The key role of glutamine for protein expression and isotopic labeling in insect cells.

Nuclear magnetic resonance studies of many physiologically important proteins have long been impeded by the necessity to express such proteins in isotope-labeled form in higher eukaryotic cells and the concomitant high costs of providing isotope-labeled amino acids in the growth medium. Economical routes use isotope-labeled yeast or algae extracts but still require expensive isotope-labeled glutamine. Here, we have systematically quantified the effect of 15N2-glutamine on the expression and isotope labeling of different proteins in insect cells. Sufficient levels of glutamine in the medium increase the protein expression by four to five times relative to deprived conditions. 1H-15N nuclear magnetic resonance spectroscopy shows that the 15N atoms from 15N2-glutamine are scrambled with surprisingly high (60-70%) efficiency into the three amino acids alanine, aspartate, and glutamate. This phenomenon gives direct evidence that the high energy demand of insect cells during baculovirus infection and concomitant heterologous protein expression is predominantly satisfied by glutamine feeding the tricarboxylic acid cycle. To overcome the high costs of supplementing isotope-labeled glutamine, we have developed a robust method for the large-scale synthesis of 15N2-glutamine and partially deuterated 15N2-glutamine-α,ß,ß-d3 from inexpensive precursors. An application is shown for the effective large-scale expression of the isotope-labeled ß1-adrenergic receptor using the synthesized 15N2-glutamine-α,ß,ß-d3.

Nanobody GPS by PCS: An Efficient New NMR Analysis Method for G Protein Coupled Receptors and Other Large Proteins.

NMR chemical shift changes can report on the functional dynamics of biomacromolecules in solution with sizes >1 MDa. However, their interpretation requires chemical shift assignments to individual nuclei, which for large molecules often can only be obtained by tedious point mutations that may interfere with function. We present here an efficient pseudocontact shift NMR method to assign biomacromolecules using bound antibodies tagged with lanthanoid DOTA chelators. The stability of the antibody allows positioning the DOTA tag at many surface sites, providing triangulation of the macromolecule nuclei at distances >60 Å. The method provides complete assignments of valine and tyrosine 1H-15N resonances of the ß1-adrenergic receptor in various functional forms. The detected chemical shift changes reveal strong forces exerted onto the backbone of transmembrane helix 3 during signal transmission, which are absorbed by its electronic structure. The assignment method is applicable to any soluble biomacromolecule for which suitable complementary binders exist.

Efficacy and Safety Profile of Montgomery T-Tube Implantation in Patients with Tracheal Stenosis.

Background: Tracheal stenosis is able to lead to airway obstruction. Objective: To evaluate the efficacy and safety profile of Montgomery T-tube implantation in patients with tracheal stenosis. Methods: Fifty-two patients with tracheal stenosis diagnosed between 2016 and 2019 were included in this retrospective cohort study. The patients were divided into observation group (n = 25 cases) and control group (n = 27). The therapeutic effect, arterial blood gas analysis, arterial oxygen partial pressure (PaO2), arterial carbon dioxide partial pressure (PaCO2), shortness of breath score, airway diameter change, dyspnea score, quality of life, and safety were compared between the two groups before and after treatment. Results: The therapeutic effect of the observation group gained better results than that of the control group (84.00% vs. 62.96%). One week after operation, the pH value, SaO2, PaCO2, shortness of breath score, airway diameter change, dyspnea score, life quality, and incidence of postoperative complications in the observation group exerted better results as compared to the control group. Conclusion: The implantation of Montgomery T-tube has effective function in terms of improving the symptoms of dyspnea and the life quality of patients with safety profile in patients harboring tracheal stenosis.

Probing the correlation between ligand efficacy and conformational diversity at the α1A-adrenoreceptor reveals allosteric coupling of its microswitches.

G protein-coupled receptors (GPCRs) use a series of conserved microswitches to transmit signals across the cell membrane via an allosteric network encompassing the ligand-binding site and the G protein-binding site. Crystal structures of GPCRs provide snapshots of their inactive and active states, but poorly describe the conformational dynamics of the allosteric network that underlies GPCR activation. Here, we analyzed the correlation between ligand binding and receptor conformation of the α1A-adrenoreceptor, a GPCR that stimulates smooth muscle contraction in response to binding noradrenaline. NMR of [13CϵH3]methionine-labeled α1A-adrenoreceptor variants, each exhibiting differing signaling capacities, revealed how different classes of ligands modulate the conformational equilibria of this receptor. [13CϵH3]Methionine residues near the microswitches exhibited distinct states that correlated with ligand efficacies, supporting a conformational selection mechanism. We propose that allosteric coupling among the microswitches controls the conformation of the α1A-adrenoreceptor and underlies the mechanism of ligand modulation of GPCR signaling in cells.

Treatment of secondary benign airway stenosis after tracheotomy with Montgomery T-tube.

Objective: With the improvement of surgical operation, increasing incidence of secondary benign airway stenosis, as a complication of long-term tracheal intubation and tracheotomy, leads to significant increases in morbidity and mortality. Previous treatment of secondary benign airway stenosis was mainly based on surgical resection and reconstruction. There is an urgent need for new treatment methods except surgery, especially for those inoperable patients. Methods: This study retrospectively reviewed 20 patients who had treatments of secondary benign airway stenosis after tracheotomy with Montgomery T-tube. The clinical data including clinical features, efficacy, complications and prognosis were retrospectively evaluated. Results: Complete airway obstruction was 12/20, partial stenosis was 8/20, combined with airway granuloma and endoscopic granulation resection was 16/20, combined with scar stenosis and endoscopic balloon dilatation was 18/20. Plugging successfully was 19/20. Complications included mucous accumulation (20/20), secondary granulation tissue formation (13/20), subcutaneous soft tissue infection (1/20), and T-tube re-implantation (3/20). Conclusions: Montgomery T-tube implantation under rigid bronchoscopy is a safe, feasible and effective tracheal forming method with well tolerance for patients with benign airway stenosis. Secondary benign airway stenosis after tracheal intubation and tracheotomy is an indication of Montgomery T-tube implantation. Compared with the traditional tracheotomy, the advantage of Montgomery T-tube implantation is easy to make the patient phonate, significantly improving the quality of life of patients. T-tube implantation is safe, and the postoperative complications include mucous accumulation and formation of secondary T-tube granulation tissue.

Determinants of Ligand Subtype-Selectivity at α1A-Adrenoceptor Revealed Using Saturation Transfer Difference (STD) NMR.

α1A- and α1B-adrenoceptors (α1A-AR and α1B-AR) are closely related G protein-coupled receptors (GPCRs) that modulate the cardiovascular and nervous systems in response to binding epinephrine and norepinephrine. The GPCR gene superfamily is made up of numerous subfamilies that, like α1A-AR and α1B-AR, are activated by the same endogenous agonists but may modulate different physiological processes. A major challenge in GPCR research and drug discovery is determining how compounds interact with receptors at the molecular level, especially to assist in the optimization of drug leads. Nuclear magnetic resonance spectroscopy (NMR) can provide great insight into ligand-binding epitopes, modes, and kinetics. Ideally, ligand-based NMR methods require purified, well-behaved protein samples. The instability of GPCRs upon purification in detergents, however, makes the application of NMR to study ligand binding challenging. Here, stabilized α1A-AR and α1B-AR variants were engineered using Cellular High-throughput Encapsulation, Solubilization, and Screening (CHESS), allowing the analysis of ligand binding with Saturation Transfer Difference NMR (STD NMR). STD NMR was used to map the binding epitopes of epinephrine and A-61603 to both receptors, revealing the molecular determinants for the selectivity of A-61603 for α1A-AR over α1B-AR. The use of stabilized GPCRs for ligand-observed NMR experiments will lead to a deeper understanding of binding processes and assist structure-based drug design.

Gastric Schwannoma: A Tumor Must Be Included in Differential Diagnoses of Gastric Submucosal Tumors.

Gastric schwannoma (GS) is a rare neoplasm of the stomach. It accounts for 0.2% of all gastric tumors and is mostly benign, slow-growing, and asymptomatic. Due to its rarity, GS is not widely recognized by clinicians, and the precise differential diagnosis between GS and other gastric submucosal tumors remains difficult preoperatively. The present study reports a case of GS misdiagnosed as gastrointestinal stromal tumor and reviews the clinical, imaging, and pathological features, treatment, and follow-up of 221 patients with GS previously reported in the English literature. Although GS is rare, the case reported in the current study highlights the importance of including GS in differential diagnoses of gastric submucosal tumors. Furthermore, the findings of the review suggest that although many cases are asymptomatic, the most common symptoms are abdominal pain or discomfort, not gastrointestinal bleeding, and malignant GSs present with clinical symptoms more commonly. Although large-sample multicenter studies on the efficacy, safety, and oncological outcomes of minimally invasive techniques are required, the findings presented herein may be helpful for clinicians when diagnosing or treating GS.

Comparison between CT and MRI in the assessment of pulmonary embolism: A meta-analysis.

OBJECTIVE: Besides pulmonary arteriography, a number of imaging techniques, such as magnetic resonance imaging (MRI) and computed tomography (CT), were adopted in the detection of identifying pulmonary embolism (PE). However, the contrast of sensitivity and specificity in these methods was studied little in a statistical way. To compare the effects of MRI and CT, this study used a series of methods to analyze data in included researches. METHODS: A comprehensive computer search was conducted through internet up to July 2016. The quality assessment was performed by the Quality Assessment Tool for Diagnostic Accuracy Studies, version 2 tool. The diagnostic value of comparison between MRI and CT was evaluated by using the pooled estimate of sensitivity, specificity, and summary receiver operating characteristic (SROC) curve. In addition, sensitivity analysis and bias analysis were applied to ensure the accuracy of the results. RESULTS: Ten studies with 590 cases were involved in the study. Only 2 trials had high risk regarding bias while other trials were supposed to be at low risk of applicability. Heterogeneity existed in analysis of both CT and MRI. The pooled sensitivity of CT was 0.90 (95% CI: 0.85-0.93), pooled specificity was 0.88 (95% CI: 0.77 to 0.95), the pooled sensitivity of MRI was 0.92 (95% CI: 0.89-0.94), and pooled specificity was 0.91 (95% CI: 0.77-0.97). The Q index of sensitivity and specificity for CT and MRI were 71.38, 19.67, 47.14, and 12.35, respectively. The SROC curve area under the curve of CT and MRI were 0.94 (95% CI: 0.91-0.96) and 0.93 (95% CI: 0.91-0.95), respectively. CONCLUSION: This meta-analysis demonstrates that MRI has better sensitivity and specificity in detecting subsegmental artery PE. MRI is a relatively better detection technique for PE. This conclusion is consistent with many published researches.

Cold snare resection for the treatment of benign airway lesions.

The objective was to assess the safety and outcome of cold snare technique used by flexible bronchoscopy in the treatment of airway benign neoplasms. The clinical data of 21 patients, who had airway benign neoplasm and were treated through the cold snare method in Sir Run Run Shaw Hospital, affiliated with the Zhejiang University, were retrospectively analyzed. The relief of the symptoms and occurrence of complications were observed and evaluated. All the tumors were benign and removed by cold snare. Postoperatively, we found that the treatment was completely effective in 12 patients, and there was a significant improvement in 7 patients and a moderate improvement in 2 patients, and no recurrence in follow-up visit. In conclusion, the cold snare technique is an economically feasible, safe, and effective method in the treatment of airway neoplasms.

[Effects of ginsenoside Rg1 on the expressions of p-eRK1/2 and p-JNK in local cerebral ischemia/reperfusion injury rats].

OBJECTIVE: To study the possible anti-apoptotic mechanism of ginsenoside Rg1 on the apoptosis of hippocampal neuron after cerebral ischemia/reperfusion (I/R) injury rats. METHODS: Totally 120 healthy male adult SD rats were randomly divided into the cerebral I/R model group (the model group), the low dose ginsenoside Rg1 group (10 mg/kg), the middle dose ginsenoside Rg1 group (20 mg/kg), the high dose ginsenoside Rg1 group (40 mg/kg), and the sham-operation group, 18 in each group. Rats received medication by peritoneal injection. Equal volume of normal saline was peritoneally injected to rats in the sham-operation group and the model group, once daily, for 7 successive days. The cerebral I/R injury model was prepared by 2-h middle cerebral artery occlusion (MCAO) followed by 24-h reperfusion. Rats in the sham-operation group received the same surgical procedure without the carotid arteries occluded. The neurofunction was assessed using Longa EZ method. The injury of hippocampal pyramidal cells was observed by Nissel staining and TUNEL assay. The nerve cell apoptosis rate was calculated. The protein expression levels of extracellular signal-regulated kinase 1/2 (ERK1/2), phosphorylated extracellular signal-regulated kinase 1/2 (p-ERK1/2), c-Jun N-terminal kinases (JNK), and phosphorylated c-Jun N-terminal kinase (p-JNK) were detected using Western blot. RESULTS: Compared with the sham-operation group, the score of neurofunction, the apoptosis rate, the expression levels of p-JNK and p-ERK1/2 increased, the survived number of pyramidal cells decreased in the model group (P < 0.05, P < 0.01). Compared with the model group, the score of neurofunction and the apoptosis rate decreased in each ginsenoside Rg1 group (P < 0.05, P < 0.01). The survived number of pyramidal cells increased in the high and middle dose ginsenoside Rg1 groups, the expression of p-JNK in the hippocampal CA1 region decreased, and the expression level of p-ERK1/2 increased (P < 0.05, P < 0.01). Compared with the low dose ginsenoside Rg1 group, the score of neurofunction, the apoptosis rate, the p-JNK protein expression decreased, the survived number of pyramidal cells increased, the expression of p-ERK1/2 increased in the high and middle dose ginsenoside Rg1 groups (P < 0.05, P < 0.01). Three to four layers of pyramidal cells were arranged tightly and compactly in the hippocampal CA1 region of the sham - operation group. The nucleus was big and round under high power lens, with 1 -2 kernel. After cerebral I/R injury, the hippocampal nerve cells were severely injured. Normal structure was lost in the CA1 region, with disarranged cell line and reduced cell amount. Partial neurons were shrunken, and the kernel was condensed and darkenedly stained. They were in triangular, long strip, fusiform, or irregular shape. The staining of nucleus was clustered and the kernel was not clear. Ginsenoside Rg1 (20 and 40 mg/kg) could improve the morphology of ischemic nerve cells, reduce their loss. Of them, stronger effects were shown in the high dose ginsenoside Rg1 group than in the middle dose ginsenoside Rg1 group. The JNK protein band was divided into two subzones, JNK1 (46 kD) and JNK2 (54 kD). ERK protein band was also divided into two subzones, ERK1 (44 kD) and ERK2 (42 kD). CONCLUSION: The protective effect of ginsenoside Rg1 on cerebral I/R injury was correlated with inhibiting the apoptosis of hippocampal neurons, regulating the expression levels of p-ERK1/2 and p-JNK.