Search PubMed⌕ Search

Biomedical subjects

S Hwang

Publications and source records attributed to S Hwang.

At least 37 records · Page 2Linked to original sources
PubMed2001

The biological significance of phospholipase C beta 1 gene mutation in mouse sperm in the acrosome reaction, fertilization, and embryo development.

PURPOSE: We carried out this study to evaluate the biological significance of phospholipase C beta 1 gene mutation in mouse sperm in the acrosome reaction, fertilization, and embryo development. METHODS: Study subjects were divided into two groups according to the sperm [intact phospholipase C (PLC) beta 1 and PLC beta 1-/- C57BL/6J x CBA F1 mouse sperm] used. The positive acrosome reaction rate labeled with fluorescein isothiocyanate-Pisum sativum agglutinin, the fertilization rate, and the rate of embryos developed to the stage of morula or blastocyst in the two groups were compared. RESULTS: The mouse sperm null for the PLC beta 1 gene showed a lower acrosome reaction rate than control sperm (69.2 vs 50.9%, P < 0.05). And the fertilization rate and the rate of embryos developed to the stage of morula or blastocyst were also lower in the group using PLC beta 1-/- mouse sperm compared to the intact group (P < 0.05; 73.5 vs 51.8% and 15.7 vs 4.3%, respectively). CONCLUSIONS: Mutation of the PLC beta 1 gene in the mouse sperm reduces the acrosome reaction rate, fertilization rate, and embryo development rate, which may be the etiologic factors responsible for the low reproductive rate of PLC beta 1-/- mouse.

Acrosome Reaction↗
PubMed2001

The expression of pseudogene cyclin D2 mRNA in the human ovary may be a novel marker for decreased ovarian function associated with the aging process.

PURPOSE: Our purpose was to investigate the expression pattern of cyclin D2 and pseudogene cyclin D2 mRNA in the human ovary with age. METHODS: After extraction of the total RNA from ovarian tissues of 23 premenopausal patients, cyclin D2 and pseudogene cyclin D2 mRNAs were measured by the reverse transcription-polymerase chain reaction technique using cyclin D2 and pseudogene cyclin D2 specific primers. Analysis of the cyclin D2 and pseudogene cyclin D2 mRNA expression pattern with age and correlation analysis were carried out. RESULTS: A 489-bp cyclin D2 band and a 441-bp pseudogene cycin D2 mRNA band were detected in the human ovarian tissue. While cyclin D2 mRNA expression showed a decreasing tendency with age (P = 0.17), pseudogene cyclin D2 mRNA expression increased with age (P < 0.05). Pseudogene cyclin D2 mRNA expression showed a negative correlation with cyclin D2 mRNA (R = -0.35, P < 0.03). CONCLUSION: The expression of pseudogene cyclin D2 mRNA in the human ovary increases with age, which may be a novel marker for decreased ovarian function associated with the aging process.

Adult↗
PubMed2001

Kaposi's sarcoma-associated herpesvirus open reading frame 50 represses p53-induced transcriptional activity and apoptosis.

Kaposi's sarcoma-associated herpesvirus (KSHV) open reading frame 50 (ORF50) encodes a viral transcriptional activator which stimulates the transcription of viral early and late genes of KSHV. Here we show that ORF50 represses transcriptional activity of p53 and p53-induced apoptosis through interaction with CREB binding protein (CBP). This inhibitory effect of ORF50 on the transcriptional activity of p53 was relieved by the addition of CBP. ORF50 mutants, which are defective in interaction with CBP, lost the inhibitory effects on p53. Our data provide a framework for delineating the regulatory mechanisms used by KSHV to modulate cellular transcription and the cell cycle.

Apoptosis↗
PubMed2001

The Kaposi's sarcoma-associated herpesvirus K8 protein interacts with CREB-binding protein (CBP) and represses CBP-mediated transcription.

Kaposi's sarcoma-associated herpesvirus (KSHV) open reading frame K8 encodes a basic region-leucine zipper protein of 237 amino acids that homodimerizes with its bZIP domain. KSHV K8 shows significant homology to the Epstein-Barr virus (EBV) immediate-early protein Zta, a key regulator in the reactivation and replication of EBV. In this study, we report that K8, like its homolog EBV Zta, interacts with cellular CREB-binding protein (CBP) in vivo and in vitro. This interaction requires the C/H3 domain of CBP and the basic region of K8. K8 represses CBP-mediated transcription by competing with limited amounts of cellular CBP, exemplified by the reduced expression from the AP-1 and human immunodeficiency virus long terminal repeat promoters.

CREB-Binding Protein↗
PubMed2001

CREB-binding protein and histone deacetylase regulate the transcriptional activity of Kaposi's sarcoma-associated herpesvirus open reading frame 50.

Kaposi's sarcoma (KS)-associated herpesvirus (KSHV) open reading frame 50 (ORF50) encodes a viral transcriptional activator, which binds to the KSHV promoter and stimulates the transcription of viral early and late genes, thus activating the lytic cycle of KSHV. We report here that KSHV ORF50 binds to the cellular proteins CREB-binding protein (CBP) and histone deacetylase (HDAC) and these binding events modulate ORF50-activated viral transcription. Binding of ORF50 to CBP and HDAC activates and represses, respectively, ORF50-mediated viral transcription. KSHV ORF50 was shown to bind to the C/H3 domain and the C-terminal transcriptional activation domain of CBP, while CBP bound to the amino-terminal basic domain and the carboxyl-terminal transactivation domain of ORF50. The LXXLL motif within the transcriptional activation domain of ORF50 is reminiscent of the CBP-binding sequence found in nuclear receptor proteins. The adenovirus E1A protein, which also binds to the C/H3 domain of CBP, repressed the transcriptional activation activity of ORF50. The cellular protein c-Jun, which binds to the kinase-induced activation domain of ORF50, stimulated ORF50-mediated viral transcription. The HDAC1-interacting domain of ORF50 was shown to be a central proline-rich sequence. Our data provide a framework for delineating the regulatory mechanisms used by KSHV to modulate its transcription and replication through interaction with both histone acetyltransferases and HDACs.

CREB-Binding Protein↗
PubMed2001

Carbon partitioning to cellulose synthesis.

This article discusses the importance and implications of regulating carbon partitioning to cellulose synthesis, the characteristics of cells that serve as major sinks for cellulose deposition, and enzymes that participate in the conversion of supplied carbon to cellulose. Cotton fibers, which deposit almost pure cellulose into their secondary cell walls, are referred to as a primary model system. For sucrose synthase, we discuss its proposed role in channeling UDP-Glc to cellulose synthase during secondary wall deposition, its gene family, its manipulation in transgenic plants, and mechanisms that may regulate its association with sites of polysaccharide synthesis. For cellulose synthase, we discuss the organization of the gene family and how protein diversity could relate to control of carbon partitioning to cellulose synthesis. Other enzymes emphasized include UDP-Glc pyrophosphorylase and sucrose phosphate synthase. New data are included on phosphorylation of cotton fiber sucrose synthase, possible regulation by Ca2+ of sucrose synthase localization, electron microscopic immunolocalization of sucrose synthase in cotton fibers, and phylogenetic relationships between cellulose synthase proteins, including three new ones identified in differentiating tracheary elements of Zinnia elegans. We develop a model for metabolism related to cellulose synthesis that implicates the changing intracellular localization of sucrose synthase as a molecular switch between survival metabolism and growth and/or differentiation processes involving cellulose synthesis.

Amino Acid Sequence↗
PubMed2000

HIV-1 TAR RNA enhances the interaction between Tat and cyclin T1.

Human immunodeficiency virus, type 1 (HIV-1), Tat activates elongation of RNA polymerase II transcription at the HIV-1 promoter through interaction with the cyclin T1 (CycT1) subunit of the positive transcription elongation factor complex, P-TEFb. Binding of Tat to CycT1 induces cooperative binding of the P-TEFb complex onto nascent HIV-1 TAR RNA. Here the specific interaction between Tat protein, human cyclin T1, and HIV-1 TAR RNA was analyzed by fluorescence resonance energy transfer, using fluorescein-labeled TAR RNA and a rhodamine-labeled Tat protein synthesized through solid-phase chemistry. We find that CycT1 remodels the structure of Tat to enhance its affinity for TAR RNA and that TAR RNA further enhances the interaction between Tat and CycT1. We conclude that TAR RNA nucleates the formation of the Tat.P-TEFb complex through an induced fit mechanism.

Base Sequence↗
PubMed2000

Molecular lens of the nonresonant dipole force

A cylindrical molecular lens is formed by focusing a nanosecond IR laser pulse. Trajectories of a CS2 molecular beam deflected by the lens are traced using the velocity map imaging technique. The characteristic lens parameters including the focal length, minimum beam width, and distance to the minimum-width position are determined. The laser intensity dependence of the parameters is in good agreement with theoretical predictions. Exciting possibilities for molecular optics and a new type of optical chromatography are opened up.

Journal Article↗
PubMed2000

Effect of dosing time on the total intestinal transit time of non-disintegrating systems.

The total gastrointestinal transit time of nondisintegrating tablets may be affected by dosing time; available literature on this topic is inconclusive. OROS systems are nondisintegrating osmotically driven tablets that release drug over a period of time during their transit through the gastrointestinal tract and are excreted intact in the feces. Total transit times following morning administration of OROS systems pooled from various studies (n = 1,163 systems) showed a distribution with peak frequencies clustering around 24 and 48 h and following night administration (n = 80 systems) was found to cluster around 12 and 36 h. The total transit time distribution appears to be different following morning and night administration. However, on reanalyzing the data considering clock time when the tablet was collected rather than time post-administration, most of the difference between the distribution patterns disappeared. This suggested that total transit times after morning or night administration may be related to the bowel movement habits of the study population. Therefore, OROS systems total transit time were compared to the intrinsic bowel movement pattern of the general population reported in the literature and indeed a good correlation was seen between the two. The total transit time appears to be determined by two factors: the defecation frequency and the probability of its inclusion in the defecation event which is related to its location in the GI tract. A tablet is more likely to be excreted if it is further down in the GI tract. The total transit time data for OROS systems suggest that with the morning dosing the tablet is more likely to be excreted in the bowel movement the next morning. With the night time dosing the tablet may not be far enough in the colon to be excreted in the next morning bowel movement and therefore, it is more likely to be excreted the following morning.

Adolescent↗
PubMed2000

Metabolizable energy of roughage in Taiwan.

The fixed metabolizable energy (ME) values from the NRC do not represent the true ME values of the various feedstuff used in livestock rations. Therefore, a rapid and effective method for evaluating the ME value of forage crops is required for proper ration formulation to improve production efficiency. Dairy goat digestion trials were conducted as the in vivo reference using the method of Menke and Steingass (1988) [Menke, K.H., Steingass, H., 1988. Feed Sci. Technol. 28, 91-97] which derived the amount of gas produced from in vitro fermentation. This method was adapted in this study to evaluate the ME value. In the goat digestion trial, six dairy goats were used for each roughage sample in a total fecal collection trial to determine the digestible nutrients, including energy (DE) and total digestible nutrient (TDN). The in vivo ME value was calculated using the method of Shiemann et al. (1971) [Shiemann, R., Nehring, K., Hoffmann, L., Jentsch, W., Chudy, A., 1971. Energetische Futterbewertung und Energienormen. VEB Deutscher Land-wirtschaftsverlag, Berlin, p. 75. (in German)] (ME(1) (MJ/kg)=5.2DCP+34.2DEE+12.8DCF+15.9DNFE, g/g). The in vitro ME value was then estimated from the chemical composition of the feed and amount of gas produced (G(b)) from in vitro fermentation. The value calculated from both with (ME(3)) and without (ME(2)) the inclusion of nitrogen free extracts (NFE) in the prediction equation. (ME(2) (MJ/kg)=0.145G(b)+4.12CP+6.5CP(2)+20.6EE+1.54, g/g; ME(3) (MJ/kg)=0.118G(b)+8.75CP+19.21EE+3.38NFE+0.691, g/g). The 12 roughage samples consisted different growth stages of Napier grass Taishi No. 2: (day of harvest; 40, 50, 60 and 65), dwarf Napier grass Taishi No. 1: (Day 40 and 65) and Pangola grass (Day 45) hay (Day 70), corn silage, imported alfalfa hay, timothy hay and Bermuda hay. The correlation between the ME values calculated from in vivo and in vitro without NFE was lower than with NFE inclusion in the equation. A higher correlation between the ME values calculated from in vivo and in vitro without NFE inclusion than with NFE inclusion in the prediction equation was obtained when alfalfa and corn silage were not included. This indicated that the ME value of forage could be estimated rapidly using this in vitro gas method adapted from Menke and Steingass (1988) [Menke, K.H., Steingass, H., 1988. Feed Sci. Technol. 28, 91-97] for practical applications in ration formulation.

Journal Article↗
PubMed2000

Beta-globin YAC transgenes exhibit uniform expression levels but position effect variegation in mice.

Expression of a construct integrated at different genomic locations often varies because of position effects that have been subcategorized as stable (decreased level of expression) and variegating (decreased proportion of expressing cells). It is well established that locus control regions (LCRs) generally overcome position effects in transgenes. However, whether stable and variegated position effects are equally overcome by an intact LCR has not been determined. We report that single-copy yeast artificial chromosome transgenes containing an unmodified human beta -globin locus were not subject to detectable stable position effects but did undergo mild to severe variegating position effects at three of the four non-centromeric integration sites tested. We also find that, at a given integration site, the distance and the orientation of the LCR relative to the regulated gene contributes to the likelihood of variegating position effects, and can affect the magnitude of its transcriptional enhancement. DNase I hypersensitive site (HSS) formation varies with the proportion of expressing cells, not the level of gene expression, suggesting that silencing of the transgene is associated with a lack of HSS formation in the LCR region. We conclude that transcriptional enhancement and variegating position effects are caused by fundamentally different but inter-dependent mechanisms.

Animals↗
PubMed2000

Relative binding affinities of alkali metal cations to

The binding affinity and selectivity of a new ionophore, [1(8)]starand (1), toward alkali metal cations in methanol were examined through NMR titration experiments and free energy perturbation (FEP) and molecular dynamics simulations. The preference was determined to be K(+) > Rb(+) > Cs(+) > Na(+) >> Li(+) in both FEP simulations and NMR experiments. The FEP simulation results were able to predict the relative binding free energies with errors less than 0.13 kcal/mol, except for the case between Li(+) and Na(+). The cation selectivity was rationalized by analyzing the radial distribution functions of the M-O and M-C distances of free metal cations in methanol and those of metal-ionophore complexes in methanol.

Journal Article↗
PubMed2000

One hundred and eleven liver resections for hilar bile duct cancer.

A positive correlation between absence of residual tumor at resection margins and long-term survival in the treatment of hilar bile duct carcinoma has encouraged some surgeons to use a more radical approach, including liver/portal vein resection and combined pancreatoduodenectomy. However, if liver resection is associated with significant morbidity and mortality, it may not produce any overall benefit. This review was undertaken in an attempt to determine whether liver resection is a safe procedure and whether if has any beneficial effect over that of local bile duct excision alone, in terms of achieving curative resection and long-term survival. The records of 151 patients with hilar bile duct carcinoma surgically treated between June 1989 and December 1997 at the Asan Medical Center, Seoul, were retrospectively analyzed. Surgical resection was possible in 128 patients. The remaining 23 patients had surgical palliative drainage. Local bile duct excision alone was performed in 17 patients. Liver resection for tumor extending to secondary bile ducts or hepatic parenchyma was performed in 111 patients; portal vein resection was necessary in 29 of these 111 patients (26.1%) and pancreatoduodenectomy was combined in 18 patients (16.2%). Seven patients died during hospitalization after liver resection, an operative mortality of 6.3%. Margins of bile duct resection were free of tumor on histologic examination in 4 of the 17 local bile duct excisions, but in 86 of the 111 liver resections. The cumulative survival rate after local bile duct excision was 85.7% at 1 year, 42.9% at 2 years, 21.4% at 3 years, and 0% at 4 years. However, the survival rate after liver resection (excluding operative mortality) was 97.1% at 1 year, 72.8% at 2 years, 55.3% at 3 years, and 24.0% at 5 years. Survival and the percentage of patients with tumor-free resection margins after liver resection were superior to those after local bile duct excision. Resection of hilar bile duct carcinoma offers long-term survival only when surgery is aggressive and includes liver resection.

Adult↗
PubMed2000

Effects of electric stimulation on bovine oocyte activation and embryo development in intracytoplasmic sperm injection procedure.

PURPOSE: This study was carried out to investigate the efficacy of electric stimulation before and/or after intracytoplasmic sperm injection (ICSI) on bovine oocyte activation and embryo development. METHODS: The oocytes were treated with electric shock before (B), before and after (B&A), and after (A) sperm injection. In each group, sham ICSI (ICSI-s) was performed to exclude the effect of parthenogenesis (B ICSI-s, B&A ICSI-s, and A ICSI-s). An electric pulse was applied with a single direct current (DC) pulse (0.8 kV/cm, 70 microseconds). RESULTS: One pronucleus (PN) formation in the B&A ICSI-s group was slightly higher than that found in B and B&A ICSI group; however, the difference was not significant. Two PN formation in B&A ICSI group was higher than that found in sham ICSI groups (P < 0.05). There were no differences among treatment groups in the cleavage rate; however, morulae and blastocyst formation in the B&A embryos was significantly higher than that of other groups (P < 0.05) and got pregnant. CONCLUSIONS: Electric stimulation before and after injection was an effective method in inducing bovine oocyte activation and in sustaining embryo development to the morulae and blastocyst stage.

Animals↗
PubMed2000

Clinical correlation of cyclin D2 mRNA expression in human luteinized granulosa cells.

PURPOSE: The aim was to evaluate whether the expression of cyclin D2 mRNA in human luteinized granulosa cells correlates with the clinical parameters of women undergoing in vitro fertilization-embryo transfer (IVF-ET) programs. METHODS: Using reverse transcriptase-polymerase chain reaction (RT-PCR) techniques, the cyclin D2 mRNA in human luteinized granulosa cells of large follicles was measured. Correlation analysis between cyclin D2 mRNA expression and clinical parameters [age; day 3 follicle-stimulating hormone (FSH), luteinizing hormone (LH), and estradiol (E2); E2 and P4 at the day of human chorionic gonadotropin (hCG); total amount of gonadotropin and the number of days of gonadotropin administration; pregnancy outcome] were performed. RESULT(S): Cyclin D2 mRNA expression showed negative correlation with patient's age (R = -0.60, P < 0.005) and total amount of gonadotropins (R = -0.45, P < 0.03), and also showed positive correlation with serum E2 levels at the day of hCG administration (R = 0.55, P < 0.02). Other clinical parameters showed no statistical significance. Cyclin D2 mRNA expression of pregnant group was higher than that of nonpregnant group (P < 0.03). CONCLUSIONS: Cyclin D2 mRNA expression in human luteinized granulosa cells positively correlates with clinical parameters of ovarian function and may be a novel marker for the health of human ovarian follicle.

Adult↗