Biomedical subjects

S Y Hwang

Publications and source records attributed to S Y Hwang.

At least 19 recordsLinked to original sources

PubMed2005

Molecular determination of the origin of acephalic cysticercus.

Acephalic cysticercus (Ac), a rarely developed multilobulated and nonencysted form of larval Taenia, causes hydrocephalus or adhesive arachnoiditis in the ventricles and subarachnoidal space that often lead to fatal outcome in affected patients. Ac has been proposed to originate from T. solium on the basis of morphological features, while no molecular data supporting the presumption have been available. In the present study, we investigated the immunological properties as well as molecular characteristics of Ac that was obtained surgically from 6 patients. Immunoblotting of the cyst fluid from Ac samples demonstrated the constitutive expression of a T. solium metacestode (TsM) 10 kDa protein. Specific antibodies against the truncated 10 kDa protein, which appears to be species specific for TsM cysticercosis, were detected in both serum and cerebrospinal fluid samples of Ac patients. Nucleotide sequences of mitochondrial cytochrome c oxidase subunit I (COI) and NADH dehydrogenase subunit 1 (ND1) genes of Ac were almost identical to those of T. solium but differed substantially from those of the other Taenia species. In phylogenetic analysis, Ac clustered with T. solium in a well-supported clade. Our results strongly suggest that Ac may have originated from T. solium.

Amino Acid Sequence↗

PubMed2004

Genetic diversity and biogeography of Cunninghamia konishii (Cupressaceae), an island species in Taiwan: a comparison with Cunninghamia lanceolata, a mainland species in China.

Luanta-fir (Cunninghamia konishii), an endemic to Taiwan, is an outcrossing, long-lived conifer. Populations of C. konishii are generally fragmented due to a once high intensity of timber exploitation. C. konishii and Cunninghamia lanceolata are two sibling taxa constituting derivative-progenitor species relationship. The amount of genetic variations within and between 11 and 10 populations of C. konishii and C. lanceolata, respectively, were assessed using amplified fragment length polymorphism (AFLP) markers in this report. Three AFLP primer pairs generated a total of 357 and 226 markers for C. konishii and C. lanceolata samples, of which 56.1 and 65.3% are polymorphic, respectively. Analysis of molecular variance indicates a 4.78% variation between C. konishii and C. lanceolata. A relatively high value of genetic variation (24.60%) was apportioned between the populations of C. konishii. In contrast, a lower divergence value (12.21%) between populations was found for C. lanceolata. The population with the highest genetic diversity was found in Nantou County, which concurred with the results of many other tree species investigated in Taiwan. The estimates of the number of migrants between populations (Nm), obtained from population pair-wise PhiST, suggest that gene flow in C. konishii is efficient in some adjacent populations but is restricted in the rest. Individual UPGMA tree, generated based on AFLP markers, suggests six evolutionary lineages for C. konishii. All evolutionary lineages of C. konishii were derived from C. lanceolata. In conclusion, the migration patterns of Cunninghamia from mainland China may have been established following multiple sources, migrant-pools, long-distance dispersal events, and via different directions.

Genetic Variation↗

PubMed2004

Management dilemmas in laryngeal trauma.

Laryngeal trauma is an uncommon injury. This has made it difficult for a common management pathway to evolve and controversies remain. Methods of airway control, usage of investigations and the role of stents or plates in surgical management are reviewed. It is important not to delay treatment due to the poor voice and airway outcome of chronic laryngeal stenosis.

Airway Obstruction↗

PubMed2003

Free radical-scavenging activity of Taiwanese native plants.

The 70% aqueous acetone extracts of ten Taiwanese native plants were evaluated by various antioxidant assays, including 1, 1-diphenyl-2-picrylhydrazyl (DPPH), hydroxyl (.OH) radicals, and reducing power assay. In the present study, extracts of Acer buerferianum var. formosanum, Cleyera japonica var. morii, Cyclobalanopsis stenophylla var. stenophylloides, and Machilus zuihoensis exhibited stronger activity against DPPH radicals, and their IC50 values ranged from 5.4 to 8.3 microg/ml. The ten selected extracts effectively inhibited the formation of .OH generated in the Fenton reaction system. Among the extracts whose reducing power activities were determined, A. buerferianum var. formosanum, C. japonica var. morii, C. stenophylla var. stenophylloides, Eriobotrya deflex, and M. zuihoensis showed high activity. The results indicate the 70% aqueous acetone extracts of A. buerferianum var. formosanum, C. japonica var. morii, C. stenophylla var. stenophylloides, and M. zuihoensis with great potency in these assay systems and may be candidates for the development of natural antioxidants.

Acer↗

PubMed2003

Degradation of phenanthrene and naphthalene by a Burkholderia species strain.

Burkholderia sp. TNFYE-5 was isolated from soil for the ability to grow on phenanthrene as sole carbon and energy source. Unlike most other phenanthrene-degrading bacteria, TNFYE-5 was unable to grow on naphthalene. Growth substrate range experiments coupled with the ring-cleavage enzyme assay data suggest that TNFYE-5 initially metabolizes phenanthrene to 1-hydroxy-2-naphthoate with subsequent degradation through the phthalate and protocatechuate and beta-ketoadipate pathway. A metabolite in the degradation of naphthalene by TNFYE-5 was isolated by high-pressure liquid chromatography (HPLC) and was identified as salicylate by UV-visible spectral and gas chromatography-mass spectrometry analyses. Thus, the inability to degrade salicylate is apparently one major reason for the incapability of TNFYE-5 to grow on naphthalene.

Biodegradation, Environmental↗

PubMed2003

An audit of parotidectomy in Singapore: a review of 31 cases.

A series of 31 consecutive parotidectomies was evaluated. FNAC could differentiate tumour from non tumour in 72.8% of cases. For actual histology, FNAC was correct in 66.6%. Frozen section was correct in differentiating between benign, malignant and inflammatory conditions in all cases. Eighty-eight percent of frozen section histology concurred with final histology. The immediate postoperative period had 13 cases of facial nerve dysfunction, but only 3 cases had residual weakness. The branch most commonly affected was the mandibular branch (92.3%). Two patients had Frey's syndrome and one had a traumatic neuroma. FNAC and CT scans improve preoperative planning, providing histological evidence and the extent of the lesion.

Adult↗

PubMed2002

Field evaluation of the CATT/Trypanosoma brucei gambiense on blood-impregnated filter papers for diagnosis of human African trypanosomiasis in southern Sudan.

Most Human African Trypanosomiasis (HAT) control programmes in areas endemic for Trypanosoma brucei gambiense rely on a strategy of active mass screening with the Card Agglutination Test for Trypanosomiasis (CATT)/T. b. gambiense. We evaluated the performance, stability and reproducibility of the CATT/T. b. gambiense on blood-impregnated filter papers (CATT-FP) in Kajo-Keji County, South-Sudan, where some areas are inaccessible to mobile teams. The CATT-FP was performed with a group of 100 people with a positive CATT on whole blood including 17 confirmed HAT patients and the results were compared with the CATT on plasma (CATT-P). The CATT-FP was repeated on impregnated filter papers stored at ambient and refrigerated temperature for 1, 3, 7 and 14 days. Another 82 patients with HAT, including 78 with a positive parasitology, were tested with the CATT-FP and duplicate filter paper samples were sent to a reference laboratory to assess reproducibility. The CATT-FP was positive in 90 of 99 patients with HAT (sensitivity: 91%). It was less sensitive than the CATT-P (mean dilution difference: -2.5). There was no significant loss of sensitivity after storage for up to 14 days both at ambient and cool temperature. Reproducibility of the CATT-FP was found to be excellent (kappa: 0.84). The CATT-FP can therefore be recommended as a screening test for HAT in areas where the use of CATT-P is not possible. Further studies on larger population samples in different endemic foci are still needed before the CATT-FP can be recommended for universal use.

Agglutination Tests↗

PubMed2001

Interleukin-2 fusion protein with anti-CD3 single-chain Fv (sFv) selectively protects T cells from dexamethasone-induced apoptosis.

Apoptosis of mature T cells may be an important pathophysiologic mechanism in diseases such as AIDS, cancer, and autoimmunity. In this study, in order to selectively protect T cells from dexamethasone (DEX)-induced apoptosis we constructed a fusion protein (anti-CD3sFv-IL-2) in which anti-CD3 single-chain Fv (sFv), the smallest unit of antibody recognizing the CD3 epsilon moiety of the T-cell receptor (TCR), was covalently linked to murine interleukin-2 (IL-2). Recombinant anti-CD3sFv protein was also expressed and used as a control. The purified anti-CD3sFv-IL-2 protein displayed IL-2 bioactivity in an IL-2 proliferation assay, which was inhibited by a neutralizing mIL-2 mAb. The anti-CD3sFv-IL-2 protein protected T lymphoma cells (S49.1) from DEX-induced apoptosis as demonstrated by oligonucleosomal genomic DNA fragmentation assay, and also recovered proliferation capacity of DEX-treated S49.1 cells and increased T cell composition both in DEX-treated spleen cell-populations and in DEX-treated mice, while the anti-CD3sFv protein did not. In addition, the anti-CD3sFv-IL-2 fusion protein was more efficient than a simple mixture of anti-CD3sFv and free rIL-2 in selectively protecting T cells from DEX-induced apoptosis. The levels of bcl-2 gene expression were significantly increased in DEX-treated T cells in the presence of the anti-CD3sFv-IL-2 protein. These studies indicate that the anti-CD3sFv-IL-2 fusion protein can selectively protect T cells from DEX-induced apoptosis and that the covalent linkage of anti-CD3sFv and IL-2 confines the anti-apoptotic effect of IL-2 to T cells.

Animals↗

PubMed2001

Efficient induction of antigen-specific, T helper type 1-mediated immune responses by intramuscular injection with ovalbumin/interleukin-18 fusion DNA.

The balance of two types of T helper (Th) cells, Th1 and Th2 subsets, is important with respect to susceptibility or resistance to particular infections, or to autoimmune diseases and allergic diseases. To effectively induce Th1 immune responses in an antigen-specific manner, we constructed a mammalian expression plasmid (pOVA/IL-18) carrying a fusion gene in which the ovalbumin (OVA; a model antigen) cDNA was covalently linked to mature interleukin-18 (IL-18) cDNA. Intramuscular injection of C57BL/6 mice with the pOVA/IL-18 DNA efficiently increased the production of both OVA-specific IFN-gamma and anti-OVA IgG2a isotype, compared with the injection with the pOVA DNA. In addition, the pOVA/IL-18 was more efficient than a simple mixture of pOVA and pIL-18 in inducing antigen-specific, Th1 immune responses and in inhibiting OVA-specific, IL-4 production. These studies indicate that vaccination with the OVA/IL-18 fusion DNA efficiently induces Th1 immune response in an antigen-specific manner.

Animals↗

PubMed2001

Presumptive mechanisms of peptic ulceration by Helicobacter pylori VacA involving mucoprotease and CagA.

Helicobacter pylori vacuolating toxin (VacA) appears to be unusually stable, not only against extreme pH conditions or high temperatures, but also against common organic solvents or detergents. Under acidic conditions, its activity was markedly increased in the manner of temperature-independent, suggesting a spontaneous activation. A similar finding was also observed under alkaline conditions, however, it should have an appropriate temperature. From these observations, the mechanisms of VacA activation were suggested to be so redundant that either the case of acidic or basic amino acid residues could be involved in the VacA activation. Separately, we also found that the VacA production by H. pylori was pH-dependent: Its production was increased at a low pH region with a broad range (1.0-5.0), and at a high pH region with a narrow range (8.0-9.0). Astonishingly, a highly immunogenic CagA did not appear to be expressed under the acidic conditions. Its expression, however, was shown to be enhanced when the surrounding pH of this bacterium was raised. In contrast, mucoproteolytic activity in the H. pylori membrane was found to be increased at acidic conditions. Considering these observations, together with the stomach and duodenal pH of humans, two presumptive mechanisms of H. pylori VacA-associated ulceration may be deduced; namely, an acid- and an alkali-dependent type, involving mucoprotease and CagA, respectively.

Antigens, Bacterial↗

PubMed2001

Expression of genes involved in mammalian meiosis during the transition from egg to embryo.

The ooplasm of higher eukaryotes provides substances necessary for completing the last stages of meiosis and initiating the first mitotic division. These processes are firmly attuned to other events in the egg and newly formed embryo, such as switching from the use of maternal transcripts to the onset of zygotic transcription. In mammals little is known about the molecular mechanisms guiding this transition, largely due to the lack of information about genes expressed in the egg and early embryos. Studies of yeast mitosis have contributed much of what is known about the vertebrate cell cycle, and recent reports indicate that homologs of yeast DNA repair genes also function during mammalian gametogenesis. To examine whether this conservation can be expanded to include genes operative in oocyte meiosis, we performed a computer-based search for homologs of yeast genes that are induced during sporulation in C. elegans, Drosophila, and mammals. Results from this study suggest that yeast and higher eukaryotes share genes that coordinate the overall process of meiosis. However intriguing differences exist, reflecting the distinctive mechanisms governing the progression of meiosis in each organism. ESTs representing more than half of the mammalian homologs are present in mouse cDNA libraries that contains genes controlling the meiosis/mitosis transition. About 50% of these genes contain potential cis-elements for cytoplasmic polyadenylation in their 3'-UTR, suggesting the importance of controlled translation in the egg and zygote.

Animals↗

PubMed2001

Inhibition of interleukin-12 production by auranofin, an anti-rheumatic gold compound, deviates CD4(+) T cells from the Th1 to the Th2 pathway.

1. Interleukin-12 (IL-12) may play a central role in the development and progression of rheumatoid arthritis by driving the immune response towards T helper 1 (Th1) type responses characterized by high IFN-gamma and low IL-4 production. In this study we investigated the effect of auranofin (AF), an anti-rheumatic gold compound, on IL-12 production in mouse macrophages and dendritic cells, and studied whether AF-mediated inhibition of IL-12 production could regulate a cytokine profile of antigen (Ag)-primed CD4(+) Th cells. 2. Treatment with AF significantly inhibited IL-12 production in lipopolysaccharide (LPS)-stimulated macrophages and also in CD40L-stimulated dendritic cells. AF-pretreated macrophages reduced their ability to induce IFN-gamma and increased the ability to induce IL-4 in Ag-primed CD4(+) T cells. AF did not influence the cell surface expression of the class II MHC molecule and the costimulatory molecules CD80 and CD86. 3. Addition of recombinant IL-12 to cultures of AF-pretreated macrophages and CD4(+) T cells restored IFN-gamma production in Ag-primed CD4(+) T cells. 4. The in vivo administration of AF resulted in the inhibition of IL-12 production by macrophages stimulated in vitro with LPS or heat-killed Listeria monocytogenes (HKL), leading to the inhibition of Th1 cytokine profile (decreased IFN-gamma and increased IL-4 production) in Ag-primed CD4(+) T cells. 5. These findings may explain some known effects of AF including anti-rheumatic effects and the inhibition of encephalitogenicity, and point to a possible therapeutic use of AF in the Th1-mediated immune diseases such as autoimmune diseases.

Animals↗

PubMed2001

Structure-function studies of Escherichia coli biotin synthase via a chemical modification and site-directed mutagenesis approach.

In Escherichia coli, biotin synthase (bioB gene product) catalyzes the key step in the biotin biosynthetic pathway, converting dethiobiotin (DTB) to biotin. Previous studies have demonstrated that BioB is a homodimer and that each monomer contains an iron-sulfur cluster. The purified BioB protein, however, does not catalyze the formation of biotin in a conventional fashion. The sulfur atom in the iron-sulfur cluster or from the cysteine residues in BioB have been suggested to act as the sulfur donor to form the biotin molecule, and yet unidentified factors were also proposed to be required to regenerate the active enzyme. In order to understand the catalytic mechanism of BioB, we employed an approach involving chemical modification and site-directed mutagenesis. The properties of the modified and mutated BioB species were examined, including DTB binding capability, biotin converting activity, and Fe(2+) content. From our studies, four cysteine residues (Cys 53, 57, 60, and 97) were assigned as the ligands of the iron-sulfur cluster, and Cys to Ala mutations completely abolished biotin formation activity. Two other cysteine residues (Cys 128 and 188) were found to be involved mainly in DTB binding. The tryptophan and histidine residues were suggested to be involved in DTB binding and dimer formation, respectively. The present study also reveals that the iron-sulfur cluster with its ligands are the key components in the formation of the DTB binding site. Based on the current results, a refined model for the reaction mechanism of biotin synthase is proposed.

Amino Acid Sequence↗

PubMed2000

Cloning of hHRI, human heme-regulated eukaryotic initiation factor 2alpha kinase: down-regulated in epithelial ovarian cancers.

Protein synthesis is regulated in response to environmental stimuli by covalent modification, phosphorylating the components of the translational machinery. Phosphorylation of the alpha subunit of eIF-2 is one of the best-characterized mechanisms for down-regulating protein synthesis in higher eukaryotes in response to various stress conditions. One of mammalian eIF-2alpha kinases is a heme-regulated inhibitor kinase (HRI), which is activated by heme deficiency and plays an important role in translational control. In this work, we have analyzed the differentially expressed genes between epithelial ovarian cancer and normal ovary. We have screened a total of 1,408 genes isolated from a human dermal papilla cell cDNA library by cDNA array hybridization. Among many differentially expressed genes, eIF2alpha kinase, a heme regulated inhibitor was down-regulated in ovarian epithelium cancer. The down-regulation of hHRI was also confirmed in other ovarian cancer tissues by Northern blot hybridization. The hHRI gene is 2,887 bp in length and the amino acid sequence deduced from the cDNA clone encodes a protein of 630 amino acids with molecular mass of 73 kDa. It contains all 12 catalytic domains of the protein kinases with consensus sequences of the protein-serine/threonine kinases. The expression pattern of hHRI mRNA showed approximately 3.0 kb bands which were expressed ubiquitously in all human tissues examined, which indicates that eIF-2alpha kinase could play an important role in the translational regulation of nonerythroid tissues.

Amino Acid Sequence↗

PubMed2000

Augmentation of antitumor immunity by genetically engineered fibroblast cells to express both B7.1 and interleukin-7.

Mouse fibroblasts (H-2(b)) were genetically engineered to express a costimulatory B7.1 and an interleukin-7 (IL-7; Fb/B7.1/IL7). The Fb/B7.1/IL7 cells were then pulsed with an ovalbumin (OVA) epitope (amino acids 257-264, SIINFEKL, H-2 K(b) restricted; Fb/B7. 1/IL7/OVA) and tested for the induction of OVA-specific cytotoxic T lymphocytes (CTLs) in C57BL/6 mice (H-2(b)). The genetically engineered fibroblasts lacking either B7.1 or IL-7 were constructed and used as controls. Immunization with the Fb/B7.1/IL7/OVA cells induced strong cytotoxic activities against OVA-expressing EL4 (EG7) tumor cells. The magnitude of the cytotoxic response in mice with the Fb/B7.1/IL7/OVA cells was significantly higher than the response in mice immunized with any other cell constructs. CD8(+) T cells were a major effector cell-type of antitumor response in the immunized mice with the Fb/B7.1/IL7/OVA cells. Furthermore, immunization with the Fb/B7.1/IL7/OVA cells significantly prolonged the survival period of mice when the mice were injected with EG7 tumor cells one week after the immunization. These results suggest that fibroblasts can be genetically modified to an efficient cell vaccine for the induction of antitumor response.

Adjuvants, Immunologic↗

PubMed2000

Injection with interleukin-4-secreting fibroblasts efficiently induces T helper type 2 cell-dominated immune response.

To determine whether the paracrine secretion of interleukin-4 (IL-4) can efficiently induce T helper type 2 (Th2) cell-dominated immune response, BLK fibroblasts were stably transfected to secrete IL-4 (750 units/10(6) cells/48 h). Their effects on T helper cell-mediated immune response were investigated in ovalbumin (OVA)-primed C57BL/6 mice, and were compared with those of free recombinant IL-4. Injection with IL-4-secreting fibroblasts (BLK/IL-4) significantly increased anti-OVA IgG1 production in OVA-primed mice. In addition, the BLK/IL-4 cells were more effective than free recombinant IL-4 in decreasing OVA-specific IFN-gamma production and in increasing OVA-specific IL-4 production by splenic CD4(+) T cells. This work suggests that IL-4-secreting fibroblasts can efficiently induce Th2 cell-dominated immune response and may be beneficial in the treatment of diseases caused by undesired Th1 cell-dominated responses.

Animals↗

PubMed2000

Induction of in vivo persistent anti-mycobacterial activity by interferon-gamma-secreting fibroblasts.

To determine whether the paracrine secretion of interferon-gamma (IFN-gamma) can efficiently stimulate the resistance to Mycobacterium avium complex (MAC) infection, 3T3 fibroblasts were stably transduced to secrete IFN-gamma (500 units/10(6) cells/48 h) and their effects on MAC infection were investigated in genetically susceptible BALB/c mice, compared with that of free recombinant IFN-gamma (rIFN-gamma). Immunization with IFN-gamma-secreting fibroblasts (3T3-IFN-gamma) during intranasal infection with MAC resulted in a significant decrease in bacterial load of lung during the entire 8-week observation period, while rIFN-gamma reduced the bacterial load at initial 1 week but not by 8 weeks postinfection. Furthermore, immunization with the 3T3-IFN-gamma cells induced and maintained significantly higher levels of cytotoxic activity and nitric oxide production by lung cells than those of rIFN-gamma immunization. This work suggest that IFN-gamma-secreting fibroblasts may serve as a vehicle for paracrine secretion of IFN-gamma in immunotherapy of MAC infection.

3T3 Cells↗

PubMed2000

The core meiotic transcriptome in budding yeasts.

We used high-density oligonucleotide microarrays to analyse the genomes and meiotic expression patterns of two yeast strains, SK1 and W303, that display distinct kinetics and efficiencies of sporulation. Hybridization of genomic DNA to arrays revealed numerous gene deletions and polymorphisms in both backgrounds. The expression analysis yielded approximately 1,600 meiotically regulated genes in each strain, with a core set of approximately 60% displaying similar patterns in both strains. Most of these (95%) are MATa/MATalpha-dependent and are not similarly expressed in near-isogenic meiosis-deficient controls. The transcript profiles correlate with the distribution of defined meiotic promoter elements and with the time of known gene function.

Binding Sites↗