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Biomedical subjects

H S Kwak

Publications and source records attributed to H S Kwak.

18 recordsLinked to original sources
PubMed2006

In vitro study of microencapsulated isoflavone and beta-galactosidase.

This study was designed to find the optimum conditions for isoflavone or beta-galactosidase microencapsulation and to examine the release efficiency of microcapsules in simulated gastrointestinal conditions. Coating materials were either medium-chain triacylglycerol (MCT) or polyglycerol monostearate (PGMS). The highest rate of microencapsulation was found at 15:1 (w/w) ratio of MCT to isoflavone or beta-galactosidase as 70.2 or 75.4%, respectively. When PGMS was used as the coating material, 91.5% beta-galactosidase was microencapsulated with 15:1 mixture (w/w). In vitro study, less than 6.3-9.3% of isoflavone was released in simulated gastric fluid (pH 2-5) during 1 h incubation. Comparatively, isoflavone release increased dramatically to 87.8% at pH 8 for 1 h incubation in simulated intestinal fluid and was maintained thereafter. The release of beta-galactosidase showed a similar trend to that of isoflavone. It appeared in the range of 12.3-15.2% at pH 2-5; however, it increased significantly to 80.6% as the highest value at pH 8. Among the released isoflavones, 53.5% was converted into the aglycone form of isoflavone at pH 8 for 3 h incubation. The present study indicated that isoflavone or beta-galactosidase could be microencapsulated with fatty acid esters and released effectively in simulated intestinal condition.

Body Fluids↗
PubMed2006

Properties of cholesterol-reduced butter made with beta-cyclodextrin and added evening primrose oil and phytosterols.

The present study was carried out to examine changes in the chemical and sensory properties of butter in which the cholesterol was reduced and to which evening primrose oil (EPO) and phytosterols were added. Crosslinked beta-cyclodextrin (beta-CD) made from adipic acid was used, and approximately 90% of the cholesterol was removed. The color measurement values "L" and "a" were significantly different between the control (butter with no beta-CD treatment and no added EPO and phytosterols) and treatment A (butter treated with 10% crosslinked beta-CD); however, the color values for "L" and "a" were similar. The color value "b" in treatment B (butter treated with 10% crosslinked beta-CD and 5% phytosterols and 3% EPO added) was significantly higher than in the other treatments. The thiobarbituric acid value of treatment B was significantly higher than that of the control and treatment A. Scores for hardness, elasticity, and cohesiveness were significantly lower in the control than in treatment A. Differences in sensory characteristics did not result from the beta-CD treatment but from the addition of EPO and phytosterols. In microscopic examinations, no noticeable differences were found among the treatments, and a smooth texture and a fine, uniform crystalline structure were observed. Results indicated that about 90% of the cholesterol was reduced by crosslinked beta-CD and that the beta-CD treatment itself did not adversely influence the chemical and sensory properties of the butter. However, the addition of EPO and phytosterols to the butter appeared to impair its sensory properties, especially in terms of rancidity and overall acceptability.

Butter↗
PubMed2004

Crosslinking of beta-cyclodextrin on cholesterol removal from milk.

This study was designed to develop crosslinking of beta-cyclodextrin (beta-CD), and determine the optimum conditions of different factors (mixing time, mixing temperature, and mixing speed) on cholesterol reduction from milk. Crosslinked beta-CD was prepared with epichlorohydrin. When milk was treated with different conditions, the cholesterol removal rate was in the range of 79.4 to 83.3% with 1% crosslinked beta-CD addition, which were not significantly different among treatments. After cholesterol removal from milk, the used crosslinked beta-CD was washed for cholesterol dissociation and reused. For recycling study, the cholesterol removal rate in first trial was 81.8%, which was mostly same as that using new crosslinked beta-CD. With five trials repeatedly using the same sample, the mean cholesterol removal rate was 81.2%. The present study indicated that the optimum conditions on cholesterol removal using crosslinked beta-CD were 10 min mixing with 400 rpm speed at 5 degrees C with about 80% cholesterol removal. In addition, crosslinked beta-CD resulted in the effective recycling efficiency almost 100%.

Animals↗
PubMed2004

Immobilized beta-cyclodextrin as a simple and recyclable method for cholesterol removal in milk.

This study was designed to determine the optimum conditions of three different factors (mixing time, mixing temperature, and tube size) in reduction of cholesterol in milk using immobilized beta-CD beads. Immobilized beta-CD glass beads were prepared at different conditions of silanization and beta-CD immobilization reactions. In result, the glass beads (diameter 1 mm) at 20 mM 3-isocyanatopropyltriethoxysilane and 30 mM beta-CD without base showed the highest cholesterol removal rate as 41%. Using above immobilized beta-CD glass beads, the cholesterol removal rate was 40.2% with 6 h of mixing time in 7 mm diameter tube at 10 degrees C. After cholesterol removal from milk, the glass beads were washed for cholesterol dissociation and reused. In recycling study, the cholesterol removal rate was 41%, which was mostly same as that using new glass beads. These results indicated that cholesterol removal rate was about 40% with beta-CD immobilized glass beads, however, the recycling efficiency was almost 100%.

Animals↗
PubMed2003

Microencapsulated iron for milk fortification.

This study was designed to develop a microencapsulated iron that could be used to fortify milk and to determine the sensory properties of milk fortified with microencapsulated iron. Coating material was polyglycerol monostearate (PGMS), and selected core material was ferric ammonium sulfate. The highest efficiency of microencapsulation was 75% with 5:1:30 ratio (w/w/v) as coating to core materials to distilled water. Iron release was 12% when stored at 4 degrees C for 3 days. The TBA value was the lowest when 100 ppm of capsulated iron was added into milk and was significantly lower in capsulated groups compared with that in uncapsulated groups. In an in vitro study, only 3-5% of iron was released in simulated gastric fluid (pH 3, 4, 5, and 6). Comparatively, iron release increased dramatically from 12.3% (pH 5) to 95.7% (pH 8) for 60 min of incubation in simulated intestinal fluid. In a sensory analysis, most aspects except for metallic taste and color were not significantly different between control and capsulated iron fortified milk at 3 days of storage. However, between capsulated and uncapsulated groups, astringency, metallic, color, and overall scores were significantly different. The present study indicated that the use of microencapsulated iron with PGMS is effective for fortifying milk.

Animals↗
PubMed2003

Microencapsulated ascorbic acid for milk fortification.

The present study was designed to develop a microencapsulated L-ascorbic acid and iron that could be used to fortify milk and to determine the sensory properties of milk fortified with microencapuslation. Coating material was medium-chain triacylglycerol (MCT), and selected core material was ferric ammonium sulfate and L-ascorbic acid. The highest efficiency of microencapsulation was 95.0% in the ratio of 15:1 as coating to core material. Ascorbic acid release was increased sharply up to 5 d storage as 6.5%. TBA value was the lowest when both capsulated iron and ascorbic acid were added during 12 d storage, compared with other treatments. In sensory analysis, most aspects were not significantly different between control and capsulated ascorbic acid fortified milk at 5 d storage. The present study indicated that the use of microencapsulated ascorbic acid with MCT is effective for fortifying milk. In addition, these results suggest that acceptable milk products can be prepared with microencapsulated ascorbic acid and iron.

Animals↗
PubMed2003

Functional properties of cholesterol-removed whipping cream treated by beta-cyclodextrin.

The present study was carried out to examine the changes in functional properties of cholesterol-removed whipping cream by beta-cyclodextrin (beta-CD) treatment. The cholesterol removal rate reached over 90% in cream before whipping in all conditions (different stirring time and speed) applied. The apparent viscosity of beta-CD treated cream after whipping increased with increased stirring time and speed. Comparatively, the overrun percentage reached to 150%, and foam instability was measured as 2.5 ml deformed cream with lower stirring time (10 min) and speed (400 rpm). The thiobarbituric acid value of cholesterol-removed whipping cream increased from 0.08 to 0.14 stored at 4 degrees C during 4 wk; however, no difference was found compared with that of control. Above results indicated that beta-CD treatment process for cholesterol removal did not show a profound adverse effect on functional properties of cream after whipping.

Animals↗
PubMed2002

Removal of cholesterol from Cheddar cheese by beta-cyclodextrin.

This study was carried out to determine the cholesterol removal rate and resulting changes in flavor, fatty acid and bitter amino acid production in reduced-cholesterol Cheddar cheese, made by cream separation followed by 10% beta-cyclodextrin (beta-CD) treatment. The cholesterol removal from the cheese was 92.1%. The production of short-chain free fatty acids (FFAs) increased the ripening time in control and cream-treated cheeses. The quantity of short-chain FFAs released between treatments during ripening was different, while not much difference was found in the production of neutral volatile compounds in the samples. Reduced-cholesterol cheese produced much higher levels of bitter amino acids than the control. In sensory analysis, the texture score of control Cheddar cheese increased significantly with ripening time; however, that of the cream treatment group decreased dramatically with ripening time. On the basis of our results, we conclude that the cheese made from beta-CD-treated cream had a higher rate of cholesterol removal and ripened rapidly.

Amino Acids↗
PubMed2001

Microencapsulation of beta-galactosidase with fatty acid esters.

The present study was carried out to find an appropriate coating material to microencapsulate lactase and the conditions under which it could be used. As a coating material, medium-chain triacylglycerol (MCT) and polyglycerol monostearate (PGMS) were superior. Three different percentages of microcapsules (2, 4, and 6%) were added and subdivided into three groups by washing time (0, 1, and 2). The highest efficiency of microencapsulation was found in the ratio of 15:1 as coating to core material with both MCT (94.9%) and PGMS (72.8%). Lactose content was not significantly changed up to 12 d with MCT and up to 8 d with PGMS with 2% of twice washed microcapsule addition. Also, sweetness was not significantly increased in storage compared with that of market milk. The present study provides evidence that emulsifiers can be used as an effective coating material to microencapsulate lactase. In addition, these results suggest that acceptable milk products can be prepared with microencapsulated lactase.

Animals↗
PubMed2000

Cloning and expression of the ccpA gene encoding catabolite control protein from Thermoactinomyces sp. E79.

The gene ccpA encoding the catabolite control protein A (CcpA) of Thermoactinomyces sp. E79 has been cloned and characterized. Nucleotide sequence analysis of the CcpA clone showed that the cloned fragment contained the full structural gene for a protein of 346 amino acids. The predicted amino acid sequence shows similarity to the transcriptional regulators of the Lacl-GalR family; a highly conserved helix-turn-helix motif, which might bind to DNA, was identified through comparison with regulator proteins in this family. The highest sequence identity was obtained when it was compared with the CcpA of Bacillus subtilis (60%) or Bacillus megaterium (60%). The expression of ccpA in Thermoactinomyces sp. E79 was dependent on glucose, which is contrast to the cases of B. subtilis, B. megaterium and S. xylosus. The complementation experiment with the B. megaterium ccpA mutant indicated that the cloned gene was a ccpA.

Amino Acid Sequence↗
PubMed2000

Technetium-99m MDP bone scintigraphic findings of hypercalcemia in accelerated phase of chronic myelogenous leukemia.

Hypercalcemia in accelerated phase of chronic myelogenous leukemia (CML) is very rare. Its pathogenesis is considered humoral hypercalcemia of malignancies mediated by parathyroid hormone-related protein (PTHrP). In severe hypercalcemia, calcifications in kidneys, skin, vessels, heart, and stomach may occur. Our two cases were admitted because of severe hypercalcemia in accelerated phase of CML. On Tc-99m methylene diphosphonate (MDP) bone scintigraphies, a marked tracer accumulation was seen in the lung, heart, stomach and kidney. We report increased tracer accumulation of multiple organs on Tc-99m MDP bone scintigraphy in two rare hypercalcemic patients with CML.

Adult↗
PubMed1999

Cholesterol removal from homogenized milk with beta-cyclodextrin.

This study was carried out to determine optimum conditions of five different factors (beta-cyclodextrin concentration, mixing temperature, mixing time, centrifugal force, and centrifugation time) in reduction of cholesterol in 3.6% fat, homogenized milk by application of beta-cyclodextrin. beta-Cyclodextrin at 0.5 to 1.5% provided 92.2 to 95.3% removal of cholesterol when mixed at 10 degrees C for 10 min. Among other factors, mixing time (5 to 20 min) did not significantly affect cholesterol removal. Removal was enhanced with increasing centrifugal forces up to 166x g (95.9%) but decreased thereafter. Various centrifugation times (5 to 20 min) did not have significant effects. Based on these results, we suggest that the optimum conditions for the process are addition of 1.5% beta-cyclodextrin, mixing temperature of 10 degrees C, 10-min mixing time, and centrifugation at 166x g for 10 min.

Animals↗
PubMed1996

A gain-of-function of an amyotrophic lateral sclerosis-associated Cu,Zn-superoxide dismutase mutant: An enhancement of free radical formation due to a decrease in Km for hydrogen peroxide.

Cu,Zn-superoxide dismutase (SOD) is known to be a locus of mutation in familial amyotrophic lateral sclerosis (FALS). Transgenic mice that express a mutant Cu,Zn-SOD, Gly-93--> Ala (G93A), have been shown to develop amyotrophic lateral sclerosis (ALS) symptoms. We cloned the FALS mutant, G93A, and wild-type cDNA of human Cu,Zn-SOD, overexpressed them in Sf9 insect cells, purified the proteins, and studied their enzymic activities for catalyzing the dismutation of superoxide anions and the generation of free radicals with H2O2 as substrate. Our results showed that both enzymes contain one copper ion per subunit and have identical dismutation activity. However, the free radical-generating function of the G93A mutant, as measured by the spin trapping method, is enhanced relative to that of the wild-type enzyme, particularly at lower H2O2 concentrations. This is due to a small, but reproducible, decrease in the value of Km for H2O2 for the G93A mutant, while the kcat is identical for both enzymes. Thus, the ALS symptoms observed in G93A transgenic mice are not caused by the reduction of Cu,Zn-SOD activity with the mutant enzyme; rather, it is induced by a gain-of-function, an enhancement of the free radical-generating function. This is consistent with the x-ray crystallographic studies showing the active channel of the FALS mutant is slightly larger than that of the wild-type enzyme; thus, it is more accessible to H2O2. This gain-of-function, in part, may provide an explanation for the association between ALS and Cu,Zn-SOD mutants.

Amyotrophic Lateral Sclerosis↗
PubMed1995

Endogenous intracellular glutathionyl radicals are generated in neuroblastoma cells under hydrogen peroxide oxidative stress.

We report the detection of endogenous intracellular glutathionyl (GS.) radicals in the intact neuroblastoma cell line NCB-20 under oxidative stress. Spin-trapping and electron paramagnetic resonance (EPR) spectroscopic methods were used for monitoring the radicals. The cells incubated with the spin trap 5,5-dimethyl-1-pyrroline 1-oxide (DMPO) were challenged with H2O2 generated by the enzymic reaction of glucose/glucose oxidase. These cells exhibit the EPR spectrum of the GS. radical adduct of DMPO (DMPO-.SG) without exogenous reduced glutathione (GSH). The identity of this radical adduct was confirmed by observing hyperfine coupling constants identical to previously reported values in in vitro studies, which utilized known enzymic reactions, such as horseradish peroxidase and Cu/Zn superoxide dismutase, with GSH and H2O2 as substrates. The formation of the GS. radicals required viable cells and continuous biosynthesis of GSH. No significant effect on the resonance amplitude by the addition of a membrane-impermeable paramagnetic broadening agent indicated that these radicals were located inside the intact cell. N-Acetyl-L-cysteine (NAC)-treated cells produced NAC-derived free radicals (NAC.) in place of GS. radicals. The time course studies showed that DMPO-.SG formation exhibited a large increase in its concentration after a lag period, whereas DMPO-NAC. formation from NAC-treated cells did not show this sudden increase. These results were discussed in terms of the limit of antioxidant enzyme defenses in cells and the potential role of the GS. radical burst in activation of the transcription nuclear factor NF-kappa B in response to oxidative stress.

Acetylcysteine↗
PubMed1986

Effect of various conditions on the formation of oligosaccharides in milk treated with beta-galactosidase.

Fresh pasteurized milk was inoculated with beta-galactosidase from two different microbial sources at three levels and analyzed for oligosaccharides by high performance liquid chromatography. Five oligosaccharides were observed in the course of hydrolysis. However, only two of these showed measurable increases in concentration. Rate of oligosaccharide formation during hydrolysis was influenced by source and amount of enzymes, reaction time, and temperature. Maximum concentrations of the two oligosaccharides occurred between .5 and 3 d at 7 degrees C and between 1 and 3 d at 1 degrees C, depending on the level of the enzyme used. The higher level of enzyme formed a higher concentration of oligosaccharides than the low level, except at 37 degrees C. After maximum concentration was reached, the two oligosaccharides decreased following hydrolysis, but rate of decrease was dependent upon time, temperature, and enzyme concentration. Hydrolysis of the oligosaccharide was faster at 7 degrees C and at the higher enzyme concentration. Maximum concentration of oligosaccharides was .374 g/100 g milk but was negligible after 7 d, except when the low level of enzyme was used. The total concentration of the oligosaccharides formed in enzyme-treated milk was insignificant.

Animals↗
PubMedDate not supplied

Small intestinal angiolipoma: MR imaging appearance.

We report the magnetic resonance imaging finding in a case of small intestinal angiolipoma. Small bowel enteroclysis showed a well-defined, lobulated polypoid lesion in the proximal ileum. The mass showed central high signal intensity with peripheral iso-signal intensity on T1-weighted in-phase images. The central high signal intensity changed to low signal intensity on T1-weighted out-of-phase images. After contrast injection, the mass had a strong enhancement along the periphery of the lesion on fat-saturated T1-weighted images. Characteristic decreased signal intensity on out-of-phase T1-weighted images and strong enhancement on postcontrast images of the small bowel mass suggest the diagnosis of angiolipoma.

Aged↗
PubMedDate not supplied

Pseudotumorous hyperplasia of the caudate lobe in the non-cirrhotic liver: MR and CT arterial portography appearance.

We describe the magnetic resonance image and computed tomographic arterial portography appearance of pseudotumorous hyperplasia in the caudate process of the caudate lobe in a non-cirrhotic patient. A prominent portal vein branch directly arising from the right main portal branch was seen in the center of the lesion on magnetic resonance imaging and computed tomographic arterial portography. We think that portal flow change of the caudate lobe by an anomalous portal branch may be correlated to pseudotumorous hyperplasia.

Diagnosis, Differential↗