Comparison of lung volume measurements by single breath helium and multiple breath nitrogen equilibration methods in normal subjects and COPD patients.

The validity of the single breath helium dilution method for accurate measurement of the total lung capacity (TLC) was investigated. Comparison was made with the multiple breath nitrogen equilibration technique in 22 normal subjects and 37 patients with chronic obstructive pulmonary disease (COPD). The single breath method underestimated the TLC in all the normal individuals and 33 of 37 patients with COPD. Possible explanations for the falsely low lung volumes include uneven distribution of inspired air due to closing volumes and induced bronchoconstriction.

Nifedipine aerosol attenuates airway constriction in dogs with hyperreactive airways.

We investigated the ability of a calcium channel blocker nifedipine, given as an aerosol, to attenuate bronchoconstriction induced by citric acid, Ascaris antigen, and methacholine in Basenji-Greyhound dogs. citric acid 10% increased pulmonary resistance (RL) 4.2-fold +/- 1.0 (mean +/- SEM) and 1.7-fold +/- 0.7 in untreated and nifedipine-pretreated dogs (P less than 0.05). Dynamic compliance (Cdyn) fell to 0.58 +/- 0.07 and 0.66 +/- 0.07 of control values in untreated and nifedipine-treated dogs, respectively (p greater than 0.05). Ascaris antigen increased RL 5.1-fold +/- 0.83 and 3-fold +/- 0.48 in untreated and nifedipine-treated dogs, respectively (p less than 0.05); Cdyn decreased to 0.33 +/- 0.04 and 0.48 +/- 0.03 in untreated and nifedipine-treated dogs, respectively (p less than 0.05). In 5 dogs challenged with 0.3 mg/ml methacholine, RL increased 6.1-fold +/- 0.7 and 4.4-fold +/- 1.0 in untreated and nifedipine-treated dogs, respectively (p less than 0.05); Cdyn fell to 0.41 +/- 0.-3 and 0.46 +/- 0.07 of control values in untreated and nifedipine-treated dogs (P greater than 0.05). Neither 40% ethanol nor nifedipine-ethanol altered resting RL and Cdyn. We conclude that nifedipine effectively attenuates bronchoconstriction induced by citric acid, Ascaris antigen, and methacholine in dogs with hyperreactive airways.

Structural studies of insulin and insulin derivatives using various immunologic indicators and antibody populations.

These studies suggest that the immunologic indicator in the radioimmune assay, 125I-iodoinsulin, selects antibody populations from within the antiserum that interact with determinants distant from the solvent surface on the insulin molecule to which iodine is substituted. Evidence is presented that the connecting peptide of proinsulin is in close proximity to regions on the solvent surface of the A-chain of insulin that include the tyrosyl residues at A-14 and A-19. A marked immunologic cross-reaction between derivatives of insulin with perturbations in the regions of tyrosyl A-14 and A-19 was noted in the radioimmune assay employing desalanine-(B-30)-desasparagine-(A-21)-insulin antiserum. This observation is consistent with the presence of a restricted population of antibodies in such antisera that is directed toward immunologic determinants in or near the insulin dimer site. The apparent immunologic activity of insulin derivatives depends on which antibody populations from the antiserum pool can react with the immunologic indicatory employed on the one hand and on the composition of antibodies in that antiserum on the other. These studies indicate that the specificity of antibody populations in a given antiserum can be identified and their levels quantitated with several assay systems, each employing one of a variety of indicators.