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Biomedical subjects

H S Kwak

Publications and source records attributed to H S Kwak.

11 recordsLinked to original sources
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↗
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

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↗