Wall shear stress and early atherosclerotic lesions in the abdominal aorta in young adults

Objectives:To study the correlation between wall shear stress and early atherosclerotic lesions in the abdominal aorta.Design:Blinded histomorphometric studies. Comparison with in vitro data.Materials:Abdominal aortic haemodynamics were simulated in a realistic pulsatile flow model. Abdominal aortas from 10 young adults with no signs of atherosclerotic disease were obtained during autopsy.Methods:Quantitative wall shear stresses were measured at rest and exercise in one suprarenal and two infrarenal positions using laser Doppler anemometry. Intimal thickening indices were measured blindedly at the corresponding locations using histomorphometric methods, and compared to wall shear stress variables using linear regression analysis.Results:Intimal thickness index increased significantly with age. Intimal thickness index was significantly lower in the suprarenal than the infrarenal aorta, and higher at the distal posterior vessel wall compared to the anterior wall. Intimal thickness index correlated significantly with mean, minimum and oscillating wall shear stresses measured at rest.Conclusion:Intimal thickness in the undiseased abdominal aorta correlated significantly with mean, minimum and oscillating wall shear stresses at rest measured in a pulsatile flow model. No correlations were found with maximum shear stress parameters. Exercise changed the local wall shear stresses away from the characteristics associated with intimal thickness index

Distribution of Early Atherosclerotic Lesions in the Human Abdominal Aorta Correlates with Wall Shear Stresses MeasuredIn Vivo

AbstractObjectives: to study the relationship between wall shear stresses measured in vivo and early atherosclerotic lesions in the abdominal aorta. Materials: eight young volunteers for in vivo wall shear-stress measurements. Abdominal aortas from 10 young adults without signs or history of atherosclerotic disease were obtained by autopsy for histomorphometric measurements. Methods: wall shear stresses were measured in the abdominal aorta above and below the renal arteries using a magnetic resonance technique with high resolution for imaging and blood velocity mapping. At identical abdominal aortic locations, intimal thickness was measured blindly using histomorphometric techniques and correlated to wall shear-stress variables using linear-regression analysis. Results: intimal thickness showed a linear decrease with mean wall shear stress (r=−0.90, p<0.01) and with maximum wall shear stress (r=−0.86, p<0.01). Conclusions: intimal thickness in the normal abdominal aorta is associated with mean, maximum and oscillating wall shear stresses. These in vivo data corroborate previous in vitro studies suggesting that low and oscillating wall shear stresses are localising factors for intimal thickening and hence the early development of atherosclerosis

Absorption Spectra of Photoactive Yellow Protein Chromophores in Vacuum

AbstractThe absorption spectra of two photoactive yellow protein model chromophores have been measured in vacuum using an electrostatic ion storage ring. The absorption spectrum of the isolated chromophore is an important reference for deducing the influence of the protein environment on the electronic energy levels of the chromophore and separating the intrinsic properties of the chromophore from properties induced by the protein environment. In vacuum the deprotonated trans-thiophenyl-p-coumarate model chromophore has an absorption maximum at 460nm, whereas the photoactive yellow protein absorbs maximally at 446nm. The protein environment thus only slightly blue-shifts the absorption. In contrast, the absorption of the model chromophore in aqueous solution is significantly blue-shifted (λmax=395nm). A deprotonated trans-p-coumaric acid has also been studied to elucidate the effect of thioester formation and phenol deprotonation. The sum of these two changes on the chromophore induces a red shift both in vacuum and in aqueous solution