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Biomedical subjects

C H Lee

Publications and source records attributed to C H Lee.

At least 127 records · Page 7Linked to original sources
PubMed2001

Dietary hematein ameliorates fatty streak lesions in the rabbit by the possible mechanism of reducing VCAM-1 and MCP-1 expression.

Hematein is a compound isolated from Caesalpinia sappan that has been used in oriental medicine as both an analgesic and an anti-inflammatory agent. In this study, we examined the anti-atherogenic potential of hematein using cholesterol-fed New Zealand White (NZW) rabbits. NZW rabbits were divided into a hematein-supplemented (0.05% in diet) group (n=6), a probucol-supplemented (0.25% in diet) group (n=6), and a control group (n=6). After 8 weeks of treatments, the extent of the atherosclerotic lesions was significantly reduced in the hematein-supplemented group and the probucol-supplemented group without changing plasma lipoprotein levels. Hematein and probucol prevented the up-regulation of the vascular cell adhesion molecule-1 (VCAM-1) expression on the descending aorta induced by cholesterol diet. In culture, hematein also significantly inhibited the secretion of soluble VCAM-1 and of monocyte chemotactic protein-1 (MCP-1) respectively induced by tumor necrotic factor alpha (TNF-alpha) and mildly oxidized low density lipoprotein in human umbilical vein endothelial cell (HUVEC) culture. Also, hematein inhibited monocyte adhesion to endothelial cell and the activation of NF-kappaB in HUVECs stimulated with TNF-alpha. The results of the present study suggest that the anti-atherogenic effect of hematein is not related to control of the plasma lipid profile but probably related to the inhibition of VCAM-1 and MCP-1 expression resulting in an amelioration of lesion development in the rabbit.

Animals↗
PubMed2001

Effect of pump shear on the performance of a crossflow membrane bioreactor.

The influences of pumping shear on the performance of a crossflow membrane bioreactor (MBR) were investigated. To compare the intensity of pumping shear, two types of pumps (a centrifugal pump and a rotary one) were used in turn to recirculate mixed liquor. Rotary pump system imposed much stronger shear to microbial floc than centrifugal one and resulted in severe floc breakage. Colloidal particles and organics were liberated from microbial floc by shear and caused rapid loss of membrane permeability by the formation of dense cake layers on the surface of membrane. Recirculation of mixed liquor with a rotary pump gradually increased the soluble COD in the bioreactor and deteriorated microbial activity. After 7 days' operation, specific oxygen uptake rate (SOUR) of microorganisms in rotary pump system reduced to 78%, of initial condition. With a centrifugal pump, however, buildup of soluble COD was not observed and change in microbial activity was negligible. Sludge yield in MBR process was lower than that (0.4-0.5 g MLVSS gCOD(-1)) reported in a conventional activated sludge process: 0.3 g MLVSS gCOD(-1) for the centrifugal pump system and 0.2 g MLVSS gCOD(-1) for the rotary pump system.

Bioreactors↗
PubMed2001

Comparison of the filtration characteristics between attached and suspended growth microorganisms in submerged membrane bioreactor.

An attached growth bioreactor was designed to minimize the effect of suspended microorganisms on membrane fouling in submerged membrane bioreactor. Comparison of mixed liquor from attached and suspended growth systems was made to elucidate major factors giving rise to different filtration characteristics. Unexpectedly, the rate of membrane fouling of the attached growth system was about 7 times higher than that of the suspended growth system despite similar characteristics of soluble fraction from the two reactors. Filtration performance proved to depend on the concentration of mixed liquor suspended solids (MLSS). Better filtration performance with suspended growth was explained by the formation of dynamic membranes with suspended solids. A series of analyses such as hydraulic resistance, specific cake resistance, scanning electron microscope, and atomic force microscope were carried out to elucidate the different filtration characteristics of the two systems.

Biomass↗
PubMed2001

Flux enhancement with gas injection in crossflow ultrafiltration of oily wastewater.

The gas injection technique was introduced to achieve flux improvement in cross-flow ultrafiltration of oil emulsion. By the nitrogen gas injection, homogeneous liquid phase oil/water emulsion was changed to heterogeneous gas- liquid phase. The injected gas causes positive effect of promoting turbulence, but it also has negative effect of decreasing the effective membrane area due to the partial occupation of membrane pores by bubbles. The efficiency of the gas injection was found out to be dependent on bubble fractions in the mixture: at sufficient bubble fractions the higher flux was observed. but at lower bubble fractions the flux rather decreased compared with that without gas injection. An attempt was made to explain the mechanisms for the dual aspects of gas injection. Turbulence dampening effect was also observed when the dependence of mass transfer coefficient on cross-flow rate was investigated with gas injection.

Air Movements↗
PubMed2001

The management of white phosphorus burns.

Phosphorus burns are a rarely encountered chemical burn, typically occurring in battle, industrial accidents, or from fireworks. Death may result even with minimal burn areas. Early recognition of affected areas and adequate resuscitation is crucial. Amongst our 2765 admissions between 1984 and 1998, 326 patients had chemical burns. Seven admissions were the result of phosphorus burns. Our treatment protocol comprises 1% copper sulfate solution for neutralization and identification of phosphorus particles, copious normal saline irrigation, keeping wounds moist with saline-soaked thick pads even during transportation, prompt debridement of affected areas, porcine skin coverage or skin grafts for acute wound management, as well as intensive monitoring of electrolytes and cardiac function in our burns center. Intravenous calcium gluconate is mandatory for correction of hypocalcemia. Of the seven, one patient died from inhalation injury and the others were scheduled for sequential surgical procedures for functional and cosmetic recovery. Cooling affected areas with tap water or normal saline, prompt removal of phosphorus particles with mechanical debridement, intensive monitoring, and maintenance of electrolyte balance are critical steps in initial management. Fluid resuscitation can be adjusted according to urine output. Early excision and skin autografts summarize our phosphorus burn treatment protocol.

Adolescent↗
PubMed2001

N-cadherin regulates target specificity in the Drosophila visual system.

Using visual behavioral screens in Drosophila, we identified multiple alleles of N-cadherin. Removal of N-cadherin selectively from photoreceptor neurons (R cells) causes deficits in specific visual behaviors that correlate with disruptions in R cell connectivity. These defects include disruptions in the pattern of neuronal connections made by all three classes of R cells (R1-R6, R7, and R8). N-cadherin is expressed in both R cell axons and their targets. By inducing mitotic recombination in a subclass of eye progenitors, we generated mutant R7 axons surrounded by largely wild-type R cell axons and a wild-type target. R7 axons lacking N-cadherin mistarget to the R8 recipient layer. We consider the implications of these findings in the context of the proposed role for cadherins in target specificity.

Animals↗
PubMed2001

Laryngeal mask insertion during target-controlled infusion of propofol.

STUDY OBJECTIVE: To compare the Laryngeal Mask Airway (LMA; The Laryngeal Mask Airway Co., Ltd., Nicosia, Cyprus) insertion conditions produced by 6 and 8 microg/mL of target plasma concentrations (Cpt) during the induction of anesthesia with target-controlled infusion (TCI) of propofol. DESIGN: Randomized, prospective, single-blind, clinical study. SETTING: University hospital. PATIENTS: 44 ASA physical status I and II patients, 16 to 54 years of age, weighing between 45 and 100 kg, undergoing minor surgery in which the use of LMA was indicated. INTERVENTIONS: Patients were randomly divided into two groups (1 and 2) of 22 to compare the effects of different propofol concentrations. Three minutes after intravenous (IV) injection of midazolam 0.04 mg/kg, group 1 and 2 received TCI of propofol with 6 and 8 microg/mL of Cpt, respectively. LMA was inserted when the effect-site concentration (EC) reached 2.5 microg/mL, which was displayed on the infusion pump. MEASUREMENTS: The LMA insertion conditions (mouth opening, gagging, coughing, head or limb movement, laryngospasm, overall ease of insertion) were assessed, and hemodynamic responses were evaluated until 3 minutes after LMA insertion. Total dose of propofol, EC, and elapsed time since the start of TCI were recorded at five times: at the loss of consciousness and eyelash reflex, at 2.5 microg/mL of EC, and immediately, 1 minute, and 3 minutes after the insertion of LMA. MAIN RESULTS: There was no significant difference between the two groups in insertion conditions, despite the significantly larger total dose and shorter elapsed time (2.6 +/- 0.08 mg/kg and 109 +/- 5.0 s) in Group 2 than those (2.1 +/- 0.02 mg/kg and 140 +/- 4.1 s) in Group 1 at 2.5 microg/mL of EC (p < 0.05). Systolic and diastolic blood pressure decreased and heart rate increased significantly throughout the study period in both groups (p < 0.05). But there was a significant decrease in arterial pressure in Group 2 compared with Group 1 1 and 3 minutes after the insertion (p < 0.05). CONCLUSIONS: Induction with 8 microg/mL of Cpt, compared with 6 microg/mL, allowed earlier LMA insertion but, could not improve the conditions for LMA insertion and required more careful attention to the decrease in blood pressure after LMA insertion.

Adolescent↗
PubMed2001

Improvement of sexual function in male patients after parathyroidectomy for secondary hyperparathyroidism.

BACKGROUND: Clinically, the severity of uremia is known to be inversely proportional to sexual desire and activity in patients with chronic renal failure. We studied sexual function and sex hormones in male patients with symptomatic hyperparathyroidism before and 3 months after parathyroidectomy. STUDY DESIGN: From October 1998 to December 2000, 20 male patients with symptomatic secondary hyperparathyroidism were enrolled in this study. They underwent total parathyridectomy and autotransplantation of 90 mg of tissue to the subcutaneous tissue of the forearm or thigh. They all had regular sexual partners and were sexually active. Preoperatively, hemoglobin, hematocrit, calcium, phosphorus, alkaline phosphatase, intact parathyroid hormone (iPTH), prolactin, testosterone, leutenizing hormone (LH), and follicle stimulation hormone (FSH) were checked routinely. Three months after operation those data were checked again. Sexual function was evaluated with the International Index of Erectile Function (IIEF). Monthly frequency of attempted sexual intercourse, satisfaction of attempted intercourse, and enjoyment of intercourse were individually analyzed preoperatively and 3 months postoperatively. RESULTS: Hemoglobin, hematocrit, testosterone, and LH were noted to have not significantly changed 3 months after surgery. Serum levels of calcium, phosphorus, alkaline phosphatase, FSH, and iPTH were significantly reduced, as were the levels of prolactin. But preoperative and postoperative FSH levels were within normal limits, and 70% of the postoperative alkaline phosphatase levels were above normal. Sexual function increased significantly 3 months after parathyroidectomy, as did monthly frequency of attempted intercourse, satisfaction of attempted intercourse, and enjoyment of intercourse. CONCLUSIONS: Sexual function of male patients with symptomatic hyperparathyroidism can possibly be improved by parathyroidectomy and autotransplantation. Decreases in the levels of prolactin, calcium, phosphorus, and iPTH are also noticed after parathyroidectomy.

Adult↗
PubMed2001

A PPAR gamma-LXR-ABCA1 pathway in macrophages is involved in cholesterol efflux and atherogenesis.

Previous work has implicated PPAR gamma in the regulation of CD36 expression and macrophage uptake of oxidized LDL (oxLDL). We provide evidence here that in addition to lipid uptake, PPAR gamma regulates a pathway of cholesterol efflux. PPAR gamma induces ABCA1 expression and cholesterol removal from macrophages through a transcriptional cascade mediated by the nuclear receptor LXR alpha. Ligand activation of PPAR gamma leads to primary induction of LXR alpha and to coupled induction of ABCA1. Transplantation of PPAR gamma null bone marrow into LDLR -/- mice results in a significant increase in atherosclerosis, consistent with the hypothesis that regulation of LXR alpha and ABCA1 expression is protective in vivo. Thus, we propose that PPAR gamma coordinates a complex physiologic response to oxLDL that involves particle uptake, processing, and cholesterol removal through ABCA1.

ATP Binding Cassette Transporter 1↗
PubMed2001

Electron spin resonance studies of free radicals in gamma-irradiated soybean paste.

Free radicals in gamma-irradiated soybean paste were investigated by electron spin resonance (ESR) spectroscopy to determine the effect of temperature (77-296 K) and moisture content (1-54%) of samples irradiated at high dose (1-40 kGy). The samples were kept in liquid nitrogen (77 K) during irradiation and subsequent ESR measurements. The spectra shown at 77 K consisted of the hydrogen atom lines at low and high field and complicated symmetric spectrum. By increasing the microwave power, the line shape of ESR spectra altered, which indicated the detection of different paramagnetic centers at different microwave powers. In saturation curves, it was possible to select four types of spectra components which were different in their relaxation times. By the different irradiation doses, the change in free radical concentration showed a curvilinearly increasing relationship with irradiation dose in wet samples, whereas a proportional relationship was observed with dried samples. This might indicate that the indirect process of free radical formation was involved with the existence of free water radicals in the wet samples.

Electron Spin Resonance Spectroscopy↗
PubMed2001

Induction of P-glycoprotein mRNA transcripts by cycloheximide in animal tissues: evidence that class I Pgp is transcriptionally regulated whereas class II Pgp is post-transcriptionally regulated.

P-glycoprotein (Pgp) are a small family of plasma membrane proteins capable of transporting substrates across cell membranes. Class I and class II Pgp are able to transport drugs and have been shown to mediate multidrug resistance (MDR). Class III Pgp is a long chain phospholipid transporter and does not mediate MDR. The expression and regulation of Pgp genes in animal tissues are not well understood. In this study, the protein synthesis inhibitor cycloheximide was used as a tool to understand Pgp gene expression and regulation in animal tissues. The sensitive RNase protection assay was used to detect changes in Pgp mRNA levels and nuclear run-on assay was used to determine whether transcription or post-transcription is important. The results showed that cycloheximide significantly induced class II Pgp expression in all tissues examined. This was predominantly through post-transcriptional effect. In contrast, the relatively modest increase in class I Pgp expression by cycloheximide was found to be mainly due to increased transcriptional activity. On the other hand, cycloheximide induced class III Pgp expression in some tissues while caused decay of class III Pgp mRNA in other tissues. The transcriptional and post-transcriptional mechanisms exerted by cycloheximide on Pgp genes are discussed. These findings have implications for our understanding of gene regulation in animal tissues and MDR reversal strategies in vivo.

ATP Binding Cassette Transporter, Subfamily B↗
PubMed2001

Real-time quantitative PCR analysis for alpha-thalassemia-1 of Southeast Asian type deletion in Taiwan.

Since homozygosity of the alpha-thalassemia-1 of Southeast Asian (SEA) type deletion results in hydrops fetalis, a novel protocol based on the real-time quantitating polymerase chain reaction (PCR) technique has been developed to quantify the intact and aberrant alpha-globin genes in adults. The ratio of the normal/SEA-bearing alpha-globin genes was expressed in cycle threshold (C(T)) values. Theoretically, a relative ratio of one to one was anticipated in individuals carrying the SEA type deletion. Twenty-five heterozygous and 20 normal cases were analyzed retrospectively with this protocol. Data showed that the CT values for the intact alpha-globin gene allele and the allele bearing the SEA type deletion in carriers were 28.74+/-1.49 and 26.46+/-2.05, respectively. Therefore, the ratio of normal/SEA type deletion-bearing alpha-globin genes in the carriers was 1.09+/-0.043. No ambiguous results were observed from other less common genotypes associated with alpha-thalassemia, such as the Philippine type deletion. Based on the results, we concluded that this protocol could provide a rapid method to mass screen carriers with alpha-thalassemia-1 of SEA type deletion in this region.

Alleles↗
PubMed2001

Solution structures of the N-terminal domain of histone H4.

Histones, nuclear proteins that interact with DNA to form nucleosomes, are essential for both the regulation of transcription and the packaging of DNA within chromosomes. The N-terminal domain of histone H4 contains four acetylation sites at lysine residues and may play a separate role in chromatin structure from the remainder of the H4 chain. We performed circular dichroism and NMR characterization of both native (H4NTP) and acetylated (Ace-H4NTP) peptides containing N-terminal acetylation domain of histone H4 for various pH environments. Data from CD and NMR suggested that H4NTP exhibited a pH-dependent conformational change, whereas the Ace-H4NTP is insensitive to pH change. However, both peptides showed a defined structural form at acidic pH environments. The solution structure for Ace-H4NTP shows two structurally independent regions comprising residues of Leu10-Gly13 and Arg19-Leu22, demonstrating relatively well-defined turn-type structures. Our results suggest that N-terminal acetylated region of H4 prefers an extended backbone conformation at neutral pH, however, upon acetylation, the regions containing lysine residues induce structural transition, having defined structural form for its optimum function.

Acetyltransferases↗
PubMed2001

Multicenter study of the frequency of contact allergy to gold.

Gold sodium thiosulfate (GSTS) is reputed to be the most reliable gold antigen, but control studies are still required. Although Koreans have more varied sources of contact with gold, such as herbal medicines with gold coatings and indwelling gold acupuncture needles, no epidemiological studies have been performed. This study examined the frequency and sources of contact allergy to gold in South Korea by a multicenter study. Patch testing with 0.5% GSTS in pet. was conducted in 255 eczema patients and 58 control subjects. Results were observed at 21 days (D) to ensure there were no undetected late reactions in 54 observed patients and 47 controls. 8 (3.1%) of the 255 patients reacted positively to GSTS, including 1 with a late reaction. 1 of the 58 controls showed a positive reaction to GSTS on D4 with a negative reaction on D14. Clinical relevance was lacking in the patients with positive reactions. Unexpectedly, the above particular sources of gold contact gave rise to few allergic reactions in our patients.

Adolescent↗
PubMed2001

Effect of P-glycoprotein modulators on the pharmacokinetics of camptothecin using microdialysis.

1. By performing microdialysis, this study investigated the pharmacokinetics of unbound camptothecin in rat blood, brain and bile in the presence of P-glycoprotein mediated transport modulators (cyclosporin A, berberine, quercetin, naringin and naringenin). Pharmacokinetic parameters of camptothecin were assessed using a non-compartmental model. 2. Camptothecin rapidly crosses the blood-brain barrier (BBB) within 20 min after camptothecin administration. The disposition of camptothecin in rat bile appeared to have a slow elimination phase and a peak concentration after 20 min of camptothecin administration. The area under the concentration versus time curve (AUC) for camptothecin in bile significantly surpassed that in blood, suggesting active transport of hepatobiliary excretion. 3. In the presence of cyclosporin A camptothecin AUC, in the brain, was significantly elevated but no significant change in the presence of berberine, quercetin, naringin and naringenin. 4. With treatment by smaller doses of quercetin (0.1 mg x kg(-1)), naringin (10 mg x kg(-1)) and naringenin (10 mg x kg(-1)), they significantly diminished the camptothecin AUC in bile, but was not altered by the treatment of berberine (20 mg x kg(-1)), a higher dose of quercetin (10 mg x kg(-1)), and cyclosporin A treated (20 mg x kg(-1)) and pretreated groups. 5. The distribution ratio (AUC(bile)/AUC(blood)) of camptothecin in bile was decreased in the cyclosporin A, quercetin, naringin and naringenin treated groups. However, the distribution ratio in the brain was increased in the cyclosporin A groups, but was decreased in the groups treated with quercetin, naringin and naringenin. These results revealed that P-glycoprotein might modulate hepatobiliary excretion and BBB penetration of camptothecin.

ATP Binding Cassette Transporter, Subfamily B↗
PubMed2001

Novel mutations of the transglutaminase 1 gene in lamellar ichthyosis.

Lamellar ichthyosis, one form of congenital autosomal recessive ichthyosis, is caused by mutations in the gene (TGM1) encoding the transglutaminase 1 enzyme. Mutations, deletions, or insertion of TGM1 have been reported so far. Here we report that three novel mutations of TGM1, D101V, N288T, and R306W, cause lamellar ichthyosis in two different families. The patient in family LI-KD has N288T and R306W mutations, and the patient in family LI-LK has D101V and R306W mutations. The activity of the transglutaminase 1 enzyme of the patient in family LI-LK was only about 15% of normal. Also, three-dimensional structural prediction analyses revealed that the N288T and R306W mutations, and possibly the D101V mutation, cause misfolding in the central catalytic core domain of the transglutaminase 1 enzyme that would probably result in reduced enzyme activity. Our data suggest that the greatly reduced transglutaminase 1 activities are due to disruptions of the native folding of transglutaminase 1, and that these mutations may play a critical role in the pathology of lamellar ichthyosis.

Amino Acid Substitution↗
PubMed2001

Changes of leptin and metabolic hormones in preterm infants: a longitudinal study in early postnatal life.

OBJECTIVES: Very little is known concerning the physiological role of leptin and growth in the early postnatal period and the association of leptin with other metabolic hormones in preterm infants. This study aims to investigate these relationships, and to explore the longitudinal and dynamic profile of leptin and metabolic hormones including insulin, ACTH, cortisol and FT4 in this category of patient. We also postulate that a rapid increase in body weight and body mass index in the first few weeks of life may be associated with a corresponding increase in serum leptin if the 'adipoinsular axis' is active at this stage. DESIGN: A longitudinal study in a cohort of preterm infants < 34 weeks gestation for the first five weeks of postnatal life. PATIENTS AND METHODS: Sixty-one preterm newborns < 34 weeks gestation were prospectively enrolled. Blood samples were collected in the morning when the newborns were 24 h of age (day 1), and on days 5, 14 and 35 of life. Serum leptin, insulin, cortisol, FT4, glucose and plasma ACTH concentrations were analysed using standard biochemical methods. Spearman's correlation coefficient was used to assess the inter-relationship of different metabolic hormones on the first day of life, and the relationship between metabolic hormones on day 1 and anthropometric or clinical parameters. The mixed-effects models were further used for analysing the multiple longitudinal measurements, and also for comparing the hormone concentrations between day 1 (baseline) and their corresponding levels on days 5, 14 and 35. RESULTS: Serum leptin on day 1 (baseline) was significantly associated with serum insulin (r = 0.30, P < 0.05) and insulin:glucose ratio (r = 0.29, P < 0.05) in infants < 34 weeks gestation. Female preterm infants had significantly higher serum leptin (P < 0.05) and insulin (P < 0.05) levels than male infants. In addition, the duration between the last dose of antenatal dexamethasone and delivery significantly influenced the serum concentrations of leptin (r = - 0.27, P < 0.05), cortisol (r = 0.52, P < 0.001), plasma ACTH (r = 0.28, P < 0.05) and insulin:glucose ratio (r = - 0.27, P < 0.05) on the first day of life. Despite significant increase in body weight (P < 0.00001) and body mass index (P < 0.00001) by day 35 when compared to birth weight, no corresponding significant changes were observed for serum leptin, insulin and FT4. However, there was an increasing though statistically nonsignificant trend in serum leptin after day 14 of life. CONCLUSION: This study characterized the longitudinal profile of leptin and metabolic hormones in preterm infants < 34 weeks gestation in the first 5 weeks of life. Serum leptin was significantly associated with serum insulin and insulin:glucose ratio supporting the hypothesis that an 'adipoinsular axis' exists and is likely to be functional before 34 weeks of gestation. Although a significant increase in body weight was demonstrated by day 35, no significant corresponding changes occurred with regard to serum leptin. We postulate that the limited quantity of adipose tissue at this stage of development might have contributed to this observation. Moreover, our results also showed that the duration between the last dose of antenatal corticosteroid and delivery could influence the postnatal concentrations of adipoinsular and pituitary-adrenal hormones. Thus, it is possible that antenatal dexamethasone might affect fetal growth and development via these neuroendocrine pathways in early intrauterine life.

Adrenocorticotropic Hormone↗