Current Ventilator and Oxygen Management during General Anesthesia: A Multicenter, Cross-sectional Observational Study.

BACKGROUND: Intraoperative oxygen management is poorly understood. It was hypothesized that potentially preventable hyperoxemia and substantial oxygen exposure would be common during general anesthesia. METHODS: A multicenter, cross-sectional study was conducted to describe current ventilator management, particularly oxygen management, during general anesthesia in Japan. All adult patients (16 yr old or older) who received general anesthesia over 5 consecutive days in 2015 at 43 participating hospitals were identified. Ventilator settings and vital signs were collected 1 h after the induction of general anesthesia. We determined the prevalence of potentially preventable hyperoxemia (oxygen saturation measured by pulse oximetry of more than 98%, despite fractional inspired oxygen tension of more than 0.21) and the risk factors for potentially substantial oxygen exposure (fractional inspired oxygen tension of more than 0.5, despite oxygen saturation measured by pulse oximetry of more than 92%). RESULTS: A total of 1,786 patients were found eligible, and 1,498 completed the study. Fractional inspired oxygen tension was between 0.31 and 0.6 in 1,385 patients (92%), whereas it was less than or equal to 0.3 in very few patients (1%). Most patients (83%) were exposed to potentially preventable hyperoxemia, and 32% had potentially substantial oxygen exposure. In multivariable analysis, old age, emergency surgery, and one-lung ventilation were independently associated with increased potentially substantial oxygen exposure, whereas use of volume control ventilation and high positive end-expiratory pressure levels were associated with decreased potentially substantial oxygen exposure. One-lung ventilation was particularly a strong risk factor for potentially substantial oxygen exposure (adjusted odds ratio, 13.35; 95% CI, 7.24 to 24.60). CONCLUSIONS: Potentially preventable hyperoxemia and substantial oxygen exposure are common during general anesthesia, especially during one-lung ventilation. Future research should explore the safety and feasibility of a more conservative approach for intraoperative oxygen therapy.

Metabolic profiling of transgenic potato tubers expressing Arabidopsis dehydration response element-binding protein 1A (DREB1A).

Untargeted metabolome analyses play a critical role in understanding possible metabolic fluctuations of crops under varying environmental conditions. This study reports metabolic profiles of transgenic potato tubers expressing the Arabidopsis DREB1A transcription factor gene, which induces expression of genes involved in environmental stress tolerance. A combination of targeted and untargeted metabolomics demonstrated considerable metabolome differences between the transgenic lines and nontransgenic parent cultivars. In the transgenic lines, stimulation of stress responses was suggested by elevated levels of the glutathione metabolite, γ-aminobutyric acid (GABA), and by the accumulation of ß-cyanoalanine, a byproduct of ethylene biosynthesis. These results suggest that the Arabidopsis DREB1A expression might directly or indirectly enhance endogenous potato stress tolerance systems. The results indicate that transgenesis events could alter the metabolic compositions in food crops, and therefore metabolomics analysis could be a most valuable tool to monitor such changes.

Inhibition of RuBisCO cloned from Thermosynechococcus vulcanus and expressed in Escherichia coli with compounds predicted by Molecular Operation Environment (MOE).

Ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBisCO) of a thermophilic cyanobacterium, Thermosynechococcus vulcanus, was cloned and expressed in Escherichia coli. The purified enzyme had higher thermostability than RuBisCOs isolated from mesophilic cyanobacteria. Prediction of the tertiary structure was performed using the software Molecular Operating Environment (MOE). The predicted structure did not give any clue about the basis of thermostability. Then, the molecular docking of substrates and inhibitors in the catalytic site were carried out to test analogs for consistency of ribulose 1,5-bisphosphate, a RuBisCO substrate. The analogs were searched in the Kyoto Encyclopedia of Genes and Genomes (KEGG), and 99 compounds were selected for the docking. The mol files from LIGAND Database in KEGG were changed to a three dimensional (3D) structure for use in docking simulation. The docking simulation was performed on ASEDock of MOE, and the SiteFinder command suggested about 20 candidates for the docking site of the compounds. Based on the homology of these candidate sites with the xylulose 1,5-bisphosphate (XBP)-binding site of RuBisCO isolated from Synechococcus PCC 6301, one site was selected for the docking simulation. The 40 compounds with the highest docking energies included synthetic organic substances that had never been demonstrated to be inhibitors of RuBisCO. The total docking energies were -102 kcal/mol, -104 kcal/mol, -94.0 kcal/mol, and -57.7 kcal/mol for ribulose 1,5-bisphosphate (RuBP), etidronate, risedronate, and citrate respectively. Kinetic analysis of RuBisCO revealed a K(m) value of 315 microM for RuBP, and K(i) values of 1.70, 0.93, and 2.04 mM for etidronate, risedronate, and citrate respectively. From these values, the binding energies were estimated to be -4.85, -3.84, -4.20, and -3.73 kcal/mol for RuBP, etidronate, risedronate, and citrate respectively. The differences between the values estimated from experimental data and by simulation may mainly depend on the dissimilarity of the environment for the protein and ligands between the experiments and the simulation. The results obtained here suggested a few new inhibitors, which might be useful as tools for studying the relationship between the structure and the function of RuBisCO.

A bacterial transgene for catalase protects translation of d1 protein during exposure of salt-stressed tobacco leaves to strong light.

During photoinhibition of photosystem II (PSII) in cyanobacteria, salt stress inhibits the repair of photodamaged PSII and, in particular, the synthesis of the D1 protein (D1). We investigated the effects of salt stress on the repair of PSII and the synthesis of D1 in wild-type tobacco (Nicotiana tabacum 'Xanthi') and in transformed plants that harbored the katE gene for catalase from Escherichia coli. Salt stress due to NaCl enhanced the photoinhibition of PSII in leaf discs from both wild-type and katE-transformed plants, but the effect of salt stress was less significant in the transformed plants than in wild-type plants. In the presence of lincomycin, which inhibits protein synthesis in chloroplasts, the activity of PSII decreased rapidly and at similar rates in both types of leaf disc during photoinhibition, and the observation suggests that repair of PSII was protected by the transgene-coded enzyme. Incorporation of [(35)S]methionine into D1 during photoinhibition was inhibited by salt stress, and the transformation mitigated this inhibitory effect. Northern blotting revealed that the level of psbA transcripts was not significantly affected by salt stress or by the transformation. Our results suggest that salt stress enhanced photoinhibition by inhibiting repair of PSII and that the katE transgene increased the resistance of the chloroplast's translational machinery to salt stress by scavenging hydrogen peroxide.

Molecular characterization and redox regulation of phosphoribulokinase from the cyanobacterium Synechococcus sp. PCC 7942.

We isolated and characterized a gene encoding phosphoribulokinase (PRK) from Synechococcus sp. PCC 7942. The isolated sequence consisted of a 999 bp open reading frame encoding 333 amino acid residues of PRK. The PRK contained a pair of cysteinyl residues corresponding to Cys16 and Cys55 of spinach PRK regulated by a ferredoxin-thioredoxin system. However, there were seventeen amino acid residues lacking between the two cysteinyl residues compared with those of the chloroplastic enzyme in higher plants. The recombinant PRK of Synechococcus sp. PCC 7942 accounted for about 6-13% of the total soluble protein in the Escherichia coli. The specific activity of the enzyme was 230 micro mol min(-1) (mg protein)(-1). The enzyme activity was completely inactivated by treatment with 5,5'-dithiobis (2-nitrobenzoic acid) (cysteinyl residue-specific oxidant) or was decreased by treatment with H(2)O(2), but was more tolerant to oxidation than that of chloroplast. The oxidized PRK was fully activated by treatment with excessive dithiothreitol. Furthermore, incubation with 3 mM ATP protected the oxidation of the enzyme by either 5,5'-dithiobis (2-nitrobenzoic acid) or H(2)O(2). These results suggest Synechococcus sp. PCC 7942 PRK can be regulated by reversible oxidation/reduction in vitro, but might be resistant to oxidative inactivation in vivo.

Regulation of the expression of ribulose-1,5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39) in a cyanobacterium, Synechococcus PCC7942.

When cyanobacterium cells are grown under extremely low CO(2) concentration, the number of carboxysomes, structures containing ribulose-bisphosphate carboxylase (Rubisco; EC 4.1.1.39), is known to increase. This suggests that Rubisco helps to regulate photosynthesis in cyanobacteria. However, no studies have been done on the changes of Rubisco content and activity in response to the extracellular CO(2) concentration, and no information is available on its effect on photosynthesis. To elucidate the relationship between the expression responses of Rubisco and extracellular CO(2), wild-type cells (Synechococcus PCC7942) and carboxysome-lacking cells were grown under various CO(2) concentrations, and Rubisco activity was determined. In both strains, Rubisco activity increased when the cells were grown under a CO(2) concentration around, or less than, K (1/2)(CO(2)) of photosynthesis. In carboxysome-lacking cells, Rubisco activity increased five to six times at most, and a simultaneous increase in the rate of photosynthesis was observed. These results suggest that stimulation of expression of Rubisco occurs to compensate for the decrease in the rate of photosynthesis under CO(2)-limited conditions.