PubMed · 4239465
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
A A Sharp. 1969. Thrombus dissolution.. https://doi.org/10.1136/jcp.22.3.369-b
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
The human sarcoma cell line HT1080 was found, by in situ hybridization, to consist of cells expressing various levels of urokinase (uPA) and tissue type (tPA) plasminogen activator (PA) suggesting clonal variation of expression of these genes. Colonies originating from single HT1080 cells were, therefore, established and screened for PA activity using a fibrin agarose overlay. Colonies inducing lysis (clone C+ and H+) or no lysis (clones B- and M-) were isolated and tested for mRNA levels of uPA, tPA, uPA receptor (uPAR) and the 3 PA inhibitors (PAI), PAI-1, PAI-2 and protease-nexin I. The different clones revealed considerable variation of expression of the different PA and PAI genes, with lysis-inducing clones expressing mainly the PA genes, whereas non-lysing clones demonstrated higher expression of the PAI genes. Amplification or loss of specific genes was excluded by Southern blotting. The protein levels of cellular and secreted PA and PAI determined by ELISA and Western blots demonstrated a pattern similar to that observed for PA and PAI mRNA concentrations, suggesting clonal differences either on the level of transcription or in RNA processing and/or stability. Due to complex interactions between PA and PAI, neither mRNA nor protein levels of the different genes were predictive for the amount of functional PA activity present in the supernatant or on the cell surface of the different clones. Receptor-bound uPA activity was found to be considerably higher in lysis-inducing than in non-lysing clones and the activity was dependent on neutralization by PAI-1 rather than on the level of uPAR mRNA.
In 20 patients with acute myocardial infarction (AMI) treated with streptokinase (SK, n = 7), recombinant single-chain tissue plasminogen activator (rt-PA, n = 7) or urokinase (UK, n = 6), the behavior of plasma von Willebrand factor (vWF) was studied before and 1.5, 3, 24, 48, and 72 hours after beginning thrombolytic therapy. vWF antigen (vWF:Ag) was high in plasma, especially after SK. The ristocetin cofactor (RiCof) activity of vWF, high before therapy, tended to decrease soon after therapy. This pattern of vWF changes was paralleled by the early loss of higher molecular weight multimers. By immunoblotting of immunopurified and reduced vWF and monoclonal antibody epitope mapping, we found that vWF was degraded after thrombolysis, especially after SK, as indicated by the higher values of two plasmin-generated fragments of 176 and 145 Kd. There were more plasmin-generated fragments in the five patients who had bleeding complications than in the remaining 15 who did not. In conclusion, quantitative and qualitative changes of vWF compatible with proteolytic degradation of the protein occur during thrombolytic therapy. Such degradation, roughly proportional to the degree of the general lytic state induced by each agent, might be a cofactor of the bleeding complications occurring in treated patients.
The fibrinolytic system controls fibrin deposition and its clearance. The efficacy of this system can be evaluated by plasminogen concentration determinations and by the behavior of factors such as histidine-rich glycoprotein (HRG) which controls plasminogen activation and alpha 2-antiplasmin which controls plasmin activity. Circulating plasminogen levels are decreased in the neonatal period. We studied factors affecting fibrinolysis in neonates and observed that an important reduction in HRG accompanied the reduced circulating plasminogen levels, with the result that 85% of circulating plasminogen was not bound to HRG and was thus free for binding to fibrin and for activation to plasmin. This condition is consistent with the increased fibrinolytic activity secondary to the "clotting activation' observed in the neonatal period particularly on the 1st day of life.