos, even though it may be potentially damaging to hair. The demand for antioxidant-rich cosmetics, on the other hand, has encouraged green cosmetics research. Brazil has vast biodiversity that can be exploited for the production of these cosmetics. This work aimed to develop a minimalist antioxidant lauryl-free shampoo formulation with leaf extracts from the Brazilian plant Hancornia speciosa Gomes. Two hydroethanolic extracts were prepared using different extraction methods, Soxhlet, and ultrasound. The extracts were characterized by the presence of saponins, polyphenol quantification, and HLPC chemical identification of the compounds. Antioxidant activity was determined using the DPPH method. The antioxidant lauryl-free shampoo was developed using hydroxyethyl cellulose with two concentrations of leaf extract obtained by Soxhlet, 0.125 mg/g (XP1) and 0.250 mg/g (XP2). Along with the antioxidant activity, the physical and chemical properties, cleaning potential, and foam quality were evaluated. The Soxhlet leaf extract revealed a more favorable chemical profile, including a positive result for saponins, as well as a larger quantity of polyphenols and increased antioxidant activity. The XP2 formulation showed better foam height, dirt dispersion, and antioxidant activity. Thus, the use of mangabeira leaf extract appears to be promising for the development of shampoos with antioxidant activity.

Multiregion neuronal activity: the forest and the trees.

The past decade has witnessed remarkable advances in the simultaneous measurement of neuronal activity across many brain regions, enabling fundamentally new explorations of the brain-spanning cellular dynamics that underlie sensation, cognition and action. These recently developed multiregion recording techniques have provided many experimental opportunities, but thoughtful consideration of methodological trade-offs is necessary, especially regarding field of view, temporal acquisition rate and ability to guarantee cellular resolution. When applied in concert with modern optogenetic and computational tools, multiregion recording has already made possible fundamental biological discoveries - in part via the unprecedented ability to perform unbiased neural activity screens for principles of brain function, spanning dozens of brain areas and from local to global scales.

Monosomy X in isogenic human iPSC-derived trophoblast model impacts expression modules preserved in human placenta.

Mammalian sex chromosomes encode homologous X/Y gene pairs that were retained on the Y chromosome in males and escape X chromosome inactivation (XCI) in females. Inferred to reflect X/Y pair dosage sensitivity, monosomy X is a leading cause of miscarriage in humans with near full penetrance. This phenotype is shared with many other mammals but not the mouse, which offers sophisticated genetic tools to generate sex chromosomal aneuploidy but also tolerates its developmental impact. To address this critical gap, we generated X-monosomic human induced pluripotent stem cells (hiPSCs) alongside otherwise isogenic euploid controls from male and female mosaic samples. Phased genomic variants in these hiPSC panels enable systematic investigation of X/Y dosage-sensitive features using in vitro models of human development. Here, we demonstrate the utility of these validated hiPSC lines to test how X/Y-linked gene dosage impacts a widely used model for human syncytiotrophoblast development. While these isogenic panels trigger a GATA2/3- and TFAP2A/C-driven trophoblast gene circuit irrespective of karyotype, differential expression implicates monosomy X in altered levels of placental genes and in secretion of placental growth factor (PlGF) and human chorionic gonadotropin (hCG). Remarkably, weighted gene coexpression network modules that significantly reflect these changes are also preserved in first-trimester chorionic villi and term placenta. Our results suggest monosomy X may skew trophoblast cell type composition and function, and that the combined haploinsufficiency of the pseudoautosomal region likely plays a key role in these changes.

What good is maths in studies of wound healing?

Wound healing is an aspect of normal physiology that we all take for granted until it goes wrong, such as, for example, the scarring that results from a severe burn, or those patients who suffer from debilitating chronic wounds that fail to heal. Ever since wound repair research began as a discipline, clinicians and basic scientists have collaborated to try and understand the cell and molecular mechanisms that underpin healthy repair in the hope that this will reveal clues for the therapeutic treatment of pathological healing. In recent decades mathematicians and physicists have begun to join in with this important challenge. Here we describe examples of how mathematical modeling married to biological experimentation has provided insights that biology alone could not fathom. To date, these studies have largely focused on wound re-epithelialization and inflammation, but we also discuss other components of wound healing that might be ripe for similar interdisciplinary approaches.

Low-Salt Diet Reduces Anti-CTLA4 Mediated Systemic Immune-Related Adverse Events while Retaining Therapeutic Efficacy against Breast Cancer.

Immune checkpoint inhibitor (ICI) therapy has revolutionized the breast cancer treatment landscape. However, ICI-induced systemic inflammatory immune-related adverse events (irAE) remain a major clinical challenge. Previous studies in our laboratory and others have demonstrated that a high-salt (HS) diet induces inflammatory activation of CD4+T cells leading to anti-tumor responses. In our current communication, we analyzed the impact of dietary salt modification on therapeutic and systemic outcomes in breast-tumor-bearing mice following anti-cytotoxic T-lymphocyte-associated protein 4 (CTLA4) monoclonal antibody (mAb) based ICI therapy. As HS diet and anti-CTLA4 mAb both exert pro-inflammatory activation of CD4+T cells, we hypothesized that a combination of these would lead to enhanced irAE response, while low-salt (LS) diet through blunting peripheral inflammatory action of CD4+T cells would reduce irAE response. We utilized an orthotopic murine breast tumor model by injecting Py230 murine breast cancer cells into syngeneic C57Bl/6 mice. In an LS diet cohort, anti-CTLA4 mAb treatment significantly reduced tumor progression (day 35, 339 ± 121 mm3), as compared to isotype mAb (639 ± 163 mm3, p < 0.05). In an HS diet cohort, treatment with anti-CTLA4 reduced the survival rate (day 80, 2/15) compared to respective normal/regular salt (NS) diet cohort (8/15, p < 0.05). Further, HS plus anti-CTLA4 mAb caused an increased expression of inflammatory cytokines (IFNγ and IL-1ß) in lung infiltrating and peripheral circulating CD4+T cells. This inflammatory activation of CD4+T cells in the HS plus anti-CTLA4 cohort was associated with the upregulation of inflammasome complex activity. However, an LS diet did not induce any significant irAE response in breast-tumor-bearing mice upon treatment with anti-CTLA4 mAb, thus suggesting the role of high-salt diet in irAE response. Importantly, CD4-specific knock out of osmosensitive transcription factor NFAT5 using CD4cre/creNFAT5flox/flox transgenic mice caused a downregulation of high-salt-mediated inflammatory activation of CD4+T cells and irAE response. Taken together, our data suggest that LS diet inhibits the anti-CTLA4 mAb-induced irAE response while retaining its anti-tumor efficacy.

The mechanics and interactions of electrically sensitive mechanoreceptive hair arrays of arthropods.

Recent investigations highlight the possibility of electroreception within arthropods through charged mechanosensory hairs. This discovery raises questions about the influence of electrostatic interaction between hairs and surrounding electrical fields within this sensory modality. Here, we investigate these questions by studying electrostatic coupling in arrays of hairs. We establish the notion of sensitivity contours that indicate regions within which point charges deflect hairs beyond a given threshold. We then examine how the contour's shape and size and the overall hair behaviour change in response to variations in the coupling between hairs. This investigation unveils synergistic behaviours whereby the sensitivity of hairs is enhanced or inhibited by neighbouring hairs. The hair spacing and ratio of a system's electrical parameters to its mechanical parameters influence this behaviour. Our results indicate that electrostatic interaction between hairs leads to emergent sensory properties for biologically relevant parameter values. The analysis raises new questions around the impact of electrostatic interaction on the current understanding of sensory hair processes, such as acoustic sensing, unveiling new sensory capabilities within electroreception such as amplification of hair sensitivity and location detection of charges in the environment.

Bone microstructure and bone mineral density are not systemically different in Antarctic icefishes and related Antarctic notothenioids.

Ancestors of the Antarctic icefishes (family Channichthyidae) were benthic and had no swim bladder, making it energetically expensive to rise from the ocean floor. To exploit the water column, benthopelagic icefishes were hypothesized to have evolved a skeleton with "reduced bone," which gross anatomical data supported. Here, we tested the hypothesis that changes to icefish bones also occurred below the level of gross anatomy. Histology and micro-CT imaging of representative craniofacial bones (i.e., ceratohyal, frontal, dentary, and articular) of extant Antarctic fish species specifically evaluated two features that might cause the appearance of "reduced bone": bone microstructure (e.g., bone volume fraction and structure linear density) and bone mineral density (BMD, or mass of mineral per volume of bone). Measures of bone microstructure were not consistently different in bones from the icefishes Chaenocephalus aceratus and Champsocephalus gunnari, compared to the related benthic notothenioids Notothenia coriiceps and Gobionotothen gibberifrons. Some quantitative measures, such as bone volume fraction and structure linear density, were significantly increased in some icefish bones compared to homologous bones of non-icefish. However, such differences were rare, and no microstructural measures were consistently different in icefishes across all bones and species analyzed. Furthermore, BMD was similar among homologous bones of icefish and non-icefish Antarctic notothenioids. In summary, "reduced bone" in icefishes was not due to systemic changes in bone microstructure or BMD, raising the prospect that "reduced bone" in icefish occurs only at the gross anatomic level (i.e., smaller or fewer bones). Given that icefishes exhibit delayed skeletal development compared to non-icefish Antarctic fishes, combining these phenotypic data with genomic data might clarify genetic changes driving skeletal heterochrony.