Biomedical subjects

L X Wang

Publications and source records attributed to L X Wang.

At least 19 recordsLinked to original sources

PubMed2006

Baculovirus-derived human immunodeficiency virus type 1 virus-like particles activate dendritic cells and induce ex vivo T-cell responses.

We have recently developed a candidate human immunodeficiency virus type 1 (HIV-1) vaccine model based on HIV-1 Pr55(gag) virus-like particles (HIV-VLPs), produced in a baculovirus expression system and presenting a gp120 molecule from a Ugandan HIV-1 isolate of clade A (HIV-VLP(A)s). The HIV-VLP(A)s show the induction in BALB/c mice of systemic and mucosal neutralizing antibodies as well as cytotoxic T lymphocytes, by intraperitoneal as well as intranasal administration. In the present article, the effects of the baculovirus-expressed HIV-VLPs on human immature monocyte-derived dendritic cells (MDDCs) have been evaluated. The HIV-VLPs efficiently induce maturation and activation of MDDCs and are incorporated into MDDCs preferentially via an actin-dependent macropinocytosis and endocytosis. The HIV-VLP-activated MDDCs show enhanced Th1- and Th2-specific cytokine production, and the effects of HIV-VLPs on MDDCs are not mediated through Toll-like receptors 2 and 4 (TLR2 and -4) signaling. Finally, HIV-VLP-loaded MDDCs are able to induce a primary and secondary response in autologous human CD4(+) T cells in an ex vivo immunization assay. Our results on the interaction and processing of baculovirus HIV-VLPs by MDDCs give an insight into the mechanisms underlying the immune response induced by HIV-VLP(A)s in vivo.

Actins↗

PubMed2002

Microsatellite mapping of the powdery mildew resistance gene Pm5e in common wheat (Triticum aestivum L.).

Powdery mildew, caused by Erysiphe graminis DM f. sp. tritici (Em. Marchal), is one of the most important diseases of common wheat world-wide. Chinese wheat variety 'Fuzhuang 30' carries the powdery mildew resistance gene Pm5e and has proven to be a valuable resistance source of powdery mildew for wheat breeding. Microsatellite markers were employed to identify the gene Pm5e in a F(2) progeny from the cross 'Nongda 15' (susceptible) x 'Fuzhuang 30' (resistant). The gene Pm5e was mapped in the distal region of chromosome 7BL. Seven microsatellite markers were found to be linked to the gene Pm5e, of which two codominant markers Xgwm783 and Xgwm1267 were relatively close to Pm5e with a linkage distance of 11.0 cM and 6.6 cM, respectively. It is possible to use the 136-bp allele of Xgwm1267 in 'Fuzhuang 30' for marker-assisted selection during the wheat resistance breeding process for facilitation of gene pyramiding. The mapping information in the present study provides a starting point for fine mapping of the Pm5 locus and map-based cloning to clarify the molecular structure and function of the different alleles at the Pm5 locus. A microsatellite linkage map of chromosome 7B was constructed with 20 microsatellite loci, nine on the short arm and 11 on the long arm. This information will be very useful for further mapping of agronomically important genes of interest on chromosome 7B.

Chromosome Mapping↗

PubMed2001

Mechanism of the cardioprotective effect of inhibition of the renin-angiotensin system on ischemia/reperfusion-induced myocardial injury.

Inhibition of the renin-angiotensin system (RAS) has been shown to be beneficial in providing cardioprotective effects in humans, but the mechanism of these effects is not well understood. In this study, we examined the effects and mechanism of RAS inhibitors on ischemia/reperfusion (IR)-induced myocardial injury in rats. Rats were randomly divided into five groups and treated with vehicle (C), angiotensin converting enzyme inhibitor (ACE-I), angiotensin II type 1 receptor antagonist (AT1-A), angiotensin II type 2 receptor antagonist (AT2-A) or ACE-I plus bradykinin B2 antagonist. Ten minutes after administration, the left main coronary artery was ligated for 45 min, and then reperfused for 120 min. IR-induced cardiomyocyte apoptosis was assessed by terminal deoxyribonucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay and confirmed by typical DNA laddering. Mitogen-activated protein kinase, extracellular signal-regulated protein kinase (ERK) and c-Jun NH2-terminal protein kinase (JNK) activity in the ischemic zone were measured by an in vitro kinase assay. The duration of ventricular tachycardia (VT) during ischemia was reduced by AT2-A and ACE-I, and increased by AT1-A and ACE-I+icatibant. ACE-I and AT2-A reduced apoptosis (by 54% and 53%) and infarct size (by 42% and 41%), while AT1-A increased apoptosis (by 86%) and infarct size (by 45%). These changes were negatively correlated with the change in ERK activity. The effects of ACE-I on apoptosis and infarct size were abolished by the coadministration of icatibant. Apoptosis was correlated with the occurrence of VT (r=0.837, p<0.001). These results suggest that both the accumulation of bradykinin and inhibition of AT2 receptor are cardioprotective against IR injury through the activation of ERK, but not JNK.

Angiotensin Receptor Antagonists↗

PubMed2001

[Molecular identification and mapping of a maize gene (Rf3) in S-type CMS using AFLP, RFLP and SCAR techniques].

The maize CMS-S near isogenic line (NIL) developed by author and the backcross progeny (BC1) derived from it were used to identify molecular markers linked to the Rf3 gene and subsequently determine its chromosomal location on the linkage map of maize. Bulk segreant analysis was performed using AFLP technique. From the survey of AFLP primer combination, two AFLP markers, (EcoRI-AGG/MseI-CAC and EcoRI-AAC/MseI-CAG), which were named RR6 and RR7 respectively, linked to the Rf3 gene were identified. However, AFLP marker RR6 showed polymorphism between parents, and bulks were used to survey the available 100 individuals of the BC1 population, 2 out of 100 shed recombination. The recombination-rate was 2%. The genetic distance between Rf3 gene and AFLP marker RR6, was approximately 2.0 cM. And then, the RR6 was successfully cloned and sequenced, primer synthesized and converted to SCAR marker so that PCR marker can be developed for the marker-assisted selection. In RFLP analysis, marker RR6 linked to Rf3 was found to be located between RFLP loci asg20 and php20581b, and mapped on chromosome 2L.

Chromosome Mapping↗

PubMed2001

[Studies on chemical constituents of Bletilla striata (Thunb) Reichb. f].

OBJECTIVE: To study the chemical constituents of Bletilla striata. METHOD: The constituents were separated and purified by column chromatography with silica gel, and identified by NMR, MS and physical data. RESULT: Three compounds were isolated and identified as hexacosanoic alcohol 3-(4-hydroxy-3-methoxybenzol)-trans-acryliceylenate(1), physcion(2) and cyclobalanol(3). CONCLUSION: Compound 1 was a new compound and compound 3 was isolated from this plant for the first time.

Acrylates↗

PubMed2000

Azido glycoside primer: a versatile building block for the biocombinatorial synthesis of glycosphingolipid analogues.

A lactoside primer, 12-azidododecyl beta-lactoside, was synthesized via the Koenigs-Knorr method by glycosylation of 1,12-dodecyldiol with perbenzoylated lactosyl bromide. The presence of the 2-O-acyl substituent in the donor gave the beta-lactoside, and an excess of acceptor ensured monoglycosylation of the diol. Mesylation of the omega-hydroxyl group in the aglycon, followed by displacement of the mesylate with azide and subsequent O-debenzoylation gave the desired omega-azidododecyl beta-lactoside. The azido glycoside primer was examined in mouse B16 melanoma cells for its feasibility as a building block for oligosaccharide biosynthesis. Uptake of the azido glycoside primer by B16 cells resulted in the sialylation of the galactose residue of the primer to give a glycosylated product having the same glycan as in ganglioside GM3. After 24 h incubation of B16 cells with the primers, the amount of sialylated omega-azidododecyl beta-lactoside primer was 75% of the amount of sialylated n-dodecyl beta-lactoside. However, after 48 h incubation, both primers gave equal amounts of the sialylated products. Interestingly, the remaining azido glycoside primer after 48 h incubation was 5.6-fold greater than that of the alkyl primer, indicating degradation of the alkyl primer to a larger extent than the omega-azido glycoside primer. The facile chemical synthesis and the efficient uptake in cells make the azido glycoside primer a versatile building block for the biocombinatorial synthesis of glycolipid oligosaccharides.

Animals↗

PubMed2000

The chitin disaccharide, N,N'-diacetylchitobiose, is catabolized by Escherichia coli and is transported/phosphorylated by the phosphoenolpyruvate:glycose phosphotransferase system.

We have previously reported that wild type strains of Escherichia coli grow on the chitin disaccharide N,N'-diacetylchitobiose, (GlcNAc)(2), as the sole source of carbon (Keyhani, N. O., and Roseman, S. (1997) Proc. Natl. Acad. Sci., U. S. A. 94, 14367-14371). A nonhydrolyzable analogue of (GlcNAc)(2,) methyl beta-N, N'-[(3)H]diacetylthiochitobioside ([(3)H]Me-TCB), was used to characterize the disaccharide transport process, which was found to be mediated by the phosphoenolpyruvate:glycose phosphotransferase system (PTS). Here and in the accompanying papers (Keyhani, N. O., Boudker, O., and Roseman, S. (2000) J. Biol. Chem. 275, 33091-33101; Keyhani, N. O., Bacia, K., and Roseman, S. (2000) J. Biol. Chem. 275, 33102-33109; Keyhani, N. O., Rodgers, M., Demeler, B., Hansen, J., and Roseman, S. (2000) J. Biol. Chem. 275, 33110-33115), we report that transport of [(3)H]Me-TCB and (GlcNAc)(2) involves a specific PTS Enzyme II complex, requires Enzyme I and HPr of the PTS, and results in the accumulation of the sugar derivative as a phosphate ester. The phosphoryl group is linked to the C-6 position of the GlcNAc residue at the nonreducing end of the disaccharide. The [(3)H]Me-TCB uptake system was induced only by (GlcNAc)(n), n = 2 or 3. The apparent K(m) of transport was 50-100 micrometer, and effective inhibitors of uptake included (GlcNAc)(n), n = 2 or 3, cellobiose, and other PTS sugars, i.e. glucose and GlcNAc. Presumably the PTS sugars inhibit by competing for PTS components. Kinetic properties of the transport system are described.

Biological Transport↗

PubMed2000

Nonhistone protein purified from porcine kidney acts as a suicide substrate inhibitor on furin-like enzyme.

AIM: To search and purify a naturally occurring protein inhibitor of the furin-like enzyme from the porcine kidney. METHODS: Recombinant kexin, a furin-like enzyme, from the yeast secretion expression was used as a target enzyme. The inhibitor component was extracted and purified from the acetone powder of porcine kidney. The inhibitory activity was monitored using a fluorogenic peptide substrate Boc-Arg-Val-Arg-MCA at spectrofluorimeter. RESULTS: The purified inhibitor component is a basic protein with an isoelectric point over 9.5. Its partial N-terminal sequence of 22 residues was determined, showing a high homology with nonhistone chromosomal protein HMG-17 in which there are four sites composed of dibasic residues, susceptible to be cleaved by the furin-like enzyme. This nonhistone protein could strongly compete with the fluorogenic substrate. However, this nonhistone protein would be degraded as a substrate by kexin if it was incubated with the enzyme for long time before adding the fluorogenic substrate, and subsequently lost its temporary inhibitory activity. CONCLUSION: The nonhistone protein isolated from the porcine kidney functioned as a suicide substrate inhibitor for the furin-like enzyme.

Amino Acid Sequence↗

PubMed2000

A preliminary study of the quantitative structure-retention relationship of ginsenosides in normal phase thin-layer chromatography.

The TLC retention of ten ginsenosides has been determined on silica gel layers developed with chloroform-ethyl acetate-methanol-water (15:40:22:10, V/V) as the mobile phase. For the quantitative structure-retention relationship (QSRR) study seventeen structure parameters of the ten ginsenosides were calculated, including topologic indices and physicochemical properties. Particularly, a novel parameter "E" was presented according to the differences of the parent substances of which the ginsenosides are composed. Of these parameters, Aw, 0B and E were selected by optimization and employed in the derived multi-parameter regression equation. The relationships between the retention and the molecular structures have been discussed.

Chemical Phenomena↗

PubMed1999

Structural characterization of the symbiotically important low-molecular-weight succinoglycan of Sinorhizobium meliloti.

The production of succinoglycan by Sinorhizobium meliloti Rm1021 is required for successful nodule invasion by the bacterium of its host plant, alfalfa. Rm1021 produces succinoglycan, an acidic exopolysaccharide composed of an octasaccharide repeating unit modified with acetyl, succinyl, and pyruvyl moieties, in both low- and high-molecular-weight forms. Low-molecular-weight (LMW) succinoglycan, previously thought to consist of monomers, trimers, and tetramers of the repeating unit, has been reported as being capable of promoting the formation of nitrogen-fixing nodules by succinoglycan-deficient derivatives of strain Rm1021. We have determined that the three size classes of LMW succinoglycan species are in fact monomers, dimers, and trimers of the repeating unit and that the trimer is the species active in promoting nodule invasion. A detailed structural analysis of the components of LMW succinoglycan by using various chromatographic techniques, along with nuclear magnetic resonance analyses, has revealed that there is considerable heterogeneity within the LMW succinoglycan oligomers in terms of noncarbohydrate substitutions, and we have determined the structural basis of this heterogeneity.

Chromatography↗

PubMed1998

Biosynthetic control of molecular weight in the polymerization of the octasaccharide subunits of succinoglycan, a symbiotically important exopolysaccharide of Rhizobium meliloti.

Succinoglycan, a symbiotically important exopolysaccharide of Rhizobium meliloti, is composed of polymerized octasaccharide subunits, each of which consists of one galactose and seven glucoses with succinyl, acetyl, and pyruvyl modifications. Production of specific low molecular weight forms of R. meliloti exported and surface polysaccharides, including succinoglycan, appears to be important for nodule invasion. In a previous study of the roles of the various exo gene products in succinoglycan biosynthesis, exoP, exoQ, and exoT mutants were found to synthesize undecaprenol-linked fully modified succinoglycan octasaccharide subunits, suggesting possible roles for their gene products in polymerization or transport. Using improved techniques for analyzing succinoglycan biosynthesis by these mutants, we have obtained evidence indicating that R. meliloti has genetically separable systems for the synthesis of high molecular weight succinoglycan and the synthesis of a specific class of low molecular weight oligosaccharides consisting of dimers and trimers of the octasaccharide subunit. Models to account for our unexpected findings are discussed. Possible roles for the ExoP, ExoQ, and ExoT proteins are compared and contrasted with roles that have been suggested on the basis of homologies to key proteins involved in the biosynthesis of O-antigens and of certain exported or capsular cell surface polysaccharides.

Dimerization↗

PubMed1998

Synthesis of aryl 3'-sulfo-beta-lactosides as fluorogenic and chromogenic substrates for ceramide glycanases.

We have previously reported that 4-methylumbelliferyl 6'-O-benzyl-beta-lactoside (2) is a useful substrate for a fluorometric assay of ceramide glycanase (CGase) (L.-X. Wang, N. V. Pavlova, S.-C. Li, Y.-T. Li and Y. C. Lee, Glycoconjugate J., 13 (1996) 359-365). The introduction of a 6-O-benzyl group at the terminal Gal efficiently protected the substrate from its hydrolysis by exo-galactosidase, permitting the assay of CGase in crude biological materials. However, a drawback of this substrate is its low water-solubility and relatively high Km (at a mM level). Introduction of a sulfate group into 4-methylumbelliferyl beta-lactoside (1) led to the formation of 4-methylumbelliferyl 3'-O-sulfo-beta-lactoside (3), which was found to be a more effective substrate than 2. Moreover, the presence of a 3'-O-sulfate group not only increases the water solubility tremendously, but also protects the substrate from cleavage by exo-beta-galactosidase as the 6'-O-benzyl group in 2 does. In addition to the fluorogenic substrate (3), two sulfated chromogenic substrates, N-tetradecanoyl-4-O(3'-sulfo-beta-lactosyl)-3-nitro-L-tyrosine methyl ester (9) and 2-N-(tetradecanoylamino)-4-nitro-phenyl 3'-sulfo-beta-lactoside (12), were synthesized and their suitability for a photometric assay of CGase was evaluated. Substrates 9 and 12, with a long fatty acid chain attached to the aglycon part, have a Km value close to that of the natural substrate GM1 (at a microM level).

Chromogenic Compounds↗

PubMed1998

Simultaneous determination of glucosamine and glucosamine 4-phosphate in Lipid A with high-performance anion-exchange chromatography (HPAEC).

A method for simultaneous determination of glucosamine (GlcN) and glucosamine 4-phosphate (GlcN-4-P) in Lipid A with high-performance anion-exchange chromatography (HPAEC) is described. Lipid A is hydrolyzed with 4 M HCl for 16 h at 100 degrees C, and the peaks of glucosamine and glucosamine 4-phosphate were measured. The true GlcN value can be computed from the GlcN value after correction for the incomplete hydrolysis of GlcN-4-P, or by the combined yield of GlcN and GlcN-4-P.

Chromatography, High Pressure Liquid↗

PubMed1997

alpha-KDOase activity in oyster and synthesis of alpha- and beta-4-methylumbelliferyl ketosides of 3-deoxy-D-manno-octulosonic acid.

Although alpha- and beta-linked 3-deoxy-D-manno-octulosonic acid (KDO) is found in lipopolysaccharides (LPSs) of Gram-negative bacteria, capsular polysaccharides of microorganisms, and plants, very little is known about its degradation. Using both thin-layer chromatography and the periodate-thiobarbituric acid reaction, we found that the hepatopancreas of oyster (Crassostrea virginica) contained an enzyme (alpha-KDOase) capable of releasing alpha-linked KDO from LPSs. To facilitate the studies of alpha-KDOase, we have carried out the synthesis of 4-methylumbelliferyl-alpha-KDO (alpha-KDO-MU) by conjugating the glycosyl chloride of the per-O-acetylated methylester of KDO with methylumbelliferone by the SN2 type reaction and the catalyzed phase-transfer. In both cases, the beta-anomer was obtained as the major product with a yield of about 80%, whereas the yield of alpha-anomer was only about 7%. Attempts to increase the yield of alpha-anomer were not successful. alpha-KDO-MU was used as substrate to follow the purification of alpha-KDOase from oyster hepatopancreas. The pH optimum for oyster alpha-KDOase was determined to be 4.5 using Re-LPS as substrate and 3.0 using alpha-KDO-MU as substrate. The enzyme was found to be stable in the pH range of 3-8. This enzyme released KDO from different LPSs, including Re-LPS from Escherichia coli and Salmonella minnesota, Rd-LPS from S. minnesota, and de-O-acyl-Re-LPS (Kiang, J., Szu, S. C., Wang, L.X., Tang, M., and Lee, Y. C. (1997) Anal. Biochem. 245, 97-101).

Animals↗

PubMed1997

Determination of 2-keto-3-deoxyoctulosonic acid (KDO) with high-performance anion-exchange chromatography (HPAEC): survey of stability of KDO and optimal hydrolytic conditions.

A new method for 2-keto-3-deoxy-octulosonic acid (KDO) determination using high-performance anion-exchange chromatography was developed. KDO is well separated from Neu5Ac, and the response was linear from 20 pmol to 5 nmol. The method was used to examine the stability of KDO under various hydrolytic, conditions and to survey optimal hydrolytic conditions for release of KDO.

Chromatography, Ion Exchange↗

PubMed1997

4-Methylumbelliferyl glycosides of N-acetyl 4-thiochito-oligosaccharides as fluorogenic substrates for chitodextrinase from Vibrio furnissii.

The degradation of chitin involves a diverse array of enzymes, some with overlapping substrate specificities. In order to distinguish between different types of enzymes, specific substrates are needed. Toward this end, two new fluorogenic substrates containing thio-glycosidic linkages, 4-methylumbelliferyl N,N'-diacetyl-4-thio-beta-chitobioside (Mu-TCB) and N,N',N"-triacetyl-4,4'-dithio-beta-chitotrioside (Mu-TCT) are described. The substitution of the glycosidic oxygens (except the one that links oligosaccharide with the fluorogenic aglycon) with a sulfur atom resulted in resistance of these compounds to N-acetyl-beta-hexosaminidases while they were specific substrates for the newly discovered chitodextrinase from Vibrio furnissii (Keyhani,N.O. and Roseman,S. (1996) J. Biol. Chem., 271, 33414-33424) and some bacterial chitinases. The enzyme kinetics of these 4-S-linked substrates, Mu-TCB and Mu-TCT, as well as the O-linked 4-methylumbelliferyl N,N'-diacetyl-beta-chitobioside (Mu-CB) and N,N',N"-triacetyl-beta-chitotrioside (Mu-CT) with the chitodextrinase were studied and compared. The usefulness of the substrates for screening for chitodextrinase and/or chitinase activity was demonstrated.

Carbohydrate Sequence↗

PubMed1997

[Effects of tetramethylpyrazine on platelet functions of advanced cases of lung carcinoma].

OBJECTIVE: To explore the role of hypercoagulation in the metastasis of carcinoma. METHODS: The effect of Tetramethylpyrazine (TTMP) on platelet functions among the 25 advanced cases of lung carcinoma, and 26 matched control subjects were investigated in the study. Their ages varied from 31-86 years (mean 58.2) in lung carcinoma group (13 male, 12 female) and 36 to 61 (mean 52.9) in the control group (16 male, 10 female). The pathologic types were as follows: 7 cases of squamous cell cancer, 12 adenocarcinoma, 2 small cell carcinoma and 4 undistinguished type. The TNM stage revealed 14 cases in stage IIIa, 3 in stage IIIb and 8 in stage IV. The site of metastasis included mediastinal lymph node, pleura, supraclavicular lymph node, brain, spine, costa, skin and pericardium. The levels of plasma TXB2, 6-keto-PGF1 alpha, VIII:C, vWF, AT-III:a, AT-III:Ag, Fg and blood PAdT, PAgT were measured before and after the intravenous infusion of 80 mg TTMP in patients with lung carcinoma. RESULTS: The levels of TXB2, 6-keto-PGF1 alpha, VIII:C, vWF and Fg in lung carcinoma group were significantly elevated, while the levels of PAdT was greatly decreased, compared with the control group, no significant differences in levels of PAgT, AT-III:a and AT-III:Ag were found between the two groups. After the infusion of TTMP the levels of PAdT, PagT, VIII:C, dWF and Fg were decreased significantly, while TXB2, 6-keto-PGF1 alpha, AT-III:a and AT-III:Ag remained unchanged. CONCLUSIONS: TTMP inhibits the adhesion and aggregatory functions of blood platelet and the activity of coagulation factors. It might be one of the mechanisms of TTMP's antimetastasis of lung carcinoma.

6-Ketoprostaglandin F1 alpha↗

PubMed1996

The chitin catabolic cascade in the marine bacterium Vibrio furnissii. Characterization of an N,N'-diacetyl-chitobiose transport system.

The disaccharide N,N'-diacetyl-chitobiose, (GlcNAc)2, is critical in chitin dissimilation by Vibrio furnissii and, as reported here, is taken up by a specific permease. Since (GlcNAc)2 is rapidly catabolized by V. furnissii, a non-hydrolyzable thioglycoside analogue was used: methyl beta-N,N'-[3H]diacetyl-thiochitobioside (Me-[3H]TCB). Me-TCB and TCB substitute for (GlcNAc)2 as chemoattractants and inducers of beta-N-acetylglucosaminidase activity. The [3H]Me-TCB uptake system was induced only by (GlcNAc)2 and by (GlcNAc)n that can be converted to (GlcNAc)2. The Km for [3H]Me-TCB uptake was </=1 microM and was not affected by Na+ or K+. Uptake appeared to be unidirectional, and in 0.4 M sucrose (+/- K+) the cells accumulated [3H]Me-TCB until it was depleted from the medium, giving an internal concentration of 0.1 M and an internal/external ratio > 1,000. The only effective inhibitors of uptake were: (GlcNAc)n, n = 2-4 > cellobiose > (GlcNAc)5. In 50% artificial sea water (or sucrose/Na+), [3H]Me-TCB accumulation attained a constant steady state level because of efflux, a Na+-dependent process. The physiological implications of these results are considered.

Biological Transport, Active↗