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Hao Q, Wang J, Shen J, Gu R, Rao Y, Feng J, Wang H, Brash JL, Chen H. Robust, Anti-biofouling 2D Nanogel Films from Poly(N-vinyl caprolactam-co-vinylimidazole) Polymers. J Mater Chem B 2022; 10:3723-3733. [DOI: 10.1039/d1tb02726c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In analogy with adsorbed protein films, we have fabricated a family of 2D nanofilms composed of poly(N-vinyl caprolactam-co-vinylimidazole) (PNVCL) nanogels. NVCL was copolymerized with 1-vinylimidazole (VIM), then cross-linked with α,ω-dibromoalkanes...
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Wang Z, Cui Y, Liu P, Zhao Y, Wang L, Liu Y, Xie J. Small Peptides Isolated from Enzymatic Hydrolyzate of Fermented Soybean Meal Promote Endothelium-Independent Vasorelaxation and ACE Inhibition. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2017; 65:10844-10850. [PMID: 29172521 DOI: 10.1021/acs.jafc.7b05026] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Fermentation of soybean is a process in which soy proteins are broken down into small peptides to exert various physiological functions beyond their nutritional value and to improve food source bioactive components responsible for health benefits. Enzymatic hydrolysis could speed up the degradation of proteins during fermentation of soybean, thus resulting in higher peptide production. In the present study, fermented soy meal (fermented with Bacillus subtilis from Douchi) was hydrolyzed by thermolysin, and the water extraction was then separated into four fractions using ultrafiltration membranes. Their vasorelaxation activities were screened, and the most potent fraction was further isolated and purified to obtain four peptides. Briefly, three peptides exerted a dose-dependent vasorelaxation (0.01-4.10 μM) in the phenylephrine preconstricted thoracic aorta ring of Sprague-Dawley rat (relaxation actions were all endothelium-independent), while one peptide induced vasoconstriction. Furthermore, an independent causal relationship between vasorelaxation and angiotensin converting enzyme (ACE) inhibition activities was found.
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Affiliation(s)
- Zhengquan Wang
- Laboratory of Quality & Safety Risk Assessment for Aquatic Products on Storage and Preservation (Shanghai), Ministry of Agriculture , Shanghai 201306, China
| | - Yunyun Cui
- College of Food Science and Technology, Shanghai Ocean University , Shanghai 201306, China
| | - Pengyang Liu
- College of Food Science and Technology, Shanghai Ocean University , Shanghai 201306, China
| | - Yong Zhao
- College of Food Science and Technology, Shanghai Ocean University , Shanghai 201306, China
| | - Liping Wang
- College of Food Science and Technology, Shanghai Ocean University , Shanghai 201306, China
| | - Yuan Liu
- College of Food Science and Technology, Shanghai Ocean University , Shanghai 201306, China
| | - Jing Xie
- Shanghai Engineering Research Center of Aquatic-Product Processing & Preservation , Shanghai 201306, China
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Ko SC, Jung WK, Lee SH, Lee DH, Jeon YJ. Antihypertensive effect of an enzymatic hydrolysate from Styela clava flesh tissue in type 2 diabetic patients with hypertension. Nutr Res Pract 2017; 11:396-401. [PMID: 28989576 PMCID: PMC5621362 DOI: 10.4162/nrp.2017.11.5.396] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2017] [Revised: 05/14/2017] [Accepted: 07/20/2017] [Indexed: 02/05/2023] Open
Abstract
BACKGROUND/OBJECTIVES In this randomized, placebo-controlled, double-blind study, we evaluated the antihypertensive effects of enzymatic hydrolysate from Styela clava flesh tissue in patients with type 2 diabetes mellitus (T2DM) and hypertension. SUBJECTS/METHODS S. clava flesh tissue hydrolysate (SFTH) (n = 34) and placebo (n = 22) were randomly allocated to the study subjects. Each subject ingested two test capsules (500 mg) containing powdered SFTH (SFTH group) or placebo capsules (placebo group) during four weeks. RESULTS In the SFTH group, systolic and diastolic blood pressure decreased significantly 4 weeks after ingestion by 9.9 mmHg (P < 0.01) and 7.8 mmHg (P < 0.01), respectively. In addition, the SFTH group exhibited a significant decrease in hemoglobin A1c with a tendency toward improvement in homeostasis model assessment of insulin resistance, triglyceride, apolipoprotein B and plasma insulin levels after 4 weeks. No adverse effects were observed in other indexes, including biochemical and hematological parameters in both groups. CONCLUSION The results of our study suggested that SFTH exerts a regulatory, antihypertensive effect in patients with T2DM and hypertension.
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Affiliation(s)
- Seok-Chun Ko
- Marine-Integrated Bionics Research Center, Pukyong National University, Busan 48513, Korea
| | - Won-Kyo Jung
- Marine-Integrated Bionics Research Center, Pukyong National University, Busan 48513, Korea.,Department of Biomedical Engineering, and Center for Marine-Integrated Biomedical Technology (BK21 Plus), Pukyong National University, Busan 48513, Korea
| | - Seung-Hong Lee
- Department of Pharmaceutical Engineering, Soonchunhyang University, 22 Soonchunhyangro, Shinchang-myeon, Asan-si, Chungnam 31538, Korea
| | - Dae Ho Lee
- Department of Internal Medicine, Gachon University Gil Medical Center, 21 Namdong-daero 774 road, Incheon 21565, Korea
| | - You-Jin Jeon
- Department of Marine Life Science, Jeju National University, 102 Jejudaehak-ro, Jeju-si, Jeju 63243, Korea
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Doron O, Cohen JE, Gomori M, Spektor S. Extensive bone erosion caused by pseudotumoral aneurysm growth. J Clin Neurosci 2016; 36:54-56. [PMID: 27842796 DOI: 10.1016/j.jocn.2016.10.028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Accepted: 10/15/2016] [Indexed: 11/18/2022]
Abstract
Carotid ophthalmic aneurysms constitute 0.9-6.5% of the aneurysms of the ICA with up to 20% of the cases presenting with visual symptoms. We report a case of an adult woman, presented with chronic headaches and protracted visual alterations progressing to left eye amaurosis. Neuroradiological exams, revealed a giant partially thrombosed carotid ophthalmic aneurysm extending anteriorly, causing pseudotumoral spheno-orbital bone erosion. The patient underwent surgical clipping, evacuation of the thrombotic mass and decompression of the optic pathways with rapid recovery of the vision. This unusual case, contributes to the available body of evidence on aneurysms growth.
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Affiliation(s)
- Omer Doron
- Department of Neurosurgery, Hadassah University Medical Center, Affiliated to the Hebrew University and Hadassah Medical School, Jerusalem, Israel.
| | - Jose E Cohen
- Department of Neurosurgery, Hadassah University Medical Center, Affiliated to the Hebrew University and Hadassah Medical School, Jerusalem, Israel
| | - Moshe Gomori
- Department of Radiology, Hadassah University Medical Center, Affiliated to the Hebrew University and Hadassah Medical School, Jerusalem, Israel
| | - Sergey Spektor
- Department of Neurosurgery, Hadassah University Medical Center, Affiliated to the Hebrew University and Hadassah Medical School, Jerusalem, Israel
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Abas A, Mokhtar NH, Ishak MHH, Abdullah MZ, Ho Tian A. Lattice Boltzmann Model of 3D Multiphase Flow in Artery Bifurcation Aneurysm Problem. COMPUTATIONAL AND MATHEMATICAL METHODS IN MEDICINE 2016; 2016:6143126. [PMID: 27239221 PMCID: PMC4864205 DOI: 10.1155/2016/6143126] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Revised: 03/05/2016] [Accepted: 03/31/2016] [Indexed: 11/17/2022]
Abstract
This paper simulates and predicts the laminar flow inside the 3D aneurysm geometry, since the hemodynamic situation in the blood vessels is difficult to determine and visualize using standard imaging techniques, for example, magnetic resonance imaging (MRI). Three different types of Lattice Boltzmann (LB) models are computed, namely, single relaxation time (SRT), multiple relaxation time (MRT), and regularized BGK models. The results obtained using these different versions of the LB-based code will then be validated with ANSYS FLUENT, a commercially available finite volume- (FV-) based CFD solver. The simulated flow profiles that include velocity, pressure, and wall shear stress (WSS) are then compared between the two solvers. The predicted outcomes show that all the LB models are comparable and in good agreement with the FVM solver for complex blood flow simulation. The findings also show minor differences in their WSS profiles. The performance of the parallel implementation for each solver is also included and discussed in this paper. In terms of parallelization, it was shown that LBM-based code performed better in terms of the computation time required.
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Affiliation(s)
- Aizat Abas
- School of Mechanical Engineering, Universiti Sains Malaysia, Engineering Campus, 14300 Nibong Tebal, Penang, Malaysia
| | - N. Hafizah Mokhtar
- School of Mechanical Engineering, Universiti Sains Malaysia, Engineering Campus, 14300 Nibong Tebal, Penang, Malaysia
| | - M. H. H. Ishak
- School of Mechanical Engineering, Universiti Sains Malaysia, Engineering Campus, 14300 Nibong Tebal, Penang, Malaysia
| | - M. Z. Abdullah
- School of Aerospace Engineering, Universiti Sains Malaysia, Engineering Campus, 14300 Nibong Tebal, Penang, Malaysia
| | - Ang Ho Tian
- School of Mechanical Engineering, Universiti Sains Malaysia, Engineering Campus, 14300 Nibong Tebal, Penang, Malaysia
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Jain RK, Martin JD, Stylianopoulos T. The role of mechanical forces in tumor growth and therapy. Annu Rev Biomed Eng 2015; 16:321-46. [PMID: 25014786 DOI: 10.1146/annurev-bioeng-071813-105259] [Citation(s) in RCA: 595] [Impact Index Per Article: 66.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Tumors generate physical forces during growth and progression. These physical forces are able to compress blood and lymphatic vessels, reducing perfusion rates and creating hypoxia. When exerted directly on cancer cells, they can increase cells' invasive and metastatic potential. Tumor vessels-while nourishing the tumor-are usually leaky and tortuous, which further decreases perfusion. Hypoperfusion and hypoxia contribute to immune evasion, promote malignant progression and metastasis, and reduce the efficacy of a number of therapies, including radiation. In parallel, vessel leakiness together with vessel compression causes a uniformly elevated interstitial fluid pressure that hinders delivery of blood-borne therapeutic agents, lowering the efficacy of chemo- and nanotherapies. In addition, shear stresses exerted by flowing blood and interstitial fluid modulate the behavior of cancer and a variety of host cells. Taming these physical forces can improve therapeutic outcomes in many cancers.
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Affiliation(s)
- Rakesh K Jain
- Edwin L. Steele Laboratory, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114;
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KABINEJADIAN FOAD, CHUA LEOKPOH, GHISTA DHANJOON, TAN YONGSENG. CABG MODELS FLOW SIMULATION STUDY ON THE EFFECTS OF VALVE REMNANTS IN THE VENOUS GRAFT. J MECH MED BIOL 2012. [DOI: 10.1142/s0219519410003587] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Venous valves and sinuses are frequently observed in vein grafts in the coronary artery bypass grafts (CABG). However, from the biomedical engineering viewpoint, vein grafts are always assumed as smooth tubes in the existing simulations, and no effort has been made to investigate the effects of jaggedness of the graft inner wall due to the valve cusps remnants and valve sinus (in case of valve-stripped saphenous vein (SV) grafts) on the blood flow patterns and hemodynamic parameters (HPs). In this paper, the effects of the inner surface irregularities of a vein graft on the blood flow is investigated in the graft as well as in the distal anastomotic region, with a more realistic geometry of valve-stripped SV, by means of numerical simulation of pulsatile, Newtonian blood flow. The simulation results demonstrate that the valve remnants and sinuses cause disturbances in the flow field within the graft (due to vortices formation within the valve sinuses) and undesirable distribution of HPs, which can result in early atherosclerotic lesion development in the graft.
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Affiliation(s)
- FOAD KABINEJADIAN
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, S. 639798, Singapore
| | - LEOK POH CHUA
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, S. 639798, Singapore
| | - DHANJOO N. GHISTA
- Parkway College, 168 Jalan Bukit Merah, Surbana One, S. 150168, Singapore
| | - YONG SENG TAN
- Mount Elizabeth Medical Centre, 3 Mount Elizabeth, S. 228510, Singapore
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Abrupt increase in rat carotid blood flow induces rapid alteration of artery mechanical properties. J Mech Behav Biomed Mater 2010; 4:9-15. [PMID: 21094476 DOI: 10.1016/j.jmbbm.2010.08.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2010] [Revised: 08/06/2010] [Accepted: 08/12/2010] [Indexed: 10/19/2022]
Abstract
Vascular remodeling is essential to proper vessel function. Dramatic changes in mechanical environment, however, may initiate pathophysiological vascular remodeling processes that lead to vascular disease. Previous work by some of our group has demonstrated a dramatic rise in matrix metalloproteinase (MMP) expression shortly following an abrupt increase in carotid blood flow. We hypothesized that there would be a corresponding change in carotid mechanical properties. Unilateral carotid ligation surgery was performed to produce an abrupt, sustained increase in blood flow through the contralateral carotid artery of rats. The flow-augmented artery was harvested after sham surgery or 1, 2, or 6 days after flow augmentation. Vessel mechanical response in the circumferential direction was then evaluated through a series of pressure-diameter tests. Results show that the extent of circumferential stretch (normalized change in diameter) at in vivo pressure levels was significantly different (p<0.05) from normo-flow controls at 1 and 2 days following flow augmentation. Measurements at 1, 2, and 6 days were not significantly different from one another, but a trend in the data suggested that circumferential stretch was largest 1 day following surgery and subsequently decreased toward baseline values. Because previous work with this model indicated a similar temporal pattern for MMP-9 expression, an exploratory set of experiments was conducted where vessels were tested 1 day following surgery in animals treated with broad spectrum MMP inhibitors (either doxycycline or GM6001). Results showed a trend for the inhibitors to minimize changes in mechanical properties. Observations demonstrate that vessel mechanical properties change rapidly following flow augmentation and that alterations may be linked to expression of MMPs.
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Pries AR, Höpfner M, le Noble F, Dewhirst MW, Secomb TW. The shunt problem: control of functional shunting in normal and tumour vasculature. Nat Rev Cancer 2010; 10:587-93. [PMID: 20631803 PMCID: PMC3109666 DOI: 10.1038/nrc2895] [Citation(s) in RCA: 185] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Networks of blood vessels in normal and tumour tissues have heterogeneous structures, with widely varying blood flow pathway lengths. To achieve efficient blood flow distribution, mechanisms for the structural adaptation of vessel diameters must be able to inhibit the formation of functional shunts (whereby short pathways become enlarged and flow bypasses long pathways). Such adaptation requires information about tissue metabolic status to be communicated upstream to feeding vessels, through conducted responses. We propose that impaired vascular communication in tumour microvascular networks, leading to functional shunting, is a primary cause of dysfunctional microcirculation and local hypoxia in cancer. We suggest that anti-angiogenic treatment of tumours may restore vascular communication and thereby improve or normalize flow distribution in tumour vasculature.
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Affiliation(s)
- Axel R Pries
- Department of Physiology and the Centre for Cardiovascular Research, Charité Berlin, Thielallee 71, D-14195 Berlin, Germany.
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Abstract
Sustained hemodynamic stresses, especially high blood flow, result in flow-induced outward vascular remodeling. Our previous study showed that macrophage depletion reduced flow-induced outward remodeling of the rat common carotid artery, indicating that macrophages are critical in flow-induced outward vascular remodeling. Macrophage is known to release proteinases, including matrix metalloproteinases (MMPs). Degradation and loosening of extracellular matrix by MMPs may facilitate vascular remodeling. Therefore, we assessed the functions of MMPs in flow-induced outward vascular remodeling by using the flow-augmented common carotid artery model in mice. We validated that ligation of the left common carotid artery increased blood flow and luminal diameter of the right common carotid artery without significant change in blood pressure of mice. To assess the functions of MMPs in flow-induced outward vascular remodeling, we used doxycycline (broad-spectrum MMP inhibitor), SB-3CT (selective MMP inhibitor), MMP-9 knockout mice, and MMP-12 knockout mice. Although there was only a trend for doxycycline treatment to reduce flow-induced outward vascular remodeling, SB-3CT treatment significantly reduced flow-induced outward vascular remodeling. In addition, flow-induced outward vascular remodeling was significantly reduced in MMP-9 knockout mice, but not in MMP-12 knockout mice. These data revealed that MMPs, especially MMP-9, are critical in flow-induced outward vascular remodeling.
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Billinger SA, Gajewski BJ, Guo LX, Kluding PM. Single limb exercise induces femoral artery remodeling and improves blood flow in the hemiparetic leg poststroke. Stroke 2009; 40:3086-90. [PMID: 19520990 DOI: 10.1161/strokeaha.109.550889] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND AND PURPOSE After stroke, individuals have decreased mobility of the hemiparetic leg, which demands less muscle oxygen consumption; thus, blood flow decreases. The purpose of this study was to determine the effect of single limb exercise (SLE) on femoral artery blood flow, diameter, and peak flow velocity in the hemiparetic leg after stroke. METHODS Twelve individuals (60.6+/-14.5 years of age; 5 male) with chronic stroke (69.1+/-82.2 months; 5 with right-sided hemiparesis) participated in the study. The intervention consisted of a SLE knee extension/flexion protocol 3 times per week for 4 weeks. Using Doppler ultrasound, bilateral femoral artery blood flow, diameter, and peak flow velocity were assessed at baseline, after 2 weeks, and after 4 weeks of SLE. RESULTS Using repeated-measures analysis of variance, femoral artery blood flow, arterial diameter, and blood flow velocity in the hemiparetic limb were significantly improved (P<0.0001) after the SLE. No significant changes occurred in the nontrained limb for any outcome measures. CONCLUSIONS These data suggest that a 4-week SLE training program that increases muscular activity in the hemiparetic limb improves femoral artery blood flow, diameter, and peak velocity. SLE may be an important training strategy in stroke rehabilitation to minimize the vascular changes that occur poststroke due to decreased activity of the hemiparetic limb.
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Affiliation(s)
- Sandra A Billinger
- Department of Physical Therapy and Rehabilitation Sciences, University of Kansas Medical Center, Kansas City, KS 66160, USA.
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Abstract
The initiation and progression of cerebral aneurysms are degenerative processes of the arterial wall driven by a complex interaction of biological and hemodynamic factors. Endothelial cells on the artery wall respond physiologically to blood-flow patterns. In normal conditions, these responses are associated with nonpathological tissue remodeling and adaptation. The combination of abnormal blood patterns and genetics predisposition could lead to the pathological formation of aneurysms. Here, we review recent progress on the basic mechanisms of aneurysm formation and evolution, with a focus on the role of hemodynamic patterns.
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Affiliation(s)
- Daniel M. Sforza
- Center for Computational Fluid Dynamics, George Mason University, Fairfax, Virginia 22030
| | - Christopher M. Putman
- Interventional Neuroradiology, Inova Fairfax Hospital, Falls Church, Virginia 22042
- Department of Neurosurgery, School of Medicine, George Washington University, Washington, DC 20037
| | - Juan Raul Cebral
- Center for Computational Fluid Dynamics, George Mason University, Fairfax, Virginia 22030
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Abstract
The functional properties of microcirculation crucially depend on its angioarchitecture, (i.e., vessel arrangement and morphology). The microcirculation is subject to continuous dynamic structural adaptation (i.e., remodeling) controlled by hemodynamic and metabolic stimuli. Due to the complexity of the interactions among stimuli, reactions, and functional properties, an adequate understanding of structural adaptation requires mathematical models in addition to experimental investigations. Mathematical models have been developed that allow the prediction of realistic vascular properties, based on generic patterns of vascular responses. These models can be used to investigate and predict distributions of vessel morphology consistent with certain putative adaptation principles of terminal vascular beds in response to local hemodynamic and metabolic conditions. They have suggested new hypotheses, including the importance of conducted responses in network adaptation, and can explain the mechanisms underlying observed structural and functional network properties. In the future, the value of such models can be enhanced by including the effects of longitudinal stretch and pulsatility, the relationship between acute tone and structural adaptation, and the description of molecular and cellular mechanisms underlying structural responses of microvessels.
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Affiliation(s)
- Axel R Pries
- Department of Physiology, Charité-Universitätsmedizin Berlin, Berlin, Germany.
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Hemodynamics and cerebrovascular disease. ACTA ACUST UNITED AC 2008; 70:447-53. [DOI: 10.1016/j.surneu.2008.07.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2008] [Accepted: 07/16/2008] [Indexed: 11/20/2022]
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Cebral JR, Castro MA, Putman CM, Alperin N. Flow-area relationship in internal carotid and vertebral arteries. Physiol Meas 2008; 29:585-94. [PMID: 18460763 DOI: 10.1088/0967-3334/29/5/005] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Subject-specific computational and experimental models of hemodynamics in cerebral aneurysms require the specification of physiologic flow conditions. Because patient-specific flow data are not always available, researchers have used 'typical' or population average flow rates and waveforms. However, in order to be able to compare the magnitude of hemodynamic variables between different aneurysms or groups of aneurysms (e.g. ruptured versus unruptured) it is necessary to scale the flow rates to the area of the inflow artery. In this work, a relationship between flow rates and vessel areas is derived from phase-contrast magnetic resonance measurements in the internal carotid arteries and vertebral arteries of normal subjects.
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Affiliation(s)
- J R Cebral
- Center for Computational Fluid Dynamics, George Mason University, Fairfax, VA 22030, USA.
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de Groot PC, Bleeker MW, van Kuppevelt DH, van der Woude LH, Hopman MT. Rapid and extensive arterial adaptations after spinal cord injury. Arch Phys Med Rehabil 2006; 87:688-96. [PMID: 16635632 DOI: 10.1016/j.apmr.2006.01.022] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2005] [Accepted: 01/27/2006] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To assess the time course of adaptations in leg vascular dimension and function within the first 6 weeks after a spinal cord injury (SCI). DESIGN Longitudinal study design. SETTING University medical center and rehabilitation clinic. PARTICIPANTS Six men were studied serially at 1, 2, 3, 4, and 6 weeks after SCI. INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES Diameter, blood flow, and shear rate levels of the common femoral artery (CFA), superficial femoral artery (SFA), brachial artery, and carotid artery were measured with echo Doppler ultrasound (diameter, blood flow, shear rate). Endothelial function in the SFA was measured with flow-mediated dilation (FMD). In addition, leg volume and blood pressure measurements were performed. RESULTS Femoral artery diameter (CFA, 25%; SFA, 16%; P<.01) and leg volume (22%, P<.01) decreased simultaneously, and these reductions were largely accomplished within 3 weeks postinjury. Significant increases were observed for basal shear rate levels (64% increase at week 3; 117% increase at week 6; P<.01), absolute FMD responses (8% increase at week 3, 23% increase at week 6; P<.05) and relative FMD responses (26% increase at week 3, 44% increase at week 6; P<.001). CONCLUSIONS Our findings show a rapid onset of adaptations in arterial dimension and function to extreme inactivity in humans. Vascular adaptations include extensive reductions in femoral diameter and leg volume, as well as increased basal shear rate levels and FMD responses, which all appear to be largely accomplished within 3 weeks after an SCI.
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Affiliation(s)
- Patricia C de Groot
- Department of Physiology, Radboud University Nijmegen Medical Centre, Nijmegen, the Netherlands
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Tateshima S, Murayama Y, Villablanca JP, Morino T, Nomura K, Tanishita K, Viñuela F. In vitro measurement of fluid-induced wall shear stress in unruptured cerebral aneurysms harboring blebs. Stroke 2003; 34:187-92. [PMID: 12511772 DOI: 10.1161/01.str.0000046456.26587.8b] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND AND PURPOSE Little attention has been focused on the role of fluid-induced wall shear stress in fully developed cerebral aneurysms. The purpose of this study is to evaluate the alternation and distribution of wall shear stress over 1 cardiac cycle in patients' aneurysms. METHODS A middle cerebral artery aneurysm and a basilar tip aneurysm with localized outpouching (blebs) in their domes were selected for this study. With the use of a stereo lithography machine, geometrically realistic aneurysm models were created on the basis of 3-dimensional CT angiograms. In vitro shearing velocity measurement was conducted with the use of laser-Doppler velocimetry at multiple points on the aneurysmal wall to calculate the value of wall shear stress. The wall shear stress was documented at multiple points in the aneurysm inflow zone, dome, and outflow zone. RESULTS Distribution of wall shear stress was not uniform in the aneurysm walls, and particular regions were exposed to relatively high wall shear stress. The wall shear stress changed dynamically throughout 1 cardiac cycle at the point where a high value of wall shear stress was noted. The blebs of both aneurysms were exposed to high wall shear stress. Unlike previous reports in which an ideal spherical aneurysm model was used, the aneurysm inflow zone was not exposed to high shear stress. CONCLUSIONS In vitro aneurysm models based on the patients' angiograms allowed us to conduct a more realistic evaluation of wall shear stress in the aneurysms harboring blebs. These results provide us with further indications of the correlation of wall shear stress with the natural history of cerebral aneurysms.
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Affiliation(s)
- Satoshi Tateshima
- Division of Interventional Neuroradiology, Department of Radiological Sciences, School of Medicine and Medical Center, University of California at Los Angeles, CA 90024, USA.
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Tateshima S, Murayama Y, Villablanca JP, Morino T, Takahashi H, Yamauchi T, Tanishita K, Vinuela F. Intraaneurysmal flow dynamics study featuring an acrylic aneurysm model manufactured using a computerized tomography angiogram as a mold. J Neurosurg 2001; 95:1020-7. [PMID: 11765817 DOI: 10.3171/jns.2001.95.6.1020] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECT To obtain precise flow profiles in patients' aneurysms, the authors developed a new in vitro study method featuring an aneurysm model manufactured using three-dimensional computerized tomography (3D CT) angiography. METHODS A clear acrylic basilar artery (BA) tip aneurysm model manufactured from a patient's 3D CT angiogram was used to analyze flow modifications during one cardiac cycle. Stereolithography was utilized to create the aneurysm model. Three-dimensional flow profiles within the aneurysm model were obtained from velocity measurements by using laser Doppler velocimetry. The aneurysm inflow/outflow zones changed dynamically in their location, size of their cross-sectional area, and also in their shapes over one cardiac cycle. The flow velocity at the inflow zone was 16.8 to 81.9% of the highest axial velocity in the BA with a pulsatility index (PI) of 1.1. The flow velocity at the outflow zone was 16.8 to 34.3% of the highest axial velocity of the BA, with a PI of 0.68. The shear stress along the walls of the aneurysm was calculated from the fluid velocity measured at a distance of 0.5 mm from the wall. The highest value of shear stress was observed at the bleb of the aneurysm. CONCLUSIONS This clear acrylic model of a BA tip aneurysm manufactured using a CT angiogram allowed qualitative and quantitative analysis of its flow during a cardiac cycle. Accumulated knowledge from this type of study may reveal pertinent information about aneurysmal flow dynamics that will help practitioners understand the relationship among anatomy, flow dynamics, and the natural history of aneurysms.
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Affiliation(s)
- S Tateshima
- Department of Radiological Sciences, University of California at Los Angeles School of Medicine and Medical Center, Los Angeles, California 90024, USA.
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Abstract
Findings from recent bed rest and spaceflight human studies have indicated that the inability to adequately elevate the peripheral resistance and the altered autoregulation of cerebral vasculature are important factors in postflight orthostatic intolerance. Animal studies with rat model have revealed that simulated microgravity may induce upward and downward regulations in the structure, function, and innervation of the cerebral and hindquarter vessels. These findings substantiate in general the hypothesis that microgravity-induced redistribution of transmural pressures and flows across and within the arterial vasculature may well initiate differential adaptations of vessels in different anatomic regions. Understanding of the mechanisms involved in vascular adaptation to microgravity is also important for the development of multisystem countermeasures. However, future studies will be required to further ascertain the peripheral effector mechanism of postflight cardiovascular dysfunction.
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Affiliation(s)
- L F Zhang
- Department of Aerospace Physiology, The Fourth Military Medical Academy, Xi'an 710032, P.R. China.
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22
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Pries AR, Reglin B, Secomb TW. Structural adaptation of microvascular networks: functional roles of adaptive responses. Am J Physiol Heart Circ Physiol 2001; 281:H1015-25. [PMID: 11514266 DOI: 10.1152/ajpheart.2001.281.3.h1015] [Citation(s) in RCA: 106] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Terminal vascular beds continually adapt to changing demands. A theoretical model is used to simulate structural diameter changes in response to hemodynamic and metabolic stimuli in microvascular networks. Increased wall shear stress and decreased intravascular pressure are assumed to stimulate diameter increase. Intravascular partial pressure of oxygen (PO(2)) is estimated for each segment. Decreasing PO(2) is assumed to generate a metabolic stimulus for diameter increase, which acts locally, upstream via conduction along vessel walls, and downstream via metabolite convection. By adjusting the sensitivities to these stimuli, good agreement is achieved between predicted network characteristics and experimental data from microvascular networks in rat mesentery. Reduced pressure sensitivity leads to increased capillary pressure with reduced viscous energy dissipation and little change in tissue oxygenation. Dissipation decreases strongly with decreased metabolic response. Below a threshold level of metabolic response flow shifts to shorter pathways through the network, and oxygen supply efficiency decreases sharply. In summary, the distribution of vessel diameters generated by the simulated adaptive process allows the network to meet the functional demands of tissue while avoiding excessive viscous energy dissipation.
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Affiliation(s)
- A R Pries
- Department of Physiology, Freie Universität Berlin, D-14195 Berlin, Germany.
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23
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Malek AM, Izumo S, Alper SL. Modulation by pathophysiological stimuli of the shear stress-induced up-regulation of endothelial nitric oxide synthase expression in endothelial cells. Neurosurgery 1999; 45:334-44; discussion 344-5. [PMID: 10449079 DOI: 10.1097/00006123-199908000-00028] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
OBJECTIVE Fluid shear stress (the frictional force resulting from blood flow) is a principal regulator of endothelial nitric oxide synthase (eNOS) expression. We examined the responses of eNOS messenger ribonucleic acid (mRNA) levels to dynamic shear stimuli in the presence of pathological risk modifiers. METHODS Confluent bovine aortic endothelial cells were subjected in vitro to shear stress (using a cone-plate viscometer) and to hydrostatic pressure (using a custom-built pressure chamber device). eNOS mRNA levels were quantitated by densitometric analysis of Northern blots. RESULTS In contrast to steady laminar shear stress, which elevated eNOS mRNA levels in a time- and dose-dependent manner (2.9- and 3.6-fold after 6 h at 4 and 20 dyn/cm2, respectively), steady hydrostatic pressure of 150 mm Hg decreased eNOS mRNA levels by 46%. eNOS mRNA up-regulation by shear stress was reversible after cessation of flow, although it was not influenced by previous shear exposure, and it was not mediated by a stable transferable factor. eNOS mRNA up-regulation by sinusoidal shear stress was frequency-dependent, with a moderate response at 1-Hz oscillating shear and no change at 0.3 Hz. Hypoxia (3% O2) suppressed eNOS mRNA expression by 78% under static conditions and by 72% under shear conditions but did not alter the fold induction by shear. Elevated glucose concentrations reduced eNOS mRNA levels in both resting and shear stress-exposed cells but did not reduce the fold induction by shear; the protein kinase C inhibitor calphostin C was without effect. Shear-induced up-regulation of eNOS mRNA was unaffected by changes in the medium partial pressure of CO2/pH, by the Na+/H+-exchanger inhibitor HOE694, or by aspirin. In contrast, the shear response was potentiated by homocysteine. CONCLUSION Both physical and chemical stimuli regulate eNOS mRNA levels in endothelial cells. Although eNOS mRNA expression is increased by shear stress, it is decreased by hydrostatic pressure, hypoxia, and elevated glucose levels. The effect of shear on eNOS mRNA expression involves a reversible, frequency-dependent process. These in vitro findings suggest possible contributions of the eNOS flow response to atherosclerosis, in the presence of systemic risk factors.
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Affiliation(s)
- A M Malek
- Department of Neurosurgery, Brigham and Women's Hospital, Children's Hospital, and Harvard Medical School, Boston, Massachusetts, USA
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24
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Keynton RS, Evancho MM, Sims RL, Rittgers SE. The effect of graft caliber upon wall shear within in vivo distal vascular anastomoses. J Biomech Eng 1999; 121:79-88. [PMID: 10080093 DOI: 10.1115/1.2798047] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Wall shear has been widely implicated as a contributing factor in the development of intimal hyperplasia in the anastomoses of chronic arterial bypass grafts. Earlier studies have been restricted to either: (1) in vitro or computer simulation models detailing the complex hemodynamics within an anastomosis without corresponding biological responses, or (2) in vivo models that document biological effects with only approximate wall shear information. Recently, a specially designed pulse ultrasonic Doppler wall shear rate (PUDWSR) measuring device has made it possible to obtain three near-wall velocity measurements nonintrusively within 1.05 mm of the vessel luminal surface from which wall shear rates (WSRs) were derived. It was the purpose of this study to evaluate the effect of graft caliber, a surgically controllable variable, upon local hemodynamics, which, in turn, play an important role in the eventual development of anastomotic hyperplasia. Tapered (4-7 mm I.D.) 6-cm-long grafts were implanted bilaterally in an end-to-side fashion with 30 deg proximal and distal anastomoses to bypass occluded common carotid arteries of 16 canines. The bypass grafts were randomly paired in contralateral vessels and placed such that the graft-to-artery diameter ratio, DR, at the distal anastomosis was either 1.0 or 1.5. For all grafts, the average Re was 432 +/- 112 and the average Womersley parameter, alpha, was 3.59 +/- 0.39 based on artery diameter. There was a sharp skewing of flow toward the artery floor with the development of a stagnation point whose position varied with time (up to two artery diameters) and DR (generally more downstream for DR = 1.0). Mean WSRs along the artery floor for DR = 1.0 and 1.5 were found to range sharply from moderate to high retrograde values (589 s-1 and 1558 s-1, respectively) upstream to high antegrade values (2704 s-1 and 2302 s-1, respectively) immediately downstream of the stagnation point. Although there were no overall differences in mean and peak WSRs between groups, there were significant differences (p < 0.05) in oscillatory WSRs as well as in the absolute normalized mean and peak WSRs between groups. There were also significant differences (p < 0.05) in mean and peak WSRs with respect to axial position along the artery floor for both DR cases. In conclusion, WSR varies widely (1558 s-1 retrograde to 2704 s-1 antegrade) within end-to-side distal graft anastomoses, particularly along the artery floor, and may play a role in the development of intimal hyperplasia through local alteration of mass transport and mechano-signal transduction within the endothelium.
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Affiliation(s)
- R S Keynton
- Department of Biomedical Engineering, University of Akron, OH 44325, USA
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25
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Pries AR, Secomb TW, Gaehtgens P. Structural autoregulation of terminal vascular beds: vascular adaptation and development of hypertension. Hypertension 1999; 33:153-61. [PMID: 9931096 DOI: 10.1161/01.hyp.33.1.153] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
-It is widely accepted that the early phase of primary hypertension is characterized by elevated cardiac output, whereas in later stages the increased blood pressure is due to increased peripheral resistance. To study long-term effects of increased blood flow on peripheral resistance, structural adaptation of microvascular networks in response to changes in blood flow was simulated using a previously developed theoretical model. The diameter of each vessel segment was assumed to change in response to local levels of shear stress, transmural pressure, a metabolic stimulus dependent on blood flow rate, and a conducted stimulus. Network morphologies and topologies were derived from intravital microscopy of the rat mesentery. Adaptive responses to the 4 stimuli were quantitatively balanced to yield stable and realistic distributions of vascular diameters and blood flow rates when the total flow rate was set to observed levels. To simulate effects of increased cardiac output, network flow resistance after structural adaptation was determined for a range of flow rates. Resistance increased with increasing flow, and increases in pressure were up to 3-fold greater than proportional to the increases in flow. According to the model, flow-dependent changes of network resistance result mainly from the vascular response to transmural pressure, which also causes arteriovenous asymmetry of diameters and pressure drops. Therefore, in vascular beds that exhibit arteriovenous asymmetry, increased flow may trigger increased flow resistance by a mechanism involving the tendency of vascular segments to reduce their luminal diameters in response to increased transmural pressure.
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Affiliation(s)
- A R Pries
- Deutsches Herzzentrum Berlin and the Department of Physiology, Freie Universität Berlin, Germany.
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26
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Keynton R, Nemer R, Neifert Q, Fatemi R, Rittgers S. Design, fabrication, and in vitro evaluation of an in vivo ultrasonic Doppler wall shear rate measuring device. IEEE Trans Biomed Eng 1995. [DOI: 10.1109/10.376147] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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27
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Rossitti S, Frisén L. Remodelling of the retinal arterioles in descending optic atrophy follows the principle of minimum work. ACTA PHYSIOLOGICA SCANDINAVICA 1994; 152:333-40. [PMID: 7872010 DOI: 10.1111/j.1748-1716.1994.tb09813.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Mathematical modelling indicates that the minimum energy cost for blood flow is achieved when the arteries are arranged in a branching hierarchy such that the radii of the vessels are adjusted to the cube root of the volumetric flow (principle of minimum work). This is known to apply over several magnitudes of vessel calibres, and in many different organs, including the brain, in humans and in animals. This paper addresses the issue of remodelling of one and the same arterial network to long-term changes in blood flow. This has not been studied previously in humans. We measured the radius of parent (r0) and branch segments (r1 and r2) of the retinal arteriolar network in fundus photographs of six patients with blinding, non-vascular retrobulbar optic nerve lesions, mostly traumatic in origin, before and after the development of descending optic atrophy. Attenuation of retinal arterioles is a well-known phenomenon in descending optic atrophy, and is attributable to decreased metabolic demand secondary to loss of the retinal ganglion cells and their axons. On average, arteriolar diameters decreased by 15.2 +/- 17.7% (SD), with 95% confidence intervals of 18.7% and 11.7%; the radii decreased significantly (P = 0.0001) (n = 99). The area ratio of the bifurcations, defined as (r2(1) + r2(2))r-2(0), was 1.23 +/- 0.2 before, and 1.18 +/- 0.2 after optic atrophy (n = 36); the change of area ratio was not significant. The branching geometry of the retinal arteriolar network obeyed strictly the optimum branching rule of the principle of minimum work, or r3(0) = r3(1) + r3(2).(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- S Rossitti
- Department of Clinical Neurosciences, University of Göteborg, Sweden
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28
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Coan DE, Wechezak AR, Viggers RF, Sauvage LR. Effect of shear stress upon localization of the Golgi apparatus and microtubule organizing center in isolated cultured endothelial cells. J Cell Sci 1993; 104 ( Pt 4):1145-53. [PMID: 8314899 DOI: 10.1242/jcs.104.4.1145] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Despite substantial evidence to suggest that directed cell migration is dependent upon positioning of the Golgi apparatus (GA) and the microtubule organizing center (MTOC), some controversy exists about whether such a relationship is relevant to endothelial cells under flow. The present study was undertaken to provide an indepth investigation of the relationship between shear stress, GA/MTOC localization, cell migration and nuclear position. Bovine carotid endothelial cells were exposed to 22 or 88 dynes/cm2 for 0.5, 2, 8 or 24 h, and localization of their GA/MTOCs was determined relative to the direction of flow. In no-flow control specimens, (0, 0.5, 2, 8 and 24 h) there was no change in the equally distributed GA/MTOCs. In contrast, during the first 8 h at 88 dynes/cm2 and by 2 h at 22 dynes/cm2 there was a significant increase in the number of cells with GA/MTOCs localized upstream to flow direction. The effect was temporary, however, and by 24 h there was no significant difference between the no-flow, 22 and 88 dynes/cm2 specimens. Analysis of GA/MTOC localization with respect to the direction of cell migration determined that 72.5% of no-flow cells possessed GA/MTOCs localized to the sides of nuclei nearest the direction of migration. In contrast, 64% of the specimens shear stressed over the same time period had GA/MTOCs localized to the sides of nuclei opposite the direction of migration. These results suggest that positioning of the GA/MTOC in endothelial cells is not dependent completely upon the direction of migration.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- D E Coan
- Hope Heart Research Institute, Seattle, Washington 98122
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29
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Abstract
Fluid transport systems mediate the transfer of materials both within an organism and between an organism and its environment. The architecture of fluid transport systems is determined by the small distances over which transfer processes are effective and by hydrodynamic and energetic constraints. All fluid transport systems within organisms exhibit one of two geometries, a simple tube interrupted by a planar transfer region or a branched network of vessels linking widely distributed transfer regions; each is determined by different morphogenetic processes. By exploiting the signal inherent in local shear stress on the vessel walls, animals have repeatedly evolved a complex branching hierarchy of vessels approximating a globally optimal system that minimizes the costs of the construction and maintenance of the fluid transport system.
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Affiliation(s)
- M LaBarbera
- Department of Organismal Biology and Anatomy, University of Chicago, IL 60637
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30
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Kamiya A, Ando J, Shibata M, Wakayama H. The efficiency of the vascular-tissue system for oxygen transport in the skeletal muscles. Microvasc Res 1990; 39:169-85. [PMID: 2352488 DOI: 10.1016/0026-2862(90)90068-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The efficiency of the vascular-tissue system for oxygen (O2) transport in the skeletal muscle was estimated by using Krogh's cylinder model for the capillary-tissue arrangement. The tissue mass supplied by a single capillary was calculated as the region of positive O2 tension. For given values of total muscle flow and tissue O2 consumption rate, total tissue mass was determined as the function of the capillary number (n). The energy cost to maintain the vascular system with n terminals (capillaries) was assessed by the minimum volume model by Kamiya and Togawa (1972). The efficiency of the entire system was evaluated by calculating the ratio of (total tissue mass) or (total O2 consumption)/(the energy cost). The results of the calculation using physiological data of muscle blood flow and O2 consumption rate in man during exercise revealed the optimum capillary number to be around 1.5 x 10(10) and the Krogh cylinder radius to be 26 microns, which agrees well with the morphological data of these values in human skeletal muscles. It was concluded that the vascular-tissue system in the skeletal muscle is constructed so as to attain the highest efficiency in O2 transport to tissue during exercise.
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Affiliation(s)
- A Kamiya
- Institute of Medical Electronics, Faculty of Medicine, Tokyo University, Japan
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