Exercise‐Induced Ventricular Arrhythmias and Cardiovascular Death

Background: Exercise‐induced ventricular arrhythmias (EIVA) are frequently observed during exercise testing. However, the clinical guidelines do not specify their significance and so we examined this issue in our population. Methods: A retrospective analysis of prospectively collected data was performed on 5754 consecutive male veterans referred for exercise testing at two university‐affiliated Veterans Affairs Medical Centers. Exercise test responses were recorded and cardiovascular mortality was assessed after a mean follow‐up of 6 ± 4 years. EIVA were defined as frequent premature ventricular complexes (PVCs) constituting more than 10% of all ventricular depolarizations during any 30‐second ECG recording, or a run of three or more consecutive PVCs during the exercise test or recovery. Results: EIVA occurred in 426 patients (7.4%). There were 550 (10.6%) cardiovascular deaths during follow‐up. Seventy two (17%) patients with EIVA died of cardiovascular causes, whereas 478 (9.0%) of patients without EIVA died of cardiovascular causes (P < 0.001). Patients with EIVA had a higher prevalence of cardiovascular disease, resting PVCs, resting ST depression, and ischemia during exercise than patients without EIVA. In a Cox hazards model adjusted for age, cardiovascular disease, exercise‐induced ischemia, ECG abnormalities, exercise capacity and risk factors, EIVA was significantly associated with time to cardiovascular death. The combination of both resting PVCs and EIVA was associated with the highest hazard ratio. Conclusions: EIVA are independent predictors of cardiovascular mortality after adjusting for other clinical and exercise test variables; combination with resting PVCs carries the highest risk.     

Characterizing asthma from a drop of blood using neutrophil chemotaxis

Asthma is a chronic inflammatory disorder that affects more than 300 million people worldwide. Asthma management would benefit from additional tools that establish biomarkers to identify phenotypes of asthma. We present a microfluidic solution that discriminates asthma from allergic rhinitis based on a patient’s neutrophil chemotactic function. The handheld diagnostic device sorts neutrophils from whole blood within 5 min, and generates a gradient of chemoattractant in the microchannels by placing a lid with chemoattractant onto the base of the device. This technology was used in a clinical setting to assay 34 asthmatic (n = 23) and nonasthmatic, allergic rhinitis (n = 11) patients to establish domains for asthma diagnosis based on neutrophil chemotaxis. We determined that neutrophils from asthmatic patients migrate significantly more slowly toward the chemoattractant compared with nonasthmatic patients (P = 0.002). Analysis of the receiver operator characteristics of the patient data revealed that using a chemotaxis velocity of 1.55 μm/min for asthma yields a diagnostic sensitivity and specificity of 96% and 73%, respectively. This study identifies neutrophil chemotaxis velocity as a potential biomarker for asthma, and we demonstrate a microfluidic technology that was used in a clinical setting to perform these measurements.Asthma is a chronic inflammatory disorder of the lungs that is associated with airway hyperresponsiveness (AHR) and obstructed airflow (1), affecting more than 300 million people worldwide (2). Over the past 30 y, asthma prevalence has increased significantly in many populations, with some indications that prevalence may be reaching a plateau in the developed world. Significant progress has been made in identifying primary mediators involved in the pathophysiology of asthma. Several cell types, such as T helper cells (T_H1/T_H2), dendritic cells, mast cells, macrophages, eosinophils, and neutrophils play central roles in the pathology of asthma (4–7). Additionally, various cytokines that regulate the leukocyte trafficking, such as interleukins, IFN-γ, and TNF-α, have been identified and targeted in drug therapies. The recruitment of leukocytes to the lungs, particularly eosinophils and neutrophils, is central to the pathogenesis of asthma. Increased numbers of eosinophils are prominently observed in the lung tissue and bronchoalveolar lavage (BAL) fluid for most asthmatics (5). Neutrophils play a more critical role in severe asthma, where elevated counts of neutrophils are often observed in the BAL fluid (7). An overview of the role of neutrophils in asthma is shown in Fig. 1A. Although significant progress has been made in uncovering mediators in the pathology of asthma, these gains have not yet greatly improved our ability to define clinically relevant phenotypes of asthma in patients.Open in a separate windowFig. 1.Overview of different diagnostic techniques and the role of neutrophils in the pathology of asthma. (A) Summary of the role of neutrophils in the pathology of asthma, showing neutrophil adhesion and transendothelial migration; chemotaxis mediated by macrophages and T-helper cells; and neutrophilia in the lung tissue that leads to airway remodeling and airflow obstruction. (B) Proposed microfluidic method (more details in Fig. S1) for phenotyping asthma patients by measuring upstream of the asthma pathology with rapid neutrophil sorting on a P-selectin–coated surface (1); neutrophil chemotaxis monitored with high-throughput microscopy and automatically tracked with software (2); and asthma characterization on the basis of chemotaxis outputs (3). (C) Traditional clinical asthma diagnostic methods occur downstream of the asthma pathophysiology by measuring the effect of leukocyte inflammation on airway obstruction, nitric oxide output, or clinical symptoms.Asthma is diagnosed clinically by physicians, informed by the patient’s medical history, spirometry tests that measure lung function, reversibility of AHR, and several other potential metrics (8). These diagnostic techniques measure the effects of the inflammatory response in the lung by assessing airway constriction, nitric oxide production, and the resulting clinical symptoms. However, all of these diagnostic tests require patient compliance, which can be challenging when diagnosing children or the elderly (9). Additionally, many asthma diagnostic tests partially rely on the patient experiencing clinical symptoms that are variable during or around the visit to the physician. Perhaps these common characteristics of current diagnostic techniques contribute to difficulties in diagnosing asthma, particularly in certain subpopulations. For example, in a recent Canadian study involving ∼500 obese and nonobese subjects, Aaron et al. (10) found that ∼30% of the test subjects had been falsely diagnosed with asthma by physicians. Additionally, it is well established that the elderly are consistently underdiagnosed for asthma (11, 12). Therefore, additional tools are needed to improve the diagnosis of asthma. Furthermore, current asthma assessments do not inform the clinician of disease severity, expected clinical course, and risk of exacerbations.To improve characterization of asthma in the clinic, we have developed a handheld microfluidic chip that can identify functional measures of asthma from a drop of whole blood. Microfluidic systems have several characteristics that make them well-suited for clinical use, including low sample-volume requirements (13, 14); simple integration with automated fluid handling systems (15); and diffusion-dominant laminar fluidic phenomena that allow for precise control of a cell’s microenvironment (16–18). Indeed, microfluidic-based tools are increasingly being used in clinical research for diagnostic purposes (19–26). Neutrophils have been used to diagnose clinical conditions in human patients based on proteomic and genomic analysis (22) and chemotaxis behavior (23, 27), demonstrating that assays measuring cell function can be used for diagnostics. In this work, we assay the neutrophil chemotactic function in a blind study to identify quantitative domains that can be used to discriminate asthma from nonasthmatic allergic rhinitis. This approach of directly measuring the effector cell in the pathology of asthma differs from traditional diagnostic tests, which measure the variable effect of inflammation on airway constriction (Fig. 1 B and C and Table S1). Importantly, we developed methods to simplify the sample preparation, assay protocol, and data analysis that offer significant time savings over traditional macroscale (28–30) and microscale (18) chemotaxis techniques, allowing for the translation of the technology into the clinic. We analyzed 34 patients, and discovered that neutrophil chemotaxis can be used to discriminate asthma from nonasthmatic, allergic rhinitis patients with sensitivity and specificity of 96% and 73%, respectively. The results of the clinical application of our microfluidic device represent a first step demonstration of how asthma can potentially be diagnosed and managed based on cellular function, rather than largely by clinical observations.     

Shedding light on a potential hazard: Dental light-curing units

BackgroundDental light-curing units (LCUs) are powerful sources of blue light that can cause soft-tissue burns and ocular damage. Although most ophthalmic research on the hazards of blue light pertains to low levels from personal electronic devices, computer monitors, and light-emitting diode light sources, the amount of blue light emitted from dental LCUs is much greater and may pose a “blue light hazard.”MethodsThe authors explain the potential risks of using dental LCUs, identify the agencies that provide guidelines designed to protect all workers from excessive exposure to blue light, discuss the selection of appropriate eye protection, and provide clinical tips to ensure eye safety when using LCUs.ResultsWhile current literature and regulatory standards regarding the safety of blue light is primarily based on animal studies, sufficient evidence exists to suggest that appropriate precautions should be taken when using dental curing lights. The authors found it difficult to find on the U.S. Food and Drug Administration database which curing lights had been cleared for use in the United States or Europe and could find no database that listed which brands of eyewear designed to protect against the blue light has been cleared for use. The authors conclude that more research is needed on the cumulative exposure to blue light in humans. Manufacturers of curing lights, government and regulatory agencies, employers, and dental personnel should collaborate to determine ocular risks from blue light exist in the dental setting, and recommend appropriate eye protection. Guidance on selection and proper use of eye protection should be readily accessible.Conclusions and Practical ImplicationsThe Centers for Disease Control and Prevention Guidelines for Infection Control in the Dental Health-Care Setting–2003 and the Occupational Safety and Health Administration Bloodborne Pathogen Standard do not include safety recommendations or regulations that are directly related to blue light exposure. However, there are additional Occupational Safety and Health Administration regulations that require employers to protect their employees from potentially injurious light radiation. Unfortunately, it is not readily evident that these regulations apply to the excessive exposure to blue light. Consequently employers and dental personnel may be unaware that these Occupational Safety and Health Administration regulations exist.     

Inhibition of plasma-mediated adherence of sickle erythrocytes to microvascular endothelium by conformationally constrained RGD-containing peptides

Adherence of sickle erythrocytes to vascular endothelium likely initiates or participates in microvascular occlusion, leading to ischemic tissue and organ damage characteristic of sickle-cell pain episodes. In vitro, sickle-cell adherence to endothelium involves adhesive plasma proteins and integrin and nonintegrin receptors on sickle cells and endothelial cells. The involvement of arginine-glycine-aspartic acid (RGD) sequences in adhesive plasma proteins and integrin receptors suggests that RGD-containing peptides may inhibit sickle-cell/endothelial-cell adherence. In the present study, inhibition of plasma-mediated sickle-erythrocyte adherence to endothelium using conformationally constrained RGD-containing peptides was quantified in vitro under continuous flow at a shear stress of 1.0 dyn/cm². Two conformationally constrained RGD peptides were investigated: 6Z (which has high affinity for α₅β₁, α_vβ₃, and α_IIIbβ₃ integrin receptors), and TP9201 (which preferentially binds to α_IIbβ₃). Peptide 6Z at 50 μM inhibited plasma-mediated sickle-cell adherence to microvascular endothelium 70% when incubated with sickle red cells, and 63% when incubated with endothelium. Under similar conditions, peptide TP9201 inhibited plasma-mediated sickle-cell adherence up to 85% at concentrations from 250 to 500 μM TP9201. The inhibition of plasma-mediated adherence by conformationally constrained RGD peptides, but not by linear or circular constructs, suggests that the tertiary structure of the peptide containing the binding sequence is important. Inhibition of plasma-mediated sickle-cell adhesion with these peptides in vitro suggests that such conformationally constrained RGD peptides could provide therapeutic interventions in the course of the disease by inhibiting receptor-ligand interactions. © 1996 Wiley-Liss, Inc.     

Voxel-based analysis of MRI detects abnormal visual cortex in children and adults with amblyopia

Amblyopia, sometimes called "lazy eye," is a relatively common developmental visual disorder well characterized behaviorally; however, the neural substrates associated with amblyopia in humans remain unclear. We hypothesized that abnormalities in the cerebral cortex of subjects with amblyopia exist, possibly as a result of experience-dependent neuronal plasticity. Anatomic magnetic resonance imaging (MRI) and psychophysical vision testing was carried out on 74 subjects divided into two age ranges, 7-12 years and 18-35 years, and three diagnoses, strabismic amblyopia, anisometropic amblyopia, and normal vision. We report a behavioral impairment in contrast sensitivity for subjects with amblyopia, consistent with previous reports. When the high-resolution MRI brain images were analyzed quantitatively with optimized voxel-based morphometry, results indicated that adults and children with amblyopia have decreased gray matter volume in visual cortical regions, including the calcarine sulcus, known to contain primary visual cortex. This finding was confirmed with a separate region-of-interest analysis. For the children with amblyopia, additional gray matter reductions in parietal-occipital areas and ventral temporal cortex were detected, consistent with recent reports that amblyopia can result in spatial location and object processing deficits. These data are the first to provide possible neuroanatomic bases for the loss of binocularity and visual sensitivity in children and adults with amblyopia.     

Poly (DL-lactide-co-glycolide) nanoparticle-based inhalable sustained drug delivery system for experimental tuberculosis

OBJECTIVES: To improve the bioavailability of antitubercular drugs (ATDs) as well as to assess the feasibility of administering ATDs via the respiratory route, this study reports the formulation of three frontline ATDs, i.e. rifampicin, isoniazid and pyrazinamide encapsulated in poly (DL-lactide-co-glycolide) nanoparticles suitable for nebulization. METHODS: Drug-loaded nanoparticles were prepared by the multiple emulsion technique, vacuum-dried and nebulized to guinea pigs. The formulation was evaluated with respect to the pharmacokinetics of each drug and its chemotherapeutic potential in Mycobacterium tuberculosis infected guinea pigs. RESULTS: The aerosolized particles exhibited a mass median aerodynamic diameter of 1.88 +/- 0.11 microm, favourable for bronchoalveolar lung delivery. A single nebulization to guinea pigs resulted in sustained therapeutic drug levels in the plasma for 6-8 days and in the lungs for up to 11 days. The elimination half-life and mean residence time of the drugs were significantly prolonged compared to when the parent drugs were administered orally, resulting in an enhanced relative bioavailability (compared to oral administration) for encapsulated drugs (12.7-, 32.8- and 14.7-fold for rifampicin, isoniazid and pyrazinamide, respectively). The absolute bioavailability [compared to intravenous (i.v.) administration] was also increased by 6.5-, 19.1- and 13.4-fold for rifampicin, isoniazid and pyrazinamide, respectively. On nebulization of nanoparticles containing drugs to M. tuberculosis infected guinea pigs at every 10th day, no tubercle bacilli could be detected in the lung after five doses of treatment whereas 46 daily doses of orally administered drug were required to obtain an equivalent therapeutic benefit. CONCLUSIONS: Nebulization of nanoparticles-based ATDs forms a sound basis for improving drug bioavailability and reducing the dosing frequency for better management of pulmonary tuberculosis.     

Evaluation of 24-locus MIRU-VNTR in extrapulmonary specimens: study from a tertiary centre in Mumbai

Genotyping of Mycobacterium tuberculosis isolates is a useful tool for epidemiological control of tuberculosis (TB) and phylogenetic exploration of the pathogen. There is a lack of information on the discriminatory power of standard 24-locus mycobacterial interspersed repetitive unit (MIRU) - variable number tandem repeats (VNTR) in India, which has the highest tuberculosis (TB) burden worldwide. Therefore, we assessed its utility on 69 M.?tuberculosis (MTB) isolates from patients with extrapulmonary tuberculosis, in comparison to standard insertion sequence (IS) 6110-Restriction fragment length polymorphism (RFLP) fingerprinting and spoligotyping. IS6110-RFLP (HGDI, 0.9987) identified a single cluster of 3 (4.3%) single-copy IS6110 isolates. Spoligotyping showed 69.5% clustering (HGDI, 0.8857). In contrast, MIRU-VNTR analysis identified 69 (100%) unique strains (HGDI, 1.0000). Within the study limits, this observed high discriminatory power suggests that 24-locus MIRU-VNTR genotyping could potentially be used to study long-term transmission of MTB infection in Mumbai. Moreover, high congruence between the MIRU-VNTR-based and spoligotyping-based strain groupings suggests that CAS, EAI and Beijing are the predominant strain lineages in the Mumbai TB patient population. The Beijing lineage isolates were found to be more significantly associated with multi-drug resistance (p?相似文献