Objective:To study the characteristics and influencing factors of coping styles of clinical ophthalmic interns under psychological stress, so as to provide scientific basis for promoting the mental health development of medical students.Methods:In 2019, 103 students of Sun Yat-sen University who participated in clinical practice of ophthalmology were investigated by cluster sampling with general situation questionnaire and simple coping style questionnaire. The database was established by Epidata, and the data was statistically analyzed by SPSS 25.0 software.Results:The scores of positive coping and negative coping were (1.70±0.10) and (1.30±0.05) respectively, which were all lower than the norm ( P < 0.001). The scores of non first time practice students were 0.087 points higher than those of first time practice students; the scores of eight-year students were 0.124 points higher than those of five-year students; the scores of positive coping increased by 0.015 points for each level of family income increase. Men scored 0.027 points higher than women in negative coping scores; eight-year students scored 0.053 points lower than five-year students in negative coping scores; family income increased by one grade, negative coping scores decreased by 0.017 points; rural registered residence students scored 0.035 points higher than urban registered residence students in negative coping scores; non first practice students scored 0.074 points higher than the first practice students in negative coping scores. Conclusion:Educators should pay close attention to the coping styles of clinical ophthalmic interns, carry out mental health education and guidance of coping methods according to the characteristics of different groups, take effective measures to improve students' stress coping ability and promote the smooth development of clinical practice in ophthalmology.

This study combines the ophthalmological postgraduate teaching practice with undergraduate clinical clerkship practice, which is called as "dual practice model". In the clinical clerkship teaching of ophthalmology, the postgraduates serve as teaching assistants and cooperate with senior doctors to carry out clinical teaching activities, implementing the "dual practice" ophthalmology clinical clerkship model. In order to improve both the quality of clinical clerkship teaching and the teaching ability for the postgraduates, we have made preparation before clerkship, planning during clerkship, and feedback after clerkship to improve the teaching.

Objective To investigate the distribution of B cells in both tumor and non-tumor tissues of gastric cancer patients,analyze their phenotypic characteristics and explore the impact on T cell proliferation.Methods Immunohistochemical staining was utilized to detect the expression of B cell surface marker CD 19 in tumor and non-tumor tissues from 33 gastric cancer patients.The expression levels of chemokine receptors and immunoglobulin molecules on B cells in both tumor and non-tumor tissues were measured using flow cytometry.Chemotaxis experiments were conducted to examine the role of the CXCL12-CXCR4 axis in B cell chemotaxis.B cells isolated and purified from both tissue types were co-cultured with autologous peripheral T cells to assess their effect on T cell proliferation.Results There were significantly more B cells infiltrated in tumor tissues than those infitrated in the non-tumor tissues of gastric cancer patients(P＜0.01),and CXCR4 was highly expressed on tumor-infiltrating B cells compared with B cells derived from non-tumor tissues(P＜0.05).The Cancer Genome Atlas(TCGA)analysis indicated that the expression level of CXCL12 in tumor tissues was positively correlated with the expression level of CD19 in gastric cancer patients(r=0.15,P＜0.01).And the expression level of CXCL12 in tumor tissues of the gastric cancer patients was also positively correlated with the number of B cells infiltrated in tumor tissues.Chemotaxis experiments confirmed that the CXCL12-CXCR4 axis was involved in promoting B cell chemotaxis(P＜0.05).Although B cells in tumor and non-tumor tissues had similar levels of IgM,IgG,and IgA expression,tumor-infiltrating B cells significantly inhibited the proliferation of T cells when compared with B cells derived from non-tumor tissues(P＜0.01).Conclusion There are more B cells infiltrated in gastric cancer tissues,which may be recruited to tumor tissues through the CXCL12-CXCR4 axis,and then inhibit T cell proliferation to promote the progression of gastric cancer.

Phenylalanine ammonia-lyase (PAL) is the key entry enzyme of plant phenylpropanoid pathway. It plays an important role in the biosynthesis of podophyllotoxin, an anti-tumor lignan that is currently produced from its main natural source Sinopodophyllum hexandrum (Royle) Ying. In this study, we cloned the gene ShPAL encoding phenylalanine ammonia-lyase by RT-PCR from the root of S. hexandrum ecotype inhabited in the Aba' district, Sichuan, based on its public SRA transcriptome data-package. Bioinformatics analyses showed that the ShPAL-encoded protein is composed of 711 amino acids, contains the conserved domains of PAL, and has the signature motif within the active center of aromatic ammonia-lyases. Moreover, ShPAL protein was predicted to have a secondary structure mainly composed of α-helix and random coil, a typical 'seahorse' shape monomer tertiary structure, and a homologous tetramer three-dimensional structure by Swiss-Modelling. The phylogenetic lineage analysis indicated ShPAL was of the highest sequence identity and the shortest evolutionary distance with the PAL of Epimedium sagittatum from the same Berberidaceae family. Subcellular localization experiments showed that ShPAL protein was mainly distributed in the cytoplasm, despite of a minority on the endoplasmic reticulum membrane. Furthermore, ShPAL protein was recombinantly expressed in Escherichia coli and purified by histidine-tag affinity chromatography. Its enzymatic activity was determined up to 20.91 U/mg, with the optimum temperature of 41 ℃ and pH of 9.0. In contrast, the enzyme activity of its F130H mutant decreased by about 23.6%, yet with the same trends of change with temperature and pH, confirming that phenylalanine at this position does affect the substrate specificity of PAL. Both the wild type and the mutant have relatively poor thermostability, but good pH-stability. These results may help to further investigate the regulatory role of PAL in the process of podophyllotoxin biosynthesis and advance the heterologous synthesis of podophyllotoxin to protect the germplasm resource of S. hexandrum. They also demonstrate that ShPAL has a potential application in biochemical industry and biomedicine.
Phenylalanine Ammonia-Lyase/metabolism* ; Podophyllotoxin ; Phylogeny ; Cloning, Molecular