Disorganization of cultured vascular endothelial cell monolayers by fibrinogen fragment D.

Fibrinogen fragment D, which is heterogeneous, has several important biological functions. Human fibrinogen fragments D94 (molecular weight, 94,000), D78 (78,000), and E (52,000) were purified. Fragments D78 and D94 but not purified fibrinogen or fragment E specifically caused disorganization of bovine aortic endothelial cells cultured as monolayers. Within 2 hours of exposure to pathophysiological concentrations of fragment D, the confluent endothelial cells retracted from each other and projected pseudopodia. These disturbed cells subsequently became rounded and detached from the substrate. The actin present in stress fibers in stationary monolayer cells was diffusely redistributed in cells with fragment D-induced alterations in morphology. This effect was not observed in monolayers of kidney epithelial cells. The results demonstrate a specific effect of fibrinogen fragment D on the disorganization of cultured vascular endothelial cell monolayers and suggest that fragment D plays a role in the pathogenesis of syndromes with vascular endothelial damage.

Isotopic studies of therapeutic anticoagulation with a coagulating enzyme.

The kinetics of the depletion of plasma fibrinogen were studied in seven patients who received fibrinogen-(131)I 1 hr before an intravenous injection of the coagulating enzyme (CE) derived from the venom of the pit viper, Agkistrodon rhodostoma. Disappearance of the clottable radioactivity labeled fibrinogen from the circulation conformed to an exponential decay with an average half-life of 0.85 hr. The mean clearance rate for protein-bound radioactivity, composed of fibrinogen and it's split products, was 12% of the intravascular pool per hour. The breakdown products of fibrin produced by CE inhibited polymerization of fibrin in vitro. Studies in five patients performed between the 3rd and 10th day following the administration of CE revealed that the absolute catabolic rates of fibrinogen were subnormal initially, but gradually increased as the fibrinogen concentration returned to normal. In rabbits, after the administration of CE, regeneration of the fibrinogen pool was markedly prolonged. This delayed regeneration time was not influenced by an excess of antivenene, but rapid regeneration to pretreatment values of plasma fibrinogen was immediately initiated by stimulating fibrinogen synthesis with subcutaneous turpentine.

Glanzmann thrombasthenia. Cooperation between sequence variants in cis during splice site selection.

Glanzmann thrombasthenia (GT), an autosomal recessive bleeding disorder, results from abnormalities in the platelet fibrinogen receptor, GP(IIb)-IIIa (integrin alpha(IIb)beta3). A patient with GT was identified as homozygous for a G-->A mutation 6 bp upstream of the GP(IIIa) exon 9 splice donor site. Patient platelet GP(IIIa) transcripts lacked exon 9 despite normal DNA sequence in all of the cis-acting sequences known to regulate splice site selection. In vitro analysis of transcripts generated from mini-gene constructs demonstrated that exon skipping occurred only when the G-->A mutation was cis to a polymorphism 116 bp upstream, providing precedence that two sequence variations in the same exon which do not alter consensus splice sites and do not generate missense or nonsense mutations, can affect splice site selection. The mutant transcript resulted from utilization of a cryptic splice acceptor site and returned the open reading frame. These data support the hypothesis that pre-mRNA secondary structure and allelic sequence variants can influence splicing and provide new insight into the regulated control of RNA processing. In addition, haplotype analysis suggested that the patient has two identical copies of chromosome 17. Markers studied on three other chromosomes suggested this finding was not due to consanguinity. The restricted phenotype in this patient may provide information regarding the expression of potentially imprinted genes on chromosome 17.

Thrombolysis in Myocardial Infarction (TIMI) Trial--phase I: hemorrhagic manifestations and changes in plasma fibrinogen and the fibrinolytic system in patients treated with recombinant tissue plasminogen activator and streptokinase.

Two hundred ninety patients with acute myocardial infarction were treated according to random assignment with an intravenous infusion of either 80 mg of recombinant tissue plasminogen activator (rt-PA) over 3 h or 1.5 million units of streptokinase over 1 h. Patients received an intravenous bolus of heparin (5,000 U [USP]) before pretreatment coronary angiography and a continuous infusion (1,000 U/h) starting 3 h later. The frequency of major and minor hemorrhagic events (33% rt-PA, 31% streptokinase) and associated transfusions (22% rt-PA, 20% streptokinase) were comparable in both groups. More than 70% of bleeding episodes in each group occurred at catheterization or vascular puncture sites. Precipitable fibrinogen levels, measured in plasma samples collected in the presence of a protease inhibitor (aprotinin), declined in rt-PA and streptokinase groups by averages of 26 and 57% at 3 h and by 33 and 58% at 5 h, respectively (rt-PA versus streptokinase, p less than 0.001). At 5 h the plasma plasminogen declined by 57% (rt-PA) and 82% (streptokinase) (p less than 0.001); plasma fibrin(ogen) degradation products were higher in streptokinase-treated patients (244 +/- 12 micrograms/ml, mean +/- SE) than in rt-PA-treated patients (97 +/- 9 micrograms/ml, p less than 0.001). At 27 h, plasma fibrinogen and plasminogen levels were lower and fibrin(ogen) degradation products higher than pretreatment levels in both groups. The frequency of hemorrhagic events was higher in patients with greater changes in plasma factors at 5 h; within treatment groups the levels of fibrin(ogen) degradation products correlated with bleeding complications (p less than 0.005). Thus, in the doses administered, rt-PA induces systemic fibrinogenolysis that is substantially less intense than that induced by streptokinase. The high frequency of bleeding encountered is related to the protocol used, including vigorous anticoagulation, arterial punctures and thrombolytic therapy. These findings emphasize the need for avoidance of invasive procedures and for meticulous care in the selection and management of patients subjected to thrombolytic therapy.

Control of bleeding in patients with immune and nonimmune thrombocytopenia with aminocaproic acid.

Patients with thrombocytopenia have an increased risk of bleeding. We have used 18 courses of aminocaproic acid in 17 patients with either immune or nonimmune thrombocytopenia to successfully control hemorrhage associated with reduced platelet counts. The types of hemorrhage controlled included the following: vaginal, gastrointestinal, intracerebral, cutaneous, mucous membrane, subconjunctival, and renal, as well as that associated with dental extractions, tracheostomy, and sites of Penrose drains. The number of platelet and red blood cell transfusions administered decreased substantially following institution of aminocaproic acid therapy. We conclude that therapy with aminocaproic acid is safe and useful in the management of bleeding in patients with both immune and nonimmune thrombocytopenia.

Circulating anticoagulant in the procainamide-induced lupus syndrome.

An elderly man with procainamide hydrochloride-induced lupus syndrome had a circulating anticoagulant against factor XI and a biologic false-positive (BFP) test result for syphilis. This was not associated with hemorrhagic problems. The activity of the circulating anticoagulant and the BFP disappeared within days following discontinuation of procainamide and the administration of corticosteroids.

Extensive thrombus formation with heparin resistance during extracorporeal circulation. A new presentation of familial antithrombin III deficiency.

Extensive thrombus formation during extracorporeal circulation despite the administration of heparin sodium prompted investigation of a 15-year-old boy with a calcified right ventricular thrombus and a history of subacute bacterial endocarditis. In vitro studies confirmed the failure of heparin in standard doses to have an anticoagulant effect. Antithrombin III concentrations were low. The patient's mother, who had no history of thromboembolic disease, was also antithrombin III deficient. Resistance to heparin is a theoretical, but inconsistently documented, feature of antithrombin III deficiency. This deficiency state should be considered whenever heparin resistance is encountered, even in the absence of a personal and family history of thromboses.

Reduction in the plasma clearance rate of warfarin induced by cimetidine.

The interaction between the histamine H-2 receptor antagonist, cimetidine, and warfarin sodium was prospectively studied in 14 patients who were previously anticoagulated for five years. The patients received warfarin and cimetidine concomitantly for a minimum of ten days. Seven of the patients experienced increases in plasma warfarin concentrations. This correspondingly resulted in abnormal prolongation of their prothrombin times. In these patients the elevation in the steady-state warfarin concentration demonstrates that coadministration of cimetidine significantly reduces the plasma clearance rate of warfarin. The serum and urine metabolite levels of warfarin were not qualitatively different in the absence in contrast to the presence of cimetidine. It is apparent that cimetidine can act as an inhibitory influence on the catabolic degradation of warfarin.

Typhoid fever. Studies of blood coagulation, bacteremia, and endotoxemia.

Patients with typhoid fever were studied to determine whether disseminated intravascular coagulation (DIC), circulating bacteria, and endotoxemia were responsible for the signs and symptoms of their illnesses. Coagulation tests in 28 patients detected thrombocytopenia in 17, hypofibrinogenemia in nine, and elevated titers of fibrinogen-related antigens in 20. Repeated testing during convalescence showed a return toward normal values. Intestinal bleeding, however, did not correlate with abnormalities of coagulation tests. Thus, DIC occurred commonly but appeared to be a subclinical event in these patients. In 25 patients with positive blood cultures for Salmonella typhi, quantitative cultures detected from less than 10 to 9 x 10(2) bacteria/ml. Limulus tests for endotoxin in plasma were negative in all 21 patients tested. These results indicated that the concentrations of circulating bacteria and endotoxin in typhoid fever are lower than in other Gram-negative bacterial infections and suggested that circulating bacteria and endotoxin do not play a major role in the pathogenesis of typhoid fever.

Role of splenectomy in immune (idiopathic) thrombocytopenic purpura.

Idiopathic thrombocytopenic purpura (ITP) is an immune disorder, which causes an acute or chronic thrombocytopenia, and may result in potentially life-threatening hemorrhage. Splenectomy is one of the treatment options that needs to be weighed in the treatment of ITP, particularly in cases that have shown response failure to medical modalities such as prednisone, i.v.Ig, or anti-D globulin therapy. Although most studies demonstrate good early response following splenectomy, the long-term outcome is less favorable. Furthermore, other negative factors, such as rendering the patient ineligible for anti-D globulin or oral tolerance therapy and vulnerable to possible life-threatening sepsis, must be weighed prior to splenectomy.

Existence of multiple peaks in plasma ethinyl estradiol and norethindrone after oral administration of a contraceptive pill.

Previous measurements of plasma ethinyl estradiol (EE2) and norethindrone (NE) over 24 h after oral administration of a contraceptive pill have demonstrated a single steroid peak occurring 1-2 h after pill ingestion, with a gradual decline over the next 22 h. In the present study plasma concentrations of EE2 and NE were measured 0, 0.5, 0.75, 1, 2, 4, 12, and 24 h after oral ingestion of a contraceptive pill containing 35 micrograms EE2 and 1 mg NE at 0, 3, 6, and 9 months of use in 58 normal healthy women. Contrary to previous reports, analysis of the 464 steroid curves (58 subjects x 4 time periods x 2 steroids) revealed the presence of multiple hormone peaks. Two peaks of EE2 were identified in 44.8% of women during the first pill cycle and in 75.9%, 55.2%, and 67.2% of women after 3, 6, and 9 months of pill use. Two hormone peaks of NE were observed in 29.3% of women during the first cycle and in 36.2%, 50%, and 44.8% at 3, 6, and 9 months, respectively. Existence of these multiple peaks at the frequency observed has not previously been reported. Further quantification of the frequency and magnitude of these peaks could be helpful in explaining differences in biological responses associated with pill use.

Long-term outcome of splenectomy for idiopathic thrombocytopenic purpura.

Idiopathic thrombocytopenic purpura (ITP) is an illness of primary acquired thrombocytopenia occurring in the absence of marrow failure. Splenectomy was first used as a treatment for ITP in 1913. However, with the realization that opsonin (critical for the optimal killing of invasive micro-organisms by white blood cells) is manufactured only in the spleen, spontaneous splenic removal was reevaluated and questioned. Splenectomy has a success rate that remains nearly identical (about 50% to 60%) whether it is performed soon after diagnosis or several months or years later. As yet, there is no consistently effective method to predict an individual ITP patient's response to splenectomy. As the time since splenectomy increases, however, the rate of excellent response decreases. Despite pneumococcal vaccination prior to splenectomy, fatal fulminant sepsis is an omnipresent possibility. Because a number of published studies, including the Johns Hopkins experience, have questioned the long-term outcome of splenectomy, splenectomy should not be the first treatment option for ITP patients. It should be performed only after all other therapeutic modalities have been exhausted, and the patient has a platelet count less than 25,000/microL and is hemorrhaging. Once patients have undergone splenectomy, they are Ineligible for potentially excellent treatment such as anti-D globulin or oral tolerance therapy.

A kinetic analysis of fibrinogenolysis during plasminogen activator therapy.

A mathematic model of the systemic fibrinogenolysis that accompanies coronary thrombolysis with recombinant tissue plasminogen activator (rt-PA) has been devised. The kinetic parameters of the model were estimated by nonlinear regression analysis with data from a clinical trial of rt-PA. The plasma elimination rate constant for rt-PA was estimated to be 10.0 hr-1, the second-order catalytic rate constant for the in vivo rt-PA-mediated conversion of plasminogen to plasmin 0.0078 (microgram rt-PA/kg body weight)-1 hr-1, the plasma elimination rate constant for plasmin 2.33 hr-1, and the second-order catalytic rate constant for the in vivo plasmin-catalyzed degradation of fibrinogen 0.466 (mg plasmin/dl)-1 hr-1. Computer simulation studies based on these parameter estimates show that the magnitude of fibrinogenolysis induced by rt-PA is related to the dose in a curvilinear fashion, showing diminishing increments in the effect at increasing doses. The degree of fibrinogenolysis induced by rt-PA administration is nearly independent of the dosing schedule.

The fibrinolytic system in man.

The existence of a system in the human body capable of inducing the dissolution of endogenous pathologically formed thrombi was appreciated in ancient times. Considered in detail in this article are the data that have elucidated the physiologic regulation of which plasmin formation is dependent on, the plasma concentration of plasminogen, availability of activators of plasminogen in the plasma and surrounding tissue environment, the concentration of naturally present inhibitors, and the existence of fibrin in the circulation. Important in this rapidly progressive scientific discipline is consideration of the factors which control the synthesis of the components of this proteolytic enzyme system. Recently abundant information has indicated that this plasminogen-plasmin proteolytic enzyme system can be utilized therapeutically. Knowledge of the mechanisms of this system has permitted identification of agents that can be exogenously administered to releave thrombotic obstruction to blood flow in the venous (pulmonary emboli, deep vein thrombosis) and arterial (peripheral and central vessels) circulatory systems. Particularly important is the demonstration that thrombolytic agents can directly attack and alleviate the immediate cause of acute myocardial infarction. As a result of the innovations in the present decade, it is evident that the plasminogen system can be advantageously employed to reverse the pathologic effects of all thrombotic diseases.

Breath ethane: a specific indicator of free-radical-mediated lipid peroxidation following reperfusion of the ischemic liver.

A major component of the organ injury mediated by toxic oxidants, such as seen following reperfusion of the ischemic liver, is due to the peroxidation of polyunsaturated fatty acids, especially of cell membranes. We utilized the measurement of exhaled breath ethane, a metabolic product unique to oxidant-mediated lipid peroxidation, as a noninvasive indicator of this process in swine liver subjected to warm ischemia/reperfusion. Under rigorously controlled anesthesia conditions, pig livers were subjected to 2 h of warm total ischemia, followed by reperfusion in situ. Expired air was collected and its ethane content quantitated by a novel gas chromatographic technique. The time course of breath ethane generation correlated closely with the appearance of hepatocellular injury as measured by impairment of Factor VII generation and other measures of liver integrity. Moreover, the administration of the specific superoxide free radical scavenger, superoxide dismutase (SOD), significantly attenuated both the elaboration of ethane and the hepatocellular injury. These findings not only provide confirmation of the previously reported link between hepatocellular injury by free radicals generated at reperfusion, but also establish the use of expired breath ethane analysis as a sensitive, specific, and noninvasive indicator of the injury process in real time.

Aspirin in the prevention of thrombosis.

More than a decade has passed since the introduction of the concept that inhibition of platelet function may be helpful in preventing the initiation of thrombus formation. Aspirin has been recognized as inhibiting normal platelet function and the mechanism has been clearly delineated. Legions of patients have been studied to answer the question of whether aspirin is efficacious in the primary prevention of acute myocardial infarction. At the present time, however, a solid, clear answer is not available and firm recommendations cannot be made. A large number of studies evaluating aspirin and other antiplatelet agents in the prevention or delay of recurrent myocardial infarction (secondary prevention) have been completed and those studies reporting a favorable beneficial effect are in the minority. In these secondary prevention studies reporting success, the doses of aspirin employed were large enough to inhibit both the cyclo-oxygenase system and thromboxane A2 production as well as the synthesis of prostacyclin. Thus, in these studies if aspirin is effective in reducing adverse cardiovascular events, its efficacy is being mediated by an unknown mechanism. If the reader of the few studies that report positive results is convinced of the benefit of aspirin, it must be emphasized that thoughtful, cautious patient selection based upon the individual's cardiovascular risk profile must be exercised. Individual variation may exist with respect to aspirin's beneficial effect. It must be absolutely recognized that aspirin or any antiplatelet agent does not in any way substitute for the removal or treatment of coexisting risk factors such as tobacco, obesity, hypercholesterolemia, hyperlipidemia, hypertension, and metabolic disease. In contrast to aspirin, control of the above risk factors has been established as beneficial. Aspirin is not free of undesirable side-effects; fatalities secondary to hemorrhage have been reported, and these must be known in detail and understood by both physician and patient before this agent is prescribed in the prophylactic treatment of cardiovascular disease.

Trousseau's syndrome and other manifestations of chronic disseminated coagulopathy in patients with neoplasms: clinical, pathophysiologic, and therapeutic features.

Analysis of 182 patients with chronic disseminated intravascular coagulopathy and malignancy shows common features. Migratory thrombophlebitis occurred in 96 patients while at least a single episode of thrombophlebitis was noted in 113. Seventy-five of the patients bled and 45 had arterial emboli in various organs. Twelve patients had the triad of thrombophlebitis, hemorrhage, and arterial emboli, often sequentially. Hematologic data showed derangements associated with intravascular coagulation, the most prominent of which were hypofibrinogenemia and thrombocytopenia. Other abnormalities included prolonged prothrombin time, increased fibrinogen-fibrin degradation products, decreased levels of factors V and VIII, cryofibrinogenemia, and microangiopathic hemolytic anemia. Forty-one patients had lesions of non-bacterial thrombotic endocarditis at autopsy; 31 of these had arterial emboli during life. None of the lesions were infected. Mitral and aortic valves were most frequently involved. No single mechanism that causes the disseminated intravascular coagulopathy has been identified. However, cell products--secretions and enzymes--and the cells themselves have been proposed as the procoagulant(s) responsible for the syndrome. In addition to treatment of the underlying neoplasm, symptomatic disseminated intravascular coagulopathy should be controlled. Heparin is the drug of choice for treatment of this problem, very little benefit having been observed with warfarin therapy. Long-term use of anticoagulants is potentially feasible for control of chronic disseminated intravascular coagulopathy, but without effective control of the underlying tumor ultimately will be unsuccessful.

Fibrinolytic agents in the treatment of thrombotic disorders.

The oncology patient is often at increased risk of bleeding when thrombolytics are administered. Fortunately, the factors placing the patient at risk are easily identified and include intracranial disease, vascular defects produced by surgery, instrumentation or tumor invasion, underlying coagulopathy, and severe thrombocytopenia. Unfortunately, new clot-specific agents have not eliminated the problem of undesirable bleeding; in fact, they may cause more bleeding by more efficiently dissolving both pathological thrombi and hemostatic plugs. The development of a means of delivering thrombolytics solely to the target clot is desirable and should be performed when possible. Despite the need for caution, thrombolytics are remarkably effective in treating both venous and arterial thrombi, and it is a disservice to the patient not to carefully consider their use.

A unique circulating inhibitor with specificity for coagulation factor X.

An 84-year-old woman presented with extensive cutaneous and gastrointestinal bleeding. Initial laboratory studies revealed a prolonged prothrombin time and activated partial thromboplastin time. Further investigations revealed a circulating anticoagulant with specificity for factor X. The patient's hemorrhage resolved with supportive measures only. Approximately 11 months after presentation, the inhibitor disappeared.

Venous thrombosis and splenic rupture in paroxysmal nocturnal hemoglobinuria.

A patient with an 11 year history of paroxysmal nocturnal hemoglobinuria presented with severe abdominal pain. On admission, the hematocrit value was 30 per cent and unchanged from repeated measurements during the previous three years. Abdominal angiography identified extensive thromboses of the splenic and portal venous systems. After initial improvement on heparin therapy, the patient experienced additional abdominal crises. A ruptured and multifragmented spleen was removed at the time of exploratory laparotomy. Postoperatively, after a several days' interval of improvement, the patient experienced additional thrombotic episodes of the abdomen, upper extremities and cerebral cortex. The latter was associated with disabling nerve paralysis. With continuous intravenous heparin plus steroid therapy, the patient's condition improved progressively. Despite the numerous thrombotic episodes during the prolonged hospital course, no hemolytic episodes were observed. This is the first report of documented splenic rupture in a patient with paroxysmal nocturnal hemoglobinuria.