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Biomedical subjects

D C Stump

Publications and source records attributed to D C Stump.

At least 37 records · Page 2Linked to original sources
PubMed1990

Abnormal regulation of coagulation/fibrinolysis in small cell carcinoma of the lung.

Components of coagulation and fibrinolysis reactions were identified in situ by immunohistochemical staining in fresh frozen sections of small cell carcinoma of the lung tissue. Tumor cells stained positively for tissue factor, a protein that is capable of activating the extrinsic pathway of coagulation (the components of which have been seen within small cell carcinoma of the lung [SCCL] tissue), and for proteins C and S antigens. Fibrin was seen in a focal distribution at the host-tumor interface, indicating that thrombin had acted upon the fibrinogen found throughout the tumor stroma. Staining with a neoepitope-specific antibody, which does not discriminate between fibrinogen fragment D and fibrin fragment D-dimer, was similar to that of the fibrin antibody. High molecular weight urokinase-type and tissue-type plasminogen activators were seen in vascular endothelium, but neither existed within the tumor. Low molecular weight urokinase was found in rare isolated foci of tumor cells primarily adjacent to areas of necrosis. Plasminogen activator inhibitor-3 occurred in tumor cell cytoplasmic blebs and in necrotic tumor cells, but plasminogen activator inhibitors 1 and 2 were not seen. Our data suggest a mechanism for thrombin generation and fibrin formation within SCCL tissues that could support cell proliferation, stroma formation, and preservation. These features could be conductive to perpetuation of this tumor and conceivably could form the basis of the beneficial effects of antithrombotic therapy seen in SCCL.

Blood Coagulation↗
PubMed1990

Malignant melanoma. Interaction with coagulation and fibrinolysis pathways in situ.

Immunohistochemical techniques applied to fresh frozen sections of metastatic malignant melanoma tissue revealed abundant fibrinogen (or fibrin I) in perivascular areas throughout the tumor connective tissue stroma. Fibrin was readily detected in a focal distribution in the connective tissue around nodules of viable tumor. Staining for D-dimer of cross-linked fibrin (using an antibody that cross-reacted with fragment D of fibrinogen) coincided with staining for fibrin. Diffuse staining of tumor cell bodies was observed for Factor X, and Factor XIII ("a" subunit) was detected in scattered areas of connective tissue throughout the tumors. Factor VII was not detected, and only rare tumor cells stained for tissue factor. These results support the concept that a tumor cell-associated, thrombin-generating pathway exists in situ in malignant melanoma tissue that includes Factor X but neither tissue factor nor Factor VII. By contrast, tumor cell staining was observed rarely for urokinase and to a variable extent for tissue plasminogen activator.

Antibodies, Monoclonal↗
PubMed1990

Validity of enzyme-linked immunosorbent assays of cross-linked fibrin degradation products as a measure of clot lysis.

Concentrations of cross-linked fibrin degradation products (XL-FDPs) in plasma, measured by enzyme-linked immunosorbent assays (ELISAs) based on monoclonal antibodies (MAbs) raised against fragment D-dimer of cross-linked fibrin, increase when patients are given fibrinolytic agents. Whether XL-FDPs derive from circulating cross-linked fibrin polymers in plasma, compared with clot-associated fibrin, has been questioned because increases in XL-FDP are measured by some assays after fibrinolysis in vitro in the absence of clot. We characterized the source of XL-FDP immunoreactivity in plasma of patients with acute myocardial infarction and ischemic heart disease and the response to plasminogen activation in vitro induced by pharmacological concentrations of tissue-type plasminogen activator (t-PA) and streptokinase. XL-FDPs were measured with two different ELISA. One, "pan-specific tag ELISA," was based on a capture MAb specific for XL-FDP and a tag MAb that recognizes an epitope exposed in the fragment D region of both fibrin and fibrinogen, whereas the other, "fibrin-specific tag ELISA," was based on a capture and tag MAbs both specific for fibrin. After plasminogen activation was induced in vitro in plasma from patients with myocardial infarction, increased concentrations of XL-FDP were measured by the pan-specific tag ELISA; however, concentrations measured with the fibrin-specific tag ELISA were not increased. To determine the mechanism for this discrepancy, plasma was subjected to immunoadsorption with a MAb specific for fragment D-dimer before and after in vitro activation of the fibrinolytic system and immunoblotting with a fragment D-dimer-specific MAb and with the pan-specific MAb. Increased concentrations of fragment D-dimer, as well as fibrinogen fragment D at high concentrations, were recognized by the specific MAb. Non-cross-linked fragments were also shown by immunoblotting with the pan-specific MAb to coprecipitate with cross-linked fibrin fragments. This suggested the increased concentrations of XL-FDP measured by the pan-specific tag ELISA after in vitro activation of the fibrinolytic system were due to detection of non-cross-linked fibrinogen fragments. However, fibrin fragment D-dimer concentrations were found to increase in plasma of 15 patients given t-PA for acute myocardial infarction. We conclude fragment D-dimer in plasma of patients during thrombolysis does not originate from circulating soluble cross-linked fibrin but rather is a marker of solid-phase fibrin dissolution, which may be quantitated with assays based on capture and tag antibodies that do not detect fibrinogen or its degradation products.

Antibodies, Monoclonal↗
PubMed1989

Indirect activation of blood coagulation in colon cancer.

Systemic activation of the coagulation mechanism is known to exist in patients with colon cancer. The mechanism of such activation was investigated using immunohistochemical techniques applied to fresh frozen sections of resected primary colon cancer specimens. Tumor cells stained for tissue factor, factor V, and urokinase-type plasminogen activator. Perivascular and intercellular areas stained for fibrinogen and the "a" subunit of factor XIII. Staining was minimal or absent for protein C, protein S, plasminogen activator inhibitors 1-3, factor VII, factor X, and fibrin (the antigenic site on the amino-terminal portion of B beta chain that is exposed following thrombin cleavage of fibrinopeptide B was not detected). The lack of an intact thrombin-generating pathway in situ associated with viable colon cancer cells is consistent with the findings of others that coagulation activation in colon cancer may be triggered by a soluble tumor product that exerts its effect at sites distant from the tumor. These results may explain the absence of clinical responsiveness of colon cancer to antithrombotic drug therapy and may clarify therapeutic strategies for this common tumor.

Blood Coagulation↗
PubMed1989

Bleeding during thrombolytic therapy for acute myocardial infarction: mechanisms and management.

Hemorrhage is the major adverse effect of thrombolytic therapy, but its incidence can be reduced by careful selection of patients and avoidance of unnecessary invasive procedures. More than 70% of bleeding episodes occur at vascular puncture sites. Hypofibrinogenemia and elevation of fibrinogen degradation products have been weakly correlated with the risk of hemorrhage. Although depletion of factors V and VIII may occur, the role of such depletion in bleeding is unknown. Several in-vitro studies have shown plasmin-induced platelet dysfunction, but clinical data are limited. Nevertheless, the role of platelet inhibition should be considered because many patients are treated with antiplatelet agents. Most patients who have bleeding can be managed by interruption of thrombolytic and anticoagulant therapy, volume replacement, and manual pressure applied to an incompetent vessel. Protamine should be considered if heparin has been administered within 4 hours of the onset of bleeding. In the few patients who fail to respond to these conservative measures, judicious use of transfusion products may be indicated. Transfusion of cryoprecipitate, fresh frozen plasma, and platelets should be considered with clinical and laboratory reassessment after each administration. A target fibrinogen level of 1 g/L is desirable with cryoprecipitate infusion. Antifibrinolytic agents are available as a last alternative. We have developed an algorithm for using these products.

Antifibrinolytic Agents↗
PubMed1989

Combined tissue-type plasminogen activator and prostacyclin therapy for acute myocardial infarction. Thrombolysis and Angioplasty in Myocardial Infarction (TAMI) 4 Study Group.

Current limitations of recombinant tissue-type plasminogen activator (rt-PA) therapy for acute myocardial infarction include failure to achieve recanalization in 25% of patients, reocclusion and reperfusion injury. Iloprost, a stable analogue of prostacyclin (PGI2), has been demonstrated to facilitate thrombolysis and reduce myocardial stunning in experimental models. To evaluate combined therapy, rt-PA (100 mg 3 h) and Iloprost (2 ng/kg per min for 48 h) were administered to 25 patients and then rt-PA alone (same dose) was given to an additional 25 patients with evolving myocardial infarction. At 90 min after drug administration, infarct-related vessel patency was observed in 11 (44%) of 25 who received rt-PA plus Iloprost compared with 15 (60%) of 25 who received rt-PA alone (p = 0.26). At 1 week, reocclusion had occurred in 3 (14%) of 21 patients who received combined therapy compared with 6 (26%) of 23 patients treated with rt-PA alone (p = 0.46). Ejection fraction increased significantly from baseline to 7 days for rt-PA alone whereas it decreased with combined therapy (rt-PA alone whereas it decreased with combined therapy (rt-PA alone: 47.3 +/- 11.5% at baseline to 50.4 +/- 9.8% at 7 days; rt-PA plus Iloprost: 51.3 +/- 10.1% at baseline to 49.0 +/- 9.4% at 7 days; difference between groups p = 0.05). At 4 h after therapy, fibrinogen decreased 33% for rt-PA plus Iloprost compared with a 52% for rt-PA alone (p = 0.001). Fibrinogen degradation products increased 60% more for rt-PA alone than for rt-PA plus Ilprost. Thus, the combination of rt-PA plus Iloprost at the doses employed did not improve immediate or follow-up coronary artery patency or left ventricular functional recovery compared with that achieved with rt-PA alone.

Cardiovascular Agents↗
PubMed1989

A randomized controlled trial of intravenous tissue plasminogen activator and early intravenous heparin in acute myocardial infarction.

To evaluate the coronary thrombolytic efficacy of tissue plasminogen activator (t-PA) and early intravenous heparin, 134 patients with acute myocardial infarction were randomly assigned to combination therapy or t-PA only. At a median of 2.78 hours from symptom onset, 64 patients received both t-PA (1.5 mg/kg/4 hr) and a bolus of 10,000 units heparin, whereas 70 patients received t-PA alone at the same dose. All patients underwent coronary angiography 90 minutes after initiation of therapy to determine infarct vessel patency status, after which time the control group patients were eligible to receive heparin. Baseline demographic and angiographic characteristics were similar for the groups. Infarct vessel patency was 50 of 63 (79%) for combination t-PA and heparin and 54 of 68 (79%) for t-PA alone. Bleeding complications, as reflected by need for transfusion, were similar in the two groups: 13% in the patients treated with t-PA and heparin compared with 18% in patients treated with t-PA only (p = 0.53). The only intracranial hemorrhage in the trial occurred in a patient initially treated without heparin. Fibrinogen at 50 minutes after therapy was 32% decreased from baseline for the t-PA and heparin-treated patients compared with a 39% decrease in the control group. Predischarge left ventricular ejection fraction was similar for the two groups: 49.0 +/- 10.1% versus 50.2 +/- 11.9% for combined versus t-PA only therapy, respectively. We conclude that early intravenous heparin does not facilitate the fibrinolytic effect of t-PA at the doses tested.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiography↗
PubMed1989

Pharmacodynamics of thrombolysis with recombinant tissue-type plasminogen activator. Correlation with characteristics of and clinical outcomes in patients with acute myocardial infarction. The TAMI Study Group.

Coagulation analysis was performed on blood samples from 386 patients with acute myocardial infarction drawn before, during, and after a continuous intravenous infusion of 150 mg recombinant tissue-type plasminogen activator (rt-PA) (Activase). Plasma rt-PA rose to peak levels of 2.1 +/- 3.1 micrograms/ml (mean +/- SD). Fibrinogen levels measured by coagulation rate and by sulfite precipitation decreased from baseline levels of 3.0 +/- 0.9 and 3.2 +/- 1.0 g/l, respectively, to nadir levels of 1.4 +/- 0.75 and 1.8 +/- 0.92 g/l, respectively, and were associated with peak levels in serum of fibrinogen-degradation products (FDP) of 230 +/- 470 micrograms/ml. Forty percent of patients experienced a nadir functional-fibrinogen level of less than 1.0 g/l, whereas 20% fell below 0.5 g/l. Nadir fibrinogen levels did not correlate with patency of the infarct-related coronary artery at 90 minutes or with risk of coronary vessel reocclusion within 7-10 days. However, the risk of coronary artery reocclusion was inversely related to the baseline functional fibrinogen level (p = 0.0008), with the magnitude of its drop to nadir level (p = 0.0003) as well as to peak levels of FDP (p = 0.038). Quantitative blood loss correlated with all markers for systemic fibrinogenolysis including nadir fibrinogen level (r = -0.20, p = 0.0011), percent decrease of fibrinogen (r = 0.22, p = 0.001), and peak FDP levels (r = 0.14, p = 0.020). Both patients who experienced intracranial hemorrhage presented with high baseline fibrinogen levels and experienced extensive degradation of coagulable fibrinogen. Overall, patients at greatest risk of systemic fibrinogenolysis tended to be relatively older women with lower body weight.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Coagulation↗
PubMed1988

Monitoring of hemostasis parameters during coronary thrombolysis with recombinant tissue-type plasminogen activator.

The monitoring of changes in the blood coagulation and fibrinolytic systems during thrombolytic therapy with recombinant tissue-type plasminogen activator (rt-PA) may be complicated by artifacts due to in vitro activation after blood collection and to interference of other agents (e.g., heparin) in the assays. In 106 patients with early acute myocardial infarction, infused with 150 mg of rt-PA (G11044) intravenously over 5 to 8 hours, blood samples were collected into liquid citrate supplemented with the plasmin inhibitor aprotinin (200 KIU/ml plasma) or on a lyophilized mixture of acidified citrate and the synthetic t-PA inhibitor D-Phe-Pro-Arg-CH2Cl (PPACK). A good correlation between precipitable (sulphite) and functional (clotting rate) fibrinogen levels was observed in plasma collected on citrate before therapy (r = 0.76) and in samples collected after 3 hours on either aprotinin (r = 0.87) or PPACK (r = 0.82). Precipitable fibrinogen levels were approximately 10% higher than functional level, in baseline samples collected on citrate alone and approximately 20% higher in 3 hour samples collected on either PPACK or aprotinin. Fibrinogen levels measured with both assays correlated well, but were somewhat higher in samples collected on PPACK than on aprotinin. rt-PA antigen levels assayed in plasma collected in either inhibitor correlated well (r = 0.90) but were 10-20% higher in PPACK containing samples. Addition of heparin up to 9 units/ml to plasma had no effect on the functional fibrinogen assay.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Chloromethyl Ketones↗
PubMed1988

Comparison of two dose regimens of intravenous tissue plasminogen activator for acute myocardial infarction.

Two dosing schedules of intravenous tissue plasminogen activator (t-PA) for acute myocardial infarction were compared in a multicenter trial. At 2.95 +/- 1.1 hours from onset of chest pain, 386 patients received 150 mg of intravenous t-PA. For the first 178 patients (group A), 60 mg were given in the first-hour dose and the remaining 90 mg were infused over 7 hours. In the subsequent 208 patients (group B), the first-hour dose was 1.0 mg/kg and the remaining 150 mg were given over 5 hours. At initial angiography 94 +/- 30 minutes into therapy, the infarct vessel patency was 64% in group A versus 75% in group B (p = 0.02). By final angiography with up to 4 selective contrast injections, patency was 68% versus 77%, respectively (p = 0.06). Repeat angiography at 7 to 10 days demonstrated reocclusion in 17% of group A and 13% of group B patients (p = 0.35). There was no difference in fibrinogen nadir or mean hematocrit drop between the 2 groups: 120 mg/dl and 11 points, respectively, in group A compared with 120 mg/dl and 10 points in group B. However, bleeding was reduced in group B patients as evident by a decrease in requirement for greater than or equal to 2 units of packed red blood cell transfusion (group A 36%, group B 27%, p = 0.05) and lower incidence of gastrointestinal bleeding (group A 12%, group B 4%, p = 0.002). To further study the importance of weight adjustment, patients were divided into 2 groups according to weight (less than or equal to 90 kg versus greater than 90 kg).(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon↗
PubMed1988

Mechanisms of thrombus formation and lysis.

Maintenance of a patent vasculature is critical to provide nutrient blood flow to dependent tissues. This is normally facilitated by vessels composed of actively nonthrombogenic endothelium and blood that contains both nonactivated platelets and inactive coagulation proenzymes. Following vessel injury, active hemostasis results from vasoconstriction, adherence and aggregation of activated platelets, and coagulation enzyme activation. The resulting thrombus contains a mixture of blood cells and the insoluble product of coagulation, fibrin, which further stimulates the activation of another blood enzyme system known as the fibrinolytic system. This results in the conversion by plasminogen activators of the circulating plasma proenzyme plasminogen into the active fibrinolytic enzyme plasmin, which dissolves the clot into degradation products. Vascular patency ultimately is restored and healing is thus facilitated. The hemostatic system is highly regulated by a variety of processes. Derangement of regulation can lead to disease manifesting either as thrombosis or hemorrhage. Furthermore, improved understanding of the molecular interactions involved in these processes has led to design of newer therapeutic interventions targeted toward amelioration of the sequelae of thromboembolic disease.

Blood Coagulation↗
PubMed1988

Thrombolytic therapy.

Thrombolytic agents are plasminogen activators that convert plasminogen, the inactive proenzyme of the fibrinolytic system in blood, to the proteolytic enzyme plasmin. Plasmin in turn dissolves the fibrin of a blood clot, but may also degrade normal components of the hemostatic system and predispose to bleeding. The first-generation thrombolytic agents, streptokinase and urokinase, are only moderately efficacious, and their administration is associated with extensive systemic fibrinogen breakdown. In three major clinical trials in patients with acute myocardial infarction, early intravenous streptokinase significantly reduced in-hospital mortality. Tissue-type plasminogen activator (t-PA) is a more effective and fibrin-specific coronary arterial thrombolytic agent than streptokinase, but its impact on mortality remains to be established. Single-chain urokinase-type plasminogen activator (scu-PA, pro-urokinase) is more fibrin specific than urokinase but has only reached the stage of early clinical investigation. The acylated plasminogen streptokinase activator complex (Apsac) has a profile of thrombolytic efficacy and fibrin specificity that is probably very similar to that of streptokinase, but it can be administered as a single bolus injection. New trends toward further improved efficacy and fibrin specificity of thrombolytic therapy include the use of combinations of synergistic thrombolytic agents, mutants of t-PA or scu-PA, chimeric t-PA/scu-PA molecules, or antibody-targeted thrombolytic agents.

Clinical Trials as Topic↗
PubMed1988

Coronary arterial thrombolysis with combined infusion of recombinant tissue-type plasminogen activator and urokinase in patients with acute myocardial infarction.

To determine whether tissue-type plasminogen activator (t-PA) and urokinase (UK) act synergistically to achieve coronary thrombolysis, incremental doses of both drugs were infused intravenously over 60 min. In 146 consecutive patients treated 3.0 +/- 1.0 hr from symptom onset, coronary angiography was performed 90 min after the start of the infusion and at 7 days. The groups of patients treated by different dose regimen were as follows: group I, 14 patients treated with t-PA 25 mg and UK 0.5 million U; group II, 20 patients given t-PA 25 mg and UK 1.0 million U; group III, 24 patients given t-PA 1.0 mg/kg and UK 0.5 million U; group IV, 33 patients treated with t-PA 1.0 mg/kg and UK 1.0 million U; and group V, 55 patients given t-PA 1.0 mg/kg and UK 2.0 million U. In groups I and II, patency of the infarct-related vessel at 90 min was only 36% and 42%, respectively. With 1 mg/kg t-PA and increasing doses of UK (groups III to V), patency ranged from 72% to 75% (overall 73%). Repeat catheterization at 7 days demonstrated reocclusion in groups III to V in 10 of 110 (9%). The patency and reocclusion rates in groups III to V were not significantly different from those in our previous study of 386 patients treated with t-PA alone (150 mg over 6 to 8 hr). In that study the patency rate of the infarct-related vessel at 90 min was 75% (p = .66) and reocclusion occurred in 15% (p = .11).(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon↗
PubMed1988

Fibrinolysis during liver transplantation in humans: role of tissue-type plasminogen activator.

Human liver transplantation is frequently associated with a coagulopathy and bleeding diathesis developing during the anhepatic phase of surgery. The hemostatic defect has been attributed in part to accelerated fibrinolysis. In this study we evaluated changes in specific blood fibrinolytic parameters occurring in eight adult patients undergoing first-time orthotopic liver transplantation. Five of the eight patients experienced moderate to severe systemic fibrinolysis as reflected by alpha 2-antiplasmin consumption and fibrinogen degradation with the concomitant appearance of fibrin(ogen) degradation products. In association with these changes, an increase in tissue-type plasminogen activator (t-PA) activity and t-PA antigen levels was also observed. Fibrinolysis was most pronounced during the anhepatic phase of surgery and decreased after revascularization of the grafted liver. Three additional patients who underwent the same procedure manifested much less evidence of systemic fibrinolytic activation and had minimal elevation of t-PA antigen levels or activity. Urokinase-type plasminogen activator levels, although elevated in three patients, were disassociated from increased t-PA levels and concomitant systemic fibrinolysis. The operative course of those patients developing t-PA-associated fibrinolysis was characterized by shock, acidosis, generalized bleeding, and a need for substantially greater blood product support during surgery. These findings suggest that the observed fibrinolytic defect is related to increased circulating plasma levels of t-PA, presumably resulting from a combination of increased intravascular release and decreased hepatic clearance of t-PA. These observations may have implications for intraoperative therapy for the transplant-related coagulopathy and its associated bleeding.

Adult↗
PubMed1987

Immunological identity of heparin-dependent plasma and urinary protein C inhibitor and plasminogen activator inhibitor-3.

Purified plasma and urinary protein C inhibitors (PCI) formed heparin-dependent complexes with activated protein C (APC) which were detected by immunoblotting after nondenaturing gel electrophoresis. Bands representing APC.PCI complexes were also seen on immunoblots after incubation of plasma with APC and heparin. The same immunoblot pattern of complexes was detected by three different methods: method A, monoclonal antibody to plasminogen activator inhibitor-3 (PAI-3, urinary urokinase inhibitor) + 125I-labeled anti-mouse IgG; method B, polyclonal antibodies to PCI + 125I-labeled purified plasma PCI; and method C, monoclonal antibody to protein C + 125I-protein C. Plasma depleted of PAI-3 by immunoadsorption with insolubilized monoclonal antibody to PAI-3 showed no detectable antigen or complexes with APC as visualized by methods A or B. This PAI-3-depleted plasma had less than 10% of the heparin-dependent inhibitory activity of normal plasma toward APC. Purified plasma PCI was fully reactive in an enzyme-linked immunoabsorbent assay for PAI-3, and plasma and urinary PCI inhibited urokinase activity in a heparin-dependent manner. These data indicate that heparin-dependent plasma and urinary PCI and PAI-3 are immunologically and functionally very similar if not identical. This observation identifies a new interrelation between the protein C anticoagulant and the fibrinolytic systems. In addition, plasma contains a heparin-independent inhibitor of APC which is not immunologically related to plasma PCI or to PAI-3.

Antibodies, Monoclonal↗