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Y S Chan

Publications and source records attributed to Y S Chan.

At least 37 records · Page 2Linked to original sources
PubMed2003

Gene expression of glutamate receptors GluR1 and NR1 is differentially modulated in striatal neurons in rats after 6-hydroxydopamine lesion.

In the present study, we attempted to address the modulation of the gene expression of N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionate (AMPA) glutamate receptors in the neostriatum of the 6-hydroxydopamine (6-OHDA)-lesioned rat, an animal model of Parkinson's disease. After 2 weeks of lesion, reverse transcriptase-polymerase chain reactions (RT-PCRs) revealed significant reduction in GluR1 mRNA expression but a significant enhancement of NR1 mRNA expression in the striatal tissues of the lesioned side. No modulation in the mRNA expression of GluR2, GluR3, GluR4 and NR2B were found. Immunofluorescence with digital imaging analysis also demonstrated a significant reduction in GluR1 immunoreactivity in the lesioned neostriatum. Interestingly, the reduction in GluR1 immunoreactivity was primarily observed in presumed striatal medium spiny neurons but not in parvalbumin-labeled striatal GABAergic interneurons. Immunoreactivity for GluR2, GluR2/3, GluR4, NR1 and NR2B was unchanged in neurons of the neostriatum of the lesioned side. The present results indicate that there is an opposite trend in modulation in the gene expressions of GluR1 and NR1 in the neostriatum of 6-OHDA-lesioned rats after dopamine denervation. Modulation of GluR1 mRNA and immunoreactivity is likely to be limited in the striatal projection neurons. These findings have implications for the use of NMDA and AMPA receptor antagonists in the treatment of Parkinson's disease.

Animals↗
PubMed2003

The striatal GABA-ergic neurons expressing substance P receptors in the basal ganglia of mice.

By using a double immunofluorescence, we have examined the distribution of striatal GABAergic neurons that expressed substance P receptor (SPR) in the basal ganglia of adult C57 mice. The distribution of GABA-immunoreactive neurons completely or partially overlapped with that of SPR-immunoreactive neurons in the striatum (i.e. the caudate-putamen), globus pallidus, ventral pallidum, and nucleus accumbens. Neurons showing both GABA- and SPR-immunoreactivities were, however, predominantly found in the caudate-putamen, and most of them were characterized by their large-sized aspiny neuronal profile. Semi-quantification indicated that only about 13% of the total GABA-immunoreactive neurons (including large and medium-sized) displayed SPR-immunoreactivity, and these double-labeled neurons constituted about 31% of the total SPR-immunoreactive cells in the striatum. Neurons double-labeled with GABA- and SPR-immunoreactivities were hardly detected in other aforementioned regions of the basal ganglia. In addition, double immunofluorescence also showed co-localization of SPR- with glutamic acid decarboxylase-immunoreactivity, but not with parvalbumin-immunoreactivity, in the striatal neurons. Taken together with previous reports, the present study has suggested that a sub-population of striatal GABA-ergic neurons, most possibly GABA-ergic interneurons, may also receive direct physiological modulation by tachykinins through SPR in the basal ganglia of mammals.

Animals↗
PubMed2003

A transitional course from high school to medical school in a new medical curriculum in Asia: how do the students see it?

The objective of this study was to examine the students' views on a transitional course for Asian freshers in a revised medical curriculum. Data were collected through the year-end questionnaire distributed to all first-year students over three academic years from 1997 to 2000. The students considered the transitional course had encouraged them to become more active and self-directed although there were different views about its overall effectiveness. Students appeared uncertain as to the depth in which they were expected to master the subjects, thus leading them to call for more clearly stated learning objectives to help relieve the anxiety they had towards the examinations. Lectures and self-assessment exercises were seen to be providing the general guides for that.

Asia↗
PubMed2003

Receptors of glutamate and neurotrophin in vestibular neuronal functions.

The last decade has witnessed advances in understanding the roles of receptors of neurotrophin and glutamate in the vestibular system. In the first section of this review, the biological actions of neurotrophins and their receptors in the peripheral and central vestibular systems are summarized. Emphasis will be placed on the roles of neurotrophins in developmental plasticity and in the maintenance of vestibular function in the adult animal. This is reviewed in relation to the developmental expression pattern of neurotrophins and their receptors within the vestibular nuclei. The second part is focused on the functional role of different glutamate receptors on central vestibular neurons. The developmental expression pattern of glutamate receptor subunits within the vestibular nuclei is reviewed in relation to the potential role of glutamate receptors in regulating the development of vestibular function.

Animals↗
PubMed2002

Nestin-containing cells express glial fibrillary acidic protein in the proliferative regions of central nervous system of postnatal developing and adult mice.

We are interested in the expression patterns of nestin, an embryonic intermediate filament that represent a neural precursor marker, in the mammalian central nervous system. With an immunohistochemical approach, distribution of nestin-containing cells and their colocalization with glial fibrillary acidic protein (GFAP) or neuronal nuclear specific protein (NeuN) were studied in adult and postnatal days 2-30 (P2-30) mice. Nestin-immunoreactivity was predominately distributed in certain proliferative regions, such as cerebral cortex, hippocampus, hypothalamus, subfornical organ, cerebellar cortex, area postrema, midline raphe glial structures, as well as ependymal and subependymal zones of the brain and spinal cord. The majority of nestin-immunoreactive cells, characterized by astroglial profiles of multiple and radial processes, showed a partial overlapping distribution with that of GFAP-immunoreactive astroglial cells. Double immunofluorescence confirmed that about 77% of these nestin-immunoreactive cells exhibited GFAP-immunoreactivity, indicating that a large percentage of nestin-expressing cells may have committed to astroglial cells. In developing mice, down-regulation of nestin expression was observed between P7 and P14. Although co-expression of nestin and NeuN occurred in cortical neurons of P2-7 mice, nestin-containing cells showing NeuN-immunoreactivity disappeared in CNS in older animals. Our results reveal the distribution pattern of nestin-containing neural precursors in the postnatal CNS and provide evidence on their differentiation fate to neurons and astrocytes, suggesting that nestin-containing glial cells may play an important role in remodeling and repairing in the postnatal and adult central nervous system.

Aging↗
PubMed2002

Significant up-regulation of nestin protein in the neostriatum of MPTP-treated mice. Are the striatal astrocytes regionally activated after systemic MPTP administration?

We are interested in the possible role of central glial cells in pathogenesis of Parkinson's disease of mammals. Parkinsonism model was induced by systemic 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) administration, and the reactive glial cells were examined by immunocytochemical visualization of nestin protein in the brains and spinal cords of C57 mice. Abundant nestin-like immunoreactivity was predominately found in the caudate putamen of MPTP-treated mice and about 481-fold of nestin-like immunoreactive cells increased compared with that of control animals, indicating that significant up-regulation of nestin protein occurred in these regions. Majority of nestin-like immunoreactive cells characterized with astrocytic profiles of multiple, radical and hypotrophic processes, and showed a distribution and dynamic patterns similar to that of glial fibrillary acid protein (GFAP)-immunoreactive cells in the caudate putamen. Double immunofluorescence confirmed that 100% of nestin-like immunoreactive cells exhibited GFAP-immunoreactivity while nestin/GFAP double-labeled cells constituted about 84% of total GFAP-immunoreactive cells in the caudate putamen, indicating these nestin-like immunoreactive cells belong to a reactive population of the astrocytes. On the other hand, no obvious changes of nestin- or GFAP-like immunoreactivities were detected in the globus pallidus, the substantia nigra and the ventral tegmental area after MPTP-treatment. The results have provided morphological evidence for the regional activation of astrocytic glial cells following systemic MPTP administration, suggesting that a large population of reactive striatal astrocytes might play an important role in initial pathogenesis or acute stage of Parkinson's disease in mammals.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed2001

Cholinergic neurons expressing substance P receptor (NK(1)) in the basal forebrain of the rat: a double immunocytochemical study.

Cholinergic neurons expressing substance P receptor (SPR, NK(1)) were examined in the rat brain using double immunofluorescence. The distribution of SPR-like immunoreactive (SPR-LI) neurons completely overlapped with that of choline acetyltransferase (ChAT)-LI neurons in the medial septal nucleus, the nucleus of diagonal band of Broca, the magnocellular preoptic nucleus, the substantia innominata of basal forebrain, the caudate-putamen, and the ventral pallidum of the basal ganglia. In the mesopontine tegmentum and the cranial motor nuclei of the brainstem, the distribution of SPR-LI and ChAT-LI neurons was partially overlapping. Neurons showing both SPR-like and ChAT-like immunoreactivities, however, were predominantly found above basal forebrain regions and 82-90% of these ChAT-LI neurons displayed SPR-like immunoreactivity, in addition to the confirmatory observation that 100% of the ChAT-LI neurons exhibit SPR-like immunoreactivity in the basal ganglia. In contrast, neurons double-labeled for SPR-like and ChAT-like immunoreactivities were hardly detected in aforementioned regions of the brainstem. The present study has provided morphological evidence for direct physiological modulation of cholinergic neurons by tachykinins through substance P receptor in the basal forebrain of the rat.

Acetylcholine↗
PubMed2001

Spontaneous discharge and response characteristics of central otolith neurons of rats during postnatal development.

To study the developmental profile of otolith-related vestibular nuclear neurons, their spontaneous activities and response dynamics were examined in decerebrate rats aged seven, 14, 21 and 84 (adult) days. Extracellular recordings were performed in the lateral and descending vestibular nucleus of animals held at the stationary position in the earth-horizontal or subjected to constant velocity off-vertical axis rotation, which selectively stimulates the otolith receptors. All neurons displayed sinusoidal position-dependent modulation in discharge rate, indicating their capability in coding spatial information during low-frequency head movement. Some neurons showed a full-cycle response to off-vertical axis rotation (non-clipped), while other neurons were silenced in discharge during parts of each rotary cycle (clipped). In seven-day-old rats, three-quarters of the responsive neurons sampled were clipped and the proportion progressively decreased to less than one-quarter in adult rats. In each age group, the clipped neurons discharged in approximately 60% of the stimulus cycle. Response gains of the neurons increased with age, reaching a plateau from 21 days of age for clipped neurons and 14 days for non-clipped neurons. The clipped neurons demonstrated higher response gains than the non-clipped neurons at or beyond 21 days of age. Spontaneous activities of the neurons at the stationary and earth-horizontal positions were analysed in relation to their response gains; a positive correlation was observed from 14 days of age onwards. Both types of neurons showed progressive increase in spontaneous activity as the rats matured, though the clipped neurons exhibited significantly lower resting rates than the non-clipped neurons at each of the age groups studied. Some neurons that responded to off-vertical axis rotation were not spontaneously active at the stationary position, but the proportion of these decreased significantly with age. The coefficient of variation of each age group showed a bimodal distribution, thereby allowing spontaneously active neurons to be assigned as regular or irregular. Though the vast majority of both the clipped and non-clipped neurons showed irregular discharge patterns at seven days of age, the overall population became more regular as the rats matured. Irregular neurons of young rats exhibited phase-stable and phase-shift responses, while those of older rats showed only the phase-stable response. This distinction was not observed amongst regular neurons over the ages studied. Our results reveal features of central otolith neurons that can be taken as signs of maturation during the first three postnatal weeks. These neuronal features provide the framework for the analysis of behaviours mediated by the otolith system during postnatal maturation.

Action Potentials↗
PubMed2001

Cholinergic neurons expressing neuromedin K receptor (NK3) in the basal forebrain of the rat: a double immunofluorescence study.

By using a double immunofluorescence method we have examined the distribution of cholinergic neurons expressing neuromedin K receptor (NK3) in the rat brain and spinal cord. The distribution of neuromedin K receptor-like immunoreactive neurons completely overlapped with that of choline acetyltransferase-positive neurons in certain regions of the basal forebrain, e.g. the medial septal nucleus, nucleus of the diagonal band of Broca, magnocellular preoptic nucleus and substantia innominata. Partially overlapping distributions of neuromedin K receptor-like immunoreactive and choline acetyltransferase-positive neurons were found in the basal nucleus of Meynert, globus pallidus, ventral pallidum of the forebrain, tegmental nuclei of the pons and dorsal motor nucleus of the vagus. Neurons showing both neuromedin K receptor-like and choline acetyltransferase immunoreactivities, however, were found predominantly in the medial septal nucleus, nucleus of the diagonal band of Broca and magnocellular preoptic nucleus of the basal forebrain: 66-80% of these choline acetyltransferase-positive neurons displayed neuromedin K receptor-like immunoreactivity. Neurons showing both neuromedin K receptor-like and choline acetyltransferase immunoreactivities were hardly detected in other aforementioned regions of the forebrain, brainstem and spinal cord. The present study has provided morphological evidence for direct physiological modulation or regulation of cholinergic neurons by tachykinins through the neuromedin K receptor in the basal forebrain of rats.

Animals↗
PubMed2001

Differential expression of AMPA receptor subunits in dopamine neurons of the rat brain: a double immunocytochemical study.

We have examined the distribution of dopamine neurons expressing alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptor subunits (glutamate receptors 1, 2/3 and 4) in the A8-A15 regions of the rat brain using double immunofluorescence. The distribution of glutamate receptor 1- or 2/3-like immunoreactive neurons completely overlapped that of tyrosine hydroxylase-like immunoreactive neurons in dopamine cell groups in the retrorubral field (A8), the substantia nigra (A9), the ventral tegmental area and the nucleus raphe linealis (A10), and the rostral hypothalamic periventricular nucleus (A14, A15). In the caudal hypothalamic periventricular nucleus (A11), arcuate nucleus (A12) and zona incerta (A13), the distribution was partially overlapping. Neurons double-labeled for tyrosine hydroxylase and glutamate receptor 1 or 2/3 immunoreactivities were, however, exclusively found in certain dopamine cell regions: in areas A14-A15, 85-88% of tyrosine hydroxylase-containing neurons expressed glutamate receptor 1 and 22-25% expressed glutamate receptor 2/3, while in areas A8-A10, 20-43% expressed glutamate receptor 1 and 63-84% expressed glutamate receptor 2/3. In contrast, the double-labeled neurons were hardly detected in the A11-A13 regions. No tyrosine hydroxylase-positive neurons displayed glutamate receptor 4 immunoreactivity, though a partially overlapping distribution of tyrosine hydroxylase- and glutamate receptor 4-immunopositive neurons was also seen in regions A8-10, A11 and A13. The present study has demonstrated the morphological evidence for direct modulation of dopamine neurons via AMPA receptors in rat mesencephalon and hypothalamus. This distribution may provide the basis for a selective dopamine neuron loss in neurodegenerative disorders, such as Parkinson's disease.

Animals↗
PubMed2001

Polymorphism and distribution of the Secretor alpha(1,2)-fucosyltransferase gene in various Taiwanese populations.

BACKGROUND: The Secretor gene (Se or FUT2), which produces alpha(1,2)-fucosyltransferase, exhibits extensive polymorphism. Six Se genes, including the weak Se (Se(w) or Se385) and three nonsecretor alleles (se571, se685, and se849) have been detected in various populations of Taiwan. The distribution of various Lewis phenotypes among the Taiwanese population groups has been shown to vary considerably. STUDY DESIGN AND METHODS: A PCR-RFLP analysis system, which was based on the nucleotide polymorphism variation of the different Se alleles and which can reveal the Se genotype of an individual easily and accurately, was developed. The distribution of the Se alleles among Taiwanese population groups, including the two major populations, Minnan and Hakka Taiwanese, and 11 indigenous groups, was analyzed by the method. RESULTS: Frequencies of the Se alleles among the Taiwanese populations were revealed. The distribution of the nonsecretor alleles, especially se849, showed a marked variation. A good correlation was observed between a person's Se genotype and Lewis phenotype. CONCLUSION: The Se genes have a polymorphic distribution among various Taiwanese populations, and this agrees with previous results for Lewis phenotype distributions. The Se(w) allele and the three se alleles are responsible for the Le(a+b+) and Le(a+b-) phenotypes, respectively.

Fucosyltransferases↗
PubMed2000

Retinal dopaminergic neurons (A17) expressing neuromedin K receptor (NK(3)): a double immunocytochemical study in the rat.

By using a double immunofluorescence method we examined the distribution of dopaminergic neurons (A17) expressing neuromedin K receptor (NKR, NK(3)) in the rat retina. The distribution of NKR-like immunoreactive (-LI) neurons partially overlapped that of tyrosine hydroxylase (TH)-LI neurons in the inner retina of section and flat-mount preparation. Neurons showing both TH- and NKR-like immunoreactivities were found in the retina (A17): 100% of these TH-LI neurons displayed NKR-like immunoreactivity, and they constituted about 3.5% of total NKR-LI neurons. The majority of double-labeled neurons with TH- and NKR-like immunoreactivities were distributed in the proximal inner nuclear layer and the upper part of inner plexiform layer of the retina, and characterized with appearance of amacrine cells. The present study has provided morphological evidence for direct physiological modulation of dopaminergic neurons by tachykinins through NKR in the rat retina (A17).

Animals↗
PubMed2000

Co-localization of NMDA receptors and AMPA receptors in neurons of the vestibular nuclei of rats.

We are interested in studying the co-localization of NMDA glutamate receptor subunits (NR1, NR2A/B) and AMPA glutamate receptor subunits (GluR1, GluR2, GluR2/3 and GluR4) in individual neurons of the rat vestibular nuclei. Immunoreactivity for NR1, NR2A/B, GluR1, GluR2, GluR2/3 and GluR4 was found in the somata and dendrites of neurons in the four major subdivisions (superior, medial, lateral, and spinal vestibular nuclei) and in two minor groups (groups x and y) of the vestibular nuclei. Double immunofluorescence showed that all the NR1-containing neurons exhibited NR2A/B immunoreactivity, indicating that native NMDA receptors are composed of NR1 and NR2A/B in a hetero-oligomeric configuration. Co-expression of NMDA receptor subunits and AMPA receptor subunits was demonstrated by double labeling of NR1/GluR1, NR1/GluR2/3, NR1/GluR4 and NR2A/B/GluR2 in individual vestibular nuclear neurons. All NR1-containing neurons expressed GluR2/3 immunoreactivity, and all NR2A/B-containing neurons expressed GluR2 immunoreactivity. However, only about 52% of NR1-immunoreactive neurons exhibited GluR1 immunoreactivity and 46% of NR1-containing neurons showed GluR4 immunoreactivity. The present data reveal that NMDA receptors are co-localized with variants of AMPA receptors in a large proportion of vestibular nuclear neurons. These results suggest that cross-modulation between NMDA receptors and AMPA receptors may occur in individual neurons of the vestibular nuclei during glutamate-mediated excitatory neurotransmission and may in turn contribute to synaptic plasticity within the vestibular nuclei.

Animals↗
PubMed2000

Non-tuberculous cold abscess of the psoas muscle--an unusual manifestation of colocutaneous fistula.

We report here a case of colocutaneous fistula drained from the retroperitoneal space mimicking a cold abscess of the psoas muscle. A 60-year-old diabetic woman with a 6-year history of a chronic draining sinus over her right thigh had been treated intermittently with antibiotics. At presentation, she had no systemic toxic signs nor other constitutional symptoms. The patient was inadequately managed by curettage at first under the tentative diagnosis of tuberculous cold abscess. After the correct diagnosis of colocutaneous fistula, right nephrectomy and right hemicolectomy with ileotransverse colostomy were done. The patient was well 5 years later without recurrence. This is an atypical presentation of enterocutaneous fistula in an immunodeficient patient that should be emphasized to facilitate the correct diagnosis and early treatment.

Colectomy↗
PubMed2000

Two-stage operation for treatment of a large dissecting popliteal cyst after failed total knee arthroplasty.

A symptomatic popliteal cyst after total knee arthroplasty (TKA) is rare, occurring most frequently as a result of intra-articular knee pathology. We present a case of a large dissecting popliteal cyst 7 years after TKA with symptoms of severe calf pain and functional disability. The symptomatic cyst was excised completely in a first-stage operation, and the severely worn TKA was corrected by a second-stage surgical procedure. The patient in this report was pain free and had satisfactory range of knee motion 5 years after the index revision TKA, without recurrence of effusion or popliteal cyst formation.

Aged↗
PubMed2000

Bipolar versus total hip arthroplasty for hip osteonecrosis in the same patient.

The authors studied 28 patients with bilateral avascular necrosis of the femoral head who were treated with a cementless bipolar endoprosthesis in one hip and cementless total hip arthroplasty in the other. All the hips selected for bipolar endoprostheses were classified as having avascular necrosis of the femoral head Ficat Stage III, and all the hips selected for total hip arthroplasty were classified as having Ficat Stage IV avascular necrosis. After a midterm followup of an average of 6.4 years (range, 4-12 years), 24 of 28 hips that received bipolar endoprostheses were considered satisfactory, whereas 23 of 28 hips in which an arthroplasty was done were considered satisfactory. After a followup of more than 6 years, the cartilaginous space of the acetabulum could be preserved in 25 hips (89.3%) that received a bipolar endoprosthesis. There were no statistical differences in both groups in terms of clinical result, thigh pain, groin pain, osteolysis, dislocation, and revision rate. Total hip arthroplasty is not the preferred treatment for all patients with hip osteonecrosis. In young patients with Ficat Stage III osteonecrosis with Grade 0 or Grade I cartilage, the use of a cementless bipolar endoprosthesis with a bone ingrowth stem may be considered as an alternative to total hip arthroplasty.

Adult↗
PubMed2000

Antibiotic-impregnated autogenic cancellous bone grafting is an effective and safe method for the management of small infected tibial defects: a comparison study.

OBJECTIVE: Bone grafting plays an important role in reconstructing infected tibial nonunions. The effects of antibiotic-impregnated bone grafting in infection elimination and bone incorporation was reported in this retrospective study. METHODS: Ninety-six patients treated for infected tibial nonunions were evaluated. These patients were managed with local antibiotic bead therapy and staged antibiotic-impregnated autogenous cancellous bone graft or pure autogenous cancellous bone graft. Patients were randomized to antibiotic-impregnated bone grafting or bone grafting-only groups on the basis of whether the admission date was odd or even. Patients were divided into two groups (antibiotic-impregnated bone grafting group and pure cancellous bone grafting group), according to the procedure used in preparing the bone grafts. The antibiotic-impregnated bone grafting group included 37 men and 9 women whose average age was 36 years (range, 17 to 72 years). The average follow-up period was 4.8 years. By using the Cierny-Mader staging classification of chronic osteomyelitis, 32 of 46 patients (70%) were stage 4A, and 14 of 36 patients (30%) were stage 4B. The pure cancellous bone grafting group included 39 men and 11 women whose average age was 37 years (range, 18 to 72 years). The average follow-up period was 4.5 years (range, 4 to 6 years). Thirty-nine of 50 patients (78%) were stage 4A, and 11 of 50 patients (22%) were stage 4B. The bone defects in both groups ranged from 2 to 4 cm. RESULTS: Wound healing and bony union were achieved in the antibiotic-impregnated bone grafting group. Only two patients had recurrent infections. The infection arrest rate was 95.6%. However, 9 of 50 patients in the pure cancellous bone grafting group had recurrent infections. The infection arrest rate was 82%. The antibiotic-impregnated bone grafting group had significantly superior results (95.6% vs. 82% chi2 test, p < 0.05) in infection elimination than the pure cancellous bone grafting group. CONCLUSION: After 4 to 6 years of follow-up, our results suggest that the use of impregnating antibiotics have no adverse effects on autogenic cancellous bone graft incorporation and could help to eliminate infection effectively.

Adolescent↗