Complex Network Of Vessels Research Articles

The arterial vascularization of the gastrointestinal tract of the Common pheasant (Phasianus colchicus)

The common pheasant has been the subject of scientific research, although it has yet to receive as thorough analysis as other domestic birds. It has spread to many world areas, adapting to diverse environments. A study was conducted on 30 carcasses of female common pheasants. The aim of the study was a comparative analysis of the anatomy of vessels supplying the digestive system of the pheasant. An anatomical study of the pheasant's arteries revealed that the celiac artery originates from the right part of the descending aorta. Its branches include the proventriculus artery, which supplies vessels to the proventriculus and esophagus. This artery also supplies the spleen, duodenum, and the initial segment of the large intestine. Both the left and right branches of the celiac artery give off numerous branches that reach different areas of the intestines and stomach, forming a complex network of vessels. The cranial mesenteric artery is a crucial vessel supplying the small and large intestines, while the caudal mesenteric artery supplies the final segment of the large intestine and cloaca. Additionally, the pudendal arteries are responsible for vascularizing the cloaca and surrounding structures in this species of bird. These detailed anatomical observations are significant for understanding the blood circulation in pheasants.

Differential regulation of lymphatic junctional morphology and the potential effects on cardiovascular diseases.

The lymphatic vasculature provides an essential route to drain fluid, macromolecules, and immune cells from the interstitium as lymph, returning it to the bloodstream where the thoracic duct meets the subclavian vein. To ensure functional lymphatic drainage, the lymphatic system contains a complex network of vessels which has differential regulation of unique cell-cell junctions. The lymphatic endothelial cells lining initial lymphatic vessels form permeable "button-like" junctions which allow substances to enter the vessel. Collecting lymphatic vessels form less permeable "zipper-like" junctions which retain lymph within the vessel and prevent leakage. Therefore, sections of the lymphatic bed are differentially permeable, regulated in part by its junctional morphology. In this review, we will discuss our current understanding of regulating lymphatic junctional morphology, highlighting how it relates to lymphatic permeability during development and disease. We will also discuss the effect of alterations in lymphatic permeability on efficient lymphatic flux in health and how it may affect cardiovascular diseases, with a focus on atherosclerosis.

Blood Clotting Decreases Pulmonary Circulation during the Coronavirus Disease

Spontaneous blood clotting in pulmonary circulation caused by thrombo-inflammation is one of the main mortality causes during the COVID-19 disease. Blood clotting leads to reduced pulmonary circulation and blood oxygenation. Lung inflammation can be evaluated with noninvasive diagnostic techniques. However, the correlation of the severity of the inflammation with the pulmonary blood flow has not been established. To address this question, in this work, we develop a multiscale model taking into account the interaction of a local model of thrombus growth with 1D hemodynamics in a vessel network. Flux reduction depending on the level of lung obstruction is evaluated. In particular, the model obtains that an obstruction level of 5% leads to a 12% reduction of blood flux. The suggested approach can be used to investigate the interaction of blood clotting and flow not only in the pulmonary network but also in other complex vessel networks.

A fast numerical method for oxygen supply in tissue with complex blood vessel network.

Angiogenesis plays an essential role in many pathological processes such as tumor growth, wound healing, and keloid development. Low oxygen level is the main driving stimulus for angiogenesis. In an animal tissue, the oxygen level is mainly determined by three effects-the oxygen delivery through blood flow in a refined vessel network, the oxygen diffusion from blood to tissue, and the oxygen consumption in cells. Evaluation of the oxygen field is usually the bottleneck in large scale modeling and simulation of angiogenesis and related physiological processes. In this work, a fast numerical method is developed for the simulation of oxygen supply in tissue with a large-scale complex vessel network. This method employs an implicit finite-difference scheme to compute the oxygen field. By virtue of an oxygen source distribution technique from vessel center lines to mesh points and a corresponding post-processing technique that eliminate the local numerical error induced by source distribution, square mesh with relatively large mesh sizes can be applied while sufficient numerical accuracy is maintained. The new method has computational complexity which is slightly higher than linear with respect to the number of mesh points and has a convergence order which is slightly lower than second order with respect to the mesh size. With this new method, accurate evaluation of the oxygen field in a fully vascularized tissue on the scale of centimeter becomes possible.

Learning-Aided Intelligent Cooperative Collision Avoidance Mechanism in Dynamic Vessel Networks

With the increasing traffic density and the highly maritime safety requirements, it is a great challenge to make the optimal motion decision for avoiding the collision in the complex vessel networks. However, the current collision avoidance mechanisms are only considering unilateral static information, ignoring the multilateral dynamic information, which is quite important. In this paper, we investigate the information transmission and the collision avoidance problem in the complex vessel networks, in which the devices are equipped with the capability of Artificial Intelligence (AI). With the empowered learning ability in the networks, we propose a novel two-step-smooth-turn cooperative collision avoidance mechanism for the dynamic vessel networks, considering the motion states of the vessels. In particular, the AI-powered vessels network motion model is designed, which can learn the motion information to predict the safety motion states by automatic collection of the information. Then, a K-Means algorithm combining with genetic algorithm is proposed by expanding the operation of cross genetic and genetic mutations, which can achieve the optimal multi-vessels coordination motion policy for the collision avoidance. Simulation results show that the proposed approach could improve the stability of genetic algorithm and weaken the early convergence of genetic algorithm efficiently. In addition, it shows that the proposed mechanism can achieve an optimal safety route plan for cooperative collision avoidance.

In Vivo Three-Dimensional Two-Photon Microscopy to Study Conducted Vascular Responses by Local ATP Ejection Using a Glass Micro-Pipette.

Maintenance of normal brain function requires a sufficient and efficient supply of oxygen and nutrition by a complex network of vessels. However, the regulation of cerebral blood flow (CBF) is incompletely understood, especially at the capillary level. Two-photon microscopy is a powerful tool widely used to study CBF and its regulation. Currently, this field is limited by the lack of in vivo two-photon microscopy studies examining (1) CBF responses in three-dimensions, (2) conducted vascular responses, and (3) localized interventions within the vascular network. Here, we describe a 3D in vivo method using two-photon microscopy to study conducted vascular responses elicited bylocal ejection of ATP with a glass micro-pipette. Our method uses fast and repetitive hyperstack two-photon imaging providing precise diameter measurements by maximal intensity projection of the obtained images. Furthermore, we show that this method can also be used to study 3D astrocytic calcium responses. We also discuss the advantages and limitations of glass micro-pipette insertion and two-photon hyperstack imaging.

Mature vessel networks in engineered tissue promote graft–host anastomosis and prevent graft thrombosis

Graft vascularization remains one of the most critical challenges facing tissue-engineering experts in their attempt to create thick transplantable tissues and organs. In vitro prevascularization of engineered tissues has been suggested to promote rapid anastomosis between the graft and host vasculatures; however, thrombotic events have been reported upon graft implantation. Here, we aimed to determine whether in vitro vessel maturation in transplantable grafts can accelerate vascular integration and graft perfusion and prevent thrombotic events in the grafts. To this end, endothelial cells and fibroblasts were cocultured on 3D scaffolds for 1, 7, or 14 d to form vasculature with different maturation degrees. Monitoring graft-host interactions postimplantation demonstrated that the 14-d in vitro-cultured grafts, bearing more mature and complex vessel networks as indicated by elongated and branched vessel structures, had increased graft-host vessel anastomosis; host vessel penetration into the graft increased approximately eightfold, and graft perfusion increased sixfold. The presence of developed vessel networks prevented clot accumulation in the grafts. Conversely, short-term cultured constructs demonstrated poor vascularization and increased thrombus formation. Elevated expression levels of coagulation factors, von Willebrand factor (vWF), and tissue factor (TF), were demonstrated in constructs bearing less mature vasculature. To conclude, these findings demonstrate the importance of establishing mature and complex vessel networks in engineered tissues before implantation to promote anastomosis with the host and accelerate graft perfusion.

Adjuvant role of anti-angiogenic drugs in the management of head and neck arteriovenous malformations

Arteriovenous malformations (AVMs) are high-flow vascular malformations characterised by a complex vessel network directly connecting feeding arteries and draining veins, typically featured by a natural history of progression, while spontaneous regressions are purely anecdotal.AVMs are very aggressive entities that possess a locally infiltrative behaviour like neoplasms. Complete “radical” surgical excision presents the highest chance of cure, but nowadays there is still considerable controversy on how to treat large AVMs that are not amenable of “radical” excision.The aim of this paper is to propose a different approach to treat vast AVMs that cannot be removed radically.The association of an antiangiogenic drug (to be initiated before surgery and to be continued in the post-operative period), could prevent the feared “explosive” growth of the remaining nidus after its partial removal. This could make recontouring and other “aesthetically” focused procedures feasible in these patients, with an obvious leap in their quality of life.The most promising antiangiogenic drug seems to be Thalidomide, but other drugs such as Sirolimus, VEGF pathway inhibitors, Interferon or Matrix Metalloproteinase (MMP) Inhibitors could serve the purpose just as well. Even Propranolol could prove useful in this sense as suggested by some recent researches on retinopathy of prematurity and tumour biology.

Microvascular blood flow resistance: Role of red blood cell migration and dispersion

Microvascular blood flow resistance has a strong impact on cardiovascular function and tissue perfusion. The flow resistance in microcirculation is governed by flow behavior of blood through a complex network of vessels, where the distribution of red blood cells across vessel cross-sections may be significantly distorted at vessel bifurcations and junctions. In this paper, the development of blood flow and its resistance starting from a dispersed configuration of red blood cells is investigated in simulations for different hematocrit levels, flow rates, vessel diameters, and aggregation interactions between red blood cells. Initially dispersed red blood cells migrate toward the vessel center leading to the formation of a cell-free layer near the wall and to a decrease of the flow resistance. The development of cell-free layer appears to be nearly universal when scaled with a characteristic shear rate of the flow. The universality allows an estimation of the length of a vessel required for full flow development, lc≲25D, for vessel diameters in the range 10 μm<D<100μm. Thus, the potential effect of red blood cell dispersion at vessel bifurcations and junctions on the flow resistance may be significant in vessels which are shorter or comparable to the length lc. Aggregation interactions between red blood cells generally lead to a reduction of blood flow resistance. The simulations are performed using the same viscosity for both external and internal fluids and the RBC membrane viscosity is not considered; however, we discuss how the viscosity contrast may affect the results. Finally, we develop a simple theoretical model which is able to describe the converged cell-free-layer thickness at steady-state flow with respect to flow rate. The model is based on the balance between a lift force on red blood cells due to cell-wall hydrodynamic interactions and shear-induced effective pressure due to cell–cell interactions in flow. We expect that these results can also be used to better understand the flow behavior of other suspensions of deformable particles such as vesicles, capsules, and cells.

Abstract W P88: THINkS: A Novel Tool for Multiscale CFD Calculations of the Cerebral Vasculature

Background: Computational Fluid Dynamics (CFD) is emerging as a tool for better assessment and management of cerebral aneurysms. However, CFD calculations are often restricted to a small arterial zone and the solution could be inaccurate depending on the boundary conditions prescribed. A 1D simulation of the complete vessel network, THINkS (Total Human Intravascular NetworK Simulation), is introduced to better describe boundary conditions and to provide flow information related to the complete complex vessel network. Methods: THINkS is a modifiable, 1D network simulation of the complete human blood circulatory system. A validation of THINkS was performed using volumetric flow rates recorded in the cerebral vasculature waveforms over the cardiac cycle. Validated waveforms of the; (1) ICA proximal to the siphon, (2) ICA proximal to circle of Willis (CoW), and (3) mid- basilar artery were obtained. THINkS predictions were compared to the experimental bounds for both absolute and dimensionless flow rate quantities. Results: THINkS calculations indicated usefulness of the model in predicting the trends of cerebral flow patterns. THINkS solutions were validated with a number of in vivo experimental data and the agreement was excellent. A comparison with experiments for the impact of incomplete CoW to the flow patterns was also made and the trend shows an excellent agreement with reported data. Conclusion: THINkS allows for more accurate boundary conditions for 3D zonal-based CFD calculations. THINkS has been validated against available experimental data and shown to respond correctly to the flow pattern change caused by the variation in CoW. It provides the detailed flow information of the entire human body including cerebral vessel network. Our aim is to use THINkS to generate accurate flow assessments, guide surgical treatment plans, and more reliably predict risks associated with vascular lesions.

In vivo flow mapping in complex vessel networks by single image correlation.

We describe a novel method (FLICS, FLow Image Correlation Spectroscopy) to extract flow speeds in complex vessel networks from a single raster-scanned optical xy-image, acquired in vivo by confocal or two-photon excitation microscopy. Fluorescent flowing objects produce diagonal lines in the raster-scanned image superimposed to static morphological details. The flow velocity is obtained by computing the Cross Correlation Function (CCF) of the intensity fluctuations detected in pairs of columns of the image. The analytical expression of the CCF has been derived by applying scanning fluorescence correlation concepts to drifting optically resolved objects and the theoretical framework has been validated in systems of increasing complexity. The power of the technique is revealed by its application to the intricate murine hepatic microcirculatory system where blood flow speed has been mapped simultaneously in several capillaries from a single xy-image and followed in time at high spatial and temporal resolution.

Arteriovenous malformations

Arteriovenous malformations (AVMs) are fast-flow vascular malformations composed of a complex vessel network directly connecting feeding arteries to draining veins. The intervening normal capillary network is absent. Proper diagnosis and treatment of AVMs is challenging and in need of an interdisciplinary team of experienced physicians. Careful analysis of the clinical features and evaluation of therapeutic options represent the basis for successful management of AVMs. This article will focus on the clinical and radiological findings and in particular on interdisciplinary management strategies of AVMs including minimally invasive endovascular and surgical treatment.

Understanding vascular development

The vasculature of an organism has the daunting task of connecting all the organ systems to nourish tissue and sustain life. This complex network of vessels and associated cells must maintain blood flow, but constantly adapt to acute and chronic changes within tissues. While the vasculature has been studied for over a century, we are just beginning to understand the processes that regulate its formation and how genetic hierarchies are influenced by mechanical and metabolic cues to refine vessel structure and optimize efficiency. As we gain insights into the developmental mechanisms, it is clear that the processes that regulate blood vessel development can also enable the adult to adapt to changes in tissues that can be elicited by exercise, aging, injury, or pathology. Thus, research in vessel development has provided tremendous insights into therapies for vascular diseases and disorders, cancer interventions, wound repair and tissue engineering, and in turn, these models have clearly impacted our understanding of development. Here we provide an overview of the development of the vascular system, highlighting several areas of active investigation and key questions that remain to be answered.

Regional effects of magnetization dispersion on quantitative perfusion imaging for pulsed and continuous arterial spin labeling

Most experiments assume a global transit delay time with blood flowing from the tagging region to the imaging slice in plug flow without any dispersion of the magnetization. However, because of cardiac pulsation, nonuniform cross-sectional flow profile, and complex vessel networks, the transit delay time is not a single value but follows a distribution. In this study, we explored the regional effects of magnetization dispersion on quantitative perfusion imaging for varying transit times within a very large interval from the direct comparison of pulsed, pseudo-continuous, and dual-coil continuous arterial spin labeling encoding schemes. Longer distances between tagging and imaging region typically used for continuous tagging schemes enhance the regional bias on the quantitative cerebral blood flow measurement causing an underestimation up to 37% when plug flow is assumed as in the standard model.

Visualization of Vessels in Tomato Seedlings Using Girdling

A novel method for the easy and detailed visualization of water pathways (i.e., xylem vessels) involving girdling after staining is proposed. This technique was applied to intact seedlings as well as seedlings whose vessels were intentionally damaged to evaluate the effectiveness of the procedure.The applicability of the technique to grafted fruit-vegetable seedlings was tested using tomato seedlings (Lycopersicon esculentum Mill. ‘Momotaro’). The vessels were stained with congo red via the roots prior to girdling. This technique is unique in that it allows the visualization of the vessel network by a simple procedure as well as the continuous and unambiguous observation of the vertical and horizontal networks of vessels. Using the technique, we can observe a complex network of vessels, including vessel branching and vessel regeneration after damage.

Open problems in computational vascular biomechanics: Hemodynamics and arterial wall mechanics

The vasculature consists of a complex network of vessels ranging from large arteries to arterioles, capillaries, venules, and veins. This network is vital for the supply of oxygen and nutrients to tissues and the removal of carbon dioxide and waste products from tissues. Because of its primary role as a pressure-driven chemomechanical transport system, it should not be surprising that mechanics plays a vital role in the development and maintenance of the normal vasculature as well as in the progression and treatment of vascular disease. This review highlights some past successes of vascular biomechanics, but emphasizes the need for research that synthesizes complementary advances in molecular biology, biomechanics, medical imaging, computational methods, and computing power for purposes of increasing our understanding of vascular physiology and pathophysiology as well as improving the design of medical devices and clinical interventions, including surgical procedures. That is, computational mechanics has great promise to contribute to the continued improvement of vascular health.

Optimal postnodal lymphatic network structure that maximizes active propulsion of lymph

The lymphatic system acts to return lower-pressured interstitial fluid to the higher-pressured veins by a complex network of vessels spanning more than three orders of magnitude in size. Lymphatic vessels consist of lymphangions, segments of vessels between two unidirectional valves, which contain smooth muscle that cyclically pumps lymph against a pressure gradient. Whereas the principles governing the optimal structure of arterial networks have been identified by variations of Murray's law, the principles governing the optimal structure of the lymphatic system have yet to be elucidated, although lymph flow can be identified as a critical parameter. The reason for this deficiency can be identified. Until recently, there has been no algebraic formula, such as Poiseuille's law, that relates lymphangion structure to its function. We therefore employed a recently developed mathematical model, based on the time-varying elastance model conventionally used to describe ventricular function, that was validated by data collected from postnodal bovine mesenteric lymphangions. From this lymphangion model, we developed a model to determine the structure of a lymphatic network that optimizes lymph flow. The model predicted that there is a lymphangion length that optimizes lymph flow and that symmetrical networks optimize lymph flow when the lymphangions downstream of a bifurcation are 1.26 times the length of the lymphangions immediately upstream. Measured lymphangion lengths (1.14 +/- 0.5 cm, n = 74) were consistent with the range of predicted optimal lengths (0.1-2.1 cm). This modeling approach was possible, because it allowed a structural parameter, such as length, to be treated as a variable.

Oxygen advection and diffusion in a three-dimensional vascular anatomical network

There is an increasing need for quantitative and computationally affordable models for analyzing tissue metabolism and hemodynamics in microvascular networks. In this work, we develop a hybrid model to solve for the time-varying oxygen advection-diffusion equation in the vessels and tissue. To obtain a three-dimensional temporal evolution of tissue oxygen concentration for realistic complex vessel networks, we used a graph-based advection model combined with a finite-element based diffusion model and an implicit time-advancing scheme. We validated this algorithm for both static and dynamic conditions. We also applied it to a complex vascular network obtained from a rodent somatosensory cortex. Qualitative agreement was found with in-vivo experiments.

Liver Microcirculation Analysis by Red Blood Cell Motion Modeling in Intravital Microscopy Images

Intravital microscopy has been used to visualize the microcirculation by imaging fluorescent labeled red blood cells (RBCs). Traditionally, microcirculation has been modeled by computing the mean velocity of a few, randomly selected, manually tracked RBCs. However, this protocol is tedious, time consuming, and subjective with technician related bias. We present a new method for analyzing the microcirculation by modeling the RBC motion through automatic tracking. The tracking of RBCs is challenging as in each image, as many as 200 cells move through a complex network of vessels at a wide range of speeds while deforming in shape. To reliably detect RBCs traveling at a wide range of speeds, a window of temporal template matching is applied. Then, cells appearing in successive frames are corresponded based on the motion behavior constraints in terms of the direction, magnitude, and path. The performance evaluation against a ground truth indicates the detection accuracy up to 84% TP at 6% FP and a correspondence accuracy of 89%. We include an in-depth discussion on comparison of the microcirculation based on motion modeling from the proposed automated method against a mean velocity from manual analysis protocol in terms of precision, objectivity, and sensitivity.

Observations on the external morphology and vasculature of a fetal heart of the bowhead whale, Balaena mysticetus

Background Specialized demands within the aquatic environment for over some 60 million years have shaped unique morphological expressions in the whales, dolphins, and porpoises (Cetacea). Detailed consideration of these features, particularly in the great whales, has often been constrained by difficulties in securing adequate specimens for study. We had the opportunity to examine external heart morphology in a rarely obtained and prepared specimen from the bowhead whale, Balaena mysticetus. Methods The external morphology and in situ relations of a formalin-perfused heart were examined grossly in a near-term bowhead fetus. Latex injections assisted visualization of coronary vasculature. Magnetic resonance imaging was used to clarify heart positioning within the thoracic cavity in two younger (early and mid-gestational) intact fetuses. Results The heart was globular in form, with a blunt apex and wide base; it was laterally broad relative to height yet considerably compressed between nearly planar atrial (diaphragmatic) and auricular (sternocostal) surfaces. The heart constituted 0.01 of body mass in the near-term fetus. Within the thoracic cavity, the heart tilted forward on its long axis, placing the great basal vessels in the region of the thoracic inlet. The aorta extended forward from mid-base in parallel with the pulmonary trunk, arched sharply to the left, producing in succession the brachiocephalic trunk, left common carotid artery, and the left subclavian artery. Bifurcation of the brachiocephalic trunk yielded the right common carotid and right subclavian arteries. The distal portion of the aortic arch was linked to the pulmonary trunk via the ductus arteriosus. The aorta then swung caudally over the heart base, descending beneath the bodies of the thoracic vertebrae. The ascending aorta featured three bulbous sinuses immediately distal to the three semilunar cusps of the aortic valve. Originating along the distal boundaries of the left and right sinuses were the left and right coronary arteries. The arteries were similar in size and, because each sent contributions along their respective coronary and interventricular grooves, the heart can be described as bilateral relative to arterial supply. Anastomoses were common within and between the two arteries. Venous return from the heart was comprised of the great, middle, and right cardiac veins, all three converging in the coronary sinus. The right cardiac vein also included tributaries that emptied directly into the right atrium. Conclusions External heart morphology in the fetal bowhead whale examined was distinguished by a laterally broad conformation with significant compression between its cranial and caudal surfaces. Aortic bulb configuration in combination with an expandable aortic arch may support blood service to the heart during diastole. Vascular service to the heart featured a complex vessel network with extensive intraarterial and intravenous anastomoses that enable many alternate blood perfusion pathways and may be adaptive to water-column-pressure fluctuations experienced by a large diving mammal. Anat. Rec. 247:556–581, 1997. © 1997 Wiley-Liss, Inc.