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Query: UMLS:C0004153 (atherosclerosis)
 77,401 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Already in the early stages of atherosclerosis still before the appearance of coarsely visible changes subendothelially fibrin-like material is found in the places of predilection known, which reveals electron-microscopically the typical periodicity. Lesions of the endothelium with increase of permeability, release of coagulation factors and mitogenic substances which stimulate the proliferation of smooth muscle cells always precede. There are several mechanisms for the penetration of fibrinogen or fibrin into the vascular wall, the proportion of which changes with the progressing of the atherosclerosis. They are discussed in detail. Mechanisms of fibrinolysis, in which plasmin or activators of plasmin occupy a key position, effect against this process. By histochemical estimation of this activator the fibrinolytical potential of the vascular system can be investigated under various clinical conditions. For this a series of instances is cited.
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PMID:[Fibrin deposits and fibrinolysis in pre and early stages of arteriosclerosis]. 15 92

Human antiplasmin, the fast-acting plasmin inhibitor in plasma, was purified to homogeneity and labeled with 125I. This material, which was indistinguishable from antiplasmin in plasma with respect to several physicochemical and functional properties, was injected intravenously and its turnover measured in control subjects and in patients undergoing thrombolytic therapy. In eight control subjects (four healthy persons and four patients with atherosclerosis), the following turnover characteristics were obtained: plasma radioactivity half-life 2.64 +/- 0.32 days, fractional catabolic rate 0.53 +/- 0.09 of the plasma pool per day, intravascular fraction 0.51 +/- 0.05, and synthetic (catabolic) rate 1.4 +/- 0.27 mg/kg/day. The half-life of the plasmin-antiplasmin complex in plasma, measured from the disappearance rate of labeled antiplasmin, plasmin or plasmin-antiplasmin complex during thrombolytic therapy was approximately 0.5 days.
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PMID:Turnover of antiplasmin, the fast-acting plasmin inhibitor of plasma. 15 73

A large amount of plasma low density lipoprotein is present in human aortic intima, and this can be removed and measured by electrophoresis directly from the minced tissue into an antibody-containing gel. We now find that, in addition to this electrophoretically mobile lipoprotein, there is an immobilized lipoprotein fraction than can be released from lesions by incubation of the tissue sample with plasmin or other proteolytic enzymes after the mobile lipoprotein has been removed. The concentration of immobilized lipoprotein is highly correlated with the concentration of the residual cholesterol (not mobile on electrophoresis) that has accumulated in the tissue (r = 0.702; P less than 0.001). Thus, in normal intima and early gelatinous lesions it is about 15% of the concentration of mobile lipoprotein, whereas in the atheroma lipid layers of fibrous or gelatinous plaques it may be 2 or 3 times greater than the concentration of mobile lipoprotein. This suggests that immobilization of plasma lipoprotein is an intermediate step in the irreversible deposition of extracellular cholesterol in atherosclerotic lesions. Incubation with plasmin allowed maximum release of lipoprotein: plasmin = crude collagenase greater than trypsin greater than "pure" collagenase greater than chondroitinase ABC in order of their relative effectiveness. The concentration of immobilized lipoprotein was significantly correlated (r = 0.793; P less than 0.001) with the concentration in the tissue of fibrin or other insoluble derivatives of fibrinogen ("fibrin"). In aliquots of lesions incubated with varying amounts of plasmin for varying times there was a constant relation between release of lipoprotein and release of fibrin-degradation products. Together, these findings suggest that the lipoprotein is associated with insoluble "fibrin". This appears to be of considerable clinical interest, suggesting a synergism between lipoprotein and fibrinogen in the accumulation of lipid in lesions.
Atherosclerosis 1976 Oct
PMID:The release of an immobilized lipoprotein fraction from atherosclerotic lesions by incubation with plasmin. 18 79

Thin layer isoelectric focusing followed by second dimension quantitative immunoelectrophoresis has been used to characterize the free and tightly bound lipoprotein (lp) fractions in human aortic intima. In 3.3% acrylamide gels plasma low density lipoprotein (LDL) focuses rapidly, but very low density lipoprotein (VLDL) fails to enter the gell and remains at the origin (point of application). Samples of normal intima and lesions were placed directly on the gel and focused for 10--12 h; in normal intima and gelatinous lesions which had not accumulated cholesterol 60--70% of the free LP focused with plasma LDL, but with increasing accumulation of cholesterol the proportion focusing with LDL decreased and the component remaining at the origin increased. In 9 of the 39 samples examined one or more components with pI acid to LDL were present, and in one sample the whole peak focused at a more acid pI. In 4 of 5 lipid-rich centres of gelatinous plaques all the free LP remained at the origin, and the bound LP released by incubation with plasmin remained at the origin in all samples in 3.3% gels although it would focus in 2.6% gels. With antiserum to apo-C this large LP did not behave like VLDL, and it appears to be an aggregated LDL. An increased proportion of aggregated LDL was associated with (a) accumulation of cholesterol, (b) topographical location towards the centre of plaques, and (c) partial destruction of endogenous LP during incubation of fresh samples of tissue.
Atherosclerosis 1979 Jul
PMID:Characterization of free and tightly bound lipoprotein in intima by thin layer isoelectric focusing. 22 7

A quantitative assay for fibrin or other insoluble fibrin-like antigens ("fibrin") in small samples of intima is described. Tissue samples were subjected to electrophoresis directly from the intima into an antibody-containing gel to remove and measure fibrinogen and other soluble fibrin reactive antigens (FRA). The residual tissue was then exhaustively incubated with plasmin, and the soluble fragments generated from the insoluble "fibrin" were measured by quantitative immunoelectrophoresis. "Fibrin" accounted for about 2% of the tissue dry weight in normal intima and the ratio fibrinogen/"fibrin" was 1-1.5. In the gelatinous lesions, which seem to be the precursors of fibrous plaques, there was a small increase in "fibrin" but a substantial increase in fibrinogen and low density (LD)-lipoprotein, and the ratio fibrinogen/"fibrin" rose to about 3, which suggests that the increase in "fibrin" is secondary to increased permeation of fibrinogen. At the edges of large plaques there was also a threefold increase in fibrinogen, but "fibrin" increased fivefold, and accounted for 10% of the tissue dry weight. The same high concentration was found in the centres of large fibrous plaques with advanced atheroma lipid. Raised levels of "fibrin" were accompanied by raised levels of fibrinogen in most tissue samples. About 80% of the total soluble FRA could be clotted with thrombin; there was no significant difference between normal intima and lesions, and the proportion clotted was not related to "fibrin" content.
Atherosclerosis
PMID:Insoluble "fibrin" in human aortic intima. Quantitative studies on the relationship between insoluble "fibrin", soluble fibrinogen and low density lipoprotein. 23 64

Traditionally, plasmin generation has been conceptualized as a process oriented on the surface of a fibrin-containing thrombus. Recent work, however, indicated that plasminogen and its activators, tissue plasminogen activator (t-PA) and urokinase, can assemble on the surface of cultured human umbilical vein endothelial cells (HUVECs). On binding to HUVECs, plasminogen is activated by t-PA approximately 12-fold more efficiently than fluid-phase plasminogen, and is converted to a plasmin-modified form, possibly unique to cell surfaces. In addition, t-PA interacts with HUVECs at two sites. The major binding site preserves its activity and represents a true (relative molecular weight 40,000) membrane-associated exoreceptor. The low-density lipoprotein (LDL)-like lipoprotein, lipoprotein(a), is highly associated with atherosclerosis, bears striking sequence homology to plasminogen, and competes with plasminogen for cell surface binding. In summary, functional assembly of plasminogen and t-PA may represent an important thromboregulatory system.
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PMID:Assembly of plasmin-generating proteins on the surface of human endothelial cells. 134 92

Most of the linkage of atherosclerosis and thrombosis with estrogens is epidemiologic in origin. Although the effects of estrogens on the mechanisms of hemostasis are wide ranging, many are benign; only a few may account for thrombus formation. Platelet function tests have provided extensive but contradictory data, and interpretation is limited because it is uncertain whether a rise in one or more of these parameters is a primary or secondary effect. The most consistent effects of estrogens on coagulation proteins are elevations of fibrinogen; factors II, VII, IX, X, and XII; protein C; and plasminogen. Although these elevations have been attributed to the estrogenic component in oral contraceptives, the progestogen concentration may also influence these increases. Among other coagulation proteins studied, the following are unaffected by oral contraceptive use: factors V, VIII, and XI; prekallikrein; and high-molecular-weight kininogen. In contrast, protein S values are decreased. The plasma concentration of plasmin inhibitor is unchanged, whereas both proteinase inhibitor and macroglobulin are significantly increased by oral contraceptive use. Cl esterase inhibitor is decreased in women taking oral contraceptives and correlates with the increase in Hageman factor. Antithrombin III is one plasma inhibitor for which a decrease in quantity and activity have been associated with a thrombotic tendency in humans. Although data on estrogen-associated changes in the quantity of antithrombin III have been conflicting, the ability of plasma to inhibit factor Xa is significantly reduced in a dose-dependent manner among pre- and postmenopausal estrogen users.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Estrogen-associated thromboembolism. 134 94

Plasmin inhibition by alpha 2-antiplasmin (alpha 2AP) is regulated by the vascular components fibrin(ogen) fragments, plasminogen and lipoprotein (a). Kinetic analysis demonstrates that CNBr-derived fibrinogen fragments completely protect plasmin from alpha 2AP. Plasminogen and 6-aminohexanoic acid decrease the rate of inhibition by 5- and 10-fold respectively. These studies show that CNBr-derived fibrinogen fragments and 6-aminohexanoic acid bind plasmin kringle(s) with binding constants of 2 micrograms/ml and 120 microM respectively, and that plasminogen binds to alpha 2AP with an affinity of 0.5 nM. The unmodulated inhibition is not effected by the presence of lipoprotein (a), but in the presence of protective CNBr-derived fibrinogen fragments the rate of inhibition is increased by the presence of the lipoprotein. The kinetics demonstrate that lipoprotein (a) binds to CNBr-derived fibrinogen fragments with an affinity of 4 nM, displacing plasmin from the protective surface. In addition, tissue-type plasminogen activator and trypsin inhibition by alpha 2AP is not slowed by the presence of CNBr-derived fibrinogen fragments or plasminogen (Pg), respectively. These kinetics suggest that the initial reversible interaction between plasmin and alpha 2AP is mediated by binding of the inhibitor to the kringle 1 domain of plasmin, with a reversible inhibition constant (Ki) of 5.0 x 10(-10) M. Under conditions where this kringle-inhibitor interaction is blocked, the reversible inhibition still occurs between the plasmin and alpha 2AP, but the initial Ki is increased to 5.0 x 10(-9) M. These data suggest that, in the circulation, plasmin inhibition by alpha 2AP may be down-regulated by fibrin, fibrin(ogen) fragments and Pg, but up-regulated by lipoprotein (a) in the presence of fibrin or fibrin(ogen) fragments. The lipoprotein (a)-mediated promotion of plasmin inhibition may provide an additional mechanism by which the lipoprotein impairs fibrinolysis and promotes atherosclerosis.
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PMID:Lipoprotein (a) promotes plasmin inhibition by alpha 2-antiplasmin. 138 85

The increased risk of thromboembolism in people with diabetes mellitus is in part due to changes in the hemostatic mechanism including abnormal platelet function leading to platelet activation, increase in several coagulation factors, decrease in natural anticoagulants, and impaired fibrinolytic activity. Both microangiopathy and atherosclerosis in people with diabetes will enhance the thrombotic potential of these abnormal hemostatic changes. The recent recognition of a role of the components of the plasminogen-plasmin system in many biologic functions at the cellular level has led to studies showing that the angiopathic complications of diabetes may also be caused by impaired plasminogen activator function.
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PMID:Changes in blood coagulation, platelet function, and plasminogen-plasmin system in diabetes. 138 26

Cadaveric aortic intimas with uncomplicated atherosclerosis were examined to determine the distribution and polypeptide chain composition of fibrinogen-related protein. Immunohistochemical staining showed deposits rich in fibrinopeptides A and B. The deposits were usually disseminated throughout intimas of moderate thickness < 0.7 mm, but were distributed focally in elongate patches bounded both lumenally and medially by deposit-free tissue in thick atheromas. Saline extracts generally showed undegraded monomers and dimers by electrophoresis. The residual protein contained A alpha and gamma-chains that were cross-linked predominantly (>80%) into unresolved high M(r) (>200 kd) derivatives, whereas B beta-chains were left non-cross-linked, as occurs in late stages of cross-linking by transglutaminases. The resolved components had electrophoretic mobilities corresponding to characteristic products of both factor XIIIa and tissue-transglutaminase. A greater incorporation of alpha- rather than gamma-chains into cross-linked products implicated tissue-transglutaminase as contributing heavily. By contrast, vascular graft pseudo-intimas and a cadaveric clot were rich in degraded fibrin devoid of fibrinopeptide A, and cross-linked in patterns typical of XIIIa with gamma 2 dimers constituting the principal product. The findings indicate that the fibrinogen in the aortic intima is comparatively well protected from thrombin and plasmin, and that much of it is deposited through direct cross-linking by tissue-transglutaminase without being converted to fibrin.
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PMID:Immunoelectrophoretic and immunohistochemical characterizations of fibrinogen derivatives in atherosclerotic aortic intimas and vascular prosthesis pseudo-intimas. 141 80


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