Biomedical subjects

J A E Spaan

Publications and source records attributed to J A E Spaan.

3 recordsLinked to original sources

PubMed2007

Relation between branching patterns and perfusion in stochastic generated coronary arterial trees.

Biological variation in branching patterns is likely to affect perfusion of tissue. To assess the fundamental consequences of branching characteristics, 50 stochastic asymmetrical coronary trees and one non-stochastic symmetrical branching tree were generated. In the stochastic trees, area growth, A, at branching points was varied: A = random; 1.00; 1.10; 1.13 and 1.15 and symmetry, S, was varied: S = random; 1.00; 0.70; 0.58; 0.50 and 0.48. With random S and A values, a large variation in flow and volume was found, linearly related to the number of vessels in the trees. Large A values resulted in high number of vessels and high flow and volume values, indicating vessels connected in parallel. Lowering symmetry values increased the number of vessels, however, without changing flow, indicating a dominant connection of vessels in series. Both large A and small S values gave more realistic gradual pressure drops compared to the symmetrical non-stochastic branching tree. This study showed large variations in tree realizations, which may reflect real biological variations in tree anatomies. Furthermore, perfusion of tissue clearly depends on the branching rules applied.

Arteries↗

PubMed2005

Visualisation of intramural coronary vasculature by an imaging cryomicrotome suggests compartmentalisation of myocardial perfusion areas.

A technique is presented for the 3D visualisation of the coronary arterial tree using an imaging cryomicrotome. After the coronary circulation of the excised heart was filled with a fluorescent plastic, the heart was frozen and mounted in the cryomicrotome. The heart was then sliced serially, with a slice thickness of 40 microm, and digital images were taken from each cutting plane of the remaining bulk material using appropriate excitation and emission filters. Using maximum intensity projections over a series of images in the cutting plane and perpendicular plane, the structural organisation of intramural vessels was visualised in the present study. The branching end in the smallest visible vessels, which define tissue areas that are well delineated from each other by 1-2 mm wide bands populated only by vessels less than 40 microm in diameter. The technique presented here allows further quantification in the future of the 3D structure of the coronary arterial tree by image analysis techniques.

Animals↗

PubMed2003

Differential structural adaptation to haemodynamics along single rat cremaster arterioles.

We tested the hypothesis that under physiological conditions, arterioles match their diameter to the level of shear stress. Haemodynamic and anatomical data were obtained in segments of the first-order arteriole of the rat cremaster muscle. Along this segment of ~10 mm in length, local blood pressure decreased from 68 +/- 4 mmHg upstream to 54 +/- 3 mmHg downstream (n = 5). Pulse pressure decreased from 8.2 +/- 1.3 mmHg upstream to 4.1 +/- 0.6 mmHg downstream. At the same locations, an increase in arteriolar diameter was measured in vivo, from 179 +/- 4 microm upstream to 203 +/- 4 microm downstream (n = 10). In vitro pressure-diameter relations of maximally dilated vessels showed that the passive diameter was larger in downstream than upstream segments over a 15-125 mmHg pressure range (n = 18). The wall stress was similar for the upstream vs. downstream location: 266 +/- 16 vs. 260 +/- 14 mN mm-2. However, shear stress decreased from 30 +/- 5 to 21 +/- 5 dyn cm-2 (3.0 +/- 0.5 to 2.1 +/- 0.5 N m-2; n = 4) along the artery. In conclusion, these results demonstrate that shear stress is not the only factor in determining vascular calibre. We suggest that arteriolar calibre may rather depend on an interplay between shear stress and the local pressure profile.

Adaptation, Physiological↗