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PubMed1978

Identification of soluble fibrinogen fibrin monomer complexes by non-enzymatic polymerisation in the tissue.

In states of plasmic hypercoagulability and consumption coagulopathy ethanol favours the non-enzymatic polymerization of circulating soluble fibrinogen fibrin monomer complexes (FFMC) in vitro. The ethanol-gelation test of Godal and Abildgaard makes use of this phenomenon, called paracoagulation. The present studies show that it is also possible to visualize soluble FFMC by means of ethanol-gelation. In the electron microscope, FFMC, polymerized non-enzymatically by ethanol in the spleen, are characterized by plump or slender mycelioid fibrillar precipitates that show a uniform rhythmic transverse striation, a period-coincidental filamentary arrangement and an average periodicity of 23 nm. The ultrastructure demonstrates these ethanol-induced filaments to be in vitro-polymerized fibrin monomer derivatives. Paracoagulation with ethanol allows the identification of soluble FFMC in the tissue prior to the formation of highly polymerized fibrin-rich microthrombi, the established equivalents of the DIC-syndrome. The electron microscope studies also show the existence of a second type of fibrillary structure in the tissue polymerized by ethanol. This second type lacks the characteristic periodicity of fibrin and the period-coincidental arrangement of the filamentary structures, but is characterized by closely packed or chain-like aligned, irregularly sized spherical bodies. There is some evidence that these spherical bodies in vitro represent non-enzymatically polymerized complexes of fibrin monomers and fibrin degradation products (FDP), the equivalent of a limited local or generalized fibrinolysis in vivo.

Animals↗
PubMed1989

Mediastinal fibrin glue: hemostatic effect and tissue response in calves.

There is continued controversy regarding the effectiveness and potential adverse effects of fibrin glue. Thus, we chose to evaluate it in a model of experimental calf aortic valve replacement that has been previously well established. Concentrated fibrinogen and topical thrombin were sprayed to form a thin layer of fibrin glue over the mediastinal tissues of 20 consecutive calves undergoing aortic valve replacement. Chest tube outputs of these animals were compared with those of the preceding 20 consecutive calves undergoing aortic valve replacement without fibrin glue. All procedures were performed by the same surgeon, and no other technical changes were made between the two series. Total postoperative chest tube output (mean +/- standard error) was 553 +/- 50 mL for the calves treated with fibrin glue and 1,155 +/- 103 mL for the control calves (p less than 0.001). On histological examination of mediastinal tissues from 5 treated calves killed 6 weeks after operation, there was no evidence of inflammation, fibrosis, or residual fibrin. To our knowledge, this is the first controlled laboratory study to show that fibrin glue spray is an effective hemostatic agent and that it produces no long-term tissue reaction.

Animals↗
PubMed1988

Characterization of the fibrin polymer structure that accelerates thrombin cleavage of plasma factor XIII.

The effect of plasmin-derived fibrin(ogen) degradation products on alpha-thrombin cleavage of plasma Factor XIII was studied to identify the fibrin polymer structure that promotes Factor XIIIa formation. Fibrin polymers derived from fibrinogen and Fragment X enhanced the rate of thrombin cleavage of plasma Factor XIII in plasma or buffered solutions. The concentrations of fibrinogen and Fragment X that promoted half-maximal rates of Factor XIIIa formation were 5 and 40 micrograms/ml, respectively. Fragments Y, D, E, D-dimer, and photooxidized fibrinogen did not enhance thrombin cleavage of Factor XIII. Although purified Fragment D1 inhibited fibrin gelation, the soluble protofibrils promoted thrombin activation of Factor XIII. Noncrosslinked fibrin fibers failed to enhance thrombin cleavage of Factor XIII. In conclusion, soluble fibrin oligomers function to promote thrombin cleavage of plasma Factor XIII during blood clotting.

Calcium↗
PubMed1982

Effects of fibrin and fibrinogen-degradation products on the growth of rabbit aortic smooth muscle cells in culture.

Fibrin contains a factor which promotes growth of the mesenchymal cells and such may be related tissue repair. Effects of fibrin and fibrinogen degradation products (FDP) on the growth of smooth muscle cells (SMC) of rabbit aortas in culture were investigated, in relation to atherogenesis. Fibrin, free from plasminogen enhanced the proliferation of SMC during the experimental period of 48 h. Fibrin, rich in plasminogen also stimulated the proliferation of SMC within 24 h, but inhibited it after 48 h. FDP (fragments D and E) inhibited the proliferation of SMC. SMC of rabbit aortas demonstrated plasminogen activator activity. Thrombin and urokinase exhibited no promoting effects on the growth of SMC. These results support the hypothesis that the proliferation of SMC is stimulated by fibrin and later inhibited by FDP, as produced by the fibrinolytic activity of SMC. It is proposed that the metabolism of fibrin in the arterial wall may be of importance in the regulation of SMC proliferation and that the coagulation-fibrinolysis system may play a significant role in atherogenesis.

Animals↗
PubMed1985

The activation of Glu- and Lys-plasminogens by streptokinase: effects of fibrin, fibrinogen and their degradation products.

Studies were performed on the activation of a native form of human plasminogen (Glu-plg) or its degraded form (Lys-plg) by streptokinase (SK) in the presence of fibrin, fibrinogen, SK-potentiator, fragment D or E. When Glu-plg (0.1 microM) was activated by 0.5 u/ml of SK in the presence of 100 micrograms of S-2251 and 0.1 microM of fibrin, fibrinogen or their degradation products (potentiating agents), fibrin enhanced the rate of the hydrolysis of S-2251 to the largest extent. Fragments D and E only slightly enhanced it. The order of effectiveness of enhancement was fibrin greater than SK-potentiator greater than fibrinogen greater than D greater than E. When Lys-plg (0.1 microM) was activated by 0.5 u/ml of SK in the presence of potentiating agents, SK-potentiator enhanced the hydrolysis of S-2251 to the largest extent. The enhancement was far less in comparison to the enhancement of the hydrolysis by Glu-plg and SK. The measurement of delta OD405/min at the time of 50% hydrolysis of the substrate was performed in order to compare the effects of concentrations of potentiating agents. The maximum enhancement was obtained at almost an equimolar ratio of plasminogen and fibrin. Fifty percent enhancement was obtained at 0.05 microM for SK-potentiator, 0.072 microM for fibrinogen, 0.21 microM for D and 0.35 microM for E. Fibrin caused the largest extent of enhancement among other potentiating agents. These results may indicate that a trimolecular complex between SK, plasminogen and potentiating agents hydrolyzes S-2251 more effectively than SK-plasminogen complex, thus a trimolecular complex being a better activator than SK-plasminogen complex. Although D and E enhanced only slightly the rate of hydrolysis of S-2251 at equimolar ratio to plasminogen, increase in their concentration resulted in the same extent of enhancement as shown in the presence of fibrinogen or SK-potentiator.

Fibrin↗
PubMed2005

Detection of fibrin generation alterations in dogs with haemangiosarcoma using resonance thrombography.

OBJECTIVE: The objective of the study was to examine the alterations of fibrin generation in dogs with haemangiosarcoma using resonance thrombography. The second objective was to evaluate the sensitivity of this method for the detection of hypofibrinogenaemia and/or increased fibrin(ogen) degradation product (FDP) concentration. ANIMALS, METHODS: Resonance thrombogram (RTG) measurements with two different instruments were performed in 30 unselected dogs with haemangiosarcoma, 14 of which had decreased fibrinogen and 28 of which had an increased FDP concentration (p<0.0001). RESULTS: The RTG-reaction time was less sensitive than the fibrin formation time (RTG-f) and fibrin amplitude (RTG-F). The RTG-f and RTG-F indicated reliably a decrease in fibrinogen concentration (sensitivity: 0.93). The sensitivity of detection of increased FDP levels was considerably higher than that of thrombin time. However, false-negative results were found even at FDP concentrations > or =120 mg/l, especially in cases with high fibrinogen level. Both machines showed similar sensitivity. CONCLUSIONS: The results of this study indicate that canine haemangiosarcoma is frequently associated with severe alterations of fibrin generation due to low fibrinogen and high FDP levels leading to distinct RTG abnormalities. The global test RTG reacts sensitively to a decreased fibrinogen level whereas its accuracy to detect FDP concentrations occurring under pathophysiological conditions is limited. A significant alteration of fibrin generation induced by FDPs may not occur until the serum FDP concentration exceeds 60 mg/l.

Animals↗
PubMed2006

Platelet-rich fibrin (PRF): a second-generation platelet concentrate. Part I: technological concepts and evolution.

Platelet-rich fibrin (PRF) belongs to a new generation of platelet concentrates geared to simplified preparation without biochemical blood handling. In this initial article, we describe the conceptual and technical evolution from fibrin glues to platelet concentrates. This retrospective analysis is necessary for the understanding of fibrin technologies and the evaluation of the biochemical properties of 3 generations of surgical additives, respectively fibrin adhesives, concentrated platelet-rich plasma (cPRP) and PRF. Indeed, the 3-dimensional fibrin architecture is deeply dependent on artificial clinical polymerization processes, such as massive bovine thrombin addition. Currently, the slow polymerization during PRF preparation seems to generate a fibrin network very similar to the natural one. Such a network leads to a more efficient cell migration and proliferation and thus cicatrization.

Animals↗
PubMed1998

Degradation of fibrinogen and cross-linked fibrin by human neutrophil elastase generates D-like fragments detected by ELISA but not latex D-dimer test.

Recently, we observed that D-dimers are degraded by human neutrophil elastase (HNE) into two D-like fragments, reacting with the monoclonal antibody in an ELISA D-dimer test but not reacting with the corresponding latex D-dimer test. To investigate this in more detail, we studied the degradation of cross-linked fibrin and fibrinogen by plasmin and HNE to see if this resulted in D-fragments or D-like fragments. Degradation of fibrinogen, both by plasmin and HNE, resulted in D- and D-like fragments, respectively, detected by the ELISA D-dimer test. Degradation of cross-linked fibrin by plasmin and HNE also resulted in D- and D-like fragments, which were detected by the ELISA method. Intact D-dimers detected by the latex D-dimer test were only observed after degradation of cross-linked fibrin with plasmin. We conclude that during lysis of cross-linked fibrin as well as fibrinogen by plasmin and HNE, D-fragments, and D-like fragments, detected by the ELISA D-dimer test, are formed. Only during degradation of cross-linked fibrin by plasmin, intact D-dimers, detected by latex D-dimer test, are formed. The ELISA D-dimer test may therefore be used to detect fibrin and fibrinogen degradation products generated by the combined action of plasmin and HNE in sepsis and other conditions with increased HNE activity, while the latex D-dimer test may be used to detect plasmin derived intact D-dimers.

Animals↗
PubMed2000

Conversion of fibrinogen to fibrin: mechanism of exposure of tPA- and plasminogen-binding sites.

Conversion of fibrinogen into fibrin results in the exposure of cryptic interaction sites and modulation of various activities. To elucidate the mechanism of this exposure, we tested the accessibility of the Aalpha148-160 and gamma312-324 fibrin-specific epitopes that are involved in binding of plasminogen and its activator tPA, in several fragments derived from fibrinogen (fragment D and its subfragments) and fibrin (cross-linked D-D fragment and its noncovalent complex with the E(1) fragment, D-D. E(1)). Neither D nor D-D bound tPA, plasminogen, or anti-Aalpha148-160 and anti-gamma312-324 monoclonal antibodies, indicating that their fibrin-specific epitopes were inaccessible. The Aalpha148-160 epitope became exposed only upon proteolytic removal of the beta- and gamma-modules from D. At the same time, both epitopes were accessible in the D-D.E(1) complex, indicating that the DD.E interaction resulted in their exposure. This exposure was reversible since the dissociation of the D-D.E(1) complex made the sites unavailable, while reconstitution of the complex made them exposed. The results indicate that upon fibrin assembly, driven primarily by the interaction between complementary sites of the D and E regions, the D regions undergo conformational changes that cause the exposure of their plasminogen- and tPA-binding sites. These changes may be involved in the regulation of fibrin assembly and fibrinolysis.

Animals↗
PubMed1994

The fibrin(ogen)olytic properties of cathepsin D.

Fibrin(ogen) is important for hemostasis and is cleared from sites of vascular injury primarily by the plasminogen activator system. However, there is emerging evidence in plasminogen activator-deficient transgenic mice that non-plasmin pathways may also be important for endogenous fibrinolysis. We have recently described an alternative, plasmin-independent fibrinolytic pathway in activated human monocytes that utilizes the integrin Mac-1 (CD11b/CD18), which directly binds and internalizes fibrin, resulting in its lysosomal degradation. The identity of the lysosomal fibrinolytic enzyme(s) responsible for monocyte/macrophage-mediated fibrinolytic is unknown. Protease inhibitor studies now suggest that an aspartyl protease is responsible for this fibrinolytic activity. We, therefore, examined the fibrinolytic properties of cathepsin D, a lysosomal aspartyl protease, and report that cathepsin D possesses both fibrinogenolytic and fibrinolytic activity. Cathepsin D cleavage of fibrinogen follows Michaelis-Menten kinetics with a Michaelis constant, Km, of 1.5 microM; catalytic rate constant, kcat, of 1.4 x 10(-3) s-1; and catalytic efficiency, kcat/Km, of 9.3 x 10(-4) microM-1 s-1. A pH-activity profile of fibrinogen digestion by cathepsin D demonstrates a pH optimum of 3.5 with 50% residual activity at pH 5.0. Fibrinolysis was assessed by fibrin plate and fibrin clot lysis assays. Cathepsin D possesses significant fibrinolytic activity over a dose range of 100 nM to 10 microM and is able to lyse fibrin, as well as albumin-enriched and albumin/red cell-enriched fibrin clots. Cathepsin D cleaves the alpha-, beta-, and gamma-chains of FGN, generating multiple low-molecular-weight fragments.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed2006

Incorporation of fragment X into fibrin clots renders them more susceptible to lysis by plasmin.

Bleeding, the most serious complication of thrombolytic therapy with tissue-type plasminogen activator (t-PA), is thought to result from lysis of fibrin in hemostatic plugs and from the systemic lytic state caused by unopposed plasmin. One mechanism by which systemic plasmin can impair hemostasis is by partially degrading fibrinogen to fragment X, a product that retains clottability but forms clots with reduced tensile strength that stimulate plasminogen activation by t-PA more than fibrin clots. The purpose of this study was to elucidate potential mechanisms by which fragment X accelerates t-PA-mediated fibrinolysis. In the presence of t-PA, clots containing fragment X were degraded faster than fibrin clots and exhibited higher rates of plasminogen activation. Although treatment with carboxypeptidase B, an enzyme that reduces plasminogen binding to fibrin, prolonged the lysis times of fragment X and fibrin clots, clots containing fragment X still were degraded more rapidly. Furthermore, plasmin or trypsin also degraded clots containing fragment X more rapidly than fibrin clots, suggesting that this effect is largely independent of plasminogen activation. Fragment X-derived degradation products were not preferentially released by plasmin from clots composed of equal concentrations of fibrinogen and fragment X, indicating that fragment X does not constitute a preferential site for proteolysis. These data suggest that structural changes resulting from incorporation of fragment X into clots promote their lysis. Thus, attenuation of thrombolytic therapy-induced fragment X formation may reduce the risk of bleeding.

Blood Coagulation↗
PubMed1991

Soluble fibrin preparations inhibit the reaction of plasmin with alpha 2-macroglobulin. Comparison with alpha 2-antiplasmin and leupeptin.

The kinetics of plasmin inhibition by alpha 2-antiplasmin (alpha 2AP), alpha 2-macroglobulin (alpha 2M) and leupeptin were studied in the presence of fibrin monomer (Fn) and CNBr fragments of fibrinogen (Fg-CNBr). Active plasmin was detected in continuous and discontinuous assays using the chromogenic substrate D-Val-L-Leu-L-Lys p-nitroanilide hydrochloride (S-2251). The two 'fibrin-like' preparations functioned as hyperbolic mixed-type inhibitors of S-2251 hydrolysis. The dissociation constants (KF) for the binding of plasmin to Fn and Fg-CNBr were 22 nM and 17 nM respectively. Fn and Fg-CNBr inhibited the reaction of plasmin with alpha 2AP: the extent of inhibition depended on the fibrin concentration. In the presence of 800 nM-Fn or 800 nM-Fg-CNBr, the experimental second-order rate constant (K"app.) was decreased from 2.4 x 10(7) M-1.s-1 to 1.2 x 10(6) and 5.3 x 10(5) M-1.s-1 respectively. The effect of Fn and Fg-CNBr on the rate of plasmin inhibition by alpha 2M was even greater. The k"app. value was decreased from 4.0 x 10(5) M-1.s-1 to 8.0 x 10(2) and 1.3 x 10(3) M-1.s-1 in the presence of 800 nM-Fn and -Fg-CNBr respectively. By contrast, the fibrin preparations caused only a small change in the rate of plasmin inhibition by leupeptin. The maximum change in k"app. was 3-fold. All plasmin inhibition curves were linear, suggesting that free and fibrin-bound forms of plasmin remained in equilibrium during the course of reaction with proteinase inhibitors. Fn and Fg-CNBr had no effect on the reaction of miniplasmin with S-2251, alpha 2AP or alpha 2M. When 125I-plasmin was incubated with Fg-CNBr and then allowed to react with a premixed solution of alpha 2AP and alpha 2M, the Fg-CNBr did not significantly change the percentage of plasmin bound to alpha 2AP. These experiments demonstrate that the reaction of plasmin with alpha 2M is inhibited by the non-covalent binding of plasmin to fibrin. We propose that plasmin bound to the surface of a clot is protected from inhibition by alpha 2M as well as by alpha 2AP.

Chromogenic Compounds↗
PubMed1991

Characterization of fibrin(ogen) fragments in gingival crevicular fluid.

Crevicular fluid (CF) samples were collected by paper strips from healthy and diseased sites. The molecular distribution of fibrin and fibronectin in CF and plasma samples was investigated using SDS-polyacrylamide gel electrophoresis and specific immunoglobulins. Intact fibrin was found in all CF samples. In addition several bands with both lower and higher molecular weights than intact fibrin were seen. These bands were not present in the plasma samples. The low molecular weight bands are suggested to represent degradation products of fibrin. The high molecular bands could be fibrin-fibronectin complexes or fragments of large fibrin polymers. Fibronectin degradation products, but not intact fibronectin, were seen in both healthy and diseased samples.

Blood↗
PubMed1993

Molecular forms and concentration of fibronectin and fibrin in human gingival crevicular fluid before and after periodontal treatment.

A total of 23 periodontitis-affected sites from seven adults was selected for the study. Crevicular fluid (CF) samples were collected with paper strips before treatment (scaling, root planing, and curettage) and 2, 5, 10, 20, and 40 days after treatment. Each sample was eluted into sterile saline and two aliquots were drawn for gel electrophoresis: one for fibronectin and one for fibrin analysis. Peptides were transferred to nitrocellulose membranes, and molecules were detected by specific antibodies. The proportions of different molecular forms of fibronectin and fibrin were analyzed by laser densitometry. Plaque Index, Papilla Bleeding Index, and pocket depth were recorded before and 40 days after treatment. Radiologic bone loss was estimated from orthopantomograms. Two days after treatment, an increase was seen in the proportions of intact fibronectin, fibronectin fragments larger than 70 kDa, and fibrin-positive material with a greater molecular mass than intact fibrin. Between days 5 and 10, the proportions of these large fragments decreased. The highest fibronectin and fibrin concentrations were seen 10 days after treatment. These changes probably reflect degradation of the subgingival fibrin clot formed after treatment, and indicate resolution of the clot during the first 10 days of healing. This agrees well with previous observations of CF plasmin activity and concentration of collagen synthesis markers in CF after periodontal treatment, and with the histologic changes seen during periodontal healing. Results of the present study, together with earlier reported findings of collagen synthesis after periodontal treatment, also support the hypothesis of sequential appearance of fibronectin and collagens during the process of wound healing.

Adult↗
PubMed2001

Modulation of fibrin cofactor activity in plasminogen activation.

Fibrin is a cofactor for the formation of plasmin from plasminogen as catalyzed by tissue plasminogen activator. Initial cleavages of fibrin by plasmin upregulates the cofactor activity of fibrin by exposing carboxyl terminal lysine residues. This effect is eliminated by a carboxypeptidase B-like enzyme generated from the precursor, thrombin activatable fibrinolysis inhibitor (TAFI) that is generated by thrombin during the formation of fibrin. Thus, TAFI and its activation to TAFIa create a link between the coagulation and fibrinolytic cascade, such that activation of the former suppresses the latter. Complete solubilization of fibrin results in a family of very large fibrin degradation products. These also have very substantial tissue plasminogen activator cofactor activity that is very highly downregulated by TAFIa.

Carboxypeptidase B2↗
PubMed2006

Polymerization of fibrin: Direct observation and quantification of individual B:b knob-hole interactions.

The polymerization of fibrin occurs primarily through interactions between N-terminal A- and B-knobs, which are exposed by the cleavage of fibrinopeptides A and B, respectively, and between corresponding a- and b-holes in the gamma- and beta-modules. Of the potential knob-hole interactions--A:a, B:b, A:b, and B:a--the first has been shown to be critical for fibrin formation, but the roles of the others have remained elusive. Using laser tweezers-based force spectroscopy, we observed and quantified individual B:b and A:b interactions. Both desA-fibrin with exposed A-knobs and desB-fibrin bearing B-knobs interacted with fragment D from the gammaD364H fibrinogen containing b-holes but no functional a-holes. The strength of single B:b interactions was found to be 15 to 20 pN, approximately 6-fold weaker than A:a interactions. B:b binding was abrogated by B-knob mimetic peptide, the (beta15-66)2 fragment containing 2 B-knobs, and a monoclonal antibody against the beta15-21 sequence. The interaction of desB-fibrin with fragment D containing a- and b-holes produced the same forces that were insensitive to A-knob mimetic peptide, suggesting that B:a interactions were absent. These results directly demonstrate for the first time B:b binding mediated by natural B-knobs exposed in a fibrin monomer.

Amino Acid Motifs↗
PubMed2000

Fibrinogen, fibrin and crosslinking in aging arterial thrombi.

The assumption that fibrin and crosslinked fibrin impart irreversibility to arterial thrombi is explored with procedure developed for measuring changes in platelet function, morphology and fibrinogen metabolism in aging occlusive thrombi, in which the condition of stasis is imposed uniformly. Arterial thrombi containing autologous (111)In labeled platelets were generated in vivo by bilateral mechanical injury of porcine carotid arteries. Vessels containing the platelet-rich thrombi were harvested and incubated intact (37 degrees C) for intervals ranging from 30 min to 12 h. The isolated vessels were then bisected and agitated in culture medium containing tick anticoagulant and hirudin for 60 min. Disaggregated platelets were evaluated for yield (from (111)In radioactivity) viability (dense body ATP secretion) and morphology (electron microscopy). Western analysis of fibrin(ogen) in thrombus extracts was performed using anti-fibrinogen Bbeta- and gamma-chain monoclonal antibodies for thrombi at each time point. A stable recovery of nearly 50% of platelets was observed during 12 h of thrombus aging. As thrombi aged, viability of disaggregated platelets gradually decreased with platelet necrosis the predominant feature beyond 6 h. By western analysis of thrombus extracts, nearly 50% of fibrinogen was cleaved to fibrin and extensively crosslinked within 30 min of injury with no evidence of fibrinolysis. With the exception of a declining proportion of gamma-monomer, these features remain relatively constant during 12 h of thrombus maturation. It is concluded that neither fibrin nor crosslinked fibrin are dominant factors imparting cohesion within platelet thrombi. Furthermore, under conditions of complete arterial occlusion imposed by this experimental design, there is no evidence of endogenous fibrinolysis.

Adenosine Triphosphate↗
PubMed1975

The scanning electron microscopy of the lysis of fibrin by endothelium.

The lysis of a fibrin clot by sheets of endothelium one cell thick was examined by scanning electron microscopy. The unlysed fibrin film appeared as a densely matted surface, without interstices. Commencing lysis appeared as parallel ovals in which the dense matting was altered to show many strands of fibrin criss-crossing the lytic "window" with many interstices. The wall of the lytic crater surrounding the sheets of endothelium revealed a network of fibrin strands. There was condensation of the fibrin at the edge of the hole at the external surface. The floor of the crater contained sheets of endothelium which were recognized by the shape and size of the nuclei. Flocculent masses of precipitate were present on the endothelial cells in the floor of the crater and occasionally within the lysed ovals at the edge. These may be fibrin degradation products.

Animals↗