The impact of self-concept and college involvement on the first-year success of medical students in China.

Students' first-year academic success plays a critical role on their overall development in college, which implies the need to concentrate on identifying ways to improve students' first-year academic success. Different from most research on the subject, this study attempted to combine the sociological perspective of college impact with a psychological perspective to synthetically explore the causal relationship of specific types of self-concept and college involvement with academic success of medical students. A longitudinal study was conducted using 519 matriculates at a medical university in mainland China. We conducted the Cooperative Institutional Research Program freshmen survey and the Your First College Year survey to collect data of the pre-college and college academic and social self-concept, college involvement components, and some input characteristics. The academic success was measured by the first-year grade point average. A pathway analysis was conducted and showed the following results. Having high academic self-concept, being engaged in class and putting effort in homework or study directly contributes to increasing college achievement. Students' pre-college achievement and self-concept, faculty interaction, and homework involvement positively affected students' college academic self-concept development, which indirectly improved average grade point. These findings contribute to our understanding of a student's ability to interact with his or her collegiate environment and to experience academic success.

Predictors of first-year GPA of medical students: a longitudinal study of 1285 matriculates in China.

BACKGROUND: Although medical education has developed rapidly in the last decade, and the National College Entrance Examination (NCEE) is used as the "gold standard" for admission to medical college in mainland China, there is a lack of literature regarding the influence of NCEE score and other factors on the academic performance of medical students. This study aimed to examine potential predictors of first-year grade point average (GPA) for medical students. METHODS: This study included 1,285 students who matriculated at a first-tier medical university in mainland China in 2011. The precollege motivational attitudes for each matriculate were investigated via questionnaire. A hierarchical linear model was fitted to regress first-year GPA on a 100-point scale on NCEE score and other student-level and major-level characteristics. RESULTS: NCEE score was a significant predictor of both within-major and between-major variation of first-year GPA for medical students. Majors with higher mean NCEE scores had higher mean GPAs, and higher GPAs were observed among those individuals with higher NCEE scores after controlling for major-level characteristics. First-year GPA differed by certain individual socio-demographic variables. Female students had a 2.44-higher GPA on average than did male students. NCEE repeaters had a 1.55-lower GPA than non-repeaters. First-year GPA was associated negatively with parental income but positively with academic self-concept. CONCLUSIONS: NCEE score is an important predictor of the first-year GPA of medical students, but it is not the sole determinant. Individual socio-demographic characteristics and major-level characteristics should be taken into account to understand better and improve the first-year GPA of medical students.

B-cell epitope KT-12 of enterohemorrhagic Escherichia coli O157:H7: a novel peptide vaccine candidate.

Enterohemorrhagic Escherichia coli (EHEC) O157:H7 is associated with hemorrhagic colitis, thrombotic thrombocytopenic purpura, and hemolytic-uremic syndrome in humans. B-cell epitopes of intimin γ from EHEC O157:H7 were predicted and synthesized for evaluating their immunogenicity and protective effect and for screening a novel synthetic peptide vaccine. In the present study, five B-cell epitopes of IntC300 were predicted by Hopp-Woods, Chou-Fasman, Karplus-Schulz, Emini, Jameson-Wolf and Kolaskar-Tongaonakar analysis. One of them, KT-12 (KASITEIKADKT) was coupled with keyhole limpet hemocyanin, and used to immunize BALB/c mice three times by subcutaneous and intranasal injection. Mouse serum titers of IgG and IgA were assessed by indirect ELISA. Oral inoculation of EHEC O157:H7 resulted in infection and death of the mice. It was found that B-cell epitopes are located within or near the peptide segments 658-669, 711-723, 824-833, 897-914, 919-931. Both subcutaneous and intranasal immunization induced higher concentrations of IgG antibodies, as detected by indirect ELISA, and nasal-mucosal immunization induced the production of high concentrations of IgA antibodies. After infection with a lethal dose of EHEC O157:H7, the survival rate of mice that had received subcutaneous immunization was not significantly different from that of the control group (P > 0.05). On the other hand, mice that received intranasal immunization showed a better survival rate than the group that received subcutaneous immunization (P < 0.05). The synthesized antigenic peptide KT-12 induced mice to produce higher concentrations of IgG and IgA after immunization, but only intranasal immunization of KT-12 succeeded in protecting most mice from infection with EHEC O157:H7. This study suggests that the synthesized antigenic peptide KT-12 is be a potential vaccine candidate against EHEC O157:H7.

[Detection of the Salmonella invasion gene invA using molecular beacon probe].

OBJECTIVE: To detect Salmonella invasion gene invA. METHODS: The invA gene of Salmonella was amplified with PCR reaction system containing the molecular beacon probe labeled with 6-carboxy fluorescein (6-FAM) at its 5' end and with (4-dimethylaminophenylazo)benzoic acid (DABCYL) at its 3' end, and the fluorescence signal was read at the end of PCR. RESULTS: The fluorescence values of S.enteritidis, S. paratyphi A, S. paratyphi B, S.typhi antigen H, S.typhi, and enteroinvasive E.coli were 161.6, 104.5, 85.9, 83.1, 94.8 and 46.1 respectively. The results of PCR of Salmonella was consistent with that of agarose gel electrophoresis. CONCLUSION: PCR with fluorogenic molecular beacon probe is rapid, specific, sensitive, and convenient for detecting Salmonella with invA gene.

Application of nanotechnology in biomedical sciences.

Nanotechnology, a new research field that holds enormous prospects in the 21th century, has by now gained wide application in biomedical sciences, and consequently gives rise to two new cross-disciplines, nanobiology and nanobiomedicine. The authors provide a brief summarization of the progress so far achieved in these two new disciplines.

Polyphosphate kinase 1 is required for the pathogenesis process of meningitic Escherichia coli K1 (RS218).

AIM: Polyphosphate kinase 1 (PPK1), encoded by the ppk1 gene, is one of the major enzymes to reversibly catalyze the synthesis of polyphosphate (poly P) from the terminal phosphate of ATP. Poly P confers resistance to stress in a number of bacterial species but its role in the virulence of meningitic bacterial pathogens is unknown. The aim of this study was to determine the role of PPK1 in the pathogenesis of Escherichia coli meningitis. MATERIALS & METHODS: An isogenic in-frame ppk1 deletion mutant (PD44) of E. coli K1 strain E44 was constructed and characterized. Human brain microvascular endothelial cells and neonatal rats were used as the in vitro and in vivo models, respectively, to evaluate bacterial adhesion/invasion and the abilities of bacteria crossing the blood-brain barrier (BBB) to cause meningitis. The survival of PD44 and E44 under osmotic and acid stress conditions were also examined. RESULTS: Poly P levels in E44 were clearly higher than those in PD44, especially at the stationary phase (SP). The ppk1 deletion mutant PD44 also showed poor survival rates during osmotic shock and acidic challenge, which the bacteria would face during pathogenesis. In vitro and in vivo assays revealed that PD44 was defective in bacterial adhesion and translocation across the BBB. By using the Evans blue method, we found that E44-induced permeability of the BBB in neonatal rats was significantly higher than that of the animals infected with PD44. Cytokine ELISA results showed that the TNF-α and IL-1ß levels in the serum and brain tissues of the neonatal rats infected with PD44 were lower than that of the E44 group. A more obvious meningeal inflammation could be observed in the brain tissues of the rats infected with E44 when compared with that of the PD44 group by histopathological examination. Furthermore, the mRNA expression of IbeR, which is an RpoS-like regulator contributing to the SP regulation in E44, was found to be decreased in PD44 when compared with the parent strain. PD44 was also deficient in mRNA expression of the invasin IbeA, the adhesin FimH and the outer member protein A, which contributes to E44 penetration across BBB and resistance to the stimulations of low pH and high osmolarity. CONCLUSION: These results indicate that ppk1 plays an important role in stress adaption and virulence in meningitic E. coli K1 strain E44, and controls the relevant phenotypes by modulating the expression of the SP regulatory gene ibeR and the virulence genes ibeA, fimH and ompA.

[Gene cloning, prokaryotic expression and functional evaluation of intimin from enterohemorrhagic Escherichia coli O157:H7].

OBJECTIVE: To obtain highly purified intimin encoded by the eae gene and study its adhesion activity. METHODS: The eae gene was amplified from enterohemorrhagic Escherichia coli O157:H7 (EHEC) chromosome by PCR and cloned into pMD19-T vector. The eae gene was cut from pMD19-T vector and subcloned into the prokaryotic expression plasmid pET28a(+), and expressed in E.coli BL21(DE3). The recombinant protein was purified with Ni(2+)-chelating affinity chromatography followed by identification with SDS-PAGE and Western blotting. The purified intimin was detected by immunofluorescence staining to test its adhesion. RESULTS: The 2805-bp eae gene fragment was obtained, and the recombinant expression plasmid pET28a(+)-eae was successfully expressed in E.coli BL21 (DE3). The molecular weight of the recombinant protein was 97 000. Purified recombinant intimin was recognized by rabbit anti-O157 antiserum, and bound to the surface of HEp-2 cells as revealed by immunofluorescence staining. CONCLUSION: Highly purified and immunoreactive intimin has been successfully obtained, which can adhere to the surface of HEp-2 cells. The acquisition of recombinant intimin provides the basis for studying its interaction with the host receptors during EHEC O157:H7 infection.