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Biomedical subjects

K Lee

Publications and source records attributed to K Lee.

At least 325 records · Page 18Linked to original sources
PubMed1999

Pharmacological characterization of Ca2+ entry channels in endothelin-1-induced contraction of rat aorta using LOE 908 and SK&F 96365.

We have recently shown that endothelin-1 (ET-1) activates two types of Ca2+-permeable nonselective cation channels (designated NSCC-1 and NSCC-2) and store-operated Ca2+ channel (SOCC). These channels can be pharmacologically discriminated using Ca2+ channel blockers such as SK&F 96365 and LOE 908. Here we characterized Ca2+ entry channels involved in ET-1-induced contractions of rat thoracic aortic rings and increases in the intracellular free Ca2+ concentration ([Ca2+]i) of single smooth muscle cells using these blockers. LOE 908 or a blocker of voltage-operated Ca2+ channel nifedipine had no effect on the contractions and increases in [Ca2+]i induced by thapsigargin or ionomycin, whereas SK&F 96365 abolished them. The contractions and increases in [Ca2+]i induced by ET-1 depended on extracellular Ca2+ but were resistant to nifedipine. The responses to lower concentrations (< or =0.1 nM) of ET-1 were abolished by either SK&F 96365 or LOE 908. The responses to higher concentrations (> or = 1 nM) were abolished by SK&F 96365, but were partially resistant to LOE 908. SK&F 96365 inhibited the LOE 908-resistant contractions induced by higher concentrations of ET-1 with IC50 values similar to those for contractions induced by thapsigargin or ionomycin. These results show that the contractions and increases in [Ca2+]i of rat aortic smooth muscles at lower concentrations of ET-1 involve only one Ca2+ entry channel which is sensitive to SK&F 96365 and LOE 908 (NSCC-2), whereas those at higher concentrations of ET-1 involve another Ca2+ entry channel which is sensitive to SK&F 96365 but resistant to LOE 908 (SOCC) in addition to the former channel.

Acetamides↗
PubMed1999

Bone formation in a carcinoma of the maxillary antrum.

Malignant tumors of the paranasal sinuses are rare: about 80% are found in the maxillary sinus123. The presence of dense radiopaque masses in combination with destruction of the bone margins suggests osteosarcoma or aspergillosis4 rather than carcinoma. We present a unique mucoepidermoid carcinoma of the maxillary antrum containing new bone formation and discuss the differential diagnosis.

Aged↗
PubMed1999

Influences of vertical occlusal discrepancies on condylar responses and craniofacial growth in growing rats.

The present study was conducted to investigate the influence of vertical occlusal discrepancies on condylar remodeling and the subsequent craniofacial growth in growing rats. Thirty 4-week-old male Wistar strain rats were used. A 1-mm-thick metal plate was bonded onto the occlusal surface of the maxillary molars to increase posterior dentoalveolar height. During the early phase of the experiment, the thickness of the proliferative and maturative/hypertrophic zones in the anterior and superior portions of the condyle was significantly smaller in the experimental group than in the controls. The number of TRAP-positive cells was significantly greater in the experimental group than in the controls. At the end of the experiment, decreased ramus height and a large gonial angle were found in the experimental group. Changes in the intra-articular environment associated with vertical occlusal discrepancies may influence condylar and craniofacial growth in growing individuals, although some adaptive response of the condyle may be induced if growth potential remains.

Acid Phosphatase↗
PubMed1999

CD36 deficiency is frequent and can cause platelet immunization in Africans.

BACKGROUND: CD36 is expressed on several cell lineages. About 5 to 10 percent of Asians lack platelet membrane CD36 (pCD36), but the frequency of pCD36 deficiency in other ethnic groups is not known. Persons who are pCD36-negative are apparently healthy but can develop CD36 isoimmunization. STUDY DESIGN AND METHODS: The pCD36 phenotype was studied in 1885 subjects belonging either to a group of 1127 healthy French blood donors (almost all of whom were white Europeans) or to a group of 758 patients of known ethnic origin. RESULTS: No pCD36-negative persons were found among the blood donors. Only 1 of the 301 white European patients was pCD36-negative. In contrast, 16 of the 206 sub-Saharan Africans was pCD36-negative, a proportion higher than that among that black Caribbeans (1/148, p<0.01). The frequency of pCD36-negative patients was similar in blacks with and without sickle cell disease. Monocyte CD36 (mCD36) expression was studied in 15 of 22 pCD36-negative individuals: it was <10 percent in 7 subjects (type I deficiency) and between 12 and 100 percent in 8 others (type II deficiency). Thirteen pCD36-negative individuals had risk factors for immunization, and 4 had anti-CD36. Some had a history resembling posttransfusion purpura (n = 2), platelet transfusion refractoriness (n = 1), and recurrent miscarriage (n = 1). No correlation was found between immunization and the amount of mCD36. Anti-CD36 from an immunized type II-deficient woman reacted with monocytes from normal controls but not with monocytes from type I- or type II-deficient individuals, and thus it is postulated that mCD36 could be structurally different in normal and type II CD36-deficient individuals. CONCLUSION: CD36 deficiency is frequent in sub-Saharan Africans; development of anti-CD36 can lead to serious complications in multiply transfused patients, such as those with sicke cell disease.

Adult↗
PubMed1999

Effects of face configuration change on shape perception: a new illusion.

We report two experiments indicating that varying the configuration of face features changes perception of an oval aperture windowing the face: as the eyes and mouth of a frontal-view face photograph are moved vertically toward face boundaries, the oval appears increasingly clongated, taller, and narrower; when eyes and mouth are moved toward the nose, the oval appears increasingly rounder, shorter, and wider. This shape illusion is maximised when faces appear upright within the oval and major face features (eyes, nose, and mouth) appear in their correct relative locations. These results establish that processing of a face configuration can affect perception of a geometric shape that shares visual space with a face. Whether the illusion is face-specific or a special case of a more general geometric illusion is discussed.

Face↗
PubMed1999

Ozone decay rates in residences.

In urban and suburban settings, indoor ozone exposures can represent a significant fraction of an individual's total exposure. The decay rate, one of the factors determining indoor ozone concentrations, is inadequately understood in residences. Decay rates were calculated by introducing outdoor air containing 80-160 parts per billion ozone into 43 residences and monitoring the reduction in indoor concentration as a function of time. The mean decay rate measured in the living rooms of 43 Southern California homes was 2.80 +/- 1.30 hr-1, with an average ozone deposition velocity of 0.049 +/- 0.017 cm/sec. The experimental protocol was evaluated for precision by repeating measurements in one residence on five different days, collecting 44 same-day replicate measurements, and by simultaneous measurements at two locations in six homes. Measured decay rates were significantly correlated with house type and the number of bedrooms. The observed decay rates were higher in multiple-family homes and homes with fewer than three bedrooms. Homes with higher surface-area-to-volume ratios had higher decay rates. The ratio of indoor-to-outdoor ozone concentrations in homes not using air conditioning and open windows was 68 +/- 18%, while the ratio of indoor-to-outdoor ozone was less than 10% for the homes with air conditioning in use.

Air Pollution, Indoor↗
PubMed1999

Expression of beta-galactosidase and pig leptin gene in vitro by recombinant adenovirus.

Adenovirus has been used in vivo and in vitro as a vector to carry a foreign gene for gene transfer. Two kinds of replication defective human recombinant adenovirus vectors were used in this study, the first containing beta-galactosidase reporter gene (AdCMVLac-Z) and the second carrying a gene for porcine leptin gene (AdCMVpLeptin). AdCMVLac-Z was tested for its ability to transfer DNA into pig kidney and pituitary cells. These cells expressed Lac-Z transiently 48 hours after the infection. In addition, when the pig kidney cells expressing the Lac-Z were replated with low density for the formation of colonies from each cell, colonies of blue cells expressing Lac-Z were observed. These results demonstrate that human recombinant adenovirus can be used as a transducing viral vector for inducing long-term expression in pig kidney cells. We also constructed a recombinant adenovirus (AdCMVpLeptin) which contained a pig leptin gene for the expression of pig leptin in vitro in the 293 human kidney cell line. 293 cells transfected with AdCMVpLeptin produced both a 15 KDa of a secretory form of porcine leptin and an 18 KDa long form containing signal peptide. Our study demonstrated that the recombinant adenovirus system offers a method for gene transfer and expression in pig cells.

Adenoviridae↗
PubMed1999

In vitro transcription assay with the purified 40kDa NF1-like protein binding to the rat p53 promoter.

The rat p53 promoter has several potential transcription factor-recognition motifs. They include NF1-like, bHLH family, and AP1-like proteins binding sites. The binding protein to NF1-like motif was previously identified. The protein has about 40kDa of molecular mass, which is smaller than that of NF1. Anti-NF1 polyclonal antibody does not recognize the protein. In this study, we isolated the 40kDa protein by sequence-specific DNA affinity chromatography. The isolated protein was assayed by DNase I footprinting analysis. To determine the transactivation effect of the protein, in vitro transcription with the purified 40kDa protein was carried out. After the addition of the purified 40kDa protein into the transcription reaction mixture, the transcription level of the p53 promoter was increased. This suggests that the 40 kDa NF1-like protein is a transcription activator for the rat p53 gene.

Animals↗
PubMed1999

A practical synthesis of L-FMAU from L-arabinose.

A practical synthesis of 2'-deoxy-2'-fluoro-5-methyl-beta-L-arabinofuranosyl uracil (14, L-FMAU) was developed from L-arabinose. L-Arabinose was converted to L-ribose 5, which was used for the synthesis of bromosugar 12 via 2,3,5-O-tribenzoyl-1-O-acetyl-beta-L-ribofuranose 8, which was subjected to condensation with silylated thymine and the resulting protected L-FMAU 13 was deprotected to afford L-FMAU in 14 steps in 8% overall yield.

Antiviral Agents↗
PubMed1999

Metabolic flux analysis: a powerful tool for monitoring tissue function.

In recent years, metabolic flux analysis has been widely used in bioprocess engineering to monitor cell viability and improve strain activity. Metabolic flux analysis refers to a methodology for investigating cellular metabolism whereby intracellular fluxes are calculated using a stoichiometric model for the major intracellular reactions and applying mass balances around intracellular metabolites. A powerful feature of this methodology is its ability to consider cellular biochemistry in terms of reaction networks. By considering the stoichiometry of biochemical reactions, it is possible to estimate the degree of engagement of each pathway participating in overall cellular activity, and hence obtain a comprehensive view of a cell s metabolic state. Given the potential impact of cellular energy metabolism on the function of engineered tissues, such comprehensive analysis of metabolic activity can be an extremely useful tool for tissue engineers. Estimates of intracellular fluxes under various environmental conditions could be used to optimize function in vivo as well as culture conditions in vitro. In this review, we provide a brief theoretical background of metabolic flux analysis and summarize the most widely used experimental approaches to obtain flux data. This review is intended as an overview of the field and as a starting point for tissue engineers wishing to learn about and eventually employ this methodology.

Animals↗
PubMed1999

Histological and histochemical quantification of root resorption incident to the application of intrusive force to rat molars.

This study was conducted to investigate the nature of root resorption resulting from intrusive forces applied to the rat lower molars, by means of histological and histochemical techniques with tartrate resistant acid phosphatase (TRAP). Thirty-eight 13-week-old Wistar strain male rats were used. Intrusive force was created by a fixed appliance which was adjusted to exert an initial force of 50 g for the duration of 1, 2, and 3 weeks. The degree of root resorption and distribution of TRAP positive cells were evaluated. On the root surface, the TRAP positive scores were low in the apical regions. Significant differences in the scores were found in the inter-radicular region of the roots between the experimental and control groups for the 2- and 3-week groups. More active resorption of bone occurred during the experimental period, as denoted by greater TRAP positive scores on the bone than on the root surface. Root resorption scores in the apical root region were larger in the 2- and 3-week groups than in the 1-week group. Significant differences in the root resorption scores were also found between the 1- and 3-week groups in the inter-radicular region, indicating that intrusive force application of a longer duration may lead to a higher frequency of root resorption. It is shown that, irrespective of the level of TRAP positive cells and root resorption scores, the degree of root resorption activity is higher in the apical root region than in the inter-radicular area. These results indicate that cellular cementum may be resorbed more easily because of its richer organic components and low mineralized structure.

Acid Phosphatase↗
PubMed1999

Effect of excited states on the ionization balance in plasmas via the enhancement of ionization and recombination rate coefficients.

The effect of excited states on the effective ionization and recombination rate coefficients for the ground states was investigated analytically and by computer simulation. The calculation was done for carbon ions. The results using carbon ions show (1) the contribution from excited states to ionization rate coefficients becomes significant even at an electron density as low as 10(15) cm(-3) and saturated from around N(e) approximately 10(20) cm(-3); (2) the lower the electron temperature, the larger the contribution; (3) in the case of recombination rate coefficients, there is still a non-negligible contribution from excited states even at a very low electron density of 10(10) cm(-3), where the contribution has been considered negligible; (4) this contribution to the recombination rate coefficients increases linearly with the electron density; (5) the enhancements of the ionization and recombination rate coefficients increase as N(e) increases and are saturated to the same value at higher densities; (6) there exists a region of temperature and density where the recombination is effectively hindered. Some of the behaviors of the ionization and recombination rate coefficients in the extreme regions of a very low and high electron density were analytically understood. The calculated ionization and recombination rate coefficients for carbon ions, including the effect of excited states, were used in a one-dimensional magnetohydrodynamic code for the calculation of the ionization balance of carbon ions in a Z-pinch carbon plasma and the gain of C VI H(alpha) (18.2 nm) line. The significant change in the evolution of the ionization balance was observed. The rapid depletion of C VII ions by the increased recombination rate reduces the gain significantly by a factor of approximately 3 compared to the case where the contribution from excited states was neglected. Such calculations can be done for other ions. The characteristics found for carbon ions are generic and applicable to other ions.

Journal Article↗
PubMed1999

Effects of nonequilibrium fluctuations on ionic transport through biomembranes.

We investigate the effects of nonequilibrium fluctuations on ionic transport through ion channels in membranes using the concept of localized ratchet. Due to the localization, the ionic population in the binding site can be enhanced or suppressed depending upon ionic potential and its fluctuations, affecting the gating kinetics of the channel. The localized dichotomic fluctuations of ionic potential are shown to give rise to a current reversal differing from the results of periodic ratchets. It is also found that strong correlations between binding energy and membrane potential fluctuations induce resonancelike behaviors in ionic current as the fluctuating rate varies.

Journal Article↗
PubMed1999

Too much versus too little: the implications of current iodine intake in the United States.

Iodine intake influences the health of Americans today, but in different ways than it has in the past. In the early 1900s, iodine deficiency was responsible for widespread endemic goiter in the United States. The incidence of goiter was markedly reduced by the introduction of iodine supplementation of salt and other foods in the 1920s. By the middle of this century iodine-related problems in the Unites States were more likely to be associated with too much rather than too little of this essential nutrient. Recent and disturbing new data suggest that there has been a sharp decline in iodine intake during the last 20 years, especially in women of reproductive age. A brief comparison of thyroid response to insufficient and excessive intakes in normal and diseased thyroid tissue is presented. The population affected and the implications for therapy are also reviewed.

Diet Surveys↗
PubMed1999

Down-regulation of Th2 responses by Brucella abortus, a strong Th1 stimulus, correlates with alterations in the B7.2-CD28 pathway.

Down-regulation of the Th2-like response induced by ovalbumin-alum (OVA/alum) immunization by heat-killed Brucella abortus was not reversed by anti-IL-12 antibody treatment or in gamma interferon (IFN-gamma) knockout mice, suggesting that induction of Th1 cytokines was not the only mechanism involved in the B. abortus-mediated inhibition of the Th2 response to OVA/alum. The focus of this study was to determine whether an alternative pathway involves alteration in expression of costimulatory molecules. First we show that the Th2-like response to OVA/alum is dependent on B7.2 interaction with ligand since it can be abrogated by anti-B7.2 treatment. Expression of costimulatory molecules was then studied in mice immunized with OVA/alum in the absence or presence of B. abortus. B7.2, but not B7.1, was up-regulated on mouse non-T and T cells following immunization with B. abortus. Surprisingly, B. abortus induced down-regulation of CD28 and up-regulation of B7.2 on murine CD4(+) and CD8(+) T cells. These effects on T cells were maximal for CD28 and B7.2 at 40 to 48 h and were not dependent on interleukin-12 (IL-12) or IFN-gamma. On the basis of these results, we propose that the IL-12/IFN-gamma-independent inhibition of Th2 responses to OVA/alum is secondary to the effects of B. abortus on expression of costimulatory molecules on T cells. We suggest that down-regulation of CD28 following activation inhibits subsequent differentiation of Th0 into Th2 cells. In addition, decreased expression of CD28 and increased expression of B7.2 on T cells would favor B7.2 interaction with CTLA-4 on T cells, and this could provide a negative signal to developing Th2 cells.

Animals↗
PubMed1999

Benzene-induced uncoupling of naphthalene dioxygenase activity and enzyme inactivation by production of hydrogen peroxide.

Naphthalene dioxygenase (NDO) is a multicomponent enzyme system that oxidizes naphthalene to (+)-cis-(1R,2S)-1,2-dihydroxy-1, 2-dihydronaphthalene with consumption of O2 and two electrons from NAD(P)H. In the presence of benzene, NADH oxidation and O2 utilization were partially uncoupled from substrate oxidation. Approximately 40 to 50% of the consumed O2 was detected as hydrogen peroxide. The rate of benzene-dependent O2 consumption decreased with time, but it was partially increased by the addition of catalase in the course of the O2 consumption by NDO. Detailed experiments showed that the total amount of O2 consumed and the rate of benzene-induced O2 consumption increased in the presence of hydrogen peroxide-scavenging agents, and further addition of the terminal oxygenase component (ISPNAP) of NDO. Kinetic studies showed that ISPNAP was irreversibly inactivated in the reaction that contained benzene, but the inactivation was relieved to a high degree in the presence of catalase and partially relieved in the presence of 0.1 mM ferrous ion. Benzene- and naphthalene-reacted ISPNAP gave almost identical visible absorption spectra. In addition, hydrogen peroxide added at a range of 0.1 to 0.6 mM to the reaction mixtures inactivated the reduced ISPNAP containing mononuclear iron. These results show that hydrogen peroxide released during the uncoupling reaction acts both as an inhibitor of benzene-dependent O2 consumption and as an inactivator of ISPNAP. It is proposed that the irreversible inactivation of ISPNAP occurs by a Fenton-type reaction which forms a strong oxidizing agent, hydroxyl radicals (. OH), from the reaction of hydrogen peroxide with ferrous mononuclear iron at the active site. Furthermore, when [14C]benzene was used as the substrate, cis-benzene 1,2-dihydrodiol formed by NDO was detected. This result shows that NDO also couples a trace amount of benzene to both O2 consumption and NADH oxidation.

Bacterial Proteins↗
PubMed1999

Two cases of Chromobacterium violaceum infection after injury in a subtropical region.

Chromobacterium violaceum is a gram-negative rod and is isolated from soil and water in tropical and subtropical regions. The species have pigmented and nonpigmented colony types. Infections caused by nonpigmented strains are rare. We report on two cases of infection caused by both pigmented and nonpigmented strains of C. violaceum. Two 24-year-old Korea Airline stewardesses were admitted to Inha University Hospital, Inchon, South Korea, on 9 August 1997, 3 days after an airplane accident in Guam. Both had multiple lacerations on exposed parts of their bodies. There was swelling, tenderness, and pus discharge. The wounds contained many small fragments of stones and weeds. A pigmented strain was isolated from the left hand and a nonpigmented strain was isolated from the left knee of one patient. For the other patient only a nonpigmented strain was isolated from a foot wound. The nonpigmented colonies from the left-knee and the left-foot wounds did not produce any pigment even after an extended period of incubation. The biochemical characteristics were the same for each strain except for oxidase and indole reactions. The pigmented strain was oxidase negative and indole positive, whereas the nonpigmented strains were oxidase positive and indole negative. The patients were successfully treated by debridement and with appropriate antibiotics.

Accidents, Occupational↗