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Achievement↗
Biomedical subjects
R Weiss
Publications and source records attributed to R Weiss.
Failure of single- and multisite high-frequency atrial pacing to terminate atrial fibrillation.
This study determined the efficacy of single- and multisite atrial pacing for terminating episodes of atrial fibrillation induced in patients in the electrophysiology laboratory. One- to 5-second bursts of atrial pacing at a cycle length of 20 ms were not effective in terminating atrial fibrillation, when delivered either in the high right atrium or when delivered simultaneously at the high right atrium, midseptum, and coronary sinus.
Atrial Fibrillation↗
Direct Radiative Forcing by Smoke from Biomass Burning
Airborne measurements in smoke from biomass burning in Brazil have yielded optical parameters that permit an improved assessment of the effects of smoke on Earth's radiation balance. The global-mean direct radiative forcing due to smoke from biomass burning worldwide is estimated to be no more than about -0.3 watt per square meter (cooling), compared with +2.45 watts per square meter (warming) due to anthropogenic greenhouse gases. On regional scales, direct radiative forcing due to smoke can be large and might indirectly affect global climate.
Journal Article↗
Ribonucleotide reductase in the archaeon Pyrococcus furiosus: a critical enzyme in the evolution of DNA genomes?
Ribonucleotide reductase (RNR), the enzyme responsible for deoxyribonucleotide synthesis, has been isolated from Pyrococcus furiosus, a deeply branching hyperthermophilic, strictly anaerobic archaeon. Its gene has been cloned, sequenced, and shown to harbor two insertions encoding inteins. The purified enzyme absolutely requires adenosylcobalamin for activity, a trait that defines it as a member of class II (adenosyl-cobalamin-dependent) prokaryotic RNRs. On the other hand, the archaeal RNR has significant amino acid sequence homology with class I (aerobic non-heme iron-dependent) and class III (anaerobic iron-sulfur-dependent) RNRs present in eukaryotes and bacteria, respectively. It is proposed that this enzyme may be the closest possible relative of the original RNR, which allowed the key "RNA world" to "DNA world" transition, and that the different classes of present-day RNRs are the products of divergent evolution.
Amino Acid Sequence↗
Comparison of effective and ineffective target sites that demonstrate concealed entrainment in patients with coronary artery disease undergoing radiofrequency ablation of ventricular tachycardia.
BACKGROUND: Concealed entrainment has been useful in guiding catheter ablation of monomorphic ventricular tachycardia in patients with coronary artery disease. However, not all sites with concealed entrainment result in successful ablation of the targeted ventricular tachycardia. The purpose of this prospective study was to identify factors at sites that demonstrate concealed entrainment that differentiate effective from ineffective target sites. METHODS AND RESULTS: In 14 consecutive patients with hemodynamically stable monomorphic ventricular tachycardia and coronary artery disease, radiofrequency ablation of 26 ventricular tachycardias was performed. Ablation was attempted at 46 sites that demonstrated concealed entrainment. Twenty-five of the targeted ventricular tachycardias (96%) were successfully ablated. The positive predictive value of concealed entrainment for successful ablation was 54%; it increased to 72% in the presence of a stimulus-QRS interval/ventricular tachycardia cycle length ratio of < or = 70%, to 82% in the presence of a match of the stimulus-QRS and electrogram-QRS interval, and to 89% in the presence of isolated mid diastolic potentials that could not be dissociated from ventricular tachycardia during entrainment. CONCLUSIONS: The positive predictive value of concealed entrainment for identification of successful ablation sites in patients with sustained ventricular tachycardia and coronary artery disease can be significantly enhanced by the presence of associated mapping criteria, particularly an isolated mid diastolic potential that cannot be dissociated from the tachycardia.
Adult↗
Fold assignments for amino acid sequences of the CASP2 experiment.
New and newly extended methods for fold assignment were tested for their abilities to assign folds to amino acid target sequences of unknown three-dimensional structure. These target sequences, released through the CASP2 experiment, are not obviously related to any sequence of known three-dimensional (3D) structure. We assigned 3D folds to target sequences and filed these predictions with CASP2 before their 3D structures were released. The methods tested were (1) Environmental 3D profiles of Bowie and colleagues [Bowie, J.U., Luthy, R., Eisenberg, D. Science 253:164-170, 1991]; (2) A variation of this is termed Directional Profiles; (3) The H3P2 five-dimensional sequence-structure substitution matrix of Rice and Eisenberg [Rice, D., Eisenberg, D.J. Mol. Biol. 267:1026-1037, 1997]; and (4) The Sequence Derived Property methods of Fischer and Eisenberg [Fischer, D., Eisenberg, D. Prot. Sci. 5:947-955, 1996]. When the 3D structures of the sequences were released, 17 of our predictions were evaluated. Of these 17, we assigned high probabilities to 11, of which 9 were correct. Five of these correct predictions were of known 3D structures similar to the targets and four of these were of new folds. The evaluation demonstrated that our methods were effective in assigning the proper fold to more than half of the CASP2 targets with known folds (5/9) and also were able to detect half of the sequences that corresponded to no known folds (4/8). Even when the correct fold is assigned to a sequence, proper alignment of the sequence to the structure remains a challenge. Our methods were able to produce accurate alignments (< 1.2 mean residue shift error from the structural alignment) for four of the targets, including the particularly difficult alignment (only 7% residue identity in the structurally aligned regions) of the ferrochelatase sequence to the fold of a periplasmic binding protein.
Amino Acid Sequence↗
Antihypertensive effects of mibefradil: a double-blind comparison with diltiazem CD.
BACKGROUND AND HYPOTHESIS: Mibefradil is the first compound of a new class of calcium antagonists with a unique chemical structure and mechanism of action. This trial compared mibefradil with diltiazem CD, a widely prescribed calcium antagonist for the treatment of hypertension. METHODS: In all, 201 patients with uncomplicated, mild-to-moderate essential hypertension with a baseline sitting diastolic blood pressure (SDBP) of > or = 95 and < or = 114 mmHg were evenly randomized to receive either mibefradil (100 mg) or diltiazem CD (360 mg) daily for 12 weeks. To determine whether antihypertensive effects persisted after 12 weeks, patients then entered a 4-week withdrawal period during which they remained on active treatment or were switched to placebo. RESULTS: Efficacy variables were the changes from baseline in SDBP to the end of the treatment period (Week 12) and during the randomized withdrawal period (Week 16). At Week 12, the reduction from baseline in SDBP at trough was significantly greater (p < 0.001) in the mibefradil group (-14.0 +/- 7.8 mmHg) than in the diltiazem CD group (-9.5 +/- 7.5 mmHg). Significantly more patients (72%) on mibefradil achieved SDBP normalization by Week 12 than did patients on diltiazem (51%) (p < 0.01). Patients maintained on mibefradil or diltiazem CD during the withdrawal period had a significantly larger reduction in trough SDBP at Week 16 than those switched to placebo. The incidence of side effects was similar in both treatment groups. CONCLUSIONS: Once-daily mibefradil was equally well tolerated as diltiazem CD, but was more effective in lowering blood pressure at the doses studied than the extended-release formulation of diltiazem.
Adult↗
Evidence for the early divergence of tryptophanyl- and tyrosyl-tRNA synthetases.
Each amino acid is attached to its cognate tRNA by a distinct aminoacyl-tRNA synthetase (aaRS). The conventional evolutionary view is that the modern complement of synthetases existed prior to the divergence of eubacteria and eukaryotes. Thus comparisons of prokaryotic and eukaryotic aminoacyl-tRNA synthetases of the same type (charging specificity) should show greater sequence similarities than comparisons between synthetases of different types-and this is almost always so. However, a recent study [Ribas de Pouplana L, Furgier M, Quinn CL, Schimmel P (1996) Proc Natl Acad Sci USA 93:166-170] suggested that tryptophanyl- (TrpRS) and tyrosyl-tRNA (TyrRS) synthetases of the Eucarya (eukaryotes) are more similar to each other than either is to counterparts in the Bacteria (eubacteria). Here, we reexamine the evolutionary relationships of TyrRS and TrpRS using a broader range of taxa, including new sequence data from the Archaea (archaebacteria) as well as species of Eucarya and Bacteria. Our results differ from those of Ribas de Pouplana et al.: All phylogenetic methods support the separate monophyly of TrpRS and TyrRS. We attribute this result to the inclusion of the archaeal data which might serve to reduce long branch effects possibly associated with eukaryotic TrpRS and TyrRS sequences. Furthermore, reciprocally rooted phylogenies of TrpRS and TyrRS sequences confirm the closer evolutionary relationship of Archaea to eukaryotes by placing the root of the universal tree in the Bacteria.
Amino Acid Sequence↗
Long-term follow-up after radiofrequency modification of the atrioventricular node in patients with atrial fibrillation.
OBJECTIVES: The purpose of this study was to describe the long-term follow-up results in 62 patients with atrial fibrillation and an uncontrolled ventricular rate, who underwent radiofrequency modification of the atrioventricular (AV) node. BACKGROUND: Previous studies in small numbers of patients have suggested that radiofrequency modification may be effective in controlling the ventricular rate in patients with atrial fibrillation, but long-term follow-up data have been lacking. METHODS: The subjects of this study were 62 consecutive patients (mean age +/- SD 65 +/- 14 years; 43 with structural heart disease) who underwent an attempt at radiofrequency modification of the AV node because of symptomatic, drug-refractory atrial fibrillation with an uncontrolled ventricular rate. The atrial fibrillation was chronic in 46 patients and paroxysmal in 16. Radiofrequency energy was applied to the posteroseptal or mid-septal right atrium to lower the ventricular rate in atrial fibrillation to 120 to 130 beats/min during an infusion of 4 micrograms/min of isoproterenol. RESULTS: Short-term control of the ventricular rate was successfully achieved without the induction of pathologic AV block in 50 (81%) of 62 patients. Inadvertent high degree AV block occurred in 10 (16%) of 62 patients, with the AV block occurring at the time of the procedure in 6 patients and 36 to 72 h after the procedure in 4. During 19 +/- 8 months of follow-up (range 4 to 33), 5 (10%) of 50 patients had a symptomatic recurrence of an uncontrolled rate during atrial fibrillation. Overall, adequate rate control at rest and during exertion, without pathologic AV block, was achieved long term in 45 (73%) of 62 patients. Among 37 patients with a successful outcome, left ventricular ejection fraction increased from (mean +/- SD) 0.44 +/- 0.14 to 0.51 +/- 0.10 one year later (p < 0.001). Complications other than AV block included polymorphic ventricular tachycardia 10 to 24 h after the procedure in two patients who had a predisposing factor for ventricular tachycardia and sudden death 1 to 5 months after the procedure in two patients with idiopathic dilated cardiomyopathy, one of whom had a pacemaker for AV block. CONCLUSIONS: In approximately 70% of properly selected patients with atrial fibrillation and an uncontrolled ventricular rate, radiofrequency modification of the AV node results in excellent long-term control of the ventricular rate at rest and during exertion.
Aged↗
Response to pacing at sites of isolated diastolic potentials during ventricular tachycardia in patients with previous myocardial infarction.
OBJECTIVES: The goal of this study was to determine whether isolated diastolic potentials (IDPs) recorded during ventricular tachycardia (VT) are generated in zones of slow conduction and whether the arcs of block that bound these zones of slow conduction are functional or anatomic in nature. BACKGROUND: No previous studies have systematically investigated the response to pacing during VT and sinus rhythm at sites where IDPs are recorded. METHODS: The study included 11 patients with a previous infarction who underwent radiofrequency catheter ablation of 15 hemodynamically stable, sustained VTs and in whom an IDP that could not be dissociated from the VT was detected during mapping. RESULTS: Pacing during VT at the site where the IDP was recorded resulted in concealed entrainment in each of the 15 VTs. In 10 of the 15 VTs, an IDP was present during sinus rhythm at the same site at which a diastolic potential was recorded during VT. In nine VTs, the isolated potential occurred early in diastole; in these cases, the QRS configuration during pacing in the setting of sinus rhythm was different from that during VT. In six VTs, the isolated potential occurred later in diastole, and in these cases, the QRS configuration during pacing in the setting of sinus rhythm was the same as that during VT. CONCLUSIONS: Isolated diastolic potentials may often be generated in an area of slow conduction bounded by arcs of block that are anatomically determined and present during sinus rhythm.
Cardiac Pacing, Artificial↗
A randomized comparison of fixed power and temperature monitoring during slow pathway ablation in patients with atrioventricular nodal reentrant tachycardia.
Temperature monitoring may be helpful for ablation of accessory pathways, however its role in ablation of atrioventricular nodal reentrant tachycardia (AVNRT) using the slow pathway approach is unclear. Therefore, the purpose of this study was to prospectively compare slow pathway ablation for AVNRT using fixed power or temperature monitoring. The study included 120 patients undergoing ablation for AVNRT. Patients were randomly assigned to receive either fixed power at 32 watts, or to temperature monitoring with a target temperature of 60 degrees C. The primary success rate was 72% in the fixed power group and 95% in the temperature monitoring group (p = 0.001). The ablation procedure duration (35 +/- 29 min vs 35 +/- 30 min; p = 0.9), fluoroscopic time (32 +/- 17 vs 35 +/- 19 min; p = 0.4), mean number of applications (10.2 +/- 8.1 vs 8.4 +/- 7.9; p = 0.2), and coagulum formation per application (0.2% vs 0.5%; p = 0.6) were statistically similar in the fixed power and temperature monitoring groups, respectively. The mean temperature (47.3 +/- 4.8 degrees C vs 48.6 +/- 3.8 degrees C; p < 0.01), and the temperature associated with junctional ectopy (48.2 +/- 3.8 degrees C vs 49.3 +/- 3.6 degrees C, p < 0.01) were less for the fixed power than the temperature monitoring group. In the temperature monitoring group, only 31% of applications achieved an electrode temperature of 60 degrees C. During follow up of 6.6 +/- 3.6 months there were two recurrences in the fixed power group and one in the temperature monitoring group (p = 1.0). In summary, power titration directed by temperature monitoring was associated with an improved primary procedural success rate. Applications of energy were associated with a temperature of approximately 50 degrees C with both techniques, suggesting that there is a low efficiency of heating in the posterior septum.
Adult↗
Risk factors for Kaposi's sarcoma in HIV-positive subjects in Uganda.
BACKGROUND: Kaposi's sarcoma (KS) is associated epidemiologically with HIV infection and with human herpesvirus 8 (HHV-8 or KSHV). Both KS and HIV infection are common in Uganda. We conducted a case-control study of 458 HIV-seropositive. Ugandan adults with KS and 568 HIV-seropositive subjects without KS to examine risk factors for HIV-associated KS. METHODS: We recruited newly diagnosed adult KS cases from five hospitals in Kampala, Uganda and controls from a large referral clinic for HIV infection at Mulago Hospital. All cases and controls were counselled and tested for HIV and answered an interviewer-administered questionnaire about their home, socio-economic conditions, lifestyle and sexual behaviour before they became ill. Only HIV-seropositive subjects were included in the analysis. RESULTS: There were 295 males and 163 females with KS and 227 male and 341 female controls. Age distribution was similar but there was a higher proportion of cases (45%) than controls (29%) residing in rural regions of Uganda. KS cases were more likely than controls to have a higher level of education (X2 for trend, 4.8; P = 0.03), to have occupations associated with affluence [chi 2 for heterogeneity, 17.3 on 5 degrees of freedom (df); P = 0.004] and to come from larger settlements [adjusted odds ratio (OR) for settlements of > 1000 versus 10-99 houses, 1.8; 95% confidence interval (CI), 1.1-3.0]. Cases were more likely than controls to have high household income (chi 2 for trend, 32.6; P < 0.001) and other markers of urban or rural wealth such as owning several cows (chi 2 for trend, 9.5; P = 0.002). Cases were more likely to travel away from home (adjusted OR, 1.6; 95% CI, 1.1-2.3) and more likely to have spent increasing time in contact with water (chi 2 for trend, 12.3; P < 0.001). Few indices of sexual behaviour were related to risk of KS, including reported number of sexual partners. Cases were more likely than controls to be married to one rather than several spouses (adjusted OR, 1.6; 95% CI, 1.2-2.2) and to have reported a history of sexually transmitted diseases (STD) (adjusted OR, 1.6; 95% CI, 1.2-2.3). CONCLUSIONS: Among HIV-infected subjects, KS cases are characterized by better education and greater affluence, compared with controls. Urban address, travel away from home, exposure to water, monogamous marriage and self-reported STD were also more frequent among KS cases than controls. The higher socio-economic status of persons with HIV and KS may be a marker for enhanced exposure to a possibly sexually transmitted agent, or for a delayed exposure to a childhood infection. The risk posed by exposure to water among KS cases requires further study.
AIDS-Related Opportunistic Infections↗
Analysis of immunoglobulin classes and subclasses in response to infection of Balb/cJ and C57BL/6J mice with Coxiella burnetii.
In order to establish defined immunological parameters for Q fever infection models, a microtitre enzyme-linked immunosorbent fluorescence assay (ELISA) was used for the first time to analyse the humoral immune response of Balb/cJ and C57BL/6J mice after experimental infection with Coxiella burnetii strain 'Nine Mile' in phase I. The experimental infection evoked a seroconversion in all mice within 10 days. Typically, the immune response measured against the whole-cell antigen showed an early increase of immunoglobulin (Ig) M followed by a later increase of the IgG subclasses. The IgA was low during the entire investigation period. Within the IgG subclasses only IgG2a and IgG2b gained higher values, whereby C57BL/6J mice produced high IgG2b titres and significantly lower IgG2a titres. In contrast, Balb/cJ mice developed IgG2a and IgG2b at equal levels. The use of partial antigens of C. burnetii demonstrated that the dominating IgG2b reaction of the C57BL/6J mice was directed against the lipopolysaccharide (LPS) of C. burnetii. This reaction was almost absent in Balb/cJ mice. In contrast, the SP27 protein antigen did not evoke different IgG2b reactions within the two breeds. No significant influence was observed within the two breeds in regard to sex or between hormone synchronized and non-hormone synchronized animals.
Animals↗
Accuracy of the unipolar electrogram for identification of the site of origin of ventricular activation.
INTRODUCTION: The purpose of this study was to determine the accuracy of the unipolar electrogram for identifying the earliest site of ventricular activation. The earliest site of ventricular activation may be identified with the unipolar electrogram by the absence of an R wave. However, the accuracy of this technique is unknown. METHODS AND RESULTS: A single ventricular premature complex was induced mechanically at the tip of an electrode catheter to simulate a ventricular premature depolarization site of origin. Unipolar electrograms were recorded from the right ventricular septum at the tip electrode and at 2, 5, 8, and 11 mm from the electrode tip in 20 patients. No R waves were detected at the ventricular premature depolarization site of origin. R waves were detected in 4 of 20 patients (20%) at 2 mm from the tip electrode and 7 of 20 patients (35%) at 5, 8, and 11 mm from the tip electrode. An R wave was not observed at distances < or = 11 mm from the site of tachycardia origin in 13 of 20 patients (65%). CONCLUSIONS: While an R wave in the unipolar electrogram can be seen as close as 2 mm from the site of impulse origin, the absence of an R wave as an indicator of the site of impulse origin in the right ventricle is highly inaccurate. Therefore, the absence of an R wave in the unipolar electrogram is unlikely to be an adequate guide for identification of an effective target site for ablation of right ventricular tachycardia.
Adult↗
Malignant gastrointestinal lymphomas in patients with AIDS.
HIV-associated malignant lymphomas are a common complication in late HIV infection, and there is a high percentage of gastrointestinal tract involvement. Non-Hodgkin's lymphoma was found in 108 of 2,750 HIV-positive patients (3.9%) in our institution, whereas gastrointestinal manifestation was diagnosed in 48 of 108 patients (44.4%). 44 of these cases were found during endoscopy of the upper and lower gastrointestinal tract (or by laparotomy or laparoscopy in 4 cases). Endoscopy is a reliable procedure for the diagnosis of lymphoma. Unusual manifestations such as oral, esophageal or perianal lesions and multifocal disease were common findings. Life-threatening complications such as gastrointestinal bleeding, perforation, and obstruction occurred in 37.5%. High-grade B-cell lymphomas were found in all cases including mainly lymphoblastic, immunoblastic, centroblastic and Burkitt subtypes. 52% of the patients had disseminated lymphoma with Ann Arbor stage III or IV. Standard chemotherapy with cyclophosphamide, adriamycin, vincristine and prednisone was started in 25 patients and resulted in a mean survival time of 4.8 months. The prognosis of AIDS patients presenting with malignant gastrointestinal lymphoma depends mainly on the presence or absence of previous AIDS-defining diseases, not CD4 cells, lymphoma-associated gastrointestinal complications or the histopathologic lymphoma type at the time of diagnosis.
Adult↗
Comparison of psychologic outcome in adult survivors of childhood acute lymphoblastic leukemia versus sibling controls: a cooperative Children's Cancer Group and National Institutes of Health study.
PURPOSE: To determine psychologic outcome, with the focus on emotional or mood state, of young adult survivors of childhood acute lymphoblastic leukemia (ALL) compared with sibling controls and to identify vulnerable subgroups at highest risk for negative mood. PATIENTS AND METHODS: Adult survivors (n = 580), aged > or = 18 years, who were treated before age 20 years on Children's Cancer Group (CCG) protocols for ALL and 396 sibling controls were administered a structured telephone interview and the Profile of Moods State (POMS), a standardized measure of affective state. RESULTS: Survivors had higher total mood scores (which indicates greater negative mood) than sibling controls (P<.01) and reported more tension (P< .01), depression (P<.01), anger (P<.01), and confusion (P<.01), but not more fatigue or less vigor. Female, minority, and unemployed survivors reported the highest total mood disturbance. Overall, survivors were more likely to be unemployed (P<.05) or working less than half-time (P<.01) compared with controls. CONCLUSION: This large, sibling-controlled, multisite study of young adult survivors of childhood ALL treated on CCG protocols after 1970 found significant increased negative mood in survivors, not accounted for by reported energy level differences, which suggests that these emotional effects are not likely the result of current illness. Survivors are less likely to be fully employed. Female, minority, and unemployed survivors are at greatest risk for emotional sequelae, a finding that indicates the need for targeted, preventive intervention.
Adult↗
[Professional cooperation in the care of AIDS patients].
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Acquired Immunodeficiency Syndrome↗
Effect of an irregular ventricular rhythm on cardiac output.
Impairment of cardiac function in atrial fibrillation has been attributed to loss of atrial contraction and to a rapid ventricular rate. The results of this study suggest that irregularity of the ventricular rhythm, independent of the ventricular rate, may also contribute to impairment of cardiac function during atrial fibrillation.
Atrial Fibrillation↗