Identification of the Human Skeletal Stem Cell.

Stem cell regulation and hierarchical organization of human skeletal progenitors remain largely unexplored. Here, we report the isolation of a self-renewing and multipotent human skeletal stem cell (hSSC) that generates progenitors of bone, cartilage, and stroma, but not fat. Self-renewing and multipotent hSSCs are present in fetal and adult bones and can also be derived from BMP2-treated human adipose stroma (B-HAS) and induced pluripotent stem cells (iPSCs). Gene expression analysis of individual hSSCs reveals overall similarity between hSSCs obtained from different sources and partially explains skewed differentiation toward cartilage in fetal and iPSC-derived hSSCs. hSSCs undergo local expansion in response to acute skeletal injury. In addition, hSSC-derived stroma can maintain human hematopoietic stem cells (hHSCs) in serum-free culture conditions. Finally, we combine gene expression and epigenetic data of mouse skeletal stem cells (mSSCs) and hSSCs to identify evolutionarily conserved and divergent pathways driving SSC-mediated skeletogenesis. VIDEO ABSTRACT.

A high internal heat flux and large core in a warm Neptune exoplanet.

Interactions between exoplanetary atmospheres and internal properties have long been proposed to be drivers of the inflation mechanisms of gaseous planets and apparent atmospheric chemical disequilibrium conditions1. However, transmission spectra of exoplanets have been limited in their ability to observationally confirm these theories owing to the limited wavelength coverage of the Hubble Space Telescope (HST) and inferences of single molecules, mostly H2O (ref. 2). In this work, we present the panchromatic transmission spectrum of the approximately 750 K, low-density, Neptune-sized exoplanet WASP-107b using a combination of HST Wide Field Camera 3 (WFC3) and JWST Near-Infrared Camera (NIRCam) and Mid-Infrared Instrument (MIRI). From this spectrum, we detect spectroscopic features resulting from H2O (21σ), CH4 (5σ), CO (7σ), CO2 (29σ), SO2 (9σ) and NH3 (6σ). The presence of these molecules enables constraints on the atmospheric metal enrichment (M/H is 10-18× solar3), vertical mixing strength (log10Kzz = 8.4-9.0 cm2 s-1) and internal temperature (>345 K). The high internal temperature is suggestive of tidally driven inflation4 acting on a Neptune-like internal structure, which can naturally explain the large radius and low density of the planet. These findings suggest that eccentricity-driven tidal heating is a critical process governing atmospheric chemistry and interior-structure inferences for most of the cool (<1,000 K) super-Earth-to-Saturn-mass exoplanet population.

Inhomogeneous terminators on the exoplanet WASP-39 b.

Transmission spectroscopy has been a workhorse technique over the past two decades to constrain the physical and chemical properties of exoplanet atmospheres 1-5. One of its classical key assumptions is that the portion of the atmosphere it probes - the terminator region - is homogeneous. Several works in the past decade, however, have put this into question for highly irradiated, hot (Teq ≳ 1000 K) gas giant exoplanets both empirically 6-10 and via 3-dimensional modelling 11-17. While models predict clear differences between the evening (day-to-night) and morning (night-to-day) terminators, direct morning/evening transmission spectra in a wide wavelength range has not been reported for an exoplanet to date. Under the assumption of precise and accurate orbital parameters on WASP-39 b, here we report the detection of inhomogeneous terminators on the exoplanet WASP-39 b, which allows us to retrieve its morning and evening transmission spectra in the near-infrared (2 - 5 µm) using JWST. We observe larger transit depths in the evening which are, on average, 405±88 ppm larger than the morning ones, also having qualitatively larger features than the morning spectrum. The spectra are best explained by models in which the evening terminator is hotter than the morning terminator by 177 - 57 + 65 K with both terminators having C/O ratios consistent with solar. General circulation models (GCMs) predict temperature differences broadly consistent with the above value and point towards a cloudy morning terminator and a clearer evening terminator.

Aged skeletal stem cells generate an inflammatory degenerative niche.

Loss of skeletal integrity during ageing and disease is associated with an imbalance in the opposing actions of osteoblasts and osteoclasts1. Here we show that intrinsic ageing of skeletal stem cells (SSCs)2 in mice alters signalling in the bone marrow niche and skews the differentiation of bone and blood lineages, leading to fragile bones that regenerate poorly. Functionally, aged SSCs have a decreased bone- and cartilage-forming potential but produce more stromal lineages that express high levels of pro-inflammatory and pro-resorptive cytokines. Single-cell RNA-sequencing studies link the functional loss to a diminished transcriptomic diversity of SSCs in aged mice, which thereby contributes to the transformation of the bone marrow niche. Exposure to a youthful circulation through heterochronic parabiosis or systemic reconstitution with young haematopoietic stem cells did not reverse the diminished osteochondrogenic activity of aged SSCs, or improve bone mass or skeletal healing parameters in aged mice. Conversely, the aged SSC lineage promoted osteoclastic activity and myeloid skewing by haematopoietic stem and progenitor cells, suggesting that the ageing of SSCs is a driver of haematopoietic ageing. Deficient bone regeneration in aged mice could only be returned to youthful levels by applying a combinatorial treatment of BMP2 and a CSF1 antagonist locally to fractures, which reactivated aged SSCs and simultaneously ablated the inflammatory, pro-osteoclastic milieu. Our findings provide mechanistic insights into the complex, multifactorial mechanisms that underlie skeletal ageing and offer prospects for rejuvenating the aged skeletal system.

Myeloid Cell Derived IL1ß Contributes to Pulmonary Hypertension in HFpEF.

BACKGROUND: Pulmonary hypertension (PH) in heart failure with preserved ejection fraction (HFpEF) is a common and highly morbid syndrome, but mechanisms driving PH-HFpEF are poorly understood. We sought to determine whether a well-accepted murine model of HFpEF also displays features of PH, and we sought to identify pathways that might drive early remodeling of the pulmonary vasculature in HFpEF. METHODS: Eight-week-old male and female C57BL/6J mice received either Nγ-nitro-L-arginine methyl ester and high-fat diet or control water and diet for 2, 5, and 12 weeks. The db/db mice were studied as a second model of HFpEF. Early pathways regulating PH were identified by bulk and single-cell RNA sequencing. Findings were confirmed by immunostain in lungs of mice or lung slides from clinically performed autopsies of patients with PH-HFpEF. ELISA was used to verify IL-1ß (interleukin-1 beta) in mouse lung, mouse plasma, and also human plasma from patients with PH-HFpEF obtained at the time of right heart catheterization. Clodronate liposomes and an anti-IL-1ß antibody were utilized to deplete macrophages and IL-1ß, respectively, to assess their impact on pulmonary vascular remodeling in HFpEF in mouse models. RESULTS: Nγ-nitro-L-arginine methyl ester/high-fat diet-treated mice developed PH, small vessel muscularization, and right heart dysfunction. Inflammation-related gene ontologies were overrepresented in bulk RNA sequencing analysis of whole lungs, with an increase in CD68+ cells in both murine and human PH-HFpEF lungs. Cytokine profiling showed an increase in IL-1ß in mouse and human plasma. Finally, clodronate liposome treatment in mice prevented PH in Nγ-nitro-L-arginine methyl ester/high-fat diet-treated mice, and IL-1ß depletion also attenuated PH in Nγ-nitro-L-arginine methyl ester/high-fat diet-treated mice. CONCLUSIONS: We report a novel model for the study of PH and right heart remodeling in HFpEF, and we identify myeloid cell-derived IL-1ß as an important contributor to PH in HFpEF.

Characterizing Interest in and Uptake of Preexposure Prophylaxis for HIV Prevention Among Men in a US State Correctional System.

BACKGROUND: People experiencing incarceration are disproportionately impacted by HIV and are potential candidates for HIV preexposure prophylaxis (PrEP). We explored factors associated with PrEP interest and PrEP uptake and described barriers to PrEP uptake among incarcerated men in a state correctional system. METHODS: From September 2019 to July 2022, incarcerated men at the Rhode Island Department of Corrections were screened for PrEP eligibility and referred to a PrEP initiation study. We used bivariate analyses and multivariable logistic regression models to explore factors associated with PrEP interest and uptake in the screening sample. RESULTS: Of the men screened and determined to be eligible for PrEP, approximately half (50%) were interested in taking PrEP. Individuals identifying as men who have sex with men (adjusted odds ratio, 4.46; 95% confidence interval, 1.86-11.4) and having multiple female sex partners (adjusted odds ratio, 2.98; 95% confidence interval, 1.47-6.27) were more likely to express interest in PrEP (interested/not interested) than those not reporting these behavioral factors. Preexposure prophylaxis uptake (yes/no) was 38%. Lack of PrEP interest, low self-perceived risk of HIV acquisition, and unpredictable lengths of incarceration were the most frequently encountered barriers to PrEP uptake. CONCLUSIONS: Men reporting sexual transmission behaviors were more interested in PrEP and had higher uptake than other men. Preexposure prophylaxis interest and HIV risk factors were both moderately high, which suggests that men experiencing incarceration should be screened for and offered PrEP as part of standard clinical care. Study findings have important implications for research and practice to adapt PrEP care to correctional systems.

Magnetic Resonance Elastography in the Study of Neurodegenerative Diseases.

Neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD) present a major health burden to society. Changes in brain structure and cognition are generally only observed at the late stage of the disease. Although advanced magnetic resonance imaging (MRI) techniques such as diffusion imaging may allow identification of biomarkers at earlier stages of neurodegeneration, early diagnosis is still challenging. Magnetic resonance elastography (MRE) is a noninvasive MRI technique for studying the mechanical properties of tissues by measuring the wave propagation induced in the tissues using a purpose-built actuator. Here, we present a systematic review of preclinical and clinical studies in which MRE has been applied to study neurodegenerative diseases. Actuator systems for data acquisition, inversion algorithms for data analysis, and sample demographics are described and tissue stiffness measures obtained for the whole brain and internal structures are summarized. A total of six animal studies and eight human studies have been published. The animal studies refer to 123 experimental animals (68 AD and 55 PD) and 121 wild-type animals, while the human studies refer to 142 patients with neurodegenerative disease (including 56 AD and 17 PD) and 166 controls. The animal studies are consistent in the reporting of decreased stiffness of the hippocampal region in AD mice. However, in terms of disease progression, although consistent decreases in either storage modulus or shear modulus magnitude are reported for whole brain, there is variation in the results reported for the hippocampal region. The clinical studies are consistent in reports of a significant decrease in either whole brain storage modulus or shear modulus magnitude, in both AD and PD and with different brain structures affected in different neurodegenerative diseases. MRE studies of neurodegenerative diseases are still in their infancy, and in future it will be interesting to investigate potential relationships between brain mechanical properties and clinical measures, which may help elucidate the mechanisms underlying onset and progression of neurodegenerative diseases. EVIDENCE LEVEL: 1. TECHNICAL EFFICACY: Stage 2.

Mechanoresponsive stem cells acquire neural crest fate in jaw regeneration.

During both embryonic development and adult tissue regeneration, changes in chromatin structure driven by master transcription factors lead to stimulus-responsive transcriptional programs. A thorough understanding of how stem cells in the skeleton interpret mechanical stimuli and enact regeneration would shed light on how forces are transduced to the nucleus in regenerative processes. Here we develop a genetically dissectible mouse model of mandibular distraction osteogenesis-which is a process that is used in humans to correct an undersized lower jaw that involves surgically separating the jaw bone, which elicits new bone growth in the gap. We use this model to show that regions of newly formed bone are clonally derived from stem cells that reside in the skeleton. Using chromatin and transcriptional profiling, we show that these stem-cell populations gain activity within the focal adhesion kinase (FAK) signalling pathway, and that inhibiting FAK abolishes new bone formation. Mechanotransduction via FAK in skeletal stem cells during distraction activates a gene-regulatory program and retrotransposons that are normally active in primitive neural crest cells, from which skeletal stem cells arise during development. This reversion to a developmental state underlies the robust tissue growth that facilitates stem-cell-based regeneration of adult skeletal tissue.

The STING in the tale of Teflon®: Delayed ureteric obstruction after subureteric transurethral injection with polytetrafluoroethylene paste for vesicoureteral reflux.

INTRODUCTION: "Subureteric Teflon INGection" (STING) of polytetrafluoroethylene (PTFE/polytef) paste to treat vesicoureteral reflux (VUR) in children was popularised in 1984. It was later abandoned as an implantation material because of the possibility of migration from the injection site. Giant-cell foreign-body granuloma to Polytef in the bladder is a rare cause of ureteric obstruction. Only a handful of cases have been reported in the literature. METHODS: We performed a prospective analysis of a series of 6 adult patients who had childhood STING and presented with foreign-body granuloma to Polytef in the bladder. We report their clinical presentation, findings and treatment. RESULTS: 1 male and 5 females with a history of STING procedure in childhood for VUR presented in later life with foreign-body granuloma to Polytef. The median age at first STING procedure and at presentation to the Urology Department was 3 and 34 years respectively. The most common clinical presentations were flank pain and urinary tract infection (UTI) and all patients had radiological findings of calcified lesions at the vesicoureteric junction(s). 4 patients had histological findings of giant-cell foreign-body granuloma. 4 patients required definitive ureteric reimplantation. CONCLUSION: Polytef granuloma causing distal ureteric obstruction may give rise to significant morbidity and renal damage. Due to the likelihood of progression of the granuloma, excision and ureteric reimplantation is considered the standard approach in the management of patients with viable kidneys. LEVEL OF EVIDENCE: Level 5.

Modeling Instantaneous Firing Rate of Deep Brain Stimulation Target Neuronal Ensembles in the Basal Ganglia and Thalamus.

OBJECTIVE: Deep brain stimulation (DBS) is an effective treatment for movement disorders, including Parkinson disease and essential tremor. However, the underlying mechanisms of DBS remain elusive. Despite the capability of existing models in interpreting experimental data qualitatively, there are very few unified computational models that quantitatively capture the dynamics of the neuronal activity of varying stimulated nuclei-including subthalamic nucleus (STN), substantia nigra pars reticulata (SNr), and ventral intermediate nucleus (Vim)-across different DBS frequencies. MATERIALS AND METHODS: Both synthetic and experimental data were used in the model fitting; the synthetic data were generated by an established spiking neuron model that was reported in our previous work, and the experimental data were provided using single-unit microelectrode recordings (MERs) during DBS (microelectrode stimulation). Based on these data, we developed a novel mathematical model to represent the firing rate of neurons receiving DBS, including neurons in STN, SNr, and Vim-across different DBS frequencies. In our model, the DBS pulses were filtered through a synapse model and a nonlinear transfer function to formulate the firing rate variability. For each DBS-targeted nucleus, we fitted a single set of optimal model parameters consistent across varying DBS frequencies. RESULTS: Our model accurately reproduced the firing rates observed and calculated from both synthetic and experimental data. The optimal model parameters were consistent across different DBS frequencies. CONCLUSIONS: The result of our model fitting was in agreement with experimental single-unit MER data during DBS. Reproducing neuronal firing rates of different nuclei of the basal ganglia and thalamus during DBS can be helpful to further understand the mechanisms of DBS and to potentially optimize stimulation parameters based on their actual effects on neuronal activity.

Change in Morphological Features of Enlarged Subarachnoid Spaces Following Treatment in Idiopathic Normal Pressure Hydrocephalus.

BACKGROUND: Focally enlarged sulci (FES) are areas of proposed extraventricular fluid entrapment that may occur within idiopathic normal pressure hydrocephalus (iNPH) with radiographic evidence of disproportionately enlarged subarachnoid-space hydrocephalus (DESH), and should be differentiated from atrophy. PURPOSE: To evaluate for change in FES size and pituitary height after shunt placement in iNPH. STUDY TYPE: Retrospective. SUBJECTS: A total of 125 iNPH patients who underwent shunt surgery and 40 age-matched controls. FIELD STRENGTH/SEQUENCE: 1.5 T and 3 T. Axial T2w FLAIR, 3D T1w MPRAGE, 2D sagittal T1w. ASSESSMENT: FES were measured in three dimensions and volume was estimated by assuming an ellipsoid shape. Pituitary gland height was measured in the mid third of the gland in iNPH patients and controls. STATISTICAL TESTS: Wilcoxon signed-rank test for comparisons between MRI measurements; Wilcoxon rank sum test for comparison of cases/controls. Significance level was P < 0.05. RESULTS: Fifty percent of the patients had FES. FES volume significantly decreased between the pre and first postshunt MRI by a median of 303 mm3 or 30.0%. Pituitary gland size significantly increased by 0.48 mm or 14.4%. FES decreased significantly by 190 mm3 or 23.1% and pituitary gland size increased significantly by 0.25 mm or 6% between the first and last postshunt MRI. DATA CONCLUSION: Decrease in size of FES after shunt placement provides further evidence that these regions are due to disordered cerebrospinal fluid (CSF) dynamics and should not be misinterpreted as atrophy. A relatively smaller pituitary gland in iNPH patients that normalizes after shunt is a less-well recognized feature of altered CSF dynamics. EVIDENCE LEVEL: 3 TECHNICAL EFFICACY: Stage 2.

Characterizing HIV Syndemics and the Role of Incarceration Among Men Who have Sex with Men Presenting for Care at a Sexually Transmitted Infections Clinic.

Men who have sex with men (MSM) with a history of incarceration experience unique risk factors for HIV acquisition. The current study examined unique risk factors for HIV among MSM with a history of incarceration presenting to a sexually transmitted infections (STI) clinic. We analyzed self-reported behavioral data from clinical encounters among patients attending the clinic between January 2012 and April 2021. There were 17,221 unique visits, of which 5988 were MSM. Of these, 4.34% (N = 206) were MSM with a history of incarceration. MSM with a history of incarceration were significantly more likely to report a range of behavioral risk factors for HIV, yet also were significantly less likely to perceive themselves at risk for HIV. Future research and practice should develop culturally tailored biobehavioral HIV prevention services and consider embedding these programs within criminal justice settings to better reach this at-risk group.

Cruel and Unusual: Reforming Carceral Systems to Protect and Affirm Transgender and Gender-Diverse Communities.

Transgender and gender-diverse communities are disproportionately incarcerated in the USA. Incarcerated gender minority populations are detained within carceral systems constructed around a cisgender (gender identity matches sex assigned at birth) binary (only male and female identities recognized) understanding of gender. This leads to marginalizing experiences while perpetuating the extreme vulnerability individuals experience in the community. In order to address this cruel and unusual experience, carceral systems should undergo "whole-setting" reforms to protect and affirm transgender and gender-diverse populations. This includes ensuring access to gender-affirming clinical care that aligns with community health standards recommended by medical professional associations. Implementing gender-affirming reforms reduces security issues and will likely improve health outcomes providing mutual benefit for both correctional staff and gender minority populations. Given the current divisive political and social environment for gender minority populations in the USA, evidence-based person-centered reforms in corrections are needed now more than ever.

Mindfulness-Based Mobile Health to Address Unhealthy Eating Among Middle-Aged Sexual Minority Women With Early Life Adversity: Mixed Methods Feasibility Trial.

BACKGROUND: Sexual minority women (lesbian, gay, bisexual, pansexual, queer, and other nonheterosexual women) remain considerably underrepresented in health research despite being at a higher risk for diabetes and obesity as well as stigma and psychological distress than their heterosexual peers. In addition, early life adversity (ELA) is prevalent among sexual minority women, which further increases risks for obesity, psychological distress, and poor cardiovascular health. App-based mindfulness interventions are potentially promising for this group in mitigating the adverse health effects of ELA, reducing food craving and unhealthy eating, addressing the risks associated with obesity. OBJECTIVE: This mixed methods feasibility trial aimed to test a mindfulness-based mobile health approach for middle-aged sexual minority women (aged 30-55 years) with ELA and overweight or obesity (BMI ≥25 kg/m2) to improve health outcomes. METHODS: The single-arm trial was advertised on social media and various lesbian, gay, bisexual, transgender, and queer web-based groups. At baseline, after the intervention (2 months), and at the 4-month follow-up, participants completed assessments of primary outcomes (food craving, emotional eating, and weight via a mailed scale) and secondary outcomes (depression, anxiety, mindfulness, and emotion dysregulation). A standardized weight measure was mailed to participants for weight reporting. Feasibility and acceptability were assessed after the intervention via surveys and semistructured exit interviews. RESULTS: We screened 442 individuals, among which 30 eligible sexual minority women (mean age 40.20, SD 7.15 years) from various US regions were enrolled in the study. At baseline, 86% (26/30) and 80% (24/30) of participants had elevated depressive and anxiety symptoms, respectively. Among the 30 enrolled participants, 20 (66%) completed all intervention modules, 25 (83%) were retained at the 2-month follow-up, and 20 (66%) were retained at the 4-month follow-up. None reported adverse effects. From baseline to the 4-month follow-up, large effects were found in food craving (Cohen d=1.64) and reward-based eating (Cohen d=1.56), whereas small effects were found with weight (Cohen d=0.20; 4.21 kg on average). Significant improvements were also found in the secondary outcomes (depression, Cohen d=0.98; anxiety, Cohen d=0.50; mindfulness, Cohen d=0.49; and emotion dysregulation, Cohen d=0.44; all P<.05). Participants with higher levels of parental verbal and emotional abuse were particularly responsive to the intervention. Participants reported that the program aligned with their goals and expectations, was easy to use, and facilitated changes in eating behavior and mental health. Barriers to engagement included the need for diverse teachers, individualized support, and body positive language. CONCLUSIONS: This early phase feasibility trial provides proof-of-concept support for a mindfulness mobile health approach to improve obesity-related outcomes among sexual minority women and warrants a larger randomized controlled trial in the future. The findings also suggest the need to address trauma and psychological health when addressing weight-related outcomes among sexual minority women.

Barriers to international physician recruitment in Nova Scotia, Canada.

A healthcare staffing crisis has been brewing in Canada since 1993. Recently worsened by the COVID-19 pandemic and increasing immigration, it has severely impacted rural and remote areas of the country like the province of Nova Scotia. Researchers have considered international physician recruitment as a long-term solution, but it comes with its own challenges. In addition to an extensive literature search, qualitative interviews were conducted with various representatives from the Nova Scotia health ecosystem as part of this article. Identifying challenges to international physician recruitment from different perspectives, recommendations include bringing legislative and/or policy changes to increase candidate seats and developing new pathways to bring international medical graduates to Nova Scotia from other countries. The article includes interview responses from official authorities involved in physician recruitment, author recommendations to remove barriers to international physician recruitment, and recruitment and retention initiatives currently being implemented in the province.

An Untargeted Metabolomics Workflow that Scales to Thousands of Samples for Population-Based Studies.

The success of precision medicine relies upon collecting data from many individuals at the population level. Although advancing technologies have made such large-scale studies increasingly feasible in some disciplines such as genomics, the standard workflows currently implemented in untargeted metabolomics were developed for small sample numbers and are limited by the processing of liquid chromatography/mass spectrometry data. Here we present an untargeted metabolomics workflow that is designed to support large-scale projects with thousands of biospecimens. Our strategy is to first evaluate a reference sample created by pooling aliquots of biospecimens from the cohort. The reference sample captures the chemical complexity of the biological matrix in a small number of analytical runs, which can subsequently be processed with conventional software such as XCMS. Although this generates thousands of so-called features, most do not correspond to unique compounds from the samples and can be filtered with established informatics tools. The features remaining represent a comprehensive set of biologically relevant reference chemicals that can then be extracted from the entire cohort's raw data on the basis of m/z values and retention times by using Skyline. To demonstrate applicability to large cohorts, we evaluated >2000 human plasma samples with our workflow. We focused our analysis on 360 identified compounds, but we also profiled >3000 unknowns from the plasma samples. As part of our workflow, we tested 14 different computational approaches for batch correction and found that a random forest-based approach outperformed the others. The corrected data revealed distinct profiles that were associated with the geographic location of participants.

Optimizing transesophageal atrial pacing in mice to detect atrial fibrillation.

Mice are routinely used to investigate molecular mechanisms underlying the atrial fibrillation (AF) substrate. We sought to optimize transesophageal rapid atrial pacing (RAP) protocols for the detection of AF susceptibility in mouse models. Hypertensive and control C57Bl/6J mice were subjected to burst RAP at a fixed stimulus amplitude. The role of parasympathetic involvement in pacing-related atrioventricular (AV) block and AF was examined using an intraperitoneal injection of atropine. In a crossover study, burst and decremental RAP at twice diastolic threshold were compared for induction of AV block during pacing. The efficacy of burst and decremental RAP to elicit an AF phenotype was subsequently investigated in mice deficient in the lymphocyte adaptor protein (Lnk-/-) resulting in systemic inflammation, or the paired-like homeodomain-2 transcription factor (Pitx2+/-) as a positive control. When pacing at a fixed stimulus intensity, pacing-induced AV block with AF induction occurred frequently, so that there was no difference in AF burden between hypertensive and control mice. These effects were prevented by atropine administration, implicating parasympathetic activation due to ganglionic stimulation as the etiology. When mice with AV block during pacing were eliminated from the analysis, male Lnk-/- mice displayed an AF phenotype only during burst RAP compared with controls, whereas male Pitx2+/- mice showed AF susceptibility during burst and decremental RAP. Notably, Lnk-/- and Pitx2+/- females exhibited no AF phenotype. Our data support the conclusion that multiple parameters should be used to ascertain AF inducibility and facilitate reproducibility across models and studies.NEW & NOTEWORTHY Methods were developed to optimize transesophageal rapid atrial pacing (RAP) to detect AF susceptibility in new and established mouse models. High stimulus intensity and pacing rates caused parasympathetic stimulation, with pacing-induced AV block and excessive AF induction in normal mice. For a given model, pacing at twice TH enabled improved phenotype discrimination in a pacing mode and sex-specific manner. Transesophageal RAP should be individually optimized when developing a mouse model of AF.

Acinetobacter baumannii Genomic Sequence-Based Core Genome Multilocus Sequence Typing Using Ridom SeqSphere+ and Antimicrobial Susceptibility Prediction in ARESdb.

Whole-genome sequencing (WGS) is rapidly replacing traditional typing methods for the investigation of infectious disease outbreaks. Additionally, WGS data are being used to predict phenotypic antimicrobial susceptibility. Acinetobacter baumannii, which is often multidrug-resistant, is a significant culprit in outbreaks in health care settings. A well-characterized collection of A. baumannii was studied using core genome multilocus sequence typing (cgMLST). Seventy-two isolates previously typed by PCR-electrospray ionization mass spectrometry (PCR/ESI-MS) provided by the Antimicrobial Resistance Leadership Group (ARLG) were analyzed using a clinical microbiology laboratory developed workflow for cgMLST with genomic susceptibility prediction performed using the ARESdb platform. Previously performed PCR/ESI-MS correlated with cgMLST using relatedness thresholds of allelic differences of ≤9 and ≤200 allelic differences in 78 and 94% of isolates, respectively. Categorical agreement between genotypic and phenotypic antimicrobial susceptibility across a panel of 11 commonly used drugs was 89%, with minor, major, and very major error rates of 8%, 11%, and 1%, respectively.

Evolutionary history limits species' ability to match colour sensitivity to available habitat light.

The spectrum of light that an animal sees-from ultraviolet to far red light-is governed by the number and wavelength sensitivity of a family of retinal proteins called opsins. It has been hypothesized that the spectrum of light available in an environment influences the range of colours that a species has evolved to see. However, invertebrates and vertebrates use phylogenetically distinct opsins in their retinae, and it remains unclear whether these distinct opsins influence what animals see, or how they adapt to their light environments. Systematically using published visual sensitivity data from across animal phyla, we found that terrestrial animals are more sensitive to shorter and longer wavelengths of light than aquatic animals and that invertebrates are more sensitive to shorter wavelengths of light than vertebrates. Using phylogenetically controlled analyses, we found that closed and open canopy habitat species have different spectral sensitivities when comparing across the Metazoa and excluding habitat generalists, while deepwater animals are no more sensitive to shorter wavelengths of light than shallow-water animals. Our results suggest that animals do adapt to their light environment; however, the invertebrate-vertebrate evolutionary divergence may limit the degree to which animals can perform visual tuning.

Impact of material homogeneity assumption on cortical stiffness estimates by MR elastography.

PURPOSE: Inversion algorithms used to convert acquired MR elastography wave data into material property estimates often assume that the underlying materials are locally homogeneous. Here we evaluate the impact of that assumption on stiffness estimates in gray-matter regions of interest in brain MR elastography. METHODS: We describe an updated neural network inversion framework using finite-difference model-derived data to train convolutional neural network inversion algorithms. Neural network inversions trained on homogeneous simulations (homogeneous learned inversions [HLIs]) or inhomogeneous simulations (inhomogeneous learned inversions [ILIs]) are generated with a variety of kernel sizes. These inversions are evaluated in a brain MR elastography simulation experiment and in vivo in a test-retest repeatability experiment including 10 healthy volunteers. RESULTS: In simulation and in vivo, HLI and ILI with small kernels produce similar results. As kernel size increases, the assumption of homogeneity has a larger effect, and HLI and ILI stiffness estimates show larger differences. At each inversion's optimal kernel size in simulation (7 × 7 × 7 for HLI, 11 × 11 × 11 for ILI), ILI is more sensitive to true changes in stiffness in gray-matter regions of interest in simulation. In vivo, there is no difference in the region-level repeatability of stiffness estimates between the inversions, although ILI appears to better maintain the stiffness map structure as kernel size increases, while decreasing the spatial variance in stiffness estimates. CONCLUSIONS: This study suggests that inhomogeneous inversions provide small but significant benefits even when large stiffness gradients are absent.