Imaging analyses of coagulation-dependent initiation of fibrinolysis on activated platelets and its modification by thrombin-activatable fibrinolysis inhibitor.

Using intravital confocal microscopy, we observed previously that the process of platelet phosphatidylserine (PS) exposure, fibrin formation and lysine binding site-dependent plasminogen (plg) accumulation took place only in the centre of thrombi, not at their periphery. These findings prompted us to analyse the spatiotemporal regulatory mechanisms underlying coagulation and fibrinolysis. We analysed the fibrin network formation and the subsequent lysis in an in vitro experiment using diluted platelet-rich plasma supplemented with fluorescently labelled coagulation and fibrinolytic factors, using confocal laser scanning microscopy. The structure of the fibrin network formed by supplemented tissue factor was uneven and denser at the sites of coagulation initiation regions (CIRs) on PS-exposed platelets. When tissue-type plasminogen activator (tPA; 7.5 nM) was supplemented, labelled plg (50 nM) as well as tPA accumulated at CIRs, from where fibrinolysis started and gradually expanded to the peripheries. The lysis time at CIRs and their peripheries (50 µm from the CIR) were 27.9 ± 6.6 and 44.4 ± 9.7 minutes (mean ± SD, n=50 from five independent experiments) after the addition of tissue factor, respectively. Recombinant human soluble thrombomodulin (TMα; 2.0 nM) attenuated the CIR-dependent plg accumulation and strongly delayed fibrinolysis at CIRs. A carboxypeptidase inhibitor dose-dependently enhanced the CIR-dependent fibrinolysis initiation, and at 20 µM it completely abrogated the TMα-induced delay of fibrinolysis. Our findings are the first to directly present crosstalk between coagulation and fibrinolysis, which takes place on activated platelets' surface and is further controlled by thrombin-activatable fibrinolysis inhibitor (TAFI).

Schmorl's node developing in the lumbar vertebra affected with metastatic carcinoma: correlation magnetic resonance imaging with histological findings.

STUDY DESIGN: Described is magnetic resonance (MR) imaging of unusual Schmorl's node occurring in the lumbar vertebra affected with metastatic carcinoma. OBJECTIVE: To know MR features of Schmorl's node with a neoplastic background. SUMMARY OF BACKGROUND DATA: Schmorl's nodes occasionally develop in the vertebrae affected with metastatic carcinoma; however, their MR images have been rarely illustrated. METHODS: The spinal column dissected from a 65-year-old man who died of esophageal carcinoma was examined. Specimen radiographs and MR images were correlated to histologic sections. RESULTS: T1-weighted spin-echo image revealed intervertebral disc displacement into the second lumbar vertebra, which showed intermediate signal intensity, and a surrounding area of lower signal intensity. Short T1 inversion recovery image exhibited a crescent area of high signal intensity surrounding a focus of intermediate signal intensity. CONCLUSIONS: MR features consisting of two different signal patterns are characteristic for Schmorl's node with a neoplastic background. The conditions should be distinguished from Schmorl's nodes in an acute phase, which show similar MR features.