[Neonatal hypoxia and hemocoagulative changes]

Coagulation abnormalities with and without haemorrhagic manifestations have been frequently reported in newborn-infants affected by hypoxia. Particularly in postmature-infants and in those ones with acute asphyxia at birth, respiratory distress syndrome (RDS), intra-uterine growth retardation (IUGR) and cyanotic congenital heart disease (CCHD). A reduction of synthesis or a consumption of blood coagulation factors are the main causes of these abnormalities. The anomalies of platelet number and of their function, of haemostasis global tests, of coagulation factors and physiologic inhibitors levels, of fibrinogenesis and fibrinolysis are examined, including authors' studies and a review of literature too. The authors think platelet count, PT, PTT, fibrinogen, factor V and VIII, and PDF determinations are necessary laboratory investigations for newborn-infants with RDS or acute asphyxia for about the first week of life, because of the risk of consumption coagulopathy. In the other hypoxic newborns (IUGR, CCHD, postmature infants) platelets count, PT, PTT and serum PDF determinations could be enough in order to value any coagulation abnormalities presence.

Factors of the extrinsic pathway of blood coagulation in fetal placental macrophages

Term human placentae were examined to identify and localize the factors contributing to extravascular fibrin formation. In addition to blood vessels, components of the extrinsic coagulation cascade were also demonstrated in intracellular localization. These cells in double and treble labeling systems expressed macrophage marker antigens, recognized by DAKO antimacrophage, RFD7, Amersham antimacrophage, and KiM7 monoclonal antibodies and showed positivity for alpha-naphthyl-acetate-esterase (ANAE). The fact that factors of the extrinsic coagulation system can be demonstrated in fetal macrophages of the chorionic stroma suggests that their role is not restricted to cellular defense and phagocytosis, but they may be involved in extravascular intraplacental fibrin formation as well.

Fibrinoid reaction after extracapsular cataract extraction and relationship to exfoliation syndrome

A transitory deposit of a fibrin-like material in the anterior chamber following extracapsular cataract extraction and intraocular lens (IOL) implantation is described. In two studies, one retrospective of 352 operations and one prospective of 189 operations, the fibrinoid reaction was observed in 17% and 11% of the eyes, respectively. The reaction appeared in the early postoperative period in an otherwise quiet eye and the signs varied from a few threads in the pupil area to a dense pupillary membrane in front of the IOL. The deposit disappeared one day to three weeks postoperatively, usually without any remnants. The majority of eyes with the fibrinoid reaction had received a posterior chamber IOL. A strong association with the exfoliation syndrome was found and an increased vascular permeability is suggested as a probable cause of the reaction.

Pathology and general significance of fibrin deposition on lens implants

The deposition of fibrin on the intraocular lens (IOL) in two cases of failed implantation is reported. In one case the network of fibrin fibers was isolated on the surface of an IOL that also showed a clear reactive protein film populated by macrophages and giant cells. In the other case the fibrin network was closely related to sessile macrophages on the implant surface. The presence of fibrin on IOLs indicates an acute phase of increased regional vascular permeability and is clinically important.

Behavior of platelets and leukocytes on the luminal surface of small caliber polyurethane grafts

With scanning electron microscopy, we examined the behavior of platelets and leukocytes on the luminal surface of small caliber polyurethane grafts implanted into small arteries of dogs. Thirty-five grafts were implanted to the carotid and/or femoral arteries. The animals were treated with aspirin and/or DN9693, an inhibitor of phosphodiesterase. In the group treated with aspirin (40 mg/kg i.v.), the deposition of platelets on the luminal surface of the implanted polyurethane grafts was suppressed and the luminal surface was covered with adherent leukocytes. Fibrin nets were formed on the adherent leukocytes. In addition, the adhesion of leukocytes on the grafts was considerably suppressed in the group treated with DN9693 (50 micrograms/kg/min i.v.), and the formation of fibrin nets was markedly reduced. In contrast, in the control group the luminal surface was covered with numerous platelets and some leukocytes, which formed thrombi. These findings suggest that leukocytes adhere primarily to the prosthetic graft and play an important role in the initiation of fibrin formation.

Antithrombogenic surfaces: characterization and bioactivity of surface immobilized PGE1-heparin conjugate

A covalently bonded conjugate of commercial grade heparin and prostaglandin E1 (PGE1) was synthesized to prevent both fibrin formation and platelet aggregation during thrombus formation. The PGE1-heparin conjugate was immobilized on an imidazole carbamate derivatized sepharose bead surface through hydrophilic spacer groups (diamino-terminated polyethylene oxides). One end of the spacer group was coupled to the derivatized surface through a urethane bond between the amine group of the spacer and the derivatized surface. The free amine group of the immobilized spacers was coupled to a carboxylic group of the PGE1-heparin conjugate through an amide bond. Bioactivity of the immobilized conjugate (heparin activity) was measured in terms of increased clotting times (thrombin time assay) and for the inactivation of Factor Xa. Bioactivity of the immobilized compound (PGE1 activity) was analyzed by platelet adhesion and platelet release reactions using C14-5-hydroxytryptamine (5-HT). The conjugate immobilized via the C2 spacer showed the highest incidence of platelet adhesion, 5-HT released and the lowest activity for coagulation factors. In contrast, the 1000 and 4000 immobilized systems showed a significant reduction in platelet activation, while having the greatest effect on coagulation factors. The results of these experiments imply that the immobilized conjugate is active in preventing both pathways of thrombus formation, and the efficacy is improved through the use of long-chain hydrophilic spacer groups.

Monitoring of fibrin generation during thrombolytic therapy of acute myocardial infarction with recombinant tissue-type plasminogen activator

Fibrinopeptide A (FPA) is a very sensitive marker of fibrin generation in vivo. Because an imbalance between thrombogenic and thrombolytic forces may be responsible for the failure to recanalize and for reocclusion of coronary arteries, such a marker could be of eminent value during thrombolytic treatment of acute myocardial infarction. Thirty-four consecutive patients with acute myocardial infarction (peak creatine kinase level, 1,869 +/- 1,543 IU/l) were treated with 100 mg recombinant tissue-type plasminogen activator (rt-PA) 3.1 +/- 1.1 hours after onset of chest pain. Angiography 12.5 +/- 6.1 days later revealed an 81% patency rate of the infarct-related vessel. FPA plasma levels (normal, 1.9 +/- 0.5 ng/ml) were 34 +/- 46 ng/ml on admission and 93 +/- 86 ng/ml (538 +/- 674% with respect to each patient's admission level) after 90 minutes of rt-PA infusion (p less than 0.01). In patients without evidence of reocclusion (including three primary failures), FPA levels fell under continuous heparin infusion to 6.7 +/- 9.7 ng/ml (24 +/- 33%, p less than 0.01) within 30 minutes and were 3.1 +/- 2.2 ng/ml (15 +/- 15%, p less than 0.01), 1.6 +/- 1.1 ng/ml (8 +/- 10%, p less than 0.01), and 2.5 +/- 3.0 ng/ml (12 +/- 16%, p less than 0.01) 30 minutes, 9 hours, and 21 hours, respectively, after completion of rt-PA therapy. Five patients sustained intermittent or permanent coronary reocclusion after primary thrombolytic success. Their early postlytic FPA levels (13-51 ng/ml) remained high or increased again despite adequate anticoagulation. FPA allows the monitoring of fibrin generation during acute myocardial infarction and thrombolytic therapy. Despite successful recanalization, fibrin generation is increased under rt-PA administration before anticoagulation. Patients under anticoagulation with postlytic FPA levels less than 5 ng/ml or below their admission value seem to be at low risk of reocclusion for several days. FPA levels that are persistently high or that increase again despite adequate anticoagulation indicate ongoing fibrin generation. However, whether FPA can indeed be considered a useful marker of reocclusion remains to be confirmed in a larger population of patients with acute myocardial infarction.

In vivo measurements of fibrin formation and fibrinolysis in operable breast cancer

Fibrin formation and fibrinolysis were estimated in 89 breast cancer patients by measurement in plasma of Fibrin Fragment B beta 15-42 and Fibrinopeptide A (FPA), serum Fibrin(ogen) Degradation Products (FDPs) and plasminogen activator by Fibrin Plate Lysis Assay. Results were compared with (a) 26 patients with benign breast diseases; and (b) 45 healthy factory workers. FPA, FDP and B beta 15-42 levels were elevated in both breast cancer patients and benign disease patients, but there were no significant differences between these two groups. Cancer stage, patient age and smoking habits did not affect these results, but Oestrogen Receptor (ER) positive patients had higher B beta 15-42 values than ER negative patients (p = 0.017). These results show that fibrin formation is enhanced preoperatively in patients with either benign or malignant breast disease. The fibrinolytic response to activated coagulation may be relatively deficient in breast cancer. The roles of malignancy, stress and other factors in the causation of these abnormalities require further assessment.

Fibrin formation and platelet activation in patients with myocardial infarction and normal coronary arteries

Coronary spasm is the mechanism most often postulated to explain the rare combination of myocardial infarction and angiographically normal coronary arteries, although the reported evidence for its role is circumstantial rather than conclusive. Whereas the importance of thrombosis in myocardial infarction is uncontested in the presence of significant coronary artery disease, there is little in vivo evidence for thrombosis in angiographically normal coronary arteries. Among 11 consecutive patients with acute myocardial infarction undergoing thrombolytic therapy with recombinant tissue plasminogen activator (rtPA) 3.2 +/- 0.7 h after onset of chest pain, and angiography 10.2 +/- 4.5 days later, three young men had normal coronary arteries. Their cases are documented electrocardiographically, enzymatically and angiographically. Mean plasma levels of fibrinopeptide A (FPA) and beta-thromboglobulin (BTG) were clearly elevated before and during rtPA therapy: FPA 52 +/- 41 ng ml-1, BTG 257 +/- 46 ng ml-1. They did not differ significantly from corresponding mean plasma levels in the eight patients with severe coronary artery disease: FPA 67 +/- 66 ng ml-1, BTG181 +/- 75 ng ml-1. We conclude that fibrin formation and platelet activation are probably equally important in the early hours of myocardial infarction, whether or not significant coronary artery disease is present.

[Multidomain structure of fibrinogen and its transformations]

Generalized concepts of some structural peculiarities of fibrinogen, its transformation into fibrin and assembly have been considered on the basis of author's and published data. The role of local conformational changes in different areas of fibrinogen molecule and of separate reaction centers in formation of single- and double-stranded rod-like equilibrium fibrin oligomers and flexible branched copolymers of fibrinogen with fibrin E fragment has been considered. The mechanism of compactization has been discussed.

[Atherogenic modifications of low density lipoproteins during fibrin formation and fibrinolysis]

Low density lipoproteins (LDL) were modified after incubation with fibrinogen and fibronectin at physiological concentrations in presence of thrombin and, following the fibrin formation, in presence of plasmin. The modified LDL (LDL-F) isolated from plasmin digested fibrin by means of gel permeation chromatography on Sepharose 6B, were associated with fibrinogen and fibronectin degradation products. The LDL-F differed from control LDL in their physico-chemical properties: LDL-F contained the degraded apoprotein B, its electrophoretic mobility was increased, cholesterol/protein ratio as well as flotation coefficient at d = 1.063 were decreased. The effect of LDL-F on lipid accumulation was studied. Content of cholesterol esters in macrophages incubated with LDL-F was higher 3.8-fold as compared with that of the cells incubated with control LDL. Thus, after incubation of LDL with fibrinogen and thrombin, 20% of the lipoprotein was bound to fibrin. The data obtained suggest that thrombosis may promote both LDL deposition in the vascular intercellular matrix and cellular lipid accumulation.

The action of Russell's viper venom on fibrin formation and fibrinolysis in vivo

Envenoming by Russell's viper caused a marked rise in FPA, B beta 15-42 fragment and fibrin derived cross-linked D-dimer fragment indicative of a consumptive coagulopathy with hyperfibrinolysis. There was no increase in tPA or tPA-I levels post envenoming, which suggests that the increase in fibrinolytic activity was not due to venom-induced release of tPA from the vessel walls but may have been attributable to a direct effect of the venom or to a secondary physiological response to fibrin deposition. The effectiveness of the antivenom is demonstrated by its ability to prevent further cleavage of fibrinogen and the return to normal fibrinogen levels by 24 h. A secondary rise in FPA at this time indicates that the initial dose of antivenom may have been too small. The antivenom alone or in combination with the venom causes the release of tPA, tPA-I and vWF by the vessel walls. This may be a consequence of the severe anaphylactic reactions seen in some patients.

Clot lysis mediated by cultured human microvascular endothelial cells

The lysis of fibrin clots on the surface of cultured human omental tissue microvascular endothelial cells (HOTMEC) and cultured human umbilical vein endothelial cells (HUVEC) was studied. Fibrin clots were made by mixing fibrinogen, plasminogen and thrombin on the surface of both cell types. Clot lysis was seen only on the surface of HOTMEC, which were found to synthesize about 100-fold more tissue plasminogen activator (tPA) antigen than HUVEC. Clot lysis of HOTMEC could be blocked by anti-tPA IgG but was not affected by the incorporation of exogenous plasminogen activator (PAI) into the clot in concentrations (75 arbitrary units) exceeding the tPA activity (21 +/- 2.5 IU) of the cells. Thus, it is likely that tPA secreted by HOTMEC is protected from inhibition by PAI in the presence of fibrin and endothelial cells. The stimulation of EC to release an excess of tPA over PAI, in contrast to the secretion of an excess of PAI over tPA found in unstimulated cells in the absence of fibrin, is obviously no prerequisite for the initiation of fibrinolysis on the surface of HOTMEC. As thrombin was used for clot formation, its influence on tPA and PAI synthesis of both cell types was investigated. In contrast to HOTMEC, which were not affected by alpha-thrombin, HUVEC revealed a dose-dependent increase in tPA and PAI synthesis upon incubation with the enzyme. This increase in tPA production by HUVEC was not sufficient to lyse the clots within 48 hours. Furthermore, HUVEC behaved differently towards thrombin as these cells in contrast to HOTMEC revealed the typical shape change reaction upon incubation with the enzyme.

Fibrin formed in plasma is composed of fibers more massive than those formed from purified fibrinogen

Reports of altered fibrin resulting from interactions with plasma proteins and cellular release products have raised the possibility that plasma fibrin may differ from purified fibrin. To investigate this possibility, the structures of thrombin-induced gels formed from platelet poor plasma and from purified fibrinogen were compared using turbidity and gel perfusion techniques. Plasma gels formed more slowly and were composed of fibers two to four times more massive than gels formed from purified fibrinogen. Increasing calcium concentration, decreasing ionic strength, decreasing thrombin concentration, or increasing fibrinogen concentration resulted in increasing fiber size. Addition of excess thrombin accelerated plasma gel formation and decreased gel fiber size, but did not totally eliminate the structural differences between the two systems. Thus, antithrombin activity, while possibly contributory, is not solely responsible for the altered gel structure. Penetration of plasma gels by fibrinolytic agents, egress to areas of injury by inflammatory cells, and gel removal by plasmin are processes at least partially dependent on gel fiber and pore size.

Influence of the subendothelial basement membrane components on fibrin assembly. Evidence for a fibrin binding site on type IV collagen

Effective repair of a vascular injury depends on establishment of a stable fibrin patch at the injury site. Data presented in this study demonstrate that structural modification of fibrin occurs as a result of fibrin interaction with naturally occurring components of the vascular basement membrane and subendothelial structures. Of the basement membrane components, type IV collagen produces the greatest structural modification, generating thick fibrin fibers; a 3-fold increase in the fiber mass/length ratio occurs when type IV collagen is increased from 0 to 100 ng/ml. Laminin and dermatan sulfate decrease the fibrin fiber mass/length ratio resulting in thinner fibers. However, the overall effect of the basement membrane on fibrin is to increase the fibrin fiber diameter. Electrophoretic light scattering and the binding of type IV collagen by fibrinogen-Sepharose further establish the interaction between type IV collagen and fibrinogen. Incorporation of laminin with type IV collagen onto coated surfaces decreases the ability of type IV collagen to bind fibrinogen. These studies emphasize that the final fibrin structure is influenced by the milieu in which the clot is assembled.

Fibrinous membrane formation on the posterior chamber lens during the early postoperative period

I observed transient membrane formation consisting primarily of fibrin on the anterior surface of the IOL in 45 (7.6%) of the 596 eyes that received posterior chamber lens implantation during the past year. The onset of the condition was generally five to six days after surgery. This membrane characteristically developed between the margins of the anterior capsule, and therefore might be the result of lens-induced uveitis from the proliferation of lens epithelial cells under the anterior capsule.

Heparin inhibits fibrin, but not leukocytes, in a model of deep-vein thrombosis

Previous studies with models of deep-vein thrombosis (DVT) have demonstrated that leukocyte (PMN)-mediated vein injury may be an initiating event in DVT (14, 17). Since heparin (H) can prevent DVT, we studied its effect on vascular injury and thrombosis in our model. Three groups of rabbits were treated with H either sc (73 and 147 U/kg) or iv (662 U/kg). Scanning electron microscopy revealed that the 73 U/kg sc dose was ineffective. All veins had PMN accumulation, fibrin deposition and complex thrombus formation. There was no increase in anti-Xa activity; activated partial thromboplastin times (APTT) and whole blood clotting times were normal. The 147 U/kg sc and the intravenous dose did not inhibit PMN-mediated vein injury. The endothelium was sloughed by migrating PMNs, basement membrane was exposed, and platelets adhered to it. Thrombosis was completely absent in the iv dose group. This correlated with increased anti-Xa activity and prolonged APTT and whole blood clotting times. Our results indicate that heparin does not inhibit the PMN adhesion and migration which produces vascular injury. However, the anticoagulant activity of heparin effectively reduces fibrin deposition and complex thrombus formation.

Role of A alpha chain of fibrinogen in coagulation and platelet interaction investigated with a monoclonal antibody

A murine monoclonal antibody (anti-C2G7), reactive with fibrinogen, was used to analyse the structure and function of the fibrinogen epitope C2G7. Anti-C2G7 was found to be reactive with fibrinogen but not with fibronectin, Factor VIII-von Willebrand Factor (FVIII-vWF), beta-thromboglobulin (beta TG), platelet factor 4 (PF4) nor with a range of normal cells and cell lines. Biochemical and plasmin digestion studies of fibrinogen revealed that C2G7 is present on the carboxy-terminal end of the alpha chain on a fragment with a Mr approximately 30-40 K. Functional studies, on the role of fibrinogen in coagulation and platelet function, demonstrated the importance of C2G7 (or a closely associated region) for thrombin-associated fibrin polymerization and collagen induced fibrinogen binding to platelets.

Enhanced fibrin formation in high-altitude pulmonary edema

Blood coagulation, fibrinolysis, and arterial blood gases were examined in 66 nonacclimatized mountaineers at 4,557 m. Subjects were classified according to a clinical score as healthy (n = 25), having mild acute mountain sickness (AMS) (n = 24), showing severe AMS (n = 13), and suffering from high-altitude pulmonary edema (HAPE) (n = 4). Coagulation times, euglobulin lysis time, and fibrin(ogen) fragment E were normal in all groups without significant changes. Fibrinopeptide A (FPA), a molecular marker of in vivo fibrin formation, was elevated in HAPE to 4.2 +/- 2.7 ng/ml (P less than 0.0001) compared with the other groups showing mean values between 1.6 +/- 0.4 and 1.8 +/- 0.7 ng/ml. FPA was normal in one patient with HAPE, however. Severe AMS was accompanied by a significant decrease in arterial PO2 due to an increase in alveolar-arterial O2 difference, whereas arterial PCO2 did not change significantly. We conclude that activation of blood coagulation is not involved in the pathogenesis of AMS and the impairment of gas exchange in this disease. Fibrin generation occurring in HAPE is probably an epiphenomenon of edema formation.

Effect of pacing-induced myocardial ischemia on platelet activation and fibrin formation in the coronary circulation

The effect of pacing-induced myocardial ischemia on platelet activation and fibrin formation was investigated in seven patients with severe proximal lesions of the left anterior descending coronary artery to determine if acute ischemia activates the coagulation system. Fibrin formation was assessed from plasma levels of fibrinopeptide A. Platelet activation was assessed by levels of platelet factor 4, beta-thromboglobulin and thromboxane B2. Plasma levels were measured before, during and after acute myocardial ischemia induced by rapid atrial pacing. Blood samples were collected from the ascending aorta and from the great cardiac vein through heparin-bonded catheters. The occurrence of anterior myocardial ischemia was established by electrocardiography and by myocardial lactate extraction. No significant transmyocardial gradients in the levels of fibrinopeptide A, platelet factor 4, beta-thromboglobulin or thromboxane B2 were found at rest, during ischemia or in the recovery period, and levels in the great cardiac vein did not change in response to ischemia. These data indicate that pacing-induced myocardial ischemia does not result in release of fibrinopeptide A, platelet factor 4, beta-thromboglobulin or thromboxane B2 into the coronary circulation, and imply that acute ischemia does not induce platelet activation or fibrin formation in the coronary circulation.

Does exercise-induced myocardial ischaemia cause enhanced platelet activation and fibrin formation in patients with stable angina and severe coronary artery disease?

In this study, betathromboglobulin (BTG) and fibrinopeptide A (FPA) in peripheral venous blood were measured in 20 patients with stable angina pectoris before and immediately after exercise-induced myocardial ischaemia; in 5 of the 20 patients stable angina was associated with typical peripheral artery disease. A total of 10 patients with angiographically documented peripheral artery disease without angina and 10 normal volunteers were taken as control groups. BTG and FPA in the 15 patients with stable angina before exercise were 41 +/- 14 ng ml-1 and 2.3 +/- 0.9 ng ml-1 and were not statistically different from the values in normal controls; after exercise-induced myocardial ischaemia no significant increase occurred in these patients. Conversely, in the 5 patients with stable angina associated with peripheral artery disease BTG and FPA before exercise were 61 +/- 10 ng ml-1 and 3.5 +/- 0.8 ng ml-1 and increased to 114 +/- 14 ng ml-1 (P less than 0.001) and 4.1 +/- 0.5 ng ml-1 (P less than 0.01): These results were similar to those found in the 10 patients with isolated peripheral artery disease. We conclude that BTG and FPA in peripheral venous blood in patients with stable angina are not elevated either at rest or after exercise-induced myocardial ischaemia. Elevated values of BTG and FPA in patients with stable angina may reflect a major interaction between blood and atherosclerotic vessel wall, suggesting the presence of associated atherosclerotic lesions in peripheral artery disease.

Spontaneous antithrombin in a patient with benign paraprotein

A 66-year-old man with peptic ulcer disease developed a paraprotein that resulted in a spontaneously prolonged prothrombin time, activated partial thromboplastin time, and thrombin clotting time. Although the reptilase time was normal, the thrombin clotting time failed to correct with the addition of normal plasma, calcium, or protamine sulfate. The patient's purified fibrinogen was normal, but his serum contained an IgG that inhibited the clotting of normal plasma and purified fibrinogen in the presence of thrombin. In contrast to previously described paraproteins, this patient's IgG appeared to inhibit the activity of thrombin per se rather than to interfere with fibrinogen cleavage or fibrin polymerization. Although immunoprecipitation between thrombin and the paraprotein could not be demonstrated, the patient's purified IgG, in the presence of thrombin, decreased the thrombin activity on a chromogenic substrate. Further, increasing concentrations of thrombin overcame the inhibitory effect of the patient's paraprotein. Thus, the patient's paraprotein appeared to possess antithrombin activity.