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Biomedical subjects

L Y Chan

Publications and source records attributed to L Y Chan.

At least 19 recordsLinked to original sources
PubMed2006

The influence of fetal position on amniotic fluid index and single deepest pocket.

OBJECTIVE: To evaluate the effect of fetal position on measurement of amniotic fluid index (AFI) and of the single deepest pocket (SDP). METHODS: This was a prospective observational study, in a university obstetric unit, of women with an uncomplicated singleton pregnancy with longitudinal lie and cephalic presentation at or beyond 28 weeks of gestation. AFI was calculated and SDP measured and the fetal position was characterized in terms of three parameters. These were: the side of the maternal abdomen on which the fetus lay; a numerical representation (laterality score) of the distance that the fetus was from the sagittal midline plane of the maternal abdomen; the orientation of the fetal trunk (ventral anterior, lateral or posterior). RESULTS: Eighty-one women were recruited into the study. There was a significant relationship between the laterality score and the AFI (P = 0.005) but not the SDP (P = 0.23): AFI was on average 4.35 cm higher in fetuses lying centrally compared with those lying laterally inside the uterus. There was no significant difference for either SDP (P = 0.8) or AFI (P = 0.3) between fetuses lying on the right or the left side of the maternal abdomen. Similarly, there was no significant difference in SDP (P = 0.9) or AFI (P = 1.0) for the different orientations of the fetal trunk. CONCLUSION: Fetal position affects the measurement of AFI but not that of SDP. Therefore, SDP may be a more consistent parameter for the estimation of amniotic fluid volume.

Abdomen↗
PubMed2006

Left ventricular diastolic function during normal pregnancy: assessment by spectral tissue Doppler imaging.

OBJECTIVE: Tissue Doppler imaging (TDI) is an echocardiographic technique for assessing the diastolic function that is relatively independent of preload. Since loading conditions change significantly during pregnancy, a load-independent technique will give a more accurate assessment of diastolic function in pregnant women. The aim of this study was to evaluate maternal diastolic function using tissue Doppler imaging. METHODS: This was a prospective observational study on 35 healthy pregnant women. M-mode, transmitral inflow (peak transmitral flow velocities during early diastole (E wave) and atrial contraction (A wave)) and TDI studies (peak myocardial velocities during early diastole (Em wave), during atrial contraction (Am wave) and peak systole in ejection phase (Sm)) were performed in each trimester and postpartum. The differences in variables between trimesters were analyzed. RESULTS: The peak transmitral inflow velocity during early diastole (E wave) was significantly decreased during the third trimester and postpartum. The peak flow velocity during atrial contraction (A wave) was increased in the second trimester, but decreased again in the third trimester and postpartum period. As a result, the E/A ratio progressively reduced as pregnancy advanced. TDI showed that peak myocardial velocities during early diastole (Em) tended to increase during the second trimester, and then decreased significantly in the third trimester or postpartum period. The peak myocardial velocities during atrial contraction (Am) increased significantly with advancing gestational age. As a consequence, both Em/Am and E/Em ratios decreased significantly throughout pregnancy. CONCLUSIONS: This study demonstrates the changes in myocardial relaxation velocity throughout pregnancy. Because of its advantage of being relatively load-independent, TDI may be a useful non-invasive technique for monitoring maternal cardiac function in high-risk pregnancies to detect the early signs of cardiac failure and to prevent further deterioration with prompt interventions.

Diastole↗
PubMed2006

Effect of time delay on survival in patients with non-small cell lung cancer--a Malaysian study.

The prognosis of lung cancer remains poor with overall five year survival figures varying between five and 10% worldwide, However, it has been shown that surgery in patients with early stage disease in non-small cell lung cancer can achieve five year survival rates up to 80%, suggesting that early or delay diagnosis can influence prognosis. Nevertheless, studies addressing this have been inconclusive and mostly derived from Western countries.

Carcinoma, Non-Small-Cell Lung↗
PubMed2005

Expression of divalent metal transporter 1 (DMT1) isoforms in first trimester human placenta and embryonic tissues.

BACKGROUND: Divalent metal transporter 1 (DMT1) is a transmembrane glycoprotein which mediates the proton-coupled transport of a variety of divalent metal ions. Two isoforms, which differ by the presence (DMT1-IRE) or absence (DMT1-nonIRE) of an iron-responsive element (IRE) in their 3' untranslated region, are implicated in apical iron transport and endosomal iron transport respectively. Although the expression pattern of DMT1 isoforms is tissue specific in adult, data regarding its expression in embryonic tissues are lacking. METHODS: Semiquantitative RT-PCR and immunohistochemistry were used to study the mRNA and protein expression of both DMT1 isoforms in embryonic tissues between 8 and 14 weeks gestational age. RESULTS: DMT1-IRE and DMT1-nonIRE expressions were ubiquitous in embryonic tissues examined. In the lung, statistically significant correlations were found between the levels of DMT1 isoform expression and gestational age. In the placenta, DMT1-IRE was the predominantly expressed isoform. Both isoform proteins were localized in embryonic epithelial cellular membrane. CONCLUSION: Both DMT1 isoforms are ubiquitously expressed in embryonic tissues in the first trimester. Predominant DMT1-IRE isoform expression in placenta suggests an iron-regulatory mechanism reminiscent of that in the adult duodenum. Epithelial distributions of both DMT1 isoforms are associated with the absorptive or excretory functions of the expressed tissues.

Adult↗
PubMed2005

All-optical add-drop node for optical packet-switched networks.

We have demonstrated all-optical packet add-drop for all-optical packet-switched networks. Intelligent all-optical add-drop of packets is performed, based on all-optical processing of packet headers. The header and payload rates are 5 and 10 Gbits/s, respectively.

Journal Article↗
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

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

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

Intrapartum cesarean delivery after successful external cephalic version: a meta-analysis.

OBJECTIVE: We sought to estimate whether the risk of intrapartum cesarean delivery is higher in pregnancies after successful external cephalic version. DATA SOURCES: We searched the MEDLINE, PubMed, EMBASE, and Cochrane Library databases to identify relevant studies. Abstracts of the American College of Obstetricians and Gynecologists Annual Clinical Meeting and the Society for Maternal-Fetal Medicine Annual Meeting were searched by hand. STUDY SELECTION: Studies published between 1980 and 2002 that provided data allowing us to estimate the cesarean rate in both pregnancies after successful version and spontaneous cephalic-presenting pregnancies were selected. TABULATION, INTEGRATION, AND RESULTS: Relative risks (RRs) and 95% confidence intervals (CIs) between the 2 compared groups were calculated. We used a meta-analysis to assess the heterogeneity of the studies and to combine the results from the included studies. Six eligible studies were identified. The cesarean rate was 27.6% in pregnancies after successful version and 12.5% in cephalic-presenting pregnancies. The combined RR and 95% CI was 2.04 (1.43-2.91). The increased cesarean rate in pregnancies after successful version was accounted for primarily by a higher incidence of emergency cesarean delivery for dystocia and fetal distress; the RR (95% CI) for these 2 events was 2.19 (1.38-3.48) and 2.10 (1.18-3.75), respectively. CONCLUSION: The intrapartum cesarean delivery rate after successful version is 2 times that in pregnancies where there is spontaneous cephalic presentation. Pregnancies after successful version should not be considered the same as a normal pregnancy.

Cesarean Section↗
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↗
PubMed2003

Preliminary measurements of aromatic VOCs in public transportation modes in Guangzhou, China.

This study examined the exposure level of aromatic volatile organic compounds (VOCs) in public transportation modes in Guangzhou, China. A total of 40 VOC samples were conducted in four popular public commuting modes (subway, taxis, non-air-conditioned buses and air-conditioned buses) while traversing in urban areas of Guangzhou. Traffic-related VOCs (benzene, toluene, ethylbenzene, m/p-xylene and o-xylene) were collected on adsorbent tubes and analyzed by thermal desorption (TD) and gas chromatography/mass-selective detector (GC/MSD) technique. The results indicate that commuter exposure to VOCs is greatly influenced by the choice of public transport. For the benzene measured, the mean exposure level in taxis (33.6 microg/m(3)) was the highest and was followed by air-conditioned buses (13.5 microg/m(3)) and non-air-conditioned buses (11.3 microg/m(3)). The exposure level in the subway (7.6 microg/m(3)) is clearly lower than that in roadway transports. The inter-microenvironment variations of other target compounds were similar to that of benzene. The target VOCs were well correlated to each other in all the measured transports. The concentration profile of the measured transport was also investigated and was found to be similar to each other. Based on the experiment results, the average B/T/E/X found in this study was about (1.0/4.3/0.7/1.4). In this study, the VOC levels measured in evening peak hours were only slightly higher than those in afternoon non-peak hours. This is due to the insignificant change of traffic volume on the measured routes between these two set times. The out-dated vehicle emission controls and slow-moving traffic conditions may be the major reasons leading elevated in-vehicle exposure level in some public commuting journeys.

Air Pollutants↗
PubMed2003

A study of teratogenicity of hydrosalpinx fluid using a whole rat embryo culture model.

BACKGROUND: Hydrosalpinx fluid may be toxic to sperm and early embryo growth. Information concerning the effect of hydrosalpinx fluid on embryo development during organogenesis is lacking. METHODS: Rat embryos at gestational day 9.5 were cultured for 48 h with 80% rat serum and 20% of either hydrosalpinx fluid (study group) or lactated Ringer's solution (control group). Embryos were scored for growth and development at the end of the culture period. RESULTS: Hydrosalpinx fluid, collected from 10 patients, was tested for embryotoxicity individually. Median total morphological scores were significantly lower in embryos exposed to hydrosalpinx fluid from three of the 10 patients (43.0 versus 47.0, P = 0.01; 36.0 versus 45.0, P < 0.001; 36.0 versus 46.5, P = 0.003). This was accompanied by a significant reduction in median yolk sac diameter (4.0 versus 5.2 mm, P < 0.001 and 4.0 versus 5.0 mm, P < 0.001) and somite number (17.5 versus 22.5, P < 0.001 and 17.0 versus 21.5, P = 0.008) in the latter two patients. CONCLUSIONS: Hydrosalpinx fluid in some patients may contain toxin(s) that is potentially teratogenic.

Animals↗
PubMed2003

An in-vitro study of ginsenoside Rb1-induced teratogenicity using a whole rat embryo culture model.

BACKGROUND: Ginseng is a commonly used herbal medicine worldwide. However, there is limited information regarding its effects on the developing embryo. METHODS: The effect of ginsenoside on the developing embryo during the critical period of organogenesis was investigated using a whole rat embryo culture model. Embryos were exposed to various concentrations of ginsenoside Rb(1) and scored for growth and differentiation at the end of the culture period. RESULTS: Median total morphological scores in embryos exposed to 30 micro g/ml of ginsenoside Rb(1) was significantly lower (P < 0.05) than that in control embryos (35 versus 45). Morphological scores for flexion, forelimb and hindlimb were also significantly reduced. The median total morphological scores further decreased to 28 when the concentration of ginsenoside Rb(1) was increased to 50 micro g/ml. At this concentration, the embryonic crown-rump length and somite number were also significantly reduced compared with control embryos (2.8 versus 3.0 mm and 16.0 versus 21.0, respectively). CONCLUSIONS: Our study has demonstrated that ginsenoside exerts direct teratogenic effects on rat embryos. Until more is known about the effects of ginsenoside in women of reproductive age, we suggest its use should be treated with caution.

Animals↗
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

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↗