Mechanical Properties of Rat Middle Cerebral Arteries With and Without Myogenic Tone

[+] Author and Article Information
Rebecca J. Coulson

Mechanical Engineering Department, University of Vermont, Burlington, VT 05405

Marilyn J. Cipolla, Lisa Vitullo

Neurology Department, University of Vermont, Burlington, VT 05405

Naomi C. Chesler

Mechanical Engineering Department, University of Vermont, Burlington, VT 05405Biomedical Engineering Department, University of Wisconsin, Madison, WI 53706

J Biomech Eng 126(1), 76-81 (Mar 09, 2004) (6 pages) doi:10.1115/1.1645525 History: Received June 20, 2002; Revised September 02, 2003; Online March 09, 2004
Copyright © 2004 by ASME
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Experimental setup. The vessel was sutured onto glass cannulas above an optically clear window in the arteriograph chamber. Through this window, the vessel image is magnified by an inverted microscope objective and digitized by a CCD camera. Vessel diameter and wall thicknesses (right and left) were measured from one scan line of this digitized image by a video dimension analyzer (VDA). Perfusate pressure was controlled by a servo-mechanism under computer control through a data acquisition and control system (DATAQ). Perfusate and bath temperature were maintained at 37°C by closed loop control of heating elements (not shown).
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Circumferential (A) and radial (B) Cauchy stress and Almansi strain for passive and active rat MCAs. Active values are reported for the 50–125 mmHg pressure range (⋄). Passive values are reported for the 5–200 mmHg pressure range (♦). Stress and strain were both calculated at the inner radius. The reference state used for the active and passive strain calculations was the passive inner radius at 0 mmHg. Values are mean±SE.
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Representative pressure-diameter relation (A) and logarithmic transformation with linear regression (B) to show how β was determined for each vessel where p is the transmural pressure, ps is a reference pressure, re is the external radius, and res is the external radius measured at the reference pressure. The reference pressure chosen within the physiologic pressure range was 75 mmHg.
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Incremental elastic modulus, Einc-p, for passive (♦) and active (⋄) vessels versus transmural pressure (A) and circumferential Almansi strain (B). Values are mean±SE. * p<0.05.
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Activation modulus, Einc-a, calculated at transmural pressures ranging from 50 to 125 mmHg. The slope of the monotonic increase is significantly greater than zero between all pressures (* p<0.001). Values are mean±SE.




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