bluuebunny/crossref_metadata_2025 huggingface dataset:
Organization of von Willebrand factor on surface-activated platelets.
Authors: Escolar G , White J G
Published: June 2011

The distribution and organization of von Willebrand factor (vWF) multimers on platelets after surface activation have not been fully characterized. In the present study, washed human platelets were allowed to interact with Formvar-coated, electron microscope grids for 20 minutes at 37 degrees C and then fixed. After fixation, cells were washed and then incubated with buffer alone, human plasma, human plasma preincubated with ristocetin (1.2 mg/mL), purified human vWF plus ristocetin, or bovine plasma. Macromolecular complexes were revealed by ultrastructural immunocytochemistry employing a polyclonal antibody against vWF and protein A-gold (PAG) as the electron-dense probe. vWF multimers were not present in discoid platelets but appeared on the central zone of dendritic cells and over larger central areas of fully spread platelets. Exposure to human plasma alone did not affect the distribution of electron-dense probes for vWF in central regions of surface-activated cells. Incubation of spread platelets with ristocetin-activated human plasma or bovine plasma resulted in the appearance of randomly dispersed, mottled areas of increased density covering the surface from edge to edge. Exposure to vWF antibody and PAG resulted in specific labeling of the dense areas in a serpentine, linear array. The gold-probe distribution suggested that the vWF multimers were not superimposed and were distributed in a random, irregular manner from edge to edge with label-free, clear areas between them. The results extend previous observations demonstrating that glycoprotein Ib-IX receptors are not spontaneously cleared from the plasma membranes of surface-activated platelets by showing that the receptor function of glycoprotein Ib-IX complex remains unchanged.
Involvement of the hemostatic system in the insulin resistance syndrome. A study of 1500 patients with angina pectoris. The ECAT Angina Pectoris Study Group.
Authors: Juhan-Vague I , Thompson S G , Jespersen J
Published: June 2011

Hyperinsulinemia, a major indicator of insulin resistance, may exert its influence on the risk of coronary artery disease partially through disturbances of the hemostatic system. The relations of fasting insulin concentrations with the degree of coronary atherosclerosis, other coronary risk factors (including some markers of the insulin resistance syndrome such as body mass index and triglyceride), markers of inflammation, and hemostatic factors were investigated in 1484 patients with angina pectoris. Mean insulin levels were higher in patients with one or more coronary vessel stenoses than in those without (9.9 microU/mL compared with 9.0 microU/mL, P < .0001). However, the association the presence of vessel stenoses was stronger in patients with a previous myocardial infarction than in those without. Insulin increased markedly (P < .0001) and independently of other risk factors with age body mass index, triglyceride concentration, and markers of inflammation, such as white blood cell count and C-reactive protein. The strongest relations between insulin and hemostatic factors were observed with fibrinolytic variables, particularly plasminogen activator inhibitor-1 (PAI-1) levels (r = .44, P < .0001). This relation decreased somewhat (r = .29) after simultaneous adjustment for markers of the insulin resistance syndrome, mainly body mass index and triglycerides, but not after adjustment for markers of inflammation. Therefore, we propose that increased PAI-1 levels, which are essentially related to the classic metabolic aspect of the insulin resistance syndrome, have to be included in this syndrome.(ABSTRACT TRUNCATED AT 250 WORDS)
Metabolism of LDL in mast cells recovering from degranulation. Description of a novel intracellular pathway leading to proteolytic modification of the lipoprotein.
Authors: Kokkonen J O , Lindstedt K A , Kovanen P T
Published: June 2011

Rat serosal mast cells contain cytoplasmic secretory granules composed of a proteoglycan matrix in which histamine and neutral proteases are embedded. On stimulation, these granules are exocytosed, but some of them remain in the degranulation channels where on exposure to the extracellular fluid, they lose their histamine and a fraction of their proteoglycans. In vitro, such granule remnants efficiently bind low density lipoprotein (LDL) present in the incubation medium. After a lag period of about 10 minutes, the granule remnants, still within the channels and coated with LDL particles, are internalized by the parent mast cells. During subsequent recovery from degranulation, the apolipoprotein B of the intracellularly located remnant-bound LDL becomes efficiently (up to 70%) degraded by the proteolytic enzymes of the granule remnants. Since the granule remnants lack cholesteryl esterase activity, no LDL cholesterol is made available for cellular nutrition. Instead, selective proteolytic degradation of the bound LDL leads to formation of LDL particles enlarged by fusion on the granule remnant surface. In response to restimulation of the mast cells, about 50% of the fused LDL particles are exocytosed with the granule remnants. Of these, about one in five are expelled into the incubation medium. The granule remnants that again remain in the degranulation channels bind and internalize more LDL. This "round trip" of LDL in mast cells exposed to repeated stimulation constitutes a hitherto-unknown intracellular pathway for modification of LDL.
Localization and smooth muscle cell composition of atherosclerotic lesions in Watanabe heritable hyperlipidemic rabbits.
Authors: Giuriato L , Scatena M , Chiavegato A , Zanellato A M , Guidolin D , Pauletto P , Sartore S
Published: June 2011

Morphological techniques (histology and electron microscopy), as well as immunofluorescence assays, were applied to the study of the localization and smooth muscle cell (SMC) composition of atherosclerotic lesions in Watanabe heritable hyperlipidemic (WHHL) rabbits during a 4.5-month period. Vascular segments from different arteries (carotid, coronary, and iliac arteries) or from the same vessel at different levels (aorta) of animals at days 7, 15, 30, 40, 60, 90, and 135 showed that the atherosclerotic lesion first became visible at the level of the aortic arch in 60-day-old WHHL animals. Histological examination of serial cryosections from this vascular region indicated that the vascular lesion arose from a cavity in the media layer, located anatomically at the level of the juncture of the ligamentum arteriosum with the aortic arch. This aortic arch cavity is formed during the postnatal closure of the ductus arteriosus and is characterized by the presence of a thickened intima, which was absent in the other vascular regions examined. Immunofluorescence comparison of normal and atherosclerotic tissues from the aortic arch cavity wall with the use of monoclonal antibodies specific for smooth muscle and nonmuscle myosin isoforms revealed the existence of distinct SMC populations. SMCs in the thickened intima showed a myosin isoform pattern peculiar to cells with a degree of maturation intermediate between the fully differentiated and the developing (fetal) aortic SMCs. By contrast, SMCs present in atherosclerotic lesions displayed a predominant fetal-type pattern of myosin isoform expression. The achievement of this myosin isoform content seems to be correlated with the accumulation of lipids in the intima. In the media subjacent to the intimal thickening or atherosclerotic lesion, SMCs primarily displayed an intermediate degree of maturation. In older WHHL animals and at this aortic level, the SMC composition of the atherosclerotic lesion did not change, whereas in the subjacent media, the cells of intermediate type almost disappeared. In the vascular regions in which the atherosclerotic lesion appeared at later stages, such as near the aortic bifurcation, the distribution of fetal and intermediate cell types in the atherosclerotic wall was similar to that taken at the aortic arch level. These results indicate that there is 1) a preferential anatomic site from which atherogenesis initiates in WHHL rabbits; 2) a time correlation between the accumulation of lipids in the wall and the phenotypic change of SMCs toward a poorly differentiated cell type; and 3) the tendency for SMCs to follow the same differentiation pattern in early atherosclerotic lesions, irrespective of the site and time at which they develop.
Decreased postprandial response to a fat meal in normotriglyceridemic men with hypoalphalipoproteinemia.
Authors: Miller M , Kwiterovich P O , Bachorik P S , Georgopoulos A
Published: June 2011

The plasma level of high density lipoprotein cholesterol (HDL-C) has been reported to be inversely correlated with the level of triglycerides (TGs) and the magnitude of postprandial lipemia because subjects with low HDL-C accompanying high TG levels often have an increased postprandial response to a fat load. However, information is limited regarding the postprandial response to a fat load in subjects with low HDL-C and normal fasting TG values (hypoalphalipoproteinemia [hypoalpha]). We administered an oral fat load (70 g/m2 of body surface area) to six subjects with hypoalpha and six aged-matched control subjects. Plasma levels of lipids and lipoproteins and the mass of triglyceride-rich lipoproteins (TRLs: Sf > 100 and Sf 20-100) were measured every 2 hours for 8 hours. The mass and chemical composition of Sf > 100 or Sf 20-100 TRLs were not different between the fasting groups; postprandial Sf > 100 but not Sf 20-100 TRLs (mean +/- SD) was significantly lower in subjects with hypoalpha (200.4 +/- 64.8 mg/dL versus 110.6 +/- 50.9 mg/dL; analysis of variance, F test, p = 0.04). In the hypoalpha subjects, the compositions of postprandial Sf > 100 TRLs were TG poor and cholesterol and phospholipid enriched (p < 0.001) while the Sf 20-100 TRLs were enriched in cholesterol and phospholipid but relatively protein depleted (p = 0.002).(ABSTRACT TRUNCATED AT 250 WORDS)
Plasma triglyceride and LDL heterogeneity in familial combined hyperlipidemia.
Authors: Hokanson J E , Austin M A , Zambon A , Brunzell J D
Published: June 2011

Familial combined hyperlipidemia (FCHL) is a genetic disorder characterized by increases in plasma cholesterol and/or triglyceride, elevated apolipoprotein B, and heterogeneous low density lipoprotein (LDL). To examine the relation between plasma triglyceride concentrations and LDL heterogeneity, 13 hypertriglyceridemic FCHL patients with a predominance of small LDL (LDL subclass phenotype B) were treated with gemfibrozil. The distribution of LDL was determined using nondenaturing gradient gel electrophoresis and nonequilibrium density gradient ultracentrifugation. Mean plasma triglyceride levels decreased 55% (p < 0.01) after 3 months of treatment. Mean LDL peak particle size remained small (247 +/- 4 versus 249 +/- 5 A), and the correlation between change in plasma triglyceride concentrations and a change in LDL peak particle size was not significant. Individual changes in LDL flotation rate (Rf) were, however, inversely correlated with changes in triglyceride concentration (R = 0.60, p < 0.05). Although mean LDL Rf increased during treatment (p < 0.005) due to an increase in buoyant LDL, dense LDL remained elevated compared with that of a control population. Thus in FCHL patients, small, dense LDL persists despite decreases in plasma triglyceride concentrations.
Modulation of the expression of human LDL-Apo B-100 epitopes by lipids and apolipoproteins.
Authors: Harduin P , Tailleux A , Fruchart J C , Fievet C
Published: June 2011

The purpose of the present study was to determine the immunochemical properties of apolipoprotein (apo) B-100 associated with low density lipoprotein (LDL) in relation to lipid and apolipoprotein composition. LDLs were isolated by sequential ultracentrifugation (1.019 < d < 1.050 g/mL) from two healthy volunteers and 21 dyslipidemic patients to obtain heterogeneous samples of LDL. Lipid (free cholesterol, cholesteryl esters, triglycerides, and phospholipids) and apolipoprotein contents (apo B, apo C-III, apo E) were determined in each LDL sample. Immunoreactivities of apo B were tested in solid-phase competitive-binding radioimmunoassays using seven monoclonal anti-LDL antibodies that reacted with defined epitopes of apo B-100. The relation between lipid and/or protein variables and the immunoreactivity of apo B was evaluated by successive use of Spearman's rank simple correlation, partial correlation, and canonical correlation analyses. The canonical correlation analysis showed that apo B-100 immunoreactivity on LDL is highly dependent on lipid and apolipoprotein composition simultaneously. The results confirmed the influence of surface and core lipids on the expression of the apo B-100 epitopes, independent of their location on the molecule. However, the lipid requirement of LDL strongly influences the expression of epitopes mapped in the LDL receptor-recognition domain. In contrast to apo E, apo C-III does not seem to influence the expression of the apo B-100 epitopes in the LDL range studied.(ABSTRACT TRUNCATED AT 250 WORDS)
HMG CoA reductase inhibitors. In vivo effects on carotid intimal thickening in normocholesterolemic rabbits.
Authors: Soma M R , Donetti E , Parolini C , Mazzini G , Ferrari C , Fumagalli R , Paoletti R
Published: June 2011

The in vivo activity of different 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase inhibitors (vastatins) on neointimal formation induced by insertion of a flexible collar around one carotid artery of normocholesterolemic rabbits was investigated. The contralateral carotid artery served as a sham control. Pravastatin, lovastatin, simvastatin, and fluvastatin were given mixed with food at daily doses of 20 mg/kg body wt for 2 weeks starting on the day of collar placement. The treatment with vastatins did not modify rabbit plasma cholesterol concentrations. The neointimal formation was assessed by measuring the cross-sectional thickness of intimal and medial tissues of fixed arteries with light microscopy. Fourteen days after collar placement, intimal hyperplasia (mostly cellular) was pronounced in treated carotid arteries. The intimal/medial (I/M) tissue ratio was 12-fold higher in treated arteries than in arteries without the collar (0.36 +/- 0.04 versus 0.03 +/- 0.02). Animals treated with lovastatin (n = 12), simvastatin (n = 12), and fluvastatin (n = 12) showed significantly less neointimal formation; I/M tissue ratios were 0.24 +/- 0.03, 0.20 +/- 0.03, and 0.17 +/- 0.03, respectively. The inhibition elicited by pravastatin (n = 12, 0.32 +/- 0.03) did not reach statistical significance. alpha-Actin antibody immunofluorescence analysis of serial sections revealed that cells present in the hyperplastic intima were mostly myocytes. Rates of intimal myocyte proliferation were also measured by incorporation of 5-bromo-2'-deoxyuridine, a thymidine analogue, into replicating DNA. Immunofluorescence analysis showed that 5-bromo-2'-deoxyuridine was actively incorporated into intimal myocytes after ++reinsertion of the collar, with a labeling index (percent of labeled myocytes) of 2.15 after 14 days.(ABSTRACT TRUNCATED AT 250 WORDS)
Two patterns of LDL metabolism in normotriglyceridemic patients with hypoalphalipoproteinemia.
Authors: Vega G L , Grundy S M
Published: June 2011

The objective of this study was to determine whether normotriglyceridemic patients with low levels of high density lipoprotein (HDL) cholesterol have concomitant defects in the metabolism of low density lipoproteins (LDLs). To address this question, measurements of turnover rates of apolipoprotein A-I (apo A-I) and LDL apolipoprotein B (apo B) were made in 36 middle-aged men with low HDL cholesterol (< 40 mg/dL), normal triglyceride (< 250 mg/dL), and normal total cholesterol (< or = 90th percentile) levels. Similar measurements were made in eight hypertriglyceridemic men having low HDL levels. For control, turnover rates of LDL apo B were measured in 24 healthy, normolipidemic men, and apo A-I kinetics were determined in 20 other healthy men with normal HDL cholesterol levels. In all patients with low HDL levels, fractional catabolic rates (FCRs) for apo A-I were increased compared with control subjects; in contrast, input rates for apo A-I in low-HDL patients were similar to control. Hypertriglyceridemic patients had significantly higher FCRs for LDL (0.463 +/- 0.040 pool/day, [mean +/- SEM]) than control subjects (0.328 +/- 0.008 pool/day, p < 0.001). In normolipidemic patients having low HDL, a bimodal pattern of LDL-apo B kinetics was observed. For 23 low-HDL patients, FCRs for LDL apo B averaged 0.450 +/- 0.017 pool/day and were significantly higher than control values. Additionally, in these patients, levels of very low density lipoprotein plus intermediate density lipoprotein (VLDL+IDL) cholesterol and VLDL+IDL apo B were higher than in control subjects (54 +/- 3 versus 32 +/- 3 mg/dL and 25 +/- 2 versus 18 +/- 1 mg/dL, respectively). The remaining 13 low-HDL patients had lower and essentially normal FCRs for LDL (0.300 +/- 0.009 pool/day); these patients also had relatively low levels of cholesterol and apo B in VLDL+IDL. Thus, two patterns of LDL kinetics were present in normotriglyceridemic patients with low HDL levels. One pattern was indistinguishable from that typically present in patients with hypertriglyceridemia, whereas the other was similar to normal control subjects. These two patterns of LDL-apo B kinetics may reflect different mechanisms for the causation of low HDL cholesterol concentrations.
Nifedipine inhibits accumulation of LDL and cholesterol in the aorta of the normocholesterolemic rabbit.
Authors: Görög P , Born G V
Published: June 2011

The effect of 5 days of oral nifedipine treatment (approximately 1 mg/kg per day in drinking water) on low density lipoprotein (LDL) and cholesterol accumulation in rabbit arteries was determined. Compared with control aortas, nifedipine treatment (n = 5) significantly reduced homologous 125I-tyramine cellobiose-LDL accumulation (control versus nifedipine: 45.93 +/- 4.3 versus 20.14 +/- 3.1 ng LDL per milligram dry weight x10(-3), p = 0.001) while the reduction of human LDL accumulation (n = 5) was not significant (49.1 +/- 6.1 versus 35.5 +/- 4.1 ng LDL per milligram dry weight x10(-3)). Aortic accumulation of orally administered [3H]cholesterol was also inhibited by nifedipine (352 +/- 34 versus 257 +/- 16 ng cholesterol per milligram dry weight x10(-3), n = 10, p = 0.022). These findings suggest a possible mechanism for the antiatherosclerotic effect of nifedipine.
Fenofibrate and LDL metabolic heterogeneity in hypercholesterolemia.
Authors: Caslake M J , Packard C J , Gaw A , Murray E , Griffin B A , Vallance B D , Shepherd J
Published: June 2011

Metabolic heterogeneity in low density lipoprotein (LDL) may be detected by examination of the daily urinary excretion rate of radioactivity after injection of trace-labeled lipoprotein. Two distinct pools are observed within LDL. The first (pool A) is cleared rapidly from the plasma, whereas the second (pool B) is catabolized more slowly. In the present study we examined LDL metabolism in seven hypercholesterolemic subjects (six women and one man) before and during fenofibrate therapy. Comparison with normocholesterolemic individuals showed that the pretreatment high LDL levels in the hypercholesterolemic subjects resulted from an accumulation of apoprotein-LDL (apo-LDL) mass in pool B (2,077 +/- 174 mg versus 787 +/- 70 mg in normal subjects, p < 0.002). Pool A apo-LDL was present at normal levels (approximately 1,000 mg), although its fractional catabolic rate was reduced (0.39 +/- 0.06 versus 0.61 +/- 0.03 pool/day in normal subjects, p < 0.01). Fenofibrate therapy (100 mg t.i.d. for 8 weeks) produced substantial reductions in plasma cholesterol (29%; p < 0.001), triglycerides (36%; p < 0.001), and LDL cholesterol (30%; p < 0.001). The latter was associated with a 30% decrease in circulating apo-LDL mass (2,312 +/- 200 mg versus 3,279 +/- 264 mg before treatment, p < 0.005). This resulted from a combination of two effects. First, although overall LDL apoprotein B production did not change, there was a shift from pool B to pool A. Pool A input was 400 +/- 74 mg/day pretreatment versus 706 +/- 62 mg/day on fenofibrate; pool B input was 422 +/- 35 mg/day pretreatment versus 258 +/- 41 mg/day on the drug. At the same time, catabolism of pool A rose from 0.39 +/- 0.06 to 0.66 +/- 0.08 pool/day (p < 0.05). We hypothesize that the shift from pool B to pool A resulted from a drug-induced decrease in the particle size of very low density lipoprotein made by the liver, which in turn favored the formation of more rapidly catabolized LDL. Overall, the rate of apo-LDL degradation by the receptor route (as detected using a combination of native and 1,2-cyclohexanedione-modified LDL tracers) rose 43% on the drug, whereas the amount cleared by the receptor-independent pathway did not change. Fenofibrate, therefore, appears not only to promote LDL catabolism via the receptor-mediated pathway but also, by lowering plasma triglyceride levels, inhibits the formation of slowly metabolized, potentially atherogenic LDL particles.
Platelet-derived growth factor and transforming growth factor-beta 1 differentially affect the synthesis of biglycan and decorin by monkey arterial smooth muscle cells.
Authors: Schönherr E , Järveläinen H T , Kinsella M G , Sandell L J , Wight T N
Published: June 2011

Platelet-derived growth factor (PDGF) and transforming growth factor-beta 1 (TGF-beta 1), two growth-regulatory peptides with opposite effects on arterial smooth muscle cell (ASMC) proliferation, were examined for their influence on the synthesis of two small chondroitin sulfate/dermatan sulfate proteoglycans (CS/DS PGs) called biglycan and decorin. Quiescent ASMCs treated with either PDGF or TGF-beta 1 for 24 hours increased [35S]sulfate incorporation into biglycan 3.3- and 2.9-fold, respectively, whereas the incorporation of [35S]sulfate into decorin was not significantly affected. Treatment with TGF-beta 1 but not PDGF more than doubled the steady-state level of messenger RNA (mRNA) transcripts hybridizing to a complementary DNA (cDNA) encoding biglycan. Both growth factors had little or no effect on steady-state levels of mRNA transcripts hybridizing to a decorin cDNA. Incorporation of [35S]sulfate into biglycan glycosaminoglycan (GAG) was maximal by 12 to 18 hours after either PDGF or TGF-beta 1 addition. Both PDGF and TGF-beta 1 increased the molecular sizes of biglycan and decorin. This increase was a result of the synthesis of longer GAG chains substituted on the core proteins of both PGs. PDGF but not TGF-beta 1 led to an increase of more than twofold in the ratio of 6'- to 4'-sulfated disaccharides in these newly synthesized GAG chains. These results indicate that PDGF and TGF-beta 1 have specific but different effects on the synthesis of small CS/DS PGs by monkey ASMCs in culture.
Lipoprotein[a] concentrations and apolipoprotein[a] phenotypes in Caucasians and African Americans. The CARDIA study.
Authors: Marcovina S M , Albers J J , Jacobs D R , Perkins L L , Lewis C E , Howard B V , Savage P
Published: June 2011

Little is known about racial differences in lipoprotein[a] (Lp[a]) concentrations and apolipoprotein[a] (apo[a]) phenotypes. Lp[a] protein concentrations were determined by a double monoclonal antibody enzyme-linked immunosorbent assay method in 4165 Caucasian and African American men and women from four US communities. Apo[a] phenotypes were determined by polyacrylamide gel electrophoresis and immunoblotting on a random subset of these participants (n = 690). The distribution of Lp[a] protein levels in Caucasians was highly skewed (mean, 6.9 mg/dL; median, 3.7 mg/dL). In contrast, the distribution in African Americans was less skewed (mean, 13.0 mg/dL; median, 11.6 mg/dL), and Lp[a] protein levels were approximately double those in Caucasians within most apo[a] phenotypes. The previously described inverse relationship between apo[a] size and Lp[a] concentration was generally confirmed in Caucasians, but the B phenotype had lower Lp[a] levels than the S1 or S2 phenotype. In African Americans, both the B and S1 phenotypes had lower Lp[a] levels than the S2 phenotype. The frequencies of the apo[a] phenotypes in African Americans differed from those in Caucasians (P < .001) and also differed from the frequencies reported in a Sudanese population (P < .002). African Americans had a lower frequency of the S2 phenotype than Caucasians (8% vs 18%; P < .01) and a higher frequency of S3 (36% vs 25%; P < .01). As compared with the data reported in Sudanese, African Americans also had a higher frequency of the S3 phenotype (36% vs 14%; P < .001) and a lower frequency of S4 (29% vs 44%; P < .01).(ABSTRACT TRUNCATED AT 250 WORDS)
Characterization of six patients who are double heterozygotes for familial hypercholesterolemia and familial defective apo B-100.
Authors: Rubinsztein D C , Raal F J , Seftel H C , Pilcher G , Coetzee G A , van der Westhuyzen D R
Published: June 2011

Familial defective apolipoprotein B-100 (FDB) and familial hypercholesterolemia (FH) are the common causes of monogenic primary hypercholesterolemia. An individual of mixed English and Afrikaner descent with both FDB and the FH Afrikaner-1 low-density lipoprotein receptor mutation was identified in our laboratory. Subsequent analysis of her extended family revealed the presence of heterozygotes for either FH Afrikaner-1, FH Afrikaner-2, or FDB as well as five additional double heterozygotes for FH Afrikaner-1 and FDB and one "complex" heterozygote with all three mutations. The hypercholesterolemic and clinical features of the pure FDB subjects were similar to those of the pure FH heterozygotes. The double heterozygotes with both FH and FDB have lipid levels and clinical features that are intermediate in severity between heterozygous and homozygous FH.
Comparison of gene expression in bovine aortic endothelium in vivo versus in vitro. Differences in growth regulatory molecules.
Authors: Liaw L , Schwartz S M
Published: June 2011

Many studies of the endothelium have assumed equivalence between cultured confluent cells and an endothelial lining in vivo. We compared gene expression of bovine aortic endothelial cells (BAECs) in culture versus freshly isolated cells from bovine aortas. Our technique of harvesting in vivo tissue yielded cells that were endothelial by the criteria of their containing von Willebrand factor (vWF) and lacking smooth muscle alpha-actin, by both immunocytochemistry and mRNA analyses. We found that several genes are overexpressed when BAECs are placed into culture, including basic fibroblast growth factor, platelet-derived growth factor B-chain, and thrombospondin. On the other hand, message for vWF is highly expressed in vivo and at lower levels in confluent cultures. The transcripts for transforming growth factor-beta, plakoglobin, and flg (fms-like gene, FGF receptor-1) are comparable in vitro and in vivo. These results demonstrate that significant changes in gene expression occur in the transition from in vivo conditions to tissue culture of endothelial cells. Studies of in vitro endothelium may poorly reflect a quiescent endothelial lining in vivo but may be more similar to cells responding to injury or angiogenic stimuli.
Responsiveness of aortic smooth muscle cells to soluble growth mediators is influenced by cell-matrix contact.
Authors: Thie M , Harrach B , Schönherr E , Kresse H , Robenek H , Rauterberg J
Published: June 2011

Excessive proliferation and overexpression of collagens by smooth muscle cells (SMCs) are important features of atherogenesis. To understand the role of the extracellular matrix in the regulation of these processes, we examined proliferation and protein/collagen synthesis of SMCs in contact with a collagen matrix. Adult pig SMCs were isolated from the aortic media by collagenase digestion, subcultured as monolayers, and then embedded into a three-dimensional network of type I collagen, ie, a collagen lattice. Cells were subsequently exposed to growth-promoting media, and their behavior was observed in comparison with monolayer cultures on plastic. Treatment of monolayers with increasing concentrations of fetal calf serum resulted in activation of the cell cycle, onset of cell proliferation, and increased protein/collagen synthesis. In contrast, similar treatment of collagen lattice-cultured SMCs failed to influence cell proliferation and protein/collagen synthesis. However, stimulation of proliferation of lattice-cultured SMCs by platelet-derived growth factor-A/B was feasible; nevertheless, the rate of proliferation was modest compared with monolayers. In addition, the onset of proliferation was accompanied by a decrease in collagen synthesis of the cells. Thus, a collagenous matrix appears to suppress the responsiveness of SMCs to soluble growth mediators. It is speculated that interactions between SMCs and the extracellular matrix may modify proliferation and protein/collagen synthesis of cells not only in vitro but also in vivo during atherogenesis by making and breaking binding sites between extracellular collagen and matrix receptors.
ACE inhibition with perindopril and atherogenesis-induced structural and functional changes in minipig arteries.
Authors: Charpiot P , Rolland P H , Friggi A , Piquet P , Scalbert E , Bodard H , Barlatier A , Latrille V , Tranier P , Mercier C
Published: June 2011

The effects of angiotensin-converting-enzyme (ACE) inhibition on atherosclerosis-induced changes in arterial function are unknown, as well as whether they are coupled to improvements of structural alterations in the arterial wall. An atherogenic (A) diet and the ACE inhibitor perindopril (P) were given concomitantly for 4 months to seven adult Pitman-Moore minipigs (7 months of age; A+P animals), which were compared with seven A and seven control (C) animals. Perindopril, at a daily dose of 4 mg PO that is commonly used in the clinical setting, induced a continuous 70% inhibition of serum ACE activity. At the end of the study, the atherosclerosis-induced impairment of arterial flow was investigated via the hemodynamics and vascular rheology of hindlimb arteries in non-barbiturate-anesthetized pigs. Structural alterations were evaluated from the histopathology of lesions in the arterial tree (abdominal aorta, left interventricular coronary artery [LIVCA], and brachiocephalic trunk [BCT]), with particular attention given to the analysis of the structure and composition of aortic elastic fibers. Atherosclerosis impaired the function of both capacitance and resistance arteries. Blood pressure (BP) rose significantly because of increased hindlimb peripheral resistance (HPR) and aortic input impedance (Zc), although blood flow was not affected. Altered aortic stress and elastic responses revealed that the stiffness of the aorta was markedly increased because of increased wall tension and reduced viscoelasticity, the viscous component being blunted in the arterial wall. Perindopril significantly opposed these alterations by reducing BP, HPR, and Zc and by returning parietal stiffness values to C values by increasing aortic compliance. ACE inhibition prevented the alteration of both stress and elastic responses. Major fibroproliferative fatty lesions were observed in the aorta and LIVCA, while moderate fibrosclerotic lesions were found in the BCT. Computerized densitometric analysis of orcein-stained elastin showed that elastic laminae fragmentation was prominent in the abdominal aorta, less in the LIVCA, and moderate in the BCT. Furthermore, the elastin content was reduced in the atherosclerotic aorta, although this loss of elastin was not associated with changes in the biochemical nature of alkali-insoluble elastin. Perindopril significantly prevented the development of atherosclerosis in the abdominal aorta, LIVCA, and BCT by decreasing the cross-sectional area of lesions as well as the number of lipid-laden cells in the abdominal aorta and LIVCA. In the abdominal aorta, ACE inhibition significantly prevented the alteration of elastic laminae by specifically preventing elastolytic fragmentation of dense elastic laminae, but it didn ot modify elastin content.(ABSTRACT TRUNCATED AT 400 WORDS)
Role of endogenous platelet-derived growth factor in arterial smooth muscle cell migration after balloon catheter injury.
Authors: Jackson C L , Raines E W , Ross R , Reidy M A
Published: June 2011

The process of intimal thickening after de-endothelializing injury to the rat carotid artery is dependent on the migration of smooth muscle cells from the media. Recent reports have suggested that platelet-derived growth factor may be an important mediator of migration after injury. We have addressed this issue by directly determining smooth muscle cell migration in injured arteries of animals depleted of platelets and after administration of an antibody that blocks platelet-derived growth factor. Because there is a reported association between plasminogen activator synthesis and smooth muscle cell migration, we assayed the activity levels of plasminogen activators after arterial injury and also assessed the effect of a plasmin inhibitor on migration. The data suggest that platelet-derived growth factor, released by platelets at sites of arterial injury, is an endogenous mediator of smooth muscle cell migration; that plasmin generation, catalyzed by tissue-type plasminogen activator, is necessary for migration; and that one way in which platelet-derived growth factor may act is by stimulation of the synthesis of tissue-type plasminogen activator by smooth muscle cells.
Influx, efflux, and accumulation of LDL in normal arterial areas and atherosclerotic lesions of white Carneau pigeons with naturally occurring and cholesterol-aggravated aortic atherosclerosis.
Authors: Schwenke D C , St Clair R W
Published: June 2011

This study investigated the hypothesis that increased influx of low-density lipoprotein (LDL) accounts for the natural development of atherosclerosis in a characteristic (susceptible) site in the distal thoracic aorta of White Carneau (WC) pigeons and the exacerbation of atherosclerosis by cholesterol feeding. The influence of dietary cholesterol-induced changes in LDL composition on LDL influx into the artery was also investigated. As a measure of the influx of LDL into the artery, we determined the arterial accumulation of radiolabeled LDL after 1 hour. Nine 50-month-old WC pigeons with naturally occurring atherosclerosis and seven 14-month-old WC pigeons with atherosclerosis accelerated by 10 months of cholesterol feeding were studied. In the absence of atherosclerotic lesions, we found no evidence for increased accumulation of LDL at the susceptible site. In fact, more LDL accumulated in less susceptible normal arterial areas near the heart (approximately 90 nl/h per square centimeter) than in the susceptible distal thoracic aorta (approximately 35 nl/h per square centimeter). In the absence of atherosclerotic lesions, LDL accumulation (nanoliters per hour per square centimeter) was not influenced by hypercholesterolemia, although mass transport of LDL cholesterol into the artery was increased. Naturally occurring atherosclerotic lesions accumulated five times as much LDL as the adjacent normal arterial area (P < .001), whereas cholesterol-aggravated atherosclerotic lesions in different arterial sites accumulated four to 26 times as much LDL as the adjacent normal artery (P < .05). Cholesterol-aggravated atherosclerotic lesions at the most susceptible site accumulated five times as much LDL as naturally occurring atherosclerotic lesions in the corresponding arterial site (823 +/- 241 vs 175 +/- 45 nl/h per square centimeter, mean +/- SEM; P < .005). Arterial accumulation of LDL was influenced very little by changes in LDL composition induced by cholesterol feeding. In another study with young WC pigeons free of atherosclerosis and other WC pigeons with cholesterol-aggravated atherosclerosis, we injected differently labeled LDL 0.5 and 1 hour before sacrifice to investigate whether efflux of LDL from the artery was significant during a 1-hour period of LDL uptake. Although efflux of LDL from all arterial sites occurred during 1 hour, differential efflux could not account for regional differences in 1-hour arterial LDL accumulation. This study suggests that the characteristic susceptibility of the distal thoracic aorta of WC pigeons to atherosclerosis and the exacerbation of atherosclerosis by cholesterol feeding cannot be explained by differences in influx or efflux of LDL.(ABSTRACT TRUNCATED AT 400 WORDS)
Abundant expression of apoprotein E by macrophages in human and rabbit atherosclerotic lesions.
Authors: Rosenfeld M E , Butler S , Ord V A , Lipton B A , Dyer C A , Curtiss L K , Palinski W , Witztum J L
Published: June 2011

Previous studies have demonstrated the presence of apoprotein (apo) E protein and message in arterial lesions. To determine the source of the synthesized apoE, we performed simultaneous in situ hybridization and immunocytochemistry on human and rabbit atherosclerotic tissue. Studies of serial sections of aortic atherosclerotic lesions from humans and hypercholesterolemic New Zealand White rabbits and Watanabe heritable hyperlipidemic rabbits revealed a similar pattern of macrophage-specific apoE expression in the rabbit and human lesions. In early lesions of rabbit atherosclerotic tissue, in which many macrophages were present, there was abundant expression of apoE mRNA. Northern blot analyses of total mRNA obtained from arterial macrophage-derived foam cells, freshly isolated from ballooned, cholesterol-fed New Zealand White rabbits, demonstrated positive hybridization with an apoE-specific riboprobe. Western blot analyses of conditioned media from the isolated foam cells placed in culture for up to 24 hours demonstrated the presence of secreted apoE. These studies demonstrated that in atherosclerotic lesions, arterial wall macrophages synthesize and secrete apoE and probably account for most of the apoE synthesized in the atherosclerotic artery.
Hypercholesterolemic effect of dietary cholesterol in diets enriched in polyunsaturated and saturated fat. Dietary cholesterol, fat saturation, and plasma lipids.
Authors: Lichtenstein A H , Ausman L M , Carrasco W , Jenner J L , Ordovas J M , Schaefer E J
Published: June 2011

Within the context of reduced-fat diets, the effects of incorporating a fat high in stearic acid and adding moderate amounts of dietary cholesterol were examined in 14 middle-aged and elderly women and men (range, 46 to 78 years) with low-density lipoprotein cholesterol (LDL-C) concentrations > 130 mg/dL (range, 133 to 219 mg/dL) at screening. The subjects consumed each of the five diets, which were as follows: (1) a baseline diet (35% fat with 13% saturated fatty acids [SFAs], 12% monounsaturated fatty acids [MUFAs], and 8% polyunsaturated fatty acids [PUFAs], and 128 mg cholesterol/1000 kcal); (2) a reduced-fat diet, in which two thirds of the fat was provided as corn oil (corn oil-enriched diet: 29% fat with 7% SFAs, 9% MUFAs, and 11% PUFAs and 85 mg cholesterol/1000 kcal), which met the National Cholesterol Education Program (NCEP) Step 2 guidelines; (3) a reduced-fat diet, in which two thirds of the fat was provided as beef tallow (beef tallow-enriched diet: 31% fat with 13% SFAs, 11% MUFAs, and 3% PUFAs and 109 mg cholesterol/1000 kcal); and two reduced-fat diets, one (4) enriched in corn oil and the other (5) enriched in beef tallow, to which moderate amounts of cholesterol in the form of egg yolk were incorporated (197 or 226 mg cholesterol/1000 kcal final cholesterol content in corn oil- or beef tallow-enriched diets, respectively). All diets were isocaloric and all food and drink were provided by the metabolic kitchen. Reducing the fat content of the diet resulted in decreased concentrations of LDL-C and high-density lipoprotein cholesterol (HDL-C).(ABSTRACT TRUNCATED AT 250 WORDS)
Lack of association between sex hormones and Lp(a) concentrations in American and Finnish men.
Authors: Haffner S M , Mykkanen L , Gruber K K , Rainwater D L , Laakso M
Published: June 2011

Sex hormones may play a role in the determination of cardiovascular disease. Recently lipoprotein(a) (Lp[a]) has been recognized as a risk factor for coronary heart disease. Estrogens and anabolic steroids have been reported to alter Lp(a) levels, yet no data are available on the association between in vivo concentrations of sex hormones and Lp(a) concentrations. We examined the possible associations of sex hormone-binding globulin, total and free testosterone, estradiol, and dehydroepiandrosterone sulfate to Lp(a) concentrations in men in two population-based studies (San Antonio Heart Study [n = 178] and a Finnish study on the association between insulin resistance and atherosclerosis [n = 87]). In neither study were sex hormones significantly related to Lp(a) concentrations. In addition, Lp(a) was significantly related to apolipoprotein(a) molecular weight (which was measured in the Finnish study only). These results were unchanged when Lp(a) concentrations were adjusted for apolipoprotein(a) molecular weight (a strong correlate of Lp[a] concentrations). We conclude that in vivo concentrations of sex hormones are unlikely to be associated with Lp(a) concentrations in men.
Epinephrine sensitizes human platelets in vivo and in vitro as studied by fibrinogen binding and P-selectin expression.
Authors: Hjemdahl P , Chronos N A , Wilson D J , Bouloux P , Goodall A H
Published: June 2011

Epinephrine (Epi) infusion influences platelet activation markers in vivo, but in vitro studies have mainly examined supraphysiological Epi concentrations and have yielded conflicting results. In this study whole-blood flow-cytometric measurements of platelet fibrinogen binding and P-selectin expression were used to compare enhancement of ADP (0.1 to 10 mumol/L)-induced platelet activation by Epi infusion in vivo (0.1 and 0.4 nmol.kg-1.min-1) and by Epi in vitro (10 and 50 nmol/L) in nine healthy volunteers. ADP caused concentration-dependent increases in the percentage of platelets that bound fibrinogen (from 4.4 +/- 0.9% to 69.9 +/- 4.2%) and that expressed P-selectin (from 4.5 +/- 0.5% to 44.2 +/- 3.8%). Fibrinogen and P-selectin binding indices (FgBI and PSBI; calculated from mean fluorescence intensity and percentage of positive cells) also increased from 0.18 +/- 0.03 to 11.70 +/- 1.99 for FgBI and from 0.22 +/- 0.03 to 2.34 +/- 0.29 for PSBI. Epi concentration-dependently enhanced fibrinogen binding and P-selectin expression in vitro (by approximately 30% at the midportion of the ADP curve at 10 nmol/L Epi; P < .001 for both by ANOVAs). High-dose Epi infusion enhanced FgBI similarly and increased maximal P-selectin expression by 38%. Epi (50 nmol/L in vitro) enhanced platelet activation further, whether samples were taken with or without prior Epi infusion. Total expression of glycoprotein IIb/IIIa was unaffected by Epi infusion, but glycoprotein Ib expression per platelet was reduced (P < .05). These in vivo and in vitro effects of Epi on platelet responses to agonist stimulation indicate a prothrombotic potential for sympathoadrenal activation in humans.
Cholesterol-fed and casein-fed rabbit models of atherosclerosis. Part 1: Differing lesion area and volume despite equal plasma cholesterol levels.
Authors: Daley S J , Herderick E E , Cornhill J F , Rogers K A
Published: June 2011

One-month-old male New Zealand White rabbits were fed either a cholesterol-free casein diet (CAS; n = 10); low-level cholesterol-supplemented (0.125% to 0.5% by weight) chow (CH; n = 10); or standard laboratory rabbit chow (n = 3) for 24 weeks, during which total plasma cholesterol (TPC) levels were matched for the two experimental groups (TPCCAS = 475 +/- 39 mg/dL; TPCCH = 515 +/- 70 mg/dL). The percentage of cholesterol partitioned into each of the lipoprotein fractions except high-density lipoprotein (HDL) was significantly different for the experimental groups: casein-fed rabbits had a primarily low-density lipoprotein (LDL) hypercholesterolemia while cholesterol-fed rabbits had approximately equal levels of very-low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL), and LDL cholesterol. Despite matched TPC, lesions in CH animals covered twice the luminal surface area (as detected by oil red O staining; P < .05) and had three times the total volume compared with lesions in the CAS group (P < .05). Lesion volume was positively correlated with TPC and IDL and LDL cholesterol for the CAS group and with TPC and IDL cholesterol for the CH group. When the experimental groups were combined, TPC and VLDL and IDL cholesterol were positively correlated with the lesion volume. Probability of occurrence maps revealed, however, that both groups were virtually identical with respect to the topographic distribution of lesions in the thoracic and abdominal aortas. The data suggested that the differential partitioning of cholesterol into the lipoprotein fractions seen in CAS and CH rabbits influenced lesion area and volume but not topographic distribution.
L-arginine attenuates platelet reactivity in hypercholesterolemic rabbits.
Authors: Tsao P S , Theilmeier G , Singer A H , Leung L L , Cooke J P
Published: June 2011

Platelets are capable of producing nitric oxide (NO) through the L-arginine-NO synthase pathway. Acute exposure to supraphysiological concentrations of L-arginine in vitro increases the production of NO by platelets and is associated with an increase in platelet cyclic GMP (cGMP) levels and a reduction in platelet aggregation. The purpose of this study was to determine if chronic oral administration of L-arginine decreases platelet aggregation in hypercholesterolemic animals and to determine if this effect is mediated by the metabolism of L-arginine to NO. Male New Zealand White rabbits were fed normal chow (Con), a 1% cholesterol diet (Chol), or a 1% cholesterol diet supplemented with a sixfold enrichment of dietary L-arginine (Arg) or L-methionine (Met). After 10 weeks, cholesterol levels were equally increased in Chol and Arg animals, whereas plasma arginine levels were doubled in the Arg group. There was no difference in maximum aggregation initiated by ADP (100 mumol/L) between washed platelets from Con, Met, and Chol animals, but aggregation of platelets from Arg animals was significantly decreased (P < .05). In aggregating platelets from Arg animals, cGMP levels were significantly higher than the other groups (P < .05). When platelets were incubated ex vivo with the NO synthase inhibitor NG-monomethyl-L-arginine, the effects of dietary L-arginine were reversed. Chronic dietary supplementation of L-arginine decreases platelet aggregation in hypercholesterolemic rabbits. This effect appears to be due to the metabolism of L-arginine to NO.