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Sulfide:quinone oxidoreductase (SQR) is a peripheral membrane enzyme that catalyzes the oxidation of sulfide and the reduction of ubiquinone. Ubiquinone binds to a conserved hydrophobic domain and shuttles electrons from a noncovalent flavin adenine dinucleotide cofactor to the membrane-bound quinone pool. Utilizing the structure of decylubiquinone bound to Acidithiobacillus ferrooxidans SQR, we combined site-directed mutagenesis and kinetic approaches to analyze quinone binding. SQR can reduce both benzoquinones and naphthoquinones. The alkyl side-chain of ubiquinone derivatives enhances binding to SQR but limits the enzyme turnover. Pentachlorophenol and 2-n-heptyl-4-hydroxyquinoline-N-oxide are potent inhibitors of SQR with apparent inhibition constants (Ki) of 0.46 μmol·L(-1) and 0.58 μmol·L(-1), respectively. The highly conserved amino acids surrounding the quinone binding site play an important role in quinone reduction. The phenyl side-chains of Phe357 and Phe391 sandwich the benzoquinone head group and are critical for quinone binding. Importantly, conserved amino acids that define the ubiquinone-binding site also play an important role in sulfide oxidation/flavin reduction.

Background:Timing of neurosurgical procedures is controversial. Challenges identified with night-time surgeries include physician fatigue and sleep deprivation, and fewer staff and resources compared with daytime surgery. These might contribute to medical errors and complications, and, hence, worse patient outcomes.Methods:This single center retrospective study of 304 patients who underwent emergent neurosurgical procedures between January 1, 2010 and December 31, 2016 included 2 groups based on the timing of surgery: daytime (7:00 amto 6:59 pm) and night-time (7:00 pmto 6:59 am) surgery groups. Patient demographics, diagnosis, surgical characteristics, complications, and neurological outcome were obtained from the medical records.Results:There was no difference in patient demographics, intraoperative complications, and length of surgery between the 2 groups. Although there was no statistically significant difference in neurological outcome between the 2 groups at hospital discharge and 1 month postdischarge, there was a higher proportion of patients in the night-time surgical group with unfavorable neurological outcome (Glasgow Outcome Score 1 to 3) at both these times. There were differences in hospital length of stay, location of postoperative management (postanesthesia care unit or intensive care unit), midline shift, baseline Glasgow Coma Scale score, and acuity of surgery between the 2 groups. Logistic regression analysis showed that age, baseline Glasgow Coma Scale score, surgery acuity status, procedure type, and intraoperative complications influenced neurological outcome.Conclusions:This study found no difference in the rate of unfavorable neurological outcome in patients undergoing emergent neurosurgical procedures during the daytime and night-time. However, our findings cannot exclude the possibility of an association between timing of surgery and outcome given its limitations, including small sample size and omission of potentially confounding variables. Further well-designed prospective trials are warranted to confirm our findings.

Background: The role of high-field 3-Tesla intraoperative magnetic resonance imaging (I-MRI) during awake craniotomy (AC) has not been extensively studied. We report the feasibility and safety of AC during 3-Tesla I-MRI.Methods: This retrospective descriptive report compared 3 groups: AC with minimal sedation and I-MRI; I-MRI-guided craniotomy under general anesthesia (GA), and; AC without I-MRI. Perioperative factors, surgical, anesthetic and radiologic complications, and postoperative morbidity and mortality were recorded.Results: Overall, 85 patients are included in this report. Five of 23 patients (22%) who underwent AC with I-MRI had anesthetic complications (nausea/vomiting and conversion to GA) compared with 3 of 40 (8%) who underwent I-MRI-guided craniotomy under GA (nausea/vomiting during extubation, and arrhythmia). Intraoperative surgical complications (seizures and speech deficits) occurred in 5 patients (22%) who underwent AC and I-MRI, excessive intraoperative bleeding occurred in 2 patients (5%) who had I-MRI-guided craniotomy under GA, and 4 of 22 (18%) patients who underwent AC without I-MRI experienced neurological complications (seizures, motor deficits, and transient loss of consciousness). Eight patients (20%) who had I-MRI with GA had postoperative complications, largely neurological. The duration of surgery and anesthesia were shortest in the group of patients receiving AC without I-MRI. Seventy-three percent of the patients in this group had residual tumor postoperatively compared with 44% and 38% in those having I-MRI with AC or GA, respectively. Patients who underwent I-MRI-guided craniotomy with GA had the highest morbidity (8%) at hospital discharge.Conclusions: Our institutional experience suggests that AC under 3-Tesla I-MRI could be an option for glioma resection, although firm conclusions cannot be drawn given the limited and heterogenous nature of our data. Future multicenter trials comparing anesthetic and imaging modalities for glioma resection are recommended.