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Biomedical subjects

S C Lee

Publications and source records attributed to S C Lee.

At least 37 records · Page 2Linked to original sources
PubMed2004

Indoor air quality investigation at air-conditioned and non-air-conditioned markets in Hong Kong.

To characterize indoor air quality at the markets in Hong Kong, three non-air-conditioned and two air-conditioned markets were selected for this study. The indoor air pollutants measured included PM(10) (particulate matters with aerodynamic diameter less than 10 microm), total bacteria count (TBC), carbon monoxide (CO), nitric oxide (NO), nitrogen dioxide (NO(2)) and sulfur dioxide (SO(2)). The indoor and outdoor concentrations of these target air pollutants at these markets were measured and compared. The effects of air conditioning, temperature/relative humidity variation and different stalls on the indoor air quality were also investigated. The results indicated that all of the average indoor concentrations of PM(10), TBC, CO and NO(2) at the markets were below the Hong Kong Indoor Air Quality Objectives (HKIAQO) standards with a few exceptions for PM(10) and TBC. The elevated PM(10) concentrations at Hung Hom, Ngau Tau Kok and Wan Chai markets were probably due to the air filtration of outdoor airborne particulates emitted from vehicular exhaust, whereas high concentrations of airborne bacteria at Sai Ying Pun and Tin Shing markets were linked to the use of air conditioning. Correlation analysis demonstrated that indoor bacteria concentrations were correlated with temperature and relative humidity. The operation of air conditioning did not significantly reduce the levels of air pollutants at the markets. However, the higher indoor/outdoor ratios demonstrated that the operation of air conditioning had influence on the levels of bacteria at the markets. It was found that average PM(10) concentration at poultry stalls was higher than the HKIAQO standard of 180 microg/m(3), and was over two times that measured at vegetable, fish and meat stalls. Furthermore, the concentration of airborne bacteria at the poultry stalls was as high as 1031 CFU/m(3), which was above the HKIAQO standard of 1000 CFU/m(3). The bacteria levels at other three stalls were all below the HKIAQO standard. Statistical analysis indicated that there were no significant differences among the four stalls for CO, NO(x) and SO(2).

Air Conditioning↗
PubMed2004

Seasonal and diurnal variations of volatile organic compounds (VOCs) in the atmosphere of Hong Kong.

Ambient VOCs samples were collected at three locations (PolyU campus (PU), Kwun Tong (KT), Hok Tsui (HT)) in Hong Kong during the periods of November 2000-February 2001 and June 2001-August 2001. Also the concentrations of VOCs in Cross Harbor tunnel in Hong Kong were obtained in order to determine the vehicular sources of VOCs. Toluene was the most abundant VOC detected in Hong Kong. At the PU station, which is close to a main road, the concentrations of most VOCs were higher in summer than in winter. However, at the background location HT, the concentrations of all VOCs except tetrachloroethene were higher in winter than in summer. Regional physical dispersion/transportation and mixing depth may be the reasons for higher VOC concentrations in winter at HT. The BTEX (benzene:toluene:ethylbenzene:xylene) ratios of PU and KT during winter period were (1.9:10.1:1.0:1.8) and (1.9:10.4:1.0:1.5), and (0.9:8.3:1.0:2.2) and (0.8:29.6:1.0:1.8) for summer season, respectively. The xylene/ethylbenzene (X/E) ratio was used to assess the relative age of the air parcels in this study. The concentrations of VOCs in the atmosphere in Hong Kong were mainly affected by direct emissions from vehicles, evaporation of fuels, photochemical reactions and few industrial emissions. The BTEX ratio in the tunnel was 2:10.4:1:3.2. The BTEX ratios at PU and KT during the winter period were similar to that in tunnel (except for xylenes). The X/E ratio in the tunnel was higher than that in the ambient air. This indicated that the freshly emitted xylenes in the tunnel decayed at different rates from OH-oxidation in the atmosphere. Good BTEX correlations (r>0.8) were found at PU and KT in winter (**P<0.01). Vehicular exhaust was the dominant source at PU and KT stations, and less evaporation of fuel or additive occurred at low temperature in winter. Diurnal variations of mean BTEX concentrations at the roadside monitoring station (PU) showed two peaks associated with traffic density and vehicle type.

Journal Article↗
PubMed2004

Factors predicting excellent outcome of percutaneous cervical discectomy: analysis of 111 consecutive cases.

Percutaneous cervical discectomy (PCD) has been developed as an effective treatment option for soft cervical disc herniation. However, no prognostic study of this procedure has yet been made. The purpose of this study was to evaluate the surgical outcome of PCD and to determine the factors predicting excellent outcome. A retrospective review was performed of 111 consecutive patients who underwent PCD with a mean follow-up period of 49.4 months (range, 29-64 months). Under local anesthesia, a percutaneous anterior approach was followed by discectomy with microforceps and endoscopic Ho:YAG laser. The surgical outcomes of the 111 patients based on the Macnab criteria were excellent in 52 patients (46.9%), good in 37 (33.3%), fair in 9 (8.1%), and poor in 13 (11.7%), thereby indicating a symptomatic improvement in 88.3% of the patients. In this study, the two major factors predicting an excellent long-term outcome were the symptom of radiating arm pain (P = 0.02) and the location of lateral disc herniation (P < 0.02). Proper patient selection remains critical for the success of this minimally invasive procedure.

Adult↗
PubMed2004

Characterization of hydrocarbons, halocarbons and carbonyls in the atmosphere of Hong Kong.

Ambient air quality measurements of 156 species including 39 alkanes, 32 alkenes, 2 alkynes, 24 aromatic hydrocarbons, 43 halocarbons and 16 carbonyls, were carried out for 120 air samples collected at two sampling stations (CW and TW) in 2001 throughout Hong Kong. Spatial variations of volatile organic compounds (VOCs) in the atmosphere were investigated. Levels of most alkanes and alkenes at TW site were higher than that at the CW site, while the BTEX concentrations at the two sites were close. The BTEX ratios at CW and TW were 1.6:10.1:1.0:1.6 and 2.1:10.8:1.0:2.0, respectively. For major halogenated hydrocarbons, the mean concentrations of chloromethane, CFCs 12 and 22 did not show spatial variations at the two sites. However, site-specific differences were observed for trichloroethene and tetrachloroethene. Furthermore, there were no significant differences for carbonyls such as formaldehyde, acetaldehyde and acetone between the two sites. The levels of selected hydrocarbons in winter were 1-5 times that in summer. There were no common seasonal trends for carbonyls in Hong Kong. The ambient level of formaldehyde, the most abundant carbonyl, was higher in summer. However, levels of acetaldehyde, acetone and benzaldehyde in winter were 1.6-3.8 times that in summer. The levels of CFCs 11 and 12, and chloromethane in summer were higher than that in winter. Strong correlation of most hydrocarbons with propene and n-butane suggested that the primary contributors of hydrocarbons were vehicular emissions in Hong Kong. In addition, gasoline evaporation, use of solvents, leakage of liquefied petroleum gas (LPG), natural gas leakage and other industrial emissions, and even biogenic emissions affected the ambient levels of hydrocarbons. The sources of halocarbons were mainly materials used in industrial processes and as solvents. Correlation analysis suggested that photochemical reactions made significant contributions to the ambient levels of carbonyls in summer whereas in winter motor vehicle emissions would be the major sources of the carbonyls. The photochemical reactivity of selected VOCs was estimated in this study. The largest contributors to ozone formation were formaldehyde, toluene, propene, m,p-xylene, acetaldehyde, 1-butene/i-butene, isoprene and n-butane, suggesting that motor vehicles, gasoline evaporation, use of solvents, leakage of LPG, photochemical processes and biogenic emission are sources in the production of ozone. On the other hand, VOCs from vehicles and gasoline evaporation were predominant with respect to reactions with OH radical.

Air Pollutants↗
PubMed2004

Outcomes in patients with hepatopulmonary syndrome undergoing liver transplantation.

Hepatopulmonary syndrome (HPS) is a condition of significant hypoxia due to intrapulmonary shunting (IPS) in patients with advanced liver disease. Reversibility of HPS after liver transplantation (LT) has been suggested, but the results of LT for HPS remain poorly defined. We studied 78 patients with decompensated liver disease who underwent LT after a preoperative evaluation including contrast echocardiography. We compared the baseline characteristics and outcomes after LT in patients with HPS (n = 13) with those of patients without HPS (n = 65, controls). Before LT, prolongation of prothrombin time was more severe and an advanced Child-Pugh class were more frequent among HPS, patients compared with controls (INR 2.5 +/- 0.8 vs 1.9 +/- 0.7, P = .01; Child-Pugh class A:B:C = 0%:31%:69% vs 14%:65%:21%, P < .01). After LT, no significant differences were observed between the two groups in: clinical outcomes, duration of endotracheal intubation (4.5 +/- 7.7 vs 4.4 +/- 15.0 days), duration of intensive care unit stay (12.0 +/- 8.7 vs 14.4 +/- 19.4 days), duration of total hospital stay (40.0 +/- 33.5 vs 39.8 +/- 23.0), rate of pulmonary complications (7.7% vs 9.2%), or 3-month survival rates (92.3% vs 86.1%). These findings suggest that the presence of HPS does not significantly affect LT outcomes in patients with decompensated liver disease.

Adult↗
PubMed2004

Risk assessment of exposure to volatile organic compounds in different indoor environments.

The lifetime cancer risks of exposure of cooks and food service workers, office workers, housewives, and schoolchildren in Hong Kong to volatile organic compounds (VOCs) in their respective indoor premises during normal indoor activities were assessed. The estimated cancer risk for housewives was the highest, and the second-highest lifetime cancer risk to VOC exposure was for the groups of food service and office workers. Within a certain group of the population, the lifetime cancer risk of the home living room was one to two orders of magnitude higher than that in other indoor environments. The estimated lifetime risks of food service workers were about two times that of office workers. Furthermore, the cancer risks of working in kitchen environments were approximately two times higher than the risks arising from studying in air-conditioned classrooms. The bus riders had higher average lifetime cancer risks than those travelling by Mass Transit Railway. For all target groups of people, the findings of this study show that the exposures to VOCs may lead to lifetime risks higher than 1 x 10(-6). Seven indoor environments were selected for the measurement of human exposure and the estimation of the corresponding lifetime cancer risks. The lifetime risks with 8-h average daily exposures to individual VOCs in individual environments were compared. People in a smoking home had the highest cancer risk, while students in an air-conditioned classroom had the lowest risk of cancer. Benzene accounted for about or more than 40% of the lifetime cancer risks for each category of indoor environment. Nonsmoking and smoking residences in Hong Kong had cancer risks associated with 8-h exposures of benzene above 1.8 x 10(-5) and 8.0 x 10(-5), respectively. The cancer risks associated with 1,1-dichloroethene, chloroform, methylene chloride, trichloroethene, and tetrachloroethene became more significant at selected homes and restaurants. Higher lifetime cancer risks due to exposure to styrene were only observed in the administrative and printing offices and air-conditioned classrooms. Higher lifetime cancer risks related to chloroform exposures were observed at the restaurant and the canteen.

Adult↗
PubMed2004

Multipathway risk assessment on disinfection by-products of drinking water in Hong Kong.

The lifetime cancer risk and the hazard index of trihalomethanes (THMs) through oral ingestion, dermal absorption, and inhalation exposure from tap water in 19 districts in Hong Kong are estimated. The most dominant THMs are chloroform and bromodichloromethane (BDCM) in Hong Kong tap water. Among the three different pathways, residents have a higher risk of cancer through oral ingestion than through the other two pathways. The lifetime cancer risks through oral ingestion and dermal absorption for BDCM make the highest percentage contribution (59%) to total risks, followed by chloroform (24%). The chloroform and BDCM are at or above the negligible risk level of 10(-6) by a factor of 10 or more in most districts. Among the 19 districts, people living in Sai Kung have the highest risk of cancer due to the THM exposure through the multipathways, mainly because of the exposure to BDCM and dibromochloromethane (DBCM). The total cancer risk analysis indicates that each year approximately 10 out of the seven million Hong Kong residents could get cancer from the daily intake of water.

Disinfectants↗
PubMed2004

Indoor air quality in ice skating rinks in Hong Kong.

Indoor air quality in ice skating rinks has become a public concern due to the use of propane- or gasoline-powered ice resurfacers and edgers. In this study, the indoor air quality in three ice rinks with different volumes and resurfacer power sources (propane and gasoline) was monitored during usual operating hours. The measurements included continuous recording of carbon monoxide (CO), carbon dioxide (CO(2)), total volatile organic compounds (TVOC), particulate matter with a diameter less than 2.5 microm (PM(2.5)), particulate matter with diameter less than 10 microm (PM(10)), nitric oxide (NO), nitrogen dioxide (NO(2)), nitrogen oxide (NO(x)), and sulfur dioxide (SO(2)). The average CO, CO(2), and TVOC concentrations ranged from 3190 to 6749 microg/m(3), 851 to 1329 ppm, and 550 to 765 microg/m(3), respectively. The average NO and NO(2) concentrations ranged from 69 to 1006 microg/m(3) and 58 to 242 microg/m(3), respectively. The highest CO and TVOC levels were observed in the ice rink which a gasoline-fueled resurfacer was used. The highest NO and NO(2) levels were recorded in the ice rink with propane-fueled ice resurfacers. The air quality parameters of PM(2.5), PM(10), and SO(2) were fully acceptable in these ice rinks according to HKIAQO standards. Overall, ice resurfacers with combustion engines cause indoor air pollution in ice rinks in Hong Kong. This conclusion is similar to those of previous studies in Europe and North America.

Air Pollution, Indoor↗
PubMed2004

Biochemical and immunological properties of cytokines conjugated to dendritic polymers.

Here we describe a post-translational modification of SC-63032, a variant of the species restricted, multi-lineage hematopoeitic factor human interleukin-3 (hIL-3). We have made two new dendritic polymer (polyamidoamine or PAMAM dendrimers, generation 5)-SC-63032 bioconjugates. Using two distinct chemistries (one of which is novel to this work), we achieved site-specific conjugation with respect to the amino acid in the proteins ligated to the dendrimers. In both bioconjugates, conjugated cytokine maintains its ability to bind the hIL-3 alpha receptor subunit, but is significantly (about 10-fold) less potent in inducing hIL-3 dependent in vitro cell proliferation than is the free cytokine. In vivo data indicates that conjugation decreases the immunogenicity of the conjugated cytokine modestly. In the absence of pharmacokinetic or biodistribution effects associated with the bioconjugates that increase their potency in vivo (which can only be tested in a higher primate, due to the species restriction of hIL-3 and its derivatives), these immune mitigation effects may be too small to be therapeutically significant. Though unmodified PAMAM dendrimers fail to elicit an antibody response in mice, protein conjugation to dendrimers haptenizes them, and a dendrimer-specific antibody response is produced. In toto, the principal limitation of the dendrimer-cytokine bioconjugates herein is in their reduced receptor affinity and potency in vitro. Were the in vivo potency of the bioconjugates to parallel the in vitro potency of the conjugates reported here, it is likely that particular dendrimer bioconjugates could not justify their higher costs of goods relative to the parent SC-63032 molecule, though retention of SC-63032 biological activities in conjugates suggests that other cytokine-dendrimer bioconjugates may be bioactive. This is good news to the nanotechnology community, in as much as PAMAM dendrimers are among the monodisperse polymeric nanomaterials available, and these results show that they can be used successfully in conjugates to bioactive proteins.

Animals↗
PubMed2004

IL-16 expression in lymphocytes and microglia in HIV-1 encephalitis.

IL-16 is a natural ligand for the CD4 molecule and is known for its chemotactic and anti-HIV-1 activities. We determined IL-16 expression in human brain tissue with HIV-1 encephalitis by specific immunocytochemistry and showed that infiltrating lymphocytes and activated microglia express IL-16. IL-16 immunoreactivity was particularly pronounced in microglial nodules. In vitro, human foetal microglia and not astrocytes produce IL-16, and HIV-1 infection up-regulates microglial IL-16 release in a Nef-dependent manner. These results support the notion that, in the brain, IL-16 is a macrophage-lineage specific modulator of the inflammatory response and HIV-1 expression. Recruitment of IL-16+ T cells and microglia/macrophages may represent an innate response to HIV-1 infection in the central nervous system that counterbalances viral stimulatory factors.

AIDS Dementia Complex↗
PubMed2004

Complications of fixation to the occiput-anatomical and design implications.

Internal fixation provides an increased immediate stability for the craniovertebral junction; however, there is no current consensus on the optimal method of occipitocervical (OC) fusion. In this report, we present 25 cases of craniovertebral instability treated with OC fusion by plates and screws instrumentation. The 25 cases comprised 12 men and 13 women, whose ages ranged 20 to 78 years. The principal aetiologies that lead to the OC instability of the patients in this series included trauma, rheumatoid arthritis, neoplasm and congenital abnormality. The fusion levels ranged from occiput-C3 to occiput-C6. Two mortalities occurred. The other patients showed satisfactory union after a follow-up of eight to 24 months. OC fusion using a plates and screws system is a safe and highly effective method for providing immediate internal stability to the OC junction. The internal occipital anatomy, which cannot be seen at surgery, is important when dealing with this taxing and potentially dangerous aspect of surgery.

Adult↗
PubMed2004

HIV-1 expression protects macrophages and microglia from apoptotic death.

Macrophages and microglia are the predominant cells infected with HIV-1 in the brain, yet the effects of productive HIV infection on the fate of these cells are poorly understood. In this study, we tested the hypothesis that HIV-1 expression influences cell death in infected macrophages and microglial cells. We detected apoptosis by terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL) in the cerebral white matter of control and HIV encephalitis (HIVE) brains, and quantitatively analysed apoptotic cells with respect to their location (vessel-associated vs. parenchymal), CD68 expression, and HIV-1 p24 expression. There were more vessel-associated, but not more parenchymal, TUNEL+ cells in HIVE cases as compared to controls. Vessel-associated TUNEL+ cells were primarily endothelial cells (von Willebrand factor+) or macrophages (CD68+). TUNEL+/CD68+ cells were present in both control and HIVE cases in similar frequencies (2.1 +/- 0.7% vs. 1.9 +/- 0.7% of total CD68+ populations, respectively). In HIVE, TUNEL+/p24+ cells were 0.4 +/- 0.2% of the total p24+ cell population, which was lower than the frequency of TUNEL+/CD68+ cells (1.9 +/- 0.7%) in the total CD68+ macrophage population. These results suggest that HIV-1-infected macrophages and microglia are resistant to apoptosis, and may contribute to the formation of a central nervous system viral reservoir.

AIDS Dementia Complex↗
PubMed2004

Fatal lactic acidosis associated with highly active antiretroviral therapy in patients with advanced human immunodeficiency virus infection in Taiwan.

Lactic acidosis (LA), a rare but life-threatening adverse effect associated with antiretroviral therapy, has been reported with an increasing frequency since the mid-1990s. From June 1994 to June 2002, a total of six patients, four males and two females with a median age of 43 years (range, 30 to 74 years), had been diagnosed with LA. The estimated incidence of LA was 5.1 per 1000 patient-years (PYs) on highly active antiretroviral therapy (HAART) (95% confidence interval [95% CI], 4.5-5.5 per 1000 PYs) and 4.4 per 1000 PY on nucleoside analogues (NAs) (95% CI, 3.9-4.7 per 1000 PYs). Their median body mass index at diagnosis of LA was 17.6 kg/m(2) (range 16.3 to 22.6 kg/m(2)). The median CD4+ lymphocyte count at the initial diagnosis of HIV infection and at the onset of LA was 38 cells/ micro L (range, 4 to 103 cells/ micro L) and 108 cells/ micro L (range, 79 to 224 cells/ micro L), respectively. The most common symptoms were nausea, vomiting, and dyspnoea. All of the patients had findings suggestive of NA-related mitochondrial toxicity, such as myositis, pancreatitis, fatty hepatitis, peripheral neuropathy or lipodystrophy. The prescribed NA related to LA were stavudine in six patients, lamivudine, five, and didanosine, one. Despite treatment, all patients died of persistent circulatory collapse following LA. The median duration from diagnosis to death was eight days (range, 4-17 days). Our report highlights that clinicians caring for patients with AIDS should be alerted to the potentially fatal LA associated with antiretroviral therapy when patients present with low body mass index, lipodystrophy, unexplained abdominal symptoms, dyspnoea, or elevated aminotransferases.

Acid-Base Imbalance↗
PubMed2003

Limit on the electron neutrino magnetic moment from the kuo-sheng reactor neutrino experiment.

A search of neutrino magnetic moment was carried out at the Kuo-Sheng Nuclear Power Station at a distance of 28 m from the 2.9 GW reactor core. With a high purity germanium detector of mass 1.06 kg surrounded by scintillating NaI(Tl) and CsI(Tl) crystals as anti-Compton detectors, a detection threshold of 5 keV and a background level of 1 kg(-1) keV(-1) day(-1) at 12-60 keV were achieved. Based on 4712 and 1250 h of reactor ON and OFF data, respectively, the limit on the neutrino magnetic moment of mu(nu;(e))<1.3x10(-10)mu(B) at 90% confidence level was derived. An indirect bound of the nu;(e) radiative lifetime of m(3)(nu)tau(nu)>2.8x10(18) eV(3) s can be inferred.

Journal Article↗
PubMed2003

A rapid and sensitive liquid chromatography/tandem mass spectrometry method for determination of docetaxel in human plasma.

A novel, rapid and sensitive isocratic liquid chromatography/tandem mass spectrometry (LC/MS/MS) method was developed for quantification of docetaxel in human plasma with paclitaxel as internal standard. The high sensitivity and specificity of MS/MS detection enabled the use of a small volume of plasma (0.05 mL) and a simple liquid-liquid extraction procedure. Furthermore, a very short run-time (3 min) fulfilled the need for monitoring plasma levels of docetaxel from large-scale clinical studies. The calibration curve for docetaxel was linear over the range 5-1000 ng/mL with coefficients of correlation >0.999 using only 0.05 mL plasma. The intra- and inter-day precisions (CV) of analysis were <7%, and accuracy ranged from 96 to 110%. The applicability of the method was demonstrated in a pharmacokinetic study of a 1-h infusion of docetaxel with dosages of 75 mg/m(2). Possible conjugated metabolites of docetaxel were not detected in patients' samples.

Antineoplastic Agents, Phytogenic↗
PubMed2003

Characterization of ambient volatile organic compounds at a landfill site in Guangzhou, South China.

Ambient air monitoring was conducted at Datianshan landfill, Guangzhou, South China in 1998 to investigate the seasonal and horizontal variations of trace volatile organic compounds (VOCs). Twelve sampling points over the Datianshan landfill were selected and samples were collected simultaneously using Carbontrap(TM) adsorption tubes. Thirty eight VOCs were detected in the winter, whereas 60 were detected in the summer. The VOC levels measured in summer were alkanes, 0.5-6.5 microg/m(3); aromatics, 2.3-1667 microg/m(3); chlorinated species, 0.2-31 microg/m(3); terpines, 0.1-34 microg/m(3); carbonyl species, 0.3-5.6 microg/m(3) and naphthalene and its derivatives, 0.4-27 microg/m(3). Compared to the summer samples the VOC levels in winter were much lower (mostly 1-2 orders of magnitude lower). The aromatics are dominant VOCs in landfill air both in winter and summer. High levels of alkylbenzene and terpines such as methyl-isopropylbenzene (max 1667 microg/m(3)) and limonene (max 162 microg/m(3)) cause undesirable odor. The similar correlation coefficients of BTEX in summer and winter suggest VOCs emissions were from landfill site sources. The variation of BTEX ratio at landfill site is different from that in the urban area of Guangzhou. It shows that the ambient VOCs at landfill site were different from the urban areas.

Air Pollutants↗