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Biomedical subjects

C K Lee

Publications and source records attributed to C K Lee.

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

Challenge model for Helicobacter pylori infection in human volunteers.

BACKGROUND: A reliable challenge model is needed to evaluate Helicobacter pylori vaccine candidates. METHODS: A cag pathogenicity island negative, OipA positive, multiple antibiotic susceptible strain of H pylori obtained from an individual with mild gastritis (Baylor strain 100) was used to challenge volunteers. Volunteers received 40 mg of famotidine at bedtime and 10(4)-10(10) cfu of H pylori in beef broth the next morning. Infection was confirmed by (13)C urea breath test ((13)C-UBT), culture, and histology. Eradication therapy was given four or 12 weeks post challenge and eradication was confirmed by at least two separate UBTs, as well as culture and histology. RESULTS: Twenty subjects (nine women and 11 men; aged 23-33 years) received a H pylori challenge. Eighteen (90%) became infected. Mild to moderate dyspeptic symptoms occurred, peaked between days 9 and 12, and resolved. Vomitus from one subject contained >10(3) viable/ml H pylori. By two weeks post challenge gastric histology showed typical chronic H pylori gastritis with intense acute and chronic inflammation. The density of H pylori (as assessed by cfu/biopsy) was similarly independent of the challenge dose. A minimal infectious dose was not found. Gastric mucosal interleukin 8 levels increased more than 20-fold by two weeks after the challenge. CONCLUSION: Challenge reliably resulted in H pylori infection. Infection was associated with typical H pylori gastritis with intense polymorphonuclear cell infiltration and interleukin 8 induction in gastric mucosa, despite absence of the cag pathogenicity island. Experimental H pylori infection is one of the viable approaches to evaluate vaccine candidates.

Adolescent↗
PubMed2004

Impact of severe respiratory syndrome on anxiety levels of front-line health care workers.

OBJECTIVE: To identify anxiety levels among front-line health care workers during the 2003 severe acute respiratory syndrome outbreak. DESIGN: Questionnaire survey. SETTING: Regional hospital, Hong Kong. PARTICIPANTS: All hospital staff were given a questionnaire; administrative staff who had not had any patient contact served as controls. MAIN OUTCOME MEASURES: Levels of contact with patients who had severe acute respiratory syndrome were measured and correlated with anxiety levels as determined by the State-Trait Anxiety Inventory. RESULTS: Of 4252 questionnaires distributed between May and June 2003, 2040 (48.0%) were returned and 1926 (45.3%) were valid for analysis. Overall, 534 (27.7%) respondents had had contact with patients with severe acute respiratory syndrome. Anxiety scores ranged from 20 to 80, and mean (standard deviation) scores were higher among staff who had had contact with patients with severe acute respiratory syndrome than among those who had not (52.6 [10.5] versus 49.8 [10.1], respectively; P<0.01). Mean anxiety levels were higher among workmen, health care assistants, and nurses than among administrative staff controls or doctors (P<0.01). Anxiety scores were correlated with burnout scores (Pearson's correlation coefficient, 0.52-0.59) and with discomfort from wearing protective gear (0.21-0.32). CONCLUSION: Severe acute respiratory syndrome has likely stressed the public health care system. Prediction and early identification of adverse factors in a crisis situation would allow early implementation of interventions to reduce and counteract the impact of this stress.

Anxiety↗
PubMed2003

Removal of Cu and Pb by tartaric acid modified rice husk from aqueous solutions.

A study on the modification of rice husk by various carboxylic acids showed that tartaric acid modified rice husk (TARH) had the highest binding capacities for Cu and Pb. The carboxyl groups on the surface of the modified rice husk were primarily responsible for the sorption of metal ions. A series of batch experiments using TARH as the sorbent for the removal of Cu and Pb showed that the sorption process was pH dependent, rapid and exothermic. The sorption process conformed to the Langmuir isotherm with maximum sorption capacities of 29 and 108 mg/g at 27 +/- 2 degrees C for Cu and Pb, respectively. The uptake increased with agitation rate. Decrease in sorbent particle size led to an increase in the sorption of metal ions and this could be explained by an increase in surface area and hence binding sites. Metal uptake was reduced in the presence of competitive cations and chelators. The affinity of TARH for Pb is greater than Cu.

Adsorption↗
PubMed2003

Prevalence and specificity of clinically significant red cell alloantibodies in Chinese women during pregnancy--a review of cases from 1997 to 2001.

Guidelines for the prevention and management of red cell alloantibodies during pregnancy, related to anti-D in particular, are well established in Caucasian populations. However, because of the racial difference of the blood group distribution, applicability to Chinese is unknown as a result of insufficient data on the prevalence and their outcome. In a retrospective review of 28,303 (21,327 Chinese) antenatal attendances from 1997 to 2001, 213 (0.79%) women were found to have a total of 230 irregular antibodies. About 137 (0.64%) were ethnic Chinese, and a total of 160 irregular antibodies were identified in their blood samples. About 58 of these Chinese women (0.27%) were found to have 66 clinically significant antibodies. There was only one case of anti-D detected in an Rh(D)-negative subject. Our study shows the overall prevalence of clinically significant antibodies in Chinese women, which was not different from that of the Western population. However, the specificities of the antibodies differ with the commonest antibodies encountered; these being anti-Mi (57.6%), anti-E (19.7%), anti-S (10.6%) and anti-c (7.6%). Neonatal jaundice was observed in 37 babies and 10 of them required phototherapy. The findings support the previous recommendation that routine antenatal antibody screening for Chinese women may not be worthwhile except in Rh(D)-negative subjects or those with an antecedent history of haemolytic disease of the newborn (HDN). The relative high incidence of anti-Mi in the present study and the local population, in general, may warrant a large-scale prospective study of pregnancy outcome in these subjects, especially in the light of the previous case reports of HDN because of anti-Mi.

Adult↗
PubMed2003

Estimation of bacterial risk in extending the shelf life of PLT concentrates from 5 to 7 days.

BACKGROUND: The use of bacterial culture to prevent bacterial contamination of blood components has renewed interest for extending the shelf life of PLT concentrates to 7 days after collection. STUDY DESIGN AND METHODS: This study was therefore conducted to determine the residual risk of bacterial contamination in PLT concentrates at the end of 5 and 7 days after collection in a center where all PLT concentrates are routinely screened by taking samples on Day 2 for culture. PLT units with no growth after 48 hours were sampled a second time on Day 5 or Day 7 after collection, followed by inoculation into aerobic culture bottles. The inoculated bottles were then monitored for up to 7 days at 35 degrees C in an automatic monitoring and detection system. RESULTS: During a 16-month study period, a total of 6020 PLT concentrates were tested 5 days (Group A, n=3010) and 7 days (Group B, n=3010) after collection. Four units in each group (0.133%) were found to be contaminated. In 6 units, bacteria were seen on direct Gram stain. In addition, 5 of the associated RBC units grew the same organisms on culture. The organisms include three coagulase-negative staphylococci and five Propionibacterium acnes. The positive rate of routine short-term bacterial culture was 0.035 percent during the same study period. CONCLUSION: Despite routine short-term bacterial culture, a significant risk of bacterial contamination remains at 5 and 7 days after collection. For now, the shelf life of PLT concentrates should remain 5 days.

Bacteria↗
PubMed2003

Acid-activated spent bleaching earth as a sorbent for chromium (VI) in aqueous solution.

Spent bleaching earth, an industrial waste produced after the bleaching of crude palm oil, was investigated for its potential in removing Cr(VI) from aqueous solution. The earth was treated with different amounts of sulfuric acid and under different activation temperatures. Results show that the optimum treatment process involved 10% sulfuric acid at 350 degrees C. The effects of contact time, pH, initial concentration, sorbent dosage, temperature, sorption isotherms and the presence of other anions on its sorption capacity were studied. Isotherm data could be fitted into a modified Langmuir isotherm model implying monolayer coverage of Cr(VI) on acid activated spent bleaching earth. The maximum sorption capacity derived from the Langmuir isotherm was 21.2 mg g(-1). This value was compared with those of some other low cost sorbents. Studies of anion effect on the uptake of Cr(VI) on acid activated spent bleaching earth provided the following order of suppression: EDTA >PO4(3-)>SO4(2-)>NO3(-)>Cl(-).

Adsorption↗
PubMed2003

Monitoring PAH-contaminated soil using laser-induced fluorescence (LIF).

The heterogeneity and opacity of soil matrices pose considerable challenges for the quantification of soil contaminants. In order to investigate the feasibility of applying the Laser-Induced Fluorescence technique to measure contamination levels of soils, statistical analyses of contaminant levels and intensity of fluorescence were investigated in relation to soil properties. A significant correlation (R2 > 0.97) between contaminant levels and intensity of fluorescence was shown under different matrix conditions, such as moisture content and particle size distribution. Higher fluorescence intensities were obtained from soils with higher sand and moisture content. The statistical results in relation to the interaction between fluorescence intensity and matrix properties rejected the hypothesis that all properties of the matrices and contaminants had an equal influence on fluorescence. This implied that the concentrations of contaminants had the greatest contribution to the fluorescence intensity, but other variables also showed a considerable influence.

Environmental Monitoring↗
PubMed2003

Sorption of Cr(VI) and Cu(II) in aqueous solution by ethylenediamine modified rice hull.

The sorption characteristics of Cr(VI) and Cu(II) by ethylenediamine modified rice hull from single and binary metal ion solutions were evaluated under various experimental conditions. Optimal Cr(VI) and Cu(II) removal from single metal ion solutions occurred at pH 2.0 and 5.5, respectively. Simultaneous removal of Cr(VI) and Cu(II) occurred at pH greater than 3.0. The sorption kinetics of Cr(VI) and Cu(II) from single and binary metal ion solutions were studied with reference to metal concentration, agitation rate and particle size. Sorption of Cr(VI) was more rapid than Cu(II). The kinetics of metal ion sorption fitted a pseudo-second order expression. The variation in the initial uptake rates was very small at an agitation rate beyond 150 rpm and sorption was generally independent of particle size. Equilibrium sorption data could be fitted into the Langmuir isotherm equation. Maximum sorption capacities of ethylenediamine modified rice hull for Cr(VI) at pH 2 and Cu(II) at pH 4 in single metal solutions were 0.45 and 0.06 mmol g(-1), respectively. This corresponds to an enhancement factor of 2.6 and 3 fold for Cr(VI) and Cu(II), respectively, compared to natural rice hull. A synergistic effect was observed for sorption of these ions in binary metal solutions.

Adsorption↗
PubMed2003

Leakage of cement in percutaneous transpedicular vertebroplasty for painful osteoporotic compression fractures.

e analysed the CT scans and radiographs of 76 vertebrae in 49 patients who underwent vertebroplasty for painful osteoporotic compression fractures. Leaks of cement were classified into three types: those via the basivertebral vein (type B), via the segmental vein (type S), and through a cortical defect (type C). More leaks were identified on CT scans than on radiographs by a factor of 1.5 (74/49). Most type-B (93%) and type-S (86%) leaks were missed or underestimated on a lateral radiograph which is usually the only view used during the injection of cement. Of the leaks into the spinal canal, only 7% (2/28) were correctly identified on radiographs. The areas on lateral radiographs where this type of leak may be observed were divided into four zones, and their diagnostic value in predicting a leak into the spinal canal was evaluated. The results showed that cement in the neural foramina had the highest positive predictive value (86%).

Aged↗
PubMed2003

Copper vapour laser ID labelling on metal dentures and restorations.

Denture marking is accepted as a means of identifying dentures and persons in geriatric institutions, or post-mortem during war, crimes, civil unrest, natural and mass disasters. Labelling on the acrylic resin component of the denture can easily be damaged or destroyed by fire but on cobalt-chromium components it would be more resistant. A copper vapour laser (CVL) can be used to label the cobalt-chromium components of dentures and metal restorations easily, and legibly, and miniaturised for the incorporation of more personal particulars necessary for the identification of the deceased person. The CVL beam is focussed by its optics and delivered to the material surface by the two-axis scanner mounted with mirrors. A personal computer controls the movement of the scanner and the firing of the CVL. The high peak power of the pulsed CVL is focussed to very high energy density producing plasma ablation of the alloy surface. Very fine markings of a few microns width can be produced enabling the storage of detailed information of the deceased person on a metal surface for the purpose of rapid identification.

Chromium Alloys↗
PubMed2002

Acute thoracolumbar burst fractures: a new view of loading mechanisms.

STUDY DESIGN: An in vitro investigation of loading mechanisms in acute thoracolumbar burst fractures. OBJECTIVES: To assess the validity of the authors' hypothesis that anterior shear forces transmitted by the facet joints are responsible for causing the severe canal compromise associated with acute thoracolumbar burst fractures. SUMMARY OF BACKGROUND DATA: Thoracolumbar burst fractures created in the laboratory rarely match the severity of clinical cases. To date, no studies have examined in great detail the role of facet joint loading in the burst-fracture mechanism. An incomplete understanding of loading mechanisms may contribute to the controversies regarding management. METHODS: Nine human cadaveric motion segments were instrumented with strain gages and subjected to axial compression or axial impact coupled with an extension moment. Failure loads, strain information, and radiographs were collected. RESULTS: Fracture patterns characteristic of acute thoracolumbar burst fractures were observed in the three specimens tested with an extension moment. In this group, high strains were also recorded at the bases of the pedicles, indicating a probable site of fracture initiation. Specimens tested in a neutral orientation experienced crush fractures without an increase in interpedicular distance. Strain patterns were more uniform in this group. CONCLUSIONS: The severity and clinical relevance of the injuries sustained by the specimens tested in extension suggest that facet joint loading plays a critical role in the acute thoracolumbar burst-fracture loading mechanism. Fracture patterns and strain concentrations are in agreement with clinical observations as well as past experimental studies.

Acute Disease↗
PubMed2002

A dose escalation study for salvage chemotherapy in patients with refractory lymphoma prior to high-dose myeloablative therapy with stem cell transplantation.

Chemosensitive response prior to transplantation has been shown to be most significant for survival post transplant. To estimate toxicity of a dose-intensive regimen that was to improve chemosensitive response rate, 15 patients with primary refractory lymphoma were enrolled in dose escalation of pre-transplant salvage chemotherapy. The first cycle had a fixed dose of ifosfamide 6 g/m2 and mitoxantrone 12 mg/m2, with arabinosyl cytosine (Ara-C) 2 g/m2, and methylprednisolone 2.0 g. Each cycle of the second and third had cisplatin 90 mg/m2, Ara-C 6 g/m2, methylprednisolone 2.0 g, and escalated doses of ifosfamide from 7.5 g/m2 to 15 g/m2 and mitoxantrone from 16 to 28 mg/m2. Blood stem cells were collected before the second cycle and > or = 3 x 10(6) CD34 cells/kg were infused 2 days after the second and third cycles, respectively. The maximum tolerated doses of ifosfamide and mitoxantrone were 11.25 g/m2 and 16 mg/m2, respectively. Acute renal failure and bacterial infection occurred as non-hematologic dose limiting toxicities. Eleven patients completed therapy. Five patients achieved complete remission and five had partial remission. Nine patients received autologous and four received allogeneic transplants. Currently, six are alive without evidence of disease, with a 3-year survival of 40%. Although preliminary, the regimen suggests acceptable toxicity and significant activity that warrants further study.

Acute Kidney Injury↗
PubMed2002

Efficacy of enzyme immunoassay for the detection of Helicobacter pylori antigens in frozen stool specimens: local validation.

AIM: To investigate the efficacy of measurement of Helicobacter pylori stool antigen (HpSA) using stored frozen stool specimens, and to assess whether there were factors affecting efficacy in Hong Kong. METHODS: Patients undergoing upper endoscopy at Tuen Mun Hospital were recruited. Stool samples were saved for HpSA testing and questionnaires were completed. Stool samples were frozen immediately upon receipt and stored at -70 degrees C until tested. HpSA results were compared with rapid urease test and histology. RESULTS: One hundred and eighty-one patients were recruited. One hundred and seventy-eight patients were suitable for analysis. Eighty-three were H. pylori positive and 95 were H. pylori negative. The mean duration of storage of the stool samples was 120 days (range, 40-225 days). The sensitivity, specificity and positive and negative predictive values were 84.3%, 97.9%, 97.2% and 88.6%, respectively. In patients with a false negative HpSA test, there was a significant delay in collecting the stool specimen after endoscopy when compared with those with a true positive HpSA test (4.2 vs. 2.3 days; P < 0.05). However, the duration of storage of the specimens was not longer, and consumption of coffee or tea and smoking habits were similar. CONCLUSIONS: HpSA testing showed good sensitivity and specificity, even with frozen stool samples stored for up to 225 days. The efficacy was not affected by coffee, tea or smoking.

Adult↗
PubMed2002

Impact of donor arm skin disinfection on the bacterial contamination rate of platelet concentrates.

BACKGROUND AND OBJECTIVES: Despite improved methods for detecting bacterial contamination of blood products, bacterial sepsis remains a significant risk in blood transfusion. This study was undertaken to investigate whether adopting a different skin disinfection protocol could reduce the rate of bacterial contamination of platelet concentrates. MATERIALS AND METHODS: Two skin disinfection protocols were consecutively used in the routine blood collection setting during two 10-month periods: 0.5% cetrimide/0.05% chlorhexidine solution followed by 70% isopropyl alcohol (first 10-month time-period); and 10% povidone-iodine followed by 70% isopropyl alcohol (second 10-month time-period). The rates of bacterial contamination of platelet concentrates were monitored by using a surveillance programme described previously. RESULTS: The overall bacterial contamination rate in the first time-period was 0.072%. After introduction of the povidone-iodine and isopropyl alcohol protocol, the bacterial contamination rate decreased to 0.042% (relative risk reduction: -0.42; 95% confidence interval, -0.12 to -0.61, P= 0.009). There were no differences in the types of micro-organisms identified (P = 0.7). CONCLUSIONS: Skin disinfection by povidone-iodine and isopropyl alcohol is more effective than that by cetrimide/chorhexidine and isopropyl alcohol in reducing venepuncture-associated contamination of platelet concentrates by skin flora. Our data indicate that the disinfection protocol should be used on a routine basis and such implementation should translate into a significant improvement in blood safety to patients receiving platelet transfusion.

2-Propanol↗
PubMed2002

Application of narrow band laser ultrasonics to the nondestructive evaluation of thin bonding layers.

In this paper, a modified laser induced grating technique (LIG) has been utilized to generate narrow band surface waves in an epoxy-bonded copper-aluminum layered structure. A high performance optical interferometer system was utilized to detect the laser-generated surface waves. The dispersion of surface wave in an epoxy-bonded copper-aluminum specimen was measured and compared with the theoretical solution. An inverse algorithm based on the simplex method was then introduced to determine the bonding thickness as well as the elastic properties of the bonding layer. The inversion results demonstrated that the thickness in the microm range or the elastic properties of the bonding layer could be successfully determined.

Journal Article↗
PubMed2002

Streptococcus pneumoniae bacteremia in southern Taiwan.

Streptococcus pneumoniae bacteremia was diagnosed in 33 patients between June 1999 and November 2000 at the Chang Gung Memorial Hospital-Kaohsiung in southern Taiwan. Antimicrobial susceptibility and serotyping of the clinical isolates were performed. Pneumonia was diagnosed in 19 patients, primary bacteremia in 13, and meningitis in one. The most common serotypes were types 14, 3, and 23F. Fourteen (42.4%) isolates of S. pneumoniae were non-susceptible to penicillin. High antimicrobial resistance rates were found to erythromycin (81.9%), tetracycline (69.7%), clindamycin (69.7%), trimethoprim-sulfamethoxazole (33.1%), and chloramphenicol (12.1%). The mortality was 42.4% and liver cirrhosis was an independent risk factor for mortality (odds ratio = 9.998; 95% confidence interval, 1.011-98.85; p=0.049). All isolated strains were covered by 23-valent the pneumococcal vaccine. Given the increasing prevalence of penicillin non-susceptible S. pneumoniae infection in the community, ongoing periodic monitoring of the evolutionary clinical situation is needed. Results of this study suggest that patients with liver cirrhosis should be inoculated with pneumococcal vaccine.

Adult↗
PubMed2001

Two ethyl 2-deoxy-alpha-D-hexo-3,7-pyranoso-3-octulosonate derivatives.

In each of the two pyranoid sugars, ethyl 2-deoxy-4,5,6,8-tetra-O-acetyl-alpha-D-gluco-3,7-pyranoso-3-octulosonate, C18H26O12, and ethyl 2-deoxy-4,5,6,8-tetra-O-benzyl-alpha-D-galacto-3,7-pyranoso-3-octulosonate, C38H42O8, the anomeric configuration is alpha. The acetoxymethyl substituent on the hexopyranose ring of the former compound and the ethoxycarbonylmethyl substituents in both sugars all have the gauche-trans conformation, while the benzyloxymethyl substituent of the galactopyranose sugar has the trans-gauche conformation. In each structure, the anomeric hydroxy group forms an intramolecular hydrogen bond with the carbonyl O atom of the ethoxycarbonylmethyl substituent.

Journal Article↗