Objective To investigate the MRI manifestations of pilomyxoid astrocytoma (PMA)at unusual sites and differential diagnosis in children.Methods The clinical and MRI data from 6 cases of PMA with atypical locations confirmed by surgery and pathology were analyzed retrospectively.Results 2 cases located at cerebral hemisphere,1 case at tegmentum mesencephali,1 case at medulla and 2 cases at cerebellar hemisphere.There were 4 cases of solid tumor and 2 case belonged to cystic-solid mass.5 cases were round or oval and 1 case was shallow lobulated.In addition,there were 2 cases with hemorrhage and 2 cases with peritumoral edema.T1WI showed hypointensity,isointense or slightly hyperintense while T2WI and fluid attented inversion recovery (FLAIR)exhibited isointensity or hyperintensity.After contrast administration,there were 3 cases of obvious multi-ring enhancement,of which 1 case showed astral enhancement of the mural nodules and the other 3 cases showed mild homogeneous or inhomogeneous enhancement.4 cases showed non-enhanced areas in the solid parts.No signs of leptomeningeal dissemination were found in all 6 cases.Conclusion The PMA at unuaual sites in children is primarily solid or cystic-solid,and the image manifestations of plain scan are varied.After enhancement,the tumors show obviously multi-circular enhancement and mild homogeneous or inhomogeneous enhancement could be observed,no enhancement areas are visible in the solid parts.It is noteworthy to distinguish this astrocytoma from other lesions.

Objective To understand the situation of college students' knowledge, attitude and practice (KAP) of innovation and entrepreneurship activities and analyze their influencing factors, in order to provide a scientific basis for further promotion of innovation and entrepreneurship activities. Methods A self-administered questionnaire survey using cluster sampling method was conducted among 850 undergraduates in a medical university in May, 2018. The demographic characteristics and questions pertaining to the KAP of innovation and entrepreneurship activities were collected, The weighted scores of KAP were calculated using the Delphi method. Chi-square test, multivariate logistic regression and linear regression analysis were used to analyze the data. Results A total of 850 questionnaires were sent out and 800 valid questionnaires were collected. The average scores and pass rates for the knowledge, attitude and practice of the 800 college students were (0.54 ±0.14), 38.1％; (0.56 ±0.23), 51.5％; and (0.37 ±0.19), 12.6％, respectively. Knowledge: the pass rate for the concepts related to innovation and entrepreneurship was 70.5％, and the pass rate for the policies related to innovation and entrepreneurship was 17.2％. The pass rate of senior students and excellent students were higher than those of junior students and students of lower academic competence (P=0.000, P=0.004). Attitudes: the pass rate for attitude towards the relationship between innovation and entrepreneurship and personal development was 63.6％, the pass rate for attitudes towards participation in innovation and entrepreneurship was 49.8％, and the pass rate for attitudes towards the school continuing to carry out innovation and entrepreneurship related activities was 23.8％. Practice:the pass rates for participation in scientific research and academic activities and social practice , voluntary cultivation of innovation ability and self-employment were 8.5％, 62.9％, 11.9％and 27.3％, respectively. The pass rate of senior grades was higher than that of junior grades (P=0.001). Scores for knowledge and those of attitude are positively correlated. Scores for practice and those of knowledge and attitude are positively correlated. Conclusion The higher pass rates for medical college students' attitude toward innovation and entrepreneurship activities as compared to those for knowledge and practice indicates high eagerness toward participation in innovation and entrepreneurship activities; a high rate knowledge is conducive to the cultivation of attitudes and the improvement of participation in activities . Therefore , it is necessary to strengthen the efforts in carrying out innovation and entrepreneurship activities , improve publicity and education, and promote the awareness-raising of innovation and entrepreneurship.

β-defensin is a primary protein immune factor in channel catfish's (Ietalurus punetaus) resistance to pathogenic microorganisms. Its primary structure contains a signal peptide composed of 24 amino acid residues at the N-terminal and a mature peptide composed of 43 amino acid residues at the C-terminal. The mature peptide region is responsible for the biological activity of β-defensin. In the present study, a recombinant strain of Pichia pastoris that produces channel catfish β-defensin, was constructed to realize the biosynthesis of channel catfish β-defensin based on eukaryotic expression. First, the β-defensin gene "IPBD" was isolated from the skin of channel catfish by RT-PCR. After linking it with the expression vector pPICZA, pPICZA-IPBD was transferred into competent P. pastoris X-33 cells to obtain recombinant P. pastoris strains. The yeast transformants with multi-copy gene inserts were obtained by using the culture medium containing 1 000 μg/mL zeocin. Using BMM culture medium (without amino nitrogen culture medium) instead of BMMY culture medium (with amino nitrogen culture medium), the fermentation and culture conditions of the recombinant strain were optimized, and the optimal conditions for producing channel catfish β-defensin were determined as follows: the expression was induced for 96 h with 1.0% methanol at 28 °C , 250 r/min. Purified protein with molecular weight of 5.98 kDa was obtained by nickel affinity chromatography, and MALDI-TOF/TOF mass spectrometry proved that it was the expected recombinant IPBD. The antibacterial test results showed that the inhibitory rates of recombinant IPBD on Gram-positive Staphylococcus aureus and Listeria monocytogenes and Gram-negative Pseudomonas aeruginosa were 69.6%, 71.6% and 65.8%, respectively. This study provides a recombinant DNA technique for the development of small molecule natural antibacterial peptide from fish.