Normal Arterial Wall Research Articles

The effects of atherosclerosis on the transmission of ultrasound

A study of the effect of atherosclerosis on the transmission of ultrasound through the arterial wall was carried out on seven aortas and iliac arteries removed at the time of autopsy. Using a pulsed echo-ranging system, the extent of the sound attenuation was measured from plane sections of the vessels. The results indicated that areas of arterial calcification attenuated the transmitted ultrasound in the 30–40 db range. Normal areas or plaques without calcification, as determined by x-ray and histologic studies, attenuated the sound in the 0–5 db range. Thus, the sound absorption due to the plaque containing calcium is larger by a factor of approximately 1000 than the absorption of the normal artery wall.

Differential resorption rates of subcutaneous implants of [ 3H]cholesterol, various [ 3H]cholesterol esters and [ 3H]cholesterol-[1- 14C]linolenate

Summary Free [ 3 H] cholesterol, various [ 3 H] cholesterol esters and [ 3 H]cholesterol-[ 14 C]linolenate were implanted subcutaneously in rats. Three weeks after implantation [ 3 H] cholesterol linolenate and arachidonate were resorbed to a significantly greater extent than free [ 3 H]cholesterol, [ 3 H] cholesterol linolenate and the more saturated labelled sterol esters. [ 3 H]Cholesterol was more rapidly mobilized than the saturated and monounsaturated [ 3 H] cholesterol esters. The resorption of esterified cholesterol did not appear to depend on rapid hydrolysis of the fatty acid moiety and slow removal of the sterol nucleus, for 3 H and 14 C labels disappeared at nearly equal rates from implants of [ 3 H]cholesterol-[l- 14 C]linolenate. Addition of antioxidants to the polyunsaturated ester implants did not significantly accelerate resorption, even though it did reduce chromolipid formation. We infer that esterification of cholesterol with linolenic or arachidonic acids would accelerate its removal from the normal or atherosclerotic arterial wall.

The distribution of intravenously administered [ 3H]Chole-sterol in the arteries and other tissues : Part 2. radioautographic findings

Summary A new method for radioautography with lipid substances has been described which is based on carbowax embedding of tissue and dipping the sections into liquid Ilford K2 and Ilford G5 photographic emulsions. The method allows lipids to stay in situ and permits proper staining of the underlying tissue sections. Thus, lipid substances labeled with low energy isotopes can be effectively traced in tissues at the level of cells, fibers, and membranes. Radioautography was performed with this method on arteries and other tissues of normal dog and monkey ( Macaca irus ) between 4 and 6 weeks after the intravenous injection of [ 3 H]cholesterol. An accumulation of radioactive cholesterol was detected along the elastic membranes of elastic type arteries including aorta and coronary artery. The findings suggest that a high concentration of cholesterol is present on the elastic membranes of arteries. Radioactive cholesterol also appeared to be located in smooth muscle cells of elastic type arteries but not in the smooth muscle cells of muscular type arteries. The radiographic findings in intact and sub-cellularly fractionated arteries indicate that blood cholesterol enters the normal arterial wall and is distributed extracellulary as weil as intracellularly.

Asymmetrical distribution of aortic nerve fibers in the pig.

AbstractThe innervation of the aortic arch and associated arterial trunks was investigated in the pig by gross dissection, by microscopic examination of normal arterial walls, and by observation of degenerative changes following selective surgical interruption of right and left cervical vagi. It is concluded that the aortic depressor fibers of the pig are organized unilaterally, being distributed by the left vagus to arterial walls, and by observation of degenerative changes following selective surgical with the absence of a dissectable right aortic nerve, there was no histological evidence of sensory innervation in the walls of the brachiocephalic, right subclavian, bicarotid or right common carotid artery. The majority of depressor endings were located in the ventral wall of the aortic arch in a band extending between the origin of the left subclavian artery and the aortic attachment of the ligamentum arteriosum. A few were present in the dorsal wall of the aortic arch and the ventral walls of the pulmonary trunk and ligamentum arteriosum. The depressor fibers were thick, heavily myelinated, varicose, extensively branched and associated with numerous terminal and intercalated neurofibrillar corpuscles. The only epithelioid body observed was a poorly innervated, rudimentary paraganglion in the interval between the aortic arch, the pulmonary artery and the ligamentum arteriosum.

Movement of labeled cholesterol between plasma lipoprotein and normal arterial wall across the intimal surface.

Normal rat aortas were incubated with their intimal surfaces in contact with a lipoprotein solution containing isotopically labeled free cholesterol. Uptake of cholesterol by the tissue increased with increasing concentration toward a plateau level. Maximum uptake of free cholesterol was estimated to be 13 µg/cm 2 per 24 hours, and uptake at physiological cholesterol concentration was 7.9 µg/cm 2 per 24 hours. Aortas containing labeled cholesterol were prepared by intragastric administration of cholesterol-7α- 3 H to normal rats. Experiments in vitro with these aortas demonstrated that efflux across the intimal surface was dependent upon presence of lipoprotein in the medium. This efflux was not retarded by prior boiling of the tissue. These results support suggestions that movement of labeled free cholesterol from plasma into the arterial wall may be largely the result of a physicochemical exchange between lipoprotein and endothelium.

The windows of the internal elastic lamella of the cerebral arteries.

The large cerebral arteries have a relatively thick, compact internal elastic lamella in which small windows occur. The nutrition of the tunica media takes place by diffusion from the lumen, because the normal cerebral arterial wall generally has no vasa vasorum. The main part of the nutritional transport probably goes through the windows because the compact portions of the elastic lamella are less permeable. The windows may thus constitute narrow gateways facilitating the passage of nourishment to the media. With increasing age the windows get smaller and less frequent at the same time as the elastic lamella increases in thickness. In the largest cerebral arteries these windows were also found to be smaller than in the cerebral arteries with a finer calibre. With increasing age the nutritional supply to the media may therefore be endangered in the largest cerebral arteries, expecially since the media of these arteries needs a greater supply than that of the smaller ones. When the nutritional transport is insufficient media fibrosis and atheromatosis may develop. These lesions are actually most common in the largest arteries.

Hemodynamic principles and end-to-side vascular anastomoses.

Bypass angioplastic procedures based on the technique originally described by Kunlin4with autologous vein grafts and more recently by Linton and Menendez6and Crawford and De Bakey2with arterial homografts and plastic prostheses are extensively used by the vascular surgeon on the treatment of segmental vascular occlusions. They allow the preservation of an already established collateral circulation and also prevent further damage to the blood supply of a limb in the event of graft failure. This technique has demonstrated the values of the end-to-side vascular anastomosis when an end-to-end suture is not feasible and emphasized the importance of determining the best hemodynamic conditions to prevent blood flow reduction or late thrombosis. It is recognized that due to the mechanical characteristics of the normal arterial wall and variations on the pressure head and physical properties of the blood, general principles of fluid flow cannot be directly applied to