Modification of Humeral Component Results in Increased Impingement Free Range of Motion in a Reverse Shoulder Arthroplasty Model.

Introduction: Shoulder arthroplasties have been demonstrated to provide reliable pain relief as well as functional benefits. The advent of the reverse shoulder arthroplasty allowed for expanded indications for shoulder replacement. Several studies comparing the outcomes of anatomic and reverse total shoulder arthroplasties have demonstrated decreased range of motion in the reverse arthroplasty cohort, especially in internal rotation.

Pulsatile Pressure Delivery of Continuous-Flow Left Ventricular Assist Devices Is Markedly Reduced Relative to Heart Failure Patients.

Although continuous-flow left ventricular assist devices (CF-LVADs) provide an augmentation in systemic perfusion, there is a scarcity of in vivo data regarding systemic pulsatility on support. Patients supported on CF-LVAD therapy (n = 71) who underwent combined left/right catheterization ramp study were included. Aortic pulsatility was defined by the pulsatile power index (PPI), which was also calculated in a cohort of high-output heart failure (HOHF, n = 66) and standard HF cohort (n = 44).

Evidence-based aerosol clearance times in a healthcare environment.

Background: As researchers race to understand the nature of COVID-19 transmission, healthcare institutions must treat COVID-19 patients while also safeguarding the health of staff and other patients. One aspect of this process involves mitigating aerosol transmission of the SARS-CoV2 virus. The U.

Regulation of arsenic methylation: identification of the transcriptional region of the human AS3MT gene.

The human enzyme As(III) S-adenosylmethionine methyltransferase (AS3MT) catalyzes arsenic biotransformations and is considered to contribute to arsenic-related diseases. AS3MT is expressed in various tissues and cell types including liver, brain, adrenal gland, and peripheral blood mononuclear cells but not in human keratinocytes, urothelial, or brain microvascular endothelial cells. This indicates that AS3MT expression is regulated in a tissue/cell type-specific manner, but the mechanism of transcriptional regulation of expression of the AS3MT gene is not known.

Mode of action assessment of the genotoxic properties of antimony and its compounds evaluated in the ToxTracker assay.

Antimony (Sb) and its compounds are negative in gene mutation assays in bacteria and cultured mammalian cells but positive in some assays for clastogenicity and/or DNA damage. In order to better understand the modes of action for antimony genotoxicity, we assessed reporter gene activation by antimony and antimony compounds in the new expanded ToxTracker assay. ToxTracker evaluates the activation of biomarkers for different cellular defense mechanisms using a series of green fluorescent protein reporters inserted into mouse embryonic stem cell lines.

Antimony and its compounds: Health impacts related to pulmonary toxicity, cancer, and genotoxicity.

Although occupational exposure to antimony and its compounds can produce pulmonary toxicity, human carcinogenic impacts have not been observed. Inhalation studies with respirable antimony trioxide particles administered to rats and mice have, however, induced carcinogenic responses in the lungs and related tissue sites. Genotoxicity studies conducted to elucidate mechanism(s) for tumor induction have produced mixed results.

Waveguide effects and implications for cardiac magnetic resonance elastography: A finite element study.

Magnetic resonance elastography (MRE) is increasingly being applied to thin or small structures in which wave propagation is dominated by waveguide effects, which can substantially bias stiffness results with common processing approaches. The purpose of this work was to investigate the importance of such biases and artifacts on MRE inversion results in: (i) various idealized 2D and 3D geometries with one or more dimensions that are small relative to the shear wavelength; and (ii) a realistic cardiac geometry. Finite element models were created using simple 2D geometries as well as a simplified and a realistic 3D cardiac geometry, and simulated displacements acquired by MRE from harmonic excitations from 60 to 220 Hz across a range of frequencies.

Factors associated with proximal femur fracture determined in a large cadaveric cohort.

Many researchers have used cadaveric fracture tests to determine the relationship between proximal femur (hip) fracture strength and a multitude of possible explanatory variables, typically considered one or two at a time. These variables include subject-specific proximal femur variables such as femoral neck areal bone mineral density (aBMD), sex, age, and geometry, as well as physiological hip fracture event variables such as fall speed and angle of impact. However, to our knowledge, no study has included all of these variables simultaneously in the same experimental dataset.

A Method to Estimate Cadaveric Femur Cortical Strains During Fracture Testing Using Digital Image Correlation.

This protocol describes the method using digital image correlation to estimate cortical strain from high speed video images of the cadaveric femoral surface obtained from mechanical testing. This optical method requires a texture of many contrasting fiduciary marks on a solid white background for accurate tracking of surface deformation as loading is applied to the specimen. Immediately prior to testing, the surface of interest in the camera view is painted with a water-based white primer and allowed to dry for several minutes.

Are DXA/aBMD and QCT/FEA Stiffness and Strength Estimates Sensitive to Sex and Age?

Dual X-ray absorptiometry (DXA) measures areal bone mineral density (aBMD) by simplifying a complex 3D bone structure to a 2D projection and is not equally effective for explaining fracture strength in women and men. Unlike DXA, subject-specific quantitative computed tomography-based finite element analysis (QCT/FEA) estimates fracture strength using 3D bone mineral distribution and geometry. By using experimentally-measured femoral stiffness and strength from a one hundred sample cadaveric cohort that included variations in sex and age, we wanted to determine if QCT/FEA estimates were able to better predict the experimental variations than DXA/aBMD.

Method and Instrumented Fixture for Femoral Fracture Testing in a Sideways Fall-on-the-Hip Position.

Mechanical testing of femora brings valuable insights into understanding the contribution of clinically-measureable variables such as bone mineral density distribution and geometry on the femoral mechanical properties. Currently, there is no standard protocol for mechanical testing of such geometrically complex bones to measure strength, and stiffness. To address this gap we have developed a protocol to test cadaveric femora to fracture and to measure their biomechanical parameters.

Nonsynonymous Polymorphisms in the Human AS3MT Arsenic Methylation Gene: Implications for Arsenic Toxicity.

Arsenic methylation, the primary biotransformation in the human body, is catalyzed by the enzyme As(III) S-adenosylmethionine (SAM) methyltransferases (hAS3MT). This process is thought to be protective from acute high-level arsenic exposure. However, with long-term low-level exposure, hAS3MT produces intracellular methylarsenite (MAs(III)) and dimethylarsenite (DMAs(III)), which are considerably more toxic than inorganic As(III) and may contribute to arsenic-related diseases.

Proximal Cadaveric Femur Preparation for Fracture Strength Testing and Quantitative CT-based Finite Element Analysis.

Cadaveric fracture testing is routinely used to understand factors that affect proximal femur strength. Because ex vivo biological tissues are prone to lose their mechanical properties over time, specimen preparation for experimental testing must be performed carefully to obtain reliable results that represent in vivo conditions. For that reason, we designed a protocol and a set of fixtures to prepare the femoral specimens such that their mechanical properties experienced minimal changes.

A method for accounting for test fixture compliance when estimating proximal femur stiffness.

Fracture testing of cadaveric femora to obtain strength and stiffness information is an active area of research in developing tools for diagnostic prediction of bone strength. These measurements are often used in the estimation and validation of companion finite element models constructed from the femora CT scan data, therefore, the accuracy of the data is of paramount importance. However, experimental stiffness calculated from force-displacement data has largely been ignored by most researchers due to inherent error in the differential displacement measurement obtained when not accounting for testing apparatus compliance.

QCT/FEA predictions of femoral stiffness are strongly affected by boundary condition modeling.

Quantitative computed tomography-based finite element models of proximal femora must be validated with cadaveric experiments before using them to assess fracture risk in osteoporotic patients. During validation, it is essential to carefully assess whether the boundary condition (BC) modeling matches the experimental conditions. This study evaluated proximal femur stiffness results predicted by six different BC methods on a sample of 30 cadaveric femora and compared the predictions with experimental data.

Quantitative computed tomography-based finite element analysis predictions of femoral strength and stiffness depend on computed tomography settings.

The aim of the present study was to compare proximal femur strength and stiffness obtained experimentally with estimations from Finite Element Analysis (FEA) models derived from Quantitative Computed Tomography (QCT) scans acquired at two different scanner settings. QCT/FEA models could potentially aid in diagnosis and treatment of osteoporosis but several drawbacks still limit their predictive ability. One potential reason is that the models are still sensitive to scanner settings which could lead to changes in assigned material properties, thus limiting their results accuracy and clinical effectiveness.

Intra-aneurysmal flow rates are reduced by two flow diverters: an experiment using tomographic particle image velocimetry in an aneurysm model.

Background: Limitations on treating large, giant, and wide-necked aneurysms with coiling have made flow diverters a promising alternative to current practice by supporting reconstruction of the parent artery.

Objective: To assess the changes to fluid dynamics within an aneurysm by studying two different endoluminal flow diverters on a simple aneurysm model, using tomographic particle image velocimetry to determine which device would better minimize fluid flow into an aneurysm and observe any significant changes in aneurysm fluid structures.

Methods: Steady velocity fields of the model's aneurysm dome and neck were measured at three inlet velocities (18, 39, and 59 cm/s) for two flow diverter diameters with different porosities and compared against a baseline case with no flow diverter.

Genetic and epigenetic effects of environmental arsenicals.

Environmental arsenic compounds and their methylated metabolites do not form adducts with DNA, but do cause oxidative DNA damage. Chromosome aberrations are seen at toxic concentrations. Genetic effects that occur at non-toxic concentrations include aneuploidy, comutagenesis (resulting from indirect effects on DNA repair), and delayed mutagenesis (probably secondary to aneuploidy and/or epigenetic effects).

Arsenite induced poly(ADP-ribosyl)ation of tumor suppressor P53 in human skin keratinocytes as a possible mechanism for carcinogenesis associated with arsenic exposure.

Arsenite is an environmental pollutant. Exposure to inorganic arsenic in drinking water is associated with elevated cancer risk, especially in skin. Arsenite alone does not cause skin cancer in animals, but arsenite can enhance the carcinogenicity of solar UV.

Mechanism of selenium-induced inhibition of arsenic-enhanced UVR carcinogenesis in mice.

Background: Hairless mice that ingested arsenite in drinking water exhibited more than a 5-fold enhancement of ultraviolet radiation (UVR) carcinogenesis, whereas arsenite alone was carcinogenically inactive. Dietary organoselenium blocked the cancer enhancement effect of arsenic but not cancer induction by UVR.

Objective: In this study we sought to explain selenium blockage of As enhancement by establishing the extent that As and Se tissue distributions are coincident or divergent.

Gene expression levels in normal human lymphoblasts with variable sensitivities to arsenite: identification of GGT1 and NFKBIE expression levels as possible biomarkers of susceptibility.

Drinking arsenic-contaminated water is associated with increased risk of neoplasias of the skin, lung, bladder and possibly other sites, as well as other diseases. Earlier, we showed that human lymphoblast lines from different normal unexposed donors showed variable sensitivities to the toxic effects of arsenite. In the present study, we used microarray analysis to compare the basal gene expression profiles between two arsenite-resistant (GM02707, GM00893) and two arsenite-sensitive lymphoblast lines (GM00546, GM00607).

Dietary chromium and nickel enhance UV-carcinogenesis in skin of hairless mice.

The skin cancer enhancing effect of chromium (in male mice) and nickel in UVR-irradiated female Skh1 mice was investigated. The dietary vitamin E and selenomethionine were tested for prevention of chromium-enhanced skin carcinogenesis. The mice were exposed to UVR (1.

Further evidence against a direct genotoxic mode of action for arsenic-induced cancer.

Arsenic in drinking water, a mixture of arsenite and arsenate, is associated with increased skin and other cancers in Asia and Latin America, but not the United States. Arsenite alone in drinking water does not cause skin cancers in experimental animals; therefore, it is not a complete carcinogen in skin. We recently showed that low concentrations of arsenite enhanced the tumorigenicity of solar UV irradiation in hairless mice, suggesting arsenic cocarcinogenesis with sunlight in skin cancer and perhaps with different carcinogenic partners for lung and bladder tumors.