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Biomedical subjects

C J Lee

Publications and source records attributed to C J Lee.

At least 19 recordsLinked to original sources
PubMed2006

Pioglitazone, a synthetic ligand for PPARgamma, induces apoptosis in RB-deficient human colorectal cancer cells.

No published data are available about the expression of peroxisome proliferator-activated receptor gamma (PPARgamma) and the role of PPARgamma in retinoblastoma protein (RB)-deficient human colorectal cancer (CRC) cells (SNU-C4 and SNU-C2A). Our aim was to investigate whether PPARgamma is expressed in SNU-C4 and SNU-C2A cells and to elucidate possible molecular mechanisms underlying the effect of pioglitazone, a synthetic ligand for PPARgamma, on cell growth in these cell lines. RT-PCR and Western blot analysis showed that both human CRC cell lines expressed PPARgamma mRNA and protein. Pioglitazone inhibited the cell growth of both cell lines through G2/M phase block and apoptosis. In addition, pioglitazone caused a down-regulation of the X chromosome-linked inhibitor of apoptosis (XIAP), Bcl-2, and cyclooxygenase-2 (COX-2) under conditions leading to PPARgamma down-regulation. These results suggest that pioglitazone may have therapeutic relevance or significance in the treatment of human CRC, and the down-regulation of XIAP, Bcl-2, and COX-2 may contribute to pioglitazone-induced apoptosis in these and other RB-deficient cell lines and tumors.

Apoptosis↗
PubMed2004

Functional similarities and differences of AMPA and kainate receptors expressed by cultured rat sensory neurons.

Dorsal root ganglion neurons express functional AMPA and kainate receptors near their central terminals. Activation of these receptors causes a decrease in glutamate release during action potential evoked synaptic transmission. Due to differences in kinetic properties and expression patterns of these two families of glutamate receptors in subpopulations of sensory neurons, AMPA and kainate receptors are expected to function differently. We used embryonic dorsal root ganglion (DRG) neurons maintained in culture to compare functional properties of kainate and AMPA receptors. Most DRG neurons in culture expressed kainate receptors and about half also expressed AMPA receptors. Most AMPA and kainate receptor-expressing DRG neurons were sensitive to capsaicin, suggesting involvement of these glutamate receptors in nociception. When activated by kainate, AMPA receptors were capable of driving a sustained train of action potentials while kainate receptors tended to activate action potential firing more transiently. Glutamate elicited more action potentials and a larger steady-state depolarization in neurons expressing both AMPA and kainate receptors than in neurons expressing only kainate receptors. Adding to their more potent activation properties, AMPA receptors recovered from desensitization much more quickly than kainate receptors. Activation of presynaptic receptors by low concentrations of kainate, but not ATPA, caused a tetrodotoxin-sensitive increase in the frequency of spontaneous EPSCs recorded in dorsal horn neurons. By recording synaptic pairs of DRG and dorsal horn neurons, we found that activation of presynaptic kainate and AMPA receptors decreased evoked glutamate release from terminals of DRG neurons in culture. Our data suggest that the endogenous ligand, glutamate, will cause a different physiological impact when activating these two types of non-NMDA glutamate receptors at central or peripheral nerve endings of sensory neurons.

Action Potentials↗
PubMed2004

A survey on the prevalence and management of hepatitis B after renal transplantation in Asian-Pacific countries.

The carrier rate for hepatitis B virus (HBV) varies from 1% to 2% to 10% in Asian-Pacific countries. A survey involving 12 transplant centers from 11 countries in this region showed that 1% to 25% of kidney transplant recipients were infected with HBV, and up to 60% of these subjects showed abnormal liver biochemistry. While nearly all centers tested anti-HBs in potential kidney transplant recipients, HBV vaccination of nonimmune subjects was routine in only 66.7%. One-third of the surveyed units rejected HBsAg-positive subjects as kidney donors, while the others demonstrated differing policies in choosing the respective recipients. Two units (16.7%) excluded HBsAg-positive patients from kidney transplantation, whereas the others only excluded those with severe liver disease. Heterogeneity also applies to the immunosuppressive regimens, the use of HBV DNA in serial monitoring, and the timing of antiviral therapy in HBsAg-positive kidney transplant recipients. The data showed that despite HBV infection being a significant problem in kidney transplantation, there is a lack of uniform management policy, attributable to the clinical complexity and deficiency of research data. Although improvement in clinical outcome is likely with the advent of nucleoside analogue therapy and better monitoring, the financial implications in the adoption of these recent advances remain realistic concerns.

Asia↗
PubMed2003

Use of the Keele injector for sample introduction for gas chromatographic analysis of vinclozolin in lettuces.

We examined a Keele injector for sample introduction for gas chromatographic analysis of vinclozolin treated in lettuces. Samples in milligram quantity were introduced into a glass tube in a Keele injector at a gas chromatograph injection port. The glass tube was then crushed to allow the sample to carry onto a capillary column in a normal manner. The standard calibration curve for quantitative detection of vinclozolin was obtained by determining vinclozolin spiked in samples at variable concentrations. The calibration curve showed a linear response to vinclozolin ranging from 0.05 to 1.0 microg/g, giving a slope value of 174.8, the y-intercept value of -2.8146 and the mean r2-value of 0.9994. Limit of quantification for vinclozolin was 0.05 microg/g by this method, comparable to 0.01 microg/g by a normal injector. When samples treated previously with vinclozolin were determined by the Keele injector, vinclozolin was found to be about 30% lower as compared to a normal method, suggesting about 70% recovery of the spiked vinclozolin by the Keele injector. From these results, the Keele injector was suggested to be potential for sample introduction in gas chromatographic analysis of vinclozolin in lettuce samples.

Chromatography, Gas↗
PubMed2003

Construction of a deep coverage BAC library from Capsicum annuum, 'CM334'.

A bacterial artificial chromosome (BAC) library consisting of 235,000 clones with an average insert size of 130 kb was constructed from Capsicum annuum, 'CM334'. Based on a pepper haploid genome size of 2,702 Mbp/C, the BAC library is estimated to contain approximately 12 genome equivalents and represents at least 99% of the pepper genome. Screening of the library with mitochondrial DNA probes (coxII, coxIII, atp6 and atp9) and chloroplast DNA probes (atpB, rbcL) indicated that contamination with cytoplasmic DNA was less than 0.5%. To estimate the possibility of isolating a specific clone, the library was screened with single or low-copy gene-specific probes and RFLP probes. Screening of high density BAC filters with RFLP markers linked to L (TMV resistance), y (fruit color), C2 (fruit color) and C (pungency) loci under high stringency conditions revealed that at least three positive BAC clones were found per each probe. This fact indicates that the library is highly reliable and represents a resource for map-based cloning, physical mapping, and characterization of upstream and downstream regulations of the chili pepper genes.

Capsicum↗
PubMed2003

Attenuation of MPTP-induced neurotoxicity and behavioural impairment in NSE-XIAP transgenic mice.

X-linked IAP protein is a potent inhibitor of cell death. Here, we describe a novel transgenic mouse in which the human XIAP gene is expressed under the control of the neuron-specific enolase promoter (NSE-xiap). We demonstrate that nigrostriatal dopamine neurons of NSE-xiap mice were resistant to the damaging effects of the dopaminergic neurotoxin MPTP. MPTP-induced reduction of striatal dopamine metabolism was also attenuated in NSE-xiap mice. Furthermore, NSE-xiap mice treated with MPTP did not exhibit deficits in exploratory behaviour in an open-field test. Taken together, these findings suggest that strategies to enhance neuronal expression of XIAP may provide therapeutic benefit for the treatment of neurodegeneration in Parkinson's disease.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed2002

Effects of polycationic peptides on mucin release from airway goblet cells: relationship between polymer size and activity.

OBJECTIVES AND DESIGN: Various sizes of poly-L-lysine (PLL) and poly-L-arginine (PLA) were tested for their possible effects on airway goblet cell mucin release using primary hamster tracheal surface epithelial (HTSE) cells in an attempt to identify the smallest size of the polycationic peptide to suppress mucin release without cytotoxicity. MATERIALS AND METHODS: HTSE cells were metabolically labeled using 3H-glucosamine and chased in the presence of varying concentrations of various sizes of the polycationic peptides. The amount of 3H-mucin in the spent media was measured by Sepharose CL-4B gel-filtration column chromatography. Possible cytotoxicity of the peptides was assessed by measuring the release of lactic dehydrogenase (LDH) during the treatment period. RESULTS: (1) PLL (MW 78,000) inhibited whereas PLA (MW 92,000) stimulated mucin release. However, these peptides were cytotoxic at the effective concentrations; (2) Both PLL (MW 9,600) and PLA (MW 8,900) could inhibit mucin release in a dose dependent manner without cytotoxicity; (3) Both PLL and PLA were effective in suppressing mucin release in 20-mer but not in either 10-mer or 5-mer; (4) 14-mers of both PLL and PLA also inhibited mucin release without cytotoxicity; (5) PLL and poly-D-lysine (PDL) of 14-mer were equipotent in its ability to suppress mucin release. CONCLUSION: Both PLL and PLA are cytotoxic at 'high' molecular weights, but have an ability to suppress mucin release without cytotoxicity at 'low' molecular weights. 14-mer seems to be the small, effective size, if not the smallest, for both PLL and PLA to suppress mucin release without cytotoxicity. The inhibitory effect of these polycationic peptides seems to be determined by the presence and the absolute number of positive charges and also to be independent of optical isomerism.

Animals↗
PubMed2002

Tissue engineered tracheal prosthesis with acceleratedly cultured homologous chondrocytes as an alternative of tracheal reconstruction.

BACKGROUND: Autologous tissue is an ideal substitue for an extensive tracheal reconstruction, but it is rarely feasible in clinical situations. Many tracheal prosthesis had been used for such an instances, but unfortunately it is still problematic. Dislocation, local infection, hemorrage, and luminal stenosis can cause prosthetic failure. To achieve clinically available autologous tracheal prosthesis, it is necessary that we have to get phenotypically functioning chondrocytes, rapid differentiation of harvested autologous chondrocytes, and the survival of free grafted cultured chondrocytes. METHODS: In this study, we investigated isolation and culture method of the chondrocytes using the rabbit costal cartilage, and the cells were characterized microscopically and biochemically first. Then we have used cultured rabbit chondrocytes to investigate the role of growth factors upon the proliferation and regulation of the cultured chondrocytes. We have examined the effect of peptide growth factors on DNA and proteoglycan synthesis to the rabbit chondrocyte. The effects of IGF-I and basic FGF were investigated individually. Secondly, acceleratedly cultured chondrocytes were embeded to polymer (PLGA) scaffold in bioreactor, and implanted to defected rabbit trachea. Six weeks later, the rabbits were sacrificed and examined their histologic characteristics. RESULTS: The harvested chondrocytes from costal arch grew well and were amplified successfully maitaining their own phenotypes. Its embedding to PLGA scaffold was accomplished successfully. The implanted tracheal prosthesis maintains its physical integrity well, but the histologic examination revealed non-viable chondrocytes. The epithelial linings were good. CONCLUSIONS: The tissue engineered tracheal prosthesis can be a promising alternative of good functional air way tube in short term experiment, but biologically not vital yet. Further investigations are necessary to see the survival of free grafted chondrocytes and the long term results.

Animals↗
PubMed2001

Risk of betel chewing for oesophageal cancer in Taiwan.

Among 104 cases of squamous-cell oesophageal carcinoma patients and 277 controls in Taiwan, after adjusting for cigarette smoking, alcohol consumption, and other confounders, we found that subjects who chewed from 1 to 495 betel-year and more than 495 betel-years (about 20 betel quid per day for 20 years) had 3.6-fold (95% Cl = 1.3-10.1) and 9.2-fold risk (95% Cl = 1.8-46.7), respectively, of developing oesophageal cancer, compared to those who did not chew betel.

Adult↗
PubMed2001

Sox8 gene expression identifies immature glial cells in developing cerebellum and cerebellar tumours.

Sox8 is a member of the E subgroup of Sox genes, the other members of which are Sox9 and Sox10, both of which are implicated in specific human disorders. Recently, Sox8 homologues have been cloned in chick, mouse and human and have been shown to be strongly expressed in the embryonic and adult brain. Nevertheless, the cell types that express Sox8 have not been determined. We show here that Sox8 is expressed in immature glia in the developing cerebellum. Sox8 is also expressed in scattered cells in the cerebellar tumour, medulloblastoma. This gene therefore provides an early glial marker that may provide more detailed insight into the cellular makeup and consequent behaviour of medulloblastomas.

Animals↗
PubMed2001

Amphetamine distorts stimulation-dependent dopamine overflow: effects on D2 autoreceptors, transporters, and synaptic vesicle stores.

Amphetamine (AMPH) is known to raise extracellular dopamine (DA) levels by inducing stimulation-independent DA efflux via reverse transport through the DA transporter and by inhibiting DA re-uptake. In contrast, recent studies indicate that AMPH decreases stimulation-dependent vesicular DA release. One candidate mechanism for this effect is the AMPH-mediated redistribution of DA from vesicles to the cytosol. In addition, the inhibition of stimulation-dependent release may occur because of D2 autoreceptor activation by DA that is released via reverse transport. We used the D2 receptor antagonist sulpiride and mice lacking the D2 receptor to address this issue. To evaluate carefully AMPH effects on release and uptake, we recorded stimulated DA overflow in striatal slices by using continuous amperometry and cyclic voltammetry. Recordings were fit by a random walk simulation of DA diffusion, including uptake with Michaelis-Menten kinetics, that provided estimates of DA concentration and uptake parameters. AMPH (10 microm) promoted the overflow of synaptically released DA by decreasing the apparent affinity for DA uptake (K(m) increase from 0.8 to 32 microm). The amount of DA released per pulse, however, was decreased by 82%. This release inhibition was prevented partly by superfusion with sulpiride (47% inhibition) and was reduced in D2 mutant mice (23% inhibition). When D2 autoreceptor activation was minimal, the combined effects of AMPH on DA release and uptake resulted in an enhanced overflow of exocytically released DA. Such enhancement of stimulation-dependent DA overflow may occur under conditions of low D2 receptor activity or expression, for example as a result of AMPH sensitization.

Amphetamine↗
PubMed2001

Genetic polymorphisms of XRCC1 and risk of the esophageal cancer.

A variety of environmental factors were identified to be associated with the risk of esophageal cancer. The variation in capacity of DNA repair might influence environmental chemical-associated carcinogenesis. We hypothesized that the polymorphic XRCC1 genes might modify cancer susceptibility of the esophagus. To investigate the effect of XRCC1 genetic polymorphisms on codons 194, 280 and 399, we evaluated data from 105 patients of esophageal squamous cell carcinoma and 264 healthy controls, matching with age (+/-3 years), gender and ethnicity. The distribution of the 3 genotypes were not significantly different among patients and controls. However, among alcohol drinkers, the XRCC1399 Arg/Arg genotype was more frequently found in patients with esophageal cancer. After adjustment with other environmental confounders, the OR for the genotype of XRCC1399 Arg/Arg was 2.78 (95% CI =1.15-6.67) as compared with the XRCC1(399) Arg/Gln and XRCC1(399) Gln/Gln genotypes in the alcohol drinkers. Similar trends were observed among cigarette smokers and areca chewers. However, they did not reach a statistical significance. Our findings suggest that the polymorphic XRCC1 genes might modify the risk of alcohol-associated esophageal cancers.

Adult↗
PubMed2001

Kainate receptors expressed by a subpopulation of developing nociceptors rapidly switch from high to low Ca2+ permeability.

Dorsal root ganglion (DRG) neurons first express kainate receptor subunits, predominantly GluR5, during embryonic development. In the DRG and throughout the nervous system, substantial editing of GluR5 mRNA occurs with developmental maturation (Bernard et al., 1999). The accompanying change in Ca(2+) permeability of functional kainate receptors that is the predicted outcome of this developmental regulation of mRNA editing has not been investigated. Here we report that kainate receptors on DRG neurons from late embryonic and newborn rats are predominantly Ca(2+) permeable but then become fully Ca(2+) impermeable later in the first postnatal week. Using multiple markers for nociceptor subpopulations, we show that this switch in Ca(2+) permeability is not caused by the appearance of a new subpopulation of nociceptors with different receptor properties. Instead, the change in Ca(2+) permeability matches the time course of post-transcriptional RNA editing of GluR5 at the Q/R site within the pore of the channel, indicating that the change is probably caused by developmentally regulated RNA editing. We also report that, on the basis of the strong correlation of receptor expression with expression of the surface markers LA4, isolectin B4, and LD2, kainate receptors are present on C-fiber-type neurons projecting to lamina II of spinal cord dorsal horn. These results raise the possibility that kainate receptors in their Ca(2+)-permeable form serve a developmental role in synapse formation between this population of C-fibers and their targets in the spinal cord dorsal horn. Thereafter, the receptors may serve a new function that does not require Ca(2+) permeability.

Animals↗
PubMed2001

Lipopolysaccharide inhibits induction of long-term potentiation and depression in the rat hippocampal CA1 area.

We examined the effects of lipopolysaccharide, a bacterial endotoxin, on synaptic plasticity in the rat hippocampal CA1 area in vitro. Lipopolysaccharide suppressed the induction of long-term potentiation elicited by tetanic stimulation and long-term depression, elicited by low-frequency stimulation of Schaffer collateral-commissural fibres at 10 and 50 microg/ml, respectively. Lipid A (1 microg/ml), the biologically active component of lipopolysaccharide, mimicked the effects of 10 microg/ml lipopolysaccharide on long-term potentiation and depression. Nifedipine, an L-type voltage-sensitive Ca(2+) channel antagonist, did not influence the induction of long-term potentiation and depression, whereas a high concentration of extracellular calcium enabled long-term potentiation induction in the presence of 10 microg/ml lipopolysaccharide. The NMDA receptor antagonist D,L-2-amino-5-phosphonovaleric acid (APV, 50 microM), nifedipine (10 microM) or lipopolysaccharide (10 or 50 microg/ml) partially reduced the magnitude of tetraethylammonium-induced long-term potentiation. Nifedipine combined with lipopolysaccharide completely blocked tetraethylammonium-induced long-term potentiation. Whole-cell voltage clamp recordings showed that lipopolysaccharide suppressed NMDA receptor-mediated excitatory postsynaptic currents (EPSCs). Our results indicate that lipopolysaccharide acutely modifies synaptic plasticity by blocking Ca(2+) entry through NMDA receptors, suggesting a possible mechanism for the amnesic action of bacterial infection.

Animals↗