Cardiac myosin motor deficits are associated with left ventricular dysfunction in human ischemic heart failure.

During ischemic heart failure (IHF), cardiac muscle contraction is typically impaired, though the molecular changes within the myocardium are not fully understood. Thus, we aimed to characterize the biophysical properties of cardiac myosin in IHF. Cardiac tissue was harvested from 10 age-matched males, either with a history of IHF or nonfailing (NF) controls that had no history of structural or functional cardiac abnormalities. Clinical measures before cardiac biopsy demonstrated significant differences in measures of ejection fraction and left ventricular dimensions. Myofibrils and myosin were extracted from left ventricular free wall cardiac samples. There were no changes in myofibrillar ATPase activity or calcium sensitivity between groups. Using isolated myosin, we found a 15% reduction in the IHF group in actin sliding velocity in the in vitro motility assay, which was observed in the absence of a myosin isoform shift. Oxidative damage (carbonylation) of isolated myosin was compared, in which there were no significant differences between groups. Synthetic thick filaments were formed from purified myosin and the ATPase activity was similar in both basal and actin-activated conditions (20 µM actin). Correlation analysis and Deming linear regression were performed between all studied parameters, in which we found statistically significant correlations between clinical measures of contractility with molecular measures of sliding velocity and ELC carbonylation. Our data indicate that subtle deficits in myosin mechanochemical properties are associated with reduced contractile function and pathological remodeling of the heart, suggesting that the myosin motor may be an effective pharmacological intervention in ischemia.NEW & NOTEWORTHY Ischemic heart failure is associated with impairments in contractile performance of the heart. This study revealed that cardiac myosin isolated from patients with ischemic heart failure had reduced mechanical activity, which correlated with the impaired clinical phenotype of the patients. The results suggest that restoring myosin function with pharmacological intervention may be a viable method for therapeutic intervention.

A numerical study of aortic flow stability and comparison with in vivo flow measurements.

The development of an engineering transitional turbulence model and its subsequent evaluation and validation for some diseased cardiovascular flows have been suggestive of its likely utility in normal aortas. The existence of experimental data from human aortas, acquired in the early 1970s with catheter-mounted hot film velocimeters, provided the opportunity to compare the performance of the model on such flows. A generic human aorta, derived from magnetic resonance anatomical and velocity images of a young volunteer, was used as the basis for varying both Reynolds number (Re) and Womersley parameter (α) to match four experimental data points from human ascending aortas, comprising two with disturbed flow and two with apparently undisturbed flow. Trials were made with three different levels of inflow turbulence intensity (Tu) to find if a single level could represent the four different cases with 4000 < Re < 10,000 and 17 < α < 26. A necessary boundary condition includes the inflow "turbulence" level, and convincing results were obtained for all four cases with inflow Tu = 1.0%, providing additional confidence in the application of the transitional model in flows in larger arteries. The Reynolds-averaged Navier-Stokes (RANS)-based shear stress transport (SST) transitional model is capable of capturing the correct flow state in the human aorta when low inflow turbulence intensity (1.0%) is specified.

Assessment of energy requirement for the retinal arterial network in normal and hypertensive subjects.

The retinal arterial network structure can be altered by systemic diseases such as hypertension and diabetes. In order to compare the energy requirement for maintaining retinal blood flow and vessel wall metabolism between normal and hypertensive subjects, 3D hypothetical models of a representative retinal arterial bifurcation were constructed based on topological features derived from retinal images. Computational analysis of blood flow was performed, which accounted for the non-Newtonian rheological properties of blood and peripheral vessel resistance. The results suggested that the rate of energy required to maintain the blood flow and wall metabolism is much lower for normal subjects than for hypertensives, with the latter requiring 49.2% more energy for an entire retinal arteriolar tree. Among the several morphological factors, length-to-diameter ratio was found to have the most significant influence on the overall energy requirement.

Comparison of LES of steady transitional flow in an idealized stenosed axisymmetric artery model with a RANS transitional model.

In this study, two different turbulence methodologies are investigated to predict transitional flow in a 75% stenosed axisymmetric experimental arterial model and in a slightly modified version of the model with an eccentric stenosis. Large eddy simulation (LES) and Reynolds-averaged Navier-Stokes (RANS) methods were applied; in the LES simulations eddy viscosity subgrid-scale models were employed (basic and dynamic Smagorinsky) while the RANS method involved the correlation-based transitional version of the hybrid k-ε/k-ω flow model. The RANS simulations used 410,000 and 820,000 element meshes for the axisymmetric and eccentric stenoses, respectively, with y(+) less than 2 viscous wall units for the boundary elements, while the LES used 1,200,000 elements with y(+) less than 1. Implicit filtering was used for LES, giving an overlap between the resolved and modeled eddies, ensuring accurate treatment of near wall turbulence structures. Flow analysis was carried out in terms of vorticity and eddy viscosity magnitudes, velocity, and turbulence intensity profiles and the results were compared both with established experimental data and with available direct numerical simulations (DNSs) from the literature. The simulation results demonstrated that the dynamic Smagorinsky LES and RANS transitional model predicted fairly comparable velocity and turbulence intensity profiles with the experimental data, although the dynamic Smagorinsky model gave the best overall agreement. The present study demonstrated the power of LES methods, although they were computationally more costly, and added further evidence of the promise of the RANS transition model used here, previously tested in pulsatile flow on a similar model. Both dynamic Smagorinsky LES and the RANS model captured the complex transition phenomena under physiological Reynolds numbers in steady flow, including separation and reattachment. In this respect, LES with dynamic Smagorinsky appeared more successful than DNS in replicating the axisymmetric experimental results, although inflow conditions, which are subject to caveats, may have differed. For the eccentric stenosis, LES with Smagorinsky coefficient of 0.13 gave the closest agreement with DNS despite the known shortcomings of fixed coefficients. The relaminarization as the flow escaped the influence of the stenosis was amply demonstrated in the simulations, graphically so in the case of LES.

Analysis of flow patterns in a patient-specific aortic dissection model.

Aortic dissection is the most common acute catastrophic event affecting the thoracic aorta. The majority of patients presenting with an uncomplicated type B dissection are treated medically, but 25% of these patients develop subsequent aneurysmal dilatation of the thoracic aorta. This study aimed at gaining more detailed knowledge of the flow phenomena associated with this condition. Morphological features and flow patterns in a dissected aortic segment of a presurgery type B dissection patient were analyzed based on computed tomography images acquired from the patient. Computational simulations of blood flow in the patient-specific model were performed by employing a correlation-based transitional version of Menter's hybrid k-epsilon/k-omega shear stress transport turbulence model implemented in ANSYS CFX 11. Our results show that the dissected aorta is dominated by locally highly disturbed, and possibly turbulent, flow with strong recirculation. A significant proportion (about 80%) of the aortic flow enters the false lumen, which may further increase the dilatation of the aorta. High values of wall shear stress have been found around the tear on the true lumen wall, perhaps increasing the likelihood of expanding the tear. Turbulence intensity in the tear region reaches a maximum of 70% at midsystolic deceleration phase. Incorporating the non-Newtonian behavior of blood into the same transitional flow model has yielded a slightly lower peak wall shear stress and higher maximum turbulence intensity without causing discernible changes to the distribution patterns. Comparisons between the laminar and turbulent flow simulations show a qualitatively similar distribution of wall shear stress but a significantly higher magnitude with the transitional turbulence model.

Curvature and tortuosity of the superficial femoral artery: a possible risk factor for peripheral arterial disease.

Atherosclerosis in the superficial femoral artery (SFA) resulting in peripheral arterial disease is more common in men than women and shows a predilection for the region of the adductor canal. Blood flow patterns are related to development of atherosclerosis, and we investigated if curvature and tortuosity of the femoral artery differed between young men and women and if differences resulted in adverse flow patterns. Magnetic resonance imaging (MRI) and computational fluid dynamics (CFD) were combined in 18 young adult volunteers (9 men) to assess the relationship of flow features to likely sites of future atherosclerosis formation. Subjects underwent MRI of the right SFA, three-dimensional vascular geometry was reconstructed, and measures of tortuosity and curvature were calculated. Tortuosity and curvature were significantly greater for men than women, and this was related to increased body surface area, body mass index, or weight in men. In both sexes, "tortuosity" increased from the midthigh to the popliteal fossa. The greatest curvature was found within the distal quarter of the SFA. CFD modeling was undertaken on MRI-based reconstructions of the SFA. Wall shear stresses (WSS) were extracted from the computations. WSS showed greater spatial variation in the men than in the women, and the men exhibited lower mean WSS. These data indicate that sex differences related to body size and anatomical course of the femoral artery may contribute to the enhanced risk of focal atherosclerosis in the adductor canal.

Aortic flow patterns before and after personalised external aortic root support implantation in Marfan patients.

Implantation of a personalised external aortic root support (PEARS) in the Marfan aorta is a new procedure that has emerged recently, but its haemodynamic implication has not been investigated. The objective of this study was to compare the flow characteristics and hemodynamic indices in the aorta before and after insertion of PEARS, using combined cardiovascular magnetic resonance imaging (CMR) and computational fluid dynamics (CFD). Pre- and post-PEARS MR images were acquired from 3 patients and used to build patient-specific models and upstream flow conditions, which were incorporated into the CFD simulations. The results revealed that while the qualitative patterns of the haemodynamics were similar before and after PEARS implantation, the post-PEARS aortas had slightly less disturbed flow at the sinuses, as a result of reduced diameters in the post-PEARS aortic roots. Quantitative differences were observed between the pre- and post-PEARS aortas, in that the mean values of helicity flow index (HFI) varied by -10%, 35% and 20% in post-PEARS aortas of Patients 1, 2 and 3, respectively, but all values were within the range reported for normal aortas. Comparisons with MR measured velocities in the descending aorta of Patient 2 demonstrated that the computational models were able to reproduce the important flow features observed in vivo.

PCR production of a digoxigenin-labeled probe for the detection of human cytomegalovirus in tissue sections.

In situ hybridization (ISH) provides a means for identifying viral genomes in the context of tissue pathology. We have developed a specific and sensitive ISH probe for the detection of cytomegalovirus (CMV) DNA in formalin-fixed, paraffin-embedded tissue sections. Digoxigenin-11-dUTP was incorporated into a 435-base pair fragment of the CMV Major Immediate Early (MIE) gene with use of the polymerase chain reaction (PCR). Hybridized probe was detected by reaction with antidigoxigenin antibody coupled to alkaline phosphatase and chromogenic substrates. This method has detected CMV infection in routine clinical specimens from a variety of tissue types, including colon, kidney, liver, and stomach. Infection in cells with and without characteristic inclusions is revealed with this probe. The background is so low that single infected cells are detected unambiguously. No cross-hybridization was observed with cells infected with other viruses of Herpesviridae. This approach may be useful for producing probes for the detection of other viral genomes in tissue sections.

Mutation of p53 in squamous cell cancer of the head and neck: relationship to tumor cell proliferation.

Rapid proliferation of squamous cell carcinomas of the head and neck (SCCHN) during therapy may contribute to treatment failure. We have investigated the presence of p53 abnormalities in patients with SCCHN as a correlate of proliferation rate and other pathologic and clinical variables. p53 Mutation, as determined by polymerase chain reaction and single-strand conformation polymorphism analysis of microdissected frozen sections of tumor biopsies, was significantly associated with a high labeling index, as determined by in vivo infusion of IUdR and BrdU (P = 0.017). p53 Protein expression was detected by immunohistochemistry with two different antibodies, followed by quantitative image analysis. Many cases exhibited strong p53 protein expression in the absence of mutations within the conserved region of the gene, and expression was not related to proliferation. The presence of p53 mutations was related to tumor differentiation in this group of patients.

Regulators of proliferation and apoptosis in carcinoma of the larynx.

Expression of interrelated gene products regulating cell proliferation and apoptosis may be disordered in squamous cell carcinoma (SCC) of the larynx compared with normal squamous mucosa. Certain of these abnormalities, alone or in combination, may be of prognostic significance in low-stage carcinomas of the larynx. A retrospective study of archival material was made. Expression of the Bcl-2 family of apoptosis-related genes (bcl-2, bcl-X, mcl-1, and bax) and the proliferation- and apoptosis-related genes p53 and cyclin D-1 were determined in 40 low-T-stage laryngeal carcinomas and in uvular epithelium from patients without SCC. Among the antiapoptotic members of the Bcl-2 family, Bcl-X and Mcl-1 showed more intense and widespread staining than Bcl-2 itself in both normal squamous mucosa and SCC. The well-ordered expression patterns of Bcl-2-related proteins found in normal epithelium were lost in SCC, and patterns of expression varied widely among individual tumors. Also, mean expression levels for Bax and cyclin D-1 were significantly lower than in normal epithelium (P = .036 and P = .009, respectively), whereas expression of p53 was higher in tumors (P = .034). Expression of Bcl-X and Mcl-1 was greater in poorly differentiated than in well-differentiated tumors (P = .014 and P = .031, respectively). No associations were seen between marker expression patterns and clinical outcome in this group of patients. Bcl-x and Mcl-1 appear to be the most abundantly expressed antiapoptotic proteins of the Bcl-2 family in both normal squamous mucosa and SCC of the larynx. Multiple genes regulating proliferation and apoptosis are expressed abnormally in laryngeal SCC compared with normal epithelium. In particular, loss or measurable decrease in expression of the proapoptotic protein Bax in tumors may contribute to the deranged growth control of SCC. Further study is needed to evaluate the prognostic significance of particular patterns of disordered expression of proteins regulating proliferation and apoptosis in SCC of different head and neck sites.

Tumor angiogenesis and p53 mutations: prognosis in head and neck cancer.

OBJECTIVES: To assess how p53 gene mutations and microvessel density (MVD) may be used as prognostic markers for the study and management of head and neck squamous cell carcinomas and to investigate putative associations between p53 gene mutations and MVD and the relationship of these factors to tumor response to radiotherapy and/or chemotherapy at 6 weeks. PATIENTS AND DESIGN: Thirty-nine patients with squamous cell carcinoma of the head and neck, stages I to IV, who were examined at Rush-Presbyterian-St Luke's Medical Center, Chicago, Ill, and its affiliated hospitals between 1993 and 1995 were monitored. Mutations in the p53 gene were identified by microdissection of tumor cells on frozen sections, followed by single-strand conformation polymorphism analysis of the products of polymerase chain reaction amplification of exons 5 to 9. The microvessels were immunostained with monoclonal antibodies to factor VIII and/or CD31. Microvessel counts were done by 2 investigators blinded to each other's counts and to the p53 gene status. Intratumoral or peritumoral microvascular "hot spots" were assessed and counts were done with an ocular grid in 3 x 200 fields of hot spots by each investigator. The mean of the highest values was considered. Statistical analysis was done with the Wilcoxon rank sum test, the log-rank test, and proportional hazard models. RESULTS: Of the 39 patients, 13 had mutations in exons 5 to 9. Mutations in the p53 gene were associated with unfavorable overall (P=.003) and disease-free (P=.02) survival. A strong inverse relationship was seen between MVD and p53 mutations (P=.01). No statistically significant relationship was seen between mean MVD and overall and disease-free survival. The response to therapy differed significantly (P=.03) by p53 mutations, whereas there was no statistical significance with MVD counts. CONCLUSION: In this study a strong inverse relationship was seen between MVD and p53 mutations. p53 Mutations in exons 5 through 9 were associated with unfavorable survival, whereas MVD showed no association with survival.

Ultrasound image-based computer model of a common carotid artery with a plaque.

Ultrasound scans were acquired from a common carotid artery in a patient with an early atherosclerotic plaque forming a mild asymmetrical stenosis. The 3D vascular geometry of the diseased arterial segment was reconstructed from a series of 2D cross-sectional images, and computational meshes for the flow and wall domains were developed. Numerical flow simulations incorporating coupled fluid-solid interaction were implemented using flow and pressure waveforms measured in vivo. The effects of wall distensibility were investigated by comparing the predictions obtained with different wall compliance, one with 'natural' compliance and another with a stiffer wall. Limited flow separation was predicted in the post-stenotic zone. The non-uniform thickness of the diseased wall restricted the wall motion locally and re-distributed the stress, giving raised concentrations at the plaque shoulders.

Predicting flow in aortic dissection: comparison of computational model with PC-MRI velocity measurements.

Aortic dissection is a life-threatening process in which the weakened wall develops a tear, causing separation of wall layers. The dissected layers separate the original true aortic lumen and a newly created false lumen. If untreated, the condition can be fatal. Flow rate in the false lumen is a key feature for false lumen patency, which has been regarded as one of the most important predictors of adverse early and later outcomes. Detailed flow analysis in the dissected aorta may assist vascular surgeons in making treatment decisions, but computational models to simulate flow in aortic dissections often involve several assumptions. The purpose of this study is to assess the computational models adopted in previous studies by comparison with in vivo velocity data obtained by means of phase-contrast magnetic resonance imaging (PC-MRI). Aortic dissection geometry was reconstructed from computed tomography (CT) images, while PC-MRI velocity data were used to define inflow conditions and to provide distal velocity components for comparison with the simulation results. The computational fluid dynamics (CFD) simulation incorporated a laminar-turbulent transition model, which is necessary for adequate flow simulation in aortic conditions. Velocity contours from PC-MRI and CFD in the two lumens at the distal plane were compared at four representative time points in the pulse cycle. The computational model successfully captured the complex regions of flow reversal and recirculation qualitatively, although quantitative differences exist. With a rigid wall assumption and exclusion of arch branches, the CFD model over-predicted the false lumen flow rate by 25% at peak systole. Nevertheless, an overall good agreement was achieved, confirming the physiological relevance and validity of the computational model for type B aortic dissection with a relatively stiff dissection flap.

Computational analysis of oxygen transport in the retinal arterial network.

PURPOSE: The retina has a high oxygen consumption, making it particularly vulnerable to vascular insults, impairing oxygen and nutrient supply. The aim of this study was to develop a detailed computational model for quantitative analysis of blood flow and oxygen transport in physiologically realistic retinal arterial networks. Such a model will allow us to examine the effect of topological changes in retinal vasculature on hemodynamics and oxygen distribution in the retinal circulation. MATERIALS AND METHODS: The Navier-Stokes equations for blood flow and the convection-diffusion equation for oxygen transfer were solved numerically to obtain detailed blood flow and oxygen distribution patterns in a retinal arterial tree. The geometrical outlines of the central retinal artery and its major branches were extracted from retinal images acquired from a healthy young adult by a Zeiss FF450+ fundus camera. The reconstructed subject-specific retinal arterial network geometry was combined with a structured tree model for the distal peripheral vessels. The non-Newtonian rheological properties of blood were incorporated by using an empirical viscosity model to account for the Fahraeus-Lindqvist effect. RESULTS: The model predicted pressure drops in the range of 11-14.6 mmHg between the inlet and outlets of the reconstructed network and non-uniform oxygen tension, which varied with the vessel diameter and distance from the optic disc. The mean oxygen saturation in retinal arteries was 93.1% for vessels larger than 50 mum in diameter and 82.2% for smaller arterioles. CONCLUSIONS: Our numerical results are in good agreement with in vivo measurements reported in the literature, demonstrating the potential of our model for prediction of oxygen distribution and intravascular oxygen tension profiles in the retinal arterial network. This paves the way for investigating the effects of parameter variation, simulating cases not available from experimental studies.

Computational analysis of oxygen transport in a patient-specific model of abdominal aortic aneurysm with intraluminal thrombus.

Abdominal aortic aneurysm (AAA) is a degenerative disease in which the afflicted person suffers from a localised dilatation of the abdominal aorta. Intraluminal thrombus (ILT), which is present in approximately 75% of all AAAs, plays an important role in the progression of the disease. It has been suggested that ILT may attenuate oxygen diffusion to the aortic wall, resulting in further degeneration and weakening of the wall. Previous numerical studies using idealised AAA models have shown the effect of ILT thickness on oxygen diffusion, but patient-specific studies of oxygen transport incorporating convection, diffusion and reaction from the lumen to AAA wall are lacking. In the present study, a coupled fluid-thrombus-wall model was developed to simulate oxygen transport in a patient-specific AAA containing ILT. Blood flow in the lumen was governed by the Navier-Stokes equations and oxygen transfer was described by the convection-diffusion equation in the lumen, diffusion equation in the thrombus, and diffusion-reaction equation in the wall. A parametric study was performed to evaluate the sensitivity of numerical predictions to oxygen diffusivity in ILT and adventitial oxygen concentration. The results not only provide further support to previous findings that the presence of ILT may significantly impair oxygen transfer from blood to the aortic wall, but also demonstrate that adventitial oxygen concentration has a profound effect on oxygen concentration in the wall, and that the oxygen supply from the lumen to the wall can be reduced by 80% if the ILT thickness is greater than 5 mm.

The effect of dynamic vessel motion on haemodynamic parameters in the right coronary artery: a combined MR and CFD study.

Human right coronary artery (RCA) haemodynamics is investigated using computational fluid dynamics (CFD) based on subject-specific information from magnetic resonance (MR) acquisitions. The dynamically varying vascular geometry is reconstructed from MR images, incorporated in CFD in conjunction with pulsatile flow conditions obtained from MR velocity mapping performed on the same subject. The effects of dynamic vessel motion on instantaneous and cycle-averaged haemodynamic parameters, such as wall shear stress (WSS), time-averaged WSS (TAWSS) and oscillatory shear index (OSI), are examined by comparing an RCA model with a time-varying geometry and those with a static geometry, corresponding to nine different time-points in the cardiac cycle. The results show that the TAWSS is similar for the dynamic and static wall models, both qualitatively and quantitatively (correlation coefficient 0.89-0.95). Conversely, the OSI shows much poorer correlations (correlation coefficient 0.38-0.60), with the best correspondence being observed with the static models constructed from images acquired in late diastole (at t = 0 and 800 ms, the cardiac cycle is 900 ms). These findings suggest that neglecting dynamic motion of the RCA is acceptable if TAWSS is the primary focus but may result in underestimation of haemodynamic parameters related to the oscillatory nature of the blood flow.

Analysis of flow disturbance in a stenosed carotid artery bifurcation using two-equation transitional and turbulence models.

In this study, newly developed two-equation turbulence models and transitional variants are employed for the prediction of blood flow patterns in a diseased carotid artery where the growth, progression, and structure of the plaque at rupture are closely linked to low and oscillating wall shear stresses. Moreover, the laminar-turbulent transition in the poststenotic zone can alter the separation zone length, wall shear stress, and pressure distribution over the plaque, with potential implications for stresses within the plaque. Following the validation with well established experimental measurements and numerical studies, a magnetic-resonance (MR) image-based model of the carotid bifurcation with 70% stenosis was reconstructed and simulated using realistic patient-specific conditions. Laminar flow, a correlation-based transitional version of Menter's hybrid k-epsilon/k-omega shear stress transport (SST) model and its "scale adaptive simulation" (SAS) variant were implemented in pulsatile simulations from which analyses of velocity profiles, wall shear stress, and turbulence intensity were conducted. In general, the transitional version of SST and its SAS variant are shown to give a better overall agreement than their standard counterparts with experimental data for pulsatile flow in an axisymmetric stenosed tube. For the patient-specific case reported, the wall shear stress analysis showed discernable differences between the laminar flow and SST transitional models but virtually no difference between the SST transitional model and its SAS variant.