Systematic calibration of epitranscriptomic maps using a synthetic modification-free RNA library.

Recent years have witnessed rapid progress in the field of epitranscriptomics. Functional interpretation of the epitranscriptome relies on sequencing technologies that determine the location and stoichiometry of various RNA modifications. However, contradictory results have been reported among studies, bringing the biological impacts of certain RNA modifications into doubt. Here, we develop a synthetic RNA library resembling the endogenous transcriptome but without any RNA modification. By incorporating this modification-free RNA library into established mapping techniques as a negative control, we reveal abundant false positives resulting from sequence bias or RNA structure. After calibration, precise and quantitative mapping expands the understanding of two representative modification types, N6-methyladenosine (m6A) and 5-methylcytosine (m5C). We propose that this approach provides a systematic solution for the calibration of various RNA-modification mappings and holds great promise in epitranscriptomic studies.

An analytical overview of the composition and characteristics of China's food safety standards.

This paper discusses the framework of China's food safety standards and provides a brief overview of the problems and developmental characteristics of food safety in China. The composition and characteristics of China's food safety standards are revealed by an analysis of the changes in China's general food standards, an overview of the characteristics of the hygiene requirements in the production and operation process, and an introduction to food product and test method standards. In conclusion, Chinese food safety standards are still being improved, but they must also be effectively implemented and followed up in real time in order to continuously improve the quality of food and reduce food safety incidents. © 2024 Society of Chemical Industry.

Circ_0000052/miR-382-3p axis induces PD-L1 expression and regulates cell proliferation and immune evasion in head and neck squamous cell carcinoma.

A better understanding of the mechanisms underlying PD-L1 aberrant expression in head and neck squamous cell carcinoma (HNSCC) will help reveal predictive biomarkers and overcome resistance to treatment. In this study, the prognostic significance of PD-L1 in forty-five HNSCC archival samples was determined by qRT-PCR. The biological function associated with malignant behaviour was assessed by PD-L1 depletion, miR-382-3p re-expression and regulation of circ_0000052. The interactions of PD-L1-miRNA and miRNA-circRNA were determined by qRT-PCR, Western blot analysis, dual-luciferase reporter assays and RNA immunoprecipitation assays. PD-L1 was highly expressed in patient samples and cancer cell lines. Higher levels of PD-L1 were associated with patient recurrences and play a pivotal role in regulating cell proliferation, migration, invasion, clonogenicity and apoptosis. In addition to demonstrating that the IFN-γ/JAK2/STAT1 signalling pathway can induce PD-L1 overexpression in HNSCC, a novel mechanism by which upregulated circ_0000052 mediates PD-L1 overexpression was also demonstrated. To do this, circ_0000052 competitively binds to miR-382-3p and alleviates its repression of PD-L1. This leads to overexpression of PD-L1, causing the aggressiveness of the cells. Our data demonstrate that circ_0000052 is oncogenic, and the circ_0000052/miR-382-3p/PD-L1 axis is critical in HNSCC progression. The manipulation of circRNAs/miRNAs in combination with anti-PD-L1 therapy may improve personalized disease management.

Cervical carcinogenesis risk association of HPV33 E6 and E7 genetic variations in Taizhou, Southeast China.

BACKGROUND: Human papillomavirus (HPV) 33 belongs to the Alphapapillomavirus 9 (α-9 HPV) species group, which also contains types 16, 31, 35, 52, 58 and 67. The purpose of this study was to investigate the genetic variations of HPV33 and to explore its carcinogenicity among women in Taizhou, Southeast China. METHODS: Exfoliated cervical cells were collected for HPV genotyping. Only single HPV33 infection cases were selected, and their E6 and E7 genes were sequenced using the ABI 3730xl sequencer and then analysed using MEGA X. RESULTS: From 2014 to 2020, a total of 185 single HPV33-positive specimens were successfully amplified. We obtained 15 distinct HPV33 E6/E7 variants, which were published in GenBank under accession numbers OQ672665-OQ672679. Phylogenetic analysis revealed that all HPV33 E6/E7 variants belonged to lineage A, of which 75.7% belonged to lineage A1. Compared with CIN1, the proportion of sublineage A1 in CIN2/3 was higher, but there was no significant difference (76.5% vs. 80.6%, P > 0.05). Altogether, 20 single nucleotide substitutions were identified, of which 6 were novel substitutions, including T196G (C30G), A447T, G458T (R117L), G531A, A704A, and C740T. In addition, no significant trends were observed between the nucleotide substitutions of HPV33 E6/E7 variants and the risk of cervical lesions. CONCLUSION: This study provides the most comprehensive data on genetic variations, phylogenetics and carcinogenicity of HPV33 E6/E7 variants in Southeast China to date. The data confirmed that cervical lesions among women in Taizhou are attributable to HPV33, which may be due to the high infection rate of sublineage A1 in the population.

Combined metabolomics and machine learning algorithms to explore metabolic biomarkers for diagnosis of acute myocardial ischemia.

Acute myocardial ischemia (AMI) remains the leading cause of death worldwide, and the post-mortem diagnosis of AMI represents a current challenge for both clinical and forensic pathologists. In the present study, the untargeted metabolomics based on ultra-performance liquid chromatography combined with high-resolution mass spectrometry was applied to analyze serum metabolic signatures from AMI in a rat model (n = 10 per group). A total of 28 endogenous metabolites in serum were significantly altered in AMI group relative to control and sham groups. A set of machine learning algorithms, namely gradient tree boosting (GTB), support vector machine (SVM), random forest (RF), logistic regression (LR), and multilayer perceptron (MLP) models, was used to screen the more valuable metabolites from 28 metabolites to optimize the biomarker panel. The results showed that classification accuracy and performance of MLP model were better than other algorithms when the metabolites consisting of L-threonic acid, N-acetyl-L-cysteine, CMPF, glycocholic acid, L-tyrosine, cholic acid, and glycoursodeoxycholic acid. Finally, 17 blood samples from autopsy cases were applied to validate the classification model's value in human samples. The MLP model constructed based on rat dataset achieved accuracy of 88.23%, and ROC of 0.89 for predicting AMI type II in autopsy cases of sudden cardiac death. The results demonstrated that MLP model based on 7 molecular biomarkers had a good diagnostic performance for both AMI rats and autopsy-based blood samples. Thus, the combination of metabolomics and machine learning algorithms provides a novel strategy for AMI diagnosis.

A novel method for determining postmortem interval based on the metabolomics of multiple organs combined with ensemble learning techniques.

Determining postmortem interval (PMI) is one of the most challenging and essential endeavors in forensic science. Developments in PMI estimation can take advantage of machine learning techniques. Currently, applying an algorithm to obtain information on multiple organs and conducting joint analysis to accurately estimate PMI are still in the early stages. This study aimed to establish a multi-organ stacking model that estimates PMI by analyzing differential compounds of four organs in rats. In a total of 140 rats, skeletal muscle, liver, lung, and kidney tissue samples were collected at each time point after death. Ultra-performance liquid chromatography coupled with high-resolution mass spectrometry was used to determine the compound profiles of the samples. The original data were preprocessed using multivariate statistical analysis to determine discriminant compounds. In addition, three interrelated and increasingly complex patterns (single organ optimal model, single organ stacking model, multi-organ stacking model) were established to estimate PMI. The accuracy and generalized area under the receiver operating characteristic curve of the multi-organ stacking model were the highest at 93% and 0.96, respectively. Only 1 of the 14 external validation samples was misclassified by the multi-organ stacking model. The results demonstrate that the application of the multi-organ combination to the stacking algorithm is a potential forensic tool for the accurate estimation of PMI.

Exploration and Practice of the "One Combination, Two Highlights, Three Combinations, Four in One" Innovative Talents Training Mode in Forensic Medicine.

Talent is one of the basic and strategic supports for building a modern socialist country in all aspects. Since the 1980s, the establishment of forensic medicine major and the cultivation of innovative talents in forensic medicine have become hot topics in higher education in forensic medicine. Over the past 43 years, the forensic medicine team of Shanxi Medical University has adhered to the joint education of public security and colleges, and made collaborative innovation, forming a training mode of "One Combination, Two Highlights, Three Combinations, Four in One" for innovative talents in forensic medicine. It has carried out "5+3/X" integrated reform, and formed a relatively complete talent training innovation mode and management system in teaching, scientific research, identification, major, discipline, team, platform and cultural construction. It has made a historic contribution to China's higher forensic education, accumulated valuable experience for the construction of first-class major and first-class discipline of forensic medicine, and provided strong support for the construction of the national new forensic talent training system. The popularization of this training mode is conducive to the rapid and sustainable development of forensic science, and provides more excellent forensic talents for national building, regional social development and the discipline construction of forensic science.

Natural product-based screening led to the discovery of a novel PXR agonist with anti-cholestasis activity.

Cholestasis is a major cause of a series of bile flow malfunction-related liver diseases. Pregnane X receptor (PXR) is a key regulator in endo- and xeno-biotics metabolism, which has been considered as a promising therapeutic target for cholestasis. In this study we conducted human PXR (hPXR) agonistic screening using dual-luciferase reporter gene assays, which led to discovering a series of potent hPXR agonists from a small Euphorbiaceae diterpenoid library, containing 35 structurally diverse diterpenoids with eight different skeleton types. The most active compound 6, a lathyrane diterpenoid (5/11/3 ring system), dose-dependently activated hPXR with a high selectivity, and significantly upregulated the expression of hPXR downstream genes CYP3A4 and UGT1A1. In LCA-induced cholestasis mouse model, administration of compound 6 (50 mg· kg-1. d-1, ip) for 7 days significantly suppressed liver necrosis and decreased serum levels of AST, ALT, Tbili, ALP, and TBA, ameliorating LCA-induced cholestatic liver injury. We further revealed that compound 6 exerted its anti-cholestatic efficacy via activation of PXR pathway, accelerating the detoxification of toxic BAs and promoting liver regeneration. These results suggest that lathyrane diterpenoids may serve as a promising scaffold for future development of anti-cholestasis drugs.

PXR mediates mifepristone-induced hepatomegaly in mice.

Mifepristone (Mif), an effective synthetic steroidal antiprogesterone drug, is widely used for medical abortion and pregnancy prevention. Due to its anti-glucocorticoid effect, high-dose Mif is also used to treat Cushing's syndrome. Mif was reported to active pregnane X receptor (PXR) in vitro and PXR can induce hepatomegaly via activation and interaction with yes-associated protein (YAP) pathway. High-dose Mif was reported to induce hepatomegaly in rats and mice, but the underlying mechanism remains unclear. Here, the role of PXR was studied in Mif-induced hepatomegaly in C57BL/6 mice and Pxr-knockout mice. The results demonstrated that high-dose Mif (100 mg · kg-1 · d-1, i.p.) treatment for 5 days significantly induced hepatomegaly with enlarged hepatocytes and promoted proliferation, but low dose of Mif (5 mg · kg-1 · d-1, i.p.) cannot induce hepatomegaly. The dual-luciferase reporter gene assays showed that Mif can activate human PXR in a concentration-dependent manner. In addition, Mif could promote nuclear translocation of PXR and YAP, and significantly induced the expression of PXR, YAP, and their target proteins such as CYP3A11, CYP2B10, UGT1A1, ANKRD, and CTGF. However, Mif (100 mg · kg-1 · d-1, i.p.) failed to induce hepatomegaly in Pxr-knockout mice, as well as hepatocyte enlargement and proliferation, further indicating that Mif-induced hepatomegaly is PXR-dependent. In summary, this study demonstrated that PXR-mediated Mif-induced hepatomegaly in mice probably via activation of YAP pathway. This study provides new insights in Mif-induced hepatomegaly, and provides novel evidence on the crucial function of PXR in liver enlargement and regeneration.

Generation of human scFv-IgG1Fc antibodies for detection of lymphatic filarial recombinant antigens, BmR1 and BmSXP.

Lymphatic filariasis is a neglected parasitic disease that affects millions in tropical and subtropical countries and is caused by Wuchereria and Brugia species. Specific and sensitive detection methods are essential in mapping infected areas where rapid tests are needed to cover underdeveloped and remote regions, which facilitates eliminating the disease as a public health problem. A few commercialized rapid tests based on antigen or antibody detection are available, but the former only detects infection by Wuchereria species and cross-reacts with nonlymphatic filaria, whereas antibody detection might provide positive results of previous infection. Here, we report the production of three different recombinant immunoglobulin gamma (IgG)1 antibodies based on scFvs previously generated via human antibody phage display technology, that is, anti-BmR1 clone 4, anti-BmXSP clone 5B, and anti-BmXSP clone 2H2. The scFv sequences were cloned into a pCMV-IgG1 vector, then transfected into a HEK293F cell line. The generated antibodies were found to be able to bind to their respective targets even at relatively low concentration. Conjugation of Fc to scFv induces binder stability and provides multiple labeling sites for probes and signaling molecules that can be used in rapid tests.

Erratum: Overexpression of lncRNA H19/miR-675 promotes tumorigenesis in head and neck squamous cell carcinoma: Erratum.

[This corrects the article DOI: 10.7150/ijms.16571.].

Comparative study on the main active components of Baoyuan decoction in plasma and urine of normal and heart failure rats.

The global morbidity and mortality of heart failure has been increasing in recent years. Traditional Chinese medicine (TCM) was increasingly used to treat cardiovascular diseases. Baoyuan decoction (BYD) was a famous classical prescription in China. Modern pharmacological studies showed that it had obvious therapeutic effects on cardiovascular diseases, but its pathological pharmacokinetic studies were unclear. In this research, the absorption of 16 bioactive components in plasma and the excretion of 9 representative components in urine of control rats and isoproterenol (ISO)-induced heart failure rats were studied using the large-volume direct-injection LC-MS method established by our research group. The results indicated that flavonoid constituents exhibited quicker absorption and elimination than saponin constituents after oral administration of BYD. The half-life period of some bioactive compounds in the model group was increased, which contributed to the longer therapeutic effect. The cumulative excretion rate of major flavonoid components of BYD decreased significantly in the ISO-induced heart failure rats.

Total Resection of Cerebellopontine Angle Meningioma via Presigmoid Transmastoid Approach: An Otologist's Perspective.

PURPOSE: Cerebellopontine angle meningiomas (CPAMs) are benign tumors that arise from the dura mater of the petrosal surface of the temporal bone, lateral to the trigeminal nerve. This study aimed to describe 1 case of CPAMs violating the mastoid and highlight the unique superiority of the presigmoid transmastoid approach for this type of CPAMs from an otologist's perspective. METHODS: One case of specific CPAMs treated by total resection via presigmoid transmastoid approach in otomicrosurgery was described. RESULTS: A patient was referred for the left intracranial space-occupying lesion found in physical examination. Surgical resection via presigmoid transmastoid approach was performed and there was no sign of recurrence of tumor 2 years after the operation. CONCLUSIONS: Presigmoid transmastoid approach in otomicrosurgery is suitable for CPAMs invading the mastoid. It is suggested that neurosurgeons and ear surgeons should comprehensively analyze the type and extent of the tumor and flexibly adopt surgical methods to ensure it is the best for patients.

Algorithmic Approach Using Negative Pressure Wound Therapy Improved Survival for Patients with Synchronous Hypopharyngeal and Esophageal Cancer Undergoing Pharyngolaryngoesophagectomy with Gastric Tube Reconstruction.

BACKGROUND: This study retrospectively analyzed the feasibility and surgical outcome of an algorithmic approach using negative pressure wound therapy for patients with synchronous hypopharyngeal and esophageal cancer undergoing pharyngolaryngoesophagectomy with gastric tube reconstruction. METHODS: Patients undergoing pharyngolaryngoesophagectomy and gastric tube reconstruction for hypopharyngeal cancer between 2011 and 2019 were candidates for this study. Data were collected on patient demographics, comorbidities, performance status, cancer stage, treatment, complication, and survival. Survival analysis was performed using the Kaplan-Meier method. The Cox proportional hazards model was used for prognostic factors. RESULTS: The study enrolled 43 patients. Anastomotic leakage was found in 21 of the patients with a conventional surgical drain (61.9%) and in 10 of the 22 patients with negative pressure wound therapy (45.5%) (p = 0.280). Nine patients in the conventional drain group (42.9%) and two patients in the negative pressure wound therapy group (9.1%) had leakage-associated complications (p = 0.011). The incidence of pulmonary complications was higher in the conventional surgical drain group (9 vs 2; p = 0.011). The number of complications requiring surgery was higher in the conventional drain group (7 vs 0; p = 0.004). The overall survival in the negative pressure wound therapy group was better (hazard ratio [HR], 0.33; 95% confidence interval [CI], 0.15-0.76; p = 0.009). Negative pressure wound therapy was independently associated with overall survival (HR, 0.31; 95% CI, 0.13-0.77; p = 0.011). CONCLUSIONS: Negative pressure wound therapy with an algorithmic approach improved the overall survival for the patients undergoing gastric tube reconstruction after pharyngolaryngoesophagectomy for hypopharyngeal and esophageal cancer by preventing deadly complications secondary to anastomotic leakage.

Effects of Different Component Contents of Colistin Methanesulfonate on the Pharmacokinetics of Prodrug and Formed Colistin in Human.

PURPOSES: To evaluate the effects of component contents in different colistin methanesulfonate (CMS) formulas on their clinical pharmacokinetics of the prodrug CMS and the formed colistin. METHODS: Two CMS formulas (CTTQ and Parkedale) were investigated in a single dose, randomized, open-label, crossover study conducted in 18 healthy Chinese subjects. Both CMS formulas met the requirements of European Pharmacopoeia 9.2 with 12.1% difference in the two major active components (CMS A and CMS B). The PK parameters after a single intravenous infusion of CMS at 2.5 mg/kg were calculated and the steady-state plasma colistin concentrations (Css,avg) following multiple dosing, once every 12 h for 7 days, were simulated with the non-compartment model. RESULTS: The systemic exposure (AUC0-inf) of CMS were 59.49 ± 5.90 h·µg/mL and 51.09 ± 4.70 h·µg/mL, and the AUC0-inf of colistin were 15.39 ± 2.63 h·µg/mL and 12.36 ± 2.10 h·µg/mL for CTTQ and Parkedale, respectively. The ratios (90% CI) of geometric mean of AUC0-inf of CTTQ to Parkedale were 116.38% (112.95%, 119.91%) and 124.49% (120.76%, 128.35%) for CMS and colistin, respectively. The predicted Css,avg (95% CI) were 0.92 (0.85, 0.99) µg/mL and 0.74 (0.69, 0.79) µg/mL for CTTQ and Parkedale, respectively. CONCLUSION: The difference in component content in the two CMS formulas had a significant (P < 0.001) impact on the systemic exposure of colistin in human, thus, warranted essential considerations in clinical applications.

Progress in the development of small molecular inhibitors of the Bruton's tyrosine kinase (BTK) as a promising cancer therapy.

Bruton tyrosine kinase (BTK) is a key kinase in the B cell antigen receptor signal transduction pathway, which is involved in the regulation of the proliferation, differentiation and apoptosis of B cells. BTK has become a significant target for the treatment of hematological malignancies and autoimmune diseases. Ibrutinib, the first-generation BTK inhibitor, has made a great contribution to the treatment of B cell malignant tumors, but there are still some problems such as resistance or miss target of site mutation. Therefore, there is an imperative need to develop novel BTK inhibitors to overcome these problems. Besides, proteolysis targeting chimera (PROTAC) technology has been successfully applied to the development of BTK degradation agents, which has opened a fresh way for the BTK targeted treatment. This paper reviews the biological function of BTK, the discovery and development of BTK targeted drugs as a promising cancer therapy. It mainly reviews the binding sites and structural characteristics of BTK, structure-activity relationships, activity and drug resistance of BTK inhibitors, as well as potential treatment strategies to overcome the resistance of BTK, which provides a reference for the rational design and development of new powerful BTK inhibitors.

Evaluation of the effects of notoginseng total saponins (NS), safflower total flavonoids (SF), and the combination of NS and SF (CNS) on the activities of cytochrome P450 enzymes using a cocktail method in rats.

Notoginseng total saponins (NS), safflower total flavonoids (SF), and the combination of NS and SF, namely CNS, are used for the treatment of cardiovascular diseases in clinic. This study developed a cocktail assay involving seven cytochrome P450 (CYP) enzymes to elucidate the effect of NS, SF, and CNS on CYP enzymes and to explore the synergistic effect of CNS in terms of CYP enzymes. Ultra-performance liquid chromatography-MS and reverse-transcription polymerase chain reaction were applied to detect the activities and mRNA expression levels of CYP enzymes. SF exhibited inhibitory effects on CYP1A2, 2B1, 2E1, and 2C11 and induction effects on CYP2C19 and 2D4. NS exhibited induction effects on CYP1A2, 2B1, 2E1, 2C11, 2C19, and 2D4. CNS exhibited induction effects on CYP1A2, 2B1, 2E1, 2C19, and 2D4 and inhibitory effects on CYP3A1 in vivo. Moreover, mRNA expression results were consistent with pharmacokinetic results. Potential herb-drug interactions should be studied closely when SF, NS, or CNS with clinical drugs are metabolized by CYP1A2, 2B1, 2E1, 2C11, 2C19, 2D4, and 3A1. CNS could change the inhibition or induction effects of CYP compared to the NS group, which might be one of the causes for the synergistic effects of the combination of NS and SF.

Single-port thoracoscopic anatomic resection for chronic inflammatory lung disease.

BACKGROUND: It is challenging to proceed thoracoscopic anatomic resection when encountering severe pleural adhesion or calcified peribronchial lymphadenopathy. Compared with multiple-port video-assisted thoracoscopic surgery (MP-VATS), how to overcome these challenges in single-port (SP-) VATS is still an intractable problem. In the present study, we reported the surgical results of chronic inflammatory lung disease and shared some useful SP-VATS techniques. METHODS: We retrospectively assessed the surgical results of chronic inflammatory lung disease, primarily bronchiectasis, and mycobacterial infection, at our institution between 2010 and 2018. The patients who underwent SP-VATS anatomic resection were compared with those who underwent MP-VATS procedures. We analyzed the baseline characteristics, perioperative data, and postoperative outcomes, and illustrated four special techniques depending on the situation: flexible hook electrocautery, hilum-first technique, application of Satinsky vascular clamp, and staged closure of bronchial stump method. RESULTS: We classified 170 consecutive patients undergoing thoracoscopic anatomic resection into SP and MP groups, which had significant between-group differences in operation time and overall complication rate (P = 0.037 and 0.018, respectively). Compared to the MP-VATS group, the operation time of SP-VATS was shorter, and the conversion rate of SP-VATS was relatively lower (3.1% vs. 10.5%, P = 0.135). The most common complication was prolonged air leakage (SP-VATS, 10.8%; MP-VATS, 2.9%, P = 0.045). CONCLUSIONS: For chronic inflammatory lung disease, certain surgical techniques render SP-VATS anatomic resection feasible and safe with a lower conversion rate.

Supplemental breast cancer-screening ultrasonography in women with dense breasts: a systematic review and meta-analysis.

BACKGROUND: Mammography is not effective in detecting breast cancer in dense breasts. METHODS: A search in Medline, Cochrane, EMBASE and Google Scholar databases was conducted from January 1, 1980 to April 10, 2019 to identify women with dense breasts screened by mammography (M) and/or ultrasound (US). Meta-analysis was performed using the random-effect model. RESULTS: A total of 21 studies were included. The pooled sensitivity values of M alone and M + US in patients were 74% and 96%, while specificity of the two methods were 93% and 87%, respectively. Screening sensitivity was significantly higher in M + US than M alone (risk ratio: M alone vs. M + US = 0.699, P < 0.001), but the slight difference in specificity was statistically significant (risk ratio = 1.060, P = 0.001). Pooled diagnostic performance of follow-up US after initial negative mammography demonstrated a high pooled sensitivity (96%) and specificity (88%). The findings were supported by subgroup analysis stratified by study country, US method and timing of US. CONCLUSIONS: Breast cancer screening by supplemental US among women with dense breasts shows added detection sensitivity compared with M alone. However, US slightly decreased the diagnostic specificity for breast cancer. The cost-effectiveness of supplemental US in detecting malignancy in dense breasts should be considered additionally.

A Rare Instance of Primary Oncocytic Schneiderian Papilloma of Middle Ear and Eustachian Tube With a Combined Trans Oto and Nasal Approach Resection.

Oncocytic Schneiderian papillomas are rare tumours which usually arise in the sinonasal region. This paper presents, to the authors' knowledge, the first reported case of oncocytic Schneiderian papilloma arising primarily from the middle ear and eustachian tube. The resection of the tumor was performed with an endoscopic approach of combined trans oto and nasal. Oncocytic Schneiderian papilloma in the middle ear and eustachian tube is extremely rare as a primary lesion and challenging to manage. Very few documents have provided guide of resection using the endoscopic approach when this tumor extends to involve the eustachian tube. Our study illustrates that the endoscopic approach of combined trans oto and nasal is a good choice for tumor resection of middle ear and eustachian tube.