PubMed · 14369192
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R E WESTON. 1955. Fluids and electrolytes.. https://doi.org/10.1016/s0025-7125(16)34672-7
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The ionic composition of the fluid lining the airways (airway surface liquid, ASL) in healthy subjects and patients with cystic fibrosis (CF) has been a matter of controversy. It has been attempted to resolve conflicting theories by using cell cultures, but published results show a wide variety of values for the ionic concentrations in the apical fluid in these cultures. To investigate CFTR-mediated HCO(3)(-) conductance and the role of HCO(3)(-) in regulating ASL pH we determined the pH of the fluid covering the apical surface of airway epithelial cells. A normal (16HBE14o (-)) and a CF (CFBE41o (-)) bronchial epithelial cell line were grown on membrane inserts in both a liquid-liquid interface culture system for 7 days, and in an air-liquid interface culture system for one month. The elemental composition of the fluid covering the apical surface was determined by X-ray microanalysis of frozen-hydrated specimens, or by X-ray microanalysis of Sephadex beads that had been equilibrated with the apical fluid. Analysis showed that the apical fluid had a Na(+) and Cl(-) concentration of about 80-100 mM and thus was slightly hypotonic. The ionic concentrations were somewhat higher in air-liquid interface than in liquid-liquid interface cultures. The apical fluid in CF cells had significantly higher concentrations of Na and Cl than that in control cultures. In control cultures, the concentrations of Na and Cl in the apical fluid increased if glibenclamide, an inhibitor of the cystic fibrosis transmembrane conductance regulator (CFTR) was added to the apical medium. Exposing the cells to the metabolic inhibitor NaCN also resulted in a significant increase of the Na and Cl concentrations in the apical fluid. The results agree with the notion that these cell cultures are mainly absorptive cells, and that ion absorption by the CF cells is reduced compared to that in normal cells. The pH measurements of the fluid covering the apical part of cell cultures support the notion that bicarbonate ions may be transported by CFTR, and that this can be inhibited by specific CFTR inhibitors.
To evaluate the diagnostic performance of a commercially available Mycobacterium tuberculosis PCR assay (Amplicor MTB-ROCHE), 2296 respiratory and nonrespiratory specimens from 2296 patients with suspected tuberculosis (TB) were collected prospectively in an 8-year period. Clinical data for each patient were abstracted, and all samples were examined blindly by direct microscopy, culture, and PCR. M. tuberculosis DNA was detected in 93 of 113 culture-positive samples and in 29 of 38 samples from patients with probable TB. The lowest sensitivity was observed in pleural fluid and abscess aspirates. The sensitivity, specificity, and positive predictive value of the assay were 97.2%, 100%, and 100% for smear-positive specimens and 75.3%, 97.0%, and 47.5% for smear-negative specimens, respectively. The PCR cost per additional correct clinical decision was Euro 2826 but would have declined to Euro 308 if the test was applied only to smear-positive specimens. The overall performance of Amplicor MTB test was excellent for smear-positive, but suboptimal for smear-negative specimens.