Airway hyperresponsiveness and calcium handling by smooth muscle: a "deeper look"

We propose that abnormal calcium handling by the airway smooth muscle may be an important determinant of airway hyperresponsiveness. The amplitude, frequency, or localization of Ca(2+) oscillations in the smooth muscle may determine the degree of airway sensitivity and reactivity, which are characteristic features of asthma.     

Low energy conversion of atrial fibrillation in the sheep.

OBJECTIVES. In this study, the feasibility, efficacy and safety of low energy internal atrial cardioversion were investigated in a sheep model. The relation between the level of energy used for atrial defibrillation and the probability of successful cardioversion was examined. BACKGROUND. Atrial fibrillation is a common clinical arrhythmia that frequently recurs after termination with high energy external cardioversion. In some patients with drug-refractory and poorly tolerated atrial fibrillation, an automatic implantable cardioverter may prove useful by providing rapid restoration of sinus rhythm. METHODS. In 16 pentobarbital-anesthetized sheep, a right atrial spring electrode was implanted percutaneously and a left thoracic cutaneous patch electrode was placed on the thorax. Sustained atrial fibrillation was induced by rapid atrial pacing and terminated by biphasic cathodal shocks synchronized to the R wave of the surface electrocardiogram (ECG). RESULTS. During 768 defibrillation attempts in 16 sheep, the percent of successful cardioversion attempts increased in a dose-response manner, reaching a plateau at the average energy level of 5 J. With greater than or equal to 1.5 and greater than or equal to 2.5 J energy levels, cardioversion was achieved, respectively, in greater than 50% and greater than 80% of attempts. Ventricular fibrillation occurred in 18 (2.4%) of 768 cardioversion attempts; in all 18 cases, the shock was poorly synchronized with the ECG R wave. CONCLUSIONS. Low energy cardioversion of atrial fibrillation to sinus rhythm is feasible with use of a right atrial spring/cutaneous patch electrode configuration. The percent of successful cardioversion attempts depends on the level of energy output, and there is a risk of ventricular fibrillation if cardioversion is poorly synchronized with ventricular depolarization.     

Comparison of anti-CD20 and anti-CD45 antibodies for conventional and pretargeted radioimmunotherapy of B-cell lymphomas

Radiolabeled anti-CD20 antibodies produce responses in 60% to 95% of patients with relapsed non-Hodgkin lymphoma (NHL); however, absorbed radiation ratios between tumors and normal organs are relatively low, and many patients have relapses. In this study we compared the abilities of anti-CD45 (BC8) and anti-CD20 (1F5) antibodies to target human Ramos lymphoma xenografts in athymic mice. When direct radioiodination was performed with conventional methods, BC8 delivered 2- to 4-fold more radioiodine to tumors than 1F5, with tumor-to-normal organ ratios as high as 20:1 using radiolabeled BC8 compared with a maximal ratio of 9.8:1 using radioiodinated 1F5. To optimize the biodistribution of radioactivity, we performed studies following a pretargeting method using streptavidin (SA)-conjugated BC8 and 1F5. Injection of a synthetic clearing agent decreased the circulating level of conjugates by 80% to 90% within 1 hour. Pretargeting with BC8-SA resulted in a 2- to 4-fold greater tumor uptake of radiolabeled biotin than with 1F5-SA, with maximal tumor-to-normal organ ratios of more than 80:1 and approximately 16:1, respectively. Therapy experiments demonstrated that 400 microCi (14.8 MBq) or more of yttrium-90-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-biotin cured 100% of mice treated with BC8-SA and more than 90% of mice pretargeted with 1F5-SA, with complete remission occurring 8 to 10 days sooner in mice receiving BC8-SA. After treatment with 200 microCi (7.4 MBq) (90)Y-DOTA-biotin, 70% of the mice treated with BC8-SA were cured, but no mice were cured using 1F5-SA. Doses up to 800 microCi (29.6 MBq) (90)Y-DOTA-biotin were delivered with minor toxicity using either antibody conjugate. These lymphoma xenograft data suggest that pretargeted radioimmunotherapy using either anti-CD20 or anti-CD45 conjugates is highly effective and minimally toxic.     

Enhanced immune activity of cytotoxic T-lymphocyte epitope analogs derived from positional scanning synthetic combinatorial libraries

The pp65(495-503) cytotoxic T-lymphocyte (CTL) epitope from cytomegalovirus (CMV) is universally recognized among CMV+ individuals who express an allele of the human leukocyte antigen A (HLA-A*0201). The relative binding affinity of the epitope to HLA-A*0201 is moderate, and its increased activity might prove beneficial in its use as a CTL epitope vaccine. A new approach to enhance the activity of T-cell epitopes is the use of positional scanning synthetic combinatorial libraries (PS-SCLs). Using a nonamer PS-SCL, the pp65(495-503) epitope was modified after screening a CMV-specific T-cell clone (TCC) (3-3F4) from which the native peptide sequence was derived. Two peptides with amino acid substitutions at P1, P3, P7, and P8 are between 10(3) and 10(4) more active than the native epitope. Although the native CTL epitope terminates as a free acid, both tetrasubstituted peptides only function as CTL epitopes when the carboxyl terminus is amidated. Selective substitution of the native sequence based on PS-SCL screening results identified 3 amidated monosubstituted and disubstituted peptides that are better recognized than the native epitope by TCCs from a cohort expressing HLA-A*0201. In vitro stimulation of peripheral blood mononuclear cells with each of the peptide epitope analogs stimulated memory CTLs, which recognized CMV-infected targets among a high percentage of CMV+ individuals. Binding studies of peptide analogs with HLA-Ig (immunoglobulin) dimers and 2 different TCCs correlated with in vitro lysis results. These data suggest that increasing the activity of CTL epitopes while maintaining broad recognition is possible, which holds promise for vaccine development in infectious disease and cancer.     

Mapping of atrial activation during sustained atrial fibrillation in dogs with rapid ventricular pacing induced heart failure: evidence for a role of driver regions

INTRODUCTION: Dogs with rapid ventricular pacing (RVP)-induced congestive heart failure (CHF) have inducible atrial tachycardia, flutter, and fibrillation (AF). We tested the hypothesis that rapid atrial activation in multiple regions and at different rates is responsible for sustained AF in this CHF model. METHODS AND RESULTS: We studied 12 episodes of sustained (>10 minutes) AF induced in 12 dogs with CHF produced by 3-6 weeks of RVP at 230 beats/minute. High-density mapping of AF was performed using 382 unipolar atrial electrograms recorded simultaneously from epicardial electrodes on the right (RA) and left atria (LA) and Bachmann's bundle. AF mechanisms were based on Fast Fourier Transform (FFT) analysis and activation sequence mapping. A driver was defined as a rapid stable activation region with a single dominant frequency peak in FFT analysis. During AF, three FFT and activation patterns were seen: (1) a single LA driver (7.8 +/- 1.1 Hz) near the pulmonary veins (PVs) with irregular activation in the rest of the atria (n = 4); (2) simultaneous, multisite, biatrial drivers at differing frequencies (LA vs RA dominant frequency gradient: 1.3 +/- 0.8 Hz) near the PVs (8.4 +/- 0.3 Hz) and high RA (8.5 +/- 1.5 Hz) (n = 7); and (3) biatrial irregular activation with multiple and/or broadband frequency peaks without a dominant frequency. (LA: 7.1-11.4 Hz; RA: 5.9-7.7 Hz) (n = 1). Atrial drivers had either a focal activation pattern or were due to a macroreentrant circuit around the PVs. CONCLUSIONS: In this CHF model, FFT analysis and activation sequence mapping demonstrate that sustained AF is characterized by single and multiple, stable LA and RA drivers with predominant sources in the PVs and high RA causing fibrillatory conduction.     

Bendamustine,lenalidomide, and dexamethasone (BRD) is highly effective with durable responses in relapsed multiple myeloma

Bendamustine is a multifunctional alkylating agent with single agent activity in myeloma. We designed the current phase 1/2 trial to determine the maximum tolerated doses (MTD) of bendamustine that can be safely combined with lenalidomide and dexamethasone and to assess the safety and efficacy of the combination. Patients with relapsed MM following at least 1 prior therapy, but no more than four lines of prior therapy and with measurable disease were enrolled. Bendamustine 75 mg/m² given on days 1 and 2, lenalidomide 25 mg given days 1–21 and dexamethasone 40 mg on days 1, 8, 15, and 22, was the recommended Phase 2 dose. Seventy‐one patients were accrued: 21 on Phase 1 and 50 on Phase 2. The median age was 62.3 years; patients had a median of three prior lines of therapy (range 1–4), with over 70% of the patients having received prior lenalidomide, bortezomib, and/or peripheral blood stem cell transplant. Thirty‐four of 70 (49%) patients had a confirmed partial response or better, including 20 patients (29%) with a very good partial response or better. An additional 4 patients had a minor response, translating to an overall 55% clinical benefit rate. Grade 3 or higher toxicity was seen in 96% of patients, with ≥grade 3 hematologic in 94% and nonhematologic in 50%. The median progression free survival was 11.8 months and the median duration of response was 23 months. The combination of bendamustine, lenalidomide, and dexamethasone is very effective in relapsed multiple myeloma with high response rates and durable responses Am. J. Hematol. 90:1106–1110, 2015. © 2015 Wiley Periodicals, Inc.