Longitudinal PBL in Undergraduate Medical Education Develops Lifelong-Learning Habits and Clinical Competencies in Social Aspects.

Problem-based learning (PBL) is popular in medical education in Japan. We wished to understand the influence of PBL on the clinical competence of medical residents, using self-assessment and observer assessment. Tokyo Women's Medical University (TWMU) implemented PBL longitudinally (long-time) for four years, and on this basis we analyzed whether long-time PBL education is useful for clinical work. A self-assessment questionnaire was sent to junior and senior residents who were alumni of several schools, and an observation-based assessment questionnaire to senior doctors instructing them. Respondents were asked if they had used the PBL process in daily clinical tasks, and if so in what processes. Senior doctors were asked whether TWMU graduates perform differently from graduates of other schools. TWMU graduates answered "used a lot" and "used a little" with regard to PBL at significantly higher rates than other graduates. As useful points of PBL, they mentioned extracting clinical problems, solving clinical problems, self-directed leaning, positive attitude, collaboration with others, presentation, doctor-patient relations, self-assessment, and share the knowledge with doctors at lower levels and students. Observer assessments of TWMU graduates by senior doctors represented them as adaptive, good at presenting, good at listening to others' opinions, practical, selfish, and eager in their instructional practice. Longitudinal PBL can be a good educational method to develop lifelong-learning habits and clinical competencies especially in terms of the social aspect.

Foregut endoderm is specified early in avian development through signal(s) emanating from Hensen's node or its derivatives.

In this study, the initial specification of foregut endoderm in the chick embryo was analyzed. A fate map constructed for the area pellucida endoderm at definitive streak-stage showed centrally-located presumptive cells of foregut-derived organs around Hensen's node. Intracoelomic cultivation of the area pellucida endoderm at this stage combined with somatic mesoderm resulted in the differentiation predominantly into intestinal epithelium, suggesting that this endoderm may not yet be regionally specified. In vitro cultivation of this endoderm for 1-1.5 day combined with Hensen's node or its derivatives but not with other embryonic structures/tissues elicited endodermal expression of cSox2 but not of cHoxb9, which is characteristic of specified foregut endoderm. When the anteriormost or posteriormost part of the area pellucida endoderm at this stage, whose fate is extraembryonic, was combined with Hensen's node or its derivatives for 1 day, then enwrapped with somatic mesoderm and cultivated for a long period intracoelomically, differentiation of various foregut organ epithelia was observed. Such epithelia never appeared in the endoderm associated with other embryonic structures/tissues and cultured similarly. Thus, Hensen's node and its derivatives that lie centrally in the presumptive endodermal area of the foregut are likely to play an important role in the initial specification of the foregut. Chordin-expressing COS cells or noggin-producing CHO cells transplanted into the anteriormost area pellucida of the definitve streak-stage embryo could induce endodermal expression of cSox2 but not of cHoxb9, suggesting that chordin and noggin that emanate from Hensen's node and its derivatives, may be involved in this process.

Facilitation of problem finding among first year medical school students undergoing problem-based learning.

BACKGROUND: Adaptation to problem-based learning (PBL) is a difficult process for high school graduates who are not used to self-directed learning, especially in the freshmen year of medical school. The difficulty includes finding problems from a given case. PURPOSE: Evaluate the effect of an intervention to facilitate case-based problem finding among medical school freshmen undergoing a PBL tutorial. METHODS: Medical school freshmen in 2000 (nonintervened group) and 2001 (intervened group) participated in the study. The intervened group received the modified problem-based program by (a) having briefings on the importance of problem finding, (b) encouragement by the tutors in problem finding, and (c) reinforcement using a self-assessment sheet. At the end of the year, the ability of students to extract problems from a short case was evaluated and compared with the nonintervened students. RESULTS: The intervened group extracted a significantly greater number of problems than the nonintervened group. When extracted problems were categorized, the intervened group was able to generate more questions in a greater number of specified categories. CONCLUSIONS: Interventions to foster problem finding significantly facilitated acquisition of problem extraction skills among young medical students.

Pre-gut endoderm of chick embryos is regionalized by 1.5 days of development.

In this study, we set out to test the ability of endoderm from 1.5-day-old chick embryos (just before digestive tube formation) to develop region-specific characteristics when cultured heterotopically. Various parts of the 1.5-day endoderm were cultured in combination with the flank somatic mesoderm of 3- to 3.5-day chick embryos, and these cultures were analyzed for the expression of several transcription factors and the differentiation of the endoderm. By 1.5 days of normal development, the transcription factors, which are expressed in specific digestive organs, cSox2, CdxA, and cHoxb9/a13 were already expressed in the endodermal cells of the presumptive areas of their later expression domains. When 1.5-day pre-gut endoderm was cultured for 14-15 days, it showed specific differentiation into appropriate organ structures. In general, the more anterior part of the pre-gut endoderm formed the more rostral digestive organ structures while the posterior part became the caudal gut. The differentiation of these regions of endoderm matches their normal fate as recently elucidated (Matsushita [1996a] Rouxs Arch. Dev. Biol. 205:225-231; Matsushita [1999] Dev. Growth Differ. 41:313-319). Expression of cSox2, CdxA, and cHoxb9/a13 in endoderm cultured for 4-5 days is also consistent with their normal fate. Thus, each part of the pre-gut endoderm appears to be already regionally committed to some extent, in accordance with its fate by 1.5 days of development.

Fate mapping study of the endoderm of the 1.5-day-old chick embryo.

Various portions of the endoderm between the levels of the first and the 10th somite of 1.5-day-old chick embryos were marked by local application of the vital dye Dil, and the fate of marked cells was analyzed after cultivation of the embryos for 2 days in vitro.The presumptive area of digestive tract ranging from the posterior pharynx to the jejunum was found to extend bilaterally from the midline of the 1.5-day embryo with a width two or three times as great as the distance between the midline and the lateral edge of the somite. Either side of this area contributed to the same side of the endodermal tube of digestive tract. The anterior and posterior portions generally contributed to the anterior and posterior regions of the digestive tract, respectively, and the cells originating from the portion farther from the midline took the more ventral and posterior position in the digestive tract endoderm. Most of the presumptive areas of the digestive organs in the endoderm of 1.5-day embryo were located in a more anterior position than those in the splanchnic mesoderm.

Chronological changes in the sucrase antigen-inducing activity and development of the regional identity in the intestinal mesoderm of the chick embryo.

Developmental changes in mesodermal activity to induce intestine-like differentiation expressing sucrase antigen in the endoderm and changes in endodermal reactivity to such an activity in the digestive tract of the chick embryo were analyzed. Digestive-tract endoderms of embryos at 3 days of incubation were highly responsive to the inductive effect of the 5 day duodenal mesenchyme, with the stomach endoderm lying nearest to the intestine having the highest reactivity. Endodermal reactivity decreased with increasing age. It was almost absent in the endoderm of the esophagus or proventriculus of 6 day embryos and in the endoderm of the gizzard of 7 day embryos. The activity of the mesoderm to induce intestine-like differentiation in 5 day gizzard endoderm was high in the 5-10 day duodenal mesenchyme, but was rarely found in 14 day duodenal mesenchyme. This activity was specific to intestinal mesenchymes, among which the duodenal mesenchyme had the highest activity in 5 day embryos. The 3 day intestinal mesenchyme may already have the inductive activity. The presumptive intestinal mesoderm of 1.5 day embryos seemed to have a slight or no activity, but it may have intestinal identity and may manifest a high inductive activity later.

Fate mapping study of the splanchnopleural mesoderm of the 1.5-day-old chick embryo.

Various portions of the splanchnopleural mesoderm lateral to the somites of 1.5-day chick embryos were marked in ovo by local injection of Dil, and the distribution of the labelled cells in the digestive-tract mesoderm formed after 3 days' reincubation was analysed. The presumptive area of the digestive organs was confined to bands of splanchnic mesoderm lying lateral to the somites, on both sides, with a width two or three times that between the midline of the embryo and the lateral edge of the somite. Each band generally contributed cells to its own side of the digestive-tract mesoderm, except for the region around the bile duct. The anterior and posterior portion of the pre-gut area contributed cells to the anterior and posterior region of the digestive tract, respectively, but label originating from the portion furthest from the somite took the more ventral and posterior position. Thus, the presumptive areas of the respective digestive organs were located anteroposteriorly in the same order as in the digestive tract with their boundaries lying oblique to the embryonic axis.

Regional difference in the responsiveness to the inductive influence of the gizzard mesenchyme among the endoderms of various small intestinal segments of the chick embryo.

The differentiation of the endoderms of duodenal, jejunal and ileal segments of the small intestine of 6 day old chick embryos cultured in recombination with the gizzard mesenchyme of 6 day chick embryos was examined. Only the duodenal endoderm differentiated in a mesenchyme-dependent fashion into gizzard-like mucous epithelium forming tubular glands that expressed no sucrase-antigen, while jejunal and ileal endoderms tended to become the sucrase-antigen-positive epithelium most likely according to their developmental fates. The analysis on the differentiation of the duodenal and gizzard endoderms in the presence of various digestive-tract mesenchymes confirmed that the duodenal endoderm had the tendency to differentiate into intestine-type and was different from the gizzard endoderm, which showed the differentiation tendency into gizzard-type. Thus, among the segments of small intestine, only the endoderm of duodenum that was situated next to the gizzard was found to have an ability to respond to the inductive influence of the gizzard mesenchyme and to change its developmental fate.

Appearance of brush-border antigens and sucrase in the allantoic endoderm cultured in recombination with digestive-tract mesenchymes.

Allantoic endoderm of 3.5-day chick embryos was cultured in recombination with digestive-tract mesenchymes of 6-day chick embryos, and the differentiation of the endoderm was studied, with special attention being given to the appearance of brush-border (BB) antigens and sucrase. Irrespective of the origin of the associated digestive-tract mesenchymes, the allantoic endoderm differentiated into a columnar epithelium, expressing BB antigens and sucrase, and also into a BB antigen-negative pseudostratified or stratified epithelium of cuboidal or columnar cells with PAS or alcian blue staining in the apical portion or a BB antigen-negative stratified squamous epithelium. These results suggest that 3.5-day allantoic endoderm has the potency to differentiate into intestinal and cloacal epithelium.