Biomedical subjects

S C Lee

Publications and source records attributed to S C Lee.

At least 73 records · Page 4Linked to original sources

PubMed2001

Indoor air quality at restaurants with different styles of cooking in metropolitan Hong Kong.

Indoor air quality (IAQ) of a restaurant has increasingly received a lot of public concerns in Hong Kong. Unfortunately, there is limited data about the IAQ of Hong Kong restaurants. In order to characterize the current IAQ of local restaurants, four restaurants in metropolitan Hong Kong including a Korean barbecue style restaurant, a Chinese hot pot restaurant, a Chinese dim sum restaurant and a Western canteen were selected for this study. The results of this study showed that the mean concentrations of CO2 at restaurants with gas stoves for food cooking in dining areas exceeded the range from 40 to 60% indoor CO2 concentrations at restaurants without gas stoves in dining areas. The average levels of PM10 and PM2.5 at the Korean barbecue style restaurant were as high as 1442 and 1167 microg/m3, respectively. At the Korean barbecue and Chinese hot pot restaurants, the levels of PM2.5 accounted for 80-93% of their respective PM10 concentrations. The 1-h average levels of CO observed at Korean barbecue style and hot pot restaurants were 15,100 and 8000 microg/m3, respectively. Relatively high concentrations of CO2, CO, PM10, PM2.5 benzene, toluene, methylene chloride and chloroform were measured in the dining areas of the Korean barbecue style and the Chinese hot pot restaurants. The operations of pan-frying food and boiling food with soup in a hot pot could generate considerable quantities of air pollutants.

Air Pollution, Indoor↗

PubMed2001

Dissolution of uranium dioxide in supercritical fluid carbon dioxide.

Uranium dioxide can be dissolved in supercritical CO2 with a CO2-philic TBP-HNO3 complexant to form a highly soluble UO2(NO3)(2).2TBP complex; this new method of dissolving UO2 that requires no water or organic solvent may have important applications for reprocessing of spent nuclear fuels and for treatment of nuclear wastes.

Journal Article↗

PubMed2001

The p53 codon 249 mutant--derived from human functional adrenal tumors--can modify the cell shape of normal adrenocortical transfected cells.

Our previous study has indicated that p53 gene mutation occurred in 73% of human functional adrenal tumors, and the mutation hot spots were focused on codons 100, 102 (exon 4), and 249 (exon 7). Furthermore, a transcriptional activity study revealed that the mutant p53 protein derived from human functional adrenal tumors lost 90% transcriptional activity and the ability to bind with the p53 sequence. In order to investigate the influence of the mutant protein extracted from adrenocortical tumors on normal adrenal cells, we first cloned p53 cDNA from the human primary aldosteronism and constituted it with isopropyl thiogalactoside (IPTG) inducible expression vector as recombinant plasmid. The recombinant plasmid was then transfected to normal bovine adrenocortical cells through electroporation. The results showed that the p53 protein mutations at codons 100 and 102 could neither affect the cell morphology nor enable cell growth on the soft agar. In addition, no significant difference was found in cortisol level between the p53 transfected and the control cells. On the other hand, cell morphological changes and cell proliferation rate increase were observed when we used IPTG to induce the expression of the p53 protein, which mutated at codon 249, in adrenocortical cells. The cell morphology changes included less flattened and decreased elongation when compared to non-transfected cells. However, the cortisol level in transfected cells was not affected by the p53 mutants. Taken together, we concluded that the mutant p53 protein indeed participates in adrenal carcinogenesis; however, it has no influence on hormone production and secretion.

Adrenal Cortex↗

PubMed2001

Structures of heparin-derived disaccharide bound to cobra cardiotoxins: context-dependent conformational change of heparin upon binding to the rigid core of the three-fingered toxin.

Glycosaminoglycans (GAGs) have been suggested to be a potential target for cobra cardiotoxin (CTX) with high affinity and specificity via a cationic belt at the concave surface of the polypeptide. The interaction of GAGs, such as high-molecular weight heparin, with CTXs not only can induce aggregation of CTX molecules but also can enhance their penetration into membranes. The binding of short chain heparin, such as a heparin-derived disaccharide [DeltaUA2S(1-->4)-alpha-D-GlcNS6S], to CTX A3 from Taiwan cobra (Naja atra), however, will not induce aggregation and was, therefore, investigated by high-resolution (1)H NMR. A novel heparin binding site on the convex side of the CTX, near the rigid disulfide bond-tightened core region of Cys38, was identified due to the observation of intermolecular NOEs between the protein and carbohydrate. The derived carbohydrate conformation using complete relaxation and conformational exchange matrix analysis (CORCEMA) of NOEs indicated that the glycosidic linkage conformation and the ring conformation of the unsaturated uronic acid in the bound state depended significantly on the charge context of CTX molecules near the binding site. Specifically, comparative binding studies of several heparin disaccharide homologues with two CTX homologues (CTX Tgamma from Naja nigricollis and CTX A3) indicated that the electrostatic interaction of N-sulfate of glucosamine with NH(3)(+)zeta of Lys12 and of the 2-O-sulfate of the unsaturated uronic acid with NH(3)(+)zeta of Lys5 played an important role. These results also suggest a model on how the CTX-heparin interaction may regulate heparin-induced aggregation of the toxin via the second heparin binding site.

Animals↗

PubMed2001

Bis-8-hydroxyquinoline-armed diazatrithia-15-crown-5 and diazatrithia-16-crown-5 ligands: possible fluorophoric metal ion sensors.

The synthesis and preliminary photophysical properties of a series of diazatrithia-15-crown-5 and diazatrithia-16-crown-5 ligands containing two 8-hydroxyquinoline sidearms are reported. The ligands were prepared by a two-step process. First, diazatrithiacrown ethers 11 and 12 were prepared by treating bis(alpha-chloroamide) 5 with various dimercaptans followed by reduction using a boron-THF complex. Hydroxymethyl-substituted macrocycle 12 was rearranged to hydroxy-substituted diazatrithia-16-crown-5 in refluxing aqueous HCl. Macrocyclic diamines 11-13 were converted to either 5-chloro-8-hydroxyquinolin-7-ylmethyl-substituted diazatrithiacrown ethers 14-16 by a Mannich aminomethylation reaction or to 8-hydroxyquinolin-2-ylmethyl-substituted diazatrithiacrown ethers 17-19 by reductive amination using 8-hydroxyquinoline-2-carboxaldehyde. Preliminary photophysical studies show that ligands 16 and 19 exhibit increased fluorescence in the presence of Zn(2+), indicating that these ligands could be chemical sensors for Zn(2+).

Journal Article↗

PubMed2001

Extracellular nucleotides differentially regulate interleukin-1beta signaling in primary human astrocytes: implications for inflammatory gene expression.

The cytokine interleukin-1beta (IL-1beta) is a potent activator of human astrocytes, inducing or modulating expression of multiple proinflammatory genes via activation of the transcription factors nuclear factor-kappaB (NF-kappaB) and activator protein-1 (AP-1). In this study, we examined whether IL-1beta signaling is regulated in these cells by extracellular nucleotides that are released at high concentrations under inflammatory conditions and act as ligands for members of the P2 receptor family. Using reporter constructs and electromobility shift assays, we found that cotreatment of astrocyte cultures with ATP (1-100 microm) significantly potentiated IL-1beta-mediated activation of NF-kappaB and AP-1 and that ATP alone activated AP-1. These effects were blocked by the P2 receptor antagonists XAMR 0721, periodate-oxidized ATP, and suramin. A role for ATP in modulating IL-1beta-mediated inflammatory gene expression was supported further by the observation that ATP potentiated the IL-1beta-induced expression of IL-8 mRNA and protein but strongly downregulated IP-10 expression. Reverse transcription-PCR and cloning demonstrated expression of the ATP-responsive P2 receptor subtypes P2Y(1), P2Y(2), and P2X(7), as well as the ATP-insensitive receptor P2Y(4). ADP, a selective agonist for P2Y(1), produced results similar to or greater than those obtained using ATP, whereas 2'-3'-O-(4-benzoyl-benzoyl)-ATP, a selective agonist for P2X(7), was less effective than ATP. In contrast, UTP, a selective agonist for P2Y(2) and P2Y(4), was ineffective. These studies indicate that different P2 receptor subtypes play distinct roles in the modulation of IL-1beta-mediated signal transduction in human astrocytes, and that signaling via P2 receptors may fine-tune the transcription of genes involved in inflammatory responses in the human CNS.

Adenosine Triphosphate↗

PubMed2001

Indoor air quality at nine shopping malls in Hong Kong.

Hong Kong is one of the most attractive shopping paradises in the world. Many local people and international tourists favor to spend their time in shopping malls in Hong Kong. Good indoor air quality is, therefore, very essential to shoppers. In order to characterize the indoor air quality in shopping malls, nine shopping malls in Hong Kong were selected for this study. The indoor air pollutants included carbon dioxide (CO2), carbon monoxide (CO), total hydrocarbons (THC), formaldehyde (HCHO), respirable particulate matter (PM10) and total bacteria count (TBC). More than 40% of the shopping malls had 1-h average CO2 levels above the 1000 ppm of the ASHRAE standard on both weekdays and weekends. Also, they had average weekday PM10 concentrations that exceeded the Hong Kong Indoor Air Quality Objective (HKIAQO). The highest indoor PM10 level at a mall was 380 microg/m3. Of the malls surveyed, 30% had indoor airborne bacteria levels above 1000 cfu/m3 set by the HKIAQO. The elevated indoor CO2 and bacteria levels could result from high occupancy combined with insufficient ventilation. The increased PM10 levels could be probably attributed to illegal smoking inside these establishments. In comparison, the shopping malls that contained internal public transport drop-off areas, where vehicles were parked with idling engines and had major entry doors close to heavy traffic roads had higher CO and PM10 indoor levels. In addition, the extensive use of cooking stoves without adequate ventilation inside food courts could increase indoor CO2, CO and PM10 levels.

Air Pollution, Indoor↗

PubMed2001

Kinetics of removal of carbonyl sulfide by aqueous monoethanolamine.

The kinetics of the reaction between carbonyl sulfide and aqueous monoethanolamine (MEA) were studied over a range in temperature (298-348 K) and amine concentrations (5-20 wt%) using a wetted-sphere absorber. The experimental data were interpreted using a zwitterion mechanism. The key physicochemical properties needed to interpret the data are the solubility and diffusivity of COS in the aqueous amine solution. These properties were estimated using the N2O analogy method. Experimental values of N2O solubility were correlated using an extended scaled-particle model, and the measured N2O diffusion coefficients were correlated using a modified Stokes-Einstein equation. Solution densities and viscosities were also measured and correlated in this work. On the basis of the zwitterion mechanism whose rate-limiting step was the deprotonation of a zwitterion, the Arrhenius relationship between the third-order rate constant and the temperature was well correlated with an absolute mean deviation of 0.3%. It could be thus concluded that the overall reaction rate was first-order in the COS concentration and second-order in the MEA concentration.

Air Pollution↗

PubMed2001

Excitotoxic injury stimulates pro-drug-induced 7-chlorokynurenate formation in the rat striatum in vivo.

Peripheral administration of L-4-chlorokynurenine (4-Cl-KYN), which is enzymatically converted in astrocytes to form the glycine(B) receptor antagonist 7-chlorokynurenic acid (7-Cl-KYNA), has been shown to provide neuroprotection against excitotoxic damage. The present study was designed to examine the metabolic fate of 4-Cl-KYN after systemic injection, and to study its brain uptake and subsequent transamination during the acute phase following an excitotoxic insult. To this end, adult rats received intrastriatal injections of vehicle (1 microl) or quinolinic acid (QUIN) (240 nmol/1 microl), and were administered 50 mg/kg 4-Cl-KYN (intraperitoneally) immediately after surgery. After 90 and 180 min, 7-Cl-KYNA concentrations in the vehicle-injected striatum were 54+/-13 and 16+/-2 nM, respectively. The contralateral, QUIN-injected striatum contained 212+/-39 and 97+/-27 nM 7-Cl-KYNA, respectively. This injury-induced increase was accompanied by slightly higher 4-Cl-KYN levels in the QUIN-treated striatum, indicating that better pro-drug availability in part accounts for the enhanced 7-Cl-KYNA formation. These data demonstrate that systemic 4-Cl-KYN application, by targeting reactive glial cells during the early, reversible stage of excitotoxic neurodegeneration, produces disproportionately large amounts of the neuroprotectant 7-Cl-KYNA at the site of the emerging lesion.

Animals↗

PubMed2001

Efficacy of a mass hepatitis B immunization program after switching to recombinant hepatitis B vaccine: a population-based study in Taiwan.

To study the efficacy of immunization against hepatitis B after plasma-derived vaccine was replaced by recombinant vaccine, 2-year-old Taiwanese children were recruited by stratification random sampling and tested for hepatitis B markers. They were grouped according to maternal infectivity and children's immunization status. Of 2010 children, 2.5% had hepatitis B surface antigen (HBsAg), 94.1% had its antibody (anti-HBs), 6.8% had core antibody, and 3.3% were seronegative. Children of highly infectious mothers immunized with hepatitis B immunoglobulin and vaccine on schedule had a lower HBsAg-positive rate and a higher anti-HBs-positive rate than those with vaccine only and off-schedule. The efficacy of the Taiwanese mass hepatitis B immunization was maintained after switching to recombinant hepatitis B vaccine.

Child, Preschool↗

PubMed2001

Expression of inducible nitric oxide synthase, interleukin-1 and caspase-1 in HIV-1 encephalitis.

Inflammatory cytokines and enzymes such as IL-1 and inducible nitric oxide synthase (iNOS) may play an important role in the pathogenesis of AIDS dementia, a condition associated with infection of the CNS cells by the HIV-1. In this report, we investigated the expression of iNOS, IL-1, and caspase-1 (interleukin-1 converting enzyme) in HIV-1 encephalitis (HIVE) by immunocytochemistry and analyzed their expression with respect to HIV-1 infection and glial activation. In HIVE, all three molecules were expressed at high levels in areas of HIV-1 infection (microglial nodules with HIV-1 p24 immunoreactivity) and in areas of diffuse white matter gliosis. Expression was cell-type specific, with IL-1 and caspase-1 being expressed in macrophages and microglia, and iNOS in activated astrocytes. Multinucleated giant cells, a hallmark of virally infected cells, showed intense staining for both IL-1 and caspase-1, suggesting induction of these molecules by HIV-1. Double immunocytochemistry demonstrated a regional co-localization of astrocyte iNOS and microglial IL-1 and caspase-1. These results support the notion that autocrine and paracrine interactions between HIV-1 infected macrophages and microglia, activated microglia, and astrocytes lead to expression of proinflammatory and neurotoxic molecules. iNOS and caspase-1 may provide additional therapeutic targets for HIVE.

AIDS Dementia Complex↗

PubMed2001

Sperm factor initiates capacitance and conductance changes in mouse eggs that are more similar to fertilization than IP(3)- or Ca(2+)-induced changes.

We used patch clamp electrophysiology and concurrent imaging with the Ca(2+)-sensitive dye, fura-2, to study the temporal relationship between membrane capacitance and conductance and intracellular free Ca(2+) concentration ([Ca(2+)](i)) during mouse egg fertilization. We found an approximately 2 pF step increase in egg membrane capacitance and a minor increase in conductance with no change in [Ca(2+)](i) at sperm fusion. This was followed approximately 1 min later by a rise in [Ca(2+)](i) that led to larger changes in capacitance and conductance. The most common pattern for these later capacitance changes was an initial capacitance decrease, followed by a larger increase and eventual return to the approximate starting value. There was some variation in this pattern, and sub-microM peak [Ca(2+)](i) favored capacitance decrease, while higher [Ca(2+)](i) favored capacitance increase. The magnitude of accompanying conductance increases was variable and did not correlate well with peak [Ca(2+)](i). The intracellular introduction of porcine sperm factor reproduced the postfusion capacitance and conductance changes with a similar [Ca(2+)](i) dependence. Raising [Ca(2+)](i) by the intracellular introduction of IP(3) initiated fertilization-like capacitance changes, but the conductance changes were slower to activate. Capacitance decrease could be induced when [Ca(2+)](i) was increased modestly by activation of an endogenous Ca(2+) current, with little effect on resting conductance. These results suggest that net turnover of the mouse egg surface membrane is sensitive to [Ca(2+)](i) and that sperm and the active component of sperm factor may be doing more than initiating the IP(3)-mediated release of intracellular Ca(2+).

Animals↗

PubMed2001

One-trial conditioning of the antibody response to hen egg lysozyme in rats.

In Wistar rats, reexposure to a novel conditioned stimulus (CS) previously paired with a protein antigen, hen egg lysozyme (HEL) on a single conditioning trial increased anti-HEL IgG levels relative to conditioned rats that were not reexposed to the CS, conditioned rats that were preexposed to the CS, and nonconditioned rats. These results confirm previous findings that a single exposure to a CS associated with immunization is sufficient to elicit an antibody response upon subsequent reexposure to the CS in the absence of exogenous antigen.

Animals↗

PubMed2001

Studies using leukemia inhibitory factor (LIF) knockout mice and a LIF adenoviral vector demonstrate a key anti-inflammatory role for this cytokine in cutaneous inflammation.

Previous work has implicated the cytokine leukemia inhibitory factor (LIF) in cutaneous inflammation, although results have differed as to whether LIF is pro- or anti-inflammatory in this setting. We examined edema, inflammatory cell infiltration, and cytokine responses following CFA injection in the adult mouse footpad. Inflammatory cell infiltration and edema are significantly enhanced when CFA is injected in LIF knockout mice as compared with injection of wild-type littermates. Moreover, local injection of an adenoviral vector encoding LIF suppresses both measures of inflammation. In contrast, injection of an adenoviral vector encoding beta-galactosidase has no discernable effect on inflammation. In addition, comparison of the CFA responses in LIF knockout vs wild-type skin reveals that LIF is an important regulator of IL-1beta, IL-6, IL-7, IL-2Ralpha, and IFN-gamma in cutaneous inflammation. These and our previous data indicate that both endogenous and exogenous LIF are anti-inflammatory in the CFA model and that LIF is a key regulator of the cytokine cascade. The results also indicate that adenoviral gene delivery can be an effective therapeutic approach in this paradigm.

Adenoviridae↗

PubMed2001

Inhibition of astrocyte TNFalpha expression by extracellular potassium.

TNFalpha and IL-6 are cytokines of great interest, given the numerous biological activities and the documented expression in several central nervous system (CNS) pathologies. In this report, we have examined cultures of IL-1- or IL-1/IFNgamma-activated human fetal astrocytes as a model to study mechanisms of cytokine regulation in the inflamed CNS. Since one of the major functions of astrocytes is spatial buffering of K(+) ions, we examined the effect of high extracellular KCl on astrocyte cytokine expression by ribonuclease protection assay and ELISA. Results demonstrate that astrocyte TNFalpha production was potently inhibited by K(+) with 44 and 89% inhibition at 25 and 55 mM K+, respectively. In contrast, astrocyte IL-6 inhibition required higher concentrations of K+ (>/=75 mM). These results demonstrate a novel role for astrocyte potassium channel activity in modulation of glial cytokine production.

Astrocytes↗

PubMed2001

Direct ultrasonic agitation for rapid extraction of organic matter from airborne particulate.

Direct ultrasonic extraction (DUE) is proposed as simple and rapid sample pretreatment method. This new approach is applied to the extraction of particulate organic matter (POM) from airborne particulate by using dichloromethane (DCM) or DCM/methanol (90/10, v/v) as extractant. The analytical determination was carried out by weighing the extractable POM on an electrobalance. Total recovery for POM could be obtained when the sample was extracted three times with 25-50 mL extractant each for about 5 min at 50 W ultrasonic power. In comparison with conventional Soxhlet extraction, less extraction time (total 15 min only) and solvent consumption (100 mL) were required by DUE. The efficiency of the DUE was similar or even higher than the routine Soxhlet method. Additionally, the new extractor is very simple and easy to use and can accelerate the extraction procedures of organic components from various solid samples.

Air↗

PubMed2001

Determination of lead in fine particulates by slurry sampling electrothermal atomic absorption spectrometry.

A simple method for determining lead in fine particulates (PM2.5) by using electrothermal atomic absorption spectrometry (ETAAS) has been developed. Particulates collected on Nuclepore filter by using a dichotomous sampler were suspended in diluted nitric acid after ultrasonic agitation. The dislodging efficiency is nearly 100% after agitation for 5 min. In order to study the suspension behavior of PM2.5 in solvents, a Brookhaven ZetaPlus Particle Size Analyzer was used to determine the particle size distribution and suspension behavior of air particulates in the solvent. The pre-digestion and modification effect of nitric acid would be discussed. Palladium was added as a chemical modifier and the temperature program of ETAAS was changed in order to improve the recovery. The slurry was introduced directly into a graphite tube for atomization. The metal content in the sample was determined by the standard addition method. In addition, a conventional acid digestion procedure was applied to verify the efficiency of the slurry sampling method. It offers a quick and efficient alternative method for heavy metal characterization in fine particulates.

Environmental Pollution↗

PubMed2001

Comparison of diagnosis of early retinal lesions of diabetic retinopathy between a computer system and human experts.

OBJECTIVE: To investigate whether a computer vision system is comparable with humans in detecting early retinal lesions of diabetic retinopathy using color fundus photographs. METHODS: A computer system has been developed using image processing and pattern recognition techniques to detect early lesions of diabetic retinopathy (hemorrhages and microaneurysms, hard exudates, and cotton-wool spots). Color fundus photographs obtained from American Indians in Oklahoma were used in developing and testing the system. A set of 369 color fundus slides were used to train the computer system using 3 diagnostic categories: lesions present, questionable, or absent (Y/Q/N). A different set of 428 slides were used to test and evaluate the system, and its diagnostic results were compared with those of 2 human experts-the grader at the University of Wisconsin Fundus Photograph Reading Center (Madison) and a general ophthalmologist. The experiments included comparisons using 3 (Y/Q/N) and 2 diagnostic categories (Y/N) (questionable cases excluded in the latter). RESULTS: In the training phase, the agreement rates, sensitivity, and specificity in detecting the 3 lesions between the retinal specialist and the computer system were all above 90%. The kappa statistics were high (0.75-0.97), indicating excellent agreement between the specialist and the computer system. In the testing phase, the results obtained between the computer system and human experts were consistent with those of the training phase, and they were comparable with those between the human experts. CONCLUSIONS: The performance of the computer vision system in diagnosing early retinal lesions was comparable with that of human experts. Therefore, this mobile, electronically easily accessible, and noninvasive computer system, could become a mass screening tool and a clinical aid in diagnosing early lesions of diabetic retinopathy.

Aged↗