Variaciones Anatómicas de la bifurcación aórtica / Anatomic variations of the aortic bifurcation

Entre las entidades anatomo-clínicas de gran interés en medicina general y especialmente en angiología, están las enfermedades arteriales obliterantes, las cuales ocurren en los sitios donde las arterias se dividen o ramifican, especialmente en el segmento aorto-ilíaco. En el presente trabajo sobre descripción de las variaciones anatómicas de la bifurcación aórtica, se estudiaron 50 cadáveres (material de morgue) y 20 segmentos aorto-ilíacos (material autopsiado). Los resultados obtenidos indicaron que la aorta abdominal se bifurca con más frecuencia sobre la cuarta vértebra lumbar (L4), en 56.80 por ciento (40 casos); que el ángulo subaórtico tiene un valor promedio de 57.48 (23 -83 ) y el valor promedio del diámetro inferior externo es de 23.71mm (11 - 40mm)

Fístula arteriovenosa pós-traumática aorto-renal: relato de caso / Traumatic aorto-renal arteriovenous fistula; a case report

Os autores descrevem um caso de fístula arteriovenosa pós-traumática entre aorta e veia renal esquerda, com evoluçäo de 18 anos. Na literatura mundial somente cinco casos säo descritos, mas nenhum com investigaçäo radiológica täo abrangente e evoluçäo täo longa. O estudo iniciou-se por arteriografia seguida de venocavografia, tomografia computadorizada e ultra sonografia. O paciente foi submetido a cirurgia e os achados cirúrgicos säo descritos. É ainda lembrada a discussäo existente a respeito do melhor método diagnóstico para patologias dessa natureza

Tissue inhibitor of metalloproteases (TIMP) is matrix associated in aortic tissue: report of a radioimmunoassay.

Tissue inhibitor of metalloproteinases (TIMP) is the major inhibitor of collagenase, gelatinase, proteoglycanase, stromelysin, and metalloelastases. An imbalance between proteases and inhibitors has been implicated in numerous disease processes including tumor invasion, rheumatoid arthritis, emphysema, and aortic aneurysm disease. The purpose of this investigation was to develop a polyclonal antibody to recombinant TIMP and establish an immunoassay to measure immunoreactive protein in normal and diseased tissues. A polyclonal antibody was produced in rabbit against recombinant human TIMP which was characterized and used to establish a radioimmunoassay. The assay was used to measure immunoreactive protein in fibroblast conditioned medium, human serum, and aortic extracts. There was more immunoreactive TIMP in matrix associated urea extracts than soluble salt extracts from human aorta, suggesting that TIMP is matrix associated. The sensitivity of the assay enables the specific measurement of this inhibitor in serum, fibroblast culture medium, and tissue extracts.

LDL accumulation in the grossly normal human iliac bifurcation and common iliac arteries.

We had previously used an electrophoretic transfer procedure to determine the topographic distribution of low density lipoprotein (LDL) accumulation in the aortic intima of normolipemic swine. In this present study we have employed a similar procedure to assess whether LDL-rich sites consistently demonstrate increased intimal thickening at the iliac bifurcation and common iliac arteries. The topographic distribution of LDL-rich sites was determined in the aortas of six subjects ranging in age from 16 to 36 years, by transferring LDL by electrophoresis from the tissue into an agarose gel containing anti-LDL, and then staining the immunofixed LDL in the gel for lipid. LDL-rich sites were found in all but two of these cases. On the basis of control studies establishing the level of nonspecific staining, we determined that the cutoff between LDL-rich and LDL-poor zones was 37 mg apoB protein/mm2 intimal surface area. Intimal thickening was found to be threefold greater in LDL-rich than in LDL-poor regions. These results confirm and extend earlier immunohistochemical studies suggesting a preferential accumulation of LDL at sites of intimal thickening in human arteries.

Chemical shift magnetic resonance imaging of human atheroma.

Fifteen necropsy specimens of human descending aorta and from eight patients with atheromatous vascular disease were studied by magnetic resonance imaging at 0.5 T. Images were acquired in coronal and transverse planes to localised protruding lesions and then chemical shift imaging was performed by techniques described by Dixon and by Hinks. These techniques produce images in which signal strength is proportional to lipid content. The signal was expressed as a percentage of that from extravascular fat. The total lipid content and its distribution within the plaques were noted. After imaging, the postmortem specimens were examined histologically and the lipid content of the plaque was assessed on a semiquantitative scale. The distribution of lipid within the plaque and between intima and media was also noted. The findings of chemical shift imaging agreed well with histological examination both for total lipid content and for distribution within each plaque. Chemical shift imaging also provided an assessment of the lipid content of the plaques measured in living patients, but validation was more difficult. The usefulness of the technique in routine clinical practice remains to be established.

Limitations of the lipid state hypothesis for atherosclerosis are revealed by X-ray diffraction measurements.

The lipid state hypothesis proposes that liquid crystalline states of cholesteryl esters play a role in the development and persistence of the fatty streak lesions characteristic of atherosclerosis. We have tested several corollaries suggested by this hypothesis and find that the ensemble of droplets in atherosclerotic tissue are predominantly in the isotropic (fluid) state at 37.0 degrees C. Furthermore, the liquid-crystalline state transition behavior of these droplets is not influenced significantly by the distribution of component cholesteryl ester species. There are no significant correlations between the transition behavior of the droplets and the age, sex, or race of the subjects from which tissue samples were taken. These results show that the lipid state hypothesis is weak, and that the origin and persistence of fatty streak lesions in humans is probably dominated by other factors.

Calcitonin gene-related peptide (CGRP) in normotensive and spontaneously hypertensive rats.

With the techniques of specific radioimmunoassay and gel filtration it was found that CGRP was distributed in various tissues of normotensive (WKY) and spontaneously hypertensive rats (SHR) with the highest concentration in the lumbar spinal cord (1197 +/- 94.8 pg/mg tissue) and the lowest in the auricle (15.0 +/- 2.1 pg/mg tissue). In comparison with WKY, CGRP concentration in the plasma was decreased and in the abdominal aorta and hypothalamus was increased in SHR. Gel filtration revealed only one major CGRP molecular form in the tissues. In addition, CGRP reduced the mean arterial pressure (MAP) in SHR in a dose-dependent manner. These data suggest that CGRP may play an important role in the pathogenesis of hypertension and its possible therapy.

Cellular, enzymatic, and genetic factors in the pathogenesis of abdominal aortic aneurysms.

Aneurysms of the abdominal aorta occur with atherosclerosis or connective tissue disorders. Changes of three components of aortic media, smooth muscle cells, elastin, and collagen, which could contribute to medial weakening, are discussed. Smooth muscle cells cultured from the aging abdominal aorta (normal, atherosclerotic, or aneurysmal) have limited replicative potential at five to six cell doublings, whereas cells from aneurysmal thoracic aorta undergo more than 20 cell doublings in culture. The elastin content is much reduced in aneurysms and this is associated with an increase in elastase activity of medial homogenates to 17.8 U/ng of deoxyribonucleic acid (DNA) compared with 8.3 and 4.4 U/ng of DNA in atherosclerotic and normal aorta, respectively. An elastinolytic enzyme has been purified from aneurysmal aorta and appears to have different properties from human leukocyte elastase. Ruptured aneurysms are associated with an increased total collagenase activity but the increase could be stimulated by, or result from, an influx of inflammatory cells and does not necessarily have a causal significance. In patients with a family history of aneurysm there appears to be a decreased content of type III collagen in aortic media: 24% +/- 4% compared with 32% +/- 5% in most aneurysms. Familial aneurysms are most common in women, and preliminary results suggest that a polymorphic variant of the type III collagen gene, defined by restriction enzyme digest, may be associated with aneurysmal disease in women. The genetic approach may define causal mechanisms predisposing patients to aneurysmal dilatation.

Characterization of the phenotype of smooth muscle cells in human fetal aorta on the basis of ultrastructure, immunofluorescence, and the composition of cytoskeletal and cytocontractile proteins.

The phenotype of smooth muscle cells (SMCs) in the aortic media of 7 human fetuses (14-20 weeks of gestation) was examined with transmission electron microscopy, immunofluorescence microscopy, and gel electrophoresis of the cytoskeletal and cytocontractile proteins. Ultrastructurally, virtually all medial cells were identified as SMCs having a poorly differentiated phenotype with a cytoplasm rich in rough endoplasmic reticulum and organelles, and with only a few myofilaments. All medial cells stained intensely with antibodies to vimentin, but only in a 20-week-old fetus could we find a few SMCs staining with antibodies to desmin. Nor was desmin detectable with SDS gel electrophoresis followed by immunoblotting, while clear bands corresponding to vimentin, myosin, and actin were present. In isoelectric focusing and two-dimensional gel electrophoresis beta-actin was the most prominent of the 3 actin isoforms in all cases. The present results show that SMCs in the media of fetal human aorta have a poorly differentiated phenotype, which morphologically and biochemically resembles that previously described in the aorta of fetal and newborn rat, in the arterial intima after endothelial injury, in atherosclerotic lesions, and after spontaneous modulation of medial SMCs in culture.

Large lipoproteins are excluded from the arterial wall in diabetic cholesterol-fed rabbits.

In diabetic hypercholesterolemic rabbits at plasma triglyceride concentrations of approximately 5000 mg/dl, 55% of plasma cholesterol (1400 mg/dl) was in lipoproteins with diameters larger than 75 nm (Sf greater than 400), 40% in smaller very low density and intermediate density lipoproteins, 4% in low density lipoproteins, and 1% in high density lipoproteins. Specific intimal clearance (nl/h.mg aortic cholesterol) of the giant Sf greater than 400 lipoproteins was about 4% of that of the low density lipoproteins. The data suggest that even very low density lipoproteins with diameters smaller than 75 nm were practically excluded from entering the arterial wall. Specific intimal clearance of low density lipoproteins in hypertriglyceridemic, diabetic cholesterol-fed rabbits was similar to that in normal cholesterol-fed rabbits, but low density lipoprotein concentrations in diabetic rabbits were low. Thus, at plasma triglyceride concentrations of approximately 5000 mg/dl, only 5% of plasma cholesterol may be readily available for infiltration of arteries. These results add further support to the hypothesis that hypertriglyceridemic, diabetic cholesterol-fed rabbits are protected against atherogenesis because the major part of plasma cholesterol is carried in large lipoproteins to which the artery is not very permeable.

Proteoglycan distribution in the intima and media of the aortas of young and aging rabbits: an ultrastructural study.

Aortas from normal healthy rabbits, approx. 3 months old, were examined by light and transmission electron microscopy. The proteoglycan of the extracellular matrix, which was stained by ruthenium red and appeared as granules by transmission electron microscopy, was quantitated morphometrically in the intima and the superficial media. The intima included areas which were thickened and which contained connective tissue, including proteoglycan, and some smooth muscle cells. In the thickened intima there was a greater proportion of extracellular space which was occupied by proteoglycan, and the proteoglycan was present in higher concentration than in the media. In the aortas of rabbits, approx. 2 years old, the extent of intimal thickening and the concentration of proteoglycan increased in the thickened intima but there was no evidence of extracellular lipid deposition. The endothelial basement membrane contained small proteoglycan granules (heparan sulphate) which decreased in concentration in older animals. It is possible that the accumulation of proteoglycan in the thickened intima increases the susceptibility of the intima to accumulate lipid following an additional stimulus, such as hyperlipaemia, in the initial stages of atherosclerosis.

Renal vein immunoreactive renin in patients with renal artery stenosis and essential hypertension.

In 36 patients with unilateral renal artery stenosis and in 24 with essential hypertension the plasma levels of total immunoreactive renin, and enzymatically active renin were measured in both renal veins (V) and in the aorta (A) by direct RIA by using monoclonal renin antibodies. Active renin and trypsin-activatable inactive renin were also measured by indirect RIA with angiotensin-I antibodies. The V/A ratio for the different forms of renin calculated from the results of direct and indirect RIA were not different. The V/A ratio of active renin for the kidney with the stenotic artery was 3.04 +/- 0.28 (mean +/- sem) with direct and 3.02 +/- 0.25 with indirect RIA. The contralateral ratio was 1.04 +/- 0.02 with the direct and 1.05 +/- 0.02 with the indirect RIA. In essential hypertension it was 1.28 +/- 0.04 with direct RIA and 1.28 +/- 0.04 with indirect RIA. Chronic treatment with captopril had no influence on this ratio in both patients groups. The V/A ratio of total immunoreactive renin was lower than that of active renin and this ratio had lost discriminative power for lateralization. This ratio was significantly greater than one on the affected side in renal artery stenosis but not contralaterally and in essential hypertension. This study shows that renin activity after trypsin-activation of plasma is an accurate measure of the total renin concentration, i.e. active renin plus prorenin. It also shows that a kidney with a stenotic artery secretes inactive renin, which is immunologically related to active renin and is likely to be prorenin. Direct RIA for measuring active renin is technically more simple than indirect RIA. Direct RIA however is somewhat less sensitive. For measuring the V/A ratio for active renin in patients with renal artery stenosis this can be overcome by stimulating the renin-angiotensin system for instance by captopril.

Cellular changes during hypertension: a quantitative study of the rat aorta.

Using rats made hypertensive by aortic ligation or by the one kidney--one clip method, we searched the aorta for morphologic clues that could explain why hypertension aggravates atherosclerosis. Both atherosclerosis and hypertension are characterized by an increased migration of mononuclear cells into the aortic intima; we therefore quantitated this phenomenon and studied its time course. In the thoracic aorta of hypertensive rats intimal cells (emigrated mononuclear cells) increased up to 15 times 2 weeks after surgery and remained stationary thereafter. In both control and experimental rats, leukocyte emigration was heavier in the thoracic aorta than in the abdominal region. A two- to threefold increase in medial smooth muscle herniae into the intima (myointimal herniae) was also found at 8 weeks, indicating a smooth muscle cell dysfunction. Electron microscopic study of the intima showed that its thickening was due to blood-borne material and also to extracellular matrix synthesized by the endothelium. Heightened secretion reflects cell activation, a condition that (in the endothelium) leads also to leukocyte adhesion. These data suggest that, in renovascular hypertension, the aortic endothelium is in an activated state, possibly through a hormonal stimulus.

Basic proteins in the human aortic intima: nonequilibrium two-dimensional electrophoretic analysis of tissue extracts.

The protein composition of atheroma-free human thoracic intima was compared with that containing fatty streaks or fibro-fatty lesions utilizing two-dimensional gel electrophoresis (2-DE) and silver staining. Intimal proteins extracted with 9 M urea were separated by nonequilibrium pH gradient electrophoresis (NEPHGE) followed by polyacrylamide gel electrophoresis (PAGE) in the second dimension. NEPHGE-PAGE of proteins extracted from atheroma-free intima revealed several major proteins: actin, tropomyosin-like proteins, proteins with relative molecular weight (Mr) of 250,000 (P250), two proteins with Mr about 15,000 (P15a, P15b), and many medium proteins such as a myosin heavy chain, two myosin light chains, and proteins P47, P44, P32, P27, P20a, P20b, P19a, P19b. Several additional proteins were observed in intimas with fatty streaks and fibro-fatty lesions. Most of them, such as albumin, transferrin, Apo A-I, alpha 1-antitrypsin, fibrinogen beta-chain, IgG, appear to originate from plasma. Differences in protein composition of intima with fibro-fatty streaks compared with adjacent lesion-free intima varied from case to case and need further study. NEPHGE-PAGE in combination with isoelectric focusing (ISO)-PAGE revealed more intimal proteins in atheroma-free and diseased aortas than either method alone, proteins which might be quantitated, isolated for binding studies, and further evaluated for their potential role in atherogenesis.

Spatial distribution and accumulation of low density lipoproteins in the abdominal aorta of swine: determination by a novel electrotransfer procedure.

An immunotransfer procedure has been developed which can determine both the spatial distribution of low density lipoproteins (LDL) along the intima-media of large blood vessels such as the aorta, and can quantify LDL accumulation along its length. Aortas which were opened longitudinally along their ventral aspect were positioned so that their intimal side abutted against a gel containing glyoxyl agarose to which anti-LDL had been covalently coupled. LDL was electrophoresed out of the agarose gel where it was immunofixed. This distribution was then visualized first by incubating the gel with 125I-anti-LDL which bound to free epitopes on the immunofixed LDL, and second by subjecting the washed and dried gel to autoradiography. Plasma LDL was applied to wells of different shapes and sizes in an agarose gel substituting for aortic tissue, and the transfer procedure was performed as described. The resultant patterns matched those of the original wells, suggesting that the spatial distribution of LDL in the autoradiogram probably mimicked that in the aortic tissue. The transfer procedure appeared to be specific for the antigen under study since minimal silver grains were observed in autoradiograms when an IgG fraction of nonimmune serum was used in place of anti-LDL. Application of increasing concentrations of LDL to wells in a gel substituting for tissue, resulted in a dose-dependent increase in autoradiographic grain density. If such standards were applied to gels adjacent to tissue samples, the amounts of LDL in the tissue could be quantified from the standard curve of grain density versus LDL concentration. The distribution of LDL along the abdominal aortas of 10- and 31-week-old swine was determined by converting autoradiographic grain densities to isopleths of LDL concentrations by computer assisted image analysis. These distributions were focal and were found to range between 10 and 225 ng of apoB/mm2 of intimal surface area. This procedure lends itself not only to studies relating lipoprotein accumulation to atherogenesis, but also to any studies dealing with tissue accumulation of macromolecules.

Intermediate filament heterogeneity in normal and hypercholesterolemic rabbit vascular smooth muscle cells.

We have examined the intermediate filament (IF) protein content of vascular smooth muscle (SM) cells from several arteries and veins in rabbits and quantitated the changes which occur in SM cell expression of these proteins in response to cholesterol feeding. Cells from control rabbit arteries expressed 30% of their IF protein as desmin, while veins expressed 50% as desmin. During development of diet-induced atherosclerosis, morphological changes in arterial SM cells in the intima correlate with changes in IF expression. There is a significant increase in total IF protein content, vimentin increased differentially in thoracic aorta and desmin in pulmonary artery. In abdominal aorta both increase equally. Cholesterol feeding also resulted in changes in the expression of subspecies of desmin, vimentin, and actin in the thoracic arch. Although cholesterol feeding did not produce obvious morphological changes in the veins examined, venous SM IF protein expression was also altered. In the vena cava of cholesterol-fed rabbits there was an increase in vimentin expression without the parallel increase in desmin that occurred in the arterial system. These studies show that cholesterol feeding of rabbits induces measurable changes in the amounts of IF proteins in both arterial atherosclerotic lesions and venous SM cells.

The static elastic properties and chemical composition of the rat aorta in spontaneously occurring and experimentally induced hypertension: the effect of an anti-hypertensive drug.

The static elasticity and scleroprotein content of the aorta have been measured in 24 Okamoto spontaneously hypertensive rats aged 22-25 weeks, and 24 Wistars of the same age in which hypertension had been induced by nephrectomy and treated with a steroid. From the age of 4 weeks half the animals in each group were treated with a diuretic drug. By the age of 15 weeks caudal artery systolic blood pressure was significantly lower than control values in both drug-treated groups and remained so until death. Both types of hypertension were associated with larger diameter, thicker-walled and heavier aortas than those in the drug-treated animals. Vessels from Okamoto animals contained more collagen than those from the Wistars, although the collagen content was unchanged by drug treatment. Neither drug nor strain had any clear-cut affect on elastin content. In spite of these differences in wall thickness and chemical composition, values of the functional stiffness of the aorta measured over a wide range of pressure were similar in all four groups of animals. Using a simple model of the aorta in which elastin and collagen bear stress in parallel we find that the relationship between vessel composition and static incremental elastic modulus (structural stiffness) is similar in both models of hypertension and is not changed by drug treatment in spite of the consequent reduction in blood pressure.

An enzyme-linked immunosorbent assay to quantitate the elastin crosslink desmosine in tissue and urine samples.

An enzyme-linked immunosorbent assay method has been developed for the determination of desmosine. The method is based on an inhibition immunoassay (under nonequilibrium conditions) and uses rabbit antisera directed against a desmosine-bovine serum albumin conjugate and microtiter plates coated with desmosine-gelatin conjugate. The assay quantitates desmosine in the range 2.5-50 pmol in tissue and urine samples. Important applications of this rapid and sensitive assay are in studying elastin metabolism and in screening for monoclonal antibodies against desmosine. Methods are described for obtaining a constant level of substitution of desmosine per molecule of bovine serum albumin and for preparing a desmosine-gelatin coating antigen. Five different antibody preparations directed against desmosine exhibit 15-20% cross-reactivity toward pyridinoline (3-hydroxypyridinium), a nonreducible collagen crosslinking compound also present in urine and many tissue samples.

The influence of age on fluid and sodium chloride distribution in rat aortic wall.

Fluid, Na+ and Cl- content and distribution have been examined in incubated segments of thoracic and abdominal aorta from male Wistar rats aged 1, 3 and 18 months. Na+ and Cl- were determined under conditions of total metabolic blockade (cyanide + iodoacetate). The total aortic mural fluid content, relative to solute-free dry weight, fell from 1 to 3 months, due mainly to relative contraction of the extracellular (e.c.) (inulin) space. It increased from 3 to 18 months due mainly to an increased intracellular (i.c.) (non-inulin) space. Total mural free and bound Na+ content, as well as i.c. Na+ content and concentration, fell from 1 to 3 months and increased from 3 to 18 months. No bound Na+ was detectable in segments which had been incubated in the presence of chondroitinase ABC. I.c. Cl- content and concentration fell from 1 to 3 months, but thereafter did not alter significantly. Bound Cl- in the aortic wall of 3-month-old rats was markedly reduced by incubation in the presence of a non-specific protease preceded by treatment with glycerol. The results are discussed in relation to previously established age-related characteristics of aortic and arterial walls.