The glycoprotein spike (S) on the surface of SARS-CoV-2 is a determinant for viral invasion and host immune response. Herein, we characterized the site-specific N-glycosylation of S protein at the level of intact glycopeptides. All 22 potential N-glycosites were identified in the S-protein protomer and were found to be preserved among the 753 SARS-CoV-2 genome sequences. The glycosites exhibited glycoform heterogeneity as expected for a human cell-expressed protein subunit. We identified masses that correspond to 157 N-glycans, primarily of the complex type. In contrast, the insect cell-expressed S protein contained 38 N-glycans, completely of the high-mannose type. Our results revealed that the glycan types were highly determined by the differential processing of N-glycans among human and insect cells, regardless of the glycosites’ location. Moreover, the N-glycan compositions were conserved among different sizes of subunits. Our study indicate that the S protein N-glycosylation occurs regularly at each site, albeit the occupied N-glycans were diverse and heterogenous. This N-glycosylation landscape and the differential N-glycan patterns among distinct host cells are expected to shed light on the infection mechanism and present a positive view for the development of vaccines and targeted drugs.

Background This study aimed to evaluate the effectiveness and efficiency of PBL–CBL combined teaching in thyroid surgery and make observations from the students’ perspectives, based on their satisfaction with the learning process. Methods We prospectively enrolled 354 fourth-year students majoring in clinical medicine, along with 232 residents, from September 2014 to June 2019. These participants were randomly allocated into either the combined PBL–CBL teaching group or the traditional lecture-based classroom group to attend a course about thyroid nodules. Both pre- and post-class quizzes were conducted. An anonymous questionnaire was also administered to both groups to evaluate the students’ perceptions and experiences. We compared the two teaching methods among all the students as well as with the fourth-year students and residents in subgroups. Results The traditional group’s pre-class quiz scores were significantly higher than the PBL–CBL group’s (as determined by a two-tailed t-test at a 95% confidence interval, T = 16.483, P < 0.001). After class, in the PBL–CBL group, the mean total quiz score and the basic knowledge and case analysis scores increased significantly (P < 0.001). The PBL–CBL group’s performance improvement was significantly higher than the traditional group’s (increasing from 52.76 to 70.51 vs. from 67.03 to 71.97). Furthermore, the scores for learning motivation, understanding, student–teacher interaction, the final examination, communication skills, clinical thinking skills, self-learning skills, teamwork skills, and knowledge absorption, as measured by the survey, were significantly higher in the PBL–CBL group than in the traditional group (P < 0.001). Meanwhile, the survey scores representing the amount of students’ free time the course consumed were significantly lower in the PBL–CBL group than in the traditional group (P < 0.001). Conclusions PBL combined with CBL may be an effective method for improving medical students’ and residents’ performance and enhancing their clinical skills.

SummaryThe glycoprotein spike (S) on the surface of SARS-CoV-2 is a determinant for viral invasion and host immune response. Herein, we characterized the site-specific N-glycosylation of S protein at the level of intact glycopeptides. All 22 potential N-glycosites were identified in the S-protein protomer and were found to be preserved among the 753 SARS-CoV-2 genome sequences. The glycosites exhibited glycoform heterogeneity as expected for a human cell-expressed protein subunits. We identified masses that correspond to 157 N-glycans, primarily of the complex type. In contrast, the insect cell-expressed S protein contained 38 N-glycans, primarily of the high-mannose type. Our results revealed that the glycan types were highly determined by the differential processing of N-glycans among human and insect cells. This N-glycosylation landscape and the differential N-glycan patterns among distinct host cells are expected to shed light on the infection mechanism and present a positive view for the development of vaccines and targeted drugs.

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Background: More and more automated efficient ultrasound image analysis techniques, such as ultrasound-based computer-aided diagnosis system (CAD), were developed to obtain accurate, reproducible, and more objective diagnosis results for thyroid nodules. So far, whether the diagnostic performance of existing CAD systems can reach the diagnostic level of experienced radiologists is still controversial. The aim of the meta-analysis was to evaluate the accuracy of CAD for thyroid nodules’ diagnosis by reviewing current literatures and summarizing the research status. Methods: A detailed literature search on PubMed, Embase, and Cochrane Libraries for articles published until December 2018 was carried out. The diagnostic performances of CAD systems vs radiologist were evaluated by meta-analysis. We determined the sensitivity and the specificity across studies, calculated positive and negative likelihood ratios and constructed summary receiver-operating characteristic (SROC) curves. Meta-analysis of studies was performed using a mixed-effect, hierarchical logistic regression model. Results: Five studies with 536 patients and 723 thyroid nodules were included in this meta-analysis. The pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, and diagnostic odds ratio (DOR) for CAD system were 0.87 (95% confidence interval [CI], 0.73–0.94), 0.79 (95% CI 0.63–0.89), 4.1 (95% CI 2.5–6.9), 0.17 (95% CI 0.09–0.32), and 25 (95% CI 15–42), respectively. The SROC curve indicated that the area under the curve was 0.90 (95% CI 0.87–0.92). The pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, and DOR for experienced radiologists were 0.82 (95% CI 0.69–0.91), 0.83 (95% CI 0.76–0.89), 4.9 (95% CI 3.4–7.0), 0.22 (95% CI 0.12–0.38), and 23 (95% CI 11–46), respectively. The SROC curve indicated that the area under the curve was 0.96 (95% CI 0.94–0.97). Conclusion: The sensitivity of the CAD system in the diagnosis of thyroid nodules was similar to that of experienced radiologists. However, the CAD system had lower specificity and DOR than experienced radiologists. The CAD system may play the potential role as a decision-making assistant alongside radiologists in the thyroid nodules’ diagnosis. Future technical improvements would be helpful to increase the accuracy as well as diagnostic efficiency.