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S Y Hong

Publications and source records attributed to S Y Hong.

At least 55 records · Page 3Linked to original sources
PubMed1998

Structure-activity analysis of brevinin 1E amide, an antimicrobial peptide from Rana esculenta.

Brevinin 1E, consisting of 24 amino acid residues, from Rana esculenta has potent antimicrobial and hemolytic activity. From a structural point of view, this peptide has a N-terminal hydrophobic region, a proline hinge region in the middle and a C-terminal loop region delineated by an intra-disulfide bridge, which is a common structural feature of antimicrobial peptides from Rana species. To investigate the structural features for antimicrobial and hemolytic activity, truncated and linearized brevinin 1E amides were synthesized and characterized. A deletion of three amino acids from the N-terminal region did not greatly affect antimicrobial activity but dramatically reduced hemolytic activity. The contribution of the intra-disulfide bridge to antimicrobial and hemolytic activity was somewhat different between brevinin 1E amide and truncated fragments. In brevinin 1E amide, the elimination of the intra-disulfide bridge did not greatly affect antimicrobial and hemolytic activity whereas the elimination of the intra-disulfide bridge in the truncated fragments did not decrease antimicrobial activity but did decrease hemolytic activity. Circular dichroism spectra and the retention time on the C18 reverse phase column revealed that the intra-disulfide bridge (i, i+6) formed an amphipathic loop which increased hydrophobicity and helped to induce the alpha-helical structure in the membrane-mimetic environment. Even though the intra-disulfide bridge and the N-terminal region were responsible for the alpha-helical structure and hydrophobicity, these two structural features were not essential for antimicrobial activity. The hemolytic activity of brevinin 1E amide and its analogs also correlated well with the retention time rather than the alpha-helicity.

Amides↗
PubMed1998

Identification and characterization of the antimicrobial peptide corresponding to C-terminal beta-sheet domain of tenecin 1, an antibacterial protein of larvae of Tenebrio molitor.

An active fragment was identified from tenecin 1, an antibacterial protein belonging to the insect defensin family, by synthesizing the peptides corresponding to the three regions of tenecin 1. Only the fragment corresponding to the C-terminal beta-sheet domain showed activity against fungi as well as Gram-positive and Gram-negative bacteria, whereas tenecin 1, the native protein, showed activity only against Gram-positive bacteria. CD spectra indicated that each fragment in a membrane-mimetic environment might adopt a secondary structure corresponding to its region in the protein. The leakage of dye from liposomes induced by this fragment suggested that this fragment acts on the membrane of pathogens as a primary mode of action. A comparison between the structure and the activity of each fragment indicated that a net positive charge was a prerequisite factor for activity. To the best of our knowledge this is the first report in which the fragment corresponding to the beta-sheet region in antibacterial proteins, which consists of alpha-helical and beta-sheet regions, has been identified as a primary active fragment.

Amino Acid Sequence↗
PubMed1998

Methylesters of L-arginine and N-nitro-L-arginine induce nitric oxide synthase in Staphylococcus aureus.

The presence of L-arginine methylester (AME), L-arginine ethylester (AEE), or N-nitro-L-arginine methylester (NAME) in the growth media of Staphylococcus aureus increased the nitric oxide synthase (NOS) activity approximately 5- to 14-fold. The increase of NOS activity was confirmed by two assay methods, namely assaying the formation of L-[3H] citrulline from L-[3H] arginine and NO formation. The increase of NOS activity was most likely due to increased de novo synthesis, demonstrated by Western immunoblot analysis. The addition of methanol to the culture medium also increased the NOS activity as much as that found with the above three compounds. Evidence is presented to show that AME, AEE, or NAME gave rise to the formation of methanol in vivo by the action of intracellular esterase(s) and that methanol is subsequently involved in the induction of NOS in this bacterial system.

Alcohols↗
PubMed1998

Nitric oxide synthase from bovine pancreas: purification and characterization.

Nitric oxide synthase, NOS (EC.1.14.13.39), was purified from bovine pancreas over 5,500-fold with a 7.6% yield using 30% ammonium sulfate precipitation, and 2',5'-ADP-agarose and calmodulin-agarose affinity chromatography. The purified bovine pancreatic NOS (bpNOS) showed a single band on SDS-PAGE corresponding to an apparent molecular mass of 160 kDa, whereas it was 320 kDa on non-denaturating gel-filtration. This indicated a homodimeric nature of the enzyme. The specific activity of the purified bpNOS was 31.67 nmol L-citrulline fored/mtn/mg protein and apparent K(m) for L-arginine was 15.72 microM. The enzyme activity was dependent on Ca2+ and calmodulin, and to a lesser extent on NADPH, FAD and FMN. H4B was not required as a cofactor for the activity. In an inhibition experiment with L-arginine analogues, NG-nitro-L-arginine (NNA) had the most potent inhibitory effect on bpNOS, and NG, NG'-dimethyl-L-arginine (symmetric; sDMA) did not have any inhibitory effect. Immunohistochemical analysis of the bovine pancreas using brain type NOS antibody (anti-bNOS antibody) revealed that acinar cells showed strong immunoreactivity against the antibody.

Animals↗
PubMed1998

NO/cGMP pathway is involved in exocrine secretion from rat pancreatic acinar cells.

The enzyme responsible for the synthesis of nitric oxide (NO) from L-arginine in mammalian tissues is known as nitric oxide synthase (NOS) (EC.1.14.13.39). In the present study, the role of NO in the regulation of exocrine secretion was investigated in rat pancreatic acinar cells. Treatment of rat pancreatic acinar cells with cholecystokinin-octapeptide (CCK-OP) resulted in an increase in the arginine conversion to citrulline, the amount of NOx, the release of amylase, and the level of cGMP. Especially, CCK-OP-stimulated increase of arginine to citrulline transformation, the amount of NOx and cGMP level were completely counteracted by the inhibitor of NOS, NG-monomethyl-L-arginine (MMA), by contrast, that of amylase release was partially reduced. Furthermore, MMA-induced decrease of NOS activity and amylase release showed dose-dependent pattern. The data on the time course of CCK-OP-induced citrulline formation and cGMP rise indicate that NOS and guanylate cyclase were activated by treatment of CCK-OP. However, the mechanism of agonist-stimulated guanylate cyclase activation in acinar cells remains unknown. Therefore, activation of NOS is one of the early events in receptor-mediated cascade of reactions in pancreatic acinar cells and NO, not completely, but partially mediate pancreatic enzyme exocrine secretion.

Amylases↗
PubMed1998

Antimicrobial activity and conformation of gaegurin-6 amide and its analogs.

A function of the intra-disulfide bridge located at the C-terminal of Rana peptides has not been extensively studied. To investigate the function of the disulfide bridge related to the activity and the structure, we chose Gaegurin-6, isolated from Rana rugosa as a model peptide and synthesized linear analogs. The reduction of the disulfide bridge resulted in the complete loss of antimicrobial activity while replacements of cysteines by serines retained antimicrobial activity. Circular dichroism spectra from a titration of the peptides in sodium dodecyl sulfate indicated that the disulfide bridge of Gaegurin-6 might stabilize the induction of an alpha helical structure in lipid membranes and the alpha helical forming propensity of the peptides correlated with antimicrobial activity.

Amino Acid Sequence↗
PubMed1998

The relationship between plasma homocysteine and amino acid concentrations in patients with end-stage renal disease.

OBJECTIVE: Observe the relationship between homocysteine and other amino acids in patients with end-stage renal disease (ESRD). DESIGN: A cross-sectional study of amino acids and homocysteine and comparison of the correlations between ESRD and control group. SETTING: Nephrology unit of Soonchunhyang University hospital in Chunan, Korea. PARTICIPANTS: Forty-five ESRD patients and 30 control volunteers. MAIN OUTCOME MEASURES: Plasma amino acids and homocysteine. RESULTS: Concentrations of asparate, proline and cysteine were higher and serine, tyrosine, valine, isoleuline, leucine, and lysine levels were lower in the ESRD group than in control group. The branched chain amino acids (BCAAs) and essential amino acid were lower in the ESRD group than in the control group, but there was no difference in non-essential amino acid and total amino acid between the two groups. The mean plasma total homocysteine concentrations were 6 +/- 1 mmol/L in the control group and 14 +/- 4 mmol/L in the ESRD group (P < .001). In the ESRD group, homocysteine concentrations showed a direct correlation with the concentration of histidine (R2: .403, P < .001), valine (R2: .324, P < .01), leucine (R2: .400, P < .01), isoleucine (R2: .351, P < .005), cysteine (R2: .287, P < .001), methionine (R2: .256, P < .01), BCAA (R2: .50, P < .01), and essential amino acid (R2: .416, P < .01). In the control group, no correlation between the homocysteine and amino acid concentrations was found. CONCLUSIONS: Contrary to the control group, the homocysteine concentrations showed a direct correlation with the concentration of valine, leucine, isoleucine, methionine, and histidine levels in the ESRD group. Altered essential amino acid metabolism, specifically BCAAs and histidine, influence hyperhomocysteinemia in ESRD. Further study is needed to confirm this theory.

Adult↗
PubMed1998

Identification and characterization of novel antimicrobial decapeptides generated by combinatorial chemistry.

Novel combinatorial libraries consisting of simplified amino acid sequences were designed to screen for peptides active against the Candida albicans membrane. A novel decapeptide, KKVVFKVKFK, that had a unique primary amino acid sequence was identified in this work. This peptide irreversibly inhibited the growth of C. albicans and showed a broad range of antibacterial activity but no hemolytic activity. Circular dichroism spectra revealed that the predominant secondary structure of this peptide strongly depended on the membrane-mimetic environments; the peptide preferred to form an amphipathic alpha-helical structure in the presence of 50% trifluoroethanol, while it preferred to adopt a distorted alpha-helical structure in the presence of sodium dodecyl sulfate micelles. Experiments in which dye was released from vesicles indicated that this novel antimicrobial peptide killed microorganisms through the action on the membrane as its primary target. Replacement of amino acids in this active decapeptide on the basis of information from the libraries could provide unique information about factors affecting its antimicrobial activity such as its secondary structure, net positive charge, and hydrophobicity.

Anti-Bacterial Agents↗
PubMed1998

Plasma homocysteine, vitamin B6, vitamin B12 and folic acid in end-stage renal disease during low-dose supplementation with folic acid.

In order to see whether conventional low-dose folic acid supplement along with vitamin B6 and B12 reduces hyperhomocysteinemia in patients with ESRD, we compared the levels of homocysteine, vitamin B6, B12 and folic acid among 3 groups of patients: 44 ESRD patients on hemodialysis with replacement of folic acid, vitamin B6, and B12 (dialysis group); 27 chronic renal failure patients without vitamin replacement (predialysis group); and 17 hypertensive patients without vitamin replacement (control group). Mean plasma total homocysteine concentration was higher in the dialysis (15.5 +/- 6.6 micromol/l) and the predialysis groups (15.7 +/- 4.2 micromol/l) than in the control group (6.2 +/- 1.5 micromol/l) (p < 0.001). However, there was no difference in homocysteine concentrations between the dialysis and predialysis groups. In the control and predialysis groups, the homocysteine concentration showed a reverse correlation with the concentrations of folic acid (r = 0.584, p = 0. 014 for the control group; r = 0.431, p = 0.247 for the predialysis group) and vitamin B12 (r = 0.485, p = 0.049 for the control group; r = -0.562, p = 0.023 for the predialysis group) but not with vitamin B6. In conclusion, plasma folic acid concentrations were 3-4 times higher in the dialysis than in the predialysis group. But these levels of folic acid are not enough to reduce hyperhomocysteinemia in ESRD.

Adult↗
PubMed1998

Comparison of plasma amino acid concentrations in end-stage renal disease patients on hemodialysis and peritoneal dialysis.

OBJECTIVES: Recent reports have suggested that patients treated by CAPD have a relatively increased risk of death compared to patients undergoing HD, although the cause of this discrepancy is poorly understood. Protein malnutrition is an important risk factor in ESRD. Also, amino acid concentrations, for which the physiological function differs from that of protein, may be an independent risk factor in ESRD. There is no doubt concerning the prevalence of low amino acid levels in both HD and CAPD patients. But the difference in plasma amino acid levels between these two groups has not been well defined. The purpose of this study is to compare plasma amino acid levels between patients with ESRD on HD and CAPD. METHODS: A cross sectional study of overnight fasting plasma amino acid concentrations was performed on 12 CAPD and 45 HD patients with ESRD, matched by age, sex and body mass index. The levels of individual plasma amino acid and TAA, EAA, NEAA and BCAA were compared for the HD and CAPD groups. In order to measure losses during HD and CAPD, amino acid and protein concentrations were measured from 10 dialysates obtained from 10 HD patients and 12 peritoneal dialysis solutions from 12 CAPD patients. RESULTS: All of the measured amino acid concentrations were found to be lower in the CAPD group compared to the HD group. Furthermore, the levels of TAA (2017.3 +/- 781.1 vs. 903.3 +/- 316.1 mumole/L), EAA(1201.8 +/- 492.6 vs. 567.6 +/- 223.2 mumole/L), NEAA(815.5 +/- 308.6 vs. 335.7 +/- 100.2 mumole/L); and BCAA (315.0 +/- 146.0 vs. 145.2 +/- 65.0 mumole/L), were all lower in the CAPD group than in the HD group. The protein loss was 2.0 +/- 0.2 g/L in the peritoneal dialysate but was not detectable in the hemodialysates. TAA loss over a one week period was about 61.8 +/- 13.0mmole for the HD group and 38.0 +/- 13.0 mmole for the CAPD group. CONCLUSIONS: Our results show that amino acid concentrations are lower in ESRD patients on CAPD than on HD. It seems likely that protein loss in the peritoneal dialysate is a contributing factor to lowered plasma amino acid concentrations in ESRD patients on CAPD than on HD. We believe that the lowered amino acid concentrations observed in CAPD patients may worsen the clinical outcome compared to HD patients.

Adult↗
PubMed1997

Identification of nitric oxide synthase in Staphylococcus aureus.

The presence of nitric oxide synthase (NOS) in Staphylococcus aureus ATCC6538P was established by western blot analysis. The identity of citrulline formed from L-arginine by the NOS was confirmed by both TLC and HPLC and the other product, NO, by directly measuring the production of nitrogen oxides (NOx) in the reaction mixture. The activity was inhibited by typical NOS inhibitors such as N-nitro-L-arginine methylester and NG,NG-dimethyl-L-arginine with the IC50 of 4.9 x 10(-4) and 2.5 x 10(-4) M, respectively. The NOS activity was maximum at pH 6.5 and at 47.5 degrees C. These results indicate that the NOS of S. aureus ATCC6538P is an isoform distinct from mammalian NOS.

Blotting, Western↗
PubMed1997

Tactile-spatial and cross-modal attention effects in the second somatosensory and 7b cortical areas of rhesus monkeys.

This study analyzed neuronal responses in the second somatosensory (SII) and 7b cortical areas during a selective attention task. Cues directed attention to one of three simultaneous stimuli: vibrotactile stimuli applied to mirror sites on both hands or to a similarly timed auditory tone. Two stimulus patterns appeared with equal probability for the cued stimulus: a constant amplitude sinewave or the latter with a superimposed brief amplitude pulse midway in the trial. Uncued stimuli always contained amplitude pulses. Monkeys demonstrated whether an amplitude pulse at the cued location was present or absent by making appropriately rewarded up and down foot pedal movements. Cue location and stimulus pattern varied trial-wise and pseudo-randomly. Average firing rates to vibrotactile stimuli in 82 of 181 SII cells and 13 of 22 area 7b cells differed significantly during at least one epoch for trials cued to the contralateral hand when compared to trials cued to the ipsilateral hand or auditory stimulus. Predominant were relatively suppressed firing rates during times prior to the epoch containing the amplitude pulses or enhanced activity during and after these pulses. Generally, different cells showed suppression early vs enhancement later in a trial. Analyses of the ratio between firing rates before and during the amplitude pulses suggested improved evoked signals to the amplitude pulses. The discussion considers attention as a mechanism for reducing distractions, early in the trial through suppressing these signals, or for selectively increasing response magnitudes in the cued channel, especially around times when amplitude pulses were present or absent.

Acoustic Stimulation↗
PubMed1997

Dextromethorphan alters the reinforcing effect of cocaine in the rat.

Dextromethorphan (DM) at supra-antitussive doses produces psychotomimetic effects in humans. In order to achieve a better understanding of the pharmacological mechanisms responsible for the behaviors induced by DM, we examined the effects of DM on the intravenous self-administration of cocaine in the rat. The effects of DM (40 mg/kg, p.o.) on responding for 0.5, 0.25, 0.125, 0.06 and 0.03 mg/kg/infusion of cocaine was assessed. DM decreased the rate of responding for higher doses of cocaine (0.5, 0.25 and 0.125 mg/kg/infusion), and increased the rate of responding for lower doses of cocaine (0.06 and 0.03 mg/kg/infusion), suggesting that DM shifted the dose-response curve for cocaine self-administration to the left. Therefore, our results indicate that the sensitivity to cocaine's behavioral effects appears to be enhanced by DM.

Animals↗
PubMed1996

Unusually stable helical kink in the antimicrobial peptide--a derivative of gaegurin.

The structure of an active analog of the antibacterial peptide gaegurin was investigated by CD and NMR spectroscopy. The NOE connectivities showed that 21 out of 24 residues formed an a-helix despite the presence of a central proline. CD and NMR analysis indicates that the helix is in fast equilibrium with random coil. From chemical shift analysis of the amide protons, the distances of hydrogen bonding in the helix were calculated, and manifested obvious periodicity which implied a kink in the middle of the helix. 1D amide proton exchange experiments provided further evidence of an exceptionally stable kink. It is inferred that this kink is important not only to the function of the peptide but also to the early stage of the folding as a nucleation site.

Anti-Infective Agents↗
PubMed1996

Effect of deamino-8-D-arginine desmopressin in uremic bleeding.

OBJECTIVES: This study is designed to evaluate the clinical outcome of uremic bleeding treated with DDAVP. DDAVP was given intravenously in nine ESRD patients who had undergone A/V fistula surgery and showed oozing of the operation site for more than one hour. METHODS: Hemostasis was observed by removing the blood from the wound site with a piece of filter paper for 3 hours after DDAVP administration. vWF, t-PA antigen, t-PA activity, total fibrinolytic activity in euglobulin fraction, fibrinopeptide A and FDP were measured before and after DDAVP administration. RESULTS: Cessation of the oozing did not occur within 3 hours after DDAVP administration in all of the cases. vWF levels and t-PA antigen were significantly increased after DDAVP administration peaked at 30 min for vWF and 60 min for t-PA antigen. t-PA activity increased in 6 cases and euglobulin fibrinolytic activity increased in 7 cases, respectively. These values fell towards pre-administration levels 120 min after the administration. There was no difference in fibrinopeptide A levels before and after DDAVP administration. FDP became positive in 4 cases after DDAVP administration. CONCLUSION: DDAVP increased both vWF and t-PA levels and cessation of the oozing from post-operative AV-fistula wounds did not occur within 3 hours after DDAVP administration in all of the cases. These results suggest that the effect of DDAVP should be reassessed in the treatment of uremic bleeding.

Adult↗
PubMed1995

Enhanced effectiveness of dimethyl-4,4'-dimethoxy-5,6,5',6'-dimethylene dioxybiphenyl-2,2'-dicarboxylate in combination with garlic oil against experimental hepatic injury in rats and mice.

The present study was designed to evaluate the effects of dimethyl-4,4'-dimethoxy-5,6,5',6'-dimethylene dioxybiphenyl-2,2'-dicarboxylate (PMC) in combination with garlic oil against chemical-induced hepatic injury in rats and mice. Rats insulted with carbon tetrachloride were concomitantly treated with PMC and/or garlic oil (50 and 100 mg kg-1, respectively) for four weeks. Whereas treatment of animals with garlic oil alone was ineffective in suppressing carbon tetrachloride-induced hepatotoxicity, administration of PMC in combination with garlic oil more effectively protected the liver against the carbon tetrachloride-induced insult than PMC alone, as monitored by serum aminotransferase activity. Hepatoprotective effects of the formulation were further supported by the changes in the numbers of Kupffer cells and dead hepatocytes. Although prior treatment of rats with PMC for three days failed to protect hepatotoxicity elicited by allyl alcohol, the formulation of PMC and garlic oil was capable of blocking allyl alcohol-induced hepatotoxicity by approximately 40%. To further examine the effect of the agents on lipid metabolism in the liver, hepatic triglycerides and cholesterol contents were assessed in mice after a diet containing PMC and/or garlic oil for one week followed by a single dose of carbon tetrachloride. Garlic oil appeared to be more effective in bringing hepatic lipid levels to those of control than PMC alone. Treatment of animals with PMC in combination with garlic oil synergistically improved chemical-induced impairment of hepatic triglycerides and cholesterol.(ABSTRACT TRUNCATED AT 250 WORDS)

1-Propanol↗