Showing papers by "Sungkyunkwan University published in 1994"

Determination of critical exponents from the multifragmentation of gold nuclei.

Abstract: Using reverse kinematics, we have studied the breakup of 1.0[ital A] GeV gold nuclei incident on a carbon target. The detector system permitted exclusive event reconstruction of nearly all charged reaction products. The moments of the resulting charged fragment distribution provide strong evidence that nuclear matter possesses a critical point observable in finite nuclei. We have determined values for the critical exponents [gamma], [beta], and [tau]. These values are close to those for liquid-gas systems and clearly different than those for 3D percolation and the liquid-gas mean field limit.

Antitumor Activity of some Phenolic Components in Plants

Abstract: The activity-guided fractionation of some medicinal plants led to yield five kinds of natural stilbene compounds namely 3,5-dihydroxy-4′-methoxystillbene(I), rhapontigenin(II), resveratrol (III), rhaponticin(IV) and piceid(V) and two common flavonoids, apigenin(VI) and luteolin(VII) as active principles of the antitumor property, in vitro, against five kinds of human tumor cell lines, A-549, SK-OV-3, SK-MEL-2, XF-498 and HCT15.

Antitumor and immunomodulating activities of the polysaccharide fractions from Artemisia selengensis and Artemisia iwayomogi

Abstract: Effects of the polysaccharide fractions purified fromArtemisia selengensis andArtemisia iwayomogi on the immune system was studied. The polysaccharide fractions, respectively called ASP1 and AIP1, may interact with macrophages and lymphocytes in spleen, increasing the population of those cell typesin vivo andin vitro. Both ASP1 and AIP1 fractions also suppress transplanted tumor cell growth and augment antibody production. This study suggests that ASP1 and AIP1 fractions may have immunomodulating and antitumor activities.

Flavonoids fromCirsium rhinoceros

Abstract: Six flavonoids were isolated from the aerial parts ofCirsium rhinoceros. The flavonoids were identified as apigenin, luteolin, pectolinarigenin-7-O-β-D-glucopyranoside, linarin, pectolinarin and hispidulin-7-O-α-L-rhamnopyranosyl-(1→2)-β-D-glucopyranoside on the basis of chemical and spectral evidence.

The mechanism of poly I:C-induced antiviral activity in peritoneal macrophage.

Abstract: Macrophages play an important role in defense against virus infection by intrinsic resistance and by extrinsic resistance. Since interferon-induced enzymes which are 2′–5′ oligoadenylate synthetase and P1/elF-2 protein kinase have been shown to be involved in the inhibition of viral replication, I examined the mechanism by which poly I:C, an interferon inducer, exerts its antiviral effects in inflammatory macrophages infected with herpes simplex virus type 1 (HSV-1). The data presented here demonstrate that poly I:C-induced antiviral activity is partially due to the activation of 2′–5′ oligoadenylate synthetase. The activation of 2′–5′ oligoadenylate A synthetase by poly I:C is also at least partly mediated via the production of interferon-β. Taken together, these data indicate that interferon-β produced in response to poly I:C acts in an autocrine manner to activate the 2′–5′ oligoadenylate synthetase and to induce resistance to HSV-1.

Compilation of a Functional Language for the Multithreaded Architecture: DAVRID

Abstract: Multithreading has been much focused on as one of the strongest parallel instruction execution paradigms for massively parallel processing. In this paper, we describe the compilation processes of parallel programming language Id- for a multithreaded architecture DAVRID(DAtaflow Von Neumann RISC hybrlD). Two fundamental issues in parallel processing, tolerance to communication latency and inexpensive synchronization, are solved by a compiler-controlled multithreading. Our compiler features a simple mechanism for handling closures, and a loop unfolding technique for handling parallel and sequential loops in separate, which can greatly contribute to parallel execution of loops.

Dynamics of Rotor Rub in Annular Clearance with Experimental Evaluation

Abstract: Rubbing phenomena in rotor dynamics are investigated by theoretical and experimental approaches. Generating conditions of forward whirling, backward rolling, backward slipping, and partial rubbing are established for system parameters and rotor speeds. Possible whirling motions of the rotor in annular clearance are calculated for full annular rub under the conditions of positive normal force and geometric constraints. The theoretical calculations show that greater clearance results in greater runout and normal force, and the whirling responses are characterized by which natural frequency of the rotor or the stator is greater than the other. Receptances of the rotor and stator are used to explain the possibility of slipping for backward slipping and forward whirling, respectively. Effect of rotor eccentricity is also considered to find the maximum rotor speed for backward slipping during increasing rotor speed and the occurrence of forward whirl. Experiments are performed for two cases. The experimental results show good agreements with the theoretical predictions.

Rapid gas chromatographic profiling and screening of acidic non-steroidal antiinflammatory drugs in biological samples

Abstract: The solid-phase extraction (SPE) with subsequenttert.-butyldimethylsilyl (TBDMS) derivatization was investigated for the rapid profiling and screening of various carboxylated non-steroidal antiinflammatory drugs (NSAIDs) simultaneously in biological fluid samples. Compared to the conventional SPE in adsorption mode using Chromosorb 102, Chromosorb 107, Carbopak B and Thermosorb, the SPE in partition mode using Chromosorb P as the adsorbent, and ethyl acetate/methylene chloride as the eluting solvents provided highest overall recoveries of the NSAIDs from aqueous solutions with good precision. The solid-phase extracted NSAIDs were silylated with N-methyl-N-(tert.-butyldimethylsilyl)trifluoroacetamide to TBDMS derivatives and directly analyzed by capillary gas chromatography and gas chromatography-mass spectrometry. The usefulness of the present method was examined for the profiling and screening of saliva, serum and urine samples for various NSAIDs simultaneously.

Ricin A immunotoxins of IgG and Fab of anti-CALLA monoclonal antibody: effect of water soluble long-chain SPDP on conjugate yield, immunoselectivity and cytotoxicity.

Abstract: The water soluble long-chain crosslinker, sulfo-succinimidyl-6-[3'-(2-pyridyldithio)-propionamido]hexanoate (S-LC-SPDP) was used to prepare ricin A chain (RTA) immunotoxins constructed with whole IgG and Fab fragments of the anti-common acute lymphoblastic leukemia antigen (CALLA) monoclonal antibody. In this study, a) S-LC-SPDP modification efficiencies of whole IgG and Fab, b) conjugation yields of the immunotoxins prepared and c) in vitro immunoreactivity and cytotoxicity of immunotoxins constructed were examined. IgG-RTA and Fab-RTA immunotoxins were prepared with 67.3% and 57.0% conjugation yields, respectively. These long spacer intermolecular linked immunotoxins were selectively immunoreactive and cytotoxic against to immunogenic Daudi cells but little or no-binding and cytotoxic against to antigen K562 cells. Both IgG-RTA and Fab-RTA immunotoxins were 210- and 45-fold more active than intact RTA in vitro, respectively.

Synthesis of antihypertensive agents via coupling reaction of benzothiazepinone and 1,4-dihydropyridine derivatives.

Abstract: The synthesis of 3a, 3b, 7a and 7b from Benzothiazepinone and 1,4-dihyropyridine derivatives is described. Benzothiazepinone and 1,4-dihydropyridine derivatives were prepared according to literature procedure. The key reactions involve esterification and amidation of benzothiazepinone and 1,4-dihydropyridine derivatives.

On-line trace enrichment for the determination of insulin in biological samples using reversed-phase high performance liquid chromatography with column switching

Abstract: Column-switching technique with a reversed-phase high performance liquid chromatographic method has been developed for the routine analysis of radioiodinated insulin and its degradation products in biological fluids. The diluted biological samples were loaded onto a precolumn packed with LiChrosorb RP-8 (25–40μm) using 0.1% trifluoroacetic acid (TFA) in water as a washing solvent. After valve switching, the concentrated insulins were eluted in the back-flush mode and separated by a W-Porex C18 column with a gradient of 0.1% TFA in water and 0.1% TFA in acetonitrile as the mobile phase. The method showed good precision, accuracy and speed with the detection limit of 20pg/ml. Total analysis time per sample was about 40 min and the coefficients of variation were less than 8.2%.

Inhibition of C-terminal O-methyltransferase by a rat liver cytosolic peptide

Abstract: The activity of S-famesylcysteine O-methyltransferase was assayed by incubating the enzyme with a syntheticin vitro substrate, [N-acetyl-S-trans, trans-famesyl-L-cysteine (AFC)], together with S-adenosyl-L-[methyl-14C]methionine. The resulting methylesterification product, [N-acetyl-S-trans, trans-famesyl-L-cysteine (methyl-14C) ester (AFCME)], was then analyzed either directly on HPLC or by converting the AFC[methyl-14C]ME to [methyl-14C] alcohol by basehydrolysis. Employing these two analytical methods, it was established that a peptide purified from rat liver cytosol fraction [Int. J. Biochem., 25, 1157 (1993)] strongly inhibited the above enzyme activity with IC50 of 7.1X10−8 M. Also, the S-famesylcysteine O-methyltransferase from several human colon cancer cells was also equally inhibited by the peptide.