Radiofrequency Catheter Ablation of Atrial Flutter Induces the Release of Platelet and Leukocyte-Derived Procoagulant Microparticles and a Prothrombotic State

Background: To assess the extent of endothelium, platelet, and leukocyte damage and coagulation activation induced by radiofrequency catheter ablation (RF) of atrial flutter. In the vasculature, procoagulant microparticles (MPs) are reliable markers of vascular damage. They provide an additional phospholipidic surface, enabling the assembly of the enzyme complexes of blood coagulation and consequent thrombin generation.
Methods: MPs were measured in the venous blood of 33 patients with isthmus-dependent atrial flutter undergoing RF before (RF₀), immediately after (RF₁), and at day 1 (RF₂) thereafter. Concentrations of PAI-1, vWF, and D-dimers were simultaneously determined. MPs procoagulant activities were determined using a functional prothrombinase assay. RF induces an early rise of platelet-derived MPs (platelet), vWF Ag, and D-dimers levels, which is concomitant with the decrease of PAI-1 concentrations. Conversely, no significant changes in endothelial-derived MPs could be evidenced. At RF₂, sustained elevation of leukocytes-derived MPs, vWF, and D-dimers testified to an ongoing prothrombotic status.
Conclusion: RF ablation of common flutter induces a prothrombotic state and the release of platelet and leukocyte-derived procoagulant microparticles. Whereas this activation of blood coagulation could be viewed as clinically marginal in right-sided procedures, its relevance in left-sided procedures should be established.     

Characterization of variable immunodominant antigens of Cowdria ruminantium by ELISA and immunoblots

Cross-immunization experiments have revealed a significant antigenic diversity of the isolate of Cowdria ruminantium which needs to be characterized for the development of vaccines. We identified polymorphic immunodominant antigens by ELISA and immunoblot. Using serum from a goat immune to the Gardel stock of Cowdria (isolated in Guadeloupe) adsorbed on antigen of the Senegal stock of this pathogen, distinct serogroups were revealed by ELISA among six isolates from different geographical origins. Furthermore, a goat serum directed against the Senegal stock and adsorbed on Gardel antigens was shown to be specific for the Senegal stock, thus confirming the existence of serotypes in Cowdria . The Major Antigenic Protein 1 (MAP1) of Cowdria was shown to have variable antigenic determinants. Also in a group of variable proteins ranging from 23 to 29 kDa, one antigen of 26–27 kDa had a determinant specific for the Gardel isolate. These polymorphic antigens may be relevant components of Cowdria ruminantium for a vaccine as the sera revealing these antigens originated from a goat surviving a lethal challenge. However, the presence of T-cell epitopes and the ability of these antigens to confer protection to ruminants remain to be investigated. The production of a rabbit antiserum against this group of polypeptides will be of great use for their purification and for the screening of expression libraries .     

Angiographic Anatomy of the Coronary Sinus and Its Tributaries

Permanent left ventricular pacing has been shown to imporve the hemodynamic and clinical status of patients with severe heart failure. To pace the left ventricle, the electrode is implanted in tributaries of the coronary sinus (CS). However, the anatomy of cardiac veins with this purpose in mind has not been described in detail. Methods: One hundred consecutive patients admitted for coronary angiography had a simultaneous coronary venography performed after the injection of 8 to 10 mL of contrast material into the left coronary artery. Cardiac veins were analyzed in antero-posterior, left anterior oblique 60±, and right anterior oblique 30± views by three different observers. The number, dimension, angulation, and position of the coronary sinus and of its tributaries were studied. Results: Two veins are consistently present: the middle cardiac vein (mean diameter 2.62 ± 1.26 mm) and the great cardiac vein (mean diameter 3.55 ± 1.24 mm). The left posterior vein(s) (LPV) (mean diameter 2.25 ± 1.2 mm) is (are) variable in number (ranging from 0 to 3), size, and angulation. The absence of LPV limits the ability to pace the left ventricle endovenously. The diameter of the vein (< 2 mm) and its angulation may also complicate the insertion of the lead. Conclusion: Angiographic analysis of dimensions, tortuosity, number, and angulation of venous tributaries of the CS seems to allow the insertion of commercially available pacing leads in approximately 85% of cases. An increase in this percentage hinges on the development of new, dedicated leads.     

Egg-hatching inhibition in mice immunized with recombinant Schistosoma bovis 28 kDa glutathione S-transferase

The capacity of a recombinant glutathione S-transferase from Schistosoma bovis (rSb 28GST) to protect BALB/c mice against homologous and heterologous infections with, respectively, S. bovis or Schistosoma mansoni has been studied. Two injections of the rSb 28GST and an intravenous boost resulted in a marked specific IgG response on the day of experimental challenge with S. bovis or S. mansoni cercariae. Immunization of BALB/c mice led to a reduction in egg maturation and egg viability after infection with S. bovis or S. mansoni. Adult worm recoveries after an S. bovis challenge infection and tissue egg densities (intestine and liver) in S. mansoni challenge infection were also reduced in the immunized groups, but these differences were not statistically significant. No association between in vitro inhibition of GST enzymatic activity induced by immunized mouse sera and worm burden reduction was recorded. The analysis of the immune response, on the day of perfusion, showed the production of immunoglobulin (Ig)G1, IgG2a and IgG2b specific antibodies and the production of interleukin (IL)-4 and IL-5 by spleen cells after rSb 28GST stimulation. These data suggest that rSb 28GST immunization induces a moderate effect upon egg maturation and egg hatching, suggesting the involvement of similar mechanisms of action and common, but not exclusive, targets during S. bovis and S. mansoni infections. As a consequence, immunization with rSb 28GST may prove useful in affecting the pathology and transmission of African schistosomes.     

Polymerization of myosin on activation of rat anococcygeus smooth muscle

The in vivo state of assembly ofmyosin in vertebrate smooth muscle is controversial. In vitrostudies on purified smooth muscle myosin show that it ismonomeric (10S) under relaxing conditions and filamentous undercontraction conditions. Electron microscopic and antibodylabelling studies of intact smooth muscles, on the other hand,suggest that myosin is filamentous in the relaxed as well as thecontracting state and that 10S myosin occurs only in traceamounts. However, birefringence, conventional EM and X-raydiffraction evidence suggests that in certain smooth muscles invivo (e.g. rat anococcygeus), while myosin filaments exist in therelaxed state, their number increases on contraction. Here, wehave used low temperature electron microscopic techniques (rapidfreezing followed by freeze-substitution), which preserve labilecomponents in close to their in vivo state, to detect any changein filament number on contraction. The results from ratanococcygeus have been compared with those from guinea pig taeniacoli, in which other techniques have revealed no change infilament number. In the anococcygeus, we find evidence for a 23%increase in filament density in transverse sections ofcontracting muscle compared with relaxed muscle. In the taeniacoli we find no change. These results are in qualitativeagreement with earlier findings. They provide evidence forpolymerization of myosin in contracting rat anococcygeus, andsuggest that this process is subtle and occurs only in somesmooth muscles     

Safety of High Energy Internal Cardioversion for Atrial Fibrillation

High energy internal cardioversion has been proposed as an alternative method to cardiovert drug refractory or external cardioversion refractory atrial fibrillation. However, the safety of this technique has not been clearly evaluated. We reviewed findings in 53 patients who underwent 55 sessions of high energy internal cardioversion (2 patients underwent 2 sessions] for termination of longstanding atrial fibrillation. Shocks energy varied from 70–270 J. Three patients had 3 shocks during the same session, 5 had 2, and 47 only 1. Success rate was 89% (success was defined as immediate conversion to normal sinus rhythm).
Low cardiac output occurred in two patients, and resulted in the death of one of these individuals, a patient with significant hypertrophic cardiomyopathy and heart failure. The other patient recovered completely. In 11% of the cases, shock induced transient atrioventricular block, necessitating ventricular pacing until sinus rhythm was restored. In three patients, a moderate but asymptomatic and uncomplicated pericardial effusion was diagnosed on echocardiogram. Finally, four patients had side effects related to venous puncture, which resolved spontaneously. These results suggest that high energy internal cardioversion is effective for conversion of atrial fibrillation. However, the technique may not be optimal in patients with advanced hypertrophic cardiomyopathy and in such cases the technique should be used carefully and only in the case of failure of external cardioversion; no more than two shocks should be delivered during the same procedure. Temporary ventricular pacing should be provided in all patients and an echocardiogram should be performed before patients are being discharged.     

Location of Probucol in Lipoproteins Inferred from Compositional Analysis of Lipoprotein Particles. An In-vitro Study

Abstract— The location of labelled probucol in lipoprotein particles was investigated in-vitro. Human serum was incubated for 4 h at 37°C with [¹⁴C]probucol to incorporate probucol into lipoproteins. Serum lipoprotein particles were then isolated according to their apolipoprotein markers by sequential immunoaffinity chromatography at 4°C, and probucol concentration was determined in each lipoprotein fraction. Analysis of probucol distribution vs lipoprotein components revealed that probucol in particles strongly correlated with phospholipid concentration. Analysis of probucol distribution vs lipoprotein physical characteristics showed that probucol strongly correlated with the surface area of the monolayer surrounding the lipidic core of particles constituting phospholipids and free cholesterol. These data support the hypothesis that probucol is preferentially located in the phospholipid/free cholesterol monolayer surrounding the lipid core, in the vicinity of cholesteryl ester at the core surface or in the vicinity of hydrophobic areas of apolipoprotein that faces the monolayer.     

Synthesis and biological activity of a destruxin analogue: d-Lac-6 destruxin E

A general strategy for the synthesis of destruxin analogues is described and applied to a particular example, d -Lac-6 destruxin E. The tetrapeptide Boc-Ile-N-MeVal-N-MeAla-β-Ala-OMe (2) was chosen as the basic starting compound, and its preparation was optimized. This fragment was then coupled with the compound (D)Lac-Pro, and the resulting peptide was cyclized by the DEPC or DPPA/HOBt/DMAP methods at 21 and 30% yield, respectively. The biological activity of the analogue obtained was established by injection to an insect host.     

Combination of Sotalol and Quinidine in a Canine Model of Torsades de Pointes

Sotalol Plus Quinidine and Torsades de Pointes. Introduction: Clinical treatment with a combination of Class IA and III antiarrhythmic drugs is not recommended, as they both favor bradycardia-dependent proarrhythmic events such as torsades de pointes (TdP). However, this theoretical additive effect on ventricular repolarization has never heen demonstrated and could be questioned as other Class I drugs, such as mexiletine, a Class IB drug, limit the number of sotalol-induced TdP in dogs with AV block, suggesting the possibility of an antagonistic action of Class I properties against Class III effects. Methods and Results: We compared the electrophysiologic and proarrhythmic effects of sotalol (Class III) alone and combined with quiuidine (Class IA) in a canine model of acquired long QT syndrome. Seven hypokalemic (K*: 3 ± 0.1 mEq/L) dogs with chronic AV block had a demand pacemaker implanted and set at a rate of 25 beats/min. They were submitted to two (sotatol-alone and sotalol-plus-quinidine) experiments 48 bours apart usiug a randomized cross-over protocol. They were pretreated with quinidine (10 mg/kg + 1.8 mg/kg per hour) or saline infused throughout the experiment, aud given sotalol (4.5 mg/kg + 1.5 mg/kg per hour) for 2 hours, 30 minutes after the beginning of the pretreatment infusion during both experiments. Ventricular and atrial cycle lengths were similarly increased by sotalol after quinidine or saline. The sotalol-induced prolongation of the QT interval was significantly shorter in quinidine-pretreated dogs (24 ± 7 msec after quinidine vs 40 ± 8 msec after saline). Fewer dogs developed TdP: significantly during the first hour of infusion (1/7 sotalol-plus-quinidine vs 6/7 sotalol-alone dogs, P < 0.05) but nonsignificantly during the second hour (3/7 vs 6/7). Conclusion: In this model, the sotalol-plus-quinidine combination is at least no more arrhythmogenic than either of the drugs given alone.     

The significance of human monocyte thrombomodulin during membrane vesiculation and after stimulation by lipopolysaccharide

Thrombomodulin acts as an essential membrane cofactor of thrombin in the triggering of the natural anticoagulant protein C pathway responsible for the inactivation of procoagulant cofactors VIIIa and Va. Because monocytes play a critical role in the coupling between infection/inflammation and thrombosis, the fate of monocyte thrombomodulin was assessed at the cell plasma membrane and on derived microparticles. A significant basal level of thrombomodulin activity was measured on unstimulated monocytes and microparticles. Lipopolysaccharide treatment resulted in increased thrombomodulin activity on monocytes (∼40%) and microparticles (∼80%), whereas tissue factor and prothrombinase activities were strongly expressed on both. Flow cytometry detection of thrombomodulin antigen confirmed its presence on unstimulated monocytes and microparticles. A decrease (∼30%) in thrombomodulin labelling was noticed on stimulated monocytes. Labelling of microparticles shed from stimulated and unstimulated monocytes remained unchanged, only an increased proportion of microparticles (∼20%) was observed. The absence of early down-regulation of thrombomodulin following monocyte stimulation suggests that it fulfils an important regulatory function of membrane-associated procoagulant activities. This would be of particular significance at the surface of microparticles having the ability to diffuse and concentrate by adherence at inflammatory sites.