Showing papers in "Arteriosclerosis, Thrombosis, and Vascular Biology in 1985"

Pulsatile flow and atherosclerosis in the human carotid bifurcation. Positive correlation between plaque location and low oscillating shear stress.

Abstract: Fluid velocities were measured by laser Doppler velocimetry under conditions of pulsatile flow in a scale model of the human carotid bifurcation. Flow velocity and wall shear stress at five axial and four circumferential positions were compared with intimal plaque thickness at corresponding locations in carotid bifurcations obtained from cadavers. Velocities and wall shear stresses during diastole were similar to those found previously under steady flow conditions, but these quantities oscillated in both magnitude and direction during the systolic phase. At the inner wall of the internal carotid sinus, in the region of the flow divider, wall shear stress was highest (systole = 41 dynes/cm2, diastole = 10 dynes/cm2, mean = 17 dynes/cm2) and remained unidirectional during systole. Intimal thickening in this location was minimal. At the outer wall of the carotid sinus where intimal plaques were thickest, mean shear stress was low (-0.5 dynes/cm2) but the instantaneous shear stress oscillated between -7 and +4 dynes/cm2. Along the side walls of the sinus, intimal plaque thickness was greater than in the region of the flow divider and circumferential oscillations of shear stress were prominent. With all 20 axial and circumferential measurement locations considered, strong correlations were found between intimal thickness and the reciprocal of maximum shear stress (r = 0.90, p less than 0.0005) or the reciprocal of mean shear stress (r = 0.82, p less than 0.001). An index which takes into account oscillations of wall shear also correlated strongly with intimal thickness (r = 0.82, p less than 0.001). When only the inner wall and outer wall positions were taken into account, correlations of lesion thickness with the inverse of maximum wall shear and mean wall shear were 0.94 (p less than 0.001) and 0.95 (p less than 0.001), respectively, and with the oscillatory shear index, 0.93 (p less than 0.001). These studies confirm earlier findings under steady flow conditions that plaques tend to form in areas of low, rather than high, shear stress, but indicate in addition that marked oscillations in the direction of wall shear may enhance atherogenesis.

Transmural organization of the arterial media. The lamellar unit revisited.

Abstract: When scanning electron micrographs of orthogonal transmural fracture surfaces of distended aortas were compared with appearances on corresponding semithin light microscopic and ultrathin transmission electron microscopic sections, medial lamellar units could be resolved into composites of overlapping, musculo-elastic fascicles lying parallel to tangential planes of section. Each fascicle consisted of a group of commonly oriented, elongated smooth muscle cells and an encompassing array of branching, similarly oriented elastic fibers. On longitudinal sections of straight segments of the aorta, fascicles appeared as closely packed, transversely transected smooth muscle cell groups within compartments formed by similarly transected elastic fibers. On transverse sections, fascicles appeared as groups of cells within cell strips or layers, each of which was bracketed on both its luminal and abluminal sides by straight elastic fibers. Fascicles were increasingly evident during growth as commonly oriented groups of cells within the already present concentric cell layers became demarcated by enlarging elastic fibers. Wavy collagen fiber bundles, distinct from the interlaced fibrils of the immediate pericellular matrix, were interposed mainly between the facing elastin systems within the fibrous regions between cell layers. Thus, the radial transmural disposition of cells and matrix fibers on transverse sections of the media in well developed aortas proved to be: elastin-cells-elastin--collagen bundles--elastin-cells-elastin--collagen bundles, etc. Medias of major branch arteries were also composed of musculo-elastic fascicles, but their encompassing elastic fiber systems were less prominent than in the aorta. In straight segments of aortas and arteries, fascicles were uniform in size at any given transmural level and oriented mainly circumferentially. At bends and branch points fascicles were smaller and less uniform in size and orientation. In relation to changes in vessel wall curvature, alignment of the fascicles was usually in the direction of presumed resultant tensile stress. The findings suggest that these subunits of medial organization correspond to the distribution and magnitude of tensile stresses.

Selective removal of low density lipoprotein by plasmapheresis in familial hypercholesterolemia.

Abstract: Plasma lipoproteins were selectively removed from familial hypercholesterolemic patients by using two types of plasmapheresis: double-membrane filtration and selective adsorption of very low density lipoproteins (VLDL) and low density lipoproteins (LDL). In both techniques, plasma was separated from blood cells by using hollow-fiber filters, and 100% of the VLDL and LDL was recovered in the filtrate. In double-membrane filtration, the second hollow-fiber filter trapped 84% of LDL + VLDL, 48% of high density lipoprotein (HDL), 24% of albumin, and 46% of the remaining plasma protein. By treating 3 liters of plasma from a patient weighing 60 kg, 60% of the LDL and 30% to 40% of the HDL were removed as a result of an exponential decay of each component with the respective trapping coefficients. When dextran sulfate-cellulose was used as a LDL sorbent, there was only loss of LDL and VLDL, and no loss of any other major plasma component or of HDL. The sorbent column (400 ml) was saturated with 7.5 g of LDL cholesterol by treatment with 3.5 liters of plasma; the maximum reduction of LDL cholesterol was thus about 300 mg/dl for the patient weighing 60 kg. No serious side effects were observed during the long-term trials (19 to 27 months for four patients on double-membrane filtration and 10 months for the two patients on dextran sulfate-cellulose treatment.

Relationship of plasma lipoprotein Lp(a) levels to race and to apolipoprotein B

Abstract: Lipoprotein Lp(a) is an atherogenic subfraction of plasma lipoproteins which has been studied predominantly in white populations. We quantified Lp(a) by electroimmunoassay in plasma from 105 black and 134 white healthy men and women. Results were correlated with clinical variables and plasma levels of lipids, other lipoproteins, and apolipoprotein (apo) B determined by radioimmunoassay. Black subjects had levels of Lp(a) that averaged twice those of whites (p less than 0.001). Among blacks, Lp(a) levels showed a bell-shaped frequency distribution, while among whites the distribution was strongly skewed, with the highest frequencies at low levels. Contrary to previously published results, the apo B levels in our study correlated significantly, though weakly, with Lp(a) (r = 0.21, p = 0.001 among whites, and r = 0.15, p = 0.02 among blacks, Kendall rank correlation). The regression slopes and variances suggested that apo B in the Lp(a) lipoprotein could account for the correlation. Lp(a) levels did not correlate significantly with any other plasma lipoprotein or lipid levels. The implications of this study are as follows: Despite the high levels of Lp(a) among blacks in the Houston area, these blacks do not experience greatly increased atherosclerotic progression and mortality. Thus, the atherogenicity of Lp(a) in blacks must be decreased or counterbalanced by other factors. The correlation between Lp(a) and apo B should be taken into account when analyzing atherogenic risk, but this correlation is not strong enough to dispute the independence of Lp(a) and apo B as risk factors.

Triglyceride-lowering effect of marine polyunsaturates in patients with hypertriglyceridemia.

Abstract: Twenty male patients with primary hypertriglyceridemia were treated for 4 weeks with daily supplements (15 g) of oil, which provided approximately 6 g of polyunsaturated fatty acid (PUFA) either of fish or of vegetable origin. Total plasma cholesterol concentrations were unaffected, but both types of supplement increased high density lipoprotein-3 (HDL3) cholesterol concentrations. The fish, but not the vegetable, oil supplement led to a decrease in plasma triglyceride concentrations. Very low density lipoprotein (VLDL), fatty acid composition, and VLDL triglyceride kinetics were subsequently studied in five patients (four male, one female) before and after 4 weeks of therapy with 15 g of the same fish oil. The fish oil led to increases in the proportion of eicosapentaenoic acid in both the VLDL triglyceride and phospholipid fractions, but the increase was greater in the latter. In contrast, the proportion of docosahexanoic acid was increased only in the VLDL triglycerides. The decrease in plasma triglyceride concentrations that occurred with fish-oil therapy was accompanied by a reduction in the absolute catabolic rate of VLDL triglyceride, implying a concomitant change in synthetic rate; the fractional catabolic rate of VLDL triglyceride was unaltered. It is suggested that polyunsaturated fatty acids of marine origin may be therapeutically useful for hypertriglyceridemia.

Structural and hemodynamic response of peripheral arteries of macaque monkeys to atherogenic diet.

Abstract: The arteries of monkeys given atherogenic diets develop marked intimal thickening and medial thinning, but luminal size apparently changes minimally. The hemodynamic significance of the atherosclerotic changes is therefore uncertain. To evaluate vascular function in atherosclerotic arteries, we studied the hind-limb vessels of adult male rhesus and cynomolgus monkeys to assess the structural and hemodynamic responses to an atherogenic diet given for about 1.5 years or for much longer periods (6.5 years for rhesus and 4.3 years for cynomolgus monkeys). The intimal cross-sectional area greatly increased after the atherogenic diet, but there was no significant luminal narrowing after either the 1.5-year diet or the longer diet periods. The media of atherosclerotic arteries showed focal atrophy and focal thinning after pressure fixation, but the total medial mass was not decreased even after the long diet periods. Hemodynamic studies indicated mild functional impairment in the atherosclerotic vessels; resting resistance increased and vasodilator responses decreased, but adrenergic responses were preserved. Thus, the marked changes that occur in the arterial wall in experimental primate atherosclerosis include adaptations to lesion formation that permit a long prestenotic phase of atherosclerosis in which vascular dysfunction is minimal.

Ovariectomy, social status, and atherosclerosis in cynomolgus monkeys.

Abstract: Evidence is contradictory regarding the effects of natural or surgical menopause on "female protection" against coronary artery atherosclerosis. We evaluated atherosclerosis, plasma lipids, blood pressure, and carbohydrate tolerance in 21 ovariectomized and 23 intact female cynomolgus macaques fed a moderately atherogenic diet for 30 months. We also evaluated the influence of social dominance status, with particular emphasis on a possible relationship with ovarian endocrine function. Atherosclerosis was two to 10 times as extensive in coronary, carotid, and iliaco-femoral arteries of the ovariectomized females; this could be explained, in part, by 15% to 20% increases in total plasma and LDL cholesterol concentrations. Socially dominant intact females were protected against advanced atherosclerotic lesions (plaques) of the coronary arteries, while subordinate females and ovariectomized females were not. Increased susceptibility to advanced coronary artery atherosclerosis in subordinate intact females may have been related in some way to chronic ovarian dysfunction observed in seven of 12 of these individuals. As a group, subordinate intact females also had enlarged adrenal glands, suggestive of mechanisms that may influence atherogenesis independently. The results indicate that, in this species, ovariectomy and chronic ovarian dysfunction related to subordinate social status are associated with a more atherogenic plasma lipid pattern and abolish "female protection" against coronary artery atherosclerosis.

Control of monocyte recruitment by chemotactic factor(s) in lesion-prone areas of swine aorta.

Abstract: Aortic areas predisposed to early atherosclerosis in swine demarcated by Evans blue uptake (blue areas) show preferential intimal penetration by blood monocytes before and during lesion formation. These cells are thought to be the major source of foam cells in these early lesions. To examine mechanisms controlling monocyte migration into these areas, extracts of aortic tissue from both blue and white areas of hypercholesterolemic (H) and normal (N) swine were tested for chemotactic activity against monocytes from N and H swine and neutrophils from H swine. The data indicate that extracts of blue areas from H swine contained at least one, and possibly two, factors chemotactic only for monocytes from H swine, but not N swine. These factors were not present in similar extracts from white areas of H swine, or either blue or white area extracts from N swine. Gel filtration chromatography of crude blue area extracts separated two chemotactically active fractions of molecular weights 68,000 and 5000 that were not present in white area extracts and that elicited a positive chemotactic effect only for H swine monocytes. These findings provide a mechanism explaining our previous findings of preferential monocyte adhesion and intimal penetration in lesion-prone areas, and indicate that control of monocyte recruitment into the artery involves not only alteration of the arterial wall, but also functional changes in the circulating monocyte.

Extracellular matrices and cell adhesion.

Abstract: E matrices are composed primarily of three types of macromolecules: collagens, proteoglycans, and glycoproteins. Collagens constitute a group of genetically distinct, but related, molecules with unique tissue distributions. Similarly, proteoglycans are a highly polymorphic group of molecules that also have specialized distributions in tissues and different types of extracellular matrices. Fibronectin has been identified as the major glycoprotein of connective tissue, while laminin is present in basement membranes. Together, these three types of molecules coalesce to form the insoluble supramolecular complexes that comprise the extracellular matrices which surround most cells in the body. Many of these extracellular matrix molecules share the ability to interact directly with cell membranes, making the matrix, as a whole, adhesive for cells. During the past several years, significant advances have been made in understanding cellular adhesion. The study of adhesive proteins has resulted in a wealth of information on the structure of extracellular matrices and has begun to reveal the molecular basis of cell adhesion. The purpose of this article is to review our current understanding of the role of extracellular matrices in cell adhesion placing special emphasis on those adhesive events relevant to vascular physiology and disease. Due to the large amount of work performed on the fibronectin molecule, including recently obtained data about its cell surface receptor, this molecule has emerged as a prototype adhesion protein. For this reason, much of the following discussion will focus on the fibronectin molecule.

Epidemiological correlates of high density lipoprotein subfractions, apolipoproteins A-I, A-II, and D, and lecithin cholesterol acyltransferase. Effects of smoking, alcohol, and adiposity.

Abstract: Recent data suggest that the protection against ischemic heart disease afforded by high density lipoprotein (HDL) cholesterol (C) may be concentrated in the HDL2 subfraction. To examine the behavioral correlates of the HDL subfractions, we recalled 33 men and 17 women of a random sample from the Pacific Northwest Bell Telephone Company Health Survey. Adiposity and very low density lipoprotein (VLDL) triglyceride were negatively correlated with HDL2C. Smoking was not correlated with HDL2C, but was negatively correlated with HDL3C (men, rs = -0.635, p = 0.001; women, rs = -0.534, p = 0.014); this relationship was independent of alcohol consumption, adiposity, and VLDL triglyceride. Alcohol consumption was also more strongly related to HDL3C (men, rs = 0.248, p = 0.082; women, rs = 0.586, p = 0.007). Lecithin cholesterol acyltransferase (LCAT) mass was negatively related with HDL2C, but was positively correlated with HDL3C and apolipoprotein A-II. Smoking was negatively correlated with LCAT mass. Since it is believed that HDL3C is not associated with the risk of ischemic heart disease and since both smoking and alcohol consumption may mainly affect HDL3C, the current study suggests that the increase in risk of ischemic heart disease with smoking and the possible decrease with alcohol consumption may be mediated through mechanisms other than their effects on HDLC.

Antiatherosclerotic effects of nicardipine and nifedipine in cholesterol-fed rabbits.

Abstract: Dutch-belted rabbits fed a 2% cholesterol diet for 8 weeks developed atherosclerotic lesions that covered 37.2% +/- 3.5% of the aortic luminal surface. In samples of aortic arch, accumulation of cholesterol and triglyceride was also observed. Oral administration of nicardipine or nifedipine at dosages of 40 mg/kg twice daily for 8 weeks reduced plaque area by 49.2% and 58.7%, respectively. Nicardipine and nifedipine reduced cholesterol accumulation in the aortic arch by 74.5% and 69%, respectively. Triglyceride accumulation was totally abolished. Neither drug significantly altered cholesterol concentration of plasma low density lipoprotein or high density lipoprotein, although nicardipine produced a 42% reduction in cholesterol concentration of the d less than 1.006 g/ml fraction. The above results suggest potential therapeutic utility of nicardipine in atherosclerosis.

Platelet interactions with Dacron vascular grafts. A model of acute thrombosis in baboons.

Abstract: We have developed a model of acute Dacron graft thrombosis in baboons in order to assess platelet alterations secondary to arterial thrombus formation. In this model, thrombus formation was initiated by Dacron vascular grafts inserted as extension segments into chronic arteriovenous Silastic shunts. Following platelet labeling with 111In-oxine, platelet deposition was measured for 1 hour following blood contact under arterial flow conditions using a scintillation camera. Graft platelet activity rapidly increased 40- to 50-fold, plateauing by 1 hour. All grafts produced equivalent reductions in circulating platelet count and blood 111In-platelet radioactivity, demonstrating that the labeled cells were functionally equivalent to the total platelet population. After graft placement, the remaining platelets survived normally. Acute platelet deposition was equivalent on grafts placed 1, 24, 48, and 72 hours following injection of the labeled cells, indicating that a variable delay between platelet labeling and graft imaging was without detectable consequence. Platelet destruction by the graft produced a tenfold increase in plasma levels of platelet factor 4 (PF4) and beta-thromboglobulin (beta TG) but did not modify either the alpha-granule (PF4, beta TG) or dense granule (ADP, ATP) contents of circulating platelets.

Postheparin plasma triglyceride lipases. Relationships with very low density lipoprotein triglyceride and high density lipoprotein2 cholesterol.

Abstract: Hepatic triglyceride (HTGL) and lipoprotein lipase (LPL) probably have major roles in the removal of triglyceride from triglyceride-rich lipoprotein and in the formation of high density lipoprotein (HDL). However, no population-based study of their activity and relationship to lipoprotein lipid levels has been reported. To determine these relationships, we recalled 33 men and 17 women of a randomly selected sample of the Lipid Research Clinics Pacific Northwest Bell Telephone Company Health Survey. The subjects were 53 +/- 7 years old (mean +/- SD) with total triglyceride levels of 120 +/- 57 mg/dl and total cholesterol levels of 224 +/- 35 mg/dl. Postheparin plasma LPL activity (127 +/- 61 nmol/min/ml) was not significantly correlated with either age, sex, or adiposity. In contrast, HTGL activity was significantly higher in men (235 +/- 84 nmol/min/ml) than women (170 +/- 91 nmol/min/ml, p less than 0.02), and was correlated with age in men and with adiposity in women. In both men and women, HTGL activity was related positively with VLDL triglyceride and inversely with HDL2 cholesterol. When the association between HTGL activity and VLDL triglyceride was examined with values from men and women pooled, the relationship was not weakened after adjustment for the linear effect of sex, adiposity, LPL, or HDL2 cholesterol.

Plasma lipoprotein levels in treated and untreated hypertensive men and women. The National Heart Foundation of Australia Risk Factor Prevalence Study.

Abstract: Experimental studies have reported that common antihypertensive drugs such as diuretics, beta-blockers, and methyldopa have adverse effects on plasma lipids and lipoproteins. To investigate whether such effects can be observed in the general population, plasma lipid and lipoprotein levels were compared in subjects receiving antihypertensive treatment, subjects with untreated high blood pressure, and subjects with normal blood pressure in a random sample of 5603 subjects screened in a national study of risk factor prevalence in Australia. In both sexes, high density lipoprotein (HDL) cholesterol was lower in the group receiving treatment than in the others (p less than 0.001). In men, triglycerides (TG) (p less than 0.001) and the ratio of total cholesterol to HDL cholesterol (TC/HDL cholesterol) (p less than 0.05) were higher in the group receiving treatment. In both sexes, the differences in plasma lipids and lipoproteins between treated and untreated hypertensive groups were independent of age, body mass index, alcohol consumption, and smoking. More than 40% of the treated or untreated hypertensive men and women had elevated total cholesterol (TC greater than 252 mg/dl) or an elevated TC/HDL cholesterol ratio (greater than 6.0). In men receiving antihypertensive treatment, the prevalence of an elevated TC/HDL cholesterol ratio was significantly greater than in men with untreated high blood pressure (p less than 0.01). The results of this study suggest that the effects of antihypertensive treatment on plasma lipids and lipoproteins can be observed in population lipid and lipoprotein levels. Even before treatment, a large proportion of high blood pressure patients have a significant plasma cholesterol abnormality, which may be aggravated by conventional antihypertensive therapy.

Kinetic mechanisms determining variability in low density lipoprotein levels and rise with age

Abstract: Levels of plasma low density lipoproteins (LDL) vary among individuals at any given age and frequently rise with increasing age. Both production rates and fractional clearance rates (FCRs) of LDL theoretically could affect the plasma levels of LDL. To evaluate the relative importance of these two factors, turnover rates of LDL apoprotein (apoLDL) were determined in two groups: 19 young adult men aged 23 to 29 years and 15 middle-aged men aged 40 to 60 years. Results were compared to a group of six healthy young adults (aged 22 to 28 years) who we previously studied and who were on a cholesterol-lowering diet. In both groups in the current study, a diet resembling the average American diet was consumed, and LDL levels ranged from low-to-high normal. On average, the 19 young adult men had lower levels of total cholesterol and LDL cholesterol than did the middle-aged men. The younger men also had significantly higher FCRs and lower production rates of apoLDL. When data from all subjects were pooled, apoLDL levels were negatively and significantly correlated with FCRs and positively and significantly correlated with production rates. Similar relations were found with LDL cholesterol levels. These results show that both FCRs and production rates of apoLDL are important regulators of plasma LDL levels; the correlation suggests that the FCR is more influential at lower LDL concentrations, and that production rates are more influential at higher LDL concentrations.

Verapamil enhances receptor-mediated endocytosis of low density lipoproteins by aortic cells in culture.

Abstract: Bovine aortic endothelial and smooth muscle cells (SMC) and human skin fibroblasts (HSF) were used to study the effect of verapamil on cellular interactions with human low density lipoprotein (LDL). Verapamil, 10 to 50 microM, increased 125I-LDL uptake and degradation by 70% to 200% in the various cells after 24 to 48 hours of incubation. The increase in the total amount of LDL endocytosed, labeled with 3H-cholesteryl linoleate (3H-CL), was comparable to that determined with 125I-LDL. In HSF and SMC, a delay in 125I-LDL degradation and hydrolysis of 3H-CL was seen in cells treated for 3 to 24 hours with verapamil. Pretreatment of HSF with 50 microM verapamil for 24 hours and incubation with 2 to 50 micrograms 125I-LDL protein/ml for 1 hour resulted in a 50% to 200% increase in heparin releasable and in a 40% to 130% increase in cellular 125I-LDL. Thus, the increase in 125I-LDL binding and uptake in verapamil-treated cells was apparently due to an increase in receptor number, rather than in receptor affinity. The effect of verapamil on LDL uptake and degradation was also seen in cells that were pretreated for 24 hours and incubated with 125I-LDL in the absence of verapamil. The effect of verapamil was not apparent in LDL receptor-negative cells. Cycloheximide blocked the verapamil effect. The Na+ channel blocker, tetrodotoxin x 10(-6) M, caused a 30% to 50% increase in the total amount of LDL endocytosed, but no delay in LDL degradation; amiloride 2 x 10(-3) M was not effective. If the presently described effect of verapamil also occurs in vivo, this might contribute to the reported beneficial effects of Ca++ channel blockers in experimental atherosclerosis by promoting transfer of LDL cholesteryl ester from the aortic interstitium to a catabolic compartment.

Characterization of a human hepatic receptor for high density lipoproteins.

Abstract: Characterization of the membrane receptor for the low density lipoproteins (LDL) has led to insights into cellular receptor physiology as well as mammalian lipid transport. Result with LDL have stimulated the search for specific receptors for other plasma lipoproteins. Receptors for high density lipoproteins (HDL) have been identified in human fibroblasts and smooth muscle cells. Specificity for this receptor has been difficult to define since normal HDL contains several apolipoproteins, and particles containing apolipoproteins B and E have been shown to compete for HDL binding. In the present study, we demonstrate that HDL isolated from a patient devoid of apolipoprotein E was bound specifically by human hepatic membranes. This binding reached saturation within 2 hours and was EDTA-resistant. Assuming a single receptor model, we found that 2.9 x 10(15) receptors/mg membrane protein bound with an affinity KD = 3.5 x 10(-7) M at 0 to 4 degrees C and KD = 1.9 x 10(-7) M at 37 degrees C. The binding was effectively competed with intact HDL3, with HDL3 that had undergone selective arginine and lysine residue modification, and with antibodies to apolipoproteins A-I and A-II. However, LDL, asialofetuin, and HDL3 which had undergone tyrosine modification by nitration, and anti-apolipoprotein B did not compete with apo A-I HDL binding. In contrast to LDL binding, the human hepatoma cell line, HEPG2, increased HDL binding with cholesterol loading that was specific for HDL3. Thus, hepatic tissue can modulate its recognition of HDL. Finally, hepatic membranes from a patient lacking normal hepatic LDL receptors bound apo A-I HDL normally. These data indicate that a saturable, specific regulatable receptor for apo E-free HDL is present in human liver.

Role of the low density lipoprotein receptor in penetration of low density lipoprotein into rabbit aortic wall.

Abstract: The present study was designed to determine whether binding of low density lipoprotein (LDL) to endothelial LDL receptors contributes significantly to the penetration of LDL into the normal rabbit aorta. Initial flux rate was used as a measure of uptake of LDL. Reductive methylation of LDL is known to block its recognition by the LDL receptor. Therefore, the difference in flux rates of native LDL and reductively methylated LDL (methyl-LDL) was assumed to represent the receptor-dependent uptake. Native LDL and methyl-LDL were labeled with different isotopes (125I or 131I) and both were injected simultaneously into the same rabbit. After 30 to 60 minutes, trichloroacetic acid-precipitable counts were determined in aortic specimens. The initial flux rates, expressed as plasma clearance (nl/g/hr), were 1787 for native LDL and 1924 for methyl-LDL. The difference was not significant, which suggests that the flux of LDL into the aorta is not significantly dependent upon, or regulated by, endothelial LDL receptors, but is mediated by other mechanisms.

Fenofibrate reduces low density lipoprotein catabolism in hypertriglyceridemic subjects.

Abstract: This study examines the kinetic basis for the increment in plasma low density lipoprotein (LDL) levels that accompanies the fenofibrate treatment of severely hypertriglyceridemic (HTG) patients. Seven HTG men with a mean plasma triglyceride level of 1470 mg/dl were treated for 6 weeks. During treatment, their plasma triglyceride level fell by 77% and their cholesterol level by 41%. The fall in very low density lipoprotein (VLDL) cholesterol level was reciprocated by increments in the cholesterol level in both LDL and high density lipoproteins (HDL); the rise in HDL was confined to HDL3. LDL catabolism was examined before and during therapy using native and chemically modified tracers in an attempt to distinguish receptor-mediated from non-receptor-mediated clearance. In their basal state, the hypertriglyceridemic subjects overcatabolized both the native and the modified lipoprotein, implying that the non-receptor pathways were hyperactive. The mean fractional clearance rate of LDL via the receptor pathway was not significantly different from normal. Fenofibrate therapy corrected the patients' hypercatabolism, reducing the receptor-independent fractional clearance of apo LDL by 50% (from 0.48 to 0.24 pools/day; p less than 0.05). The mean fractional catabolic activity of the receptor route did not change, but when the increment in the plasma apo LDL concentration was taken into account, it was clear that the drug treatment was associated with an increase in the net amount cleared by the receptor pathway and with a reduction of lipoprotein uptake into receptor-independent routes.

Topographic study of sudanophilic lesions in cholesterol-fed minipigs by image analysis.

Abstract: A new morphometric technique using image analysis has been developed to express the topographic distribution of atherosclerotic lesions in unambiguous statistical terms. Computer-stored images of opened Sudan IV-stained aortas and iliac and coronary arteries from hypercholesterolemic minipigs (n = 39) were used in this study. The image processing methods included transformation of the data to standard templates, automated image segmentation, and creation of probability-of-occurrence maps. These maps have shown that sudanophilic lesions are localized with a characteristic topography along the aortas and iliac and coronary arteries. Areas of high probability are associated with the entrance regions of vessels and the lateral leading edges of the major flow dividers. Regions immediately distal to large branches were found to be areas of low probability. Despite the association of areas of sudanophilia with entrance regions and branch points, a major portion of sudanophilic lesions was not associated with any orifice region (e.g., ductus scar, dorsolateral surface of abdominal aorta, and ventral surface of terminal aorta). The present study provides the necessary information for the development of a rational sampling strategy for the experimental study of the distribution of localizing factors (e.g., hemodynamic, biochemical, cellular, mass transport, histological) and their relationships to putative atherogenic mechanisms.

Estrogen-mediated cytoplasmic and nuclear distribution of rat cardiovascular estrogen receptors.

Abstract: We used either the synthetic estrogen R2858 (moxestrol) or estradiol-17 beta to characterize estrogen receptors in cytoplasmic (R2858) and nuclear (estradiol-17 beta) preparations from rat aorta and myocardium. Relative steroid specificity studies showed that only estrogens were effective inhibitors of R2858 or estradiol-17 beta binding to aortic and myocardial estrogen receptors, whereas androgens, progestins, and cortisol were ineffective inhibitors. Low ionic strength sucrose density gradient analyses showed that myocardial estrogen receptors that localized in the cytoplasmic fraction migrated as macromolecules with sedimentation coefficients of 8S to 9S. In contrast, two binding components of sedimentation coefficients 8S to 9S and 10S to 11S were characteristic of the estrogen receptors localized in aortic cytoplasmic preparations. High ionic strength sucrose density gradient analysis showed that aortic and myocardial estrogen receptors localized in the nuclear fraction migrated as macromolecules with sedimentation coefficients of 4S to 6S. Saturation analyses showed that aortic and myocardial cytoplasmic preparations from intact young mature male rats contained 50.6 +/- 12.9 (mean +/- SD) and 51.0 +/- 14.1 fmol receptor/mg DNA, respectively. The respective R2858 dissociation constants were 0.42 and 0.15 nM. Estrogen receptors could not be demonstrated in nuclear preparations from cardiovasculature of intact males. Estradiol-17 beta injection of intact young mature male rats caused "depletion" of aortic and myocardial cytoplasmic fraction estrogen receptors and resulted in the appearance of 51.9 +/- 21.0 and 36.9 +/- 9.5 fmol receptor/mg DNA in the corresponding nuclear fractions. The respective estradiol-17 beta dissociation constants were 1.56 and 0.71 nM. Increased estrogen receptor content of cardiovascular nuclear fractions of estradiol-17 beta injected male rats correlated well with the concomitant decreased cytoplasmic fraction receptor content. The ability of estradiol-17 beta to affect localization of cardiovascular estrogen receptors between cytoplasmic and nuclear fractions suggests these estrogen receptors are physiologically functional and indicates that estrogen may directly regulate cardiovascular cell function.

Effects of apoprotein E polymorphism on serum lipoprotein concentration.

Abstract: Serum concentrations for the cholesterol and triglyceride content of very low density lipoprotein (VLDL) and the cholesterol content of intermediate density lipoprotein (IDL), low density lipoprotein (LDL), and the high density lipoprotein fractions (HDL2), HDL3) were measured in 337 men and women with the apo E phenotype who were born in the Grampian Region of North East Scotland. The subjects' ages ranged from 45 to 60 years (mean, 53 years). Cigarette smoking and alcohol consumption were recorded and were shown to have minor, but suggestive, effects on serum lipoprotein concentrations. The LDL concentration of E-3/2 subjects was compared with the commonest category, E-3/3, and was found to be about 20% lower in men and about 12% lower in women, in whom the VLDL and IDL concentrations were substantially elevated. In E-4/3 women, the serum LDL concentration was about 10% higher than in E-3/3 women, and the other differences were minor. The effect of allelic substitutions differed between the sexes. The relations between C-peptide ratios and serum lipoprotein concentration differed by gender and phenotype. A comparison with earlier estimates of LDL heritability suggests that in this population, a substantial fraction of the genetic variance of LDL is due to segregation at the apo E locus. The implications of this significant finding are discussed.

Metabolism of atherogenic lipoproteins by smooth muscle cells of different phenotype in culture.

Abstract: Smooth muscle cells of the rabbit aorta, when grown in vitro, express three distinguishable forms of phenotype (contractile, reversible synthetic, and irreversible synthetic). We compared the interactions of these three smooth muscle phenotypes with rabbit very low density lipoprotein (VLDL), low density lipoprotein (LDL), and very low density lipoprotein from cholesterol-fed rabbits (beta-VLDL). beta-VLDL showed saturable. high-affinity binding characteristics with each phenotype predominantly through the B/E receptor. The irreversible synthetic cells displayed the greatest binding capacity and the contractile cells, the least. Binding and degradation of normal VLDL was less than that of beta-VLDL and higher than that of LDL. Only the irreversible synthetic cells showed substantial (about threefold) cholesteryl ester formation and cholesterol accumulation, and then only when incubated with beta-VLDL. Substantial stainable lipid, shown chemically to include triglyceride, cholesterol and cholesteryl ester, was also observed only when irreversible synthetic cells were exposed to beta-VLDL. The high capacity of irreversible synthetic-state, smooth muscle cells to bind and accumulate beta-VLDL in contrast to the relative immunity of contractile cells may be relevant to the genesis of atherosclerosis in the rabbit and possibly also in humans.

Quantitative ultrastructural analysis of perifibrous lipid and its association with elastin in nonatherosclerotic human aorta.

Abstract: Nonatherosclerotic areas in human arteries display an age-related accumulation of cholesteryl ester in the form of small, perifibrous lipid droplets in the deeper intimal layers. We treated human aortic specimens with an osmium-thiocarbohydrazide-osmium sequence en bloc after glutaraldehyde fixation in order to provide electron dense staining of neutral lipid for ultrastructural study. Neutral lipid was quantified in terms of area fractions on thin sections. Extracellular lipid, primarily in the form of small (less than 300 nm) droplets, accounted for 91% of the lipid found in the deep intimal region. Seventy-four percent of extracellular lipid appeared in droplets or aggregates that were demonstrated as adjacent to or within elastic fibers in the plane of section. The fraction of lipid adjacent to elastin in three dimensions is likely to be considerably higher than 74%. The results support the concept that an interaction between elastin or its associated components and lipids or lipoproteins may be important in extracellular lipid deposition in human arteries.

Effect of chronic smoking on fibrinolysis.

Abstract: The aim of the study was to investigate the long-term chronic effects of smoking on the fibrinolytic enzyme system by comparing two groups of healthy male volunteers (aged 30 to 40 years). One group consisted of 15 habitual smokers who consumed 20 or more cigarettes a day; the other consisted of 15 nonsmokers. Fibrinolysis was studied at rest (baseline) and after infusion of 1-desamino-8-D-arginine vasopressin (DDAVP; 0.4 micrograms/kg body weight). Smokers had significantly lower baseline blood fibrinolytic activity as determined by the overall assays: dilute blood clot lysis (p less than or equal to 0.05) and euglobulin-fibrin plate assay (p less than or equal to 0.05). Further analysis showed that these low activities could be attributed to a lower baseline level of extrinsic tissue-type plasminogen activator (t-PA) activity (p less than or equal to 0.05) in the smokers. There were no significant differences between the groups in various fibrinolytic inhibitors or in the intrinsic fibrinolytic activation pathways. The increased levels of t-PA activity and factor VIII R:Ag in response to DDAVP were also reduced in the smokers (p less than or equal to 0.01). The relative increase (ratio of post-DDAVP activity/baseline activity) for these parameters was not significantly different for the two groups. Smokers also had significantly higher levels of the acute phase reactants, alpha 1-antitrypsin (p less than or equal to 0.02) and plasminogen (p less than or equal to 0.02) and C-reactive protein (p less than or equal to 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

George Lyman Duff memorial lecture. Role of the liver in atherosclerosis.

Abstract: G Lyman Duff was a pioneer in relating the quality as well as the quantity of plasma lipoproteins to experimental atherosclerosis. His investigations and those of John Gofman foreshadowed much contemporary research on the interactions of lipoproteins with cells and other components of the arterial wall. This current research has, I believe, put to rest past criticisms of the meetings of our Council, at which it seemed to some that the artery is hardly involved in the pathogenesis of atherosclerosis. Perhaps I can then be forgiven for taking as the subject of this lecture the role of the liver in lipoprotein metabolism and atherosclerosis, and for daring to suggest that if the liver would only do correctly its job of secreting the \"right\" kinds of lipoproteins and of taking up, catabolizing, and excreting lipoprotein components, it would be unnecessary for us to be so concerned about the mechanisms by which lipoprotein-cholesterol accumulates in the arterial intima.

Serum lipids in the People's Republic of China. Comparison of Western and Eastern populations.

Abstract: Serum cholesterol and HDL cholesterol levels were measured in an urban and a rural population of the People's Republic of China and compared with cholesterol values obtained in Belgium and in the Republic of Korea, with use of the same methodology. Total cholesterol levels were markedly lower in the People's Republic of China than in Belgium and generally lower than in Korea, both in male and female subjects. However, the differences in HDL cholesterol levels among the three populations were small in males and only significantly higher in Belgium in the age classes below 34 years. In women of all age groups, HDL cholesterol values were significantly higher in Belgium than in China and Korea. Total cholesterol levels below 100 mg/dl were found in the People's Republic of China in about 2% of the participants. Apolipoprotein B was significantly lower, and the apolipoprotein A1/B ratio was significantly higher, in China and Korea compared to Belgium.

Association of low HDL and HDL2 cholesterol with coronary heart disease in noninsulin-dependent diabetics.

Abstract: Lipids and lipoproteins were measured in 139 men and 145 women who were noninsulin-dependent diabetics (NIDDs) aged 45 to 64 years. Of these, 27 men and 16 women had had a previous definite myocardial infarction (MI). The NIDDs with MI (MI+) showed lower values of HDL and HDL2 cholesterol concentrations than NIDDs without previous MI (MI-) or NIDDS without any symptoms or electrocardiographic signs of coronary heart disease (CHD-). The inverse relationship between HDL, HDL2, and CHD was evident in both sexes, but it was particularly strong among male NIDDs. The difference in HDL and HDL2 cholesterol concentrations between the MI+ and MI- groups or between the MI+ and CHD- groups persisted after adjustment by analysis of covariance for the effect of physical activity, alcohol intake, obesity, duration of diabetes, and glycemic control. It is concluded that in a cross-sectional study, even among NIDDs with generally low HDL and HDL2 cholesterol concentrations, the presence of CHD is associated with a further depression of HDL and HDL2 cholesterol levels. Prospective studies are needed, however, to confirm that the association is predictive and not a consequence of CHD.

Spontaneous and diet-induced coronary atherosclerosis in normal swine and swine with von Willebrand disease.

Abstract: We have observed that pigs with impaired platelet function in the form of severe von Willebrand's disease (vWd) are resistant to spontaneous and to diet-induced aortic atherosclerosis. However, it has been reported that vWd pigs are susceptible to coronary atherosclerosis produced by balloon-induced injury of coronary arteries combined with an atherogenic diet. We have evaluated the development of coronary atherosclerosis in normal control (NC) and homozygous vWd pigs in two prospective studies: 1) as a spontaneous process in five NC and vWd pigs receiving a regular diet from the age of 3 months to 4 years; and 2) in nine NC and five vWd receiving a high-fat and high-cholesterol (2%) diet from the age of 3 to 9 months. All of the coronary arteries were analyzed postmortem in 5-mm sections. None of the NC nor the vWd pigs in the spontaneous study showed coronary atherosclerosis or myocardial lesions. In the study of diet-induced atherosclerosis, only one NC and one vWd pig had discrete stenoses; the stenoses affected the three coronary arteries and were significant (50% to 80%) in the NC and mild (greater than 25%) in the vWd pigs; no pigs showed myocardial lesions. Pigs with vWd are resistant to atherosclerosis of the aorta. To assess the resistance or susceptibility to coronary disease in these pigs, a longer follow-up study would be necessary.