Identification and expression of isoflavone synthase, the key enzyme for biosynthesis of isoflavones in legumes

Isoflavones have drawn much attention because of their benefits to human health. These compounds, which are produced almost exclusively in legumes, have natural roles in plant defense and root nodulation. Isoflavone synthase catalyzes the first committed step of isoflavone biosynthesis, a branch of the phenylpropanoid pathway. To identify the gene encoding this enzyme, we used a yeast expression assay to screen soybean ESTs encoding cytochrome P450 proteins. We identified two soybean genes encoding isoflavone synthase, and used them to isolate homologous genes from other leguminous species including red clover, white clover, hairy vetch, mung bean, alfalfa, lentil, snow pea, and lupine, as well as from the nonleguminous sugarbeet. We expressed soybean isoflavone synthase in Arabidopsis thaliana, which led to production of the isoflavone genistein in this nonlegume plant. Identification of the isoflavone synthase gene should allow manipulation of the phenylpropanoid pathway for agronomic and nutritional purposes.

Clinical experience with implantable atrial and combined atrioventricular defibrillators

The high prevalence of atrial fibrillation (AF) and its clinical complications, the poor efficacy of medical therapy for preventing recurrences, and dissatisfaction with alternative modes of therapy stimulated interest in implantable atrial and combined atrioventricular defibrillators. In a multicenter study, the safety and efficacy of a stand alone implantable atrial defibrillator, the Metrix system, were evaluated. The device was implanted in 51 patients with highly symptomatic episodes of AF refractory to pharmacological treatment. During a follow-up of 9 months, 96% of 227 spontaneous AF episodes were successfully converted to sinus rhythm in 41 patients. In 62 episodes (27%), several shocks and/or additional drug treatment were required to maintain stable sinus rhythm because of early recurrences of AF. A total of 3719 shocks were delivered and no induction of ventricular proarrhythmia or inaccurately synchronized shocks occurred. The AF detection algorithm exhibited a 100% specificity for the recognition of sinus rhythm and a 92.3% sensitivity for the detection of AF. The combined atrioventricular defibrillator, Jewel AF 7250, was evaluated in a multicenter, randomized, cross-over trial. The primary study objectives included: overall safety as determined by complications-free survival at 6 months, efficacy of tiered atrial pacing and defibrillation therapies for termination of spontaneous atrial tachycardias (AT) and AF, and relative sensitivity of a new dual-chamber detection algorithm. The device was implanted in 211 patients with either a history of ventricular tachyarrhythmias (VT/VF) alone or with a history of both AT/AF and VT/VF. During a mean follow-up of 4.5 months, it has been shown that the Jewel AF is safe and effective in treating atrial and ventricular tachyarrhythmias. Pace termination of 85% of AT episodes were achieved with painless delivery of antitachycardia pacing; additional 35% of AT episodes were terminated by high frequency burst pacing.

CONCLUSIONS

The stand alone implantable atrial defibrillator may be safe and clinically useful in selected patients for the treatment of highly symptomatic, drug resistant recurrences of AF. The combined atrioventricular defibrillator may be particularly indicated in patients presenting with both a history of atrial and ventricular tachyarrhythmias.

Quality of life in atrial fibrillation

In patients with atrial fibrillation (AF), the restoration and maintenance of sinus rhythm is the primary therapeutic goal. Once sinus rhythm is maintained, physiological rate control is restored, and left ventricular ejection fraction, cardiac output, and exercise capacity are increased. This improved cardiovascular performance thereby enhances the patient's ability to perform the functions of normal daily life. The primary intervention for maintaining sinus rhythm after restoration is the use of anti-arrhythmic agents. Although physicians mostly use class 1A anti-arrhythmic drugs, these oral agents only maintain sinus rhythm in a limited number of cases and are accompanied by considerable side effects. Therefore, more effective tools are needed. Effective treatment for AF is based on the above objective criteria, but subjective criteria such as the quality of life are growing in importance. To address these quality-of-life issues, we have initiated a prospective study in which patients are assigned to one of two groups: those with paroxysmal AF who are candidates for permanent implantable atrial defibrillators and those with chronic or paroxysmal AF who are not candidates for atrial defibrillators. Specifically designed questionnaires and various standardized and validated instruments are used to measure quality of life. The questionnaires cover social demographic data, including age, education, occupation level, driving behavior, return to work, and sexual activity. Quality of life is a multidimensional construct, and thus its definition must consider the many factors mentioned above. In the final analysis, therefore, both objective and subjective criteria are necessary to define appropriate treatment of AF.

Predictors of success in radiofrequency catheter ablation of atrial flutter

Radiofrequency catheter ablation of typical atrial flutter at the isthmus between the tricuspid annulus and the inferior vena cava is established. However in selected patients, the creation of a continuous linear lesion at the targeted isthmus requires a lengthened procedure or is not feasible at all and atrial flutter recurrences are common. In a retrospective analysis, we found that an intraoperatively determined distance between the tricuspid annulus and the inferior vena cava of <.2.5 cm is an independent predictor of a lengthened or failed ablation procedure. Additional equipment, e.g., long introducer sheaths, adapted ablation catheter design, or irrigated tip ablation, as well as alternative ablation approaches, e.g., linear lesions between the tricuspid annulus and Eustachian ridge, have been invented in order to increase the acute success rate or decrease fluoroscopy and procedure time. In a prospective study on the effects of various conduction properties at the isthmus between tricuspid annulus and inferior vena cava following radiofrequency ablation of atrial flutter, we showed previously that others than a complete bidirectional conduction block predicts a high recurrence rate of atrial flutter. For determination of transisthmal conduction properties following ablation, established mapping approaches are documentation of double potentials at the ablation line and right atrial activation sequence following posteroseptal and low lateral right atrial pacing. Novel threedimensional mapping systems, i.e., Carto(R) and EnSite(R), may further enhance the accuracy of conventional mapping techniques.

Right atrial appendage thrombosis in atrial fibrillation: its frequency and its clinical predictors

This study assesses the incidence of right atrial (RA) chamber and appendage thrombosis in patients with atrial fibrillation (AF) in relation to RA appendage morphology and function. Transthoracic and multiplane transesophageal echocardiography were performed in 102 patients with AF to assess the incidence of RA and left atrial (LA) thrombi and spontaneous echo contrast. Both right and left ventricular sizes, atrial chamber and appendage sizes and function were measured. Twenty-two patients in sinus rhythm served as the control group (SR). Complete visualization of the RA appendage was feasible in 90 patients with AF. Patients with AF had lower tricuspid annular excursion (p = 0.008) and larger RA chamber area (p = 0.0001) than patients in SR. In addition, RA appendage areas were larger (p <0.05) and RA ejection fraction and peak emptying velocities (both p <0.0001) were lower in patients with AF patients than in those in SR. Equivalent differences were found for the LA appendage. Six thrombi were found in the RA appendage and 11 thrombi in the LA appendage in AF patients. Spontaneous echo contrast was found in 57% and 66% in the right atrium and in the left atrium, respectively. AF patients with RA appendage thrombi had a larger RA area (p = 0.0001), and lower RA appendage ejection fraction and emptying velocities (both p = 0.0001) than patients without thrombi. Spontaneous echo contrast was detected in all patients with thrombi. Spontaneous echo contrast was the only independent predictor of RA (p = 0.03) and LA appendage thrombosis (p = 0.036). In conclusion, multiplane transesophageal echocardiography allows the assessment of RA appendage morphology and function. RA spontaneous echo contrast is the only independent predictor of RA appendage thrombosis.

Characterization of an alkali-extracted peptidoglycan from Korean Ganoderma lucidum

The biologically active peptidoglycan was purified from the alkali fraction of the fruiting bodies of Ganoderma lucidum and the composition of the peptidoglycan was investigated by conventional analyses. The alkali-extracted peptidoglycan showed differences in chemical compositions from the water-extracted. The alkali-extracted peptidoglycan contained 6.9% protein and 75.9% carbohydrates composed mainly of beta-glucose, mannose, and alpha-glucose. The molecular weight range of the peptidoglycan was determined as 2,000 kDa-17 kDa. The peptidoglycan is considered to be a hybrid molecule of polysaccharide chains covalently bound as a side chain to the polypeptide core.

[Clinical experience with the implantable atrial defibrillator (atrioverter) in patients with atrial fibrillation. Metrix Investigators]

Due to the limited efficacy of drug therapy in atrial fibrillation and the high rate of recurrence, strong efforts were made to find non-pharmacological strategies. For three years now, the implantable atrial defibrillator Metrix from InControl has been available as an alternative therapy. From October 1995 to the present the atrial defibrillator was implanted in 179 patients worldwide. The sensitivity of the system and its algorithms to detect atrial fibrillation is 90%; the specificity to detect sinus rhythm is 100%. In 121 of 179 patients, 748 episodes of spontaneous atrial fibrillation were treated with 2.4 shocks per episode. No proarrhythmic event or stroke was seen. A cardioversion to sinus rhythm could be achieved in 95% of patients; the overall clinical success rate was 88%. In 7% of all patients, early recurrence of atrial fibrillation (ERAF) occurred that could not be converted into stable sinus rhythm after further cardioversions and antiarrhythmic therapy. In 4.1% there were lead-related complications, in 4 patients the device had to be explanted because of ineffective therapy, and in 3 patients the device had to be changed because of loss of telemetry or early depletion of battery. In 8 patients, postoperative complications were seen (infections, pneumothorax and thrombosis of the subclavian vein). Overall, the implantable atrial defibrillator Metrix is an effective and safe alternative in treating atrial fibrillation.

Transverse conduction capabilities of the crista terminalis in patients with atrial flutter and atrial fibrillation

OBJECTIVES

In this study, the transverse conduction capabilities of the crista terminalis (CT) were determined during pacing in sinus rhythm in patients with atrial flutter and atrial fibrillation.

BACKGROUND

It has been demonstrated that the CT is a barrier to transverse conduction during typical atrial flutter. Mapping studies in animal models provide evidence that this is functional. The influence of transverse conduction capabilities of the CT on the development of atrial flutter remains unclear.

METHODS

The CT was identified by intracardiac echocardiography. The atrial activation at the CT was determined during programmed stimulation with one extrastimulus at five pacing sites anteriorly to the CT in 10 patients with atrial flutter and 10 patients with atrial fibrillation before and after intravenous administration of 2 mg/kg disopyramide. Subsequently, atrial arrhythmias were reinduced.

RESULTS

At baseline, pacing with longer coupling intervals resulted in a transverse pulse propagation across the CT. During shorter coupling intervals, split electrograms and a marked alteration of the activation sequence of its second component were found, indicating a functional conduction block. In patients with atrial flutter, the longest coupling interval that resulted in a complete transverse conduction block at the CT was significantly longer than that in patients with atrial fibrillation (285 +/- 49 ms vs. 221 +/- 28 ms; p < 0.05). After disopyramide administration, a transverse conduction block occurred at longer coupling intervals as compared with baseline (287 +/- 68 ms vs. 250 +/- 52 ms; p < 0.05). Subsequently, a sustained atrial arrhythmia was inducible in 15 of 20 patients. This was atrial flutter in three patients with previously documented atrial fibrillation and in eight patients with history of atrial flutter. Mapping revealed a conduction block at the CT in all of these patients.

CONCLUSIONS

It was found that the CT provides transverse conduction capabilities and that the conduction block during atrial flutter is functional. Limited transverse conduction capabilities of the CT seem to contribute to the development of atrial flutter.

Intra-atrial defibrillation in humans

The frequency of atrial fibrillation (AF) and its economic impact on the health-care system ensure that AF will be a focus for future research. At present, the chronic use of an atrioverter (IAD) is a major challenge in the nonpharmacological treatment of AF. Studies in animals as well as in humans have demonstrated the feasibility and safety of internal atrial defibrillation. The major issues that have to be addressed are the pain perception and the potential risk of inducing life-threatening ventricular arrhythmias during delivery of low-energy atrial shocks. A first step to this novel approach is a physician activated device. At the very beginning, the IAD should be restricted to highly selected patients with drug refractory, poorly tolerated, recurrent AF episodes. The extenuation of this therapy to wider subsets of patients should be dependent on the initial results with regard to clinical efficacy and safety as well as patient tolerance. Finally, cost-effectiveness as well as quality of life studies are needed to demonstrate the benefit of this specific therapy among other therapeutic strategies available for the management of AF. A new arrhythmia management system that combines both detection and treatment in the atrium as well as in the ventricle may represent an important milestone and a significant improvement in the management of patients with both supraventricular and ventricular tachyarrhythmias.

Radiofrequency catheter ablation of frequent monomorphic ventricular ectopic activity

INTRODUCTION

Frequent ventricular ectopic beats can result in severe symptoms and may even be incapacitating in some patients. Although radiofrequency catheter ablation is an effective and safe therapy for drug refractory idiopathic ventricular tachycardia, it has not been widely used in ventricular ectopy. The purpose of this study was: (1) to assess the potential role of catheter ablation in eliminating monomorphic ventricular ectopy in symptomatic patients regarding feasibility and safety and (2) to determine the usefulness of various mapping strategies.

METHODS AND RESULTS

Forty-one patients with symptomatic ventricular ectopic activity (right ventricular origin in 23 patients, left ventricular origin in 18 patients) were enrolled. The mean frequency of ventricular ectopic beats was 1512+/-583/hour documented by Holter ECG monitoring. These patients had previously been unable to tolerate or had been unsuccessfully treated with a mean of 3+/-1 antiarrhythmic agents. The site of origin was mapped using earliest endocardial activation times, unipolar electrograms and pace mapping. Radiofrequency ablation was successful in 34 (83 %) of 41 patients. Multivariate logistic regression analysis revealed pace mapping as the only independent predictor for a successful ablation site (P < 0.01). After a follow-up of 3 months, the overall success rate was 71%. The mean frequency of ventricular ectopic beats after successful ablation was 12+/-10 ventricular premature beat/hour.

CONCLUSION

Radiofrequency catheter ablation is an effective and safe treatment for frequent symptomatic drug refractory monomorphic ventricular ectopic activity. Pace mapping predicts best successful ablation of ventricular ectopic beats.

Percutaneous extraction of an abandoned coiled pacing lead

Abandoning redundant pacing leads has been an accepted practice in most cases. Late migration of a lead is a rare, unpredictable, and potentially lethal complication of this approach and requires immediate removal. We report the case of an atrial pacing lead that had migrated and was found coiled in the right atrium. It was removed by a snare catheter via a femoral approach.

Inappropriate implantable defibrillator discharge caused by a retained pacemaker lead fragment

INTRODUCTION

Inappropriate discharge is still a major issue of implantable cardioverter defibrillator therapy. The diagnostic options of modern devices facilitate classification of the underlying abnormality.

METHODS AND RESULTS

A 65-year-old woman with depressed left ventricular performance received spurious shocks from an ICD, implanted for ventricular tachycardia. A lead fragment of an explanted VVI pacemaker system could be identified as cause of erroneous ventricular fibrillation detection by the ICD. The electrical noise caused by interaction between the lead remnant and the ICD lead was detectable even on the surface ECG.

CONCLUSION

Based on our findings, removal of fragmented lead material should be considered prior to ICD implantation, to avoid potentially adverse and harmful interactions with ICD systems.

Hemodynamic and cardiorespiratory function following internal atrial defibrillation for chronic atrial fibrillation

Internal atrial defibrillation (IAD) is able to restore sinus rhythm in patients with chronic atrial fibrillation (AF) and failed external electrical and/or pharmacologic cardioversion. To assess whether cardiorespiratory and hemodynamic function improve after IAD, 35 patients were prospectively investigated during constant workload exercise by spiroergometry and Doppler echocardiography before IAD, and 1 day and 1 month after IAD. Oxygen uptake kinetics, ventilation, left atrial mechanical function, and pulmonary artery pressure were determined simultaneously at rest and during steady state. During the serial follow-up, 20 patients maintained sinus rhythm. The time interval for achieving the steady state (146 +/- 53 vs 132 +/- 42 seconds; p = 0.5) and the oxygen deficit (645 +/- 190 vs 670 +/- 174 ml; p = 0.7) were not different before and 1 day after IAD, but decreased significantly after 1 month (98 +/- 16 seconds, p = 0.01 and 487 +/- 72 ml, p = 0.02). Exercise pulmonary artery systolic pressures were 38 +/- 13 mm Hg before IAD, increased significantly to 46 +/- 11 mm Hg on day 1 (p = 0.03), and decreased below baseline values at 1 month to 31 +/- 12 mm Hg (p = 0.07). Peak A-wave velocities increased from 0.51 +/- 0.1 m/s after 1 day to 0.67 +/- 0.2 m/s after 1 month (p = 0.03). Restoration of sinus rhythm in patients with AF resistant to external electrical and/or pharmacologic cardioversion improves hemodynamic and cardiorespiratory function at daily activity exercise levels.

Verification of linear lesions using a noncontact multielectrode array catheter versus conventional contact mapping techniques

INTRODUCTION

Creation of linear lesions is an established ablation goal. Verification of complete conduction block at the ablation line is required to determine ablation success. Conventional mapping techniques are sequential endocardial activation mapping and documentation of double potentials. Recently, a noncontact multielectrode array catheter was developed that allows instantaneous three-dimensional mapping by simultaneous reconstruction of > 3,000 electrograms. In this study, we prospectively compared the accuracy of noncontact mapping to identify discontinuities in linear lesions and to verify a conduction block with that of conventional mapping techniques.

METHODS AND RESULTS

In 12 patients with atrial flutter, radiofrequency pulses were applied between the tricuspid annulus and either the inferior vena cava or the eustachian ridge. Following each application, pulse propagation at the ablation line was determined during pacing by conventional mapping techniques. The findings were compared to high-density isopotential mapping using the noncontact multielectrode array catheter. It was found that noncontact mapping reliably distinguished conduction delays from a conduction block as defined by contact mapping. In addition, noncontact mapping instantaneously identified the area where a discontinuity in the line of block was present. In these patients, complete conduction block was achieved by radiofrequency pulses guided by the noncontact mapping system.

CONCLUSION

Noncontact mapping is highly accurate in distinguishing conduction delays from a complete conduction block. By providing an instantaneous high-density propagation vector at all sites along the ablation line, three-dimensional isopotential mapping is helpful in localizing discontinuities of linear lesions and, thus, may facilitate the creation of a complete conduction block.

Oxygen uptake to work rate relation throughout peak exercise in normal subjects: relevance for rate adaptive pacemaker programming

The oxygen uptake to work rate (VO2/WR) relationship observed throughout peak exercise testing is already being applied for rate adaptive pacemaker programming. However, the detailed curve design of VO2/WR with respect to the anaerobic threshold (AT) has not yet been investigated. It was the purpose of this study to determine the VO2/WR slope below and above the AT in a healthy control group. Seventy-eight healthy control subjects (45.9 +/- 17.4 years; 34 women: 49.9 +/- 18.6 years 44 men: 43.6 +/- 16.6 years) were exercised on a treadmill with "breath-by-breath" gas exchange monitoring using the symptom limited "ramping incremental treadmill exercise" (RITE) protocol. The slope of the VO2/WR relationship from rest to peak exercise (r-p), rest to AT (slope A), and AT to peak exercise (slope B) in mL oxygen uptake per watt of external treadmill work was determined by linear regression analysis. [table: see text] The oxygen uptake to work rate relationship throughout peak exercise in the entire study group generated a significant slope change at the AT (31%, P < 0.0001) with a decreasing slope during higher work load intensities. Female subjects demonstrated a greater percentage of slope change at AT (43%), as compared to men (22%, P < 0.01). When using the oxygen uptake to work rate relationship for the programming of the pacemaker's rate response to exercise, the significant slope change at the AT should be considered to more appropriately pace during higher work intensities supported by anaerobic metabolism. Female pacemaker patients should be programmed to generate a steeper VO2/WR slope below AT with a greater slope change at AT, as compared to men. Abnormally high oxygen uptake to work rate ratios above the AT may be possibly used as an indicator of overpacing.

Reduction of natural killer cytotoxic activity in major depression: interaction between depression and cigarette smoking

OBJECTIVE

Epidemiological data suggest that the presence of a depressed mood combined with cigarette smoking increases the risk of cancer at sites associated with smoking and at sites not associated with smoking. This study tested the hypothesis that major depression and smoking together contribute to a decline of natural killer cell (NK) activity, an immune parameter thought to be important in immune surveillance.

METHODS

A sample of 245 men were stratified into four groups: control subjects who were not smokers, control subjects who were smokers, subjects with major depression who were not smokers, and subjects with major depression who were smokers. Blood samples were obtained for measurement of total white blood cell (WBC) counts, differential cell counts, and assay of NK activity.

RESULTS

Major depression and cigarette smoking interact and were together associated with changes in WBC counts and NK activity. Depressed subjects who were smokers had higher WBC counts (p < .001) and lower NK activity (p < .01) than depressed nonsmoking subjects. However, WBC counts and NK activity were similar in control smokers and nonsmokers. Backward elimination regression analyses showed that the interaction of depression and smoking significantly (p < .001) predicted WBC counts and NK activity.

CONCLUSIONS

This study extends previous findings of immune alterations in patients with major depression. Major depression and smoking interact and together contribute to an elevation of total WBC count and a decline of NK activity.

Inward and outward rectifying potassium currents set membrane potentials in activated rat microglia

Activation of cultured rat microglial cells with lipopolysaccharide (LPS), induced outward rectifying K+ (K(V)) current in addition to already existing inward rectifying K+ current (K(IR)). By measuring zero-current membrane-potentials using whole-cell patch-clamp method, we showed that K(V) current plays a direct role in setting membrane potential to near -45 mV. Since the membrane potentials of microglia show two prominent peaks at -45 and -70 mV, we hypothesize that K(IR) current might set the membrane potential to near -70 mV. We observed that cells with larger K(IR) current had a zero-current membrane-potential at around -70 mV, and that blocking of K(IR) current with Ba2+ depolarized membrane potentials to near -45 mV. These results indicate that the amounts of K(IR), and K(V) current determine the zero-current membrane-potentials in LPS-activated microglia.

Radiofrequency ablation of atrial flutter due to administration of class IC antiarrhythmic drugs for atrial fibrillation

In selected patients, atrial fibrillation (AF) converts to atrial flutter (AFI) due to treatment with class IC antiarrhythmic drugs. In this study, we prospectively investigated the effects of AFI ablation and continuation of drug therapy in patients with AF who developed AFI due to long-term administration of class IC antiarrhythmic drugs. The study population consisted of 187 patients from an AF registry with paroxysmal AF who were orally treated with flecainide (n = 96) or propafenone (n = 91). Twenty-four patients (12.8%) developed AFI during the course of treatment. In 20 of these patients (10.7%), electrophysiologic study revealed typical AFI. These patients underwent radiofrequency ablation of AFI. Ablation failed in 1 patient. All patients continued preexisting drug treatment. Recurrence of AF was assessed by ambulatory Holter monitoring and serial questionnaires. During a mean follow-up of 11 +/- 4 months, the incidence of AF episodes was significantly lower in patients with a combined therapy (2.7 +/- 3.6 per year) than in control subjects with a sole drug treatment (7.8 +/- 9.2 per year, p <0.05) and than before therapy (10.2 +/- 5.4 per year, p <0.001). Subgroup analysis revealed that 7 patients (36.8%) remained symptom free with no evidence of atrial tachyarrhythmia. Eight additional patients (42.1%) had ongoing paroxysmal AF, however, with a significantly lower incidence of AF episodes than before therapy (2.3 +/- 1.6 per year vs 11.5 +/- 5.0 per year, p <0.001). In the remaining 4 patients (14.7%), no beneficial effect of AFI ablation was found. It is concluded that in patients with AF who develop typical AFI due to administration of class IC antiarrhythmic agents, a combined therapy with catheter ablation of AFI and continuation of drug treatment is highly effective in reducing occurrence and duration of atrial tachyarrhythmias.