Blood coagulation factor Va's key interactive residues and regions for prothrombinase assembly and prothrombin binding

Blood coagulation factor Va serves an indispensable role in hemostasis as cofactor for the serine protease factor Xa. In the presence of an anionic phospholipid membrane and calcium ions, factors Va and Xa assemble into the prothrombinase complex. Following formation of the ternary complex with the macromolecular zymogen substrate prothrombin, the latter is rapidly converted into thrombin, the key regulatory enzyme of coagulation. Over the years, multiple binding sites have been identified in factor Va that play a role in the interaction of the cofactor with factor Xa, prothrombin, or the anionic phospholipid membrane surface. In this review, an overview of the currently available information on these interactive sites in factor Va is provided, and data from biochemical approaches and 3D structural protein complex models are discussed. The structural models have been generated in recent years and provide novel insights into the molecular requirements for assembly of both the prothrombinase and the ternary prothrombinase‐prothrombin complexes. Integrated knowledge of functionally important regions in factor Va will allow for a better understanding of factor Va cofactor activity.     

Health state preferences associated with weight status in children and adolescents

Background  

Childhood obesity is a substantial public health problem. The extent to which health state preferences (utilities) are related to a child's weight status has not been reported. The aims of this study were (1) to use a generic health state classification system to measure health related quality of life and calculate health utilities in a convenience sample of children and adolescents and (2) to determine the extent to which these measures are associated with weight status and body mass index (BMI).     

cAMP regulates DEP domain-mediated binding of the guanine nucleotide exchange factor Epac1 to phosphatidic acid at the plasma membrane

Epac1 is a cAMP-regulated guanine nucleotide exchange factor for the small G protein Rap. Upon cAMP binding, Epac1 undergoes a conformational change that results in its release from autoinhibition. In addition, cAMP induces the translocation of Epac1 from the cytosol to the plasma membrane. This relocalization of Epac1 is required for efficient activation of plasma membrane-located Rap and for cAMP-induced cell adhesion. This translocation requires the Dishevelled, Egl-10, Pleckstrin (DEP) domain, but the molecular entity that serves as the plasma membrane anchor and the possible mechanism of regulated binding remains elusive. Here we show that Epac1 binds directly to phosphatidic acid. Similar to the cAMP-induced Epac1 translocation, this binding is regulated by cAMP and requires the DEP domain. Furthermore, depletion of phosphatidic acid by inhibition of phospholipase D1 prevents cAMP-induced translocation of Epac1 as well as the subsequent activation of Rap at the plasma membrane. Finally, mutation of a single basic residue within a polybasic stretch of the DEP domain, which abolishes translocation, also prevents binding to phosphatidic acid. From these results we conclude that cAMP induces a conformational change in Epac1 that enables DEP domain-mediated binding to phosphatidic acid, resulting in the tethering of Epac1 at the plasma membrane and subsequent activation of Rap.     

Reduction in infarct size, but no functional improvement after bone marrow cell administration in a porcine model of reperfused myocardial infarction.

AIMS: Stem cell therapy after myocardial infarction (MI) has been studied in models of permanent coronary occlusion. We studied the effect of intracoronary administration of unselected bone marrow (BM) and mononuclear cells (MNC) in a porcine model of reperfused MI. METHODS AND RESULTS: In 34 swine, the left circumflex coronary artery was balloon-occluded for 2 h followed by reperfusion. Ten swine without MI served as controls. All swine underwent magnetic resonance imaging (MRI) 1 week post-MI. The next day, 10 of the 30 surviving MI swine received BM, 10 other MI swine received MNC, and the remaining MI swine received medium intracoronary. Four weeks later, all swine underwent a follow-up MRI. One week after MI, end-diastolic volume (92+/-16 mL) and left ventricular (LV) weight (78+/-12 g) were greater, whereas ejection fraction (40+/-8%) was lower than in controls (69+/-11 mL, 62+/-13 g, and 53+/-6%). Injection of BM or MNC had no effect on the MI-induced changes in global or regional LV-function. However, there was a significant reduction in infarct size 4 weeks after MNC injection (-6+/-3%) compared with the medium (-3+/-5%). CONCLUSION: Intracoronary injection of BM or MNC in swine does not improve regional or global LV-function 4 weeks after injection. However, a reduction in infarct-size was noted after MNC injection.     

One-year hemodynamic comparison of Perimount Magna with St Jude Epic aortic bioprostheses

Introduction

Cardiac surgeons are using more bioprosthetic valves due to the ageing population as well as to improvements that have been made to these implants. We sought to compare the 1-year hemodynamics of two commercially available valves by echocardiographic parameters.

Material and methods

Retrospective review of our institutional database revealed 69 patients who received either Perimount Magna (n = 33) or St Jude Epic (n = 36) valves in the aortic position with no other valve surgery between June 2004 and March 2006. All patients received transthoracic echocardiography at 1 year. Comparisons between groups were made at baseline and at 1-year follow-up. In addition, a pairwise comparison was performed in each patient to determine the change in echocardiographic parameters between baseline and follow-up.

Results

Mean implanted valve size was similar (Magna 24.3 ±2.0 mm vs. Epic 24.1 ±2.2 mm). Pre- and intraoperative patient variables were similar between the two groups. There were lower peak and mean pressure gradients in the Magna group, both at discharge and one year after surgery. This correlated with a larger indexed effective orifice area (Magna 0.8 ±0.2 cm²/m² vs. Epic 0.67 ±0.2 cm²/m², p = 0.02). In spite of these findings, left ventricular mass regression was not different.

Conclusions

These findings suggest that in a series with relatively low indexed effective orifice areas, the peak and mean gradients obtained were acceptable. More clinical follow-up of these patients is required to assess the true impact of prosthesis patient mismatch.     

RAS gene mutations in acute and chronic myelocytic leukemias, chronic myeloproliferative disorders, and myelodysplastic syndromes.

We report on investigations aimed at detecting mutated RAS genes in a variety of preleukemic disorders and leukemias of myeloid origin. DNA transfection analyses (tumorigenicity assay) and hybridization to mutation-specific oligonucleotide probes established NRAS mutations in codon 12 or 61 of 4/9 acute myelocytic leukemias (AML) and three AML lines. Leukemic cells of another AML patient showed HRAS gene activation. By using a rapid and sensitive dot-blot screening procedure based on the combination of in vitro amplification of RAS-specific sequences and oligonucleotide hybridization we additionally screened 15 myelodysplastic syndromes, 26 Philadelphia chromosome-positive chronic myelocytic leukemias in chronic or acute phase, and 19 other chronic myeloproliferative disorders. A mutation within NRAS codon 12 could thus be demonstrated in a patient with idiopathic myelofibrosis and in another with chronic myelomonocytic leukemia. Moreover, mutated NRAS sequences were detected in lymphocytes, in granulocytes, as well as in monocytes/macrophages of the latter case.     

25 years of aortic valve replacement using mechanical valves: Risk factors for early and late mortality

This study describes the changes that have taken place in patientcharacteristics in 25 years of aortic valve replacement usingmechanical valves, and looks for risk factors for early andlate mortality. During this period, 1449 mechanical valves wereimplanted. Overall early mortality (<30 days) was 5·3%and for aortic valve replacement without concomitant procedures3·9%. Overall survival rates at 5, 10 and 15 years were80%, 63% and 49%, respectively. Despite an increased proportionof higher risk patients (older age, more reoperations, moreconcomitant coronary bypass surgery) survival rates improvedthroughout the study period. Early mortality was related toan early year of operation, urgency, reoperation and concomitantsurgery to the tricuspid valve or ascending aorta. Late mortalitywas higher for patients of older age, with an early year ofoperation, male gender, concomitant coronary bypass surgery,mitral valve surgery or replacement of the ascending aorta.Aortic regurgitation did not have a major influence on earlynor late mortality. The improvement in early and late mortalityin more recent years was largely the result of the introductionof cardioplegia. A changing, non-proportional effect was observedfor several risk factors during the follow-up period. This studyillustrates the changes and improvements in medical care thathave taken place in patients requiring aortic valve replacement.