Capillary Network Morphology and Capillary Flow

Groom, A. C.; Ellis, Christopher G.; Wrigley, S J; Potter, Richard F.

doi:10.1159/000179022

Cited by 27 publications

(22 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Mean capillary diameters were consistent with previously reported measurements of rat muscle from functional images (12), histological sections (21), and microvascular corrosion casts (22). Similarly, mean capillary length, capillary length density, and Krogh radius coincided with the findings of others (9,18). Comparison between the measured capillary area and volume density illustrates the reliability of the virtual histology (Fig.…”

Section: Discussionsupporting

confidence: 88%

“…To provide a clear picture of the microcirculation as a whole, a variety of tools have been developed to quantify network morphology and flow hemodynamics and to measure conditions within the blood itself. These tools include stereology, microscopy, histology, spectrophotometry, and a variety of mathematical constructs (9,11,16,20,22,27). Drawing on several of these tools, integrated approaches have been made to represent blood flow and O 2 delivery using computer modeling (8,23,25).…”

mentioning

confidence: 99%

See 1 more Smart Citation

Mapping 3-D functional capillary geometry in rat skeletal muscle in vivo

Fraser

Milkovich

Goldman

et al. 2012

American Journal of Physiology-Heart and Circulatory Physiology

View full text Add to dashboard Cite

Fraser GM, Milkovich S, Goldman D, Ellis CG. Mapping 3-D functional capillary geometry in rat skeletal muscle in vivo. Am J Physiol Heart Circ Physiol 302: H654 -H664, 2012. First published December 2, 2011; doi:10.1152/ajpheart.01185.2010.-We have developed a novel mapping software package to reconstruct microvascular networks in three dimensions (3-D) from in vivo video images for use in blood flow and O2 transport modeling. An intravital optical imaging system was used to collect video sequences of blood flow in microvessels at different depths in the tissue. Functional images of vessels were produced from the video sequences and were processed using automated edge tracking software to yield location and geometry data for construction of the 3-D network. The same video sequences were analyzed for hemodynamic and O 2 saturation data from individual capillaries in the network. Simple user-driven commands allowed the connection of vessel segments at bifurcations, and semiautomated registration enabled the tracking of vessels across multiple focal planes and fields of view. The reconstructed networks can be rotated and manipulated in 3-D to verify vessel connections and continuity. Hemodynamic and O2 saturation measurements made in vivo can be indexed to corresponding vessels and visualized using colorized maps of the vascular geometry. Vessels in each reconstruction are saved as text-based files that can be easily imported into flow or O2 transport models with complete geometry, hemodynamic, and O2 transport conditions. The results of digital morphometric analysis of seven microvascular networks showed mean capillary diameters and overall capillary density consistent with previous findings using histology and corrosion cast techniques. The described mapping software is a valuable tool for the quantification of in vivo microvascular geometry, hemodynamics, and oxygenation, thus providing rich data sets for experiment-based computational models. microcirculation; oxygen transport; microvascular network geometry; functional capillary density; computer-assisted vascular mapping SINCE AUGUST KROGH first developed a simple model of O 2 diffusion from an idealized capillary into the surrounding tissue (15), researchers have worked to more accurately characterize the microvasculature to develop more realistic models of tissue oxygenation and to provide data for testing these models. To provide a clear picture of the microcirculation as a whole, a variety of tools have been developed to quantify network morphology and flow hemodynamics and to measure conditions within the blood itself. These tools include stereology, microscopy, histology, spectrophotometry, and a variety of mathematical constructs (9,11,16,20,22,27). Drawing on several of these tools, integrated approaches have been made to represent blood flow and O 2 delivery using computer modeling (8,23,25). The majority of modeling efforts have been concentrated on the simplification of complex network geometry using predominantly parallel arrays of microvessels co...

show abstract

Section: Discussionsupporting

confidence: 88%

mentioning

confidence: 99%

Mapping 3-D functional capillary geometry in rat skeletal muscle in vivo

Fraser

Milkovich

Goldman

et al. 2012

American Journal of Physiology-Heart and Circulatory Physiology

View full text Add to dashboard Cite

show abstract

“…19 -21 Intermittent recruitment of capillaries after ischemia increases oxygenated blood content and leads to a more uniform and efficient O 2 exchange between capillary blood and surrounding tissues. 16,22 Shortly after hyperemia, elevated tissue O 2 tension may cause an intermittent decrease in O 2 extraction until the preischemic equilibrium is reinstalled. The mechanism is amplified by flowmediated NO release.…”

Section: Discussionmentioning

confidence: 99%

“…However, when we accounted for the relative blood volume expansion during hyperperfusion an increase in the relative blood volume from 3% to 4% resulted in a relative BOLD SI change of 1.8% for SNP6. 16,17 …”

Section: Comparison With Theoretical Modelsmentioning

confidence: 99%

Blood Oxygen Level–Dependent MRI of Tissue Oxygenation

Utz

Jordan

Niendorf

et al. 2005

ATVB

View full text Add to dashboard Cite

Objectives-The contribution of endothelial function to tissue oxygenation is not well understood. Muscle blood oxygen level-dependent MRI (BOLD MRI) provides data largely dependent on hemoglobin (Hb) oxygenation. We used BOLD MRI to assess endothelium-dependent signal intensity (SI) changes. Methods and Results-We investigated mean BOLD SI changes in the forearm musculature using a gradient-echo technique at 1.5 T in 9 healthy subjects who underwent a protocol of repeated acetylcholine infusions at 2 different doses (16 and 64 g/min) and N G -monomethyl-L-arginine (L-NMMA; 5 mg/min) into the brachial artery. Sodium nitroprusside was used as a control substance. For additional correlation with standard methods, the same protocol was repeated, and forearm blood flow was measured by strain gauge plethysmography. We obtained a significant increase in BOLD SI during acetylcholine infusion (64 g/min) and a significant decrease for L-NMMA infusion (PϽ0.005 for both). BOLD SI showed a different kinetic signal than did blood flow, particularly after intermittent ischemia and at high flow rates. Key Words: magnetic resonance imaging Ⅲ endothelial function Ⅲ BOLD Ⅲ plethysmography T he vascular endothelium regulates tone and tissue perfusion through release of vasoactive substances such as NO. Numerous studies assessed the effect of endothelial function, and particularly endothelial dysfunction, in humans. However, the contribution of endothelial function to the regulation of tissue oxygenation in humans is poorly understood. 1 Perfusion is not the sole mechanism that determines tissue oxygenation and metabolism. Therefore, blood flow measurements may have limited utility in this regard. Blood oxygen level-dependent MRI (BOLD MRI) reflects changes in the ratio of oxyhemoglobin to deoxyhemoglobin attributable to their different properties in a magnetic field. 2,3 The BOLD technique is well established for functional brain MRI 4 and has also been used to assess myocardial 5-9 and skeletal muscle ischemia. 10,11 More recently, the technique was applied to assess exercise-induced hyperemia in skeletal muscle. 12,13 Available MRI systems are able to generate BOLD-sensitive small volume data sets in Ͻ1 s. Thus, BOLD MRI can noninvasively detect changes in intravascular tissue oxygenation with high spatial and temporal resolution. Furthermore, the tissue access is potentially unrestricted. We investigated changes of tissue oxygenation as defined by BOLD MRI signal intensity (SI) compared with blood flow changes after validated standard effectors on vascular tone and applied direct vasodilation and vasodilation attributable to stimulation of the endothelium. Conclusions-In Methods ProtocolWe studied 9 normal healthy men (25Ϯ4 years of age; 75Ϯ9 kg weight; 180Ϯ9 cm height). They received no medications. Our internal review board approved all studies, and written informed consent was obtained. All studies were conducted between 9 AM and noon after an overnight fast. A catheter (18G; Braun AG) was introduced into the brachial artery ...

show abstract

“…Globalement, le tonus vasculaire contrôle la pression sanguine du réseau pulmonaire et du réseau systémique. En aval du réseau artériolaire, le fl ux sanguin microvasculaire est passivement distribué à travers le lit capillaire [5] ou d'autres lits vasculaires tels que les sinusoïdes hépatiques. Le fl ux sanguin de la microcirculation est dépendant des résistances locales des vaisseaux (diamètre et longueur) et des facteurs rhéolo-giques du sang (déformabilité des globules rouges et viscosité sanguine).…”

Section: La Micro Vascularisation : Système Fonctionnel De Distributiunclassified