Inactivation of factor XIa in human plasma assessed by measuring factor XIa-protease inhibitor complexes: major role for C1-inhibitor

From experiments with purified proteins, it has been concluded that factor XIa (FXIa) is inhibited in plasma mainly by alpha 1-antitrypsin (a1AT), followed by antithrombin III (ATIII), C1-inhibitor (C1Inh), and alpha 2-antiplasmin (a2AP). However, the validity of this concept has never been studied in plasma. We established the relative contribution of different inhibitors to the inactivation of FXIa in human plasma, using enzyme-linked immunosorbent assays (ELISAs) for the quantification of complexes of FXIa with a1AT, C1Inh, a2AP, and ATIII. We found that 47% of FXIa added to plasma formed complexes with C1Inh, 24.5% with a2AP, 23.5% with a1AT, and 5% with ATIII. The distribution of FXIa between these inhibitors in plasma was independent of whether FXIa was added to plasma, or was activated endogenously by kaolin, celite, or glass. However, in the presence of heparin (1 or 50 U/mL), C1Inh appeared to be the major inhibitor of FXIa, followed by ATIII. Furthermore, at lower temperatures, less FXIa-C1Inh and FXIa-a1AT complexes but more FXIa-a2AP complexes were formed. These data demonstrate that the contribution of the different inhibitors to inactivation of FXIa in plasma may vary, but C1Inh is the principal inhibitor under most conditions.     

Intraoperative Real Time Three-Dimensional Transesophageal Echocardiographic Measurement of Hemodynamic, Anatomic and Functional Changes after Aortic Valve Replacement

The traditional intraoperative two-dimensional transesophageal echocardiography (2DTEE) has limitations in measuring left ventricular ejection fraction (LVEF) because measurements rely on geometric assumptions. The availability of online software and real time three-dimensional transesophageal echocardiography (RT3D-TEE) makes intraoperative LVEF measurements fast and easy. This is the first report of intraoperative measurement of LVEF and aortic valve area (AVA) by RT3-DTEE in a patient who received transcatheter-based transapical aortic valve implantation .     

Activation of coagulation factor XI, without detectable contact activation in dengue haemorrhagic fever

A prospective cohort study was performed in 50 patients with dengue haemorrhagic fever (DHF) to determine the potential role of the contact activation system and factor XI activation (intrinsic pathway) in the coagulation disorders in DHF. To establish whether TAFI (thrombin-activatable fibrinolysis inhibitor) was involved in the severity of the coagulation disorders, the TAFI antigen and activity levels were also determined. Markers of contact activation (kallikrein--C1-inhibitor complexes), the intrinsic pathway of coagulation (factor XIa--C1-inhibitor complexes) and TAFI were measured and correlated to thrombin generation markers (thrombin--anti-thrombin complexes (TAT), prothrombin fragment 1+2 (F1+2)) and a marker for fibrinolysis [plasmin--alpha 2--anti-plasmin complexes (PAP)]. Activation of the intrinsic pathway of coagulation was clearly demonstrated by elevated levels of factor XIa--C1-inhibitor complexes, without evidence of contact activation, reflected by undetectable kallikrein--C1-inhibitor complexes. Both TAFI antigen and activity levels were decreased in all patients, which may contribute to the severity of bleeding complications in DHF because of the impaired capacity of the coagulation system to protect the fibrin clot from fibrinolysis. These findings in a human viral infection model are in accordance with earlier findings in bacterial sepsis.     

Delivery of Chlamydia pneumoniae to the vessel wall aggravates atherosclerosis in LDLr-/- mice

OBJECTIVE: The role of Chlamydia pneumoniae in atherosclerosis is still debated. In this study a novel mouse model was applied to determine the direct impact of C. pneumoniae on the arterial wall and the development of atherosclerosis. METHODS: Direct effects of C. pneumoniae on collar-induced atherosclerosis were studied after local delivery of C. pneumoniae to carotid arteries of LDL receptor-deficient (LDLr-/-) mice. RESULTS: The presence of C. pneumoniae in the vessel wall was quantified by RT-PCR (6.2 x 10(4) copies/artery) and resulted in a 2.0-fold increase in intima/media ratios (p<0.05) and a 1.7-fold increase in stenosis (p<0.05). Immunostaining revealed a 2.98-fold (p<0.01) increased macrophage content and a tendency towards lower numbers of smooth muscle cells and collagen in lesions of infected carotid arteries. Direct delivery of another respiratory pathogen, Mycoplasma pneumoniae, to the carotids did not affect size or composition of the atherosclerotic lesions. Presence of C. pneumoniae in the carotid arteries resulted within 7 days in a marked upregulation of the expression of MCP-1 (p<0.01) and ICAM-1 as determined on mRNA and protein levels. These in vivo data were in line with data obtained with in vitro infections of macrophages and endothelial cells with C. pneumoniae. CONCLUSIONS: We conclude that C. pneumoniae in carotid arteries leads to more pronounced atherosclerotic lesions with a more vulnerable morphology and that this model is suitable to monitor direct effects of C. pneumoniae on atherogenesis.     

Dose-related safety and immunogenicity of a trivalent baculovirus-expressed influenza-virus hemagglutinin vaccine in elderly adults

BACKGROUND: Influenza-virus hemagglutinin (HA) protein expressed in insect cells by recombinant baculovirus is a candidate influenza vaccine. METHODS: In a randomized, double-blind trial conducted in 399 adults > or = 65 years of age, the efficacy of trivalent inactivated influenza vaccine (TIV) licensed for intramuscular injection was compared with that of trivalent baculovirus-expressed HA vaccine administered at doses of 15 microg, 45 microg, or 135 microg of each HA. RESULTS: Compared with TIV, baculovirus-expressed HA vaccine was safe and induced better serum antibody responses to the H3 component when administered at doses of 45 microg or 135 microg of each HA. CONCLUSIONS: Baculovirus-expressed HA is a safe and immunogenic influenza vaccine in elderly adults.     

Rapid and accurate measurement of left ventricular function with a new second-harmonic fast-rotating transducer and semi-automated border detection

Measurement of left ventricular (LV) volume and function are the most common clinical referral questions to the echocardiography laboratory. A fast, practical, and accurate method would offer important advantages to obtain this important information. To validate a new practical method for rapid measurement of LV volume and function. We developed a continuous fast-rotating transducer, with second-harmonic capabilities, for three-dimensional echocardiography (3DE). Fifteen cardiac patients underwent both 3DE and magnetic resonance imaging (reference method) on the same day. 3DE image acquisition was performed during a 10-second breath-hold with a frame rate of 100 frames/sec and a rotational speed of 6 rotations/sec. The individual images were postprocessed with Matlab software using multibeat data fusion. Subsequently, with these images, 12 datasets per cardiac cycle were reconstructed, each comprising seven equidistant cross-sectional images for analysis in the new TomTec 4DLV analysis software, which uses a semi-automated border detection (ABD) algorithm. The ABD requires an average analysis time of 15 minutes per patient. A strong correlation was found between LV end-diastolic volume (r = 0.99; y = 0.95x - 1.14 ml; SEE = 6.5 ml), LV end-systolic volume (r = 0.96; y = 0.89x + 7.91 ml; SEE = 7.0 ml), and LV ejection fraction (r = 0.93; y = 0.69x + 13.36; SEE = 2.4%). Inter- and intraobserver agreement for all measurements was good. The fast-rotating transducer with new ABD software is a dedicated tool for rapid and accurate analysis of LV volume and function.     

Pacemaker-related myocardial perfusion defects worsen during higher pacing rate and coronary flow augmentation.

BACKGROUND: Asynchronous activation resulting from right ventricular apical (RVA) pacing can adversely affect left ventricular function and myocardial perfusion despite normal coronary arteries. This situation makes detection of coronary heart disease in paced patients difficult. OBJECTIVES: The purpose of this study was to assess the distribution, extent, and severity of myocardial perfusion defects with RVA pacing at low and high rates and increased coronary blood flow with adenosine. METHODS: Fourteen patients with permanent RVA pacing and angiographically normal coronary arteries underwent myocardial perfusion single-photon emission computed tomography at rest at low and high pacing rates and with pacing at low rates with adenosine. Data were analyzed semi-quantitatively using a 20-segment scoring model and coded using a four-point scoring system. RESULTS: At rest, 23 (55%) of 42 coronary flow territories showed abnormal perfusion and 52 (19%) of 280 corresponding segments demonstrated abnormal perfusion; mean perfusion score was 0.22. After high-rate pacing, perfusion was abnormal in 31 (74%) of 42 flow territories and 122 (44%) of 280 segments; mean perfusion score was 0.67. Adenosine infusion resulted in 28 (67%) of 42 abnormal flow territories and 90 (32%) of 280 abnormal segments; mean perfusion score was 0.44. Perfusion defects were observed most often in close proximity to the origin of the pacing site. CONCLUSION: RVA pacing results in myocardial perfusion defects. The false-positive findings are present at rest and more obvious with high-rate pacing than during adenosine infusion. Detection of coronary artery disease should be performed with caution in RVA paced patients because of the high number of perfusion defects observed in the absence of coronary artery disease.     

Functional reconstitution of human eukaryotic translation initiation factor 3 (eIF3)

Protein fate in higher eukaryotes is controlled by three complexes that share conserved architectural elements: the proteasome, COP9 signalosome, and eukaryotic translation initiation factor 3 (eIF3). Here we reconstitute the 13-subunit human eIF3 in Escherichia coli, revealing its structural core to be the eight subunits with conserved orthologues in the proteasome lid complex and COP9 signalosome. This structural core in eIF3 binds to the small (40S) ribosomal subunit, to translation initiation factors involved in mRNA cap-dependent initiation, and to the hepatitis C viral (HCV) internal ribosome entry site (IRES) RNA. Addition of the remaining eIF3 subunits enables reconstituted eIF3 to assemble intact initiation complexes with the HCV IRES. Negative-stain EM reconstructions of reconstituted eIF3 further reveal how the approximately 400 kDa molecular mass structural core organizes the highly flexible 800 kDa molecular mass eIF3 complex, and mediates translation initiation.     

Effects of percutaneous transluminal septal myocardial ablation for obstructive hypertrophic cardiomyopathy on systolic and diastolic left ventricular function assessed by pressure-volume loops

The aim of the present study was to determine the long-term effects of percutaneous transluminal septal myocardial ablation (PTSMA) on systolic and diastolic left ventricular (LV) functions in patients with obstructive hypertrophic cardiomyopathy (HC). Ten consecutive patients with symptomatic HC despite optimal medical treatment were referred for PTSMA at our center. LV systolic and diastolic functions were assessed by online LV pressure-volume loops obtained by conductance catheter at baseline and at 6 months after the procedure. At follow-up, the mean gradients at rest and after extrasystole were significantly decreased compared with baseline (88 +/- 29 to 21 +/- 11 mm Hg and 130 +/- 50 to 35 +/- 22 mm Hg, respectively, p <0.01 for the 2 comparisons). End-systolic and end-diastolic pressures significantly decreased (p <0.01), whereas end-systolic and end-diastolic LV volumes significantly increased (p <0.01 for the 2 comparisons). Cardiac output and stroke volume were unchanged, as were ejection fraction (p = 0.25) and maximum dP/dt (p = 0.13). The slope of the end-systolic pressure-volume relation was not decreased, indicating a preserved contractility. The relaxation constant time, end-diastolic stiffness, projected volume of the end-diastolic pressure-volume relation at 30 mm Hg, and diastolic stiffness constant showed a significant improvement of active and passive myocardial diastolic properties. In conclusion, PTSMA is an effective method in the treatment of symptomatic patients with HC. At 6-month follow-up, the LV-aortic gradient was decreased and active and passive LV diastolic properties were increased. Myocardial contractility was not decreased and general hemodynamics was maintained.     

Left ventricular solid body rotation in non‐compaction cardiomyopathy: A potential new objective and quantitative functional diagnostic criterion?

BACKGROUND: Left ventricular (LV) twist originates from the interaction between myocardial fibre helices that are formed during the formation of compact myocardium in the final stages of the development of myocardial architecture. Since non-compaction cardiomyopathy (NCCM) is probably caused by intrauterine arrest of this final stage, it may be anticipated that LV twist characteristics are altered in NCCM patients, beyond that seen in patients with impaired LV function and normal compaction. AIMS: The purpose of this study was to assess LV twist characteristics in NCCM patients compared to patients with non-ischaemic dilated cardiomyopathy (DCM) and normal subjects. METHODS AND RESULTS: The study population consisted of 10 patients with NCCM, 10 patients with DCM, and 10 healthy controls. LV twist was determined by speckle tracking echocardiography. In all controls and DCM patients, rotation was clockwise at the basal level and counterclockwise at the apical level. In contrast, in all NCCM patients the LV base and apex rotated in the same direction. CONCLUSIONS: These findings suggest that 'LV solid body rotation', with near absent LV twist, may be a new sensitive and specific, objective and quantitative, functional diagnostic criterion for NCCM.