bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of Copper-Binding Sites on Low Density Lipoprotein
Authors: Roland Alexander , Patterson Rebecca A. , Leake David S.
Published: June 2011

Abstract
—Copper is often used to oxidize low density lipoprotein (LDL) in experiments in vitro and is a candidate for oxidizing LDL in atherosclerotic lesions. The binding of copper ions to LDL is usually thought to be a prerequisite for LDL oxidation by copper, although estimates of LDL copper binding vary widely. We have developed and validated an equilibrium dialysis assay in a MOPS-buffered system to measure copper binding to LDL and have found 38.6±0.7 (mean±SEM, n=25) copper binding sites on LDL. The binding was saturated at a copper concentration of 10 μmol/L at LDL concentrations of up to 1 mg protein/mL. Copper-binding capacity increased progressively and markedly when LDL was oxidized to increasing extents. Chemical modification of histidyl and lysyl residues on apolipoprotein B-100 reduced the number of binding sites by 56% and 23%, respectively. As an example of the potential of this method to assess the effects of antioxidants on copper binding to LDL, we have shown that the flavonoids myricetin, quercetin, and catechin (but not epicatechin, kaempferol, or morin), at concentrations equimolar to the copper present (10 μmol/L), significantly decreased copper binding to LDL by 82%, 56%, and 20%, respectively.
Procoagulant Activity on Platelets Adhered to Collagen or Plasma Clot
Authors: Ilveskero Sorella , Siljander Pia , Lassila Riitta
Published: June 2011

Abstract
—In a new 2-stage assay of platelet procoagulant activity (PCA), we first subjected gel-filtered platelets to adhesion on collagen (as a model of primary hemostasis) or plasma clots (as a model of preformed thrombus) for 30 minutes, and then the adherent platelets were supplemented with pooled, reptilase-treated, diluted plasma. Defibrinated plasma provided coagulation factors for assembly on platelet membranes without uncontrolled binding of thrombin to fibrin(ogen). Platelet adhesion to both surfaces showed modest individual variation, which increased at platelet densities that allowed aggregation. However, adhesion-induced PCA varied individually and surface-independently >3-fold, suggesting a uniform platelet procoagulant mechanism. Permanently adhered platelets showed markedly enhanced PCA when compared with the platelet pool in suspension, even after strong activation. The rate of thrombin generation induced by clot-adherent platelets was markedly faster than on collagen-adherent platelets during the initial phase of coagulation, whereas collagen-induced PCA proceeded slowly, strongly promoted by tissue thromboplastin. Therefore at 10 minutes, after adjustment for adhered platelets, collagen supported soluble thrombin formation as much as 5 times that of the thrombin-retaining clots. Activation of platelets by their firm adhesion was accompanied by formation of microparticles, representing about one third of the total soluble PCA. Collagen-adhered platelets provide soluble thrombin and microparticles, whereas the preformed clot serves to localize and accelerate hemostasis at the injury site, with the contribution of retained thrombin and microparticles.
Upregulatory Expression of Furin and Transforming Growth Factor-β by Fluid Shear Stress in Vascular Endothelial Cells
Authors: Negishi Mitsuko , Lu Danhong , Zhang You-Qing , Sawada Yoshie , Sasaki Toshiki , Kayo Tsuyoshi , Ando Joji , Izumi Tetsuro , Kurabayashi Masahiko , Kojima Itaru , Masuda Hirotake , Takeuchi Toshiyuki
Published: June 2011

Abstract
—Furin, a yeast Kex2-family endoprotease, converts many vasoregulatory propeptides, including pro-transforming growth factor (TGF)-β to their mature forms. We examined whether furin expression is regulated by shear stress in vivo and in vitro. When an arteriovenous shunt was placed between the carotid artery and external jugular vein in rabbits, furin and TGF-β were highly expressed in shear stress–loaded endothelial cells. Exposure of bovine aortic endothelial cells in culture to shear stress induced furin and TGF-β expression in a similar manner. Molecular analysis of furin expression in bovine aortic endothelial cells revealed that shear stress increases the furin gene expression at transcriptional levels. Furthermore, TGF-β itself increased the furin mRNA levels. Shear-mediated furin expression was partly mediated by TGF-β because shear-induced furin mRNA levels were considerably decreased by overexpression of the truncated form of the TGF-β type II receptor. Likewise, blockade of furin activity by a furin inhibitor significantly decreased the endothelial production of mature TGF-β. Taken together, the results indicate that furin expression is induced and maintained by a coordination of shear stress and TGF-β. Increased furin expression may facilitate the formation of mature TGF-β, resulting in the enhanced effects of TGF-β on endothelial cells and vascular smooth muscle cells in the vasculature.
Circulating Oxidized LDL Is a Useful Marker for Identifying Patients With Coronary Artery Disease
Authors: Holvoet Paul , Mertens Ann , Verhamme Peter , Bogaerts Kris , Beyens Guy , Verhaeghe Raymond , Collen Désiré , Muls Erik , Van de Werf Frans
Published: June 2011

Abstract
—Our aim was to determine the usefulness of circulating oxidized low density lipoprotein (LDL) in the identification of patients with coronary artery disease (CAD). A total of 304 subjects were studied: 178 patients with angiographically proven CAD and 126 age-matched subjects without clinical evidence of cardiovascular disease. The Global Risk Assessment Score (GRAS) was calculated on the basis of age, total and high density lipoprotein cholesterol, blood pressure, diabetes mellitus, and smoking. Levels of circulating oxidized LDL were measured in a monoclonal antibody 4E6–based competition ELISA. Compared with control subjects, CAD patients had higher levels of circulating oxidized LDL (
P
<0.001) and a higher GRAS (
P
<0.001). The sensitivity for CAD was 76% for circulating oxidized LDL (55% for men and 81% for women) compared with 20% (24% for men and 12% for women) for GRAS, with a specificity of 90%. Logistic regression analysis revealed that the predictive value of oxidized LDL was additive to that of GRAS (
P
<0.001). Ninety-four percent of the subjects with high (exceeding the 90th percentile of distribution in control subjects) circulating oxidized LDL and high GRAS had CAD (94% of the men and 100% of the women). Thus, circulating oxidized LDL is a sensitive marker of CAD. Addition of oxidized LDL to the established risk factors may improve cardiovascular risk prediction.
Prevalence and Correlates of Coronary Calcification in Black and White Young Adults
Authors: Bild Diane E. , Folsom Aaron R. , Lowe Lynn P. , Sidney Stephen , Kiefe Catarina , Westfall Andrew O. , Zheng Zhi-Jie , Rumberger John
Published: June 2011

Abstract
—Whereas cardiovascular risk factor levels are substantially different in black and white Americans, the relative rates of cardiovascular disease in the 2 groups are not always consistent with these differences. To compare the prevalence of coronary calcification, an indicator of coronary atherosclerosis, in young adult blacks and whites, we performed electron-beam computed tomography of the heart in 443 men and women aged 28 to 40 years recruited from a population-based cohort. The presence of calcium, defined as at least 1 focus of at least 2.05 mm
2
in area and >130 Hounsfield units in density within the coronary arteries, was identified in 16.1% of black men, 11.8% of black women, 17.1% of white men, and 4.6% of white women (
P
=0.04 for comparison across groups). Coronary calcium was associated with age and male sex, and after adjustment for age, race, and sex, coronary calcium was positively associated with body mass index, weight, systolic blood pressure, total cholesterol, low density lipoprotein cholesterol, triglycerides, and fasting insulin and negatively associated with education (all
P
<0.05). Independent risk factors included male sex, body mass index, and low density lipoprotein cholesterol. Race was not significantly associated with coronary calcium in men or women, before or after adjustment for risk factors. Coronary calcification is associated with increased levels of cardiovascular risk factors in young adults, and its prevalence is not significantly different in blacks and whites.
Preeclampsia and Fetal Loss in Women With a History of Venous Thromboembolism
Authors: Pabinger Ingrid , Grafenhofer Helga , Kaider Alexandra , Ilic Adriana , Eichinger Sabine , Quehenberger Peter , Husslein Peter , Mannhalter Christine , Lechner Klaus
Published: June 2011

Abstract
—A higher prevalence of risk factors for venous thromboembolism (VTE) has been found in women with preeclampsia and fetal loss. We investigated whether women with a history of VTE have a higher prevalence of pregnancy-associated complications compared with control subjects. In 395 patients with a history of VTE and in 313 control women, the prevalence of complications during pregnancy and the mean birth weight of viable infants were evaluated. The prevalence of pregnancy-induced hypertension and preeclampsia was higher in patients (5.1% and 3.0%, respectively) compared with control subjects (1.3% each). The odds ratio was 4.13 for pregnancy-induced hypertension (95% CI 1.4 to 12.22,
P
=0.0058) and 2.43 for preeclampsia (95% CI 0.78 to 7.6,
P
=0.133). Stillbirth was slightly more frequent in patients (4.3%) than in control subjects (3.2%); the difference was not statistically significant. Miscarriage was equally frequent in patients (21.8%) and control subjects (21.3%). The birth weight of viable infants born to patients was, on average, 109 g lower than that of the infants born to the control subjects (
P
=0.014) after adjustment for the mother’s body mass index. Our study demonstrates that women with a predisposition to VTE have, overall, a good chance for a successful pregnancy outcome. However, the findings from our study support the assumption that a predisposition to venous thrombosis is associated with a higher risk for complications during pregnancy and lower infant birth weight.
Effect of Immune Deficiency on Lipoproteins and Atherosclerosis in Male Apolipoprotein E–Deficient Mice
Authors: Reardon Catherine A. , Blachowicz Lydia , White Traci , Cabana Veneracion , Wang Yougen , Lukens John , Bluestone Jeffrey , Getz Godfrey S.
Published: June 2011

Abstract
—To determine whether T cells and B cells influence lipid metabolism and atherosclerosis, we crossed apolipoprotein E–deficient (apoE°) mice with recombination activating gene 2–deficient (RAG2°) mice. Total plasma cholesterol levels were ≈20% higher in male apoE° mice compared with the apoE°RAG2° mice at 8 weeks of age, and plasma triglyceride levels were 2.5-fold higher in the apoE° mice even when plasma cholesterol levels were similar. Male mice with plasma cholesterol levels between 400 and 600 mg/dL at 8 weeks of age were euthanized at 27 and 40 weeks of age. The aortic root lesion area in the apoE°RAG2° mice, compared with that in the immune-competent apoE° mice, was 81% and 57% smaller at 27 and 40 weeks of age, respectively. In contrast, there was no difference in the size of the brachiocephalic trunk lesions. Similar results were obtained with mice euthanized at 40 weeks of age that had 8-week cholesterol levels between 300 and 399 mg/dL. In apoE°RAG2° mice, aortic root atherosclerosis was more profoundly suppressed at lower cholesterol levels. Thus, T and B cells and their products differentially influence the development of atherosclerosis at different sites. We also demonstrate a profound effect of the immune system on plasma lipid homeostasis.
Mechanism of Endothelial Dysfunction in Apolipoprotein E–Deficient Mice
Authors: d’Uscio Livius V. , Baker Timothy A. , Mantilla Carlos B. , Smith Leslie , Weiler Deborah , Sieck Gary C. , Katusic Zvonimir S.
Published: June 2011

Abstract
—Endothelium-dependent relaxations mediated by NO are impaired in a mouse model of human atherosclerosis. Our objective was to characterize the mechanisms underlying endothelial dysfunction in aortas of apolipoprotein E (apoE)-deficient mice, treated for 26 to 29 weeks with a lipid-rich Western-type diet. Aortic rings from apoE-deficient mice showed impaired endothelium-dependent relaxations to acetylcholine (10
−
9
to 10
−
5
mol/L) and Ca
2+
ionophore (10
−
9
to 10
−
6
mol/L) and endothelium-independent relaxations to diethylammonium (
Z
)-1-(
N
,
N
-diethylamino)diazen-1-ium-1,2-diolate (DEA-NONOate, 10
−
10
to 10
−
5
mol/L) compared with aortic rings from C57BL/6J mice (
P
<0.05). By use of confocal microscopy of an oxidative fluorescent probe (dihydroethidium), increased superoxide anion (O
2
−
) production was demonstrated throughout the aortic wall but mainly in smooth muscle cells of apoE-deficient mice. CuZn–superoxide dismutase (SOD) and Mn-SOD protein expressions were unaltered in the aorta exposed to hypercholesterolemia. A cell-permeable SOD mimetic, Mn(III) tetra(4-benzoic acid) porphyrin chloride (10
−
5
mol/L), reduced O
2
−
production and partially normalized relaxations to acetylcholine and DEA-NONOate in apoE-deficient mice (
P
<0.05). [
14
C]
l
-Citrulline assay showed a decrease of Ca
2+
-dependent NOS activity in aortas from apoE-deficient mice compared with C57BL/6J mice (
P
<0.05), whereas NO synthase protein expression was unchanged. In addition, cGMP levels were significantly reduced in the aortas of apoE-deficient mice (
P
<0.05). Our results demonstrate that in apoE-deficient mice on a Western-type fat diet, impairment of endothelial function is caused by increased production of O
2
−
and reduced endothelial NO synthase enzyme activity. Thus, chemical inactivation of NO with O
2
−
and reduced biosynthesis of NO are key mechanisms responsible for endothelial dysfunction in aortas of atherosclerotic apoE-deficient mice.
Interactive Effect of
PAI-1
4G/5G Genotype and Salt Intake on PAI-1 Antigen
Authors: Brown Nancy J. , Murphey Laine J. , Srikuma Nadarajah , Koschachuhanan Natapong , Williams Gordon H. , Vaughan Douglas E.
Published: June 2011

Abstract
—Activation of the renin-angiotensin-aldosterone system (RAAS) is associated with increased circulating PAI-1 antigen and increased risk of thrombotic cardiovascular events. A 4G/5G polymorphism located 675 bp upstream from the transcription start site of the
PAI-1
gene affects PAI-1 antigen concentrations. To test the hypothesis that
PAI-1
4G/5G genotype influences the effect of activation of the RAAS on PAI-1 expression, we measured morning PAI-1 antigen concentrations in 76 subjects with essential hypertension during low (10 mmol/d) and high (200 mmol/d) salt intake. Low salt intake was associated with activation of the RAAS as measured by plasma renin activity (2.3±0.2 versus 0.5±0.0 ng angiotensin I · mL
−1
· h
−1
,
P
<0.001) and aldosterone (529±40 versus 145±12 pmol/L). PAI-1 antigen concentrations were 17.9±2.7, 19.2±2.5, and 27.8±4.0 ng/mL during high salt intake and 19.2±2.7, 21.6±2.9, and 38.9±7.2 ng/mL during low salt intake in the 5G/5G (n=14), 4G/5G (n=40), and 4G/4G (n=22) groups, respectively. There was a significant effect of both salt intake (F=6.0,
P
=0.017) and
PAI-1
4G/5G genotype (F=7.6,
P
=0.001) on PAI-1 antigen. More importantly, there was a significant interactive effect (F=7.8,
P
=0.001) of salt intake and
PAI-1
4G/5G genotype on PAI-1 antigen.
PAI-1
4G/5G genotype influenced the relationship between serum triglycerides and PAI-1 antigen such that the relationship was significant only in 4G homozygotes during either high (
R
2
=0.31,
P
=0.014) or low (
R
2
=0.37,
P
=0.006) salt intake. This study identifies an important gene-by-environment interaction that may influence cardiovascular morbidity and the response to pharmacological therapies that interrupt the RAAS.
Foam cells in explants of atherosclerotic rabbit aortas have receptors for beta-very low density lipoproteins and modified low density lipoproteins.
Authors: Pitas R E , Innerarity T L , Mahley R W
Published: June 2011

Beta-migrating very low density lipoproteins (beta--VLDL) and chemically modified low density lipoproteins (LDL), labeled with the fluorescent probe 3,3'-dioctadecylindocarbocyanine (Dil), were used to determine whether foam cells from atherosclerotic lesions have lipoprotein receptors similar to those of macrophages. The advantage of the Dil probe is that it produces a brilliant fluorescence due to its retention by the cells. When cells grown from intimal-medial explants of atherosclerotic rabbit aortas were incubated with Dil-labeled beta-VLDL, both smooth muscle cells and foam cells became fluorescent. However, when large amounts of unlabeled LDL were added to compete with the beta-VLDL for binding to the LDL receptors, Dil-labeled beta-VLDL binding to smooth muscle cells was blocked, and only the foam cells became highly fluorescent, due to the presence of specific receptors for beta-VLDL on those cells. The foam cells in the explants also became fluorescent when incubated with Dil-labeled acetoacetylated (AcAc) LDL. The same fluorescently labeled foam cells avidly bound IgG-coated erythrocytes. It was possible to inhibit the binding of the Dil-labeled AcAc LDL to aortic foam cells by the addition of fucoidin, a known inhibitor of modified LDL binding to macrophages. Foam cells that became fluorescent were similar to cells grown from the explants that contained an abundance of Oil red O positive lipid droplets and demonstrated high acid lipase activity. These results suggest that macrophages were the precursors of the foam cells derived from explants of atherosclerotic rabbit aortas. One difference we noted between these foam cells and macrophages, however, was that foam cells from the explants retained their cholesteryl esters under the same culture conditions that resulted in the loss of lipid from macrophages loaded with lipoproteins in vitro. The existence of receptors for beta-VLDL on aortic foam cells supports the contention that dietary cholesterol-induced beta-VLDL may be atherogenic lipoproteins in vivo.
Enhanced macrophage degradation of biologically modified low density lipoprotein.
Authors: Henriksen T , Mahoney E M , Steinberg D
Published: June 2011

Low density lipoprotein (LDL) conditioned by incubation in the presence of rabbit aortic or human umbilical vein endothelial cells (endothelial cell-modified LDL) was degraded by macrophages three to five times more rapidly than LDL incubated in the absence of cells (control LDL). This enhanced degradation occurred mostly via a high affinity, saturable pathway related to the pathway for macrophage uptake of acetylated LDL. Conditioning LDL with cultured aortic smooth muscle cells had a qualitatively similar but smaller effect; conditioning with fibroblasts had no effect. Conditioning very low density lipoproteins or high density lipoproteins with endothelial cells did not affect subsequent metabolism of these lipoproteins by macrophages. Endothelial cell-modified LDL, while degraded more rapidly than control LDL by macrophages, was degraded more slowly by cultured smooth muscle cells and by human skin fibroblasts. Degradation of endothelial cell-modified LDL by macrophages was accompanied by stimulation of cholesterol esterification, inhibition of cholesterol synthesis, and a net increment in total cellular cholesterol content. Thus, a biologically generated modification of LDL is described that markedly alters cholesterol metabolism of macrophages and, consequently, may play a role in foam cell formation during atherogenesis.
Risk factors and atherosclerotic lesions. A review of autopsy studies.
Authors: Solberg L A , Strong J P
Published: June 2011

This review assesses the current status of knowledge concerning the relationship of risk factors to atherosclerotic lesions. Risk factors for atherosclerotic lesions per se need not necessarily be identical to those related to clinically overt coronary heart disease (CHD). This review is based on 1) autopsy studies where information risk factors was gathered in a retrospective fashion; and 2) autopsy studies where information on risk factors was gathered prospectively. In spite of differences in study designs and grading methods among the studies, the general findings were similar. Elevated serum cholesterol and blood pressure are positively and significantly related to atherosclerotic lesions. High density lipoprotein cholesterol is inversely related to coronary and probably also to cerebral atherosclerosis. Almost all studies indicate a significant association between cigarette smoking and degree of aortic atherosclerosis; a positive relationship between smoking and coronary atherosclerosis is found between obesity or physical activity and the degree of atherosclerosis. Data from the Community Pathology Study in New Orleans indicate that the average extent of coronary atherosclerosis in a population may be subject to changes within a relatively short period of time; these changes might be expected to parallel changes in risk factors in the population.
Effect of age on arterial distensibility in Asymptomatic humans.
Authors: Smulyan H , Csermely T J , Mookherjee S , Warner R A
Published: June 2011

This report describes a noninvasive method by which the volume distensibility of forearm arteries can be calculated from direct measurements of pulse wave velocity. Such measurements are made at a variety of transmural arterial pressures (TMP) accomplished by placing the forearm in a cylinder and changing the pressures within. This technique eliminates arterial blood pressure as a variable, which strongly influences arterial distensibility. We studied 48 asymptomatic men and women, ages 21 to 98 years. There was considerable scatter, but significant positive relationships were demonstrated between increasing arterial distensibility and age at ambient and lower TMPs. This finding can be explained by an age-related reduction in arterial luminal diameter and an increase in arterial wall thickness which reduces arterial wall tension and more than offsets the increased stiffness produced by changes in wall composition. In six subjects, pulse tracings were simultaneously recorded on paper and analog tape. The taped curves were digitized and subjected to Fourier analysis to determine the wave velocity of individual harmonics. The characteristic wave velocity was defined and found comparable to the hand method used in the same beats (regression coefficient = + 0.97). These data indicate that the automatic and manual methods measured the same variable.
Endothelial regeneration in hypertensive and genetically hypercholesterolemic rats.
Authors: Prescott M F , Müller K R
Published: June 2011

Endothelial regeneration after a narrow, superficial aortic injury was studied in rats with chronic Goldblatt hypertension, genetic hypercholesterolemia, or a combination of hypertension and genetic hypercholesterolemia. In all groups, endothelial continuity was restored within 24 to 36 hours by a combination of endothelial migration and proliferation. A line of increased endothelial density covering the previous wound was seen through 16 weeks after injury. Intimal thickening after injury did not occur in any of the groups. These results indicate that hypertension and hypercholesterolemia neither delay endothelial regeneration nor cause intimal thickening after a small injury in the rat.
Lipoprotein oxidation and lipoprotein-induced cytotoxicity.
Authors: Hessler J R , Morel D W , Lewis L J , Chisolm G M
Published: June 2011

The results of this study indicate that when human VLDL or LDL is prepared under conditions allowing oxidation, such oxidation renders the molecular complexes highly toxic to human skin fibroblasts growing in culture. The cytotoxicity can be predicted by assaying for the presence of thiobarbituric acid-reacting substances on the lipoprotein. However, malondialdehyde, which reacts with thiobarbituric acid and is known to be injurious to cells, was not cytotoxic in the same experimental system when dissolved in culture medium or covalently bound to non-toxic LDL. The toxic agent(s) on oxidized LDL is(are) located in a lipid-extractable moiety. Since lipid peroxides and oxidized sterols can occur in vivo under various pathological conditions, the cytotoxicity of these lipoprotein-associated substances observed in vitro may be related to certain manifestations of these conditions.
Increased catabolism of native and cyclohexanedione-modified low density lipoprotein in subjects with myeloproliferative diseases.
Authors: Ginsberg H , Goldberg I J , Wang-Iverson P , Gitler E , Le N A , Gilbert H S , Brown W V
Published: June 2011

We previously demonstrated reduced levels of low density lipoprotein (LDL) cholesterol in association with increased total fractional catabolic rates (FCR( of LDL apoprotein B (apo B) in individuals with myeloproliferative diseases (MPD). The removal of LDL from plasma and interstitial fluid is mediated via receptor and nonreceptor pathways. We attempted to quantitate LDL catabolism via each of these pathways in subjects with MPD and control subjects. The total FCR of LDL apo B was measured using radiolabeled native LDL. The FCR of radiolabeled cyclohexanedione-modified LDL (CHD-LDL) was used to assess the nonreceptor-mediated catabolism of LDL. Total FCR (mean +/- SD) was elevated in MPD vs controls (0.78 +/- 0.32 vs 0.45 +/- 0.11, p less than 0.01). CHD-LDL FCR was also increased in MPD vs controls (0.62 +/- 0.53 vs 0.23 +/- 0.04, p less than 0.01). Studies of the plasma decay of radiolabeled native and CHD-LDL preparations after their injection into cynomolgus monkeys indicated that CHD-LDL preparations from MPD and controls were removed at the same rates in those primates and that all CHD-LDL preparations were catabolized more slowly than the native LDL preparations. Studies in vitro indicated that CHD modification of LDL significantly reduced the rate of degradation of this lipoprotein by a specific high-affinity receptor pathway in normal human monocyte-derived macrophages and cultured human fibroblasts. We conclude that the catabolism of both native and CHD-LDL apo B is increased in subjects with MPD. If CHD-LDL is a valid tracer of nonreceptor-mediated removal of native LDL in individuals with MPD, our results indicate that the reduced LDL cholesterol concentrations demonstrated in these subjects are associated with increased nonreceptor-mediated catabolism of LDL apo B. At this time, both neoplastic cells and activated monocyte-macrophages appear to be likely sites of these abnormalities.
A system for long-term perfusion of rabbit aorta in vitro.
Authors: Björnheden T , Bylock A , Hansson G K , Bondjers G
Published: June 2011

In an in vitro system for the perfusion of arterial tissue, the volume of the incubation chamber should be small, and the composition of the medium should be easily modified. The tissue should consist of media and intima only, and the interaction with the medium should occur via the intimal side. Consecutive sampling of the medium and the tissue should be possible. This paper describes a system with these characteristics. Scanning and transmission electron microscopy of the perfused tissue indicated that the endothelium was intact during the first day and that it still covered more than 95% of the surface after 3 days. On the 2nd day, the nonthrombogenic properties of the endothelium were maintained. The medial smooth muscle cells of the inner two-thirds of the preparation were viable during the perfusion, while the cells in the outer one-third were dead from the start. Still, the metabolic activity of the tissue was stable, at least during the 2nd day as assessed by the study of DNA, protein, and lipid synthesis, as well as by oxygen consumption. We conclude that the perfusion system presented here might be useful in the study of the interaction between cellular and humoral components of the blood and the arterial wall.
Plasma phosphatidylcholine/free cholesterol ratio as an indicator for atherosclerosis.
Authors: Kuksis A , Roberts A , Thompson J S , Myher J J , Geher K
Published: June 2011

Plasma lipid profiles were determined in two inbred strains of mice, C57BR/cdJ and CBA/J, fed either a normal chow or an atherogenic diet for a 15-week period, starting at 10 weeks of age. On the chow diet, the C57BR/cdJ had significantly higher mean free cholesterol, esterified cholesterol, and total lipid values, and a significantly lower mean phosphatidylcholine/free cholesterol ratio than the CBA/J mice. On the atherogenic diet, the C57BR/cdJ had significantly higher mean levels for all lipids classes, except triacylglycerols, than the CBA/J mice. The mean plasma free cholesterol and esterified cholesterol levels of the C57BR/cdJ were four times greater than those of the CBA/J strain on the atherogenic diet. The mean plasma phosphatidylcholine/free cholesterol ratio of the C57BR/cdJ mice on the high cholesterol diet was 0.87 compared to 1.91 for CBA/J mice. These plasma lipid changes were associated with a marked development of atheromatous deposits in the wall of the aortic sinus of the C57BR/cdJ compared to the CBA/J animals. The phosphatidylcholine/free cholesterol ratios of the liver lipids of both strains decreased from 2.5-2.7 on the chow diet to 1.0-1.1 on the high cholesterol diet. It is suggested that a plasma phosphatidylcholine/free cholesterol ratio less than 1 represents a supersaturation of the vascular system and the vessel wall with cholesterol, which leads to a destabilization of the plasma membranes of the endothelial and smooth muscle cells, and an infiltration of the vessel wall by the plasma lipids.
Effects of high density lipoprotein subfractions on cholesterol homeostasis in human fibroblasts and arterial smooth muscle cells.
Authors: Oram J F
Published: June 2011

Ultracentrifugally isolated high density lipoprotein (HDL) particles of d greater than 1.125 g/ml promote net transport of cholesterol from cultured cells. Consequently, when cultured human fibroblasts and arterial smooth muscle cells were incubated with HDL3 (d = 1.125-1.21 g/ml) and "very high" density lipoprotein (VHDL, d = 1.21-1.25 g/ml), low density lipoprotein (LDL) receptor activity was induced and the rate of LDL degradation by the cells was increased. Enhancement of LDL degradation by HDL3 and VHDL was sustained over incubation periods of 5 days at medium LDL concentrations greater than needed to saturate the LDL receptors. Even during these long-term incubations with LDL, HDL3 and VHDL caused marked reductions in cellular cholesterol content. Thus, an increase in the rate of cholesterol transport from cells may lead to a steady-state decrease in cellular cholesterol content and a sustained increase in the rate of clearance of LDL from the extracellular fluid. In contrast to the effects of HDL3 and VHDL, the major subclasses of HDL2 (HDL2b, d = 1.063-1.100 g/ml; HDL2a, d = 1.100-1.125 g/ml) did not promote net cholesterol transport from cells. Moreover, by apparent direct blockage of the effects that HDL3 and VHDL had on cholesterol transport, HDL2 reversed the increased rate of LDL degradation induced by HDL3 and VHDL. These results suggest that the relative proportion of HDL subfractions in the extracellular fluid may be an important determinant of both the rate of cholesterol transport from cells and the rate of receptor-mediated catabolism of LDL.
Uptake and degradation of human chylomicrons by macrophages in culture. Role of lipoprotein lipase.
Authors: Ostlund-Lindqvist A M , Gustafson S , Lindqvist P , Witztum J L , Little J A
Published: June 2011

Because macrophages secrete lipoprotein lipase (LPL), we sought to determine if LPL activity would influence the metabolism of chylomicrons by macrophages. In initial studies, we showed that normal chylomicrons were a substrate for the macrophage's LPL activity. Uptake of normal chylomicrons occurred in a saturable fashion and was effectively competed for by human chylomicrons, very low density lipoproteins (VLDL), and rabbit beta-VLDL, but not by acetyl-low density lipoprotein (LDL), and only modestly by native LDL. When apoprotein C-II-deficient chylomicrons were incubated with macrophages, no hydrolysis of triglyceride occurred, yet saturable uptake of chylomicron protein and lipid occurred, demonstrating that LPL activity is not a prerequisite for saturable uptake. However, addition of apo C-II led to marked hydrolysis and enhanced uptake of protein and lipid moieties. When albumin was present in the medium, there was approximately equal enhancement of cellular content of triglyceride and cholesteryl ester, despite the fact that chylomicrons are triglyceride-rich. This was due to uptake of a triglyceride-depleted particle produced by LPL, as well as a preferential re-release of triglyceride. These studies suggest potential pathways by which triglyceride-rich lipoproteins could contribute to accumulation of cholesteryl esters in macrophages, even while only small amounts of triglyceride accumulate.
Diminished platelet adherence to type V collagen.
Authors: Parsons T J , Haycraft D L , Hoak J C , Sage H
Published: June 2011

Different types of collagen vary in their influence on platelet reactivity. Collagen Types III, IV, and V were obtained from human placental tissue, and Type I collagen was prepared from rat skin. Each collagen type was coated onto a plastic surface. Each collagen-coated surface or appropriate plastic surface control was studied using citrated human 51Cr-labeled platelet-rich plasma in both the presence and absence of 10 microM adenosine 5'-diphosphate (ADP). Both unstimulated and ADP-induced platelet adherence were: 1) reduced by Type V collagen coating in comparison to uncoated wells; and 2) increased by Types III and IV collagen coating in comparison to Type V coated or plastic surfaces. Addition of the fast-acting thrombin inhibitor dansylarginine (DAPA) had no significant effect on unstimulated and ADP-induced platelet adherence to Type III, IV or V collagen-coated surfaces. Type I collagen-coated surfaces, studied only in the presence of DAPA, caused greater platelet adherence than those coated with Types III, IV, or V collagen. We conclude that Type V collagen may be less thrombogenic than Types, I, III, or IV.
Family aggregation of high density lipoprotein cholesterol. Collaborative lipid research clinics program family study.
Authors: Namboodiri K K , Green P P , Kaplan E B , Tyroler H A , Morrison J A , Chase G A , Elston R C , Rifkind B M , Glueck C J
Published: June 2011

High density lipoprotein cholesterol data on a population-based random sample of 858 white and 72 black probands and their 3935 white and 205 black relatives were collected from nine North American clinics using a common protocol and standardized methodology. Familial associations were examined within clinics for whites and pooled across clinics for blacks. The influence of covariates and varying family size on correlations was examined using several sets of transformed and adjusted values and a variety of weighting schemes. Parent-offspring and sibling correlations were significant in most cases, but spouse correlations were not, suggesting a stronger influence of shared genes than shared environment on high density lipoprotein cholesterol. Adjustment for covariates tended to weaken the correlations, but the effect of variable family size was imperceptible. Although pairs involving pediatric offspring or siblings tended to show higher correlation than their adult counterparts, the differences were not significant. All correlations except father-daughter and brother-brother were homogeneous across clinics in whites. There was no asymmetry in parent-child correlations by the sex of the offspring, but the pooled mother-child correlation was significantly higher than father-child values, suggesting a possible maternal influence on high density lipoprotein cholesterol. No heterogeneity in correlations in high density lipoprotein cholesterol was detected between blacks and whites except for mother-son pairs.
Alteration in prostacyclin and prostaglandin E2 production. Correlation with changes in human aortic atherosclerotic disease.
Authors: Rolland P H , Jouve R , Pellegrin E , Mercier C , Serradimigni A
Published: June 2011

Prostacyclin (PGI2) and prostaglandin E2 (PGE2) production was investigated in human aortas (five controls and 27 with atherosclerotic lesions). The specific activities of PGI2 and PGE2 synthetase were studied using radioimmunoassays of PGE2 and 6-keto-PGE1 alpha of aortic microsomes incubated in the presence of additional substrate and cofactors. The atherosclerotic lesions were examined under the light microscope and were classified as Stage 1 when the disease was restricted to the intima and as Stages 2 and 3 when there were moderate or advanced lesions. Prostaglandin production for the control group (n = 5), Stage 1 (n = 7), Stage 2 (n = 10), and Stage 3 (n = 10) were as follows: 454 +/- 15, 162 +/- 81, 92 +/- 90, and 65 +/- 61 pmol 6-K-PGF1 alpha/50 mg protein/10 minutes; and 15 +/- 12, 399 +/- 406, 227 +/- 174, and 366 +/- 362 pmol PGE2/50 mg protein/10 minutes (mean +/- SD) respectively. We conclude that: 1) In normal aortas, PGE2 production was low, while PGI2 synthesis activity was elevated. The reverse situation was observed in aortas with atherosclerosis lesions (p less than 0.05). 2) There was an inverse relationship between PGE2 and PGI1 production (p less than 0.05). 3) There was a direct histologic relationship between lower PGI2 production and atherosclerosis progression. A decided decline in 6-K-PGF1 alpha production was detected in aortas in the early stages (65% of control values). 4) By contrast, a progressive increase in PGE2 production was found in Stage 2 and Stage 3 groups (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
Smooth muscle cell proliferation in response to endothelial injury in coronary arteries of normal and von Willebrand's disease swine.
Authors: Lamb M A , Manning J E , Reddick R L , Griggs T R
Published: June 2011

The proliferative response of medial smooth muscle cells to balloon-induced endothelial denudation was measured in coronary arteries of normal and von Willebrand's disease swine, a strain of swine with a genetic defect affecting platelet-vessel wall interactions. Animals were sacrificed 48 hours following endothelial injury. Incorporation of a 1-hour pulse label of 3H-thymidine was determined by measuring DNA specific activity. Autoradiography of coronary artery step segments was also performed. The ratio of DNA specific activity in ballooned vessels to that in nonballooned vessels ranged from 1.2 to 26.2. No statistically significant difference in 3H-thymidine incorporation between the two phenotypes was documented (p greater than 0.25). Similarly, DNA incorporation of 3H-thymidine as determined by autoradiography was accelerated to the same degree in ballooned vessels in both phenotypes. The results suggest that von Willebrand factor-mediated platelet activation is not essential for the release of platelet-derived growth factor or that in vivo factors other than platelet-derived growth factor play a significant role in the response of medial smooth muscle cells to acute intimal injury causing endothelial denudation.
Human apolipoprotein A-I--C-III gene complex is located on chromosome 11.
Authors: Bruns G A , Karathanasis S K , Breslow J L
Published: June 2011

The genes for two of the apolipoproteins, apo A-I and apo C-III, previously shown to be within 3kb in the genome, were localized to human chromosome 11 by Southern blot analysis of DNA from human-rodent somatic cell hybrids. These two genes were shown to exhibit polymorphisms associated with dyslipoproteinemia and premature atherosclerosis, and it will now be possible to examine the relationship of these genes to the many others that have been assigned to this chromosome.
Low density lipoprotein receptor mutations in South African homozygous familial hypercholesterolemic patients.
Authors: van der Westhuyzen D R , Coetzee G A , Demasius I P , Harley E H , Gevers W , Baker S G , Seftel H C
Published: June 2011

The binding and catabolism of low density lipoprotein (LDL) were studied in cultured skin fibroblasts and/or Epstein-Barr virus-transformed lymphoblastoid cells from 20 familial hypercholesterolemic (FH) homozygotes of 14 Afrikaner kindreds. Cells from available heterozygotes were also analyzed. Good resolution between the normal, heterozygote, and homozygote groups was obtained on the basis of these assays using either cell type. Results obtained with fibroblasts allowed the classification of 13 of these kindreds as being typically receptor-defective, and one kindred with two homozygotes as being receptor-negative. Fibroblasts from homozygotes of the receptor-defective class expressed LDL receptor activities which varied between 3% and 25% of normal. Where two homozygotes from the same family were available for assays (six families), both yielded similar activities. In contrast to fibroblasts, all the lymphoblastoid cells derived from FH homozygotes yielded LDL receptor activities equal to or less than 10% of normal; in a number of cases no significant 125I-LDL binding was detectable. The use of lymphoblastoid cells provides a convenient means for screening for FH at the cellular level. Our results indicate a predominance of a receptor-defective type of abnormality, which is consistent with a founder gene effect in the Afrikaner population.
In vivo catabolism of biologically modified LDL.
Authors: Nagelkerke J F , Havekes L , van Hinsbergh V W , van Berkel T J
Published: June 2011

Incubation of human low density lipoprotein (LDL) at 37 degrees C in the presence of human umbilical vein endothelial cells (EC) caused a time-dependent shift in the charge and density of LDL. The physical changes of the human LDL occurred parallel with an increase in its clearance from the serum and uptake in the liver when injected into rats. The serum decay of the EC-modified LDL (44 hours incubation) was 20 times faster than for control LDL. EC-modified LDL, cleared from the blood, was quantitatively recovered in the liver. Isolation of the different liver cell types (parenchymal, Kupffer, and endothelial cells) after in vivo injection of 125I-EC-modified LDL showed that approximately 30 times more radioactivity was associated with the endothelial cells than with the parenchymal cells (per milligram of cell protein). In vitro experiments indicated that EC-modified-LDL was processed by the rat liver endothelial cells via a high affinity, saturable pathway related to the pathway by which these cells processed acetyl-LDL. We concluded that, if EC-modified LDL is generated in vivo, the liver, and in particular the endothelial cells, forms the major protection system against the occurrence of atherogenic particles in the blood.
Metabolism of low density lipoprotein by bovine endothelial cells as a function of cell density.
Authors: Kenagy R , Bierman E L , Schwartz S , Albers J J
Published: June 2011

The amount of low density lipoprotein (LDL) bound to the LDL receptor of bovine aortic endothelial cells at widely varying cell densities was measured by two methods: the commonly used dextran-sulfate-release method after LDL binding at 0-4 degrees C, and the method of assay of the LDL internalized in 30 minutes at 37 degrees C after LDL binding at 0-4 degrees C. Values obtained for LDL binding by the two methods were similar. At cell densities ranging from very sparse (6 X 10(3) to very dense (greater than 10(6) cells/cm2), both binding and degradation of 125I-LDL decreased in a nonlinear but parallel manner as cell density increased. This change began to occur at subconfluent densities and appeared to be not simply the result of establishment of a confluent cell layer. Thus, endothelial cells respond to changes in cell density with reciprocal changes in LDL metabolism in the same manner as reported for fibroblasts, so that at confluency both LDL receptor activity and LDL degradation are very low.
Cholesterol and bile acid synthesis in two families with homozygous and heterozygous hypercholesterolemia.
Authors: Miettinen T A
Published: June 2011

Measurements of cholesterol and bile acid synthesis and of cholesterol precursors were performed in two hypercholesterolemic families with two homozygous girls under basal conditions and during treatment with cholestyramine. The concentrations of serum methyl sterols, squalene, cholesterol, and triglycerides, and the responses to cholestyramine were not consistently different in the two families. However, in both families stimulation of cholesterol synthesis by cholestyramine markedly increased the methyl sterol content of serum lipoproteins both in heterozygotes (with a lowering of serum cholesterol) and in homozygotes (with virtually no lowering of serum cholesterol concentration). The bile acid and cholesterol synthesis rates were modestly low in one family and markedly high in the other both with and without cholestyramine treatment, the baseline production rates being significantly correlated with the increments in the synthesis caused by cholestyramine. The two families apparently represent low and high producing types of familial hypercholesterolemia. Cholesterol synthesis in the two homozygous girls was about twice that of their respective heterozygous parents with and without cholestyramine treatment, suggesting that the double dose of the mutant gene doubled cholesterol production. Furthermore, close child-to-parent correlations for the bile acid and cholesterol synthesis rates point to a genetic control of cholesterol metabolism.
No effect of nifedipine on atherogenesis in cholesterol-fed rabbits.
Authors: Stender S , Stender I , Nordestgaard B , Kjeldsen K
Published: June 2011

It was recently reported that the calcium antagonist nifedipine suppresses aortic cholesterol accumulation in cholesterol-fed rabbits without reducing hypercholesterolemia. We extended this study on plasma lipoprotein levels and aortic influx of cholesteryl ester. We gave 40 mg per day of nifedipine orally to 17 rabbits fed a 2% cholesterol diet for 8 weeks. For the same period of time 15 control rabbits received placebo capsules and the same diet. During the study, total cholesterol, HDL, LDL, and VLDL cholesterol concentrations in plasma were not significantly different in the experimental and control animals. At the end of the study we found no difference in the two groups in accumulation of cholesterol in the intima media of the proximal thoracic aorta, the distal thoracic aorta, and the corresponding media layers. Furthermore, aortic influx of free cholesterol, cholesteryl ester, and albumin from plasma measured by radioactive tracers was not significantly affected by nifedipine.