SIRT3 facilitates mitochondrial structural repair and functional recovery in rats after ischemic stroke by promoting OPA1 expression and activity.

BACKGROUND: Optical atrophy 1 (OPA1), a protein accountable for mitochondrial fusion, facilitates the restoration of mitochondrial structure and function following cerebral ischemia/reperfusion (I/R) injury. The OPA1-conferred mitochondrial protection involves its expression and activity, which can be improved by SIRT3 in non-cerebral ischemia. Nevertheless, it remains obscure whether SIRT3 enhances the expression and activity of OPA1 after cerebral I/R injury. METHODS: Mature male Sprague Dawley rats were intracranially injected with adeno-associated viral-Sirtuin-3(AAV-SIRT3) and AAV-sh_OPA1, followed by a 90-min temporary blockage of the middle cerebral artery and subsequent restoration of blood flow. Cultured cortical neurons of rats were transfected with LV-SIRT3 or LV-sh_OPA1 before a 2-h oxygen-glucose deprivation and reoxygenation. The rats and neurons were subsequently treated with a selective OPA1 activity inhibitor (MYLS22). The interaction between SIRT3 and OPA1 was assessed by molecular dynamics simulation technology and co-immunoprecipitation. The expression, function, and specific protective mechanism of SIRT3 were examined by various analyses. RESULTS: SIRT3 interacted with OPA1 in the rat cerebral cortex before and after cerebral I/R. After cerebral I/R damage, SIRT3 upregulation increased the OPA1 expression, which enhanced deacetylation and OPA1 activity, thus alleviating cerebral infarct volume, neuronal apoptosis, oxidative pressure, and impairment in mitochondrial energy production; SIRT3 upregulation also improved neuromotor performance, repaired mitochondrial ultrastructure and membrane composition, and promoted the mitochondrial biogenesis. These neuroprotective effects were partly reversed by OPA1 expression interference and OPA1 activity inhibitor MYLS22. CONCLUSION: In rats, SIRT3 enhances the expression and activity of OPA1, facilitating the repair of mitochondrial structure and functional recovery following cerebral I/R injury. These findings highlight that regulating SIRT3 may be a promising therapeutic strategy for ischemic stroke.

3D Bioprinting of Artificial Skin Substitute with Improved Mechanical Property and Regulated Cell Behavior through Integrating Patterned Nanofibrous Films.

Three-dimensional (3D) bioprinting has advantages for constructing artificial skin tissues in replicating the structures and functions of native skin. Although many studies have presented improved effect of printing skin substitutes in wound healing, using hydrogel inks to fabricate 3D bioprinting architectures with complicated structures, mimicking mechanical properties, and appropriate cellular environments is still challenging. Inspired by collagen nanofibers withstanding stress and regulating cell behavior, a patterned nanofibrous film was introduced to the printed hydrogel scaffold to fabricate a composite artificial skin substitute (CASS). The artificial dermis was printed using gelatin-hyaluronan hybrid hydrogels containing human dermal fibroblasts with gradient porosity and integrated with patterned nanofibrous films simultaneously, while the artificial epidermis was formed by seeding human keratinocytes upon the dermis. The collagen-mimicking nanofibrous film effectively improved the tensile strength and fracture resistance of the CASS, making it sewable for firm implantation into skin defects. Meanwhile, the patterned nanofibrous film also provided the biological cues to guide cell behavior. Consequently, CASS could effectively accelerate the regeneration of large-area skin defects in mouse and pig models by promoting re-epithelialization and collagen deposition. This research developed an effective strategy to prepare composite bioprinting architectures for enhancing mechanical property and regulating cell behavior, and CASS could be a promising skin substitute for treating large-area skin defects.

SIRT1 restores mitochondrial structure and function in rats by activating SIRT3 after cerebral ischemia/reperfusion injury.

Mitochondrial dysfunction contributes to cerebral ischemia-reperfusion (CI/R) injury, which can be ameliorated by Sirtuin-3 (SIRT3). Under stress conditions, the SIRT3-promoted mitochondrial functional recovery depends on both its activity and expression. However, the approach to enhance SIRT3 activity after CI/R injury remains unelucidated. In this study, Sprague-Dawley (SD) rats were intracranially injected with either adeno-associated viral Sirtuin-1 (AAV-SIRT1) or AAV-sh_SIRT1 before undergoing transient middle cerebral artery occlusion (tMCAO). Primary cortical neurons were cultured and transfected with lentiviral SIRT1 (LV-SIRT1) and LV-sh_SIRT1 respectively before oxygen-glucose deprivation/reoxygenation (OGD/R). Afterwards, rats and neurons were respectively treated with a selective SIRT3 inhibitor, 3-(1H-1,2,3-triazol-4-yl) pyridine (3-TYP). The expression, function, and related mechanism of SIRT1 were investigated by Western Blot, flow cytometry, immunofluorescence staining, etc. After CI/R injury, SIRT1 expression decreased in vivo and in vitro. The simulation and immune-analyses reported strong interaction between SIRT1 and SIRT3 in the cerebral mitochondria before and after CI/R. SIRT1 overexpression enhanced SIRT3 activity by increasing the deacetylation of SIRT3, which ameliorated CI/R-induced cerebral infarction, neuronal apoptosis, oxidative stress, neurological and motor dysfunction, and mitochondrial respiratory chain dysfunction, promoted mitochondrial biogenesis, and retained mitochondrial integrity and mitochondrial morphology. Meanwhile, SIRT1 overexpression alleviated OGD/R-induced neuronal death and mitochondrial bioenergetic deficits. These effects were reversed by AAV-sh_SIRT1 and the neuroprotective effects of SIRT1 were partially offset by 3-TYP. These results suggest that SIRT1 restores the structure and function of mitochondria by activating SIRT3, offering neuroprotection against CI/R injury, which signifies a potential approach for the clinical management of cerebral ischemia.

Discovery and development of novel 10,12-disubstituted aloperine derivatives against HCoV-OC43 by targeting allosteric site of host TMPRSS2.

By inducing steric activation of the 10CH bond with a 12-acyl group to form a key imine oxime intermediate, 20 novel (10S)-10,12-disubstituted aloperine derivatives were successfully synthesized and assessed for their antiviral efficacy against HCoV-OC43. Of them, compound 3i exhibited the moderate activities against HCoV-OC43, as well as against the SARS-CoV-2 variant EG.5.1 with the comparable EC50 values of 4.7 and 4.1 µM. A mechanism study revealed that it inhibited the protease activity of host TMPRSS2 by binding to an allosteric site, rather than the known catalytic center, different from that of camostat. Also, the combination of compound 3i and molnupiravir, as an RdRp inhibitor, showed an additive antiviral effect against HCoV-OC43. The results provide a new binding mode and lead compound for targeting TMPRSS2, with an advantage in combating broad-spectrum coronavirus.

Hypoxia promotes metastasis by relieving miR-598-3p-restricted glycolysis in gastric cancer.

The activation of glycolysis, particularly in the context of reprogrammed energy metabolism, is increasingly recognized as a significant characteristic of cancer. However, the precise mechanisms by which glycolysis is promoted in metastatic gastric cancer cells under normal oxygen conditions remain poorly understood. MicroRNAs (miRNAs) play a crucial role in the development of malignant phenotypes in gastric cancer. Nevertheless, our understanding of the specific involvement of miRNAs in hypoxia-induced metabolic shifting and the subsequent metastatic processes is limited. Hypoxia-induced downregulation of miR-598-3p mechanistically leads to the upregulation of RMP and IGF1r, thereby promoting glycolysis. Either overexpression of miR-598-3p or R406 treatment effectively suppresses the metastasis of gastric cancer cells both in vitro and in vivo. Collectively, the depletion of miR-598-3p alters glucose metabolism from oxidative phosphorylation to glycolysis, thereby exacerbating the malignancy of gastric cancer cells. The present findings indicate a potential target for the development of therapeutics against gastric cancers with increased miR-598-3p expression.

Design, synthesis and biological evaluation of biaryl amide derivatives against SARS-CoV-2 with dual-target mechanism.

The COVID-19 pandemic highlights the urgent need to develop effective small-molecule antivirals. Thirty-three novel biaryl amide derivatives were synthesized and evaluated for anti-coronaviral activity. Some significant SARs were uncovered and the intensive structure modifications led to the most active compounds 8b and 8h. The broad-spectrum anti-coronaviral effects of 8h were validated at RNA and protein levels. 8h inhibits coronavirus replication at multiple stages, from virus entry to virus dsRNA synthesis. The mechanism of action showed that 8h may simultaneously act on 3CLpro and TMPRSS2 to display anti-coronaviral effects. 8h combined with RdRp inhibitor showed synergistic inhibitory activity against coronavirus. This study confirmed that biaryl amide derivatives may be a new class of potential therapeutic agents against coronavirus with multiple target effect, worthy of further investigation.

Risk factors for pharyngalgia and xerostomia undergoing supraglottic jet oxygenation and ventilation in gastrointestinal endoscopy: a retrospective study.

Supraglottic jet oxygenation/ventilation (SJOV) can reduce hypoxemia in sedated endoscopy but may increase minor side effects like pharyngalgia and xerostomia. This study aimed to identify risk factors for pharyngalgia/xerostomia with SJOV during gastrointestinal endoscopy. From January 1 to December 31, 2021, 5313 patients with propofol sedation and SJOV underwent gastrointestinal endoscopy or removal of gastrointestinal polyps was analyzed retrospectively. Data included patient characteristics, operation details, postoperative adverse events, and potential risk factors for postoperative adverse events. Parameters considered as potential risk factors were identified based on study results published previously and based on the researcher's idea and clinical experience. The patient factors and the incidence of pharyngalgia/xerostomia at 30 min post-procedure were assessed. Descriptive statistics were calculated using SPSS software. Evaluation potential risk factors using univariate and multivariate logistic regression. Pharyngalgia/xerostomia occurred in 18.7% of patients at 30 min after procedure. A multivariable analysis showed that procedure time and pharyngalgia/xerostomia within 2 weeks were independent risk factors. Procedure time had the strongest association with postoperative pharyngalgia/xerostomia (OR, 8.09 [95% CI, 4.197-6.312]). No factors were significantly associated with hypoxemia risk (1.7% incidence). There were no barotrauma or other serious morbidity or mortality. Procedure duration and recent pharyngalgia/xerostomia increased risk of pharyngalgia/xerostomia with SJOV during endoscopy. Limiting SJOV duration may reduce side effects in susceptible patients. No predictors of hypoxemia were identified.

Argonaute protein-based nucleic acid detection technology.

It is vital to diagnose pathogens quickly and effectively in the research and treatment of disease. Argonaute (Ago) proteins are recently discovered nucleases with nucleic acid shearing activity that exhibit specific recognition properties beyond CRISPR-Cas nucleases, which are highly researched but restricted PAM sequence recognition. Therefore, research on Ago protein-mediated nucleic acid detection technology has attracted significant attention from researchers in recent years. Using Ago proteins in developing nucleic acid detection platforms can enable efficient, convenient, and rapid nucleic acid detection and pathogen diagnosis, which is of great importance for human life and health and technological development. In this article, we introduce the structure and function of Argonaute proteins and discuss the latest advances in their use in nucleic acid detection.

Efficient enzymatic synthesis of chiral 2,3-dihydro-1,4-benzodioxane motif using engineered Candida antarctica lipase B.

Chiral motifs of 2,3-dihydro-1,4 benzodioxane are extensively utilized in diverse medicinal substances and bioactive natural compounds, exhibiting significant biological activities. Notable examples of such therapeutic agents include prosympal, dibozane, piperoxan, and doxazosin. In this work, using 1,4-benzodioxane-2-carboxylic acid methyl ester as the substrate, after screening 38 CALB covariant residues, we found that mutants A225F and A225F/T103A can catalyze the kinetic resolution of the substrate. The effect of temperature, cosolvent, and cosolvent concentration on kinetic resolution was investigated, revealing that the best results were achieved at 30 °C with 20% n-butanol as a cosolvent, resulting in an optimal resolution (e.e.s 97%, E = 278) at 50 mM substrate concentration. Structure analysis showed that mutation sites 225 and 103 are not among the sites that interact directly with the substrate, which means that covariant amino acids that interact remotely with the substrate also regulate enzyme catalysis. This research may provide us with a new strategy for enzyme evolution.

Neuropilin-1 promotes mitochondrial structural repair and functional recovery in rats with cerebral ischemia.

OBJECTIVES: Available literature documents that ischemic stroke can disrupt the morphology and function of mitochondria and that the latter in other disease models can be preserved by neuropilin-1 (NRP-1) via oxidative stress suppression. However, whether NRP-1 can repair mitochondrial structure and promote functional recovery after cerebral ischemia is still unknown. This study tackled this very issue and explored the underlying mechanism. METHODS: Adeno-associated viral (AAV)-NRP-1 was stereotaxically inoculated into the cortex and ipsilateral striatum posterior of adult male Sprague-Dawley (SD) rats before a 90-min transient middle cerebral artery occlusion (tMCAO) and subsequent reperfusion. Lentivirus (LV)-NRP-1 was transfected into rat primary cortical neuronal cultures before a 2-h oxygen-glucose deprivation and reoxygenation (OGD/R) injury to neurons. The expression and function of NRP-1 and its specific protective mechanism were investigated by Western Blot, immunofluorescence staining, flow cytometry, magnetic resonance imaging, transmission electron microscopy, etc. The binding was detected by molecular docking and molecular dynamics simulation. RESULTS: Both in vitro and in vivo models of cerebral ischemia/reperfusion (I/R) injury presented a sharp increase in NRP-1 expression. The expression of AAV-NRP-1 markedly ameliorated the cerebral I/R-induced damage to the motor function and restored the mitochondrial morphology. The expression of LV-NRP-1 alleviated mitochondrial oxidative stress and bioenergetic deficits. AAV-NRP-1 and LV-NRP-1 treatments increased the wingless integration (Wnt)-associated signals and ß-catenin nuclear localization. The protective effects of NRP-1 were reversed by the administration of XAV-939. CONCLUSIONS: NRP-1 can produce neuroprotective effects against I/R injury to the brain by activating the Wnt/ß-catenin signaling pathway and promoting mitochondrial structural repair and functional recovery, which may serve as a promising candidate target in treating ischemic stroke.

MXene Contact Engineering for Printed Electronics.

MXenes emerging as an amazing class of 2D layered materials, have drawn great attention in the past decade. Recent progress suggest that MXene-based materials have been widely explored as conductive electrodes for printed electronics, including electronic and optoelectronic devices, sensors, and energy storage systems. Here, the critical factors impacting device performance are comprehensively interpreted from the viewpoint of contact engineering, thereby giving a deep understanding of surface microstructures, contact defects, and energy level matching as well as their interaction principles. This review also summarizes the existing challenges of MXene inks and the related printing techniques, aiming at inspiring researchers to develop novel large-area and high-resolution printing integration methods. Moreover, to effectually tune the states of contact interface and meet the urgent demands of printed electronics, the significance of MXene contact engineering in reducing defects, matching energy levels, and regulating performance is highlighted. Finally, the printed electronics constructed by the collaborative combination of the printing process and contact engineering are discussed.

Inversion of chlorophyll content under the stress of leaf mite for jujube based on model PSO-ELM method.

During the growth season, jujube trees are susceptible to infestation by the leaf mite, which reduces the fruit quality and productivity. Traditional monitoring techniques for mites are time-consuming, difficult, subjective, and result in a time lag. In this study, the method based on a particle swarm optimization (PSO) algorithm extreme learning machine for estimation of leaf chlorophyll content (SPAD) under leaf mite infestation in jujube was proposed. Initially, image data and SPAD values for jujube orchards under four severities of leaf mite infestation were collected for analysis. Six vegetation indices and SPAD value were chosen for correlation analysis to establish the estimation model for SPAD and the vegetation indices. To address the influence of colinearity between spectral bands, the feature band with the highest correlation coefficient was retrieved first using the successive projection algorithm. In the modeling process, the PSO correlation coefficient was initialized with the convergent optimal approximation of the fitness function value; the root mean square error (RMSE) of the predicted and measured values was derived as an indicator of PSO goodness-of-fit to solve the problems of ELM model weights, threshold randomness, and uncertainty of network parameters; and finally, an iterative update method was used to determine the particle fitness value to optimize the minimum error or iteration number. The results reflected that significant differences were observed in the spectral reflectance of the jujube canopy corresponding with the severity of leaf mite infestation, and the infestation severity was negatively correlated with the SPAD value of jujube leaves. The selected vegetation indices NDVI, RVI, PhRI, and MCARI were positively correlated with SPAD, whereas TCARI and GI were negatively correlated with SPAD. The accuracy of the optimized PSO-ELM model (R 2 = 0.856, RMSE = 0.796) was superior to that of the ELM model alone (R 2 = 0.748, RMSE = 1.689). The PSO-ELM model for remote sensing estimation of relative leaf chlorophyll content of jujube shows high fault tolerance and improved data-processing efficiency. The results provide a reference for the utility of UAV remote sensing for monitoring leaf mite infestation of jujube.

Huang Qin Decoction inhibits the initiation of experimental colitis associated carcinogenesis by controlling the PAD4 dependent NETs.

BACKGROUND: Colorectal cancer is associated with ulcerative colitis (UC). The infiltration of neutrophils is the main cause of DNA damage produced by inflammation in the intestinal epithelium. Under the action of peptidyl arginine deaminase 4 (PAD4), neutrophils dissociate chromatin and form neutrophil extracellular traps (NETs), which can aggravate tissue inflammation and encourage tumor development. Although Huang Qin Decoction (HQD) was found to be useful in treating UC and was used to gradually prevent and treat digestive tract cancers, the underlying reasons were unclear. METHODS: To demonstrate HQD could inhibits the initiation of colitis associated carcinogenesis by controlling NETs related inflammation, we first performed an AOM/DSS-generated colitis-associated carcinogenesis model to assess the efficacy of HQD in reducing neutrophil infiltration and anti-tumor activity. Then, using network pharmacology research, we investigated the potential mechanisms underlying those medicinal effects, as demonstrated by the detection of NETs aggregation and PAD4 expression changes in the colon. RESULTS: HQD substantially reduced the number of colon cancers and the expression of Ki67, restored the level of intestinal tight junction protein occludin and ZO-1, and relieved the intestinal inflammation caused by TNF-α, IL-1ß. At the same time, it inhibited neutrophil infiltration in the colon and improved the immunosurveillance of CD8+T cells. The potential mechanisms of HQD intervention against UC and UC with neoplasia (UCN) were studied using network pharmacology, and 156 conjunct genes as well as numerous inflammation-related pathways were identified. Protein-protein interaction (PPI) analysis indicated that HQD inhibition of intestinal tumors might be related to the deactivation of PAD4, which was verified by the down-regulation of NETs, MPO-DNA complex levels, and PAD4 expression after HQD treatment. CONCLUSION: Huang Qin Decoction inhibits the initiation of colitis associated carcinogenesis by controlling PAD4-dependent neutrophil extracellular traps.

Baicalein ameliorates ulcerative colitis by improving intestinal epithelial barrier via AhR/IL-22 pathway in ILC3s.

Ulcerative colitis (UC) is a chronic inflammatory disease of the gastrointestinal tract, which is closely related to gut barrier dysfunction. Emerging evidence shows that interleukin-22 (IL-22) derived from group 3 innate lymphoid cells (ILC3s) confers benefits on intestinal barrier, and IL-22 expression is controlled by aryl hydrocarbon receptor (AhR). Previous studies show that baicalein protects the colon from inflammatory damage. In this study we elucidated the molecular mechanisms underlying the protective effect of baicalein on intestinal barrier function in colitis mice. Mice were administered baicalein (10, 20, 40 mg·kg-1·d-1, i.g.) for 10 days; the mice freely drank 3% dextran sulfate sodium (DSS) on D1-D7 to induce colitis. We showed that baicalein administration simultaneously ameliorated gut inflammation, decreased intestinal permeability, restored tight junctions of colons possibly via promoting AhR/IL-22 pathway. Co-administration of AhR antagonist CH223191 (10 mg/kg, i.p.) partially blocked the therapeutic effects of baicalein in colitis mice, whereas AhR agonist FICZ (1 µg, i.p.) ameliorated symptoms and gut barrier function in colitis mice. In a murine lymphocyte line MNK-3, baicalein (5-20 µM) dose-dependently increased the expression of AhR downstream target protein CYP1A1, and enhanced IL-22 production through facilitating AhR nuclear translocation, these effects were greatly diminished in shAhR-MNK3 cells, suggesting that baicalein induced IL-22 production in AhR-dependent manner. To further clarify that, we constructed an in vitro system consisting of MNK-3 and Caco-2 cells, in which MNK-3 cell supernatant treated with baicalein could decrease FITC-dextran permeability and promoted the expression of tight junction proteins ZO-1 and occluding in Caco-2 cells. In conclusion, this study demonstrates that baicalein ameliorates colitis by improving intestinal epithelial barrier via AhR/IL-22 pathway in ILC3s, thus providing a potential therapy for UC.

Supraglottic jet oxygenation and ventilation reduces desaturation during bronchoscopy under moderate to deep sedation with propofol and remifentanil: A randomised controlled clinical trial.

BACKGROUND: Hypoxaemia is frequently seen during flexible bronchoscopies that are done with a nasal approach under the traditional sedation with propofol. This study investigated the potential benefits of supraglottic jet oxygenation and ventilation (SJOV) using the Wei nasal jet tube (WNJ) in reducing hypoxaemia in patients undergoing bronchoscopy under moderate to deep intravenous sedation using a propofol, lidocaine and remifentanil cocktail. OBJECTIVES: Our primary objective was to evaluate the efficacy and complications of SJOV via the WNJ during flexible bronchoscopy under moderate to heavy sedation with propofol and remifentanil. DESIGN: A randomised controlled clinical trial. SETTING: The 180th Hospital of People's Liberation Army, Quanzhou, China, from 1 June to 1 November 2019. PATIENTS: A total of 280 patients aged ≥18 years with American Society of Anesthesiologists' physical status 1 to 3 undergoing flexible bronchoscopy were studied. INTERVENTIONS: Patients were assigned randomly into one of two groups, a nasal cannula oxygenation (NCO) group (n = 140) using a nasal cannula to deliver oxygen (4 l min-1) or the SJOV group (n = 140) using a WNJ connected to a manual jet ventilator to provide SJOV at a driving pressure of 103 kPa, respiratory rate 20 min-1, FiO2 1.0 and inspiratory:expiratory (I:E) ratio 1:2. MAIN OUTCOME MEASURES: The primary outcome was an incidence of desaturation (defined as SpO2 < 90%) during the procedure. Other adverse events related to the sedation or SJOV were also recorded. RESULTS: Compared with the NCO group, the incidence of desaturation in the SJOV group was lower (NCO 37.0% vs. SJOV 13.1%) (P < 0.001). Patients in the SJOV group had a higher incidence of a dry mouth at 1 min (13.1% vs. 1.5%, P < 0.001) than at 30 min (1.5% vs. 0%, P = 0.159) or at 24 h (0% vs. 0%). There was no significant difference between the groups in respect of sore throat, subcutaneous emphysema or nasal bleeding. CONCLUSIONS: SJOV via a WNJ during flexible bronchoscopy under moderate to deep sedation with propofol and remifentanil significantly reduces the incidence of desaturation when compared with regular oxygen supplementation via a nasal cannula. Patients in the SJOV group had an increased incidence of transient dry mouth. TRIAL REGISTRATION: Registered at www.chictr.org.cn (ChiCTR1900023514).

Algorithm-based coevolution network identification reveals key functional residues of the α/ß hydrolase subfamilies.

Covariant residues identified by computational algorithms have provided new insights into enzyme evolutionary routes. However, the reliability and accuracy of routine statistical coupling analysis (SCA) are unable to satisfy the needs of protein engineering because SCA depends only on sequence information. Here, we set up a new SCA algorithm, SCA.SIM, by integrating structure information and MD simulation data. The more reliable covariant residues with high-quality scores are obtained from sequence alignment weighted by residual movement for eight related subfamilies, belonging to α/ß hydrolase family, with Candida antarctica lipase B (CALB). The 38 predicted covariant residues are tested for function by high-throughput quantitative evaluation in combination with activity and thermostability assays of a mutant library and deep sequencing. Based on the landscapes of both activity and thermostability, most mutants play key roles in catalysis, and some mutants gain 2.4- to 6-fold increase in half-life at 50°C and 9- to 12-fold improvement in catalytic efficiency. The activity of double mutants for A225F/T103A is higher than those of A225F and T103A which means that SCA.SIM method might be useful for identifying the allosteric coupling. The SCA.SIM algorithm can be used for protein coevolution and enzyme engineering research.

Molecular characteristic of mcr-1 producing Escherichia coli in a Chinese university hospital.

BACKGROUND: Colistin has been considered as a last-line treatment option in severe infections caused by multidrug-resistant (MDR) gram-negative pathogens. However, the emergence of the mobile colistin resistance gene (mcr-1) has challenged this viewpoint. The aim of this study is to explore the prevalence of mcr-1 in Escherichia coli (E. coli) in a Chinese teaching hospital, and investigate their molecular characteristics. METHODS: A total of 700 E. coli isolates were used to screen mcr-1 by PCR and sequencing in a Chinese university hospital from August 2014 to August 2015. Susceptibility test of mcr-1-producing isolates was determined by Vitek -2 Compact system. 26 virulence factors (VFs), phylogenetic groups, Multi-locus sequence typing (MLST), and DNA Fingerprinting (ERIC-PCR) of strains were investigated by PCR. RESULTS: Four (0.6%) mcr-1 producing E. coli isolates were found in this study. The results of antibiotic susceptibility test showed that all four isolates were resistant to colistin, ciprofloxacin, levofloxacin, cefazolin, and trimethoprim/sulfamethoxazole, and were susceptible to amikacin, ertapenem and imipenem. In addition, all 4 isolates exhibited high-level resistance to aztreonam, cefotaxime and gentamicin. The numbers of VFs contained in mcr-1 positive isolates were no more than 4 in our study. MLST result demonstrated that these isolates were assigned to two sequence types: ST156 and ST167. The result of phylogenetic analysis showed that four mcr-1-positive isolates belong to two phylogenetic groups: A and B1 group. ERIC-PCR showed that four mcr-1 positive strains were categorized into three different genotypes. CONCLUSIONS: Our study demonstrated a low prevalence of mcr-1 in E. coli clinical isolates in a Chinese teaching hospital, and we have gained insights into the molecular characteristics of these mcr-1-positive strains. Increasing the surveillance of these infections, as well as taking effective infection control measures are urgently needed to take to control the transmission of mcr-1 gene.

Exploring the thermostable properties of halohydrin dehalogenase from Agrobacterium radiobacter AD1 by a combinatorial directed evolution strategy.

As a crucial factor for biocatalysts, protein thermostability often arises from a combination of factors that are often difficult to rationalize. In this work, the thermostable nature of halohydrin dehalogenase from Agrobacterium radiobacter AD1 (HheC) was systematically explored using a combinatorial directed evolution approach. For this, a mutagenesis library of HheC mutants was first constructed using error-prone PCR with low mutagenesis frequency. After screening approximately 2000 colonies, six mutants with eight mutation sites were obtained. Those mutation sites were subsequently combined by adopting several rounds of iterative saturation mutagenesis (ISM) approach. After four rounds of saturation mutagenesis, one best mutant ISM-4 with a 3400-fold improvement in half-life (t 1/2) inactivation at 65 °C, 18 °C increase in apparent T m value, and 20 °C increase in optimum temperature was obtained, compared to wild-type HheC. To the best of our knowledge, the mutant represents the most thermostable HheC variant reported up to now. Moreover, the mutant was as active as wild-type enzyme for the substrate 1,3-dichloro-2-propanol, and they remained most enantioselectivity of wild-type enzyme in the kinetic resolution of rac-2-chloro-1-phenolethanol, exhibiting a great potential for industrial applications. Our structural investigation highlights that surface loop regions are hot spots for modulating the thermostability of HheC, the residues located at these regions contribute to the thermostability of HheC in a cooperative way, and protein rigidity and oligomeric interface connections contribute to the thermostability of HheC. All of these essential factors could be used for further design of an even more thermostable HheC, which, in turn, could greatly facilitate the application of the enzyme as a biocatalyst.

Supraglottic jet oxygenation and ventilation saved a patient with 'cannot intubate and cannot ventilate' emergency difficult airway.

The emergency difficult airway with the 'cannot intubate and cannot ventilate' (CICV) situation contributes to a high percentage of anesthesia- and emergency medicine-related morbidity and mortality. A new technique of supraglottic jet oxygenation and ventilation (SJOV) via the nasal approach was successfully used in an emergency to save a patient with a CICV difficult airway from a catastrophic outcome.