Background: Exhaled nitric oxide has been proposed as a marker for airway inflammation in asthma. The aim of this study was to compare exhaled nitric oxide levels with inflammatory cells and mediators in bronchoalveolar lavage fluid from asthmatic and normal children. Methods: Children were recruited from elective surgical lists and a non-bronchoscopic bronchoalveolar lavage (BAL) was performed after induction of anaesthesia. Exhaled nitric oxide (parts per billion) was measured by two techniques: tidal breathing and restricted breath. Results: Median (interquartile range) exhaled nitric oxide measured by restricted breath was increased in asthmatics compared with normal children (24.3 (10.5-66.5) v 9.7 (6.5-16.5), difference between medians 14.6 (95% CI 5.1 to 29.9), p=0.001). In asthmatic children exhaled nitric oxide correlated significantly with percentage eosinophils (r=0.78, p<0.001 (tidal breathing) and r=0.78, p<0.001 (restricted breath)) and with eosinophilic cationic protein (r=0.53, p<0.01 (restricted breath)), but not with other inflammatory cells in the BAL fluid. The area under the receiver operator characteristic curves for the prediction of the presence of eosinophilic airways inflammation by exhaled nitric oxide (tidal and restricted) was 0.80 and 0.87, respectively. Conclusions: Exhaled nitric oxide correlates closely with percentage eosinophils in BAL fluid in asthmatic children and is therefore likely to be a useful non-invasive marker of airway inflammation.

The availability of cysteine is thought to be the rate limiting factor for synthesis of the tripeptide glutathione (GSH), based on studies in rodents. GSH status is compromised in various disease states and by certain medications leading to increased morbidity and poor survival. To determine the possible importance of dietary cyst(e)ine availability for whole blood glutathione synthesis in humans, we developed a convenient mass spectrometric method for measurement of the isotopic enrichment of intact GSH and then applied it in a controlled metabolic study. Seven healthy male subjects received during two separate 10-day periods an L-amino acid based diet supplying an adequate amino acid intake or a sulfur amino acid (SAA) (methionine and cysteine) free mixture (SAA-free). On day 10, L-[1-13 C]cysteine was given as a primed, constant i.v. infusion (3mol⅐kg ؊1 ⅐h ؊1 ) for 6 h, and incorporation of label into whole blood GSH determined by GC͞MS selected ion monitoring. The fractional synthesis rate (mean ؎ SD; day -1 ) of whole blood GSH was 0.65 ؎ 0.13 for the adequate diet and 0.49 ؎ 0.13 for the SAA-free diet (P < 0.01). Whole blood GSH was 1,142 ؎ 243 and 1,216 ؎ 162 M for the adequate and SAA-free periods (P > 0.05), and the absolute rate of GSH synthesis was 747 ؎ 216 and 579 ؎ 135 mol⅐liter ؊1 ⅐day ؊1 , respectively (P < 0.05). Thus, a restricted dietary supply of SAA slows the rate of whole blood GSH synthesis and diminishes turnover, with maintenance of the GSH concentration in healthy subjects.

RSV induced remarkably similar, albeit quantitatively lower, cytopathogenesis and proinflammatory responses in WD-PNECs compared with WD-PBECs that reproduce many hallmarks of RSV pathogenesis in infants. WD-PNECs may provide an authentic surrogate model with which to study RSV cytopathogenesis in infant airway epithelium.

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Whole blood glutathione synthesis rates are decreased, by about 60%, in critically ill septic children receiving limited nutritional support. Plasma cysteine fluxes and concentration of cysteine were increased in the septic patients, suggesting a hypermetabolic state with increased protein breakdown. The mechanisms whereby GSH synthesis rates are decreased in these patients are probably multifactorial, presumably involving an inflammatory response in the presence of limited nutritional support. The role of nutritional modulation and the use of cysteine prodrugs in maintaining GSH concentration and synthesis remain to be established.