The effect of deep inspiration on methacholine dose-response curves in normal subjects.

Normal subjects develop exaggerated airway narrowing when deep inspiration (DI) is voluntarily suppressed during methacholine challenge. Failure of periodic inflation may interfere with the bronchodilating effect of DI, and this may be fundamental to the difference in bronchodilation caused by DI in asthmatics and normal subjects. To determine whether repeated exhalations to residual volume (RV) and/or incomplete inspiration to baseline total lung capacity (TLC) could contribute to exaggerated narrowing during challenge, we tested 10 subjects on three separate days using modified methacholine challenge protocols. On Day 1, partial and complete flow volume curves were obtained after each dose. On Day 2, DI was prohibited, but partial curves were performed. On Day 3, DI and exhalation to RV were prohibited. TLC was measured pre- and post-challenge on each day. After comparable doses of methacholine, there was a greater change in FEV1 on Day 2 (27+/-15) and Day 3 (38+/-17) than on Day 1 (14+/-8) (p < 0.05). There were no differences in changes in FEV1 and FVC between Days 2 and 3, or in TLC between all 3 d. We conclude that exaggerated airway narrowing occurs in normal subjects when DI is prohibited and that this effect is not due to repeated expiration to RV, nor due to an artifact caused by a failure to inhale to TLC.

Shape and position of the complete dose-response curve for inhaled methacholine in normal subjects.

Plateaus on the inhalation concentration-response curve have been described in normal subjects and patients with mild asthma. To determine the prevalence of plateaus on inhalation concentration-response curves, and the position of the curves in normal subjects, we measured complete dose-response curves for methacholine (1 mg/ml to 256 mg/ml) in 73 nonatopic, nonsmoking, nonasthmatic normal subjects between the ages of 20 and 76 yr. Measurements included FEV1, maximal expiratory flow at 50% and 30% of vital capacity on partial and complete forced expiratory flow-volume curves (Vmax50p, Vmax50c, Vmax30p, Vmax30c) and pulmonary resistance (RL). Plateau responses, EC50 values and slopes were measured. Plateaus were present in 25, 27, 24, 34, 35, and 16 subjects for FEV1, Vmax50c, Vmax30c, Vmax50p, Vmax30p, and RL, respectively. In those who achieved a plateau, the mean maximal decrease in FEV1 (+/- SD) was 21 +/- 8%, in Vmax50c it was 46 +/- 16%, in Vmax50p it was 67 +/- 12%, in Vmax30c it was 58 +/- 21%, and in Vmax30p it was 75 +/- 15%, and the increase in RL was 213 +/- 89%. In summary, the results of this study showed that easily identifiable plateaus develop on the inhalation concentration-response curves of approximately 40% of normal subjects after only moderate decreases in maximum flow and increases in RL. Maximal response at the plateau was greater on partial flow-volume curves and at lower lung volumes (30% versus 50% of VC). Comparison of these data with data from patients at risk for airway hyperresponsiveness will allow definition of the mechanisms leading to airway hyperresponsiveness.

Neutrophil activation and lung injury associated with chronic endotoxemia in rabbits.

Chronic endotoxemia produces emphysematous lung destruction in several animal models. The present study was designed to examine changes in the polymorphonuclear leukocytes (PMN) and the lung parenchyma of rabbits that received either saline (control, n = 6) or Escherichia coli endotoxin (LPS, n = 6) 2-3 times weekly for 15 to 28 weeks. Peripheral blood was collected just before and after each intravenous injection and lung tissue was processed at the end of the experiment. PMN myeloperoxidase was stained with diaminobenzidine tetrahydrochloride (DAB)-H2O2, and CD11/CD18 was detected with immunogold. The changes in the PMN and the lung parenchyma were quantitatively analyzed. The results show that each dose of LPS produced an initial fall, followed by a rise in the circulating mature and immature PMN cell counts. Repeated doses of LPS induced PMN activation, degranulation, and an increase in the mean thickness of the alveolar wall (control, 4.1 +/- 0.2; LPS, 5.1 +/- 0.5; p < .05) at 28 weeks without evidence of alveolar septa destruction. Morphometric analysis of intravascular PMN showed an increase in the volume (V) of myeloperoxidase-containing azurophil granules (control, 6.1 +/- 1.3 microns3; LPS, 13.1 +/- 2.8 microns3; p < .05); a trend for a decrease in the V of specific granules (control, 15.8 +/- 3.4 microns3; LPS, 10.2 +/- 1.5 microns3; p = .09); an increase in the V of the cytoplasm (control, 37.3 +/- 6.4 microns3; LPS, 54.5 +/- 7.1 microns3; p < .05); and an increase in CD11/CD18 expressed as the number of gold particles per micrometer of cell surface membrane (G/micron) (control, 7.1 +/- 1.4 G/micron; LPS, 18.1 +/- 7.8 G/micron; p < .05). The results indicate that chronic endoxemia in rabbits, accelerates the release of PMN from the bone marrow, enhances the retention of both mature and immature activated PMN in the pulmonary microvessels, and causes alveolar wall thickening rather than emphysematous lung destruction.

Overexpression of Bcl-2 and mutations in p53 and K-ras in resected human non-small cell lung cancers.

We investigated expression of Bcl-2, mutations in p53, and K-ras oncogene in 51 resected human non-small cell lung cancers. The studies were designed to test for the possibility of cooperativity between these oncogenes and p53 in the pathogenesis of lung cancer. An inverse relationship was found between expression of Bcl-2 and mutant p53 by immunohistochemistry (P < 0.01; Fisher exact test), suggesting that either Bcl-2 overexpression or mutations in p53 may fulfill a critical function in the pathogenesis of human non-small cell lung cancers. Tumors that harbored K-ras codon 12 mutations seldom had p53 mutations or overexpressed Bcl-2. Statistical analysis of these data showed that mutations in p53 and K-ras or overexpression of Bcl-2 and mutations in K-ras occurred at a frequency that could be explained only by chance [P > 0.1 in each case (Fisher exact tests)]. This suggests that cooperativity between mutant K-ras and mutant p53 or mutant K-ras and overexpressed Bcl-2 is not a common mechanism in the pathogenesis of human non-small cell lung cancers.

Measurement of lung expansion with computed tomography and comparison with quantitative histology.

The total and regional lung volumes were estimated from computed tomography (CT), and the pleural pressure gradient was determined by using the milliliters of gas per gram of tissue estimated from the X-ray attenuation values and the pressure-volume curve of the lung. The data show that CT accurately estimated the volume of the resected lobe but overestimated its weight by 24 +/- 19%. The volume of gas per gram of tissue was less in the gravity-dependent regions due to a pleural pressure gradient of 0.24 +/- 0.08 cmH2O/cm of descent in the thorax. The proportion of tissue to air obtained with CT was similar to that obtained by quantitative histology. We conclude that the CT scan can be used to estimate total and regional lung volumes and that measurements of the proportions of tissue and air within the thorax by CT can be used in conjunction with quantitative histology to evaluate lung structure.