bluuebunny/crossref_metadata_2025 huggingface dataset:
Metabolism of low density lipoproteins by pigeon skin fibroblasts and aortic smooth muscle cells. Comparison of cells from atherosclerosis-susceptible and atherosclerosis-resistant pigeons.
Authors: St Clair R W , Leight M A , Barakat H A
Published: June 2011

Aortic smooth muscle cells from atherosclerosis-susceptible White Carneau (WC) pigeons lack a functional low density lipoprotein (LDL) receptor pathway. The purpose of the present study was to determine if atherosclerosis-resistant Show Racer pigeons (SR) shared this lack of an LDL receptor pathway and if LDL from normal and hypercholesterolemic pigeons were metabolized similarly. The amount of LDL bound, internalized, and degraded by skin fibroblasts, embryo fibroblasts, and aortic smooth muscle cells from WC and SR pigeons were similar and averaged from 2% to 25% of that seen with monkey smooth muscle cells incubated with the same LDL. LDL uptake by pigeon cells was due largely to nonspecific processes, while specific uptake predominated in monkey cells. A similar lack of specific uptake was obtained with LDL from normal and hypercholesterolemic pigeons. Sterol synthesis and HMG-CoA reductase activity were 10- to 35-fold higher in pigeon cells than in monkey cells incubated in serum-containing medium. LDL had little effect on cholesterol esterification and cholesteryl ester accumulation in pigeon cells. These results indicate that despite major changes in the size and composition of LDL from hypercholesterolemic pigeons, this LDL, like normal pigeon and monkey LDL, was not metabolized by specific uptake processes by pigeon cells. Cells from both WC and SR pigeons lack a functional LDL receptor pathway.
Conservation of the low density lipoprotein receptor-binding domain of apoprotein B. Demonstration by a new monoclonal antibody, MB47.
Authors: Young S G , Witztum J L , Casal D C , Curtiss L K , Bernstein S
Published: June 2011

The fact that low density lipoprotein (LDL) from multiple animal species binds to the human LDL receptor suggested that the LDL-receptor binding domain of apoprotein (apo)B must be evolutionarily conserved. To determine if a common receptor domain epitope existed on apo B, we generated a monoclonal antibody that was specific for the LDL-receptor domain of apo B. This was accomplished by using a screening procedure that selected for a hybridoma supernatant that could block specific cellular uptake and degradation of LDL. Western blots showed that this antibody, termed MB47, was specific for apo B-100. Fluid phase assays indicated a high binding affinity (Ka = 4 X 10(9) M-1) and demonstrated that all human LDL particles expressed the MB47 epitope. Scatchard analysis indicated that a maximum of one MB47 molecule bound to each LDL particle. In solid phase assays, antibody MB47 bound to plasma or LDL of multiple mammalian species, including guinea pig, rabbit, pig, dog, cat, seal, whale, bear, and lion, but it did not bind to mouse or rat LDL. In contrast, a rabbit antiserum to LDL and two other anti-apo B monoclonal antibodies, MB3 and MB19, which do not bind to the receptor domain, were specific only for human LDL. LDL from multiple species, including mouse LDL, competed effectively with 125I-human LDL for binding to human fibroblasts. MB47 effectively inhibited uptake and degradation of labeled human, guinea pig, and rabbit LDL by both human and guinea pig fibroblasts. We conclude that antibody MB47 binds to a single receptor domain on LDL and identifies a vital region conserved through mammalian evolution.
Correlation of endothelial cell shape and wall shear stress in a stenosed dog aorta.
Authors: Levesque M J , Liepsch D , Moravec S , Nerem R M
Published: June 2011

The pattern of endothelial geometry at various locations along stenosed dog aortas was examined. This was done to test the hypotheses that the shape of an endothelial cell is related to the local wall shear stress associated with the flowing blood and that alterations in hemodynamics, produced by vascular geometrical changes, influence endothelial cell geometry. Aortic stenosis with a reduction of 71% of the cross-sectional area was produced. The animals were sacrificed 12 weeks later, and the endothelial cell geometry and orientation were studied using the vascular casting technique and a computerized analysis to determine cell area and shape index. The regions of the stenosis examined were those known to experience different hemodynamic conditions. The value of the shape index was found to fall rapidly in the convergent region of the stenosis and to increase suddenly in the divergent region, eventually returning to the prestenotic value at a more distal site. Using a model of a stenosis made from a vascular cast, laser Doppler anemometry was applied to measure velocity profiles and to estimate the local wall shear stress in a stenosed aorta. It is shown that the shape index distribution along these stenosed vessels may be correlated with the level of wall shear stress, with more elongated cells occurring in regions of higher shear stress.
Immediate and long-term effects of angioplasty-balloon dilation on normal rabbit iliac artery.
Authors: Consigny P M , Tulenko T N , Nicosia R F
Published: June 2011

The present study was performed to determine the immediate (hours) and long-term (28-day) effects of angioplasty-balloon dilatation on arterial wall diameter, histology, response to vasoconstrictors, and passive mechanics. Dilated left iliac arteries of New Zealand rabbits were compared to control, right iliac arteries. In the immediate studies, dilation increased arteriographic diameter by 32%, denuded the endothelium, stretched and may have lysed smooth muscle cells, decreased arterial wall thickness, and increased passive stress and incremental elastic modulus. The dilated arteries failed to contract to norepinephrine or potassium chloride. In contrast, 28 days after dilation, arteriographic diameter had returned to normal, an intimal thickening had formed, passive stress and the incremental elastic modulus had decreased to below normal, and the arteries contracted, but to only 53% to 67% of control. Angioplasty had no long-term effect on arterial sensitivity (EC50) to potassium chloride or serotonin but did produce a decreased sensitivity (6X) to norepinephrine. These studies demonstrate that the effects of dilatation of the normal artery are partially reversible, suggest that restenosis after angioplasty is more likely to be due to intimal proliferation than increased arterial stiffness, and suggest that vasospasm of arteries after long-term recovery from the dilation is more likely to be mediated by serotonin than by norepinephrine.
Tissue sites of degradation of high density lipoprotein apolipoprotein A-IV in rats.
Authors: Dallinga-Thie G M , Van 't Hooft F M , Van Tol A
Published: June 2011

The in vivo metabolism of high density lipoprotein (HDL), labeled by incorporation of 125I-apolipoprotein (apo) A-IV, was studied in the rat and compared with the metabolism of HDL labeled with 131I-apo A-I. The 125I-apo A-IV labeled HDL was obtained by adding small amounts of radioiodinated apo A-IV to rat serum, followed by separation of the different lipoprotein fractions by chromatography on 6% agarose columns in order to avoid "stripping" of apolipoproteins by ultracentrifugation. Under both in vitro and in vivo conditions, the 125I-apo A-IV remained an integral component of HDL and was not exchanged to other lipoproteins, including the "free" apo A-IV fraction. The serum half-life, measured at between 8 and 28 hours after intravenous injection of labeled HDL, was 8.5 +/- 0.5 hours for HDL apo A-IV and 10.2 +/- 0.7 hours for HDL apo A-I. The tissue sites of catabolism of HDL apo A-IV and HDL apo A-I were analyzed in the "leupeptin-model." Only the kidneys and liver showed a significant leupeptin-dependent accumulation of radioactivity. At 4 hours after injection of 125I-apo A-IV/131I-apo A-I labeled HDL, 3.5% +/- 1.0% and 8.4% +/- 2.0% of HDL apo A-IV and 4.6% +/- 1.3% and 2.6% +/- 0.6% of the HDL apo A-I were accumulated in a leupeptin-dependent process in the kidneys and liver, respectively. Immunocytochemical studies revealed that the renal localization of apo A-IV was intracellular and confined to the epithelial cells of the proximal tubuli.(ABSTRACT TRUNCATED AT 250 WORDS)
Hyperapobetalipoproteinemia. Plasma lipoprotein responses to oral fat load.
Authors: Genest J , Sniderman A , Cianflone K , Teng B , Wacholder S , Marcel Y , Kwiterovich P
Published: June 2011

To better define lipid transport in patients with hyperapobetalipoproteinemia (HyperapoB), the response to an oral fat load was studied in six normotriglyceridemic patients with the disorder. Plasma triglycerides; Sf greater than 400, and Sf 20 to 400 triglycerides; Sf greater than 20 B100; total HDL and HDL subfractions (HDL2 and HDL3) were measured serially for a 7-hour period after an oral fat load and changes in these parameters were compared to those observed in six normolipidemic controls. In addition, plasma triglyceride levels and HDL2 and HDL3 cholesterol were also determined in seven patients with Type IV hyperlipoproteinemia: three with normal LDL apo B levels and four with HyperapoB. When the two normotriglyceridemic groups were compared, the patients with HyperapoB had significantly higher fasting levels of SF greater than 400 lipoproteins and higher fasting VLDL and LDL levels than the normal patients. After the fat load, Sf 20 to 400 triglycerides and Sf greater than 20 B100 levels increased in both groups. Plasma triglycerides rose to a higher level in the HyperapoB patients than in the normal group, but more strikingly, remained elevated in the HyperapoB patients, an elevation due principally to a persistant increase in Sf greater than 400 triglycerides. On the other hand, HDL2 cholesterol dropped substantially in the HyperapoB patients but not in the normal patients. Finally, in the hypertriglyceridemic group, after the fat load, HDL2 cholesterol levels did not change in the patients with normal LDL apo B levels but did decrease in those with elevated plasma LDL apo B.
Influence of arterial damage and wall shear rate on platelet deposition. Ex vivo study in a swine model.
Authors: Badimon L , Badimon J J , Galvez A , Chesebro J H , Fuster V
Published: June 2011

To study the influence of blood flow on platelet interaction with selected biological surfaces, we have developed an ex vivo perfusion chamber system. In the present experiments, deendothelialized pig aorta and collagen Type I bundles from Achilles tendon were exposed to either native or heparinized pig blood for periods of time ranging from 1 to 30 minutes, and for flow rates corresponding to wall shear rates of 106 to 3380 sec-1. On the deendothelialized vessel wall, platelet deposition increased with both exposure time and wall shear rate, reaching a maximum value between 5 and 10 minutes of perfusion. At high shear rates and long exposure time (over 10 minutes), platelet deposition decreased from maximum values, indicating that some platelets were embolized by the flow. Ultrastructure analysis of the specimens showed platelet activation, spreading, and degranulation. Collagen induced a progressive accumulation of platelets following a power type curve of aggregate growth with exposure time without reaching a saturation level, even after long perfusion times (30 minutes) and high wall shear rates (3380 sec-1). In conclusion, the reactivity of the exposed materials and the local shear rate, defined by the blood flow and the patent luminal cross section, regulate platelet deposition to injured vascular wall.
Micropipette aspiration of human platelets after exposure to aggregating agents.
Authors: Burris S M , Smith C M , Tukey D T , Clawson C C , White J G
Published: June 2011

The present study examined the influence of activation on platelet deformability. Aspiration of cells after exposure to thrombin, adenosine 5' -diphosphate, or the calcium ionophore A23187 at concentrations producing shape change and stickiness revealed significant changes from control cells. At the lowest negative pressure, 4 X 10(-2) dynes/cm (-1 cm H2O), there were no differences in lengths of membrane segments aspirated from control and activated platelets. Each subsequent increase in negative pressure up to 35 X 10(-2) dynes/cm (-7.5 cm H2O) resulted in significantly longer aspirated segments on activated cells compared to control cells. Greater negative pressures did not cause further increases in lengths of membrane segments drawn into the pipette. Thus, activation, which results in constriction of the circumferential microtubule, makes more membrane available for aspiration as negative pressure is increased. In both control and activated platelets, the microtubule coils served as a barrier to further lengthening of aspirated membrane segments as negative pressure was increased beyond 35 X 10(-2) dynes (-7.5 cm H2O).
Plasma lipoproteins, apolipoproteins, and triglyceride metabolism in familial hypertriglyceridemia.
Authors: Stalenhoef A F , Demacker P N , Lutterman J A , van 't Laar A
Published: June 2011

Several parameters of lipoprotein metabolism were examined in 38 men with primary hypertriglyceridemia (phenotype IV). Family investigation showed that 17 men had familial combined hyperlipidemia (FCH), seven had familial hypertriglyceridemia (FHT), and 14 had unclassified hypertriglyceridemia (UNC). In all three groups, plasma high density lipoprotein (HDL) cholesterol and the concentrations of apolipoprotein A-I and A-II were decreased, and apolipoprotein B was increased, each to the same extent. These results are compatible with an increased risk of cardiovascular disease in both FCH and FHT patients. The mean concentration of LDL cholesterol and the ratio of LDL to HDL cholesterol were significantly higher in FCH subjects, which could explain their increased risk. Postheparin lipoprotein lipase and hepatic lipase were the same in both groups. Determination of apolipoprotein C composition, which may modulate lipoprotein lipase activity, did not reveal any abnormalities in the different groups. In both FCH and FHT, the mean turnover rate of plasma triglycerides was almost twice normal, indicating that overproduction of plasma triglyceride plays an important role in both disorders. However, there was an overlap with normal controls, indicating impaired triglyceride removal in some subjects. The underlying mechanism of hypertriglyceridemia in FCH and FHT therefore seems to be heterogeneous.
Short-term effect of natural disasters on coronary heart disease risk factors.
Authors: Trevisan M , Celentano E , Meucci C , Farinaro E , Jossa F , Krogh V , Giumetti D , Panico S , Scottoni A , Mancini M
Published: June 2011

In this analysis of the data from a longitudinal study on coronary heart disease risk factors, it was found that participants screened a few weeks after a major disaster (earthquake) had a higher heart rate, serum cholesterol levels, and serum triglyceride levels than matched participants that were screened shortly before the catastrophic event. The two groups of participants did not differ with regard to their characteristics at the baseline examination carried out 5 years previously. The lack of difference in blood pressure between exposed and nonexposed participants could be explained by the lag-time between the earthquake and the blood pressure measurements. We conclude that the acute stress associated with major disasters can influence risk factors for coronary heart disease. Permanent elevation of these risk factors due to the disruption of the social environment of the individuals affected by major disasters might be responsible for the apparent long-term adverse effects on cardiovascular mortality discussed previously in the literature.
Macrophage oxidation of low density lipoprotein generates a modified form recognized by the scavenger receptor.
Authors: Parthasarathy S , Printz D J , Boyd D , Joy L , Steinberg D
Published: June 2011

Incubation of low density lipoprotein (LDL) with endothelial cells or smooth muscle cells overnight has resulted in an oxidative modification of LDL that results in its recognition by macrophages by way of the acetyl LDL receptor. In the present study, we examined whether macrophages themselves can oxidize and modify LDL in a manner similar to that of endothelial cells. Incubation of 125I-labeled LDL with resident or thioglycollate-elicited macrophages for 24 hours in Ham's F-10 medium resulted in the appearance of thiobarbituric acid (TBA) reactive materials and trichloroacetic acid (TCA) soluble radioactivity in the medium. The LDL harvested from these incubations showed increased electrophoretic mobility and was degraded rapidly when added to fresh macrophages as compared to LDL previously incubated in the absence of cells. These macrophage-induced modifications could be prevented if the first incubation was carried out in the presence of the antioxidant butylated hydroxytoluene (BHT) or in Dulbecco's modified Eagle's medium (DMEM). The degradation of 125I-labeled macrophage-modified LDL by macrophages was competitively inhibited by unlabeled acetyl LDL or unlabeled endothelial cell-modified LDL but not by native LDL, indicating that the degradation was mediated by the acetyl LDL receptor.
Iliac artery mural thrombus formation. Effect of antiplatelet therapy on 111In-platelet deposition in baboons.
Authors: Hanson S R , Paxton L D , Harker L A
Published: June 2011

To measure the rate, extent, and time course of arterial mural thrombus formation in vivo and to assess the effects of antiplatelet therapy in that setting, we have studied autologous 111In-platelet deposition induced by experimental iliac artery aneurysms in baboons. Scintillation camera imaging analyses were performed at 1, 24, 48, and 72 hours after implantation of the device. Correction for tissue attenuation was determined by using a small, comparably located 111In source implanted at the time of surgery. In five animals, 111In-platelet activity accumulated progressively after device implantation, reaching a maximum after the third day. Repeat image analysis carried out 2 weeks after the surgical procedure also showed progressive accumulation of 111In-platelets over 3 days but at markedly reduced amounts as compared with the initial study. In five additional animals, treatment with a combination of aspirin and dipyridamole begun 1 hour after surgical implantation reduced 111In-platelet deposition to negligible levels by the third day. Although platelet survival time was shortened and platelet turnover was reciprocally increased in all operated animals, platelet survival and turnover were not affected by antiplatelet therapy. We conclude that, in contrast to platelet survival and turnover measurements, 111In-platelet imaging is a reliable and sensitive method for localizing and quantifying focal arterial thrombi and for assessing the effects of antiplatelet therapy.
Time course of release into the medium of newly synthesized proteins by cultured aortic endothelial cells. Role of serum in preventing proteolytic degradation.
Authors: Dickinson E S , Dennis P A , Slakey L L
Published: June 2011

Endothelial cells from pig aortas were labeled with 35S-methionine, and the soluble proteins that were released into the culture medium were examined by SDS-PAGE. Proteins were collected during labeling, and during the intervals 0 to 3, 3 to 6, 6 to 12, and 12 to 24 hours of chase after a 1-hour labeling period, and during the intervals 0 to 12, 12 to 24, and 24 to 48 hours of chase after a 24-hour labeling period. Release of radiolabeled soluble protein from cells into the medium continued over the longest time periods examined. If the cells were labeled for 1 hour, characteristic patterns of proteins appeared in the medium during the labeling period, early (0- to 3-hour postlabeling) and late (6- to 24-hour postlabeling). The time course of release of fibronectin (Fn) and of angiotensin-converting enzyme (ACE) was determined by using immunoprecipitation. ACE appeared only after 6 hours of chase. Fn appeared throughout the chase period. The effects of serum and of the protease inhibitors alpha-2 macroglobulin, pepstatin, and leupeptin on protein release were examined. In the absence of serum, endothelial cell culture medium contained substantial protease activity capable of completely degrading most of the released proteins; a major effect of serum was to protect newly released protein from degradation.
Dietary effects on serum lipoproteins of dyslipoproteinemic baboons with high HDL1.
Authors: McGill H C , McMahan C A , Kushwaha R S , Mott G E , Carey K D
Published: June 2011

Some progeny of baboons (Papio sp.) selectively bred for a high response of serum cholesterol to an atherogenic diet have high serum levels of unusual lipoproteins with flotation rates of F degrees 1.20 9-28, intermediate between those of low and high density lipoproteins (HDL). They are similar to the fraction of HDL commonly called HDL1. We conducted a cross-over experiment to determine the roles of dietary cholesterol and saturated fat in eliciting these lipoproteins in the progeny of two affected sires. Half of the progeny of each sire manifested the trait (high HDL1 phenotype) while consuming an atherogenic diet and half did not (low HDL1 phenotype). While consuming a chow diet, high HDL1 progeny had higher total serum cholesterol concentrations than did low HDL1 progeny. This difference was exaggerated when the animals consumed diets enriched in either cholesterol or saturated fat (lard), and was greatest when the diet contained both. High HDL1 animals also had considerably higher serum apo E concentrations, and slightly higher serum apo A-I concentrations. High HDL1 progeny had much higher levels of cholesterol (twofold) and of apo A-I (three- to eightfold) in HDL1 fractions than did low HDL1 progeny. There were significant interactions between HDL1 class and both dietary cholesterol and saturated fat in their effects on other lipoprotein fractions. High HDL1 animals had an exaggerated elevation of cholesterol and apo B in very low, intermediate, and low density lipoproteins in response to dietary cholesterol. They also had an exaggerated elevation of cholesterol in the lighter HDL1 fraction (d = 1.041-1.053), and lesser elevation of cholesterol and apo A-I in HDL2.
Differential distribution of von Willebrand factor in endothelial cells. Comparison between normal pigs and pigs with von Willebrand disease.
Authors: Wu Q Y , Drouet L , Carrier J L , Rothschild C , Berard M , Rouault C , Caen J P , Meyer D
Published: June 2011

Endothelial cells were cultured from the thoracic aorta, inferior vena cava, and pulmonary artery of normal adult and young pigs as well as from pigs with von Willebrand disease (vWD). The von Willebrand factor (vWF) was estimated by ELISA in endothelial cell supernatants and lysates as well as by immunofluorescence of cells by use of either a polyclonal or a monoclonal antibody to vWF. In normal adult pigs, the content of vWF in supernatants and cell lysates was the highest in the pulmonary artery, lower in the inferior vena cava, and almost nil in the thoracic aorta. In the normal young pigs, vWF was higher in the inferior vena cava endothelial cell supernatants and lysates than in the pulmonary artery. Thus the synthesis of vWF by endothelial cells varies along the vascular tree and appears to be modulated by the age of the animals. In pigs with vWD, levels of vWF were slightly detectable in endothelial cells from the pulmonary artery (contrasting with levels of plasmatic vWF below 0.01 U/ml), but were undetectable in the thoracic aorta and inferior vena cava. Thus, if vWF plays a role in atherogenesis, this involves circulating, not its intracellular, form.
Decrease in reactive amino groups during oxidation or endothelial cell modification of LDL. Correlation with changes in receptor-mediated catabolism.
Authors: Steinbrecher U P , Witztum J L , Parthasarathy S , Steinberg D
Published: June 2011

The monocyte/macrophage appears to be the precursor of many of the lipid-laden cells in atherosclerotic lesions, but the mechanism by which these cells accumulate cholesterol to become foam cells remains unclear. We have previously reported that cultured endothelial cells can modify low density lipoprotein (LDL) in a manner that leads to rapid uptake by the acetyl LDL receptor of macrophages. This modification involves free radical-induced peroxidation of LDL and is accompanied by many changes in the physicochemical properties of LDL including increased electrophoretic mobility, increased density, decreased content of esterified cholesterol, hydrolysis of phosphatidylcholine, and fragmentation of apolipoprotein B. Under conditions highly favorable to oxidation, a similar modification can occur even in the absence of cells. In the present studies, oxidation of LDL simply by exposure to 5 microM Cu++ resulted in a modification that was indistinguishable from that produced by endothelial cells. Moreover, it was demonstrated that LDL oxidation by either method is accompanied by a marked decreased in amino group reactivity, comparable to that seen with the chemical modifications of LDL that lead to recognition by the acetyl LDL receptor. Inhibitors of proteolytic enzymes did not reduce fragmentation of apolipoprotein B during oxidation. The rate of catabolism of intravenously injected oxidized LDL in guinea pigs was very rapid, and over 80% of the degradation occurred in the liver. The studies demonstrate that all of the changes associated with endothelial cell modification of LDL can be attributed to oxidation. The cells can, however, promote oxidation under conditions where it would otherwise occur very slowly.(ABSTRACT TRUNCATED AT 250 WORDS)
Hydroxymethylglutaryl-coenzyme A reductase exhibits graded distribution in normal and mevinolin-treated ileum.
Authors: Singer I I , Kawka D W , McNally S E , Scott S , Alberts A W , Chen J S , Huff J W
Published: June 2011

Because the small bowel is a site of significant cholesterol synthesis, we determined the ileal distribution of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoA reductase), the rate-limiting enzyme of the cholesterol biosynthetic pathway. Immunofluorescence microscopy on unfixed snap-frozen sections of ileum and jejunum from untreated rats or dogs showed HMG-CoA reductase in the absorptive villus epithelial cells and this appeared to be strikingly localized in their apical cytoplasm. This pattern of HMG-CoA reductase staining approximated a gradient along the villus-crypt axis with the distal villi labeling most intensely. Treatment of rats with mevinolin and/or cholestyramine for 12 days induced a 5- to 11-fold increase in ileal HMG-CoA reductase activity, and yielded a higher intensity of immunostaining without altering the pattern of enzyme distribution observed in control intestines. Also, rats with maximal induction of ileal HMG-CoA reductase exhibited a twofold increase in the number of epithelial villus cells containing prominent stacks of smooth-surfaced membranes in their apical cytoplasm as seen with electron microscopy. These observations suggest that the distal villus absorptive epithelial cells of the ileum contain high concentrations of HMG-CoA reductase, and therefore might be capable of contributing significant quantities of cholesterol to the circulation.
Pregnancy-associated inhibition of coronary artery atherosclerosis in monkeys. Evidence of a relationship with endogenous estrogen.
Authors: Adams M R , Kaplan J R , Koritnik D R , Clarkson T B
Published: June 2011

We investigated the influence of repeated pregnancy on diet-induced atherosclerosis in cynomolgus monkeys and sought to determine if circulating endogenous reproductive steroid levels were associated with the extent of coronary artery atherosclerosis. At necropsy, females which were pregnant one or more times were found to have coronary artery atherosclerosis which was one-fourth as extensive as that of intact females which had not been pregnant. Extent of coronary artery atherosclerosis correlated positively with mean total plasma cholesterol (Rho = 0.52, p less than 0.01) and inversely with high density lipoprotein (HDL) cholesterol (Rho = -0.48, p less than 0.01) concentrations; both decreased during pregnancy. Additionally, the extent of coronary artery atherosclerosis was found to have a strong inverse association (Rho = -0.66, p less than 0.001) with an index (area-under-the-curve) of magnitude and duration of the pregnancy-induced elevation in plasma 17-beta estradiol concentration. This association could not be explained by an interrelationship between estradiol area-under-the-curve and either plasma total or HDL cholesterol concentrations. There was no relationship between atherosclerosis extent and a similar index of plasma progesterone concentrations. These findings provide evidence for an inhibitory effect of endogenous estrogen on the progression of coronary artery atherosclerosis.
Plasma lipoprotein distribution of apolipoprotein E in familial hypercholesterolemia.
Authors: Gibson J C , Goldberg R B , Rubinstein A , Ginsberg H N , Brown W V , Baker S , Joffe B I , Seftel H C
Published: June 2011

Although familial hypercholesterolemia (FH) has been well characterized in terms of the etiology of the major lipoprotein abnormality, that of low density lipoproteins (LDL), less information is available on changes in other lipoproteins which could influence the atherogenic process in this disorder. The present study has focused on such potential abnormalities by studying in detail the lipoprotein association of apolipoprotein E (apo E) in a large group of subjects homozygous for FH. Total plasma apo E levels in homozygous subjects were significantly elevated (p less than 0.001) relative to heterozygous subjects which were, in turn, significantly greater (p less than 0.001) than controls (137.6 micrograms/ml, 69.4 micrograms/ml, 46.5 micrograms/ml respectively). After separation of plasma lipoproteins by 4% agarose chromatography, an increased mass of apo E in lipoproteins of intermediate size was present; this may reflect the absence of LDL receptors that normally mediate their clearance. Homozygous FH subjects also demonstrated an increased mass of apo E-enriched high density lipoproteins (HDL) of large size, but a reduction in HDL cholesterol and apo A-I. The increase in the potentially atherogenic remnant lipoproteins and the decrease in HDL are associated with an increased risk for atherosclerosis, even in the absence of the LDL elevation, which is characteristic of FH. The increase in apo E-enriched HDL could reflect a compensatory mechanism that permits reverse cholesterol transport in the absence of LDL receptors.
Fish oil inhibits development of atherosclerosis in rhesus monkeys.
Authors: Davis H R , Bridenstine R T , Vesselinovitch D , Wissler R W
Published: June 2011

The effect of feeding fish oil (Menhaden) on the progression of rhesus monkey atherosclerosis was determined by feeding diets containing 2% cholesterol and either 25% coconut oil (Group I), 25% fish oil/coconut oil (1:1) (Group II), or 25% fish oil/coconut oil (3:1) (Group III) for 12 months (n = 8/group). The average serum cholesterol levels were 875 mg/dl for Group I, 463 mg/dl for Group II, and 405 mg/dl for Group III. HDL cholesterol levels were 49 mg/dl for Group I, 29 mg/dl for Group II, and 20 mg/dl for Group III. An average of 79% of the aortic intima was involved with atherosclerosis in Group I, 48% in Group II, and 36% in Group III. The aortas of both fish-oil groups (II or III) contained significantly less cholesterol (total, free, and esterified), as well as less acid lipase, cholesteryl esterase, and ACAT activities when compared to the coconut-oil group (I) (p less than 0.05). Microscopically, the aortic and carotid artery lesions were smaller in cross-sectional area and in thickness, and contained less macrophages in the fish-oil groups (II and III) when compared to the coconut-oil group (I) (p less than 0.05). This protective effect was not consistently enhanced by increasing the proportion of fish oil to 3:1 (Group III) over 1:1 (Group II). The results indicate that fish oil-containing diets reduce serum cholesterol levels and inhibit atherosclerosis even in the face of lowered HDL cholesterol levels when compared to a pure coconut oil/cholesterol diet in rhesus monkeys. Therefore, fish-oil diets exert effective protective control of progression of atherosclerosis during severe atherogenic stimuli.
Long-term effects of verapamil on aortic smooth muscle cells cultured in the presence of hypercholesterolemic serum.
Authors: Stein O , Halperin G , Stein Y
Published: June 2011

Smooth muscle cells derived from rabbit and bovine aorta were cultured for up to 5 weeks in the presence of d less than 1.019 g/ml fraction of hypercholesterolemic rabbit serum. When this fraction was added to serum containing culture medium, there was a significant increase in DNA, protein, and cholesteryl ester per dish. Addition of 50 microM verapamil markedly reduced the stimulatory effect of the d less than 1.019 g/ml fraction on both DNA and protein content per dish. The effect of verapamil on cholesteryl ester content was more complex: there was an increase within the first week, but later the net accumulation of cholesteryl ester per dish was lower than in untreated dishes. The recovery of less DNA in verapamil-treated dishes was not due to increased cell loss, as evidenced by retention of a residualizing marker, 3H-cholesteryl linoleyl ether. Moreover, verapamil did reduce incorporation of 3H-thymidine into DNA. In verapamil-treated dishes, there was flattening and a cobblestone appearance of the cells. A hypothesis is proposed to explain the inhibitory effect of verapamil on the development of atheroma formation in cholesterol-fed rabbits: Assuming that macrophages play an active role in cholesteryl ester removal from atheroma, verapamil, which reduces lysosomal cholesteryl ester hydrolysis in macrophages, would permit the lipid-laden macrophage to remove more cholesteryl ester per cell from the arterial wall. In addition, the presently reported results support the possibility that verapamil may impede the development of atheroma formation by reduction of smooth muscle cell proliferation.
Modulation of glycosaminoglycan production and antithrombin III binding by cultured aortic endothelial cells treated with 4-methylumbelliferyl-beta-D-xyloside.
Authors: Shimada K , Ozawa T
Published: June 2011

The interaction between antithrombin III and heparinlike glycosaminoglycan molecules present on the vascular surface seems to play a significant role in the regulation of coagulation. We have tested the hypothesis that altered synthesis of glycosaminoglycans by endothelial cells could influence this interaction by using 4-methylumbelliferyl-beta-D-xyloside for metabolic perturbation of glycosaminoglycan production. Incubation of purified porcine 125I-antithrombin III with cultured porcine aortic endothelial cells demonstrated specific, time-dependent, saturable binding of this protease inhibitor to the endothelial cell surface with antithrombin III concentration at half-maximal binding of approximately 40 nM. This binding was displaced by heparin and was completely abolished by selective removal of heparan sulfate from cells with heparitinase, indicating that antithrombin III binds to heparan sulfate on the surface of endothelial cells. Incubation of cell cultures with beta-D-xyloside resulted in a reduction of maximum antithrombin III binding by approximately 65% with little alteration in binding affinity. beta-D-Xyloside did not affect the cellular growth or morphology. Reduction of the binding after exposure to various concentrations (33 to 500 microM) of xyloside occurred in parallel with the decrease in incorporation of both 35S-sulfate and 3H-glucosamine into cell surface heparan sulfate. Whereas the size of heparan sulfate chains derived from the cell surface was not altered by xyloside treatment, they appeared to have slightly less net negative charge and a significantly reduced proportion of the molecule with high affinity for antithrombin III in the presence of xyloside. On the other hand, secretion of free chondroitin sulfate (and dermatan sulfate) chains into the medium was markedly increased (16-fold) in the presence of xyloside, accompanied by a smaller increase in secretion of free heparan sulfate chains. There was a good correlation between conditions with decreased antithrombin III binding and an inhibition of the endothelial cell-mediated acceleration of thrombin inactivation by antithrombin III. These results suggest that beta-D-xyloside caused a dose-dependent decrease in production as well as some subtle structural alterations of cell-surface-associated heparan sulfate, which could serve as binding sites for antithrombin III on the endothelial cells and mediate enhancing the anticoagulant activity of this protein. This system may offer a potentially useful model to investigate the possible mechanisms responsible for the development of a procoagulant state involving these endothelial macromolecules.
Effects of saturated and polyunsaturated dietary fat on the concentrations of HDL subpopulations in African green monkeys.
Authors: Babiak J , Lindgren F T , Rudel L L
Published: June 2011

The effect of the type of dietary fat on the concentrations and compositions of high density lipoprotein (HDL) subpopulations was studied in groups of African green monkeys consuming 40% of calories as fat supplied as saturated fat (P/S = 0.3) or polyunsaturated fat (P/S = 2.2) in the presence of either 0.8 mg or 0.03 mg cholesterol/kcal. Plasma HDL cholesterol concentrations were lower in polyunsaturated fat-fed animals. The distribution of mass among HDL subfractions was assessed by analytic ultracentrifugation (AnUC), density gradient ultracentrifugation (DGUC), and polyacrylamide gradient gel electrophoresis (GGE). This made it possible to characterize and quantitate the HDL subpopulations HDL2b, HDL2a, HDL3a, HDL3b, and HDL3c (arranged in order of decreasing particle size and decreasing cholesterol content). Polyunsaturated fat-fed animals had lower concentrations of the large, cholesterol-rich HDL2b subpopulation, as well as higher concentrations of intermediate size HDL (HDL2a and HDL3a on the high cholesterol diet; HDL3a and HDL3b on the low cholesterol diet). Consistent with the observed fat-related redistribution of HDL mass, the saturated fat-fed monkeys had higher apo A-I/apo A-II ratios. The larger HDL often contained detectable apo E; however, the concentration of apo E in HDL was low in both saturated and polyunsaturated fat-fed animals. Thus, compared to saturated fat, dietary polyunsaturated fat induced the formation of smaller size HDL subpopulations and, therefore, an overall lower cholesterol content per particle for plasma HDL.
Ca++ antagonists and ACAT inhibitors promote cholesterol efflux from macrophages by different mechanisms. II. Characterization of intracellular morphologic changes.
Authors: Robenek H , Schmitz G
Published: June 2011

The effects of the slow Ca++ channel blocker, nifedipine, and ACAT inhibitor, octimibate, on cholesterol-loaded macrophages were compared at the ultrastructural level. The Ca++ antagonist induced the formation of membrane-surrounded "lamellar bodies" originating from lysosomes. The macrophages secreted these lamellar bodies, which were rich in phospholipids and cholesterol, into the culture medium even in the absence of cholesterol acceptors. In contrast, the ACAT inhibitor induced the formation of lamellar bodies originating from lipid droplets, which were also surrounded by membranes. There is strong evidence that these latter membranes were newly synthesized at the margin of the lipid droplets by the endoplasmic reticulum. The lamellar bodies descending from lipid droplets after ACAT inhibitor treatment were not secreted by the cells. They were stored in the cytoplasmic compartment in the absence of high density lipoproteins (HDL). When HDL were added to the medium, the lamellar bodies specifically interacted with endosomes containing the internalized HDL particles and disappeared concomitantly with an enhanced HDL-mediated cholesterol efflux. From the biochemical data in the accompanying article and the morphological data here, we conclude that macrophages release cholesterol by two major pathways: 1) an HDL-independent secretion of lamellar bodies containing cholesterol, which originate from lysosomes, and 2) an HDL-dependent release of cholesterol via the formation of lamellar bodies descending from lipid droplets, which intracellularly fuse with HDL-containing endosomes. The cholesterol-enriched HDL are then secreted as intact lipoproteins.
Tissue-type plasminogen activator antigen and plasminogen activator inhibitor in diabetes mellitus.
Authors: Auwerx J , Bouillon R , Collen D , Geboers J
Published: June 2011

Parameters of fibrinolysis, including euglobulin fibrinolytic activity, tissue-type plasminogen activator (t-PA) antigen, plasminogen activator inhibitor (PA-inhibitor) activity, and plasmin-alpha 2-antiplasmin complex (PAP) were studied in 62 patients (35 women and 27 men; ages 53 +/- 16 years) with either insulin-dependent (IDDM) or noninsulin-dependent (NIDDM) diabetes mellitus. Compared to a control group of similar age (n = 57), the diabetic patients had a significantly lower mean euglobulin fibrinolytic activity (1.2 +/- 0.7 vs. 1.7 +/- 1.1 ng/ml, p less than 0.01) but significantly higher mean t-PA antigen (15.7 +/- 8.4 vs. 6.6 +/- 2.9 ng/ml, p less than 0.001) and PA-inhibitor activity (2.6 +/- 1.3 vs. 1.5 +/- 0.7 IU/ml, p less than 0.001) levels. Significant univariate correlations were observed between PA-inhibitor activity and age (r = 0.32, p less than 0.05), diastolic blood pressure (r = 0.42, p less than 0.01) and euglobulin fibrinolytic activity (r = -0.40, p less than 0.01). In multivariate analysis, only body mass index (positively) and euglobulin fibrinolytic activity (negatively) remained significantly related to PA-inhibitor activity in the total diabetic population as well as in the NIDDM group. The only parameter in the IDDM group significantly related to PA-inhibitor activity was diastolic blood pressure. These results suggest that PA-inhibitor plays a role in the regulation of fibrinolysis in diabetes patients and that factors like obesity and hypertension may be related to reduced fibrinolysis via PA-inhibitor levels.
Presence of a modified low density lipoprotein in humans.
Authors: Avogaro P , Bon G B , Cazzolato G
Published: June 2011

Low density lipoproteins (LDL) collected from 18 fasting humans were subjected to ion exchange chromatography on DEAE Sepharose. By this procedure, a LDL subfraction was isolated with an electric charge more negative than the LDL bulk. This LDL appeared to be mainly characterized by low phospholipid content, high free cholesterol and protein content, low esterified/free cholesterol ratio, and a high content of conjugated dienes, particularly of cholesterol esters. This subfraction, in an amount ranging from 5% to 20% of total LDL, was characterized by the presence of apo B-100 and protein aggregates that were reactive to anti-apo B monoclonal antibodies. Electron microscopy showed the more electronegative LDL to be heterogeneous in size with a tendency to aggregate. This LDL had low binding capacity with high affinity receptors of fibroblasts and low immunoreactivity with the monoclonal antibodies that recognize the receptor binding domain of apo B. Finally, the incubation of this LDL subfraction with cultured macrophages led to a higher increase in cellular cholesterol in spite of a lower rate of uptake as compared to the LDL bulk and to acetyl-LDL. The more electronegative LDL subfraction that we isolated for chemico-physical behavior and conjugated diene content may represent the peroxidized aliquot of human LDL.
George Lyman Duff memorial lecture. Progression and regression of atherosclerotic lesions. Insights from lipid physical biochemistry.
Authors: Small D M
Published: June 2011

This review summarizes the evidence that the physical properties of lipids which accumulate in the intima play major roles in the progression and regression of lesions of atherosclerosis. All of the three major classes of lipids that accumulate in lesions (phospholipids, cholesterol, and cholesterol esters) are water insoluble. Phospholipids and cholesterol esters are almost mutually insoluble, but cholesterol, a crystalline solid at 37 degrees C, has considerable solubility in phospholipid bilayers and cholesterol esters. In normal infant intima, cholesterol is solubilized by phospholipid membranes. During fatty streak development, groups of cells are stimulated to take up more cholesterol than they excrete. The excess cholesterol is biochemically converted to cholesterol ester, which separates as droplets to form foam cells. Some fatty streaks then undergo a transition to an intermediate lesion containing excess cholesterol which is carried in cholesterol-supersaturated membranes and droplets. When nucleation of this excess cholesterol occurs, it precipitates as crystals; their formation coincides with the onset of necrosis and plaque formation. The hallmark of plaque is the presence of inert cholesterol crystals. They appear to form from hydrolysis of the older deposits of cholesterol esters in the base of intermediate lesions. Thus, the lipids in plaques are stratified, with recently deposited cholesterol esters present in the luminal part of the intima and older deposits in the deeper regions. When plasma cholesterol is lowered below about 150 mg/dl, lipids are mobilized from lesions and regression gradually occurs. Early in the regression process, cholesterol esters are reduced at least partly by hydrolysis to yield cholesterol, some of which may crystallize and inhibit rapid regression. After prolonged periods of low plasma cholesterol, cholesterol esters and foam cells disappear and crystalline cholesterol gradually dissolves, leading to true regression.
Coordinate changes in levels of human serum low and high density lipoprotein subclasses in healthy men.
Authors: Krauss R M , Williams P T , Lindgren F T , Wood P D
Published: June 2011

Measurement of serum lipoproteins by analytic ultracentrifugation revealed significant correlations involving subfractions of low density (LDL) and high density (HDL) lipoproteins in 81 men studied cross-sectionally at baseline and longitudinally during a 1-year exercise trial. One-year changes in lipoprotein levels in 38 exercising men and in 30 sedentary controls showed correlations that paralleled those observed at baseline. Positive correlations observed between plasma levels of larger, more buoyant LDL of flotation rate (Sof) 7 to 10 (LDL-I) and HDL2 may be due to processes that also coregulate changes in levels of these lipoprotein subclasses. Similarly, positive correlations among smaller, more dense LDL of Sof 2 to 6 (LDL-III), IDL, and HDL3 suggest that levels of these lipoprotein species are also coordinately regulated. An inverse correlation of change in LDL-I with change in LDL-III raises the possibility of precursor-product relationships between LDL in these categories. Thus, changes in lipoproteins which are related to coronary disease risk are not independent of one another, and the development of coronary disease may be influenced by processes linking the metabolism of individual IDL, LDL, and HDL components.