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Biomedical subjects

S Y Han

Publications and source records attributed to S Y Han.

At least 19 recordsLinked to original sources

Regulation of mouse DNA topoisomerase IIIalpha gene expression by YY1 and USF transcription factors.

To investigate the mechanisms responsible for the regulation of DNA topoisomerase IIIalpha (TOP3alpha) gene expression, the promoter region of the mouse gene has been cloned and analyzed. The promoter region is moderately high in GC content and lacks a canonical TATA box, typical for promoters of a number of housekeeping genes. Transient expression of a luciferase reporter gene under the control of serially deleted 5'-flanking sequences demonstrated that the 34-bp region from -137 to -170 upstream of the transcription initiation site contains a positive regulatory element(s) for the efficient expression of mouse TOP3alpha gene. Combined analyses by gel mobility shift and supershift assays revealed that both YY1 and USF transcription factors were capable of binding to the 34-bp region. When YY1 and USF-binding elements were selectively mutated, the luciferase activity of the resulted constructs was greatly reduced, indicating that both YY1 and USF function as transcriptional activators. Interestingly, YY1 and USF-binding elements are conserved in both human and mouse TOP3alpha promoters. This suggests that mammalian TOP3alpha genes may possess a common mechanism of transcription regulation through these elements.

3T3 Cells↗

Lysophosphatidylcholine derived from deer antler extract suppresses hyphal transition in Candida albicans through MAP kinase pathway.

A family of 2-lysophosphatidylcholines (lyso-PCs) was isolated from deer antler extract, guided exclusively by hyphal transition inhibitory activity in Candida albicans. Structural determination of the isolated lyso-PCs by spectroscopic methods, including infrared spectroscopy, 1H nuclear magnetic resonance (NMR), 13C NMR, 2D correlation spectroscopy NMR, fast atom bombardment mass spectrometry and tandem mass spectrometry, confirmed that the natural products were composed of at least four different lyso-PCs varying in fatty acid moiety at the sn-1 position of the glycerol backbone. The major lyso-PCs were confirmed as 1-stearoyl-, 1-oleoyl-, 1-linoleoyl- and 1-palmitoyl-2-lyso-sn-glycero-3-phosphatidylcholines. Lyso-PC specifically suppressed the morphogenic transition from yeast to hyphae in C. albicans, without affecting the growth of either yeast or hyphae. Lyso-PC exerted hyphal transition that suppressed activity in the broad spectrum of the Candida species, such as C. albicans, Candida krusei, Candida guilliermondii and Candida parapsilosis. Northern analysis indicated that the suppression was mediated through the mitogen-activated protein kinase pathway.

Animals↗

Somatic mutations of TRAIL-receptor 1 and TRAIL-receptor 2 genes in non-Hodgkin's lymphoma.

Tumor necrosis factor-related apoptosis-inducing ligand-receptor 1 (TRAIL-R1) and tumor necrosis factor-related apoptosis-inducing ligand-receptor 2 (TRAIL-R2) are cell-surface receptors involved in tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced cell-death signaling. TRAIL-R1 and TRAIL-R2 genes have recently been mapped to chromosome 8p21-22, which is a frequent site of allelic deletions in many types of human tumors, including non-Hodgkin's lymphoma (NHL). Because TRAIL/TRAIL receptor system plays an important role in lymphocyte homeostasis, we hypothesized that the mutations of TRAIL-R1 and TRAIL-R2 may be involved in the development of NHL and that such mutations may be responsible for the allelic losses of 8p21-22 in NHL. In this study, we analysed the entire coding region of TRAIL-R2 gene and the death domain region of TRAIL-R1 gene for the detection of the somatic mutations in a series of 117 human NHLs using polymerase chain reaction (PCR)-based single strand conformation polymorphism (SSCP) analysis. Overall, eight tumors (6.8%) were found to have two TRAIL-R1 gene mutations or six TRAIL-R2 gene mutations. Interestingly, of the eight mutations, six missense mutations (two TRAIL-R1 and four TRAIL-R2) were detected in the death domains and one nonsense mutation of TRAIL-R2 was detected just before the death domain. Our data suggest that somatic mutations of TRAIL-R1 and TRAIL-R2 genes may play a role in the pathogenesis of some NHLs and that TRAIL-R1 and TRAIL-R2 genes might be the relevant genes to the frequent loss of chromosome 8p21-22 in human NHL.

Humans↗

Induction of cytosolic phospholipase A2 by oncogenic Ras is mediated through the JNK and ERK pathways in rat epithelial cells.

Mutations in ras genes have been detected with high frequency in nonsmall cell lung cancer cells (NSCLC) and contribute to transformed growth of these cells. It has previously been shown that expression of oncogenic forms of Ras in these cells is associated with elevated expression of cytosolic phospholipase A(2) (cPLA(2)) and cyclooxygenase-2 (COX-2), resulting in high constitutive levels of prostaglandin production. To determine whether expression of constitutively active Ras is sufficient to induce expression of these enzymes in nontransformed cells, normal lung epithelial cells were transfected with H-Ras. Stable expression of H-Ras increased expression of cPLA(2) and COX-2 protein. Transient transfection with H-Ras increased promoter activity for both enzymes. H-Ras expression also activated all three families of MAP kinase: ERKs, JNKs, and p38 MAP kinase. Expression of constitutively active Raf did not increase either cPLA(2) or COX-2 promoter activity, but inhibition of the ERK pathway with pharmacological agents or expression of dominant negative ERK partially blocked the H-Ras-mediated induction of cPLA(2) promoter activity. Expression of dominant negative JNK kinases decreased cPLA(2) promoter activity in NSCLC cell lines and inhibited H-Ras-mediated induction in normal epithelial cells, whereas expression of constructs encoding constitutively active JNKs increased promoter activity. Inhibition of p38 MAP kinase or NF-kappaB had no effect on cPLA(2) expression. Truncational analysis revealed that the region of the cPLA(2) promoter from -58 to +12 contained sufficient elements to mediate H-Ras induction. We conclude that expression of oncogenic forms of Ras directly increases cPLA(2) expression in normal epithelial cells through activation of the JNK and ERK pathways.

Animals↗

Frequent nuclear accumulation of beta-catenin in pituitary adenoma.

BACKGROUND: Beta-catenin (CTNNB1) is known to be a member of the cadherin-catenin superfamily and to function in cell-cell adhesion. However, it also has been reported that CTNNB1 plays an important role in carcinogenesis. In the current study, the authors observed expression of the CTNNB1 protein in primary pituitary adenomas to investigate the role of CTNNB1 in the development of pituitary adenomas. METHODS: A total of 37 pituitary adenomas were analyzed. Expression of CTNNB1 and the cell proliferation marker Ki-67 were observed immunohistochemically. In addition, the authors performed direct sequencing to detect somatic mutations of exon 3 of the CTNNB1 gene. RESULTS: Twenty-one of 37 pituitary adenomas (57%) demonstrated abnormal nuclear accumulation of CTNNB1. It is interesting to note that tumors with an accumulation of CTNNB1 in the nucleus showed a statistical tendency toward an association with increased immunoreactivity of Ki-67 (P < 0.05) whereas no significant correlation was detected between the status of CTNNB1 and other clinicopathologic features. Missense mutations in exon 3 of the CTNNB1 gene also were detected in the cases with abnormal nuclear accumulation of the CTNNB1 protein. CONCLUSIONS: The results of the current study suggest that up-regulation of the Wnt signaling pathway, including accumulation of mutant CTNNB1 in the nuclei, plays an important role in the tumorigenesis and development of adenoma in the pituitary gland.

Adenoma↗

Expression of Fas and Fas-related molecules in human hepatocellular carcinoma.

Many tumor cells, including hepatocellular carcinoma (HCC), express both Fas and its ligand on their surfaces, and it has remained a mystery why such cells do not spontaneously become apoptotic. In the current study, we analyzed the alterations of Fas structure and the expression of Fas and Fas ligand (FasL) and of Fas pathway inhibitors, including soluble Fas (sFas), Fas-associated phosphatase-1 (FAP-1), and bcl-2, in 50 cases of human HCC. Monoallelic loss of the Fas gene, as determined by loss of heterozygosity with intragenic polymorphisms, was observed in 5 of the 34 informative cases (15%), but none of the 50 cases showed Fas gene mutation. Expression of Fas and FasL was detected in 44 (88%) and 50 (100%) cases, respectively. sFas messenger RNA, as analyzed by in situ reverse-transcription polymerase chain reaction was expressed in 42 of the 50 cases (84%), and FAP-1 expression was observed in 40 of the 50 cases (80%). In contrast, none of the 50 cases showed bcl-2 expression. Our results showed that the majority of the HCCs (88%) coexpressed a death receptor, Fas and its cognate ligand, FasL, but all HCCs showed one or more alterations of the Fas pathway molecules known to inhibit Fas-mediated apoptosis. These findings suggest that the expression of sFas and FAP-1 and, in part, loss of Fas expression, rather than Fas gene alteration or bcl-2 expression, may be involved in the Fas resistance of HCC in vivo and that these mechanisms may play important roles in the pathogenesis of human HCC. HUM PATHOL 32:250-256.

Adult↗

TFIIAalpha/beta-like factor is encoded by a germ cell-specific gene whose expression is up-regulated with other general transcription factors during spermatogenesis in the mouse.

TFIIAalpha/beta-like factor (ALF) is a testis-specific counterpart of the large subunit of human general transcription factor TFIIA. Northern analysis shows that ALF mRNA first appears in mouse testis at Postnatal Day 14. Similarly, expression of the general transcription factors TBP, TRF2, TFIIAalpha/beta, TFIIAgamma, and TFIIIB(90) is also increased beginning at Postnatal Day 14, suggesting that there is a coordinated induction of many general transcription factors during male germ cell differentiation. Analysis of male germ cells separated by Staput sedimentation shows that ALF is present in pachytene spermatocytes and haploid spermatids. In addition, in situ hybridization experiments with adult mouse testis shows that ALF is present in haploid spermatids. Searches of the human genome sequence database using the basic local alignment search tool reveal that the ALF and TFIIAalpha/beta(GTF2A1) genes are both composed of nine exons, whereas the TFIIAgamma (GTF2A2) gene is composed of five exons. Furthermore, nucleotide and amino acid comparisons among human and mouse ALF, TFIIAalpha/beta, and TFIIAgamma cDNA sequences show that ALF has diverged more rapidly than either TFIIAalpha/beta or TFIIAgamma. Finally, the ALF and SBLF (Stoned B-Like Factor) sequences present in the chimeric SALF cDNA are both present on human chromosome 2, and an analysis of the corresponding genes suggests a model for the formation of SALF.

Amino Acid Sequence↗

Altered remodeling of nucleolar machineries in cultured hepatocytes treated with thioacetamide.

Thioacetamide (TA) is converted into a hyperacetylating agent which causes hepatic necrosis, regeneration, cirrhosis and cancerous transformation. One of the most characteristic toxicities of TA in rat is observed with a 50 mg/kg per day which induces nucleolar enlargement different from that in regenerating liver. From TA-treated liver, the nucleoli were isolated and characterized for an altered nucleolar signal transduction system. Immunochemistry revealed that the poisoned nucleoli had increased levels of both nucleolus specific proteins (nucleophosmin and nucleolin) and various signal molecules (CK2, Erk1/2, p38, protein kinases A and C, and cyclin A). Using flow cytometry, the nucleoli were found to be in G2-arrested nuclei. Manifestation of the nucleolar enlargement could be readily observed using an ex vivo hepatocyte culture. There were two types of nucleolar enlargement. One was observed in normal hepatocytes with light density of enlarged nucleoli. The other was in TA-treated hepatocytes with dense and compact density of enlarged nucleoli, which contained a 3 to 5-fold higher nudeophosmin content than the control. In vitro induction of nucleolar enlargement with TA was possible. As soon as the hepatocytes anchored on a collagen coat, exogeneous TA (higher than 1 microg/mL) could induce dense and compact nucleoli. However, when an exogeneous drug was added after monolayer formation (1 day), no drug-induced nucleolar enlargement was observed.

Animals↗

[Study on effect of ABA, PEG4000 and AgNO3 on number of somatic embryos of Larix Principis-Rupprechtii by 311-A regression design].

This paper, the effects of ABA, PEG400 and AgNO3 on the number of somatic embryos of Larix Principis-Rupprechtii were carried out by 311-A regression design. The regression equation was established which expresses the number of somatic embryos of Larix Principis-Rupprechtii as function, and the ABA, PEG400 and AgNO3 on as variable respectively. Using the regression equation, the single factor effect and mutual effect between the number of somatic embryos of Larix Principis-Rupprechtii and ABA, PEG400 and AgNO3 was studied; the optimum concentration recipes can be obtained by computer processing, that are ABA: 18.9138 mg/L, PEG400: 88.8007 g/L and AgNO3: 10.7513 mg/L, the target somatic embryos number is 107.5278 each gram callus. The results of experiment showed that this method is simple, practical and rapid for selecting several hormone category and concentration recipes media of conifer somatic embryogenesis.

Abscisic Acid↗

Effects of ochratoxin A on cytotoxicity and cell differentiation in cultured rat embryonic cells.

In the present study, the effects of ochratoxin A (OTA) on cytotoxicity, cell differentiation, and other cell functions in the embryonic midbrain cells, which are dopaminergic, were compared to those in the limb bud cells, which are nondopaminergic, to assess the selectivity of OTA central action. Twelve-day rat embryo midbrain and limb bud cells were cultured in Dulbecco's modified Eagle's medium nutrient and Ham's F12 (1:1) mix ture containing 10% Nuserum for 96 h in the presence of various concentrations of OTA. OTA signicfiantly reduced the levels of protein, DNA and glutathione, and [H]thymidine incorporation into DNA in both embryonic midbrain and limb bud cells in a similar concentration-dependent manner. The IC50 values for cytotoxicity measured by neutral red uptake were 1.10 microM in the midbrain cells and 1.05 microM in the limb bud cells. The IC50 values of cell differentiation were 1.10 microM in the midbrain cells and 1.0 microM in the limb bud cells. The addition of exogenous glutathione (32.5 microM) did not change the OTA-induced fall in protein and DNA levels, or the IC50 values of cytotoxicity and differentiation in the midbrain and limb bud cells. Data show that OTA does not appear to exert a selective toxic dopaminergic cell action and that OTA-induced cytotoxicity and inhibition of cell differentiation were not prevented by exogenous glutathione.

Animals↗

Freezing immature oocytes.

The establishment of a long-term preservation system for mammalian oocytes is important for the development of both biological and medical sciences. A number of efforts have been made to develop this system. In human reproductive medicine, the development of an oocyte cryopreservation system can improve the efficacy of the current assisted reproductive technology (ART) for infertile patients with severe reproductive disorders. In this article, the technical development of cryopreservation programs for human oocytes and its biological background were reviewed. Clinical outcome after the use of this technology was further introduced.

Cell Culture Techniques↗

Identification of Rab6 as an N-ethylmaleimide-sensitive fusion protein-binding protein.

In this study we show the interaction of N-ethylmaleimide-sensitive fusion protein (NSF) with a small GTP-binding protein, Rab6. NSF is an ATPase involved in the vesicular transport within eukaryotic cells. Using the yeast two-hybrid system, we have isolated new NSF-binding proteins from the rat lung cDNA library. One of them was Rab6, which is involved in the vesicular transport within the Golgi and trans-Golgi network as a Ras-like GTPase. We demonstrated that the N-terminal domain of NSF interacted with the C-terminal domain of Rab6, and these proteins were co-immunoprecipitated from the rat brain extract. This interaction was maintained preferentially in the presence of hydrolysable ATP. Recombinant NSF-His(6) can also bind to C-terminal Rab6-glutathione S-transferase under the conditions to allow the ATP hydrolysis. Surprisingly, Rab6 stimulates the ATPase activity of NSF by approx. 2-fold as does alpha-soluble NSF attachment protein receptor. Anti-Rab6 polyclonal antibodies significantly inhibited the Rab6-stimulated ATPase activity of NSF. Furthermore, we found that Rab3 and Rab4 can also associate with NSF and stimulate its ATPase activity. Taken together, we propose a model in which Rab can form an ATP hydrolysis-regulated complex with NSF, and function as a signalling molecule to deliver the signal of vesicle fusion through the interaction with NSF.

Adenosine Triphosphate↗

Pharmacokinetic disposition and tissue distribution of bisphenol A in rats after intravenous administration.

This study examined the dose-linearity pharmacokinetics of bisphenol A, a U.S. Environmental Protection Agency (EPA) classified endocrine disruptor, in rats following iv administration. Upon iv injection of 0.2, 0.5, 1, or 2 mg/kg, serum levels of bisphenol A declined biexponentially, with mean initial distribution and elimination half-life ranges of 4-8.2 min and 38.6-62.2 min, respectively. There were no significant alterations in the systemic clearance rate (mean range 90.1-123.6 ml/min/kg) and the steady-state volume of distribution (mean range 4.6-6.0 L/kg) as a function of the administered dose. In addition, the area under the serum concentration-time curve linearly rose as the dose was increased. In a second study, bisphenol A was given by simultaneous iv bolus injection plus infusion to steady state, and levels were measured in serum and various organs. When expressed in concentration terms (e.g., amount accumulated per gram organ weight), bisphenol A was found predominantly in the lung, followed by kidneys, thyroid, stomach, heart, spleen, testes, liver, and brain. Ratios of the organ to serum bisphenol A concentrations exceeded unity for all the organs examined (ratio range 2.0-5.8) except for brain (ratio 0.75). Given the high systemic clearance and short elimination half-life, bisphenol A is unlikely to accumulate significantly in the rat.

Air Pollutants, Occupational↗

Induction of smooth muscle alpha-actin in vascular smooth muscle cells by arginine vasopressin is mediated by c-Jun amino-terminal kinases and p38 mitogen-activated protein kinase.

Exposure of vascular smooth muscle cells to arginine vasopressin (AVP) increases smooth muscle alpha-actin (SM-alpha-actin) expression through activation of the SM- alpha-actin promoter. The goal of this study was to determine the role of the mitogen-activated protein kinase (MAP kinase) family in regulation of SM-alpha-actin expression. AVP activated all three MAP kinase family members: ERKs, JNKs, and p38 MAP kinase. Inhibition of JNKs or p38 decreased AVP-stimulated SM-alpha-actin promoter activity, whereas inhibition of ERKs had no effect. A 150-base pair region of the promoter containing two CArG boxes was sufficient to mediate regulation by vasoconstrictors. Mutations in either CArG box decreased AVP-stimulated promoter activity. Electrophoretic mobility shift assays using oligonucleotides corresponding to either CArG box resulted in a complex of similar mobility whose intensity was increased by AVP. Antibodies against serum response factor (SRF) completely super-shifted this complex, indicating that SRF binds to both CArG boxes. Overexpression of SRF increased basal promoter activity, but activity was still stimulated by AVP. AVP stimulation rapidly increased SRF phosphorylation. These data indicate that both JNKs and p38 participate in regulation of SM- alpha-actin expression. SRF, which binds to two critical CArG boxes in the promoter, represents a potential target of these kinases.

Actins↗

Functional evaluation of PTEN missense mutations using in vitro phosphoinositide phosphatase assay.

The tumor suppressor gene PTEN is frequently mutated in diverse human cancers and in autosomal dominant cancer predisposition disorders. Recent studies have shown that the lipid phosphatase activity of PTEN is critical for its tumor suppressor function and that PTEN negatively regulates the phosphatidylinositol 3'-kinase-protein kinase B pathway. Although more than half of PTEN mutations result in protein truncation, a significant fraction of PTEN mutations are missense mutations. To examine whether tumor-derived and germ-line-derived missense mutations inactivate PTEN lipid phosphatase function, we constructed 42 distinct types of PTEN missense mutations and expressed them in Escherichia coli. The purified (His)6-tagged PTEN proteins were tested for their ability to dephosphorylate inositol 1,3,4,5-tetrakisphosphate and phosphatidylinositol 3,4,5-triphosphate. In addition, we examined the effect of mutant PTENs on the ability of PTEN to bind to the phospholipid membrane. The results revealed that the majority of PTEN missense mutations [38 of 42 (90%)] eliminated or reduced phosphatase activity and that all of the mutations examined had no effect on the membrane binding activity of PTEN. Our study indicated that phosphoinositide phosphatase activity is important for the tumor suppressor function of PTEN and that there may be other mechanisms of PTEN inactivation that are not monitored by in vitro phosphatase assay and in vitro membrane binding assay.

Escherichia coli↗

Differential effects of retinoic acid on growth and apoptosis in human colon cancer cell lines associated with the induction of retinoic acid receptor beta.

Retinoids are well known as potential chemopreventive and chemotherapeutic agents against a variety of human cancers. Here, we report that retinoic acid (RA) induced differential growth inhibition in human colon cancer cell lines: while DLD-1, HT-29, and WiDr were relatively resistant, HCT-15 and Colo201 were relatively sensitive. All-trans-retinoic acid caused morphological and biochemical changes such as membrane shrinkage, chromatin condensation, and DNA cleavage, which are typical features of cells undergoing apoptosis in sensitive cell lines. Although retinoic acid receptor (RAR)alpha, beta, gamma and retinoid X receptor alpha were expressed in all cell lines examined, a significant induction of RARbeta by all-trans-RA was observed only in sensitive cell lines, suggesting important roles of RARbeta in RA sensitivity. When a vector containing the RARbeta gene was introduced into a relatively resistant cell line, DLD-1, the cells acquired RA sensitivity. Further, we found that the RARbeta transfectants of DLD-1 expressed an enhanced level of c-Myc and Bax proteins, which may result in the increased susceptibility of the cells to all-trans-RA-induced apoptosis. In summary, our data demonstrated that RA induced growth inhibition and apoptosis in human colon cancer cells and that the induction of RAR3 may mediate the retinoid action.

Antineoplastic Agents↗

Identification of triacylglycerols containing two short-chain fatty acids at sn-2 and sn-3 positions from bovine udder by fast atom bombardment tandem mass spectrometry.

Several triacylglycerol (TAG) molecular species, that contain two short-chain fatty acids (C4 to C8) at the sn-2 and sn-3 positions of the glycerol backbone, were isolated from bovine udder by using solvent extraction and silica gel column chromatography. Their structures were identified by fast atom bombardment (FAB) tandem mass spectrometry (MS/MS), based on the information obtained from collision-induced dissociation (CID) spectra of sodium-adducted molecules ([M + Na](+)) of model TAG compounds which had been synthesized from glycerol and appropriate fatty acids. For each species, the relative positions of the three fatty acids on the glycerol backbone, as well as fatty acid composition and double-bond position in the fatty acyl group, were determined. A majority of sodium-adducted molecules observed in the FAB mass spectrum were mixtures of at least two components that have different fatty acid composition but the same molecular mass. In addition, all the components present in mixtures of all the species contain a long-chain fatty acid (C12 to C18) at the sn-1 position, a short-chain fatty acid (C4 to C8) at the sn-2 position, and a butyric acid uniquely at the sn-3 position.

Animals↗

Pregnancies and deliveries after in vitro maturation culture followed by in vitro fertilization and embryo transfer without stimulation in women with polycystic ovary syndrome.

OBJECTIVE: To improve the efficacy of an IVF-ET program for unstimulated patients with polycystic ovary syndrome (PCOS) with the use of culture for oocyte maturation. DESIGN: Prospective studies with the comparison of different ET procedures from March 1995 through February 1998. SETTING: University-affiliated hospital. PATIENT(S): Ninety-four cycles in 64 consenting patients with PCOS. INTERVENTION(S): Immature oocytes were retrieved from unstimulated patients with PCOS and subsequently cultured and fertilized in vitro. Zygote intrafallopian transfer (ZIFT), uterine ET, or a combined approach of ZIFT + uterine ET was subsequently performed. MAIN OUTCOME MEASURE(S): Laboratory and clinical data. RESULT(S): Among 1, 280 immature oocytes (13.6 +/- 7.5 oocytes per patient) retrieved, 89% (1,139) were morphologically normal, and 62.2% (708/1,139) of the normal oocytes matured in vitro after culture for 48 hours. When intracytoplasmic sperm injection was performed, 68% (481/708) developed to the normal pronuclear stage, and 88.1% of the embryos cocultured with Vero cells (266/302) cleaved. Eighty-five ET cycles were conducted and pregnancy was established in 23 cycles (27.1%), which consisted of 8 after uterine ET and 15 after a combined approach. Seventeen patients delivered 20 normal infants. CONCLUSION(S): The IVF-ET method using no ovarian stimulation followed by in vitro maturation culture can be a feasible assisted reproductive technology for treatment of PCOS with various complications.

Adult↗