scholarly journals Relationship between Concentration Difference of Different Density Lipoproteins and Shear Stress in Atherosclerosis

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Wei Meng ◽  
Fengxu Yu ◽  
Huaiqing Chen ◽  
Jianmin Zhang ◽  
Eryong Zhang ◽  
...  
Keyword(s):  
Shear Stress ◽  
Concentration Polarization ◽  
Carotid Bifurcation ◽  
High Flow ◽  
Arterial System ◽  
Low Flow ◽  
Wall Surface ◽  
Concentration Difference ◽  
Recirculation System ◽  
The Relationship

Previous research has observed concentration polarization in LDL and HDL in the arterial system. However, there is no report that links this concentration polarization to the development of vascular atherosclerosis (AS). Therefore, the purpose of this study is to establish the relationship between concentration difference of LDL and HDL and shear stress using a carotid bifurcation vascular model. PTFE was employed to create the carotid bifurcation model. Endothelial cells were coated on the inner wall of the graft. In a recirculation system, HDL and LDL concentration were measured under two different ICA flow velocities at 5 different locations within our model. We report the following: (1) LDL and HDL concentration difference was observed in both high flow and low flow environments; (2) the degree of LDL and HDL concentration polarization varied depending of high flow and low flow environment; (3) absolute values of concentration difference between LDL and HDL at the inner wall surface decreased with the increase in shear stress when shear stress was more than 1.5 Pa. This variation trend would be more pronounced if shear stress were less than 0.5 Pa. Our study suggests that under the action of shear stress, concentration differences of LDL or HDL create a disturbance in the balance of atherogenic factors and anti-As factors, resulting in the occurrence of AS.

The Effect of Altered Cerebral Blood Flow on the Cerebral Kinetics of Thiopental and Propofol in Sheep

2000 ◽  
Vol 93 (4) ◽  
pp. 1085-1094 ◽  
Author(s):  
Richard N. Upton ◽  
Guy L. Ludbrook ◽  
Cliff Grant ◽  
David J. Doolette
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Random Order ◽  
High Flow ◽  
Low Flow ◽  
Flow State ◽  
Concentration Difference ◽  
Blood Flows ◽  
Kinetics Of ◽  
The Brain

Background Thiopental and propofol are highly lipid-soluble, and their entry into the brain often is assumed to be limited by cerebral blood flow rather than by a diffusion barrier. However, there is little direct experimental evidence for this assumption. Methods The cerebral kinetics of thiopental and propofol were examined over a range of cerebral blood flows using five and six chronically instrumented sheep, respectively. Using anesthesia (2.0% halothane), three steady state levels of cerebral blood flow (low, medium, and high) were achieved in random order by altering arterial carbon dioxide tension. For each flow state, 250 mg thiopental or 100 mg propofol was infused intravenously over 2 min. To quantify cerebral kinetics, arterial and sagittal sinus blood was sampled rapidly for 20 min from the start of the infusion, and 1.5 h was allowed between consecutive infusions. Various models of cerebral kinetics were examined for their ability to account for the data. Results The mean baseline cerebral blood flows for the "high" flow state were over threefold greater than those for the low. For the high-flow state the normalized arteriovenous concentration difference across the brain was smaller than for the low-flow state, for both drugs. The data were better described by a model with partial membrane limitation than those with only flow limitation or dispersion. Conclusions The cerebral kinetics of thiopental and propofol after bolus injection were dependent on cerebral blood flow, despite partial diffusion limitation. Higher flows produce higher peak cerebral concentrations.

scholarly journals Study on the Relationship between Manganese Concentrations in Rural Drinking Water and Incidence and Mortality Caused by Cancer in Huai’an City

2014 ◽  
Vol 2014 ◽  
pp. 1-5 ◽  
Author(s):  
Qin Zhang ◽  
Enchun Pan ◽  
Linfei Liu ◽  
Wei Hu ◽  
Yuan He ◽  
...  
Keyword(s):  
Drinking Water ◽  
Cancer Incidence ◽  
Shallow Groundwater ◽  
High Flow ◽  
Low Flow ◽  
Deep Groundwater ◽  
Incidence And Mortality ◽  
The Relationship ◽  
Mn Concentration ◽  
Mn Concentrations

Background. Cancer is a significant disease burden in the world. Many studies showed that heavy metals or their compounds had connection with cancer. But the data conflicting about the relationship of manganese (Mn) to cancer are not enough. In this paper, the relationship was discussed between Mn concentrations in drinking water for rural residents and incidence and mortality caused by malignant tumors in Huai’an city.Methods. A total of 158 water samples from 28 villages of 14 towns were, respectively, collected during periods of high flow and low flow in 3 counties of Huai’an city, along Chinese Huai’he River. The samples of deep groundwater, shallow groundwater, and surface water were simultaneously collected in all selected villages. Mn concentrations in all water samples were determined by inductively coupled plasma-mass spectrometry (ICP-MS 7500a). The correlation analysis was used to study the relationship between the Mn concentration and cancer incidence and mortality.Results. Mn concentrations detectable rate was 100% in all water samples. The mean concentration was 452.32 μg/L ± 507.76 μg/L. There was significant difference between the high flow period and low flow period (t=-5.23,P<0.05) and also among deep groundwater, shallow groundwater, and surface water (F=5.02,P<0.05). The ratio of superscale of Mn was 75.32%. There was significant difference of Mn level between samples in the high flow period and low flow period (χ2=45.62, P<0.05) and also among deep groundwater, shallow groundwater, and surface water (χ2=10.66,P<0.05). And also we found that, during the low flow period, Mn concentration has positive correlation with cancer incidence and mortality; for a 1 μg/L increase in Mn concentration, there was a corresponding increase of 0.45/100000 new cancer cases and 0.35/100000 cancer deaths (P<0.05).Conclusions. In Huai’an city, the mean concentration of Mn in drinking water was very high. Mn concentration correlated with cancer incidence and mortality.

Abstract 442: Flow-Dependent Regulation of Angiopoietin-2

Circulation ◽  
2007 ◽  
Vol 116 (suppl_16) ◽  
Author(s):  
Winfried Goettsch ◽  
Corina Gryczka ◽  
Thomas Korff ◽  
Evelyn Ernst ◽  
Claudia Goettsch ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Shear Stress ◽  
Transcription Factor ◽  
High Flow ◽  
Low Flow ◽  
Laminar Shear Stress ◽  
Forkhead Box ◽  
Angiopoietin 2 ◽  
Laminar Shear

Background: Endothelial cells are constantly exposed to high or low shear stress in arteries and veins by the flowing blood. Angiopoietin-2 (Ang-2) is acting as a critical regulator of vessel maturation and endothelial cell quiescence. In this study, we determined the effect of low and high laminar shear stress on the expression and release of angiopoietin (Ang-)2 in human endothelial cells, studied the role of nitric oxide and protein kinases in this context, determined the impact of VEGF on Ang-2, studied the expression, activity and translocation of the forkhead box O transcription factor FOXO1 by low and high shear stress, and analyzed the vessel- and flow-dependent expression of Ang-2 in vivo . Methods and Results: Primary cultures of human umbilical vein endothelial cells (HUVEC) were subjected to laminar shear stress at different physiological levels of laminar shear stress of 1, 5, 10, 15, and 30 dyne/cm 2 in a cone-and-plate viscometer. Ang-2 mRNA, protein expression and release was upregulated by 24 h of low (1 dyne/cm 2 ), but downregulated by high flow (30 dyne/cm 2 ) in human endothelial cells. Increased endothelial NO synthase expression and NO formation was not affecting regulation of Ang-2 by low or high flow. Tie2 protein expression, but not Tie2 phosphorylation was induced by high flow. Furthermore, low and high flow increased VEGF-A expression. Inhibition of VEGFR-2 prevented upregulation of Ang-2 by low flow, but not downregulation of Ang-2 by high flow. Upregulation of Ang-2 by VEGF was reduced by application of high flow. Forkhead box O (FOXO) transcription factor FOXO1 has been shown to regulate Ang-2 expression in endothelial cells. FOXO1 binding activity was reduced by high flow. Nuclear localization of transcription factor FOXO1 was not changed by low flow, but reduced by high flow. In vivo , Ang-2 was higher expressed in veins compared to arteries. Arterial ligation augmented Ang-2 expression in distal arterial low flow areas. Conclusion: Our results support a VEGF-dependent induction of Ang-2 in low flow areas, and FOXO1-dependent downregulation of Ang-2 in high flow areas. These data suggest a new mechanism of flow-dependent regulation of vessel stability and differentiation.

scholarly journals Concentration Polarization of High-Density Lipoprotein and Its Relation with Shear Stress in an In Vitro Model

2009 ◽  
Vol 2009 ◽  
pp. 1-8 ◽  
Author(s):  
Wei Meng ◽  
Fengxu Yu ◽  
Huaiqing Chen ◽  
Jianmin Zhang ◽  
Eryong Zhang ◽  
...  
Keyword(s):  
Shear Stress ◽  
Carotid Artery ◽  
High Density Lipoprotein ◽  
High Speed ◽  
Concentration Polarization ◽  
Density Lipoprotein ◽  
Carotid Bifurcation ◽  
High Density ◽  
Vitro Model

The purpose of this study was to determine the concentration polarization of high-density lipoprotein (HDL) at the surface of the carotid artery under conditions of steady flow and to establish its relationship with shear stress using an in vitro vascular simulation model of carotid bifurcation. Shear stress, HDL concentration at the surface, and the ratio of HDL concentration at the surface to concentration in bulk flow were measured at different locations within the model under high-speed (1.451 m/s) and low-speed (0.559 m/s) flow. HDL showed concentration polarization at the surface of the carotid artery model, particularly in the internal carotid artery sinus. With decreasing flow velocity, the shear stress at the surface also decreased, and HDL concentration polarization increased. The concentration polarization of HDL was negatively and strongly correlated with shear stress at both low- (r=−0.872,P<.001) and high-speed flow (r=−0.592,P=.0018).

scholarly journals Traumatic Arteriovenous Fistula of the Scalp in the Left Temporoparietal Region with Intra- and Extracranial Blood Supply

2016 ◽  
Vol 2016 ◽  
pp. 1-4 ◽  
Author(s):  
Feng Zheng ◽  
Herbert Augustus Pitts ◽  
Roland Goldbrunner ◽  
Boris Krischek
Keyword(s):  
Arteriovenous Fistula ◽  
Blood Supply ◽  
Superficial Temporal Artery ◽  
Temporal Artery ◽  
High Flow ◽  
Arterial System ◽  
Low Flow ◽  
Radiological Features ◽  
Feeding Vessels ◽  
Capillary Bed

Traumatic AVF of the scalp is a rare abnormal vascular disease. It is defined as a communication between the high flow arterial system and the low flow venous network, which directly connects the arterial feeding vessels of the scalp and the draining veins without an intervening capillary bed. The superficial temporal artery (STA) was involved in 90% of the cases, and 71% of the patients only had one dominant feeding STA. Here, we report the case of a rare large traumatic arteriovenous fistula (AVF) of the scalp that is fed by intra- and extracranial blood supply. The clinical and radiological features are presented, and the possible pathogenesis and surgical technique are discussed.

Hydrodynamics Analysis of Air Flow over Pitted Surface

2013 ◽  
Vol 461 ◽  
pp. 712-724
Author(s):  
Xue Peng Zhang ◽  
Yong Hua Wang ◽  
Lei Shi
Keyword(s):  
Shear Stress ◽  
Surface Morphology ◽  
Stream Flow ◽  
Viscous Drag ◽  
Wall Surface ◽  
Pressure Drag ◽  
Bionic Surface ◽  
Flow Drag ◽  
Distribution Of Stress ◽  
The Relationship

The pits is a typical biomimetic surface morphology, typically it is beneficial to reduce the flow drag on the wall surface. In this paper, a method combining theoretical analysis and numerical simulation is adopted, it carries out a flow and stress analysis on the wall surface distributed by 3mm-diameter pits with typical bionic surface morphology, reveals the forms down stream flow field and the pit internal as well as the distribution of stress, it also analyzes the relationship between the viscous drag of the pit wall surface, the pressure drag and the flow drag, comparing the size of the downstream shear stress of the smooth wall and wall surface distributed with pits, investigates the mechanism of the downstream shear stress decreases on the biomimetic pit wall surface.

Flow regulation of ecNOS and Cu/Zn SOD mRNA expression in porcine coronary arterioles

1999 ◽  
Vol 276 (3) ◽  
pp. H1058-H1063 ◽  
Author(s):  
Christopher R. Woodman ◽  
Judy M. Muller ◽  
James W. E. Rush ◽  
M. Harold Laughlin ◽  
Elmer M. Price
Keyword(s):  
Shear Stress ◽  
Mrna Expression ◽  
Threshold Level ◽  
Flow Regulation ◽  
High Flow ◽  
Low Flow ◽  
Rt Pcr ◽  
Flow Through ◽  
Oxide Synthase ◽  
Coronary Arterioles

The purpose of this study was to test the hypothesis that increased flow through coronary arterioles increases endothelial cell nitric oxide synthase (ecNOS) and Cu/Zn superoxide dismutase (SOD) mRNA expression. Single porcine coronary arterioles (ID 100–160 μm; pressurized) were cannulated, perfused, and exposed to intraluminal flow sufficient to produce maximal flow-induced dilation of coronary arterioles (high flow; 7.52 ± 0.22 μl/min), low flow (0.84 ± 0.05 μl/min), or no flow for 2 or 4 h. Mean shear stress was calculated to be 5.7 ± 1.0 dyn/cm2 for high-flow arterioles and 1.6 ± 1.0 dyn/cm2 for low-flow arterioles. At the end of the treatment period, mRNA was isolated from each vessel, and ecNOS and SOD mRNA expression was assessed using a semiquantitative RT-PCR. All data were standardized by coamplifying ecNOS or SOD with glyceraldehyde-3-phosphate dehydrogenase. The results indicate that ecNOS mRNA expression is increased in arterioles exposed to 2 or 4 h of high flow. In contrast, SOD mRNA expression was increased only after 4 h of high flow. Neither gene is induced by exposure to low flow. On the basis of these data, we concluded that ecNOS and SOD mRNA expression is regulated by flow in porcine coronary arterioles. In addition, we concluded that a threshold level of flow and shear stress must be sustained to elicit the upregulation of ecNOS and SOD mRNA expression.

scholarly journals Characteristics and Controlling Factors of the Drought Runoff Coefficient

Water ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1259
Author(s):  
Rei Itsukushima
Keyword(s):  
Land Use ◽  
Resource Management ◽  
Water Resource ◽  
Water Resource Management ◽  
Controlling Factors ◽  
Low Flow ◽  
Drought Risk ◽  
Runoff Coefficient ◽  
Topographical Factors ◽  
The Relationship

Increasing water demand due to population growth, economic development, and changes in rainfall patterns due to climate change are likely to alter the duration and magnitude of droughts. Understanding the relationship between low-flow conditions and controlling factors relative to the magnitude of a drought is important for establishing sustainable water resource management based on changes in future drought risk. This study demonstrates the relationship between low-flow and controlling factors under different severities of drought. I calculated the drought runoff coefficient for six types of occurrence probability, using past observation data of annual total discharge and precipitation in the Japanese archipelago, where multiple climate zones exist. Furthermore, I investigated the pattern of change in the drought runoff coefficient in accordance with the probability of occurrence of drought, and relationships among the coefficient and geological, land use, and topographical factors. The drought runoff coefficient for multiple drought magnitudes exhibited three behaviors, corresponding to the pattern of precipitation. Results from a generalized linear model (GLM) revealed that the controlling factors differed depending on the magnitude of the drought. During high-frequency droughts, the drought runoff coefficient was influenced by geological and vegetation factors, whereas land use and topographical factors influenced the drought runoff coefficient during low-frequency droughts. These differences were caused by differences in runoff, which dominated stream discharge, depending on the magnitude of the drought. Therefore, for effective water resource management, estimation of the volume of drought runoff needs to consider the pattern of precipitation, geology, land use, and topography.

scholarly journals Soil microbial inoculation during flood events shapes headwater stream microbial communities and diversity

2021 ◽  
Author(s):  
Florian Caillon ◽  
Katharina Besemer ◽  
Peter Peduzzi ◽  
Jakob Schelker
Keyword(s):  
Microbial Diversity ◽  
Bacterial Diversity ◽  
Soil Water ◽  
Headwater Streams ◽  
High Flow ◽  
Low Flow ◽  
Flood Events ◽  
Flow Conditions ◽  
Soil Microbial ◽  
Microbial Inoculation

AbstractFlood events are now recognized as potentially important occasions for the transfer of soil microbes to stream ecosystems. Yet, little is known about these “dynamic pulses of microbial life” for stream bacterial community composition (BCC) and diversity. In this study, we explored the potential alteration of stream BCC by soil inoculation during high flow events in six pre-alpine first order streams and the larger Oberer Seebach. During 1 year, we compared variations of BCC in soil water, stream water and in benthic biofilms at different flow conditions (low to intermediate flows versus high flow). Bacterial diversity was lowest in biofilms, followed by soils and highest in headwater streams and the Oberer Seebach. In headwater streams, bacterial diversity was significantly higher during high flow, as compared to low flow (Shannon diversity: 7.6 versus 7.9 at low versus high flow, respectively, p < 0.001). Approximately 70% of the bacterial operational taxonomic units (OTUs) from streams and stream biofilms were the same as in soil water, while in the latter one third of the OTUs were specific to high flow conditions. These soil high-flow OTUs were also found in streams and biofilms at other times of the year. These results demonstrate the relevance of floods in generating short and reoccurring inoculation events for flowing waters. Moreover, they show that soil microbial inoculation during high flow enhances microbial diversity and shapes fluvial BCC even during low flow. Hence, soil microbial inoculation during floods could act as a previously overlooked driver of microbial diversity in headwater streams.

Corrosion Rate Measurement by Hydrogen Effusion In Dynamic Aqueous Systems At Elevated Temperature and Pressure

CORROSION ◽  
1959 ◽  
Vol 15 (4) ◽  
pp. 29-32
Author(s):  
M. KRULFELD ◽  
M. C. BLOOM ◽  
R. E. SEEBOLD
Keyword(s):  
Elevated Temperature ◽  
Corrosion Rate ◽  
Flow Velocity ◽  
High Flow ◽  
Low Flow ◽  
Aqueous Systems ◽  
Effusion Rates ◽  
Temperature And Pressure ◽  
Effusion Method ◽  
Hydrogen Effusion

Abstract A method of applying the hydrogen effusion method to the measurement of corrosion rates in dynamic aqueous systems at elevated temperature and pressure is described. Data obtained in low carbon steel systems are presented, including (1) reproducibility obtained in measured hydrogen effusion rates at a flow velocity of 1 foot per second at a temperature of 600 F and 2000 psi, and (2) a quantitative comparison between the hydrogen effusion rates in static and in low flow velocity dynamic systems at this temperature and pressure. Some observations are included on corrosion rate measurements in a high flow velocity (30 feet per second) loop by the hydrogen effusion method. Implications of these measurements with regard to the comparison between high flow velocity corrosion and low flow velocity corrosion are mentioned and some data indicating high local sensitivity of the hydrogen effusion method are noted. Some possible difficulties involved in the method are pointed out. 2.3.4

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