Objective To evaluate the opening level and optimal time window of the blood-brain barrier induced by adenosine A2 receptor agonist ( Lexiscan) via dynamic enhanced MRI. Methods Twen-ty New Zealand white rabbits were divided into experiment group ( group A, n=10) and control group ( group B, n=10) . Rabbits in group A were injected with Lexiscan and rabbits in group B were injected with physiological salt via ear vein, then the coronary scanning was performed. Contrast enhanced MRI was performed at different time points ( 5, 10, 15, 20 min, and then every 10 min, until 2 h) following the in-fusion of Gd-diethylene triamine pentaacetic acid (DTPA). The signal intensity (SI) of region of interest ( ROI) was measured and the percent enhancement of SI was calculated. Evens blue staining results in brain tissues were observed. Pair t test was used to analyze the data. Results The percent enhancement of SI in group A significantly increased to (40. 93±3.70)％ at 5 min, reached the maximum of (43.03±3.62)％ at 30 min, slowly decreased until 50 min, and got to a stable level at almost 80 min. At each time point, the per-cent enhancement of SI in group A was significantly higher than that in group B ( t values:6.88-20.28, all P<0. 05) . The staining was evident in group A. Conclusions Lexiscan can open blood-brain barrier tem-porarily and reversibly, and the optimal opening time window is 10-50 min post-injection.

Objective:To explore the effect of mini-clinical evaluation exercise (Mini-CEX) combined with simulation teaching + case-based learning (CBL) in pediatric clinical teaching.Methods:A total of 60 medical students who practiced in Department of Pediatrics, Affiliated Hospital of Jining Medical College from August 2019 to August 2020 were selected as the research objects. According to different teaching methods, they were divided into control group ( n=30) and observation group ( n=30). The control group received traditional teaching, and the observation group received Mini-CEX combined with simulated teaching + CBL. The assessment results, comprehensive ability of medical interview, critical thinking ability and teaching satisfaction of the two groups were compared. SPSS 20.0 was performed for t-test and Chi-square test. Results:The test scores and total scores of the observation group were significantly higher than those of the control group ( P<0.05). After teaching, the Mini-CEX scores, the CTDI-CV (critical thinking disposition inventory Chinese version) scores and the total scores of the two groups increased significantly, and the above scores were significantly higher in the observation group than the control group ( P<0.05). The scores of the teaching program satisfaction questionnaire in the observation group were significantly higher than those in the control group ( P<0.05). Conclusion:The application of Mini-CEX combined with simulation teaching + CBL in pediatric clinical teaching can help to cultivate the medical interview ability, clinical practice ability and critical thinking ability of interns, improve the examination results, and improve the teaching satisfaction.

Background The altered expressions of hippocampal N-methyl-D-aspartate (NMDA) receptors induced by benzo[ɑ]pyrene (BaP) causes short-term spatial learning and memory impairment in humans and animals, but whether BaP causes alterations of NMDA receptor subunits in other brain regions and the associated neurotoxic mechanism is still essentially unknown. Objective To observe the mRNA expressions of NR1, NR2A, and NR2B of NMDA receptor subunits in different brain regions in SD rat model with subchronic exposure to BaP, and to provide a basis for in-depth study of the mechanism of BaP-induced neurotoxicity. Methods Forty male SD rats were selected and randomly divided into a control group and 1.00, 2.50, and 6.25 mg·kg⁻¹ BaP exposure groups with 10 rats in each group. The exposure rats received intraperitoneal injection of BaP every other day for 90 d.The average latency to platform, the average total distance, and the duration spent in previous quadrant were measured by the Morris Water Maze. Real-time fluorescence quantitative PCR was used to detect the mRNA expressions of NR1, NR2A, and NR2B in hippocampus, cortex, cerebellum, and striatum of rats. Results The average latency to platform and the average total distance in the 2.50 and 6.25 mg·kg⁻¹ BaP groups were significantly prolonged compared with the control group (P<0.05), and the duration that rats spent in previous quadrant in the 6.25 mg·kg⁻¹ BaP group was significantly shortened (P<0.05). Compared with the control group, the mRNA expressions of NR1 and NR2B in the hippocampus in the 2.50 and 6.25 mg·kg⁻¹ BaP groups were significantly reduced (P<0.05), and the NR2A mRNA expression in the hippocampus in the 6.25 mg·kg⁻¹ BaP group was significantly reduced (P<0.05); the mRNA expressions of NR1 and NR2B in the cortical tissue in the 6.25 mg·kg⁻¹ BaP group were significantly reduced (P<0.05), and the mRNA expression of NR2A in the cortical tissue in the 1.00 mg·kg⁻¹ BaP group was reduced; the mRNA expression of NR2B in the cerebellar tissue in the 6.25 mg·kg⁻¹ BaP group was significantly reduced (P<0.05); there were no differences in the mRNA expressions of NMDA receptor subunits in the striatum tissue (P>0.05). Conclusion Subchronic BaP exposure can cause short-term spatial learning and memory impairment in rats, which may be related to the down-regulation of mRNA expressions of NR1, NR2A, and NR2B in hippocampus, changes of mRNA expressions of NR1, NR2A, and NR2B in cortical area, and the down-regulation of NR2B mRNA expression in cerebellum.