bluuebunny/crossref_metadata_2025 huggingface dataset:
Efficacy of disinfectants containing accelerated hydrogen peroxide against conidial arthrospores and isolated infective spores of Microsporum canis and Trichophyton sp.
Authors: Moriello Karen A. , Hondzo Hanna
Published: March 2014

Background

Accelerated hydrogen peroxide is a proprietary disinfectant formulation that is available for both commercial and home use and is labelled as antifungal.

Hypothesis/Objectives

To determine the antifungal efficacy of accelerated hydrogen peroxide disinfectants against Microsporum and Trichophyton spp.

Methods

Three products formulated as ready to use and three concentrates were used. Concentrates were tested at dilutions of 1:8, 1:16 (recommended dilution) and 1:32. One product was a surgical instrument disinfectant. Sterile water, sodium hypochlorite (1:32 dilution) and over‐the‐counter 3% hydrogen peroxide were used as controls. Conidial suspensions contained ~9.6 × 105/mL Microsporum canis, ~1.0 × 107/mL M. gypseum or ~2.0 × 107/mL Trichophyton sp. and were tested at 1:10 dilution. Isolated infective spore suspensions of M. canis from an untreated cat and T. erinacei from an untreated hedgehog were tested at 1:10, 1:5 and 1:1 spore‐to‐disinfectant dilutions.

Results

Too many colonies to count were present on untreated control plates. Accelerated hydrogen peroxide and household hydrogen peroxide inhibited growth of both pathogens in conidial (1:10 dilution) and spore suspensions (1:10, 1:5 and 1:10 dilution). There was no lack of efficacy of products that were >12 months old.

Conclusions and clinical importance

Accelerated hydrogen peroxide products are an option for environmental disinfection of surfaces exposed to M. canis and Trichophyton sp. after appropriate gross decontamination and mechanical cleaning with a detergent. The results from conidial testing were identical to those of isolated infected spore testing, which suggests that accelerated hydrogen peroxide products with label claim as antifungal against Trichophyton mentagrophytes may be suitable as an alternative disinfectant to sodium hypochlorite.
TRANSTHORACIC LUNG ULTRASOUND IN NORMAL DOGS AND DOGS WITH CARDIOGENIC PULMONARY EDEMA: A PILOT STUDY
Authors: Rademacher Nathalie , Pariaut Romain , Pate Julie , Saelinger Carley , Kearney Michael T. , Gaschen Lorrie
Published: March 2014

Pulmonary edema is the most common complication of left‐sided heart failure in dogs and early detection is important for effective clinical management. In people, pulmonary edema is commonly diagnosed based on transthoracic ultrasonography and detection of B line artifacts (vertical, narrow‐based, well‐defined hyperechoic rays arising from the pleural surface). The purpose of this study was to determine whether B line artifacts could also be useful diagnostic predictors for cardiogenic pulmonary edema in dogs. Thirty‐one normal dogs and nine dogs with cardiogenic pulmonary edema were prospectively recruited. For each dog, presence or absence of cardiogenic pulmonary edema was based on physical examination, heartworm testing, thoracic radiographs, and echocardiography. A single observer performed transthoracic ultrasonography in all dogs and recorded video clips and still images for each of four quadrants in each hemithorax. Distribution, sonographic characteristics, and number of B lines per thoracic quadrant were determined and compared between groups. B lines were detected in 31% of normal dogs (mean 0.9 ± 0.3 SD per dog) and 100% of dogs with cardiogenic pulmonary edema (mean 6.2 ± 3.8 SD per dog). Artifacts were more numerous and widely distributed in dogs with congestive heart failure (P < 0.0001). In severe cases, B lines increased in number and became confluent. The locations of B line artifacts appeared consistent with locations of edema on radiographs. Findings from the current study supported the use of thoracic ultrasonography and detection of B lines as techniques for diagnosing cardiogenic pulmonary edema in dogs.
COMPARISON BETWEEN COMPUTED TOMOGRAPHY, FLUOROSCOPY, AND ULTRASONOGRAPHY FOR GUIDING PERCUTANEOUS INJECTION OF THE CANINE INTERVERTEBRAL DISC
Authors: MacKenzie Shawn D. , Caswell Jeff L. , Brisson Brigitte A. , Gaitero Luis , Chalmers Heather J.
Published: March 2014

A minimally invasive method for delivering injectable therapeutic agents would be desirable for the treatment of intervertebral disc disease in dogs. The purpose of this study was to compare computed tomography (CT), ultrasonography (US), and fluoroscopy modalities for guiding percutaneous injection into canine intervertebral discs. Intervertebral discs of 14 dog cadavers were injected with a gelified ethanol therapeutic agent. Successful injectate placement and injectate leakage were determined based on necropsy inspection of discs. Injection into the nucleus pulposus was successful in 55 of 78 (71%) of all injected discs. Injections guided using CT and fluoroscopy were significantly more successful than US‐guided injections. Odds of successful injection without leakage were greater for CT vs. US (P= 0.0026) but there was no significant difference between CT and fluoroscopy (P= 0.0620). Injection success rates did not differ among vertebral sites or dog cadavers of varying weights. Forty‐nine (63%) of injection sites had injectate leakage outside the disc and 10 of these involved structures within the vertebral canal. The highest rate of injection success with the least amount of leakage was achieved with CT guidance. Findings indicated that CT, fluoroscopy, and US are feasible modalities for guiding percutaneous injection of a gelified ethanol therapeutic agent into the canine intervertebral disc, with moderate to high success rates for different regions of the spine. However, a moderately high rate of injectate leakage occurred outside of the disc and this should be taken into consideration for future safety and efficacy studies.
An Evaluation of Rabies Vaccination Rates among Canines and Felines Involved in Biting Incidents within the Wellington–Dufferin–Guelph Public Health Department
Authors: Bottoms K. , Trotz‐Williams L. , Hutchison S. , MacLeod J. , Dixon J. , Berke O. , Poljak Z.
Published: March 2014

The objectives of this study were to determine the rate of animal bite incidents occurring in the human population of a local health department, and to determine the proportion of these canines and felines that were not up to date on their rabies vaccination at the time the incident occurred. Data were obtained from animal bite incidents reported to Wellington–Dufferin–Guelph Public Health during 2010 and 2011. Descriptive statistics of 718 eligible reports revealed the average rate of animal biting was 1.55 bites per 1000 residents per year. Approximately 54% of these animals were vaccinated against rabies, 32% were not up to date with their rabies vaccination, and the remaining 14.5% were of unknown status. The unit of analysis was the municipality, and the four outcomes of interest were: (i) number of animal bite incidents per 1000 residents, (ii) number of dog bite incidents per 1000 residents, (iii) proportion of animals involved in bite incidents that were not up to date with their rabies vaccination, and (iv) proportion of dogs that were not up to date. Associations between the outcomes and selected demographic variables were investigated using regression analysis. The number of veterinary clinics per 10 000 residents, and whether the municipality was urban or rural were identified as significant predictors for the number of animal bites per 1000 residents, and the number of dog bites. There were no significant predictors for the proportion of unvaccinated animals or dogs. Spatial clustering and the location of spatial clusters were assessed using the empirical Bayes index and spatial scan test. This analysis identified five municipalities within the health department that have a high rate of biting incidents and a high proportion of animals that were not up to date on their rabies vaccination. Such municipalities are ideal for targeted educational campaigns regarding the importance of vaccination in pets.
Review and Projections of Integrated Cooling Systems for Three-Dimensional Integrated Circuits
Authors: Kandlikar Satish G.
Published: March 2014

In an effort to increase processor speeds, 3D IC architecture is being aggressively pursued by researchers and chip manufacturers. This architecture allows extremely high level of integration with enhanced electrical performance and expanded functionality, and facilitates realization of VLSI and ULSI technologies. However, utilizing the third dimension to provide additional device layers poses thermal challenges due to the increased heat dissipation and complex electrical interconnects among different layers. The conflicting needs of the cooling system requiring larger flow passage dimensions to limit the pressure drop, and the IC architecture necessitating short interconnect distances to reduce signal latency warrant paradigm shifts in both of their design approach. Additional considerations include the effects due to temperature nonuniformity, localized hot spots, complex fluidic connections, and mechanical design. This paper reviews the advances in 3D IC cooling in the last decade and provides a vision for codesigning 3D IC architecture and integrated cooling systems. For heat fluxes of 50–100 W/cm2 on each side of a chip in a 3D IC package, the current single-phase cooling technology is projected to provide adequate cooling, albeit with high pressure drops. For future applications with coolant surface heat fluxes from 100 to 500 W/cm2, significant changes need to be made in both electrical and cooling technologies through a new level of codesign. Effectively mitigating the high temperatures surrounding local hot spots remains a challenging issue. The codesign approach with circuit, software and thermal designers working together is seen as essential. The through silicon vias (TSVs) in the current designs place a stringent limit on the channel height in the cooling layer. It is projected that integration of wireless network on chip architecture could alleviate these height restrictions since the data bandwidth is independent of the communication lengths. Microchannels that are 200 μm or larger in depth are expected to allow dissipation of large heat fluxes with significantly lower pressure drops.
Investigation of Drug Release From Biodegradable PLG Microspheres: Experiment and Theory
Authors: Berchane Nader S. , Carson Kenneth H. , Rice-Ficht Allison C. , Andrews Malcolm J.
Published: March 2014

Piroxicam containing PLG microspheres having different size distributions were fabricated, and in vitro release kinetics were determined for each preparation. Based on the experimental results, a suitable mathematical theory has been developed that incorporates the effect of microsphere size distribution and polymer degradation on drug release. We show from in vitro release experiments that microsphere size has a significant effect on drug release rate. The initial release rate decreased with an increase in microsphere size. In addition, the release profile changed from first order to concave-upward (sigmoidal) as the system size was increased. The mathematical model gave a good fit to the experimental release data.
Effects of Improved Near-Wall Modeling on Micro-Particle Deposition in Oral Airway Geometries
Authors: Xi Jinxiang , Longest P. Worth
Published: March 2014

Direct Lagrangian particle tracking provides an effective method for simulating micro-aerosol deposition in the upper respiratory airways. However, Xi and Longest [1] have shown that errors occurred in the predicted deposition rates of smaller particles in comparison to measurements. Matida et al. [2] attributed a similar discrepancy to the assumption of isotropic turbulent fluctuations near the wall. Matida et al. [2] implemented a near-wall anisotropic turbulence model and reported significantly improved agreement with experimental data. Longest and Xi [3] investigated nanoparticle deposition in oral airway models and showed that a Lagrangian transport model with a user-defined near-wall interpolation (NWI) algorithm provided an effective approach to accurately predict deposition in comparison to available experimental results. It is proposed that implementing both an anisotropic turbulence model with a NWI routine may further improve agreement between numerical and experimental results. The objective of this study is to evaluate the effect both near-wall anisotropic and interpolation models on regional deposition values in the oral airway geometry. Comparisons will be made to available in vitro test results. Models considered will include (1) the anisotropic correction only, and (2) anisotropic and NWI routines.
Comparison of Muscle Function in 2D and 3D Walking Simulations
Authors: Xiao Ming , Higginson Jill
Published: March 2014

Walking requires muscle coordination to provide support and forward progression of the center of mass. Previous modeling and simulation studies [1,2] have made significant progress to understand different muscle contributions in normal gait. However, it is difficult to compare results since they were based on different models (2D vs. 3D) and experimental data [1,2].
Closed Loop Glycemic Control in Critically Ill Patients: Feasibility Study and Experimental Design
Authors: Oliveros Alexandra , Vehí Josep , Gutiérrez Alfredo , García-Gabín Winston
Published: March 2014

Some studies, published recently, affirm that blood glucose levels are closely related with an increased risk in the moratality of critically ill patients [1].
A Novel Method for Frictional Testing on Adherent Cells
Authors: Cobb Jessica A. , Dunn Alison C. , Kwan Jiwoon , Sarntinoranont Malisa , Sawyer Gregory , Tran-Son-Tay Roger
Published: March 2014

Understanding the physical interaction between biomaterials and tissues within the body is critical for the development of medical devices. For instance, the coefficient of friction between the two must be low enough to avoid damaging the cells that make up the tissue. Therefore, a method for obtaining friction data on cells is needed. In the present work, human corneal epithelial (HCE-T) cells are cultured within specialized cell holders and friction experiments are performed with a micro-tribometer. Cell damage is assessed via microscopy and a trypan blue viability assay. Preliminary experiments provide data for an intact monolayer of HCE-Ts being abraded by the glass pin of the micro-tribometer. The coefficient of friction for the glass pin rubbing on an intact cell layer is 0.037 ± 0.016. Additionally, these data show a direct correlation between the friction coefficients obtained and the amount of cell damage that occurs. The protocols developed thus far can be used to conduct friction testing on various adherent cell types (e.g.epithelial cells, endothelial cells, etc.). Furthermore, the micro-tribometer set-up can be modified in order to obtain friction coefficient measurements between cells and various biomaterials.
Facet Joint Capsule Strains as a Result of Normal and Degenerate Intervertebral Discs
Authors: Saldanha Anita C. , Qin Yi-Xian , Goel Vijay K. , Khalsa Partap S.
Published: March 2014

The normal spine is a flexible column designed to maintain stability, position and can carry a considerable load. Degeneration weakens the spine by adversely affecting spinal stability, which is observed when a motion segment exhibits abnormally large displacements under applications of physiological load[1]. Furthermore, degeneration noticeably changes the load-bearing role of the intervertebral disc (IVD) during compression and extension by shifting significantly to the facet joint (FJ)[2].
Is Flow in the Common Carotid Artery Fully-Developed?
Authors: Xie Joyce , Ford Matthew D. , Steinman David A.
Published: March 2014

It is usually assumed, in both clinical and experimental settings, that blood velocity profiles in the common carotid artery (CCA) are fully-developed. This allows for a simpler estimation of CCA flow rates or wall shear stresses (WSS) from limited velocity data, such as peak velocities acquired using Doppler ultrasound (DUS) [1]. However, the assumption of a long, straight CCA may be incorrect, as the CCA does possess some curvature [2], which may alter the velocity profile from the assumed Poiseuille or Womersley shapes, and thus lead to incorrect inferences about flow rate or WSS. Consequently, this may have an impact on our understanding and diagnoses of cardiovascular related diseases. The aim of this study was to characterize the real shape of CCA velocity profiles in vivo.
Experimental Modal Analysis of Intervertebral Disc Joint Dynamics
Authors: Maleskian M. , Park S. S. , Hunter C. J.
Published: March 2014

The intervertebral discs provide mobility and a degree of shock absorbance to the spinal column. It has been shown that the mechanical properties of the intervertebral discs play an important role in their functionality [1, 2]. While static models of the intervertebral disc have significance, dynamic models characterize more accurately the in situ nature of the tissues. Some researchers [3] have studied dynamic disc loading from the perspective of biomedical performance and fatigue failure. Other studies have reported on the viscoelastic properties of discs under high frequency vibration [4]. However, the authors did not find any study which used experimental modal analysis (EMA) and the receptance coupling (RC) method to extract the dynamic characteristics, i.e. stiffness, damping, and natural frequencies, of the intervertebral discs.
Morphogenetic and Residual Strains in the Embryonic Chick Brain
Authors: Filas Benjamen A. , Xu Gang , Knutsen Andrew K. , Bayly Philip V. , Taber Larry A.
Published: March 2014

The brain of the chick embryo first becomes a fully sealed tube containing embryonic cerebrospinal fluid (ECSF) at Hamburger and Hamilton [1] stage 11 (HH11, approximately 42 hours of a 21-day incubation period). During the subsequent 40 hours of development, the brain undergoes dramatic changes in size and shape in response to increases in luminal pressure [2]. These changes include local regions that bulge outwards to create the primitive forebrain, midbrain, and hindbrain. While it has been shown that the internal ECSF can regulate cell proliferation and neurogenesis [3] in early brain development, possible biophysical factors contributing to this process have not been well characterized.
Quantifying Dynamics of the Ascending Thoracic Aorta in Patients With and Without Aneurysms Using 4D-CT
Authors: Segalova Polina A. , Morrison Tina M. , Taylor Charles A.
Published: March 2014

Endovascular repair of the thoracic aorta is becoming the preferred treatment for aneurysms due to lower mortality rates and shorter recovery time in the ICU [1]. The success of endovascular treatment greatly depends on the anatomy and dynamic characteristics of the aneurismal region, with the descending thoracic aorta (DTA) presenting a less challenging environment than the ascending thoracic aorta (ATA). As such, devices and methods for endovascular treatment of the ATA remain to be developed. In fact, there is currently no FDA-approved implantable device to treat aneurysms in the ATA.
Regional Cartilage Thinning Occurs First in the Walking Weight Bearing Regions of the Femur in Medial Compartment Knee Osteoarthritis
Authors: Erhart Jennifer C. , Mündermann Anne , Koo Seungbum , Merrick Ben , Deagon Andrew , Giori Nicholas J. , Andriacchi Thomas P.
Published: March 2014

Osteoarthritis (OA) of the knee affects an estimated 20–40% of individuals over the age of 65 [1], and is nearly 10 times more common in the medial compartment than the lateral compartment [2]. Plain radiography measurements using the Kellgren and Lawrence (KL) scale have been the gold standard for diagnosis of knee osteoarthritis [3]. However, for new treatment interventions for medial compartment knee OA such as load modifying footwear, it would be important to know if the disease-related cartilage loss in the medial compartment occurs initially and predominantly in regions that are weight bearing during walking. Because walking results in highest weight bearing occurring in the anterior and middle regions of the femoral condyle and the anterior region of the tibial plateau, seeing a pattern of thinning in these areas would suggest that walking is an important activity for understanding both the cause and treatment of osteoarthritis.
In Situ Measurement and Modeling of Human Cadaveric Soft Tissue Mechanical Properties for Use in Real Time Surgical Simulation
Authors: Lim Yi-Je , Deo Dhannanjay , De Suvranu
Published: March 2014

Development of a realistic surgery simulator that delivers high fidelity visual and haptic (force) feedback, based on the physical models of soft tissues, requires the use of empirical data on the mechanical behavior of intra-abdominal organs under the action of external forces. Measurement of mechanical properties of soft tissues on live human patients presents significant risks, making the use of cadavers a logical alternative. In this paper we present techniques of measuring and modeling the mechanical response of human cadaveric tissue for the purpose of developing a “virtual cadaver” model. The major contribution of this paper is the development of physics-based models of soft tissues that range from linear elastic models to nonlinear viscoelastic models which are efficient for application within the framework of a real time surgery simulator.
Synergistic and Additive Effects of Hydrostatic Pressure and Growth Factor Application on Engineered Articular Cartilage Constructs
Authors: Elder Benjamin D. , Athanasiou Kyriacos A.
Published: March 2014

It has previously been demonstrated that hydrostatic pressure (HP) enhances the biochemical properties of self-assembled articular cartilage constructs [1]. However, studies that systematically assess the effects of HP magnitude and frequency are lacking. Additionally, studies examining the combined effects of hydrostatic pressure and growth factors are limited. To this end, this study sought to test the hypotheses that static HP will have the greatest enhancement of construct biomechanical and biochemical properties, and that there will be additive or synergistic effects when combining growth factors and HP stimulation.
Numerical Study of Tumour Blood Perfusion Based on 3D Tumour Angiogenic Microvasculatures
Authors: Wu Jie , Long Quan , Xu Shixiong , Gao Hao , Padhani Anwar R.
Published: March 2014

The coupling of intravascular and interstitial flow is a distinct feature of tumour microcirculation, due to the high vessel permeability, the low osmotic pressure gradient as well as the absence of functional lymphatic system inside tumours. In this paper, a coupled mathematical model of tumour blood perfusion based on 3D angiogenic vasculatures is developed, which provides the link between microvasculature and interstitial space perfusion through the matrices describing the local vascular connection (3D matrix B) and density (3D matrix A), accordingly combines the intravascular and interstitial flow by vascular leaky terms. In addition, the compliance of tumour vessels, blood rheology with hematocritic distribution at branches is also considered. The microvascular network, on which the microcirculation calculation is carried out, is generated from a 3-dimensional 7-point model of tumour angiogenesis.
Optimization-Based Inverse Finite Element Analysis for Material Parameter Identification of a Biphasic Viscoelastic Hydrogel
Authors: Liu Kaifeng , Thomas Brian , Fryman J. Craig , Bischoff Jeff , Ovaert Timothy , Mason James
Published: March 2014

Hydrogels are a cross-linked network of polymer swollen with a liquid, and are promising replacements for diseased or damaged load bearing tissues such as articular cartilage [1]. Recently, a linear biphasic model, developed originally for cartilage [2], has been applied to characterize the mechanical behavior of hydrogels [3, 4]. However, the linear elastic assumption for the solid phase ignores the intrinsic viscoelasticity of the polymer network [3, 4]. Some attempts have been made in the literature to simulate hydrogels with a biphasic viscoelastic model using a self-developed finite element code [5]. This study is aimed at simulating hydrogels with a biphasic viscoelastic model and investigating an inverse finite element (FE) technique to identify material parameters of hydrogels via combined creep testing and FE modeling. Creep testing of hydrogels is simulated in the commercial software ABAQUS, which makes this approach easy to adapt to other test geometries. Material parameters are identified by fitting the FE results to the experimental results using an optimization method.
Quantifying Effects of Artery Shrinkage Using In Vivo MRI-Based 3D FSI Models for Carotid Atherosclerotic Plaques With Bifurcation
Authors: Huang Xueying , Yang Chun , Yuan Chun , Hatsukami Thomas , Liu Fei , Canton Gador , Zheng Jie , Woodard Pamela K. , Sicard Gregorio A. , Tang Dalin
Published: March 2014

Atherosclerotic vascular disease leads to changes of the arterial wall and lumen narrowing, and it is the No.1 killer in the western world. Magnetic resonance image (MRI)-based computational models with fluid-structure interactions (FSI) for atherosclerotic plaques have been introduced to perform mechanical analysis to quantify critical flow and stress/strain conditions related to plaque rupture which often leads directly to heart attack or stroke [2]. There are three groups of information needed as model input: plaque morphology, material properties, and flow conditions. Pre shrinkage-stretch process is used to recover the in vivo geometry from zero-stress state with associated initial conditions which are required to achieve building the computational model. An important issue for this process is how to determine zero stress state from in vivo plaque geometry. However, few publications can be found in the current literature about how to quantify human carotid artery shrinkage.
Permeability Calculations in Three-Dimensional Fiber Networks
Authors: Stylianopoulos T. , Yeckel A. , Derby J. J. , Luo X. J. , Shephard M. S. , Sander E. A. , Barocas V. H.
Published: March 2014

The study of creeping flow in fibrous media is of considerable interest in many biological and biomedical applications. There is little work, however, on permeability calculations in three-dimensional random networks. Computational power is now sufficient to calculate permeabilities directly by constructing artificial fiber networks and simulating flow through them. Even with today’s high-performance computers, however, such an approach would be infeasible for large simulations. It is therefore necessary to develop a correlation based on fiber volume fraction, radius and orientation, preferably by incorporating previous studies on isotropic or structured networks. In this work, the direct calculations were performed, using the finite element method, on networks with varying degrees of orientation, and combinations of results for flow parallel and perpendicular to a single fiber or an array thereof, using a volume averaging theory, were compared to the detailed analysis.
Residual Stress in the Mouse Brain
Authors: Xu Gang , Bayly Philip V. , Taber Larry A.
Published: March 2014

Proper folding of the cerebral cortex is critical to normal human brain function. The mechanisms of cortical folding, however, remain incompletely understood, although they have intrigued neuroscientists for more than a century. Clearly a biomechanical problem, cortical folding has been speculated to result from stresses induced by differential or constrained growth [1]. More recently, investigators have postulated that tension in neural axons of cerebral white matter causes specific folding patterns [2]. However, it is uncertain if sustained tension exists in axons in both the developing and mature brain.
Mitral Valve Annulus Tension
Authors: He Zhaoming , Bhattacharya Shamik
Published: March 2014

The mitral valve annulus is an anatomical structure joining the leaflets and left ventricle wall. It is divided into the fibrous annulus in the anteromedial section and the myocardium annulus in the posterolateral section, according to annulus histology. Two trigones are in the fibrous annulus. Mitral annulus supports leaflets in the valve coaptation and controls inflow hemodynamics during a cardiac cycle. When the mitral valve is fully open during diastole, inflow drag force on the leaflets and chordae pulls the leaflets approximately apically. As mitral valve leaflets coaptate during systole, trans-mitral pressure acts on the leaflets and induces leaflet tension which is transferred to the annulus and chordae. The leaflet tension at the annulus per unit length is defined as annulus tension (AT). Annulus dilatation is a mitral valve pathology that is related to AT and its interaction with the myocardium. Little is known about the detailed mechanism of annulus dilatation. But from mechanics standpoint, there are two possible mechanisms that change annulus size. AT pulls annulus towards the center of mitral valve orifice and is balanced by myocardium force on the annulus that pulls the annulus outward. Annulus size depends upon which force is predominant in annulus mechanics. It is hypothesized that the AT is one of the important mechanism to control annulus size. This hypothesis suggests that annulus size can be controlled by the AT and its interaction with the myocardium. We aim to understand annulus dilatation by the AT. The objective of the current study was to understand the tension transferred to the mitral annulus by the leaflets during the valve coaptation.
Ultra-Fast Vitrification of Murine Embryonic Stem Cells Using a Low Concentration of Cryoprotectants
Authors: He Xiaoming , Park Eric Y. H. , Fowler Alex , Yarmush Martin L. , Toner Mehmet
Published: March 2014

Effective cryopreservation of important mammalian cells and their derivatives is critical to the success of cell based medicine in 21st century [1]. There are currently two approaches to achieve cryopreservation of mammalian cells: conventional slow freezing and vitrification without ice formation. Although conventional slow freezing only requires a low relatively nontoxic concentration of cryoprotectants (1–2 M), it is always associated with cell injury due to ice formation and freeze concentration (i.e., solute effect) [2]. Cryopreservation by vitrification avoids ice formation all together. Existing protocols for vitrification, however, require a very high concentration of cryoprotectants (CPAs, generally more than 4M) that is usually toxic to most mammalian cells [3]. Therefore, it is of great interest to achieve vitrification using a low nontoxic concentration of cryoprotectants, which combines the advantages of the existing slow freezing and vitrification approaches while avoiding their shortcomings. In this study, we report the successful vitrification of murine embryonic stem (ES) cells at a low nontoxic level of cryoprotectants utilizing a thin walled (10μm) quartz microcapillary (outer diameter, 200μm). The ES cells post-vitrification retained high immediate viability, attachment efficiency and similar proliferation characteristic to fresh ES cells. Expression of markers characteristic to the ES cells suggests the ES cells retained the undifferentiated properties of pluripotent cells post-vitrification.
Diffuse Axonal Injury and Degradation in Mechanical Characteristics of Brain White Matter
Authors: Abolfathi Nabi , Naik Abhai , Sotudeh Mahdi , Karami Ghodrat , Ziejewski Mariusz
Published: March 2014

Diffuse Axonal Injury (DAI) can happen due to sudden motions of head and is one of the major causes of fatality and severe disabilities. To study DAI, any change in material characteristics of brain tissue post injury needs to be well understood. In this study, the focus will be on changes in the viscoelastic material properties of white mater in the brain due to DAI resulting in axonal disconnections. Using a micromechanics fibrous composite modeling for white mater, we have developed an algorithm to analyze the effect of discontinuity due to breakage of axons inside the surrounded matrix. Repeated unit cell (RUC) was assumed to represent the axonal distribution within the extracellular matrix. Relaxation test were conducted for characterization of the viscoelastic behavior. The result of this study provides a modeling technique for characterization of injured brain tissue in white mater and proposes necessity of including the appropriate post injury axonal mechanical properties. These findings can improve the understanding of injury from mechanical perspective and help in predicting vulnerability of any such injured tissue against further injuries.
Quantification of In Vivo Stresses in the Ovine Anterior Mitral Valve Leaflet
Authors: Krishnamurthy Gaurav , Itoh Akinobu , Bothe Wolfgang , Ennis Daniel B. , Swanson Julia C. , Kuhl Ellen , Miller D. Craig , Ingels Neil B.
Published: March 2014

Mitral valve (MV) disease affects millions worldwide. An important goal of present-day heart valve research is to create bioengineered tissue valves to replace diseased mitral valves, if it is judged that mitral repair will not be durable. The design of such valves will pivot on understanding the stresses acting in the native MV leaflets to design a bioprosthesis which will withstand these stresses. In order to quantify such stresses in vivo, we utilized radiopaque marker technology and performed an “inverse” finite element analysis of the resulting 4-D data to determine the material properties of the anterior MV leaflet in the beating ovine heart. We then used these material properties in a “forward” finite element analysis to estimate the stresses in the native anterior MV leaflet.
In Vivo Effects and Ex Vivo Characteristics Following Implantation of a Tissue Engineered Urethral Wrap
Authors: Haworth Donna J. , Miyazato Minoru , Furuta Akira , Kim Dae Kyung , Chew Douglas W. , Yoshimura Naoki , Chancellor Michael B. , Vorp David A.
Published: March 2014

Urethral dysfunction is a common complication of diabetes mellitus, spinal cord injury, vaginal childbirth, and pelvic trauma. Stress urinary incontinence (SUI) is the involuntary loss of urine due to the inability of the urethral sphincter to maintain a tight seal during the storage phase and is a condition that physically and emotionally affects 25 million American women annually [1]. There are currently several treatments for SUI including surgery, Kegel exercises, and electrical stimulation, each accompanied by limited effectiveness and/or complications [2–3]. We believe that regenerative medicine techniques, applied to the native urethra, may aid in improving the function and support of the diseased urethra. Thus, we have begun the development of a tissue engineered urethral wrap (TEUW) for placement as a cuff around the native urethra and integration with the host tissue. The goal of this work was to explore structural and mechanical effects following implantation of a TEUW.
Simulation of Stent Deployment in Patient-Specific Cerebral Aneurysm Models for Their Hemodynamics Analysis
Authors: Mut Fernando , Appanaboyina Sunil , Cebral Juan R.
Published: March 2014

Cerebral aneurysms are a mayor cause of hemorrhagic stroke which is a highly significant and devastating disease. Currently there is an increased interest in using endovascular devices for flow diversion such as stents, for treating intracranial aneurysms [1]. Several studies have proven that the geometry and position of the stent in its deployed state play a mayor role in the way the blood flow is diverted. The design of flow diverters and the selection of the most appropriate device for a given aneurysm require a computational model to study the changes in the blood flow patterns after stenting. In this paper an innovative methodology for virtual deployment of stents within patient-specific anatomical models is presented. One remarkable property of this technique is the ability to easily interchange different stent designs within the same model in order to perform fast comparative characterizations.
Effect of Cell-to-Surface Interaction on Freeze Tolerance and Osmotic Response of Cells
Authors: Yoshimori Takashi , Fukagawa Masaki , Takamatsu Hiroshi
Published: March 2014

Cryopreservation of tissues and organs, including artificial organs, could be one of the important steps in the medical service that brings the progress in the tissue engineering to realization. In this case, high viability of cryopreserved cells is critical to recovery after transplantation. In contrast, in the cryosurgery, which is expected to expand its application as a minimally invasive treatment of cancer, malignant cells should be destructed completely to prevent from recurrence. The appropriate freeze-thaw protocol is therefore needed to be established for cryopreservation or cryosurgery depending on specific type of tissues and organs. Although it is determined empirically, the underlying mechanism of cell injury by freezing has been explored for a long time to give a scientific basis of the process. The experiments with a cell suspension showed that the cell injury during slow freezing to a relatively higher sub-zero temperature was attributed to the mechanical stress from the extracellular ice, while the effect of elevated concentration of solutes became more crucial to cell damage at lower temperatures [1]. However, there are some studies that indicates the difference in the freeze tolerance between cell suspensions and attached monolayers, some of which indicated higher susceptibility of monolayers to freezing than cell suspension [2] and the other suggested reverse [3,4]. The goal of our study is thus to validate the difference in freezing injury between isolated cells and tissues that are more important in aforementioned applications and clarify the mechanism. We used cells adhered to a surface as a first simple model of cells in tissues. The cells adhered on a surface at low number density were used to highlight the effect of cell-to-surface interaction without cell-to-cell interactions. In the present study we first demonstrate that the survival of cells adhered on a surface is lower than those in the suspension after a freeze-thaw manipulation. Then the osmotic response to concentration increase was examined to clarify if the extent of dehydration is different between these two types of cells. The cells were observed by a laser confocal scanning microscope that allows real-time 3-D observation.
Different Approaches to the Choice of Coordinate System for Left-Ventricular FE-Mesh Generation
Authors: Choi Hon Fai , Wu Ming , D’hooge Jan , Rademakers Frank E. , Claus Piet
Published: March 2014

The modern in-vivo evaluation of cardiac patho-physiology requires the integration of different data on cardiac function, tissue characterization, perfusion etc. and aims at the extraction of relevant physiological parameters that combine these data. For these purposes, the use of finite element (FE) models is becoming an increasingly important part of cardiac analysis [1].
Shape Effects of Filaments Versus Spherical Particles in Flow and Drug Delivery
Authors: Discher Dennis E.
Published: March 2014

Interaction of spherical particles with cells and within animals has been studied extensively, but the effects of shape have received little attention. Here we use highly stable, block copolymer micelle assemblies known as filomicelles to compare the transport and trafficking of flexible filaments with spheres of similar chemistry.
Effect of Cytoskeletal Structure and Mechanics on Epithelial Cell Adhesion During Airway Reopening
Authors: Hallow K. Melissa , Ghadiali Samir N.
Published: March 2014

Patients suffering from acute respiratory distress syndrome (ARDS) require mechanical ventilation in order to maintain adequate gas exchange. However, ventilation can contribute to further lung damage through overdistension and/or the reopening of fluid-filled airways which causes epithelial cell (EpC) death and detachment and an upregulated inflammatory response [1]. While previous research has focused on minimizing the injurious mechanical forces generated during ventilation [2], an alternative approach is to alter the way that forces are transmitted from the cell surface to its structural elements (cell membrane, cytoskeleton, focal adhesions, cell-cell attachments). One way to alter force transmission is to alter the cell’s intrinsic biomechanical or biostructural properties. For example, our lab has previously shown that depolymerization of the actin cytoskeletal structure can reduce cell necrosis during airway reopening [3].
Energy-Based Failure Criterion in a Structural Model for Ligaments
Authors: Guo Zheying , De Vita Raffaella
Published: March 2014

Ligaments are bands of fibrous tissues that transmit loads between bones and support internal organs. Their main function is to guide and restrain joints’ motion in order to maintain their stability. Injuries to ligaments such as sprains are among the most common orthopedic injuries. The medical treatment varies with the severity of injury from the simple RICE (rest, ice, compression, elevation) rule to graft implantation. The choice between conservative treatment with no repair and surgical treatment with repair of the torn ligaments remains controversial among orthopedics.
Cellular Mechanotransduction Studies Using Microposts, Nanoposts, and Magnetic Posts
Authors: Sniadecki Nathan J.
Published: March 2014

Cells use mechanical forces as a means to probe and examine the physical properties of their microenvironment. They use this physical information to adapt their structure and regulate their migration, growth, and development. Using nanotechnology and microfabrication is a novel way to build measurement tools for quantitative studies into the role that mechanical forces have in cellular biology. Here, I describe our recent approaches using microposts, nanoposts, and magnetic microposts to reveal that how cells respond to external mechanical forces can be a key controller of cytoskeletal tension.
A Technique for Quantitative Characterization of Pulmonary Vascular Morphology and Application in a Normal Rat
Authors: Razavi Hedi , Zarafshar Shahrzad Y. , Xu Chengpei , Feinstein Jeffrey A. , Taylor Charles A.
Published: March 2014

Congenital heart defects are structural problems with the heart and/or major blood vessels which in the U.S. alone affect as many as 1.3 million people [1]. A common form of abnormality is a stenosis or narrowing of the pulmonary arteries. Chronic pulmonary artery stenosis may lead to differential lung growth and reduced cardiac performance. Treatment, however, may result in no significant improvements in flow distribution or pressure because of the properties of the vascular bed downstream of the stenosis.
Dynamic Control of Sliding Directions of Kinesin-Driven Microtubules With Rotating Electric Fields
Authors: Sugita Shukei , Sakamoto Naoya , Ohashi Toshiro , Sato Masaaki
Published: March 2014

Kinesins, biomolecular motors that move along microtubules (MTs) can potentially be utilized as an actuator in nanoscale transporting systems. Recent studies have reported inverted geometry in vitro, in which MTs randomly moved on kinesins fixed to substrates. To develop the transporting systems, one of key elements includes precise control of the direction of sliding MTs. One possible method is to utilize electric field (EF) to direct the MTs because MTs are negatively charged in neutral solutions [1,2]. For example, MTs have been shown to orient to the direction of uniaxially or biaxially applied EFs [3,4]. However, for a reliable transporting system, further studies are still required to control the direction of sliding MTs dynamically and effectively. In our previous study [5], we applied EF to MTs in random direction and showed that the rate of change in angle (angular velocity) was proportional to the sin of the angle between the directions of MTs and the generated electrophoretic force. The result indicates that it is most efficient to continuously apply EF perpendicular to the direction of MTs. In this study, the direction of sliding MTs was dynamically controlled with EF, particularly demonstrating a circular movement of MTs.
Correlating Leaflet Design and Closing Dynamics With Turbulent Flows Near Bileaflet Mechanical Heart Valves
Authors: Herbertson Luke H. , Deutsch Steven , Manning Keefe B.
Published: March 2014

Significant advances have been made in the field of heart valve replacement, especially in terms of anticoagulation therapy and valve design. Mechanical heart valves have been successfully implanted for decades to replace irreparable diseased or failing native valves. However, heart valve patients remain more susceptible to hemolysis and thrombosis [1]. In this experimental study, we focus on the closing dynamics of bileaflet mechanical heart valves to better understand the roles that valve design and environmental conditions have on the local fluid mechanics.
Validation of 1D Model of the Systemic Arterial Tree Including the Cerebral Circulation
Authors: Reymond Philippe , Merenda Fabrice , Perren Fabienne , Rüfenacht Daniel , Stergiopulos Nikos
Published: March 2014

The aim of this study is to develop a distributed model of the entire systemic arterial tree, coupled to a heart model and including a detailed description of the cerebral arteries. Distributed models of the arterial tree have been studied extensively in the past (Avolio [1], Stergiopulos et al [2], Westerhof et al [3]), however, no model has been developed so far that offers a physiologically relevant coupling to the heart and includes the entire cerebral arterial tree.
Toward Patient-Specific Cervical Spine Functional Spinal Unit FE Modeling and Validation
Authors: Kallemeyn Nicole A. , Tadepalli Srinivas C. , Shivanna Kiran H. , Grosland Nicole M.
Published: March 2014

Preventive measures and treatment modalities for correcting spinal disorders benefit significantly from advancements aimed at understanding the biomechanics of the human spine in the normal as well as altered states [1]. Finite element (FE) modeling is a useful tool to understand the behavior of the cervical spine under such conditions. In order for an FE model to yield clinically relevant results, the geometry must be as realistic as possible [2], in addition to incorporating accurate material properties and boundary conditions. The spine’s anatomy is very complex, rendering it difficult to acquire accurate geometrical representations for FE analysis. Many meshes in the literature are based on simplified or idealized geometries, or are assumed to be symmetric about the sagittal plane [3]. Traditional meshing techniques are time consuming and tedious, and lack remeshing capabilities [2]. The ability to create hexahedral cervical spine FE models on a patient-specific basis is a desirable task because it can account for variations in anatomy, as well as provide insight for surgical planning/treatment. Our mesh development methods improve on existing multi-block meshing methods to make this possible. We have created a C45 functional spinal unit (FSU) using these techniques, and to date have validated it by comparison to data presented in the literature.
Simulated Deep Flexion With Muscle Loading: Whole Leg Versus Knee Kinematics
Authors: Reeve Amber N. , Clary Chadd W. , Mane Amit M. , Maletsky Lorin P.
Published: March 2014

Many activities of daily living during work, exercise, religious worship, and hobbies require deep knee flexion. Activities such as rising from a low chair or getting into or out of a bath require between 100° and 160° of knee flexion [1]. Other activities such as kneeling or squatting to pick an item off the ground can be difficult with a limited range of motion. Beside deep knee flexion being important for daily living activities, it is essential in non-Western cultures that commonly sit in deep knee-bending positions. In vitro studies looking at knee function often focus solely on the knee joint, ignoring the effect of the muscle, ligament, and tendon constraints of the ankle, and simplifying or neglecting muscle loads. The effects of these assumptions on kinematics are unknown. The purpose of this study was to compare a squatting activity for: 1) whole leg versus knee specimens, and 2) different combinations of quadriceps and hamstrings loading.