ATS statement on six-minute walk test.
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Biomedical subjects
William J Gibbons
Publications and source records attributed to William J Gibbons.
Synthesis and conformational studies of a transmembrane domain from a diverged microsomal Delta(12)-desaturase.
Transmembrane domains of the acyl-coenzyme A and acyl phosphatidylcholine-utilizing desaturases may control interactions with electron transport domains, be involved in substrate specificity and/or serve as a structural foundation for the enzyme. To experimentally define these domains and as a prelude to detailed NMR studies, a segment of the microsomal Delta(12)-desaturase/acetylenase CREP-1 predicted to contain the amino-proximate transmembrane domain TM-A was chemically synthesized. A modified 9-fluorenylmethoxycarbonyl procedure was used that ensured complete deprotections at each homologation and the peptide was purified in good yield by reverse-phase high-performance liquid chromatography. Conformational studies of the hydrophobic peptide TM-A demonstrated its strong propensity for folding into an alpha-helical secondary structure. The helical content was 58-65% in aqueous solutions containing 40-80% 2,2,2-trifluoroethanol, a lipomimetic solvent, and was maximal at low temperatures. The peptide assumed a largely helical character when incorporated into phospholipid bilayers and detergent micelles. Experimental evidence is in agreement with neural network predictions that a transmembrane domain exists between residues R-44 and I-67 in this diverged Delta(12)-desaturase.
Amino Acid Sequence↗
Isokinetic muscle function in COPD.
AIM: Exercise limitation in patients with COPD has been attributed to impaired ventilation and reduced skeletal muscle function. We have previously used a combination of FEV(1) and leg muscle function (work achieved during a 30-s isokinetic sprint test) to predict progressive exercise capacity. However, the 30-s test may not be well tolerated in patients with advanced lung disease. We studied the relationship between progressive exercise capacity, FEV(1), and isokinetic work in patients with COPD and in healthy control subjects to assess whether the work accomplished at time intervals of < 30 s could also be used to predict progressive maximal exercise capacity (Wmax). METHODS: Twenty-seven patients with COPD and 29 control subjects underwent anthropometric measures, spirometry, progressive cycle ergometry, and 30-s isokinetic cycling. RESULTS: There was no significant difference for weight, height, or body mass index between the groups. The COPD group was slightly older and had a significantly lower FEV(1) than control subjects. They also had a lower Wmax (56 +/- 28.3 W vs 141.9 +/- 46.7 W) and isokinetic work accomplished over 10 s (W10), over 15 s (W15), over 20 s (W20), over 25 s (W25), and over 30 s (W30). Wmax correlated in both patients with COPD and in control subjects with W10, W15, W20, W25, W30, and FEV(1). Combining FEV(1) and isokinetic work (W10, W15, W20, W25, or W30) in a two-factor model to predict Wmax, the coefficients of determination (r(2)) for patients with COPD were 0.57, 0.57, 0.58, 0.59, and 0.58, and for control subjects were 0.69, 0.69, 0.71, 0.71, and 0.73, respectively. Wmax correlated with weight only in control subjects. CONCLUSIONS: Both ventilatory function and leg muscle function contribute to exercise limitation, and a 20-s isokinetic test can be utilized to assess leg function in patients with COPD.
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