Students' perception of problem-based learning at a Japanese medical school: an exploratory sequential mixed method.

Objectives: This study aimed to assess the perception of PBL among Japanese medical students. Methods: Learning effects and challenges of PBL from the students' viewpoint were assessed with an exploratory sequential mixed method. Focus group discussions followed by thematic analysis were conducted with 27 students and residents. Then a questionnaire survey was carried out. A total of 119 out of 258 students (46.1%) responded. The results from 24 questions were analyzed with a residual analysis. Results: Thematic analysis extracted 14 themes from four discussion topics. The participants in focus group discussion regarded the PBL program as a better learning method than lectures. But some key phrases on the challenge of social interaction, including reluctance to actively discuss and collaborate with unfamiliar peers, were found. The questionnaire survey revealed a significantly lower adjusted standardized residual (ASR) for the positive response in five of six questions in the category of social interaction; improvement of communication skills (ASR = -3.303, n = 118, p < .001), enhancement of responsibility at group discussions (ASR = -2.078, n = 119, p = .038), building social networking (ASR = -3.006, n = 119, p = .003), becoming to sympathize with patients (ASR = -2.449, n = 119, p = .014) and understanding social aspects of clinical practice (ASR = -5.790, n = 119, p < .001). Conclusion: The Japanese medical students perceived PBL as an effective learning strategy. However, they had a problem with social interactions.

Peer evaluations of group work in different years of medical school and academic achievement: how are they related?

BACKGROUND: To develop the skills needed in health care teams, training communication and teamwork skills are important in medical education. Small group collaborative learning is one of the methods utilized in such trainings, and peer evaluation is suggested to be useful in reinforcing the effectiveness of group learning activities. In Mie University Faculty of Medicine, group work consisting of book review sessions of liberal arts education in the first grade and problem-based learning (PBL) sessions in preclinical years were conducted using the same peer evaluation system that included three domains: degree of prior learning, contribution to group discussion, and cooperative attitude. This study was conducted to determine the relationships among behaviors during group work and the academic achievement of medical students. METHODS: With the data from a cohort of medical students in three consecutive academic years (n = 340), peer evaluation scores in groupworks of book review sessions, those in PBL sessions and paper test scores of preclinical years were analyzed. The correlations were analyzed with Spearman's correlation coefficient, and the respective scores were compared by using the Wilcoxon signed-ranked test. RESULTS: Significant correlations were observed among the evaluation scores of respective domains in group work and paper test scores. The degree of prior learning had the strongest relationship among the three domains (rs = 0.355, p < 0.001 between book review sessions and PBL; rs = 0.338, p < 0.001 between book review sessions and paper test score; rs = 0.551, p < 0.001 between PBL and paper test score). Peer evaluation scores of respective domains were found to be significantly higher in PBL. CONCLUSION: Medical students maintained their groupwork behaviors to some extent from early school to preclinical years. Those behaviors were positively related to their academic achievement in the later years of the medical education curriculum. Our study highlighted the importance of the early introduction of group work. The results will be useful to motivate medical students to put more effort into group work.

The effects of prenatal exposure to valproic acid on the initial development of serotonergic neurons.

In utero exposure to valproic acid (VPA) may cause symptoms related to autism spectrum disorder (ASD). An abnormal serotonergic (5-HT) system has been implicated in the etiology of ASD. In the present study, we have examined the expression and distribution of two early inducers of 5-HT neurons in rat embryos, to elucidate the prenatal development of 5-HT neurons after VPA exposure at embryonic day (E) 9.5. Whole-embryo in situ hybridization at E11.5 showed that the expression of sonic hedgehog, one of the early inducers of 5-HT neurons, was reduced around the isthmus in the VPA-exposed group. Furthermore, whole-mount immunohistochemistry of the hindbrain and quantitative analysis of 5-HT neurons in the rostral raphe nucleus (rRN) revealed that neuronal distribution in the caudal part of the rRN was narrower at E15.5 in the VPA-exposed group than in controls. Thus, the early development of 5-HT neurons was altered after VPA exposure in utero. The observed prenatal alteration may be significant in the etiology of autism.

Prenatal exposure to organomercury, thimerosal, persistently impairs the serotonergic and dopaminergic systems in the rat brain: implications for association with developmental disorders.

Thimerosal, an organomercury compound, has been widely used as a preservative. Therefore, concerns have been raised about its neurotoxicity. We recently demonstrated perturbation of early serotonergic development by prenatal exposure to thimerosal (Ida-Eto et al. (2011) [11]). Here, we investigated whether prenatal thimerosal exposure causes persistent impairment after birth. Analysis on postnatal day 50 showed significant increase in hippocampal serotonin following thimerosal administration on embryonic day 9. Furthermore, not only serotonin, striatal dopamine was significantly increased. These results indicate that embryonic exposure to thimerosal produces lasting impairment of brain monoaminergic system, and thus every effort should be made to avoid the use of thimerosal.

Subtype-specific parafollicular localization of the neuropeptide manserin in the rat thyroid gland.

The thyroid gland is an endocrine organ which is involved in metabolism, neuroexcitability, body growth and development. The thyroid gland is also involved in the regulation of calcium metabolism, which is not yet fully understood. In this study, we investigated the localization of the granin-derived neuropeptide, manserin, in the adult rat thyroid gland. Manserin immunoreactivity was detected in thyroid follicular epithelial cells. Intense manserin signals were also detected in some, but not all, parafollicular cells, indicating that parafollicular manserin may be subtype-specific. These results indicate that thyroid manserin may play pivotal roles in parafollicular cells and follicular epithelial cells such as in calcium metabolism and/or thyroid hormone secretion.

Morphology of the facial motor nuclei in a rat model of autism during early development.

The development of facial nuclei in animal models of disease is poorly understood, but autism is sometimes associated with facial palsy. In the present study, to investigate migration of facial neurons and initial facial nucleus formation in an animal model of autism, rat embryos were treated with valproic acid (VPA) in utero at embryonic day (E) 9.5 and their facial nuclei were analyzed by in situ hybridization at E13.5, E14.5 and E15.5. Signals for Tbx20, which is expressed in early motor neurons, appeared near the floor plate at the level of the vestibular ganglion and extended caudolaterally, where they became ovoid in shape. This pattern of development was similar between control and VPA-exposed embryos. However, measurements of the migratory pathway and the size of the facial nuclei revealed that exposure to VPA hindered the caudal migration of neurons to the facial nuclei. Signals for cadherin 8, which is expressed in mature facial nuclei, revealed that exposure to VPA caused a significant reduction in the size of the facial nuclei. Our findings provide the first quantitative description of tangential migration and nucleus formation in the developing hindbrain in a rat model of autism.

Existence of manserin, a secretogranin II-derived neuropeptide, in the rat inner ear: relevance to modulation of auditory and vestibular system.

Manserin is a 40-amino acid neuropeptide derived from rat brain. Manserin has been shown to distribute in the neuroendocrine system, such as the pituitary and adrenal glands, but it has been little studied in other organs. In this study, the authors examined localization of manserin in the inner ear of the adult Wistar rat using immunohistochemical analyses. Manserin immunoreactivity was detected in the neuronal terminals of the organ of Corti and type II spiral ganglion cells. In addition to being identified in the auditory system, manserin was detected at the synapses of the vestibular system, such as saccule, utricle, and semicircular canal. These results suggest that inner ear manserin may be involved in the function of peripheral auditory and vestibular systems.

Embryonic exposure to thimerosal, an organomercury compound, causes abnormal early development of serotonergic neurons.

Even though neuronal toxicity due to organomercury compounds is well known, thimerosal, an organomercury compound, is widely used in pediatric vaccine preservation. In the present study, we examined whether embryonic exposure to thimerosal affects early development of serotonergic neurons. Thimerosal (1mg Hg/kg) was intramuscularly administered to pregnant rats on gestational day 9 (susceptible time window for development of fetal serotonergic system), and fetal serotonergic neurons were assessed at embryonic day 15 using anti-serotonin antibodies. A dramatic increase in the number of serotonergic neurons localized to the lateral portion of the caudal raphe was observed in thimerosal group (1.9-fold increase, p<0.01 compared to control). These results indicate that embryonic exposure to thimerosal affects early development of serotonergic neurons.

Morphological abnormalities of embryonic cranial nerves after in utero exposure to valproic acid: implications for the pathogenesis of autism with multiple developmental anomalies.

Autism is often associated with multiple developmental anomalies including asymmetric facial palsy. In order to establish the etiology of autism with facial palsy, research into developmental abnormalities of the peripheral facial nerves is necessary. In the present study, to investigate the development of peripheral cranial nerves for use in an animal model of autism, rat embryos were treated with valproic acid (VPA) in utero and their cranial nerves were visualized by immunostaining. Treatment with VPA after embryonic day 9 had a significant effect on the peripheral fibers of several cranial nerves. Following VPA treatment, immunoreactivity within the trigeminal, facial, glossopharyngeal and vagus nerves was significantly reduced. Additionally, abnormal axonal pathways were observed in the peripheral facial nerves. Thus, the morphology of several cranial nerves, including the facial nerve, can be affected by prenatal VPA exposure as early as E13. Our findings indicate that disruption of early facial nerve development is involved in the etiology of asymmetric facial palsy, and may suggest a link to the etiology of autism.

Manserin, a secretogranin II-derived peptide, distributes in the rat endocrine pancreas colocalized with islet-cell specific manner.

Manserin is a recently characterized 40-amino acid neuropeptide derived from secretogranin II, a protein belonging to the chromogranin family. Although the physiological roles of manserin have not been elucidated to date, manserin has been shown to distribute in not only the brain but also the endocrine system such as the pituitary and adrenal glands, suggesting its role in the endocrine system. The present study aimed to explore the occurrence and distribution of manserin in the rat pancreas using an immunohistochemical technique with a polyclonal antibody against rat manserin. Immunoreactivity for manserin was readily detected in almost whole islets of Langerhans whereas not at all in the exocrine pancreas. Manserin-expressing cells were not colocalized with the glucagon-secreting cells (alpha cells), whereas they colocalized with insulin-secreting cells (beta cells) and somatostatin-secreting cells (delta cells), although their intracellular distribution was different. These results indicate that manserin, occurring in the endocrine pancreas, may have a potential role in the endocrine system.

Postnatal development of axosomatic synapses in the rat nucleus tractus solitarius: dorsal and ventral subnuclei differences.

Inhibitory axosomatic synapses could effectively suppress the excitability of postsynaptic cells. It is important to examine the development of inhibitory axosomatic synapses to understand the maturation of information processing. The caudal nucleus tractus solitarius (cNTS), which regulates the autonomic system, consists of several subnuclei. In the present study, development of axosomatic synapses in the dorsal and ventral subnuclei was examined by electron microscopy. In dorsal subnuclei, the percentage of GAD-positive terminals on the somata, the percentage of small cell somata with synapses and axosomatic synapse density drastically decreased from postnatal day (P) 5 to P10. In ventral subnuclei, the percentage of GAD-positive terminals on the soma, the percentage of small or large cell somata with synapses and axosomatic synapse density were maintained or increased from P5 to P10. Thus, decrease of inhibitory axosomatic synapses in dorsal subnuclei might facilitate maturation of fine receptive areas for peripheral inputs, while increase of inhibitory axosomatic synapses in ventral subnuclei might facilitate the establishment of an effective regulation system for cNTS output.

Quantitative and immunohistochemical analysis of neuronal types in the mouse caudal nucleus tractus solitarius: focus on GABAergic neurons.

gamma-Aminobutyric acid-ergic (GABAergic) neurons are major inhibitory interneurons that are widely distributed in the central nervous system. The caudal nucleus tractus solitarius (cNTS), which plays a key role in respiratory, cardiovascular, and gastrointestinal function, contains GABAergic neurons for regulation of neuronal firing. In the present study, GABAergic neuronal organization was analyzed in relation to the location of subnuclei in the mouse cNTS. According to the differential expression of glutamate decarboxylase 67 (GAD67), vesicular glutamate transporter 2 (VGLUT2), calbindin, and tyrosine hydroxylase (TH) mRNAs, the cNTS was divided into four subnuclei: the subpostrema, dorsomedial, commissural, and medial subnuclei. The numerical density and size of soma in the four subnuclei were then quantified by an unbiased dissector analysis. Calbindin-positive cells constituted subpopulations of small non-GABAergic neurons preferentially localized in the subpostrema subnucleus. TH-positive cells constituted large neurons preferentially localized in the medial subnucleus. GABAergic neurons constituted a subpopulation of small neurons, preferentially localized in the commissural and medial subnuclei, which represented > or =50% of small cells in these subnuclei. Thus, the GABAergic small neurons were located around TH-positive large cells in the ventrolateral portion of the cNTS. This finding, in combination with results of previous studies in the rat cNTS showing that large cells originate efferents from the cNTS, suggests that GABAergic small neurons in the commissural and medial subnuclei might regulate output from the cNTS.

Glial coverage of the small cell somata in the rat nucleus of tractus solitarius during postnatal development.

Astrocytes are thought to be active participants in synaptic plasticity in the developing nervous system. Previous studies suggested that axosomatic synapses decreased in number on the small cells of the rat caudal nucleus of tractus solitarius (cNTS) toward the end of the first postnatal week. Astrocytes might be involved in this phenomenon. We examined the morphological development of astrocytic processes around the small cell soma in the rat cNTS using light and electron microscopy. Glial fibrillary acidic protein (GFAP), glutamate-aspartate transporter (GLAST), and glutamate transporter-1 (GLT-1)-positive structures within the cNTS became more intensely stained as development proceeded. GLAST-positive structures encompassed calbindin-positive small cell somata after postnatal day 10. Electron microscopic observations indicated that astrocytic processes encompass the small cell soma, while the number of axosomatic synapses decreases as development proceeds. The timing for glial coverage of the small cell soma appears to be consistent with the decrease in axosomatic synapses on the small cells. These observations imply that astrocytes may participate actively in regulating the decrease of axosomatic synapses on small cells in the cNTS during postnatal development.

Development and migration of GABAergic neurons in the mouse myelencephalon.

GABAergic neurons are the major inhibitory interneurons that are widely distributed in the central nervous system. It is well established that they originate from a focal region in the embryonic forebrain during development, and then migrate to other regions such as the neocortex. However, the migration of GABAergic neurons remains obscure in other axial levels of the brain. We examined the early development of myelencephalic GABAergic neurons using glutamate decarboxylase 67 / green fluorescent protein (GAD67-GFP) knocking mice. Observation of fixed tissues in coronal sections and flat whole-mount preparations indicated that, while GFP-positive cells are restricted to the subpial region in the ventral aspect of the myelencephalon at an early stage, they spread dorsally and eventually occupy the entire region of the myelencephalon as development proceeds. We developed a flat-mount in vitro preparation in which these patterns of development could be recapitulated. Transplantation of dorsal myelencephalic tissue of a wildtype embryo to a corresponding region of GAD67-GFP mouse embryos clearly demonstrated invasion of dorsally oriented GABAergic neurons from host to donor tissue. These results indicate that ventral-to-dorsal tangential migration of GABAergic neurons takes place in the myelencephalon. Our results extend the observations in the forebrain that inhibitory and excitatory neurons in a specific brain compartment take distinct migratory paths.

Postnatal development of GABAergic axon terminals in the rat nucleus of tractus solitarius.

The proper function of the brain depends on a precise arrangement of excitatory and inhibitory synapses. Although the caudal nucleus of tractus solitarius (cNTS) plays a pivotal role in cardiorespiratory reflexes, we know little about the formation of the local neural network in the cNTS. In the present study, we have focused on GABAergic axon terminals and investigated postnatal changes in GABAergic synaptic organizations in the rat cNTS immunocytochemically at both light and electron microscopic levels. Counting synaptic and non-synaptic GABAergic axon terminals revealed that GABAergic axon terminal number in the cNTS seemed constant until the second postnatal week and that GABAergic axon terminals were reorganized around postnatal day 10 (P10). Electron microscopic observation revealed that more than 20% GABAergic axon terminals formed axosomatic synapses at P2 to P4, but the number of GABAergic axosomatic synapse on neurons with smaller soma (smaller neurons) decreased considerably after P8. Orphan GABAergic boutons were present around somata of smaller neurons at P10, and axodendritic synapse number on thicker dendrites decreased gradually during postnatal development. These results show that GABAergic axon terminals detach from somata of smaller neurons at the second postnatal week. Such morphologic changes in axon terminals could cause changes in electrophysiological activity and might contribute to reorganization of the local network within the cNTS from neonatal to adult type. These postnatal changes in the cNTS local network might be prerequisite for the cardiorespiratory reflexes of the adult type.

Pathfinding and growth termination of primary trigeminal sensory afferents in the embryonic rat hindbrain.

Axons of the trigeminal ganglion convey sensory information from mechanoreceptors, thermoreceptors, and nociceptors in the face and nasal mucosa, then terminate on several groups of neurons including the principal sensory nucleus and the nuclei of the spinal trigeminal tract. To understand guidance mechanisms during the development of trigeminal sensory axons (TA) in the embryonic brain, we first investigated the growth pattern of TA in relation to organization in the hindbrain using flat whole-mount preparation from rat. We found that the primary TA from the trigeminal ganglion entered the brainstem and grew longitudinally within the hindbrain. Whereas descending axons ran just medial to the primary vestibular axons to innervate the spinal nucleus, ascending axons stayed near the entry point. In flat whole-mount culture, the TA extended both ascending and descending branches as they do in vivo. Rostral hindbrain was found to be a less permissive substrate for the TA compared to caudal hindbrain. In addition, the nonpermissive property of the ventral hindbrain substrate restricted the invasion of TA along the entire length of the hindbrain. Thus, cooperation of absolute and relative permissiveness of the substrate plays important roles in the guidance of TA to their targets.