Evaluation of the airway mechanics of modified toggle laryngoplasty constructs using a vacuum chamber airflow model.

OBJECTIVE: To evaluate the airway mechanics of modified toggle LP constructs in an airflow chamber model and compare these to the airway mechanics of standard LP constructs. STUDY DESIGN: Ex-vivo experimental study. SAMPLE POPULATION: Fifty-one equine cadaveric larynges. METHODS: Bilateral LP constructs were performed using a modified toggle (n = 23) or a standard (n = 21) LP technique. Constructs were tested in an airflow model before and after cyclic loading which was designed to mimic postoperative swallowing. The cross-sectional area (CSA), peak translaryngeal airflow (L/s), and impedance (cmH2 0/L/s) were determined and compared between LP constructs before and after cycling. RESULTS: The mean CSA of the rima glottidis of the modified toggle LP constructs was 15.2 ± 2.6 cm2 before and 14.7 ± 2.6 cm2 after cyclic loading, and the mean CSA of the rima glottidis of the standard LP constructs was 16.4 ± 2.9 cm2 before and 15.7 ± 2.8 cm2 after cyclic loading. The modified toggle LP constructs had similar peak translaryngeal impedance before and after cyclic loading (p = .13); however, the standard LP constructs had higher peak translaryngeal impedance after cyclic loading (p = .02). CONCLUSION: The modified toggle and standard LP constructs had comparable airway mechanics in an ex-vivo model. CLINICAL SIGNIFICANCE: Further investigation is warranted to determine the extent to which the modified toggle LP technique restores normal airway function in horses with RLN.

Tyrosine triad at the interface between the Rieske iron-sulfur protein, cytochrome c1 and cytochrome c2 in the bc1 complex of Rhodobacter capsulatus.

A triad of tyrosine residues (Y152-154) in the cytochrome c(1) subunit (C1) of the Rhodobacter capsulatus cytochrome bc(1) complex (BC1) is ideally positioned to interact with cytochrome c(2) (C2). Mutational analysis of these three tyrosines showed that, of the three, Y154 is the most important, since its mutation to alanine resulted in significantly reduced levels, destabilization, and inactivation of BC1. A second-site revertant of this mutant that regained photosynthetic capacity was found to have acquired two further mutations-A181T and A200V. The Y152Q mutation did not change the spectral or electrochemical properties of C1, and showed wild-type enzymatic C2 reduction rates, indicating that this mutation did not introduce major structural changes in C1 nor affect overall activity. Mutations Y153Q and Y153A, on the other hand, clearly affect the redox properties of C1 (e.g. by lowering the midpoint potential as much as 117 mV in Y153Q) and the activity by 90% and 50%, respectively. A more conservative Y153F mutant on the other hand, behaves similarly to wild-type. This underscores the importance of an aromatic residue at position Y153, presumably to maintain close packing with P184, which modeling indicates is likely to stabilize the sixth heme ligand conformation.