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Biomedical subjects

S C Lee

Publications and source records attributed to S C Lee.

At least 55 records · Page 3Linked to original sources
PubMed2003

Endoscopic 13C-urea breath test for the diagnosis of Helicobacter pylori infection.

BACKGROUND: Endoscopic 13C-urea breath test may avoid contamination of oral urease and rapidly discriminate Helicobacter pylori-positive and Helicobacter pylori-negative patients. AIMS: To compare the accuracy of endoscopic 13C-urea breath test with conventional invasive methods in diagnosis of Helicobacter pylori infection. PATIENTS: One hundred patients who attended for routine upper gastrointestinal endoscopy were included. METHODS: 13C-urea was applied to the stomach through the working channel of endoscope at the end of endoscopic examination. Breath samples were collected before endoscopy and 2, 4, 6, 8, 10 min after consumption of 100 or 50 mg 13C-urea. Helicobacter pylori infection was defined as those with positive culture or positive results of both histology and CLO test. RESULTS: The accuracy of 100 mg endoscopic 13C-urea breath test was significantly higher than that of culture and CLO test (100% vs. 88% and 92%, p = 0.02 and 0.03, respectively). The accuracy of 50 mg endoscopic 13C-urea breath test was higher than that of histology and CLO test (98% vs. 90% and 96%, respectively), although the differences were not statistically significant. CONCLUSIONS: Endoscopic 13C-urea breath test has a higher accuracy compared with biopsy-based modalities. It may be a good choice to diagnose Helicobacter pylori infection if endoscopy is indicated for a dyspeptic patient.

Adult↗
PubMed2003

Contribution of the gastrointestinal tract below the stomach to the 13C-urea breath test.

BACKGROUND: Graham et al. [Lancet, I (1987) 1174] found a late increase of 13C enrichment in the 13C-urea breath test 120 min after administration of labeled urea to patients without Helicobacter pylori infection. This may give false positive results. AIM: We designed this study to elucidate the contribution of the gastrointestinal tract below the stomach to the 13C-urea breath test. PATIENTS: Twenty-eight patients with dyspeptic symptoms who gave their consent were enrolled. METHODS: Patients underwent the 13C-urea breath tests both via the mouth (as usual) and the duodenum (labeled urea introduced to the second portion). Breath samples were collected at baseline, 5, 15, 30, 45, 60, 90, 120, 150 and 180 min for analysis. H. pylori status was defined by the CLOtest and by histological examination. RESULTS: There was no late increase in 13C enrichment of 13C-urea breath test for eight H. pylori negative patients either via the mouth or the duodenum. For those H. pylori positive patients, seventeen had no late rise 13C enrichment of the 13C-urea breath test via the duodenum and three patients had a rise after 15 min. CONCLUSIONS: No late rise in 13CO2 excretion to cause a positive 13C-urea breath test up to 180 min after the administration of labeled urea was found in the present study.

Adult↗
PubMed2003

Isolated fatal renal mucormycosis in a patient with chronic obstructive pulmonary disease and tuberculosis.

Renal mucormyosis is a rare entity and normally diagnosed at postmortem. Isolated cases diagnosed antemortem are even rarer and only a few cases have been reported. The disease is associated with a high mortality rate, especially in patients with underlying disease. Clinical presentation is non-specific and includes flank pain, fever and pyuria with or without haematuria. Identifying fungal hyphae microscopically is essential for diagnosis. We present a rare isolated fatal case of renal mucormycosis in a 77-year-old man with chronic obstructive pulmonary disease (COPD) and old tuberculosis (TB) who had been diagnosed after a right nephrectomy. We believe early diagnosis and appropriate treatment for fungal infection, together with the predisposing underlying disease, is crucial for survival.

Aged↗
PubMed2002

Carbonaceous characteristics of atmospheric particulate matter in Hong Kong.

To determine the characteristic of carbonaceous species in atmospheric particles in Hong Kong, PM10 and PM2.5 samples were collected using high volume (hi-vol.) air samplers from November 2000 to February 2001. The organic carbon (OC) and elemental carbon (EC) were analyzed by the selective thermal manganese dioxide oxidation (TMO) method. The ratios of PM2.5/PM10 mass ratios were 0.61, 0.78 and 0.53 for particulate matter collected at PolyU station (PolyU, near a major traffic corridor), Kwun Tong station (KT, mixed residential/commercial/industrial) and the Hok Tsui background station (HT), respectively. These results indicate that the PM2.5 concentrations constitute the majority of the PM10) concentrations, especially in urban and industrial areas of Hong Kong. The average concentrations at the three sites ranged from 73.11 to 83.52 microg/m3 for PM10 and from 42.37 to 57.38 microg/m3 for PM2.5. The highest daily mass concentrations of PM10 and PM2.5 were 125.89 microg/m3 and 116.89 microg/m3 at KT, respectively. The correlation between PM10 and PM2.5 was high at KT and HT (r > 0.9, P < 0.01). This means that the sources of PM10 and PM2.5 may be the same at both sites. The highest mean concentration of OC (12.02 microg/m3) and EC (6.86 microg/m3) in PM10 was found at the PolyU among the three sites. For PM2.5, the highest mean concentration of OC (10.16 microg/m3) was at KT while the highest mean concentration of EC (7.95 microg/m3) was at PolyU. However, the background concentrations at HT were higher than another background area, Kosan, Korea. Transportation of pollutants from the Asian continent may be responsible for the elevations of EC+ OC at the remote site. More than 74% of the EC and more than 79% of the OC were found in the PM2.5 fraction at the three sampling locations. At PolyU station, PM2.5 consisted of 18.18% OC and 11.16% EC while 17.70% OC and 8.81% EC were found in KT station. Thus OC and EC are major constituents of aerosols in Hong Kong. OC/EC ratios for PM10 and PM2.5 were less than 2 at PolyU and KT stations while the ratio exceeded 3 at HT background station. This indicates that OC measured in the urban area may be emitted directly as a primary aerosol.

Aerosols↗
PubMed2002

Identification of atmospheric volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs) and carbonyl compounds in Hong Kong.

Volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs) and carbonyl compounds are the major organic pollutants in the atmosphere. Emissions from motor vehicles have been one of the primary pollution sources in the metropolitan area of Hong Kong. A 12-month monitoring program for VOCs, PAHs and carbonyl compounds was performed at a roadside urban station at Hong Kong Polytechnic University (HKPU) in order to determine the correlations of each selected pollutant. The monitoring program ran from 16 April 1999 to 10 April 2000 for a period of 1 year, and a 2-week winter intensive sampling was carried out during January 2000. Traditionally, emission sources are identified from organic compounds in air particulates. Since many of the gaseous and particulate phases of organic compounds are from the same sources, correlations between the major exhausts are to be expected. Therefore, it would be more effective to apportion the sources using the combined gaseous and particulate phases of organic compounds. Correlations of selected pollutants within two other toxic air pollutants (TAPs) monitoring stations in Tsuen Wan (TW) and Central/Western (CW) were analyzed. Good correlations were found between pollutants that came from vehicle exhaust, especially in intensive sampling periods at HKPU roadside station. This was because the washing out effect for particulates during rainy days and photochemical degradation during high solar radiation were minimized in wintertime.

Air Pollutants↗
PubMed2002

Endothelin-1 in citric acid aerosol inhalation-induced airway constriction of guinea pigs.

Endotheline-1 (ET-1) has been shown to enhance tachykinin-induced airway constriction. This study was designed to test whether ET-1 is involved in citric acid-induced bronchoconstriction. Forty-eight anesthetized-paralyzed guinea pigs were divided into six groups of 8 animals each: saline control; citric acid; ET-1; ET-1 + citric acid; BQ123 + ET-1 + citric acid; and BQ788 + ET-1 + citric acid. BQ123 and BQ788 are specific ETA and ETB receptor antagonists, respectively. Each animal in the saline control group received 50 breaths of 4 ml saline aerosol and in all citric acid-treated groups was given 50 breaths of 4 ml aerosol generated from 0.6 M citric acid. In all ET-1-treated groups, each animal was exposed to aerosol generated from 10(-8) M ET-1. The animal in the ET-1 + citric acid group was exposed to ET-1 5 min prior to the citric acid. For the last two groups, each animal was first exposed to aerosol generated from either 10(-5) M BQ123 or 10(-5) M BQ788. Five min later, the animal was exposed to ET-1; and then 5 min later was followed by citric acid. Dynamic respiratory compliance (Crs), forced expiratory volume in 0.1 sec (FEV(0.1)), and maximal expiratory flow at 30% total lung capacity (Vmax 30) were obtained before and 3-15 min after citric acid. Either citric acid or ET-1 inhalation caused significant decreases in Crs, FEV(0.1), and Vmax 30, indicating airway constriction. Citric acid-induced airway constriction, for most cases, was not significantly augmented by ET-1. However, either BQ123 or BQ 788 significantly attenuated the airway constriction induced by the combination of ET-1 and citric acid. Also, in an additional study, either BQ123 or BQ788 significantly attenuated citric acid-induced airway constriction. These data suggest that endogenous ET-1 plays an important role in citric acid aerosol-induced airway constriction in guinea pigs.

Administration, Inhalation↗
PubMed2002

Volatile organic compounds (VOCs) in urban atmosphere of Hong Kong.

The assessment of volatile organic compounds (VOCs) has become a major issue of air quality network monitoring in Hong Kong. This study is aimed to identify, quantify and characterize volatile organic compounds (VOCs) in different urban areas in Hong Kong. The spatial distribution, temporal variation as well as correlations of VOCs at five roadside sampling sites were discussed. Twelve VOCs were routinely detected in urban areas (Mong Kok, Kwai Chung, Yuen Long and Causeway Bay). The concentrations of VOCs ranged from undetectable to 1396 microg/m3. Among all of the VOC species, toluene has the highest concentration. Benzene, toluene, ethylbenzene and xylenes (BTEX) were the major constituents (more than 60% in composition of total VOC detected), mainly contributed from mobile sources. Similar to other Asian cities, the VOC levels measured in urban areas in Hong Kong were affected both by automobile exhaust and industrial emissions. High toluene to benzene ratios (average T/B ratio = 5) was also found in Hong Kong as in other Asian cities. In general, VOC concentrations in the winter were higher than those measured in the summer (winter to summer ratio > 1). As toluene and benzene were the major pollutants from vehicle exhausts, there is a necessity to tighten automobile emission standards in Hong Kong.

Air Pollutants↗
PubMed2002

Degradation of IkappaBalpha in activated RAW264.7 cells is blocked by the phosphatidylinositol 3-kinase inhibitor LY294002.

The mechanism by which lipopolysaccharide (LPS) or phorbol 12-myristate 13-acetate (PMA) induces production of proinflammatory cytokines in murine macrophages, and the role of phosphatidylinositol 3-kinase (PI3-kinase) have not been well investigated. Activation of nuclear factor kappaB (NF-kappaB) is initiated by the phosphorylation of the inhibitory subunit, IkappaB, which targets IkappaB for degradation and leads to the release of active NF-kappaB. In this study we demonstrate that 2-(4-morpholinyl)-8-phenylchromone (LY294002), which inhibits PI3-kinase, specifically inhibited degradation of IkappaBalpha in RAW264.7 cells stimulated with interferon-gamma (IFN-gamma) plus LPS or IFN-gamma plus PMA. To elucidate the importance of this activity in RAW264.7 cells, we examined tumor necrosis factor-alpha (TNF-alpha) and interleukin (IL)-6 production in the activated cells. Pretreatment of the cells with LY294002 resulted in the inhibition of TNF-alpha and IL-6 production in RAW264.7 cells stimulated with IFN-gamma plus LPS or IFN-gamma plus PMA. Furthermore, LY294002 inhibited the production of nitric oxide (NO) in RAW264.7 cells stimulated with IFN-gamma plus LPS or IFN-gamma plus PMA. LY294002 also inhibited inducible NO synthase (iNOS) mRNA expression in the activated RAW264.7 cells. In conclusion, the present results suggest that PI3-kinase is involved in the signal transduction pathway responsible for LPS- or PMA-mediated TNF-alpha and IL-6 production, and that LY294002 inhibits NO generation through blocking the degradation of IkappaBalpha in activated RAW264.7 cells.

Animals↗
PubMed2002

Coiling of lumbar epidural catheters.

BACKGROUND: The difficulties in threading an epidural catheter to vertebral levels remote to the puncture level have been well documented. This study was undertaken to determine the length that a single orifice epidural catheter can be threaded into the lumbar space without coiling (coiling length), and whether this is affected by the direction of the epidural needle bevel. METHODS: Forty-five young male patients scheduled for surgery under epidural analgesia were enrolled. The epidural space was identified using a midline approach at the L(2-3) or L(3-4) interspace with the loss of resistance to air technique. A 19-G single-orifice epidural catheter (Flextip Plus, Arrow International, Inc, Reading, PA, USA) was inserted through a Tuohy needle oriented either cephalad (n=20) or caudad (n=25). During insertion, the path and the position of the catheter tip was determined by fluoroscopy using iohexol dye. RESULTS: The median coiling length was 2.8 cm, ranging from 1.0 to 8.0 cm. Only 13% of epidural catheters could be threaded 4 cm beyond the tip of the needle without coiling. No significant difference was found in coiling length between the cephalad group (2.9 cm) and the caudad group (2.5 cm). CONCLUSION: This study demonstrates that coiling length is independent of whether the bevel of the Tuohy needle is directed cephalad or caudad. We recommend that an optimal insertion depth of an end-hole single orifice catheter is 3 cm.

Adult↗
PubMed2002

Atlantoaxial rotatory subluxation in skeletally immature patients.

Treatments of atlanto-axial rotatory subluxation in children are generally conservative. Previous reports have proposed that surgical treatment be reserved for fixed rotatory subluxation of more than 3 months duration, irreducible deformity or cases of recurrence. Six skeletally immature patients with Fielding type III atlanto-axial rotatory subluxation were treated conservatively with or without subsequent atlanto-axial arthrodesis. The follow-up period for all the cases exceeded 18 months. Results and outcomes were analysed with an emphasis on the delay until diagnosis, causes of delays in diagnosis and factors influencing the necessity of surgical intervention. Neither mortality nor major morbidity was noted in any cases in this study. In our experience, type III fixed rotatory subluxation of 6 weeks duration will potentially recur. We recommend early surgery for type III fixed rotatory subluxation of more than than 3 months' duration, with atlanto-axial arthrodesis being a safe and effective procedure in children.

Atlanto-Axial Joint↗
PubMed2002

Risk factors for epistaxis during nasotracheal intubation.

We performed a study to confirm which risk factors are significantly associated with epistaxis during nasotracheal intubation. One hundred patients who underwent nasotracheal intubation were included. Risk factors for epistaxis were analysed using the multiple logistic regression analysis with stepwise variable selection method. Epistaxis was most likely to occur if transit of the tube through the nasal passage was difficult (P=0.0001, odds ratio 625, 95% confidence interval 3.14-14.26). On the other hand, age and gender, obesity, smoking, tube size, repeated attempts of intubation, and intubation performed with the aid of Magillforceps were not significantly related with risk of epistaxis. The presence of nasal anatomical abnormalities also did not correlate significantly with epistaxis. Strategies to ensure smooth transit of the tube through the nasal passageways are essential to reduce the incidence of epistaxis.

Adult↗
PubMed2001

Biomechanical evaluation of diagonal fixation in pedicle screw instrumentation.

STUDY DESIGN: Flexibility tests and finite element analyses were performed for the biomechanical evaluation of diagonal transfixation in pedicle screw instrumentation. OBJECTIVE: To assess the biomechanical advantages of diagonal transfixation compared with conventional horizontal transfixation. SUMMARY AND BACKGROUND DATA: A few pedicle screw instrumentation systems allow the use of cross-links in the diagonal direction. Such a diagonal transfixation is anticipated to improve the surgical construct stability, but its biomechanical qualities have not been completely evaluated. METHODS: Flexibility tests were performed on 10 calf lumbar spines (L2-L5). Specimens were subjected to pure moments up to 8.2 Nm in flexion, extension, lateral bending, and extension while the resulting movements of L3 and L4 were measured by a three-dimensional motion analysis system. The tested cases included (1) intact, (2) pedicle screw fixation without transfixation after total removal of the L3-L4 disc, (3) pedicle screw fixation with diagonal transfixation, and (4) pedicle screw fixation with horizontal transfixation. Three-dimensional finite element models of the tested surgical constructs were also developed by use of three-dimensional beam elements to investigate the effect of diagonal transfixation and horizontal transfixation on the construct stability and the corresponding stress changes in the screws. RESULTS: When compared with no transfixation, horizontal transfixation significantly improved the lateral bending and axial rotation stability by 15.7% and 13.9%, respectively, but there was no improvement of stability in flexion and extension. By contrast, diagonal transfixation significantly improved the flexion and extension stability by 12% and 10.7%, respectively, but not the lateral bending and axial rotation stability in comparison with no transfixation. Comparison between horizontal transfixation and diagonal transfixation showed that the stabilizing effect of diagonal transfixation was greater in flexion and extension (13% and 11%, P < 0.01) than that of horizontal transfixation but smaller in lateral bending (11%, P < 0.05) and axial rotation (6.6%, P > 0.1). Finite element model predictions of the motion changes were similar to the changes observed in flexibility tests. In horizontal transfixation, the load changes, compared with no transfixion, were a 0.02% increase in flexion-extension, a 27.5% increase in lateral bending, and a 58% decrease in axial rotation, and the magnitudes of the moments applied on both the right and left pedicle screws were identical. However, when diagonal transfixation was achieved by connecting the left superior screw and the right inferior screw, the loads in the left screw were increased by 11.5% in flexion-extension, 43.6% in lateral bending, and 7.9% in axial rotation, whereas the loads in the right screw were decreased by 10.9% in flexion-extension, increased by 0.06% in lateral bending, and decreased by 18.1% in axial rotation. CONCLUSIONS: The results of this study showed that diagonal transfixation provides more rigid fixation in flexion and extension but less in lateral bending and axial rotation in comparison with horizontal transfixation. Furthermore, greater stresses in the pedicle screws were predicted in the diagonal transfixation model. These limitations of diagonal transfixation should be considered carefully for clinical application.

Animals↗
PubMed2001

Lactate dehydrogenase genes of caiman and Chinese soft-shelled turtle, with emphasis on the molecular phylogenetics and evolution of reptiles.

L-Lactate dehydrogenase (LDH) cDNAs encoding for LDH-A(4) (muscle) and LDH-B(4) (heart) isozymes from caiman (Caiman crocodilus apaporiensis) belonging to the order Crocodilia and Chinese soft-shelled turtle (Pelodiscus sinensis) belonging to the order Chelonia were sequenced. The phylogenetic relationships of the newly determined cDNA and their deduced protein sequences, as well as the previously published sequences of vertebrate LDH isozymes, were analyzed by various phylogenetic tree construction methods. These results indicated that Chelonia is indeed more closely related to Crocodilia. The divergent times between caiman and alligator, turtle and soft-shelled turtle, and Chelonia and Crocodilia were estimated to be approximately 36, 100 and 177 million years, respectively.

Alligators and Crocodiles↗