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Y Lee

Publications and source records attributed to Y Lee.

At least 379 records · Page 21Linked to original sources
PubMed1995

Synthesis of 3,4-di-O-acetyl-2,5-anhydro-1,6-dideoxy-1,6-diiodo-D-mannitol. Comparison of NMR spectral results for the solid state and solution with those of the X-ray structural determination.

3,4-Di-O-acetyl-2,5-anhydro-1,6-dideoxy-1,6-diiodo-D-mannitol (3) is prepared from 2,5-anhydro-D-mannitol (1) in three steps. The solution and solid-state NMR spectra of 3 indicate considerable variation in conformation. In solution, it adopts, on average, a symmetric 4T3 conformation, whereas in the solid state it adopts an asymmetric conformation as revealed by 13C NMR cross polarization and magic angle spinning techniques. A single-crystal X-ray structure analysis confirmed the asymmetric conformation of 3 in a monoclinic crystal, space group P2(1) with a = 8.9608(4), b = 8.6348(5), c = 9.6468(4) A, beta = 96.139(4) degrees, V = 742.1(1) A3, Dc = 2.085 g cm-3, mu (MoK alpha) = 4.2 mm-1, and Z = 2. The structure was refined to R = 0.039 and Rw = 0.047 for 5181 observed reflections. The furanoid ring of 3 adopts an envelope E5 conformation slightly distorted towards 4T5, with puckering parameters psi = 313.49 degrees and q = 0.37 A. The asymmetric conformation is rationalized in terms of the weak packing forces in the crystal.

Crystallography, X-Ray↗
PubMed1995

In vivo analyses of the internal control region in the 5S rRNA gene from Saccharomyces cerevisiae.

The internal control region of the Saccharomyces cerevisiae 5S rRNA gene has been characterized in vivo by genomic DNase I footprinting and by mutational analyses using base substitutions, deletions or insertions. A high copy shuttle vector was used to efficiently express mutant 5S rRNA genes in vivo and isotope labelling kinetics were used to distinguish impeded gene expression from nascent RNA degradation. In contrast to mutational studies in reconstituted systems, the analyses describe promoter elements which closely resemble the three distinct sequence elements that have been observed in Xenopus laevis 5S rRNA. The results indicate a more highly conserved structure than previously reported with reconstituted systems and suggest that the saturated conditions which are used in reconstitution studies mask sequence dependence which may be physiologically significant. Footprint analyses support the extended region of protein interaction which has recently been observed in some reconstituted systems, but mutational analyses indicate that these interactions are not sequence specific. Periodicity in the footprint provides further detail regarding the in vivo topology of the interacting protein.

Base Sequence↗
PubMed1995

Collateral sensitivity to radiation and cis-platinum in a multidrug-resistant human leukemia cell line.

Although collateral sensitivity to gamma radiation has previously been described in multidrug-resistant tumor cell lines, we describe here a multidrug-resistant human T-cell acute lymphatic leukemia cell line, L100, which displayed increased sensitivity to both gamma radiation and cis-platinum. Cis-platinum cytotoxicity of parental L0 cells and L100 cells was enhanced, whereas radiation sensitivity of L0 and L100 cells was unaltered by glutathione depletion. These results indicate that disparate mechanisms are operative in the collateral sensitivity of L100 cells to gamma radiation and cis-platinum.

Antineoplastic Agents↗
PubMed1995

Position of the sulfhydryl group and the disulfide bonds of human glucocerebrosidase.

Purified human glucocerebrosidase isolated from placenta was modified with [14C]-iodoacetic acid without reduction and digested with both protease-V8 at pH 4.0 followed by alpha-chymotrypsin at pH 7.5. The majority of radioactivity was found in a peptide that contained the [14C]-carboxymethylated-cysteine identified as CM-Cys18. Direct sequencing of the N-terminus of the intact labeled protein confirmed the modification of Cys18. For identification of disulfide bond-containing peptides, another portion of glucocerebrosidase was alkylated with nonlabeled iodoacetic acid and then digested with protease V8 and alpha-chymotrypsin as before. Twenty-eight HPLC fragments were collected. These purified peaks were then reduced with beta-mercaptoethanol followed by S-carboxymethylation with [14C]-iodoacetic acid. Three peptides among these 28 peptides generated two radioactive daughter peptides. These peptides were sequenced and the position of the radioactive CM-cysteines identified. The locations of these disulfides are Cys4-Cys16, Cys23-Cys342, and Cys126-Cys248. Attempts to reproduce the free sulfhydryl labeling experiments using the glucocerebrosidase isolated from Ceredase proved unsuccessful. No label was incorporated by this enzyme prior to reduction. This result suggests that the form of the protein used in the clinic differs from the native protein.

Amino Acid Sequence↗
PubMed1995

Learning rules to predict rodent carcinogenicity of non-genotoxic chemicals.

The results of short-term assays (induction of chromosomal aberrations and sister-chromatid exchanges, oncogenic transformations and cellular toxicity) together with MTD (maximum tolerated dose) values and physical chemical properties of non-genotoxic (i.e. Salmonella non-mutagens) carcinogens and non-carcinogens were submitted to RL, an inductive learning program. RL was able to learn rules that correctly predicted between 70 and 80% of non-genotoxic chemicals. This is a marked improvement over current predictions using only the results of short-term assays and exceeds the predictions of human experts that used the whole spectrum of acute and subchronic toxicity results as well as human knowledge and intuition.

Animals↗
PubMed1995

A cellular automaton model for the proliferation of migrating contact-inhibited cells.

A cellular automaton is used to develop a model describing the proliferation dynamics of populations of migrating, contact-inhibited cells. Simulations are carried out on two-dimensional networks of computational sites that are finite-state automata. The discrete model incorporates all the essential features of the cell locomotion and division processes, including the complicated dynamic phenomena occurring when cells collide. In addition, model parameters can be evaluated by using data from long-term tracking and analysis of cell locomotion. Simulation results are analyzed to determine how the competing processes of contact inhibition and cell migration affect the proliferation rates. The relation between cell density and contact inhibition is probed by following the temporal evolution of the population-average speed of locomotion. Our results show that the seeding cell density, the population-average speed of locomotion, and the spatial distribution of the seed cells are crucial parameters in determining the temporal evolution of cell proliferation rates. The model successfully predicts the effect of cell motility on the growth of isolated megacolonies of keratinocytes, and simulation results agree very well with experimental data. Model predictions also agree well with experimentally measured proliferation rates of bovine pulmonary artery endothelial cells (BPAE) cultured in the presence of a growth factor (bFGF) that up-regulates cell motility.

Algorithms↗
PubMed1995

Laparoscopically assisted transperineal interstitial brachytherapy with omental flap for locally recurrent endometrial cancer.

In most cases, Syed-Neblett template placement is blind with respect to intraperitoneal structures. We evaluated the feasibility of laparoscopic assistance to add a potentially useful dimension to this technique. Two patients successfully underwent laparoscopic lysis of pelvic adhesions, assisted needle placement and creation of an omental pelvic carpet to protect the small intestine. The procedure resulted in avoidance of direct vascular and bowel injury and more appropriate depth of needle placement at 24 and 26 month follow-up, there is no evidence of radiation induced complications. The technique of laparoscopically assisted Syed-Neblett placement as described is feasible and may decrease operative and radiation associated morbidity.

Brachytherapy↗
PubMed1995

Generation and characterization of monoclonal antibodies specific to surface antigens of human trophoblast cells.

PROBLEM: To generate and utilize specific monoclonal antibodies for routine fetal cell isolation from the maternal circulation. METHODS: Monoclonal antibodies specific to human trophoblast cell surface antigens were generated and characterized. After cell fusion, antibodies secreted by hybridomas were screened by enzyme-linked immunosorbent assay and immunohistochemical assays. RESULTS: By using cultured BeWo choriocarcinoma cells or the membrane fraction of human placenta as the immunogen, seven (BW-108, 110, 123, 124, HP-15, 16 and 17) antibodies specific to the surface antigens of trophoblast were produced. They were shown to have little cross-reactivity to other human tissues. Among the antibodies raised against human sperm, HSA-10 was also found to cross-react with human trophoblast, but not detected in other tissues. When immobilized to magnetic beads, these antibodies were shown to react only with BeWo cells in suspension, but not blood cells and ovarian carcinoma cell line, OC-3-VGH. CONCLUSION: Therefore, these antibodies may have potential application in fetal trophoblast cell isolation from the maternal circulation for prenatal genetic diagnosis.

Acrosome↗
PubMed1995

Sambutoxin-producing isolates of fusarium species and occurrence of sambutoxin in rotten potato tubers.

A total of 50 Fusarium isolates representing 13 species from various sources were surveyed to determine their potential to produce sambutoxin. Sambutoxin production was restricted to Fusarium sambucinum and F. oxysporum, with the exception of one isolate of F. semitectum. Sambutoxin was produced by high percentages of F. sambucinum (80.0%) and F. oxysporum (84.6%) isolates at levels of 1.1 to 101.0 (mu)g/g. In addition, 9 (42.9%) of 21 rotten potato samples were contaminated with sambutoxin at levels of 15.8 to 78.1 ng/g.

Journal Article↗
PubMed1995

Cultural differences in Korean- and Anglo-American preschoolers' social interaction and play behaviors.

48 Korean- and 48 Anglo-American children were observed in their preschool settings to examine the role of culture in organizing children's activities and in shaping their pretend play behavior. Observes recorded the presence or absence of preselected social behaviors and levels of play complexity. Parents completed a questionnaire about play in the home, teachers rated children's social competence, and children were given the PPVT-R and a sociometric interview. Korean parents completed an acculturation questionnaire. The findings revealed cultural differences in children's social interaction, play complexity, adult-child interaction and play in the home and in the preschool, adult beliefs about play, scores on the PPVT-R, and children's social functioning with peers. The results suggest that children's social interaction and pretend play behavior are influenced by culture-specific socialization practices that serve adaptive functions.

Acculturation↗
PubMed1995

Radiation-induced superior vena cava syndrome.

A 59-year-old man developed superior vena caval obstruction 20 years after receiving a radiation treatment for primary germinal cell tumor of the mediastinum. Venous decompression was achieved by anastomosing a 10-mm ringed polytetrafluoroethylene graft from the left internal jugular vein to the right atrium, which yielded immediate relief of symptoms. A left internal jugular venogram demonstrated graft patency 11 months post-operatively, and the patient remained free of symptoms of superior vena caval obstruction 29 months postoperatively.

Cobalt Radioisotopes↗