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K J Lee

Publications and source records attributed to K J Lee.

At least 37 records · Page 2Linked to original sources
PubMed2001

Resetting wave forms in dictyostelium territories.

The mechanism by which spiral wave patterns appear in populations of Dictyostelium was probed experimentally by external chemical perturbation. Spiral waves, which often arise from the breakup of circular waves driven by pacemakers, typically entrain those pacemakers. We studied these processes by resetting the waves with a spatially uniform pulse of extrinsic cyclic AMP. A pattern of spirals reappeared if resetting was early in the signaling stage, but only targets emerged following late resetting, in a manner analogous to cardiac defibrillation. This supports recent hypotheses that wave pattern selection naturally occurs by slow temporal variation of the excitability of the cells.

Animals↗
PubMed2001

Restriction fragment length dimorphism-PCR method for the detection of extended-spectrum beta-lactamases unrelated to TEM- and SHV-types.

The diagnostic ability of the restriction fragment length dimorphism-polymerase chain reaction (RFLD-PCR) method was evaluated. Seven primer pairs, newly designed from 44 beta-lactamase genes encoding extended-spectrum beta-lactamases not related to TEM- and SHV-types, were used to differentiate OXA-2, FOX-3, CMY-3, IMP-1, and IMI-1 beta-lactamases. The RFLD-PCR was carried out successfully, and these genes were differentiated by the sizes of their PCR products and by the difference in restriction fragment length when each amplicon was digested with a unique restriction enzyme. This discriminatory detection of the genes was confirmed by sequencing the PCR products.

Bacterial Proteins↗
PubMed2001

Substance p plays a critical role in photic resetting of the circadian pacemaker in the rat hypothalamus.

Glutamate is considered to be the primary neurotransmitter in the retinohypothalamic tract (RHT), which delivers photic information from the retina to the suprachiasmatic nucleus (SCN), the locus of the mammalian circadian pacemaker. However, substance P (SP) also has been suggested to play a role in retinohypothalamic transmission. In this study, we sought evidence that SP from the RHT contributes to photic resetting of the circadian pacemaker and further explored the possible interaction of SP with glutamate in this process. In rat hypothalamic slices cut parasagittally, electrical stimulation of the optic nerve in early and late subjective night produced a phase delay (2.4 +/- 0.5 hr; mean +/- SEM) and advance (2.6 +/- 0.3 hr) of the circadian rhythm of SCN neuronal firing activity, respectively. The SP antagonist L-703,606 (10 microm) applied to the slices during the nerve stimulation completely blocked the phase shifts. Likewise, a cocktail of NMDA (2-amino-5-phosphonopentanoic acid, 50 microm) and non-NMDA (6,7-dinitroquinoxaline-2,3-dione, 10 microm) antagonists completely blocked the shifts. Exogenous application of SP (1 microm) or glutamate (100 microm) to the slices in early subjective night produced a phase delay ( approximately 3 hr) of the circadian firing activity rhythm of SCN neurons. Coapplication of the NMDA and non-NMDA antagonist cocktail (as well as L-703,606) resulted in a complete blockade of the SP-induced phase delay, whereas L-703,606 (10 microm) had no effect on the glutamate-induced delay. These results suggest that SP, as well as glutamate, has a critical role in photic resetting. Furthermore, the results suggest that the two agonists act in series, SP working upstream of glutamate.

Animals↗
PubMed2001

[Identification of proteome molecules by proteomics using two-dimensional gel electrophoresis and MALDI-TOF MS].

Genomic technologies have enabled rapid accumulation of information from complex biological systems over the last two decades. The complete DNA sequence is now known for many organisms and the informational database obtained from genome sequencing projects has provided the base for the specification of proteome - the protein complement of genome. Genomic functions can be inferred from the analysis of gene structure and gene expression profiles because proteins are the functional molecules of an organism. Integrated technologies including protein separation, identification, characterization and information manage system are essential to analyze the proteins in complex cellular matrix. This study is focusing on the strategies of proteome analysis using sample preparation, 2-dimensional gel electrophoresis, processing of protein spots and identification of proteins, protein-protein interaction and posttranslational modification using MALDI-TOF-MS. 2-D gel electrophoresis is currently the most powerful protein separation technique and MALDI-TOF MS is powerful identification technique for protein and peptides as a sensitive, rapid, and high resolution analytical method. The developed integrated proteome technologies are very useful to understand the biological phenomena at molecular level by identifying the new molecules and their modifications in various cellular processes, and can be applied for biotechnology including medical science.

Databases, Protein↗
PubMed2001

ABO-incompatible heart transplantation in infants.

BACKGROUND: Transplantation of hearts from ABO-incompatible donors is contraindicated because of the risk of hyperacute rejection mediated by preformed antibodies in the recipient to blood-group antigens of the donor. This contraindication may not apply to newborn infants, who do not yet produce antibodies to T-cell-independent antigens, including the major blood-group antigens. METHODS: We studied 10 infants 4 hours to 14 months old (median, 2 months) who had congenital heart disease or cardiomyopathy and who received heart transplants from donors of incompatible blood type between 1996 and 2000. Serum isohemagglutinin titers were measured before and after transplantation. Plasma exchange was performed during cardiopulmonary bypass; no other procedures for the removal of antibodies were used. Standard immunosuppressive therapy was given, and rejection was monitored by means of endomyocardial biopsy. The results were compared with those in 10 infants who received heart transplants from ABO-compatible donors. RESULTS: The overall survival rate among the 10 recipients with ABO-incompatible donors was 80 percent, with 2 early deaths due to causes presumed to be unrelated to ABO incompatibility. The duration of follow-up ranged from 11 months to 4.6 years. Two infants had serum antibodies to antigens of the donor's blood group before transplantation. No hyperacute rejection occurred; mild humoral rejection was noted at autopsy in one of the infants with antibodies. No morbidity attributable to ABO incompatibility has been observed. Despite the eventual development of antibodies to antigens of the donor's blood group in two infants, no damage to the graft has occurred. Because of the use of ABO-incompatible donors, the mortality rate among infants on the waiting list declined from 58 percent to 7 percent. CONCLUSIONS: ABO-incompatible heart transplantation can be performed safely during infancy before the onset of isohemagglutinin production; this technique thus contributes to a marked reduction in mortality among infants on the waiting list.

ABO Blood-Group System↗
PubMed2001

Gossypol isomers bind specifically to blood plasma proteins and spermatozoa of rainbow trout fed diets containing cottonseed meal.

We investigated the role of gossypol isomers binding to blood plasma, seminal plasma and spermatozoa to elucidate gossypol anti-fertility action in the teleost fish, rainbow trout (Oncorhynchus mykiss). Growth and hematological indicators of males were depressed when fish meal protein in diets was completely replaced with cottonseed meal. The cottonseed meal contained equal proportions of (-) (47.8+/-1.6%) and (+) gossypol isomers. Concentrations of spermatozoa were decreased with increasing proportions of gossypol in diets (from 0.22% to 0.95%); however, sperm motility and fertilizing ability were not affected. In contrast to mammals, steroid hormone concentrations were not suppressed in fish given diets with gradual increase of gossypol level. Gossypol concentrations were 100-fold higher in blood plasma than in seminal plasma, confirming a barrier in gossypol transfer between the general circulation and the testis. Spermatozoa accumulated predominantly (+) enantiomer (65-75%) with decreasing proportions as dietary gossypol concentrations increased. Spermatozoa bound most of the gossypol contained in the semen; however, this did not result in impairment of the sperm motility apparatus. Teleost fish sperm rely on ATP stores that accumulate during maturation as a source of energy during activation. In addition, the duration of sperm movement is short in these fish. As such, we hypothesize that the major action of gossypol on mammalian sperm, which is uncoupling of oxidative phosphorylation, does not impair the energy supply required for flagellar beating in fish spermatozoa.

Animals↗
PubMed2001

Facile oxidation of fused 1,4-dimethoxybenzenes to 1,4-quinones using NBS: fine-tuned control over bromination and oxidation reactions.

[figure: see text] Fused 1,4-dimethoxybenzenes could be oxidized to benzoquinones by either direct oxidation or demethylation-oxidation. The oxidative demethylation of 5,8-dimethoxy-2-methylquinoline using 1.1 equiv of NBS in aqueous THF and a catalytic amount of H2SO4 at 20 degrees C for 5 min gave 2-methylquinoline-5,8-dione in 98% yield without bromination. Moreover, we can control either bromination or oxidative demethylation, or both reactions.

Anisoles↗
PubMed2001

Distinct roles for Ku protein in transcriptional reinitiation and DNA repair.

Transcriptional reinitiation is a distinct phase of the RNA polymerase II transcription cycle. Prior work has shown that reinitiation is deficient in nuclear extracts from Chinese hamster ovary cells lacking the 80-kDa subunit of Ku, a double-strand break repair protein, and that activity is rescued by expression of the corresponding cDNA. We now show that Ku increases the amount or availability of a soluble factor that is limiting for reinitiation, that the factor increases the number of elongation complexes associated with the template at all times during the reaction, and that the factor itself does not form a tight complex with DNA. The factor may consist of a preformed complex of transcription proteins that is stabilized by Ku. A Ku mutant, lacking residues 687-728 in the 80-kDa subunit, preferentially suppresses transcription in Ku-containing extracts, suggesting that Ku interacts directly with proteins required for reinitiation. The Ku mutant functions normally in a DNA end-joining system, indicating that the functions of Ku in transcription and repair are genetically separable. Based on our results, we present a model in which Ku is capable of undergoing a switch between a transcription factor-associated and a repair-active state.

Animals↗
PubMed2001

Comparison of two transcatheter closure methods of persistently patent arterial duct.

A randomized trial of arterial duct occlusion with a double umbrella (DU) or wire coil (WC) was undertaken for patients <18 years of age, weighing >10 kg with isolated ducts < or = 3 mm in diameter. Baseline, procedural, and outcome characteristics were compared in an intention-to-treat analysis according to randomization group. From 40 consecutively screened patients, 2 were not enrolled due to a ductal diameter of >3 mm on initial aortography, 38 patients were randomized to either the DU (n = 20) or WC (n = 18) groups. The groups did not differ significantly with respect to age, weight, gender, duct size, type, or branch pulmonary artery diameters. Crossover occurred only in the DU group, where 4 patients (20%) had a ductal diameter of < or = 1 mm and could not be entered for umbrella placement. All remaining DU group patients had ductal diameters of > or = 1.3 mm (p <0.0001). There were no embolizations or secondary implants in the DU group, but in the WC group there was 1 early and 1 late embolization, with 6 patients (33%) with > or = 2 coils. Mean times for the procedure (DU 68+/-19 minutes; WC 65+/-27 minutes; p = 0.70) and fluoroscopy (DU 14+/-4 minutes; WC 11+/-6 minutes; p = 0.22) did not differ significantly. Angiographic duct closure was documented in 4 of 13 patients (31%) of the DU group and 4 of 18 patients (22%) of the WC group (p = 0.69). Combined with an echocardiogram, closure in 11 of 17 patients with DU (65%) and 13 of 18 patients with WC (72%) (p = 0.64) was documented before hospital discharge. One WC group patient received thrombolytic therapy for a femoral artery thrombus. Follow-up at a median of 6.5 months (range 3.2 to 37) showed closure by Doppler echocardiography in 15 of 19 patients with DU (79%) versus 14 of 18 patients with WC (78%) (p = 1.0). Thus, with a tendency toward similar procedural characteristics and outcomes, the higher cost of the DU system compared with coil implants favors the use of coils for closure of the small arterial duct.

Analysis of Variance↗
PubMed2001

Occurrence of a diploid type and a new first intermediate host of a human lung fluke, Paragonimus westermani, in Korea.

The biology, chromosome number, and karyotype of a lung fluke, Paragonimus westermani (Kerbert, 1878) collected in Haenam, Haenam-gun Chollanam-do, Korea were analyzed. We compared the size of metacercariae from Haenam with those taken from a crayfish collected at Youngam, Youngam-gun, Chollanam-do, Korea. The mean length of P. westermani metacercariae from Haenam was 300.3 microm and that from Youngam was 362.0 microm. Adult worms were recovered from the lungs of experimentally infected dogs. The mean egg sizes obtained from adult flukes were 72.1 x 46.8 microm from Haenam and 93.5 x 54.2 microm from Youngam. Semisulcospira tegulata collected in the Youngam area were found to be infected with cercariae of P. westermani, one of the snail-borne human lung fluke trematodes in Korea. Of 4218 snails studied, 5 (0.12%) harbored P. westrermani larvae. This is the first report of S. tegulata serving as the initial intermediate host of P. westermani. The chromosome numbers of P. westermani from Haenam and Youngam were 2n = 22 and 3n = 33. The diploid type of P. westermani has not been previously reported in Korea.

Animals↗
PubMed2001

Design of a wavelet interpolation filter for enhancement of the ST-segment.

A wavelet interpolation filter (WIF) is designed for the removal of motion artifacts in the ST-segment of stress ECGs. The WIF consists of two parts. One part is a wavelet transform that decomposes the stress ECG signal into several frequency bands using a Haar wavelet. The other part is an interpolation method, such as the spline technique, that is used to enhance the reconstruction performance of the signal decomposed by the wavelet transform. To evaluate the performance of the WIF, three indices are used: signal-to-noise ratio (SNR), reconstruction square error (RSE) and standard deviation (SD). The MIT/BIH arrhythmia database, the European ST-T database and the triangular wave are used for evaluation. A noisy ECG signal, corrupted by motion artifacts, is simulated by the addition of two types of random noise to the original ECG signal. For comparison, three indices for the other methods are also computed: mean, median and hard thresholding. The performance of the WIF shows that RSE, SNR and SD are 392.7, 18.3dB and 2.6, respectively, in the case of a noisy signal with an SNR of 7.1 dB. This result is much better than those for the other methods.

Artifacts↗
PubMed2001

Efficacy of use of colonoscopy in dextran sulfate sodium induced ulcerative colitis in rats: the evaluation of the effects of antioxidant by colonoscopy.

The goals in developing animal models of inflammatory bowel disease (IBD) are to determine the underlying mechanisms and the action of currently available drugs and to evaluate the value of new therapeutic approaches. Because of the difficulty in determining the severity of colitis in living animals, it has been necessary to kill the experimental animals at varying stages in the studies. If colonoscopic evaluation or endoscopic biopsy is feasible in these experimental animals, continuous observations could be possible, thus avoiding the need to kill them. The aims of the current study were to assess the efficacy of endoscopic examination as a monitoring tool for the severity of colitis in rats and to the efficacy of DA-9601, an extract from Artemisia asiatica which has both antioxidative and cytoprotective actions, on dextran sulfate sodium induced ulcerative colitis in rats endoscopically. Sprague-Dawley rats received 4% DSS in drinking water for 5 consecutive days. Either DA-9601 or sulfasalazine was administered twice a day for 8 days, starting 3 days before DSS administration. After the colonoscopic evaluations on days 2, 4, and 5 after DSS administration the rats were also killed for gross and histopathological evaluations. Simultaneous measurements of malondialdehyde (MDA) and myeloperoxidase (MPO) activities were performed. There was a statistically significant correlation between the scores evaluated by the gross examination and colonoscopic scores, between the colonoscopic scores and the levels of MDA or mucosal MPO activities, and between colonoscopic scores and histopathological activity index. DA-9601 showed excellent improvement in gross lesion scores, decreased MDA amounts and MPO activities compared to sulfasalazine. In conclusion, the introduction of appropriate colonoscopic examination in animal models of IBD could avoid the sacrifice of experimental animals for interim evaluation and provide the valuable information on the course and efficacy of treatment. The potential usefulness of antioxidants in treating IBD is very promising based on the colonoscopic intervention of IBD.

Animals↗
PubMed2001

Evolving strategies and improving outcomes of the modified norwood procedure: a 10-year single-institution experience.

BACKGROUND: This study reviews our 10-year experience with the modified Norwood procedure to determine its early and midterm outcomes. The focus is on the impact of evolving management strategies and accumulated institutional experience. METHODS: A modified Norwood operation was performed in 171 infants over a 10-year period. Sixty-eight percent of the infants were male, the median age at operation was 6 days (range 1 to 175 days), and the median weight was 3.3 kg (range 1.7 to 4.8 kg). The 10-year period was divided into three eras: era I; 1990 through 1993; era II; 1994 through 1997; and era III; 1998 into 2000. Outcomes and risk factors for mortality were sought. RESULTS: Hypoplastic left heart syndrome or a variant was the primary diagnosis in 118 infants (69%). The overall 5-year survival rate was 43%. Multivariate analysis revealed that only need of preoperative ventilatory support, earlier date of operation, and lower weight at operation were significant independent predictors of increased time-related mortality. Morphologic features such as a diagnosis other than hypoplastic left heart syndrome, ascending aortic size, and noncardiac anomalies were not significantly associated with an increased risk of death. The hospital survival rate for stage-one palliation in era III was 82%, significantly better than that in the preceding eras (p < 0.001). Attrition between stages one and two accounted for a 15% mortality rate among hospital survivors. CONCLUSIONS: With increasing experience and improvements in perioperative care and surgical technique, good outcomes can be expected for the first-stage modified Norwood procedure. Greater monitoring of patients in the interstage period may reduce interval mortality and improve overall survival.

Female↗
PubMed2001

A study on the distribution of chlorination by-products (CBPs) in treated water in Korea.

Fifteen chlorination by-products were analyzed in 416 water samples collected from 35 water treatment plants in Korea from 1996 to 1998. These samples were divided into five groups according to water sources (Han-river, Nakdong-river, Youngsan-river, Kum-river and Cheju) and detected CBPs were classified into six classes (trihalomethanes; THMs, haloacetic acids; HAAs, haloacetonitriles: HANs haloketones; HKs, chloralhydrate; CH, chloropicrin; CP) and then, it was observed the detection tendency and frequency of CBPs in each water source. The total concentration of CBPs in treated water from Nakdong-river or Han-river was higher than those from the other rivers. And the distribution pattern of each class of CBPs was similar in all water sources. THMs were the highest portion in the range of 40-50%, and HAAs and HANs were 28-35 and 9-15%, respectively. And there was a strong correlation between HANs and HKs (r=0.813). Each and total concentrations of CBPs showed to be more affected by the water source in two-way analysis of variance (two-way ANOVA) among the concentration of CBPs, the source of water and season.

Acetates↗
PubMed2001

A new inhibitor design strategy for carboxypeptidase A as exemplified by N-(2-chloroethyl)-N-methylphenylalanine.

N-(2-Chloroethyl)-N-methylphenylalanine was designed and synthesized in an optically active form as a novel class of mechanism-based inactivator for carboxypeptidase A (CPA). It was anticipated that the chloroethylamino moiety of the CPA bound inhibitor undergoes an intramolecular SN2 reaction to generate a chemically reactive species (an aziridinium ion) which is expectedly subjected to a nucleophilic attack by the carboxylate of Glu-270, leading to covalent modification of the carboxylate. The irreversible nature of the inhibition of CPA by the inhibitor was supported by the kinetic data: the enzyme lost its enzymic activity in a time-dependent manner in the presence of the inhibitor and the inactivated CPA failed to regain the activity upon dialysis. Interestingly, the (R)-isomer that belongs to the D-series was more potent than its enantiomer.

Animals↗
PubMed2001

Development of a personal dosimetry system based on optically stimulated luminescence of alpha-Al2O3:C for mixed radiation fields.

To develop a personal optically stimulated luminescence (OSL) dosimetry system for mixed radiation fields using alpha-Al2O3:C, a discriminating badge filter system was designed by taking advantage of its optically stimulable properties and energy dependencies. This was done by designing a multi-element badge system for powder layered alpha-Al2O3:C material and an optical reader system based on high-intensity blue light-emitting diode (LED). The design of the multielement OSL dosimeter badge system developed allows the measurement of a personal dose equivalent value Hp(d) in mixed radiation fields of beta and gamma. Dosimetric properties of the personal OSL dosimeter badge system investigated here were the dose response, energy response and multi-readability. Based on the computational simulations and experiments of the proposed dosimeter design, it was demonstrated that a multi-element dosimeter system with an OSL technology based on alpha-Al2O3:C is suitable to obtain personal dose equivalent information in mixed radiation fields.

Aluminum Oxide↗