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Biomedical subjects

C W Lee

Publications and source records attributed to C W Lee.

At least 73 records · Page 4Linked to original sources
PubMed2001

Chemical degradation of composite restoratives.

The chemical environment is one aspect of the oral environment, which could have an appreciable influence on the in vivo degradation of composite restoratives. The effects of chemical media on surface hardness of four composite restoratives (Silux [SX], Z100 [ZO], Ariston [AR] and Surefil [SF]) were investigated. The relationship between hardness and the thickness of the degradation layer was also studied. Thirty six specimens (3 x 4 x 2 mm) were made for each material. Following polymerization, the specimens were stored in artificial saliva at 37 degrees C for 24 h. The specimens were then randomly divided into six groups of six, subjected to microhardness testing (load = 500 gf, dwell time = 15 s) and stored in the following chemicals for 1 week at 37 degrees C: artificial saliva (S), distilled water (W), 0.02 N citric acid (C), 0.02 N lactic acid (L), heptane (H) and 75-25% ethanol-water solution (E). After conditioning, the specimens were again subjected to hardness testing and sectioned. Change in hardness (DH) was computed and the thickness of the degradation layer (DL) was measured using a computerized image analysis system at 600x magnification. Results of statistical analysis (ANOVA/Scheffe's [P < 0.05]) of DH based on materials were as follows: SX - E > all other mediums; ZO - W > C; and AR - S, W, E > H (> indicates significantly greater hardness change). No significant difference in DH was observed between the different chemicals for SF. The effects of chemical media on DH were found to be material dependent. A significant but weak positive correlation (Pearson's correlation [P < 0.05]) exists between change in hardness and thickness of the degradation layer.

Analysis of Variance↗
PubMed2001

Six-month angiographic follow-up after intravascular ultrasound-guided stenting of infarct-related artery: comparison with non-infarct-related artery.

BACKGROUND: Compared with balloon angioplasty, stenting has been established as an effective treatment modality to reduce restenosis in patients with acute myocardial infarction. However, the immediate results that predict favorable long-term outcomes in the acute infarct stenting are unknown. Therefore, we evaluated long-term outcomes of stenting for infarct-related artery (IRA) lesions by using intravascular ultrasound (IVUS) compared with that of stenting for non-IRA lesions. METHODS: IVUS-guided coronary stenting was successfully performed in 510 native coronary lesions (105 IRA vs 405 non-IRA). A 6-month follow-up angiogram was performed in 419 (82.2%) lesions: 87 (82.9%) IRA lesions and 332 (82.0%) non-IRA lesions. Coronary stenting on the IRA lesions was successfully performed within 7 to 10 days after onset of infarction in 42 patients and within 12 hours in 45 patients. Results were evaluated by clinical, angiographic, and IVUS methods. RESULTS: There were no significant differences in clinical and angiographic variables between the two groups. IVUS variables including reference vessel area and minimal stent area were also similar between the two groups. There was no significant difference in angiographic restenosis rate between the two groups in cases of minimal stent area > or = 7 mm(2): 12.8% (6 of 47) in IRA versus 19.1% (33 of 173) in non-IRA lesions (P = .315). However, the angiographic restenosis rate in cases of minimal stent area <7 mm(2) was 50% (20 of 40) in IRA lesions versus 31.5% (50 of 159) in non-IRA lesions (P = .028). CONCLUSIONS: Angiographic restenosis is significantly higher in stenting for IRA lesions compared with that for non-IRA lesions in cases of minimal stent area < 7 mm(2).

Angioplasty, Balloon, Coronary↗
PubMed2001

Adsorptive characteristics of cadmium and lead on the goethite-coated sand surface.

This study was conducted to develop a heating process for coating crystalline goethite on the sand surface to utilize the adsorbent properties of the coating. Goethite-coated sand was investigated for adsorbing cadmium and lead ions from water by batch and column experiments. Chemical analysis (energy dispersive analysis of X-ray, EDAX) was used for characterizing the cadmium and lead adsorption sites on goethite-coated sand. From the results of the batch experiments, the cadmium and lead ions could be adsorbed effectively on the goethite-coated sand. Maximum adsorption capacity values for cadmium and lead were 319, 704 micrograms-Cd/g-sand and 702, 1241 micrograms-Pb/g-sand at pH = 5.0, pH = 6.0, respectively. The interaction between cadmium, lead ions and goethite on sand surface was primarily to cause the chemical bonding. Results from column experiments indicated that the cadmium and lead ions could be removed higher than 95% before 110, 130 and 66, 85 numbers of pore volume of influent were treated at pH = 5.0 and pH = 6.0, respectively.

Adsorption↗
PubMed2001

A system to impose prescribed homogenous strains on cultured cells.

There is presently significant interest in cellular responses to physical forces, and numerous devices have been developed to apply stretch to cultured cells. Many of the early devices were limited by the heterogeneity of deformation of cells in different locations and by the high degree of anisotropy at a particular location. We have therefore developed a system to impose cyclic, large-strain, homogeneous stretch on a multiwell surface-treated silicone elastomer substrate plated with pulmonary epithelial cells. The pneumatically driven mechanism consists of four plates each with a clamp to fix one edge of the cruciform elastomer substrate. Four linear bearings set at predetermined angles between the plates ensure a constant ratio of principal strains throughout the stretch cycle. We present the design of the device and membrane shape, the surface modifications of the membrane to promote cell adhesion, predicted and experimental measurements of the strain field, and new data using cultured airway epithelial cells. We present for the first time the relationship between the magnitude of cyclic mechanical strain and the extent of wound closure and cell spreading.

Algorithms↗
PubMed2001

Clinical characteristics of constrictive pericarditis diagnosed by echo-Doppler technique in Korea.

A retrospective analysis of clinical data of 71 patients with constrictive pericarditis (CP) diagnosed by echo-Doppler technique (mean age, 49+/-17) was done. In 27 patients (38%), the etiology was unknown, and the three most frequent identifiable causes were tuberculosis (23/71, 32%), cardiac surgery (8/71, 11%), and mediastinal irradiation (6/71, 9%). Pericardiectomy was performed in 35 patients (49%) with a surgical mortality of 6% (2/35), and 11 patients (15%, 11/ 71) showed complete resolution of constrictive physiology with medical treatment. Patients with transient CP were characterized by absence of pericardial calcification, shorter symptom duration, and higher incidence of fever, weight loss, and tuberculosis. The 5-yr survival rates of patients with transient CP and those undergoing pericardiectomy were 100% and 85+/-6%, respectively, which were significantly higher than that of patients without undergoing pericardiectomy (33+/-17%, p=0.0083). Mediastinal irradiation, higher functional class, low voltage in ECG, low serum albumin, and old age were the independent variables associated with a higher mortality. Tuberculosis is still the most important etiology of CP in Korea, and not infrequently, it may cause transient CP. Early diagnosis and decision-making using follow-up echocardiography are crucial to improve the prognosis of patients with CP.

Adult↗
PubMed2001

Epidemiologic and clinical survey of Behcet's disease in Korea: the first multicenter study.

The prevalence of Behcet's disease is the highest in the East Asian and the Mediterranean countries. Behcet's disease is also distributed in the Asian countries, but the nationwide survey has not been performed in Korea yet. The Korean Study Group for Behcet's Disease, founded in 1999, conducted a multicenter, retrospective survey on epidemiologic and clinical features of the patients with Behcet's disease from 20 hospitals around the nation from 1997 to 1999. Of 3,497 patients, 1,527 were classified into complete or incomplete type of Behcet's disease according to the revised Shimizu's classification. The sex ratio was 1:1.75 with the female predominance. Geographical distribution showed the highest frequency in Seoul (38.5%). Clinically, 98.8% had oral ulcers, 83.2% had genital ulcers, 84.3% had skin lesions and 50.9% had ocular lesions. As for the minor clinical manifestations, articular symptoms were the most frequent. The pathergy test showed positive in 15.4% of patients and revealed a higher positive rate in males (20.2%) than in females (12.7%). In conclusion, we performed the first multicenter study on Behcet's disease in Korea and revealed the female predominance, higher frequency of ocular lesions, and lower positivity of pathergy test in the patients.

Adolescent↗
PubMed2001

Retinal vein occlusion in two patients with primary antiphospholipid syndrome.

Primary antiphospholipid syndrome (APS) is a disease producing vascular thrombus with antiphospholipid antibody without association with autoimmune diseases as systemic lupus erythematosus. Retinal vein occlusion is a rare vascular manifestation in primary APS. We describe 2 cases of primary APS presenting with developing blurred vision. Each had central retinal vein occlusion and high titer of IgG anticardiolipin antibody.

Adult↗
PubMed2001

Improved interactive medical and public health education in Japan and Korea.

We have carried out case based comparative studies in Japan, US and Korea with special reference to the medical education programme using standardized patients (SPs). The schools in US we have visited are still in the process further reforming interactive medical education. In Daegu, Korea, five medical schools have jointly started a working group for the betterment of medical education on a regular basis from the year 1999. The emphasis is on cooperative research on standardized patient training and its application. In Japan, the substantial activities for training and implementing SPs were later followed by several citizens who are active in training and providing SPs to medical schools and hospitals in need. In comparison to the established research oriented framework and flexible application of SPs in US and new & dynamic developmental discussions of SPs in Korea, the Japanese reality is a bit behind with less opportunity for research oriented trials.

Competency-Based Education↗
PubMed2001

Cecal rupture by Anoplocephala perfoliata infection in a thoroughbred horse in Seoul Race Park, South Korea.

A 7-year-old Thoroughbred horse was admitted to the Equine Hospital, Korea Racing Association with signs of colic. Based on the size of impactions, the clinical signs, the results of abdominal paracentesis and medical treatment, the prognosis was poor. The horse died 3 hours later following hopeless discharge. At necropsy, the caecum and large colon were fully filled with fecal contents and there was a rupture (10 cm in dia) in the latero- ventral caecum. The mucosa of the ileo-caecal and caeco- colic valves appeared to the hyperemic, edematous and ulcerous. There were many tapeworms in the affected mucosa. Histopathologically, lesions included hyperaemia, a deep necrotic inflammatory lesion and ulcers in the mucosa and submucosa of ileo-caecal and caeco-colic valves. One hundred thirty four faecal samples were obtained from 16 stables and submitted to parasitic examination. A total of 4 genera of eggs were recovered: Stongylus spp (82.1%), Anoplocephala perfoliata (10.5%), Bovicola equi (0.7%) and Parascaris equorum (1.5%). The major findings in this study are the presence of A perfoliata and its suspected association with the colic which led into an eventual caecal rupture. This study indicates the needs for an epidemiological survey of colic that is associated with Anoplocephala.

Animals↗
PubMed2000

Long-term outcomes of minor dissection at the edge of stents detected with intravascular ultrasound.

We evaluated the influences of minor edge dissections on late angiographic in-stent restenosis in 327 patients with 348 lesions (281 lesions without edge dissection and 67 lesions [19.3%] with edge dissection); the angiographic restenosis rate was 29.9% in the lesions with edge dissections versus 25.3% without edge dissections (p = 0.540). The minor non-flow-limiting dissections at the edge of stents may not be associated with the development of late angiographic in-stent restenosis.

Coronary Angiography↗
PubMed2000

Effects of cilostazol on angiographic restenosis after coronary stent placement.

This study evaluates the impact of cilostazol on post-stenting restenosis. Cilostazol is a potent antiplatelet agent with antiproliferative properties. Few data are available about the effect of cilostazol on poststenting restenosis. Four hundred nine patients (494 lesions) who were scheduled for elective stenting were randomized to receive aspirin plus ticlopidine (group I, n = 201, 240 lesions) or aspirin plus cilostazol (group II, n = 208, 254 lesions), starting 2 days before stenting. Ticlopidine was given for 1 month and cilostazol for 6 months. Follow-up angiography was performed at 6 months, and clinical evaluation at regular intervals. Baseline characteristics were similar between the 2 groups. The procedural success rate was 99.6% in group I and 100% in group II. There were no cases of stent thrombosis after stenting. Angiographic follow-up was performed in 380 of the 494 eligible lesions and the angiographic restenosis rate was 27% in group I and 22.9% in group II (p = NS). However, diffuse type in-stent restenosis was more common in group I than in group II (54.2% vs 26.8%, respectively, p <0.05). In diabetic patients, the angiographic restenosis rate was 50% in group I and 21.7% in group II (p <0.05). Clinical events during follow-up did not differ between the 2 groups. In conclusion, aspirin plus cilostazol seems to be an effective antithrombotic regimen with comparable results to aspirin plus ticlopidine, but it does not reduce the overall angiographic restenosis rate after elective coronary stenting.

Angioplasty, Balloon, Coronary↗
PubMed2000

Origin of the high affinity and selectivity of novel receptors for NH4+ over K+: charged hydrogen bonds vs cation-pi interaction.

[structure: see text]Given the recent report of a novel pyrazole receptor exhibiting a high selectivity for NH4+ over K+, it would be interesting to investigate the origin of this selectivity and affinity so that better receptors could be designed. On the basis of extensive theoretical studies, we conclude that the origin arises from a subtle interplay of charged H-bonds and cation-pi interactions. The approach employed herein would be very useful in the rational design of novel functional molecular systems.

Cations↗
PubMed2000

Effect of intravenous omeprazole on recurrent bleeding after endoscopic treatment of bleeding peptic ulcers.

BACKGROUND: After endoscopic treatment of bleeding peptic ulcers, bleeding recurs in 15 to 20 percent of patients. METHODS: We assessed whether the use of a high dose of a proton-pump inhibitor would reduce the frequency of recurrent bleeding after endoscopic treatment of bleeding peptic ulcers. Patients with actively bleeding ulcers or ulcers with nonbleeding visible vessels were treated with an epinephrine injection followed by thermocoagulation. After hemostasis had been achieved, they were randomly assigned in a double-blind fashion to receive omeprazole (given as a bolus intravenous injection of 80 mg followed by an infusion of 8 mg per hour for 72 hours) or placebo. After the infusion, all patients were given 20 mg of omeprazole orally per day for eight weeks. The primary end point was recurrent bleeding within 30 days after endoscopy. RESULTS: We enrolled 240 patients, 120 in each group. Bleeding recurred within 30 days in 8 patients (6.7 percent) in the omeprazole group, as compared with 27 (22.5 percent) in the placebo group (hazard ratio, 3.9; 95 percent confidence interval, 1.7 to 9.0). Most episodes of recurrent bleeding occurred during the first three days, which made up the infusion period (5 in the omeprazole group and 24 in the placebo group, P<0.001). Three patients in the omeprazole group and nine in the placebo group underwent surgery (P=0.14). Five patients (4.2 percent) in the omeprazole group and 12 (10 percent) in the placebo group died within 30 days after endoscopy (P=0.13). CONCLUSIONS: After endoscopic treatment of bleeding peptic ulcers, a high-dose infusion of omeprazole substantially reduces the risk of recurrent bleeding.

Aged↗
PubMed2000

Stereoselectivity of macrocyclic ring-closing olefin metathesis.

[reaction: see text] Macrocyclic ring-closing olefin metathesis using ruthenium catalyst 3 was performed to produce a 14-membered lactone. The E/Z ratio of lactone was high regardless of the R group (auxiliary) or the initial alkene stereochemistry. A kinetic study demonstrates that the high E/Z ratio is due to secondary metathesis reactions that isomerize the product to the thermodynamic E/Z ratio.

Alkenes↗
PubMed2000

The statistical variability of blood alcohol concentration measurements in drink-driving cases.

Like many other places in the world, Hong Kong has drink-driving legislation which prohibits a driver from having in his blood alcohol exceeding a prescribed limit while in control of a motor vehicle. The accuracy of measuring this alcohol concentration is obviously of prime concern as an erroneous result can avert the administration of justice. The common practice is to deduct all errors from the measured value and compare the deducted value with the prescribed limit, so that the benefit of all errors of the measurement is given to the driver. It is therefore important for any laboratory responsible for measuring blood alcohol concentrations to identify and quantify all errors associated with the measurement. The present study examined 900 blood alcohol determinations carried out by the Hong Kong Government Laboratory (HKGL) on cases of suspected drink driving. The determinations were performed by 5 different analysts with two different sets of instruments during 1995-1997. Statistical analysis indicated that the instruments had no bearing on the random error or variability and that even though analyst was a significant factor on variability, the deviation from the mean so caused was only 0.3% and of no practical significance. When the systematic error introduced by the tolerance limits of the certified alcohol standards (purchased from the Laboratory of Government Chemists, UK) was taken into account, the total uncertainty (random plus systematic errors) of an alcohol determination at 99.5% confidence level was found to be 4%. It is recommended that laboratories engaged in blood alcohol determination should adopt similar statistical treatment of their analytical results to find out the error and to ensure that the results are independent of analyst and instrument used.

Automobile Driving↗
PubMed2000

Pressure-derived fractional collateral blood flow: a primary determinant of left ventricular recovery after reperfused acute myocardial infarction.

OBJECTIVES: We evaluated the relation between pressure-derived fractional collateral flow (PDCF) and left ventricular (LV) recovery after reperfused acute myocardial infarction (AMI). BACKGROUND: The functional significance of collateral flow remains uncertain in AMI. METHODS: The PDCF was measured in 70 patients with first AMI (pain onset <12 h) treated with primary angioplasty (PA), being determined by simultaneous measurement of mean aorta pressure (Pa), distal coronary pressure during the balloon occlusion (Poc), and central venous pressure (CVP): (Poc - CVP)/(Pa - CVP)*100. Sufficient collateral (group I) was defined as PDCF index >24% and insufficient collateral (group II) as PDCF index <24%. Echocardiography was performed before, and on day 3, day 7, and day 30 after PA. Wall-motion recovery index (RI) was obtained by dividing the number of improved wall-motion segments (>grade 1) at follow-up by the number of abnormal wall-motion segments within the infarct zone at baseline. RESULTS: Baseline characteristics were similar between both groups. Peak levels of creatine kinase were lower in group I than in group II (2,600+/-1,900 U/liter vs. 4,100+/-3,000, p < 0.05). At one month, infarct zone wall-motion score index (1.65+/-0.54 vs. 2.31+/-0.46, p < 0.01) and LV volume indexes were smaller in group I than in group II, whereas, LV ejection fraction was higher in group I than in group II (52.8+/-8.3 vs. 45.9+/-9.0, p < 0.01). The PDCF index was the strongest predictor of RI at one month (r = 0.61, p < 0.01). Time to reperfusion was not related to RI at one month. However, it was significantly related to RI in group II (r = -0.34, p < 0.05). CONCLUSIONS: The LV recovery after reperfused AMI is primarily determined by PDCF and is less dependent on time to reperfusion in patients with sufficient collaterals.

Adult↗
PubMed2000

The demonstration of Pasteurella multocida in the alimentary tract of chickens after experimental oral infection.

A selective medium containing polymyxin B, crystal violet, thallous acetate, bacitracin and cycloheximide in 10% sheep blood dextrose starch agar, and a modified Pasteurella multocida-specific polymerase chain reaction (PCR) assay were developed for the respective isolation and detection of P. multocida from chicken alimentary tract. The selective medium and the PCR assay were highly sensitive, detecting 100 cfu from colon contents. These techniques were used to follow the localisation of an orally administered virulent P. multocida in chickens. Pasteurellae could be isolated from the crop of some birds up to 30 h, occasionally from other sites after 28 h. It was concluded that the crop was a likely site for colonisation and that infection was most likely to occur through the mucosa of the jejunum or ileum.

Administration, Oral↗