Effects of all-trans retinoic acid or chemotherapy on the molecular regulation of systemic blood coagulation and fibrinolysis in patients with acute promyelocytic leukemia

We studied the pathogenesis of the bleeding disorder in acute promyelocytic leukemia by measuring procoagulant, profibrinolytic, and proinflammatory mediators in peripheral blood and bone marrow cells from 25 previously untreated patients. Patients were induced with either all-trans retinoic acid (ATRA) or chemotherapy. Plasma levels of fibrinopeptide A (FPA), fibrin d-dimer, thrombin antithrombin (TAT) complex, prothrombin fragment 1.2 (F1.2), urokinase-type plasminogen activator (uPA), tissue-type plasminogen activator (t-PA) and plasminogen activator-inhibitor 1 (PAI-1) were measured before and after therapy, as was the cellular expression of the genes for tissue factor (TF) and interleukin-1 beta (IL-1 beta). The mean plasma levels of fibrin d-dimer, F1.2, TAT and FPA were markedly elevated prior to therapy and declined during the first 30 days of treatment with either ATRA or chemotherapy, but more rapidly and to a greater extent in patients treated with ATRA. ATRA treatment was associated with a significant decrease in TF gene expression in bone marrow cells during the first 30 days of treatment, whereas IL-1 beta gene expression, which decreased in the cells of six patients treated with either chemotherapy or ATRA, actually increased in the remaining six patients treated with either chemotherapy or ATRA. In patients with APL, treatment with either chemotherapy or ATRA rapidly ameliorates the coagulopathy, as indicated by an abrupt decline in markers of clotting activation. An increase in cytokine gene expression (e.g. IL-1 beta) may provide an explanation for the persistent hypercoagulability observed in some patients with APL, regardless of therapeutic approach. Our data confirms and extends earlier observations by others that ATRA is more effective than chemotherapy alone in rapidly reducing the procoagulant burden of APL tumor cells. However, our data also suggests that cytokine expression in some patients may be accelerated by either chemotherapy or ATRA. The implications of this observation for understanding the retinoic acid syndrome will require further studies.

Expression of receptors for plasminogen activators on endothelial cell surface depends on their origin

Receptors for plasminogen activators present on endothelial cell (EC) surface regulate local plasmin activity. Plasmin generation by human ECs, derived from cerebral cortex, skin and lung, iliac artery, iliac vein, aorta and coronary artery, was studied. The respective ECs were treated with recombinant tissue plasminogen activator (rt-PA) or with recombinant urokinase-type plasminogen activator (ru-PA), washed, plasminogen added and the plasmin generated then assayed. The largest amounts of plasmin were generated by cerebral ECs, under baseline conditions or after exposure to rt-PA or ru-PA (P < 0.0001). Exposure to rt-PA also resulted in more plasmin generation than ru-PA in the cerebral ECs (P < 0.0001) but not in the other ECs. Heparin enhanced plasmin generation by both rt-PA and ru-PA. Specific antibody against annexin II, a t-PA receptor, blocked plasmin generation by rt-PA. Western blotting showed higher amounts of annexin II on the cell membrane in cerebral ECs. This suggests that expression of annexin II in ECs depends on their location, being greatest in cerebral ECs. In contrast, expression of u-PA receptor was the same for all ECs. This has implications for higher risk of intracranial bleeding during thrombolytic therapy, and for a role of t-PA in neurological development and function.

Thrombogenic role of cells undergoing apoptosis

Apoptosis is involved in many biological processes, especially during chemotherapy in cancer patients. Chemotherapy is also associated with an increased risk of thrombosis. The relationship between thrombogenicity and apoptosis was studied in various human tumour cell lines and non-tumour cell lines. Apoptosis was induced by the chemotherapeutic agent camptothecin and by Fas ligand, then quantified by staining with fluorescein isothiocyanate-conjugated annexin V and propidium iodide. A significant correlation between thrombin generation and degree of apoptosis was observed (P < 0.0005). Addition of anti-tissue factor antibody in excess or of tissue factor pathway inhibitor partially inhibited thrombin generation, suggesting that tissue factor activation was responsible for this process. A statistical correlation between tissue factor activity and degree of apoptosis was also found (P < 0.005). Both thrombin generation and tissue factor activity were blocked by the addition of annexin V, which binds and inhibits phosphatidylserine. This indicates that the exteriorization and exposure of phosphatidylserine on the cell surface membrane during apoptosis were essential for both thrombin generation and tissue factor activation.

Thrombotic microangiopathy in the cancer patient

Thrombotic microangiopathy, manifesting as thrombotic thrombocytopenic purpura (TTP) or hemolytic uremic syndrome, is a common complication in cancer patients. It shares the pathogenic microvascular occlusive lesion and many clinical manifestations as the classical TTP, but the spectrum of complications varies widely. Several subsets are seen, including a microangiopathic hemolytic anemia in advanced cancer, chemotherapeutic drug-associated microangiopathy and those with the transplant setting. The prognosis is not as favorable as in classical TTP. Anecdotal reports indicate that responses are seen with plasma exchange and with immunoadsorption.

The Pathogenetic Role of Apoptosis in Hypercoagulable States

Hypercoagulable states are common disorders with high risk of thrombosis associated with cardiovascular and malignant diseases. The pathogenesis of hypercoagulability is multifactorial. The basic physiological mechanism is the imbalance between anticoagulant activities and procoagulant activities in hemostatic system. In this review, we discuss the correlation between apoptosis and thrombogenesis in hypercoagulable states. Some cell-associated cofactors in coagulation system, including phosphatidylserine, tissue factor, thrombomodulin and cancer procoagulant, are regulated during apoptosis of various cell types. Vascular endothelial cells may act as one of the most important aspects affecting the balance of anticoagulant and procoagulant activities. When endothelial cells are activated or induced to undergo apoptosis by a number of physiological factors, such as inflammatory cytokines and bacterial lipopolysaccharide, the procoagulant activities of endothelial cells are enhanced. Other cell types such as apoptotic vascular smooth muscle cells, monocytes and macrophages may also contribute to the pathogenesis in atherosclerosis. Apoptotic tumor cells, which express high level of procoagulant activities, may act as a direct trigger for coagulation activation.

Atypical hairy cell leukemia

The morphologic differential diagnosis of mature B-cell neoplasms with cytoplasmic projections includes splenic lymphoma with villous lymphocytes and hairy cell leukemia. Although the classification of hairy cell leukemia is not universally recognized, 3 variants have been described, namely, classic, variant, and Japanese variant, each of which has different clinical and immunophenotypic features. Classic hairy cell leukemia is virtually always CD11c(+), CD25(+), and CD103(+). Variant and Japanese variant hairy cell leukemias are usually CD11c(+), always CD25(-), and occasionally CD103(+). Each variant is characteristically CD10(-). We present a case of hairy cell leukemia with a unique immunoprofile in that the cells were CD10(+), CD25(+), and CD103(-), and we review the criteria helpful in differentiating "hairy" B-cell neoplasms. This case emphasizes the variability of hairy cell leukemia and the need to correlate all clinical and pathologic data in reaching a diagnosis.

Plasminogen activator inhibitor 1 may promote tumour growth through inhibition of apoptosis

Plasminogen activator inhibitor 1 (PAI-1) has been found to be a bad prognostic factor in a number of tumours but the reason has not been fully explained. The human prostate cancer cell line PC-3 and the human promyelocytic leukaemia cell line HL-60 were used in this study to determine the effect of PAI-1 on spontaneous and induced apoptosis in culture. Apoptosis was induced with camptothecin or etoposide. Addition of a stable variant of PAI-1 or wild-type PAI-1 to these cells resulted in a significant inhibition of apoptosis. In contrast, both the latent form of PAI-1 and the stable variant of PAI-1 inactivated by a specific neutralizing monoclonal antibody, or the stable variant of PAI-1 in a complex with recombinant urokinase did not inhibit apoptosis. This indicated that the inhibitory activity of PAI-1 was required for its anti-apoptotic effect but the urokinase-type plasminogen activator receptor was not involved. These findings provide an explanation for the bad prognostic correlation of high PAI-1 levels in tumours. The anti-apoptotic effect was also found in non-tumoural cells including human umbilical vein endothelial cells and the benign human breast epithelial cell line MCF-10A, suggesting that this is a novel physiologic function of PAI-1.

Hereditary defects in fibrinolysis associated with thrombosis

The plasminogen-plasmin system involves proteolytic enzymes which are primarily responsible for the degradation of fibrin deposits in blood vessels. Through intricate interactions between the various components and inhibitors, a balance is maintained between profibrinolysis and impaired fibrinolytic activity. Several hereditary defects have been described affecting functional plasminogen concentrations, plasminogen activator levels, and plasminogen activator inhibitor activity. These defects have been implicated as risk factors for thrombosis based on a multitude of case reports associating impaired fibrinolysis with thrombosis. However, under close scrutiny, the role of decreased fibrinolysis as an etiologic factor in thrombosis has not been firmly established. Rather, dysfibrinolysis may manifest itself through an accentuation of an underlying thrombophilic state such as recurrent thrombotic episodes. Further evaluation of impaired fibrinolytic activity in conjunction with an underlying thrombophilic condition is warranted.

The hyperviscosity syndromes

Impaired blood flow due to abnormal rheologic characteristics results in a multiplicity of clinical manifestations, collectively termed the hyperviscosity syndrome. A basic knowledge of the principles of rheology is important in the understanding of its pathophysiology, especially the relationship between viscosity and flow conditions. The flow characteristics in different types of blood vessels are also determinants in the location of the clinical manifestation. The syndrome can occur in a wide variety of diseases and is best grouped according to the causative element or elements in blood. Abnormalities in the cellular components of blood can occur in the quantity and the quality of erythrocytes, leukocytes, and platelets. Abnormal plasma components can also be in both the quantity and quality of the plasma proteins. Clinical manifestations are the result of vascular occlusion, especially in the microcirculation. The altered rheologic characteristics of either the cellular or the protein component may be temperature dependent, being abnormal only at temperatures below 37 degrees C, so that only the cooler parts of the body are affected. The management of these conditions should be primarily directed at the removal of the abnormal component. At the same time, it should be accompanied by measures that can control the production of the causative element.

Thrombotic microangiopathy manifesting as thrombotic thrombocytopenic purpura/hemolytic uremic syndrome in the cancer patient

The complication of thrombotic thrombocytopenic purpura or hemolytic uremic syndrome (TTP/HUS) can occur in cancer patients. It is characterized by a microangiopathic hemolytic anemia, severe thrombocytopenia, and renal failure. Pulmonary manifestations, especially pulmonary edema, are a common observation. Neurologic changes are also frequently seen. The etiology is unknown at this time. It has been observed in many different types of cancer and is most commonly seen in gastric adenocarcinoma followed by carcinoma of the breast, colon, and small cell lung carcinoma. The hemolysis can be massive and is due to red cell fragmentation, as schistocytes are present in all the cases. Though immune complexes are present in the plasma, the antiglobulin (Coomb's) test is negative. Chemotherapeutic agents, especially mitomycin C, have been implicated as causative factors. There is a correlation of this complication with the cumulative dose. However, chemotherapy cannot account for all the cases as the syndrome can occur in untreated patients. It can be differentiated from disseminated intravascular coagulation by the absence of a coagulopathy. Management should consist of plasma exchange, use of a Staphylococcus aureus column (Prosorba), and control of hypertension. Because of the susceptibility to pulmonary edema, blood volume overloading should be avoided.

Endothelial cell hyperplasia contributes to thrombosis in heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia (HIT), a well recognized complication of heparin administration, is associated with thrombotic complications. An immunologic mechanism is believed to be responsible for the thrombocytopenia, but the cause of thrombosis is not fully understood. We report a histological and immunohistochemical study of thrombosed vessels in surgically removed ischemic tissues in patients with HIT complicated by gangrene of the lower limbs. Tissue sections were studied by: (1) hematoxylin and eosin staining and immunoperoxidase staining using a monoclonal antibody against platelet surface glycoprotein Ib(GPIb) for the identification of platelets, and (2) polyclonal antibodies against tissue-type plasminogen activator (tPA) and factor VIII for the identification of endothelial cells. We observed small arteries occluded by multiple small platelet thrombi surrounded by proliferative endothelial cells. In addition, depositions of IgG, IgA, and IgM were found in the occluded arteries. We postulate that the endothelial cell hyperplasia is caused by immunologic injury to endothelial cells as a result of immunoglobulin deposition, and by various mitogens derived from the activated platelets in the thrombi. Such endothelial cell hyperplasia is a major contributory factor, in addition to the microthrombi, of the occlusive vasculature in this disease.

Current Clinical Practice: Current Management of Thrombotic Thrombocytopenic Purpura

Historically, the mortality rate of thrombotic thrombocytopenic purpura (TTP) approached 100%. However, by the 1980's, new therapy was instituted with a vast improvement in survival to 90%. The exact pathogenesis of TTP remains elusive. Yet, despite incomplete understanding of the pathophysiology, outcome has improved due to increased awareness of the symptomatology leading to earlier diagnosis and better supportive care, in addition to effective therapy with plasma exchange. TTP represents a disease in which prompt diagnosis and treatment can lead to a critical difference in clinical outcome.

Oestradiol regulation of the components of the plasminogen-plasmin system in MDA-MB-231 human breast cancer cells stably expressing the oestrogen receptor

To understand the hormonal regulation of the components of the plasminogen-plasmin system in human breast cancer, we examined the oestradiol (E2) regulation of plasminogen activators (PAs), namely urokinase-type plasminogen activator (uPA) and tissue-type plasminogen activator (tPA), plasminogen activator inhibitor type 1 (PAI-1) and uPA receptor (uPAR), in our model system. We used stable transfectants of the MDA-MB-231 human breast cancer cells that express either the wild-type (S30 cells) or the mutant 351asp-->tyr oestrogen receptor (ER) (BC-2 cells). Northern blot analysis showed that there was a concentration-dependent down-regulation of uPA, tPA and PAI-1 mRNAs by E2. In contrast, uPAR mRNA was not modulated by E2. The pure anti-oestrogen ICI 182,780 was able to block E2 action, indicating that the regulation of these genes is ER mediated. The E2 also inhibited the expression and secretion of uPA, tPA and PAI-1 proteins as determined by enzyme-linked immunosorbent assay (ELISA) in cell extracts (CEs) and conditioned media (CM). Zymography of the CM confirmed the inhibitory effect of E2 on uPA activity. Thus, we now report the regulation of uPA, PAI-1 and tPA by E2 in both mRNA and protein levels in ER transfectants. The association between down-regulation of the uPA by E2 and known E2-mediated growth inhibition of these cells was also explored. Our findings indicate that down-regulation of uPA by E2 is an upstream event of inhibitory effects of E2 on growth of these cells as the addition of exogenous uPA did not block the growth inhibition by E2.

Thrombotic thrombocytopenic purpura associated with ticlopidine. A review of 60 cases

BACKGROUND

Thrombotic thrombocytopenic purpura, a life-threatening multisystem disease, has been infrequently associated with use of ticlopidine, a platelet anti-aggregating agent.

PURPOSE

To review 60 cases of ticlopidine-associated thrombotic thrombocytopenic purpura.

DATA SOURCES

Medical records, published case reports, and case reports submitted to the U.S. Food and Drug Administration.

STUDY SELECTION

Instances of ticlopidine-associated thrombotic thrombocytopenic purpura were identified.

DATA SYNTHESIS

Ticlopidine had been prescribed for less than 1 month in 80% of the patients, and normal platelet counts had been found within 2 weeks of the onset of thrombotic thrombocytopenic purpura in most patients. Mortality rates were higher among patients who were not treated with plasmapheresis than among those who underwent plasmapheresis (50% compared with 24%; P < 0.05).

CONCLUSIONS

Ticlopidine use may be associated with the development of thrombotic thrombocytopenic purpura, usually within 1 month of initiation of therapy. The onset of ticlopidine-associated thrombotic thrombocytopenic purpura is difficult to predict, despite close monitoring of platelet counts.

Agonist activity of antiestrogen-receptor complexes to regulate urokinase plasminogen activator (uPA) and plasminogen activator inhibitor type 1 (PAI-1) endogenous gene expression in breast cancer cells

We have shown that 4-hydroxytamoxifen (4-OHT) has estrogen-like effects on induction of TGFalpha mRNA in estrogen receptor (ER)-negative MDA-MB-231 human breast cancer cells, transfected with either wildtype (S30 cells) or a codon 351asp-->tyr mutant ER (BC-2 cells). The mutant receptor used to produce the stable transfectants was identified in a tamoxifen-stimulated human breast tumor. We have also demonstrated that raloxifene exhibits a gene-specific estrogen-like effect with mutant ER (BC-2 cells) but not with wildtype ER (S30 cells) (Levenson, A.S., Catherino, W.H. and Jordan, V.C. (1997) Estrogenic activity is increased for an antiestrogen by a natural mutation of the estrogen receptor. J. Steroid Biochem. Mol. Biol., 60, 261-268). We now describe the regulation of urokinase plasminogen activator (uPA) and plasminogen activator inhibitor type 1 (PAI-1) endogenous gene expression by estradiol (E2) and different antiestrogens in BC-2 cells. Northern blot analyses revealed that 4-OHT and raloxifene have concentration-dependent agonistic (E2-like) effects on the regulation of these genes. In contrast, the pure antiestrogen ICI 182780 alone had no effect but could block the action of E2, 4-OHT and raloxifene. The E2-like effects of non-steroidal antiestrogens in this model system cannot be explained by the mutation in the ER alone because 4-OHT acts as an agonist with wildtype receptor as well. We propose that the clear cut biological expression of estrogen-like qualities with different antiestrogens will in the future serve as an important model to dissect the signal transduction pathway.

Digital ischemia and gangrene due to red blood cell aggregation induced by acquired dysfibrinogenemia

Digital gangrene was observed in a patient who had angiographic findings of digital arterial occlusion. The patient's blood showed a marked red blood cell aggregation with rouleaux formation in long chains, which could not be dispersed at shear rates up to 200 sec-1. Studies of the patient's blood revealed the presence of an abnormal fibrinogen capable of aggregating normal red blood cells. This fibrinogen was found by Raman spectroscopy to have an increased alpha-helical content, whereas the beta-sheet content was decreased. Defibrinogenation therapy with ancrod resulted in a dramatic symptomatic relief. The disappearance of the abnormal fibrinogen 6 months later and an absence of a family history indicate that this dysfibrinogenemia was acquired.

The mechanism of cancer-mediated conversion of plasminogen to the angiogenesis inhibitor angiostatin

Angiostatin, a potent naturally occurring inhibitor of angiogenesis and growth of tumor metastases, is generated by cancer-mediated proteolysis of plasminogen. Human prostate carcinoma cells (PC-3) release enzymatic activity that converts plasminogen to angiostatin. We have now identified two components released by PC-3 cells, urokinase (uPA) and free sulfhydryl donors (FSDs), that are sufficient for angiostatin generation. Furthermore, in a defined cell-free system, plasminogen activators [uPA, tissue-type plasminogen activator (tPA), or streptokinase], in combination with one of a series of FSDs (N-acetyl-L-cysteine, D-penicillamine, captopril, L-cysteine, or reduced glutathione] generate angiostatin from plasminogen. An essential role of plasmin catalytic activity for angiostatin generation was identified by using recombinant mutant plasminogens as substrates. The wild-type recombinant plasminogen was converted to angiostatin in the setting of uPA/FSD; however, a plasminogen activation site mutant and a catalytically inactive mutant failed to generate angiostatin. Cell-free derived angiostatin inhibited angiogenesis in vitro and in vivo and suppressed the growth of Lewis lung carcinoma metastases. These findings define a direct mechanism for cancer-cell-mediated angiostatin generation and permit large-scale production of bioactive angiostatin for investigation and potential therapeutic application.

Elevations of tissue-type plasminogen activator and differential expression of urokinase-type plasminogen activator in diseased aorta

PURPOSE

Elevations of plasmin have been implicated in the pathogenesis of abdominal aortic aneurysms (AAA) because of its ability to digest extracellular matrix proteins. Plasminogen activators regulate the conversion of plasminogen to plasmin. Tissue-type plasminogen activator (tPA) is more important in modulation of fibrinolysis, and urokinase-type plasminogen activator (uPA) is predominant in tissue remodeling. The purpose of this study was to determine the levels of plasminogen activators in diseased aorta because they may be responsible for the increased plasmin levels previously described in AAA.

METHODS

Levels of tPA and uPA in AAA, occlusive, and normal (organ donor) aorta were studied in tissue explant supernatants. Supernatant tPA and uPA levels were measured with an enzyme-linked immunosorbent assay. Northern analysis was used to quantitate uPA messenger RNA (mRNA) levels in aortic tissue.

RESULTS

Levels of tPA in the supernatants were similar in occlusive (20 +/- 4 ng/ml) and AAA (23 +/- 8) aorta, but threefold higher than in normal aorta (7 +/- 5; p < 0.005 for normal vs occlusive and p < 0.001 for normal vs AAA). In contrast, uPA supernatant levels were differentially expressed, with the highest level existing in AAA (9.7 +/- 2.7 ng/ml), followed by occlusive (4.9 +/- 3.5), and the lowest levels in normal aorta (1.2 +/- 0.7; p < 0.05 for normal vs occlusive, p < 0.001 for normal vs AAA, and p < 0.005 for occlusive vs AAA). Inhibition of protein or RNA synthesis by addition of cyclohexamide or actinomycin D, respectively, revealed no significant difference between treated and control supernatants, suggesting that the increases were caused by protein release rather than active synthesis. Levels of uPA mRNA followed the same trend as the supernatant uPA levels (AAA 1.07 +/- 0.54, occlusive 0.54 +/- 0.08, and normal aorta 0.01 +/- 0.01).

CONCLUSIONS

Levels of tPA were similar in aneurysmal and occlusive aorta, but exhibited a threefold increase over normal aorta, suggesting that the elevations of tPA are associated with the arteriosclerosis present in both aneurysmal and occlusive disease. Differences in uPA levels were significant between all three groups, with the highest levels in AAA and the lowest levels in normal specimens. Northern analysis of uPA mRNA followed the same trend, suggesting that the increase in uPA may be regulated at the level of transcription. As uPA plays an important role in tissue remodeling, our findings may also reflect the relative tissue repair activities in these three types of specimens and may explain the previously reported increased levels of plasmin seen in AAA.

Plasminogen activator levels are influenced by location and varicosity in greater saphenous vein

PURPOSE

The plasminogen system, which includes tissue type plasminogen activator (tPA), urokinase type plasminogen activator (uPA), and their main inhibitor, plasminogen activator inhibitor type 1 (PAI-1), plays a major role in both fibrinolysis and tissue remodeling. This study compares the levels of tPA, uPA, and PAI-1 at the groin and ankle in normal and varicose greater saphenous vein (GSV).

METHODS

GSV was collected from patients undergoing varicose vein (VV) removal and from normal vein (NV) from arterial bypass procedures. Portions of the GSV at the groin and the ankle were minced and placed in serum-free media for 48 hours. Assays of the supernatants were obtained for tPA, uPA, and PAI-1 protein by enzyme-linked immunosorbent assay. Cyclohexamide and actinomycin D were also added to the media of the VV tissue explant supernatants to inhibit protein and RNA synthesis, respectively.

RESULTS

Levels of tPA were significantly higher at the groin (11 +/- 2) than the ankle (5 +/- 1) in the VV (p < 0.005), and this trend was also seen in the NV (groin 10 +/- 2 and ankle 7 +/- 3). Levels of uPA were significantly higher in the groin VV (14 +/- 4.3) than in NV (3.0 +/- 0.8, p < 0.05). This difference, although not statistically significant, applied to the ankle as well (VV 14.5 +/- 6.3 and NV 5.3 +/- 2.7). No significant difference was seen between NV and VV for PAI-1 (NV, groin 155 +/- 73 and ankle 113 +/- 53, VV, groin 161 +/- 20 and ankle 142 +/- 38) or tPA. Inhibitor studies revealed no significant difference among control, cyclohexamide, and actinomycin D supernatants for tPA, suggesting release of protein rather than active synthesis. In contrast, inhibitor supernatants were significantly lower for uPA and PAI-1 than control supernatants (p < 0.05), suggesting that uPA and PAI-1 were actively synthesized.

CONCLUSIONS

In the tissue explant supernatant model uPA and PAI-1 are actively synthesized, but tPA is not. Levels of PAI-1 were comparable in all four groups. Levels of uPA in the varicose GSV were higher than in NV, suggesting a role for uPA in the pathologic makeup of VV. Levels of tPA were higher at the groin versus the ankle position, potentially explaining the previously described increased fibrinolytic activity seen at the groin.

Human prostate carcinoma cells express enzymatic activity that converts human plasminogen to the angiogenesis inhibitor, angiostatin

Angiostatin is an inhibitor of angiogenesis and metastatic growth that is found in tumor-bearing animals and can be generated in vitro by the proteolytic cleavage of plasminogen. The mechanism by which angiostatin is produced in vivo has not been defined. We now demonstrate that human prostate carcinoma cell lines (PC-3, DU-145, and LN-CaP) express enzymatic activity that can generate bioactive angiostatin from purified human plasminogen or plasmin. Affinity purified PC-3-derived angiostatin inhibited human endothelial cell proliferation, basic fibroblast growth factor-induced migration, endothelial cell tube formation, and basic fibroblast growth factor-induced corneal angiogenesis. Studies with proteinase inhibitors demonstrated that a serine proteinase is necessary for angiostatin generation. These data indicate that bioactive angiostatin can be generated directly by human prostate cancer cells and that serine proteinase activity is necessary for angiostatin generation.

Elevated levels of plasminogen-activator inhibitor type 1 in atherosclerotic aorta

PURPOSE

Plasminogen activator inhibitor type I (PAI-1) inhibits the plasminogen activators that convert plasminogen to plasmin. In addition to initiating fibrinolysis, plasmin activates tissue matrix metalloproteinases, which cause degradation of the extracellular matrix (ECM) in the arterial wall. Elevated levels of PAI-1 ultimately decrease plasmin formation and may lead to an accumulation of ECM and arteriosclerosis.

METHODS

PAI-1 was studied by four methods in atherosclerotic (aneurysmal and occlusive) and normal (organ donor) aorta: (1) PAI-1 secretion by tissue explant supernatants, including time course and inhibition studies; (2) tissue PAI-1 by protein extraction; (3) PAI-1 mRNA was quantitated by Northern analysis using glyceraldehyde-3-phosphate dehydrogenase to normalize for RNA loading; and (4) in situ hybridization was used to localize the cells that produced PAI-1 mRNA.

RESULTS

Supernatant PAI-1 levels at 48 hours were 776 +/- 352, ng/ml in 11 atherosclerotic aortas and 248 +/- 98 ng/ml in 8 normal aortas (p < 0.005). Tissue PAI-1 levels per 100 mg of tissue were 99 +/- 58 ng in 11 atherosclerotic aortas and 38 +/- 20 ng in 5 normal aortas (p < 0.05). PAI-1 mRNA levels by Northern analysis were 0.91 +/- 0.49 in seven atherosclerotic aortas and 0.44 +/- 0.27 in five normal aortas. Supernatant time-course experiments revealed that PAI-1 increased over time. Inhibitor studies revealed that PAI-1 decreased to approximately one third of control values when cycloheximide or actinomycin D were added to the media, indicating that active synthesis of PAI-1 had occurred. In-situ hybridization localized PAI-1 mRNA predominately to endothelial cells and a few scattered vascular smooth muscle and inflammatory cells. Subgroup analysis revealed no statistically significant differences between aneurysmal and occlusive PAI-1 levels in any of the experiments.

CONCLUSION

PAI-1 secretion, as measured by tissue explant supernatants, and total tissue PAI-1 in the protein extracts were significantly increased in atherosclerotic aorta. This elevation was also observed in the mRNA, which suggests that the increase is controlled at the level of transcription. PAI-1 mRNA was localized to endothelial, vascular smooth muscle, and inflammatory cells. We conclude that elevated levels of PAI-1 exist in diseased aorta. These elevated levels may lead to an accumulation of ECM, thereby contributing to the arteriosclerosis found in aortic occlusive and aneurysmal disease.

Expression of plasminogen activator inhibitor type 1 by human prostate carcinoma cells inhibits primary tumor growth, tumor-associated angiogenesis, and metastasis to lung and liver in an athymic mouse model

Expression of urokinase-type plasminogen activator (uPA) by malignant cells correlates with an aggressive phenotype, including increased invasiveness, tumor-associated angiogenesis, and metastases. Plasminogen activator inhibitor type 1 (PAI-1) is undetectable in cells of some aggressive malignancies, but present in the stroma of tumor-associated microvasculature. This analysis of an athymic mouse model of prostate carcinoma further defines the role of the uPA/PAI-1/plasmin system in primary growth and metastasis. A marked increase in PAI-1 expression was induced in clones of the aggressive human prostate carcinoma line, PC-3, by stable transfection. Primary PC-3 tumors, in mice, were significantly smaller when derived from PAI-1 expressing versus control cells. PAI-1 expression reduced the density of tumor-associated microvasculature by 22-38%. Microscopic metastases were quantitated using stable expression of the chromogenic label (beta-galactosidase) in control and PAI-1 expressing cells. PAI-1 expression resulted in a significant inhibition of lung metastases, and liver metastases. Expression of PAI-1 by malignant prostate cells resulted in a less aggressive phenotype, presumably by inhibition of uPA activity, suggesting pharmacologic or molecular inhibition of uPA activity as a potential therapeutic target.

Plasminogen activator and plasminogen activator inhibitor expression by normal and aneurysmal human aortic smooth muscle cells in culture

OBJECTIVES

Matrix metalloproteinases may play a major role in aortic wall degeneration causing abdominal aortic aneurysm (AAA). Available plasmin, required for MMP zymogen activation, is regulated by plasminogen activators (uPA, tPA) and plasminogen activator inhibitors (PAI-1, PAI-2). To appraise the impact of these regulatory proteins on aortic wall degeneration, expression at the level of translation and transcription was determined in human aortic smooth muscle cell (SMC) cultures.

METHODS

Explants were derived from aneurysmal aortic tissue (n = 6) and from three male organ donors. Cells were also stimulated with 0.1-1.0 ng/ml IL-1 beta.

RESULTS

uPA antigen and tPA antigen in the conditioned medium (CM) of normal SMCs were not detectable but AAA SMCs produced uPA (values are given as median (interquartile range)), [1.97 ng/ml/10(6) cells (1.50-8.21)] and tPA [7.02 ng/ml/10(6) cells (6.20-14.90)]. uPA antigen was absent from normal SMC cell extract (CE) but present in small amounts in AAA SMC CE [0.80 ng/mg protein (0.40-1.24)]. tPA was detectable in the CE of normal SMCs [3.2 ng/mg protein (1.90-3.40)] but at a lower concentration than in AAA SMCs [13.14 ng/mg protein (7.20-27.00)] (p < 0.05). IL-1 beta suppressed production of uPA and tPA in both types of SMCs. The difference in baseline PAI-1 release from normal SMCs and AAA SMCs was not statistically significant. Selective upregulation of PAI-1 was observed for AAA SMC after IL-1 beta stimulation. Northern analysis of AAA SMCs grown in serum containing medium exhibited clear bands for uPA.

CONCLUSIONS

Human AAA SMCs are a source of elevated plasminogen activators. In the absence of a reciprocal rise of PAI an imbalance is created favouring proteolysis.

Reinfusion of postoperative wound drainage in total joint arthroplasty. Red blood cell survival and coagulopathy risk

Fifty patients with total joint arthroplasties (28 total hip arthroplasties, 11 total knee arthroplasties, and 11 bilateral total knee arthroplasties) received autotransfusions from their postoperative wound drainage. The blood was collected in a closed sterile drainage system without any additional anticoagulant. Pre- and postoperative measurements were made of the patient's hemoglobin, platelets, fibrinogen, haptoglobin, fibrin degradation products, and D-dimer (a specific type of fibrin degradation product). Red blood cell survival was assessed in 16 of the patients by labeling the shed blood with 51Cr sodium chromate prior to reinfusion. To control for fluid shifts, continued bleeding, and dilution effects of further transfusions in the immediate postoperative period, 10 patients also had their native blood labeled with 111In oxime. In this study, the mean estimated blood loss was 1,062 mL (+/- 1,247) with a mean wound drainage of 836 mL (+/- 338). Of this, a mean of 450 mL (+/- 261) of blood was was given back to the patient in addition to routine, preoperative autologous donated blood. Six (12%) patients experienced transient fevers at the time of retransfusion. Detailed hematologic studies were performed on the shed blood in 19 patients. The collected blood was completely defibrinated, but did contain fibrin degradation products, as indicated by the D-dimer level, and hemolyzed blood as the haptoglobin was reduced. Even though the blood containing the above breakdown products was reinfused to the patients, there were no clinical manifestations of disseminated intravascular coagulation. Both the hemolyzed and defibrinated products were subsequently cleared by the body.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of fibrinogens on phase transitions in lipid model membrane systems

An abnormal fibrinogen that caused aggregation of red blood cells (RBC) in a patient with gangrene was examined by real-time X-ray diffraction to determine its effects on dipalmitoylphosphatidylcholine (DPPC) and 1-palmitoyl-2-oleoylphosphatidylethanolamine (POPE) phase transitions. Similar studies were done with normal fibrinogen and results were compared. Both types of fibrinogen slightly increased the L alpha-->HII phase transition temperature and the HII phase parameters for POPE, while neither fibrinogen significantly affected the order-disordered acyl chain transitions in the lipid bilayer phase. However, fibrinogen differentially influenced the bilayer unit cell parameter of the gel and disordered bilayer and the gel state ripple phase. These results can be interpreted as indicating that fibrinogen has little effect on the balance of gel and disordered acyl chains in the lipid bilayer, but may influence membrane functions dependent on non-bilayer phases.

Enhancement of the expression of urokinase-type plasminogen activator from PC-3 human prostate cancer cells by thrombin

The presence of procoagulants and fibrin deposition have been demonstrated in malignant tumors. Although thrombin, a key enzyme in coagulation, has other various biological functions, the significance of its presence in tumors is not known. We studied the effects of thrombin on the expression of urokinase-type plasminogen activator (uPA) which is known to play a role in tumor invasion, using a human prostate cancer cell line PC-3. Human alpha-thrombin added to cultures of PC-3 produced a dose-dependent and time-dependent increased secretion of uPA that was greatest at 3-6 h after exposure to thrombin. Increase in uPA antigen paralleled the increase in mRNA level, which reached a maximum at 4 h. Thrombin showed the maximum effect on uPA expression at a concentration 1-2 units/ml. Zymography showed that transient exposure to thrombin induced an increase in fibrinolytic activity which could be quenched by anti-uPA antibody. The thrombin receptor-activating peptide also caused an increase in uPA protein and mRNA level, indicating the presence of the same thrombin specific receptor on PC-3 cells as on platelets and endothelial cells. Thrombin did not affect the expression of other components of the plasminogen activation system, tissue-type plasminogen activator and type-1 plasminogen activator inhibitor, and uPA receptor. These results indicate that thrombin increases uPA expression selectively by the stimulation of a functional thrombin receptor on PC-3 cells. Since uPA is known to play a role in pericellular proteolysis of extracellular matrix, thrombin may be involved in the regulation of tumor invasion and metastasis.

The concomitant augmentation of urokinase-type plasminogen activator and collagenase-like proteinase activities in X-ray irradiated cells of a human metastatic carcinomatous line

The enzymatic activities of uPA, and a collagenase-like proteinase in the post-nuclear fraction of cell homogenates of a metastatic carcinomatous cell line following X-ray irradiation were examined by the use of chromogenic substrates and by casein- or gelatin-containing zymographies and electrophoretic gel stained with avidin-conjugated peroxidase. Enhanced activities were observed in these cells, while those of 5'nucleotidase and Na(+)-K(+)-ATPase were attenuated. A partial purification and characterization of the collagenase showed that it was able to hydrolyze the heat-denatured type-I collagen more efficiently than the native one. The activation of both uPA and collagenase enables an efficient degradation of matrix barrier proteins. These findings suggest that following a certain dose range of X-ray irradiation, tumor cells may increase their ability to migrate and invade through the enhancement of uPA and collagenase activities.

Elevated levels of urokinase-type plasminogen activator and plasminogen activator inhibitor type-1 in malignant human brain tumors

The plasminogen-plasmin system has been found to modulate neoplastic spread and angiogenesis in tumors outside the central nervous system (CNS), but there have been no quantitative studies on the invasive and vascular tumors of the CNS. Quantitative zymography and enzyme-linked immunosorbent assay were used to determine the amounts of urokinase-type plasminogen activator (u-PA), tissue-type plasminogen activator, and plasminogen activator inhibitors type 1 and type 2 (PAI-1 and PAI-2) in benign and malignant primary brain tumors (n = 28) as well as nonneoplastic brain (n = 5). u-PA and PAI-1 antigen were undetectable in normal brain but significantly elevated in glioblastoma multiforme (u-PA, 2.86 +/- 3.01 ng/mg; PAI-1, 8.19 +/- 5.57 ng/mg; P < 0.001). There was no difference, however, in tissue-type plasminogen activator antigen levels among control, benign, or malignant tissues except for a 4- to 7-fold increase in acoustic neuroma. PAI-2 was detected at low levels in 2 of the 33 specimens. These findings indicate that malignancy in primary CNS neoplasms is associated with elevated levels of u-PA and PAI-1, supporting the role of the plasminogen-plasmin system in the pathogenesis of CNS malignancy and as a potential biomarker and therapeutic target.

Use of enoxaparin, a low-molecular-weight heparin, and unfractionated heparin for the prevention of deep venous thrombosis after elective hip replacement. A clinical trial comparing efficacy and safety. Enoxaparin Clinical Trial Group

A randomized, parallel-group, open-label clinical trial (the physicians, patients, and staff were not blinded with regard to the regimen that had been used) was conducted, between December 1988 and September 1990, to compare the safety and efficacy of enoxaparin, a low-molecular-weight heparin, with the safety and efficacy of unfractionated heparin for the prevention of deep venous thrombosis after elective hip replacement. Six hundred and ten patients were randomized, and 607 patients received one of the study medications. The evaluations of efficacy included contrast-media venography, non-invasive vascular examination, and clinical examination. Data on efficacy were available for 604 patients, who had been assigned to one of three treatment groups: thirty milligrams of enoxaparin every twelve hours (194 patients), forty milligrams of enoxaparin once daily (203 patients), or 5000 units of unfractionated heparin every eight hours (207 patients). All drugs were administered subcutaneously. Dosages were not adjusted on the basis of the results of coagulation tests or the body weight of the patient. Treatment was initiated within twenty-four hours after the operation and continued for a maximum of seven days. The primary safety outcome was the occurrence of bleeding episodes. An intent-to-treat patient analysis revealed that deep venous thrombosis occurred in nine (5 per cent) of the 194 patients who received thirty milligrams of enoxaparin every twelve hours, thirty (15 per cent) of the 203 patients who received forty milligrams of enoxaparin once daily, and twenty-four (12 per cent) of the 207 patients who received unfractionated heparin. The rate of deep venous thrombosis was significantly lower in the group that received thirty milligrams of enoxaparin every twelve hours than in the group that received unfractionated heparin (p = 0.03) and in the group that received forty milligrams of enoxaparin once daily (p = 0.0002). No clinically symptomatic pulmonary embolism was observed during the treatment or follow-up phase of this study in the group that received thirty milligrams of enoxaparin every twelve hours. Analysis of evaluable patients revealed a marked reduction in the rate of deep venous thrombosis in the group that received thirty milligrams of enoxaparin every twelve hours (eight [6 per cent] of 136 patients) compared with the group that received heparin (twenty-one [15 per cent] of 145 patients) (p = 0.10); however, this difference was not significant because of the small number of patients included in this analysis.(ABSTRACT TRUNCATED AT 400 WORDS)

New insights into the pathogenesis of coagulation dysfunction in acute promyelocytic leukemia

Patients with acute promyelocytic leukemia (APL) are at high risk for the development of life-threatening thrombotic and hemorrhagic complications, particularly during induction chemotherapy. This propensity has been attributed to the release of tissue factor (TF)-like procoagulants from the leukemic cells leading to disseminated intravascular coagulation (DIC). However, recent data suggest that the pathogenesis of the coagulopathy is more complicated and may involve activation of the generalized proteolytic cascade resulting in either clotting and/or excessive fibrinolysis. Furthermore, controversy exists regarding the mechanism(s) responsible for the activation of either clotting or fibrinolysis. The malignant promyelocyte may act directly to activate coagulation and/or fibrinolysis. Alternatively, reactive inflammatory cells, which express procoagulant and/or profibrinolytic activities may play an essential role. A third possibility may involve endothelial cell expression of mediators with procoagulant/profibrinolytic properties. Putative profibrinolytic mechanisms include the release of urokinase-type and tissue-type plasminogen activators, decreases in plasminogen activator inhibitor-1 and 2, and decreases in alpha-2 plasmin inhibitor. Putative procoagulant mechanisms include the release of tissue factor, Cancer Procoagulant, or cytokines such as interleukin-1, tumor necrosis factor and vascular permeability factor. Putative anticoagulant mediators include annexins, a group of proteins in human tissue which bind phospholipids and have anticoagulant activity, which have been reported in patients with APL. The current treatment of APL is rapidly evolving because of the efficacy of all-trans retinoic acid (ATRA). All-trans retinoic acid promotes terminal differentiation of leukemic promyelocytes leading to complete remission in the majority of patients with APL with rapid resolution of the coagulopathy. Although the mechanism by which this occurs has not been established, preliminary data suggest that ATRA blocks the downregulation of the thrombomodulin gene and the up-regulation of the tissue factor gene induced by tumor necrosis factor. Since APL is a relatively uncommon disorder, the collaboration of cooperative oncology groups will be important to study patients receiving ATRA or conventional chemotherapy to further elucidate the mechanism(s) of the coagulopathy.

The plasminogen-plasmin system in malignancy

The study of the plasminogen-plasmin system has, in the past, contributed much to the understanding of fibrinolysis and thrombolysis. Attention is now focused on the role of the components of this system in many biologic functions. Findings of uPA, its receptor and its inhibitor in many tumor tissues and tumor cell lines, strongly implicate their involvement in tumor invasion, tumor cell proliferation and metastasis. The characteristics of the plasminogen activators, the uPA receptor and the plasminogen activator inhibitors as well as their expression and regulation in tumors and tumor cell lines are reviewed.

Changes in blood coagulation, platelet function, and plasminogen-plasmin system in diabetes

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

Comparison of dosage schedules of rt-PA in the treatment of proximal deep vein thrombosis

This study assessed the efficacy and safety of increasing durations of constant-dose intravenous recombinant tissue-type plasminogen activator (rt-PA) in the treatment of deep vein thrombosis. Patients with venogram-documented proximal lower limb (popliteal, iliofemoral) or upper limb (axillary, subclavian) thrombi were given an initial 2-hour rt-PA infusion at 4 micrograms/kg/min, followed by a maintenance infusion of 1 microgram/kg/min for an additional 4, 22, or 33 hours (mean total rt-PA dosages of 54, 127, and 185 mg). A new quantitative venogram scoring system was applied to the study, based on measurements of thrombus volume before and after completion of treatment. Whereas none of the seven patients given treatment for 6 hours and only one of four given treatment for 24 hours showed significant lysis, four of seven who received a prolonged infusion for 35 hours showed lysis of more than 40% of the original thrombus. Overall, the prolonged 35-hour infusion induced 51% lysis of original thrombus, representing a thrombus volume of 16.7 ml dissolved. Hemorrhagic complications were common in all three groups, with four of 18 patients having significant bleeding, including one massive gastrointestinal hemorrhage, two patients with a decrease in hematocrit of more than 10%, and one patient with an intracranial hemorrhage who recovered completely. Pharmacokinetics of the rt-PA showed a steady state antigen concentration of 240 ng/ml and activity of 200 IU/ml during the initial 2-hour infusion and a postinfusion half-life of 5 minutes. Plasma fibrinogen concentrations decreased to approximately 40% to 50% of initial values with all three treatment regimens, but the nadir fibrinogen concentrations did not correlate with either therapeutic efficacy or bleeding complications. One patient with systemic lupus erythematosus had an unusual allergic reaction that manifested primarily as angioedema. This study suggests that rt-PA infusion of 35 hours induces greater thrombolysis of deep vein thrombosis than does a shorter course of 6 or 24 hours, without an increase in hemorrhagic complications.

Enzymatic properties of the phosphorylated urokinase-type plasminogen activator isolated from a human carcinomatous cell line

Enzymatic properties of phosphorylated urokinase plasminogen activator (P-uPA) (1) extracted from human carcinomatous cell line Detroit 562 cells were compared with those of non-phosphorylated uPA of urinary origin (nP-uPA). Using plasminogen as a substrate, the Km and Kcat of P-uPA were higher than that of nP-uPA while the Kcat/Km was lower. By zymography, a greater degree of plasminogen activation was observed. Concanavalin A reacted to both the enzymes. P-uPA had a low affinity for the inhibitors of plasminogen activator PAI-1 and PAI-2, and was inhibited only by the excess amounts of inhibitors. For PAI-1, and the KIs of P-uPA was greater and for PAI-2, KI was higher for P-uPA. These alterations by phosphorylation enable uPA to be more efficient in a focal proteolysis through plasminogen activation.

Phosphorylation of a surface receptor bound urokinase-type plasminogen activator in a human metastatic carcinomatous cell line

The 32P-labeled urokinase (uPA) bound to surface receptors of Detroit 562 cells was immunoprecipitated by anti-uPA antibody. Amino acid analysis showed that tyrosines and serines were the acceptors. Inhibition of protein kinases greatly reduced the 32P incorporation, suggesting that the respective cellular src gene product and protein kinase C were involved in the phosphorylations. Proteins purified on chromatographic columns contained two forms of uPA, a high (HMW) and a low (LMW) molecular weight. Tyrosine-phosphorylation occurs in the HMW and A-chain. Such modifications might modulate the extracellular activities of uPA.

Heterogeneity in plasminogen activator (PA) levels in human prostate cancer cell lines: increased PA activity correlates with biologically aggressive behavior

Plasminogen activators (PA), particularly the lower Mr urokinase (u-PA) type, have been associated with tumor cell invasion and metastasis. We have examined the expression of PA by two human prostate cancer cell lines (PC-3 and DU-145) using functional and immunologic techniques. The culture media and cell extracts of the more aggressive PC-3 cell line contained more than two-fold greater PA activity than the relatively indolent DU-145 cell line. Zymographic studies identified the PA expressed as u-PA. PC-3 cells expressed an additional lower molecular weight form of u-PA not noted in DU-145 cells. Heterogeneity in u-PA expression was shown by the fibrin lysis assay, immunohistochemistry, and dual parameter flow cytometry indicating the presence of phenotypically divergent cell populations. Increased u-PA expression may identify those tumor cells that possess aggressive biological potential.

Neurovascular fibrinolytic activity in normal Lewis rats and rats with cell-transferred experimental allergic encephalomyelitis

Fibrinolytic activity in the form of plasminogen activator (PA) was assessed using a histochemical fibrin slide technique in spinal cords of normal Lewis rats and rats with the cell-transferred form of experimental allergic encephalomyelitis (EAE). PA was localized exclusively to blood vessels. Vessels in the leptomeninges had maximum activity. A precipitous decrease in PA activity occurred in recipient rats which coincided with onset of clinical neurologic signs. A subsequent return in activity occurred in association with clinical remission of disease but remained well below the activity level of normal rats for as long as the recipient animals were followed. Vessels containing perivascular cellular infiltrates of EAE had little or no detectable PA activity. Furthermore, PA could not be demonstrated to be associated with infiltrating inflammatory cells, including macrophages. These findings provide further support for involvement of the coagulation and fibrinolytic systems in the early clinical manifestations of EAE in Lewis rats.

Quantitation of venous clot lysis with the D-dimer immunoassay during fibrinolytic therapy requires correction for soluble fibrin degradation

Plasma cross-linked fibrin-degradation products were analyzed using a D-dimer (DD) immunoassay in patients with deep vein thrombosis (DVT) or acute myocardial infarction (MI) treated with fibrinolytic therapy, and the results were correlated with clot lysis documented angiographically. In 13 patients with DVT, the mean DD concentration increased 10-fold (1,074 +/- 252 to 10,333 +/- 1,004 ng/ml) during therapy, but neither the peak level nor the DD concentration integrated over the course of therapy correlated with clot lysis. Since plasma DD can derive from degradation of soluble plasma fibrin as well as from thrombi, the contribution of the former was estimated by in vitro incubation of the pretreatment plasma with plasminogen activator. Subtraction of this value from the measured posttreatment DD concentration provided a "corrected" level that represented DD originating from lysis of thrombi. This modification resulted in improved correlation of DD levels with clot lysis. The mean corrected peak DD was higher in patients with successful thrombolysis (8,780 +/- 1,352 ng/ml) compared with patients without lysis (3,075 +/- 589 ng/ml, p less than 0.001). There was a moderate correlation between the volume of clot lysed and the corrected peak DD (r = 0.62) and a higher correlation with the corrected DD integrated over the course of treatment (r = 0.97). By contrast, the corrected DD concentrations were near zero in patients treated for MI with or without thrombolytic reperfusion, suggesting that fibrin in small coronary thrombi did not contribute significantly to total plasma DD during therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

V.A. Cooperative Study of antiplatelet agents in diabetic patients after amputation for gangrene: unobserved, sudden, and unexpected deaths

We report on unobserved, sudden, and unexpected deaths that occurred in a randomized multicenter trial. The long-term effects of aspirin plus dipyridamole on major vascular outcome variables were studied in 231 non insulin-dependent diabetic men with either a recent amputation for gangrene or active gangrene. Depending upon the definition of sudden death used, there were 14, 22, or 17 deaths in the drug group versus 6, 6, or 3 deaths in the placebo group (p = 0.04, 0.001, or 0.001, respectively). Total deaths from atherosclerotic vascular disease or deaths from all causes did not differ in the two treatment groups. Since this finding of a secondary end point is found only after multiple analyses of the data, it must be interpreted with caution. However, it is suggested that further studies on effects of antiplatelet agents on sudden deaths should be performed.