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Biomedical subjects

T H Lee

Publications and source records attributed to T H Lee.

At least 19 recordsLinked to original sources
PubMed2006

Short-term effects of hyposmotic shock on Na+/K+ -ATPase expression in gills of the euryhaline milkfish, Chanos chanos.

Changes in expression of gill Na+/K+ -ATPase (NKA) on a short-term (96 h) time-course following hyposmotic shock (direct transfer to fresh water) of the euryhaline, marine milkfish were studied on gene, protein, and cell levels in this paper. Plasma osmolality and [Na+] responded with rapid declines in 3 h post-transfer yet, thereafter, remained constant. Plasma [Cl-] gradually fell to a significantly lower level at 6 h post-transfer. Gills responded to hyposmotic shock by a dual phase enhancement of NKA activity and protein abundance; (a) Before 24 h: NKA activity increased as early as 3 h and reached a maximum level from 6 to 12 h post-transfer coincided with the sustained lower levels of plasma osmolality, [Na+], and [Cl-] since 3 h post-transfer. This was followed by a gradual rise in alpha-subunit protein levels that peaked at 12 h post-transfer. Meanwhile, alpha-mRNA of NKA did no show significant change. (b) After 24 h: NKA activity as well as the amounts of alpha-subunit mRNA and protein increased significantly. Direct freshwater transfer induced a prompt and significant decrease of NKA immunoreactive (NKIR) cell abundance in filaments before 24 h, followed by a significant increase after 24 h due to their development in filaments and lamellae. Increased number of NKIR cells after 24 h of hyposmotic shock may occur in conjunction with rise of NKA activity as well as alpha-subunit mRNA and protein abundance. In conclusion, milkfish is able to avoid an excessive drop in plasma ions immediately upon hyposmotic shock and maintain plasma ions on a marginal lower level in fresh water. Notably, the initial increase in NKA activity (adjustive phase; 3-12 h) and delayed increase in NKA mRNA and protein abundance (regulatory phase; 48-96 h) indicate the importance of a higher level of the gill enzyme in milkfish upon hyposmotic shock.

Animals↗
PubMed2006

Intelligent compensation of friction, ripple, and hysteresis via a regulated chatter.

In this paper, a hybrid control scheme utilizing a PID feedback control with an additional regulated chatter signal is developed to compensate motion impeding influences such as the effects due to friction, force ripples, and hysteresis in linear piezoelectric motor. The regulated chatter signal is a pulse sequence superimposed on the PID control signal. It has a fixed amplitude, and a pulse width regulated via iterative learning control. As such, the scheme is expected to be useful for applications involving iterative motion sequences. An analysis of the closed-loop performance is presented in the paper. Simulation and experimental results are also furnished to demonstrate that the proposed control scheme can reduce tracking errors significantly.

Algorithms↗
PubMed2006

Face recognition using recursive Fisher linear discriminant.

Fisher linear discriminant (FLD) has recently emerged as a more efficient approach for extracting features for many pattern classification problems as compared to traditional principal component analysis. However, the constraint on the total number of features available from FLD has seriously limited its application to a large class of problems. In order to overcome this disadvantage, a recursive procedure of calculating the discriminant features is suggested in this paper. The new algorithm incorporates the same fundamental idea behind FLD of seeking the projection that best separates the data corresponding to different classes, while in contrast to FLD the number of features that may be derived is independent of the number of the classes to be recognized. Extensive experiments of comparing the new algorithm with the traditional approaches have been carried out on face recognition problem with the Yale database, in which the resulting improvement of the performances by the new feature extraction scheme is significant.

Algorithms↗
PubMed2006

Nonlinear adaptive control of interconnected systems using neural networks.

In this letter, we solve the problem of decentralized adaptive asymptotic tracking for a class of large scale systems with significant nonlinearities and uncertainties. Neural networks (NNs) are used as a control part to cancel the effect of the unknown nonlinearity. Semiglobal asymptotic stability results are obtained and the tracking error converges to zero.

Algorithms↗
PubMed2006

Practical approach to parameter estimation for ASM3+ bio-P module applied to five-stage step-feed EBPR process.

Various parameter optimization approaches to a five-stage step-feed EBPR process modeled using the ASM3+bio-P module were examined. Five stoichiometric (Y(STO,NO), Y(H,O2, Y(H,NO,) Y(PAO,O2), Y(PO4)) and seven kinetic parameters (k(STO), eta(NO), b(H), mu(max),PAO, q(PHA), q(PP), mu(max),A) were estimated. The optimization approaches could be classified based on the data sources (batch experiments or CSTR operation data) and the number of target variables used in calculating the objective function. Optimized parameter values obtained by each approach were validated with CSTR operation data that were not used for parameter optimization. The results showed that the parameter optimization only with batch experimental results could not be directly applied to CSTR operation data. ASM3 + bio-P module parameters could be finely optimized only with CSTR operation data when sufficient target variables for objective function calculation were applied. When the number of target variables was increased, prediction performance was significantly improved. Once optimized, the model was able to predict the characteristic features of the five-stage step-feed process; namely, a high PAO yield, fast PAO growth, fast X(pp) storage, slow X(STO) and X(PHA) storage.

Bioreactors↗
PubMed2006

Identification of the adverse effect of nitrate on the phosphate release rate and improvement of EBPR process models.

The adverse effect of nitrate on the phosphate release rate in the anaerobic phase was observed and was hardly explainable with conventional EBPR process models. Four possible mechanisms were proposed including substrate competition, reduced fermentation, parallel reaction and sequential reaction. Batch experiments were designed and conducted to identify the dominant mechanism. Results showed that the sequential reaction was the only possible mechanism where only denitrification occurred if any nitrate existed in the anaerobic phase. Then the phosphate release following after the nitrate was completely removed. Nitrate inhibition effect was added into the PHA storage rate to incorporate the sequential reaction in the conventional ASM3 plus EAWAG bio-P module (ASM3 + P). Nitrate inhibition coefficient, K(I,NO,PAO) was found to be as low as 0.05 mg/L. This correlated well with experimental observation where no also meant that the anaerobic compartment of a continuous flow reactor could be seriously affected by the residual nitrate contained in the sludge recycle flow. This phenomenon caused overestimation of the phosphate uptake rate and consequently underestimation of PO4(3-) -P concentration. This problem was resolved by incorporation of a nitrate inhibition term in the ASM3 + P for more accurate simulation of the EBPR process.

Bacteria, Anaerobic↗
PubMed2006

Monitoring biodegradation of diesel fuel in bioventing processes using in situ respiration rate.

An in situ measuring system of respiration rate was applied for monitoring biodegradation of diesel fuel in a bioventing process for bioremediation of diesel contaminated soil. Two laboratory-scale soil columns were packed with 5 kg of soil that was artificially contaminated by diesel fuel as final TPH (total petroleum hydrocarbon) concentration of 8,000 mg/kg soil. Nutrient was added to make a relative concentration of C:N:P = 100:10:1. One soil column was operated with continuous venting mode, and the other one with intermittent (6 h venting/6 h rest) venting mode. On-line O2 and CO2 gas measuring system was applied to measure O2 utilisation and CO2 production during biodegradation of diesel for 5 months. Biodegradation rate of TPH was calculated from respiration rate measured by the on-line gas measuring system. There were no apparent differences between calculated biodegradation rates from two columns with different venting modes. The variation of biodegradation rates corresponded well with trend of the remaining TPH concentrations comparing other biodegradation indicators, such as C17/pristane and C18/phytane ratio, dehydrogenase activity, and the ratio of hydrocarbon utilising bacteria to total heterotrophic bacteria. These results suggested that the on-line measuring system of respiration rate would be applied to monitoring biodegradation rate and to determine the potential applicability of bioventing process for bioremediation of oil contaminated soil.

Aerobiosis↗
PubMed2006

Monitoring of pH inhibition on microbial activity in a continuous flow reactor by pseudo toxic concentration (C(PT)) concept and time delay model.

The pseudo toxic concentration (C(PT)) concept was introduced as a quantification method to describe pH as an inhibitor concentration. In this research, the applicability of the C(PT) concept model for the detection of pH inhibitions was expanded for a continuous flow activated sludge reactor. A pilot equipped with an inhibition detection system was installed. Inhibitory wastewater was injected for 1 h and the relative activity was calculated by the maximum respiration rate. At the same time, the coefficients for the C(PT) concept model were estimated. At the dynamic conditions, the estimated relative activity by the C(PT) concept model showed time lag compared to the measured one. However, the time lag problem was successfully resolved by introducing a transfer function into the C(PT) concept model. The C(PT) concept model combined with a transfer function (C(PT) + TF model) successfully tracked the variation of the relative activity under dynamic conditions. The C(PT) + TF model could detect 50% inhibition faster than the respirometry based method by approximately 10 min. Moreover, it had additional advantages such as being inexpensive, easy to install and simple to operate. In conclusion, the C(PT) + TF model was an effective and convenient detection method of pH inhibition.

Bioreactors↗
PubMed2006

Identification of Salmonella enterica serovar Typhimurium using specific PCR primers obtained by comparative genomics in Salmonella serovars.

Salmonella enterica serovar Typhimurium is a major foodborne pathogen throughout the world. Until now, the specific target genes for the detection and identification of serovar Typhimurium have not been developed. To determine the specific probes for serovar Typhimurium, the genes of serovar Typhimurium LT2 that were expected to be unique were selected with the BLAST (Basic Local Alignment Search Tool) program within GenBank. The selected genes were compared with 11 genomic sequences of various Salmonella serovars by BLAST. Of these selected genes, 10 were expected to be specific to serovar Typhimurium and were not related to virulence factor genes of Salmonella pathogenicity island or to genes of the O and H antigens of Salmonella. Primers for the 10 selected genes were constructed, and PCRs were evaluated with various genomic DNAs of Salmonella and non-Salmonella strains for the specific identification of Salmonella serovar Typhimurium. Among all the primer sets for the 10 genes, STM4497 showed the highest degree of specificity to serovar Typhimurium. In this study, a specific primer set for Salmonella serovar Typhimurium was developed on the basis of the comparison of genomic sequences between Salmonella serovars and was validated with PCR. This method of comparative genomics to select target genes or sequences can be applied to the specific detection of microorganisms.

Base Sequence↗
PubMed2005

Increase in daytime symptoms is a sensitive and specific criterion for predicting corticosteroid-treated exacerbations in a clinical asthma trial.

BACKGROUND: To determine which diary card variables are the most predictive for administration of additional courses of corticosteroids using the TRUST (The Regular Use of Salbutamol Trial) data set. METHODS: Logistic regression models were used to identify the extent to which a change in diary card variable affected the odds ratio (OR) for administering a course of oral or increased inhaled corticosteroids. The complete TRUST diary card data were used with over 200,000 days of diary card observations from 983 mild to moderate asthmatic subjects. RESULTS: An increase in daytime symptoms of 1-5 U over baseline was associated with an increase in the OR for starting all types of corticosteroids from two- to 60-fold. CONCLUSIONS: These results indicate that an increase in daytime symptoms of two or more over baseline strongly predicts the administration of additional corticosteroids. The results have significant implications for both clinical practice and design of clinical trials in asthma.

Acute Disease↗
PubMed2005

Improvements in an oral aspirin challenge protocol for the diagnosis of aspirin hypersensitivity.

Oral aspirin challenge (OAC) is used to confirm aspirin hypersensitivity (AHs) but there is no consensus on a standardized protocol. As a prior clinical history of adverse reactions to aspirin is poorly predictive of a positive result from formal aspirin challenge, many patients have an OAC performed. We retrospectively identified and prospectively validated how a 1-day OAC protocol could be modified, and patient selection improved, to deliver a safe and more efficient service. In a retrospective audit of 45 OACs using a 2 h dose interval, all reactions occurred within 90 min of the threshold dose. Forty OACs were then performed using a 90-min dose interval. This reduced the mean duration of a positive and negative OAC from 6 to 5 h and from 8 to 6 h, respectively. Histories of multiple manifestations of AHs were found in 91.6% (11) of those with asthma, 87.5% (7) with angiooedema, 70.6% (12) with rhinosinusitis, 63.6% (7) with chronic non-vasculitic urticaria and all with anaphylaxis, who developed a positive OAC. None of those with anaphylaxis, 8.3% (1) with asthma and 12.5% (1) with angiooedema, with a positive OAC, had a history of a single manifestation of AHs. The efficiency of an OAC service can safely be improved by reduction of the dose interval from 2 to 1 (1/2) h, and more targeted patient selection, as the likelihood of a positive OAC increases among patients with a history of asthma, angiooedoema or anaphylaxis with multiple manifestations of AHs.

Administration, Oral↗
PubMed2005

Treadmill running promotes functional recovery and decreases brain-derived neurotrophic factor mRNA expression following sciatic crushed nerve injury in rats.

AIM: Peripheral nerve injuries are commonly encountered clinical problems and often result in severe functional deficits. In the present study, the effects of treadmill running on the recovery rate of locomotor function and the expression of brain-derived neurotrophic factor (BDNF) mRNA following sciatic crushed nerve injury in rats were investigated. METHODS EXPERIMENTAL DESIGN: Comparative investigation was performed over 14 days. SETTING: Experimental animal laboratory. PARTICIPANTS: 24 male Sprague-Dawley rats weighing 200+/-10 g. Animals were randomly assigned into 3 groups: the sham-operation group, the sciatic nerve injury group, and the sciatic nerve injury and running group. INTERVENTIONS: The right sciatic nerve was crushed for 30 s using a surgical clip. Rats of the running group were made to run on a treadmill for 30 min once a day for 12 consecutive days. MEASURES: Functional recovery was analyzed using a walking track analysis which can be quantified with the sciatic function index (SFI) and BDNF mRNA expression was analyzed using reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: Sciatic crushed nerve injury showed characteristic gait changes showing decrease of SFI value and treadmill running significantly enhanced the SFI value. The level of BDNF mRNA expression was increased following sciatic crushed nerve injury and treadmill running significantly suppressed the sciatic nerve injury-induced increment of BDNF mRNA expression. CONCLUSIONS: It can be suggested that treadmill running after peripheral nerve injury is effective in the functional recovery by inhibition on the over-expression of BDNF mRNA.

Animals↗
PubMed2004

Molecular analysis of bacterial community based on 16S rDNA and functional genes in activated sludge enriched with 2,4-dichlorophenoxyacetic acid (2,4-D) under different cultural conditions.

Differential emergence and diversity of bacterial communities from activated sludge in response to varied cultural conditions using 2,4-dichlorophenoxyacetic acid (2,4-D) were investigated by coupling molecular analyses based on 16S rDNA with functional genes. We employed three different cultural conditions: (1) a culture sequentially fed a high concentration (300 mg/L) of 2,4-D (HS); (2) a culture continuously fed a low concentration (10 mg/L) of 2,4-D (LC); and (3) a serial batch culture in which 1% (v/v) of culture was transferred to a fresh medium containing a high concentration (300 mg/L) of 2,4-D (HB). The HS and LC bioreactors were operated for 3 months and HB was repeatedly transferred for 1 month. The 2,4-D was stably degraded under all the cultural conditions tested. PCR amplification and cloning-based analysis of functional genes using community DNAs from the cultures revealed five different oxygenase genes that may be involved in the initial step of 2,4-D degradation. All five gene-types were present in HS, while one of the five genes, type V (tftA) was not detected in LC. Quantitative PCR analysis showed that in HS, Ralstonia eutropha JMP 134 type-tfdA4 (type I) was the most abundant in copy number (2.0 +/- 0.1 x 10(7) copies/microg DNA) followed by RASC type-tfdA (type II) (1.8 +/- 1.0 x 10(6) copies/microg DNA), putative cadA-like gene (type IV) (2.6 +/- 0.8 x 10(5) copies/microg DNA), cadA gene (type III) (1.3 +/- 1.0 x 10(4) copies/microg DNA), and tftA gene (type V) (3.5 +/- 1.1 x 10(3) copies/microg DNA). Similar results were obtained in LC. In contrast, HB contained only type I and type III genes, and the type I gene was five orders of magnitude greater in copy number than the type III gene. Denaturing gel gradient electrophoresis (DGGE) analysis of PCR, amplified 16S rDNA fragments of bacterial communities in the three different cultures showed low similarity coefficient values (< or =0.35) when compared to the original activated sludge, suggesting that 2,4-D amendment caused a drastic change in the bacterial community. Particularly, HB showed only six bands (16-18 bands in the other cultures) and very low similarity coefficient values when compared to the other communities (0.10 to HS, 0.17 to LC, and 0.0 to original sludge). These results indicated that serial batch culturing (HB) resulted in a phylogenetically limited number of 2,4-D degrading bacteria carrying limited catabolic genes whereas more diverse 2,4-D degraders and catabolic genes were present in HS and LC. Therefore, the approach used for monitoring should be taken into account when one evaluates the population dynamics of contaminant-degrading bacteria at bioremediation sites.

2,4-Dichlorophenoxyacetic Acid↗
PubMed2004

Expression and distribution of Na, K-ATPase in gill and kidney of the spotted green pufferfish, Tetraodon nigroviridis, in response to salinity challenge.

Freshwater (FW) spotted green pufferfish (Tetraodon nigroviridis) were transferred directly from a local aquarium to fresh water (FW; 0 per thousand ), brackish water (BW; 15 per thousand ), and seawater (SW; 35 per thousand ) conditions in the laboratory and reared for at least two weeks. No mortality was found. To investigate the efficient mechanisms of osmoregulation in the euryhaline teleost, distribution and expression of Na,K-ATPase (NKA) in gill and kidney of the pufferfish were examined and the osmolality, [Na+] and [Cl-] of the blood were assayed. The lowest levels of both relative protein abundance and activity were found to be exhibited in the BW group, and higher levels in the SW group than FW group. In all salinities, branchial NKA immunoreactivity was found in epithelial cells of the interlamellar region of the filament and not on the lamellae. Relative abundance of kidney NKA alpha-subunit, as well as the NKA activity, was found to be higher in the FW pufferfish than fish in BW or SW. Renal NKA appeared in the epithelial cells of distal tubules, proximal tubules, and collecting tubules, but not in glomeruli, in fish groups of various salinities. Plasma osmolality and chloride levels were significantly lower in FW pufferfish than those in BW and SW, whereas plasma sodium did not differ among the groups. Although identical distributions of NKA were found in either gill or kidney of FW-, BW- or SW-acclimated spotted green pufferfish, differential NKA expression in fish of various salinity groups was associated with physiological homeostasis (stable blood osmolality), and illustrated the impressive osmoregulatory ability of this freshwater and estuarine species in response to salinity challenge.

Animals↗
PubMed2004

Effects of polyhemoglobin-antioxidant enzyme complex on ischemia-reperfusion in kidney.

INTRODUCTION: The kidney suffers ischemia-reperfusion (I/R) injury during transplantation. The purpose of the present study was to investigate the therapeutic effect of artificials cells on renal I/R injury through biochemical assays and histological examination. METHODS: We prepared artificial cells using cross-linked hemoglobin (Hb), superoxide dismutase (SOD), and catalase. Normal male Sprague-Dawley rats were divided into 6 groups: the sham-operated control group, the group treated with polyHb,and the group treated with polyHb-SOD-catalase (PSC) (per groups were subjected to ischemia for 1 hour or 2 hours). After reperfusion for 4 hours, kidney and blood samples were obtained. RESULTS: The levels of SOD and catalase in the PSC group were 15 and 50 times higher than those of the control group, respectively. In the polyHb group, the levels of blood urea nitrogen (BUN), serum creatinine, renal hydrogen peroxide, and renal malondialdehyde were increased. However, their levels were significantly decreased by PSC administration. Renal SOD activity did not show any significant changes in the polyHb group, but renal catalase activity was decreased by polyHb treatment in comparison with the control group. The activities of renal SOD and catalase were increased using PSC treatment. In the histological findings, the PSC group showed no evidence of acute tubular necrosis in proximal convoluted tubules; their microvilli and cytoplasmic microorganelles were relatively well preserved. CONCLUSIONS: These results show that PSC effectively reduces renal damage via diminished oxygen free radical-mediated injury after I/R.

Animals↗
PubMed2004

Robust adaptive neural network control of uncertain nonholonomic systems with strong nonlinear drifts.

In this paper, robust adaptive neural network (NN) control is presented to solve the control problem of nonholonomic systems in chained form with unknown virtual control coefficients and strong drift nonlinearities. The robust adaptive NN control laws are developed using state scaling and backstepping. Uniform ultimate boundedness of all the signals in the closed-loop are guaranteed, and the system states are proven to converge to a small neighborhood of zero. The control performance of the closed-loop system is guaranteed by appropriately choosing the design parameters. The proposed adaptive NN control is free of control singularity problem. An adaptive control based switching strategy is used to overcome the uncontrollability problem associated with x0 (t0) = 0. The simulation results demonstrate the effectiveness of the proposed controllers.

Artificial Intelligence↗