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Biomedical subjects

B K Min

Publications and source records attributed to B K Min.

10 recordsLinked to original sources
PubMed2006

Efficient CO oxidation at low temperature on Au(111).

The rate of CO oxidation to CO2 depends strongly on the reaction temperature and characteristics of the oxygen overlayer on Au(111). The factors that contribute to the temperature dependence in the oxidation rate are (1) the residence time of CO on the surface, (2) the island size containing Au-O complexes, and (3) the local properties, including the degree of order of the oxygen layer. Three different types of oxygen--defined as chemisorbed oxygen, a surface oxide, and a bulk oxide--are identified and shown to have different reactivity. The relative populations of the various oxygen species depend on the preparation temperature and the oxygen coverage. The highest rate of CO oxidation was observed for an initial oxygen coverage of 0.5 monolayers that was deposited at 200 K where the density of chemisorbed oxygen is maximized. The rate decreases when two-dimensional islands of the surface oxide are populated and further decreases when three-dimensional bulk gold oxide forms. Our results are significant for designing catalytic processes that use Au for CO oxidation, because they suggest that the most efficient oxidation of CO occurs at low temperature--even below room temperature--as long as oxygen could be adsorbed on the surface.

Journal Article↗
PubMed2005

Water dissociation associated with NO2 coadsorption on Mo(110)-(1 x 6)-O: effect of coverage and electronic properties of oxygen.

Water dissociation on an oxygen-covered Mo(110) surface was investigated using temperature-programmed reaction spectroscopy (TPRS) and infrared reflectance absorbance spectroscopy (IRAS). Adsorbed hydroxyl formation is enhanced by increasing the coverage of chemisorbed oxygen prior to exposure to water up to saturation (0.66 ML). Additional oxidation of the surface using NO(2) suppresses the formation of hydroxyl species (OH). There is no detectable change in the reaction of NO(2) on Mo(110)-(1 x 6)-O when either the water or hydroxyl is adsorbed on the Mo(110)-(1 x 6)-O surface prior to NO(2) adsorption. In contrast, NO(2) induces the displacement of water into the gas phase and the conversion of hydroxyl species to molecular water. Infrared spectra show that the dissociation of NO(2) populates three types of terminal oxygen sites on Mo(110)-(1 x 6)-O, and the population of the terminal oxygen at step sites increases with respect to the amount of NO(2) deposited. Overall, these results suggest that the oxidic property of oxygen results in a lack of activity for the water dissociation.

Journal Article↗
PubMed2000

The effects of N-methyl-N-nitrosourea and azoxymethane on focal cerebral infarction and the expression of p53, p21 proteins.

If the activity of pro-apoptotic genes can be down-regulated by certain chemicals, cells may be protected from apoptosis. To test this hypothesis in a cerebral infarction model, we used N-methyl-N-nitrosourea (MNU) and azoxymethane (AOM), which were approved gene-modulating chemicals. A focal cerebral infarction was created by coagulation of the right middle cerebral artery and ipsilateral common carotid artery (CCA) and simultaneous transient occlusion of the contralateral CCA for 30 min in 25 adult Sprague-Dawley rats that were sacrificed 24 h later. In one group (n=7), MNU (5 mg/kg) was injected intravenously 30 min before initiation of ischemia. In another group (n=7), AOM (15 mg/kg) was administered intraperitoneally before 24 h of ischemia. The infarction volumes were checked and the brains were stained for p53 and p21 proteins. The width in micrometers of the peri-infarct area containing p53 or p21 protein-positive cells, and the number of p53 or p21 protein-positive cells (cells/HPF) were measured at an adjacent peri-infarct area. The AOM-treated group showed a significantly reduced infarction volume (by 42.5%, p<0.001), a significantly greater number of p53 positive cells (by 12.0%, p<0. 05), and a significantly wider p53 protein-positive area (by 15.6%, p<0.01) than the untreated group. AOM did not show any influence on the expression pattern of the p21 protein. MNU had no effect in the expression of p53 or p21 proteins. As a result, we concluded that AOM revealed a protective effect in ischemia by suppressing the pro-apoptotic activity of the p53 gene. Safer chemicals that can modulate apoptotic genes, if any, will provide a new therapeutic modality for cerebral infarction.

Animals↗
PubMed2000

Flavonol glycoside gallate and ferulate esters from Persicaria lapathifolia as inhibitors of superoxide production in human monocytes stimulated by unopsonized zymosan.

Aerial parts of Persicaria lapathifolia S.F. Gray (Polygonaceae) exhibited an inhibitory effect on superoxide production in unopsonized zymosan-stimulated human monocytes. Two known compounds, quercetin 3-O-beta-(2"-galloyl)-glucopyranoside and quercetin 3-O-beta-(2"-galloyl)-rhamnopyranoside, and a new compound, quercetin 3-O-beta-(6"-feruloyl)-galactopyranoside, were isolated as the inhibitors of superoxide production by activity-guided fractionation. IC50 values were shown at the concentrations of 2.1 microM by quercetin 3-O-beta-(2"-galloyl)-glucopyranoside, 1.9 microM by quercetin 3-O-beta-(2"-galloyl)-rhamnoypranoside, and 3.5 microM by quercetin 3-O-beta-(6"-feruloyl)-galactopyranoside whose inhibitory potencies were similar to oxyphenylbutazone (IC50 = 1.9 microM) as a positive control.

Adult↗
PubMed1999

Inhibitory effect of luteolin 4'-O-glucoside from Kummerowia striata and other flavonoids on interleukin-5 bioactivity.

Interleukin (IL)-5 is a chemotactic factor of eosinophils, and promotes the growth and survival of eosinophils, which plays an important role in the eosinophilia-associated allergic inflammation. In this study, luteolin 4'-O-glucopyranoside was identified as the IL-5 inhibitor from Kummerowia striata Thunb. (Leguminosae) by activity-guided fractionation followed by structural analysis compared with reported spectral data. The flavone compound exhibited dose-dependent inhibitory effect on IL-5 bioactivity with 95% inhibition at 30 microM, 79% at 15 microM, 60% at 7.5 microM, 54% at 3.8 microM and 29% at 1.9 microM, where 50% of inhibition (IC50) value was shown at the concentration of 3.7 microM. Furthermore, the inhibitory effect on IL-5 bioactivity by other flavonoid compounds available was estimated. In view of the IC50 values, the inhibitory potency on IL-5 bioactivity was in order of luteolin 4'-O-glucopyranoside > cosmosiin (14.2 microM) approximately equal to apigenin (16.4 microM) approximately equal to luteolin (18.7 microM) > quercimeritrin (27.3 microM) approximately equal to kaempferol (30.0 microM).

Animals↗
PubMed1996

Rapid determination of in vivo and in vitro antibody responses by suspension hemolytic assay.

A suspension hemolytic (SH) assay newly modified in this laboratory was applied to the measurement of primary IgM antibody responses, such as T-dependent, T-independent, and polyclonal B cell responses in in vivo and in vitro assays. All results of the SH assay were equal to those of the conventional plaque-forming cell (PFC) assay. With the SH assay in in vitro assays, we could separately measure the amount of the IgM that had been produced during the whole immunization period and measure the IgM newly produced during the shorter time of the assay. The immunomodulations by dioxin and glycopeptide were accurately evaluated by the SH and the PFC assay. Our study suggested that the SH assay modified in this laboratory was more advantageous because of the simplicity of the assay and better analysis of data than the PFC assay, and could be used as the primary method in studying the effects of pharmaceutical and toxic agents on humoral immune functions.

Animals↗
PubMed1992

Incidence estimation of genitourinary cancer in Korea.

A nation-wide study was performed to estimate the incidence of bladder, kidney, renal pelvis and ureter, prostate, testicular and other genitourinary cancer among Koreans in Korea using medical records of the inpatients of the beneficiaries of the Korea Medical Insurance Corporation (KMIC) from Jan. 1, 1989 to Dec. 31, 1989. The crude incidence rate of bladder cancer (ICD-9 188) is estimated to be 4.43 and 0.98 per 100,000 in males and females, respectively. Around 1,093 new cases of bladder cancer (895 male and 198 female) are estimated to occur in a year. The adjusted rate for the world population is 7.76 in males and 1.19 in females which is similar to that of Japanese in Osaka and Chinese in Shanghai, but lower than in American whites and blacks. The crude incidence of kidney, renal pelvis and ureteral cancer (ICD-9 189) is estimated to be 1.61 and 0.87 in males and females, respectively. Around 507 new cases of kidney, renal pelvis and ureteral cancer (332 male and 175 female) are estimated to occur in a year. The adjusted rate for the world population is 2.69 in males and 1.04 in females. In the prostate (ICD-9 185), the crude incidence rate of cancer is estimated to be 1.36. Around 274 new cases of prostate cancer are occurring in a year. The adjusted rate for the world population is 2.98 which is similar to the Chinese rate. The incidence of genitourinary cancer continuously increases with age.

Adult↗
PubMed1987

Safety and immunogenicity of a new heat-inactivated hepatitis B virus vaccine in adult recipients.

A new heat inactivated HBV vaccine has been evaluated for safety and immunogenicity in 203 adult recipients. The vaccine was found to be safe and highly immunogenic. Three doses of 3 micrograms given at 0, 1 and 6 months, resulted in 96% seroconversion. Three doses of 3 micrograms given at 0, 1 and 2 months produced, more rapidly, seroconversion in 92% of those immunized. Antibody to a pre-S determinant developed in four of six subjects tested.

Adult↗
PubMed1975

Enzymatic studies on the skeletal myosin A and actomyosin of aging rats.

Myosin A and actomyosin were isolated from the skeletal muscle of old and young rats. The velocity of the Ca2+ activated myosin A ATPase was increased in the case of the older animals. On the other hand the velocity of the Mg-2plus activated actomyosin ATPase was decreased in the skeletal muscle of the aging rats. At 5 X 10-5M EGTA concentration the inhibition of the Mg-2plus activated myosin B ATPase of the 1-month-old rats was two- to threefold smaller than that of the older animals. It was shown that the myosin A component of the actomyosin was responsible for the decreased troponin inhibition in the case of the 1-month-old rats. Between the ages of 1 month and 29 months the number of free myosin A SH groups decreases by 50%. The lipid peroxidation in the muscle of the 1-month-old animals.

Actins↗