Two-dimensional Maps of Short-term Albumin Uptake by the Immature and Mature Rabbit Aortic Wall Around Branch Points

[+] Author and Article Information
Benjamin A. Ewins, Jonathan Majewicz, Tracey J. Staughton, Peter D. Weinberg

School of Animal and Microbial Sciences, University of Reading, Reading, UK

J Biomech Eng 124(6), 684-690 (Dec 27, 2002) (7 pages) doi:10.1115/1.1517063 History: Received December 01, 2001; Revised June 01, 2002; Online December 27, 2002
Copyright © 2002 by ASME
Topics: Bifurcation
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Grahic Jump Location
(A) Diagram of a segment of aortic wall showing the regions in which tracer concentrations were measured. The intimal surface of the aortic wall is represented en face, with one intercostal branch ostium in the center. Mean aortic flow (heavy arrow) is from top to bottom. Serial longitudinal sections 2 μm thick were cut through the wall, perpendicular to the luminal surface, starting with a section along the midline (CC′ ). A notch scored on the surface of the block permitted correct alignment of sections in the longitudinal direction. Sections were cut until approximately 80 or 345 μm past the edge of the ostium (light arrows) to create narrow field and wide field maps, respectively. Bar=500 μm (B) Sections along the lines CC′ and DD′ are shown in diagrammatic form (the real section along DD′ is shown in Fig 3); in upstream and downstream regions of each section, the wall was divided into 6 strips, indicated by dotted lines in section CC′ ; tracer concentrations were averaged in the intima-media of each strip. When constructing the wide field maps, an additional 6 strips, indicated in the section DD′ , were analyzed in the region lateral to the branch for those sections beyond the edge of the ostium. Thus the dark gray area in diagram (A) was used to create narrow field maps, whilst wide field maps additionally used the light gray area.
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A, narrow field and B, wide field maps of average tracer concentration in the aortic intima-media around 5 intercostal branches from 2 immature animals. The aortic wall is shown en face, with mean flow from top to bottom (arrow). The half intercostal branch ostium is represented by the hatched area. Concentrations are shown in squares 20 μm wide and 57 μm long, and were scaled to give a mean value of 100 in each map. To indicate more clearly the pattern of uptake, squares with concentrations greater than or equal to the mean value, twice that value and four times that value are indicated by increasing shades of gray. Dotted lines in the narrow field map delineate areas described in the text. X=concentration not determined, bar=200 μm.
Grahic Jump Location
Montage of three digital images of fluorescence from a single longitudinal section through the aortic wall of a young rabbit, displaced laterally from the branch ostium (291st section from the centerline through the branch) as indicated in Fig 1. The aortic lumen is at the top of the image, and the adventitia is at the bottom; a discontinuity in the profile of the luminal surface corresponding to the extended lip of the flow divider is visible. The image has had spatial biases and offsets removed, as described in the text. Brighter intensities indicate greater uptake of rhodamine labeled albumin. Uptake is highest in the intima and inner media near the center of the section (“V”) corresponding to the region lateral to the ostium. Arrow=direction of mean aortic flow, bar=100 μm.
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A, narrow field and B, wide field maps of average tracer concentration in the aortic intima-media around 6 intercostal branches from 5 mature animals. Geometry and concentrations are represented as in Fig. 2. Comparison of the two maps suggests that the left hand edge of the narrow field map is actually inset a small distance past the centerline. Arrow=direction of mean aortic flow, bar=200 μm.
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Maps of the frequency of aortic lipid deposition around intercostal branch ostia. A, spontaneous deposits in young rabbits; B, spontaneous deposits in aged rabbits; C, diet-induced deposits in young rabbits, D, diet-induced deposits in mature rabbits (Harlan Interfauna strain). Each map represents an area of aortic wall, approx. 2.4×3.6 mm, viewed en face with mean aortic flow from top to bottom. Areas where lesions could not be mapped due to the presence of the ostium are indicated by a central square. Increasing shading indicates increasing lesion frequencies. (Thresholds for each gray level are described in references 12 and 13.) In the young rabbits, lipid deposition occurred in a triangular area downstream and at the sides of branches. (Occasional disease upstream, along the midline, has also been reported 7.) In the mature rabbits, downstream regions were generally spared (although some rabbits have shown disease on the flow divider lip itself 13). Instead, disease occurred in longitudinal strips at either side of the branch, and to a lesser extent upstream of it. Arrow=direction of mean aortic flow, bar=1.2 mm.




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