Three-dimensional reconstructed glomerular capillary network: blood flow distribution and local filtration

1992 ◽  
Vol 263 (3) ◽  
pp. F562-F572 ◽  
Author(s):  
A. Remuzzi ◽  
B. M. Brenner ◽  
V. Pata ◽  
G. Tebaldi ◽  
R. Mariano ◽  
...  
Keyword(s):  
Blood Flow ◽  
Theoretical Model ◽  
Three Dimensional ◽  
Capillary Network ◽  
Rheological Parameters ◽  
Image Analysis System ◽  
Heterogeneous Distribution ◽  
Filtration Pressure ◽  
Pressure Equilibrium ◽  
Topological Organization

We developed a mathematical model to simulate blood flow and filtration in individual capillary segments of a glomerular network reconstructed from a normal Munich-Wistar (MW) rat. Three-dimensional geometric reconstruction was obtained by semithin serial sections (1 micron) of one glomerulus after perfusion fixation of kidney. Photomicrographs of each section were digitized and processed, using a computer-based image-analysis system, to derive the topological organization of the capillary network and mean diameter and length of individual capillary segments. Blood flow rate in capillary segments was calculated using a theoretical model that considers apparent viscosity of blood in small capillaries as a function of local rheological parameters, partition of cells at bifurcations, and local filtration dependent on transmembrane hydraulic and oncotic pressure gradients along the network. In accord with previous observations, the topological organization of the capillary network disclosed a three-lobular structure. The ultrafiltration coefficient (Kf) calculated for the euvolemic MW rat with the present network approach was compared with that derived from a theoretical model that assumes identical capillaries in parallel. The latter model is shown to underestimate Kf, particularly under conditions in which filtration pressure equilibrium is approached. Calculation of local blood flow and filtration along the network indicates a heterogeneous distribution of these parameters and that some parts of the capillary network operate at filtration pressure equilibrium even if the overall network operates at filtration disequilibrium.

scholarly journals High-speed volumetric two-photon fluorescence imaging of neurovascular dynamics

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Jiang Lan Fan ◽  
Jose A. Rivera ◽  
Wei Sun ◽  
John Peterson ◽  
Henry Haeberle ◽  
...  
Keyword(s):  
Blood Flow ◽  
High Speed ◽  
Laser Scanning ◽  
Three Dimensional ◽  
Laser Scanning Microscopy ◽  
Fluorescence Signal ◽  
Imaging Method ◽  
Spatiotemporal Resolution ◽  
Two Photon

AbstractUnderstanding the structure and function of vasculature in the brain requires us to monitor distributed hemodynamics at high spatial and temporal resolution in three-dimensional (3D) volumes in vivo. Currently, a volumetric vasculature imaging method with sub-capillary spatial resolution and blood flow-resolving speed is lacking. Here, using two-photon laser scanning microscopy (TPLSM) with an axially extended Bessel focus, we capture volumetric hemodynamics in the awake mouse brain at a spatiotemporal resolution sufficient for measuring capillary size and blood flow. With Bessel TPLSM, the fluorescence signal of a vessel becomes proportional to its size, which enables convenient intensity-based analysis of vessel dilation and constriction dynamics in large volumes. We observe entrainment of vasodilation and vasoconstriction with pupil diameter and measure 3D blood flow at 99 volumes/second. Demonstrating high-throughput monitoring of hemodynamics in the awake brain, we expect Bessel TPLSM to make broad impacts on neurovasculature research.

Blood flow and high-energy phosphates in microregions of left ventricular subendocardium

1981 ◽  
Vol 240 (5) ◽  
pp. H804-H810 ◽  
Author(s):  
H. D. Kleinert ◽  
H. R. Weiss
Keyword(s):  
Blood Flow ◽  
Linear Relationship ◽  
Tissue Perfusion ◽  
High Energy ◽  
Left Ventricular ◽  
Significant Loss ◽  
Tissue Blood Flow ◽  
High Energy Phosphates ◽  
Tissue Samples ◽  
Heterogeneous Distribution

Blood flow and high-energy phosphate (HEP) content were determined simultaneously in multiple microregions of left ventricular subendocardium in 29 normal anesthetized open-chest rabbits by use of a new micromethod to determine whether a direct linear relationship existed between these parameters. Tissue samples weighed 1-2 mg. ATP and creatine phosphate (CP) content were quantitated in quick-frozen hearts by fluorometry at sites where tissue perfusion was measured by H2 clearance by use of bare-tipped platinum electrodes. A series of validation studies were conducted to ensure that 1) no significant damage to the tissue surrounding the electrode occurred during the period of experimentation and 2) no significant loss of biochemical constituents had occurred due to labile processes during freezing or storage of the tissue. Blood flow, ATP, and CP values averaged 79.1 +/- 24.1 (SD) ml.min-1.100 g-1, 4.9 +/- 1.3 mumol/g tissue, and 8.0 +/- 3.0 mumol/g tissue, respectively, and are similar to those reported in studies using larger tissue samples. Correlation between the heterogeneous distribution of tissue perfusion and HEP revealed no direct linear relationship between these parameters in the normal unstressed rabbit subendocardium.

Modeling of aortic valve stenosis using fluid-structure interaction method

Perfusion ◽  
2021 ◽  
pp. 026765912199854
Author(s):  
Mohammad Javad Ghasemi Pour ◽  
Kamran Hassani ◽  
Morteza Khayat ◽  
Shahram Etemadi Haghighi
Keyword(s):  
Blood Flow ◽  
Aortic Valve ◽  
Fluid Structure Interaction ◽  
Three Dimensional ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Relaxation Phase ◽  
Exercise Condition ◽  
Time Dependent Domain ◽  
Comparison Of The Results

Background and objectives: Fluid structure interaction (FSI) is defined as interaction of the structures with contacting fluids. The aortic valve experiences the interaction with blood flow in systolic phase. In this study, we have tried to predict the hemodynamics of blood flow through a normal and stenotic aortic valve in two relaxation and exercise conditions using a three-dimensional FSI method. Methods: The aorta valve was modeled as a three-dimensional geometry including a normal model and two others with 25% and 50% stenosis. The geometry of the aortic valve was extracted from CT images and the models were generated by MMIMCS software and then they were implemented in ANSYS software. The pulsatile flow rate was used for all cases and the numerical simulations were conducted based on a time-dependent domain. Results: The obtained results including the velocity, pressure, and shear stress contours in different systolic time sequences were explained and discussed. The maximum blood flow velocity in relaxation phase was obtained 1.62 m/s (normal valve), 3.78 m/s (25% stenosed valve), and 4.73 m/s (50% stenosed valve). In exercise condition, the maximum velocities are 2.86, 4.32, and 5.42 m/s respectively. The maximum blood pressure in relaxation phase was calculated 111.45 mmHg (normal), 148.66 mmHg (25% stenosed), and 164.21 mmHg (50% stenosed). However, the calculated values in exercise situation were 129.57, 163.58, and 191.26 mmHg. The validation of the predicted results was also conducted using existing literature. Conclusions: We believe that such model are useful tools for biomechanical experts. The further studies should be done using experimental data and the data are implemented on the boundary conditions for better comparison of the results.

scholarly journals Non-contact scanning diffuse correlation tomography system for three-dimensional blood flow imaging in a murine bone graft model

2015 ◽  
Vol 6 (7) ◽  
pp. 2695 ◽  
Author(s):  
Songfeng Han ◽  
Johannes Johansson ◽  
Miguel Mireles ◽  
Ashley R. Proctor ◽  
Michael D. Hoffman ◽  
...  
Keyword(s):  
Blood Flow ◽  
Bone Graft ◽  
Three Dimensional ◽  
Flow Imaging ◽  
Blood Flow Imaging ◽  
Tomography System

scholarly journals Regional Distribution and Kinetics of Three Sites on the GABAA Receptor: Lack of Effect of Portacaval Shunting

1992 ◽  
Vol 12 (2) ◽  
pp. 334-346 ◽  
Author(s):  
Anke M. Mans ◽  
Kelli M. Kukulka ◽  
Keith J. McAvoy ◽  
Norman C. Rokosz
Keyword(s):  
Kinetic Parameters ◽  
Regional Distribution ◽  
Three Dimensional ◽  
Portacaval Shunt ◽  
Brain Regions ◽  
Significant Heterogeneity ◽  
Heterogeneous Distribution ◽  
Dimensional Reconstruction ◽  
Benzodiazepine Site ◽  
Gaba Neurotransmission

The regional distribution of binding sites on the GABAA receptor and their kinetic parameters were measured by quantitative autoradiography in brains from normal rats and rats with a portacaval shunt, a model of portal systemic encephalopathy in which GABA neurotransmission may be altered. The ligands used were [3H]flunitrazepam (a benzodiazepine-site agonist), [3H]-Ro 15-1788 (a benzodiazepine-site antagonist), [3H]muscimol (a GABA-site agonist), and [35S] t-butylbicyclo-phosphorothionate (35S-TBPS, a convulsant that binds to a site near the chloride channel). Some brains were analyzed by computerized image analysis and three-dimensional reconstruction. The regional distribution of binding of the benzodiazepines was very similar, but the patterns obtained with [3H]muscimol and [35S]TBPS were different in many areas, suggesting a heterogeneous distribution of several subtypes of the GABAA receptor. The kinetic parameters were determined in brain regions for [3H]flunitrazepam, [3H]Ro15-1788, and [3H]muscimol. For each ligand, the Kd showed a significant heterogeneity among brain regions (at least threefold), contrary to conclusions drawn from earlier studies. In portacaval shunted rats, binding of all four ligands was essentially unchanged from that in control rats, indicating that, if there was an abnormality in GABA neurotransmission during portal systemic shunting, it was not reflected by altered binding to the main sites on the GABAA receptor.

Thermal Mapping, via Liquid Crystals, of the Temperature Field near a Heated Surgical Probe

1973 ◽  
Vol 95 (2) ◽  
pp. 250-256 ◽  
Author(s):  
T. E. Cooper ◽  
J. P. Groff
Keyword(s):  
Blood Flow ◽  
Temperature Field ◽  
Liquid Crystals ◽  
Theoretical Model ◽  
Wheatstone Bridge ◽  
Visual Display ◽  
Two Dimensional ◽  
Test Medium ◽  
One Dimensional ◽  
Water Test

This paper discusses the use of heat for producing clinical lesions in tissue and presents the design and analysis of a resistively heated surgical probe. The probe surface temperature is accurately maintained and controlled by using a Wheatstone bridge. The probe was embedded in a clear agar–water test medium, and the temperature field generated by the probe was measured with liquid crystals, a material that provides a visual display of certain isotherms. Experimental results compare within approximately 10 percent of a two-dimensional numerical solution. A one-dimensional theoretical model is also developed which examines the influence of blood flow on the temperature field.

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