Expression and release of platelet protein disulphide isomerase in patients with haemophilia A.

INTRODUCTION: Despite similar residual factor VIII activity, patients with haemophilia A (HA) show significant interindividual variability with regard to bleeding frequency and severity, suggesting that additional factors modulate thrombin generation and fibrin deposition. Protein disulphide isomerase (PDI) is an abundant oxidoreductase that exerts pleiotropic effects in primary and secondary haemostasis and contributes to thrombosis and vascular inflammation. AIM: We conducted a pilot study to explore a potential role of platelet PDI in patients with HA. METHODS: Expression and release of platelet PDI were studied by flow cytometry and enzyme-linked immunosorbent assay, respectively. RESULTS: Compared to healthy male controls (n = 12), patients with HA (n = 24) showed significantly increased expression of PDI antigen on ADP- or TRAP-6-, but not on buffer-treated platelets, a finding that could not be explained by enhanced platelet activation, as indicated by expression of the α-granule protein, CD62P (P-selectin). While platelet agonists did not affect PDI secretion in healthy male controls, increased levels of PDI antigen were found in supernatants of TRAP-6-treated platelets from patients with HA. Importantly, in two patients with exceedingly high TRAP-6-induced PDI release over baseline, findings were consistent when platelets were isolated and stimulated on a separate occasion. No obvious association was found between platelet PDI and bleeding phenotype in this patient cohort. CONCLUSION: Agonist-induced expression and release of platelet PDI were increased in patients with HA. Larger studies are needed to clarify if variations in this platelet response contribute to the diversity in bleeding frequency and severity among patients with congenital factor VIII deficiency.

Relevant bleeding diathesis due to acquired factor XIII deficiency.

BACKGROUND: Acquired factor XIII (FXIII) deficiency is associated with reduced clot firmness and increased bleeding in patients undergoing major surgery. In contrast, only limited information is available on the haemostatic relevance of acquired FXIII deficiency in non-surgical patients. CASE REPORT: An 81-year-old patient, who had experienced acute type-A dissection of the aorta eight years earlier, presented with a 3-year history of progressive mucocutaneous and soft-tissue bleeding. Diagnostic work-up was unremarkable for global coagulation tests, but FXIII and alpha2-antiplasmin were decreased to 33% and 27%, respectively, while plasma D-dimer was elevated to > 35 mg/l. A FXIII inhibitor was excluded by mixing studies. CT scanning revealed a massively elongated and progressively dilated aorta with a false lumen reaching from the left carotid artery to the iliac bifurcation. Bleeding control was achieved by single doses of FXIII at 20-30 IU/kg body weight and tailored oral tranexamic acid. CONCLUSION: Acquired FXIII deficiency with activity levels of 30-35% may confer a severe bleeding tendency in non-surgical patients, especially in the context of increased thrombin an fibrin generation.

Medication safety improves after implementation of positive patient identification.

OBJECTIVE: To report the incidence and severity of medication safety events before and after initiation of barcode scanning for positive patient identification (PPID) in a large teaching hospital. METHODS: Retrospective analysis of data from an existing safety reporting system with anonymous and non-punitive self-reporting. Medication safety events were categorized as "near-miss" (unsafe conditions or caught before reaching the patient) or reaching the patient, with requisite additional monitoring or treatment. Baseline and post-PPID implementation data on events per 1,000,000 drug administrations were compared by chi-square with p<0.05 considered significant. RESULTS: An average of 510,541 doses were dispensed each month in 2008. Total self-reported medication errors initially increased from 20 per million doses dispensed pre-barcoding (first quarter 2008) to 38 per million doses dispensed immediately post-intervention (last quarter 2008), but errors reaching the patient decreased from 3.26 per million to 0.8 per million despite the increase in "near-misses". A number of process issues were identified and improved, including additional training and equipment, instituting ParX scanning when filling Pyxis machines, and lobbying for a manufacturing change in how bar codes were printed on bags of intravenous solutions to reduce scanning failures. CONCLUSION: Introduction of barcoding of medications and patient wristbands reduced serious medication dispensing errors reaching the patient, but temporarily increased the number of "near-miss" situations reported. Overall patient safety improved with the barcoding and positive patient identification initiative. These results have been sustained during the 18 months following full implementation.

Changes in electronic structure and chemical bonding upon crystallization of the phase change material GeSb2Te4.

High-resolution photoelectron spectroscopy of in situ prepared films of GeSb2Te4 reveals significant differences in electronic and chemical structure between the amorphous and the crystalline phase. Evidence for two different chemical environments of Ge and Sb in the amorphous structure is found. This observation can explain the pronounced property contrast between both phases and provides new insight into the formation of the amorphous state.

tRNase Z: the end is not in sight.

Although the enzyme tRNase Z has only recently been isolated, a plethora of data has already been acquired concerning the enzyme. tRNase Z is the endonuclease that catalyzes the removal of the tRNA 3' trailer, yielding the mature tRNA 3' end ready for CCA addition and aminoacylation. Another substrate cleaved by tRNase Z is the small chromogenic phosphodiester bis(p-nitrophenyl)phosphate (bpNPP), which is the smallest tRNase Z substrate known so far. Hitherto the biological function as tRNA 3'-end processing enzyme has been shown only in one prokaryotic and one eukaryotic organism, respectively. This review summarizes the present information concerning the two tRNase Z substrates pre-tRNA and bpNPP, as well as the metal requirements of tRNase Z enzymes.

Experimental metastasis and primary tumor growth in mice with hemophilia A.

During experimental lung metastasis, tumor cells adhere to the pulmonary microvasculature and activate coagulation via surface-expressed tissue factor (TF), leading to local fibrin deposition and platelet aggregation. While interventional studies have demonstrated great efficacy of anticoagulants and antiplatelet agents in inhibiting metastasis, no information is available on how tumor biology may be affected by congenital bleeding disorders such as hemophilia A. We therefore used a syngeneic model to study experimental metastasis and primary tumor growth in factor VIII (FVIII)-deficient mice. By conventional reverse transcription-polymerase chain reaction, flow cytometry, and one-stage clotting assays, we demonstrated constitutive expression of TF mRNA, antigen, and procoagulant activity in the murine B16F10 melanoma cell line. In hemophilic mice, B16F10 lung metastasis was significantly (P < 0.001) enhanced by a single dose of human FVIII (100 U kg(-1)), suggesting that FVIII played a critical role during the early blood-borne phase of the metastatic cascade. In contrast, lung seeding was significantly (P < 0.05) reduced by lepirudin, a direct thrombin inhibitor, suggesting that thrombin generation contributed to pulmonary metastasis even in the absence of FVIII. Consistent with this finding, intravenous injection of B16F10 cell-evoked laboratory changes of a hemolytic thrombotic microangiopathy and consumptive coagulopathy in both hemophilic and non-hemophilic mice. Subcutaneous implantation of B16F10 cells into mice with hemophilia A gave rise to primary tumors in an exponential growth pattern similar to that observed in non-hemophilic mice. Although TF expression by B16F10 cells may promote thrombin-dependent metastasis in mice with hemophilia A, amplification of coagulation by host FVIII appears to be necessary for maximum lung seeding.