Laryngotracheal and pharyngoesophageal traumatic injuries from US military operations in Iraq and Afghanistan, 2003-2017.

INTRODUCTION: Laryngotracheal and pharyngo-oesophageal trauma present military providers with especially difficult, life-threatening challenges. Although effective treatment strategies are crucial, there is no clear consensus. This study of combat injuries from Iraq and Afghanistan describes initial treatment outcomes. METHODS: US service members who sustained 'laryngotracheal' and 'pharyngoesophageal' injuries while deployed in military operations from 2003 to 2017 were identified from the Expeditionary Medical Encounter Database. Those with inhalation or ingestion injuries and an Injury Severity Score (ISS) <16 were excluded. Data on demographics, survival, mechanism and type of injury and diagnostic and therapeutic intervention were recorded. RESULTS: A total of 111 service members met inclusion criteria. Nearly one-third (32.4%) were killed in action (KIA) or died of wounds (DoW). Fatality was not significantly associated with age, theatre of operation, type of injury or mechanism of injury, but was associated with a higher ISS and those in the Marines. Although survival rates were not significantly different, the frequency of these injuries decreased after the introduction of cervical collar protection in 2007. Of those who DoW or survived, 41.1% required a surgical airway. Tracheobronchoscopy was performed in 25.6%, oesophagoscopy in 20.0% and oesophagram in 6.7%. Of the 85 with penetrating neck injuries, 43 (50.6%) underwent neck exploration, in which 31 (72.1%) required intervention. CONCLUSIONS: Severe laryngotracheal and pharyngo-oesophageal injuries have a high fatality rate and demand prompt treatment from skilled providers. Further work will elucidate preventive measures and clear management algorithms to optimise outcomes.

Structure of intercalated Cs in zeolite ITQ-4: an array of metal ions and correlated electrons confined in a pseudo-1D nanoporous host.

The presence of Cs+ ions in the pseudo-1D nanopores of zeolite ITQ-4, Si32O64, is confirmed by x-ray diffraction and atomic pair distribution function analysis. Inside the nanopores the Cs+ ions are found to assemble in zigzag chains and thus form an extended, positively charged sublattice providing charge balance for a low-density electron gas also confined to the nanopores.

Magnetic state of the alpha 3 center of cytochrome c oxidase and some of its derivatives.

The temperature dependence of the magnetic susceptibility was used to investigate the nature of the coupling between cytochrome alpha 3 and CuB in resting and oxidized cyanide- and formate-bound cytochrome oxidase. Resting and formate-bound enzymes were found to have strong antiferromagnetic coupling with an S = 5/2 cytochrome alpha 3, results that were independent of the dispersing detergent and the enzyme isolation method. The cyanide-bound enzyme was heterogeneous, with a minor fraction showing intermediate strength antiferromagnetic coupling. The magnitude of this coupling was independent of the enzyme isolation method and depended moderately on the identity of the dispersing detergent. The major fraction of the cyanide-bound enzyme had a lowest energy state of Ms = 0. The coupling constant for this fraction did not depend on the isolation technique or on the identity of the dispersing detergent. The use of glucose-glucose oxidase to deoxygenate samples influenced the susceptibility behavior of some preparations of both the resting and formate-bound enzymes, with results indicating an S = 3/2 cytochrome alpha 3 in the resting enzyme samples. Retention of a 417-nm Soret band for formate-bound enzyme concomitant with peroxide-induced changes in susceptibility behavior indicates different sites of enzyme interactions for the formate ion and hydrogen peroxide.

Electrides: ionic salts with electrons as the anions.

Electrides are ionic compounds that have alkali metal cations complexed by a crown ether or cryptand, with trapped electrons as counterions. The crystal structures and properties of two electrides illustrate the diversity that is encountered. One Cs(+) (18-crown-6)(z)e(-), has relatively isolated, trapped electrons apparently centered at each anionic site. It has a low conductivity consistent with electron localization, with an activation energy for conductivity of at least 0.45 electron volt. The other, K(+) (cryptand[2.2.2])e(-), has electron pairs trapped in an elongated cavity in a singlet ground state, but there is also a thermally accessible paramagnetic state available. This electride is much more conducting, with an activation energy of only 0.02 electron volt.

The use of principal component analysis to resolve the spectra and kinetics of cytochrome c oxidase reduction by 5,10-dihydro-5-methyl phenazine.

The method of principal component analysis (PCA) was applied to the absorption-wavelength-time surfaces generated by rapid scanning stopped-flow spectrophotometry (RSSFS). The method was used to resolve the absorption surfaces generated during the reduction of cytochrome c oxidase by 5,10-dihydro-5-methyl phenazine (MPH) into the individual spectral shapes and time courses of the component chromophores. Two forms of resting cytochrome oxidase were used in these analyses: one that has its maximum absorption in the Soret region at 418 nm (418-nm species) and the other has its absorption maximum at 424 nm (424-nm species). A weighting scheme suitable for RSSFS data was developed. The optical absorption spectra obtained by W.H. Vanneste (1966, Biochemistry, 5:838-848) for the oxidase components were found to fit adequately as components of the experimental surfaces. Among these spectra were the oxidized forms of cytochromes a and a3 in the wavelength region 330-520 nm for the 418-nm species. Vanneste's spectral shape for the oxidized cytochrome a3 did not fit as a component in the spectrum of the 424-nm species. After accounting for the spectral shape of all components present, PCA provided a straightforward method for determining the separate time courses of each chromophore. We have found for both forms used that cytochrome a is reduced by MPH in the initial stages of the reaction, while cytochrome a3 is reduced in subsequent, slow phases. An important aspect of PCA is that it provided confirmation of the spectra of the various oxidase components without requiring the use of inhibitors or the use of simplifying mechanistic assumptions. The resolution of time profiles of strongly overlapping chromophores is also demonstrated.

Reduction of cytochrome oxidase by 5,10-dihydro-5-methylphenazine: kinetic parameters from rapid-scanning stopped-flow experiments.

The kinetics of the reduction of resting cytochrome oxidase and of its cyanide complex by 5,10-dihydro-5- methylphenazine (MPH) have been characterized by rapid-scan and fixed-wavelength stopped-flow spectrophotometry in the Soret, visible, and near-IR spectral regions. In this study, we focused on a form of the resting enzyme that is characterized by a Soret absorption maximum at 424 nm. These experiments complement earlier work on the reduction of a 418 nm absorbing form of the resting enzyme [ Halaka , F.G., Babcock , G. T., & Dye, J. L. (1981) J. Biol. Chem. 256, 1084-1087]. The reduction of cytochrome a is accomplished in a second-order reaction with a rate constant of 3 X 10(5) M-1 s-1. The reduction of the 830-nm absorber, Cua, is closely coupled to but lags the reduction of cytochrome a; we have resolved a rate constant of about 20 s-1 for the copper reduction. The reduction of cytochrome a proceeds with a rate constant that is nearly independent of the spectral properties of the resting enzyme and of the ligation state of cytochrome a3. The reduction of cytochrome a3 occurs by slow, intramolecular electron transfer. We have resolved two phases for this process that have rate constants of approximately 0.2 s-1 and approximately 0.02 s-1 for both the 418- and 424-nm forms of the resting enzyme. It appears, therefore, that spectroscopic heterogeneity at the cytochrome a3 site in the resting enzyme exerts very little influence on the kinetics of the anaerobic reduction of the oxidase metal centers. From this we conclude that the rate of electron transfer to the a3 site is probably controlled by the protein conformation and not primarily by local factors within the a3 environment.

Properties of 5-methylphenazinium methyl sulfate. Reaction of the oxidized form with NADH and of the reduced form with oxygen.

Rapid-scan and fixed-wavelength stopped-flow spectrophotometry were used to characterize the 5-methylphenazinium methyl sulfate (PMS)/reduced nicotinamide adenine dinucleotide couple at pH 7.4. Under anaerobic conditions, NADH reduces PMS to 5,10-dihydro-5-methylphenazine with a second order rate constant of 3.8 +/- 0.4 X 10(3) M-1 s-1. Oxygen reacts with 5,10-dihydro-5-methylphenazine to form PMS with a rate constant of about 180 M-1 s-1. When NADH reacts with PMS under aerobic conditions, a situation commonly encountered in carrying out routine enzymatic assays, the NADH reduction reaction and the O2 oxidation reaction proceed simultaneously with rate constants essentially the same as those determined for the two isolated reactions. The anaerobic photoreaction of PMS at pH = 7.4, which was studied by optical absorption spectroscopy, produces the 1-hydroxy-5-methylphenazinium cation (pyocyanine) and 5,10-dihydro-5-methylphenazine in nearly equal concentrations. When oxygen is present, the only detectable product is pyocyanine. These results, particularly the relatively slow rate of reaction between PMS and NADH, are used to point out potential complications in the use of the PMS/NADH couple.

Computer-interfaced rapid scanning molecular absorption and emission spectrophotometer for stopped-flow studies of enzyme reactions.

An improved stopped-flow system with a rapid-scanning spectrometer permits measurement of either light absorption or emission at scan speeds of up to 150 spectra per second. The entire flow system, including valves, syringes and quartz flow cell is contained in a thermostat bath and is leak-tight from 5 to 45 degrees C. Pneumatic valves control the flow through Teflon tubing. Quartz fiber-optic light guides are used to transmit light to and from the flow cell. Experimental data are given to demonstrate the absorbance and fluorescence modes. The growth and decay of the fluorescence spectrum of NADH was followed in a reaction catalyzed by lactate dehydrogenase (LDH). The kinetics of binding of 1-anilino-8-naphthalene sulfonate (ANS) to bovine serum albumin (BSA) was studied by both scanning and fixed-wavelength fluorescence emission. The fluorescence of BSA was completely quenched within two milliseconds accompanied by an abrupt increase in the fluorescence of ANS which was followed by a slower first-order growth.

Kinetics of pH-dependent interconversion of tryptophanase spectral forms studied by scanning stopped-flow spectrophotometry.

Morino and Snell [Morino, Y., & Snell, E. E. (1967) J. Biol. Chem. 242, 5591-5601] previously showed that the relative amplitudes of the 337- and 420-nm absorption bands of tryptophanase depended on both pH and the nature of a required monovalent cation activator. An investigation of the kinetics of interconversion of the 337- and 420-nm forms following a rapid incremental increase (jump) or decrease (drop) in pH over the range of enzyme stability in 0.2 M KCl at 24 +/- 0.3 degrees C by scanning stopped-flow spectrophotometry showed three distinct time-dependent phases. They were (1) an abrupt phase which is complete in less than 6.5 ms, (2) a fast first-order interconversion of the 420- and 337-nm absorbances, and (3) a slow first-order process involving growth at 355 nm coupled to two decays centered at 325 and 430 nm in the incremental pH jumps and decay at 355 nm with concomitant growth at 430 and 290 nm in the incremental pH-drop experiments. The results of these experiments were analyzed in terms of a scheme involving enzyme forms E alpha, E beta, E beta H+, E gamma, E gamma H+, and E delta. The E alpha form predominates in the absence of activating monovalent cations and absorbs at 420 nm. Those in the beta manifold, E beta and E beta H+, also absorb at 420 nm while those in the gamma manifold, E gamma and E gamma H+, absorb at 337 nm. The form E delta absorbs at 335 nm. E beta H+ and E gamma H+ represent the protonated form of the enzyme in each manifold. Analysis of the abrupt phase showed no significant systematic changes in absorbance above 330 nm for either the pH-jump or pH-drop experiments. The fast second phase involves the first-order interconversion of the beta and gamma manifolds while the slow third phase describes the buildup or decay of the delta manifold. Presumably conformational changes control the rate of these interconversions. The pH dependence of the fast first-order beta to gamma conversion was described and evaluated in terms of five independent equilibrium and rate constants and three independent amplitude terms by simultaneously fitting the amplitude data and first-order rate constants to an equation describing the overall scheme with a nonlinear least-squares program KINFIT4 [Dye, J. L., & Nicely, V. A. (1971) J. Chem. Educ. 48, 443-448]. The pK for protonation of the beta form = 9.70 +/- 0.12, for protonation of the gamma form (337-nm absorber) = 6.77 +/- 0.10, and for the pH-dependent interconversion of the beta and gamma manifolds, pKa = 8.11 +/- 0.04. The computed equilibrium distribution among the four species of the beta and gamma manifolds showed that E beta H+ and E gamma predominate.

Kinetic distinction between cytochromes a and a3 in cytochrome c oxidase. Rapid scanning stopped flow study of anaerobic reduction by a neutral and a negatively charged donor.

Anaerobic reduction of cytochrome c oxidase by 5,10-dihydro-5-methylphenazine (reduced PMS) and by sodium dithionite were studied by rapid scanning stopped flow spectrophotometry. In both cases the decay of the Soret band of the oxidized oxidase is not uniform. With reduced PMS, the reduction involves two molecules of reductant (4 electrons)/oxidase molecule. The first stage of the reduction exhibits an isosbestic point in the Soret region at 437 nm. This shifts to 428 nm in later stages of the reaction. The reduction of the oxidase by sodium dithionite is also complete and apparently involves SO2 radical. In this case the spectra show an isosbestic point at approximately 420 nm which shifts to 432 nm as the reaction proceeds. For each of the reductants the reaction is best described by three phases: the first is a second order reaction between the oxidase and the reductant, followed by two first order processes which appear to describe the intramolecular electron redistribution within the oxidase molecule. The results agree with the assignment of the Soret band of the oxidase molecule to cytochrome a3 with an absorption maximum near 410 nm and to cytochrome a which has its maximum absorption hear 430 nm. If these assignments are correct, the present data show that reduced PMS, an uncharged molecule, reacts more rapidly with cytochrome a than it does with cytochrome a3, while the negatively charged radical anion, SO2, appears to have more direct access to cytochrome a3.