Influence of critical thinking disposition on the learning efficiency of problem-based learning in undergraduate medical students.

BACKGROUND: Problem-based learning (PBL), a pedagogical approach, is widely accepted in medical education. Manipulated by many factors, the internal motivation of learner is the most crucial determinant that affects the nature of the outcome, in which the influences of critical thinking (CT) remained elusive. METHODS: One hundred two third-year undergraduate medical students at Peking University were involved in this study. A Chinese version of the Critical Thinking Disposition Inventory (CTDI-CV) was used to assess the CT disposition, and the performance scores of students in PBL tutorials were compiled. A parametric bivariate correlation analysis was performed between the students' CT scores and their PBL average scores. The PBL scores were compared between the strong and weak CT disposition groups using independent t-test. The analysis of numerical data was conducted using SPSS 16.0. RESULTS: CT disposition of third-year undergraduate medical students at Peking University was at a positive level, with an average score of 297.72. The total CT scores had a positive correlation with the scores of the PBL performance and its five dimensions significantly. In the majority, students with Strong-CT disposition obtained higher scores in PBL tutorials compared with students with Weak-CT disposition. The performance of these two groups was significantly different in the Late-Half but not in the Early-Half PBL tutorials. Furthermore, a significant improvement was observed in the students with strong CT but not weak CT dispositions. CONCLUSION: CT disposition positively correlates to a students' PBL performance. Students with stronger CT dispositions perform better in the PBL process and obtain higher scores. Our work suggested that the open-mindedness of the CT disposition is the primary factor that determines the improvement of the preparation dimensions in the PBL process.

[Organotypic cerebral slice culture and the course of neuronal development in it].

OBJECTIVE: To establish a method of organotypic cerebral culture. So as to pave the way for building some neurodegenerative disease models. METHODS: Organotypic cerebral cultures were prepared from prefrontal brain of neonatal SD rats. After culturing 7 to 14 days, 3 weeks, 4 weeks and 8 weeks, respectively, cerebral slices were fixed, dehydrated and sectioned in cryostat. The sections proceeded with Nissl staining and neurofilament high molecular weight (NFH) immunohistochemical staining. The difference was observed between controls and cultured slices using normal rats as controls. RESULTS: Nissl staining showed that pyramidal neurons in cultured slices were increased in volume and lightened in staining. The delaminating construction was clear from 1 to 4 weeks after culturing. In cultured slices, immunohistochemical staining showed that NFH positive pyramidal cells appeared on layer V on the tenth day and on both layers V and III after culturing 12 days. In the control group, NFH positive pyramidal cells appeared on layer V in 5-day-old rats, and appeared on both layers V and III in over 3-week-old rats. In cultured cerebral slices, the number of pyramidal neurons on layer V in M1 area was invariable from 12 days to 2 months. CONCLUSION: Orgaotypic cerebral culture can be used to study postnatal development for neocortex and build some in vitro models for neurodegenerative diseases.

[Establishment of the organotypic model of amyotrophic lateral sclerosis from the SD rats' spinal cord].

OBJECTIVE: To establish an in vitro model of amyotrophic lateral sclerosis (ALS) from the organotypic culture of SD rats' lumber spinal cord induced by the mitochondrial inhibitor,malonate sodium. METHOD: The lumber spinal cord prepared from the 6-day-old SD rats was cut into 350 microm coronarily, cultured on the Millicell-CM inserts which make the spinal cord culturing on the interface between air and fluid. First, the optimum malonate sodium dose was determined by adding different doses into the medium and counting the living motor neuron numbers by using immuno-histochemistry staining. Second, the ALS model was established as following: the cultures were divided into the malonate groups and the control groups, adding 2 mmol/L sodium malonate into the medium of the malonate groups an the 3rd day, continue culture to 12 days with this concentration; the control groups culturing without malonate. RESULTS: The organotypic characteristics are still kept till the end of the curlturing. After adding the sodium malonate, counting the number of motor neurons and interneurons on the different spinal slices in the different groups, the number of motor neuron in the cultured spinal cord was less than control (11.00+/-2.45 vs 15.29+/-1.70 per semislice at the end of the culturing, P<0.01), but the difference of the interneuron was not significant. CONCLUSION: The amyotrophic lateral sclerosis model is successful with selective injury of motor neuron, and this model can be used for the exploring of the theraptic method and its pathogenesis.

[Ion channels on T lymphocyte].

There is increasing evidence to show that ion channels on lymphocytes play a very important role in the regulation of immune functions. In T lymphocytes, there are three types of ion channels on cell membrane: Ca2+, K+ and Cl- channel. The influx of Ca2+ into T lymphocyte through Ca2+ channel (CRAC) may act as a second messenger to activate T lymphocyte when antigen binds to the receptor (TCR). The efflux of K+ from T lymphocyte through the K+ channel contributes to the formation of T cell membrane potential. The level of the membrane potential may affect the influx of Ca2+ into T cells. Therefore, the activation and the functions of T cell can be regulated by K+ channel indirectly. Cl- channel in T lymphocyte was found in recent years and it is probably involved in the regulation of cell volume. The recent progress on ion channels in T lymphocyte is summarized briefly in the present paper.

Inhibition of poly(ADP-ribose) polymerase activity by Bcl-2 in association with the ribosomal protein S3a.

We screened a human lymphocyte cDNA library using the yeast two-hybrid system and an automodification domain of PARP as a probe. The DNA sequence of an isolated clone (clone 3-9) was identical to the partial cDNA sequence of the human ribosomal protein S3a. We confirmed that PARP interacts with clone 3-9 by performing binding studies using a GST-3-9 fusion protein as bait. We also demonstrated that native S3a in nuclear extracts of HL-60 cells interacts with the automodification domain of PARP and that PARP from nuclear extracts is coprecipitated with the GST-3-9 fusion protein. Furthermore, we demonstrated that Bcl-2 interacts with PARP in association with S3a and that the interaction of S3a and Bcl-2 with PARP causes a significant decrease in PARP activity. Since Bcl-2 failed to inhibit PARP activity in the absence of S3a, we suggest that Bcl-2 together with S3a prevents apoptosis probably by inhibiting PARP activity.