The maintenance of adult peripheral adult nerve and microvascular networks in the rat mesentery culture model

Techniques that model microvascular hemodynamics have been developed for decades. While the physiological significance of pressure pulsatility is acknowledged, most of the microcirculatory models use steady flow approaches. To theoretically study the extent and transmission of pulsatility in microcirculation, dynamic models need to be developed. In this paper, we present a one-dimensional model to describe the dynamic behavior of microvascular blood flow. The model is applied to a microvascular network from a rat mesentery. Intravital microscopy was used to record the morphology and flow velocities in individual vessel segments, and boundaries are defined according to the experimental data. The system of governing equations constituting the model is solved numerically using the discontinuous Galerkin method. An implicit integration scheme is adopted to increase computing efficiency. The model allows the simulation of the dynamic properties of blood flow in microcirculatory networks, including the pressure pulsatility (quantified by a pulsatility index) and pulse wave velocity (PWV). From the main input arteriole to the main output venule, the pulsatility index decreases by 66.7%. PWV obtained along arterioles declines with decreasing diameters, with mean values of 77.16, 25.31, and 8.30 cm/s for diameters of 26.84, 17.46, and 13.33 μm, respectively. These results suggest that the 1D model developed is able to simulate the characteristics of pressure pulsatility and wave propagation in complex microvascular networks.

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Relationship between structural and hemodynamic heterogeneity in microvascular networks

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1996.270.2.h545 ◽

1996 ◽

Vol 270 (2) ◽

pp. H545-H553 ◽

Cited By ~ 14

Author(s):

A. R. Pries ◽

T. W. Secomb ◽

P. Gaehtgens

Keyword(s):

Mathematical Model ◽

Blood Flow ◽

Topological Structure ◽

Blood Rheology ◽

Experimental Information ◽

Microvascular Networks ◽

Rat Mesentery ◽

Hemodynamic Characteristics ◽

Flow Through ◽

The Relationship

The relationship between structural and hemodynamic heterogeneity of microvascular networks is examined by analyzing the effects of topological and geometric irregularities on network hemodynamics. Microscopic observations of a network in the rat mesentery provided data on length, diameter, and interconnection of all 913 segments. Two idealized network structures were derived from the observed network. In one, the topological structure was made symmetric; in another a further idealization was made by assigning equal lengths and diameters to all segments with topologically equivalent positions in the network. Blood flow through these three networks was simulated with a mathematical model based on experimental information on blood rheology. Overall network conductance and pressure distribution within the network were found to depend strongly on topological heterogeneity and less on geometric heterogeneity. In contrast, mean capillary hematocrit was sensitive to geometric heterogeneity but not to topological heterogeneity. Geometric and topological heterogeneity contributed equally to the dispersion of arteriovenous transit time. Hemodynamic characteristics of heterogeneous microvascular networks can only be adequately described if both topological and geometric variability in network structure are taken into account.

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Lysophosphatidic acid does not cause blood/lymphatic vessel plasticity in the rat mesentery culture model

Physiological Reports ◽

10.14814/phy2.12857 ◽

2016 ◽

Vol 4 (13) ◽

pp. e12857

Author(s):

Richard S. Sweat ◽

Mohammad S. Azimi ◽

Ariana D. Suarez-Martinez ◽

Prasad Katakam ◽

Walter L. Murfee

Keyword(s):

Lysophosphatidic Acid ◽

Lymphatic Vessel ◽

Rat Mesentery ◽

Culture Model

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Structure and hemodynamics of microvascular networks: heterogeneity and correlations

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1995.269.5.h1713 ◽

1995 ◽

Vol 269 (5) ◽

pp. H1713-H1722 ◽

Cited By ~ 28

Author(s):

A. R. Pries ◽

T. W. Secomb ◽

P. Gaehtgens

Keyword(s):

Vessel Diameter ◽

Hemodynamic Parameters ◽

Strong Correlations ◽

Microvascular Networks ◽

True Value ◽

Rat Mesentery ◽

Coefficients Of Variation ◽

Network Properties ◽

The Mean ◽

Intravascular Pressure

The objective of this study was to quantify the heterogeneity of topological, morphological, and hemodynamic parameters in microvascular networks and to identify functionally relevant correlations among these parameters. Seven networks in the rat mesentery (383-913 vessel segments per network) were examined, and measurements were made of segment generation, diameter, length, and hematocrit in all segments (n = 3,129) and of flow velocity (only in 3 networks, 1,321 segments). In addition, hematocrit, flow rate, and pressure were derived for all segments from a mathematical simulation. All parameters obtained exhibit heterogeneous distributions with coefficients of variation ranging from 0.28 (capillary diameter) to > 1.5 (volume flow and pressure gradient). Several strong correlations exist between parameters, e.g., discharge hematocrit increases with vessel diameter, and shear rate increases with intravascular pressure. Because of such correlations, the extrapolation from average values for "typical vessels" to network properties can lead to substantial errors. For example, the mean network transit time estimated based on averaged quantities is 6.5 s, which is about 60% higher than the true value (4.08 s). Simplified models of the vascular bed may therefore be inadequate to describe functional properties of the microcirculation.

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VEGF-C Induces Lymphangiogenesis and Angiogenesis in the Rat Mesentery Culture Model

Microcirculation ◽

10.1111/micc.12132 ◽

2014 ◽

Vol 21 (6) ◽

pp. 532-540 ◽

Cited By ~ 24

Author(s):

Richard S. Sweat ◽

David C. Sloas ◽

Walter L. Murfee

Keyword(s):

Rat Mesentery ◽

Culture Model

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Structural adaptation and stability of microvascular networks: theory and simulations

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1998.275.2.h349 ◽

1998 ◽

Vol 275 (2) ◽

pp. H349-H360 ◽

Cited By ~ 70

Author(s):

A. R. Pries ◽

T. W. Secomb ◽

P. Gaehtgens

Keyword(s):

Network Flow ◽

Equilibrium States ◽

Structural Adaptation ◽

Microvascular Networks ◽

Vascular Walls ◽

Rat Mesentery ◽

Vascular Segment ◽

Complete Networks ◽

Intravascular Pressure

A theoretical model was developed to simulate long-term changes of vessel diameters during structural adaptation of microvascular networks in response to tissue needs. The diameter of each vascular segment was assumed to change with time in response to four local stimuli: endothelial wall shear stress (τw), intravascular pressure (P), a flow-dependent metabolic stimulus (M), and a stimulus conducted from distal to proximal segments along vascular walls (C). Increases in τw, M, or C or decreases in P were assumed to stimulate diameter increases. Hemodynamic quantities were estimated using a mathematical model of network flow. Simulations were continued until equilibrium states were reached in which the stimuli were in balance. Predictions were compared with data from intravital microscopy of the rat mesentery, including topological position, diameter, length, and flow velocity for each segment of complete networks. Stable equilibrium states, with realistic distributions of velocities and diameters, were achieved only when all four stimuli were included. According to the model, responses to τwand P ensure that diameters are smaller in peripheral than in proximal segments and are larger in venules than in corresponding arterioles, whereas M prevents collapse of networks to single pathways and C suppresses generation of large proximal shunts.

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