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Biomedical subjects

Y K Chang

Publications and source records attributed to Y K Chang.

At least 19 recordsLinked to original sources
PubMed2005

Enhanced degradation of chlorinated ethylenes in groundwater from a paint contaminated site by two-stage fluidized-bed reactor.

Groundwater, used in this study, contaminated predominantly with aromatic compounds, was biologically treated in a fluidized-bed reactor (FBR) with immobilized cells. The aromatics were completely decomposed, while cis-1,2-dichloroethylene (cis-DCE) and trichloroethylene (TCE) were decomposed only approximately 20% and 5%, respectively. In these studies a significant improvement of the decomposition efficiency for chlorinated ethylenes was achieved by utilizing cometabolism. Methanol (MeOH) and toluene were used as the substrate in the case of one-stage reactor (Single Reactor). MeOH (187 mg l(-1)) increased the decomposition efficiency up to 40% and 60% for cis-DCE and TCE, respectively, while toluene (20 mg l(-1)) increased the decomposition efficiency of cis-DCE to 92% and the decomposition efficiency of TCE to 76%. In the case of two-stage reactor system (Reactor 1 and Reactor 2), MeOH and methane (CH4) were used as the substrate. In this system, cells grown on MeOH or CH4 in the Reactor 1 were continuously fed into Reactor 2 and groundwater was fed into Reactor 2 only. When MeOH (384 mg l(-1) d(-1)) was used as substrate the decomposition efficiency of cis-DCE and TCE were 60% and 70%, respectively. Similar decomposition efficiency was observed for a small amount of CH4 (19.3 mg l(-1) d(-1)).

Biodegradation, Environmental↗
PubMed2001

High-rate continuous production of lactic acid by Lactobacillus rhamnosus in a two-stage membrane cell-recycle bioreactor.

It is important to produce L(+)-lactic acid at the lowest cost possible for lactic acid to become a candidate monomer material for promising biodegradable polylactic acid. In an effort to develop a high-rate bioreactor that provides high productivity along with a high concentration of lactic acid, the performance of membrane cell-recycle bioreactor (MCRB) was investigated via experimental studies and simulation optimization. Due to greatly increased cell density, high lactic acid productivity, 21.6 g L(-1) h(-1), was obtained in the reactor. The lactic acid concentration, however, could not be increased higher than 83 g/L. When an additional continuous stirred tank reactor (CSTR) was attached next to the MCRB a higher lactic acid concentration of 87 g/L was produced at significant productivity expense. When the two MCRBs were connected in series, 92 g/L lactic acid could be produced with a productivity of 57 g L(-1) h(-1), the highest productivity among the reports of L(+)-lactic acid that obtained lactic acid concentration higher than 85 g/L using glucose substrate. Additionally, the investigation of lactic acid fermentation kinetics resulted in a successful model that represents the characteristics of lactic acid fermentation by Lactobacillus rhamnosus. The model was found to be applicable to most of the existing data with MCRBs and was in good agreement with Levenspiel's product-inhibition model, and the Luedeking-Piret equation for product-formation kinetics appeared to be effective in representing the fermentation kinetics. There was a distinctive difference in the production potential of cells (cell-density-related parameter in Luedeking-Piret equation) as lactic acid concentration increases over 55 g/L, and this finding led to a more precise estimation of bioreactor performance.

Bioreactors↗
PubMed2001

X-ray absorption studies of carbon-related materials.

X-ray absorption near-edge structure (XANES) measurements have been performed on nitrogen-doped diamond films with three different dopant concentrations and iron-layer-stabilized carbon nanotube (CNT) structures with various diameters at the C K-absorption edge using the sample drain current mode. The C K-edge XANES spectra of these N-doped diamond films resemble that of the undoped diamond regardless of the dopant concentration, which suggest that the overall bonding configuration of the C atom is unaltered. N dopants are found to reduce the intensities of both the sp2- and sp3-bond-derived resonance features in the XANES spectra. On the other hand, the C K-edge XANES spectra of CNTs indicate that the intensities of the pi* and sigma* bands and the interlayer-state features vary with the diameter of the CNT. This phenomenon may be caused by the Fe-layer-catalysed bending of the graphite sheet and the interaction between C and Fe atoms.

Journal Article↗
PubMed2001

Twin-screw extrusion of cassava starch and isolated soybean protein blends.

The effects of the extrusion parameters on isolated soybean protein (ISP) and cassava starch (CS) blends were studied. Extruded samples were prepared by using a ZSK-30 Werner and Pfleiderer twin-screw extruder. The study was carried out using Response Surface Methodology. The ISP followed by the moisture content were the most important linear variables significantly affecting axial expansion, specific volume, water solubility index and colour difference. The radial and axial expansion ranged from 2.30 to 3.77 and from 1.02 to 2.62, respectively. The highest ISP concentrations in the blends resulted in the highest specific volumes of the extrudates. Simultaneous increases of the barrel temperature and ISP level increased the water absorption index and lowered the water solubility index of the extrudates. Extruded products were softer at higher barrel temperature. The greatest difference in colour values was for the blends with the highest ISP concentration.

Color↗
PubMed2001

Serum cystatin C is an independent predictor of total homocysteine levels in stable Korean renal transplant recipients with normal serum creatinine.

OBJECTIVES: To examine the determinants of fasting plasma total homocysteine (tHcy) levels such as cystatin C, serum creatinine (SCr), estimated glomerular filtration rate (GFR) from Cockroft-Gault equation, albumin, plasma folate, vitamin B12, and pyridoxal-5'-phosphate (PLP) among Korean renal transplant recipients (RTR) with normal SCr levels (< or =1.4 mg/dL). DESIGN: Cross-sectional study. SETTING: Nephrology and Transplant Service, Catholic University Kangnam St. Mary's Hospital, Seoul, Korea. PARTICIPANTS: Fifty-one chronic stable Korean RTR with normal SCr levels (< or =1.4 mg/dL) 6 months or more following transplantation. MEASURES: Medical record review, anthropometric measurements, and overnight (10 to 14 hours) fasting blood samples for measurement of plasma tHcy, folate, vitamin B12, PLP, SCr, albumin, and cystatin C. RESULTS: General linear regression model including age, gender, vitamin status, and measurements of renal function showed that cystatin C and folate were independent predictors of tHcy levels. The partial regression coefficient for folate was -0.444 (P <.01) and for cystatin C, it was +0.334 (P <.05). SCr, estimated GFR, vitamin B12, PLP, age, and gender were not independent predictors of tHcy levels in this model. CONCLUSION: Both cystatin C and folate status were major independent determinants of fasting tHcy levels in the subgroup of Korean RTR with normal SCr.

Adult↗
PubMed2000

Desulfurization of light gas oil in immobilized-cell systems of Gordona sp. CYKS1 and Nocardia sp. CYKS2.

Desulfurizations of a model oil (hexadecane containing dibenzothiophene (DBT)) and a diesel oil by immobilized DBT-desulfurizing bacterial strains, Gordona sp. CYKS1 and Nocardia sp. CYKS2, were carried out. Celite bead was used as a biosupport for cell immobilization. Seven-eight cycles of repeated-batch desulfurization were conducted for each strain. Each batch reaction was carried out for 24 h. In the case of model oil treatment with strain CYKS1, about 4.0 mM of DBT in hexadecane (0.13 g sulfur l(oil)(-1)) was desulfurized during the first batch, while 0.25 g sulfur l(oil)(-1) during the final eighth batch. The mean desulfurization rate increased from 0.24 for the first batch to 0.48 mg sulfur l(dispersion)(-1) h(-1) for the final batch. The sulfur content in the light gas oil was decreased from 3 to 2.1 g l(oil)(-1) by strain CYKS1 in the first batch. The mean desulfurization rate was 1.81 mg sulfur l(dispersion)(-1) h(-1), which decreased slightly when the batch reaction was repeated. No significant changes in desulfurization rate were observed with strain CYKS2 when the batch reaction was repeated. When the immobilized cells were stored at 4 degrees C in 0.1 M phosphate buffer (pH 7.0) for 10 days, the residual desulfurization activity was about 50 approximately 70% of the initial value.

Actinomycetales↗
PubMed2000

Effects of selected process parameters in extrusion of yam flour (Dioscorea rotundata) on physicochemical properties of the extrudates.

Raw yam (Dioscorea rotundata) flour was cooked and extruded in a Brabender single-screw laboratory scale extruder. Response surface methodology using an incomplete factorial design was applied with various combinations of barrel temperature [100, 125, 150 degrees C], feed moisture content [18, 22, 26%] and screw speed [100, 150, 200 rpm]. Initial viscosity at 30 degrees C, water solubility index, expansion and hardness were determined. The highest values of initial viscosity were at the highest barrel temperatures and the highest moisture contents. At high feed moisture content and high barrel temperatures the yam extrudate flour showed the greatest values of water solubility index. The physical properties of the extruded product showed that at high temperature the lower the moisture content the greater the expansion index. Hardness was influenced directly by moisture content and inversely by extrusion temperature. The extrusion of yam flour led to the production of snacks and pre-gelatinized flours of diverse properties. Also extruded yam flour can be successfully used in the preparation of 'futu' (pre-cooked compact dough), a yam-based food, popular in Western Africa.

Chemical Phenomena↗
PubMed2000

Anti-inflammatory effects of fangchinoline and tetrandrine.

Fangchinoline and tetrandrine are the major alkaloids from Stephania tetrandrae S. Moore which has been used traditionally for the treatment of inflammatory diseases in oriental countries including Korea. Both fangchinoline and tetrandrine showed anti-inflammatory effects on mouse ear edema induced by croton oil. In addition, the effects of fangchinoline and tetrandrine on cyclooxygenase, murine interleukin-5 (mIL-5) and human interleukin-6 (hIL-6) were examined in vitro to investigate the anti-inflammatory action mechanisms. One hundred micromolar of fangchinoline showed 35% of inhibition on cyclooxygenase, but the same concentration of tetrandrine did not show any inhibition. On the other hand, 12.5 microM of tetrandrine exhibited 95% of inhibition on mIL-5 activity, while fangchinoline did not show any effects. However, 4 microM of fangchinoline and 6 microM of tetrandrine showed 63 and 86% of inhibitions on hIL-6 activity, respectively. These results suggest that biochemical mechanisms of fangchinoline and tetrandrine on anti-inflammation are significantly different even though they are similar in chemical structure.

Alkaloids↗
PubMed2000

Mechanism of high susceptibility of iron-overloaded mouse to Vibrio vulnificus infection.

Vibrio vulnificus produces fulminant septicemia in humans with underlying conditions, particularly those with diseases that elevate the iron level. The effect of a high iron level on the virulence of V. vulnificus was therefore investigated in mice treated with iron dextran. The mice loaded with iron became highly susceptible to V. vulnificus infection, the LD50 (50% lethal dose) decreased five logs when infected per peritoneum. However, when infected via the oral route, the LD50 was affected little unless the mouse was treated with an additional drug such as cyclophosphamide or D-galactosamine. Mice with or without iron-overloading died when the bacterial concentration in the blood reached 10(5) cfu/ml or above. Iron increased the growth rate of the bacteria, both inside and outside of the animal, quickly reaching a lethal concentration in the iron-overloaded mouse. V. vulnificus, grown with or without the addition of iron, showed strong cytotoxicity on the isolated cells or within the animal at high bacterial concentration. Iron overload stimulated the production of tumor necrosis factor alpha (TNF-alpha), a major factor of septic shock, in mice upon infection with the bacteria, probably caused by the endotoxin; however, the neutrophils, whose migration is effected by TNF-alpha, appeared to be less active. Taken together, the major virulence factor of V. vulnificus appeared to be the accelerated growth of bacteria to quickly reach the lethal level and the lower activity of immune cells including neutrophil as a result of iron-overloading. These two effects manifest other virulence factors, the host's as well as bacterial. Such factors, other than TNF-alpha stimulated by the endotoxin, enhanced cytotoxicity, which kills the host cells including the host's immune cells.

Animals↗
PubMed1999

Intracervical misoprostol as an effective method of labor induction at term.

OBJECTS: The purpose of this study was to evaluate the safety and effectiveness of intracervical misoprostol for the induction of labor at term. METHODS: Eighty-nine term pregnancies requiring induction of labor were treated intracervically with 50 microg of misoprostol. The dose was repeated every 4 h until adequate uterine contraction and cervical dilatation were achieved. Status of cervical ripening, uterine contraction, cervical dilatation, labor course and side effects were recorded and analyzed. RESULTS: Among the 89 patients, 58 had an unfavorable cervix (Bishop score < or = 4) and 31 had a favorable cervix (Bishop score > 4). Labor was successfully induced in all cases, most (93.3%) of which required a single dose of misoprostol. Seventy-two patients (81%) proceeded to spontaneous vaginal delivery, and 61 (85%) deliveries were achieved within 12 h. The other 17 cases received cesarean delivery with indications of fetopelvic disproportion (six cases), failure of induction (seven cases) and acute fetal distress (four cases). The mean duration from induction to regular uterine contraction and to delivery was 483+/-537 min and 79.2+/-38.2 min, respectively, with no significant difference between the two groups with differing status of cervical ripening. Complications of uterine contraction, including tachysystole (15 cases), hypertonus (one case) and hyperstimulation (10 cases) were more common in the group of unfavorable cervix (45%) than that of favorable cervix (23%) (P < 0.05). CONCLUSION: In addition to the oral and intravaginal routes of administration, intracervical misoprostol at a single dose of 50 microg appears to be an effective method for induction of labor at term, but caution should be taken with cases with unfavorable cervix.

Abortifacient Agents, Nonsteroidal↗
PubMed1999

Minilaparoscopy to reduce complications from cannula insertion in patients with previous pelvic or abdominal surgery.

STUDY OBJECTIVE: To evaluate the safety and efficacy of minilaparoscopy for visualization and adhesiolysis of intraabdominal adhesions for safe insertion of a primary umbilical cannula in patients who had previous pelvic or abdominal surgery. DESIGN: Prospective, observational study (Canadian Task Force classification II-1). SETTING: University-affiliated hospital. PATIENTS: Twenty women who had previous pelvic or abdominal surgery, excluding tubal ligation and simple appendectomy. INTERVENTION: Minilaparoscopy was carried for visualization and adhesiolysis at the entry site before insertion of an umbilical cannula. MEASUREMENTS AND RESULTS: Eleven patients had Pfannenstiel scars and nine had vertical midline scars from previous surgeries (4 total abdominal hysterectomies, 13 adnexal surgery, 7 cesarean sections, 3 ectopic pregnancies, 1 ruptured appendix, 1 unknown bowel surgery). Thirteen women (65%) had had one previous surgery, five (25%) had had two, and two (10%) had had three. Nine patients (45%) had significant adhesions of omentum or intestine that required adhesiolysis. Mean operating time for minilaparoscopy was 5 minutes for 11 women who had no or minimal adhesions that did not interfere with safe insertion of the umbilical cannula and effective use of a 10-mm telescope, and 25 minutes in 9 patients who required adhesiolysis before insertion of the umbilical cannula because of dense adhesions of omentum or intestine at the entry site. No complications with minilaparoscopy occurred. CONCLUSION: Minilaparoscopy can be performed safely and effectively to reduce serious vascular or visceral injury from insertion of primary cannula in patients who had previous pelvic and/or abdominal surgery. However, conclusions cannot be derived from this study due to the small number of subjects. Further study is necessary in a larger patient population to evaluate efficacy, safety, and advantages of minilaparoscopy over other techniques. (J Am Assoc Gynecol Laparosc 6(1):91-95, 1999)

Abdomen↗
PubMed1999

Microbial removal of Fe(III) impurities from clay using dissimilatory iron reducers.

Fe(III) impurities, which detract refractoriness and whiteness from porcelain and pottery, could be biologically removed from low-quality clay by indigenous dissimilatory Fe(III)-reducing microorganisms. Insoluble Fe(III) in clay particles was leached out as soluble Fe(II), and the Fe(III) reduction reaction was coupled to the oxidation of sugars such as glucose, maltose and sucrose. A maximum removal of 44-45% was obtained when the relative amount of sugar was 5% (w/w; sugar/clay). By the microbial treatment, the whiteness of the clay was increased from 63.20 to 79.64, whereas the redness was clearly decreased from 13.47 to 3.55.

Journal Article↗
PubMed1999

Degradation of chloronitrobenzenes by a coculture of Pseudomonas putida and a Rhodococcus sp.

A single microorganism able to mineralize chloronitrobenzenes (CNBs) has not been reported, and degradation of CNBs by coculture of two microbial strains was attempted. Pseudomonas putida HS12 was first isolated by analogue enrichment culture using nitrobenzene (NB) as the substrate, and this strain was observed to possess a partial reductive pathway for the degradation of NB. From high-performance liquid chromatography-mass spectrometry and 1H nuclear magnetic resonance analyses, NB-grown cells of P. putida HS12 were found to convert 3- and 4-CNBs to the corresponding 5- and 4-chloro-2-hydroxyacetanilides, respectively, by partial reduction and subsequent acetylation. For the degradation of CNBs, Rhodococcus sp. strain HS51, which degrades 4- and 5-chloro-2-hydroxyacetanilides, was isolated and combined with P. putida HS12 to give a coculture. This coculture was confirmed to mineralize 3- and 4-CNBs in the presence of an additional carbon source. A degradation pathway for 3- and 4-CNBs by the two isolated strains was also proposed.

Acetylation↗
PubMed1999

Ethanol production using concentrated oak wood hydrolysates and methods to detoxify.

Ethanol production from concentrated oak wood hydrolysate was carried out to obtain a high ethanol concentration and a high ethanol yield. The effect of added inhibitory compounds, which are typically produced in the pretreatment step of steam-explosion on ethanol fermentation, was also examined. p-Hydroxybenzoic aldehyde, a lignin-degradation product, was the most inhibitory compound tested in this study. Compounds with additional methyl groups had reduced toxicity and the aromatic acids were less toxic than the corresponding aldehydes. The lignin-degradation products were more inhibitory than the sugar-derived products, such as furfural and 5-hydroxymethylfurfural (HMF). Adaptation of yeast cells to the wood hydrolysate and detoxification methods, such as using charcoal and overlime, had some beneficial effects on ethanol production using the concentrated wood hydrolysate. After treatment with charcoal and low-temperature sterilization, the yeast cells could utilize the concentrated wood hydrolysate with 170 as well as 140 g/L glucose, and produce 69.9 and 74.2 g/L ethanol, respectively, with a yield of 0.46-0.48 g ethanol/g glucose. In contrast, the cells could not completely utilize untreated wood hydrolysate with 100 g/L glucose. Low-temperature sterilization, with or without charcoal treatment, was very effective for ethanol production when highly concentrated wood hydrolysates were used. Low-temperature sterilization has advantages over traditional detoxification methods, such as using overlime, ion exchange, and charcoal, because of the reduction in the total cost of ethanol production.

Journal Article↗
PubMed1998

Neonatal gastric aspirates as a predictor of perinatal hepatitis B virus infections.

OBJECTIVE: To elucidate possible routes and predictors of perinatal transmission of hepatitis B virus (HBV). METHOD: This was a prospective follow-up study. One hundred and forty-seven out of 1762 pregnant women who were screened in the antenatal clinic of a university teaching hospital were HBsAg carriers. Enzyme immunoassay was used for determination of hepatitis B markers. Occurrence of HBsAg in newborns' gastric aspirates, newborns' and infants' blood, and maternal milk samples were determined. Their relationship with delivery routes and duration of the first stage of labor were analyzed by chi square test. RESULTS: The presence of HBsAg in newborns' gastric aspirates was strongly associated with the acquisition of HBsAg by the babies. There was no correlation between the rate of infant antigenemia and the duration of the first stage of labor, nor did cesarean section decrease the rate of vertical transmission of HBV. CONCLUSIONS: This is the first report to provide direct evidence for the major role of the oral route in vertical transmission of HBV during delivery. In addition to maternal serum HBeAg, HBsAg status in newborn's gastric aspirates is another important determinant for vertical transmission of HBV.

Biomarkers↗