Biomedical subjects

Y C Kim

Publications and source records attributed to Y C Kim.

At least 199 records · Page 11Linked to original sources

PubMed1997

Sequence analysis of the phnD gene encoding 2-hydroxymuconic semialdehyde hydrolase in Pseudomonas sp. strain DJ77.

The 6.8-kb XhoI fragment of chromosomal DNA of Pseudomonas sp. DJ77 contains the phnDEFG genes involved in the degradation of polyaromatic hydrocarbons and chlorinated aromatics. Here, we report the nucleotide sequence of the phnD gene encoding a 2-hydroxymuconic semialdehyde hydrolase and its substrate specificity. The PhnD hydrolase contains 286 amino acids with a M(r) of 31301. The deduced amino acid sequence of the PhnD enzyme is 31.0-50.5% identical to those of homologous enzymes encoded by the dmp, tod, xyl, and bph operons. The PhnD enzyme is required for conversion of 2-hydroxymuconic semialdehyde, which is produced from catechol by the PhnE catechol 2,3-dioxygenase, to 2-hydroxypent-2,4-dienoate. We now confirm that the phnD gene is located immediately upstream of the catechol 2,3-dioxygenase gene (phnE) unlike other meta-cleavage operons.

Amino Acid Sequence↗

PubMed1997

Adenosine A3 receptor agonists protect HL-60 and U-937 cells from apoptosis induced by A3 antagonists.

The effects of novel, selective adenosine (ADO) A3 receptor antagonists of diverse structure on cells of the human HL-60 leukemia and U-937 lymphoma cell lines were examined. Both 3-ethyl 5-benzyl 2-methyl-6-phenyl-4-phenylethynyl-1,4-(+/-)-dihydropyridine-3, 5-dicarboxylate (MRS 1191, 0.5 microM) and 6-carboxy-methyl-5, 9-dihydro-9-methyl-2-phenyl-[1,2,4]-triazolo [5,1-a][2,7]naphthyridine (L-249313, 0.5 microM) induced apoptotic cell death and expression of bak protein. Low concentrations of the A3 receptor agonist 2-chloro-N6-(3-iodobenzyl)adenosine-5'-N-methyluronamide (Cl-IB-MECA, 10 nM or 1 microM) protected against antagonist-induced cell death. At concentrations > or = 10 microM, the agonist alone produced apoptosis and bak expression in various cell lines. It is suggested that there exists a tonic low level of A3 receptor activation, possibly induced by release of endogenous adenosine, that results in cell protection.

Adenosine↗

PubMed1997

Anatomy and magnetic resonance imaging of the posterolateral structures of the knee.

The purpose of the present study was to provide detailed information of the morphological and radiological characteristics of the posterolateral structures of the knee. Muscles and ligaments of the posterolateral part of the knee were studied by dissections of 50 adult cadaver knees and by Magnetic Resonance Imaging (MRI) before and after dissections for comparisons. Diverse morphological characteristics of the arcuate ligament were found. The fabellofibular ligament was present in 42.1% of the knees dissected, whereas the popliteofibular ligament was found in 37.5%. A ligamentous structure, which could be called the posterior tibial ligament, was found in 31.6% of the cases that originated from the lateral part of the capsule proximally and inserted distally on the mid portion of the proximal tibia. By comparing the cross sections and the dissections of the cadaver knees, the popliteus muscle, the arcuate ligament, the fibular collateral ligament, the popliteofibular ligament, and the fabellofibular ligament could be identified in MRI. Comprehensive understanding of the posterolateral anatomy of the knee and improved identification of the structures in MRI will help clinicians to make a more accurate and noninvasive diagnosis of posterolateral instability.

Adult↗

PubMed1997

Dichloromethane potentiation of carbon tetrachloride hepatotoxicity in rats.

Concomitant treatment of rats with a nonhepatotoxic dose of dichloromethane (6 mmol/kg, i.p.) significantly potentiated the hepatotoxicity of carbon tetrachloride (2 mmol/kg, i.p.). Toxicity was determined by increases in serum sorbitol dehydrogenase and alanine aminotransferase activities measured 24 hr following the treatments. Dichloromethane did not affect the lipid peroxidation induced by carbon tetrachloride as determined by conjugated diene formation in hepatic microsomal lipids. The covalent binding of [14C]Cl4 metabolites to microsomal lipids was increased significantly by dichloromethane. The results suggest that dichloromethane potentiates carbon tetrachloride hepatotoxicity by increasing covalent binding of its metabolites to hepatic microsomal lipids.

Alanine Transaminase↗

PubMed1997

Tendinous insertion of semimembranosus muscle into the lateral meniscus.

Forty-two cadaver knees were used for morphologic and MRI observations of the tendinous distal expansions of the semimembranosus m. and the posterior capsular structures of the knee. A tendinous branch of the semimembranosus m. inserting into the posterior horn of the lateral meniscus was found in 43.2% of the knees dissected, besides five already known insertional branches; capsular, direct, anterior and inferior, as well as the oblique popliteal ligament. The tendon had three morphologic types; thin, broad and round. All three types moved the lateral meniscus posteriorly when pulled on. Thus, the semimembranosus m. may also have a protective function for the lateral meniscus as well as the already well established function of protecting the medial meniscus in knee flexion. When a semimembranosus tendon attachment to the posterior horn of the lateral meniscus is present, its normal insertion is difficult to differentiate from a lateral meniscus tear in MRI and this may cause misdiagnosis.

Genetic Variation↗

PubMed1997

Effects of myosin light chain kinase inhibitors on carbachol-activated nonselective cationic current in guinea-pig gastric myocytes.

The effects of myosin light chain kinase inhibitors on muscarinic stimulation-activated nonselective cationic current (ICCh) in guinea-pig gastric antral myocytes were studied using the whole-cell patch-clamp technique. ICCh was induced by carbachol (CCh, 50 microM) at a holding potential of -30 mV or -60 mV. ML-7, a chemical inhibitor of myosin light chain kinase (MLCK), inhibited ICCh concentration dependently in a reversible manner (53 +/- 8.6% at 1 microM, mean +/- SE, n = 11). In addition, amplitudes of ICCh were only 37 +/- 2.7% of the daily control values following the addition of a peptide inhibitor of MLCK to the pipette solution. On the other hand, ML-7 had an inhibitory effect on voltage-operated Ca2+ channel current. The peak value of Ba2+ current at 0 mV was reduced to 35 +/- 7.4% (n = 9) by 3 microM of ML-7. As ICCh is known to have an intracellular Ca2+ dependence, we tried to exclude the possibility that ML-7 inhibited ICCh indirectly via suppression of Ca2+ current and the similar inhibitory effects of ML-7 on ICCh were confirmed under the following conditions: (1) clamp of membrane potential at -60 mV; (2) clamp of intracellular [Ca2+] to 1 microM by 10 mM BAPTA; (3) pre-inhibition of Ca2+ channel by verapamil. Different from the effects on ICCh, ML-7 barely inhibited the same cationic current induced by guanosine 5'-O-(3-thiotriphosphate) (GTP[gammaS], 0.2 mM) in the pipette solution. These results suggest that a Ca2+/calmodulin-MLCK-dependent pathway can modulate the activation of ICCh in guinea-pig gastric antral myocytes.

Animals↗

PubMed1997

Pharmacological characterization of novel A3 adenosine receptor-selective antagonists.

The effects of putative A3 adenosine receptor antagonists of three diverse chemical classes (the flavonoid MRS 1067, the 6-phenyl-1,4-dihydropyridines MRS 1097 and MRS 1191, and the triazoloquinazoline MRS 1220) were characterized in receptor binding and functional assays. MRS1067, MRS 1191 and MRS 1220 were found to be competitive in saturation binding studies using the agonist radioligand [125I]AB-MECA (N6-(4-amino-3-iodobenzyl)adenosine-5'-N-methyluronamide) at cloned human brain A3 receptors expressed in HEK-293 cells. Antagonism was demonstrated in functional assays consisting of agonist-induced inhibition of adenylate cyclase and the stimulation of binding of [35S]guanosine 5'-O-(3-thiotriphosphate) ([35S]GTP-gamma-S) to the associated G-proteins. MRS 1220 and MRS 1191, with KB values of 1.7 and 92 nM, respectively, proved to be highly selective for human A3 receptor vs human A1 receptor-mediated effects on adenylate cyclase. In addition, MRS 1220 reversed the effect of A3 agonist-elicited inhibition of tumor necrosis factor-alpha formation in the human macrophage U-937 cell line, with an IC50 value of 0.3 microM.

Adenosine↗

PubMed1997

Control of cholesterol access to cytochrome P450scc in rat adrenal cells mediated by regulation of the steroidogenic acute regulatory protein.

Cholesterol conversion to pregnenolone by cytochrome P450scc in steroidogenic cells, including those of the adrenal cortex, is determined by hormonal control of cholesterol availability. Intramitochondrial cholesterol movement to P450scc, which retains hormonal activation in isolated mitochondria, is apparently dependent on peripheral benzodiazepine receptor and the recently cloned steroidogenic acute regulatory (StAR) protein. In rat adrenal cells, StAR is formed as a 37-kDa precursor that is transferred to the mitochondrial inner membrane following phosphorylation by hormonally activated protein kinase A, and processed to multiple forms, some of which turn over very rapidly. In bovine cells, StAR undergoes three modifications forming a set of eight proteins seen in both glomerulosa and fasciculata cells. In the former, cyclic AMP and angiotensin II each decrease two forms and elevate six forms. Significantly, the major change seen after activation may not involve phosphorylation of StAR. Cholesterol transfer across mitochondrial membranes is also activated in isolated mitochondria by GTP and low concentrations of Ca2+, apparently prior to activation by StAR. Depletion of StAR by cycloheximide inhibits cholesterol transfer but is overcome by uptake of Ca2+ into the matrix. This activation of cellular cholesterol transport is sustained in adrenal cells permeabilized by Streptolysin O. In rat adrenal cells cAMP elevates 3.5- and 1.6-kb mRNA, hybridized by a 1.0-kb StAR cDNA. A 3.5-kb rat adrenal cDNA that encodes all except the 5' end of the longest StAR mRNA has been characterized. The corresponding gene sequence is distributed across seven exons. The shorter mRNA may arise from polyadenylation signals early in exon 7. However, the 3.5-kb mRNA comprises 80-90% of untreated rat adrenal StAR mRNA and may therefore provide the prime source for in vivo translation of StAR protein.

Adrenal Glands↗

PubMed1997

Effect of the aqueous extract of Aquilaria agallocha stems on the immediate hypersensitivity reactions.

We investigated the effects of the aqueous extract of Aquilaria agallocha Roxb. (Thymelaeaceae) on the immediate hypersensitivity reactions. The aqueous extract of Aquilaria agallocha stems showed inhibitory effects on passive cutaneous anaphylaxis, anaphylaxis induced by compound 48/80, and histamine release from rat peritoneal mast cells (RPMC). The morphological examination also clearly showed that the extract prevented the degranulation of RPMC in rats. The level of compound 48/80-induced intracellular cAMP in RPMC, when the extract was added, significantly increased about 8-fold at 10 s compared with that of basal cells. These results suggest that the aqueous extract of Aquilaria agallocha stems inhibits the immediate hypersensitivity reaction by inhibition of histamine release from mast cells.

Animals↗

PubMed1997

Metabolic cleavage of frangufoline in rodents: in vitro and in vivo study.

Frangufoline, a sedative 14-membered frangulanine-type cyclopeptide alkaloid, was found to be rapidly converted, via enzymatic process, in vitro and in vivo in rodents to M1 ((S)-(N,N-dimethylphenylalanyl)-(2S,3S)-3-[(p-formylphenoxy) leucyl]-(S)-leucine); which is a substituted linear tripeptide. The reaction did not require low molecular weight cofactors, and mammalian serum failed to catalyze the reaction. Structure-reactivity study of cyclopeptide alkaloid analogs suggested that the enamide bond is the site being cleaved, and the reaction was inhibited by organophosphorus esters such as BPNP and by eserine at higher concentrations but not by eserine at lower concentrations or by EDTA and PCMB. On the basis of these results, a possible mechanism for metabolic conversion of frangufoline to M1 was proposed, in which oxidation of the vinyl group and enzyme-catalyzed hydrolysis of the adjacent amide bond, possibly by B-esterase-like enzyme, proceed in a concerted manner.

Animals↗

PubMed1997

New antihepatotoxic cerebroside from Lycium chinense fruits.

Two cerebrosides isolated from Lycium chinense fruits have been characterized as 1-O-beta-D-glucopyranosyl-(2S, 3R,4E,8Z)-2-N-palmitoyloctadecasphinga-4,8-dienine+ ++ (1) and 1-O-beta-D-glucopyranosyl -(2S,3R,4E,8Z)-2-N-(2'-hydroxypalmitoyl)octadecasph inga-4,8-dienine (2). While 2 is already known, the structure of 1 was determined by spectral and chemical studies. Incubation of CCl4-intoxicated hepatocytes with 1 and 2, respectively, significantly reduced the levels of glutamic pyruvic transaminase (GPT) and sorbitol dehydrogenase (SDH) released by injured cells.

Animals↗

PubMed1997

Prospective study of microvascular decompression in hemifacial spasm.

OBJECTIVES: Although, in most cases, the symptoms of hemifacial spasm (HFS) disappear immediately after microvascular decompression (MVD), in some cases, they disappear more gradually. The objectives of this study were to observe the time course and the rate of the delayed resolution and to attempt to explain the phenomenon through long-term follow-up of HFS after MVD. METHODS: Two hundred and sixty-one patients with HFS who underwent MVD were followed up to observe clinical changes. Two hundred and twenty-six of the 261 patients were followed up for a duration of 6 months to 2 years, from 1985 to 1995. RESULTS: After the 1st week of the surgery, 61.1% of the patients were rated as having achieved excellent results. When the patients were followed up for more than 6 months, however, the rate improved to 82.7%. The clinical results of HFS after MVD improved significantly with time (P < 0.05). Delayed resolution of HFS was observed in 37.4% of the patients who experienced complete resolution; it was the most important factor for clinical improvement during the follow-up period. Abnormal muscle response immediately after MVD in the operating room was also positively correlated with resolution during the follow-up period (correlation coefficient = 0.3099, P < 0.05). CONCLUSIONS: In conclusion, the clinical picture of HFS after MVD improves with time, and abnormal muscle response can be used as a prognostic indicator for the resolution of HFS during the follow-up period.

Adult↗

PubMed1997

A mutational analysis of residues essential for ligand recognition at the human P2Y1 receptor.

We conducted a mutational analysis of residues potentially involved in the adenine nucleotide binding pocket of the human P2Y1 receptor. Mutated receptors were expressed in COS-7 cells with an epitope tag that permitted confirmation of expression in the plasma membrane, and agonist-promoted inositol phosphate accumulation was assessed as a measure of receptor activity. Residues in transmembrane helical domains (TMs) 3, 5, 6, and 7 predicted by molecular modeling to be involved in ligand recognition were replaced with alanine and, in some cases, by other amino acids. The potent P2Y1 receptor agonist 2-methylthio-ATP (2-MeSATP) had no activity in cells expressing the R128A, R310A, and S314A mutant receptors, and a markedly reduced potency of 2-MeSATP was observed with the K280A and Q307A mutants. These results suggest that residues on the exofacial side of TM3 and TM7 are critical determinants of the ATP binding pocket. In contrast, there was no change in the potency or maximal effect of 2-MeSATP with the S317A mutant receptor. Alanine replacement of F131, H132, Y136, F226, or H277 resulted in mutant receptors that exhibited a 7-18-fold reduction in potency compared with that observed with the wild-type receptor. These residues thus seem to subserve a less important modulatory role in ligand binding to the P2Y1 receptor. Because changes in the potency of 2-methylthio-ADP and 2-(hexylthio)-AMP paralleled the changes in potency of 2-MeSATP at these mutant receptors, the beta- and gamma-phosphates of the adenine nucleotides seem to be less important than the alpha-phosphate in ligand/P2Y1 receptor interactions. However, T221A and T222A mutant receptors exhibited much larger reductions in triphosphate (89- and 33-fold versus wild-type receptors, respectively) than in diphosphate or monophosphate potency. This result may be indicative of a greater role of these TM5 residues in gamma-phosphate recognition. Taken together, the results suggest that the adenosine and alpha-phosphate moieties of ATP bind to critical residues in TM3 and TM7 on the exofacial side of the human P2Y1 receptor.

Adenosine Monophosphate↗

PubMed1997

Cloning and mutational analysis of the gene for the stationary-phase inducible catalase (catC) from Pseudomonas putida.

Pseudomonas putida, a bacterium that colonizes plant roots and enhances plant growth, produces three isozymes of catalase (A, B, and C) in stationary-phase cells. A catalase probe, generated by PCR analysis of P. putida genomic DNA with oligomers based on typical catalase sequences, hybridized to a genomic clone that expressed catalase C in Escherichia coli. The catC gene from this clone had a 2,133-bp open reading frame with a high level of identity to the stationary-phase-specific E. coli katE. Chromosomal mutants of P. putida deficient in catalase C, obtained by gene interruption with a luxAB-npt cassette, demonstrated enhanced catC transcription in stationary-phase cells and, upon exposure to phenol, in logarithmic-phase cells. The catalase C-deficient cells were not impaired in their ability to colonize roots of bean or wheat plants grown under sterile conditions.

Amino Acid Sequence↗

PubMed1997

Effects of Poncirus trifoliata on type I hypersensitivity reaction.

A study was carried out to examine the effect of an aqueous extract from immature fruit of Poncirus trifoliata L. (Rutaceae) (PTIFE) on the type I hypersensitivity reaction. Forty-eight hour PCA (passive cutaneous anaphylaxis) in rats was significantly inhibited by the oral administration of PTIFE (200 mg/kg). It also inhibited histamine release from rat peritoneal mast cells (RPMC) induced by mouse anti-dinitrophenyl (DNP)-IgE and dinitrophenyl-human serum albumin (DNP-HSA). These results suggest that PTIFE has anti-allergic action against the type I hypersensitivity reaction.

Administration, Oral↗

PubMed1997

Changes in intracellular Ca2+ concentration induced by L-type Ca2+ channel current in guinea pig gastric myocytes.

We investigated the relationship between voltage-operated Ca2+ channel current and the corresponding intracellular Ca2+ concentration ([Ca2+]i) change (Ca2+ transient) in guinea pig gastric myocytes. Fluorescence microspectroscopy was combined with conventional whole cell patch-clamp technique, and fura 2 (80 microM) was added to CsCl-rich pipette solution. Step depolarization to 0 mV induced inward Ca2+ current (ICa) and concomitantly raised [Ca2+]i. Both responses were suppressed by nicardipine, an L-type Ca2+ channel blocker, and the voltage dependence of Ca2+ transient was similar to the current-voltage relation of ICa. When pulse duration was increased by up to 900 ms, peak Ca2+ transient increased and reached a steady state when stimulation was for longer. The calculated fast Ca2+ buffering capacity (B value), determined as the ratio of the time integral of ICa divided by the amplitude of Ca2+ transient, was not significantly increased after depletion of Ca2+ stores by the cyclic application of caffeine (10 mM) in the presence of ryanodine (4 microM). The addition of cyclopiazonic acid (CPA, 10 microM), a sarco(endo)plasmic reticulum Ca(2+)-ATPase inhibitor, decreased B value by approximately 20% in a reversible manner. When KCl pipette solution was used, Ca(2+)-activated K+ current [IK(Ca)] was also recorded during step depolarization. CPA sensitively suppressed the initial peak and oscillations of IK(Ca) with irregular effects on Ca2+ transients. The above results suggest that, in guinea pig gastric myocyte, Ca2+ transient is tightly coupled to ICa during depolarization, and global [Ca2+]i is not significantly affected by Ca(2+)-induced Ca2+ release from sarcoplasmic reticulum during depolarization.

Animals↗

PubMed1997

Dual roles of phorbol 12, 13-dibutyrate in the regulation of guinea-pig gastric contraction.

We performed experiments to investigate the actions of protein kinase C(PKC) on mechanical contraction during agonist stimulation in guinea pig stomach. We used carbachol and high K condition to enhance mechanical contraction by mobilizing intracellular Ca2+ and increasing Ca2+ influx through voltage-dependent Ca(2+)-channel, respectively. Phorbol 12, 13-dibutyrate (PDBu) increased spontaneous contractions sensitive to verapamil (438 +/- 82.2%, n = 7) and potentiated high K-induced contraction (189 +/- 22.5%, n = 5). However, carbachol (CCh)-induced contractions in PDBu-treated condition depended on extracellular Ca2+. In the presence of extracellular Ca2+, CCh-induced contraction was potentiated, while it was suppressed in the absence of extracellular Ca(2+)-preloaded muscle strips. To prove the hypothesis that such phenomena might be related with changes of myoplasmic Ca2+ concentration, we investigated the effect of PDBu on voltage-dependent Ca2+ current(ICa) and CCh-induced Ca2+ activated K current(IK(Ca)) transient using whole-cell voltage clamp technique. For recording voltage-dependent Ca2+ current(ICa), 10 mM Ba2+, instead of Ca2+, was used to enhance the current size. Voltage-dependent Ba2+ current(IBa) was increased by PDBu (212 +/- 32.2% of steady state currents, n = 5), while CCh-induced increase of IK(Ca) transient was inhibited by PDBu (n = 5), the changes of which were similar to those of muscle contractions. To analyze the steps involved in the inhibition of CCh-induced IK(Ca) transient by PDBu, we investigated the effect of PDBu on IK(Ca) in the cells perfused with Ins (1, 4, 5)P3. However, Ins (1, 4, 5)P3 induced IK(Ca) was not inhibited by the treatment with phorbol ester. From these results, it is concluded that inhibition of phosphatidylinositol phospholipase C(PI-PLC) system and potentiation of ICa by PKC are important regulatory mechanisms in agonist-induced muscle contraction.

Animals↗

PubMed1997

Combining ADA, protein and IFN-gamma best allows discrimination between tuberculous and malignant pleural effusion.

BACKGROUND: The purpose of this study is to assess the usefulness of various enzymes, cytokines and biochemical studies of pleural fluid for the differential diagnosis of tuberculosis from malignant pleural effusions, and to clarify the role of combining diagnostic tests. METHODS: The study group included 39 cases with tuberculous effusions and 31 cases with malignant effusions, whose diagnoses were confirmed by pleural biopsy, cytology or microbiological methods. We compared pleural fluid levels of ADA, TNF-alpha, IFN-gamma, IL-2, IL-6, IL-8, pH, protein, glucose, cholesterol, triglyceride, amylase and lactic dehydrogenase between tuberculous and malignant effusions. Using stepwise logistic regression analysis, we evaluated the benefit of combining various parameters. Receiver operating characteristic(ROC) curves of ADA, cytokines and equations generated from regression analyses were plotted and compared with the area under curve(AUC). Cut-off values showing the best diagnostic accuracy were selected and compared. RESULTS: Compared to malignant effusion, tuberculous effusion showed significantly higher levels of ADA, IFN-gamma, TNF-alpha and IL-2. There was a good correlation between IFN-gamma and TNF-alpha. By stepwise logistic regression analysis, IFN-gamma, protein and ADA were independent variables predicting tuberculous from malignant effusions. The diagnostic accuracy and AUC of regression equation was greater than any other single parameters. CONCLUSION: For the differential diagnosis of tuberculosis and malignant pleural effusions, combining ADA, protein and IFN-gamma best allows discrimination.

Adenosine Deaminase↗