Biomedical subjects

K S Huang

Publications and source records attributed to K S Huang.

At least 19 recordsLinked to original sources

PubMed2001

[Prolactin in normal pregnancy and severe pregnancy-induced hypertension].

OBJECTIVE: This study was to investigate the relationship between serum prolactin and pregnancy-induced hypertension. METHOD: Maternal serum prolactin was estimated by radioimmunoassay in 89 normal pregnant women and 52 patients with severe pregnancy-induced hypertension at 28 to 42 week gestation. RESULTS: In normal pregnancy, prolactin level increased progressively from a mean value of 270 mg.L-1 in the 24th week to 440 mg.L-1 in the 34th week and decreased progressively from the 38th week to the 40th week. In severe pregnancy-induced hypertension increased progressively too; 31 of 52 patients with severe prolactin showed high prolactin levels in zone A (> mean value + standard of prolactin values in the normal pregnancy), 10 patients in zone B (mean + standard to mean) and 11 patients in zone C (< mean). CONCLUSION: These results suggest that high prolactin levels may play an important role in the pathogenesis of severe pregnancy-induced hypertension.

Adult↗

PubMed2001

Synthesis and reactions of some heterocyclic azacyanines.

The one-step reaction of some amino-substituted heterocycles with diiodomethane to give azacyanines is reported. This useful reaction is of wider application than initially reported and includes the synthesis of new substituted pyrido-, isoquino-, benzimadazo-, and benzothiazoazacyanines 7. Furthermore, treatment of these azacyanines with base generally affects a facile opening of the dihydrotriazinium ring resulting in the formation of new heterocycles 10, 11, and 12, which would be difficult to prepare by other means. This reaction takes an additional direction in the case of halo-substituted azacyanines 7b/c/d where treatment with base gives rise to new interesting derivatives of dipyridotriazines 14b/c/d.

Journal Article↗

PubMed2001

Anti-inflammatory tetramers of resveratrol from the roots of Vitis amurensis and the conformations of the seven-membered ring in some oligostilbenes.

Five resveratrol tetramers, amurensins I-M, were isolated from the roots of Vitis amurensis (Rupr.), together with five known resveratrol tetramers, (+)-hopeaphenol, isohopeaphenol, vitisin A, (+)-vitisifuran A, and heyneanol A. Their structures and stereochemistry were determined by chemical and spectroscopic methods, especially by use of 2D NMR analysis. Some of them had an ampelopsin A or a balanocarpol unit, in which the conformations of the seven-membered carbon ring were described for the first time. The anti-inflammatory activities of the tetramers were also tested. Among them, (+)-hopeaphenol, isohopeaphenol, vitisin A, (+)-vitisifuran A and heyneanol A showed potent inhibition on the biosynthesis of leukotriene B4 (LTB4), and amurensins I and L showed strong antagonism of the histamine acceptor.

Anti-Inflammatory Agents↗

PubMed2001

Biosynthetic pathway to the cancer chemopreventive secoisolariciresinol diglucoside-hydroxymethyl glutaryl ester-linked lignan oligomers in flax (Linum usitatissimum) seed.

Application of stable and radioisotope precursor/tracer experiments resulted in the identification of various phenylpropanoid, monolignol, and lignan metabolites involved in the biosynthesis of the cancer chemopreventive secoisolariciresinol diglucoside (SDG; 1)-containing ester-linked "polymer(s)" in flax (Linum usitatissimum) seed. Individual analysis of size-segregated flax seed capsules at five early stages of their development provided a metabolic profile of intermediates leading to "biopolymer" biosynthesis. The use of (1)H and (13)C NMR and HRMS analyses resulted in the identification of 6a-HMG (hydroxymethyl glutaryl) SDG (17) and 6a,6a'-di-HMG SDG (18) as the two major components of the ester-linked "biopolymer(s)". Based on metabolic tracer analyses and relative radioisotopic incorporations throughout each of these five stages of seed development, a biochemical pathway is proposed from phenylalanine to SDG (1), with subsequent mono- and di-substitutions of SDG (1) with HMG CoA. These metabolites then serve as precursors for formation of the SDG-HMG ester-linked oligomers. Results from this study will facilitate future isolation and characterization of the proteins and enzymes involved in biosynthesis of the SDG-HMG ester-linked oligomers in flax seed.

Benzimidazoles↗

PubMed2001

Three new stilbene trimers from the lianas of Gnetum hainanense.

Three new stilbene trimers, gnetuhainins M-O (1-3), were isolated from the lianas of Gnetum hainanense. Their structures and relative configurations were determined by spectroscopic evidence, especially on 2D NMR analysis. The anti-inflammatory activity has been tested for the isolated compounds.

Molecular Structure↗

PubMed2001

Four new stilbene dimers from the lianas of Gnetum hainanense.

Four new stilbene dimers, gnetuhainins P (1), Q (2), K (3) and L (4), were isolated from the lianas of Gnetum hainanense C. Y. Cheng. Their structures and relative configurations were determined on the basis of spectroscopic evidence, especially 2D NMR techniques.

China↗

PubMed2001

Kinetic measurements of cell surface E-selectin/carbohydrate ligand interactions.

Selectin/ligand interactions initiate the multistep adhesion and signaling cascades in the recruitment of leukocytes from circulation to inflamed tissues and may also play a role in tumor metastasis. Kinetic properties of these interactions are essential determinants governing blood-borne cells' tethering to and rolling on the vessel wall. Extending our recently developed micropipette method, we have measured the kinetic rates of E-selectin/ligand interactions. Red cells coated with an E-selectin construct were allowed to bind HL-60 or Colo-205 cells bearing carbohydrate ligands. Specific adhesions were observed to occur at isolated points, the frequency of which followed a Poisson distribution. These point attachments were formed at the same rate with both the HL-60 and Colo-205 cells (0.14 +/- 0.04 and 0.13 +/- 0.03 microm2 s(-2) per unit density of E-selectin, respectively) but dissociated from the former at a rate twice as fast as did from the latter (0.92 +/- 0.23 and 0.44 +/- 0.10 s(-1), respectively). The reverse rates agree well with those measured by the flow chamber. The forward rates are orders of magnitude higher than those of Fcgamma receptors interacting with IgG measured under similar conditions, consistent with the rapid kinetics requirement for the function of E-selectin/ligand binding, which is to capture leukocytes on endothelial surfaces from flow.

Animals↗

PubMed2000

Stilbene dimers from the lianas of Gnetum hainanense.

Five stilbene dimers, gnetuhainins F-J, were isolated together with gnetulin, rhapontigenin, isorhapontigenin and gnetol from the lianas of Gnetum hainanense C. Y. Cheng. Their structures and stereochemistry have been established on the basis of spectral evidence, especially 2D NMR spectroscopic techniques.

Molecular Structure↗

PubMed2000

Five new stilbene dimers from the lianas of Gnetum hainanense.

Five new stilbene dimers, gnetuhainins A-E (1-5), were isolated together with resveratrol trans-dehydrodimer (6), resveratrol, oxyresveratrol, and (-)-epsilon-viniferin from the lianas of Gnetum hainanense. Their structures and stereochemistry were determined on the basis of their chemical and spectral data. Compounds 1-5 are dimers formed by a resveratrol unit and an oxyresveratrol unit and belong to a new type of oligostilbenes polymerized from two different stilbene units.

Dimerization↗

PubMed2000

Nitric oxide modulates interleukin-1beta and tumor necrosis factor-alpha synthesis by alveolar macrophages in pulmonary tuberculosis.

Interleukin (IL)-1beta and tumor necrosis factor (TNF)-alpha released from alveolar macrophages (AM) in pulmonary tuberculosis (TB) are important in host defense against mycobacterial infection. Nitric oxide (NO) production is enhanced in AM of TB patients. We examined whether NO was implicated in (IL)-1beta and TNF-alpha synthesis by AM of TB patients. Purified AM were retrieved by bronchoalveolar lavage from 11 TB patients and 10 normal subjects, and were cultured with or without the NO inhibitor N(G)-monomethyl-L-arginine (L-NMMA). The release of IL-1beta and TNF-alpha, and expression of their messenger RNAs (mRNAs), were determined by enzyme-linked immunosorbent assay and Northern blot analysis. The release of IL-1beta and TNF-alpha was greater from AM of TB patients than from AM of normal subjects. L-NMMA inhibited nitrite, IL-1beta, and TNF-alpha production in TB patients. The mRNA expression for IL-1beta and TNF-alpha was upregulated in TB patients and was depressed by L-NMMA. Immunocytochemistry done with a monoclonal antibody against the p65 subunit of nuclear factor (NF)-kappaB showed that NF-kappaB was highly expressed and translocated to the nuclei of AM from TB patients, and was inhibited by L-NMMA. Inhibition of NF-kappaB by pyrrolidine dithiocarbamate attenuated IL-1beta and TNF-alpha synthesis. In conclusion, enhanced NO generation by AM of TB patients plays an autoregulatory role in amplifying the synthesis of proinflammatory cytokines, probably through NF-kappaB activation.

Adult↗

PubMed1999

Morphine tolerance in arthritic rats and serotonergic system.

To understand whether chronic inflammation alters the development of morphine tolerance, the tail-flick test was used to evaluate the analgesic effect of morphine (75 mg tablet, s.c.) in the arthritic rats at the day 9-12 after the inoculation with Freund's adjuvant. Spinal cord monoamines and amino acid neurotransmitters were concomitantly measured. Chronic inflammation attenuated the antinociceptive effect of morphine as tolerance developed faster in the arthritic rats compared to the vehicle-treated controls. In addition, ratio of 5-hydroxyindole-3-acetic acid/5-hydroxytryptamine (5-HIAA/5-HT) increased in the lumbar spinal cord of arthritic rats without any change in the concentrations of norepinephrine, glutamate, aspartate or GABA. Interestingly, increased serotonin turnover in the spinal cord was observed in both control and arthritic rats 24 hours after morphine treatment. Overall, the results suggest a significant role of serotonin up-regulation in the spinal cord during chronic pain and the development of morphine tolerance.

Analgesics, Opioid↗

PubMed1999

Oligostilbenes from the roots of Vitis amurensis.

Two new oligostilbenes, amurensin A (1) and amurensin B (2), were isolated from the roots of Vitis amurensis Rupr. together with five known oligostilbenes. Their structures were elucidated by means of spectroscopic evidence, and amurensin B was the first naturally occurring stilbene trimer with a cis dihydrobenzofuran moiety.

Magnoliopsida↗

PubMed1995

Development of scintillation proximity assays for E-selectin and their application in testing potential antagonists.

E-selectin, a cell adhesion molecule expressed on endothelial cells, is involved in the trafficking of neutrophils to areas of inflammation. The tetrasaccharide sialyl Lewis x (sLe(x)) and other analogues have been shown to be weak affinity antagonists. To study the structure/activity relationship of these weak affinity antagonists, we have developed several scintillation proximity assays (SPAs) for E-selectin. Two of these involve immobilizing E-selectin to streptavidin-coated SPA beads through a biotinylated anti-E-selectin monoclonal antibody. These beads are incubated with 125I-labeled carcinoembryonic antigen (an sLe(x)-containing protein) or 3H-labeled HL-60 cells and the amount of bound ligand is quantitated by counting in a beta-scintillation counter. In addition, we have developed a method to prepare a functionally active biotinylated E-selectin, which can be directly coupled to SPA beads and assayed for ligand binding. These SPAs are sensitive, reproducible, and suitable for screening antagonists and studying structure/activity relationships of lead compounds. By using the SPA, we have also showed that an sLe(x) polyacrylamide polymer is 10 times more potent than the monomer, suggesting that the potency of E-selectin antagonists can be greatly enhanced by multivalent presentation.

Antibodies, Monoclonal↗

PubMed1995

Modulation of E-selectin structure/function by metal ions. Studies on limited proteolysis and metal ion regeneration.

E-selectin is a member of the selectin family of proteins that recognize carbohydrate ligands in a Ca(2+)-dependent manner. In order to better understand the role of Ca2+ in E-selectin-ligand interactions, we examined the E-selectin structure by limited proteolysis. Apo-Lec-EGF-CR6, a Ca(2+)-free form of soluble E-selectin containing the entire extracellular domain, was sensitive to limited proteolysis by Glu-C endoproteinase. Amino-terminal sequencing analysis of the proteolytic fragments revealed that the major cleavage site is at Glu98 which is in the loop (residues 94-103) adjacent to the Ca2+ binding region of the lectin domain. Upon Ca2+ binding, Lec-EGF-CR6 was protected from proteolysis. This Ca(2+)-dependent protection was further augmented upon sialyl Lewis x (sLex) ligand binding. These results implied that Ca2+ binding to E-selectin induces a conformational change and perhaps facilitates ligand binding. The sLex-bound complex in turn stabilizes Ca2+ binding. Lec-EGF-CR6 contains only one high-affinity Ca2+ site (Kd = approximately 3.5 microM) as determined by equilibrium dialysis. In addition, we found that Ba2+ was a potent antagonist in blocking Lec-EGF-CR6-mediated HL-60 cell adhesion. By competitive equilibrium dialysis and proteolysis analysis, we demonstrated that Ba2+ bound to apo-Lec-EGF-CR6 5-fold tighter than Ca2+ and abolished ligand binding activity. Sr2+ also bound to apo-Lec-EGF-CR6 tighter than Ca2+. However, Sr(2+)-regenerated Lec-EGF-CR6 showed 50% ligand binding activity. Mg2+ bound to apo-Lec-EGF-CR6 with much weaker affinity than Ca2+ and did not show any activity. Thus, E-selectin function can be modulated by different metal ions.

Amino Acid Sequence↗

PubMed1994

Structural features of GPI-specific phospholipase D revealed by proteolytic fragmentation and Ca2+ binding studies.

Glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD) is abundant in plasma and is potentially capable of degrading the anchor utilized by many cell surface proteins. The goal of this work was to study structural features of the GPI-PLD that might be involved in regulation of its activity. Trypsin cleaved the 100-110 kDa GPI-PLD polypeptide into three major fragments (two of approximately 40 kDa and a carboxyl-terminal fragment of 30 kDa) which were relatively resistant to further proteolysis. Pretreatment of the GPI-PLD with chelators resulted in complete degradation. During the cleavage process the GPI-PLD enzymatic activity increased approximately 3-4-fold but no other major change in its properties (e.g. inhibition by chelators and lipids, thermal stability, oligomerization, etc.) was observed. Intact or trypsinized GPI-PLD bound 45Ca2+ (approximately 5.5 ions/molecule GPI-PLD; Kd approximately 16.1 microM as determined by equilibrium dialysis) which could not be blocked by the addition of other divalent metal ions. However, inhibition of enzymatic activity by divalent cation chelators appeared to involve removal of bound Zn2+ rather than Ca2+. A metal analysis of GPI-PLD revealed approximately 5 and 10 atom/molecule of calcium and zinc, respectively. The data suggest that the predicted integrin E-F hand-like sites in GPI-PLD are functional but not directly involved in enzymatic activity.

Amino Acid Sequence↗

PubMed1994

Temporal regulation of the IgE-dependent 1,2-diacylglycerol production by tyrosine kinase activation in a rat (RBL 2H3) mast-cell line.

We explored the possible role of tyrosine kinases in the IgE-dependent regulation of 1,2-diacylglycerol (DAG) production in RBL 2H3 cells. When triggered via their high-affinity IgE receptors (Fc epsilon RI), there was a rapid phosphorylation of tyrosine residues on a number of proteins. The phosphorylation of these proteins and ultimately histamine release were inhibited in a concentration-dependent manner by the tyrosine kinase inhibitor, tyrphostin. In cells labelled with [3H]myristic acid, we observed a characteristic biphasic increase in [3H]DAG production. In the presence of tyrosine kinase inhibitor, the initial increase in DAG was still observed, but the secondary increase, which was dependent on phosphatidylcholine-specific phospholipase D (PC-PLD) activation, was completely abolished. Tyrphostin significantly inhibited IgE-dependent activation of PC-PLD, suggesting that PC-PLD activation was regulated by tyrosine phosphorylation. Furthermore, when proteins from RBL 2H3 cells were immunoprecipitated with an anti-phosphotyrosine antibody, PC-PLD activity was recovered from the immunoprecipitated fraction. These results demonstrate that the secondary, but not the initial, phase of 1,2-DAG production in response to Fc epsilon RI aggregation is regulated by the initial activation of tyrosine kinases and that PC-PLD may be regulated directly by this mechanism.

Animals↗

PubMed1994

Insight into E-selectin/ligand interaction from the crystal structure and mutagenesis of the lec/EGF domains.

The three-dimensional structure of the ligand-binding region of human E-selectin has been determined at 2.0 A resolution. The structure reveals limited contact between the two domains and a coordination of Ca2+ not predicted from other C-type lectins. Structure/function analysis indicates a defined region and specific amino-acid side chains that may be involved in ligand binding. These features of the E-selectin/ligand interaction have important implications for understanding the recruitment of leukocytes to sites of inflammation.

Amino Acid Sequence↗

PubMed1994

A ligand binding assay for E-selectin.

We describe here a cell-free ligand binding assay for E-selectin. The assay involves immobilizing soluble E-selection onto microtiter plates and incubating with 125I-labeled carcinoembryonic antigen (CEA) which carries the tetrasaccharide sialyl Lewis x (sLex). The bound CEA is eluted by ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N',-tetraacetic acid and monitored by radioactivity. The binding is abolished by preincubation of either CEA with an anti-sLex antibody or E-selectin with a neutralizing anti-E-selectin antibody, indicating that this is an E-selectin/sLex-specific interaction. The binding is Ca2+ and pH dependent (the optimal pH at 7.0) and also requires sialic acid. Removal of sialic acid from CEA by neuraminidase digestion abrogates the binding. When the protein but not carbohydrate constituent of CEA was denatured by reduction and alkylation, the binding was partially eliminated, indicating that the interaction may also be dependent on either protein conformation or carbohydrate orientation. The assay is simple, sensitive, and comparable to other methods as indicated by an IC50 of 1 mM for sLex. Thus, the assay should be useful for screening antagonists and studying E-selectin structure/function.

Antibodies↗