Sreekala Prabhakaran

Glucose stimulates calcium-activated chloride secretion in small intestinal cells

The sodium-coupled glucose transporter-1 (SGLT1)-based oral rehydration solution (ORS) used in the management of acute diarrhea does not substantially reduce stool output, despite the fact that glucose stimulates the absorption of sodium and water. To explain this phenomenon, we investigated the possibility that glucose might also stimulate anion secretion. Transepithelial electrical measurements and isotope flux measurements in Ussing chambers were used to study the effect of glucose on active chloride and fluid secretion in mouse small intestinal cells and human Caco-2 cells. Confocal fluorescence laser microscopy and immunohistochemistry measured intracellular changes in calcium, sodium-glucose linked transporter, and calcium-activated chloride channel (anoctamin 1) expression. In addition to enhancing active sodium absorption, glucose increased intracellular calcium and stimulated electrogenic chloride secretion. Calcium imaging studies showed increased intracellular calcium when intestinal cells were exposed to glucose. Niflumic acid, but not glibenclamide, inhibited glucose-stimulated chloride secretion in mouse small intestines and in Caco-2 cells. Glucose-stimulated chloride secretion was not seen in ileal tissues incubated with the intracellular calcium chelater BAPTA-AM and the sodium-potassium-2 chloride cotransporter 1 (NKCC1) blocker bumetanide. These observations establish that glucose not only stimulates active Na absorption, a well-established phenomenon, but also induces a Ca-activated chloride secretion. This may explain the failure of glucose-based ORS to markedly reduce stool output in acute diarrhea. These results have immediate potential to improve the treatment outcomes for acute and/or chronic diarrheal diseases by replacing glucose with compounds that do not stimulate chloride secretion.

Plastic bronchitis: Resolution after heart transplantation

Plastic bronchitis (PB) is a rare cause of obstructive airway disease in patients who have undergone partially corrective surgery for congenital heart disease (CHD). The etiology of plastic bronchitis in such patients is ill‐defined, and treatment is ineffective. We report resolution of PB and severe obstructive airway disease after heart transplantation in a patient with CHD. Pediatr. Pulmonol. 2011; 46:824–825.

Response to Albuterol MDI Delivered Through an Anti-Static Chamber During Nocturnal Bronchospasm

BACKGROUND: Decreasing electrostatic charge on valved holding chambers increases the amount of drug delivered. However, there are no data demonstrating that this increases bronchodilatation. OBJECTIVE: To investigate the influence of reducing electrostatic charge on the bronchodilator response to albuterol inhaler during nocturnal bronchospasm. METHODS: This randomized double-blind, double-dummy crossover study included subjects, 18–40 years old, with nocturnal bronchospasm (20% overnight decrease in peak flow on 3 of 7 nights during run-in), FEV1 60–80% predicted during the day, and ≥ 12% increase after albuterol. Subjects slept in the clinical research center up to 3 nights for each treatment. FEV1 and heart rate were measured upon awakening spontaneously or at 4:00 am, and 15 min after each dose of 1, 2, and 4 cumulative puffs of albuterol via metered-dose inhaler. The drug was administered through an anti-static valved holding chamber (AeroChamber Plus Z-Stat) or a conventional valved holding chamber containing a static charge (AeroChamber Plus). RESULTS: Of 88 consented subjects, 11 were randomized and 7 completed the study. Most exclusions were due to lack of objective evidence of nocturnal bronchospasm. Upon awakening, FEV1 was 44 ± 9% of predicted before the anti-static chamber and 48 ± 7% of predicted before the static chamber. The mean ± SD percent increase in FEV1 after 1, 2, and 4 cumulative puffs using the anti-static versus the static chamber, respectively, were 52 ± 26% versus 30 ± 19%, 73 ± 28% versus 48 ± 26%, and 90 ± 34% versus 64 ± 35%. The point estimates for the differences (and 95% CIs) between the devices (anti-static vs static) were 21% (4–38%) (P = .03), 23% (6–41%) (P = .02), and 25% (7–42%) (P = .01) for 1, 2, and 4 cumulative puffs, respectively. There was no significant difference in heart rate between treatments. CONCLUSIONS: Delivery of albuterol through an anti-static chamber provides a clinically relevant improvement in bronchodilator response during acute, reversible bronchospasm such as nocturnal bronchospasm.

Methacholine Challenge as a Clinical Bioassay of Pulmonary Delivery of a Long-Acting β2-Adrenergic Agonist

Study Objective. To determine whether the methacholine challenge method used for albuterol can be applied to assess long‐acting β2‐adrenergic agonist (LABA) bioequivalence, which would require a sufficiently steep dose‐response curve.

Benzalkonium chloride; a bronchoconstricting preservative in continuous albuterol nebulizer solutions

For convenience, many pediatric hospitals are preparing solutions for continuous nebulized albuterol using the 0.5% 20‐ml multidose albuterol dropper bottle. This product contains benzalkonium chloride (BAC) that, by itself, produces bronchospasm that is dose dependent and cumulative. The bronchoconstrictive effects of BAC are greater in patients with more severe airway obstruction and increased airway responsiveness. Use of BAC‐containing albuterol during severe acute asthma exacerbations may antagonize the bronchodilator response to albuterol, prolong treatment, and increase the risk of albuterol‐related systemic adverse effects. Such a deleterious effect of BAC is difficult to detect because some patients improve slowly or may even worsen during treatment. We recommend that only preservative‐free albuterol products be used.

Long-term variability of exhaled nitric oxide measurements

Measurement of fractional exhaled nitric oxide (FENO) is recommended as an adjunct in the diagnosis of eosinophilic airway inflammation, to determine the likelihood of corticosteroid responsiveness, to monitor therapy, and to assess adherence to inhaled corticosteroid therapy. The American Thoracic Society Guidelines for the interpretation of FENO concentrations identify cut points in children of greater than 35 parts per billion (ppb) for eosinophilic airway inflammation and less than 20 ppb for no inflammation. For adults, the guidelines recommend greater than 50 ppb and less than 25 ppb, respectively. The NIOX MINO (Aerocrine AB, Solna, Sweden) is a commonly used portable method of analyzing FENO that does not require calibration. The accuracy and precision of this device were largely determined by extensive in vitro testing for US Food and Drug Administration clearance. The same is true for its successor, the NIOX VERO. The clinical study in the MINO FDA submission was a single measurement before and after beginning inhaled corticosteroids, which demonstrated a decrease in FENO. Other published clinical studies are single visit comparisons with other methods or multiple technicians. Only one study compared 2 measurements on different days. Because there are no published reports on the long-term reproducibility of devices used to measure FENO, we undertook the following study. We analyzed 451 quality control measurements obtained over a 2-year period from 5 devices. There were 5 nonasthmatic technicians (quality control subjects) who performed these measurements on each day that the device was used for a clinical study or patient care (see Table E1 in this article’s Online Repository at www.jaci-inpractice.org for more details). All control subjects met the manufacturer’s criteria, which included >18 years old, no ongoing cold or known airway disorder, nonsmoker, expected stable exhaled nitric oxide values between 5 and 40 ppb during the qualification period, and preferably no allergies (except seasonal) or asthma. To obtain a control FENO measurement, each technician was required to empty his or her lungs by slowly exhaling and then forming a tight seal around the mouthpiece, making sure not to let the air leak out. Then, they inhaled to total lung capacity and exhaled forcefully for approximately 10 seconds through the mouthpiece while responding to sound and light cues on the LCD to guide the rate of exhalation. The general linear model procedure was used to determine whether there was a device*subject interaction. Because the interaction was significant (P .05). Measurements for subjects 3-5 who used device 5 were 31.79 (7.2), 11.51 (4.2), and 15.0 (4.1) ppb, respectively (Figure 2). Measurements for subject 3 were significantly higher than those for subjects 4 and 5 (P < .0001). Eighty-two percent of her values were above 25 ppb. The NIOX MINO portable device employing an electrochemical methodology was cleared by FDA as “substantially equivalent” to the chemiluminescence stationary method (NIOX), largely based on extensive in vitro testing using certified nitric oxide in nitrogen calibration gas. Similarly, the new NIOX VERO was cleared in the same way as “substantially

Bioassay of salmeterol in children using methacholine challenge with impulse oscillometry

Bronchoprovocation with methacholine (MC) is the most sensitive method of determining bioequivalence of inhaled bronchodilators. FEV1 is used to determine the endpoint, but many children cannot perform spirometry reproducibly. The purpose of this study was to determine whether MC, using impulse oscillometry (IOS) as the endpoint, can differentiate between two doses of salmeterol (SM).

Traversing and labeling interconnected vascular tree structures from 3D medical images

Purpose: Detailed characterization of pulmonary vascular anatomy has important applications for the diagnosis and management of a variety of vascular diseases. Prior efforts have emphasized using vessel segmentation to gather information on the number or branches, number of bifurcations, and branch length and volume, but accurate traversal of the vessel tree to identify and repair erroneous interconnections between adjacent branches and neighboring tree structures has not been carefully considered. In this study, we endeavor to develop and implement a successful approach to distinguishing and characterizing individual vascular trees from among a complex intermingling of trees. Methods: We developed strategies and parameters in which the algorithm identifies and repairs false branch inter-tree and intra-tree connections to traverse complicated vessel trees. A series of two-dimensional (2D) virtual datasets with a variety of interconnections were constructed for development, testing, and validation. To demonstrate the approach, a series of real 3D computed tomography (CT) lung datasets were obtained, including that of an anthropomorphic chest phantom; an adult human chest CT; a pediatric patient chest CT; and a micro-CT of an excised rat lung preparation. Results: Our method was correct in all 2D virtual test datasets. For each real 3D CT dataset, the resulting simulated vessel tree structures faithfully depicted the vessel tree structures that were originally extracted from the corresponding lung CT scans. Conclusion: We have developed a comprehensive strategy for traversing and labeling interconnected vascular trees and successfully implemented its application to pulmonary vessels observed using 3D CT images of the chest.