摘要:

The heparin-releasable proteins are a group of proteins that are targeted to the endothelial surface by attachment to glycosaminoglycans and may have functions specific to the endothelium-blood interface. In this study, heparin-affinity chromatography of human postheparin plasma was used as a method to identify and study novel heparin-releasable proteins. Six proteins seen on sodium dodecyl sulfatepolyacrylamide gel electrophoresis gels have increased levels in plasma after intravenous heparin. The six proteins are platelet factor 4, midkine, pleiotrophin, and several novel proteins. Midkine and pleiotrophin are related cytokines that are developmentally regulated, neurotrophic, and mitogenic. Additional studies show that levels of midkine and pleiotrophin peak at 10 to 30 minutes after injection of heparin. Heparin-releasable midkine and pleiotrophin do not originate from blood cells or the kidney. Heparinreleasable midkine may originate from endothelial cells. Soft agar culture of an adenocarcinoma cell line (SW-13) demonstrates growth-stimulating activity similar to that described for pleiotrophin in the heparin-agarose eluate of postheparin plasma but not in the heparin-agarose eluate of preheparin plasma. It is concluded there are more heparin-releasable proteins than previously identified, including midkine and pleiotrophin, and that heparin-affinity chromatography of postheparin plasma is a useful technique for identifying novel heparin-releasable proteins.

ISSN:1049-8834    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

An important aspect of blood-material interactions is the activation, adhesion, and subsequent aggregation of blood platelets on the artificial surface, all of which are directly affected by local fluid dynamics. The objective of this work was to directly correlate changing local fluid dynamic conditions produced by various vessel geometries, including stenosis, aneurysm, and separate contraction and expansion geometries, with quantitative in vitro measurements of regional platelet deposition. We directly measured platelet deposition as a function of axial position along four Lexan flow chambers with axisymmetric models of these geometries using '"In-labeled platelets. Platelet deposition was maximum in observed areas of flow recirculation and reattachment and minimum in locations of high shear and separation. For the stenosis geometry, two distinct regions of increased platelet deposition were apparent, one proximal to and one distal to the stenosis throat. An approximately linear increase in platelet densities was produced in the aneurysm region, increasing in the direction of flow. Through a comparison of platelet deposition with local fluid streamline orientation, we have shown that platelet deposition is increased in certain areas due to the enhanced convective transport of platelets and blood cells to the vessel wall along locally curved streamlines with velocity components perpendicular to the vessel wall.

ISSN:1049-8834    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

The consequences of the lack of apolipoprotein A-I (apoA-I) were evaluated in mice made to lack apoA-I by gene targeting. Inbred strain 129 mice homozygous for the inactive Apoal gene and maintained on regular mouse chow had markedly reduced total cholesterol (26% normal) and high-density lipoprotein (HDL) cholesterol (25% normal) levels in their plasma. Their plasma lipoproteins lacked apoA-I and were reduced in all other apolipoproteins but apoE. ApoE comprises about one third of the protein of HDL particles in homozygotes, whereas it is present in only trace amounts in normal HDL. Despite the reduction of HDL cholesterol, no atherosclerotic lesions were observed in any of the homozygous mice evaluated (up to 15 months of age). After being maintained on an atherogenic diet for 4 weeks, total plasma cholesterol of the homozygous mutants increased by 20 mg/dL, while that of normals increased by 60 mg/dL. Mice with mixed 129 and C57BL/6J genetic backgrounds were fed the atherogenic diet for 20 weeks. A small number of foam cells were found attached to the aortic surface in some of the animals, but the extent and occurrence of these depositions were not related to the apoA-I genotype. Our results demonstrate that a lack of apoA-I does not by itself cause atherosclerosis in mice.

ISSN:1049-8834    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Because of the frequent occurrence of premature cardiovascular disease in patients with non-insulindependent, type II diabetes mellitus (NIDDM), the attenuated fibrinolytic activity of plasma from type II diabetic patients with increased concentrations of plasminogen activator inhibitor type-1 (PAI-1), and the fact that insulin stimulates synthesis of PAI-1 by human hepatic cells in vitro, we and others have hypothesized that accelerated vascular disease in type II diabetes may result in part from impaired fibrinolysis secondary to excessive elaboration of PAI-1 stimulated by insulin. Alternatively, the hyperglycemia associated with type II diabetes could influence the synthesis and secretion of PAI-1 directly. The present study was performed to determine whether PAI-1 secretion is or is not sensitive to the prevailing concentration of glucose in the conditioned medium of endothelial and liver cells, which are thought to be the major sources of circulating PAI-1 in vivo. Confluent cells were exposed to 0, 2.8, 5.6, 11.1, or 22.2 mmol/L (0, 50,100, 200, or 400 mg/dL) glucose in medium without serum and subsequently to media with or without insulin (7.3 nmoI/L). Secretion of PAI-1 by highly differentiated human hepatoma (Hep G2) cells did not increase as a function of increasing concentrations of glucose, whether or not insulin was present. In contrast, with pig aortic endothelial cells, the secretion of PAI-1 increased significantly with extracellular glucose with or without insulin. The increases in PAI-1 were specific (as shown by metabolic labeling experiments) and not attributable to osmotic effects (as shown by replacement of glucose by sorbitol). Furthermore, the changes were paralleled by a specific, significant increase in the concentration of PAI-1 mRNA. These results indicate that increases in PAI-1 activity in type II diabetic patients are likely to be attributable to direct effects of glucose on the synthesis of PAI-1 by arterial endothelial cells, in addition to the effects of insulin on the synthesis of PAI-1 by liver cells. The effects of glucose on endothelial cells may contribute to reduced local fibrinolysis, thereby exacerbating atherogenesis.

ISSN:1049-8834    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

The relation of hemostatic factor levels to the occurrence of cardiovascular disease is incompletely established. The Atherosclerosis Risk in Communities Study measured fibrinogen, factor VII, factor VIII, von Willebrand factor, antithrombin HI, protein C, activated partial thromboplastin time, and other cardiovascular risk factors in nearly 15 000 men and women aged 45 to 64. This analysis assessed the relations of these hemostatic factors with prevalent cardiovascular disease and asymptomatic carotid artery intimal-medial thickness measured by B-mode ultrasound. Compared with participants without cardiovascular disease, those with cardiovascular disease had higher levels of fibrinogen, factor VIII, and von Willebrand factor in both sexes. The other hemostatic factors were less consistently associated with prevalent cardiovascular disease. Only fibrinogen was associated with carotid intimal-medial thickness. Adjusted for age, race, and field center, the odds ratio for carotid wall thickness in the 90th percentile or greater, compared with <50th percentile, for each SD higher fibrinogen concentration (65 mg/dL) was 1.42 (95% confidence interval, 1.25, 1.62) in men and 1.43 (1.25, 1.64) in women. This population-based study provides further evidence that fibrinogen and possibly factor VIII and von Willebrand factor are risk factors for cardiovascular disease.

ISSN:1049-8834    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Lipid transfer protein (LTP) activity is modulated by a distinct plasma protein termed lipid transfer inhibitor protein (LTIP). The objective of this study was to establish an assay for LTIP that could be used to quantify its activity in lipoprotein-deficient plasma. A straightforward heating protocol (56°C for 60 minutes) was found to inactivate more than 90% of LTIP activity. The responses of individual lipoprotein-deficient plasma samples to this heating procedure were unique. Among normolipidemic donors, inactivation of LTIP caused a 230% to 600% increase in LTP activity. Essentially all measurable transfer activity in native and heated samples was inhibited by an antibody to LTP. Whole-plasma samples from these donors were spiked with radiolabeled lipoproteins to measure the rates of lipid transfer among the major lipoprotein classes. In general, plasma lipid transfer rates were negatively correlated with LTIP activity in these samples. However, the decrease in lipid transfers from very-lowdensity lipoprotein (VLDL) to low-density lipoprotein (LDL) and from LDL to VLDL was from 2.4- to 5.1-fold greater than in the transfers from VLDL to high-density lipoprotein (HDL) or from HDL to VLDL. In these samples, the molecular weight of HDL2was negatively correlated with LTIP activity. Thus, LTIP activities among normolipidemic individuals were observed to vary severalfold; compared with other lipoprotein transfers, higher LTIP activities were associated with a relative reduction in LDL-VLDL lipid transfer events.

ISSN:1049-8834    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

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°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/niL), 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 on 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.

ISSN:1049-8834    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Activin-A has a mitogenic effect on vascular smooth muscle cells (SMCs) and is produced by monocyte/macrophage lineage cells. Here, we studied the expression of follistatin, an activin-binding protein, in both A10 cells, a rat aortic SMC line, and vascular SMCs derived from adult rat aorta. Follistatin mRNA was detected in these cells by Northern blot analysis. Ligand blot and immunoblot analyses demonstrated that follistatin was produced in the conditioned medium at a higher level by A10 cells than by SMCs. Furthermore, immunostaining and in situ hybridization of the arteriosclerotic lesions showed that follistatin was highly expressed in the diseased artery, where abnormal proliferation of SMCs occurred. We suggest that follistatin is produced by vascular SMCs and is involved in the course of atherogenesis.

ISSN:1049-8834    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

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 (9.9fiU/mLcompared with 9.0fiV/mh,p<.0001). However, the association with 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 (PA1-1) 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. Insulin concentrations were also significantly related to a lesser extent with hemostatic variables that are considered as acute-phase markers, such as fibrinogen, von Willebrand factor, and factor VIII: c; these correlations were independent of joint associations with other coronary risk factors, including body mass index and triglyceride. Simultaneous adjustments for markers of inflammation substantially reduced the fibrinogen relation to insulin but only slightly modified those between insulin and von Willebrand factor and factor VIII:c. These results indicate that the insulin-fibrinogen relation is more related to the accompanying acute-phase reaction, whereas the link between insulin and von Willebrand factor and factor VIII: c may be due to nonspecific endothelial cell damage.

ISSN:1049-8834    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Intimal thickening in human arteries is considered as a site of predilection for atherosclerosis. The placement of a flexible, physically nonconstrictive, silicone cuff around the rabbit carotid artery induced a neointima composed of smooth muscle cells (SMCs) within 14 days. To investigate possible alterations of the endothelial cells (ECs) during neointima formation, their morphology was examined with scanning electron microscopy (SEM), transmission electron microscopy (TEM), and confocal microscopy. In the early postoperative period (6 hours), both cuffed and sham-operated arteries demonstrated small foci (5 to 200 fim) of denudation, presumably as a consequence of the manipulation. Within 24 hours the luminal surface of the cuffed and sham-operated arteries was completely covered with endothelium, which remained continuous throughout the study. However, after 1 week the ECs of the cuffed arteries contained a pronounced rough endoplasmic reticulum. From 6 hours until 3 days, polymorphonuclear leukocytes infiltrated the cuffed but not the sham-operated arteries from the lumen. Subendothelial SMC accumulation in the cuffed arteries began after this time period. At day 14 a full-blown neointima composed of longitudinally oriented SMCs had formed in the cuffed arteries. The sham-operated arteries did not develop a neointima. During neointima formation immunoreactivity for von Willebrand factor (vWf) increased in the ECs, and vWf was deposited in the extracellular spaces of the neointima. At day 14 the area of vWf deposits correlated positively with the area of the neointima (r=.73, /><.001). In subsequent weeks, the intimal area did not increase, and vWf deposits vanished from the neointimal matrix. The endothelium of the sham-operated arteries showed no change in vWf immunoreactivity compared with untreated arteries throughout the study. The altered ultrastructural morphology of the ECs and the concurrent vWf deposition in cuffed but not in sham-operated arteries point to alterations in EC function during the development of the neointima. The vWf secretion could possibly lead to increased adhesiveness of the extracellular matrix for the ECs as well as modulate neointima formation.

ISSN:1049-8834    

出版商:OVID    

年代:1993

数据来源: OVID