Objective To investigate the present situation of social practice of medical students and to analyze its influencing factors, to provide scientific basis for improving students' participation and quality of participation. Methods The survey of 374 medical students of Peking University was conducted in July 2015, using a self-made questionnaire including the cognition of social practice, social practice experience, etc. The sample of students was selected by cluster sampling from 2007 to 2014 grades. There were 370 valid questionnaires; the effective response rate was 98.8%. IBM SPSS statistics 20.0 was used to make statistical analysis and data were processed by description analysis and ordinal regression analysis. Results 328 persons (88.6%) affirmed the importance of social practice. However, 120 students (32.4%) did not take part in social practice in last school year. There were 357 students participating in social practice during the university. 341 students (95.5%) achieved and even exceeded the practice expectations. Secondly, it depicted the influence factors of students' participation in social practice, including family economic factor, former social practice experience before entering university, and the personal factors which included grade, overall rating scores points, and position. Moreover, factors influencing the quality of their participation included the preparation time of social practice, the output, the awards and the guide teacher. Conclusions It showed that the situation of medical students' participation in social practice was not satisfactory. It sug-gested schools set social practice credit requirements, and strengthen the freshmen education, to establish students' inertia effect of social practice.

A rapid resolution liquid chromatography coupled with quadrupole-time-of-flight mass spectrometric (RRLC-Q-TOF-MS) method was established and optimized for the analysis of pharmacokinetic behavior of ginsenoside Rb2 in rats by intravenous injection administration.The metabolism of ginsenosides Rb2 in vivo rat was also explored.In the experiment,Agilent SB C18 column was selected for the sample separation with 0.1％ aqueous formic acid solution as mobile phase (A) and acetonitrile as mobile phase (B) at a flow rate of 0.2 mL/min,and the injection volume was set to 5 μL.Q-TOF-MS was carried out in electron pray ionization (ESI) negative ion mode.The limit of quantification (LOQ,S/N =10) and limit of detection (LOD,S/N=3) were 0.10 and 0.08 μg/mL,respectively,and the linear range was 0.1-1.26 μg/mL.The experiment results showed that the concentration-time profile of ginsenoside Rb2 conformed to a two-compartment pharmacokinetic model after intravenous administration for rats.The mean plasma elimination half-lives were (23.58±1.10) min (t1/2α),(1306.55±147.23) min (t1/2β) for Rb2.By analyzing the urine of rats after intravenous administration and the fecal samples after oral administration of ginsenoside Rb2,it was found that the metabolites were M6,M2 (CY),F2,and C-K.

Genome miniaturization drives key evolutionary innovations of adaptive traits in verte-brates,such as the flight evolution of birds.However,whether similar evolutionary processes exist in invertebrates remains poorly understood.Derived from the second-largest animal phylum,scallops are a special group of bivalve molluscs and acquire the evolutionary novelty of the swimming lifestyle,providing excellent models for investigating the coordinated genome and lifestyle evolution.Here,we show for the first time that genome sizes of scallops exhibit a generally negative correlation with loco-motion activity.To elucidate the co-evolution of genome size and swimming lifestyle,we focus on the Asian moon scallop(Amusium pleuronectes)that possesses the smallest known scallop genome while being among scallops with the highest swimming activity.Whole-genome sequencing of A.pleuronectes reveals highly conserved chromosomal macrosynteny and microsynteny,suggestive of a highly con-tracted but not degenerated genome.Genome reduction of A.pleuronectes is facilitated by significant inactivation of transposable elements,leading to reduced gene length,elevated expression of genes involved in energy-producing pathways,and decreased copy numbers and expression levels of biomineralization-related genes.Similar evolutionary changes of relevant pathways are also observed for bird genome reduction with flight evolution.The striking mimicry of genome miniaturization underlying the evolution of bird flight and scallop swimming unveils the potentially common,pivotal role of genome size fluctuation in the evolution of novel lifestyles in the animal kingdom.