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Biomedical subjects

T J Park

Publications and source records attributed to T J Park.

At least 19 recordsLinked to original sources

Parameter sensitivity analysis for activated sludge models No. 1 and 3 combined with one-dimensional settling model.

The aim of this study was to suggest a sensitivity analysis technique that can reliably predict effluent quality and minimize calibration efforts without being seriously affected by influent composition and parameter uncertainty in the activated sludge models No. 1 (ASM1) and No. 3 (ASM3) with a settling model. The parameter sensitivities for ASM1 and ASM3 were analyzed by three techniques such as SVM-Slope, RVM-SlopeMA, and RVM-AreaCRF. The settling model parameters were also considered. The selected highly sensitive parameters were estimated with a genetic algorithm, and the simulation results were compared as deltaEQ. For ASM1, the SVM-Slope technique proved to be an acceptable approach because it identified consistent sensitive parameter sets and presented smaller deltaEQ under every tested condition. For ASM3, no technique identified consistently sensitive parameters under different conditions. This phenomenon was regarded as the reflection of the high sensitivity of the ASM3 parameters. But it should be noted that the SVM-Slope technique presented reliable deltaEQ under every influent condition. Moreover, it was the simplest and easiest methodology for coding and quantification among those tested. Therefore, it was concluded that the SVM-Slope technique could be a reasonable approach for both ASM1 and ASM3.

Algorithms↗

ICA and water in Korea--overview.

The natural water quality in Korea has improved significantly in the last 20 years since major collective national initiatives were implemented by governmental agencies, non-governmental organizations, and professionals among many others. Recently instrumentation, control, and automation (ICA) technology has become one of the most important technologies for carrying out this task. Korea has become especially well known with a strong reputation for information technology and international business with commercial products like semi-conductors, computers, mobile phones, computer games, and other electronic products. In this paper the background of Korean water quality is reviewed and several of the most significant national projects related to ICA are discussed. The major projects may include the Automatic Monitoring Network of River Water Quality and the Integrated Management System of Wastewater Treatment Plants in Upper Basin Area of Multi-purpose Dams.

Automation↗

Forecasting influent flow rate and composition with occasional data for supervisory management system by time series model.

The information on the incoming load to wastewater treatment plants is not often available to apply modelling for evaluating the effect of control actions on a full-scale plant. In this paper, a time series model was developed to forecast flow rate, COD, NH4(+)-N and PO4(3-)-P in influent by using 250 days data of field plant operation data. The data for 150 days and 100 days were used for model development and model validation, respectively. The missing data were interpolated by the spline method and the time series model. Three different methods were proposed for model development: one model and one-step to seven-step ahead forecasting (Method 1); seven models and one-step-ahead forecasting (Method 2); and one model and one-step-ahead forecasting (Method 3). Method 3 featured only one-step-ahead forecasting that could avoid the accumulated error and give simple estimation of coefficients. Therefore, Method 3 was the reliable approach to developing the time series model for the purpose of this research.

Forecasting↗

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↗

Equipment fault diagnosis system of sequencing batch reactors using rule-based fuzzy inference and on-line sensing data.

The importance of a detection technique to prevent process deterioration is increasing. For the fast detection of this disturbance, a diagnostic algorithm was developed to determine types of equipment faults by using on-line ORP and DO profile in sequencing batch reactors (SBRs). To develop the rule base for fault diagnosis, the sensor profiles were obtained from a pilot-scale SBR when blower, influent pump and mixer were broken. The rules were generated based on the calculated error between an abnormal profile and a normal profile, e(ORP)(t) and e(DO)(t). To provide intermediate diagnostic results between "normal" and "fault", a fuzzy inference algorithm was incorporated to the rules. Fuzzified rules could present the diagnosis result "need to be checked". The diagnosis showed good performance in detecting and diagnosing various faults. The developed algorithm showed its applicability to detect faults and make possible fast action to correct them.

Algorithms↗

Activity of sulphate reducing bacteria according to COD/SO4(2-) ratio of acrylonitrile wastewater containing high sulphate.

This study was performed to evaluate the biodegradability of acrylonitrile wastewater, microbial inhibition effect of acrylonitrile wastewater on removal efficiency and the activity of sulphate reducing bacteria (SRB) according to COD/sulphate ratio. Acrylonitrile wastewater was hardly biodegradable in a biodegradability test, however, SRB activity was 57% for overall consumption of electron donor and it was relatively high value compared to 17% of reference test with glucose. COD removal of acrylonitrile wastewater was improved to 57% and 61% from 20% as the COD/sulphate ratio were 0.5 and 0.3 by sulphate addition to acrylonitrile wastewater. First order reaction rate constants k on organic removal of acrylonitrile wastewater were 0.001, 0.004 and 0.004 at each COD/sulphate ratio of 0.9, 0.5 and 0.3. Thus it was suggested that the activity of SRB was a significant factor for removing organics and sulphate simultaneously in acrylonitrile wastewater.

Acrylonitrile↗

Automatic control of external carbon source addition for nitrogen removal in sewage with low C/N ratios.

For cost-effective nitrogen removal from sewage with low C/N ratios, an automatic control system for the addition of external carbon based on oxidation-reduction potential (ORP) data in an anoxic reactor has been developed. In this study, it was carried out with a pilot-scale modified Bardenpho process. This consisted of anoxic1, aerobic1, anoxic2 and aerobic2 stages with an external recycle ratio of 150% (Q/Qinf), and a media packing ratio of 2.4%-2.9% (v/v) in the aerobic reactor. As a result of applying the automatic control system for the minimization of the external carbon source dosage, the dosage was decreased by about 20%. This estimate was based on ORP compared with a stable dosage of 75 mg/L based on the C/NOx-N ratio of the anoxic influent. It was necessary that the ORP set-value be regulated from -120 mV to -80 mV because influent NH4+-N concentration varied from 12 to 15 mg/L due to rainfall. Correspondingly, the demanded dosages were decreased. Drift of the the real-time value in control system was more stable after changing the ORP set-value from -120 mV to -80 mV.

Automation↗

Methylation of O(6)-methylguanine-DNA methyltransferase gene is associated significantly with K-ras mutation, lymph node invasion, tumor staging, and disease free survival in patients with gastric carcinoma.

BACKGROUND: O(6)-methylguanine-DNA methyltransferase (MGMT) can remove O(6)alkylG DNA adducts. If they are not removed, then the adducts mispair with T during DNA replication, resulting in G-to-A mutation. Interrelations between MGMT gene inactivation by promoter methylation, K-ras mutation, and clinicopathologic features in patients with gastric carcinoma were studied. METHODS: Surgically removed tumor tissues from 79 patients were analyzed with MGMT methylation by genomic DNA modification and methylation specific polymerase chain reaction analysis, K-ras mutation by mutant allele specific amplification, TNM classification according to the International Union Against Cancer system, and MGMT protein expression by immunohistochemistry. RESULTS: MGMT-promoter methylation was found in 18 of 79 tumors. Among those 18 tumors, K-ras mutations were found in 33% and 11% of tumors at codons 12 and 13, respectively, corresponding to 20 times and 7 times greater rates of mutation compared with unmethylated tumors. MGMT methylation was associated significantly with lymph node invasion (P < 0.01), tumor stage (P < 0.03) and 5-year disease free survival (P < 0.02). MGMT protein expression was detected in intestinal metaplasia and adenocarcinoma samples, whereas no expression was detected in normal foveolar cells. CONCLUSIONS: MGMT-promoter methylation in patients with gastric carcinoma was associated significantly with point mutations of K-ras at codons 12 and 13, lymph node invasion, tumor stage, and disease free survival. These associations indicate a significant role of MGMT methylation during gastric carcinogenesis.

Adenocarcinoma↗

Noncompetitive inhibition by camphor of nicotinic acetylcholine receptors.

The effect of camphor, a monoterpenoid, on catecholamine secretion was investigated in bovine adrenal chromaffin cells. Camphor inhibited [3H]norepinephrine ([3H]NE) secretion induced by a nicotinic acetylcholine receptor (nAChR) agonist, 1,1-dimethyl-4-phenylpiperazinium iodide (DMPP), with a half-maximal inhibitory concentration (IC50) of 70 +/- 12 microM. In addition, camphor inhibited the rise in cytosolic calcium ([Ca2+]i) and sodium ([Na+]i) induced by DMPP with IC50 values of 88 +/- 32 and 19 +/- 2 microM, respectively, suggesting that the activity of nAChRs is also inhibited by camphor. On the other hand, binding of [3H]nicotine to nAChRs was not affected by camphor. [Ca2+]i increases induced by high K+, veratridine, and bradykinin were not affected by camphor. The data suggest that camphor specifically inhibits catecholamine secretion by blocking nAChRs without affecting agonist binding.

Animals↗

Selective left-lobe atrophy by nodularin treatment accompanied by reduced protein phosphatase 1/2A and increased peroxisome proliferation in rat liver.

The effect of nodularin on selective atrophy of left lobes in the liver was investigated in F344 rats. Nodularin was injected for 10 weeks from the third week of initiation with saline or N-nitrosodiethylamine (DEN), grouped as S/N and D/N, respectively. Nodularin significantly decreased weights of left (LL) and caudate (CL) lobes but increased right (RL) and middle (ML) lobes in S/N rats. Activity of protein phosphatases [types 1 (PPI) and 2A (PP2A)] was more severely reduced in S/N than D/N rats; moreover, in LL compared with RL of S/N rats, activity was significantly inhibited by nodularin treatment from week 4, which corresponded to 2 weeks after nodularin injection. However, nodularin significantly induced peroxisomal palmitoyl-CoA oxidase and cytochrome P-450 4A1 expression in S/N compared with D/N rats. An effect of nodularin on apoptosis was evident since expression of Bcl-Xs was clearly induced in LL of S/N rats as opposed to various inductions of Bcl-XL. However, Bcl-XL in RL was persistently induced, with undetectable Bcl-Xs expression. These results demonstrate biochemical evidence of selective atrophy of LL by inhibition of PP1 and PP2A activity, increase of peroxisomal enzymes and induction of Bcl-Xs expression, in contrast to proliferation of RL in rats treated with nodularin alone. However, nodularin endowed DEN-altered hepatocytes with regenerating power and concomitant restoration of phosphatase activity as well as persistent expression of Bcl-XL in D/N rats.

Alkylating Agents↗

Sequential changes in hepatocarcinogenesis induced by diethylnitrosamine plus thioacetamide in Fischer 344 rats: induction of gankyrin expression in liver fibrosis, pRB degradation in cirrhosis, and methylation of p16(INK4A) exon 1 in hepatocellular carcinoma.

To clarify the sequential changes in pRB and p16 during different stages of hepatocarcinogenesis such as fibrosis, cirrhosis, hepatocellular adenoma (HCA), and hepatocellular carcinoma (HCC), male Fischer 344 rats were singly injected with diethylnitrosamine (DEN), immediately followed with phenobarbital for 1 wk and then thioacetamide (TAA) for 39 wk in drinking water. Rats were killed at 9, 20, 30, and 40 wk after DEN initiation and changes of pRB level, p16 gene hypermethylation, and in vivo gankyrin expression were examined. Histologic examination showed stepwise appearances of fibrosis, cirrhosis, HCA, and HCC at weeks 9, 20, 30, and 40, respectively. Hypermethylation of p16 exon 1 was not found until HCA but appeared in 50% of the rats with HCC accompanied by complete loss of its mRNA expression. The amount of glutathione S-transferase--gankyrin bound to pRB and pRB degradation in the liver depended on the concentration of gankyrin and incubation time. Gankyrin expression preceded pRB degradation in liver cirrhosis. In conclusion, gankyrin expression induced in liver fibrosis accelerated the degradation of pRB during liver cirrhosis, and inactivation of p16 exon 1 by DNA hypermethylation occurred during the progression of tumor cells to poorly differentiated HCC. Inactivation of pRB and/or p16 resulted in complete loss of regulation in the cell-division cycle during early and late stages, respectively, of hepatocarcinogenesis. Mol. Carcinog. 30:138--150, 2001.

Animals↗

Coupling of L-type voltage-sensitive calcium channels to P2X(2) purinoceptors in PC-12 cells.

Extracellular ATP elevates cytosolic Ca(2+) by activating P2X and P2Y purinoceptors and voltage-sensitive Ca(2+) channels (VCCCs) in PC-12 cells, thereby facilitating catecholamine secretion. We investigated the mechanism by which ATP activates VSCCs. 2-Methylthioadenosine 5'-triphosphate (2-MeS-ATP) and UTP were used as preferential activators of P2X and P2Y, respectively. Nifedipine inhibited the ATP- and 2-MeS-ATP-evoked cytosolic Ca(2+) concentration increase and [(3)H]norepinephrine secretion, but not the UTP-evoked responses. Studies with Ca(2+) channel blockers indicated that L-type VSCCs were activated after the P2X activation. Mn(2+) entry profiles and studies with thapsigargin revealed that Ca(2+) entry, rather than Ca(2+) release, was sensitive to nifedipine. Although P2X(2) and P2X(4) receptor mRNAs were detected, studies with pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid revealed that P2X(2) was mainly coupled to the L-type VSCCs. The inhibitory effect of nifedipine did not occur in the absence of extracellular Na(+), suggesting that Na(+) influx, which induces depolarization, was essential for the P2X(2)-mediated activation of VSCCs. We report that depolarization induced by Na(+) entry through the P2X(2) purinoceptors effectively activates L-type VSCCs in PC-12 cells.

Adenosine Triphosphate↗

Analytical derivation of interference dips in molecular absorption spectra: molecular properties and relationships to Fano's antiresonance.

An analytical expression is derived for the decrease in the absorption cross section that occurs when two molecular electronic states are coupled by spin-orbit coupling. The loss of intensity, or interference dip, is common in the spectra of metal compounds. The derivation is based on a coupling of a single forbidden donor state to a broadened harmonic acceptor potential, and leads to simple analytical expressions. The new expressions give line shape functions different from those in the commonly used Fano antiresonance interpretation and are based on interpretable molecular properties.

Journal Article↗

Phosphorylation of methylated-DNA-protein-cysteine S-methyltransferase at serine-204 significantly increases its resistance to proteolytic digestion.

In a previous paper [Lim, Park, Jee, Lee and Paik (1999) J. Cancer Res. Clin. Oncol. 125, 493-499], we showed two major forms of active DNA-6-O-methylguanine:protein-L-cysteine S-methyltransferase (MGMT; EC 2.1.1.63) in the liver with N-nitrosodiethylamine (DEN)-induced carcinogenesis: these were 26 and 24 kDa species. Here we show that a 2 kDa C-terminal fragment was cleaved from the 26 kDa species in vitro by thrombin or microsomal fractions isolated from DEN-treated rat livers. When Ser(204) of the 26 kDa protein was replaced with Ala by site-directed mutagenesis, phosphorylation of the protein was completely abolished, indicating Ser(204) to be the site of phosphorylation. We also show that the phosphorylation was performed by Ca(2+)-independent protein kinase isoenzymes, and that the phosphorylated rat MGMT protein was resistant to digestion by protease(s) whose activity was increased during DEN-induced hepatocarcinogenesis and also by digestion with endopeptidase Glu-C (V8 protease).

Amino Acid Sequence↗

Structure and function of the bat superior olivary complex.

The superior olivary complex (SOC) is a mammalian auditory brainstem structure that contains several nuclei. Some of them are part of the ascending system projecting to higher auditory centers, others belong to the descending system projecting to the cochlear nuclei or the cochlea itself. The main nuclei of the ascending system, the lateral and medial superior olive (LSO, MSO), as well as the lateral and medial nuclei of the trapezoid body (LNTB, MNTB), have been traditionally associated with sound localization. Here we review the results of recent studies on the main SOC nuclei in echolocating bats. These studies suggest that some SOC structures and functions are highly conserved across mammals (e.g., the LSO, which is associated with interaural intensity difference processing), while others are phylogenetically highly variable in both form and function (e.g., the MSO, traditionally associated with interaural time difference processing). For the MSO, these variations indicate that we should broaden our view regarding what functions the MSO might participate in, since its function in echolocation seems to lie in the context of pattern recognition rather than sound localization. Furthermore, across bat species, variations in the form and physiology of the MSO can be linked to specific behavioral adaptations associated with different echolocation strategies. Finally, the comparative approach, including auditory specialists such as bats, helps us to reach a more comprehensive view of the functional anatomy of auditory structures that are still poorly understood, like the nucleus of the central acoustic tract (NCAT).

Animals↗

Inhibition of nicotinic receptor-mediated catecholamine secretion by Dryobalanops aromatica in bovine adrenal chromaffin cells.

Effect of the aqueous extract from a medicinal plant Dryobalanops aromatica(Dipterocarpaceae) on catecholamine secretion was investigated in bovine adrenal chromaffin cells. The aqueous extract inhibited [(3)H]norepinephrine ([(3)H]NE) secretion induced by 1,1-dimethyl-4-phenylpiperazinium iodide (DMPP), a nicotinic acetylcholine receptor (nAChR) agonist, with a half-maximal inhibitory concentration (IC(50)) of 8.4 +/- 1.7 microgml(-1). Increases in cytosolic calcium ([Ca(2+)](i)) and sodium ([Na(+)](i)) induced by DMPP were also inhibited by the extract. However, the binding of [(3)H]nicotine to nAChRs was not affected by the addition of the extract in receptor binding competition analysis, suggesting that active components in the extract and nicotine do not share the binding site in the nAChR. On the other hand, [Ca(2+)](i)increases induced by high K(+), ionomycin, bradykinin, angiotensin II, and thapsigargin were not inhibited by the extract. The data suggest that the extract from D. aromatica specifically inhibits catecholamine secretion by blocking nAChR in a noncompetitive manner.

Animals↗

Latency as a function of intensity in auditory neurons: influences of central processing.

The response latencies of sensory neurons typically shorten with increases in stimulus intensity. In the central auditory system this phenomenon should have a significant impact on a number of auditory functions that depend critically on an integration of precisely timed neural inputs. Evidence from previous studies suggests that the auditory system not only copes with the potential problems associated with intensity-dependent latency change, but that it also modifies latency change to shape the response properties of many cells for specific functions. This observation suggests that intensity-dependent latency change may undergo functional transformations along the auditory neuraxis. The goal of our study was to explore these transformations by making a direct, quantitative comparison of intensity-dependent latency change among a number of auditory centers from the lower brainstem to the thalamus. We found two main ways in which intensity-dependent latency change transformed along the neuraxis: (1) the range of latency change increased substantially and (2) one particular type of latency change, which has been suggested to be associated with sensitivity to temporally segregated stimulus components, occurred only at the highest centers tested, the midbrain and thalamus. Additional testing in the midbrain (inferior colliculus) indicated that inhibitory inputs are involved in shaping latency change. Our findings demonstrate that the central auditory system modifies intensity-dependent latency changes. We suggest that these changes may be functionally incorporated, actively enhanced, or modified to suit specific functions of the auditory system.

Animals↗

Nongenomic inhibition of catecholamine secretion by 17beta-estradiol in PC12 cells.

We investigated the effects of 17beta-estradiol, an estrogen, on [(3)H]norepinephrine ([(3)H]NE) secretion in PC12 cells. Pretreatment with 17beta-estradiol reduced 70 mM K(+)-induced [(3)H]NE secretion in a concentration-dependent manner with a half-maximal inhibitory concentration (IC(50)) of 2 +/- 1 microM. The 70 mM K(+)-induced cytosolic free Ca(2+) concentration ([Ca(2+)](i)) rise was also reduced when the cells were treated with 17beta-estradiol (IC(50) = 15 +/- 2 microM). Studies with voltage-sensitive calcium channel (VSCC) antagonists such as nifedipine and omega-conotoxin GVIA revealed that both L- and N-type VSCCs were affected by 17beta-estradiol treatment. The 17beta-estradiol effect was not changed by pretreatment of the cells with actinomycin D and cycloheximide for 5 h. In addition, treatment with pertussis or cholera toxin did not affect the inhibitory effect of 17beta-estradiol. 17beta-Estradiol also inhibited the ATP-induced [(3)H]NE secretion and [Ca(2+)](i) rise. In PC12 cells, the ATP-induced [Ca(2+)](i) rise is known to occur through P2X(2) receptors, the P2Y(2)-mediated phospholipase C (PLC) pathway, and VSCCs. 17beta-Estradiol pretreatment during complete inhibition of the PLC pathway and VSCCs inhibited the ATP-induced [Ca(2+)](i) rise. Our results suggest that 17beta-estradiol inhibits catecholamine secretion by inhibiting L- and N-type Ca(2+) channels and P2X(2) receptors in a nongenomic manner.

Adenosine↗