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The dialysis catheter indwelling in human bodies has a high risk of inducing thrombus and stenosis. Biomechanical research showed that such physiological complications are triggered by the wall shear stress of the vascular vessel. This study aimed to assess the impact of CVC implantation on central venous haemodynamics and the potential alterations in the haemodynamic environment related to thrombus development. The SVC structure was built from the images from computed tomography. The blood flow was calculated using the Carreau model, and the fluid domain was determined by CFD. The vascular wall and the CVC were computed using FEA. The elastic interaction between the vessel wall and the flow field was considered using FSI simulation. With consideration of the effect of coupling, it was shown that the catheter vibrated in the vascular systems due to the periodic variation of blood pressure, with an amplitude of up to 10% of the vessel width. Spiral flow was observed along the catheter after CVC indwelling, and recirculation flow appeared near the catheter tip. High OSI and WSS regions occurred at the catheter tip and the vascular junction. The arterial lumen tip had a larger effect on the WSS and OSI values on the vascular wall. Considering FSI simulation, the movement of the catheter inside the blood flow was simulated in the deformable vessel. After CVC indwelling, spiral flow and recirculation flow were observed near the regions with high WSS and OSI values. [ABSTRACT FROM AUTHOR]

The deformability of blood vessels in one‐dimensional blood flow models is typically described through a pressure‐area relation, known as the tube law. The most used tube laws take into account the elastic and viscous components of the tension of the vessel wall. Accurately parametrizing the tube laws is vital for replicating pressure and flow wave propagation phenomena. Here, we present a novel mathematical‐property‐preserving approach for the estimation of the parameters of the elastic and viscoelastic tube laws. Our goal was to estimate the parameters by using ovine and human in vitro data, while constraining them to meet prescribed mathematical properties. Results show that both elastic and viscoelastic tube laws accurately describe experimental pressure‐area data concerning both quantitative and qualitative aspects. Additionally, the viscoelastic tube law can provide a qualitative explanation for the observed hysteresis cycles. The two models were evaluated using two approaches: (i) allowing all parameters to freely vary within their respective ranges and (ii) fixing some of the parameters. The former approach was found to be the most suitable for reproducing pressure‐area curves. [ABSTRACT FROM AUTHOR]

Objectives: Intrapulpal calcifications can occur in the dental pulp of patients with diabetes. We focused on the association between ectopic calcifications in the dental pulp and advanced glycation end products (AGEs) in Spontaneously Diabetic Torii (SDT)‐fatty rats, an obese type 2 diabetic rat model, to determine the mechanism of calcification with pulp stone in the dental pulp. Materials and Methods: Pathologic calcification in the dental pulp of SDT‐fatty rats was observed using electron microscopy and immunohistochemical analysis. Moreover, mechanical analysis of periapical region of molar tooth against occlusal force was performed. Results: In SDT‐fatty rats, pathogenic pulpal calcifications occurred during blood glucose elevation after 6 weeks, and granular calcification was observed in the dental pulp after 11 weeks. Pentosidine, a major AGE, and the receptor for AGEs were strongly expressed in the dental pulp of SDT‐fatty rats. S100A8, TNF‐α, and IL‐6 also showed positive response in the dental pulp of the SDT‐fatty rat, which indicated pulpal inflammation. Blood flow disorder and hypoxic dental pulp cells were also observed. In silico simulation, strain from occlusal force concentrates on the root apex. Conclusions: Glycation makes blood vessels fragile, and occlusal forces damage the vessels mechanically. These are factors for intrapulpal calcification of diabetes. [ABSTRACT FROM AUTHOR]

The reconstruction of blood velocity in a vessel from contrast enhanced x‐ray computed tomography projections is a complex inverse problem. It can be formulated as reconstruction problem with a partial differential equation constraint. A solution can be estimated with the a variational adjoint method and proper orthogonal decomposition (POD) basis. In this work, we investigate new inversion approaches based on PODs coupled with deep learning methods. The effectiveness of the reconstruction methods is shown with simulated realistic stationary blood flows in a vessel. The methods outperform the reduced adjoint method and show large speed‐up at the online stage. [ABSTRACT FROM AUTHOR]

Prediction of blood cell flow is known as the difficult research by reason of the complexity of blood vessel. In this study, considering the complex structure of blood vessels, a mechanical model for red blood cell (RBC) based on unstructured grid has been established to study the flow characteristics of RBCs in complex blood vessels. In the model, the strain‐energy function by Skalak is employed to model the shear elasticity and surface‐area conservation of the membrane, and the hinge spring is used to describe the forces originating from local bending of the membrane. The immersed boundary method is utilized to couple the interphase force. Using the model, the stretching test of RBC is compared with the experiment data, and the good agreement verified the validation of the present model. The morphology of red blood cell and the blood viscosity in micro‐vessel are studied. RBCs move with a symmetric shape (parachute shape) in small blood vessels, and the buckling instability is observed when the RBC flow slowly through a micro‐vessel or a converging–diverging capillary. When the vessel diameter is around 10 μm, the reverse Fahraeus‐Lindqvist effect is presented. The blood apparent viscosity shows linear increase with the blood hematocrit. In addition, Malaria infection can make the RBC deformability decreased and the blood apparent viscosity increased. [ABSTRACT FROM AUTHOR]

The article discusses Raynaud's phenomenon, a medical condition characterized by the constriction of small arterial vessels, resulting in reduced blood flow to the extremities. The condition is often triggered by exposure to cold or stressful conditions and primarily affects acral areas such as fingers and toes. The symptoms include numbness, tingling, discoloration, and, in severe cases, gangrene. Despite advancements in understanding the condition, there is still no effective treatment. The article also mentions recent research on vasomotion and the regulation of blood vessel tone in various vascular beds. Additionally, it highlights a genetic predisposition to Raynaud's phenomenon and proposes individual shear rate therapy as a potential non-invasive treatment option. The authors emphasize the need for further research and improved treatment options for patients with Raynaud's phenomenon. [Extracted from the article]

New Findings: What is the central question of this study?High‐intensity interval exercise (HIIE) is recommended for its favourable haemodynamic stimulation, but excessive haemodynamic fluctuations may stress the brain: is the cerebral vasculature protected against exaggerated systemic blood flow fluctuation during HIIE?What is the main finding and its importance?Time‐ and frequency‐domain indices of aortic–cerebral pulsatile transition were lowered during HIIE. The findings suggest that the arterial system to the cerebral vasculature may attenuate pulsatile transition during HIIE as a defence mechanism against pulsatile fluctuation for the cerebral vasculature. High‐intensity interval exercise (HIIE) is recommended because it provides favourable haemodynamic stimulation, but excessive haemodynamic fluctuations may be an adverse impact on the brain. We tested whether the cerebral vasculature is protected against systemic blood flow fluctuation during HIIE. Fourteen healthy men (age 24 ± 2 years) underwent four 4‐min exercises at 80–90% of maximal workload (Wmax) interspaced by 3‐min active rest at 50–60% Wmax. Transcranial Doppler measured middle cerebral artery blood velocity (CBV). Systemic haemodynamics (Modelflow) and aortic pressure (AoP, general transfer function) were estimated from an invasively recorded brachial arterial pressure waveform. Using transfer function analysis, gain and phase between AoP and CBV (0.39–10.0 Hz) were calculated. Stroke volume, aortic pulse pressure and pulsatile CBV increased during exercise (time effect: P < 0.0001 for all), but a time‐domain index of aortic–cerebral pulsatile transition (pulsatile CBV/pulsatile AoP) decreased throughout the exercise bouts (time effect: P < 0.0001). Furthermore, transfer function gain reduced, and phase increased throughout the exercise bouts (time effect: P < 0.0001 for both), suggesting the attenuation and delay of pulsatile transition. The cerebral vascular conductance index (mean CBV/mean arterial pressure; time effect: P = 0.296), an inverse index of cerebral vascular tone, did not change even though systemic vascular conductance increased during exercise (time effect: P < 0.0001). The arterial system to the cerebral vasculature may attenuate pulsatile transition during HIIE as a defence mechanism against pulsatile fluctuation for the cerebral vasculature. [ABSTRACT FROM AUTHOR]

Introduction: We aimed to describe physiological changes in endometrial blood flow (minute arterioles running through the endometrium) from ovulation to the mid‐luteal phase using superb microvascular imaging. Material and methods: The study involved 17 women (median age, 32.5 years; first to third interquartile range, 29.8–40.0 years) with regular menstrual cycles who were managed in our institute from 2020 to 2021. The uterus was delineated at the sagittal section using transvaginal ultrasonography incorporated with superb microvascular imaging. For each participant, a total of 28 cycles were observed; 17 cycles observed within one day of ovulation and the implantation period, 5–7 days (D5–7) after ovulation in the same cycle, and nine cycles in which only ovulation was observed, and two cycles in which only D5–7 was observed. Therefore, 26 and 19 images at ovulation and D5–7, respectively, were acquired. Endometrial blood flow was evaluated by depth of the vascular signal in the endometrium and categorized as follows: signals only in the basal layer of the endometrium (grade 1), reaching up to half the endometrium (grade 2), and covering the whole endometrium (grade 3). Changes in the grade of endometrial blood flow from ovulation to D5–7 after ovulation, and the relationship between the grade of endometrial blood flow and the endometrial thickness on ovulation and D5–7 after ovulation, were analyzed. Statistical significance was set at p < 0.05. Results: The endometrial blood flow from ovulation to D5–7 after ovulation during the same menstrual period showed a downgrade in 14 of 17 cycles (82.3%) and no change in the remaining three cycles (17.6%), indicating a decrease in the endometrial blood flow from ovulation to D5–7 after ovulation (p = 0.001). There were differences between the grade of endometrial blood flow and median endometrial thickness on ovulation (grade 1: 5.9 mm, grade 2: 9.1 mm, and grade 3: 11.2 mm); however, no differences in the endometrial thickness were found between the grades on D5–7 after ovulation. Conclusions: In the normal menstrual cycle, endometrial blood flow decreased from ovulation to the mid‐luteal phase, and the endometrial thickness in the ovulatory phase was related to the endometrial perfusion. [ABSTRACT FROM AUTHOR]

Networks of neurons are the primary substrate of information processing. Conversely, blood vessels in the brain are generally viewed to have physiological functions unrelated to information processing, such as the timely supply of oxygen, and other nutrients to the neural tissue. However, recent studies have shown that cerebral microvessels, like neurons, exhibit tuned responses to sensory stimuli. Tuned neural responses to sensory stimuli may be enhanced with experience‐dependent Hebbian plasticity and other forms of learning. Hence, it is possible that the microvascular network might also be subject to some form of competitive learning rules during early postnatal development such that its fine‐scale structure becomes optimized for metabolic delivery to a given neural micro‐architecture. To explore the possibility of adaptive lateral interactions and tuned responses in cerebral microvessels, we modelled the cortical neurovascular network by interconnecting two laterally connected self‐organizing networks. The afferent and lateral connections of the neural and vascular networks were defined by trainable weights. By varying the topology of lateral connectivity in the vascular network layer, we observed that the partial correspondence of feature selectivity between neural and hemodynamic responses could be explained by lateral coupling across local blood vessels such that the central domain receives an excitatory drive of more blood flow and a distal surrounding region where blood flow is reduced. Critically, our simulations suggest a new role for feedback from the vascular to the neural network because the radius of vascular perfusion determines whether the cortical neural map develops into a clustered vs. salt‐and‐pepper organization. [ABSTRACT FROM AUTHOR]

Low‐flow vascular malformations are rare congenital anomalies due to errors in vascular development and may be associated with known pathogenic genetic variants. Slow flow through the blood vessels can lead to localized intralesional thromboses, which can cause debilitating pain and impair quality of life. We present a case of venous malformation due to a variant in the TEK gene in a 38‐year‐old woman in whom treatment with low dose rivaroxaban was successful in controlling symptoms of chronic localized intravascular coagulation. [ABSTRACT FROM AUTHOR]

Summary: The mechanism of many cardiovascular diseases can be understood by studying the pressure distribution in blood vessels. Direct pressure measurements, however, require invasive probing and provide only single‐point data. Alternatively, relative pressure fields can be reconstructed from imaging‐based velocity measurements by considering viscous and inertial forces. Both contributions can be potential troublemakers in pressure reconstruction: the former due to its higher‐order derivatives, and the latter because of the quadratic nonlinearity in the convective acceleration. Viscous and convective terms can be treated in various forms, which, although equivalent for ideal measurements, can perform differently in practice. In fact, multiple versions are often used in literature, with no apparent consensus on the more suitable variants. In this context, the present work investigates the performance of different versions of relative pressure estimators. For viscous effects, in particular, two new modified estimators are presented to circumvent second‐order differentiation without requiring surface integrals. In‐silico and in‐vitro data in the typical regime of cerebrovascular flows are considered, allowing a systematic noise sensitivity study. Convective terms are shown to be the main source of error, even for flows with pronounced viscous component. Moreover, the conservation (often integrated) form of convection exhibits higher noise sensitivity than the standard convective description, in all three families of estimators considered here. For the classical pressure Poisson estimator, the present modified version of the viscous term tends to yield better accuracy than the (recently introduced) integrated form, although this effect is in most cases negligible when compared to convection‐related errors. [ABSTRACT FROM AUTHOR]

Transcatheter arterial embolization (TAE) is wildly used in clinical treatments. However, the online monitoring of the thrombosis formation is limited due to the challenges of the direct visualization of embolic agents and the real‐time monitoring of dynamic blood flow. Thus, we developed a photochemical afterglow implant with strong afterglow intensity and a long lifetime for embolization and imaging. The liquid pre‐implant injected into the abdominal aorta of mice was rapidly transformed into a hydrogel in situ to embolize the blood vessel. The vascular embolism position can be observed by the enhanced afterglow of the fixed implant, and the long lifetime of afterglow can also be used to monitor the effect of embolization. This provides an excellent candidate in bio‐imaging to avoid the autofluorescence interference from continuous light excitation. The study suggests the potential usefulness of the implant as an embolic agent in TAE and artery imaging during a surgical procedure. [ABSTRACT FROM AUTHOR]

Computational hemodynamics is being developed as an alternative approach for assisting clinical diagnosis and treatment planning for liver diseases. The technology is non‐invasive, but the computational time could be high when the full geometry of the blood vessels is taken into account. Existing approaches use either one‐dimensional model of the artery or simplified three‐dimensional tubular geometry in order to reduce the computational time, but the accuracy is sometime compromised, for example, when simulating blood flows in arteries with plaque. In this work, we study a highly parallel method for the transient incompressible Navier–Stokes equations for the simulation of the blood flows in the full three‐dimensional patient‐specific hepatic artery, portal vein and hepatic vein. As applications, we also simulate the flow in a patient with hepatectomy and calculate the S (PPG). One of the advantages of simulating blood flows in all hepatic vessels is that it provides a direct estimate of the PPG, which is a gold standard value to assess the portal hypertension. Moreover, the robustness and scalability of the algorithm are also investigated. A 83% parallel efficiency is achieved for solving a problem with 7 million elements on a supercomputer with more than 1000 processor cores. [ABSTRACT FROM AUTHOR]

Peristaltic transport of Newtonian nanofluid in an inclined annulus terms of radii regarding peristalsis and elasticity. It is noticed that with an increase in amplitude ratio, flux is getting enhanced in the absence of nanoparticles when compared with viscous fluid with nanoparticles. Our results reduce to the corresponding ones of Rubinow and Keller as a special case for the viscous flow in an elastic tube. The effect of various emerging parameters bounded by two concentric cylinders is studied under the assumption of long wavelength and dominance of viscous effects over inertial effects. The outer cylinder is elastic in nature and has a sinusoidal wave traveling down in its wall, whereas the inner cylinder is rigid. Analytical solutions have been established for velocity, flux, pressure rise, temperature distribution, and nanoparticle concentration. The flux, pressure rise, and frictional forces have been obtained in on the flow characteristic are presented and discussed. Obtained results may be useful in understanding the behavior of peristaltic transport of blood flow in small blood vessels and blood flow through elastic arteries. [ABSTRACT FROM AUTHOR]

In this work, we introduce an algorithmic approach to generate microvascular networks starting from larger vessels that can be reconstructed without noticeable segmentation errors. Contrary to larger vessels, the reconstruction of fine‐scale components of microvascular networks shows significant segmentation errors, and an accurate mapping is time and cost intense. Thus there is a need for fast and reliable reconstruction algorithms yielding surrogate networks having similar stochastic properties as the original ones. The microvascular networks are constructed in a marching way by adding vessels to the outlets of the vascular tree from the previous step. To optimise the structure of the vascular trees, we use Murray's law to determine the radii of the vessels and bifurcation angles. In each step, we compute the local gradient of the partial pressure of oxygen and adapt the orientation of the new vessels to this gradient. At the same time, we use the partial pressure of oxygen to check whether the considered tissue block is supplied sufficiently with oxygen. Computing the partial pressure of oxygen, we use a 3D‐1D coupled model for blood flow and oxygen transport. To decrease the complexity of a fully coupled 3D model, we reduce the blood vessel network to a 1D graph structure and use a bi‐directional coupling with the tissue which is described by a 3D homogeneous porous medium. The resulting surrogate networks are analysed with respect to morphological and physiological aspects. [ABSTRACT FROM AUTHOR]

The goldfish hindbrain develops from a segmented (rhombomeric) neuroepithelial scaffold, similar to other vertebrates. Motor, reticular and other neuronal groups develop in specific segmental locations within this rhombomeric framework. Teleosts are unique in possessing a segmental series of unpaired, midline central arteries that extend from the basilar artery and penetrate the pial midline of each hindbrain rhombomere (r). This study demonstrates that the rhombencephalic arterial supply of the brainstem forms in relation to the neural segments they supply. Midline central arteries penetrate the pial floor plate and branch within the neuroepithelium near the ventricular surface to form vascular trees that extend back towards the pial surface. This intramural branching pattern has not been described in any other vertebrate, with blood flow in a ventriculo‐pial direction, vastly different than the pial‐ventricular blood flow observed in most other vertebrates. Each central arterial stem penetrates the pial midline and ascends through the floor plate, giving off short transverse paramedian branches that extend a short distance into the adjoining basal plate to supply ventromedial areas of the brainstem, including direct supply of reticulospinal neurons. Robust r3 and r8 central arteries are significantly larger and form a more interconnected network than any of the remaining hindbrain vascular stems. The r3 arterial stem has extensive vascular branching, including specific vessels that supply the cerebellum, trigeminal motor nucleus located in r2/3 and facial motoneurons found in r6/7. Results suggest that some blood vessels may be predetermined to supply specific neuronal populations, even traveling outside of their original neurovascular territories in order to supply migrated neurons. [ABSTRACT FROM AUTHOR]

It is becoming increasingly apparent that disorders of the brain microvasculature contribute to many neurological disorders. In recent years it has become clear that a major player in these events is the capillary pericyte which, in the brain, is now known to control the blood–brain barrier, regulate blood flow, influence immune cell entry and be crucial for angiogenesis. In this review we consider the under‐explored possibility that peripheral diseases which affect the microvasculature, such as hypertension, kidney disease and diabetes, produce central nervous system (CNS) dysfunction by mechanisms affecting capillary pericytes within the CNS. We highlight how cellular messengers produced peripherally can act via signalling pathways within CNS pericytes to reshape blood vessels, restrict blood flow or compromise blood–brain barrier function, thus causing neuronal dysfunction. Increased understanding of how renin–angiotensin, Rho‐kinase and PDGFRβ signalling affect CNS pericytes may suggest novel therapeutic approaches to reducing the CNS effects of peripheral disorders. [ABSTRACT FROM AUTHOR]

Summary: Exercise capacity as well as many resting central and peripheral haemodynamic features declines by age. We aimed to investigate which haemodynamic features change the most during life and which change in parallel to exercise capacity. We performed a maximal bicycle exercise test with gas exchange in 103 healthy subjects (24 young, 55 middle‐aged and 24 elderly). Endothelial function, arterial compliance/stiffness and heart rate variability (HRV) were evaluated, and the myocardium and carotid arteries were investigated by ultrasound. Exercise capacity declined by almost 50% over the lifespan. Several markers reflecting arterial compliance/stiffness and HRV, as well as carotid intima–media thickness (IMT), showed lifetime impairments by >100%, while markers of LV systolic function, diastolic blood pressure and carotid artery blood flow showed only minor changes with age. The decline in exercise capacity clusters closely with many other variables measured during the exercise test, but also to resting vital capacity, left ventricular end‐diastolic diameter and resting gas exchange (VO2, VCO2) to a lesser degree. Resting vital capacity was closely related to exercise capacity in the middle‐aged group. We conclude that many of the resting markers of central and peripheral haemodynamics declined during life, in parallel to the decline in exercise capacity. However, some haemodynamic features, such as LF/HF ratio at HRV, stiffness index beta of the carotid artery, and heart rate reserve at the exercise test, showed a more exaggerated decline, indicating that those are not closely linked to exercise capacity. [ABSTRACT FROM AUTHOR]

Key points: Intrauterine growth restriction (IUGR) increases offspring risk of chronic diseases later in life, including cardiovascular dysfunction.Our prior studies suggest biventricular cardiac dysfunction and vascular impairment in baboons who were IUGR at birth because of moderate maternal nutrient reduction.The current study reveals changes in artery sizes, distensibility, and blood flow pattern in young adult IUGR baboons, which may contribute to cardiac stress.The pattern of abnormality observed suggests that vascular redistribution seen with IUGR in fetal life may continue into adulthood. Maternal nutrient reduction induces intrauterine growth restriction (IUGR), increasing risks of chronic diseases later in life, including cardiovascular dysfunction. Using ultrasound, we determined regional blood flow, blood vessel sizes, and distensibility in IUGR baboons (8 males, 8 females, 8.8 years, similar to 35 human years) and controls (12 males, 12 females, 9.5 years). The measured blood vessels were larger in size in the males compared to females before but not after normalization to body surface area. Smaller IUGR normalized blood vessel sizes were observed in the femoral and external iliac arteries but not the brachial or common carotid arteries and not correlated significantly with birth weight. Mild decrease in distensibility in the IUGR group was seen in the iliac but not the carotid arteries without between‐sex differences. In IUGR baboons there was increased carotid arterial blood flow velocity during late systole and diastole. Overall, our findings support the conclusion that region specific vascular and haemodynamic changes occur with IUGR, which may contribute to the occurrence of later life cardiac dysfunction. The pattern of alteration observed suggests vascular redistribution efforts in response to challenges in the perinatal period may persist into adulthood. Further studies are needed to determine the life course progression of these changes. Key points: Intrauterine growth restriction (IUGR) increases offspring risk of chronic diseases later in life, including cardiovascular dysfunction.Our prior studies suggest biventricular cardiac dysfunction and vascular impairment in baboons who were IUGR at birth because of moderate maternal nutrient reduction.The current study reveals changes in artery sizes, distensibility, and blood flow pattern in young adult IUGR baboons, which may contribute to cardiac stress.The pattern of abnormality observed suggests that vascular redistribution seen with IUGR in fetal life may continue into adulthood. [ABSTRACT FROM AUTHOR]

Purpose: Four‐dimensional (4D) DSA reconstruction provides three‐dimensional (3D) time‐resolved visualization of contrast bolus passage through arterial vasculature in the interventional setting. The purpose of this study was to evaluate the feasibility of using these data in measuring blood velocity and flow. Methods: The pulsatile signals in the time concentration curves (TCCs) measured at different points along a vessel are markers of the movement of a contrast bolus and thus of blood flow. When combined with the spatial content, that is, geometry of the vasculature, this information then provides the data required to determine blood velocity. A Fourier‐based algorithm was used to identify and follow the pulsatility signal. A Side Band Ratio (SBR) metric was used to reduce uncertainty in identifying the pulsatility in regions where the signal was weak. We tested this method using 4D‐DSA reconstructions from vascular phantoms as well as from human studies. Results: In five studies using 3D printed patient‐specific cerebrovascular phantoms, velocities calculated from the 4D‐DSAs were found to be within 10% of velocities measured with a flow meter. Calculated velocity and flow values from three human studies were within the range of those reported in the literature. Conclusions: 4D‐DSA provides temporal and spatial information about blood flow and vascular geometry. This information is obtained using conventional rotational angiographic systems. In this small feasibility study, these data allowed calculations of velocity values that correlated well with measured values. The availability of velocity and blood flow information in the interventional setting would support a more quantitative approach to diagnosis, treatment planning and post‐treatment evaluations of a variety of cerebrovascular diseases. [ABSTRACT FROM AUTHOR]

Abstract: Endothelial dysfunction is known to be the early stage of arteriosclerosis. The flow‐mediated dilation (FMD) test is the most commonly used method to diagnose the endothelial function. The test measures the maximum vasodilation (FMD response) on the brachial artery induced by the increases in blood flow after cuff deflation on the forearm. The vessel diameter must be captured clearly with the ultrasonic probe during the test. The vasodilation is induced in response to changes in the mechanical property of the vessel wall due to the blood flow stimulation. The changes are supposed to affect the pulsatile flow, but the influence of continuous behavior of vascular property on hemodynamics has not been clarified. In this study, in order to clarify the influence of the FMD response on hemodynamics, we propose a mathematical model that can simulate hemodynamics and vasomotor responses. As a result, it was shown that vessel wall dynamics affected the pulsatile flow. This result suggests that the endothelial function can be evaluated from blood flow. [ABSTRACT FROM AUTHOR]

Abstract: Objective: In SSc, vascular injury leads to endothelial dysfunction with reduced capillary blood flow and tissue hypoxia. In SSc, the angiogenesis is impaired and implicated in the microvascular damage. In severe vascular damage, VEGF is reduced and endostatin is increased. The aim of this study was to evaluate the correlation between endostatin serum levels and microvascular and digital arteries damage. Methods: Seventeen patients with SSc were enrolled in this study. Serum endostatin levels were determined. All patients underwent a NVC, CDUS, and LDPI. Results: The serum level of endostatin significantly (P < .05) increased with NVC progression damage. The mean perfusion significantly (P < .05) decreased with NVC progression damage. Multiple regression analysis showed a significant correlation between endostatin serum level and RI (r = .34, P < .05), PI (r = .60, P < .01), S/D ratio (r = .76, P < .0001), and mean perfusion (r = −.68, P < .001). Endostatin serum levels significantly (P < .05) increased with progression of CDUS damage. Conclusions: Increased serum endostatin levels are associated with digital vascular damage. In patients with SSc, endostatin is a marker of skin perfusion and digital arteries damage of hands. [ABSTRACT FROM AUTHOR]

Tunneled central venous catheters with ports are increasingly used for therapeutic apheresis procedures. Vortex ports have been used as access for therapeutic apheresis procedures, but are not ideal for therapeutic plasma exchange (TPE) procedures due to lower flow rates. We performed an in vitro experiment to compare flow characteristics of the single-lumen Vortex port (AngioDynamics) with the single-lumen TidalPort (Norfolk Medical). We used expired red blood cell units and adjusted the hematocrit to 40% with normal saline in a 2-L bag. We programmed the Spectra Optia (Terumo BCT) to run a 1.0-volume TPE with 5% albumin as replacement fluid. The TidalPort achieved flow rates of up to 110 mL/min without triggering alarms. Due to crucial alarms, the Vortex Port was not able to run at a flow rate higher than 90 mL/min, and multiple caution alarms were triggered at flow rates of 80 to 90 mL/min. These findings suggest that the TidalPort may be a suitable access option that provides flow rates similar to peripheral or central venous catheters for TPE procedures. [ABSTRACT FROM AUTHOR]

Background: Central venous access devices are commonly used in extracorporeal photopheresis, but their performance has not been systematically evaluated. The primary objective of this study was to compare pressures at various flow rates for central venous access devices in an ex vivo simulation of photopheresis.Study Design and Methods: Diluted, heparinized red blood cells were circulated through central access devices in series with a photopheresis system, and pressures at several flow rates were recorded. The devices tested were the Trifusion catheter (Hickman), the Vortex single-lumen and dual-lumen ports (Angiodynamics), and the TidalPort device (Norfolk). Flow rates were also compared for silicone and polyurethane catheters and for different catheter internal diameters.Results: The Vortex dual-lumen port generated pressure alarms above flow rates of 60 mL/minute. Throughout flow rates from 5 to 100 mL/minute, the Trifusion catheter and the TidalPort device operated at lower pressures than the Vortex ports. Within typical clinical flow rates, neither catheter material nor internal diameter substantially affected pressure.Conclusion: Central venous access devices show large differences in pressure within flow rates used routinely in clinical settings. These differences cannot be fully attributed to catheter material composition or catheter internal diameter. [ABSTRACT FROM AUTHOR]

Therapeutic plasma exchange is an apheresis modality in which plasma is separated from the blood cellular components ex vivo, discarded, and replaced with an isosmotic fluid (most commonly 5% albumin) to maintain appropriate oncotic pressure in the patient. Therapeutic plasma exchange is used in the treatment of many diseases and indications. The recent seventh edition of the American Society for Apheresis guidelines indicates approximately 72 diseases and 116 indications for which therapeutic plasma exchange may be effective. One of the critical aspects for the successful performance of therapeutic plasma exchange is appropriate vascular access to provide high blood flow for the collection and return phases of the procedure, especially because most patients who need therapeutic plasma exchange will require more than one treatment over days to weeks. This article provides an overview of the characteristics of therapeutic plasma exchange, the clinical diseases and indications that may be treated with therapeutic plasma exchange, and the different types of vascular access employed, with their advantages and disadvantages. The latter may include peripheral venous access and intravascular or implantable access devices, such as arteriovenous grafts and fistulas, central venous catheters, and central venous catheters tunneled with ports. [ABSTRACT FROM AUTHOR]

In the etiology of Achilles tendinopathy ( AT), it is frequently suggested that excessive pronation causes a vascular constriction of the Achilles tendon, described as the 'whipping phenomenon' (Clement et al., 1984). Although previous studies focused on the association between pronation and AT, it is striking that the underlying association between foot pronation and blood flow has not been studied yet. Therefore, the aim of this study was to investigate whether the amount of pronation during running influences the Achilles tendon blood flow. Twenty-five experienced runners, aged 34.5±10.2 years, participated in this study. 2D-lower limb kinematics during barefoot and shod running in both frontal and sagittal plane were assessed. Blood flow of the Achilles tendon was measured before and after barefoot and shod running, using the oxygen-to-see device. The results of this study showed a significant effect of eversion excursion on the increase in Achilles tendon blood flow after shod running. More specifically, the more the eversion excursion observed, the lower the increase in blood flow ( P=.013). We therefore suggest, in individuals with increased inversion at touchdown and increased eversion around midstance during shod running, that antipronation measures could be useful in both preventing and managing Achilles tendinopathy. [ABSTRACT FROM AUTHOR]

Our laboratory reported that facial skin blood flow may serve as a sensitive tool to assess an emotional status. Cerebral neural correlates during emotional interventions should be sought in relation to the changes in facial skin blood flow. To test the hypothesis that prefrontal activity has positive relation to the changes in facial skin blood flow during emotionally charged stimulation, we examined the dynamic changes in prefrontal oxygenation (with near-infrared spectroscopy) and facial skin blood flows (with two-dimensional laser speckle and Doppler flowmetry) during emotionally charged audiovisual challenges for 2 min (by viewing comedy, landscape, and horror movie) in 14 subjects. Hand skin blood flow and systemic hemodynamics were simultaneously measured. The extents of pleasantness and consciousness for each emotional stimulus were estimated by subjective rating from -5 (the most unpleasant; the most unconscious) to +5 (the most pleasant; the most conscious). Positively charged emotional stimulation (comedy) simultaneously decreased (P < 0.05) prefrontal oxygenation and facial skin blood flow, whereas negatively charged (horror) or neutral (landscape) emotional stimulation did not alter or slightly decreased them. Any of hand skin blood flow and systemic cardiovascular variables did not change significantly during positively charged emotional stimulation. The changes in prefrontal oxygenation had a highly positive correlation with the changes in facial skin blood flow without altering perfusion pressure, and they were inversely correlated with the subjective rating of pleasantness. The reduction in prefrontal oxygenation during positively charged emotional stimulation suggests a decrease in prefrontal neural activity, which may in turn elicit neurally mediated vasoconstriction of facial skin blood vessels. [ABSTRACT FROM AUTHOR]

Astrocytes are the most common glial cells in the brain with fine processes and endfeet that intimately contact both neuronal synapses and the cerebral vasculature. They play an important role in mediating neurovascular coupling (NVC) via several astrocytic Ca2+-dependent signalling pathways such as K+ release through BK channels, and the production and release of arachidonic acid metabolites. They are also involved in maintaining the resting tone of the cerebral vessels by releasing ATP and COX-1 derivatives. Evidence also supports a role for astrocytes in maintaining blood pressure-dependent change in cerebrovascular tone, and perhaps also in blood vessel-to-neuron signalling as posited by the 'hemo-neural hypothesis'. Thus, astrocytes are emerging as new stars in preserving the intricate balance between the high energy demand of active neurons and the supply of oxygen and nutrients from the blood by maintaining both resting blood flow and activity-evoked changes therein. Following neuropathology, astrocytes become reactive and many of their key signalling mechanisms are altered, including those involved in NVC. Furthermore, as they can respond to changes in vascular pressure, cardiovascular diseases might exert previously unknown effects on the central nervous system by altering astrocyte function. This review discusses the role of astrocytes in neurovascular signalling in both physiology and pathology, and the impact of these findings on understanding BOLD-fMRI signals. [ABSTRACT FROM AUTHOR]

Background Cutaneous blood flow plays an important role in the thermoregulation, oxygen supply, and nutritional support necessary to maintain the skin. However, there is little evidence for a link between blood flow and skin physiology. Therefore, we conducted surveys of healthy volunteers to determine the relationship(s) between dry skin properties and cutaneous vascular function. Methods Water content of the stratum corneum, transepidermal water loss, and visual dryness score were investigated as dry skin parameters. Cutaneous blood flow in the resting state, the recovery rate ( RR) of skin temperature on the hand after a cold-stress test, and the responsiveness of facial skin blood flow to local cooling were examined as indices of cutaneous vascular functions. The relationships between dry skin parameters and cutaneous vascular functions were assessed. Results The RR correlated negatively with the visual dryness score of skin on the leg but correlated positively with water content of the stratum corneum on the arm. No significant correlation between the resting state of blood flow and dry skin parameters was observed. In both the face and the body, deterioration in skin dryness from summer to winter was significant in subjects with low RR. The RR correlated well with the responsiveness of facial skin blood flow to local cooling, indicating that the RR affects systemic dry skin conditions. Conclusions These results suggest that the RR but not blood flow at the resting state is associated with dry skin conditions and is involved in skin homeostasis during seasonal environmental changes. [ABSTRACT FROM AUTHOR]

Two equids weighing <250 kg were examined several days after suffering severe mid-diaphyseal dorsal metatarsal lacerations. Distal limb vascular disruption was suspected in both cases. Nonselective computed tomography angiography with contrast medium injected peripherally via the jugular veins was used to evaluate the vascular supply to the distal limb. The use of this imaging technique demonstrated either intact or disrupted distal limb vasculature. The imaging results were verified with a positive long-term outcome in the case with a diagnosis of an intact vasculature and with histological findings of avascular necrosis in the case with a diagnosis of disrupted vasculature. [ABSTRACT FROM AUTHOR]

In recent years, the complexity of vessel networks for one-dimensional blood flow models has significantly increased, because of enhanced anatomical detail or automatic peripheral vasculature generation, for example. This fact, along with the application of these models in uncertainty quantification and parameter estimation poses the need for extremely efficient numerical solvers. The aim of this work is to present a finite volume solver for one-dimensional blood flow simulations in networks of elastic and viscoelastic vessels, featuring high-order space-time accuracy and local time stepping (LTS). The solver is built on (i) a high-order finite volume type numerical scheme, (ii) a high-order treatment of the numerical solution at internal vertexes of the network, often called junctions, and (iii) an accurate LTS strategy. The accuracy of the proposed methodology is verified by empirical convergence tests. Then, the resulting LTS scheme is applied to arterial networks of increasing complexity and spatial scale heterogeneity, with a number of one-dimensional segments ranging from a few tens up to several thousands and vessel lengths ranging from less than a millimeter up to tens of centimeters, in order to evaluate its computational cost efficiency. The proposed methodology can be extended to any other hyperbolic system for which network applications are relevant. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

There has been a consistent growth in research involving imaging of microvasculature over the past few decades. By 2008, publications mentioning the microcirculation had grown more than 2000 per annum. Many techniques have been demonstrated for the measurement of the microcirculation ranging from the earliest invasive techniques to the present high-speed, high-resolution noninvasive imaging techniques. Understanding the microvasculature is vital in tackling fundamental research questions as well as to understand the effects of disease progression on the physiological well-being of an individual. We have previously provided a wide-ranging review covering most of the available techniques and their applications. In this review, we discuss the recent advances made and applications in the field of microcirculation imaging. [ABSTRACT FROM AUTHOR]

In aortic dissections blood flows not only in the regular, true lumen but also between separated lamellae within the media of the aortic wall, in the so‐called false lumen. Both lumina are separated by a dissection membrane, which may move substantially during the cardiac cycle, linking blood flow and vessel deformation. We employ strongly coupled fluid‐structure interaction simulations incorporating an anisotropic, fiber‐reinforced, hyperelastic continuum including layer‐specific tissue parameters. [ABSTRACT FROM AUTHOR]

SUMMARY An extension of a total variation diminishing (TVD) scheme to solve one-dimensional (1D) blood flow for human circulation is proposed. This method is simple as it involves only a few modifications to existing shock-capturing TVD schemes. We have applied the method to a wide range of test cases including a complete simulation of the human vascular network. Excellent solutions have been demonstrated for problems involving varying and discontinuous mechanical properties of blood vessels. For 1D network simulations, the method has been shown to agree well with the reported computational results. Finally, the method has been demonstrated to compare favorably with in vivo experiments set up to study the impact of circle of Willis anomalies on flow patterns in the cerebral arterial system. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Key points The reduction in skin blood flow during whole-body cooling is impaired in healthy older adults. However, the relative contributions of altered skin sympathetic nerve activity (SSNA), transduction of this efferent neural outflow to the cutaneous vasculature, and peripheral vascular responsiveness to adrenergic stimuli to the impaired reflex vasoconstrictor response to whole-body cooling in human ageing remain unclear., We report that the SSNA response to whole-body cooling is blunted in healthy older adults, and this attenuated sympathetic response is related to a marked impairment in reflex cutaneous vasoconstriction. Further, the reflex SSNA response to a non-thermoregulatory stimulus was preserved in older adults during cooling., We additionally show that cutaneous vascular responsiveness to adrenergic stimuli is not reduced in older adults., These results further our understanding of the physiological mechanisms underlying impaired thermal-cardiovascular integration in healthy ageing., Abstract Reflex cutaneous vasoconstriction is impaired in older adults; however, the relative roles of altered skin sympathetic nerve activity (SSNA) and end-organ peripheral vascular responsiveness are unclear. We hypothesized that in older adults whole-body cooling would elicit a blunted SSNA response and cutaneous adrenergic responsiveness would be reduced. Twelve young adults (Y; 24 ± 1 years) and 12 older adults (O; 57 ± 2 years) participated in two protocols. In Protocol 1, SSNA (peroneal microneurography) and red cell flux in the affected dermatome (laser Doppler flowmetry; dorsum of foot) were measured during whole-body cooling (mean skin temperature ( Tsk) 30.5°C; water-perfused suit). Mental stress was performed at mean Tsk 34.0°C (thermoneutral) and at 30.5°C. In Protocol 2, an intradermal microdialysis fibre was placed in the skin of the lateral calf for graded infusions of noradrenaline (norepinephrine) (NA; 10−12 to 10−2 m). Cutaneous vascular conductance (CVC = flux/mean arterial pressure) was expressed as a change from baseline (ΔCVCbase). Vasoconstriction was attenuated in O. SSNA increased significantly during cooling in Y (+184 ± 37%; P < 0.05) but not O (+51 ± 12%; P > 0.05). Mental stress at Tsk 30.5°C further increased SSNA in both groups. There was no age-related difference in adrenergic responsiveness to exogenous NA (logEC50: −6.41 ± 0.24 in Y, −6.37 ± 0.25 in O; P > 0.05). While the SSNA response to whole-body cooling is impaired with ageing, SSNA can be further increased by a non-thermoregulatory stimulus. Cutaneous adrenergic sensitivity is not reduced in O. These findings suggest that alterations in afferent signalling or central processing likely contribute to blunted SSNA responses to cooling and subsequent impairments in reflex cutaneous vasoconstriction in ageing. [ABSTRACT FROM AUTHOR]

Objective Models based on the Krogh-cylinder concept are developed to analyze the washout from tissue by blood flow of an inert diffusible solute that permeates blood vessel walls. During the late phase of washout, the outflowing solute concentration decays exponentially with time. This washout decay rate is predicted for a range of conditions. Methods A single capillary is assumed to lie on the axis of a cylindrical tissue region. In the classic 'Krogh-cylinder' approach, a no-flux boundary condition is applied on the outside of the cylinder. An alternative 'infinite-domain' approach is proposed that allows for solute exchange across the boundary, but with zero net exchange. Both models are analyzed, using finite-element and analytical methods. Results The washout decay rate depends on blood flow rate, tissue diffusivity and vessel permeability of solute, and assumed boundary conditions. At low blood flow rates, the washout rate can exceed the value for a single well-mixed compartment. The infinite-domain approach predicts slower washout decay rates than the Krogh-cylinder approach. Conclusions The infinite-domain approach overcomes a significant limitation of the Krogh-cylinder approach, while retaining its simplicity. It provides a basis for developing methods to deduce transport properties of inert solutes from observations of washout decay rates. [ABSTRACT FROM AUTHOR]

Avascular areas on contrast-enhanced magnetic resonance imaging have been considered to be areas of localized prostate cancer successfully treated by high-intensity focused ultrasound. However, the optimal timing of magnetic resonance imaging has not been discussed. The thermal effect of high-intensity focused ultrasound is degraded by regional prostatic blood flow. Conversely, the mechanical effect of high-intensity focused ultrasound (cavitation) is not affected by blood flow, and can induce vessel damage. In this series, the longitudinal change of blood flow on contrast-enhanced magnetic resonance imaging was observed from postoperative day 1 to postoperative day 14 in 10 patients treated with high-intensity focused ultrasound. The median rates of increase in the non-enhanced volume of the whole gland, transition zone and peripheral zone from postoperative day 1 to postoperative day 14 were 36%, 39%, and 34%, respectively. In another pathological analysis of the prostate tissue of 17 patients immediately after high-intensity focused ultrasound without neoadjuvant hormonal therapy, we observed diffuse coagulative degeneration and partial non-coagulative prostate tissue around arteries with vascular endothelial cell detachment. These observations on contrast-enhanced magnetic resonance imaging support a time-dependent change of the blood flow in the prostate treated with high-intensity focused ultrasound. Additionally, our pathological findings support the longitudinal changes of these magnetic resonance imaging findings. Further large-scale studies will investigate the most appropriate timing of contrast-enhanced magnetic resonance imaging for evaluation of the effectiveness of high-intensity focused ultrasound for localized prostate cancer. [ABSTRACT FROM AUTHOR]

Purpose: To analyse retinal neurovascular coupling (NVC) in a plexus‐specific manner at baseline and during flicker light stimulation using optical coherence tomography angiography (OCTA) and to thereby use the retina as a model for non‐invasive microvascular assessment of NVC in humans. Methods: 22 healthy subjects were included in the study. Macular 10°x10° volume scans were acquired at baseline and during flicker light stimulation using the Spectralis OCTA module (Heidelberg Engineering, Heidelberg, Germany). Vessel densities (VDs) in the superficial (SCP), intermediate (ICP) and deep capillary plexus (DCP) as well as in the full retina (FR) were assessed after thresholding the respective slabs by mean values. Large vessels and resulting projection artefacts were removed using a threshold‐based approach. Capillary representation was optimized using a "Frangi filter". Volumetric blood flow and vessel diameters were measured using a Doppler‐OCT prototype. Results: Flicker light stimulation induced a significant FR VD increase from 39.7 ± 1.7 to 41.2 ± 1.6% (+3.8 ± 2.7%; p < 0.001). Upon separate analysis of the three retinal plexus, VD significantly increased by +9.9 ± 6.7% in SCP, by ±6.6 ± 1.7% in ICP and by +4.9 ± 2.3% in DCP (p<0.001 for all three). This increase was significantly higher in SCP than in ICP (p = 0.02) and DCP (p = 0.002). Arterial diameters increased by +3.7 ± 3.1% (p < 0.001), venous diameters rose by +4.5 ± 3.0% (p<0.001). Volumetric blood flow increased by +39.9±34.9% (p<0.001) in arteries and by +29.8 ± 16.8% (p < 0.001) in veins. Conclusions: In summary, a robust increase of retinal VD which was most pronounced in SCP could be observed upon flicker light stimulation. These data propose a plexus‐specific mechanism, to precisely meet the metabolic needs of retinal cells. The location of SCP in the inner retinal layers, where increase of metabolic demands is suggested to be greatest during flicker light stimulation, could be explanatory for the locally bigger response. [ABSTRACT FROM AUTHOR]

Vascular smooth muscle contraction and the myogenic response regulate blood flow in the resistance vascular and contribute to systemic blood pressure. Three pathways are currently known to contribute to the development of the myogenic response: (i) Ca2+-dependent phosphorylation of LC20; (ii) Ca2+ sensitization through inhibition of myosin phosphatase; and (iii) cortical actin polymerization. A number of regulatory smooth muscle proteins are integrated with these pathways to fine tune the response and facilitate adaptations to vascular (patho)physiologies. Of particular interest is the SMTN family of proteins, consisting of SMTN-A, SMTN-B, and the SMTN-like protein, SMTNL1. The SMTN-B and SMTNL1 proteins are both implicated in regulating smooth muscle contractility and contributing to vascular adaptations associated with hypertension, pregnancy, and exercise training. In the case of SMTNL1, the protein plays multiple roles in regulating contraction through functional interactions with contractile regulators as well as transcriptional control of the contractile phenotype and Ca2+-sensitizing capacity. For the first time, preliminary results suggest SMTNL1 is involved in the myogenic response of the cerebral resistance vasculature. In this regard, global SMTNL1 deletion is associated with greater myogenic reactivity of cerebral arterioles, although the precise mechanism accounting for this finding remains to be defined. [ABSTRACT FROM AUTHOR]

Altered vasculature and the resultant chaotic tumor blood flow lead to the appearance in fast-growing tumors of regions with gradients of oxygen tension and acute hypoxia (less than 1.4 % oxygen). Due to its roles in tumorigenesis and resistance to therapy, hypoxia represents a problem in cancer therapy., Insufficient delivery of therapeutic agents to the hypoxic regions in solid tumors is recognized as one of the causes of resistance to therapy., This led to the development of hypoxia imaging agents, and the use of hypoxia-activated anticancer prodrugs. Here we show the first example of the hypoxia-induced siRNA uptake and silencing using a nanocarrier consisting of polyethyleneglycol 2000, azobenzene, polyethyleneimine (PEI)(1.8 kDa), and 1,2-dioleyl- sn-glycero-3-phosphoethanolamine (DOPE) units (the nanocarrier is referred to as PAPD), where azobenzene imparts hypoxia sensitivity and specificity. We report hypoxia-activated green fluorescent protein (GFP) silencing in vitro and its downregulation in GFP-expressing tumors after intravenous administration. The proposed nanoformulation represents a novel tumor-environment-responsive modality for cancer targeting and siRNA delivery. [ABSTRACT FROM AUTHOR]

Herein, we review mechanisms regulating cerebral blood flow (CBF), with specific focus on humans. We revisit important concepts from the older literature and describe the interaction of various mechanisms of cerebrovascular control. We amalgamate this broad scope of information into a brief review, rather than detailing any one mechanism or area of research. The relationship between regulatory mechanisms is emphasized, but the following three broad categories of control are explicated: (1) the effect of blood gases and neuronal metabolism on CBF; (2) buffering of CBF with changes in blood pressure, termed cerebral autoregulation; and (3) the role of the autonomic nervous system in CBF regulation. With respect to these control mechanisms, we provide evidence against several canonized paradigms of CBF control. Specifically, we corroborate the following four key theses: (1) that cerebral autoregulation does not maintain constant perfusion through a mean arterial pressure range of 60-150 mmHg; (2) that there is important stimulatory synergism and regulatory interdependence of arterial blood gases and blood pressure on CBF regulation; (3) that cerebral autoregulation and cerebrovascular sensitivity to changes in arterial blood gases are not modulated solely at the pial arterioles; and (4) that neurogenic control of the cerebral vasculature is an important player in autoregulatory function and, crucially, acts to buffer surges in perfusion pressure. Finally, we summarize the state of our knowledge with respect to these areas, outline important gaps in the literature and suggest avenues for future research. [ABSTRACT FROM AUTHOR]

ABSTRACT Objective Recordings of blood flow velocity waveforms in the ductus venosus ( DV) and umbilical vein ( UV) are routinely used in order to predict fetal condition in high-risk pregnancies. The aim of this study was to investigate the relationship between pathological blood flow in the two vessels and perinatal outcome. Methods High-risk pregnancies ( n = 11 863) admitted from 1993 to 2011 for blood-flow examination, including recordings of DV pulsatility index for veins ( DV-PIV) and UV pulsations, were included. The results were related to perinatal outcome, using the last Doppler examination prior to delivery in the analysis. Results Abnormal DV-PIV was observed in 3.9% of cases, intra-abdominal UV pulsations in 1.3% and pulsations in the cord in 0.7%. As expected, the rate of UV pulsations increased with increasing DV-PIV Z-score. Fetuses with a pathological DV-PIV, but without UV pulsations, showed fewer signs of compromise. This was also true for cases with a DV-PIV ≥ 4 SDs above the mean (53.7% had steady flow in the UV). In contrast, the occurrence of UV pulsations seemed to be an indicator of fetal compromise, regardless of level of DV-PIV. Conclusions Abnormal fetal venous blood velocity is related to adverse outcome in high-risk pregnancies. However, abnormal DV-PIV is not a reliable indicator of fetal compromise unless UV pulsations are concurrently present, and should not be regarded an indication for emergency delivery. Copyright © 2013 ISUOG. Published by John Wiley & Sons Ltd. [ABSTRACT FROM AUTHOR]

The control of arteriolar diameters in microvasculature has been in the focus of studies on mechanisms matching oxygen demand and supply at the tissue level. Functionally, important vascular elements include EC, VSMC, and RBC. Integration of these different cell types into functional units aimed at matching tissue oxygen supply with tissue oxygen demand is only achieved when all these cells can respond to the signals of tissue oxygen demand. Many vasoactive agents that serve as signals of tissue oxygen demand have their receptors on all these types of cells ( VSMC, EC, and RBC) implying that there can be a coordinated regulation of their behavior by the tissue oxygen demand. Such functions of RBC as oxygen carrying by Hb, rheology, and release of vasoactive agents are considered. Several common extra- and intracellular signaling pathways that link tissue oxygen demand with control of VSMC contractility, EC permeability, and RBC functioning are discussed. [ABSTRACT FROM AUTHOR]

Mental stress can trigger myocardial infarction, with poor vascular responses to stress implicated as a pathway. Vascular stress reactivity can be assessed by different methods, such as total peripheral resistance ( TPR) and forearm blood flow ( FBF). Little is known about how these vascular assessments are linked. This was examined in two separate studies. Healthy men (Study 1: N = 29, Study 2: N = 23) completed rest and mental arithmetic (Study 1: 8 min, Study 2: 16 min). In both studies, heart rate, mean arterial pressure, and FBF increased in response to stress. In Study 1, no changes in TPR were seen, but Study 2 found stress-induced increases in TPR. FBF was not linked to TPR at any time (all ps > .05). It appears that limb vasculature and TPR responses to stress do not give the same information about impairments of the vasculature. These findings are relevant to the interpretation of prior research findings and the design of future studies on stress and vascular responses. [ABSTRACT FROM AUTHOR]

The conceptual technique of vascular imaging and blood flow functional imaging based on Hall Effect is presented in this article. With this non-invasive approach, both 3D anatomical imaging of the vasculature and functional imaging of blood flow in the deep structure of the human body can be obtained without radiation risk. The technique is based on the fact that the induced charges can be generated when the blood flows through the magnetic field. The induced electric field strength is measured by two groups of detector arrays, which captures not only the position of vasculature in each section, but also the velocity of blood flow and vessel size. The captured images can also be used for 3D reconstruction of the anatomical models. The designed system architecture including both hardware and software is described. © 2013 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 23, 85-96, 2013 [ABSTRACT FROM AUTHOR]

SUMMARY A coupled computational model of the foot consisting of a three-dimensional soft tissue continuum and a one-dimensional (1D) transient blood flow network is presented in this article. The primary aim of the model is to investigate the blood flow in major arteries of the pathologic foot where the soft tissue stiffening occurs. It has been reported in the literature that there could be up to about five-fold increase in the mechanical stiffness of the plantar soft tissues in pathologic (e.g. diabetic) feet compared with healthy ones. The increased stiffness results in higher tissue hydrostatic pressure within the plantar area of the foot when loaded. The hydrostatic pressure acts on the external surface of blood vessels and tend to reduce the flow cross-section area and hence the blood supply. The soft tissue continuum model of the foot was modelled as a tricubic Hermite finite element mesh representing all the muscles, skin and fat of the foot and treated as incompressible with transversely isotropic properties. The details of the mechanical model of soft tissue are presented in the companion paper, Part 1. The deformed state of the soft tissue continuum because of the applied ground reaction force at three foot positions (heel-strike, midstance and toe-off) was obtained by solving the Cauchy equations based on the theory of finite elasticity using the Galerkin finite element method. The geometry of the main arterial network in the foot was represented using a 1D Hermite cubic finite element mesh. The flow model consists of 1D Navier-Stokes equations and a nonlinear constitutive equation to describe vessel radius-transmural pressure relation. The latter was defined as the difference between the fluid and soft tissue hydrostatic pressure. Transient flow governing equations were numerically solved using the two-step Lax-Wendroff finite difference method. The geometry of both the soft tissue continuum and arterial network is anatomically-based and was developed using the data derived from visible human images and magnetic resonance images of a healthy male volunteer. Simulation results reveal that a two-fold increase in tissue stiffness leads to about 28% reduction in blood flow to the affected region.Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The purpose of this study was to determine (i) the cardiovascular responses to acute blood-flow-restricted ( BFR) resistance exercise and (ii) the influence of applied BFR cuff type on the cardiovascular and perceptual responses. Methods In a randomized, crossover design, 27 participants wore either a 5·0 cm wide elastic cuff or a 13·5 cm wide non-elastic cuff around the thigh while performing four sets of knee extension exercise using 20% of 1- RM. Brachial and central blood pressure ( BP) and aortic augmentation index ( AIx) were measured before and after the restrictive cuffs were applied and inflated, after the 2nd and 4th set of resistance exercise, and 5 and 15 min following the 4th set of exercise. Ratings of perceived exertion and pain were obtained before exercise and after the 2nd and 4th set of exercise. Results Both brachial and central BPs increased and AIx decreased during BFR exercise but returned to baseline levels within 15 min following exercise. The wide cuffs caused a greater elevation in heart rate, brachial and central BPs, perceived effort and pain and a greater decrease in AIx during the BFR exercise. Conclusions These findings suggest that low-intensity BFR resistance exercise does not appear to acutely negatively affect the vasculature. Also, cuff type will greatly affect cardiovascular and perceptual responses to BFR resistance exercise and thus is an important consideration in study design. [ABSTRACT FROM AUTHOR]

Please cite this paper as: Al-Khazraji BK, Novielli NM, Goldman D, Medeiros PJ, Jackson DN. A simple 'Streak Length Method' for quantifying and characterizing red blood cell velocity profiles and blood flow in rat skeletal muscle arterioles. Microcirculation 19: 327-335, 2012. Abstract Objectives: To develop a valid experimental method for quantifying blood flow in continuously branching skeletal muscle arterioles, and to derive an empirical relationship between velocity ratio ( VMax/ VMean) and arteriolar diameter. Methods: We evaluated arteriolar trees using IVVM of rat gluteus maximus muscle and developed a method to acquire single fluorescent-labeled RBC velocities across arteriolar lumens to create velocity profiles. These data were used to calculate the blood flow for 37 vessel segments (diameters: 21-115 μm). Results: Mass balance at arteriolar bifurcations had 0.6 ± 3.2% error. Velocity ratios ranged from 1.35 to 1.98 and were positively correlated with diameter ( p < 0.0001), and VRBC profiles were blunted with decreasing diameter. Conclusions: We present a means for quantifying blood flow in continuously branching skeletal muscle arterioles. Further, we provide an equation for calculating velocity ratios based on arteriolar diameter, which may be used by others for blood flow calculations. [ABSTRACT FROM AUTHOR]

Please cite this paper as: Davis MJ. Perspective: Physiological Role(s) of the Vascular Myogenic Response. Microcirculation 19: 99-114, 2012. Abstract The vascular myogenic response is an inherent property of VSM in the walls of small arteries and arterioles, allowing these principal resistance segments of the microcirculation to respond to changes in transmural pressure. Elevated intraluminal pressure leads to myogenic constriction, whereas reduced pressure leads to myogenic dilation. This review focuses on the physiological significance of the myogenic response in microvascular networks. First, historical concepts related to the detection of stretch by the vessel wall are reviewed, including the wall tension hypothesis, and the implications of the proposal that the arteriolar network responds to Pp changes as a system of series-coupled myogenic effectors. Next, the role of the myogenic response in the local regulation of blood flow and/or Pc is examined. Finally, the interaction of myogenic constriction and dilation with other local control mechanisms, including metabolic, neural and shear-dependent mechanisms, is discussed. Throughout the review, an attempt is made to integrate historical and current literature with an emphasis on the physiological role, rather than the underlying signaling mechanisms, of this important component of vascular control. [ABSTRACT FROM AUTHOR]

Arterioles are the blood vessels in the arterial side of the vascular tree that are located proximal to the capillaries and, in conjunction with the terminal arteries, provide the majority of resistance to blood flow. Consequently, arterioles are important contributors to the regulation of mean arterial pressure and tissue perfusion. Their wall consists of cellular and extracellular components that have been traditionally classified as conforming three layers: an intima containing endothelial cells sited on a basement membrane; a media made of an internal elastic lamina apposed by one or two layers of smooth muscle; and an adventitia composed mostly of collagen bundles, nerve endings and some fibroblasts. These components of the arteriolar wall are dynamically interconnected, providing a level of plasticity to the arteriolar wall that blurs the traditional boundaries of a rigid layered classification. This MiniReview focuses on the structural conformation of the arteriolar wall and shows how wall components interact spatially, functionally and temporally to control vascular diameter, regulate blood flow and maintain vascular permeability. [ABSTRACT FROM AUTHOR]