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Biomedical subjects

K Han

Publications and source records attributed to K Han.

At least 55 records · Page 3Linked to original sources
PubMed1999

[A study of the maximal mouth opening movement of normal subjects].

OBJECTIVE: The aim of this paper was to study condyle movement and the relation between it and incisor movement when the subjects performed maximal open-closed movement. METHODS: 38 normal students were tested by a six degrees of freedom mandibular movement recorder MT-1602. The traces and velocity curves of the condyle movement were analized on the horizontal plane. RESULTS: (1) The horizontal traces of condyle movements included straight line and smooth curve. (2) The velocity curve was like triangle. Acceleration was constant before and behind the peak respectively. (3) Unequal velocity of the bilateral condyles was common. (4) The appearances of traces correlated with the beginning relative horizontal velocity of bilateral condyles. The tracing vector was inclined to the rapid side. (5) The incisor pathway was affected by both the relative horizontal velocity and the corresponding horizontal trace of the bilateral condyles. CONCLUSION: The movement of condyle were adaptable to the stomatognathic system.

Adult↗
PubMed1998

An analysis of two tandem promoters of the Drosophila purple gene.

We have analyzed two tandem promoters, separated by only about 400 bp, of the purple (pr) gene of Drosophila melanogaster, by fusing them to the firefly luciferase reporter gene and employing a transient expression assay with Drosophila S2 cells. Both the distal promoter and the proximal promoter were found to function in S2 cells and an about 700 bp long region (-270 to +421), containing both promoters, was sufficient to effect maximal promoter activity. When the two promoters were analyzed separately, the distal promoter was found to be much stronger in its function than the proximal promoter. At least three different kinds of cis elements near the transcription start site appear to play crucial roles in driving constitutive expression from the distal promoter. On the other hand, only a single cis element, which may play a role in tissue-specific expression, appears to be important for the activity of the proximal promoter in S2 cells. We propose that the clustering of important cis elements near the transcription start sites may be responsible for the selective regulation of the two tandem promoters.

Animals↗
PubMed1998

Promoter analysis of the Drosophila genes encoding TFIIB and TATA box-binding protein.

We have analyzed the 5'-flanking regions of the Drosophila genes encoding the TFIIB and TATA box-binding proteins (TBP) and mapped the regulatory regions required for their efficient expression. We found that the 500 bp long region (-439 to +60) and the 401 bp long region (-261 to +138) are required for the efficient expression of TFIIB and TBP genes, respectively. In the TFIIB promoter region, the upstream DNA between -439 and -280 and the downstream DNA between +8 and +60 are necessary for the stimulation of promoter activity. The upstream DNA between -439 and -280 stimulates transcription in an orientation dependent manner. In the TBP promoter region, the upstream DNA between -261 and -207, and the downstream DNA between +15 and +138 are necessary for the stimulation of promoter activity. The upstream DNA (-261 to -207) required for TBP promoter activity contains a 11 bp long palindromic sequence and a DNA replication-related element sequence. Particularly, we could find that the downstream promoter regions of TFIIB and TBP genes contain the conserved nucleotide sequences, suggesting the presence of a common regulatory mechanism for the expression of these two genes.

Animals↗
PubMed1998

IL-4 inhibits mouse mast cell Fc epsilonRI expression through a STAT6-dependent mechanism.

Mast cell activation by IgE-mediated stimuli is a central event in atopic disease. The regulation of the mast cell high affinity receptor, Fc epsilonRI, is poorly understood. We show that IL-4 can inhibit Fc epsilonRI expression on mouse bone marrow-derived mast cells and fetal liver-derived mast cell progenitors. This effect could be observed at 2.5 ng/ml IL-4 and was dose dependent. IL-4-mediated inhibition of cultured BMMC required 4 days of stimulation and was sustained at maximum levels for at least 21 days. The inhibition of Fc epsilonRI expression resulted in decreased sensitivity to IgE-mediated stimulation, as measured by serotonin release, and the induction of mRNA for IL-4, IL-5, IL-6, and IL-13. Additionally, IL-4 could abrogate the IgE-mediated increase in Fc epsilonRI expression. Lastly, IL-4-mediated inhibition was dependent upon expression of the STAT6 transcription factor, as STAT6-deficient bone marrow-derived mast cells did not decrease Fc epsilonRI levels in response to IL-4. These data argue for a homeostatic role of IL-4 in the regulation of Fc epsilonRI expression, a role that could be critical to understanding atopic disease.

Animals↗
PubMed1998

Isolation and characterization of the Drosophila melanogaster cDNA encoding the sepiapterin reductase.

We have isolated and characterized the cDNA encoding Drosophila melanogaster sepiapterin reductase (SR). The amino acid sequence deduced from the cDNA sequence was 29% identical to those of mammalian SRs. The active site residues proposed from the three-dimensional structure of mouse SR are well conserved in Drosophila SR. The protein-coding region of the cDNA was expressed in Escherichia coli as a histidine fusion protein, and the resulting recombinant protein proved to have SR activity. The SR activity of the recombinant protein was inhibited by two indoleamines, N-acetyl serotonin and melatonin. Southern analysis suggests that the Drosophila SR gene is encoded by a single copy gene. RNA blot analysis revealed that the gene expresses 1.5 kb mRNA in both adult heads and bodies.

Alcohol Oxidoreductases↗
PubMed1998

Molecular characterization of the Drosophila melanogaster gene encoding the pterin 4alpha-carbinolamine dehydratase.

We have isolated and characterized the cDNA and the genomic DNA encoding Drosophila melanogaster pterin 4alpha-carbinolamine dehydratase (PCD). The amino acid sequence deduced from the cDNA sequence was very similar to those of PCDs previously reported in other species (19-57% identity). The protein coding region of the cDNA was expressed in E. coli as a histidine fusion protein, and the expressed protein proved to have PCD activity. The characterization of the Drosophila genomic clone revealed that the Drosophila PCD gene is interrupted by two introns. The potential promoter region, deduced from the determination of the transcription start point (tsp), lacks the distinct TATAAA box consensus sequence.

Amino Acid Sequence↗
PubMed1998

Suppression of hepatoma growth and angiogenesis by a fumagillin derivative TNP470: possible involvement of nitric oxide synthase.

TNP470, a derivative of fumagillin, suppressed in vivo growth of human PLC/PRF/5 hepatoma and ameliorated cachexia of hepatoma-bearing mice. These in vivo effects were associated with reductions in microvessel and macrophage counts. In in vitro experiments, TNP470 inhibited the growth and migration of human hepatoma and bovine vascular endothelial (VE) cells. TNP470 did not inhibit the production of VE growth factor by the hepatoma, which suggests that this compound acts directly on VE cells in vivo. In contrast, TNP470 inhibited the production of leukemia inhibitory factor, which may be related to the amelioration of cancer cachexia. TNP470 induced apoptosis and enhanced the expression of beta-galactosidase, a biomarker of senescence, which was partly mimicked by a nitric oxide (NO) donor S-nitroso-N-acetyl penicillamin. TNP470 inhibited myristoylation and membrane translocation of NO synthase and increased the cellular content of NO synthase and production of NO. Therefore, it is suggested that the actions of TNP470 are mediated, at least in part, through the inhibition of membrane translocation of biologically active proteins.

Animals↗
PubMed1998

2-Methoxyestradiol, an endogenous metabolite of estrogen, enhances apoptosis and beta-galactosidase expression in vascular endothelial cells.

2-Methoxyestradiol (2ME) is an endogenous metabolite of estradiol (E2) and is known to inhibit tumor angiogenesis. In the present study, the direct effects of 2ME on the vascular endothelial cells were examined. 2ME enhanced apoptosis and beta-galactosidase expression in bovine vascular endothelial cells. A nitric oxide (NO) donor S-nitroso-N-acetyl penicillamin (SNAP) also enhanced beta-galactosidase expression, suggesting a possible role of NO in mediating the action of 2ME. 2ME increased the cellular content of nitric oxide synthase (NOS) and the production of NO. In addition, 2ME altered the membrane localization pattern of NOS. These suggest that the effects of 2ME on apoptosis and senescence of vascular endothelial cells were mediated, at least partly, by NOS and NO.

2-Methoxyestradiol↗
PubMed1998

Recombinant flounder growth hormone from Escherichia coli: overexpression, efficient recovery, and growth-promoting effect on juvenile flounder by oral administration.

An efficient production method for recombinant flounder growth hormone (r-fGH) from Escherichia coli was developed and the biological activity of purified r-fGH was examined using juvenile flounder. The use of bicistronic construction in the expression plasmid resulted in the production of over 40% of the E. coli cellular protein as r-fGH. The r-fGH was recovered from cell lysates following inclusion body washing, solubilization and refolding in sodium dodecylsulfate (SDS) solution, and removal of contaminated proteins with secondary butanol treatment. The SDS content in purified r-fGH solution was adjusted to appropriate levels by diafiltration. More than 47% of the r-fGH was recovered from the E. coli cell lysates and the purity of recovered r-fGH was 98%. The oral administration of purified r-fGH to juvenile flounder, once a week for 4 weeks at a dosage of 40 micrograms r-fGH g-1 fish body weight, resulted in significant increases both in weight and length. These results of overexpression, simple purification with high recovery yield and purity, and good growth-promoting activity of the r-fGH suggest that the production scheme described in this study is useful for the potential application of r-fGH in fish farming.

Administration, Oral↗
PubMed1998

A comparison of multileaf-collimator and alloy-block field shaping.

PURPOSE: The purpose of this report was to compare the dose distribution at a field edge defined with divergent alloy blocks to the distribution obtained with a multileaf collimator (MLC). The comparison is made for simple block replacement situations. METHODS AND MATERIALS: A tertiary multileaf collimator mounted on a linear accelerator operating at 6 MV was compared to divergent alloy blocks positioned at the level of the blocking tray. The leaves of the MLC were positioned to give maximum stepping (leaf displacement equals leaf width), and the blocking produced the same field shape. Three different treatment plans were compared: single field, opposed fields, and a four-field "box." Dose distributions were determined using radiographic film scanned with a laser densitometer with a 0.45-mm spot size. One experiment was repeated using radiochromic film with reduced energy dependence. Dose distributions were examined on the isocenter plane, and on planes displaced by 1.0 and 2.5 cm. The effect of daily setup variations was also studied by comparing a single fraction treatment with a fractionated treatment consisting of 15 fields slightly displaced relative to each other. The magnitude of these displacements was determined using available literature on treatment reproducibility. RESULTS: For a single field plan, maximum stepping of an MLC-defined edge produces an obvious undulating dose pattern compared to an alloy block edge. At the isocenter plane, this pattern is unchanged when parallel opposed fields are used. However, blurring occurs for both MLC and block edges when planes displaced from the isocenter are examined. The gradient for the block edge is 8%/mm for opposed fields and a plane 2.5 cm from the isocenter, compared to 15%/mm for the isocenter plane. Adding two additional fields does not change the dose pattern in the isocenter plane, but does reduce the gradient across the steepest portion of the penumbra to 8%/mm, and shifts the isodose line with the most pronounced stepping to higher values (from 50 to 80%). Introducing daily setup variations results in a reduction of the sharp dose gradient along the sides of a single field, and around the periphery of the beam at the isocenter plane of opposed fields. Smaller changes are found for edges already blurred by other factors. Radiochromic film was generally noisier than radiographic film, but comparison of the two films did not show a significant difference, indicating that the energy dependence of the radiographic film was not a problem. CONCLUSIONS: The obvious dose stepping seen on a portal image of a single field with MLC shaping is shown to be partially erased by the addition of other fields, and for planes away from the isocenter. However, the effects of daily setup variations must be included to more effectively blur dose stepping along the external envelope of a single field or near the isocenter plane of opposed fields. This result conflicts with attempts to improve immobilization.

Particle Accelerators↗
PubMed1998

Metabolism of an anionic fluorescent dye, 1-anilino-8-naphthalene sulfonate (ANS) by rat liver microsomes.

The present study was designed to examine the metabolism of 1-anilino-8-naphthalene sulfonate (ANS), an anionic compound which is transported into liver via "multispecific organic anion transporter", with rat hepatic microsomes. TLC analysis indicated that the fluorescent metabolites were not produced to a measurable extent, which made it possible to assess the ANS metabolism by measuring the fluorescence disappearance. The metabolism of ANS was remarkably inhibited by the presence of SKF-525A as well as by the substitution of O2 by CO gas. ANS metabolism by microsomes also required NADPH as a cofactor. These results indicated that the microsomal monooxygenase system might be mainly responsible for the ANS metabolism. The maximum velocity (Vmax) and Michaelis constant (K(m)) were calculated to be 4.3 +/- 0.2 nmol/min/mg protein and 42.1 +/- 2.0 microM, respectively. Assuming that 1 g of liver contains 32 mg of microsomal protein, the Vmax value was extrapolated to that per g of liver (Vmax'). The intrinsic metabolic clearance (CLint) under linear conditions calculated from this in vitro metabolic study was 3.3 ml/min/g liver, being comparable with that (3.0 ml/min/g liver) calculated by analyzing the in vivo plasma disappearance curve in a previous study. Furthermore, the effects of other organic anions on the metabolism of ANS were examined. Bromophenolblue (BPB) and rose bengal (RB) competitively inhibited the metabolism of ANS, while BSP inhibited it only slightly. The inhibition constant (Ki) of BPB (6 microM) was much smaller than that of RB (200 microM). In conclusion, the microsomal monooxygenase system plays a major role in the metabolism of ANS, and other unmetabolizable organic anions (BPB and RB) compete for this metabolism.

Anilino Naphthalenesulfonates↗
PubMed1998

Ocular absorption of Pz-peptide and its effect on the ocular and systemic pharmacokinetics of topically applied drugs in the rabbit.

PURPOSE: To determine the corneal and conjunctival penetration of 4-phenylazobenzyloxycarbonyl-L-Pro-L-Leu-Gly-L-Pro-D-Arg (Pz-peptide) and to evaluate its effect on the corneal and conjunctival penetration of hydrophilic solutes as well as on the ocular and systemic absorption of topically applied atenolol and propranolol in the rabbit. The hydrophilic solutes were mannitol, fluorescein, FITC-dextran 4,000, and FITC-dextran 10,000. METHODS: Drug penetration across the rabbit cornea and conjunctiva was evaluated using the modified Ussing chamber. Ocular and systemic absorption of topically applied atenolol and propranolol was evaluated by analyzing the drug concentration in various anterior segment tissues at 45 min and in the blood over 240 min, respectively, following topical instillation of 25 microl of 20 mM atenolol or propranolol solution to the rabbit eye. RESULTS: The conjunctiva was 29 times more permeable than the cornea to 3 mM Pz-peptide. Conjunctival Pz-peptide transport was 1.7 times more extensive in the mucosal-to-serosal than in the opposite direction, whereas corneal Pz-peptide transport showed no directionality. The apparent permeability coefficient of Pz-peptide across the cornea and the conjunctiva increased over the 1-5 mM range, suggesting that Pz-peptide enhanced its own transport across both epithelial tissues. The cornea appeared to be more sensitive than the conjunctiva to the penetration enhancement effect of Pz-peptide. Thus, whereas Pz-peptide elevated the corneal transport of mannitol, fluorescein, and FD4 by 50%, 57%, and 106%, respectively, it did not affect the conjunctival transport of mannitol and fluorescein, while enhancing FD4 transport by only 46%. Moreover, while Pz-peptide enhanced the ocular absorption of topically applied hydrophilic atenolol, it did not affect the ocular absorption of lipophilic propranolol. Interestingly, Pz-peptide did not affect the systemic absorption of either beta adrenergic antagonist. CONCLUSIONS: Pz-peptide appears to facilitate its own penetration across the cornea and the conjunctiva. Pz-peptide appears to increase the ocular absorption of topically applied hydrophilic but not lipophilic drugs, while not affecting the systemic absorption of either type of drugs.

Actins↗
PubMed1998

Acute lymphoblastic leukemia with maturation--a new entity with clinical significance.

The diagnosis of 'ALL with maturation' (ALLm) is proposed. One hundred and one patients with untreated ALL were entered into this study. The diagnosis of ALLm was made when more than 20% of all nucleated elements in the bone marrow showed maturation beyond prolymphocytes by light microscopic examination. The mature-appearing leukemic cells showed the same immunophenotype to remaining lymphoblasts. The number of ALLm cases was 19 (18.8%). The mean age at presentation of ALLm was 29 +/- 18, older than that of 18 +/- 16 of the remaining typical ALL (ALLt) (P = 0.015). Remission was induced with daunorubicin, vincristine, prednisone and L-asparaginase. Only two of 19 ALLm patients achieved CR after 4 weeks induction chemotherapy. In contrast, 57 of 82 (69.5%) ALLt patients achieved CR after the same induction chemotherapy. There was no significant difference in immunophenotype of ALLm compared with ALLt. Labeling index of DNA topoisomerase IIalpha (TopoLI) was studied by immunohistochemistry. Initial TopoLI of ALLm (221 +/- 147) was much lower than that of ALLt (609 +/- 262, P = 0.005). Furthermore, the remaining leukemic cells after chemotherapy were not labeled with anti-DNA topoisomerase IIalpha. The P53 protein was expressed in nine of 18 ALLm cases (50.0%) and P-glycoprotein was not expressed in ALLm cases. Twelve of 19 ALLm cases were studied for carrying bcr/abl fusion by karyotyping and/or fluorescent in situ hybridization. Only two cases revealed bcr/abl fusion. In conclusion, ALLm is a separate entity of ALL which has a very poor clinical course and is independent of other prognostic factors. The morphologically mature leukemic cells are in resting GO phase.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1998

Cloning of the Alcaligenes latus polyhydroxyalkanoate biosynthesis genes and use of these genes for enhanced production of Poly(3-hydroxybutyrate) in Escherichia coli.

Polyhydroxyalkanoates (PHAs) are microbial polyesters that can be used as completely biodegradable polymers, but the high production cost prevents their use in a wide range of applications. Recombinant Escherichia coli strains harboring the Ralstonia eutropha PHA biosynthesis genes have been reported to have several advantages as PHA producers compared with wild-type PHA-producing bacteria. However, the PHA productivity (amount of PHA produced per unit volume per unit time) obtained with these recombinant E. coli strains has been lower than that obtained with the wild-type bacterium Alcaligenes latus. To endow the potentially superior PHA biosynthetic machinery to E. coli, we cloned the PHA biosynthesis genes from A. latus. The three PHA biosynthesis genes formed an operon with the order PHA synthase, beta-ketothiolase, and reductase genes and were constitutively expressed from the natural promoter in E. coli. Recombinant E. coli strains harboring the A. latus PHA biosynthesis genes accumulated poly(3-hydroxybutyrate) (PHB), a model PHA product, more efficiently than those harboring the R. eutropha genes. With a pH-stat fed-batch culture of recombinant E. coli harboring a stable plasmid containing the A. latus PHA biosynthesis genes, final cell and PHB concentrations of 194.1 and 141.6 g/liter, respectively, were obtained, resulting in a high productivity of 4.63 g of PHB/liter/h. This improvement should allow recombinant E. coli to be used for the production of PHB with a high level of economic competitiveness.

Acyltransferases↗
PubMed1998

Reconstruction of three-dimensional digital teeth.

OBJECTIVE: Dental anatomy is one of the most important basic courses in the education of dentistry. The deep understanding of both the external and internal morphologic characteristics is very important to the teaching, research and clinical practice of dentistry. METHODS: In the present study, 32 permanent teeth from the skull specimen of a young man were individually embedded in black fluid resin, each in special containers. They were ground by a numerically-controlled grinding machine at intervals of 0.2 mm per layer. A distinct outline of the tooth could be seen on every section. Black and white photographs were taken and scanned into a computer by a film-scanner to obtain sequences of two-dimensional images of the tooth sections. After pattern recognition, all of the images of each tooth were piled up at intervals of 0.2 mm by the technique of computerized reconstruction. RESULTS: The three-dimensional stereo tooth models were built up from two-dimensional data. On the basis of those models, computer graphic techniques were used to highlight, smooth, and shade the teeth. These digital teeth and dentitions could function as a series of computerized teaching models. Their high resolution and accuracy could meet the basic demands of dentistry. CONCLUSIONS: The present study developed new techniques of model preparation, image input, and 3-D reconstruction. These digital teeth and dentitions provide an important foundation for the application of computer imaging, CAD/CAM, computer-assisted instruction, and virtual reality in dentistry.

Anatomy, Cross-Sectional↗