A Computational Model of Mechanical Stretching of Cultured Cells on a Flexible Membrane.

Mechanical forces applied to cells are known to regulate a wide variety of biological processes. Recent studies have supported that mechanical forces can cause nuclear deformation, leading to significant alterations in the gene expression and chromatin landscape of the cell. While the stresses and strains applied to cells is it is often known or controlled experimentally on a macroscopic length scale, it is often unclear what the actual forces and displacements are at the microscopic level of the cell. In this work, we created a model of cell deformation during application of mechanical stretch to cultured cells growth on a flexible membrane. This configuration is commonly used is in experimental studies as a means to apply controlled mechanical strains to adherent cultured cells. The parameters used in the study were used for application of strain to a mesenchymal stem cell stretched on a membrane. computational model was created to simulate the stresses and strains within the cell under a variety of stain amplitudes, waveforms and frequencies of mechanical loading with the range of commonly used experimental systems. The results demonstrate the connection between mechanical loading parameters applied through the flexible membrane and the resulting stresses and strains within the cell and nucleus. Using a viscoelastic model of chromatin, we connected the results provide to a rough model of resulting deformation within chromatin from the forces applied to the nucleus. Overall, the model is useful in providing insight between experimentally applied mechanical forces and the actual forces within the cell to better interpret the results of experimental studies. Statement of Significance: In this work, we created a computational model of the mechanical stretching of cell on a flexible membrane under cyclic mechanical loading. This model provides insight into the forces and displacements inside of cell that result from that application of stretch. As many experiments use this set up, our work is relevant to interpreting many studies that use mechanical stretch to stimulate mechanotransduction.

Mechanical Rejuvenation of Mesenchymal Stem Cells from Aged Patients.

Mesenchymal stem cells (MSC) are an appealing therapeutic cell type for many diseases. However, patients with poor health or advanced age often have MSCs with poor regenerative properties. A major limiter of MSC therapies is cellular senescence, which is marked by limited proliferation capability, diminished multipotency, and reduced regenerative properties. In this work, we explored the ability of applied mechanical forces to reduce cellular senescence in MSCs. Our studies revealed that mechanical conditioning caused a lasting enhancement in proliferation, overall cell culture expansion potential, multipotency, and a reduction of senescence in MSCs from aged donors. Mechanistic studies suggested that these functional enhancements were mediated by oxidative stress and DNA damage repair signaling with mechanical load altering the expression of proteins of the sirtuin pathway, the DNA damage repair protein ATM, and antioxidant proteins. In addition, our results suggest a biophysical mechanism in which mechanical stretch leads to improved recognition of damaged DNA in the nucleus. Analysis of the cells through RNA-seq and ATAC-seq, demonstrated that mechanical loading alters the cell's genetic landscape to cause broad shifts in transcriptomic patterns that related to senescence. Overall, our results demonstrate that mechanical conditioning can rejuvenate mesenchymal stem cells derived from aged patients and improve their potential as a therapeutic cell type.

Variable Peripheral Ligand Donation Tunes Electronic Structure and NIR II Emission in Tetrathiafulvalene Tetrathiolate Diradicaloids.

Near-infrared (NIR) lumiphores are promising candidates for numerous imaging, communication, and sensing applications, but they typically require large, conjugated scaffolds to achieve emission in this low-energy region. Due to the extended conjugation and synthetic complexity required, it is extremely difficult to tune the photophysical properties of these systems for desired applications. Here, we report facile tuning of deep NIR-emitting diradicaloid complexes through simple modification of peripheral ligands. These new lumiphores are rare examples of air-, acid-, and water-stable emissive diradicaloids. We apply a simple Hammett parameter-based strategy to tune the electron donation of the capping ligand across a series of commercially available triarylphosphines. This minor peripheral modification significantly alters the electronic structure, and consequently, the electrochemical, photophysical, and magnetic properties of the tetrathiafulvalene tetrathiolate (TTFtt)-based lumiphores. The resultant ∼100 nm absorption and emission range spans common laser lines and the desirable telecom region (ca. 1260-1550 nm). Furthermore, these lumiphores are sensitive to local dielectrics, distinguishing them as promising candidates for ratiometric imaging and/or barcoding in the deep NIR region.

Serological evidence of zoonotic filovirus exposure among bushmeat hunters in Guinea.

Human Ebola virus (EBOV) outbreaks caused by persistent EBOV infection raises questions on the role of zoonotic spillover in filovirus epidemiology. To characterise filovirus zoonotic exposure, we collected cross-sectional serum samples from bushmeat hunters (n = 498) in Macenta Prefecture Guinea, adjacent to the index site of the 2013 EBOV-Makona spillover event. We identified distinct immune signatures (20/498, 4.0%) to multiple EBOV antigens (GP, NP, VP40) using stepwise ELISA and Western blot analysis and, live EBOV neutralisation (5/20; 25%). Using comparative serological data from PCR-confirmed survivors of the 2013-2016 EBOV outbreak, we demonstrated that most signatures (15/20) were not plausibly explained by prior EBOV-Makona exposure. Subsequent data-driven modelling of EBOV immunological outcomes to remote-sensing environmental data also revealed consistent associations with intact closed canopy forest. Together our findings suggest exposure to other closely related filoviruses prior to the 2013-2016 West Africa epidemic and highlight future surveillance priorities.

HDAC activity is dispensable for repression of cell-cycle genes by DREAM and E2F:RB complexes.

Histone deacetylases (HDACs) play a crucial role in transcriptional regulation and are implicated in various diseases, including cancer. They are involved in histone tail deacetylation and canonically linked to transcriptional repression. Previous studies suggested that HDAC recruitment to cell-cycle gene promoters via the retinoblastoma (RB) protein or the DREAM complex through SIN3B is essential for G1/S and G2/M gene repression during cell-cycle arrest and exit. Here we investigate the interplay among DREAM, RB, SIN3 proteins, and HDACs in the context of cell-cycle gene repression. Knockout of SIN3B does not globally derepress cell-cycle genes in non-proliferating HCT116 and C2C12 cells. Loss of SIN3A/B moderately upregulates several cell-cycle genes in HCT116 cells but does so independently of DREAM/RB. HDAC inhibition does not induce general upregulation of RB/DREAM target genes in arrested transformed or non-transformed cells. Our findings suggest that E2F:RB and DREAM complexes can repress cell-cycle genes without relying on HDAC activity.

Obesity Differs from Diabetes Mellitus in Antibody and T Cell Responses Post COVID-19 Recovery.

Obesity and type 2 diabetes (DM) are risk factors for severe COVID-19 outcomes, which disproportionately affect South Asian populations. This study aims to investigate the humoral and cellular immune responses to SARS-CoV-2 in adult COVID-19 survivors with obesity and DM in Bangladesh. In this cross-sectional study, SARS-CoV-2-specific antibody and T cell responses were investigated in 63 healthy and 75 PCR-confirmed COVID-19 recovered individuals in Bangladesh, during the pre-vaccination first wave of the COVID-19 pandemic in 2020. In COVID-19 survivors, SARS-CoV-2 infection induced robust antibody and T cell responses, which correlated with disease severity. After adjusting for age, sex, DM status, disease severity, and time since onset of symptoms, obesity was associated with decreased neutralising antibody titers, and increased SARS-CoV-2 spike-specific IFN-γ response along with increased proliferation and IL-2 production by CD8+ T cells. In contrast, DM was not associated with SARS-CoV-2-specific antibody and T cell responses after adjustment for obesity and other confounders. Obesity is associated with lower neutralising antibody levels and higher T cell responses to SARS-CoV-2 post COVID-19 recovery, while antibody or T cell responses remain unaltered in DM.

Surgical Site Infections in Trauma Exploratory Laparotomies Preoperative Ceftriaxone and Metronidazole Versus Cefoxitin.

Surgical site infections (SSIs) remain a significant cause of morbidity and mortality in patients undergoing traumatic exploratory laparotomy. The goal of this study was to compare antibiotic usage and subsequent outcomes in patients undergoing traumatic exploratory laparotomy. A retrospective chart analysis and a chi-square test of independence were performed to examine the relation between preoperative cefoxitin versus ceftriaxone and metronidazole and the rate of SSI development. 323 patients were analyzed, 111 patients receiving cefoxitin and 212 patients receiving ceftriaxone and metronidazole. The proportion of patients who developed SSI was 16.2% for the cefoxitin group and 9.9% for the ceftriaxone and metronidazole group, X2 (1, N = 323) = 2.7, P = .098, thus displaying no statistical difference in the development of SSIs between patients in the cefoxitin group when compared to the ceftriaxone and metronidazole group.

Effect of proteasome inhibitors on canine lymphoma cell response to CHOP chemotherapy in vitro.

The standard treatment for canine lymphoma is the CHOP chemotherapy regimen. Proteasome inhibitors have been employed with CHOP for the treatment of human haematological malignancies but remain to be fully explored in canine lymphoma. We identified an association between poor response to CHOP chemotherapy and high mRNA expression levels of proteasomal subunits in a cohort of 15 canine lymphoma patients, and sought to determine the effect of proteasome inhibitors on the viability of a canine B-cell lymphoma cell line (CLBL-1). The aim of this study was to investigate whether proteasome inhibitors sensitize these cells to the CHOP agents doxorubicin, vincristine and cyclophosphamide (as 4-hydroxycyclophosphamide/4-HC). CLBL-1 cells were sensitive to proteasome inhibition by bortezomib and ixazomib. The IC50 of bortezomib was 15.1 nM and of ixazomib was 59.14 nM. Proteasome inhibitors plus doxorubicin had a synergistic effect on CLBL-1 viability; proteosome inhibitors plus vincristine showed different effects depending on the combination ratio, and there was an antagonistic effect with 4-HC. These results may have clinical utility, as proteasome inhibition could potentially be used with a synergizing CHOP compound to improve responsiveness to chemotherapy for canine lymphoma patients.

Comparative Analysis of the Donor Properties of Isomeric Pyrrolyl Phosphine Ligands.

Understanding the net donor and electronic properties of pyrrole-based phosphines is critical for guiding their use as ligands. In this study, we compare two isomeric 1- and 2-(diphenylphosphino)methylpyrroles (L1 and L2, respectively) to determine the degree to which N-(phosphino)pyrroles are distinct from aryl- and 2-pyrrolyl phosphines. Ruthenium, rhodium, platinum, and gold complexes as well as selenide derivatives of these ligands are examined using NMR and IR spectroscopy, X-ray crystallography, and cyclic voltammetry. Ligand L2 exhibits net donor properties similar to those of the o-tolyl analogue L3, while L1 shows attenuated electron donation ability. Additionally, a model nickel-catalyzed Kumada coupling reaction using these three ligands was investigated.

Traumatic Transradial Forearm Amputation Temporized With Extracorporeal Membrane Oxygenation: A Brief Report.

INTRODUCTION: Extracorporeal membrane oxygenation (ECMO) is typically used to provide mechanical perfusion and gas exchange to critically ill patients with cardiopulmonary failure. We present a case of a traumatic high transradial amputation in which the amputated limb was placed on ECMO to allow for limb perfusion during bony fixation and preparations and coordination of orthopedic and vascular soft tissue reconstructions. MATERIALS AND METHODS: This is a descriptive single case report which underwent managment at a level 1 trauma center. Instutional review board (IRB) approval was obtained. RESULTS: This case highlights many important factors of limb salvage. First, complex limb salvage requires a well-organized, pre-planned multi-disciplinary approach to optimize patient outcomes. Second, advancements in trauma resuscitation and reconstructive techniques over the past 20 years have drastically expanded the ability of treating surgeons to preserve limbs that would have otherwise been indicated for amputation. Lastly, which will be the focus of further discussion, ECMO and EP have a role in the limb salvage algorithm to extend current timing limitations for ischemia, allow for multidisciplinary planning, and prevent reperfusion injury with increasing literature to support its use. CONCLUSIONS: ECMO is an emerging technology that may have clinical utility for traumatic amputations, limb salvage, and free flap cases. In particular, it may extend current limitations of ischemia time and reduce the incidence of ischemia reperfusion injury in proximal amputation, thus expanding the current indications for proximal limb replantation. It is clear that developing a multi-disciplinary limb salvage team with standardized treatment protocols is paramount to optimize patient outcomes and allows limb salvage to be pursued in increasingly complex cases.

Serum HCoV-spike specific antibodies do not protect against subsequent SARS-CoV-2 infection in children and adolescents.

SARS-CoV-2 infections in children are generally asymptomatic or mild and rarely progress to severe disease and hospitalization. Why this is so remains unclear. Here we explore the potential for protection due to pre-existing cross-reactive seasonal coronavirus antibodies and compare the rate of antibody decline for nucleocapsid and spike protein in serum and oral fluid against SARS-CoV-2 within the pediatric population. No differences in seasonal coronaviruses antibody concentrations were found at baseline between cases and controls, suggesting no protective effect from pre-existing immunity against seasonal coronaviruses. Antibodies against seasonal betacoronaviruses were boosted in response to SARS-CoV-2 infection. In serum, anti-nucleocapsid antibodies fell below the threshold of positivity more quickly than anti-spike protein antibodies. These findings add to our understanding of protection against infection with SARS-CoV-2 within the pediatric population, which is important when considering pediatric SARS-CoV-2 immunization policies.

Stepwise provisional versus systematic culotte for stenting of true coronary bifurcation lesions: five-year follow-up of the multicentre randomised EBC TWO Trial.

BACKGROUND: The multicentre European Bifurcation Club Trial (EBC TWO) showed no significant differences in 12-month clinical outcomes between patients randomised to a provisional stenting strategy or systematic culotte stenting in non-left main true bifurcations. AIMS: This study aimed to investigate the 5-year clinical results of the EBC TWO Trial. METHODS: A total of 200 patients undergoing stent implantation for non-left main bifurcation lesions were recruited into EBC TWO. Inclusion criteria required a side branch diameter ≥2.5 mm and side branch lesion length >5 mm. Five-year follow-up was completed for 197 patients. The primary endpoint was the composite of all-cause mortality, myocardial infarction, or target vessel revascularisation. RESULTS: The mean side branch stent diameter was 2.7±0.3 mm and mean side branch lesion length was 10.3±7.2 mm. At 5-year follow-up, the primary endpoint occurred in 18.4% of provisional and 23.7% of systematic culotte patients (hazard ratio [HR] 0.75, 95% confidence interval [CI]: 0.41-1.38). No significant differences were identified individually for all-cause mortality (7.8% vs 7.2%, HR 1.11, 95% CI: 0.40-3.05), myocardial infarction (8.7% vs 13.4%, HR 0.64, 95% CI: 0.27-1.50) or target vessel revascularisation (6.8% vs 9.3%, HR 1.12, 95% CI: 0.37-3.34). Stent thrombosis rates were also similar (1.9% vs 3.1%, HR 0.63, 95% CI: 0.11-3.75). There was no significant interaction between the extent of side branch disease and the primary outcome (p=0.34). CONCLUSIONS: In large non-left main true bifurcation lesions, the use of a systematic culotte strategy showed no benefit over provisional stenting for the composite outcome of all-cause mortality, myocardial infarction, or target vessel revascularisation at 5 years. The stepwise provisional approach may be considered preferable for the majority of true coronary bifurcation lesions. CLINICALTRIALS: gov: NCT01560455.

Pipeline to Military Orthopaedic Leadership: 20 Years of Race and Gender Diversity Trends Within Military Orthopaedic Surgery Fellowship Training.

Background: The lack of trainees from underrepresented race and gender backgrounds in orthopaedic surgery fellowship training has been well reported in the literature. The purpose of this study was to investigate the demographic trends of federally sponsored military orthopaedic surgery fellows in the Army, Navy, and Air Force. We hypothesize that there has been an increase in women selected for fellowship but that there has been no change in the race demographics of military fellows over the past 2 decades. Methods: A retrospective review of all available demographic data collected by the Army, Air Force, and Navy since the beginning of tracking federally funded fellowship training in orthopaedic surgery was completed (1998-2021). Data were grouped into 4-year periods for analysis to closely mirror the military assignment cycle. Results: Three hundred sixty-two military orthopaedic surgery fellowship board selectees were included in our analysis. The proportion of women fellows increased from 3% (n = 2/69) over 2001 to 2004 to 21% (n = 17/82) during 2017 to 2020 (p < 0.05). Fellows who identified as White comprised 82% (n = 297) of the cohort during the study period. Individuals who identified as Asian were the next highest proportion of fellows at 4% (n = 16), followed by Black (n = 14, 4%) and Hispanic (n = 13, 3%). Individuals who identified as Native Hawaiian/Pacific Islander represented 1% (n = 3), and an additional 6% (n = 20) fellows identified as "other" or "undeclared." Over the 20-year study period, representation of Asian, Black, Native Hawaiian, and Hispanic fellows did not increase (p = 0.79, 0.81, 0.45, 0.34, respectively). Conclusions: Within military orthopaedics, there has been increased representation of women in fellowship training over the past 20 years. However, the proportion of fellows from underrepresented racial and ethnic groups has remained stagnant. One barrier to improving gender and race representation is the currently imprecise and inconsistent collection of demographic information. Importantly, fellowship training has a direct effect on future leadership opportunities within the military orthopaedic surgery community. A more diverse leadership may help to inspire future generations of military orthopaedic surgeons. Level of Evidence: IV.

Inhibition of phosphodiesterase 12 results in antiviral activity against several RNA viruses including SARS-CoV-2.

The 2',5'- oligoadenylate synthetase (OAS) - ribonuclease L (RNAseL) - phosphodiesterase 12 (PDE12) pathway is an essential interferon-induced effector mechanism against RNA virus infection. Inhibition of PDE12 leads to selective amplification of RNAseL activity in infected cells. We aimed to investigate PDE12 as a potential pan-RNA virus antiviral drug target and develop PDE12 inhibitors that elicit antiviral activity against a range of viruses. A library of 18 000 small molecules was screened for PDE12 inhibitor activity using a fluorescent probe specific for PDE12. The lead compounds (CO-17 or CO-63) were tested in cell-based antiviral assays using encephalomyocarditis virus (EMCV), hepatitis C virus (HCV), dengue virus (DENV), West Nile virus (WNV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), in vitro. Cross reactivity of PDE12 inhibitors with other PDEs and in vivo toxicity were measured. In EMCV assays, CO-17 potentiated the effect of IFNα by 3 log10. The compounds were selective for PDE12 when tested against a panel of other PDEs and non-toxic at up to 42 mg kg-1 in rats in vivo. Thus, we have identified PDE12 inhibitors (CO-17 and CO-63), and established the principle that inhibitors of PDE12 have antiviral properties. Early studies suggest these PDE12 inhibitors are well tolerated at the therapeutic range, and reduce viral load in studies of DENV, HCV, WNV and SARS-CoV-2 in human cells and WNV in a mouse model.

Pre-clinical models to define correlates of protection for SARS-CoV-2.

A defined immune profile that predicts protection against a pathogen-of-interest, is referred to as a correlate of protection (CoP). A validated SARS-CoV-2 CoP has yet to be defined, however considerable insights have been provided by pre-clinical vaccine and animal rechallenge studies which have fewer associated limitations than equivalent studies in human vaccinees or convalescents, respectively. This literature review focuses on the advantages of the use of animal models for the definition of CoPs, with particular attention on their application in the search for SARS-CoV-2 CoPs. We address the conditions and interventions required for the identification and validation of a CoP, which are often only made possible with the use of appropriate in vivo models.

The effects of strain history on aortic valve interstitial cell activation in a 3D hydrogel environment.

Aortic valves (AVs) undergo unique stretch histories that include high rates and magnitudes. While major differences in deformation patterns have been observed between normal and congenitally defective bicuspid aortic valves (BAVs), the relation to underlying mechanisms of rapid disease onset in BAV patients remains unknown. To evaluate how the variations in stretch history affect AV interstitial cell (AVIC) activation, high-throughput methods were developed to impart varied cyclical biaxial stretch histories into 3D poly(ethylene) glycol hydrogels seeded with AVICs for 48 h. Specifically, a physiologically mimicking stretch history was compared to two stretch histories with varied peak stretch and stretch rate. Post-conditioned AVICs were imaged for nuclear shape, alpha smooth muscle actin (αSMA) and vimentin (VMN) polymerization, and small mothers against decapentaplegic homologs 2 and 3 (SMAD 2/3) nuclear activity. The results indicated that bulk gel deformations were accurately transduced to the AVICs. Lower peak stretches lead to increased αSMA polymerization. In contrast, VMN polymerization was a function of stretch rate, with SMAD 2/3 nuclear localization and nuclear shape also trending toward stretch rate dependency. Lower than physiological levels of stretch rate led to higher SMAD 2/3 activity, higher VMN polymerization around the nucleus, and lower nuclear elongation. αSMA polymerization did not correlate with VMN polymerization, SMAD 2/3 activity, nor nuclear shape. These results suggest that a negative feedback loop may form between SMAD 2/3, VMN, and nuclear shape to maintain AVIC homeostatic nuclear deformations, which is dependent on stretch rate. These novel results suggest that AVIC mechanobiological responses are sensitive to stretch history and provide insight into the mechanisms of AV disease.

Quantifying the value of viral genomics when inferring who infected whom in the 2014-16 Ebola virus outbreak in Guinea.

Transmission trees can be established through detailed contact histories, statistical or phylogenetic inference, or a combination of methods. Each approach has its limitations, and the extent to which they succeed in revealing a 'true' transmission history remains unclear. In this study, we compared the transmission trees obtained through contact tracing investigations and various inference methods to identify the contribution and value of each approach. We studied eighty-six sequenced cases reported in Guinea between March and November 2015. Contact tracing investigations classified these cases into eight independent transmission chains. We inferred the transmission history from the genetic sequences of the cases (phylogenetic approach), their onset date (epidemiological approach), and a combination of both (combined approach). The inferred transmission trees were then compared to those from the contact tracing investigations. Inference methods using individual data sources (i.e. the phylogenetic analysis and the epidemiological approach) were insufficiently informative to accurately reconstruct the transmission trees and the direction of transmission. The combined approach was able to identify a reduced pool of infectors for each case and highlight likely connections among chains classified as independent by the contact tracing investigations. Overall, the transmissions identified by the contact tracing investigations agreed with the evolutionary history of the viral genomes, even though some cases appeared to be misclassified. Therefore, collecting genetic sequences during outbreak is key to supplement the information contained in contact tracing investigations. Although none of the methods we used could identify one unique infector per case, the combined approach highlighted the added value of mixing epidemiological and genetic information to reconstruct who infected whom.

The P323L substitution in the SARS-CoV-2 polymerase (NSP12) confers a selective advantage during infection.

BACKGROUND: The mutational landscape of SARS-CoV-2 varies at the dominant viral genome sequence and minor genomic variant population. During the COVID-19 pandemic, an early substitution in the genome was the D614G change in the spike protein, associated with an increase in transmissibility. Genomes with D614G are accompanied by a P323L substitution in the viral polymerase (NSP12). However, P323L is not thought to be under strong selective pressure. RESULTS: Investigation of P323L/D614G substitutions in the population shows rapid emergence during the containment phase and early surge phase during the first wave. These substitutions emerge from minor genomic variants which become dominant viral genome sequence. This is investigated in vivo and in vitro using SARS-CoV-2 with P323 and D614 in the dominant genome sequence and L323 and G614 in the minor variant population. During infection, there is rapid selection of L323 into the dominant viral genome sequence but not G614. Reverse genetics is used to create two viruses (either P323 or L323) with the same genetic background. L323 shows greater abundance of viral RNA and proteins and a smaller plaque morphology than P323. CONCLUSIONS: These data suggest that P323L is an important contribution in the emergence of variants with transmission advantages. Sequence analysis of viral populations suggests it may be possible to predict the emergence of a new variant based on tracking the frequency of minor variant genomes. The ability to predict an emerging variant of SARS-CoV-2 in the global landscape may aid in the evaluation of medical countermeasures and non-pharmaceutical interventions.

Management of Venous and Arterial Bullet Emboli.

Gunshot wounds account for significant morbidity and mortality in the United States. A rare and potentially fatal complication of a gunshot wound is bullet embolus. Potential complications include distal limb ischemia, coronary infarct, renal infarction, stroke, pulmonary embolization, cardiac valvular injury, thrombophlebitis, and dysrhythmias. Overall, surgical embolectomy and endovascular retrieval are the preferred treatments for bullet emboli. We report one case of venous bullet embolus and one case of arterial bullet embolus, both of which were successfully treated with endovascular retrieval. A thorough physical exam and appropriate imaging are vital to prompt identification and treatment of bullet emboli, as the repercussions of missed injuries can be devastating.