「問題導向學習」教案之品質改善：香港大學醫學院一年級生之經驗與回饋

To improve the quality of paper cases used for problem-based learning in the medical curriculum of the University of Hong Kong, Year 1 students were asked at the end of the year to fill in a questionnaire which addresses specific issues related to problem based learning. In addition, for each of the 6 new cases of PBL which were introduced into the first year, tutorials groups were asked to rate which of the learning objectives as specified in the cased were covered under the 4 themes: Biology of Health and Disease (Knowledge Component); Doctors and Patients (Clinical and communication Skills); Medicine and the Community (Societal and Population Medicine) and Professional Development (Medical Ethics and Law). Over eighty percent of the students found the PBL process to facilitate self directed learning and contributed to their learning. Over forty percent found there was unequal representation of the 4 themes with the issue of Professional Development to be the most inadequately covered. Various factors can be identified for the under representation and inadequate coverage of professional development issues. Possible solutions may include case modifications to ensure a fairer balance of 4 themes, alternative formats of enhancing the discussion of professional development issues, tutor training and coaching the students to address professional development issues

Matching patterns of line segments by eigenvector decomposition

This paper presents an algorithm for matching line segments in two images which are related by an affine transformation. Images are represented as patterns Of line segments. Areas defined between line segments are used to describe a line pattern in the form of a proximity matrix. Matches are determined by comparing the feature vectors obtained from eigenvalue decomposition of the proximity matrices. Reliable matches of line segments are obtained in both synthetic and real images.published_or_final_versio

Downregulation of miR-199b-5p is associated with chemoresistance via Jagged1 mediated notch signaling in human ovarian cancer cells

This journal suppl. entitled: 22nd Biennial Congress of the European Association for Cancer Research - proceedings of EACR 22BACKGROUND: Ovarian cancer is one of the most deadly gynaecological malignancies worldwide. Adjuvant chemotherapy combined with other treatments is the current management of the advanced ovarian cancers. However, the acquisition of resistance to initially responsive tumors limits the successful curative rate. The underlying molecular mechanism remains largely unknown. Here, we report that the downregulation of miR-199b-5p leading to elevated JAG1-mediated NOTCH signal...postprin

Local polynomial modeling of time-varying autoregressive models with application to time-frequency analysis of event-related EEG

This paper proposes a new local polynomial modeling (LPM) method for identification of time-varying autoregressive (TVAR) models and applies it to time-frequency analysis (TFA) of event-related electroencephalogram (ER-EEG). The LPM method models the TVAR coefficients locally by polynomials and estimates the polynomial coefficients using weighted least-squares with a window having a certain bandwidth. A data-driven variable bandwidth selection method is developed to determine the optimal bandwidth that minimizes the mean squared error. The resultant time-varying power spectral density estimation of the signal is capable of achieving both high time resolution and high frequency resolution in the time-frequency domain, making it a powerful TFA technique for nonstationary biomedical signals like ER-EEG. Experimental results on synthesized signals and real EEG data show that the LPM method can achieve a more accurate and complete time-frequency representation of the signal. © 2006 IEEE.published_or_final_versio

Development of the vestibular system

This review mainly focuses on the development of the vestibular system in humans and other mammals, but reference is made to anurans and other species where applicable. In the first section, the steps involved in the development of undifferentiated cells into mature vestibular receptors are analysed. Available data indicate that in humans, maturation of the vestibular receptor and its afferent innervations involves a similar sequence of events as in other mammalian species. In the second section, morphological and physiological aspects of the maturation of the central vestibular system are presented. Undifferentiated neuron precursors have been identified in specific segregrated domains of the hindbrain neural tube, and these can develop into secondary vestibular neurons with unique properties. Several neuronal populations in the vestibulospinal and vestibulo-ocular pathways have been found to correlate with rhombomeric domains at early embryonic stages. In rodents, the vestibular system continues to develop postnatally in terms of morphology and function until it achieves its final form. The postnatal changes in the properties of vestibular nuclear neurons are chronologically matched with structural changes and serve to prime the development of vestibular-induced reflexes. Copyright © 2002 S. Karger AG, Basel.published_or_final_versio

Local polynomial modelling of time-varying autoregressive processes and its application to the analysis of event-related electroencephalogram

This paper proposes a new method for identification of time-varying autoregressive (TVAR) models based on local polynomial modeling (LPM) and applies it to investigate the dynamic spectral information of event-related electroencephalogram (EEG). The proposed method models the TVAR coefficients locally by polynomials and estimates those using least-squares estimation with a kernel having a certain bandwidth. A data-driven variable bandwidth selection method is developed to obtain the optimal bandwidth, which minimizes the mean squared error (MSE). Simulation results show that the LPM-based TVAR identification method outperforms conventional methods for different scenarios. The advantages of the LPM method make it a useful high-resolution timefrequency analysis (TFA) technique for nonstationary biomedical signals like EEG. Experimental results show that the LPM method can reveal more meaningful time-frequency characteristics than wavelet transform. ©2010 IEEE.published_or_final_versionThe IEEE International Symposium on Circuits and Systems (ISCAS 2010), Paris, France, 30 May-2 June 2010. In Proceedings of ISCAS, 2010, p. 3124-312

Dichlorodiphenyltrichloroethane specifically depletes dopaminergic neurons in primary cell culture

Toxicity of dichlorodiphenyltrichloroethane (DDT) to dopaminergic neurons in primary cell culture was investigated in the present study. Developing neurons from the substantia nigra of neonatal rats were cultured. After treatments with different concentrations of DDT (5-12.5 μM), specific cell death of tyrosine-hydroxylase-immunoreactive dopaminergic neurons was observed in the culture by flow cytometric analysis. More than 60% of dopaminergic neurons were depleted after treatments with 10 and 12.5 μM of DDT. In addition, significant reductions of intensity levels of tyrosine hydroxylase immunofluorescence were observed in dopaminergic neurons after DDT treatments even at low concentrations of DDT. The present findings indicate that dopaminergic neurons are more susceptible to DDT toxicity than other types of neurons in the primary cell culture. Moreover, it is shown that the synthesis of dopamine in dopaminergic neurons is also depressed. Previous studies have demonstrated that perinatal exposure of DDT causes neurons to be more susceptible to neurotoxic damages in later adult life. The present findings thus provide evidence that dopaminergic neurons that are undergoing growth and development are targets of DDT neurotoxic effects. Exposure to DDT from contaminated environments is therefore a potential risk of onset of Parkinson's disease. Copyright © 2003 S. Karger AG, Basel.published_or_final_versio

Corticofugal Gating of Auditory Information in the Thalamus: An In Vivo Intracellular Recording Study

In the present study, we investigated the auditory responses of the medial geniculate (MGB) neurons, through in vivo intracellular recordings of anesthetized guinea pigs, while the auditory cortex was electrically activated. Of the 63 neurons that received corticofugal modulation of the membrane potential, 30 received potentiation and 33 received hyperpolarization. The corticofugal potentiation of the membrane potential (amplitude, mean ± SD, 8.6 ± 5.5 mV; duration, 125.5 ± 75.4 msec) facilitated the auditory responses and spontaneous firing of the MGB neurons. The hyperpolarization of -11.3 ± 4.9 mV in amplitude and 210.0 ± 210. 1 msec in duration suppressed the auditory responses and spontaneous firing of the MGB neurons. Four of the five neurons that were histologically confirmed to be located in the lemniscal MGB received corticofugal facilitatory modulation, and all of the four neurons that were confirmed to be located in the non-lemniscal MGB received corticofugal inhibitory modulation. The present intracellular recording provides novel results on how the corticofugal projection gates the sensory information in the thalamus: via the spatially selective depolarization of lemniscal MGB neurons and hyperpolarization of non-lemniscal MGB neurons. It is speculated that the systematic selectivity of facilitation and inhibition over the lemniscal and non-lemniscal MGB is related to the attention shift within the auditory modality and across the sensory modalities.published_or_final_versio

Lowered Immune Cell Function in Liver Recipients Recovered From Posttransplant Lymphoproliferative Disease Who Developed Graft Tolerance

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Molecular and cellular aspects of plasticity after neural injury

This review focuses on our effort to address plasticity of the nervous system after neural injury. We have used different animal models to examine cellular mechanisms of plasticity underlying the pathological and repair processes. After severance of sensory input from one inner ear, topographic representations of spacecentered coordinates in the brain undergo plastic changes. During vestibular compensation, tissue plasticity constitutes an important component for functional recovery of neuronal network. In Parkinsonian animals, modulation of signaling via glutamatergic synapses, neurotrophins and neurokinins contributes to the protection of basal ganglion neurons from degeneration, thereby delaying deterioration of motor functions. With the use of animal models of neural injury, we further overcome the molecular restriction at the glial scar to enhance neural regrowth and remyelination, pointing to the possibility of developing new therapeutic strategies to stimulate neural plasticity and repair in the adult nervous system.published_or_final_versio