Arterial wall, composition

Low-density lipoproteins in plasma and arterial wall are susceptible to oxidation to form oxidized LDL, which are thought to promote the development of atherosclerosis. LDL particles have a density of about 1.05, a molecular weight of about 2.5 x 106, and a diameter of about 20 nm [119]. LDL composition from different donors varies widely an average LDL particle contains about 1200 molecules of unsaturated acids and antioxidants about six molecules of a-tocopherol, about 0.53 molecule of 7-tocopherol, about 0.33 molecule of (3-carotene, and about 0.18 molecule of lycopene [120], Rapid oxidation of LDL is started only after the depletion of tocopherols and carotenoids [121]. 

PS/PIB/PS block copolymers have been shown to be vascularly compatible. When loaded with paclitaxel and coated on a coronary stent, the composite can deliver the drug directly to arterial walls. 

In the preceding two examples, Raman spectra were obtained from tissues and cell samples ex vivo. Recently, Buschman et al. (46) were able to measure Raman spectra of sheep arterial walls in vivo using a miniature fiberoptic probe. They have demonstrated that the in vivo intravascular Raman signal obtained directly from a blood vessel is a simple summation of signals from the blood vessel wall and blood itself. This technique may be useful in predicting the risk of arterial plaque rapture and determining plaque composition in human arteries. 

F. S., Ultrasound characterization of coronary artery wall in vitro using temperature-dependent wave speed, IEEE Trans Ultrason. Ferroelectr. Ereq. Control 50,1474-1485, 2003 Bhardwaj, R Mohanty, A.K., Drzal, L.T. et al.. Renewable resource-based composites from recycled cellulose liber and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) bioplastic. Biomacromolecules 7, 2044-2051, 2006. 

A carotid plaque s variable composition may affect the associated stroke risk. The structure of the carotid artery wall, including the composition, ranodeling, and... 

S. Glagov, R. Vito, D.R Giddens, C.K. Zarins, Micro-architecture and composition of artery walls relationship to location, diameter and the distribution of mechanical stress, J. Hypertens. Suppl. 10 (1992) S101-S104. 

The composition of normal human arterial tissues is altered with age in many aspects. Table B6.7 lists the observed changes in human aorta, pulmonary and femoral arteries [20]. There is a tendency that both the dry matter and nitrogen content of arterial tissues decreases with age. However, the relative quantity of collagen [22] and elastin [23, 24] in the arterial wall remains almost unchanged with age. Below the age of 39, the wall of human thoracic aorta has 32.1 5.5% elastin, between the age 40-69, the wall contains 34.4 9.3%, and from 70-89, the elastin content is 36.5 10.1 [24]. 

Rees, P.M. and Jepson, P. (1970) Measurement of arterial geometry and wall composition in the carotid sinus baroreceptor area. Circ. Res., 26, 461-467. 

Fig. 15.4. The same software also may provide information about the composition of atherosclerotic plaque. The final way of quantifying these lesions in the coronary artery wall has not yet been determined and remains problematic, since the display of these lesions is very much influenced hy partial volume effects...

Eecause ascorbic acid and other antioxidants in plasma effectively prevent lipid peroxidation and, hence, oxidative modification of LDL, it is likely that LDL oxidation in vivo occurs in microenvironments of the arterial wall rather than the circulation (Steinberg et al., 1989). Water-soluble antioxidants such as ascorbic acid may be excluded from these lipid-rich microenvironments in the artery wall (Eelcher et al, 1993), or these antioxidants may be rapidly depleted due to high levels of local oxidative stress (e.g., in the microenvironment of activated macrophages). Thus, in the above cited study of ODS rats (Kimura et al, 1992), it is unlikely that LDL oxidation occurred in the circulation. Rather, vitamin C deficiency may have facilitated LDL oxidation in the arterial wall, followed by release of some modified LDL into the circulation. Although the antioxidant composition of the extracellular fluid in the arterial wall has not been characterized, we have found that a model of human interstitial fluid (Vessby et al, 1987) is characterized by an ascorbic acid concentration that is similar to plasma (Dabbagh and Frei, 1994). 

HP Buschman, ET Marple, ML Wach, B Bennett, TC Bakker Schut, HA Bruining, AV Bruschke, A van der Laare, GJ Puppels. In vivo determination of the molecular composition of artery walls by intravascular Raman spectroscopy. Anal Chem 72 3771-3775, 2000. 

Examples of Raman spectra from three different types of human coronary artery are shown in Fig. 17. The top spectrum was obtained from a sample of nonatherosclerotic (normal) coronary artery, the middle from a noncalcified atheromatous plaque, and the bottom from a calcified plaque. The spectra from these different artery types are distinct and provide clear features for the determination of the chemical composition and for a histological classification of the arterial wall. For example, the normal coronary artery spectrum is dominated by protein features such as the amide I and III modes at 1650 and 1250 cm respectively, and the CH2 bending modes at —1450 cm In noncalcified atheromatous plaques, spectral features of cholesterol and cholesterol esters constitute the major part of the spectrum. The symmetric stretch at 960 cm of the calcium hydroxyapatite phosphate group dominates the spectrum of calcified plaques. 

Martin A. Zulliger, Pieire Fridez, Kozaburo Hayashi, Nikos Steigio-pulos, (2004) A strain energy function for arteries accounting for wall composition and structure. Journal of Biomechanics 37 989-1000... 

The important landmarks along this tortuous road are, of course, a function of what part of the elephant this particular blind man is examining. If one accepts that atherosclerosis is a disease of the vessel wall, perhaps in response to compositional changes in the blood, one has to be concerned with metabolic aberrations within this structure. The demonstration by Chernick et al. (1949) that rat aorta was capable of fatty acid biosynthesis was perhaps the most significant illumination in this area of scientific exploration. This demonstration that the arterial wall was a compleat organ possessing all the complex metabolic machinery to carry out biosynthetic work elevated the arterial wall to a new and lofty position. 

Elastin constitutes the yellow elastic fibers in ligaments, and the outer wall of arteries. It is not affected by dilute acids or alkalies in the cold, but is digested by pepsin and hydrochloric acid. It yields 25 per cent of glycine and 21 per cent of leucine on hydrolysis. Fibroin, which is the chief constituent of the fibers of silk, differs markedly from the other albuminoids and albumins in composition. It contains about 19 per cent of nitrogen, and yields on hydrolysis 36 per cent of glycine, 21 per cent alanine, and 10 per cent tyrosine. 

Macroscopic vessels represent only a small fraction of the circulatory system. Approximately lO blood vessels are the capillaries whose diameters are comparable with the dimensions of the red blood cells, i.e., 5-10 p,m [18]. In the smallest capillaries with diameters 10 m, where the pressure drops to 1 kPa, blood flow represents a composite system with sharp interface between liquid and solid phases. In this spatial scale, the red blood cells (RBC) describe the phase volume with distinct elastic properties. In contrast to the macroscale, at the microscopic scale blood flow can be viewed at as the collective motion of an ensemble of microscopically interacting discrete particles. Unlike in large blood arteries, in the blood capillaries the wall consists of a layer of endothelial cells [18] responding to the shear flow. 

Several studies have shown that microbial cellulose can be molded into tubular form with diameter < 6 mm. Klemm et al. [101] prepared a microbial cellulose tube having 1 mm diameter and 5 mm length with a wall thickness of 0.7 mm. The tensile strength of the material was foxmd to be comparable to that of normal blood vessels (800 mN) and is employed as blood vessel to replace part of the carotid artery. Alter four weeks, the microbial cellulose/carotid artery complex was covered with connective tissue. The in-vivo bicompatibility tests show that microbial cellulose can be used as a replacement blood vessel. Recently, Brown et al [102] have prepared small tubes of microbial cellulose-fibrin composites treated with glutaraldehyde in order to crosslink the polymers and allow a better match of the mechanical properties with those of native small-diameter blood vessels. 

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