Biomedical subjects

S Hong

Publications and source records attributed to S Hong.

At least 109 records · Page 6Linked to original sources

PubMed1999

"Dip-Pen" nanolithography

A direct-write "dip-pen" nanolithography (DPN) has been developed to deliver collections of molecules in a positive printing mode. An atomic force microscope (AFM) tip is used to write alkanethiols with 30-nanometer linewidth resolution on a gold thin film in a manner analogous to that of a dip pen. Molecules are delivered from the AFM tip to a solid substrate of interest via capillary transport, making DPN a potentially useful tool for creating and functionalizing nanoscale devices.

Journal Article↗

PubMed1999

Noncompetitive, Ca(2+)-independent inhibition of pyruvate dehydrogenase phosphatase by fluphenazine.

The effects of two different classes of calmodulin antagonists on the catalytic activities of purified pyruvate dehydrogenase (PDH) phosphatase and PDH complex (PDC) were studied. In general, PDH phosphatase was more strongly inhibited than PDC by the calmodulin antagonists with the following potency order: fluphenazine > chlorpromazine > thioridazine > triflupromazine. Promazine and two sulfonamides (W-5 and W-7) did not suppress PDH phosphatase activity at 1 mM concentrations, while about 20% of PDC activity was inhibited by these antagonists. Fluphenazine-mediated inhibition of PDH phosphatase was observed with the purified PDC as well as intact mitochondria. Although Ca2+ stimulates PDH phosphatase activity, the addition of exogenous Ca2+ did not overcome the inhibition by calmodulin antagonists. These results suggest that the suppression of PDH phosphatase activity is dependent upon the structure of the individual calmodulin antagonist and appears to be Ca(2+)-independent. Kinetic analysis showed a noncompetitive inhibition of PDH phosphatase by fluphenazine, indicating that it binds to different site(s) from the catalytic site of the enzyme.

Animals↗

PubMed1999

Peptide dependency of alloreactive CD4+ T cell responses.

Alloreactivity, the capacity of a large number of T lymphocytes to react with foreign MHC molecules, represents the cellular basis for the rejection of tissue grafts. Although it was originally assumed that the TCR of alloreactive T cells focus their recognition on the polymorphic residues that differ between the MHC molecules of responder and stimulator cells, studies in the MHC class I system have clearly demonstrated that MHC-bound peptides can influence this interaction. It remains unclear, however, whether peptides play an equally important role for the recognition of MHC class II molecules by alloreactive CD4+ T cells. Another issue that remains unresolved is the overall frequency of peptide-dependent versus peptide-independent alloreactive T cells. We have addressed these questions with antigen-presenting cells (APC) from H2-M mutant mice that predominantly express a single MHC class II-peptide complex, H2-Ab bound by a peptide (CLIP) derived from the class II-associated invariant chain. APC from these mice were used as targets and stimulators for alloreactive CD4+ T cells. Results demonstrated that the vast majority of CD4+ alloreactive T cells recognize MHC class II molecules in a peptide-dependent fashion.

Amino Acid Sequence↗

PubMed1999

Lipid antigen presentation in the immune system: lessons learned from CD1d knockout mice.

CD1 molecules represent a distinct lineage of antigen-presenting molecules that are evolutionarily related to the classical major histocompatibility complex (MHC) class I and class II molecules. Unlike the classical MHC products that bind peptides, CD1 molecules have evolved to bind lipids and glycolipids. Murine and human CD1d molecules can present glycolipid antigens such as alpha-galactosylceramide (alpha-GalCer) to CD1d-restricted natural killer (NK) T cells. Using CD1d knockout mice we demonstrated that CD1d expression is required for the development of NK T cells. These animals were also deficient in the rapid production of interleukin-4 and interferon-gamma in response to stimulation by anti-CD3 antibodies. Despite these defects, CD1d knockout animals were able to generate strong T-helper type 1 (TH1) and TH2 responses. Spleen cells from these animals neither proliferated nor produced cytokines in response to stimulation by alpha-GalCer. Repeated injection of alpha-GalCer into wild-type but not CD1d mutant mice was able to clear metastatic tumors. We further showed that alpha-GalCer can inhibit disease in diabetes-prone non-obese diabetic mice. Collectively, these findings with CD1d knockout animals indicate a critical role for CD1d-dependent T cells in various disease conditions, and suggest that alpha-GalCer may be useful for therapeutic intervention in these diseases.

Animals↗

PubMed1999

Identification of a cytoplasmic targeting/retention signal in a retroviral Gag polyprotein.

Retroviral capsid assembly can occur by either of two distinct morphogenic processes: in type C viruses, the capsid assembles and buds at the plasma membrane, while in type B and D viruses, the capsid assembles within the cytoplasm and is then transported to the plasma membrane for budding. We have previously reported that a single-amino-acid substitution of a tryptophan for an arginine in the matrix protein (MA) of Mason-Pfizer monkey virus (MPMV) converts its capsid assembly from that of a type D retrovirus to that of the type C viruses (S. S. Rhee and E. Hunter, Cell 63:77-86, 1990). Here we identify a region of 18 amino acids within the MA of MPMV that is responsible for type D-specific morphogenesis. Insertion of these 18 amino acids into the MA of type C Moloney murine leukemia virus causes it to assemble an immature capsid in the cytoplasm. Furthermore, fusion of the MPMV MA to the green fluorescent protein resulted in altered intracellular targeting and a punctate accumulation of the fusion protein in the cytoplasm. These 18 amino acids, which are necessary and sufficient to target retroviral Gag polyproteins to defined sites in the cytoplasm, appear to define a novel mammalian cytoplasmic targeting/retention signal.

3T3 Cells↗

PubMed1999

Is ethanol an important antioxidant in alcoholic beverages associated with risk reduction of cataract and atherosclerosis?

It has been reported in the epidemiological literature that cataract, stroke, and atherosclerosis risk is reduced by 50% in people consuming one alcoholic drink per day. Peroxide has been implicated as a causative agent in cataractogenesis, and LDL oxidation appears to play a role in atherosclerosis. The antioxidant activity of alcohol was measured by: (i) use of a luminescent assay developed in our laboratory, confirmed as appropriate; (ii) electron spin resonance (ESR) spin-trapping; and (iii) copper-catalysed oxidation of LDL and VLDL from hamsters fed 6% ethanol in their drinking water. Ethanol reduced the luminescent counts/min from peroxide and superoxide. It significantly reduced the spin-trapped signal of hydroxyl radical, but not the superoxide signal. Other alcohols also showed large reductions in counts from hydrogen peroxide. Plasma from hamsters fed 6% ethanol had lower lipid peroxides and the oxidizability of LDL and VLDL was significantly reduced compared to controls. These data provide a possible explanation for the effect of beverages containing ethanol in the reduction of cataract and atherosclerosis risk observed in human population studies.

Alcohol Drinking↗

PubMed1999

The alpha-subunit of human choriogonadotropin interacts with the exodomain of the luteinizing hormone/choriogonadotropin receptor.

The LH/CG receptor, a G protein-coupled receptor, consists of two parts, the N-terminal extracellular segment (exodomain) and the membrane-associated C-terminal segment (endodomain). hCG initially binds the exodomain of the receptor and then, the hormone/exodomain complex is thought to make the secondary contact with the endodomain of the receptor and generate a hormone signal. However, little direct evidence is available about which hormone subunits (alpha or beta) interact with which domains of the receptor. To determine whether the alpha-subunit contacts the exodomain of its receptor, hCG containing [125I]alpha and truncated exodomain lacking the endodomain were prepared. They were chemically cross-linked, and the resulting cross-linked complexes were solubilized and electrophoresed. The results indicate that the alpha-subunit of hCG was directly and specifically cross-linked to the exodomain. To verify the cross-linked exodomain by the independent method, the Flag epitope was inserted between the signal sequence and the mature exodomain. hCG containing [125I]alpha was cross-linked to the Flag exodomain, and the resulting cross-linked hCG/Flag exodomain complexes were immunoprecipitated with anti-Flag antibody. The results show that the material cross-linked to hCG containing [125I]alpha is indeed the exodomain. In conclusion, our results show the direct interaction of the alpha-subunit with the exodomain and, therefore, its crucial role in the hormone-receptor interaction in addition to its involvement in signal generation.

Affinity Labels↗

PubMed1999

Generating correlation matrices with model error for simulation studies in factor analysis: a combination of the Tucker-Koopman-Linn model and Wijsman's algorithm.

Most simulation studies in factor analysis follow a process of constructing population correlation matrices from the common-factor model and generating sample correlation matrices from the population matrices. In the common-factor model, the population correlation matrix is perfectly fit by the model's containing common and unique factors. However, since no mathematical model accounts exactly for the real-world phenomena that it is intended to represent, the Tucker-Koopman-Linn model (1969) is more realistic for generating correlation matrices than the conventional common-factor model because the former incorporates model error. In this paper, a procedure for generating population and sample correlation matrices with model error by combining the Tucker-Koopman-Linn model and Wijsman's algorithm (1959) is presented. The SAS/IML program for generating correlation matrices is described, and an example is also provided.

Algorithms↗

PubMed1999

[Application of modified ultrafiltration to cardiac surgery in adults].

Modified Ultrafiltration (MUF) was developed for blood concentration and reduction of postoperative edema in cardiac surgery in children. Its beneficial effects on postoperative hemodynamics have been reported. We applied MUF to cardiac surgery in adults and evaluated its usefulness. Between August, 1995 and April, 1997, MUF was performed in 41 adult patients. MUF was carried out immediately after the cessation of cardiopulmonary bypass. The mean fluid volume removed was 1,135.9 +/- 274.1 ml. The patient's haematocrit significantly increased from 23.2 +/- 2.6% to 26.9 +/- 3.2% (p < 0.0001). The dose of inotropes administered was maintained constant during MUF, and no changes were observed in CVP and the heart rate. However, the systolic blood pressure increased from 99.5 +/- 14.7 to 113.2 +/- 16.2 mmHg (p < 0.0001) and cardiac index from 4.2 +/- 0.9 to 4.9 +/- 1.3 l/min/m2 (p = 0.0006). It was suggested that MUF was an useful technique of haemoconcentration and appeared to have beneficial effects on postoperative hemodynamics in adult cardiac surgery.

Adult↗

PubMed1999

[Study of autoimmunity in progeny of pregnant women with systemic lupus erythematosus].

OBJECTIVE: To study the effect of systemic lupus erythematosus (SLE) on physical, mental development and plasma antibody level of SLE in their progenies. METHODS: Routine physical examinations of 49 children from 48 SLE mothers were conducted. Compared immuno-fluorescence anti-nuclear antibody (IFANA), anticardiolipin (ACL), extractable nuclear antigen (ENA) and anti-ds-DNA plasma levels of SLE mothers and their progenies with that levels during pregnancy and in umbilical blood. RESULTS: The physical development (height and weight) in 47 out of 49 children were within normal range while the remaining 2 were in the lower limit. The autoimmune antibodies were all negative in the umbilical blood with autoimmune negative mothers, while the anti-ribonucleoprotein (anti-RNP), anti-Smith surface antigen (anti-SSA), anti-specific soluble ribonucleic acid (anti-SSB) and ACL could be transferred to fetus through placenta. During follow up study, compared the autoimmune positive rates in progenies with that of mothers, the positive rates of IFANA and anti-ds-DNA decreased significantly (P < 0.01), while no changes in ACL. Compared the autoimmune positive rates in progenies with that of their own umbilical levels, the positive rates of IFANA, anti-RNP, anti-SSA decreased significantly (P < 0.01), while no difference existed in ACL. Boys showed faster disappearance of autoimmune positive rates than that of girls. CONCLUSIONS: SLE did not show significant effects on the physical development of their progenies. Most autoimmune antibodies existed in umbilical blood were transferred through placenta during pregnancy and would disappear within 9 years after birth. Autoimmune antibodies decreased quicker in boys, and it indicated that girls should be follow-up more carefully. Autoimmune antibodies in the umbilical blood is an easy method for the screening of SLE progeny.

Adult↗

PubMed1999

[A case-control study on cerebral palsy in children].

OBJECTIVE: To identify the risk factors for cerebral palsy (CP) in children. METHODS: A population-based 1:2 matched case-control study was conducted during May to June 1997 in southern Jiangsu Province of China. RESULTS: Risk factors for CP in children could be summarized into four categories, i.e.; (1) fetal growth retardation, preterm delivery and low birth weight; (2) asphyxia at birth, intracranial hemorrhage, ischemic and hypoxic encephalopathy and hyperbilirubinemic encephalopathy; (3) delivery with vaccum suction and traumatic brain injury; and (4) other prenatal factors. CONCLUSION: The first and second categories of risk factors correlated strongly and reproducibly with CP in children. It is emphasized that antenatal care be enforced to prevent occurrence of risk factors, such as low birth weight, etc., and the newborns with asphyxia be vigorously rescued and put under close supervision. For risk factors in the third category, the key measures should be obstetric practice and health education for the parents. But, little about the knowledge of the risk factors in the fourth category has been understood, which could be associated with those in the first two categories.

Asphyxia Neonatorum↗

PubMed1999

[Study on the combination of isotachophoresis and high performance liquid chromatography for the separation of complex samples].

A method on the combination of isotachophoresis (ITP) and high performance liquid chromatography (HPLC) for the separation and analysis of the complex samples containing proteins and metals is proposed. The instrumental system consisted of a self-made Model OCEP-1 isotachophoresis analyser, main parts of Waters high performance liquid chromatograph and a self-made Model IHI-1 interface. The interface is simple and convenient to use. The injection volume of the interface was determined accurately with a neutralization titration method. In ITP experiment the leading electrolyte was 2.5 mmol/L HCl containing 30 mmol/L of 18-crown-6; the terminating electrolyte was 5 mmol/L Tris+Cl-(pH 6.0); ITP current, 40 microA; detection of metal ions, potential gradient detector. In HPLC experiment the column was a mu-Bondapak C18, reversed-phase column, 4 mm x 200 mm, 10 microns, 12.5 nm; the mobile phase A, V(isopropanol with 5% volume fraction):V(butanol) = 2:1 containing 2.2 mmol/L HCl (pH 2.63); the mobile phase B, V(isopropanol with 50% volume fraction):V(butanol) = 2:1; low pressure gradient elution, mobile phase B changed from 0 to 70% in 17.5 minutes; flow rate, 1.0 mL/min; detection wavelength 225 nm; temperature, 25 degrees C. The experimental results showed that proteins were interfered in the determination of the metals with ITP method. It also showed that HPLC with the use of C18 column can separate the proteins but not the metal ions. By using this new combination system, a complex sample of the proteins and metal ions was injected to the HPLC, the proteins Lys, BSA and OVA were well separated in HPLC, while NH4+, K+, Na+, and Ca2+ were less retained and eluted first. Then the latter was introduced into the system of the ITP with the aid of the interface for separation. Satisfactory results were obtained.

Calcium↗

PubMed1999

[Detection of IgM-antibody to hepatitis G virus and its clinical significance].

OBJECTIVE: To provide a rapid and early serodiagnostic technique for the patients with hepatitis G virus(HGV). METHODS: A capture ELISA was developed to detect anti-HGV IgM in sera using synthetic peptides of HGV NS3 NS5 gene regions conjugated with horseradish peroxidase. RESULTS: This assay was not disturbed by competition of specific IgG or interfered by RF and did not cross-react with HAV, HBV, HCV, HEV, CMV and EBV. Among 46 sera of non-A-E hepatitis, 14 were positive for anti-HGVIgM, the positive rate was 30.43%, 6 was positive for HGV RNA the positive rate was 42.86%. 12 paired sera from acute stage of HGV patients were all positive by capture-ELISA. CONCLUSION: This method is sensitive, specific, rapid and stable for detecting anti-HGV IgM, and is useful in the early diagnosis of HGV infection.

Enzyme-Linked Immunosorbent Assay↗

PubMed1998

The amino-terminal region of the luteinizing hormone/choriogonadotropin receptor contacts both subunits of human choriogonadotropin. I. Mutational analysis.

The luteinizing hormone/choriogonadotropin receptor is a seven-transmembrane receptor. Unlike most seven-transmembrane receptors, it is composed of two halves of equal size, the N-terminal extracellular exodomain and the C-terminal membrane-associated endodomain. The exodomain is exclusively responsible for high affinity hormone binding, whereas receptor activation occurs only in the endodomain. This mutually exclusive physical separation of the two functional domains sets the lutropin receptor and its subfamily of receptors apart from all other seven-transmembrane receptors. The mechanisms of hormone binding and receptor activation also appear to be different from those of other receptors in that binding occurs in at least two steps. However, the precise hormone contact sites in the exodomain are unknown. To determine the hormone/receptor contact sites, we have examined the receptor using progressive truncation from the C terminus, Ala scanning, immunofluorescence microscopy, and antibody binding. Progressive truncation from the C terminus of the receptor indicates several discrete regions that impact hormone binding. These regions are around the boundaries of exons 1-2, 4-5, 6-7, and 9-10. Ala scanning of the Asp17-Arg26 region near the exon 1-2 junction uncovered three alternating residues (Leu20, Cys22, and Gly24) crucial for hormone binding. Ala substitution for any one of these residues abolished hormone binding, although the resulting mutant receptors were successfully expressed on the cell surface. In contrast, Ala substitution for their flanking and intervening residues did not impair hormone binding. These results and the data in the accompanying article (Phang, T., Kundu, G., Hong, S., Ji, I., and Ji, T. (1998) J. Biol. Chem. 273, 13841-13847) indicate that this region directly contacts the hormone and suggest a novel mode of embracing the hormone.

Antibodies↗

PubMed1998

The amino-terminal region of the luteinizing hormone/choriogonadotropin receptor contacts both subunits of human choriogonadotropin. II. Photoaffinity labeling.

The luteinizing hormone/choriogonadotropin receptor, a seven-transmembrane receptor, is composed of two equal halves, the N-terminal extracellular exodomain and the C-terminal membrane-associated endodomain. Unlike most seven-transmembrane receptors, the exodomain alone is responsible for high affinity hormone binding, whereas signal is generated in the endodomain. These physical separations of hormone-binding and receptor activation sites are attributed to unique mechanisms for hormone binding and receptor activation of this receptor and its subfamily members. However, the precise hormone contact sites in the exodomain are unclear. In the preceding article (Hong, S., Phang, T., Ji, I., and Ji, T. H. (1998) J. Biol. Chem. 273, 13835-13840), a region immediately downstream of the N terminus of the exodomain was shown to be crucial for hormone binding. To test if the region interacts with the hormone, human choriogonadotropin (hCG) was photoaffinity-labeled with a peptide mimic corresponding to Gly18-Tyr36 of the receptor. This peptide mimic specifically photoaffinity-labeled both the alpha- and beta-subunits of hCG. Interestingly, hCGalpha was preferentially labeled. On the other hand, denatured hCG was not labeled, and a mutant analog of the peptide failed to label hCG. Furthermore, the affinity labeling was UV-dependent and saturable, indicating the specificity of the photoaffinity labeling. Our results indicate that the region of the exodomain interacts with hCG and that the contact points are near both subunits of hCG. Particularly, the alternate residues (Leu20, Cys22, and Gly24) are crucial for hCG binding. In addition, the results underscore the fact that there is a crucial hormone contact site outside of the popularly believed primary hormone-binding site that is composed of Leu-rich repeats and is located in the middle of the exodomain. Our observations are crucial for understanding the molecular mechanism through which the initial high affinity hormone binding leads to receptor activation in the endodomain.

Amino Acid Sequence↗

PubMed1998

Mitogen-activated protein kinases activated by lipopolysaccharide and beta-amyloid in cultured rat microglia.

To test whether mitogen-activated protein kinases (MAPKs) are involved in microglial activation, pure microglia prepared from 1- to 3-day-old rat brains were activated with either 100 ng/ml lipopolysaccharide (LPS) or 5 nM synthetic beta-amyloid (Abeta) (25-35). The patterns of MAPK activation following LPS and Abeta treatment were very similar. Three MAPK subtypes, p38, extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase/stress-activated protein kinase (JNK/SAPK) were activated within 15 min and the activities of p38 and ERK were rapidly reduced to background level within 30 min while that of JNK was maintained for over 1 h. Both inhibitors of p38 (SB203580) and ERK pathway (PD098059) reduced LPS-induced nitric oxide (NO) release and Abeta-induced tumor necrosis factor-alpha (TNF-alpha) release. Furthermore, co-treatment of SB203580 and PD098059 additively reduced NO and TNF-alpha release. These results suggest that MAPK, at least p38 and ERK, mediate LPS-, and Abeta-induced microglial activation.

Amyloid beta-Peptides↗

PubMed1998

Discovery of LB30057, a benzamidrazone-based selective oral thrombin inhibitor.

Systematic variation of the so-called P-pocket moiety of benzamidrazone-based selective thrombin inhibitors led to the discovery of LB30057. It is potent (Ki = 0.38 nM for human thrombin), selective (Ki = 3290 nM for bovine trypsin), and orally bioavailable (58% oral bioavailability in dogs). LB30057 was efficacious in thrombosis animal models.

Animals↗

PubMed1998

Heavy metals in antarctic ice from Law Dome: initial results.

Pb, Cd, Cu, and Zn have been measured using ultraclean procedures in eight sections taken from two well-dated ice cores from Law Dome, an independent small size ice cap with high accumulation rate situated in the coastal area of East Antarctica. Seven sections were dated from the 1830s to 1940s and one was dated from three millennia ago. The data show that there are strong seasonal variations in the concentrations of Pb and Cd, with values approximately tow-to fourfold higher in winter than in spring-summer. Evaluation of the contributions from the different sources suggests that contribution from sea salt spray is relatively important, especially for Cd. Contribution from marine biogenic emissions could also be very significant. The importance of marine contributions is consistent with strong intrusions of marine air masses at this coastal site, especially during wintertime.

Aluminum↗